1. The effect of nicotinic acid on the metabolism of acylglycerols was investigated in human adipose tissue incubated with [U-14C]-glucose.
2. Nicotinic acid caused a 25% inhibition of the conversion of [U-14C]glucose into total lipids of adipose tissue, which was solely attributed to a decrease in the formation of the glycerideglycerol moiety of triacylglycerols. There was no effect on the conversion of [U-14C]glucose to carbon dioxide by nicotinic acid. The drug inhibited the rate of glycerol release by 50% and significantly reduced the tissue level of diacylglycerols but did not alter the tissue concentration of monoacylglycerols.
3. It is concluded that in human adipose tissue nicotinic acid inhibits both the synthesis and hydrolysis of triacylglycerols and influences the metabolism of diacylglycerols.