Use of Genomic Profiling to Assess Risk for Cardiovascular ...
Appendix 1:
Detailed information for each gene/polymorphism/SNP included in this review and its relationship with Coronary Heart Disease (CHD) and Stroke
Gene abbreviation (aka) Gene Name Appendix Page
ACE (ACED, ACE-1) Angiotensin-converting enzyme D ……………………. 2
AGT (serpin peptidase inhibitor) Angiotensinogen………………………………………….. 5
AGTR1 Angiotensin II receptor, type 1 …………………………. 7
APOB Apolipoprotein B …………………………………………… 9
APOC3 (APOC-III) Apolipoprotein C-III ………………………………………. 11
APOE Apolipoprotein E ....................................................... 16
CBS (HIP4) Cystathionine-beta-synthase ………………………….. 19
CETP (HDLCQ10) Cholesteryl ester transfer protein ……………………… 20
CYBA (p22-PHOX) Cytochrome b-245, alpha polypeptide …………………. 23
CYP11B2 Cytochrome P450, family 11, subfamily B, polypeptide 2 .. 24
F2 (FII, prothrombin) Coagulation factor II ……………………………………….. 25
F5 (FV, FVL, PCCF) Coagulation factor V …………………………………… 28
GNB3 (beta polypeptide 3) Guanine nucleotide binding protein ……………………… 31
GPX1 Glutathione peroxidase 1 ………………………………. 34
IL1B (IL-1, IL1F2, IL1-BETA) Interleukin 1, beta ………………………………………... 36
IL6 (HGF, IL-6, IFNB2) Interleukin 6 ………………………………………………… 38
ITGB3 (GP3a, CD61) Integrin, beta 3 ……………………………………………. 41
LPL (KID, HDLCQ11) Lipoprotein lipase ……………………………………….. 44
MTHFR 5,10-methylenetetrahydrofolate reductase ……………... 48
MTR (MS) 5-methyltetrahydrofolate-homocysteine methyltransferase … 53
MTRR (MSR) 5-MTR reductase ……………………………………….. 56
NOS3 (eNOS, ECNOS, NOS III) Nitric oxide synthase 3 (endothelial cell) ……………… 58
PAI-1 (SERPINE, SERBP1, PAI) Plasminogen activator inhibitor type 1 …………………. 61
PON1 (ESA, PON) Paraoxonase 1 ……………………………………………. 65
SELE (ELAM, ESEL, CD62E) Selectin E ………………………………………………… 68
SOD2 (MNSOD, Mn-SOD) Superoxide dismutase 2 ………………………………. 70
SOD3(EC-SOD) Superoxide dismutase 3 ………………………………. 71
TNF (DIF, TNFA, TNF-alpha) Tumor necrosis factor …………………………………… 72
9p21 SNPs ……………………………………………………………….. 75
References ……………………………………………………..………… 77
ACE (angiotensin-converting enzyme D)
The ACE gene (aka ACED, ACE-1) is located on chromosome 17 (17q23.3). According to NCBI Entrez Gene, “This gene encodes an enzyme involved in catalyzing the conversion of angiotensin I into a physiologically active peptide angiotensin II. Angiotensin II is a potent vasopressor and aldosterone-stimulating peptide that controls blood pressure and fluid-electrolyte balance. This enzyme plays a key role in the renin-angiotensin system. Studies have associated the presence [Insertion] or absence [Deletion] of a 287 bp Alu repeat element in this gene with the levels of circulating enzyme or cardiovascular pathophysiologies. The two most abundant alternatively spliced variants of this gene encode two isozymes - the somatic form and the testicular form that are equally active.”
Literature search
A HuGE Navigator (V1.1) search for the ACE gene identified 1,161 articles on 343 disease terms. A search for meta-analyses (ACE and Meta-analysis[Text+MeSH)>>Brain Ischemia, Cardiovascular disease, unspecified, Apoplexy, Coronary heart disease, Congestive heart failure, Myocardial Infarction, Myocardial ischemia, Subarachnoid Hemorrhage[MeSH]) identified eight articles. Four studies were excluded from analysis due to a non-Caucasian population (Asian, non-European), or because they focused on diseases that were outside of our categorization areas (premature CHD, cardiac function).1-4 The remaining four articles are summarized below.
Genotype frequencies
For the ACE gene insertion/deletion polymorphism, I represents the presence of the sequence (insertion) while D indicates the deletion. The at-risk genotype is homozygous for the deletion (DD). In a general Caucasian population, genotype frequencies for the wild (II) and heterozygous (ID) combined is 73%, while homozygotes (DD) represent the remaining 27%. Under Hardy-Weinberg, the three genotypes separately would be approximately 23%, 50% and 27%, respectively.5
Coronary Heart Disease (Primary Myocardial Infarction)
A meta-analysis from 20035 provided a systematic review of published studies, abstracts and letters regarding the relationship between ACE (and two other markers) and primary myocardial infarction (MI). Studies that were family based, reported on recurrent disease or focused on subgroups (e.g., pregnant women, diabetics) were also excluded. Analytic methods included random effects modeling, formal tests for heterogeneity, and identification of possible publication bias. Overall, 43 studies were included in the analysis. The summary odds ratio for the recessive model (DD vs. II+ID) was 1.22 (95% CI 1.11 to 1.34), p Coronary heart disease, Congestive heart failure, Myocardial Infarction, Myocardial ischemia[MeSH]) identified four articles.7,10-12 A 2008 meta-analysis10 was selected as being the most recent, and the most complete.
Genotype frequencies
The at-risk genotype is TT. In a general Caucasian population, genotype frequencies for the wild (MM) and heterozygous (MT) combined is 57%, while homozygotes (TT) represent the remaining 43%. Under Hardy-Weinberg, the three genotypes separately would be approximately 32%, 50% and 18%, respectively.5
Coronary Heart Disease (Myocardial Infarction)
A 2007 meta-analysis11 provided a review of the AGT polymorphism M235T (T allele) and CHD. The authors excluded studies of recurrent events, case-only studies, insufficient data to create confidence intervals, and studies containing duplicate data. Analytic methods include fixed effects modeling, formal tests for heterogeneity, stratified analyses and identification of possible publication bias. Overall, 38 studies were included in the analysis and for a total of 32,005 subjects. The summary odds ratio for the model MT vs. MM was 1.02 (95% CI 0.91 to 1.14), p=0.7 and for the model TT vs. MM was 1.15 (95% CI 1.00 to 1.32), p = 0.05. However, there was significant heterogeneity (Q = 76, p < 0.001, I2 = 51% for the former and Q = 79, p < 0.001, I2 = 53% for the latter). The majority of heterogeneity was explained by study size, with small studies showing larger effects.
Venice criteria6 for evaluating the credibility of genetic association meta-analysis were applied and resulted in the three grades of ‘A’ (size: over 8,000 cases/controls with a TT genotype), ‘C’ (replication: I2 of 56% indicating considerable heterogeneity), and ‘-‘ (bias: not evaluated due to at least one already assigned grade of C).
A 2008 meta-analysis examined the M235T polymorphism of AGT and MI.10 Analytic methods included random effects modeling, formal tests for heterogeneity and the evaluation of potential publication bias. There were 38 studies included in this meta-analysis; however, only 25 studies were conducted in Caucasian populations for a total of 26,489 study participants. The summary odds ratio for the model MT vs. MM was 1.03 (95% CI 0.94 to 1.14), p = 0.5 and for the model TT vs. MM was 1.19 (95% CI 1.02 to 1.38), p = 0.02. However, there was significant heterogeneity (Q = 32, p = 0.1, I2 = 25% for the former and Q = 60, p < 0.001, I2 = 60% for the latter). Some of the heterogeneity was explained by study size, while the violation of Hardy-Weinberg equilibrium also contributed to the heterogeneity.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘A’ (size: over 4,700 cases/controls with a TT genotype in the Caucasian studies), ‘C’ (replication: I2 of 25% - 60% indicating considerable heterogeneity), and ‘-‘ (bias: not evaluated due to an earlier grade of C).
Large study analysis -- When the analysis was restricted to the seven studies with 500 or more cases of MI10, the summary OR for the MT vs. MM comparison (Figure B.3) was reduced to 1.00 (95% CI 0.92 to 1.08), p = NS. The heterogeneity was low (Q = 3.3, I2 = 0%, p = 0.8). The summary OR for the TT vs. MM comparison (Figure B.4) was reduced to 1.03 (95% CI 0.90 to 1.17) with moderate heterogeneity (Q = 8.2, I2 = 27%, p = 0.2).
Figure B.3 Summary analysis of the AGT MT vs. MM polymorphism and MI, after restriction to the seven large studies.
Figure B.4 Summary analysis of the AGT TT vs. MM polymorphism and MI, after restriction to the seven large studies.
AGTR1 (angiotensin II receptor, type 1)
The AGTR1 gene (aka AT1R) is located on chromosome 1 (3q21-q25). The most widely studied polymorphism is A1166C. According to NCBI Entrez Gene, “Angiotensin II is a potent vasopressor hormone and a primary regulator of aldosterone secretion. It is an important effector controlling blood pressure and volume in the cardiovascular system. It acts through at least two types of receptors. This gene encodes the type 1 receptor which is thought to mediate the major cardiovascular effects of angiotensin II. This gene may play role in the generation of reperfusion arrhythmias following restoration of blood flow to ischemic or infarcted myocardium. It was previously thought that a related gene, denoted as AGTR1B, existed; however, it is now believed that there is only one type 1 receptor gene in humans. At least five transcript variants have been described for this gene. Additional variants have been described but their full-length nature has not been determined.”
Literature search
A HuGE Navigator (V1.1) search (AGTR1 and Clinical Trial, HuGE Review, Meta-analysis[StudyType)>>Myocardial Infarction) identified one article13 which is summarized below.
Genotype frequencies
The at-risk genotype is CC. In a general Caucasian population, genotype frequencies for the wild (AA) and heterozygous (AC) combined is 72%, while homozygotes (CC) represent the remaining 28%. Under Hardy-Weinberg, the three genotypes separately would be approximately 52%, 40% and 8%, respectively.5
Coronary Heart Disease (Myocardial Infarction)
A 2007 HuGE review13 systematically reviewed the literature relating the AGTR1 A1166C polymorphism (C is the risk allele) to MI. Analytic methods include random effects modeling, formal tests for heterogeneity, stratified analyses and identification of possible publication bias. 20 studies reported effect measures for the recessive model in European Caucasians. A total of 24,331 study participants were included. The summary OR for the recessive model (CC vs. AC+AA) was 1.32 (95% CI 1.10 to 1.59), p = NR. Heterogeneity was high (Q = 46, I2 = 56%, p=NR). 21 studies reported effect measures for the dominant model in European Caucasians. A total of 25,388 study participants were included. The summary OR for the dominant model was 1.11 (95% CI 1.01 to 1.21), p = NR. Heterogeneity was moderate (Q = 37, I2 = 44%, p = NR).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘A’ (size: estimated at least 6,750 cases/controls with a CC genotype using 28% genotype frequency), ‘C’ (replication: I2 of 44% and 56% indicating considerable heterogeneity), and ‘-‘ (bias: not evaluated due to at least one already assigned grade of C). According to the original analysis13 there is a clear indication that bias related to sample size and other sources of bias (such as publication bias) contribute to the between-study heterogeneity in this meta-analysis.
Large study analysis (Figure B.5) – Raw numbers were not available from the meta-analysis, so the point estimate and 95% confidence intervals were used for the three studies with the smallest confidence intervals, corresponding to studies having approximately 500 cases, the allele-specific OR (*C allele) was 0.98, (95% CI 0.93 to 1.01), p = NS. Heterogeneity was low (Q = 1.7, I² = 0%, p = 0.4).
Figure B.5 Summary analysis of the AGTR1 gene (C allele) and MI, after restriction to the three large studies.
APOB (apolipoprotein B)
The APOB gene is located on chromosome 2 (2p24-p23). Polymorphisms are Xbal, signal peptide, and EcoR1. According to NCBI Entrez Gene, “this gene product is the main apolipoprotein of chylomicrons and low density lipoproteins. It occurs in plasma as two main isoforms, apoB-48 and apoB-100: the former is synthesized exclusively in the gut and the latter in the liver. The intestinal and the hepatic forms of apoB are encoded by a single gene from a single, very long mRNA. The two isoforms share a common N-terminal sequence. The shorter apoB-48 protein is produced after RNA editing of the apoB-100 transcript at residue 2180 (CAA->UAA), resulting in the creation of a stop codon, and early translation termination.”
Literature search
A HuGE Navigator (V1.1) query (APOB[Text+MeSH]>>Meta-analysis, HuGE Review[StudyType] identified two summary analyses, both performed in 2003.14,15 We chose the Chiodini et al., analysis15, as it included heterozygotes in their odds ratios. Boekholdt et al14, computed ORs for only the wild and homozygous groups (heterozygotes were ignored).
Genotype frequencies
• For the polymorphism Xbal (C2488T), the at-risk genotype is TT. In a European Caucasian population in the US, the C allele frequency is about 0.51.16 Under Hardy-Weinberg, the three genotypes separately would be approximately 42%, 46% and 12%, respectively.
• For the polymorphism EcoRI (G4154A), the at-risk genotype is AA. In a European Caucasian population in the US, the G allele frequency is about 0.82.16 Under Hardy-Weinberg, the three genotypes separately would be approximately 70%, 27% and 3%, respectively.
• For the signal peptide insertion/deletion (Sp Ins/Del), the at-risk genotype is DD. In a European Caucasian population in the US, the I allele frequency is about 0.67.16 Under Hardy-Weinberg, the three genotypes separately would be approximately 47%, 43% and 10%, respectively.
Coronary Heart Disease (Myocardial Infarction)
A 2003 HuGE review15 systematically reviewed the literature relating APOB to MI/CAD. Analytic methods include random effects modeling, formal tests for heterogeneity, stratified analyses and identification of possible publication bias.
• For the Xbal polymorphism, 19 studies (including various races) were included for the recessive model and 20 studies were included for the dominant model. The summary odds ratio for the recessive model was 1.19 (95% CI 1.01 to 1.39), p = 0.03, and for the dominant model was 1.14 (95% CI 0.88 to1.48), p = 0.3. However, there was moderate heterogeneity (I2 = 29%) for the former and significant heterogeneity for the latter (I2 = 49%). Only one included study reported on more than 500 cases.
• For the EcoRI polymorphism, 14 studies (including various races) were included. The summary odds ratio for the recessive model was 1.73 (95% CI 1.19 to 2.50), p=0.004 and for the dominant model was 1.32 (95% CI 1.14 to 1.54), p < 0.001 with low heterogeneity (I2 = 0% and I2 = 13%, respectively). None of the included studies reported on 500 or more cases.
• For the polymorphism Sp Ins/Del, 22 studies (including various races) were included. The summary odds ratio for the recessive model was 1.19 (95% CI 1.05 to 1.35), p = 0.006 and for the dominant model was 1.15 (95% CI 1.06 to 1.24), p < 0.001 with modest evidence of heterogeneity (I2 = 23% and I2 = 12%, respectively). Only one included study reported on 500 or more cases.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for
• Xbal: ‘A’ (size: approximately 1,104 cases with a TT genotype (2,628 cases * 0.42 reported frequency of TT in the analysis), ‘B’ (replication: I2 of between 29% and 49%, depending on model, indicating considerable heterogeneity), and ‘C‘ (bias: the authors reported clear indication of bias related to sample size.
• EcoRI: ‘C’ (size: approximately 46 cases with an AA genotype (1,721 * 0.027), ‘A’ (replication: I2 of 0% indicating a low level of heterogeneity) and ‘-‘ (no value assigned given a grade of C in a previous category).
• Ins/Del: ‘B’ (size: approximately 595 cases with a DD genotype (6,007 * 9.9%), ‘A’ (replication: I2 of 0% indicating a low level of heterogeneity), ‘B‘ (bias: none obvious, but considerable missing information).
APOC3 (apolipoprotein C-III)
The APOC3 gene (aka APOCIII, APOC-III) is located on chromosome 11 (11q23.1-q23.2). The most widely studied polymorphism is C3238G, but several others have also been studied. According to NCBI Entrez Gene, “Apolipoprotein C-III is a very low density lipoprotein (VLDL) protein. APOC3 inhibits lipoprotein lipase and hepatic lipase; it is thought to delay catabolism of triglyceride-rich particles. The APOA1, APOC3 and APOA4 genes are closely linked in both rat and human genomes. The A-I and A-IV genes are transcribed from the same strand, while the A-1 and C-III genes are convergently transcribed. An increase in APOC3 levels induces the development of hypertriglyceridemia.”
Literature search
A HuGE Navigator (V1.1) search for APOC3 gene identified 135 articles on 54 disease terms. No meta-analyses were found in the area of CVD. A search (APOC3[Text+MeSH]>>Arterial Sclerosis, Atherosclerosis, Cardiovascular disease, unspecified, coronary artery disease, coronary artery disease, Coronary heart disease, Vascular Diseases[Mesh]) identified 40 articles; none of which were summary articles. Of these, the majority looked at intermediate outcomes (e.g., lipid measurements) or studied subpopulations (e.g., diabetics). Ten studies remained.17-26 Four additional studies were examined after searching references.27-30 After limiting studies to the Caucasian population with a primary CVD outcome, nine studies remained and are summarized below.
Genotype frequencies
• For the polymorphism Sst-1 (also referred to as the C3238G variant), the at-risk allele is S2. In a US population of 371 healthy predominately Caucasian controls, the S1 (wild) allele frequency is 0.90 and the S2 (at-risk) allele is 0.10.27 The reported genotype frequencies were 80%, 19% and 1%, for S1/S1, S1/S2 and S2/S2, respectively. Under Hardy-Weinberg, the three genotypes would be approximately 81%, 18% and 1%, respectively. Because of the low prevalence of the S2/S2 genotype, the usual grouping is S1/S2 + S2/S2 vs. S1/S1. In some publications, these genotypes would be reported as CC, CG and GG, respectively.
• For the T455C polymorphism, the at-risk allele is C. In a cohort study of 505 European Caucasians (English), the T allele frequency is 0.65 and the C allele is 0.35.28 The reported genotype frequencies were 42%, 46% and 12%, for TT, TC and CC, respectively. Under Hardy-Weinberg, the three genotypes are expected to be 42%, 45% and 12%, respectively.
• For the C482T polymorphism, the at-risk allele is T. In a cohort study of 505 European Caucasians (English), the C allele frequency is 0.75 and the T allele is 0.25.28 The reported genotype frequencies were 56%, 38% and 6%, for CC, CT and TT, respectively. Under Hardy-Weinberg, the three genotypes are expected to be 56%, 38% and 6%, respectively.
Coronary Heart Disease
• S1S2: Seven studies24-30 were available for analysis using the recessive model (S1S2 + S2S2 vs. S1S1). Total numbers included are 2,541 cases and 6,316 controls. None of the individual studies found a significant effect. Figure B.6 shows that the summary OR is 1.00 (95% CI 0.89 to 1.13), p = NS. The heterogeneity is low (Q = 5.8, I2 = 0%, p = 0.4. Similar results were found for the S1S1 + S1S2 vs. S2S2 model (data not shown).
Figure B.6. Analysis of seven APOC3 studies (S1S1 vs. S1S2 + S2S2) for CHD/MI
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the APOC3 Sst1 polymorphism results in three grades: ‘B’ (size: approximately 500 cases with a TT genotype (2,541 cases * 20% reported genotype frequency for S2+ in the analysis), ‘A’ (replication: I2 of between 29% and 49%, depending on model, indicating considerable heterogeneity), and ‘B‘ (bias: none obvious, but considerable missing information).
Large study analysis (Figure B.7) – Five of the studies included 500 or more subjects. The large study OR is 1.03 (95% CI 0.91 to 1.16), p = NS. Heterogeneity was low (Q = 3.3, I2 = 0%, p = 0.5)
[pic]
Figure B.7 Summary analysis of the APOC3 gene (Sst1 polymorphism) and CHD/MI, after restriction to the five large studies.
• T455C: Four studies21,25,28,29 were available for the TC vs. TT (Figure B.8) and CC vs. TT (Figure B.9) comparisons.
The summary OR for the heterozygous comparison (TC vs. TT) was 1.07 (95% CI 0.91 to 1.25), p= 0.4. The results showed modest heterogeneity (Q = 4.3, I2 = 30%, p = 0.3). For this analysis, 2,126 cases and 1,751 controls were availble for this analysis.
Figure B.8. Analysis of four APOC3 studies of the T455C polymorphism (TC vs. TT) for CHD/MI
The summary OR for the homozygous comparison (CC vs. TT) was 1.32 (95% CI 0.82 to 2.12), p = 0.3. The results showed high heterogeneity (Q = 16.3, I2 = 82%, p = 0.001). For this analysis, 1,321 cases and 1,073 controls were availble for study.
Figure B.9. Analysis of four APOC3 studies of the T455C polymorphism (CC vs. TT) for CHD/MI
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the APOC3 T455C polymorphism results in three grades: ‘B’ (size: approximately 300 cases with a TT genotype (2,541 cases * 12% reported genotype frequency for TT in the analysis), ‘C’ (replication: I2 values of 30% and 82%, depending on model, indicating considerable heterogeneity), and ‘-‘ (bias: no value assigned given a grade of C in a previous category).
Large study analysis – For both comparisons, all four studies are considered large, so the same summary OR’s and measures of heterogeneity apply.
• C482T: Three studies19,28,29 were available for the TC vs. TT (Figure B.8) and CC vs. TT (Figure B.10) comparisons.
The summary OR for the heterozygous comparison (CT vs. CC) was 0.99 (95% CI 0.85 to 1.15), p = 0.9. The results showed modest heterogeneity (Q = 2.5, I2 = 21%, p = 0.3). For this analysis, 1,814 cases and 1,800 controls were availble for study.
Figure B.10 Analysis of three APOC3 studies of the C482T polymorphism (CT vs. CC) for CHD/MI
The summary OR for the homozygous comparison (TT vs. CC) was 0.91 (95% CI 0.74 to 1.12), p = 0.4. The results showed low heterogeneity (Q = 1.6, I2 = 0%, p = 0.4). For this analysis, 1,142 cases and 1,148 controls were availble for study.
Figure B.11 Analysis of three APOC3 studies of the C482T polymorphism (TT vs. CC) for CHD/MI
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the APOC3 C482T polymorphism results in three grades: ‘B’ (size: approximately 120 cases with a TT genotype (2,046 cases * 6% reported genotype frequency for TT in the analysis), ‘A’ (replication: I2 values of 0% and 21%, depending on comparison, indicating low heterogeneity), and ‘B‘ (bias: none obvious, but considerable missing information).
Large study analysis – For both comparisons, all three studies are considered large, so the same summary OR’s and measures of heterogeneity apply.
Stroke
A HuGE Navigator (V1.1) search for APOC3 gene (articlesAPOC3[Text+MeSH]>>Arterial Sclerosis, Atherosclerosis, Brain Ischemia, Apoplexy[Mesh]) identified 5 articles, none of which were relevant. No analyses were performed.
APOE (apolipoprotein E)
The APOE gene is located on chromosome 19 (19q13.2). The most widely studied polymorphisms are ε2 (C112/C158), ε3 (C112/A158) and ε4 (A112/A158). According to NCBI Entrez Gene, “[c]hylomicron remnants and very low density lipoprotein (VLDL) remnants are rapidly removed from the circulation by receptor-mediated endocytosis in the liver. Apolipoprotein E, a main apoprotein of the chylomicron, binds to a specific receptor on liver cells and peripheral cells. APOE is essential for the normal catabolism of triglyceride-rich lipoprotein constituents. The APOE gene is mapped to chromosome 19 in a cluster with APOC1 and APOC2. Defects in apolipoprotein ε results in familial dysbetalipoproteinemia, or type III hyperlipoproteinemia (HLP III), in which increased plasma cholesterol and triglycerides are the consequence of impaired clearance of chylomicron and VLDL remnants.”
Literature search
A HuGE Navigator (V1.1) search (APOE[Text+MeSH]>>Meta-analysis, Clinical trial, HuGE review[StudyType]>>Brain Ischemia, Cardiovascular disease, unspecified, Cerebral Hemorrhages, Apoplexy, Coronary heart disease, Intracranial Arteriosclerosis, Intracranial Hemorrhages, Ischemia, Myocardial Infarction, Apoplexy, Subarachnoid Hemorrhage[Mesh]). Articles were excluded if they evaluated only intermediate outcomes, examined non-Caucasian populations, were not being published in English or have a more recent study published on the same topic. Five meta-analyses remained.8,31-34 Two of these31,34 related to CHD. We chose the analysis by Bennet and colleagues31 because it was more recent (2007 vs. 2004 for Song and colleagues) and it was restricted to only large studies. Among the three meta-analyses of stroke8,32,33, we chose the analysis by Sudlow and colleagues33 as it was larger and more recent. The Lanterna report32 was a summary of case-only studies.
Genotype frequencies
Allele frequencies in a mainly Caucasian population of controls are 7% for ε2, 82% for ε3, and 11% for ε4.31 The at-risk genotype includes at least one ε4 allele. In a general Caucasian population, the wild genotype is ε3/ε3. Under Hardy-Weinberg, the six genotypes (to the nearest 1%) would be approximately 1%, 11%, 2%, 67%, 18% and 1%, for ε2/ε2, ε2/ε3, ε2/ε4, ε3/ε3, ε3/ε4, ε4/ε4, respectively. The ε2/* group (ε2/ε2 and ε2/ε3) is about 12%, while the ε4/* group (ε2/ε4, ε3/ε4 and ε4/ε4 is about 21%). The reference group is usually the remaining ε3/ε3.
Coronary Heart Disease (Myocardial Infarction)
A meta-analysis from 200731 provided a systematic review of published studies of APOE genotypes and MI. Studies with fewer than 1,000 participants cases were excluded, coronary stenosis defined as one or more vessels > 50% occlusion and collected some grey data from the original authors. Analytic methods included random effects modeling, formal tests for heterogeneity and tests for publication bias. Overall 17 studies were included in the analysis. The odds ratio for ε2/* vs. ε3/ε3 is 0.80 (95% CI 0.70 to 0.90). There was significant heterogeneity (I2 = 72%). The odds ratio for ε4* vs. ε3/ε3 is 1.06 (95% CI 0.99 to 1.13). There was modest heterogeneity (I2 = 44%). Because of the large sample size the authors were able to show a dose-response relationship from lower to higher odds of disease. Genotypes ε2/ε2, ε2/ε3, ε2/ε4, had reduced ORs, ε3/ε3 was the referent category with OR=1, and the genotypes ε3/ε4, ε4/ε4 had gradually higher ORs.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘A’ (size: estimated at least 2500 cases/controls with an ε2/* genotype using a 12% genotype frequency), ‘C’ (replication: I2 of 72% and 44% indicating considerable heterogeneity), and ‘-‘ (bias: not evaluated due to at least one already assigned grade of C).
Although all studies were relatively large, the authors compared smaller versus larger studies and found a strong protective effect of ε2 in large studies that was absent from smaller studies, and virtually no effect for ε4* in large studies, but a strong and significant effect in small studies (OR = 1.66, 95% CI 1.50 to 1.84). These findings reinforce the replication grade of C.
Stroke (Ischemic Stroke)
A meta-analysis from 200633 provided a systematic review of published studies
of APOE genotypes and various forms of stroke. Studies were excluded if the disorder was not explicitly stated or if the study focused on recurrent events. Ethnicity/race was not restricted and varied widely; 50% were Caucasian. A total of 4,096 cases and 16,117 controls were included. Analytic methods included the Mantel-Haenszel method of pooling ORs and examination of results for publication bias. Overall 24 studies were included in the analysis of ischemic stroke.
• The OR for the ε4+ vs. ε4- was 1.11 (95% CI 1.01 to 1.22), p = 0.03. There was significant heterogeneity (I2 = 68%).
• The OR for the ε2+ vs. ε2- was 0.99 (0.87 to 1.13), p = NS. There was no report for the heterogeneity.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘A’ (size: over 1,000 ε4+ cases/controls with an ε4+ genotype), ‘C’ (replication: I2 of 72% and 44% indicating considerable heterogeneity), and ‘-‘ (bias: not evaluated due to at least one already assigned grade of C). The authors reported smaller and non-significant associations when only studies of 200 or more subjects were used, or when studies with selection bias of controls were removed.
Large study analysis - Seven of the included studies reported results for 500 or more cases/controls for the ε4+/ε4- comparison (Figure B.12). The summary OR is 0.91 (95% CI 0.79 to 1.03), p = NS. The heterogeneity was low (Q = 5.3, I2 = 0%, p = 0.6).
Figure B.12 Summary analysis of the APOE gene (ε4-/ε4+ genotype) and stroke, after restriction to the seven large studies.
CBS (cystathionine-beta-synthase)
The CBS gene (aka HIP4) is located on chromosome 21 (21q22.3). The most widely studied polymorphisms is c.844ins68. According to NCBI Entrez Gene, “the protein encoded by this gene is involved in the transsulfuration pathway. The first step of this pathway, from homocysteine to cystathionine, is catalyzed by this protein. CBS deficiency can cause homocystinuria which affects many organs and tissues, including the eyes and the skeletal, vascular and central nervous systems.”
Literature search
A HuGE Navigator (V1.1) search for the CBS gene identified 81 articles on 57 disease terms. Four meta-analyses/HuGE Reviews were found, but none were in the area of CVD (three on various cancers, and on congenital anomalies). A search (CBS[Text+MeSH]>>Arterial Sclerosis, Brain Ischemia, Cardiovascular disease, unspecified, Apoplexy, Cerebrovascular Disorders, coronary artery disease, Coronary heart disease, Myocardial Infarction, Myocardial ischemia, Vertebral Artery Dissection[Mesh]) identified 20 articles. Of these, 16 were considered non-relevant, mostly because they focused exclusively on intermediate outcomes. The two remaining studies are summarized below.35,36
Genotype frequencies
W represents the wild allele, while M represents the presence of the insertion. The at-risk genotype is MM with a prevalence of 2.5%. In a general Caucasian population, allele frequencies are .85 and .15, respectively (based on 591 control individuals.35 Under Hardy-Weinberg, the three genotypes separately would be approximately 72%, 25.5% and 2.5%, respectively.
Coronary Heart Disease (Coronary Artery Disease)
A 2003 study35 reported on 869 Caucasians from the Czech Republic; 278 cases (confirmed WHO criteria) and 591 control individuals. The OR for the recessive model (MM vs. WW+WM) was 0.55 (95% 0.36 to 0.88), p = 0.015.
Coronary Heart Disease (Myocardial Infarction)
A 2001 study36 from Atlanta reported on 295 African Americans; 110 cases (65 and younger patients for follow-up of clinically defined MI) and 185 matched controls (outpatients at the same hospital with no history of MI, matched for age sex and race). The odds ratio for recessive model (WW+WM) vs. MM) comparison was 1.10 (95% 0.69 to 1.86), p = 0.6.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘C’ (size: less than 100 in the smallest category), ‘C’ (replication: failed replication is subsequent study), and ‘-‘ (bias: not evaluated because both earlier grades were C).
Large study analysis -- No studies were sufficiently large to perform this analysis.
Stroke (Ischemic Stroke)
No studies were found that reported CBS genotypes and stroke outcomes.
CETP (cholesteryl ester transfer protein)
The CETP gene (aka HDLCQ10) is located on chromosome 16 (16q21). The most widely studied polymorphisms is TaqIB (C629A). According to NCBI Entrez Gene, “Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters between lipoproteins. CETP may affect susceptibility to atherosclerosis. “
Literature search
A HuGE Navigator (V1.1) search for the CETP gene identified 177 articles on 57 disease terms. Two (CETP[Text+MeSH]>>Clinical trial, Meta-analysis[StudyType]>>Cardiovascular disease, unspecified[Mesh]) identified two articles. One dealt with natural genetic variation and the role of CETP in lipid levels and disease.14 The remaining meta-analysis is summarized below. To investigate stroke the search (CETP[Text+MeSH]>>Arterial Sclerosis, Atherosclerosis, Apoplexy, Apoplexy[Mesh]) identified seven studies, two of which are summarized below.
Genotype frequencies
B1 represents the wild allele, while B2 represents the presence of the variant. The at-risk genotype is B2/B2 with a 17.6% prevalence. In a general Caucasian population, allele frequencies are 0.57 and 0.42, respectively (based on over 10,000 controls individuals.35 Under Hardy-Weinberg, the three genotypes separately would be approximately 33.6%, 48.7% and 17.6%, respectively.
Coronary Heart Disease (Coronary Artery Disease - CAD)
The 2005 meta-analysis37 was restricted to studies reporting on 500 or more Caucasian individuals. Patient specific data were available for analysis from the original authors. Analytic methods included random effects modeling, adjusting for confounding variables, formal tests for heterogeneity and identification of possible publication bias. Overall, seven studies included in the analysis reported results in 2,857 cases and 8,815 controls. It appears that the authors mislabeled Figure 2. The three columns should be B2/B2, B1/B2 and B1/B1 (the first and last column labels seem reversed). The odds ratios were adjusted for age, sex, smoking, diabetes, BMI, blood pressure, LDL and use of alcohol (the odds ratios without adjustment are nearly identical). Among large studies, the adjusted summary OR for the B1/B2 vs. B1/B1 comparison was 0.96 (95% CI 0.92 to 0.99), p = 0.03. Unadjusted OR was 0.97 (95% CI 0.88 to 1.06), p = 0.5. The adjusted summary odds ratio for the B2/B2 vs. B1/B1 comparison was 0.82 (95% CI 0.75 to 0.91), p < 0.001. Unadjusted OR was 0.97 (0.76 to 0.99), p = 0.3. There was significant heterogeneity reported for both summaries, but no statistical results were provided.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘A’ (size: approximately 18% of the 2,857 cases would be B1/B1 of 515 with more than that number of controls). ‘B’ (reliability: we reanalyzed the raw data37 to obtain a reliable estimate of heterogeneity. For both the B1/B2 (Q = 1.5, I2 = 0%, p = 0.9) and the B2/B2 (Q = 3.7, I2 = 0%, p = 0.7) comparison to B1/B1, heterogeneity was low. ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis – The seven studies summarized above were already ‘large’.
Stroke (Ischemic Stroke)
A 2007 study38 involved 451 Caucasians in Sardinia. Of these, 215 had an ischemic stroke (clear clinical parameters persisting for 24+ hours confirmed by CT scan). Controls were unrelated individuals from the same hospital who had no known history of CVD. The study included both males and females. The OR for the recessive model [(B1/B1 + B1/B2) vs. B2/B2] was 0.53 (95% CI 0.32 to 0.88), p = 0.01. The effect was larger for females than for males. A second study of 98 case and 100 control individuals39 did not report specific numbers, but concluded that “neither polymorphism examined in this study appears to be significantly associated with ischemic stroke”.
Overall, we conclude that there is low quality evidence that no significant association exists between this CETP polymorphism and stroke.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘C’ (size: less than 100 in the smallest category), ‘C’ (replication: failed replication is subsequent study), and ‘-‘ (bias: not evaluated because both earlier grades were C.
Large study analysis -- No studies were sufficiently large to perform this analysis.
CYBA (cytochrome b-245, alpha polypeptide)
The CYBA gene (aka p22-PHOX, CYBA8) is located on chromosome 16 (16q24). The most widely studied polymorphism is C242T. According to NCBI Entrez Gene, “Cytochrome b is comprised of a light chain (alpha) and a heavy chain (beta). This gene encodes the light, alpha subunit which has been proposed as a primary component of the microbicidal oxidase system of phagocytes. Mutations in this gene are associated with autosomal recessive chronic granulomatous disease (CGD), which is characterized by the failure of activated phagocytes to generate superoxide, which is important for the microbicidal activity of these cells.”
Literature search
A HuGE Navigator (V1.1) search (CYBA[Text+MeSH]>>Meta-analysis[StudyType]>>) identified one article that is summarized below.
Genotype frequencies
For the C242T polymorphism, C represents the wild allele, T represents the at-risk variant. The at-risk genotypes are TT and CT. In the US population, the T allele frequency is 0.34. Under Hardy-Weinberg, the three genotypes separately would be approximately 12% (TT), 44% (TC) and 44% (CC), respectively.
Coronary Heart Disease (Coronary Artery Disease - CAD)
A 2008 meta-analysis reported the association of CYBA with CHD, with eight reports having the outcome of coronary artery disease (CAD). Three additional publications found by that group that focused on other vascular risk, including diabetes, were not included.40 Overall, 6,253 cases and 3,984 controls were included. Statistical analyses included verification of Hardy-Weinberg, fixed and random effects modeling, and formal analysis of heterogeneity.
• For the CT+TT vs. CC (dominant) model the random effects OR is 0.94 (95% CI 0.77 to 1.14). Heterogeneity was high using a fixed effects model (I2 = 65%). Significant heterogeneity was also reported for the random effects model, but no I2 value was reported.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘A’ (size: 16% of 6,253 cases), ‘C’ (replication: high heterogeneity), and ‘-‘ (bias: not evaluated because of a replication grade of C).
Large study analysis -- Figure B.13 shows the analysis of the four large studies. The summary OR for the dominant model is 0.92 (95% CI 0.77 to 1.10), p = 0.4. Heterogeneity is high (Q = 7.5, I2 = 60%, p = 0.06).
Figure B.13 Summary analysis of the CYBA gene (CC vs. CT+TT ) and CHD, after restriction to the four large studies.
• For the CC+CT vs. TT (recessive) model, the random effects OR is 1.17 (95% CI 0.97 to 1.41), p = NS. No evidence of heterogeneity (I2 = 4%).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘A’ (size: 16% of 6,253 cases), ‘A’ (replication: high heterogeneity), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis -- Figure B.14 shows the analysis of the four large studies. The summary OR for the recessive model is 1.16 (95% CI 0.86 to 1.57), p = NS. Heterogeneity is moderate to high (Q = 6.0, I2 = 49%, p = 0.1).
Figure B.14 Summary analysis of the CYBA gene (CC+CT vs. TT ) and CHD, after restriction to the four large studies.
CYP11B2 (cytochrome P450, family 11, subfamily B, polypeptide 2)
The CYP11B2 gene is located on chromosome 8 (8q21-q22). The polymorphism of interest is C344T. According to NCBI Entrez Gene, “[t]his gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. This protein localizes to the mitochondrial inner membrane. The enzyme has steroid 18-hydroxylase activity to synthesize aldosterone and 18-oxocortisol as well as steroid 11 beta-hydroxylase activity. Mutations in this gene cause corticosterone methyl oxidase deficiency.”
Literature search
A HuGE Navigator (V1.0) search (CYP11B2[Text+MeSH]>>Cardiovascular disease, unspecified, Coronary heart disease, Coronary restenosis, Myocardial Infarction[Mesh]) identified 10 articles. Only a single paper from 200441 was found, and it is summarized below.
Genotype frequencies
For the C344T polymorphism, T represents the wild allele, C represents the at-risk variant. The at-risk genotypes are TC and CC. In the US population, the CC genotype is approximately 20% (Payne 2004). Under Hardy-Weinberg, the three genotypes separately would be approximately 20% (CC), 49% (TC) and 31% (TT, the referent category), respectively.
Coronary Heart Disease (Coronary Artery Disease - CAD)
A 2004 study reported the association of CYP11B2 with CAD in a cohort of 187 cases and 2,303 controls.41 The study group was all Caucasian males after exclusion of people with diabetes and those with unstable angina. CAD was defined as sudden cardiac death or a symptomatic MI, silent MI or coronary revascularization. Controls were middle-aged Caucasian males screened for a negative history of CHD. The summary OR for the TC vs. TT genotypes was 1.25 (no CI, but termed ‘not significant’). The OR for the CC vs. TT genotype was 0.80 (no CI but termed ‘not significant’).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades for both models of ‘C’ (size: 1>Meta-analysis[StudyType]) which returned 11 meta-analyses. Four of these related to CVD.42-45 We chose to use Burzotta and colleagues for CHD as it is more recent and larger.42 We used the meta-analysis by Kim for the stroke analysis43 as it was the most recent one for this outcome.
Genotype frequencies
For the C20210A polymorphism, G represents the wild allele and A represents the presence of the variant. The allele frequency for the ‘A’ variant in a general Caucasian population is only 0.011; the frequency for ‘G’ is then .989.46 Based on Hardy-Weinberg, the expected genotype frequencies are 97.8% GG and 2.2% GA or AA. Because of the very low frequency for the A allele and therefore, the AA genotype, the homozygous variant (AA) is usually combined with the heterozygote (AG) and the evaluation comparisons are reported as (AG + AA) vs. GG (dominant model).
Coronary Heart Disease (Ischemic Heart Disease)
A 2004 meta-analysis included 19 studies that evaluated the 20210 variant and its association to ischemic heart disease.42 A total of 4,944 cases and 7,090 controls were included in the meta-analysis. Because of the rare homozygosity for the A allele, the homozygous (AA) and heterozygous (AG) variants were combined and compared to the wild genotype of GG. Analytic methods included X² analysis and pooling according to Mantel-Haenszel. The summary odds ratio was 1.21 (95% CI 0.99 – 1.58). Heterogeneity was moderate (Q = 26, i2 = 36% p = 0.1).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘B’ (size: about 150 cases/control with the at-risk genotypes), ‘B’ (replication: I2 of 36% indicating moderate heterogeneity), and ‘B‘ (bias: large amount of data relating to bias that was not reported). There is, however, the possibility of bias related to sample size.
Large study analysis -- Eight of the individual studies included more than 500 study subjects. The results of the analysis are shown in Figure B.15. The summary OR is 1.10 (95% CI 0.80 to 1.51), p = 0.6. There was moderate heterogeneity (Q = 8.2, I2 = 32%, p = 0.3).
Figure B.15 Summary analysis of the F2 gene and IHD, after restriction to the eight large studies.
Stroke (Ischemic Stroke)
A 2003 meta-analysis43 evaluated the relationship between the F2 G20210A variant and ischemic stroke from 10 published studies. Overall, 1,625 cases and 5,050 controls were included. Four of these studies involved patients of all ages, while the remaining six only included patients diagnosed prior to age 55. The reported summary OR for all studies is 1.30 (95% CI 0.91 to 1.87), p = NS. Heterogeneity was low (Q = 11.5, I2 = 22%, p = 0.2). In order to determine whether the restriction to age at diagnosis was important, we stratified the 10 trials (Figure B.16) by age of diagnosis. The summary OR for the general population was 0.93 (95% CI 0.60 to 1.47), p = 0.7. The summary OR for the six studies with early age of diagnosis was 1.67 (95% CI 1.05 to 2.67), p = 0.02. The test for between group differences was nearly significant (p = 0.08), indicating that the association may be very week in the general population of stroke victims, but much stronger for the less common early stroke (under age 55).
Figure B.16 Reanalysis of F2 versus stroke, stratified by age of stroke diagnosis.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘B’ (size: about 50 cases and 150 controls have the at-risk genotype), ‘B’ (replication: I2 of 22% indicating moderate heterogeneity), and ‘B‘ (bias: large amount of data relating to bias that was not reported). Given the issue of age at diagnosis, we have chosen to report the OR of 0.93 (95% CI 0.60 to 1.47), based on the four general population studies.
Large study analysis -- Only two of the four general population stroke studies had 500 or more subjects, and only one of the six early diagnosis studies were large. No large study analysis was done.
F5 (coagulation factor V)
The F5 gene (aka Factor V, Factor V Leiden, FVL) is located on chromosome 1 (1q23). The polymorphism of interest is G1691A (alleles G and A; ‘A’ is the at-risk allele). This polymorphism is also referred to as the ‘Leiden’ mutation, Arg534Gln, R506Q or rs6025. According to NCBI Entrez Gene, “[t]his gene encodes coagulation factor V which is an essential factor of the blood coagulation cascade. This factor circulates in plasma, and is converted to the active form by the release of the activation peptide by thrombin during coagulation. This generates a heavy chain and a light chain which are held together by calcium ions. The active factor V is a cofactor that participates with activated coagulation factor X to activate prothrombin to thrombin. Defects in this gene result in either an autosomal recessive hemorrhagic diathesis or an autosomal dominant form of thrombophilia, which is known as activated protein C resistance.”
Literature search
A HuGE Navigator (V1.1) search was performed (Factor V[Text+MeSH]>>Meta-analysis[StudyType]>>Cardiovascular disease, unspecified, Coronary heart disease, Coronary Restenosis, Myocardial Infarction, Myocardial ischemia[Mesh]) and 14 articles were identified. Four of these were relevant.43-45,47 We chose to use the most recent43 and included more studies and more study subjects. These data are summarized below.
Genotype frequencies
For the G1691A polymorphism, G represents the wild allele and A represents the presence of the variant. The allele frequency for the ‘A’ variant in a general Caucasian population is only 0.026; the frequency for ‘G’ is then 0.974.46 Because of the very low frequency for the A allele and therefore, for the AA genotype, the homozygous variant (AA) is often combined with the heterozygote (AG) and the evaluation comparisons are reported as AG+AA vs. GG. Under Hardy-Weinberg, the expected genotype frequencies for GG and AG+AA are 90% and 10%, respectively.
Coronary Heart Disease (Myocardial Infarction)
A 2003 meta-analysis43 reported on the association between the F5 polymorphism G1691A and several outcomes. We focused on MI as the outcome of interest. Patient specific data were available for analysis from the original authors. Analytic methods included random effects modeling, but did not perform formal tests for heterogeneity or examine possible publication bias. A total of 20 studies were included for MI, representing 5,313 cases and 14,047 controls. There was no restriction by race noted by the authors. Using the dominant model (AG+AA vs. GG), the summary OR was 1.10, (95% CI 0.88 to 1.36), p = 0.4. The corresponding Forest plot appeared to be symmetric (no obvious publication bias). We reentered the data and performed a formal test of heterogeneity. There was moderate heterogeneity (Q = 29, I2 = 35%, p = 0.06).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘A’ (size: about 1900 with the least common genotype studied - 10% of about 19,000 study subjects with the AG or AA genotypes), ‘B’ (replication: I2 of 35% indicating moderate heterogeneity), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis – There were six studies of 500 or more study subjects (Figure B.17). The summary OR for these large studies was 0.94 (95% CI 0.75 to 1.19), p = 0.6. There was moderate heterogeneity (Q = 7.1, I2 = 30%, p = 0.2).
Figure B.17 Summary analysis of the F5 gene (AG+AA vs. GG) and MI, after restriction to the six large studies included in a published meta-analysis
Stroke (Ischemic Stroke)
A 2004 meta-analysis8 reported on the association between the F5 R506Q (Leiden) polymorphism and ischemic stroke. Overall, 26 individual studies and 4,588 cases and 13,798 controls were included in the analysis. Analytic methods included random effects modeling, formal tests for heterogeneity and examination for possible publication bias. The summary OR for the dominant model (AG+AA vs. GG) was 1.31 (95% CI 1.10 to 1.56), p = 0.001. There was modest heterogeneity (I2 = 35%). The authors identified one report that was responsible for much of the heterogeneity and recomputed the OR to be 1.18 (95% CI 0.98 to 1.42), p = 0.08. The heterogeneity was then considered low (I2=0%).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘B’ (size: about 1,800 with the at-risk genotypes – about 10% of nearly 18,000 cases/controls with a AG or AA genotype), ‘B’ (replication: I2 of 0% after removal of one outlying study), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis -- The summary OR (AG + AA vs. GG) for the six studies having 500 or more combined cases and controls was 1.22, (95% CI 0.69 to 2.16); p = 0.5. There was high heterogeneity (Q=28, I² = 82%, p = >Arterial Sclerosis, Atherosclerosis, Cardiovascular disease, unspecified, coronary artery disease, Coronary heart disease, Myocardial Infarction, Myocardial ischemia, Vascular Diseases[Mesh]) and 21 articles were identified. None were meta-analyses. All but five studies49-53 were excluded. These studies are summarized below.
Genotype frequencies
For the C825T polymorphism in the GNB3 gene, the reported genotype frequencies in 1,332 control non-Hispanic Caucasians from the US were 50%, 41% and 9% for the CC, CT and TT genotype, respectively.53 The at-risk genotype is TT. The corresponding allele frequencies were 0.704 and 0.296 for C and T, respectively. Under Hardy-Weinberg, the expected genotype frequencies would be 8.8%, 41.6%, and 49.6%, respectively. Usually, the comparisons reported are for TT vs. (CT + CC), but often both TT and CT are compared separately against the wild genotype CC.
Coronary Heart Disease (Coronary Artery Disease, Myocardial Infarction, Peripheral Arterial Disease).
Among the five included studies, three studied MI alone50-52, one studied CAD49 and one studied both CAD and PAD.53 All examined the same polymorphism (C825T) and provided raw data so that both heterozygotes (CT) and homozygotes (TT) could separately be compared with the wild genotype of CC. Figures B.19 and B.20 show these comparisons. Overall, there were 2,865 cases and 4,568 controls included. The OR for the heterozygotes was 1.05 (95% CI 0.94 to 1.19), p = 0.4. The heterogeneity was low (Q = 5.7, I2 = 13%), p = 0.3. The corresponding OR for the homozygotes was 1.13 (95% CI 0.95 to 1.35), p = 0.2. The heterogeneity was low (Q = 4.4, I2 = 0%, p = 0.5).
Figure B.19 Analysis of five GNB3 studies of the C825T polymorphism (CT vs. CC) for CHD
Figure B.20 Analysis of five GNB3 studies of the C825T polymorphism (TT vs. CC) for CHD
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘B’ (size: about 273 with TT genotype (7,433 study subjects with 8.8%), ‘A’ (replication: both estimates of heterogeneity >coronary artery disease, Coronary heart disease, Coronary Restenosis, Myocardial Infarction[Mesh]) identified 3 articles. Two of these56,57 were excluded because they only measured intermediate outcomes (restenosis after coronary stenting or artery calcification). The remaining study58, is summarized in the Coronary Heart Disease section below. Searching (GPX1[Text+Mesh]>>Apoplexy[Mesh]) yielded 1 individual study59 which is summarized in the Stroke section below.
Genotype Frequencies
For the ALAn polymorphism, ALA6 represents the at-risk allele and ALA5 or ALA7 represents the wild allele. The allele frequencies in a Northern European population of 146 are 0.54, 0.21 and 0.25 for ALA5 through ALA7, respectively.58 The reported genotype frequencies for ALA6 present and ALA6 absent are 40% and 60%, respectively.58
Coronary Heart Disease (Coronary Artery Disease)
A single paper from 200358 described an association between the GPX1 ALA6 allele being present or absent and CAD. A total of 88 men with CAD and 146 control men were studied. All cases had >50 stenosis of one or more major arteries. The OR for ALA6 allele-carriers vs. non-carriers (ALA6+ vs. ALA6-) was 1.30 (95% CI 0.85 to 2.0), p = 0.2.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results in the three grades of ‘C’ (size: 1Arterial Occlusive Diseases, Arterial Sclerosis, Atherosclerosis, Brain Ischemia, coronary artery disease, Coronary heart disease, Coronary Restenosis, Coronary Stenosis, Myocardial Infarction, Apoplexy, Subarachnoid Hemorrhage[Mesh]) identified 29 articles. Eleven were excluded from analysis because they examined either intermediate or irrelevant outcomes. Two articles were excluded because they were published in a language other than English. One article did not investigate the variant of interest. Two more articles were excluded because the studies were conducted in solely non-Caucasian populations. Of the remaining nine studies, only one was suitable for CHD60 and three were suitable for stroke.61-63 None of the four articles were meta-analyses.
Genotype frequencies
For the C511T polymorphism, C represents the wild allele and T represents the presence of the variant. Allele frequencies were calculated from the 122 genotyped individuals in a general Northern Italian Caucasian population. The allele frequency for the C variant is 0.642; the frequency for T allele is 0.357.60 The reported genotype frequencies from that same report the genotype frequencies for IL1B C511T are CC = 37%, CT = 54% and TT = 9%. Using Hardy-Weinberg, the expected genotype frequencies are 41%, 46% and 13%, respectively.
Coronary Heart Disease (Myocardial Infarction)
Licastro and colleagues60 reported data from Northern Italy. A total of 139 elderly males with MI and randomly selected males in good health (somewhat younger than cases). Patients with MI who were included did not have any associated neoplastic, autoimmune diseases, coagulation disorders or chronic renal failure. The authors did not report an OR, but it could be computed from the raw data. The summary OR for the TT vs. CC comparison is 0.90 (95% CI, 0.38 to 2.2), p = 0.8. The summary OR for the CT vs. CC comparison is 0.65 (95% CI 0.39 to 1.1), p = 0.1. Using the dominant model, the OR is 0.69 (95% CI 0.42 to 1.1), p = 0.1.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘C’ (size: less than 100 in the smallest category), ‘C’ (replication: no other studies), and ‘-‘ (bias: not evaluated because both earlier grades were C. Both OR estimates received this grade.
Large study analysis -- No studies were sufficiently large to perform this analysis.
Stroke (Ischemic Stroke)
Three articles61-63 reported the IL1B C511T polymorphism and risk of ischemic stroke. Overall, 586 cases and 533 controls were examined. Using a random effects model, we were able to pool the results of these three studies (Figures B.21 and B.22). The summary OR for the CT vs. CC comparison is 1.07 (95% CI 0.83 to 1.38), p = 0.6, with little heterogeneity (I² = 0%, p = 0.6). The summary OR for the TT vs. CC comparison is 1.52 (95% CI 0.65 to 3.59), p = 0.3, with high heterogeneity (I² = 75%).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘C’ (size: less than 100 in the smallest category), ‘C’ (replication: no other studies), and ‘-‘ (bias: not evaluated because both earlier grades were C). Both OR estimates receive this score.
Large study analysis -- No studies were sufficiently large to perform this analysis for either comparison.
Figure B.21 Analysis of the three IL1B studies of the C511T polymorphism (CT vs. CC) for Stroke
Figure B.22 Analysis of the three IL1B studies of the C511T polymorphism (TT vs. CC) for Stroke
IL6 (interleukin 6)
The IL6 gene (aka HGF, IL-6, IFNB2) is located on chromosome 7 (7p21). The polymorphism of interest is G174C. According to NCBI Entrez Gene, “IL6 is an immunoregulatory cytokine that activates a cell surface signaling assembly composed of IL6, IL6RA (IL6R; MIM 147880), and the shared signaling receptor gp130 (IL6ST; MIM 600694).”
Literature search
A HuGE Navigator (V1.1) search on the IL6 gene identified 675 articles on 361 disease terms. A search for meta-analyses (IL6 [Text+MeSH]>>Meta-analysis, HuGE Review, Clinical trial[StudyType]) identified 11 such studies; only one of which was relevant to CVD.64 That study is summarized below. A separate search was performed for stroke (IL6[Text+MeSH]>>Atherosclerosis, Intracranial Hemorrhages, Apoplexy, Subarachnoid Hemorrhage[Mesh]). No meta-analyses were identified, but 18 articles were retrieved. Of these articles, 13 were excluded for various reasons. Two only looked at those with a history of stroke, three studied stroke in patient subpopulations (those with type 2 diabetes, pediatric patients, or post operative stroke victims), six measured non-stroke or intermediate outcomes only, and three were conducted exclusively in non-Caucasian populations. The remaining five articles65-69 are described in the stroke section below.
Genotype frequencies
For the G174C polymorphism, G represents the wild allele, while C represents the presence of the variant. The at-risk genotype is CC with a prevalence of 17%. In a general Caucasian population, allele frequencies are 0.59 and 0.41, respectively (based on 5,674 control individuals.64 The observed genotype frequencies were similar to observed (GG = 36%, GC= 47% and CC=17%).
Coronary Heart Disease (CHD and MI)
A 2006 meta-analysis64 identified 7 studies reporting the G174C polymorphism and the risk of CHD and/or MI in European individuals. The authors then included their own data as well. Analytic methods included random effects modeling, formal tests for heterogeneity and identification of possible publication bias. Data from eight studies (6,927 cases and 12,871 controls) were included in the analysis. The summary odds ratio for the model (GC+CC vs. GG) was 1.12 (95% CI 0.97 to 1.29), p = 0.12. There was evidence for heterogeneity (I² = 67%), but much of that was due to one small study60 with a high OR. If this one study were to be removed, the OR is 1.06 (95% CI 0.95 to 1.18), p = 0.3. Heterogeneity is reduced to (Q = 10.7, I2 = 44%, p = 0.1).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘A’ (size: more than 1000 in the smallest genotype category), ‘C’ (replication: I2 of 67%), and ‘-‘ (bias: not evaluated because of an earlier grade of C).
Large study analysis -- When restricted to the six studies with 500 or more cases (Figure B.23), the summary odds ratio was 1.04 (95% CI 0.93 to 1.15), p = 0.5. There was still moderate heterogeneity (I²=41%).
Figure B.23 Summary analysis of the IL6 gene (GC+CC vs. GG) and CAD, after restriction to the six large studies
Stroke (Ischemic Stroke, Aneurysmal Subarachnoid Haemorrhage).
Five studies reported the association between various forms of stroke and the IL6 G174C polymorphism.65-69 One of these studies was a case-only68 and another69 did not give sufficient information to compute an OR, but did state that “no relation was observed for genotype of the IL6 G174G polymorphisms and stroke (data not shown)”. Chamorro and colleagues studied four types of stroke (89 lacunar, 82 large vessel disease, 53 embolic and 49 undetermined cause) in 273 patients and 105 control individuals.65 The OR for CC vs. (CG + GG) was 1.57 (95% CI 0.69 to 3.66), p = 0.2. They also reported that the strongest association was with lacunar stroke with an OR of 3.22 (95% CI 1.1 to 9.1), p = 0.3. This finding has not been confirmed (or refuted) in subsequent studies. Lalouschek and colleagues reported on 404 cases of ischemic stroke or transient ischemic attack and 415 control individuals.66 The OR for CC vs. (CG + GG) was 1.10 (95% CI 0.82 to 1.48), p = 0.5. The group also reported that “the exclusion of patients with transient ischemic attack (N=81) also had no notable effect”. Fontanella and colleagues studied 179 cases (aneurysmal subarachnoid hemorrhage) and 156 controls.67 The OR for CC vs. (CG + GG) was 0.66 (95% CI 0.30 to 1.42), p = 0.2.
For the three studies, 856 cases and 676 control subjects were included (Figure B.24), and the combined OR is 1.07 (95% CI 0.77 to 1.48), p = 0.7. The heterogeneity was low (I² = 11%).
Figure B.24 Summary analysis of the IL6 gene (GC+CC vs. GG) and stroke
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘B’ (size: about 260 in the smallest genotype category: 1,532 * 17%), ‘A’ (replication: ), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis -- Only one study included more than 500 subjects, so no analysis was performed.
ITGB3 (integrin, GP3A)
The ITGB3 gene (aka GP3A, CD61, integrin) is located on chromosome 17 (17q21). The polymorphism of interest is C1565T (aka Leu/Pro). According to NCBI Entrez Gene, “The ITGB3 protein product is the integrin beta chain beta 3. Integrins are integral cell-surface proteins composed of an alpha chain and a beta chain. A given chain may combine with multiple partners resulting in different integrins. Integrin beta 3 is found along with the alpha IIb chain in platelets. Integrins are known to participate in cell adhesion as well as cell-surface mediated signaling.”
Literature search
A HuGE Navigator (V1.1) search on the ITGB3 gene (ITGB3[Text+MeSH]>>Meta-analysis[StudyType]) identified seven meta-analyses. Of these, five were potentially useful.5,45,70-72 We chose to use the review by Morgan and colleagues, as it includes far more publications and study subjects, and applied more refined statistical analyses than the others. The selected meta-analysis is described in more detail below.5
Genotype frequencies
For the C1565T polymorphism, C represents the wild allele, while T represents the presence of the variant. The at-risk genotype is TT. In a meta-analysis based mainly on Caucasians, the allele frequencies in 5,674 controls were 0.85 and 0.15 for the C and T allele, respectively.70 Under Hardy-Weinberg, the expected genotype frequencies would be about 72%, 26% and 2% for the CC, CT and TT genotypes, respectively. Because of the low allele frequency of T, studies usually grouped CT and TT genotype together.
Coronary Heart Disease (Myocardial Infarction)
A 2003 meta-analysis5 identified 30 studies reporting the ITGB3 C1565T polymorphism and the risk of MI in mainly Caucasian individuals. Analytic methods included random effects modeling, formal tests for heterogeneity and identification of possible publication bias. There were 6,173 cases and 6,994 controls included in the analysis. The summary OR for the dominant model (CT+TT vs. CC) was 1.13 (95% CI 1.02 to 1.26) p = 0.2. There was evidence for heterogeneity (Q = 42.9, I² = 42%, p = 0.047). They explored the possibility of publication bias using a funnel plot (p = 0.04 for the existence of bias).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘A’ (size: over 3,000 in the smallest genotype category: 13,000 * 28%), ‘B’ (replication: I2 value of 42%), and ‘C‘ (bias: significant evidence of publication bias).
Large study analysis -- When restricted to the eight studies with 500 or more cases (Figure B.25), the summary odds ratio was 1.08 (95% CI 0.97 to 1.21), p = 0.2. There was low heterogeneity (Q = 8.5, I² = 18%, p = 0.3).
Figure B.25 Summary analysis of the ITGB3 gene and the C1565T polymorphism (CT+TT vs. CC) and MI, after restriction to the eight large studies
Stroke (Cerebral Vascular Accident)
A 2001 meta-analysis45 provided information about the ITGB3 C1565T polymorphism and the risk of stroke in mainly Caucasian individuals. They identified three studies that reported information on 479 cases and 1,376 controls. Analytic methods did not include any of the standard methodology (random effects modeling, formal tests for heterogeneity and identification of possible publication bias). The summary OR for the dominant model (CT+TT vs. CC) was 0.80 (95% CI 0.62 to 1.04). Unfortunately, the summary OR is smaller than that reported by any of the three individual studies bringing this result into question.
We retrieved the three original articles73-75 and reanalyzed the data (Figure B.26). We found the overall OR for the (CT+TT vs. CC) comparison to be 0.99 (95% CI 0.74 to 1.34), p = 0.9. There was low heterogeneity (Q = 0.4, I2 = 0%, p = 0.8).
Figure B.26 Our re-analysis of the data from a 2001 meta-analysis of stroke and ITGB3 gene (CT+TT vs. CC) and stroke
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘B’ (size: 500 in the smallest genotype category: about 1,800 * 28%), ‘A’ (replication: I2 value of 42%), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis -- Only one study included more than 500 subjects, so no analysis was performed.
LPL (lipoprotein lipase)
The LPL gene (aka KID, HDLCQ11) is located on chromosome 8 (8p22). The most common polymorphisms are S447X, Ans291Ser and PvuII. According to NCBI Entrez Gene, “LPL encodes lipoprotein lipase, which is expressed in heart, muscle, and adipose tissue. LPL functions as a homodimer, and has the dual functions of triglyceride hydrolase and ligand/bridging factor for receptor-mediated lipoprotein uptake. Severe mutations that cause LPL deficiency result in type I hyperlipoproteinemia, while less extreme mutations in LPL are linked to many disorders of lipoprotein metabolism.”
Literature search
A HuGE Navigator (V1.1) search on the LPL gene identified 207 articles on 77 disease terms. A search for meta-analyses (LPL[Text+MeSH]>>Meta-analysis, Clinical Trial[StudyType]) identified four such studies; all were relevant to CVD.76-79 For the S447X polymorphism, we also included one additional study80 found in one of the reference lists. Results from these studies are summarized below. A separate search (v1.3) was performed for stroke (LPL[Text+MeSH]>> Brain Ischemia, Cerebral Infarction, Apoplexy, Transient Ischemic Attack, Apoplexy[Mesh]). No meta-analyses were identified, but 11 articles were retrieved. Of these, nine were removed from consideration because of language, exclusively non-Caucasian population or studied an intermediate outcome. The two included studies39,53 are examined below.
Genotype frequencies
• S447X: S represents the wild allele, while X represents the presence of the variant. The at-risk ‘protective’ genotype (SX + XX) is found in 19% of the Caucasian population. Allele frequencies are 0.9 and 0.1, respectively (based on about 8,000 control individuals.79 The expected genotype frequencies were 81%, 18% and 1%, respectively.
• Ans291Ser: A represents the wild allele, while S represents the presence of the variant. The at-risk genotype (AS + SS) is found in 5% of the Caucasian population. Allele frequencies are 0.975 and 0.025, respectively.80 The expected genotype frequencies were 95%, 5% and < 0.1%, respectively.
• PvuII: P- represents the wild allele and P+ represents the presence of the variant. The at-risk genotype (P+/P+) with an 18% prevalence. In a general Caucasian population, allele frequencies are 0.58 and 0.42, respectively (based on 800 control individuals.76 The expected genotype frequencies were 35%, 47% and 18%, respectively.
Coronary Heart Disease (Ischemic Heart Disease - IHD)
• S447X: The 2002 meta-analysis79 reported S447X and the risk of IHD from six studies in men and two studies in women.
o Data in the six studies of men (unknown model) showed an overall OR of 0.82 (95% CI 0.71 to 0.95), p = 0.01. Heterogeneity was low (I² = 0%). Overall 2,509 cases and 7,007 controls were included in the analysis. Using the dominant model, the OR is 0.85 (95% CI 0.74 to 0.98), p=0.025. Heterogeneity was low (I2=0%).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘A’ (size: about 1800 in the smallest genotype category: 9,516 * 19%), ‘A’ (replication: I2 of 0%), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis – Three studies included 500 or more subjects (cases and controls). The revised OR using these large studies was 0.86 (95% CI 0.73 to 1.0), p = 0.06. There was limited heterogeneity (I² = 0%). Figure B.27 shows this analysis.
Figure B.27 Summary analysis of the LPL gene (SX+XX vs. SS) and IHD, after restriction to the three large studies
o Data in two studies of women (413 cases and 6,101 controls) showed an overall OR of 0.97 (95% CI 0.68 to 1.38), p = 0.9.79 Heterogeneity was low (I² = 0%).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘B’ (size: about 140 in the smallest genotype category: 413*2 NB: used twice the number of cases as the Venice criteria assume an approximate 1:1 case/control ratio), ‘A’ (replication: I2 of 0%), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis -- Only two studies, so no analysis was performed.
• Ans291Ser: The 2006 meta-analysis77 published on an unknown number of studies reporting the relationship between the Ans291Ser polymorphism and CHD. A total of 1,203 carriers and 6,192 non-carriers were included. Using a random effects model the summary OR for the AS+SS vs AA comparison was 1.48 (95% CI 1.09 to 2.00), p = 0.01. There was significant unexplained heterogeneity (χ2 = 13.8, p = 0.003). It was not possible to verify or reanalyze this data as only this summary information was provided. By examining the reference list, we estimated that the author included eight studies. This would result in an I2 value of 49%.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘C’ (size: about 60 in the smallest genotype category: 1,203*2 NB: used twice the number of cases as the Venice criteria assume an approximate 1:1 case/control ratio), ‘B’ (replication: I2 estimated to be 49%), and ‘-‘ (bias: not evaluated because of an earlier grade of C).
Large study analysis – Without raw data, the analysis could not be performed.
• PvuII: A 2007 meta-analysis76 examined the polymorphism for CAD in seven published studies (six in Caucasians). Only four studies provided sufficient information to compare PvuII genotype and CAD. No formal analysis was performed and no summary statistic was reported. We analyzed the data from these four studies1,092 cases and 800 controls and found the OR for heterozygotes vs. the wild genotype (P+/P- vs. P-/P-) was 1.17 (95% CI 0.94 to 1.46), p = 0.2 (Figure B.28). Heterogeneity was low (Q = 3.1, I² = 4%, p = 0.4). The corresponding OR for homozygous vs. wild (P-/P- vs. P+/P+) is 0.93 (95% CI 0.60 to 1.46), p = 0.8 (Figure B.29). Heterogeneity was high (Q=6.1, I² = 51%, p = 0.1).
Figure B.28 Analysis of four LPL studies of the Pvull polymorphism (P+/P- vs. P-/P-) for CAD
Figure B.29 Analysis of four LPL studies of the Pvull polymorphism (P+/P+ vs. P-/P-) for CAD
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘B’ (size: about 340 in the smallest genotype category of P+/P+: 18% of about 1900 subjects), ‘C’ (replication: I2 estimated to be 51% and 4%), and ‘-‘ (bias: not evaluated because of an earlier grade of C).
Large study analysis – Only two of these studies81,82 have 500 or more study subjects, so no analysis could be performed.
Stroke (Incident Ischemic Stroke)
Two studies were relevant.39,53 One study from the US53 reported on the LPL S447X polymorphism in stroke patients (incident ischemic stroke confirmed by hospitalizations, hospital records and death records for cerebrovascular events – subclinical stroke was defined by MRI). We restricted the analysis to incident ischemic stroke (removing the subclinical stroke patients). There were 113 male cases and 540 controls; 100 females cases and 397 controls. The population was racially diverse and ranged in age from 45 to 64. They reported ORs separately for men and women. Among males, the corresponding crude OR was 0.69. Among females, the crude OR for the (SX + XX) vs. SS comparison was 1.58. After adjusting for age and race, the estimates changed dramatically. The adjusted rates were 1.94 and 0.95 for males and females, respectively. We chose to use these latter rates. The second study39 reported on a cohort of Greek stroke patients aged 65 – 92 years; control group was age and sex matched. The population was approximately half male and half female. The results were not separated by gender.
Figure B.30 shows the summary analysis for these two studies with a total of 311 cases and 1,030 controls. Overall, the OR is 1.33 (95% CI 0.88 to 2.02), p = 0.2. There was low heterogeneity (Q = 2.2, I² = 11%, p = 0.3).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘B’ (size: about 120 in the smallest genotype category: 311*2 * 20%), ‘B’ (replication: I2 estimated to be 11%), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis -- Only one study had more than 500 subjects, so no analysis could be performed.
Figure B.30 Analysis of two LPL studies of the S447X polymorphism (SX+XX vs. SS) for stroke
MTHFR (5,10-methylenetetrahydrofolate reductase)
The MTHFR gene is located on chromosome 1 (1p36.3). According to Entrez Gene, “Methylenetetrahydrofolate reductase (EC 1.5.1.20) catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine.”
Literature search
A HuGE Navigator (V1.1) search on the MTHFR gene identified 1,363 articles on 376 disease terms. Sixty-five meta-analyses or HuGE Reviews were identified. Among these articles, the search (MTHFR[Text+MeSH]>>Meta-analysis, HuGE Review[StudyType]>>Arterial Sclerosis, Brain Ischemia, Cardiovascular disease, unspecified, Apoplexy, coronary artery disease, Coronary heart disease, Myocardial Infarction, Peripheral Vascular Diseases[Mesh]) identified 12 meta-analyses/HuGE Reviews. We chose to use original meta-analyses that were most recent and most methodologically advanced.
Genotype frequency
For the C677T polymorphism, C represents the wild allele while T represents the presence of the variant. The at-risk genotype (TT) has a 12.2% prevalence in North American Caucasians.83 In a general Caucasian population, this translates in approximate allele frequencies of 0.65 and 0.35, respectively (based on more than 2,500 control individuals.83 The expected genotype frequencies for CC, CT and TT are about 42%, 45% and 12%, respectively.
Coronary Heart Disease (Cardiovascular Disease, Ischemic Heart Disease, Coronary, Heart Disease, Myocardial Infarction and Angina)
Lewis and colleagues is the most recent meta-analysis in which they explored the association between the MTHFR C677T polymorphism and CHD (using the search terms listed above).84 Analytic methods included random effects modeling, adjusting for confounding variables, formal tests for heterogeneity and identification of possible publication bias. Overall, 80 studies were included in the analysis with 26,000 cases and 31,183 controls. With all studies included, the summary OR for the TT vs. CC genotypes was 1.14 (95% CI 1.05 to 1.24), p = 0.01. There was moderate heterogeneity (I² = 38%) with much of the variability explained by geographical region (Europe, Australia and North America showing smaller effects than the Middle East and Asia).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analyses, results in the three grades of ‘A’ (size: over 1000 in the smallest genotype category: over 50,000*12%), ‘B’ (replication: I2 estimated to be 38%), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis -- When restricted to the 12 European studies (mainly Caucasians) having 500 or more cases (Figure B.31), the summary OR for the TT vs. CC comparison was 1.03 (95% CI 0.94 to 1.13), p = NS. There was low heterogeneity (Q = 6.4, I2 = 0%, p = 0.8). Fewer large studies were available from the US, but the summary OR for three large studies85-87 with >500 cases) was 1.07, (95% CI 0.71 to 1.24), p = 0.6, consistent with the larger experience in Europe (data not shown).
Figure B.31 Summary analysis of the MTHFR gene (TT vs. CC) and CHD, after restriction to the 12 large studies
The meta-analysis by Lewis and colleagues84 did not contain data for the heterozygote comparison (CT vs. CC genotypes) with CHD. However, an earlier 2002 meta-analysis did.83 Among 11,162 cases and 12,758 controls, the OR for this comparison was 1.04 (95% CI 0.98 to 1.10). p = NS. There was significant heterogeneity (I² = 60%). We applied the Venice criteria to the data and assigned ‘A’ for size (more than 1000 subjects with least common genotype), ‘C’ for replication (I2 >50%), and ‘-‘ for bias (previous grade of C).
Large study analysis - Insufficient data were available to conduct a large study analysis.
Stroke (Ischemic Stroke)
A meta-analysis88 included all published studies (1996 to 2004) using the terms “cerebrovascular accident and cerebrovascular disorders” and limited studies to those with “a clinical syndrome consistent with recent ischemic stroke (TIA excluded), with neuroimaging confirmation”. A total of 31 studies were included with 6,110 cases and 8,760 controls. Analytic methods included random effects modeling, formal tests for heterogeneity and identification of possible publication bias. Twelve of these studies were in Asians and one in Blacks; these were removed and the remaining 19 studies reanalyzed by us. There were 3,527 cases and 4,141 controls remaining. The summary OR for the CT vs. CC comparison was 1.03 (95% CI 0.89 to 1.18), p = 0.7. Figure B.32 shows the results ordered by study size, from small to large. Moderate between study heterogeneity was identified (Q = 31, I2 = 41%, p = 0.03).
Figure B.32 Re-analysis of 19 MTHFR studies of the C677T polymorphism (CT vs. CC) for stroke
The corresponding summary OR for the TT vs. CC comparison (Figure B.33) was 1.19 (95% CI 0.96 to 1.48), p = 0.11. There was moderate heterogeneity (Q = 29, I2 = 38%, p = 0.045).
[pic]
Figure B.33 Our re-analysis of 19 MTHFR studies of the C677T polymorphism (TT vs. CC) for stroke
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the MTHFR C677T polymorphism and stroke results in three grades: ‘B’ (size: approximately 423 cases with a TT genotype (3,527 cases * 12% TT), ‘C’ (replication: I2 of 50% or higher for both models, indicating considerable heterogeneity), and ‘-‘ (bias: not evaluated due to an earlier grade of C).
Large study analysis -- Four studies performed in a Caucasian population reported at least 500 participants.48,89-91 The summary OR for the CT vs. CC comparison was 1.15 (95% CI 0.99 to 1.33), p = 0.07. There was low heterogeneity (Q = 0.2, I² = 0%, p = 0.9). For the TT vs. CC comparison, the OR was 1.24 (95% CI 0.98 to 1.57), p = 0.08. There was low heterogeneity (Q = 3.6, I² = 17%, p = 0.3). The corresponding data are shown in Figures B.34 and B.35.
Figure B.34 Summary analysis of the MTHFR gene (CT vs. CC ) and stroke, after restriction to the four large studies.
Figure B.35 Summary analysis of the MTHFR gene (TT vs. CC ) and stroke, after restriction to the four large studies.
MTR (5-methyltetrahydrofolate-homocysteine methyltransferase)
The MTR gene (aka MS – methionine synthase) is located on chromosome 1 (1q43). According to Entrez Gene, “MTR encodes the enzyme 5-methyltetrahydrofolate-homocysteine methyltransferase. This enzyme, also known as cobalamin-dependent methionine synthase, catalyzes the final step in methionine biosynthesis. Mutations in MTR have been identified as the underlying cause of methylcobalamin deficiency complementation group G.”
Literature search
A HuGE Navigator (V1.1) search on the MTR gene identified 124 articles on 83 disease terms. Five meta-analyses or HuGE Reviews were identified; none were relevant to CVD. The search (MTR[Text+MeSH]>>Cardiovascular disease, unspecified, Apoplexy, Cerebrovascular Disorders, coronary artery disease, Coronary heart disease, Ischemia, Myocardial Infarction, Myocardial ischemia[Mesh]) identified nine studies. Of these, five contained sufficient data for either CHD or stroke. One of these studies92 was removed because controls were patients undergoing clinically indicated angiography that had negative findings. The remaining three studies are summarized below.
Genotype frequencies
The polymorphism of interest in the MTR gene is A2756G, where A is the wild allele and G is the at-risk allele. The at-risk genotype is GG with a frequency of about 3%. The allele frequencies for A and G are 0.84 and 0.16, respectively (based on 361 control individuals.93,94 The expected genotype frequencies of AA, AG and GG would be about 71%, 26% and 3%, respectively.
Coronary Heart Disease (Myocardial Infarction-MI, Coronary Heart Disease – CHD, Coronary Artery Disease - CAD)
One study95 studied the A2756G polymorphism in a Caucasian population of 381 cases (confirmed MI) and 767 control individuals. The OR for the AG vs. AA comparison (without adjustments) was 1.03 (95% CI 0.78 to 1.35), p = 0.8. The OR for the GG vs. AA comparison (with adjustments) was 0.56 (95% CI 0.23 to 1.31), p = 0.1. The authors adjusted these ORs for age and smoking status as well as for age, smoking status, MTHFR genotype, diabetes, angina, hypertension, BMI, aspirin use, alcohol intake and family history (adjusted OR 0.97 and 0.51). None of the adjusted ORs were statistically significant. Another study96 studied 123 individuals with CHD (patients undergoing angiography with at least 90% occlusion in one major coronary vessel and at least 40% occlusion in another major coronary vessel) and 540 control individuals. The OR for the AG vs. AA comparison (without adjustments) was 1.01 (95% CI 0.65 to 1.58), p = NS. The OR for the GG vs. AA comparison (with adjustments) was 3.48 (95% CI 1.48 to 8.54), p 50% occlusion in at least one major coronary or peripheral vessel) and 248 age and sex matched control individuals. We estimated the numbers of cases and controls with each genotype under Hardy-Weinberg in order to combine this information with the other two studies (365, 150 and 15 in cases and 171, 70 and 7 in controls for AA, AG and GG genotype, respectively). A fourth study94 also reported no association between MTR genotype and CAD in 140 patients (before age 55, at least one episode of MI, angina pectoris and/or coronary artery bypass surgery) and 113 control individuals matched for age, sex and geographic area. The allele frequencies were again provided and we estimated the genotypes (101, 36, 3 in cases and 82, 29 and 3 in controls).
We combined results from these four studies using a random effects model (Figures B.36 and B.37). Overall, there were 1,175 cases and 1,668 controls. The OR for the AG to AA comparison was 1.02 (95% CI 0.85 to 1.22) p = 0.8. There was low heterogeneity (Q = 1.9, I2 = 0%, p = 0.7). The OR for the GG to AA comparison was 1.25 (95% CI 0.52 to 3.0), p = 0.6. There was low heterogeneity (Q = 4.5, I2 = 10%, p = 0.3).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the MTR A2756G polymorphism and CHD results in three grades: ‘C’ (size: approximately 23 cases with a TT genotype (1,176 cases * 3% TT), ‘A’ (replication: I2 of 10% or lower for both models, indicating considerable heterogeneity), and ‘-‘ (bias: not evaluated due to an earlier grade of C).
Large study Analysis – Because three of these four studies already included 500 or more subjects, there would have been little difference between the large study analysis and the summary analysis shown in Figure B.36 and B.37.
Figure B.36 Analysis of four MTR studies of the A2745G polymorphism (AG vs. AA) for CAD
Figure B.37 Analysis of four MTR studies of the A2745G polymorphism (GG vs. AA) for CAD
Stroke (Ischemic Cerebral Vascular Disease)
One study97 examined 131 cases (with cortical lesions documented by CAT scan or MRI) and 121 control individuals. All were European Caucasians (Sicily). The OR for the AG to AA comparison is 1.18 (95% CI 0.67 to 2.07), p = 0.5. The corresponding OR for the GG to AA comparison is 4.00 (95% CI 0.41 to 96), p = 0.2. Only one homozygote control and four cases were included in the study, leading to the wide confidence interval. No other studies were identified. Based on this single study, we conclude there is low confidence in a non-significant relationship between stroke and the MTR A2756G polymorphism. There is not enough evidence to report a summary measure.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the MTR A2756G polymorphism and stroke results in three grades: ‘C’ (size: fewer than 100 with a TT genotype, ‘C’ (replication: single study), and ‘-‘ (bias: not evaluated due to an earlier grade of C).
Large study analysis – Not performed as no studies had 500 or more study subjects.
MTRR (5-methyltetrahydrofolate-homocysteine methyltransferase reductase)
The MTRR gene (aka MSR - methionine synthase reductase) is located on chromosome 5 (5p15.3-p15.2). The most common polymorphism studied is A66G. According to Entrez Gene, “[m]ethionine is an essential amino acid required for protein synthesis and one-carbon metabolism. Its synthesis is catalyzed by the enzyme methionine synthase. Methionine synthase eventually becomes inactive due to the oxidation of its cob(I)alamin cofactor. The protein encoded by this gene regenerates a functional methionine synthase via reductive methylation. It is a member of the ferredoxin-NADP(+) reductase (FNR) family of electron transferases. Patients of the cbl-E complementation group of disorders of folate/cobalamin metabolism are defective in reductive activation of methionine synthase. Alternative splicing of this gene results in multiple transcript variants encoding distinct isoforms.”
Literature search
A HuGE Navigator (V1.1) search on the MTRR gene identified 97 articles on 66 disease terms. Four meta-analyses were identified; none were relevant. The search (MTRR[Text+MeSH]>>Cardiovascular disease, unspecified, Cerebrovascular Disorders, coronary artery disease, Coronary heart disease, Myocardial ischemia[Mesh]) identified seven studies. Three of these seven were excluded because one reported on pediatric stroke, another on DNA damage and a third was conducted in a patient sub-population. One of these studies92 was removed because controls were patients undergoing clinically indicated angiography that had negative findings. The remaining three studies provided sufficient information for analysis; three for CAD and one for stroke. These are summarized below.
Genotype frequency
For the A66G polymorphism, A represents the wild allele while G represents the presence of the variant. The at-risk genotype (GG) with a prevalence of 22%. In a general Caucasian population, allele frequencies are 0.53 and 0.47, respectively (based on about 234 control individuals.94,97 The expected genotype frequencies were 28%, 50% and 22%, respectively.
Coronary Heart Disease (Coronary Artery Disease – CAD, Cardiovascular Disease – CVD)
Three articles93,94,98 provided information about MTRR genotype and CAD risk (usually defined as one or more major arteries with 50% or more occlusion). The studies included a total of 1,052 cases and 483 controls. Two of the studies93,94 provided only allele frequencies and we estimated genotype frequencies under the assumption of Hardy-Weinberg (both studies reported agreement with HWE). We combined all three studies together in a random effects model (Figure B.38) and found a summary OR of 1.06 (95% CI 0.53 to 2.13), p = 0.9. Heterogeneity was high (Q = 12, I² = 83%, p 50%), and ‘-‘ (bias: not evaluated due to an earlier grade of C).
Large study analysis – Only two studies had 500 or more subjects98 so no analysis is possible.
Stroke (Ischemic Cerebrovascular Disease - ICVD)
One article97 reported on 131 Italians (Sicily) with ischemic stroke and corticoid lesions documented by imaging at least one year earlier. Controls consisted of 121 individuals with a normal clinical report (exclusion criteria also included any family history of hypertension, CVD, diabetes or cerebral occlusions). The A66G polymorphism was measured in all. The OR (AG+GG v AA) was 0.79 (95% CI 0.45 to 1.40), p = NS.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the MTRR A66G polymorphism and stroke results in three grades: ‘C’ (size: fewer than 100 subjects with an AA genotype), ‘C’ (replication: single study), and ‘-‘ (bias: not evaluated due to an earlier grade of C).
Large study analysis – Not performed as there was only one large study.
NOS3 (nitric oxide synthase 3 (endothelial cell))
The NOS3 gene (aka eNOS; ECNOS; NOS III) is located on chromosome 7 (7q36). The most common polymorphisms are G894T (aka Gly298Asp), intron4, T786C. According to Entrez Gene, “Nitric oxide is a reactive free radical which acts as a biologic mediator in several processes, including neurotransmission and antimicrobial and antitumoral activities. Nitric oxide is synthesized from L-arginine by nitric oxide synthases. Variations in this gene are associated with susceptibility to coronary spasm. Multiple transcript variants encoding different isoforms have been found for this gene.”
Literature search
A HuGE Navigator (V1.1) search on the NOS gene identified 1359 articles on 455 disease terms. A search for meta-analyses (NOS[Text+MeSH]>>Meta-analysis, HuGE Review, Clinical trial[StudyType]) identified 11 such studies. The most important one99 is summarized below.
Genotype frequencies
• G894T (or Glu298Asp) G represents the wild allele, while T represents the presence of the at-risk polymorphism. The at-risk genotype is TT with a 25% prevalence. In a general Caucasian population, allele frequencies are 0.50 and 0.50, respectively (based on over 13,042 controls individuals.99 Under Hardy-Weinberg, the three genotypes separately would be approximately 25%, 50% and 25%, respectively.
• Intron4 B (4B) represents the wild allele, while A represents the presence of the at-risk polymorphism. The at-risk genotype is AA with a 2% prevalence. In a general Caucasian population, allele frequencies are 0.86 and 0.14, respectively (based on 3,222 control individuals).100 Under Hardy-Weinberg, the three genotypes separately would be approximately 74%, 24% and 2%, respectively.
• T786C C represents the wild allele, while T represents the presence of the at-risk polymorphism. The at-risk genotype is TT with a 18% prevalence. In a general Caucasian population, allele frequencies are 0.58 and 0.42, respectively (based on 13,562 control individuals.99 Under Hardy-Weinberg, the three genotypes separately would be approximately 33%, 49% and 18%, respectively.
Coronary Heart Disease
The 2006 meta-analysis99 summarized the published literature in Caucasians for the association between CHD and the three NOS3 polymorphisms referred to above. Analytic methods included random effects modeling, formal tests for heterogeneity and identification of possible publication bias.
• G894T Overall, 40 studies were included in the analysis with 13,876 cases and 13,042 controls were included in the analysis. The OR for an allele model was 1.17 (95% CI 1.07 to 1.28), p = 0.001. There was significant heterogeneity (I2=68%, p >Cerebral Infarction, Apoplexy, Apoplexy[Mesh] identified 14 studies. Of these, eight were excluded because they were conducted in patient subpopulations, their outcome of interest was an intermediate outcome or there were no Caucasians in the study population. The remaining 6 studies contained sufficient data for stroke and one or both of the polymorphisms of interest. These are also summarized below.
Genotype frequency
• Q192R polymorphism - Q represents the wild allele and R represents the presence of the variant. In a general Caucasian population, the expected genotype frequencies are 47%, 42% and 11% for the QQ, QR and RR genotypes, respectively.
• L55M polymorphism - L represents the wild allele and M represents the presence of the variant. In a general Caucasian population, the expected genotype frequencies are 50%, 40% and 10% for the LL, LM and MM genotypes, respectively.
Coronary Heart Disease (Myocardial Infarction)
• The Wheeler 2004 meta-analysis107 included 19 studies that evaluated the association between the Q192R polymorphism and MI. A total of 5,723 cases and 8,063 controls were included. Using a random effects model, the OR reported for the QR vs. QQ comparison was 1.32 (95%CI 1.04 – 1.67), p = 0.03. Heterogeneity was high (I² = 85%). The OR for the RR vs. QQ comparison was 1.38 (95% CI 1.04 to 1.80), p = 0.02. Heterogeneity was again high (I²=71%).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the PON1 Q192R polymorphism and MI results in three grades: ‘A’ (size: over 1,000 subjects with the RR genotype - 11% of nearly 14,000 subjects), ‘C’ (replication: high heterogeneity with I2 >50% in the both comparisons), and ‘-‘ (bias: not evaluated due to an earlier grade of C).
Large study analysis – When restricted to the six large studies these estimates from publication bias (as was also done in the original analysis107 to avoid possible publication bias), the OR for QR vs. QQ became 1.52 (95%CI 1.08-2.15), p = 0.02. The heterogeneity was still high (I² = 91%). The OR for RR vs. QQ comparison became 1.58 (95%CI 1.07-2.33), p = 0.02. The heterogeneity was still high (I² = 81%).
• The same 2004 meta-analysis107 included 9 studies that evaluated the association between the L55M polymorphism and myocardial infarction (only eight studies reported on the MM vs. LL comparison). A total of 3,189 cases and 3,650 controls were included. Using a random effects model, the OR reported for the LM vs. LL comparison was 0.99 (95%CI 0.86 to1.15), p = 0.9. Heterogeneity was moderate (I² = 33%). The OR reported for the MM vs. LL comparison was 0.99 (95% CI 0.83 to 1.19), p = 0.9. There was low heterogeneity (Q = 6.4, I² = 0%, p = 0.5).
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the PON1 L55M polymorphism and MI results in three grades: ‘B’ (size: about 700 subjects with the MM genotype - 10% of nearly 7,000 subjects), ‘B’ (replication: moderate heterogeneity with I2 = 33% in the heterozygous comparison), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis – When restricted to the five large studies, the OR for the LM vs. LL comparison became 0.95 (95%CI 0.84 -1.08), p = 0.5. Heterogeneity was low (I² = 0%). The OR for the MM vs. LL comparison became 0.95 (95%CI 0.76 – 1.17), p = 0.7. The heterogeneity was low (I² = 0%).
Stroke (Small vessel disease, large vessel disease, cardio-embolic stroke, cerebrovascular disease, ischemic stroke, arterial ischemic stroke)
• Q192R Six articles108-113 reported the Q192R polymorphism and risk of stroke. Overall, 1,300 cases and 1,468 controls were examined. One study110 took place in a Polish population and reported three effect measures, each evaluating a different type of stroke; small vessel disease, large vessel disease and cardioembolic stroke. Topic et al.111 reported on 56 Croatian stroke patients and 124 healthy volunteers. Can Demirdöğen’s study population comprised 108 unrelated, Caucasian patients with acute ischemic stroke from Anatolia, Turkey.112 A total of 78 controls were selected from the same geographic region and were described as “symptom-free”. Another study, Schiavon108, enrolled 126 survivors that had been referred to the stroke unit of Legnago Hospital in Legnago, Italy. 92 volunteer controls were matched for sex and age and had no history of stroke or other cardiovascular conditions. In the UK, 397 Caucasian ischaemic stroke patients and 405 controls were evaluated by Pasdar.109 In the final study, Aydin et al.113, 65 patients with acute ischemic cerebrovascular disease from a research hospital in Istanbul, Turkey were evaluated along with 84 healthy volunteers with no history of stroke as the control group.
Using a random effects model, we pooled the results of these six studies (Figure B.43) and found that the summary OR for the QR vs. QQ comparison was 1.00 (95% CI 0.80 to 1.24), p=0.9. There was moderate heterogeneity (Q=11.4, I² = 39%, p = 0.1). The summary OR for the RR vs. QQ comparison (Figure B.44) was 1.35 (95% CI 1.01 to 1.81), p = 0.04) with very little heterogeneity (I² = 3%).
Figure B.43 Analysis of six PON1 studies of the Q192R polymorphism (QR vs. QQ) for stroke
Figure B.44 Analysis of six PON1 studies of the Q192R polymorphism (RR vs. QQ) for stroke
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the PON1 Q192 polymorphism and stroke and results in three grades: ‘B’ (size: about 300 subjects with the MM genotype - 11% of nearly 3000 subjects), ‘B’ (replication: moderate heterogeneity with I2 = 39% in the heterozygous comparison), and ‘B‘ (bias: large amount of data relating to bias that was not reported).
Large study analysis – Only one study included more than 500 study subjects so no analysis was possible.
• L55M All but one of these studies111 also reported results for the L55M polymorphism and stroke. A total of 1,244 cases and 1,341 controls were included in the analysis. Using a random effects model, we pooled the results of these studies to obtain a summary OR for the LM vs. LL comparison (Figure B.45) of 1.04 (95% CI 0.88 to 1.23), p = 0.6. There was low heterogeneity (Q = 4.6, I² = 0%, p = 0.6). The summary OR for the MM vs. LL comparison (Figure B.46) was 0.92 (95% CI .72 to 1.19), p = 0.52. There was low heterogeneity (Q = 3.8, I2 = 0%, p = 0.7).
Figure B.45 Analysis of five PON1 studies of the L55M polymorphism (LM vs. LL) for stroke
Figure B.46 Analysis of five PON1 studies of the L55M polymorphism (MM vs. LL) for stroke
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the PON1 L55M polymorphism and stroke and results in three grades: ‘B’ (size: about 250 subjects with the MM genotype - 10% of about 2,500 subjects), ‘A’ (replication: low heterogeneity with I2 >Acute Coronary Syndrome, Arterial Sclerosis, Atherosclerosis, Brain Ischemia, Cardiovascular disease, unspecified, Apoplexy, Cerebrovascular Disorders, coronary artery disease, Coronary heart disease, Ischemia, Myocardial Infarction, Apoplexy[Mesh]) resulted in 29 articles being identified; none were meta-analyses or HuGE reviews. Eight appeared relevant after reviewing the title and abstract and three contained sufficient data relating SELE genotypes and CVD outcomes.114-116 None of these articles studied a European Caucasian population, but are summarized below.
Genotype frequencies
For the S128R polymorphisms, S is the wild allele and R is the at-risk allele. In a European Caucasian population of 244 control adults117, the S128A genotype frequencies were 81.1%, 18.4% and 0.4% for the SS, SR and RR genotypes, respectively. The corresponding allele frequencies for S and R are 0,904 and 0.096, respectively. Interestingly, the S allele frequency is even higher in South Asians (0.92) and those of African origin (0.96). Due to the low frequency of the RR genotype, SR and RR are usually combined together.
Coronary Heart Disease (Myocardial Infarction, Coronary Artery Disease)
The study by Yoshida114 was performed in a Japanese population of 135 patients with MI and 327 control subjects. The study by Abu-Amero116 was performed in an Arabic population of 1,112 patients with angiographically determined CAD (>70% narrowing or at least one vessel) along with 427 controls. However, this study appeared to be performed in a diabetes setting, as 67% of controls and 92% of cases were diabetic. In both of these studies, about two-thirds of cases and controls were males. In the study by Leshinsky-Silver115, the 1,000 patients with CVD (part of the BIP – bezafibrate infarction prevention study) were Israeli, and the 1,480 controls were French, from the Stanislas cohort. An argument can be made that none of these studies are appropriate for use. However, in order to provide some estimate of the effect and of the reliability of existing data, we chose to combine these three studies using a random effects model. The summary OR for the (SR+RR vs. SS) comparison (Figure B.47) was 1.51 (95% CI 1.21 to 1.90), p Atherosclerosis, Cardiovascular disease, unspecified[Mesh]) identified four studies. Of these, only one provided CHD or stroke related outcomes.118
Genotype frequency
For the C47T polymorphism, C represents the wild allele while T represents the presence of the variant. The at-risk genotype (TT) has a prevalence of 23%. In a general Caucasian population, allele frequencies are 0.52 and 0.48, respectively (based on about 5,773 control individuals.118 Under Hardy-Weinberg, the expected genotype frequencies are 27%, 50% and 23% for CC, CT and TT, respectively.
Cardiovascular Disease
The 2006 Genkinger article118 studied ‘deaths due to CVD’ in Maryland (racial distribution not provided). The population was followed-up for 15 years and cause of death identified. Among the 6,151 individuals studied (2/3 women) a total of 378 deaths due to CVD were observed. Existing sample banks were used to obtain SOD2 genotypes. The OR for the heterozygote comparison (CC vs. CT) was 1.04 (95% CI 0.82 to 1.33), p = NS. The OR for the homozygote comparison (CC vs. TT) was 0.86 (95% CI 0.64 to1.16), p = NS.
The application of the Venice criteria6 for evaluating the credibility of genetic association meta-analysis results for the SOD2 C47T polymorphism and CVD results in three grades: ‘B’ (size: about 190 have the TT genotype NB: used 2 * cases as Venice assumes controls are about equal to cases), ‘C’ (replication: single study), and ‘-‘ (bias: not evaluated due to an earlier grade of C).
Large study analysis -- There were too few large studies for analysis.
Stroke
No studies were identified for stroke and SOD2 polymorphisms.
SOD3 (superoxide dismutase 3)
The SOD3 gene is located on chromosome 4 (4p15.3-p15.1). The most common polymorphism is C47T. According to NCBI Entrez Gene, “[t]his gene is a member of the superoxide dismutase (SOD) protein family. SODs are antioxidant enzymes that catalyze the dismutation of two superoxide radicals into hydrogen peroxide and oxygen. The product of this gene is thought to protect the brain, lungs, and other tissues from oxidative stress. The protein is secreted into the extracellular space and forms a glycosylated homotetramer that is anchored to the extracellular matrix (ECM) and cell surfaces through an interaction with heparan sulfate proteoglycan and collagen. A fraction of the protein is cleaved near the C-terminus before secretion to generate circulating tetramers that do not interact with the ECM.”
Literature search
A HuGE Navigator (V1.1) search on the SOD3 gene identified 10 articles on 10 disease terms. Five meta-analyses or HuGE Reviews were identified; none were relevant to CVD. The search (SOD3[Text+MeSH]>>Cardiovascular disease, unspecified[Mesh]) identified two articles.119,120 Neither of these articles were appropriate for our analysis because they did not evaluate risk of cardiovascular disease; they focused on pulmonary function measures119 and cigarette-induced cardiovascular disease.120
No Venice score and no large study analyses were possible.
TNF (tumor necrosis factor)
The TNF gene (aka DIF; TNFA; TNFSF2; TNF-alpha) is located on chromosome 6 (6p21.3). The most widely studied polymorphisms are G308A (A is the at-risk allele) and G238A (A is the at-risk allele). According to NCBI Entrez Gene, “[t]his gene encodes a multifunctional proinflammatory cytokine that belongs to the tumor necrosis factor (TNF) superfamily. This cytokine is mainly secreted by macrophages. It can bind to, and thus functions through its receptors TNFRSF1A/TNFR1 and TNFRSF1B/TNFBR. This cytokine is involved in the regulation of a wide spectrum of biological processes including cell proliferation, differentiation, apoptosis, lipid metabolism, and coagulation. This cytokine has been implicated in a variety of diseases, including autoimmune diseases, insulin resistance, and cancer.”
Literature search
A HuGE Navigator (V1.3) search (TNF [Text+MeSH]>>Meta-analysis[StudyType]) identified a total of 33 meta-analyses or HuGE Reviews; two were relevant to CVD. One evaluated coronary artery disease121 and the other evaluated the risk of ischemic heart disease as well as ischemic stroke.122
Genotype frequencies
• G308A Where G represents the wild allele, while A represents the at-risk allele. According to the first meta-analysis121, the allele frequencies for G and A are 0.83 and 0.17, respectively in 250 controls. Under Hardy-Weinberg, the expected genotype frequencies are 68%, 30% and 2% for GG, GA and AA, respectively.
• G238A Where G also represents the wild allele, while A represents the at-risk allele. The same meta-analysis listed allele frequencies for G and A as 0.94 and 0.06 respectively. Under Hardy-Weinberg, the expected genotype frequencies are 88%, 12% and >Brain Ischemia, Apoplexy[MeSH]) identified one study.124 Reviewing the publications from the earlier search identified an additional reference.125 We identified an electronically published letter via an internet search126 that was eventually published in 2009. This communication summarized the literature (including known abstracts) regarding stroke and 9p21 SNPs and is summarized below
Genotype frequencies
Although the exact genotype frequencies for each of the 9p21 SNPs vary slightly, the allele frequencies of the at-risk genotype is slightly above (or below) 0.5. We have to assume that, on average, genotype frequencies of 25%, 50%, and 25% for the wild (low risk), heterozygotes (referent group) and homozygotes (higher risk), respectively. The choice of heterozygotes rather than wild type individuals to be the referent group is reasonable, because they are the most common genotype.
CHD/MI
The summary analysis by Palomaki123 identified 16 articles that met inclusion criteria. There were 37 distinct datasets comprising four of the SNPs in the 9p21 region to be investigated with respect to coronary heart disease (rs10757274, rs1333049, rs2383207 and rs2891168). The summary OR using a random effects model for individuals with two at-risk alleles compared with one at-risk allele was 1.27 (95% CI 1.23 to 1.32, P C and S19W APOA5 gene polymorphisms are associated with high levels of triglycerides and apolipoprotein C-III, but not with coronary artery disease: an angiographic study. Atherosclerosis 2007;191:409-417.
18. Vaessen SF, Schaap FG, Kuivenhoven JA, et al. Apolipoprotein A-V, triglycerides and risk of coronary artery disease: the prospective Epic-Norfolk Population Study. J Lipid Res 2006;47:2064-2070.
19. Dallongeville J, Cottel D, Montaye M, et al. Impact of APOA5/A4/C3 genetic polymorphisms on lipid variables and cardiovascular disease risk in French men. Int J Cardiol 2006;106:152-156.
20. Chhabra S, Narang R, Lakshmy R, et al. Apolipoprotein C3 SstI polymorphism in the risk assessment of CAD. Mol Cell Biochem 2004;259:59-66.
21. Olivieri O, Bassi A, Stranieri C, et al. Apolipoprotein C-III, metabolic syndrome, and risk of coronary artery disease. J Lipid Res 2003;44:2374-2381.
22. Baroni MG, Berni A, Romeo S, et al. Genetic study of common variants at the Apo E, Apo AI, Apo CIII, Apo B, lipoprotein lipase (LPL) and hepatic lipase (LIPC) genes and coronary artery disease (CAD): variation in LIPC gene associates with clinical outcomes in patients with established CAD. BMC Med Genet 2003;4:8.
23. Wong WM, Hawe E, Li LK, et al. Apolipoprotein AIV gene variant S347 is associated with increased risk of coronary heart disease and lower plasma apolipoprotein AIV levels. Circ Res 2003;92:969-975.
24. Izar MC, Fonseca FA, Ihara SS, et al. Risk Factors, biochemical markers, and genetic polymorphisms in early coronary artery disease. Arq Bras Cardiol 2003;80:379-395.
25. Olivieri O, Stranieri C, Bassi A, et al. ApoC-III gene polymorphisms and risk of coronary artery disease. J Lipid Res 2002;43:1450-1457.
26. Russo GT, Meigs JB, Cupples LA, et al. Association of the Sst-I polymorphism at the APOC3 gene locus with variations in lipid levels, lipoprotein subclass profiles and coronary heart disease risk: the Framingham offspring study. Atherosclerosis 2001;158:173-181.
27. Liu S, Song Y, Hu FB, et al. A prospective study of the APOA1 XmnI and APOC3 SstI polymorphisms in the APOA1/C3/A4 gene cluster and risk of incident myocardial infarction in men. Atherosclerosis 2004;177:119-126.
28. Tobin MD, Braund PS, Burton PR, et al. Genotypes and haplotypes predisposing to myocardial infarction: a multilocus case-control study. Eur Heart J 2004;25:459-467.
29. Ruiz-Narvaez EA, Yang Y, Nakanishi Y, Kirchdorfer J, Campos H. APOC3/A5 haplotypes, lipid levels, and risk of myocardial infarction in the Central Valley of Costa Rica. J Lipid Res 2005;46:2605-2613.
30. Relvas WG, Izar MC, Helfenstein T, et al. Relationship between gene polymorphisms and prevalence of myocardial infarction among diabetic and non-diabetic subjects. Atherosclerosis 2005;178:101-105.
31. Bennet AM, Di Angelantonio E, Ye Z, et al. Association of apolipoprotein E genotypes with lipid levels and coronary risk. JAMA 2007;298:1300-1311.
32. Lanterna LA, Ruigrok Y, Alexander S, et al. Meta-analysis of APOE genotype and subarachnoid hemorrhage: clinical outcome and delayed ischemia. Neurology 2007;69:766-775.
33. Sudlow C, Martinez Gonzalez NA, Kim J, Clark C. Does apolipoprotein E genotype influence the risk of ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage? Systematic review and meta-analyses of 31 studies among 5961 cases and 17,965 controls. Stroke 2006;37:364-370.
34. Song Y, Stampfer MJ, Liu S. Meta-analysis: apolipoprotein E genotypes and risk for coronary heart disease. Ann Intern Med 2004;141:137-147.
35. Janosikova B, Pavlikova M, Kocmanova D, et al. Genetic variants of homocysteine metabolizing enzymes and the risk of coronary artery disease. Mol Genet Metab 2003;79:167-175.
36. Dilley A, Hooper WC, El-Jamil M, et al. Mutations in the genes regulating methylene tetrahydrofolate reductase (MTHFR C-->T677) and cystathione beta-synthase (CBS G-->A919, CBS T-->c833) are not associated with myocardial infarction in African Americans. Thromb Res 2001;103:109-115.
37. Boekholdt SM, Sacks FM, Jukema JW, et al. Cholesteryl ester transfer protein TaqIB variant, high-density lipoprotein cholesterol levels, cardiovascular risk, and efficacy of pravastatin treatment: individual patient meta-analysis of 13,677 subjects. Circulation 2005;111:278-287.
38. Quarta G, Stanzione R, Evangelista A, et al. A protective role of a cholesteryl ester transfer protein gene variant towards ischaemic stroke in Sardinians. J Intern Med 2007;262:555-561.
39. Fidani L, Hatzitolios AI, Goulas A, et al. Cholesteryl ester transfer protein TaqI B and lipoprotein lipase Ser447Ter gene polymorphisms are not associated with ischaemic stroke in Greek patients. Neurosci Lett 2005;384:102-105.
40. Di Castelnuovo A, Soccio M, Iacoviello L, et al. The C242T polymorphism of the p22phox component of NAD(P)H oxidase and vascular risk. Two case-control studies and a meta-analysis. Thromb Haemost 2008;99:594-601.
41. Payne JR, Dhamrait SS, Toor IS, et al. The -344T>C promoter variant of the gene for aldosterone synthase (CYP11B2) is not associated with cardiovascular risk in a prospective study of UK healthy men. Atherosclerosis 2004;174:81-86.
42. Burzotta F, Paciaroni K, De Stefano V, et al. G20210A prothrombin gene polymorphism and coronary ischaemic syndromes: a phenotype-specific meta-analysis of 12 034 subjects. Heart 2004;90:82-86.
43. Kim RJ, Becker RC. Association between factor V Leiden, prothrombin G20210A, and methylenetetrahydrofolate reductase C677T mutations and events of the arterial circulatory system: a meta-analysis of published studies. Am Heart J 2003;146:948-957.
44. Boekholdt SM, Bijsterveld NR, Moons AH, et al. Genetic variation in coagulation and fibrinolytic proteins and their relation with acute myocardial infarction: a systematic review. Circulation 2001;104:3063-3068.
45. Wu AH, Tsongalis GJ. Correlation of polymorphisms to coagulation and biochemical risk factors for cardiovascular diseases. Am J Cardiol 2001;87:1361-1366.
46. Chang MH, Lindegren ML, Butler MA, et al. Prevalence in the United States of selected candidate gene variants: Third National Health and Nutrition Examination Survey, 1991-1994. Am J Epidemiol 2009;169:54-66.
47. Juul K, Tybjaerg-Hansen A, Steffensen R, et al. Factor V Leiden: The Copenhagen City Heart Study and 2 meta-analyses. Blood 2002;100:3-10.
48. Margaglione M, D'Andrea G, Giuliani N, et al. Inherited prothrombotic conditions and premature ischemic stroke: sex difference in the association with factor V Leiden. Arterioscler Thromb Vasc Biol 1999;19:1751-1756.
49. Renner W, Hoffmann MM, Grunbacher G, et al. G-protein beta3 subunit (GNB3) gene polymorphisms and cardiovascular disease: the Ludwigshafen Risk and Cardiovascular Health (LURIC) study. Atherosclerosis 2007;192:108-112.
50. Klintschar M, Stiller D, Schwaiger P, Kleiber M. DNA polymorphisms in the tyrosine hydroxylase and GNB3 genes: association with unexpected death from acute myocardial infarction and increased heart weight. Forensic Sci Int 2005;153:142-146.
51. Hengstenberg C, Schunkert H, Mayer B, et al. Association between a polymorphism in the G protein beta3 subunit gene (GNB3) with arterial hypertension but not with myocardial infarction. Cardiovasc Res 2001;49:820-827.
52. Naber CK, Husing J, Wolfhard U, Erbel R, Siffert W. Interaction of the ACE D allele and the GNB3 825T allele in myocardial infarction. Hypertension 2000;36:986-989.
53. Morrison AC, Ballantyne CM, Bray M, et al. LPL polymorphism predicts stroke risk in men. Genet Epidemiol 2002;22:233-242.
54. Morrison AC, Doris PA, Folsom AR, Nieto FJ, Boerwinkle E. G-protein beta3 subunit and alpha-adducin polymorphisms and risk of subclinical and clinical stroke. Stroke 2001;32:822-829.
55. Zhang L, Zhang H, Sun K, et al. The 825C/T polymorphism of G-protein beta3 subunit gene and risk of ischaemic stroke. J Hum Hypertens 2005;19:709-714.
56. Nemoto M, Nishimura R, Sasaki T, et al. Genetic association of glutathione peroxidase-1 with coronary artery calcification in type 2 diabetes: a case control study with multi-slice computed tomography. Cardiovasc Diabetol 2007;6:23.
57. Oguri M, Kato K, Hibino T, et al. Genetic risk for restenosis after coronary stenting. Atherosclerosis 2007;194:e172-178.
58. Winter JP, Gong Y, Grant PJ, Wild CP. Glutathione peroxidase 1 genotype is associated with an increased risk of coronary artery disease. Coron Artery Dis 2003;14:149-153.
59. Forsberg L, de Faire U, Marklund SL, et al. Phenotype determination of a common Pro-Leu polymorphism in human glutathione peroxidase 1. Blood Cells Mol Dis 2000;26:423-426.
60. Licastro F, Chiappelli M, Caldarera CM, et al. The concomitant presence of polymorphic alleles of interleukin-1beta, interleukin-6 and apolipoprotein E is associated with an increased risk of myocardial infarction in elderly men. Results from a pilot study. Mech Ageing Dev 2004;125:575-579.
61. Dziedzic T, Slowik A, Pera J, Szczudlik A. Interleukin 1 beta polymorphism (-511) and risk of stroke due to small vessel disease. Cerebrovasc Dis 2005;20:299-303.
62. Vohnout B, Di Castelnuovo A, Trotta R, et al. Interleukin-1 gene cluster polymorphisms and risk of coronary artery disease. Haematologica 2003;88:54-60.
63. Iacoviello L, Di Castelnuovo A, Gattone M, et al. Polymorphisms of the interleukin-1beta gene affect the risk of myocardial infarction and ischemic stroke at young age and the response of mononuclear cells to stimulation in vitro. Arterioscler Thromb Vasc Biol 2005;25:222-227.
64. Sie MP, Sayed-Tabatabaei FA, Oei HH, et al. Interleukin 6 -174 g/c promoter polymorphism and risk of coronary heart disease: results from the rotterdam study and a meta-analysis. Arterioscler Thromb Vasc Biol 2006;26:212-217.
65. Chamorro A, Revilla M, Obach V, Vargas M, Planas AM. The -174G/C polymorphism of the interleukin 6 gene is a hallmark of lacunar stroke and not other ischemic stroke phenotypes. Cerebrovasc Dis 2005;19:91-95.
66. Lalouschek W, Schillinger M, Hsieh K, et al. Polymorphisms of the inflammatory system and risk of ischemic cerebrovascular events. Clin Chem Lab Med 2006;44:918-923.
67. Fontanella M, Rainero I, Gallone S, et al. Interleukin 6 gene polymorphisms are not associated with aneurysmal subarachnoid haemorrhage in an Italian population. J Neurol Neurosurg Psychiatry 2008;79:471-473.
68. Ruigrok YM, Slooter AJ, Bardoel A, et al. Genes and outcome after aneurysmal subarachnoid haemorrhage. J Neurol 2005;252:417-422.
69. Strand M, Soderstrom I, Wiklund PG, et al. Polymorphisms at the osteoprotegerin and interleukin-6 genes in relation to first-ever stroke. Cerebrovasc Dis 2007;24:418-425.
70. Zhu MM, Weedon J, Clark LT. Meta-analysis of the association of platelet glycoprotein IIIa PlA1/A2 polymorphism with myocardial infarction. Am J Cardiol 2000;86:1000-1005, A1008.
71. Burr D, Doss H, Cooke GE, Goldschmidt-Clermont PJ. A meta-analysis of studies on the association of the platelet PlA polymorphism of glycoprotein IIIa and risk of coronary heart disease. Stat Med 2003;22:1741-1760.
72. Wiwanitkit V. PIA1/A2 polymorphism of the platelet glycoprotein receptor IIb/IIIIa and its correlation with myocardial infarction: an appraisal. Clin Appl Thromb Hemost 2006;12:93-95.
73. Ridker PM, Hennekens CH, Schmitz C, Stampfer MJ, Lindpaintner K. PIA1/A2 polymorphism of platelet glycoprotein IIIa and risks of myocardial infarction, stroke, and venous thrombosis. Lancet 1997;349:385-388.
74. Kekomaki S, Hamalainen L, Kauppinen-Makelin R, et al. Genetic polymorphism of platelet glycoprotein IIIa in patients with acute myocardial infarction and acute ischaemic stroke. J Cardiovasc Risk 1999;6:13-17.
75. Reiner AP, Kumar PN, Schwartz SM, et al. Genetic variants of platelet glycoprotein receptors and risk of stroke in young women. Stroke 2000;31:1628-1633.
76. Cagatay P, Susleyici-Duman B, Ciftci C. Lipoprotein lipase gene PvuII polymorphism serum lipids and risk for coronary artery disease: meta-analysis. Dis Markers 2007;23:161-166.
77. Hu Y, Liu W, Huang R, Zhang X. A systematic review and meta-analysis of the relationship between lipoprotein lipase Asn291Ser variant and diseases. J Lipid Res 2006;47:1908-1914.
78. Baum L, Ng HK, Wong KS, et al. Associations of apolipoprotein E exon 4 and lipoprotein lipase S447X polymorphisms with acute ischemic stroke and myocardial infarction. Clin Chem Lab Med 2006;44:274-281.
79. Wittrup HH, Nordestgaard BG, Steffensen R, Jensen G, Tybjaerg-Hansen A. Effect of gender on phenotypic expression of the S447X mutation in LPL: the Copenhagen City Heart Study. Atherosclerosis 2002;165:119-126.
80. Wittrup HH, Tybjaerg-Hansen A, Abildgaard S, et al. A common substitution (Asn291Ser) in lipoprotein lipase is associated with increased risk of ischemic heart disease. J Clin Invest 1997;99:1606-1613.
81. Abu-Amero KK, Wyngaard CA, Al-Boudari OM, Kambouris M, Dzimiri N. Lack of association of lipoprotein lipase gene polymorphisms with coronary artery disease in the Saudi Arab population. Arch Pathol Lab Med 2003;127:597-600.
82. Anderson JL, King GJ, Bair TL, et al. Association of lipoprotein lipase gene polymorphisms with coronary artery disease. J Am Coll Cardiol 1999;33:1013-1020.
83. Klerk M, Verhoef P, Clarke R, et al. MTHFR 677C-->T polymorphism and risk of coronary heart disease: a meta-analysis. JAMA 2002;288:2023-2031.
84. Lewis SJ, Ebrahim S, Davey Smith G. Meta-analysis of MTHFR 677C->T polymorphism and coronary heart disease: does totality of evidence support causal role for homocysteine and preventive potential of folate? BMJ 2005;331:1053.
85. Hanson NQ, Aras O, Yang F, Tsai MY. C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase gene: incidence and effect of combined genotypes on plasma fasting and post-methionine load homocysteine in vascular disease. Clin Chem 2001;47:661-666.
86. Verhoeff BJ, Trip MD, Prins MH, Kastelein JJ, Reitsma PH. The effect of a common methylenetetrahydrofolate reductase mutation on levels of homocysteine, folate, vitamin B12 and on the risk of premature atherosclerosis. Atherosclerosis 1998;141:161-166.
87. Topol EJ, McCarthy J, Gabriel S, et al. Single nucleotide polymorphisms in multiple novel thrombospondin genes may be associated with familial premature myocardial infarction. Circulation 2001;104:2641-2644.
88. Cronin S, Furie KL, Kelly PJ. Dose-related association of MTHFR 677T allele with risk of ischemic stroke: evidence from a cumulative meta-analysis. Stroke 2005;36:1581-1587.
89. Markus HS, Ali N, Swaminathan R, et al. A common polymorphism in the methylenetetrahydrofolate reductase gene, homocysteine, and ischemic cerebrovascular disease. Stroke 1997;28:1739-1743.
90. Gaustadnes M, Rudiger N, Moller J, et al. Thrombophilic predisposition in stroke and venous thromboembolism in Danish patients. Blood Coagul Fibrinolysis 1999;10:251-259.
91. Szolnoki Z, Somogyvari F, Kondacs A, et al. Evaluation of the modifying effects of unfavourable genotypes on classical clinical risk factors for ischaemic stroke. J Neurol Neurosurg Psychiatry 2003;74:1615-1620.
92. Laraqui A, Allami A, Carrie A, et al. Influence of methionine synthase (A2756G) and methionine synthase reductase (A66G) polymorphisms on plasma homocysteine levels and relation to risk of coronary artery disease. Acta Cardiol 2006;61:51-61.
93. Gueant-Rodriguez RM, Juilliere Y, Candito M, et al. Association of MTRRA66G polymorphism (but not of MTHFR C677T and A1298C, MTRA2756G, TCN C776G) with homocysteine and coronary artery disease in the French population. Thromb Haemost 2005;94:510-515.
94. Urreizti R, Asteggiano C, Vilaseca MA, et al. A CBS haplotype and a polymorphism at the MSR gene are associated with cardiovascular disease in a Spanish case-control study. Clin Biochem 2007;40:864-868.
95. Chen J, Stampfer MJ, Ma J, et al. Influence of a methionine synthase (D919G) polymorphism on plasma homocysteine and folate levels and relation to risk of myocardial infarction. Atherosclerosis 2001;154:667-672.
96. Klerk M, Lievers KJ, Kluijtmans LA, et al. The 2756A>G variant in the gene encoding methionine synthase: its relation with plasma homocysteine levels and risk of coronary heart disease in a Dutch case-control study. Thromb Res 2003;110:87-91.
97. Bosco P, Gueant-Rodriguez RM, Anello G, et al. Association of homocysteine (but not of MTHFR 677 C>T, MTR 2756 A>G, MTRR 66 A>G and TCN2 776 C>G) with ischaemic cerebrovascular disease in Sicily. Thromb Haemost 2006;96:154-159.
98. Brilakis ES, Berger PB, Ballman KV, Rozen R. Methylenetetrahydrofolate reductase (MTHFR) 677C>T and methionine synthase reductase (MTRR) 66A>G polymorphisms: association with serum homocysteine and angiographic coronary artery disease in the era of flour products fortified with folic acid. Atherosclerosis 2003;168:315-322.
99. Casas JP, Cavalleri GL, Bautista LE, et al. Endothelial nitric oxide synthase gene polymorphisms and cardiovascular disease: a HuGE review. Am J Epidemiol 2006;164:921-935.
100. Zintzaras E, Kitsios G, Stefanidis I. Endothelial NO synthase gene polymorphisms and hypertension: a meta-analysis. Hypertension 2006;48:700-710.
101. Szolnoki Z, Havasi V, Bene J, et al. Endothelial nitric oxide synthase gene interactions and the risk of ischaemic stroke. Acta Neurol Scand 2005;111:29-33.
102. Hassan A, Gormley K, O'Sullivan M, et al. Endothelial nitric oxide gene haplotypes and risk of cerebral small-vessel disease. Stroke 2004;35:654-659.
103. Tsantes AE, Nikolopoulos GK, Bagos PG, et al. Plasminogen activator inhibitor-1 4G/5G polymorphism and risk of ischemic stroke: a meta-analysis. Blood Coagul Fibrinolysis 2007;18:497-504.
104. Attia J, Thakkinstian A, Wang Y, et al. The PAI-1 4G/5G gene polymorphism and ischemic stroke: an association study and meta-analysis. J Stroke Cerebrovasc Dis 2007;16:173-179.
105. Duval S, Tweedie R. Trim and fill: A simple funnel-plot-based method of testing and adjusting for publication bias in meta-analysis. Biometrics 2000;56:455-463.
106. Bhattacharyya T, Nicholls SJ, Topol EJ, et al. Relationship of paraoxonase 1 (PON1) gene polymorphisms and functional activity with systemic oxidative stress and cardiovascular risk. JAMA 2008;299:1265-1276.
107. Wheeler JG, Keavney BD, Watkins H, Collins R, Danesh J. Four paraoxonase gene polymorphisms in 11212 cases of coronary heart disease and 12786 controls: meta-analysis of 43 studies. Lancet 2004;363:689-695.
108. Schiavon R, Turazzini M, De Fanti E, et al. PON1 activity and genotype in patients with arterial ischemic stroke and in healthy individuals. Acta Neurol Scand 2007;116:26-30.
109. Pasdar A, Ross-Adams H, Cumming A, et al. Paraoxonase gene polymorphisms and haplotype analysis in a stroke population. BMC Med Genet 2006;7:28.
110. Slowik A, Wloch D, Szermer P, et al. Paraoxonase 2 gene C311S polymorphism is associated with a risk of large vessel disease stroke in a Polish population. Cerebrovasc Dis 2007;23:395-400.
111. Topic E, Simundic AM, Ttefanovic M, et al. Polymorphism of apoprotein E (APOE), methylenetetrahydrofolate reductase (MTHFR) and paraoxonase (PON1) genes in patients with cerebrovascular disease. Clin Chem Lab Med 2001;39:346-350.
112. Can Demirdogen B, Turkanoglu A, Bek S, et al. Paraoxonase/arylesterase ratio, PON1 192Q/R polymorphism and PON1 status are associated with increased risk of ischemic stroke. Clin Biochem 2008;41:1-9.
113. Aydin M, Gencer M, Cetinkaya Y, et al. PON1 55/192 polymorphism, oxidative stress, type, prognosis and severity of stroke. IUBMB Life 2006;58:165-172.
114. Yoshida M, Takano Y, Sasaoka T, Izumi T, Kimura A. E-selectin polymorphism associated with myocardial infarction causes enhanced leukocyte-endothelial interactions under flow conditions. Arterioscler Thromb Vasc Biol 2003;23:783-788.
115. Leshinsky-Silver E, Cheng S, Grow MA, et al. Candidate gene polymorphism in cardiovascular disease: the BIP cohort. Isr Med Assoc J 2006;8:103-105.
116. Abu-Amero KK, Al-Mohanna F, Al-Boudari OM, Mohamed GH, Dzimiri N. The interactive role of type 2 diabetes mellitus and E-selectin S128R mutation on susceptibility to coronary heart disease. BMC Med Genet 2007;8:35.
117. Miller MA, Kerry SM, Dong Y, et al. Circulating soluble E-selectin levels and the Ser 128Arg polymorphism in individuals from different ethnic groups. Nutr Metab Cardiovasc Dis 2005;15:65-70.
118. Genkinger JM, Platz EA, Hoffman SC, et al. C47T polymorphism in manganese superoxide dismutase (MnSOD), antioxidant intake and survival. Mech Ageing Dev 2006;127:371-377.
119. Wilk JB, Walter RE, Laramie JM, Gottlieb DJ, O'Connor GT. Framingham Heart Study genome-wide association: results for pulmonary function measures. BMC Med Genet 2007;8 Suppl 1:S8.
120. Wang XL, Raveendran M, Wang J. Genetic influence on cigarette-induced cardiovascular disease. Prog Cardiovasc Dis 2003;45:361-382.
121. Allen RA, Lee EM, Roberts DH, Park BK, Pirmohamed M. Polymorphisms in the TNF-alpha and TNF-receptor genes in patients with coronary artery disease. Eur J Clin Invest 2001;31:843-851.
122. Pereira TV, Rudnicki M, Franco RF, Pereira AC, Krieger JE. Effect of the G-308A polymorphism of the tumor necrosis factor alpha gene on the risk of ischemic heart disease and ischemic stroke: a meta-analysis. Am Heart J 2007;153:821-830.
123. Palomaki GE, Melillo, S., Bradley, L.A. The association between 9p21 genonic markers and heart disease: a meta-analysis of clinical validity. JAMA 2009;submitted.
124. Matarin M, Brown WM, Singleton A, Hardy JA, Meschia JF. Whole genome analyses suggest ischemic stroke and heart disease share an association with polymorphisms on chromosome 9p21. Stroke 2008;39:1586-1589.
125. Helgadottir A, Thorleifsson G, Manolescu A, et al. A common variant on chromosome 9p21 affects the risk of myocardial infarction. Science 2007;316:1491-1493.
126. Di Castelnuovo A, Pezzini A, Latella MC, Lichy C, Iacoviello L. Polymorphisms in chromosome 9 and risk of ischemic stroke in two European white populations, and a meta-analysis. J Thromb Haemost 2009;7:365-367.
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related download
- evaluation and management of the medically complex patient
- use of genomic profiling to assess risk for cardiovascular
- diagnosing acute myocardial infarction in the emergency
- section e cardiovascular system conditions u s
- chapter 18 cardiovascular system the heart
- guidelines for the secondary prevention of ischaemic heart
- a study was conducted on rajiv gandhi university of
Related searches
- ways to assess ell students
- drugs for cardiovascular disease
- use of the verb to be
- use of mm for billion
- medication for cardiovascular disease
- how to assess homan s sign
- proper use of for example
- icd 10 codes for cardiovascular diseases
- at risk for cardiovascular disease icd 10
- screening for cardiovascular disease icd 10
- exercises for cardiovascular disease
- treatment for cardiovascular disease