Variants at the APOA5 locus, association with carotid atherosclerosis, and modification by obesity: the Framingham Study

Walking the VLDL tightrope in cardiometabolic diseases

Very-low-density lipoprotein (VLDL), a triglyceride-rich lipoprotein secreted by hepatocytes, is pivotal for supplying peripheral tissues with fatty acids for energy production. As if walking on a tightrope, perturbations in the balance of VLDL metabolism contribute to cardiometabolic dysfunction, promoting pathologies such as cardiovascular disease (CVD) or metabolic dysfunction-associated steatotic liver disease (MASLD). Despite the advent of lipid-lowering therapies, including statins and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, risks for cardiovascular events persist. With limitations to currently available CVD therapeutics and no US Food and Drug Administration (FDA)-approved treatment for MASLD, this review summarizes the current understanding of VLDL metabolism that sheds light on novel therapeutic avenues to pursue for cardiometabolic disorders.

Genetic association analysis of rs662799 ( − 1131A > G) polymorphism of APOA5 gene with morphometric and physio-metric traits using multiplex PCR

Background

The apolipoprotein A5 (APOA5) gene, significantly expressed in liver, has been involved in regulation of triglyceride metabolism, plasma lipid levels, serum adipokine levels and cardiovascular traits. A single-nucleotide polymorphism rs662799 ( − 1131A > G), 2 Kb upstream in the promoter region of this gene, causes decrease in the concentration of the product coded by this gene; hence, it may be responsible for impairments in normal function of the gene, ultimately leading to disease condition. Keeping in view the importance of APOA5 gene, the aim of the present study was to examine the association of genetic variant rs662799 of APOA5 gene with two quantitative traits simultaneously, viz. body mass index and blood pressure.

Results

The study involved a population of 246 subjects from North Indian region. Measurements of morphometric and physio-metric parameters were recorded using standard measures. Genotyping of APOA5 gene polymorphism (rs662799) using Tetra-primer amplification refractory mutation system PCR was performed. Statistical analyses were carried out using MS-Excel and SigmaPlot, and significance level was setup as p < 0.05. The allelic distribution of rs662799 polymorphism in this population was 77% for major allele (A) and 23% for minor allele (G). Significant association of rs662799 with increased body mass index and blood pressure was observed, with the presence of allele G. Under recessive genetic model, rs662799 polymorphism conferred a 17.71-fold risk of elevated body mass index (OR = 17.71, p < 0.001, CI (95%) = 4.05–77.46), and for increase in blood pressure, 3.79- and 3.83-fold risk of systolic blood pressure and diastolic blood pressure (OR = 3.792, p = 0.023, CI (95%) = 1.25–11.509 and OR = 3.83, p = 0.012, CI (95%) = 1.375–10.68, respectively) was observed. Under dominant genetic model, it showed a 3.060-fold risk of increase in body mass index (OR = 3.060, p < 0.001, CI (95%) = 1.78–5.25).

Conclusions

G allele of rs662799 of APOA5 gene showed significant susceptible association with BMI and BP. This study may be helpful for clinicians and researchers to investigate the diagnostic and prognostic value of the gene in question.

Association of c.56C > G (rs3135506) Apolipoprotein A5 Gene Polymorphism with Coronary Artery Disease in Moroccan Subjects: A Case-Control Study and an Updated Meta-Analysis

PURPOSE

Coronary artery diseases (CAD) are clinical cardiovascular events associated with dyslipidemia in common. The interaction between environmental and genetic factors can be responsible for CAD. The present paper aimed to examine the association between c.56C > G (rs3135506) APOA5 gene polymorphism and CAD in Moroccan individuals and to perform an association update meta-analysis.

MATERIALS AND METHODS

The c.56C > G variant was genotyped in 122 patients with CAD and 134 unrelated controls. Genetic association analysis and comparison of biochemical parameters were performed using R statistical language. In addition, a comprehensive meta-analysis including eleven published studies in addition to our case-control study results was conducted using Review Manager 5.3. Publication bias was examined by Egger's test and funnel plot.

RESULTS

The case-control study data showed that the c.56C > G polymorphism was associated with CAD susceptibility under codominant (P-value = 0.001), recessive (P-value <0.001) and log-additive (P-value = 0.008) inheritance models. In addition, this polymorphism was significantly associated with increased levels of systolic and diastolic blood pressures, triglycerides, glycemia, and total cholesterol. Furthermore, meta-analysis showed a significant association between the c.56C > G gene polymorphism and increased risk of CAD under recessive (OR = 3.39[1.77-6.50], P value <0.001) and homozygote codominant (OR = 3.96[2.44-6.45], P value <0.001) models.

CONCLUSION

Our case-control study revealed a significant association between c.56C > G polymorphism and CAD in the Moroccan population. In addition, meta-analysis data supported the implication of this polymorphism in CAD susceptibility.

New Insights into Apolipoprotein A5 and the Modulation of Human Adipose-derived Mesenchymal Stem Cells Adipogenesis

Background:

The hallmark of obesity is the excessive accumulation of triglyceride (TG) in adipose tissue. Apolipoprotein A5 (ApoA5) has been shown to influence the prevalence and pathogenesis of obesity. However, the underlying mechanisms remain to be clarified.

Methods:

Human adipose-derived mesenchymal stem cells (AMSCs) were treated with 600 ng/ml human recombinant ApoA5 protein. The effect of ApoA5 on intracellular TG content and adipogenic related factors expression were determined. Furthermore, the effect of ApoA5 on CIDE-C expression was also observed.

Results:

During the process of adipogenesis, ApoA5 treatment reduced the intracellular accumulation of lipid droplets and the TG levels; meanwhile, ApoA5 down-regulated the expression levels of adipogenic related factors, including CCAAT enhancer-binding proteins α/β (C/EBPα/β), fatty acid synthetase (FAS), and fatty acid-binding protein 4 (FABP4). Furthermore, the suppression of adipogenesis by ApoA5 was mediated through the inhibition of CIDE-C expression, an important factor which promotes the process of adipogenesis. However, over-expressing intracellular CIDE-C could lead to the loss-of-function of ApoA5 in inhibiting AMSCs adipogenesis.

Conclusions:

In conclusion, ApoA5 inhibits the adipogenic process of AMSCs through, at least partly, down-regulating CIDE-C expression. The present study provides novel mechanisms whereby ApoA5 prevents obesity via AMSCs in humans.

Early Subclinical Atherosclerosis in Gestational Diabetes: The Predictive Role of Routine Biomarkers and Nutrigenetic Variants

Gestational diabetes mellitus (GDM) can be considered a silent risk for out-of-pregnancy diabetes mellitus (DM) and cardiovascular disease (CVD) later in life. We aimed to assess the predictive role of 3^rd trimester lipid profile during pregnancy for the susceptibility to markers of subclinical atherosclerosis (CVD susceptibility) at 3 years in a cohort of women with history of GDM. A secondary aim is to evaluate the usefulness of novel nutrigenetic markers, in addition to traditional parameters, for predicting early subclinical atherosclerosis in such women in order to plan adequate early prevention interventions. We assessed 28 consecutive GDM women in whom we collected socio-demographic characteristics and clinical and anthropometric parameters at the 3^rd trimester of pregnancy. In a single blood sample, from each patient, we assessed 9 single nucleotide polymorphisms (SNPs) from 9 genes related to nutrients and metabolism, which were genotyped by High Resolution Melting analysis. All women then attended a 3-year-postpartum follow-up and on that occasion performed an oral glucose tolerance test (OGTT, with 75 g oral glucose), the measurement of carotid artery intima-media thickness (cIMT), and analyses of metabolic parameters. In addition, we evaluated the physical activity level and the adherence to Mediterranean diet (MedDiet) using the International Physical Activity Questionnaire (IPAQ-short version) and PREDIMED questionnaires. We found an association between 3^rd trimester triglycerides and cIMT (p = 0.014). We also found significant associations between the APOA5 CC genotype and cIMT after adjustments for age and body mass index (p = 0.045) and between the interaction CC APOA5/CC LDLR and cIMT (p = 0.010). At the follow-up, the cohort also featured a mean BMI in the overweight range and a high mean waist circumference. We found no difference in the MedDiet adherence, physical activity, and smoking but an inverse correlation between the PREDIMED and the IPAQ scores with the IMT. In conclusion, this preliminary study provides insight into the predictive role of lipid profile during pregnancy and of some genetic variants on cIMT taken as a parameter of subclinical CVD susceptibility in GDM.

A promoter variant of the APOA5 gene increases atherogenic LDL levels and arterial stiffness in hypertriglyceridemic patients

Hypertriglyceridemia is recognized as an independent risk factor for coronary artery disease. The apolipoprotein A5 gene (APOA5) is a key regulator of triglyceride levels. We aimed to evaluate the associations of single nucleotide polymorphisms (SNPs) in APOA5, including -1131T>C and c.553G>T, with hypertriglyceridemia, apoA5 concentrations, atherogenic LDL cholesterol levels, and arterial stiffness in hypertriglyceridemic patients. The study population included 599 hypertriglyceridemic patients (case) and 1,549 untreated normotriglyceridemic subjects (control). We genotyped two APOA5 variants, -1131T>C (rs662799) and c.553G>T (rs2075291). The frequencies of the CC genotype of -1131T>C (0.165) and the T allele of c.553G>T (0.119) were significantly higher in hypertriglyceridemic patients than in normotriglyceridemic subjects (0.061 and 0.070, respectively; all p<0.001). In the control and case groups, both the -1131T>C and c.553G>T variants were associated with higher triglyceride and lower HDL cholesterol levels. Controls with the -1131CC variant had lower apoA5 concentrations than controls with the -1131TT variant. Similar effects of the -1131T>C variant on apoA5 were observed in the cases. In the hypertriglyceridemic group, the -1131T>C variant was associated with a smaller LDL particle size, higher levels of oxidized LDL and malondialdehyde, and higher brachial-ankle pulse wave velocity. The -1131T>C and c.553G>T polymorphisms were associated with hypertriglyceridemia in the study population, but only the -1131T>C polymorphism directly affected apoA5 concentrations. Hypertriglyceridemic patients carrying the APOA5 -1131T>C polymorphism exhibited increased atherogenic LDL levels and arterial stiffness, probably due to an effect of the -1131T>C polymorphism on apoA5 concentrations.

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.

The impact of APOA5, APOB, APOC3 and ABCA1 gene polymorphisms on ischemic stroke: Evidence from a meta-analysis

BACKGROUND AND AIMS

Genetic studies have been reported on the association between APOA5, APOB, APOC3 and ABCA1 gene polymorphisms and ischemic stroke, but results remain controversial. Hence, this meta-analysis aimed to infer the causal relationships of APOA5 (rs662799, rs3135506), APOB (rs693, rs1042031, rs1801701), APOC3 (rs4520, rs5128, rs2854116, rs2854117) and ABCA1 rs2230806 with ischemic stroke risk.

METHODS

A systematic review was performed for all the articles retrieved from multiple databases, up until March 2017. Data were extracted from all eligible studies, and meta-analysis was carried out using RevMan 5.3 and R package 3.2.1. The strength of association between each studied polymorphism and ischemic stroke risk was measured as odds ratios (ORs) and 95% confidence intervals (CIs), under fixed- and random-effect models.

RESULTS

A total of 79 studies reporting on the association between the studied polymorphisms and ischemic stroke risk were identified. The pooled data indicated that all genetic models of APOA5 rs662799 (ORs = 1.23-1.43), allelic and over-dominant models of APOA5 rs3135506 (ORs = 1.77-1.97), APOB rs1801701 (ORs = 1.72-2.13) and APOB rs1042031 (ORs = 1.66-1.88) as well as dominant model of ABCA1 rs2230806 (OR = 1.31) were significantly associated with higher risk of ischemic stroke. However, no significant associations were observed between ischemic stroke and the other five polymorphisms, namely ApoB (rs693) and APOC3 (rs4520, rs5128, rs2854116 and rs2854117), under any genetic model.

CONCLUSIONS

The present meta-analysis confirmed a significant association of APOA5 rs662799 CC, APOA5 rs3135506 CG, APOB rs1801701 GA, APOB rs1042031 GA and ABCA1 rs2230806 GG with increased risk of ischemic stroke.

Genetic predisposition of human plasma triglyceride concentrations

The issue of plasma triglyceride levels relative to the risk of development of cardiovascular disease, as well as overall mortality, has been actively discussed for many years. Like other cardiovascular disease risk factors, final plasma TG values have environmental influences (primarily dietary habits, physical activity, and smoking), and a genetic predisposition. Rare mutations (mainly in the lipoprotein lipase and apolipoprotein C2) along with common polymorphisms (within apolipoprotein A5, glucokinase regulatory protein, apolipoprotein B, apolipo-protein E, cAMP responsive element binding protein 3-like 3, glycosylphosphatidylinositol-anchored HDL-binding protein 1) play an important role in determining plasma TG levels.

Frameshift mutation in the APOA5 gene causing hypertriglyceridemia in a Pakistani family: Management and considerations for cardiovascular risk

We report a novel homozygous apolipoprotein A5 (APOA5) frameshift mutation (c.G425del-C, p.Arg143AlafsTer57) identified in a 12-year-old boy of Pakistani origin with severe hypertriglyceridemia (up to 35 mmol/L) and type V hyperlipoproteinemia. The patient did not respond to fibrate therapy, but his condition improved under a very low fat diet, although compliance was suboptimal. Heterozygous status was detected in both parents (consanguineous union) and one sibling, all showing moderate hypertriglyceridemia (between 5 and 10 mmol/L). There was a significant family history of premature cardiovascular disease. The index case was also diagnosed with a coronary artery anomaly. Considering the recently reported association of rare mutations in APOA5 with the risk of early myocardial infarction, we discuss the implications of these findings for the young man and his family.

Polymorphisms in LPL, CETP, and HL protect HIV-infected patients from atherogenic dyslipidemia in an allele-dose-dependent manner

HIV-infected patients treated with highly active antiretroviral therapy (HAART) may be predisposed to a lipid profile, associated with increased cardiovascular risk, derived from having high triglycerides (TG) and low high-density lipoprotein cholesterol (HDLc) levels. We propose that genetic variability leaves some HIV-infected patients more predisposed to this lipid profile than others. We performed a cross-sectional, observational study including 321 antiretroviral-treated HIV-infected patients classified as normolipidemic (n=173) or presenting with high TG (≥1.7 mmol/liter) and low HDLc [<1.02 (men) or 1.28 mmol/liter (women)] (n=148) to investigate the impact of 13 polymorphisms of 9 genes affecting lipid metabolism (APOA5, APOC3, LPL, CETP, HL, MTP, APOE, LRP5, and VLDLR genes). The polymorphism rs328 in LPL was 40% significantly more frequent in normolipidemics (p=0.018), and in the same group, polymorphisms rs708272 in CETP and rs1800588 in HL were 10% significantly more frequent (p=0.037 for both polymorphisms). Patients who presented a combination of one to six alleles from these polymorphisms had 10% increased HDLc levels [1.13 (0.40) vs. 1.24 (0.23) mmol/liter, p=0.002] and a trend toward lower triglycerides [2.23 (2.34) vs. 1.89 (1.24) mmol/liter] and lower remnant-like particle cholesterol (RLPc) [16.41 (11.42) vs. 12.99 (11.69) mmol/liter]. This effect was dependent on the number of protective alleles and independent of the regimen administered. Polymorphisms in LPL, CETP, and HL protect HIV-infected patients from developing the dyslipidemia derived from high TG and low HDLc levels in a dose-dependent manner.

APOA5 variants predispose hyperlipidemic patients to atherogenic dyslipidemia and subclinical atherosclerosis

BACKGROUND

Triglycerides (TG) are the initiators of the metabolic changes leading to the atherogenic dyslipidemia, which is a major inducer of atherosclerosis as a result of quantitative and qualitative changes in lipoprotein subclass distributions. We hypothesized that variation at the of APOA5 gene locus, encoding apoAV, a key regulator of TG levels, significantly affect lipoprotein subclass distributions toward a more atherogenic pattern in both hyperTG patients and dyslipemic patients.

METHODS

We recruited four hundred and twenty-two subjects attending a Lipid Clinic, prior to lipid-lowering treatment. We genotyped two APOA5 variants, rs662799 (-1131T>C) and rs3135506 (S19W). Circulating lipoproteins were determined by nuclear magnetic resonance (NMR). Intima-media thickness (IMT) was evaluated using B-mode ultrasound.

RESULTS

Carriers of the rare alleles of rs662799 and rs3135506 compared to common allele homozygotes, had a significantly proatherogenic profile of the VLDL and LDL subclasses, resulting in increased concentrations of the proatherogenic subclasses, large VLDLs (+133%, p<0.001) and small LDLs (+34%, p=0.014). Significant changes in smaller HDL (+71%, p=0.032), as well as an 18% decrease in large HDL (p=0.046), were also been observed. This atherogenic NMR subclass distribution was significantly associated with increased carotid IMT. The observed effects were significantly stronger in patients with a BMI≥25 kg/m2 and in male and female patients with a waist circumference≥90 cm or ≥85 cm, respectively.

CONCLUSION

In a dyslipemic population, genetic variants of APOA5 modulate lipoprotein subclass distributions, inducing an atherogenic profile associated with IMT defined subclinical atherosclerosis.

Mosaicism of mitochondrial genetic variation in atherosclerotic lesions of the human aorta

OBJECTIVE

The aim of the present study was an analysis of heteroplasmy level in mitochondrial mutations 652delG, A1555G, C3256T, T3336C, 652insG, C5178A, G12315A, G13513A, G14459A, G14846A, and G15059A in normal and affected by atherosclerosis segments of morphologically mapped aortic walls.

METHODS

We investigated the 265 normal and atherosclerotic tissue sections of 5 human aortas. Intima of every aorta was divided according to morphological characteristics into segments with different types of atherosclerotic lesions: fibrous plaque, lipofibrous plaque, primary atherosclerotic lesion (fatty streak and fatty infiltration), and normal intima from human aorta. PCR-fragments were analyzed by a new original method developed in our laboratory on the basis of pyrosequence technology.

RESULTS

According to the obtained data, mutations G12315A and G14459A are significantly associated with total and primary atherosclerotic lesions of intimal segments and lipofibrous plaques (P ≤ 0.01 and P ≤ 0.05, accordingly). Mutation C5178A is significantly associated with fibrous plaques and total atherosclerotic lesions (P ≤ 0.01). A1555G mutation shows an antiatherosclerotic effect in primary lesion in lipofibrous plaques (P ≤ 0.05). Meanwhile, G14846A mutation is antiatherogenic for lipofibrous plaques (P ≤ 0.05).

CONCLUSION

Therefore, mutations C5178A, G14459A, G12315A, A1555G, and G14846A were found to be associated with atherosclerotic lesions.

Genetics and causality of triglyceride-rich lipoproteins in atherosclerotic cardiovascular disease

Triglycerides represent 1 component of a heterogeneous pool of triglyceride-rich lipoproteins (TGRLs). The reliance on triglycerides or TGRLs as cardiovascular disease (CVD) risk biomarkers prompted investigations into therapies that lower plasma triglycerides as a means to reduce CVD events. Genetic studies identified TGRL components and pathways involved in their synthesis and metabolism. We advocate that only a subset of genetic mechanisms regulating TGRLs contribute to the risk of CVD events. This "omic" approach recently resulted in new targets for reducing CVD events.

Apolipoprotein A-V level may contribute to the development of obesity-associated dyslipidemia

AIM

In a mice study, insulin suppressed apolipoprotein A-V (apoA-V) gene expression in a dose dependent manner. Thus, we investigated the association between apoA-V levels and dyslipidemias in obese children with hyperinsulinemia.

METHODS

The subjects were 17 obese children (15 male, 2 female) aged 11.8 ± 2.4 years. Total cholesterol (TC), high-density lipoprotein cholesterol (HDLC), triglyceride (TG), apoA-V and insulin levels were determined.

RESULTS

Obese children with hyperinsulinemia had greater percent overweight, higher TG level, lower HDLC level and lower apoA-V level than those without hyperinsulinemia. In simple regression analysis, apoA-V level correlated negatively with TG (r = -0.613, p = 0.0152) and insulin levels (r = -0.566, p = 0.0279), and positively correlated with HDLC (r = 0.811, p = 0.0002). In stepwise regression analysis, insulin level emerged as the independent determinant of TG level after apoA-V level was taken into account, whereas apoA-V emerged as the independent determinant of HDLC level after adjusting for insulin level.

CONCLUSIONS

Insulin may be a potent regulator of serum apoA-V level in obesity, and apoA-V level may partly contribute to the development of obesity-associated dyslipidemia.

Effects of APOA5 -1131T>C (rs662799) on fasting plasma lipids and risk of metabolic syndrome: evidence from a case-control study in China and a meta-analysis

The apolipoprotein A5 (APOA5) gene −1131T>C (rs662799) has been suggested to be involved in the pathway of lipid homeostasis and the development of metabolic syndrome (MetS). However, the findings are not consistent. To systematically evaluate the associations between −1131T>C polymorphism and fasting lipid parameters and the risk of MetS, we conducted a case-control study in a Chinese population and a meta-analysis. The findings from 1840 Chinese participants indicated that the C allele carriers had significantly higher fasting total cholesterol (TC), triglycerides (TG) and lower HDL-cholesterol (HDL-C) than the TT homozygotes carriers. The −1131C allele was also found to be significantly associated with increased risk of MetS (OR  =  1.40, 95% confidence interval (CI)  =  1.15, 1.69) compared to the TT homozygotes. In the meta-analysis of 51,868 participants from 46 East Asian studies, 26 European studies and 19 studies of other ethnic groups, the −1131C allele was associated with higher fasting TC (weighted mean difference (WMD)  =  0.08 mmol/L, 95% CI  =  0.05, 0.10, P = 1.74×10⁻⁹), TG (WMD  =  0.30 mmol/L, 95% CI  =  0.26, 0.33, P =  1.87×10⁻⁵⁵), LDL-cholesterol (LDL-C) (WMD  =  0.04 mmol/L, 95% CI  =  0.02, 0.07, P = 0.002), and lower HDL-C (WMD  =  −0.05 mmol/L, 95% CI  =  −0.06,−0.04, P = 1.88×10⁻²¹), respectively. Based on 12 studies with 5,573 MetS cases and 8,290 controls from 5 East Asian studies, 5 European studies and 2 studies of other ethnic groups, the −1131C allele was associated with increased risk of MetS with an OR (95% CI)  =  1.33 (1.16, 1.53) in the overall population, 1.43 (1.29, 1.58) in East Asian and 1.30 (0.94, 1.78) in European populations. In conclusion, the −1131C allele may be associated with elevated levels of fasting TG, TC, LDL-C and decreased HDL-C, and increased risk of MetS, especially in East Asians.

The paradox of ApoA5 modulation of triglycerides: evidence from clinical and basic research

Apolipoprotein A5 (ApoA5) is a key regulator of plasma triglycerides (TG), even though its plasma concentration is very low compared to other known apoproteins. Over the years, researchers have attempted to elucidate the molecular mechanisms by which ApoA5 regulates plasma TG in vivo. Though still under debate, two theories broadly describe how ApoA5 modulates TG levels: (i) ApoA5 enhances the catabolism of TG-rich lipoproteins and (ii) it inhibits the rate of production of very low-density lipoprotein (VLDL), the major carrier of TGs. This review will summarize the basic and clinical studies that describe the importance of ApoA5 in TG metabolism. Population studies conducted in various countries have demonstrated an association between single nucleotide polymorphisms (SNPs) in ApoA5 and the increased risk to cardiovascular disease and metabolic syndrome (including diabetes and obesity). ApoA5 is also highly expressed during liver regeneration and is an acute phase protein associated with HDL, which is independent of its effects on TG metabolism.

CONCLUSION

Despite considerable evidences available from clinical and basic research studies on the role of ApoA5 in TG metabolism and its indirect link to metabolic diseases, additional investigations are needed to understand the paradoxical role of this important apoprotein is modulated by both diet and its polymorphism variants.

Nutritional status, genetic susceptibility, and insulin resistance--important precedents to atherosclerosis

Atherosclerosis is a progressive disease that starts early in life and is manifested clinically as coronary artery disease (CAD), cerebrovascular disease, or peripheral artery disease. CAD remains the leading cause of morbidity and mortality in Western society despite the great advances made in understanding its underlying pathophysiology. The key risk factors associated with CAD include hypercholesterolemia, hypertension, poor diet, obesity, age, male gender, smoking, and physical inactivity. Genetics also play an important role that may interact with environmental factors, including diet, nutritional status, and physiological parameters. Furthermore, certain chronic inflammatory conditions also predispose to the development of CAD. The spiraling increase in obesity rates worldwide has made it more pertinent than ever before to understand the metabolic perturbations that link over nutrition to enhanced cardiovascular risk. Great breakthroughs have been made at the pharmacological level to manage CAD; statins and aspirin have revolutionized treatment of CAD and prolonged lifespan. Nonetheless, lifestyle intervention prior to clinical presentation of CAD symptoms would negate/delay the need for chronic pharmacotherapy in at-risk individuals which in turn would relieve healthcare systems of a costly burden. Throughout this review, we debate the relative impact of nutrition versus genetics in driving CAD. We will investigate how overnutrition affects adipose tissue biology and drives IR and will discuss the subsequent implications for the cardiovascular system. Furthermore, we will discuss how lifestyle interventions including diet modification and weight loss can improve both IR and metabolic dyslipidemia that is associated with obesity. We will conclude by delving into the concept that nutritional status interacts with genetic susceptibility, such that perhaps a more personalized nutrition approach may be more effective in determining diet-related risk as well as response to nutritional interventions.

Impact of apolipoprotein A5 (APOA5) polymorphisms on serum triglyceride levels in schizophrenic patients under long-term atypical antipsychotic treatment

OBJECTIVES

Schizophrenic patients treated with clozapine or olanzapine often develop hypertriglyceridemia. The apolipoprotein A5 gene (APOA5), which affects VLDL production and lipolysis, has been implicated in the triglyceride (TG) metabolism. This study examined the association of common APOA5 genetic variants and TG levels in chronically institutionalized schizophrenic patients, on a stable dose of atypical antipsychotic (clozapine, olanzapine or risperidone.

METHODS

The TG levels in 466 schizophrenic patients treated with clozapine (n = 182), olanzapine (n = 89) or risperidone (n = 195) were measured. Patients were genotyped for the three APOA5 single nucleotide polymorphisms (SNPs) rs662799 (-1131T > C), rs651821 (3A > G) and rs2266788 (1891T > C).

RESULTS

A gene × drug interaction with TG levels was observed. In single-marker-based analysis, the minor alleles of the two polymorphisms (-1131C and -3G) were observed to be associated with increased TGs in patients treated with risperidone, but not with clozapine or olanzapine. Haplotype analysis further revealed that carriers of the haplotype constructed with the three minor alleles had higher TG levels than those who did not carry this haplotype in patients taking risperidone (CGC((+/+)) vs. = 125.4 ± 59.1 vs. 82.2 ± 65.8, P = 0.015; CGC((-/+ )) vs. CGC((-/-)) = 113.7 ± 80.4 vs. 82.2 ± 65.8, P = 0.012).

CONCLUSIONS

Our findings extend and add new information to the existing data regarding the association between APOA5 and TG regulation during long-term atypical antipsychotic treatment.

Variants in the APOA5 gene region and the response to combination therapy with statins and fenofibric acid in a randomized clinical trial of individuals with mixed dyslipidemia

OBJECTIVE

Atherogenic dyslipidemia is highly associated with coronary heart disease and is characterized by elevated triglycerides (TG), low high-density lipoprotein cholesterol (HDL-C), and elevated low-density lipoprotein cholesterol (LDL-C). The combination of statins and fibrates is a common modality to treat individuals with atherogenic dyslipidemia. We sought to identify single nucleotide polymorphisms (SNPs) associated with HDL-C, TG, and apolipoprotein A1 (ApoA-I) response to combination therapy with statins and fenofibric acid (FA) in individuals with atherogenic dyslipidemia.

METHODS

2228 individuals with mixed dyslipidemia who were participating in a multicenter, randomized, double-blind, active-controlled study comparing FA alone, in combination with a statin, or statin alone for a 12-week period, were genotyped for 304 candidate SNPs. A multivariate linear regression analysis for percent change in HDL-C, ApoA-I and TG levels was performed.

RESULTS

SNPs in the apolipoprotein (APO) A5-ZNF259 region rs3741298 (P = 1.8 × 10(-7)), rs964184 (P = 3.6 × 10(-6)), rs651821 (P = 4.5 × 10(-5)), and rs10750097 (P = 1 × 10(-4)), were significantly associated with HDL-C response to combination therapy with statins and FA, with a similar association identified for ApoA-I. A haplotype composed of the minor alleles of SNPs rs3741298, rs964184, and rs10750097, was associated with a positive response to statins and FA (P = 8.7 × 10(-7)) and had a frequency of 18% in the study population.

CONCLUSION

In a population with atherogenic dyslipidemia, common SNPs and haplotypes within the APOA5-ZNF259 region are highly associated with HDL-C and ApoA-I response to combination therapy with statins and FA.

Genetics of ischemic stroke: where are we now?

As stroke is the third leading cause of death after heart failure and tumors worldwide, cerebrovascular diseases reached substantial attention. In the past few years, significant progression has been seen in identification of genetic variants in the background of stroke and other cerebrovascular and cardiovascular events. Examination of these variants is a new approach to recognize pathogenesis of disorders that hopefully helps in future prevention and prospects of screening and, optimistically, it contributes to special care of patients susceptible for stroke. In the background of ischemic stroke several genetic variants have been identified, which localize in genes encoding proteins involved in hemostasis, renin-angiotensin system and lipid metabolism. The number of these variants exponentially increases permanently due to rapid spreading of genome wide association studies. The goal of this review is to summarize the results of genetic studies on ischemic stroke. Here the authors focus on genetic variants which can have major role in personalized medicine and prevention of stroke. Orv. Hetil., 2011, 152, 455–463.

A candidate gene study revealed sex-specific association between the OLR1 gene and carotid plaque

BACKGROUND AND PURPOSE

Sex differences have been recognized in stroke risk; however, the sex-dependent genetic contribution to stroke is unclear. We sought to examine the sex-dependent associations between genes involved in lipid metabolism and carotid atherosclerotic plaque, a subclinical precursor of stroke.

METHODS

For the Genetic Determinant of Subclinical Carotid Disease study, 287 Dominicans ascertained through the Northern Manhattan Study were examined for carotid plaque using high-resolution ultrasound. Sixty-four single nucleotide polymorphisms (SNPs) in 11 lipid-related genes were genotyped. Plaque presence and plaque subphenotypes, including multiple, thick, irregular, and calcified plaque, were analyzed. First, the interaction between each SNP and sex was evaluated for association with each plaque phenotype using multiple logistic regression and controlling for age, smoking, and the main effects of sex and SNP. For SNPs with suggestive evidence for interaction with sex (P<0.1 for the interaction term), stratification analysis by sex was performed to evaluate the sex-specific association between the SNP and plaque phenotypes.

RESULTS

The most compelling finding is with the missense SNP rs11053646 (K167N) in the OLR1 gene, which encodes lectin-like oxidized low-density lipoprotein receptor. Stratification analysis revealed a strong association between rs11053646 and all plaque phenotypes in women (OR, 2.44 to 5.86; P=0.0003 to 0.0081) but not in men (OR, 0.85 to 1.22; P=0.77 to 0.92).

CONCLUSIONS

Genetic variation in genes involved in lipid metabolism may have sex-dependent effects on carotid plaque burden. Our findings provide a plausible biological basis underlying the sex difference in cardiovascular risk.

APOA5 gene variation interacts with dietary fat intake to modulate obesity and circulating triglycerides in a Mediterranean population

APOA5 is one of the strongest regulators of plasma TG concentrations; nevertheless, its mechanisms of action are poorly characterized. Genetic variability at the APOA5 locus has also been associated with increased cardiovascular disease risk; however, this predisposition could be attenuated in the context of a prudent diet as traditionally consumed in the Mediterranean countries. We have investigated the interaction between a single nucleotide polymorphism (SNP) at the APOA5 gene (-1131T > C) and dietary fat that may modulate TG-rich lipoprotein concentrations and anthropometric measures in overweight and obese participants. We recruited 1465 participants from a Spanish population (20-65 y old; BMI 25-40 kg/m(2)) attending outpatient obesity clinics. Consistent with previous reports, we found an association between the APOA5-1131T > C SNP and TG-rich lipoprotein concentrations that were higher in carriers of the minor allele than in noncarriers (P < 0.001). Moreover, we found a significant genotype-dietary fat interaction for obesity traits. Participants homozygous for the -1131T major allele had a positive association between fat intake and obesity, whereas in those carrying the APOA5-1131C minor allele, higher fat intakes were not associated with higher BMI. Likewise, we found genotype-dietary fat interactions for TG-rich lipoproteins (P < 0.001). In conclusion, we have replicated previous gene-diet interactions between APOA5 -1131T > C SNP and fat intake for obesity traits and detected a novel interaction for TG-rich lipoprotein concentrations. Our data support the hypothesis that the minor C-allele may protect those consuming a high-fat diet from obesity and elevated concentrations of TG-rich lipoproteins.

Association of apolipoprotein A5 gene promoter region -1131T>C with risk of stroke in Han Chinese

BACKGROUND

Ischemic stroke is a suddenly developing temporary or often permanent damage of the brain. Several candidate genes have been shown to have an impact in the pathogenesis of ischemic stroke. Recently, the -1131T>C polymorphism in apolipoprotein A5 (APOA5) gene has been reported to be associated with ischemic stroke in different racial groups, but no data is available currently in Han Chinese. Our study is to investigate the association between the APOA5 gene polymorphism -1131T>C and the susceptibility to ischemic stroke in Han Chinese.

METHODS

310 controls and 342 patients with classified ischemic stroke were performed to detect the -1131T>C alleles genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis in independent case-control study.

RESULTS

TG levels of subjects carrying -1131C allele were elevated compared to the subjects with -1131T allele in all ischemic stroke subgroups and in controls. The serum TC, LDL-C and HDL-C levels did not differ between subjects with T or C alleles in each group. The overall distribution of APOA5 -1131T>C genotype among stroke patients and controls was significantly different (P<0.01). Frequencies of CC homozygote and C allele were significantly higher in all stroke subgroups than those in control group. After adjustment for conventional risk factors, logistic regression analysis showed that C allele carrier (CC+CT) of -1131T>C was an independent risk factor for all stroke subgroups (P<0.05).

CONCLUSIONS

APOA5 gene -1131T>C polymorphism is independently associated with the development of ischemic stroke in Chinese Han population, and CC homozygote may have a promoting effect on ischemic stroke.

Strong association of the APOA5-1131T>C gene variant and early-onset acute myocardial infarction

BACKGROUND

Epidemiological studies support the role for a strong genetic component in the occurrence of early-onset myocardial infarction (MI), although the specific genetic variants responsible for familial clustering remain largely unknown.

METHODS

The Italian study of early-onset MI is a nationwide case-control study involving 1864 case patients <45 years old who were hospitalized for a first MI, and age/sex/place of origin-matched controls (n = 1864). We investigated the association between early-onset MI, lipid levels and 20 single nucleotide polymorphisms (SNPs) in the candidate genes ADIPOQ, APOA5, ALOX5AP, CYBA, IL6, LPL, PECAM1, PLA2G2A and PLA2G7, chosen because of previously reported associations with Coronary Heart Disease (CHD) or with CHD risk factors.

RESULTS

Of all the SNPs investigated, APOA5-1131T>C [(rs662799), minor allele frequency 0.084 (95% confidence interval (CI) 0.07-0.09)] alone showed a statistically significant association with risk of early-onset MI (p = 6.7 × 10(-5)), after Bonferroni correction, with a per C allele odds ratio of 1.44 (95% CI 1.23-1.69). In controls, APOA5-1131T>C was significantly associated with raised plasma triglyceride levels (p = 0.001), compared with non-carriers, the per C allele increase being 11.4% (95% CI 4-19%), equivalent to 0.15 mmol/L (95% CI 0.11-0.20 mmol/L). In cases, the association with early MI risk remained statistically significant after adjustment for triglycerides (p = 0.006).

CONCLUSIONS

The APOA5-1131C allele, associated with higher fasting triglyceride levels, strongly affects the risk for early-onset MI, even after adjusting for triglycerides. This raises the possibility that APOA5-1131T>C may affect the risk of early MI over and above effects mediated by triglycerides.

Haplotype analysis of the apolipoprotein A5 gene in patients with the metabolic syndrome

BACKGROUND AND AIMS

In recent studies, the T-1131C variant of apolipoprotein A5 (APOA5) gene was found to confer a risk for metabolic syndrome (MS). Here we determined four haplotype-tagging polymorphisms (T-1131C, IVS3+G476A, T1259C, and C56G), and studied the distribution of the naturally occurring major haplotype profiles in MS.

METHODS AND RESULTS

A total of 343 MS patients and 284 controls were genotyped using PCR-RFLP methods. Both in MS and control groups, we confirmed the already known association of -1131C, IVS3+473A and 1259C minor alleles with elevated triglyceride levels. The prevalence of the APOA5*2 haplotype (the combination of T-1131C, IVS3+G476A and T1259C SNPs) was 13.1% in MS patients, and 4.9% in controls (p<0.001); multiple logistic regression analysis revealed that this haplotype confers risk for the development of MS (OR=2.880; 95% CI: 1.567-5.292; p=0.001). We also observed a gender effect: in males a more prominent degree of susceptibility was found. Contrary to the APOA5*2 haplotype, the prevalence rate of APOA5*4 (determined by the T-1131C SNP alone) did not differ between MS patients and controls. We identified a novel haplotype, designated here as APOA5*5 (1259C allele alone); which appears to be protective against MS.

CONCLUSION

Our results refined the role of SNP T-1131C in the development of MS. The susceptibility nature of this SNP is limited to the APOA5*2 haplotype, while in APOA5*4 haplotype it did not confer a risk for the disease. In addition, as our current data suggest, the novel APOA5*5 haplotype can confer protection against MS.

Association of the apolipoprotein A5 gene -1131 T>C polymorphism with fasting blood lipids: a meta-analysis in 37859 subjects

BACKGROUND

Studies examining the association of apolipoprotein A5 (APOA5) gene -1131 T>C polymorphism with blood lipids produced inconsistent results. In this meta-analysis encompassing all the relevant studies, we aimed to investigate the association of the -1131 T>C polymorphism with fasting blood lipids.

METHODS

We limited our analysis to the following four blood lipid variables: total cholesterol (TC), triglycerides (TG), low density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C). Subjects were confined to adults who were at least 18 years old. A dominant model was used for this meta-analysis. 37 studies with 37859 subjects were included in this meta-analysis.

RESULTS

The results showed that the carriers of -1131C allele have higher blood TC and TG than the non-carriers: standardized mean difference (SMD) = 0.08, 95% confidence interval (CI, 0.05, 0.11), P < 0.00001, P(heterogeneity) = 0.42, and SMD = 0.31, 95% CI (0.27, 0.34), P < 0.00001, P(heterogeneity) = 0.0003, respectively. Significant association between the -1131 T>C polymorphism and lower blood HDL-C was also detected under the dominant model: SMD = -0.17, 95% CI (-0.21, -0.14), P < 0.00001, P(heterogeneity) = 0.003.

CONCLUSIONS

Our meta-analysis supports the strong association of the APOA5 -1131 T>C polymorphism with higher levels of TC and TG, and lower levels of HDL-C.

A single nucleotide polymorphism in APOA5 determines triglyceride levels in Hong Kong and Guangzhou Chinese

Single nucleotide polymorphisms (SNPs) in the apolipoprotein A5 (APOA5) gene have been associated with hypertriglyceridaemia. We investigated which SNPs in the APOA5 gene were associated with triglyceride levels in two independent Chinese populations. In all, 1375 subjects in the Hong Kong Cardiovascular Risk Factor Prevalence Study were genotyped for five tagging SNPs chosen from HapMap. Replication was sought in 1996 subjects from the Guangzhou Biobank Cohort Study. Among the five SNPs, rs662799 (-1131T>C) was strongly related to log-transformed triglyceride levels among Hong Kong subjects (β=0.192, P=2.6 × 10(-13)). Plasma triglyceride level was 36.1% higher in CC compared to TT genotype. This association was confirmed in Guangzhou subjects (β=0.159, P=1.3 × 10(-12)), and was significantly irrespective of sex, age group, obesity, metabolic syndrome, hypertension, diabetes, smoking and alcohol drinking. The odds ratios and 95% confidence interval for plasma triglycerides ≥1.7 mmol/l associated with TC and CC genotypes were, respectively, 1.81 (1.37-2.39) and 2.22 (1.44-3.43) in Hong Kong and 1.27 (1.05-1.54) and 1.97 (1.42-2.73) in Guangzhou. Haplotype analysis suggested the association was due to rs662799 only. The corroborative findings in two independent populations indicate that the APOA5-1131T>C polymorphism is an important and clinically relevant determinant of plasma triglyceride levels in the Chinese population.

Molecular cloning, expression and polymorphism of the porcine apolipoprotein A5 gene in a Jinhua × Pietrain F2 reference population

As a newly described member of the apolipoprotein gene family, apolipoprotein A5 (APOA5) has been suggested to play a key role in the triglyceride metabolism in both human and mice. The aim of this study was to identify the porcine (Sus scrofa) APOA5 gene, determine its mRNA and its mutations that are associated with lipid accumulation. The porcine APOA5 cDNA was amplified by reverse transcriptase polymerase chain reaction using the information of the mouse or other mammals. It had been determined that the open reading frame of the porcine APOA5 gene consists of 1092 bp, which encodes a predicted protein composed of 363 amino acids with a similarity to bovine (80.43%) and to human (78.47%). The expression analysis indicated that the porcine APOA5 gene was expressed in hypophysis, fat and liver. Twelve single nucleotide polymorphisms (SNPs), including 4 SNPs in the 5' end, 1 SNP in second intron, 1 SNP in third exon and 6 SNPs in the 3' end, were identified in the porcine APOA5 gene and genotyped on the Jinhua × Pietrain F2 reference population, it had revealed that the SNP of C1834T was significantly associated with average backfat thickness and leaf fat weight (P < 0.01 and P < 0.05, respectively). In conclusion, this study has got basic information of the porcine APOA5 gene and provides evidence that the APOA5 gene could be a potential candidate gene for fat deposition.

Niacin and fibrates in atherogenic dyslipidemia: pharmacotherapy to reduce cardiovascular risk

Although statin therapy represents a cornerstone of cardiovascular disease (CVD) prevention, a major residual CVD risk (60-70% of total relative risk) remains, attributable to both modifiable and non-modifiable risk factors. Among the former, low levels of HDL-C together with elevated triglyceride (TG)-rich lipoproteins and their remnants represent major therapeutic targets. The current pandemic of obesity, metabolic syndrome, and type 2 diabetes is intimately associated with an atherogenic dyslipidemic phenotype featuring low HDL-C combined with elevated TG-rich lipoproteins and small dense LDL. In this context, there is renewed interest in pharmacotherapeutic strategies involving niacin and fibrates in monotherapy and in association with statins. This comprehensive, critical review of available data in dyslipidemic subjects indicates that niacin is more efficacious in raising HDL-C than fibrates, whereas niacin and fibrates reduce TG-rich lipoproteins and LDL comparably. Niacin is distinguished by its unique capacity to effectively lower Lp(a) levels. Several studies have demonstrated anti-atherosclerotic action for both niacin and fibrates. In contrast with statin therapy, the clinical benefit of fibrates appears limited to reduction of nonfatal myocardial infarction, whereas niacin (frequently associated with statins and/or other agents) exerts benefit across a wider range of cardiovascular endpoints in studies involving limited patient numbers. Clearly the future treatment of atherogenic dyslipidemias involving the lipid triad, as exemplified by the occurrence of the mixed dyslipidemic phenotype in metabolic syndrome, type 2 diabetes, renal, and auto-immune diseases, requires integrated pharmacotherapy targeted not only to proatherogenic particles, notably VLDL, IDL, LDL, and Lp(a), but also to atheroprotective HDL.

Genetic association and interaction analysis of USF1 and APOA5 on lipid levels and atherosclerosis

OBJECTIVE

USF1 is a ubiquitous transcription factor governing the expression of numerous genes of lipid and glucose metabolism. APOA5 is a well-established candidate gene regulating triglyceride (TG) levels and has been identified as a downstream target of upstream stimulatory factor. No detailed studies about the effect of APOA5 on atherosclerotic lesion formation have been conducted, nor has its potential interaction with USF1 been examined.

METHODS AND RESULTS

We analyzed allelic variants of USF1 and APOA5 in families (n=516) ascertained for atherogenic dyslipidemia and in an autopsy series of middle-aged men (n=300) with precise quantitative measurements of atherosclerotic lesions. The impact of previously associated APOA5 variants on TGs was observed in the dyslipidemic families, and variant rs3135506 was associated with size of fibrotic aortic lesions in the autopsy series. The USF1 variant rs2516839, associated previously with atherosclerotic lesions, showed an effect on TGs in members of the dyslipidemic families with documented coronary artery disease. We provide preliminary evidence of gene-gene interaction between these variants in an autopsy series with a fibrotic lesion area in the abdominal aorta (P=0.0028), with TGs in dyslipidemic coronary artery disease subjects (P=0.03), and with high-density lipoprotein cholesterol (P=0.008) in a large population cohort of coronary artery disease patients (n=1065) in which the interaction for TGs was not replicated.

CONCLUSIONS

Our findings in these unique samples reinforce the roles of APOA5 and USF1 variants on cardiovascular phenotypes and suggest that both genes contribute to lipid levels and aortic atherosclerosis individually and possibly through epistatic effects.

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.

Genotype-phenotype associations: modulation by diet and obesity

Changes in diet are likely to reduce chronic disorders, but after decades of active research and heated discussion, the question still remains: what is the optimal diet to achieve this elusive goal? Is it a low-fat diet, as traditionally recommended by multiple medical societies? Or a high monounsaturated fat (MUFA) diet as predicated by the Mediterranean diet? Perhaps a high polyunsaturated fat (PUFA) diet based on the cholesterol-lowering effects? The right answer may be all of the above but not for everybody. A well-known phenomenon in nutrition research and practice is the dramatic variability in interindividual response to any type of dietary intervention. There are many other factors influencing response, and they include, among many others, age, sex, physical activity, alcohol, and smoking as well as genetic factors that will help to identify vulnerable populations/individuals that will benefit from a variety of more personalized and mechanistic-based dietary recommendations. This potential could and needs to be developed within the context of nutritional genomics that in conjunction with systems biology may provide the tools to achieve the holy grail of dietary prevention and therapy of chronic diseases and cancer. This approach will break with the traditional public health approach of "one size fits all." The current evidence based on nutrigenetics has begun to identify subgroups of individuals who benefit more from a low-fat diet, whereas others appear to benefit more from high MUFA or PUFA diets. The continuous progress in nutrigenomics will allow some time in the future to provide targeted gene-based dietary advice.

Clinical significance of apolipoprotein A5

PURPOSE OF REVIEW

We have examined the evidence from recent human studies examining the role of apolipoprotein A-V in triglyceride-rich lipoprotein metabolism and cardiovascular disease risk. Special emphasis was placed on the evidence emerging from the association between genetic variability at the apolipoprotein A5 locus, lipid phenotypes and disease outcomes. Moreover, we address recent reports evaluating apolipoprotein A5 gene-environment interactions in relation to cardiovascular disease and its common risk factors.

RECENT FINDINGS

Several genetic association studies have continued to strengthen the position of APOA5 as a major gene that is involved in triglyceride metabolism and modulated by dietary factors and pharmacological therapies. Moreover, genetic variants at this locus have been significantly associated with both coronary disease and stroke risks.

SUMMARY

Apolipoprotein A-V has an important role in lipid metabolism, specifically for triglyceride-rich lipoproteins. However, its mechanism of action is still poorly understood. Clinical significance at present comes largely from genetic studies showing a consistent association with plasma triglyceride concentrations. Moreover, the effects of common genetic variants on triglyceride concentrations and disease risk are further modulated by other factors such as diet, pharmacological interventions and BMI. Therefore, these genetic variants could be potentially used to predict cardiovascular disease risk and individualize therapeutic options to decrease cardiovascular disease risk.

Apoprotein A-V: an important regulator of triglyceride metabolism

Apolipoprotein A-V (apoA-V) was discovered in 2001 both by comparative sequencing and as a liver regeneration protein. The gene is a located at the APOA1/C3/A4/A5 gene cluster on chromosome 11q23, a locus well known for playing a major role in regulating plasma cholesterol and triglyceride (TG) levels. ApoA-V is produced in the liver and has very low plasma concentrations (0.1-0.4 mug/ml). Mice lacking apoA-V have 4-fold increased TG levels, whereas apoA-V overexpression leads to 40% plasma TG reduction. Based on metabolic studies in vivo, apoA-V enhances the catabolism of TG rich lipoproteins rather than affecting their intestinal or hepatic production. By activating proteoglycans-bound lipoprotein lipase (LPL), apoA-V can accelerate TG hydrolysis from VLDL and chylomicrons independent from other apoproteins. Several variants at the APOA5 gene locus have been detected in humans. Some single nucleotide polymorphisms (SNPs) are associated with significantly higher plasma TG levels in patients (e.g., -1131T > C, S19W, G185C). In addition, these SNPs may affect fibrate response and obesity. However, data for a possible association of APOA5 variants with coronary heart disease are not consistent. Severe structural mutations (Q139X, Q148X, IVS3 + 3G > C) predispose to familial hypertriglyceridaemia and late-onset chylomicronaemia. Thus, despite its low plasma concentration, apoA-V is a major regulator of plasma TG metabolism in humans. However, the precise mechanism of its function is not yet clear.

Genetic links between diabetes mellitus and coronary atherosclerosis

Diabetes mellitus is one of the most common endocrine disorders. It affects almost 6% of the world's population, and its prevalence continues to increase. The causes of diabetes mellitus are multifactorial, and in the general population both genetic and environmental factors contribute evenly to its development. Several genes have been consistently associated with type 2 diabetes mellitus; however, it is not clear how many of those translate into increased cardiovascular disease risk. Recent evidence suggests that genetic variation at the CALPN10, FABP4, GK, GST, PPARA, and PPARG loci may confer higher cardiovascular disease risk in patients with type 2 diabetes mellitus. However, the evidence is scattered and inconclusive and its translation into practical clinical testing will require studies properly designed to examine not only simple genetic associations but also gene-gene and gene-environment interactions.