Estrogen controls lipolysis by up-regulating alpha2A-adrenergic receptors directly in human adipose tissue through the estrogen receptor alpha. Implications for the female fat distribution

Impact of walking on adipose tissue lipoprotein lipase activity and expression in pre- and postmenopausal women

OBJECTIVE

The aim of this study was to examine regional variation in adipose tissue lipoprotein lipase (AT-LPL) activity and expression in pre-and postmenopausal women, before and after training, once differences in chronological age or obesity degree are taken into account.

METHODS

Sixteen late pre- and 14 early postmenopausal (49 +/- 2 vs. 52 +/- 2 years; p < 0.001) moderately obese women (body mass index 29-35 kg/m(2)) were subjected to a 16-week walking program (3 sessions/week of 45 min at 60% heart rate reserve). Abdominal and femoral AT-LPL activity and expression, fasting lipid-lipoprotein profile, body composition, and cardiorespiratory fitness (CRF) were measured before and after our intervention. Statistical analyses were performed using covariance analysis for age differences.

RESULTS

AT-LPL activity and expression, lipid-lipoprotein metabolism, body fatness, and CRF were similar at baseline, irrespective of the group considered. Slight reductions in plasma cholesterol and high-density lipoprotein (HDL) cholesterol levels, fat mass and waist girth reductions, CRF increases as well as femoral AT-LPL activity and expression decreases after our intervention were comparable, regardless of menopausal status (0.0001 < p < 0.05).

CONCLUSIONS

Lipid storage is decreased in the femoral depot after walking, regardless of menopausal status. Reduction in AT-LPL activity or expression does not lead to a more deleterious lipid-lipoprotein profile, despite the modest decrease noted in HDL cholesterol concentrations.

Reduced cannabinoid receptor 1 protein in subcutaneous adipose tissue of obese

BACKGROUND

Cannabinoid 1 receptors are identified in various tissues involved in the internal metabolism including adipose tissue and the endocannabinoid system is claimed to be overactive in the obese state. To study the potential involvement of cannabinoid receptor 1 in the endocannabinoid system over-activity in adipose tissue in the obese state, we investigated the cannabinoid receptor 1 levels in adipose tissue from different fat depots in lean and obese humans.

MATERIALS AND METHODS

The adipose tissue samples were analysed by Western blot and by RT-PCR.

RESULTS

Both the gene expression and the protein of cannabinoid receptor 1 were lower in subcutaneous abdominal adipose tissue from obese subjects as compared with lean subjects (P < 0.01 and P = 0.058). Moreover, in lean subjects, the level of cannabinoid receptor 1 was significantly higher in subcutaneous adipose tissue compared with visceral adipose tissue (P < 0.05) for both gene expression and protein. The level of cannabinoid receptor 1 was similar between the two depots in obese subjects. The expression of cannabinoid receptor 1 was higher in subcutaneous gluteal adipose tissue as compared with subcutaneous abdominal adipose tissue (P < 0.05).

CONCLUSION

We found in lean subjects, a robust lower level of cannabinoid receptor 1 in visceral adipose tissue compared with subcutaneous adipose tissue (both RNA and protein levels), but similar levels of cannabinoid receptor 1 between the two depots in obese subjects. Our present findings do not indicate that cannabinoid receptor 1 is directly involved in the endocannabinoid system over-activity in adipose tissue in obesity.

Visceral fat dominant distribution in male type 2 diabetic patients is closely related to hepatic insulin resistance, irrespective of body type

Background

All previous studies that investigated the association between abdominal fat distribution and insulin resistance evaluated subcutaneous and visceral fat area and/or volume, but these values were not related to the body type of each subject. In the present study we have examined the association between abdominal fat distribution and peripheral (muscle)/hepatic sensitivity to insulin using the visceral to abdominal subcutaneous fat area ratio (VF/SF ratio) in male patients with type 2 diabetes mellitus. This ratio defines the predominancy of visceral or subcutaneous abdominal adiposity, independent of the body type of each individual.

Methods

Thirty-six type 2 diabetic male patients underwent a euglycemic insulin clamp (insulin infusion rate = 40 mU/m²·min) with 3-³H-glucose to measure insulin-mediated total body (primarily reflects muscle) glucose disposal (TGD) and suppression of endogenous (primarily reflects liver) glucose production (EGP) in response to a physiologic increase in plasma insulin concentration. Abdominal subcutaneous (SF) and intraabdominal visceral fat (VF) areas were quantitated with magnetic resonance imaging (MRI) at the level of L_4–5.

Results

TGD and TGD divided by steady state plasma insulin concentration during the insulin clamp (TGD/SSPI) correlated inversely with body mass index (BMI), total fat mass (FM) measured by ³H₂O, SF and VF areas, while VF/SF ratio displayed no significant relationship with TGD or TGD/SSPI. In contrast, EGP and the product of EGP and SSPI during the insulin clamp (an index hepatic insulin resistance) correlated positively with VF/SF ratio, but not with BMI, FM, VF or SF.

Conclusion

We conclude that, independent of the individual's body type, visceral fat dominant accumulation as opposed to subcutaneous fat accumulation is associated with hepatic insulin resistance, whereas peripheral (muscle) insulin resistance is more closely related to general obesity (i.e. higher BMI and total FM, and increased abdominal SF and VF) in male patients with type 2 diabetes.

Does oestrogen allow women to store fat more efficiently? A biological advantage for fertility and gestation

In normal healthy-weight humans, women have a higher percentage body fat than men, a difference that commences at puberty and continues throughout adult life, suggesting that the mechanism is related to sex steroids. The first half of pregnancy is also a stage of body fat gain in women. From an energy balance point, there is no explanation why women should be fatter than men, as the latter consume more calories proportionately. Moreover, women store fat in early pregnancy when caloric intake does not significantly change. The aim of this review is to focus on evidence supporting one mechanism that may account for these findings. That is, oestrogen reduces postprandial fatty acid oxidation leading to an increase in body fat which may account for the greater fat mass observed in women compared with men and the fat gain in early pregnancy. Therefore, female puberty and early pregnancy could be seen as states of efficient fat storage of energy in preparation for fertility, foetal development and lactation providing an obvious biological advantage. Further research into this mechanism of fat storage may provide further insights into the regulation of body fat.

Gender-specific care of diabetes mellitus: particular considerations in the management of diabetic women

In the past 30 years, the all-cause mortality and cardiovascular mortality rates for women with diabetes mellitus (DM), in contrast to men, have not declined. Furthermore, the difference between all-cause mortality rates in women with DM and those without DM has more than doubled. This urgently needs addressing. This review will analyse published medical literature relating to the specific management of DM in women and try to identify areas where gender affects care. We have identified specific gender differences in the pathophysiology of glucose homeostasis disorder, diabetes-related complications and any female gender-specific features of women with diabetes, such as contraception and the menopause. These gender-specific features of DM may offer a route to improved care for women and new therapeutic possibilities.

Gender-specific expression and mechanism of regulation of estrogen sulfotransferase in adipose tissues of the mouse

Although primarily regarded as a sex steroid, estrogen plays an important role in many other physiological processes including adipose development and disposition. Estrogen sulfotransferase (EST) regulates estrogen activity by catalyzing the sulfoconjugation and inactivation of estrogens. In the present study, we report the gender-specific expression of EST in adipose tissues of the mouse and describe contrasting mechanisms of EST regulation in the fat and liver. EST is expressed in the white adipose tissues of the male but not female mouse. Within the various fat depots of male mice, it is most abundantly expressed in the epididymal fat pad, with variable levels in other white fats and no expression in the brown fat. Fractionation of epididymal fat cells showed EST to be predominantly associated with stromal vascular cells (preadipocyte). EST expression in male mouse adipose tissues is dependent on testosterone as castration ablated, and administration of exogenous testosterone restored, EST expression. Furthermore, testosterone treatment induced abnormal EST expression in the parametrial fat of female mice. EST induction by testosterone in female mice is tissue specific because testosterone treatment had no effect on liver EST expression. Conversely, the liver X receptor agonist TO-901317 induced EST expression in female mouse liver but not in their adipose tissues. Finally, we demonstrate that male EST knockout mice developed increased epididymal fat accumulation with enlarged adipocyte size. We conclude that EST is expressed in adipose tissues in a sexually dimorphic manner, is regulated by testosterone, and plays a physiological role in regulating adipose tissue accumulation in male mice.

Effects of estrogen therapy on bone marrow adipocytes in postmenopausal osteoporotic women

One-year treatment of osteoporotic postmenopausal women with transdermal estrogen resulted in significant decreases in bone marrow adipocyte volume and prevented increases in adipocyte number as compared to placebo-treated controls. Estrogen treatment also prevented increases in mean adipocyte size over 1 year.

INTRODUCTION

Aging is associated not only with bone loss but also with increases in bone marrow adipocytes. Since osteoblasts and adipocytes are derived from a common precursor, it is possible that with aging, there is a preferential "switch" in commitment of this precursor to the adipocyte over the osteoblast lineage. We tested the hypothesis that the apparent "age-related" increase in marrow adipocytes is due, at least in part, to estrogen (E) deficiency.

METHODS

Reanalysis of bone biopsies from a randomized, placebo-controlled trial involving 56 postmenopausal osteoporotic women (mean age, 64 years) treated either with placebo (PL, n = 27) or transdermal estradiol (0.1 mg/d, n = 29) for 1 year.

RESULTS

Adipocyte volume/tissue volume (AV/TV) and adipocyte number (Ad#) increased (by 20%, P < 0.05) in the PL group, but were unchanged (Ad#) or decreased (AV/TV, by -24%, P < 0.001) in the E group. E treatment also prevented increases in mean adipocyte size over 1 year.

CONCLUSIONS

These findings represent the first in vivo demonstration in humans that not only ongoing bone loss, but also the increase in bone marrow adipocyte number and size in postmenopausal osteoporotic women may be due, at least in part, to E deficiency.

Low Sirt1 expression, which is upregulated by fasting, in human adipose tissue from obese women

OBJECTIVE

Calorie restriction increases the life span in a number of different organisms. This effect is dependent upon activation of the Sirt1 enzyme, and many of the beneficial effects of calorie restriction can be mimicked using resveratrol, which activates the Sirt1 enzyme. Nothing is known about this system in human adipose tissue; therefore, we investigated this system in human adipose tissue.

DESIGN

Sirt1 mRNA was measured in adipose tissue biopsies from human volunteers before and after 6 days of total fasting. In addition, adipose tissue from lean and obese individuals was compared and in vitro investigations were performed.

RESULTS

Long-term total fasting (6 days) of nine human volunteers increased Sirt1 mRNA expression in subcutaneous adipose tissue more than twofold (0.197-0.454 arbitrary units, P<0.05). Likewise, lean women (n=12) had more than twofold higher Sirt1 expression in subcutaneous adipose tissue compared to obese women (n=12; 0.33-0.73 arbitrary units, P<0.05). Sirt1 was equally expressed in the stroma-vascular fraction and the isolated adipocyte fraction. Finally, in vitro, we demonstrated that resveratrol (a Sirt1 activator) significantly enhanced the lipolytic effect of epinephrine in human adipose tissue (P<0.05).

CONCLUSION

Human adipose tissue contains Sirt1 and the expression of Sirt1 can be regulated by calorie restriction as in other species. Furthermore, we demonstrated that resveratrol affects human fat-cell metabolism similar to the effects in rodents (that is, increased epinephrine induced lipolysis). These findings indicated that the beneficial effects of calorie restriction in humans might involve the activation of Sirt1. Thus, based on these findings, we propose that Sirt1 might play important roles for the beneficial effects of calorie restriction in humans.

Lipoaugmentation of the vocal folds: a survey on alternative donor sites for graft harvesting

Lipoaugmentation is a treatment option for patients suffering from glottic insufficiency. Autologous fat is a nearly ideal material for vocal-fold augmentation from the view of biocompatibility and viscoelasticity, but there is still the problem of high graft resorption. As distribution and biological behavior of fatty tissue is very different in the human body, the aim of the study was to elucidate possible donor sites with respect to the quantity of harvested fat, the surgical accessibility to the region, the donor site morbidity and possibility of aesthetic defects and the quality of harvested tissue. Possible donor sites for harvesting were examined by magnetic resonance imaging in thirty-five patients with special emphasis to the buccal fat pad, the neck, the dorsolateral side of the proximal upper extremity, the subcutaneous layer of the abdominal wall, the superficial trochanteric region, the medial thigh, and the infrapatellar fat pad. Identified regions that failed to be chosen into consideration because of an elaborate surgical approach (superficial axillary's space, ischio-anal fossa, subcutaneous layer of buttock, popliteal fossa) were not taken into consideration. The mean volume of the buccal fat was 3.994 cm(3); the average thickness of the fat at the level of C7 was 1.721 cm, the mean value in the upper extremities was 1.913 cm laterally and 1.275 cm dorsally. The subcutaneous fat of the abdominal wall was divided into a superficial compartment (mean: 1.527 cm) and a deep one (average: 3.545 cm). In the superficial trochanteric region, the mean thickness was 2.536 cm, in the medial thigh 2.127 cm; the mean volume of the infrapatellar fat pad was 20.198 cm(3). All regions of interest showed reproducible and sufficient amounts of harvestable tissue, we found significant intersexual differences in dorsolateral side of the upper arm, subcutaneous layer of the abdominal wall and superficial trochanteric region. When harvesting subcutaneous tissue of the abdominal wall, grafts of the deep layer should be preferred, in the upper extremity the deep, muscle-neighbored parts. An alternative method is the surgically accessible fat of the neck. Solid fat pads could be harvested from the buccal region or the infrapatellar fat.

Oxidative stress, body fat composition, and endocrine status in pre- and postmenopausal women

OBJECTIVE

To evaluate the role of menopause on the regional composition and distribution of fat in women and eventual correlations with the oxidative state.

DESIGN

In this observational clinical investigation, 90 women (classified for menopause status according to Stages of Reproductive Aging Workshop criteria) were evaluated for body mass composition and fat distribution by dual-energy x-ray absorptiometry and for oxidative status by determination of serum hydroperoxide levels and residual antioxidant activity.

RESULTS

Total body fat mass increases significantly in postmenopause (P < 0.05) by 22% in comparison with premenopause, with specific increases in fat deposition at the level of trunk (abdominal and visceral) (P < 0.001) and arms (P < 0.001). Concomitantly, the antioxidant status increases significantly (P < 0.001) by 17%. When data were adjusted for age by analysis of covariance, statistical significance disappeared for the increase in fat mass, but it was retained for antioxidant status (P < 0.05). Both antioxidant status and hydroperoxide level increased with trunk fat mass, as shown by linear correlation analysis (r = 0.46, P < 0.001 and r = 0.26, P < 0.05, respectively).

CONCLUSIONS

The results of our investigation demonstrate that fat content increases in the upper part of the body (trunk and arms) in postmenopause and that age is the main determinant of this increase. During the comparison of premenopausal and postmenopausal women, we also detected a significant increase in antioxidant status. Apparently this change is mainly related to menopausal endocrine and fat changes.

Gender aspects of the role of the metabolic syndrome as a risk factor for cardiovascular disease

BACKGROUND

The interaction of the risk factors of abdominal obesity, disturbed glucose homeostasis, dyslipidemia, and hypertension is believed to represent a distinct entity, termed the metabolic syndrome (MetS), that leads to a greater increase in cardiovascular risk than does the sum of its components.

OBJECTIVE

We reviewed currently available information regarding gender differences in the role of the MetS as a risk factor for cardiovascular disease (CVD).

METHODS

Using the search terms women, men, sex, gender, sex differences, and gender differences in combination with the metabolic syndrome, we conducted a systematic review of the available literature on sex differences in the MetS. The National Institutes of Health, PubMed, and MEDLINE databases were searched retrospectively from 2007 to 1987. Reference lists of identified articles were also used as a source, and articles were not restricted to the English language.

RESULTS

In recent years, the MetS has been more prevalent in men than in women but has risen particularly in young women, where it is mainly driven by obesity. Diagnostic criteria for the MetS vary for the cutoff points and definition of its components in a gender-specific manner. Based on the definition of impaired glucose homeostasis and pathologic abdominal circumference or waist/hip ratio, more or fewer women are included. Glucose and lipid metabolism are directly modulated by estrogen and testosterone, with a lack of estrogen or a relative increase in testosterone inducing insulin resistance and a proatherogenic lipid profile. Hypertension is a strong risk factor in both sexes, but the prevalence of hypertension increases more rapidly in aging women than in men. Menopause and polycystic ovary syndrome contribute to the development of MetS by the direct effects of sex hormones. Some components of the MetS (eg, diabetes and hypertension) carry a greater risk for CVD in women.

CONCLUSIONS

Future gender-related clinical and research activities should focus on the identification of sex- and gender-specific criteria for risk management in patients with the MetS. We propose small, focused, mechanistic studies on sex-specific surrogate end points and sex-specific studies in animal models for diabetes and aging.

Increased visceral fat and decreased energy expenditure during the menopausal transition

OBJECTIVE

This study assessed longitudinal changes in body composition, fat distribution and energy balance in perimenopausal women. We hypothesized that total fat and abdominal body fat would increase at menopause due to decreased energy expenditure (EE) and declining estrogen, respectively.

DESIGN

Observational, longitudinal study with annual measurements for 4 years.

SUBJECTS

Healthy women (103 Caucasian; 53 African-American), initially premenopausal. During follow-up, lack of menstruation for 1 year and follicle-stimulating hormone >30 mIU ml(-1) defined a subject as postmenopausal.

MEASUREMENTS

Fat and lean mass (dual-energy X-ray absorptiometry), visceral (VAT) and subcutaneous abdominal fat (SAT) (computed tomography), dietary intake (4-day food record), serum sex hormones and physical activity (tri-axial accelerometry). Twenty-four hour EE was measured by whole-room calorimeter in a subset of 34 women at baseline and at year 4.

RESULTS

Body fat and weight increased significantly over time only in those women who became postmenopausal by year 4 (n=51). All women gained SAT over time; however, only those who became postmenopausal had a significant increase in VAT. The postmenopausal group also exhibited a significant decrease in serum estradiol. Physical activity decreased significantly 2 years before menopause and remained low. Dietary energy, protein, carbohydrate and fiber intake were significantly higher 3-4 years before the onset of menopause compared with menopause onset. Twenty-four hour EE and sleeping EE decreased significantly with age; however, the decrease in sleeping EE was 1.5-fold greater in women who became postmenopausal compared with premenopausal controls (-7.9 vs -5.3%). Fat oxidation decreased by 32% in women who became postmenopausal (P<0.05), but did not change in those who remained premenopausal.

CONCLUSION

Middle-aged women gained SAT with age, whereas menopause per se was associated with an increase in total body fat and VAT. Menopause onset is associated with decreased EE and fat oxidation that can predispose to obesity if lifestyle changes are not made.

Impact of estrogen receptor gene polymorphisms and mRNA levels on obesity and lipolysis--a cohort study

Background

The estrogen receptors α and β (ESR1, ESR2) have been implicated in adiposity, lipid metabolism and feeding behaviour. In this report we analyse ESR1 and ESR2 gene single nucleotide polymorphisms (SNPs) for association with obesity. We also relate adipose tissue ESR1 mRNA levels and ESR1 SNPs to adipocyte lipolysis and lipogenesis phenotypes.

Methods

23 ESR1 and 11 ESR2 tag-SNPs, covering most of the common haplotype variation in each gene according to HAPMAP data, were analysed by Chi² for association with obesity in a cohort comprising 705 adults with severe obesity and 402 lean individuals. Results were replicated in a cohort comprising 837 obese and 613 lean subjects. About 80% of both cohorts comprised women and 20% men. Adipose tissue ESR1 mRNA was quantified in 122 women and related to lipolysis and lipogenesis by multiple regression. ESR1 SNPs were analysed for association with adipocyte lipolysis and lipogenesis phenotypes in 204 obese women by simple regression.

Results

No ESR1 SNP was associated with obesity. Five ESR2 SNPs displayed nominal significant allelic association with obesity in women and one in men. The two ESR2 SNPs associated with obesity with nominal P value < 0.01 were genotyped in a second cohort where no association with obesity was observed. There was an inverse correlation between ESR1 mRNA levels in abdominal subcutaneous (sc) adipose tissue and basal lipolysis, as well as responsiveness to adrenoceptor agonists independent of age and BMI (P value 0.009–0.045). ESR1 rs532010 was associated with lipolytic sensitivity to noradrenaline (nominal P value 0.012), and ESR1 rs1884051 with responsiveness to the non-selective beta-adrenoceptor agonist isoprenaline (nominal P value 0.05). These associations became non-significant after Bonferroni correction.

Conclusion

ESR1 gene alleles are unlikely to be a major cause of obesity in women. A minor importance of ESR2 on severe obesity cannot be excluded. The inverse correlation between ESR1 mRNA levels and lipolytic responsiveness to adrenoceptor agonists implies that low adipose tissue ESR1 levels attenuate catecholamine resistance in sc fat cells of obese women hereby contributing to loss of sc and gain of visceral fat. There is no evidence for a genetic impact of ESR1 on lipolysis or lipogenesis.

Evaluating the correlation and prediction of trunk fat mass with five anthropometric indices in Chinese females aged 20-40 years

BACKGROUND AND AIMS

Obesity is a worldwide problem, and excess trunk fat mass (FM(trunk)) has been associated with an increased risk of diseases. The early measurement of FM(trunk) has potential importance to evaluate trunk obesity. We sought to evaluate the correlation and predication of FM(trunk) with five anthropometric indices in Chinese females.

METHODS AND RESULTS

A sample of 850 China females aged 20-40 years were recruited and divided into four age groups with a 5-year range in each group. Five anthropometric indices were measured or calculated. FM(trunk) in kg was measured using a dual-energy X-ray absorptiometry scanner. Principal component analysis (PCA) and multiple regression analysis were performed to develop prediction equations. There was an increasing trend of FM(trunk) and five anthropometric indices in successively older age groups. Four formed principal components (PCs) interpreted over 99% of the total variation of five relative anthropometric indices in all age groups. Regression analyses showed that four PCs combined explained a greater variance (R(2)=45.2-81.6%) in FM(trunk) than did each of the five indices alone (R(2)=2.4-72.2%).

CONCLUSIONS

Our results suggested that there is an increasing trend of FM(trunk) and five anthropometric indices with aging; that age obviously influences the relationship of FM(trunk) and the anthropometric indices studied; and that the accuracy of predicting the FM(trunk) using five anthropometric indices combined is greater than using the five indices alone.

Sex differences in fat storage, fat metabolism, and the health risks from obesity: possible evolutionary origins

Human beings are susceptible to sustained weight gain in the modern environment. Although both men and women can get fat, they get fat in different ways, and suffer different consequences. We review differences between men and women in the incidence of obesity, fat deposition patterns, fat metabolism, and the health consequences of obesity, and examine potential evolutionary explanations for these differences. Women generally have a larger proportion of body mass as fat, and are more likely to deposit fat subcutaneously and on their lower extremities; men are more likely to deposit fat in the abdominal region. Excess adipose tissue in the abdominal region, especially visceral fat, is associated with more health risks. Women have higher rates of reuptake of NEFA into adipose tissue; however, they also have higher rates of fat oxidation during prolonged exercise. Oestrogen appears to underlie many of these differences. Women bear higher nutrient costs during reproduction. Fat and fertility are linked in women, through leptin. Low leptin levels reduce fertility. Ovarian function of adult women is associated with their fatness at birth. In our evolutionary past food insecurity was a frequent occurrence. Women would have benefited from an increased ability to store fat in easily metabolisable depots. We suggest that the pattern of central obesity, more commonly seen in men, is not adaptive, but rather reflects the genetic drift hypothesis of human susceptibility to obesity. Female obesity, with excess adiposity in the lower extremities, reflects an exaggeration of an adaptation for female reproductive success.

Protein metabolism in Turner syndrome and the impact of hormone replacement therapy

BACKGROUND

Studies have documented an altered body composition in Turner syndrome (TS). Body fat is increased and muscle mass is decreased. Ovarian failure necessitates substitution with female hormone replacement therapy (HRT), and HRT induces favourable changes in body composition. It is unknown how HRT affects protein metabolism.

AIM

To test whether alterations in body composition before and after HRT in TS are a result of altered protein metabolism.

DESIGN

We performed a randomized crossover study with active treatment (HRT in TS and oral contraceptives in controls) or no treatment.

MATERIALS AND METHODS

We studied eight women (age 29.7 +/- 5.6 (mean +/- SD) years) with TS, verified by karyotype, and eight age-matched controls (age 27.3 +/- 4.9 years). All subjects underwent a 3-h study in the postabsorptive state. Protein dynamics of the whole body and of the forearm muscles were measured by an amino acid tracer dilution technique using [(15)N]phenylalanine and [(2)H(4)]tyrosine. Substrate metabolism was examined by indirect calorimetry.

RESULTS

Energy expenditure was comparable among TS and controls, and did not change during active treatment. Whole-body phenylalanine and tyrosine fluxes were similar in the untreated situations, and did not change during active treatment. Amino acid degradation and protein synthesis were similar in all situations. Muscle protein breakdown was similar among groups, and was not affected by treatment. Muscle protein synthesis rate and forearm blood flow did not differ among groups or due to treatment.

CONCLUSION

Protein metabolism in TS is comparable to controls, and is not affected by HRT.

Circulating sex hormones and gene expression of subcutaneous adipose tissue oestrogen and alpha-adrenergic receptors in HIV-lipodystrophy: implications for fat distribution

OBJECTIVE

Circulating oestradiol and testosterone, which have been shown to increase in human immunodeficiency virus (HIV)-infected patients following highly active antiretroviral therapy (HAART), may influence fat distribution and insulin sensitivity. Oestradiol increases subcutaneous adipose tissue in humans possibly through binding to oestrogen-receptor-alpha, which in turn activates anti-lipolytic alpha2A-adrenergic-receptor.

DESIGN AND METHODS

To address these issues circulating pituitary-gonadal-axis hormones and gene expression of receptors in subcutaneous adipose tissue were determined in 31 nondiabetic HIV-infected male patients receiving HAART (16 with lipodystrophy), in whom measures of fat distribution (CT and DEXA-scans) and insulin sensitivity (hyperinsulinaemic euglycaemic clamp) were available.

RESULTS

Total and free oestradiol and testosterone were decreased in lipodystrophic patients compared to nonlipodystrophic patients, whereas luteinizing hormone, follicle-stimulating hormone and prolactin were similar and normal in both study groups. Ratio of subcutaneous to total abdominal fat mass, limb fat, and insulin sensitivity, which were all decreased in lipodystrophic patients, correlated positively with both plasma oestradiol and testosterone (n = 31). Glycerol concentration during clamp (a marker of lipolysis) correlated inversely with expression of alpha2A-adrenergic-receptor, ratio of subcutaneous to total abdominal fat mass, and limb fat, respectively. Expression of alpha2A-adrenergic-receptor correlated positively with expression of oestrogen-receptor-alpha.

CONCLUSIONS

The results fit the hypothesis that sex hormones play a role in altered fat distribution and insulin sensitivity of male patients with HIV-lipodystrophy. The effect of oestradiol on the subcutaneous fat depot and lipolysis may be mediated in part through binding to the oestrogen-receptor-alpha, in turn activating anti-lipolytic alpha2A-adrenergic-receptor.

Association of the estrogen receptor-alpha gene with the metabolic syndrome and its component traits in African-American families: the Insulin Resistance Atherosclerosis Family Study

OBJECTIVE

We previously detected an association between a region of the estrogen receptor-alpha (ESR1) gene and type 2 diabetes in an African-American case-control study; thus, we investigated this region for associations with the metabolic syndrome and its component traits in African-American families from the Insulin Resistance Atherosclerosis Family Study.

RESEARCH DESIGN AND METHODS

A total of 17 single nucleotide polymorphisms (SNPs) from a contiguous 41-kb intron 1-intron 2 region of the ESR1 gene were genotyped in 548 individuals from 42 African-American pedigrees. Generalized estimating equations were computed using a sandwich estimator of the variance and exchangeable correlation to account for familial correlation.

RESULTS

Significant associations were detected between ESR1 SNPs and the metabolic syndrome (P = 0.005 to P = 0.029), type 2 diabetes (P = 0.001), insulin sensitivity (P = 0.0005 to P = 0.023), fasting insulin (P = 0.022 to P = 0.033), triglycerides (P = 0.021), LDL (P = 0.016 to P = 0.034), cholesterol (P = 0.046), BMI (P = 0.016 to P = 0.035), waist circumference (P = 0.012 to P = 0.023), and subcutaneous adipose tissue area (P = 0.016).

CONCLUSIONS

It appears likely that ESR1 contributes to type 2 diabetes and CVD risk via pleiotropic effects, leading to insulin resistance, a poor lipid profile, and obesity.

Effect of an estrogen receptor-alpha intron 4 polymorphism on fat mass in 11-year-old children

CONTEXT

Polymorphisms in the ESR1 gene encoding estrogen receptor (ER)-alpha may be associated with fat mass in adults.

OBJECTIVES

The objective of the study was to establish whether ESR1 polymorphisms influence fat mass in childhood.

DESIGN

This was a cross-sectional analysis after genotyping of rs9340799, rs2234693, and rs7757956 ESR1 polymorphisms.

SETTING

The Avon Longitudinal Study of Parents and Children (ALSPAC) was a population-based prospective study.

PARTICIPANTS

Participants included 3097 11-yr-old children with results for ESR1 genotyping, puberty measures, and dual-energy x-ray absorptiometry results.

OUTCOMES

Relationships between ESR1 polymorphisms and indices of body composition were measured.

RESULTS

The rs7757956 polymorphism was associated with fat mass (P = 0.002). Total body fat mass (adjusted for height) was reduced by 6% in children with TA/AA genotypes, and risk of being overweight (> or =85th centile of fat mass) was decreased by 20%. This genetic effect appeared to interact with puberty in girls (P = 0.05 for interaction): in those with the TT genotype, total body fat mass (adjusted for height) was 18% higher in Tanner stages 3-5 vs. stages 1-2; the equivalent difference was 7% in those with TA/AA genotypes. Furthermore, the risk of being overweight was 36% lower in girls with TA/AA genotypes in Tanner stages 3-5, but no reduction was seen in those in stages 1-2. Neither rs9340799 nor rs2234693 polymorphisms were associated with body composition measures.

CONCLUSIONS

Fat mass in 11-yr-old children was related to the rs7757956 ESR1 polymorphism. This association was strongest in girls in more advanced puberty, in whom the risk of being overweight was reduced by 36% in those with the TA/AA genotype.

Women's health and the metabolic syndrome

The metabolic syndrome is a cluster of cardiovascular risk factors that identifies individuals at a relatively high, long-term risk for atherosclerosis, cardiovascular disease, and type 2 diabetes. Insulin resistance and central obesity are the main risk conditions underlying the metabolic syndrome. As obesity rates increase worldwide especially in women, accompanying rising frequency of insulin resistance, dyslipidemia, diabetes, and hypertension contribute to increasing rates of cardiovascular morbidity and mortality. According to the latest NCEP/ATPIII definition of the metabolic syndrome almost 25% (from 6.7 up to 43.5% according to age) of the United States and European adult population appear to have the syndrome and in the recent years it has been more prevalent in men than in women. Prevalence is increasing and the increase seems to be steeper in women. The contribution of the different components of the syndrome differs between genders. Age, endocrine dysfunction (especially loss of ovarian estrogens) as well as genetic factors modify the response to underlying factors. Physical inactivity, which diminishes by age, is more prevalent in women than in men. Treatment goals are to prevent cardiovascular disease by both altering the risk factors that are components of the syndrome and more importantly applying lifestyle modifications with caloric restriction and exercise.

Effects of testosterone and estrogen treatment on lipolysis signaling pathways in subcutaneous adipose tissue of postmenopausal women

OBJECTIVE

The aim of this study was to investigate the treatment effects of testosterone and estrogen on the expression of proteins and genes involved in adipocyte signal transduction to lipolysis in abdominal subcutaneous adipose tissue of postmenopausal women.

DESIGN

An open, randomized clinical study with parallel group comparison.

SETTING

Women's health clinical research unit and a research laboratory at a university hospital.

PATIENT(S)

Thirty-six healthy naturally postmenopausal women.

INTERVENTION(S)

The participants were randomly given testosterone undecanoate (40 mg every second day) or estradiol valerate (2 mg daily) for 3 months.

MAIN OUTCOME MEASURE(S)

Expression of proteins and genes involved in adipocyte signal transduction to lipolysis in abdominal subcutaneous adipose tissue, determined by quantitative real-time polymerase chain reaction and Western blot, respectively, and related to plasma glycerol before or during a euglycemic hyperinsulinemic clamp.

RESULT(S)

Testosterone treatment decreased the expression of hormone-sensitive lipase and increased the expression of phosphodiesterase-3B, whereas no effect of estrogen was observed. Testosterone-induced changes in hormone-sensitive lipase expression correlated positively with corresponding changes in basal or clamp-induced plasma glycerol concentrations.

CONCLUSION(S)

Treatment with testosterone in postmenopausal women down-regulates hormone-sensitive lipase and up-regulates phosphodiesterase-3B expressions in abdominal subcutaneous adipose tissue in relation to changes in vivo of lipolytic activity, which may promote the accumulation of fat.

Acute modulation of adipose tissue lipolysis by intravenous estrogens

OBJECTIVE

The aim of this study was to determine whether intravenous (IV) conjugated estrogens (EST) acutely enhance the suppression of whole-body or regional subcutaneous adipose tissue (SAT) lipolysis by insulin in postmenopausal women.

RESEARCH METHODS AND PROCEDURES

We assessed whole-body lipolysis by [(2)H(5)]glycerol rate of appearance (Glyc(RA)) and abdominal and femoral SAT lipolysis (interstitial glycerol; Glyc(IS)) by subcutaneous microdialysis. Postmenopausal women (n = 12) were studied on two occasions, with IV EST or saline control (CON), under basal conditions and during a 3-stage (4, 8, and 40 mU/m(2)/min) hyperinsulinemic, euglycemic clamp. Ethanol outflow/inflow ratio and recovery of [(13)C]glycerol during microdialysis were used to assess blood flow changes and interstitial glycerol concentrations, respectively.

RESULTS

Compared with CON, EST did not affect systemic basal or insulin-mediated suppression of lipolysis (Glyc(RA)) or SAT nutritive blood flow. Basal Glyc(IS) in SAT was reduced on the EST day. However, insulin-mediated suppression of lipolysis in SAT was not significantly influenced by EST.

DISCUSSION

These findings suggest that estrogens acutely reduce basal lipolysis in SAT through an unknown mechanism but do not alter whole-body or SAT suppression of lipolysis by insulin.

Distribuição centrípeta da gordura corporal, sobrepeso e aptidão cardiorrespiratória: associação com sensibilidade insulínica e alterações metabólicas

O objetivo do presente estudo foi investigar associações entre a distribuição centrípeta da gordura corporal e lipídios-lipoproteínas séricos, pressão arterial e índice Homa-IR de resistência insulínica, mediante ajuste estatístico de indicadores quanto ao sobrepeso e à aptidão cardiorrespiratória. Foram analisados 89 voluntários (44 homens e 45 mulheres). A distribuição centrípeta da gordura foi analisada através de circunferência da cintura (CC) e o sobrepeso pelo índice de massa corporal (IMC). A aptidão cardiorrespiratória foi acompanhada pelo VO2máx estimado por teste de caminhada. Após ajuste pelos valores de IMC verificamos coeficientes de correlação significativos entre CC e níveis de pressão arterial e ApoB em homens, e entre CC e índice Homa-IR e triglicerídios em mulheres. Após ajuste pelos valores de VO2máx observamos correlações significativas entre CC e ApoB e índice Homa-IR em homens, e entre CC e índice Homa-IR em mulheres. Conclui-se que, dependendo do sexo, a quantidade e a distribuição da gordura corporal podem apresentar ações distintas na resistência insulínica e nas disfunções associadas. A aptidão cardiorrespiratória per se parece não contribuir na minimização da associação entre a distribuição centrípeta da gordura e o índice Homa-IR; porém, apresenta considerável impacto na associação entre a distribuição centrípeta da gordura e o metabolismo lipídico e os níveis de pressão arterial, sobretudo nos homens.

Adipose tissue-derived factors: impact on health and disease

The endocrine functions of the adipose organ are widely studied at this stage. The adipose organ, and in particular adipocytes, communicate with almost all other organs. Although some adipose tissue pads assume the functions as distinct "miniorgans," adipocytes can also be present in smaller numbers interspersed with other cell types. Although fat pads have the potential to have a significant systemic impact, adipocytes may also affect neighboring tissues through paracrine interactions. These local or systemic effects are mediated through lipid and protein factors. The protein factors are commonly referred to as adipokines. Their expression and posttranslational modifications can undergo dramatic changes under different metabolic conditions. Due to the fact that none of the mutations that affect adipose tissue trigger embryonic lethality, the study of adipose tissue physiology lends itself to genetic analysis in mice. In fact, life in the complete absence of adipose tissue is possible in a laboratory setting, making even the most extreme adipose tissue phenotypes genetically amenable to be analyzed by disruption of specific genes or overexpression of others. Here, we briefly discuss some basic aspects of adipocyte physiology and the systemic impact of adipocyte-derived factors on energy homeostasis.

Changes in intra-abdominal fat in early postmenopausal women: effects of hormone use

OBJECTIVE

Intra-abdominal fat (IAF) accumulates with age, is greater among postmenopausal vs. premenopausal women, and is linked to risk for both type 2 diabetes and cardiovascular disease. Whether hormone replacement therapy (HRT) prevents or attenuates changes in IAF and related risk factors is not clear. The objectives of this observational study were to 1) determine whether HRT attenuated the expected age-related increase in IAF and 2) identify the independent effects of HRT and fat distribution on changes in disease risk factors.

RESEARCH METHODS AND PROCEDURES

Subjects were early postmenopausal white women 45 to 55 years of age. Women either used HRT at the time of enrollment (n = 33) or did not (n = 17). Subjects were evaluated at baseline and 2 years for body composition (DXA), body fat distribution (computed tomography), insulin sensitivity (Si; minimal model), and serum lipids.

RESULTS

IAF increased significantly over 2 years, and this increase was not attenuated by HRT. HRT users had less IAF throughout the study. HRT users showed an increase in Si, whereas non-users showed a decrease. Superficial subcutaneous adipose tissue was significantly and independently related to total cholesterol, whereas IAF was related to high-density lipoprotein cholesterol, triglycerides, and Si.

DISCUSSION

HRT users had less IAF at baseline and throughout the study. Whether HRT altered the relationship between total body fat and IAF or whether differences between groups existed before the study should be addressed through a randomized, interventional study design. HRT had a significant effect on Si; IAF and superficial subcutaneous adipose tissue were significant determinants of disease risk factors.

Genetic and environmental correlations between obesity phenotypes and age at menarche

OBJECTIVE

To assess the extent that the genetic and environmental factors contribute to the phenotypic correlations between obesity traits and age at menarche (AAM), and also to examine the influence of AAM on obesity in both pre- and postmenopausal women.

METHODS

F ive hundred and twelve pedigrees with 2667 Caucasian female subjects from two to four generations were recruited. Fat mass and lean mass (both in kg) were measured by dual-energy X-ray absorptiometry scanner. Body mass index (BMI) (kg/m(2)) was calculated. We performed bivariate quantitative genetic analyses in the total sample containing 2667 Caucasian women. We also selected 206 unrelated premenopausal women and 140 unrelated postmenopausal women from the total sample, and computed the respective phenotypic correlation between obesity and AAM in these two subgroups.

RESULTS

For fat mass, lean mass and BMI, we detected their significant negative genetic correlations with AAM after adjustment for significant covariates, which were -0.3170 (P<0.001), -0.1721 (P<0.05) and -0.3665 (P<0.001), respectively. However, their environmental correlations with AAM were all nonsignificant (P>0.05), ranging from -0.0016 to 0.0192. In the premenopausal subgroup, significant associations were observed between fat mass and AAM (rho=-0.231, P<0.01) as well as between BMI and AAM (rho=-0.257, P<0.01). In the postmenopausal subgroup, no such associations were observed.

CONCLUSION

Our results for the first time suggested that significant phenotypic association between obesity phenotypes and AAM is mainly attributable to shared genetic rather than environmental factors, and AAM may have stronger effects on obesity phenotypes in pre- than in postmenopausal women.

Addition of aerobic exercise to dietary weight loss preferentially reduces abdominal adipocyte size

OBJECTIVE

To determine if hypocaloric diet, diet plus low-intensity exercise, and diet plus high-intensity exercise differentially influence subcutaneous abdominal and gluteal adipocyte size in obese individuals.

DESIGN

Longitudinal intervention study of hypocaloric diet, diet plus low-intensity exercise, and diet plus high-intensity exercise (calorie deficit = 2800 kcal/week, 20 weeks).

SUBJECTS

Forty-five obese, middle-aged women (BMI = 33.0+/-0.6 kg/m2, age = 58+/-1 years).

MEASUREMENTS

Body composition testing and adipose tissue biopsies were conducted before and after the interventions. Subcutaneous abdominal and gluteal adipocyte size was determined.

RESULTS

All three interventions reduced body weight, fat mass, percent fat, and waist and hip girths to a similar degree. Diet only did not change subcutaneous abdominal adipocyte size, whereas both diet plus exercise groups significantly reduced abdominal adipocyte size. Changes in abdominal adipocyte size in the diet plus exercise groups were significantly different from that of the diet group. Gluteal adipocyte size decreased similarly in all three groups.

CONCLUSION

Addition of exercise training to dietary weight loss preferentially reduces subcutaneous abdominal adipocyte size in obese women. This may be of importance for the treatment of health complications associated with subcutaneous abdominal adiposity.

Gender differences in the metabolic syndrome and their role for cardiovascular disease

Women live longer than men and develop cardiovascular disease (CVD) at an older age. The metabolic syndrome represents a major risk factor for the development of CVD, and gender differences in this syndrome may contribute to gender differences in CVD. In recent years, the metabolic syndrome has been more prevalent in men than in women. Prevalence is increasing and this increase has been steeper in women, particularly in young women, during the last decade. The contributions of the different components of the metabolic syndrome differ between genders and in different countries. In a recent survey in Germany, 40% of the adult population had been diagnosed with disturbed glucose tolerance or type 2 diabetes. Undiagnosed diabetes was more frequent in men than in women, and risk factors for undiagnosed diabetes differed between the sexes. Worldwide, in individuals with impaired glucose tolerance, impaired fasting glucose was observed more frequently in men, whereas impaired glucose tolerance occurred relatively more often in women. Lipid accumulation patterns differ between women and men. Premenopausal women more frequently develop peripheral obesity with subcutaneous fat accumulation, whereas men and postmenopausal women are more prone to central or android obesity. In particular, android obesity is associated with increased cardiovascular mortality and the development of type 2 diabetes. Visceral adipocytes differ from peripheral adipocytes in their lipolytic activity and their response to insulin, adrenergic and angiotensin stimulation and sex hormones. Visceral fat is a major source of circulating free fatty acids and cytokines, which are directly delivered via the portal vein to the liver inducing insulin resistance and an atherogenic lipid profile. Inflammation increases cardiovascular risk particularly in women. A relatively greater increase in cardiovascular risk by the appearance of diabetes in women has been reported in many studies.Thus, the presently available data suggest that the pathophysiology of the metabolic syndrome and its contribution to the relative risk of cardiovascular events and heart failure show gender differences, which might be of potential relevance for prevention, diagnostics, and therapy of the syndrome.

Role of estrogens in adipocyte development and function

Estrogen has historically been viewed as a major regulator of adipose tissue in adult females, but recent work has indicated that estrogen's role in adipose biology may be broader than initially appreciated and has also provided important insights into the mechanism of estrogen effects on adipose tissue. Estrogen has direct effects on adipocytes to inhibit lipogenesis and may also have direct effects on other cellular constituents of adipose tissue, as well as metabolic effects on other target organs that can regulate adipose tissue. Estrogen has central effects on food consumption and energy expenditure that contribute to its overall inhibitory effects on adipose deposition. Estrogen also plays an important role in regulating adipose deposition in males and recently has been shown to be an important factor in the determination of adipocyte number, indicating that it regulates key developmental events in adipogenesis. Although critical questions still remain in our understanding of the overall role of estrogen in adipose tissue, it is clear that estrogen plays a more important role in adipose tissue than originally realized and that it is a major regulator of adipose tissue in both sexes during development and adulthood.

Resistin mRNA levels are downregulated by estrogen in vivo and in vitro

Resistin, a hormone secreted by adipocytes, is suggested to be an important link between obesity and diabetes. The aim of this study was to evaluate the regulatory effect of estrogen on adipocyte resistin gene expression in ovariectomized (OVX) rats and in isolated rat adipocytes in vitro. Subcutaneous injection of estradiol benzoate reduced resistin mRNA levels in adipocytes isolated from the inguinal, parametrial, perirenal, retroperitoneal, or periovarian fat deposits of OVX rats, while an in vitro study showed that estradiol treatment decreased resistin mRNA levels in cultured rat periovarian fat adipocytes. Results of Western blotting analysis also showed that estrogen decreased adipose resistin contents in vivo and in vitro. These data suggest that estrogen is a pivotal negative regulator of resistin gene expression.

Direct effects of sex steroid hormones on adipose tissues and obesity

Sex steroid hormones are involved in the metabolism, accumulation and distribution of adipose tissues. It is now known that oestrogen receptor, progesterone receptor and androgen receptor exist in adipose tissues, so their actions could be direct. Sex steroid hormones carry out their function in adipose tissues by both genomic and nongenomic mechanisms. In the genomic mechanism, the sex steroid hormone binds to its receptor and the steroid-receptor complex regulates the transcription of given genes. Leptin and lipoprotein lipase are two key proteins in adipose tissues that are regulated by transcriptional control with sex steroid hormones. In the nongenomic mechanism, the sex steroid hormone binds to its receptor in the plasma membrane, and second messengers are formed. This involves both the cAMP cascade and the phosphoinositide cascade. Activation of the cAMP cascade by sex steroid hormones would activate hormone-sensitive lipase leading to lipolysis in adipose tissues. In the phosphoinositide cascade, diacylglycerol and inositol 1,4,5-trisphosphate are formed as second messengers ultimately causing the activation of protein kinase C. Their activation appears to be involved in the control of preadipocyte proliferation and differentiation. In the presence of sex steroid hormones, a normal distribution of body fat exists, but with a decrease in sex steroid hormones, as occurs with ageing or gonadectomy, there is a tendency to increase central obesity, a major risk for cardiovascular disease, type 2 diabetes and certain cancers. Because sex steroid hormones regulate the amount and distribution of adipose tissues, they or adipose tissue-specific selective receptor modulators might be used to ameliorate obesity. In fact, hormone replacement therapy in postmenopausal women and testosterone replacement therapy in older men appear to reduce the degree of central obesity. However, these therapies have numerous side effects limiting their use, and selective receptor modulators of sex steroid hormones are needed that are more specific for adipose tissues with fewer side effects.