Genetic polymorphisms of the apolipoprotein A-IV in a Greek population and their relation to plasma lipid and lipoprotein levels

Vertical sleeve gastrectomy restores glucose homeostasis in apolipoprotein A-IV KO mice

Bariatric surgery is the most successful strategy for treating obesity, yet the mechanisms for this success are not clearly understood. Clinical literature suggests that plasma levels of apolipoprotein A-IV (apoA-IV) rise with Roux-en-Y gastric bypass (RYGB). apoA-IV is secreted from the intestine postprandially and has demonstrated benefits for both glucose and lipid homeostasis. Because of the parallels in the metabolic improvements seen with surgery and the rise in apoA-IV levels, we hypothesized that apoA-IV was necessary for obtaining the metabolic benefits of bariatric surgery. To test this hypothesis, we performed vertical sleeve gastrectomy (VSG), a surgery with clinical efficacy very similar to that for RYGB, in whole-body apoA-IV knockout (KO) mice. We found that VSG reduced body mass and improved both glucose and lipid homeostasis similarly in wild-type mice compared with apoA-IV KO mice. In fact, VSG normalized the impairment in glucose tolerance and caused a significantly greater improvement in hepatic triglyceride storage in the apoA-IV KO mice. Last, independent of surgery, apoA-IV KO mice had a significantly reduced preference for a high-fat diet. Altogether, these data suggest that apoA-IV is not necessary for the metabolic improvements shown with VSG, but also suggest an interesting role for apoA-IV in regulating macronutrient preference and hepatic triglyceride levels. Future studies are necessary to determine whether this is the case for RYGB as well.

TheAPOA4Thr347→Ser347Polymorphism Is Not a Major Risk Factor of Obesity

OBJECTIVE

The goal of this study was to assess the association between the APOA4 Thr(347)-->Ser(347) polymorphism and BMI and obesity.

RESEARCH METHODS AND PROCEDURES

Men and women (n = 3320), randomly recruited in three independent population surveys from the north, east, and south of France, were genotyped for the APOA4 Thr(347)-->Ser(347) polymorphism.

RESULTS

There were 1327 overweight (825 men, 502 women) and 611 obese (313 men, 298 women) subjects. The prevalences of subjects carrying at least one Ser(347) allele (*/Ser(347)) were 36.5%, 33.8%, and 34.3% in controls, overweight, and obese subjects, respectively (not significant), and those of the Ser(347)/Ser(347) genotype were 4.5%, 3.0%, and 2.2%, respectively (not significant). In both men and women, mean BMI and body weight were not significantly different among APOA4 genotypes. There was no evidence of heterogeneity among centers, smoking status, alcohol intake, physical activity, and educational level categories. In men, mean waist girth was lower in Ser(347)/Ser(347) (92.2 +/- 9.4 cm) than in Thr(347) carriers (95.9 +/- 10.9 cm; p = 0.01), and plasma triglycerides levels were lower in Ser(347) (1.41 +/- 1.04 mM) than in Thr(347)/Thr(347) carriers (1.55 +/- 1.23 mM; p = 0.01).

DISCUSSION

These results suggest that the APOA4 347Ser allele is not a major risk factor for obesity or overweight.

The APOA5 Trp19 allele is associated with metabolic syndrome via its association with plasma triglycerides

BACKGROUND

The goal of the present study was to assess the effect of genetic variability at the APOA5/A4/C3/A1 cluster locus on the risk of metabolic syndrome.

METHODS

The APOA5 Ser19Trp, APOA5 -12,238T>C, APOA4 Thr347Ser, APOC3 -482C>T and APOC3 3238C>G (SstI) polymorphisms were analyzed in a representative population sample of 3138 men and women from France, including 932 individuals with metabolic syndrome and 2206 without metabolic syndrome, as defined by the NCEP criteria.

RESULTS

Compared with homozygotes for the common allele, the odds ratio (OR) [95% CI] for metabolic syndrome was 1.30 [1.03-1.66] (p = 0.03) for APOA5 Trp19 carriers, 0.81 [0.69-0.95] (p = 0.01) for APOA5 -12,238C carriers and 0.84 [0.70-0.99] (p = 0.04) for APOA4 Ser347 carriers. Adjustment for plasma triglycerides, (but not for waist girth, HDL, blood pressure or glycemia - the other components of metabolic syndrome) abolished these associations and suggests that triglyceride levels explain the association with metabolic syndrome. There was no association between the APOC3 -482C>T or APOC3 3238C>G polymorphisms and metabolic syndrome. The decreased risk of metabolic syndrome observed in APOA5 -12,238C and APOA4 Ser347 carriers merely reflected the fact that the APOA5 Trp19 allele was in negative linkage disequilibrium with the common alleles of APOA5 -12,238T>C and APOA4 Thr347Ser polymorphisms.

CONCLUSION

The APOA5 Trp19 allele increased susceptibility to metabolic syndrome via its impact on plasma triglyceride levels.

Genetic and environmental factors affecting the response to statin therapy in patients with molecularly defined familial hypercholesterolaemia

Familial hypercholesterolaemia (FH) is the most common inherited metabolic disease characterized by elevated serum levels of low-density lipoprotein cholesterol (LDL-C) and ischaemic heart disease early in life. Early diagnosis and treatment are essential to prevent premature atherosclerosis in FH patients. The aim of our study was the evaluation of the effects of genetic [class of the LDL receptor (LDLR) gene mutation, apolipoprotein (apo)E, apoA-IV and cholesterol ester transfer protein gene polymorphisms] and environmental factors (age, sex, smoking habit and body mass index) on the lipid-lowering response to statin therapy in patients with molecularly defined FH. Atorvastatin 20 mg/day was prescribed in 49 patients with heterozygous FH. The lipid profile was examined before and after 12 weeks of therapy. Statin therapy resulted in a decrease of 37% and 36% in LDL-C and apoB levels, respectively. The study population was then divided into 2 groups according to the class of the LDLR mutation [patients sharing a class V mutation (the G1775A mutation, n=21) and patients sharing class II mutations (the G1646A and the C858A mutations, n=28)]. In both groups, the percentage decrement in LDL-C and apoB levels were correlated with the initial LDL-C and apoB levels, respectively. The class of the LDLR mutation affected the LDL-C and apoB-lowering response of heterozygous FH patients to statin therapy. In detail, heterozygotes sharing a class V mutation of the LDLR showed a higher percentage decrement in LDL-C and apoB levels after atorvastatin administration compared to patients sharing class II mutations (49+/-9% versus 34+/-9%, P=0.001 for LDL-C and 42+/-16% versus 35+/-20%, P=0.001 for apoB). The influence of the classes of the LDLR gene mutations on the change of LDL-C and apoB levels to atorvastatin was still significant in a multivariate analysis. None of the other genetic and environmental factors studied affected the lipid-lowering response to atorvastatin therapy in patients with heterozygous FH in a multivariate analysis. Our data indicate that the class of the LDLR gene mutation affects the LDL-C and apoB-lowering response of heterozygous FH patients to statin therapy. Specifically, patients with a class V mutation exhibit higher percentage decrease in LDL-C and apoB levels after statin therapy compared to patients sharing class II mutations.

Gene polymorphisms affecting HDL-cholesterol levels in the normolipidemic population

BACKGROUND AND AIM

HDL-cholesterol (HDL-C) is inversely related to the risk of ischemic heart disease. Many genes are reported to affect HDL-C serum levels in both hyperlipidemic and normolipidemic populations, though the data are controversial. We examined the effect of common gene polymorphisms known to interfere with HDL-C metabolism (apolipoprotein E, cholesterol ester transfer protein and apolipoprotein A-IV gene polymorphisms) on HDL-C plasma levels in normolipidemic subjects.

METHODS AND RESULTS

The study population consisted of 200 normolipidemic individuals visiting our clinic for a routine check-up. None of the above gene polymorphisms affected HDL-C levels in our population. However, participants carrying the allele E4 of the apolipoprotein (apo) E gene, the allele B1 of the TaqIB polymorphisms in the cholesterol ester transfer protein (CETP) gene and the allele T of the apoA-IV gene (A to T polymorphism at site 347) (n = 28) had statistically significantly lower HDL-C levels compared to those not carrying the above allele combination (0.99+/-0.33 vs 1.28+/-0.35 mmol/L, p = 0.04).

CONCLUSION

In this study, we describe a subgroup of normolipidemic individuals with low HDL-C levels due to genetic variability, and we discuss the underlying possible mechanisms involved.

Association of apo A-IV 360 (Gln → His) polymorphism with plasma lipids and lipoproteins: the Framingham Offspring Study

The effect of a common apolipoprotein (apo) A-IV polymorphism (substitution of histidine for glutamine at position 360) on plasma lipid, lipoprotein cholesterol and lipoprotein(a) (Lp(a)) levels, and on low-density lipoprotein (LDL) particle size was examined by genotyping in 2322 Caucasian men and women (mean age: 48.9+/-10.1 years) participating in the Framingham Offspring Study (FOS). The relative frequencies of the apo A-IV-Gln (apo A-IV-1) and the apo A-IV-His (apo A-IV-2) alleles were 0.932 and 0.068, respectively, and were in Hardy-Weinberg equilibrium. No effect of the apo A-IV-2 genotype was observed on plasma triglyceride, total and lipoprotein cholesterol, and LDL particle size in either men or women after adjustment for age and body mass index. To avoid a possible interaction between the apo E genotype and the apo A-IV genotype, subgroup analyses were undertaken in 1,414 male and female subjects with the apo E3/3 genotype. Among women in this group there was a significant effect of the apo A-IV-2 allele on triglyceride levels (p=0.046). This effect was no longer significant after adjustment for age and BMI (p=0.074). No significant allele effect on other lipoprotein levels, including Lp(a), was noted in apo E3/3 men or women. We have also conducted a meta-analysis of our own data and of other studies found in the literature, indicating a significant lowering effect of apo A-IV-2 on plasma triglycerides, but no effects on other parameters. In conclusion, the apo A-IV-2 allele is associated with a modest reduction in plasma triglyceride levels in the general population.