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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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UCP3 over expression in human islets increases glucose-stimulated insulin secretion.A Western blot analysis of UCP-3 expression in transduced islets. B Isolated human pancreatic islets were cultured on extracellular matrix-coated dishes and transduced with adenoviruses expressing control virus (luciferase, Luc), UCP-3 or dnUCP-2. Basal and stimulated insulin secretion indicate the amount secreted during 1-hour incubations at 2.8 (basal) and 16.7 mM (stimulated) glucose following the 2-day culture period after transduction, normalized to whole islet insulin content. C Stimulatory index denotes the amount of stimulated divided by the amount of basal insulin secretion. Data represent results of two different experiments from two different organ donors in quadruplicate. Results are means±SE, *p<0.05 compared to control.
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pone-0001397-g004: UCP3 over expression in human islets increases glucose-stimulated insulin secretion.A Western blot analysis of UCP-3 expression in transduced islets. B Isolated human pancreatic islets were cultured on extracellular matrix-coated dishes and transduced with adenoviruses expressing control virus (luciferase, Luc), UCP-3 or dnUCP-2. Basal and stimulated insulin secretion indicate the amount secreted during 1-hour incubations at 2.8 (basal) and 16.7 mM (stimulated) glucose following the 2-day culture period after transduction, normalized to whole islet insulin content. C Stimulatory index denotes the amount of stimulated divided by the amount of basal insulin secretion. Data represent results of two different experiments from two different organ donors in quadruplicate. Results are means±SE, *p<0.05 compared to control.

Mentions: To investigate the effect of UCP-3 overexpression on GSIS, we prepared UCP-3 adenoviruses. Adenoviral overexpression of UCP-3 resulted in an approximate 3-fold increase in UCP-3 protein expression compared to control human islets (Fig. 4A). Forty-eight hr after transduction, we performed GSIS assays in human islets. No significant changes in insulin secretion were observed at basal levels at 2.8 mM glucose in UCP-3 expressing islets compared to control islets. However, as already seen in the perifusion experiment, dnUCP-2 increased basal insulin secretion by 1.5-fold compared to untreated control islets (p<0.05). Stimulated insulin secretion at 16.7 mM glucose was significantly increased in human islets expressing UCP-3 or dnUCP-2 (1.8- and 2.1-fold, respectively, p<0.05, Fig. 4B) compared to scrambled control. This resulted in a 37% and 40% increase in the stimulatory index by UCP-3 and dnUCP-2, respectively in human islets (p<0.05, Fig. 4C).


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

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

UCP3 over expression in human islets increases glucose-stimulated insulin secretion.A Western blot analysis of UCP-3 expression in transduced islets. B Isolated human pancreatic islets were cultured on extracellular matrix-coated dishes and transduced with adenoviruses expressing control virus (luciferase, Luc), UCP-3 or dnUCP-2. Basal and stimulated insulin secretion indicate the amount secreted during 1-hour incubations at 2.8 (basal) and 16.7 mM (stimulated) glucose following the 2-day culture period after transduction, normalized to whole islet insulin content. C Stimulatory index denotes the amount of stimulated divided by the amount of basal insulin secretion. Data represent results of two different experiments from two different organ donors in quadruplicate. Results are means±SE, *p<0.05 compared to control.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2164968&req=5

pone-0001397-g004: UCP3 over expression in human islets increases glucose-stimulated insulin secretion.A Western blot analysis of UCP-3 expression in transduced islets. B Isolated human pancreatic islets were cultured on extracellular matrix-coated dishes and transduced with adenoviruses expressing control virus (luciferase, Luc), UCP-3 or dnUCP-2. Basal and stimulated insulin secretion indicate the amount secreted during 1-hour incubations at 2.8 (basal) and 16.7 mM (stimulated) glucose following the 2-day culture period after transduction, normalized to whole islet insulin content. C Stimulatory index denotes the amount of stimulated divided by the amount of basal insulin secretion. Data represent results of two different experiments from two different organ donors in quadruplicate. Results are means±SE, *p<0.05 compared to control.
Mentions: To investigate the effect of UCP-3 overexpression on GSIS, we prepared UCP-3 adenoviruses. Adenoviral overexpression of UCP-3 resulted in an approximate 3-fold increase in UCP-3 protein expression compared to control human islets (Fig. 4A). Forty-eight hr after transduction, we performed GSIS assays in human islets. No significant changes in insulin secretion were observed at basal levels at 2.8 mM glucose in UCP-3 expressing islets compared to control islets. However, as already seen in the perifusion experiment, dnUCP-2 increased basal insulin secretion by 1.5-fold compared to untreated control islets (p<0.05). Stimulated insulin secretion at 16.7 mM glucose was significantly increased in human islets expressing UCP-3 or dnUCP-2 (1.8- and 2.1-fold, respectively, p<0.05, Fig. 4B) compared to scrambled control. This resulted in a 37% and 40% increase in the stimulatory index by UCP-3 and dnUCP-2, respectively in human islets (p<0.05, Fig. 4C).

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