Dipartimento di Medicina Clinica e Sperimentale, Università Degli Studi di Perugia, Perugia, Italy.
J Cell Mol Med. 2010 Jan;14(1-2):79-92. doi: 10.1111/j.1582-4934.2009.00997.x.
Atherosclerosis is the leading cause of illness and death. Therapeutic strategies aimed at reducing cholesterol plasma levels have shown efficacy in either reducing progression of atherosclerotic plaques and atherosclerosis-related mortality. The farnesoid-X-receptor (FXR) is a member of metabolic nuclear receptors (NRs) superfamily activated by bile acids. In entero-hepatic tissues, FXR functions as a bile acid sensor regulating bile acid synthesis, detoxification and excretion. In the liver FXR induces the expression of an atypical NR, the small heterodimer partner, which subsequently inhibits the activity of hepatocyte nuclear factor 4alpha repressing the transcription of cholesterol 7a-hydroxylase, the critical regulatory gene in bile acid synthesis. In the intestine FXR induces the release of fibroblast growth factor 15 (FGF15) (or FGF19 in human), which activates hepatic FGF receptor 4 (FGFR4) signalling to inhibit bile acid synthesis. In rodents, FXR activation decreases bile acid synthesis and lipogenesis and increases lipoprotein clearance, and regulates glucose homeostasis by reducing liver gluconeogenesis. FXR exerts counter-regulatory effects on macrophages, vascular smooth muscle cells and endothelial cells. FXR deficiency in mice results in a pro-atherogenetic lipoproteins profile and insulin resistance but FXR(-/-) mice fail to develop any detectable plaques on high-fat diet. Synthetic FXR agonists protect against development of aortic plaques formation in murine models characterized by pro-atherogenetic lipoprotein profile and accelerated atherosclerosis, but reduce HDL levels. Because human and mouse lipoprotein metabolism is modulated by different regulatory pathways the potential drawbacks of FXR ligands on HDL and bile acid synthesis need to addressed in relevant clinical settings.
动脉粥样硬化是导致疾病和死亡的主要原因。旨在降低胆固醇血浆水平的治疗策略已被证明在减少动脉粥样硬化斑块的进展和与动脉粥样硬化相关的死亡率方面有效。法尼醇 X 受体(FXR)是代谢核受体(NRs)超家族的成员,被胆汁酸激活。在肠肝组织中,FXR 作为胆汁酸传感器发挥作用,调节胆汁酸的合成、解毒和排泄。在肝脏中,FXR 诱导非典型 NR 小异二聚体伴侣的表达,后者抑制肝细胞核因子 4alpha 的活性,从而抑制胆固醇 7a-羟化酶的转录,胆固醇 7a-羟化酶是胆汁酸合成的关键调节基因。在肠道中,FXR 诱导成纤维细胞生长因子 15(FGF15)(或人类中的 FGF19)的释放,其激活肝 FGF 受体 4(FGFR4)信号以抑制胆汁酸合成。在啮齿动物中,FXR 激活可降低胆汁酸合成和脂肪生成,增加脂蛋白清除,并通过减少肝糖异生来调节葡萄糖稳态。FXR 对巨噬细胞、血管平滑肌细胞和内皮细胞发挥反调节作用。FXR 缺乏症在小鼠中导致促动脉粥样硬化脂蛋白谱和胰岛素抵抗,但 FXR(-/-)小鼠在高脂肪饮食下不能形成任何可检测的斑块。合成 FXR 激动剂可预防具有促动脉粥样硬化脂蛋白谱和加速动脉粥样硬化的小鼠模型中主动脉斑块形成,但会降低 HDL 水平。由于人类和小鼠脂蛋白代谢受不同调节途径调节,因此需要在相关临床环境中解决 FXR 配体对 HDL 和胆汁酸合成的潜在缺点。