title: Adiponectin stimulates autophagy and reduces oxidative stress to enhance insulin sensitivity during high-fat diet feeding in mice.
abstract: Numerous studies have characterized the antidiabetic effects of adiponectin, yet the precise cellular mechanisms in skeletal muscle, in particular, changes in autophagy, require further clarification. In the current study, we used a high-fat diet (HFD) to induce obesity and insulin resistance in wild-type (WT) or adiponectin knockout (Ad-KO) mice with and without adiponectin replenishment. Temporal analysis of glucose tolerance and insulin sensitivity using hyperinsulinemic-euglycemic clamp and muscle insulin receptor substrate and Akt phosphorylation demonstrated exaggerated and more rapid HFD-induced insulin resistance in skeletal muscle of Ad-KO mice. Superoxide dismutase activity, the reduced glutathione-to-glutathione disulfide ratio, and lipid peroxidation indicated that HFD-induced oxidative stress was corrected by adiponectin. Gene array analysis implicated several antioxidant enzymes, including Gpxs, Prdx, Sod, and Nox4, in mediating this effect. Adiponectin also attenuated palmitate-induced reactive oxygen species production in cultured myotubes and improved insulin-stimulated glucose uptake in primary muscle cells. Increased LC3-II and decreased p62 expression suggested that HFD induced autophagy in muscle of WT mice; however, these changes were not observed in Ad-KO mice. Replenishing adiponectin in Ad-KO mice increased LC3-II and Beclin1 and decreased p62 protein levels, induced fibroblast growth factor-21 expression, and corrected HFD-induced decreases in LC3, Beclin1, and ULK1 gene expression. In vitro studies examining changes in phospho-ULK1 (Ser555), LC3-II, and lysosomal enzyme activity confirmed that adiponectin directly induced autophagic flux in cultured muscle cells in an AMPK-dependent manner. We overexpressed an inactive mutant of Atg5 to create an autophagy-deficient cell model, and together with pharmacological inhibition of autophagy, demonstrated reduced insulin sensitivity under these conditions. In summary, adiponectin stimulated skeletal muscle autophagy and antioxidant potential to reduce insulin resistance caused by HFD.
authors: Department of Biology, York University, Toronto, ON, Canada.
authors: Ying
authors: Y
authors: Liu
authors: Department of Biology, York University, Toronto, ON, Canada.
authors: Rengasamy
authors: R
authors: Palanivel
authors: Department of Biology, York University, Toronto, ON, Canada.
authors: Esther
authors: E
authors: Rai
authors: Department of Biology, York University, Toronto, ON, Canada.
authors: Min
authors: M
authors: Park
authors: Department of Biology, York University, Toronto, ON, Canada.
authors: Tim V
authors: TV
authors: Gabor
authors: Department of Biology, York University, Toronto, ON, Canada.
authors: Michael P
authors: MP
authors: Scheid
authors: State Key Laboratory of Pharmaceutical Biotechnology and Department of Medicine, the University of Hong Kong, Hong Kong.
authors: Aimin
authors: A
authors: Xu
authors: Department of Biology, York University, Toronto, ON, Canada gsweeney@yorku.ca.
authors: Gary
authors: G
authors: Sweeney
mesh_terms: D052242:Adiponectin / Q000097:blood* / Q000235:genetics; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001343:Autophagy / Q000502:physiology*; D000071187:Autophagy-Related Protein 5; D002401:Cathepsin B / Q000378:metabolism; D002460:Cell Line; D059305:Diet, High-Fat; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test; D049452:Green Fluorescent Proteins / Q000235:genetics; D006946:Hyperinsulinism / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology*; D061251:Primary Cell Culture; D013482:Superoxide Dismutase / Q000378:metabolism; D000097573:Red Fluorescent Protein
chemical_list: D052242:Adiponectin; D000975:Antioxidants; D000071187:Autophagy-Related Protein 5; D002401:Cathepsin B; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008869:Microtubule-Associated Proteins; D013482:Superoxide Dismutase; D000097573:Red Fluorescent Protein; C499919:Adipoq protein, mouse; C495773:Atg5 protein, mouse; C533915:Ctsb protein, mouse