Inhibition of the malate-aspartate shuttle in mouse pancreatic islets abolishes glucagon secretion without affecting insulin secretion

Altered secretion of insulin as well as glucagon has been implicated in the pathogenesis of Type 2 Diabetes, but the mechanisms controlling glucagon secretion from α-cells largely remain unresolved. Therefore, we studied the regulation of glucagon secretion from αTC1-6 cells and compared it to insulin release from INS-1 832/13 cells. We found that INS-1 832/13 and αTC1-6 cells, respectively, secreted insulin and glucagon concentration-dependently in response to glucose. In contrast, tight coupling of glycolytic and mitochondrial metabolism was observed only in INS-1 832/13 cells. While glycolytic metabolism was similar in the two cell-lines, Krebs-cycle metabolism, respiration and ATP-levels were less glucose-responsive in αTC1-6 cells. Inhibition of the malate-aspartate shuttle, using phenyl succinate, abolished glucose-provoked ATP production and hormone secretion from αTC1-6, but not INS-1 832/13 cells. Blocking the malate-aspartate shuttle increased levels of glycerol-3-phosphate only in INS-1 832/13 cells. Accordingly, relative expression of constituents in the glycerolphosphate shuttle compared to malate-aspartate shuttle was lower in αTC1-6 cells. Our data suggest that the glycerolphosphate shuttle augments the malate-aspartate shuttle in the INS-1 832/13 but not in αTC1-6 cells. These results were confirmed in mouse islets, where phenyl succinate abrogated secretion of glucagon but not insulin. Furthermore, expression o...

Source: BJ Cell - March 3, 2015 Category: Biochemistry Authors: J A Stamenkovic, L E Andersson, A E Adriaenssens, A Bagge, V V Sharoyko, F Gribble, F Reimann, C B Wollheim, H Mulder, P Spégel Tags: BJ Metabolism Source Type: research