Cholesterol metabolism pathways - are the intermediates more important than the products?

Every cell in vertebrates possesses the machinery to synthesise cholesterol and to metabolise it. The major route of cholesterol metabolism is conversion to bile acids. Bile acids themselves are interesting molecules being ligands to nuclear and G protein-coupled receptors, but perhaps the intermediates in the bile acid biosynthesis pathways are even more interesting and equally important. Here, we discuss the biological activity of the different intermediates generated in the various bile acid biosynthesis pathways. We put forward the hypothesis that the acidic pathway of bile acid biosynthesis has primary evolved to generate signalling molecules and its utilisation by hepatocytes provides an added bonus of producing bile acids to aid absorption of lipids in the intestine.

Automated summary

In vertebrates, every cell is capable of synthesizing and metabolizing cholesterol, with the major pathway being conversion to bile acids. The intermediates in the bile acid biosynthesis pathways are important signaling molecules and play a key role in aiding lipid absorption in the intestine. The acidic pathway of bile acid biosynthesis may have evolved primarily to generate these signaling molecules, with the production of bile acids being an added bonus for hepatocytes.