小肠吸收胆固醇的分子生物学研究进展

Molecular bidogy mechanism of cholesterol absorption in the intestine

胆固醇通过分布于十二指肠和近段空肠黏膜上皮细胞刷状缘膜的Niemann—Pick C1样蛋白1摄取，ATP结合盒G5、G8抑制小肠对胆固醇的摄取过程。进入上皮细胞的胆固醇大多数被乙酰辅酶A，胆固醇转乙酰基酶2酯化，随后通过组装形成乳糜微粒，经淋巴管进入血循环；另一部分胆固醇则以未酯化形式直接进入血循环形成高密度脂蛋白颗粒。这些过程受核受体——肝脏X受体的调控。年龄、性别、黏膜屏障和小肠传输速度也影响胆固醇的吸收。

Several proteins are important in the cholesterol absorption pathway. The Niemann-Pick C1 like 1 protein and ATP binding cassette GS/G8 are intestinal membrane gatekeepers for cholesterol influx and efflux, respectively. The majority of ingested cholesterol is esterified to cholesteryl easter by acyl coenzyme A, cholesterol acyl transferase, and then assembled into chylomicrons prior to its excretion into the plasma circulation through lymphatics. The remaining unesterified cholesterol is excreted directly into the plasma circulation by intestinal ATP binding cassette A1 to form high density lipoprotein. Some steps are regulated by liver X receptors. Age, gender, the diffusion barrier and the transit time of small bowel may be the factors influencing the cholesterol absorption in the intestine.