title: Irisin has no effect on lipolysis in 3T3-L1 adipocytes or fatty acid metabolism in HepG2 hepatocytes.
abstract: Irisin, a newly identified myokine responsible for browning of white or beige adipocytes, has been reported to be present at reduced levels in diabetic patients and associated with obesity, serum triglyceride (TG) levels, and intrahepatic TG levels. We wondered whether irisin could directly affect fatty acid and TG metabolism in adipocytes and hepatocytes. We examined the effects of various concentrations of irisin on lipolysis (according to Oil Red O staining, free fatty acid release, and glycerol release), protein expression of HSL and ATGL, and mRNA expression of other lipid-related genes (UCP-1, PPARγ, FABP-4, HSL, ATGL, PPARα, and CPT-1) in mature 3T3-L1 adipocytes, as well as mRNA levels of genes involved in the synthesis (SREBP-1C and FAS) and β-oxidation (PPARα and CPT-1) of fatty acids in HepG2 hepatocytes under physiological or hyperglycemic conditions. Our results revealed that although irisin significantly increased the mRNA levels of UCP-1 and PPARα, it failed to show detectable effects on lipolysis, HSL or ATGL protein levels, or the mRNA expression of other lipid-related genes in mature 3T3-L1 adipocytes. In HepG2 hepatocytes, high glucose induced the upregulation of SREBP-1C and FAS and the downregulation of PPARα; however, no significant effect of irisin on gene expression was observed under either physiological or hyperglycemic conditions. We therefore conclude that irisin has no significant direct effect on lipolysis in 3T3-L1 adipocytes or on fatty acid metabolism in HepG2 hepatocytes.
authors.affiliation: Department of Endocrinology, Qilu Hospital of Shandong University, Jinan, 250012, China.
authors.forename: Chuan
authors.initials: C
authors.lastname: Wang
authors.forename: Lingshu
authors.initials: L
authors.lastname: Wang
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Li
authors.forename: Fei
authors.initials: F
authors.lastname: Yan
authors.forename: Meng
authors.initials: M
authors.lastname: Tian
authors.forename: Chuanlong
authors.initials: C
authors.lastname: Wu
authors.forename: Lin
authors.initials: L
authors.lastname: Qi
authors.forename: Xuping
authors.initials: X
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Song
authors.forename: Xinguo
authors.initials: X
authors.lastname: Hou
authors.forename: Li
authors.initials: L
authors.lastname: Chen
mesh_terms: D041721:3T3-L1 Cells / Q000378:metabolism*; D000818:Animals; D005227:Fatty Acids / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism*; D056945:Hep G2 Cells / Q000378:metabolism*; D006801:Humans; D008066:Lipolysis / Q000502:physiology*; D051379:Mice; D014280:Triglycerides / Q000378:metabolism
chemical_list: C577593:FNDC5 protein, human; D005227:Fatty Acids; D005353:Fibronectins; D014280:Triglycerides