Cdkn2a deficiency promotes adipose tissue browning

Abstract

ObjectivesGenome-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.MethodsWe 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.ResultsWe 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.ConclusionOur 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.

Emerging Roles for the INK4a/ARF (CDKN2A) Locus in Adipose Tissue: Implications for Obesity and Type 2 Diabetes

“…This suggests a cell-autonomous requirement of CDKN2A to the browning process. Consistent with these findings, silencing CDKN2A expression during human iPSCs adipogenic differentiation promotes UCP1 expression and browning markers [ 60 ]. We also observed that CDKN2A expression was increased in adipocytes from obese patients.…”

“…Recently, the INK4a/ARF locus has been suggested to play a major role in the molecular switch of white-to-beige adipocyte conversion and thus is a key determinant of brown adipocyte fate ( Figure 2 ). In support of this notion, we showed that CDKN2A -deficient mice were protected against DIO exhibiting sWAT browning and increased thermogenesis and insulin sensitivity [ 60 ]. Differentiated SVF cells from sWAT displayed elevated oxidative activity with upregulation of brown fat-specific gene and increase in PKA activity and adrenergic receptor signaling pathways.…”

“…In this review, we will present data supporting the role of the INK4a/ARF locus as a key regulatory hub to maintain AT in a healthy state. As indicated in Figure 2 , this locus regulates the balance between adipogenesis and senescence [ 49 , 50 , 51 , 52 , 53 ] and plays a role in adipocyte insulin sensitivity and lipid storage [ 34 , 36 , 54 , 55 ], inflammation [ 56 , 57 , 58 ] as well as oxidative activity and browning [ 59 , 60 , 61 ]. Targeting these metabolic pathways have recently emerged as a new putative therapy to alleviate the effects of obesity and prevent insulin resistance and T2D [ 62 ].…”

PamgeneAnalyzeR open and reproducible pipeline for kinase profiling

“…Kinome profiling to investigate biological processes is becoming easily accessible thanks to methods such as PamGene PamChip ® arrays that provide a valuable tool for direct exploration of cellular kinase activities 8,9,10 . The ability to develop bioinformatic tools to extract and analyze the data in a reproducible and robust manner is critical.…”

Global Transcriptome Analysis of Brown Adipose Tissue of Diet-Induced Obese Mice

“…DESeq2 is an advanced methodology that analyzes comparative RNA-seq data using shrinkage estimators for fold change, standard error, and dispersion, and provides quality assessment and clustering of overdispersed data [ 54 ]. Besides accounting for non-normality and dependence of variance of RNA-seq data, DESeq2 is highly sensitive and precise for using small sample sizes, often as few as two or three replicates per experimental condition, in typical high-throughput sequencing studies [ 23 , 55 , 56 ], including the first hit [ 57 ] of the current PubMed search ( Table S1 ).…”