高糖高脂对β细胞脂肪酸转位酶基因表达的影响

Effects of supraphysiologic glucose and palmitate on fatty acid translocase mRNA expression in pancreatic β-cells

目的观察高糖高脂对β细胞脂质含量及脂肪酸转位酶(FAT/CD36)基因表达的影响。方法体外培养NIT-1细胞,分别以5mmol/L葡萄糖(对照组,NC)、25mmol/L葡萄糖(高糖组,HG)、0.25mmol/L棕榈酸+5mmol/L葡萄糖(高脂组,HP)以及0.25mmol/L棕榈酸+25mmol/L葡萄糖(高糖高脂组,GP)培养24h后,酶法测定细胞内三酰甘油(TG)含量,放免法测定胰岛素分泌,RT-PCR检测FAT/CD36mRNA表达。结果与NC组比较,各处理组细胞内TG含量增加,而葡萄糖刺激的胰岛素分泌(GSIS)下降,以GP组变化最明显(P<0.01),且GP组与HG组和HP组间的差异也有显著性。在高糖的孵育下,HG组和GP组FAT/CD36mRNA表达显著高于NC组(P<0.01),但无论是5mmol/L还是25mmol/L葡萄糖添加棕榈酸后的各组与相应的单纯葡萄糖组比较FAT/CD36mRNA表达均无明显改变。结论在高脂的环境下,高糖可进一步促进β细胞脂质沉积、抑制GSIS;其中高糖上调FAT/CD36mRNA表达可能是其重要机制之一。

[Objective] To observe the effects of supraphysiologic levels of glucose and palmitate on the content of intracellular triglyceride and gene expression of fatty acid translocase （FAT/CD36） in pancreatic β-cells. [Methods] NIT-1 cells were exposed to 25 mmol/L glucose （HG group） and 0.25mmol/L palmitate without （HP group） or with （GP group） 25 mmol/L glucose for 24 hours in vitro, control group was provided by cells cultured at 5mmol/l glucose. Based on the colorimetric determination of glycerol produced by hydrolysis of neutral lipids, intracellular triglyceride （TG） content was determined. Meanwhile, insulin secretions were measured with radioimmunoassay and FAT/CD36mRNA levels were detected by RT-PCR. [Results] Compared with NC group, cells cultured in elevated glucose and/or palmitate showed an increased intracellular TG content and a decreased glucose-stimulated insulin secretion （GSIS）. An obvious change of TG and GSIS was observed in GP group （P 〈0.01）, and in comparison with CP group, a significant difference of TG and GSIS was apparent in HG and HP groups. FAT/CD36mRNA expression was significantly enhanced in both HG and GP groups compared with NC group （P 〈0.01）, but palmitate did not show any effect on the FAT/CD36mRNA at either 5 mmoUL or 25 mmol/L glucose. [Conclusion] Prolonged exposure of β-cells to supraphysiologic concentrations of glucose could further increase intracellular triglyceride content and inhibit GSIS in the presence of elevated palmitate levels. Enhanced FAT/CD36mRNA expression induced by high glucoses maybe one of important meehanisms.