Steroid feedback on gonadotropin release and pituitary gonadotropin subunit mRNA in mice lacking a functional estrogen receptor alpha

Steroid hormones regulate levels of gonadotropin mRNA in the pituitary, and gonadotropic hormones in plasma. To determine whether estrogen receptor a (ERα) mediates steroid negative feedback, wild type (WT) and estrogen receptor a knockout (ERαKO) mice of both sexes were gonadectomized and implanted with a Silastic capsule containing either estradiol (E₂), dihydrotestosterone (DHT), testosterone, or a blank capsule. Ten days later, plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were measured. Pituitary mRNA levels of gonadotro-pin subunit (α, LHβ, FSHβ) and prolactin (PRL) were quantified. LH levels in gonad-intact ERαKO females were elevated, similar to values seen following gona-dectomy. By contrast, serum LH concentrations in gonad-intact ER a KO males were low and rose follow-ing gonadectomy, suggesting androgen feedback. Estradiol treatment significantly decreased plasma LH in WT animals, but not in ER a KOs. In fact, in female ER a KOs, our dose of E₂ increased plasma levels of LH as compared with untreated, ovariectomized ER a KOs. All the steroid treatments suppressed LH in WT ani-mals whereas only DHT consistently suppressed LH concentrations in ER a KO mice. The postgonadectomy rise in plasma FSH was prevented by steroid treatments in WT females, but not in any of the other groups. Gonadotropin subunit and PRL mRNA responses to E₂ treatment (both inhibitory and stimulatory) were absent in ER a KO mice, suggesting a critical role for ERα. Although E₂ can exert negative feedback effects on LH release in both males and females by actions at the ERα, the androgen receptor plays the primary physiological role in the male mouse.     

Suppressive effect of ethanol on the expression of hepatic asialoglycoprotein receptors augmented by interleukin-1β, interleukin-6, and tumor necrosis factor-α

Blood levels of inflammatory-related cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, are elevated in patients with alcoholic liver diseases. We investigated the effects of these cytokines and ethanol on the expression of hepatic asialoglycoprotein receptors (AGPRs) in a human hepatoblastoma cell line, HepG2. An [¹²⁵I]-asialo-orosomucoid binding assay showed significant increases in surface AGPR numbers in HepG2 cells by treatment with IL-1β, IL-6, and TNF-α, to levels which were approximately 130% of the values in untreated control cells. However, the enhanced AGPR numbers induced by treatment with these cytokines were markedly suppressed, to 70%–80% of the number in the untreated cells, by treatment with ethanol. Immunological detection of AGPR with a specific antibody demonstrated that the modulation of surface AGPR numbers was correlated with the cellular expression levels of AGPR. These results suggest that, although IL-1β, IL-6, and TNF-α stimulate the synthesis of hepatic AGPR, ethanol suppresses the expression of AGPR augmented by these cytokines. This leads to an increase in serum asialo-orosomucoid levels caused by the disordered catabolism mediated by AGPR in patients with alcoholic liver disease. (Received Dec. 5, 1997; accepted May 22, 1998)     

Distribution of peroxisome proliferator-activated receptors (PPARs) in human skeletal muscle and adipose tissue: relation to insulin action

Aims/hypothesis. To evaluate the tissue distribution and possible role of the peroxisome proliferator-activated receptors (PPARs) in insulin action in fat and muscle biopsy specimens from lean, obese and subjects with Type II (non-insulin-dependent) diabetes mellitus.¶Methods. We measured PPARα, PPARβ(δ) and PPARγ protein expression by western blot analysis. The PPARγ protein was also measured in muscle before and after 3-h hyperinsulinaemic (300 mU · m^–2· min^–1) euglycaemic clamps.¶Results. The PPARα protein was expressed preferentially in muscle relative to fat (more than sevenfold). The PPARβ protein was similar in fat and muscle. The amount of PPARγ protein found in muscle was, on average, two-thirds of that present in fat. There was no statistically significant difference between non-diabetic and diabetic subjects in baseline (pre-clamp) muscle PPAR (α, β or γ) protein expression. Subgroup analysis showed, however, significantly higher PPARγ protein in the most insulin resistant diabetic subjects with glucose disposal rates of 3–6 mg · kg^–1· min^–1 compared with their age and weight matched counterparts with glucose disposal rates of 6–9 (147 ± 23 vs 88 ± 10 AU/μg protein, p≤ 0.01 in diabetic and vs 94 ± 15, p≤ 0.04 in non-diabetic subjects). Muscle PPARγ protein and glucose disposal rates were inversely correlated in diabetic subjects (r = –0.47, p≤ 0.05).¶Conclusion/interpretation. All PPARs (α, β or γ) are present in skeletal muscle and adipose tissue with different relative distributions. The PPARγ protein is abundant in skeletal muscle as well as adipose tissue. The altered expression of skeletal muscle PPARγ is consistent with a role for this nuclear protein in the impaired insulin action of Type II diabetes. [Diabetologia (2000) 43: 304–311]     

Differential effects of ovarian steroids and raloxifene on serotonin 1A and 2C receptor protein expression in macaques

To further understand the role of ovarian hormones in the function of the serotonin neural system, we investigated the effects of estradiol (E), progesterone (P), and raloxifene on 5HT 1A and 2C receptor protein expression in the dorsal raphe region using Western blot analysis. Adult rhesus macaques (Macaca mulatta) were ovariectomized (Ovx) and implanted with Silastic capsules containing E or P. In the first paradigm, animals that had been Ovx for 6–16 months were treated for 1 month with E (E1) or E + P (EP1) and compared to animals that were untreated and Ovx for 5 months (n = 4 per group). In the second paradigm, comparisons were made between animals that were Ovx and untreated for 5 months, or Ovx and immediately implanted with Silastic capsules containing E or E + P for 5 months (E5, EP5), or administered raloxifene in the diet for 5 months (Ral5) (n = 4 per group). The dorsal raphe region was harvested, homogenized and a crude membrane fraction was obtained for examination of receptor proteins. In the first paradigm, 5HT1A receptor protein expression was significantly lower in E1 and EP1 treatment groups compared to the Ovx-control group (ANOVA P = 0.01; posthoc P < 0.03), but 5HT2C receptor expression was unaffected by 1 month of E or EP treatment. In the second paradigm, there was no difference in 5HT1A receptor expression between the Ovx-control group and the E5 group, but 5HT1A receptor expression was significantly suppressed in the EP5 group (ANOVA P = 0.04; posthoc P < 0.05). In addition, 5HT2C expression increased in the E5 treatment group relative to the Ovx-control group. Addition of P to the E5 regimen prevented the E5-induced increase in 5HT2C receptor expression and significantly reduced 5HT2C receptor expression to a level below that observed in the Ovx-control group (ANOVA P = 0.001; posthoc P < 0.05). Thus, 5HT1A receptor may lose sensitivity to the suppressive effect of E after 5 months, whereas the 5HT2C receptor increases. However, addition of P in the EP5 regimen maintains the regulatory effects observed with 1 month of treatment. 5HT1A receptor protein levels were higher with raloxifene treatment than in Ovx-control animals (P < 0.01), suggesting that raloxifene may antagonize residual E in Ovx animals.     

Plasma cytokine levels in young and elderly twins: genes versus environment and relation to in vivo insulin action

Aims/hypothesis We studied the impact of genetic versus pre- and postnatal environmental factors on the plasma levels of IL6, TNF and the soluble TNF receptor superfamily, member 1A (TNFRSF1A, previously known as TNF receptor type1 [TNFR1]). Materials and methods Using the hyperinsulinaemic–euglycaemic clamp, we assessed the association between cytokine levels and both peripheral insulin sensitivity and hepatic glucose production. Fasting plasma IL6, TNF and soluble TNFRSF1A levels were measured using ELISA in 55 young and 43 elderly twin pairs. Results Plasma IL6 and TNF were influenced by genetic factors in young and elderly twins respectively, while no significant impact of genetics was found for soluble TNFRSF1A. Significant intra-twin pair correlations between birthweight and both IL6 and soluble TNFRSF1A levels were found. In addition to the effect of birthweight on IL6, age and fat % also significantly influenced IL6 levels, whereas soluble TNFRSF1A levels were significantly influenced by zygosity, age, fat % and sex. Plasma soluble TNFRSF1A was associated with higher plasma NEFA and to some extent with reduced insulin sensitivity. Plasma IL6 was associated positively with basal NEFA. TNF level was not associated with in vivo glucose or fat metabolism after correction for known confounders. Conclusions/interpretation Plasma IL6 and soluble TNFRSF1A are influenced by the intrauterine environment. We found some evidence of a genetic component for TNF and IL6 in young and elderly twins respectively. Plasma IL6 may influence basal lipolysis, but neither plasma TNF nor IL6 levels are independently associated with hepatic or peripheral insulin action. Nevertheless, plasma soluble TNFRSF1A may play some role in the control of insulin action.     

Potential involvement of mt1 receptor and attenuated sex steroid-induced calcium influx in the direct anti-proliferative action of melatonin on androgen-responsive LNCaP human prostate cancer cells

Melatonin, a pineal secretory product, has been shown to exert a direct anti-proliferative action on the androgen-sensitive LNCaP prostate cancer cell line through hitherto undefined mechanisms. In this communication, expression of mt1 melatonin receptor protein in human prostate cancer tissues and LNCaP cells was demonstrated by immunohisto(cyto)chemistry and western blotting, hence supporting the use of LNCaP cell line as a model for the study of melatonin signaling in prostate cancer cell growth. Using 3H-thymidine incorporation assay, LNCaP cell proliferation was inhibited by 2-iodomelatonin, a high-affinity melatonin receptor agonist. Furthermore, melatonin inhibited 3H-thymidine incorporation into LNCaP cells and attenuated 5alpha-dihydrotestosterone (DHT) or 17beta-estradiol (E2)-induced stimulation of LNCaP cell proliferation at physiological and pharmacological concentrations. Similar concentration-dependent inhibition of sex steroid-induced stimulation of thymidine incorporation into LNCaP cells by 2-iodomelatonin was also observed. Interestingly, attenuation of sex steroid-stimulated calcium influx into LNCaP cells by pharmacological concentrations of melatonin was recorded, whereas 2-iodomelatonin had no effect on cytosolic calcium changes induced by sex steroids. In addition, proliferative and cytosolic calcium changes were associated with inhibition of total prostate-specific antigen (PSA) production by LNCaP cells at high physiological and pharmacological concentrations of melatonin. Our data suggest that activated mt1 receptor and attenuated sex steroid-induced calcium influx are two important mechanisms mediating the direct anti-proliferative action of melatonin on androgen-responsive human prostate cancer cells.     

Synergistic effect of polymorphisms in uncoupling protein 1 and β3-adrenergic receptor genes on basal metabolic rate in obese Finns

Summary The polymorphisms in the uncoupling protein 1 (UCP1, A to G) and β ₃-adrenergic receptor (β ₃-AR, Trp64Arg) genes have been suggested to be associated with an increased tendency to gain weight. We investigated the frequency of the A to G polymorphism of the UCP1 gene and its effect on basal metabolic rate (BMR) among obese Finns. We also examined the effects of the simultaneous occurrence of the polymorphisms in the UCP1 and β ₃-AR genes on BMR. Altogether 170 obese subjects (29 men, 141 women, BMI 34.7 ± 3.8 kg/m², age 43 ± 8 years, mean ± SD) participated in the study. The A to G substitution of the UCP1 gene was verified by digestion of the PCR product with Bcl I. The frequency of the A to G polymorphism of the UCP1 gene in obese subjects did not differ significantly from the population-based control subjects (5 vs 1 % for homozygotes (GG) and 35 vs 42 % for heterozygotes (AG), p = 0.077, for trend). BMR adjusted for lean body mass, age and sex (adjBMR) was similar among the three UCP1 gene genotypes of obese subjects (AA n = 90, AG n = 72 or GG n = 8). However, the subjects with the polymorphisms in both UCP1 and β ₃-AR genes (n = 18) had a 79 kcal/day (95 % CI 30–128) lower adjBMR than the subjects without these polymorphisms (n = 76) (1551 ± 77 vs 1629 ± 141 kcal/day, p = 0.002). Furthermore, adjBMR was 63 kcal/day (95 % CI 7–118 kcal/day) lower in the subjects with both polymorphisms (n = 18) compared with the subjects (n = 14) who had only the polymorphism in the β ₃-AR gene (1551 ± 77 vs 1613 ± 76 kcal/day, p = 0.028). The A to G polymorphism of the UCP1 gene did not have an independent effect on BMR, but its simultaneous existence with the Trp64Arg polymorphism of the β ₃-AR gene resulted in more lowered BMR than the Trp64Arg polymorphism of β ₃-AR gene alone. [Diabetologia (1998) 41: 357–361] Received: 12 June 1997 and in final revised form: 7 November 1997     

Estrogen replacement regimen and brain infusion of lipopolysaccharide differentially alter steroid receptor expression in the uterus and hypothalamus

The regimen of estrogen replacement can alter the consequences of estrogen therapy and stressors. To determine the long-term effects and interaction of these systems on the brain and periphery, adult female rats were infused with lipopolysaccharide (LPS) into the fourth ventricle of the brain for 4 weeks, and ovariectomized rats were administered either constant or pulsed regimens of estrogen replacement (17β-estradiol) until sacrifice at 8 weeks. Constant, but not pulsed, estrogen replacement reduced ERα and increased HSP90, HSP70, and PR_B uterine protein levels. Both estrogen regimens increased ERβ, HSP27, and PR_A uterine proteins. Both regimens reduced hypothalamic levels of ERα, but not ERβ, HSP, or PR. No changes were observed in the hippocampus. Long-term brain infusion of LPS activated microglia and reduced body weight, but did not alter corticosterone or nitrotyrosine levels. LPS infusion into intact rats suppressed uterine weight, increased ERα and decreased HSP90 in the uterus. LPS did not alter uterine weight in ovariectomized rats treated with constant or pulsed estrogen. Together, these data suggest the timing of estrogen replacement and neuroinflammatory stressors can profoundly affect uterine and hypothalamic steroid receptor expression and may be important parameters to consider in the post-menopausal intervention with estrogen.     

Adacolumn Selective Leukocyte Adsorption Apheresis in Patients with Active Ulcerative Colitis: Clinical Efficacy,Effects on Plasma IL-8, and Expression of Toll-like Receptor 2 on Granulocytes

Adacolumn selective granulocyte and monocyte apheresis (GMA) depletes activated leukocytes in patients with ulcerative colitis (UC). However, this per se cannot fully explain the efficacy of GMA. We have investigated the effects of GMA on the expression of toll-like receptors (TLRs) and plasma interleukin-8 (IL-8). Twenty-two patients with clinical activity index (CAI) of 5–17, 15 with total colitis and 7 with left-sided colitis, were included. Each patient could receive up to 10 GMA sessions, at 1 or 2 sessions per week. GMA was added to the patients’ ongoing medication following a relapse or worsening UC, but no additional medication was given. Further, at entry and pre-GMA, blood samples were taken for full blood cell count, expression of TLRs on leukocytes, and plasma IL-8. Seventy-five percent of patients achieved remission after the 10th session (CAI, ≤4; P < 0.005) and there was a marked fall in C-reactive protein (P < 0.01), plasma IL-8 (P < 0.001), and granulocytes (P < 0.05) but an increase in lymphocytes (P < 0.05). The expression of TLR2 on granulocytes was down-modulated (P < 0.05) together with suppression of inflammatory cytokines produced by peripheral blood leukocytes. In conclusion, GMA appears to be an effective adjunct therapy to induce remission in the majority of patients, who are then spared from excess drug therapy. The procedure is associated with sustained immunomodulation. Control studies should strengthen these findings.