Racial disparities in metabolism, central obesity, and sex hormone-binding globulin in postmenopausal women

Metabolomics in Autoimmune Diseases: Focus on Rheumatoid Arthritis, Systemic Lupus Erythematous, and Multiple Sclerosis

The metabolomics approach represents the last downstream phenotype and is widely used in clinical studies and drug discovery. In this paper, we outline recent advances in the metabolomics research of autoimmune diseases (ADs) such as rheumatoid arthritis (RA), multiple sclerosis (MuS), and systemic lupus erythematosus (SLE). The newly discovered biomarkers and the metabolic mechanism studies for these ADs are described here. In addition, studies elucidating the metabolic mechanisms underlying these ADs are presented. Metabolomics has the potential to contribute to pharmacotherapy personalization; thus, we summarize the biomarker studies performed to predict the personalization of medicine and drug response.

On the joint role of non-Hispanic Black race/ethnicity and weight status in predicting postmenopausal weight gain

OBJECTIVES

To determine how baseline weight status contributes to differences in postmenopausal weight gain among non-Hispanic Blacks (NHBs) and non-Hispanic Whites (NHWs).

METHODS

Data were included from 70,750 NHW and NHB postmenopausal women from the Women's Health Initiative Observational Study (WHI OS). Body Mass Index (BMI) at baseline was used to classify women as having normal weight, overweight, obese class I, obese class II or obese class III. Cox proportional hazards was used to estimate the hazard of a 10% or more increase in weight from baseline.

RESULTS

In both crude and adjusted models, NHBs were more likely to experience ≥10% weight gain than NHWs within the same category of baseline weight status. Moreover, NHBs who were normal weight at baseline were most likely to experience ≥10% weight gain in both crude and adjusted models. Age-stratified results were consistent with overall findings. In all age categories, NHBs who were normal weight at baseline were most likely to experience ≥10% weight gain. Based on the results of adjusted models, the joint influence of NHB race/ethnicity and weight status on risk of postmenopausal weight gain was both sub-additive and sub-multiplicative.

CONCLUSION

NHBs are more likely to experience postmenopausal weight gain than NHWs, and the disparity in risk is most pronounced among those who are normal weight at baseline. To address the disparity in postmenopausal obesity, future studies should focus on identifying and modifying factors that promote weight gain among normal weight NHBs.

Obstacles to Translating Genotype-Phenotype Correlates in Metabolic Disease

Type 2 diabetes mellitus is a polygenic disease with a variable phenotype. Many genetic associations have been described; however, understanding their underlying pathophysiological role in Type 2 diabetes mellitus is important for development of future therapeutic targets. Here, we review the physiological mechanisms of diabetes-associated variants that affect glycemia.

Low Levels of Sex Hormone-Binding Globulin Constitute an Independent Risk Factor for Arterial Stiffness in Korean Women

The association between sex hormone-binding globulin (SHBG) and arterial stiffness in women is not conclusive. In addition, obesity might also be involved in the relationship between SHBG and atherosclerosis. The aim of this study was to determine the relationship between SHBG and arterial stiffness in association with central obesity in women. This cross-sectional study included 381 women who participated in the health checkup programs in one hospital. The brachial-ankle pulse wave velocity (baPWV) was measured as a marker for arterial stiffness. A negative correlation was observed between SHBG levels and baPWV (rho = -0.281). The relationship was significant even after adjusting for potential confounders (beta = -0.087 in fully adjusted model). After considering the interaction between central obesity and SHBG levels, the significant association was evident only in obese women (P for interaction = 0.025). Adjustment for a 10-year atherosclerotic cardiovascular disease (ASCVD) risk scores, instead of each cardiovascular risk factor individually, did not affect the significance of the relationship between SHBG levels and baPWV. Serum levels of SHBG were negatively associated with arterial stiffness independent of cardiovascular risk factors or 10-year ASCVD risk scores in Korean women. The relationship may be potentiated by central obesity.

Serum vitamin D and sex hormones levels in men and women: The Multi-Ethnic Study of Atherosclerosis (MESA)

INTRODUCTION

25-hydroxyvitamin D [25(OH)D] deficiency has been associated with low testosterone levels in men, but there are conflicting reports of its associations with sex hormones in women. Less is known about whether these associations are independent of adiposity and lifestyle factors, and whether they differ by race/ethnicity.

AIM

To examine associations of 25(OH)D concentrations with sex hormone levels.

METHODS

Cross-sectional analysis of 3017 men and 2929 women in a multi-ethnic cohort.

MAIN OUTCOME MEASURES

Testosterone, estradiol, dehydroepiandrosterone (DHEA), sex hormone binding globulin (SHBG), and free testosterone.

RESULTS

The mean (SD) levels of 25(OH)D in men and women were 25.7(10.4) and 26.1(12.0)ng/ml, respectively. In men, after adjusting for demographic and lifestyle variables, a 10ng/ml [25nmol/L] decrease in 25(OH)D was associated with an average difference of -0.70nmol/L (95%CI -1.36, -0.05) in SHBG and 0.02 percent (0.01, 0.04) in free testosterone, but was not associated with low total testosterone level (<10.41nmol/L). In women, a 10ng/ml decrease in 25(OH)D levels was associated with an average difference of -0.01nmol/L (-0.01, -0.00) for estradiol, -8.29nmol/L (-10.13, -6.45) for SHBG, 0.06 percent (0.04, 0.07) for free testosterone, and 0.40nmol/L (0.19, 0.62) for DHEA. There was no significant interaction by race/ethnicity.

CONCLUSIONS

Lower 25(OH)D concentrations were associated with lower SHBG levels and higher free testosterone levels in both men and women, and lower estradiol and higher DHEA levels in women, independent of adiposity and lifestyle. We observed no significant association of 25(OH)D with total testosterone in men. Future studies are needed to determine whether vitamin D supplementation influences sex hormone levels.

Feasibility and Acceptability of an Internet-Based, African Dance-Modified Yoga Program for African-American Women with or at Risk for Metabolic Syndrome

African-American (AA) women are the segment of the population that experiences the highest mortality from metabolic syndrome (MetS). Yoga decreases risk of MetS, yet there have been no yoga studies of AA women with or at risk for MetS. The purpose of this 4-week study was to test the feasibility and acceptability of a culturally tailored, Internet-based intervention, yogic dance (YD), using digital videos in a sample of AA women (ages 35-64) at risk for or with MetS. The investigators examined the rates of accrual, attrition, and reasons for attrition; the feasibility of using the Internet to deliver the intervention; the acceptability of the intervention as structured; and any other benefits and/or limitations of YD. The study used a single-group, mixed-methods design underpinned by social constructivist theory and Pender's Health Promotion Model. Twenty-four women provided consent to enroll in the study. After completing in-person semi-structured interviews and Internet-based measures, including the Physical Activity Readiness Questionnaire, and the modified International Physical Activity Questionnaire, consented participants engaged in 4-weeks of the yogic dance intervention via daily video-based instructions located on the study Web site. After the intervention, four women participated in focus groups to voice their perceptions of barriers to and benefits from YD and the acceptability of using the YD intervention. The investigators analyzed focus group data using content/thematic analysis and validated themes with baseline semi-structured interviews. The majority of the women (79%) found YD acceptable. Themes that emerged from the descriptive data include: (1) Culture is an important aspect of yogic dance; and (2) Increased social support would enhance yogic dance participation. The integrated results from this feasibility study will inform research exploring the complex correlates that influence health behaviors in AA women.

Immunologic and mass-spectrometric estimates of SHBG concentrations in healthy women

OBJECTIVE

Sex-hormone binding globulin (SHBG) concentrations across the adult female lifespan are not well defined. To address this knowledge gap, SHBG was quantified by both immunological and criterion methods, viz, mass spectrometry (MS).

SETTING

Center for Translational Science Activities (CTSA).

PARTICIPANTS

Healthy nonpregnant women (N=120) ages 21 to 79 years.

OUTCOMES

SHBG, testosterone (T), estradiol (E2) and estrone (E1) each determined by MS. Uni- and multivariate regression of SHBG concentrations on age, body mass index (BMI), total and visceral abdominal fat (TAF, AVF), albumin, glucose, insulin, sex steroids, selected cytokines, blood pressure, and lipids.

RESULTS

By univariate regression, MS-estimated SHBG correlated negatively with BMI, TAF, AVF, insulin, free T and bioavailable T (bio T) (each P≤10(-4)), but not with blood pressure or lipids. By stepwise multivariate regression analysis, free and total T (both positive) and bio T (negative) were correlated with SHBG in all 4 assays (each P<10(-15), R(2)≥0.481). In addition, TAF and BMI were negatively associated with SHBG (P≤0.0066) in 2 SHBG assays, and estrone and IL-8 with SHBG weakly (P≤0.035) in one SHBG assay each. When nonsignificant cytokines were excluded, SHBG was jointly associated with AVF, total T and HDL (P<10(-9), R(2)=0.358).

CONCLUSION

According to MS, three metabolic factors, T, AVF and HDL, together explain more than one-third of the interindividual variation in SHBG levels. We speculate that these measures reflect insulin action.

Prediction of metabolic syndrome among postmenopausal Ghanaian women using obesity and atherogenic markers

BACKGROUND

Metabolic syndrome (MetS) is an important health problem which puts individuals at risk for cardiovascular diseases and type 2 diabetes as well as obesity-related cancers such as colon and renal cell in men, and endometrial and oesophageal in women.

OBJECTIVE

This study was aimed at examining how obesity indicators and related determinants influence metabolic syndrome, and how the factors can be used to predict the syndrome and its cut-offs in postmenopausal Ghanaian women.

METHODS

Two hundred and fifty (250) Ghanaian subjects were involved in the study with one hundred and forty-three (143) being premenopausal women and one hundred and seven (107) postmenopausal women. The influence of traditional metabolic risk factors including high blood pressure, dyslipidemia and glucose intolerance on obesity and atherogenic indices i.e. body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), Waist-to-thigh ratio (WTR), waist-to-height ratio (WHtR), high density lipoprotein cholesterol to total cholesterol ratio (HDL-C/TC), high density lipoprotein cholesterol to low density lipoprotein ratio (HDL-C/LDL-C) and triglyceride to high density lipoprotein cholesterol ratio (TG/HDL-C) were identified according to the Harmonization (H_MS) criterion.

RESULTS

The predominant anthropometric marker that significantly influence metabolic risk factors among the pre- and postmenopausal women was waist-to-hip ratio (premenopausal: p- 0.004, 0.026 and 0.002 for systolic blood pressure (SBP), fasting blood glucose (FBG) and HDL-C; postmenopausal: p-0.012, 0.048, 0.007 and 0.0061 for diastolic blood pressure (DBP), FBG, triglyceride (TG) and high density lipoprotein cholesterol (HDL-C) respectively). Using the receiver operating characteristic (ROC) analysis, the area under the curve for WC, WHR, TG/HDL-C and HDL-C/TC among postmenopausal women were estimated at 0.6, 0.6, 0.8 and 0.8 respectively. The appropriate cut-off values for WC, WHR, TG/HDL-C and HDL-C/TC that predicted the presence of metabolic syndrome were 80.5 cm, 0.84, 0.61 and 0.34 respectively.

CONCLUSION

The presence of metabolic syndrome among Ghanaian postmenopausal women can be predicted using WC, WHR, TG/HDL-C and HDL-C/TC.

The association of diabetes with breast cancer incidence and mortality in the Long Island Breast Cancer Study Project

PURPOSE

Diabetes has been associated with increased risk of breast cancer in a number of epidemiologic studies, but its effects on survival among women diagnosed with breast cancer have been examined less frequently. Importantly, prior investigations have rarely considered the influence of factors associated with diabetes such as obesity, age at diabetes diagnosis, duration of diabetes, or diabetes treatments.

METHODS

We evaluated the effect of self-reported diabetes on breast cancer incidence and mortality in the Long Island Breast Cancer Study Project, which includes 1,447 breast cancer cases and 1,453 controls. Follow-up data for all-cause (n = 395) and 5-year breast cancer-specific mortality (n = 104) through December 2005 were determined for case women from the National Death Index. Adjusted logistic regression and Cox proportional hazards models were used to estimate odds ratios (OR) and hazards ratios (HR), respectively.

RESULTS

Postmenopausal women with diabetes were at increased risk of developing breast cancer [OR = 1.35; 95 % confidence interval (CI) = 0.99-1.85], as were those who were not of white race regardless of menopausal status [OR = 3.89; 95 % CI = 1.66-9.11]. Among case women, diabetes was associated with a modestly increased risk of death from all causes [HR = 1.65; 95 % CI = 1.18-2.29], an association that was stronger in women who were obese at breast cancer diagnosis [HR = 2.49; 94 % CI = 1.58-3.93]. In analyses restricted to diabetics, there was no statistically significant effect of duration of diabetes or type of treatment on breast cancer incidence or mortality.

CONCLUSIONS

Our findings suggest that diabetes may increase incidence of breast cancer in older women and non-whites, and mortality due to all causes.

Comparisons of trabecular and cortical bone in late adolescent black and white females

Few childhood studies have investigated racial differences in volumetric bone mineral density (vBMD), bone geometry, and bone strength indices measured by three-dimensional bone imaging. The purpose of this study was to compare trabecular and cortical bone parameters at the radius and tibia between late adolescent white and black females using peripheral quantitative computed tomography (QCT). White (n = 25) and black females (n = 25), 18-19 years of age, were pair-matched for age, height, and fat-free soft tissue mass. Peripheral QCT scans were obtained at the 4% (trabecular bone), 20% (cortical bone), and 66% [muscle cross-sectional area (CSA)] sites from the distal metaphyses. Bone strength was determined from vBMD and bone geometry to calculate bone strength index (BSI; trabecular site) and polar strength-strain index (SSI; cortical site). Radial SSI was not different between groups; however, blacks had greater radial BSI (P = 0.02) than whites. After adjustment for the longer forearm in blacks, the greater radial BSI in blacks no longer remained. At the tibia, blacks versus whites had greater bone strength at the trabecular and cortical bone sites (BSI, P = 0.03; SSI, P = 0.04, respectively). When controlling for differences in tibial length and muscle CSA, the higher estimates of bone strength persisted in blacks versus whites (BSI, P = 0.01; SSI, P = 0.02). Our data suggest that when differences in body size are considered, late adolescent black versus white females have a stronger bone profile, due to greater bone geometry and vBMD, at the trabecular and cortical regions of the tibia but not at the radius.

Racial differences in the association between sex hormone-binding globulin and adiposity in premenopausal women: the BioCycle study

OBJECTIVE

To assess the associations between measures of adiposity and sex hormone- binding globulin (SHBG) and to evaluate whether such associations differ by race.

RESEARCH DESIGN AND METHODS

Adiposity was measured by anthropometry and dual-energy X-ray absorptiometry among women (146 white, 50 black, and 25 Asian) aged 18-44 years in the BioCycle study. SHBG was repeatedly measured over one to two menstrual cycles. The ratio of trunkal to leg fat (T/L) was used to assess upper to lower body adiposity.

RESULTS

Among whites, all adiposity measures were significantly and inversely associated with SHBG. Among blacks, BMI (β = -0.032), waist circumference (β = -0.016), and T/L (β = -0.033) were significantly associated with SHBG, whereas total and trunkal fat were not (P interaction with race <0.04). Among Asians, measures of central and upper body fat were significantly associated with SHBG (e.g., T/L, β = -0.84) but not BMI.

CONCLUSIONS

Associations between SHBG and adiposity differ by race among premenopausal women.

Comparison of serum androgens and endometrial thickness in obese and non-obese postmenopausal women

OBJECTIVE

In this study, we investigated whether serum androgen levels and endometrial thickness differed in obese and non-obese women.

MATERIAL AND METHODS

Thirtytwo non-obese (BMI <30) and 48 obese (BMI ≥ 30) women were enrolled. Blood samples were analyzed for testosterone, free testosterone, androstenedione, DHEAS, and SHBG, and transvaginal ultrasonography was performed.

RESULTS

Obese women had significantly higher free testosterone and endometrial thickness and significantly lower SHBG. Eight of 17 women with endometrial thickness >5 mm had significant pathology.

CONCLUSION

These results suggest that obesity may be a risk factor for endometrial carcinoma and other pathologies in post-menopausal women through an action on androgen concentrations.

Testosterone and visceral fat in midlife women: the Study of Women's Health Across the Nation (SWAN) fat patterning study

Visceral fat (VF) increases with the menopause and is an independent predictor of the metabolic syndrome, diabetes, and cardiovascular disease (CVD) in women. Little is known about how hormonal changes during the menopausal transition are related to the increase in VF. We aimed to determine the relationship between bioavailable testosterone and VF in middle-aged women at various stages of the menopausal transition and whether this relationship is independent of age and other CVD risk factors. The Study of Women's Health Across the Nation (SWAN) is a longitudinal, community-based study. This report uses baseline data from a population-based longitudinal ancillary study at the Chicago site to examine the cross-sectional relationship between testosterone and computed tomography (CT)-assessed VF in women at different stages of the menopausal transition. Included are 359 women (47.2% black), aged 42-60 years, who were randomly selected from a complete community census in which a 72% participation rate was achieved. In multivariate models, bioavailable testosterone was associated with VF independent of age, race, percent total body fat, and other cardiovascular risk factors. Bioavailable testosterone was a stronger predictor than estradiol and was interchangeable in its strength of association with sex hormone-binding globulin (SHBG). As bioavailable testosterone was associated with VF even after adjusting for insulin resistance, this suggests that it plays an important role in regional fat distribution. Our findings may have direct implications in explaining the effect of menopause-related testosterone predominance on VF accumulation and subsequent cardiovascular risk.

Abdominal adiposity and hot flashes among midlife women

OBJECTIVE

Two competing hypotheses suggest how adiposity may affect menopausal hot flashes. The "thin hypothesis" asserts that aromatization of androgens to estrogens in body fat should be associated with decreased hot flashes. Conversely, thermoregulatory models argue that body fat should be associated with increased hot flashes. The study objective was to examine associations between abdominal adiposity and hot flashes, including the role of reproductive hormones in these associations.

DESIGN

The Study of Women's Health Across the Nation Heart Study (2001-2003) is an ancillary study to the Study of Women's Health Across the Nation, a community-based cohort study. Participants were 461 women (35% African American, 65% white) ages 45 to 58 years with an intact uterus and at least one ovary. Measures included a computed tomography scan to assess abdominal adiposity; reported hot flashes over the previous 2 weeks; and a blood sample for measurement of follicle-stimulating hormone, estradiol, and sex hormone-binding globulin-adjusted estradiol (free estradiol index). Associations were evaluated within multivariable logistic and linear regression models.

RESULTS

Every 1-SD increase in total (odds ratio [OR]=1.28; 95% CI: 1.06-1.55) and subcutaneous (OR=1.30; 95% CI: 1.07-1.58) abdominal adiposity was associated with increased odds of hot flashes in age- and site-adjusted models. Visceral adiposity was not associated with hot flashes. Associations were not reduced when models included reproductive hormone concentrations.

CONCLUSION

Increased abdominal adiposity, particularly subcutaneous adiposity, is associated with increased odds of hot flashes, favoring thermoregulatory models of hot flashes. Body fat may not protect women from hot flashes as once thought.

Changes over 14 years in androgenicity and body mass index in a biracial cohort of reproductive-age women

BACKGROUND

Body mass index (BMI) is directly related to testosterone (total T and free T) and inversely to SHBG cross-sectionally, but little is known about how changes in body fat and androgen markers affect each other over time.

METHODS

Participants included 969 White and Black women from the Coronary Artery Risk Development in Young Adults (CARDIA) cohort, who were ages 18-30 at entry into the study and were pre- or perimenopausal 16 yr later at the time of the CARDIA Women's Study (CWS). Total T and SHBG were assayed from specimens drawn at the CWS examination and stored serum from the yr 2 and 10 CARDIA exams. Free T was calculated based on total T and SHBG. BMI and waist circumference were measured at yr 2, 10, and 16.

RESULTS

Despite clinically significant increases in BMI and waist circumference, total T and free T tended to decline, whereas SHBG remained relatively constant. BMI and waist circumference were directly correlated with free T and inversely correlated with SHBG in cross-sectional analyses. In longitudinal, multivariable analyses, an annualized increase in BMI was inversely related to a concurrent annualized decrease in SHBG (beta = -0.79 ng/dl, and se = 0.22 in Blacks; beta = -1.07 ng/dl; and se = 0.31 in Whites). However, early increases in BMI were not related to later decreases in SHBG.

CONCLUSION

Increases in adiposity are closely tied to decreases in SHBG, but changes in BMI and SHBG may occur concurrently rather than sequentially.

Sex hormones, sex hormone binding globulin, and abdominal aortic calcification in women and men in the multi-ethnic study of atherosclerosis (MESA)

BACKGROUND

Conflicting findings exist regarding the associations of sex hormones with subclinical atherosclerosis.

METHODS

This is a substudy from MESA of 881 postmenopausal women and 978 men who had both abdominal aortic calcification (AAC) quantified by computed tomography and sex hormone levels assessed [Testosterone (T), estradiol (E2), dehydroepiandrosterone (DHEA), and sex hormone binding globulin (SHBG)]. We examined the association of sex hormones with presence and extent of AAC.

RESULTS

For women, SHBG was inversely associated with both AAC presence [OR=0.62, 95% CI 0.42-0.91 for 1 unit greater log(SHBG) level] and extent [0.29 lower log(AAC) for 1 unit greater log(SHBG) level, beta=-0.29 (95% CI -0.57 to -0.006)] adjusting for age, race, hypertension, smoking, diabetes, BMI, physical activity, and other sex hormones. After further adjustment for total and HDL-cholesterol, SHBG was not associated with ACC presence or extent. In men, there was no association between SHBG and AAC. In both men and women, neither T, E2, nor DHEA was associated with AAC presence or extent.

CONCLUSION

After adjustment for non-lipid cardiovascular risk factors, SHBG levels are inversely associated with both the presence and severity of AAC in women but not in men, which may be accounted for by HDL.

Truncal fat in relation to total body fat: influences of age, sex, ethnicity and fatness

OBJECTIVE

To investigate the influence of age, sex, ethnicity and total fatness on central obesity in four ethnic populations.

DESIGN

Cross-sectional analysis of study subjects enrolled from 1993 to 2005.

SUBJECTS

A multi-ethnic (Caucasian (CA), African-American (AA), Hispanic-American (HA) and Asian (As)) convenience sample of 604 men and 1192 women (aged 18-96 years, body mass index 15.93-45.80 kg/m(2)).

MEASUREMENTS

Total body fat (TBF) and truncal fat were measured by dual-energy X-ray absorptiometry. General linear regression models were used to test for independent associations with log(10)-transformed truncal fat.

RESULTS

For all ethnicities, men had a lower percent body fat and more truncal fat than women. Log(10-)transformed truncal fat increased with TBF approximately as a square root function. At older ages, there was a greater amount of truncal fat in CA, HA and As men (approximately 0.20-0.25 kg/decade) with the effect more pronounced in AA men ( approximately 0.33 kg/decade). For women, the increment of truncal fat per decade was reduced in CA and AA women (approximately 0.07 kg) compared with As and HA women (approximately 0.33 kg). Adjusted for mean values of covariates in our sample, AA had less truncal fat than As.

CONCLUSION

The accumulation of truncal fat is strongly related to age, ethnicity and total fatness in both men and women.