Visión filogenética de los ácidos biliares / Phylogenic diversity of bile acids

ABSTRACT

Bile acids are the most important solutes of bile; they are essential in cholesterol degradation, solubilization and excretion; they are determinants of bile flow and secretion and their role is crucial in the intestinal absorption of lipids and lipid soluble vitamins. In amphibia and in cartilaginous fish, the 27C cholestane molecule is hydroxylated to vertebrates of a more recent evolutionary origin, the lateral chain is shortened to 24C and oxydated to cholestanoic acids. Further transformations include chemical changes in the cholestane skeleton and in the lateral chain (hydroxylations, dehydroxylations, epimerization, etc.) Inthe intestinal lumen, the saprophytic flora provides enzymes catalysing new changes that originate secondary bile acids. During entero-hepatic circulation, another variety of bile acids appear, commonly termed tertiary bile acids. A recet study of Lee R Hagey characterized bile acid composition of over 600 species of vertebrates, showing that bile acid composition of bile has been the subject of an interesting evolutionary phenomenon and that it is a chemical marker of biodiversity in vertebrates