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Insufficient TRPM5 Mediates Lipotoxicity-induced Pancreatic β-cell Dysfunction
Kai-Yuan Wang1, Shi-Mei Wu1, Zheng-Jian Yao1
1Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 211166, China.
Objective:
While the reduction of transient receptor potential channel subfamily M member 5 (TRPM5) has been reported in islet cells from type 2 diabetic (T2D) mouse models, its role in lipotoxicity-induced pancreatic β-cell dysfunction remains unclear. This study aims to study its role.
Methods:
Pancreas slices were prepared from mice subjected to a high-fat-diet (HFD) at different time points, and TRPM5 expression in the pancreatic β cells was examined using immunofluorescence staining. Glucose-stimulated insulin secretion (GSIS) defects caused by lipotoxicity were mimicked by saturated fatty acid palmitate (Palm). Primary mouse islets and mouse insulinoma MIN6 cells were treated with Palm, and the TRPM5 expression was detected using qRT-PCR and Western blotting. Palm-induced GSIS defects were measured following siRNA-based Trpm5 knockdown. The detrimental effects of Palm on primary mouse islets were also assessed after overexpressing Trpm5 via an adenovirus-derived Trpm5 (Ad-Trpm5).
Results:
HFD feeding decreased the mRNA levels and protein expression of TRPM5 in mouse pancreatic islets. Palm reduced TRPM5 protein expression in a time- and dose-dependent manner in MIN6 cells. Palm also inhibited TRPM5 expression in primary mouse islets. Knockdown of Trpm5 inhibited insulin secretion upon high glucose stimulation but had little effect on insulin biosynthesis. Overexpression of Trpm5 reversed Palm-induced GSIS defects and the production of functional maturation molecules unique to β cells.
Conclusion:
Our findings suggest that lipotoxicity inhibits TRPM5 expression in pancreatic β cells both in vivo and in vitro and, in turn, drives β-cell dysfunction.
Insights
Lipotoxicity, caused by high-fat diets, reduces TRPM5 expression in pancreatic beta cells, leading to impaired insulin secretion and beta-cell dysfunction. Restoring TRPM5 levels can reverse these harmful effects.
Area of Science:
- Endocrinology
- Cell Biology
- Metabolic Diseases
Background:
- Transient receptor potential channel subfamily M member 5 (TRPM5) reduction is observed in type 2 diabetic mouse models.
- The specific role of TRPM5 in lipotoxicity-induced pancreatic beta-cell dysfunction is not fully understood.
Purpose of the Study:
- To investigate the role of TRPM5 in pancreatic beta-cell dysfunction induced by lipotoxicity.
Main Methods:
- Examined TRPM5 expression in pancreatic islets from high-fat-diet (HFD) fed mice using immunofluorescence.
- Induced lipotoxicity in primary mouse islets and MIN6 cells using palmitate (Palm).
- Assessed TRPM5 expression via qRT-PCR and Western blotting, and measured glucose-stimulated insulin secretion (GSIS) after Trpm5 knockdown or overexpression.
Main Results:
- HFD feeding and palmitate treatment significantly decreased TRPM5 mRNA and protein levels in pancreatic islets and MIN6 cells.
- Trpm5 knockdown impaired GSIS but did not affect insulin biosynthesis.
- Trpm5 overexpression reversed palmitate-induced GSIS defects and restored beta-cell maturation markers.
Conclusions:
- Lipotoxicity inhibits TRPM5 expression in pancreatic beta cells both in vivo and in vitro.
- Reduced TRPM5 expression is a key mechanism driving lipotoxicity-induced beta-cell dysfunction.
