Uncoupling of nutrient metabolism from insulin secretion by overexpression of cytosolic phospholipase A(2)
UNSPECIFIED. (2005) Uncoupling of nutrient metabolism from insulin secretion by overexpression of cytosolic phospholipase A(2). DIABETES, 54 (1). pp. 116-124. ISSN 0012-1797Full text not available from this repository.
We have generated MIN6 beta-cells that stably overexpress cytosolic phospholipase A(2) (cPLA(2)) and show a ninefold increase in cPLA2 activity. Overexpression of cPLA2 did not affect the capacity of MINE cells to show elevations in intracellular Ca2+ concentration ([Ca2+](i)) in response to tolbutamide and KCl, and these depolarizing stimuli produced insulin secretion profiles in cPLA(2)-overexpressing cells similar to those they produced in passage-matched nontransfected MINE cells. However, cPLA2-overexpressing MIN6 cells did not respond to elevations in extracellular glucose with increases in ATP, [Ca2+](i), or insulin secretion. Nontransfected MIN6 cells showed a rapid and sustained increase in NAD(P)H autofluorescence in response to 25 mmol/l glucose, and this was reduced by similar to95% in MIN6 cells overexpressing cPLA2. This effect was mimicked in nontransfected MIN6 cells by p-(trifluoromethoxy) phenylylhydrazone, a mitochondrial uncoupler. Quantitative RT-PCR indicated that mRNA for uncoupling protein-2 (UCP-2) was increased in the cPLA2-overexpressing MIN6 cells, and this could be prevented by exposure to 100 mumol/l methyl arachidonyl fluorophosphate, a cPLA2 inhibitor. Glucose caused a decrease in rhodamine 123 fluorescence in control cells, but not in those overexpressing cPLA2, consistent with the transfected cells being unable to maintain mitochondrial proton gradients as a consequence of UCP-2 upregulation. Our data indicate that overexpression of cPLA2 results in severe impairment of the calcium and secretory responses of beta-cells to glucose through upregulation of UCP-2 and uncoupling of mitochondrial metabolism from ATP generation.
|Item Type:||Journal Article|
|Subjects:||R Medicine > RC Internal medicine|
|Journal or Publication Title:||DIABETES|
|Publisher:||AMER DIABETES ASSOC|
|Number of Pages:||9|
|Page Range:||pp. 116-124|
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