High fatty acid reduces insulin secretion in pancreatic β-cells and miR-139-5p is increased in diabetic pancreatic tissues and induces islet β-cell apoptosis. However, to date, there is no study exploring whether or not miR-139-5p is involved in high fatty acid-induced insulin secretion. In the present study, INS-1 cells were exposed to different concentrations (0.1, 0.2, and 0.4 mM) of palmitate for different time periods (12, 24, and 48 h). The expression levels of miR-139-5p and neuronal pentraxin 1 (NPTX1) were evaluated by real-time PCR and western blot analysis. The regulation of NPTX1 by miR-139-5p was examined by luciferase assay. Cell transfection was conducted using Lipo8000 or Lipofectamine RNAiMAX. Potassium or glucose-stimulated insulin secretion levels were used to verify the function of miR-139-5p or NPTX1 in insulin secretion. Insulin secretion levels were detected by radioimmunoassay. We found that miR-139-5p was increased in INS-1 cells stimulated with palmitate. In addition, miR-139-5p was also elevated in islets of high-fat diet-fed mice and db/db mice compared to those in islets of normal diet-fed mice and wild-type mice. Knockdown of miR-139-5p could reverse high fatty acid-induced insulin secretion defects in INS-1 cells. Furthermore, we demonstrated that NPTX1 is a target of miR-139-5p. miR-139-5p mediated palmitate-induced insulin secretion defects by targeting NPTX1. Moreover, palmitate treatment declined the expression of NPTX1 and the NPTX1 expression was also decreased in islets of high-fat diet-fed mice and db/db mice. Impaired NPTX1 expression is involved in fatty acid-induced insulin secretion defects. Collectively, our results illustrate that the induction of β-cell insulin secretion defects by fatty acids is mediated, at least in part, by miR-139-5p via downregulation of NPTX1 expression.

中文翻译：

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miR-139-5p 通过靶向 INS-1 细胞中的神经元五联蛋白 1 介导棕榈酸酯诱导的胰岛素分泌抑制

高脂肪酸减少胰腺β细胞中的胰岛素分泌，糖尿病胰腺组织中的miR-139-5p增加并诱导胰岛β细胞凋亡。然而，迄今为止，还没有研究探讨 miR-139-5p 是否参与高脂肪酸诱导的胰岛素分泌。在本研究中，INS-1 细胞在不同的时间段（12、24 和 48 小时）暴露于不同浓度（0.1、0.2 和 0.4 mM）的棕榈酸酯。通过实时 PCR 和蛋白质印迹分析评估 miR-139-5p 和神经元五联蛋白 1 (NPTX1) 的表达水平。通过荧光素酶测定检查了 miR-139-5p 对 NPTX1 的调节。使用 Lipo8000 或 Lipofectamine RNAiMAX 进行细胞转染。钾或葡萄糖刺激的胰岛素分泌水平用于验证 miR-139-5p 或 NPTX1 在胰岛素分泌中的功能。通过放射免疫测定法检测胰岛素分泌水平。我们发现用棕榈酸酯刺激的 INS-1 细胞中 miR-139-5p 增加。此外，与正常饮食喂养的小鼠和野生型小鼠的胰岛相比，高脂肪饮食喂养的小鼠和 db/db 小鼠的胰岛中的 miR-139-5p 也升高。敲除 miR-139-5p 可以逆转 INS-1 细胞中高脂肪酸诱导的胰岛素分泌缺陷。此外，我们证明 NPTX1 是 miR-139-5p 的靶标。miR-139-5p 通过靶向 NPTX1 介导棕榈酸诱导的胰岛素分泌缺陷。此外，棕榈酸酯处理降低了 NPTX1 的表达，并且在高脂饮食喂养的小鼠和 db/db 小鼠的胰岛中，NPTX1 的表达也降低了。NPTX1 表达受损与脂肪酸诱导的胰岛素分泌缺陷有关。总的来说，