Observations on the cholesterol-lowering mechanism of nicotinic acid and nicotinyl alcohol tartrate

Critical role of cholesterol ester transfer protein in nicotinic acid-mediated HDL elevation in mice

Nicotinic acid is a commonly used anti-dyslipidemic agent that increases plasma levels of HDL-cholesterol and decrease triglycerides (TG), and VLDL- and LDL-cholesterol. The most well-studied effect of nicotinic acid is its ability to lower plasma free fatty acids, which has been observed in humans and many animal models. However, its ability to raise HDL in humans has not been replicated in animal models, which precludes studying the mechanism of HDL elevation. Here we studied lipid-modulating effects of nicotinic acid in mice carrying genomic DNA fragments that drive expression of various human genes in the mouse liver. Treatment with nicotinic acid reduced serum levels of HDL cholesterol in wild-type and human apolipoprotein B100 (apoB100)-transgenic mice. In contrast, nicotinic acid treatment of mice that express human cholesteryl ester transfer protein (CETP), with or without concomitant apoB100 expression, resulted in a significant increase of HDL cholesterol and reduction of TG, VLDL- and LDL-cholesterol. These data demonstrate a critical role of CETP in nicotinic acid-mediated HDL elevation, and suggest that mice carrying the human CETP gene may be useful animal models for studying the HDL-elevating effect of nicotinic acid.

Antihyperlipidemic properties of beta-pyridylcarbinol. A review of preclinical studies

The available preclinical literature on the antihyperlipidemic properties of beta-pyridylcarbinol is reviewed. Similarities between the pharmacological profiles for beta-pyridylcarbinol and nicotinic acid, and evidence for the metabolic conversion of beta-pyridylcarbinol to nicotinic acid are discussed. Several reviews discussing the antihyperlipidemic effects of beta-pyridylcarbinol (beta-PC, nicotinyl alcohol, Roniacol) and nicotinic acid (NA) have appeared during the last 15 years (1-6). However, continuing clinical interest in the ability of nicotinic acid analogs to reduce plasma lipids indicated that an update and critical evaluation of the preclinical literature on this subject would be of value in order to permit a more complete assessment of the relevance of several animal models to effects in human subjects. The literature reviewed included (a) preclinical studies of beta-PC where it was the sole compound examined; (b) comparative studies of beta-PC and NA; and (c) studies relating to the metabolism of beta-PC. The literature chosen included experiments involving fasted animals, satiated animals, and effects of Triton-induced hyperlipidemia. Data on other pharmacological properties of beta-PC and/or NA that might contribute to antihyperlipidemic efficacy (e.g., fibrinolysis, inhibition of platelet aggregation, erythrocyte membrane changes) were also included where available.

Determination of nicotinic acid in serum by high-performance liquid chromatography with fluorescence detection

A sensitive method for the determination of nicotinic acid in serum is described which employs high-performance liquid chromatography with fluorescence detection. Nicotinic acid and 2-chloronicotinic acid as an internal standard in deproteinized serum are reacted with N,N'-dicyclohexyl-O-(7-methoxycoumarin-4-yl)methylisourea in acetone to give the corresponding fluorescent 4-hydroxymethyl-7-methoxycoumarin esters. The compounds are separated by reversed-phase chromatography on LiChrosorb RP-18 with isocratic elution using aqueous acetonitrile containing a small amount of sodium 1-hexanesulphonate as a mobile phase. The detection limit of nicotinic acid in serum was 0.2 nmol/ml. The method requires only 100 microliters of serum.

Comparative evaluation of some pharmacological properties and side effects of D-glucitol hexanicotinate (sorbinicate) and nicotinic acid correlated with the plasma concentration of nicotinic acid

In rabbits kept on a diet containing 1 g/day cholesterol for 12 weeks, the nicotinic acid derivative sorbinicate displayed greater hypolipemic and antiatherogenic activity than an equidose of plain nicotinic acid at much lower and more constant plasma nicotinic acid levels. In normocholesterolemic rats, nicotinic acid given at a level of 300 mg/kg per dose for 3 weeks induced plasma FFA and triglyceride rebound and triglyceride accumulation in the liver and possibly in the heart (all parameters determined 24 h after the last dosing), whereas an equidose of sorbinicate was free from these effects, potentially the two most dangerous side effects of nicotinic acid. By modulating the bioavailability of nicotinic acid, sorbinicate maintains and in some cases enhances the pharmacological activity of the acid, avoiding at least some of its major side effects.

Serum lipid-lowering properties of 6-chloro-9-[2-(6-methyl-3-pyridyl)ethyl]-1,2,3,4-tetrahydrocarbazole-2-carboxylic acid

6-Chloro-9-[2-(6-methyl-3-pyridyl)ethyl]-1,2,3,4-tetrahydrocarbazole-2-carboxylic acid hydrochloride lowered serum cholesterol, triglyceride, phospholipid, and free fatty acid levels in normal rats. The compound appeared to have a low toxicity and to be well tolerated in mice, adult and neonatal rats, and rabbits. At hypolipidemic doses, it caused a slight hepatomegaly associated with an increase in liver phospholipid and protein content. Liver N-demethylase and catalase activities were increased by the drug treatment. This acid had no in vitro antilipolytic activity and did not affect serum desmosterol-cholesterol ratios. The results indicate that it has a mechanism of action similar to clofibrate.