Interrelationships of serum estradiol, estrone, and estrone sulfate, adiposity, biochemical bone markers, and leptin in post-menopausal women

Higher testosterone and testosterone/estradiol ratio in men are associated with decreased Pheno-/GrimAge and DNA-methylation based PAI1

Sex hormones are hypothesized to drive sex-specific health disparities. Here, we study the association between sex steroid hormones and DNA methylation-based (DNAm) biomarkers of age and mortality risk including Pheno Age Acceleration (AA), Grim AA, and DNAm-based estimators of Plasminogen Activator Inhibitor 1 (PAI1), and leptin concentrations. We pooled data from three population-based cohorts, the Framingham Heart Study Offspring Cohort, the Baltimore Longitudinal Study of Aging, and the InCHIANTI Study, including 1,062 postmenopausal women without hormone therapy and 1,612 men of European descent. Sex-stratified analyses using a linear mixed regression were performed, with a Benjamini-Hochberg (BH) adjustment for multiple testing. Sex Hormone Binding Globulin (SHBG) was associated with a decrease in DNAm PAI1 among men (per 1 standard deviation (SD): -478 pg/mL; 95%CI: -614 to -343; P:1e-11; BH-P: 1e-10), and women (-434 pg/mL; 95%CI: -589 to -279; P:1e-7; BH-P:2e-6). The testosterone/estradiol (TE) ratio was associated with a decrease in Pheno AA (-0.41 years; 95%CI: -0.70 to -0.12; P:0.01; BH-P: 0.04), and DNAm PAI1 (-351 pg/mL; 95%CI: -486 to -217; P:4e-7; BH-P:3e-6) among men. In men, testosterone was associated with a decrease in DNAm PAI1 (-481 pg/mL; 95%CI: -613 to -349; P:2e-12; BH-P:6e-11). SHBG was associated with lower DNAm PAI1 among men and women. Higher testosterone and testosterone/estradiol ratio were associated with lower DNAm PAI and a younger epigenetic age in men. A decrease in DNAm PAI1 is associated with lower mortality and morbidity risk indicating a potential protective effect of testosterone on lifespan and conceivably cardiovascular health via DNAm PAI1.

Higher testosterone and testosterone/estradiol ratio in men are associated with better epigenetic estimators of mortality risk

Introduction

Sex hormones are hypothesized to drive sex-specific health disparities. Here, we study the association between sex steroid hormones and DNA methylation-based (DNAm) biomarkers of age and mortality risk including Pheno Age Acceleration (AA), Grim AA, and DNAm-based estimators of Plasminogen Activator Inhibitor 1 (PAI1), and leptin concentrations.

Methods

We pooled data from three population-based cohorts, the Framingham Heart Study Offspring Cohort (FHS), the Baltimore Longitudinal Study of Aging (BLSA), and the InCHIANTI Study, including 1,062 postmenopausal women without hormone therapy and 1,612 men of European descent. Sex hormone concentrations were standardized with mean 0 and standard deviation of 1, for each study and sex separately. Sex-stratified analyses using a linear mixed regression were performed, with a Benjamini-Hochberg (BH) adjustment for multiple testing. Sensitivity analysis was performed excluding the previously used training-set for the development of Pheno and Grim age.

Results

Sex Hormone Binding Globulin (SHBG) is associated with a decrease in DNAm PAI1 among men (per 1 standard deviation (SD): -478 pg/mL; 95%CI: -614 to -343; P:1e-11; BH-P: 1e-10), and women (-434 pg/mL; 95%CI: -589 to -279; P:1e-7; BH-P:2e-6). The testosterone/estradiol (TE) ratio was associated with a decrease in Pheno AA (-0.41 years; 95%CI: -0.70 to -0.12; P:0.01; BH-P: 0.04), and DNAm PAI1 (-351 pg/mL; 95%CI: -486 to -217; P:4e-7; BH-P:3e-6) among men. In men, 1 SD increase in total testosterone was associated with a decrease in DNAm PAI1 (-481 pg/mL; 95%CI: -613 to -349; P:2e-12; BH-P:6e-11).

Conclusion

SHBG was associated with lower DNAm PAI1 among men and women. Higher testosterone and testosterone/estradiol ratio were associated with lower DNAm PAI and a younger epigenetic age in men. A decrease in DNAm PAI1 is associated with lower mortality and morbidity risk indicating a potential protective effect of testosterone on lifespan and conceivably cardiovascular health via DNAm PAI1.

Gender-specific association between body mass index and all-cause mortality in patients with atrial fibrillation

Background

Elevated body mass index (BMI) is related with reduced mortality in various cardiovascular diseases.

Hypothesis

Gender‐specific association between BMI and mortality exists in atrial fibrillation (AF).

Methods

In this multicenter observational study with a mean follow‐up of 1 year, a total of 1991 AF patients were enrolled and divided into two groups based on the gender. The primary endpoint was all‐cause mortality while the secondary endpoints were defined as cardiovascular mortality, stroke, and major adverse events during 1‐year follow‐up. Cox regression was performed to identify the association between BMI and clinical outcomes according to gender.

Results

Female patients with AF tended to be older (P = .027) and thinner (P < .001) than male patients with AF. They were more likely to have heart failure, hyperthyroidism, and valvular AF (all P < .05), but less likely to have coronary artery disease and prior myocardial infarction (all P < .01). Multivariate analysis revealed that overweight (HR(95%CI): 0.55(0.41‐0.75), P < .001) and obese patients (HR(95%CI): 0.56(0.34‐0.94), P = .028) were associated with significant lower all‐cause mortality compared with normal weight patients for the entire cohort. Similar association between elevated BMI and reduced all‐cause mortality were only identified in female patients with AF (overweight vs normal weight: HR(95%CI): 0.43(0.27‐0.70); obesity vs normal weight: HR(95%CI): 0.46(0.22‐0.97)), but not in male patients with AF.

Conclusion

This study indicates that overweight and obesity were related with improved survival in patients with AF. The association between elevated BMI and reduced mortality was dependent on gender, which was only significant in female patients, rather than male patients.

Role of estrone on the regulation of osteoblastogenesis

Although estradiol bone contribution has been deeply studied, little is known about the action of estrone. We investigated the direct action of estrone on osteoblasts growth and differentiation, with focus on the biochemical mechanism displayed by the estrogen. Murine calvarial osteoblast cultures in vitro exposed to 10 nM estrone were employed. Estrone enhanced gene expression of the osteogenic differentiation marker, Runx2 mRNA (150% above control). The hormone significantly increased cell proliferation (38% above control), nitric oxide production (108% above control), alkaline phosphatase activity (50% above control), in addition to stimulation of extracellular matrix mineralization. Using specific antagonists, we found that the mechanism of action of estrone involves estrogen receptor, nitric oxide synthase and MAPK signalling pathways participation. The hormone acts by its own and probably not via conversion to estradiol, since 17 B HSD inhibition did not affect the hormonal action. This work shows a novel action of estrone on bone cells promoting osteoblastogenesis.

Increased body fat mass explains the positive association between circulating estradiol and insulin resistance in postmenopausal women

The relationship between circulating estrogen levels and cardiometabolic risk factors such as insulin resistance is unclear in postmenopausal women. High estradiol (E₂) levels have been reported to predict increased risk of type 2 diabetes in this population. We aimed to examine associations among estrogen levels, adiposity measurements, and cardiometabolic risk variables including insulin resistance in postmenopausal women. One hundred-one healthy participants (mean ± SD: age 57 ± 4 yr, BMI 27.9 ± 4.8 kg/m²) were included in the analysis. Fifteen plasma steroids or metabolites were measured by liquid chromatography-tandem mass spectrometry. Insulin sensitivity was assessed with a hyperinsulinemic-euglycemic clamp. Body composition and fat distribution were determined with hydrostatic weighing and computed tomography, respectively. Blood lipids and circulating cytokines were also measured. Circulating E₂ was positively correlated with all adiposity indexes ( r = 0.62 to 0.42, P < 0.0001) except waist-to-hip ratio. E₂ was positively correlated with VLDL-cholesterol, plasma-, VLDL-, and HDL-triglyceride levels ( r = 0.31 to 0.24, P < 0.02) as well as with hs-CRP and IL-6 ( r = 0.52 and 0.29, P < 0.005) and negatively with HDL-cholesterol, adiponectin, and insulin sensitivity ( r = -0.36 to -0.20, P < 0.02). With adjustments for percent body fat, correlations between E₂ and metabolic risk variables were no longer significant. Similar results were observed for circulating estrone (E₁) and estrone-sulfate (E₁-S) levels. In conclusion, circulating estrogen concentrations are proportional to adipose mass in postmenopausal women, although they remain in the low range. Insulin resistance as well as altered blood lipids and cytokines are observed when circulating estrogen levels are high within that range, but these differences are explained by concomitant variation in total adiposity.

Metabolic Syndrome and Menopause: Pathophysiology, Clinical and Diagnostic Significance

Menopause is a risk factor for cardiometabolic diseases, including metabolic syndrome (MetS), type 2 diabetes, and cardiovascular diseases. MetS is a constellation of interdependent factors such as insulin resistance, abdominal obesity, dyslipidemia, and hypertension. The prevalence of MetS in postmenopause is due to loss of the protective role of estrogens and increased circulating androgens resulting in changes to body fat distribution and development of abdominal obesity. Excessive visceral adipose tissue plays an important role due to synthesis and secretion of bioactive substances such as adipocytokines, proinflammatory cytokines, reactive oxygen species, prothrombotic, and vasoconstrictor factors. MetS may also impact risk assessment of breast cancer, osteoporosis and chronic kidney disease, and quality of life during the menopausal transition. Increased MetS has stimulated the exploration of new laboratory tests for early detection and therapies.

Association of body mass index with risk of acute myocardial infarction and mortality in Norwegian male and female patients with suspected stable angina pectoris: a prospective cohort study

BACKGROUND

A number of previous studies have suggested that overweight or obese patients with coronary artery disease (CAD) may have lower morbidity and mortality than their leaner counterparts. Few studies have addressed possible gender differences, and the results are conflicting. We examined the association between body mass index (BMI) and risk of acute myocardial infarction (AMI), cardiovascular (CV) death and all-cause mortality in men and women with suspected stable angina pectoris.

METHOD

The cohort included 4164 patients with suspected stable angina undergoing elective coronary angiography between 2000 and 2004. Events were registered until the end of 2006. Hazard ratios (HR) (95% confidence intervals) were estimated using Cox regression by comparing normal weight (18.5-24.9 kg/m2) with overweight (25-29.9 kg/m2) and obese (≥30 kg/m2) patients. Underweight (<18.5 kg/m2) patients were excluded from the study.

RESULTS

Of 4131 patients with complete data, 72% were males and 75% were diagnosed with significant CAD. The mean (standard deviation (SD)) age in the total population was 62 (10) years. Mean (SD) BMI was 26.8 (3.9) kg/m2, 34% was normal weight, 48% overweight and 19% obese. During follow up, a total of 337 (8.2%) experienced an AMI and 302 (7.3%) patients died, of whom 165 (4.0%) died from cardiovascular causes. We observed a significant interaction between BMI groups and gender with regards to risk of AMI (p = 0.011) and CV death (p = 0.031), but not to risk of all-cause mortality; obese men had a multivariate adjusted increased risk of AMI (HR 1.80 (1.28, 2.52)) and CV death (HR 1.60 (1.00, 2.55)) compared to normal weight men. By contrast, overweight women had a decreased risk of AMI (HR 0.56 (0.33, 0.98)) compared to normal weight women. The risk of all-cause mortality did not differ between BMI categories.

CONCLUSION

Compared with normal weight subjects, obese men had an increased risk of AMI and CV death, while overweight women had a decreased risk of AMI. These findings may potentially explain some of the result variation in previous studies reporting on the obesity paradox.

Obesity and increased risk of cancer: does decrease of serum 25-hydroxyvitamin D level with increasing body mass index explain some of the association?

Low levels of vitamin D and excess body weight are both factors associated with increased risk of cancer. The increased risk seems to be proportional to the increase in BMI, and to decrease in serum 25-hydroxyvitamin D (25(OH)D) level. Our earlier investigations suggest that serum 25(OH)D levels decrease with increasing BMI. Although the connection between cancer risk, BMI and vitamin D status might be arbitrary, it has not been discussed in the literature so far. In this study, we analyze data published in current meta-analysis, prospective studies, and systematic reviews on cancer-specific risk attributed to high BMI and low vitamin D status. The contribution of low 25(OH)D levels associated with high BMI to increased cancer risk was calculated for 13 vitamin-D-sensitive cancers with a focus on colorectal and breast cancer as the most frequently studied vitamin-D-sensitive cancer types. Our study suggests that a low vitamin D status may explain at least 20% of the cancer risk attributable to high BMI. The contribution of low 25(OH)D to the increased cancer risk with increasing BMI may be different for different cancer types. Thus, we find 40% for breast cancer, and 26 and 75% for colorectal cancer in men and women, respectively.

Reference intervals of biochemical bone turnover markers for Saudi Arabian women: a cross-sectional study

Biochemical bone turnover markers (BTMs) provide important information on the diagnosis, therapy and monitoring of metabolic bone diseases including osteoporosis. One goal of antiresorptive therapy in women is to decrease biochemical BTMs to the lower half of reference intervals for healthy pre-menopausal counterparts, using newly developed automated assays of such markers. The main objectives of the present study were to: (1) establish reference interval values for the following biochemical BTMs: serum osteocalcine (s-OC), bone alkaline phosphatase (s-bone ALP), procollagen type 1 N-terminal propeptide (s-PINP), crosslinked C-terminal telopeptide of Type 1 collagen (s-CTX), tartarate-resistant acid phosphatase isoform 5b (s-TRACP-5b) and urinary: CTX (u-CTX), N-telopeptides of type 1 collagen (u-NTX), pyridinoline (u-PYD) and deoxypyridinoline (u-DPD) in randomly selected Saudi healthy pre-menopausal women; (2) study the changes in biochemical BTMs in relation to age in pre- and post-menopausal women and the factors reported to influence bone turnover and (3) determine the effect of menopausal status on BTMs. A total of 2125 women were studied [including (n=1557) pre-, and (n=568) post-menopausal women, respectively, aged 20-79 years]. A total of 765 healthy pre-menopausal women (aged 35-45 years) were used to establish reference intervals for biochemical BTMs. All women studied were medically examined and had their bone mineral density (BMD) values obtained for the lumbar spine (L(1)-L(4)) and femoral neck according to detailed inclusion criteria. In all women, values of biochemical BTMs, decreased with increasing age up to the age of 45 years, increased steeply among women in their 50s and remained increased in post-menopausal women. Significant increases were evident in all biochemical BTMs in post-menopausal women with >5 years since menopause with the exception of s-OC, u-DPD, and u-PYD. Using stepwise multiple linear regression analysis, several variables were identified (depending on the BTM) as determinants of BTMs including age, BMI, parity, FSH, LH, PTH, s-Ca, s-Mg, s-PO(4) and 25(OH)D. In the reference intervals group, there are no significant correlations between any of the biochemical BTMs and age of menarche, day of menstrual cycle, physical activity, total daily dietary calcium and caffeine intakes and parity. It is recommended that the age range 35-45 years should be used when establishing biochemical BTMs reference intervals in Saudi Arabian pre-menopausal women.

Predictors of breast discomfort among women initiating menopausal hormone therapy

OBJECTIVE

The aim of this study was to analyze the determinants of breast discomfort among postmenopausal women initiating menopausal hormone therapy (HT).

METHODS

We analyzed questionnaire, anthropometric, and serum estrone data from the Postmenopausal Estrogen/Progestin Interventions (PEPI) Trial, a randomized trial comparing placebo, conjugated equine estrogens (CEE) alone, or CEE with a progestogen (continuous or cyclical medroxyprogesterone acetate or cyclical micronized progesterone) among postmenopausal women. HT users could join the PEPI Trial after stopping HT for 2 months. We modeled the relation between smoking, body weight, alcohol consumption, age, quitting HT for the PEPI Trial, physical activity, and alpha-tocopherol consumption and new-onset breast discomfort at the 12-month follow-up among 662 participants without baseline breast discomfort.

RESULTS

The associations of new-onset breast discomfort with weight and with strenuous exercise varied by treatment assignment. Among women assigned to CEE + progestogen, strenuous exercise was associated with a 49% lower odds of new-onset breast discomfort (odds ratio, 0.51; 95% CI, 0.29-0.89; P = 0.02), whereas among women assigned to placebo or CEE alone, strenuous exercise was not significantly associated with new-onset breast discomfort. Surprisingly, among women taking CEE alone, each kilogram higher weight was associated with a 6% lower odds of new-onset breast discomfort (P = 0.04), whereas among women taking placebo, the association was in the opposite direction (P = 0.04). Adjustment for estrone level had negligible effects on odds ratios. alpha-Tocopherol intake, age, smoking, and alcohol intake were not significantly associated with new-onset breast discomfort in adjusted analyses.

CONCLUSIONS

Strenuous exercise and higher body weight may decrease the odds of new-onset breast discomfort among postmenopausal women initiating HT.

Emerging role of estrogen in the control of cardiometabolic disease

Menopause is associated with an increased risk of cardiovascular and metabolic disease that is partly independent of aging. This increased risk is largely due to postmenopausal estrogen loss. Estrogen improves insulin sensitivity and ss-cell function. This is consistent with the increased risk of diabetes after menopause and the finding that menopausal hormone therapy (MHT) lowers the incidence of diabetes. Experimental data suggest that estrogen has anti-atherosclerotic and pro-thrombotic properties. This is consistent with observational and interventional studies suggesting that MHT reduces the risk of cardiovascular disease if initiated early in women with a low-risk profile, but might increase risk in older women and/or those with other risk factors (e.g. dyslipidemia). Future research focusing on improving prevention of cardiometabolic disease through MHT may help to identify agents with higher tissue- and estrogen receptor-isoform specificity than currently used hormones.

Serum leptin levels, hormone levels, and hot flashes in midlife women

OBJECTIVE

To examine the associations between serum leptin levels, sex steroid hormone levels, and hot flashes in normal weight and obese midlife women.

DESIGN

Cross-sectional study.

SETTING

University clinic.

PATIENT(S)

201 Caucasian, nonsmoking women aged 45 to 54 years with a body mass index of <25 kg/m2 or >or=30 kg/m2.

INTERVENTION(S)

Questionnaire, fasting blood samples.

MAIN OUTCOME MEASURE(S)

Serum leptin and sex steroid hormone levels.

RESULT(S)

Correlation and regression models were performed to examine associations between leptin levels, hormone levels, and hot flashes. Leptin levels were associated with BMI, with "ever experiencing hot flashes" (questionnaire), with hot flashes within the last 30 days, and with duration of hot flashes (>1 year, P=.03). Leptin was positively correlated with testosterone, free testosterone index, and free estrogen index and inversely associated with levels of sex hormone-binding globulin. In women with a body mass index>or=30 kg/m2, leptin levels no longer correlated with testosterone levels.

CONCLUSION(S)

Serum leptin levels are associated with the occurrence and duration of hot flashes in midlife women; however, no correlation was found between leptin and serum estradiol.

Postmenopausal vaginal atrophy correlates with decreased estradiol and body mass index and does not depend on the time since menopause

OBJECTIVE

To evaluate the relationship between morphologic cell characteristics in Papanicolaou (Pap) smears and serum estradiol, body mass index (BMI) and the time elapsed since menopause. Study design. In 92 women Pap smears were grouped into atrophic and mature cell patterns and compared with estradiol, BMI and the time since menopause.

RESULTS

Forty-one patients with mature cell pattern were on average 7.1 years from menopause and 51 patients with atrophic pattern 8.2 years, but this difference was not significant. Estradiol in patients with mature cell pattern was significantly higher (52.1 +/- 48.5 pmol/l) than in patients with atrophic pattern (25.6 +/- 40.0 pmol/l). Similarly, BMI was significantly higher (27.9 +/- 4.2 kg/m(2)) in patients with mature cell pattern than in patients with atrophic pattern (25.7 +/- 3.8 kg/m(2)). There was no significant correlation between the time since menopause and estradiol among patients with mature and atrophic cell pattern. The same was true for the correlation between the time from menopause and BMI in patients with mature and atrophic pattern.

CONCLUSIONS

Estradiol and BMI are associated with vaginal cell maturation and atrophy in postmenopausal women. Vaginal cell atrophy does not depend on the time since menopause.

Obesity, estrone, and coronary artery disease in postmenopausal women

OBJECTIVES

The link between obesity and endogenous estrogen with coronary artery disease (CAD) in postmenopausal women is uncertain. In this prospective study we analyzed the association of body mass index (BMI) and blood levels of estrone in postmenopausal women with known CAD or with a high risk factor score for CAD.

METHODS

Participants were 251 female clinic patients aged 50-90 years who were postmenopausal and not using estrogen therapy. Clinical and behavioral characteristics and fasting blood for estrone and heart disease risk factors were collected at baseline, and again at 1 and 2 years. Women were grouped according to their BMI (kg/m2) as normal (18.5< or =BMI<25), overweight (25< or =BMI<30) or obese (BMI > or =30), and by low and high estrone levels (<15 and > or =15pg/mL, respectively). Fatal and nonfatal events were recorded for 2 years after baseline.

RESULTS

Women with a low estrone level were older, thinner, and had less hypertension, diabetes, and lower triglyceride and glucose levels. BMI was positively associated with estrone levels, hypertension, and diabetes and inversely associated with HDL cholesterol. There were 14 deaths, 8 attributed to CAD. The Kaplan-Meier survival curve showed a nonsignificant trend (p=0.074) of greater all cause mortality in women with low estrone levels (<15mL). In this model, adjusted for BMI, age [OR=1.08; p=0.03], C-reactive protein [OR=1.24; p=0.024] and hypertension [OR=6.22; p=0.003] were independent predictors of all cause mortality.

CONCLUSIONS

Postmenopausal women with low estrone levels (<15pg/mL) had a trend for increased mortality over the next 2 years. Larger, longer studies are needed.

Element analysis in femur of diabetic osteoporosis model by SRXRF microprobe

Diabetes mellitus affects bone metabolism and leads to osteopenia and osteoporosis, but its pathogenic mechanism remains unknown. To address this problem, mineral element of bone was analyzed in experimental diabetic osteoporosis model. Male Wistar rats were randomly divided into streptozotocin (STZ)-induced diabetic group (n=5) and control group (n=5). The experiment lasted 68 days and at the end of the experiment, femoral bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry and element content in femur of animals was determined by synchrotron radiation X-ray fluorescence (SRXRF) microprobe analysis technique. Results showed that femoral BMD in diabetic group was significantly lower than that in control (P<0.01). Relative mineral content of calcium (Ca), phosphorus (P) and zinc (Zn) in diabetic femurs decreased significantly compared to controls. And strontium (Sr) in diabetics reduced 11% (P=0.09). Relative content of sulfur (S) in average was statistically higher (P<0.01) in diabetics than that in controls. But no obvious difference was observed in relative content of chromium (Cr), iron (Fe), copper (Cu), and lead (Pb) between the two groups. Statistical analysis revealed that Ca correlated positively with P (R=0.85 and P<0.001), with Sr (R=0.38 and P<0.05) and with Zn (R=0.37 and P<0.05). Whereas, Zn correlated negatively with S (R=-0.40 and P<0.05). Our results reveal that loss of minerals accounts for the BMD reduction in diabetics.

Lack of evidence for effect modification by estrogen of association between body mass index and colorectal cancer risk among postmenopausal women

OBJECTIVE

Previous studies of the association between body mass index (BMI) and colorectal cancer among women found increased risk only among women who were premenopausal or used hormone replacement therapy (HRT). These results led to the hypothesis that BMI may increase risk more strongly among women with higher levels of circulating estrogen. We examined the association between BMI and colorectal cancer incidence by use of HRT, and number of postmenopausal years without HRT, a measure of duration of exposure to lower levels of estrogen.

METHODS

During follow-up from 1992-2003, 814 incident colorectal cancer cases were identified among 73,842 postmenopausal women in the Cancer Prevention Study-II Nutrition Cohort. Information on BMI and other risk factors was obtained from questionnaires completed at enrollment in 1992-1993 and during follow-up. Hazard ratios were calculated using proportional hazards modeling.

RESULTS

The association between BMI and colorectal cancer incidence was similar among never-users of HRT (hazard ratio 1.13, 95% confidence interval 1.02-1.25 per 5-unit increase in BMI) and current-users of HRT (hazard ratio 1.08, 95% confidence interval 0.92-1.27 per 5-unit increase in BMI). Among women not currently using HRT, the association between BMI and colorectal cancer did not differ by postmenopausal years without HRT.

CONCLUSIONS

Our results do not support the hypothesis that BMI increases risk of colorectal cancer more strongly among women with higher levels of estrogen.

Plasma levels of leptin and mammographic density among postmenopausal women: a cross-sectional study

Introduction

Obesity has been linked to increased risk of breast cancer in postmenopausal women. Increased peripheral production of estrogens has been regarded as the main cause for this association, but other features of increased body fat mass may also play a part. Leptin is a protein produced mainly by adipose tissue and may represent a growth factor in cancer. We examined the association between leptin plasma levels and mammographic density, a biomarker for breast cancer risk.

Methods

We included data from postmenopausal women aged 55 and older, who participated in a cross-sectional mammography study in Tromsø, Norway. Mammograms, plasma leptin measurements as well as information on anthropometric and hormonal/reproductive factors were available from 967 women. We assessed mammographic density using a previously validated computer-assisted method. Multiple linear regression analysis was applied to investigate the association between mammographic density and quartiles of plasma leptin concentration. Because we hypothesized that the effect of leptin on mammographic density could vary depending on the amount of nondense or fat tissue in the breast, we also performed analyses on plasma leptin levels and mammographic density within tertiles of mammographic nondense area.

Results

After adjusting for age, postmenopausal hormone use, number of full-term pregnancies and age of first birth, there was an inverse association between leptin and absolute mammographic density (P_trend = 0.001). When we additionally adjusted for body mass index and mammographic nondense area, no statistically significant association between plasma leptin and mammographic density was found (P_trend = 0.16). Stratified analyses suggested that the association between plasma leptin and mammographic density could differ with the amount of nondense area of the mammogram, with the strongest association between leptin and mammographic absolute density in the stratum with the medium breast fat content (P_trend = 0.003, P for interaction = 0.05).

Conclusion

We found no overall consistent association between the plasma concentration of leptin and absolute mammographic density. Although weak, there was some suggestion that the association between leptin and mammographic density could differ with the amount of fat tissue in the breast.

Influence of photoperiod and gonadal status on food intake, adiposity, and gene expression of hypothalamic appetite regulators in a seasonal mammal

We studied the effects of photoperiod on metabolic profiles, adiposity, and gene expression of hypothalamic appetite-regulating peptides in gonad-intact and castrated Soay rams. Groups of five to six animals were studied 6, 18, or 30 wk after switching from long photoperiod (LP: 16 h of light) to short photoperiod (SP: 8 h of light). Reproductive and metabolic indexes were measured in blood plasma. Expression of neuropeptide Y (NPY), proopiomelanocortin (POMC), and leptin receptor (ObRb) in the arcuate nucleus was measured using in situ hybridization. Testosterone levels of intact animals were low under LP, increased to a peak at 16 wk under SP, and then declined. Voluntary food intake (VFI) was high under LP in both intact and castrated animals, decreased to a nadir at 12–16 wk under SP, and then recovered, but only in intact rams as the reproductive axis became photorefractory to SP. NPY gene expression varied positively and POMC expression varied negatively with the cycle in VFI, with differences between intact and castrate rams in the refractory phase. ObRb expression decreased under SP, unrelated to changes in VFI. Visceral fat weight also varied between the intact and castrated animals across the cycle. We conclude that 1) photoperiodic changes in VFI reflect changes in NPY and POMC gene expression, 2) changes in ObRb gene expression are not necessarily determinants of changes in VFI, 3) gonadal status affects the pattern of VFI that changes with photoperiod, and 4) in the absence of gonadal factors, animals can eat less but gain adiposity.

Modulatory effects of Aroclors 1221 and 1254 on bone turnover and vertebral histology in intact and ovariectomized rats

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants. Two PCB mixtures, Aroclors 1221 and 1254 have been suggested to have estrogenic and anti-estrogenic properties, respectively. We have examined whether these PCB mixtures modulate bone turnover and vertebral histology in intact and ovariectomized (ovx) rat models. Thirty-two adult female rats were divided into four groups subcutaneously receiving 4% DMSO (control), A1221 (10 mg/kg), A1254 (10 mg/kg) oestradiol (E2, 30 microg/kg). These compounds were injected to the animals for a period of 6 weeks at two daily intervals. In the second model, rats (n=32) were ovx and allowed to recover for a period of 3 weeks. Control group received vehicle (4% DMSO) alone. Remaining rats were divided into three groups and injected (s.c.) with A1221, A1254 and E2 for 5 weeks. Urine samples were collected prior to end of the experiments. Then, all animals were decapitated. Serum parathyroid hormone (PTH), calcitonin and osteocalcin levels were determined by immunoradiometric method. Serum concentrations of alkaline phosphatase (ALP), calcium and inorganic phosphate were determined by enzymatic-colorimetric method. Urinary deoxypyridinoline (DPD) was measured by ELISA. Lumbar vertebrae (L2) of all animals were dissected out and processed for light microscopy. Levels of urinary DPD were significantly lowered in E2 -treated intact rats (p<0.001). Ovx significantly increased urinary DPD excretion (p<0.01) compared to intact control values. Administration of A1221 and A1254 had no significant effects in intact rats, however, they significantly reduced (p<0.05) and increased (p<0.001) urinary DPD levels in ovx rats, respectively. Neither of the PCB mixtures significantly changed serum osteocalcin and ALP levels in intact or ovx rats (except A1221 increased ALP in intact model, p<0.01). Both PCB mixtures had differential effects on serum PTH, calcitonin, calcium and inorganic phosphate concentrations. Treatment with A1221 reversed the adverse effects of ovariectomy on L2 histology. However, A1254 produced necrotic areas in vertebral bone, and this effect was expanded in ovx animals. Our findings suggest that both Aroclor compounds interfere with bone turnover mechanisms, particularly in ovx rats.