Gene polymorphisms affecting HDL-cholesterol levels in the normolipidemic population

Depression Augments Plasma APOA4 without Changes of Plasma Lipids and Glucose in Female Adolescents Carrying G Allele of APOA4 rs5104

The association of apolipoprotein AIV (APOA4) with depression or plasma levels of lipids and glucose has been inconsistently reported. However, interplays between APOA4 and depression on the levels have not been explored yet. The present study aimed to investigate plasma levels of APOA4, lipids, and glucose in adolescents with different genotypes of APOA4 rs5104 and with or without depression. Depressive symptoms were assessed in 631 adolescents by Beck Depression Inventory (BDI). A total score of 14 was defined as the cutoff point for depression. Plasma levels of triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), glucose, and insulin were measured by routine methods, and APOA4 by enzyme-linked immunosorbent assays. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism analyses and verified by DNA sequencing. Female adolescents had higher prevalence of depression than male subjects only in G allele carriers (p = 0.015), but not in AA homozygotes. Risk factors of depression and predictors of depression severity were different between G allele carriers and AA homozygotes. Lower levels of glucose (p = 0.003) were observed in male G allele carriers than those in male AA homozygotes and increased TG levels (p = 0.008) in female G allele carriers when compared with those in female AA homozygotes. When both APOA4 rs5104 and depression were taken into account, subjects with depression had higher levels of plasma APOA4 than adolescents without depression only in female G allele carriers (p = 0.043), but no significant changes of plasma lipids and glucose. Depression augments plasma APOA4 levels without changes of plasma lipids and glucose in female adolescents carrying G allele of APOA4 rs5104. These results may provide a novel explanation for the inconsistent relationship between depression, APOA4, and plasma levels of lipids and glucose in the literature.

Association between lipids and apolipoproteins on type 2 diabetes risk; moderating effects of gender and polymorphisms; the ATTICA study

BACKGROUND AND AIMS

Type 2 diabetes mellitus (T2DM) is a condition defined by hyperglycaemia, but also often presents with dyslipidaemia and suppressed HDL cholesterol. Mendelian randomization studies have suggested a causal link between low HDL cholesterol and T2DM. However, influences of gender, polymorphisms and lifestyle, all known to influence HDL cholesterol, have not been fully explored in a prospective cohort.

METHODS AND RESULTS

In 2001-2002, a random sample of 1514 males (18-87 years old) and 1528 females (18-89 years old) were recruited in the ATTICA study. The 10-year follow-up (2011-2012) included 1485 participants. Lipids and lipoproteins levels, glucose and insulin levels were measured together with apolipoprotein A1 (apoA1) 75 G/A genotype, which is known to influence HDL-cholesterol. In total, 12.9% of the study sample developed T2DM within the 10-year follow-up period. In multivariable models, for each mg/dL increase in apoA1 levels in males, 10-year T2DM risk decreased 1.02%; while every unit increase in apoB/LDL-cholesterol ratio increased risk 4-fold. Finally, for every unit increase in triglycerides/apoA1 ratio, the risk increased 85%. HOMA-IR independently predicted T2DM 10-year incidence only for carriers of GG polymorphism (all, p < 0.05), but not in carriers of the GA polymorphism (all, p > 0.05).

CONCLUSION

ApoA1 was associated with decreased T2DM risk and TG/ApoA1 and apoB/LDL were associated with increased risk of T2DM, only in males. ApoA1 polymorphism, which is associated with lower HDL cholesterol, influenced the predictive effects of HOMA-IR on T2DM incidence, which appeared to be moderated by physical activity, suggesting potential scope for more targeted preventative strategies.

ApoE genotype: from geographic distribution to function and responsiveness to dietary factors

ApoE is a key protein in lipid metabolism with three major isoforms.ApoEallele frequencies show non-random global distribution especially in Europe with highapoEε3frequency in the Mediterranean area, whereas theapoEε4genotype is enriched in Northern Europe. TheapoEε4genotype is one of the most important genetic risk factors for age-dependent chronic diseases, including CVD and Alzheimer's disease (AD). The apoE polymorphism has been shown to impact on blood lipids, biomarkers of oxidative stress and chronic inflammation, which all may contribute to the isoform-dependent disease risk. Studies in mice and human subjects indicate that theapoEε3but not theapoEε4genotype may significantly benefit from dietary flavonoids (e.g. quercetin) andn-3 fatty acids. Metabolism of lipid soluble vitamins E and D is likewise differentially affected by theapoEgenotype. Epidemiological and experimental evidence suggest a better vitamin D status inapoEε4than ε3subjects indicating a certain advantage of ε4over ε3. The present review aims at evaluation of current data available on interactions between apoE polymorphism and dietary responsiveness to flavonoids, fat soluble vitamins andn-3 fatty acids. Likewise, distinct geographic distribution and chronic disease risk of the different apoE isoforms are addressed.

Interactions between alcohol intake and the polymorphism of rs708272 on serum high-density lipoprotein cholesterol levels in the Guangxi Hei Yi Zhuang population

Both alcohol consumption and the polymorphism of the cholesteryl ester transfer protein (CETP) TaqIB gene (rs708272) influence plasma high-density lipoprotein cholesterol (HDL-C) levels. However, their interactions on serum HDL-C levels is not well known. The present study was undertaken to detect the interactions between alcohol consumption and the rs708272 polymorphism on serum lipid levels in the Guangxi Hei Yi Zhuang population. Genotyping of the rs708272 in 342 nondrinkers and 416 drinkers aged 15-70 years was performed by polymerase chain reaction and restriction fragment length polymorphism. Interactions between rs708272 genotype and alcohol consumption was assessed using a cross-product term between genotypes and the aforementioned factor. Statistical significance was evaluated with analysis of co-variance. The frequency of B1 allele was 65.8% in nondrinkers and 64.7% in drinkers (P>.05), respectively. The frequencies of B1B1, B1B2, and B2B2 genotypes were 45.0%, 41.5%, and 13.5% in nondrinkers, and 41.3%, 46.6%, and 12.0% in drinkers (P>.05), respectively. The levels of HDL-C and apolipoprotein (Apo) AI in nondrinkers were higher in B2B2 genotype than in B1B1 genotype (P<.05 for each), whereas triglyceride (TG) levels in drinkers were higher in B1B1 genotype than in B1B2 genotype (P<.05). The levels of TG, HDL-C, Apo AI in B1B1 genotype, and HDL-C and Apo AI in B1B2 genotype were higher in drinkers than in nondrinkers (P<.05-.01), whereas the levels of low-density lipoprotein cholesterol (LDL-C) and Apo B in B2B2 genotype, and the levels of LDL-C in B1B1 genotype were lower in drinkers than in nondrinkers (P<.05-.01). The levels of HDL-C were positively correlated with female sex and genotype in nondrinkers (P<.001 for each), and were positively associated with age and alcohol consumption in drinkers (P<.005 and<.01, respectively). This study suggests that the B1 carriers benefited more from alcohol consumption than the B2 carriers in increasing serum HDL-C and Apo AI levels, and lowering LDL-C levels.

Increasing apoA-I production as a target for CHD risk reduction

Dyslipidemia leading to coronary heart diseases (CHD) enables venues to prevent or treat CHD by other strategies than only lowering serum LDL cholesterol (LDL-C) concentrations, which is currently the most frequently targeted change. Unlike LDL-C, elevated high-density lipoprotein cholesterol (HDL-C) concentrations may protect against the development of CHD as demonstrated in numerous large-scale epidemiological studies. In this review we describe that besides elevating serum HDL-C concentrations by increasing alpha-HDL particles, approaches to elevate HDL-C concentrations by increasing pre-beta HDL particle concentrations seems more attractive. Besides infusion of apoA-I(Milano), using apoA-I mimetics, or delipidation of alpha-HDL particles, elevating de novo apoA-I production may be a suitable target to functionally increase pre-beta HDL particle concentrations. Therefore, a detailed description of the molecular pathways underlying apoA-I synthesis and secretion, completed with an overview of known effects of pharmacological and nutritional compounds on apoA-I synthesis will be presented. This knowledge may ultimately be applied in developing dietary intervention strategies to elevate apoA-I production and serum HDL-C concentrations and consequently lower CHD risk.

ApoE genotype, cardiovascular risk and responsiveness to dietary fat manipulation

Cardiovascular risk is determined by the complex interactions between genetic and environmental factors. The apoE genotype represents the most-widely-studied single nucleotide polymorphism in relation to CVD risk, with >3600 publications cited in PubMed. Although originally described as a mediator of lipoprotein metabolism, the lipoprotein-independent functions of apoE are being increasingly recognised, with limited data available on the potential impact of genotype on these metabolic processes. Furthermore, although meta-analyses suggest that apoE4 carriers may have a 40-50% increased CVD risk, the associations reported in individual studies are highly heterogeneous and it is recognised that environmental factors such as smoking status and dietary fat composition influence genotype-phenotype associations. However, information is often derived from observational studies or small intervention trials in which retrospective genotyping of the cohort results in small group sizes in the rarer E2 and E4 subgroups. Either larger well-standardised intervention trials or smaller trials with prospective recruitment according to apoE genotype are needed to fully establish the impact of diet on genotype-CVD associations and to establish the potential of dietary strategies such as reduced total fat, saturated fat, or increased antioxidant intakes to counteract the increased CVD burden in apoE4 carriers.

Genetic factors affecting HDL levels, structure, metabolism and function

PURPOSE OF REVIEW

HDL is a recognized negative risk factor for the cardiovascular diseases. Establishing the genetic determinants of HDL concentration and functions would add to the prediction of cardiovascular risk and point to the biochemical mechanisms underlying this risk. The present review focuses on various approaches to establish genetic determinants of the HDL concentration, structure and function.

RECENT FINDINGS

While many genes contribute to the HDL concentration and collectively account for half of the variability, polymorphism of individual candidate genes contributes little. There are strong interactions between environmental and genetic influences. Recent findings have confirmed that APOA1 and ABCA1 exert the strongest influence on HDL concentrations and risk of atherosclerosis. CETP and lipases also affect the HDL concentration and functionality, but their connection to the atherosclerosis risk is conditional on the interaction between environmental and genetic factors.

SUMMARY

Analysis of genetic determinants of HDL-cholesterol in patients with specific disease states or in response to the environmental condition may be a more accurate way to assess variations in HDL concentration. This may result in defining the rules of interaction between genetic and environmental factors and lead to understanding the mechanisms responsible for the variations in HDL concentration and functionality.

Different Genes and Polymorphisms Affecting High-Density Lipoprotein Cholesterol Levels in Greek Familial Hypercholesterolemia Patients

Familial Hypercholesterolemia (FH) is a genetic disorder characterized by high low-density lipoprotein cholesterol (LDL-C) concentrations that frequently gives rise to premature coronary artery disease. The clinical expression of FH is highly variable, even in patients carrying the same LDL receptor gene mutation. This variability may be due to environmental and other genetic factors. We investigated the effect of APOCIII T1100C, FV Gln506Arg, ADRB2 Glu27Gln, SELE Ser128Arg, SELE Leu554Phe, and ENaCa Ala663Thr polymorphisms on the HDL-C variations in 84 patients with FH. For ApoCIII T1100C, subjects with the TT genotype presented higher HDL-C levels than the other genotype groups (p = 0.046). Similarly the presence of the Gln allele in ADRB2 27 Glu/Gln heterozygotes and ADRB2 27 Gln/Gln homozygotes was associated with higher HDL-C levels (p = 0.014). Among the other polymorphisms tested, none of them were associated with variations in HDL-C levels. The influence of each polymorphism on lipid concentrations was evaluated with linear regression analyses after adjustment for age and sex. Among the variables studied including total cholesterol, LDL-C, high-density lipoprotein (HDL)-C, triglycerides, apolipoprotein A (Apo-A) and B (Apo-B), and lipoprotein alpha (LP alpha), HDL-C concentration was significantly different in models applied for polymorphisms ApoCIII T1100C, FV Gln506Arg, and ADRB2 Glu27Gln (p = 0.01, p = 0.018, p = 0.04, respectively). These results suggest that HDL-C levels in FH heterozygotes may be affected by several different genetic variants.

The effect of the APOE polymorphism on HDL-C concentrations depends on the cholesterol ester transfer protein gene variation in a Southern European population

BACKGROUND

Apolipoprotein E (ApoE) locus has consistently shown a significant association with low-density lipoprotein cholesterol (LDL-C). However, its impact on high-density lipoprotein cholesterol (HDL-C) has been highly controversial suggesting that it may be context-dependent. We examined the gene-gene interaction between the common ApoE and the CETP polymorphisms in determining HDL-C concentrations in men and women from the general population.

METHODS

550 unrelated Caucasian subjects were randomly selected from a Mediterranean Region in Spain. Plasma lipids, anthropometric, clinical and lifestyle variables were measured. Common ApoE and CETP-TaqIB polymorphisms were determined.

RESULTS

We have found a gene-gene interaction between and ApoE and the CETP loci in determining HDL-C concentrations. Thus, after adjustment for gender, age, body mass index, tobacco smoking, alcohol consumption, physical exercise and medication, carriers of the E4 allele had lower HDL-C concentrations [mean and (standard error): 40.1 (2.6) mg/dL] than E2 subjects [47.7 (3.2) mg/dL; p=0.019], and even lower than those of the E3 subjects [44.7 (1.4) mg/dL; p=0.042], only if they had the B1B1 genotype. However, mean HDL-C concentrations were higher among those with E4 allele carrying the B2 allele at the CETP gene locus [50.5 (2.3) mg/dL], and lower among E2 subjects carrying the B2 allele [45.5 (2.6) mg/dL]. This interaction was observed in both men and women. This gene-gene interaction remained statistically significant even after additional adjustment for triglycerides.

CONCLUSIONS

The effect of the ApoE polymorphism on HDL-C concentrations depends on the CETP polymorphism, explaining some of the controversial results previously reported for this polymorphism.