Screening of preformed oxidised low density lipoprotein isolated by a polyanion precipitation method. Its correlation with serum triglyceride levels.

For clinical and epidemiological screening a simple and sensitive methodology was developed for detection of preformed lipid peroxides (LPO) in low density lipoprotein (LDL). For this purpose, the iodometric assay of El-Saadani et al. (J Lipid Res 1989;30:627-30) was adapted to the fraction containing LDL isolated by polyanion precipitation avoiding ultracentrifugation. This fraction also includes intermediate density lipoprotein. Stratifying 53 individuals by their serum triglyceride levels (TG) the highest quartile showed a highly significant elevation of LDL-LPO compared with the lowest one (69.2 +/- 41.2 vs 22.9 +/- 10.0 nmol mg-1 LDL-apo B, P < 0.001). LDL-LPO concentration also showed a strong correlation with TG (r = 0.73, P < 0.00001) and significant inverse correlations with high density lipoprotein cholesterol (HDL-C) and HDL3-C subfraction (r = -0.37, P < 0.01 and r = -0.38, P = 0.01, respectively). The TG/HDL-C ratio, which is closely associated with insulin resistance, was strongly correlated with LDL-LPO (r = 0.83, P < 0.00001). Significant elevations of LPO were observed in phenotypic hyperlipoproteinemias (HLP) IIb and IV (P < 0.01 and P < 0.02, respectively) and when expressing LPO in mol/mol of LDL-apo B, two- and 2.5-fold higher values were found in types IIb and IV HLP, respectively, compared with normolipidemic subjects, suggesting a more oxidative environment for apo B in both phenotypes. No variations in LPO were found in type IIa HLP. This simple assay for in vivo detection of LDL-LPO, emphasises the possible atherogenic effect of TG through their oxidative capacity and suggests the integration of LPO to the cluster of associated risk factors: high TG, low HDL-C and insulin resistance.

Significant increase of high-density lipoprotein2-cholesterol under prolonged simvastatin treatment.

In a contribution to a prolonged multicenter study 15 patients with primary hypercholesterolemia were treated with simvastatin, a competitive inhibitor of HMG-CoA reductase. The first part of the study was done in a double-blind fashion comparing the effect of this new drug with that of gemfibrozil during 12 weeks, and after this period on open-label treatment was started with the administration to all the patients of simvastatin in doses ranging from 2.5 to 40 mg q.p.m. Persistent and significant reductions (P less than 0.001) were achieved for total serum cholesterol (TC), LDL-cholesterol (LDL-C), apo B and triglycerides: by 38, 49, 44 and 33%, respectively, after 40 weeks of the open-label extension. From week 12, LDL-C levels were maintained at a cut point less than or equal to 140 mg/dl in every patient throughout the study. At week 40, cholesterol values of HDL subfractions showed a significant increase in HDL2-C (28%, P less than 0.01) and a concomitant reduction in HDL3-C (12%, P less than 0.01) in spite of a nonsignificant elevation of total HDL-C (by 6%). The HDL2-C/HDL3-C ratio rose by 47% (P less than 0.001) and the TC/HDL-C ratio was significantly reduced by 43%: from 6.1 +/- 1.2 to 3.5 +/- 0.7 (mean +/- SD, P less than 0.001). No adverse effects were detected. Our results suggest a conversion of HDL3 into HDL2, which could imply a beneficial effect of simvastatin upon the so-called reverse cholesterol transport, in addition to the striking reduction in atherogenic lipoproteins.

Evaluation of the high density lipoprotein cholesterol protective effect against atherogenesis in rabbits fed cholesterol supplemented diets.

Plasma high density lipoprotein cholesterol (HDL-C) was evaluated in 15 rabbits fed cholesterol supplemented diets to assess its protective effect on the atherogenic process. From a baseline level of 29 +/- 11 mg/dl (mean +/- SD) the maximum attained for HDL-C was twofold in only three rabbits, whereas total cholesterol (TC) increased 20 fold. Plasma TC/HDL-C ratio rose 80 fold from the baseline (2.4 +/- 0.9) and it was the best parameter that correlated with aortic cholesterol accumulation and pathological scores. Aortic TC content increased 10 fold and free cholesterol/cholesterol esters ratio decreased 20 fold. Pathological studies showed that aortic lesion scores rose from 0 to 4. It can be concluded that the high correlations obtained when TC/HDL-C ratio was plotted against both aortic cholesterol deposition and lesion scores, support the theory of the reverse cholesterol transport and the effectiveness of this index to predict the degree of the atherogenic process. On the other hand, the poor response of HDL-C in this model encourages future research using drugs to increase this parameter in order to normalize TC/HDL-C ratio and avoid lesions.

Evaluation of the high density lipoprotein cholesterol protective effect against atherogenesis in rabbits fed cholesterol supplemented diets.

Plasma high density lipoprotein cholesterol (HDL-C) was evaluated in 15 rabbits fed cholesterol supplemented diets to assess its protective effect on the atherogenic process. From a baseline level of 29 +/- 11 mg/dl (mean +/- SD) the maximum attained for HDL-C was twofold in only three rabbits, whereas total cholesterol (TC) increased 20 fold. Plasma TC/HDL-C ratio rose 80 fold from the baseline (2.4 +/- 0.9) and it was the best parameter that correlated with aortic cholesterol accumulation and pathological scores. Aortic TC content increased 10 fold and free cholesterol/cholesterol esters ratio decreased 20 fold. Pathological studies showed that aortic lesion scores rose from 0 to 4. It can be concluded that the high correlations obtained when TC/HDL-C ratio was plotted against both aortic cholesterol deposition and lesion scores, support the theory of the reverse cholesterol transport and the effectiveness of this index to predict the degree of the atherogenic process. On the other hand, the poor response of HDL-C in this model encourages future research using drugs to increase this parameter in order to normalize TC/HDL-C ratio and avoid lesions.

Effect of bezafibrate on low levels of high density lipoprotein cholesterol in normolipidemia. Study in coronary patients and their first degree relatives.

A pharmacological study was carried out in a group of 20 subjects composed of 13 coronary patients and 7 normal close relatives (first degree) who were considered at a high risk for coronary heart disease (CHD) because of their low levels of high density lipoprotein cholesterol (HDLch) (mean +/- SD: 34.1 +/- 5.2 mg/dl) and their high total cholesterol/HDLch (Tch/HDLch) ratio (mean +/- SD:6.7 +/- 1.1), despite their normal serum lipid values. With the purpose of normalizing these parameters they were submitted to a 4-month treatment with bezafibrate, a hypolipidemic agent which has a known effect in increasing HDLch and in decreasing the Tch/HDLch ratio. At the end of the study total serum cholesterol and triglycerides decreased significantly by 10 and 30%, respectively (p less than 0.01). HDL increased in its cholesterol content by 33% reaching a value of 45.4 +/- 9.8 mg/dl (mean +/- SD, p less than 0.01) as well as in its apolipoprotein A1 (Apo A1) content (13%, p less than 0.02). HDL2 subfraction also rose in cholesterol and in Apo A1: by 90 and 38%, respectively (p less than 0.01). HDL3 subfraction rised only its cholesterol content by 24% (p less than 0.01). Tch/HDLch ratio was significantly reduced (p less than 0.01) to a value of 4.6 +/- 0.9 (mean +/- SD). Total serum Apo B diminished by 14% (p less than 0.01). No adverse effects were observed during the follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Pilot study of the effect of raubasine on platelet biological activity.

A pilot study was carried out to determine the action of raubasine (ajmalicine) an alkaloid derived from Rauwolfia serpentina, on platelet biological function in 14 patients selected because they were at risk due to complications of atherosclerosis. The determinations of platelet aggregation were done ex vivo and the following substances were used as inducing agents: adenosine diphosphate (2.5 and 5.0 X 10(-6) mol/l), collagen (0.05 mg/ml), and epinephrine (adrenaline) (1.68 X 10(-4) mol/l). 12 out of the 14 patients treated showed a reduction in platelet aggregation in at least 2 of the 3 test curves. This reduction was statistically significant for collagen (p less than 0.02) and epinephrine (p less than 0.01). A statistically significant (p less than 0.05) prolongation of the latency period of aggregation produced by collagen was found in 12 out of 14 patients and a prolongation of recalcification time produced by the reduction in platelet factor 3 was found in 9 out of 14 patients. In addition to the fact that the effect of a reduction in platelet aggregation was more evident in the second wave, these results suggest that raubasine has an inhibitory action on the release reaction of the platelets. The results obtained merit further study to confirm this property of the drug.

Elevation of high density lipoprotein cholesterol (cHDL) and reduction of the total cholesterol/cHDL index in the treatment of hyperlipoproteinaemias IIb and IV with bezafibrate.

A study was carried out in 21 patients with Type IIb or Type IV hyperlipoproteinaemia to evaluate the effect of treatment with 600 mg bezafibrate per day over a period of 3 months. The results of the lipid parameters studied showed that there were significant reductions after 1 and 3-months' treatment, respectively, of 19% and 16% total cholesterol, 55% and 57% triglycerides, 19% and 15% calculated cLDL, and 55% and 58% calculated cVLDL. Over the same times, there was a significant increase in cHDL of 35% and 41%, respectively. The cT/cHDL index decreased significantly from a mean basal value of 7.81 +/- 1.44 to 4.76 +/- 0.96 after 1 month and to 4.75 +/- 0.90 after 3 months, corresponding to a 39% reduction in both instances. This index was reduced to 5.0 or less in 76% of the patients. At the end of the trial there was normalization of hyperlipoproteinaemia in 17 (81%) of the 21 patients. Tolerance of bezafibrate was satisfactory. Only 2 patients suffered mild abdominal pain, which disappeared within a few days. One patient presented slight, transitory neutropenia at the end of the 3 months of treatment.