Werner Gross

A randomized crossover comparison of two low-dose contraceptives: Effects on serum lipids and lipoproteins

The effect of a triphasic combination of ethinyl estradiol and levonorgestrel upon various lipoprotein parameters was compared to that of a preparation that contained ethinyl estradiol and desogestrel on days 6, 11, 21, and 28 of a control cycle, the third cycle of treatment with either ethinyl estradiol/levonorgestrel or ethinyl estradiol/desogestrel (11 volunteers each), the third cycle of a 3-month washout period, and the third treatment cycle after crossover change of the preparations. Significant increases were found in total triglycerides (15% to 20%) and phospholipids (8%) with both preparations, whereas total cholesterol and lipoprotein Lp(a) were not altered. High-density lipoprotein triglycerides (50% to 60%) and high-density lipoprotein-3 cholesterol (10% to 15%) were elevated by both contraceptives, high-density lipoprotein cholesterol and alpha-lipoprotein cholesterol only by ethinyl estradiol/desogestrel (11%), whereas high-density lipoprotein phospholipids, high-density lipoprotein-2 phospholipids, high-density lipoprotein-3 phospholipids, and high-density lipoprotein-2 cholesterol were not influenced. Both ethinyl estradiol/levonorgestrel and ethinyl estradiol/desogestrel increased apolipoproteins A (14%), A-I (20% to 30%), and A-II (25% to 35%) significantly. Very low-density lipoprotein triglycerides were elevated (30%) only by ethinyl estradiol/desogestrel, and low-density lipoprotein phospholipids (20%) by both ethinyl estradiol/levonorgestrel and ethinyl estradiol/desogestrel, whereas the other parameters, very low-density lipoprotein phospholipids, very low-density lipoprotein cholesterol, pre-beta-lipoprotein cholesterol, low-density lipoprotein triglycerides, low-density lipoprotein cholesterol, beta-lipoprotein cholesterol, and apolipoprotein B, were not significantly changed. Provided that the assumption is correct that high low-density lipoprotein cholesterol and apolipoprotein B and low high-density lipoprotein subfractions and apolipoprotein A are associated with an elevated risk of atherosclerosis, the results seem to represent beneficial rather than deleterious side effects of the low-dose oral contraceptives.

Analysis of plasma lipoproteins by ultracentrifugation in a new fixed angle rotor: Evaluation of a phosphotungstic acid/MgCl2 precipitation and a quantitative lipoprotein electrophoresis assay

A routine procedure for the ultracentrifugal analysis of human plasma lipoproteins by means of a fixed angle rotor was developed. It was applied as reference method for the evaluation of two widely used procedures of lipoprotein analysis, i.e. measurement of HDL-cholesterol after precipitation of the apolipoprotein B containing lipoproteins with a new phosphotungstic acid/MgCl2 reagent, and a quantitative lipoprotein electrophoresis system. A new statistical approach to the multivariate comparison of analytical methods, the linear structural relationship model, has been applied. The HDL-cholesterol levels measured after phosphotungstic acid/MgCl2 precipitation agreed well to those determined by ultracentrifugation, whereas electrophoretically quantified alpha-lipoprotein-cholesterol exceeded the ultracentrifugal HDL-cholesterol. The Friedewald formula obviously underestimated LDL-cholesterol due to an overestimation of VLDL-cholesterol, whereas the electrophoretically quantified pre-beta- and beta-lipoprotein-cholesterol levels fairly coincided with the respective ultracentrifugal measurements. The inter-assay reproducibility of the HDL-cholesterol determination after phosphotungstic acid/MgCl2 precipitation and subsequent LDL-cholesterol quantification according to Friedewald was statistically equivalent to that of ultracentrifugation, whereas the quantitative lipoprotein electrophoresis proved less precise.

Effect of two oral contraceptives containing ethinyl estradiol and gestodene or norgestimate on different lipid and lipoprotein parameters

The effect of a triphasic oral contraceptive containing ethinyl estradiol and gestodene (EE/GSD) on various lipid and lipoprotein parameters was compared with that of a monophasic formulation containing 35 micrograms ethinyl estradiol and 250 micrograms norgestimate (EE/NGM). Blood samples were collected from 46 women on days 2, 11, and 21 of the preceding control cycle and of the third, sixth, and twelfth treatment cycles. There was no significant difference between formulations with regard to the influence on any measured parameter. As compared with controls, a significant increase was observed in the plasma levels of total triglycerides (24-78%), total phospholipids (7-20%), very low density lipoprotein (VLDL) triglycerides (61-76%), VLDL-phospholipids (14-60%), low density lipoprotein (LDL) triglycerides (8-35%), LDL-phospholipids (28-30%), high density lipoprotein (HDL) cholesterol (8-16%), HDL 3-cholesterol (11-20%), HDL-triglycerides (17-66%), HDL-phospholipids, HDL 3-phospholipids (7-11%), apolipoprotein (apo) A-I (5-20%) and apo A-II (10-40%) during treatment with both formulations. In contrast, the LDL-cholesterol levels were significantly decreased. These changes in lipid metabolism appear to reflect a predominance of the effect of the estrogen component. The results indicate that both low dose oral contraceptives containing different progestins and different amounts of EE do not exert a deleterious effect on lipoprotein metabolism, as high HDL-cholesterol and low LDL-cholesterol levels are known as low risk factors of cardiovascular disease. In contrast to endogenous hypertriglyceridemia, an EE-induced rise in triglyceride levels does not appear to increase cardiovascular risk if LDL is not increased.

Time-dependent alterations in lipid metabolism during treatment with low-dose oral contraceptives

The effect of sex steroids on lipid metabolism depends on the type and dose of the compounds, the route of administration, and the duration of treatment. Therefore the composition of an oral contraceptive determines the resultant effect on lipids and lipoproteins. During 12 months of treatment, the effects of two oral contraceptives containing 30 micrograms of ethinyl estradiol and 150 micrograms of desogestrel (EE/DG) or 75 micrograms of gestodene (EE/GSD) on 19 serum parameters of lipid metabolism were followed in 11 women each. There was no change in total cholesterol and phospholipids. Total triglyceride levels were significantly elevated only by EE/GSD. After 3 and 6 months of intake of both preparations, a transitory increase in the triglyceride content of very low-density lipoprotein and low-density lipoprotein and a decrease in low-density lipoprotein-phospholipids was observed. After 12 months, very low-density lipoprotein cholesterol, very low-density lipoprotein phospholipids, and apolipoprotein B were significantly elevated, whereas very low-density lipoprotein triglycerides and all components of low-density lipoprotein were unchanged. Most of the components of high-density lipoprotein (HDL) were increased as a result of a rise in HDL3 and apolipoprotein A2, whereas HDL2 and apolipoprotein A1 were not altered. There was no significant difference between the effects of the two preparations, although those of EE/GSD were mostly more pronounced. The increase in high-density lipoprotein, very low-density lipoprotein, and total triglycerides reflects a slight preponderance of the effect of the estrogen component. Because low-density lipoprotein cholesterol and total cholesterol were not changed, treatment with both formulations is in all probability not associated with an elevated risk of atherosclerosis.

Changes in lipid metabolism during 12 months of treatment with two oral contraceptives containing 30 μg ethinylestradiol and 75 μg gestodene or 150 μg desogestrel

Abstract The effect of two oral contraceptives containing 30 μ g ethinylestradiol + 75 μ g gestodene ( EE GSD ) or 30 μ g ethinylestradiol + 150 μ g desogestrel ( EE DG ) upon serum lipids and lipoproteins were measured in 11 women each on days 1, 10, and 21 of the first, third, sixth, and twelfth treatment cycle and compared to the levels on days 1, 10, and 21 of the preceding control cycle. There was no change in total cholesterol (CH) and phospholipids (PL), while total triglycerides (TG) were significantly elevated only during treatment with EE GSD . After 3 and 6 months of intake of both oral contraceptives, a transitory increase in the TG content of very lowdensity lipoprotein (VLDL) and low-density lipoprotein (LDL), and a decrease in LDL-PL was observed. After 12 months, VLDL-CH, VLDL-PL, and apolipoprotein B were significantly elevated, while VLDL-TG and all components of LDL were unchanged. Most of the components of highdensity lipoprotein (HDL) were increased due to a rise in HDL3 and apolipoprotein A-II, while HDL2 and apolipoprotein A-I were not altered. There was no significant difference between the effects of the two preparations, although those of EE GSD were mostly more pronounced. The time-dependent change in the effects of the oral contraceptives on various parameters of lipid metabolism demonstrates that the relevance of results of short-time studies may be questionable. There was also a significant alteration in some parameters between day 1 and 10 of the treatment cycles and a tendency to return to the pretreatment levels during the pill-free week, e.g., in total TG and in the PL component of VLDL, LDL and HDL. The increase in HDL, VLDL, and total TG reflects a slight preponderance of the effect of ethinylestradiol on lipid metabolism. The unchanged total CH and LDL-CH and the elevated HDL levels indicate that the risk of the development of atherosclerosis is in all probability not increased during treatment with both preparations.

Effect on lipid metabolism of a biphasic desogestrel-containing oral contraceptive: Divergent changes in apolipoprotein B and E and transitory decrease in LP(a) levels

The effect of a low dose biphasic oral contraceptive containing 40 micrograms ethinylestradiol + 25 micrograms desogestrel (7 tablets) and 30 micrograms ethinylestradiol + 125 micrograms desogestrel (15 tablets) on lipid metabolism was investigated in 19 women during 6 cycles of treatment and compared to the values of the pre- and post-treatment cycle. During treatment, all components of HDL increased reversibly by 10 to 30%. The levels of total cholesterol (CH), LDL-CH and IDL-CH rose only slightly, while those of total triglycerides (TG), VLDL-TG and LDL-TG rose continuously by more than 100% until the 6th cycle. At the same time, plasma levels of VLDL-CH increased by 60% and of apolipoprotein B by 20%. Contrary to this, apolipoprotein E decreased by 25% during treatment, and Lp(a) was transitorily reduced during the 3rd cycle. After termination of intake, total CH, LDL-CH, IDL-CH and apolipoprotein B remained elevated, while total TG, VLDL-TG, VLDL-CH and LDL-TG decreased significantly, but were still elevated during the post-treatment cycle. The levels of apolipoprotein E returned to pre-treatment values. The results indicate a marked preponderance of the effect of the estrogen component. The rise in TG and VLDL synthesis seems to be outweighed by an enhanced removal of apolipoprotein E-containing remnants which might offer protection from the development of atherosclerosis.

Quantification of human serum lipoprotein Lp(a): zone immunoelectrophoresis assay, a new sensitive method as compared to electroimmuno assay

This study aimed at improving the immunological procedures for the quantification of human serum lipoprotein Lp(a). Lipoprotein Lp(a) was estimated by two immunoelectrophoretic methods: electroimmunoassay and zone immunoelectrophoresis assay. Whereas the electroimmunoassay gave curvilinear calibration lines (in peak height versus concentration plots) the zone immunoelectrophoresis assay revealed linearity in the same concentration range. The results obtained are in good agreement with each other (r = 0.975). The inter-assay coefficient of variation for the zone immunoelectrophoresis assay was 12% as determined by the use of a lyophilised reference serum. Zone immunoelectrophoresis assay is recommended for the routine quantification of lipoprotein Lp(a). Although the levels for total cholesterol (p less than 0.0025), HDL-cholesterol (p less than 0.001) and triglycerides (p less than 0.025) differed significantly between male (n = 24) and female (n = 22) individuals, no difference could be detected comparing the frequency distributions of Lp(a)-levels found for the male and the female group.

Precipitation of LDL with sulfated polyanions: three methods compared

Three precipitation methods for the determination of low density lipoproteins have been evaluated. In n = 113 normolipidemic samples mean LDL-cholesterol levels have been 2.90 mmol/l, 2.77 mmol/l, 3.21 mmol/l after precipitation with heparin, dextran sulfate, and polyvinylsulfate, respectively. As compared to a combined ultracentrifugation and precipitation reference procedure (mean 3.22 mmol/l) two precipitation methods tend to underrate LDL-cholesterol. Elevated plasma triglycerides may interfere with the precipitation of LDL. The clinical relevance of the precipitation procedures has been studied by discriminant analysis in n = 28 consecutive patients admitted for coronary bypass operation and n = 28 controls. The data suggest that, statistically, the determination of LDL-cholesterol with either precipitation method only provides redundant information as in relation to the Friedewald approximation for LDL-cholesterol. Immunologically determined apolipoprotein B proved a better predictor for group separation than either precipitation method.

Short- and Long-Term Effects on Lipid Metabolism of Oral Contraceptives Containing 30 µg Ethinylestradiol and 150 µg Desogestrel or 3-Keto-Desogestrel

During a cross-over study with young female volunteers, the effects of a combination of 30 µg ethinylestradiol (EE) and 150 µg desogestrel (DG) or 3-keto-desogestrel (KDG) upon lipid metabolism were investigated on day 3 of the first cycle (day 3/1) and on day 21 of the third cycle of treatment (day 21/III). As compared to the control cycle, total cholesterol (CH), low-density lipoprotein CH (LDL-CH), and the apolipoproteins A-II and B were reduced already on day 3/1, the effects being more pronounced with the DG-containing formulation. On day 21/III of treatment with EE/DG, the levels of total CH, LDL-CH and apolipoprotein B did not differ from controls, while apolipoprotein A-II was significantly increased. The effects of EE/KDG were similar, except that on LDL-CH which was still reduced on day 21/III. The serum concentrations of total triglycerides (TG), very low-density lipoprotein CH (VLDL-CH), VLDL-TG, LD-TG, high-density lipoprotein CH (HDL-CH), HDL-TG, and apolipoprotein A-I were not significantly affected on day 3/1, but elevated on day 21/III. As during treatment with EE/KDG the peak level of KDG was higher than with EE/DG, the results indicate a more pronounced antagonistic effect of EE/KDG on some EE-induced changes on lipoproteins during the first days of intake. These short-term changes possibly reflect a rapid enhancement of hepatic uptake of remnants and LDL by EE. During long-term treatment, the other effects of EE, e.g. the stimulation of hepatic synthesis of TG, VLDL, and HDL and the inhibition of hepatic lipoprotein lipase, become apparent.

10 Lipoprotein(a) Quantitation

Lipoprotein(a) (Lp[a]) was first discovered in 1963, by Kare Berg, as a variant of the beta-lipoproteins. Many years later, Lp(a) has been identified as an independent risk factor for the development of coronary heart disease (1). During the last two decades the structure and composition of Lp(a) has been investigated using different physicochemical and biochemical methods (2,3). These studies revealed that Lp(a) resembles the cholesterol-rich low-density lipoprotein (LDL) particle, except for an additional glycoprotein called apolipoprotein(a) (apo[a]), which is mainly produced in the liver. Apo(a) is covalently linked via a disulfide bridge to apolipoprotein B-100, the major protein constituent of LDL. In contrast to apolipoprotein B-100, which is important for the structure of the lipoprotein particle, it is supposed that apo(a) is loosely adhered to the surface of the particle.