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Pyruvate dehydrogenase kinase 1 controls mitochondrial metabolism and insulin secretion in INS-1 832/13 clonal beta-cells

Author:
  • Ulrika Krus
  • Olga Kotova
  • Peter Spégel
  • Elna Hallgard
  • Vladimir Sharoyko
  • Anna Vedin
  • Thomas Moritz
  • Mary C. Sugden
  • Thomas Köck
  • Hindrik Mulder
Publishing year: 2010
Language: English
Pages: 205-213
Publication/Series: Biochemical Journal
Volume: 429
Document type: Journal article
Publisher: Portland Press Limited

Abstract english

Tight coupling between cytosolic and mitochondrial metabolism is key for GSIS (glucose-stimulated insulin secretion). In the present study we examined the regulatory contribution of PDH (pyruvate dehydrogenase) kinase 1, a negative regulator of PDH, to metabolic coupling in 832/13 clonal beta-cells. Knockdown of PDH kinase 1 with siRNA (small interfering RNA) reduced its mRNA (>80 %) and protein level (>40 %) after 72 h. PDH activity, glucose-stimulated cellular oxygen consumption and pyruvate-stimulated mitochondrial oxygen consumption increased 1.7- (P < 0.05), 1.6- (P < 0.05) and 1.6-fold (P < 0.05) respectively. Gas chromatography/MS revealed an altered metabolite profile upon silencing of PDH kinase 1, determined by increased levels of the tricarboxylic acid cycle intermediates malate, fumarate and alpha-ketoglutarate. These metabolic alterations were associated with exaggerated GSIS (5-fold compared with 3.1-fold in control cells; P < 0.01). Insulin secretion, provoked by leucine and dimethylsuccinate, which feed into the tricarboxylic acid cycle bypassing PDH, was unaffected. The oxygen consumption and metabolic data strongly suggest that knockdown of PDH kinase 1 in beta-cells permits increased metabolic flux of glucose-derived carbons into the tricarboxylic acid cycle via PDH. Enhanced insulin secretion is probably caused by increased generation of tricarboxylic acid cycle-derived reducing equivalents for mitochondrial electron transport to generate ATP and/or stimulatory metabolic intermediates. On the basis of these findings, we suggest that PDH kinase 1 is an important regulator of PDH in clonal beta-cells and that PDH kinase 1 and PDH are important for efficient metabolic coupling. Maintaining low PDH kinase I expression/activity, keeping PDH in a dephosphorylated and active state, may be important for beta-cells to achieve the metabolic flux rates necessary for maximal GSIS.

Keywords

  • Biochemistry and Molecular Biology
  • pyruvate dehydrogenase kinase 1
  • oxygen
  • mitochondria
  • insulin secretion
  • beta-cell
  • electron transport
  • stimulus-secretion coupling

Other

Published
  • Islet patophysiology
  • ISSN: 0264-6021
Peter Spegel
E-mail: peter.spegel [at] chem.lu.se

Researcher

Centre for Analysis and Synthesis

1

Lund University Diabetes Centre, CRC, SUS Malmö, Entrance 72, House 91:12. SE-205 02 Malmö. Telephone: +46 40 39 10 00