title: Stimulation of autophagy improves endoplasmic reticulum stress-induced diabetes.
abstract: Accumulation of misfolded proinsulin in the β-cell leads to dysfunction induced by endoplasmic reticulum (ER) stress, with diabetes as a consequence. Autophagy helps cellular adaptation to stress via clearance of misfolded proteins and damaged organelles. We studied the effects of proinsulin misfolding on autophagy and the impact of stimulating autophagy on diabetes progression in Akita mice, which carry a mutation in proinsulin, leading to its severe misfolding. Treatment of female diabetic Akita mice with rapamycin improved diabetes, increased pancreatic insulin content, and prevented β-cell apoptosis. In vitro, autophagic flux was increased in Akita β-cells. Treatment with rapamycin further stimulated autophagy, evidenced by increased autophagosome formation and enhancement of autophagosome-lysosome fusion. This was associated with attenuation of cellular stress and apoptosis. The mammalian target of rapamycin (mTOR) kinase inhibitor Torin1 mimicked the rapamycin effects on autophagy and stress, indicating that the beneficial effects of rapamycin are indeed mediated via inhibition of mTOR. Finally, inhibition of autophagy exacerbated stress and abolished the anti-ER stress effects of rapamycin. In conclusion, rapamycin reduces ER stress induced by accumulation of misfolded proinsulin, thereby improving diabetes and preventing β-cell apoptosis. The beneficial effects of rapamycin in this context strictly depend on autophagy; therefore, stimulating autophagy may become a therapeutic approach for diabetes.
authors.affiliation: Endocrinology and Metabolism Service, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Etty
authors.initials: E
authors.lastname: Bachar-Wikstrom
authors.forename: Jakob D
authors.initials: JD
authors.lastname: Wikstrom
authors.forename: Yafa
authors.initials: Y
authors.lastname: Ariav
authors.forename: Boaz
authors.initials: B
authors.lastname: Tirosh
authors.forename: Nurit
authors.initials: N
authors.lastname: Kaiser
authors.forename: Erol
authors.initials: E
authors.lastname: Cerasi
authors.forename: Gil
authors.initials: G
authors.lastname: Leibowitz
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects* / Q000502:physiology; D003920:Diabetes Mellitus / Q000188:drug therapy* / Q000209:etiology; D004721:Endoplasmic Reticulum / Q000502:physiology*; D005260:Female; D007166:Immunosuppressive Agents / Q000494:pharmacology / Q000627:therapeutic use*; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D046912:Multiprotein Complexes; D009154:Mutation; D009287:Naphthyridines / Q000494:pharmacology; D011384:Proinsulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D011506:Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology / Q000627:therapeutic use*; D013312:Stress, Physiological; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors
chemical_list: C553294:1-(4-(4-propionylpiperazin-1-yl)-3-(trifluoromethyl)phenyl)-9-(quinolin-3-yl)benzo(h)(1,6)naphthyridin-2(1H)-one; D007166:Immunosuppressive Agents; D046912:Multiprotein Complexes; D009287:Naphthyridines; D011506:Proteins; D011384:Proinsulin; C546843:mTOR protein, mouse; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus