Metformin and exenatide upregulate hepatocyte nuclear factor-4α, sex hormone binding globulin levels and improve hepatic triglyceride deposition in polycystic ovary syndrome with insulin resistance rats

OBJECTIVE

To explore the efficacy and underlying mechanisms of metformin and exenatide in reversing reproductive and metabolic disturbances in letrozole combined with high-fat diet-induced polycystic ovary syndrome (PCOS) rats.

METHODS

Rats with PCOS and insulin resistance (IR) were induced by intra-gastric instillation of letrozole combined with a high-fat diet and verified by histological screening of vaginal exfoliated cells. After metformin and exenatide supplementation, body weight, chow intake and ovarian morphology were observed. Serum biochemical profiles were analyzed using ELISA, while the levels of key anabolism-related proteins, including sex hormone binding globulin (SHBG), hepatocyte nuclear factor-4α (HNF-4α), PI3K, and AKT, were determined using western blotting.

RESULTS

The estrus cycle and ovarian morphology of rats with PCOS and IR were significantly recovered following metformin and exenatide treatment, with decreased body weight and chow intake. Furthermore, PCOS-induced changes in metabolic disorders including IR and hepatic triglyceride (TG) deposition, and hyperandrogenemia were reversed by treatment with both drugs. Specifically, the levels of HNF-4α and SHBG in liver tissue of rats with PCOS and IR were upregulated significantly.

CONCLUSIONS

Both metformin and exenatide could recover the estrous cycle and ovarian morphology, reduce body weight and high-fat chow intake, and improve glycolipid metabolism disorders and hyperandrogenemia in PCOS with IR rat models. Interestingly, our findings also highlight the potential of both therapeutic agents for improving IR by regulating the liver PI3K/AKT pathway, reducing the deposition of hepatic TG, as well as upregulating the levels of SHBG and HNF-4α in PCOS with IR rat liver tissue.

SHBG as a Marker of NAFLD and Metabolic Impairments in Women Referred for Oligomenorrhea and/or Hirsutism and in Women With Sexual Dysfunction

PCOS is one of the most common endocrine disorders and NAFLD is one of its most dangerous metabolic consequences. The diagnosis of NAFLD is not a practical task and the condition is at risk of being overlooked. The use of simpler but still reliable surrogate markers is necessary to identify women with a high likelihood of NAFLD. The aim of this study was to evaluate the clinical correlates of NAFLD Liver Fat Score (NAFLD-LFS) in women with oligomenorrhea and/or hirsutism. Furthermore, the study aimed to evaluate whether, among the hormonal parameters evaluated in such women, possible hallmarks of NAFLD may be identified. To this purpose, 66 women who attended our Outpatient Clinic for oligomenorrhea and/or hyperandrogenism were included in the study. In order to validate the results obtained in the first cohort, a second independent sample of 233 women evaluated for female sexual dysfunction (FSD) was analyzed. In cohort 1, NAFLD-LFS positively correlated with metabolic and inflammatory parameters. Among the hormone parameters, NAFLD-LFS showed no significant relationships with androgens but a significant negative correlation with SHBG (p<0.0001) that therefore appeared as a candidate hallmark for pathologic NAFLD-LFS. The ROC analysis showed a significant accuracy (81.1%, C.I.69.1-93.0, p <0.0001) for SHBG in identifying women with a pathological NAFLD-LFS. In particular, a SHBG 33.4 nmol/l was recognized as the best threshold, with a sensitivity of 73.3% and a specificity of 70.7%. In order to validate this SHBG as a marker of metabolic impairment possible related with the presence of NAFLD, we tested this threshold in cohort 2. FSD women with SHBG <33.4 nmol/l had worse metabolic parameters than women with SHBG ≥33.4 nmol/l and a significantly higher NAFLD-LFS even after adjusting for confounders (B=4.18 [2.05; 6.31], p=0.001). In conclusion, this study provides a new evidence in the diagnostic process of NAFLD, showing that the measurement of SHBG, which is routinely assessed in the workup of women referred for possible PCOS, could identify women at higher metabolic risk, thus detecting those who may deserve further targeted diagnostic assessment.

A Phase I/II Trial of BNC105P with Everolimus in Metastatic Renal Cell Carcinoma

PURPOSE

BNC105P inhibits tubulin polymerization, and preclinical studies suggest possible synergy with everolimus. In this phase I/II study, efficacy and safety of the combination were explored in patients with metastatic renal cell carcinoma (mRCC).

EXPERIMENTAL DESIGN

A phase I study in patients with clear cell mRCC and any prior number of therapies was conducted using a classical 3 + 3 design to evaluate standard doses of everolimus with increasing doses of BNC105P. At the recommended phase II dose (RP2D), patients with clear cell mRCC and one to two prior therapies (including ≥ 1 VEGF-TKI) were randomized to BNC105P with everolimus (arm A) or everolimus alone (arm B). The primary endpoint of the study was 6-month progression-free survival (6MPFS). Secondary endpoints included response rate, PFS, overall survival, and exploratory biomarker analyses.

RESULTS

In the phase I study (N = 15), a dose of BNC105P at 16 mg/m(2) with everolimus at 10 mg daily was identified as the RP2D. In the phase II study, 139 patients were randomized, with 69 and 67 evaluable patients in arms A and B, respectively. 6MPFS was similar in the treatment arms (arm A: 33.82% vs. arm B: 30.30%, P = 0.66) and no difference in median PFS was observed (arm A: 4.7 mos vs. arm B: 4.1 mos; P = 0.49). Changes in matrix metalloproteinase-9, stem cell factor, sex hormone-binding globulin, and serum amyloid A protein were associated with clinical outcome with BNC105P.

CONCLUSIONS

Although the primary endpoint was not met in an unselected population, correlative studies suggest several biomarkers that warrant further prospective evaluation.

Adiponectin upregulates SHBG production: molecular mechanisms and potential implications

Epidemiological studies have shown that plasma SHBG levels correlate with plasma adiponectin levels, both in men and women. There are no reports describing any molecular mechanism by which adiponectin regulates hepatic SHBG production. The aim of the present study is to explore whether adiponectin regulates SHBG production by increasing HNF-4α levels through reducing hepatic lipid content. For this purpose, in vitro studies using human HepG2 cells, as well as human liver biopsies, were performed. Our results show that adiponectin treatment increased SHBG production via AMPK activation in HepG2 cells. Adiponectin treatment decreased the mRNA and protein levels of enzymes related to hepatic lipogenesis (ACC) and increased those related to fatty acid oxidation (ACOX and CPTI). These adiponectin-induced changes in hepatic enzymes resulted in a reduction of total TG and FFA and an increase of HNF-4α. When HNF-4α expression was silenced by using siRNA, adiponectin-induced SHBG overexpression was blocked. Furthermore, adiponectin-induced upregulation of SHBG production via HNF-4α overexpression was abrogated by the inhibition of fatty acid oxidation or by the induction of lipogenesis with a 30mM glucose treatment in HepG2 cells. Finally, adiponectin levels correlated positively and significantly with both HNF-4α and SHBG mRNA levels in human liver biopsies. Our results suggest for the first time that adiponectin increases SHBG production by activating AMPK, which reduces hepatic lipid content and increases HNF-4α levels.

Sperm parameters: paradigmatic index of good health and longevity

Since the discovery of spermatozoon by Anton van Leeuwenhoek in 1677, there has been an ever increasing understanding of its role in reproduction. Many factors adversely affect sperm quality, including varicocele, accessory gland infection, immunological factors, congenital abnormalities, and iatrogenic systemic and endocrine causes, such as diabetes mellitus, obesity, metabolic syndrome, and smoking. The mechanisms responsible for the association between poor sperm parameters and ill health may include oxidative stress, low-grade inflammation, low testosterone, and low sex-hormone-binding globulin. Oxidative stress in the testicular microenvironment may result in decreased spermatogenesis and sperm DNA damage, loss of sperm motility, and abnormal sperm morphology. Low testosterone caused by advanced age, visceral obesity, and inflammation is associated with the development of cardiovascular disease. Hence, semen analysis has an important role in the routine evaluation of idiopathic male infertility, usually manifested as low sperm counts, impaired sperm motility, or absence of sperm, and remains the most common single diagnostic tool. Several studies have shown an inverse relationship between semen quality and medical disorders. This review elucidates the effect of medical disorders and social habits on sperm quality, the mechanisms that are involved in the impairment of sperm quality, and whether or not sperm quality can be used as an index of good health and longevity in a man.

Testosterone is associated with erectile dysfunction: a cross-sectional study in Chinese men

BACKGROUND

Testosterone is essential for the regulation of erectile physiology, but the relationship between low testosterone and erectile dysfunction (ED) has not been firmly established.

PURPOSE

To examine the association between serum total, free and bio-available testosterone and ED in a population-based sample.

METHODS

A consecutive series of 1776 men aged 20-77 participated in the routine physical examination from September 2009 to December 2009 in Guangxi, China. ED was assessed using the five-item International Index of Erectile Function (IIEF-5) questionnaire. Total testosterone (TT), sex hormone binding globulin (SHBG) and other biochemical profiles were measured. Free testosterone (FT) and bio-available testosterone (BT) were calculated based on Vermeulen's formula. Data were collected with regard to smoking, alcoholic drinking, physical activity and metabolic syndrome.

RESULTS

The prevalence of ED (IIEF-5<22) was 47.6%. Men with ED were significantly older, and more prone to smoke cigarettes (≥20 cigarettes/day) or drink alcohol (≥3 drinks/week), and more likely to have elevated blood pressure (P = 0.036) or hyperglycemia (P<0.001) compared with those without ED. The significant increase in SHBG with age was parallel to its increase with increasing severity of ED (P<0.001). The obscure increase in TT across the ED status was detected without significance (P = 0.418), but TT was positively associated with ED after adjustment for age [odds ratio (OR)  = 1.02, 95% CI (confidence internal): 1.00-1.04]. FT and BT were inversely associated with ED (OR = 0.14, 95%CI: 0.06-0.33; OR = 0.92 (95%CI: 0.89-0.96, respectively) in the univariate analysis, and this inverse association appeared to be independent of smoking status, alcoholic drinking, physical activity, hyper-triglyceridemia and hyperglycemia.

CONCLUSIONS

FT and BT are inversely related to worsening ED, whereas the positive association between TT and ED is most likely due to the increase in SHBG.

Thyroid hormones act indirectly to increase sex hormone-binding globulin production by liver via hepatocyte nuclear factor-4alpha

Thyroid hormones increase hepatic sex hormone-binding globulin (SHBG) production, which is also regulated by hepatocyte nuclear factor-4alpha (HNF-4alpha) in response to changes in the metabolic state of the liver. Since the human SHBG promoter lacks a typical thyroid hormone response element, and because thyroid hormones influence metabolic state, we set out to determine whether thyroid hormones mediate SHBG expression indirectly via changes in HNF-4alpha levels in HepG2 human hepatoblastoma cells, and in the livers of transgenic mice that express a 4.3 kb human SHBG transgene under the control of its own 0.8 kb promoter sequence. Thyroid hormones (triiodothyronine (T(3)) and thyroxine (T(4))) increase SHBG accumulation in HepG2 cell culture medium over 5 days, and increase cellular SHBG mRNA levels. In addition, T(4) treatment of HepG2 cells for 5 days increased HNF-4alpha mRNA and HNF-4alpha levels in concert with decreased cellular palmitate levels. Plasma SHBG levels were also increased in mice expressing a human SHBG transgene after 5 days treatment with T(3) along with increased hepatic HNF-4alpha levels. In HepG2 cells, the human SHBG promoter failed to respond acutely (within 24 h) to T(4) treatment, but a 4-day pre-treatment with T(4) resulted in a robust response that was prevented by co-treatment with HNF-4alpha siRNA, or by blocking the beta-oxidation of palmitate through co-treatment with the carnitine palmitoyltransferase I inhibitor, etomoxir. These data lead us to conclude that thyroid hormones increase SHBG production indirectly by increasing HNF-4alpha gene expression, and by reducing cellular palmitate levels that further contribute to increased HNF-4alpha levels in hepatocytes.

Polycystic ovary syndrome in obese adolescents

PURPOSE OF REVIEW

As the prevalence of pediatric obesity escalates, polycystic ovary syndrome is an increasingly common morbidity for adolescent females. This review describes recent insights into the pathophysiology and treatment of polycystic ovary syndrome, with special attention given to the relationship between polycystic ovary syndrome and obesity.

RECENT FINDINGS

Recent research has elucidated three key concepts in our understanding of polycystic ovary syndrome. First, patients may enter the hyperandrogenism-hyperinsulinism cycle of polycystic ovary syndrome via several pathways, including genetic polymorphisms that affect androgen synthesis, fetal programming that alters lipid and glucose metabolism, and obesity accompanied by insulin resistance. Second, obesity plays a significant role in the pathophysiology of polycystic ovary syndrome by increasing free androgen concentrations through multiple mechanisms. Finally, just as the etiology of polycystic ovary syndrome is multifactorial, successful treatment will probably require a combination of lifestyle modification and therapeutic interventions.

SUMMARY

Obesity contributes to the pathophysiology of polycystic ovary syndrome and increases the likelihood of associated metabolic and cardiovascular morbidities.

Obesity and sex steroids during gonadotropin-releasing hormone agonist treatment for prostate cancer

PURPOSE

To evaluate effects of obesity on sex steroid levels during treatment with a gonadotropin-releasing hormone agonist in men with prostate cancer.

EXPERIMENTAL DESIGN

Forty-nine hormone-naïve men with recurrent or locally advanced prostate cancer were included in the analyses. All subjects were treated with leuprolide 3-month depot for 48 weeks. Serum levels of estradiol, sex hormone-binding globulin, total testosterone, and free testosterone were assessed at baseline, 24 weeks, and 48 weeks. Subjects were categorized by body mass index (BMI) and percent body fat.

RESULTS

Pretreatment serum sex hormone-binding globulin and total testosterone levels were significantly lower in overweight and obese men than in men with normal BMI. In the overall study population, mean serum testosterone concentrations decreased from 372 +/- 18 ng/dL at baseline to 13 +/- 1 ng/dL at week 48 (P < 0.001). Free testosterone decreased from 6.75 +/- 0.33 ng/dL at baseline to 0.21 +/- 0.02 ng/dL at week 48 (P < 0.001). During treatment with leuprolide, obese men had significantly higher total and free testosterone levels than men with normal BMI. Compared with normal men, total and free testosterone levels during treatment were 1.8-fold and 2.3-fold higher in obese men. Similar results were observed when subjects were categorized by body fat.

CONCLUSIONS

Despite lower pretreatment serum testosterone levels, obese men have higher total and free testosterone levels during leuprolide treatment than men with normal BMI. These differences may contribute to the association between obesity and increased prostate cancer mortality.

The (TAAAA)n microsatellite polymorphism in the SHBG gene influences serum SHBG levels in women with polycystic ovary syndrome

BACKGROUND

Hyperandrogenaemia is a common feature of polycystic ovary syndrome (PCOS). The sex hormone-binding globulin (SHBG) gene was proposed as being a PCOS candidate gene. A possible influence of the microsatellite polymorphism (TAAAA)(n) in the SHBG gene on serum SHBG levels in PCOS patients was investigated.

METHODS

One hundred and twenty-three PCOS patients and 110 age-matched controls were included in the study. Peripheral blood samples were obtained. Genotyping of the (TAAAA)(n) polymorphism in the SHBG gene was performed. Serum LH, FSH, SHBG and total testosterone concentrations were determined.

RESULTS

SHBG alleles with 6-11 TAAAA repeats were found. None of the SHBG alleles or genotypes were present at a significantly more frequent rate in PCOS patients compared with controls. Serum SHBG levels were significantly lower (P < 0.001) in PCOS patients compared with controls and were found to be strongly influenced by the (TAAAA)(n) SHBG polymorphism, in both the PCOS (55.3%) and control (33.1%) groups of patients.

CONCLUSIONS

The (TAAAA)(n) SHBG gene polymorphism might be an important predictor for serum SHBG levels and, consequently, for hyperandrogenaemic clinical presentation of PCOS.

Low sex hormone-binding globulin is associated with low high-density lipoprotein cholesterol and metabolic syndrome in women with PCOS

BACKGROUND

Decreased high-density lipoprotein cholesterol (HDL-C) and sex hormone-binding globulin (SHBG) levels, and the metabolic syndrome, are all closely associated with a higher prevalence of atherosclerotic cardiovascular disease. We investigated the association between HDL-C, SHBG and the metabolic syndrome in women with polycystic ovary syndrome (PCOS).

METHODS AND RESULTS

Among 106 young Taiwanese women (mean age +/- SD, 24.9 +/- 4.8 years) with PCOS, 69 (65.1%) women had an HDL-C level <50 mg dl(-1). The level of HDL-C was highly correlated with that of serum SHBG (gamma = 0.6034, P < 0.0001). The SHBG level was significantly lower in subjects with an HDL-C <50 mg dl(-1) than that in subjects with an HDL-C > or =50 mg dl(-1). Using multiple linear regression models with adjustment for age, BMI and other anthropometric, metabolic, liver function and hormonal variables, we showed serum SHBG to be independently correlated with HDL-C. Based on logistic regression analysis with adjustment for age, the SHBG level was significantly lower in women with PCOS with the metabolic syndrome (odds ratio = 0.92, P = 0.003).

CONCLUSIONS

Low levels of SHBG in women with PCOS were associated with low levels of HDL-C, independent of insulin resistance and obesity. The SHBG level was inversely related to the occurrence of metabolic syndrome, further strengthening the potential link between SHBG levels and cardiovascular disease in women with PCOS.

Pathways of endocrine disruption during male sexual differentiation and masculinization

After testis formation, further development of a male phenotype (masculinization) is driven by three hormones from the foetal testis: anti-Müllerian hormone, insulin-like factor 3, and testosterone. These hormones divert the development of reproductive and other organs from female to male and also play a role in testis development. The hormone dependence of masculinization renders this process inherently susceptible to disruption by factors that interfere with hormone production, bioavailability, metabolism, or action. This susceptibility is illustrated by the high prevalence of congenital masculinization disorders (cryptorchidism, hypospadias) and disorders in young adult men (low sperm counts, testis cancer), which may also stem from maldevelopment (dysgenesis) of the foetal testis. Testicular dysgenesis occurring in humans, or which is induced in animal models by foetal exposure to certain phthalates, is associated with impaired hormone production by the foetal testis. There is currently no definitive evidence that exposure of humans to environmental chemicals can induce testicular dysgenesis and/or impair masculinization, though pathways via which this could potentially occur are established.

Endocrine and metabolic effects of rosiglitazone in overweight women with PCOS: a randomized placebo-controlled study

BACKGROUND

The objective of the study was to assess the therapeutic effects of rosiglitazone in overweight women with polycystic ovary syndrome (PCOS).

METHODS

A double-blind, placebo-controlled study was conducted on 30 (BMI > 25 kg/m2, mean age 29.1 +/- 1.2 years) overweight women with PCOS treated with rosiglitazone or placebo for 4 months. Waist-to-hip ratios (WHRs), serum concentrations of sex hormones and binding proteins, blood glucose, serum insulin and serum C-peptide during a 75-g oral glucose tolerance test (OGTT), first-phase insulin secretion as determined by an intravenous glucose tolerance test (IVGTT), M values (expressing insulin sensitivity using a euglycaemic clamp) and calorimetric data were assessed at 0 and 4 months of treatment.

RESULTS

Rosiglitazone improved menstrual cyclicity, increased serum sex hormone-binding globulin (SHBG) levels and decreased serum levels of androstenedione, 17-hydroxyprogesterone (17-OHP), dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulphate (DHEA-S). Glucose tolerance [expressed as AUC(glucose) during the OGTT] improved (P = 0.002) and peripheral insulin response (expressed as AUC(insulin)) decreased (P = 0.004) in the rosiglitazone group (ROSI group). M value improved in the ROSI group from 33.4 +/- 3.27 to 40.0 +/- 5.51 micromol/kg min (P = 0.04).

CONCLUSION

Rosiglitazone, by improving menstrual cyclicity, hyperandrogenism, insulin resistance and hyperinsulinaemia, represents an alternative treatment for overweight anovulatory women with PCOS and no pregnancy desire.

Repression of the human sex hormone-binding globulin gene in Sertoli cells by upstream stimulatory transcription factors

Expression of the sex hormone-binding globulin gene (SHBG) in the liver produces SHBG, which transports sex steroids in the blood. In rodents, the SHBG gene is also expressed in Sertoli cells giving rise to the testicular androgen-binding protein, which is secreted into the seminiferous tubule where it presumably controls testosterone action. Evidence that the SHBG gene functions in this way in the human testis is lacking, and mice containing a human SHBG transgene (shbg4) under the control of its own promoter sequence are characterized by SHBG gene expression in the liver but not in the testis. A potential cis-element, defined as footprint 4 (FP4) within the human SHBG promoter, is absent in SHBG promoters of mammals that produce the testicular androgen-binding protein, and we have produced mice harboring a shbg4 transgene in which FP4 was deleted to evaluate its functional significance. Remarkably, these mice express the modified human SHBG transgene in the testis as well as the liver. Human SHBG transcripts were found within their Sertoli cells, primary cultures of which secrete human SHBG, and this was increased by treatment with follicle-stimulating hormone, retinoic acid, and estradiol but not testosterone. We have also found that the upstream stimulatory factors (USF-1 and USF-2) bind FP4 in vitro by electromobility shift assay of Sertoli cell nuclear extracts and in vivo by chromatin immunoprecipitation assay and conclude that USF transcription factors repress human SHBG transcription in Sertoli cells through an interaction with FP4 within its proximal promoter.

Comparative studies on the regulation of insulin-like growth factor-binding protein-1 (IGFBP-1) and sex hormone-binding globulin (SHBG) production by insulin and insulin-like growth factors in human hepatoma cells

Production of insulin-like growth factor-binding protein-1 (IGFBP-1) by the liver is efficiently inhibited by insulin both in vivo and in vitro. Consequently, serum IGFBP-1 concentration reflects insulin bioactivity in portal vein. Sex hormone-binding globulin (SHBG) is another insulin-regulated liver-derived protein that has appeared promising in detecting individuals with portal hyperinsulinemia. We compared the regulation of IGFBP-1 and SHBG production by insulin and insulin-like growth factors (IGF-I and IGF-II) in human hepatoma cell cultures. Insulin equipotently inhibited IGFBP-1 and SHBG production, with maximal decrease in culture medium concentrations being about 35% for both proteins during 48 h of culture in serum-free medium. IGF-I and IGF-II also inhibited the IGFBP-1 and SHBG levels. We conclude that IGFBP-1 and SHBG are equally sensitive to ambient insulin concentrations in human hepatoma cell cultures, and the production of both proteins is also attenuated by the IGFs.

Plasma sex steroid hormones and breast cancer risk in Chinese women

Estrogens regulate the growth and differentiation of mammary cells and play an important role in the development of breast cancer. High circulating levels of estrogens are associated with increased risk of breast cancer in Caucasian women. Because Asian women have low estrogens in the circulation compared with their Caucasian counterparts, the effect of estrogens on breast cancer risk in populations with low circulating estrogens remains to be elucidated. We conducted a population-based case-control study in China to evaluate the association of sex steroid hormones with breast cancer risk in Chinese women. Our study included 300 incident cases with primary breast cancer and 300 age- and menopausal status-matched healthy controls randomly selected from the general population in Shanghai. Fasting blood samples were collected from cases prior to any treatment and from their matched controls. Commercial immunoassays were used to measure plasma concentrations of estradiol, estrone, estrone sulfate, testosterone, progesterone, dehydroepiandrosteindian sulfate (DHEA-S) and steroid hormone-binding globulin (SHBG). Conditional logistic regression analysis was performed to examine the association between steroid hormones and breast cancer risk. The results showed that breast cancer risk was elevated with increasing levels of estrone and testosterone (p for trend < 0.05) but not with DHEA-S, estradiol, estrone sulfate, progesterone or SHBG. The estimated relative risks between upper and lower tertiles were 2.07 (95% confidence interval [CI] 0.97-4.41) for estrone in postmenopausal women, 2.01 (95% CI 0.96-4.21) for testosterone in premenopausal women, and 2.40 (95% CI 1.11-5.21) for testosterone in postmenopausal women, after adjusting for age at first live birth, waist-to-hip ratio, total calorie intake, a history of fibroadenoma, a family history of breast cancer and SHBG. These results, in general, are consistent with the findings in Caucasian women and indicate that high sex steroid hormones in the circulation, both androgen and estrogen, are associated with increased risk of breast cancer even in populations with relatively low sex hormones.

Plasma thiols and androgen levels in polycystic ovary syndrome

Homocysteine is a risk factor for ischemic heart disease; similarly as is hyperlipidemia or insulin resistance, which frequently occur in women with polycystic ovary syndrome. We examined the relationships between thiols and hormonal status or insulin resistance in 40 women (aged 25.8 +/- 7 years) with polycystic ovary syndrome and in 11 controls (33 +/- 5 years). Blood levels of homocysteine, glutathione, total and high density lipoprotein (HDL)-cholesterol, triglycerides, insulin, sex hormone-binding globulin, testosterone, androstenedione, dehydroepiandrosterone sulfate, and estradiol were determined. Student's t test and Spearman correlations were computed after adjustment for body mass index (BMI) and age. Homocysteine was significantly higher in polycystic ovary syndrome patients than in the control group (10.3 +/- 2.87 vs. 8.78 +/- 2.75 micromol/l; p < 0.05). In women with polycystic ovary syndrome, there were significant positive correlations between homocysteine and androstenedione (r = 0.329; p < 0.05) and glutathione and dehydroepiandrosterone sulfate (DHEA-S) (r = 0.469; p < 0.05). We conclude that homocysteine is increased in women with polycystic ovary syndrome and is probably linked to androgen levels but not to markers of insulin resistance or with lipid metabolism.

Sex hormone-binding globulin is synthesized in target cells

Sex hormone-binding globulin (SHBG) is a multifunctional protein that acts in humans to regulate the response to steroids at several junctures. It was originally described as a hepatically secreted protein that is the major binding protein for sex steroids in plasma, thereby regulating the availability of free steroids to hormone-responsive tissues. SHBG also functions as part of a novel steroid-signaling system that is independent of the classical intracellular steroid receptors. Unlike the intracellular steroid receptors that are ligand-activated transcription factors, SHBG mediates androgen and estrogen signaling at the cell membrane by way of cAMP. We have reviewed the current state of knowledge on the SHBG gene and the role of SHBG in steroid signaling (we shall not address its function as a plasma-binding protein).

Environmental estrogens interact with and modulate the properties of plasma sex steroid-binding proteins in juvenile Atlantic salmon (Salmo salar)

Environmental chemicals may modulate the endocrine system through interaction with plasma sex steroid-binding proteins (SBP) and SBP-regulated processes. Some of these chemicals, which are known to interact with the estrogen receptor (ER), were found to bind competitively to the Atlantic salmon (Salmo salar) SBP and potentially disrupt the endocrine function of these proteins. Furthermore, both weakly acting (di-n-butyl phthalate) and potent estrogen mimics (ethynylestradiol), were able to induce a substantial up-regulation of circulating levels of SBP in vivo. Interestingly, modulation of SBP-levels was found to be a more sensitive endpoint than chemically induced interference with classical ER-mediated mechanisms for weakly acting estrogen mimics like di-(n-butyl) phthalate. Interference with the endocrine function of SBPs may thus introduce a novel mechanism for endocrine disruption. and give additional answers to the question why some weakly acting xenoestrogens are causing "estrogen-like" reproductive disturbances in developing males.

Sex hormone-binding globulin in the human prostate is locally synthesized and may act as an autocrine/paracrine effector

Sex hormone-binding globulin (SHBG) is a plasma protein synthesized and secreted by the liver. Its initial description stemmed from its ability to bind estrogens and androgens and its capacity to regulate the free concentration of the steroids that bind to it. Additionally, it participates in signal transduction for certain steroid hormones at the cell membrane. It binds with high affinity to a specific membrane receptor (R(SHBG)) in prostate stromal and epithelial cells, wherein the SHBG.R(SHBG) complex forms. An appropriate steroid binds to this complex and results in increases of intracellular cAMP. These two disparate functions of SHBG, regulation of the concentration of free steroids in plasma and signal transduction in selected tissues, raise the question of how its synthesis and secretion might be regulated so as to best perform these two disparate functions. In this paper we demonstrate that SHBG is produced in human prostate cancer cell lines (LNCaP, DU 145, and PC 3) as well as in cultured human prostate epithelial and stromal cells. In addition, in tissue sections of human prostate, we demonstrate the presence of SHBG (immunocytochemistry) and SHBG mRNA (in situ hybridization). These observations are consistent with the hypothesis that SHBG, destined to participate in signaling at the cell membrane, is locally regulated and produced.

Endogenous sex hormones and breast cancer in postmenopausal women: reanalysis of nine prospective studies

BACKGROUND

Reproductive and hormonal factors are involved in the etiology of breast cancer, but there are only a few prospective studies on endogenous sex hormone levels and breast cancer risk. We reanalyzed the worldwide data from prospective studies to examine the relationship between the levels of endogenous sex hormones and breast cancer risk in postmenopausal women.

METHODS

We analyzed the individual data from nine prospective studies on 663 women who developed breast cancer and 1765 women who did not. None of the women was taking exogenous sex hormones when their blood was collected to determine hormone levels. The relative risks (RRs) for breast cancer associated with increasing hormone concentrations were estimated by conditional logistic regression on case-control sets matched within each study. Linear trends and heterogeneity of RRs were assessed by two-sided tests or chi-square tests, as appropriate.

RESULTS

The risk for breast cancer increased statistically significantly with increasing concentrations of all sex hormones examined: total estradiol, free estradiol, non-sex hormone-binding globulin (SHBG)-bound estradiol (which comprises free and albumin-bound estradiol), estrone, estrone sulfate, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, and testosterone. The RRs for women with increasing quintiles of estradiol concentrations, relative to the lowest quintile, were 1.42 (95% confidence interval [CI] = 1.04 to 1.95), 1.21 (95% CI = 0.89 to 1.66), 1.80 (95% CI = 1.33 to 2.43), and 2.00 (95% CI = 1.47 to 2.71; P(trend)<.001); the RRs for women with increasing quintiles of free estradiol were 1.38 (95% CI = 0.94 to 2.03), 1.84 (95% CI = 1.24 to 2.74), 2.24 (95% CI = 1.53 to 3.27), and 2.58 (95% CI = 1.76 to 3.78; P(trend)<.001). The magnitudes of risk associated with the other estrogens and with the androgens were similar. SHBG was associated with a decrease in breast cancer risk (P(trend) =.041). The increases in risk associated with increased levels of all sex hormones remained after subjects who were diagnosed with breast cancer within 2 years of blood collection were excluded from the analysis.

CONCLUSION

Levels of endogenous sex hormones are strongly associated with breast cancer risk in postmenopausal women.

Hypothalamic-pituitary-testicular function in prepubertal children with chronic liver disease

Adult patients with chronic liver disease (CLD) show clinical and biochemical signs of hypogonadism and estrogenization. However, no information is available on hypothalamo-pituitary-testicular function in prepubertal or early pubertal children with CLD. Eighteen prepubertal children with CLD, aged 5.8+/-5.5 years (mean +/- SD; range 0.32-12.8), were studied. Most of them had moderate liver function abnormality. Height was slightly decreased (SDS: -1.44-/+1.88) but weight for height was adequate. Serum gonadotropins were evaluated as a function of age. In the age group younger than 1 year (n = 7), serum LH was elevated (4.88+/-6.22 IU/l) when compared with a group of 39 control children (1.2+/-1.65), while serum FSH was normal. In this young group, serum testosterone was normal, but serum estradiol was significantly increased (24.1+/-19.7 pg/ml) when compared with the control group (6.5+/-3.54). In contrast, in the age group older than 2 years, no difference between patients with CLD and controls was observed, either in serum gonadotropins or in serum sex hormones. Taking the 18 patients with CLD together, serum SHBG (113.7+/-51 nmol/l; mean +/- SD) was significantly higher than in normal controls (76+/-38 nmol/l, n = 91, p <0.001). Moreover, and different from normal controls, no change with age was observed in serum SHBG, total testosterone or bioavailable testosterone (non-SHBG-bound). Normal testosterone response to hCG stimulation (>1 ng/ml) was found in a subgroup of 11 children with CLD. By contrast, eight of 11 patients with CLD had an inadequate decrease in SHBG after androgen stimulation. In conclusion, we observed that during the first year of life, a period which includes the postnatal activation of the hypothalamo-pituitary-testicular axis, there is an elevation of serum LH and serum estradiol that suggests the existence of a moderate deficiency of Leydig cell function. This disorder is no longer observed in older prepubertal children. Similar to reports in adults, children with CLD have elevation of serum SHBG levels. Furthermore, the lack of SHBG decrease and bioavailable testosterone increase with age, probably modulated by GH, suggests some degree of hepatic GH resistance in prepubertal patients with CLD.

Plasma and urinary markers of oral testosterone undecanoate misuse

Orally administered testosterone undecanoate (TU), an anabolic, androgenic steroid, can potentially be abused by athletes. Indirect evidence for detecting oral TU intake could be deduced from the changes in steroid profile post-administration. Direct evidence could be obtained by detection of unchanged TU in plasma. To this end, both urinary and plasma steroid profiles of six healthy male subjects given a single oral dose of 120 mg of TU were studied by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/tandem mass spectrometry (GC/MS/MS). The increased concentration of glucuronidated testosterone in plasma appears to be the most characteristic sign of oral TU intake. The testosterone glucuronide (TG)/nonconjugated testosterone (T) ratio, TG/17-hydroxyprogesterone (17OHP) ratio, and TG/luteinizing hormone (LH) ratio were observed to be significantly elevated above their basal levels for 10 h, 10 h, and 6 h, respectively. Urinary ratios of TG/epitestosterone glucuronide (EG) were found to be higher than the cut-off value of 6 for the period 4 approximately 8 h post-administration, but only in three subjects. One subject failed to respond with respect to all of the above-mentioned indirect markers, as TG was not significantly increased in either plasma or urine. Unchanged TU was directly detected in plasma of all six subjects from 1 approximately 1.5 h to 4 approximately 6 h after oral TU intake by GC/MS/MS, providing unequivocal proof of exogenous testosterone intake. Distinct and complementary markers for detecting oral TU intake could be obtained from plasma and urine, respectively.

Altered balance between the 5 alpha-reductase and aromatase pathways of androgen metabolism during controlled ovarian hyperstimulation with human menopausal gonadotropins

PURPOSE

To evaluate androgen production and metabolism during controlled ovarian hyperstimulation.

METHODS

Five women, aged 33-42, were studied. All participants were undergoing controlled ovarian hyperstimulation with gonadotropin-releasing hormone agonist and human menopausal gonadotropins. Serum estradiol, estrone, androstenedione, testosterone, 3 alpha-androstanediol glucuronide, and sex hormone-binding globulin levels were measured at 6 time points during the cycle.

RESULTS

The levels of all steroids increased significantly from baseline during controlled ovarian hyperstimulation. Mean total testosterone levels increased from 0.29 +/- 0.05 ng/mL to 0.58 +/- 0.07 ng/mL after gonadotropin stimulation. Sex hormone-binding gonadotropin levels increased from 50 +/- 16 nM to 73 +/- 12 nM after gonadotropin stimulation. Estrone/androstenedione and estradiol/testosterone ratios, reflecting the aromatase pathway, increased whereas 3 alpha-androstanediol glucuronide/androstenedione and 3 alpha-androstanediol glucuronide/testosterone ratios, reflecting 5 alpha-reductase activity, decreased.

CONCLUSIONS

Controlled ovarian hyperstimulation with human menopausal gonadotropins results in increased serum testosterone and androstenedione levels. Whereas there is an enhancement in androgen metabolism by aromatase, 5 alpha-reductase activity with regard to androgen metabolism is diminished.

Human sex hormone-binding globulin promoter activity is influenced by a (TAAAA)n repeat element within an Alu sequence

Sex hormone-binding globulin (SHBG) is the major sex steroid-binding protein in human plasma and is produced by the liver. Plasma SHBG levels vary considerably between individuals and are influenced by hormonal, metabolic, and nutritional factors. We have now found that a (TAAAA)(n) pentanucleotide repeat, located within an alu sequence at the 5' boundary of the human SHBG promoter, influences its transcriptional activity in association with downstream elements, including an SP1-binding site. Furthermore, SHBG alleles within the general population contain at least 6-10 TAAAA repeats, and the transcriptional activity of a human SHBG promoter-luciferase reporter construct containing 6 TAAAA repeats was significantly lower than for similar reporter constructs containing 7-10 TAAAA repeats when tested in human HepG2 hepatoblastoma cells. This difference in transcriptional activity reflected the preferential binding of a 46-kDa liver-enriched nuclear factor to an oligonucleotide containing 6 rather than 7-10 TAAAA repeats. Thus, a (TAAAA)(n) element within the human SHBG promoter influences transcriptional activity in HepG2 cells and may contribute to differences in plasma SHBG levels between individuals.

Rabbit sex hormone-binding globulin: expression in the liver and testis during postnatal development and structural characterization by truncated proteins

Although sex hormone binding globulin (SHBG) is found in the blood plasma of adult humans and rabbits and the gene is expressed in their livers, it is not detected in the plasma of adult rodents nor is it expressed in adult rodent livers. Thus the rabbit represents a good model to study the metabolism and function of SHBG in the blood. We have used a cloned rabbit SHBG cDNA to detect mRNA expression in rabbits during the postnatal period, and to construct truncated SHBG proteins for structure/function analysis. The SHBG mRNA appeared in the testis as early as 3 days after birth. The level increased gradually in abundance throughout postnatal development, and attained a maximum at 12 weeks of age when the gonads were fully matured. In contrast, SHBG mRNA in the livers of male and female animals increased to a maximum by 4 weeks of age, and were maintained at this level until 12 weeks before subsiding to the initial levels. The increase and decrease in SHBG mRNA levels in the liver were accompanied by similar changes in serum SHBG. This suggests that SHBG in the blood circulation comes from the liver and this might also provide a source of SHBG for the male reproductive tract before formation of the blood-testis barrier. To elucidate the minimal sequence of rabbit SHBG responsible for steroid-binding, a panel of 13 truncated SHBG proteins was constructed, expressed in Escherichia coli, and biochemically purified for study. It was shown that the complete protein sequence of rabbit SHBG was important for maintaining a stable steroid-protein complex. Unlike human SHBG for which a truncated protein of the first 206 residues of the 373 amino acid protein can still bind steroid, removal of 43 or more residues from the C-terminus of rabbit SHBG completely abolished steroid-binding.

Insulin-like growth factor-1 and breast cancer risk in postmenopausal African-American women

We explored the relationship between insulin-like growth factor-1 (IGF-1) concentrations and breast cancer risk. Also, we examined whether obesity, sex hormone-binding globulin (SHBG), and estradiol influenced IGF-1 concentrations. A pilot study of 60 postmenopausal African-American women (30 cases and 30 controls) was used. Plasma concentrations of IGF-1 were higher among the cases, as compared to the controls. A negative trend was seen for plasma concentrations of IGF-1 and TNM (tumor-node-metastasis) stage and IGF-1 and body mass index. IGF-1 was found to be associated negatively with SHBG. After adjustment, plasma concentrations of IGF-1 remained significantly and positively associated with breast cancer risk (odds ratio, 1.183; 95% confidence interval, 1.167-1.201). No significant associations for breast cancer risk were observed for estradiol, SHBG, and body mass index. Further research with a larger sample is needed to clarify the relationships between obesity and IGF-1 concentrations to breast cancer risk in this population.

Sex hormone-binding globulin in gestational diabetes

BACKGROUND

Insulin is an important regulator of serum sex hormone-binding globulin (SHBG) concentration which works by inhibiting its production in hepatocytes. Low SHBG level is associated with increased insulin resistance and hyperinsulinemia. Our purpose was to compare maternal serum SHBG level between normal and gestational diabetic pregnant women and to study the relationships between SHBG, SHBG/insulin and SHBG/glucose ratio and several endocrine, metabolic and clinical parameters.

METHODS

Serum SHBG concentrations were measured in 34 women with gestational diabetes and in 32 matched controls. Glucose, insulin, C-peptide, fructosamine, beta-HCG, cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, apolipoprotein A, apolipoprotein B, total and free T4, total and free estriol, T3 and IGF-1 were measured. Insulin sensitivity was estimated using the short insulin tolerance test.

RESULTS

SHBG, SHBG/insulinemia ratio and SHBG/glucose ratio were significantly lower in the diabetic group (309.54 +/- 112.22 vs 460.54 +/- 144.54, p = 0.00001), (33.55 +/- 16.62 vs 72.56 +/- 66.50, p = 0.0006 using log-transformed values), (5.88 +/- 1.87 vs 3.39 +/- 1.23, p < 0.00001). SHBG was negatively correlated with insulinemia (r = -0.40, p = 0.001), C-peptide (r = -0.41, p = 0.001), glycemia (r = -0.27, p = 0.02), diastolic blood pressure (r = -0.41, p = 0.001) and beta-HCG (r = -0.41, p = 0.001) and positively correlated with LDL-c (r = 0.25, p = 0.04) and apolipoprotein B (r = 0.33, p = 0.007).

CONCLUSIONS

SHBG concentrations are lower in gestational diabetic pregnant women and are related to insulin levels but not to peripheral insulin sensitivity. Since insulinemia was similar in normal and gestational diabetic pregnant women, we speculate that gestational diabetes is characterized by a higher peripheral insulin resistance, a fasting normal insulinemia and a higher hepatic insulin sensitivity, at least in other actions than on carbohydrate metabolism. The role of sex steroids, T4 and IGF-1 in regulating SHBG appears to be limited during pregnancy.

Synthesis and regulation of sex hormone-binding globulin in obesity

Sex hormone-binding globulin (SHBG) is a plasma glycoprotein with high binding affinity for testosterone and dihydrotestosterone and lower affinity for estradiol. SHBG is synthesized in the liver, and its plasma level is important in the regulation of plasma free and albumin-bound androgens and estrogens. Obesity and particularly excess visceral fat, known risk factors for cardiovascular and metabolic diseases, are associated with decreased testosterone levels in males and SHBG levels in both sexes. SHBG is usually positively correlated with high-density lipoprotein cholesterol and negatively correlated with triglyceride and insulin concentrations. A positive association between SHBG and various measures of insulin sensitivity has been demonstrated in both sexes, suggesting that decreased SHBG levels may be one of the components of the metabolic syndrome. We have examined pituitary-adrenocortical function, glucose tolerance, and lipoprotein and hormone levels in a large cohort of Finnish males. Abdominal obesity appears to be associated with slight hypocortisolemia and increased sensitivity to exogenous adrenocorticotropin stimulation, which may contribute to the hyperinsulinemia and related metabolic changes including decreased SHBG levels in males.

Conjugated estrogens and breast cancer risk

Available epidemiologic data suggest the possibility that the use of oral conjugated equine estrogens (CEE) 0.625 mg/day as a first-choice dose could be associated with a very limited (if any) breast cancer risk increase. Some biological peculiarities of oral CEE back the possibility of a limited detrimental effect on breast tissue, due to either direct or indirect actions. Direct actions. Some experimental findings suggest that the 17 alpha-dihydroderivatives of equilenin and equilin (15% of the CEE components) have a non-estrogenic or even an anti-estrogenic effect on breast tissue. This could partially counterbalance the stimulatory action of the other CEE components. Indirect actions. Oral estrogens, through their metabolic and hepatocellular effects (emphasized by the first liver passage) cause a sharp increase in sex hormone binding globulin (SHBG) level which is followed by a lower quantity of both estrogen and androgen in the free, bioavailable, form. More importantly, they cause a decrease in circulating insulin-like growth factor I (IGF-I) activity, due to both a reduction in IGF-I synthesis by the liver and an increase in IGF-binding protein-1 level. A strong relationship between breast cancer risk and the concentration of circulating IGF-I in premenopausal women has been recently found. Actually, estrogens and IGF-I have a synergistic effect on cell proliferation, and IGF-I is necessary for maximum estrogen-receptor activation in breast cancer cell lines. The possibility does exist that the SHBG level increase and the IGF-I bioavailability decrease, caused by oral CEE, balance the increased estrogen stimulation on breast tissue.

Estradiol increases the production of sex hormone-binding globulin but not insulin-like growth factor binding protein-1 in cultured human hepatoma cells

OBJECTIVE

To study the effects of E2 on insulin-like growth factor binding protein-1 (IGFBP-1) and sex hormone-binding globulin (SHBG) production with cultured human HepG2 hepatoma cells.

DESIGN

Experimental cell culture.

SETTING

Academic medical center.

PATIENT(S)

None.

INTERVENTION(S)

Addition of E2 to cell culture medium.

MAIN OUTCOME MEASURE(S)

Intracellular and released concentrations of IGFBP-1 and SHBG.

RESULT(S)

Estradiol did not affect the intracellular or extracellular IGFBP-1 concentration, whereas the intracellular SHBG concentration increased significantly in response to 0.5-2.5 microM of E2.

CONCLUSION(S)

Whereas the two binding proteins share a number of regulatory factors, their regulation by E2 is dissimilar in human hepatoma cells. Estradiol does not affect the intracellular or secreted IGFBP-1 concentration, but it does increase the production of SHBG.

Heterologous expression of wild type and deglycosylated human sex steroid-binding protein (SBP or SHBG) in the yeast, Pichia pastoris. Characterization of the recombinant proteins

Wild type, partially and fully-deglycosylated human sex steroid-binding protein (SBP or SHBG) cDNAs lacking the native cucaryotic signal sequence were cloned into a yeast expression vector containing the Saccharomyces cerevisiae alpha-factor for extracellular secretion. Following transformation into Pichia pastoris, the wild type and all constructed mutants were successfully expressed. The levels were lower for the deglycosylated mutants indicating that oligosaccharide side chains may play a role in SBP secretion. Under fermentation conditions, the wild type protein was expressed at a level of 4 mg/l while the fully-deglycosylated mutant T7A/N351Q/N367Q was expressed at about 1.5 mg/l. The latter was purified from several fermentation runs and was found to be completely deglycosylated, electrophoretically homogeneous and fully active. The aminoterminus was found to have the sequence NH2QSAHDPPAV- indicating that cleavage of the alpha-factor occurred at the A(+7)-Q(+8) peptide bond. The molecular mass of the subunit was determined to be 39,717.8 Da, which is in complete agreement with the amino acid sequence of the T7A/N351Q/N367/Q mutant. The equilibrium constants for the dissociation of 5alpha-dihydrotestosterone and steroid binding specificity were found to be identical to that of the human plasma protein indicating that the missing N-terminal segment NH2-LRPVLPT and the removal of oligosaccharide side chains do not affect the stability and active conformation of the protein. In conclusion, the data presented reveal that the SBP mutant T7A/N351Q/N367/Q is the protein of choice for solving the three-dimensional structure.

Hepatocyte nuclear factor-4 controls transcription from a TATA-less human sex hormone-binding globulin gene promoter

Hepatocytes are the major source of sex hormone-binding globulin (SHBG), a glycoprotein that transports sex steroids in the blood and regulates their access to target tissues. The human SHBG proximal promoter was analyzed by DNase I footprinting, and the functional significance of 6 footprinted regions (FP1-FP6) within the proximal promoter was studied in human HepG2 hepatoblastoma cells. Two footprinted regions (FP1 and FP3) contain binding sites for the chicken ovalbumin upstream promoter-transcription factor (COUP-TF) and hepatocyte nuclear factor-4 (HNF-4). In experiments where SHBG promoter-luciferase reporter gene constructs were co-transfected into HepG2 cells with COUP-TF and/or HNF-4 expression vectors, HNF-4 markedly increased transcription, whereas COUP-TF suppressed this probably by displacing HNF-4 from their common FP1-binding site. This COUP-TF/HNF-4-binding site within FP1 includes a TTTAA sequence, located at nucleotides -30/-26 upstream of the transcription start site, which fails to interact with human TFIID, TATA-binding protein in vitro. When this sequence was replaced with an idealized HNF-4-binding site, the transcriptional activity of the promoter increased in HepG2 cells. Taken together, these data imply that an interplay between COUP-TF and HNF-4 at a site within FP1 regulates human SHBG expression and that HNF-4 controls transcription from this TATA-less promoter by somehow substituting for TATA-binding protein in the recruitment of a transcription preinitiation complex.

Human sex hormone-binding globulin gene expression in transgenic mice

The sex hormone-binding globulin gene (shbg) is expressed in the liver and testis as well as in several other tissues that play important roles in reproduction. Expression of shbg in the human liver results in the production of plasma sex hormone-binding globulin (SHBG), which regulates the bioavailability of sex steroids in the blood. Although shbg is not expressed in rodent livers postnatally, it gives rise to the androgen-binding protein in their testes upon sexual maturation. Human shbg is also expressed in the testis, but its products and their function are less well characterized. To study the expression of human shbg in different tissues and the consequences of overexpressing this gene in vivo, we have produced several lines of mice containing approximately 11-kilobase (kb; shbg11) or 4.3-kb (shbg4) human shbg genomic fragments that comprise all eight exons encoding SHBG as well as approximately 6 kb or approximately 0.9 kb of 5'-flanking DNA, respectively. Northern blots indicated that human shbg transcripts were most abundant in liver, kidney, and testis of the shbg11 mice. The 4.3-kb shbg transgenes were expressed at similar levels in liver and kidney, but the abundance of human shbg transcripts in their testes was much lower than that in shbg11 mice. Primer extension analysis indicated that transcription starts 60 bp from the translation initiation codon for SHBG in liver and kidney of shbg11 mice, and that the shbg transcripts in their testis are derived from a separate promoter flanking an alternative exon that replaces the exon containing the translation initiation codon for SHBG or androgen-binding protein. At the cellular level, the human shbg transgenes are expressed in clusters of hepatocytes located mainly within the periportal region of hepatic lobules and in the epithelial cells lining the proximal convoluted tubules of the kidney. This results in high levels of human SHBG in serum (1.45-1.72 nmol/ml) and urine (6-16 pmol/ml) of mature male shbg mice. The abundance and distribution of human shbg transcripts in the Sertoli cells of shbg11 mice vary throughout the spermatogenic cycle, with levels increasing in the Sertoli cell cytoplasm until stage VII of spermatogenesis and declining after stage IX. At stages X-XII of spermatogenesis, these transcripts concentrate at the adluminal compartment of the Sertoli cells, and this suggests that they have a role in the elongation phase of spermiogenesis. The presence of human SHBG in the blood of shbg transgenic mice may result in serum levels of testosterone that are 10-100 times higher than those in wild-type littermates. Despite this, their reproductive performance is normal, and there is no obvious phenotypic abnormalities even in animals homozygous for the transgenes.

Expression of sex hormone-binding globulin exon VII splicing variant messenger RNA in human uterine endometrial cancers

We have demonstrated the intracellular expression of sex hormone-binding globulin (SHBG) exon VII splicing variant mRNA in human uterine endometrial cancer using the reverse transcription-PCR-Southern blot and DNA sequencing analyses. Analysis of the missing base pairs proved that they corresponded to the entire exon VII, which is considered to encode a portion of the steroid-binding site, suggesting that the steroid-binding affinity of this variant might be different from that of the SHBG wild type. In uterine endometrial cancers, the wild-type mRNA levels significantly (P < 0.01) decreased, and the ratio of the SHBG variant to wild-type mRNA levels (P < 0.01) increased with the advance of histological dedifferentiation. These results suggest that dedifferentiation of endometrial cancers might induce a reduction in their estrogen-dependent properties via intracellular SHBG.

Expression of sex hormone-binding globulin and corticosteroid-binding globulin mRNAs in corpus luteum of human subjects

To understand the biology of sex steroids in human ovarian corpus luteum, the expression of intracellular sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) mRNAs as a manifestation of intracellular SHBG and CBG expression was determined. The expression of SHBG and CBG mRNAs was detected in all samples analyzed. Luteal SHBG mRNA level showed no significant change during the endometrial secretory phase of the menstrual cycle. On the other hand, luteal CBG mRNA level was significantly higher (p < 0.05) at the mid-secretory phase than that at the early and late secretory phases of the endometrium. These findings suggest that human ovarian corpus luteum synthesizes SHBG and CBG intracellularly, CBG being plausibly involved in the functional life span of corpus luteum.

Reduced testosterone, 17 beta-oestradiol and sexual hormone binding globulin, and increased insulin-like growth factor-1 concentrations, in healthy nulligravid women aged 19-25 years who were first and/or second degree relatives to breast cancer patients

Differences in hormonal and constitutional parameters between women with at least one first and/or second degree relative with breast cancer (RBC) and women without such affected relatives were studied in a group of healthy, nulligravid women aged 19-25 years. Present oral contraceptive (OC) users were analysed separately. In women not presently exposed to OCs we found significant correlations between RBC and reduced concentrations of testosterone during both the follicular (P < 0.001) and luteal menstrual cycle phases (P = 0.016). 17 beta-oestradiol was also significantly negatively correlated with RBC in the follicular (P = 0.044) and in the luteal phase (P = 0.027). RBC was significantly correlated with a lower waist/hip ratio (P = 0.044) compared with women without such a history. In multivariate analyses, the results for testosterone but not 17 beta-oestradiol remained significant. In these analyses high IGF-1 (P = 0.05) in the follicular phase and low sexual hormone-binding globulin (SHBG) (P = 0.04) in the luteal phase were also related to RBC. Including all 66 women in a multivariate model that analysed the specific effects from OCs and RBC on plasma testosterone showed that plasma testosterone was significantly lower among present OC users (P = 0.004) and in women with RBC (P = 0.005) during cycle days 5-10, with a significant positive two-way interaction between present OC use and RBC (P = 0.007). During cycle days 18-23 plasma testosterone showed a significant negative relationship with present OC use (P < 0.001) and RBC (P = 0.016) no significant interaction was seen during cycle days 18-23. Factors not significantly related to RBC were height, weight, breast size, age at menarche, p-progesterone and p-prolactin. It is concluded that a family history of breast cancer significantly lowered plasma testosterone concentrations in both cycle phases among healthy, nulligravid women compared with women without such history.

Characterization of the "estrogenicity" of tamoxifen and raloxifene in HepG2 cells: regulation of gene expression from an ERE controlled reporter vector versus regulation of the endogenous SHBG and PS2 genes

The estrogenic character of tamoxifen and raloxifene was studied on three different genes, an ERE-reporter construct and two endogenous genes, sex hormone binding globulin (SHBG) and pS2, in two variants of the human liver carcinoma cell line HepG2. On the ERE-reporter construct and the pS2 gene both tamoxifen and raloxifene acted as pure estrogen antagonists, whereas on the SHBG gene they functioned as partial estrogens/antiestrogens at concentrations below 1 microM and as full "agonists" at concentrations higher than 1 microM. The fold stimulatory effect of tamoxifen and raloxifene on SHBG protein expression was similar in the estrogen receptor (ER) expressing HepG2 cells (HepER3) and the parental non-ER expressing HepG2 cells at concentrations above 1 microM. In contrast, the 17beta-estradiol analogue moxestrol stimulated SHBG expression only in the HepER3 cells. Both tamoxifen and raloxifene had an additive effect to estrogen receptor-dependent SHBG gene expression in the HepER3 cells in the presence of saturating concentrations of moxestrol. However, a significant difference was observed in that a much higher concentration of moxestrol was required to see an additive effect of raloxifene compared to tamoxifen. The cytokine IL1-beta completely blocked the tamoxifen-dependent induction of SHBG gene expression in HepER3 cells, but only partly blocked the effect of moxestrol mediated by the ER. In conclusion, our results suggest that the mechanism for the liver-selective "estrogenic" character of tamoxifen and raloxifene is mediated by a non-ER dependent pathway.

Expression of sex hormone-binding globulin mRNA in uterine cervical cancers

To explore the role of sex hormone-binding globulin (SHBG) in the intracellular steroidal actions in human uterine cervical cancers, the expression of SHBG mRNA as a manifestation of intracellular SHBG expression was investigated using the competitive reverse transcription-polymerase chain reaction-Southern blot analysis. The expression of SHBG mRNA was detected in all cervical endometria and cancers analyzed. The levels of SHBG mRNA in cervical cancers were significantly lower (p < 0.01) than in the normal cervical endometrium. In cervical cancers, the levels of SHBG mRNA in cervical adenocarcinomas were significantly higher (p < 0.01) than in keratinizing and small cell nonkeratinizing squamous cell carcinomas, and tended to be higher than in large cell nonkeratinizing squamous cell carcinomas. There was no difference in expression among the clinical stages of cervical cancers. These data suggest that human uterine cervical cancers, especially adenocarcinomas, might synthesize SHBG intracellularly, and might conserve the activity of SHBG-related steroidal mechanisms to some extent.

A study of serum androgen and cortisol levels in female patients with rheumatoid arthritis. Correlation with disease activity

Androgen status and the role played by androgens in the pathogenesis of rheumatoid arthritis (RA) in female patients are a matter of debate. In the present study serum testosterone (T), DHEAS, sex hormone binding globulin (SHBG) and cortisol levels were determined in 55 RA women, both in pre- and post-menopausal (M) status, and in a group of healthy subjects. Patients were divided into two groups according to disease activity and a correlation analysis of hormonal levels against serum IL1beta levels was performed. No significant differences were found in serum T levels between RA patients and controls, both in preM (1.38 +/- 0.4 vs 1.35 +/- 0.3 nmol/l; p = ns) and in postM status (1.21 +/- 0.2 vs 1.10 +/- 0.2 nmol/l; p = ns). Serum SHBG levels were lower in RA patients than in control subjects, both in pre and in postM status. DHEAS levels were significantly lower in preM RA patients than in controls (2.34 +/- 1.2 vs 5.93 +/- 1.6 mu mol/l; p < 0.001) while cortisol levels were significantly higher in preM active RA patients than in controls (466.2 +/- 30.3 vs 411 +/- 66.2 nmol/l; p = 0.02). IL1beta levels were significantly higher in RA patients than in controls both in pre- and postM subjects (70 +/- 33.8 vs 23.1 +/- 2.9 and 92 +/- 27.4 vs 31.9 +/- 3.1 fmol/l, p < 0.001, respectively). Although androgen status could play a role in the pathogenesis of RA, at present it is not possible to exclude the influence of RA itself on sex hormone profile.

Roles of estrogen and SHBG in prostate physiology

Heretofore, the function of estrogen in the prostate, other than as an antiandrogen, has been unclear. In this review of a growing fund of knowledge about both estrogen and the plasma protein, sex hormone-binding globulin (SHBG), or testosterone-estradiol binding globulin (TeBG), the hypothesis is proposed that estrogen, mediated by SHBG, participates with androgen in setting the pace of prostatic growth and function. It is suggested that the estrogen not only directs stromal proliferation and secretion, but also, through IGF-I, conditions the response of the epithelium to androgen.

Hepatic expression of sex hormone-binding globulin associated with the postnatal surge of serum androgen-binding activity in the Djungarian hamster

Serum androgen-binding capacity in Djungarian hamsters, as in many other mammals, increases within days after birth and remains elevated until puberty. This increased activity has been attributed to a hepatic glycoprotein, sex hormone-binding globulin (SHBG), but expression of SHBG by the postnatal liver has not been demonstrated. Therefore, a full-length SHBG cDNA was cloned from the liver of neonatal hamsters and the expression of SHBG during development was examined. Hepatic SHBG RNA levels, as measured by both competitive RT-PCR and Northern analysis, were very low in fetal animals but increased significantly within 24 h of birth. Maximal values were maintained for 1 week after parturition, and then declined to basal adult levels. The developmental pattern in hepatic SHBG immunoactivity, as determined by Western analysis, mirrored that of hepatic SHBG mRNA. However, changes in serum SHBG immunoactivity and steroid-binding activity occurred approximately 1 week later. There were no sex differences in the levels of hepatic SHBG mRNA or protein during development, but serum immunoactivity tended to be higher in females at puberty. Sex- and age-related differences in the relative abundance of SHBG isoforms were also noted. Results of these studies demonstrate that Djungarian hamsters express an authentic SHBG and indicate that the postnatal surge in serum androgen-binding activity is due to perinatal up-regulation of SHBG expression.

Phytoestrogens: epidemiology and a possible role in cancer protection

Because many diseases of the Western Hemisphere are hormone-dependent cancers, we have postulated that the Western diet, compared to a vegetarian or semivegetarian diet, may alter hormone production, metabolism, or action at the cellular level by some biochemical mechanisms. Recently, our interest has been mainly focused on the cancer-protective role of some hormonelike diphenolic phytoestrogens of dietary origin, the lignans and the isoflavonoids. The precursors of the biologically active compounds originate in soybean products (mainly isoflavonoids), whole grain cereal food, seeds, and probably berries and nuts (mainly lignans). The plant lignan and isoflavonoid glycosides are converted by intestinal bacteria to hormonelike compounds with weak estrogenic but also antioxidative activity; they have now been shown to influence not only sex hormone metabolism and biological activity but also intracellular enzymes, protein synthesis, growth factor action, malignant cell proliferation, differentiation, and angiogenesis in a way that makes them strong candidates for a role as natural cancer-protective compounds. Epidemiologic investigations strongly support this hypothesis because the highest levels of these compounds in the diet are found in countries or regions with low cancer incidence. This report is a review on recent results suggesting that the diphenolic isoflavonoids and lignans are natural cancer-protective compounds.

Regulation of sex hormone-binding globulin production by isoflavonoids and patterns of isoflavonoid conjugation in HepG2 cell cultures

The effect of the isoflavonoid phytoestrogens daidzein, equol, and genistein on sex hormone-binding globulin (SHBG) levels, SHBG mRNA transcript levels, and SHBG gene methylation was studied in HepG2 cell cultures by fluoroimmunometric SHBG assay and Northern and Southern hybridizations, respectively. The effect of 17 beta-estradiol on these parameters was studied as a control. The metabolism of isoflavonoids in HepG2 cells was determined by isotope dilution gas chromatography-mass spectrometry, after ion-exchange chromatography. Daidzein and equol increased SHBG levels in parallel intracellularly and extracellularly, whereas genistein increased SHBG levels only within the cells, resembling thus the effect of 17 beta-estradiol. The difference may originate from the fact that genistein has more hydroxyl groups than daidzein and equol. The regulation of SHBG production by phytoestrogens appears to occur at the post-transcriptional level. Firstly, daidzein, equol, or genistein did not have a clear effect on the steady-state SHBG mRNA levels. Secondly, no effect on SHBG gene methylation was observed by genistein. The findings applied also to 17 beta-estradiol. However, as the SHBG gene was more methylated in SHBG-negative MCF-7 cells than in SHBG-positive HepG2 cells, DNA methylation may play a role in the tissue-specific activation of this gene. The metabolism of isoflavonoids in HepG2 cells yielded mainly unconjugated and sulfated compounds. Similar metabolism in hepatocytes in vivo might retain their biological activity in tissues responsive to estrogens.

Regulation of sex hormone-binding globulin secretion and gene expression by cycloheximide in vitro

The role of protein synthesis in sex hormone-binding globulin (SHBG) secretion and gene expression was studied in HepG2 cell cultures. Inhibition of protein synthesis by cycloheximide suppressed SHBG levels. Triiodothyronine and estradiol increased SHBG production, and cycloheximide reduced their effects to an extent which correlated with the degree of suppression obtained with the drug alone. Insulin decreased SHBG production, and the effect of the treatment with insulin and cycloheximide together did not differ from that with cycloheximide alone. Cycloheximide did not, alone or with the hormones, decrease SHBG levels more markedly extra- than intracellularly. Therefore, cycloheximide does not impair the secretion of SHBG which is synthesized in the presence of the drug. In contrast to SHBG protein levels, cycloheximide increased SHBG mRNA levels. When the effect of cycloheximide on the rate of SHBG mRNA decay was tested, the drug was found to extend the half-life of SHBG mRNA. Of the hormones, insulin decreased and triiodothyronine modestly increased SHBG mRNA levels, whereas estradiol had no clear effect. Treatment with cycloheximide together with any of the hormones resulted in an increase in SHBG mRNA levels. We conclude that protein synthesis inhibition does not impair the secretion of SHBG produced under such conditions, but stabilizes SHBG mRNA by removing some hepatic protein species involved in the regulation of its degradation.

Body mass and physical activity are important predictors of serum androgen concentrations in young healthy men

The relative importance of body mass index (BMI), demographic, and life-style factors in predicting androgen and sex hormone-binding globulin (SHBG) concentrations of young healthy men has not been clearly established. We evaluated the role of age, BMI, height, habitual physical activity, education, smoking, coffee and alcohol intake as predictors of serum testosterone, dihydrotestosterone, dehydroepiandrosterone sulfate, androstenedione, and SHBG concentrations in 100 healthy men 18-22 years old. BMI was the only independent predictor of dihydrotestosterone and dehydroepiandrosterone sulfate, and both BMI and physical activity were independent predictors of serum testosterone concentrations, whereas other variables did not appear to play a role of comparable importance.

Serum soluble interleukin-2 receptors as an index of the biological activity of thyroid hormones in hyperthyroidism

In order to examine whether serum soluble Interleukin-2 Receptors (sIL-2R) could be used as a marker of the biological effects of the thyroid hormones, we measured the sIL-2R, sex hormone binding globulin and beta-2 microglobulin levels in thirty-three hyperthyroid patients (14 with Graves' disease, 17 with Toxic Nodular Goiter and 2 with toxic adenoma) before and during treatment with antithyroid drugs. We found that serum sIL-2R concentrations of the patients, at diagnosis, were significantly higher compared with normal controls (2424 +/- 1447 vs 459 +/- 184 U/ml). All hyperthyroid patients had sIL-2R levels > mean + 2SD of normal controls, with 28 of the 33 patients having sIL-2R concentrations higher than 1011 U/ml (mean + 3SD of normal controls). Only 15 patients had SHBG levels higher than 3SD above the mean for the normal controls and 28 had SHBG levels 2SD above the mean for the normal controls. Three of the 5 hyperthyroid patients with normal SHBG levels at presentation had abnormally high sIL-2R levels. In all patients sIL-2R levels decreased gradually during therapy down to normal levels when euthyroidism was achieved. A strong positive correlation was found between sIL-2R, SHBG and T3 and T4 concentrations. Serum B2-microglobulin (B2-m) levels were higher than the upper normal limit only in 9 patients, but a significant decrement was observed in all patients when euthyroidism was achieved. The above results indicate that serum sIL-2R levels could be a useful marker of the in vivo biological effects of the thyroid hormones on lymphocytes in hyperthyroid patients.

Over-expression of human sex steroid-binding protein (hSBP/hABP or hSHBG) in insect cells infected with a recombinant baculovirus. Characterization of the recombinant protein and comparison to the plasma protein

Human sex steroid-binding protein (hSBP/hABP or hSHBG) was over-expressed in High Five and Sf9 cells adhered to plates and in suspension. The adherent cells expressed to levels of 2.3 mg/l and 1.4 mg/l after 4 and 6 days, respectively, while Sf9 cells grown in suspension yielded 4.67 mg/l after 6 days. Recombinant hSBP/hABP, purified to homogeneity by immunoadsorption, was found to fold similarly to native plasma hSBP/hABP and to display similar sequence epitopes after heat denaturation. The recombinant protein binds dihydrotestosterone, testosterone, and 17 beta-estradiol with KdS of 0.6, 2.4, and 14.2 nM, respectively, which are similar to plasma hSBP/hABP. The recombinant protein contains N-linked and O-linked oligosaccharide side-chains but the monomer exhibits a slightly lower molecular weight than plasma hSBP/hABP (40 kDa vs 44 kDa) which may be due to the absence of one N-linked side-chain or to shorter oligosaccharide side-chains. The partial N-terminal sequence LRPVLP(T)Q of recombinant hSBP/hABP is identical to plasma hSBP/hABP but appears to be less heterogeneous. These results indicate that recombinant baculovirus SBP represents a good model for investigating the structure of plasma hSBP/hABP. The expression system will allow the isolation of preparative amounts of SBP mutants generated by combinatorial site-directed mutagenesis to advance investigations on structure-function relationships and undertake crystallization trials for X-ray diffraction analyses.

Regulation of sex-hormone-binding globulin production by endogenous estrogens in vitro

The effect of endogenous estrogens on sex-hormone-binding globulin (SHBG) production was studied in HepG2 cells. 17 beta-estradiol, estrone, and estrogens from both 2- and 16 alpha-hydroxylative pathways stimulated SHBG production, but not in parallel with their binding affinities for the estrogen receptor. Thus, the underlying mechanism may be other than a pure interaction with the estrogen receptor.

Stimulation of sex hormone-binding globulin mRNA and attenuation of corticosteroid-binding globulin mRNA by triiodothyronine in human hepatoma cells

We examined the time course and dose response of the triiodothyronine (T3) effect on mRNAs for sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) in cells of the human hepatoma line HepG2. After 7 h of exposure to a saturating dose of T3, SHBG mRNA was unchanged but increased to 1.5 +/- 0.1 times the unstimulated control at 22 h. Maximal stimulation (2.3 +/- 0.6) was observed at 2-3 days. Corticosteroid-binding globulin mRNA was unchanged for 22 h after exposure to T3 but diminished thereafter to 64% by day 3. At 3-4 days of exposure, the changes in both SHBG mRNA and CBG mRNA were dose-responsive to the T3 concentration. For both mRNAs, half-maximal response occurred between 10 and 20 pmol/l bioavailable T3. Cortisol-binding proteins secreted by HepG2 cells after 3 days in culture also were T3 dose-responsive. No re-uptake of secreted CBG by the cells was observed, suggesting that the T3 effect on CBG secretion occurs during production of the mature protein. These data suggest that T3 stimulates the expression of the SHBG gene and attenuates the expression of the CBG gene. The effects of T3 on these genes are consistent with the increase in circulating SHBG and decrease in circulating CBG observed in hyperthyroidism. The HepG2 cells may be a useful human cell line in which to study the diversity of the molecular mechanisms of T3 action.