Contribution of APOA5 gene variants to plasma triglyceride determination and to the response to both fat and glucose tolerance challenges

Association between Genotype and the Glycemic Response to an Oral Glucose Tolerance Test: A Systematic Review

The inter-individual variability of metabolic response to foods may be partly due to genetic variation. This systematic review aims to assess the associations between genetic variants and glucose response to an oral glucose tolerance test (OGTT). Three databases (PubMed, Web of Science, Embase) were searched for keywords in the field of genetics, OGTT, and metabolic response (PROSPERO: CRD42021231203). Inclusion criteria were available data on single nucleotide polymorphisms (SNPs) and glucose area under the curve (gAUC) in a healthy study cohort. In total, 33,219 records were identified, of which 139 reports met the inclusion criteria. This narrative synthesis focused on 49 reports describing gene loci for which several reports were available. An association between SNPs and the gAUC was described for 13 gene loci with 53 different SNPs. Three gene loci were mostly investigated: transcription factor 7 like 2 (TCF7L2), peroxisome proliferator-activated receptor gamma (PPARγ), and potassium inwardly rectifying channel subfamily J member 11 (KCNJ11). In most reports, the associations were not significant or single findings were not replicated. No robust evidence for an association between SNPs and gAUC after an OGTT in healthy persons was found across the identified studies. Future studies should investigate the effect of polygenic risk scores on postprandial glucose levels.

Genetic Regulatory Networks of Apolipoproteins and Associated Medical Risks

Apolipoproteins (APO proteins) are the lipoprotein family proteins that play key roles in transporting lipoproteins all over the body. There are nearly more than twenty members reported in the APO protein family, among which the A, B, C, E, and L play major roles in contributing genetic risks to several disorders. Among these genetic risks, the single nucleotide polymorphisms (SNPs), involving the variation of single nucleotide base pairs, and their contributing polymorphisms play crucial roles in the apolipoprotein family and its concordant disease heterogeneity that have predominantly recurred through the years. In this review, we have contributed a handful of information on such genetic polymorphisms that include APOE, ApoA1/B ratio, and A1/C3/A4/A5 gene cluster-based population genetic studies carried throughout the world, to elaborately discuss the effects of various genetic polymorphisms in imparting various medical conditions, such as obesity, cardiovascular, stroke, Alzheimer's disease, diabetes, vascular complications, and other associated risks.

Quantile-dependent expressivity of postprandial lipemia

Purpose

“Quantile-dependent expressivity” describes an effect of the genotype that depends upon the level of the phenotype (e.g., whether a subject’s triglycerides are high or low relative to its population distribution). Prior analyses suggest that the effect of a genetic risk score (GRS) on fasting plasma triglyceride levels increases with the percentile of the triglyceride distribution. Postprandial lipemia is well suited for testing quantile-dependent expressivity because it exposes each individual’s genotype to substantial increases in their plasma triglyceride concentrations. Ninety-seven published papers were identified that plotted mean triglyceride response vs. time and genotype, which were converted into quantitative data. Separately, for each published graph, standard least-squares regression analysis was used to compare the genotype differences at time t (dependent variable) to average triglyceride concentrations at time t (independent variable) to assess whether the genetic effect size increased in association with higher triglyceride concentrations and whether the phenomenon could explain purported genetic interactions with sex, diet, disease, BMI, and drugs.

Results

Consistent with the phenomenon, genetic effect sizes increased (P≤0.05) with increasing triglyceride concentrations for polymorphisms associated with ABCA1, ANGPTL4, APOA1, APOA2, APOA4, APOA5, APOB, APOC3, APOE, CETP, FABP2, FATP6, GALNT2, GCKR, HL, IL1b, LEPR, LOX-1, LPL, MC4R, MTTP, NPY, SORT1, SULF2, TNFA, TCF7L2, and TM6SF2. The effect size for these polymorphisms showed a progressively increasing dose-response, with intermediate effect sizes at intermediate triglyceride concentrations. Quantile-dependent expressivity provided an alternative interpretation to their interactions with sex, drugs, disease, diet, and age, which have been traditionally ascribed to gene-environment interactions and genetic predictors of drug efficacy (i.e., personalized medicine).

Conclusion

Quantile-dependent expressivity applies to the majority of genetic variants affecting postprandial triglycerides, which may arise because the impaired functionalities of these variants increase at higher triglyceride concentrations. Purported gene-drug interactions may be the manifestations of quantile-dependent expressivity, rather than genetic predictors of drug efficacy.

From genome-wide association studies to Mendelian randomization: novel opportunities for understanding cardiovascular disease causality, pathogenesis, prevention, and treatment

The Mendelian randomization approach is an epidemiological study design incorporating genetic information into traditional epidemiological studies to infer causality of biomarkers, risk factors, or lifestyle factors on disease risk. Mendelian randomization studies often draw on novel information generated in genome-wide association studies on causal associations between genetic variants and a risk factor or lifestyle factor. Such information can then be used in a largely unconfounded study design free of reverse causation to understand if and how risk factors and lifestyle factors cause cardiovascular disease. If causation is demonstrated, an opportunity for prevention of disease is identified; importantly however, before prevention or treatment can be implemented, randomized intervention trials altering risk factor levels or improving deleterious lifestyle factors needs to document reductions in cardiovascular disease in a safe and side-effect sparse manner. Documentation of causality can also inform on potential drug targets, more likely to be successful than prior approaches often relying on animal or cell studies mainly. The present review summarizes the history and background of Mendelian randomization, the study design, assumptions for using the design, and the most common caveats, followed by a discussion on advantages and disadvantages of different types of Mendelian randomization studies using one or more samples and different levels of information on study participants. The review also provides an overview of results on many of the risk factors and lifestyle factors for cardiovascular disease examined to date using the Mendelian randomization study design.

Genome-wide association study identifies a missense variant at APOA5 for coronary artery disease in Multi-Ethnic Cohorts from Southeast Asia

Recent genome-wide association studies (GWAS) have identified multiple loci associated with coronary artery disease (CAD) among predominantly Europeans. However, their relevance to multi-ethnic populations from Southeast Asia is largely unknown. We performed a meta-analysis of four GWAS comprising three Chinese studies and one Malay study (Total N = 2,169 CAD cases and 7,376 controls). Top hits (P < 5 × 10-8) were further evaluated in 291 CAD cases and 1,848 controls of Asian Indians. Using all datasets, we validated recently identified loci associated with CAD. The involvement of known canonical pathways in CAD was tested by Ingenuity Pathway Analysis. We identified a missense SNP (rs2075291, G > T, G185C) in APOA5 for CAD that reached robust genome-wide significance (Meta P = 7.09 × 10-10, OR = 1.636). Conditional probability analysis indicated that the association at rs2075291 was independent of previously reported index SNP rs964184 in APOA5. We further replicated 10 loci previously identified among predominantly Europeans (P: 1.33 × 10-7-0.047). Seven pathways (P: 1.10 × 10-5-0.019) were identified. We identified a missense SNP, rs2075291, in APOA5 associated with CAD at a genome-wide significance level and provided new insights into pathways contributing to the susceptibility to CAD in the multi-ethnic populations from Southeast Asia.

Glucose added to a fat load suppresses the postprandial triglyceridemia response in carriers of the -1131C and 56G variants of the APOA5 gene

Apolipoprotein A-V plays an important role in the determination of plasma triglyceride (TG) concentration. We aimed to determine whether polymorphisms -1131T>C (rs662799) and 56C>G (rs3135506) of the APOA5 gene have an impact on the course of postprandial lipemia induced by a fat load and a fat load with added glucose. Thirty healthy male volunteers, seven heterozygous for the -1131C variant and three for the 56G variant (HT) carriers, and 20 wild-type (WT) carriers underwent two 8-hour tests of postprandial lipemia - one after an experimental breakfast consisting of 75 g of fat and second after a breakfast consisting of 75 g of fat and 25 g of glucose. HT carriers had a higher postprandial response after fat load than WT carriers (AUC TG: 14.01+/-4.27 vs. 9.84+/-3.32 mmol*h/l, respectively, p=0.016). Glucose added to the test meal suppressed such a difference. Heterozygous carriers of the variants of APOA5 (-1131C and 56G) display more pronounced postprandial lipemia after pure fat load than WT carriers. This statistically significant difference disappears when glucose is added to a fat load, suggesting that meal composition modulates the effect of these polymorphisms on the magnitude of postprandial lipemia.

INSIG2 rs7566605 single nucleotide variant and global DNA methylation index levels are associated with weight loss in a personalized weight reduction program

Single nucleotide polymorphisms associated with lipid metabolism and energy balance are implicated in the weight loss response caused by nutritional interventions. Diet-induced weight loss is also associated with differential global DNA methylation. DNA methylation has been proposed as a predictive biomarker for weight loss response. Personalized biomarkers for successful weight loss may inform clinical decisions when deciding between behavioral and surgical weight loss interventions. The aim of the present study was to investigate the association between global DNA methylation, genetic variants associated with energy balance and lipid metabolism, and weight loss following a non-surgical weight loss regimen. The present study included 105 obese participants that were enrolled in a personalized weight loss program based on their allelic composition of the following five energy balance and lipid metabolism-associated loci: Near insulin-induced gene 2 (INSIG2); melanocortin 4 receptor; adrenoceptor β2; apolipoprotein A5; and G-protein subunit β3. The present study investigated the association between a global DNA methylation index (GDMI), the allelic composition of the five energy balance and lipid metabolism-associated loci, and weight loss during a 12 month program, after controlling for age, sex and body mass index (BMI). The results demonstrated a significant association between the GDMI and near INSIG2 locus, after adjusting for BMI and weight loss, and significant trends were observed when stratifying by gender. In conclusion, a combination of genetic and epigenetic biomarkers may be used to design personalized weight loss interventions, enabling adherence and ensuring improved outcomes for obesity treatment programs. Precision weight loss programs designed based on molecular information may enable the creation of personalized interventions for patients, that use genomic biomarkers for treatment design and for treatment adherence monitoring, thus improving response to treatment.

Apolipoprotein A5 regulates intracellular triglyceride metabolism in adipocytes

It has previously been demonstrated that apolipoprotein A5 (apoA5) can be internalized by human adipocytes and significantly decreases intracellular triglyceride content. In the present study, endocytosis of apoA5 by adipocytes under different conditions, and the underlying mechanism by which apoA5 regulates cellular triglyceride storage, was investigated. The results revealed that the apoA5 protein was detected in human subcutaneous abdominal adipose tissues. In addition, the uptake of apoA5 was attenuated in human obese adipose tissues and in cultured adipocytes with hypertrophy or insulin resistance. Low-density lipoprotein receptor protein 1 (LRP1) knockdown in adipocytes resulted in a decrease in internalized apoA5 content, suggesting that LRP1 serves a role in apoA5 uptake. Treatment of adipocytes with apoA5 decreased the expression of the lipid droplet-associated proteins such as cidec and perilipin. ApoA5-treated adipocytes demonstrated an increase in lipolysis activity and expression of uncoupling protein 1, which is the molecular effector of thermogenesis in brown adipocytes. These results suggested that decreased triglyceride accumulation in adipocytes induced by apoA5 may be associated with enhanced lipolysis and energy expenditure, which may result from reduced expression of cidec and perilipin. In conclusion, the present study demonstrated a novel role of apoA5 in regulating the intracellular triglyceride metabolism of adipocytes. The results of the present study suggested that apoA5 may serve as a potential therapeutic target for the treatment of obesity and its related disorders.

Common variants in the genes of triglyceride and HDL-C metabolism lack association with coronary artery disease in the Pakistani subjects

Background

Serum Triglyceride (TG) and High Density Lipoprotein (HDL-C) levels are modifiable coronary artery disease (CAD) risk factors. Polymorphisms in the genes regulating TG and HDL-C levels contribute to the development of CAD. The objective of the current study was to investigate the effect of four such single nucleotide polymorphism (SNPs) in the genes for Lipoprotein Lipase (LPL) (rs328, rs1801177), Apolipoprotein A5 (APOA5) (rs66279) and Cholesteryl ester transfer protein (CETP) (rs708272) on HDL-C and TG levels and to examine the association of these SNPs with CAD risk.

Methods

A total of 640 subjects (415 cases, 225 controls) were enrolled in the study. The SNPs were genotyped by KASPar allelic discrimination technique. Serum HDL-C and TG were determined by spectrophotometric methods.

Results

The population under study was in Hardy Weinberg equilibrium and minor allele of SNP rs1801177 was completely absent in the studied subjects. The SNPs were association with TG and HDL-C levels was checked through regression analysis. For rs328, the effect size of each risk allele on TG and HDL-C (mmol/l) was 0.16(0.08) and −0.11(0.05) respectively. Similarly, the effect size of rs662799 for TG and HDL-C was 0.12(0.06) and −0.13(0.0.3) and that of rs708272 was 0.08(0.04) and 0.1(0.03) respectively. The risk allele frequencies of the SNPs were higher in cases than controls, but the difference was not significant (p > 0.05) and SNPs were not associated with CAD risk (p > 0.05). The combined gene score of four SNPs significantly raised TG and lowered HDL-C but did not increase CAD risk.

Conclusion

The studied SNPs were associated with TG and HDL-C levels, but not with CAD in Pakistani population under study.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-017-0419-4) contains supplementary material, which is available to authorized users.

The c.553G>T Genetic Variant of the APOA5 Gene and Altered Triglyceride Levels in the Asian Population: A Meta-Analysis of Case-Control Studies

AIM

To explore the association of the APOA5 gene c.553G>T polymorphism with hypertriglyceridemia (HTG) susceptibility and altered triglyceride levels.

METHODS

We searched the PubMed, Google Scholar, and CNKI databases for published studies relating to analyses of these associations. Case-control and comparative studies of the association between the APOA5 c.553G>T variant and altered triglyceride levels were included. In total, the meta-analysis involved 10 studies on HTG, which provided 2219 cases and 3401 controls. To measure the correlation between the c.553G>T polymorphism and HTG susceptibility, odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. The overall OR was calculated using a random-effects model.

RESULTS

Compared with APOA5 c.553 GG carriers, c.553T carriers displayed an increased risk of HTG in the Asian population, with an overall random effects OR of 3.55 (95% CI: 2.46-5.13) in the dominant model. There was significant heterogeneity among the studies (P_{heterogeneity}: Chi² = 45.80, I² = 75.98%), which may be largely explained by certain patient types. Both the sensitivity analysis and publication bias suggested that the overall result was acceptable. Subgroup analysis showed a large difference in serum triglyceride levels based on the c.553 G > T polymorphism in healthy individuals and HTG patients. APOA5 c.553T carriers exhibit higher triglyceride levels than GG carriers.

CONCLUSION

Our results suggest that APOA5 c. 553T is an independent risk factor for HTG and increased triglyceride levels in the Asian population. APOA5 c. 553T could be employed as a genetic risk marker for HTG and increased triglyceride levels.

Review: Genetics of the cardiometabolic syndrome: new insights and therapeutic implications

Although the definition of the phenotype is imprecise, cardiometabolic syndrome (CMS) includes a constellation of complex diseases such as type 2 diabetes, dislipidemias, central obesity and hypertension, proinflammatory and prothrombotic states, ovarian polycystosis and fatty liver. The genetics of each disease is complex in itself and varies in spectrum from monogenic and syndromic models of inheritance, usually rare, to the most common polygenic and multifactorial forms. In addition, human studies using the candidate-gene approach indicate that common genetic variants of several genes are associated with the development of CMS. Genome-wide scans have also provided several chromosomal regions associated with some of the components of CMS. In addition, through comparative genomics animal models can generate a map for candidate loci in humans and a promising approach is offered by bioinformatic tools for gene prioritization. Lastly, the involvement of genes whose products are already the targets for approved drugs, such as SLC6A4, PPARα and PPARγ , in the development of CMS suggests new avenues for CMS pharmacological treatment.

Association of polymorphisms of genes involved in lipid metabolism with blood pressure and lipid values in mexican hypertensive individuals

Hypertension and dyslipidemia exhibit an important clinical relationship because an increase in blood lipids yields an increase in blood pressure (BP). We analyzed the associations of seven polymorphisms of genes involved in lipid metabolism (APOA5 rs3135506, APOB rs1042031, FABP2 rs1799883, LDLR rs5925, LIPC rs1800588, LPL rs328, and MTTP rs1800591) with blood pressure and lipid values in Mexican hypertensive (HT) patients. A total of 160 HT patients and 160 normotensive individuals were included. Genotyping was performed through PCR-RFLP, PCR-AIRS, and sequencing. The results showed significant associations in the HT group and HT subgroups classified as normolipemic and hyperlipemic. The alleles FABP2 p.55T, LIPC −514T, and MTTP −493T were associated with elevated systolic BP. Five alleles were associated with lipids. LPL p.474X and FABP2 p.55T were associated with decreased total cholesterol and LDL-C, respectively; APOA5 p.19W with increased HDL-C; APOA5 p.19W and FABP2 p.55T with increased triglycerides; and APOB p.4181K and LDLR c.1959T with decreased triglycerides. The APOB p.E4181K polymorphism increases the risk for HT (OR = 1.85, 95% CI: 1.17–2.93; P = 0.001) under the dominant model. These findings indicate that polymorphisms of lipid metabolism genes modify systolic BP and lipid levels and may be important in the development of essential hypertension and dyslipidemia in Mexican HT patients.

Effects of a 3-year dietary intervention on age-related changes in triglyceride and apolipoprotein A-V levels in patients with impaired fasting glucose or new-onset type 2 diabetes as a function of the APOA5 -1131 T > C polymorphism

Background

The purpose of this study was to estimate the effects of a 3-year dietary intervention on age-related changes in triglyceride and apolipoprotein (apo A-V) levels in patients with impaired fasting glucose (IFG) or new-onset type 2 diabetes as a function of the APOA5 -1131 T > C polymorphism.

Methods

We genotyped the APOA5 -1131 T > C polymorphism in 203 Korean individuals with IFG or new-onset type 2 diabetes for the TT (n = 91), TC (n = 98), and CC (n = 14) alleles. Plasma apo A-V and triglyceride levels were evaluated at baseline and after a 3-year dietary intervention.

Results

Our results showed that HDL, glucose, insulin, HOMA-IR index, free fatty acids, and apo A-V decreased and brachial-ankle pulse wave velocity (ba-PWV) and malondialdehyde (MDA) increased at the 3-year follow-up visit compared with baseline. Plasma apo A-V levels were reduced in subjects with the C allele (TC or CC) (P = 0.036) and triglyceride levels were reduced in subjects with the TT allele (P = 0.047). Subjects with the C allele showed lower post-treatment apo A-V and higher post-treatment fasting triglyceride levels than subjects with the TT allele. Changes in apo A-V and triglyceride levels were negatively correlated in subjects with the TT allele and positively correlated in subjects with the C allele.

Conclusions

This study showed that the dietary intervention prevented an age-related increase in triglyceride levels in individuals with IFG or new-onset type 2 diabetes who possess the TT allele, but not the CT or CC allele, of the APOA5 -1131 T > C polymorphism.

Association of APOA5 rs662799 and rs3135506 polymorphisms with arterial hypertension in Moroccan patients

BACKGROUND

The goal of the study is to investigate the association between the APOA5 polymorphisms and haplotypes with Arterial Hypertension (AHT) in Moroccan patients.

METHODS

The study was performed in 283 subjects, 149 patients with AHT and 134 controls. All subjects were genotyped for the APOA5 -1131 T > C (rs662799), 56C > G (rs3135506) and c.553G > T (rs2075291) polymorphisms.

RESULTS

There was a strong association between -1131 T > C and 56C > G polymorphisms with AHT. The -1131 T > C and 56C > G polymorphisms were significantly associated with increased systolic blood pressure (SBP) and triglycerides (TG) levels. There were 4 haplotypes with a frequency higher than 5%, constructed from APOA5 polymorphisms, with the following order: -1131 T > C, 56C > G and c.553G > T. Haplotype H1 (TCG) was associated with decreased risk of AHT, whereas the haplotypes H2 (CCG) and H4 (CGG) were significantly associated with an increased risk of AHT. Carriers of H1 haplotype had a lower SBP and DBP and TG. In contrast, significant elevated SBP, DBP and TG were found in H4 haplotypes carriers.

CONCLUSIONS

Our data demonstrate for the first time that several common SNPs in the APOA5 gene and their haplotypes are closely associated with modifications of blood pressure and serum lipid parameters in the AHT patient.

Genetic polymorphism of apolipoprotein A5 gene and susceptibility to type 2 diabetes mellitus: a meta-analysis of 15,137 subjects

BACKGROUND

Several studies have investigated whether the polymorphism in the apolipoprotein A5 (APOA5) is associated with type 2 diabetes mellitus (T2DM) risk. However, those studies have produced inconsistent results. The purpose of this study was to investigate whether the APOA5 -1131T/C polymorphism (rs662799) confers significant susceptibility to T2DM using a meta-analysis.

METHODS

PubMed, Embase, Web of Science, Cochrane database, CBMdisc, CNKI and Google Scholar were searched to get the genetic association studies. All statistical analyses were done with Stata 11.0.

RESULTS

A total of 19 studies included 4,767 T2DM cases and 10,370 controls (four studies involving 555 T2DM cases and 2958 controls were performed among Europeans and 15 studies involving 4212 T2DM cases and 7412 controls were performed among Asians) were combined showing significant association between the APOA5 -1131T/C polymorphism and T2DM risk (for C allele vs. T allele: OR = 1.28, 95% CI = 1.17-1.40, p<0.00001; for C/C vs. T/T: OR = 1.57, 95% CI = 1.35-1.83, p<0.00001; for C/C vs. T/C+T/T: OR = 1.36, 95% CI = 1.18-1.57, p<0.0001; for C/C+T/C vs. T/T: OR = 1.32, 95% CI = 1.16-1.51, p<0.0001). In the subgroup analysis by ethnicity, significant association was also found among Asians (for C allele vs. T allele: OR = 1.31, 95% CI = 1.22-1.40, p<0.00001; for C/C vs. T/T: OR = 1.61, 95% CI = 1.38-1.88, p<0.00001; for C/C vs. T/C+T/T: OR = 1.39, 95% CI = 1.20-1.61, p<0.0001; for C/C+T/C vs. T/T: OR = 1.42, 95% CI = 1.25-1.62, p<0.00001). However, no significant association was found between the APOA5 -1131T/C polymorphism and T2DM risk among Europeans.

CONCLUSIONS

The present meta-analysis suggests that the APOA5 -1131T/C polymorphism is associated with an increased T2DM risk in Asian population.

The association of common SNPs and haplotypes in CETP gene with HDL cholesterol levels in Latvian population

The heritability of high-density lipoprotein cholesterol (HDL-C) level is estimated at approximately 50%. Recent genome-wide association studies have identified genes involved in regulation of high-density lipoprotein cholesterol (HDL-C) levels. The precise genetic profile determining heritability of HDL-C however are far from complete and there is substantial room for further characterization of genetic profiles influencing blood lipid levels. Here we report an association study comparing the distribution of 139 SNPs from more than 30 genes between groups that represent extreme ends of HDL-C distribution. We genotyped 704 individuals that were selected from Genome Database of Latvian Population. 10 SNPs from CETP gene showed convincing association with low HDL-C levels (rs1800775, rs3764261, rs173539, rs9939224, rs711752, rs708272, rs7203984, rs7205804, rs11076175 and rs9929488) while 34 SNPs from 10 genes were nominally associated (p<0.05) with HDL-C levels. We have also identified haplotypes from CETP with distinct effects on determination of HDL-C levels. Our conclusion: So far the SNPs in CETP gene are identified as the most common genetic factor influencing HDL-C levels in the representative sample from Latvian population.

Apolipoprotein A5 polymorphisms in Turkish population: association with serum lipid profile and risk of ischemic stroke

Atherosclerosis, a major cause of ischemic stroke, may be associated with variability of triglyceride (TG) levels. Apolipoprotein A5 (APOA5) genetic polymorphisms are associated with altered TG levels. The objective of this study was to investigate the coding region polymorphisms S19W (rs3135506) and G185C (rs2075291) and the promoter region polymorphism -1131T>C (rs662799) of the APOA5 gene as risk factors for ischemic stroke in Turkish population. Study group consisted of 272 ischemic stroke patients and 123 controls. Genotypes were determined by real-time polymerase chain reaction (PCR) for S19W and PCR-restriction fragment length polymorphism analysis (PCR-RFLP) for -1131T>C and G185C. 19W allele frequency was 0.090 in stroke patients and 0.062 in controls (P = 0.191). Minor allele frequencies of -1131T>C and G185C in patients were 0.106 and 0.004, respectively, and were nearly the same in controls. Total cholesterol and LDL-cholesterol levels were significantly higher for stroke patients having at least one 19W allele compared to non-carriers. A significant difference was also found for LDL-cholesterol levels of stroke patients; higher in -1131C allele carriers compared to wild type patients. There was a trend for higher frequency of ischemic stroke among -1131C allele carrier hypertensive, diabetic or obese subjects compared to non-carriers. However, APOA5 genotypes were not associated with the risk of ischemic stroke by logistic regression analysis. The present study demonstrated that carrying rare alleles of APOA5 S19W, -1131T>C and G185C alone do not constitute a risk for ischemic stroke in the studied Turkish subjects.

Nutrigenomics: a case for the common soil between cardiovascular disease and cancer

The border between health and disease is often set by a complex equilibrium between two elements, genetics on one hand, lifestyle on the other, To know it better, means to give new weapons, often crucial, in the hands of the doctors and their patients. It also means to adjust therapies, to find out which drug is good for a patient and which prevention strategy will work better for him/her. Nutrigenomics is an approach to individualize or personalize food and nutrition, and ultimately health, by tailoring the food to the individual genotype. In this review, we present the interaction between certain genetic polymorphisms and diet and increased cardiovascular or cancer risk. It is, indeed, now clear that a large number of bioactive food components may provide risk or protection at several stages of both atherosclerosis and cancer formation processes. We are giving here few examples of gene-food interactions relevant for both the risk of cardiovascular disease and cancer, since a common soil could exist in the genesis of cardiovascular disease and of some types of cancer (mainly gastrointestinal tract and hormone-dependent).

Effects of APOA5 S19W polymorphism on growth, insulin sensitivity and lipoproteins in normoweight neonates

Apolipoprotein (Apo) A5 is a protein involved in the activation of lipoprotein lipase (LPL) and the metabolism of triglyceride (TG)-rich lipoproteins. LPL plays a major role in the metabolism of TG-rich lipoproteins, and placental LPL activity is known to correlate positively with foetal fat deposition and size. We examine the association between the common APOA5 S19W polymorphism and neonatal anthropometrical measurements, lipoprotein and hormone concentrations, and insulin sensitivity in 58 normal weight Caucasian newborns from the Mérida cohort. Neonates with the W allele displayed lower BMI (P < 0.001), ponderal index (P < 0.001), birth weight (P < 0.01), insulin levels (P < 0.05), the insulin/cortisol ratio (P < 0.05), HOMA-R (P < 0.05) and Apo B values (P < 0.01), but higher oxidised LDL (LDLox) values and a higher LDLox/low-density lipoprotein (LDL) ratio (both P < 0.05) than S-homozygous newborns. The APOA5 S19W polymorphism was associated with foetal growth as well as with glucose and lipoprotein metabolism in the neonates. Concurrence of the S19W polymorphism in neonates and their mothers did not affect neonatal lipid and lipoprotein concentrations but was associated with impaired foetal growth. Specifically, W allele carriers displayed a higher degree of LDL oxidation and lower body weight, plasma insulin values, insulin/cortisol ratio and Apo B concentrations than homozygotes for the common S allele. In conclusion, these findings suggest that the W allele carriers received a less optimal nutrition during gestation and that their lipoprotein antioxidant status was inferior to that of their homozygous S allele counterparts.

Gender- and obesity-specific effect of apolipoprotein C3 gene (APOC3) -482C>T polymorphism on triglyceride concentration in Turkish adults

BACKGROUND

Apolipoprotein C3 (APOC3) gene polymorphisms are associated with cardiometabolic risk factors, varying in ethnicities. This study aimed to investigate such association between the APOC3 -482C>T polymorphism and cardiometabolic risk factors in the turkish adult risk factor (TARF) study cohort, stratifying by gender and obesity.

METHODS

Randomly selected 1548 individuals (757 male and 791 female, mean age 49.9±11.8 years) were genotyped for -482C>T polymorphism using hybridization probes in a Real-Time PCR LC480 device.

RESULTS

The -482TT genotype prevailed 9.9% in men and 11.5% in women. Association between 482C>T polymorphism and dyslipidemia (p=0.036, OR=1.42, 95%Cl=1.02-1.97) was found only in men. Analysis of variance showed that anthropometric and metabolic variables were not differently distributed in APOC3 -482C>T genotypes in the study population. In relation to dyslipidemia and obesity, the -482C>T polymorphism showed significant gender-by-genotype interactions (p<0.01). When the study population was stratified according to gender and obesity, homozygotes for the T allele were associated strongly with (by 45%) elevated fasting triglyceride concentrations in obese men (p=0.009) and homeostatic model assessment (HOMA) index in non-obese women (p=0.013). Furthermore, in the same subgroups, the associations of the fasting triglyceride concentrations and HOMA index with the TT genotype remained after adjustment for risk factors (p<0.05).

CONCLUSIONS

APOC3 -482TT genotype is independently associated with elevated fasting triglyceride concentrations in obese men. Presence of obesity seems to be required for this genotype to induce markedly elevated triglycerides. Furthermore, it is associated with the dyslipidemia in men, without requirement of obesity.

Interactions of the apolipoprotein A5 gene polymorphisms and alcohol consumption on serum lipid levels

BACKGROUND

Little is known about the interactions of apolipoprotein (Apo) A5 gene polymorphisms and alcohol consumption on serum lipid profiles. The present study was undertaken to detect the interactions of ApoA5-1131T>C, c.553G>T and c.457G>A polymorphisms and alcohol consumption on serum lipid levels.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 516 nondrinkers and 514 drinkers were randomly selected from our previous stratified randomized cluster samples. Genotyping was performed by polymerase chain reaction and restriction fragment length polymorphism. The levels of serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), ApoA1 and ApoB were higher in drinkers than in nondrinkers (P<0.05-0.001). The genotypic and allelic frequencies of three loci were not different between the two groups. The interactions between -1131T>C genotypes and alcohol consumption on ApoB levels (P<0.05) and the ApoA1/ApoB ratio (P<0.01), between c.553G>T genotypes and alcohol consumption on low-density lipoprotein cholesterol (LDL-C) levels (P<0.05) and the ApoA1/ApoB ratio (P<0.05), and between c.457G>A genotypes and alcohol consumption on TG levels (P<0.001) were detected by factorial regression analysis after controlling for potential confounders. Four haplotypes (T-G-G, C-G-G, T-A-G and C-G-T) had frequencies ranging from 0.06 to 0.87. Three haplotypes (C-G-G, T-A-G, and C-G-T) were significantly associated with serum lipid parameters. The -1131T>C genotypes were correlated with TG, and c.553G>T and c.457G>A genotypes were associated with HDL-C levels in nondrinkers (P<0.05 for all). For drinkers, the -1131T>C genotypes were correlated with TC, TG, LDL-C, ApoB levels and the ApoA1/ApoB ratio (P<0.01 for all); c.553G>T genotypes were correlated with TC, TG, HDL-C and LDL-C levels (P<0.05-0.01); and c.457G>A genotypes were associated with TG, LDL-C, ApoA1 and ApoB levels (P<0.05-0.01).

CONCLUSIONS

The differences in some serum lipid parameters between the drinkers and nondrinkers might partly result from different interactions of the ApoA5 gene polymorphisms and alcohol consumption.

Influence of genetic variants in the apolipoprotein A5 and C3 gene on lipids, lipoproteins, and its association with coronary artery disease in Indians

Indians worldwide demonstrate a triad of elevated triglyceride (TG) with high low-density lipoprotein cholesterol and low high-density lipoprotein cholesterol levels. In the present study, we aim to investigate the effect of -1131T > C, -3A > G, c.56 C > G, and c.553 G > T SNPs in the apolipoprotein A5 (APOA5) gene and 1100C > T and 3238C > G in the apolipoprotein C3 (APOC3) on plasma lipid and lipoprotein levels and risk of coronary artery disease (CAD) in Indians. Genotyping and lipid assays were carried out using standard protocols in a study population that included 150 controls and 90 cases with CAD. Significant associations between minor alleles and higher TG levels were seen for -1131T > C (P < 0.001), -3A > G (P < 0.001), c.56C > G (P = 0.026), and c.553G > T (P = 0.003) SNPs in the APOA5 gene and 1100C > T (P = 0.001) and 3238C > G (P = 0.009) in the APOC3 gene. The haplotypes 11211, 22111, 11112, and 22112 were significantly associated with TG levels (P = 0.025, P = 0.017, P = 0.027, and P < 0.001, respectively) and very-low-density lipoprotein cholesterol levels (P = 0.025, P = 0.017, P < 0.001, and P = 0.002) in males. The 22111, 11112, and 22112 were associated with elevated TG (P = 0.030, P = 0.036, and P = 0.024) but not VLDL-C levels in females. No association with other lipid parameters was seen. In the logistic regression model, the rare S2 allele was a significant risk factor (P = 0.030, 95% CI 1.186-31.432) along with smoking (P < 0.0001, 95% CI 2.018-10.397) for CAD. The APOA5 and APOC3 locus is a strong determinant of plasma TG levels in Indians. The APOC3 3238G is a risk factor for CAD and a higher frequency was also seen with type 2 diabetes mellitus.

APOA1/A5 variants and haplotypes as a risk factor for obesity and better lipid profiles in a Brazilian Elderly Cohort

Genetic variations in the APOA1/C3/A4/A5 gene cluster have been studied and proposed to be the leading key for susceptibility to cardiovascular diseases and age-associated disorders. We aimed to investigate the associations of rs12721026 (APOA1) and rs1729408 (APOA5) polymorphisms and their haplotypes with some age-related diseases, as well as with lipids and proteins serum levels in a cohort from a Brazilian Elderly Longitudinal Study (EPIDOSO). Genotyping was performed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Statistical analyses were carried out using logistic regression analysis, Student's t-test, and linkage disequilibrium (LD) analysis. Polymorphic allele frequencies were 0.095 and 0.449 for rs12721026 and rs1729408, respectively. The C-allele of rs1729408 was associated with higher high-density lipoprotein (HDL) (P = 0.022) and glycated hemoglobin levels (P = 0.020). We also showed that rs12721026 and rs1729408 were in LD. The GC haplotype, which is composed of the G-allele of rs12721026 and the C-allele of rs1729408, was significantly associated with obesity (P = 0.028), with higher glycated hemoglobin (P = 0.006), and fasting glucose (P = 0.0003) compared to the TT haplotype, which includes the wild-type alleles of both polymorphisms. Moreover, we found an association between the TC haplotype and higher HDL levels (P = 0.0039). This is the first time that haplotypes involving these polymorphisms were evaluated. Our results showed that these polymorphisms were involved in the development of obesity and in alterations of lipids and proteins serum levels in a Brazilian population. The present findings might also clarify the role of these polymorphisms and their haplotypes in lipids and proteins metabolism.

Different effects of apolipoprotein A5 SNPs and haplotypes on triglyceride concentration in three ethnic origins

Several polymorphisms in the ApoA5 gene emerged as important candidate genes in triglyceride metabolism. The aim of this study was to determine the associations between ApoA5 polymorphisms, plasma triglyceride concentrations and the presence of cardiovascular disease (CVD) in three ethnic origins. Genotypes for 15 single nucleotide polymorphisms (SNPs) were determined in 659 older adults (mean age 71+/-7 years) who immigrated to Israel or whose ancestors originated from East Europe (Ashkenazi), North Africa, Asia (Sephardic) or Yemen (Yemenite). The minor alleles of the four common SNPs (rs662799, rs651821, rs2072560 and rs2266788) are associated with an increase of 27-38% in triglyceride concentration among Ashkenazi and Yemenite Jews compared with the major alleles, but not among those of Sephardic origin. Conversely, among the Sephardic group, the presence of the minor allele in SNP rs3135506 compared with the major allele was associated with an increase of 34% in triglyceride concentration. The four SNPs were in significant linkage disequilibrium (D'=0.96-0.99), resulting in three haplotypes H1, H2 and H3, representing 98-99% of the population. Haplotype H2 was significantly associated with triglyceride concentration among Ashkenazi and Yemenite but not among Sephardic Jews. Conversely, haplotype H3 was associated with triglyceride concentration in Sephardic but not in Ashkenazi and Yemenite Jews. Ashkenazi carriers of H2 haplotype had a CVD odds ratio of 2.19 (95% CI: 1.05-4.58) compared with H1 (the most frequent), after adjustment for all other risk factors. These results suggest that different SNPs in ApoA5 polymorphisms may be associated with triglyceride concentration and CVD in each of these ethnic origins.

Genetic variants influencing effectiveness of weight loss strategies

Body weight excess has an increasingly high prevalence in the world. Obesity is a complex disease of multifactorial origin with a polygenic condition affected by environmental factors. Weight loss is a primary strategy to treat obesity and its morbidities. Weight changes through life depend on the interaction of environmental, behavioral and genetic factors. Interindividual variation of weight loss in response to different types of interventions (behavioral, caloric restriction, exercise, drug or surgery) has been observed. In this article, currently available data on the role of candidate gene polymorphisms in weight loss are reviewed. Even though control of weight loss by genotype was described in twin and family studies, it is premature to recommend use of genotyping in the design of therapeutic diets or drug treatment. Future studies will have to be large in order to assess the effects of multiple polymorphisms, and will have to control factors other than diet.

Effects of variations in the APOA1/C3/A4/A5 gene cluster on different parameters of postprandial lipid metabolism in healthy young men

The APOA1/C3/A4/A5 gene cluster encodes important regulators of fasting lipids, but the majority of lipid metabolism takes place in the postprandial state and knowledge about gene regulation in this state is scarce. With the aim of characterizing possible regulators of lipid metabolism, we studied the effects of nine single nucleotide polymorphisms (SNPs) during postprandial lipid metabolism. Eighty-eight healthy young men were genotyped for APOA1 -2630 (rs613808), APOA1 -2803 (rs2727784), APOA1 -3012 (rs11216158), APOC3 -640 (rs2542052), APOC3 -2886 (rs2542051), APOC3 G34G (rs4520), APOA4 N147S (rs5104), APOA4 T29T (rs5092), and A4A5_inter (rs1263177) and were fed a saturated fatty acid-rich meal (1g fat/kg of weight with 60% fat, 15% protein and 25% carbohydrate). Serial blood samples were extracted for 11 h after the meal. Total cholesterol and fractions [HDL-cholesterol, LDL-cholesterol, trifacylglycerols (TGs) in plasma, TG-rich lipoproteins (TRLs) (large TRLs and small TRLs), apolipoprotein A-I and apolipoprotein B] were determined. APOA1 -2803 homozygotes for the minor allele and A4A5_inter carriers showed a limited degree of postprandial lipemia. Carriers of the rare alleles of APOA4 N147S and APOA4 T29T had lower APOA1 plasma concentration during this state. APOC3 -640 was associated with altered TG kinetics but not its magnitude. We have identified new associations between SNPs in the APOA1/C3/A4/A5 gene cluster and altered postprandial lipid metabolism.

Apolipoprotein A5 polymorphisms interact with total dietary fat intake in association with markers of metabolic syndrome in Puerto Rican older adults

APOA5 -1131T > C and S19W single nucleotide polymorphisms (SNP) have been consistently associated with plasma lipid concentration and metabolic syndrome (MetS), alone and in modulation by dietary factors. Puerto Ricans have a high prevalence of metabolic conditions and high minor allele frequency for these SNP, suggesting a possible role in disease for this population. We aimed to determine the association of APOA5 -1131T > C and S19W with plasma lipids and markers of MetS, alone and in interaction with total fat intake, as a percent of total energy intake, in Puerto Ricans. Anthropometric and demographic data, FFQ, and blood samples were collected at baseline from participants in the Boston Puerto Rican Health Study (n = 802, 45-75 y). APOA5 S19W was associated with plasma HDL cholesterol (HDL-C) (P = 0.044); minor allele carriers had lower HDL-C [1.12 +/- 0.03 (mean +/- SE)] than those with the common variant (1.18 +/- 0.01 mmol/L), even after adjustment for plasma triglycerides (TG) (P = 0.012). Neither polymorphism was associated with TG or other lipids. Interaction of the -1131T > C SNP with total fat energy intake was observed for plasma TG (P = 0.032) and total cholesterol (P = 0.034). APOA5 S19W interacted with total fat intake in association with systolic (P = 0.002) and diastolic (P = 0.007) blood pressure. Neither SNP was associated with MetS in the overall analysis or after stratifying by total energy intake as fat. In conclusion, Puerto Ricans present a distinctive lipid profile in association with APOA5 polymorphisms. Dietary fat intake seems to modulate these associations. The results contribute to the understanding of health disparities in this population.

Overexpression of apolipoprotein A5 in mice is not protective against body weight gain and aberrant glucose homeostasis

Apolipoprotein A5 (APOA5) is expressed primarily in the liver and modulates plasma triglyceride levels in mice and humans. Mice overexpressing APOA5 exhibit reduced plasma triglyceride levels. Because there is a tight association between plasma triglyceride concentration and traits of the metabolic syndrome, we used transgenic mice overexpressing human APOA5 to test the concept that these mice would be protected from diet-induced obesity and insulin resistance. Male and female transgenic and wild-type mice on the FVB/N genetic background were fed standard rodent chow or a diet rich in fat and sucrose for 18 weeks, during which time clinical phenotypes associated with obesity and glucose homeostasis were measured. We found that APOA5 transgenic (A5tg) mice were resistant to diet-induced changes in plasma triglyceride but not total cholesterol levels. Body weights were similar between the genotypes for females and males, although male A5tg mice showed a modest but significant increase in the relative size of inguinal fat pads. Although male A5tg mice showed a significantly increased ratio of plasma glucose to insulin, profiles of glucose clearance as evaluated after injections of glucose or insulin failed to reveal any differences between genotypes. Overall, our data showed that there was no advantage to responses to diet-induced obesity with chronic reduction of plasma triglyceride levels as mediated by overexpression of APOA5.

Nutrigenetics and personalised nutrition: how far have we progressed and are we likely to get there?

Nutrigenetics and personalised nutrition are components of the concept that in the future genotyping will be used as a means of defining dietary recommendations to suit the individual. Over the last two decades there has been an explosion of research in this area, with often conflicting findings reported in the literature. Reviews of the literature in the area of apoE genotype and cardiovascular health, apoA5 genotype and postprandial lipaemia and perilipin and adiposity are used to demonstrate the complexities of genotype–phenotype associations and the aetiology of apparent between-study inconsistencies in the significance and size of effects. Furthermore, genetic research currently often takes a very reductionist approach, examining the interactions between individual genotypes and individual disease biomarkers and how they are modified by isolated dietary components or foods. Each individual possesses potentially hundreds of ‘at-risk’ gene variants and consumes a highly-complex diet. In order for nutrigenetics to become a useful public health tool, there is a great need to use mathematical and bioinformatic tools to develop strategies to examine the combined impact of multiple gene variants on a range of health outcomes and establish how these associations can be modified using combined dietary strategies.

The association of common genetic variants in the APOA5, LPL and GCK genes with longitudinal changes in metabolic and cardiovascular traits

AIMS/HYPOTHESIS

Common genetic variants influence plasma triacylglycerol, HDL-cholesterol (HDL-C) and glucose levels in cross-sectional studies. However, the longitudinal effects of these established variants have not been studied. Our aim was to examine the longitudinal associations of four such variants in the apolipoprotein A-V (APOA5), lipoprotein lipase (LPL), and glucokinase (GCK) genes with fasting glucose or lipid levels.

METHODS

The individuals analysed were participants in the Busselton Health Survey (n = 4,554). Cross-sectional analyses of family data used the total association test. Longitudinal association analyses of unrelated participant data (n = 2,864) used linear mixed-effects models.

RESULTS

The findings of cross-sectional association analyses replicated those of previous studies. We observed associations of the G and C alleles at the APOA5 single nucleotide polymorphisms (SNPs) rs662799 and rs3135506 with raised triacylglycerol levels (p = 0.0003 and p < 0.0001, respectively), the 447X allele at the LPL SNP rs328 with reduced triacylglycerol levels (p = 0.0004) and raised HDL-C levels (p = 0.0004), and the A allele of the GCK SNP rs1799884 with raised fasting glucose level (p = 0.015). Longitudinal association analyses showed that most of these associations did not change in the same individuals over an average follow-up time of 17.4 years, though there was some evidence that the association of the 447X allele of rs328 with raised HDL-C level significantly increased with age (p = 0.01), and that the association of the C allele of rs3135506 with raised triacylglycerol level significantly increased over time (p = 0.0007).

CONCLUSIONS/INTERPRETATION

The current study suggests that the effects of established gene variants on lipid and glucose traits do not tend to alter with age during adulthood or over time.

Polymorphism of apolipoprotein A5 is a risk factor for cerebral infarction in type 2 diabetes

This study investigated the association of apolipoprotein A5 (apoA5) gene polymorphism at position -1131T>C with cerebral infarction in patients with type 2 diabetes. A total of 256 type 2 diabetic patients without cerebral infarction (T2DM), 220 type 2 diabetic patients with cerebral infarction (T2DMCI) and 340 healthy subjects were recruited from the same region (Hubei province, China). The genotype of apoA5 -1131T[Symbol: see text]C was analyzed by polymerase chain reaction, followed by restriction fragment length polymorphism (PCR-RFLP). Total cholesterol, HDL cholesterol, LDL-cholesterol and triglycerides were quantitatively detected by using standard enzymatic techniques. The results showed that the prevalence of the apoA5 -1131C allele was significantly higher in T2DMCI group than that in control group (42.7% versus 31.2%, P<0.01). The carriers of rare C allele had higher TG levels as compared with carriers of common allele in the three groups (P<0.01). Logistic regression models, which were adjusted for age, gender, blood pressure, BMI, FBS, smoking, LDL-C and HDL-C, revealed that patients carrying the apoA5 -1131C allele and CC homozygotes were at high risk for T2DMCI. It was concluded that the apoA5 -1131C allele variant is an independent genetic risk factor for T2DMCI.

Determinants of plasma apolipoprotein A-V and APOA5 gene transcripts in humans

OBJECTIVE

Apolipoprotein A-V (apoAV) contributes to the regulation of triglyceride metabolism, which plays a role in the pathogenesis of atherosclerotic diseases. We therefore ascertained determinants of hepatic APOA5 transcript and apoAV plasma levels in humans.

DESIGN

We determined influences of anthropometric variables, biochemical factors related to lipid and glucose metabolism, hepatic mRNA levels transcribed from the APOA1/C3/A4/A5 cluster and transcription factor genes implicated in the regulation of APOA5 as well as common single nucleotide polymorphisms (SNPs) at the APOA5 locus on APOA5 expression in 89 obese patients and 22 non-obese controls.

RESULTS

Mean, age and sex adjusted, hepatic APOA5 mRNA or apoAV plasma levels did not differ by obesity status, homoeostasis model assessment insulin resistance or inflammatory markers. In multivariate regression models, the c56C > G SNP, plasma apoCIII, plasma nonesterified fatty acids, hepatic APOA5 transcripts, sex and a weak association with obesity status explained 61% of the variance in apoAV plasma levels. Hepatic transcript levels of carnitine palmitoyltransferase 1 (CPT1A1) and peroxisome proliferator-activated receptor alpha (PPARA), plasma nonesterified fatty acids and the c56C > G SNP explained 48% of the variance in hepatic APOA5 transcript levels.

CONCLUSION

Apolipoprotein A-V plasma levels are independently associated with plasma free fatty acid and hepatic APOA5 mRNA levels. Associations of APOA5 transcripts with PPARA and CPT1A1 transcripts suggest that APOA5 expression is intimately linked to hepatic lipid metabolism.

Influence of genetic factors in the modulation of postprandial lipemia

Postprandial lipemia is traditionally defined by the extent and duration of the increase in plasma triglycerides in response to a fat-enriched meal. The relationship between alimentary lipemia and coronary disease is of great interest in view of the epidemiological and experimental evidence that underlies it. The rate of synthesis of triglyceride-rich lipoproteins, lipoprotein lipase-mediated triglyceride hydrolysis, and the hepatic capture of chylomicron remnants via the interaction of the lipoprotein receptor with APOE and LPL, are the fundamental pillars of the metabolism and modification of these lipoproteins. The modulation of such phenomena is influenced by both genetic and environmental factors, thus explaining their extraordinary individual variance. This review presents the current evidence linking a number of candidate genes to the modulation of postprandial lipid metabolism.

An apolipoprotein A-V gene SNP is associated with marked hypertriglyceridemia among Asian-American patients

Apolipoprotein A-V (apoA-V) is an important regulator of plasma levels of triglyceride (TG) in mice. In humans, APOA5 genetic variation is associated with TG in several populations. In this study, we determined the effects of the p.185Gly>Cys (c.553G>T; rs2075291) polymorphism on plasma TG levels in subjects of Chinese ancestry living in the United States and in a group of non-Chinese Asian ancestry. The frequency of the less common cysteine allele was 4-fold higher (15.1% vs. 3.7%) in Chinese high-TG subjects compared with a low-TG group (Chi-square = 20.2; P < 0.0001), corresponding with a 4.45 times higher risk of hypertriglyceridemia (95% confidence interval, 2.18-9.07; P < 0.001). These results were replicated in the non-Chinese Asians. Heterozygosity was associated, in the high-TG group, with a doubling of TG (P < 0.001), mainly VLDL TG (P = 0.014). All eleven TT homozygotes had severe hypertriglyceridemia, with mean TG of 2,292 +/- 447 mg/dl. Compared with controls, carriers of the T allele had lower postheparin lipoprotein lipase activity but not hepatic lipase activity. In Asian populations, this common polymorphism can lead to profound adverse effects on lipoprotein profiles, with homozygosity accounting for a significant number of cases of severe hypertriglyceridemia. This specific apoA-V variant has a pronounced effect on TG metabolism, the mechanism of which remains to be elucidated.

Apolipoprotein A-V gene polymorphisms in subjects with metabolic syndrome

BACKGROUND

Genetic variation at the apolipoprotein A-V locus, recently discovered proximal to the APOA1/C3/A4 gene cluster, is associated with elevated triglyceride concentrations, a risk factor for atherosclerosis.

METHODS

The goal of our study was to determine the association of two apolipoprotein A-V (APOA5) gene polymorphisms in a group of urban Romanian subjects with the prevalence of the metabolic syndrome. For this purpose, we assayed -1.131T>C and c.56C>G polymorphisms for 279 subjects divided into three groups: a control group, a metabolic syndrome group and a cardiovascular disease group. Then we correlated the minor allele frequencies with body mass index and biochemical parameters.

RESULTS

We obtained higher frequency for -1.131C compared to c.56G alleles, both mainly distributed in overweight subjects. Body mass index and triglyceride levels were higher in -1.131C allele carriers in metabolic syndrome patients, but were not significantly different in c.56G carriers compared to those with the native gene. Metabolic syndrome -1.131C homozygotes presented lower high-density lipoprotein cholesterol and higher glucose levels compared to subjects with the native gene. Total cholesterol, low-density lipoprotein cholesterol and insulin were not different between -1.131C or c.56G allele carriers and those with the native gene.

CONCLUSIONS

Our results demonstrate an independent risk for -1.131T>C APOA5 gene polymorphisms in the development of metabolic syndrome.

APOA5 variants and metabolic syndrome in Caucasians

Apolipoprotein A5 (APOA5) gene variants were reported to be associated with two components of metabolic syndrome (MetS): higher TG levels and lower HDL levels. Moreover, a recent Japanese case-control study found variant -1131T>C associated with MetS itself. Thus, our study systematically analyzed the APOA5 gene for association with lipid parameters, any other features of MetS, including waist circumference, glucose-related parameters, blood pressure, uric acid, and MetS itself in Caucasians. Ten polymorphisms were analyzed in a large fasting sample of the population-based Cooperative Health Research in the Region of Augsburg (KORA) survey S4 (n = 1,354; southern Germany) and in a second fasting sample, the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR) study (n = 1,770; Austria). Minor alleles of variants -1131T>C, -3A>G, c.56C>G, 476G>A, and 1259T>C were significantly associated with higher TG levels in single polymorphism (P < 0.001) and haplotype (P <or= 6.6 x 10(-6)) analysis. Besides associations with lower HDL levels in SAPHIR (P <or= 0.001), there were no significant findings with any other features of MetS. Variant c.56C>G was associated with higher risk for MetS [odds ratio (95% confidence interval) = 1.43 (1.04, 1.99), P = 0.03 for KORA and 1.48 (1.10, 1.99), P = 0.009 for SAPHIR). Our study confirms the association of the APOA5 locus with TG and HDL levels in humans. Furthermore, the data suggest a different mechanism of APOA5 impact on MetS in Caucasians, as variant c.56C>G (not analyzed in the Japanese study) and not -1131T>C, as in the Japanese subjects, was associated with MetS.

Apolipoprotein A5 T-1131C variant confers risk for metabolic syndrome

The -1131C is a naturally occurring variant of the apolipoprotein A5 (ApoA5) gene, which has been shown to associate with increased triglyceride levels. This variant has also been shown to confer risk for development of ischemic heart disease and stroke. The gene is in linkage disequilibrium with factors known to correlate with impaired glucose homeostasis. These observations prompted us to study the prevalence of the ApoA5 -1131C allele in patients with metabolic syndrome. A total of 201 metabolic syndrome patients and 210 controls were studied. In both groups the triglyceride levels of patients with -1131C allele were significantly increased compared to the subjects with -1131T allele (3.22+/-0.43 mmol/l vs. 2.24+/-0.12 mmol/l, p<0.01 in the metabolic syndrome patients; 2.10+/-0.19 mmol/l vs. 1.22+/-0.05 mmol/l, p<0.01 in the controls). In metabolic syndrome patients the prevalence of the ApoA5 -1131C variant was increased compared to the healthy controls (11% vs. 6.20%). Multiplex regression analysis model adjusted for age, gender, serum total cholesterol levels, acute myocardial infarction and stroke events revealed that the examined ApoA5 variant confers risk for the development of metabolic syndrome: the odds ratio at 95% confidence interval was 3.622 (1.200-10.936), p=0.02. Our findings strongly suggest that this variant is a risk factor for the development of hypertriglyceridemia and metabolic syndrome.

Gene-environment interactions in the pathogenesis of type 2 diabetes and metabolism

PURPOSE OF REVIEW

Gene-environment interaction can be viewed as a departure from an otherwise expected additivity of genetic and environmental factors on a given outcome measure. Important genetic and environmental factors contribute to the pathogenesis of type 2 diabetes and intermediary traits, probably modulated by their complex interaction. This paper provides an update on the current literature investigating gene-environment interactions of type 2 diabetes and metabolic phenotypes, and discusses the future perspectives of this research.

RECENT FINDINGS

Recent advances in gene-environment interaction studies of metabolism have involved LIPC, APOA5 and PPARG variation, and nutrition and physical activity, of which the most consistently replicated observations have been obtained for APOA5. Also, intervention studies of the promising TCF7L2 type 2 diabetes gene and possible future strategies are discussed.

SUMMARY

Possibly as a result of the complexity of these multifactorial diseases, recent years have seen only limited success in unravelling significant gene-environment interactions, but important insights have been gained and they hold promise for implementation in lifestyle intervention strategies. We need to evolve to more complex, but realistic, scenarios involving several genes and environmental factors. Recent progress in statistical methods allowing for higher-order interactions may make this possible.

Familial aggregation of metabolic syndrome among the Chinese: report from the Chin-Shan community family study

Genetic study on metabolic syndrome is a great challenge, due to its complex traits and the pleiotropic manifestation of atherosclerosis. Familial aggregation and recurrence risk ratio can provide the insight of possible genetic mechanism. The Chin-Shan community family study was based on adolescent probands and their relatives (1356 subjects) who were recruited from one junior high school in the community. Structured questionnaires and biochemical measures were obtained in standard procedures. Definition of metabolic syndrome was followed using the criteria defined by the third adult treatment panel, with a modification of the criteria for adolescent and Asian population. Grandmothers had the highest frequencies (70%) in metabolic syndrome and various atherosclerotic risks. Three factors were found and thus explained 68% of the overall variance. Estimated heritability was the highest in LDL and cholesterol factor (0.36 and 0.40), then blood pressure/obesity factor (0.27), and insulin resistance/dyslipidemia (0.27). Recurrence risk ratio among siblings was 2.95 (95% confidence interval [CI]: 1.39-6.26). The adjusted odds ratio (OR) of proband's metabolic syndrome status was 1.99 (95% CI: 1.08-3.66). The adjusted odds ratios for the three factors for predicting metabolic syndrome were all significant, with highest risk in blood pressure/obesity factor (OR: 1.27, CI: 1.22-1.33), then insulin resistance/dyslipidemia (OR: 1.29, CI: 1.16-1.23). This study demonstrated clearly familial aggregation and recurrence risk ratio of metabolic syndrome and components among the general ethnic Chinese population in Taiwan.

A case-control study of apoA5 -1131T-->C polymorphism that examines the role of triglyceride levels in diabetic nephropathy

Patients with diabetic nephropathy (DN) have increased plasma fasting triglyceride (TG) levels, and most prospective studies report that elevated TG precedes DN. TG-rich lipoprotein particles might promote progression of DN. To test the hypothesis that elevated TG levels contribute to the development of DN, one may examine whether a polymorphism strongly associated with TG levels affects DN risk. The apolipoprotein A5 (apoA5) -1131T-->C polymorphism has a large effect on the TG level, and all three genotypes are relatively common in East Asians. Therefore, we sought to examine the association of this polymorphism with DN. We genotyped the apoA5 -1131T-->C polymorphism in a case-control study involving 367 Chinese Type 2 diabetes patients with DN and 382 without DN, as well as 198 subjects without diabetes. Mean fasting TG levels were higher in CC than in TT carriers by 41%, 54%, and 62% in each of the three subject groups, respectively. However, the genotype distributions did not differ between patients with and without nephropathy (P=.69). Therefore, these results weigh against the hypothesis that high fasting TG per se causes DN. The strong association between TG level and DN may be due to a factor that is usually closely linked to TG level but that is not affected by the apoA5 polymorphism.