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 (T2D), but the mechanisms controlling glucagon secretion from α-cells largely remain unresolved. Therefore, we studied the regulation of glucagon secretion from αTC1-6 (αTC1 clone 6) cells and compared it with 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. Although glycolytic metabolism was similar in the two cell lines, TCA (tricarboxylic acid) cycle metabolism, respiration and ATP levels were less glucose-responsive in αTC1-6 cells. Inhibition of the malate-aspartate shuttle, using phenyl succinate (PhS), 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 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 αTC1-6 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.
*Unit of Molecular Metabolism, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, CRC, Lund University, Skåne University Hospital, Malmö 205 02, Sweden.
Jelena A
JA
Stamenkovic
*Unit of Molecular Metabolism, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, CRC, Lund University, Skåne University Hospital, Malmö 205 02, Sweden.
Lotta E
LE
Andersson
†MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Sciences, Addenbrooke's Hospital, Cambridge CB2 0XY, U.K.
Alice E
AE
Adriaenssens
*Unit of Molecular Metabolism, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, CRC, Lund University, Skåne University Hospital, Malmö 205 02, Sweden.
Annika
A
Bagge
*Unit of Molecular Metabolism, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, CRC, Lund University, Skåne University Hospital, Malmö 205 02, Sweden.
Vladimir V
VV
Sharoyko
†MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Sciences, Addenbrooke's Hospital, Cambridge CB2 0XY, U.K.
Fiona
F
Gribble
†MRC Metabolic Diseases Unit, Wellcome Trust-MRC Institute of Metabolic Sciences, Addenbrooke's Hospital, Cambridge CB2 0XY, U.K.
Frank
F
Reimann
‡Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, CRC, Lund University, Skåne University Hospital, Malmö 205 02, Sweden.
Claes B
CB
Wollheim
*Unit of Molecular Metabolism, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, CRC, Lund University, Skåne University Hospital, Malmö 205 02, Sweden.
Hindrik
H
Mulder
*Unit of Molecular Metabolism, Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, CRC, Lund University, Skåne University Hospital, Malmö 205 02, Sweden.
Peter
P
Spégel
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D002460:Cell Line; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism / Q000503:physiopathology; D005934:Glucagon / Q000378:metabolism*; D050416:Glucagon-Secreting Cells / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D005994:Glycerophosphates / Q000378:metabolism; D006019:Glycolysis; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008293:Malates / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism; D055442:Metabolome; D051379:Mice; D008809:Mice, Inbred C3H; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism
D005994:Glycerophosphates; D007328:Insulin; D008293:Malates; D026901:Membrane Transport Proteins; C021723:oxoglutarate translocator; D001224:Aspartic Acid; D005934:Glucagon; C029620:alpha-glycerophosphoric acid; D005947:Glucose