Increased weight gain after ovariectomy is not a consequence of leptin resistance

Estrogen deficiency reduces maximal running capacity and affects serotonin levels differently in the hippocampus and nucleus accumbens in response to acute exercise

Introduction

Estrogen deficiency is associated with unfavorable changes in body composition and metabolic health. While physical activity ameliorates several of the negative effects, loss of ovarian function is associated with decreased physical activity levels. It has been proposed that the changes in brain neurochemical levels and /or impaired skeletal muscle function may underlie this phenomenon.

Methods

We studied the effect of estrogen deficiency induced via ovariectomy (OVX) in female Wistar rats (n = 64). Rats underwent either sham or OVX surgery and were allocated thereafter into four groups matched for body mass and maximal running capacity: sham/control, sham/max, OVX/control, and OVX/max, of which the max groups had maximal running test before euthanasia to induce acute response to exercise. Metabolism, spontaneous activity, and maximal running capacity were measured before (PRE) and after (POST) the surgeries. Three months following the surgery, rats were euthanized, and blood and tissue samples harvested. Proteins were analyzed from gastrocnemius muscle and retroperitoneal adipose tissue via Western blot. Brain neurochemical markers were measured from nucleus accumbens (NA) and hippocampus (HC) using ultra-high performance liquid chromatography.

Results

OVX had lower basal energy expenditure and higher body mass and retroperitoneal adipose tissue mass compared with sham group (p ≤ 0.005). OVX reduced maximal running capacity by 17% (p = 0.005) with no changes in muscle mass or phosphorylated form of regulatory light chain (pRLC) in gastrocnemius muscle. OVX was associated with lower serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) level in the NA compared with sham (p = 0.007). In response to acute exercise, OVX was associated with low serotonin level in the HC and high level in the NA (p ≤ 0.024).

Discussion

Our results highlight that OVX reduces maximal running capacity and affects the response of brain neurochemical levels to acute exercise in a brain region-specific manner. These results may offer mechanistic insight into why OVX reduces willingness to exercise.

Calcium Deficiency Decreases Bone Mass without Affecting Adiposity in Ovariectomized Rats Fed a High-Fat Diet

Obesity induced by a high-fat (HF) diet increases bone resorption and/or decreases bone formation, resulting in reduced bone mass and strength in various animal models. Studies showed that Ca intake is a modifiable factor for osteoporosis and obesity. This study investigated whether Ca deficiency affects bone structure and adiposity in ovariectomized (OVX) rats fed a HF diet. We hypothesized that Ca deficiency further decreases bone mass and increases fat mass in HF-fed OVX rats. Forty-seven OVX at 6-month-old were randomly assigned to four groups in a 2 × 2 factorial design: normal-fat (NF, 10% fat as energy) or HF (45% fat as energy) diet with either low Ca (LC, 1 g/4057 kcal) or normal Ca (NC, 6 g/4057 kcal). In addition, 12 sham-operated rats at 6 months old were fed a NFNC diet as a control for the OVX procedure. Rats were fed the respective diet for 4 months. Dietary Ca content did not affect body weight, fat mass, lean mass, food intake, energy intake, and serum cytokines. Compared to NC, LC resulted in lower tibial bone volume/total volume (BV/TV, p < 0.01), connectivity density (p < 0.01), trabecular number (Tb.N, p = 0.01), bone mineral density (BMD, p < 0.01), and femur weight (p < 0.01), femur content of Ca (p < 0.01), Cu (p = 0.03), Zn (p < 0.01), and greater trabecular separation (Tb.Sp, p < 0.01) at proximal tibia indicating bone structure deterioration. Compared to rats on the NF diet, animals fed the HF had lower BV/TV (p = 0.03) and Tb.N (p < 0.01) with greater body weight (p < 0.01), fat mass (p < 0.01), Tb.Sp (p = 0.01), the content of Ca, Cu, and Zn in the femur, and serum leptin (p < 0.01). There were no significant interactions between Ca and fat for body composition and bone structural parameters. Compared to Sham, OVX resulted in greater body weight and fat mass. The trabecular bone structure of the tibia, but not the cortical bone, was significantly impaired by the OVX procedure. These data indicate that inadequate Ca intake and a high-fat diet have independent negative effects on bone structure and that Ca deficiency does not affect adiposity in OVX rats.

Prefrontal representation of affective stimuli: importance of stress, sex, and context

Stress-related disorders such as depression and anxiety exhibit sex differences in prevalence and negatively impact both mental and physical health. Affective illness is also frequently accompanied by changes in ventromedial prefrontal cortical (vmPFC) function. However, the neurobiology that underlies sex-specific cortical processing of affective stimuli is poorly understood. Although rodent studies have investigated the prefrontal impact of chronic stress, postmortem studies have focused largely on males and yielded mixed results. Therefore, genetically defined population recordings in behaving animals of both sexes were used to test the hypothesis that chronic variable stress (CVS) impairs the neural processing of affective stimuli in the rodent infralimbic region. Here, we targeted expression of a calcium indicator, GCaMP6s, to infralimbic pyramidal cells. In males, CVS reduced infralimbic responses to social interaction and restraint stress but increased responses to novel objects and food reward. In contrast, females did not have CVS-induced changes in infralimbic activity, which was partially dependent on the ovarian status. These results indicate that both male and female vmPFC cells encode social, stress, and reward stimuli. However, chronic stress effects are sex-dependent and behavior-specific. Ultimately, these findings extend the understanding of chronic stress-induced prefrontal dysfunction and indicate that sex is a critical factor for cortical processing of affective stimuli.

Ovariectomy Increases Circulating Retinol-Binding Protein Concentrations Independently of Sex-Dependent Differences in Retinol Concentrations in Rats

BACKGROUND

There is a sex-dependent difference in blood retinol and RBP concentrations, and plasma RBP is associated with insulin resistance.

OBJECTIVES

We aimed to clarify sex-dependent variations in body concentrations of retinol and RBPs and their association with sex hormones in rats.

METHODS

Plasma and liver retinol concentrations and hepatic mRNA and plasma concentrations of RBP4 were analyzed in 3- and 8-wk-old male and female Wistar rats before and after sexual maturity (experiment 1) and in orchiectomized male Wistar rats (experiment 2) and ovariectomized female Wistar rats (experiment 3). Furthermore, the mRNA and protein concentrations of RBP4 in adipose tissue were measured in ovariectomized female rats (experiment 3).

RESULTS

There were no sex-dependent differences in liver retinyl palmitate and retinol concentrations; however, the plasma retinol concentration was significantly higher in male rats than that in female rats after sexual maturity. Furthermore, the plasma retinol concentrations did not differ between the ovariectomized or orchiectomized rats and the control rats. Plasma Rbp4 mRNA concentrations were higher in male rats than those in female rats but not in castrated and control rats, a change consistent with plasma retinol concentration. Plasma RBP4 concentrations were also higher in male rats than those in female rats; however, unlike liver Rbp4 gene expression, plasma RBP4 concentrations were 7-fold higher in the ovariectomized rats than those in the control rats. Moreover, the Rbp4 mRNA concentrations in inguinal white adipose tissue was significantly higher in the ovariectomized rats than those in the control rats and correlated with plasma RBP4 concentrations.

CONCLUSIONS

Hepatic Rbp4 mRNA is higher in male rats through a sex hormone-independent mechanism, which may contribute to sex differences in blood retinol concentrations. Furthermore, ovariectomy leads to an increase in adipose tissue Rbp4 mRNA and blood RBP4 concentrations, which may contribute to insulin resistance in ovariectomized rats and postmenopausal women.

Food-seeking behavior is triggered by skin ultraviolet exposure in males

Sexual dimorphisms are responsible for profound metabolic differences in health and behavior. Whether males and females react differently to environmental cues, such as solar ultraviolet (UV) exposure, is unknown. Here we show that solar exposure induces food-seeking behavior, food intake, and food-seeking behavior and food intake in men, but not in women, through epidemiological evidence of approximately 3,000 individuals throughout the year. In mice, UVB exposure leads to increased food-seeking behavior, food intake and weight gain, with a sexual dimorphism towards males. In both mice and human males, increased appetite is correlated with elevated levels of circulating ghrelin. Specifically, UVB irradiation leads to p53 transcriptional activation of ghrelin in skin adipocytes, while a conditional p53-knockout in mice abolishes UVB-induced ghrelin expression and food-seeking behavior. In females, estrogen interferes with the p53-chromatin interaction on the ghrelin promoter, thus blocking ghrelin and food-seeking behavior in response to UVB exposure. These results identify the skin as a major mediator of energy homeostasis and may lead to therapeutic opportunities for sex-based treatments of endocrine-related diseases.

Effects of long term diabetogenic high fat diet on bone in ovariectomized female rats

A diabetogenic high fat diet (HFD) can be used to induce insulin resistance and obesity in animal models; however, its effects on bone are unknown. We investigated the effects of long term HFD on bone in ovariectomized (OVX) female rats. We used 12-week-old female rats divided randomly into four groups: sham operation (sham), sham operation with HFD (SHFD), OVX and OVX with HFD (OVX + HFD). Ovaries were removed in the OVX and OVX + HFD groups and the SHFD and OVX + HFD groups were fed a HFD for 28 weeks. Serum estrogen, testosterone, lipid, adiponectin, leptin, tartrate-resistant acid phosphatase (TRAP) and N-mid fragment of osteocalcin (N-MID-OT) levels were measured. Structure, apoptosis and specific transcription factors in bone were evaluated using pathologic, densitometric and immunohistochemical analysis. Body weight, serum leptin, TRAP and testosterone levels were increased, while serum N-MID-OT, estrogen and adiponectin levels were decreased in the SHFD, OVX and OVX + HFD groups. Expression of BCL2-associated X protein, caspase-3, matrix metalloproteinase-9 and calcitonin was increased, while bone mineral density (BMD) and content (BMC) in femurs and lumbar spine, and expression of B cell lymphoma 2, type 1 collagen and osteocalcin were decreased in the bones of the SHFD, OVX and OVX + HFD groups. All indices were greatest in the OVX + HFD group and HFD produced a detrimental effect on bone in both normal and OVX rats, which may be due to increased apoptosis in bone and increased leptin and decreased adiponectin levels in serum. The effects of HFD and OVX may be synergistic.

Characterization of the metabolic differences between male and female C57BL/6 mice

AIMS

The present study aims to compare the responses between male and female C57BL/6 mice to multiple metabolic challenges to understand the importance of sex in the control of energy homeostasis.

MAIN METHODS

Male and female C57BL/6 mice were subjected to nutritional and hormonal challenges, such as food restriction and refeeding, diet-induced obesity, feeding response to ghrelin and leptin, ghrelin-induced growth hormone secretion, and central responsiveness to ghrelin and leptin. The hypothalamic expression of transcripts that control energy homeostasis was also evaluated.

KEY FINDINGS

Male mice lost more weight and lean body mass in response to food restriction, compared to females. During refeeding, males accumulated more body fat and exhibited lower energy expenditure and glycemia, as compared to females. Additionally, female mice exhibited a higher protection against diet-induced obesity and related metabolic imbalances in comparison to males. Low dose ghrelin injection elicited higher food intake and growth hormone secretion in male mice, whereas the acute anorexigenic effect of leptin was more robust in females. However, the sex differences in the feeding responses to ghrelin and leptin were not explained by variations in the central responsiveness to these hormones nor by differences in the fiber density from arcuate nucleus neurons. Female, but not male, mice exhibited compensatory increases in hypothalamic Pomc mRNA levels in response to diet-induced obesity.

SIGNIFICANCE

Our findings revealed several sexually differentiated responses to metabolic challenges in C57BL/6 mice, highlighting the importance of taking into account sex differences in metabolic studies.

Modulation by Estradiol of L-Dopa-Induced Dyskinesia in a Rat Model of Post-Menopausal Hemiparkinsonism

Treatment with levodopa (L-dopa) in Parkinson’s disease (PD) leads to involuntary movements termed L-dopa-induced dyskinesia (LID). There are contradictory data about the influence of hormone therapy in female PD patients with LID and of 17-β-estradiol (E2) on animal correlates of LID-abnormal involuntary movements (AIMs). Our aim was to characterize the influence of E2 on motor impairment and AIMs in ovariectomized 6-hydroxydopamine (6-OHDA) rat model of PD. Half of the rats received empty and the other half implants filled with E2. Following the 6-OHDA surgery, the rats received daily treatment with either L-dopa or saline for 16 days. They were assessed for AIMs, contralateral rotations, and FAS. In the L-dopa-treated rats, E2 intensified and prolonged AIMs and contralateral rotations. On the other hand, it had no effect on motor impairment. Postmortem tyrosine hydroxylase immunostaining revealed an almost complete unilateral lesion of nigrostriatal dopaminergic neurons. E2 partially prevented the upregulation of striatal ΔFosB caused by dopamine depletion. L-dopa potentiated the upregulation of ΔFosB within the dopamine-depleted striatum and this effect was further enhanced by E2. We speculate that the potentiating effects of E2 on AIMs and on contralateral rotations could be explained by the molecular adaptations within the striatal medium spiny neurons of the direct and indirect striatofugal pathways.

Emerging roles for kisspeptin in metabolism

Kisspeptin, a neuropeptide hormone, has been firmly established as a key regulator of the hypothalamic-pituitary-gonadal axis and mammalian reproductive behaviour. In recent years, a growing body of evidence has emerged suggesting a role for kisspeptin in regulating metabolic processes. This data suggest that kisspeptin exerts its metabolic effects indirectly via gonadal hormones and/or directly via the kisspeptin receptor in the brain, pancreas and brown adipose tissue. Kisspeptin receptor knockout studies indicate that kisspeptin may play sexually dimorphic roles in the physiological regulation of energy expenditure, food intake and body weight. Some, but not all, in vitro work demonstrates positive effects on glucose-stimulated insulin secretion, which is more marked at higher kisspeptin concentrations. Acute and chronic in vivo rodent, non-human primate and human studies reveal enhancement of glucose-stimulated insulin secretion in response to pharmacological doses of kisspeptin. Although significant progress has been made in elucidating the metabolic effects of kisspeptin, further mechanistic work and translational studies are required to address unanswered questions and establish the metabolic effects of kisspeptin in diverse human populations (including women, people with obesity and people with diabetes).

The effects of eggshell calcium (Biomin H® ) and its combinations with alfacalcidol (1α-hydroxyvitamin D3) and menaquinone-7 (vitamin K2) on ovariectomy-induced bone loss in a rat model of osteoporosis

The purpose of this study was to investigate the impact of eggshell calcium (Biomin H® dietary supplement) and its combinations with alfacalcidol (1α-hydroxyvitamin D3 ) and menaquinone-7 (vitamin K2 ) on ovariectomy-induced bone loss in rats. Adult female rats (n = 48) were divided into 6 groups of 8 individuals each: sham-operated rats (SHAM); ovariectomized (OVX) rats untreated; OVX rats treated with Biomin H® (BIO); OVX rats simultaneously receiving Biomin H® , vitamin D3 (BIO + D3 ); OVX rats simultaneously treated with Biomin H® , vitamin K2 (BIO + K2 ) and OVX rats treated with Biomin H® , vitamin D3 , vitamin K2 (BIO + D3  + K2 ) during 8 weeks. Biochemical parameters, bone mineral density (BMD), bone mineral content (BMC) and femoral bone microstructure were determined. Plasma calcium and phosphate were increased in BIO + D3 and BIO + D3  + K2 groups as compared to OVX. Alkaline phosphatase was elevated in OVX, BIO versus SHAM, BIO + D3  + K2 groups. When compared to OVX group, decreased urine deoxypyridinoline was observed in all treated groups and femoral BMD, BMC were higher in BIO, BIO + D3 , BIO + D3  + K2 groups. The BIO + K2 rats had similar densitometrical values than OVX individuals. Microcomputed tomography revealed increased trabecular relative bone volume (due to an increase in trabecular number) in BIO + D3 , BIO + D3  + K2 as compared to OVX. The higher relative bone volume in BIO + D3 , BIO + D3  + K2 groups was also accompanied by an increase in bone surface. In the cortical bone, an enhanced periosteal bone apposition was identified in BIO, BIO + D3 , BIO + K2 , BIO + D3  + K2 groups. The rats from BIO + D3  + K2 group had a higher area of primary osteon's vascular canals. In BIO + D3 , BIO + K2 , BIO + D3  + K2 groups, an increased area of secondary osteons was determined in comparison with OVX. Our results indicate the beneficial effect of triple application of Biomin H® , vitamin D3 , vitamin K2 , as well as simultaneous administration of Biomin H® , vitamin D3 on the inhibition of ovariectomy-induced bone loss in a rat model of osteoporosis.

Sex differences impact the pancreatic response to chronic immobilization stress in rats

Chronic stress has been related to multiple diseases. Inflammation is proposed strongly to link stress to stress-related diseases in different organs, such as small intestine, colon, and brain. However, stress cellular effect on the pancreatic tissue, especially the exocrine one, had received relatively little attention. This work aimed to evaluate the cellular effect of chronic immobilization stress on the pancreatic tissue function and structure along with evaluating the sex role in this type of pancreatic injury. Thirty rats were equally divided into 5 groups: control male, control female, stressed male, stressed female, and stressed female with bilateral ovariectomy. Stressed rats were exposed to immobilization for 1 h/day, 6 days/week, for 3 weeks. Rats were then decapitated for further biochemical, histological, histo-morphometric, and immunohistochemical study. The results showed that, in male and female rats, chronic immobilization stress produced hypoinsulinemia and hyperglycemia, with increasing exocrine pancreatic injury markers by increasing oxidative and inflammatory status of the pancreatic tissue, and exhibited a degenerative effect on the pancreatic tissue. However, the stress-induced pancreatic effects were more obvious in male rats and female rats with bilateral ovariectomy than that in female rats. It could be concluded that male animals were more susceptible to stress-induced pancreatic damage than females. The ovarian hormones are responsible, at least partly, for pancreatic tissue protection since the stress-induced pancreatic injury in females was exacerbated by ovariectomy. In this study, inflammatory and oxidative stress differences in both sexes could provide a plausible explanation for sex differences.

Sleeve gastrectomy-induced endocrine changes in the remnant stomachs of premenopausal and postmenopausal rats: role of the estrogen receptors

BACKGROUND

Although alterations in the plasma levels of leptin, glucagon-like peptide-1, and gastrin were linked with bariatric surgery outcomes, gastric production of these peptides was not elucidated before.

OBJECTIVE

The aim was to evaluate the impact of estrogen depletion and estrogen receptors (ERs) on sleeve gastrectomy (SG)-induced alterations in gastric hormone production, gastric mucosal integrity, and bone mass.

SETTING

Physiology Research Lab at the University.

METHODS

Female Sprague-Dawley rats underwent ovariectomy or sham operation (control), and 2 months later SG or sham SG was performed. Rats received either nonselective agonist 17 β, ER-α agonist, ER-β agonist, or vehicle for 3 weeks. Trunk blood and gastric tissues were collected for biochemical measurements, while histopathologic examination was performed in gastric and femur samples.

RESULTS

In the presence of intact ovaries, SG-induced weight loss was accompanied by reductions in the gastric synthesis of leptin and gastrin, while gastric glucagon-like peptide-1 was additionally decreased when SG was performed at the postmenopausal state. SG elevated the depleted serum estradiol levels of menopause, implicating a beneficial effect, but the occurrence of severe gastric mucosal injury was triggered. On the other hand, using ER agonists upregulated gastrin-expressing cells, ameliorated gastric injury, and improved bone loss.

CONCLUSIONS

SG, either at premenopausal or postmenopausal state, resulted in considerable loss in bone mass, along with reductions in the gastric levels of gastrin and leptin. Functional status of the ovaries needs to be taken into consideration when monitoring the outcomes of SG, and ER agonists could be of value in controlling SG-induced complications.

Oral Delivery of Teriparatide Using a Nanoemulsion System: Design, in Vitro and in Vivo Evaluation

PURPOSE

Investigate the possibility of delivering teriparatide orally using nanoemulsion.

METHOD

Teriparatide was allowed to interact with chitosan in the presence of HPβCD.The formed polyelectrolyte complex (PEC) was characterized by DSC, FTIR, DLS and for entrapment efficiency. PEC was the incorporated in an oil phase consisting of Oleic Acid, Labrasol and Plurol Oleique to form a nanoemulsion. This preparation was characterized for refractive index, viscosity, pH, conductivity, particle size, and morphology.Bioavailability of the preparation was evaluated using rabbits against SC injection. The efficacy of the formula was tested using ovariectomized rats (an osteoporosis animal model) and mechanical and histological tests were conducted on their bones. The stability of the preparation was evaluated by storing samples at 4^o C, 25^o C and 40^o C for three months.

RESULTS

PEC testing demonstrate a complex formation with particle size of 208 nm, zeta potential of +17 mV and entrapment efficiency of 49%. For the nanoemulsion, the results demonstrate the formation of a nano-sized dispersed system (108 nm) with a drug loading of 98% and a percent protection of 90% and 71% in SGF and SIF respectively. Bioavailability results showed a sustained release profile was achieved following the oral formulation administration. Efficacy studies showed improvement in the strength, thickness and connectivity of bones. Short-term stability study demostrated that the nanoemulsion is mostly stable at 4^o C.

CONCLUSION

These findings demonstrate the ability of delivering Teriparatide orally using oleic acid based dispersion in combination with chitosan PEC.

Integrin β3 Deficiency Results in Hypertriglyceridemia via Disrupting LPL (Lipoprotein Lipase) Secretion

OBJECTIVE

Integrin β3 is implicated in numerous biological processes such as its relevance to blood triglyceride, yet whether β3 deficiency affects this metabolic process remains unknown. Approach and Results: We showed that the Chinese patients with β3-deficient Glanzmann thrombasthenia had a 2-fold higher serum triglyceride level together with a lower serum LPL (lipoprotein lipase) level than those with an αIIb deficiency or healthy subjects. The β3 knockout mice recapitulated these phenotypic features. The elevated plasma triglyceride level was due to impaired LPL-mediated triglyceride clearance caused by a disrupted LPL secretion. Further analysis revealed that β3 directly bound LPL via a juxtamembrane TIH (threonine isoleucine histidine)^720-722 motif in its cytoplasmic domain and functioned as an adaptor protein by interacting with LPL and PKD (protein kinase D) to form the PKD/β3/LPL complex that is required for β3-mediated LPL secretion. Furthermore, the impaired triglyceride clearance in β3 knockout mice could be corrected by adeno-associated virus serotype 9 (AAV9)-mediated delivery of wild-type but not TIH^720-722-mutated β3 genes.

CONCLUSIONS

This study reveals a hypertriglyceridemia in both β3-deficient Chinese patients and mice and provides novel insights into the molecular mechanisms of the significant roles of β3 in LPL secretion and triglyceride metabolism, drawing attention to the metabolic consequences in patients with β3-deficient Glanzmann thrombasthenia.

Comparison of high-fat style diet-induced dysregulation of baroreflex control of renal sympathetic nerve activity in intact and ovariectomized female rats: Renal sympathetic nerve activity in high-fat style diet fed intact and ovariectomized female rats

IMPACT STATEMENT

Over activation of renal sensory nerve in obesity blunts the normal regulation of renal sympathetic nerve activity. To date, there is no investigation that has been carried out on baroreflex regulation of renal sympathetic nerve activity in obese ovarian hormones deprived rat model, and the effect of renal denervation on the baroreflex regulation of renal sympathetic nerve activity. Thus, we investigated the role of renal innervation on baroreflex regulation of renal sympathetic nerve activity in obese intact and ovariectomized female rats. Our data demonstrated that in obese states, the impaired baroreflex control is indistinguishable between ovarian hormones deprived and non-deprived states. This study will be of substantial interest to researchers working on the impact of diet-induced hypertension in pre- and postmenopausal women. This study provides insight into health risks amongst obese women regardless of their ovarian hormonal status and may be integrated in preventive health strategies.

The capacity for oestrogen to influence obesity through brown adipose tissue thermogenesis in animal models: A systematic review and meta-analysis

Pharmacological interventions to aid weight loss have historically targeted either appetite suppression or increased metabolic rate. Brown adipose tissue (BAT) possesses the capacity to expend energy in a futile cycle, thus increasing basal metabolic rate. In animal models, oestrogen has been implicated in the regulation of body weight, and it is hypothesized that oestrogen is acting by modulating BAT metabolism. A systematic search was performed, to identify research articles implementing in vivo oestrogen-related interventions and reporting outcome measures that provide direct or indirect measures of BAT metabolism. Meta-analyses were conducted where sufficient data were available. The final library of 67 articles were predominantly in rodent models and provided mostly indirect measures of BAT metabolism. Results of this review found that oestrogen's effects on body weight, in rats and possibly mice, are likely facilitated by both metabolic and appetitive mechanisms but are largely only found in ovariectomized models. There is a need for further studies to clarify the potential effects of oestrogen on BAT metabolism in gonad-intact and castrated male animal models.

miR-146b-5p has a sex-specific role in renal and cardiac pathology in a rat model of chronic kidney disease

Chronic kidney disease presents a complex and distinct pathological landscape in men and women, yet this difference is poorly understood. microRNAs are powerful molecular regulators of pathophysiology in the kidney and other organs. We previously reported a significant upregulation of miR-146b-5p in the 5/6 nephrectomy rat model of chronic kidney disease. Here we investigated the sex-specific contribution of miR-146b-5p to renocardiac pathology by generating a novel miR-146b^-/- rat and characterized the expression of miR-146b-5p in both wild-type and knockout animals. The 5/6 nephrectomy or sham surgery was performed on rats of each genotype and sex. Renal pathology was examined through gross histology, plasma and urinary analysis of electrolytes and metabolites, and by chronic blood pressure monitoring. Cardiac pathology was monitored via echocardiography and pressure-volume analysis. The miR-146b^-/- rats show functional knockout of miR-146b-5p in both the kidney and heart. While 5/6 nephrectomy induced tissue hypertrophy, miR-146b^-/- female rats displayed exacerbated renal hypertrophy. Additionally, miR-146b^-/- female rats exhibited a marked elevation of renal fibrosis and significant renal dysfunction yet lower blood pressure and less pronounced cardiac remodeling. These phenotypic differences were not exhibited in miR-146b^-/- male rats. Ovariectomy ameliorated renal pathology and abolished genotypic differences. In vitro examination of transforming growth factor-β signaling in combination with miR-146b-5p manipulation supports a role for miR-146b-5p in mediating the protective benefit of estrogen from renal pathologies. Thus, our data highlight an important role of miR-146b-5p in modulating kidney disease progression and provide new avenues for the study of sex-specific pathology.

Rehmanniae Radix Preparata suppresses bone loss and increases bone strength through interfering with canonical Wnt/β-catenin signaling pathway in OVX rats

Rehmanniae Radix Preparata (RRP) improves bone quality in OVX rats through the regulation of bone homeostasis via increasing osteoblastogenesis and decreasing osteoclastogenesis, suggesting it has a potential for the development of new anti-osteoporotic drugs.

INTRODUCTION

Determine the anti-osteoporotic effect of RRP in ovariectomized (OVX) rats and identify the signaling pathway involved in this process.

METHODS

OVX rats were treated with RRP aqueous extract for 14 weeks. The serum levels of tartrate-resistant acid phosphatase (TRAP), receptor activator of nuclear factor kappa-Β ligand (RANKL), alkaline phosphatase (ALP), and osteoprotegerin (OPG) were determined by ELISA. Bone histopathological alterations were evaluated by H&E, Alizarin red S, and Safranin O staining. Bone mineral density (BMD) and bone microstructure in rat femurs and lumbar bones were determined by dual-energy X-ray absorptiometry and micro-computed tomography. Femoral bone strength was detected by a three-point bending assay. The expression of Phospho-glycogen synthase kinase 3 beta (p-GSK-3β), GSK-3β, Dickkopf-related protein 1 (DKK1), cathepsin K, OPG, RANKL, IGF-1, Runx2, β-catenin, and p-β-catenin was determined by western blot and/or immunohistochemical staining.

RESULTS

Treatment of OVX rats with RRP aqueous extract rebuilt bone homeostasis demonstrated by increasing the levels of OPG as well as decreasing the levels of TRAP, RANKL, and ALP in serum. Furthermore, RRP treatment preserved BMD and mechanical strength by increasing cortical bone thickness and epiphyseal thickness as well as improving trabecular distribution in the femurs of OVX rats. In addition, RRP downregulated the expression of DKK1, sclerostin, RANKL, cathepsin K, and the ratio of p-β-catenin to β-catenin, along with upregulating the expression of IGF-1, β-catenin, and Runx2 and the ratio of p-GSK-3β to GSK-3β in the tibias and femurs of OVX rats. Echinacoside, jionoside A1/A2, acetoside, isoacetoside, jionoside B1, and jionoside B2 were identified in the RRP aqueous extract.

CONCLUSION

RRP attenuates bone loss and improves bone quality in OVX rats partly through its regulation of the canonical Wnt/β-catenin signaling pathway, suggesting that RRP has the potential to provide a new source of anti-osteoporotic drugs.

Increased sleep time and reduced energy expenditure contribute to obesity after ovariectomy and a high fat diet

In this study we examined if sleep time, caloric intake and energy expenditure are important contributors to development of ovariectomy-induced obesity in mice fed control or high fat diet (HFD). Twelve female mice at 6 weeks of age were divided into 2 groups: Sham (n = 5) and ovariectomized (OVX, n = 7). Mice were fed control diet for 9 weeks and shifted to HFD for additional 9 weeks. Food intake and body weight were measured daily and body composition was measured weekly by EchoMRI. Energy expenditure (EE), oxygen consumption (VO2), motor activity (MA) and sleep time were monitored at week 9 during control diet and HFD. OVX did not alter caloric intake, body weight or body composition, MA, sleep time or fasting blood glucose, but slightly reduced EE compared to Sham mice on control diet. After HFD feeding, OXV mice had similar caloric intake, lean mass, MA, and blood glucose levels but had significantly greater weight gain (8.2 ± 1.0 vs. 4.8 ± 1.2 g, p < 0.05), increased fat mass and sleep time, and reduced EE (3.3 ± 0.4 vs. 5.5 ± 0.2 kcal/h) and VO2 (1.12 ± 0.01 vs. 1.83 ± 0.05 ml/min) compared to Sham group. Daytime blood pressure was higher while nighttime heart rate was lower in OVX group. These results suggest that OVX may not substantially alter body weight or body composition in mice fed a normal diet, but when combined with HFD it increases sleep time and reduces EE, leading to greater weight gain and adiposity without altering food intake.

Altered Feeding Behaviors and Adiposity Precede Observable Weight Gain in Young Rats Submitted to a Short-Term High-Fat Diet

Information regarding the early effects of obesogenic diets on feeding patterns and behaviors is limited. To improve knowledge regarding the etiology of obesity, young male Wistar rats were submitted to high-fat (HFD) or regular chow diets (RCDs) for 14 days. Various metabolic parameters were continuously measured using metabolic chambers. Total weight gain was similar between groups, but heavier visceral fat depots and reduced weight of livers were found in HFD rats. Total calorie intake was increased while individual feeding bouts were shorter and of higher calorie intake in response to HFD. Ambulatory activity and sleep duration were decreased in HFD rats during passive and active phase, respectively. Acylated and unacylated ghrelin levels were unaltered by the increased calorie intake and the early changes in body composition. This indicates that at this early stage, the orexigenic signal did not adapt to the high-calorie content of HFD. We hereby demonstrate that, although total weight gain is not affected, a short-term obesogenic diet alters body composition, feeding patterns, satiation, ambulatory activity profiles, and behaviours in a young rat model. Moreover, this effect precedes changes in weight gain, obesity, and ensuing metabolic disorders.

Adipogenic and Lipolytic Effects of Ascorbic Acid in Ovariectomized Rats

PURPOSE

Ascorbic acid has been reported to have an adipogenic effect on 3T3-L1 preadipocytes, while evidence also suggests that ascorbic acid reduces body weight in humans. In this study, we tested the effects of ascorbic acid on adipogenesis and the balance of lipid accumulation in ovariectomized rats, in addition to long-term culture of differentiated 3T3-L1 adipocytes.

MATERIALS AND METHODS

Murine 3T3-L1 fibroblasts and ovariectomized rats were treated with ascorbic acid at various time points. In vitro adipogenesis was analyzed by Oil Red O staining, and in vivo body fat was measured by a body composition analyzer using nuclear magnetic resonance.

RESULTS

When ascorbic acid was applied during an early time point in 3T3-L1 preadipocyte differentiation and after bilateral ovariectomy (OVX) in rats, adipogenesis and fat mass gain significantly increased, respectively. However, lipid accumulation in well-differentiated 3T3-L1 adipocytes showed a significant reduction when ascorbic acid was applied after differentiation (10 days after induction). Also, oral ascorbic acid administration 4 weeks after OVX in rats significantly reduced both body weight and subcutaneous fat layer. In comparison to the results of ascorbic acid, which is a well-known cofactor for an enzyme of collagen synthesis, and the antioxidant ramalin, a potent antioxidant but not a cofactor, showed only a lipolytic effect in well-differentiated 3T3-L1 adipocytes, not an adipogenic effect.

CONCLUSION

Taking these results into account, we concluded that ascorbic acid has both an adipogenic effect as a cofactor of an enzymatic process and a lipolytic effect as an antioxidant.

Mast Cell Inhibition Attenuates Cardiac Remodeling and Diastolic Dysfunction in Middle-aged, Ovariectomized Fischer 344 × Brown Norway Rats

The incidence of left ventricular diastolic dysfunction (LVDD) increases in women after menopause, yet the mechanisms are unclear. Because mast cells participate in the pathological processes of various cardiac diseases, we hypothesized that mast cell inhibition would protect against estrogen loss-induced LVDD. The mast cell stabilizer, cromolyn sodium (30 mg·kg·d), or vehicle was administered subcutaneously by osmotic minipump to ovariectomized (OVX) female Fischer 344 × Brown Norway (F344BN) rats starting at 4 weeks after surgery. Eight weeks after OVX, systolic blood pressure increased by 20% in OVX versus sham rats, and this effect was attenuated after 4 weeks of cromolyn treatment. Also, cromolyn mitigated the adverse reductions in myocardial relaxation (e') and increases in left ventricle (LV) filling pressures (E/e'), LV mass, wall thicknesses, and interstitial fibrosis from OVX. Although cardiac mast cell number was increased after OVX, cardiac chymase activity was not overtly altered by estrogen status and tended to decrease by cromolyn. Contrariwise, Ang II content was greater in hearts of OVX versus sham rats, and cromolyn attenuated this effect. Taken together, mast cell inhibition with cromolyn attenuates LV remodeling and LVDD in OVX-Fischer 344 × Brown Norway rats possibly through actions on the heart level and/or through vasodilatory effects at the vascular level.

Ovarian hormones and obesity

BACKGROUND

Obesity is caused by an imbalance between energy intake, i.e. eating and energy expenditure (EE). Severe obesity is more prevalent in women than men worldwide, and obesity pathophysiology and the resultant obesity-related disease risks differ in women and men. The underlying mechanisms are largely unknown. Pre-clinical and clinical research indicate that ovarian hormones may play a major role.

OBJECTIVE AND RATIONALE

We systematically reviewed the clinical and pre-clinical literature on the effects of ovarian hormones on the physiology of adipose tissue (AT) and the regulation of AT mass by energy intake and EE.

SEARCH METHODS

Articles in English indexed in PubMed through January 2016 were searched using keywords related to: (i) reproductive hormones, (ii) weight regulation and (iii) central nervous system. We sought to identify emerging research foci with clinical translational potential rather than to provide a comprehensive review.

OUTCOMES

We find that estrogens play a leading role in the causes and consequences of female obesity. With respect to adiposity, estrogens synergize with AT genes to increase gluteofemoral subcutaneous AT mass and decrease central AT mass in reproductive-age women, which leads to protective cardiometabolic effects. Loss of estrogens after menopause, independent of aging, increases total AT mass and decreases lean body mass, so that there is little net effect on body weight. Menopause also partially reverses women's protective AT distribution. These effects can be counteracted by estrogen treatment. With respect to eating, increasing estrogen levels progressively decrease eating during the follicular and peri-ovulatory phases of the menstrual cycle. Progestin levels are associated with eating during the luteal phase, but there does not appear to be a causal relationship. Progestins may increase binge eating and eating stimulated by negative emotional states during the luteal phase. Pre-clinical research indicates that one mechanism for the pre-ovulatory decrease in eating is a central action of estrogens to increase the satiating potency of the gastrointestinal hormone cholecystokinin. Another mechanism involves a decrease in the preference for sweet foods during the follicular phase. Genetic defects in brain α-melanocycte-stimulating hormone-melanocortin receptor (melanocortin 4 receptor, MC4R) signaling lead to a syndrome of overeating and obesity that is particularly pronounced in women and in female animals. The syndrome appears around puberty in mice with genetic deletions of MC4R, suggesting a role of ovarian hormones. Emerging functional brain-imaging data indicates that fluctuations in ovarian hormones affect eating by influencing striatal dopaminergic processing of flavor hedonics and lateral prefrontal cortex processing of cognitive inhibitory controls of eating. There is a dearth of research on the neuroendocrine control of eating after menopause. There is also comparatively little research on the effects of ovarian hormones on EE, although changes in ovarian hormone levels during the menstrual cycle do affect resting EE.

WIDER IMPLICATIONS

The markedly greater obesity burden in women makes understanding the diverse effects of ovarian hormones on eating, EE and body adiposity urgent research challenges. A variety of research modalities can be used to investigate these effects in women, and most of the mechanisms reviewed are accessible in animal models. Therefore, human and translational research on the roles of ovarian hormones in women's obesity and its causes should be intensified to gain further mechanistic insights that may ultimately be translated into novel anti-obesity therapies and thereby improve women's health.

Adipose triglyceride lipase protein abundance and translocation to the lipid droplet increase during leptin-induced lipolysis in bovine adipocytes

Proper regulation of lipid metabolism is critical for preventing the development of metabolic diseases. It is clear that leptin plays a critical role in the regulation of energy homeostasis by regulating energy intake. However, leptin can also regulate energy homeostasis by inducing lipolysis in adipocytes, but it is unclear how the major lipases are involved in leptin-stimulated lipolysis. Therefore, the objectives of this study were to determine if (1) leptin acts directly to induce lipolysis in bovine adipocytes, (2) the potential lipases involved in leptin-induced lipolysis in bovine adipocytes, and (3) increases translocation of adipose triglyceride lipase (ATGL) and hormone sensitive lipase (HSL) during leptin-stimulated lipolysis in bovine stromal vascular cell-derived adipocytes. As hypothesized, leptin induced a lipolytic response (P = 0.02) in isolated adipocytes which was accompanied by an increase in phosphorylation of signal transducer and activator of transcription (STAT)3 (P = 0.03), a well-documented secondary messenger of leptin, and ATGL protein abundance (P < 0.01). Protein abundance of STAT3, perilipin, HSL, and phosphorylation of HSL by PKA and AMPK were not altered during leptin-stimulated lipolysis (P > 0.05). Immunostaining techniques were employed to determine the location of HSL and ATGL. Both lipases translocated to the lipid droplet after 2 h of exposure to isoproterenol (P < 0.02). However, only ATGL was translocated to the lipid droplet during leptin-stimulated lipolysis (P = 0.04), indicating ATGL may be the active lipase in leptin-stimulated lipolysis. In summary, leptin stimulates lipolysis in bovine adipocytes. The lack of phosphorylated HSL and translocation of HSL to the lipid droplet during leptin-stimulated lipolysis suggest minimal activity by PKA. Interestingly, leptin-stimulated lipolysis is accompanied by an increase in ATGL protein abundance and translocation to the lipid droplet, indicating its involvement in leptin-stimulated lipolysis either due to an increase in protein abundance or through a novel lipolytic cascade.

Anti-Hyperglycemic Effect of a Kudzu (Pueraria lobata) Vine Extract in Ovariectomized Mice

Postmenopausal diabetes is exacerbated by estrogen deficiency. Ovariectomized (OVX) animal models can be used to develop strategies for preventing or treating postmenopausal symptoms. We previously found that a diet containing kudzu (Pueraria lobata) vine ethanol extract (PVEE) suppressed weight gain in OVX mice. Therefore, this study further elucidated how PVEE affected OVX mice. Ten-week-old OVX or sham-operated mice were fed diets containing either no PVEE (control) or 20 mg•kg^-1•d^-1 PVEE for 8 wk, 5 mg•kg^-1•d^-1 PVEE for 24 wk, or 20 mg•kg^-1•d^-1 puerarin (daidzein-8-C-glucoside), a major isoflavone present in PVEE, for 10 wk. The effects of puerarin on glucose tolerance were also tested in OVX mice. The experimental diets were not associated with any abnormalities in any mice tested in the present study. Weight gain and serum glucose levels were increased in OVX mice and these effects were significantly attenuated in OVX mice that consumed PVEE (5 or 20 mg•kg^-1•d^-1) or puerarin. Puerarin-treated OVX mice also showed reduced serum glucose levels following administration of 1,000 mg•kg^-1 glucose. These results suggested that puerarin contributed to PVEE-mediated improvements in glucose metabolism in OVX mice. Although further studies are needed to clarify the molecular mechanism underlying these observations, PVEE and puerarin could provide effective approaches to the amelioration of postmenopausal diabetes.

Estrogen Effects on Skeletal Muscle Insulin-Like Growth Factor–1 and Myostatin in Ovariectomized Rats

Previous work showed that estrogen replacement attenuates muscle growth in immature rats. The present study examined muscle insulin-like growth factor–1 (IGF-1) and myostatin expression to determine whether these growth regulators might be involved in mediating estrogen’s effects on muscle growth. IGF-1 and myostatin message and protein expression in selected skeletal muscles from 7-week-old sham-ovariectomized (SHAM) and ovariectomized rats that received continuous estrogen (OVX/E2) or solvent vehicle (OVX/CO) from an implant for 1 week or 5 weeks was measured. In the 1-week study, ovariectomy increased IGF-1 mRNA expression in fast extensor digitorum longus and gastrocnemius muscles; the increase was reversed by estrogen replacement. A similar trend was observed in the slow soleus muscle, although the change was not statistically significant. In contrast to mRNA, muscle IGF-1 protein expression was not different between SHAM and OVX/ CO animals in the 1-week study. One week of estrogen replacement significantly decreased IGF-1 protein level in all muscles examined. Myostatin mRNA expression was not different among the 1-week treatment groups. One week of estrogen replacement significantly increased myostatin protein in the slow soleus muscle but not the fast extensor digitorum longus and gastrocnemius muscles. There was no treatment effect on IGF-1 and myostatin expression in the 5-week study; this finding suggested a transient estrogen effect or upregulation of a compensatory mechanism to counteract the estrogen effect observed at the earlier time point. This investigation is the first to explore ovariectomy and estrogen effects on skeletal muscle IGF-1 and myostatin expression. Results suggest that reduced levels of muscle IGF-1 protein may mediate estrogen’s effect on growth in immature, ovariectomized rats. Increased levels of muscle myostatin protein may also have a role in mediating estrogen’s effects on growth in slow but not fast skeletal muscle.

The influence of sex and gonadectomy on hepatic and brain fatty acid composition, lipogenesis and β-oxidation

The aim of this study was to investigate the influence of sex and castration of rats on liver and brain fatty acid profile and liver mRNA expression of genes involved in lipogenesis and β-oxidation. Castration significantly increased body weight and liver index and decreased serum triglyceride content in the female rats. The fatty acid composition of the liver tissue was influenced by sex and castration. Male rats had higher content of C16:0, C18:1n7, C18:2n6 and C22:5n3, while female rats had higher content of C18:0, C20:4n6 and C22:6n3. Castration of male rats decreased differences caused by sex for C18:2n6, C20:4n6 and C22:6n3. Values for C16:1n7 were higher in the castrated male rats in comparison with all other groups. Liver phospholipids showed a distribution of fatty acids similar to the total lipids. Brain total lipids and phospholipids were not influenced by sex or castration. Castration increased ∆6D gene expression in both the sexes, while ∆5D and ∆9D increased in females and males respectively. Gonadectomy increased expression of the FASN gene in the females and decreased CPT1 and ACOX1 gene expression in the liver tissue of male rats. The observed results of lipid peroxidation, measured by TBARS, were the lowest in the intact females in comparison with all other groups. In conclusion, sex strongly influences both SFA and PUFA in liver tissue, and castration decreases these differences only for PUFA. Castration also influences the expression of the genes involved in lipid metabolism differently in male and female rats, with an increase in lipogenic genes in female rats and a decrease in key genes for mitochondrial and peroxisomal β-oxidation in male rats.

A high-fat diet increases body weight and circulating estradiol concentrations but does not improve bone structural properties in ovariectomized mice

Bone health is influenced by body mass and estrogen. The objective of the study was to determine whether high-fat diet-induced obesity affects bone structure and alters markers of bone turnover in ovariectomized (OVX) mice. We hypothesized that a high-fat diet would increase body weight gain and serum estradiol levels in OVX mice but would not improve bone structural parameter in OVX mice. Thirty-five C57BL/6 mice were either sham operated or OVX at the age of 4 months and then fed either a normal-fat diet (10% energy as fat) or a high-fat diet (45% energy as fat with extra fat from lard) ad libitum for 11 weeks. Ovariectomy increased body weight, serum tartrate-resistant acid phosphatase concentration, and expression of cathepsin K in bone; decreased serum estradiol concentration; and induced significant bone loss manifested by decreased bone volume/total volume (BV/TV), connectivity density (Conn.D), trabecular number, and trabecular thickness with increased trabecular separation and structural model index (P < .01). The high-fat diet increased body weight (P < .01) in OVX mice and nonsignificantly decreased BV/TV (P = .08) and Conn.D (P = .10). Despite having similar serum estradiol concentrations and higher body weight, OVX mice consuming the high-fat diet had lower BV/TV, Conn.D, trabecular number, trabecular thickness, and higher structural model index and trabecular separation than did sham mice fed the normal-fat diet. These findings indicate that increased body weight and elevated serum estradiol concentration induced by a high-fat diet do not mitigate ovariectomy-induced bone loss in mice.

Effects of estradiol, estrogen receptor subtype-selective agonists and genistein on glucose metabolism in leptin resistant female Zucker diabetic fatty (ZDF) rats

The leptin resistant Zucker diabetic fatty (ZDF) rats are hyperphagic and become obese, but whereas the males develop type 2 diabetes mellitus (T2DM), the females remain euglycaemic. As estrogen deficiency is known to increase the risk of developing T2DM, we evaluated the role of ER subtypes alpha and beta in the development of glucose tolerance in leptin resistant ovariectomized (OVX) ZDF rats. At least six rats per group were treated with either vehicle (OVX), 17β-estradiol (E2), ER subtype-selective agonists (Alpha and Beta), or genistein (Gen) for 17 weeks. At the end of the treatment period a glucose tolerance assay was performed and the metabolic flux of (13)C-glucose for the E2 group was investigated. OVX ZDF rats treated with E2, Alpha, Beta, and Gen tolerated the glucose significantly better than untreated controls. E2 treatment increased absorbance/flux of (13)C-glucose to metabolic relevant tissues such liver, adipose tissue, gastrocnemius, and soleus muscle. Moreover, whereas Alpha treatment markedly increased mRNA expression of GLUT4 in gastrocnemius muscle, Beta treatment resulted in the largest fiber sizes of the soleus muscle. Treatment with Gen increased both the mRNA expression of GLUT 4 and the fiber sizes in the skeletal muscle. In addition, E2 and Alpha treatment decreased food intake and body weight gain. In summary, estrogen-improved glucose absorption is mediated via different molecular mechanisms: while activation of ER alpha seems to stimulate muscular GLUT4 functionality, activation of ER beta results in a hypertrophy of muscle fibers. In addition, selective activation of ER alpha decreased food intake and body weight gain. Our data further indicate that ER subtype-selective agonists and genistein improve systemic glucose tolerance also in the absence of a functional leptin signaling pathway.

Prevention of hyperphagia prevents ovariectomy-induced triacylglycerol accumulation in liver, but not plasma

Menopause is associated with higher plasma and liver triacylglycerol (TAG) and increased risk for cardiovascular disease. Lowering TAG in menopause may be beneficial; however, the mechanism underlying menopause-induced TAG accumulation is not clear. Ovariectomy is a model for menopause and is associated with metabolic alterations and hyperphagia. This study investigated the role of hyperphagia in ovariectomy-induced increases in blood and tissue TAG, as well as differences in lipid metabolism enzymes and resting metabolic measures. It was hypothesized that prevention of hyperphagia would restore blood and tissue TAG, enzyme expression, and metabolic measures to eugonadal levels. Ovariectomized rats were fed ad libitum (OVX + AL) or pair-fed (OVX + PF) relative to sham-operated rats (SHAM) to prevent hyperphagia. OVX + AL had higher TAG concentrations in liver and plasma than SHAM (60% and 50%, respectively), and prevention of hyperphagia in OVX + PF normalized TAG concentrations to SHAM levels in liver, but not plasma. OVX + AL also had 141% higher hepatic stearoyl-CoA desaturase 1 which was almost completely normalized to SHAM levels by pair-feeding, suggesting normalization of hepatic lipid storage. In contrast, skeletal muscle carnitine palmitoyl transferase 1 was 40% lower in OVX + AL than SHAM and was intermediate in OVX + PF, suggesting lower muscle fatty acid oxidation that may underlie the higher plasma TAG in OVX. No differences were seen in energy expenditure, VO2, or VCO2. Overall, this study indicates that prevention of hyperphagia resulting from ovarian hormone withdrawal normalizes hepatic TAG to eugonadal levels but has no effect on ovariectomy-induced increases in plasma TAG.

Liver glycogen reduces food intake and attenuates obesity in a high-fat diet-fed mouse model

We generated mice that overexpress protein targeting to glycogen (PTG) in the liver (PTG(OE)), which results in an increase in liver glycogen. When fed a high-fat diet (HFD), these animals reduced their food intake. The resulting effect was a lower body weight, decreased fat mass, and reduced leptin levels. Furthermore, PTG overexpression reversed the glucose intolerance and hyperinsulinemia caused by the HFD and protected against HFD-induced hepatic steatosis. Of note, when fed an HFD, PTG(OE) mice did not show the decrease in hepatic ATP content observed in control animals and had lower expression of neuropeptide Y and higher expression of proopiomelanocortin in the hypothalamus. Additionally, after an overnight fast, PTG(OE) animals presented high liver glycogen content, lower liver triacylglycerol content, and lower serum concentrations of fatty acids and β-hydroxybutyrate than control mice, regardless of whether they were fed an HFD or a standard diet. In conclusion, liver glycogen accumulation caused a reduced food intake, protected against the deleterious effects of an HFD, and diminished the metabolic impact of fasting. Therefore, we propose that hepatic glycogen content be considered a potential target for the pharmacological manipulation of diabetes and obesity.

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.

Ovariectomy-associated changes in interradicular septum and in tibia metaphysis in different observation periods in rats

In order to standardize an experimental model to study the effects of absence of ovarian hormones in maxillary bones compared with long bones, the aim of this research was to analyze the influence of ovariectomy (OVX) on rat alveolar bone and tibiae, in different observation periods. Thirty-six female rats were ovariectomized or sham operated. After 60, 90 or 120 days, the animals were sacrificed and their hemimandibles, maxillae and tibiae were removed and routinely prepared for hematoxylin and eosin staining. The percentage of bone matrix area in bone septum in the first molar furcation region, and in tibial metaphysis was calculated, and data were submitted to statistical analysis (p<0.05). As regards the histomorphometrical analysis in jaw bones, there was no statistical difference between groups, while the effects of ovariectomy on tibiae were seen as early as 60 days. According to the methods used, there was no significant influence of absence of ovarian hormones on interradicular septum of mandibular or maxillary first molars in the periods studied, despite the reduction in bone matrix area in tibia metaphysis as early as 60 days.

Leptin resistance is not the primary cause of weight gain associated with reduced sex hormone levels in female mice

Several studies have shown that estrogens mimic leptin's effects on energy balance regulation. However, the findings regarding the consequences of reduced sex hormone levels on leptin sensitivity are divergent. In the present study, we employed different experimental paradigms to elucidate the interaction between estrogens, leptin, and energy balance regulation. We confirmed previous reports showing that ovariectomy caused a reduction in locomotor activity and energy expenditure leading mice to obesity and glucose intolerance. However, the acute and chronic anorexigenic effects of leptin were preserved in ovariectomized (OVX) mice despite their increased serum leptin levels. We studied hypothalamic gene expression at different time points after ovariectomy and observed that changes in the expression of genes involved in leptin resistance (suppressors of cytokine signaling and protein-tyrosine phosphatases) did not precede the early onset of obesity in OVX mice. On the contrary, reduced sex hormone levels caused an up-regulation of the long form of the leptin receptor (LepR), resulting in increased activation of leptin signaling pathways in OVX leptin-treated animals. The up-regulation of the LepR was observed in long-term OVX mice (30 d or 24 wk after ovariectomy) but not 7 days after the surgery. In addition, we observed a progressive decrease in the coexpression of LepR and estrogen receptor-α in the hypothalamus after the ovariectomy, resulting in a low percentage of dual-labeled cells in OVX mice. Taken together, our findings suggest that the weight gain caused by reduced sex hormone levels is not primarily caused by induction of a leptin-resistance state.

The role of hypothalamic estrogen receptors in metabolic regulation

Estrogens regulate key features of metabolism, including food intake, body weight, energy expenditure, insulin sensitivity, leptin sensitivity, and body fat distribution. There are two 'classical' estrogen receptors (ERs): estrogen receptor alpha (ERS1) and estrogen receptor beta (ERS2). Human and murine data indicate ERS1 contributes to metabolic regulation more so than ESR2. For example, there are human inactivating mutations of ERS1 which recapitulate aspects of the metabolic syndrome in both men and women. Much of our understanding of the metabolic roles of ERS1 was initially uncovered in estrogen receptor α-null mice (ERS1(-/-)); these mice display aspects of the metabolic syndrome, including increased body weight, increased visceral fat deposition and dysregulated glucose intolerance. Recent data further implicate ERS1 in specific tissues and neuronal populations as being critical for regulating food intake, energy expenditure, body fat distribution and adipose tissue function. This review will focus predominantly on the role of hypothalamic ERs and their critical role in regulating all aspects of energy homeostasis and metabolism.

An acute method to test leptin responsiveness in rats

Continuous subcutaneous administration of leptin normalizes blood glucose levels in rodent models of Type 1 and Type 2 diabetes independent of changes in food intake, body weight, and plasma insulin. We tested whether an acute intravenous leptin infusion changed blood glucose in normal and diet-induced leptin-resistant rats to determine whether this measure could be used as a marker of leptin sensitivity. Leptin-responsive chow-fed rats and diet-induced leptin-resistant male Sprague-Dawley rats were fitted with thoracic jugular vein catheters. Four days after surgery, conscious rats were infused intravenously with either saline for 32 min, low-dose (LD) leptin (1.9 μg·kg(-1)·min(-1)) followed by high-dose (HD) leptin (3.8 μg·kg(-1)·min(-1)) for 16 min each, or only HD leptin for 16 min. There was no change in blood glucose after an acute intravenous infusion of either LD leptin or HD leptin alone for 16 min. An intravenous infusion of LD followed by HD leptin for 16 min each significantly decreased serum glucose in leptin-responsive rats but not in leptin-resistant rats. Leptin infusions increased serum leptin in all rat groups but had no effect on plasma glucagon or 12-h weight gain and energy intake in any group of rats. These results show that leptin has an acute glucose-lowering effect that reflects the leptin responsiveness of the rat. This effect is consistent across controls and different leptin-resistant rat models, and the acute nonlethal test provides a novel method of testing leptin responsiveness in rats.

Osteocytes regulate primary lymphoid organs and fat metabolism

Osteocytes act as mechanosensors to control local bone volume. However, their roles in the homeostasis of remote organs are largely unknown. We show that ablation of osteocytes in mice (osteocyte-less [OL] mice) leads to severe lymphopenia, due to lack of lymphoid-supporting stroma in both the bone marrow and thymus, and complete loss of white adipose tissues. These effects were reversed when osteocytes were replenished within the bone. In contrast, neither in vivo supply of T cell progenitors and humoral factors via shared circulation with a normal parabiotic partner nor ablation of specific hypothalamic nuclei rescued thymic atrophy and fat loss in OL mice. Furthermore, ablation of the hypothalamus in OL mice led to hepatic steatosis, which was rescued by parabiosis with normal mice. Our results define a role for osteocytes as critical regulators of lymphopoiesis and fat metabolism and suggest that bone acts as a central regulator of multiple organs.

Upregulation of genes related to bone formation by γ-amino butyric acid and γ-oryzanol in germinated brown rice is via the activation of GABAB-receptors and reduction of serum IL-6 in rats

Background

Osteoporosis and other bone degenerative diseases are among the most challenging non-communicable diseases to treat. Previous works relate bone loss due to osteoporosis with oxidative stress generated by free radicals and inflammatory cytokines. Alternative therapy to hormone replacement has been an area of interest to researchers for almost three decades due to hormone therapy-associated side effects.

Methods

In this study, we investigated the effects of gamma-amino butyric acid (GABA), gamma-oryzanol (ORZ), acylated steryl glucosides (ASG), and phenolic extracts from germinated brown rice (GBR) on the expression of genes related to bone metabolism, such as bone morphogenic protein-2 (BMP-2), secreted protein acidic and rich in cysteine (SPARC), runt-related transcription factor 2 (RUNX-2), osteoblast-specific transcription factor osterix (Osx), periostin, osteoblast specific factor (Postn), collagen 1&2 (Col1&2), calcitonin receptor gene (CGRP); body weight measurement and also serum interleukin-6 (IL-6) and osteocalcin, in serum and bone. Rats were treated with GBR, ORZ, GABA, and ASG at (100 and 200 mg/kg); estrogen (0.2 mg/kg), or remifemin (10 and 20 mg/kg), compared to ovariectomized non-treated group as well as non-ovariectomized non-treated (sham) group. Enzyme-linked immunosorbent assay was used to measure the IL-6 and osteocalcin levels at week 2, 4, and 8, while the gene expression in the bone tissue was determined using the Genetic Analysis System (Beckman Coulter Inc., Brea, CA, USA).

Results

The results indicate that groups treated with GABA (100 and 200 mg/kg) showed significant upregulation of SPARC, calcitonin receptor, and BMP-2 genes (P < 0.05), while the ORZ-treated group (100 and 200 mg/kg) revealed significant (P < 0.05) upregulation of Osx, Postn, RUNX-2, and Col1&2. Similarly, IL-6 concentration decreased, while osteocalcin levels increased significantly (P < 0.05) in the treated groups as compared to ovariectomized non-treated groups.

Conclusion

GABA and ORZ from GBR stimulates osteoblastogenesis by upregulation of bone formation genes, possibly via the activation of GABA_B receptors and by inhibiting the activity of inflammatory cytokines and reactive oxygen species. Therefore, it could be used effectively in the management of osteoporosis.

Sex differences in the physiology of eating

Hypothalamic-pituitary-gonadal (HPG) axis function fundamentally affects the physiology of eating. We review sex differences in the physiological and pathophysiological controls of amounts eaten in rats, mice, monkeys, and humans. These controls result from interactions among genetic effects, organizational effects of reproductive hormones (i.e., permanent early developmental effects), and activational effects of these hormones (i.e., effects dependent on hormone levels). Male-female sex differences in the physiology of eating involve both organizational and activational effects of androgens and estrogens. An activational effect of estrogens decreases eating 1) during the periovulatory period of the ovarian cycle in rats, mice, monkeys, and women and 2) tonically between puberty and reproductive senescence or ovariectomy in rats and monkeys, sometimes in mice, and possibly in women. Estrogens acting on estrogen receptor-α (ERα) in the caudal medial nucleus of the solitary tract appear to mediate these effects in rats. Androgens, prolactin, and other reproductive hormones also affect eating in rats. Sex differences in eating are mediated by alterations in orosensory capacity and hedonics, gastric mechanoreception, ghrelin, CCK, glucagon-like peptide-1 (GLP-1), glucagon, insulin, amylin, apolipoprotein A-IV, fatty-acid oxidation, and leptin. The control of eating by central neurochemical signaling via serotonin, MSH, neuropeptide Y, Agouti-related peptide (AgRP), melanin-concentrating hormone, and dopamine is modulated by HPG function. Finally, sex differences in the physiology of eating may contribute to human obesity, anorexia nervosa, and binge eating. The variety and physiological importance of what has been learned so far warrant intensifying basic, translational, and clinical research on sex differences in eating.

Differences in sensitivity to ethanol-induced conditioned taste aversions emerge after pre- or post-pubertal gonadectomy in male and female rats

We have previously demonstrated that gonadectomy either prior to (early) or after (late) puberty elevated ethanol consumption in males to levels similar to intact adult females-effects that were attenuated by testosterone replacement. To assess whether alterations in the aversive effects of ethanol might contribute to gonadectomy-associated increases in ethanol intake in males, the present study examined the impact of gonadectomy on conditioned taste aversions (CTA) to ethanol in male and female Sprague-Dawley rats. Animals were gonadectomized, received sham surgery (SH) or non-manipulated (NM) on postnatal (P) day 23 (early) or 67 (late) and tested for CTA to ethanol in adulthood. Water-deprived rats were given 1 hr access every-other-day to 10% sucrose followed by an injection of ethanol (0, 1g/kg) for 5 test sessions. Test data were analyzed to determine the first day significant aversions emerged in each ethanol group (i.e., sucrose intakes significantly less than their saline-injected counterparts). Early gonadectomized males acquired the CTA more rapidly than did early SH and NM males (day 1 vs 3 and 4 respectively), whereas a gonadectomy-associated enhancement in ethanol CTA was not evident in late males. Among females, gonadectomy had little impact on ethanol-induced CTA, with females in all groups showing an aversion by the first or second day, regardless of surgery age. These data suggest that previously observed elevations in ethanol intake induced by either pre- or post-pubertal gonadectomy in males are not related simply to gonadectomy-induced alterations in the aversive effects of ethanol indexed via CTA.

TM-25659 enhances osteogenic differentiation and suppresses adipogenic differentiation by modulating the transcriptional co-activator TAZ

BACKGROUND AND PURPOSE

The transcriptional co-activator with PDZ-binding motif (TAZ) is characterized as a transcriptional modulator of mesenchymal stem cell differentiation into osteoblasts and adipocytes. Moreover, increased TAZ activity in the nucleus enhances osteoblast differentiation and suppresses adipocyte development by interacting with runt-related transcription factor 2 (RUNX2) and PPARγ, respectively. Therefore, it would be of interest to identify low MW compounds that modulate nuclear TAZ activity.

EXPERIMENTAL APPROACH

High-throughput screening was performed using a library of low MW compounds in order to identify TAZ modulators that enhance nuclear TAZ localization. The effects and molecular mechanisms of a TAZ modulator have been characterized in osteoblast and adipocyte differentiation.

KEY RESULTS

We identified 2-butyl-5-methyl-6-(pyridine-3-yl)-3-[2'-(1H-tetrazole-5-yl)-biphenyl-4-ylmethyl]-3H-imidazo[4,5-b]pyridine] (TM-25659) as a TAZ modulator. TM-25659 enhanced nuclear TAZ localization in a dose-dependent manner and attenuated PPARγ-mediated adipocyte differentiation by facilitating PPARγ suppression activity of TAZ. In addition, TAZ-induced RUNX2 activity activation was further increased in osteoblasts, causing increased osteoblast differentiation. Accordingly, TM-25659 suppressed bone loss in vivo and decreased weight gain in an obesity model. After oral administration, TM-25659 had a favourable pharmacokinetic profile.

CONCLUSION AND IMPLICATIONS

TM-25659 stimulated nuclear TAZ localization and thus caused TAZ to suppress PPARγ-dependent adipogenesis and enhance RUNX2-induced osteoblast differentiation in vitro and in vivo. Our data suggest that TM-25659 could be beneficial in the control of obesity and bone loss.

Osteoprotective effects of Cimicifuga racemosa and its triterpene-saponins are responsible for reduction of bone marrow fat

PURPOSE

Elderly people often develop visceral obesity accompanied by osteoporosis. Visceral adipocytes secrete a number of adipokines and cytokines which augment the development of arteriosclerosis and type 2 diabetes. Bone marrow fat cells also secrete these pro-inflammatory cytokines which stimulate osteoclast and inhibit osteoblast activity. Ovariectomized (ovx) rats also develop general and bone marrow obesity and osteoporosis both of which can be partially prevented by estradiol (E2) and the special extract of Cimicifuga racemosa (CR) BNO 1055. Whether this extract or the thereof isolated triterpene-saponins or polar substances can also prevent bone marrow obesity and thereby the development of osteoporosis was compared with the effects of estradiol (E2).

METHODS

Rats were ovx and fed with food containing either CR BNO 1055 or its triterpene-saponin or polar constituents or with E2 for 4 weeks. Histomorphometry and STRUT analyses were applied to histological preparations to determine the amount of trabecles, hematopoietic and fat tissue in the bone marrow.

RESULTS

Ovx rats lost significant amounts of trabecular BMD, surface and nodes while the number of free trabecular ends and fat load in the marrow increased. This was totally prevented by E2 and partially by CR BNO 1055 and the triterpene-saponin but not by the polar fraction. High serum osteocalcin and CrossLaps levels were reduced by E2 and the S-fraction.

CONCLUSIONS

It is well established that E2 prevents osteoporosis. It is also known that CR BNO 1055 does not contain estrogenic substances. CR BNO 1055 and the triterpene-saponin-fraction reduced the development of osteoporosis most likely by a reduction of the bone marrow fat load and possibly by reducing the secretion of pro-inflammatory cytokines. Hence, the triterpene-saponin-fraction may serve as a basis for a new osteoporosis preventing preparation also in human patients.

Cimicifuga racemosa and its triterpene-saponins prevent the Metabolic Syndrome and deterioration of cartilage in the knee joint of ovariectomized rats by similar mechanisms

PURPOSE

An unphysiologic accumulation of fat cells in many parts of the body including abdomen and joints results in increased production of pro-inflammatory cytokines which have adverse effects on serum lipids, glucose and on joint cartilage. The special extract of Cimicifuga racemosa CR BNO 1055 was shown to reduce the size of the abdominal fat depot. It was therefore tempting to test whether this extract, its saponin and its unpolar and polar fractions S- and R-fraction respectively (no quotation) also reduce fat depots and fat cell accumulation in a fat depot located in the lower hind leg (called paratibial fat depot = PFD), in joint fat pads (in the knee joint this is called Hoffa's fat pad) that occur in response to ovariectomy and whether this was accompanied by reduced serum lipids, glucose and improved cartilage features in the knee joint.

METHODS

Rats (n = 10/group) were ovariectomized (ovx) and fed with CR BNO 1055, S- or R-fraction containing food (average intake 8.2, or 2.05 or 7.07 mg/day/animal) for 4 weeks. Ovx rats kept under no additive-containing food served as controls. The sizes of the PFD, of Hoffa's fat pad and of the cartilage thickness of the knee joints were determined by quantitative computer tomography and histomorphometrically. In the serum cholesterol, leptin and glucose levels were measured.

RESULTS

High load with fat tissue in the PFD and in the knee joints was present in the ovx rats. Treatment with CR BNO 1055 and its S-fraction reduced fat load of both, Hoffa's fat pad and of the PFD significantly and this resulted in reduced body weight which was significant under CR BNO 1055. Fat load in the PFD correlated significantly with the height of serum leptin and cholesterol. The fat load in the knee joint correlated inversely with the size of knee cartilage tissue.

CONCLUSIONS

High fat load of the body increases following ovx and this causes increased serum leptin, cholesterol and glucose levels. Following ovx the size of Hoffa's fat pad increases also significantly and this has adverse effects on knee cartilage tissue. Therefore, increased fat tissue in joints appears to belong to the Metabolic Syndrome. This effect can be largely prevented by CR BNO 1005 and its S- but not by its R-fraction. Hence, the saponins in CR BNO 1055 may be useful in preventing the Metabolic Syndrome and osteoarthritis.

Alpha-1 antitrypsin reduces ovariectomy-induced bone loss in mice

Proinflammatory cytokines are primary mediators of bone loss in estrogen deficiency. This study determined whether alpha-1 antitrypsin (AAT), a multifunctional protein with proteinase inhibitor and anti-inflammatory activities, mitigates bone loss induced by estrogen deficiency. Mice were either sham-operated or ovariectomized and injected with either AAT or phosphate buffered saline (PBS). Ovariectomy resulted in decreased wet uterus weight, significant bone loss, increased serum leptin concentrations, and higher body weight compared to sham. AAT injection increased tibial trabecular bone volume/total volume and trabecular thickness compared to PBS injection in ovariectomized mice. Ovariectomized mice with AAT treatment had higher uterus weight, lower serum osteocalcin levels, fewer bone marrow tartrate-resistant acid phosphatase-positive osteoclasts, and less expression of calcitonin receptor in bone than that in PBS-injected mice. These data demonstrate that AAT mitigates ovariectomy-induced bone loss in mice possibly through inhibiting osteoclast activity and bone resorption.

Selective estrogen receptor modulator promotes weight loss in ovariectomized female rhesus monkeys (Macaca mulatta) by decreasing food intake and increasing activity

The effect of hormone replacement therapy (HRT) on body weight in postmenopausal women is controversial, with studies reporting an increase, a decrease, and no change in body weight. To examine estrogen receptor actions on body weight, we investigated the effects of treatment with a selective estrogen receptor modulator (SERM) on body weight, food intake, and activity and metabolic rate in a nonhuman primate model. Eighteen ovariectomized female rhesus monkeys were treated with a nonsteroidal SERM (GSK232802A, 5 mg/kg po) for 3 mo. GSK232802A decreased lutenizing hormone (P < 0.0001) and follicle-stimulating hormone levels (P < 0.0001), consistent with the estrogenic action of the compound. GSK232802A treatment produced a small but sustained weight loss (4.6 ± 1.0%, P < 0.0001) and reduced adiposity (P < 0.0001), which was due at least in part to a suppression of food intake (3.6 ± 3.7%, P < 0.0001). Physical activity increased during the 3rd mo of treatment (P = 0.04). Baseline activity level and the change in activity due to treatment were correlated, with the most sedentary individuals exhibiting increased physical activity during the 1st mo of treatment (P = 0.02). Metabolic rate did not change (P = 0.58). These results indicate that GSK232802A treatment reduces body weight and adiposity in ovariectomized nonhuman primates by suppressing food intake and increasing activity, particularly in the most sedentary individuals. These findings suggest that SERM treatment may counteract weight gain in postmenopausal women.

Ovariectomy and overeating palatable, energy-dense food increase subcutaneous adipose tissue more than intra-abdominal adipose tissue in rats

BACKGROUND

Menopause is associated with increased adiposity, especially increased deposition of intra-abdominal (IA) adipose tissue (AT). This differs from common or 'dietary' obesity, i.e., obesity apparently due to environmentally stimulated overeating, in which IAAT and subcutaneous (S) AT increase in similar proportions. The effect of menopause on adiposity is thought to be due to the decreased secretion of ovarian estrogens. Ovariectomy in rats and other animals is a commonly used model of menopause. It is well known that ovariectomy increases adiposity and that this can be reversed by estradiol treatment, but whether ovariectomy selectively increases IAAT has not been measured directly. Therefore, we used micro-computed tomography (microCT) to investigate this question in both chow-fed and dietary-obese rats.

METHODS

Ovariectomized, ovariectomized and estradiol treated, and sham-operated (intact) rats were fed chow or chow plus Ensure (Abbott Nutrition; n = 7/group). Total (T) AT, IAAT and SAT were measured periodically by microCT. Regional distribution of AT was expressed as IAAT as a percentage of TAT (%IAAT). Excesses in these measures were calculated with respect to chow-fed intact rats to control for normal maturational changes. Chemical analysis of fat was done in chow-fed intact and ovariectomized rats at study end. Data were analyzed by t-tests and planned comparisons.

RESULTS

Body mass, TAT, total fat mass, fat-free body mass, and %IAAT all increased in chow-fed intact rats during the 41 d study. In chow-fed rats, ovariectomy increased excess body mass, TAT, fat mass, fat-free body mass, and SAT, but had little effect on IAAT, in chow-fed rats, leading to a decrease in %IAAT. Ensure feeding markedly increased SAT, IAAT and TAT and did not significantly affect %IAAT. Ovariectomy had similar effects in Ensure-fed rats as in chow-fed rats, although less statistically reliable. Estradiol treatment prevented all the effects of ovariectomy.

CONCLUSIONS

Both ovariectomy in rats and menopause are associated with increased TAT. After ovariectomy, fat is preferentially deposited as SAT and lean body mass increases, whereas after menopause fat is preferentially deposited as IAAT and lean body mass decreases. These opposite effects of ovariectomy and menopause on regional AT distribution and lean body mass indicate that ovariectomy in rats is not a homologous model of menopause-associated changes in body composition that should be used with great caution in investigations of adiposity-related diseases.

The role of hypothalamic AMP-activated protein kinase in ovariectomy-induced obesity in rats

OBJECTIVE

Adenosine monophosphate-activated protein kinase (AMPK) acts as a cellular energy sensor, being activated during states of low energy charge. Hypothalamic AMPK is altered by hormonal and metabolic signals and mediates the feeding response. The aims of this study were to examine whether the phosphorylation of AMPKα in the hypothalamus is affected by ovariectomy (Ovx) and thus would be involved in the development of obesity in rats.

METHODS

Body weight, food intake, hypothalamic phosphorylated AMPKα (pAMPKα) protein expression, and plasma leptin and adiponectin levels were measured in female rats after either Ovx or sham operations. These patterns were also observed after treatment with 17β-estradiol, compound C, and leptin in Ovx rats.

RESULTS

Compared with control rats, Ovx led to increased body weight and food intake at 2 to 8 weeks after operation. Meanwhile, plasma leptin and adiponectin levels and hypothalamic pAMPKα expression were significantly increased after Ovx. Replacement of estradiol significantly reversed these effects. Treatment with compound C, an AMPKα inhibitor, for 1 week produced a reduction in food intake, body weight, and plasma leptin and adiponectin levels. Meanwhile, these effects were reversed upon withdrawal of compound C. In addition, central injection of leptin also significantly reduced body weight, food intake, plasma leptin and adiponectin levels, and hypothalamic pAMPKα expression relative to those of the Ovx group.

CONCLUSIONS

Increased hypothalamic pAMPKα expression may contribute to hyperphagia during the development of Ovx-induced obesity in rats.