title: Downregulation of miR-181a upregulates sirtuin-1 (SIRT1) and improves hepatic insulin sensitivity.
abstract: OBJECTIVE
  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 miR-181a 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
  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.
authors.affiliation: Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 294 Taiyuan Road, Shanghai 200031, People's Republic of China.
authors.forename: B
authors.initials: B
authors.lastname: Zhou
authors.forename: C
authors.initials: C
authors.lastname: Li
authors.forename: W
authors.initials: W
authors.lastname: Qi
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: F
authors.initials: F
authors.lastname: Zhang
authors.forename: J X
authors.initials: JX
authors.lastname: Wu
authors.forename: Y N
authors.initials: YN
authors.lastname: Hu
authors.forename: D M
authors.initials: DM
authors.lastname: Wu
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: T T
authors.initials: TT
authors.lastname: Yan
authors.forename: Q
authors.initials: Q
authors.lastname: Jing
authors.forename: M F
authors.initials: MF
authors.lastname: Liu
authors.forename: Q W
authors.initials: QW
authors.lastname: Zhai
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D002478:Cells, Cultured; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D006801:Humans; D015151:Immunoblotting; D007333:Insulin Resistance; D008099:Liver / Q000378:metabolism*; D051379:Mice; D035683:MicroRNAs / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D056564:Sirtuin 1 / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D020413:3' Untranslated Regions; D035683:MicroRNAs; D012333:RNA, Messenger; C529100:mirn181 microRNA, mouse; C470545:Sirt1 protein, mouse; D056564:Sirtuin 1