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Palmitate-induced beta-cell dysfunction is associated with excessive NO production and is reversed by thiazolidinedione-mediated inhibition of GPR40 transduction mechanisms.

Meidute Abaraviciene S, Lundquist I, Galvanovskis J, Flodgren E, Olde B, Salehi A - PLoS ONE (2008)

Bottom Line: We examined palmitate effects on pancreatic islet function in relation to FFA receptor GPR40, NO generation, insulin release, and the PPARgamma agonistic thiazolidinedione, rosiglitazone.Rosiglitazone reversed these effects.We conclude that, in addition to mediating acute FFA-stimulated insulin release, GPR40 is an important regulator of iNOS expression and dysfunctional insulin release during long-term exposure to FFA.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Science, Division of Endocrine Pharmacology, the Malmö University Hospital (UMAS), Malmö, Sweden.

ABSTRACT

Background: Type 2 diabetes often displays hyperlipidemia. We examined palmitate effects on pancreatic islet function in relation to FFA receptor GPR40, NO generation, insulin release, and the PPARgamma agonistic thiazolidinedione, rosiglitazone.

Principal findings: Rosiglitazone suppressed acute palmitate-stimulated GPR40-transduced PI hydrolysis in HEK293 cells and insulin release from MIN6c cells and mouse islets. Culturing islets 24 h with palmitate at 5 mmol/l glucose induced beta-cell iNOS expression as revealed by confocal microscopy and increased the activities of ncNOS and iNOS associated with suppression of glucose-stimulated insulin response. Rosiglitazone reversed these effects. The expression of iNOS after high-glucose culturing was unaffected by rosiglitazone. Downregulation of GPR40 by antisense treatment abrogated GPR40 expression and suppressed palmitate-induced iNOS activity and insulin release.

Conclusion: We conclude that, in addition to mediating acute FFA-stimulated insulin release, GPR40 is an important regulator of iNOS expression and dysfunctional insulin release during long-term exposure to FFA. The adverse effects of palmitate were counteracted by rosiglitazone at GPR40, suggesting that thiazolidinediones are beneficial for beta-cell function in hyperlipidemic type 2 diabetes.

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Confocal microscopy of mouse islets.Isolated islets were cultured for 24 h at a basal glucose concentration of 5 mmol/l (A–C); 5G+palmitate (1 mmol/l) (D–F); 5G+palmitate+rosiglitazone (1 μmol/l) (G–I) or 20G (J–L) and 20G+rosiglitazone (1 μmol/l) (M-O). After the culturing period the islets were double-immunolabelled for insulin (appears as red) (A, D, G, J and M) and iNOS (appears as green) (B, E, H, K and N) and analyzed by confocal microscopy. Co-localization of insulin/iNOS is seen as a yellowish fluorescence (C, F, I, L and O). Fluorescence intensity data of iNOS (green) were normalized to 100% as measured in E (5G+palmitate) and gave the following results (n = 12). B = 1.50±0.75; E = 100.6±2.52; H = 4.33±1.50; K = 99.0±2.96; N = 106.1±3.22.
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pone-0002182-g004: Confocal microscopy of mouse islets.Isolated islets were cultured for 24 h at a basal glucose concentration of 5 mmol/l (A–C); 5G+palmitate (1 mmol/l) (D–F); 5G+palmitate+rosiglitazone (1 μmol/l) (G–I) or 20G (J–L) and 20G+rosiglitazone (1 μmol/l) (M-O). After the culturing period the islets were double-immunolabelled for insulin (appears as red) (A, D, G, J and M) and iNOS (appears as green) (B, E, H, K and N) and analyzed by confocal microscopy. Co-localization of insulin/iNOS is seen as a yellowish fluorescence (C, F, I, L and O). Fluorescence intensity data of iNOS (green) were normalized to 100% as measured in E (5G+palmitate) and gave the following results (n = 12). B = 1.50±0.75; E = 100.6±2.52; H = 4.33±1.50; K = 99.0±2.96; N = 106.1±3.22.

Mentions: The cellular distribution of iNOS protein was examined with confocal microscopy. Fig. 4 shows that after culture with palmitate (D–F) or high glucose (J–L) iNOS immunoreactivity was expressed in most islet cells, which also displayed insulin immunoreactivity. No iNOS immunoreactivity was detected in islets cultured at basal glucose (A–C). Addition of ROZ to culture medium suppressed palmitate-induced iNOS expression in β-cells (G–I), whereas glucose-induced expression of iNOS induced by high glucose was not affected (M–O).


Palmitate-induced beta-cell dysfunction is associated with excessive NO production and is reversed by thiazolidinedione-mediated inhibition of GPR40 transduction mechanisms.

Meidute Abaraviciene S, Lundquist I, Galvanovskis J, Flodgren E, Olde B, Salehi A - PLoS ONE (2008)

Confocal microscopy of mouse islets.Isolated islets were cultured for 24 h at a basal glucose concentration of 5 mmol/l (A–C); 5G+palmitate (1 mmol/l) (D–F); 5G+palmitate+rosiglitazone (1 μmol/l) (G–I) or 20G (J–L) and 20G+rosiglitazone (1 μmol/l) (M-O). After the culturing period the islets were double-immunolabelled for insulin (appears as red) (A, D, G, J and M) and iNOS (appears as green) (B, E, H, K and N) and analyzed by confocal microscopy. Co-localization of insulin/iNOS is seen as a yellowish fluorescence (C, F, I, L and O). Fluorescence intensity data of iNOS (green) were normalized to 100% as measured in E (5G+palmitate) and gave the following results (n = 12). B = 1.50±0.75; E = 100.6±2.52; H = 4.33±1.50; K = 99.0±2.96; N = 106.1±3.22.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2366067&req=5

pone-0002182-g004: Confocal microscopy of mouse islets.Isolated islets were cultured for 24 h at a basal glucose concentration of 5 mmol/l (A–C); 5G+palmitate (1 mmol/l) (D–F); 5G+palmitate+rosiglitazone (1 μmol/l) (G–I) or 20G (J–L) and 20G+rosiglitazone (1 μmol/l) (M-O). After the culturing period the islets were double-immunolabelled for insulin (appears as red) (A, D, G, J and M) and iNOS (appears as green) (B, E, H, K and N) and analyzed by confocal microscopy. Co-localization of insulin/iNOS is seen as a yellowish fluorescence (C, F, I, L and O). Fluorescence intensity data of iNOS (green) were normalized to 100% as measured in E (5G+palmitate) and gave the following results (n = 12). B = 1.50±0.75; E = 100.6±2.52; H = 4.33±1.50; K = 99.0±2.96; N = 106.1±3.22.
Mentions: The cellular distribution of iNOS protein was examined with confocal microscopy. Fig. 4 shows that after culture with palmitate (D–F) or high glucose (J–L) iNOS immunoreactivity was expressed in most islet cells, which also displayed insulin immunoreactivity. No iNOS immunoreactivity was detected in islets cultured at basal glucose (A–C). Addition of ROZ to culture medium suppressed palmitate-induced iNOS expression in β-cells (G–I), whereas glucose-induced expression of iNOS induced by high glucose was not affected (M–O).

Bottom Line: We examined palmitate effects on pancreatic islet function in relation to FFA receptor GPR40, NO generation, insulin release, and the PPARgamma agonistic thiazolidinedione, rosiglitazone.Rosiglitazone reversed these effects.We conclude that, in addition to mediating acute FFA-stimulated insulin release, GPR40 is an important regulator of iNOS expression and dysfunctional insulin release during long-term exposure to FFA.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Science, Division of Endocrine Pharmacology, the Malmö University Hospital (UMAS), Malmö, Sweden.

ABSTRACT

Background: Type 2 diabetes often displays hyperlipidemia. We examined palmitate effects on pancreatic islet function in relation to FFA receptor GPR40, NO generation, insulin release, and the PPARgamma agonistic thiazolidinedione, rosiglitazone.

Principal findings: Rosiglitazone suppressed acute palmitate-stimulated GPR40-transduced PI hydrolysis in HEK293 cells and insulin release from MIN6c cells and mouse islets. Culturing islets 24 h with palmitate at 5 mmol/l glucose induced beta-cell iNOS expression as revealed by confocal microscopy and increased the activities of ncNOS and iNOS associated with suppression of glucose-stimulated insulin response. Rosiglitazone reversed these effects. The expression of iNOS after high-glucose culturing was unaffected by rosiglitazone. Downregulation of GPR40 by antisense treatment abrogated GPR40 expression and suppressed palmitate-induced iNOS activity and insulin release.

Conclusion: We conclude that, in addition to mediating acute FFA-stimulated insulin release, GPR40 is an important regulator of iNOS expression and dysfunctional insulin release during long-term exposure to FFA. The adverse effects of palmitate were counteracted by rosiglitazone at GPR40, suggesting that thiazolidinediones are beneficial for beta-cell function in hyperlipidemic type 2 diabetes.

Show MeSH
Related in: MedlinePlus