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

Deletion of the Murine Ortholog of the Human 9p21.3 Locus Leads to Insulin Resistance and Obesity in Hypercholesterolemic Mice

The 9p21.3 genomic locus is a hot spot for disease-associated single-nucleotide polymorphisms (SNPs), and its strongest associations are with coronary artery disease (CAD). The disease-associated SNPs are located within the sequence of a long noncoding RNA ANRIL, which potentially contributes to atherogenesis by regulating vascular cell stress and proliferation, but also affects pancreatic β-cell proliferation. Altered expression of a neighboring gene, CDKN2B, has been also recognized to correlate with obesity and hepatic steatosis in people carrying the risk SNPs. In the present study, we investigated the impact of 9p21.3 on obesity accompanied by hyperlipidemia in mice carrying a deletion of the murine ortholog for the 9p21.3 (Chr4Δ70/Δ70) risk locus in hyperlipidemic Ldlr-/-ApoB100/100 background. The Chr4Δ70/Δ70 mice showed decreased mRNA expression of insulin receptors in white adipose tissue already at a young age, which developed into insulin resistance and obesity by aging. In addition, the Sirt1-Ppargc1a-Ucp2 pathway was downregulated together with the expression of Cdkn2b, specifically in the white adipose tissue in Chr4Δ70/Δ70 mice. These results suggest that the 9p21.3 locus, ANRIL lncRNA, and their murine orthologues may regulate the key energy metabolism pathways in a white adipose tissue-specific manner in the presence of hypercholesterolemia, thus contributing to the pathogenesis of metabolic syndrome.

An Atlas of Promoter Chromatin Modifications and HiChIP Regulatory Interactions in Human Subcutaneous Adipose-Derived Stem Cells

The genome of human adipose-derived stem cells (ADSCs) from abdominal and gluteofemoral adipose tissue depots are maintained in depot-specific stable epigenetic conformations that influence cell-autonomous gene expression patterns and drive unique depot-specific functions. The traditional approach to explore tissue-specific transcriptional regulation has been to correlate differential gene expression to the nearest-neighbor linear-distance regulatory region defined by associated chromatin features including open chromatin status, histone modifications, and DNA methylation. This has provided important information; nonetheless, the approach is limited because of the known organization of eukaryotic chromatin into a topologically constrained three-dimensional network. This network positions distal regulatory elements in spatial proximity with gene promoters which are not predictable based on linear genomic distance. In this work, we capture long-range chromatin interactions using HiChIP to identify remote genomic regions that influence the differential regulation of depot-specific genes in ADSCs isolated from different adipose depots. By integrating these data with RNA-seq results and histone modifications identified by ChIP-seq, we uncovered distal regulatory elements that influence depot-specific gene expression in ADSCs. Interestingly, a subset of the HiChIP-defined chromatin loops also provide previously unknown connections between waist-to-hip ratio GWAS variants with genes that are known to significantly influence ADSC differentiation and adipocyte function.

Deciphering the genetic architecture of atrial fibrillation offers insights into disease prediction, pathophysiology and downstream sequelae

Aims

The study aimed to discover novel genetic loci for atrial fibrillation (AF), explore the shared genetic etiologies between AF and other cardiovascular and cardiometabolic traits, and uncover AF pathogenesis using Mendelian randomization analysis.

Methods and results

We conducted a genome-wide association study meta-analysis including 109,787 AF cases and 1,165,920 controls of European ancestry and identified 215 loci, among which 91 were novel. We performed Genomic Structural Equation Modeling analysis between AF and four cardiovascular comorbidities (coronary artery disease, ischemic stroke, heart failure, and vneous thromboembolism) and found 189 loci shared across these diseases as well as a universal genetic locus shared by atherosclerotic outcomes (i.e., rs1537373 near CDKN2B). Three genetic loci (rs10740129 near JMJD1C, rs2370982 near NRXN3, and rs9931494 near FTO) were associated with AF and cardiometabolic traits. A polygenic risk score derived from this genome-wide meta-analysis was associated with AF risk (odds ratio 2.36, 95% confidence interval 2.31-2.41 per standard deviation increase) in the UK biobank. This score, combined with age, sex, and basic clinical features, predicted AF risk (AUC 0.784, 95% CI 0.781-0.787) in Europeans. Phenome-wide association analysis of the polygenic risk score identified many AF-related comorbidities of the circulatory, endocrine, and respiratory systems. Phenome-wide and multi-omic Mendelian randomization analyses identified associations of blood lipids and pressure, diabetes, insomnia, obesity, short sleep, and smoking, 27 blood proteins, one gut microbe (genus.Catenibacterium), and 11 blood metabolites with risk to AF.

Conclusions

This genome-wide association study and trans-omic Mendelian randomization analysis provides insights into disease risk prediction, pathophysiology and downstream sequelae.

Knocking Down CDKN2A in 3D hiPSC-Derived Brown Adipose Progenitors Potentiates Differentiation, Oxidative Metabolism and Browning Process

Human induced pluripotent stem cells (hiPSCs) have the potential to be differentiated into any cell type, making them a relevant tool for therapeutic purposes such as cell-based therapies. In particular, they show great promise for obesity treatment as they represent an unlimited source of brown/beige adipose progenitors (hiPSC-BAPs). However, the low brown/beige adipocyte differentiation potential in 2D cultures represents a strong limitation for clinical use. In adipose tissue, besides its cell cycle regulator functions, the cyclin-dependent kinase inhibitor 2A (CDKN2A) locus modulates the commitment of stem cells to the brown-like type fate, mature adipocyte energy metabolism and the browning of adipose tissue. Here, using a new method of hiPSC-BAPs 3D culture, via the formation of an organoid-like structure, we silenced CDKN2A expression during hiPSC-BAP adipogenic differentiation and observed that knocking down CDKN2A potentiates adipogenesis, oxidative metabolism and the browning process, resulting in brown-like adipocytes by promoting UCP1 expression and beiging markers. Our results suggest that modulating CDKN2A levels could be relevant for hiPSC-BAPs cell-based therapies.

Assessing Genetic Diversity and Searching for Selection Signatures by Comparison between the Indigenous Livni and Duroc Breeds in Local Livestock of the Central Region of Russia

Indigenous pig breeds are mainly associated with the adaptive capacity that is necessary to respond adequately to climate change, food security, and livelihood needs, and natural resources conservation. Livni pigs are an indigenous fat-type breed farmed in a single farm in the Orel region and located in the Central European part of the Russian Federation. To determine the genomic regions and genes that are affected by artificial selection, we conducted the comparative study of two pig breeds with different breeding histories and breeding objectives, i.e., the native fat-type Livni and meat-type Duroc breeds using the Porcine GGP HD BeadChip, which contains ~80,000 SNPs. To check the Livni pigs for possible admixture, the Landrace and the Large White breeds were included into the study of genetic diversity as these breeds participated in the formation of the Livni pigs. We observed the highest level of genetic diversity in Livni pigs compared to commercial breeds (UHE = 0.409 vs. 0.319–0.359, p < 0.001; AR = 1.995 vs. 1.894–1.964, p < 0.001). A slight excess of heterozygotes was found in all of the breeds. We identified 291 candidate genes, which were localized within the regions under putative selection, including 22 and 228 genes, which were specific for Livni and Duroc breeds, respectively, and 41 genes common for both breeds. A detailed analysis of the molecular functions identified the genes, which were related to the formation of meat and fat traits, and adaptation to environmental stress, including extreme temperatures, which were different between breeds. Our research results are useful for conservation and sustainable breeding of Livni breed, which shows a high level of genetic diversity. This makes Livni one of the valuable national pig genetic resources.

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.

Altered regulation of mesenchymal cell senescence in adipose tissue promotes pathological changes associated with diabetic wound healing

Pathologic diabetic wound healing is caused by sequential and progressive deterioration of hemostasis, inflammation, proliferation, and resolution/remodeling. Cellular senescence promotes wound healing; however, diabetic wounds exhibit low levels of senescent factors and accumulate senescent cells, which impair the healing process. Here we show that the number of p15^INK4B + PDGFRα + senescent mesenchymal cells in adipose tissue increases transiently during early phases of wound healing in both non-diabetic mice and humans. Transplantation of adipose tissue from diabetic mice into non-diabetic mice results in impaired wound healing and an altered cellular senescence–associated secretory phenotype (SASP), suggesting that insufficient induction of adipose tissue senescence after injury is a pathological mechanism of diabetic wound healing. These results provide insight into how regulation of senescence in adipose tissue contributes to wound healing and could constitute a basis for developing therapeutic treatment for wound healing impairment in diabetes.

Type-2 diabetic adipose tissue impairs transient senescence during wound healing with expression of different components of the senescence-associated secretory phenotype (SASP), and this is associated with deteriorated wound healing.

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.

Dietary patterns interact with chromosome 9p21 rs1333048 polymorphism on the risk of obesity and cardiovascular risk factors in apparently healthy Tehrani adults

PURPOSE

Gene-dietary patterns may contribute to determining body composition and related biochemical indices. The aim of this study was to evaluate interactions between rs1333048 polymorphism and major dietary patterns on body fat percentage, general and central obesity, and related biochemical measurements.

METHODS

This cross-sectional study was conducted on 265 healthy Tehrani adults with mean age of 35 years (47.5% men, 52.5% women). Dietary patterns (DPs) were extracted by factor analysis. Bioelectrical impedance analysis was used for body analysis and rs1333048 was genotyped by the restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

Three DPs were extracted: restricted refined grains DP, legumes DP and healthy DP. AA genotype compared to CC genotype had greater odds for general obesity before (OR 3.14; 95% CI 1.008-9.60, P = 0.045) and after (OR 3.11; 95% CI 1.008-9.60, P = 0.048) adjusting for potential confounders. Individuals with AA genotype were more likely to be centrally obese before (OR 2.09; 95% CI 1.006-4.35, P = 0.048) and after (OR 2.63; 95% CI 1.12-6.17, P = 0.026) controlling for potential confounders. Significant interactions were observed between Legumes DP and rs1333048 SNP on waist circumference (P = 0.047), body fat % (BFP) (P = 0.048), hs-Crp (P = 0.042), BMI (P = 0.073), WHtR (P = 0.063) and odds for general obesity (P = 0.051). Following this DP reduced all these items for individuals with CC genotype, whereas increased them for people who carry CA or AA genotypes.

CONCLUSIONS

The findings indicate that there are significant associations between AA genotype of rs1333048 SNP and general and central obesity, and significant interaction between alleles of this SNP and major dietary patterns on the odds of general obesity, BFP, waist circumference, BMI, WHtR and hs-Crp.

Long Noncoding RNA ANRIL: Lnc-ing Genetic Variation at the Chromosome 9p21 Locus to Molecular Mechanisms of Atherosclerosis

Ever since the first genome-wide association studies (GWAS) on coronary artery disease (CAD), the Chr9p21 risk locus has emerged as a top signal in GWAS of atherosclerotic cardiovascular disease, including stroke and peripheral artery disease. The CAD risk SNPs on Chr9p21 lie within a stretch of 58 kilobases of non-protein-coding DNA, containing the gene body of the long noncoding RNA (lncRNA) antisense non coding RNA in the INK4 locus (ANRIL). How risk is affected by the Chr9p21 locus in molecular detail is a matter of ongoing research. Here we will review recent advances in the understanding that ANRIL serves as a key risk effector molecule of atherogenesis at the locus. One focus of this review is the shift in understanding that genetic variation at Chr9p21 not only affects the abundance of ANRIL, and in some cases expression of the adjacent CDKN2A/B tumor suppressors, but also impacts ANRIL splicing, such that 3′-5′-linked circular noncoding ANRIL RNA species are produced. We describe how the balance of linear and circular ANRIL RNA, determined by the Chr9p21 genotype, regulates molecular pathways and cellular functions involved in atherogenesis. We end with an outlook on how manipulating circular ANRIL abundance may be exploited for therapeutic purposes.

Elevated methylation of cyclin dependent kinase inhibitor 2B contributes to the risk of coronary heart disease in women

Cyclin dependent kinase inhibitor 2B (CDKN2B) encodes a cyclin-dependent kinase inhibitor that may enhance the formation of atherosclerotic plaques. The aim of the present study was to investigate the contribution of CDKN2B promoter methylation on the risk of coronary heart disease (CHD). The present results indicated a significant association between increased CDKN2B methylation and the risk of CHD (adjusted P=0.043). A breakdown analysis according to sex demonstrated that CDKN2B methylation was significantly associated with the risk of CHD in women (adjusted P=0.010), but not in men. A further breakdown analysis by age indicated a significant association of CHD in the women >60 years (P=0.024). Luciferase reporter gene assay results indicated that the CDKN2B promoter fragment significantly enhanced luciferase activity (P<0.001). In addition, CDKN2B transcription was significantly enhanced following treatment with 5-aza-2′-deoxycytidine methylation inhibitor in human aortic endothelial cells (HAEC) and human primary coronary artery smooth muscle cells (HPCASMC; P<0.05 and P<0.01), but not in 293 cells. Notably, estrogen treatment reduced CDKN2B methylation of several CpGs and significantly increased CDKN2B gene expression levels in HAEC, HPCASMC and 293 cells (P<0.05 and P<0.01). Additionally, treatment of HAEC and HPCASMC with simvastatin and γ-carboxy-L-glutamic acid reduced CDKN2B promoter methylation and increased CDKN2B transcription concomitantly. The present study suggests that CDKN2B promoter methylation may be associated with sex dimorphism in the pathogenesis of CHD.

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.

Developmental pathways to adiposity begin before birth and are influenced by genotype, prenatal environment and epigenome

BACKGROUND

Obesity is an escalating health problem worldwide, and hence the causes underlying its development are of primary importance to public health. There is growing evidence that suboptimal intrauterine environment can perturb the metabolic programing of the growing fetus, thereby increasing the risk of developing obesity in later life. However, the link between early exposures in the womb, genetic susceptibility, and perturbed epigenome on metabolic health is not well understood. In this study, we shed more light on this aspect by performing a comprehensive analysis on the effects of variation in prenatal environment, neonatal methylome, and genotype on birth weight and adiposity in early childhood.

METHODS

In a prospective mother-offspring cohort (N = 987), we interrogated the effects of 30 variables that influence the prenatal environment, umbilical cord DNA methylation, and genotype on offspring weight and adiposity, over the period from birth to 48 months. This is an interim analysis on an ongoing cohort study.

RESULTS

Eleven of 30 prenatal environments, including maternal adiposity, smoking, blood glucose and plasma unsaturated fatty acid levels, were associated with birth weight. Polygenic risk scores derived from genetic association studies on adult adiposity were also associated with birth weight and child adiposity, indicating an overlap between the genetic pathways influencing metabolic health in early and later life. Neonatal methylation markers from seven gene loci (ANK3, CDKN2B, CACNA1G, IGDCC4, P4HA3, ZNF423 and MIRLET7BHG) were significantly associated with birth weight, with a subset of these in genes previously implicated in metabolic pathways in humans and in animal models. Methylation levels at three of seven birth weight-linked loci showed significant association with prenatal environment, but none were affected by polygenic risk score. Six of these birth weight-linked loci continued to show a longitudinal association with offspring size and/or adiposity in early childhood.

CONCLUSIONS

This study provides further evidence that developmental pathways to adiposity begin before birth and are influenced by environmental, genetic and epigenetic factors. These pathways can have a lasting effect on offspring size, adiposity and future metabolic outcomes, and offer new opportunities for risk stratification and prevention of obesity.

CLINICAL TRIAL REGISTRATION

This birth cohort is a prospective observational study, designed to study the developmental origins of health and disease, and was retrospectively registered on 1 July 2010 under the identifier NCT01174875 .

Perivascular adipose tissue alleviates inflammatory factors and stenosis in diabetic blood vessels

Adipose tissue can modulate disease processes in a depot-specific manner. However, the functional properties of perivascular adipocytes, and their influence on the pathophysiology of blood vessel walls, remain to be determined. In this study, we aimed to investigate whether perivascular adipose tissue could have an ameliorative effect on blood vessels damaged in diabetes. Using in vitro coculture, and in vivo transplantation model simulating diabetic angioplasty-induced injury, we showed that perivascular adipose tissue has an important function in protecting blood vessels from high glucose impairment. Levels of inflammatory cytokines, including intercellular cell adhesion molecule-1 and osteopontin, were markedly reduced, whereas that of endothelial nitric-oxide synthase was markedly elevated in vascular walls. These depot-specific differences in blood vessels exposed to high levels of glucose were demonstrable both in vivo, with transplanted adipose tissues, and in vitro, when vascular endothelial cells were cocultured with adipocytes. In addition, intimal hyperplasia was also decreased by transplanted perivascular adipose tissue after balloon injury combined with hyperglycemia. We conclude that perivascular adipocytes can reduce inflammation in blood vessels and promote the normal function of endothelium, which could afford a new therapeutic strategy in vascular walls damaged by diabetes.

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.

CDKN2B Regulates TGFβ Signaling and Smooth Muscle Cell Investment of Hypoxic Neovessels

RATIONALE

Genetic variation at the chromosome 9p21 cardiovascular risk locus has been associated with peripheral artery disease, but its mechanism remains unknown.

OBJECTIVE

To determine whether this association is secondary to an increase in atherosclerosis, or it is the result of a separate angiogenesis-related mechanism.

METHODS AND RESULTS

Quantitative evaluation of human vascular samples revealed that carriers of the 9p21 risk allele possess a significantly higher burden of immature intraplaque microvessels than carriers of the ancestral allele, irrespective of lesion size or patient comorbidity. To determine whether aberrant angiogenesis also occurs under nonatherosclerotic conditions, we performed femoral artery ligation surgery in mice lacking the 9p21 candidate gene, Cdkn2b. These animals developed advanced hindlimb ischemia and digital autoamputation, secondary to a defect in the capacity of the Cdkn2b-deficient smooth muscle cell to support the developing neovessel. Microarray studies identified impaired transforming growth factor β (TGFβ) signaling in cultured cyclin-dependent kinase inhibitor 2B (CDKN2B)-deficient cells, as well as TGFβ1 upregulation in the vasculature of 9p21 risk allele carriers. Molecular signaling studies indicated that loss of CDKN2B impairs the expression of the inhibitory factor, SMAD-7, which promotes downstream TGFβ activation. Ultimately, this manifests in the upregulation of a poorly studied effector molecule, TGFβ1-induced-1, which is a TGFβ-rheostat known to have antagonistic effects on the endothelial cell and smooth muscle cell. Dual knockdown studies confirmed the reversibility of the proposed mechanism, in vitro.

CONCLUSIONS

These results suggest that loss of CDKN2B may not only promote cardiovascular disease through the development of atherosclerosis but may also impair TGFβ signaling and hypoxic neovessel maturation.

Functional genomics of the CDKN2A/B locus in cardiovascular and metabolic disease: what have we learned from GWASs?

Genome-wide association studies (GWASs) provide an unprecedented opportunity to examine, on a large scale, the association of common genetic variants with complex diseases like type 2 diabetes (T2D) and cardiovascular disease (CVD), thus allowing the identification of new potential disease loci. Using this approach, numerous studies have associated SNPs on chromosome 9p21.3 situated near the cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) locus with the risk for coronary artery disease (CAD) and T2D. However, identifying the function of the nearby gene products (CDKN2A/B and ANRIL) in the pathophysiology of these conditions requires functional genomic studies. We review the current knowledge, from studies using human and mouse models, describing the function of CDKN2A/B gene products, which may mechanistically link the 9p21.3 risk locus with CVD and diabetes.

Diabetes susceptibility in Mayas: Evidence for the involvement of polymorphisms in HHEX, HNF4α, KCNJ11, PPARγ, CDKN2A/2B, SLC30A8, CDC123/CAMK1D, TCF7L2, ABCA1 and SLC16A11 genes

Association of type 2 diabetes (T2D) with common variants in HHEX, HNF4α, KCNJ11, PPARγ, CDKN2A/2B, SLC30A8, CDC123/CAMK1D, TCF7L2, ABCA1 and SLC16A11 genes have been reported, mainly in populations of European and Asian ancestry and to a lesser extent in Latin Americans. Thus, we aimed to investigate the contribution of rs1111875 (HHEX), rs1800961 (HNF4α), rs5219 (KCNJ11), rs1801282 (PPARγ), rs10811661 (CDKN2A/2B), rs13266634 (SLC30A8), rs12779790 (CDC123/CAMK1D), rs7903146 (TCF7L2), rs9282541 (ABCA1) and rs13342692 (SLC16A11) polymorphisms in the genetic background of Maya population to associate their susceptibility to develop T2D. This is one of the first studies designed specifically to investigate the inherited component of T2D in the indigenous population of Mexico. SNPs were genotyped by allelic discrimination method in 575 unrelated Maya individuals. Two SNPs rs10811661 and rs928254 were significantly associated with T2D after adjusting for BMI; rs10811661 in a recessive and rs9282541 in a dominant model. Additionally, we found phenotypical alterations associated with genetic variants: HDL to rs9282541 and insulin to rs13342692. In conclusion, these findings support an association of genetic polymorphisms to develop T2D in Maya population.