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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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Short-time effects of palmitate and rosiglitazone (ROZ) on phosphatidyl inositol (PI) hydrolysis, in HEK293 and MIN6c4 cells, insulin release in MIN6c4 cells as well as NO production and insulin release in isolated islets.(A) PI hydrolysis in nontransfected and GPR40-transfected HEK293 cells in response to palmitate (1 mmol/l) and ROZ (50 μmol/l) (n = 8–12) and (B); dose-dependent effect of ROZ on palmitate-induced PI hydrolysis (n = 8-12). (C, D) PI hydrolysis and insulin release in MIN6c4 cells in response to palmitate (1 mmol/l)±ROZ at different concentrations (n = 6). (E) NO production from neuronal constitutive nitric oxide synthase (ncNOS), inducible NOS (iNOS) and total NOS as well as insulin release in response to palmitate (1 mmol/l) after 60 min incubation of freshly isolated mouse islets at 5 mmol/l glucose (5G) (n = 4). (F) Effect of the NOS inhibitor L-NAME on insulin release induced by palmitate (1 mmol/l) in the presence of 5 mmol/l glucose (n = 8). (G) Effects of palmitate±ROZ or diazoxide on insulin release from freshly isolated mouse islets incubated at low (1 mmol/l) or high (20 mmol/l) glucose for 60 min. The concentrations of the different test agent were; palmitate (1 mmol/l), ROZ (1 μmol/l), diazoxide (dz) (250 μmol/l) (n = 8-12). Values are mean±s.e.m for. ** p<0.01; *** p<0.001.
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pone-0002182-g001: Short-time effects of palmitate and rosiglitazone (ROZ) on phosphatidyl inositol (PI) hydrolysis, in HEK293 and MIN6c4 cells, insulin release in MIN6c4 cells as well as NO production and insulin release in isolated islets.(A) PI hydrolysis in nontransfected and GPR40-transfected HEK293 cells in response to palmitate (1 mmol/l) and ROZ (50 μmol/l) (n = 8–12) and (B); dose-dependent effect of ROZ on palmitate-induced PI hydrolysis (n = 8-12). (C, D) PI hydrolysis and insulin release in MIN6c4 cells in response to palmitate (1 mmol/l)±ROZ at different concentrations (n = 6). (E) NO production from neuronal constitutive nitric oxide synthase (ncNOS), inducible NOS (iNOS) and total NOS as well as insulin release in response to palmitate (1 mmol/l) after 60 min incubation of freshly isolated mouse islets at 5 mmol/l glucose (5G) (n = 4). (F) Effect of the NOS inhibitor L-NAME on insulin release induced by palmitate (1 mmol/l) in the presence of 5 mmol/l glucose (n = 8). (G) Effects of palmitate±ROZ or diazoxide on insulin release from freshly isolated mouse islets incubated at low (1 mmol/l) or high (20 mmol/l) glucose for 60 min. The concentrations of the different test agent were; palmitate (1 mmol/l), ROZ (1 μmol/l), diazoxide (dz) (250 μmol/l) (n = 8-12). Values are mean±s.e.m for. ** p<0.01; *** p<0.001.

Mentions: We first tested the acute action-interaction of palmitate in relation to ROZ on PI hydrolysis in HEK293 cells transiently expressed with mouse GPR40. HEK293 cells do not express endogenous GPR40 [21] and is well suited to explore the immediate response to GPR40 ligands after transient expression of the receptor. Fig. 1A shows that PI hydrolysis after 30 min incubation of GPR40-transfected HEK293 cells in presence of 1 mmol/l palmitate is highly increased compared with nontransfected controls and that ROZ by itself has a significant agonistic action. Fig. 1B, on the other hand, shows that ROZ has an inhibitory action on the palmitate-stimulated PI hydrolysis in transfected cells.


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)

Short-time effects of palmitate and rosiglitazone (ROZ) on phosphatidyl inositol (PI) hydrolysis, in HEK293 and MIN6c4 cells, insulin release in MIN6c4 cells as well as NO production and insulin release in isolated islets.(A) PI hydrolysis in nontransfected and GPR40-transfected HEK293 cells in response to palmitate (1 mmol/l) and ROZ (50 μmol/l) (n = 8–12) and (B); dose-dependent effect of ROZ on palmitate-induced PI hydrolysis (n = 8-12). (C, D) PI hydrolysis and insulin release in MIN6c4 cells in response to palmitate (1 mmol/l)±ROZ at different concentrations (n = 6). (E) NO production from neuronal constitutive nitric oxide synthase (ncNOS), inducible NOS (iNOS) and total NOS as well as insulin release in response to palmitate (1 mmol/l) after 60 min incubation of freshly isolated mouse islets at 5 mmol/l glucose (5G) (n = 4). (F) Effect of the NOS inhibitor L-NAME on insulin release induced by palmitate (1 mmol/l) in the presence of 5 mmol/l glucose (n = 8). (G) Effects of palmitate±ROZ or diazoxide on insulin release from freshly isolated mouse islets incubated at low (1 mmol/l) or high (20 mmol/l) glucose for 60 min. The concentrations of the different test agent were; palmitate (1 mmol/l), ROZ (1 μmol/l), diazoxide (dz) (250 μmol/l) (n = 8-12). Values are mean±s.e.m for. ** p<0.01; *** p<0.001.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2366067&req=5

pone-0002182-g001: Short-time effects of palmitate and rosiglitazone (ROZ) on phosphatidyl inositol (PI) hydrolysis, in HEK293 and MIN6c4 cells, insulin release in MIN6c4 cells as well as NO production and insulin release in isolated islets.(A) PI hydrolysis in nontransfected and GPR40-transfected HEK293 cells in response to palmitate (1 mmol/l) and ROZ (50 μmol/l) (n = 8–12) and (B); dose-dependent effect of ROZ on palmitate-induced PI hydrolysis (n = 8-12). (C, D) PI hydrolysis and insulin release in MIN6c4 cells in response to palmitate (1 mmol/l)±ROZ at different concentrations (n = 6). (E) NO production from neuronal constitutive nitric oxide synthase (ncNOS), inducible NOS (iNOS) and total NOS as well as insulin release in response to palmitate (1 mmol/l) after 60 min incubation of freshly isolated mouse islets at 5 mmol/l glucose (5G) (n = 4). (F) Effect of the NOS inhibitor L-NAME on insulin release induced by palmitate (1 mmol/l) in the presence of 5 mmol/l glucose (n = 8). (G) Effects of palmitate±ROZ or diazoxide on insulin release from freshly isolated mouse islets incubated at low (1 mmol/l) or high (20 mmol/l) glucose for 60 min. The concentrations of the different test agent were; palmitate (1 mmol/l), ROZ (1 μmol/l), diazoxide (dz) (250 μmol/l) (n = 8-12). Values are mean±s.e.m for. ** p<0.01; *** p<0.001.
Mentions: We first tested the acute action-interaction of palmitate in relation to ROZ on PI hydrolysis in HEK293 cells transiently expressed with mouse GPR40. HEK293 cells do not express endogenous GPR40 [21] and is well suited to explore the immediate response to GPR40 ligands after transient expression of the receptor. Fig. 1A shows that PI hydrolysis after 30 min incubation of GPR40-transfected HEK293 cells in presence of 1 mmol/l palmitate is highly increased compared with nontransfected controls and that ROZ by itself has a significant agonistic action. Fig. 1B, on the other hand, shows that ROZ has an inhibitory action on the palmitate-stimulated PI hydrolysis in transfected cells.

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