Effects of clofibrate, nicotinic acid and diet on the properties of the plasma lipoproteins in a subject with type III hyperlipoproteinemia

Dietary recommendations for dysbetalipoproteinemia: A need for better evidence

The increased risk of cardiovascular disease in patients with dysbetalipoproteinemia (DBL) is well documented and is associated with the dysfunctional metabolism of remnant lipoproteins. Although these patients are known to respond well to lipid-lowering medication including statins and fibrates, the best dietary approach to lower remnant lipoprotein accumulation and to prevent cardiovascular outcomes remain unclear. Indeed, current evidence is based on studies published mainly in the 1970s, which comprise small sample sizes and methodological limitations. This review aims to summarize nutritional studies performed in DBL patients to date and to discuss potential avenues in this field and future areas of research.

Long term efficacy and safety of atorvastatin in the treatment of severe type III and combined dyslipidaemia

BACKGROUND

Fibric acid derivatives and HMG-CoA reductase inhibitors are effective in combination for treating patients with familial dysbetalipoproteinaemia and severe combined dyslipidaemia, but combination therapy affects compliance and increases the risk of side effects.

AIM

To evaluate the efficacy and safety of monotherapy with atorvastatin, an HMG-CoA reductase inhibitor with superior efficacy in lowering low density lipoprotein cholesterol and triglyceride concentrations, in patients with dysbetalipoproteinaemia and severe combined dyslipidaemia.

METHODS

Atorvastatin was tested as single drug treatment in 36 patients with familial dysbetalipoproteinaemia and 23 patients with severe combined dyslipidaemia.

RESULTS

After 40 weeks of 40 mg atorvastatin treatment decreases in total cholesterol, triglycerides, and apolipoprotein B of 40%, 43%, and 41%, respectively, were observed in the combined dyslipidaemia group, and of 46%, 40%, and 43% in the dysbetalipoproteinaemic patients. Target concentrations of total cholesterol (< 5 mmol/l) were reached by 63% of the patients, and target concentrations of triglycerides (< 3.0 mmol/l) by 66%. Treatment with atorvastatin was well tolerated and no serious side effects were reported.

CONCLUSIONS

Atorvastatin is very effective as monotherapy in the treatment of familial dysbetalipoproteinaemia and severe combined dyslipidaemia.

Mode of action of fibrates

Fibrates are a class of hypolipidaemic drugs that effectively reduce plasma triglyceride and cholesterol levels, but also raise HDL cholesterol. In recent years the attention of pharmacologists and clinicians to fibrates has been renewed also in the light of a multifaceted action on plasma lipids as well as on factors modulating the thrombotic homeostasis in blood. The mechanisms of actions underlying these effects are discussed in this short review.

Lipoprotein composition changes induced by fenofibrate in dysbetalipoproteinemia type III

Fenofibrate (300 mg daily) was given to 9 subjects (7 men, 2 women) with dysbetalipoproteinemia type III. The treatment brought about important plasma level reductions in cholesterol (-35%), triglycerides (-56%), VLDL-cholesterol (-63%) and VLDL-triglycerides (-59%). The VLDL-C/TG ratio, which was 0.40 before treatment, was 0.30 after 4 weeks of fenofibrate, still suggestive of type III. LDL-C, when measured by conventional methods, was unchanged but isolation of the IDL (1.006-1.019 g/ml) fraction from the 1.006 g/ml infranatant revealed that true LDL-C levels actually increased in 6 individuals while IDL-C decreased considerably. The total HDL-C increase was mostly due to a 33% HDL3-C change. Apolipoprotein levels were considerably modified, notably apo B, C-III and E which were decreased, as well as the lipoprotein particles containing combinations of these apolipoproteins, namely LpE:B and LpC-III:B. Apo A-I was slightly modified as LpA-I: A-II particle levels increased and LpA-I decreased. There were marked compositional modifications of apo B-containing lipoproteins which corresponded to changes of the whole lipoprotein profile. Some abnormal classes of lipoproteins (e.g., beta-VLDL, dense LDL), characteristic of this disease, tended to disappear and were in some cases replaced by material of different size and density.

Effect of gemfibrozil on lipids, apoproteins, and postheparin lipolytic activities in normolipidemic subjects

The lipid lowering agent Gemfibrozil was tested in 8 normolipidemic subjects during a three-month intake. Plasma triglycerides decreased by 41% and Very Low Density Lipoprotein (VLDL) triglycerides decreased by 54%. The reduction of plasma cholesterol, less marked (by 10%), was due to a decrease of Low Density Lipoprotein by 20% while High Density Lipoprotein (HDL) increased up to 30%. The separation of HDL demonstrated that only HDL3 were increased. The determination of the apoproteins in plasma and lipoprotein fractions showed similar results with a decrease of apo B (by 20%) and an increase of apo A-I and apo A-II, mainly in the HDL3 fraction. Plasma postheparin lipolytic activities (PHLA) were not influenced by the therapy and no correlation was found between these activities and any of the plasma or lipoprotein lipids. The apo C-III/apo C-II ratio in VLDL decreased by 30%; however, no correlation was found between this ratio in plasma as well as VLDL and triglycerides. In addition, the Intra Venous Fat Tolerance Test did not demonstrate any improvement of the clearance of exogenous fat. The lipid lowering efficacy of Gemfibrozil, its collateral effects, and the possible mechanisms of action are discussed.

Fatty acyl composition of the major lipid classes of HDL2 and HDL3 of human serum

High density lipoprotein subfractions 2 and 3 were isolated from the sera of normolipidaemic males by rate zonal ultracentrifugation. The fatty acyl compositions of their major lipid classes--phospholipids, cholesteryl esters and triacylglycerols--were determined. The average chain length and degree of unsaturation of the fatty acyl components of the phospholipids and cholesteryl esters of the HDL3 subfraction were found to be significantly higher than those of the HDL2 subfraction. The triacylglycerol moieties of the HDL3 subfraction had a higher proportion of unsaturated fatty acyl components than HDL2, but there was no difference in the average chain length between the two subfractions. These results are not consistent with an equilibration of the lipid components between the two HDL subfractions, as would be expected from the results of tracer studies. A role for the fatty acyl composition of high density lipoproteins in the determination of high density lipoprotein subfraction distribution is proposed.

Effects of Acipimox on plasma lipids and biliary lipids in healthy subjects

The effects of Acipimox (5-methylpyracine-2-carboxylic acid-4-oxide, 3 X 250 mg/day) on plasma lipids, lipoproteins, and biliary lipids were studied in 14 healthy male volunteers using a double blind cross-over design. There was a significant (P less than 0.05) rise of HDL-cholesterol by 9.8%, while effects on other lipids and lipoproteins were small and insignificant (total cholesterol minus 6.5%, LDL-cholesterol minus 11.8%, free cholesterol minus 4.2%, total triglycerides plus 13.5% and phospholipids plus 3.9%). There was a significant rise of the HDL-cholesterol/LDL-cholesterol ratio by 23.6% (P less than 0.02) and of the HDL-cholesterol/total cholesterol ratio by 16% (P less than 0.05). Apolipoproteins AI, AII, and B were not significantly affected. The ratio of HDL-cholesterol/Apo AI increased significantly (P less than 0.05), and the ratio of HDL-cholesterol/Apo AII rose from 1.22 to 1.32 (P less than 0.05), while the ratio LDL-cholesterol/Apo B fell from 1.96 to 1.73. The composition of HDL and LDL, therefore, must have been altered by Acipimox. The relative cholesterol concentration in bile was significantly (P less than 0.05) increased by treatment with Acipimox, while bile acids and phospholipids were not significantly affected. The lithogenic index rose significantly by 15.1% (P less than 0.02) as calculated according to Admirand and Small, while calculations according to Hegard and Dam yielded a slight insignificant rise (P less than 0.1). The findings suggest that treatment with Acipimox might be associated with an increased risk of cholelithiasis. However, only long-term epidemiologic studies can ultimately demonstrate whether or not Acipimox increases the risk of gallstone formation.

A comparative study of the effects of acipimox and clofibrate in type III and type IV hyperlipoproteinemia

Acipimox, an analogue of nicotinic acid, is a hypolipidemic drug with antilipolytic activity. Ten patients with type III and 10 with type IV hyperlipoproteinemia participated in a comparative open cross-over study of the effect of acipimox (750 mg/day) and clofibrate (2 g/day) on lipoproteins, apoliproproteins and postheparin lipase activities during 6 weeks. During acipimox treatment 2 type III patients complained of flushing, resulting in one drop-out. In the type III patients serum cholesterol decreased 30% (P less than 0.01) during treatment with acipimox and 24% (P less than 0.01) with clofibrate, and serum triglycerides 48% (P less than 0.01) and 34% (P less than 0.01), respectively. In the type IV patients serum cholesterol remained unchanged and serum triglycerides decreased 34% (P less than 0.05) and 35% (P less than 0.01), respectively. HDL cholesterol increased during treatment with both drugs in both groups between 6 and 15% (P less than 0.05) mainly due to a rise in HDL3 cholesterol (d greater than 1.100 g/ml). LDL cholesterol increased significantly during treatment with clofibrate, but not with acipimox. There were no or slight changes in the apoproteins A and B. Postheparin lipoprotein lipase increased during clofibrate treatment and hepatic lipase decreased during acipimox treatment. We concluded that acipimox in a dose of 750 mg/day has a similar hypolipidemic effect as 2 g clofibrate daily in type III and IV hyperlipoproteinemia.

Long-term treatment of type III hyperlipoproteinemia with clofibrate

In this retrospective study we report the results of treatment with clofibrate during at least 7 years in 9 patients with severe type III hyperlipoproteinemia. Initial treatment consisted of a diet, restricted in fat and calories, because of insufficient response additional therapy with 2 g clofibrate daily was given. Serum cholesterol decreased significantly from 14.3 +/- 4.4 mmol/l (mean +/- SD), on diet therapy, to average annual values ranging from 9.0 +/- 4.9 to 7.9 +/- 2.0 and serum triglycerides decreased significantly from 5.6 +/- 1.9 to average annual values from 3.8 +/- 1.8 to 2.0 +/- 0.7, despite a slight gain in bodyweight. Serious side-effects did not occur. After several years of treatment with clofibrate the drug was withdrawn temporarily. Serum lipids increased significantly in all patients to a level, not different from that before the start of drug therapy. It is concluded that clofibrate is a strong hypolipidemic drug for the treatment of type III hyperlipoproteinemia, which does not lose efficacy even after 7 years of use.

Comparison of the effects of colestipol hydrochloride and clofibrate on plasma lipids and lipoproteins in the treatment of hypercholesterolemia

The effects of colestipol HCl resin and clofibrate on plasma lipid and lipoprotein levels were compared in 65 patients with primary hypercholesterolemia. Patients were randomly assigned to treatment with colestipol (in progressive doses of 15, 20, and 30 g/day), clofibrate (2 g/day), or placebo resin; lipoprotein levels were determined at months 0, 2, 4, 6, and 9. The colestipol group received both colestipol and clofibrate during months 7 through 9 of the study. After 6 months of treatment, mean plasma total cholesterol fell from 333 to 266 (P less than 0.01) on colestipol, and from 329 to 270 (P less than 0.05) on clofibrate. More patients responded, however, to colestipol than to clofibrate. Both drugs also produced significant reductions in LDL cholesterol levels, and clofibrate lowered plasma triglycerides as well. HDL cholesterol level did not change significantly on either medication. The placebo group showed no change in any of the parameters studied. A significant difference was not observed between the effects of 15 g/day of colestipol and those of the higher doses studies. Addition of clofibrate to colestipol did not enhance the latter's hypocholesterolemic action.

The concentration of high density lipoprotein in patients with type IV hyperlipoproteinemia and the effect of clofibrate

Lipid and lipoprotein concentrations, including high density lipoproteins (HDL) and its subfractions, were contrasted in subjects with Type IV hyperlipoproteinemia, before and after therapy with clofibrate. Very low density lipoprotein (VLDL) levels were raised, whereas both low density lipoprotein (LDL) and HDL values were reduced in the patient group. Clofibrate reversed this trend and VLDL cholesterol and protein levels fell to approximate control values. LDL and HDL cholesterol increased but remained significantly lower than in normal controls. However, LDL and HDL protein did approach control values. Of the HDL subfractions, HDL-3 was significantly reduced in the group with Type IV hyperlipoproteinemia. Clofibrate resulted in a significant increase in the HDL-2: HDL-3 cholesterol ratio, but had only a modest effect on HDL-3 concentrations. HDL-3 may be the critical HDL subfraction responsible for the inverse correlation between levels of HDL and the development of ischemic heart disease.

Structure, immunology, and cell reactivity of low density lipoprotein from umbilical vein of a newborn type II homozygote

In this report we compare the cord blood lipoproteins of a newborn boy homozygote who has low density lipoprotein (LDL) receptor-defective familial hypercholesterolemia (FH) with the lipoproteins from cord blood of normal newborns. Plasma LDL-cholesterol and apoprotein (Apo)B were 612 and 233 mg/dl (vs. 31+/-16 and 24+/-12 mg/dl, respectively, for normals, n = 21). LDL-cholesterol/ApoB ratio was 2.6 vs. 1.4+/-0.5. Levels of ApoA-I, ApoA-II, and HDL-cholesterol were similar to normal cord plasma. Thus, the lipoprotein abnormality is apparent at birth and is definitely present in LDL. Abnormalities in other lipoprotein, lipid, and in plasma apoprotein levels were not detected. On zonal ultracentrifugation, FH LDL was comprised of two populations (LDL(a) and LDL(b)), both faster floating than normal cord LDL (LDL(c)). This difference was due to the larger diameters of the particles on electron microscopy (LDL(a) = 276A+/-32 and LDL(b) = 260A+/-38 vs. LDL(c) = 237A+/-26, n = 200 each, mean+/-1 SD), and their higher contents of lipids relative to protein (86 and 82% vs. 74%, LDL(a), LDL(b), and LDL(c), respectively). More than 94% of the protein in both the FH and the normal preparations consisted of ApoB. FH LDL were more effective than control LDL in competing with (125)I-LDL (adult) for limiting amounts of anti-LDL antibodies in radioimmunoassay. FH LDL also competed more effectively for binding to LDL receptors on cultured fibroblasts at 4 degrees C, and FH LDL also delivered more cholesterol into the cells. Cells grown in lipoprotein-deficient serum contained 44+/-2 mug cholesterol/mg cell protein, incubation of cells for 18 h at 37 degrees C in 5 mug/ml FH LDL (protein) or in normal LDL raised cellular cholesterol levels to 75+/-2 and 60+/-2 mug/mg, respectively.LDL isolated from the FH patient's plasma at 6 mo of age and from his brother's plasma (a 5-yr-old boy FH homozygote) were similar to LDL isolated from normolipemic subjects in flotation properties, chemical composition, and immunochemical and cell reactivity. The fact that differences between normal cord LDL and FH cord LDL were present at birth, but that the differences between control and FH LDL were no longer present postnatally suggests that the altered immunologic and cell interactive properties of FH cord LDL were probably related to its unusually high contents of core lipids.