Corticosterone's dual metabolic actions

Exploring the Effect of Age on the Reproductive and Stress Physiology of Octopus bimaculoides Using Dermal Hormones

Our goal was to validate the use of dermal swabs to evaluate both reproductive and stress physiology in the California two-spot octopus, Octopus bimaculoides. Our objectives were to (1) use dermal swabs to evaluate glucocorticoids and reproductive hormones of O. bimaculoides; (2) determine the influence of life stage on hormone production (glucocorticoids in all individuals; testosterone, estrogen, and progesterone in females; and testosterone in males) of reproductive (n = 4) and senescent (n = 8) individuals to determine the effect of age on hormonal patterns; and (3) determine whether these hormones change significantly in response to an acute stressor. For the stress test, individuals were first swabbed for a baseline and then chased around the aquarium with a net for 5 min. Afterward, individuals were swabbed for 2 h at 15 min intervals to compare to the pre-stress test swab. Reproductive individuals responded to the stressor with a 2-fold increase in dermal cortisol concentrations at 15 and 90 min. Six of the eight senescent individuals did not produce a 2-fold increase in dermal cortisol concentrations. Reproductive individuals had significantly higher sex hormone concentrations compared to senescent individuals (progesterone and estradiol measured in females, and testosterone for both sexes). After the stressor, only reproductive males produced a 2-fold increase in dermal testosterone concentrations, while sex hormones in females showed no change. The stress hormone cortisol was significantly higher in senescent than in reproductive individuals, independent of sex. Dermal corticosterone concentrations were highest in senescent females followed by senescent males, and lowest in reproductive individuals regardless of sex. Dermal swabs provide an effective and noninvasive means for evaluating octopus hormones. Application of these indicators may be imperative as cephalopods are more commonly cultured in captivity for experimentation, display, and consumption.

Vamorolone improves Becker muscular dystrophy and increases dystrophin protein in bmx model mice

There is no approved therapy for Becker muscular dystrophy (BMD), a genetic muscle disease caused by in-frame dystrophin deletions. We previously developed the dissociative corticosteroid vamorolone for treatment of the allelic, dystrophin-null disease Duchenne muscular dystrophy. We hypothesize vamorolone can treat BMD by safely reducing inflammatory signaling in muscle and through a novel mechanism of increasing dystrophin protein via suppression of dystrophin-targeting miRNAs. Here, we test this in the bmx mouse model of BMD. Daily oral treatment with vamorolone or prednisolone improves bmx grip strength and hang time phenotypes. Both drugs reduce myofiber size and decrease the percentage of centrally nucleated fibers. Vamorolone shows improved safety versus prednisolone by avoiding or reducing key side effects to behavior and growth. Intriguingly, vamorolone increases dystrophin protein in both heart and skeletal muscle. These data indicate that vamorolone, nearing approval for Duchenne, shows efficacy in bmx mice and therefore warrants clinical investigation in BMD.

Effects of Injectable Administration of Dexamethasone Alone or in Combination with Vitamin E/Se in Newborn Low Birth Weight Piglets

Increasing litter size may lead to low-birth-weight piglets (LBW) and further negative long-term effects. This study aimed to evaluate the effects of intramuscular administration (IM) of dexamethasone (Dexa) alone or in combination with vitamin E/Se on LBW piglets during the early postnatal period. The study included a total of 100 LBW piglets that were divided into 5 groups (20 LBW piglets per group) and treated with IM Dexa alone or in combination with vitamin E/Se (Vit E/Se) after birth as follows: (a) Group A-Cont: Control group, (b) Group B-Dexa1: Dexa on D1 (1st day of life), (c) Group C-Dexa3: Dexa on D1, D2, D3 (D2: 2nd day of life, D3: 3rd day of life), (d) Group D-Dexa + VitE/S1: Dexa + Vit E/Se on D1, and (e) Group E-Dexa + VitE/S3: Dexa + Vit E/Se (IM) on D1, D2, D3. Body weight (BW) and the Average Daily Weight Gain (ADWG) were recorded for all piglets on days 1, 7, 14, and 25, and vitality score (VS) was recorded on days 1, 2, 3, 4, and 14. A significant increase in BW and ADWG in Group E-Dexa + VitE/S3 and a significant reduction in Group C-Dexa3 were noticed in comparison to other groups. VS in groups Group B-Dexa1 and Group C-Dexa3 were significantly lower in comparison to other groups. Furthermore, piglets of Group C-Dexa3 had a significantly higher frequency of clinical findings compared to other groups. In conclusion, the administration of Dexa and vitamin E/Se combined after the birth of LBW piglets for 1-3 days has beneficial effects on their growth and survival scores.

Evaluation of stress response in black-tailed prairie dogs (Cynomys ludovicianus) in arid regions from colonies in Chihuahua Mexico

Among all the regulatory homeostatic networks in vertebrates, the activation of the hypothalamic-pituitaryadrenal axis during the stress response, has gained considerable attention, and the measurement of fecal glucocorticoids (FGC) has become an invaluable tool to assess adrenocortical activity related to stressful events in wild and captive animals. However, the use of FGC requires the validation of measurement techniques and the proper selection of the specific hormone according to the study species. The main objective of this study was to identify the dominant glucocorticoid (GC) hormone in the stress response of black-tailed prairie dogs (Cynomys ludovicianus) in an arid grassland of Chihuahua, Mexico. A capture stress challenge in the field was developed to determine if the levels of glucocorticoids (cortisol and corticosterone) both in serum and fecal samples could be attributed to stress in Cynomys ludovicianus. The samples were analysed with the technique of liquid phase radioimmunoassay , and this study showed that both cortisol and corticosterone are present at measurable levels in serum and fecal samples of black-tailed prairie dogs. We found that both GCs were present in similar concentrations in serum, however, corticosterone concentration in fecal samples was higher than cortisol. Likewise, biochemical validations performed in this study to test the assay reached acceptable levels of reliability. Therefore, we confirm that fecal analysis can be implemented as a method to measure stress responses in wild prairie dogs.

Multi metabolomics-based analysis of application of Astragalus membranaceus in the treatment of hyperuricemia

Hyperuricemia (HUA) is a common metabolic disease that is an independent risk factor for comorbidities such as hypertension, chronic kidney disease, and coronary artery disease. The prevalence of HUA has increased over the last several decades with improved living standards and increased lifespans. Metabolites are considered the most direct reflection of individual physiological and pathological conditions, and represent attractive candidates to provide deep insights into disease phenotypes. Metabolomics, a technique used to profile metabolites in biofluids and tissues, is a powerful tool for identification of novel biomarkers, and can be used to provide valuable insights into the etiopathogenesis of metabolic diseases and to evaluate the efficacy of drugs. In this study, multi metabolomics-based analysis of the blood, urine, and feces of rats with HUA showed that HUA significantly altered metabolite profiles. Astragalus membranaceus (AM) and benbromomalone significantly mitigated these changes in blood and feces, but not in urine. Some crucial metabolic pathways including lipid metabolism, lipid signaling, hormones synthesis, unsaturated fatty acid (UFAs) absorption, and tryptophan metabolism, were seriously disrupted in HUA rats. In addition, AM administration exerted better treatment effects on HUA than benbromomalone. Furthermore, additional supplementation with UFAs and tryptophan may also induce therapeutic effects against HUA.

High and fluctuating levels of ovarian hormones induce an anxiogenic effect, which can be modulated under stress conditions: Evidence from an assisted reproductive rodent model

Elevated levels of endogenous ovarian hormones are conditions commonly experienced by women undergoing assisted reproductive technologies (ART). Additionally, infertility-associated stress and treatment routines are factors that together may have a highly negative impact on female emotionality, which can be aggravated when several cycles of ART are needed to attempt pregnancy. This study aimed to investigate the effect of high and fluctuating levels of gonadal hormones induced by repeated ovarian stimulation on the stress response in rodents. To mimic the context of ART, female rats were exposed to an unpredictable chronic mild stress (UCMS) paradigm for four weeks. During this time, three cycles of ovarian stimulation (superovulation) (150 IU/Kg of PMSG and 75 IU/Kg of hCG) were applied, with intervals of two estrous cycles between them. The rats were distributed into four groups: Repeated Superovulation/UCMS; Repeated Superovulation/No Stress; Saline/UCMS; and Saline/No Stress. Anxiety-like and depressive-like behaviors were evaluated in a light-dark transition box and by splash test, respectively. Corticosterone, estradiol, progesterone, and biometric parameters were assessed. Data were analyzed using a two-way Generalized Linear Model (GzLM). Our results showed that repeated ovarian stimulation exerts by itself an expressive anxiogenic effect. Surprisingly, when high and fluctuating levels of ovarian hormones were combined with chronic stress, anxiety-like behavior was no longer observed, and a depressive-like state was not detected. Our findings suggest that females subjected to emotional overload induced by repeated ovarian stimulation and chronic stress seem to trigger the elaboration of adaptive coping strategies.

Determining the effectiveness of using dermal swabs to evaluate the stress physiology of laboratory cephalopods: A preliminary investigation

To better comprehend the physiology of cephalopods, we used a minimal invasive technique of skin mucus swabs to measure immunoreactive corticosteroids in three cephalopod species commonly kept in captivity and promoted as new model organisms: Euprymna berryi, Sepia bandensis, and Octopus chierchiae. We compared results between sexes and age classes and then evaluated their stress responses during acclimation to a new habitat. To better understand glucocorticoid production, we conducted an adrenocorticotropic hormone, using Cosyntropin (an adrenocorticotropin (ACTH) analogue) challenge with a saline control and swabbed their mantles at 15-minute intervals for 2 h. Results showed cortisol was higher for younger individuals. Additionally, cortisol and corticosterone concentrations decreased by 2-fold after 2 to 4 days of acclimation to a new habitat. We were able to successfully measure 2-fold increase in immunoreactive corticosteroids which reacted with cortisol and corticosterone assays for all the species following ACTH injection, although not all individuals responded similarly. With further investigation, this technique can increase our understanding and management of cephalopods in captivity.

Baseline corticosterone is associated with parental care in virgin Japanese quail (Coturnix japonica)

Glucocorticoids (GCs) are thought to impact reproductive success, and ultimately fitness. In this study we focus specifically on the relationship between GCs and parental care. Captive bred Japanese quail (Coturnix japonica) do not show spontaneous parental care behavior, however this behavior can be induced through a sensitization procedure. We investigated how the GC status of Japanese quail relates to parental care in animals of both sexes exposed or not to a chick sensitization treatment. To assess GC status, we obtained baseline plasma and feather cort samples, and used the HPA-axis function test to assess stress responsiveness by examining the response to a standardized stressor as well as negative feedback efficacy through dexamethasone injection. Next, birds were either exposed to chicks overnight in a small enclosure (sensitization treatment) or were enclosed but not exposed to chicks (control). The following morning, adult behaviors were filmed in the presence of a fresh set of chicks for 20 min. A final serum GC sample was obtained to assess if exposure to novel chicks was perceived as stressful. In control animals, baseline GCs were associated with increased total parental care duration and decreased latency to first parental care event. Interestingly, the opposite relationship was found in the sensitization group. Finally, exposure to novel chicks was not associated with an increase in corticosterone in either group. Overall it appears that baseline GCs are correlated with parental care in captive bred Japanese quail, and that the relationship changes direction depending on whether or not sensitization has occurred.

Use of the ACTH challenge test to identify the predominant glucocorticoid in the southern sea otter (Enhydra lutris nereis)

After nearly being hunted to extinction during the fur trade of the late 20th Century, sea otter (Enhydra lutris) populations have recovered to varying degrees of their historical range. While overall population numbers and range have increased, there are regions in which expansion has occurred at a slower rate and/or animal numbers have decreased, which may be a result of chronic stress from a variety of sources. Some have employed glucocorticoid analysis in their attempts to validate these explanations. Our goal was to conduct a controlled study using sea otters managed under human care to validate the use of serum glucocorticoid analysis to monitor stress physiology in the sea otter. We used a standard ACTH challenge test to compare cortisol and corticosterone responses, thereby identifying the primary glucocorticoid in the sea otter. Fourteen sea otters of both sexes (five males, nine females), including juveniles, sub-adults and adults, participated in the study. The results of the testing supported cortisol as the primary glucocorticoid in the sea otter. Sex and age did not affect how the individual responded to the ACTH or saline injection. Interestingly, the saline injection not only confirmed the effects of the ACTH on glucocorticoid release from the adrenal glands but also provided information on how long it takes the sea otter's glucocorticoid levels to return to baseline after capture and sedation. The insight gained from this study will aid in future efforts to better understand the role of stress in free-ranging sea otter populations. Recognition of the primary glucocorticoid will facilitate evaluation of more stable biological material, such as fur or whiskers, which tend to be less affected by the diurnal cycling of glucocorticoids.

WITHDRAWN: Sex differences in glucocorticoids-induced anabolic effects on energy balance

This article has been withdrawn: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been withdrawn at the request of the editor and publisher. The publisher regrets that an error occurred which led to the premature publication of this paper. This error bears no reflection on the article or its authors. The publisher apologizes to the authors and the readers for this unfortunate error.

Transcriptom analysis revealed regulation of dexamethasone induced microRNAs in chicken thymus

Stress-induced immunosuppression is one of the serious threats to the poultry industry, especially obvious for young chicken. However, the molecular mechanism of stress-induced immunosuppression has not been clear in chicken. Here, we established an immunosuppression model of 7-day-old chickens with injecting dexamethasone (Dex) to analyze the molecular regulation in the chicken thymus. The microRNAs (miRNAs) transcripts profiles of thymuses from the model and control group were identified by the Solexa sequencing technology. The results showed 121 significantly differently expressed (SDE) miRNAs, including 119 known and two novel miRNAs (novel-58 and novel-350). A total of 391 target genes of the SDE miRNAs were predicted and annotated. We verified the potential negative correlation between gga-miR-103-3p and TGM2 by quantitative real-time polymerase chain reaction (qRT-PCR), as well as between novel-350 and PCBD2, and the results were positive. Gene ontology (GO) enrichment analysis showed that there was 298 significant enrichment GO terms, in which 31 were related to immune or stress, such as lymphocyte apoptotic process and response to stress. KEGG pathway analysis suggested that the SDE miRNAs were involved in autophagy regulation, cytokine-cytokine receptor interaction, Toll-like receptor signaling pathway, Jak-STAT signaling pathway, and so on (although not significantly enriched). In these immune signaling pathways, the SDE miRNAs (such as gga-miR-2954, gga-miR-146b-3p, gga-miR-106-3p, and gga-miR-214) and the predicted target genes (such as IL11Ra, CSF3R, IFNGR1, CNTF, and MAP2K2) might affect the thymus immune function of chicken. The above results would provide a basis for uncovering the molecular regulation mechanism of immunosuppression in poultry.

INVITED REVIEW: The usefulness of measuring glucocorticoids for assessing animal welfare

Glucocorticoids (corticosterone in birds and rodents and cortisol in all other mammals) are glucoregulatory hormones that are synthesized in response to a range of stimuli including stress and are regularly measured in the assessment of animal welfare. Glucocorticoids have many normal or non-stress-related functions, and glucocorticoid synthesis can increase in response to pleasure, excitement, and arousal as well as fear, anxiety, and pain. Often, when assessing animal welfare, little consideration is given to normal non-stress-related glucocorticoid functions or the complex mechanisms that regulate the effects of glucocorticoids on physiology. In addition, it is rarely acknowledged that increased glucocorticoid synthesis can indicate positive welfare states or that a stress response can increase fitness and improve the welfare of an animal. In this paper, we review how and when glucocorticoid synthesis increases, the actions mediated through type I and type II glucocorticoid receptors, the importance of corticosteroid-binding globulin, the role of 11 β-hydroxysteroid dehydrogenase, and the key aspects of neurophysiology relevant to activating the hypothalamo-pituitary-adrenal axis. This is discussed in the context of animal welfare assessment, particularly under the biological functioning and affective states frameworks. We contend that extending the assessment of animal welfare to key brain regions afferent to the hypothalamus and incorporating the aspects of glucocorticoid physiology that affect change in target tissue will advance animal welfare science and inspire more comprehensive assessment of the welfare of animals.

A Mechanistic Basis for the Beneficial Effects of Caloric Restriction On Longevity and Disease: Consequences for the Interpretation of Rodent Toxicity Studies

Caloric restriction in rodents has been repeatedly shown to increase life span while reducing the severity and retarding the onset of both spontaneous and chemically induced neoplasms. These effects of caloric restriction are associated with a spectrum of biochemical and physiological changes that characterize the organism's adaptation to reduced caloric intake and provide the mechanistic basis for caloric restriction's effect on longevity. Here, we review evidence suggesting that the primary adaptation appears to be a rhythmic hypercorticism in the absence of elevated adrenocorticotropin (ACTH) levels. This characteristic hypercorticism evokes a spectrum of responses, including reduced body temperature and increased metabolic efficiency, decreased mitogenic response coupled with increased rates of apoptosis, reduced inflammatory response, reduced oxidative damage to proteins and DNA, reduced reproductive capacity, and altered drug-metabolizing enzyme expression. The net effect of these changes is to (1) decrease growth and metabolism in peripheral tissues to spare energy for central functions, and (2) increase the organism's capacity to withstand stress and chemical toxicity. Thus, caloric restriction research has uncovered an evolutionary mechanism that provides rodents with an adaptive advantage in conditions of fluctuating food supply. During periods of abundance, body growth and fecundity are favored over endurance and longevity. Conversely, during periods of famine, reproductive performance and growth are sacrificed to ensure survival of individuals to breed in better times. This phenomena can be observed in rodent populations that are used in toxicity testing. Improvements over the last 30 years in animal husbandry and nutrition, coupled with selective breeding for growth and fecundity, have resulted in several strains now exhibiting larger animals with reduced survival and increased incidence of background lesions. The mechanistic data from caloric restriction studies suggest that these large animals will also be more susceptible to chemically induced toxicity. This creates a problem in comparing tests performed on animals of different weights and comparing data generated today with the historical database. The rational use of caloric restriction to control body weight to within preset guidelines is a possible way of alleviating this problem.

Altered lipid partitioning and glucocorticoid availability in CBG-deficient male mice with diet-induced obesity

OBJECTIVE

To evaluate how deficiency in corticosteroid-binding globulin (CBG), the specific carrier of glucocorticoids, affects glucocorticoid availability and adipose tissue in obesity.

METHODS

C57BL/6 (WT) and CBG-deficient (KO) male mice were fed during 12 weeks with standard or hyperlipidic diet (HL). Glucocorticoid availability and metabolic parameters were assessed.

RESULTS

Body weight and food intake were increased in KO compared with WT mice fed a standard diet and were similar when fed a HL diet. Expression of CBG was found in white adipose tissue by immunochemistry, real-time PCR, and Western blot. In obesity, the subcutaneous depot developed less in KO mice compared with WT, which was associated with a minor adipocyte area and peroxisome proliferator-activated receptor-γ expression. Conversely, the epididymal depot displayed higher weight and adipocyte area in KO than in WT mice. CBG deficiency caused a fall of hepatic 11β-hydroxysteroid dehydrogenase type 2 expression and an increase in epidymal adipose tissue, particularly in HL mice.

CONCLUSIONS

Deficiency in CBG drives lipid partitioning from subcutaneous to visceral adipose depot under a context of lipid excess and differentially modulates 11β-hydroxysteroid dehydrogenase type 2 expression.

Novel aspects of glucocorticoid actions

Normal hypothalamic-pituitary-adrenal (HPA) axis activity leading to the rhythmic and episodic release of adrenal glucocorticoids (GCs) is essential for body homeostasis and survival during stress. Acting through specific intracellular receptors in the brain and periphery, GCs regulate behaviour, as well as metabolic, cardiovascular, immune and neuroendocrine activities. By contrast to chronic elevated levels, circadian and acute stress-induced increases in GCs are necessary for hippocampal neuronal survival and memory acquisition and consolidation, as a result of the inhibition of apoptosis, the facilitation of glutamatergic neurotransmission and the formation of excitatory synapses, and the induction of immediate early genes and dendritic spine formation. In addition to metabolic actions leading to increased energy availability, GCs have profound effects on feeding behaviour, mainly via the modulation of orexigenic and anorixegenic neuropeptides. Evidence is also emerging that, in addition to the recognised immune suppressive actions of GCs by counteracting adrenergic pro-inflammatory actions, circadian elevations have priming effects in the immune system, potentiating acute defensive responses. In addition, negative-feedback by GCs involves multiple mechanisms leading to limited HPA axis activation and prevention of the deleterious effects of excessive GC production. Adequate GC secretion to meet body demands is tightly regulated by a complex neural circuitry controlling hypothalamic corticotrophin-releasing hormone (CRH) and vasopressin secretion, which are the main regulators of pituitary adrenocorticotrophic hormone (ACTH). Rapid feedback mechanisms, likely involving nongenomic actions of GCs, mediate the immediate inhibition of hypothalamic CRH and ACTH secretion, whereas intermediate and delayed mechanisms mediated by genomic actions involve the modulation of limbic circuitry and peripheral metabolic messengers. Consistent with their key adaptive roles, HPA axis components are evolutionarily conserved, being present in the earliest vertebrates. An understanding of these basic mechanisms may lead to novel approaches for the development of diagnostic and therapeutic tools for disorders related to stress and alterations of GC secretion.

Effect of a high-fat--high-fructose diet, stress and cinnamon on central expression of genes related to immune system, hypothalamic-pituitary-adrenocortical axis function and cerebral plasticity in rats

The intake of a high-fat/high-fructose (HF/HFr) diet is described to be deleterious to cognitive performances, possibly via the induction of inflammatory factors. An excess of glucocorticoids is also known to exert negative effects on cerebral plasticity. In the present study, we assessed the effects of an unbalanced diet on circulating and central markers of inflammation and glucocorticoid activity, as well as their reversal by dietary cinnamon (CN) supplementation. A group of male Wistar rats were subjected to an immune challenge with acute lipopolysaccharide under a HF/HFr or a standard diet. Another group of Wistar rats were fed either a HF/HFr or a control diet for 12 weeks, with or without CN supplementation, and with or without restraint stress (Str) application before being killed. We evaluated the effects of such regimens on inflammation parameters in the periphery and brain and on the expression of actors of brain plasticity. To assess hypothalamic-pituitary-adrenocortical axis activity, we measured the plasma concentrations of corticosterone and the expression of central corticotrophin-releasing hormone, mineralocorticoid receptor, glucocorticoid receptor and 11β-hydroxysteroid dehydrogenase. We found that the HF/HFr diet induced the expression of cytokines in the brain, but only after an immune challenge. Furthermore, we observed the negative effects of Str on the plasma concentrations of corticosterone and neuroplasticity markers in rats fed the control diet but not in those fed the HF/HFr diet. Additionally, we found that CN supplementation exerted beneficial effects under the control diet, but that its effects were blunted or even reversed under the HF/HFr diet. CN supplementation could be beneficial under a standard diet. [corrected].

Dexamethasone reduces energy expenditure and increases susceptibility to diet-induced obesity in mice

OBJECTIVE

To investigate how long-term treatment with dexamethasone affects energy expenditure and adiposity in mice and whether this is influenced by feeding on a high-fat diet (HFD).

DESIGN AND METHODS

Mice were placed on a HFD for 2 weeks and started on dexamethasone at 5 mg/kg every other day during the next 7 weeks.

RESULTS

Treatment with dexamethasone increased body fat, an effect that was more pronounced in the animals kept on HFD; dexamethasone treatment also worsened liver steatosis caused by the HFD. At the same time, treatment with dexamethasone lowered the respiratory quotient in chow-fed animals and slowed nightly metabolic rate in the animals kept on HFD. In addition, the acute VO2 acceleration in response to β3 adrenergic-stimulation was significantly limited in the dexamethasone-treated animals, as a result of marked decrease in UCP-1 mRNA observed in the brown adipose tissue of these animals.

CONCLUSIONS

Long-term treatment with dexamethasone in a mouse model of diet-induced obesity decreases brown adipose tissue thermogenesis and exaggerates adiposity and liver steatosis. © 2013 American Institute of Chemical Engineers AIChE J, 2013.

Small increases in corticosterone before the breeding season increase parental investment but not fitness in a wild passerine bird

Correlative evidence from field studies has suggested that baseline concentrations of corticosterone, the main avian glucocorticoid hormone, affect reproductive strategies in vertebrate species. Such a role is conceivable in light of corticosterone's function as a metabolic hormone in regulating glucose and fat metabolism. From such correlational studies, however, the question has remained open whether glucocorticoid concentrations change in advance of reproductive activities or whether corticosterone concentrations vary passively as a consequence of the individual's reproductive investment and workload. To test such causal relationships, we manipulated corticosterone concentrations prior to the breeding season in adult great tits (Parus major) and quantified reproductive investment and success. Two weeks before egg-laying, we administered subcutaneous silastic implants filled with corticosterone that elevated circulating levels within the baseline range for approximately 30 days to adult males and females. Corticosterone manipulation did not affect lay date or yearly offspring production. However, reproductive behaviors were affected by corticosterone treatment: males fed their mates more often during incubation, and females increased incubation of eggs and brooding of nestlings compared to control individuals. Other behaviors during the nestling stage, when the implants were no longer effective, did not differ between the two treatment groups. Our findings do not support the view that baseline corticosterone concentrations, at least at the time of year when we administered implants, change reproductive strategies per se. The current data suggest that baseline corticosterone levels represent internal signals that causally mediate reproductive effort in individuals of a wild bird species. By increasing reproductive investment, baseline corticosterone concentrations may have functions during the breeding season that diverge from the suppressive effects of stress-induced concentrations.

Association study of molecular polymorphisms in candidate genes related to stress responses with production and meat quality traits in pigs

The hypothalamic-pituitary-adrenal (HPA) axis exerts a large range of effects on metabolism, the immune system, inflammatory processes, and brain functions. Together with the sympathetic nervous system, it is also the most important stress-responsive neuroendocrine system. Both systems influence production traits, carcass composition, and meat quality. The HPA axis may be a critical target for genetic selection of more robust animals. Indeed, numerous studies in various species have demonstrated the importance of genetic factors in shaping the individual HPA axis phenotype, and genetic polymorphism can be found at each level of the axis, including hormone production by the adrenal cortices under stimulation by adrenocorticotropic hormone (ACTH), hormone bioavailability, or receptor and postreceptor mechanisms. The aim of the present experiment was to extend these findings to the brain neurochemical systems involved in stress responses. To this end, a number of candidate genes were sequenced for molecular polymorphisms and their association was studied with stress neuroendocrine and production traits in a genetically diverse population consisting of 100 female pigs from an advanced intercross (F10-F12) between 2 highly divergent breeds, Large White (LW) and Meishan (MS). The LW breed has a high production potential for lean meat and a low HPA axis activity, and the MS breed has low growth rate, fat carcasses-but large litters of highly viable piglets-and a high HPA axis activity. Candidate genes were chosen in the catecholaminergic and serotonergic pathways, in the pituitary control of cortisol production, among genes previously demonstrated to be differentially expressed in ACTH-stimulated adrenal glands from LW and MS pigs, and in cortisol receptors. Sixty new polymorphisms were found. The association study with carcass and meat quality traits and with endocrine traits showed a number of significant results, such as monoamine oxidase (MAOA) polymorphisms with growth rate (P = 0.01); lean content and intramuscular fat (P < 0.01), which are the most important traits for carcass value; dopamine receptor D3 (DRD3) with carcass composition (P < 0.05); and vasopressin receptor 1B (AVPR1B) with meat quality traits (P ≤ 0.05). The effect of these polymorphisms on neuroendocrine parameters (eg DRD3 and HPA axis or AVPR1B and catecholamines) indicates information regarding their biological mechanism of action.

Diabetes mellitus type 2: a new indication for hypercortisolism screening?

Current review discusses novel data concerning prevalence of Cushing syndrome without characteristic clinical signs among patients with type 2 diabetes mellitus. We also provide detailed analysis of difficulties in diagnostics and management of this condition

Molecular genetics of the adrenocortical axis and breeding for robustness

The concept of robustness refers to the combination of a high production potential and a low sensitivity to environmental perturbations. The importance of robustness-related traits in breeding objectives is progressively increasing toward the production of animals with a high production level in a wide range of climatic conditions and production systems, together with a high level of animal welfare. Current strategies to increase robustness include selection for "functional traits," such as skeletal and cardiovascular integrity, disease resistance, and mortality at various stages. It is also possible to use global evaluation of sensitivity to the environment (eg reaction norm analysis or canalization), but these techniques are difficult to implement in practice. The glucocorticoid hormones released by the adrenal cortex exert a wide range of effects on metabolism, the cardiovascular system, inflammatory processes, and brain function, for example. Protein catabolism toward energy production and storage (lipids and glycogen) supports their pivotal role in stress responses aiming at the adaptation and survival of individuals under strong environmental pressure. Large individual variations have been described in adrenocortical axis activity, with important physiopathological consequences. In terms of animal production, higher cortisol levels have negative effects on growth rate and feed efficiency and increase the fat:lean ratio of carcasses. On the contrary, cortisol has positive effects on functional traits and adaptation. Intense selection for lean tissue growth and more generally high protein output during the past decades has concomitantly reduced cortisol production, which may be responsible for the negative effects of selection on functional traits. In this paper, we review experimental evidence suggesting that the balance between production and functional traits was modified in favor of improved robustness by selecting animals with higher adrenocortical axis activity, as well as the molecular genetic tools that can be used to fine-tune this objective.

Deep-brain stimulation for anorexia nervosa

OBJECTIVE

Anorexia nervosa (AN) is a complex and severe, sometimes life-threatening, psychiatric disorder with high relapse rates under standard treatment. After decades of brain-lesioning procedures offered as a last resort, deep-brain stimulation (DBS) has come under investigation in the last few years as a treatment option for severe and refractory AN.

METHODS AND RESULTS

In this jointly written article, Sun et al. (the Shanghai group) report an average of 65% increase in body weight in four severe and refractory patients with AN after they underwent the DBS procedure (average follow-up: 38 months). All patients weighed greater than 85% of expected body weight and thus no longer met the diagnostic criteria of AN at last follow-up. Nuttin et al. (the Leuven group) describe other clinical studies that provide evidence for the use of DBS for AN and further discuss patient selection criteria, target selection, and adverse event of this evolving therapy.

CONCLUSION

Preliminary results from the Shanghai group and other clinical centers showed that the use of DBS to treat AN may be a valuable option for weight restoration in otherwise-refractory and life-threatening cases. The nature of this procedure, however, remains investigational and should not be viewed as a standard clinical treatment option. Further scientific investigation is essential to warrant the long-term efficacy and safety of DBS for AN.

Breeding for robustness: the role of cortisol

Robustness in farm animals was defined by Knap as 'the ability to combine a high production potential with resilience to stressors, allowing for unproblematic expression of a high production potential in a wide variety of environmental conditions'. The importance of robustness-related traits in breeding objectives is progressively increasing towards the production of animals with a high production level in a wide range of climatic conditions and production systems, together with a high level of animal welfare. Current strategies to increase robustness include selection for 'functional traits', such as skeletal and cardiovascular integrity, disease resistance and mortality in various stages. It is also possible to use global evaluation of sensitivity to the environment (e.g. reaction norm analysis or canalization), but these techniques are difficult to implement in practice. The hypothalamic-pituitary-adrenocortical (HPA) axis is the most important stress-responsive neuroendocrine system. Cortisol (or corticosterone) released by the adrenal cortices exerts a large range of effects on metabolism, the immune system, inflammatory processes and brain function, for example. Large individual variations have been described in the HPA axis activity with important physiopathological consequences. In terms of animal production, higher cortisol levels have negative effects on growth rate and feed efficiency and increase the fat/lean ratio of carcasses. On the contrary, cortisol has positive effects on traits related to robustness and adaptation. For instance, newborn survival was shown to be directly related to plasma cortisol levels at birth, resistance to bacteria and parasites are increased in animals selected for a higher HPA axis response to stress, and tolerance to heat stress is better in those animals that are able to mount a strong stress response. Intense selection for lean tissue growth during the last decades has concomitantly reduced cortisol production, which may be responsible for the negative effects of selection on piglet survival. One strategy to improve robustness is to select animals with higher HPA axis activity. Several sources of genetic polymorphism have been described in the HPA axis. Hormone production by the adrenal cortices under stimulation by adrenocorticotropin hormone is a major source of individual differences. Several candidate genes have been identified by genomic studies and are currently under investigation. Bioavailability of hormones as well as receptor and post-receptor mechanisms are also subject to individual variation. Integration of these different sources of genetic variability will allow the development of a model for marker-assisted selection to improve animal robustness without negative side effects on production traits.

Microsatellite mapping of quantitative trait loci affecting meat quality, stress hormones and production traits in Duroc × Large White F2 pigs

An F2 cross between Duroc and Large White pigs was carried out in order to detect quantitative trait loci (QTL) for 11 meat quality traits (L*, a* and b* Minolta coordinates and water-holding capacity (WHC) of two ham muscles, ultimate pH of two ham and one loin muscles), 13 production traits (birth weight, average daily gain during post-weaning and fattening periods, carcass fat depths at three locations, estimated lean meat content, carcass length and weights of five carcass cuts) and three stress hormone-level traits (cortisol, adrenaline and noradrenaline). Animals from the three generations of the experimental design (including 456 F2 pigs) were genotyped for 91 microsatellite markers covering all the autosomes. A total of 56 QTL were detected: 49 reached the chromosome-wide level (suggestive QTL with a maximal probability of 0.05) and seven were significant at the genome-wide level (with a probability varying from 6 × 10(-4) to 3 × 10(-3)). Twenty suggestive QTL were identified for ultimate pH, colour measurements and WHC on chromosome (SSC) 5, 6, 7, 8, 9, 11, 13, 14, 15 and 17. For production traits, 33 QTL were detected on all autosomes except SSC6, 8 and 9. Seven of these QTL, located on SSC2, 3, 10, 13, 16 and 17, exceeded the genome-wide significance threshold. Finally, three QTL were identified for levels of stress hormones: a QTL for cortisol level on SSC7 in the cortisol-binding globulin gene region, a QTL for adrenaline level on SSC10 and a QTL for noradrenaline level on SSC13. Among all the detected QTL, seven are described for the first time: a QTL for ultimate pH measurement on SSC5, two QTL affecting birth weight on SSC2 and 10, two QTL for growth rate on SSC15 (during fattening) and 17 (during post-weaning) and two QTL affecting the adrenaline and noradrenaline levels. For each QTL, only one to five of the six F1 sires were found to be heterozygous. It means that all QTL are segregating in at least one of the founder populations used in this study. These results suggest that both meat quality and production traits can be improved in purebred Duroc and Large White pigs through marker-assisted selection. It is of particular interest for meat quality traits, which are difficult to include in classical selection programmes.

Chronic non-invasive corticosterone administration abolishes the diurnal pattern of tph2 expression

Both hypothalamic-pituitary-adrenal (HPA) axis activity and serotonergic systems are commonly dysregulated in stress-related psychiatric disorders. We describe here a non-invasive rat model for hypercortisolism, as observed in major depression, and its effects on physiology, behavior, and the expression of tph2, the gene encoding tryptophan hydroxylase 2, the rate-limiting enzyme for brain serotonin (5-hydroxytryptamine; 5-HT) synthesis. We delivered corticosterone (40 μg/ml, 100 μg/ml or 400 μg/ml) or vehicle to adrenal-intact adult, male rats via the drinking water for 3 weeks. On days 15, 16, 17 and 18, respectively, the rats' emotionality was assessed in the open-field (OF), social interaction (SI), elevated plus-maze (EPM), and forced swim tests (FST). On day 21, half of the rats in each group were killed 2h into the dark phase of a 12/12 h reversed light/dark cycle; the other half were killed 2h into the light phase. We then measured indices of HPA axis activity, plasma glucose and interleukin-6 (IL-6) availability, and neuronal tph2 expression at each time point. Chronic corticosterone intake was sufficient to cause increased anxiety- and depressive-like behavior in a dose-dependent manner. It also disrupted the diurnal pattern of plasma adrenocorticotropin (ACTH), corticosterone, and glucose concentrations, caused adrenal atrophy, and prevented regular weight gain. No diurnal or treatment-dependent changes were found for plasma concentrations of IL-6. Remarkably, all doses of corticosterone treatment abolished the diurnal variation of tph2 mRNA expression in the brainstem dorsal raphe nucleus (DR) by elevating the gene's expression during the animals' inactive (light) phase. Our data demonstrate that chronic elevation of corticosterone creates a vulnerability to a depression-like syndrome that is associated with increased tph2 expression, similar to that observed in depressed patients.

Physiological trade-offs in self-maintenance: plumage molt and stress physiology in birds

Trade-offs between self-maintenance processes can affect life-history evolution. Integument replacement and the stress response both promote self-maintenance and affect survival in vertebrates. Relationships between the two processes have been studied most extensively in birds, where hormonal stress suppression is down regulated during molt in seasonal species, suggesting a resource-based trade-off between the two processes. The only species found to differ are the rock dove and Eurasian tree sparrow, at least one of which performs a very slow molt that may reduce resource demands during feather growth, permitting investment in the stress response. To test for the presence of a molt–stress response trade-off, we measured hormonal stress responsiveness during and outside molt in two additional species with extended molts, red crossbills (Loxia curvirostra) and zebra finches (Taeniopygia guttata). We found that both species maintain hormonal stress responsiveness during molt. Further, a comparative analysis of all available species revealed a strong relationship between molt duration and degree of hormonal suppression. Though our results support trade-off hypotheses, these data can also be explained by alternative hypotheses that have not been formally addressed in the literature. We found a strong relationship between stress suppression and seasonality of breeding and evidence suggesting that the degree of suppression may be either locally adaptable or plastic and responsive to local environmental conditions. We hypothesize that environmental unpredictability favors extended molt duration, which in turn allows for maintenance of the hormonal stress response, and discuss implications of a possible trade-off for the evolution of molt schedules.

Differential effects of glucocorticoids on energy homeostasis in Syrian hamsters

Syrian hamsters, like many humans, increase food intake and body adiposity in response to stress. We hypothesized that glucocorticoids (cortisol and corticosterone) mediate these stress-induced effects on energy homeostasis. Because Syrian hamsters are dual secretors of cortisol and corticosterone, differential effects of each glucocorticoid on energy homeostasis were investigated. First, adrenal intact hamsters were injected with varying physiological concentrations of cortisol, corticosterone, or vehicle to emulate our previously published defeat regimens (i.e., 1 injection/day for 5 days). Neither food intake nor body weight was altered following glucocorticoid injections. Therefore, we investigated the effect of sustained glucocorticoid exposure on energy homeostasis. This was accomplished by implanting hamsters with supraphysiological steady-state pellets of cortisol, corticosterone, or cholesterol as a control. Cortisol, but not corticosterone, significantly decreased food intake, body mass, and lean and fat tissue compared with controls. Despite decreases in body mass and adiposity, cortisol significantly increased circulating free fatty acids, triglyceride, cholesterol, and hepatic triglyceride concentrations. Although corticosterone did not induce alterations in any of the aforementioned metabolic end points, Syrian hamsters were responsive to the effects of corticosterone since glucocorticoids both induced thymic involution and decreased adrenal mass. These findings indicate that cortisol is the more potent glucocorticoid in energy homeostasis in Syrian hamsters. However, the data suggest that cortisol alone does not mediate stress-induced increases in food intake or body mass in this species.

Glucocorticoids decrease body weight and food intake and inhibit appetite regulatory peptide expression in the hypothalamus of rats

The aim of the present study was to investigate the effects of glucocorticoids (GCs) on appetite and gene expression of the hypothalamic appetite regulatory peptides, neuropeptide Y (NPY), agouti-related protein (AGRP) and cocaine and amphetamine-regulated transcript (CART), in non-obese and obese rats. Both non-obese and obese rats were randomly assigned to three groups: normal saline, low- and high-dose GC groups (NSG, LDG and HDG, respectively), which received an intraperitoneal injection with normal saline (0.2 ml/100 g) or hydrocortisone sodium succinate at 5 and 15 mg/kg, respectively, for 20 days. The expression levels of NPY, AGRP and CART mRNA in the hypothalamus were measured by real-time quantitative PCR. Non-obese and obese rats were found to undergo weight loss after GC injection, and a higher degree of weight loss was observed in the HDG rats. The average and cumulative food intakes in the obese and non-obese rats injected with high-dose GC were lower compared to that in the NSG (p<0.05). mRNA expression levels of the orexigenic neuropeptides, NPY and AGRP, and the anorexigenic neuropeptide, CART, were significantly lower in the HDG than levels in the NSG for both the obese and non-obese rats (p<0.05). GC treatment decreased appetite and body weight, induced apparent glucolipid metabolic disturbances and hyperinsulinemia, while down-regulated mRNA expression levels of the orexigenic neuropeptides, NPY and AGRP, and anorexigenic neuropeptide, CART, in the hypothalamus in the rats. The mechanism which induces this neuropeptide expression requires further study.

Pros and cons of screening for occult Cushing syndrome

Systematic screening studies performed mainly in patients with diabetes mellitus have revealed an unexpectedly high prevalence of occult Cushing syndrome. Such studies may provide a rationale for systematically screening obese patients with type 2 diabetes mellitus. However, a screening strategy is only justified if it is supported by enough evidence of its efficacy and if the benefits will outweigh drawbacks. To date, the natural history of occult Cushing syndrome and its possible effect on long-term morbidity are unknown. The clinical spectrum of occult Cushing syndrome and its relatively low prevalence may potentially negatively affect the performance of endocrine tests used to diagnose overt Cushing syndrome and generate false positives. Whether the cure of occult Cushing syndrome favorably influences clinical outcomes and is more beneficial than treatment of diabetes mellitus and cardiovascular risk factors with currently available pharmacological tools remains to be demonstrated. Last, the acceptability of a screening program by professionals and the health-care system in terms of workload and costs is highly questionable. Thus, an assessment of the indications for and against screening for occult Cushing syndrome on the basis of currently available data suggests that, to date, the cons surpass the pros.

Dynamic modeling of methylprednisolone effects on body weight and glucose regulation in rats

Influences of methylprednisolone (MPL) and food consumption on body weight (BW), and the effects of MPL on glycemic control including food consumption and the dynamic interactions among glucose, insulin, and free fatty acids (FFA) were evaluated in normal male Wistar rats. Six groups of animals received either saline or MPL via subcutaneous infusions at the rate of 0.03, 0.1, 0.2, 0.3 and 0.4 mg/kg/h for different treatment periods. BW and food consumption were measured twice a week. Plasma concentrations of MPL and corticosterone (CST) were determined at animal sacrifice. Plasma glucose, insulin, and FFA were measured at various times after infusion. Plasma MPL concentrations were simulated by a two-compartment model and used as the driving force in the pharmacodynamic (PD) analysis. All data were modeled using ADAPT 5. The MPL treatments caused reduction of food consumption and body weights in all dosing groups. The steroid also caused changes in plasma glucose, insulin, and FFA concentrations. Hyperinsulinemia was achieved rapidly at the first sampling time of 6 h; significant elevations of FFA were observed in all drug treatment groups; whereas only modest increases in plasma glucose were observed in the low dosing groups (0.03 and 0.1 mg/kg/h). Body weight changes were modeled by dual actions of MPL: inhibition of food consumption and stimulation of weight loss, with food consumption accounting for the input of energy for body weight. Dynamic models of glucose and insulin feedback interactions were extended to capture the major metabolic effects of FFA: stimulation of insulin secretion and inhibition of insulin-stimulated glucose utilization. These models of body weight and glucose regulation adequately captured the experimental data and reflect significant physiological interactions among glucose, insulin, and FFA. These mechanism-based PD models provide further insights into the multi-factor control of this essential metabolic system.

Free fatty acids as mediators of adaptive compensatory responses to insulin resistance in dexamethasone-treated rats

BACKGROUND

Chronic low-dose dexamethasone (DEX) treatment in rats is associated to insulin resistance with compensatory hyperinsulinaemia and reduction in food intake. We tested the hypothesis that the elevation in circulating free fatty acids (FFAs) induced by DEX is the common mediator of both insulin resistance and insulin hyperproduction.

METHODS

For this purpose, an anti-lipolytic agent was administered during DEX treatment to lower lipacidaemia for several hours prior to glucose and insulin tolerance tests. Leptin expression in adipose tissue (by Northern blot) and plasma leptin levels (by radioimmunoassay) were also investigated to verify whether a rise in circulating leptin could be responsible for the anorectic effect of DEX.

RESULTS

Our data show that a transient pharmacological reduction of elevated plasma FFA levels abates the post-loading hyperinsulinaemia and counteracts the insulin resistance induced by DEX, supporting the hypothesis that the chronic elevation in FFAs is the common mediator of DEX-induced changes. Despite enhanced leptin expression in white adipose tissue, DEX-treated rats show no significant increase in plasma leptin levels. This suggests that the anorectic effect of DEX should be mediated, at least partially, by other factors, possibly related to the influence of concomitantly elevated plasma FFA and insulin levels on the hypothalamic centers regulating feeding.

CONCLUSIONS

Our results sustain the idea that a prolonged increase in plasma FFA levels plays an important role in the adaptive regulation of glucose and energy homeostasis, not only by potentiating insulin secretion but also by providing a signal of 'nutrient abundance' capable of restraining food intake.

Methionine restriction effects on 11 -HSD1 activity and lipogenic/lipolytic balance in F344 rat adipose tissue

Methionine restriction (MR) limits age-related adiposity in Fischer 344 (F344) rats. To assess the mechanism of adiposity resistance, the effect of MR on adipose tissue (AT) 11beta-hydroxysteroid dehydrogenase-1 (11beta-HSD1) was examined. MR induced 11beta-HSD1 activity in all ATs, correlating with increased tissue corticosterone. However, an inverse relationship between 11beta-HSD1 activity and adipocyte size was observed. Because dietary restriction controls lipogenic and lipolytic rates, MR's effects on lipogenic and lipolytic enzymes were evaluated. MR increased adipose triglyceride lipase and acetyl-coenzyme A carboxylase (ACC) protein levels but induced ACC phosphorylation at serine residues that render the enzyme inactive, suggesting alterations of basal lipolysis and lipogenesis. In contrast, no changes in basal or phosphorylated hormone-sensitive lipase levels were observed. ACC-phosphorylated sites were specific for AMP-activated protein kinase (AMPK); therefore, AMPK activation was evaluated. Significant differences in AMPKalpha protein, phosphorylation, and activity levels were observed only in retroperitoneal fat from MR rats. No differences in protein kinase A phosphorylation and intracellular cAMP levels were detected. In vitro studies revealed increased lipid degradation and a trend toward increased lipid synthesis, suggesting the presence of a futile cycle. In conclusion, MR disrupts the lipogenic/lipolytic balance, contributing importantly to adiposity resistance in F344 rats.

Exploration of the hypothalamic–pituitary–adrenal function as a tool to evaluate animal welfare

Measuring HPA axis activity is the standard approach to the study of stress and welfare in farm animals. Although the reference technique is the use of blood plasma to measure glucocorticoid hormones (cortisol or corticosterone), several alternative methods such as the measurement of corticosteroids in saliva, urine or faeces have been developed to overcome the stress induced by blood sampling itself. In chronic stress situations, as is frequently the case in studies about farm animal welfare, hormonal secretions are usually unchanged but dynamic testing allows the demonstration of functional changes at several levels of the system, including the sensitization of the adrenal cortex to ACTH and the resistance of the axis to feedback inhibition by corticosteroids (dexamethasone suppression test). Beyond these procedural aspects, the main pitfall in the use of HPA axis activity is in the interpretation of experimental data. The large variability of the system has to be taken into consideration, since corticosteroid hormone secretion is usually pulsatile, follows diurnal and seasonal rhythms, is influenced by feed intake and environmental factors such as temperature and humidity, age and physiological state, just to cite the main sources of variation. The corresponding changes reflect the important role of glucocorticoid hormones in a number of basic physiological processes such as energy metabolism and central nervous system functioning. Furthermore, large differences have been found across species, breeds and individuals, which reflect the contribution of genetic factors and environmental influences, especially during development, in HPA axis functioning. Usually, these results will be integrated with data from behavioral observation, production and pathology records in a comprehensive approach of farm animal welfare.

Corticosterone inhibits the lipid-mobilizing effects of oleoyl-estrone in adrenalectomized rats

Oleoyl-estrone (OE) is an adipose-derived signal that decreases energy intake and body lipid, maintaining energy expenditure and glycemic homeostasis. Glucocorticoids protect body lipid and the metabolic status quo. We studied the combined effects of OE and corticosterone in adrenalectomized female rats: daily OE gavages (0 or 10 nmol/g) and slow-release corticosterone pellets at four doses (0, 0.5, 1.7, and 4.8 mg/d). Intact and sham-operated controls were also included. After 8 d, body composition and plasma metabolites and hormones were measured. OE induced a massive lipid mobilization (in parallel with decreased food intake and maintained energy expenditure). Corticosterone increased fat deposition and inhibited the OE-elicited mobilization of body energy, even at the lowest dose. OE enhanced the corticosterone-induced rise in plasma triacylglycerols, and corticosterone blocked the OE-induced decrease in leptin. High corticosterone and OE increased insulin resistance beyond the effects of corticosterone alone. The presence of corticosterone dramatically affected OE effects, reversing its decrease of body energy (lipid) content, with little or no change on food intake or energy expenditure. The maintenance of glycemia and increasing insulin in parallel to the dose of corticosterone indicate a decrease in insulin sensitivity, which is enhanced by OE. The reversal of OE effects on lipid handling, insulin resistance, can be the consequence of a corticosterone-induced OE resistance. Nevertheless, OE effects on cholesterol were largely unaffected. In conclusion, corticosterone administration effectively blocked OE effects on body lipid and energy balance as well as insulin sensitivity and glycemia.

Metabolic action of peroxisome proliferator-activated receptor γ agonism in rats with exogenous hypercorticosteronemia

OBJECTIVE

The beneficial metabolic actions of peroxisome proliferator-activated receptor gamma (PPARgamma) agonism are associated with modifications in adipose tissue metabolism that include a reduction in local glucocorticoid (GC) production by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). This study aimed to assess the contribution of GC attenuation to PPARgamma agonism action on gene expression in visceral adipose tissue and global metabolic profile.

DESIGN

Rats were treated (2 weeks) with the PPARgamma agonist rosiglitazone (RSG, 10 mg/kg/day) with concomitant infusion of vehicle (cholesterol implant) or corticosterone (HiCORT, 75 mg/implant/week) to defeat PPARgamma-mediated GC attenuation.

MEASUREMENTS

mRNA levels of enzymes involved in lipid uptake (and lipoprotein lipase activity), storage, lipolysis, recycling, and oxidation in retroperitoneal white adipose tissue (RWAT). Serum glucose, insulin and lipids, and lipid content of oxidative tissues.

RESULTS

Whereas HiCORT did not alter RWAT mass, RSG increased the latter (+33%) independently of the corticosterone status. Both HiCORT and RSG increased lipoprotein lipase activity, the mRNA levels of the de novo lipogenesis enzyme fatty acid synthase, and that of the fatty acid retention-promoting enzyme acyl-CoA synthase 1, albeit in a nonadditive fashion. Expression level of the lipolysis enzyme adipose triglyceride lipase was increased additively by HiCORT and RSG. PPARgamma agonism increased mRNA of the fatty acid recycling enzymes glycerol kinase and cytosolic phosphoenolpyruvate carboxykinase and those of the fatty acid oxidation enzymes muscle-type carnitine palmitoyltransferase 1 and acyl-CoA oxidase, whereas HiCORT remained without effect. HiCORT resulted in liver steatosis and hyperinsulinemia, which were abrogated by RSG, whereas the HiCORT-induced elevation in serum nonesterified fatty acid levels was only partially prevented. The hypotriglyceridemic action of RSG was maintained in HiCORT rats.

CONCLUSION

The GC and PPARgamma pathways exert both congruent and opposite actions on specific aspects of adipose tissue metabolism. Both the modulation of adipose gene expression and the beneficial global metabolic actions of PPARgamma agonism are retained under imposed high ambient GC, and are therefore independent from PPARgamma effects on 11beta-HSD1-mediated GC production.

Corticosterone in thin-billed prion Pachyptila belcheri chicks: diel rhythm, timing of fledging and nutritional stress

Glucocorticosteroids (GCs) of the hypothalam-pituitary-adrenal axis play a role in association with both stressful events and daily life processes. However, relatively little is known about the role of GCs in relation to daily and seasonal life processes in animals in the wild. In this paper, we present data on basal levels of plasma corticosterone CORT in chicks of a pelagic seabird, the thin-billed prion, Pachyptila belcheri, during two predictable changes in demands, the daily activity pattern and the preparation for fledging. By comparing chicks fed recently with unfed chicks, we test how GC levels are modified according to nutritional condition. In accordance with their nocturnal feeding rhythm, chicks had a clear daily rhythm with increased CORT secretion at night, but CORT levels during the active phase were also highly elevated in unfed chicks compared with fed chicks. Close to fledging, chicks rapidly increased basal CORT levels, and again unfed chicks had higher levels than fed chicks, although the age effect here was stronger than the effect of recent feeding. The present data thus support the hypothesis that GC levels are adjusted to life stages with predictable changes in demands, but food availability and/or internal energy stores also affect the level to which GCs increase.

Leptin and the regulation of the hypothalamic-pituitary-adrenal axis

Leptin, the product of the obesity gene (ob) predominantly secreted from adipocytes, plays a major role in the negative control of feeding and acts via a specific receptor (Ob-R), six isoforms of which are known at present. Evidence has been accumulated that leptin, like other peptides involved in the central regulation of food intake, controls the function of the hypothalamic-pituitary-adrenal (HPA) axis, acting on both its central and peripheral branches. Leptin, along with Ob-R, is expressed in the hypothalamus and pituitary gland, where it modulates corticotropin-releasing hormone and ACTH secretion, probably acting in an autocrine-paracrine manner. Only Ob-R is expressed in the adrenal gland, thereby making it likely that leptin affects it by acting as a circulating hormone. Although in vitro and in vivo findings could suggest a glucocorticoid secretagogue action in the rat, the bulk of evidence indicates that leptin inhibits steroid-hormone secretion from the adrenal cortex. In keeping with this, leptin was found to dampen the HPA axis response to many kinds of stress. In contrast, leptin enhances catecolamine release from the adrenal medulla. This observation suggests that leptin activates the sympathoadrenal axis and does not appear to agree with its above-mentioned antistress action. Leptin and/or Ob-R are also expressed in pituitary and adrenal tumors, but little is known about the role of this cytokine in the pathophysiology.

Actions of glucocorticoids at a seasonal baseline as compared to stress-related levels in the regulation of periodic life processes

For decades, demands associated with the predictable life-history cycle have been considered stressful and have not been distinguished from stress that occurs in association with unpredictable and life-threatening perturbations in the environment. The recent emergence of the concept of allostasis distinguishes behavioral and physiological responses to predictable routines as opposed to unpredictable perturbations, and allows for their comparison within one theoretical framework. Glucocorticosteroids (GCs) have been proposed as important mediators of allostasis, as they allow for rapid readjustment and support of behavior and physiology in response to predictable and unpredictable demands (allostatic load). Much work has already been done in defining GC action at the high concentrations that accompany life-threatening perturbations. However, less is known about the role of GCs in relation to daily and seasonal life processes. In this review, we summarize the known behavioral and physiological effects of GCs relating to the predictable life-history cycle, paying particular attention to feeding behavior, locomotor activity and energy metabolism. Although we utilize a comparative approach, emphasis is placed on birds. In addition, we briefly review effects of GCs at stress-related concentrations to test the hypothesis that different levels of GCs play specific and distinct roles in the regulation of life processes and, thus, participate in the promotion of different physiological states. We also examine the receptor types through which GC action may be mediated and suggest mechanisms whereby different GC concentrations may exert their actions. In conclusion, we argue that biological actions of GCs at "non-stress" seasonal concentrations play a critical role in the adjustment of responses that accompany predictable variability in the environment and demand more careful consideration in future studies.