Effect Of Rheb1 On Islet β Cell Proliferation

Objective:Diabetes mellitus is characterized by insulin resistance with insufficient insulin secretion.The mechanism of diabetes isβ-cell deterioration andβ-cell mass reduction.Under pathophysiological conditions,the proliferation and differentiation of beta cells are compensatory.Proliferation is a hotspot in the field of isletβ-cell research and one of the key points in the prevention and treatment of diabetes mellitus.In this study,the effects of Rheb1 on pancreaticβcell proliferation and its related mechanisms were studied.Methods:（1）We detected the expression of Rheb1 protein in different tissues of mice by Western blot（WB）.（2）Pancreatic specific Rheb1^flox/floxmice were mated with Pdx1-Cre mice to obtain Rheb1 KO mice（pRheb1 KO）.（3）Western blot and immunofluorescence（IF）were used to determine whether the mouse model was successfully constructed.（4）We measured the weight,food intake,body fat and pancreas quality of Rheb1（pRheb1 KO）male mice and WT male mice after 6 weeks of normal diet;（5）Glucose tolerance and insulin sensitivity of mice were detected by glucose tolerance test and insulin tolerance test;（6）The function of mouse isletβcells was detected by high glucose clamp technique,and the isletβcell mass,αcell mass,proliferation rate and apoptosis rate were detected by immunofluorescence assay and TUNEL assay,respectively;（7）Rheb1 was overexpressed by adenovirus or knocked out by siRNA;（8）Rapamycin was used to inhibit rapamycin complex 1（mTORC1）signaling pathway,and AICAR was used to activate AMPK signaling pathway,and the relationship between phenotypic changes induced by Rheb1 and mTORC1 and AMPK signaling pathway was determined.Results:（1）Rheb1 is highly expressed in the islets of mice,suggesting a potential regulatory role inβcell function;（2）Data showed that pancreatic specific Rheb1 gene knockout results in inhibition of beta cell mass and insulin content and reduced insulin secretion in mice;（3）Cell and mouse islet experiments showed that Rheb1 promotes pancreaticβcell proliferation partly dependent on mTORC1 signaling;（4）In terms of mechanism,neither AICAR nor rapamycin could completely inhibit the proliferation of human and mouse isletβcells induced by Rheb1,but the combination of AICAR and rapamycin could completely inhibit the proliferation signal of human and mouse isletβcells induced by Rheb1.These results suggest that the deletion of pancreatic Rheb1 gene may inhibit the proliferation ofβcells through mTORC1 and AMPK signaling pathway.Conclusions:In this study,we found that Rheb1 in pancreatic tissue promotes the proliferation ofβcells by promoting mTORC1 and inhibits AMPK signaling pathway,which provides a new understanding of the function of pancreaticβcells and provides a new basis for improving glucose metabolism and diabetes treatment.