Biosynthesis of Sterols and Fatty Acids as Affected by Nicotinic Acid and Related Compounds

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Abstract
The incorporation of acetate-1-C14 into sterols and fatty acids was examined with liver slices from rats and chicks fed nicotinic acid (NAc), nicotinamide (NAm), isonicotinic acid (INA) or benzoic acid; these compounds were also added to liver slices in vitro. Liver from rats or chicks fed NAc or related compounds showed an increased incorporation of acetate into sterols and a decreased incorporation into fatty acids. This altered incorporation varied with the length of time during which NAc or related compounds had been fed. Incubations of rat liver slices in a buffer 0.01 to 0.10 M in NAc, NAm, or INA resulted in substantial decreases in fatty acid synthesis, the most marked depressions occurring with INA; this was accompanied at certain concentrations by increases in sterol synthesis, the more marked elevations occurring with NAc. Significant depressions in fatty acid synthesis with 0.05 M NAc, NAm or INA occurred before changes in sterol synthesis were detectable. These results, plus observations by others, suggest that a primary change in fatty acid synthesis may determine an altered partition of acetate between fatty acids and sterols.