Massive hypertriglyceridemia associated with atenolol.
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4 h after intravenous injection of recombinant HuTNF-alpha to fed rats, an increase in heart, diaphragm, and plasma lipoprotein lipase activity was observed. At the same time, a 40-60% decrease in enzymic activity in epididymal fat pad and kidney and 40% decrease in hepatic lipase activity in liver had occurred. Similar results were obtained 20 h after injection of recombinant HuTNF-alpha into fasted rats. Pretreatment with Indomethacin did not affect the changes in tissue lipoprotein lipase activity observed following recombinant HuTNF-alpha administration. Serum triacylglycerol concentration increased by 2- and 6-fold; 4 and 20 h after recombinant HuTNF-alpha administration. Disappearance of 14C-labeled triacylglycerol from the circulation after injection of small chylomicrons, biosynthetically labeled in their triacylglycerol and cholesterol moieties, was lower in TNF-treated than in control rats. However, the clearance rate of triacylglycerol was the same or even higher in recombinant HuTNF-alpha treated rats (assuming that 14C-labeled chylomicron triacylglycerol represents the serum triacylglycerol pool). The livers of recombinant HuTNF-alpha-treated rats and controls contained similar amounts of 14C-labeled lipids, but less [3H]cholesterol, suggesting that in recombinant HuTNF-alpha-treated rats, the liver took up chylomicron remnant particles enriched with triacylglycerol. Separation of the d less than 1.04 g/ml fraction of serum obtained from control and recombinant HuTNF-alpha treated rats by zonal ultracentrifugation revealed that in recombinant HuTNF-alpha-treated rats the lipoprotein particles were less lipolyzed than in controls. The secretion rate of [3H]triacylglycerol into the serum was determined 90 min after injection of [3H]palmitate albumin complex and Triton WR 1339. In recombinant HuTNF-alpha-treated rats, the secretion of [3H]triacylglycerol into plasma was 48% higher than in controls. It is suggested that the increase in lipoprotein lipase activity of heart and diaphragm resulted from an indirect effect of TNF. It is concluded that the increase in serum triacylglycerol in the recombinant HuTNF-alpha-treated rats is due mainly to an increased secretion of triacylglycerol by the liver. Impaired lipolysis, probably due to a fall in hepatic lipase could also contribute to the rise in plasma triacylglycerol.
One 300 mg i.p. injection of the nonionic surfactant poloxamer 407 (Pluronic F-127) produces a significant increase above control of both circulating cholesterol and triglyceride (TG) concentrations. The present study was conducted to determine the effect of poloxamer 407 (P-407) on the capacity to hydrolyze circulating TG by lipoprotein lipase (LPL) in an attempt to determine the mechanism of action of P-407. The concentration of TG in the rat following a single 300 mg i.p. injection of P-407 was marked, increasing from 84 +/- 10 to 3175 +/- 322 mg/dL at 24 hr. The maximal rate of TG accumulation (5.74 mg/dL/min) in the plasma of P-407-injected rats occurred between 2 and 4 hr post-injection. In vitro incubation of LPL with P-407 significantly inhibited enzyme activity with an inhibitory concentration at which 50% of the enzymatic activity was lost of approximately 24 microM. Concentrations of P-407 exceeding 350 microM in vitro completely inhibited LPL activity. The effects of P-407 on the enzymatic activity of LPL in post-heparin plasma obtained following a single 300 mg dose of P-407 to rats demonstrated greater than 95% suppression of LPL activity 3 hr post-injection compared with controls. Inhibition of LPL activity was greater than 90% as long as 24 hr following a single i.p. injection of P-407. However, while the heparin-releasable fraction of capillary-bound LPL was inhibited in the plasma, LPL activity significantly increased in cardiac and skeletal muscle in poloxamer-injected animals compared with sham-injected controls. Although there was no significant change in LPL activity in adipose tissue, testes, and lung resulting from P-407 treatment, LPL activity increased by 37% in myocardium, 69% in soleus, and 66% in gastrocnemius muscle in P-407-injected rats when compared with controls. Our studies would suggest that the predominant mechanism by which P-407 induced an increase in circulating TG was by a reduction in the rate at which TG was hydrolyzed due to inhibition of heparin-releasable LPL by the surfactant.
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Modifications in plasma low and high density lipoprotein (LDL and HDL) subfraction distribution, as well as the regulation of cellular LDL metabolism by hypertriglyceridemic LDL were tested before and after treatment with acipimox, a nicotinic acid derivative, in 11 type IV hyperlipidemic patients. Large, less dense LDL particles were found in plasma after acipimox treatment, reflecting compositional changes, characterized by a 25.4% increase in cholesteryl ester content and by a 46.2% reduction of triglycerides in LDL. HDL subfractions were only slightly modified, with an increase of dense, cholesteryl ester-enriched and triglyceride poor HDL3 particles. The LDL (B,E) receptor activity in humans skin fibroblasts of LDL isolated before and after treatment was also evaluated. Hypertriglyceridemic LDL proved rather inefficient in regulating receptor activity with a close to 30% reduction vs. normal LDL in the capacity to inhibit receptor-mediated uptake and degradation of 125I-LDL. Such abnormality was fully corrected after acipimox. The reported findings indicate that acipimox treatment in type IV patients, in spite of a relatively modest plasma triglyceride reduction, can markedly modify LDL distribution and composition, normalizing the defective interaction of hypertriglyceridemic LDL with the LDL (B,E) receptor.
Small (Sf 20-100) very low density lipoprotein (VLDL) particles were prepared by density gradient ultracentrifugation of plasma from normolipidemic and type IV hypertriglyceridemic post-infarction patients and healthy controls. The small VLDL separated from the plasma of severely hypertriglyceridemic post-infarction patients were found to contain twice the amount of cholesteryl esters per particle, compared with small VLDL from normolipidemic patients and healthy controls. There was a linear increase in the percentage of cholesterol that was esterified in the small VLDL with the serum VLDL triglyceride concentration (r = 0.66). When incubated for two hours with bovine lipoprotein lipase in excess and bovine albumin as a free fatty acid acceptor at one and the same triglyceride concentration in the medium, the end-product isolated by ultracentrifugation varied as a function of the serum VLDL triglyceride level. The amount of glyceride-glycerol recovered after two hours of incubation with lipoprotein lipase was 13.3 +/- 1.3% (mean +/- SEM) of the initial values and did not correlate with the VLDL triglyceride level. With rising serum VLDL triglyceride concentration, the product isolated in the low density lipoprotein (LDL) density region (1.006 less than d less than 1.063 kg/l) contained more total cholesterol and phospholipids. The linear correlation coefficients for these relations were 0.65 and 0.58 for cholesterol and phospholipids respectively. The ratio of total cholesterol to insoluble protein in the LDL density range after lipolysis rose with increasing serum VLDL triglyceride level (r = 0.68). The end-product was further characterized by density gradient ultracentrifugation of the incubate. In vitro LDL derived by lipolysis of normolipidemic small VLDL was denser than in vitro LDL of hypertriglyceridemic small VLDL. A significant relation was found between the percentage of cholesteryl esters of total cholesterol in the substrate and the relative amount of total cholesterol recovered in the LDL density fraction after lipolysis (r = 0.69). We suggest that the enrichment with cholesteryl esters of small VLDL from type IV hypertriglyceridemic patients is caused by lipid transfer from LDL and high density lipoprotein (HDL) and that the change in VLDL particle composition influences the precursor-product relationship to LDL.
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The relationship between uric acid metabolism and lipid levels was analyzed in 148 male subjects with primary gout. The subjects were divided into three groups according to their alcohol consumption: heavy drinkers, moderate drinkers, and nondrinkers or mild drinkers. There was no correlation between urinary uric acid excretion and serum triglyceride (TG) levels in the heavy group, but a marginally significant correlation was shown in the moderate group (P less than .05), and a significant correlation was observed in the nondrinker or mild group (P less than .001). This relationship in the nondrinker or mild group was also found to be significant after adjustment for BMI and age by multiple regression analysis. Serum lipoproteins were analyzed by sequential preparative ultracentrifugation in 21 patients with primary gout who neither drank alcohol nor were obese; VLDL-TG level, but not the VLDL cholesterol level, was found to be significantly correlated with 24-hour urinary uric acid excretion. These results indicate that there is a close correlation between the degree of uric acid production, as judged by 24-hour urinary uric acid excretion, and lipoprotein TG metabolism when the influence of alcohol intake is excluded.
Hypercholesterolemia (HC) is one of the primary risk factors for atherosclerosis. Patients with familial hypercholesterolemia (FH) or combined hypercholesterolemia-hypertriglycerinemia (CHH) are at risk to develop premature atherosclerosis. Animal models have revealed that diet-induced HC in vivo leads to an increased adhesion of monocytes to the endothelium of the vessel wall. Changes in the monocytes, endothelial cells, or serum components may lead to the increased monocyte adhesion that results in atherosclerotic plaque formation. In the present study, we investigated the binding of the monocyte in an in vitro system. Incubation of freshly isolated monocytes from CHH patients with cultured human umbilical vein endothelial cells (HUVEC) gave a significant 60% increase in monocyte adhesion when compared with monocytes from healthy subjects. No such increase was observed using monocytes from nontreated FH patients. These data suggest that CHH results in in vivo alterations of the monocytes that lead to an increased in vitro adhesion to HUVEC, and that an increased level of plasma triglycerides is the major determinant, since HC alone does not induce this alteration.
Late pregnancy is a unique metabolic state where there are transient increases in the concentrations of plasma triglyceride (TG), cholesterol, and apolipoprotein (apo) B. Despite the hypertriglyceridemic environment, we recently reported that there is an unusual shift in high-density lipoprotein (HDL) subclass distribution from smaller HDL subclasses to the largest, most buoyant HDL2b subclass. In the present investigation, we determined whether the subclasses of low-density lipoprotein (LDL) also change during this transient hyperlipidemic state and whether such changes were associated with plasma TG and apolipoprotein concentrations. Thirty-six Hispanic subjects at 35 to 36 weeks' gestation and at 6 weeks' postpartum were studied. At 35 to 36 weeks of gestation, plasma concentrations of TG, cholesterol, and apo B were increased (218 +/- 62, 234 +/- 48, and 130 +/- 35 mg/dL, respectively) over levels at 6 weeks' postpartum (112 +/- 69, 197 +/- 36, and 97 +/- 25 mg/dL respectively). However, lipoprotein(a) [Lp(a)] concentrations were not changed during pregnancy compared with postpartum. LDL subclass patterns (A, B, or I) were determined by nondenaturing polyacrylamide gradient gel electrophoresis in our group of 36 pregnant women. During late pregnancy, 97% of subjects were categorized as LDL subclass patterns B or I, indicating that small, dense LDL particles predominated. This predominance of small, dense LDL was associated with plasma TG concentration, where there was a significant inverse relationship (r = -.45, P < .01) between the LDL peak particle diameter and plasma TG concentration. In an apparent anomaly, there were significant increases in the concentrations of HDL cholesterol (HDL-C) and HDL2 mass, even though small, dense LDL particles predominated.(ABSTRACT TRUNCATED AT 250 WORDS)
BACKGROUND: To investigate the alterations of high-density lipoprotein (HDL) subclasses in endogenous hypertriglyceridemic subjects. METHODS: Apolipoprotein A-I contents of plasma HDL subclasses were quantitated by 2-dimensional gel electrophoresis in 236 normolipidemic subjects (including 146 males and 90 females) and 176 endogenous hypertriglyceridemic subjects (including 103 males and 73 females). RESULTS: Apolipoprotein A-I contents of small-sized pre-beta1-HDL and HDL3a were significantly higher (P < .01 and P < .01, respectively), but those of large-sized HDL2a and HDL2b were significantly lower (P < .01 and P < .01, respectively) in hypertriglyceridemic subjects versus normolipidemic subjects. Moreover, with the elevation of triglyceride levels, small-sized pre-beta1-HDL and HDL3a increased successively; however, large-sized HDL2a and HDL2b decreased successively. Males had significantly higher apolipoprotein A-I contents of small-sized pre-beta1-HDL and HDL3b (P < .05 and P < .05, respectively), but lower contents of large-sized HDL2b (P < .01) than females in both normolipidemic and hypertriglyceridemic subjects. CONCLUSIONS: The particle size of HDL shifted toward smaller size in hypertriglyceridemic subjects, especially in male subjects. Of note, the shift was more obvious with the elevation of triglyceride levels. The changes mentioned above indicate that HDL maturation might be abnormal and reverse cholesterol transport might be weakened.
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