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UCP-2 and UCP-3 proteins are differentially regulated in pancreatic beta-cells.

Li Y, Maedler K, Shu L, Haataja L - PLoS ONE (2008)

Bottom Line: Increased uncoupling protein-2 (UCP-2) expression has been associated with impaired insulin secretion, whereas UCP-3 protein levels are decreased in the skeleton muscle of type-2 diabetic subjects.Immunohistochemical analysis confirmed co-localization of UCP-3 protein with mitochondria in human beta-cells.UCP-2 and UCP-3 may have distinct roles in regulating beta-cell function.

View Article: PubMed Central - PubMed

Affiliation: Larry L. Hillblom Islet Research Center, The David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California, USA.

ABSTRACT

Background: Increased uncoupling protein-2 (UCP-2) expression has been associated with impaired insulin secretion, whereas UCP-3 protein levels are decreased in the skeleton muscle of type-2 diabetic subjects. In the present studies we hypothesize an opposing effect of glucose on the regulation of UCP-2 and UCP-3 in pancreatic islets.

Methodology: Dominant negative UCP-2 and wild type UCP-3 adenoviruses were generated, and insulin release by transduced human islets was measured. UCP-2 and UCP-3 mRNA levels were determined using quantitative PCR. UCP-2 and UCP-3 protein expression was investigated in human islets cultured in the presence of different glucose concentrations. Human pancreatic sections were analyzed for subcellular localization of UCP-3 using immunohistochemistry.

Principal findings: Dominant negative UCP-2 expression in human islets increased insulin secretion compared to control islets (p<0.05). UCP-3 mRNA is expressed in human islets, but the relative abundance of UCP-2 mRNA was 8.1-fold higher (p<0.05). Immunohistochemical analysis confirmed co-localization of UCP-3 protein with mitochondria in human beta-cells. UCP-2 protein expression in human islets was increased approximately 2-fold after high glucose exposure, whereas UCP-3 protein expression was decreased by approximately 40% (p<0.05). UCP-3 overexpression improved glucose-stimulated insulin secretion.

Conclusions: UCP-2 and UCP-3 may have distinct roles in regulating beta-cell function. Increased expression of UCP-2 and decreased expression of UCP-3 in humans with chronic hyperglycemia may contribute to impaired glucose-stimulated insulin secretion. These data imply that mechanisms that suppress UCP-2 or mechanisms that increase UCP-3 expression and/or function are potential therapeutic targets to offset defects of insulin secretion in humans with type-2 diabetes.

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UCP-2 protein is upregulated by glucose and oleic acid in human islets.A Human islets were cultured at 5.5 or 11 mM glucose for 24 hr. B Human islets were cultured at 11 mM glucose plus 1% BSA containing medium (control) or supplemented with 0.45 mM oleic acid for 24 hr. Total protein extracts were analyzed on a Western blot using UCP-2 antibodies. Upper panel, The intensities of the protein signal were quantified by scanning of images; lower panel, the UCP-2 and β-actin in one representative experiment. All values are mean±SE of at least four independent experiments from separate human islet donors (t-test; *, p<0.05 relative to control).
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pone-0001397-g001: UCP-2 protein is upregulated by glucose and oleic acid in human islets.A Human islets were cultured at 5.5 or 11 mM glucose for 24 hr. B Human islets were cultured at 11 mM glucose plus 1% BSA containing medium (control) or supplemented with 0.45 mM oleic acid for 24 hr. Total protein extracts were analyzed on a Western blot using UCP-2 antibodies. Upper panel, The intensities of the protein signal were quantified by scanning of images; lower panel, the UCP-2 and β-actin in one representative experiment. All values are mean±SE of at least four independent experiments from separate human islet donors (t-test; *, p<0.05 relative to control).

Mentions: UCP-2 protein expression was increased 2.6±0.6 (p<0.05) fold in islets cultured for 24 hr at 11 mM glucose, when compared to islets cultured at 5.5 mM glucose (Fig. 1A). Insulin release from human islets increased 4±1-fold in response to 11 mM glucose (p<0.05, data not shown). In order to evaluate the effect of free fatty acids on UCP-2 protein expression in the presence of high glucose, isolated human islets were cultured for 24 hr in 11 mM glucose containing medium with or without 0.45 mM oleic acid. As shown in figure 1B, oleic acid potentiated the effect of high glucose by increasing UCP-2 expression 1.5±0.1-fold (p<0.05) in human islets in the presence of 11 mM glucose when compared to islets cultured with 11 mM glucose without oleic acid. Insulin release from human islets increased (1.6±0.2-fold, p<0.05) in response to oleic acid (data not shown). We also examined the effect of 0.45 mM oleic acid on UCP-2 expression at 4 mM glucose. Under these conditions, oleic acid increased UCP-2 expression by 1.3±0.1-fold (data not shown).


UCP-2 and UCP-3 proteins are differentially regulated in pancreatic beta-cells.

Li Y, Maedler K, Shu L, Haataja L - PLoS ONE (2008)

UCP-2 protein is upregulated by glucose and oleic acid in human islets.A Human islets were cultured at 5.5 or 11 mM glucose for 24 hr. B Human islets were cultured at 11 mM glucose plus 1% BSA containing medium (control) or supplemented with 0.45 mM oleic acid for 24 hr. Total protein extracts were analyzed on a Western blot using UCP-2 antibodies. Upper panel, The intensities of the protein signal were quantified by scanning of images; lower panel, the UCP-2 and β-actin in one representative experiment. All values are mean±SE of at least four independent experiments from separate human islet donors (t-test; *, p<0.05 relative to control).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2164968&req=5

pone-0001397-g001: UCP-2 protein is upregulated by glucose and oleic acid in human islets.A Human islets were cultured at 5.5 or 11 mM glucose for 24 hr. B Human islets were cultured at 11 mM glucose plus 1% BSA containing medium (control) or supplemented with 0.45 mM oleic acid for 24 hr. Total protein extracts were analyzed on a Western blot using UCP-2 antibodies. Upper panel, The intensities of the protein signal were quantified by scanning of images; lower panel, the UCP-2 and β-actin in one representative experiment. All values are mean±SE of at least four independent experiments from separate human islet donors (t-test; *, p<0.05 relative to control).
Mentions: UCP-2 protein expression was increased 2.6±0.6 (p<0.05) fold in islets cultured for 24 hr at 11 mM glucose, when compared to islets cultured at 5.5 mM glucose (Fig. 1A). Insulin release from human islets increased 4±1-fold in response to 11 mM glucose (p<0.05, data not shown). In order to evaluate the effect of free fatty acids on UCP-2 protein expression in the presence of high glucose, isolated human islets were cultured for 24 hr in 11 mM glucose containing medium with or without 0.45 mM oleic acid. As shown in figure 1B, oleic acid potentiated the effect of high glucose by increasing UCP-2 expression 1.5±0.1-fold (p<0.05) in human islets in the presence of 11 mM glucose when compared to islets cultured with 11 mM glucose without oleic acid. Insulin release from human islets increased (1.6±0.2-fold, p<0.05) in response to oleic acid (data not shown). We also examined the effect of 0.45 mM oleic acid on UCP-2 expression at 4 mM glucose. Under these conditions, oleic acid increased UCP-2 expression by 1.3±0.1-fold (data not shown).

Bottom Line: Increased uncoupling protein-2 (UCP-2) expression has been associated with impaired insulin secretion, whereas UCP-3 protein levels are decreased in the skeleton muscle of type-2 diabetic subjects.Immunohistochemical analysis confirmed co-localization of UCP-3 protein with mitochondria in human beta-cells.UCP-2 and UCP-3 may have distinct roles in regulating beta-cell function.

View Article: PubMed Central - PubMed

Affiliation: Larry L. Hillblom Islet Research Center, The David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California, USA.

ABSTRACT

Background: Increased uncoupling protein-2 (UCP-2) expression has been associated with impaired insulin secretion, whereas UCP-3 protein levels are decreased in the skeleton muscle of type-2 diabetic subjects. In the present studies we hypothesize an opposing effect of glucose on the regulation of UCP-2 and UCP-3 in pancreatic islets.

Methodology: Dominant negative UCP-2 and wild type UCP-3 adenoviruses were generated, and insulin release by transduced human islets was measured. UCP-2 and UCP-3 mRNA levels were determined using quantitative PCR. UCP-2 and UCP-3 protein expression was investigated in human islets cultured in the presence of different glucose concentrations. Human pancreatic sections were analyzed for subcellular localization of UCP-3 using immunohistochemistry.

Principal findings: Dominant negative UCP-2 expression in human islets increased insulin secretion compared to control islets (p<0.05). UCP-3 mRNA is expressed in human islets, but the relative abundance of UCP-2 mRNA was 8.1-fold higher (p<0.05). Immunohistochemical analysis confirmed co-localization of UCP-3 protein with mitochondria in human beta-cells. UCP-2 protein expression in human islets was increased approximately 2-fold after high glucose exposure, whereas UCP-3 protein expression was decreased by approximately 40% (p<0.05). UCP-3 overexpression improved glucose-stimulated insulin secretion.

Conclusions: UCP-2 and UCP-3 may have distinct roles in regulating beta-cell function. Increased expression of UCP-2 and decreased expression of UCP-3 in humans with chronic hyperglycemia may contribute to impaired glucose-stimulated insulin secretion. These data imply that mechanisms that suppress UCP-2 or mechanisms that increase UCP-3 expression and/or function are potential therapeutic targets to offset defects of insulin secretion in humans with type-2 diabetes.

Show MeSH
Related in: MedlinePlus