👤 B Duga

Roma people are underprivileged, neglected population worldwide, with severe healthcare problems. They have significantly increased prevalence of cardiovascular morbidity, presumably related to their poor social status, alcohol consumption and smoking habits. Assuming that genetic background also plays a role in their susceptibility for cardiovascular diseases, we hypothesized that APOA5 gene polymorphisms, an important role-player in lipid metabolism and in the development of metabolic syndrome and cardio/cerebrovascular events, may also be involved. We examined four APOA5 polymorphisms in 363 Roma and 404 Hungarian DNA samples. For rs662799, rs2266788, rs207560 and rs3135506 we found elevated plasma triglyceride levels in the risk allele carriers compared to non-carriers in both populations. At least a two-fold significant increase was detected in minor allele frequencies in Roma when compared to Hungarians, except the rs2266788 variant. Haplotype analysis revealed significant increase of APOA5*2, APOA5*4 in Roma, as opposed to the higher levels of APOA5*5 found in Hungarians. Different linkage disequilibrium was found between rs207560 and rs3135506 variants in Roma compared to Hungarians. The profound differences observed in almost all APOA5 polymorphisms in Roma require special attention, since these variants are known to associate with cardio/cerebrovascular susceptibility. Show less

Therapies that inhibit CETP (cholesteryl ester transfer protein) have failed to demonstrate a reduction in risk for coronary heart disease (CHD). Human DNA sequence variants that truncate the To test whether protein-truncating variants (PTVs) at the We sequenced the exons of the Compared with noncarriers, carriers of PTV at Show less

Genome-wide association studies have so far identified 56 loci associated with risk of coronary artery disease (CAD). Many CAD loci show pleiotropy; that is, they are also associated with other diseases or traits. This study sought to systematically test if genetic variants identified for non-CAD diseases/traits also associate with CAD and to undertake a comprehensive analysis of the extent of pleiotropy of all CAD loci. In discovery analyses involving 42,335 CAD cases and 78,240 control subjects we tested the association of 29,383 common (minor allele frequency >5%) single nucleotide polymorphisms available on the exome array, which included a substantial proportion of known or suspected single nucleotide polymorphisms associated with common diseases or traits as of 2011. Suggestive association signals were replicated in an additional 30,533 cases and 42,530 control subjects. To evaluate pleiotropy, we tested CAD loci for association with cardiovascular risk factors (lipid traits, blood pressure phenotypes, body mass index, diabetes, and smoking behavior), as well as with other diseases/traits through interrogation of currently available genome-wide association study catalogs. We identified 6 new loci associated with CAD at genome-wide significance: on 2q37 (KCNJ13-GIGYF2), 6p21 (C2), 11p15 (MRVI1-CTR9), 12q13 (LRP1), 12q24 (SCARB1), and 16q13 (CETP). Risk allele frequencies ranged from 0.15 to 0.86, and odds ratio per copy of the risk allele ranged from 1.04 to 1.09. Of 62 new and known CAD loci, 24 (38.7%) showed statistical association with a traditional cardiovascular risk factor, with some showing multiple associations, and 29 (47%) showed associations at p < 1 × 10 We identified 6 loci associated with CAD at genome-wide significance. Several CAD loci show substantial pleiotropy, which may help us understand the mechanisms by which these loci affect CAD risk. Show less

Myocardial infarction (MI), a leading cause of death around the world, displays a complex pattern of inheritance. When MI occurs early in life, genetic inheritance is a major component to risk. Previously, rare mutations in low-density lipoprotein (LDL) genes have been shown to contribute to MI risk in individual families, whereas common variants at more than 45 loci have been associated with MI risk in the population. Here we evaluate how rare mutations contribute to early-onset MI risk in the population. We sequenced the protein-coding regions of 9,793 genomes from patients with MI at an early age (≤50 years in males and ≤60 years in females) along with MI-free controls. We identified two genes in which rare coding-sequence mutations were more frequent in MI cases versus controls at exome-wide significance. At low-density lipoprotein receptor (LDLR), carriers of rare non-synonymous mutations were at 4.2-fold increased risk for MI; carriers of null alleles at LDLR were at even higher risk (13-fold difference). Approximately 2% of early MI cases harbour a rare, damaging mutation in LDLR; this estimate is similar to one made more than 40 years ago using an analysis of total cholesterol. Among controls, about 1 in 217 carried an LDLR coding-sequence mutation and had plasma LDL cholesterol > 190 mg dl(-1). At apolipoprotein A-V (APOA5), carriers of rare non-synonymous mutations were at 2.2-fold increased risk for MI. When compared with non-carriers, LDLR mutation carriers had higher plasma LDL cholesterol, whereas APOA5 mutation carriers had higher plasma triglycerides. Recent evidence has connected MI risk with coding-sequence mutations at two genes functionally related to APOA5, namely lipoprotein lipase and apolipoprotein C-III (refs 18, 19). Combined, these observations suggest that, as well as LDL cholesterol, disordered metabolism of triglyceride-rich lipoproteins contributes to MI risk. Show less

The role of triglyceride metabolism in different diseases, such as cardiovascular or cerebrovascular diseases is still under extensive investigations. In genome-wide studies several polymorphisms have been reported, which are highly associated with plasma lipid level changes. Our goal was to examine eight variants: rs12130333 at the ANGPTL3, rs16996148 at the CILP2, rs17321515 at the TRIB1, rs17145738 and rs3812316 of the MLXIPL, rs4846914 at GALNT2, rs1260326 and rs780094 residing at the GCKR loci. A total of 399 Roma (Gypsy) and 404 Hungarian population samples were genotyped using PCR-RFLP method. Significant differences were found between Roma and Hungarian population samples in both MLXIPL variants (C allele frequency of rs17145738: 94.1% vs. 85.6%, C allele frequency of rs3812316: 94.2% vs. 86.8% in Romas vs. in Hungarians, p < 0.05), in ANGPTL3 (T allele frequency of rs1213033: 12.2% vs. 18.5% in Romas vs. Hungarians, p < 0.05) and GALNT2 (G allele frequency of rs4846914: 46.6% vs. 54.5% Romas vs. in Hungarians, p < 0.05), while no differences over SNPs could be verified and the known minor alleles showed no correlation with triglyceride levels in any population samples. The current study revealed fundamental differences of known triglyceride modifying SNPs in Roma population. Failure of finding evidence for affected triglyceride metabolism shows that these susceptibility genes are much less effective compared for example to the apolipoprotein A5 gene. Show less

Plasma triglyceride levels are heritable and are correlated with the risk of coronary heart disease. Sequencing of the protein-coding regions of the human genome (the exome) has the potential to identify rare mutations that have a large effect on phenotype. We sequenced the protein-coding regions of 18,666 genes in each of 3734 participants of European or African ancestry in the Exome Sequencing Project. We conducted tests to determine whether rare mutations in coding sequence, individually or in aggregate within a gene, were associated with plasma triglyceride levels. For mutations associated with triglyceride levels, we subsequently evaluated their association with the risk of coronary heart disease in 110,970 persons. An aggregate of rare mutations in the gene encoding apolipoprotein C3 (APOC3) was associated with lower plasma triglyceride levels. Among the four mutations that drove this result, three were loss-of-function mutations: a nonsense mutation (R19X) and two splice-site mutations (IVS2+1G→A and IVS3+1G→T). The fourth was a missense mutation (A43T). Approximately 1 in 150 persons in the study was a heterozygous carrier of at least one of these four mutations. Triglyceride levels in the carriers were 39% lower than levels in noncarriers (P<1×10(-20)), and circulating levels of APOC3 in carriers were 46% lower than levels in noncarriers (P=8×10(-10)). The risk of coronary heart disease among 498 carriers of any rare APOC3 mutation was 40% lower than the risk among 110,472 noncarriers (odds ratio, 0.60; 95% confidence interval, 0.47 to 0.75; P=4×10(-6)). Rare mutations that disrupt APOC3 function were associated with lower levels of plasma triglycerides and APOC3. Carriers of these mutations were found to have a reduced risk of coronary heart disease. (Funded by the National Heart, Lung, and Blood Institute and others.). Show less

Apoliporotein A5 (APOA5), a member of the apolipoprotein family, plays a key regulatory role in triglyceride (TG) metabolism. Even though the exact biochemical background of its mechanism is not yet fully understood, diseases associated with this particular gene highlighted its key role in the metabolism of triglycerides in humans. Naturally occurring functional variants of the gene and their natural major haplotypes are known to associate with moderately elevated triglyceride levels, and are also known to confer risk or protection for major polygenic diseases, like coronary heart disease, stroke, or metabolic syndrome. On the other hand, case reports and even robust resequencing studies verified APOA5 mutations as underlying genetic defects behind extreme hypertriglyceridemic phenotype. Soon after the recognition of the first cases, there were indications which suggest the existence of less frequent genetic variants which, in combination with the common allelic variants of the gene, can define haplotypes that are associated with substantial triglyceride level increase. In addition, it became evident, that there are rare mutations of the APOA5 gene which can be associated with specific complex phenotypes and different types of hyperlipoproteinemia, which includes extremely high triglyceride levels with multiple organ pathology. These rare mutations may cause inheritable hypertriglyceridemia, but they presented at a low frequency and could not be captured by standard genotyping array screenings. The identification of new mutations still relies on the direct sequencing of APOA5 gene of patients with hypertriglyceridemia with an unusual pattern, individually or in huge resequencing studies. Show less

The common functional variants of the apolipoprotein A5 (APOA5) and the glucokinase regulatory protein genes (GCKR) have been shown to associate with increased fasting triglyceride (TG) levels. Albeit the basic association has been extensively investigated in several populations of different origin, less is known about quantitative traits of them. In our study accumulation rates of four APOA5 (T-1131, IVS3 + G476A, T1259C and C56G) and two GCKR (C1337T and rs780094) functional SNPs were analyzed in patients stratified into four TG quartile groups. Randomly selected 325 metabolic syndrome patients were separated into four quartile (q) groups based on the TG levels as follows q1: TG <1.38 mmol/l; q2: 1.38-1.93 mmol/l; q3: 1.94-2.83 mmol/l; and q4: TG >2.83 mmol/l. We observed significant stepwise increase of prevalence rates of minor allele frequencies in the four plasma TG quartiles for three APOA5 SNPs: -1131C (q1: 4.94%; q2: 8.64%; q3: 11.6%; q4: 12.3%), IVS3 + 476A (q1: 4.32%; q2: 7.4%; q3: 10.36%; q4: 11.1%), and 1259C (q1: 4.94%; q2: 7.41%; q3: 10.4%; q4: 11.7%). The haplotype analysis revealed, that the frequency of APOA5*2 haplotype gradually increased in q2, q3 and q4 (q1: 9.87%; q2: 14.8%; q3: 18.3%; q4: 21%). The distribution of the homozygotes of the two analyzed GCKR variants resembled to the APOA5 pattern. Contrary to the hypothetically predictable linear association coming from the current knowledge about the APOA5 and GCKR functions, the findings presented here revealed a unique, TG raise dependent gradual accumulation of the functional variants of in MS patients. Thus, the findings of the current study serve indirect evidence for the existence of rare APOA5 and GCKR haplotypes in metabolic syndrome patients with higher TG levels, which contribute to the complex lipid metabolism alteration in this disease. Show less