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Palmitate induces reactive oxygen species production and β-cell dysfunction by activating nicotinamide adenine
Yuichi Sato1, Shimpei Fujimoto2, Eri Mukai1
1Department of Diabetes and Clinical Nutrition Graduate School of Medicine Kyoto University Kyoto Japan.
Aims/Introduction:
Chronic hyperlipidemia impairs pancreatic β-cell function, referred to as lipotoxicity. We have reported an important role of endogenous reactive oxygen species (ROS) overproduction by activation of Src, a non-receptor tyrosine kinase, in impaired glucose-induced insulin secretion (GIIS) from diabetic rat islets. In the present study, we investigated the role of ROS production by Src signaling in palmitate-induced dysfunction of β-cells.
Materials And Methods:
After rat insulinoma INS-1D cells were exposed to 0.6 mmol/L palmitate for 24 h (palmitate exposure); GIIS, ROS production and nicotinamide adenine dinucleotide phosphate oxidase (NOX) activity were examined with or without exposure to10 μmol/L 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), a Src inhibitior, for 30 or 60 min.
Results:
Exposure to PP2 recovered impaired GIIS and decreased ROS overproduction as a result of palmitate exposure. Palmitate exposure increased activity of NOX and protein levels of NOX2, a pathological ROS source in β-cells. Palmitate exposure increased the protein level of p47 (phox) , a regulatory protein of NOX2, in membrane fraction compared with control, which was reduced by PP2. Transfection of small interfering ribonucleic acid of p47 (phox) suppressed the augmented p47 (phox) protein level in membrane fraction, decreased augmented ROS production and increased impaired GΙIS by palmitate exposure. In addition, exposure to PP2 ameliorated impaired GIIS and decreased ROS production in isolated islets of KK-A(y) mice, an obese diabetic model with hyperlipidemia.
Conclusions:
Activation of NOX through Src signaling plays an important role in ROS overproduction and impaired GΙIS caused by chronic exposure to palmitate, suggesting a lipotoxic mechanism of β-cell dysfunction of obese mice.
Insights
Src signaling activates reactive oxygen species (ROS) production, impairing pancreatic beta-cell function in obesity. Inhibiting Src signaling with PP2 restored insulin secretion and reduced ROS in palmitate-exposed cells and diabetic mouse islets.
Area of Science:
- Cell Biology
- Endocrinology
- Metabolic Syndrome
Background:
- Chronic hyperlipidemia leads to pancreatic beta-cell dysfunction (lipotoxicity).
- Endogenous reactive oxygen species (ROS) overproduction, via Src activation, impairs glucose-induced insulin secretion (GIIS).
Purpose of the Study:
- Investigate the role of Src signaling-mediated ROS production in palmitate-induced beta-cell dysfunction.
Main Methods:
- INS-1D cells and KK-A(y) mouse islets exposed to palmitate.
- Assessed GIIS, ROS production, and nicotinamide adenine dinucleotide phosphate oxidase (NOX) activity.
- Utilized a Src inhibitor (PP2) and p47(phox) siRNA.
Main Results:
- Palmitate exposure impaired GIIS and increased ROS production and NOX activity.
- Src inhibition (PP2) restored GIIS and reduced ROS.
- Palmitate increased NOX2 and membrane-bound p47(phox); PP2 and p47(phox) siRNA reversed these effects.
Conclusions:
- Src signaling activation of NOX drives ROS overproduction and beta-cell dysfunction in palmitate-exposed cells.
- This highlights a lipotoxic mechanism contributing to beta-cell dysfunction in obese mice.