Apolipoprotein B-gene DNA polymorphisms associated with myocardial infarction

Role of APOC3 3238C/G, APOB 12669G/A and SCARB1 1050C/T polymorphisms, their expression in patients of HIV-associated lipodystrophy

Apolipoproteins and Scavenger Receptor Class B1 (SCARB1) proteins are involved in the etiology of HIV-associated lipodystrophy (HIVLD). APOC3 3238C/G, APOB 12669G/A and SCARB1 1050C/T polymorphisms were linked with increased level of APOB, TG, HDL-C and risk of cardiovascular diseases (CVDs). Hence, we evaluated the genetic variations of APOC3 3238C/G, APOB 12669G/A and SCARB1 1050C/T in 187 patients of HIV (64 with HIVLD, 123 without HIVLD) and 139 healthy controls using PCR-RFLP and expression by qPCR. The genotypes of SCARB1 1050 TT and APOB 12669AA showed a risk to severe HIVLD (P = 0.23, OR = 4.95; P = 0.16, OR = 2.02). The APOC3 3238 GG genotype was associated with a lesser risk of severe HIVLD (P = 0.07, OR = 0.22). The APOB 12669 GA genotype was associated with a greater risk of HIVLD severity in patients with impaired LDL, triglyceride (TG), and cholesterol levels (P = 0.34, OR = 4.13; P = 0.25, OR = 3.64; P = 0.26, OR = 5.47). Similarly, APOB 12669AA genotypes in the presence of impaired triglyceride levels displayed the susceptibility to severity of HIVLD (P = 0.77, OR = 2.91). APOB 12669 GA genotype along with impaired HDL and cholesterol levels indicated an increased risk for HIVLD acquisition among patients without HIVLD (P = 0.42, OR = 2.42; P = 0.26, OR = 2.27). In patients with and without HIVLD, APOC3 3238CG genotypes having impaired cholesterol and glucose levels had higher risk for severity and development of HIVLD (P = 0.13, OR = 2.84, P = 0.34, OR = 1.58; P = 0.71, OR = 1.86; P = 0.14, OR = 2.30). An increased expression of APOB and SCARB1 genes were observed in patients with HIVLD (+0.51 vs. -0.93; +4.78 vs. +3.29), and decreased expression of APOC3 gene was observed in patients with HIVLD (-0.35 vs. -1.65). In conclusion, the polymorphisms mentioned above were not associated with the modulation of HIVLD. However, in the presence of impaired triglyceride, HDL, cholesterol and glucose levels, APOB 12669AA and 12669 GA, APOC3 3238CG genotypes indicated a risk for the development and severity of HIVLD.

Role of APOC3 3238C/G polymorphism in HIV-associated neurocognitive disorder

Apolipoprotein not only have a role in cholesterol metabolism but also play a role in normal brain function. Apolipoprotein gene polymorphisms are known risk factors for a number of mental and neurological disorders. The expression of brain apolipoproteins is significantly altered in several brain disorders. Therefore, we assed ApoC33238C/G polymorphism in a total of 248 patient infected with HIV (45 with HAND, 89 without HAND, 114 without ART) and 134 healthy controls using PCR-RFLP. ApoC3 3238CG, 3238GG genotypes and 3238G allele showed a non-significant increased risk for severity of HAND (P = 0.16, OR = 1.83; P = 0.32, OR = 2.78; P = 0.10, OR = 1.65) while comparing individuals with and without HAND. ApoC3 3238GG genotype and 3238G allele revealed an increased risk for disease progression when compared between HIV patients with and without ART (P = 0.55, OR = 1.76; P = 0.65, OR = 1.12) though risk could not reach statistical significance. ApoC3 3238GG genotype and 3238G allele were associated with the reduced risk of acquiring HIV infection when comparing HIV patients who are not on ART with healthy controls (P = 0.05, OR = 0.29; P = 0.04, OR = 0.66). In HIV patients on ART,ApoC3 3238GG genotype showed an increased susceptibility to development of HAND (P = 0.48, OR = 2.24) when comparing alcohol drinkers and non-drinkers however risk could not reach statistical significance. In conclusion, the genotype ApoC33238GG displayed an inclination of risk for the severity of HAND and HIV disease progression. The polymorphism of APOC3 3238C/G may have a role to reduce the risk for acquisition of HIV infection. ApoC33238GG genotype in presence of alcohol may increase susceptibility to development of HAND.

Macronutrient intake modulates impact of EcoRI polymorphism of ApoB gene on lipid profile and inflammatory markers in patients with type 2 diabetes

We sought to examine whether dietary intakes may affect the relationship between ApoB EcoRI and lipid profile, as well as serum inflammatory markers, in patients with type 2 diabetes (T2DM). This current study consisted of 648 diabetic patients. Dietary intake was calculated by a food frequency questionnaire. Biochemical markers (high-density lipoprotein (HDL), total cholesterol (TC), LDL, TG, CRP, IL-18, PGF2α) were measured based on standard protocols. Genotyping of the Apo-B polymorphisms (rs1042031) was conducted by the PCR–RFLP method. The gene-diet interactions were evaluated using GLMs. In comparison to GG homozygotes, A-allele carriers with above the median -CHO intake (≥ 54 percent of total energy) had considerably greater TC and PGF2a concentrations. Furthermore, as compared to GG homozygotes, A-allele carriers with above the median protein intake (≥ 14 percent of total energy) had higher serum levels of TG (P = 0.001), CRP (P = 0.02), TG/HDL (P = 0.005), and LDL/HDL (P = 0.04) ratios. Moreover, A-allele carriers with above the median total fat intake (≥ 35 percent of total calories) had significantly higher TC level (P = 0.04) and LDL/HDL (P = 0.04) ratios compared to GG homozygotes. Furthermore, when compared to GG homozygotes, A-allele carriers who consumed above the median cholesterol (> 196 mg) had greater TG (P = 0.04), TG/HDL (P = 0.01) ratio, and IL-18 (P = 0.02). Furthermore, diabetic patients with the GA, AA genotype who consume above the median cholesterol had lower ghrelin levels (P = 0.01). In terms of LDL/HDL ratio, ApoB EcoRI and dietary intakes of specific fatty acids (≥ 9 percent for SFA and ≥ 12 percent for MUFA) had significant interaction. LDL/HDL ratio is greater in A-allele carriers with above the median SFA intake (P = 0.04), also when they consumed above the median MUFA this association was inverse (P = 0.04). Our study showed that plasma lipid levels in participants carrying the (AA or AG) genotype were found to be more responsive to increasing the percentage of energy derived from dietary fat, CHO, protein, SFA, and cholesterol consumption. Therefore, patients with a higher genetic susceptibility (AA or AG) seemed to have greater metabolic markers with a higher percentage of macronutrient consumption. Also, ApoB EcoRI correlations with metabolic markers might be attenuated with above the median MUFA consumption.

Etiologic Puzzle of Coronary Artery Disease: How Important Is Genetic Component?

In the modern era, coronary artery disease (CAD) has become the most common form of heart disease and, due to the severity of its clinical manifestations and its acute complications, is a major cause of morbidity and mortality worldwide. The phenotypic variability of CAD is correlated with the complex etiology, multifactorial (caused by the interaction of genetic and environmental factors) but also monogenic. The purpose of this review is to present the genetic factors involved in the etiology of CAD and their relationship to the pathogenic mechanisms of the disease. Method: we analyzed data from the literature, starting with candidate gene-based association studies, then continuing with extensive association studies such as Genome-Wide Association Studies (GWAS) and Whole Exome Sequencing (WES). The results of these studies revealed that the number of genetic factors involved in CAD etiology is impressive. The identification of new genetic factors through GWASs offers new perspectives on understanding the complex pathophysiological mechanisms that determine CAD. In conclusion, deciphering the genetic architecture of CAD by extended genomic analysis (GWAS/WES) will establish new therapeutic targets and lead to the development of new treatments. The identification of individuals at high risk for CAD using polygenic risk scores (PRS) will allow early prophylactic measures and personalized therapy to improve their prognosis.

2019 George Lyman Duff Memorial Lecture: Three Decades of Examining DNA in Patients With Dyslipidemia

Dyslipidemias include both rare single gene disorders and common conditions that have a complex underlying basis. In London, ON, there is fortuitous close physical proximity between the Lipid Genetics Clinic and the London Regional Genomics Centre. For >30 years, we have applied DNA sequencing of clinical samples to help answer scientific questions. More than 2000 patients referred with dyslipidemias have participated in an ongoing translational research program. In 2013, we transitioned to next-generation sequencing; our targeted panel is designed to concurrently assess both monogenic and polygenic contributions to dyslipidemias. Patient DNA is screened for rare variants underlying 25 mendelian dyslipidemias, including familial hypercholesterolemia, hepatic lipase deficiency, abetalipoproteinemia, and familial chylomicronemia syndrome. Furthermore, polygenic scores for LDL (low-density lipoprotein) and HDL (high-density lipoprotein) cholesterol, and triglycerides are calculated for each patient. We thus simultaneously document both rare and common genetic variants, allowing for a broad view of genetic predisposition for both individual patients and cohorts. For instance, among patients referred with severe hypertriglyceridemia, defined as ≥10 mmol/L (≥885 mg/dL), <1% have a mendelian disorder (ie, autosomal recessive familial chylomicronemia syndrome), ≈15% have heterozygous rare variants (a >3-fold increase over normolipidemic individuals), and ≈35% have an extreme polygenic score (a >3-fold increase over normolipidemic individuals). Other dyslipidemias show a different mix of genetic determinants. Genetic results are discussed with patients and can support clinical decision-making. Integrating DNA testing into clinical care allows for a bidirectional flow of information, which facilitates scientific discoveries and clinical translation.

Population-based Study of Risk Polymorphisms Associated with Vascular Disorders and Dementia

Introduction:

Cardiovascular and neurodegenerative disorders are among the major causes of mortality in the developed countries. Population studies evaluate the genetic risk, i.e. the probability of an individual carrying a specific disease-associated polymorphism. Identification of risk polymorphisms is essential for an accurate diagnosis or prognosis of a number of pathologies.

Aims:

The aim of this study was to characterize the influence of risk polymorphisms associated with lipid metabolism, hypertension, thrombosis, and dementia, in a large population of Spanish individuals affected by a variety of brain and vascular disorders as well as metabolic syndrome.

Material & Method:

We performed a cross-sectional study on 4415 individuals from a widespread regional distribution in Spain (48.15% males and 51.85% females), with mental, neurodegenerative, cerebrovascular, and metabolic disorders. We evaluated polymorphisms in 20 genes involved in obesity, vascular and cardiovascular risk, and dementia in our population and compared it with representative Spanish and European populations. Risk polymorphisms in ACE, AGT(235), IL6(573), PSEN1, and APOE (specially the APOE-ε4 allele) are representative of our population as compared to the reference data of Spanish and European individuals.

Conclusion:

The significantly higher distribution of risk polymorphisms in PSEN1 and APOE-ε4 is characteristic of a representative number of patients with Alzheimer’s disease; whereas polymorphisms in ACE, AGT(235), and IL6(573), are most probably related with the high number of patients with metabolic syndrome or cerebrovascular damage.

Genetic Risk Factors in Cerebrovascular Disorders and Cognitive Deterioration

INTRODUCTION

The study of variations in genes involved in the different events that trigger the atherogenic process, such as lipid metabolism (modification of LDL-cholesterol), endothelial function and hypertension, immune response (recruitment of macrophages and foam cell formation) and stability of atherosclerotic plaques (thrombosis), established the risk for suffering a vascular disorder. A total of 2455 cases over 50 years of age were genotyped for a panel of 19 SNPs in 15 genes encoding for proteins involved in the atherogenic process. This study shows the relevance of polymorphisms in APOB (odds ratio (OR), 1.17; 95% confidence interval (95% CI), 0.74-1.85), APOC3 (OR, 1.33; 95% CI, 0.82-2.17) and APOE (OR, 1.75; 95% CI, 1.09-2.80), as genetic risk markers for hypercholesterolemia; polymorphisms in ACE (OR, 1.68; 95% CI, 0.32-8.77) and AGT (OR, 1.74; 95% CI, 0.97-3.14) for hypertension; and in APOE*3/*4 (OR, 2.06; 95% CI, 1.70-2.51) and APOE*4/*4 (OR, 3.08; 95% CI, 1.85-5.12) as unambiguous markers of dementia.

RESULT

Our results also showed the transversal importance of proinflammatory cytokines in different stages of atherogenesis, with special relevance of IL6 (OR, 1.39; 95% CI, 0.56-3.49) and TNF (OR, 1.40; 95% CI, 0.92-2.15) related to hypercholesterolemia and hypertension. The set of markers involved in this genetic risk panel makes it a powerful tool in the management of patients with different vascular disorders.

Associations of the APOB rs693 and rs17240441 polymorphisms with plasma APOB and lipid levels: a meta-analysis

BACKGROUND

The associations of the apolipoprotein B gene (APOB) rs693 and rs17240441 polymorphisms with plasma levels of APOB and lipids have been widely explored, but the results were inconclusive. This meta-analysis aimed to clarify the associations of the rs693 and rs17240441 polymorphisms with fasting APOB and lipid levels.

METHODS

Sixty-one studies (50,018 subjects) and 23 studies (8425 subjects) were respectively identified for the rs693 and rs17240441 polymorphisms by searching in PubMed, Google Scholar, Web of Science, Cochrane Library, Wanfang, VIP and CNKI databases. The following information was collected for each study: first author, age, gender, ethnicity, health condition, sample size, genotyping, lipid assay method, mean and standard deviation or standard error of APOB and lipid variables by genotypes. A dominant model was used for this meta-analysis.

RESULTS

The carriers of the rs693 variant allele (T) had higher levels of APOB [standardized mean difference (SMD) = 0.26, 95% confidence interval (CI) = 0.16-0.36, P < 0.01], triglycerides (TG) (SMD = 0.12, 95% CI = 0.05-0.20, P < 0.01), total cholesterol (TC) (SMD = 0.24, 95% CI = 0.17-0.30, P < 0.01) and low-density lipoprotein cholesterol (LDL-C) (SMD = 0.22, 95% CI = 0.14-0.30, P < 0.01), and lower levels of high-density lipoprotein cholesterol (HDL-C) (SMD = -0.06, 95% CI = -0.11-0.01, P = 0.01) than the non-carriers. The carriers of the rs17240441 deletion allele had higher levels of APOB (SMD = 0.13, 95% CI = 0.06-0.20, P < 0.01), TC (SMD = 0.17, 95% CI = 0.07-0.26, P < 0.01) and LDL-C (SMD = 0.15, 95% CI = 0.07-0.23, P < 0.01) than the non-carriers.

CONCLUSIONS

The rs693 polymorphism is significantly associated with higher levels of APOB, TG, TC and LDL-C, and lower levels of HDL-C. The rs17240441 polymorphism is significantly associated with higher levels of APOB, TC and LDL-C. Further studies are needed to elucidate the underlying mechanisms.

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.

ApoB gene SpIns/Del, XbaI polymorphisms and myocardial infarction: a meta-analysis of 7169 participants

BACKGROUND

Apolipoprotein B (ApoB) gene signal peptide insertion/deletion (SpIns/Del, I/D) and XbaI polymorphisms have been associated with susceptibility to myocardial infarction (MI). However, the results of studies on this association are still controversial.

OBJECTIVE AND METHODS

This study explored reports published from 1986 to 2008 regarding the association of ApoB gene SpIns/Del and XbaI polymorphisms with MI. A meta-analysis including 7169 participants from 19 individual studies was performed. The pooled odds ratios (ORs) and their corresponding 95% confidence intervals (95% CIs) were evaluated by fixed-effect or random-effect models.

RESULTS

A significant relationship between ApoB SpIns/Del gene polymorphism and MI was found under allelic (OR: 1.270, 95% CI: 1.090-1.480, P = 0.002), recessive (OR: 1.360, 95% CI: 1.130-1.630, P = 0.0009), dominant (OR: 1.091, 95% CI: 1.037-1.146, P = 0.001), homozygous (OR: 1.610, 95% CI: 1.330-1.950, P <0.00001) and heterozygous (OR: 1.081, 95% CI: 1.020-1.146, P = 0.009) genetic models. A marginal relationship between ApoB XbaI polymorphism and MI was found under a dominant genetic model (OR: 1.083, 95% CI: 1.004-1.168, P = 0.039). No significant association was detected under other genetic models (P >0.05). However, in the non-European subgroup analysis, increased MI risk emerged under all genetic models (P <0.05).

CONCLUSION

ApoB SpIns/Del gene polymorphism was positively associated with increased MI risk. D allele and DD genotype carriers might be predisposed to MI susceptibility. The ApoB XbaI gene polymorphism locus had a significant positive association with increased MI risk only in the non-European population. T allele and TT genotype carriers might be susceptible to MI in the non-European population. On the contrary, the ApoB gene XbaI restriction fragment length polymorphism was not associated with increased MI risk in the entire population, particularly in the European population.

The APOB gene polymorphism in the pathogenesis of gallstone disease in pre- and postmenopausal women

Aim of the study

The decrease in estrogen levels in the postmenopausal period changes the lipid profile by the expression of hepatic genes related to metabolism of cholesterol and bile acid synthesis that could be important in the pathogenesis of cholelithiasis. The aim of the study was to determine the APOB gene 7673C>T and 12669G>A polymorphisms in the pathogenesis of gallstones and analysis of the composition of gallstones in pre- and postmenopausal women.

Material and methods

The study group consisted of 94 women qualified to the laparoscopic cholecystectomy while the control group consisted of 81 women in whom gallstones and other changes in the bile ducts were excluded. Gallstones composition analysis was performed using commercially available assays. The prevalence of the APOB gene polymorphisms was determined using the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP).

Results

When assessing the composition of gallstones in pre- and postmenopausal women, we observed differences in the studied parameters. Analysis of genetic variants of APOB gene 7673C>T and 12669G>A polymorphisms showed no significant statistical differences between studied groups and controls.

Conclusions

Analysis of 7673C>T and 12669G>A polymorphisms showed no relationship between specific genetic variants and the risk of gallstones in pre- and postmenopausal women, pointing to the fact that the investigated polymorphisms are not relevant as prognostic factors in gallstone disease in the Caucasian population. Because of the possible contribution of a variety of factors in gallstones pathogenesis the studies are required to take account of additional environmental factors, what may indicate different occurrence between investigated polymorphisms, gallstone disease development and gallstones composition in Caucasians.

Apolipoprotein Gene Polymorphisms (APOB, APOC111, APOE) in the Development of Coronary Heart Disease in Ethnic Groups of Kazakhstan

BACKGROUND

Previous Analysis of polymorphism of genes associated with the development of coronary heart disease (CHD) reveals that the frequency distribution of genotypes and alleles depends on the ethnic characteristics of the populations under study. Further impetus is derived from the well -established links between alcoholism (high prevalence in Kazakhstan region) and cardiovascular disorders.

OBJECTIVES

The purpose of this study was to examine a number of apolipoprotein gene polymorphisms and correlate these alleles with changes of lipid profile in CHD patients of Kazakh and Uyghur nationalities.

METHODS

Four-Hundred Forty Eight (448) males of Kazakh and Uyghur nationalities residing in Kazakhstan were evaluated and genotyped. The age range of these subjects was 30-55 years which included both afflicted and controls. Specifically, 161- Kazakhs suffered from myocardial infarction compared to 112 health controls; 80- Uyghurs suffered from CHD compared to 95 health controls. Blood lipid profiles were examined in the total cohort. Genotyping was performed by polymerase chain reaction (PCR) using oligonucleotide primers identifying; ApoB; ApoC111; and APOE gene polymorphisms.

RESULTS

Initial screening revealed a significant inter-ethnic difference on the frequency of alleles associated with both the ApoB and APOE genes. We found that the X1 ApoB gene polymorphism is overrepresented in healthy Kazakhs relative to Uyghurs [86.4% in Kazakhs vs. 69.4% in Uyghurs]. Moreover, we found that the E4APOE allele was also overrepresented in healthy Kazakhs relative to Uyghurs [16.8% in Kazakhs vs. 9.5% in Uyghurs]. There was a significant relationship of polymorphisms of APOE such as ApoB and ApoC 111 with the value of lipid indices in Kazakhs. Additionally, we found that the E4 allele of the APOE gene also correlated with the value of lipid indices in Kazakhs. Further evaluation showed that the X2 allele of the ApoB and the S2 allele of the ApoCIII gene significantly associated with the lipid indices of Uyghurs.

CONCLUSION

This systematic investigation confirms the association of various alleles of Apolipoprotein gene polymorphisms and contribution to aberrant lipid metabolism. Putatively at least in our population we are proposing that certain gene polymorphisms of Apolipoprotein genes such as ApoB; ApoC111; APOE ; X2 of ApoB; and S2 of ApoCIII differentially represented in either Kazakhs or Uyghurs are genetic markers of hypertriglyceridemia.

Apolipoproteins AI/B/E gene polymorphism and their plasma levels in patients with coronary artery disease in a tertiary care-center of Eastern India

AIM

The present study was designed to investigate whether the three-apolipoprotein (AI, B, E) gene polymorphisms were related to alter their plasma protein levels and hence associated to coronary artery disease (CAD).

METHODS

We determined distribution of MspI apo AI, EcoRI apo B, HhaI apo E gene polymorphisms, plasma apolipoproteins and lipids levels among 150 patients having CAD admitted to the Department of Cardiology, N.R.S. Medical College & Hospital, Kolkata, India during June 2010-June 2012 and 150 age sex matched healthy controls.

RESULTS

We found that ApoAI concentration of studied population was significantly different in each genotypes of -75 G/A apo AI (p < 0.0001) gene polymorphism. A significant association was found in multivariate analysis for the genotypes with apo E4 allele [odds ratio (OR): 3.639; 95% confidence interval (CI): 1.019-12.995, p = 0.040] with four conventional risk factors (i.e. smoking, low-density lipoprotein, ApoAI and ApoB) with CAD. In contrast E2 allele has reverse effect, but the genotypes with apo E2 allele was no longer significant in the multivariate model (OR: 1.788; 95% CI: 0.400-8.001, p = 0.447) where as being significant in univariate analysis (OR: 0.219; 95% CI: 0.087-0.552, p = 0.001).

CONCLUSIONS

Our findings suggest that the polymorphisms apo AI MspI and apo B EcoRI do not seem to affect CAD. But the genotype with E4 allele of apo E gene independent of other risk factors is associated with this disease.

The roles of genetic polymorphisms and human immunodeficiency virus infection in lipid metabolism

Dyslipidemia has been frequently observed among individuals infected with human immunodeficiency virus type 1 (HIV-1), and factors related to HIV-1, the host, and antiretroviral therapy (ART) are involved in this phenomenon. This study reviews the roles of genetic polymorphisms, HIV-1 infection, and highly active antiretroviral therapy (HAART) in lipid metabolism. Lipid abnormalities can vary according to the HAART regimen, such as those with protease inhibitors (PIs). However, genetic factors may also be involved in dyslipidemia because not all patients receiving the same HAART regimen and with comparable demographic, virological, and immunological characteristics develop variations in the lipid profile. Polymorphisms in a large number of genes are involved in the synthesis of structural proteins, and enzymes related to lipid metabolism account for variations in the lipid profile of each individual. As some genetic polymorphisms may cause dyslipidemia, these allele variants should be investigated in HIV-1-infected patients to identify individuals with an increased risk of developing dyslipidemia during treatment with HAART, particularly during therapy with PIs. This knowledge may guide individualized treatment decisions and lead to the development of new therapeutic targets for the treatment of dyslipidemia in these patients.

Genetic variants associated with VLDL, LDL and HDL particle size differ with race/ethnicity

Specific constellations of lipoprotein particle features, reflected as differences in mean lipoprotein particle diameters, are associated with risk of insulin resistance (IR) and cardiovascular disease (CVD). The associations of lipid profiles with disease risk differ by race/ethnicity, the reason for this is not clear. We aimed to examine whether there were additional genetic differences between racial/ethnic groups on lipoprotein profile. Genotypes were assessed using the Affymetrix 6.0 array in 817 related Caucasian participants of the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN). Association analysis was conducted on fasting mean particle diameters using linear models, adjusted for age, sex and study center as fixed effects, and pedigree as a random effect. Replication of associations reaching P < 1.97 × 10(-05) (the level at which we achieved at least 80% power to replicate SNP-phenotype associations) was conducted in the Caucasian population of the Multi-Ethnic Study of Atherosclerosis (MESA; N = 2,430). Variants which replicated across both Caucasian populations were subsequently tested for association in the African-American (N = 1,594), Chinese (N = 758), and Hispanic (N = 1,422) populations of MESA. Variants in the APOB gene region were significantly associated with mean VLDL diameter in GOLDN, and in the Caucasian and Hispanic populations of MESA, while variation in the hepatic lipase (LIPC) gene was associated with mean HDL diameter in both Caucasians populations only. Our findings suggest that the genetic underpinnings of mean lipoprotein diameter differ by race/ethnicity. As lipoprotein diameters are modifiable, this may lead new strategies to modify lipoprotein profiles during the reduction of IR that are sensitive to race/ethnicity.

Role of the APOB Gene Polymorphism (c.12669G>A, p. Gln4154Lys) in Coronary Artery Disease in the Indian Punjabi Population

High concentration of apolipoprotein B (apoB) is a risk factor for coronary artery disease (CAD). The association of the APOB gene polymorphism c.12669G>A, p.Gln4154Lys with the risk of CAD varies considerably in different populations. The present study represents the first investigation regarding the role of this APOB gene polymorphism with CAD in the Indian Punjabi population. We have studied the APOB gene polymorphism c.12669G>A, p.Gln4154Lys and its relationship with lipid, apoB, low-density lipoprotein (LDL) heterogeneity and oxidation in subjects suffering from CAD. The study was conducted on 87 patients with CAD; 75 healthy subjects served as controls. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to determine the DNA polymorphism in the APOB gene. Frequency of R- (mutant) allele was significantly high (p <0.05) in CAD patients when compared to controls. Variations in serum lipid levels in the R+R+ and R+R- APOB genotypes were insignificant (p >0.05). However, serum apoB levels were significantly raised (p <0.05) in CAD patients with the R+R- genotype as compared to those with the R+R+ APOB genotype. Coronary artery disease patients had raised significantly raised (p <0.01) Log triglyceride/high density lipoprotein-cholesterol (HDL-C) ratio, apoB carbonyl content and increased malondialdehyde-low density lipoprotein (MDA-LDL levels, irrespective of APOB genotype as compared to controls. Carriers of the R- allele are at higher risk of CAD, probably because of elevated serum apoB levels in the Indian Punjabi population. Overall, it may be concluded that the R- allele might be associated with increased susceptibility towards CAD development in the Indian Punjabi population, and one of the linking factor is the elevation in serum apoB levels. However, this association needs further evaluation in a larger population. Secondly, the robust mechanism behind the positive association of the R- allele with raised serum apoB levels needs to be explored, which might be helpful in the strengthening the observed results.

XbaI polymorphisms of apolipoprotein B gene: Another risk factor of gallstone formation after radical gastrectomy

AIM: To prospectively investigate the association between the XbaI polymorphisms of apolipoprotein B (APOB) gene and gallstone formation following gastrectomy.

METHODS: The study was conducted between January 2005 and December 2006. A total of 186 gastric cancer patients who had undergone radical gastrectomy were grouped according to XbaI polymorphisms of APOB gene (X⁺X^- group, n = 24 and X^-X^- group, n = 162) and compared. The XbaI polymorphisms of APOB gene were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS: The incidence of gallstone was significantly higher in the X⁺X^- group than in the X^-X^- group [54.2% vs 9.3%, RR = 5.85 (2.23-15.32), P < 0.001]. The serum levels of total cholesterol (TC) and low-density lipoprotein (LDL) were higher in the X⁺X^- than in the X^-X^- group (4.02 ± 1.12 vs 3.48 ± 0.88, P = 0.004 before surgery and 3.88 ± 1.09 vs 3.40 ± 0.86, P = 0.008 after surgery). LDL was 2.21 ± 0.96 vs 1.89 ± 0.84 (P = 0.042) before surgery and 2.09 ± 0.95 vs 1.72 ± 0.85 (P = 0.029) after surgery in the two groups. No relationship was found between XbaI polymorphisms and gallbladder motility.

CONCLUSION: In Chinese patients after radical gastrectomy, X⁺ allele of APOB gene is another risk factor for the development of gallstone besides the gallbladder motility disorder after surgery.

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.

Molecular genetics of myocardial infarction

Myocardial infarction (MI) is an important clinical problem because of its large contribution to mortality. The main causal and treatable risk factors for MI include hypertension, hypercholesterolemia or dyslipidemia, diabetes mellitus, and smoking. In addition to these risk factors, recent studies have shown the importance of genetic factors and interactions between multiple genes and environmental factors. Disease prevention is an important strategy for reducing the overall burden of MI, with the identification of markers for disease risk being key both for risk prediction and for potential intervention to lower the chance of future events. Although genetic linkage analyses of families and sib-pairs as well as candidate gene and genome-wide association studies have implicated several loci and candidate genes in predisposition to coronary heart disease (CHD) or MI, the genes that contribute to genetic susceptibility to these conditions remain to be identified definitively. In this review, we summarize both candidate loci for CHD or MI identified by linkage analyses and candidate genes examined by association studies. We also review in more detail studies that have revealed the association with MI or CHD of polymorphisms in MTHFR, LPL, and APOE by the candidate gene approach and those in LTA and at chromosomal region 9p21.3 by genome-wide scans. Such studies may provide insight into the function of implicated genes as well as into the role of genetic factors in the development of CHD and MI.

Influence of apolipoprotein B signal peptide insertion/deletion polymorphism on serum lipids and apolipoproteins in a Chinese population

Insertion/deletion polymorphism of the apo B gene encoding signal peptide and its influence on serum lipids and apolipoproteins was studied in 269 Chinese of both sexes in Singapore. The frequency of the Del allele was found to be 0.20, which is significantly lower than that in Caucasians (France) (0.34). The distribution of genotypes of ins/del polymorphism was at Hardy-Weinberg equilibrium in this population. There was an excess of individuals with the deletion allele in hypercholesterolemic subjects compared to those with normal cholesterol levels (P less than 0.05). All the lipid and apolipoprotein values were regressed for age, sex and BMI by multiple regression analysis. Individuals with one or two del alleles had significantly higher levels of serum total cholesterol (248.8 +/- 13.0 and 255.4 +/- 20.4 mg/dl, respectively) compared to those in individuals with only the Ins allele (218.4 +/- 7.8 mg/dl) (P less than 0.05). Serum LDL cholesterol level was also significantly higher in individuals with del allele (173.4 +/- 11.7 mg/dl) compared to that in those without the del allele (141.1 +/- 7.4 mg/dl) (P = 0.02). The percentages of sample variance of different lipid traits explained by apo B signal peptide polymorphism were estimated by analysis of variance (ANOVA) with sex, age and BMI as covariates. 2.3% of variability of serum total cholesterol (F = 3.27, P = 0.040) and 2.8% of LDL cholesterol (F = 3.87, P = 0.023) could be explained by the ins/del polymorphism of the apo B signal peptide gene.

Higher alleles of apolipoprotein B gene 3' VNTR: Risk for gallstone disease

BACKGROUND

Imbalance in cholesterol homeostasis may lead to gallstone disease. Apolipoprotein B is sole component of low-density lipoprotein and plays an important role in cholesterol metabolism. The present study was carried out to explore the association of APOB 3' VNTR, exon 26 XbaI and signal peptide insertion/ deletion polymorphisms with gallstone disease. 214 ultrasonographically proven gallstone patients and 322 healthy, age and sex matched controls were taken for the study. Genotyping was done using PCR followed by polyacrylamide gel electrophoresis for VNTR and insertion/ deletion analysis. For APOB XbaI polymorphism PCR product was digested with XbaI restriction enzyme, followed by agarose gel electrophoresis. All statistical analyses were done using SPSS v11.5. Higher repeat alleles of APOB 3' VNTR polymorphism were more frequent in gallstone patients than in controls. Alleles with more than 57 repeats were present only in patient group. Long (L) alleles with repeat higher than 49, were significantly higher (P=0.000; OR=3.705, 95% CI 2.577-5.326) and medium (M) alleles were lower (P=0.000; OR=0.406, 95% CI 0.304-0.542) in patients than in controls. To nullify the effect of gender, data was further stratified into male and female population. APOB 3' VNTR, L alleles were imposing risk and M alleles were protective in both male and female population. APOBXbaI and insertion/deletion polymorphisms were not found to be associated with the gallstone disease. Longer alleles of APOB 3' VNTR occur more frequently in gallstone patients, and may be an important risk factor for the development of gallstone disease. APOB XbaI and signal peptide insertion/deletion polymorphisms may not be contributing to the risk for gallstone disease.

Effect of the 3'APOB-VNTR polymorphism on the lipid profiles in the Guangxi Hei Yi Zhuang and Han populations

BACKGROUND

Apolipoprotein (Apo) B is the major component of low-density lipoprotein (LDL), very low-density lipoprotein (VLDL) and chylomicrons. Many genetic polymorphisms of the Apo B have been described, associated with variation of lipid levels. However, very few studies have evaluated the effect of the variable number of tandem repeats region 3' of the Apo B gene (3'APOB-VNTR) polymorphism on the lipid profiles in the special minority subgroups in China. Thus, the present study was undertaken to study the effect of the 3'APOB-VNTR polymorphism on the serum lipid levels in the Guangxi Hei Yi Zhuang and Han populations.

METHODS

A total of 548 people of Hei Yi Zhuang were surveyed by a stratified randomized cluster sampling. The epidemiological survey was performed using internationally standardized methods. Serum lipid and apolipoprotein levels were measured. The 3'APOB-VNTR alleles were determined by polymerase chain reaction (PCR) followed by electrophoresis in polyacrylamide gels, and classified according to the number of repeats of a 15-bp hypervariable elements (HVE). The sequence of the most common allele was determined using the PCR and direct sequencing. The possible association between alleles of the 3'APOB-VNTR and lipid variables was examined. The results were compared with those in 496 people of Han who also live in that district.

RESULTS

Nineteen alleles ranging from 24 to 64 repeats were detected in both Hei Yi Zhuang and Han. HVE56 and HVE58 were not be detected in Hei Yi Zhuang whereas HVE48 and HVE62 were totally absent in Han. The frequencies of HVE26, HVE30, HVE46, heterozygote, and short alleles (< 38 repeats) were higher in Hei Yi Zhuang than in Han. But the frequencies of HVE34, HVE38, HVE40, homozygote, and long alleles (> or = 38 repeats) were lower in Hei Yi Zhuang than in Han (P < 0.05-0.01). The levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and Apo B in Hei Yi Zhuang but not in Han were higher in VNTR-LS (carrier of one long and one short alleles) than in VNTR-LL (the individual carrying two long alleles) genotypes. The levels of TC, triglycerides (TG), LDL cholesterol, and Apo B in Hei Yi Zhuang were higher in both HVE34 and HVE36 alleles than in HVE32 allele. The levels of TC, TG, HDL-C and Apo B in Hei Yi Zhuang were also higher in homozygotes than in heterozygotes. There were no significant differences in the detected lipid parameters between the VNTR-SS (carrier of two short alleles) and VNTR-LS or VNTR-LL genotypes in both ethnic groups.

CONCLUSION

There were significant differences of the 3'APOB-VNTR polymorphism between the Hei Yi Zhuang and Han populations. An association between the 3'APOB-VNTR polymorphism and serum lipid levels was observed in the Hei Yi Zhuang but not in the Han populations.

Apolipoprotein B gene variants are involved in the determination of blood glucose and lipid levels in patients with non-insulin dependent diabetes mellitus

We have examined the frequency of the EcoRI, XbaI and MspI RFLPs of the apolipoprotein B (apo B) gene in 110 type 2 diabetic patients and 91 healthy control subjects in order to ascertain whether variation in this gene may influence the development of non-insulin dependent diabetes mellitus (type 2 diabetes). Serum lipids including total-cholesterol (T-Chol), triacylglycerol (TAG), apolipoprotein E (apo E), apolipoprotein AI (apo AI), apolipoprotein B and lipoprotein (a) (Lp(a)) were analysed. Genomic DNA was extracted and the apo B polymorphic regions amplified by the polymerase chain reaction. Regions carrying EcoRI, XbaI, and MspI restriction sites present in the apo B gene were amplified and digested separately by the respective enzymes. No significant difference for genotypic frequencies was observed for the EcoRI, XbaI and MspI restriction sites in type 2 diabetic patients as compared to controls. Type 2 diabetic patients and controls with EcoRI +/+ and XbaI +/+ genotypes had higher apo E levels. The MspI +/+ genotype is more frequent in the patient and control groups with elevated T-Chol. Furthermore, the EcoRI -/-, XbaI -/-, and MspI +/+ genotypes were found to be significantly more frequent in type 2 diabetic patients with higher blood glucose levels. This study identifies the apo B gene polymorphisms in modulating plasma lipid/lipoprotein and glucose levels in patients with type 2 diabetes.

Genetic variations of the apolipoprotein B gene in Turkish patients with coronary artery disease

BACKGROUND

The results of studies that clarify the association of genetic markers at the apolipoprotein B (apo B) gene (EcoRI and XbaI polymorphisms) with coronary artery disease (CAD) are not consistent and suggest that the effect is context dependent (dependent on ethnicity and sex). The present study represents the first investigation of the apo B gene polymorphisms in Turkish patients with CAD and their influence on lipid levels.

AIM

The study investigated the association of apo B gene EcoRI and XbaI polymorphisms with CAD and with variation in lipid levels (total cholesterol (T-Chol), high-density lipoprotein cholesterol (HDL-Chol), low-density lipoprotein cholesterol (LDL-Chol), and triacylglycerol (TAG)).

SUBJECTS AND METHODS

The study group was composed of 150 individuals with angiographically documented CAD and 100 angiographically proven to be healthy controls. PCR-RFLP was used to determine the DNA polymorphisms of the apo B gene.

RESULTS

The frequencies of apo B genotypes detected with EcoRI (AA, AG, GG) and XbaI (CC, CT, TT) did not differ significantly between case and control subjects. A significant association between EcoRI genotypes and T-Chol (p < or = 0.05), and LDL-Chol (p < or = 0.001) was observed only in CAD patients. Patients with the AA genotype had higher levels of serum T-Chol and LDL-Chol compared with AG. With logistic regression analysis the XbaI TT genotype was found to be associated with CAD prevention. However, no significant differences in lipid variables were determined for the XbaI polymorphisms in the patients with CAD.

CONCLUSIONS

Apo B EcoRI genotypes were not found as risk factors for CAD, whereas XbaI TT genotype was detected to prevent against CAD in our study group.

How frequent is altered gene expression among susceptibility genes to human complex disorders?

It is regularly thought that human complex disorder susceptibility genes show differences in gene expression between normal and pathologic tissues. Thus, differences of transcript amounts could be indicative of complex disorder susceptibility loci and, therefore, be used for the discovery or the validation of human susceptibility genes to complex disorders/traits. Whether human complex disorder susceptibility genes effectively display differences in transcript amounts was tested by meta-analysis of the published literature comparing transcript amounts of well-validated human susceptibility genes to complex traits/disorders. A total of 94 gene-disease associations, which were studied in at least three independent studies and showed strong evidence of positive association, were analyzed. For 23 out of these 94 well-validated gene-disease associations, 120 gene expression studies comparing normal and pathologic human tissues were found. For 60 out of these 120 gene expression studies, the difference of level expression between normal and pathologic human tissues was statistically significant. This result was highly significant, as only 6 significant results were expected randomly under the null hypothesis (P < 10(-112)). A large excess of replication studies were also found, which were in agreement with the original report (P = 6 x 10(-4)). However, the overall level of expression change between normal and pathologic human tissues was relatively moderate, because only 36 (60%) and 19 (31.6%) out of the 62 statistically significant gene expression studies reached 2- or 3-fold changes in expression level, respectively. The present meta-analysis confirms statistical differences of expression levels between normal and pathologic human tissues for human susceptibility genes to complex traits/disorders. However, the levels of differences in transcript amounts appear to be relatively weak. These findings rationalize the use of gene expression for the discovery/validation of human susceptibility genes, but the weak differences of expression typically found should be taken into account for the design of such studies.

Apolipoprotein B-gene DNA polymorphisms (Xbal andEcoRI), serum lipids, and apolipoproteins in healthy Chinese

The frequency of restriction fragment length polymorphisms (RFLPs) of the apolipoprotein B (apo B) gene, detected by XbaI and EcoRI, and their influence on serum lipids and apolipoproteins were studied in healthy Chinese of both sexes in Singapore. A total of 221 subjects (150 males, 71 females) were investigated for the XbaI and 159 subjects for the EcoRI polymorphisms, while serum lipids and apolipoprotein levels were available for 196 subjects. The frequency of the X2 allele was found to be significantly lower in the Chinese than that reported in Caucasians from the United Kingdom (0.09 vs. 0.51, P less than 0.001). The haplotype frequencies were also significantly different between the Chinese and Caucasians with a higher frequency of X1R1 in the former compared to the latter (0.85 vs. 0.34, P less than 0.0001). The distribution of RFLP genotypes at both of the restriction sites was at Hardy-Weinberg equilibrium in all groups. The influence of the apo B RFLPs on serum lipids and apolipoprotein levels (apo AI, AII, and B) was studied by both residual and multiple regression analyses considering age, sex, body mass index (BMI), and genotypes as independent variables in all possible combinations. No association was observed between the apo B genotypes and serum lipids or apolipoprotein levels except for high density lipoprotein cholesterol (HDLC), apo AI and AII, with the X2 being associated with significantly lower levels of HDLC as well as apo AI and AII, the effect being stronger in males. These data raise the possibility that the mechanism of reported association between apo B polymorphism and coronary artery disease may be through effects on HDLC.

Exploration of multilocus effects in a highly polymorphic gene, the apolipoprotein (APOB) gene, in relation to plasma apoB levels

A detailed exploration of all the polymorphisms in candidate genes is required to better characterize the relationship between gene variability and complex traits. We propose a novel strategy for investigating the association between a highly polymorphic gene and a phenotype, by combining a multilocus genotype analysis and an haplotype analysis. For the multilocus genotype analysis, a data mining tool--termed DICE (Detection of Informative Combined Effects)--was developed to identify the best subset of polymorphisms that are associated--individually or in combination--with the phenotype. For the haplotype analysis, we used our recently developed method of haplotype-phenotype association to determine the most informative and parsimonious haplotype model fitting the data. We illustrate this strategy by investigating the association between twelve polymorphisms of the APOB gene and plasma apoB levels in 1442 European subjects. After exploring all main effects and interactions between polymorphisms, DICE identified the N4311S polymorphism as the most informative polymorphism in relation to apoB levels. Haplotype analysis led to the same conclusion. Additionally, DICE identified the E4154K (EcoRI) and the T2488T (XbaI) polymorphisms as potentially interesting. This selection was not modified by inclusion of the common APOE polymorphism in the analysis.

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.

Relation between XbA1 apolipoprotein B gene polymorphism and cardiovascular risk in a type 2 diabetic cohort

AIM

To evaluate in a prospective study the association of XbA1 apolipoprotein B (apoB) gene polymorphism with lipid parameters and cardiovascular (CV) events in a type 2 diabetic cohort.

METHODS AND RESULTS

A cohort of 212 type 2 diabetic patients, free of any cardiovascular complication, was studied. Cardiovascular events were registered for all the patients for 5 years. XbA1 apolipoprotein B gene polymorphism was analysed by PCR-RFLP method. A mild increase in HbA1c was found in X+X+ carriers (P = 0.014). Despite this lower glycemic control, there were no differences between genotype subgroups for lipid parameters except for apoB, significantly higher in X+X+ than in X-X- subjects. In univariate analysis, the cardiovascular events rate was higher in X-X- but did not reach statistical significance (P =0.07). In stepwise multivariate regression analysis, cardiovascular events risk was significantly higher in X- carriers (P = 0.014) and also in smokers, microalbuminuric and older patients.

CONCLUSIONS

We report for the first time in a prospective study the association of XbA1 apolipoprotein B gene polymorphism and cardiovascular events in a diabetic population. The mechanism underlying the excess of cardiovascular risk in X- carriers, despite a better metabolic profile, is likely to involve a linkage disequilibrium between apolipoprotein B gene locus and another gene locus related to cardiovascular risk.

A study of the average effect of the 3'APOB-VNTR polymorphism on lipidemic parameters could explain why the short alleles (<35 repeats) are rare in centenarians

Background

In studies on the genetics of human aging, we observed an age-related variation of the 3'APOB-VNTR genotypic pool (alleles: Short, S, <35 repeats; Medium, M, 35–39 repeats; Long, L, >39 repeats) with the homozygous SS genotype showing a convex frequency trajectory in a healthy aging population. This genotype was rare in centenarians, thus indicating that the S alleles are unfavorable to longevity, while common in adults, thus indicating a protective role at middle age. This apparent paradox could be due to possible effects exerted by the above polymorphism on lipidemic parameters. Aim of the work was to get insights into these puzzling findings

Methods

We followed a double strategy. Firstly, we analyzed the average effects of S (α_S), M (α_M), and L (α_L) alleles on lipidemic parameters in a sample of healthy people (409 subjects aged 20–102 years) recruited in Calabria (southern Italy). The (α_S), (α_M), and (α_L) values were estimated by relating 3'APOB-VNTR genotypes to lipidemic parameters, after adjustment for age, sex and body mass index (multiple regression). Then, we analyzed the S alleles as susceptibility factors of Cardiovascular Atherosclerotic Disease (CD) in CD patients characterized either by low serum HDL-Cholesterol or by high serum LDL-Cholesterol (CD-H and CD-L patients, 40 and 40 subjects respectively). The Odds Ratios (OR) were computed for carriers of S alleles in CD-H and CD-L patients matched for origin, sex and age with controls extracted from the sample of healthy subjects.

Results

By the analysis of the healthy sample group we found that the S alleles lower the average values of serum Total Cholesterol (α_S = -5.98 mg/dL with [-11.62 ÷ -0.74] 95% confidence interval) and LDL-Cholesterol (α_S = -4.41 mg/dL with [-8.93 ÷ -0.20] 95% confidence interval) while the alleles M and L have no significant effect on the lipidemic phenotype. In line with these findings, the analysis of CD patients showed that the S alleles are protective as for CD-L (O.R. = 0.55 with [0.21 ÷ 0.98] 95% confidence interval) while neutral as for CD-H (O.R. = 0.75 with [0.32 ÷ 1.60] 95% confidence interval).

Conclusion

On the whole, the S alleles would be advantageous in adults (by protecting from CD-L) while dangerous in the elderly, probably by lowering serum cholesterol below a critical threshold. This could explain the convex frequency trajectory of SS genotypes previously observed in a healthy aging population.

The X-X-/E+E+ genotype of the XbaI/EcoRI polymorphisms of the apolipoprotein B gene as a marker of coronary artery disease in a Brazilian sample

Studies that consider polymorphisms within the apolipoprotein B (apo B) gene as risk factors for coronary artery disease (CAD) have reported conflicting results. The aim of the present study was to search for associations between two DNA RFLPs (XbaI and EcoRI) of the apo B gene and CAD diagnosed by angiography. In the present study we compared 116 Brazilian patients (92 men) with CAD (CAD+) to 78 control patients (26 men) without ischemia or arterial damage (CAD-). The allele frequencies at the XbaI (X) and EcoRI (E) sites did not differ between groups. The genotype distributions of CAD+ and CAD- patients were different (chi (1) = 6.27, P = 0.012) when assigned to two classes (X-X-/E+E+ and the remaining XbaI/EcoRI genotypes). Multivariate logistic regression analysis showed that individuals with the X-X-/E+E+ genotype presented a 6.1 higher chance of developing CAD than individuals with the other XbaI/EcoRI genotypes, independently of the other risk factors considered (sex, tobacco consumption, total cholesterol, hypertension, and triglycerides). We conclude that the X-X-/E+E genotype may be in linkage disequilibrium with an unknown variation in the apo B gene or with a variation in another gene that affects the risk of CAD.

Variations of cardiovascular disease associated genes exhibit sex-dependent influence on human longevity

This article investigates the relationship between the polymorphic variations in genes associated with cardiovascular disease and longevity in the Danish population. A new procedure that combines both demographic and the individual genetic information in determining the relative risks of the observed genetic variations is applied. The sex-dependent influences can be found by introducing sex-specific population survival and incorporating the risk of gene-sex interaction. Three genetic polymorphisms, angiotensinogen M/T235, blood coagulation factor VII (FVII) R/Q353 and FVII-323ins10, manifest significant influences on survival in males, with reduced hazards of death for carriers of the angiotensinogen M235 allele, the F VII Q353 allele, and the FVII-323P10 allele. The results show that some of these genotypes associated with lower risk of CVD could also reduce the carrier's death rate and contribute to longevity. However, the presence of sex-dependent effects and the fact that major CVD-associated genes failed to impose detrimental influence on longevity lead us to concur that the aging process is highly complicated.

Apolipoprotein B gene polymorphisms: prevalence and impact on serum lipid concentrations in hypercholesterolemic individuals from Brazil

Genetic polymorphisms at the apolipoprotein B (apo B) have been associated with elevated plasma concentrations of low-density lipoprotein (LDL) cholesterol, atherosclerosis and increased risk for coronary artery disease (CAD). In the present study, four apo B gene polymorphisms (MspI, XbaI, Ins/Del and 3'HVR) have been investigated to determine their frequencies and influence on the lipid profile of 177 hypercholesterolemic white Brazilian subjects (HG) and 100 control individuals (CG). The genotype distribution and allele frequency of MspI, XbaI and Ins/Del polymorphisms of apo B gene were similar between HG and CG groups. The frequency of the alleles smaller than 43 repeats (< or =43) of 3'HVR polymorphism in the HG group was higher when compared to controls (16.4 vs. 8.5%, P<0.05). Moreover, these alleles were associated with higher total cholesterol concentrations in serum of hypercholesterolemic individuals (P<0.05). In addition, an association between Ins/Del and 3'HVR polymorphism was observed. The alleles < or =43 and Del were more frequent in the HG when compared to the CG individuals (P<0.05). We concluded that 3'HVR polymorphism at the apo B gene may be an important genetic marker to evaluate atherosclerotic disease risk.

Seven DNA polymorphisms at the candidate genes of atherosclerosis in Brazilian women with angiographically documented coronary artery disease

The possible association of genetic markers at the apolipoprotein E (HhaI polymorphism), apolipoprotein B (XbaI, EcoRI and Ins/Del polymorphisms), and low-density lipoprotein receptor (LDLR) (AvaII, HincII and PvuII polymorphisms) with coronary artery disease (CAD) was evaluated in 50 Brazilian women with CAD diagnosed by angiography and in 100 healthy women (controls). The frequency of E3/E4 genotype for HhaI polymorphism at the Apo E gene was significantly higher in CAD patients than in controls (40% vs. 14%, respectively, P<0.001). Similarly, the X-X- genotype for XbaI polymorphism was more frequent in CAD individuals than controls (42% vs. 12%, P<0.0001). The A+A+ and P1P1 genotypes for AvaII and PvuII polymorphisms at the LDLR locus were also higher in CAD subjects than controls (44% vs. 16%, P<0.001 and 64% vs. 39%, P<0.05, respectively). The estimated relative risks for CAD in women carrying the E3/E4, X-X-, A+A+ and P1P1 genotypes were 4.1 [95% confidence interval (CI), 3.0-5.6], 5.3 (95% CI, 3.8-7.5), 4.1 (95% CI, 3.0-5.5), and 2.8 (95% CI, 2.2-3.6), respectively. This study demonstrates that Apo E, Apo B and LDLR gene polymorphisms are associated with CAD in Brazilian Caucasian women.

The contribution of candidate genes to the response of plasma lipids and lipoproteins to dietary challenge

The possible role of four candidate genes in lipid and lipoprotein response to diet was examined in 214 members of two large kibbutz settlements in Israel. Four site polymorphisms (signal peptide insertion/deletion, XbaI, EcoRI and MspI) of the apo B gene, the common apo E genotypes, three common mutations (T-93G, S447stop and N291S) of the LPL gene and the CETP I405V RFLP were determined. The average reduction induced by diet in participants with the absence of the EcoRI restriction site (L4154) of the apo B gene compared with those found to be homozygotes for the restriction site (G/G4154) were: 16.2 and 8.0 mg/dl for total cholesterol (TC) (P=0. 01); and 15.6 and 6.2 mg/dl for LDL-C (P=0.007), respectively. TC and LDL-C baseline levels were significantly different among the apo-E genotypes, yet there were no significant effects on lipid and lipoprotein dietary response. Triglyceride baseline values were significantly lower (P=0.007) among subjects with the LPL S447stop mutation and HDL-C was significantly lower (P=0.008) among subjects found to be heterozygous for the LPL N291S mutation. A heterogeneous response for triglyceride was observed for individuals with the S291 allele as compared to those individuals who were found to be homozygous for the N291 allele. No differences in dietary responsiveness were observed among the apo E and CETP genotypes. In conclusion, our results suggest that sequence variation(s) in the coding region of the apo B gene linked to the EcoRI polymorphism are associated with total cholesterol and LDL-C responsiveness to dietary manipulation. In our study population, LPL mutations had a significant effect on TG and HDL-C baseline levels and on their response to diet.

Association of the apolipoprotein B gene polymorphisms with cholesterol levels and response to fluvastatin in Brazilian individuals with high risk for coronary heart disease

The influence of genetic polymorphism of the apolipoprotein B on lipid metabolism and coronary heart disease (CHD) risk has been demonstrated in different populations, but few studies have shown the contribution of this risk factor in individuals from Brazil. The Ins/del, Xbal and EcoRI polymorphisms of apo B were evaluated in 93 controls and in 104 Caucasian individuals presenting with a high risk lipid profile (HR1) for CHD; 54 of these subjects (HR2) were treated with fluvastatin during 16 weeks. DNA polymorphisms of the apo B gene were analyzed by polymerase chain reaction-restriction fragment length polymorphism. The X(-)X(-) genotype for Xbal polymorphism was associated with higher serum concentrations of total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) (p<0.01) in women of the HR1 group. The Ins/del and EcoRI polymorphisms were not associated with variation of lipid profile. After treatment with fluvastatin, TC and LDL-C levels of HR2 individuals were reduced by 23% and 30%, respectively. Individuals with II genotype had significantly greater reduction (34%) of LDL-C than those with ID/DD genotypes (27%). These results indicate that the Xbal polymorphism is associated with variation of serum TC and LDL-C levels in Brazilian women with lipid profile of risk for CHD and the Ins/del polymorphism is associated with the therapeutic response to fluvastatin.

Low-density lipoprotein receptor gene mutations in a Southeast Asian population with familial hypercholesterolemia

The aim of this study was to detect mutations in the genes coding for the low-density lipoprotein receptor and apolipoprotein B in patients of Southeast Asian origin with clinically diagnosed familial hypercholesterolemia (FH) and to relate these findings with the observed lower incidence of coronary heart disease in this part of the world. A total of 86 unrelated patients with FH were selected on clinical grounds, and complete DNA analysis of the low-density lipoprotein (LDL)-receptor and apolipoprotein B (apoB) genes by DGGE and DNA-sequencing was performed. In the majority (73%) of the cohort studied, no mutations could be detected, even after extensive analysis of the LDL-receptor and apoB genes. However, the 22 patients with a mutation had significantly more xanthomas and a higher incidence of coronary heart disease and levels of low-density lipoproteins were also significantly different. There was no correlation between the type of the mutation and lipoprotein levels or clinical signs of atherosclerosis. The fact that the majority of the FH patients studied had no detectable mutation and that this group had a significant milder phenotype, suggests the presence of a third gene in the Southeast Asian population, predominantly leading to a disorder resembling a milder form of FH. A similar, but less frequent, trait has recently been described in a number of European families.

APO B 3' HVR polymorphism in healthy population: relationships to serum lipid levels

We have analyzed allele frequency distribution at the hypervariable locus 3' to the apolipoprotein B gene in a healthy population sample (241 women and 246 men) from the Belgrade area. The bimodal distribution of sixteen different hypervariable region (HVR) alleles and the heterozygosity index (average 0.76) in both samples are similar to ones reported for other Caucasian populations. However, we found the hypervariable element containing 34 repeats-HVE34 allele to be the most common one in both female and male samples, and that there was a lower frequency of the HVE>36 alleles. For further analysis of 3'HVR allele frequency and its possible association with serum lipid levels, all HVR alleles were grouped into five main types (HVE<32, HVE32, HVE34, HVE36, and HVE>36), and the samples were divided into lipid quartiles. We found that (1) apo B gene 3'HVR polymorphism is associated with variation of normal lipid levels in males, (2) HVE32 alleles are associated with decreased serum levels of total cholesterol, LDL cholesterol, and triglycerides, and (3) HVR genotypes containing HVE34 and HVE36 alleles are associated with elevated serum levels of total cholesterol, low density lipoprotein (LDL) cholesterol, and triglycerides.

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.

Apolipoprotein B gene polymorphisms and serum lipids: meta-analysis of the role of genetic variation in responsiveness to diet

BACKGROUND

The genetic variance determining plasma lipid and lipoprotein concentrations may modify individual responsiveness to alterations in dietary fat and cholesterol content.

OBJECTIVE

The aim was to examine the role of apolipoprotein (apo) B DNA polymorphisms in responsiveness of plasma lipids and lipoproteins to diet.

DESIGN

A controlled dietary intervention study was conducted in 44 healthy, middle-aged subjects with a 3-mo baseline, a 1-mo fat-controlled, a 1-mo high-fat, and a 1-mo habitual diet period. We also conducted a meta-analysis of all published dietary trials, including our own.

RESULTS

In our own dietary study, the apo B XbaI restriction-site polymorphism affected the responsiveness to diet of the plasma LDL-cholesterol concentration (P < 0.05, repeated-measures analysis of variance). Especially during the high-fat diet, homozygous absence of the XbaI restriction site (X(-)/X(-)) was associated with a greater increase in LDL cholesterol (44 +/- 5%) than was X(+)/X(+) (27 +/- 7%) or X(+)/X(-) (40 +/- 5%). The high-fat diet also induced a larger increase in plasma LDL cholesterol in subjects with the R(-)/R(-) genotype (homozygous absence of the EcoRI restriction site) (59 +/- 10%) than in those with the R(+)/R(-) (39 +/- 6%) or R(+)/R(+) (36 +/- 4%) genotype. The M(+)/M(+) genotype (homozygous presence of the MspI restriction site) was also more responsive (41 +/- 3% increase in LDL cholesterol) than the M(+)/M(-) genotype (27 +/- 10% increase). The meta-analysis supported the finding of the significant role of the EcoRI and MspI polymorphisms, but not that of the XbaI polymorphism.

CONCLUSIONS

The present study indicated that the apo B EcoRI and MspI polymorphisms are associated with responsiveness to diet.

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.

Variation of apolipoprotein B as a possible cause of decreased low density lipoprotein clearance and hypercholesterolemia

The fractional catabolic rate (FCR) for low density lipoprotein (LDL) apolipoprotein B (apo B) was studied to explore the variations in apo B as a possible cause of hypercholesterolemia. The FCR of radioiodine labelled autologous LDL and homologous LDL isolated from a normocholesterolemic subject were compared in forty-nine type II hypercholesterolemic males and females with the mean plasma concentration of total cholesterol of 7.78 mmol/l, LDL-cholesterol 5.41 mmol/l and triglycerides 2.09 mmol/l. In most patients the autologous LDL was catabolized at an equal rate and sometimes even faster than the homologous LDL. However, twelve out of forty-nine patients catabolized homologous LDL 0.8-19.3% faster than autologous LDL and several apo B polymorphisms were determined. No apo B-3500 or apo B-3531 mutations were detected. Patients with XbaI -/- (absence of cutting site) had lower total, IDL and LDL cholesterol and LDL apoB than the other genotypes. Patients with EcoRI +/+ (presence of cutting site) had higher total, VLDL and LDL cholesterol and slower FCR for autologous LDL, and their VLDL was richer in cholesterol than that of patients with the EcoRI +/-. The MspI and ins/del polymorphisms were not associated with variations in the measured parameters. The apo E 4 was associated with higher VLDL and IDL cholesterol, higher triglycerides and LDL apo B than E 3/3. Overall, the determined apo B polymorphisms were not related to the slow clearance of autologous LDL among the 12 patients, in whom autologous LDL was cleared at a slower rate than homologous LDL. In conclusion, hypercholesterolemia can be due to particle-related slow clearance of LDL in some patients. However, this is not a common cause of hypercholesterolemia.