Expression of PPARα modifies fatty acid effects on insulin secretion in uncoupling protein-2 knockout miceReportar como inadecuado

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Nutrition and Metabolism

, 4:6

First Online: 06 March 2007Received: 14 November 2006Accepted: 06 March 2007


Aims-hypothesisIn uncoupling protein-2 UCP2 knockout KO mice, protection of beta cells from fatty acid exposure is dependent upon transcriptional events mediated by peroxisome proliferator-activated receptor-α PPARα.

MethodsPPARα expression was reduced in isolated islets from UCP2KO and wild-type WT mice with siRNA for PPARα siPPARα overnight. Some islets were also cultured with oleic or palmitic acid, then glucose stimulated insulin secretion GSIS was measured. Expression of genes was examined by quantitative RT-PCR or immunoblotting. PPARα activation was assessed by oligonucleotide consensus sequence binding.

ResultssiPPARα treatment reduced PPARα protein expression in KO and WT islets by >85%. In siPPARα-treated UCP2KO islets, PA but not OA treatment significantly decreased the insulin response to 16.5 mM glucose. In WT islets, siPPARα treatment did not modify GSIS in PA and OA exposed groups. In WT islets, PA treatment significantly increased UCP2 mRNA and protein expression. Both PA and OA treatment significantly increased PPARα expression in UCP2KO and WT islets but OA treatment augmented PPARα protein expression only in UCP2KO islets p < 0.05. PA treatment induced carnitine palmitoyltransferase I, acyl CoA oxidase and malonyl CoA decarboxylase mRNA in UCP2KO islets.

ConclusionThese data show that the negative effect of saturated fatty acid on GSIS is mediated by PPARα-UCP2. Knockout of UCP2 protects beta-cells from PA exposure. However, in the absence of both UCP2 and PPARα even a short exposure 24 h to PA significantly impairs GSIS.

AbbreviationsPPARαperoxisome proliferator-activated receptor-α, UCP2: uncoupling protein-2, PA: Palmitic acid, OA: Oleic acid, GSIS: glucose stimulated insulin secretion, FFA: Free fatty acids, TTBS: Tween Tris-buffered saline, GAPDH: Glyceraldehyde-3-phosphate dehyrogenase, CPTI: carnitine palmitoyltransferase I, ACO: acyl CoA oxidase, ACC: Acetyl CoA carboxylase, MCD: malonyl CoA decarboxylase, EGFP: enhanced green fluorescence protein, KO: knockout, WT: wild-type, DMEM: Dulbecco-s modified Eagle medium.

Electronic supplementary materialThe online version of this article doi:10.1186-1743-7075-4-6 contains supplementary material, which is available to authorized users.

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Autor: Zahra Fatehi-Hassanabad - Catherine B Chan


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