On the Mechanism of Action of Nicotinic Acid in Lowering Serum Lipids

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Abstract
Nicotinic acid does not lower serum cholesterol levels by increasing the fecal excretion of bile acids or sterols. It does not seem to function by competing for methyl groups of lipotropic factors or with glycine for the formation of bile acids. Although the ethyl ester of nicotinuric acid was found to be more readily absorbed than free nicotinuric acid, the esterified compound was found to be inactive in lowering serum lipid levels. It seems probable that nicotinuric acid is converted to nicotinic acid when it is effective in decreasing serum cholesterol levels. The precise mechanism of action of nicotinic acid has not been elucidated fully, but the bulk of the evidence supports the view that the biosynthesis of cholesterol (perhaps other lipids) is impaired by nicotinic acid administration. The possible mechanisms by which nicotinic acid causes lowering of lipid concentrations as investigated in our laboratory and by others has been reviewed.