11ß-Hydroxysteroid dehydrogenase type 1 within muscle protects against the adverse effects of local inflammation.

Muscle wasting is a common feature of inflammatory myopathies. Glucocorticoids (GCs), although effective at suppressing inflammation and inflammatory muscle loss, also cause myopathy with prolonged administration. 11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1) is a bidirectional GC-activating enzyme that is potently upregulated by inflammation within mesenchymal-derived tissues. We assessed the regulation of this enzyme with inflammation in muscle, and examined its functional impact on muscle. The expression of 11ß-HSD1 in response to proinflammatory stimuli was determined in a transgenic murine model of chronic inflammation (TNF-Tg) driven by overexpression of tumour necrosis factor (TNF)-α within tissues, including muscle. The inflammatory regulation and functional consequences of 11ß-HSD1 expression were examined in primary cultures of human and murine myotubes and human and murine muscle biopsies ex vivo. The contributions of 11ß-HSD1 to muscle inflammation and wasting were assessed in vivo with the TNF-Tg mouse on an 11ß-HSD1 null background. 11ß-HSD1 was significantly upregulated within the tibialis anterior and quadriceps muscles from TNF-Tg mice. In human and murine primary myotubes, 11ß-HSD1 expression and activity were significantly increased in response to the proinflammatory cytokine TNF-α (mRNA, 7.6-fold, p < 0.005; activity, 4.1-fold, p < 0.005). Physiologically relevant levels of endogenous GCs activated by 11ß-HSD1 suppressed proinflammatory cytokine output (interkeukin-6, TNF-α, and interferon-γ), but had little impact on markers of muscle wasting in human myotube cultures. TNF-Tg mice on an 11ß-11ß-HSD1 knockout background developed greater muscle wasting than their TNF-Tg counterparts (27.4% less; p < 0.005), with smaller compacted muscle fibres and increased proinflammatory gene expression relative to TNF-Tg mice with normal 11ß-HSD1 activity. This study demonstrates that inflammatory stimuli upregulate 11ß-HSD1 expression and GC activation within muscle. Although concerns have been raised that excess levels of GCs may be detrimental to muscle, in this inflammatory TNF-α-driven model, local endogenous GC activation appears to be an important anti-inflammatory response that protects against inflammatory muscle wasting in vivo. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

11ß-HSD1 is the major regulator of the tissue-specific effects of circulating glucocorticoid excess.

The adverse metabolic effects of prescribed and endogenous glucocorticoid (GC) excess, Cushing syndrome, create a significant health burden. We found that tissue regeneration of GCs by 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1), rather than circulating delivery, is critical to developing the phenotype of GC excess; 11ß-HSD1 KO mice with circulating GC excess are protected from the glucose intolerance, hyperinsulinemia, hepatic steatosis, adiposity, hypertension, myopathy, and dermal atrophy of Cushing syndrome. Whereas liver-specific 11ß-HSD1 KO mice developed a full Cushingoid phenotype, adipose-specific 11ß-HSD1 KO mice were protected from hepatic steatosis and circulating fatty acid excess. These data challenge our current view of GC action, demonstrating 11ß-HSD1, particularly in adipose tissue, is key to the development of the adverse metabolic profile associated with circulating GC excess, offering 11ß-HSD1 inhibition as a previously unidentified approach to treat Cushing syndrome.

Impaired oxidoreduction by 11ß-hydroxysteroid dehydrogenase 1 results in the accumulation of 7-oxolithocholic acid.

11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) mediates glucocorticoid activation and is currently considered as therapeutic target to treat metabolic diseases; however, biomarkers to assess its activity in vivo are still lacking. Recent in vitro experiments suggested that human 11ß-HSD1 metabolizes the secondary bile acid 7-oxolithocholic acid (7-oxoLCA) to chenodeoxycholic acid (CDCA) and minor amounts of ursodeoxycholic acid (UDCA). Here, we provide evidence from in vitro and in vivo studies for a major role of 11ß-HSD1 in the oxidoreduction of 7-oxoLCA and compare its level and metabolism in several species. Hepatic microsomes from liver-specific 11ß-HSD1-deficient mice were devoid of 7-oxoLCA oxidoreductase activity. Importantly, circulating and intrahepatic levels of 7-oxoLCA and its taurine conjugate were significantly elevated in mouse models of 11ß-HSD1 deficiency. Moreover, comparative enzymology of 11ß-HSD1-dependent oxidoreduction of 7-oxoLCA revealed that the guinea-pig enzyme is devoid of 7-oxoLCA oxidoreductase activity. Unlike in other species, 7-oxoLCA and its glycine conjugate are major bile acids in guinea-pigs. In conclusion, the oxidoreduction of 7-oxoLCA and its conjugated metabolites are catalyzed by 11ß-HSD1, and the lack of this activity leads to the accumulation of these bile acids in guinea-pigs and 11ß-HSD1-deficient mice. Thus, 7-oxoLCA and its conjugates may serve as biomarkers of impaired 11ß-HSD1 activity.

Inflammatory regulation of glucocorticoid metabolism in mesenchymal stromal cells.

OBJECTIVE: Tissue glucocorticoid (GC) levels are regulated by the GC-activating enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1). This enzyme is expressed in cells and tissues arising from mesenchymal stromal cells. Proinflammatory cytokines dramatically increase expression of 11ß-HSD1 in stromal cells, an effect that has been implicated in inflammatory arthritis, osteoporosis, obesity, and myopathy. Additionally, GCs act synergistically with proinflammatory cytokines to further increase enzyme expression. The present study was undertaken to investigate the mechanisms underlying this regulation. METHODS: Gene reporter analysis, rapid amplification of complementary DNA ends (RACE), chemical inhibition experiments, and genetic disruption of intracellular signaling pathways in mouse embryonic fibroblasts (MEFs) were used to define the molecular mechanisms underlying the regulation of 11ß-HSD1 expression. RESULTS: Gene reporter, RACE, and chemical inhibitor studies demonstrated that the increase in 11ß-HSD1 expression with tumor necrosis factor α (TNFα)/interleukin-1ß (IL-1ß) occurred via the proximal HSD11B1 gene promoter and depended on NF-κB signaling. These findings were confirmed using MEFs with targeted disruption of NF-κB signaling, in which RelA (p65) deletion prevented TNFα/IL-1ß induction of 11ß-HSD1. GC treatment did not prevent TNFα-induced NF-κB nuclear translocation. The synergistic enhancement of TNFα-induced 11ß-HSD1 expression with GCs was reproduced by specific inhibitors of p38 MAPK. Inhibitor and gene deletion studies indicated that the effects of GCs on p38 MAPK activity occurred primarily through induction of dual-specificity phosphatase 1 expression. CONCLUSION: The mechanism by which stromal cell expression of 11ß-HSD1 is regulated is novel and distinct from that in other tissues. These findings open new opportunities for development of therapeutic interventions aimed at inhibiting or stimulating local GC levels in cells of mesenchymal stromal lineage during inflammation.

11ß-HSD1 contributes to age-related metabolic decline in male mice.

The aged phenotype shares several metabolic similarities with that of circulatory glucocorticoid excess (Cushing's syndrome), including type 2 diabetes, obesity, hypertension, and myopathy. We hypothesise that local tissue generation of glucocorticoids by 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1), which converts 11-dehydrocorticosterone to active corticosterone in rodents (corticosterone to cortisol in man), plays a role in driving age-related chronic disease. In this study, we have examined the impact of ageing on glucocorticoid metabolism, insulin tolerance, adiposity, muscle strength, and blood pressure in both wildtype (WT) and transgenic male mice with a global deletion of 11ß-HSD1 (11ß-HSD1-/-) following 4 months high-fat feeding. We found that high fat-fed 11ß-HSD1-/- mice were protected from age-related glucose intolerance and hyperinsulinemia when compared to age/diet-matched WTs. By contrast, aged 11ß-HSD1-/- mice were not protected from the onset of sarcopenia observed in the aged WTs. Young 11ß-HSD1-/- mice were partially protected from diet-induced obesity; however, this partial protection was lost with age. Despite greater overall obesity, the aged 11ß-HSD1-/- animals stored fat in more metabolically safer adipose depots as compared to the aged WTs. Serum analysis revealed both WT and 11ß-HSD1-/- mice had an age-related increase in morning corticosterone. Surprisingly, 11ß-HSD1 oxo-reductase activity in the liver and skeletal muscle was unchanged with age in WT mice and decreased in gonadal adipose tissue. These data suggest that deletion of 11ß-HSD1 in high fat-fed, but not chow-fed, male mice protects from age-related insulin resistance and supports a metabolically favourable fat distribution.

Regulation of 11ß-HSD1 by GH/IGF-1 in key metabolic tissues may contribute to metabolic disease in GH deficient patients.

Patients with growth hormone deficiency (GHD) have many clinical features in common with Cushing's syndrome (glucocorticoid excess) - notably visceral obesity, insulin resistance, muscle myopathy and increased vascular mortality. Within key metabolic tissues, 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) converts cortisone to the active glucocorticoid, cortisol (11-dehydrocorticosterone and corticosterone in rodents respectively), and thus amplifies local glucocorticoid action. We hypothesize that 11ß-HSD1 expression is negatively regulated by growth hormone (GH), and that GHD patients have elevated 11ß-HSD1 within key metabolic tissues (leading to increased intracellular cortisol generation) which contributes to the clinical features of this disease. To identify the impact of GH excess/resistance on 11ß-HSD1 in vivo, we measured mRNA expression in key metabolic tissues of giant mice expressing the bovine GH (bGH) gene, dwarf mice with a disrupted GH receptor (GHRKO) gene and mice expressing a gene encoding a GH receptor antagonist (GHA). Additionally, we assessed urine steroid markers of 11ß-HSD1 activity in both GHRKO and bGH animals. 11ß-HSD1 expression was decreased in gastrocnemius muscle (0.43-fold, p < 0.05), subcutaneous adipose (0.53-fold, p < 0.05) and epididymal adipose tissue (0.40-fold, p < 0.05), but not liver, in bGH mice compared to WT controls. This was paralleled by an increased percentage of 11-DHC (inactive glucocorticoid) present in the urine of bGH mice compared to WT controls (2.5-fold, p < 0.01) - consistent with decreased systemic 11ß-HSD1 activity. By contrast, expression of 11ß-HSD1 was increased in the liver of GHRKO (2.7-fold, p < 0.05) and GHA mice (2.0-fold, p < 0.05) compared to WT controls, but not gastrocnemius muscle, subcutaneous adipose tissue or epididymal adipose tissue. In summary, we have demonstrated a negative relationship between GH action and 11ß-HSD1 expression which appears to be tissue specific. These data provide evidence that increased intracellular cortisol production within key tissues may contribute to metabolic disease in GHD patients.

11ß-HSD1 Modulates the Set Point of Brown Adipose Tissue Response to Glucocorticoids in Male Mice.

Glucocorticoids (GCs) are potent regulators of energy metabolism. Chronic GC exposure suppresses brown adipose tissue (BAT) thermogenic capacity in mice, with evidence for a similar effect in humans. Intracellular GC levels are regulated by 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) activity, which can amplify circulating GC concentrations. Therefore, 11ß-HSD1 could modulate the impact of GCs on BAT function. This study investigated how 11ß-HSD1 regulates the molecular architecture of BAT in the context of GC excess and aging. Circulating GC excess was induced in 11ß-HSD1 knockout (KO) and wild-type mice by supplementing drinking water with 100 µg/mL corticosterone, and the effects on molecular markers of BAT function and mitochondrial activity were assessed. Brown adipocyte primary cultures were used to examine cell autonomous consequences of 11ß-HSD1 deficiency. Molecular markers of BAT function were also examined in aged 11ß-HSD1 KO mice to model lifetime GC exposure. BAT 11ß-HSD1 expression and activity were elevated in response to GC excess and with aging. 11ß-HSD1 KO BAT resisted the suppression of uncoupling protein 1 (UCP1) and mitochondrial respiratory chain subunit proteins normally imposed by GC excess. Furthermore, brown adipocytes from 11ß-HSD1 KO mice had elevated basal mitochondrial function and were able to resist GC-mediated repression of activity. BAT from aged 11ß-HSD1 KO mice showed elevated UCP1 protein and mitochondrial content, and a favorable profile of BAT function. These data reveal a novel mechanism in which increased 11ß-HSD1 expression, in the context of GC excess and aging, impairs the molecular and metabolic function of BAT.

25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 exert distinct effects on human skeletal muscle function and gene expression.

Age-associated decline in muscle function represents a significant public health burden. Vitamin D-deficiency is also prevalent in aging subjects, and has been linked to loss of muscle mass and strength (sarcopenia), but the precise role of specific vitamin D metabolites in determining muscle phenotype and function is still unclear. To address this we quantified serum concentrations of multiple vitamin D metabolites, and assessed the impact of these metabolites on body composition/muscle function parameters, and muscle biopsy gene expression in a retrospective study of a cohort of healthy volunteers. Active serum 1,25-dihydroxyvitamin D3 (1α,25(OH)2D3), but not inactive 25-hydroxyvitamin D3 (25OHD3), correlated positively with measures of lower limb strength including power (rho = 0.42, p = 0.02), velocity (Vmax, rho = 0.40, p = 0.02) and jump height (rho = 0.36, p = 0.04). Lean mass correlated positively with 1α,25(OH)2D3 (rho = 0.47, p = 0.02), in women. Serum 25OHD3 and inactive 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) had an inverse relationship with body fat (rho = -0.30, p = 0.02 and rho = -0.33, p = 0.01, respectively). Serum 25OHD3 and 24,25(OH)2D3 were also correlated with urinary steroid metabolites, suggesting a link with glucocorticoid metabolism. PCR array analysis of 92 muscle genes identified vitamin D receptor (VDR) mRNA in all muscle biopsies, with this expression being negatively correlated with serum 25OHD3, and Vmax, and positively correlated with fat mass. Of the other 91 muscle genes analysed by PCR array, 24 were positively correlated with 25OHD3, but only 4 were correlated with active 1α,25(OH)2D3. These data show that although 25OHD3 has potent actions on muscle gene expression, the circulating concentrations of this metabolite are more closely linked to body fat mass, suggesting that 25OHD3 can influence muscle function via indirect effects on adipose tissue. By contrast, serum 1α,25(OH)2D3 has limited effects on muscle gene expression, but is associated with increased muscle strength and lean mass in women. These pleiotropic effects of the vitamin D 'metabolome' on muscle function indicate that future supplementation studies should not be restricted to conventional analysis of the major circulating form of vitamin D, 25OHD3.

The CRH-Transgenic Cushingoid Mouse Is a Model of Glucocorticoid-Induced Osteoporosis.

Glucocorticoids (GCs) have unparalleled anti-inflammatory and immunosuppressive properties, which accounts for their widespread prescription and use. Unfortunately, a limitation to GC therapy is a wide range of negative side effects including Cushing's syndrome, a disease characterized by metabolic abnormalities including muscle wasting and osteoporosis. GC-induced osteoporosis occurs in 30% to 50% of patients on GC therapy and thus, represents an important area of study. Herein, we characterize the molecular and physiologic effects of GC-induced osteoporosis using the Cushing's mouse model, the corticotropin releasing hormone (CRH) transgenic mouse (CRH-Tg). The humeri, femurs, and tibias from wild-type (WT) and CRH-Tg male mice, aged 13 to 14 weeks old were subjected to multiple bone tests including, micro-computed tomography (µCT), static and dynamic histomorphometry, strength testing, and gene expression analyses. The CRH-Tg mice had a 38% decrease in cortical bone area, a 35% decrease in cortical thickness, a 16% decrease in trabecular thickness, a sixfold increase in bone adiposity, a 27% reduction in osteoid width, a 75% increase in bone-resorbing osteoclast number/bone surface, a 34% decrease in bone formation rate, and a 40% decrease in bone strength compared to WT mice. At the gene expression level, CRH-Tg bone showed significantly increased osteoclast markers and decreased osteoblast markers, whereas CRH-Tg muscle had increased muscle atrophy gene markers compared to WT mice. Overall, the CRH-Tg mouse model aged to 14 weeks recapitulated many features of osteoporosis in Cushing's syndrome and thus, represents a useful model to study GC-induced osteoporosis and interventions that target the effects of GCs on the skeleton. © 2017 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

MECHANISMS IN ENDOCRINOLOGY: Tissue-specific activation of cortisol in Cushing's syndrome.

Glucocorticoids are widely prescribed for their anti-inflammatory properties, but have 'Cushingoid' side effects including visceral obesity, muscle myopathy, hypertension, insulin resistance, type 2 diabetes mellitus, osteoporosis, and hepatic steatosis. These features are replicated in patients with much rarer endogenous glucocorticoid (GC) excess (Cushing's syndrome), which has devastating consequences if left untreated. Current medical therapeutic options that reverse the tissue-specific consequences of hypercortisolism are limited. In this article, we review the current evidence that local GC metabolism via the enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) plays a central role in mediating the adverse metabolic complications associated with circulatory GC excess - challenging our current view that simple delivery of active GCs from the circulation represents the most important mode of GC action. Furthermore, we explore the potential for targeting this enzyme as a novel therapeutic strategy for the treatment of both endogenous and exogenous Cushing's syndrome.

Male 11ß-HSD1 Knockout Mice Fed Trans-Fats and Fructose Are Not Protected From Metabolic Syndrome or Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) defines a spectrum of conditions from simple steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis and is regarded as the hepatic manifestation of the metabolic syndrome. Glucocorticoids can promote steatosis by stimulating lipolysis within adipose tissue, free fatty acid delivery to liver and hepatic de novo lipogenesis. Glucocorticoids can be reactivated in liver through 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) enzyme activity. Inhibition of 11ß-HSD1 has been suggested as a potential treatment for NAFLD. To test this, male mice with global (11ß-HSD1 knockout [KO]) and liver-specific (LKO) 11ß-HSD1 loss of function were fed the American Lifestyle Induced Obesity Syndrome (ALIOS) diet, known to recapitulate the spectrum of NAFLD, and metabolic and liver phenotypes assessed. Body weight, muscle and adipose tissue masses, and parameters of glucose homeostasis showed that 11ß-HSD1KO and LKO mice were not protected from systemic metabolic disease. Evaluation of hepatic histology, triglyceride content, and blinded NAFLD activity score assessment indicated that levels of steatosis were similar between 11ß-HSD1KO, LKO, and control mice. Unexpectedly, histological analysis revealed significantly increased levels of immune foci present in livers of 11ß-HSD1KO but not LKO or control mice, suggestive of a transition to NASH. This was endorsed by elevated hepatic expression of key immune cell and inflammatory markers. These data indicate that 11ß-HSD1-deficient mice are not protected from metabolic disease or hepatosteatosis in the face of a NAFLD-inducing diet. However, global deficiency of 11ß-HSD1 did increase markers of hepatic inflammation and suggests a critical role for 11ß-HSD1 in restraining the transition to NASH.

Glucocorticoids and 11ß-HSD1 are major regulators of intramyocellular protein metabolism.

The adverse metabolic effects of prescribed and endogenous glucocorticoid excess, 'Cushing's syndrome', create a significant health burden. While skeletal muscle atrophy and resultant myopathy is a clinical feature, the molecular mechanisms underpinning these changes are not fully defined. We have characterized the impact of glucocorticoids upon key metabolic pathways and processes regulating muscle size and mass including: protein synthesis, protein degradation, and myoblast proliferation in both murine C2C12 and human primary myotube cultures. Furthermore, we have investigated the role of pre-receptor modulation of glucocorticoid availability by 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) in these processes. Corticosterone (CORT) decreased myotube area, decreased protein synthesis, and increased protein degradation in murine myotubes. This was supported by decreased mRNA expression of insulin-like growth factor (IGF1), decreased activating phosphorylation of mammalian target of rapamycin (mTOR), decreased phosphorylation of 4E binding protein 1 (4E-BP1), and increased mRNA expression of key atrophy markers including: atrogin-1, forkhead box O3a (FOXO3a), myostatin (MSTN), and muscle-ring finger protein-1 (MuRF1). These findings were endorsed in human primary myotubes, where cortisol also decreased protein synthesis and increased protein degradation. The effects of 11-dehydrocorticosterone (11DHC) (in murine myotubes) and cortisone (in human myotubes) on protein metabolism were indistinguishable from that of CORT/cortisol treatments. Selective 11ß-HSD1 inhibition blocked the decrease in protein synthesis, increase in protein degradation, and reduction in myotube area induced by 11DHC/cortisone. Furthermore, CORT/cortisol, but not 11DHC/cortisone, decreased murine and human myoblast proliferative capacity. Glucocorticoids are potent regulators of skeletal muscle protein homeostasis and myoblast proliferation. Our data underscores the potential use of selective 11ß-HSD1 inhibitors to ameliorate muscle-wasting effects associated with glucocorticoid excess.

Gender-Specific Differences in Skeletal Muscle 11ß-HSD1 Expression Across Healthy Aging.

CONTEXT: Cushing's syndrome is characterized by marked changes in body composition (sarcopenia, obesity, and osteoporosis) that have similarities with those seen in aging. 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) converts glucocorticoids to their active form (cortisone to cortisol in humans), resulting in local tissue amplification of effect. OBJECTIVE: To evaluate 11ß-HSD1 expression and activity with age, specifically in muscle. To determine putative causes for increased activity with age and its consequences upon phenotypic markers of adverse aging. DESIGN: Cross-sectional observational study. SETTING: National Institute for Health Research-Wellcome Trust Clinical Research Facility, Birmingham, United Kingdom. PATIENTS OR OTHER PARTICIPANTS: Healthy human volunteers age 20 to 81 years (n = 134; 77 women, 57 men). INTERVENTIONS: Day attendance at research facility for baseline observations, body composition analysis by dual-energy x-ray absorptiometry, jump-plate mechanography, grip strength analysis, baseline biochemical profiling, urine collection, and vastus lateralis muscle biopsy. MAIN OUTCOME MEASURE(S): Skeletal muscle gene expression, urine steroid profile, bivariate correlations between expression/activity and phenotypic/biochemical variables. RESULTS: Skeletal muscle 11ß-HSD1 expression was increased 2.72-fold in women over 60 years of age compared to those aged 20-40 years; no differences were observed in men. There was a significant positive correlation between skeletal muscle 11ß-HSD1 expression and age in women across the group (rho = 0.40; P = .009). No differences in expression of 11ß-HSD type 2, glucocorticoid receptor, or hexose-6-phosphate dehydrogenase between age groups were observed in either sex. Urinary steroid markers of 11ß-HSD1, 11ß-HSD type 2, or 5α-reductase were similar between age groups. Skeletal muscle 11ß-HSD1 expression was associated with reduced grip strength in both sexes and correlated positively with percentage of body fat, homeostasis model of assessment for insulin resistance, total cholesterol, LH, and FSH and negatively with bone mineral content and IGF-1 in women. CONCLUSIONS: Skeletal muscle 11ß-HSD1 is up-regulated with age in women and is associated with reduced grip strength, insulin resistance, and an adverse body composition profile. Selective inhibition of 11ß-HSD1 may offer a novel strategy to prevent and/or reverse age-related sarcopenia.

11ß-Hydroxysteroid dehydrogenase-1 is involved in bile acid homeostasis by modulating fatty acid transport protein-5 in the liver of mice.

11ß-Hydroxysteroid dehydrogenase-1 (11ß-HSD1) plays a key role in glucocorticoid receptor (GR) activation. Besides, it metabolizes some oxysterols and bile acids (BAs). The GR regulates BA homeostasis; however, the impact of impaired 11ß-HSD1 activity remained unknown. We profiled plasma and liver BAs in liver-specific and global 11ß-HSD1-deficient mice. 11ß-HSD1-deficiency resulted in elevated circulating unconjugated BAs, an effect more pronounced in global than liver-specific knockout mice. Gene expression analyses revealed decreased expression of the BA-CoA ligase Fatp5, suggesting impaired BA amidation. Reduced organic anion-transporting polypeptide-1A1 (Oatp1a1) and enhanced organic solute-transporter-ß (Ostb) mRNA expression were observed in livers from global 11ß-HSD1-deficient mice. The impact of 11ß-HSD1-deficiency on BA homeostasis seems to be GR-independent because intrahepatic corticosterone and GR target gene expression were not substantially decreased in livers from global knockout mice. Moreover, Fatp5 expression in livers from hepatocyte-specific GR knockout mice was unchanged. The results revealed a role for 11ß-HSD1 in BA homeostasis.

Hormonal regulation of lipogenesis.

Obesity has reached epidemic proportions with severe heath consequences including type 2 diabetes, nonalcoholic fatty liver disease, and premature cardiovascular mortality. Understanding the biological processes that govern fat deposition in a tissue-specific manner is therefore crucial if we are to try to design novel and efficacious treatments that might limit fat accumulation and improve metabolic phenotype and clinical prognosis. Lipid accumulation within a given cell type represents a balance between synthesis, mobilization, and utilization. Common endocrine conditions characterized by hormonal excess and deficiency are often associated with profound abnormalities in body composition and fat deposition. This undoubtedly reflects the complex regulation of lipid metabolism by endocrine factors. In this review, we will outline the current literature that has investigated the hormonal regulation of lipogenesis. This is a complex field, and in many studies, its assessment has been oversimplified with a focus on individual hormones acting in isolation and this bears little relationship to the in vivo situation where multiple hormones act in concert. Further, regulation may be different between rodents and humans and this will be explored. Limitation of lipid accumulation still represents a valid therapeutic target, and it is possible that manipulation of hormonal action has the potential to offer a new therapeutic horizon.

11ß-Hydroxysteroid dehydrogenase 1: translational and therapeutic aspects.

11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1) interconverts the inactive glucocorticoid cortisone and its active form cortisol. It is widely expressed and, although bidirectional, in vivo it functions predominantly as an oxoreductase, generating active glucocorticoid. This allows glucocorticoid receptor activation to be regulated at a prereceptor level in a tissue-specific manner. In this review, we will discuss the enzymology and molecular biology of 11ß-HSD1 and the molecular basis of cortisone reductase deficiencies. We will also address how altered 11ß-HSD1 activity has been implicated in a number of disease states, and we will explore its role in the physiology and pathologies of different tissues. Finally, we will address the current status of selective 11ß-HSD1 inhibitors that are in development and being tested in phase II trials for patients with the metabolic syndrome. Although the data are preliminary, therapeutic inhibition of 11ß-HSD1 is also an exciting prospect for the treatment of a variety of other disorders such as osteoporosis, glaucoma, intracranial hypertension, and cognitive decline.

Regulation of lipid metabolism by glucocorticoids and 11ß-HSD1 in skeletal muscle.

The prevalences of insulin resistance and type 2 diabetes mellitus are rising dramatically, and, as a consequence, there is an urgent need to understand the pathogenesis underpinning these conditions to develop new and more efficacious treatments. We have tested the hypothesis that glucocorticoid (GC)-mediated changes in insulin sensitivity may be associated with changes in lipid flux. Furthermore, prereceptor modulation of GC availability by 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) may represent a critical regulatory step. Dexamethasone (DEX) decreased lipogenesis in both murine C2C12 and human LHC-NM2 myotubes. Inactivating p-Ser-79/218 of acetyl-CoA carboxylase 1/2 and activating p-Thr-172 of AMP-activated protein kinase were both increased after DEX treatment in C2C12 myotubes. In contrast, DEX increased ß-oxidation. Selective 11ß-HSD1 inhibition blocked the 11-dehydrocorticosterone (11DHC)-mediated decrease in lipogenic gene expression and increase in lipolytic gene expression. Lipogenic gene expression was decreased, whereas lipolytic and ß-oxidative gene expression increased in corticosterone (CORT)- and 11DHC-treated wild-type mice and CORT (but not 11DHC)-treated 11ß-HSD1(-/-) mice. Furthermore, CORT- and 11DHC-treated wild-type mice and CORT (but not 11DHC)-treated 11ß-HSD1(-/-) mice had increased p-Ser-79/218 acetyl-CoA carboxylase 1/2, p-Thr-172 AMP-activated protein kinase and intramyocellular diacylglyceride content. In summary, we have shown that GCs have potent actions on intramyocellular lipid homeostasis by decreasing lipid storage, increasing lipid mobilization and utilization, and increasing diacylglyceride content. It is plausible that dysregulated intramyocellular lipid metabolism may underpin GC-induced insulin resistance of skeletal muscle.

11ß-Hydroxysteroid dehydrogenase blockade prevents age-induced skin structure and function defects.

Glucocorticoid (GC) excess adversely affects skin integrity, inducing thinning and impaired wound healing. Aged skin, particularly that which has been photo-exposed, shares a similar phenotype. Previously, we demonstrated age-induced expression of the GC-activating enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) in cultured human dermal fibroblasts (HDFs). Here, we determined 11ß-HSD1 levels in human skin biopsies from young and older volunteers and examined the aged 11ß-HSD1 KO mouse skin phenotype. 11ß-HSD1 activity was elevated in aged human and mouse skin and in PE compared with donor-matched photo-protected human biopsies. Age-induced dermal atrophy with deranged collagen structural organization was prevented in 11ß-HSD1 KO mice, which also exhibited increased collagen density. We found that treatment of HDFs with physiological concentrations of cortisol inhibited rate-limiting steps in collagen biosynthesis and processing. Furthermore, topical 11ß-HSD1 inhibitor treatment accelerated healing of full-thickness mouse dorsal wounds, with improved healing also observed in aged 11ß-HSD1 KO mice. These findings suggest that elevated 11ß-HSD1 activity in aging skin leads to increased local GC generation, which may account for adverse changes occurring in the elderly, and 11ß-HSD1 inhibitors may be useful in the treatment of age-associated impairments in dermal integrity and wound healing.

Loss of 5α-reductase type 1 accelerates the development of hepatic steatosis but protects against hepatocellular carcinoma in male mice.

Nonalcoholic fatty liver disease (NAFLD) has been associated with glucocorticoid excess and androgen deficiency, yet in the majority of patients with steatohepatitis, circulating cortisol and androgen levels are normal. The enzyme 5α-reductase (5αR) has a critical role in androgen and glucocorticoid action. We hypothesize that 5αR has an important role in the pathogenesis of steatohepatitis through regulation of intracrine/paracrine hormone availability. Human liver samples from patients with NAFLD and normal donor tissue were used for gene expression and immunohistochemical analysis. NAFLD samples were scored using the Kleiner classification. In addition, 5αR1(-/-), 5αR2(-/-), and wild-type (WT) mice were fed normal chow or American lifestyle-induced obesity syndrome (ALIOS) diet for 6 or 12 months. Liver histology was graded and staged. Hepatic and circulating free fatty acid and triglyceride levels were quantified, and gene and protein expression was measured by real-time PCR and immunohistochemistry. 5αR1 and -2 were highly expressed in human liver, and 5αR1 protein expression increased with severity of NAFLD. 5αR1(-/-) (but not 5αR2(-/-)) mice fed an ALIOS diet developed greater hepatic steatosis than WT mice, and hepatic mRNA expression of genes involved in insulin signaling was decreased. Furthermore, 60% of WT mice developed focal hepatocellular lesions consistent with hepatocellular carcinoma after 12 months of the ALIOS diet, compared with 20% of 5αR2(-/-) and 0% of 5αR1(-/-) mice (P < .05). 5αR1 deletion accelerates the development of hepatic steatosis but may protect against the development of NAFLD-related hepatocellular neoplasia and therefore has potential as a therapeutic target.

Lack of significant metabolic abnormalities in mice with liver-specific disruption of 11ß-hydroxysteroid dehydrogenase type 1.

Glucocorticoids (GC) are implicated in the development of metabolic syndrome, and patients with GC excess share many clinical features, such as central obesity and glucose intolerance. In patients with obesity or type 2 diabetes, systemic GC concentrations seem to be invariably normal. Tissue GC concentrations determined by the hypothalamic-pituitary-adrenal (HPA) axis and local cortisol (corticosterone in mice) regeneration from cortisone (11-dehydrocorticosterone in mice) by the 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) enzyme, principally expressed in the liver. Transgenic mice have demonstrated the importance of 11ß-HSD1 in mediating aspects of the metabolic syndrome, as well as HPA axis control. In order to address the primacy of hepatic 11ß-HSD1 in regulating metabolism and the HPA axis, we have generated liver-specific 11ß-HSD1 knockout (LKO) mice, assessed biomarkers of GC metabolism, and examined responses to high-fat feeding. LKO mice were able to regenerate cortisol from cortisone to 40% of control and had no discernible difference in a urinary metabolite marker of 11ß-HSD1 activity. Although circulating corticosterone was unaltered, adrenal size was increased, indicative of chronic HPA stimulation. There was a mild improvement in glucose tolerance but with insulin sensitivity largely unaffected. Adiposity and body weight were unaffected as were aspects of hepatic lipid homeostasis, triglyceride accumulation, and serum lipids. Additionally, no changes in the expression of genes involved in glucose or lipid homeostasis were observed. Liver-specific deletion of 11ß-HSD1 reduces corticosterone regeneration and may be important for setting aspects of HPA axis tone, without impacting upon urinary steroid metabolite profile. These discordant data have significant implications for the use of these biomarkers of 11ß-HSD1 activity in clinical studies. The paucity of metabolic abnormalities in LKO points to important compensatory effects by HPA activation and to a crucial role of extrahepatic 11ß-HSD1 expression, highlighting the contribution of cross talk between GC target tissues in determining metabolic phenotype.