Effects of Nicotinic Acid and Related Compounds on Sterol Metabolism in the Chick and Rat

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Abstract
High levels of nicotinic acid (NAc), comparable to those used in human therapy, were fed to rats and chicks, and the effects compared with those resulting from nicotinamide (NAm), isonicotinic acid (INA) or benzoic acid. Nicotinic acid did not alter the blood cholesterol level of rats fed a hypercholesterolemia-inducing diet (basal plus 0.5% of cholic acid and 1% of cholesterol). The blood cholesterol level of chicks fed a cholesterol-containing diet (0.5%) was depressed by NAc and altered only slightly by NAm. Nicotinic acid and INA significantly depressed blood cholesterol levels of chicks fed a low cholesterol diet while NAm produced less significant depressions and benzoic acid was without effect. Blood cholesterol of rats fed the basal diet was depressed only by INA, while NAc significantly elevated the level. Liver pyridine nucleotide levels were markedly elevated by both NAc and NAm while INA and benzoic acid produced no alteration in either the chick or the rat. The liver fat levels of chicks were elevated by NAm and depressed by INA; INA also depressed the liver fat levels of rats. No marked changes were observed in the liver sterol levels. Nicotinic acid did not alter total sterol, bile acid or fatty acid excretion by the rat. Bile acid excretion was increased somewhat by high dietary levels of NAm or INA.