Downregulation of miR-181a upregulates sirtuin-1 (SIRT1) and improves hepatic insulin sensitivity

Abstract

Aims/hypothesis Sirtuin-1 (SIRT1) is a potential therapeutic target to combat insulin resistance and type 2 diabetes. This study aims to identify a microRNA (miRNA) targeting SIRT1 to regulate hepatic insulin sensitivity. Methods Luciferase assay combined with mutation and immunoblotting was used to screen and verify the bioinformatically predicted miRNAs. miRNA and mRNA levels were measured by real-time PCR. Insulin signalling was detected by immunoblotting and glycogen synthesis. Involvement of SIRT1 was studied with adenovirus, inhibitor and SIRT1-deficient hepatocytes. The role of miR-181a in vivo was explored with adenovirus and locked nucleic acid antisense oligonucleotides. Results miR-181a targets the 3′ untranslated region (3′UTR) of Sirt1 mRNA through a miR-181a binding site, and downregulates SIRT1 protein abundance at the translational level. miR-181a is increased in insulin-resistant cultured hepatocytes and liver, and in the serum of diabetic patients. Overexpression of miR-181a decreases SIRT1 protein levels and activity, and causes insulin resistance in hepatic cells. Inhibition of miR-181a by antisense oligonucleotides increases SIRT1 protein levels and activity, and improves insulin sensitivity in hepatocytes. Ectopic expression of SIRT1 abrogates the effect of miR-181a on insulin sensitivity, and inhibition of SIRT1 activity or SIRT1 deficiency markedly attenuated the improvement in insulin sensitivity induced by antisense miR-181a. In addition, overexpression of miR181a by adenovirus impairs hepatic insulin signalling, and intraperitoneal injection of locked nucleic acid antisense oligonucleotides for miR-181a improves glucose homeostasis in diet-induced obesity mice. Conclusions/interpretation miR-181a regulates SIRT1 and improves hepatic insulin sensitivity. Inhibition of miR-181a might be a potential new strategy for treating insulin resistance and type 2 diabetes.

The miR-181d-regulated metalloproteinase Adamts1 enzymatically impairs adipogenesis via ECM remodeling

“…49 Moreover, miR-181a could promote adipogenesis via targeting TNFα, 50 and downregulation of miR-181a could improve hepatic insulin sensitivity by upregulating sirtuin-1. 51 In this study, miR-181d was predicted to be a putative regulator of Adamts1. Interestingly, miR-181d has been reported to have a general role in regulating lipid content of hepatocytes via targeting Adamts5, which functions similarly with Adamts1.…”

Application of microRNAs in diabetes mellitus

“…Hepatic Sirt1 deficiency in mice has been demonstrated to impair mTORC2/AKT signaling and results in hyperglycemia and insulin resistance . The upregulation of miR-181a in diabetic liver and hepatocytes decreases Sirt1, inactivating insulin signaling and glucose metabolism (Zhou et al 2012). miR-96 and miR-126 directly target the insulin receptor substrate 1 (IRS1) 3 0 UTR.…”

“…Inhibition of miR-320 using anti-miR-320 oligonucleotides restored the insulin sensitivity in insulinresistant 3T3-L1 adipocytes, evidenced by activation of insulin -PI3K signaling pathways and insulin-stimulated glucose uptake (Ling et al 2009). Treatment with antisense oligonucleotides (2 0 -O-methyl-miR-181a) increases SIRT1 protein levels and activity, and improves insulin sensitivity in HepG2 hepatocytes (Zhou et al 2012). The inhibition of miR-29 with LNA antisense-based anti-miR29 increased insulin-induced AKT signaling, but barely augmented insulin-dependent glucose uptake (He et al 2007).…”

“…Overexpression of miR-181a using adenovirus-based transfection in C57/BL6 mice by tail vein injection impaired hepatic insulin signaling and attenuated glucose homeostasis, while downregulation of miR-181a with i.p. injection of LNA antisense oligonucleotides improved glucose homeostasis in mice with diet-induced obesity (Zhou et al 2012). Recently, nonviral-based miRNA regulation has been successfully developed to treat diabetic complications and other diseases, such as diabetic nephropathy, lung fibrosis, and cardiac fibrosis (Xiao et al 2012, Chen et al 2014, Zhang et al 2014.…”

Biological roles of microRNAs in the control of insulin secretion and action

“…Screening miRNA expression in liver of mouse models of obesity and diabetes (leptin-deficient ob/ob, leptin receptordeficient db/db, HFD-fed mice), in obese patients, and in cellular systems revealed systematic overexpression of miR-143 (30), miR-802 (38), and miR-181a (89). These miRNAs target distinct sets of transcripts with different functions, including the oxysterol-binding-protein-related protein 8 (target of miR-143), which provides a link to mechanisms of energy metabolism and cell growth and differentiation mediated by the serine/threonine kinase AKT (protein kinase B, PKB), the transcription factor HNF1B (target of miR-802), and the NADϩ-dependent deacetylase SIRT1 (target of miR-181a).…”