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Journal of Lipid Research, Vol. 44, 399-407, February 2003 Hepatic overexpression of sterol carrier protein-2 inhibits VLDL production and reciprocally enhances biliary lipid secretion
* Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica, Santiago, Chile
1 To whom correspondence should be addressed. e-mail: fnervi{at}med.puc.cl We examined in vivo a role for sterol carrier protein-2 (SCP-2) in the regulation of lipid secretion across the hepatic sinusoidal and canalicular membranes. Recombinant adenovirus Ad.rSCP2 was used to overexpress SCP-2 in livers of mice. We determined plasma, hepatic, and biliary lipid concentrations; hepatic fatty acid (FA) and cholesterol synthesis; hepatic and biliary phosphatidylcholine (PC) molecular species; and VLDL triglyceride production. In Ad.rSCP2 mice, there was marked inhibition of hepatic fatty acids and cholesterol synthesis to <62% of control mice. Hepatic triglyceride contents were decreased, while cholesterol and phospholipids concentrations were elevated in Ad.rSCP2 mice. Hepatic VLDL triglyceride production fell in Ad.rSCP2 mice to 39% of control values. As expected, biliary cholesterol, phospholipids, bile acids outputs, and biliary PC hydrophobic index were significantly increased in Ad.rSCP2 mice. These studies indicate that SCP-2 overexpression in the liver markedly inhibits lipid synthesis as well as VLDL production, and alters hepatic lipid contents. In contrast, SCP-2 increased biliary lipid secretion and the proportion of hydrophobic PC molecular species in bile. These effects suggest a key regulatory role for SCP-2 in hepatic lipid metabolism and the existence of a reciprocal relationship between the fluxes of lipids across the sinusoidal and canalicular membranes.
Abbreviations: apo, apolipoprotein; bw, body weight; FA-acyl-CoA, long chain fatty acids-acyl CoA; SCP-2, sterol carrier protein-2; SCP-X, sterol carrier protein-X Supplementary key words hepatic lipid metabolism bile SCP-2
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