A rodent model of rapid-onset diabetes induced by glucocorticoids and high-fat feeding

Investigating the Impact of Ashwagandha and Meditation on Stress Induced Obesogenic Eating Behaviours

Obesity has been identified as a rapidly rising pandemic within the developed world, potentially increasing the risks of type 2 diabetes and cardiovascular disease. Various studies have identified a positive association between stress, elevated cortisol levels and obesity. Mechanisms of the stress response lead to hyperpalatable food preference and increased appetite through the activation of the HPA axis, elevated cortisol and the resulting interactions with the dopaminergic system, neuropeptide Y, ghrelin, leptin and insulin. The methodology of this review involved a Systematic Search of the Literature with a Critical Appraisal of papers considering ashwagandha, mediation and mindfulness in relation to mechanisms of the stress response. It incorporated 12 searches yielding 330 hits. A total of 51 studies met the inclusion criteria and were critically appraised with ARRIVE, SIGN50 and Strobe checklists. Data from the 51 studies was extracted, coded into key themes and summarized in a narrative analysis. Thematic analysis identified 4 key themes related to ashwagandha and 2 key themes related to meditation. Results provide an overview of evidence assessing the efficacy of ashwagandha and meditation in relation to weight loss interventions by supporting the stress response and the pathways highlighted. Results of Clinical studies indicate that ashwagandha supports weight loss through reduced stress, cortisol and food cravings. Pre-clinical studies also suggest that ashwagandha possesses the capacity to regulate food intake by improving leptin and insulin sensitivity and reducing addictive behaviors through dopamine regulation. Clinical studies on meditation indicate it may enhance a weight loss protocol by reducing the stress response, cortisol release and blood glucose and improving eating behaviors.

PPARα suppresses low-intensity-noise-induced body weight gain in mice: the activated HPA axis plays an critical role

BACKGROUND

As the second most risky environmental pollution, noise imposes threats to human health. Exposure to high-intensity noise causes hearing impairment, psychotic disorders, endocrine modifications. The relationship among low-intensity noise, obesity and lipid-regulating nuclear factor PPARα is not yet clear.

METHODS

In this study, male wild-type (WT) and Pparα-null (KO) mice on a high-fat diet (HFD) were exposed to 75 dB noise for 12 weeks to explore the effect of low-intensity noise on obesity development and the role of PPARα. 3T3-L1 cells were treated with dexamethasone (DEX) and sodium oleate (OA) to verify the down-stream effect of hypothalamic-pituitary-adrenal (HPA) axis activation on the adipose tissues.

RESULTS

The average body weight gain (BWG) of WT mice on HFD exposed to noise was inhibited, which was not observed in KO mice. The mass and adipocyte size of adipose tissues accounted for the above difference of BWG tendency. In WT mice on HFD, the adrenocorticotropic hormone level was increased by the noise challenge. The aggravation of fatty liver by noise exposure occurred in both mouse lines, and the transport of hepatic redundant lipid to adipose tissues were similar. The lipid metabolism in adipose tissue driven by HPA axis accorded with the BWG inhibition in vivo, validated in 3T3-L1 adipogenic stem cells.

CONCLUSION

Chronic exposure to low-intensity noise aggravated fatty liver in both WT and KO mice. BWG inhibition was observed only in WT mice, which covered up the aggravation of fatty liver by noise exposure. PPARα mediates the activation of HPA axis by noise exposure in mice on HFD. Elevated adrenocorticotropic hormone (ACTH) promoted lipid metabolism in adipocytes, which contributed to the disassociation of BWG and fatty liver development in male WT mice. Summary of PPARα suppresses noise-induced body weight gain in mice on high-fat-diet. Chronic exposure to low-intensity noise exposure inhibited BWG by PPARα-dependent activation of the HPA axis.

Stress, rhythm, choice and the munchies - tribute to Mary F. Dallman

In December 2021, we lost a pioneer in the field of stress research who inspired generations of scientists. Mary Dallman was an expert on the hypothalamic-pituitary-adrenal (HPA) axis, its interactions with a wide variety of other physiological systems and the impact of chronic changes of HPA function on energy metabolism and adiposity. She was not only an excellent scientist, she was a great role model and mentor for young scientists, especially women. She encouraged and supported many of her trainees even long after they left the lab. Her outside-the-box thinking, the fun and crazy discussions we had in the lab proved to be a beautiful basis for my own future research.

Effect of nebivolol on altered skeletal and cardiac muscles induced by dyslipidemia in rats: impact on oxidative and inflammatory machineries

AIM

High cholesterol diet is greatly linked to deleterious health consequences. In this work we tried to explore direct effects of high cholesterol diet on striated (skeletal and cardiac) muscle tissues and the mechanisms by which nebivolol could improve such harmful effects.

METHODS

The study included 24 healthy adult male albino rats weighing 200-220 grams that were assigned into four groups: control group, control drug group, high cholesterol diet fed groups; one untreated the other was treated with nebivolol.

RESULTS

In the cholesterol fed group, we found decreased blood HDL and NO with elevated total cholesterol, triglycerides, myoglobin, CK, LDH, ALP, in addition to elevated muscle tissue levels of HIF-1, NF-kB, MDA, and decreased expression of both eNOS, reduced GSH. Wire hanging test time was shorter in the high cholesterol group than control group rats, which was confirmed histologically by increased striated muscle fibre thickness and cytochrome area %. Nebivolol treatment ameliorated the effects of high cholesterol diet.

CONCLUSION

High cholesterol diet caused myopathic changes in rat striated muscle tissues mostly due to oxidative stress associated with enhanced NF-kB and HIF-1 expression. Nebivolol appears beneficial in the management of hypercholesterolaemia-induced striated muscle injury.

Xenobiotic-Induced Aggravation of Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD), which is often linked to obesity, encompasses a large spectrum of hepatic lesions, including simple fatty liver, steatohepatitis, cirrhosis and hepatocellular carcinoma. Besides nutritional and genetic factors, different xenobiotics such as pharmaceuticals and environmental toxicants are suspected to aggravate MAFLD in obese individuals. More specifically, pre-existing fatty liver or steatohepatitis may worsen, or fatty liver may progress faster to steatohepatitis in treated patients, or exposed individuals. The mechanisms whereby xenobiotics can aggravate MAFLD are still poorly understood and are currently under deep investigations. Nevertheless, previous studies pointed to the role of different metabolic pathways and cellular events such as activation of de novo lipogenesis and mitochondrial dysfunction, mostly associated with reactive oxygen species overproduction. This review presents the available data gathered with some prototypic compounds with a focus on corticosteroids and rosiglitazone for pharmaceuticals as well as bisphenol A and perfluorooctanoic acid for endocrine disruptors. Although not typically considered as a xenobiotic, ethanol is also discussed because its abuse has dire consequences on obese liver.

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.

Chronic glucocorticoid treatment induces hepatic lipid accumulation and hyperinsulinaemia in part through actions on AgRP neurons

Glucocorticoids (GCs) are widely prescribed anti-inflammatory medicines, but their use can lead to metabolic side-effects. These may occur through direct actions of GCs on peripheral organs, but could also be mediated by the hypothalamic AgRP neurons, which can increase food intake and modify peripheral metabolism. Therefore, the aim of this study was to examine the metabolic effects of chronic treatment with the GC corticosterone (Cort, 75 μg/ml in drinking water) in mice lacking the glucocorticoid receptor (GR) on AgRP neurons. Female AgRP-GR KO mice had delayed onset of Cort-induced hyperphagia. However, AgRP-GR KO had little impact on the increased body weight or adiposity seen with 3 weeks Cort treatment. Cort caused hepatic steatosis in control mice, but in Cort treated female AgRP-GR KO mice there was a 25% reduction in liver lipid content and lower plasma triglycerides. Additionally, Cort treatment led to hyperinsulinaemia, but compared to controls, Cort-treated AgRP-GR KO mice had both lower fasting insulin levels and lower insulin levels during a glucose tolerance test. In conclusion, these data indicate that GCs do act through AgRP neurons to contribute, at least in part, to the adverse metabolic consequences of chronic GC treatment.

Liver alanine catabolism promotes skeletal muscle atrophy and hyperglycaemia in type 2 diabetes

Both obesity and sarcopenia are frequently associated in ageing, and together may promote the progression of related conditions such as diabetes and frailty. However, little is known about the pathophysiological mechanisms underpinning this association. Here we show that systemic alanine metabolism is linked to glycaemic control. We find that expression of alanine aminotransferases is increased in the liver in mice with obesity and diabetes, as well as in humans with type 2 diabetes. Hepatocyte-selective silencing of both alanine aminotransferase enzymes in mice with obesity and diabetes retards hyperglycaemia and reverses skeletal muscle atrophy through restoration of skeletal muscle protein synthesis. Mechanistically, liver alanine catabolism driven by chronic glucocorticoid and glucagon signalling promotes hyperglycaemia and skeletal muscle wasting. We further provide evidence for amino acid-induced metabolic cross-talk between the liver and skeletal muscle in ex vivo experiments. Taken together, we reveal a metabolic inter-tissue cross-talk that links skeletal muscle atrophy and hyperglycaemia in type 2 diabetes.

Metformin Attenuates the Metabolic Disturbance and Depression-like Behaviors Induced by Corticosterone and Mediates the Glucose Metabolism Pathway

BACKGROUND

Metabolism disturbances are common in patients with depression. The drug metformin has been reported to exhibit antidepressant activity. The purpose of this study was to investigate metabolism disturbances induced by corticosterone (CORT) and determine if metformin can reverse these effects and their accompanying depression-like behaviors.

METHODS

Rats were exposed to corticosterone with or without metformin administration. Depression-like behaviors were tested. Gene expression was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot analysis. In addition, the metabolites were quantified by LC-MS/MS analysis.

RESULTS

Metformin attenuated the depression-like behaviors induced by CORT. Furthermore, metformin reversed disturbances in body weight, serum glucose, and triglyceride levels, as well as hepatic TG levels induced by CORT. Metformin normalized the alterations in the expression of glucose metabolism-related genes (PGC-1α, G6pc, Pepck, Gck, PYGL, Gys2, PKLR, GLUT4) and insulin resistance-related genes (AdipoR1, AdipoR2) in the muscles and livers of rats induced by CORT. Metabolomic analysis showed that metformin reversed the effects of CORT on 11 metabolites involved in the pathways of the tricarboxylic acid cycle, glycolysis, and gluconeogenesis (3-phospho-D-glycerate, β-D-fructose 6-phosphate, D-glucose 6-phosphate, and pyruvate).

CONCLUSION

Our findings suggest that metformin can attenuate metabolism disturbances and depression-like behaviors induced by CORT mediating the glucose metabolism pathway.

From Obesity to Hippocampal Neurodegeneration: Pathogenesis and Non-Pharmacological Interventions

High-caloric diet and physical inactivity predispose individuals to obesity and diabetes, which are risk factors of hippocampal neurodegeneration and cognitive deficits. Along with the adipose-hippocampus crosstalk, chronically inflamed adipose tissue secretes inflammatory cytokine could trigger neuroinflammatory responses in the hippocampus, and in turn, impairs hippocampal neuroplasticity under obese and diabetic conditions. Hence, caloric restriction and physical exercise are critical non-pharmacological interventions to halt the pathogenesis from obesity to hippocampal neurodegeneration. In response to physical exercise, peripheral organs, including the adipose tissue, skeletal muscles, and liver, can secret numerous exerkines, which bring beneficial effects to metabolic and brain health. In this review, we summarized how chronic inflammation in adipose tissue could trigger neuroinflammation and hippocampal impairment, which potentially contribute to cognitive deficits in obese and diabetic conditions. We also discussed the potential mechanisms underlying the neurotrophic and neuroprotective effects of caloric restriction and physical exercise by counteracting neuroinflammation, plasticity deficits, and cognitive impairments. This review provides timely insights into how chronic metabolic disorders, like obesity, could impair brain health and cognitive functions in later life.

Current perspectives of oleic acid: Regulation of molecular pathways in mitochondrial and endothelial functioning against insulin resistance and diabetes

Insulin resistance (IR) and type 2 diabetes mellitus (T2DM) is a leading cause of deaths due to metabolic disorders in recent years. Molecular mechanisms involved in the initiation and development of IR and T2DM are multiples. The major factors include mitochondrial dysfunction which may cause incomplete fatty acid oxidation (FAO). Oleic acid upregulates the expression of genes causing FAO by deacetylation of PGC1α by PKA-dependent activation of SIRT1-PGC1α complex. Another potent factor for the development of IR and T2DM is endothelial dysfunction as damaged endothelium causes increased release of inflammatory mediators such as TNF-α, IL-6, IL-1β, sVCAM, sICAM, E-selectin and other proinflammatory cytokines. While, on the other hand, oleic acid has the ability to regulate E-selectin, and sICAM expression. Rest of the risk factors may include inflammation, β-cell dysfunction, oxidative stress, hormonal imbalance, apoptosis, and enzyme dysregulation. Here, we have highlighted how oleic acid regulates underlying causatives factors and hence, keeps surpassing effect in prevention and treatment of IR and T2DM. However, the percentage contribution of these factors in combating IR and ultimately averting T2DM is still debatable. Thus, because of its exceptional protective effect, it can be considered as an improved therapeutic agent in prophylaxis and/or treatment of IR and T2DM.

Obesity Augments Glucocorticoid-Dependent Muscle Atrophy in Male C57BL/6J Mice

Glucocorticoids promote muscle atrophy by inducing a class of proteins called atrogenes, resulting in reductions in muscle size and strength. In this work, we evaluated whether a mouse model with pre-existing diet-induced obesity had altered glucocorticoid responsiveness. We observed that all animals treated with the synthetic glucocorticoid dexamethasone had reduced strength, but that obesity exacerbated this effect. These changes were concordant with more pronounced reductions in muscle size, particularly in Type II muscle fibers, and potentiated induction of atrogene expression in the obese mice relative to lean mice. Furthermore, we show that the reductions in lean mass do not fully account for the dexamethasone-induced insulin resistance observed in these mice. Together, these data suggest that obesity potentiates glucocorticoid-induced muscle atrophy.

Moderate Aerobic Exercise Training Prevents the Augmented Hepatic Glucocorticoid Response Induced by High-Fat Diet in Mice

Glucocorticoids (GCs) are critical regulators of energy balance. Their deregulation is associated with the development of obesity and metabolic syndrome. However, it is not understood if obesity alters the tissue glucocorticoid receptor (GR) response, and moreover whether a moderate aerobic exercise prevents the alteration in GR response induced by obesity. Methods: To evaluate the GR response in obese mice, we fed C57BL6J mice with a high-fat diet (HFD) for 12 weeks. Before mice were sacrificed, we injected them with dexamethasone. To assess the exercise role in GR response, we fed mice an HFD and subjected them to moderate aerobic exercise three times a week. Results: We found that mice fed a high-fat diet for 12 weeks developed hepatic GC hypersensitivity without changes in the gastrocnemius or epididymal fat GR response. Therefore, moderate aerobic exercise improved glucose tolerance, increased the corticosterone plasma levels, and prevented hepatic GR hypersensitivity with an increase in epididymal fat GR response. Conclusion: Collectively, our results suggest that mice with HFD-induced obesity develop hepatic GR sensitivity, which could enhance the metabolic effects of HFD in the liver. Moreover, exercise was found to be a feasible non-pharmacological strategy to prevent the deregulation of GR response in obesity.

Air Pollution, Stress, and Allostatic Load: Linking Systemic and Central Nervous System Impacts

 Air pollution is a risk factor for cardiovascular and respiratory morbidity and mortality. A growing literature also links exposure to diverse air pollutants (e.g., nanoparticles, particulate matter, ozone, traffic-related air pollution) with brain health, including increased incidence of neurological and psychiatric disorders such as cognitive decline, dementia (including Alzheimer’s disease), anxiety, depression, and suicide. A critical gap in our understanding of adverse impacts of pollutants on the central nervous system (CNS) is the early initiating events triggered by pollutant inhalation that contribute to disease progression. Recent experimental evidence has shown that particulate matter and ozone, two common pollutants with differing characteristics and reactivity, can activate the hypothalamic-pituitary-adrenal (HPA) axis and release glucocorticoid stress hormones (cortisol in humans, corticosterone in rodents) as part of a neuroendocrine stress response. The brain is highly sensitive to stress: stress hormones affect cognition and mental health, and chronic stress can produce profound biochemical and structural changes in the brain. Chronic activation and/or dysfunction of the HPA axis also increases the burden on physiological stress response systems, conceptualized as allostatic load, and is a common pathway implicated in many diseases. The present paper provides an overview of how systemic stress-dependent biological responses common to particulate matter and ozone may provide insight into early CNS effects of pollutants, including links with oxidative, inflammatory, and metabolic processes. Evidence of pollutant effect modification by non-chemical stressors (e.g., socioeconomic position, psychosocial, noise), age (prenatal to elderly), and sex will also be reviewed in the context of susceptibility across the lifespan.

The adiponectin receptor agonist AdipoRon normalizes glucose metabolism and prevents obesity but not growth retardation induced by glucocorticoids in young mice

OBJECTIVE

Glucocorticoids (GCs) are highly effective anti-inflammatory and immunosuppressive drugs. However, prolonged GC therapy may cause numerous adverse effects leading to diabetes and obesity, as well as bone disorders such as osteoporosis in adults and growth retardation in children and adolescents. Prevention and care of the GC-induced adverse effects remain challenging. We have previously demonstrated the efficacy of a treatment with a non-peptidic agonist of adiponectin receptors, AdipoRon, to reverse behaviour disorders and fat mass gain induced by long-term GC treatment. In this work, we have established a relevant model of GC-induced growth and metabolic disorders and determined that AdipoRon is a potential therapeutic tool to reverse these metabolic disturbances.

METHODS

5-Week-old mice were treated continuously with or without corticosterone (35 mg/L) in drinking water for seven consecutive weeks. Taking advantage of this mouse model displaying various growth and metabolic disorders, we assayed whether AdipoRon (daily intraperitoneal injection of 1 mg/kg/day for the last 20 days) might prevent the GC-induced adverse effects. The control group was treated with vehicle only. Nutritional behaviors and metabolic parameters were followed-up throughout the treatment. Serum insulin and leptin levels were measured by ELISA. Computed tomography and histological analysis of adipose tissue were assessed at the end of the experimental procedure.

RESULTS

We found that GC treatment in young mice resulted in continuously increased body weight gain associated with a food intake increase. Compared to vehicle-, GC-treated mice displayed early major hyperleptinemia (up to 6-fold more) and hyperinsulinemia (up to 20-fold more) maintained throughout the treatment. At the end of the experimental procedure, GC-treated mice displayed bone growth retardation (e.g. femur length 15.1 versus 14.0 mm, P < 0.01), higher abdominal adipose tissue volume (4.1 versus 2.3, P < 0.01) and altered glucose metabolism compared to control mice. Interestingly, AdipoRon prevented GC-induced effects on energy metabolism such as abdominal adiposity, insulinemia and leptinemia. However, AdipoRon failed to counteract bone growth retardation.

CONCLUSION

We characterized the very early pathological steps induced by long-term GC in young mice in a relevant model, including growth retardation, fat mass gain and glucose homeostasis dysregulation. The adiponectin system stimulation enabled normalization of the adipose tissue and metabolic features of GC-treated mice. Adiponectin receptor agonists such as AdipoRon might constitute a novel way to counteract some GC-induced adverse effects.

Individual differences in glucocorticoid regulation: Does it relate to disease risk and resilience?

Glucocorticoid (GC) signaling varies among individuals, and this variation may relate to individual differences in health outcomes. To determine if and which aspects of signaling (basal, circadian, integrative, or reactivity) are associated with specific health outcomes, we reviewed recent studies that relate GCs to health outcomes. We identified papers through PubMed and reviewed 100 original research articles related to mental health, cardiovascular health, cancer, diabetes, obesity, pulmonary health, sleep, and fitness. Many studies reported elevated GC secretion associated with worse health, but this was only particularly true for integrative GC measures. On the other hand, accentuated cortisol awakening response and a steeper circadian rhythm were both associated with positive health outcomes. Overall, relationships between GC secretion and health outcomes were relatively weak. This systematic review of relationships between GC metrics and health outcomes highlights the importance of careful consideration when selecting methods to measure GC regulation in health research.

Protocatechuic acid exhibits hepatoprotective, vasculoprotective, antioxidant and insulin-like effects in dexamethasone-induced insulin-resistant rats

Protocatechuic acid (PCA), the natural phenolic antioxidant, reportedly exhibited hypoglycemic and insulin-like effects. Recent studies have reported its cardioprotective effect in glucocorticoid (GC)-induced hypertensive rats. Nevertheless, its beneficial role has not been investigated in the setting of GCs excess-induced insulin resistance. This study aimed to investigate the possible protective potential and the plausible mechanisms of pretreatment with PCA against GCs-induced insulin resistance, liver steatosis and vascular dysfunction. Insulin resistance was induced in male Wistar rats by a 7-day treatment with dexamethasone (DEX) (1 mg/kg/day, i.p.). PCA (50, 100 mg/kg/day, orally) was started 7 days before DEX administration and continued during the test period. PCA significantly and dose-dependently attenuated DEX-induced a) glucose intolerance (↓ AUC_OGTT), b) hyperglycemia (↓ fasting blood glucose), c) impaired insulin sensitivity [↓fasting plasma insulin and homeostasis model assessment of insulin resistance (HOMA-IR) index)] and d) dyslipidemia (↓total cholesterol, triglycerides, low-density lipoprotein-cholesterol and very low-density lipoprotein-cholesterol). PCA mitigated DEX-induced liver steatosis with associated reduction in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity. Moreover, PCA ameliorated DEX-induced vascular dysfunction and enhanced ACh-induced relaxation in aortic rings. The metabolic ameliorating effects of PCA might be attributed to the enhanced insulin signaling in soleus muscles (↑AKT phosphorylation) and mitigating gluconeogenesis (↓ hepatic mRNA expression of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). The vasculoprotective effect of PCA might be related to its ability to restore normal mRNA expression of [endothelial nitric oxide synthase (eNOS) and NADPH Oxidase 4 (NOX4)]. PCA restored normal oxidative balance [↓ oxidant species, malondialdehyde (MDA) and (↑ antioxidant superoxide dismutase (SOD)]. The findings herein reveal for the first time that PCA may be taken as a supplement with GCs to limit their metabolic and vascular side effects through its hypoglycemic, insulin-sensitizing, hypolipidemic and antioxidant effects.

Glucocorticoid aggravates bone micro-architecture deterioration and skeletal muscle atrophy in mice fed on high-fat diet

High fat diet (HFD) induced obesity has deleterious effect on bone micro-architecture and is associated with low-grade chronic inflammation. Exogenous glucocorticoids (GC) are used to treat inflammatory conditions but with concomitant adverse effect on musculoskeletal system. This study aims to highlight the effect of exogenous GCs on musculoskeletal system in mice fed on HFD. Adult BALB/c mice were fed either normal chow or high fat diet and were exogenously administered with GC for 10 weeks. At the end of the study, animals were autopsied and bone, muscle, serum samples were collected for micro-CT, gene expression and histological study. HFD induced obesity resulted in deterioration in bone micro-architecture predominant in trabecular region of long bones and was significantly amplified with GC administration. Approximately, 37% and 25% loss in femoral and tibial bone volume was observed in obese animals with exogenous GC. Further, deteriorating bone pathology was apparent from reduced bone mineral density (BMD) and bone strength parameter which was correlated to alteration in osteoblast and adipocytes pool of cells in bone marrow. Transcriptional analysis of osteoblast marker genes, bone morphogenetic protein 2 (BMP-2), osteocalcin (OCN) exhibited decreased formation. Moreover, similar degeneration was observed in skeletal muscle physiology with stimulation in muscle atrophy genes atrogin-1, muscle ring finger motif-1 (MuRF-1) and inflammatory markers accompanied with intra-myocellular lipid accumulation. Thus, our results showed that detrimental effect of GC on bone and skeletal muscle is aggravated with HFD, attributed to alteration in bone marrow cell population and skeletal muscle atrophy.

Insulin reverses major portal hypertension-related derangements in rats with liver cirrhosis and diabetes

Liver cirrhosis is accompanied by increased intrahepatic resistance and angiogenesis-related portosystemic collaterals formation. Diabetic patients suffer from abnormal vasoresponsiveness and angiogenesis that can be ameliorated by glucose control. However, the relevant presentation is not clear in those with cirrhosis and diabetes, in whom insulin is the treatment of choice. Liver cirrhosis was induced in Sprague–Dawley rats with common bile duct ligation (BDL) and sham rats were used as controls. Streptozotocin 60 mg/kg (STZ, i.p., to induce diabetes) or vehicle was injected. The rats received BDL and STZ injections were injected with insulin or vehicle. On the 29th day after the procedure, the groups were surveyed for (1) systemic and portal hemodynamics; (2) mesenteric vascular density; (3) severity of portosystemic collaterals; (4) hepatic resistance using in situ liver perfusion; (5) histology survey of mesentery and liver; and (6) mesentery angiogenesis- and liver fibrogenesis-related protein expressions. Compared with the cirrhotic rats, the cirrhotic diabetic rats had lower body weight, cardiac output, superior mesenteric arterial (SMA) resistance and portal venous (PV) resistance, and higher SMA and PV flow, which were mostly reversed by insulin. The cirrhotic diabetic rats also had increased mesenteric vascular density, and enhanced pERK, pAkt, VEGF, VEGFR2 protein expressions that were reversed by insulin. Insulin decreased the degree of shunting in the diabetic cirrhotic rats. Hepatic perfusion pressure and severity of liver fibrosis were not significantly influenced by diabetes and insulin treatment in the cirrhotic rats. In conclusion, diabetes aggravated hemodynamic derangements, mesenteric angiogenesis and collaterals in the cirrhotic rats, which were mostly ameliorated by insulin. Further clinical investigations are warranted.

Early life stress accelerates age-induced effects on neurogenesis, depression, and metabolic risk

Early life stress (ELS) affects hippocampal neurogenesis, increases depressive-like behavior, and causes mild metabolic imbalance in early adulthood (2 months). However, whether these effects worsen in mid life remains unclear. To test whether age-dependent effects of ELS on hippocampal neurogenesis are related to deficient hypothalamic-pituitary-adrenal (HPA) axis feedback that causes increased comorbidity of depression and metabolic risk, we evaluated the effects of periodic maternal separation (MS180) in young (4-months-old) and middle-aged (10-months-old) adult rats. MS180 caused more severe depressive-like behavior in middle-aged adults than in young animals. There were no behavioral phenotypic differences between young MS180 and control middle-aged groups. MS180 similarly affected glucose tolerance, increased fasting corticosterone, insulin, and the quantitative insulin sensitivity check index (QUICKI) at both ages. However, middle-aged adult MS180 rats showed more severe age-induced obesity (>40% BW) than controls (>22% BW). MS180 differentially affected dorsal and ventral neurogenesis. In young adults, MS180 animals only showed a decrease in dorsal hippocampal neurogenesis as compared to their age-matched counterparts. In contrast, at 10 months of age, MS180 caused a similar decrease in both dorsal and ventral hippocampal neurogenesis as compared to age-matched controls, and a more severe decrease as compared to young animals. Taken together, our data indicate that MS180 animals show an early onset of age-induced alterations on depression and metabolic risk, and these effects relate to alterations in hippocampal neurogenesis.

Glucocorticoid-Induced Metabolic Disturbances Are Exacerbated in Obese Male Mice

The purpose of this study was to determine the effects of glucocorticoid-induced metabolic dysfunction in the presence of diet-induced obesity. C57BL/6J adult male lean and diet-induced obese mice were given dexamethasone, and levels of hepatic steatosis, insulin resistance, and lipolysis were determined. Obese mice given dexamethasone had significant, synergistic effects on fasting glucose, insulin resistance, and markers of lipolysis, as well as hepatic steatosis. This was associated with synergistic transactivation of the lipolytic enzyme adipose triglyceride lipase. The combination of chronically elevated glucocorticoids and obesity leads to exacerbations in metabolic dysfunction. Our findings suggest lipolysis may be a key player in glucocorticoid-induced insulin resistance and fatty liver in individuals with obesity.

The Extending Spectrum of NPC1-Related Human Disorders: From Niemann-Pick C1 Disease to Obesity

The Niemann-Pick type C1 (NPC1) protein regulates the transport of cholesterol and fatty acids from late endosomes/lysosomes and has a central role in maintaining lipid homeostasis. NPC1 loss-of-function mutations in humans cause NPC1 disease, a rare autosomal-recessive lipid-storage disorder characterized by progressive and lethal neurodegeneration, as well as liver and lung failure, due to cholesterol infiltration. In humans, genome-wide association studies and post-genome-wide association studies highlight the implication of common variants in NPC1 in adult-onset obesity, body fat mass, and type 2 diabetes. Heterozygous human carriers of rare loss-of-function coding variants in NPC1 display an increased risk of morbid adult obesity. These associations have been confirmed in mice models, showing an important interaction with high-fat diet. In this review, we describe the current state of knowledge for NPC1 variants in relationship to pleiotropic effects on metabolism. We provide evidence that NPC1 gene variations may predispose to common metabolic diseases by modulating steroid hormone synthesis and/or lipid homeostasis. We also propose several important directions of research to further define the complex roles of NPC1 in metabolism. This review emphasizes the contribution of NPC1 to obesity and its metabolic complications.

The superoxide dismutase mimetic tempol does not alleviate glucocorticoid-mediated rarefaction of rat skeletal muscle capillaries

Sustained elevations in circulating glucocorticoids elicit reductions in skeletal muscle microvascular content, but little is known of the underlying mechanisms. We hypothesized that glucocorticoid‐induced oxidative stress contributes to this phenomenon. In rats that were implanted with corticosterone (CORT) or control pellets, CORT caused a significant decrease in muscle glutathione levels and a corresponding increase in protein carbonylation, an irreversible oxidative modification of proteins. Decreased endothelial nitric oxide synthase and increased endothelin‐1 mRNA levels were detected after 9 days of CORT, and blood flow to glycolytic muscles was diminished. Control and CORT rats were treated concurrently with drinking water containing the superoxide dismutase mimetic tempol (172 mg/L) or the α‐1 adrenergic receptor antagonist prazosin (50 mg/L) for 6 or 16 days. Both tempol and prazosin alleviated skeletal muscle protein carbonylation. Tempol failed to prevent CORT‐mediated capillary rarefaction and was ineffective in restoring skeletal muscle blood flow. In contrast, prazosin blocked capillary rarefaction and restored skeletal muscle blood flow to control levels. The failure of tempol to prevent CORT‐induced skeletal muscle microvascular rarefaction does not support a dominant role of superoxide‐induced oxidative stress in this process. Although a decrease in protein carbonylation was observed with prazosin treatment, our data suggest that the maintenance of skeletal muscle microvascular content is related more closely with counteracting the CORT‐mediated influence on skeletal muscle vascular tone.

Inhibition of the Mitochondrial Pyruvate Carrier by Tolylfluanid

Several recent studies have suggested that compounds known as endocrine-disrupting chemicals (EDCs) can promote obesity by serving as ligands for nuclear receptors, including the peroxisome proliferator-activated receptor γ (PPARγ) and the glucocorticoid receptor (GR). Thiazolidinedione insulin sensitizers, which act as ligands for PPARγ, also interact with and regulate the activity of the mitochondrial pyruvate carrier (MPC). We evaluated whether several EDCs might also affect MPC activity. Most of the EDCs evaluated did not acutely affect pyruvate metabolism. However, the putative endocrine disruptors tributyltin (TBT) and tolylfluanid (TF) acutely and markedly suppressed pyruvate metabolism in isolated mitochondria. Using mitochondria isolated from brown adipose tissue in mice with adipocyte-specific deletion of the MPC2 protein, we determined that the effect of TF on pyruvate metabolism required MPC2, whereas TBT did not. We attempted to determine whether the obesogenic effects of TF might involve MPC2 in adipose tissue. However, we were unable to replicate the published effects of TF on weight gain and adipose tissue gene expression in wild-type or fat-specific MPC2 knockout mice. Treatment with TF modestly enhanced adipogenic gene expression in vitro but had no effect on GR activation or phosphorylation in cultured cells. These data suggest that TF may affect mitochondrial pyruvate metabolism via the MPC complex but also call into question whether this compound affects GR activity and is obesogenic in mice.

Dairy Attenuates Weight Gain to a Similar Extent as Exercise in Rats Fed a High-Fat, High-Sugar Diet

OBJECTIVE

To compare the individual and combined effects of dairy and endurance exercise training in reducing weight gain and adiposity in a rodent model of diet-induced obesity.

METHODS

An 8-week feeding intervention of a high-fat, high-sugar diet was used to induce obesity in male Sprague-Dawley rats. Rats were then assigned to one of four groups for 6 weeks: (1) casein sedentary (casein-S), (2) casein exercise (casein-E), (3) dairy sedentary (dairy-S), and (4) dairy exercise (dairy-E). Rats were exercise trained by treadmill running 5 d/wk.

RESULTS

Dairy-E prevented weight gain to a greater extent than either dairy or exercise alone. Adipose tissue and liver mass were reduced to a similar extent in dairy-S, casein-E, and dairy-E groups. Differences in weight gain were not explained by food intake or total energy expenditure. The total amount of lipid excreted was greater in the dairy-S compared to casein-S and dairy-E groups.

CONCLUSIONS

This study provides evidence that dairy limits weight gain to a similar extent as exercise training and the combined effects are greater than either intervention alone. While exercise training reduces weight gain through increases in energy expenditure, dairy appears to increase lipid excretion in the feces.

Effects of conjugated linoleic acid/n-3 and resistance training on muscle quality and expression of atrophy-related ubiquitin ligases in middle-aged mice with high-fat diet-induced obesity

PURPOSE

To investigate the effects of conjugated linoleic acid (CLA)/n-3 supplements and resistance exercise training (RT) for 20 weeks on muscle quality and genes related to protein synthesis/degradation in middle-aged mice with high-fat diet (HFD)-induced obesity.

METHODS

Nine-month-old C57BL/6 male mice were randomly assigned to five groups: 1) normal diet (C), 2) high-fat diet (H), 3) H+RT (HRT), 4) H+CLA/n-3 (H-CN), and 5) H+RT+CLA/n-3 (H-RTCN). HFD groups were given a diet containing 60% fat for 20 weeks, and exercised groups underwent progressive RT using weighted ladder climbing. The CLA/n-3 mixed diet contained 1% CLA and 1% n-3. Grip strength was assessed, and triceps were removed. RT-PCR was used to analyze transcript levels.

RESULTS

Grip strength of the H group was significantly lower than that of the C group; however, those in the H-CN, H-RT, and H-RTN groups were significantly greater than that in the H group. However, the muscle quality was significantly greater only in the H-RT group compared with the H and H-CN groups. Akt expression decreased in the H-CN, H-RT, and H-RTCN groups compared with those in the C and H groups, whereas mammalian target of rapamycin expression increased in the H, H-CN, H-RT, and H-RTCN groups compared with that in the C group. However, atrogin1 was significantly downregulated in the H-RTCN group compared with that in the H and H-CN groups, and MuRF1 expression was also decreased in the H-RT and H-RTCN groups. Interestingly, atrogin1 and MuRF1 were downregulated in the H-RTCN group compared with that in the H-CN group.

CONCLUSION

HFD-mediated gene expression involved in protein degradation was attenuated following 20-week RT with CLA/n-3. Furthermore, RT with or without CLA/n-3 improved grip strength and muscle quality in middle-aged mice during HFD. Therefore, RT with CLA/n-3 during HFD may improve muscle strength and quality by suppressing protein degradation.

Type 2 diabetes mellitus and psychological stress - a modifiable risk factor

Psychological stress is common in many physical illnesses and is increasingly recognized as a risk factor for disease onset and progression. An emerging body of literature suggests that stress has a role in the aetiology of type 2 diabetes mellitus (T2DM) both as a predictor of new onset T2DM and as a prognostic factor in people with existing T2DM. Here, we review the evidence linking T2DM and psychological stress. We highlight the physiological responses to stress that are probably related to T2DM, drawing on evidence from animal work, large epidemiological studies and human laboratory trials. We discuss population and clinical studies linking psychological and social stress factors with T2DM, and give an overview of intervention studies that have attempted to modify psychological or social factors to improve outcomes in people with T2DM.

Transendothelial movement of adiponectin is restricted by glucocorticoids

Altered permeability of the endothelial barrier in a variety of tissues has implications both in disease pathogenesis and treatment. Glucocorticoids are potent mediators of endothelial permeability, and this forms the basis for their heavily prescribed use as medications to treat ocular disease. However, the effect of glucocorticoids on endothelial barriers elsewhere in the body is less well studied. Here, we investigated glucocorticoid-mediated changes in endothelial flux of Adiponectin (Ad), a hormone with a critical role in diabetes. First, we used monolayers of endothelial cells in vitro and found that the glucocorticoid dexamethasone increased transendothelial electrical resistance and reduced permeability of polyethylene glycol (PEG, molecular weight 4000 Da). Dexamethasone reduced flux of Ad from the apical to basolateral side, measured both by ELISA and Western blotting. We then examined a diabetic rat model induced by treatment with exogenous corticosterone, which was characterized by glucose intolerance and hyperinsulinemia. There was no change in circulating Ad but less Ad protein in skeletal muscle homogenates, despite slightly higher mRNA levels, in diabetic vs control muscles. Dexamethasone-induced changes in Ad flux across endothelial monolayers were associated with alterations in the abundance of select claudin tight junction (TJ) proteins. shRNA-mediated knockdown of one such gene, claudin-7, in HUVEC resulted in decreased TEER and increased adiponectin flux, confirming the functional significance of Dex-induced changes in its expression. In conclusion, our study identifies glucocorticoid-mediated reductions in flux of Ad across endothelial monolayers in vivo and in vitro This suggests that impaired Ad action in target tissues, as a consequence of reduced transendothelial flux, may contribute to the glucocorticoid-induced diabetic phenotype.

Effects of high-intensity interval versus mild-intensity endurance training on metabolic phenotype and corticosterone response in rats fed a high-fat or control diet

The aim of the present study was to compare the effects of high-intensity interval training (HI) to mild-intensity endurance training (ME), combined with a high-fat diet (HFD) or control diet (CD) on metabolic phenotype and corticosterone levels in rats. Fifty-three rats were randomized to 6 groups according to diet and training regimen as follows: CD and sedentary (CS, n = 11), CD and ME (CME, n = 8), CD and HI (CHI, n = 8), HFD and sedentary (HS, n = 10), HFD and ME (HME, n = 8), and HFD and HI (HHI, n = 8). All exercise groups were trained for 10 weeks and had matched running distances. Dietary intake, body composition, blood metabolites, and corticosterone levels were measured. Histological lipid droplets were observed in the livers. The HFD led to hyperglycemia, hyperlipidemia and higher body fat (all, P < 0.01, η² > 0.06), as well as higher corticosterone levels (P < 0.01, η² = 0.09) compared with the CD groups. Exercise training improved fat weight, glucose, and lipid profiles, and reduced corticosterone levels (P < 0.01, η² = 0.123). Furthermore, body and fat weight, serum glucose and triglycerides, lipid content in the liver, and corticosterone levels (P < 0.05) were lower with HI training compared to ME training. Reductions in HFD-induced body weight gain, blood glucose and lipid profiles, and corticosterone levels, as well as improvements in QUICKI were better with HHI compared to HME. Correlation analyses revealed that corticosterone levels were significantly associated with phenotype variables (P < 0.01). Corticosterone level was inversely correlated with QUICKI (r = −0.38, P < 0.01). Altogether, these results indicate that HFD may elicit an exacerbated basal serum corticosterone level and thus producing a metabolic imbalance. Compared with ME training, HI training contributes to greater improvements in metabolic and corticosterone responses, leading to a greater reduction in susceptibility to HFD-induced disorders.

Neu-P11, a novel MT1/MT2 agonist, reverses diabetes by suppressing the hypothalamic-pituitary-adrenal axis in rats

Excessive glucocorticoid (GC) in type 2 diabetes mellitus (T2DM) reduces insulin sensitivity, impairs β-cell function, increases gluconeogenesis and glycogenolysis, impairs glucose uptake and metabolism, and reduces the insulinotropic effects of glucagon-like peptide 1. Melatonin, which serves as a physiological regulator of the hypothalamic-pituitary-adrenal (HPA) axis, has been suggested to have anti-diabetic effects. The objective of the present study was to investigate the effect of the MT1/MT2 melatonin agonist Neu-P11 on glucose and lipid metabolism in T2DM rats induced by a high fat diet combined with low doses of streptozotocin. T2DM rats were intragastrically administered melatonin (20mg/kg), Neu-P11 (20, 10, 5mg/kg), or a vehicle for 4 weeks. The results showed that the increased food intake, water consumption, hyperglycemia, glucose intolerance, and insulin resistance in T2DM rats were all improved by Neu-P11 treatment. Neu-P11 increased GC receptor expression and suppressed 11β-hydroxysteroid dehydrogenase 1 activity in the hippocampus by enhancing GC sensitivity and HPA feedback, thus decreasing the high GC levels. Transcript levels of the glucose metabolism-related genes peroxisome proliferator-activated receptor-γ, glucose transporter type-4, and adiponectin in adipose tissue were significantly increased after Neu-P11 treatment, while leptin mRNA was significantly decreased. Furthermore, MT1 and MT2 protein levels were enhanced by Neu-P11. These data suggest that normalization of the hyperactivated HPA axis by melatonin and Neu-P11 in T2DM regulates metabolic profiles and insulin sensitivity, which may attenuate insulin resistance and glucose homeostasis. Because Neu-P11 has superior pharmacokinetics and a longer half-life than melatonin, it might be beneficial in treating obesity and T2DM.

Nuclear Receptor Function through Genomics: Lessons from the Glucocorticoid Receptor

Unlocking the therapeutic potential of the glucocorticoid receptor (GR) has motivated a search for small molecules that selectively modulate its ability to activate or repress gene transcription. Recently, breakthrough studies in the field of genomics have reinvigorated debate over longstanding transcriptional models explaining how GR controls tissue-specific gene expression. Here, we highlight these genomic studies with the dual goals of advancing understanding of nuclear receptor-mediated transcription and stimulating thought on the development of anti-inflammatory and immunosuppressive ligands for GR that have reduced harmful effects on metabolism.

Stress, overeating, and obesity: Insights from human studies and preclinical models

Eating disorders and obesity have become predominant in human society. Their association to modern lifestyle, encompassing calorie-rich diets, psychological stress, and comorbidity with major diseases are well documented. Unfortunately the biological basis remains elusive and the pharmacological treatment inadequate, in part due to the limited availability of valid animal models. Human research on binge eating disorder (BED) proves a strong link between stress exposure and bingeing: state-levels of stress and negative affect are linked to binge eating in individuals with BED both in laboratory settings and the natural environment. Similarly, classical animal models of BED reveal an association between acute exposure to stressors and binging but they are often associated with unchanged or decreased body weight, thus reflecting a negative energy balance, which is uncommon in humans where most commonly BED is associated with excessive or unstable body weight gain. Recent mouse models of subordination stress induce spontaneous binging and hyperphagia, altogether more closely mimicking the behavioral and metabolic features of human BED. Therefore the translational relevance of subordination stress models could facilitate the identification of the neurobiological basis of BED and obesity-associated disease and inform on the development of innovative therapies.

11β-Hydroxysteroid Dehydrogenase Type 1 in Obese Subjects With Type 2 Diabetes Mellitus

Obesity is one of the most significant contributors to the development of type 2 diabetes mellitus. Tissue-specific glucocorticoids regulated by 11β-hydroxysteroid dehydrogenase enzyme (11β-HSD) type 1 are involved in central obesity and obesity-related comorbidities. Moderate downregulation of 11β-HSD1 can attenuate insulin insensitivity and the impairment of glucose-stimulated insulin secretion. Some of the beneficial effects of 11β-HSD1 inhibition may be mediated, at least in part, through inactivation of tissue-specific glucocorticoid action related to insulin signaling mechanisms, alleviation of abnormal cytokine profile and the improvement of β-cell function. Thus, 11β-HSD1 is a promising target for the treatment and prevention of type 2 diabetes mellitus with obesity.

Metabolic effects of prazosin on skeletal muscle insulin resistance in glucocorticoid-treated male rats

High-dose glucocorticoids (GC) induce skeletal muscle atrophy, insulin resistance, and reduced muscle capillarization. Identification of treatments to prevent or reverse capillary rarefaction and metabolic deterioration caused by prolonged elevations in GCs would be therapeutically beneficial. Chronic administration of prazosin, an α₁-adrenergic antagonist, increases skeletal muscle capillarization in healthy rodents and, recently, in a rodent model of elevated GCs and hyperglycemia. The purpose of this study was to determine whether prazosin administration would improve glucose tolerance and insulin sensitivity, through prazosin-mediated sparing of capillary rarefaction, in this rodent model of increased GC exposure. Prazosin was provided in drinking water (50 mg/l) to GC-treated or control rats (400 mg implants of either corticosterone or a wax pellet) for 7 or 14 days (n = 5-14/group). Whole body measures of glucose metabolism were correlated with skeletal muscle capillarization (C:F) at 7 and 14 days in the four groups of rats. Individual C:F was found to be predictive of insulin sensitivity (r² = 0.4781), but not of glucose tolerance (r² = 0.1601) and compared with water only, prazosin treatment decreased insulin values during oral glucose challenge by approximately one-third in corticosterone (Cort)-treated animals. Cort treatment, regardless of duration, induced significant glycolytic skeletal muscle atrophy (P < 0.05), decreased IRS-1 protein content (P < 0.05), and caused elevations in FOXO1 protein expression (P < 0.05), which were unaffected with prazosin administration. In summary, it appears that α₁-adrenergic antagonism improves Cort-induced skeletal muscle vascular impairments and reduces insulin secretion during an oral glucose tolerance test, but is unable to improve the negative alterations directly affecting the myocyte, including muscle size and muscle signaling protein expression.

The Metabolic Implications of Glucocorticoids in a High-Fat Diet Setting and the Counter-Effects of Exercise

Glucocorticoids (GCs) are steroid hormones, naturally produced by activation of the hypothalamic-pituitary-adrenal (HPA) axis, that mediate the immune and metabolic systems. Synthetic GCs are used to treat a number of inflammatory conditions and diseases including lupus and rheumatoid arthritis. Generally, chronic or high dose GC administration is associated with side effects such as steroid-induced skeletal muscle loss, visceral adiposity, and diabetes development. Patients who are taking exogenous GCs could also be more susceptible to poor food choices, but the effect that increasing fat consumption in combination with elevated exogenous GCs has only recently been investigated. Overall, these studies show that the damaging metabolic effects initiated through exogenous GC treatment are significantly amplified when combined with a high fat diet (HFD). Rodent studies of a HFD and elevated GCs demonstrate more glucose intolerance, hyperinsulinemia, visceral adiposity, and skeletal muscle lipid deposition when compared to rodents subjected to either treatment on its own. Exercise has recently been shown to be a viable therapeutic option for GC-treated, high-fat fed rodents, with the potential mechanisms still being examined. Clinically, these mechanistic studies underscore the importance of a low fat diet and increased physical activity levels when individuals are given a course of GC treatment.

Prazosin Can Prevent Glucocorticoid Mediated Capillary Rarefaction

Glucocorticoids (GC) elicit skeletal muscle capillary rarefaction, which can subsequently impair blood distribution and muscle function; however, the mechanisms have not been established. We hypothesized that CORT would inhibit endothelial cell survival signals but that treatment with the alpha-1 adrenergic receptor inhibitor prazosin, which leads to angiogenesis in skeletal muscle of healthy rats, would reverse these effects and induce angiogenesis within the skeletal muscle of corticosterone (CORT)-treated rats. Male Sprague Dawley rats were implanted subcutaneously with CORT pellets (400 mg/rat), with or without concurrent prazosin treatment (50mg/L in drinking water), for 1 or 2 weeks. Skeletal muscle capillary rarefaction, as indicated by a significant reduction in capillary-to-fiber ratio (C:F), occurred after 2 weeks of CORT treatment. Concurrent prazosin administration prevented this capillary rarefaction in CORT-treated animals but did not induce angiogenesis or arteriogenesis as was observed with prazosin treatment in control rats. CORT treatment reduced the mRNA level of Angiopoietin-1 (Ang-1), which was partially offset in the muscles of rats that received 2 weeks of co-treatment with prazosin. In 2W CORT animals, prazosin treatment elicited a significant increase in vascular endothelial growth factor-A (VEGF-A) mRNA and protein. Conversely prazosin did not rescue CORT-induced reductions in transforming growth factor beta-1 (TGFβ1 and matrix metalloproteinase-2 (MMP-2) mRNA. To determine if CORT impaired shear stress dependent signaling, cultured rat skeletal muscle endothelial cells were pre-treated with CORT (600nM) for 48 hours, then exposed to 15 dynes/cm² shear stress or maintained with no flow. CORT blunted the shear stress-induced increase in pSer473 Akt, while pThr308 Akt, ERK1/2 and p38 phosphorylation and nitric oxide (NO) production were unaffected. This study demonstrates that GC-mediated capillary rarefaction is associated with a reduction in Ang-1 mRNA within the skeletal muscle microenvironment and that concurrent prazosin treatment effectively increases VEGF-A levels and prevents capillary loss.

Elevated Hypothalamic Glucocorticoid Levels Are Associated With Obesity and Hyperphagia in Male Mice

Glucocorticoid (Gc) excess, from endogenous overproduction in disorders of the hypothalamic-pituitary-adrenal axis or exogenous medical therapy, is recognized to cause adverse metabolic side effects. The Gc receptor (GR) is widely expressed throughout the body, including brain regions such as the hypothalamus. However, the extent to which chronic Gcs affect Gc concentrations in the hypothalamus and impact on GR and target genes is unknown. To investigate this, we used a murine model of corticosterone (Cort)-induced obesity and analyzed Cort levels in the hypothalamus and expression of genes relevant to Gc action. Mice were administered Cort (75 μg/mL) or ethanol (1%, vehicle) in drinking water for 4 weeks. Cort-treated mice had increased body weight, food intake, and adiposity. As expected, Cort increased plasma Cort levels at both zeitgeber time 1 and zeitgeber time 13, ablating the diurnal rhythm. Liquid chromatography dual tandem mass spectrometry revealed a 4-fold increase in hypothalamic Cort, which correlated with circulating levels and concentrations of Cort in other brain regions. This occurred despite decreased 11β-hydroxysteroid dehydrogenase (Hsd11b1) expression, the gene encoding the enzyme that regenerates active Gcs, whereas efflux transporter Abcb1 mRNA was unaltered. In addition, although Cort decreased hypothalamic GR (Nr3c1) expression 2-fold, the Gc-induced leucine zipper (Tsc22d3) mRNA increased, which indicated elevated GR activation. In keeping with the development of hyperphagia and obesity, Cort increased Agrp, but there were no changes in Pomc, Npy, or Cart mRNA in the hypothalamus. In summary, chronic Cort treatment causes chronic increases in hypothalamic Cort levels and a persistent elevation in Agrp, a mediator in the development of metabolic disturbances.

Animal models of metabolic syndrome: a review

Metabolic syndrome (MetS) consists of several medical conditions that collectively predict the risk for cardiovascular disease better than the sum of individual conditions. The risk of developing MetS in human depends on synergy of both genetic and environmental factors. Being a multifactorial condition with alarming rate of prevalence nowadays, establishment of appropriate experimental animal models mimicking the disease state in humans is crucial in order to solve the difficulties in evaluating the pathophysiology of MetS in human. This review aims to summarize the underlying mechanisms involved in the pathophysiology of dietary, genetic, and pharmacological models of MetS. Furthermore, we will discuss the usefulness, suitability, pros and cons of these animal models. Even though numerous animal models of MetS have been established, further investigations on the invention of new animal model and clarification of plausible mechanisms are still necessary to confer a better understanding to researchers on the selection of animal models for their studies.

Development of a diet-induced murine model of diabetes featuring cardinal metabolic and pathophysiological abnormalities of type 2 diabetes

The persistent rise in global incidence of type 2 diabetes (T2D) continues to have significant public health and economic implications. The availability of relevant animal models of T2D is critical to elucidating the complexity of the pathogenic mechanisms underlying this disease and the implications this has on susceptibility to T2D complications. Whilst many high-fat diet-induced rodent models of obesity and diabetes exist, growing appreciation of the contribution of high glycaemic index diets on the development of hyperglycaemia and insulin resistance highlight the requirement for animal models that more closely represent global dietary patterns reflective of modern society. To that end, we sought to develop and validate a murine model of T2D based on consumption of an energy-dense diet containing moderate levels of fat and a high glycaemic index to better reflect the aetiopathogenesis of T2D. Male C57BL/6 mice were fed an energy-dense (ED) diet and the development of pathological features used in the clinical diagnosis of T2D was assessed over a 30-week period. Compared with control mice, 87% of mice fed an ED diet developed pathognomonic signs of T2D including glucose intolerance, hyperglycaemia, glycosylated haemoglobin (HbA1c) and glycosuria within 30 weeks. Furthermore, dyslipidaemia, chronic inflammation, alterations in circulating leucocytes and renal impairment were also evident in ED diet-fed mice compared with mice receiving standard rodent chow. Longitudinal profiling of metabolic and biochemical parameters provide support of an aetiologically and clinically relevant model of T2D that will serve as a valuable tool for mechanistic and therapeutic studies investigating the pathogenic complications of T2D.

High Fat Diet-Induced Skeletal Muscle Wasting Is Decreased by Mesenchymal Stem Cells Administration: Implications on Oxidative Stress, Ubiquitin Proteasome Pathway Activation, and Myonuclear Apoptosis

Obesity can lead to skeletal muscle atrophy, a pathological condition characterized by the loss of strength and muscle mass. A feature of muscle atrophy is a decrease of myofibrillar proteins as a result of ubiquitin proteasome pathway overactivation, as evidenced by increased expression of the muscle-specific ubiquitin ligases atrogin-1 and MuRF-1. Additionally, other mechanisms are related to muscle wasting, including oxidative stress, myonuclear apoptosis, and autophagy. Stem cells are an emerging therapy in the treatment of chronic diseases such as high fat diet-induced obesity. Mesenchymal stem cells (MSCs) are a population of self-renewable and undifferentiated cells present in the bone marrow and other mesenchymal tissues of adult individuals. The present study is the first to analyze the effects of systemic MSC administration on high fat diet-induced skeletal muscle atrophy in the tibialis anterior of mice. Treatment with MSCs reduced losses of muscle strength and mass, decreases of fiber diameter and myosin heavy chain protein levels, and fiber type transitions. Underlying these antiatrophic effects, MSC administration also decreased ubiquitin proteasome pathway activation, oxidative stress, and myonuclear apoptosis. These results are the first to indicate that systemically administered MSCs could prevent muscle wasting associated with high fat diet-induced obesity and diabetes.

Impact of Glucocorticoid Excess on Glucose Tolerance: Clinical and Preclinical Evidence

Glucocorticoids (GCs) are steroid hormones that exert important physiological actions on metabolism. Given that GCs also exert potent immunosuppressive and anti-inflammatory actions, synthetic GCs such as prednisolone and dexamethasone were developed for the treatment of autoimmune- and inflammatory-related diseases. The synthetic GCs are undoubtedly efficient in terms of their therapeutic effects, but are accompanied by significant adverse effects on metabolism, specifically glucose metabolism. Glucose intolerance and reductions in insulin sensitivity are among the major concerns related to GC metabolic side effects, which may ultimately progress to type 2 diabetes mellitus. A number of pre-clinical and clinical studies have aimed to understand the repercussions of GCs on glucose metabolism and the possible mechanisms of GC action. This review intends to summarize the main alterations that occur in liver, skeletal muscle, adipose tissue, and pancreatic islets in the context of GC-induced glucose intolerance. For this, both experimental (animals) and clinical studies were selected and, whenever possible, the main cellular mechanisms involved in such GC-side effects were discussed.

Some GCR Polymorphisms (N363S, ER22/23EK, and Bcl-1) May Influence Steroid-induced Toxicities and Survival Rates in Children With ALL

We investigated whether an altered individual glucocorticoid sensitivity due to particular glucocorticoid receptor single-nucleotide polymorphisms (SNPs) (N363S, ER22/23EK, and Bcl-1) influences the susceptibility to steroid-related toxicities, prognostic factors, and survival rates in children with acute lymphoblastic leukemia. In total, 346 pediatric patients with acute lymphoblastic leukemia were enrolled in our study. Their carrier status was investigated by allele-specific polymerase chain reaction analysis. Clinical and laboratory signs of glucocorticoid-related toxicities, day-8 prednisone response, 5-year event-free survival, and 5-year overall survival rates were analyzed and compared retrospectively. Hepatotoxicity occurred significantly more often in 363S carriers (P=0.004), and glucose metabolism abnormalities were more common in 363S carriers (P=0.001), but did not occur in patients with the ER22/23EK SNP. Hypertension and central nervous system/behavioral changes did not occur in patients with the ER22/23EK SNP. None of the patients with the N363S SNP, the ER22/23EK polymorphism, or the GG genotype for the Bcl-1 polymorphism had a poor prednisone response. The 363S carriers had significantly better 5-year event-free survival (P=0.012) and 5-year overall survival (P=0.013) rates compared with noncarriers. The Bcl-1 SNP was not associated with any of the toxicities investigated or survival. Children with the N363S polymorphism in the glucocorticoid receptor gene were more prone to steroid-related toxicities, whereas those with the ER22/23EK polymorphism were less susceptible. Children with the N363S polymorphism may have more favorable survival rates.

Glucocorticoid antagonism limits adiposity rebound and glucose intolerance in young male rats following the cessation of daily exercise and caloric restriction

Severe caloric restriction (CR), in a setting of regular physical exercise, may be a stress that sets the stage for adiposity rebound and insulin resistance when the food restriction and exercise stop. In this study, we examined the effect of mifepristone, a glucocorticoid (GC) receptor antagonist, on limiting adipose tissue mass gain and preserving whole body insulin sensitivity following the cessation of daily running and CR. We calorically restricted male Sprague-Dawley rats and provided access to voluntary running wheels for 3 wk followed by locking of the wheels and reintroduction to ad libitum feeding with or without mifepristone (80 mg·kg(-1)·day(-1)) for 1 wk. Cessation of daily running and CR increased HOMA-IR and visceral adipose mass as well as glucose and insulin area under the curve during an oral glucose tolerance test vs. pre-wheel lock exercised rats and sedentary rats (all P < 0.05). Insulin sensitivity and glucose tolerance were preserved and adipose tissue mass gain was attenuated by daily mifepristone treatment during the post-wheel lock period. These findings suggest that following regular exercise and CR there are GC-induced mechanisms that promote adipose tissue mass gain and impaired metabolic control in healthy organisms and that this phenomenon can be inhibited by the GC receptor antagonist mifepristone.

Corticosterone administration in drinking water decreases high-fat diet intake but not preference in male rats

One of the mechanisms through which regular exercise contributes to weight maintenance could be by reducing intake and preference for high-fat (HF) diets. Indeed, we previously demonstrated that wheel-running rats robustly reduced HF diet intake and preference. The reduced HF diet preference by wheel running can be so profound that the rats consumed only the chow diet and completely avoided the HF diet. Because previous research indicates that exercise activates the hypothalamic-pituitary-adrenal axis and increases circulating levels of corticosterone, this study tested the hypothesis that elevation of circulating corticosterone is involved in wheel running-induced reduction in HF diet preference in rats.Experiment 1 measured plasma corticosterone levels under sedentary and wheel-running conditions in the two-diet-choice (high-carbohydrate chow vs. HF) feeding regimen. The results revealed that plasma corticosterone is significantly increased and positively correlated with the levels of running in wheel-running rats with two-diet choice.Experiments 2 and 3 determined whether elevated corticosterone without wheel running is sufficient to reduce HF diet intake and preference. Corticosterone was elevated by adding it to the drinking water. Compared with controls, corticosterone-drinking rats had reduced HF diet intake and body weight, but the HF diet preference between groups did not differ. The results of this study support a role for elevated corticosterone on the reduced HF diet intake during wheel running. The elevation of corticosterone alone, however, is not sufficient to produce a robust reduction in HF diet preference.

Somatic and Neuroendocrine Changes in Response to Chronic Corticosterone Exposure During Adolescence in Male and Female Rats

Prolonged stress and repeated activation of the hypothalamic-pituitary-adrenal axis can result in many sex-dependent behavioural and metabolic changes in rats, including alterations in feeding behaviour and reduced body weight. In adults, these effects of stress can be mimicked by corticosterone, a major output of the hypothalamic-pituitary-adrenal axis, and recapitulate the stress-induced sex difference, such that corticosterone-treated males show greater weight loss than females. Similar to adults, chronic stress during adolescence leads to reduced weight gain, particularly in males. However, it is currently unknown whether corticosterone mediates this somatic change and whether additional measures of neuroendocrine function are affected by chronic corticosterone exposure during adolescence in a sex-dependent manner. Therefore, we examined the effects of non-invasively administered corticosterone (150 or 300 μg/ml) in the drinking water of male and female rats throughout adolescent development (30-58 days of age). We found that adolescent animals exposed to chronic corticosterone gain significantly less weight than controls, which may be partly mediated by the effects of corticosterone on food consumption, fluid intake and gonadal hormone function. Our data further show that, despite similar circulating corticosterone levels, males demonstrate a greater sensitivity to these changes than females. We also found that Npy1 and Npy5 receptor mRNA expression, genes implicated in appetite regulation, was significantly reduced in the ventral medial hypothalamus of corticosterone-treated males and females compared to controls. Finally, parameters of gonadal function, such as plasma sex steroid concentrations and weight of reproductive tissues, were reduced by adolescent corticosterone treatment, although only in males. The data obtained in the present study indicate that chronic corticosterone exposure throughout adolescent development results in significant and sex-dependent somatic and neuroendocrine changes, and the results also provide an experimental framework for further investigating the impact of corticosterone on metabolic and neuroendocrine function during adolescence.

Chronic subordination stress selectively downregulates the insulin signaling pathway in liver and skeletal muscle but not in adipose tissue of male mice

Chronic stress has been associated with obesity, glucose intolerance, and insulin resistance. We developed a model of chronic psychosocial stress (CPS) in which subordinate mice are vulnerable to obesity and the metabolic-like syndrome while dominant mice exhibit a healthy metabolic phenotype. Here we tested the hypothesis that the metabolic difference between subordinate and dominant mice is associated with changes in functional pathways relevant for insulin sensitivity, glucose and lipid homeostasis. Male mice were exposed to CPS for four weeks and fed either a standard diet or a high-fat diet (HFD). We first measured, by real-time PCR candidate genes, in the liver, skeletal muscle, and the perigonadal white adipose tissue (pWAT). Subsequently, we used a probabilistic analysis approach to analyze different ways in which signals can be transmitted across the pathways in each tissue. Results showed that subordinate mice displayed a drastic downregulation of the insulin pathway in liver and muscle, indicative of insulin resistance, already on standard diet. Conversely, pWAT showed molecular changes suggestive of facilitated fat deposition in an otherwise insulin-sensitive tissue. The molecular changes in subordinate mice fed a standard diet were greater compared to HFD-fed controls. Finally, dominant mice maintained a substantially normal metabolic and molecular phenotype even when fed a HFD. Overall, our data demonstrate that subordination stress is a potent stimulus for the downregulation of the insulin signaling pathway in liver and muscle and a major risk factor for the development of obesity, insulin resistance, and type 2 diabetes mellitus.

Comparative analysis of growth characteristics of Sprague Dawley rats obtained from different sources

Genetic background in animal models is an intrinsic research variable in biomedical research. Although inbred strains offer genetic uniformity, the outbred stocks, known for genetic variability are often used to develop animal models of human disease. The genetic variability is considered to be even higher when outbred stocks are obtained from different sources. In order to examine the degree of variability of an outbred stock obtained from various sources, Sprague Dawley (SD) rat lines obtained from two sources were evaluated for their growth characteristics. The SD rats from Charles River laboratories (CRL) and Harlan Laboratories (HAR) were monitored for weight gain from the age of 6 weeks to 24 weeks. Food intake was monitored between 13 and 24 weeks. Body composition, organ weights, tibial lengths and blood parameters were measured. There was no difference observed in food intake per 100 gram body weight at most of the time points. CRL rats showed higher body fat mass (49.6%), higher gross liver weights (22.2%), lower testicular weights (30.8%) and lower cholesterol levels (25.4%) than HAR rats. Phenotypic differences may be attributed to genetic heterogeneity of the SD outbred stock between the two sources and represent a significant research variable impacting studies especially related to metabolic diseases. Therefore, in order the minimize research variables for those studies where genetic diversity is not a basis for experimental design, the use of single source genetically uniform inbred animal models is highly recommended over the use of outbred stocks.

Voluntary exercise improves metabolic profile in high-fat fed glucocorticoid-treated rats

Diabetes is rapidly induced in young male Sprague-Dawley rats following treatment with exogenous corticosterone (CORT) and a high-fat diet (HFD). Regular exercise alleviates insulin insensitivity and improves pancreatic β-cell function in insulin-resistant/diabetic rodents, but its effect in an animal model of elevated glucocorticoids is unknown. We examined the effect of voluntary exercise (EX) on diabetes development in CORT-HFD-treated male Sprague-Dawley rats (∼6 wk old). Animals were acclimatized to running wheels for 2 wk, then given a HFD, either wax (placebo) or CORT pellets, and split into 4 groups: placebo-sedentary (SED) or -EX and CORT-SED or -EX. After 2 wk of running combined with treatment, CORT-EX animals had reduced visceral adiposity, and increased skeletal muscle type IIb/x fiber area, oxidative capacity, capillary-to-fiber ratio and insulin sensitivity compared with CORT-SED animals (all P < 0.05). Although CORT-EX animals still had fasting hyperglycemia, these values were significantly improved compared with CORT-SED animals (14.3 ± 1.6 vs. 18.8 ± 0.9 mM). In addition, acute in vivo insulin response to an oral glucose challenge was enhanced ∼2-fold in CORT-EX vs. CORT-SED (P < 0.05) which was further demonstrated ex vivo in isolated islets. We conclude that voluntary wheel running in rats improves, but does not fully normalize, the metabolic profile and skeletal muscle composition of animals administered CORT and HFD.

Genistein modulation of streptozotocin diabetes in male B6C3F1 mice can be induced by diet

Diet and phytoestrogens affect the development and progression of diabetes. The objective of the present study was to determine if oral exposure to phytoestrogen genistein (GE) by gavage changed blood glucose levels (BGL) through immunomodulation in streptozotocin (STZ)-induced diabetic male B6C3F1 mice fed with three different diets. These three diets were: NTP-2000 diet (NTP), soy- and alfalfa-free 5K96 diet (SOF) and high fat diet (HFD) with 60% of kcal from fat, primarily rendered fat of swine. The dosing regimen for STZ consisted of three 100mg/kg doses (i.p.): the first dose was administered at approximately 2weeks following the initiation of daily GE (20mg/kg) gavage, and the second dose was on day 19 following the first dose, and the third dose was on day 57 following the first dose. In mice on the NTP diet, GE treatment decreased BGL with statistical significances observed on days 33 and 82 following the first STZ injection. In mice fed the HFD diet, GE treatment produced a significant decrease and a significant increase in BGL on days 15 and 89 following the first STZ injection, respectively. In mice fed the SOF diet, GE treatment had no significant effects on BGL. Although GE treatment affected phenotypic distributions of both splenocytes (T cells, B cells, natural killer cells and neutrophils) and thymocytes (CD4/CD8 and CD44/CD25), and their mitochondrial transmembrane potential and generation of reactive oxygen species, indicators of cell death (possibly apoptosis), GE modulation of neutrophils was more consistent with its diabetogenic or anti-diabetic potentials. The differential effects of GE on BGL in male B6C3F1 mice fed with three different diets with varied phytoestrogen contents suggest that the estrogenic properties of this compound may contribute to its modulation of diabetes.