Glucose-stimulated insulin secretion does not require activation of pyruvate dehydrogenase: impact of adenovirus-mediated overexpression of PDH kinase and PDH phosphate phosphatase in pancreatic islets.
Glucose-stimulated increases in mitochondrial metabolism are generally thought to be important for the activation of insulin secretion. Pyruvate dehydrogenase (PDH) is a key regulatory enzyme, believed to govern the rate of pyruvate entry into the citrate cycle. We show here that elevated glucose concentrations (16 or 30 vs 3 mM) cause an increase in PDH activity in both isolated rat islets, and in a clonal beta-cell line (MIN6). However, increases in PDH activity elicited with either dichloroacetate, or by adenoviral expression of the catalytic subunit of pyruvate dehydrogenase phosphatase, were without effect on glucose-induced increases in mitochondrial pyridine nucleotide levels, or cytosolic ATP concentration, in MIN6 cells, and insulin secretion from isolated rat islets. Similarly, the above parameters were unaffected by blockade of the glucose-induced increase in PDH activity by adenovirus-mediated over-expression of PDH kinase (PDK). Thus, activation of the PDH complex plays an unexpectedly minor role in stimulating glucose metabolism and in triggering insulin release.
Nicholls
Linda I
LI
Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD, United Kingdom
Ainscow
Edward K
EK
Rutter
Guy A
GA
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D002478:Cells, Cultured; D002999:Clone Cells; D003999:Dichloroacetic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005822:Genetic Vectors; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D030481:Pyruvate Dehydrogenase (Lipoamide) / Q000378:metabolism*; D011769:Pyruvate Dehydrogenase (Lipoamide)-Phosphatase / Q000235:genetics / Q000378:metabolism; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D051381:Rats; D017208:Rats, Wistar; D014162:Transfection
D004791:Enzyme Inhibitors; D007328:Insulin; D047428:Protein Kinase Inhibitors; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D003999:Dichloroacetic Acid; D030481:Pyruvate Dehydrogenase (Lipoamide); D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011769:Pyruvate Dehydrogenase (Lipoamide)-Phosphatase; D005947:Glucose