Scavenger receptor BI facilitates hepatic very low density lipoprotein production in mice

J Lipid Res. 2010 Mar;51(3):544-53. doi: 10.1194/jlr.M000844. Epub 2009 Sep 1.

Abstract

Scavenger receptor BI (SR-BI) is a selective uptake receptor for HDL cholesterol but is also involved in the catabolism of apolipoprotein (apo)B-containing lipoproteins. However, plasma levels of apoB-containing lipoproteins increase following hepatic SR-BI overexpression, suggesting that SR-BI not solely mediates their catabolism. We therefore tested the hypothesis that hepatic SR-BI impacts on VLDL production. On day 7 following adenovirus (Ad)-mediated overexpression of SR-BI, VLDL-triglyceride and VLDL-apoB production rates were significantly increased (P < 0.001), whereas VLDL production was significantly lower in SR-BI knockout mice compared with controls (P < 0.05). In mice injected with AdSR-BI, hepatic cholesterol content increased (P < 0.001), microsomal triglyceride transfer protein activity was higher (P < 0.01) and expression of sterol-regulatory element binding protein (SREBP)2 and its target genes was decreased (P < 0.01). Conversely, in SR-BI knockout mice, microsomal triglyceride transfer protein activity was lower and expression of SREBP2 target genes was increased (P < 0.01). Finally, we demonstrate in vitro in isolated primary hepatocytes as well as in vivo that cholesterol derived from HDL and taken up via SR-BI into the liver can be resecreted within VLDL. These data indicate that hepatic SR-BI expression is linked to VLDL production, and within liver, a metabolic shunt might exist that delivers HDL cholesterol, at least in part, to a pool from which cholesterol is mobilized for VLDL production. These results might have implications for HDL-based therapies against atherosclerotic cardiovascular disease, especially with SR-BI as target.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apolipoproteins B / biosynthesis
  • Carrier Proteins / metabolism
  • Cholesterol, HDL / blood
  • Cholesterol, HDL / metabolism
  • Gene Knockout Techniques
  • Humans
  • Lipoproteins, VLDL / biosynthesis*
  • Lipoproteins, VLDL / blood
  • Liver / metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Scavenger Receptors, Class B / deficiency
  • Scavenger Receptors, Class B / genetics
  • Scavenger Receptors, Class B / metabolism*
  • Triglycerides / biosynthesis

Substances

  • Apolipoproteins B
  • Carrier Proteins
  • Cholesterol, HDL
  • Lipoproteins, VLDL
  • Scarb1 protein, mouse
  • Scavenger Receptors, Class B
  • Triglycerides
  • microsomal triglyceride transfer protein