Obesity is defined as the excessive accumulation of body fat that ultimately leads to chronic metabolic diseases. Diets rich in saturated fatty acids (SFA) exacerbate obesity and hepatic steatosis, which increase the risk of hepatic insulin resistance and type 2 diabetes (T2DM). Although microRNAs (miRNAs) play an important role in a range of biological processes, the implications of SFA-induced miRNAs in metabolic dysregulation, particularly in the pathogenesis of hepatic insulin resistance, are not well understood. This study investigated the implications of miR-96, which is induced strongly by SFA, in the development of hepatic insulin resistance. The liver of HFD mice and the palmitate-treated hepatocytes exhibited an impairment of insulin signaling due to the significant decrease in INSR and IRS-1 expression. According to expression profiling and qRT-PCR analysis of the miRNAs, the expression level of miR-96 was higher in hepatocytes treated with palmitate. Moreover, miR-96 was also upregulated in the liver of HFD mice. Interestingly, miR-96 targeted the 3’UTRs of INSR and IRS-1 directly, and repressed the expression of INSR and IRS-1 at the post-transcriptional level. Accordingly, the overexpression of miR-96 was found to cause a significant decrease in INSR and IRS-1 expression, thereby leading to an impairment of insulin signaling and glycogen synthesis in hepatocytes. These results reveal a novel mechanism whereby miR-96 promotes the pathogenesis of hepatic insulin resistance resulted from SFA or obesity.

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A previous study indicated a causal link between certain miRNAs induced by obesity and the development of hepatic insulin resistance and type 2 diabetes. Here we provide accompanying data collected using Affymetrix GeneChip miRNAs microarrays to identify the changes in miRNAs expression in the liver of mice fed a high fat diet (HFD). Differentially expressed microRNA analyses in the liver of the HFD-fed mice revealed a range of upregulated (>1.5-fold) or downregulated (<0.5-fold) miRNAs. Among those upregulated miRNAs, in silico target analysis, such as TargetScan, PicTar, and miRWalk, identified miRNAs with the putative binding sites on the 3’UTRs of INSR and/or IRS-1. Interpretation of the data and further extensive insights into the implication of miRNAs, particularly miR-15b, in hepatic insulin resistance can be found in "Obesity-induced miR-15b is linked causally to the development of insulin resistance through the repression of the insulin receptor in hepatocytes." (W.M. Yang, H.J. Jeong, S.W. Park, W. Lee, 2015)[1].