Lamontagne, JulienAl-Mass, AnfalNolan, ChristopherCorkey, Barbara EMurthy Madiraju, S.RJoly, ErikPrentki, Marc2022-06-162022-06-160021-9258http://hdl.handle.net/1885/267344Metabolic deceleration in pancreatic -cells is associated with inhibition of glucose-induced insulin secretion (GIIS), but only in the presence of intermediate/submaximal glucose concentrations. Here, we used acute metformin treatment as a tool to induce metabolic deceleration in INS1 (832/13) -cells, with the goal of identifying key pathways and metabolites involved in GIIS. Metabolites and pathways previously implicated as signals for GIIS were measured in the cells at 2-25 mm glucose, with or without 5 mm metformin. We defined three criteria to identify candidate signals: 1) glucose-responsiveness, 2) sensitivity to metformin-induced inhibition of the glucose effect at intermediate glucose concentrations, and 3) alleviation of metformin inhibition by elevated glucose concentrations. Despite the lack of recovery from metformin-induced impairment of mitochondrial energy metabolism (glucose oxidation, O-2 consumption, and ATP production), insulin secretion was almost completely restored at elevated glucose concentrations. Meeting the criteria for candidates involved in promoting GIIS were the following metabolic indicators and metabolites: cytosolic NAD(+)/NADH ratio (inferred from the dihydroxyacetone phosphate:glycerol-3-phosphate ratio), mitochondrial membrane potential, ADP, Ca2+, 1-monoacylglycerol, diacylglycerol, malonyl-CoA, and HMG-CoA. On the contrary, most of the purine and nicotinamide nucleotides, acetoacetyl-CoA, H2O2, reduced glutathione, and 2-monoacylglycerol were not glucose-responsive. Overall these results underscore the significance of mitochondrial energy metabolism-independent signals in GIIS regulation; in particular, the candidate lipid signaling molecules 1-monoacylglycerol, diacylglycerol, and malonyl-CoA; the predominance of K-ATP/Ca2+ signaling control by low ADPMg(2+) rather than by high ATP levels; and a role for a more oxidized state (NAD(+)/NADH) in the cytosol during GIIS that favors high glycolysis rates.This study was supported by grants from Canadian Institutes of Health Research (to MP and SRMM) and a scholarship from Kuwait University to AA. MP holds the Canada Research Chair in Diabetes and Metabolismapplication/pdfen-AUCopyright 2017 by The American Society for Biochemistry and Molecular Biology, Inc.https://creativecommons.org/licenses/by/4.0/beta cellglucose metabolisminsulin secretionmetforminmetabolic coupling factorsmetabolic decelerationmitochondrial metabolism201710.1074/jbc.M117.8081052022-06-26Creative Commons Attribution License