Key Laboratory of Human Functional Genomics of Jiangsu Province, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 211166, China.
Curr Med Sci. 2024 Apr;44(2):346-354. doi: 10.1007/s11596-023-2795-5. Epub 2024 Mar 22.
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.
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).
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.
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.
虽然有报道称 2 型糖尿病（T2D）小鼠模型的胰岛细胞中瞬时受体电位通道亚家族 M 成员 5（TRPM5）减少，但它在脂毒性诱导的胰岛β细胞功能障碍中的作用尚不清楚。本研究旨在研究其作用。
从不同时间点接受高脂肪饮食（HFD）的小鼠中制备胰腺切片，并使用免疫荧光染色检查胰腺β细胞中的 TRPM5 表达。用饱和脂肪酸棕榈酸（Palm）模拟脂毒性引起的葡萄糖刺激胰岛素分泌（GSIS）缺陷。用 Palm 处理原代小鼠胰岛和小鼠胰岛素瘤 MIN6 细胞，并使用 qRT-PCR 和 Western blot 检测 TRPM5 表达。用 siRNA 敲低 Trpm5 后测量 Palm 诱导的 GSIS 缺陷。用腺病毒衍生的 Trpm5（Ad-Trpm5）过表达 Trpm5 后，还评估了 Palm 对原代小鼠胰岛的有害影响。
HFD 喂养降低了小鼠胰岛中 TRPM5 的 mRNA 水平和蛋白表达。棕榈酸在 MIN6 细胞中以时间和剂量依赖的方式降低 TRPM5 蛋白表达。棕榈酸还抑制了原代小鼠胰岛中 TRPM5 的表达。Trpm5 敲低抑制高葡萄糖刺激下的胰岛素分泌，但对胰岛素生物合成影响不大。过表达 Trpm5 逆转了 Palm 诱导的 GSIS 缺陷和β细胞特有的功能成熟分子的产生。
我们的研究结果表明，脂毒性在体内和体外均抑制胰岛β细胞中 TRPM5 的表达，并进而导致β细胞功能障碍。
