目的:激活法尼醇X受体(FXR),胆汁酸核受体,可能与糖尿病肾病的病理生理学有关。我们探索了FXR激活在高脂饮食(HFD)喂养的小鼠中预防肾纤维化的可能作用。
方法:我们在体内和体外研究了HFD对小鼠肾脏和肾小管上皮细胞的影响,观察FXR和β-catenin通路的变化。FXR激动剂也用于缓解这种HFD诱导的作用,进一步验证了FXR与β-catenin的相互作用。
结果:饲喂60%千卡脂肪饮食20周的小鼠出现了代谢综合征的典型特征,随后的肾脏脂质积累和肾脏损伤。用FXR激动剂CDCA或GW4064治疗可降低体重,肾脏脂质积累,以及肾损伤。此外,在HFD喂养的小鼠中,FXR-激动剂治疗激活并改善了肾β-catenin信号传导.为了检查FXR是否影响β-连环蛋白信号,并参与了肾小管间质纤维化,我们探讨了FXR在ox-LDL诱导的肾小管损伤中的表达和功能。在ox-LDL刺激的大鼠近端肾小管上皮细胞(NRK-52E)中,与对照组相比,FXR蛋白降低,磷酸化(Ser675)β-catenin被ox-LDL以剂量和时间依赖性方式激活。Ox-LDL增强α-SMA和纤连蛋白表达并降低E-cadherin水平,而FXR激动作用或FXR过表达抑制纤连蛋白和α-SMA表达并恢复E-cadherin。此外,FXR激动剂治疗也降低了磷酸化(Ser675)β-连环蛋白,ox-LDL在NRK-52E细胞中诱导核易位和β-catenin介导的转录。我们表明FXR可以通过AF1结构域与β-catenin结合,并破坏核心β-连环蛋白/TCF4复合物的组装。
结论:这些实验数据表明FXR激活,通过调节β-连环蛋白信号,可能有助于减轻脂质介导的小管间质纤维化的发展。
OBJECTIVE: Activation of farnesoid X receptor (FXR), a bile acid nuclear receptor, may be implicated in the pathophysiology of diabetic nephropathy. We explored a possible role for FXR activation in preventing renal fibrosis in high fat diet (HFD)-fed mice.
METHODS: We investigated the effects of HFD on mouse kidney and renal tubular epithelial cells both in vivo and in vitro, and observed the changes of FXR and β-catenin pathway. FXR agonist was also used to alleviate this HFD-induced effect, and the interaction between FXR and β-catenin was further verified.
RESULTS: Mice were fed by a 60% kcal fat diet for 20 weeks developed the typical traits of metabolic syndrome with subsequent renal lipid accumulation and renal injury. Treatment with the FXR agonist CDCA or GW4064 decreased body weight, renal lipid accumulation, as well as renal injury. Moreover, renal β-catenin signaling was activated and improved with FXR-agonist treatment in HFD-fed mice. To examine whether FXR affected β-catenin signaling, and was involved in tubulo-interstitial fibrosis, we explored the FXR expression and function in ox-LDL induced-renal tubular injury. In rat proximal tubular epithelial cells (NRK-52E) stimulated by ox-LDL, FXR protein was decreased compared to control group, and phosphorylated (Ser675) β-catenin was activated by ox-LDL in a dose- and time-dependent manner. Ox-LDL enhanced α-SMA and fibronectin expressions and reduced E-cadherin levels, whereas FXR agonism or FXR overexpression inhibited fibronectin and α-SMA expressions and restored E-cadherin. Moreover, FXR agonist treatment also decreased phosphorylated (Ser675) β-catenin, nuclear translocation and β-catenin-mediated transcription induced by ox-LDL in NRK-52E cells. We showed that FXR could bind with β-catenin via the AF1 domain, and disrupt the assembly of the core β-catenin/TCF4 complex.
CONCLUSIONS: These experimental data suggest that FXR activation, via modulating β-catenin signaling, may contribute to attenuating the development of lipid-mediated tubulo-interstitial fibrosis.