Effect of microRNA-196a on regulation of body-fat distribution in man

Abstract

BackgroundMicroRNAs are small non-coding RNAs that have a role in adipose tissue biology. Fat depots differ in terms of the metabolic risk that they confer. Therefore, we aimed to identify microRNAs that contribute to the differences between fat depots. MethodsMicroRNAs expressed in human adipose tissue were identified by a microarray screen followed by confirmatory quantitative PCR (qPCR) on within-subject paired subcutaneous abdominal and gluteal adipose tissue biopsy samples from 40 individuals. After we found that miR-196a was strongly differentially expressed between the depots, we investigated mRNA expression of putative targets of miR-196a. In addition, 5650 individuals from the Oxford Biobank were genotyped for rs11614913, a single nucleotide polymorphism (SNP) in miR-196a-2, to determine whether there was an association with body fat distribution as measured by dual-energy X-ray absorptiometry. Expression of miR-196a was then measured by qPCR in paired abdominal and gluteal whole subcutaneous fat biopsy samples from 30 individuals of each genotype. FindingsExpression of miR-196a was 2·1 times higher within subcutaneous gluteal adipose tissue than within subcutaneous abdominal adipose tissue (p=0·0001). miR-196a was expressed from within HOX gene clusters and was predicted to target the developmental genes HOXA5, HOXB8, and HOXC8, which correspondingly showed an inverse pattern of expression to miR-196a. These expression patterns were replicated in both primary pre-adipocytes derived from abdominal and gluteal adipose tissue and in immortalised pre-adipocyte cell lines, suggesting that they are intrinsic to pre-adipocytes rather than being a function of their environment. In addition, we found that the SNP rs11614913 was significantly associated with an increase in android to lower body fat ratio of 6·7% in individuals with the TT genotype (p=0·013) compared with individuals with a C allele. The TT genotype was also associated with reduced expression of miR-196a in abdominal subcutaneous adipose tissue (−32%, p=0·005). There was no difference in expression of pre-miR-196a-2. Bioinformatic modelling predicted that rs11614913 altered the folding of pre-miR-196a-2, decreasing its stability. InterpretationTo our knowledge, this is the first demonstration of a microRNA affecting human adipose tissue developmental features and fat distribution. We propose that rs11614913 destabilises pre-miR-196a, leading to reduced efficiency of processing pre-miR-196a-2 to mature miR-196a in abdominal fat and predisposing to increased central body-fat distribution. FundingUK Medical Research Council, Novo Nordisk UK Research Foundation.