TY - JOUR

T1 - Inhibition of the malate-aspartate shuttle in mouse pancreatic islets abolishes glucagon secretion without affecting insulin secretion

AU - Stamenkovic, Jelena A.

AU - Andersson, Lotta E.

AU - Adriaenssens, Alice E.

AU - Bagge, Annika

AU - Sharoyko, Vladimir V.

AU - Gribble, Fiona

AU - Reimann, Frank

AU - Wollheim, Claes B.

AU - Mulder, Hindrik

AU - Spégel, Peter

N1 - Publisher Copyright: © The Authors Journal compilation © 2015 Biochemical Society.

PY - 2015/5/15

Y1 - 2015/5/15

N2 - Altered secretion of insulin as well as glucagon has been implicated in the pathogenesis of Type 2 diabetes (T2D), but the mechanisms controlling glucagon secretion from α -cells largely remain unresolved. Therefore, we studied the regulation of glucagon secretion from α TC1-6 (α TC1 clone 6) cells and compared it with insulin release from INS-1 832/13 cells. We found that INS-1 832/13 and α TC1-6 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. Although glycolytic metabolism was similar in the two cell lines, TCA (tricarboxylic acid) cycle metabolism, respiration and ATP levels were less glucose-responsive in α TC1-6 cells. Inhibition of the malate-aspartate shuttle, using phenyl succinate (PhS), abolished glucose-provoked ATP production and hormone secretion from α TC1-6 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 glycerol phosphate shuttle compared with malate-aspartate shuttle was lower in αTC1- 6 cells. Our data suggest that the glycerol phosphate shuttle augments the malate-aspartate shuttle in INS-1 832/13 but not α TC1-6 cells. These results were confirmed in mouse islets, where PhS abrogated secretion of glucagon but not insulin. Furthermore, expression of the rate-limiting enzyme of the glycerol phosphate shuttle was higher in sorted primary β - than in α -cells. Thus, suppressed glycerol phosphate shuttle activity in the α -cell may prevent a high rate of glycolysis and consequently glucagon secretion in response to glucose. Accordingly, pyruvate- and lactate-elicited glucagon secretion remains unaffected since their signalling is independent of mitochondrial shuttles.

AB - Altered secretion of insulin as well as glucagon has been implicated in the pathogenesis of Type 2 diabetes (T2D), but the mechanisms controlling glucagon secretion from α -cells largely remain unresolved. Therefore, we studied the regulation of glucagon secretion from α TC1-6 (α TC1 clone 6) cells and compared it with insulin release from INS-1 832/13 cells. We found that INS-1 832/13 and α TC1-6 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. Although glycolytic metabolism was similar in the two cell lines, TCA (tricarboxylic acid) cycle metabolism, respiration and ATP levels were less glucose-responsive in α TC1-6 cells. Inhibition of the malate-aspartate shuttle, using phenyl succinate (PhS), abolished glucose-provoked ATP production and hormone secretion from α TC1-6 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 glycerol phosphate shuttle compared with malate-aspartate shuttle was lower in αTC1- 6 cells. Our data suggest that the glycerol phosphate shuttle augments the malate-aspartate shuttle in INS-1 832/13 but not α TC1-6 cells. These results were confirmed in mouse islets, where PhS abrogated secretion of glucagon but not insulin. Furthermore, expression of the rate-limiting enzyme of the glycerol phosphate shuttle was higher in sorted primary β - than in α -cells. Thus, suppressed glycerol phosphate shuttle activity in the α -cell may prevent a high rate of glycolysis and consequently glucagon secretion in response to glucose. Accordingly, pyruvate- and lactate-elicited glucagon secretion remains unaffected since their signalling is independent of mitochondrial shuttles.

KW - Coupling factors

KW - Glucagon

KW - Glucose metabolism

KW - Insulin

KW - Islets

KW - Mitochondrial transport

UR - http://www.scopus.com/inward/record.url?scp=84935009831&partnerID=8YFLogxK

U2 - 10.1042/BJ20140697

DO - 10.1042/BJ20140697

M3 - Article

C2 - 25731850

VL - 468

SP - 49

EP - 63

JO - Biochemical Journal

JF - Biochemical Journal

SN - 0264-6021

IS - 1

ER -