CDKN2B expression in adipose tissue of familial combined hyperlipidemia patients

Effect of 9p21.3 (lncRNA and CDKN2A/2B) variant on lipid profile

Background

Several 9p21.3 variants, such as rs1333049, rs4977574, rs10757274, rs10757278, and rs10811661, identified from recent genome-wide association studies (GWASs) are reported to be associated with coronary artery disease (CAD) susceptibility but independent of dyslipidemia. This study investigated whether these 9p21.3 variants influenced lipid profiles.

Methods and results

By searching the PubMed and Cochrane databases, 101,099 individuals were included in the analysis. The consistent finding for the rs1333049 C allele on lipid profiles increased the triglyceride (TG) levels. Moreover, the rs4977574 G allele and the rs10757274 G allele, respectively, increased low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) levels. However, the rs10811661 C allele largely reduced LDL-C levels. Subgroup analyses indicated that the effects of the rs1333049 C allele, rs4977574 G allele, and rs10757274 G allele on lipid profiles were stronger in Whites compared with Asians. In contrast, the effect of the rs10811661 C allele on lipid profiles was stronger in Asians compared with Whites.

Conclusion

The rs1333049 C allele, rs4977574 G allele, and rs10757274 G allele of lncRNA, and the rs10811661 G allele of CDKN2A/2B had a significant influence on lipid levels, which may help the understanding of the underlying mechanisms between 9p21.3 variants and CAD.

Visceral adipose tissue phenotype and hypoadiponectinemia are associated with aortic Fluorine-18 fluorodeoxyglucose uptake in patients with familial dyslipidemias

BACKGROUND

The role of adipose tissue (AT) in arterial inflammation in familial dyslipidaemias is poorly studied. We investigated the relationship between AT and arterial inflammation in patients with heterozygous familial hypercholesterolemia (heFH) and familial combined hyperlipidemia (FCH).

METHODS AND RESULTS

A total of 40 patients (20 heFH/20 FCH) and a subgroup of 20 of non-heFH/FCH patients were enrolled. Participants underwent blood sampling for serum adipokine measurements and Fluorine-18 fluorodeoxyglucose (18F-FDG) PET/CT imaging. Abdominal visceral (VAT) and subcutaneous (SAT) AT volumes and AT and abdominal aorta 18F-FDG uptake were quantified. FCH patients had increased VAT (pANOVA = 0.004) and SAT volumes (pANOVA = 0.003), lower VAT metabolic activity (pANOVA = 0.0047), and lower adiponectin levels (pANOVA = 0.007) compared to heFH or the control group. Log(Serum adiponectin) levels were correlated with aortic TBR (b = - 0.118, P = 0.038). In mediation analysis, VAT volume was the major determinant of circulating adiponectin, an effect partly mediated via VAT TBR. Clustering of the population of heFH/FCH by VAT volume/TBR and serum adiponectin identified two distinct patient clusters with significant differences in aortic TBR levels (2.11 ± 0.06 vs 1.89 ± 0.05, P= 0.012).

CONCLUSIONS

VAT phenotype (increased VAT volume and/or high VAT TBR) and hypoadiponectinemia may account for the observed differences in arterial inflammation levels between heFH and FCH patients.

Analysis of the interaction effect of 48 SNPs and obesity on type 2 diabetes in Chinese Hans

INTRODUCTION

Both environmental and genetic factors contribute to type 2 diabetes (T2D) risk. Dozens of T2D susceptibility loci have been identified by genome-wide association study. However, these loci account for only a small fraction of the familial T2D risk. We hypothesized that the gene-obesity interaction may contribute to the missing heritability.

RESEARCH DESIGN AND METHOD

Forty-eight T2D-associated variants were genotyped using the TaqMan OpenArray Genotyping System and iPLEX Sequenom MassARRAY platform in two separate studies. Obesity was defined according to multiple indexes (body mass index (BMI), waist circumference and waist-hip ratio). Multiplicative interactions were tested using general logistic regression to assess the gene-obesity interaction effect on T2D risk among a total of 6206 Chinese Hans.

RESULTS

After adjusting for the main effects of genes and obesity, as well as covariates (age, sex, smoking and alcohol consumption status), robust multiplicative interaction effects were observed between rs10811661 in CDKN2A/CDKN2B and multiple obesity indices (p ranged from 0.001 to 0.043 for BMI, waist circumference and waist-hip ratio). Obese individuals with the TT genotype had a drastically higher risk of T2D than normal weight individuals without the risk allele (OR=17.58, p<0.001). There were no significant differences between subgroups in the stratification analysis. Plausible biological explanations were established using a public database. However, there were no significant interaction effects between the other 47 single nucleotide polymorphism (SNPs) and obesity.

CONCLUSION

Our findings indicated that the CDKN2A/CDKN2B gene-obesity interaction significantly increases T2D risk in Chinese Hans. The interaction effect identified in our study may help to explain some of the missing heritability in the context of T2D susceptibility. In addition, the interaction effect may play a role in the precise prevention of T2D in Chinese individuals.

Polymorphism analysis of miR182 and CDKN2B genes in Greek patients with primary open angle glaucoma

Glaucoma is a progressive optic neuropathy resulting from retinal ganglion cells death; it represents one of the leading causes of irreversible blindness worldwide. Although, primary open angle glaucoma (POAG) is the most common type of the disease, the pathogenesis of POAG and the genetic factors contributing to disease development remain poorly understood. The aim of this study was to investigate whether the polymorphisms rs76481776 in miR182 gene and rs3217992 in cyclin-dependent kinase inhibitor-2B (CDKN2B) gene are risk factors for POAG in a series of patients of Greek origin. A case-control study was conducted including 120 patients with POAG and 113 unaffected healthy controls of Greek origin, surveyed for polymorphisms with potential correlation to POAG. DNA from each individual was tested for the miR182 rs76481776 and CDKN2B rs3217992 polymorphisms. Regarding the miR182 rs76481776 polymorphism, the T allele occurred with significantly higher frequency in POAG patients compared to controls (OR: 2.62, 95% CI: 1.56-4.39; p = 0.0002). The CDKN2B rs3217992 A allele frequency was found significantly increased in POAG patients compared to healthy individuals (OR: 1.72, 95% CI: 1.18-2.49; p = 0.005). Therefore, both rs76481776 polymorphism in miR182 gene and rs3217992 polymorphism in CDKN2B gene seem to be associated with the development of POAG in a Greek population. The carriers of the T allele of rs76481776 in miR182 and the carriers of the A allele of rs3217992 in CDKN2B have an increased risk of developing POAG.

Long non-coding RNA CDKN2B-AS1 contributes to atherosclerotic plaque formation by forming RNA-DNA triplex in the CDKN2B promoter

BACKGROUND

Atherosclerosis involves a slow process of plaque formation on the walls of arteries, and comprises a leading cause of cardiovascular disease. Long non-coding RNAs (lncRNAs) have been implicated in the pathogenesis of atherosclerosis. In this study, we aim to explore the possible involvement of lncRNA 'cyclin-dependent kinase inhibitor 2B antisense noncoding RNA' (CDKN2B-AS1) and CDKN2B in the progression of atherosclerosis.

METHODS

Initially, we quantified the expression of CDKN2B-AS1 in atherosclerotic plaque tissues and, in THP-1 macrophage-derived, and human primary macrophage (HPM)-derived foam cells. Next, we established a mouse model of atherosclerosis using apolipoprotein E knockout (ApoE-/-) mice, where lipid uptake, lipid accumulation, and macrophage reverse cholesterol transport (mRCT) were assessed, in order to explore the contributory role of CDKN2B-AS1 to the progression of atherosclerosis. RIP and ChIP assays were used to identify interactions between CDKN2B-AS1, CCCTC-binding factor (CTCF), enhancer of zeste homologue 2 (EZH2), and CDKN2B. Triplex formation was determined by RNA-DNA pull-down and capture assay as well as EMSA experiment.

FINDINGS

CDKN2B-AS1 showed high expression levels in atherosclerosis, whereas CDKN2B showed low expression levels. CDKN2B-AS1 accelerated lipid uptake and intracellular lipid accumulation whilst attenuating mRCT in THP-1 macrophage-derived foam cells, HPM-derived foam cells, and in the mouse model. EZH2 and CTCF were found to bind to the CDKN2B promoter region. An RNA-DNA triplex formed by CDKN2B-AS1 and CDKN2B promoter was found to recruit EZH2 and CTCF in the CDKN2B promoter region and consequently inhibit CDKN2B transcription by accelerating histone methylation.

INTERPRETATION

The results demonstrated that CDKN2B-AS1 promotes atherosclerotic plaque formation and inhibits mRCT in atherosclerosis by regulating CDKN2B promoter, and thereby could be a potential therapeutic target for atherosclerosis.

Genetic risk scores in lipid disorders

PURPOSE OF REVIEW

Extensive work has gone into understanding the genetics of cardiovascular disease (CVD) and implicating genes involved in hyperlipidaemia. Translation into routine practise involves using genetic risk scores (GRS) to identify high-risk individuals in the general population. Some of these risk scores are beginning to disentangle the complex nature of CVD and inherited dyslipidaemias.

RECENT FINDINGS

GRS of varying complexity have been used to identify high-risk groups of patients with polygenic CVD including some individuals with risk equivalent to monogenic disease. In phenotypic familial hypercholesterolaemia a six or 12 gene lipid GRS may identify polygenic cases that comprise up to 50% of cases. In high triglyceride syndromes including even cases of familial chylomicronaemia syndrome more than 80% of cases are polygenic and not even associated with rare variants. In both familial hypercholesterolaemia and familial chylomicronaemia syndrome individuals with polygenic disease have a lower risk than those with monogenic disease.

SUMMARY

GRS show promise in identifying individuals with high risks of CVD. They have a close relationship with imaging markers. It is unclear whether GRS, imaging or both will be used to identify individuals at high risk of future events.

MiR-323b-5p acts as a novel diagnostic biomarker for critical limb ischemia in type 2 diabetic patients

Type 2 diabetes mellitus (T2DM) is a major contributor to peripheral artery disease (PAD), especially in cases that advance to critical limb ischemia (CLI). Accumulating evidence indicates that miRNAs play an important role in the development of PAD and T2DM. Due to the limited value of current diagnostic methods for CLI in T2DM patients, we compared the miRNA expression profiles of Chinese T2DM patients with or without CLI to find out whether distinctive miRNAs could serve as potential diagnostic biomarkers. We statistically identified 7 miRNAs (hsa-miR-200b-3p, hsa-miR-2115-3p, hsa-miR-431-5p, hsa-miR-486-5p, hsa-miR-210-3p, hsa-miR-1264, hsa-miR-323b-5p) which were up-regulated in the CLI group, whereas other 4 miRNAs (hsa-miR-5579-3p, hsa-miR-665, hsa-miR-4285, hsa-miR-500a-3p) were down-regulated. Our validation test suggested a relatively high diagnostic accuracy of serum hsa-miR-323b-5p levels for the detection of CLI in T2DM patients, with a sensitivity of 62.67% and a specificity of 80.65%. The area under the curve (AUC) for miR-323b-5p + confounding risk factors was 0.94 (95% CI: 0.884-0.994, P < 0.001), which was higher than that for miR-323b-5p. Taken together, our results indicate that circulating hsa-miR-323b-5p could be a promising serum biomarker for the diagnosis of critical limb ischemia in type 2 diabetic patients.

Haplotype-based association of two SNPs in miR-323b with unexplained recurrent spontaneous abortion in a Chinese Han population

Single nucleotide polymorphisms (SNPs) in miRNAs are associated with the risk to development of certain human diseases and affect the regulatory capacity of miRNAs. However, the relationship between miRNAs polymorphisms and recurrent pregnancy loss (RPL) is still largely unknown. Our study found that one SNP rs56103835 T>C in miR-323b coding region was associated with the increase risk of human unexplained RPL (URPL), but no differences were found in another SNP rs75330474 C>T. However, in two-locus haplotype analysis, T-C haplotype was associated with an increased risk of URPL. The level of mature miR-323b was obviously up-regulated in cells transfected with T-C haplotype. T-C haplotype inhibited HTR-8/SVneo cells proliferation and migration and promoted cells apoptosis. Further experiments identified that paired-box 8 (Pax8) was a functionally relevant target of miR-323b, and its expression was reversely regulated by miR-323b. Besides, the expressions of Pax8 in villous chorionic tissues from URPL patients were lower than controls, contrary to the high expression of miR-323. More importantly, dual-luciferase assay indicated T-C haplotype, increasing miR-323b expression, could down-regulated Pax8 expression. Collectively, our data suggest that T-C haplotype in pre-miR-323b may aggravate the risk of developing URPL and influence the level of mature miR-323b and its target gene Pax8.

Interaction between a variant of chromosome 9p21.3 locus and diet antioxidant capacity on metabolic syndrome in Tehrani adults

BACKGROUND

Genome-wide association studies have shown that risk alleles on chromosome 9p21.3 locus, are associated with increasing the risk of cardiovascular diseases (CVDs). Several epidemiological studies have found that metabolic syndrome (MetS) is associated with CVDs. Dietary antioxidants also have shown to have potential favorable effects on MetS prevention. This study examined the interactions between rs1333048 genotypes on 9p21 genetic region and Total antioxidant capacity (TAC) on odds of MetS.

METHODS

263 Tehrani adults were enrolled in this cross-sectional study. The MetS was defined according to the ATPIII. Dietary intake was assessed daily using a FFQ with 147 items. Dietary TAC was assessed according to United States Department of Agriculture database for oxygen radical absorbance capacity (ORAC). Bioelectrical impedance analysis method was used for body analysis and rs1333048 were genotyped by restriction fragment length polymorphism method. Participants were categorized into three groups based on rs1333048 genotypes.

RESULTS

The results demonstrate that, prevalence of C allele was 52.85% and A allele was 47.15%. After adjustment for confunder variable, this study demonstrated an interaction between AA genotype and high Lyophilic oxygen radical absorbance capacity (L-ORAC) and high Hydrophilic oxygen radical absorbance capacity (H-ORAC) intake on low odds of MetS (OR = 0.24, 95% CI = 0.06-0.94, P for interaction = 0.04, OR = 0.26, 95% CI = 0.06-0.99, P for interaction = 0.04). Also, our result indicated, there was no interaction between AA genotype and high total oxygen radical absorbance capacity (T-ORAC) and total phenolic intakes on reduce odds of MetS (OR = 0.07, 95% CI = 0.07-1.10, P for interaction = 0.07, OR = 0.58, 95% CI = 0.16-2.07, P for interaction = 0.40) respectively.

CONCLUSION

The results of the present study indicate that high L-ORAC and high H-ORAC intake may modify the elevated odds of MetS in AA genotype of rs1333048 on the 9p21 genetic locus.

Cdkn2a deficiency promotes adipose tissue browning

Objectives

Genome-wide association studies have reported that DNA polymorphisms at the CDKN2A locus modulate fasting glucose in human and contribute to type 2 diabetes (T2D) risk. Yet the causal relationship between this gene and defective energy homeostasis remains elusive. Here we sought to understand the contribution of Cdkn2a to metabolic homeostasis.

Methods

We first analyzed glucose and energy homeostasis from Cdkn2a-deficient mice subjected to normal or high fat diets. Subsequently Cdkn2a-deficient primary adipose cells and human-induced pluripotent stem differentiated into adipocytes were further characterized for their capacity to promote browning of adipose tissue. Finally CDKN2A levels were studied in adipocytes from lean and obese patients.

Results

We report that Cdkn2a deficiency protects mice against high fat diet-induced obesity, increases energy expenditure and modulates adaptive thermogenesis, in addition to improving insulin sensitivity. Disruption of Cdkn2a associates with increased expression of brown-like/beige fat markers in inguinal adipose tissue and enhances respiration in primary adipose cells. Kinase activity profiling and RNA-sequencing analysis of primary adipose cells further demonstrate that Cdkn2a modulates gene networks involved in energy production and lipid metabolism, through the activation of the Protein Kinase A (PKA), PKG, PPARGC1A and PRDM16 signaling pathways, key regulators of adipocyte beiging. Importantly, CDKN2A expression is increased in adipocytes from obese compared to lean subjects. Moreover silencing CDKN2A expression during human-induced pluripotent stem cells adipogenic differentiation promoted UCP1 expression.

Conclusion

Our results offer novel insight into brown/beige adipocyte functions, which has recently emerged as an attractive therapeutic strategy for obesity and T2D. Modulating Cdkn2a-regulated signaling cascades may be of interest for the treatment of metabolic disorders.

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Cdkn2a deficiency protects mice against high fat diet-induced obesity.

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Cdkn2a modulates brown-like/beige fat gene networks involved in energy production and lipid metabolism.

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Increased CDKN2A expression in human obese adipocytes.

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Increased UCP1 levels in adipocytes differentiated from CDKN2A-silenced hiPS cells.

A Genome-Wide Scan for MicroRNA-Related Genetic Variants Associated With Primary Open-Angle Glaucoma

Purpose

To identify microRNAs (miRNAs) involved in primary open-angle glaucoma (POAG), using genetic data. MiRNAs are small noncoding RNAs that posttranscriptionally regulate gene expression. Genetic variants in miRNAs or miRNA-binding sites within gene 3'-untranslated regions (3'UTRs) are expected to affect miRNA function and contribute to disease risk.

Methods

Data from the recent genome-wide association studies on intraocular pressure, vertical cup-to-disc ratio (VCDR), cupa area and disc area were used to investigate the association of miRNAs with POAG endophenotypes. Putative targets of the associated miRNAs were studied according to their association with POAG and tested in cell line by transfection experiments for regulation by the miRNAs.

Results

Of 411 miRNA variants, rs12803915:A/G in the terminal loop of pre-miR-612 and rs2273626:A/C in the seed sequence of miR-4707 were significantly associated with VCDR and cup area (P values < 1.2 × 10-4). The first variant is demonstrated to increase the miR-612 expression. We showed that the second variant does not affect the miR-4707 biogenesis, but reduces the binding of miR-4707-3p to CARD10, a gene known to be involved in glaucoma. Moreover, of 72,052 miRNA-binding-site variants, 47 were significantly associated with four POAG endophenotypes (P value < 6.9 × 10-6). Of these, we highlighted 10 variants that are more likely to affect miRNA-mediated gene regulation in POAG. These include rs3217992 and rs1063192, which have been shown experimentally to affect miR-138-3p- and miR-323b-5p-mediated regulation of CDKN2B.

Conclusions

We identified a number of miRNAs that are associated with POAG endophenotypes. The identified miRNAs and their target genes are candidates for future studies on miRNA-related therapies for POAG.

Rare coding variants associated with blood pressure variation in 15 914 individuals of African ancestry

OBJECTIVES

Hypertension is a major risk factor for all cardiovascular diseases, especially among African Americans. This study focuses on identifying specific blood pressure (BP) genes using 15 914 individuals of African ancestry from eight cohorts (Africa America Diabetes Mellitus, Atherosclerosis Risk in Communities Study, Coronary Artery Risk Development in young Adults, Genetics Network, Genetic Epidemiology Network of Arteriopathy, Howard University Family Study, Hypertension Genetic Epidemiology Network, and Loyola University Chicago Cohort) to further genetic findings in this population which has generally been underrepresented in BP studies.

METHODS

We genotyped and performed various single variant and gene-based exome-wide analyses on 15 914 individuals on the Illumina HumanExome Beadchip v1.0 or v1.1 to test association with SBP and DBP long-term average residuals that were adjusted for age, age-squared, sex, and BMI.

RESULTS

We identified rare variants affecting SBP and DBP in 10 genes: AFF1, GAPDHS, SLC28A3, COL6A1, CRYBA2, KRBA1, SEL1L3, YOD1, CCDC13, and QSOX1. Prior experimental evidence for six of these 10 candidate genes supports their involvement in cardiovascular mechanisms, corroborating their potential roles in BP regulation.

CONCLUSION

Although our results require replication or validation due to their low numbers of carriers, and an ethnicity-specific genotyping array may be more informative, this study, which has identified several candidate genes in this population most susceptible to hypertension, presents one of the largest African-ancestry BP studies to date and the largest including analysis of rare variants.

Analysis of Cyclin-Dependent Kinase Inhibitor-2B rs1063192 Polymorphism in Saudi Patients with Primary Open-Angle Glaucoma

AIMS

To investigate whether the polymorphism rs1063192 (A>G) in the cyclin-dependent kinase Inhibitor-2B (CDKN2B) gene is a risk factor for primary open-angle glaucoma (POAG).

METHOD

A case-control study was conducted wherein we genotyped 87 unrelated POAG cases and 94 control subjects from Saudi Arabia using the Taq-Man^® assay.

RESULTS

The minor allele frequency was 0.20 in POAG cases and 0.21 in controls. Both the genotype and allele frequencies were not significantly different between cases and controls. No significant association was found between genotypes and glaucoma clinical indices, except that the mutant homozygous genotype (G/G) was associated with the family history of glaucoma (p = 0.024).

CONCLUSION

Polymorphism rs1063192 in CDKN2B is not a risk factor for POAG in Saudi cohort.

Islet biology, the CDKN2A/B locus and type 2 diabetes risk

Type 2 diabetes, fuelled by the obesity epidemic, is an escalating worldwide cause of personal hardship and public cost. Diabetes incidence increases with age, and many studies link the classic senescence and ageing protein p16(INK4A) to diabetes pathophysiology via pancreatic islet biology. Genome-wide association studies (GWASs) have unequivocally linked the CDKN2A/B locus, which encodes p16 inhibitor of cyclin-dependent kinase (p16(INK4A)) and three other gene products, p14 alternate reading frame (p14(ARF)), p15(INK4B) and antisense non-coding RNA in the INK4 locus (ANRIL), with human diabetes risk. However, the mechanism by which the CDKN2A/B locus influences diabetes risk remains uncertain. Here, we weigh the evidence that CDKN2A/B polymorphisms impact metabolic health via islet biology vs effects in other tissues. Structured in a bedside-to-bench-to-bedside approach, we begin with a summary of the evidence that the CDKN2A/B locus impacts diabetes risk and a brief review of the basic biology of CDKN2A/B gene products. The main emphasis of this work is an in-depth look at the nuanced roles that CDKN2A/B gene products and related proteins play in the regulation of beta cell mass, proliferation and insulin secretory function, as well as roles in other metabolic tissues. We finish with a synthesis of basic biology and clinical observations, incorporating human physiology data. We conclude that it is likely that the CDKN2A/B locus influences diabetes risk through both islet and non-islet mechanisms.

Retinoic Acid Mediates Visceral-Specific Adipogenic Defects of Human Adipose-Derived Stem Cells

Increased visceral fat, rather than subcutaneous fat, during the onset of obesity is associated with a higher risk of developing metabolic diseases. The inherent adipogenic properties of human adipose-derived stem cells (ASCs) from visceral depots are compromised compared with those of ASCs from subcutaneous depots, but little is known about the underlying mechanisms. Using ontological analysis of global gene expression studies, we demonstrate that many genes involved in retinoic acid (RA) synthesis or regulated by RA are differentially expressed in human tissues and ASCs from subcutaneous and visceral fat. The endogenous level of RA is higher in visceral ASCs; this is associated with upregulation of the RA synthesis gene through the visceral-specific developmental factor WT1. Excessive RA-mediated activity impedes the adipogenic capability of ASCs at early but not late stages of adipogenesis, which can be reversed by antagonism of RA receptors or knockdown of WT1. Our results reveal the developmental origin of adipocytic properties and the pathophysiological contributions of visceral fat depots.

Association study of the miRNA-binding site polymorphisms of CDKN2A/B genes with gestational diabetes mellitus susceptibility

AIMS

Gestational diabetes mellitus (GDM) is a complex disease induced by a combination of genetic factors and environmental exposures. Growing evidence suggests that common single nucleotide polymorphisms within miRNA-binding sites (miR-binding SNPs) contribute to the development of various diseases. However, the roles of miR-binding SNPs in GDM have not been fully elucidated. The CDKN2A/B genes have been identified as two of the strongest genetic determinants for diabetes risk. The aim of the study was to first investigate the associations between miR-binding SNPs of CDKN2A/B, GDM susceptibility, and quantitative metabolism traits.

METHODS

Three miR-binding SNPs of CDKN2A/B gene (rs1063192, rs3217992, and rs3088440) were selected and genotyped using TaqMan allelic discrimination assays in 839 cases of GDM and 900 controls.

RESULTS

The CC genotype of CDKN2B rs1063192, which is located in the hsa-miR-323b-5p binding site, was significantly associated with GDM [OR 1.418 (1.143, 1.908); p = 0.003]. The C allele of rs1063192 occurred with significantly higher frequency in GDM [OR 1.22 (1.03, 1.44); p = 0.021]. The rs1063192 genotype CC exhibited increased glucose levels at 1 h and 3 h, as well as higher insulin levels at 3 h during an OGTT compared with the control TT genotype (p < 0.05). We also found that the rs1063192 CC genotype was associated with lower total cholesterol and LDL cholesterol levels (p < 0.05).

CONCLUSIONS

The CC genotype of CDKN2B rs1063192 in the hsa-miR-323b-5p binding site increased the risk of GDM in pregnant Chinese Han women. Importantly, our study provides evidence that miR-binding SNPs are a novel source of GDM susceptibility loci.

Genetic Variations in MicroRNA-Binding Sites Affect MicroRNA-Mediated Regulation of Several Genes Associated With Cardio-metabolic Phenotypes

BACKGROUND

Genome-wide association studies enabled us to discover a large number of variants and genomic loci contributing to cardiovascular and metabolic disorders. However, because the vast majority of the identified variants are thought to merely be proxies for other functional variants, the causal mechanisms remain to be elucidated. We hypothesized that the part of the functional variants involved in deregulating cardiometabolic genes is located in microRNA (miRNA)-binding sites.

METHODS AND RESULTS

Using the largest genome-wide association studies available on glycemic indices, lipid traits, anthropometric measures, blood pressure, coronary artery diseases, and type 2 diabetes mellitus, we identified 11,067 variants that are associated with cardiometabolic phenotypes. Of these, 230 variants are located within miRNA-binding sites in the 3'-untranslated region of 155 cardiometabolic genes. Thirty-seven of 230 variants were found to fulfill our predefined criteria for being functional in their genomic loci. Ten variants were subsequently selected for experimental validation based on genome-wide association studies results, expression quantitative trait loci (eQTL) analyses, and coexpression of their host genes and regulatory miRNAs in relevant tissues. Luciferase reporter assays revealed an allele-specific regulation of genes hosting the variants by miRNAs. These cotransfection experiments showed that rs174545 (FADS1:miR-181a-2), rs1059611 (LPL:miR-136), rs13702 (LPL:miR-410), rs1046875 (FN3KRP:miR-34a), rs7956 (MKRN2:miR-154), rs3217992 (CDKN2B:miR-138-2-3p), and rs11735092 (HSD17B13:miR-375) decrease or abrogate miRNA-dependent regulation of the genes. Conversely, 2 variants, rs6857 (PVRL2:miR-320e) and rs907091 (IKZF3:miR-326), were shown to enhance the activity of miRNAs on their host genes.

CONCLUSIONS

We provide evidence for a model in which polymorphisms in miRNA-binding sites can both positively and negatively affect miRNA-mediated regulation of cardiometabolic genes.

Familial combined hyperlipidemia: from molecular insights to tailored therapy

PURPOSE OF REVIEW

This review presents recent basic and clinical developments in familial combined hyperlipidemia (FCHL).

RECENT FINDINGS

A variety of experiments have contributed to the elucidation of this complex disease. They consist of dynamic and gene expression studies in adipocytes, confirming the role of dysfunctional adipose tissue in the pathogenesis of FCHL and identifying potential new pathways, such as complement activation. Whole exome sequencing and classical linkage studies in FCHL pedigrees, some conducted with new traits (e.g. plasma proprotein convertase subtilisin/kexin type 9 [PCSK9] and phospholipid transfer protein activity), have revealed new genes of interest, among which SLC25A40 and LASS4. Finally, gene expression studies in liver biopsies and liver cell culture experiments have gained further insight in the role of upstream stimulatory factor 1, one of the most replicated genes in FCHL, in its pathogenesis.On the basis of these observations and recent phase II clinical trials, PCSK9 antagonizing is the most promising lipid-lowering therapy to be added to our current arsenal of statins and fibrates in FCHL treatment.

SUMMARY

Ongoing basic research provides a steady growth in our knowledge on the genes that are involved in FCHL as well as their metabolic function(s). This field of research may be enhanced when data are expanded and integrated for systems biology approaches. Our growing insights in the cause of FCHL allow for better, targeted treatment of dyslipidemia and prevention of cardiovascular complications.

CDKN2B expression and subcutaneous adipose tissue expandability: possible influence of the 9p21 atherosclerosis locus

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The tumor suppressor gene CDKN2B is highly expressed in human adipose tissue.

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Risk alleles at the 9p21 locus modify CDKN2B expression in a BMI-dependent fashion.

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There is an inverse relationship between expression of CDKN2B and adipogenic genes.

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CDKN2B expression influences to postprandial triacylglycerol clearance.

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CDKN2B expression in adipose tissue is linked to markers of hepatic steatosis.

Risk alleles within a gene desert at the 9p21 locus constitute the most prevalent genetic determinant of cardiovascular disease. Previous research has demonstrated that 9p21 risk variants influence gene expression in vascular tissues, yet the biological mechanisms by which this would mediate atherosclerosis merits further investigation. To investigate possible influences of this locus on other tissues, we explored expression patterns of 9p21-regulated genes in a panel of multiple human tissues and found that the tumor suppressor CDKN2B was highly expressed in subcutaneous adipose tissue (SAT). CDKN2B expression was regulated by obesity status, and this effect was stronger in carriers of 9p21 risk alleles. Covariation between expression of CDKN2B and genes implemented in adipogenesis was consistent with an inhibitory effect of CDKN2B on SAT proliferation. Moreover, studies of postprandial triacylglycerol clearance indicated that CDKN2B is involved in down-regulation of SAT fatty acid trafficking. CDKN2B expression in SAT correlated with indicators of ectopic fat accumulation, including markers of hepatic steatosis. Among genes regulated by 9p21 risk variants, CDKN2B appears to play a significant role in the regulation of SAT expandability, which is a strong determinant of lipotoxicity and therefore might contribute to the development of atherosclerosis.