Synthesis of very low density lipoproteins in the cockerel. Effects of estrogen.

The effect of estrogen on the synthesis of plasma very low density lipoproteins (VLDL) in the cockerel was studied both in vivo and in vitro. Synthesis was studied by immunoprecipitation techniques with antisera prepared against VLDL and a major VLDL protein. VLDL were isolated from the plasma of white Leghorn hens and estrogen-treated white Leghorn cockerels by ultracentrifugal flotation at d 1.006 g/ml. After delipidation, the lipid-free proteins (apoproteins) were fractionated on Sephadex G-150 and DEAE-cellulose. Both the hen and the estrogen-treated cockerel VLDL were shown to contain an identical apoprotein with a mol wt of approximately 12,000; the apoprotein is designated fraction B. Reduction and S-carboxy-methylation of fraction B resulted in a reduction of the molecular weight by approximately one-half, indicating a dimer-monomer relationship. Antiserum prepared to the hen VLDL dimer protein gave precipitin lines of complete identity to both the hen and cockerel dimer, monomer, VLDL, apoVLDL, low density lipoproteins, and plasma; no precipitin line was formed with either hen or cockerel high density lipoproteins. After a single subcutaneous injection of diethylstilbestrol into the cockerel, plasma VLDL protein, cholesterol, and triglyceride increased, reaching a maximum 24--48 h after hormone administration. Liver slices from similarly treated animals were incubated in vitro in culture medium in the presence of [3H]lysine for 2 h. Immunoprecipitable radioactivity in VLDL increased within 2 h of diethylstilbestrol treatment and reached a maximum at 24 h; VLDL radioactivity returned to base-line levels by 72 h. At the peak of induction, newly synthesized VLDL represented 11% of the total soluble protein synthesized. When actinomycin-D (5 mg/kg) was administered simultaneously with estrogen, the induction of VLDL synthesis was totally inhibited. To determine whether the effect of estrogen on VLDL synthesis was mediated at the level of transcription, partially-purified cockerel liver mRNA was prepared from estrogen-treated animals and the mRNA activity for fraction B was quantitated in a wheat germ translation system. Fraction B mRNA was found to increase from a low base-line value to a maximum 16-24 h after estrogen treatment, returning towards baseline values at 30 h. At the peak of induction, fraction B constituted 12% of the total protein synthesized. The kinetics of induction of fraction B mRNA activity in the cell-free translation system is very similar to that observed in liver slice experiments. This finding suggests that estrogen stimulates VLDL synthesis, at least partially, by enhancing the accumulation of the mRNA for one of their major apoproteins.

PIP: In vivo and in vitro studies were undertaken to investigate the mechanism of the induction of the synthesis of very low density lipoproteins (VLDL) by estrogens in the cockerel. VLCL were isolated from plasma of white Leghorn hens and estrogen-treated white Leghorn cockerels. VLCL from both these groups contained an identical apoprotein (Fraction B) with a molecular weight of about 12,000. Reduction and S-carboxy-methylation of this fraction reduced its molecular weight by approximately 50%, thus indicating a dimer-monomer relationship. When antiserum was prepared against the hen VLDL dimer protein, completely identical precipitin lines were found for both the hen and cockerel dimer, monomer, VLDL, apoVLDL, low density proteins, and plasma. However, no precipitin line was formed with hen and cockerel high density lipoptoteins. A single sc injection of diethylstilbestrol (DES) into the cockerel increased levels of plasma VLDL protein, cholesterol, and triglyceride, with maximum values occurring 24-48 hours after injection. Immunoprecipitation of liver slices from similarly treated animals showed an increase of radioactivity of VLDL within 2 hours of injection. Values reached a maximum at 24 hours and returned to baseline levles by 72 hours. Newly synthesized VLDL comprised 11% of the total soluble protein synthesized during the period of peak values. Actinomycin-D (5 mg/kg), when administered simultaneously with the estrogen, completely inhibited the induction of VLDL synthesis. In another experiment, partially purified cockerel liver mRNA was prepared from estrogen-treated animals and the mRNA acitivity for Fraction B was measured in a wheat germ translation system. Values for Fraction B mRNA reached a maximum 16-24 hours after estrogen-treatment and returned to baseline levels by 30 hours. Fraction B represented 12% of the total protein synthesized at the peak of induction. The results suggest that estrogen stimulates the synthesis of VLDL by enhancing the accumulationg of the mRNA of 1 of their major components.

Effects of low dose oral contraceptives on very low density and low density lipoprotein metabolism.

Oral contraceptives (OC) raise plasma triglyceride and VLDL levels, which may be of concern, since some conditions characterized by elevated triglycerides are associated with atherosclerosis. To identify the responsible mechanism, we studied 11 healthy premenopausal women, 5 of whom were taking OC containing 0.035 mg ethinyl estradiol, and 6 of whom were not. Their rates of VLDL and LDL metabolism were measured by endogenously labeling apoB, the protein component of VLDL and LDL, by an intravenous infusion of deuterated leucine. OC use had the greatest effect on the large, triglyceride-rich VLDL subfraction (Sf 60-400), increasing plasma levels threefold and production rates fivefold (P < 0.05). Among OC users, small VLDL (Sf 20-60) levels were 2.2 times higher, and production rates were 3.4-fold higher (P < 0.05). The fractional catabolic rates of large and small VLDL were similar among OC users and nonusers. LDL levels and metabolic rates were not significantly different between the two groups. Thus, contemporary low dose OC substantially raise VLDL levels by increasing the production rate of large, triglyceride-rich VLDL, and not by slowing VLDL catabolism. Since VLDL catabolism is not impaired, we speculate that the hypertriglyceridemia induced by OC may be less atherogenic than that of hypertriglyceridemia resulting from impaired lipolysis. This may explain why long-term OC use does not appear to promote atherosclerosis.

PIP: At Brigham and Women's Hospital in Boston, Massachusetts, data on 5 women aged 22-24 years using low-dose oral contraceptives (OCs) containing .035 mg ethinyl estradiol were compared with data on 6 women aged 23-27 years not using OCs so researchers could study the metabolism of individual very low density lipoprotein (VLDL) subfractions of low density lipoprotein (LDL) in users of low-dose OCs and nonusers. Specifically, they wanted to determine the mechanisms by which OC use increases plasma VLDL and triglyceride levels. They infused a nonradioactive amino acid tracer (D3-leucine) intravenously into the 11 women to endogenously label the primary protein component of VLDL and of LDL, apoB, allowing them to measure VLDL and LDL synthesis and catabolism. OC users had large triglyceride-rich VLDL subfraction plasma levels 3 times higher than those of nonusers (20.2 nmol/l vs. 6.7 nmol/l; p , .05). OC use increased large, triglyceride-rich VLDL subfraction production rates 5-fold (16.7 nmol/kg/d vs. 3.4 nmol/kg/d; p .005). OC users had 2.2 times higher small VLDL subfraction levels (36.7 nmol/l vs. 16.7 nmol/l; p .05) and 3.4 times higher small VLDL subfraction production rates (22.5 nmol/kg/d vs. 6.7 nmol/kg/d; p .01) than nonusers. The fractional catabolic rates of large and small VLDL were essentially the same for OC users and nonusers (19.4 pool/d vs. 18.2 pool/d and 15.1 pool/d vs. 17 pool/d). Thus, low-dose OC use increases VLDL levels via a rise in the production rate of large VLDL and not by impeding VLDL catabolism. Learning that low-dose OCs do not curb VLDL catabolism, the researchers proposed that the OC-induced hypertriglyceridemia is less likely to be atherogenic than impaired lipolysis induced hypertriglyceridemia. This hypothesis may provide the answer as to why longterm OC use does not apparently foster atherosclerosis.

Clinical toxicology of estrogens.

PIP: This paper reviews both minor and major adverse reactions caused by estrogenic substances (natural and synthetic, steroidal and nonsteroidal) of which diethylstilbestrol is the prototype of nonsteroidal synthetic estrogen. Minor side effects include nausea, breast tenderness, and excessive cervical secretions (most common), headache, and water and salt retention (less common and often eradicated by lowering estrogen dosage). Vertigo, yeast infections, depression, and photosensitivity are other minor effects. Major side effects are discussed in some detail. Major effects include those on the endocrine system (e.g., feminization in boys and men and precocious puberty in girls); breast tumors; endometrial carcinoma; ovarian tumors; hypertension; thromboembolism; blood clotting excesses; various metabolic effects (including lipid metabolism and carbohydrate metabolism alterations); liver changes (bile alterations and neoplasms); porphyria; melanoma; and effects on a fetus in situ during maternal estrogen administration. In general, lowering doses of estrogen should help eradicate or alleviate most of these effects.^ieng

Desogestrel- and levonorgestrel-containing oral contraceptives have different effects on urinary excretion of prostacyclin metabolites and serum high density lipoproteins.

Prostacyclin synthesis is stimulated in vitro by high density lipoproteins (HDL), which themselves are differently affected by desogestrel (DG)- and levonorgestrel (LN)- containing oral contraceptives. In this study we measured the urinary excretion of the metabolites of prostacyclin [6-keto-prostaglandin F 1 alpha(6-keto) and 2,3-dinor-6-keto-prostaglandin F1 alpha (dinor)] and of thromboxane A2 [thromboxane B2 (TxB2)] as well as serum HDL- and HDL2 cholesterol concentrations before and during DG and LN administration alone or in combination with ethinyl estradiol (EE) in 26 women. Before the trial, urinary dinor excretion correlated with serum total HDL cholesterol (r = 0.499; P less than 0.01) and HDL2 cholesterol levels (r = 0.668; P less than 0.001; n = 26). Administration of DG (150 micrograms/day; 14 women) or LN (150 micrograms/day; 12 women) for 2 weeks caused no changes in the excretion of these prostanoids, but LN administration decreased serum HDL cholesterol levels. After that, the women underwent a monophasic regimen of 150 micrograms DG or LN plus 30 micrograms EE for 3 months and thereafter polyphasic regimens of the same steroids for a further 3 months. The DG-containing pills increased urinary dinor excretion by 25-40%, but caused no changes in 6-keto and TxB2 excretion, as measured on days 19-21 of the cycles. LN-containing pills reduced urinary 6-keto excretion by 22% at the end of polyphasic treatment, but caused no changes in dinor and TxB2 output. DG plus EE, but not LN plus EE, increased serum total HDL and HDL2 cholesterol concentrations by a maximum of 25%. Thus, a DG plus EE combination may stimulate PGI2 synthesis by increasing the levels of HDL/HDL2. Theoretically, this stimulation protects against occlusive vascular disorders.

PIP: The effects of desogestrel or levonorgestrel alone and in combination with ethinyl estradiol on the urinary excretion of metabolites of antiaggregatory prostacyclin (PGI2) and thromboxane A2 (TxA2) and on serum high density lipoprotein (HDL) and HDL2 cholesterol concentrations were investigated in 26 women. Baseline urinary 6-keto, dinor, and TxB2 excretion and serum HDL or HDL2 cholesterol concentrations did not differ between study groups. Administration of desogestrel and levonorgestrel alone for 2 weeks caused no changes in PG excretion, but it reduced serum HDL and HDL2 cholesterol concentrations. The desogestrel-estradiol combination was accompanied by 40% and 25% rises in urinary dinor excretion and 20% and 15% rises in urinary 6-keto and dinor excretion at the end of the monophasic and polyphasic regimens, respectively, but no significant changes in urinary TxB2 excretion. The levonorgestrel-estradiol combination produced a 22% decrease in urinary 6-keto excretion during polyphasic treatment, but led to no change in the excretion of the other prostanoids. Both monophasic and polyphasic levonorgestrel and estradiol administration lowered serum HDL and HDL2 cholesterol levels, while monophasic desogestrel plus estradiol increased serum HDL2. The mean relative changes in serum HDL2 cholesterol and urinary dinor excretion were parallel in users of desogestrel plus estradiol, suggesting that a serum HDL cholesterol increase induced by this regimen could be related to increased vascular PGI2 production. Although the mechanism that causes increases in PGI2 and HDL during desogestrel-estradiol administration remains unknown, such a combination has the potential to reduce the risk of occlusive-thrombotic vascular disorders--currently the most serious side effect of oral contraceptive use.

Divergent effects of weight reduction and oral anticonception treatment on adrenergic lipolysis regulation in obese women with the polycystic ovary syndrome.

The influence of weight reduction and female sex hormones on the regulation of lipolysis was investigated in isolated abdominal sc adipocytes from 20 obese hyperandrogenic women with polycystic ovary syndrome (PCOS). Nine PCOS women were reinvestigated after 8-12 weeks of weight reduction therapy (WR) with a very low calorie diet, inducing a mean loss of 8 +/- 3 kg, and 8 PCOS women were reinvestigated after 12 weeks of treatment with combined oral contraceptives (OC), containing ethinyl estradiol and norethisterone; the remaining 3 subjects were drop-outs. Both WR and OC normalized hyperandrogenicity. WR caused a 50% reduction of basal lipolysis rate and a 5- to 7-fold increased noradrenaline and terbutaline sensitivity (P < 0.02); the latter could be ascribed to a 2-fold increased beta2-adrenoceptor density (P < 0.02) as determined with radioligand binding. There was no change with regard to dobutamine (beta1-adrenoceptor sensitivity) or clonidine, (alpha2-adrenoceptor sensitivity) or to beta1-adrenoceptor density. OC treatment did not influence the basal lipolysis rate or beta2- or alpha2-adrenoceptor sensitivity, but lowered the beta1-adrenoceptor sensitivity 7-fold (P < 0.03) without a reduction in beta1-adrenoceptor density. The OC treatment effect was not observed when forskolin and dibutyryl cAMP, acting on adenylate cyclase or protein kinase A, respectively, were used, suggesting a partial uncoupling of beta1-adrenoceptors. WR therapy, but not OC therapy, caused, in addition to changes in lipolysis function, improved in vivo insulin sensitivity and lower plasma noradrenaline levels. These findings suggest that factors other than hyperandrogenicity modulate lipolysis regulation in obese subjects with PCOS. Disturbances in sympathetic pathways could be of pathogenic importance.

Differences in the low density lipoprotein subfraction profile between oral contraceptive users and controls.

To investigate the effect of low dose oral contraceptives on the low density lipoprotein (LDL) subfraction profile, the distribution of the LDL subfraction patterns in 20 premenopausal women on oral contraceptive (OC) therapy and 41 premenopausal women not taking gonadal hormones was studied. The LDL subfraction patterns were identified by density gradient ultracentrifugation and each individual LDL subfraction pattern was characterized by the relative contribution of three major LDL subfractions: light, LDL1; intermediate, LDL2; and dense, LDL3 to total LDL. Serum lipid and lipoprotein levels were similar in OC users and controls, except for significantly higher triglyceride levels in OC users. As for the LDL subfraction patterns, among the OC users the mean relative contribution of dense LDL3 to total LDL was significantly higher than in the controls (32% +/- 8% vs. 26% +/- 13%, P < 0.05), whereas the relative contribution of light LDL1 to total LDL was significantly lower (27% +/- 8% vs. 34% +/- 10%, P < 0.01), indicating a higher prevalence of the more dense LDL subfraction patterns among OC users. Furthermore, the distribution of the LDL subfraction patterns in OC users (27% LDL1, 41% LDL2, and 32% LDL3) resembled that of men (25% LDL1, 43% LDL2, and 33% LDL3, n = 59). Statistical analysis revealed that OC use was significantly associated with a more dense LDL subfraction pattern, characterized by an increased relative contribution of LDL3 (+6%, P < 0.05) and a decreased relative contribution of LDL1 (-6%, P < 0.01), even after correcting for the influence of lipid and lipoprotein levels, which in controls were shown to have a significant relation to LDL3 and LDL1, respectively. So, independent of the lipid and lipoprotein levels, low dose OC alter the composition of LDL to a heavy, dense LDL subfraction profile, which reportedly has been associated with an increased risk of atherosclerosis.

Influence of low estrogen-containing oral contraceptives on lipoprotein phospholipid composition and mononuclear cell membrane fluidity.

Since the effects of the new low estrogen-containing oral contraceptive (OC) preparations on lipoprotein phospholipid (PL) composition are unknown, we studied 3 groups of 10 young women before and after 6 months of use of 3 commonly prescribed agents containing almost identical amounts of ethinyl estradiol (0.30-0.35 microgram) and differing progestogens, and correlated these changes with their estrogen to progestin (E/P) ratio. The directional changes in both plasma neutral lipid and PL concentrations tended to correlate with the E/P ratio, with plasma HDL-cholesterol (HDL-C) falling slightly and the low density lipoprotein-cholesterol (LDL-C)/HDL-C ratio increasing in the women taking the OC with the lowest E/P ratio; in contrast, plasma HDL-C increased and the LDL-C/HDL-C ratio fell in those receiving the preparation with the highest E/P ratio. In HDL, the ratio of the 2 principal PL, sphingomyelin and lecithin, an index of lipid fluidity, tended to increase, suggesting that the surface of this lipoprotein class had become more rigid. This change was most apparent in women receiving the agent in which the progestin was predominant; in women receiving the preparations with the higher E/P ratios the sphingomyelin/lecithin ratio actually declined. The membrane fluidity of mononuclear cells obtained from five women taking an OC with a relatively high E/P ratio, however, was significantly increased (P less than 0.007) compared to that in normal women. These findings demonstrate that, even with substantial reductions in their estrogen content, the use of these newer OC is associated with quantitative and qualitative changes in lipoprotein PL composition that parallel their E/P balance and are associated with altered fluidity of mononuclear cell membranes.

Oral contraceptive and postmenopausal estrogen effects on lipoprotein triglyceride and cholesterol in an adult female population: relationships to estrogen and progestin potency.

PIP: A study of the prevalence of hyperlipidemia has been conducted among female telephone company employees using oral contraceptives (OCs) or estrogenic hormones. This paper relates hormone formulation and estrogen/progestin potency to striglyceride and cholesterol concentrations in total plasma and lipoprotein fractions and relative lipid composition. Changes in these lipid parameters are of interest because they may predict atherosclerosis risk. Results in 148 hormone users are compared with those in 306 nonhormone users. All data are adjusted for the effects of age, relative body weight, cigarette smoking, and alcohol intake. Triglyceride concentrations in whole plasma, very low density lipoprotein (VLDL), and high density lipoprotein (HDL) are elevated 1.5-2.5 fold with increasing estrogen potency. Low density lipoprotein (LDL) triglyceride concentration is elevated to a similar degree among OC users regardless of estrogen potency, but there is no significant effect of postmenopausal estrogen use on LDL triglyceride concentrations. The LDL cholesterol concentration shows an increasing trend with increasing estrogen potency in a random sample of OC-treated women, but is slightly lower than control in postmenopausal women treated with estrogen alone. The HDL cholesterol concentration in plasma is highest with hormones having the greatest estrogen potency and lowest with those having the greatest progestin potency. The VLDL cholesterol to triglyceride ratio adjusted for triglyceride concentration is significantly increased with the use of Ovral, a progestin-predominant contraceptive preparation. The LDL cholesterol to triglyceride ratio is reduced with the use of all OCs examined, except for Ovral, where the ratio is above average. The HDL cholesterol to triglyceride ratio is reduced for all combination OCs examined. The use of a sequential OC or postmenopausal estrogens is not associated with a significant alteration in the cholesterol to triglyceride ratio in any lipoprotein fraction. Knowledge of estrogen and progestin potency and kind of progestin are important in predicting the effect of OCs on plasma and lipoprotein lipids. On the basis of observed differences in lipoprotein lipid concentrations and relationships, the potential arteriosclerotic risk from sex hormones may vary among OC formulations.^ieng

Effects of a new oral contraceptive containing an antimineralocorticoid progestogen, drospirenone, on the renin-aldosterone system, body weight, blood pressure, glucose tolerance, and lipid metabolism.

Combined hormonal oral contraceptives (OCs) may lead to a mild rise in blood pressure and body weight. In rare instances, large increments in blood pressure are measured. We investigated the effect of a combination of ethinyl estradiol (EE) plus a progestogen with antimineralocorticoid, i.e. natriuretic, properties [Drospirenone (DRSP)] on body weight, blood pressure, the renin-aldosterone system, atrial natriuretic factor, plasma lipids, and glucose tolerance. It is anticipated that this will lead to the development of an OC that does not raise body weight or blood pressure. Four groups of 20 women each received 30 micrograms EE plus 3 mg DRSP (group A), 20 micrograms EE plus 3 mg DRSP (group B), 15 micrograms EE plus 3 mg DRSP (group C), and, as a control OC, 30 micrograms EE plus 150 micrograms levonorgestrel (Microgynon, Schering; group D) for 6 months. During the OC-free control cycles before and after treatment and throughout treatment, the target parameters were measured. Between the pretreatment cycle and the sixth treatment cycle, mean body weight fell by 0.8 to 1.7 kg in groups A, B, and C (P < 0.05 vs. D), whereas it rose by 0.7 kg in group D. Systolic and diastolic blood pressures fell by 1-4 mm Hg in groups A, B, and C (significant for A and C vs. D) and increased by 1-2 mm Hg in group D. Renin substrate rose equally in all groups (P < 0.05), whereas PRA and plasma aldosterone rose significantly only in the DRSP groups, presumably due to sodium loss. In the DRSP groups, high density lipoprotein cholesterol rose (P < 0.05), in contrast to group D. Low density lipoprotein cholesterol fell slightly (P > 0.05), whereas triglyceride levels showed a stronger increase in the DRSP groups (P < 0.05) than in group D. All groups attained good cycle control; group A had the best. Side-effects were minimal. To our knowledge, this is the first report on a combined OC that leads to a small decrease in body weight and blood pressure. It may be especially beneficial for women susceptible for a gain in weight and a rise in blood pressure.

PIP: The potential of a new oral contraceptive (OC) containing drospirenone (DRSP) to avert the moderate increases in body weight and blood pressure often associated with use of existing combined OCs was investigated in a study of four groups of 20 German women each. Group A received 30 mcg of ethinyl estradiol (EE) and 3 mg of DRSP, Group B was administered 20 mcg of EE and 3 mg of DRSP, Group C received 15 mcg of EE and 3 mg of DRSP, and Group D was given a standard OC containing 30 mcg of EE and 150 mcg of levonorgestrel. Between the pretreatment cycle and the last (sixth) treatment cycle, mean body weight fell by 0.8-1.7 kg in Groups A, B, and C, but rose by 0.7 kg in Group D. Systolic and diastolic blood pressures fell by 1-4 mm Hg in Groups A, B, and C and rose by 1-2 mm Hg in Group D. Renin substrate rose equally in all four groups, while plasma renin activity, plasma aldosterone, and high density lipoprotein cholesterol rose significantly only in the three DRSP groups and serum triglyceride levels were significantly higher in Group D than in the three DRSP groups. Glucose tolerance increases were similar in all four groups. Finally, all groups--but especially Group A--experienced good cycle control and there were no serious side effects. These findings suggest that a combined OC containing DRSP may be especially beneficial for women who have a tendency to gain weight or experience a rise in blood pressure while taking OCs.

Inhibition of antipyrine metabolism by low-dose contraceptives with gestodene and desogestrel.

To examine the effects of the two newest monophasic oral contraceptives on liver microsomal drug metabolism, plasma kinetics and urinary metabolite excretion of antipyrine, a model substrate for liver microsomes, were evaluated. Plasma lipid and lipoprotein levels, and in particular the high-density lipoprotein subfractions, were also monitored in view of their apparent regulation by a P450-dependent system. Ten healthy volunteers were treated with each contraceptive for a period of 3 months in a crossover trial. Both contraceptives significantly reduced antipyrine clearance by 34.6% (gestodene) and 43.3% (desogestrel) by impairing the oxidative metabolism, particularly to the 4-hydroxy and 3-hydroxymethyl metabolites, with little difference between the two associations. In addition, with both a comparable highly significant rise of plasma triglyceride levels, apolipoproteins A-I and A-II and the high-density lipoprotein-3 subfraction was observed. Treatment with these new monophasic contraceptives may reduce the metabolism of concomitantly given drugs undergoing oxidative transformations.

Effect of estrogen on triacylglycerol metabolism: inhibtion of post-heparin plasma lipoprotein lipase by phosvitin, an estrogen-induced protein.

PIP: The effects of phosvitin and lipovittelin on partially purified postheparin plasma levels of lipoprotein lipase (LPL) and triacylglycerol (TGL) and adipose tissue LPL were studied in laying and nonlaying female turkeys and estrogen-treated male turkeys. Postheparin plasma lipolytic activities and those of LPL and TGL decreased 2- to 3-fold after the onset of egg production, while a 24-fold increase in triacylglycerol (TG) was observed. Lipovittelin had no effect on either TGL or LPL, while phosvitin, in a dose of 3 mcg protein/ml assay mixture, had a strong inhibitory effect on plasma LPL and chicken adipose tissue LPL. TGL was not affected by phosvitin. The results suggest that phosvitin may have a role in the regulation of adipose tissue and plasma levels of TG in laying birds.^ieng

The effect of kind of carbohydrate in the diet and use of oral contraceptives on metabolism of young women. II. Serum lipid levels.

The response of lipids in the blood between two groups of six young women was compared. Group 1 took oral contraceptives and group 2 had never taken oral contraceptives. Two experimental diets supplied about 13% of the calories from protein, 36% from fat, and 51% from carbohydrate. Of the carbohydrate, 84% was either sucrose or wheat starch. Each diet was fed for 4 weeks in a cross-over design. In the portion of the research presented here, subjects were fed a high sucrose meal before each dietary period and after weeks 1 and 3 of each dietary period. Blood lipids were measured before and 30, 60, 120, and 180 min after each meal. Cholesterol and lipoproteins were not affected by the sucrose meal, but free fatty acid levels decreased significantly in both groups. The serum levels of triglycerides, beta-lipoproteins, and cholesterol were significantly higher in users than in nonusers of oral contraceptives. Free fatty acid levels were affected by an interaction between diet and time, and the decrease in response was greater after the sucrose than after the wheat starch diet. Triglycerides, cholesterol, and total lipids were not significantly different after the two carbohydrate diets.

PIP: The response of lipids in the blood between 2 groups of 6 young women, ages 19-25, was compared. Group 1 took (OCS) oral contraceptives and group 2 had never taken OCS. 2 experimental diets supplied about 13% of the calories from protein, 36% from fat, and 51% from carbohydrates. Of the carbohydrate, 84% was either sucrose or wheat starch. Each diet was administered for 4 weeks in a cross-over design. In a portion of the research here presented, subjects were fed a high sucrose meal before each dietary period and after weeks 1 and 3 of each dietary period. Blood lipids were measured before and 30, 60, 120, and 180 minutes after each meal. Cholesterol and lipoproteins were not affected by the sucrose meal, but free fatty acid levels decreased significantly in both groups. The serum levels of triglycerides, beta-lipoproteins, and cholesterol were significantly higher in users of OCS than in non-users. Free fatty acid levels were affected by an interaction between diet and time, and the decrease in response was geater after the sucrose than after the wheat starch diet. Triglycerides, cholesterol, and total lipids were not significantly different after the 2 carbohydrate diets.

Effect of oral alanine loads on the serum triglycerides of oral contraceptive users and normal subjects.

The effect of orally administered L-alanine loads on serum triglycerides, and plasma insulin and glucose, was studied in 23 women using an estrogen-containing oral contraceptive and 13 healthy female controls. Oral contraceptive users had significantly higher fasting serum triglycerides than the controls. Serum triglycerides concentrations udnerwent little changes in the controls after alanine ingestion, whereas the oral contraceptive users showed increases which were maintained throughout the 3-hr sampling period. The two groups had similar elevations in plasma insulin after alanine loading; the glucose concentrations were unchanged. The changes in serum triglycerides may have resulted from increased metabolism of alanine to pyruvate, and its incorporation into lipids under the stimulus of elevated insulin levels.

PIP: 23 women using various combined oral contraceptive (OC) preparations were studied for the effect of oral L-alanine loads on serum triglycerides and plasma insulin and glucose levels. Fasting serum triglyceride levels were significantly (p less than .001) higher in women taking OCs than in the 13 control subjects. OC users also had significantly (p less than .001) higher serum triglyceride levels at all test times following alanine loading than controls. There were no marked differences between the preparations used. Increases in plasma insulin after alanine loading were similar for users and nonusers, while glucose concentrations were unchanged. It is suggested that the alteration in serum triglycerides may have been due to an increase metabolism of alanine to pyruvate, and its incorporation into lipids under insulin stimulus.

Relationship between levels of blood lipids, vitamins C, A, and E, serum copper compounds, and urinary excretions of tryptophan metabolites in women taking oral contraceptive therapy.

To evaluate which women using oral contraceptive agents might be at risk, biochemical indices known to be affected by the estrogens and progestogens were studied in women who take oral contraceptive agents, in women who do not use oral contraceptive agents, in women in third trimester of pregnancy and 6 weeks after parturition, and in men with normal and high blood lipid levels. The most consistent changes due to oral contraceptive agents were in serum levels of copper, triglycerides, and vitamin A and in the urinary excretion of xanthurenic acid and niacin derivatives before and after a tryptophan load test. There was only a slight suggestion, with no statistical significance, that serum vitamin C levels decreased when the serum levels of ceruloplasmin were high. The highest blood pressures and serum triglycerides and vitamin A levels were obtained in those women who ingested the highest level of estrogens. Pregnant women had the lowest levels of serum vitamin A. The oral contraceptive agents users had the lowest average levels of carotenoids corresponding to the highest average levels of vitamin A in the serum. Thus, estrogens not only increase the rate of change of tryptophan to niacin but may also increase the rate of conversion of carotene to vitamin A. Relative reactivity to oral contraceptive agents and possible risk to a patient might be evaluated by a profile of blood pressure and serum triglycerides, copper, and vitamin A.

PIP: To determine if methods can be developed which will show those patients for whom oral contraceptive agents (OCAs) constitute a hazard, data on blood lipids, serum levels of Vitamis-A, E, and C and copper are reported. Results of the tryptophan load test are also given. This tes t is related to the levels of pyridoxine in the tissues. The program was designed to show the relationship of any changes to each other, and to get a better understanding of their significance. Results are compared from subjects taking OCAs, from those not taking OCAs, from women in the last trimester of pregnancy, from women after parturition, and from males. All blood and urine samples were taken at 21 days after the beginning of subjects' menstrual periods, except for those who were pregnant and males. There were 49 women taking a variety of OCAs. 32 not taking OCAs served as controls. Included were 22 pregnant women in the last trimesters of their pregnancies. Of these, 11 were tested again 6 weeks postpartum. 9 men with high blood lipids and 12 men with normal lipid levels were also tested. Diastolic blood pressures averaged higher in the group taking OCAs (p less than .01), except for the males who were older or who wer known to have high lipids. Serum cholesterol levels in OCA users were unaltered. Serum phospholipids showed some increase in OCA users (p less than .05). Triglycerides show ed the greatest increase in OCA users (p less than .001), especially in those taking the most estrogen. The pregnant women had high serum levels of cholesterol, triglycerides, phospholipids, and total lipids. All of these levels were found to be less at 6 weeks postpartum. Serum copper levels were increased in all OCA users to above 1.5 mcg/ml but in only 2 of the nonusers to this level. Serum Vitamin-A was increased in the OCA user group (p less than .001). The pregnant women had relatively low levels of Vitamin-A. This increased by 6 weeks after parturition to the level of OCA users. An 8-hour urine collection after a 2-g tryptophan load showed at 6 times increased excretion of xanthurenic acid in those using OCAs as compared with nonusers. An increased ability of pregnant women to convert tryptophan to nictionic acid was shown. It is not known to what degree the biological changes caused by OCAs are undesirable. However, it is assumed that women showing the greatest changes are at greater risk. Analyses which may serve as incicators of potential risk include serum triglycerides, copper, and Vitamin-A levels. Carbohydrate intolerance and triglyceride elevation have been associated. Blood pressure measurements should be included in any profile.

Different effects of two progestins on plasma high density lipoprotein (HDL2) and postheparin plasma hepatic lipase activity.

Two progestins with different androgenic activity were compared for their effects on plasma high density lipoproteins and postheparin plasma lipase activities in premenopausal women. Levonorgestrel, a nortestosterone-derived steroid with androgenic activity reduced plasma HDL cholesterol by 17% (P less than 0.05) and HDL2 cholesterol by 30% (P less than 0.05), without changing the HDL3 cholesterol concentration. At the same time the postheparin plasma hepatic lipase activity was increased by 56% (P less than 0.01) whereas the lipoprotein lipase was not changed. None of these effects was reproduced during administration of medroxyprogesterone acetate, a progestin with low androgenic activity. The results suggest, first, that the decrease of HDL cholesterol observed during treatment with progestins is related to the androgenic activity of the steroid used, and, second, that the change in HDL (HDL2) is caused by androgen-induced increase of hepatic lipase activity.

Distribution of lipoproteins triglyceride and lipoprotein cholesterol in an adult population by age, sex, and hormone use- The Pacific Northwest Bell Telephone Company health survey.

This report describes the distribution of lipoprotein triglyceride and lipoprotein cholesterol in employees of the Pacific Northwest Bell Telephone Company. Means, medians, and selected percentiles are presented for very low, low, and high density lipoproteins (VLDL, LDL, and HDL, respectively) in 606 randomly selected white subjects aged 20-59. Results are specific for age decade, sex, and female sex hormone usage. Women who use sex hormones have significantly higher concentrations of triglycerides in all of the fractions across all age decades from 20 to 59 than do women not taking hormones. The average VLDL, LDL, and HDL triglyceride levels in women taking hormones are 69, 25 and 18 mg/dl which are considerably higher than the corresponding averages of 44, 17 and 12 mg/dl noted in women not taking hormones. Men have the highest average VLDL triglyceride value (85 mg/dl) but their average triglyceride concentrations in the LDL and HDL fractions (18 and 12 mg/dl) approximate those of women not taking hormones. This study in a well-defined population provides references standards for lipoprotein triglyceride concentrations. These results can be used to evaluate the effect of sex hormone treatment on the lipoprotein triglyceride content in VLDL, LDL and HDL, and to assess triglyceride content as a potential risk factor in men and older women.

PIP: A study of lipoprotein triglyceride and lipoprotein cholesterol distribution was done between 1973-76 on a randomly selected group of 606 white male and female employees, aged 20-59, of the Pacific Northwest Bell Telephone Company. Data obtained were used to ascertain whether triglyceride content of lipoprotein differs in men and women by observing mean, standard and percentile distribution of VLDL, LDL, and HDL (very low, low, and high density lipoprotein). A high proportion of women, i.e. 50% in the age group 20-29, and 50-59, reported current use of some form of exogenous sex hormone preparation. The average VLDL, LDL, and HDL triglyceride level in women taking hormones were 69, 25, and 18 mg/dl, considerably higher than the corresponding averages of 44, 17, and 12 mg/dl observed in women not taking hormones. For VLDL triglyceride, the youngest and oldest male groups had lower average levels than females in the same age taking hormones; in the middle-age group the levels were the same among men and women. For VLDL cholesterol, the 20-29 year old male and female hormone users had similar concentration levels, but male values were higher in each of the remaining age strata. These data confirm the fact that lipoprotein triglyceride rise is associated with the type of oral contraceptives used in the U.S., and with postmenopausal treatment as well.

Comparison of the lipoprotein and hemostatic changes after a triphasic and a monophasic low dose oral contraceptive in premenopausal middle-aged women.

Metabolic and hemostatic effects of 2 low dose oral contraceptives (OCs), a triphasic (ethinylestradiol + (-)-norgestrel) and a monophasic (ethinylestradiol + desogestrel) preparation, were compared in a cross-over trial in fertile women over 35 years of age. Both combinations moderately affected plasma lipids, with 17-24% increases of total triglyceridemia. Triglycerides accumulate in low density lipoproteins, thus suggesting the possible formation of an atherogenic lipoprotein particle. Only the monophasic preparation increased high density lipoprotein (HDL)-cholesterol levels significantly, with a rise in HDL3 mass and cholesterol. OC treatment led to slight changes in HDL2 and HDL3 structure, with a rise of the cholesteryl ester and triglyceride contents, indicative of a stimulated cholesterol esterification and reverse transport. Changes in the hemostatic indexes (fibrinogen, antithrombin III and protein C) were negligible. The new low dose OCs, even when prescribed to relatively older women, affect to a relatively small extent lipid/lipoprotein metabolism, with the exception of changes in the low density lipoprotein composition.

The relationship of abnormal circulating insulin levels to atherosclerosis.

The evidence linking insulin with atherosclerosis can be divided into two parts. First, there is evidence that a proportion of subjects who have atherosclerosis or who are at risk of developing atherosclerosis hav elevated circulating insulin levels. The high insulin levels may be associated with another metabolic abnormality such as obesity, hypertriglyceridaemia, uraemia or consumption of oral contraceptives, may be inappropriate to the blood sugar levels as in mild diabetes, or may be of exogenous origin as in insulin-treated diabetics. The tissues of these subjects are exposed to high concentrations of insulin, and it seems reasonable to suggest that elevated insulin levels may have pathological effects on these tissues. Secondly, there is increasing evidence that the arterial wall is an insulin sensitive tissue. Exposure of arterial tissue to insulin results in proliferation of smooth muscle cells, inhibition of lipolysis, and synthesis of cholesterol, phospholipid and triglyceride. Chronic exposure to high concentrations of insulin results in the development of lipid filled lesions similar to those of early atherosclerosis. Thus, insulin has the ability to promote changes in the artery which, in the long term, may progress to atherosclerosis. The two lines of evidence together suggest that high levels of circulating insulin may have a role in the development of atherosclerosis.

PIP: Lipid and carbohydrate metabolism abnormalities are reviewed with particular emphasis on the role of insulin and interrelationships between carbohydrate and lipid metabolism. The pathogenesis of atherosclerosis is discussed in terms of the association of abnormal circulating insulin levels. Some of the conditions associated with abnormal insulin levels and atherosclerosis are diabetes mellitis, hypertriglyceridemia, obesity, uremia, and oral contraceptive use. There is evidence that a proportion of subjects who have atherosclerosis or at risk have elevated circulating insulin levels. There is also increasing evidence that the arterial wall is an insulin-sensitive tissue. More women with myocardial infarction take oral contraceptives than controls do. Those who take the pill have 9 times the risk of others to develop cerebral ischemia or thrombosis. Many oral contraceptives cause abnormalities in glucose tolerance associated with elevated plasma insulin levels, and a degree of insulin resistance is induced. A number of the metabolic consequences of the pill may be caused by the elevated insulin levels.

Serum high density lipoprotein cholesterol levels in Chinese healthy subjects and patients with certain diseases.

Serum high density lipoprotein cholesterol (HDL-C), total cholesterol (TC) and triglycerides (TG) were determined, and values of low density lipoprotein cholesterol (LDL-C), HDL-C/TC (%), and the LDL-C/HDL-C (ratio) were calculated in 1101 healthy Chinese men and women, 77 patients with coronary heart disease (CHD), 70 patients with cerebral vascular disease (CVD), 64 patients with diabetes mellitus (DM), 40 bilaterally oophorectomized women and 95 women using oral contraceptives. Serum HDL-C levels seemed higher and LDL-C levels lower in the healthy Chinese population as compared with those previously reported from European and American whites. Serum HDL-C was significantly higher in fertile females than in males of comparable ages. We failed to demonstrate any sharp fall in HDL-C after the menopause or bilateral oophorectomy. Serum HDL-C levels were significantly lower in both CHD and CVD patients than in healthy subjects of comparable sex and age. Concomitant increases in serum TC, LDL-C and TG, however, were found in CHD patients but not in CVD patients. No abnormality in the mean serum HDL-C level was found in DM patients. However, those complicated with CHD had significantly lower HDL-C than those without CHD. A striking serum HDL-C lowering effect was found with some kinds of oral contraceptives.

PIP: Serum high density lipoprotein cholesterol (HDL-C), total cholesterol (TC), and triglycerides (TG) were determined, and values of low density lipoprotein cholesterol (LDL-C), HDL-C/TC (%), and the LDL-C/HDL-C (ratio) were calculated in 1101 healthy Chinese men and women, 77 patients with coronary heart disease (CHD), 70 with cerebral vascular disease (CVD), 64 patients with diabetes mellitus (DM), 40 bilaterally oophorectomized women, and 95 women using oral contraceptives (OCs). Serum HDL-C levels seemed higher and LDL-C levels lower in the healthy Chinese population as compared with those previously reported from European and American whites. Serum HDL-C was significantly higher in fertile females than in males of comparable ages. The authors failed to demostrate any sharp fall in HDL-C after the menopause or bilateral oophorectomy. Serum HDL-C levels were significantly lower in both CHD and CVD patients than in healthy subjects of comparable sex and age. Concomitant increases in serum TC, LDL-C, and TG, however, were found in CHD patients but not in CVD patients. No abnormality in mean serum HDL-C level was found in DM patients. However, those complicated with CHD had significantly lower HDL-C than those without CHD. A striking serum HDL-C lowering effect was found with some kinds of OCs.

Sex hormones, lipoproteins, and cardiovascular risk.

PIP: Reduced cardiovascular mortality is evidenced in persons undergoing hormone replacement therapy (HRT). Studying the effects of gonadal steroids on lipoproteins is therefore encouraged, not only because of this important revelation, but also due to the information to be gleaned on lipoprotein metabolism, the large numbers of women taking oral contraceptives and HRT, and the rising demand for the therapy. Thus far, studies have been performed on men and animals. This paper reviews some work on estrogens and androgens, and discusses oral contraceptives, HRT, and lipoproteins. In sum, estrogen administered via any route reduces low density lipoprotein concentrations. Given that animal studies demonstrate the ability of HRT to both inhibit the development of atherosclerosis and alter vasomotor tone in atherosclerotic coronary arteries, women with confirmed coronary disease may also be likely to benefit from the therapy. Greater information should be sought on the benefits of HRT for secondary prevention, therapy effects should be monitored, and the effects of estrogen/progestogen combinations should be investigated.^ieng