Progress in genetic association studies of plasma lipids

Association of Atherogenic Index of Plasma with Cardiometabolic Risk Factors and Markers in Lean 14-to-20-Year-Old Individuals: A Cross-Sectional Study

Cardiometabolic risk factors at a young age pose a significant risk for developing atherosclerotic cardiovascular disease in adulthood. Atherogenic dyslipidemia is highly associated with obesity and metabolic syndrome already in young age. It remains unclear whether cardiometabolic risk factors associate with the atherogenic index of plasma (AIP = log (TAG/HDL-C) in lean subjects with low atherogenic risk. As both the AIP and markers of cardiometabolic risk are continuous variables, we expected their association to be linear before the manifestation of obesity and atherogenic dyslipidemia. We analyzed the prevalence of increased atherogenic risk (AIP ≥ 0.11) in 2012 lean 14-to-20-year-old subjects (55% females) and the trends of cardiometabolic risk factors across the quartiles (Q) of AIP in a subgroup of 1947 (56% females) subjects with low atherogenic risk (AIP < 0.11). The prevalence of AIP ≥ 0.11 reached 3.6% in females and 8.5% in males. HDL-C, non-HDL-C, triglycerides, and the continuous metabolic syndrome score showed a stepwise worsening across the AIP quartiles in both sexes. Measures of obesity and insulin resistance were worse in Q4 vs. Q1 groups, and leukocyte counts were higher in Q4 and Q3 vs. Q1. Females in Q4 presented with a higher C-reactive protein and lower adiponectin, estradiol, and testosterone levels. The multivariate regression model selected non-HDL-C, QUICKI, and erythrocyte counts as significant predictors of AIP in males; and non-HDL-C and C-reactive protein in females. A question arises whether the lean individuals on the upper edge of low atherogenic risk are prone to earlier manifestation of metabolic syndrome and shift to the higher AIP risk group.

Determination of genetic scores to estimate disturbances in circulating lipid profile biomarkers of adolescents: A preliminary report

OBJECTIVE

The aim of this study was to develop genetic scores based on single-nucleotide polymorphisms (SNPs) related to lipid metabolism and evaluate whether they used to estimate disturbances in the circulating lipid profile biomarkers of adolescents.

METHODS

In a preliminary cross-sectional approach, 113 Brazilian adolescents (10-19 y of age) with cardiovascular disease risk factors were evaluated. Genetic scores from 20 SNPs related to lipid metabolism were calculated by codifying each of them as the rescaled sum of risk allele frequencies. All scores were distributed in classes between 0 (absence of risk alleles) and 10 (presence of all risk alleles) to evaluate the additive effect of risk alleles on the lipid profile outcomes in the same interval. Multiple linear regression analyses were performed to evaluate the association between each score and blood lipid profile biomarkers.

RESULTS

Significant associations between genetic scores and unfavorable outcomes in all evaluated lipid profile biomarkers were found. The mean ± SD of the genetic scores for the circulating lipid profile biomarkers in the 0 to 10 scale were 4.4 ± 2 for triacylglycerol, 5.3 ± 1.5 for total cholesterol, 5.6 ± 1.2 for high-density lipoprotein cholesterol, 4.9 ± 1.6 for low-density lipoprotein cholesterol, and 3.6 ± 1.9 for minimally modified low-density lipoprotein cholesterol. For each point obtained in each genetic score, a mean increase ± SE of 15.8 ± 4.2 mg/dL in triacylglycerol (P = 0.0001), 5.3 ± 1.7 mg/dL in total cholesterol (P = 0.0032), 4.8 ± 1.3 mg/dL in low-density lipoprotein cholesterol (P = 0.0003), and 1.1 ± 0.3 U/L in minimally modified low-density lipoprotein cholesterol (P = 0.0020) and a mean decrease of 3.7 ± 0.7 mg/dL in high-density lipoprotein cholesterol (P < 0.0001) concentrations were obtained.

CONCLUSION

The calculated genetic scores could be used to estimate disturbances in circulating lipid profile biomarkers of adolescents and be applied in clinical practice to better target interventions to reduce cardiovascular disease risk throughout life.

Genetic susceptibility, dietary cholesterol intake, and plasma cholesterol levels in a Chinese population

Accompanied with nutrition transition, non-HDL-C levels of individuals in Asian countries has increased rapidly, which has caused the global epicenter of nonoptimal cholesterol to shift from Western countries to Asian countries. Thus, it is critical to underline major genetic and dietary determinants. In the current study of 2,330 Chinese individuals, genetic risk scores (GRSs) were calculated for total cholesterol (TC; GRS_TC, 57 SNPs), LDL-C (GRS_LDL-C, 45 SNPs), and HDL-C (GRS_HDL-C, 65 SNPs) based on SNPs from the Global Lipid Genetics Consortium study. Cholesterol intake was estimated by a 74-item food-frequency questionnaire. Associations of dietary cholesterol intake with plasma TC and LDL-C strengthened across quartiles of the GRS_TC (effect sizes: -0.29, 0.34, 2.45, and 6.47; P _interaction = 0.002) and GRS_LDL-C (effect sizes: -1.35, 0.17, 5.45, and 6.07; P _interaction = 0.001), respectively. Similar interactions with non-HDL-C were observed between dietary cholesterol and GRS_TC (P _interaction = 0.001) and GRS_LDL-C (P _interaction = 0.004). The adverse effects of GRS_TC on TC (effect sizes across dietary cholesterol quartiles: 0.51, 0.82, 1.21, and 1.31; P _interaction = 0.023) and GRS_LDL-C on LDL-C (effect sizes across dietary cholesterol quartiles: 0.66, 0.52, 1.12, and 1.56; P _interaction = 0.020) were more profound in those having higher cholesterol intake compared with those with lower intake. Our findings suggest significant interactions between genetic susceptibility and dietary cholesterol intake on plasma cholesterol profiles in a Chinese population.

Prediction of Blood Lipid Phenotypes Using Obesity-Related Genetic Polymorphisms and Lifestyle Data in Subjects with Excessive Body Weight

BACKGROUND AND AIM

Individual lipid phenotypes including circulating total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), and triglycerides (TG) determinations are influenced by gene-environment interactions. The aim of this study was to predict blood lipid level (TC, LDL-c, HDL-c, and TG) variability using genetic and lifestyle data in subjects with excessive body weight-for-height.

METHODS

This cross-sectional study enrolled 304 unrelated overweight/obese adults of self-reported European ancestry. A total of 95 single nucleotide polymorphisms (SNPs) related to obesity and weight loss were analyzed by a targeted next-generation sequencing system. Relevant genotypes of each SNP were coded as 0 (nonrisk) and 1 (risk). Four genetic risk scores (GRS) for each lipid phenotype were calculated by adding the risk genotypes. Information concerning lifestyle (diet, physical activity, alcohol drinking, and smoking) was obtained using validated questionnaires. Total body fat (TFAT) and visceral fat (VFAT) were determined by dual-energy X-ray absorptiometry.

RESULTS

Overall, 45 obesity-related genetic variants were associated with some of the studied blood lipids. In addition to conventional factors (age, sex, dietary intakes, and alcohol consumption), the calculated GRS significantly contributed to explain their corresponding plasma lipid trait. Thus, HDL-c, TG, TC, and LDL-c serum concentrations were predicted by approximately 28% (optimism-corrected adj. R 2 = 0.28), 25% (optimism-corrected adj. R 2 = 0.25), 24% (optimism-corrected adj. R 2 = 0.24), and 21% (optimism-corrected adj. R 2=0.21), respectively. Interestingly, GRS were the greatest contributors to TC (squared partial correlation (PC2) = 0.18) and LDL-c (PC2 = 0.18) features. Likewise, VFAT and GRS had a higher impact on HDL-c (PC2 = 0.09 and PC2 = 0.06, respectively) and TG levels (PC2 = 0.20 and PC2 = 0.07, respectively) than the rest of variables.

CONCLUSIONS

Besides known lifestyle influences, some obesity-related genetic variants could help to predict blood lipid phenotypes.

Genetic factors exist behind the high prevalence of reduced high-density lipoprotein cholesterol levels in the Roma population

BACKGROUND AND AIMS

Previous findings showed that reduced plasma high-density lipoprotein cholesterol (HDL-C) levels are more frequent in all age groups of the Hungarian Roma compared to the general population. It suggests that genetic factors may exist behind this phenomenon. Our present study was designed to test this hypothesis, i.e., to define whether genetic factors contribute to the higher prevalence of reduced HDL-C among Roma. Single nucleotide polymorphisms (N = 21) contributing to the variation in plasma HDL-C concentrations were analysed in the Hungarian Roma (N = 646) and general (N = 1542) populations.

METHODS

Genetic risk scores, unweighted (GRS) and weighted (wGRS), were computed and compared. Associations between the GRSs and the prevalence of reduced HDL-C levels were analysed.

RESULTS

The GRS and wGRS were significantly higher in the Roma compared to the general population (GRS: 22.2 ± 3.2 vs. 21.5 ± 3.3; wGRS: 0.57 ± 0.1 vs. 0.53 ± 0.1; p<0.001). One half per cent of Roma subjects were in the bottom fifth of the wGRS (wGRS≤ 0.3) compared with 1.8% of those in the general population (p=0.025), while 5% of the Roma subjects were in the top fifth of the wGRS (wGRS≥ 0.75) compared with 2.6% of those in the general population (p=0.004). The GRS showed similar correlation with reduced plasma HDL-C levels in the two populations, whilst the wGRS showed stronger correlation with the trait among Roma after controlling for confounders.

CONCLUSIONS

These results strongly suggest that genetic factors contribute to the higher prevalence of reduced HDL-C levels among Roma, so interventions aiming to improve Roma health status need to consider their increased genetic susceptibility.

Recruitment to doping and help-seeking behavior of eight female AAS users

BACKGROUND

Doping with anabolic androgenic steroids in sports has now developed to a widespread use of these agents among young people outside the sport. This is of major concern to the society. The purpose of the use is mainly for aesthetic reasons and is seen as a male phenomenon. But use also occurs in women where the knowledge is scarce. Our aim was to identify the pattern of doping agents in eight female cases and compare them with similar data from men.

METHODS

Eight female users were recruited through Anti-Doping Hot-Line, a national telephone counseling service on doping issues during the years 1998-2004. The use was confirmed with urine doping analysis at the Doping Laboratory. The characteristic of use, co-use of narcotics/other doping agents, exercise pattern, adverse-side effects, family history and reason to begin was evaluated.

RESULTS

The women used on average 1.9 different anabolic androgenic steroids and clenbuterol preparations. Ephedrine and growth hormone were co-used in five and one of the women, respectively. Three women reported co-use of narcotics (cannabis and cocaine). The average duration of anabolic agent use before contacting health care was 58 weeks (range 7-104). Side effects for anabolic androgenic steroids (n = 5) included voice changes, clitoral enlargement, body hair growth, whereas women using clenbuterol (n = 2) reported tachycardia and depression. All women except one had a man in close relationship encouraging them to begin with the doping agents.

CONCLUSIONS

The use of doping agents in our eight women was different from that in male users. The women used less doping agents and were more prone to contact the health care, at an earlier stage, probably due to the adverse effects. The co-use with ephedrine, growth hormone and cannabis appeared to be in the same range as in men. This is the first study showing that a man in close relationship may motivate a woman to use anabolic agents.

SHBG gene polymorphism (rs1799941) associates with metabolic syndrome in children and adolescents

Background

Metabolic syndrome (MetS) is a complex disorder characterized by coexistence of several cardiometabolic (CM) factors, i.e. hyperlipidemia, obesity, high blood pressure and insulin resistance. The presence of MetS is strongly associated with increased risk of cardiovascular disease (CVD). The syndrome was originally defined as an adult disorder, but MetS has become increasingly recognized in children and adolescents.

Methods

Genetic variants influence biological components common to the CM factors that comprise MetS. We investigated single locus associations between six single nucleotide polymorphisms (SNPs), previously shown to modulate lipid or sex hormone binding globulin (SHBG) levels, with MetS in a Turkish pediatric cohort (37 cases, 323 controls).

Results

Logistic regression analysis revealed a significant association between rs1799941, located in SHBG, and MetS (OR = 3.09, p-value = 0.006). The association with MetS remained after sequential adjustment for each CM factor included in the syndrome definition, indicating that the identified association is not being driven by any single trait. A relationship between rs1799941 and SHBG levels, was also discovered, but it was dependent on MetS status. In control subjects, the A allele of rs1799941 associated with a significant increase in SHBG levels (p = 0.012), while in cases there was no association between rs1799941 and SHBG levels (p = 0.963).

Conclusions

The significant association between rs1799941 and MetS in children is not contingent on any single CM trait. Additionally, the presence of MetS may abrogate effect of rs1799941 polymorphism on SHBG levels in children.

Prevalence of metabolic syndrome among Roma: a comparative health examination survey in Hungary

OBJECTIVES

The objective of our study was to compare the health status of the Roma people with that of the general population in Hungary.

METHODS

A health examination survey to define the prevalence of metabolic syndrome and its components was performed in a representative random sample (n = 646) of the Roma population aged 20-64 years living in segregated colonies, and data were compared with that obtained in a representative random sample (n = 1819) of the Hungarian population.

RESULTS

The risks for central obesity, hypertension and raised triglyceride level among Roma adults were not different from the Hungarian references, while raised fasting plasma glucose or known type 2 diabetes mellitus (OR = 2.65, 95%CI 1.90-3.69), reduced HDL cholesterol level or treated lipid disorder (OR = 2.15, 95%CI 1.65-2.79) were significantly more frequent in all age groups in the Roma sample. The prevalence of metabolic syndrome (OR = 1.37, 95%CI 1.03-1.83) was also significantly higher among Roma than in the general Hungarian population.

CONCLUSIONS

Besides tackling the socio-economic determinants of the poor health of Roma people, specific public health interventions considering increased genetic susceptibility to metabolic disturbances are needed to improve their health status.

Serum cholesterol and variant in cholesterol-related gene CETP predict white matter microstructure

Several common genetic variants influence cholesterol levels, which play a key role in overall health. Myelin synthesis and maintenance are highly sensitive to cholesterol concentrations, and abnormal cholesterol levels increase the risk for various brain diseases, including Alzheimer's disease. We report significant associations between higher serum cholesterol (CHOL) and high-density lipoprotein levels and higher fractional anisotropy in 403 young adults (23.8 ± 2.4 years) scanned with diffusion imaging and anatomic magnetic resonance imaging at 4 Tesla. By fitting a multi-locus genetic model within white matter areas associated with CHOL, we found that a set of 18 cholesterol-related, single-nucleotide polymorphisms implicated in Alzheimer's disease risk predicted fractional anisotropy. We focused on the single-nucleotide polymorphism with the largest individual effects, CETP (rs5882), and found that increased G-allele dosage was associated with higher fractional anisotropy and lower radial and mean diffusivities in voxel-wise analyses of the whole brain. A follow-up analysis detected white matter associations with rs5882 in the opposite direction in 78 older individuals (74.3 ± 7.3 years). Cholesterol levels may influence white matter integrity, and cholesterol-related genes may exert age-dependent effects on the brain.