Atshaves Barbara P, McIntosh Avery L, Martin Gregory G, Landrock Danilo, Payne H Ross, Bhuvanendran Shivaprasad, Landrock Kerstin K, Lyuksyutova Olga I, Johnson Jeffery D, Macfarlane Ronald D, Kier Ann B, Schroeder Friedhelm
Department of Physiology and Pharmacology, Texas A&M University, Texas Veterinary Medical Center, College Station, TX 77843-4466, USA.
J Lipid Res. 2009 Jul;50(7):1429-47. doi: 10.1194/jlr.M900020-JLR200. Epub 2009 Mar 16.
Although in vitro studies suggest a role for sterol carrier protein-2 (SCP-2) in cholesterol trafficking and metabolism, the physiological significance of these observations remains unclear. This issue was addressed by examining the response of mice overexpressing physiologically relevant levels of SCP-2 to a cholesterol-rich diet. While neither SCP-2 overexpression nor cholesterol-rich diet altered food consumption, increased weight gain, hepatic lipid, and bile acid accumulation were observed in wild-type mice fed the cholesterol-rich diet. SCP-2 overexpression further exacerbated hepatic lipid accumulation in cholesterol-fed females (cholesterol/cholesteryl esters) and males (cholesterol/cholesteryl esters and triacyglycerol). Primarily in female mice, hepatic cholesterol accumulation induced by SCP-2 overexpression was associated with increased levels of LDL-receptor, HDL-receptor scavenger receptor-B1 (SR-B1) (as well as PDZK1 and/or membrane-associated protein 17 kDa), SCP-2, liver fatty acid binding protein (L-FABP), and 3alpha-hydroxysteroid dehydrogenase, without alteration of other proteins involved in cholesterol uptake (caveolin), esterification (ACAT2), efflux (ATP binding cassette A-1 receptor, ABCG5/8, and apolipoprotein A1), or oxidation/transport of bile salts (cholesterol 7alpha-hydroxylase, sterol 27alpha-hydroxylase, Na(+)/taurocholate cotransporter, Oatp1a1, and Oatp1a4). The effects of SCP-2 overexpression and cholesterol-rich diet was downregulation of proteins involved in cholesterol transport (L-FABP and SR-B1), cholesterol synthesis (related to sterol regulatory element binding protein 2 and HMG-CoA reductase), and bile acid oxidation/transport (via Oapt1a1, Oatp1a4, and SCP-x). Levels of serum and hepatic bile acids were decreased in cholesterol-fed SCP-2 overexpression mice, especially in females, while the total bile acid pool was minimally affected. Taken together, these findings support an important role for SCP-2 in hepatic cholesterol homeostasis.
尽管体外研究表明固醇载体蛋白2(SCP-2)在胆固醇转运和代谢中发挥作用,但这些观察结果的生理意义仍不清楚。通过检查过表达生理相关水平SCP-2的小鼠对富含胆固醇饮食的反应来解决这个问题。虽然SCP-2过表达和富含胆固醇的饮食均未改变食物摄入量,但在喂食富含胆固醇饮食的野生型小鼠中观察到体重增加、肝脏脂质和胆汁酸积累增加。SCP-2过表达进一步加剧了喂食胆固醇的雌性小鼠(胆固醇/胆固醇酯)和雄性小鼠(胆固醇/胆固醇酯和甘油三酯)的肝脏脂质积累。主要在雌性小鼠中,SCP-2过表达诱导的肝脏胆固醇积累与低密度脂蛋白受体、高密度脂蛋白受体清道夫受体-B1(SR-B1)(以及PDZK1和/或17 kDa膜相关蛋白)、SCP-2、肝脏脂肪酸结合蛋白(L-FABP)和3α-羟基类固醇脱氢酶水平升高有关,而参与胆固醇摄取(小窝蛋白)、酯化(ACAT2)、流出(ATP结合盒A-1受体、ABCG5/8和载脂蛋白A1)或胆汁盐氧化/转运(胆固醇7α-羟化酶、固醇27α-羟化酶、Na(+)/牛磺胆酸盐共转运体、Oatp1a1和Oatp1a4)的其他蛋白质未发生改变。SCP-2过表达和富含胆固醇饮食的影响是下调参与胆固醇转运的蛋白质(L-FABP和SR-B1)、胆固醇合成(与固醇调节元件结合蛋白2和HMG-CoA还原酶相关)以及胆汁酸氧化/转运(通过Oapt1a1、Oatp1a4和SCP-x)。喂食胆固醇的SCP-2过表达小鼠的血清和肝脏胆汁酸水平降低,尤其是在雌性小鼠中,而总胆汁酸池受到的影响最小。综上所述,这些发现支持SCP-2在肝脏胆固醇稳态中起重要作用。
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