Apolipoprotein polymorphisms fail to define risk of coronary artery disease. Results of a prospective, angiographically controlled study

Association between apolipoprotein B EcoRI polymorphisms and coronary heart disease : A meta-analysis

OBJECTIVE

The study was carried out to examine the association between apolipoprotein B (ApoB) EcoRI polymorphism (E^- vs. E⁺) (rs1042031) and coronary heart disease (CHD) risk by systematically analyzing multiple independent studies.

METHODS

The Hardy-Weinberg equilibrium (HWE) test was applied to assess genotype frequency distribution in healthy controls. The quality of the studies was assessed using the Newcastle-Ottawa scale (NOS). Power analysis was performed with Power and Precision V4 software. A fixed effect model was used because no deviation from homogeneity was found. Publication bias was quantified and examined with Begg's funnel plot test and Egger's linear regression method. The meta-analysis was performed by Stata 12.0 software.

RESULTS

A total of 21 eligible association studies were merged in this meta-analysis and the pooled sample consisted of 2994 CHD patients and 3258 healthy controls. No significant publication bias and heterogeneity were observed in these studies. The pooled odds ratio (OR) and 95% confidence interval (CI) of E^- vs. E⁺ were 1.18 (1.06-1.32). The pooled OR (95% CI) of E⁺ E^- + E^- E^- vs. E⁺ E⁺ was 1.18 (1.04-1.34).

CONCLUSIONS

This meta-analysis indicated that ApoB EcoRI confers a moderate risk for CHD and the E^- allele at this locus might be a susceptibility allele for the development of CHD.

Association of the 12669G>A Apolipoprotein B Gene Polymorphism with Apo-B Serum Level and Lipid Profile in Patients with Coronary Artery Disease Comparing with Individuals Without Coronary Artery Disease in Zanjan Population of Iran

Atherosclerosis is a pathologic disorder which has an important role in the occurrence of coronary heart disease. It is determined as a focal, inflammatory proliferative response to several types of endothelial damage. Apolipoprotein B which is a requirement in the sustenance of cholesterol homeostasis, and is the major protein component of low density lipoprotein, characterized by multitude polymorphic sites, one of which (12669G>A) is related to the levels of serum lipid profiles, coronary artery disease and/or myocardial infarction. One Common polymorphism which is more important in this process is 12669G>A that is appraised in this research. We recruited 80 patients from the Mousavi hospital, Zanjan, Iran, diagnosed with coronary artery disease by the clinician on the basis of clinical symptoms, echocardiogram result, and angiography. Seventy-seven healthy individuals without any evident symptoms of Coronary stenosis and any past history of the disease were taken as controls from the general population. We carried out PCR using specific primers. Then, we digested PCR product by RFLP. Lipid parameters by biochemical methods and Apolipoprotein B serum level by immunoturbidometry method were done. Genotype frequencies for 12669G>A polymorphism were determined: 55 % R+R+, 45 % R+R- in case group, and 55.8 R+R+, 44.2 % R+R- in controls. The R-R- genotype was not seen. There was no significant relationship between this polymorphism and the risk of Coronary stenosis (P = 0.6). In the present study, higher plasma levels of cholesterol and low density lipoproteins in the subjects with R+R- genotype were found while there was no association between this polymorphism and coronary stenosis with ≥50 % in the Zanjan population.

Association between apolipoprotein B gene polymorphisms and the risk of coronary heart disease (CHD): an update meta-analysis

OBJECTIVE

Polymorphisms in the apolipoprotein B (apoB) gene have been reported to be associated with coronary heart disease (CHD). However, the results on this topic are conflicting. The present study aims to derive a more precise estimation of the relationship between CHD and apoB genetic polymorphisms by meta-analysis.

METHODS

We identified a total of 54 studies involving 7236, 10,912, and 14,102 individuals, respectively, for EcoRI, XbaI, and SpIns/Del polymorphisms by searching in PubMed, Web of Science, Google Scholar, the Cochrane Library, Wanfang Data, SinoMed, and CNKI. We utilized RevMan 5.0 software to perform the meta-analyses.

RESULTS

A significant statistical association between apoB EcoRI polymorphism and CHD was observed under an allelic (p = 0.001, odds ratio (OR) = 1.33, 95% confidence interval (CI) = 1.12-1.57), dominant (p = 0.005, OR = 1.22, 95% CI = 1.06-1.40), and recessive (p = 0.04, OR = 1.33, 95% CI = 1.01-1.74) model. We also found similar association of apoB SpIns/Del polymorphism with CHD. However, we did not find association between apoB XbaI polymorphism and CHD.

CONCLUSION

The current meta-analysis found an association of EcoRI polymorphism and SpIns/Del polymorphism with an increased risk of CHD. No significant association between apoB XbaI polymorphism and CHD we observed in the present study.

Meta-Analysis of miR-146a Polymorphisms Association with Coronary Artery Diseases and Ischemic Stroke

Coronary artery disease (CAD) and ischemic stroke (IS) are manifestations of atherosclerosis, with a high death rate. miR-146a is a microRNA that participates in the progress of CAD and IS. A single nucleotide polymorphism (SNP) in the precursor of miR-146a, rs2910164, was found to be associated with the risks of CAD and IS. However, the results were inconsistent and inconclusive. A meta-analysis was performed to assess the relationship of rs2910164 and CAD as well as IS susceptibility. The database Pubmed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), Chinese National Knowledge Infrastructure (CNKI), and Chinese Biomedical Literature Database (CBM) were searched for related studies. Crude odds ratios with 95% confidence intervals were used to investigate the strength of the association by random- or fixed-effect model. A total of eight studies, with 3138 cases and 3097 controls were identified for the meta-analysis. The results shows that rs2910164 is associated with the risk of CAD significantly in allelic model (OR = 0.86), homozygous model (OR = 0.70), heterozygous model (OR = 0.80) and dominant model (OR = 0.76). The subjects carrying the GG genotype, GG + GC genotype or G allele are at lower risks of CAD. For the susceptibility of IS, there are no significant associations between rs2910164 and total studies. However, in subgroup analysis by sample size and ethnicity, the GG, GG + GC and G allele of rs2910164 are found to be associated with higher risks of IS in large sample size group and in Koreans, under homozygous and dominant models. In conclusion, the current meta-analysis suggests lower risks of CAD for GG, GG + GC genotype and G allele of rs2910164, while rs2910164 is not associated with the risk of IS. Thus rs2910164 might be recommended as a predictor for susceptibility of CAD, but not IS.

DNA polymorphisms of the lipoprotein lipase gene and their association with coronary artery disease in the Saudi population

Coronary heart disease (CHD) is a major health problem and a major cause of death in most countries. Evidence has been presented that gene polymorphisms (HindIII, PvuII and Ser447Ter) of lipoprotein lipase (LPL) are risk factors of coronary artery disease (CAD).

AIM

Our objective of the present investigation was to determine whether 3 LPL polymorphisms (LPL-HindIII, LPL-PvuII and LPL-Ser447Ter) can be considered as independent risk factors for CAD in the Saudi population.

METHODS

We recruited 120 CAD subjects, confirmed angiographically with identical ethnic backgrounds and 65 control subjects. Polymerase chain reaction-restriction fragment length polymorphisms (RFLP) technique was used to detect the polymorphisms of the LPL gene.

RESULTS AND CONCLUSION

For the HindIII genotype, within the CAD group, the frequencies of the H(+)H(+) were found in 50.8%, whereas 44.2% carried the H(-)H(+) genotype, and 5% carried the H(-)H(-) genotype. Within the control group, the H(+)H(+) genotype was found in 44.6%, whereas 35.4% carried the H(-)H(+) genotype, 20% carried the H(-)H(-) genotype. The odds ratio (OR) of HindIII genotype H(+)H(+)vs. H(-)H(-) genotype at 95% Confidence Interval (CI) were 4.6 (1.57-13.2) and p < 0.005, hence showing no significant association with CAD. For the PvuII genotype, within the CAD group the frequencies of the P(+)P(+) found in 41.7% whereas 43.3.2% carried the P(-)P(+) genotype, and 15% carried the P(-)P(-) genotype. Within the control group the P(+)P(+) was found in 38.5%, 43.0% carried the P(-)P(+) genotype, and 18.5% carried the P(-)P(-) genotype. The OR of PvuII genotype P(+)P(+)vs. P(-)P(-) genotypes (95% CI) is 1.33 and p = 0.52; hence, it was also insignificant to show association with the disease. For the Ser447Ter genotype, within the CAD group, the frequencies of the C/C found in 83.3%, whereas 16.7% carried the C/G genotype. Within the control group, the C/C was found in 87.7% and 12.3% carried the C/G genotype. We did not get any GG genotypes in control as well as patients for this gene. It can be concluded that C allele of gene masks the presence of G allele in the Saudi population. The OR of CG + GG vs. CC (95% CI) is 1.43 from 0.59 to 3.44 which is insignificant. Hence this gene also has no significant association with CAD in the Saudi population.

The apolipoprotein E polymorphism and cardiovascular diseases--an autopsy study

BACKGROUND

Numerous studies have addressed the association between the apolipoprotein E polymorphism and cardiovascular disease, but only a few reports are based on findings at autopsy. In the present retrospective study, we have used autopsy findings from a general hospital population to further investigate this issue.

METHODS AND RESULTS

We collected information from 1522 consecutive autopsy reports (886 men, mean age 65.7 years; 636 women, mean age 69.7 years) conducted at Oslo University Hospital, Norway, in the period from 1996 to 2000. Cause of death and signs related to cardiovascular disease including the degree of atherosclerosis in the aorta and the coronary arteries, signs of myocardial infarction, heart weight, and signs of cerebrovascular disease were recorded. The patients were genotyped, and the apolipoprotein E allele frequencies (ɛ2, 8.0%; ɛ3, 72.6%; and ɛ4, 19.4%) were not statistically different from a group of healthy controls. Approximately 35% of the patients died from a cardiovascular disease. Genotypes differed significantly (P<.05), with more ɛ4-carriers (34.3% vs. 29.6%) and fewer ɛ2-carriers (11.8% vs. 13.9%) among patients who died from cardiovascular disease compared to those who died from other causes. A similar distribution of genotypes was seen in patients recorded with myocardial infarction or cerebrovascular disease. There was an association between the presence of ɛ4 and atherosclerosis in the aorta and coronary arteries, but this did not reach statistical significance. Among patients with signs of coronary heart disease, standardized heart weights were significantly higher in ɛ2-carriers compared to ɛ4-carriers.

CONCLUSION

The present autopsy study suggests that the risk of developing and dying from cardiovascular disease, including coronary heart disease and cerebrovascular disease, is influenced by the apolipoprotein E polymorphism.

Apolipoprotein B genetic variants modify the response to fenofibrate: a GOLDN study

Hypertriglyceridemia, defined as a triglyceride measurement > 150 mg/dl, occurs in up to 34% of adults. Fenofibrate is a commonly used drug to treat hypertriglyceridemia, but response to fenofibrate varies considerably among individuals. We sought to determine if genetic variation in apolipoprotein B (APOB), an essential core of triglyceride-rich lipoprotein formation, may account for some of the inter-individual differences observed in triglyceride (TG) response to fenofibrate treatment. Participants (N = 958) from the Genetics of Lipid Lowering Drugs and Diet Network study completed a three-week intervention with fenofibrate 160 mg/day. Associations of four APOB gene single nucleotide polymorphisms (SNP) (rs934197, rs693, rs676210, and rs1042031) were tested for association with the TG response to fenofibrate using a mixed growth curve model where the familial structure was modeled as a random effect and cardiovascular risk factors were included as covariates. Three of these four SNPs changed the amino acid sequence of APOB, and the fourth was in the promoter region. TG response to fenofibrate treatment was associated with one APOB SNP, rs676210 (Pro2739Leu), such that participants with the TT genotype of rs676210 had greater TG lowering than those with the CC genotype (additive model, P = 0.0017). We conclude the rs676210 variant may identify individuals who respond best to fenofibrate for TG reduction.

Saturated fat intake and alcohol consumption modulate the association between the APOE polymorphism and risk of future coronary heart disease: a nested case-control study in the Spanish EPIC cohort

The association is still not clear between the common APOE polymorphism and coronary heart disease (CHD) risk, nor its modulation by diet. Thus, our aim was to study the association between the APOE genotypes and incident CHD and how dietary fat and alcohol consumption modify these effects. We performed a nested case-control study in the Spanish European Prospective Investigation into Cancer and Nutrition cohort. Healthy men and women (41,440, 30-69 years) were followed up over a 10-year period, with the incident CHD cases being identified. We analyzed 534 incident CHD cases and 1123 controls. APOE, dietary intake and plasma lipids were determined at baseline. The APOE polymorphism was significantly associated with low-density lipoprotein cholesterol (LDL-C), and gene-alcohol interactions in determining LDL-C were detected. In the whole population, the E2 allele was significantly associated with a lower CHD risk than E3/E3 subjects [odds ratio (OR), 0.58; 95% confidence interval (CI), 0.38-0.89]. The E4 allele did not reach statistical significance vs. E3/E3 (OR, 1.17; 95% CI, 0.88-1.58). However, saturated fat intake modified the effect of the APOE polymorphism in determining CHD risk. When saturated fat intake was low (<10% of energy), no statistically significant association between the APOE polymorphism and CHD risk was observed (P=.682). However, with higher intake (≥10%), the polymorphism was significant (P=.005), and the differences between E2 and E4 carriers were magnified (OR for E4 vs. E2, 3.33; 95% CI, 1.61-6.90). Alcohol consumption also modified the effect of the APOE on CHD risk. In conclusion, in this Mediterranean population, the E2 allele is associated with lower CHD risk, and this association is modulated by saturated fat and alcohol consumption.

The effects of apoA-I/C-III/A-IV, apoE and apoB polymorphisms on carotid artery intima-media thickness

Different apolipoprotein combinations explain most of the functional differences between plasma lipoproteins. This emphasizes the pivotal role of apolipoproteins in the homeostasis and physiological control of lipid metabolism. Genetic polymorphisms of apolipoprotein (apo)A-I/C-III/A-IV, apoE and apoB have been suggested to modulate plasma lipid levels as well as the risk of coronary artery disease and stroke. Carotid artery intima-media thickness has been shown to represent preclinical atherosclerosis and has, therefore, been used as a surrogate in quantifying the early stages of atherosclerosis. The effects of the polymorphisms in apoA-I/C-III/A-IV and apoB on carotid intima-media thickness are poorly known. The corresponding influence of apoE polymorphisms has been studied more extensively, but the results are not yet conclusive. In this review, these results are presented in detail and the potential reasons and mechanisms for the discrepancies are discussed.

Angiotensin-converting enzyme and apolipoproteins genes polymorphism in coronary artery disease

BACKGROUND

Association between angiotensin-converting enzyme (ACE) as well as apolipoprotein (apo) AI, B, and E polymorphisms and dyslipidemia and coronary artery disease (CAD) is controversial.

HYPOTHESIS

This study assessed the distribution of ACE insertion/deletion, apo AI A/G mutation, apo B signal peptide insertion/deletion, apo B XbaI restriction fragment length, and apo E polymorphisms in 388 nondiabetic patients.

METHODS

The study population included 112 patients with stable CAD, 139 patients with acute myocardial infarction (AMI), and 137 age-matched control subjects.

RESULTS

Univariate analysis showed higher prevalence of XbaI X+/X+ genotype in patients with CAD (p = 0.02). Angiotensin-converting enzyme and apo polymorphisms were not associated with lipid levels or severity of CAD. When all genotypes known to be related to CAD; such as ACE DD, apo AI GG, apo B del/del, and XbaI X+X+, and E4 allele of apo E, were pooled, again no significant differences among groups were seen. Multivariate regression analysis disclosed traditional risk factors and elevated levels of apo B for men and reduced levels of apo AI for women as independent variables for CAD.

CONCLUSIONS

In addition to traditional coronary risk factors, apo B and AI could be considered predictors of CAD. No association between either form of CAD and polymorphisms was noted.

Genetic studies on the APOA1-C3-A5 gene cluster in Asian Indians with premature coronary artery disease

BACKGROUND

The APOA1-C3-A5 gene cluster plays an important role in the regulation of lipids. Asian Indians have an increased tendency for abnormal lipid levels and high risk of Coronary Artery Disease (CAD). Therefore, the present study aimed to elucidate the relationship of four single nucleotide polymorphisms (SNPs) in the Apo11q cluster, namely the -75G>A, +83C>T SNPs in the APOA1 gene, the Sac1 SNP in the APOC3 gene and the S19W variant in the APOA5 gene to plasma lipids and CAD in 190 affected sibling pairs (ASPs) belonging to Asian Indian families with a strong CAD history.

METHODS & RESULTS

Genotyping and lipid assays were carried out using standard protocols. Plasma lipids showed a strong heritability (h2 48% - 70%; P < 0.0001). A subset of 77 ASPs with positive sign of Logarithm of Odds (LOD) score showed significant linkage to CAD trait by multi-point analysis (LOD score 7.42, P < 0.001) and to Sac1 (LOD score 4.49) and -75G>A (LOD score 2.77) SNPs by single-point analysis (P < 0.001). There was significant proportion of mean allele sharing (pi) for the Sac1 (pi 0.59), -75G>A (pi 0.56) and +83C>T (pi 0.52) (P < 0.001) SNPs, respectively. QTL analysis showed suggestive evidence of linkage of the Sac1 SNP to Total Cholesterol (TC), High Density Lipoprotein-cholesterol (HDL-C) and Apolipoprotein B (ApoB) with LOD scores of 1.42, 1.72 and 1.19, respectively (P < 0.01). The Sac1 and -75G>A SNPs along with hypertension showed maximized correlations with TC, TG and Apo B by association analysis.

CONCLUSION

The APOC3-Sac1 SNP is an important genetic variant that is associated with CAD through its interaction with plasma lipids and other standard risk factors among Asian Indians.

Apolipoprotein A-I/C-III/A-IV SstI and apolipoprotein B XbaI polymorphisms do not affect early functional and structural changes in atherosclerosis: the Cardiovascular Risk in Young Finns study

BACKGROUND

The present study was designed to investigate the effects of apoB XbaI and apoA-I/C-III/A-IV SstI polymorphisms to carotid artery intima-media thickness (IMT), carotid artery compliance (CAC) and brachial artery flow-mediated vasodilatation (FMD).

METHODS AND RESULTS

As part of the Cardiovascular Risk in Young Finns Study, the carotid IMT, CAC and brachial FMD of 2,265 subjects (mean age +/- SD 32 +/-5 years) were measured with ultrasonography, and genotyping of the apolipoprotein polymorphisms was performed. The frequencies of the genotypes did not differ between the groups with high (above median 0.57 mm) and low (below median) IMT, CAC or FMD. The average carotid IMT differed between the 3 apoB XbaI genotypes (ANOVA, p=0.04), but not between the apoA-I/C-III/A-IV SstI genotypes (ANOVA, p=0.53). The relationship between the polymorphisms and carotid IMT was not significant in any of the covariate-adjusted logistic and linear regression analyses. CAC and FMD were not influenced by either of the polymorphisms in ANOVA and regression analyses.

CONCLUSIONS

The polymorphisms apoA-I/C-III/A-IV SstI and apoB XbaI do not seem to affect carotid artery characteristics or brachial artery FMD in young adulthood.

Protective effect of apolipoprotein E2 on coronary artery disease in African Americans is mediated through lipoprotein cholesterol

We studied the relationship of apolipoprotein E (apoE) isoforms and coronary artery disease (CAD) in 224 African Americans and 326 Caucasians undergoing diagnostic coronary angiography. The presence of CAD was defined as >50% stenosis in at least one artery. ApoE allele frequencies were 0.12, 0.62, and 0.26 for epsilon 2, epsilon 3, and epsilon 4, respectively, in African Americans and 0.08, 0.78, and 0.14 for epsilon 2, epsilon 3, and epsilon 4, respectively, in Caucasians. Among African Americans, CAD was present in 9 of 34 epsilon 2 carriers (26%), significantly smaller (P < 0.05) in proportion compared with 39 of 82 epsilon 3 carriers and 43 of 92 epsilon 4 carriers (48% and 47%, respectively), suggesting a protective effect of the epsilon 2 allele. No such difference was seen in Caucasians. In African Americans but not Caucasians, LDL cholesterol was lower in epsilon 2 carriers than in epsilon 3 and epsilon 4 carriers (106 vs. 127 and 134 mg/dl, respectively; P < 0.005). After adjusting for lipid levels, the association between apoE2 and CAD was no longer significant. Thus, the protective effect of apoE2 seen in African Americans could be explained by a favorable lipid profile in epsilon 2 carriers, whereas in Caucasians, the absence of such a protective effect could be attributable to the lack of effect of apoE2 on the lipid profile.

APOA1 polymorphism influences risk for early-onset nonfamiliar AD

Alterations in cholesterol homeostasis influence the risk for Alzheimer's disease (AD). Apolipoprotein A1 is the major apolipoprotein of the high-density lipoprotein and is involved in reverse cholesterol transport. Variation in the apolipoprotein A1 gene (APOA1) might influence the function of the protein, and thus brain cholesterol metabolism, leading to an increased risk for AD. Two polymorphisms of APOA1, a G/A substitution at position -75bp and a C/T and G/A base substitution at position +83bp or +84bp, or both, in the APOA1 promoter, have been described. We investigated the effect of these polymorphisms on the risk for AD in 427 AD patients and 500 healthy control subjects of German and English descent. The A allele of the APOA1 -75bp G/A polymorphism was associated with an increased risk for AD in subjects with an age at onset of 66 years or younger. Further data analysis indicated that AD patients homozygous for the A allele at position -75bp presented with disease onset 8 years earlier than carriers of at least one G allele. No influence of the +83/84bp polymorphism on the risk for AD was observed. These results suggest that variants of APOA1 might influence the onset and the risk for AD.

Candidate genes of cerebral infarction and traditional classification in Koreans with cerebral infarction

Sasang constitutional medicine is a major branch of Korean traditional Oriental medicine. The differences of disease susceptibility to be shown in Sasang constitution may be due to genetic factors. Therefore, the authors examined relationship between candidate genes of cerebral infarction (CI) and Sasang constitution. The homozygous deletion allele of the angiotensin converting enzyme gene (ACE/DD), homozygous threonine allele of the angiotensinogen gene (AGN/TT), and the e4 allele of the apolipoprotein E gene (ApoE/e4) are reported to be associated with ischemic heart disease. CI is another atherosclerotic disease; and the effects of these polymorphisms on CI have been confusing. This study investigated whether ACE/DD, AGN/TT, and ApoE/e4 genotypes are associated with CI and whether genetic risk is enhanced by Sasang constitutional classification. The authors ascertained these genotypes in patients with CI (N=211), diagnosed by brain computed tomography. Control subjects for the infarction group were randomly selected from 319 subjects matched for age, sex, and history of hypertension with patients. The ACE/DD genotype was not associated with CI. However, there was significant association between ApoE polymorphism and CI (chi2=15.089, p<.05). Furthermore, frequency of AGN/TT genotype was higher in the patients with CI than in the controls (chi2=20.072, p<.05). The frequency of T allele was 0.91 in patients and 0.82 in controls (chi2=17.237, p<.05). However, Sasang constitutional classification did not increase the relative risk for CI in the subjects with ApoE/e4 or AGN/T allele. These results suggest that ApoE and AGN polymorphism predict CI, but Sasang constitutional classification does not enhance the risk for CI associated with ApoE/e4 or AGN/TT in a Korean population.

Apolipoprotein A-I/C-III/A-IV SstI and apolipoprotein B XbaI polymorphisms and their association with carotid artery intima-media thickness in the Finnish population. The Cardiovascular Risk in Young Finns Study

Apolipoprotein A-I/C-III/A-IV (apoA-I/C-III/A-IV) SstI and apolipoprotein B (apoB) XbaI polymorphisms have been shown to affect serum low-density lipoprotein (LDL) cholesterol concentrations in a sample of Finnish children. We studied whether these polymorphism are associated with carotid artery intima-media thickness (IMT), a marker of pre-clinical atherosclerosis, measured in the same subjects during their adulthood. A random sub-sample of 214 individuals from the "Cardiovascular Risk in Young Finns" study, for whom genotypes, cardiovascular risk factor data and carotid artery IMT measured in 2001 were available, were studied. Mean carotid IMT values increased according to the apoA-I/C-III/A-IV SstI genotype groups in the order of S1S1 (0.58+/-0.08 mm), S1S2 (0.61+/-0.08 mm), and S2S2 (0.70+/-0.16 mm, p=0.02, ANOVA). In multiple linear regression analysis after adjusting for age, sex and body mass index the mean IMT thickness among the S2 allele carriers was higher (p=0.02) compared to non-carriers. In logistic regression analysis the frequency of S2 allele carriers was higher among the high IMT group compared to the low IMT group (OR=4.02, CI: 1.68-9.61, p=0.002). No significant association between apoB XbaI polymorphism and carotid IMT was found. However, serum total and LDL cholesterol and apoB concentrations were significantly different among apoB genotype groups (p<0.001 for all traits). The apoA-I/C-III/A-IV SstI polymorphism is associated with carotid IMT in young Finns.

Polymorphism of angiotensin-converting enzyme, angiotensinogen, and apolipoprotein E genes in Korean patients with cerebral infarction

The homozygous deletion allele of the angiotensin-converting enzyme gene (ACE/DD), homozygous threonine allele of the angiotensinogen gene (AGN/TT), and the epsilon4 allele of the apolipoprotein E gene (apoE/epsilon4) are reported to be associated with ischemic heart disease. Cerebral infarction (CI) is another atherosclerotic disease, and the effects of these polymorphisms on CI have been confusing. The frequency of the DD genotype of the ACE gene, but not the TT genotype of the AGN gene and the epsilon4 allele of ApoE, was significantly higher in subjects with than those without CI in Japan. In this study, we investigated whether ACE/DD, AGN/TT, and apoE/epsilon4 genotypes are associated with CI and whether genetic risk is enhanced by the effect of one upon another. We ascertained these genotypes in patients with CI (n = 365), diagnosed by brain computed tomography. Control subjects for the infarction group were randomly selected from 319 subjects matched for age, gender, and history of hypertension with patients. The ACE/DD genotype was not associated with CI. Frequency of the AGN/TT genotype was higher in patients with CI than in controls (chi2 = 12.287, p < 0.05). The frequency of t allele was 0.88 in patients and 0.82 in controls (chi2 = 11.041, p < 0.05; odds ratio, 1.7). Furthermore, the AGN/TT genotype increased the relative risk for CI in subjects with the ACE/DD genotype (chi2 = 7.8, p < 0.05; odds ratio, 1.9). There was no significant association between apoE/epsilon4 and CI. These results suggest that AGN/TT predicts CI and ACE/DD enhances the risk for CI associated with AGN/TT in a Korean population.

An association analysis between ApoA1 polymorphisms and the high-density lipoprotein (HDL) cholesterol level and myocardial infarction (MI) in Japanese

Association studies were performed to confirm the effect of polymorphisms in apolipoprotein A1 ( ApoA1) on the high-density lipoprotein cholesterol (HDL-C) level and the incidence of myocardial infarction (MI). A sequence analysis identified nine polymorphisms in ApoA1. After considering linkage disequilibrium, four polymorphisms in ApoA1 and four polymorphisms in the 5'-flanking regions and 3'-flanking regions from the JSNP database were determined in 1,880 subjects recruited from the Suita study, which represents the general population in Japan. Of the eight polymorphisms tested, the ApoA1 T84C polymorphism had the greatest effect on the levels of HDL-C ( P=0.0005, P(c)=0.0040 corrected by the Bonferroni method) and triglyceride ( P<0.0001, P(c)=0.0008). The ApoA1 MspI polymorphism was not associated with HDL-C or triglyceride levels. We confirmed that the ApoA1 T84C polymorphism was associated with the HDL-C level but not the triglyceride level in patients with MI ( n=637). Moreover, this polymorphism was associated with the incidence of MI in male subjects ( P=0.0326). A logistic analysis indicated that the frequency of MI in the CC genotype was lower than that in the CT+TT genotype ( P=0.0145, OR=0.4955, 95% CI: 0.2746-0.8525). The ApoA1 T84C polymorphism is an important marker for the HDL-C level and may be a new risk marker for MI in Japanese.

Fractional esterification rate of cholesterol and ratio of triglycerides to HDL-cholesterol are powerful predictors of positive findings on coronary angiography

BACKGROUND

We examined the predictive value of various clinical and biochemical markers for angiographically defined coronary artery disease (aCAD). Specifically, we assessed the value of the ratio of plasma triglyceride (TGs) to HDL-cholesterol (HDL-C) and the fractional esterification rate of cholesterol in plasma depleted of apolipoprotein B (apoB)-containing lipoproteins (FER(HDL)), a functional marker of HDL and LDL particle size.

METHODS

Patients (788 men and 320 women) undergoing coronary angiography were classified into groups with positive [aCAD(+)] and negative [aCAD(-)] findings. Patient age, body mass index, waist circumference, blood pressure (BP), medications, drinking, smoking, exercise habits, and plasma total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-unesterified cholesterol, HDL-C, TGs, FER(HDL), apoB, log(TG/HDL-C), and TC/HDL-C were assessed. Lipids and apoproteins were measured by standard laboratory procedures; FER(HDL) was determined by a radioassay.

RESULTS

Members of the aCAD(+) group were older and had a higher incidence of smoking and diabetes than those in the aCAD(-) group. The aCAD(+) group also had higher TG, apoB, FER(HDL), and log(TG/HDL-C) and lower HDL-C values. aCAD(+) women had greater waist circumference and higher plasma TC and TC/HDL-C. aCAD(+) men, but not women, had higher plasma LDL-C. In the multivariate logistic model, the significant predictors of the presence of aCAD(+) were FER(HDL), age, smoking, and diabetes. If only laboratory tests were included in the multivariate logistic model, FER(HDL) appeared as the sole predictor of aCAD(+). Log(TG/HDL-C) was an independent predictor when FER(HDL) was omitted from multivariate analysis.

CONCLUSIONS

FER(HDL) was the best laboratory predictor of the presence of coronary atherosclerotic lesions.

Molecular variation at the apolipoprotein B gene locus in relation to lipids and cardiovascular disease: a systematic meta-analysis

Apolipoprotein B (apoB) is the sole protein component of low-density lipoprotein (LDL) and is thought to play an important role in atherogenesis. We performed a meta-analysis of the associations between the three most frequently investigated polymorphisms (XbaI, signal peptide insertion/deletion, EcoRI) in the apolipoprotein B (APOB) gene, lipid parameters, and the risk of ischemic heart disease (IHD). We restricted our analysis to Caucasians. Homozygotes for the XbaI X+ allele had significantly elevated levels of LDL cholesterol (LDL-C) and apoB, but a decreased risk (OR=0.80; 95%CI: 0.66-0.96) of IHD. Homozygosity for the signal peptide deletion allele was associated with similarly increased levels of LDL-C and apoB, and with an increased risk of IHD (OR=1.30; 95%CI: 1.08-1.58). Subjects homozygous for the rare EcoRI allele had significantly decreased levels of total and LDL cholesterol, but unaltered risk of IHD. We conclude that all three polymorphic apoB sites are associated with altered lipid levels, but not necessarily with a consistently altered risk of IHD. These data suggest that the relationship between apoB levels, hypercholesterolemia and IHD risk cannot have a simple molecular basis in the apoB gene.

Interaction between SREBP-1a and APOB polymorphisms influences total and low-density lipoprotein cholesterol levels in patients with coronary artery disease

In this study, we examined the insertion/deletion (Ins/Del) and XbaI polymorphisms of the apolipoprotein B (APOB) gene and the -36delG polymorphism in the sterol regulatory element binding protein-1a (SREBP-1a) gene in 298 patients with non-diabetic angiographically assessed coronary artery disease (CAD), and 188 healthy controls, from a Brazilian population of European descent. Del/X+ haplotype carriers had higher levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in patients (TC, p = 0.05; LDL-C, p = 0.049) and controls (TC, p = 0.004; LDL-C, p = 0.013). No association was detected between the SREBP-1a-36delG polymorphism and lipid levels, but a significant interaction effect between APOB and SREBP-1a polymorphisms was observed in the patient sample on TC (p = 0.005) and on LDL-C (p = 0.019) levels. Carriers of the APOB Del/X+ haplotype and SREBP-1a G-G- genotype showed the highest levels of these lipid parameters. This effect of interaction was not observed in the control sample. Despite the associations with lipids, these polymorphisms were not associated with CAD risk or severity in this sample.

A prospective study of the association between APOE genotype and the risk of myocardial infarction among apparently healthy men

BACKGROUND

Apolipoprotein E (apoE) plays an important role in lipid metabolism. Three common alleles in the APOE gene, E2/E3/E4, have been associated with lipoprotein disorders but their effects on myocardial infarction (MI) risk remain uncertain.

METHODS

In a prospective cohort of 14916 apparently healthy men enrolled in the Physicians' Health Study, APOE genotyping was conducted to determine three common alleles (E2/E3/E4) among 385 incident cases of first MI and among 373 age- and smoking-matched controls.

RESULTS

No significant differences in allele or genotype frequency for the APOE gene were detected between cases and controls. As expected, we observed significant positive associations between dyslipidemia (low HDL/high TG or high LDL) and MI risk (P<0.001) and between genotypes and levels of LDL (P<0.001), HDL (P=0.04) or TG (P=0.02). Compared with men homozygous for the E3 allele and after adjusting for multiple MI risk factors, men carrying the E4 allele (E4/4 or E4/3) had a relative risk of 0.93 (95% CI 0.63-1.37) and men carrying the E2 allele (E2/2 or E2/3) a relative risk of 1.03 (0.62-1.74). Moreover, no significant difference in MI risk was observed among different genotypes across different levels of lipids or smoking status.

CONCLUSIONS

These data from a prospective study of apparently healthy men do not support the simple view of E2 as a protective factor and E4 as a susceptibility factor in predicting future risk of MI independent of lipid parameters. Nor did we observe any interaction between smoking and apoE4 allele on MI risk.

Evidence of reduced coronary artery disease risk for apolipoprotein epsilon2/3 heterozygotes

BACKGROUND: Polymorphism in the gene for apolipoprotein E (apo E) influences lipid metabolism. Relative to the epsilon3 allele, the epsilon4 allele tends to increase and the epsilon2 allele tends to decrease total and serum cholesterol, but uncertainty remains concerning an influence on the risk of coronary artery disease (CAD). It is possible that the influence of apo E alleles on CAD risk is influenced by the age of subjects studied. In this study, we examine the influence of the epsilon2 and epsilon4 alleles on the risk of CAD in relatively young subjects. METHODS: We determined the apo E genotype of 564 Caucasian CAD subjects below 50 years of age presenting with symptomatic CAD, either with or without prior myocardial infarction, and documented by angiography, and 639 similarly aged Caucasian control subjects without symptomatic CAD randomly selected from the community. RESULTS: The frequency of subjects with the epsilon2/3 genotype was significantly lower in CAD subjects than controls (6 vs. 11%, P<0.01) and, relative to epsilon3/3, the epsilon2/3 genotype was associated with a significant reduction in total and LDL-cholesterol in male and female control subjects. In contrast, there was no difference in the frequency of epsilon4/4 or epsilon4/3 genotypes in CAD cases and controls (30 vs. 26%, NS), and the latter genotypes had little influence on total or LDL-cholesterol. CONCLUSION: The results indicate a beneficial effect of the epsilon2/3 genotype not only on LDL cholesterol but in decreasing the risk of CAD in Caucasians at a young age.

[Genes and coronary heart disease]

The causes of atherosclerotic cardiovascular disease have been intensely scrutinized for the last few decades. Since the classic risk factors have been found to be incomplete predictors of the disease, additional risk factors based on molecular genetics are now being sought. Polymorphisms are gene variations that have only modest effects on the function of coded proteins or enzymes. However, they are common and may be risk factors in the presence of environmental risk factors (cholesterol, stress, tobacco). Recent advances in molecular biology have made it possible to detect numerous polymorphisms that might have a detrimental effect on vascular biology, suggesting the hypothesis that multiple polymorphisms in the presence of environmental factors could act synergistically in the pathogenesis of atherosclerosis and coronary heart disease, which are typically polygenic and multifactorial diseases. In this review, the current status of our knowledge of polymorphisms and mutations potentially implicated in the mechanisms of coronary artery disease is discussed. Genotype/phenotype, gene-gene, and gene-environmental interactions related to lipid metabolism, the renin-angiotensin-aldosterone and adrenergic systems, insulin resistance, oxidative stress and endothelial function, inflammation and thrombosis are analyzed. Individual coronary risk might be related to the presence of a critical accumulation detrimental polymorphisms.

Angiotensin-converting enzyme and apolipoprotein B polymorphisms in coronary artery disease

The association between angiotensin-converting enzyme (ACE) as well as apolipoprotein B polymorphisms and dyslipidemia and coronary artery disease (CAD) is controversial. We assessed the distribution of ACE insertion and/or deletion, apolipoprotein B signal peptide insertion and/or deletion, and apolipoprotein B XbaI restriction fragment length polymorphisms in 388 nondiabetic patients. We studied 112 patients with angiographically defined asymptomatic CAD or with stable functional classes I and II angina and 139 patients with acute myocardial infarction who were age matched to 137 control subjects. Univariate analysis showed higher prevalence of Xba50% reduction of lumen diameter. Overall, multivariable regression disclosed traditional risk factors and elevated levels of apolipoprotein B for men and reduced levels of apolipoprotein AI for women as independent variables for CAD. After adjustment for the most important subset of risk factors (age, hypertension, hypercholesterolemia, and smoking), apolipoprotein B XbaI polymorphism was disclosed as an independent variable for CAD. Apolipoprotein B XbaI was also selected as an independent variable for acute myocardial infarction after adjusting for age, hypertension, hypercholesterolemia, and smoking. Thus, in addition to traditional coronary risk factors, apolipoproteins B and AI, and apolipoprotein B XbaI polymorphism could be considered predictors of CAD.

Genetic determinants of plasma lipid response to dietary intervention: the role of the APOA1/C3/A4 gene cluster and the APOE gene

Polymorphisms at the APOA1/C3/A4 gene cluster and the APOE gene have been extensively studied in order to examine their potential association with plasma lipid levels, coronary heart disease risk and more recently with inter-individual variability in response to dietary therapies. Although the results have not been uniform across studies, the current research supports the concept that variation at these genes explains a significant, but still rather small, proportion of the variability in fasting and postprandial plasma lipid responses to dietary interventions. This information constitutes the initial frame to develop panels of genetic markers that could be used to predict individual responsiveness to dietary therapy for the prevention of coronary heart disease. Future progress in this complex area will come from experiments carried out using animal models, and from carefully controlled dietary protocols in humans that should include the assessment of several other candidate gene loci coding for products that play a relevant role in lipoprotein metabolism (i.e. APOB, CETP, LPL, FABP2, SRBI, ABC1 and CYP7).

Genetic variation in coronary heart disease and myocardial infarction: methodological overview and clinical evidence

The precise molecular mechanisrms that lead to coronary artery disease (CAD) and myocardial infarction (MI) are not understood, despite a wealth of knowledge on predisposing risk factors and pathomechanisms. CAD and MI are complex genetic diseases; neither the environment alone nor a single gene cause disease, but a mix of environmental and genetic factors lead to atherosclerosis of the coronary arteries and subsequent manifestation of clinical disease. The biological complexity of atherosclerotic disease results from unknown or unpredictable interactions of many genetic and environmental factors which, by themselves, have only been partially identified. According to current knowledge, genetic variations in causative or susceptihility genes form the basis of molecular mechanisms that, together with environmental impact, lead to CAD/MI and determine its clinical course. Linkage analysis, which follows 'disease' alleles in families, or genetic association in a population of unrelated individuals are tools used in the search for chromosomal loci and candidate genes that are involved in these complex diseases. Progress in sequencing and mapping of the human genorne and efforts to identify all of the expected one million single nucleotide polymorphisms (SNPs) expected to be present in mankind will allow new approaches such as genome-wide association studies. The contribution of the current state of knowledge on genetic variation in man towards the dissection of CAD/MI as complex traits is sobering. Raised expectations with regard to the power of molecular genetic studies as compared to the traditional pathophysiological experimental approaches, lack of precise clinical phenotyping, lack of functional characterisation of gene variants, and the vast number of yet undetected genes may provide some explanation. Except for certain polymorphisms in lipid genes (i.e., apolipoprotein E [apo E]) or rare genetic variations (i.e., LDL receptor), which have a causal effect on both the intermediate (LDL-cholesterol level in plasma) and the clinical phenotypes (CAD/MI), the role of most gene polymorphisms is controversial or unknown. Despite the enormous progress in sequencing the human genome and in molecular genetic and bioinformatic techniques during the past decade, the progress in mapping and identifying genes responsible for complex traits such as CAD/MI has been modest and presents a formidable challenge to medical research in the 21st century.

Association of lipoprotein lipase gene polymorphisms with coronary artery disease

OBJECTIVES

The purpose of this study was to test whether the HindIII (+) and PvuII (-) or (+) restriction enzyme-defined alleles are associated with angiographic coronary artery disease (CAD).

BACKGROUND

Lipoprotein lipase (LPL) plays a central role in lipid metabolism, hydrolyzing triglyceride in chylomicrons and very low density lipoproteins. Polymorphic variants of the LPL gene are common and might affect risk of CAD.

METHODS

Blood was drawn from 725 patients undergoing coronary angiography. Leukocyte deoxyribonucleic acid segments containing the genomic sites were amplified by the polymerase chain reaction and digested, and polymorphisms were identified after electrophoresis in 1.5% agarose gel.

RESULTS

In no-CAD control subjects (n = 168), HindIII (-) and (+) allelic frequencies were 28.6% and 71.4%, and (-) and (+) alleles were carried by 44.0% and 86.9% of subjects, respectively. Control PvuII (-) and (+) allelic frequencies were 41.7% and 58.3%, and (-) and (+) alleles were carried by 64.3% and 81.0%, respectively. In CAD patients (>60% stenosis; n = 483), HindIII (+) allelic carriage was increased (93.8% of patients, odds ratio [OR] = 2.28, confidence interval [CI] 1.27 to 4.00). Also, PvuII (-) allelic carriage tended to be more frequent in CAD patients (OR = 1.33, CI 0.92 to 1.93). Adjusted for six CAD risk factors and the other polymorphism, HindIII (+) carriage was associated with an OR = 2.86, CI 1.50 to 5.42, p = 0.0014, and PvulI (-) carriage, OR = 1.42, CI 0.95 to 2.12, p = 0.09. The two polymorphisms were in strong linkage disequilibrium, and a haplotype association was suggested.

CONCLUSIONS

The common LPL polymorphic allele, HindIII (+), is moderately associated with CAD, and the PvuII (-) allele is modestly associated (trend). Genetic variants of LPL deserve further evaluation as risk factors for CAD.

Associations between a polymorphism in the gene encoding glycoprotein IIIa and myocardial infarction or coronary artery disease

OBJECTIVES

The purpose of this study was to determine whether a common variant (PIA2) of the membrane glycoprotein (GP) IIIa gene is associated with myocardial infarction (MI) or coronary artery disease (CAD).

BACKGROUND

Platelet GP IIb/IIIa is believed to play a central role in MI, binding fibrinogen, cross-linking platelets and initiating thrombus formation. Genetically determined differences in binding properties of GP IIb/IIIa might result in changes in platelet activation or aggregation and affect the risk of MI or CAD.

METHODS

To determine associations (odds ratios [OR] > or =1.5 to 2.0) of genotype with MI or CAD, blood was drawn from 791 patients (pt) undergoing angiography. A 266 base pair fragment of the GP IIIa gene was amplified by the polymerase chain reaction and digested with the MspI restriction enzyme. Genotypes were identified after electrophoresis of digestion products in 1.5% agarose gel.

RESULTS

Of the 791 pt, 225 had acute (n = 143) or previous MI, and 276 did not have MI or unstable angina. The PI(A2) allele was carried by 33.8% of MI pt versus 26.9% of no-MI control subjects, OR = 1.39 (95% CI, 0.95 to 2.04, p = 0.09). Angiographically, 549 pt had severe (>60% coronary stenosis) CAD, and 170 had normal coronary arteries (<10% stenosis). The PI(A2) allele was found in 31.0% of CAD pt versus 28.2% of no-CAD control subjects, OR = 1.14 (CI, 0.78 to 1.67, p = 0.50). When adjusted for six standard risk factors, ORs were 1.47 (CI, 0.98 to 2.20, p = 0.062) for MI and 1.20 (CI, 0.80 to 1.81, p = 0.38) for CAD.

CONCLUSIONS

The PI(A2) variant of the gene encoding GP IIIa is modestly associated (OR approximately 1.5) with nonfatal MI but shows little if any association with CAD per se.

The genetics of serum lipid responsiveness to dietary interventions

CHD is a multifactorial disease that is associated with non-modifiable risk factors, such as age, gender and genetic background, and with modifiable risk factors, including elevated total cholesterol and LDL-cholesterol levels. Lifestyle modification should be the primary treatment for lowering cholesterol values. The modifications recommended include dietary changes, regular aerobic exercise, and normalization of body weight. The recommended dietary changes include restriction in the amount of total fat, saturated fat and cholesterol together with an increase in the consumption of complex carbohydrate and dietary fibre, especially water-soluble fibre. However, nutrition scientists continue to question the value of these universal concepts and the public health benefits of low-fat diets, and an intense debate has been conducted in the literature on whether to focus on reduction of total fat or to aim efforts primarily towards reducing the consumption of saturated and trans fats. Moreover, it is well known that there is a striking variability between subjects in the response of serum cholesterol to diet. Multiple studies have examined the gene-diet interactions in the response of plasma lipid concentrations to changes in dietary fat and/or cholesterol. These studies have focused on candidate genes known to play key roles in lipoprotein metabolism. Among the gene loci examined, APOE has been the most studied, and the current evidence suggests that this locus might be responsible for some of the inter-individual variability in dietary response. Other loci, including APOA4, APOA1, APOB, APOC3, LPL and CETP have also been found to account for some of the variability in the fasting and fed states.

Association of the insertion/deletion gene polymorphism of the apolipoprotein B signal peptide with myocardial infarction

The Del allele of the apolipoprotein B (apoB) signal peptide (SP) insertion/deletion (Ins/Del) polymorphism has been shown to be associated with elevated plasma levels of apoB, cholesterol and low density lipoprotein. It was the aim of the present study to analyse the relation of this gene variation to the risk of coronary artery disease (CAD) and of myocardial infarction (MI) in a population of 2259 male Caucasians, whose coronary anatomy was defined by means of coronary angiography. ApoB SP DelDel genotypes had significantly higher apoB plasma concentrations than InsIns homozygotes (P = 0.0001) and InsDel heterozygotes (P = 0.002); however, the apoB plasma levels of InsIns and InsDel genotypes were essentially the same (P = 0.54). Similar observations were made with respect to ApoB SP genotype-dependent cholesterol plasma concentrations. Since the apoB plasma level was not only associated with the apoB SP Ins/Del gene variation but also to the extent of coronary artery disease (P <0.0001), individuals with an InsIns genotype and without CAD had the lowest and subjects with a DelDel genotype and triple vessel disease the highest apoB plasma levels (P <0.0001). An association of the apoB SP Ins/Del gene variation with CAD was not detected, neither in the total population nor in low risk groups. In contrast, the gene variation was associated with MI (P <0.05). An Odds ratio of 1.18 (95% CI, 1.01-1.39) associated with the Del allele was detected in the total sample (P <0.02). In a subpopulation of individuals with low plasma triglyceride levels ( <154 mg/dl; mean value) and an DD genotype of the angiotensin I-converting enzyme insertion/deletion gene polymorphism an Odds ratio of 2.01 (1.42-3.05) was calculated (P <0.001). The present study presents evidence for a statistically significant difference in the development of MI between genotype classes of the apoB SP Ins/Del gene polymorphism.

Angiotensin-converting enzyme genotypes and risk for myocardial infarction in women

OBJECTIVES

We tested for an association between the angiotensin-converting enzyme (ACE) DD polymorphic genotype and myocardial infarction (MI) in a sample group composed exclusively of women.

BACKGROUND

The human ACE gene occurs with either an insertion (I allele) or a deletion (D allele) of a 287-base pair (bp) Alu element. Part of the variance in serum ACE levels may be accounted for by this polymorphism. Also, the DD genotype has been associated with an increased risk of MI in predominantly male populations. However, the risk in women is poorly defined.

METHODS

Genomic DNA was extracted from buffy coat blood using a phenol/chloroform method. Angiotensin-converting enzyme alleles were identified using primers to bracket the insertion region in intron 16. Amplification using polymerase chain reaction allowed identification of a 490-bp (I allele) or a 190-bp (D allele) product, or both.

RESULTS

Allelic and genotypic frequencies in control subjects were similar to those reported in mostly male populations, and frequencies of genotypes were in the Hardy-Weinberg equilibrium. In contrast, the distribution of genotypes in patients with MI diverged from the equilibrium. Specifically, DD genotypic frequency was increased in women with (n = 141) versus without (n = 338) a previous MI (39% vs. 29%, odds ratio [OR] 1.54, 95% confidence interval 1.02 to 2.32, p < 0.04). Risk was particularly increased in women <60 years old (OR 2.04, p < 0.05). In contrast, the DD genotype did not predict angiographic coronary artery disease.

CONCLUSIONS

Consistent with findings in male-dominated populations, a modest association of the ACE DD genotype with MI was found in women. The basis for this association requires further study.

A mutation in the methylenetetrahydrofolate reductase gene is not associated with increased risk for coronary artery disease or myocardial infarction

OBJECTIVES

We sought to determine whether the C677T transition in the methylenetetrahydrofolate reductase (MTHFR) gene is associated with increased risk for coronary artery disease (CAD) or myocardial infarction (MI).

BACKGROUND

Elevated plasma homocysteine has been identified as a risk factor for coronary atherosclerosis. Homocysteinemia may result from deficient MTHFR activity. A thermolabile form of MTHFR, associated with a C677T genetic transition, shows reduced activity and may be a risk factor for CAD.

METHODS

Blood was withdrawn from patients undergoing coronary angiography, and DNA was extracted by a phenol-chloroform method. Genotyping was done by polymerase chain reaction (PCR) amplification of a 198-base pair segment of the MTHFR gene that brackets nucleotide 677. The amplicon was digested with the HinfI restriction enzyme. Products were visualized after electrophoresis in 1.5% agarose with ethidium bromide.

RESULTS

Among 200 patients with a diagnosis of MI, the polymorphic allelic frequency was 33.3%, compared with 32.1% among 554 control subjects (p = 0.68); homozygosity was present in 11.5% of patients and 10.6% of control subjects (p = 0.74, odds ratio [OR] 1.09, 95% confidence interval [CI] 0.63 to 1.82). Among 510 patients with severe CAD (>60% stenosis), allelic frequency was 32.0%, compared with 34.8% for 168 subjects without CAD (<10% stenosis, p = 0.33); 11.2% of patients with CAD compared with 13.1% of control subjects were homozygous (p = 0.50, OR 0.83, 95% CI 0.5 to 1.40).

CONCLUSIONS

Patients with angiographic evidence of CAD or clinical MI do not show an increased frequency of the C677T transition in the MTHFR gene. Our findings do not support this polymorphism as a risk factor for CAD or MI in a predominantly white, well nourished population of unrestricted age.

Response to dietary fat and cholesterol and genetic polymorphisms

1. We examined common polymorphisms in the genes encoding the LDL receptor, lipoprotein lipase, apoAI, apoB, apoAIV and cholesteryl ester transfer protein and related them to changes in LDL and HDL cholesterol after high fat/high cholesterol diets. 2. The only significant association was seen with the apoIV polymorphism, which leads to a structural change in the protein. The response to fat and cholesterol in subjects with at least one apoAIV 2 allele was only 30% of that seen in subjects with the common apoIV 1 allele (P < 0.01), accounting for 6-7% of the variance in response. This confirms the results of two previous studies in which dietary cholesterol intake was changed. 3. No association were seen with polymorphisms of the other five genes examined.

Genetic determinants of atherosclerosis-related dyslipidemias and their clinical implications

New approaches to the study of the genetics of premature coronary heart disease (CHD) have been made possible by the introduction of DNA probes for the apolipoproteins, the receptors and enzymes involved in lipid transport. Initially these were used to identify restriction fragment length polymorphisms for use as genetic markers to locate genes involved in the pathogenesis of atherosclerosis. More recent developments have allowed direct analysis of etiological mutations by such methods as single stranded conformational polymorphism (SSCP) analysis and denaturing gradient gel electrophoresis (DGGE). Loci that have been incriminated by such techniques include the apolipoprotein A-I--C-III--A-IV gene cluster, the apo B gene and the lipoprotein lipase locus. It is to be anticipated that these and other techniques will eventually identify all the major determinants involved in disorders of lipid transport and the development of premature atherosclerosis.

A variant of human paraoxonase/arylesterase (HUMPONA) gene is a risk factor for coronary artery disease

Coronary artery disease (CAD) is a complex trait caused by a number of genetic and environmental factors. Recently, paraoxonase/arylesterase (PONA) enzyme has been implicated in the pathogenesis of atherosclerosis. There is a 10-40-fold variability in the activity of this enzyme among individuals. This variability is due to the presence of an A/G polymorphism in the coding region of the gene (HUMPONA). The A and G alleles code for glutamine (A genotype) and arginine (B genotype), respectively. Individuals with A genotype have a lower enzymatic activity than those with B genotype. We determined the HUMPONA genotypes and alleles in 223 patients with angiographically documented CAD and in 247 individuals in the general population. The distribution of genotypes were in Hardy-Weinberg equilibrium in patients and in controls. Genotypes A and B were present in 120 (49%) and 28 (11%) individuals in controls and in 68 (30%) and 40 (18%) patients with CAD, respectively (chi squared= 16.5, P= 0.0003). The frequency of the A allele was 0.69 in controls and 0.56 in patients (OR= 1.7, P= 0.0001). There were no differences in the distribution of HUMPONA genotypes in the subgroups of patients with restenosis, myocardial infarction, or any of the conventional risk factors for CAD as compared with corresponding subgroups. In summary, variants of the HUMPONA gene are involved in predisposition to coronary atherosclerosis.

Apolipoprotein E and Alzheimer's disease

The past year has seen widespread confirmation that the epsilon 4 allele of the apolipoprotein E gene is a major risk factor for Alzheimer's disease. The epsilon 4 allele also appears to correlate with life expectancy. This allele has been found to be present in over 50% of Alzheimer patients, regardless of whether or not they have a family history of dementia. It is not yet clear how the epsilon 4 allele mediates its actions; however, recent evidence suggests that apolipoprotein E4 may be responsible for the accelerated formation of beta-pleated amyloid from soluble beta-amyloid peptide, as is seen in the neuritic plaques of Alzheimer patients, as well as interacting with intraneuronal microtubular transport mechanisms.