Ameliorative effect of nicotine exposure on insulin resistance is accompanied by decreased cardiac glycogen synthase kinase-3 and plasminogen activator inhibitor-1 during oral oestrogen-progestin therapy.

CONTEXT: Cigarette smoking is considered to be a major risk factor for the development of diabetes and cardiovascular disease. Oestrogen-progestin combined oral contraceptive (COC) use has been associated with adverse cardiometabolic events. OBJECTIVE: We hypothesized that nicotine would ameliorate insulin resistance (IR) that is accompanied by decreased cardiac glycogen synthase kinase-3 (GSK-3) and plasminogen activator inhibitor-1 (PAI-1). METHODS: Female Wistar rats received (po) low-(0.1 mg/kg) or high-nicotine (1.0 mg/kg) with or without COC containing 5.0 µg levonorgestrel plus 1.0 µg ethinylestradiol daily for 8 weeks. RESULTS: Data showed that COC treatment or nicotine exposure led to IR, glucose deregulation, atherogenic dyslipidemia, increased corticosterone, aldosterone, cardiac and circulating GSK-3 values and PAI-1. However, these effects with the exception of corticosterone and aldosterone were ameliorated in COC + nicotine-exposed rats. CONCLUSION: Amelioration of IR induced by COC treatment is accompanied by decreased circulating PAI-1, cardiac PAI-1 and GSK-3 instead of circulating aldosterone and corticosterone.

Role of AMP-activated protein kinase α1 in 17α-ethinylestradiol-induced cholestasis in rats.

Estrogen-induced cholestasis occurs in many women who are susceptible due to pregnancy or hormone replacement therapy for postmenopausal syndrome. 17α-Ethinylestradiol (EE), as a synthetic estrogen, has been widely used to study the underlying mechanisms of estrogen-induced cholestasis. Recent studies have also reported that liver kinase B1 (LKB1)-mediated activation of AMP-activated protein kinase (AMPK) plays a critical role in the regulation of canalicular network formation. However, the role of AMPK in EE-induced cholestasis remains to be determined. In this study, the effects of EE (1-100 µM) on AMPK activation and the expression of farnesoid X receptor (FXR) and hepatic bile acid transporters were examined in in vitro using 3D-cultured rat primary hepatocytes and in in vivo using rat cholestasis models. We also used specific chemical agonist and antagonist of AMPK, AMPK subunit-specific antibodies and lentiviral shRNAs for AMPKα1 and AMPKα2 to delineate the role of AMPK in EE-induced cholestasis and potential cellular mechanisms. We found that EE-induced phosphorylation of AMPKα1 via extracellular signal-regulated kinases-LKB1-mediated signaling pathways and subsequent nuclear translocation accounted for the down-regulation of FXR and bile acid transporters and disruption of bile acid homeostasis. Inhibition of AMPK activation using an AMPK antagonist Compound C (2 µM) or down-regulation of AMPKα1 using gene-specific shRNA attenuated EE-induced cholestasis both in in vitro and in in vivo. In conclusion, these results revealed that activation of cAMP-ERK-LKB1-AMPKα1 signaling pathway plays a critical role in EE-mediated dysregulation of the expression of FXR and bile acid transporters. AMPKα1 may represent an important therapeutic target for estrogen-induced cholestasis.

The effect of triclosan on the uterotrophic response to extended doses of ethinyl estradiol in the weanling rat.

Triclosan (TCS), an antibacterial, has been shown to be an endocrine disruptor in the rat. We reported previously that TCS potentiated the estrogenic effect of ethinyl estradiol (EE) on uterine growth in rats exposed to EE and TCS in the uterotrophic assay, whereas TCS alone had no effect. To further characterize this potentiation, we evaluated the effect of co-exposure with lower doses of EE that are comparable to the concentrations in hormone replacement regimens and began to assess the mechanisms by which this potentiation occurs. Changes in uterine weight, epithelial cell growth, and estrogen-sensitive gene expression were assessed. TCS expectedly enhanced the uterotrophic response to EE, however at significantly lower doses of EE. Similarly, TCS increased the EE-induced stimulation of epithelial cell height following cotreatment. Cotreatment also enhanced the estrogen-induced change in gene expression, which was reversed with an ER antagonist. Furthermore, the TCS-induced potentiation was independent of ER activation, as no effects were observed in the ER TA assay.

Fluorescence of sediment humic substance and its effect on the sorption of selected endocrine disruptors.

Humic substances (HS) have a critical influence on the sorption of organic contaminants by soils and sediments. This paper describes investigations into the sorption behavior of three representative endocrine disruptors, bisphenol A (BPA), 17beta-estradiol (E2), and 17alpha-ethynylestradiol (EE2), onto sediments and HS extracted sediments using a batch technique. The organic carbon-normalized partition coefficients (K(oc)) for the extracted HS (K(oc)(hs)) were calculated, and the fluorescence spectra of the HS extraced from different sediment samples were gained using excitation/emission matrix (EEM). Particular attention was paid to the correlations between the fluorescence characteristics of HS and the log K(oc)(hs) of selected endocrine disruptors. The results show that the log K(oc)(hs) values range from 3.14 to 4.09 for BPA, from 3.47 to 4.33 for E2, and from 3.65 to 4.32 for EE2. Two characteristic excitation-emission peaks were observed for HS samples extracted from sediments. They are located at Ex/Em=250-260 nm/400-450 nm (peak alpha') and Ex/Em=310-330 nm/390-400 nm (peak alpha) respectively. The alpha' and alpha peak relative intensities I(alpha')/I(alpha) vary from 0.46 to 1.64 for different extracted HS samples. The similarity between fulvic acids (FA) Ex/Em pairs and those observed for HS indicates that FA is the predominant fraction of HS extracted from sediments. Moreover, the log K(oc)(hs) values of BPA, E2, and EE2 have a negative linear correlation to I(alpha')/I(alpha) values. Peak alpha is often attributed to relatively stable and high molecular weight aromatic fulvic-like matter. Therefore, the result presented here reveals that the abundance of aromatic rings in HS molecular structure plays a critical role in the sorption of selected endocrine disruptors.

Does St. John's wort interfere with the antiandrogenic effect of oral contraceptive pills?

BACKGROUND: St. John's wort (SJW), a commonly used herbal remedy, has been shown to compromise the efficacy of drugs, including oral contraceptive pills (OCPs), by inducing cytochrome P-450. We investigated whether the simultaneous use of SJW with OCPs resulted in elevated serum androgen levels with implications of impaired OCP treatment of hirsutism and acne. MATERIALS AND METHODS: Fifteen healthy women were treated with the low-dose OC Loestrin 1/20trade mark for 2 months and then additionally with SJW for 2 months. Androgen and sex hormone-binding globulin (SHBG) levels were measured in serum by immunoassay methods; free testosterone (fT) was calculated. Results were analyzed using the Wilcoxon signed-rank test. RESULTS: There were no statistically significant differences in androgen levels after the addition of SJW in women using Loestrin 1/20trade mark. However, there were decreases in total testosterone and fT levels (10.7% and 15.8%, respectively) along with a small increase in SHBG levels (7.0%). CONCLUSIONS: In women using OCPs and SJW simultaneously, it appears that SJW does not interfere with the antiandrogenic properties of OCPs.

3alpha-6alpha-Dihydroxy-7alpha-fluoro-5beta-cholanoate (UPF-680), physicochemical and physiological properties of a new fluorinated bile acid that prevents 17alpha-ethynyl-estradiol-induced cholestasis in rats.

3alpha-6alpha-Dihydroxy-7alpha-fluoro-5beta-cholanoate (UPF-680), the 7alpha-fluorine analog of hyodeoxycholic acid (HDCA), was synthesized to improve bioavailability and stability of ursodeoxycholic acid (UDCA). Acute rat biliary fistula and chronic cholestasis induced by 17alpha-ethynyl-estradiol (17EE) models were used to study and compare the effects of UPF-680 (dose range 0.6-6.0 micromol/kg min) with UDCA on bile flow, biliary bicarbonate (HCO(3)(-)), lipid output, biliary bile acid composition, hepatic enzymes and organic anion pumps. In acute infusion, UPF-680 increased bile flow in a dose-related manner, by up to 40.9%. Biliary HCO(3)(-) output was similarly increased. Changes were observed in phospholipid secretion only at the highest doses. Treatment with UDCA and UPF-680 reversed chronic cholestasis induced by 17EE; in this model, UDCA had no effect on bile flow in contrast to UPF-680, which significantly increased bile flow. With acute administration of UPF-680, the biliary bile acid pool became enriched with unconjugated and conjugated UPF-680 (71.7%) at the expense of endogenous cholic acid and muricholic isomers. With chronic administration of UPF-680 or UDCA, the main biliary bile acids were tauro conjugates, but modification of biliary bile acid pool was greater with UPF-680. UPF-680 increased the mRNA for cytochrome P450 7A1 (CYP7A1) and cytochrome P450 8B (CYP8B). Both UDCA and UPF-680 increased the mRNA for Na(+) taurocholate co-transporting polypeptide (NCTP). In conclusion, UPF-680 prevented 17EE-induced cholestasis and enriched the biliary bile acid pool with less detergent and cytotoxic bile acids. This novel fluorinated bile acid may have potential in the treatment of cholestatic liver disease.

Beta-naphthoflavone inhibits the induction of hepatic oestrogen-dependent proteins by 17alpha-ethynylestradiol in mosquitofish (Gambusia holbrooki).

The interactive effects of an aryl hydrocarbon receptor (AhR) agonist and of a xenoestrogen on biomarker responses were studied in the liver of male mosquitofish (Gambusia holbrooki). Hepatic 7-ethoxyresorufin O-deethylase (EROD) enzymatic activity was measured as a biomarker of exposure to the model AhR agonist beta-naphthoflavone (bNF). Hepatic proteins indicating the exposure of males to the synthetic oestrogen 17alpha-ethynylestradiol (EE2) were monitored by Western blot analysis using immunoserum prepared for this study. After a semi-static exposure only to waterborne EE2, Western blot analysis of liver homogenate revealed the induction of two protein bands (a double band at 205 kDa and a single band at 125 kDa). The interaction between bNF and EE2 was investigated by analysing, on the one hand, EROD activity and, on the other hand, immunoreactivity corresponding to the two oestrogen-dependent protein bands in the liver of fish exposed to different concentrations of bNF for 2 days, then to the same concentrations of bNF plus 0.1 microg l(-1) EE2 for 5 days. EE2 changed neither the basal activity of EROD nor its rate of induction with 1.0 and 4.0 microg l(-1) bNF. On the other hand, the induction of oestrogen-dependent proteins with 0.1 microg l(-1) EE2 was inhibited by exposure to 4.0 microg l(-1) bNF. These results together with literature data suggest that field monitoring of xenoestrogen contamination through the analysis of oestrogen-dependent protein in male fish as a biomarker should take into account the possible negative interference of AhR agonists.

Importance of estrogen receptors in hepatic LDL receptor regulation.

Treatment with pharmacological doses of estrogen is the most potent way to stimulate hepatic LDL receptor expression in vivo. The mechanism for this effect is unclear, in part because of difficulties in inducing this stimulation in vitro. A fundamental question, whether estrogen receptors (ERs) mediate this stimulation, has not been addressed. The aim of the current study was to determine the involvement of ERs in the estrogen-induced stimulation of LDL receptors. Treatment of rats with high doses of ethynylestradiol for 7 days increased the hepatic LDL receptor protein and mRNA levels four- and threefold, respectively. LDL receptor stimulation in estrogen-treated rats was not due to their reduced food intake because hepatic LDL receptor expression did not increase in rats fasted for 72 hours. Treatment with antiestrogen (tamoxifen or clomiphene) abolished the LDL receptor stimulatory effect of ethynylestradiol at both the protein and mRNA levels. Antiestrogen alone had no effect on hepatic LDL receptor expression and did not influence the strong resistance to dietary cholesterol normally present in rats. It is concluded that ERs are critically involved in the induction of hepatic LDL receptor expression by ethynylestradiol. The known role of growth hormone for the expression of hepatic ERs may therefore play a role in the modulation of the effects of estrogen on cholesterol metabolism and hepatic LDL receptors in the rat.

Antiestrogenic properties of raloxifene.

This 21-day, open-label study evaluated the effects of raloxifene and tamoxifen on estrogen-induced changes in serum levels of anterior pituitary hormones (prolactin, luteinizing hormone, and follicle-stimulating hormone), sex steroids (testosterone, estradiol), and binding globulins [thyroid binding globulin (T3 resin uptake), transcortin, sex steroid binding globulin]. Seventeen healthy male volunteers completed the study after being randomized to one of three treatments: raloxifene, tamoxifen, or placebo. Six subjects received raloxifene (200 mg daily) for 10 days, 6 subjects received tamoxifen [20 mg twice a day (b.i.d.)] for 10 days, and 5 subjects received placebo for 10 days. All subjects received ethinyl estradiol (20 micrograms b.i.d.) for 7 days starting 3 days after initiation of study drug or placebo treatment. Results of the primary analysis of this study indicate that for six of the seven analyzable parameters of estrogen action (excluding luteinizing hormone) raloxifene blunted the estrogen response; this effect was significant only for T3 resin uptake. Tamoxifen administration significantly blunted or reversed the estrogen effect in all six of these parameters. Raloxifene, an effective antiestrogen in animal models, is also antiestrogenic in humans.

Abrogation by a potent gonadotropin-releasing hormone antagonist of the estrogen/progesterone-stimulated surge-like release of luteinizing hormone and follicle-stimulating hormone in postmenopausal women.

In both the rodent and primate, administration of progesterone elicits an acute surge-like release of LH in the setting of prior estrogen treatment. Whether these facilitative effects of estrogen and progesterone on gonadotropin secretion reside at pituitary or hypothalamic loci is not known. To further investigate the mechanisms by which estrogen combined with progesterone amplifies gonadotropin secretion, we studied the responses of seven estrogen-primed postmenopausal women to progesterone administration with or without cotreatment with a potent GnRH antagonist, [Ac-D2Nal1,D4ClPhe2,D3Pal3,Arg5,DGlu6(AA), DAla10]GnRH. Repetitive blood sampling for the later measurement of serum concentrations of LH, FSH, and PRL was begun 4 h before the administration of progesterone and continued for 36 h. We observed that progesterone administration after 72 h of priming with ethinyl estradiol resulted in a surge-like release of LH and FSH in all subjects. Concomitant administration of the GnRH antagonist abolished the surge-like release of both gonadotropins in all subjects. In contrast, administration of the antagonist had no effect on PRL release. These results indicate that endogenous GnRH action is an obligatory component of the progesterone-induced surge-like release of both gonadotropic hormones in the estrogen-primed human.

Reversal of ethinylestradiol-induced cholestasis by epomediol in rat. The role of liver plasma-membrane fluidity.

Epomediol (EPO) is a synthetic terpenoid compound shown to be active in increasing bile flow and some enzymatic activities of liver plasma membranes in the rat. The possible effect of EPO treatment in the ethinyl-estradiol (EE) induced cholestasis in the rat was investigated by measuring the hepatic transport of sulfobromophthalein (BSP) (plasma clearance and biliary secretion) and bile flow. Liver plasma membrane fluidity was also determined by the steady state fluorescence polarization (P) of diphenylhexatriene (DPH). EE administration (5 mg/kg s.c. for 5 days) was followed by a significant, comparable reduction (P less than 0.001) in BSP plasma clearance and biliary excretion and in bile flow. Intraperitoneal administration of EPO (100 mg/kg) to EE-treated rats restored both parameters of BSP transport, as well as bile flow, to control values. Liver plasma membrane fluidity was markedly (P less than 0.01) decreased by EE administration with a concomitant reduction (P less than 0.01) in Na+/K+-ATPase activity. EPO administration significantly increased membrane fluidity to values higher either to cholestatic (P less than 0.05) or control (P less than 0.05) animals. On the contrary, EPO did not influence Na+/K+-ATPase activity in either EE-treated or control animals. These data indicate that EPO fully reverses the impairments of BSP transport and bile flow induced by EE, possibly by reversing the decrease in liver plasma membrane fluidity induced by the synthetic estrogen. On the contrary, the EE-mediated decrease in Na+/K+-ATPase activity was not reversed by EPO.

Retinyl acetate inhibits estrogen-induced mammary carcinogenesis in female ACI rats.

Two groups of female ACI rats were placed on powdered AIN-76 diets containing retinyl acetate (412,000 i.u. per kg diet) and two groups of rats were placed on placebo diets. Two weeks later one group from each diet was subcutaneously implanted with a 20 mg pellet containing 1 mg of 17 alpha-ethinylestradiol (EE2) mixed with cholesterol, and the remaining groups received 20 mg cholesterol pellet implants. The four groups of animals were maintained on their respective diet for 24 weeks after pellet implantation. The EE2-treated rats were hyperphagic and weighed less than the cholesterol-treated rats. Retinyl acetate had no effect on food consumption or body wt changes. None of the rats that received pellets composed of cholesterol only exhibited mammary carcinomas (MC) or pituitary tumors. All rats with an EE2 implant had pituitary tumors: 88% of the rats on the placebo diet had one or more MC; 70% of the rats on the retinyl acetate diet had one or more MC. The difference between the two EE2-treated groups for incidence of animals with at least one MC was not significant (chi 2). However, the EE2-treated rats on the placebo diet had approximately twice as many MC as the EE2-treated rats on the retinyl acetate diet. Thus, retinyl acetate inhibited estrogen-induced mammary carcinogenesis in female ACI rats, without evidence of gross toxicity.

S-adenosyl-L-methionine antagonizes oral contraceptive-induced bile cholesterol supersaturation in healthy women: preliminary report of a controlled randomized trial.

Recent experimental investigations have shown that S-adenosyl-L-methionine (SAMe) reverses estrogen-induced bile secretion impairment. The mechanism of this action seems to be related to the capability of SAMe both to inactivate catecholestrogens by methylation reaction and to methylate membrane phospholipids increasing the liver plasma membrane fluidity reduced by the estrogens. Aim of this investigation was to know whether SAMe also prevents oral contraceptive-induced cholesterol supersaturation of gallbladder bile in humans. To six healthy nonobese women whose bile cholesterol saturation index increased from a mean basal value of 0.77 (SD 0.22) to 1.20 (SD 0.38) (p less than 0.01) after two cycles of treatment with oral contraceptives containing 50 micrograms ethynylestradiol, plus 250 micrograms d-norgestrel, 200 mg SAMe per os tid was administered in addition to the oral contraceptive for other two cycles. The bile cholesterol saturation index decreased to 0.88 (SD 0.26) (p less than 0.05 versus oral contraceptive value). These results indicate that SAMe antagonizes biliary lipid changes induced by estrogen-progestin containing oral contraceptive and suggest its potential usefulness in women on oral contraceptive treatment to prevent lithogenic bile secretion.

S-adenosyl-L-methionine antagonizes ethynylestradiol-induced bile cholesterol supersaturation in humans without modifying the estrogen plasma kinetics.

Previous investigations have shown that S-adenosyl-L-methionine antagonizes both cholestasis and bile lipid alterations induced by ethynylestradiol in the rat. Since it is still unknown whether S-adenosyl-L-methionine prevents ethynylestradiol-induced cholesterol supersaturation of bile in humans also and how methynation interferes with plasma ethynylestradiol disappearance, the present study has been carried out. On different days, 5 nonobese subjects with indwelling biliary drainage and reestablished enterohepatic bile circulation received 200 micrograms of intravenous ethynylestradiol or ethynylestradiol plus 200 mg of S-adenosyl-L-methionine intramuscularly. S-adenosyl-L-methionine administration prevented any ethynylestradiol-induced changes in hepatic bile saturation index. Moreover, S-adenosyl-L-methionine did not affect ethylnylestradiol pharmacokinetics which was evaluated in a group of 6 nonobese women receiving 100 micrograms of intravenous ethynylestradiol or ethynylestradiol plus 100 mg of S-adenosyl-L-methionine intramuscularly. These findings indicate that S-adenosyl-L-methionine prevents ethynylestradiol-induced bile lipid changes without interfering with ethynylestradiol kinetics in humans.

Reversal of ethinyl estradiol-induced bile secretory failure with Triton WR-1339.

The effects of Triton WR-1339 and phenobarbital on ethinyl estradiol bile secretory failure were examined to determine the mechanism responsible for decreased bile salt excretion. When administered to ethinyl estradiol-treated rats, Triton WR-1339 restored bile salt independent bile flow and maximum taurocholate transport, whereas phenobarbital corrected bile flow only. Ethinyl estradiol decreased the activities of Na(+)-K(+)-ATPase, 5'-nucleotidase, while increasing the activities of Mg(++)-ATPase and alkaline phosphatase. In contrast to these heterogeneous changes in surface membrane enzyme activities, the number and affinity of [(14)C]cholic acid carriers were not altered. When administered in vivo or added directly to surface membrane fractions Triton WR-1339 restored the activities of Na(+)-K(+)-ATPase and Mg(++)-ATPase of rats treated with ethinyl estradiol through a process that did not require protein synthesis (unaffected by cycloheximide). Phenobarbital also restored the activity of Na(+)-K(+)-ATPase to control levels, but, unlike Triton WR-1339 it did not correct the defect responsible for reduced bile salt secretion. Ethinyl estradiol increased the concentration of cholesterol esters in surface membrane fractions. When administered to ethinyl estradiol-treated rats, Triton WR-1339 restored cholesterol ester concentrations to normal, whereas phenobarbital did not. These combined data suggest that decreased or altered bile salt carriers or reduced sodium driving forces resulting from impaired activity of Na(+)-K(+)-ATPase are not responsible for decreased bile salt excretion in ethinyl estradiol-treated rats. It is proposed that the diverse changes in surface membrane function, which are associated with ethinyl estradiol bile secretory failure, may be the result of a generalized alteration in membrane lipid structure.

Alterations of hepatic Na+,K+-atpase and bile flow by estrogen: effects on liver surface membrane lipid structure and function.

Administration of the synthetic estrogen ethinyl estradiol (17alpha-ethinyl-1,3,5-estratriene-3,17beta-diol) decreases hepatic Na(+),K(+)-ATPase (ATP phosphohydrolase; EC 3.6.1.3) activity and bile flow to 50% and alters the composition and structure of surface membrane lipid in rats. Although the content of phospholipids was not changed by treatment, free cholesterol (130%) and cholesterol esters (400%) were increased in liver surface membrane fractions. These observations correlate with changes in membrane viscosity, as shown by electron spin resonance probes. Both rotational correlation time, using the isotropic probe methyl (12-nitroxyl)stearate, and the order parameter, determined by the anisotropic probe 5-nitroxylstearic acid, were significantly increased in liver surface membrane fractions from rats treated with ethinyl estradiol. Administration of Triton WR-1339, a nonionic detergent that corrects hepatic and serum lipid changes caused by ethinyl estradiol treatment, restored toward normal elevated membrane lipids and viscosity as well as Na(+),K(+)-ATPase activity and bile flow. Although restoration of normal liver surface membrane structure and function may be due to reversal of abnormal lipid composition, detergents also may directly alter membrane enzyme activity. Addition of Triton WR-1339 in vitro increased Na(+),K(+)-ATPase activity and reduced membrane viscosity of surface membranes from rats treated with ethinyl estradiol. Triton had no effect on either parameter in normal membrane preparations. Studies of membrane structure and function both in vivo and in vitro suggest that alterations in lipid composition may alter Na(+),K(+)-ATPase function and bile flow.

Molecular biology and oral contraception.

Recent developments in knowledge of sex hormone receptors and steroid analogue metabolism allow a rational selection of oral contraceptive steroids from among the numerous available products. Dose related metabolic effects of synthetic estrogens have been demonstrated. Many of these estrogenic actions are antagonised by norgestrel but not by any other commercially available progestogen. Generalised activation of lysosomal enzymes can be demonstrated in oral contraceptive users and is shown to be related to the total steroid dose per cycle, rather than to particular products. These findings suggest that the lowest dose combination of ethynylestradiol and d-norgestrel is the product of choice. Clinical results with such a product are described.