Anxiety- and depression-like behavior are correlated with leptin and leptin receptor expression in prefrontal cortex of streptozotocin-induced diabetic rats

Anxiety and depression are common in diabetics. Diabetes also may cause reduced leptin levels in the blood. We investigated the relation between diabetes induced anxiety- and depression-like behavior, and leptin and leptin receptor expression levels in diabetic rats. The anxiety- and depression-like behaviors of rats were assessed 4 weeks after intraperitoneal injection of streptozotocin. Diabetic rats exhibited greater anxiety-like behavior; they spent more time in closed branches of the elevated plus maze test and less time in the center cells of the open field arena. Increased depression-like behavior was observed in diabetic rats using the Porsolt swim test. Prefrontal cortex (PFC), blood leptin levels and PFC neuron numbers were decreased, and leptin receptor expression and apoptosis were increased in diabetic rats. Blood corticosterone levels also were increased in diabetic rats. These results indicate that reduction of leptin up-regulates leptin receptor expression and may affect PFC neurons, which eventually triggers anxiety- and depression-like behaviors in diabetic rats.     

Decreased plasma leptin levels in lean and obese Zucker rats after treatment with the serotonin reuptake inhibitor fluoxetine.

Leptin inhibits feeding, stimulates thermogenesis and decreases body weight. Serotonin reduces food intake when injected into the hypothalamus and may interact with other neurotransmitters in the control of appetite. We therefore investigated the effects of the serotonergic drug fluoxetine, which inhibits serotonin reuptake, on food intake and plasma leptin levels in lean and obese Zucker rats. Fluoxetine significantly reduced food intake in lean and obese rats, both acutely after a single injection (10 mg/kg) and during continuous subcutaneous infusion (10 mg/kg/day for 7 days). Plasma leptin levels were reduced after both 4 hours and 7 days of fluoxetine administration in lean and after 7 days in fatty rats (all p<0.01). We have previously suggested that serotonin may decrease food intake by inhibiting neuropeptide Y neurones, and we further suggest that it also inhibits leptin, possibly by an effect on white adipose tissue.     

Total body aromatization in postmenopausal breast cancer patients is strongly correlated to plasma leptin levels

The adipocytokine leptin has recently been shown to enhance the expression of aromatase via promoter II and I.3 using an AP-1 motif. Thus, we evaluated the correlation between plasma leptin concentrations and total body aromatization (TBA) as well as plasma levels of estrone (E(1)), estradiol (E(2)) and estrone sulfate (E(1)S) in postmenopausal breast cancer patients. Twenty-two postmenopausal women with metastatic breast cancer, participating in tracer studies for the measurement of total body aromatization (TBA) in vivo, were available. In addition, blood samples for plasma estrogens and leptin measurements were available from another 22 breast cancer patients and 114 healthy postmenopausal women participating in the mammography-screening program. Values for TBA varied from 1.46 to 4.72% while plasma leptin levels ranged from 1.83 to 95.51 ng/ml in the same group of patients. All plasma estrogen levels were in the normal range expected for postmenopausal women. We found a significant correlation between pretreatment leptin levels and TBA (r(s) 0.452, P=0.01). In contrast, basal levels of TBA did not correlate to body mass index (BMI) in the same group of patients. Plasma leptin levels correlated to plasma levels of estradiol (r(s) 0.659, P=0.007), and estrone sulfate (r(s) 0.562, P=0.01) in the group of breast cancer patients (n=44) as well as in the group of healthy postmenopausal women (estradiol, r(s) 0.363, P< or =0.001, estrone sulfate r(s) 0.353, P< or =0.001). In conclusion, we found plasma leptin levels to correlate to TBA in breast cancer patients and to plasma levels of estradiol and estrone sulfate in breast cancer patients as well as in healthy postmenopausal females. These findings suggest that leptin may influence on aromatase activity in vivo, providing a possible link between body weight and plasma estrogen levels as well as breast cancer risk.     

Intrarenal oxidative stress and augmented angiotensinogen are precedent to renal injury in Zucker diabetic fatty rats

The Zucker diabetic fatty (ZDF) rat is a model of type II diabetes and metabolic syndrome based on impaired glucose tolerance caused by the inherited insulin-resistance gene. The ZDF rat exhibits progressive nephropathy; however, the detailed mechanisms have remained unclear. This study was performed to examine the possible involvement of enhanced intrarenal angiotensinogen in the development of renal injury in ZDF rats. Genetic pairs of male ZDF rats and control lean rats (N=6 each) were maintained from 12 to 17 weeks of age. At 17 weeks of age, fasting blood glucose and urinary 8-isoprostane levels were significantly higher in ZDF rats compared with the controls. Systolic blood pressure progressively increased in ZDF rats from 120+/-1 to 137+/-1 mmHg during this period. In contrast, systolic blood pressure did not increase in the controls. Kidney angiotensinogen protein levels were significantly increased in ZDF rats compared with the controls (1.83+/-0.34 vs. 1.00+/-0.17, relative ratio). Expression of angiotensin II type 1a receptor mRNA was similar between these groups. The measured indices of renal damage in the present study (glomerular sclerosis, interstitial expansion, glomerular macrophage infiltration, and renal arterial proliferation) were not significantly increased at this stage in ZDF rats. However, we previously showed that the increased reactive oxygen species-related angiotensinogen enhancement plays an important role in the development of renal injury in a genetic salt-sensitive hypertension. Thus, the present data suggest that elevated reactive oxygen species and reactive oxygen species-associated augmentation of intrarenal angiotensinogen may initiate the development of renal injury in ZDF rats.     

Relationship between plasma leptin and zinc levels and the effect of insulin and oxidative stress on leptin levels in obese diabetic patients

Leptin is thought to be a lipostatic signal that contributes to body weight regulation. Zinc plays an important role in appetite regulation also. Our aim is to evaluate the relationship between leptin and zinc in obese and nonobese type 2 diabetic patients and its relationship with oxidative stress and insulin. We studied 25 nonobese nondiabetic women (controls); 35 nonobese diabetic women; and 45 obese diabetic women. Plasma leptin concentration was determined by immunoradiometric assay. Thiobarbituric acid reactive substances (TBARS), markers of oxidative stress, were assayed by the spectrofotometric method. Plasma levels of zinc and insulin were measured by atomic absorption spectrophotometer and electrochemiluminescence methods, respectively. We found that nonobese diabetic patients had significantly lower zinc and higher TBARS levels than control subjects (P<0.01). There was no difference in plasma leptin levels between nonobese diabetic subjects and controls. Obese diabetic subjects had significantly higher plasma leptin, TBARS, and insulin levels and significantly lower plasma zinc levels than nonobese diabetic subjects (for each comparison; P<0.01). The univariate and multivariate analyses demonstrated a significant positive correlation between leptin and body mass index (P<0.01) and insulin (P<0.01), and a significant negative correlation between leptin and zinc in obese subjects. Additionally, TBARS levels was positive correlated with insulin and negative correlated with zinc in obese diabetic subjects. We conclude that zinc may be a mediator of the effects of leptin, although the detailed mechanism is still unknown and requires further investigation. Free radical induced mechanism(s) may be involved in this process.     

High insulin levels are required for FAT/CD36 plasma membrane translocation and enhanced fatty acid uptake in obese Zucker rat hepatocytes

In myocytes and adipocytes, insulin increases fatty acid translocase (FAT)/CD36 translocation to the plasma membrane (PM), enhancing fatty acid (FA) uptake. Evidence links increased hepatic FAT/CD36 protein amount and gene expression with hyperinsulinemia in animal models and patients with fatty liver, but whether insulin regulates FAT/CD36 expression, amount, distribution, and function in hepatocytes is currently unknown. To investigate this, FAT/CD36 protein content in isolated hepatocytes, subfractions of organelles, and density-gradient isolated membrane subfractions was analyzed in obese and lean Zucker rats by Western blotting in liver sections by immunohistochemistry and in hepatocytes by immunocytochemistry. The uptake of oleate and oleate incorporation into lipids were assessed in hepatocytes at short time points (30-600 s). We found that FAT/CD36 protein amount at the PM was higher in hepatocytes from obese rats than from lean controls. In obese rat hepatocytes, decreased cytoplasmatic content of FAT/CD36 and redistribution from low- to middle- to middle- to high-density subfractions of microsomes were found. Hallmarks of obese Zucker rat hepatocytes were increased amount of FAT/CD36 protein at the PM and enhanced FA uptake and incorporation into triglycerides, which were maintained only when exposed to hyperinsulinemic conditions (80 mU/l). In conclusion, high insulin levels are required for FAT/CD36 translocation to the PM in obese rat hepatocytes to enhance FA uptake and triglyceride synthesis. These results suggest that the hyperinsulinemia found in animal models and patients with insulin resistance and fatty liver might contribute to liver fat accumulation by inducing FAT/CD36 functional presence at the PM of hepatocytes.     

The connection of plasma triiodothyronine levels with the sex-dependent body weight loss after bilateral pallidal lesion in rats.

Previous data showed that after bilateral pallidal lesion (GPL) the weight loss of animals is higher in males than females. Data in the literature have called attention to the possible involvement of thyroid hormones. The sex dependence of weight loss was prevented by neonatal castration. In the present experiments, plasma triiodothyronine level was determined in neonatally castrated and non-castrated male and female rats on the 4th day after GPL. Body weight changes in food and water deprived male and female rats were compared after 4 days of T3 administration. A positive correlation between weight loss and T3 levels was found but there was no difference in mean T3 values between male and females. In the non-castrated group, T3 levels were higher in lesioned than in food and water deprived animals. In neonatally castrated animals no such difference was found. T3 administration caused a uniform weight loss in both sexes. It seems that while they play a role in the mechanism of weight loss after GPL, the sex-dependence is not due to changes in factors involved in regulation of the thyroid hormone level.     

Clinical symptoms in fibromyalgia are better associated to lipid peroxidation levels in blood mononuclear cells rather than in plasma

Background

We examined lipid peroxidation (LPO) in blood mononuclear cells (BMCs) and plasma, as a marker of oxidative damage, and its association to clinical symptoms in Fibromyalgia (FM) patients.

Methods

We conducted a case–control and correlational study comparing 65 patients and 45 healthy controls. Clinical parameters were evaluated using the Fibromyalgia Impact Questionnaire (FIQ), visual analogues scales (VAS), and the Beck Depression Inventory (BDI). Oxidative stress was determined by measuring LPO in BMCs and plasma.

Results

We found increased LPO levels in BMCs and plasma from FM patients as compared to normal control (P<0.001). A significant correlation between LPO in BMCs and clinical parameters was observed (r = 0.584, P<0.001 for VAS; r = 0.823, P<0.001 for FIQ total score; and r = 0.875, P<0.01 for depression in the BDI). We also found a positive correlation between LPO in plasma and clinical symptoms (r = 0.452, P<0.001 for VAS; r = 0.578, P<0.001 for FIQ total score; and r = 0.579, P<0.001 for depression in the BDI). Partial correlation analysis controlling for age and BMI, and sex, showed that both LPO in cells and plasma were independently associated to clinical symptoms. However, LPO in cells, but not LPO in plasma, was independently associated to clinical symptoms when controlling for depression (BDI scores).

Discussion

The results of this study suggest a role for oxidative stress in the pathophysiology of fibromyalgia and that LPO in BMCs rather than LPO in plasma is better associated to clinical symptoms in FM.     

Serum leptin levels, body fat deposition, and weight in females with anorexia or bulimia nervosa.

The objective of this retrospective study was to investigate the relation between serum leptin level and fat deposition in patients with eating disorders. 40 female inpatients with anorexia (n=24) or bulimia nervosa (n=16) were assessed for leptin level, body mass index (BMI), and percentage body fat by dual-energy X-ray absorbometry (DXA). The results show that percentage body fat is a better predictor for leptin level and clinical findings in eating disordered patients than BMI. We discuss the necessity for DXA measurements in anorectic patients for prognostic and research purposes.     

Tissue leptin and plasma insulin are associated with lipoprotein lipase activity in severely obese patients

The development of metabolic complications of obesity has been associated with the existence of depot-specific differences in the biochemical properties of adipocytes. The aim of this study was to investigate, in severely obese men and women, both gender- and depot-related differences in lipoprotein lipase (LPL) expression and activity, as well as the involvement of endocrine and biometric factors and their dependence on gender and/or fat depot. Morbidly obese, nondiabetic, subjects (9 men and 22 women) aged 41.1+/-1.9 years, with a body mass index (BMI) of 54.7+/-1.7 kg/m(2) who had undergone abdominal surgery were studied. Both expression and activity of LPL and leptin expression were determined in adipose samples from subcutaneous and visceral fat depots. In both men and women, visceral fat showed higher LPL mRNA levels as well as lower ob mRNA levels and tissue leptin content than the subcutaneous one. In both subcutaneous and visceral adipose depots, women exhibited higher protein content, decreased fat cell size and lower LPL activity than men. The gender-related differences found in abdominal fat LPL activity could contribute to the increased risk for developing obesity-associated diseases shown by men, even in morbid obesity, in which the massive fat accumulation could mask these differences. Furthermore, the leptin content of fat depots as well as plasma insulin concentrations appear in our population as the main determinants of adipose tissue LPL activity, adjusted by gender, depot and BMI.     

Glucokinase overexpression restores glucose utilization and storage in cultured hepatocytes from male Zucker diabetic fatty rats.

Zucker diabetic fatty rats develop type 2 diabetes concomitantly with peripheral insulin resistance. Hepatocytes from these rats and their control lean counterparts have been cultured, and a number of key parameters of glucose metabolism have been determined. Glucokinase activity was 4.5-fold lower in hepatocytes from diabetic rats than in hepatocytes from healthy ones. In contrast, hexokinase activity was about 2-fold higher in hepatocytes from diabetic animals than in healthy ones. Glucose-6-phosphatase activity was not significantly different. Despite the altered ratios of glucokinase to hexokinase activity, intracellular glucose 6-phosphate concentrations were similar in the two types of cells when they where incubated with 1-25 mM glucose. However, glycogen levels and glycogen synthase activity ratio were lower in hepatocytes from diabetic animals. Total pyruvate kinase activity and its activity ratio as well as fructose 2,6-bisphosphate concentration and lactate production were also lower in cells from diabetic animals. All of these data indicate that glucose metabolism is clearly impaired in hepatocytes from Zucker diabetic fatty rats. Glucokinase overexpression using adenovirus restored glucose metabolism in diabetic hepatocytes. In glucokinase-overexpressing cells, glucose 6-phosphate levels increased. Moreover, glycogen deposition was greatly enhanced due to the activation of glycogen synthase. Pyruvate kinase was also activated, and fructose-2,6-bisphosphate concentration and lactate production were increased in glucokinase-overexpressing diabetic hepatocytes. Overexpression of hexokinase I did not increase glycogen deposition. In conclusion, hepatocytes from Zucker diabetic fatty rats showed depressed glycogen and glycolytic metabolism, but glucokinase overexpression improved their glucose utilization and storage.     

Effective control of glycemic status and toxicity in Zucker diabetic fatty rats with an orally administered vanadate compound

A novel black tea decoction containing vanadate has successfully replaced insulin in a rat model of insulin-dependent diabetes but is untested in non-insulin-dependent diabetic animals. A tea-vanadate decoction (TV) containing 30 or 40 mg sodium orthovanadate was administered by oral gavage to two groups of Zucker diabetic fatty rats and a conventional water vehicle containing 30 or 40 mg of sodium orthovanadate to two others. In the latter group receiving the 30-mg dose, vanadate induced diarrhea in 50% of the rats and death in 10%. In contrast, TV-treated rats had no incidence of diarrhea and no deaths. Symptoms were more severe in both groups with higher vanadate doses, so these were discontinued. After approximately 16 weeks, the level of vanadium in plasma and tissue extracts was negligible in a further group of untreated rats but highly elevated after vanadate treatment. Vanadium levels were not significantly different between the TV-treated diabetic rats and the diabetic rats given vanadate in a water vehicle. Over the 115 days of the study, blood glucose levels increased from approximately 17 to 25 mmol/L in untreated diabetic rats. This was effectively lowered (to <10 mmol/L) by TV treatment. Fasting blood glucose levels were 5, 7, and 20 mmol/L in control (nondiabetic, untreated), TV-treated and untreated diabetic rats, respectively. Rats required treatment with TV for only approximately 50% of the days in the study. Increase in body mass during the study was significantly lower in untreated diabetic rats (despite higher food intake) than the other groups. Body mass gain and food intake were normal in TV-treated rats. Water intake was 28 mL/rat daily in control rats, 130 mL/rat daily in untreated diabetic rats, and 52 mL/rat daily in TV-treated diabetic rats. Plasma creatinine and aspartate aminotransferase levels were significantly depressed in untreated diabetic rats, and TV treatment normalized this. Our results demonstrate that a novel oral therapy containing black tea and vanadate possesses a striking capacity to regulate glucose and attenuates complications in a rat model of type II diabetes.     

Caloric restriction induces changes in insulin and body weight measurements that are inversely associated with subsequent weight regain

Background

Successful weight maintenance following weight loss is challenging for many people. Identifying predictors of longer-term success will help target clinical resources more effectively. To date, focus has been predominantly on the identification of predictors of weight loss. The goal of the current study was to determine if changes in anthropometric and clinical parameters during acute weight loss are associated with subsequent weight regain.

Methodology

The study consisted of an 8-week low calorie diet (LCD) followed by a 6-month weight maintenance phase. Anthropometric and clinical parameters were analyzed before and after the LCD in the 285 participants (112 men, 173 women) who regained weight during the weight maintenance phase. Mixed model ANOVA, Spearman correlation, and linear regression were used to study the relationships between clinical measurements and weight regain.

Principal Findings

Gender differences were observed for body weight and several clinical parameters at both baseline and during the LCD-induced weight loss phase. LCD-induced changes in BMI (Spearman’s ρ = 0.22, p = 0.0002) were inversely associated with weight regain in both men and women. LCD-induced changes in fasting insulin (ρ = 0.18, p = 0.0043) and HOMA-IR (ρ = 0.19, p = 0.0023) were also associated independently with weight regain in both genders. The aforementioned associations remained statistically significant in regression models taking account of variables known to independently influence body weight.

Conclusions/Significance

LCD-induced changes in BMI, fasting insulin, and HOMA-IR are inversely associated with weight regain in the 6-month period following weight loss.     

Prostatic androgen receptor and plasma testosterone levels in streptozotocin-induced diabetic rats.

Diabetes was induced in male Sprague-Dawley (S-D) rats by streptozotocin (STZ) administration. Following STZ injection, plasma glucose levels in the treated rats were significantly elevated from values of untreated controls. Over the experimental period (140 days) plasma testosterone (T) levels, prostatic nuclear androgen receptor (AR) contents and prostatic weights declined with increasing age in the rats. The declines in both STZ-treated and untreated rats were similar in manner and no notable differences were discerned in the data obtained from the two groups. On the contrary, prostatic cytosolic AR contents in untreated rats remained unchanged with advancing age, but was reduced to 50% of normal control values in diabetic rats following STZ treatment. Correlation analyses revealed that prostatic nuclear AR contents correlated positively with plasma T levels while prostatic cytosolic AR contents correlated negatively with plasma glucose levels. These data support former claims that prostatic nuclear AR content is dependent on circulating T level and suggest a possible link between prostatic cytosolic AR content and plasma glucose concentrations.     

Increased body fat in streptozotocin diabetic rats treated with intensive subcutaneous insulin therapy vs. islet transplantation

The continued development of novel insulin treatment is predicated on the hypothesis that strict glycemic control is necessary to prevent the secondary complications of diabetes. Although dramatically successful in reducing selected secondary complications, intensive insulin therapy has consequences. These include hypoglycemia, weight gain, and body fat accumulation. In the present studies we compared a model of intensive insulin therapy in diabetic rats and contrasted weight gain and body fat accumulation with pancreatic islet transplantation. Female Wistar Furth rats (173 g) administered streptozotocin (55 mg x kg(-1), iv) remained diabetic (DB) for four or nine weeks. At week three, a third group was transplanted (TRAN) with islets of Langerhans (3519 +/- 838 150 microm islets); one week later group four began intensive subcutaneous insulin therapy (ISIT; 4 x 0.5-1.0 U regular insulin x day(-1)). Within one week ISIT rats had normalized plasma glucose; levels were not different from age matched controls (CN) or TRAN animals (ISIT 10.6 +/- 1.7, CN 7.2 +/- 0.4, TRAN 7.7 +/- 0.8 mmol x L(-1), P > 0.05). The cumulative occurrence of one episode of hypoglycemia (< 2.8 mmol x L(-1)) occurred in 50% of ISIT rats. At study termination, body weight of ISIT and CN rats did not differ (199 +/- 4 vs. 207 +/- 3, P > 0.05). While carcass protein content was similar for TRAN, ISIT, and CN animals, the body fat of ISIT animals was 24% greater than in CN rats and 21% greater than in TRAN rats (P < 0.05). Correlation of body fat vs. plasma glucose illustrated hypoglycemia contributed to the body fat gain of ISIT rats (n = 8, r = -0.70, P = 0.0535). These studies illustrate a disproportionate gain of body fat from ISIT, an effect not observed with islet transplantation. Thus, the metabolic benefit ascribed to islet transplantation appears related to the absence of hypoglycemia.     

Reduced plasma dehydroepiandrosterone sulfate levels are significantly correlated with fatigue severity in patients with primary biliary cirrhosis

Fatigue is a common debilitating complication of primary biliary cirrhosis (PBC), the pathophysiologic mechanism of which is poorly understood. Recently, the neuroactive steroid dehydroepinadrosterone sulfate (DHEAS) was reported to be implicated in Chronic Fatigue Syndrome in the absence of liver disease. The present study was undertaken to analyse fatigue scores and their relationship with disease severity and circulating levels of DHEAS as well as its precursors DHEA and pregnenolone in PBC patients with (n=15) or without fatigue (n=10) compared to control subjects (n=11). Fatigue was assessed using the fatigue impact scale (FIS) including cognitive, physical and psychosocial subclasses. Steroids were measured by radioimmunoassay or gas chromatography/mass spectrometry. Plasma concentrations of DHEAS were significantly reduced in PBC patients with fatigue as compared to controls, while those of its precursors DHEA and pregnenolone remained within the control range. Plasma levels of DHEAS in PBC patients were significantly correlated with fatigue severity as reflected by total FIS scores including total (rp=-0.42; p=0.018), as well as the cognitive (rp=-0.37; p=0.03), physical (rp=-0.48; p=0.006) and psychosocial (rp=-0.35; p=0.04) subclasses of fatigue scores. No correlation of fatigue scores was observed with indices of liver function. These findings suggest that reduced levels of the neurosteroid DHEAS may contribute to fatigue in patients with PBC; substitutive therapy using DHEAS or its precursor DHEA could be beneficial in the management of fatigue in patients with low levels of DHEAS.     

Glucose tolerance, plasma and pancreatic insulin levels in zinc deficient rats.

Two experiments were conducted to examine the effect of zinc deficiency on glucose tolerance, and on blood and pancreatic insulin concentrations. In the first study, no significant differences in blood glucose or plasma insulin levels were noted between pair-weighted zinc deficient and zinc sufficient rats after an oral glucose load. In the second experiment, the concentration of pancreatic insulin in pair-fed zinc sufficient rats did not differ significantly from that of zinc deficient rats. However, a zinc deficient group fed ad libitum had significantly lower pancreatic insulin levels, suggesting that food restriction may cause increased pancreatic insulin. Thus, zinc deficiency per se had no apparent effect on oral glucose tolerance or pancreatic insulin concentrations.     

Effect of serum estradiol and leptin levels on thyroid function, food intake and body weight gain in female Wistar rats

We evaluated the interplay among estrogen, leptin and thyroid function in the regulation of body mass in female rats. Adult female rats were divided into four groups: control (C, sham-operated), ovariectomized (OVX), ovariectomized treated with estradiol benzoate (Eb) 0.7 or 14 μg/100 g bw per day, during 21 days. OVX led to an increase in body mass, food intake and food efficiency (change in body mass as function of the amount of food ingested) which were normalized by the lower Eb dose, and decreased significantly when the higher dose was given. Serum leptin levels were increased more than two-fold in all ovariectomized groups. Serum T4 levels of the Eb treated OVX were significantly lower than in the controls. Serum T3 and TSH were unaffected by OVX or by Eb treatment. Uterine type 2 iodothyronine deiodinase (D2) activity changed in parallel with serum estradiol: decreased after OVX, returned to control levels after the lower E2 treatment, and increased significantly after the high Eb dosage. The hypothalamic D2 activity was reduced around 30% in all castrated groups, treated or not with estrogen, whereas in the brown adipose tissue the enzyme was not changed. Interestingly, although estrogen-treated OVX rats had lower body weight, serum leptin was high, suggesting that estrogen increases leptin secretion. Our results show that estradiol is necessary for the hypothalamic action of leptin, since the increase in leptin levels observed in all ovariectomized rats was associated with a decrease in food intake and food efficiency only in the rats treated with estrogen.