Metabolism of sterols of varying ring unsaturation and methylation by Caenorhabditis elegans.

The metabolism of three dietary 4,4-desmethylsterols and two 4 alpha-methylsterols was investigated in the free-living nematode Caenorhabditis elegans. Dietary cholestanol was converted mostly to lathosterol. Dietary lathosterol, 7-dehydrocholesterol, 4 alpha-methylcholest-7-enol and 4 alpha-methylcholest-8(14)-enol each remained largely unchanged. An absolute requirement for a substantial quantity of 7-dehydrocholesterol in C. elegans did not exist. C. elegans was unable to remove a 4 alpha-methyl group or introduce a double bond at C-5 and also demonstrated the lack of a delta 7-reductase. Its nutritional sterol requirement was satisfied by cholestanol, lathosterol or 7-dehydrocholesterol; growth was comparable to that obtained previously in media containing delta 5-sterols. However, the two 4 alpha-methylsterols appeared to be unsatisfactory sterol nutrients. The possible physiological importance of 4 alpha-methylsterols is discussed briefly.