1863-P: The Hepatic Role of Heat Shock Protein 72 in the Pathogenesis of Type 2 Diabetes

Abstract

Cell stresses, such as ER stress or oxidative stress are considered to be key mediators in pathophysiology of type 2 diabetes. Heat shock protein (HSP) 72, a major inducible HSP against heat, serves to protect cells from those cellular stresses and works in protein quality control. Induction of HSP72 improves glucose intolerance in type 2 diabetic model mice. In this study, we investigated glucose metabolism in whole body HSP72 deficient (KO) mice. The effects of hepatic HSP72 induction in KO mice were also investigated. KO mice and control mice were subjected to a high-fat diet regimen. Metabolic parameters and pathophysiological examination were performed. HSP72 was overexpressed in mice by lenti-virus to investigate the role of HSP72 in liver. There were no significant differences in body weight and food intake between two groups. Fasting and random-fed blood glucose levels were significantly higher in KO mice than those in control mice. The fasting insulin level was significantly lower in KO mice. Upon glucose challenge, blood glucose levels were higher in KO mice. On insulin tolerance test, KO mice exhibited insulin resistant phenotype. Visceral fat mass was increased and hepatic steatosis was obvious in KO mice with increased SREBP-1c mRNA expression. Upon insulin stimulation, phosphorylation of Akt was decreased in KO liver, with increased activation of JNK. Hepatic gluconeogenesis was not suppressed in KO accompanied by increased gluconeogenic enzymes. When restoring HSP72 expression in liver by lenti-virus on KO mice, blood glucose, hepatic steatosis and gluconeogenesis were ameliorated. Interestingly, visceral fat size and macrophage infiltration were both reversed by hepatic HSP72 induction. Deficiency of HSP72 leads to type 2 diabetic phenotype. As induction of HSP72 in liver is beneficial to improve glucose homeostasis in KO, the abundance of HSP72 in liver is critical in diabetic pathophysiology, and appropriate HSP72 induction may serve as a target in the treatment of type 2 diabetes. Disclosure T. Kondo: None. S. Kitano: None. N. Miyakawa: None. T. Watanabe: None. R. Goto: None. K. Ono: None. M. Igata: None. J. Kawashima: None. H. Motoshima: None. T. Matsumura: None. E. Araki: Research Support; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Novo Nordisk Inc., Takeda Pharmaceutical Company Limited. Speaker's Bureau; Self; Astellas Pharma Inc., Merck & Co., Inc., Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Sanofi. Funding Japan Society for the Promotion of Science