Qicheng Ni1,2, Jiaxi Song1,2, Yichen Wang1,2, Jiajun Sun1,2, Jing Xie3, Jun Zhang4, Guang Ning1,2, Weiqing Wang1,2, Qidi Wang1,2,5. 1. Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. 2. Shanghai National Clinical Research Center for Metabolic Diseases, Key Laboratory for Endocrine and Metabolic Diseases of the National Health Commission of the PR China, Shanghai National Center for Translational Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. 3. Department of Pathology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. 4. Department of General Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. 5. Sino-French Research Center for Life Sciences and Genomics, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Abstract
CONTEXT: The mechanistic target of rapamycin complex I (mTORC1) is crucial for β-cell identity and function in rodents. However, its possible relevance to the physiopathology of diabetes in humans remains unclear. OBJECTIVE: This work aimed to understand the participation of mTORC1 in human β cells in prediabetes and diabetes. DESIGN: We evaluated the PS6 immunofluorescence intensity in islets of pancreatic sections from 12 nondiabetic (ND), 11 impaired fasting glucose (IFG), and 11 glycemic-controlled type 2 diabetic (T2D) individuals. We also assessed the dynamic change of mTORC1 activity in β cells of db/db mice with new-onset diabetes. RESULTS: There exists intercellular heterogeneity of mTORC1 activities in human islets. Islet mTORC1 activity was independently and positively correlated with FBG in ND, but not in IFG and T2D. Moreover, we did not detect significant change in mTORC1 activities between T2D and ND. Of note, the islet mTORC1 activities were significantly higher in IFG than in ND. We further stratified IFG individuals according to their islet PS6 levels and found that IFG-PS6high exhibited remarkably higher urocortin3 and glucose transporter 2 expression in their β cells compared to IFG-PS6low. Consistently, we also detected a significant increase in mTORC1 activities in prediabetic db/db mice compared to nondiabetic littermates. Interestingly, mTORC1 activities determined β-cell adaptation or failure in db/db mice: A strong negative correlation was found between islet mTORC1 activities and fasting glucose levels in db/db mice during their diabetes progression. CONCLUSIONS: Our finding highlights a dynamic islet mTORC1 response in β-cell adaption/failure in human T2D.
CONTEXT: The mechanistic target of rapamycin complex I (mTORC1) is crucial for β-cell identity and function in rodents. However, its possible relevance to the physiopathology of diabetes in humans remains unclear. OBJECTIVE: This work aimed to understand the participation of mTORC1 in human β cells in prediabetes and diabetes. DESIGN: We evaluated the PS6 immunofluorescence intensity in islets of pancreatic sections from 12 nondiabetic (ND), 11 impaired fasting glucose (IFG), and 11 glycemic-controlled type 2 diabetic (T2D) individuals. We also assessed the dynamic change of mTORC1 activity in β cells of db/db mice with new-onset diabetes. RESULTS: There exists intercellular heterogeneity of mTORC1 activities in human islets. Islet mTORC1 activity was independently and positively correlated with FBG in ND, but not in IFG and T2D. Moreover, we did not detect significant change in mTORC1 activities between T2D and ND. Of note, the islet mTORC1 activities were significantly higher in IFG than in ND. We further stratified IFG individuals according to their islet PS6 levels and found that IFG-PS6high exhibited remarkably higher urocortin3 and glucose transporter 2 expression in their β cells compared to IFG-PS6low. Consistently, we also detected a significant increase in mTORC1 activities in prediabetic db/db mice compared to nondiabetic littermates. Interestingly, mTORC1 activities determined β-cell adaptation or failure in db/db mice: A strong negative correlation was found between islet mTORC1 activities and fasting glucose levels in db/db mice during their diabetes progression. CONCLUSIONS: Our finding highlights a dynamic islet mTORC1 response in β-cell adaption/failure in human T2D.