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Role of lipid peroxidation and PPAR-δ in amplifying glucose-stimulated insulin secretion.

Cohen G, Riahi Y, Shamni O, Guichardant M, Chatgilialoglu C, Ferreri C, Kaiser N, Sasson S - Diabetes (2011)

Bottom Line: The latter mimicked the GSIS-amplifying effect of high glucose preexposure and of the PPAR-δ agonist GW501516 in INS-1E cells and isolated rat islets.Cytotoxic effects of 4-HNE were observed only above the physiologically effective concentration range.This molecule is an endogenous ligand for PPAR-δ, which amplifies insulin secretion in β-cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Institute for Drug Research, Hebrew University, Jerusalem, Israel.

ABSTRACT

Objective: Previous studies show that polyunsaturated fatty acids (PUFAs) increase the insulin secretory capacity of pancreatic β-cells. We aimed at identifying PUFA-derived mediators and their cellular targets that are involved in the amplification of insulin release from β-cells preexposed to high glucose levels.

Research design and methods: The content of fatty acids in phospholipids of INS-1E β-cells was determined by lipidomics analysis. High-performance liquid chromatography was used to identify peroxidation products in β-cell cultures. Static and dynamic glucose-stimulated insulin secretion (GSIS) assays were performed on isolated rat islets and/or INS-1E cells. The function of peroxisome proliferator-activated receptor-δ (PPAR-δ) in regulating insulin secretion was investigated using pharmacological agents and gene expression manipulations.

Results: High glucose activated cPLA(2) and, subsequently, the hydrolysis of arachidonic and linoleic acid (AA and LA, respectively) from phospholipids in INS-1E cells. Glucose also increased the level of reactive oxygen species, which promoted the peroxidation of these PUFAs to generate 4-hydroxy-2E-nonenal (4-HNE). The latter mimicked the GSIS-amplifying effect of high glucose preexposure and of the PPAR-δ agonist GW501516 in INS-1E cells and isolated rat islets. These effects were blocked with GSK0660, a selective PPAR-δ antagonist, and the antioxidant N-acetylcysteine or by silencing PPAR-δ expression. High glucose, 4-HNE, and GW501516 also induced luciferase expression in a PPAR-δ-mediated transactivation assay. Cytotoxic effects of 4-HNE were observed only above the physiologically effective concentration range.

Conclusions: Elevated glucose levels augment the release of AA and LA from phospholipids and their peroxidation to 4-HNE in β-cells. This molecule is an endogenous ligand for PPAR-δ, which amplifies insulin secretion in β-cells.

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4-HNE mimics high glucose amplification of insulin secretion. A: Rat islets and INS-1E cells were incubated with RPMI-1640 medium containing the indicated glucose levels in the absence or presence of 1 μmol/L GSK0660 for 48 and 24 h, respectively. GSIS was evaluated by 1-h static incubations at 3.3 mmol/L glucose (white bars), followed by a 1-h incubation at 16.7 mmol/L glucose (black bars). Insulin secretion is presented as percent of insulin content. Glc, glucose. Results are mean ± SEM, n = 3. *P < 0.05 for the difference of stimulated secretion (16.7 mmol/L glucose) compared with untreated controls maintained at 5 mmol/L glucose. #P < 0.05 for differences from the respective GSK0660-free incubation. B: Isolated rat islets and INS-1E cells were incubated for 48 or 24 h, respectively, in standard RPMI-1640 medium (11 mmol/L glucose) in the absence or presence of increasing concentrations of 4-HNE. GSIS was measured as in A. The vehicle ethanol, at a 1:1,000 dilution, did not affect GSIS in either β-cell preparation. Insulin secretion is presented as percent of insulin content. Results are mean ± SEM, n = 3. *P < 0.05 relative to the stimulated secretion of vehicle-treated controls. #P < 0.05 relative to the maximal stimulatory level. C: Rat islets and INS-1E cells were incubated for 48 and 24 h, respectively, at 5, 11, or 25 mmol/L glucose in the absence or presence of 4-HNE (15 or 1 µmol/L, respectively) followed by GSIS analysis. Results are mean ± SEM, n = 3. *P < 0.05 for difference from the respective untreated controls, exposed to the same glucose concentration.
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Figure 3: 4-HNE mimics high glucose amplification of insulin secretion. A: Rat islets and INS-1E cells were incubated with RPMI-1640 medium containing the indicated glucose levels in the absence or presence of 1 μmol/L GSK0660 for 48 and 24 h, respectively. GSIS was evaluated by 1-h static incubations at 3.3 mmol/L glucose (white bars), followed by a 1-h incubation at 16.7 mmol/L glucose (black bars). Insulin secretion is presented as percent of insulin content. Glc, glucose. Results are mean ± SEM, n = 3. *P < 0.05 for the difference of stimulated secretion (16.7 mmol/L glucose) compared with untreated controls maintained at 5 mmol/L glucose. #P < 0.05 for differences from the respective GSK0660-free incubation. B: Isolated rat islets and INS-1E cells were incubated for 48 or 24 h, respectively, in standard RPMI-1640 medium (11 mmol/L glucose) in the absence or presence of increasing concentrations of 4-HNE. GSIS was measured as in A. The vehicle ethanol, at a 1:1,000 dilution, did not affect GSIS in either β-cell preparation. Insulin secretion is presented as percent of insulin content. Results are mean ± SEM, n = 3. *P < 0.05 relative to the stimulated secretion of vehicle-treated controls. #P < 0.05 relative to the maximal stimulatory level. C: Rat islets and INS-1E cells were incubated for 48 and 24 h, respectively, at 5, 11, or 25 mmol/L glucose in the absence or presence of 4-HNE (15 or 1 µmol/L, respectively) followed by GSIS analysis. Results are mean ± SEM, n = 3. *P < 0.05 for difference from the respective untreated controls, exposed to the same glucose concentration.

Mentions: The insulin secretory capacity of isolated rat islets and INS-1E cells after preexposure to increasing glucose concentrations was determined. The preexposure periods for rat islets (48 h) and INS-1E cells (24 h) were selected empirically to allow maximal glucose-stimulated insulin secretion (GSIS) with no apparent depletion of cellular insulin content. As expected, GSIS was significantly amplified in a glucose-dependent manner in both β-cell preparations (Fig. 3A). The marked reduction of the response in the presence of the selective PPAR-δ antagonist GSK0660 indicated that this nuclear receptor plays a role in the insulin secretion amplifying action of glucose preexposure.


Role of lipid peroxidation and PPAR-δ in amplifying glucose-stimulated insulin secretion.

Cohen G, Riahi Y, Shamni O, Guichardant M, Chatgilialoglu C, Ferreri C, Kaiser N, Sasson S - Diabetes (2011)

4-HNE mimics high glucose amplification of insulin secretion. A: Rat islets and INS-1E cells were incubated with RPMI-1640 medium containing the indicated glucose levels in the absence or presence of 1 μmol/L GSK0660 for 48 and 24 h, respectively. GSIS was evaluated by 1-h static incubations at 3.3 mmol/L glucose (white bars), followed by a 1-h incubation at 16.7 mmol/L glucose (black bars). Insulin secretion is presented as percent of insulin content. Glc, glucose. Results are mean ± SEM, n = 3. *P < 0.05 for the difference of stimulated secretion (16.7 mmol/L glucose) compared with untreated controls maintained at 5 mmol/L glucose. #P < 0.05 for differences from the respective GSK0660-free incubation. B: Isolated rat islets and INS-1E cells were incubated for 48 or 24 h, respectively, in standard RPMI-1640 medium (11 mmol/L glucose) in the absence or presence of increasing concentrations of 4-HNE. GSIS was measured as in A. The vehicle ethanol, at a 1:1,000 dilution, did not affect GSIS in either β-cell preparation. Insulin secretion is presented as percent of insulin content. Results are mean ± SEM, n = 3. *P < 0.05 relative to the stimulated secretion of vehicle-treated controls. #P < 0.05 relative to the maximal stimulatory level. C: Rat islets and INS-1E cells were incubated for 48 and 24 h, respectively, at 5, 11, or 25 mmol/L glucose in the absence or presence of 4-HNE (15 or 1 µmol/L, respectively) followed by GSIS analysis. Results are mean ± SEM, n = 3. *P < 0.05 for difference from the respective untreated controls, exposed to the same glucose concentration.
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Figure 3: 4-HNE mimics high glucose amplification of insulin secretion. A: Rat islets and INS-1E cells were incubated with RPMI-1640 medium containing the indicated glucose levels in the absence or presence of 1 μmol/L GSK0660 for 48 and 24 h, respectively. GSIS was evaluated by 1-h static incubations at 3.3 mmol/L glucose (white bars), followed by a 1-h incubation at 16.7 mmol/L glucose (black bars). Insulin secretion is presented as percent of insulin content. Glc, glucose. Results are mean ± SEM, n = 3. *P < 0.05 for the difference of stimulated secretion (16.7 mmol/L glucose) compared with untreated controls maintained at 5 mmol/L glucose. #P < 0.05 for differences from the respective GSK0660-free incubation. B: Isolated rat islets and INS-1E cells were incubated for 48 or 24 h, respectively, in standard RPMI-1640 medium (11 mmol/L glucose) in the absence or presence of increasing concentrations of 4-HNE. GSIS was measured as in A. The vehicle ethanol, at a 1:1,000 dilution, did not affect GSIS in either β-cell preparation. Insulin secretion is presented as percent of insulin content. Results are mean ± SEM, n = 3. *P < 0.05 relative to the stimulated secretion of vehicle-treated controls. #P < 0.05 relative to the maximal stimulatory level. C: Rat islets and INS-1E cells were incubated for 48 and 24 h, respectively, at 5, 11, or 25 mmol/L glucose in the absence or presence of 4-HNE (15 or 1 µmol/L, respectively) followed by GSIS analysis. Results are mean ± SEM, n = 3. *P < 0.05 for difference from the respective untreated controls, exposed to the same glucose concentration.
Mentions: The insulin secretory capacity of isolated rat islets and INS-1E cells after preexposure to increasing glucose concentrations was determined. The preexposure periods for rat islets (48 h) and INS-1E cells (24 h) were selected empirically to allow maximal glucose-stimulated insulin secretion (GSIS) with no apparent depletion of cellular insulin content. As expected, GSIS was significantly amplified in a glucose-dependent manner in both β-cell preparations (Fig. 3A). The marked reduction of the response in the presence of the selective PPAR-δ antagonist GSK0660 indicated that this nuclear receptor plays a role in the insulin secretion amplifying action of glucose preexposure.

Bottom Line: The latter mimicked the GSIS-amplifying effect of high glucose preexposure and of the PPAR-δ agonist GW501516 in INS-1E cells and isolated rat islets.Cytotoxic effects of 4-HNE were observed only above the physiologically effective concentration range.This molecule is an endogenous ligand for PPAR-δ, which amplifies insulin secretion in β-cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, School of Pharmacy, Faculty of Medicine, Institute for Drug Research, Hebrew University, Jerusalem, Israel.

ABSTRACT

Objective: Previous studies show that polyunsaturated fatty acids (PUFAs) increase the insulin secretory capacity of pancreatic β-cells. We aimed at identifying PUFA-derived mediators and their cellular targets that are involved in the amplification of insulin release from β-cells preexposed to high glucose levels.

Research design and methods: The content of fatty acids in phospholipids of INS-1E β-cells was determined by lipidomics analysis. High-performance liquid chromatography was used to identify peroxidation products in β-cell cultures. Static and dynamic glucose-stimulated insulin secretion (GSIS) assays were performed on isolated rat islets and/or INS-1E cells. The function of peroxisome proliferator-activated receptor-δ (PPAR-δ) in regulating insulin secretion was investigated using pharmacological agents and gene expression manipulations.

Results: High glucose activated cPLA(2) and, subsequently, the hydrolysis of arachidonic and linoleic acid (AA and LA, respectively) from phospholipids in INS-1E cells. Glucose also increased the level of reactive oxygen species, which promoted the peroxidation of these PUFAs to generate 4-hydroxy-2E-nonenal (4-HNE). The latter mimicked the GSIS-amplifying effect of high glucose preexposure and of the PPAR-δ agonist GW501516 in INS-1E cells and isolated rat islets. These effects were blocked with GSK0660, a selective PPAR-δ antagonist, and the antioxidant N-acetylcysteine or by silencing PPAR-δ expression. High glucose, 4-HNE, and GW501516 also induced luciferase expression in a PPAR-δ-mediated transactivation assay. Cytotoxic effects of 4-HNE were observed only above the physiologically effective concentration range.

Conclusions: Elevated glucose levels augment the release of AA and LA from phospholipids and their peroxidation to 4-HNE in β-cells. This molecule is an endogenous ligand for PPAR-δ, which amplifies insulin secretion in β-cells.

Show MeSH
Related in: MedlinePlus