The influence of ovariectomy on ob gene expression in rats

Blood leptin concentrations in Japanese Black cattle

The objective of this study was to examine the changes of serum leptin levels in heifers and steers during fattening. Seven steers and seven heifers at 14 months of age were used in the experiment. Live weight and serum leptin levels were determined at 2-month intervals. Initial live weight was greater in steers than heifers and a similar trend of growth was recorded during the experiment. As a result, live weight was higher in the steers than in the heifers during the experiment. Serum leptin concentration in both groups increased during the experiment and reached optimum level at 22 months of age and did not change thereafter. The increase in serum leptin level was more marked in heifers and leptin level was higher (P < 0·05) in heifers than steers between 18 and 26 months of age. The results suggest that serum leptin level increases during fattening in cattle and the trend is possibly affected by gender.

Effect of estrodiol on leptin receptors expression in regulating fat distribution and adipocyte genesis

OBJECTIVE

To examine how estradiol influence fat distribution and adipocyte genesis through regulating leptin function.

DESIGN AND METHODS

We randomized female SD rats into ovariectomy and sham group. After 14 weeks, we examined leptin receptor expression in perigenital, mesenteric and subcutaneous adipose tissues and leptin in serum. We further introduced mesenchymal stem cells (MSCs) to figure out the effect of 17-β estradiol on expression of leptin receptors (OBRb and OBRa), leptin and PPARγ2.

RESULTS

Weight and Lee's index was both significantly higher in ovariectomized group than sham group (p < 0.001). The interaction of serum E2 and leptin was negatively correlated with body weight. Expression of leptin receptor protein was extremely upregulated in ovariectomized group in perigenital and mesenteric fat. Both estradiol and leptin upregulated mRNA expression of OBRb, and created a dose-dependent decreasing manner in MSCs. Higher doses of estradiol (10(-7)-10(-5) M) inhibited adipogenic markers mRNA expression of leptin and PPARγ2, but low doses promoted leptin expression.

CONCLUSIONS

In ovariectomized rats, low level of serum estradiol may change body composition and promote adipocyte genesis through affecting leptin function.

Effect of alendronate sodium on tooth movement in ovariectomized rats

OBJECTIVES

The aim of the present study was to evaluate the effect of two different dosages of alendronate on induced orthodontic movement in an experimental model involving rats with osteoporosis following ovariectomy.

DESIGN

Female Wistar rats (Rattus norvegicus) eight weeks of age were divided into four groups (n=12/group): ovariectomized (OVX group); ovariectomized and treated with alendronate sodium at 1mg/kg (Group OVX+ALN1); ovariectomized and treated with alendronate sodium at 2mg/kg (Group OVX+ALN2); and sham operated (control). Three months after ovariectomy, the maxillary right first molar was submitted to movement for five and seven days. After the death of the animals, the maxilla were removed and processed for microscopic evaluation. The maxillary left first molar (without movement) was used for comparison purposes in all groups. The samples were processed for the quantification of alveolar bone and tooth movement.

RESULTS

Intragroup comparisons showed significant movement after five and seven days (p<0.05) for all groups. Comparison among groups revealed greater tooth movement in the OVX group (p<0.05), on day 7.

CONCLUSIONS

Both alendronate sodium doses similarly decreased tooth movement in ovariectomized rats (p>0.05). Movement in ovariectomized+alendronate groups were also smaller than non-ovariectomized rats, however without statistical difference.

The impact of leptin on perinatal development and psychopathology

Leptin has long been associated with metabolism as it is a critical regulator of both food intake and energy expenditure, but recently, leptin dysregulation has been proposed as a mechanism of psychopathology. This review discusses the evidence supporting a role for leptin in mental health disorders and describes potential mechanisms that may underlie this association. Leptin plays a critical role in pregnancy and in fetal growth and development. Leptin's role and profile during development is examined in available human studies, and the validity of applying studies conducted in animal models to the human population are discussed. Rodents experience a postnatal leptin surge, which does not occur in humans or larger animal models. This suggests that further research using large mammal models, which have a leptin profile across pregnancy and development similar to humans, are of high importance. Maternal obesity and hyperleptinemia correlate with increased leptin levels in the umbilical cord, placenta, and fetus. Leptin levels are thought to impact fetal brain development; likely by activating proinflammatory cytokines that are known to impact many of the neurotransmitter systems that regulate behavior. Leptin is likely involved in behavioral regulation as leptin receptors are widely distributed in the brain, and leptin influences cortisol release, the mesoaccumbens dopamine pathway, serotonin synthesis, and hippocampal synaptic plasticity. In humans, both high and low levels of leptin are reported to be associated with psychopathology. This inconsistency is likely due to differences in the metabolic state of the study populations. Leptin resistance, which occurs in the obese state, may explain how both high and low levels of leptin are associated with psychopathology, as well as the comorbidity of obesity with numerous mental illnesses. Leptin resistance is likely to influence disorders such as depression and anxiety where high leptin levels have been correlated with symptomatology. Schizophrenia is also associated with both low and high leptin levels. However, as anti-psychotics pharmacotherapy induces weight gain, which elevates leptin levels, drug-naïve populations are needed for further studies. Elevated circulating leptin is consistently found in childhood neurodevelopmental disorders including autism spectrum disorders and Rhett disorder. Further, studies on the impact of leptin and leptin resistance on psychopathology and neurodevelopmental disorders are important directions for future research. Studies examining the mechanisms by which exposure to maternal obesity and hyperleptinemia during fetal development impact brain development and behavior are critical for the health of future generations.

Effects of estrogen on food intake, serum leptin levels and leptin mRNA expression in adipose tissue of female rats

The integration of metabolism and reproduction involves complex interactions of hypothalamic neuropeptides with metabolic hormones, fuels, and sex steroids. Of these, estrogen influences food intake, body weight, and the accumulation and distribution of adipose tissue. In this study, the effects of estrogen on food intake, serum leptin levels, and leptin mRNA expression were evaluated in ovariectomized rats. Seven-week-old female Wistar-Imamichi rats were ovariectomized and divided into three treatment groups: group 1 (the control group) received sesame oil, group 2 was given 17β-estradiol benzoate, and group 3 received 17β-estradiol benzoate plus progesterone. The body weight and food consumption of each rat were determined daily. Serum leptin levels and leptin mRNA expression were measured by ELISA and quantitative RT-PCR, respectively. Food consumption in the control group was significantly higher (P<0.05) than that in groups 2 and 3, although body weight did not significantly differ among the three groups. The serum leptin concentration and leptin mRNA expression were significantly higher (P<0.05) in groups 2 and 3 than in group 1, but no significant difference existed between groups 2 and 3. In conclusion, estrogen influenced food intake via the modulation of leptin signaling pathway in ovariectomized rats.

G protein-coupled estrogen receptor in energy homeostasis and obesity pathogenesis

Obesity and its related metabolic diseases have reached a pandemic level worldwide. There are sex differences in the prevalence of obesity and its related metabolic diseases, with men being more vulnerable than women; however, the prevalence of these disorders increases dramatically in women after menopause, suggesting that sex steroid hormone estrogens play key protective roles against development of obesity and metabolic diseases. Estrogens are important regulators of several aspects of metabolism, including body weight and body fat, caloric intake and energy expenditure, and glucose and lipid metabolism in both males and females. Estrogens act in complex ways on their nuclear estrogen receptors (ERs) ERα and ERβ and transmembrane ERs such as G protein-coupled estrogen receptor. Genetic tools, such as different lines of knockout mouse models, and pharmacological agents, such as selective agonists and antagonists, are available to study function and signaling mechanisms of ERs. We provide an overview of the evidence for the physiological and cellular actions of ERs in estrogen-dependent processes in the context of energy homeostasis and body fat regulation and discuss its pathology that leads to obesity and related metabolic states.

Dietary pseudopurpurin effects on bone mineral density and bone geometry architecture in rats

The objective of our study was to evaluate whether feeding pseudopurpurin affects bone mineral density and bone geometry architecture in rats. Pseudopurpurin was extracted, analyzed and purified using an HLPC-ESI-MS. Rats were given 0% and 0.5% pseudopurpurin powder in their diet. Femurs of rats were examined at 0.5, 1 and 2 months after pseudopurpurin feeding. Compared with rats in the group 0%, the bone mineral density, and the calcium, magnesium, zinc and manganese concentrations in the rats femur in the group 0.5% increased significantly at 1 month and 2 months after pseudopurpurin feeding. Analytical results of micro-computed tomography showed that the group 0.5% displayed an increase in the trabecular volume fraction, trabecular thickness and trabecular number of the distal femur at 1 and 2 months after pseudopurpurin feeding, and the mean thickness, inner perimeter, outer perimeter, and area of the femur diaphysis were significantly increased at 2 months after pseudopurpurin feeding compared with the group 0%. In parallel, the trabecular separation and structure model index of the distal femur were decreased, compared with the group 0% at 1 and 2 months after pseudopurpurin feeding. In the 0.5% and 0% groups, there was no damage to kidney and liver by histopathology analysis. The long-term feeding of pseudopurpurin is safe for rats. The feeding of 0.5% pseudopurpurin which has specific chemical affinities for calcium for bone improvement and level of bone mineral density, enhances the geometry architecture compared with the 0% group.

Tissue-Specific Effects of Loss of Estrogen during Menopause and Aging

The roles of estrogens have been best studied in the breast, breast cancers, and in the female reproductive tract. However, estrogens have important functions in almost every tissue in the body. Recent clinical trials such as the Women's Health Initiative have highlighted both the importance of estrogens and how little we know about the molecular mechanism of estrogens in these other tissues. In this review, we illustrate the diverse functions of estrogens in the bone, adipose tissue, skin, hair, brain, skeletal muscle and cardiovascular system, and how the loss of estrogens during aging affects these tissues. Early transcriptional targets of estrogen are reviewed in each tissue. We also describe the tissue-specific effects of selective estrogen receptor modulators (SERMs) used for the treatment of breast cancers and postmenopausal symptoms.

Anti-osteoporosis activity of Cibotium barometz extract on ovariectomy-induced bone loss in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Recent research has confirmed that Cibotium barometz could inhibits osteoclast formation with no affect on BMM cell viability. However, the influence of Cibotium barometz on osteoporosis in animals is relatively unknown. The purpose of this study is to systemically investigate the effects of Cibotium barometz extract (CBE) on ovariectomy-induced osteoporosis in rats.

MATERIALS AND METHODS

A total of Seventy-two 3-month-old female Sprague-Dawley rats were used and randomly divided into sham-operated group and five ovariectomized (OVX) groups: OVX with vehicle; OVX with 17β-estradiol (E2, 25 μg/kg/day); OVX with CBE of graded doses (100, 300, or 500 mg/kg/day). Daily oral administration of E2 or CBE began 4 weeks after the surgery and lasted for 16 weeks. Bone mass, bone turnover and strength were analyzed by DEXA, biochemical markers and three-point bending test. The trabecular bone microarchitecture was evaluated by MicroCT.

RESULTS

CBE prevented total BMD decrease in the femur induced by OVX, which was accompanied by a significant decrease in skeletal remodeling, as was evidenced by the decreased levels of the bone turnover markers, such as osteocalcin (OC), alkaline phosphatese (ALP), deoxypyridinoline (DPD), and urinary Ca and P excretions. The treatment could also enhance the bone strength and prevent the deterioration of trabecular microarchitecture.

CONCLUSIONS

The present study indicated that Cibotium barometz extract might be a potential alternative medicine for the prevention and treatment of postmenopausal osteoporosis.

Relation between obesity and adenomatous polyps of the large bowel

BACKGROUND

We compared the prevalence of colorectal adenoma (polyps) in men and women and examined the role of body mass index (BMI) on polyp risk according to patient age and gender.

METHODS

The risk of developing colorectal polyps was studied in 15 380 subjects (7155 men and 8225 women) who underwent colonoscopy for the first time from April 1998 to March 2006 at our 'Human Dry Dock', which is the check-up service provided in Japan. Eligible subjects were 20-86 years old (mean age +/- SD, 47.3 +/- 8.5) and were free of invasive cancer, hyperplastic polyps and familial polyposis. Polyps were found in 1590 subjects (1062 men and 528 women). The odds ratio (OR) of detection of polyps in relation to obesity was determined in all cases by multivariate logistic regression analysis after making an adjustment for gender and age.

RESULTS

The OR of polyp detection in obese subjects (BMI >or= 25) versus non-obese subjects (BMI < 25, OR = 1) was 1.34 (P < 0.001) in men and 1.13 (P = 0.26) in women. As the BMI increased in increments of one, the OR in men increased significantly to 1.01 (P < 0.001), whereas the OR in women was unchanged at 1.00 (P = 0.23), which was without significance.

CONCLUSIONS

We conclude that obesity in men is a risk factor for the development of polyps. These results must be confirmed by additional epidemiological studies.

Role of estrogen receptor-alpha and -beta in regulating leptin expression in 3T3-L1 adipocytes

We investigated the effects of the estrogen receptor-alpha (ERalpha) and -beta (ERbeta) in the regulation of leptin, resistin, and adiponectin expression in 3T3-L1 adipocytes. Mature adipocytes were exposed to estradiol (E2), ERalpha agonist (PPT (4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol)), ERbeta agonist (DPN (2,3-bis(4-Hydroxyphenyl)-propionitrile)), E2 with ERalpha antagonist (MPP (1,3-Bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride)), and E2 with ERbeta antagonist (R,R-THC ((R,R)-5,11-diethyl-5,6,11,12-tetrahydro-2,8-chrysenediol)) at different concentrations. To clarify the expression and regulation of adipokines by ER subtypes, total RNA was extracted from cells and measured using quantitative PCR. Western blot analysis was performed to evaluate the protein expression of adipokines, ERalpha, and ERbeta. The leptin expression was significantly increased in the cells treated with high concentrations (10(-5) and 10(-6) mol/l) of the PPT (P < 0.01, P < 0.05). By contrast, the leptin expression decreased in a dose-dependent manner in the MPP-treated groups (P < 0.05). High concentrations (10(-5) mol/l) of R,R-THC with E2 (10(-7) mol/l) caused a significant increase of the leptin expression (P < 0.01). The leptin mRNA levels were positively correlated with the ERalpha mRNA levels (r = 0.584, P < 0.01) and negatively correlated with the ERbeta mRNA levels (r = -0.236, P = 0.03) in the adipocytes. The ratio of the ERalpha to ERbeta mRNA levels in the adipocytes was significantly associated with leptin mRNA levels (r = 0.454, P < 0.01). ERalpha induced leptin expression and ERbeta inhibited its expression in 3T3-L1 adipocytes. The ratio of the ERalpha-to-ERbeta expression in 3T3-L1 adipocytes may be an important potential regulatory factor in leptin expression.

Effects of ovariectomy or orchidectomy and estradiol valerate or testosterone enanthate replacement on serum insulin in rats

Various clinical observations and experimental data from in vitro studies suggest that insulin and sex hormones interact. The main purpose of the present study was to examine the effects of testosterone and estradiol on serum insulin in rats. Seven week old male and female albino (Wistar) rats were used in our study. Testosterone enanthate (50 mg kg(-1) day(-1)) or estradiol valerate (200 microg kg(-1) day(-l)) were injected intraperiotenally or subcutaneously in orchidectomised or ovariectomised rats, respectively. In orchidectomised rats, serum insulin was decreased compared with control animals (p < 0.01), on the other hand, decreasing of serum insulin was prevented by testosterone replacement (p < 0.001). In ovariectomised rats, serum insulin was also decreased compared with control group (p < 0.01) and decreasing of serum insulin was prevented by estradiol replacement (p < 0.05). Conclusively, present findings indicated that testosterone or estradiol were serum insulin enhancer hormones in male or female rats, respectively.

Protective effect of apigenin on ovariectomy-induced bone loss in rats

Recent studies have shown that apigenin not only inhibits bone resorption by osteoclasts but also induces osteoclast apoptosis. However, the influence of apigenin on osteoporosis in animals is relatively unknown. The purpose of this study was to examine the bone-protective effects of apigenin in estrogen-deficient ovariectomized rats. Three-month-old female Sprague-Dawley rats were either sham-operated or ovariectomized and fed AIN-93G diet for 7 weeks to induce bone loss. To confirm bone loss, we used a newly developed non-invasive technique involving zoom-in micro-computed tomography. Apigenin was administered at a dose of 10 mg/kg three times a week for 15 weeks. Our results indicate that apigenin not only increased the mineral content and density of the trabecular bone at the neck of the left femur, but also decreased body weight and dietary consumption. Moreover, our biochemical results indicate that apigenin has a positive effect on bone turnover. The present data suggest that apigenin should be considered for use in the treatment of osteoporosis.

Longitudinal evaluation of serum leptin and bone mineral density in early postmenopausal women

OBJECTIVE

To evaluate total and site-specific bone mineral density (BMD) and serum leptin levels in postmenopausal women treated with a calcium supplement and in postmenopausal women receiving estrogen plus progestin therapy.

DESIGN

Forty-four women were randomized to receive either calcium supplementation (group A, n = 22) or transdermal 17beta-estradiol at a dose of 50 mug/day in a continuous regimen and nomegestrol at a dose of 5 mg/day for 12 days per month in a sequential regimen (group B, n = 22). All women underwent dual-energy x-ray absorptiometry determination of BMD and blood sampling in the morning at the beginning of the study and after 12 months. Leptin was determined by radioimmunoassay in all samples.

RESULTS

After 12 months, serum leptin levels were significantly higher in group A (control) in comparison with group B and baseline values, whereas both total and pelvic BMDs were significantly lower in group A in comparison with group B and baseline values. At baseline, a significant correlation was found between leptin levels, body mass index, and total-body BMD. After 12 months, leptin was still correlated to body mass index in both groups, but the association with BMD was lost.

CONCLUSIONS

This study confirms previous evidence of a significant correlation between serum leptin and BMD in early postmenopausal women. Furthermore, this correlation is lost over time during the progression of the postmenopausal period, independently from the administration of estrogen-progestin therapy. Further studies and longer follow-up periods are needed to better understand theses issues.

Estrogen deficiency and periodontal condition in rats: a radiographic and macroscopic study

The purpose of this study was to evaluate the impact of ovariectomy-induced estrogen deficiency as a risk factor of periodontal disease in rats. Forty 90-day old female rats were either ovariectomized (OVX; n=20) or sham operated (SHAM; n=20). After 30 days, periodontitis was induced by placement of a cotton ligature around the upper second molars of 10 OVX and 10 SHAM animals. All animals were sacrificed 5 weeks later. Body weight was assessed before all surgical procedures. The left hemimaxillas were removed and the percentage of periodontal bone support was determined radiographically and buccal alveolar bone loss was determined macroscopically using an image-analysis software. Furcation involvement was also evaluated. Data were analyzed statistically by ANOVA at 5% significance level. Within the evaluated period, the ovariectomized rats gained more weight than the sham-operated animals (p<0.001). The animals in which periodontitis was induced had less bone support, greater alveolar bone loss and furcation involvement than those without ligature (p<0.001). However, there was no difference between ovariectomized and sham-operated animals (p>0.05). Based on the findings of this study, estrogen deficiency could not be considered as a risk factor for periodontal disease.

Effects of exogenous estradiol and progesterone on plasma concentrations of leptin in ewes in non-breeding season

Estradiol and progesterone may play a role in controlling leptin secretion by utilizing their receptors in adipocytes and the genomic mechanisms of the leptin gene. This study was conducted to evaluate the effects of exogenous sex steroids on the blood leptin concentrations in ewes in the non-breeding season. Multiparous ewes were fed to maintenance level for their live weights. Blood samples were collected at 12-h intervals from Days -3 to -1 to determine the basal leptin levels (pre-injection period). From Day 0 to Day 5 (injection period), blood sampling continued at 12-h intervals, and the ewes were injected intramuscularly at 24-h intervals with oil, 50 mg progesterone in oil, 1 mg of estradiol in oil, or both steroids in oil. Leptin was measured using a sensitive and specific radioimmunoassay based on recombinant bovine leptin. Overall, plasma concentrations of leptin were not affected by any of the steroid treatments, and there were no differences in the value of leptin between the pre-injection and injection periods among the 4 groups. Therefore, the exogenous estrogen and progesterone used in this study do not have a strong effect on the blood leptin concentrations of ewes in the non-breeding season.

Effects of oral continuous 17beta-estradiol plus norethisterone acetate replacement therapy on abdominal subcutaneous fat, serum leptin levels and body composition

AIM

To evaluate the effects of oral continuous 17beta-estradiol plus norethisterone acetate (E2/NETA) replacement therapy on abdominal subcutaneous fat, serum leptin level (SLL) and body composition in postmenopausal women.

MATERIALS AND METHODS

A 6-month, prospective, randomized, double-blind and placebo-controlled study was conducted. Forty-three healthy naturally postmenopausal women aged 43-65 years were randomly assigned to receive E2/NETA (2 mg E2 plus 1 mg NETA, n = 22) or placebo (n = 21). Fasting SLL by enzyme-linked immunosorbent assay, subcutaneous abdominal fat thickness (STh) by ultrasound and the anthropometric indices of body weight (BW), body mass index (BMI), waist and hip circumference (WC, HC) and waist-to-hip ratio (WHR) were recorded at the beginning and the end of the study.

RESULTS

After 6 months of therapy, BW and SLL increased in the placebo group (p = 0.043 and 0.033, respectively). WC, HC and STh decreased significantly in the E2/NETA group (p = 0.002, 0.006 and 0.000, respectively) and they were also significantly lower in women receiving E2/NETA than in women taking placebo (p = 0.000, 0.034 and 0.000, respectively). At baseline, SLL and STh were positively correlated with all anthropometric indices except WHR.

CONCLUSION

Oral continuous combined regimen of E2/NETA significantly reduced central fat accumulation as assessed by WC and STh, and attenuated the increase in SLL. The observed changes in SLL were highly and positively related to changes in STh. The oral continuous combined E2/NETA regimen appears to have protective effects on cardiovascular function and probably on metabolic diseases by its slimming effect upon WC in postmenopausal women.

Leptin in pregnancy: an update

Leptin influences satiety, adiposity, and metabolism and is associated with mechanisms regulating puberty onset, fertility, and pregnancy in various species. Maternal hyperleptinemia is a hallmark of mammalian pregnancy, although both the roles of leptin and the mechanisms regulating its synthesis appear to be taxa specific. In pregnant humans and nonhuman primates, leptin is produced by both maternal and fetal adipose tissues, as well as by the placental trophoblast. Specific receptors in the uterine endometrium, trophoblast, and fetus facilitate direct effects of the polypeptide on implantation, placental endocrine function, and conceptus development. A soluble isoform of the receptor may be responsible for inducing maternal leptin resistance during pregnancy and/or may facilitate the transplacental passage of leptin for the purpose of directly regulating fetal development. The steroid hormones are linked to the regulation of leptin and the leptin receptor and probably interact with other pregnancy-specific, serum-borne factors to regulate leptin dynamics during pregnancy. In addition to its effects on normal conceptus development, leptin is linked to mechanisms affecting a diverse array of pregnancy-specific pathologies that include preeclampsia, gestational diabetes, and intrauterine growth restriction. Association with these anomalies and with mechanisms pointing to a fetal origin for a range of conditions affecting the individual's health in adult life, such as obesity, diabetes mellitus, and cardiovascular disease, reiterate the need for continued research dedicated to elucidating leptin's roles and regulation throughout gestation.

Plasma leptin concentration in tamoxifen-treated ovariectomized rats

Leptin, the ob gene product, has an important role in the regulation of body weight. Although tamoxifen, a nonsteroidal antiestrogenic agent, is known to have estrogenic effects on fat metabolism, its influence on adipose tissue remains unknown. In the present study, the effect of tamoxifen on the concentration of leptin was investigated in ovariectomized rats treated with tamoxifen or vehicle. The dosage of tamoxifen was extrapolated from the human dosage. Food intake, adipose tissue weight, and plasma insulin were assessed at the end of the experiment.

RESULTS

Tamoxifen-treated rats showed a significant reduction of body weight gain, food intake, adipose tissue weight and leptin concentration (p < 0.001). The plasma insulin level was significantly higher after tamoxifen treatment (p = 0.01) in tamoxifen-treated rats than in control rats. We concluded that tamoxifen reduces food intake in the acute phase and a reduction of adipose tissue gain may result in reduced levels of plasma leptin in ovariectomized rats. Furthermore, rats treated with tamoxifen may be resistant to insulin action.

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.

Leptin and soluble leptin receptor in follicular fluid

PURPOSE

Previous studies suggest that follicular fluid leptin levels predict successful assisted reproduction. The relationship between intrafollicular leptin and the soluble leptin receptor, ovarian hormones, and oocyte quality was examined to determine potential factors contributing to this finding.

METHODS

Follicular fluid leptin, soluble leptin receptor, hormones, and oocyte quality were examined in 84 individual follicles from 30 women undergoing in vitro fertilization.

RESULTS

Follicular fluid leptin and soluble leptin receptor levels correlated inversely with each other (r = -0.354; p = 0.001). Follicular fluid leptin levels correlated with intrafollicular estradiol (r = 0.42; p < 0.001), progesterone (r = 0.48; p < 0.001), and androstenedione (r = 0.49; p < 0.001), whereas soluble leptin receptor levels correlated with activin (r = 0.38; p < 0.001) and follistatin (r = 0.35; p < 0.002). There was no relationship between follicular fluid leptin or soluble leptin receptor levels and pretreatment serum hormone levels, stimulated serum estradiol, follicle number, oocyte quality, fertilization, or embryo grade.

CONCLUSION

The data demonstrate that leptin and the soluble leptin receptor are highly interrelated with each other and with other intrafollicular hormones, but not with markers of oocyte quality, fertilization, or embryo grade.

Influência da ooforectomia na variação ponderal em ratas jovens e adultas

Para avaliar a influência do tempo de ooforectomia na variação ponderal, foram utilizadas 60 ratas, divididas em dois grupos (30 em cada grupo): Grupo A - jovens; e Grupo B - adultas. Os animais de cada grupo foram subdivididos em três subgrupos: Subgrupo 1 - controle (n= 6); Subgrupo 2 - laparotomia (n= 6); Subgrupo 3 (n= 18) - ooforectomia total bilateral. Os animais foram pesados semanalmente durante 13 semanas e os resultados foram avaliados pelo teste t de Student, com significância para p<0,05. As ratas ooforectomizadas tiveram ganho ponderal maior do que as demais, sendo a diferença significativa a partir da 11ª semana no Grupo A e 9ª semana no Grupo B, persistindo até o fim do experimento. No presente trabalho, a ooforectomia bilateral em ratas relacionou-se com maior ganho ponderal, independente da idade dos animais.

Leptin, ghrelin, and proinflammatory cytokines: compounds with nutritional impact in chronic kidney disease?

Metabolic and nutritional derangements are prominent features of the uremic syndrome. Recent evidence suggest that several large-molecular-weight molecules that often are elevated in uremia, such as leptin, ghrelin, and proinflammatory cytokines, may have nutritional impact in this patient group. On the basis of present knowledge, these compounds could be regarded as suspected but not established uremic toxins. The discovery of the ob gene, its product leptin, and cerebral leptin receptors has undoubtedly widened our understanding of obesity and the underlying molecular and physiologic mechanisms that regulate food intake and body weight. Moreover, the recent discovery of leptin receptor isoforms in several peripheral organs suggests that leptin besides having a central function also has several important peripheral biological functions. Because uremic patients in general have an inappropriate elevation of circulatory leptin, further research is necessary to determine the potential biological effects of elevated leptin levels in end-stage renal disease. Also, because many symptoms and findings prevalent in the uremic syndrome are known to be associated with elevated levels of proinflammatory cytokines, such as interleukin-6, future studies are needed to evaluate the role of specific anti-inflammatory treatment strategies in malnourished uremic patients.

Changes in serum leptin levels during GnRH agonist therapy

The purpose of the present study was to investigate changes in serum leptin levels during GnRH agonist therapy. Twenty regularly menstruating women with uterine leiomyomas were enrolled. These subjects were given GnRH agonist (leuprorelin acetate, 3.75 mg) monthly for 4 months. Serum leptin and estradiol (E2) levels were measured at the two time points of day 1 or 2 of the menstrual cycle and the end of GnRH agonist therapy. Weight, total body fat mass, percentage of body fat, and total body lean mass were measured by whole body scanning with dual-energy X-ray absorptiometry. The ratio of serum leptin levels to total body fat mass (leptin-fat mass ratio), and the ratio of serum leptin levels to total body lean mass (leptin-lean mass ratio) were calculated. All subjects became amenorrheic after the initial administration of GnRH agonist. Baseline E2 levels were 45.4 +/- 21.0 pg/mL, which significantly decreased after GnRH agonist therapy (13.3 +/- 4.2 pg/mL, p<0.01). Baseline leptin levels were 8.7 +/- 8.1 ng/mL, which did not differ from the values after 4 months of GnRH agonist administration (8.9 +/- 6.8 ng/mL). Total body fat mass significantly increased from 20.0 +/- 10.4 to 21.0 +/- 9.4 kg (p<0.05), while total body lean mass significantly decreased (34.5 +/- 4.2 kg to 33.3 +/- 3.9 kg, p<0.01). However, leptin-fat mass ratio after GnRH agonist therapy did not differ from the baseline values (0.39 +/- 0.16 ng/mL/kg vs 0.38 +/- 0.16 ng/mL/kg). Hypogonadism does not have a major impact on circulating leptin levels.

Differential sensitivity to central leptin and insulin in male and female rats

The distribution of fat in the body differs between the male and female sexes and is associated with the relative secretion of the two "adiposity" hormones leptin and insulin. We now report that the brains of male and female rats are differentially sensitive to the catabolic actions of small doses of these two hormones. Leptin (1 or 3.5 microg/2 microl) or saline (2 microl) was administered into the third cerebral ventricle of age- and weight-matched male and female rats. Leptin significantly reduced food intake in female and male rats over 4 h; however, leptin reduced 24-h intake in female but not in male rats. When the same rats were administered insulin (1 or 4 mU/2 microl) or saline (2 microl), male but not female rats had a robust reduction in food intake over 24 h. Previous research demonstrates the melanocortins are a central mediator of the effects of both leptin and insulin. However, we found no sex differences in sensitivity to the melanocortin agonist MTII (0.01, 0.1, 0.3, and 1.0 nmol/2 microl). These results suggest that the sex differences in sensitivity to leptin and insulin at the doses that we injected occur upstream of the melanocortin receptors. Because insulin and leptin reflect different fat beds and are differentially distributed in the male and female sexes, the implication is that the male and female sexes regulate adiposity-relevant parameters differently.

The influence of luteinizing hormone-releasing hormone analog on serum leptin and body composition in women with solitary uterine myoma

OBJECTIVE

The purpose of this study was to examine the influence of luteinizing hormone-releasing hormone analog goserelin on serum leptin and body composition in women with solitary uterine myoma.

STUDY DESIGN

Fifteen women who were regularly menstruating and not obese were included. In all subjects, serum concentrations of leptin, insulin, testosterone, progesterone, and estradiol and body mass index and waist-to-hip ratio were measured before and after 4, 8, and 12 weeks of treatment with goserelin (3.6 mg every 4 weeks). Fat mass and lean body mass were measured by dual energy radiographic densitometry at baseline and after 12 weeks of therapy. Data were analyzed by multiple way analysis of variance and both simple and multiple regression.

RESULTS

The treatment caused a significant regression of myoma. Body weight, fat, and lean mass were unchanged. No changes in plasma leptin (even after correction for fat mass) were noted during the treatment. Plasma estradiol decreased below castrate levels. Plasma progesterone decreased significantly, and testosterone tended to decline during the study. At baseline a highly significant positive correlation was found between serum leptin and fat mass. In a multiple regression analysis, neither the change in fat mass nor any of the hormonal parameters explained the significant portion of variance of plasma leptin during the treatment.

CONCLUSION

Pharmacologic gonadectomy does not influence plasma leptin concentrations in women if body fat mass is unchanged.

The obesity in bilateral ovariectomized rats is related to a decrease in the expression of leptin receptors in the brain

We investigated the expression levels of leptin receptors in the brain of ovariectomized (OVX) rats. The mean expression level of ob mRNA in adipose tissues of OVX rats was significantly (P < 0.01) lower than that in the SHAM operation group rats, and the mean body weight of OVX rats was significantly (P < 0.01) greater than that in the SHAM group rats. However, there were no differences between serum leptin concentrations in these two groups. The mean level of leptin receptor (OB-R) mRNA expression in the brain tissue and the mean level of long form type OB-R (OB-RL) mRNA expression in the hypothalamus of the OVX rats were significantly (P < 0.05) lower than those in the SHAM group rats. These changes were cancelled by supplementation with 17 beta-estradiol in OVX rats. These results suggested that not only changes in the expression level of ob mRNA in adipose tissue and the serum leptin concentration but also changes in the OB-R mRNA in the brain are involved in the body weight increase in OVX rats and that a decrease in OB-R makes transmission of signals to suppress the amount of food intake difficult, thus leading to an increase in body weight.

Leptin and reproduction

Since the cloning of leptin by Friedman's laboratory in 1994, over 3000 papers have been published on leptin, making it one of the most active research areas in all of science. Leptin appears to be a pleiotrophic hormone affecting many different tissues in the body. This review focuses on the role of leptin in reproduction. Evidence is accumulating that leptin potentially has roles in the regulation of GnRH and LH secretion, puberty, pregnancy, and lactation. Reciprocal regulation of leptin and its receptors by gonadal hormones and the implications and controversies thereof are also discussed in the review. Signaling pathways utilized by leptin are starting to become more clear, particularly JAK/STAT, MAPK, and SOCS3 have been implicated as mediators/modulators of leptin effects at the cellular level. At the hypothalamic level, there is also evidence that CART (cocaine and amphetamine-related transcript) is involved as a downstream mediator of leptin effects, especially with regards to control of GnRH secretion. While leptin clearly has many effects upon the reproductive axis, defining its precise roles is not without controversies. This review presents both pro and con findings, thereby demarking controversial areas that undoubtedly will be fertile ground for future investigation.

Estrogen deficiency causes central leptin insensitivity and increased hypothalamic neuropeptide Y

OBJECTIVE

Altered fat distribution is a consequence of menopause, but the mechanisms responsible are unknown. Estrogen insufficiency in humans can be modeled using ovariectomized rats. We have shown that increased adiposity in these rats is due to reduced physical activity and transient hyperphagia, and can be reversed with 17beta-estradiol treatment. The aims of this study were to examine whether this altered energy balance is associated with circulating leptin insufficiency, central leptin insensitivity, decreased hypothalamic leptin receptor (Ob-Rb) expression, and/or increased hypothalamic neuropeptide Y (NPY).

METHODS

Plasma leptin levels, adipose tissue ob gene expression, energy balance responses to i.c.v. leptin, hypothalamic Ob-Rb expression and NPY concentration in five separate hypothalamic regions were measured in adult female rats after either ovariectomy or sham operations.

RESULTS

Obesity was not associated with hypoleptinemia or decreased ob gene expression in ovariectomized rats; however, it was associated with insensitivity to central leptin administration. Food intake was less suppressed and spontaneous physical activity was less stimulated by leptin. This was not due to decreased hypothalamic Ob-Rb expression. NPY concentration in the paraventricular nucleus of the hypothalamus was elevated in the ovariectomized rats, consistent with leptin insensitivity; however this effect was transient and disappeared as body fat and leptin levels increased further and hyperphagia normalized.

CONCLUSION

Impaired central leptin sensitivity and overproduction of NPY may contribute to excess fat accumulation caused by estrogen deficiency.

Oestradiol plus progesterone treatment increases serum leptin concentrations in normal women

BACKGROUND

Previous studies have alluded to a role for both oestradiol and progesterone in the secretion of leptin from fat cells in the human, although direct evidence has yet to be obtained. The study aim was to assess serum leptin concentrations in normally cycling women receiving exogenous oestradiol and progesterone.

METHODS

Normally cycling women were investigated in an untreated spontaneous cycle (control, n = 10), a cycle treated with oestradiol (oestradiol cycle, n = 10) and a cycle treated with oestradiol plus progesterone (oestradiol+progesterone cycle, n = 6). Oestradiol was given to the women through skin patches on cycle days 2, 3 and 4, and progesterone intravaginally on cycle days 3, 4 and 5. Serum concentrations of leptin, oestradiol, progesterone, FSH and LH were measured in daily blood samples.

RESULTS

During the treatment, serum oestradiol and progesterone concentrations increased significantly. In the oestradiol cycles, leptin concentrations were not affected by treatment and did not differ from those in controls. In the oestradiol+progesterone cycles, leptin concentrations (mean +/- SEM) increased in all women from cycle day 3 (8.6 +/- 1.1 ng/ml) to days 5 (12.2 +/- 1.8 ng/ml, P < 0.01) and 6 (11.9 +/- 2.0, P < 0.05), and were at these points significantly higher than in the control cycles (P < 0.05). The mean percentage increase from day 3 to the peak concentration on days 5 or 6 was 62.6 +/- 6.8%. Leptin concentrations returned to the pretreatment value on day 7, together with the concentrations of oestradiol and progesterone. In the oestradiol+progesterone cycles, leptin concentrations correlated significantly with oestradiol and progesterone concentrations, but not with FSH and LH concentrations.

CONCLUSIONS

These results show, for the first time, that leptin secretion can be stimulated in women by the administration of oestradiol plus progesterone. This may explain the increased concentrations of leptin during the luteal phase of the normal menstrual cycle.

Metabolic effects of physical training in ovariectomized and hyperestrogenic rats

This study was undertaken to evaluate the effects of regular endurance-type exercise on glucose tolerance and glucose-stimulated insulin response (GSIR) in ovariectomized (OVX) rats with and without estrogen replacement. To do that, OVX Sprague-Dawley rats were compared with an OVX estradiol-treated group (OVXE2) and a sham-operated (Sham) group. Each of these groups was subdivided into a sedentary and a treadmill-trained (8 wk) group. Intravenous glucose tolerance tests (0.5 g/kg) were conducted in all rats 48 h after the last training session. Plasma levels of 17beta-estradiol and the uterus weight were significantly (P < 0.05) lower in OVX compared with results in Sham and significantly (P < 0.01) higher in OVXE2 (hyperestrogenic) compared with results in Sham. Body weights were significantly (P < 0.01) different among groups, in the following decreasing order: OVX, Sham, and OVXE2. The average daily food intake was significantly (P < 0.01) increased in OVX rats compared with Sham, whereas estradiol treatment diminished this effect (P < 0.01). Exercise training was found to alter none of the above-mentioned variables in all three experimental conditions. Although the mean integrated area under the glucose and insulin curves was not affected by OVX, training induced a significant (P < 0.01) reduction in the mean integrated area under the insulin curve in all three experimental conditions. It is concluded that the positive effects of physical training on improving GSIR in OVX and hyperestrogenic animals are similar to what has been found in Sham.

Steroid-dependent up-regulation of adipose leptin secretion in vitro during pregnancy in mice

Circulating leptin levels are elevated during the later stages of pregnancy in mammals, suggesting that maternal leptin may play a role in maintenance of pregnancy and/or preparation for parturition and lactation. The regulation and source of circulating leptin during pregnancy remains undetermined, but leptin mRNA levels increase in adipose tissue during this time in some species. Considerable controversy exists whether placenta is also a leptin-secreting tissue during pregnancy. Here, we directly demonstrate that leptin secretion rates from mouse adipose tissue in vitro are decreased during early pregnancy and up-regulated during late pregnancy and lactation. Changes in leptin secretion rates in vitro paralleled those of circulating leptin in vivo during gestation. Subcutaneous implants of estradiol or corticosterone into lactating mice for 48 h stimulated adipose leptin secretion rates in vitro to the level of that in pregnant mice. However, corticosterone, but not estradiol, increased leptin secretion when added to isolated adipose tissue in vitro. Placentae obtained at two stages of pregnancy did not secrete leptin in vitro, either when acutely isolated or when dissociated into cells for long-term cultures. Placental tissue (or cells) secreted progesterone, however, demonstrating placental viability. We conclude that hyperleptinemia during late pregnancy in mice primarily results from corticosterone-dependent up-regulation of leptin secretion from adipose tissue, and that the placenta does not contribute to leptin secretion. The initial decrease in leptin secretory rates from adipose tissue during early pregnancy may facilitate energy storage for the subsequent, increased metabolic demands of later pregnancy and lactation.

Effects of exogenous gonadal steroids on leptin homeostasis in rats

BACKGROUND

In humans, circulating concentrations of the hormone leptin, normalized to body fat mass, are significantly higher in females compared to males. This experiment was designed to determine whether the administration of exogenous androgen or estrogen would significantly alter the relationship between plasma leptin and fat mass in rats.

METHODS

In the first experiment, plasma leptin and retroperitoneal and parametrial (female)/epididymal (male) adipose tissue expression of leptin mRNA were measured in five male and five female 9.5-week-old Sprague-Dawley rats. In a second experiment, gonadectomized 10.5-week-old female Sprague-Dawley rats received 1 or 2 weeks of daily intraperitoneal injections (in oil) of 750 mg testosterone propionate, 2.5 microg of estradiol benzoate or vehicle. At 0, 1, and 2 weeks, plasma concentrations of leptin, fat pad weight of parametrial and retroperitoneal fat pads, and leptin mRNA expression by Northern blot in retroperitoneal fat pads were determined. Daily weight and food intake of animals were monitored throughout the study.

RESULTS

Circulating leptin concentrations per unit of fat pad mass and leptin mRNA expression normalized to actin mRNA were higher in gonadally intact female compared to male rats. Compared to placebo, estrogen administration decreased food intake and body weight, but had no significant effect on leptin mRNA expression or on circulating leptin concentration. Testosterone administration increased body weight and decreased expression of leptin mRNA (only after 2 weeks), but did not change food intake or circulating leptin concentration.

CONCLUSIONS

Administration of estrogen did not affect either leptin expression or the circulating concentration of leptin. Administration of androgen decreased expression of leptin mRNA. However, even after 2 weeks of testosterone administration to gonadectomized females, plasma leptin concentration, corrected for fat pad weight, was higher in gonadectomized females than in intact males. Thus, sex steroid-associated changes in plasma leptin concentration and leptin mRNA expression are not sufficient to explain the observed sexual dimorphism in plasma leptin concentrations in rats.

Effects of short-term hormone replacement on serum leptin levels in postmenopausal women

OBJECTIVE

Leptin is a hormone which is secreted by adipocytes and appears to influence the reproductive axis. Previous studies have demonstrated higher leptin levels in relation to body fat mass in women compared to men, higher levels in normally cycling compared to postmenopausal women, and a decrease in leptin levels with increased age. The purpose of this study was to determine whether oestrogen replacement with or without progesterone increases serum leptin levels in postmenopausal women, independently of changes in body fat, and to determine if ageing affects leptin levels at baseline or in response to hormone replacement.

PATIENTS

Twenty-one healthy postmenopausal women on no hormone replacement were studied at baseline, after 1 month of oestrogen (E2: estraderm 50 microg/day) and after a further month of oestrogen and 7 days of progesterone (P: progesterone 100 mg per vagina bid) designed to achieve physiological hormone levels. Subjects included 11 younger (45-55 years) and 10 older (70-80 years) postmenopausal women.

RESULTS

The relationship between leptin and the absolute fat mass (% body fat x weight [kg]) at baseline was not different between the younger and older postmenopausal women. The adequacy of physiological hormone replacement was confirmed in all subjects. Despite the absence of an effect of hormone replacement on weight, body mass index (BMI), % and absolute fat mass (bioimpedance) or waist-hip ratio, there was an increase in serum leptin levels with hormone replacement (15.4 +/- 1.7, 17.6 +/- 1.7, and 18.1 +/- 1.6 microg/l; mean +/- SEM at baseline, with E2, and with E2 + P, respectively; P < 0.001 vs. baseline) for the group as a whole. An increase in leptin with hormonal treatment was seen in both the younger (15.1 +/- 2.1, 18.1 +/- 2.4, and 18.5 +/- 1.9 microg/l; P < 0.01) and the older (15.7 +/- 2.8, 17.0 +/- 2.5, 17.7 +/- 2.8 microg/l; P = 0.06) postmenopausal women.

CONCLUSIONS

(1) Short-term physiological oestrogen replacement increases serum leptin levels in postmenopausal women independently of changes in fat mass; and (2) physiological progesterone replacement does not influence leptin levels in postmenopausal women.

Fluctuation of serum leptin level in rats after ovariectomy and the influence of estrogen supplement

In order to understand the mechanism of increasing body fat in perimenopausal and postmenopausal women, an ovariectomy-induced obesity model was used to study the role of leptin. In this investigation, a long-term study lasted for 13 weeks was conducted to monitoring the change of serum leptin level in rats after the loss of estrogen, and also to examine the influence of estrogen replacement. The results showed that three weeks after the removal of ovaries the body weight of Ovx rats was already significantly higher than the other two groups, and continued to gain more weight thereafter. Accompanying with the significant weight gain was the changes in the serum leptin levels. The leptin concentration declined gradually during the first half of experimental period, dropping down to an almost undetectable level at week 7 (0.216+/-0.132 ng/ml). Subsequently, its concentration began to elevate, and by the end of experiment leptin level was significantly higher (3.182+/-0.936 ng/ml) than the value before the operation (0.818+/-0.242 ng/ml). This fluctuation of serum leptin level caused by ovariectomy was eliminated by the replacement of estrogen. The present data indicate that ovariectomy-induced weight gain is caused by the early drop in leptin level. The later rise in leptin production is connected to the increased body weight probably originated from a reduced sensitivity in leptin signal.

Does estradiol mediate leptin's effects on adiposity and body weight?

The role of estradiol in mediating leptin's effects on body weight was assessed in ovariectomized (OVX) mice before and after the onset of obesity. Ovariectomy did not alter leptin levels before the onset of obesity, and estradiol adminstration (0.05-17 microgram/day for 14 days) did not significantly alter leptin levels if they were corrected for the estradiol-induced reduction in body fat. The converse was also true, in that leptin administration (0.4-140 microgram/day) did not alter estradiol levels in intact mice. Furthermore, neither estradiol reduction (via ovariectomy) nor addition (via exogenous administration) significantly altered leptin's ability to reduce fat mass. Leptin was equally effective in reducing body weight in lean or obese OVX mice and intact controls. Finally, estradiol did not change the magnitude of leptin's effect on fat mass reduction when it was given in combination with leptin to lean intact or OVX mice. Estradiol may have indirectly affected leptin efficacy, because leptin did not produce as large a change in fat mass at lower doses in lean OVX mice as it did in intact counterparts. Taken together, these data suggested that 1) estradiol does not directly regulate leptin secretion or its effects on fat mass and 2) leptin does not directly regulate estradiol secretion or its effects on fat mass. Leptin and estradiol, however, may interact in an indirect fashion to affect fat utilization.

In vivo and in vitro ob gene expression and leptin secretion in rat adipocytes: evidence for a regional specific regulation by sex steroid hormones

As a sexual dimorphism appears in plasma leptin levels, the aim of the present study was to investigate, in vivo and in vitro, the influence of sex steroid hormones on ob messenger RNA (mRNA) and leptin expressions in rat fat cells from various anatomical localizations. In male rats, castration resulted in a modulation of ob gene mRNA expression which was increased by 2-fold in perirenal and half-reduced in sc adipocytes. Moreover, in isolated fat cells from both perirenal and s.c. fat depots, ob gene mRNA expression was reduced by 20% after a 24-h in vitro exposure to dihydrotestosterone (10(-8) M). This effect of dihydrotestosterone on ob mRNA was prevented by exposure to the antiandrogen cyproterone acetate and also by actinomycin D. In contrast, leptin secretion from both perirenal and sc adipocytes was unchanged after 24 h exposure to dihydrotestosterone. In female rats, ovariectomy induced a 25% decrease in ob gene mRNA expression in perirenal fat cells. In vitro studies revealed that a 24-h exposure to 17-beta estradiol (10(-8) M) induced a 1.4-, 1.2-, and 1.75-fold increase in ob mRNA expression and a 3.8-, 1.65- and 2-fold increase in leptin secretion in sc, perirenal and parametrial adipocytes, respectively. Moreover, these effects were prevented by the antiestrogen ICI182780 and also by actinomycin D. Altogether, these results demonstrate that in rat adipocytes, estrogens, and androgens modulate ob gene expression at the mRNA level through sex steroid receptor-dependent transcriptional mechanisms.