The molecular mechanism of the induction of the low density lipoprotein receptor by chenodeoxycholic acid in cultured human cells

In a cultured human hepatoblastoma cell line, Hep G2, chenodeoxycholic acid (CDCA) induced LDL receptor mRNA levels approximately 4 fold and mRNA levels for HMG-CoA reductase and HMG-CoA synthase two fold. In contrast, the mRNA levels for mevalonate kinase, farnesyl pyrophosphate synthase and squalene synthase were not changed significantly. The pattern of the induction of the sterol-sensitive genes was similar to the induction by N-acetyl-leucyl-leucyl-norleucinal (ALLN), an SREBP degradation inhibitor, suggesting that CDCA may increase mature SREBPs. CDCA could inhibit the 25-hydroxycholesterol mediated inactivation of SREBP without affecting mRNA levels of SREBPs. These results suggest that CDCA can affect sterol metabolism by a novel mechanism involving the inhibition of the oxysterol-mediated inactivation of SREBP.