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Expression of PPARalpha modifies fatty acid effects on insulin secretion in uncoupling protein-2 knockout mice.

Fatehi-Hassanabad Z, Chan CB - Nutr Metab (Lond) (2007)

Bottom Line: In siPPARalpha-treated UCP2KO islets, PA but not OA treatment significantly decreased the insulin response to 16.5 mM glucose.In WT islets, siPPARalpha treatment did not modify GSIS in PA and OA exposed groups.These data show that the negative effect of saturated fatty acid on GSIS is mediated by PPARalpha/UCP2.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada. zfatehi@upei.ca

ABSTRACT

Aims/hypothesis: In 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-alpha (PPARalpha).

Methods: PPARalpha expression was reduced in isolated islets from UCP2KO and wild-type (WT) mice with siRNA for PPARalpha (siPPARalpha) 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. PPARalpha activation was assessed by oligonucleotide consensus sequence binding.

Results: siPPARalpha treatment reduced PPARalpha protein expression in KO and WT islets by >85%. In siPPARalpha-treated UCP2KO islets, PA but not OA treatment significantly decreased the insulin response to 16.5 mM glucose. In WT islets, siPPARalpha 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 PPARalpha expression in UCP2KO and WT islets but OA treatment augmented PPARalpha 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.

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

No MeSH data available.


Related in: MedlinePlus

The effects of BSA, PA or OA on PPARα mRNA (A) and protein expression (B). Groups of islets isolated from KO and/or WT mice were exposed to control media (BSA, open bars), PA (closed bars) or OA (dashed bars) for 24 h. Treatment of WT and KO islets with PA and OA significantly increased PPARα mRNA expression compared to BSA (*P < 0.05). PPARα protein expression was significantly increased only in KO islets treated with OA (*P < 0.05). Two-way ANOVA performed on PPARα protein expression in KO and WT islets showed a significant difference between two genotypes (P < 0.05). Data are presented as means ± SE, N = 4–6 for each group.
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Figure 5: The effects of BSA, PA or OA on PPARα mRNA (A) and protein expression (B). Groups of islets isolated from KO and/or WT mice were exposed to control media (BSA, open bars), PA (closed bars) or OA (dashed bars) for 24 h. Treatment of WT and KO islets with PA and OA significantly increased PPARα mRNA expression compared to BSA (*P < 0.05). PPARα protein expression was significantly increased only in KO islets treated with OA (*P < 0.05). Two-way ANOVA performed on PPARα protein expression in KO and WT islets showed a significant difference between two genotypes (P < 0.05). Data are presented as means ± SE, N = 4–6 for each group.

Mentions: To assess the effect of UCP2KO on PPARα mRNA expression, we performed real-time PCR. PPARα gene expression was not significantly different between UCP2KO and WT islets (Figure 5A). Incubation of WT and UCP2KO islets with PA and OA caused a significant induction (~100-fold) in PPARα mRNA (Figure 5A).


Expression of PPARalpha modifies fatty acid effects on insulin secretion in uncoupling protein-2 knockout mice.

Fatehi-Hassanabad Z, Chan CB - Nutr Metab (Lond) (2007)

The effects of BSA, PA or OA on PPARα mRNA (A) and protein expression (B). Groups of islets isolated from KO and/or WT mice were exposed to control media (BSA, open bars), PA (closed bars) or OA (dashed bars) for 24 h. Treatment of WT and KO islets with PA and OA significantly increased PPARα mRNA expression compared to BSA (*P < 0.05). PPARα protein expression was significantly increased only in KO islets treated with OA (*P < 0.05). Two-way ANOVA performed on PPARα protein expression in KO and WT islets showed a significant difference between two genotypes (P < 0.05). Data are presented as means ± SE, N = 4–6 for each group.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1828157&req=5

Figure 5: The effects of BSA, PA or OA on PPARα mRNA (A) and protein expression (B). Groups of islets isolated from KO and/or WT mice were exposed to control media (BSA, open bars), PA (closed bars) or OA (dashed bars) for 24 h. Treatment of WT and KO islets with PA and OA significantly increased PPARα mRNA expression compared to BSA (*P < 0.05). PPARα protein expression was significantly increased only in KO islets treated with OA (*P < 0.05). Two-way ANOVA performed on PPARα protein expression in KO and WT islets showed a significant difference between two genotypes (P < 0.05). Data are presented as means ± SE, N = 4–6 for each group.
Mentions: To assess the effect of UCP2KO on PPARα mRNA expression, we performed real-time PCR. PPARα gene expression was not significantly different between UCP2KO and WT islets (Figure 5A). Incubation of WT and UCP2KO islets with PA and OA caused a significant induction (~100-fold) in PPARα mRNA (Figure 5A).

Bottom Line: In siPPARalpha-treated UCP2KO islets, PA but not OA treatment significantly decreased the insulin response to 16.5 mM glucose.In WT islets, siPPARalpha treatment did not modify GSIS in PA and OA exposed groups.These data show that the negative effect of saturated fatty acid on GSIS is mediated by PPARalpha/UCP2.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada. zfatehi@upei.ca

ABSTRACT

Aims/hypothesis: In 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-alpha (PPARalpha).

Methods: PPARalpha expression was reduced in isolated islets from UCP2KO and wild-type (WT) mice with siRNA for PPARalpha (siPPARalpha) 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. PPARalpha activation was assessed by oligonucleotide consensus sequence binding.

Results: siPPARalpha treatment reduced PPARalpha protein expression in KO and WT islets by >85%. In siPPARalpha-treated UCP2KO islets, PA but not OA treatment significantly decreased the insulin response to 16.5 mM glucose. In WT islets, siPPARalpha 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 PPARalpha expression in UCP2KO and WT islets but OA treatment augmented PPARalpha 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.

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

No MeSH data available.


Related in: MedlinePlus