title: Insulin up-regulates heme oxygenase-1 expression in 3T3-L1 adipocytes via PI3-kinase- and PKC-dependent pathways and heme oxygenase-1-associated microRNA downregulation.
abstract: Heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme catabolism, has antioxidant, antiinflammatory, and antiapoptotic effects in many physiological systems. HO-1 activity in obese mice is lower than in controls, and a sustained increase in HO-1 protein levels ameliorates insulin resistance and compensatory hyperinsulinemia. In the present study, we explored the regulatory effect of insulin on HO-1 expression in 3T3-L1 adipocytes and the underlying mechanism. We investigated the time- and dose-effect of insulin on HO-1 expression in 3T3-L1 adipocytes. Using specific inhibitors acting on insulin signaling pathways, we clarified the involvement of insulin downstream signaling molecules in insulin-regulated HO-1 expression. We also investigated the involvement of microRNAs (miRNAs) in insulin-regulated HO-1 expression using microarray and real-time RT-PCR assays. In an in vivo study, we performed insulin/glucose coinfusion in rats to increase circulating insulin levels for 8 h, then measured adipocyte HO-1 expression. Insulin caused a significant increase in HO-1 expression that was time- and dose-dependent, and this effect was blocked by inhibition of phosphatidylinositol 3 (PI3)-kinase activation using LY294002 (50 μM) or of protein kinase C activation using Ro-318220 (2 μM), but not by an Akt inhibitor, triciribine (10 μM). Furthermore, incubation of 3T3-L1 adipocytes with 100 nm insulin resulted in a significant decrease in levels of the miRNAs mir-155, mir-183, and mir-872, and this effect was also blocked by pretreatment with LY294002 or Ro-318220, but not triciribine. An in vivo study in rats showed that 8 h of a hyperinsulinemic euglycemic state resulted in a significant increase in adipocyte HO-1 expression. In conclusion, insulin increases HO-1 protein expression in 3T3-L1 adipocytes via PI3-kinase and protein kinase C-dependent pathways and miRNAs down-regulation.
authors.affiliation: Department of Physiology, National Yang-Ming University, Number 155, Section 2, Li-nong Street, Taipei, Taiwan.
authors.forename: Chih-Ling
authors.initials: CL
authors.lastname: Chang
authors.forename: Lo-Chun
authors.initials: LC
authors.lastname: Au
authors.forename: Seng-Wong
authors.initials: SW
authors.lastname: Huang
authors.forename: Ching
authors.initials: C
authors.lastname: Fai Kwok
authors.forename: Low-Tone
authors.initials: LT
authors.lastname: Ho
authors.forename: Chi-Chang
authors.initials: CC
authors.lastname: Juan
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D007211:Indoles / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012263:Ribonucleosides / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D002867:Chromones; D051547:Heme Oxygenase-1; D007211:Indoles; D007328:Insulin; D035683:MicroRNAs; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D051057:Proto-Oncogene Proteins c-akt; D012263:Ribonucleosides; C023764:triciribine; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C064758:Ro 31-8220