Dexamethasone reduces food intake, weight gain and the hypothalamic 5-HT concentration and increases plasma leptin in rats

Dexamethasone-Induced Insulin Resistance Attenuation by Oral Sulfur-Oxidovanadium(IV) Complex Treatment in Mice

Vanadium compounds are known to exert insulin-enhancing activity, normalize elevated blood glucose levels in diabetic subjects, and show significant activity in models of insulin resistance (IR). Faced with insulin resistance, the present work investigates the antidiabetic performance of a known oxidovanadium(IV)-based coordination compound-[VIVO(octd)]-and effects associated with glucocorticoid-induced insulin resistance in mice. The effects of [VIVO(octd)] were evaluated in a female Swiss mice model of insulin resistance induced by seven days of dexamethasone treatment in comparison with groups receiving metformin treatment. Biological assays such as hematological, TyG index, hepatic lipids, glycogen, oxidative stress in the liver, and oral glucose tolerance tests were evaluated. [VIVO(octd)] was characterized with 51V NMR, infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), electronic absorption spectroscopy, and mass spectrometry (ESI-FT-MS). The [VIVO(octd)] oral treatment (50 mg/kg) had an antioxidant effect, reducing 50% of fast blood glucose (p < 0.05) and 25% of the TyG index, which is used to estimate insulin resistance (p < 0.05), compared with the non-treated group. The oxidovanadium-sulfur compound is a promising antihyperglycemic therapeutic, including in cases aggravated by insulin resistance induced by glucocorticoid treatment.

Acute Effects of Systemic Glucocorticoids on the Vocal Folds in a Pre-Clinical Model

OBJECTIVES/HYPOTHESIS

Systemic glucocorticoids (GC)s are employed to treat various voice disorders. However, GCs have varying pharmacodynamic properties with adverse effects ranging from changes in epithelial integrity, skeletal muscle catabolism, and altered body weight. We sought to characterize the acute temporal effects of systemic dexamethasone and methylprednisolone on vocal fold (VF) epithelial glucocorticoid receptor (GR) nuclear translocation, epithelial tight junction (ZO-1) expression, thyroarytenoid (TA) muscle fiber morphology, and body weight using an established pre-clinical model. We hypothesized dexamethasone and methylprednisolone will elicit changes in VF epithelial GR nuclear translocation, epithelial ZO-1 expression, TA muscle morphology, and body weight compared to placebo-treated controls.

METHODS

Forty-five New Zealand white rabbits received intramuscular injections of methylprednisolone (4.5 mg; n = 15), dexamethasone (450 µg; n = 15), or volume matched saline (n = 15) into the iliocostalis/longissimus muscle for 6 consecutive days. Vocal folds from 5 rabbits from each treatment group were harvested at 1-, 3-, or 7 days following the final injection and subjected to immunohistochemistry for ZO-1 and GR as well as TA muscle fiber cross-sectional area (CSA) measures.

RESULTS

Dexamethasone increased epithelial GR nuclear translocation and ZO-1 expression 1-day following injections compared to methylprednisolone (P = .024; P = .012). Dexamethasone and methylprednisolone increased TA CSA 1-day following injections (P = .011). Methylprednisolone decreased body weight 7 days following injections compared to controls (P = .004).

CONCLUSIONS

Systemic dexamethasone may more efficiently activate GR in the VF epithelium with a lower risk of body weight loss, suggesting a role for more refined approaches to GC selection for laryngeal pathology.

Glucocorticoids, their uses, sexual dimorphisms, and diseases: new concepts, mechanisms, and discoveries

The normal stress response in humans is governed by the hypothalamic-pituitary-adrenal (HPA) axis through heightened mechanisms during stress, raising blood levels of the glucocorticoid hormone cortisol. Glucocorticoids are quintessential compounds that balance the proper functioning of numerous systems in the mammalian body. They are also generated synthetically and are the preeminent therapy for inflammatory diseases. They act by binding to the nuclear receptor transcription factor glucocorticoid receptor (GR), which has two main isoforms (GRα and GRβ). Our classical understanding of glucocorticoid signaling is from the GRα isoform, which binds the hormone, whereas GRβ has no known ligands. With glucocorticoids being involved in many physiological and cellular processes, even small disruptions in their release via the HPA axis, or changes in GR isoform expression, can have dire ramifications on health. Long-term chronic glucocorticoid therapy can lead to a glucocorticoid-resistant state, and we deliberate how this impacts disease treatment. Chronic glucocorticoid treatment can lead to noticeable side effects such as weight gain, adiposity, diabetes, and others that we discuss in detail. There are sexually dimorphic responses to glucocorticoids, and women tend to have a more hyperresponsive HPA axis than men. This review summarizes our understanding of glucocorticoids and critically analyzes the GR isoforms and their beneficial and deleterious mechanisms and the sexual differences that cause a dichotomy in responses. We also discuss the future of glucocorticoid therapy and propose a new concept of dual GR isoform agonist and postulate why activating both isoforms may prevent glucocorticoid resistance.

SUCNR1 signaling in adipocytes controls energy metabolism by modulating circadian clock and leptin expression

Adipose tissue modulates energy homeostasis by secreting leptin, but little is known about the factors governing leptin production. We show that succinate, long perceived as a mediator of immune response and lipolysis, controls leptin expression via its receptor SUCNR1. Adipocyte-specific deletion of Sucnr1 influences metabolic health according to nutritional status. Adipocyte Sucnr1 deficiency impairs leptin response to feeding, whereas oral succinate mimics nutrient-related leptin dynamics via SUCNR1. SUCNR1 activation controls leptin expression via the circadian clock in an AMPK/JNK-C/EBPα-dependent manner. Although the anti-lipolytic role of SUCNR1 prevails in obesity, its function as a regulator of leptin signaling contributes to the metabolically favorable phenotype in adipocyte-specific Sucnr1 knockout mice under standard dietary conditions. Obesity-associated hyperleptinemia in humans is linked to SUCNR1 overexpression in adipocytes, which emerges as the major predictor of adipose tissue leptin expression. Our study establishes the succinate/SUCNR1 axis as a metabolite-sensing pathway mediating nutrient-related leptin dynamics to control whole-body homeostasis.

The sex-dependent response to psychosocial stress and ischaemic heart disease

Stress is an important risk factor for modern chronic diseases, with distinct influences in males and females. The sex specificity of the mammalian stress response contributes to the sex-dependent development and impacts of coronary artery disease (CAD). Compared to men, women appear to have greater susceptibility to chronic forms of psychosocial stress, extending beyond an increased incidence of mood disorders to include a 2- to 4-fold higher risk of stress-dependent myocardial infarction in women, and up to 10-fold higher risk of Takotsubo syndrome-a stress-dependent coronary-myocardial disorder most prevalent in post-menopausal women. Sex differences arise at all levels of the stress response: from initial perception of stress to behavioural, cognitive, and affective responses and longer-term disease outcomes. These fundamental differences involve interactions between chromosomal and gonadal determinants, (mal)adaptive epigenetic modulation across the lifespan (particularly in early life), and the extrinsic influences of socio-cultural, economic, and environmental factors. Pre-clinical investigations of biological mechanisms support distinct early life programming and a heightened corticolimbic-noradrenaline-neuroinflammatory reactivity in females vs. males, among implicated determinants of the chronic stress response. Unravelling the intrinsic molecular, cellular and systems biological basis of these differences, and their interactions with external lifestyle/socio-cultural determinants, can guide preventative and therapeutic strategies to better target coronary heart disease in a tailored sex-specific manner.

Discovery and Optimization of N-Acyl-6-sulfonamide-tetrahydroquinoline Derivatives as Novel Non-Steroidal Selective Glucocorticoid Receptor Modulators

Selective glucocorticoid receptor modulators (SGRMs), which can dissociate the transactivation from the transrepression of the glucocorticoid receptor (GR), are regarded as very promising therapeutics for inflammatory and autoimmune diseases. We previously discovered a SGRM HP-19 based on the passive antagonistic conformation of GR and bioassays. In this study, we further analyzed the dynamic changes of the passive antagonistic state upon the binding of HP-19 and designed and synthesized 62 N-acyl-6-sulfonamide-tetrahydroquinoline derivatives by structural optimization of HP-19. Therein, compound B53 exhibits the best transrepression activity (IC_{50 NF-κB} = 0.009 ± 0.001 μM) comparable with dexamethasone (IC_{50 NF-κB} = 0.005 ± 0.001 μM) and no transactivation activity. B53 can efficiently reduce the expression of inflammatory factors IL-6, IL-1β, TNF-α, and so on and makes a milder adverse effect and is highly specific to GR. Furthermore, B53 is able to significantly relieve dermatitis on a mouse model via oral drug intervention.

Dexamethasone Enhances Achilles Tendon Healing in an Animal Injury Model, and the Effects Are Dependent on Dose, Administration Time, and Mechanical Loading Stimulation

BACKGROUND

Corticosteroid treatments such as dexamethasone are commonly used to treat tendinopathy but with mixed outcomes. Although this treatment can cause tendon rupture, it can also stimulate the tendon to heal. However, the mechanisms behind corticosteroid treatment during tendon healing are yet to be understood.

PURPOSE

To comprehend when and how dexamethasone treatment can ameliorate injured tendons by using a rat model of Achilles tendon healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

An overall 320 rats were used for a sequence of 6 experiments. We investigated whether the drug effect was time-, dose-, and load-dependent. Additionally, morphological data and drug administration routes were examined. Healing tendons were tested mechanically or used for histological examination 12 days after transection. Blood was collected for flow cytometry analysis in 1 experiment.

RESULTS

We found that the circadian rhythm and drug injection timing influenced the treatment outcome. Dexamethasone treatment at the right time point (days 7-11) and dose (0.1 mg/kg) significantly improved the material properties of the healing tendon, while the adverse effects were reduced. Local dexamethasone treatment did not lead to increased peak stress, but it triggered systemic granulocytosis and lymphopenia. Mechanical loading (full or moderate) is essential for the positive effects of dexamethasone, as complete unloading leads to the absence of improvements.

CONCLUSION

We conclude that dexamethasone treatment to improve Achilles tendon healing is dose- and time-dependent, and positive effects are perceived even in a partly unloaded condition.

CLINICAL RELEVANCE

These findings are promising from a clinical perspective, as the positive effect of this drug was seen even when given at lower doses and in a moderate loading condition, which better mimics the load level in patients with tendon ruptures.

Effect of anaerobic resistance training on gastric emptying of solids, nutritional parameters and food behavior in the rats treated with dexamethasone

Dexamethasone (Dexa) is a potent glucocorticoid that can trigger side effects, such as neuromuscular, cardiovascular, and gastric motility disorders. Exercise can ameliorate gastrointestinal disorders. However, it is not clear whether exercise can modulate the side effects of using Dexa on gastric motility. To investigate the role of anaerobic resistance training (ART) on gastric motility and feeding behavior of rats treated with dexamethasone, rats were divided into three groups: control (Ctrl), dexamethasone (Dexa), and anaerobic resistance training + dexamethasone (ARTDexa). Anaerobic resistance training (ART) consisted of climbing a vertical ladder 5 days/week (with intensity of 50% to 100% of the maximum overload/8 weeks). At the end of the ART or control period, the rats received Dexa (1 mg/kg i.p) for 10 consecutive days. In the end, we evaluated anthropometric parameters and feeding behavior, heart rate, gastric emptying, and lipid profile in all groups. We observed significant decrease (p < 0.05) in body weight and food intake in the Dexa and ARTDexa groups compared to the control. Dexa promoted significant tachycardia (p < 0.05) and a decrease (p < 0.05) in the r-r' interval. The ART significantly prevented (p < 0.05) cardiovascular effects. Dexa induced a decrease (p < 0.05) in gastric emptying compared to the control group. On the other hand, ART significantly prevented (p < 0.05) the decrease in gastric emptying compared to Dexa. The chronic use of Dexa caused tachycardia, decreased food intake, and decreased gastric emptying. The ART modulated cardiovascular parameters, improving tachycardia. In addition, this exercise prevented gastric dysmotility induced by dexamethasone.

Clinical and Anatomopathological Evaluation of BALB/c Murine Models Infected with Isolates of Seven Pathogenic Sporothrix Species

Background: Sporotrichosis is a subcutaneous mycosis with worldwide distribution and caused by seven pathogenic species of Sporothrix genus: S. schenckii sensu stricto, S. brasiliensis, S. globosa and S. luriei (clinical clade), and the species S. mexicana, S. pallida and S. chilensis (environmental clade). Isolates of the same species of Sporothrix may have different pathogenicities; however, few isolates of this fungus have been studied. Thus, the aim of this work was to analyze the clinical and anatomopathological changes in immunocompetent and immunosuppressed BALB/c mice infected with clinical and environmental isolates of seven different species of Sporothrix, from both clades. One human clinical isolate of S. schenckii sensu stricto, S. brasiliensis, S. globosa, S. luriei, S. mexicana and S. chilensis species and one environmental isolate of S. pallida were inoculated subcutaneously in immunocompetent mice and the same isolates of S. brasiliensis and S.schenckii sensu stricto were inoculated in immunossupressed mice. Clinical manifestations as external lesions, apathy, and alopecia were observed. At 21, 35, and 49 days after fungal inoculation, four mice from each group were weighed, euthanized and necropsied for evaluation of splenic index, recovery of fungal cells, macroscopic and histopathological analysis of livers, lungs, kidneys, and hearts. The survival assessment was observed for 50 days following inoculation. Our results demonstrated that, clinical S. schenckii isolate, followed by clinical S. mexicana, and environmental S. pallida isolates, the last two, species grouped in the environmental clade, were capable of inducing greater anatomopathological changes in mice, which was reflected in the severity of the clinical signs of these animals. Thus, we reinforce the hypothesis that the pathogenicity of Sporothrix is not only related to the species of this fungus, but also shows variation between different isolates of the same species.

Environmental enrichment modulates silent information regulator 1 (SIRT1) activity to attenuate central presbycusis in a rat model of normal aging

Age-related hearing loss (ARHL) is sensory impairment in the elderly. This study aimed to identify a critical molecular mechanism that can maintain young phenotypes. We focused on the effect of exposure to environmental enrichment (EE) for 12 weeks in the central auditory pathway and limbic system of aged rats. The effects of EE were compared with the effects of dexamethasone administration. We found that in 74-week-old rats hearing function was significantly reduced and the number of neuronal specific nuclear protein (NeuN)-positive cells was decreased by 10-15% in the auditory cortex, amygdala, and hippocampus. EE exposure did not significantly affect the number of neurons, but DX administration significantly decreased their numbers in the amygdala compared with untreated aged rats. Both treatments reduced inducible nitric oxide synthase (iNOS) expression in the auditory pathway and limbic system. Exposure to EE significantly increased silent information regulator 1 (SIRT1) expression and activity, and nicotinamide phosphoribosyltransferase (NAMPT) concentration. In this study, the exposure to EE resulted in attenuated age-related hearing loss accompanied by reduction of iNOS expression and increase SIRT1 activity and NAMPT level. These data showed that EE may be a potential therapeutic to prevent ARHL.

Chronic Variable Stress Induces Hepatic Fe(II) Deposition by Up-Regulating ZIP14 Expression via miR-181 Family Pathway in Rats

Simple Summary

Modern intensive production methods attract accusations of poor animal welfare due to long-term exposure to stressors including high temperature, persistent humidity and overcrowding. Stress can be defined as any condition that threatens the physiological homoeostasis and hypothalamic-pituitary-adrenal (HPA) axis responses that tend to restore the prior stable status of the organism. Uncontrollable and unpredictable sources of stress can cause various forms of damage to the liver, which is the central mediator of systemic iron balance. Iron, notably, is an essential element for maintaining health in virtually all organisms. We found that chronic variable stress can cause weight loss and disorders of the liver iron metabolism in rats, thereby triggering liver oxidative damage. Our results also suggest that the miR-181 family is a potential target for treating iron overload-associated diseases.

Abstract

It is well-known that hepatic iron dysregulation, which is harmful to health, can be caused by stress. The aim of the study was to evaluate chronic variable stress (CVS) on liver damage, hepatic ferrous iron deposition and its molecular regulatory mechanism in rats. Sprague Dawley rats at seven weeks of age were randomly divided into two groups: a control group (Con) and a CVS group. CVS reduces body weight, but increases the liver-to-body weight ratio. The exposure of rats to CVS increased plasma aspartate aminotransferase (AST), alkaline phosphatase (ALP) and hepatic malondialdehyde (MDA) levels, but decreased glutathione peroxidase (GSH-Px) activity, resulting in liver damage. CVS lowered the total amount of hepatic iron content, but induced hepatic Fe(II) accumulation. CVS up-regulated the expression of transferrin receptor 1 (TFR1) and ZRT/IRT-like protein 14 (ZIP14), but down-regulated ferritin and miR-181 family members. In addition, miR-181 family expression was found to regulate ZIP14 expression in HEK-293T cells by the dual-luciferase reporter system. These results indicate that CVS results in liver damage and induces hepatic Fe(II) accumulation, which is closely associated with the up-regulation of ZIP14 expression via the miR-181 family pathway.

Tissue Lipidomic Alterations Induced by Prolonged Dexamethasone Treatment

Dexamethasone is a synthetic glucocorticoid medication vastly used to treat abnormal immune responses and inflammation. Although the medication is well-established in the medical community, the prolonged treatment with high dosages of dexamethasone may lead to severe adverse effects through mechanisms that are not yet well-known. Lipids are a large class of hydrophobic molecules involved in energy storage, signaling, modulation of gene expression, and membranes. Hence, untargeted lipidomics may help unravel the biochemical alterations following prolonged treatment with high dosages of dexamethasone. We performed comprehensive lipidomic analyses of brain, heart, kidney, liver, and muscle samples obtained from rats that were treated with intramuscular injections of dexamethasone for 14 weeks compared to healthy controls. The employed methodology and statistical analysis showed that phosphatidic acids, glycerophospholipids, plasmalogens, and fatty acids are deeply affected by prolonged use of the medication. Brain tissue was only mildly affected, but skeletal muscle showed a strong accumulation of lipids that may be correlated with alterations in the energy metabolism, myopathy, and oxidative processes. This work provides new insights into the mechanisms of action and adverse effects for one of the most commonly prescribed class of drugs in the world.

Anti-Asthmatic Effects of Saffron Extract and Salbutamol in an Ovalbumin-Induced Airway Model of Allergic Asthma

Introduction: Asthma is a chronic inflammatory disorder of the airways often characterized by airway remodeling and influx of inflammatory cells into the airways. Saffron (C. sativus) has been reported to possess anti-inflammatory, anti-allergic and immunomodulatory properties. Salbutamol is known to relax airway smooth muscles. Objective: To investigate the combined anti-asthmatic effect of C. sativus extract (CSE) and salbutamol in an ovalbumin (OVA)-induced asthma in rats. Materials and methods: Airway hyperresponsiveness (AHR) was induced in male Sprague-Dawley rats by OVA challenge and treated with CSE (30 mg/kg and 60 mg/kg i.p.) and salbutamol (0.5 mg/kg p.o) for 28 days. After the induction period, various hematological, biochemical, molecular (ELISA) and histological analyses were performed. Results: OVA-induced alterations observed in hematological parameters (total and differential cell counts observed in Bronchoalveolar Lavage Fluid (BALF) were significantly attenuated (p < 0.01) by CSE (30 mg/kg and 60 mg/kg) and salbutamol (0.5 mg/kg). The treatment combination also significantly decreased (p < 0.01) the levels of total protein and albumin in serum, BALF and lung tissues. Treatment with CSE and salbutamol significantly attenuated (p < 0.01) increase in OVA induced Th2 cytokine levels (TNF-α, IL-1β, IL-4, IL-13). Histopathological analysis of lung tissue showed that combined effect of CSE and salbutamol treatment ameliorated OVA-induced inflammatory influx and ultrastructural aberrations. Conclusion: The results obtained from this study show that the combined effect of CSE and salbutamol exhibited anti-asthmatic properties via its anti-inflammatory effect and by alleviating Th2 mediated immune response. Thus, this treatment combination could be considered as a new therapeutic strategy for management of asthma.

Shifts in the gut microbiota of mice in response to dexamethasone administration

Glucocorticoids (GCs) are an important anti-inflammatory drug, used widely, regardless of its side effects. GCs can affect intestinal flora directly or indirectly, though few studies have focused on the changes of gut microbiota composition. In this study, ICR mice were randomly divided into three groups, gavage administration with saline, and different doses of dexamethasone (DEX): 0.1 mg/kg and 1 mg/kg. Five days later, the microbial diversity of the colon contents was analyzed. A significant loss in weight was observed in the DEX1.0 group as compared with the control group (P = 0.011). The gut microbiota richness (ACE, P = 0.01; Chao, P = 0.013) and diversity (Shannon, P = 0.035; Simpson, P = 0.032) were decreased in DEX group. The proportions of genus Butyricicoccus, Oscillibacter, Anaerotruncus, Ruminiclostridium, Ruminococcaceae, and Lachnospiraceae were the most abundant and predominant followed by Lactobacillus, Pseudomonas, and Enterorhabdus. Dex administration led to changes in the liver/body ratio and spleen/body ratio. The results obtained from our study indicate that DEX can decrease the level of WBC and change the structure of the gut microbiota composition; moreover, the results of this study provide new insight into alleviating the clinical side effects of GC therapy.

Effects of combined glucocorticoid/mineralocorticoid receptor modulation (CORT118335) on energy balance, adiposity, and lipid metabolism in male rats

Psychological stress and excess glucocorticoids are associated with metabolic and cardiovascular diseases. Glucocorticoids act primarily through mineralocorticoid (MR) and glucocorticoid receptors (GR), and compounds modulating these receptors show promise in mitigating metabolic and cardiovascular-related phenotypes. CORT118335 (GR/MR modulator) prevents high-fat diet-induced weight gain and adiposity in mice, but the ability of this compound to reverse obesity-related symptoms is unknown. Adult male rats were subcutaneously administered CORT118335 (3, 10, or 30 mg/kg) or vehicle once daily. A 5-day treatment with CORT118335 at 30 mg/kg induced weight loss in rats fed a chow diet by decreasing food intake. However, lower doses of the compound attenuated body weight gain primarily because of decreased calorific efficiency, as there were no significant differences in food intake compared with vehicle. Notably, the body weight effects of CORT118335 persisted during a 2-wk treatment hiatus, suggesting prolonged effects of the compound. To our knowledge, we are the first to demonstrate a sustained effect of combined GR/MR modulation on body weight gain. These findings suggest that CORT118335 may have long-lasting effects, likely due to GR/MR-induced transcriptional changes. Prolonged (18 days) treatment of CORT118335 (10 mg/kg) reversed body weight gain and adiposity in animals fed a high-fat diet for 13 wk. Surprisingly, this occurred despite a worsening of the lipid profile and glucose homeostasis as well as a disrupted diurnal corticosterone rhythm, suggesting GR agonistic effects in the periphery. We conclude that species and tissue-specific targeting may result in promising leads for exploiting the metabolically beneficial aspects of GR/MR modulation.

Insulin signaling pathway in the masseter muscle of dexamethasone-treated rats

Background and aims

The treatment with glucocorticoids may induce molecular changes in the level and/or degree of phosphorylation of proteins located downstream of the insulin receptor/insulin-like growth factor receptor (IR/IGF1R) in many tissues. However, few studies have investigated the intracellular insulin pathway in the masseter muscle. Therefore, this study aimed to analyze the IR/IGF1R signaling pathway in the masseter muscle of rats treated with dexamethasone.

Materials and methods

Male Wistar rats were divided into two groups: control group (intraperitoneally injected with 0.9% NaCl solution) and dexamethasone group [intraperitoneally injected with 1 mg/kg (bw) dexamethasone solution] for 10 consecutive days. Sections of the masseter muscle were removed at time zero and after the infusion of regular insulin into the portal vein.

Results

Dexamethasone administration induces body weight loss without changing masseter muscle weight and reduces the expression of total IR and PI3K proteins; total levels of IRS1, Akt, and ERK1 remain unchanged between groups. The degree of phosphorylation/activity of IRS1 after insulin stimulus increased only in the control group; degree of phosphorylation of Akt increased in both groups, but this increase was attenuated in the dexamethasone group.

Discussion and conclusion

The degree of phosphorylation/activity in the masseter muscle is different from that in other muscle territories.

Chronic dexamethasone exposure retards growth without altering the digestive tract microbiota composition in goats

Background

Dexamethasone (Dex), an artificially synthetic cortisol substitute, is commonly used as an anti-inflammatory drug, and is also employed to mimic the stress state experimentally. It is well known that chronic stress disturbs the gut microbiota community and digestive functions. However, no relevant studies have been conducted in ruminants.

Results

In this study, a low dosage of Dex (0.2 mg/kg body weight, Dex group, n = 5) was consecutively injected intramuscularly for 21 days to simulate chronic stress in growing goats. Goats were injected with saline (0.2 mg/kg body weight) as the control group (Con, n = 5). Dex-treated goats showed a higher number of white blood cells and blood glucose levels (p < 0.01), but lower dry matter intake (DMI) and body weight (p < 0.01) than those of saline-injected goats. Plasma cortisol concentration decreased significantly in response to the Dex injection compared to the control (p < 0.05). The Dex treatment did not change most ruminal volatile fatty acid (VFAs) concentrations before the morning feeding after 1–21 days of treatment (p > 0.05); however, ruminal VFA concentrations decreased dramatically 2, 4, 6, and 8 h after the morning feeding on day 21 of the Dex injections. In this study, chronic Dex exposure did not alter the community structure of microbes or methanogenes in the rumen, caecum, or colonic digesta. Only Prevotella increased on days 7 and 14 of Dex treatment, but decreased on day 21, and Methanosphaera was the only genus of methanogene that decreased.

Conclusions

Our results suggest that chronic Dex exposure retards growth by decreasing DMI, which may be mediated by higher levels of blood glucose and lower ruminal VFA production. Microbiota in the digestive tract was highly resistant to chronic Dex exposure.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1253-1) contains supplementary material, which is available to authorized users.

Chronic treatment with dexamethasone alters clock gene expression and melatonin synthesis in rat pineal gland at night

BACKGROUND

Melatonin is a neuroendocrine hormone that regulates many functions involving energy metabolism and behavior in mammals throughout the light/dark cycle. It is considered an output signal of the central circadian clock, located in the suprachiasmatic nucleus of the hypothalamus. Melatonin synthesis can be influenced by other hormones, such as insulin and glucocorticoids in pathological conditions or during stress. Furthermore, glucocorticoids appear to modulate circadian clock genes in peripheral tissues and are associated with the onset of metabolic diseases. In the pineal gland, the modulation of melatonin synthesis by clock genes has already been demonstrated. However, few studies have shown the effects of glucocorticoids on clock genes expression in the pineal gland.

RESULTS

We verified that rats treated with dexamethasone (2 mg/kg body weight, intraperitoneal) for 10 consecutive days, showed hyperglycemia and pronounced hyperinsulinemia during the dark phase. Insulin sensitivity, glucose tolerance, melatonin synthesis, and enzymatic activity of arylalkylamine N-acetyltransferase, the key enzyme of melatonin synthesis, were reduced. Furthermore, we observed an increase in the expression of Bmal1, Per1, Per2, Cry1, and Cry2 in pineal glands of rats treated with dexamethasone.

CONCLUSION

These results show that chronic treatment with dexamethasone can modulate both melatonin synthesis and circadian clock expression during the dark phase.

Fat-brain connections: Adipocyte glucocorticoid control of stress and metabolism

Glucocorticoids act via multiple mechanisms to mobilize energy for maintenance and restoration of homeostasis. In adipose tissue, glucocorticoids can promote lipolysis and facilitate adipocyte differentiation/growth, serving both energy-mobilizing and restorative processes during negative energy balance. Recent data suggest that adipose-dependent feedback may also be involved in regulation of stress responses. Adipocyte glucocorticoid receptor (GR) deletion causes increased HPA axis stress reactivity, due to a loss of negative feedback signals into the CNS. The fat-to-brain signal may be mediated by neuronal mechanisms, release of adipokines or increased lipolysis. The ability of adipose GRs to inhibit psychogenic as well as metabolic stress responses suggests that (1) feedback regulation of the HPA axis occurs across multiple bodily compartments, and (2) fat tissue integrates psychogenic stress signals. These studies support a link between stress biology and energy metabolism, a connection that has clear relevance for numerous disease states and their comorbidities.

Extra-adrenal glucocorticoids contribute to the postprandial increase of circulating leptin in mice

Leptin, an adipokine secreted by white adipocytes, is known for its function in regulating food intake and energy expenditure, but the mechanisms regulating its circulating levels is not fully understood. Our previous findings suggest that as yet unidentified humoral factors released from enterocytes are involved. The present study tested glucocorticoids (GCs) as candidate factors. Supplementation of corticosterone and cortisol promoted leptin production in murine adipocytes from the 3T3-L1 cell strain and human adipocytes from the Simpson Golabi-Behmel syndrome (SGBS) cell strain, respectively. These changes were observed in the absence but not presence of the GC-receptor antagonist mifepristone. The cortisol concentration in conditioned medium (CM) of human enterocyte-like Caco-2 cells was increased by phorbol-12-myristate 13-acetate and decreased by metyrapone. When SGBS adipocytes were cultured in these CMs, leptin production was positively associated with cortisol concentrations. During a 2-h refeeding after fasting, plasma leptin levels continued to increase in sham-operated mice, transiently increased at 60 min in adrenalectomized mice, and were unchanged in mifepristone-administered mice. These results suggest that extra-adrenal GCs contribute to the GC-receptor signaling-dependent increase of postprandial circulating leptin, whereas further studies will be required to determine whether enterocytes participate in the GCs-mediated increase of postprandial circulating leptin.

Long-Term Dexamethasone Exposure Down-Regulates Hepatic TFR1 and Reduces Liver Iron Concentration in Rats

Exposure to stress is known to cause hepatic iron dysregulation, but the relationship between prolonged stress and liver iron metabolism is not yet fully understood. Thirty 13-week-old female Sprague-Dawley rats were randomly divided into two groups, as follows: the control group (saline-injection) and the dexamethasone group (Dexamethasone (Dex)-injection 0.1 mg/kg/day). After the 21-day stress trial, the results showed that chronic Dex administration not only impaired serum corticosterone (p = 0.00) and interleukin-6 (IL-6) (p = 0.01) levels, but also decreased white blood cell counts (p = 0.00), and reduced blood lymphocyte counts (p = 0.00). The daily Dex-injection also significantly reduced body weight (p < 0.01) by inhibiting food intake. Consecutive Dex administration resulted in decreased iron intake (p = 0.00), enhanced serum iron levels (p = 0.01), and increased the serum souble transferrin receptor (sTfR) content (p = 0.00) in rats. Meanwhile, long-term Dex exposure down-regulated duodenal cytochrome b (DCYTB) (p = 0.00) and the divalent metal transporter 1 (DMT1) (p = 0.04) protein expression, but up-regulated ferroportin (FPN) protein expression (p = 0.04). Chronic Dex administration reduced liver iron concentration (p = 0.02) in rats. Hepatic transferrin receptor 1 (TFR1) expression was lowered at the protein level (p = 0.03), yet with uncoupled mRNA abundance in Dex-treated rats. Enhanced iron-regulatory protein (IRP)/iron-responsive element (IRE) binding activity was observed, but did not line up with lowered hepatic TFR1 protein expression. This study indicates that long-term Dex exposure reduces liver iron content, which is closely associated with down-regulated hepatic TFR1 protein expression.

Subchronic glucocorticoids, glutathione depletion and a postpartum model elevate monoamine oxidase a activity in the prefrontal cortex of rats

Recent human brain imaging studies implicate dysregulation of monoamine oxidase-A (MAO-A), in particular in the prefrontal cortex (PFC) and anterior cingulate cortex (ACC), in the development of major depressive disorder (MDD). This study investigates the influence of four alterations underlying important pathologies of MDD, namely, chronic elevation of glucocorticoid levels, glutathione depletion, changes in female gonadal sex hormones and serotonin concentration fluctuation, on MAO-A and MAO-B activities in rats. Young adult rats exposed chronically to the synthetic glucocorticoid dexamethasone at 0, 0.05, 0.5, and 2.0mg/kg/day (osmotic minipumps) for eight days showed significant dose-dependent increases in activities of MAO-A in PFC (+17%, p<0.001) and ACC (+9%, p<0.01) and MAO-B in PFC (+14%, p<0.001) and increased serotonin turnover in the PFC (+31%, p<0.01), not accounted for by dexamethasone-induced changes in serotonin levels, since neither serotonin depletion nor supplementation affected MAO-A activity. Sub-acute depletion of the major antioxidant glutathione by diethyl maleate (5mmol/kg, i.p.) for three days, which resulted in a 36% loss of glutathione in PFC (p=0.0005), modestly, but significantly, elevated activities of MAO-A in PFC and MAO-B in PFC, ACC and hippocampus (+6-9%, p<0.05). Changes in estrogen and progesterone representing pseudopregnancy were associated with significantly elevated MAO-A activity in the ACC day 4-7 postpartum (10-18%, p<0.05 to p<0.0001) but not the PFC or hippocampus. Hence, our study provides data in support of strategies targeting glucocorticoid and glutathione systems, as well as changes in female sex hormones for normalization of MAO-A activities and thus treatment of mood disorders.

Early life stress experience may blunt hypothalamic leptin signalling

The aim of this study was to investigate whether neonatal maternal separation (MS) - chronic stress experience in early life - affects the anorectic efficacy of leptin in the offspring at adolescence. Sprague-Dawley pups were separated from the dam daily for 3 h during postnatal day 1-14 or left undisturbed as non-handled controls (NH). NH and MS male pups received an intraperitoneal leptin (100 μg/kg) or saline on postnatal day (PND) 28, and then food intake and body weight gain were recorded. The hypothalamic levels of leptin-signalling-related genes, phosphorylated signal transducer and activator of transcription-3 (pSTAT3) and protein-tyrosine phosphatase 1B (PTP1B) were examined at 40 min after a single injection of leptin on PND 39 by immunohistochemistry and Western blot analysis. Leptin-induced suppressions in food intake and weight gain was observed in NH pups, but not in MS. Leptin increased pSTAT3 in the hypothalamic arcuate nucleus of NH pups, but not of MS. Interestingly, basal levels of the hypothalamic PTP1B and pSTAT3 were increased in MS pups compared with NH controls. The results suggest that neonatal MS experience may blunt the anorectic efficacy of leptin later in life, possibly in relation with increased expressions of PTP1B and/or pSTAT3 in the hypothalamus.

Antihypertensive effect of allicin in dexamethasone-induced hypertensive rats

BACKGROUND

Glucocorticoid is among the most commonly prescribed medicine. Unfortunately, Excess glucocorticoid level leads hypertension in 80-90% patients. Garlic (Allium sativum) has been used since ancient times and even nowadays as a part of popular medicine for various ailments and physiological disorders. Hence this study was undertaken to investigate the antihypertensive activity of allicin in dexamethasone induced hypertension in wistar rats.

METHODS

The animals were randomly divided into four groups comprising of six rats per group. Hypertension was induced by subcutaneous injection of dexamethasone (10 μg/rat/day) in hypertensive rats. Two hypertensive group animals were treated with nicorandil (6 mg/kg/day, po) and allicin (8 mg/kg/day, po) respectively for 8 weeks. While systolic blood pressure (SBP) was measured by the tail-cuff method weekly up to 8 weeks.

RESULTS

Dexamethasone treatment resulted in significant increase in SBP while allicin treatment significantly decreases the SBP. Thus, this study confirmed that allicin treatment for 8 weeks partially reverse dexamethasone induced hypertension in rats. Allicin treatment also attenuated dexamethasone-induced anorexia and loss of total body weight.

CONCLUSION

This result suggests antihypertensive effects of allicin in dexamethasone induced hypertension. However, further studies are needed to explore the detailed mechanism of antihypertensive effect of allicin.

Steroid Profiling in Male Wobbler Mouse, a Model of Amyotrophic Lateral Sclerosis

The Wobbler mouse is an animal model for human motoneuron diseases, especially amyotrophic lateral sclerosis (ALS), used in the investigation of both pathology and therapeutic treatment. ALS is a fatal neurodegenerative disease, characterized by the selective and progressive death of motoneurons, leading to progressive paralysis. Previous limited studies have reported steroidal hormone dysregulation in Wobbler mouse and in ALS patients, suggesting endocrine dysfunctions which may be involved in the pathogenesis of the disease. In this study, we established a steroid profiling in brain, spinal cord, plasma, adrenal glands, and testes in 2-month-old male Wobbler mice and their littermates by gas chromatography coupled to mass spectrometry. Our results show in Wobbler mice the following: 1) a marked up-regulation of corticosterone levels in adrenal glands, plasma, spinal cord regions (cervical, thoracic, lumbar) and brain; 2) a strong decrease in T levels in the testis, plasma, spinal cord, and brain; and 3) increased levels of progesterone and especially of its reduced metabolites 5α-dihydroprogesterone, allopregnanolone, and 20α-dihydroprogesterone in the brain, spinal cord, and adrenal glands. Furthermore, Wobbler mice showed a hypothalamic-pituitary-gonadal hypoactivity. Interestingly, plasma concentrations of corticosterone and T correlate well with their respective levels in cervical spinal cord in both control and Wobbler mice. T down-regulation is probably the consequence of adrenal hyperactivity, and the up-regulation of progesterone and its reduced metabolites may correspond to an endogenous protective mechanism in response to motoneuron degeneration. Our findings suggest that increased levels of corticosterone and decreased levels of T in plasma could be a signature of motoneuron degeneration.

Timing of glucocorticoid administration determines severity of lipid metabolism and behavioral effects in rats

Glucocorticoids (GCs) are a group of steroid hormones secreted by the adrenal glands in circadian cycles, and the dysregulation of GC signaling has been suggested to cause metabolic syndrome. Even though prolonged GC exposure is associated with serious side effects such as metabolic syndrome and central nervous system disorders, the use of GCs in anti-inflammatory and immunosuppressive therapies has been continuously rising. Meanwhile, the exact mechanisms by which GCs can influence the lipid metabolism as well as behavior and how they are affected by time remain unknown. In this study, the effects of two different long-term GC dosing regimens on lipid metabolism and behavior were investigated. Male Wistar rats received daily administrations of the GC dexamethasone sodium phosphate (DEX, 0.5 mg/kg body weight) at either ZT0 (Dex0) or ZT12 (Dex12). After 6 weeks of treatment, DEX-treated rats, especially those treated at ZT0, had higher hepatic lipid accumulation and serum triglyceride levels and less locomotor activity than did control rats. In addition, serum levels of corticosterone, 5-hydroxy tryptamine and norepinephrine were decreased in the Dex0 group but not in the Dex12 group compared to the control group. Furthermore, quantitative real-time polymerase chain reaction analysis indicated that the chronic administration of GCs at ZT0 upregulated genes related to glycolysis and lipid synthesis and downregulated genes related to fatty acid β-oxidation in the liver more remarkably than administration at ZT12. Both DEX-treated groups displayed severely altered expression patterns of the core clock genes Bmal1 and Per2 in the liver and in fat. In addition, the expression of glutamate aspartate transporter, glial fibrillary acidic protein and glutamate transporter-1, astrocyte-related genes important for maintaining nervous system functions, was drastically decreased in the hippocampus of DEX-treated rats, especially when DEX was given at ZT0. In conclusion, our findings confirm that the severity of side effects, indicated by altered lipid metabolism and behavioral activity, depends on the timing of GC administration and is associated with the degree of glucocorticoid receptor dysfunction after dosing at disparate time points.

Limiting glucocorticoid secretion increases the anorexigenic property of Exendin-4

Objective

Glucagon-like peptide-1 (GLP-1) analogs are attractive options for the treatment of type II diabetes and obesity because of their incretin and anorexigenic effects. Peripheral administration of the GLP-1R agonist Exendin-4 (Ex-4) also increases glucocorticoid secretion in rodents and humans, but whether the released glucocorticoids interact with Ex-4's anorexigenic effect remains unclear.

Methods

To test this, we used two experimental approaches that suppress corticosterone secretion and then assessed Ex-4 effects on eating in adult male rats. First, we combined acute and chronic low dose dexamethasone treatment with Ex-4. Second, we ablated hindbrain catecholamine neurons projecting to the hypothalamus with anti-dopamine-β-hydroxylase-saporin (DSAP) to block Ex-4-induced corticosterone secretion.

Results

Combining dexamethasone and Ex-4 produced a larger acute anorexigenic effect than Ex-4 alone. Likewise, chronic dexamethasone and Ex-4 co-treatment produced a synergistic effect on eating and greater body weight loss in diet-induced obese rats than Ex-4 alone. DSAP lesions not only blunted Ex-4's ability to increase corticosterone secretion, but potentiated the anorexigenic effect of Ex-4, indicating that Ex-4-dependent corticosterone secretion opposes Ex-4's actions. Consistent with the enhancement of Ex-4's anorexigenic effect, DSAP lesion altered Ex-4-dependent changes in neuropeptide Y, preproglucagon, and corticotropin releasing hormone gene expression involved in glucocorticoid feedback.

Conclusions

Our findings demonstrate that limiting glucocorticoid secretion and actions with low dose dexamethasone or DSAP lesion increases Ex-4's ability to reduce food intake and body weight. Novel glucocorticoid receptor based mechanisms, therefore, may help enhance GLP-1-based obesity therapies.

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Blocking HPA axis by low dose dexamethasone increased the anorexigenic property of Ex-4.

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Dexamethasone/Ex-4 co-treatment reduced food intake and body weight in diet-induced obese rats more than Ex-4 alone.

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A brain lesion model identified a potential central interaction between glucocorticoids and GLP-1 in food intake control.

Time-course changes of catabolic proteins following muscle atrophy induced by dexamethasone

This study was designed to describe the time-course changes of catabolic proteins following muscle atrophy induced by 10 days of dexamethasone (DEX). Rats underwent DEX treatment for 1, 3, 5, 7 and 10 days. Body weight (BW) and lean mass were obtained using a dual energy X-ray absorptiometry (DEXA) scan. Muscle ringer finger1 (MuRF-1), atrogin-1 and myostatin protein levels were analyzed in the tibialis anterior (TA), flexor hallucis longus (FHL) and soleus muscles. DEX treatment reduced lean mass since day-3 and reduced BW since day-5. Specific muscle weight reductions were observed after day-10 in TA (-23%) and after day-5 in FHL (-16%, -17% and -29%, for days 5, 7 and 10, respectively). In TA, myostatin protein level was 36% higher on day-5 and its values were normalized in comparison with controls on day-10. MuRF-1 protein level was increased in TA muscle from day-7 and in FHL muscle only on day-10. This study suggests that DEX-induced muscle atrophy is a dynamic process which involves important signaling factors over time. As demonstrated by DEXA scan, lean mass declines earlier than BW and this response may involve other catabolic proteins than myostatin and MuRF-1. Specifically for TA and FHL, it seems that myostatin may trigger the catabolic process, and MuRF-1 may contribute to maintain muscle atrophy. This information may support any intervention in order to attenuate the muscle atrophy during long period of treatment.

Restriction of spontaneous and prednisolone-induced leptin production to dedifferentiated state in human hip OA chondrocytes: role of Smad1 and β-catenin activation

OBJECTIVE

The aetiology of OA is not fully understood although several adipokines such as leptin are known mediators of disease progression. Since leptin levels were increased in synovial fluid compared to serum in OA patients, it was suggested that joint cells themselves could produce leptin. However, exact mechanisms underlying leptin production by chondrocytes are poorly understood. Nevertheless, prednisolone, although displaying powerful anti-inflammatory properties has been recently reported to be potent stimulator of leptin and its receptor in OA synovial fibroblasts. Therefore, we investigated, in vitro, spontaneous and prednisolone-induced leptin production in OA chondrocytes, focusing on transforming growth factor-β (TGFβ) and Wnt/β-catenin pathways.

DESIGN

We used an in vitro dedifferentiation model, comparing human freshly isolated hip OA chondrocytes cultivated in monolayer during 1 day (type II, COL2A1 +; type X, COL10A1 + and type I collagen, COL1A1 -) or 14 days (COL2A1 -; COL10A1 - and COL1A1+).

RESULTS

Leptin expression was not detected in day1 OA chondrocytes whereas day14 OA chondrocytes produced leptin, significantly increased with prednisolone. Activin receptor-like kinase 1 (ALK1)/ALK5 ratio was shifted during dedifferentiation, from high ALK5 and phospho (p)-Smad2 expression at day1 to high ALK1, endoglin and p-Smad1/5 expression at day14. Moreover, inactive glycogen synthase kinase 3 (GSK3) and active β-catenin were only found in dedifferentiated OA chondrocytes. Smad1 and β-catenin but not endoglin stable lentiviral silencing led to a significant decrease in leptin production by dedifferentiated OA chondrocytes.

CONCLUSIONS

Only dedifferentiated OA chondrocytes produced leptin. Prednisolone markedly enhanced leptin production, which involved Smad1 and β-catenin activation.

Investigations into the involvement of leptin in responses to stress

Stress is defined as a state that can threaten homeostasis in an organism to initiate the adaptive process. Stress mediators, which include the classic neuroendocrine hormones and a number of neurotransmitters, cytokines, and growth factors, regulate both basal and threatened homeostasis to help control the stress. Severity of stress, as well as malfunctioning of stress pathways, may impair its controllability, leading to the pathogenesis of psychiatric illnesses including depression. Leptin was initially identified as an antiobesity hormone, acting as a negative feedback adiposity signal to control energy homeostasis by binding to its receptors in the hypothalamus. Accumulating evidence has expanded the function of leptin from the control of energy balance to the regulation of other physiological and psychological processes. The aim of this paper is to evaluate the potential role of leptin in stress controllability. To this end, studies on the role of leptin in stress-induced activation of the hypothalamus-pituitary-adrenocortical axis, feeding behavior, learned helplessness, and other depression models have been accumulated. The knowledge accumulated in this article may facilitate the development of alternative treatment strategies, beyond serotonin and noradrenaline reuptake inhibition, for psychiatric care and stress-related disorders.

Protective effects of necrostatin-1 on glucocorticoid-induced osteoporosis in rats

The inhibition of bone formation has been suggested to play a central role in the pathogenesis of glucocorticoid-induced osteoporosis (GIOP). Recently, many studies suggested that there may be another mechanism involved in GIOP besides apoptosis. The aim of this study was to investigate the protective effect of Necrostatin-1 on GIOP rats. Forty male Sprague-Dawley rats were randomly divided into four groups (n=10): controls; GIOP rats; GIOP rats pretreated with alendronate; and GIOP rats pretreated with Necrostatin-1. Their bone mineral density (BMD) and body weight were measured at the beginning and at the end of the experiment. TUNEL assay, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to observe the change of cellular morphology induced by Nec-1. The biochemical analysis and histomorphometric analysis were used to evaluate the change of bone formation by Nec-1. RIP-1, RIP-3 and caspase-8 expression were evaluated by immunohistochemistry. We found more TUNEL positive osteocytes and larger lacunae volume in GIOP rats compared with the control group. However, most of the osteocytes displayed a necrotic morphology and mitochondria lesions under TEM. In contrast to alendronate, Necrostatin-1 significantly elevated the level of bone formation markers, while it had no effect on bone resorption markers. Necrostatin-1 also markedly ameliorated trabecular bone. In addition, Necrostatin-1 significantly weaken the immunoreactivity of RIP-1 in GIOP rats while had no effect on RIP-3 and caspase-8. These data suggest, for the first time, that Necrostatin-1 accelerate bone formation of glucocorticoid-induced osteoporosis in rats.

Low-intensity resistance training attenuates dexamethasone-induced atrophy in the flexor hallucis longus muscle

This study investigated the potential protective effect of low-intensity resistance training (RT) against dexamethasone (DEX) treatment induced muscle atrophy. Rats underwent either an 8 week period of ladder climbing RT or remained sedentary. During the last 10 days of the exercise protocol, animals were submitted to a DEX treatment or a control saline injection. Muscle weights were assessed and levels of AKT, mTOR, FOXO3a, Atrogin-1 and MuRF-1 proteins were analyzed in flexor hallucis longus (FHL), tibialis anterior (TA), and soleus muscles. DEX induced blood glucose increase (+46%), body weight reduction (-19%) and atrophy in FHL (-28%) and TA (-21%) muscles, which was associated with a decrease in AKT and an increase in MuRF-1 proteins levels. Low-intensity RT prevented the blood glucose increase, attenuated the FHL atrophy effects of DEX, and was associated with increased mTOR and reductions in Atrogin-1 and MuRF-1 in FHL. In contrast, TA muscle atrophy and signaling proteins were not affected by RT. These are the first data to demonstrate that low-intensity ladder-climbing RT specifically mitigates the FHL atrophy, which is the main muscle recruited during the training activity, while not preventing atrophy in other limb muscle not as heavily recruited. The recruitment-dependent prevention of atrophy by low intensity RT likely occurs by a combination of attenuated muscle protein degradation signals and enhanced muscle protein synthesis signals including mTOR, Atrogin-1 and MuRF-1.

Dexamethasone and acetate modulate cytoplasmic leptin in bovine preadipocytes

Hormonal and nutrient signals regulate leptin synthesis and secretion. In rodents, leptin is stored in cytosolic pools of adipocytes. However, not much information is available regarding the regulation of intracellular leptin in ruminants. Recently, we demonstrated that leptin mRNA was expressed in bovine intramuscular preadipocyte cells (BIP cells) and that a cytoplasmic leptin pool may be present in preadipocytes. In the present study, we investigated the expression of cytoplasmic leptin protein in BIP cells during differentiation as well as the effects of various factors added to the differentiation medium on its expression in BIP cells. Leptin mRNA expression was observed only at 6 and 8 days after adipogenic induction, whereas the cytoplasmic leptin concentration was the highest on day 0 and decreased gradually thereafter. Cytoplasmic leptin was detected at 6 and 8 days after adipogenic induction, but not at 4 days after adipogenic induction. The cytoplasmic leptin concentration was reduced in BIP cells at 4 days after treatment with dexamethasone, whereas cytoplasmic leptin was not observed at 8 days after treatment. In contrast, acetate significantly enhanced the cytoplasmic leptin concentration in BIP cells at 8 days after treatment, although acetate alone did not induce adipocyte differentiation in BIP cells. These results suggest that dexamethasone and acetate modulate the cytoplasmic leptin concentration in bovine preadipocytes.

Meta-modeling of methylprednisolone effects on glucose regulation in rats

A retrospective meta-modeling analysis was performed to integrate previously reported data of glucocorticoid (GC) effects on glucose regulation following a single intramuscular dose (50 mg/kg), single intravenous doses (10, 50 mg/kg), and intravenous infusions (0.1, 0.2, 0.3 and 0.4 mg/kg/h) of methylprednisolone (MPL) in normal and adrenalectomized (ADX) male Wistar rats. A mechanistic pharmacodynamic (PD) model was developed based on the receptor/gene/protein-mediated GC effects on glucose regulation. Three major target organs (liver, white adipose tissue and skeletal muscle) together with some selected intermediate controlling factors were designated as important regulators involved in the pathogenesis of GC-induced glucose dysregulation. Assessed were dynamic changes of food intake and systemic factors (plasma glucose, insulin, free fatty acids (FFA) and leptin) and tissue-specific biomarkers (cAMP, phosphoenolpyruvate carboxykinase (PEPCK) mRNA and enzyme activity, leptin mRNA, interleukin 6 receptor type 1 (IL6R1) mRNA and Insulin receptor substrate-1 (IRS-1) mRNA) after acute and chronic dosing with MPL along with the GC receptor (GR) dynamics in each target organ. Upon binding to GR in liver, MPL dosing caused increased glucose production by stimulating hepatic cAMP and PEPCK activity. In adipose tissue, the rise in leptin mRNA and plasma leptin caused reduction of food intake, the exogenous source of glucose input. Down-regulation of IRS-1 mRNA expression in skeletal muscle inhibited the stimulatory effect of insulin on glucose utilization further contributing to hyperglycemia. The nuclear drug-receptor complex served as the driving force for stimulation or inhibition of downstream target gene expression within different tissues. Incorporating information such as receptor dynamics, as well as the gene and protein induction, allowed us to describe the receptor-mediated effects of MPL on glucose regulation in each important tissue. This advanced mechanistic model provides unique insights into the contributions of major tissues and quantitative hypotheses for the multi-factor control of a complex metabolic system.

The endocrinology of food intake

Many questions must be considered with regard to consuming food, including when to eat, what to eat and how much to eat. Although eating is often thought to be a homeostatic behaviour, little evidence exists to suggest that eating is an automatic response to an acute shortage of energy. Instead, food intake can be considered as an integrated response over a prolonged period of time that maintains the levels of energy stored in adipocytes. When we eat is generally determined by habit, convenience or opportunity rather than need, and meals are preceded by a neurally-controlled coordinated secretion of numerous hormones that prime the digestive system for the anticipated caloric load. How much we eat is determined by satiation hormones that are secreted in response to ingested nutrients, and these signals are in turn modified by adiposity hormones that indicate the fat content of the body. In addition, many nonhomeostatic factors, including stress, learning, palatability and social influences, interact with other controllers of food intake. If a choice of food is available, what we eat is based on pleasure and past experience. This article reviews the hormones that mediate and influence these processes.

Nongenomic, glucocorticoid receptor-mediated regulation of serotonin transporter cell surface expression in embryonic stem cell derived serotonergic neurons

Depressive disorders have been linked to the combined dysregulation of the hypothalamus-pituitary-adrenal (HPA)-axis and the serotonergic system. The HPA-axis and serotonergic (5-HT) neurons exert reciprocal regulatory actions. It has been reported that glucocorticoid-glucocorticoid receptor (GR) signaling influences serotonin transporter (5-HTT) transcription but data also points to the fact that 5-HTT expression is regulated nongenomically via redistribution of 5-HTT from the cell surface into intracellular compartments. In order to analyze the acute effects of glucocorticoids on 5-HTT cell surface localization we differentiated serotonergic neurons from mouse embryonic stem (ES) cells derived from the C57BL/6N blastocysts. These postmitotic 5-HT neurons express all relevant serotonergic markers following the application of a growth factor-based differentiation protocol. Increasing concentrations of the GR agonist dexamethasone (Dex) resulted in enhanced, dose-dependent 5-HTT cell surface localization in the presence of the protein synthesis inhibitor cycloheximide already 1h after incubation. Inhibition of GR function by the specific GR-antagonist mifepristone abolished the increase in 5-HTT cell surface localization. Hence, our data account for a nongenomic upregulation of 5-HTT cell surface expression by glucocorticoid-GR interaction which likely constitutes a rapid physiological response to increased levels of glucocorticoids as seen during stress. Taken together, we provide a cellular model to analyze and dissect glucocorticoid-5HTT interactions on a molecular level that corresponds to in vivo animal models using C57BL/6N mice.

Stress induced obesity: lessons from rodent models of stress

Stress was once defined as the non-specific result of the body to any demand or challenge to homeostasis. A more current view of stress is the behavioral and physiological responses generated in the face of, or in anticipation of, a perceived threat. The stress response involves activation of the sympathetic nervous system and recruitment of the hypothalamic-pituitary-adrenal (HPA) axis. When an organism encounters a stressor (social, physical, etc.), these endogenous stress systems are stimulated in order to generate a fight-or-flight response, and manage the stressful situation. As such, an organism is forced to liberate energy resources in attempt to meet the energetic demands posed by the stressor. A change in the energy homeostatic balance is thus required to exploit an appropriate resource and deliver useable energy to the target muscles and tissues involved in the stress response. Acutely, this change in energy homeostasis and the liberation of energy is considered advantageous, as it is required for the survival of the organism. However, when an organism is subjected to a prolonged stressor, as is the case during chronic stress, a continuous irregularity in energy homeostasis is considered detrimental and may lead to the development of metabolic disturbances such as cardiovascular disease, type II diabetes mellitus and obesity. This concept has been studied extensively using animal models, and the neurobiological underpinnings of stress induced metabolic disorders are beginning to surface. However, different animal models of stress continue to produce divergent metabolic phenotypes wherein some animals become anorexic and lose body mass while others increase food intake and body mass and become vulnerable to the development of metabolic disturbances. It remains unclear exactly what factors associated with stress models can be used to predict the metabolic outcome of the organism. This review will explore a variety of rodent stress models and discuss the elements that influence the metabolic outcome in order to further extend our understanding of stress-induced obesity.

Quercetin prevents experimental glucocorticoid-induced osteoporosis: a comparative study with alendronate

Glucocorticoid-induced osteoporosis (GIO) is the most common type of secondary osteoporosis. The aim of this study was to compare the efficacy of quercetin, a plant-derived flavonoid, with alendronate in the prevention of GIO. Fifty-six Sprague–Dawley rats were randomly distributed among 7 groups (8 rats per group) and treated for 6 weeks with one of the following: (i) normal saline; (ii) 40 mg methylprednisolone sodium succinate (MP)/kg body mass; (iii) MP + 40 μg alendronate/kg; (iv) MP + 50 mg quercetin/kg; (v) MP + 40 μg alendronate/kg + 50 mg quercetin/kg; (vi) MP + 150 mg quercetin/kg; and (vii) MP + 40 μg alendronate/kg + 150 mg quercetin/kg. MP and alendronate were injected subcutaneously and quercetin was administered by oral gavage 3 days a week. At the end of the study, femur breaking strength was significantly decreased as a consequence of MP injection. This decrease was completely compensated for in groups receiving 50 mg quercetin/kg plus alendronate, and 150 mg quercetin/kg with or without alendronate. Quercetin noticeably elevated osteocalcin as a bone formation marker, while alendronate did not show such an effect. In addition, administration of 150 mg quercetin/kg increased femoral trabecular and cortical thickness by 36% and 22%, respectively, compared with the MP-treated group. These data suggest that 150 mg quercetin/kg, alone or in combination with alendronate, can completely prevent GIO through its bone formation stimulatory effect.

Dexamethasone administration to the neonatal rat results in neurological dysfunction at the juvenile stage even at low doses

Dexamethasone (DEX), a synthetic glucocorticoid, has been widely used to prevent the development of a variety of poor health conditions in premature infants including chronic lung disease, inflammation, circulatory failure, and shock. Although there are some reports of neurologic complications related to DEX exposure, its full effects on the premature brain have not been examined in detail. To investigate the effects of DEX on neural development, we first administered low doses (0.2 mg/kg bodyweight or less) of the glucocorticoid to neonatal rats on a daily basis during the first postnatal week and examined subsequent behavioral alterations at the juvenile stage. DEX-treated rats exhibited not only a significant reduction in both somatic and brain weights but also learning disabilities as revealed in the shuttle avoidance test. The hippocampi of DEX-treated rats displayed a high apoptotic and a low mitotic cell density compared to control rats on day 7 after birth. In a subsequent experiment, neural stem/progenitor cells were cultured in the presence of DEX for 6 days. The glucocorticoid inhibited cell growth without an increase in cell death. These results suggest that administration of DEX to premature infants induces neurological dysfunction via inhibition of the proliferation of neural stem/progenitor cells.

The effect of chronic immobilization stress on leptin signaling in the ovariectomized (OVX) rat

Previous studies have shown that both 17β-estradiol (E2) treatment and chronic stress may attenuate post-OVX weight gain in the female rat. However, the interaction between E2 and stress is unclear. This study examined the effect of E2 treatment and chronic immobilization stress on body weight. Adult OVX Sprague-Dawley rats were randomly assigned to one of four treatment groups in a 2X2 factorial design examining hormone treatment [vehicle (VEH) or E2, sc] and stress (no stress vs stress 60 min/day for 22 days). After 22 days, E2 significantly inhibited weight gain and food intake in OVX rats. In contrast, chronic stress reduced body weight only in control OVX animals but did not affect food intake. E2 reduced circulating leptin levels in non-stressed animals, but not in animals subjected to chronic immobilization. Western blot analysis indicated that E2 treatment increased leptin receptor (Ob-Rb) expression in the medial basal hypothalamus (MBH); however, this treatment also increased suppressor of cytokine signaling 3 (SOCS3), which is an inhibitor of leptin signaling. Chronic immobilization stress blunted the E2-induced increase in Ob-Rb and SOCS3 levels. These results suggest that chronic stress counteracts E2 effects on leptin signaling in the MBH without altering body weight.

Chronic prednisolone treatment aggravates hyperglycemia in mice fed a high-fat diet but does not worsen dietary fat-induced insulin resistance

Synthetic glucocorticoids such as prednisolone have potent antiinflammatory actions. Unfortunately, these drugs induce severe adverse effects in patients, many of which resemble features of the metabolic syndrome, such as insulin resistance. In this study, we investigated whether adverse effects of prednisolone on glucose homeostasis are aggravated in mice with compromised insulin sensitivity due to a high-fat diet by applying various methods to analyze changes in insulin sensitivity in mice. C57BL/6J mice were fed a high-fat diet for 6 wk and treated with either prednisolone (10 mg/kg · d) or vehicle for the last 7 d. Insulin sensitivity and blood glucose kinetics were analyzed with state-of-the-art stable isotope procedures in different experimental conditions. Prednisolone treatment aggravated fasting hyperglycemia and hyperinsulinemia caused by high-fat feeding, resulting in a higher homeostatic assessment model of insulin resistance. In addition, prednisolone-treated high-fat diet-fed mice appeared less insulin sensitive by detailed analysis of basal glucose kinetics. Remarkably, using hyperinsulinemic-euglycemic or hyperglycemic clamp techniques, neither hepatic nor peripheral insulin resistance was worsened in the group that was treated with prednisolone. Yet analysis of hepatic glucose metabolism revealed that prednisolone did alter glycogen balance by reducing glycogen synthase flux under hyperinsulinemic as well as hyperglycemic conditions. In addition to elevated insulin levels, prednisolone-treated mice showed a major rise in plasma leptin and fibroblast growth factor 21 levels. Our data indicate that prednisolone-induced adverse effects on glucose metabolism in high-fat diet-fed mice do not reflect impaired insulin sensitivity but may be caused by other changes in the hormonal regulatory network controlling glucose metabolism such as fibroblast growth factor 21 and leptin.

Glucocorticoids are required for meal-induced changes in the expression of hypothalamic neuropeptides

Glucocorticoid deficiency is associated with a decrease of food intake. Orexigenic peptides, neuropeptide Y (NPY) and agouti related protein (AgRP), and the anorexigenic peptide proopiomelanocortin (POMC), expressed in the arcuate nucleus of the hypothalamus (ARC), are regulated by meal-induced signals. Orexigenic neuropeptides, melanin-concentrating hormone (MCH) and orexin, expressed in the lateral hypothalamic area (LHA), also control food intake. Thus, the present study was designed to test the hypothesis that glucocorticoids are required for changes in the expression of hypothalamic neuropeptides induced by feeding. Male Wistar rats (230-280 g) were subjected to ADX or sham surgery. ADX animals received 0.9% NaCl in the drinking water, and half of them received corticosterone in the drinking water (B: 25 mg/L, ADX+B). Six days after surgery, animals were fasted for 16 h and they were decapitated before or 2 h after refeeding for brain tissue and blood collections. Adrenalectomy decreased NPY/AgRP and POMC expression in the ARC in fasted and refed animals, respectively. Refeeding decreased NPY/AgRP and increased POMC mRNA expression in the ARC of sham and ADX+B groups, with no effects in ADX animals. The expression of MCH and orexin mRNA expression in the LHA was increased in ADX and ADX+B groups in fasted condition, however there was no effect of refeeding on the expression of MCH and orexin in the LHA in the three experimental groups. Refeeding increased plasma leptin and insulin levels in sham and ADX+B animals, with no changes in leptin concentrations in ADX group, and insulin response to feeding was lower in this group. Taken together, these data demonstrated that circulating glucocorticoids are required for meal-induced changes in NPY, AgRP and POMC mRNA expression in the ARC. The lower leptin and insulin responses to feeding may contribute to the altered hypothalamic neuropeptide expression after adrenalectomy.

Mechanistic role for a novel glucocorticoid-KLF11 (TIEG2) protein pathway in stress-induced monoamine oxidase A expression

Chronic stress is a risk factor for psychiatric illnesses, including depressive disorders, and is characterized by increased blood glucocorticoids and brain monoamine oxidase A (MAO A, which degrades monoamine neurotransmitters). This study elucidates the relationship between stress-induced MAO A and the transcription factor Kruppel-like factor 11 (KLF11, also called TIEG2, a member of the Sp/KLF- family), which inhibits cell growth. We report that 1) a glucocorticoid (dexamethasone) increases KLF11 mRNA and protein levels in cultured neuronal cells; 2) overexpressing KLF11 increases levels of MAO A mRNA and enzymatic activity, which is further enhanced by glucocorticoids; in contrast, siRNA-mediated KLF11 knockdown reduces glucocorticoid-induced MAO A expression in cultured neurons; 3) induction of KLF11 and translocation of KLF11 from the cytoplasm to the nucleus are key regulatory mechanisms leading to increased MAO A catalytic activity and mRNA levels because of direct activation of the MAO A promoter via Sp/KLF-binding sites; 4) KLF11 knockout mice show reduced MAO A mRNA and catalytic activity in the brain cortex compared with wild-type mice; and 5) exposure to chronic social defeat stress induces blood glucocorticoids and activates the KLF11 pathway in the rat brain, which results in increased MAO A mRNA and enzymatic activity. Thus, this study reveals for the first time that KLF11 is an MAO A regulator and is produced in response to neuronal stress, which transcriptionally activates MAO A. The novel glucocorticoid-KLF11-MAO A pathway may play a crucial role in modulating distinct pathophysiological steps in stress-related disorders.