A new framework for reverse cholesterol transport: Non-biliary contributions to reverse cholesterol transport

Figure 1 Biliary and non-biliary fecal cholesterol excretion. In this proposed model, cholesterol is effluxed from peripheral cells onto high-density lipoprotein (HDL) and then delivered to the liver or small intestine via HDL or very low density lipoprotein (VLDL)/low-density lipoprotein (LDL) following cholesterol ester transfer protein-mediated transfer. The cholesterol internalized or de novo synthesized by the liver is secreted into bile through the action of ABCG5/G8 and subsequently excreted in the feces. Alternatively, the liver secretes the cholesterol in apoB-containing lipoproteins or HDL containing apoAI or apoE, which are specifically targeted to the small intestine. After being internalized by scavenger receptor, class B, type I (SR-BI), LDL receptor (LDLR), or another lipoprotein receptor system, the cholesterol is trafficked across the enterocytes to the brush border membrane and effluxed into the intestinal lumen by ABCG5/G8 or a currently unidentified cholesterol transporter.