Effect of nicotinic acid on plasma lipids in patients with hyperlipoproteinemia during the first week of treatment

Extended-release niacin acutely suppresses postprandial triglyceridemia

OBJECTIVE

Postprandial triglyceridemia predicts cardiovascular events. Niacin might lower postprandial triglycerides by restricting free fatty acids. Immediate-release niacin reduced postprandial triglycerides, but extended-release niacin failed to do so when dosed the night before a fat challenge. The study aims were to determine whether extended-release niacin dosed before a fat challenge suppresses postprandial triglycerides and whether postprandial triglycerides are related to free fatty acid restriction.

METHODS

A double-blinded, placebo-controlled, random-order crossover experiment was performed, in which healthy volunteers took 2 g extended-release niacin or placebo 1 hour before heavy cream. We sampled blood over 12 hours and report triglycerides and free fatty acid as means ± standard deviation for incremental area under the curve (AUC) and nadir.

RESULTS

By combining 43 fat challenges from 22 subjects, postprandial triglycerides incremental AUC was +312 ± 200 mg/dL*h on placebo versus +199 ± 200 mg/dL*h on extended-release niacin (33% decrease, P=.02). The incremental nadir for free fatty acid was -0.07 ± 0.15 mmol/L on placebo versus -0.27 ± 0.13 mmol/L on extended-release niacin (P<.0001), and free fatty acid incremental AUC decreased from +2.9 ± 1.5 mmol/L*h to +1.5 ± 1.5 mmol/L*h on extended-release niacin (20% decrease, P=.0015). The incremental AUC for triglycerides was strongly related to the post-dose decrease in free fatty acid (r = +0.58, P=.0007).

CONCLUSIONS

Given right before a fat meal, even a single dose of extended-release niacin suppresses postprandial triglyceridemia. This establishes that postprandial triglycerides suppression is an acute pharmacodynamic effect of extended-release niacin, probably the result of marked free fatty acid restriction. Further study is warranted to determine whether mealtime dosing would augment the clinical efficacy of extended-release niacin therapy.

The effects of different dose regimens of niceritrol of serum lipid concentrations in man

The lipid-lowering effects of 3 g of the nicotinic acid derivative pentaerythritoltetranicotinate (niceritrol) given either 1 g X 3 or 1.5 g X 2 have been evaluated in 18 subjects with hyperlipoproteinaemia. When 1 g niceritrol was given three times daily, the serum TG concentration fell from 3.14 +/- 0.48 to 1.86 +/- 0.18 mmol/1 (41% reduction) and the serum cholesterol concentration from 282 +/- 9 to 227 +/- 11 mg/100 ml (20% reduction). The same daily dose, given 1.5 g twice, did not significantly lower the serum TG concentration, and serum cholesterol was lowered by only 12%. Niceritrol tablets prepared with a dissolution time of 60 or 90 min had identical lipid-lowering properties. Although patients may find it practical to take niceritrol only twice daily, such a dose regimen has considerably less effect on elevated serum lipids than a thrice-daily regimen.

Nicotinic acid: an old drug with a promising future

Nicotinic acid has been used for decades to treat dyslipidaemic states. In particular its ability to raise the plasma HDL cholesterol concentration has led to an increased interest in its pharmacological potential. The clinical use of nicotinic acid is somewhat limited due to several harmless but unpleasant side effects, most notably a cutaneous flushing phenomenon. With the recent discovery of a nicotinic acid receptor, it has become possible to better understand the mechanisms underlying the metabolic and vascular effects of nicotinic acid. Based on these new insights into the action of nicotinic acid, novel strategies are currently under development to maximize the pharmacological potential of this drug. The generation of both flush-reducing co-medications of nicotinic acid and novel drugs targeting the nicotinic acid receptor will provide future therapeutic options for the treatment of dyslipidaemic disorders.

Niaspan, the prolonged release preparation of nicotinic acid (niacin), the broad-spectrum lipid drug

Niacin (nicotinic acid) is the broad-spectrum lipid drug, which lowers the concentration of all atherogenic plasma lipids/lipoproteins and at the same time raises the levels of the protective HDL (high-density lipoprotein). Niaspan is a prolonged release (PR) formulation of niacin, which has considerable advantages over both immediate release (IR) and slow release (SR) formulations of this drug. The major early side effect of IR niacin, the flush, is reduced with Niaspan. The hepatotoxic effects with SR niacin are not present with Niaspan. It is suitable for once daily prescription at bedtime. Niaspan is effective as monotherapy and in combination with other lipid-lowering drugs such as statins and fibrates. It is particularly useful for treatment of the dyslipidaemia of type 2 diabetes, where IR but not PR niacin may deteriorate the diabetic condition. Overall, niacin, now available as the well-tolerable drug formulation Niaspan, is the unique broad-spectrum lipid drug for the prevention and treatment of clinical atherosclerosis.

Lipids and atherosclerosis: clinical management of hypercholesterolaemia

Hypercholesterolaemia is a major risk factor for the development of atherosclerosis which, in turn, underlies most ischaemic heart disease (IHD). This review deals briefly with the pathophysiology of lipids in humans and follows with a discussion of current lipid-lowering therapies. In those patients with a history of myocardial infarction (MI) or unstable angina, appropriate lipid-lowering therapy has been convincingly shown to reduce not only cardiac events but also overall mortality. The advent of the HMG CoA reductase inhibitors in the late 1980s has had a revolutionary impact in the clinical management of hypercholesterolaemia, not only because of their efficacy but especially because they are well-tolerated. The use of other treatments such as the fibrates and bile acid resins are also discussed. Given the successful use of the statins, it is felt that an emergence of a different class of LDL-cholesterol lowering compound is unlikely in the near future and rather that compounds which can increase HDL-cholesterol while lowering LDL will be of greater impact. There may also be a shifting trend towards such naturally occurring compounds as plant stanols and phytoestrogens.

Hyperlipidemia and diabetes mellitus

The increased risk of coronary artery disease in subjects with diabetes mellitus can be partially explained by the lipoprotein abnormalities associated with diabetes mellitus. Hypertriglyceridemia and low levels of high-density lipoprotein are the most common lipid abnormalities. In type 1 diabetes mellitus, these abnormalities can usually be reversed with glycemic control. In contrast, in type 2 diabetes mellitus, although lipid values improve, abnormalities commonly persist even after optimal glycemic control has been achieved. Screening for dyslipidemia is recommended in subjects with diabetes mellitus. A goal of low-density lipoprotein cholesterol of less than 130 mg/dL and triglycerides lower than 200 mg/dL should be sought. Several secondary prevention trials, which included subjects with diabetes, have demonstrated the effectiveness of lowering low-density lipoprotein cholesterol in preventing death from coronary artery disease. The benefit of lowering triglycerides is less clear. Initial approaches to lowering the levels of lipids in subjects with diabetes mellitus should include glycemic control, diet, weight loss, and exercise. When goals are not met, the most common drugs used are hydroxymethylglutaryl coenzyme A reductase inhibitors or fibrates.

Acipimox in combination with low dose cholestyramine for the treatment of type II hyperlipidaemia

1. This study was designed to examine the effects of acipimox 250 mg three times daily and cholestyramine 4 g three times daily on plasma lipids and lipoproteins in 28 hypercholesterolaemic individuals in a prospective double-blind placebo controlled parallel group fashion. 2. Combined treatment with the two agents produced a mean reduction of 27% in plasma total cholesterol and a 32% fall in LDL cholesterol. Plasma triglyceride was reduced by 13% due to a 38% decrement in VLDL cholesterol. 3. In comparison treatment with cholestyramine alone resulted in a 12% fall in plasma cholesterol and a 15% fall in LDL cholesterol. In this group triglycerides and VLDL showed no significant change. 4. Studies of HDL subfraction mass showed that the addition of acipimox to resin therapy produced a mean increment of 45% in HDL2. 5. These results demonstrate the effectiveness of such a well tolerated low dosage combination therapy.

Treatment of diet-resistant polygenic hypercholesterolaemic patients with a new nicotinate derivative; in vivo and in vitro low density lipoprotein metabolic studies

Six patients (four women and two men) with mild to moderate hypercholesterolemia, but with no clinical evidence of the disease being monogenic familial hypercholesterolaemia and who, over the previous 3 months on a rigidly controlled hypolipidaemic diet therapy, showed no reduction in plasma cholesterol levels, were recruited into a study to assess the metabolic effects of Pirozadil, a new nicotinic acid derivative. After a 3 month treatment period, a significant reduction in plasma cholesterol from 299.8 +/- 31.2 mg/dl (mean +/- SD) to 256.8 +/- 18.1 mg/dl (P less than 0.02) and Low Density Lipoprotein (LDL) cholesterol from 211.7 +/- 44.9 mg/dl to 168.8 +/- 19.0 mg/dl (P less than 0.05) was observed. Although there was a trend toward decreased plasma and Very Low Density Lipoprotein (VLDL) triglyceride, the differences did not reach statistical significant. High Density Lipoprotein (HDL) cholesterol was unchanged. The drug was well tolerated with no side effects noted. To assess the mode of action, autologous125I-labelled LDL was injected and apoprotein B (apo B) kinetic parameters were measured; production rate (PR) and fractional catabolic rate (FCR). An in vitro measurement of the in vivo catabolism (LDL-apo B receptor activity in freshly isolated lymphocytes) was also measured pre- and post-treatment. The pharmacological intervention resulted in a significant decrease of 19.9% in PR from 10.5 +/- 1.81 mg/kg/d to 8.41 +/- 1.13 mg/kg/d (P less than 0.05) while the FCR remained relatively unchanged (0.260 +/- 0.042 vs 0.248 +/- 0.040 pools/d) as did the LDL receptor activity (78.2 +/- 20.9 vs 69.3 +/- 21.4 ng LDL/mg cell protein/hr).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical, biochemical, and genetic features in familial disorders of high density lipoprotein deficiency

This review assesses current knowledge of the clinical, genetic, and biochemical features of familial high density lipoprotein (HDL) deficiency syndromes. The focus is on HDL deficiency states occurring in the absence of severe hypertriglyceridemia or lecithin/cholesterol acyltransferase deficiency. Specific entities falling within this category include Tangier disease, familial HDL deficiency with planar xanthomas, familial apolipoprotein A-I and C-III deficiency (formerly known as apolipoprotein A-I absence), familial deficiency of apolipoprotein A-I and C-III, fish-eye disease, familial hypoalphalipoproteinemia, and apolipoprotein A-I variants (apo A-I Milano, apo A-I Marburg, apo A-I Giessen, and apo A-I Munster 1-3). Diffuse corneal opacification and premature coronary artery disease are common features in many of these kindreds. No striking clinical abnormalities have been noted in patients with currently known apolipoprotein A-I variants, possibly because these subjects are heterozygotes for their respective defects. The HDL deficiency in many of these disorders has been associated with abnormalities or deficiencies of apolipoprotein A-I. Further research will undoubtedly define the defects in all the disorders that have been described, uncover new mutations, as well as provide additional insights into the precise relationship between HDL deficiency and atherosclerosis.

Experimental studies on the hypolipidemic activity of chloridarol

The efficacy of chloridarol (2-benzofuryl-p-chlorophenyl carbinol) as hypolipidemic agent was evaluated in rats and rabbits. In normolipidemic rats chloridarol, at doses ranging from 50 to 200 mg/kg/day, decreased plasma triglycerides without affecting cholesterolemia and fast- or norepinephrine-induced lipolysis. The drug proved effective in reducing fructose-induced hypertriglyceridemia and dietary hypercholesterolemia in rats; in the latter model chloridarol significantly raised both the HDL cholesterol and the HDL/VLDL + LDL cholesterol ratio. In hyperlipidemic rabbits the drug had no effect on plasma cholesterol, but it lowered triglyceridemia. The action of chloridarol on rat liver ultrastructure was also investigated. Treatment for one month induced peroxisome proliferation, less marked, however, than that elicited by clofibrate; after a prolonged chloridarol treatment (9 months), this effect had almost completely disappeared and the ultrastructure of the hepatocytes was close to that of controls.

Familial type II hyperlipoproteinemia with coronary heart disease: effect of diet-colestipol-nicotinic acid treatment

Heterozygous familial type II hyperlipoproteinemia (F type II) is primarily manifested in hypercholesterolemia (due to low density lipoprotein-cholesterol [LDL-C] elevation) and premature coronary heart disease (CHD). We studied sequentially the effects of low cholesterol-low saturated fat-low simple carbohydrate diet; diet and colestipol, 30 g/day; and diet, colestipol, plus nicotinic acid (NA) 3 to 7 g/day on plasma cholesterol (Ch), LDL-C, triglyceride (TG), high density lipoprotein-cholesterol (HDL-C) and angiographically documented coronary arterial lesions of 32 F type II patients. Effective control of F type II resulted in arresting the progression of angiographically demonstrated coronary arterial lesions.

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.

Nocturnal inhibition of lipolysis in man by nicotinic acid and derivatives

The effect of nicotinic acid and several derivatives on the nocturnal level of free fatty acids was studied in 12 healthy young women and men. Free fatty acids are an important precursor of plasma triglycerides and their concentration is highest at night. The drugs used were nictinic acid, beta-pyridyl-carbinol, mesoinositol hexanicotinate and xantinol nicotinate. The highest plasma nicotinic acid level was observed with beta-pyridyl-carbinol, but significant reduction in free fatty acids during the entire night was only achieved with inositolhexanicotinate and xantinol nicotinate. There was no correlation between the plasm levels of free fatty acids and nicotinic acid at any sampling time. If prolonged reduction in free fatty acid concentration is desired in the therapy of hyperlipidemias, the inositol and xantinol esters of nicotinic acid appear to be superior to the other preparations.

Pharmacological profile of BR-931, a new hypolipidemic agent that increases high-density lipoproteins

BR-931 [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio-(N-beta-hydroxyethyl)-acetamide], a new hypolipidemic agent of low toxicity, was evaluated in several tests of lipolysis and hyperlipidemia in rats, and in the cholesterol-induced atherosclerosis in rabbits. Significant hypolipidemic activity was observed in rats with doses of the agent at 12.5--50 mg/kg. In the Triton-induced hyperlipidemia, 50 mg BR-931 per kg was equieffective as 200 mg of clofibrate (CPIB) per kg. In contrast with CPIB, BR-931 exerted a powerful antilipolytic activity against epinephrine, ACTH, nicotine and cold exposure. BR-931 was particularly effective in diet-induced hyperlipidemias. Ethanol lipemia was totally prevented by the agent at 100 mg/kg. With Nath's diet, doses as low as 25 mg/kg significantly reduced hypercholesterolemia and hypertriglyceridemia. In these last two tests, the distribution of lipoprotein cholesterol was also determined. CPIB did not affect HDL cholesterol levels that had been decreased by the diets; in contrast, BR-931, already at doses of 50 mg/kg, brought the HDL/total cholesterol ratio back toward normal. A significant HDL cholesterol increase, together with some reduction of atheromatosis, was also observed in cholesterol-fed rabbits. BR-931, a potent inducer of liver peroxisones and of mitochondrial carmitine acetyltransferase, appears to be a hypolipidemic agent of high efficacy and low toxicity for the clinical treatment of hyperlipidemias and atherosclerosis.

Importance of apolipoproteins in lipid metabolism

Lipids, which serve as a source of energy and are an important constituent of cell membrane structure, are readily stored in the body. By definition they are insoluble in water. Specific proteins called apolipoproteins interact with lipids to form soluble lipid-protein complexes called lipoproteins. It is in this form that the major lipids--cholesterol, triglyceride and phospholipid--circulate in plasma. Unesterified fatty acids, another major lipid group, are bound to albumin in the circulation. The plasma lipoproteins are complex macromolecules composed of lipids, apolipoproteins and carbohydrates. The relative proportions of these components differ markedly between lipoprotein classes. Hyperlipidemia is a term used for increased concentrations of plasma cholesterol and/or triglycerides. Any one plasma lipid is present in several types of lipoproteins. Thus, hyperlipidemia implies the presence of hyperlipoproteinemia. The latter has important therapeutic implications. Most of the recent attempts at classification have been directed at the lipoprotein level of plasma lipid organization. Decreased concentrations of lipids in plasma can be achieved by altering the rates of metabolism of lipoproteins. Decrease in lipoprotein synthesis, increased catabolism or impaired release from cells into the blood stream may all result in a decrease of plasma lipids. Drugs which affect one or more of these factors are used to treat hyperlipoproteinemia. In order to elucidate the mechanism of action of hypolipidemic drugs it is necessary to understand the lipoprotein defect at the molecular level. This requires a more detailed knowledge of lipoprotein metabolism than is presently available for most of the hyperlipoproteinemias. This paper will review some of the generally accepted properties of the plasma lipoproteins, describe some difficulties which hamper the understanding of lipoprotein metabolism, and identify possible mechanisms by which drugs may affect lipoprotein metabolism.

[Drug treatment of primary hyperlipoproteinemia (author's transl)]

Cardiovascular disease has become the major cause of death in the Western countries. There is strong evidence that elevations of serum lipids contribute to the pathogenesis of premature atherosclerosis. The classification of the hyperlipoproteinemias has been most beneficial as a guide to development of dietary and pharmacological regimens for lowering serum lipid concentrations. The results of dietary and drug prevention trials are discussed. Insight into the mechanisms involved in lipoprotein metabolism as well as the mode of action and of side-effects of hypolipidemic drugs is reviewed. Using present knowledge of heart disease research, it is reasonable to suggest dietary and drug treatments for the high risk patient.

Potentiation of ethanol fatty liver in rats by chronic administration of nicotinic acid

Two groups of rats were fed isocalorically on alcohol and control semi-liquid diet for 28 days; two other groups had the same diets except for supplementation with nicotinic acid at 50 mg/100 ml of diet, Blood ethanol levels were unaffected by nicotinic acid administration, even though nicotinic acid was well absorbed and stored in the liver. Lipid analyses of liver and plasma after 28 days revealed that nicotinic acid, per se, stimulated fatty infiltration of the liver and this effect was potentiated when given in conjunction with ethanol.

Clofibrate-induced low density liporotein elevation. Therapeutic implications and treatment by colestipol resin

Plasma lipid and lipoprotein responses to clofibrate were assessed in fifteen hypertriglyceridemic patients for the purpose of ascertaining low-density lipoprotein (LDL) changes. Subjects were grouped into either Type IV (11) or IIB (4) subgroups according to initial LDL level. Clofibrate was without effect on LDL in the IIB group, but consistent, often large, elevations were noted in Type IV cases (mean increase, 37.6%, P less than 0.001). In the IIB subgroup, addition of the bile-acid sequestrant, colestipol, lowered LDL (27.8%, P less 0.02) and total cholesterol (21.3%, P less 0.01) below pre-treatment values. In the Type IV subgroup, LDL fell to 19.5% above baseline (P great than 0.05). Significant LDL elevations induced by clofibrate in three of six subjects were restored to initial levels. In both groups, triglycerides and very-low density lipoproteins (VLDL) were not affected. The efficacy of colestipol in reducing LDL levels, expressed as either absolute or percentage reductions, increased as a function of increasing post-clofibrate LDL concentration (r = 0.84, P less than 0.001). In these subjects the level of LDL after treatment with clofibrate depended upon their LDL level prior to drug therapy, the effect of clofibrate on this level, and lipoprotein phenotype. Thus colestipol was most effective in IIB subjects, Type IV subjects with the lowest baseline VLDL and hence reciprocally highest LDL, and Type IV individuals who exhibited the largest LDL induction by clofibrate. The reported ineffectiveness of clofibrate on mortality and morbidity in patients with established coronary heart disease might be related to elevations and infrequent reductions of LDL. From the perspective of lipoprotein lowering, the combination with colestipol appears more favorable.

Drug treatment of hyperlipidemia

The most frequent indication for treatment of hyperlipidemia is for prevention of arteriosclerosis, a suspected but unproved benefit. The cornerstone of treatment of primary hyperlipidemia is diet; drugs may be added to, but do not replace, diet. When a drug is used with any patient, its potential benefits and hazards must be carefully weighed for the given subject. The subjects should be carefully followed and observed for side effects. Plasma lipids should be monitored during the course of treatment. Five drugs have been approved by the U.S. Food and Drug Administration for the treatment of hyperlipidemia: cholestyramine, clofibrate, nicotinic acid, sodium dextrothyroxine and beta-sitosterol. The use, the actions and the side effects of each and of several nonapproved agents are discussed.

The effect of nicotinic acid on the metabolism of the plasma lipoproteins of rhesus monkeys

The effect of nicotinic acid was investigated in Rhesus monkeys. Subcutaneous injections of nicotinic acid lower the plasma very low density lipoprotein (VVLDL) and low density lipoprotein (HDL) concentration. The fall in LDL concentration is not accompained by any change in the lipid or protein composition of either lipoprotein. Analysis by Sephadex gel chromatography and polyacrylamide-gel electrophoresis showed that the proteins of monkey VLDL and LDL are qualitatively similar to those of human VLDL and LDL, although there are differences in the proportions of the various proteins present in the two species. Subcutaneous injections of nicotinic acid diminish the maximum incorporation of 14C from [14C]threonine into VLDL and LDL apoproteins, but have no effect on incorporation into albumin or HDL apoprotein. Peak incorporations into the apo-B and apo-C of VLDL are diminished to about equal extents by nicotinic acid. Comparison of the amount of 14C lost from apo-B of VLDL after the peak of incorporation, with that gained by apo-B of LDL during the same period, suggests that some of the circulating apo-B of LDL IS DERIVED FROM SOURCES OTHER THAN CIRCULATING VLDL.

Metabolic relationships among the plasma lipoproteins. Reciprocal changes in the concentrations of very low and low density lipoproteins in man

The changes in other plasma lipoproteins which accompany alterations in very low density lipoproteins (VLDL) were studied in 31 normal and hyperlipidemic men and women who underwent weight reduction, carbohydrate induction, or clofibrate treatment. Plasma lipids and individual lipoprotein cholesterol concentrations were measured serially during control and treatment periods. Low density lipoprotein (LDL) protein was determined by radial immunodiffusion. Oppositely directed changes in VLDL and LDL were found with each of the three metabolic perturbations. Changes in high density lipoprotein (HDL) cholesterol generally paralleled those in LDL but were less consistent. Two patients with type III hyperlipoproteinemia failed to demonstrate reciprocal increases in LDL despite more than 40% reduction in plasma glycerides or VLDL with weight reduction or clofibrate therapy. After clofibrate therapy, LDL increased in proportion to the absolute decrease in VLDL cholesterol during treatment. LDL protein changed relatively less than did LDL cholesterol. The mechanism for the interdependency of plasma VLDL and LDL concentrations over the long term is not known and may be the result of altered rates of interconversion of these lipoproteins, or to feedback inhibition by VLDL of LDL production and release.