Glycerol-stimulated proinsulin biosynthesis in isolated pancreatic rat islets via adenoviral-induced expression of glycerol kinase is mediated via mitochondrial metabolism.
In this study, we examined whether adenoviral-mediated glycerol kinase (AdV-CMV-GlyK) expression in isolated rat pancreatic islets could introduce glycerol-induced proinsulin biosynthesis. In AdV-CMV-GlyK-infected islets, specific glycerol-induced proinsulin biosynthesis translation and insulin secretion were observed in parallel from the same islets. The threshold concentration of glycerol required to stimulate proinsulin biosynthesis was lower (0.25-0.5 mmol/l) than that for insulin secretion (1.0-1.5 mmol/l), reminiscent of threshold differences for glucose-stimulated proinsulin biosynthesis versus insulin secretion. The dose-dependent glycerol-induced proinsulin biosynthesis correlated with the rate of glycerol oxidation in AdV-CMV-GlyK-infected islets, indicating that glycerol metabolism was required for the response. However, glycerol did not significantly increase lactate output from AdV-CMV-GlyK-infected islets, but the dihydroxyacetone phosphate (DHAP) to alpha-glycerophosphate (alpha-GP) ratio significantly increased in AdV-CMV-GlyK-infected islets incubated at 2 mmol/l glycerol compared with that at a basal level of 2.8 mmol/l glucose (P < or = 0.05). The DHAP:alpha-GP ratio was unaffected in AdV-CMV-GlyK-infected islets incubated at 2 mmol/l glycerol in the added presence of alpha-cyanohydroxycinnaminic acid (alpha-CHC), an inhibitor of the plasma membrane and mitochondrial lactate/pyruvate transporter. However, alpha-CHC inhibited glycerol-induced proinsulin biosynthesis and insulin secretion in AdV-CMV-GlyK-infected islets (>75%; P = 0.05), similarly to glucose-induced proinsulin biosynthesis and insulin secretion in AdV-CMV-GlyK-infected and control islets. These data indicated that in AdV-CMV-GlyK-infected islets, the importance of mitochondrial metabolism of glycerol was required to generate stimulus-response coupling signals to induce proinsulin biosynthesis and insulin secretion.
Skelly
R H
RH
Pacific Northwest Research Institute and Department of Pharmacology, University of Washington, Seattle, WA 98112, USA.
Wicksteed
B
B
Antinozzi
P A
PA
Rhodes
C J
CJ
D000256:Adenoviridae; D000818:Animals; D002478:Cells, Cultured; D003373:Coumaric Acids / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003587:Cytomegalovirus; D004099:Dihydroxyacetone Phosphate / Q000378:metabolism; D017930:Genes, Reporter; D005947:Glucose / Q000494:pharmacology; D005991:Glycerol Kinase / Q000235:genetics / Q000378:metabolism*; D005994:Glycerophosphates / Q000378:metabolism; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D011384:Proinsulin / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D001616:beta-Galactosidase / Q000235:genetics
D003373:Coumaric Acids; D015853:Cysteine Proteinase Inhibitors; D005994:Glycerophosphates; D007773:Lactates; D011994:Recombinant Proteins; C007175:alpha-cyano-4-hydroxycinnamate; D004099:Dihydroxyacetone Phosphate; D011384:Proinsulin; C029620:alpha-glycerophosphoric acid; D005991:Glycerol Kinase; D001616:beta-Galactosidase; D005947:Glucose