Disrupting hypothalamic glucocorticoid receptors causes HPA axis hyperactivity and excess adiposity

Exploring causal mechanisms of psychosis risk

Robust epidemiological evidence of risk and protective factors for psychosis is essential to inform preventive interventions. Previous evidence syntheses have classified these risk and protective factors according to their strength of association with psychosis. In this critical review we appraise the distinct and overlapping mechanisms of 25 key environmental risk factors for psychosis, and link these to mechanistic pathways that may contribute to neurochemical alterations hypothesised to underlie psychotic symptoms. We then discuss the implications of our findings for future research, specifically considering interactions between factors, exploring universal and subgroup-specific factors, improving understanding of temporality and risk dynamics, standardising operationalisation and measurement of risk and protective factors, and developing preventive interventions targeting risk and protective factors.

Transgenic female mice producing trans 10, cis 12-conjugated linoleic acid present excessive prostaglandin E2, adrenaline, corticosterone, glucagon, and FGF21

Dietary trans 10, cis 12-conjugated linoleic acid (t10c12-CLA) is a potential candidate in anti-obesity trials. A transgenic mouse was previously successfully established to determine the anti-obesity properties of t10c12-CLA in male mice that could produce endogenous t10c12-CLA. To test whether there is a different impact of t10c12-CLA on lipid metabolism in both sexes, this study investigated the adiposity and metabolic profiles of female Pai mice that exhibited a dose-dependent expression of foreign Pai gene and a shift of t10c12-CLA content in tested tissues. Compared to their gender-match wild-type littermates, Pai mice had no fat reduction but exhibited enhanced lipolysis and thermogenesis by phosphorylated hormone-sensitive lipase and up-regulating uncoupling proteins in brown adipose tissue. Simultaneously, Pai mice showed hepatic steatosis and hypertriglyceridemia by decreasing gene expression involved in lipid and glucose metabolism. Further investigations revealed that t10c10-CLA induced excessive prostaglandin E2, adrenaline, corticosterone, glucagon and inflammatory factors in a dose-dependent manner, resulting in less heat release and oxygen consumption in Pai mice. Moreover, fibroblast growth factor 21 overproduction only in monoallelic Pai/wt mice indicates that it was sensitive to low doses of t10c12-CLA. These results suggest that chronic t10c12-CLA has system-wide effects on female health via synergistic actions of various hormones.

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

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

The Translational Future of Stress Neurobiology and Psychosis Vulnerability: A Review of the Evidence

Psychosocial stress is a well-established risk factor for psychosis, yet the neurobiological mechanisms underlying this relationship have yet to be fully elucidated. Much of the research in this field has investigated hypothalamic-pituitary-adrenal (HPA) axis function and immuno-inflammatory processes among individuals with established psychotic disorders. However, as such studies are limited in their ability to provide knowledge that can be used to develop preventative interventions, it is important to shift the focus to individuals with increased vulnerability for psychosis (i.e., high-risk groups). In the present article, we provide an overview of the current methods for identifying individuals at high-risk for psychosis and review the psychosocial stressors that have been most consistently associated with psychosis risk. We then describe a network of interacting physiological systems that are hypothesised to mediate the relationship between psychosocial stress and the manifestation of psychotic illness and critically review evidence that abnormalities within these systems characterise highrisk populations. We found that studies of high-risk groups have yielded highly variable findings, likely due to (i) the heterogeneity both within and across high-risk samples, (ii) the diversity of psychosocial stressors implicated in psychosis, and (iii) that most studies examine single markers of isolated neurobiological systems. We propose that to move the field forward, we require well-designed, largescale translational studies that integrate multi-domain, putative stress-related biomarkers to determine their prognostic value in high-risk samples. We advocate that such investigations are highly warranted, given that psychosocial stress is undoubtedly a relevant risk factor for psychotic disorders.

Transgenic mice producing the trans 10, cis 12-conjugated linoleic acid present reduced adiposity and increased thermogenesis and fibroblast growth factor 21 (FGF21)

Trans 10, cis 12-conjugated linoleic acid (t10c12-CLA) from ruminant-derived foodstuffs can induce body fat loss after oral administration. In the current study, a transgenic mouse that produced t10c12-CLA had been generated by inserting the Propionibacterium acnes isomerase (Pai) expression cassette into the Rosa26 locus, and its male offspring were used to elucidate the enduring influence of t10c12-CLA on overall health. Compared to their wild-type (wt) C57BL/6J littermates, both biallelic Pai/Pai and monoallelic Pai/wt mice exhibited reduced plasma triglycerides levels, and Pai/wt mice exclusively showed increased serum fibroblast growth factor 21. Further analysis of Pai/Pai mice found a decrease in white fat and an increase in brown fat, with more heat release and less physical activity. Analysis of Pai/Pai brown adipose tissues revealed that hyperthermia was associated with the over-expression of carnitine palmitoyltransferase 1B, uncoupling proteins 1 and 2. These findings suggest that the systemic and long-term impact of t10c12-CLA on obesity might be mediated through the pathway of fibroblast growth factor 21 when low doses are administered or through enhanced thermogenesis of brown adipose tissues when high doses are employed.

Exposure to war and conflict: The individual and inherited epigenetic effects on health, with a focus on post-traumatic stress disorder

War and conflict are global phenomena, identified as stress-inducing triggers for epigenetic modifications. In this state-of-the-science narrative review based on systematic principles, we summarise existing data to explore the outcomes of these exposures especially in veterans and show that they may result in an increased likelihood of developing gastrointestinal, auditory, metabolic and circadian issues, as well as post-traumatic stress disorder (PTSD). We also note that, despite a potential "healthy soldier effect", both veterans and civilians with PTSD exhibit the altered DNA methylation status in hypothalamic-pituitary-adrenal (HPA) axis regulatory genes such as NR3C1. Genes associated with sleep (PAX8; LHX1) are seen to be differentially methylated in veterans. A limited number of studies also revealed hereditary effects of war exposure across groups: decreased cortisol levels and a heightened (sex-linked) mortality risk in offspring. Future large-scale studies further identifying the heritable risks of war, as well as any potential differences between military and civilian populations, would be valuable to inform future healthcare directives.

Sex-differences in anxiety, neuroinflammatory markers, and enhanced fear learning following chronic heroin withdrawal

Post-traumatic stress disorder (PTSD) and opioid use disorder (OUD) are comorbid in clinical populations. However, both pre-clinical and clinical studies of these co-occurring disorders have disproportionately represented male subjects, limiting the applicability of these findings. Our previous work has identified chronic escalating heroin administration and withdrawal can produce enhanced fear learning. This behavior is associated with an increase in dorsal hippocampal (DH) interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and glial fibrillary acidic protein (GFAP) immunoreactivity. Further, we have shown that these increases in IL-1β and TNF-α are mechanistically necessary for the development of enhanced fear learning. Although these are exciting findings, this paradigm has only been studied in males. The current studies aim to examine sex differences in the behavioral and neuroimmune effects of chronic heroin withdrawal and future enhanced fear learning. In turn, we determined that chronic escalating heroin administration can produce withdrawal in female rats comparable to male rats. Subsequently, we examined the consequence of heroin withdrawal on future enhanced fear learning and IL-1β, TNF-α, and GFAP immunoreactivity. Strikingly, we identified sex differences in these neuroimmune measures, as chronic heroin administration and withdrawal does not produce enhanced fear learning or immunoreactivity changes in females. Moreover, we determined whether heroin withdrawal produces short-term and long-term anxiety behaviors in both female and males. Collectively, these novel experiments are the first to test whether heroin withdrawal can sensitize future fear learning, produce neurobiological changes, and cause short-term and long-term anxiety behaviors in female rats.

Female and male C57BL/6J offspring exposed to maternal obesogenic diet develop altered hypothalamic energy metabolism in adulthood

Maternal obesity is exceedingly common and strongly linked to offspring obesity and metabolic disease. Hypothalamic function is critical to obesity development. Hypothalamic mechanisms causing obesity following exposure to maternal obesity have not been elucidated. Therefore, we studied a cohort of C57BL/6J dams, treated with a control or high-fat-high-sugar diet, and their adult offspring to explore potential hypothalamic mechanisms to explain the link between maternal and offspring obesity. Dams treated with obesogenic diet were heavier with mild insulin resistance, which is reflective of the most common metabolic disease in pregnancy. Adult offspring exposed to maternal obesogenic diet had no change in body weight but significant increase in fat mass, decreased glucose tolerance, decreased insulin sensitivity, elevated plasma leptin, and elevated plasma thyroid-stimulating hormone. In addition, offspring exposed to maternal obesity had decreased energy intake and activity without change in basal metabolic rate. Hypothalamic neurochemical profile and transcriptome demonstrated decreased neuronal activity and inhibition of oxidative phosphorylation. Collectively, these results indicate that maternal obesity without diabetes is associated with adiposity and decreased hypothalamic energy production in offspring. We hypothesize that altered hypothalamic function significantly contributes to obesity development. Future studies focused on neuroprotective strategies aimed to improve hypothalamic function may decrease obesity development.NEW & NOTEWORTHY Offspring exposed to maternal diet-induced obesity demonstrate a phenotype consistent with energy excess. Contrary to previous studies, the observed energy phenotype was not associated with hyperphagia or decreased basal metabolic rate but rather decreased hypothalamic neuronal activity and energy production. This was supported by neurochemical changes in the hypothalamus as well as inhibition of hypothalamic oxidative phosphorylation pathway. These results highlight the potential for neuroprotective interventions in the prevention of obesity with fetal origins.

Animal Models of Cushing's Syndrome

Endogenous Cushing's syndrome is characterized by unique clinical features and comorbidities, and progress in the analysis of its genetic pathogenesis has been achieved. Moreover, prescribed glucocorticoids are also associated with exogenous Cushing's syndrome. Several animal models have been established to explore the pathophysiology and develop treatments for Cushing's syndrome. Here, we review recent studies reporting animal models of Cushing's syndrome with different features and complications induced by glucocorticoid excess. Exogenous corticosterone (CORT) administration in drinking water is widely utilized, and we found that CORT pellet implantation in mice successfully leads to a Cushing's phenotype. Corticotropin-releasing hormone overexpression mice and adrenal-specific Prkar1a-deficient mice have been developed, and AtT20 transplantation methods have been designed to examine the medical treatments for adrenocorticotropic hormone-producing pituitary neuroendocrine tumors. We also review recent advances in the molecular pathogenesis of glucocorticoid-induced complications using animal models.

Stress-induced glucocorticoid desensitizes adrenoreceptors to gate the neuroendocrine response to somatic stress in male mice

Noradrenergic afferents to hypothalamic corticotropin releasing hormone (CRH) neurons provide a major excitatory drive to the hypothalamic-pituitary-adrenal (HPA) axis via α1 adrenoreceptor activation. Noradrenergic afferents are recruited preferentially by somatic, rather than psychological, stress stimuli. Stress-induced glucocorticoids feed back onto the hypothalamus to negatively regulate the HPA axis, providing a critical autoregulatory constraint that prevents glucocorticoid overexposure and neuropathology. Whether negative feedback mechanisms target stress modality-specific HPA activation is not known. Here, we describe a desensitization of the α1 adrenoreceptor activation of the HPA axis following acute stress in male mice that is mediated by rapid glucocorticoid regulation of adrenoreceptor trafficking in CRH neurons. Glucocorticoid-induced α1 receptor trafficking desensitizes the HPA axis to a somatic but not a psychological stressor. Our findings demonstrate a rapid glucocorticoid suppression of adrenergic signaling in CRH neurons that is specific to somatic stress activation, and they reveal a rapid, stress modality-selective glucocorticoid negative feedback mechanism.

Physical and psychological stressors activate neuroendocrine secretion of corticosteroid. Noradrenaline circuits are critical to the neuroendocrine response to physical but not psychological stress. Jiang et al. show that stress-induced corticosteroids decrease noradrenaline sensitivity in the brain, which suppresses the response to subsequent physical stressors but leaves the psychological stress response intact.

Gene Dysregulation in the Adult Rat Paraventricular Nucleus and Amygdala by Prenatal Exposure to Dexamethasone

Fetal programming is the concept that maternal stressors during critical periods of fetal development can alter offspring phenotypes postnatally. Excess glucocorticoids can interact with the fetus to effect genetic and epigenetic changes implicated in adverse developmental outcomes. The present study investigates how chronic exposure to the synthetic glucocorticoid dexamethasone during late gestation alters the expression of genes related to behavior in brain areas relevant to the regulation and function of the hypothalamic–pituitary–adrenal axis. Pregnant Wistar Kyoto rats received subcutaneous injections of dexamethasone (100 μg/kg) daily from gestational day 15–21 or vehicle only as sham controls. The amygdala and paraventricular nucleus (PVN) were micro-punched to extract mRNA for reverse transcription and quantitative polymerase chain reaction for the analysis of the expression of specific genes. In the PVN, the expression of the glucocorticoid receptor NR3C1 was downregulated in female rats in response to programming. The expression of CACNA1C encoding the Ca_v1.2 pore subunit of L-type voltage-gated calcium channels was downregulated in male and female rats prenatally exposed to dexamethasone. Collectively, the results suggest that prenatal exposure to elevated levels of glucocorticoids plays a role in the dysregulation of the hypothalamic–pituitary–adrenal axis and potentially learning and memory by altering the expression of specific genes within the amygdala and PVN.

A pilot investigation of genetic and epigenetic variation of FKBP5 and response to exercise intervention in African women with obesity

We investigated gluteal (GSAT) and abdominal subcutaneous adipose tissue (ASAT) DNA methylation of FKBP5 in response to a 12-week intervention in African women with obesity, as well as the effect of the rs1360780 single nucleotide polymorphism (SNP) on FKBP5 methylation, gene expression and post-exercise training adaptations in obesity and metabolic related parameters. Exercise (n = 19) participants underwent 12-weeks of supervised aerobic and resistance training while controls (n = 12) continued their usual behaviours. FKBP5 methylation was measured in GSAT and ASAT using pyrosequencing. SNP and gene expression analyses were conducted using quantitative real-time PCR. Exercise training induced FKBP5 hypermethylation at two CpG dinucleotides within intron 7. When stratified based on the rs1360780 SNP, participants with the CT genotype displayed FKBP5 hypermethylation in GSAT (p < 0.05), and ASAT displayed in both CC and CT carriers. CC allele carriers displayed improved cardiorespiratory fitness, insulin sensitivity, gynoid fat mass, and waist circumference (p < 0.05) in response to exercise training, and these parameters were attenuated in women with the CT genotype. These findings provide a basis for future studies in larger cohorts, which should assess whether FKBP5 methylation and/or genetic variants such as the rs1360780 SNP could have a significant impact on responsiveness to exercise interventions.

Antidepressant-like activity of gestational administration of vitamin D is suppressed by prenatal overexposure to dexamethasone in female Wistar rats

Overexposure to glucocorticoids during gestation can lead to long-term mental disorders. Given the higher prevalence of depression in females, we investigated whether late gestational administration of dexamethasone could generate a depressive-like phenotype in the adult female offspring and if vitamin D could have a neuroprotective effect in this context. Pregnant rats received vitamin D (VitD, 500 IU/day) or vehicle (CTL) during gestation. Other pregnant rats received dexamethasone (Dex 0.1 mg/kg/ - 14th to the 19th gestational day) or dexamethasone + vitamin D (DexVitD). The offspring were tested for anhedonia (sucrose preference) and depressive-like behavior (forced swimming test) at postnatal months (PNM) 3, 6 and 12. Components of the serotonergic system, as well as glucocorticoids' receptors, were evaluated in the dorsal raphe nucleus at PNM 6 and 12. Prenatal vitamin D and dexamethasone increased sucrose preference at PNM 12. Prenatal vitamin D had an antidepressant-like effect at PNM 3 in rats overexposed to dexamethasone. However, at PNM 12, this effect was blunted in the DexVitD group. Prenatal dexamethasone reduced the protein content of SERT, TPH, and 5-HT_1A receptors in the dorsal raphe nucleus at 6 but not at 12 PNM. The glucocorticoids' receptors expression was similar in all groups. We concluded that prenatal overexposure to dexamethasone does not change emotional behaviors in females, but it blunts the antidepressant-like effect of gestational vitamin D in an age-dependent manner. The antidepressant-like activity of vitamin D in the offspring was not related either to alterations of the serotonergic system or the glucocorticoids' receptors expression in the dorsal raphe nucleus.

Novel Pharmacological Approaches to the Treatment of Depression

Major depressive disorder is one of the most prevalent mental health disorders. Monoamine-based antidepressants were the first drugs developed to treat major depressive disorder. More recently, ketamine and other analogues were introduced as fast-acting antidepressants. Unfortunately, currently available therapeutics are inadequate; lack of efficacy, adverse effects, and risks leave patients with limited treatment options. Efforts are now focused on understanding the etiology of depression and identifying novel targets for pharmacological treatment. In this review, we discuss promising novel pharmacological targets for the treatment of major depressive disorder. Targeting receptors including N-methyl-D-aspartate receptors, peroxisome proliferator-activated receptors, G-protein-coupled receptor 39, metabotropic glutamate receptors, galanin and opioid receptors has potential antidepressant effects. Compounds targeting biological processes: inflammation, the hypothalamic-pituitary-adrenal axis, the cholesterol biosynthesis pathway, and gut microbiota have also shown therapeutic potential. Additionally, natural products including plants, herbs, and fatty acids improved depressive symptoms and behaviors. In this review, a brief history of clinically available antidepressants will be provided, with a primary focus on novel pharmaceutical approaches with promising antidepressant effects in preclinical and clinical studies.

Child maltreatment and NR3C1 exon 1F methylation, link with deregulated hypothalamus-pituitary-adrenal axis and psychopathology: A systematic review

BACKGROUND

Epigenetics offers one promising method for assessing the psychobiological response to stressful experiences during childhood. In particular, deoxyribonucleic acid (DNA) methylation has been associated with an altered hypothalamus-pituitary-adrenal (HPA) axis and the onset of mental disorders. Equally, there are promising leads regarding the association between the methylation of the glucocorticoid receptor gene (NR3C1-1_F) and child maltreatment and its link with HPA axis and psychopathology.

OBJECTIVE

The current study aimed to assess the evidence of a link among child maltreatment, NR3C1-1_F methylation, HPA axis deregulation, and symptoms of psychopathology.

METHODS

We followed the Prisma guidelines and identified 11 articles that met our inclusion criteria.

RESULTS

We found that eight studies (72.72%) reported increased NR3C1-1_F methylation associated with child maltreatment, specifically physical abuse, emotional abuse, sexual abuse, neglect, and exposure to intimate partner violence, while three studies (27.27%) found no significant association. Furthermore, a minority of studies (36.36%) provided additional measures of symptoms of psychopathology or cortisol in order to examine the link among NR3C1-1_F methylation, HPA axis deregulation, and psychopathology in a situation of child maltreatment. These results suggest that NR3C1-1_F hypermethylation is positively associated with higher HPA axis activity, i.e. increased production of cortisol, as well as symptoms of psychopathology, including emotional lability-negativity, externalizing behavior symptoms, and depressive symptoms.

CONCLUSION

NR3C1-1_F methylation could be one mechanism that links altered HPA axis activity with the development of psychopathology.

Excess sucrose intake during pregnancy programs fetal brain glucocorticoid receptor expression in female but not male C57Bl/6J mice

BACKGROUND

Sex-specific mechanisms explaining the association between mothers with obesity and the development of obesity in children are poorly characterized. Permanent changes in fetal brain glucocorticoid receptor (GR) expression caused by exposure to overnutrition in utero may program aberrant energy homeostasis, thereby predisposing the offspring to obesity. This study explores sex differences in brain GR expression using an established mouse model of overnutrition during pregnancy.

METHODS

Female C57Bl/6J mice were fed control (CON) or high-fat-high-sucrose (HFHS) diets. Dam cholesterol, insulin, and triglycerides were measured by colorimetric assays. Fetal corticosterone exposure was measured by placental Abca1, Hsd11β1, Hsd11β2, and brain Nr3c1 (GR); Pomc expression measured by RT-qPCR.

RESULTS

Female, but not male, HFHS fetuses had 46% decreased brain GR and twofold increased Pomc expression. There was decreased Abca1 and Hsd11β1 but not Hsd11β2 expression in HFHS placentas. Caloric and sucrose intake, but not fat intake, in dams inversely correlated with fetal GR expression in both sexes. Excess sucrose consumption by dams inversely correlated with female fetal GR and directly correlated with female fetal Pomc expression.

CONCLUSIONS

Excess sucrose consumption in pregnant dams caused lower GR and higher Pomc expression in the female fetal brain. Clinical investigation of excess sucrose intake during pregnancy and its subsequent effect on hypothalamic-pituitary-adrenal axis activity and appetite in offspring may lead to novel, sex-specific obesity prevention strategies in the development of obesity in children.

A guide to changing paradigms of glucocorticoid receptor function-a model system for genome regulation and physiology

The glucocorticoid receptor (GR) is a bona fide ligand-regulated transcription factor. Cloned in the 80s, the GR has become one of the best-studied and clinically most relevant members of the nuclear receptor superfamily. Cooperative activity of GR with other transcription factors and a plethora of coregulators contribute to the tissue- and context-specific response toward the endogenous and pharmacological glucocorticoids (GCs). Furthermore, nontranscriptional activities in the cytoplasm are emerging as an additional function of GR. Over the past 40 years, the concepts of GR mechanisms of action had been constantly changing. Different methodologies in the pregenomic and genomic era of molecular biological research and recent cutting-edge technology in single-cell and single-molecule analysis are steadily evolving the views, how the GR in particular and transcriptional regulation in general act in physiological and pathological processes. In addition to the development of technologies for GR analysis, the use of model organisms provides insights how the GR in vivo executes GC action in tissue homeostasis, inflammation, and energy metabolism. The model organisms, namely the mouse, but also rats, zebrafish, and recently fruit flies carrying mutations of the GR became a major driving force to analyze the molecular function of GR in disease models. This guide provides an overview of the exciting research and paradigm shifts in the GR field from past to present with a focus on GR transcription factor networks, GR DNA-binding and single-cell analysis, and model systems.

Neu1 deficiency induces abnormal emotional behavior in zebrafish

NEU1 sialidase hydrolyzes sialic acids from glycoconjugates in lysosomes. Deficiency of NEU1 causes sialidosis with symptoms including facial dysmorphism, bone dysplasia, and neurodegeneration. However, the effects of NEU1 deficiency on emotional activity have not been explored. Here, we conducted the behavioral analysis using Neu1-knockout zebrafish (Neu1-KO). Neu1-KO zebrafish showed normal swimming similar to wild-type zebrafish (WT), whereas shoaling was decreased and accompanied by greater inter-fish distance than WT zebrafish. The aggression test showed a reduced aggressive behavior in Neu1-KO zebrafish than in WT zebrafish. In the mirror and 3-chambers test, Neu1-KO zebrafish showed more interest toward the opponent in the mirror and multiple unfamiliar zebrafish, respectively, than WT zebrafish. Furthermore, Neu1-KO zebrafish also showed increased interaction with different fish species, whereas WT zebrafish avoided them. In the black-white preference test, Neu1-KO zebrafish showed an abnormal preference for the white region, whereas WT zebrafish preferred the black region. Neu1-KO zebrafish were characterized by a downregulation of the anxiety-related genes of the hypothalamic-pituitary-adrenal axis and upregulation of lamp1a, an activator of lysosomal exocytosis, with their brains accumulating several sphingoglycolipids. This study revealed that Neu1 deficiency caused abnormal emotional behavior in zebrafish, possibly due to neuronal dysfunction induced by lysosomal exocytosis.

Mineralocorticoid receptors dampen glucocorticoid receptor sensitivity to stress via regulation of FKBP5

Responding to different dynamic levels of stress is critical for mammalian survival. Disruption of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) signaling is proposed to underlie hypothalamic-pituitary-adrenal (HPA) axis dysregulation observed in stress-related psychiatric disorders. In this study, we show that FK506-binding protein 51 (FKBP5) plays a critical role in fine-tuning MR:GR balance in the hippocampus. Biotinylated-oligonucleotide immunoprecipitation in primary hippocampal neurons reveals that MR binding, rather than GR binding, to the Fkbp5 gene regulates FKBP5 expression during baseline activity of glucocorticoids. Notably, FKBP5 and MR exhibit similar hippocampal expression patterns in mice and humans, which are distinct from that of the GR. Pharmacological inhibition and region- and cell type-specific receptor deletion in mice further demonstrate that lack of MR decreases hippocampal Fkbp5 levels and dampens the stress-induced increase in glucocorticoid levels. Overall, our findings demonstrate that MR-dependent changes in baseline Fkbp5 expression modify GR sensitivity to glucocorticoids, providing insight into mechanisms of stress homeostasis.

Environmental enrichment modulates HPA axis reprogramming in adult male rats exposed to early adolescent stress

Exposure to early stressful events increases susceptibility to post-traumatic stress disorder (PTSD) in adulthood, in which the hypothalamic-pituitary-adrenal (HPA) axis plays a crucial role. Studies have found that environmental enrichment (EE) mitigates the detrimental outcomes of early adversity. However, the HPA-related mechanism remains unclear. In this study, we used the single prolonged stress (SPS) paradigm to explore the long-term effects of early adolescent stress on behavior, HPA axis activity, as well as expression levels of the glucocorticoid receptor (GR), mineralocorticoid receptor (MR), corticotropin-releasing hormone receptor 1 (CRF1R) and CRF2R in the hypothalamus and hippocampus. Meanwhile, the protective effects of EE intervention were examined. We found that adult male rats exposed to adolescent stress showed reduced locomotor activity, increased anxiety-like behaviors, enhanced contextual fear memory, elevated basal plasma ACTH levels, and enhanced HPA negative feedback inhibition, as indicated by decreased plasma ACTH levels in the dexamethasone suppression test (DST). Furthermore, EE normalized the behavioral abnormalities and enhanced HPA negative feedback in stressed rats, possibly through down-regulating GR expression in the hippocampus and hypothalamus. These findings suggested that EE could ameliorate adolescent stress-induced PTSD-like behaviors and aberrant reprogramming of the HPA axis, reducing the risk of developing PTSD in adulthood.

Experience and activity-dependent control of glucocorticoid receptors during the stress response in large-scale brain networks

The diversity of actions of the glucocorticoid stress hormones among individuals and within organs, tissues and cells is shaped by age, gender, genetics, metabolism, and the quantity of exposure. However, such factors cannot explain the heterogeneity of responses in the brain within cells of the same lineage, or similar tissue environment, or in the same individual. Here, we argue that the stress response is continuously updated by synchronized neural activity on large-scale brain networks. This occurs at the molecular, cellular and behavioral levels by crosstalk communication between activity-dependent and glucocorticoid signaling pathways, which updates the diversity of responses based on prior experience. Such a Bayesian process determines adaptation to the demands of the body and external world. We propose a framework for understanding how the diversity of glucocorticoid actions throughout brain networks is essential for supporting optimal health, while its disruption may contribute to the pathophysiology of stress-related disorders, such as major depression, and resistance to therapeutic treatments.

Central Type II Glucocorticoid Receptor Regulation of Ventromedial Hypothalamic Nucleus Glycogen Metabolic Enzyme and Glucoregulatory Neurotransmitter Marker Protein Expression in the Male Rat

The ventromedial hypothalamic nucleus (VMN) glucoregulatory neurotransmitters γ-aminobutyric acid (GABA) and nitric oxide (NO) signal adjustments in glycogen mobilization. Glucocorticoids control astrocyte glycogen metabolism in vitro. The classical (type II) glucocorticoid receptor (GR) is expressed in key brain structures that govern glucostasis, including the VMN. Current research addressed the hypothesis that forebrain GR regulation of VMN glycogen synthase (GS) and phosphorylase (GP) protein expression correlates with control of glucoregulatory transmission. Groups of male rats were pretreated by intracerebroventricular (icv) delivery of the GR antagonist RU486 or vehicle prior to insulin-induced hypoglycemia (IIH), or were pretreated icv with dexamethasone (DEX) or vehicle before subcutaneous insulin diluent injection. DEX increased VMN GS and norepinephrine-sensitive GP-muscle type (GPmm), but did not alter metabolic deficit-sensitive GP-brain type (GPbb) expression. RU486 enhanced GS and GPbb profiles during IIH. VMN astrocyte (MCT1) and neuronal (MCT2) monocarboxylate transporter profiles were up-regulated in euglycemic and hypoglycemic animals by DEX or RU486, respectively. Glutamate decarboxylase65/67 and neuronal nitric oxide synthase (nNOS) proteins were both increased by DEX, yet RU486 augmented hypoglycemic nNOS expression patterns. Results show that GR exert divergent effects on VMN GS, MCT1/2, and nNOS proteins during eu- (stimulatory) versus hypoglycemia (inhibitory); these findings imply that up-regulated NO transmission may reflect, in part, augmented glucose incorporation into glycogen and/or increased tissue lactate requirements. Data also provide novel evidence for metabolic state-dependent GR regulation of VMN GPmm and GPbb profiles; thus, GABA signaling of metabolic stability may reflect, in part, stimulus-specific glycogen breakdown during eu- versus hypoglycemia.

Dietary Fibers and Proteins Modulate Behavior via the Activation of Intestinal Gluconeogenesis

INTRODUCTION

Several studies have suggested that diet, especially the one enriched in microbiota-fermented fibers or fat, regulates behavior. The underlying mechanisms are currently unknown. We previously reported that certain macronutrients (fermentable fiber and protein) regulate energy homeostasis via the activation of intestinal gluconeogenesis (IGN), which generates a neural signal to the brain. We hypothesized that these nutriments might control behavior using the same gut-brain circuit.

METHODS

Wild-type and IGN-deficient mice were fed chow or diets enriched in protein or fiber. Changes in their behavior were assessed using suited tests. Hippocampal neurogenesis, extracellular levels of serotonin, and protein expression levels were assessed by immunofluorescence, in vivo dialysis, and Western blotting, respectively. IGN was rescued by infusing glucose into the portal vein of IGN-deficient mice.

RESULTS

We show here that both fiber- and protein-enriched diets exert beneficial actions on anxiety-like and depressive-like behaviors. These benefits do not occur in mice lacking IGN. Consistently, IGN-deficient mice display hallmarks of depressive-like disorders, including decreased hippocampal neurogenesis, basal hyperactivity, and deregulation of the hypothalamic-pituitary-adrenal axis, which are associated with increased expression of the precursor of corticotropin-releasing hormone in the hypothalamus and decreased expression of the glucocorticoid receptor in the hippocampus. These neurobiological alterations are corrected by portal glucose infusion mimicking IGN.

CONCLUSION

IGN translates nutritional information, allowing the brain to finely coordinate energy metabolism and behavior.

Zinc Finger Transcription Factor Zbtb16 Coordinates the Response to Energy Deficit in the Mouse Hypothalamus

The central nervous system controls feeding behavior and energy expenditure in response to various internal and external stimuli to maintain energy balance. Here we report that the newly identified transcription factor zinc finger and BTB domain containing 16 (Zbtb16) is induced by energy deficit in the paraventricular (PVH) and arcuate (ARC) nuclei of the hypothalamus via glucocorticoid (GC) signaling. In the PVH, Zbtb16 is expressed in the anterior half of the PVH and co-expressed with many neuronal markers such as corticotropin-releasing hormone (Crh), thyrotropin-releasing hormone (Trh), oxytocin (Oxt), arginine vasopressin (Avp), and nitric oxide synthase 1 (Nos1). Knockdown (KD) of Zbtb16 in the PVH results in attenuated cold-induced thermogenesis and improved glucose tolerance without affecting food intake. In the meantime, Zbtb16 is predominantly expressed in agouti-related neuropeptide/neuropeptide Y (Agrp/Npy) neurons in the ARC and its KD in the ARC leads to reduced food intake. We further reveal that chemogenetic stimulation of PVH Zbtb16 neurons increases energy expenditure while that of ARC Zbtb16 neurons increases food intake. Taken together, we conclude that Zbtb16 is an important mediator that coordinates responses to energy deficit downstream of GCs by contributing to glycemic control through the PVH and feeding behavior regulation through the ARC, and additionally reveal its function in controlling energy expenditure during cold-evoked thermogenesis via the PVH. As a result, we hypothesize that Zbtb16 may be involved in promoting weight regain after weight loss.

Brain mechanisms of HPA axis regulation: neurocircuitry and feedback in context Richard Kvetnansky lecture

Regulation of stress reactivity is a fundamental priority of all organisms. Stress responses are critical for survival, yet can also cause physical and psychological damage. This review provides a synopsis of brain mechanisms designed to control physiological responses to stress, focusing primarily on glucocorticoid secretion via the hypothalamo-pituitary-adrenocortical (HPA) axis. The literature provides strong support for multi-faceted control of HPA axis responses, involving both direct and indirect actions at paraventricular nucleus (PVN) corticotropin releasing hormone neurons driving the secretory cascade. The PVN is directly excited by afferents from brainstem and hypothalamic circuits, likely relaying information on homeostatic challenge. Amygdala subnuclei drive HPA axis responses indirectly via disinhibition, mediated by GABAergic relays onto PVN-projecting neurons in the hypothalamus and bed nucleus of the stria terminalis (BST). Inhibition of stressor-evoked HPA axis responses is mediated by an elaborate network of glucocorticoid receptor (GR)-containing circuits, providing a distributed negative feedback signal that inhibits PVN neurons. Prefrontal and hippocampal neurons play a major role in HPA axis inhibition, again mediated by hypothalamic and BST GABAergic relays to the PVN. The complexity of the regulatory process suggests that information on stressors is integrated across functional disparate brain circuits prior to accessing the PVN, with regions such as the BST in prime position to relay contextual information provided by these sources into appropriate HPA activation. Dysregulation of the HPA in disease is likely a product of inappropriate checks and balances between excitatory and inhibitory inputs ultimately impacting PVN output.

Loss of CREBRF Reduces Anxiety-like Behaviors and Circulating Glucocorticoids in Male and Female Mice

Glucocorticoid signaling controls many key biological functions ranging from stress responses to affective states. The putative transcriptional coregulator CREB3 regulatory factor (CREBRF) reduces glucocorticoid receptor levels in vitro, suggesting that CREBRF may impact behavioral and physiological outputs. In the present study, we examined adult male and female mice with global loss of CREBRF (CrebrfKO) for anxiety-like behaviors and circulating glucocorticoids in response to various acute stress conditions. Results demonstrate that both male and female CrebrfKO mice have preserved locomotor activity but reduced anxiety-like behaviors during the light-dark box and elevated plus maze. These behavioral phenotypes were associated with lower plasma corticosterone after restraint stress. Further studies using unhandled female mice also demonstrated a loss of the diurnal circulating corticosterone rhythm in CrebrfKO mice. These results suggest that CREBRF impacts anxiety-like behavior and circulating glucocorticoids in response to acute stressors and serves as a basis for future mechanistic studies to define the impact of CREBRF in glucocorticoid-associated behavioral and physiological responses.

Maternal High-Fat-High-Carbohydrate Diet-Induced Obesity Is Associated with Increased Appetite in Peripubertal Male but Not Female C57Bl/6J Mice

Diet-induced maternal obesity might play a critical role in altering hypothalamic development, predisposing the offspring to obesity and metabolic disease later in life. The objective of this study was to describe both phenotypic and molecular sex differences in peripubertal offspring energy homeostasis, using a mouse model of maternal obesity induced by a high-fat-high-carbohydrate (HFHC) diet. We report that males, not females, exposed to a maternal HFHC diet had increased energy intake. Males exposed to a maternal HFHC diet had a 15% increased meal size and a 46% increased frequency, compared to the control (CON) males, without a change in energy expenditure. CON and HFHC offspring did not differ in body weight, composition, or plasma metabolic profile. HFHC diet caused decreased hypothalamic glucocorticoid expression, which was further decreased in males compared to females. Maternal weight, maternal caloric intake, and male offspring meal frequency were inversely correlated with offspring hypothalamic insulin receptor (IR) expression. There was a significant interaction between maternal-diet exposure and sex in hypothalamic IR. Based on our preclinical data, we suggest that interventions focusing on normalizing maternal nutrition might be considered to attenuate nutritional influences on obesity programming and curb the continuing rise in obesity rates.

DNA methylation of FKBP5 in South African women: associations with obesity and insulin resistance

BACKGROUND

Disruption of the hypothalamic-pituitary-adrenal (HPA) axis, a neuroendocrine system associated with the stress response, has been hypothesized to contribute to obesity development. This may be mediated through epigenetic modulation of HPA axis-regulatory genes in response to metabolic stressors. The aim of this study was to investigate adipose tissue depot-specific DNA methylation differences in the glucocorticoid receptor (GR) and its co-chaperone, FK506-binding protein 51 kDa (FKBP5), both key modulators of the HPA axis.

METHODS

Abdominal subcutaneous adipose tissue (ASAT) and gluteal subcutaneous adipose tissue (GSAT) biopsies were obtained from a sample of 27 obese and 27 normal weight urban-dwelling South African women. DNA methylation and gene expression were measured by pyrosequencing and quantitative real-time PCR, respectively. Spearman's correlation coefficients, orthogonal partial least-squares discriminant analysis and multivariable linear regression were performed to evaluate the associations between DNA methylation, messenger RNA (mRNA) expression and key indices of obesity and metabolic dysfunction.

RESULTS

Two CpG dinucleotides within intron 7 of FKBP5 were hypermethylated in both ASAT and GSAT in obese compared to normal weight women, while no differences in GR methylation were observed. Higher percentage methylation of the two FKBP5 CpG sites correlated with adiposity (body mass index and waist circumference), insulin resistance (homeostasis model for insulin resistance, fasting insulin and plasma adipokines) and systemic inflammation (c-reactive protein) in both adipose depots. GR and FKBP5 mRNA levels were lower in GSAT, but not ASAT, of obese compared to normal weight women. Moreover, FKBP5 mRNA levels were inversely correlated with DNA methylation and positively associated with adiposity, metabolic and inflammatory parameters.

CONCLUSIONS

These findings associate dysregulated FKBP5 methylation and mRNA expression with obesity and insulin resistance in South African women. Additional studies are required to assess the longitudinal association of FKBP5 with obesity and associated co-morbidities in large population-based samples.

The selective glucocorticoid receptor antagonist CORT125281 has tissue-specific activity

Glucocorticoids mediate numerous essential processes in the human body via binding to the glucocorticoid receptor (GR). Excessive GR signaling can cause disease, and GR antagonists can be used to treat many symptoms of glucocorticoid-induced pathology. The purpose of this study was to characterize the tissue-specific properties of the selective GR antagonist CORT125281. We evaluated the antagonistic effects of CORT125281 upon acute and subchronic corticosterone exposure in mice. In the acute corticosterone setting, hypothalamus-pituitary-adrenal-axis activity was investigated by measurement of basal- and stress-induced corticosterone levels, adrenocorticotropic hormone levels and pituitary proopiomelanocortin expression. GR signaling was evaluated by RT-PCR analysis of GR-responsive transcripts in liver, muscle, brown adipose tissue (BAT), white adipose tissue (WAT) and hippocampus. Pretreatment with a high dose of CORT125281 antagonized GR activity in a tissue-dependent manner. We observed complete inhibition of GR-induced target gene expression in the liver, partial blockade in muscle and BAT and no antagonism in WAT and hippocampus. Tissue distribution only partially explained the lack of effective antagonism. CORT125281 treatment did not disinhibit the hypothalamus-pituitary-adrenal neuroendocrine axis. In the subchronic corticosterone setting, CORT125281 partially prevented corticosterone-induced hyperinsulinemia, but not hyperlipidemia and immune suppression. In conclusion, CORT125281 antagonizes GR transcriptional activity in a tissue-dependent manner and improves corticosterone-induced hyperinsulinemia. Tailored dosing of CORT125281 may allow tissue-specific inhibition of GR transcriptional activity.

Disrupted hypothalamic CRH neuron responsiveness contributes to diet-induced obesity

The current obesity epidemic mainly results from high-fat high-caloric diet (HFD) feeding and may also be contributed by chronic stress; however, the neural basis underlying stress-related diet-induced obesity remains unknown. Corticotropin-releasing hormone (CRH) neurons in the paraventricular hypothalamus (PVH), a known body weight-regulating region, represent one key group of stress-responsive neurons. Here, we found that HFD feeding blunted PVH CRH neuron response to nutritional challenges as well as stress stimuli and dexamethesone, which normally produce rapid activation and inhibition on these neurons, respectively. We generated mouse models with the activity of these neurons clamped at high or low levels, both of which showed HFD-mimicking, blunted PVH CRH neuron responsiveness. Strikingly, both models developed rapid HFD-induced obesity, associated with HFD-mimicking, reduced diurnal rhythmicity in feeding and energy expenditure. Thus, blunted responsiveness of PVH CRH neurons, but not their absolute activity levels, underlies HFD-induced obesity and may also contribute to stress-induced obesity.

Selective effects of dorsal raphé nucleus glucocorticoid receptor deletion on depression-like behavior in female C57BL/6J mice

We have shown differing effects of glucocorticoid receptor (GR) deletion from the dorsal raphé nucleus (DRN) and locus coeruleus (LC) on depression-relevant behavior in male mice, but DRN GR deletion has not been tested in female mice. Female floxed GR mice were given DRN injections of AAV2/9 pseudotype viral vectors transducing Cre recombinase to produce DRN GR gene deletion (Cre) and compared with mice receiving DRN injections of AAV2/9 transducing green fluorescent protein (GFP). Social interaction, a measure of depression-like withdrawal, was unaffected by DRN GR deletion, but forced swim immobility, a measure of despair-like passivity, was reduced in female Cre vs. GFP mice. Behavioral effects were not attributable to changes in basal corticosterone or LC GR deletion. Combined with our prior studies, the current findings suggest that DRN GR have sex-independent effects to promote forced swim immobility, but influence social interaction only in male mice. Differential effects of DRN GR deletion in female mice may provide insight into the greater incidence of depression and specific depression symptoms in women.

Chronic psychosocial stress during pregnancy affects maternal behavior and neuroendocrine function and modulates hypothalamic CRH and nuclear steroid receptor expression

Postpartum depression (PPD) affects up to 20% of mothers and has negative consequences for both mother and child. Although exposure to psychosocial stress during pregnancy and abnormalities in the hypothalamic pituitary adrenal (HPA) axis have been linked to PPD, molecular changes in the brain that contribute to this disease remain unknown. This study utilized a novel chronic psychosocial stress paradigm during pregnancy (CGS) to investigate the effects of psychosocial stress on maternal behavior, neuroendocrine function, and gene expression changes in molecular regulators of the HPA axis in the early postpartum period. Postpartum female mice exposed to CGS display abnormalities in maternal behavior, including fragmented and erratic maternal care patterns, and the emergence of depression and anxiety-like phenotypes. Dysregulation in postpartum HPA axis function, evidenced by blunted circadian peak and elevation of stress-induced corticosterone levels, was accompanied by increased CRH mRNA expression and a reduction in CRH receptor 1 in the paraventricular nucleus of the hypothalamus (PVN). We further observed decreased PVN expression of nuclear steroid hormone receptors associated with CRH transcription, suggesting these molecular changes could underlie abnormalities in postpartum HPA axis and behavior observed. Overall, our study demonstrates that psychosocial stress during pregnancy induces changes in neuroendocrine function and maternal behavior in the early postpartum period and introduces our CGS paradigm as a viable model that can be used to further dissect the molecular defects that lead to PPD.

Temporally Tuned Corticosteroid Feedback Regulation of the Stress Axis

Activity of the hypothalamic-pituitary-adrenal (HPA) axis is tuned by corticosteroid feedback. Corticosteroids regulate cellular function via genomic and nongenomic mechanisms, which operate over diverse time scales. This review summarizes recent advances in our understanding of how corticosteroid feedback regulates hypothalamic stress neuron function and output through synaptic plasticity, changes in intrinsic excitability, and modulation of neuropeptide production. The temporal kinetics of corticosteroid actions in the brain versus the pituitary have important implications for how organisms respond to stress. Furthermore, we will discuss, some of the technical limitations and missing links in the field, and the potential implications these may have on our interpretations of corticosteroid negative feedback experiments.

Obesity increases the risk of chronic pain development after motor vehicle collision

Obesity has been found to increase the risk of musculoskeletal pain (MSP) in other settings, but to our knowledge, the influence of increased body mass index on pain outcomes after common trauma exposures such as motor vehicle collision (MVC) has not been assessed. In addition, obesity results in biomechanical changes, as well as physiologic changes including reduced hypothalamic pituitary adrenal axis negative feedback inhibition, but mechanisms by which obesity may result in worse post-traumatic outcomes remain poorly understood. In this study, we evaluated the influence of body mass index on axial and overall MSP severity (0-10 numeric rating scale) 6 weeks, 6 months, and 1 year after MVC among 917 European Americans who presented to the emergency department for initial evaluation. After adjusting for an array of sociodemographic factors, obesity (particularly morbid obesity) was an independent risk factor for worse MSP after MVC (eg, RR 1.41 [95% CI 1.11, 1.80] for moderate or severe MSP 6 months after MVC among morbidly obese vs normal weight MVC survivors). Interestingly, substantial effect modification was observed between obesity risk and a genetic variant known to reduce hypothalamic pituitary adrenal axis negative feedback inhibition (FKBP5 rs9380526). (eg, 41% vs 16% increased risk of moderate or severe MSP at 6 months among obese individuals with and without the risk allele.) Further studies are needed to elucidate mechanisms underlying chronic pain development in obese trauma survivors and to develop interventions that will reduce chronic pain severity among this common, at-risk group.

Glucocorticoid receptor deletion from locus coeruleus norepinephrine neurons promotes depression-like social withdrawal in female but not male mice

Abnormal glucocorticoid levels can cause psychiatric symptoms ranging from depression to euphoria that have been implicated in mood disorders. My overarching hypothesis is that these opposing effects are mediated by glucocorticoid receptors (GR) in different brain regions. My laboratory has shown that GR in the serotonergic dorsal raphé nucleus (DRN) promote depression-like social and behavioral withdrawal in mice. We have also shown that GR in the DRN and noradrenergic locus coeruleus (LC) exhibit divergent regulation by antidepressants that have differential efficacy for depression subtypes with opposing abnormalities in glucocorticoids. The current study tested the hypothesis that LC GR would have effects opposite to those in the DRN by preventing rather than promoting social withdrawal. GR was deleted from LC NE neurons in female and male floxed GR mice by bilateral injections of lentivirus transducing Cre recombinase under control of a multimerized Phox 2a/2b response sequence (PRS) from the dopamine β-hydroxylase promoter (PRS-Cre). Female but not male PRS-Cre mice exhibited lower social interaction compared to controls injected with lentivirus transducing green fluorescent protein (PRS-GFP). Differences in social interaction between PRS-GFP and PRS-Cre females were not associated with differences in exploratory behavior, plasma corticosterone, male-female differences in LC GR expression, or changes in LC mineralocorticoid receptor or tyrosine hydroxylase gene expression. These results indicate that LC NE GR have sex-dependent effects to prevent social withdrawal, supporting the concept that glucocorticoids exert opposing effects on depression symptoms via different brain targets, and potentially revealing novel drug targets to treat depression, particularly in women.

Role of glucocorticoid negative feedback in the regulation of HPA axis pulsatility

The hypothalamic-pituitary-adrenal (HPA) axis is the major neuroendocrine axis regulating homeostasis in mammals. Glucocorticoid hormones are rapidly synthesized and secreted from the adrenal gland in response to stress. In addition, under basal conditions glucocorticoids are released rhythmically with both a circadian and an ultradian (pulsatile) pattern. These rhythms are important not only for normal function of glucocorticoid target organs, but also for the HPA axis responses to stress. Several studies have shown that disruption of glucocorticoid rhythms is associated with disease both in humans and in rodents. In this review, we will discuss our knowledge of the negative feedback mechanisms that regulate basal ultradian synthesis and secretion of glucocorticoids, including the role of glucocorticoid and mineralocorticoid receptors and their chaperone protein FKBP51. Moreover, in light of recent findings, we will also discuss the importance of intra-adrenal glucocorticoid receptor signaling in regulating glucocorticoid synthesis.

Deletion of exchange proteins directly activated by cAMP (Epac) causes defects in hippocampal signaling in female mice

Previous studies demonstrate essential roles for the exchange proteins directly activated by cAMP 1 and 2 (Epac1 and Epac2; here collectively referred to as Epac) in the brain. In the hippocampus, Epac contributes to the control of neuronal growth and differentiation and has been implicated in memory and learning as well as in anxiety and depression. In the present study we address the hypothesis that Epac affects hippocampal cellular responses to acute restraint stress. Stress causes activation of the hypothalamus-pituitary-adrenal (HPA)-axis, and glucocorticoid receptor (GR) signaling is essential for proper feedback regulation of the stress response, both in the brain and along the HPA axis. In the hippocampus, GR expression is regulated by cAMP and the brain enriched micro RNA miR-124. Epac has been associated with miR-124 expression in hippocampal neurons, but not in regulation of GR. We report that hippocampal expression of Epac1 and Epac2 increased in response to acute stress in female wild type mice. In female mice genetically deleted for Epac, nuclear translocation of GR in response to restraint stress was significantly delayed, and moreover, miR-124 expression was decreased in these mice. Male mice lacking Epac also showed abnormalities in miR-124 expression, but the phenotype was less profound than in females. Serum corticosterone levels were slightly altered immediately after stress in both male and female mice deleted for Epac. The presented data indicate that Epac1 and Epac2 are involved in controlling cellular responses to acute stress in the mouse hippocampus and provide novel insights into the underlying transcriptional and signaling networks. Interestingly, we observe sex specific differences when Epac is deleted. As the incidence and prevalence of stress-related diseases are higher in women than in men, the Epac knockout models might serve as genetic tools to further elucidate the cellular mechanisms underlying differences between male and female with regard to regulation of stress.

Importance of the brain corticosteroid receptor balance in metaplasticity, cognitive performance and neuro-inflammation

Bruce McEwen's discovery of receptors for corticosterone in the rat hippocampus introduced higher brain circuits in the neuroendocrinology of stress. Subsequently, these receptors were identified as mineralocorticoid receptors (MRs) that are involved in appraisal processes, choice of coping style, encoding and retrieval. The MR-mediated actions on cognition are complemented by slower actions via glucocorticoid receptors (GRs) on contextualization, rationalization and memory storage of the experience. These sequential phases in cognitive performance depend on synaptic metaplasticity that is regulated by coordinate MR- and GR activation. The receptor activation includes recruitment of coregulators and transcription factors as determinants of context-dependent specificity in steroid action; they can be modulated by genetic variation and (early) experience. Interestingly, inflammatory responses to damage seem to be governed by a similarly balanced MR:GR-mediated action as the initiating, terminating and priming mechanisms involved in stress-adaptation. We conclude with five questions challenging the MR:GR balance hypothesis.

Role of 11β-HSD type 1 in abnormal HPA axis activity during immune-mediated arthritis

Patients with chronic immune-mediated arthritis exhibit abnormal hypothalamo-pituitary-adrenal (HPA) axis activity. The basis for this abnormality is not known. Immune-mediated arthritis is associated with increased extra-adrenal synthesis of active glucocorticoids by the 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) enzyme. 11β-HSD1 is expressed in the central nervous system, including regions involved in HPA axis regulation. We examined whether altered 11β-HSD1 expression within these regions contributes to HPA axis dysregulation during arthritis. The expression of 11β-HSD1, and other components of glucocorticoid signaling, were examined in various brain regions and the pituitary gland of mice with experimentally induced arthritis. Two arthritis protocols were employed: The K/BxN spontaneous arthritis model for chronic arthritis and the K/BxN serum transfer arthritis model for acute arthritis. 11β-HSD1 mRNA (Hsd11b1) was expressed in the hippocampus, hypothalamus, cortex, cerebellum and pituitary gland. Hypothalamic Hsd11b1 expression did not change in response to arthritis in either model. Pituitary Hsd11b1 expression was however significantly increased in both chronic and acute arthritis models. Hippocampal Hsd11b1 was decreased in acute but not chronic arthritis. Chronic, but not acute, arthritis was associated with a reduction in hypothalamic corticotropin-releasing hormone and arginine vasopressin expression. In both models, serum adrenocorticotropic hormone and corticosterone levels were no different from non-inflammatory controls. These findings demonstrate inflammation-dependent regulation of Hsd11b1 expression in the pituitary gland and hippocampus. The upregulation of 11β-HSD1 expression in the pituitary during both chronic and acute arthritis, and thus, an increase in glucocorticoid negative feedback, could contribute to the abnormalities in HPA axis activity seen in immune-mediated arthritis.

Glucocorticoid Signaling in Health and Disease: Insights From Tissue-Specific GR Knockout Mice

Glucocorticoids are adrenally produced hormones critically involved in development, general physiology, and control of inflammation. Since their discovery, glucocorticoids have been widely used to treat a variety of inflammatory conditions. However, high doses or prolonged use leads to a number of side effects throughout the body, which preclude their clinical utility. The primary actions of glucocorticoids are mediated by the glucocorticoid receptor (GR), a transcription factor that regulates many complex signaling pathways. Although GR is nearly ubiquitous throughout the body, glucocorticoids exhibit cell- and tissue-specific effects. For example, glucocorticoids stimulate glucose production in the liver, reduce glucose uptake in the skeletal muscle, and decrease insulin secretion from the pancreatic β-cells. Mouse models represent an important approach to understanding the dynamic functions of GR signaling in normal physiology, disease, and resistance. In the absence of a viable GR null model, gene-targeting techniques utilizing promoter-driven recombination have provided an opportunity to characterize the tissue-specific actions of GR. The aim of the present review is to describe the organ systems in which GR has been conditionally deleted and summarize the functions ascribed to glucocorticoid action in those tissues.

A naturally hypersensitive glucocorticoid receptor elicits a compensatory reduction of hypothalamus-pituitary-adrenal axis activity early in ontogeny

We comprehensively characterized the effects of a unique natural gain-of-function mutation in the glucocorticoid receptor (GR), GRAla610Val, in domestic pigs to expand current knowledge of the phenotypic consequences of GR hypersensitivity. Cortisol levels were consistently reduced in one-week-old piglets, at weaning and in peripubertal age, probably due to a reduced adrenal capacity to produce glucocorticoids (GC), which was indicated by an adrenocortical thinning in GRAla610Val carriers. Adrenocorticotrophic hormone (ACTH) levels were significantly reduced in one-week-old piglets only. Expression analyses in peripubertal age revealed significant downregulation of hypothalamic expression of CRH and AVP, the latter only in females, and upregulation of hepatic expression of SERPINA6, by GRAla610Val Transcriptional repression of proinflammatory genes in peripheral blood mononuclear cells (PBMCs) from GRAla610Val carriers was more sensitive to dexamethasone treatment ex vivo However, no significant effects on growth, body composition, blood chemistry or cell counts were observed under baseline conditions. These results suggest that GRAla610Val-induced GR hypersensitivity elicits a compensatory reduction in endogenous, bioactive glucocorticoid levels via readjustment of the hypothalamus-pituitary-adrenal (HPA) axis early in ontogeny to maintain an adequate response, but carriers are more sensitive to exogenous GC. Therefore, GRAla610Val pigs represent a valuable animal model to explore GR-mediated mechanisms of HPA axis regulation and responses to glucocorticoid-based drugs.

Hyperactivity of Hypothalamic-Pituitary-Adrenal Axis Due to Dysfunction of the Hypothalamic Glucocorticoid Receptor in Sigma-1 Receptor Knockout Mice

Sigma-1 receptor knockout (σ₁R-KO) mice exhibit a depressive-like phenotype. Because σ₁R is highly expressed in the neuronal cells of hypothalamic paraventricular nuclei (PVN), this study investigated the influence of σ₁R deficiency on the regulation of the hypothalamic-pituitary-adrenocortical (HPA) axis. Here, we show that the levels of basal serum corticosterone (CORT), adrenocorticotropic hormone (ACTH) and corticotrophin releasing factor (CRF) as well as the level of CRF mRNA in PVN did not significantly differ between adult male σ₁R-KO mice and wild-type (WT) mice. Acute mild restraint stress (AMRS) induced a higher and more sustainable increase in activity of HPA axis and CRF expression in σ₁R-KO mice. Percentage of dexamethasone (Dex)-induced reduction in level of CORT was markedly attenuated in σ₁R^-/- mice. The levels of glucocorticoid receptor (GR) and protein kinase C (PKC) phosphorylation were reduced in the PVN of σ₁R-KO mice and σ₁R antagonist NE100-treated WT mice. The exposure to AMRS in σ₁R-KO mice induced a stronger phosphorylation of cAMP-response element binding protein (CREB) in PVN than that in WT mice. Intracerebroventricular (i.c.v.) injection of PKC activator PMA for 3 days in σ₁R-KO mice not only recovered the GR phosphorylation and the percentage of Dex-reduced CORT but also corrected the AMRS-induced hyperactivity of HPA axis and enhancement of CRF mRNA and CREB phosphorylation. Furthermore, the injection (i.c.v.) of PMA in σ₁R-KO mice corrected the prolongation of immobility time in forced swim test (FST) and tail suspension test (TST). These results indicate that σ₁R deficiency causes down-regulation of GR by reducing PKC phosphorylation, which attenuates GR-mediated feedback inhibition of HPA axis and facilitates the stress response of HPA axis leading to the production of depressive-like behaviors.

Glucocorticoid receptor action in metabolic and neuronal function

Glucocorticoids via the glucocorticoid receptor (GR) have effects on a variety of cell types, eliciting important physiological responses via changes in gene expression and signaling. Although decades of research have illuminated the mechanism of how this important steroid receptor controls gene expression using in vitro and cell culture–based approaches, how GR responds to changes in external signals in vivo under normal and pathological conditions remains elusive. The goal of this review is to highlight recent work on GR action in fat cells and liver to affect metabolism in vivo and the role GR ligands and receptor phosphorylation play in calibrating signaling outputs by GR in the brain in health and disease. We also suggest that both the brain and fat tissue communicate to affect physiology and behavior and that understanding this “brain-fat axis” will enable a more complete understanding of metabolic diseases and inform new ways to target them.

NPY1 Receptor Agonist Modulates Development of Depressive-Like Behavior and Gene Expression in Hypothalamus in SPS Rodent PTSD Model

Delivery of neuropeptide Y (NPY) to the brain by intranasal infusion soon after traumatic stress has shown therapeutic potential, and prevented development of many behavioral and neuroendocrine impairments in the single prolonged stress (SPS) animal model of PTSD. Therefore, we examined whether the Y1R preferring agonist [Leu³¹Pro³⁴]NPY is sufficient to prevent development of SPS induced depressive-like behavioral changes, and hypothalamic gene expression as obtained with intranasal NPY intervention. Male Sprague-Dawely rats were given intranasal infusion of either NPY (150 μg/rat), a low (68 μg /rat), or high (132 μg/rat) dose of [Leu³¹Pro³⁴]NPY or vehicle immediately following the last SPS stressor, left undisturbed for 1 week and then tested for depressive-like behavior together with naïve unstressed controls. Vehicle treated animals had elevated immobility forced swim test (FST) and reduced sucrose preference, which were not observed in animals given NPY or the higher dose of [Leu³¹Pro³⁴]NPY. This dose of [Leu³¹Pro³⁴]NPY, like NPY, also prevented the SPS-elicited induction of CRF mRNA in the mediobasal hypothalamus. However, [Leu³¹Pro³⁴]NPY did not prevent, but rather enhanced, the SPS-triggered induction of GR and FKBP5 mRNA levels in the mediobasal hypothalamus. Thus, [Leu³¹Pro³⁴]NPY may be as effective as NPY and displays therapeutic potential for preventing development of depressive-like behaviors and dysregulation of the CRF/HPA system in PTSD. However, due to its different effects compared to NPY on GR and FKBP5 a broader agonist, such as NPY, may be more desirable.

Forebrain glutamatergic, but not GABAergic, neurons mediate anxiogenic effects of the glucocorticoid receptor

Anxiety disorders constitute a major disease and social burden worldwide; however, many questions concerning the underlying molecular mechanisms still remain open. Besides the involvement of the major excitatory (glutamate) and inhibitory (gamma aminobutyric acid (GABA)) neurotransmitter circuits in anxiety disorders, the stress system has been directly implicated in the pathophysiology of these complex mental illnesses. The glucocorticoid receptor (GR) is the major receptor for the stress hormone cortisol (corticosterone in rodents) and is widely expressed in excitatory and inhibitory neurons, as well as in glial cells. However, currently it is unknown which of these cell populations mediate GR actions that eventually regulate fear- and anxiety-related behaviors. In order to address this question, we generated mice lacking the receptor specifically in forebrain glutamatergic or GABAergic neurons by breeding GR^flox/flox mice to Nex-Cre or Dlx5/6-Cre mice, respectively. GR deletion specifically in glutamatergic, but not in GABAergic, neurons induced hypothalamic-pituitary-adrenal axis hyperactivity and reduced fear- and anxiety-related behavior. This was paralleled by reduced GR-dependent electrophysiological responses in the basolateral amygdala (BLA). Importantly, viral-mediated GR deletion additionally showed that fear expression, but not anxiety, is regulated by GRs in glutamatergic neurons of the BLA. This suggests that pathological anxiety likely results from altered GR signaling in glutamatergic circuits of several forebrain regions, while modulation of fear-related behavior can largely be ascribed to GR signaling in glutamatergic neurons of the BLA. Collectively, our results reveal a major contribution of GRs in the brain's key excitatory, but not inhibitory, neurotransmitter system in the regulation of fear and anxiety behaviors, which is crucial to our understanding of the molecular mechanisms underlying anxiety disorders.

The Molecular Apgar Score: A Key to Unlocking Evolutionary Principles

One of the first "tools" used for systematically evaluating successful newborn transitional physiology at birth was the Apgar Score, devised by Virginia Apgar in 1953. This objective assessment tool allowed clinicians to immediately gauge the relative success of a newborn infant making the transition from the in utero liquid immersive environment to the ex utero gas environment in the delivery room during the first minutes after birth. The scoring system, although eponymous, is generally summarized as an acronym based on Appearance, Pulse, Grimace, Activity, and Respiration, criteria evaluated and scored at 1 and 5 min after birth. This common clinical appraisal is a guide for determining the elements of integrated physiology involved as the infant makes the transition from a "sea water" environment of 3% oxygen to a "land" environment in 21% oxygen. Appearance determines the perfusion of the skin with oxygenated blood-turning it pink; Pulse is the rate of heart beat, reflecting successful oxygen delivery to organs; Grimace, or irritability, is a functional marker for nervous system integration; Activity represents locomotor capacity; and, of course, Respiration represents pulmonary function as well as the successful neuro-feedback-mediated drive to breathe, supplying oxygen by inspiring atmospheric gas. Respiration, locomotion, and metabolism are fundamental processes adapted for vertebrate evolution from a water-based to an atmosphere-based life and are reflected by the Apgar Score. These physiologic processes last underwent major phylogenetic changes during the water-land transition some 300-400 million years ago, during which specific gene duplications occurred that facilitated terrestrial adaptation, in particular the parathyroid hormone-related protein receptor, the β-adrenergic receptor, and the glucocorticoid receptor. All these genetic traits and the gene regulatory networks they comprise represent the foundational substructure of the Apgar Score. As such, these molecular elements can be examined using a Molecular Apgar evaluation of keystone evolutionary events that predict successful evolutionary adaptation of physiologic functions necessary for neonatal transition and survival.

The metabolic sensor Sirt1 and the hypothalamus: Interplay between peptide hormones and pro-hormone convertases

The last decade had witnessed a tremendous progress in our understanding of the causes of metabolic diseases including obesity. Among the contributing factors regulating energy balance are nutrient sensors such as sirtuins. Sirtuin1 (Sirt1), a NAD + - dependent deacetylase is affected by diet, environmental stress, and also plays a critical role in metabolic health by deacetylating proteins in many tissues, including liver, muscle, adipose tissue, heart, endothelium, and in the complexity of the hypothalamus. Because of its dependence on NAD+, Sirt1 also functions as a nutrient/redox sensor, and new novel data show a function of this enzyme in the maturation of hypothalamic peptide hormones controlling energy balance either through regulation of specific nuclear transcription factors or by regulating specific pro-hormone convertases (PCs) involved in the post-translational processing of pro-hormones. The post-translational processing mechanism of pro-hormones is critical in the pathogenesis of obesity as recently shown that metabolic and physiological triggers affect the biosynthesis and processing of many peptides hormones. Specific regulation of pro-hormone processing is likely another key step where final amounts of bioactive peptides can be tightly regulated. Different factors stimulate or inhibit pro-hormones biosynthesis in concert with an increase in the PCs involved in the maturation of bioactive hormones. Adding more complexity to the system, the new studies describe here suggest that Sirt1 could also regulate the fate of peptide hormone biosynthesis. The present review summarizes the recent progress in hypothalamic SIRT1 research with a particular emphasis on the tissue-specific control of neuropeptide hormone maturation. The series of studies done in mouse and rat models strongly advocate for the first time that a deacetylating enzyme could be a regulator in the maturation of peptide hormones and their processing enzymes. These discoveries are the culmination of the first in-depth understanding of the metabolic role of Sirt1 in the brain. It suggests that Sirt1 behaves differently in the brain than in organs such as the liver and pancreas, where the enzyme has been more commonly studied.

Hepatic Glucocorticoid Receptor Plays a Greater Role Than Adipose GR in Metabolic Syndrome Despite Renal Compensation

Exogenous glucocorticoid administration results in hyperglycemia, insulin resistance, hepatic dyslipidemia, and hypertension, a constellation of findings known as Cushing's syndrome. These effects are mediated by the glucocorticoid receptor (GR). Because GR activation in liver and adipose has been implicated in metabolic syndrome (MS), we wanted to determine the role of GR in these tissues in the development of MS. Because GR knockout (KO) mice (whole-body KO) exhibit perinatal lethality due to respiratory failure, we generated tissue-specific (liver or adipose) GRKO mice using cre-lox technology. Real-time PCR analysis of liver mRNA from dexamethasone-treated wildtype (WT) and liver GRKO mice indicated that hepatic GR regulates the expression of key genes involved in gluconeogenesis and glycogen metabolism. Interestingly, we have observed that liver-specific deletion of GR resulted in a significant increase in mRNA expression of key genes involved in gluconeogenesis and glycogen metabolism in kidney tissue, indicating a compensatory mechanism to maintain glucose homeostasis. We have also observed that GR plays an important role in regulating the mRNA expression of key genes involved in lipid metabolism. Liver GRKO mice demonstrated decreased fat mass and liver glycogen content compared with WT mice administered dexamethasone for 2 weeks. Adipose-specific deletion of GR did not alter glucose tolerance or insulin sensitivity of adipose GRKO mice compared with WT mice administrated dexamethasone. This indicates that liver GR might be more important in development of MS in dexamethasone-treated mice, whereas adipose GR plays a little role in these paradigms.