Association between CETP, MLXIPL, and TOMM40 polymorphisms and serum lipid levels in a Latvian population

Exogenous exposures shape genetic predisposition to lipids, Alzheimer's, and coronary heart disease in the MLXIPL gene locus

Associations of single nucleotide polymorphisms (SNPs) of the MLXIPL lipid gene with Alzheimer's (AD) and coronary heart disease (CHD) and potentially causal mediation effects of their risk factors, high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG), were examined in two samples of European ancestry from the US (22,712 individuals 587/2,608 AD/CHD cases) and the UK Biobank (UKB) (232,341 individuals; 809/15,269 AD/CHD cases). Our results suggest that these associations can be regulated by several biological mechanisms and shaped by exogenous exposures. Two patterns of associations (represented by rs17145750 and rs6967028) were identified. Minor alleles of rs17145750 and rs6967028 demonstrated primary (secondary) association with high TG (lower HDL-C) and high HDL-C (lower TG) levels, respectively. The primary association explained ~50% of the secondary one suggesting partly independent mechanisms of TG and HDL-C regulation. The magnitude of the association of rs17145750 with HDL-C was significantly higher in the US vs. UKB sample and likely related to differences in exogenous exposures in the two countries. rs17145750 demonstrated a significant detrimental indirect effect through TG on AD risk in the UKB only (βIE = 0.015, pIE = 1.9 × 10-3), which suggests protective effects of high TG levels against AD, likely shaped by exogenous exposures. Also, rs17145750 demonstrated significant protective indirect effects through TG and HDL-C in the associations with CHD in both samples. In contrast, rs6967028 demonstrated an adverse mediation effect through HDL-C on CHD risk in the US sample only (βIE = 0.019, pIE = 8.6 × 10-4). This trade-off suggests different roles of triglyceride mediated mechanisms in the pathogenesis of AD and CHD.

Maternal vitamin B12 deficiency in rats alters DNA methylation in metabolically important genes in their offspring

Vitamin B₁₂ deficiency is a critical problem worldwide and peri-conceptional deficiency of this vitamin is associated with the risk of complex cardio-metabolic diseases. Nutritional perturbations during these stages of development may lead to changes in the fetal epigenome. Using Wistar rat model system, we have earlier shown that low maternal B₁₂ levels are associated with low birth weight, adiposity, insulin resistance, and increased triglyceride levels in the offspring, which might predispose them to the risk of cardio-metabolic diseases in adulthood. In this study, we have investigated the effects of maternal B₁₂ deficiency on genome-wide DNA methylation profile of the offspring and the effect of rehabilitation of mothers with B₁₂ at conception. We have performed methylated DNA immunoprecipitation sequencing of liver from pups in four groups of Wistar rats: Control (C), B₁₂-restricted (B₁₂R), B₁₂-rehabilitated at conception (B₁₂RC), and B₁₂-rehabilitated at parturition (B₁₂RP). We have analyzed differentially methylated signatures between the three groups as compared to controls. We have identified a total of 214 hypermethylated and 142 hypomethylated regions in the 10 kb upstream region of transcription start site in pups of B₁₂-deficient mothers, which are enriched in genes involved in fatty acid metabolism and mitochondrial transport/metabolism. B₁₂ rehabilitation at conception and parturition is responsible for reversal of methylation status of many of these regions to control levels suggesting a causal association with metabolic phenotypes. Thus, maternal B₁₂ restriction alters DNA methylation of genes involved in important metabolic processes and influences the offspring phenotype, which is reversed by B₁₂ rehabilitation of mothers at conception.

Glucose-Sensing Transcription Factor MondoA/ChREBP as Targets for Type 2 Diabetes: Opportunities and Challenges

The worldwide increase in type 2 diabetes (T2D) is becoming a major health concern, thus searching for novel preventive and therapeutic strategies has become urgent. In last decade, the paralogous transcription factors MondoA and carbohydrate response element-binding protein (ChREBP) have been revealed to be central mediators of glucose sensing in multiple metabolic organs. Under normal nutrient conditions, MondoA/ChREBP plays vital roles in maintaining glucose homeostasis. However, under chronic nutrient overload, the dysregulation of MondoA/ChREBP contributes to metabolic disorders, such as insulin resistance (IR) and T2D. In this review, we aim to provide an overview of recent advances in the understanding of MondoA/ChREBP and its roles in T2D development. Specifically, we will briefly summarize the functional similarities and differences between MondoA and ChREBP. Then, we will update the roles of MondoA/ChREBP in four T2D-associated metabolic organs (i.e., the skeletal muscle, liver, adipose tissue, and pancreas) in physiological and pathological conditions. Finally, we will discuss the opportunities and challenges of MondoA/ChREBP as drug targets for anti-diabetes. By doing so, we highlight the potential use of therapies targeting MondoA/ChREBP to counteract T2D and its complications.

Genetic variants influencing lipid levels and risk of dyslipidemia in Chinese population

Recently, several human genetic and genomewide association studies (GWAS) have discovered many genetic loci that are associated with the concentration of the blood lipids. To confirm the reported loci in Chinese population, we conducted a crosssection study to analyse the association of 25 reported SNPs, genotyped by the ABI SNaPshot method, with the blood levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) in 1900 individuals by multivariate analysis. Logistic regression was applied to assess the association of the genetic loci with the risk of different types of dyslipidemia. Our study has convincingly identified that 12 of 25 studied SNPs were strongly associated with one or more blood lipid parameters (TC, LDL, HDL and TG). Among the 12 associated SNPs, 10 significantly influence the risk of one or more types of dyslipidemia.We firstly found four SNPs (rs12654264 in HMGCR; rs2479409 in PCSK9; rs16996148 in CILP2, PBX4; rs4420638 in APOE-C1-C4-C2) robustly and independently associate with four types of dyslipidemia (MHL, mixed hyperlipidemia; IHTC, isolated hypercholesterolemia; ILH, isolated low HDL-C; IHTG, isolated hypertriglyceridemia). Our results suggest that genetic susceptibility is different on the same candidate locus for the different populations. Meanwhile, most of the reported genetic variants strongly influence one or more plasma lipid levels and the risk of dyslipidemia in Chinese population.

Sweet Sixteenth for ChREBP: Established Roles and Future Goals

With the identification of ChREBP in 2001, our interest in understanding the molecular control of carbohydrate sensing has surged. While ChREBP was initially studied as a master regulator of lipogenesis in liver and fat tissue, it is now clear that ChREBP functions as a central metabolic coordinator in a variety of cell types in response to environmental and hormonal signals, with wide implications in health and disease. Celebrating its sweet sixteenth birthday, we review here the current knowledge about the function and regulation of ChREBP throughout usual and less explored tissues, to recapitulate ChREBP's role as a whole-body glucose sensor.

MondoA/ChREBP: The usual suspects of transcriptional glucose sensing; Implication in pathophysiology

Identification of the Mondo glucose-responsive transcription factors family, including the MondoA and MondoB/ChREBP paralogs, has shed light on the mechanism whereby glucose affects gene transcription. They have clearly emerged, in recent years, as key mediators of glucose sensing by multiple cell types. MondoA and ChREBP have overlapping yet distinct expression profiles, which underlie their downstream targets and separate roles in regulating genes involved in glucose metabolism. MondoA can restrict glucose uptake and influences energy utilization in skeletal muscle, while ChREBP signals energy storage through de novo lipogenesis in liver and white adipose tissue. Because Mondo proteins mediate metabolic adaptations to changing glucose levels, a better understanding of cellular glucose sensing through Mondo proteins will likely uncover new therapeutic opportunities in the context of the imbalanced glucose homeostasis that accompanies metabolic diseases such as type 2 diabetes and cancer. Here, we provide an overview of structural homologies, transcriptional partners as well as the nutrient and hormonal mechanisms underlying Mondo proteins regulation. We next summarize their relative contribution to energy metabolism changes in physiological states and the evolutionary conservation of these pathways. Finally, we discuss their possible targeting in human pathologies.

Genetic and Environmental Biomarkers Associated with Triglyceride Levels in Two Groups of Slovak Women

OBJECTIVE

This study analyzed the association between the MLXIPL gene polymorphism (rs3812316) and triglyceride (TG) levels and selected environmental biomarkers in Slovak women at risk for cardiovascular disease compared to a reference sample.

MATERIALS AND METHODS

The studied sample consisted of 200 women at cardiovascular risk (mean age 52.96 ± 6.01 years) and 244 healthy women (mean age 47.52 ± 5.34 years). Participants gave details of their health and lifestyle during their medical examination, and peripheral blood samples were used for biochemical analyses and DNA genotyping. A nested polymerase chain reaction-restriction fragment length polymorphism assay was used to detect the rs 3812316 SNP.

RESULTS

We determined that there were significantly different genotype distributions in two TG categories: (1) subjects with normal TG values had a significantly higher G allele frequency than those with elevated TG levels (χ² = 6.1556, df = 2, p = 0.046); and (2) the rare G allele frequency was 0.11 in the cardiovascular risk group and 0.15 in the reference group. Binary regression analysis showed that women with at least one G allele had a significantly lower relative risk of hypertriglyceridemia than women with the CC genotype (OR = 0.399, p = 0.022, 95% CI = 0.182-0.876).

CONCLUSION

This cross-sectional study suggests that MLXIPL rs3812316 genotypes may be associated with TG levels. However, further analysis is advisable because of study limitations.

A common variant association study reveals novel susceptibility loci for low HDL-cholesterol levels in ethnic Arabs

The genetic susceptibility to acquiring low high density lipoprotein-cholesterol (LHDLC) levels is not completely elucidated yet. In this study, we performed a common variant association study for harboring this trait in ethnic Arabs. We employed the Affymetrix high-density Axiom Genome-Wide ASI Array (Asian population) providing a coverage of 598,000 single nucleotide variations (SNPs) to genotype 5495 individuals in a two-phase study involving discovery and validation sets of experiments. The rs1800775 [1.31 (1.22-1.42); p = 3.41E-12] in the CETP gene and rs359027 [1.26 (1.16-1.36); p = 2.55E-08] in the LMCD1 gene were significantly associated with LHDLC levels. Furthermore, rs3104435 [1.26 (1.15-1.38); p = 1.19E-06] at the MATN1 locus, rs9835344 [1.16 (1.08-1.26); p = 8.75E-06] in the CNTN6 gene, rs1559997 [1.3 (1.14-1.47); p = 9.48E-06] in the SDS gene and rs1670273 [1.2 (1.1-1.31); p = 4.81E-06] in the DMN/SYNM gene exhibited suggestive association with the disorder. Seven other variants including rs1147169 in the PLCL1 gene, rs10248618 in the DNAH11, rs476155 in the GLIS3, rs7024300 in the ABCA1, intergenic rs10836699, rs11603691 in P2RX3 and rs750134 in CORO1C gene exhibited borderline protective properties. Validation and joint meta-analysis resulted in rs1800775, rs3104435 and rs359027 retaining their predisposing properties, while rs10836699 and rs11603691 showed protective properties. Our data show several predisposing variants across the genome for LHDLC levels in ethnic Arabs.

Next-generation-sequencing-based identification of familial hypercholesterolemia-related mutations in subjects with increased LDL-C levels in a latvian population

BACKGROUND

Familial hypercholesterolemia (FH) is one of the commonest monogenic disorders, predominantly inherited as an autosomal dominant trait. When untreated, it results in early coronary heart disease. The vast majority of FH remains undiagnosed in Latvia. The identification and early treatment of affected individuals remain a challenge worldwide. Most cases of FH are caused by mutations in one of four genes, APOB, LDLR, PCSK9, or LDLRAP1. The spectrum of disease-causing variants is very diverse and the variation detection panels usually used in its diagnosis cover only a minority of the disease-causing gene variants. However, DNA-based tests may provide an FH diagnosis for FH patients with no physical symptoms and with no known family history of the disease. Here, we evaluate the use of targeted next-generation sequencing (NGS) to identify cases of FH in a cohort of patients with coronary artery disease (CAD) and individuals with abnormal low-density lipoprotein-cholesterol (LDL-C) levels.

METHODS

We used targeted amplification of the coding regions of LDLR, APOB, PCSK9, and LDLRAP1, followed by NGS, in 42 CAD patients (LDL-C, 4.1-7.2 mmol/L) and 50 individuals from a population-based cohort (LDL-C, 5.1-9.7 mmol/L).

RESULTS

In total, 22 synonymous and 31 nonsynonymous variants, eight variants in close proximity (10 bp) to intron-exon boundaries, and 50 other variants were found. We identified four pathogenic mutations (p.(Arg3527Gln) in APOB, and p.(Gly20Arg), p.(Arg350*), and c.1706-10G > A in LDLR) in seven patients (7.6 %). Three possible pathogenic variants were also found in four patients.

CONCLUSION

NGS-based methods can be used to detect FH in high-risk individuals when they do not meet the defined clinical criteria.