BACKGROUND Tacrolimus (FK506)-induced diabetes mellitus is one of the most important factors of post-transplant diabetes mellitus (PTDM). However, the detailed mechanisms underlying PTDM are still unclear. Farnesoid X receptor (FXR) regulates glycolipid metabolism. The objective of this study was to explore whether FXR is involved in the development of tacrolimus-induced diabetes mellitus. METHODS After C57BL/6J mice were treated with tacrolimus (FK506) for 3 months, the fasting blood glucose levels, body weights, renal morphological alterations, and mRNA expression levels of phosphoenolpyruvate carboxykinase (PEPCK) and glucose transporter 2 (GLUT2) among the control group, the FK506 group and the FK506 + GW4064 (a FXR agonist) group (n = 7) were measured. The intracellular location of peroxisome proliferator activated receptor γ coactivator-1α (PGC1α) and forkhead box O1 (FOXO1) was detected by immunofluorescence. Human renal cortex proximal tubule epithelial cells (HK-2) were treated with 15 μM FK506 or 4 μM FXR agonist (GW4064) for 24, 48 and 72 h, and the expression levels of FXR, gluconeogenesis and glucose uptake, representing the enzymes PEPCK and GLUT2, were detected with real-time PCR and western blot analyses. Finally, the mRNA levels of PEPCK and GLUT2 in HK-2 cells were measured after FXR was upregulated. RESULTS FK506 significantly inhibited the mRNA and protein levels of FXR at 48 h and 72 h in HK-2 cells (P < 0.05). Meanwhile, FK506 promoted gluconeogenesis and inhibited glucose uptake in HK-2 cells (P < 0.05). However, overexpression of FXR in transfected HK-2 cell lines significantly inhibited gluconeogenesis and promoted glucose uptake (P < 0.05). The FXR agonist GW4064 significantly decreased the fasting blood glucose in mice challenged with FK506 for 3 months (P < 0.05), inhibited gluconeogenesis (P < 0.05) and significantly promoted glucose uptake (P < 0.05). Immunofluorescence staining and western blot analyses further revealed that FXR activation may affect the translocation of PGC1α and FOXO1 from the nucleus to the cytoplasm. CONCLUSIONS FXR activation may mitigate tacrolimus-induced diabetes mellitus by regulating gluconeogenesis as well as glucose uptake of renal cortex proximal tubule epithelial cells in a PGC1α/FOXO1-dependent manner, which may be a potential therapeutic strategy for the prevention and treatment of PTDM.

中文翻译：

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FXR激活通过调节肾脏糖异生和葡萄糖摄取来减轻他克莫司诱导的移植后糖尿病。

背景技术他克莫司（FK506）诱导的糖尿病是移植后糖尿病（PTDM）的最重要因素之一。但是，仍然不清楚PTDM的详细机制。法尼醇X受体（FXR）调节糖脂代谢。这项研究的目的是探讨FXR是否参与他克莫司诱导的糖尿病的发展。方法用他克莫司（FK506）治疗C57BL / 6J小鼠3个月，对照组中空腹血糖，体重，肾脏形态学改变，磷酸烯醇丙酮酸羧激酶（PEPCK）和葡萄糖转运蛋白2（GLUT2）的mRNA表达水平。分别测量FK506组和FK506 + GW4064（FXR激动剂）组（n = 7）。通过免疫荧光检测过氧化物酶体增殖物激活受体γcoactivator-1α（PGC1α）和叉头盒O1（FOXO1）在细胞内的位置。用15μMFK506或4μMFXR激动剂（GW4064）处理人肾皮质近端小管上皮细胞（HK-2）24、48和72小时，FXR的表达水平，糖异生和葡萄糖摄取代表PEPCK酶实时荧光定量PCR和Western印迹分析检测GLUT2和GLUT2。最后，在上调FXR后测量HK-2细胞中PEPCK和GLUT2的mRNA水平。结果FK506显着抑制HK-2细胞在48 h和72 h FXR的mRNA和蛋白水平（P <0.05）。同时，FK506促进了HK-2细胞的糖异生并抑制了葡萄糖的摄取（P <0.05）。然而，在转染的HK-2细胞系中FXR的过表达显着抑制糖异生并促进葡萄糖摄取（P <0.05）。FXR激动剂GW4064显着降低了用FK506攻击3个月的小鼠的空腹血糖（P <0.05），抑制了糖异生（P <0.05），并显着促进了葡萄糖摄取（P <0.05）。免疫荧光染色和蛋白质印迹分析进一步表明，FXR激活可能影响PGC1α和FOXO1从细胞核到细胞质的转运。结论FXR激活可以通过依赖于PGC1α/ FOXO1的方式调节糖原异生以及肾皮质近端小管上皮细胞的葡萄糖摄取来减轻他克莫司诱导的糖尿病，这可能是预防和治疗PTDM的潜在治疗策略。