Hippocampal 11beta-hydroxysteroid dehydrogenase type 1 messenger ribonucleic acid expression has a diurnal variability that is lost in the obese Zucker rat

The Role of Very Low Calorie Ketogenic Diet in Sympathetic Activation through Cortisol Secretion in Male Obese Population

Adipose tissue is considered an endocrine organ, and its excess compromises the immune response and metabolism of hormones and nutrients. Furthermore, the accumulation of visceral fat helps to increase the synthesis of cortisol. The hypothalamus-pituitary-adrenal (HPA) axis is a neuroendocrine system involved in maintaining homeostasis in humans under physiological conditions and stress, and cortisol is the main hormone of the HPA axis. It is known that a stress-induced diet and cortisol reactivity to acute stress factors may be related to dietary behavior. In obesity, to reduce visceral adipose tissue, caloric restriction is a valid strategy. In light of this fact, the aim of this study was to assess the effects of a commercial dietary ketosis program for weight loss on the sympathetic nervous system and HPA axis, through evaluation of salivary cortisol and GSR levels. Thirty obese subjects were recruited and assessed before and after 8 weeks of Very Low Calorie Ketogenic Diet (VLCKD) intervention to evaluate body composition and biochemical parameters. Salivary cortisol levels and GSR significantly decreased after dietary treatment; in addition, body composition and biochemical features were ameliorated. The VLCKD had a short-term positive effect on the SNS and HPA axes regulating salivary cortisol levels. Finally, the effects of the VLCKD on the SNS and HPA axis may lead to more individualized treatment strategies that integrate obesity and stress and support the usefulness of such therapeutic interventions in promoting the reduction of the individual disease burden.

Endogenous Glucocorticoid Metabolism in Bone: Friend or Foe

The role of tissue specific metabolism of endogenous glucocorticoids (GCs) in the pathogenesis of human disease has been a field of intense interest over the last 20 years, fuelling clinical trials of metabolism inhibitors in the treatment of an array of metabolic diseases. Localised pre-receptor metabolism of endogenous and therapeutic GCs by the 11β-hydroxysteroid dehydrogenase (11β-HSD) enzymes (which interconvert endogenous GCs between their inactive and active forms) are increasingly recognised as being critical in mediating both their positive and negative actions on bone homeostasis. In this review we explore the roles of endogenous and therapeutic GC metabolism by the 11β-HSD enzymes in the context of bone metabolism and bone cell function, and consider future strategies aimed at modulating this system in order to manage and treat various bone diseases.

Evidence for disruption of diurnal salivary cortisol rhythm in childhood obesity: relationships with anthropometry, puberty and physical activity

Background

The aim of this study was to examine the characteristics of diurnal cortisol rhythm in childhood obesity and its relationships with anthropometry, pubertal stage and physical activity.

Methods

Thirty-five children with obesity (median age: 11.80[interquartile range 10.30, 13.30] and median BMI z-score: 3.21[interquartile range 2.69, 3.71]) and 22 children with normal weight (median age: 10.85[interquartile range 8.98, 12.13] and median BMI z-score: − 0.27[interquartile range − 0.88, 0.35]) were recruited. Saliva samples were collected at 08:00, 16:00 and 23:00 h. Cortisol concentrations at 3 time points, corresponding areas under the curve (AUCs) and diurnal cortisol slope (DCS) were compared between the two groups. Anthropometric measures and pubertal stage were evaluated, and behavioural information was obtained via questionnaires.

Results

Children with obesity displayed significantly lower cortisol_08:00 (median [interquartile range]: 5.79[3.42,7.73] vs. 8.44[5.56,9.59] nmol/L, P = 0.030) and higher cortisol_23:00 (median [interquartile range]: 1.10[0.48,1.46] vs. 0.40[0.21,0.61] nmol/L, P < 0.001) with a flatter DCS (median [interquartile range]: − 0.29[− 0.49, 0.14] vs. -0.52[− 0.63, 0.34] nmol/L/h, P = 0.006) than their normal weight counterparts. The AUC increased with pubertal development (AUC_{08:00–16:00}:P = 0.008; AUC_{08:00–23:00}: P = 0.005). Furthermore, cortisol_08:00 was inversely associated with BMI z-score (β = − 0.247, P = 0.036) and waist-to-height ratio (WHtR) (β = − 0.295, P = 0.027). Cortisol_23:00 was positively associated with BMI z-score (β = 0.490, P<0.001), WHtR (β = 0.485, P<0.001) and fat mass percentage (FM%) (β = 0.464, P<0.001). Absolute values of DCS were inversely associated with BMI z-score (β = − 0.350, P = 0.009), WHtR (β = − 0.384, P = 0.004) and FM% (β = − 0.322, P = 0.019). In multivariate analyses adjusted for pubertal stage and BMI z-score, Cortisol_08:00, AUC_{08:00–16:00} and absolute values of DCS were inversely associated with the relative time spent in moderate to vigorous intensity physical activity (P < 0.05). AUC_{16:00–23:00} was positively associated with relative non-screen sedentary time and negatively associated with sleep (P < 0.05).

Conclusions

The disorder of diurnal salivary cortisol rhythm is associated with childhood obesity, which is also influenced by puberty development and physical activity. Thus, stabilizing circadian cortisol rhythms may be an important approach for childhood obesity.

Neurovascular glucocorticoid receptors and glucocorticoids: implications in health, neurological disorders and drug therapy

Glucocorticoid receptors (GRs) are ubiquitous transcription factors widely studied for their role in controlling events related to inflammation, stress and homeostasis. Recently, GRs have reemerged as crucial targets of investigation in neurological disorders, with a focus on pharmacological strategies to direct complex mechanistic GR regulation and improve therapy. In the brain, GRs control functions necessary for neurovascular integrity, including responses to stress, neurological changes mediated by the hypothalamic-pituitary-adrenal axis and brain-specific responses to corticosteroids. Therefore, this review will examine GR regulation at the neurovascular interface in normal and pathological conditions, pharmacological GR modulation and glucocorticoid insensitivity in neurological disorders.

The Functional and Clinical Significance of the 24-Hour Rhythm of Circulating Glucocorticoids

Adrenal glucocorticoids are major modulators of multiple functions, including energy metabolism, stress responses, immunity, and cognition. The endogenous secretion of glucocorticoids is normally characterized by a prominent and robust circadian (around 24 hours) oscillation, with a daily peak around the time of the habitual sleep-wake transition and minimal levels in the evening and early part of the night. It has long been recognized that this 24-hour rhythm partly reflects the activity of a master circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus. In the past decade, secondary circadian clocks based on the same molecular machinery as the central master pacemaker were found in other brain areas as well as in most peripheral tissues, including the adrenal glands. Evidence is rapidly accumulating to indicate that misalignment between central and peripheral clocks has a host of adverse effects. The robust rhythm in circulating glucocorticoid levels has been recognized as a major internal synchronizer of the circadian system. The present review examines the scientific foundation of these novel advances and their implications for health and disease prevention and treatment.

Circadian Clocks and the Interaction between Stress Axis and Adipose Function

Many physiological processes and most endocrine functions show fluctuations over the course of the day. These so-called circadian rhythms are governed by an endogenous network of cellular clocks and serve as an adaptation to daily and, thus, predictable changes in the organism's environment. Circadian clocks have been described in several tissues of the stress axis and in adipose cells where they regulate the rhythmic and stimulated release of stress hormones, such as glucocorticoids, and various adipokine factors. Recent work suggests that both adipose and stress axis clock systems reciprocally influence each other and adrenal-adipose rhythms may be key players in the development and therapy of metabolic disorders. In this review, we summarize our current understanding of adrenal and adipose tissue rhythms and clocks and how they might interact to regulate energy homoeostasis and stress responses under physiological conditions. Potential chronotherapeutic strategies for the treatment of metabolic and stress disorders are discussed.

Adrenal Clocks and the Role of Adrenal Hormones in the Regulation of Circadian Physiology

The mammalian circadian timing system consists of a master pacemaker in the suprachiasmatic nucleus (SCN) and subordinate clocks that disseminate time information to various central and peripheral tissues. While the function of the SCN in circadian rhythm regulation has been extensively studied, we still have limited understanding of how peripheral tissue clock function contributes to the regulation of physiological processes. The adrenal gland plays a special role in this context as adrenal hormones show strong circadian secretion rhythms affecting downstream physiological processes. At the same time, they have been shown to affect clock gene expression in various other tissues, thus mediating systemic entrainment to external zeitgebers and promoting internal circadian alignment. In this review, we discuss the function of circadian clocks in the adrenal gland, how they are reset by the SCN and may further relay time-of-day information to other tissues. Focusing on glucocorticoids, we conclude by outlining the impact of adrenal rhythm disruption on neuropsychiatric, metabolic, immune, and malignant disorders.

Changing glucocorticoid action: 11β-hydroxysteroid dehydrogenase type 1 in acute and chronic inflammation

Since the discovery of cortisone in the 1940s and its early success in treatment of rheumatoid arthritis, glucocorticoids have remained the mainstay of anti-inflammatory therapies. However, cortisone itself is intrinsically inert. To be effective, it requires conversion to cortisol, the active glucocorticoid, by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Despite the identification of 11β-HSD in liver in 1953 (which we now know to be 11β-HSD1), its physiological role has been little explored until recently. Over the past decade, however, it has become apparent that 11β-HSD1 plays an important role in shaping endogenous glucocorticoid action. Acute inflammation is more severe with 11β-HSD1-deficiency or inhibition, yet in some inflammatory settings such as obesity or diabetes, 11β-HSD1-deficiency/inhibition is beneficial, reducing inflammation. Current evidence suggests both beneficial and detrimental effects may result from 11β-HSD1 inhibition in chronic inflammatory disease. Here we review recent evidence pertaining to the role of 11β-HSD1 in inflammation. This article is part of a Special Issue entitled 'CSR 2013'.

Procyanidins target mesenteric adipose tissue in Wistar lean rats and subcutaneous adipose tissue in Zucker obese rat

Visceral and subcutaneous adipose depots have different metabolic roles that may be involved in the development of obesity-related pathologies. Procyanidins have beneficial effects on insulin resistance, and they target adipose tissue. We analyse whether procyanidins exert different effects, depending on the adipose tissue depot, and whether these effects show a relation to the amount of phenolic compound in the tissue. We studied the effects of a grape seed procyanidin extract (GSPE) treatment at the transcriptional level on genes expressed differentially between mesenteric and subcutaneous adipose tissue depots and genes previously shown to be targets of procyanidins. Procyanidins target mesenteric adipose tissue in Wistar lean rats but subcutaneous adipose tissue in Zucker obese rats. Non-modified structures also accumulated, preferentially in the same respective tissues that were responsive to GSPE. Thus, procyanidins target and accumulate differently in mesenteric and subcutaneous adipose tissue depots, depending on the metabolic condition of the animal model.

Alteration of 11β-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptor by ethanol in rat liver and mouse hepatoma cells

Alcohol is a potential risk factor of type 2 diabetes, but its underlying mechanism is unclear. To explore this issue, Wistar rats and mouse hepatoma cells (Hepa 1-6) were exposed to ethanol, 8 g·kg(-1) ·d(-1) for 3 months and 100 mM for 48 h, respectively. Glucose and insulin tolerance tests in vivo were performed, and protein levels of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and glucocorticoid receptor (GR) in liver and Hepa 1-6 cells were measured. Alterations of key enzymes of gluconeogenesis phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6 phosphatase (G6Pase), as well as glycogen synthase kinase 3a (GSK3 α ), were also examined. The results revealed that glucose levels were increased, and insulin sensitivity was impaired accompanied with liver injury in rats exposed to ethanol compared with controls. The 11β-HSD1, GR, PEPCK, G6Pase, and GSK3 α proteins were increased in the liver of rats treated with ethanol compared with controls. Ethanol-exposed Hepa 1-6 cells also showed higher expression of 11β-HSD1, GR, PEPCK, G6Pase, and GSK3 α proteins than control cells. After treatment of Hepa 1-6 cells exposed to ethanol with the GR inhibitor RU486, the expression of 11β-HSD1 and GR was significantly decreased. At the same time the increases in PEPCK, G6Pase, and GSK3 α levels induced by ethanol in Hepa 1-6 cells were also attenuated by RU486. The results indicate that ethanol causes glucose intolerance by increasing hepatic expression of 11β-HSD1 and GR, which leads to increased expression of gluconeogenic and glycogenolytic enzymes.

Stress and Its Effects on Glucose Metabolism and 11β-HSD Activities in Rats Fed on a Combination of High-Fat and High-Sucrose Diet with Glycyrrhizic Acid

Chronic stress has been shown to have a strong link towards metabolic syndrome (MetS). Glycyrrhizic acid (GA) meanwhile has been shown to improve MetS symptoms caused by an unhealthy diet by inhibiting 11 β -HSD 1. This experiment aimed to determine the effects of continuous, moderate-intensity stress on rats with and without GA intake on systolic blood pressure (SBP) across a 28-day period, as well as glucose metabolism, and 11 β -HSD 1 and 2 activities at the end of the 28-day period. Adaptation to the stressor (as shown by SBP) resulted in no significant defects in glucose metabolism by the end of the experimental duration. However, a weakly significant increase in renal 11 β -HSD 1 and a significant increase in subcutaneous adipose tissue 11 β -HSD 1 activities were observed. GA intake did not elicit any significant benefit in glucose metabolism, indicating that the stress response may block its effects. However, GA-induced improvements in 11 β -HSD activities in certain tissues were observed, although it is uncertain if these effects are manifested after adaptation due to the withdrawal of the stress response. Hence the ability of GA to improve stress-induced disturbances in the absence of adaptation needs to be investigated further.

The effects of dietary fatty acid composition in the post-sucking period on metabolic alterations in adulthood: can ω3 polyunsaturated fatty acids prevent adverse programming outcomes?

Early life nutrition is important in the regulation of metabolism in adulthood. We studied the effects of different fatty acid composition diets on adiposity measures, glucose tolerance, and peripheral glucocorticoid (GC) metabolism in overfed neonatal rats. Rat litters were adjusted to a litter size of three (small litters (SLs)) or ten (normal litters (NLs)) on postnatal day 3 to induce overfeeding or normal feeding respectively. After weaning, SL and NL rats were fed a ω6 polyunsaturated fatty acid (PUFA) diet (14% calories as fat, soybean oil) or high-saturated fatty acid (high-fat; 31% calories as fat, lard) diet until postnatal week 16 respectively. SL rats were also divided into the third group fed a ω3 PUFA diet (14% calories as fat, fish oil). A high-fat diet induced earlier and/or more pronounced weight gain, hyperphagia, glucose intolerance, and hyperlipidemia in SL rats compared with NL rats. In addition, a high-fat diet increased 11β-hsd1 (Hsd11b1) mRNA expression and activity in the retroperitoneal adipose tissue of both litter groups compared with standard chow counterparts, whereas high-fat feeding increased hepatic 11β-hsd1 mRNA expression and activity only in SL rats. SL and a high-fat diet exhibited significant interactions in both retroperitoneal adipose tissue and hepatic 11β-HSD1 activity. Dietary ω3 PUFA offered protection against glucose intolerance and elevated GC exposure in the retroperitoneal adipose tissue and liver of SL rats. Taken together, the results suggest that dietary fatty acid composition in the post-sucking period may interact with neonatal feeding and codetermine metabolic alterations in adulthood.

Neonatal overfeeding induced by small litter rearing causes altered glucocorticoid metabolism in rats

Elevated glucocorticoid (GC) activity may be involved in the development of the metabolic syndrome. Tissue GC exposure is determined by the tissue-specific GC-activating enzyme 11β-hydroxysteriod dehydrogenase type 1 (11β-HSD1) and the GC-inactivating enzyme 5α-reductase type 1 (5αR1), as well as 5β-reductase (5βR). Our aim was to study the effects of neonatal overfeeding induced by small litter rearing on the expression of GC-regulating enzymes in adipose tissue and/or liver and on obesity-related metabolic disturbances during development. Male Sprague-Dawley rat pup litters were adjusted to litter sizes of three (small litters, SL) or ten (normal litters, NL) on postnatal day 3 and then given standard chow from postnatal week 3 onward (W3). Small litter rearing induced obesity, hyperinsulinemia, and higher circulating corticosterone in adults. 11β-HSD1 expression and enzyme activity in retroperitoneal, but not in epididymal, adipose tissue increased with postnatal time and peaked at W5/W6 in both groups before declining. From W8, 11β-HSD1 expression and enzyme activity levels in retroperitoneal fat persisted at significantly higher levels in SL compared to NL rats. Hepatic 11β-HSD1 enzyme activity in SL rats was elevated from W3 to W16 compared to NL rats. Hepatic 5αR1 and 5βR expression was higher in SL compared to NL rats after weaning until W6, whereupon expression decreased in the SL rats and remained similar to that in NL rats. In conclusion, small litter rearing in rats induced peripheral tissue-specific alterations in 11β-HSD1 expression and activity and 5αR1 and 5βR expression during puberty, which could contribute to elevated tissue-specific GC exposure and aggravate the development of metabolic dysregulation in adults.

Metabolic gene expression changes in the hippocampus of obese epileptic male rats in the pilocarpine model of temporal lobe epilepsy

Chronically epileptic male adult rats in the pilocarpine model of temporal lobe epilepsy (TLE), exhibited gross expansion of abdominal fat mass and significant weight gain several months after induction of status epilepticus (SE) when compared to control rats. We hypothesized that epileptogenesis can induce molecular changes in the hippocampus that may be associated with metabolism. We determined the expression levels of genes Hsd11b1, Nr3c1, Abcc8, Kcnj11, Mc4r, Npy, Lepr, Bdnf, and Drd2 that are involved in regulation of energy metabolism, in the hippocampus of age-matched control and chronic epileptic animals. Taqman-based quantitative real time polymerase chain reaction (qPCR) and the delta-delta cycle threshold (CT) methods were used for the gene expression assays. Gene expression of Hsd11b1 (cortisol generating enzyme) was significantly higher in epileptic versus control rats at 24h and 2 months, after induction of SE. Nr3c1 (glucocorticoid receptor) mRNA levels on the other hand were down-regulated at 24h, 10 days and 2 months, post SE. Abcc8 (Sur1; subunit of ATP-sensitive potassium (K(ATP)) channel) was significantly down-regulated at 10 days post SE. Kcnj11 (Kir6.2; subunit of ATP-sensitive potassium (K(ATP)) channel) was significantly up-regulated at 24h, 1 month and 2 months post SE. Thus, we demonstrated development of obesity and changes in the expression of metabolic genes in the hippocampus during epileptogenesis in male rats in the pilocarpine model of TLE.

11β-hydroxysteroid dehydrogenases and the brain: from zero to hero, a decade of progress

Glucocorticoids have profound effects on brain development and adult CNS function. Excess or insufficient glucocorticoids cause myriad abnormalities from development to ageing. The actions of glucocorticoids within cells are determined not only by blood steroid levels and target cell receptor density, but also by intracellular metabolism by 11β-hydroxysteroid dehydrogenases (11β-HSD). 11β-HSD1 regenerates active glucocorticoids from their inactive 11-keto derivatives and is widely expressed throughout the adult CNS. Elevated hippocampal and neocortical 11β-HSD1 is observed with ageing and causes cognitive decline; its deficiency prevents the emergence of cognitive defects with age. Conversely, 11β-HSD2 is a dehydrogenase, inactivating glucocorticoids. The major central effects of 11β-HSD2 occur in development, as expression of 11β-HSD2 is high in fetal brain and placenta. Deficient feto-placental 11β-HSD2 results in a life-long phenotype of anxiety and cardiometabolic disorders, consistent with early life glucocorticoid programming.

Microglia express functional 11 beta-hydroxysteroid dehydrogenase type 1

Glucocorticoids are potent regulators of inflammation exerting permissive, stimulatory, and suppressive effects. Glucocorticoid access to intracellular receptors is regulated by the activity of two distinct enzymes known as 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) Type 1 and Type 2, which catalyze the activation or deactivation of glucocorticoids. Although expression of these enzymes in major organ systems and their roles in the metabolic effects of glucocorticoids have been described, their role in the inflammatory response has only recently started to be addressed. In this report, we have studied the expression and activity of 11 beta HSD Type 1 and Type 2 in microglia cells. Microglia, the brain's resident macrophages, initiate and orchestrate CNS inflammatory responses. Importantly, activated microglia are implicated in most neurodegenerative conditions, making them key subjects of study. We found that microglia expressed 11 beta HSD-1, but not 11 beta HSD-2, both in ex vivo FACS-sorted adult cells and in vitro primary cultures. 11 beta HSD-1 expression was increased in LPS-activated microglia. Moreover, 11 beta HSD-1 catalyzed the metabolic conversion of 11-dehydro-corticosterone into corticosterone (CORT), which potently reduced cytokine production in activated microglia. We propose that 11 beta HSD-1 may provide microglia with an intrinsic mechanism to autoregulate and inhibit proinflammatory mediator production through CORT formation.

Testosterone stimulates adipose tissue 11beta-hydroxysteroid dehydrogenase type 1 expression in a depot-specific manner in children

CONTEXT

Activation of the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in adipose tissue results in the production of excess tissue glucocorticoids and the induction of adiposity and visceral obesity in particular. Androgens may affect body fat distribution by regulating the local metabolism of cortisol.

OBJECTIVE

Our objective was to study 11beta-HSD1 mRNA expression in abdominal sc and omental (om) adipose tissue in children after in vitro testosterone and cortisol treatment.

SUBJECTS AND METHODS

Paired fat biopsies (sc and om) were obtained from 19 boys (age 6-14 yr, body mass index 14.6-25.3 kg/m(2), BMI sd score SDS -1.6-3.1) undergoing open abdominal surgery. Pieces of adipose tissue were incubated with testosterone, cortisol, or both hormones for 24 h, whereupon mRNA expression of 11beta-HSD1 and hexose-6-phosphate dehydrogenase (H6PDH) were measured by real-time PCR, and 11beta-HSD1 enzyme activity was determined.

RESULTS

Testosterone treatment up-regulated 11beta-HSD1 mRNA expression compared with control incubations in the absence of testosterone (P < 0.05) in om adipose tissue. Testosterone and cortisol both increased 11beta-HSD1 mRNA expression in om but not sc adipose tissue in a depot-specific manner by 2.5- and 2.9-fold, respectively (P < 0.001). However, there was no synergistic effect of the two hormones. 11beta-HSD1 enzyme activity correlated positively to mRNA expression (r = 0.610; P = 0.001). Adipose tissue mRNA expression of H6PDH was affected in a similar fashion to 11beta-HSD1 after hormonal treatment.

CONCLUSIONS

Testosterone and cortisol stimulated 11beta-HSD1 and H6PDH mRNA expression and 11beta-HSD1 activity in om but not in sc adipose tissue. This suggests that these hormones may contribute to fat distribution and accumulation during childhood.

11beta-Hydroxysteroid dehydrogenase type 1 is an important regulator at the interface of obesity and inflammation

Systemic glucocorticoid excess, as exemplified by the Cushing syndrome, leads to obesity and all further symptoms of the metabolic syndrome. The current obesity epidemic, however, is not characterized by increased plasma cortisol concentrations, but instead comes along with chronic low-grade inflammation in adipose tissue and concomitant increased levels of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1, gene HSD11B1), a parameter known to cause obesity in a mouse model. 11beta-HSD1 represents an intracellular amplifier of active glucocorticoid, thus enhances the associated effects on the inflammatory response as well as on nutrient and energy metabolism, and may therefore cause and exacerbate obesity by local increase of glucocorticoid concentrations. Obtained by extensive literature and database searching, the present review includes comprehensive lists of primary glucocorticoid-sensitive genes and gene products as well as of the thus far known regulators of HSD11B1 expression with implication in inflammation and metabolic disease. Collectively, the data clearly show that, in addition to amplifying active glucocorticoid and thus profoundly modulating inflammation and nutrient metabolism, 11beta-HSD1 is subject to tight control of multiple additional immunomodulatory and metabolic regulators. Hence, 11beta-HSD1 acts at the interface of inflammation and obesity and represents an efficient integrator and effector of local inflammatory and metabolic state.

Estrogen reduces 11beta-hydroxysteroid dehydrogenase type 1 in liver and visceral, but not subcutaneous, adipose tissue in rats

Following menopause, body fat is redistributed from peripheral to central depots. This may be linked to the age related decrease in estrogen levels. We hypothesized that estrogen supplementation could counteract this fat redistribution through tissue-specific modulation of glucocorticoid exposure. We measured fat depot masses and the expression and activity of the glucocorticoid-activating enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) in fat and liver of ovariectomized female rats treated with or without 17beta-estradiol. 11betaHSD1 converts inert cortisone, or 11-dehydrocorticosterone in rats into active cortisol and corticosterone. Estradiol-treated rats gained less weight and had significantly lower visceral adipose tissue weight than nontreated rats (P < 0.01); subcutaneous adipose weight was unaltered. In addition, 11betaHSD1 activity/expression was downregulated in liver and visceral, but not subcutaneous, fat of estradiol-treated rats (P < 0.001 for both). This downregulation altered the balance of 11betaHSD1 expression and activity between adipose tissue depots, with higher levels in subcutaneous than visceral adipose tissue of estradiol-treated animals (P < 0.05 for both), opposite the pattern in ovariectomized rats not treated with estradiol (P < 0.001 for mRNA expression). Thus, estrogen modulates fat distribution, at least in part, through effects on tissue-specific glucocorticoid metabolism, suggesting that estrogen replacement therapy could influence obesity related morbidity in postmenopausal women.

Time of the day for 11beta-HSD1 inhibition plays a role in improving glucose homeostasis in DIO mice

AIMS

The physiological effects of glucocorticoids in a given tissue are driven by the local level of the active glucocorticoid, which is determined by two sources: the plasma cortisol in human (or corticosterone in rodents) and the cortisol produced locally through 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) activity. Because of the circadian variation of plasma glucocorticoids, the pharmacological efficacy of 11beta-HSD1 inhibition may depend on the time of the day for inhibitor administration.

METHODS

The circadian profile of corticosterone was established in lean and diet-induced obesity (DIO) C57BL/6 mice from blood collected at different time of the day. 11beta-HSD1 enzyme activity was also measured throughout the day in DIO mice. To determine the optimal timing for administration of an 11beta-HSD1 inhibitor to obtain maximum efficacy, we used a DIO mouse model and a small molecule inhibitor of 11beta-HSD1 from our thiazolinone series. Based on the circadian profile of corticosterone obtained, we administered the 11beta-HSD1 inhibitor to these animals at different times of the day and evaluated the effects on plasma glucose levels and glucose tolerance.

RESULTS

We report that corticosterone circadian rhythm was similar between lean and DIO C57BL/6 mice, and 11beta-HSD1 enzyme activity undergoes minimal variations throughout the day. Interestingly, the compound exhibited maximum efficacy if dosed in the afternoon when plasma corticosterone is high; the morning dosing when plasma corticosterone is low did not lead to efficacy.

CONCLUSION

These data suggest that because of the circadian rhythm of circulating glucocorticoids, the time of the day for 11beta-HSD1 inhibitor administration is important in achieving efficacy.

Glucocorticoids and the circadian clock

Glucocorticoids, hormones produced by the adrenal gland cortex, perform numerous functions in body homeostasis and the response of the organism to external stressors. One striking feature of their regulation is a diurnal release pattern, with peak levels linked to the start of the activity phase. This release is under control of the circadian clock, an endogenous biological timekeeper that acts to prepare the organism for daily changes in its environment. Circadian control of glucocorticoid production and secretion involves a central pacemaker in the hypothalamus, the suprachiasmatic nucleus, as well as a circadian clock in the adrenal gland itself. Central circadian regulation is mediated via the hypothalamic-pituitary-adrenal axis and the autonomic nervous system, while the adrenal gland clock appears to control sensitivity of the gland to the adrenocorticopic hormone (ACTH). The rhythmically released glucocorticoids in turn might contribute to synchronisation of the cell-autonomous clocks in the body and interact with them to time physiological dynamics in their target tissues around the day.