ApoCIII gene variants modulate postprandial response to both glucose and fat tolerance tests

FoxO6-mediated ApoC3 upregulation promotes hepatic steatosis and hyperlipidemia in aged rats fed a high-fat diet

FoxO6, an identified factor, induces hyperlipidemia and hepatic steatosis during aging by activating hepatic lipoprotein secretion and lipogenesis leading to increased ApoC3 concentrations in the bloodstream. However, the intricate mechanisms underlying hepatic steatosis induced by elevated FoxO6 under hyperglycemic conditions remain intricate and require further elucidation. In order to delineate the regulatory pathway involving ApoC3 controlled by FoxO6 and its resultant functional impacts, we employed a spectrum of models including liver cell cultures, aged rats subjected to HFD, transgenic mice overexpressing FoxO6 (FoxO6-Tg), and FoxO6 knockout mice (FoxO6-KO). Our findings indicate that FoxO6 triggered ApoC3-driven lipid accumulation in the livers of aged rats on an HFD and in FoxO6-Tg, consequently leading to hepatic steatosis and hyperglycemia. Conversely, the absence of FoxO6 attenuated the expression of genes involved in lipogenesis, resulting in diminished hepatic lipid accumulation and mitigated hyperlipidemia in murine models. Additionally, the upregulation of FoxO6 due to elevated glucose levels led to increased ApoC3 expression, consequently instigating cellular triglyceride mediated lipid accumulation. The transcriptional activation of FoxO6 induced by both the HFD and high glucose levels resulted in hepatic steatosis by upregulating ApoC3 and genes associated with gluconeogenesis in aged rats and liver cell cultures. Our conclusions indicate that the upregulation of ApoC3 by FoxO6 promotes the development of hyperlipidemia, hyperglycemia, and hepatic steatosis in vivo, and in vitro. Taken together, our findings underscore the significance of FoxO6 in driving hyperlipidemia and hepatic steatosis specifically under hyperglycemic states by enhancing the expression of ApoC3 in aged rats.

APOC3 rs2070667 Associates with Serum Triglyceride Profile and Hepatic Inflammation in Nonalcoholic Fatty Liver Disease

Single-nucleotide polymorphisms (SNPs) of apolipoprotein C3 (APOC3) play important role in lipid metabolism, and dyslipidemia underlies nonalcoholic fatty liver disease (NAFLD). But the correlation of serum lipidomics, APOC3 SNPs, and NAFLD remains limited understood. Enrolling thirty-four biopsy-proven NAFLD patients from Tianjin, Shanghai, Fujian, we investigated their APOC3 genotype and serum lipid profile by DNA sequencing and ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), respectively. Scoring of hepatocyte steatosis, ballooning, lobular inflammation, and liver fibrosis was then performed to reveal the role of lipidomics-affecting APOC3 SNPs in NAFLD-specific pathological alterations. Here, we reported that APOC3 SNPs (rs4225, rs4520, rs5128, rs2070666, and rs2070667) intimately correlated to serum lipidomics in NAFLD patients. A allele instead of G allele at rs2070667, which dominated the SNPs underlying lipidomic alteration, exhibited downregulatory effect on triacylglycerols (TGs: TG 54 : 7, TG 54 : 8, and TG 56 : 9) containing polyunsaturated fatty acid (PUFA). Moreover, subjects with low-level PUFA-containing TGs were predisposed to high-grade lobular inflammation (TG 54 : 7, rho = -0.454 and P = 0.007; TG 54 : 8, rho = -0.411 and P =0.016; TG 56 : 9, rho = -0.481 and P = 0.004). The significant correlation of APOC3 rs2070667 and inflammation grading [G/G vs. G/A+A/A: 0.00 (0.00 and 1.00) vs. 1.50 (0.75 and 2.00), P = 0.022] further confirmed its pathological action on the basis of lipidomics-impacting activity. These findings suggest an inhibitory effect of A allele at APOC3 rs2070667 on serum levels of PUFA-containing TGs, which are associated with high-grade lobular inflammation in NAFLD patients.

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.

The association between apolipoprotein A1-C3-A5 gene cluster promoter polymorphisms and risk of ischemic stroke in the northern Chinese Han population

Objective

Given its effects on lipid metabolism, the apolipoprotein A1-C3-A5 (APOA1-C3-A5) gene cluster is thought to play an important role in ischemic stroke pathogenesis. Here, we evaluated whether the APOA1-C3-A5 cluster is associated with ischemic stroke in the northern Chinese Han population.

Methods

This case–control study analyzed 812 patients with ischemic stroke and 844 healthy controls with regard to four APOA1-C3-A5 cluster promoter single nucleotide polymorphisms (SNPs), rs670, rs2854116, rs2854117, and rs662799, using the SNaPshot Multiplex sequencing assay. Potential associations among ischemic stroke, genotyping, and allele frequencies were assessed.

Results

APOA1 rs670 CT/TT genotypes, APOA5 rs662799 AG/GG genotypes, and the APOC3 rs2854116 CC genotype were associated with an increased risk of ischemic stroke according to multivariate logistic analysis after adjusting for confounding factors. A significantly increased risk for ischemic stroke was also identified among high-risk haplotypes (C-C-T-A and T-T-C-A) for rs670–rs2854116–rs2854117–rs662799.

Conclusion

This study showed that rs670, rs2854116, and rs662799 SNPs of the APOA1-C3-A5 cluster are associated with ischemic stroke in the northern Chinese Han population.

Replication of association of the apolipoprotein A1-C3-A4 gene cluster with the risk of gout

OBJECTIVE

Gout is associated with dyslipidaemia. Association of the apolipoprotein A1-C3-A4 gene cluster with gout has previously been reported in a small study. To investigate a possible causal role for this locus in gout, we tested the association of genetic variants from APOA1 (rs670) and APOC3 (rs5128) with gout.

METHODS

We studied data for 2452 controls and 2690 clinically ascertained gout cases of European and New Zealand Polynesian (Māori and Pacific) ancestry. Data were also used from the publicly available Atherosclerosis Risk in Communities study (n = 5367) and the Framingham Heart Study (n = 2984). Multivariate adjusted logistic and linear regression was used to test the association of single-nucleotide polymorphisms with gout risk, serum urate, triglyceride and high-density lipoprotein cholesterol (HDL-C).

RESULTS

In Polynesians, the T-allele of rs670 (APOA1) increased (odds ratio, OR = 1.53, P = 4.9 × 10(-6)) and the G-allele of rs5128 (APOC3) decreased the risk of gout (OR = 0.86, P = 0.026). In Europeans, there was a strong trend to a risk effect of the T-allele for rs670 (OR = 1.11, P = 0.055), with a significant protective effect of the G-allele for rs5128 being observed after adjustment for triglycerides and HDL-C (OR = 0.81, P = 0.039). The effect at rs5128 was specific to males in both Europeans and Polynesians. Association in Polynesians was independent of any effect of rs670 and rs5128 on triglyceride and HDL-C levels. There was no evidence for association of either single-nucleotide polymorphism with serum urate levels (P ⩾ 0.10).

CONCLUSION

Our data, replicating a previous study, supports the hypothesis that the apolipoprotein A1-C3-A4 gene cluster plays a causal role in gout.

Effect of apolipoprotein C3 genetic polymorphisms on serum lipid levels and the risk of intracerebral hemorrhage

BACKGROUND

Serum lipid levels are associated with the risk of intracerebral hemorrhage (ICH). Genetic variants in the apolipoprotein C3 (APOC3) gene were associated with plasma triglyceride (TG) and very-low-density lipoprotein (VLDL) levels. The aim of this study was to evaluate the effect of two genetic variants (1100 C/T and 3238 C/G) of APOC3 on serum lipid levels and risk of ICH.

METHODS

A prospective hospital-based case-control design and logistic regression analysis were utilized. We enrolled 150 ICH patients and 150 age- and gender-matched controls. The APOC3 gene polymorphisms were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

ICH patients had a significantly higher frequency of APOC3 3238 GG genotype [odds ratio (OR)=.97, 95% confidence interval (CI)=1.20, 7.38; P=0.02] and APOC3 3238 G allele (OR=.53, 95% CI=1.03, 2.27; P=0.04) than controls. The APOC3 3238 G allele was significantly associated with increasing plasma TG levels and VLDL levels both in ICH cases (P=0.01) and controls (P=0.02). No association was found between APOC3 1100 C/T polymorphisms and ICH.

CONCLUSION

To the best of our knowledge, this is the first report in the literature that the APOC3 3238 GG genotype and G allele might contribute to an increased risk of ICH as a result of its effect on serum lipid levels.

Apolipoprotein C3 genetic polymorphisms are associated with lipids and coronary artery disease in a Chinese population

BACKGROUND

The disorder of triglyceride (TG) metabolism leading to hypertriglyceridemia is an independent risk factor for coronary artery disease (CAD). Variants in the apolipoprotein C3 (APOC3) gene were found to be associated with elevated TG levels. The purpose of this study was to investigate the effect of two polymorphisms (1100 C/T and 3238 C/G) of APOC3 on plasma lipid and risk of CAD in a Chinese population.

METHODS

The study population consisted of 600 patients with CAD and 600 age- and gender-matched controls. The APOC3 gene polymorphism was analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Patients with CAD had a significantly higher frequency of APOC3 3238 GG genotype [odds ratio (OR) =1.64, 95% confidence interval (CI) =1.10, 2.43; P = 0.01] and APOC3 3238 G allele (OR =1.27, 95% CI =1.04, 1.55; P = 0.02) than controls. The findings are still emphatic by the Bonferroni correction. When stratifying by hyperlipidemia, CAD patients with hyperlipidemia had a significantly higher frequency of APOC3 3238 GG genotype (OR =1.73, 95% CI =1.13, 2.64; P = 0.01) than without hyperlipidemia. The APOC3 3238 G allele was significantly associated with increasing plasma TG levels and very-low-density lipoprotein cholesterol (VLDL-C) levels both in cases and controls (P < 0.001).

CONCLUSIONS

The APOC3 3238 G allele might contribute to an increased risk of CAD as a result of its effect on TG and VLDL-C metabolism.

Fasting, non-fasting glucose and HDL dysfunction in risk of pre-diabetes, diabetes, and coronary disease in non-diabetic adults

We determined in non-diabetic persons the risk of fasting and non-fasting glucose levels for pre-diabetes, diabetes, and coronary heart disease (CHD), including the roles of serum C-reactive protein (CRP) and HDL cholesterol, and delineated risk profiles of the pre-diabetic states. Over 7¼ years, 2,619 middle-aged Turkish adults free of diabetes and CHD were studied prospectively. Using different serum glucose categories including impaired fasting glucose (IFG, 6.1-6.97 mmol/L) and impaired glucose tolerance (IGT), outcomes were analyzed by Cox regression. IFG was identified at baseline in 112 and IGT in 33 participants. Metabolic syndrome components distinguished individuals with IFG from those with normoglycemia. Participants with IGT tended to differ from adults in normal postprandial glucose categories in regard to high levels of triglycerides, apoA-I, and CRP. Diabetes risk, adjusted for sex, age, waist circumference, CRP, and HDL cholesterol, commenced at a fasting 5.6-6.1 mmol/L threshold, was fourfold at levels 6.1-6.97 mmol/L. Optimal glucose values regarding CHD risk were 5.0-6.1 mmol/L. Fasting and postprandial glucose values were not related to CHD risk in men; IGT alone predicted risk in women (HR 3.74 [1.16;12.0]), independent of age, systolic blood pressure, non-HDL cholesterol, waist circumference, smoking status, and CRP. HDL cholesterol was unrelated to the development of IFG, IGT, and diabetes, while CRP elevation independently predicted the development of diabetes. IGT independently predicts CHD risk, especially in women. HDL dysfunction associated with low-grade inflammation is a co-determinant of pre-diabetic states and their progression to diabetes.

Postprandial hypertriglyceridemia and cardiovascular disease: current and future therapies

Exaggerated postprandial hypertriglyceridemia is a risk factor for cardiovascular disease. This metabolic abnormality is principally due to overproduction and/or decreased catabolism of triglyceride-rich lipoproteins (TRLs) and is a consequence of pathogenic genetic variations and other coexistent medical conditions, particularly obesity and insulin resistance. Accumulation of TRL in the postprandial state promotes the formation of small, dense low-density lipoproteins, as well as oxidative stress, inflammation, and endothelial dysfunction, all of which compound the risk of cardiovascular disease. The cardiovascular benefits of lifestyle modification (weight loss and exercise) and conventional lipid-lowering therapies (statins, fibrates, niacin, ezetimibe, and n-3 fatty acid supplementation) could involve their favorable effects on TRL metabolism. New agents, such as dual peroxisome-proliferator-activated receptor α/δ agonists, diacylglycerol, inhibitors of diacylglycerol acyltransferase 1 and microsomal triglyceride transfer protein, antisense oligonucleotides for apolipoprotein B-100 and apolipoprotein C-III, and incretin-based therapies, may enhance the treatment of postprandial lipemia, but their efficacy needs to be tested in clinical end point trials. Further work is required to develop a simple clinical protocol for investigating postprandial lipemia, as well as internationally agreed management guidelines for this type of dyslipidemia.

Apolipoprotein CIII overexpressing mice are predisposed to diet-induced hepatic steatosis and hepatic insulin resistance

Nonalcoholic fatty liver disease (NAFLD) and insulin resistance have recently been found to be associated with increased plasma concentrations of apolipoprotein CIII (APOC3) in humans carrying single nucleotide polymorphisms within the insulin response element of the APOC3 gene. To examine whether increased expression of APOC3 would predispose mice to NAFLD and hepatic insulin resistance, human APOC3 overexpressing (ApoC3Tg) mice were metabolically phenotyped following either a regular chow or high-fat diet (HFD). After HFD feeding, ApoC3Tg mice had increased hepatic triglyceride accumulation, which was associated with cellular ballooning and inflammatory changes. ApoC3Tg mice also manifested severe hepatic insulin resistance assessed by a hyperinsulinemic-euglycemic clamp, which could mostly be attributed to increased hepatic diacylglycerol content, protein kinase C-ϵ activation, and decreased insulin-stimulated Akt2 activity. Increased hepatic triglyceride content in the HFD-fed ApoC3Tg mice could be attributed to a ≈ 70% increase in hepatic triglyceride uptake and ≈ 50% reduction hepatic triglyceride secretion.

CONCLUSION

These data demonstrate that increase plasma APOC3 concentrations predispose mice to diet-induced NAFLD and hepatic insulin resistance.

Genetic variants and the metabolic syndrome: a systematic review

Several candidate gene studies on the metabolic syndrome (MetS) have been conducted. However, for most single nucleotide polymorphisms (SNPs) no systematic review on their association with MetS exists. A systematic electronic literature search was conducted until the 2nd of June 2010, using HuGE Navigator. English language articles were selected. Only genes of which at least one SNP-MetS association was studied in an accumulative total population ≥ 4000 subjects were included. Meta-analyses were conducted on SNPs with three or more studies available in a generally healthy population. In total 88 studies on 25 genes were reviewed. Additionally, for nine SNPs in seven genes (GNB3, PPARG, TCF7L2, APOA5, APOC3, APOE, CETP) a meta-analysis was conducted. The minor allele of rs9939609 (FTO), rs7903146 (TCF7L2), C56G (APOA5), T1131C (APOA5), C482T (APOC3), C455T (APOC3) and 174G>C (IL6) were more prevalent in subjects with MetS, whereas the minor allele of Taq-1B (CETP) was less prevalent in subjects with the MetS. After having systematically reviewed the most studied SNP-MetS associations, we found evidence for an association with the MetS for eight SNPs, mostly located in genes involved in lipid metabolism.

Association of an APOC3 promoter variant with type 2 diabetes risk and need for insulin treatment in lean persons

AIMS/HYPOTHESIS

An APOC3 promoter haplotype has been previously associated with type 1 diabetes. In this population-based study, we investigated whether APOC3 polymorphisms increase type 2 diabetes risk and need for insulin treatment in lean participants.

METHODS

In the Rotterdam Study, a population-based prospective cohort (n = 7,983), Cox and logistic regression models were used to analyse the associations and interactive effects of APOC3 promoter variants (-482C > T, -455T > C) and BMI on type 2 diabetes risk and insulin treatment. Analyses were followed by replication in an independent case-control sample (1,817 cases, 2,292 controls) and meta-analysis.

RESULTS

In lean participants, the -482T allele was associated with increased risk of prevalent and incident type 2 diabetes: OR -482CT 1.47 (95% CI 1.13-1.92), -482TT 1.40 (95% CI 0.83-2.35), p = 0.009 for trend; HR -482CT 1.35 (95% CI 0.96-1.89), -482TT 1.68 (95% CI 0.91-3.1), p = 0.03 for trend, respectively. These results were confirmed by replication. Meta-analysis was highly significant (-482T meta-analysis p = 1.1 × 10(-4)). A borderline significant interaction was observed for insulin use among participants with type 2 diabetes (-482CT*BMI p = 0.06, -455TC*BMI p = 0.02).

CONCLUSIONS/INTERPRETATION

At a population-based level, the influence of APOC3 promoter variants on type 2 diabetes risk varies with the level of adiposity. Lean carriers of the -482T allele had increased type 2 diabetes risk, while such an effect was not observed in overweight participants. Conversely, in overweight participants the -455C allele seemed protective against type 2 diabetes. The interaction of the variants with need for insulin treatment may indicate beta cell involvement in lean participants. Our findings suggest overlap in the genetic backgrounds of type 1 diabetes and type 2 diabetes in lean patients.

Cerebrovascular atherosclerosis in type III hyperlipidemia is modulated by variation in the apolipoprotein A5 gene

Objective

Type III Hyperlipoproteinemia is a rare lipid disorder with a frequency of 1-5 in 5000. It is characterized by the accumulation of triglyceride rich lipoproteins and patients are at increased risk of developping atherosclerosis. Type III HLP is strongly associated with the homozygous presence of the ε2 allele of the APOE gene.

However only about 10% of subjects with APOE2/2 genotype develop hyperlipidemia and it is therefore assumed that further genetic and environmental factors are necessary for the expression of disease. It has recently been shown that variation in the APOA5 gene is one of these co-factors. The aim of this study is to investigate the development of cerebrovascular atherosclerosis in patients with Type III hyperlipoproteinemia (Type III HLP) and the role of variation in the APOA5 gene as a risk factor.

Methods

60 patients with type III hyperlipidemia and ApoE2/2 genotype were included in the study after informed consent. The presence of cerebrovascular atherosclerosis was investigated using B-mode ultra-sonography of the carotid artery. Serum lipid levels were measured by standard procedures. The APOE genotype and the 1131T > C and S19W SNPs in the APOA5 gene and the APOC3 sstI SNP were determined by restriction isotyping Allele frequencies were determined by gene counting and compared using Fisher's exact test. Continuous variables were compared using the Mann Whitney test. A p value of 0.05 or below was considered statistically significant. Analysis was performed using Statistica 7 software.

Results

The incidence of the APOA5 SNPs, -1131T > C and S19W and the APOC3 sstI SNP were determined as a potential risk modifier. After correction for conventional risk factors, the C allele of the 1131T > C SNP in the APOA5 gene was associated with an increased risk for the development of carotid plaque in patients with Type III HLP with an odds ratio of 3.69. Evaluation of the genotype distribution was compatible with an independent effect of APOA5.

Conclusions

The development of atherosclerosis in patients with Type III HLP is modulated by variation in the APOA5 gene.

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.

Association of apolipoprotein A1-C3 gene cluster polymorphisms with gallstone disease

INTRODUCTION

Genetic polymorphisms in apolipoprotein genes may be associated with alteration in lipid profile and susceptibility to gallstone disease.

AIM

To determine the association between apolipoprotein A1 (APOA1) -75 guanine [G] to adenine [A] and +83/84 M2(+/-), MspI) and apolipoprotein C3 (APOC3) (SstI) polymorphisms with gallstone disease.

METHODS

MspI polymorphisms of the APOA1 gene and SstI polymorphisms of APOC3 were analyzed in DNA samples of 214 gallstone patients and 322 age- and sex-matched healthy controls. All statistical analyses were performed using SPSS version 11.5 (SPSS, USA) and Arlequin version 2.0 (Arlequin, Switzerland).

RESULTS

The APOA1 -75 G/A polymorphism was significantly associated with gallstone disease. Patients with the GG genotype (P=0.015) and G allele carriers (P=0.004) had a significantly higher risk of gallstone disease (1.087-fold and 1.561-fold, respectively), whereas patients with AA genotypes (P=0.011) and A allele carriers (P=0.004) were protected (OR 0.230 and 0.641, respectively) against gallstone disease. APOA1 +83 M2(+/-) and APOC3 SstI polymorphisms were not associated with gallstone disease. Case-control analysis of haplotypes showed a significant association in males only. G-M2(+)-S1 conferred risk for gallstone disease (P=0.036; OR 1.593, 95% CI 1.029 to 2.464), while A-M2(+)-S1 was protective (P=0.002; OR 0.370, 95% CI 0.197 to 0.695) against gallstone disease. In APOA1(-75)-APOA1(+83) bilocus haplotypes, G-M2(+) was associated (P=0.0001) with very high risk (OR 3.173, 95% CI 1.774 to 5.674) for gallstone disease in males only. APOA1(-75)-APOC3(SstI) haplotypes also showed significant association while APOA1(+83)-APOC3(SstI) haplotypes showed no association with gallstone disease.

CONCLUSIONS

The APOA1 -75 G/A polymorphism is associated with gallstone disease and shows sex-specific differences. On the other hand, APOA1 M2(+/-) and APOC3 SstI polymorphisms may not be associated with gallstone disease. Haplotype analysis is a better predictor of risk for gallstone disease.

Polymorphisms in the APOA1/C3/A4/A5 gene cluster and cholesterol responsiveness to dietary change

BACKGROUND

The relationship between dietary composition and plasma lipids is to some extent genetically determined. It has been found that variants of some genes (e.g., apolipoprotein E and cholesterol 7-alpha hydroxylase) play an important role in changes in plasma lipid levels in response to dietary intervention. We analyzed the effect of variation in the apolipoprotein (APO) APOA1/C3/A4/A5 gene cluster on decreases in plasma cholesterol levels over an 8-year follow-up study.

METHODS

Men (n=133) from the Czech population, for which dietary composition has markedly changed (red meat 80-->68 kg/person/year, animal fat 16-->9 kg/person/year, fruits and vegetables 133-->150 kg/person/year) were recruited. APOA1 (G-75>A and C83>T), APOC3 (C-482>T and C3238>G), APOA4 (Thr347>Ser and Gln360His) and APOA5 (T-1131>C, Ser19>Trp and Val153>Met) variants were analyzed by PCR and restriction analysis. Lipid levels were analyzed in 1988 and 1996. Dietary information was obtained from the Institute of Agricultural Economy.

RESULTS

In APOA5 Ser19Ser homozygotes (n=105), plasma cholesterol was relatively stable over the years (6.1+/-1.3 and 5.6+/-1.0 mmol/L in 1988 and 1996), but the decrease was much higher in Trp19 carriers (n=27; 6.5+/-1.6 vs. 5.1+/-1.1 mmol/L). This difference in change is significant at p<0.005. Similarly, a better response to dietary changes was detected in carriers of the common APOA4 haplotypes Thr-347Thr/Gln360Gln and Thr347Ser/Gln360Gln (n=102; 6.3+/-1.3 and 5.5+/-1.1 mmol/L in 1988 and 1996, p<0.001). Total cholesterol was relatively stable over time in carriers (n=18) of at least one His360 allele and/or two Ser347 alleles (5.7+/-1.1 and 5.5+/-0.9 mmol/L in 1988 and 1996, n.s.). Other variants analyzed did not influence the change in lipid measurements over time.

CONCLUSIONS

APOA4 and APOA5 variants may play an important role in the individual sensitivity of lipid parameters to dietary composition in men.

APOC3 promoter polymorphisms C-482T and T-455C are associated with the metabolic syndrome

BACKGROUND

Despite the growing epidemic of the metabolic syndrome (MetS), few studies have evaluated genetic polymorphisms associated with the MetS phenotype. One candidate, APOC3, modulates lipid and lipoprotein metabolism and the promoter polymorphisms C-482T/T-455C are associated with loss of insulin downregulation.

METHODS

One hundred twenty two consecutive MetS cases were matched by age, sex and race in a 1:1 case-control design to evaluate the prevalence of common polymorphisms in the following candidate genes: APOC3, APOE, B3AR, FABP2, GNB3, LPL, and PPARalpha and PPARgamma.

RESULTS

Compared to controls, MetS subjects exhibited a greater prevalence of APOC3 promoter polymorphisms. Specifically, the frequency of the variant C-482T and T-455C alleles was 70.5 and 81.9% of cases compared to 43.4 and 54.1% in controls, respectively (p <0.0001). Overall, APOC3 promoter variants were associated with a greater likelihood of MetS compared to wild type [C-482T (OR: 4.3; 95% CI: 2.2, 8.6 [p <0.0001]), T-455C (OR: 3.6; 95% CI: 2.0, 6.7 [p <0.0001])]. No material differences were identified between the other genetic variants tested and prevalence of MetS.

CONCLUSIONS

These data, therefore, suggest that the APOC3 promoter polymorphisms C-482T and T-455C are associated with the MetS.

Longitudinal analysis of haplotypes and polymorphisms of the APOA5 and APOC3 genes associated with variation in serum triglyceride levels: the Bogalusa Heart Study

Polymorphisms in the APOC3 and APOA5 genes, from the APOA1/APOC3/APOA4/APOA5 gene cluster on chromosome 11q23, have been associated with interindividual variation in plasma triglycerides. APOA5 polymorphisms implicated include 2 in the promoter region (-1131 T/C and -3 A/G) and 1 in exon 2 (+56 C/G). APOC3 polymorphisms implicated include 1 (SstI) in the 3' untranslated region and 1 (-2854 G/T) in the APOC3-APOA4 intergenic region. We analyzed the associations of haplotypes and multilocus genotypes of these polymorphisms on longitudinal serum triglyceride profiles in 360 African American and 823 white subjects from the Bogalusa Heart Study. Subjects were examined from 2 to 8 times (mean +/- SD, 5.4 +/- 1.3) between 1973 and 1996, at ages ranging from 4 to 38 years, with 1978 observations in African Americans and 4465 in whites. Serum triglycerides were significantly higher among whites across all ages. Allele frequencies differed significantly between African Americans and whites at all but the APOA5 +56 C/G locus. Linkage disequilibrium among the loci was higher in whites and haplotype diversity lower: 6 haplotypes had estimated frequencies of more than 1% in African Americans, 5 in whites. Individually, all polymorphisms except APOC3 -2854 G/T showed significant associations with triglyceride levels in the full sample. However, genotype models including all 5 loci showed significant triglyceride associations for only 3 (APOC3 SstI, APOA5 -1131 T/C, and APOA5 +56 C/G); significant interactions among them indicated their effects were not independent. Neither APOC3 -2854 G/T nor APOA5 -3 A/G had significant effects when the other 3 loci were in the models. The EM algorithm was used to estimate haplotype frequencies and assign haplotype probabilities to individuals, which is conditional on their genotypes; individuals' haplotype probability vectors were then used as predictors in multilevel mixed models of longitudinal triglyceride profiles. Of haplotypes comprising, in order, APOC3 SstI and -2854 G/T and APOA5 -1131 T/C, -3 A/G, and +56 C/G, 3 were significantly associated with higher triglycerides, even after adjusting for multiple tests: GGTAG (P = .002), GTTAG (P < .0001), and CGCGC (P = .0002). Each GGTAG haplotype carried would be expected to raise triglyceride levels (relative to those of GTTAC homozygotes) by approximately 19 mg/dL, each GTTAG haplotype by approximately 15 mg/dL, and each CGCGC haplotype by approximately 7 mg/dL. Haplotypes comprising the 3 loci implicated by genotype analyses (SstI, -1131 T/C, and +56 C/G) were also tested: haplotypes C_C_C and G_T_G significantly raised triglycerides, even after adjustment for multiple comparisons (P < .002 for both), with each copy of C_C_C expected to raise triglycerides by approximately 7 mg/dL and each copy of G_T_G by approximately 15 mg/dL. Overall, our findings support those of others in associating specific polymorphisms and haplotypes in the APOA1/C3/A4/A5 gene cluster with higher serum triglyceride levels. However, the degree to which polymorphisms in the APOC3 and APOA5 genes may be independently associated with triglyceride levels remains to be determined.

Effect of SstI polymorphism of the apolipoprotein CIII gene and environmental factors on risks of hypertriglyceridemia in Taiwan aborigines

BACKGROUND

Hypertriglyceridemia (HTG) is a heterogeneous metabolic disorder. The aim of this study was to examine associations among genetic polymorphisms, SstI polymorphism of apolipoprotein CIII (ApoCIII) and Hind III polymorphism of lipoprotein lipase (LPL), environmental factors and risks of HTG.

METHODS AND RESULTS

Two hundred and forty-nine southern Taiwanese aborigines were recruited for a cross-sectional study, which included 90 subjects with triglyceride (TG)>150 mg/dl (HTG) and 159 with TG<or=150 mg/dl (NTG). The frequencies of SstI major allele (S1) and minor allele (S2) of ApoCIII were 66.1% and 33.9% in HTG and 73.6% and 26.4% in NTG (p<0.1). In female subjects, the frequencies of the S2 allele was significantly higher in HTG (0.38) than NTG (0.27) (p<0.04). The frequencies of the LPL HindIII major allele (H+) and minor allele (H-) were similar between HTG (H+ 84.3%; H- 15.7%) and NTG (H+ 78.9%; H- 21.1%). In a multivariate adjusted logistic model, education<or=6 year (odds ratio (OR)=3.71, 95% confidence interval (CI): 1.24-8.13), Amis tribe (OR=3.08, 95% CI: 1.41-6.77), body mass index (BMI)>or=25 (OR=2.22, 95% CI: 1.18-4.16), starchy food consumption>or=3 times/week (OR=1.89, 95% CI: 1.00-3.59) and ApoCIII S2S2 genotype (OR=3.35, 95% CI: 1.10-10.19) were independently (p<0.05) associated with HTG risks. Among ApoCIII S1S1, S1S2 and S2S2 genotypes, ApoCIII and TG concentrations increased (p<0.01) in a dose-responsive manner.

CONCLUSIONS

The ApoCIII S2 variant and environmental factors, including education, tribal background, BMI and starchy food intake, modulate the risks of HTG in aboriginal Taiwanese. Interaction between genetic and environmental factors warrants further investigation.

Susceptibility to type 1 diabetes is associated with ApoCIII gene haplotypes

Type 1 diabetes is a disease of beta-cell destruction leading to insulin deficiency. Genes for type 1 diabetes have been identified; however, much of the genetic risk remains unexplained. Genetic variation within the apolipoprotein CIII (apoCIII) gene alters apoCIII levels, which are increased in type 1 diabetes and induce beta-cell apoptosis. We therefore hypothesize haplotypes within the apoCIII gene are associated with type 1 diabetes. DNA from 584 type 1 diabetic patients and 591 control subjects were genotyped for six single nucleotide polymorphisms (SNPs) in the apoCIII gene (C-641A, C-482T, T-455C, C1100T, C3175G, and T3206G). Two alleles of a haplotype block (promoter SNPs + C3175G) were associated with type 1 diabetes. The A-T-C-C allele frequency was higher in type 1 diabetes (0.19 vs. 0.16, P = 0.05), and the C-C-T-C allele was reduced in type 1 diabetes (0.60 vs. 0.65, P = 0.04). The odds ratio (OR) for A-T-C-C allele increased with 0, 1, and 2 copies (OR of 1.00, 1.24, and 1.60, respectively; P = 0.05) and decreased for the C-C-T-C allele (1.00, 0.97, and 0.73, respectively; P = 0.03). This haplotype block contains an insulin response element. Screening for this haplotype may identify at-risk individuals, and this pathway may offer a target for prevention of type 1 diabetes.

Associations between plasma lipid parameters and APOC3 and APOA4 genotypes in a healthy population are independent of dietary cholesterol intake

To determine whether APOC3 and APOA4 genotypes influence plasma cholesterol fluctuations following a high cholesterol diet, a healthy population of 40 men and 51 women were studied. The crossover intervention randomly assigned participants to an EGG (640 mg/d cholesterol) or placebo (0 mg/d cholesterol) diet for 30 days, with a 3-week washout between periods. Allele-specific oligonucleotide hybridization was utilized to determine the presence or absence of APOC3 and APOA4 polymorphisms. Differences in plasma cholesterol between hyper- and hypo-responders were not influenced by genotype. However, an interaction (P < 0.0001) did exist between APOA4 allele, diet and gender with regard to triglycerides (TG). While female carriers of the APOA4(347) S allele had lower TG concentrations than those with the common T/T allele, males with the S allele had higher concentrations. The APOC3 SstI polymorphism analysis revealed that heterozygous carriers of the S2 allele had higher (P < 0.05) plasma apo C-III and TG concentrations, regardless of gender or dietary period. In addition, carriers of the S2 allele had smaller LDL peak particle diameter than those having the common APOC3 genotype. The presence of individual alleles in this population was associated with differences in plasma lipids and LDL size. However, these relationships were independent of dietary cholesterol.

Variations in plasma apolipoprotein C-III levels are strong correlates of the triglyceride response to a high-monounsaturated fatty acid diet and a high-carbohydrate diet

The objective of this study was to examine how a diet rich in carbohydrates (high-CHO) vs a diet rich in monounsaturated fatty acids (high MUFA) consumed ad libitum modulated plasma apolipoprotein C-III (apo C-III) levels and to examine the extent to which diet-induced changes in plasma apo C-III were associated with concurrent variations in plasma triglyceride (TG) levels. Forty-seven men (mean age, 35.7 +/- 11.4 years; body mass index, 29.0 +/- 5.1 kg/m2) were randomly assigned to either a high-CHO diet (CHO, 58%; fat, 26%; n = 23) or a high-MUFA diet (CHO, 45%; fat, 40%; MUFA, 22.5%; n = 24), which they consumed for 6 to 7 weeks. Fasting and postprandial lipemia after an oral fat load and fasting plasma apo C-III were measured at the beginning and at the end of the dietary intervention. Ad libitum consumption of the high-CHO diet induced a significant reduction in body weight (-2.6%, P < .0001), but had no impact on plasma apo C-III concentrations and on fasting and postprandial plasma TG levels. In contrast, ad libitum consumption of the high-MUFA diet also resulted in a significant reduction in body weight (-2.3%, P < .01) as well as in significant reductions in plasma apo C-III (-11%, P = .05) and fasting plasma TG (-17%, P < .01). Diet-induced variations in plasma apo C-III concentrations were correlated with changes in fasting and postprandial TG levels both in the high-CHO (r > 0.70, P < .001) and the high-MUFA groups (r > 0.42, P < .05). These results indicate that variations in plasma apo C-III levels are strong correlates of the fasting and postprandial plasma TG responses to high-MUFA and high-CHO diets.

Interaction between insulin (VNTR) and hepatic lipase (LIPC−514C>T) variants on the response to an oral glucose tolerance test in the EARSII group of young healthy men

Insulin resistance is polygenic in origin, and can be observed at an early age. We have shown that variations in APOC3-482T>C and hepatic lipase (LIPC)-514C>T), individually (APOC3 alone) and interactively, modulate insulin and glucose levels after an OGTT in young healthy men participating in the European Atherosclerosis Research Study II (EARSII). Variation in the insulin gene (INS) variable number tandem repeat (VNTR) has been found to predispose to type 1 and type 2 diabetes. We have evaluated the HphI site 23 bp upstream of the INS gene (a surrogate marker for the VNTR) in EARSII (n=822), to determine if variation in INS contributes to insulin resistance. Carriers of the INS VNTR class III (HphI-) allele (frequency=0.29 (95%CI 0.27, 0.31)) had significantly higher 60-min insulin concentrations after the OGTT (P=0.014) and a marginally higher AUC insulin (P=0.07), compared to class I (HphI+) homozygotes. However, this effect on AUC insulin was modified by the level of physical activity, displaying significant gene:environment interaction (P=0.03). We tested for gene:gene interaction between the INS VNTR and both the LIPC-514C>T and APOC3-482T>C. While there was a significant interaction between INS VNTR and LIPC-514C>T on AUC glucose (P=0.013) and on AUC insulin (P=0.015), there was no interaction with APOC3-482T>C. Thus, despite a modest effect of the INS VNTR alone, the influence of this variant on insulin sensitivity was modified by gene:environment and gene:gene interactions, illustrating the biological complexity of insulin resistance.

Population prevalence of APOE, APOC3 and PPAR-α mutations associated to hypertriglyceridemia in French Canadians

Hypertriglyceridemia (HTG) is known as a common metabolic disorder associated with increased production, decrease catabolism and/or decreased hepatic uptake of triglyceride (TG)-rich particles. We assessed, in the Quebec City population, the allele frequency and haplotype distributions of mutations in genes related to HTG, such as the apolipoprotein E (APOE) (C112R and C158R), the apolipoprotein CIII (APOC3) (C-482T and C3238G) and the peroxisome proliferator-activated receptor alpha (PPARalpha) (L162V) genes. A total of 938 anonymous unlinked newborns from the metropolitan Quebec City area have been genotyped. Allele frequencies observed in the Quebec City population differed from known frequencies determined in other Caucasian populations. The co-transmitted allele distribution between the two-marker genotypes APOE/APOC3(C3238G) and APOC3(C-482T)/PPARalpha(L162V) presented a weak deviation from the assumption of genetic independence. Also, we observed a non-independent distribution of the T-482/G3238 allele combinations within the APOC3 gene, suggesting strong linkage disequilibrium between the C-482T and C3238G polymorphisms. Moreover, comparisons of allele frequencies observed in the population of Québec City to those obtained in other Caucasian populations suggested that the population of Québec City may be at a lower risk of developing HTG due to APOE, APOC3 and PPARalpha genetic variants. However, the strong linkage disequilibrium and the two-marker genotype distributions observed in the APOC3 gene suggest that these two variants may functionally interact in the Québec City population.

Isotretinoin and fenofibrate induce adiposity with distinct effect on metabolic profile in a rat model of the insulin resistance syndrome

OBJECTIVE

To investigate the effect of transcription-modulating drugs, fenofibrate and isotretinoin, on metabolic profile, insulin sensitivity of adipose and muscle tissues and gene expression in a genetic model of insulin resistance syndrome, polydactylous rat strain (PD/Cub).

DESIGN

Administration of fenofibrate (100 mg/kg/day), isotretinoin (30 mg/kg/day) or vehicle to adult male PD/Cub rats fed standard laboratory chow for 15 days.

MEASUREMENTS

Parameters of lipid and carbohydrate metabolism-oral glucose tolerance test, serum concentrations of insulin, triglycerides (TG), free fatty acids (FFA), glycerol, total cholesterol (CH); morphometric variables, in vitro insulin sensitivity of adipose and muscle tissues, catecholamine-stimulated lipolysis and the expression of ApoC-III and Hnf-4 genes in liver.

RESULTS

Both experimental groups displayed an increase in adiposity with contrasting effects on TG (lowered by fenofibrate and increased by isotretinoin) and gene expression (no change in fibrate-treated rats and increased expression of ApoC-III and Hnf-4 in isotretinoin-treated group). Fenofibrate-treated rats also showed decreased concentrations of FFA and CH with concomitant decrease of catecholamine-induced lipolysis in adipocytes, but also hyperinsulinemia and the highest insulin/glucose ratio. Isotretinoin increased glycerol concentrations and decreased the insulin sensitivity of peripheral tissues.

CONCLUSION

The PD/Cub rat showed a distinct pharmacogenetic reaction to fenofibrate and isotretinoin administration. Several lines of evidence now implicate specific variant(s) of ApoC-III and/or ApoA-V alleles as responsible for the dyslipidemia observed in this genetic model. The PD/Cub strain may also serve as a pharmacogenetic model for dissection of the retinoid-induced hypertriglyceridemia.

Variation in USF1 shows haplotype effects, gene : gene and gene : environment associations with glucose and lipid parameters in the European Atherosclerosis Research Study II

Upstream stimulatory factor 1 (USF 1), is a transcription factor controlling expression of several genes involved in lipid and glucose homeostasis and co-localizes with familial combined hyperlipidemia (FCHL) and type 2 diabetes on chromosome 1q22-23. We sequenced USF1 in 24 UK FCHL probands, but found no rare or common cSNPs. Three common intronic single nucleotide ploymorphisms (SNP), 306A>G, 475C>T and 1748C>T, were identified and their association was examined with fasting and postprandial lipids and after an oral glucose tolerance test (OGTT) in the European Atherosclerosis Research Study II offspring study. There were no significant differences in allelic frequencies of the SNPs between cases and controls. Individually none of the SNPs showed significant associations with any parameter. In haplotype analysis, compared with other haplotypes, 475C/1748T showed significantly higher and 475T/1748T showed lower peak glucose (P=0.004 and 0.07, respectively) during the OGTT. There was significant case-control heterogeneity in the interaction of genotype with body mass index, on fasting low density lipoprotein with 306A>G and 1748C>T, and on borderline significance with fasting glucose with 475C>T (P=0.002, 0.0007 and 0.015, respectively). Furthermore, 475C>T showed interaction with both HSL-60C>G (case-control heterogeneity P=0.0002) on AUC TG and APOC3 -482C>T on plasma apoE levels (P=0.0012). Thus, in these healthy young men, variation in USF1 was the influencing feature of both glucose and lipid homeostasis showing case-control heterogeneity.

The role and mode of action of apolipoproteins CIII and AV: synergistic actors in triglyceride metabolism?

PURPOSE OF REVIEW

Apolipoprotein (apo)CIII and apoAV play an important role in triglyceride metabolism as evidenced by the unambiguous and opposing phenotypes of transgenic and knockout mouse models. In this review we discuss studies on the genetics, protein structure, and regulation of apoCIII and apoAV and compare their potential molecular mechanisms of action in triglyceride metabolism. We examine the hypothesis that apoCIII and apoAV synergistically affect triglyceride metabolism.

RECENT FINDINGS

It has now been firmly established that variation in plasma triglyceride levels in a wide range of human populations is strongly associated with genetic variation at the chromosomal locus encoding both the APOC3 and APOA5 genes, the APOA1/C3/A4/A5 gene cluster. The close physical linkage of these genes and the frequent concurrence of genetic variants, however, complicate the assignment of specific metabolic defects to specific polymorphisms. Recent insight into the regulation of APOC3 and APOA5 gene expression and structural modeling studies on the apoAV protein have provided novel clues for the potential molecular mechanisms responsible for the effects of apoCIII and apoAV on triglyceride metabolism.

SUMMARY

Hypertriglyceridemia is a major independent risk factor in the development of cardiovascular disease. Moreover, triglyceride-derived fatty acids are thought to play a key role in the development and progression of the metabolic syndrome. As modulators of triglyceride metabolism, apoCIII and apoAV are key players and potential therapeutic targets. However, little is known of their molecular mechanism and potential cooperativity. Rational therapeutic application will require the filling of this hiatus in our knowledge.

Contribution of polymorphisms in the apolipoprotein AI-CIII-AIV cluster to hyperlipidaemia in patients with gout

BACKGROUND

Studies have shown that hyperuricaemia is independently related to the insulin resistance syndrome and that polymorphisms of the apolipoprotein AI-CIII-AIV cluster are also related to insulin resistance.

OBJECTIVE

To study the prevalence of polymorphisms of the apolipoprotein AI-CIII-AIV cluster in persons with gout and to determine whether these polymorphisms contribute to the pathophysiology of gout or to altered lipid concentrations.

METHODS

Plasma cholesterol, triglycerides, uric acid, VLDL, LDL, IDL, and HDL triglycerides, cholesterol, and the renal excretion of uric acid were measured in 68 patients with gout with gout and 165 healthy subjects. Polymorphisms were studied by amplification and RFLP in all subjects, using XmnI and MspI in the apolipoprotein AI gene and SstI in the apolipoprotein CIII gene.

RESULTS

The A allele at position -75 bp in the apolipoprotein AI gene was more common in patients with gout than in controls (p = 0.01). Levels of cholesterol, triglycerides, uric acid, basal glycaemia, and HDL cholesterol were higher in the patients (p<0.001). In the patients there was also an interaction between mutations at the two polymorphic loci studied in the apolipoprotein AI gene (p = 0.04). An absence of the mutation at position -75 bp of the apolipoprotein AI gene resulted in increased plasma triglyceride levels.

CONCLUSIONS

Gouty patients have an altered allelic distribution in the apolipoprotein AI-CIII-AIV cluster, which could lead to changes in levels of lipoproteins. This is not caused by a single mutation but rather by a combination of different mutations.

Genetic effect of two polymorphisms in the apolipoprotein A5 gene and apolipoprotein C3 gene on serum lipids and lipoproteins levels in a Chinese population

Two polymorphisms, apolipoprotein A5 (APOA5) -1131T>C and apolipoprotein C3 (APOC3) -482C>T, were examined in a healthy Chinese group. Analysis of covariance (ancova) showed that both -1131T>C and -482C>T minor alleles were associated with triglyceride (TG)-raising effects (p < 0.001 and p = 0.012, respectively) after adjustment of sex, age, and body mass index (BMI). Moreover, -1131T>C minor alleles were also found to be associated with total cholesterol (TC)-raising effects (p = 0.045). However, the relationship between -482C>T minor alleles and TC-raising effects was not observed after adjustment of sex, age, and BMI. By contrast, significant inverse associations were noted between minor alleles (-1131T>C and -482C>T) and high-density lipoprotein cholesterol (HDL-C) concentrations (p = 0.021 and p = 0.021, respectively). Linear regression analysis showed that the effects of -1131T>C and -482C>T polymorphisms on TG and HDL-C (0.001 and 0.008; 0.041 and 0.005, respectively) are independent and additive and that -1131T>C can seriously affect the levels of TG (0.001 vs 0.008). The additive effect of the two polymorphisms was confirmed further by haplotype analysis. Our results strongly support that the two single nucleotide polymorphisms, -1131T>C in APOA5 and -482C>T in APOC3, are related to the levels of serum TG and HDL-C and those of other several lipids and lipoproteins in the Chinese population.

Lipoprotein concentrations in newborns are associated with allelic variations in their mothers

BACKGROUND

Factors determining lipoprotein concentrations in the fetus are not yet fully understood. We postulated that an important factor is the genetic make-up of the mother. In the present study, we examined the associations between the cord blood concentrations of lipoproteins of 525 newborns and the polymorphisms present in their mothers on the genes of apolipoprotein E (APOE*E2, *E3, *E4), apolipoprotein C-III (APOC3*C3238G also called APOC3*S2) and lipoprotein lipase (LPL*S447X).

RESULTS

Newborns born of mothers with APOE*E2 allele had significantly lower cord blood LDL-C (P < 0.01) and apoB (P < 0.01) and significantly higher cord blood HDL-C and apoA1 (all P-values < 0.03) compared to those born of mothers with APOE*E3E3 genotype. These associations were independent of the presence of APOE*E2 allele in the newborns. Similarly, APOC3*S2 in mothers was associated with significantly lower (all P < 0.001) cord blood LDL-C, apoB, HDL-C and apoA1. In contrast, LPL*S447X in mothers lowered significantly cord blood LDL-C and apoB only when LPL*S447X was present in newborns. Most of the effects of these maternal polymorphisms on the newborns were independent of the changes of maternal lipoproteins generated by these polymorphisms.

CONCLUSIONS

This is the first evidence that maternal genetic variations influence fetal lipoprotein concentrations, independent of the genetic status of the fetus and of the variations of maternal lipoprotein concentrations generated by these genetic variants. It suggests that proteic components of maternal lipoproteins strongly control the metabolism of maternal lipoproteins carried out at the surface of the placenta to assure the cholesterol delivery to the fetus.

Linkage and association between distinct variants of the APOA1/C3/A4/A5 gene cluster and familial combined hyperlipidemia

OBJECTIVE

Combined hyperlipidemia is a common disorder, characterized by a highly atherogenic lipoprotein profile and a substantially increased risk of coronary heart disease. The purpose of this study was to establish whether variations of apolipoprotein A5 (APOA5), a newly discovered gene of lipid metabolism located 30 kbp downstream of the APOA1/C3/A4 gene cluster, contributes to the transmission of familial combined hyperlipidemia (FCHL).

METHODS AND RESULTS

We performed linkage and association tests on 128 families. Two independent alleles, APOA5c.56G and APOC3c.386G, of the APOA1/C3/A4/A5 gene cluster were overtransmitted in FCHL (P=0.004 and 0.007, respectively). This was paired with reduced transmission of the common APOA1/C3/A4/A5 haplotype (frequency 0.4461) to affected subjects (P=0.012). The APOA5c.56G genotype accounted for 7.3% to 13.8% of the variance in plasma triglyceride levels in probands (P<0.004). The APOC3c.386G genotypes accounted for 4.4% to 5.1% of the variance in triglyceride levels in FCHL spouses (P<0.007), suggesting that this allele marks a FCHL quantitative trait as well as representing a susceptibility locus for the condition.

CONCLUSIONS

A combined linkage and association analysis establishes that variation at the APOA1/C3/A4/A5 gene cluster contributes to FCHL transmission in a substantial proportion of northern European families.

The apolipoprotein CIII T2854G variants are associated with postprandial triacylglycerol concentrations in normolipidemic Korean men

This study investigated associations between the apolipoprotein (apo) CIII polymorphism and triacylglycerol (TAG) concentrations in fasting and postprandial plasma. Polymerase chain reaction followed by a restriction fragment length genotyping was conducted to assess the allele frequency of the apo CIII T2854G variants in healthy and normolipidemic Korean men ( n=262). Waist circumference, body mass index (kilograms per meter squared), fasting plasma concentrations of TAG, total cholesterol, high-density lipoprotein cholesterol (HDLC), low-density lipoprotein cholesterol (LDLC), glucose, and insulin were compared across the genotypes. Compared to TT homozygotes and TG heterozygotes, GG homozygotes had 22% higher fasting TAG concentrations, respectively ( p<0.05). A subgroup of 60 subjects (TT homozygotes=20, TG heterozygotes=22, GG homozygotes= 18) were further invited to participate in a high-fat meal test to assess postprandial TAG concentrations. During the high-fat meal test, the GG homozygotes had 21% higher TAG area under the curve (AUC) than the TT homozygotes ( p<0.05) and 22% higher TAG AUC than the TG heterozygotes ( p<0.05). In conclusion, this is the first study to show that the apo CIII T2854G variants are associated with elevated postprandial TAG concentrations in the study population of Korean men.

Obesity risk is associated with carbohydrate intake in women carrying the Gln27Glu beta2-adrenoceptor polymorphism

Interindividual differences in the response to dietary intake are, in some cases, genotype dependent. Moreover, genotype-environment interactions may appear when the impact of lifestyle factors (e.g., diet) on a phenotype (e.g., BMI > 30 kg/m(2)) differs by genotype. A case-control study (obese subjects vs. normal weight controls) was conducted to assess a possible effect modification on obesity risk of the Gln27Glu polymorphism for the beta(2)-adrenoceptor gene depending on dietary intake. The sample included 159 subjects with BMI > 30 kg/m(2) and 154 controls with BMI < 25 kg/m(2). The allele frequency for the Glu27 polymorphism, as assessed by the polymerase chain reaction-restriction fragment length polymorphism methodology, was 0.40 in cases (obese) and 0.37 in controls (lean), which was similar to that of other Caucasian populations. The dietary intake was estimated by using a previously validated food frequency questionnaire. Obesity incidence was not directly affected by the polymorphism [odds ratio (OR) = 1.40; P = 0.246]. However, a significant interaction (effect modification) between carbohydrate (CHO) intake and the presence of the Glu27 variant in the probability of obesity was apparent. Thus, females with the polymorphism and a higher CHO intake [>49% energy (E)] had a higher obesity risk (OR = 2.56, P = 0.051). The product-term introduced in the logistic model to assess effect modification revealed a marginally significant interaction (P = 0.058) between both factors. Furthermore, a high intake of CHO (E > 49%) was associated with higher insulin levels among women carrying the Gln27Glu polymorphism (P < 0.01). This gene-nutrient interaction emphasizes the importance of examining the outcome of some obesity-related mutations depending on lifestyle (including diet) and may explain the heterogeneity of findings from previous studies.

Effect of apoC-III gene polymorphisms on the lipoprotein-lipid profile of viscerally obese men

Abdominal visceral adipose tissue (AT) accumulation is associated with an atherogenic metabolic profile that includes increased plasma triglyceride (TG), low HDL cholesterol levels, and an insulin-resistant hyperinsulinemic state. Whereas the apolipoprotein (apo) C-III C3238G gene variant, often referred to as the SstI polymorphism, has been related to variations in plasma TG concentrations, another variation within the insulin responsive element (C-482T) of the apoC-III gene has been associated with greater glucose and insulin responses to an oral glucose tolerance test (OGTT); however, these results were obtained in nonobese individuals. We therefore investigated the effects of three apoC-III gene polymorphisms, namely SstI, C-482T, and T-455C, on fasting plasma lipoprotein-lipid levels and response to a 75 g OGTT in a sample of 122 viscerally obese men (abdominal visceral AT area >or=130 cm(2)). Among the three gene variants that were examined, the SstI variation was the only one found to be associated with hypertriglyceridemia. Indeed, S1/S2 heterozygotes (n = 24) were characterized by increased fasting plasma TG concentrations compared with S1/S1 homozygotes (n = 98) (mean +/- SD: 3.03 +/- 1.58 vs. 2.34 +/- 0.95 mmol/l respectively, P < 0.05). The higher TG concentrations in S1/S2 were associated with the presence of smaller, denser LDL particles compared with S1/S1 subjects (LDL peak particle diameter: 24.8 +/- 0.5 nm vs. 25.1 +/- 0.5 nm respectively, P < 0.05). Furthermore, there was no association between the response to the OGTT and any of the apoC-III gene variants (SstI, T-455C, or C-482T) examined. Results of the present study support the notion of a hypertriglyceridemic effect associated with the apoC-III SstI polymorphism that could modulate the magnitude of the dyslipidemic state in abdominally obese patients.

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

The aim of this study was to investigate the influence of APOA5 variants on fasting lipids and to the response to both an oral fat tolerance test (OFTT) and an oral glucose tolerance test (OGTT). The association of two APOA5 SNPs [S19W (SNP5), -1131T>C (SNP3)] and an APOA4/A5 intergenic SNP [-12238T>C (SNP4)] were examined in healthy young men (n=774) who had undergone both an OFTT and an OGTT. Both -1131T>C and S19W rare alleles were associated with triglyceride (TG)-raising effects (11%, P=0.008; 21% (in cases), P<0.026, respectively) and showed additive effects on TG. None of the variants influenced the responsiveness to the OFTT after correcting for baseline TG. Homozygosity for the -12238T>C rare allele was associated with higher waist to hip ratio (P<0.0006), systolic blood pressure (P=0.012) and AUC and peak of insulin after OGTT (P=0.003 and P=0.027, respectively), traits that define the metabolic syndrome. Our results strongly support the role of APOA5 in determining plasma TG levels in an age-independent manner and highlight the importance of the APOC3/A4/A5 gene cluster in both TG and metabolic homeostasis.

Variants in the APOC3 promoter insulin responsive element modulate insulin secretion and lipids in middle-aged men

Variation in the insulin responsive element (IRE) of the APOC3 promoter has been shown to be associated with insulin and glucose concentrations after an oral glucose tolerance test (OGTT) in young healthy men. We evaluated two variants in the IRE (-455T>C and -482C>T) in the Ely study, a prospective cohort study of middle-aged men (n=223) and women (n=279), to determine if the effect of these variants on glucose homeostasis could be explained by altered nonesterified fatty acid (NEFA) levels and if these effects are modulated by age and gender. Both variants had significant effects on the 30-min insulin incremental response in men alone (-482C>T, P=0.007; -455T>C, P=0.0155), with rare allele homozygotes having a 33.3% and 23.3% lower insulin increment as compared to common allele homozygotes, respectively. Thirty-minute NEFA concentrations were also significantly associated with genotype in men and levels were approximately 10% higher in carriers homozygous for the rare alleles as compared to subjects homozygous for the common alleles (-482C>T, P=0.04; -455T>C, P=0.006). In addition, there was a strong interaction between both variants and cigarette smoking affecting fasting triglyceride levels in both men (interaction: -455T>C, P=0.02; -482C>T, P=0.008) and women (interaction: -455T>C, P=0.007; -482C>T, P=0.013). Taken together, the data shows that men who carry the rare alleles of the IRE variants have disturbed glucose homeostasis and an unfavourable lipid phenotype. The finding of an elevated 30-min NEFA may be an important mechanistic link between triglyceride-rich lipoprotein (TRL) metabolism and glucose homeostasis.

The apolipoprotein AV gene and diurnal triglyceridaemia in normolipidaemic subjects

The newly recognised apolipoprotein (apo) AV gene (APOAV) has been linked to fasting plasma triglyceride (TG) concentrations with some polymorphisms associated with elevated fasting TGs. Since fasting plasma TGs are mainly determined by the hepatic production of TG-rich particles (very low density lipoprotein; VLDL), and fasting TGs are the major determinants of postprandial lipaemia, we have evaluated the effects of an APOAV polymorphism on postprandial triglyceridaemia, which is largely determined by the intestinal production and clearance of chylomicrons. For this purpose, diurnal capillary triglyceridaemia (reflecting postprandial lipaemia) was determined in a cohort of 88 healthy volunteers (48 males and 40 females) in relation with a -1131T>C variant in the promoter of APOAV. Thirteen of these subjects (7 males and 6 females) were carriers of the -1131C allele, which has been associated with higher fasting plasma TG levels. The carriers had higher fasting capillary TG concentrations, although plasma TGs were not significantly different from non-carriers in this cohort. Surprisingly, total diurnal triglyceridaemia calculated as the area under the capillary TG curve was similar in carriers compared to non-carriers but after correction for fasting capillary TG levels, incremental diurnal triglyceridaemia was significantly lower in carriers (1.74 (5.27) mmol/h/l) than in non-carriers (4.91 (4.90) mmol/h/l; p = 0.036). The same trends were found for both males and females when analysed separately. Since dietary intake, which is a major determinant of incremental diurnal triglyceridaemia, did not differ between the two groups, we believe that these differences are at least partly explained by the APOAV. In summary, the APOAV assessed by means of the -1131T>C variant seemed to have a paradoxical effect on postprandial lipaemia when compared to fasting TG levels.

Apolipoprotein and apolipoprotein receptor genes, blood lipids and disease

PURPOSE OF REVIEW

Apolipoproteins and their receptors are the main controllers of lipid metabolism and, as such, have a major impact not only on the risk of cardiovascular disease but also on the development and degeneration of the central nervous system. Variations in the genes coding for these apolipoproteins and their receptors and the interaction with the environment determine individual susceptibility to metabolic disturbances, the response to dietary or pharmacological intervention and, finally, to disease.

RECENT FINDINGS

This review will focus on recent findings, such as the latest concepts regarding apolipoprotein E in neurodevelopment, the newly identified apolipoprotein A-V and its influence in triglyceride metabolism, and the improved understanding of apolipoprotein A-I and HDL metabolism in the light of the discovery of the ABC family of transporters. Other key aspects of lipoprotein metabolism and cardiovascular disease risk such as apolipoprotein B-100, the LDL receptor, apolipoprotein C-III or apolipoprotein (a) will be updated.

SUMMARY

Variations in these genes will be analysed in relation to plasma lipid levels, their interactions with diet, treatment or other environmental stimuli, and their influence on the risk of cardiovascular disease and neurological disorders.

Clinical Utility and Approach to Estimate Postprandial Hypertriglycemia by A Newly Designed Oral Fat-loading Test

The objective of this study was to estimate postprandial hypertriglycemia by a newly designed oral fat-loading test. Twenty-three healthy normolipidemic volunteers were orally administered a test meal consisting of a mixture of Telmeal 2.0 and 20 g of salt-free butter after fasting for 12 h. To measure the levels of total cholesterol (T-Cho), triglycerides (TG), high-density lipoprotein-cholesterol (HDL-C), remnant-like particle-cholesterol (RLP-C), lipoprotein (a) [Lp (a)], free fatty acid, apolipoproteins (Apos), plasma glucose (PG), immunoreactive insulin (IRI), and high-sensitivity C-reactive protein (hs-CRP), venous blood samples were collected before the meal and at each hour until 9 h after fat-loading. The levels of both TG and RLP-C were drastically elevated at 2 h after fat-loading and these levels remained high until 4 h (p < 0.01). A significant correlation between TG and RLP-C was also observed at 2, 3 and 4 h, and the values of the correlation coefficients (r) were 0.837, 0.838, and 0.908, respectively. In contrast, the levels of T-Cho, HDL-C, Lp (a), Apos, PG, and hs-CRP did not change. Furthermore, there were no gastrointestinal symptoms during or after the study. These results strongly suggested that this newly designed fat-loading test was very useful for evaluating postprandial hypertriglycemia, including remnant concentrations.

ApoC-III gene polymorphisms and risk of coronary artery disease

Several polymorphisms in the apolipoprotein C-III (apoC-III) gene have been associated with hypertriglyceridemia, but the link with coronary artery disease risk is still controversial. In particular, apoC-III promoter sequence variants in the insulin responsive element (IRE), constitutively resistant to downregulation by insulin, have never been investigated in this connection. We studied a total of 800 patients, 549 of whom had angiographically documented coronary atherosclerosis, whereas 251 had normal coronary arteriograms. We measured plasma lipids, insulin, apoA-I, apoB, and apoC-III and assessed three polymorphisms in the apoC-III gene, namely, T-455C in the IRE promoter region, C1100T in exon 3, and Sst1 polymorphic site (S1/S2) in the 3' untranslated region. Each variant influenced triglyceride levels, but only the T-455C (in homozygosity) and S2 alleles influenced apoC-III levels. In coronary artery disease (CAD) patients, 18.6% were homozygous for the -455C variant compared with only 9.2% in CAD-free group (P < 0.001). In logistic regression models, homozygosity for -455C variant was associated with a significantly increased risk of CAD (OR = 2.5 and 2.18 for unadjusted and adjusted models, respectively) suggesting that it represents an independent genetic susceptibility factor for CAD.

Influence of the APOC3 -2854T>G polymorphism on plasma lipid levels: effect of age and gender

The APOC3 -2854T>G polymorphism lies in the APOC3-A4 intergenic region. In a group of healthy adults, this polymorphism was associated with circulating triglycerides, with 55% lower fasting levels in the homozygous wild-type (TT) compared to the homozygous rare allele (GG) genotype. Age and gender had a significant impact on genotype-triglyceride interactions.

Genetic determinants of the response to bezafibrate treatment in the lower extremity arterial disease event reduction (LEADER) trial

Genetic determinants of baseline levels and the fall in plasma triglyceride and fibrinogen levels in response to bezafibrate treatment were examined in 853 men taking part in the lower extremity arterial disease event reduction (LEADER) trial. Three polymorphisms in the peroxisome proliferator activated receptor alpha (PPARalpha) gene were investigated (L162V, G>A in intron 2 and G>C in intron 7), two in the apolipoprotein CIII (APOC3) gene (-482C>T and -455T>C) and one in the beta-fibrinogen (FIBB) gene (-455G>A). The presence of diabetes (n=158) was associated with 15% higher triglyceride levels at baseline compared to non-diabetics (n=654) (P<0.05). Among the diabetic group, carriers of the PPARalpha intron 7 C allele had 20% lower triglyceride levels compared to homozygotes for the common G allele (P<0.05), with a similar (non-significant) trend for the L162V polymorphism, which is in linkage disequilibrium with the intron 7 polymorphism. For the APOC3 gene, carriers of the -482T allele had 13% lower baseline triglyceride levels compared to -482C homozygotes (P<0.02), but no effect was observed with the -455T>C substitution. In the non-diabetic patients, the PPARalpha V162 allele was significantly associated with 9% higher baseline triglyceride levels (P<0.03) and a similar, but non-significant trend was seen for the intron 7 polymorphism. Overall, triglyceride levels fell by 26% with 3 months of bezafibrate treatment, and current smokers showed a poorer response compared to ex/non-smokers (23% fall compared to 28% P=0.03), but none of the genotypes examined had a significant influence on the magnitude of response. Carriers of the -455A polymorphism of the FIBB gene had, as expected, marginally higher baseline fibrinogen levels, 3.43 versus 3.36 g/l (P=0.055), but this polymorphism did not affect response to treatment. Overall, fibrinogen levels fell by 12%, with patients with the highest baseline fibrinogen levels showing the greatest decrease in response to bezafibrate. For both the intron 2 and the L162V polymorphisms of the PPARalpha gene there was a significant interaction (both P<0.01) between genotype and baseline levels of fibrinogen on the response of fibrinogen levels to bezafibrate, such that individuals carrying the rare alleles in the lowest tertile showed essentially no overall decrease compared to a 0.18 g/l fall in homozygotes for the common allele. Thus while these genotypes are a minor determinant of baseline triglyceride and fibrinogen levels, there is little evidence from this study that the magnitude of response to bezafibrate treatment in men with peripheral vascular disease is determined by variation at these loci.

Apolipoprotein C-III and E polymorphisms and cardiovascular syndrome, hyperlipidemia, and insulin resistance in renal transplantation

Hyperlipidemia and insulin resistance frequently develop after renal transplantation, contributing to cardiovascular disease. Individual differences in response based upon genetic variations in proteins regulating lipidic and glucose tolerance metabolism could be expected. In the general population, the S2 allelic variant of the apoprotein (apo) C-III gene has been associated with hypertriglyceridemia and an insulin resistant state, whereas the E4 allele of the apo E has been associated with hypercholesterolemia and atherosclerosis. Its influence in renal transplant patients remains to be seen. In order to assess the impact of apo E and C-III major polymorphisms on atherosclerotic vascular disease, lipid profile and impaired glucose tolerance in renal transplant patients, we studied 110 consecutively examined patients undergoing kidney transplantation (age range 24-73 years). Atherosclerotic complications were detected in 25% of patients, with age, male sex and hypercholesterolemia being significant atherosclerotic risk factors. Among the male patients with E4 allele, the odds ratio for coronary disease and global atherosclerosis were 10.2 (95% CI) and 6.4 (95% CI), respectively. There were no significant differences in the frequency of any of the polymorphisms among patients with dyslipidemia and impaired glucose tolerance. As the number of patients in our sample was small, larger studies are needed to verify these issues. While in the studied population C-III polymorphism appears to have little association with the prevalence of atherosclerotic complications, E4 allele should be considered as a genetic marker of coronary artery disease and global atherosclerosis in renal transplant patients.

An interaction between apo C-III variants and protease inhibitors contributes to high triglyceride/low HDL levels in treated HIV patients

BACKGROUND

Long-term therapy with protease inhibitors (PI) is associated with hypertriglyceridaemia, low high-density lipoprotein (HDL) levels and accumulation of apolipoprotein (apo) E- and apo C-III-containing lipoproteins.

OBJECTIVES

To evaluate the impact, on this dyslipaemic phenotype, of three polymorphisms of the apo C-III gene: two on an insulin response element and one in the 3'-region. Apo E genotypes were evaluated also.

DESIGN

Sixty consecutive male patients attending the HIV follow-up consultation were included during a 3-month period. All patients received at least one PI. Apo C-III and apo E genotypes were determined. Besides routine bio-clinical examination, a detailed exploration of lipoproteins and of insulin secretion markers was carried out.

METHODS

Plasma lipoparticles, insulin, proinsulin and C-peptide were measured by specific immuno-assays. Determination of apo C-III genotypes (-455C/T, -482C/T and SstI) and of apo E alleles (epsilon2, epsilon3 and epsilon4) were performed by amplification and endonuclease digestion and were confirmed by allele-specific oligonucleotide hybridization.

RESULTS

Distribution of apo C-III alleles defined four major haplotypes. Carriers of the -455C variant had 30% lower levels of HDL-cholesterol than non-carriers. Plasma triglycerides increased according to the number of variant alleles. In multivariate analysis, a model including age, body mass index, clinical stage and treatment length, plasma insulin and apo C-III haplotypes explained around 43% of the HDL-cholesterol and triglycerides variability. Measurements of lipids before and after the use of PI demonstrated synergistic effects of the treatment and apo C-III variants on triglyceride levels.

CONCLUSIONS

Apo C-III polymorphisms might identify a genetic predisposition to develop dyslipidaemia under PI therapy.

Two newly identified SNPs in the APO AI-CIII intergenic region are strongly associated with familial combined hyperlipidaemia

BACKGROUND

We previously reported linkage and association of the apoAI-CIII-AIV gene region on chromosome 11 with familial combined hyperlipidaemia (FCHL). However, the observed epistasis resulting in an increased susceptibility to FCHL still remains unexplained. We hypothesize that the region between the apo AI and apo CIII genes may harbour functional mutations that might be in linkage disequilibrium with the already identified SstI and MspI polymorphisms, and provide an alternative explanation for the observed relationship.

METHODS

Using sequence analysis, we identified four new single nucleotide polymorphisms (SNPs) in the apo AI-CIII intergenic region. These four variants, T(3213)C, A(3235)C, T(3287)C and A(5132)C, were studied in 30 FCHL probands, 159 hyperlipidaemic relatives, 327 normolipidaemic relatives, and 218 spouses from the same families in which the original results were obtained.

RESULTS

The allele frequencies were significantly different between probands and spouses (P < 0.05). Transmission/disequilibrium test (TDT) analyses revealed more frequent transmission of the minor alleles to the affected offspring. The minor genotype was associated with elevated plasma cholesterol and triglyceride levels. The T(3213)C and MspI, and the A(3235)C and SstI SNPs were in complete linkage disequilibrium, resulting in two different major haplotypes 2-2-1-2-2-1 and 1-1-2-2-2-2 (MspI-T(3213)C-A(3235)C-T(3287)C-A(5132)C-SstI). Both haplotypes appear to predispose to FCHL independently, and account, together with the wild-type, for almost 90% of those occurring in these FCHL families, extending the high-risk combination of haplotypes that were reported previously.

CONCLUSION

These newly identified additional intergenic SNPs therefore provide an alternative explanation for the observed association of the SstI and MspI polymorphisms to the increased susceptibility for FCHL.