Long-term treatment of type III hyperlipoproteinemia with clofibrate

Beta-VLDL accumulation in familial dysbetalipoproteinemia is associated with increased exchange or diffusion of chylomicron lipids to apo B-100 containing triglyceride-rich lipoproteins

To gain more insight into the accumulation of beta-very low density lipoprotein (beta-VLDL) in familial dysbetalipoproteinemia (FD), we followed the courses of the levels of retinyl palmitate (rp), alpha-tocopherol (alpha-T) and apolipoprotein (apo) B-48 in various lipoprotein fractions for up to 48 h in eight patients with FD and six normolipidemic control subjects after an oral fat load (50 g fat/m2 containing 150000 IU of rp and 5000 IU of alpha-T). Alpha-T was added because of its rapid transfer to other lipoproteins. Fasting apo B-48 concentration in FD was normal to strongly elevated, dependent on the fasting lipid concentrations. 3 h after fat loading, total apo B-48 content did not abnormally increase; while the apo B-100 content in the triglyceride-rich lipoprotein fraction remained stable. The levels of both vitamins increased considerably, especially in the remnant fraction (Sf 15-100), which in due course exclusively contained apo B-100 in most hyperlipidemic patients. This, together with the observation that peaks for rp and alpha-T were observed 3-6 h later than for apo B-48 strongly suggests that both vitamins transfer or diffuse rapidly towards the apo B-100 containing VLDL. RP is thus more a marker for this process, which also comprises chylomicron lipids, than a specific marker for chylomicrons. This process, first described here, appears decisive in the pathogenesis of FD.

Long-term effects of simvastatin in familial dysbetalipoproteinaemia

The long-term effects (66 weeks) of simvastatin (40 mg in one or two doses per day), an inhibitor of HMG CoA-reductase, were evaluated in 12 patients with familial dysbetalipoproteinaemia (type III hyperlipoproteinaemia). Simvastatin had a persistent hypolipidaemic effect; the mean reduction in serum cholesterol was 36-51%, and the mean reduction in serum triglycerides was 32-55%. The decrease in serum lipids was caused by a decline in VLDL-cholesterol and LDL-cholesterol levels; the mean ratio between VLDL-cholesterol and serum triglycerides decreased significantly from 1.06 to 0.73. There was no significant difference between the once-a-day and twice-a-day regimens. Simvastatin was well tolerated; no serious side-effects were observed. These data demonstrate the usefulness of simvastatin in the therapy of familial dysbetalipoproteinaemia.

Two hypolipidemic peroxisome proliferators increase the number of lamellar bodies in alveolar cells type II of the rat lung

Male rats treated with either clofibrate or nafenopin, two peroxisome proliferating compounds with potent hypolipidemic properties, show identical structural changes in their lungs. In both cases, two types of lung cells were affected by these agents: (i) the alveolar epithelial cells type II and (ii) the intraalveolar macrophages. These lung cells are known to be involved in the metabolism of the pulmonary surfactant which serves to reduce the surface tension within alveoli. The size of the alveolar cells type II was conspicuously increased in the treated lungs. Compared to controls, intraalveolar macrophages apparently were slightly more numerous. Their enlarged cytoplasm was strongly vacuolated. The osmiophilic lamellar bodies within alveolar cells type II represent the intracellular presecretory pulmonary surfactant. Their number per individual alveolar cell type II was estimated by means of light microscopic morphometry on Epon-embedded semithin sections. Compared to control lungs, the number was increased by about 30% in rats treated with clofibrate (11.4 +/- 0.5 lamellar inclusions in the control cells; P less than 0.001). The increase in the number of lamellar bodies per type II cell was close to 60% in animals fed the nafenopin diet. In contrast the frequency of alveolar cells type II, estimated per area of lung tissue, remained unchanged. These results demonstrate that clofibrate and nafenopin, two drugs with hypolipidemic properties, cause identical structural changes in the rodent lung. It is concluded from these data that (i) the morphological changes observed in the surfactant metabolizing cells represent a specific action of hypolipidemic agents at the lungs and (ii) hypolipidemic peroxisome proliferators influence the metabolism of the pulmonary surfactant.

Modification of surfactant metabolizing cells in rat lung by clofibrate, a hypolipidemic peroxisome proliferating agent. Evidence to suggest that clofibrate influences pulmonary surfactant metabolism

The influence of clofibrate (ethyl-alpha-p-chlorophenoxy-isobutyrate), a hypolipidemic peroxisome proliferating agent, has been tested on the lungs of adult male rats. Drug administration for 7 days caused structural changes in two types of lung cells, both of which are involved in the metabolism of the pulmonary surfactant. By light microscopy the prominent features were the presence of enlarged type II alveolar epithelial cells and foamy intraalveolar macrophages. Compared with controls, type II cells in treated rats apparently contained more numerous surfactant-containing lamellar bodies, as visualized in semi-thin sections of Epon-embedded tissue. This difference was quantified morphometrically by light microscopy: the number of lamellar bodies was estimated as the profile number per individual type II alveolar cell, transsected at its nucleus. Clofibrate administration for 7 days resulted in a significant increase in the number of the lamellar inclusions. In contrast the number of type II alveolar cells per area of lung remained unchanged. There was no evidence of atelectasis or inflammatory infiltration in the drug-treated lungs, a finding confirmed in sections of perfusion-fixed, paraffin-embedded whole lung-lobes. By electron microscopy the lamellar inclusion bodies in the type II alveolar cells in treated rats, apart from being more numerous and sometimes smaller, were morphologically identical to those in controls. The vacuolated alveolar macrophages seen in treated rats also contained various lamellar phospholipid inclusions.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein E phenotypes in hyperlipidaemic patients and their implications for treatment

Apolipoprotein E phenotypes were determined on 417 consecutive lipid clinic patients using an isoelectric focussing technique. Of the 15 patients with phenotype E2/2, 13 (3.1%) had type III hyperlipoproteinaemia and 2 obese identical twins had type V. A further 20 patients (4.8%) had similar plasma and lipoprotein lipid levels but were E2 heterozygotes (14 E3/2 and 6 E4/2). They displayed a widened pre-beta-band almost confluent with the beta-band rather than the broad beta-band shown in classical E2/2 type III patients. In view of the similarities between these heterozygotes and the classical homozygous (E2/2) type III patients and their occurrence in the same families we suggest the nomenclature homozygous and heterozygous type III. In a subsequent comparison between 30 E2/2, 22 E3/2 and 8 E4/2 type III individuals the only significant difference in plasma and lipoprotein lipid parameters was a lower VLDL cholesterol to triglyceride ratio of 0.85 in E3/2 patients than that of 1.24 in E2/2 patients (P less than 0.01). Both homozygous and heterozygous patients showed premature ischaemic heart disease and both responded dramatically and similarly to treatment with clofibrate. These observations indicate that apo E phenotyping is worthwhile in all patients with combined hyperlipidaemia and that homozygous and heterozygous type III hyperlipoproteinaemia is not uncommon.

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.