Plasma sex steroid hormones and risk of developing type 2 diabetes in women: a prospective study

The effects of atypical antipsychotic usage duration on serum adiponectin levels and other metabolic parameters

OBJECTIVE

Although atypical antipsychotics are well-tolerated and effective treatment options for schizophrenia, they have metabolic side effects, including weight gain and increased risk of Type II Diabetes Mellitus (DM). Adiponectin, produced exclusively in adipocytes, is the most abundant serum adipokine. Low levels of adiponectin are correlated with DM, insulin resistance and coronary heart disease. Usage of atypical antipsychotics may create a risk of metabolic syndrome. The aim of this study was to evaluate the effects of antipsychotic usage on parameters related to development of metabolic syndrome.

MATERIALS AND METHODS

A total of 27 patients (n=27) (13 women and 14 men) were recruited from our out-patient psychiatry clinic. All patients had been treated with atypical antipsychotics for at least 3 months and were in remission. Patients were evaluated for levels of HDL (High Density Lipoprotein), LDL (Low Density Lipoprotein), TG (Triglyceride) total cholesterol and fasting blood glucose, body weight, BMI (Body Mass Index), waist circumference and serum adiponectin levels.

RESULTS

Serum adiponectin levels were significantly lower (p:0.000) and body weights were significantly higher (p:0.003) in the patients who had been using atypical antipsychotics for longer than a year in comparison to patients who had been using atypical antipsychotics for one year or less.

CONCLUSION

Our findings supported the hypothesis that the length of administration of atypical antipsychotics has an effect on metabolic changes. They also highlight the fact that when investigating metabolic changes generated by atypical antipsychotic effects, the length of time that the patient has been on the atypical antipsychotics should also be considered.

Exercise and sex steroid hormones in skeletal muscle

Sex steroid hormones are secreted mainly by the ovary and testis and regulate diverse physiological processes in target tissues. Recent studies have shown that sex steroidogenesis-related mRNA and protein expressions, such as for 17β-hydroxysteroid dehydrogenase (HSD), 3β-HSD, 5α-reductase and aromatase cytochrome P-450 (P450arom) enzymes, are detected in the skeletal muscle, while testosterone, estradiol, and 5α-dihydrotestosterone (DHT) were locally synthesized in skeletal muscle from dehydroepiandrosterone (DHEA). Moreover, in animal and human studies, the sex steroidogenesis enzymes and sex steroid hormone levels in skeletal muscle are upregulated by acute and chronic exercise stimulation. The enhanced muscle sex steroidgenesis is associated with glycemic control via upregulation of muscle glucose transporter-4 (GLUT-4) signaling in obese and diabetic rats and with muscle mass and strength in older men. Thus, an exercise-induced increase of sex steroid hormone in muscle may positively impact age-related concerns such as life-related diseases and sarcopenia.

Weight loss increases follicle stimulating hormone in overweight postmenopausal women [corrected]

OBJECTIVES

To examine the impact of a weight loss intervention upon follicle stimulating hormone (FSH) levels in postmenopause.

METHODS

Participants were postmenopausal, overweight, glucose-intolerant women not using exogenous estrogen (n = 382) in the Diabetes Prevention Program. Women were randomized to intensive lifestyle change (ILS) with the goals of weight reduction of at least 7% of initial weight and 150 min per week of moderate-intensity exercise, metformin 850 mg twice a day, or placebo administered twice a day.

RESULTS

Randomization to ILS led to small increases in FSH between baseline and 1-year follow-up vs. placebo (2.3 IU/l vs. -0.81 IU/l, P < 0.01). Increases in FSH were correlated with decreases in weight (r = -0.165, P < 0.01) and estradiol (E2) (r = -0.464, P < 0.0001) after adjustment for age, race/ethnicity, and randomization arm. Changes in FSH were still significantly associated with changes in weight even after adjustment for E2 levels. Metformin users had reductions in weight but non-significant changes in FSH and E2 levels vs. placebo.

CONCLUSIONS

Weight loss leads to small increases in FSH among overweight, postmenopausal women, potentially through pathways mediated by endogenous estrogen as well as other pathways.

The association between vasomotor symptoms and metabolic health in peri- and postmenopausal women: a systematic review

The objective of this study was to systematically review studies describing the association between vasomotor symptoms and metabolic syndrome, type 2 diabetes and insulin resistance in peri- and postmenopausal women. A systematic search of studies was performed in EMBASE, MEDLINE, Web-of-science, Scopus, PubMed publisher, Cochrane Library, Google scholar. To identify studies eligible for inclusion, the following criteria were defined: randomised trials, cohort, case-control, and cross-sectional studies investigating the association between vasomotor symptoms and metabolic syndrome, type 2 diabetes and insulin resistance in peri- and postmenopausal women with natural menopause. Methodological quality was assessed using a modified NewCastle Ottawa Assessment Scale. After screening 2660 titles and abstracts, four studies, of which two cohort studies met the criteria of high methodological quality, were included in the review. Because of the heterogeneity and the limited number of studies, there is no sufficient evidence on the potential role of vasomotor symptoms in metabolic health. However, both high-quality cohort studies, with large study populations and adjustment for multiple confounding variables showed positive associations between vasomotor symptoms and insulin resistance and type 2 diabetes mellitus. These findings suggest that there is an association between vasomotor symptoms and metabolic health outcomes. To confirm this and to strengthen the evidence, more high quality longitudinal research on this topic is needed.

Negative regulation of glucose metabolism in human myotubes by supraphysiological doses of 17β-estradiol or testosterone

OBJECTIVE

Exposure of skeletal muscle to high levels of testosterone or estrogen induces insulin resistance, but evidence regarding the direct role of either sex hormone on metabolism is limited. Therefore, the aim of this study was to investigate the direct effect of acute sex hormone exposure on glucose metabolism in skeletal muscle.

MATERIALS/METHODS

Differentiated human skeletal myotubes were exposed to either 17β-estradiol or testosterone and metabolic characteristics were assessed. Glucose incorporation into glycogen, glucose oxidation, palmitate oxidation, and phosphorylation of key signaling proteins were determined.

RESULTS

Treatment of myotubes with either 17β-estradiol or testosterone decreased glucose incorporation into glycogen. Exposure of myotubes to 17β-estradiol reduced glucose oxidation under basal and insulin-stimulated conditions. However, testosterone treatment enhanced basal palmitate oxidation and prevented insulin action on glucose and palmitate oxidation. Acute stimulation of myotubes with testosterone reduced phosphorylation of S6K1 and p38 MAPK. Exposure of myotubes to either 17β-estradiol or testosterone augmented phosphorylation GSK3β(Ser9) and PKCδ(Thr505), two negative regulators of glycogen synthesis. Treatment of myotubes with a PKC specific inhibitor (GFX) restored the effect of either sex hormone on glycogen synthesis. PKCδ silencing restored glucose incorporation into glycogen to baseline in response to 17β-estradiol, but not testosterone treatment.

CONCLUSION

An acute exposure to supraphysiological doses of either 17β-estradiol or testosterone regulates glucose metabolism, possibly via PKC signaling pathways. Furthermore, testosterone treatment elicits additional alterations in serine/threonine kinase signaling, including the ribosomal protein S6K1 and p38 MAPK.

Estrogen can modulate menopausal women's heart rate variability

The aim of our study was to compare the responses of heart rate variability (HRV) with two different types of hormonal substitution therapy (HT) in post-menopausal women (cross-sectional study) and to reveal an effect of HT shortly after beginning of its administration (follow-up study). To elucidate the influence of menopause and effects of different protocols of a HT on autonomic control of heart rate, we evaluated the heart rate variability (HRV) in 5 groups: premenopausal women (n=140), postmenopausal women without HT (n=360), women on HT with conjugated estrogen only (n=168), women on continuous combined estrogen-progesterone HT (n=117), and men (n=140). Frequency-domain of short-term stationary R-R intervals was performed to evaluate the total variance, low frequency power (LF; 0.04-0.15 Hz), high frequency power (HF; 0.15-0.40 Hz), portion of low frequency power (LF%) and ratio of LF to HF (LF/HF). Significantly lower portion of the LF was found in premenopausal women [46.9 (+/-2.7) nu] when compared to untreated postmenopausal women [54.3 (+/-2.9) nu] and men [55.2 (+/-3.0) nu]. Treatment by estrogen only was proved to decrease the LF% [40.1 (+/-2.1) nu] while no effect on HRV was observed in women treated with combination of estrogen and progesterone [57.2 (+/-3.1) nu]. Also the HF was lower in postmenopausal women [4.16 (+/-0.16) ms(2)] than in premenopausal women [4.79 (+/-0.22) ms(2)] and women treated with estrogen only [4.98 (+/-0.25) ms(2)] while in women treated with combined hormonal therapy the average value [3.99 (+/-0.21) ms(2)] did not significantly differ from that of untreated postmenopausal women. The follow-up study also proved increase of high frequency power already after two months of estrogen substitution therapy [4.86 (+/-0.14) ms(2) vs. 4.19 (+/-0.15) ms(2)]. These results suggest that higher vagal modulation of heart rate that seems typical for younger women becomes after menopause similar to that of men. We also proved a positive shift of HRV parameters toward more beneficial values as for a cardiovascular risk in postmenopausal women treated with estrogens but not in those treated by combined estrogen - progesterone substitution therapy.

Association of FSH with metabolic syndrome in postmenopausal women: a comparison with CRP, adiponectin and leptin

Aim: The aim of this study was to evaluate the usefulness of follicle-stimulating hormone (FSH) determination in the postmenopausal women with metabolic syndrome (MetS) in a comparative analysis with biomarkers such as C-reactive protein (CRP), adiponectin, leptin and leptin-to-adiponectin ratio (L/A). Material & methods: 135 postmenopausal women with MetS and 153 without MetS were subjected to examinations. Results: The increase in the probability of MetS, when the value of the marker concentration decreased or increased by 1 standard deviation, was two times higher for FSH-based models than for models including CRP and leptin, and was similar to models including adiponectin and L/A. The areas under the ROC curves were 0.78 for FSH, 0.68 for CRP, 0.72 for leptin, 0.76 for adiponectin and 0.80 for L/A. Conclusions: Our results suggest that the FSH concentration assesses the probability of MetS similarly to L/A or adiponectin and better than CRP or leptin in postmenopausal women.

Estrogen suppresses adipogenesis by inhibiting S100A16 expression

The aim of this study is to determine the effects of E2 on metabolic syndrome and the molecular mechanisms involving S100A16. Ovariectomized (OVX) rat models and mouse embryonic fibroblasts cell models were used. E2 loss in OVX rats induced body weight gain and central abdominal fat accumulation, which were ameliorated by E2 treatment under chow and high-fat diet (HFD) conditions. E2 decreased the expression of the adipocyte marker genes PPARγ, aP2, C/EBPα, and S100A16. E2 inhibited adipogenesis. Overexpression of S100A16 reversed the E2-induced adipogenesis effect. A luciferase assay showed that E2 inhibited the expression of S100A16. E2 treatment decreased body weight gain and central abdominal fat accumulation under both chow and HFD conditions. Also, E2 suppressed adipogenesis by inhibiting S100A16 expression.

Endogenous sex hormones, metabolic syndrome, and diabetes in men and women

Endogenous sex hormones predict impairments of glucose regulation. Cross-sectional studies suggest that lower levels of testosterone in men and higher levels in women increase risk of metabolic syndrome and diabetes, whereas lower levels of sex hormone binding globulin in both men and women increase risk of metabolic syndrome and diabetes. In a systematic review, we summarize existing longitudinal studies, which suggest similar patterns. However, these studies are often limited to a single sex steroid measure. Whether these associations are primarily a marker of adiposity, and whether these associations differ between younger eugonadal vs older hypogonadal adults is also uncertain. The impact of exogenous sex steroid therapy may not reflect relationships between sex hormones and impaired glucose regulation that occur without supplementation. Therefore, examination of endogenous sex steroid trajectories and obesity trajectories within individuals might aid our understanding of how sex steroids contribute to glucose regulation.

Prepregnancy SHBG concentrations and risk for subsequently developing gestational diabetes mellitus

OBJECTIVE

Lower levels of sex hormone-binding globulin (SHBG) have been associated with increased risk of diabetes among postmenopausal women; however, it is unclear whether they are associated with glucose intolerance in younger women. We examined whether SHBG concentrations, measured before pregnancy, are associated with risk of gestational diabetes mellitus (GDM).

RESEARCH DESIGN AND METHODS

This was a nested case-control study among women who participated in the Kaiser Permanente Northern California Multiphasic Health Check-up examination (1984-1996) and had a subsequent pregnancy (1984-2009). Eligible women were free of recognized diabetes. Case patients were 256 women in whom GDM developed. Two control subjects were selected for each case patient and were matched for year of blood draw, age at examination, age at pregnancy, and number of intervening pregnancies.

RESULTS

Compared with the highest quartile of SHBG concentrations, the odds of GDM increased with decreasing quartile (odds ratio 1.06 [95% CI 0.44-2.52]; 2.33 [1.07-5.09]; 4.06 [1.90-8.65]; P for trend < 0.001), after adjusting for family history of diabetes, prepregnancy BMI, race/ethnicity, alcohol use, prepregnancy weight changes, and homeostasis model assessment of insulin resistance. Having SHBG levels below the median (<64.5 nmol/L) and a BMI ≥25.0 kg/m(2) was associated with fivefold increased odds of GDM compared with normal-weight women with SHBG levels at or above the median (5.34 [3.00-9.49]).

CONCLUSIONS

Low prepregnancy SHBG concentrations were associated with increased risk of GDM and might be useful in identifying women at risk for GDM for early prevention strategies.

Gender Difference in Blood pressure, Blood Sugar, and Cholesterol in Young Adults with Comparable Routine Physical Exertion

Context:

Gender differences in the risk of developing non-communicable diseases (NCD) are a matter of debate. The susceptibility of a woman to NCD should be evaluated taking into consideration the social factors that limit the physical activity among women. It will be interesting to note what will happen if women are allowed to take part in physical exercise to the extent of men.

Aims:

To find out the gender difference in the pattern of the clinical and biochemical indices related to NCD in young adults with comparable daily physical activity.

Settings and Design:

This is an institution-based cross-sectional study and the setting was Lekshmibhai National College for Physical Education (LNCPE), Thiruvananthapuram, Kerala, India.

Materials and Methods:

The study participants were students who were regularly involved in more than three hours of physical exercise daily at least for the previous one year. The information on socio-demography, anthropometry, and blood pressure was recorded. Blood samples were taken for laboratory examination.

Results:

Out of 150 students registered, 126 (84%) in the age group of 17 to 25 years who fulfilled the eligibility criteria were studied. Fifty-five (43.7%) of them were women. Systolic blood pressure, fasting blood sugar, and low-density lipoprotein were found significantly lower in women. No significant difference was noted in the case of diastolic blood pressure and total cholesterol.

Conclusion:

Gender differences exist for NCD risk factors among young adults with comparable physical activity and physical exertion seems to be more protective for females.

Estrogen: a master regulator of bioenergetic systems in the brain and body

Estrogen is a fundamental regulator of the metabolic system of the female brain and body. Within the brain, estrogen regulates glucose transport, aerobic glycolysis, and mitochondrial function to generate ATP. In the body, estrogen protects against adiposity, insulin resistance, and type II diabetes, and regulates energy intake and expenditure. During menopause, decline in circulating estrogen is coincident with decline in brain bioenergetics and shift towards a metabolically compromised phenotype. Compensatory bioenergetic adaptations, or lack thereof, to estrogen loss could determine risk of late-onset Alzheimer's disease. Estrogen coordinates brain and body metabolism, such that peripheral metabolic state can indicate bioenergetic status of the brain. By generating biomarker profiles that encompass peripheral metabolic changes occurring with menopause, individual risk profiles for decreased brain bioenergetics and cognitive decline can be created. Biomarker profiles could identify women at risk while also serving as indicators of efficacy of hormone therapy or other preventative interventions.

Ovariectomy increases the participation of hyperpolarizing mechanisms in the relaxation of rat aorta

This study examines the downstream NO release pathway and the contribution of different vasodilator mediators in the acetylcholine-induced response in rat aorta 5-months after the loss of ovarian function. Aortic segments from ovariectomized and control female Sprague-Dawley rats were used to measure: the levels of superoxide anion, the superoxide dismutases (SODs) activity, the cGMP formation, the cGMP-dependent protein kinase (PKG) activity and the involvement of NO, cGMP, hydrogen peroxide and hyperpolarizing mechanisms in the ACh-induced relaxation. The results showed that ovariectomy did not alter ACh-induced relaxation; incubation with L-NAME, a NO synthase inhibitor, decreased the ACh-induced response to a lesser extent in aorta from ovariectomized than from control rats, while ODQ, a guanylate cyclase inhibitor, decreased that response to a similar extent; the blockade of hyperpolarizing mechanisms, by precontracting arteries with KCl, decreased the ACh-induced response to a greater extent in aortas from ovariectomized than those from control rats; catalase, that decomposes hydrogen peroxide, decreased the ACh-induced response only in aorta from ovariectomized rats. In addition, ovariectomy increased superoxide anion levels and SODs activity, decreased cGMP formation and increased PKG activity. Despite the increased superoxide anion and decreased cGMP in aorta from ovariectomized rats, ACh-induced relaxation is maintained by the existence of hyperpolarizing mechanisms in which hydrogen peroxide participates. The greater contribution of hydrogen peroxide in ACh-induced relaxation is due to increased SOD activity, in an attempt to compensate for increased superoxide anion formation. Increased PKG activity could represent a redundant mechanism to ensure vasodilator function in the aorta of ovariectomized rats.

Endogenous sex steroid levels and cardiovascular disease in relation to the menopause: a systematic review

Heart disease remains a major cause of death among women in the United States. This article focuses on physiologic endogenous estrogen levels with a systematic review of literature related to endogenous sex steroid levels and coronary artery disease (CAD) among postmenopausal women with natural or surgical menopause. There is adequate reason to seek evidence for associations of circulating estrogen levels and CAD. In the future, even if ovarian senescence-associated hormonal changes are confirmed to be associated with CAD in cohort studies of postmenopausal women, there may be other components explaining the gender differences in CAD patterns.

The role of estrogens in control of energy balance and glucose homeostasis

Estrogens play a fundamental role in the physiology of the reproductive, cardiovascular, skeletal, and central nervous systems. In this report, we review the literature in both rodents and humans on the role of estrogens and their receptors in the control of energy homeostasis and glucose metabolism in health and metabolic diseases. Estrogen actions in hypothalamic nuclei differentially control food intake, energy expenditure, and white adipose tissue distribution. Estrogen actions in skeletal muscle, liver, adipose tissue, and immune cells are involved in insulin sensitivity as well as prevention of lipid accumulation and inflammation. Estrogen actions in pancreatic islet β-cells also regulate insulin secretion, nutrient homeostasis, and survival. Estrogen deficiency promotes metabolic dysfunction predisposing to obesity, the metabolic syndrome, and type 2 diabetes. We also discuss the effect of selective estrogen receptor modulators on metabolic disorders.

Age at menopause, reproductive life span, and type 2 diabetes risk: results from the EPIC-InterAct study

OBJECTIVE

Age at menopause is an important determinant of future health outcomes, but little is known about its relationship with type 2 diabetes. We examined the associations of menopausal age and reproductive life span (menopausal age minus menarcheal age) with diabetes risk.

RESEARCH DESIGN AND METHODS

Data were obtained from the InterAct study, a prospective case-cohort study nested within the European Prospective Investigation into Cancer and Nutrition. A total of 3,691 postmenopausal type 2 diabetic case subjects and 4,408 subcohort members were included in the analysis, with a median follow-up of 11 years. Prentice weighted Cox proportional hazards models were adjusted for age, known risk factors for diabetes, and reproductive factors, and effect modification by BMI, waist circumference, and smoking was studied.

RESULTS

Mean (SD) age of the subcohort was 59.2 (5.8) years. After multivariable adjustment, hazard ratios (HRs) of type 2 diabetes were 1.32 (95% CI 1.04-1.69), 1.09 (0.90-1.31), 0.97 (0.86-1.10), and 0.85 (0.70-1.03) for women with menopause at ages <40, 40-44, 45-49, and ≥55 years, respectively, relative to those with menopause at age 50-54 years. The HR per SD younger age at menopause was 1.08 (1.02-1.14). Similarly, a shorter reproductive life span was associated with a higher diabetes risk (HR per SD lower reproductive life span 1.06 [1.01-1.12]). No effect modification by BMI, waist circumference, or smoking was observed (P interaction all > 0.05).

CONCLUSIONS

Early menopause is associated with a greater risk of type 2 diabetes.

Reductions in glucose among postmenopausal women who use and do not use estrogen therapy

OBJECTIVE

Among postmenopausal women who do not use estrogen therapy (ET), we have previously reported that intensive lifestyle modification (ILS) leads to increases in sex hormone-binding globulin (SHBG) and that such increases are associated with reductions in fasting plasma glucose (FPG) and 2-hour postchallenge glucose (2HG). Oral ET decreases FPG and increases 2HG while increasing both SHBG and estradiol (E2). It is unknown if ILS reduces glucose among ET users, if changes in SHBG and E2 might mediate any glucose decreases in ET users, and if these patterns differ from those in non-ET users.

METHODS

We conducted a secondary analysis of postmenopausal women in the Diabetes Prevention Program who used ET at baseline and 1-year follow-up (n = 324) and who did not use ET at either time point (n = 382). Participants were randomized to ILS, metformin, or placebo administered at 850 mg BID.

RESULTS

ET users were younger, more often white, and more likely to have had bilateral oophorectomy than non-ET users. Among ET users, ILS reduced FPG (P < 0.01) and 2HG (P < 0.01), and metformin reduced FPG (P < 0.01) but not 2HG (P = 0.56), compared with placebo. Associations between SHBG and total E2 with FPG and 2HG were not significant among women randomized to ILS or metformin. These patterns differed from those observed among women who did not use ET.

CONCLUSIONS

We conclude that among glucose-intolerant ET users, interventions to reduce glucose are effective but possibly mediated through different pathways than among women who do not use ET.

SHBG in GDM maternal serum, placental tissues and umbilical cord serum expression changes and its significance

AIMS

To compare the expression of sex hormone binding globulin (SHBG) in normal placental tissues and serum with placental tissues from patients with gestational diabetes mellitus (GDM) and to deduce the mechanism affecting placental SHBG in GDM.

METHODS

Enzyme-linked immunosorbent assay (ELISA) method were used to detect SHBG levels changes in normal and GDM maternal serum, umbilical cord serum and placental. We measured SHBG mRNA and protein using reverse-transcription polymerase chain reaction, and Western blotting, respectively, in normal and GDM placental tissues.

RESULTS

In maternal serum, compared with the control group, GDM group: glucose, insulin increased, SHBG decreased. In the placenta, compared with the control group, GDM group: SHBG, SHBG mRNA and SHBG protein decreased. There is no correlation between placenta SHBG and maternal serum SHBG respectively in control and GDM group, but in GDM group maternal serum insulin and placenta SHBG are linear correlation.

CONCLUSIONS

GDM serum and placental SHBG levels are reduced, hyperinsulinemia may lead to a reduction of SHBG in circulating blood, but also damage the placenta cells which led to placental synthesis and secretion of SHBG decrease.

Is bisphenol-A exposure during pregnancy associated with blood glucose levels or diagnosis of gestational diabetes?

Recent epidemiological studies indicate bisphenol A (BPA), an estrogenic chemical used in production of epoxy, polycarbonate, and plastic may increase risk of insulin resistance and type 2 diabetes. Exposure to BPA during pregnancy may contribute to development of gestational diabetes mellitus (GDM), a precursor to type 2 diabetes in women. This pilot study examined the association between BPA exposure, fasting blood glucose levels (FBG), and GDM diagnosis during pregnancy. Banked urine samples from 22 cases of GDM and 72 controls were analyzed for total (free BPA + conjugates) urinary BPA concentrations (μg/L). FBG levels (mg/dl) were obtained from 1-h 50-g glucose tolerance tests (GTT) that women underwent for routine GDM screening (mean gestational age = 26.6 weeks, SD = 3.8). Those with an initial screening value ≥ 135 mg/dl underwent 3-h 100 g oral GTT. GDM diagnoses were made when the initial screening value was ≥ 200 mg/dl or when values at ≥ 2 time points exceeded 3-h oral GTT thresholds. Among controls, median FBG levels (mg/dL) did not differ across exposure tertiles, defined according to the distribution of total specific-gravity-adjusted urinary BPA concentrations. Logistic regression models controlling for race/ethnicity did not provide evidence of association between BPA exposure and case status across increasing tertiles of BPA exposure (number of GDM cases/controls in tertile1: 13/24; in tertile 2: 6/24; in tertile 3: 3/24). Findings do not support a relationship between total urinary BPA concentrations and altered glucose metabolism during pregnancy. However, due to study limitations, findings need to be interpreted with caution.

The cellular and molecular mechanisms by which insulin influences breast cancer risk and progression

Epidemiological studies have related hyperinsulinemia and type 2 diabetes to an increased breast cancer risk, an aggressive and metastatic phenotype, and a poor prognosis. Furthermore, diabetic retinopathy arises from pathological angiogenesis, which is also essential for breast cancer growth and metastasis. Insulin stimulates the proliferation of some human breast cancer cell lines in vitro by mechanisms that use both the phosphatidylinositol-3 kinase and the mitogen-activated protein kinase/Akt signaling pathways; it is also a cell survival (anti-apoptotic) agent and enhances tumor cell migration and invasive capacity. Hyperinsulinemia affects breast cancer cells via the endocrine system, but experimental studies suggest the importance of paracrine mechanisms operating by the effects of insulin on the secretion of adipokines from tumor-associated adipose tissue. In such a system, one adipokine, leptin, has stimulatory paracrine effects on breast cancer cell proliferation and survival, while a second, adiponectin, is inhibitory. Leptin, vascular endothelial growth factor, another insulin-regulated adipokine, and insulin itself also stimulate angiogenesis. Insulin has complex interactions with estrogens: it induces adipose stromal cell aromatase and tumor cell sex steroid hormone receptor expression and suppresses sex hormone-binding globulin, which may enhance estrogen synthesis and bioactivity with consequent promotion of estrogen-dependent breast cancer. All these actions influence the later steps in breast cancer development but genetic studies are also revealing connections between gene abnormalities related to type 2 diabetes and the initiation stage of breast carcinogenesis. Understanding the various mechanisms by which insulin participates in breast cancer cell biology provides opportunities for novel approaches to treatment.

The effects of caffeinated and decaffeinated coffee on sex hormone-binding globulin and endogenous sex hormone levels: a randomized controlled trial

Background

Findings from observational studies suggest that sex hormone-binding globulin (SHBG) and endogenous sex hormones may be mediators of the putative relation between coffee consumption and lower risk of type 2 diabetes. The objective of this study was to evaluate the effects of caffeinated and decaffeinated coffee on SHBG and sex hormone levels.

Findings

After a two-week run-in phase with caffeine abstention, we conducted an 8-week parallel-arm randomized controlled trial. Healthy adults (n = 42) were recruited from the Boston community who were regular coffee consumers, nonsmokers, and overweight. Participants were randomized to five 6-ounce cups of caffeinated or decaffeinated instant coffee or water (control group) per day consumed with each meal, mid-morning, and mid-afternoon. The main outcome measures were SHBG and sex hormones [i.e., testosterone, estradiol, dehydroepiandrosterone sulfate].

No significant differences were found between treatment groups for any of the studied outcomes at week 8. At 4 weeks, decaffeinated coffee was associated with a borderline significant increase in SHBG in women, but not in men. At week 4, we also observed several differences in hormone concentrations between the treatment groups. Among men, consumption of caffeinated coffee increased total testosterone and decreased total and free estradiol. Among women, decaffeinated coffee decreased total and free testosterone and caffeinated coffee decreased total testosterone.

Conclusions

Our data do not indicate a consistent effect of caffeinated coffee consumption on SHBG in men or women, however results should be interpreted with caution given the small sample size. This is the first randomized trial investigating the effects of caffeinated and decaffeinated coffee on SHBG and sex hormones and our findings necessitate further examination in a larger intervention trial.

Extremes of an aromatase index predict increased 25-year risk of cardiovascular mortality in older women

BACKGROUND

Peripheral conversion of androgens to oestrogens via aromatase is the primary source of oestrogen in postmenopausal women and may play a role in cardiovascular health.

DESIGN

Prospective. PARTICIPANTS, MEASUREMENTS: The association of an index of aromatase activity (AROM), the serum oestrone-to-androstenedione ratio, with 25-year cardiovascular disease (CVD) mortality was examined in 819 postmenopausal non-oestrogen using women (mean age at baseline = 72).

RESULTS

Overall, 247 deaths were attributed to CVD. The median AROM value was 60 (95% range 17-129). AROM was positively correlated with age (r = 0·28) and body mass index (BMI) (r = 0·22) (P < 0·001). The age-adjusted risk for CVD mortality was significantly elevated for women in the lowest (HR = 2·01, 95% CI 1·31-3·12) and highest (HR = 1·51, 95%CI 1·02-2·22) quintiles of AROM, compared with the middle quintile. This U-shaped association persisted after additional adjustment for BMI, waist-to-hip ratio, exercise, smoking, alcohol use and traditional CVD risk factor covariates. There was a significant interaction of AROM and BMI (P = 0·001), such that high AROM was associated with a 63% reduction in risk of CVD death for women with low BMI (<22 kg/m(2) ), but with 2·1- to 2·5-fold increased risk in women with mid-range (22-<25 kg/m(2) ) and high (≥25 kg/m(2) ) BMI. Oestradiol did not influence AROM associations and was not independently related to CVD death.

CONCLUSIONS

These results suggest that aromatase is a novel endocrine factor predictive of CVD mortality among postmenopausal women. If confirmed, additional studies are needed to determine whether extremes of aromatase reflect genetic influences or underlying disease processes.

Polycystic ovary syndrome is a risk factor for type 2 diabetes: results from a long-term prospective study

Polycystic ovary syndrome (PCOS) recently has been identified as a risk factor associated with type 2 diabetes. However, the evidence derives from cross-sectional observational studies, retrospective studies, or short-term prospective studies. This long-term prospective study of a large cohort of women with PCOS, followed from youth to middle age, aimed at estimating, for the first time, the incidence and potential predictors of type 2 diabetes in this population. A total of 255 women with PCOS were followed for at least 10 years (mean follow-up 16.9 years). Six women were patients with diabetes at baseline, and another 42 women developed type 2 diabetes during the follow-up. The incidence rate of type 2 diabetes in the study population was 1.05 per 100 person-years. The age-standardized prevalence of diabetes at the end of follow-up was 39.3%, which is significantly higher with respect to that of the general Italian female population of a similar age (5.8%). The likelihood of developing type 2 diabetes significantly increased as BMI, fasting glucose, and glucose area under the curve at baseline increased and significantly decreased as sex hormone-binding globulin (SHBG) levels at follow-up increased. This study demonstrates that the risk of type 2 diabetes is markedly elevated in middle-aged women with PCOS and suggests including BMI, glucose, and SHBG-circulating levels in the risk stratification.

Higher levels of endogenous estradiol are associated with frailty in postmenopausal women from the toledo study for healthy aging

BACKGROUND

Adverse effects of higher endogenous estradiol (E2) levels on various clinical outcomes and on determinants of the frailty syndrome have recently been reported. However, there are no data about the potential relationship between E2 and frailty. We aimed to study the association between E2 levels and frailty among older postmenopausal women not taking hormonal therapy.

METHODS

We used data from the Toledo Study for Healthy Aging, a Spanish population-based cohort study. Frailty was defined according to Fried's approach. Multivariate odds ratios (OR) and 95% confidence intervals (CI) associated with E2 levels were estimated using polytomous logistic regression.

RESULTS

E2 levels decreased significantly with age and educational level, whereas they increased with body mass index, high-sensitivity C-reactive protein (hs-CRP), and impairment in Katz activities of daily living. Higher E2 levels were associated with the prevalence of frailty among women younger than 79 yr, but not in the oldest group (p interaction = 0.047). After adjustment, OR of frailty associated with a 1 sd increase of E2 was 1.51 (95% CI, 1.04-2.20; P = 0.03). We identified an interaction between E2 and hs-CRP on the prevalence of frailty (P value = 0.042). Women with both higher E2 and hs-CRP (defined as values into the upper tertile) had an age-adjusted OR of 4.2 (95% CI, 1.7-10.5; P = 0.002), compared with women with low levels of both E2 and hs-CRP.

CONCLUSION

Higher E2 levels were associated with frailty in postmenopausal women. The synergism between higher E2 and hs-CRP levels suggests the existence of physiopathological mechanisms connecting inflammation and estrogen to frailty.

Endogenous sex hormone changes in postmenopausal women in the diabetes prevention program

CONTEXT

Whether endogenous sex hormones (ESH) [SHBG, estradiol, testosterone, and dehydroepiandrosterone (DHEA)] are altered by intensive lifestyle modification (ILS) or metformin and whether such changes affect glucose levels among dysglycemic postmenopausal women is unclear.

OBJECTIVES

Our objective was to examine intervention impact on ESH and associations with fasting plasma glucose (FPG) and 2-h glucose changes among postmenopausal glucose-intolerant women.

DESIGN

We performed a secondary analysis of a randomized controlled trial.

PARTICIPANTS

Participants included postmenopausal, overweight, glucose-intolerant women not using exogenous estrogen (n = 382) who participated in the Diabetes Prevention Program.

INTERVENTIONS

Interventions included ILS with the goals of weight reduction of at least 7% of initial weight and 150 min/wk of moderate intensity exercise or metformin or placebo administered 850 mg twice a day.

MAIN OUTCOME MEASURES

Intervention-related changes in ESH and associations of changes in ESH and glucose levels were evaluated.

RESULTS

ILS significantly increased SHBG and decreased DHEA before and after adjustment for changes in waist circumference and fasting insulin. ILS did not alter estradiol or testosterone. Metformin did not change any ESH. ILS-induced increases in SHBG and declines in DHEA were associated with decreases in FPG and 2-h glucose, and declines in estradiol were associated with decreases in FPG, before and after adjustment for age, FSH, race/ethnicity, changes in waist circumference, and 1/fasting insulin.

CONCLUSIONS

Among postmenopausal glucose-intolerant women not using estrogen, ILS increased SHBG levels and lowered DHEA levels. These changes were associated with lower glucose independent of adiposity and insulin. Metformin effects upon ESH were not significant.

High level of plasma estradiol as a new predictor of ischemic arterial disease in older postmenopausal women: the three-city cohort study

Background

Despite evidence that estrogens may be involved in atherothrombosis, the role of endogenous sex steroid hormones in ischemic arterial disease among postmenopausal women remains uncertain.

Methods and Results

In the Three-City prospective cohort study of subjects (n=9294) >65 years of age, we investigated the association of total 17β-estradiol, bioavailable 17β-estradiol, and total testosterone with the 4-year incidence of ischemic arterial disease among postmenopausal women who did not use any hormone therapy. We designed a case–cohort study including a random sample of 537 subjects and 106 incident cases of first cardiovascular events. Weighted Cox proportional-hazards models with age as the time scale were used to estimate hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) for ischemic arterial disease by a 1–standard deviation increase in sex steroid hormones. In univariate analysis, HR of ischemic arterial disease was positively and significantly associated with both total and bioavailable estradiol levels. These associations remained significant after adjustment for traditional cardiovascular risk factors, including body mass index, diabetes, hypercholesterolemia, hypertension, and smoking status (HR: 1.42, 95% CI: 1.12–1.79, P<0.01; and HR: 1.42, 95% CI: 1.12–1.78, P<0.01, respectively). Separate analysis for coronary heart disease yielded similar results (adjusted HR: 1.49, 95% CI: 1.10–2.02, P=0.01; and adjusted HR: 1.50, 95% CI: 1.11–2.04, P<0.01, respectively), and a borderline significant trend was observed for ischemic stroke (HR: 1.34, 95% CI: 0.95–1.89, P=0.08; and HR: 1.32, 95% CI: 0.94–1.84, P=0.11, respectively). By contrast, no significant association was found between total testosterone and ischemic arterial disease in both univariate and adjusted analyses.

Conclusions

High plasma level of endogenous estradiol emerges as a new predictor of ischemic arterial disease in older postmenopausal women. (J Am Heart Assoc. 2012;1:e001388 doi: 10.1161/JAHA.112.001388.)

Does Menopause Increase Diabetes Risk? Strategies for Diabetes Prevention in Midlife Women

Menopause is a significant milestone for midlife women. The characteristic changes in sex hormones and associated symptoms mark a time of increased risk for chronic disease, most notably cardiovascular disease. The diabetes epidemic, combined with recent epidemiologic studies linking sex hormone profiles with incident diabetes risk, have recently raised the possibility that the menopause may increase diabetes risk as well. This report reviews studies of menopause and diabetes risk, as well as the potential mechanisms through which menopause might affect traditional and more novel diabetes risk factors. Diabetes risk appears to be more strongly linked with factors associated with chronological aging and sex hormones rather than changes in menopausal status per se. Strategies to reduce diabetes risk, namely lifestyle changes, hormone therapy and other pharmacologic interventions are also discussed vis à vis midlife women and menopause.

Expression changes of sex hormone binding globulin in GDM placental tissues

OBJECTIVE

To compare the expression of sex hormone binding globulin (SHBG) in normal placental tissues with placental tissues from patients with gestational diabetes mellitus (GDM) and to deduce the mechanism affecting placental SHBG in GDM.

METHODS

We detected SHBG localization and measured SHBG mRNA and protein using immunohistochemistry, reverse-transcription polymerase chain reaction, and Western blotting, respectively, in normal and GDM placental tissues. The distribution of SHBG in placental cells was examined using immune electron microscopy.

RESULTS

Compared to controls, placental tissues from patients in the GDM group displayed disordered cell surface microvilli that were decreased in quantity, swollen, and had narrowed and broken gap junctions. Intracellular abnormalities included expanded rough endoplasmic reticula, swollen mitochondria, and irregular nuclear morphologies with non-uniform chromatin. SHBG localized primarily to trophoblast cell membranes and cytoplasm. SHBG was strongly expressed on the microvilli side and weakly expressed on the basement membrane with uneven staining. SHBG also was expressed in villous stromal cells and vascular endothelial cells. Compared to the controls, placental tissues from the GDM group displayed significantly decreased immunostaining rates for SHBG, as well as significantly lower levels of SHBG mRNA and protein expression (P<0.05).

CONCLUSION

SHBG was detected in placental trophoblast cells from patients with GDM, and the synthesis and secretion of SHBG were reduced when trophoblast cells were irregular. A decrease in SHBG could affect placental function or aggravate GDM. Our results suggest that placental SHBG plays an important role in the pathogenesis of GDM.

Circulating testosterone and SHBG concentrations are heritable in women: the Framingham Heart Study

CONTEXT

Many factors influence the concentration of circulating testosterone and its primary binding protein, SHBG. However, little is known about the genetic contribution to their circulating concentrations in women, and their heritability in women is not well established.

OBJECTIVE

Our objective was to estimate the heritability of circulating total testosterone (TT), free testosterone (FT), and SHBG in women in families from the Framingham Heart Study.

METHODS

Women in the Framingham Heart Study who were not pregnant, had not undergone bilateral oophorectomy, and were not using exogenous hormones were eligible for this investigation. TT was measured using liquid chromatography tandem mass spectrometry and SHBG using an immunofluorometric assay (Delfia-Wallac), and FT was calculated. Heritability estimates were calculated using variance-components methods in Sequential Oligogenic Linkage Analysis Routines (SOLAR) and were adjusted for age, age(2), body mass index (BMI), BMI(2), diabetes, smoking, and menopausal status. Bivariate analyses were done to assess genetic correlation between TT, FT, and SHBG.

RESULTS

A total of 2685 women were studied including 868 sister pairs and 688 mother-daughter pairs. Multivariable adjusted heritability estimates were 0.26 ± 0.05 for FT, 0.26 ± 0.05 for TT, and 0.56 ± 0.05 for SHBG (P < 1.0 × 10(-7) for all). TT was genetically correlated with SHBG [genetic correlation coefficient (ρG) = 0.31 ± 0.10] and FT (ρG = 0.54 ± 0.09), whereas SHBG was inversely correlated with FT (ρG = -0.60 ± 0.08).

CONCLUSION

Circulating TT, FT, and SHBG concentrations in women are significantly heritable, underscoring the importance of further work to identify the specific genes that contribute significantly to variation in sex steroid concentrations in women. The strong shared genetic component among pairs of TT, FT, and SHBG concentrations suggests potential pleiotropic effects for some of the underlying genes.

Regulation of K(ATP) channel by 17β-estradiol in pancreatic β-cells

ATP-sensitive potassium channels (K(ATP)) regulate electrical activity and insulin secretion in pancreatic β-cells. When glucose concentration increases, the [ATP]/[ADP] ratio rises closing K(ATP) channels, and the membrane potential depolarizes, triggering insulin secretion. This pivotal role of K(ATP) channels is used not only by glucose but also by neurotransmitters, hormones and other physiological agents to modulate electrical and secretory β-cell response. In recent years, it has been demonstrated that estrogens and estrogen receptors are involved in glucose homeostasis, and that they can modulate the electrical activity and insulin secretion of pancreatic β-cells. The hormone 17β-estradiol (E2), at physiological levels, is implicated in maintaining normal insulin sensitivity for β-cell function. Long term exposure to E2 increases insulin content, insulin gene expression and insulin release via the estrogen receptor α (ERα), while rapid responses to E2 can regulate K(ATP) channels increasing cGMP levels through the estrogen receptor β (ERβ) and type A guanylate cyclase receptor (GC-A). This review summarizes the main actions of 17β-estradiol on K(ATP) channels and the subsequent insulin release in pancreatic β-cells.

Associations of polychlorinated biphenyl exposure and endogenous hormones with diabetes in post-menopausal women previously employed at a capacitor manufacturing plant

There is an increasing body of literature showing associations of organochlorine exposure with risk of diabetes and insulin resistance. Some studies suggest that associations differ by gender and that diabetes risk, in turn, may be affected by endogenous steroid hormones. This report examines the relationships of serum PCBs and endogenous hormones with history of diabetes in a cohort of persons previously employed at a capacitor manufacturing plant. A total of 118 women were post-menopausal with complete data, of whom 93 were not using steroid hormones in 1996, at the time of examination, which included a survey of exposure and medical history, height, weight and collection of blood and urine for measurements of lipids, liver function, hematologic markers and endogenous hormones. This analysis examines relationships of serum polychlorinated biphenyls (PCBs), work exposure and endogenous hormones with self-reported history of diabetes after control for potential confounders. All PCB exposure groups were significantly related to history of diabetes, but not to insulin resistance as measured by the homeostatic model assessment of insulin resistance (HOMA-IR) in non-diabetics. Diabetes was also independently and inversely associated with follicle stimulating hormone (FSH), dehydroepiandrosterone sulfate (DHEAS) and triiodothyronine (T3) uptake. HOMA-IR was positively associated with body mass index (BMI) and C-reactive protein (CRP) and inversely associated with sex hormone binding globulin (SHBG) and T3 uptake after control for PCB exposure. Possible biologic mechanisms are discussed. This study confirms previous reports relating PCB exposure to diabetes and suggests possible hormonal pathways deserving further exploration.

Endogenous estrogen may prevent bone loss in postmenopausal hemodialysis patients throughout life

SUMMARY

Postmenopausal hemodialysis patients are at risk of complications related to renal mineral and bone disorder, and postmenopausal osteoporosis. In 112 postmenopausal hemodialysis patients, free estrogen index was positively correlated with bone mineral density (BMD) Z-score and the annual percent change of BMD in multiple regression analysis. Endogenous estrogen may prevent bone loss in postmenopausal hemodialysis patients throughout life.

INTRODUCTION

Women on dialysis are not only at risk of developing mineral and bone disorder, but also suffer from postmenopausal osteoporosis. We assessed the effect of sex hormones on bone metabolism in postmenopausal hemodialysis patients.

METHODS

We enrolled 112 postmenopausal hemodialysis patients with a mean age of 68.4 ± 10.4 years. We measured the serum levels of estradiol, testosterone, sex hormone-binding globulin (SHBG), and intact parathyroid hormone (intact-PTH), as well as bone metabolism parameters and radial bone mineral density (BMD). The free estrogen index (FEI) was calculated from the estradiol and SHBG values. After conventional dialysis was performed for 12 months, BMD was measured again and the annual percent change was calculated. Estradiol and SHBG were also measured in 25 postmenopausal women without chronic kidney disease.

RESULTS

Estradiol levels were higher in the hemodialysis patients than in the postmenopausal women without chronic kidney disease. In patients with relatively normal bone turnover (intact-PTH: from 150 to 300 pg/ml), the FEI showed a positive correlation with the BMD Z-score. The annual percent change of BMD showed a positive correlation with the FEI according to multiple regression analysis.

CONCLUSIONS

Endogenous estrogen may prevent bone loss in postmenopausal hemodialysis patients throughout life.

Endocrine factors in the hypothalamic regulation of food intake in females: a review of the physiological roles and interactions of ghrelin, leptin, thyroid hormones, oestrogen and insulin

Controlling energy homeostasis involves modulating the desire to eat and regulating energy expenditure. The controlling machinery includes a complex interplay of hormones secreted at various peripheral endocrine endpoints, such as the gastrointestinal tract, the adipose tissue, thyroid gland and thyroid hormone-exporting organs, the ovary and the pancreas, and, last but not least, the brain itself. The peripheral hormones that are the focus of the present review (ghrelin, leptin, thyroid hormones, oestrogen and insulin) play integrated regulatory roles in and provide feedback information on the nutritional and energetic status of the body. As peripheral signals, these hormones modulate central pathways in the brain, including the hypothalamus, to influence food intake, energy expenditure and to maintain energy homeostasis. Since the growth of the literature on the role of various hormones in the regulation of energy homeostasis shows a remarkable and dynamic expansion, it is now becoming increasingly difficult to understand the individual and interactive roles of hormonal mechanisms in their true complexity. Therefore, our goal is to review, in the context of general physiology, the roles of the five best-known peripheral trophic hormones (ghrelin, leptin, thyroid hormones, oestrogen and insulin, respectively) and discuss their interactions in the hypothalamic regulation of food intake.

Coffee and caffeine consumption in relation to sex hormone-binding globulin and risk of type 2 diabetes in postmenopausal women

OBJECTIVE

Coffee consumption has been inversely associated with type 2 diabetes risk, but its mechanisms are largely unknown. We aimed to examine whether plasma levels of sex hormones and sex hormone-binding globulin (SHBG) may account for the inverse association between coffee consumption and type 2 diabetes risk.

RESEARCH DESIGN AND METHODS

We conducted a case-control study nested in the prospective Women's Health Study (WHS). During a median follow-up of 10 years, 359 postmenopausal women with newly diagnosed type 2 diabetes were matched with 359 control subjects by age, race, duration of follow-up, and time of blood draw.

RESULTS

Caffeinated coffee was positively associated with SHBG but not with sex hormones. Multivariable-adjusted geometric mean levels of SHBG were 26.6 nmol/l among women consuming ≥4 cups/day of caffeinated coffee and 23.0 nmol/l among nondrinkers (P for trend = 0.01). In contrast, neither decaffeinated coffee nor tea was associated with SHBG or sex hormones. The multivariable-adjusted odds ratio (OR) of type 2 diabetes for women consuming ≥4 cups/day of caffeinated coffee compared with nondrinkers was 0.47 (95% CI 0.23-0.94; P for trend = 0.047). The association was largely attenuated after further adjusting for SHBG (OR 0.71 [95% CI 0.31-1.61]; P for trend = 0.47). In addition, carriers of rs6259 minor allele and noncarriers of rs6257 minor allele of SHBG gene consuming ≥2 cups/day of caffeinated coffee had lower risk of type 2 diabetes in directions corresponding to their associated SHBG.

CONCLUSIONS

Our findings suggest that SHBG may account for the inverse association between coffee consumption and type 2 diabetes risk among postmenopausal women.

Estrogen and androgen receptors: regulators of fuel homeostasis and emerging targets for diabetes and obesity

Because of increasing life expectancy, the contribution of age-related estrogen or androgen deficiency to obesity and type 2 diabetes will become a new therapeutic challenge. This review integrates current concepts on the mechanisms through which estrogen receptors (ERs) and androgen receptor (AR) regulate energy homeostasis in rodents and humans. In females, estrogen maintains energy homeostasis via ERα and ERβ, by suppressing energy intake and lipogenesis, enhancing energy expenditure, and ameliorating insulin secretion and sensitivity. In males, testosterone is converted to estrogen and maintains fuel homeostasis via ERs and AR, which share related functions to suppress adipose tissue accumulation and improve insulin sensitivity. We suggest that ERs and AR could be potential targets in the prevention of age-related metabolic disorders.

Low testosterone levels predict all-cause mortality and cardiovascular events in women: a prospective cohort study in German primary care patients

OBJECTIVE

Although associations between testosterone and cardiovascular (CV) morbidity in women have been proposed, no large prospective study has evaluated potential associations between testosterone and mortality in women. The objective was to determine whether baseline testosterone levels in women are associated with future overall or CV morbidity and mortality.

DESIGN

Prospective cohort study with a 4.5-year follow-up period.

METHODS

From a representative sample of German primary care practices, 2914 female patients between 18 and 75 years were analyzed for the main outcome measures: CV risk factors, CV diseases, and all-cause mortality.

RESULTS

At baseline, the study population was aged 57.96±14.37 years with a mean body mass index of 26.71±5.17 kg/m(2). No predictive value of total testosterone for incident CV risk factors or CV diseases was observed in logistic regressions. Patients with total testosterone levels in the lowest quintile Q1, however, had a higher risk to die of any cause or to develop a CV event within the follow-up period compared to patients in the collapsed quintiles Q2-Q5 in crude and adjusted Cox regression models (all-cause mortality: Q2-Q5 versus Q1: crude hazard ratios (HR) 0.49, 95% confidence interval (CI) 0.33-0.74; adjusted HR 0.62, 95% CI 0.42-0.939; CV events: Q2-Q5 versus Q1: crude HR 0.54, 95% CI 0.38-0.77; adjusted HR 0.68, 95% CI 0.48-0.97). Kaplan-Meier curves revealed similar data.

CONCLUSIONS

Low baseline testosterone in women is associated with increased all-cause mortality and incident CV events independent of traditional risk factors.

Modulation of insulin sensitivity and caveolin-1 expression by orchidectomy in a nonobese type 2 diabetes animal model

Previously, we found that male JYD mice developed type 2 diabetes but female mice did not, and that decreased expression levels of caveolin-1 were correlated with the development of a diabetic phenotype in these mice. Therefore, we hypothesized that sex hormones affect the expression of caveolin-1 and contribute to the development of insulin resistance and hyperglycemia in JYD mice. We used glucose and insulin tolerance tests to examine insulin sensitivity in male, female and orchidectomized male JYD mice. Glucose uptake was analyzed by using (18)F-fluorodeoxyglucose positron emission tomography. We also examined insulin-signaling molecules and caveolin proteins in various tissues in these mice by Western blotting. In addition, we examined changes of caveolin-1 expression in L6 skeletal muscle cells treated with 17-β estradiol or dihydroxytestosterone. We found that glucose and insulin tolerance were impaired and hyperglycemia developed in male, but not female, JYD mice. Expression of insulin-signaling molecules such as insulin receptor, protein kinase B, and glucose transporter-4 were decreased in male JYD mice compared with female mice. Orchidectomized JYD male mice showed improved glucose and insulin tolerance with a concomitant increase in the expression of insulin-signaling molecules and caveolin-1 in adipose tissue and skeletal muscle. Moreover, 17-β-estradiol treatment increased the expression of caveolin-1 in differentiated skeletal muscle cells. We conclude that sex hormones modulate the expression of caveolin-1 and insulin-signaling molecules, subsequently affecting insulin sensitivity and the development of type 2 diabetes in JYD mice.

Gender differences in cardiovascular disease: hormonal and biochemical influences

OBJECTIVE

Atherosclerosis is a complex process characterized by an increase in vascular wall thickness owing to the accumulation of cells and extracellular matrix between the endothelium and the smooth muscle cell wall. There is evidence that females are at lower risk of developing cardiovascular disease (CVD) as compared to males. This has led to an interest in examining the contribution of genetic background and sex hormones to the development of CVD. The objective of this review is to provide an overview of factors, including those related to gender, that influence CVD.

METHODS

Evidence analysis from PubMed and individual searches concerning biochemical and endocrine influences and gender differences, which affect the origin and development of CVD.

RESULTS

Although still controversial, evidence suggests that hormones including estradiol and androgens are responsible for subtle cardiovascular changes long before the development of overt atherosclerosis.

CONCLUSION

Exposure to sex hormones throughout an individual's lifespan modulates many endocrine factors involved in atherosclerosis.

Comparison of sex hormonal and metabolic profiles between omnivores and vegetarians in pre- and post-menopausal women

The purpose of the present study was to investigate the sex hormonal and metabolic profiles in vegetarians and compare these with the profiles in omnivores. The design of the present study was cross-sectional. The study sample of pre- and post-menopausal women included forty-one omnivores and twenty-one vegetarians. Thereafter we determined: (1) plasma sex hormones, (2) fasting insulin, NEFA as well as apo-A and apo-B, (3) BMI, (4) a dietary profile (3 d dietary records), (5) physical activity and (6) total faecal excretion per 72 h and total urinary excretion per 72 h. Vegetarians showed higher levels of sex hormone-binding globulin (SHBG), apo-A, total faecal excretion per 72 h and total fibre intake as well as lower levels of apo-B, free oestradiol, free testosterone, dehydroepiandrosterone sulfate (DHEA-s) and BMI. Interestingly, after controlling for BMI, significant differences between groups still persisted except for apo-B. Moreover, stepwise regression analysis showed that total fibre intake explained 15.2 % of the variation in SHBG in our cohort, which accounted for the greatest source of unique variance. Results of the present study indicate that pre- and post-menopausal vegetarians present higher concentrations of SHBG, which could be explained, in part, by higher levels of fibre intake. This may explain, at least in part, the lower risk of developing type 2 diabetes.

Age at menarche and risk of type 2 diabetes: results from 2 large prospective cohort studies

The authors investigated the association between age at menarche and risk of type 2 diabetes mellitus (T2DM) among 101,415 women from the Nurses' Health Study (NHS) aged 34-59 years (1980-2006) and 100,547 women from Nurses' Health Study II (NHS II) aged 26-46 years (1991-2005). During 2,430,274 and 1,373,875 person-years of follow-up, respectively, 7,963 and 2,739 incident cases of T2DM were documented. Young age at menarche was associated with increased risk of T2DM after adjustment for potential confounders, including body figure at age 10 years and body mass index (BMI; weight (kg)/height (m)(2)) at age 18 years. Relative risks of T2DM across age-at-menarche categories (< or =11, 12, 13, 14, and > or =15 years) were 1.18 (95% confidence interval (CI): 1.10, 1.27), 1.09 (95% CI: 1.02, 1.17), 1.00 (referent), 0.92 (95% CI: 0.83, 1.01), and 0.95 (95% CI: 0.84, 1.06), respectively, in the NHS (P for trend < 0.0001) and 1.40 (95% CI: 1.24, 1.57), 1.13 (95% CI: 1.00, 1.27), 1.00 (referent), 0.98 (95% CI: 0.82, 1.18), and 0.96 (95% CI: 0.78, 1.19), respectively, in NHS II (P for trend < 0.0001). Associations were substantially attenuated after additional control for updated time-varying BMI. These data suggest that early menarche is associated with increased risk of T2DM in adulthood. The association may be largely mediated through excessive adult adiposity. The association was stronger among younger women, supporting a role for sex hormones in younger onset of T2DM, in addition to BMI.

The association of endogenous sex hormones, adiposity, and insulin resistance with incident diabetes in postmenopausal women

CONTEXT

In postmenopausal women, endogenous bioavailable testosterone (T) and estradiol (E2) have been positively associated, and SHBG has been negatively associated, with incident type 2 diabetes (T2DM). Previous studies have not explored possible factors explaining these relationships.

OBJECTIVE

Our objective was to examine the association of endogenous sex hormones with incident T2DM in postmenopausal women and possible explanatory factors.

DESIGN, SETTING, AND PARTICIPANTS

The Multi-Ethnic Study of Atherosclerosis (MESA) is a prospective study that included 1612 postmenopausal women aged 45-84 yr, followed between the years 2000-2006, who were not taking hormone replacement therapy, had no prevalent cardiovascular disease or diabetes, and had complete ascertainment of sex hormones.

MAIN OUTCOME MEASURES

T2DM was defined based on fasting glucose and/or treatment for diabetes.

RESULTS

There were 116 incident cases of diabetes during follow-up. Across higher quartiles of bioavailable T and E2 and lower quartiles of SHBG, we found significantly greater hazards of developing incident T2DM (all P for trend <or=0.001). After adjustment for body mass index and insulin resistance estimated by homeostasis model assessment of insulin resistance, bioavailable T was no longer associated with incident T2DM. The associations of E2 and SHBG with incident T2DM were partially explained by body mass index and insulin resistance but persisted in fully adjusted models (both P for trend <0.02). Dehydroepiandrosterone had no relationship with incident T2DM.

CONCLUSIONS

Adiposity and insulin resistance explained most of the association of bioavailable T but only partially explained the associations of E2 and SHBG with incident T2DM among postmenopausal women.

Relationship between higher estradiol levels and 9-year mortality in older women: the Invecchiare in Chianti study

OBJECTIVES

To investigate the relationship between total estradiol (E2) levels and 9-year mortality in older postmenopausal women not taking hormone replacement therapy (HRT).

DESIGN

Population-based study of persons living in the Chianti geographic area (Tuscany, Italy).

SETTING

Community.

PARTICIPANTS

A representative sample of 509 women aged 65 and older with measures of total E2.

MEASUREMENTS

Serum total E2 was measured at the University of Parma using ultrasensitive radioimmunoassay (RIA).

RESULTS

Women who died (n=135) during 9 years of follow up were older; had higher total E2 levels; and were more likely to have evidence of stroke, hypertension, diabetes mellitus, and congestive heart failure at baseline than survivors. Higher E2 levels were associated with a greater likelihood of death (hazard ratio (HR)=1.03, 95% confidence interval (CI)=1.01-1.06), and the relationship was independent of age, waist:hip ratio, C-reactive protein, education, cognitive function, physical activity, caloric intake, smoking, and chronic disease (HR=1.08 pg/mL, 95% CI=1.03-1.13, P=.003). The excessive risk of death associated with higher total E2 was not attenuated after adjustment for total testosterone (HR=1.12, 95% CI=1.02-1.18, P<.001) and after further adjustment for insulin resistance evaluated using the homeostasis model assessment (HR=1.07, 95% CI=1.03-1.17, P<.001). Total E2 was highly predictive of death after more than 5 years (HR=1.42: CI 1.01-1.91, P=.04) and not predictive of death for less than 5 years (P=.78).

CONCLUSION

Higher total E2 concentration predicts mortality in older women not taking HRT.

Sex hormone-binding globulin and risk of type 2 diabetes in women and men

BACKGROUND

Circulating sex hormone-binding globulin levels are inversely associated with insulin resistance, but whether these levels can predict the risk of developing type 2 diabetes is uncertain.

METHODS

We performed a nested case-control study of postmenopausal women in the Women's Health Study who were not using hormone therapy (359 with newly diagnosed type 2 diabetes and 359 controls). Plasma levels of sex hormone-binding globulin were measured; two polymorphisms of the gene encoding sex hormone-binding globulin, SHBG, that were robustly associated with the protein levels were genotyped and applied in mendelian randomization analyses. We then conducted a replication study in an independent cohort of men from the Physicians' Health Study II (170 with newly diagnosed type 2 diabetes and 170 controls).

RESULTS

Among women, higher plasma levels of sex hormone-binding globulin were prospectively associated with a lower risk of type 2 diabetes: multivariable odds ratios were 1.00 for the first (lowest) quartile of plasma levels, 0.16 (95% confidence interval [CI], 0.08 to 0.33) for the second quartile, 0.04 (95% CI, 0.01 to 0.12) for the third quartile, and 0.09 (95% CI, 0.03 to 0.21) for the fourth (highest) quartile (P<0.001 for trend). These prospective associations were replicated among men (odds ratio for the highest quartile of plasma levels vs. the lowest quartile, 0.10; 95% CI, 0.03 to 0.36; P<0.001 for trend). As compared with homozygotes of the respective wild-type allele, carriers of a variant allele of the SHBG single-nucleotide polymorphism (SNP) rs6259 had 10% higher sex hormone-binding globulin levels (P=0.005), and carriers of an rs6257 variant had 10% lower plasma levels (P=0.004); variants of both SNPs were also associated with a risk of type 2 diabetes in directions corresponding to their associated sex hormone-binding globulin levels. In mendelian randomization analyses, the predicted odds ratio of type 2 diabetes per standard-deviation increase in the plasma level of sex hormone-binding globulin was 0.28 (95% CI, 0.13 to 0.58) among women and 0.29 (95% CI, 0.15 to 0.58) among men, a finding that suggests that sex hormone-binding globulin may have a causal role in the risk of type 2 diabetes.

CONCLUSIONS

Low circulating levels of sex hormone-binding globulin are a strong predictor of the risk of type 2 diabetes in women and men. The clinical usefulness of both SHBG genotypes and plasma levels in stratification and intervention for the risk of type 2 diabetes warrants further examination.

Sex steroid hormones in diabetes-induced sexual dysfunction: focus on the female gender

INTRODUCTION

Diabetes is associated with gender-specific changes in sex steroid hormones. However, the mechanisms responsible for these associations as well as the link to sexual dysfunction are not well understood.

AIM

To discuss key clinical and laboratory findings linking diabetes, sex steroid hormones, and sexual dysfunction, with particular focus on the female gender.

METHODS

A comprehensive literature review was conducted using the PubMed database. Search terms were used in appropriate combinations, including diabetes, insulin, insulin sensitivity, androgen, estrogen, sexual function, women, men, estrogen receptor, and androgen receptor. Over 400 citations were selected, based on topical relevance, and examined for study methodology and major findings.

MAIN OUTCOME MEASURES

Data from peer-reviewed publications.

RESULTS

Imbalances in sex steroid hormone levels are strongly associated with diabetes and this may negatively impact upon sexual function. Although numerous factors are likely to contribute to the development of diabetes and its complications, the role of sex steroid hormones must be acknowledged.

CONCLUSIONS

Research related to diabetic women and sexual dysfunction is severely lacking. Identifying underlying causes for a given hormonal imbalance in diabetic patients, as well as determination of genetic and age-dependent factors, will become important in identifying the subpopulations in which hormonal replacement regimens will be most effective. Investigation into treating diabetic patients with adjunct hormonal therapies or steroid hormone receptor modulators holds much promise.

Associations of the estrogen receptors 1 and 2 gene polymorphisms with the metabolic syndrome in women

BACKGROUND

Genetic variation of the estrogen receptor alpha (ESR1) and beta (ESR2) has been associated with components of the metabolic syndrome.

METHODS

The relationships of two ESR1 (rs2234693 and rs9340799) and three ESR2 (rs1271572, rs1256049, and rs4986938) polymorphisms with the metabolic syndrome were examined in 532 Caucasian female participants (median age 63.1 years) in the Women's Health Study. Most women (99.1%) were postmenopausal. The associations between ESR1 and ESR2 genotypes and haplotypes with the metabolic syndrome were evaluated. Effect modification by hormone therapy was also assessed.

RESULTS

Genotype and haplotype distributions were similar between women with and without metabolic syndrome. We found no consistent associations between the genotypes and haplotypes tested and the metabolic syndrome, or its components, in logistic regression models. No effect modification by hormone therapy use was noted.

CONCLUSIONS

No association between these genetic variants in ESR1 and ESR2 and the metabolic syndrome was observed among these Caucasian women. Further investigation regarding the potential involvement of estrogen receptor genes and the metabolic syndrome may be warranted in other ethnic groups.