The mTORC2/PKC pathway sustains compensatory insulin secretion of pancreatic β cells in response to metabolic stress

Publication date: Available online 20 April 2017
Source:Biochimica et Biophysica Acta (BBA) - General Subjects
Author(s): Yun Xie, Canqi Cui, Aifang Nie, Yan Wang, Qicheng Ni, Yun Liu, Qinglei Yin, Hongli Zhang, Yong Li, Qidi Wang, Yanyun Gu, Guang Ning
BackgroundCompensation of the pancreatic β cell functional mass in response to metabolic stress is key to the pathogenesis of Type 2 Diabetes. The mTORC2 pathway governs fuel metabolism and β cell functional mass. It is unknown whether mTORC2 is required for regulating metabolic stress-induced β cell compensation.MethodsWe challenged four-week-old β-cell-specific Rictor (a key component of mTORC2)-knockout mice with a high fat diet (HFD) for 4weeks and measured metabolic and pancreatic morphological parameters. We performed ex vivo experiments to analyse β cell insulin secretion and electrophysiology characteristics. Adenoviral-mediated overexpression and lentiviral-ShRNA-mediated knocking down proteins were applied in Min6 cells and cultured primary mouse islets.ResultsβRicKO mice showed a significant glucose intolerance and a reduced plasma insulin level and an unchanged level β cell mass versus the control mice under HFD but not NCD. A HFD or palmitate treatment enhanced both glucose-induced insulin secretion (GIIS) and the PMA (phorbol 12-myristate 13-acetate)-induced insulin secretion in the control islets but not in the βRicKO islets. The KO β cells showed similar glucose-induced Ca²⁺ influx but lower membrane capacitance increments versus the control cells. The enhanced mTORC2/PKC proteins levels in the control HFD group were ablated by Rictor deletion. Replenishing PKCα by overexpression of PKCα-T638D restored the defective GIIS in βRicKO islets.ConclusionsThe mTORC2/Rictor pathway modulates β cell compensatory GIIS under nutrient overload mediated by its phosphorylation of PKCα.General significanceThis study suggests that the mTORC2/PKC pathway in β cells is involved in the pathogenesis of T2D.



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