Pandak William M, Kakiyama Genta
Department of Internal Medicine, Virginia Commonwealth University, Richmond, VA, USA.
Department of Veterans Affairs, Richmond, VA, USA.
Liver Res. 2019 May 21;3(2):88-98. doi: 10.1016/j.livres.2019.05.001.
Over the last two decades, the prevalence of obesity, and metabolic syndromes (MS) such as non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM), have dramatically increased. Bile acids play a major role in the digestion, absorption of nutrients, and the body's redistribution of absorbed lipids as a function of their chemistry and signaling properties. As a result, a renewed interest has developed in the bile acid metabolic pathways with the challenge of gaining insight into novel treatment approaches for this rapidly growing healthcare problem. Of the two major pathways of bile acid synthesis in the liver, the foremost role of the acidic (alternative) pathway is to generate and control the levels of regulatory oxysterols that help control cellular cholesterol and lipid homeostasis. Cholesterol transport to mitochondrial sterol 27-hydroxylase (CYP27A1) by steroidogenic acute regulatory protein (StarD1), and the subsequent 7α-hydroxylation of oxysterols by oxysterol 7α-hydroxylase (CYP7B1) are the key regulatory steps of the pathway. Recent observations suggest CYP7B1 to be the ultimate controller of cellular oxysterol levels. This review discusses the acidic pathway and its contribution to lipid, cholesterol, carbohydrate, and energy homeostasis. Additionally, discussed is how the acidic pathway's dysregulation not only leads to a loss in its ability to control cellular cholesterol and lipid homeostasis, but leads to inflammatory conditions.
在过去二十年中,肥胖以及代谢综合征(如非酒精性脂肪性肝病(NAFLD)和2型糖尿病(T2DM))的患病率急剧上升。胆汁酸在消化、营养物质吸收以及身体对吸收脂质的重新分配中发挥着重要作用,这取决于它们的化学性质和信号特性。因此,人们对胆汁酸代谢途径重新产生了兴趣,试图深入了解针对这一迅速增长的医疗保健问题的新治疗方法。在肝脏中胆汁酸合成的两条主要途径中,酸性(替代)途径的首要作用是生成并控制调节性氧化甾醇的水平,这些氧化甾醇有助于控制细胞胆固醇和脂质稳态。由类固醇生成急性调节蛋白(StarD1)将胆固醇转运至线粒体甾醇27-羟化酶(CYP27A1),随后由氧化甾醇7α-羟化酶(CYP7B1)对氧化甾醇进行7α-羟化,是该途径的关键调节步骤。最近的观察表明,CYP7B1是细胞氧化甾醇水平的最终控制器。本文综述讨论了酸性途径及其对脂质、胆固醇、碳水化合物和能量稳态的贡献。此外,还讨论了酸性途径的失调如何不仅导致其控制细胞胆固醇和脂质稳态能力的丧失,还会引发炎症反应。