Depot-specific modulation of rat intraabdominal adipose tissue lipid metabolism by pharmacological inhibition of 11beta-hydroxysteroid dehydrogenase type 1

Endocrine disorders associated with obesity

Several endocrine disorders, including diabetes, insulinoma, Cushing syndrome, hypothyroidism, polycystic ovarian syndrome, and growth hormone deficiency, are associated with obesity. The mechanisms underlying the development of obesity vary according to the abnormalities of endocrine function. The primary actions of insulin, glucocorticoids (GCs), thyroid hormone, and growth hormone are associated with energy metabolism in the liver, muscle, adipose tissue, and other tissues. This chapter describes the pathogenesis of obesity and metabolic dysfunction associated with excess insulin or GCs and the deficiency of thyroid hormone or growth hormone.

Novel targets for potential therapeutic use in Diabetes mellitus

Future targets are a promising prospect to overcome the limitation of conventional and current approaches by providing secure and effective treatment without compromising patient compliance. Diabetes mellitus is a fast-growing problem that has been raised worldwide, from 4% to 6.4% (around 285 million people) in past 30 years. This number may increase to 430 million people in the coming years if there is no better treatment or cure is available. Ageing, obesity and sedentary lifestyle are the key reasons for the worsening of this disease. It always had been a vital challenge, to explore new treatment which could safely and effectively manage diabetes mellitus without compromising patient compliance. Researchers are regularly trying to find out the permanent treatment of this chronic and life threatening disease. In this journey, there are various treatments available in market to manage diabetes mellitus such as insulin, GLP-1 agonist, biguanides, sulphonyl ureas, glinides, thiazolidinediones targeting the receptors which are discovered decade before. PPAR, GIP, FFA1, melatonin are the recent targets that already in the focus for developing new therapies in the treatment of diabetes. Inspite of numerous preclinical studies very few clinical data available due to which this process is in its initial phase. The review also focuses on the receptors like GPCR 119, GPER, Vaspin, Metrnl, Fetuin-A that have role in insulin regulation and have potential to become future targets in treatment for diabetes that may be effective and safer as compared to the conventional and current treatment approaches.

Association between Selected Polymorphisms rs12086634, rs846910, rs4844880, rs3753519 of 11β-Hydroxysteroid Dehydrogenase Type 1 (HSD11B1) and the Presence of Insulin Resistance in the Polish Population of People Living in Upper Silesia

Background: Many factors influence the development of insulin resistance, among other genetic factors. Cortisol is one of the factors that has a significant impact on the development of insulin resistance. The proteins that have a substantial effect on blood cortisol levels include 11β-hydroxysteroid dehydrogenase type 1. HSD11B1 is a microsomal enzyme that catalyzes the conversion of the stress hormone cortisol to the inactive metabolite cortisone. Gene encoding HSD11B1 is located on 1q32.2. This study was designed to assess the association between four polymorphic sides in HSD11B1 (rs12086634, rs846910, rs4844880, rs3753519) between subjects with and without insulin resistance in the Polish population of people living in Upper Silesia. Methods: The study included a total of 507 consecutive patients, 374 (73.77%) with and 133 (26.23%) without insulin resistance. Results: The results show that there were no statistically significant differences in the distribution of genotypes and alleles of the examined polymorphisms of the 11β-hydroxysteroid dehydrogenase type 1 gene between subjects with and without insulin resistance (determined using the HOMA-IR, insulin resistance index) and that rs846910 and rs1208663 polymorphisms of the 11β-hydroxysteroid dehydrogenase type 1 gene in the examined subjects have a significant effect on the magnitude of the HOMA-IR insulin resistance index. Conclusions: The study results suggested that genetic variation of rs846910 and rs1208663 polymorphism of the HSD11B1 gene is related to the susceptibility to insulin resistance. Our results provide a basis to begin basic research on the role of the HSD11B1 gene in the pathogenesis of insulin resistance.

11β-hydroxysteroid dehydrogenase type 1 inhibitor use in human disease-a systematic review and narrative synthesis

INTRODUCTION

11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is an intracellular enzyme that catalyses conversion of cortisone into cortisol; correspondingly, 11β-HSD1 inhibitors inhibit this conversion. This systematic review focuses on the use of 11β-HSD1 inhibitors in diseases known to be associated with abnormalities in hypothalamic pituitary adrenal (HPA) axis function.

METHODS

The databases screened for suitable papers were: MedLine, EMBASE, Web of Science, ClinicalTrials.gov, and Cochrane Central.

RESULTS

1925 papers were identified, of which 29 were included in the final narrative synthesis. 11β-HSD1 and its inhibitors have been studied in diabetes, obesity, metabolic syndrome (MetS), and Alzheimer's disease (AD). Higher expression of 11β-HSD1 is seen in obesity and MetS, but has not yet been described in obesity or AD. Genetic studies identify 11β-HSD1 SNPs of interest in populations with diabetes, MetS, and AD. One phase II trial successfully reduced HbA1c in a diabetic population, however trials in MetS, obesity, and AD have not met primary endpoints.

CONCLUSIONS

Translation of this research from preclinical studies has proved challenging so far, however this is a growing area of research and more studies should focus on understanding the complex relationships between 11β-HSD1 and disease pathology, especially given the therapeutic potential of 11β-HSD1 inhibitors in development.

Association of HSD11B1 gene polymorphisms with type 2 diabetes and metabolic syndrome in South Indian population

BACKGROUND

11beta-hydroxysteroid dehydrogenase Type 1 (11β-HSD1) is an NADP or NADPH-dependent enzyme that generates cortisol from cortisone for a local glucocorticoid action. Functional polymorphisms within 11beta-hydroxysteroid dehydrogenase Type 1 (HSD11B1) gene have shown an association with various factors, including insulin resistance (IR) and hypertension. In our study, we have assessed the association of HSD11B1 (rs12086634 and rs846910) gene polymorphisms with type 2 diabetes (T2D) and metabolic syndrome (metS).

METHODS

In the present study, 616 subjects were enrolled. DNA from T2D subjects (n=207), metS subjects (n=101), and their age and sex matched control subjects were analyzed. Genotyping of HSD11B1 rs12086634 and rs846910 single nucleotide polymorphisms was performed using tetra-primer amplification refractory mutation system-polymerase chain reaction (T-ARMS-PCR). An odds ratio and 95% confidence interval were calculated to determine the association of HSD11B1 gene polymorphisms with T2D and metS.

RESULTS

The association analysis indicated that HSD11B1 rs12086634 TG contributed to an increased risk of both T2D (OR=1.91; 95% CI-1.33-2.76, P=0.0005) and metS (OR=2.37; 95% CI-1.39-4.05, P=0.0015), but HSD11B1 rs846910 AG contributed to an increased risk of T2D (OR=1.62; 95% CI-1.02-2.57, P=0.03) only. There was a statistically significant difference in systolic blood pressure between the control group with HSD11B1 rs12086634 TG genotype (128.96±13.19mmHg) and the control group with HSD11B1 rs12086634 TT genotype (123.27±10.84mmHg).

CONCLUSIONS

The results of our study indicated that the HSD11B1 rs12086634 is associated with both T2D and metS, but HSD11B1 rs846910 is associated with only T2D in South Indian population.

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

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

Heterogeneity of white adipose tissue: molecular basis and clinical implications

Adipose tissue is a highly heterogeneous endocrine organ. The heterogeneity among different anatomical depots stems from their intrinsic differences in cellular and physiological properties, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, insulin sensitivity, hormonal control, thermogenic ability and vascularization. Additional factors that influence adipose tissue heterogeneity are genetic predisposition, environment, gender and age. Under obese condition, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. For instance, individuals with central obesity are more susceptible to developing diabetes and cardiovascular complications, whereas those with peripheral obesity are more metabolically healthy. This review summarizes the clinical and mechanistic evidence for the depot-specific differences that give rise to different metabolic consequences, and provides therapeutic insights for targeted treatment of obesity.

Mineralocorticoid Excess or Glucocorticoid Insufficiency: Renal and Metabolic Phenotypes in a Rat Hsd11b2 Knockout Model

Obesity and hypertension are 2 major health issues of the 21st century. The syndrome of apparent mineralocorticoid excess is caused by deficiency of 11β-hydroxysteroid dehydrogenase type 2 (Hsd11b2), which normally inactivates glucocorticoids, rendering the mineralocorticoid receptor aldosterone–specific. The metabolic consequences of Hsd11b2 knockout in the rat are investigated in parallel with electrolyte homeostasis. Hsd11b2 was knocked out, by pronuclear microinjection of targeted zinc-finger nuclease mRNAs, and 1 line was characterized for its response to renal and metabolic challenges. Plasma 11-dehydrocorticosterone was below detection thresholds, and Hsd11b2 protein was undetected by Western blot, indicating complete ablation. Homozygotes were 13% smaller than wild-type littermates, and were polydipsic and polyuric. Their kidneys, adrenals, and hearts were significantly enlarged, but mesenteric fat pads and liver were significantly smaller. On a 0.3% Na diet, mean arterial blood pressure was ≈65 mm Hg higher than controls but only 25 mm Hg higher on a 0.03% Na⁺ diet. Urinary Na/K ratio of homozygotes was similar to controls on 0.3% Na⁺ diet but urinary albumin and calcium were elevated. Corticosterone and aldosterone levels showed normal circadian variation on both a 0.3% and 0.03% Na⁺ diet, but plasma renin was suppressed in homozygotes on both diets. Plasma glucose responses to an oral glucose challenge were reduced despite low circulating insulin, indicating much greater sensitivity to insulin in homozygotes. The rat model reveals mechanisms linking electrolyte homeostasis and metabolic control through the restriction of Hsd11b1 substrate availability.

Estrogens protect male mice from obesity complications and influence glucocorticoid metabolism

BACKGROUND

Although the prevalence of obesity is higher among women than men, they are somewhat protected from the associated cardiometabolic consequences. The increase in cardiovascular disease risk seen after the menopause suggests a role for estrogens. There is also growing evidence for the importance of estrogen on body fat and metabolism in males. We hypothesized that that estrogen administration would ameliorate the adverse effects of obesity on metabolic parameters in males.

METHODS

Male and female C57Bl/6 mice were fed control or obesogenic (DIO) diets from 5 weeks of age until adulthood. Glucose tolerance testing was performed at 13 weeks of age. Mice were killed at 15 weeks of age and liver and adipose tissue were collected for analysis of gene expression. A second cohort of male mice underwent the same experimental design with the addition of estradiol pellet implantation or sham surgery at 6 weeks.

RESULTS

DIO males had greater mesenteric adipose deposition and more severe increases in plasma glucose, insulin and lipids than females. Treatment of males with estradiol from 6 weeks of age prevented DIO-induced increases in adipose tissue mass and alterations in glucose-insulin homeostasis. We also identified sex differences in the transcript levels and activity of hepatic and adipose glucocorticoid metabolizing enzymes. Estrogen treatment feminized the pattern of DIO-induced changes in glucocorticoid metabolism, rendering males similar to females.

CONCLUSIONS

Thus, DIO induces sex-specific changes in glucose-insulin homeostasis, which are ameliorated in males treated with estrogen, highlighting the importance of sex steroids in metabolism. Given that altered peripheral glucocorticoid metabolism has been observed in rodent and human obesity, our results also suggest that sexually dimorphic expression and activity of glucocorticoid metabolizing enzymes may have a role in the differential metabolic responses to obesity in males and females.

Maternal restraint stress during pregnancy in mice induces 11β-HSD1-associated metabolic changes in the livers of the offspring

In rats, maternal exposure to restraint stress during pregnancy can induce abnormalities in the cardiovascular and central nervous systems of the offspring. These effects are mediated by long-lasting hyperactivation of the hypothalamic–pituitary–adrenal axis. However, little is known about the potential effects of stress during pregnancy on metabolic systems. We examined the effect of restraint stress in pregnant mice on the liver function of their offspring. The offspring of stressed mothers showed significantly higher lipid accumulation in the liver after weaning than did the controls; this accumulation was associated with increased expression of lipid metabolism-related proteins such as alanine aminotransferase 2 diglyceride acyltransferase 1, peroxisome proliferator-activated receptor gamma and glucocorticoid receptor. Additionally, we observed increased levels of 11β-hydroxysteroid dehydrogenase type 1, an intercellular mediator that converts glucocorticoid from the inactive to the active form, in the foetal and postnatal periods. These results indicate that restraint stress in pregnancy in mice induces metabolic abnormalities via 11β-hydroxysteroid dehydrogenase type 1-related pathways in the foetal liver. It is therefore possible that exposure to stress in pregnant women may be a risk factor for metabolic syndromes (e.g. fatty liver) in children.

11β-Hydroxysteroid dehydrogenase type 1 shRNA ameliorates glucocorticoid-induced insulin resistance and lipolysis in mouse abdominal adipose tissue

Long-term glucocorticoid exposure increases the risk for developing type 2 diabetes. Prereceptor activation of glucocorticoid availability in target tissue by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) coupled with hexose-6-phosphate dehydrogenase (H6PDH) is an important mediator of the metabolic syndrome. We explored whether the tissue-specific modulation of 11β-HSD1 and H6PDH in adipose tissue mediates glucocorticoid-induced insulin resistance and lipolysis and analyzed the effects of 11β-HSD1 inhibition on the key lipid metabolism genes and insulin-signaling cascade. We observed that corticosterone (CORT) treatment increased expression of 11β-HSD1 and H6PDH and induced lipase HSL and ATGL with suppression of p-Thr(172) AMPK in adipose tissue of C57BL/6J mice. In contrast, CORT induced adipose insulin resistance, as reflected by a marked decrease in IR and IRS-1 gene expression with a reduction in p-Thr(308) Akt/PKB. Furthermore, 11β-HSD1 shRNA attenuated CORT-induced 11β-HSD1 and lipase expression and improved insulin sensitivity with a concomitant stimulation of pThr(308) Akt/PKB and p-Thr(172) AMPK within adipose tissue. Addition of CORT to 3T3-L1 adipocytes enhanced 11β-HSD1 and H6PDH and impaired p-Thr(308) Akt/PKB, leading to lipolysis. Knockdown of 11β-HSD1 by shRNA attenuated CORT-induced lipolysis and reversed CORT-mediated inhibition of pThr(172) AMPK, which was accompanied by a parallel improvement of insulin signaling response in these cells. These findings suggest that elevated adipose 11β-HSD1 expression may contribute to glucocorticoid-induced insulin resistance and adipolysis.

Glucocorticoid receptor gene expression in adipose tissue and associated metabolic risk in black and white South African women

BACKGROUND

Black women have lower visceral adipose tissue (VAT) but are less insulin sensitive than white women; the mechanisms responsible are unknown.

OBJECTIVE

The study aimed to test the hypothesis that variation in subcutaneous adipose tissue (SAT) sensitivity to glucocorticoids might underlie these differences.

METHODS

Body fatness (dual energy X-ray absorptiometry) and distribution (computerized tomography), insulin sensitivity (SI, intravenous and oral glucose tolerance tests), and expression of 11β-hydroxysteroid dehydrogenase-1 (11HSD1), hexose-6-phosphate dehydrogenase and glucocorticoid receptor-α (GRα), as well as genes involved in adipogenesis and inflammation were measured in abdominal deep SAT, superficial SAT and gluteal SAT (GLUT) depots of 56 normal-weight or obese black and white premenopausal South African (SA) women. We used a combination of univariate and multivariate statistics to evaluate ethnic-specific patterns in adipose gene expression and related body composition and insulin sensitivity measures.

RESULTS

Although 11HSD1 activity and mRNA did not differ by ethnicity, GRα mRNA levels were significantly lower in SAT of black compared with white women, particularly in the GLUT depot (0.52±0.21 vs 0.91±0.26 AU, respectively, P<0.01). In black women, lower SAT GRα mRNA levels were associated with increased inflammatory gene transcript levels and abdominal SAT area, and reduced adipogenic gene transcript levels, VAT/SAT ratio and SI. Abdominal SAT 11HSD1 activity associated with increased VAT area and decreased SI in white, but not in black women.

CONCLUSIONS

In black SA women, downregulation of GRα mRNA levels with obesity and reduced insulin sensitivity, possibly via increased SAT inflammation, is associated with reduced VAT accumulation.

Mechanisms of glucocorticoid-induced insulin resistance: focus on adipose tissue function and lipid metabolism

Glucocorticoids (GCs) are critical in the regulation of the stress response, inflammation and energy homeostasis. Excessive GC exposure results in whole-body insulin resistance, obesity, cardiovascular disease, and ultimately decreased survival, despite their potent anti-inflammatory effects. This apparent paradox may be explained by the complex actions of GCs on adipose tissue functionality. The wide prevalence of oral GC therapy makes their adverse systemic effects an important yet incompletely understood clinical problem. This article reviews the mechanisms by which supraphysiologic GC exposure promotes insulin resistance, focusing in particular on the effects on adipose tissue function and lipid metabolism.

Pharmacological evaluation of adipose dysfunction via 11β-hydroxysteroid dehydrogenase type 1 in the development of diabetes in diet-induced obese mice with cortisone pellet implantation

Signals from intracellular glucocorticoids (GCs) via 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in adipose tissues have been reported to serve as amplifiers leading to deterioration of glucose metabolism associated with obesity. To elucidate adipose dysfunction via 11β-HSD1 activation in the development of obesity-related diabetes, we established novel diabetic mice by implanting a cortisone pellet (CP) in diet-induced obesity (DIO) mice. Cortisone pellet-implanted DIO mice (DIO/CP mice) showed hyperglycemia, insulin resistance, hyperlipidemia, and ectopic fat accumulation, whereas cortisone pellet implantation in lean mice did not induce hyperglycemia. In DIO/CP mice, indexes of lipolysis such as plasma glycerol and nonesterified fatty acids (NEFAs) increased before hyperglycemia appeared. Furthermore, the adipose mRNA level of 11β-HSD1 was up-regulated in DIO/CP mice compared with sham-operated DIO mice. RU486 (mifepristone, 11β-[p-(dimethylamino)phenyl]-17β-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one), a glucocorticoid receptor antagonist, decreased adipose mRNA levels of 11β-HSD1 as well as adipose triglyceride lipase. RU486 also improved plasma NEFA, glycerol, and glucose levels in DIO/CP mice. These results demonstrate that lipolysis in adipose tissues caused by GC activation via 11β-HSD1 serves as a trigger for diabetes with ectopic fat accumulation. Our findings also indicate the possibility of a vicious circle of GC signals via 11β-HSD1 up-regulation in adipose tissues, contributing to deterioration of glucose metabolism to result in diabetes. Our DIO/CP mouse could be a suitable model of type 2 diabetes to evaluate adipose dysfunction via 11β-HSD1.

11β-hydroxysteroid dehydrogenases: intracellular gate-keepers of tissue glucocorticoid action

Glucocorticoid action on target tissues is determined by the density of "nuclear" receptors and intracellular metabolism by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) which catalyze interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone. 11β-HSD type 1, a predominant reductase in most intact cells, catalyzes the regeneration of active glucocorticoids, thus amplifying cellular action. 11β-HSD1 is widely expressed in liver, adipose tissue, muscle, pancreatic islets, adult brain, inflammatory cells, and gonads. 11β-HSD1 is selectively elevated in adipose tissue in obesity where it contributes to metabolic complications. Similarly, 11β-HSD1 is elevated in the ageing brain where it exacerbates glucocorticoid-associated cognitive decline. Deficiency or selective inhibition of 11β-HSD1 improves multiple metabolic syndrome parameters in rodent models and human clinical trials and similarly improves cognitive function with ageing. The efficacy of inhibitors in human therapy remains unclear. 11β-HSD2 is a high-affinity dehydrogenase that inactivates glucocorticoids. In the distal nephron, 11β-HSD2 ensures that only aldosterone is an agonist at mineralocorticoid receptors (MR). 11β-HSD2 inhibition or genetic deficiency causes apparent mineralocorticoid excess and hypertension due to inappropriate glucocorticoid activation of renal MR. The placenta and fetus also highly express 11β-HSD2 which, by inactivating glucocorticoids, prevents premature maturation of fetal tissues and consequent developmental "programming." The role of 11β-HSD2 as a marker of programming is being explored. The 11β-HSDs thus illuminate the emerging biology of intracrine control, afford important insights into human pathogenesis, and offer new tissue-restricted therapeutic avenues.

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'.

11β-Hydroxysteroid dehydrogenase 1: translational and therapeutic aspects

11β-Hydroxysteroid dehydrogenase type 1 (11β-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 11β-HSD1 and the molecular basis of cortisone reductase deficiencies. We will also address how altered 11β-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 11β-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 11β-HSD1 is also an exciting prospect for the treatment of a variety of other disorders such as osteoporosis, glaucoma, intracranial hypertension, and cognitive decline.

Deconstructing the roles of glucocorticoids in adipose tissue biology and the development of central obesity

Central obesity is associated with insulin resistance and dyslipidemia. Thus, the mechanisms that control fat distribution and its impact on systemic metabolism have importance for understanding the risk for diabetes and cardiovascular disease. Hypercortisolemia at the systemic (Cushing's syndrome) or local levels (due to adipose-specific overproduction via 11β-hydroxysteroid dehydrogenase 1) results in the preferential expansion of central, especially visceral fat depots. At the same time, peripheral subcutaneous depots can become depleted. The biochemical and molecular mechanisms underlying the depot-specific actions of glucocorticoids (GCs) on adipose tissue function remain poorly understood. GCs exert pleiotropic effects on adipocyte metabolic, endocrine and immune functions, and dampen adipose tissue inflammation. GCs also regulate multiple steps in the process of adipogenesis. Acting synergistically with insulin, GCs increase the expression of numerous genes involved in fat deposition. Variable effects of GC on lipolysis are reported, and GC can improve or impair insulin action depending on the experimental conditions. Thus, the net effect of GC on fat storage appears to depend on the physiologic context. The preferential effects of GC on visceral adipose tissue have been linked to higher cortisol production and glucocorticoid receptor expression, but the molecular details of the depot-dependent actions of GCs are only beginning to be understood. In addition, increasing evidence underlines the importance of circadian variations in GCs in relationship to the timing of meals for determining their anabolic actions on the adipocyte. In summary, although the molecular mechanisms remain to be fully elucidated, there is increasing evidence that GCs have multiple, depot-dependent effects on adipocyte gene expression and metabolism that promote central fat deposition. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.

Carbenoxolone treatment ameliorated metabolic syndrome in WNIN/Ob obese rats, but induced severe fat loss and glucose intolerance in lean rats

BACKGROUND

11beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) regulates local glucocorticoid action in tissues by catalysing conversion of inactive glucocorticoids to active glucocorticoids. 11β-HSD1 inhibition ameliorates obesity and associated co-morbidities. Here, we tested the effect of 11β-HSD inhibitor, carbenoxolone (CBX) on obesity and associated comorbidities in obese rats of WNIN/Ob strain, a new animal model for genetic obesity.

METHODOLOGY/PRINCIPAL FINDINGS

Subcutaneous injection of CBX (50 mg/kg body weight) or volume-matched vehicle was given once daily for four weeks to three month-old WNIN/Ob lean and obese rats (n = 6 for each phenotype and for each treatment). Body composition, plasma lipids and hormones were assayed. Hepatic steatosis, adipose tissue morphology, inflammation and fibrosis were also studied. Insulin resistance and glucose intolerance were determined along with tissue glycogen content. Gene expressions were determined in liver and adipose tissue. CBX significantly inhibited 11β-HSD1 activity in liver and adipose tissue of WNIN/Ob lean and obese rats. CBX significantly decreased body fat percentage, hypertriglyceridemia, hypercholesterolemia, insulin resistance in obese rats. CBX ameliorated hepatic steatosis, adipocyte hypertrophy, adipose tissue inflammation and fibrosis in obese rats. Tissue glycogen content was significantly decreased by CBX in liver and adipose tissue of obese rats. Severe fat loss and glucose- intolerance were observed in lean rats after CBX treatment.

CONCLUSIONS/SIGNIFICANCE

We conclude that 11β-HSD1 inhibition by CBX decreases obesity and associated co-morbidities in WNIN/Ob obese rats. Our study supports the hypothesis that inhibition of 11β-HSD1 is a key strategy to treat metabolic syndrome. Severe fat loss and glucose -intolerance by CBX treatment in lean rats suggest that chronic 11β-HSD1 inhibition may lead to insulin resistance in normal conditions.

11β-Hydroxysteroid dehydrogenase type 1: relevance of its modulation in the pathophysiology of obesity, the metabolic syndrome and type 2 diabetes mellitus

Recent evidence strongly argues for a pathogenic role of glucocorticoids and 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in obesity and the metabolic syndrome, a cluster of risk factors for atherosclerotic cardiovascular disease and type 2 diabetes mellitus (T2DM) that includes insulin resistance (IR), dyslipidaemia, hypertension and visceral obesity. This has been partially prompted not only by the striking clinical resemblances between the metabolic syndrome and Cushing's syndrome (a state characterized by hypercortisolism that associates with metabolic syndrome components) but also from monogenic rodent models for the metabolic syndrome (e.g. the leptin-deficient ob/ob mouse or the leptin-resistant Zucker rat) that display overall increased secretion of glucocorticoids. However, systemic circulating glucocorticoids are not elevated in obese patients and/or patients with metabolic syndrome. The study of the role of 11β-HSD system shed light on this conundrum, showing that local glucocorticoids are finely regulated in a tissue-specific manner at the pre-receptor level. The system comprises two microsomal enzymes that either activate cortisone to cortisol (11β-HSD1) or inactivate cortisol to cortisone (11β-HSD2). Transgenic rodent models, knockout (KO) for HSD11B1 or with HSD11B1 or HSD11B2 overexpression, specifically targeted to the liver or adipose tissue, have been developed and helped unravel the currently undisputable role of the enzymes in metabolic syndrome pathophysiology, in each of its isolated components and in their prevention. In the transgenic HSD11B1 overexpressing models, different features of the metabolic syndrome and obesity are replicated. HSD11B1 gene deficiency or HSD11B2 gene overexpression associates with improvements in the metabolic profile. In face of these demonstrations, research efforts are now being turned both into the inhibition of 11β-HSD1 as a possible pharmacological target and into the role of dietary habits on the establishment or the prevention of the metabolic syndrome, obesity and T2DM through 11β-HSD1 modulation. We intend to review and discuss 11β-HSD1 and obesity, the metabolic syndrome and T2DM and to highlight the potential of its inhibition for therapeutic or prophylactic approaches in those metabolic diseases.

Lack of significant metabolic abnormalities in mice with liver-specific disruption of 11β-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 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) enzyme, principally expressed in the liver. Transgenic mice have demonstrated the importance of 11β-HSD1 in mediating aspects of the metabolic syndrome, as well as HPA axis control. In order to address the primacy of hepatic 11β-HSD1 in regulating metabolism and the HPA axis, we have generated liver-specific 11β-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 11β-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 11β-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 11β-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 11β-HSD1 expression, highlighting the contribution of cross talk between GC target tissues in determining metabolic phenotype.

Anti-diabetic and anti-adipogenic effects of a novel selective 11β-hydroxysteroid dehydrogenase type 1 inhibitor in the diet-induced obese mice

Glucocorticoid excess (Cushing's syndrome) causes metabolic syndrome such as visceral obesity, insulin resistance, diabetes mellitus, dyslipidaemia and hypertension. The selective inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) have considerable potential for treating type 2 diabetes mellitus and metabolic syndrome. In the present study, we investigated the anti-diabetic and anti-adipogenic effects of 4-(2-(1,1-dioxido-6-(2,4,6-trichlorophenyl)-1,2,6-thiadiazinan-2-yl)acetamido)adamantane-1-carboxamide (KR-67183), a novel selective 11β-HSD1 inhibitor; we also investigated the underlying molecular mechanisms in the cortisone-induced 3T3-L1 adipogenesis model system and diet-induced obese (DIO) mice. KR-67183 concentration-dependently inhibited 11β-HSD1 activity in human and mouse 11β-HSD1 over-expressed cells and in the ex vivo assay of C57BL/6 mice. In the study with DIO mice, the administration of KR-67183 (20 and 50mg/kg/day, orally for 28 days) improved the glucose tolerance and insulin sensitivity with suppressed 11β-HSD1 activity in the liver and fat. However, KR-67183 showed no change in the adrenal gland weight/body weight ratio and plasma corticosterone concentration in DIO mice. Further, KR-67183 suppressed adipocyte differentiation on cortisone-induced adipogenesis in 3T3-L1 cells is associated with the suppression of the cortisone-induced mRNA levels of FABP4, PPARγ2 and GLUT4, and 11β-HSD1 activity. Taken together, it is suggested that a selective 11β-HSD1 inhibitor, KR-67183, may provide a new therapeutic window in the prevention and treatment without toxicity in type 2 diabetes with obesity.

Regulation of lipogenesis by glucocorticoids and insulin in human adipose tissue

Patients with glucocorticoid (GC) excess, Cushing's syndrome, develop a classic phenotype characterized by central obesity and insulin resistance. GCs are known to increase the release of fatty acids from adipose, by stimulating lipolysis, however, the impact of GCs on the processes that regulate lipid accumulation has not been explored. Intracellular levels of active GC are dependent upon the activity of 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) and we have hypothesized that 11β-HSD1 activity can regulate lipid homeostasis in human adipose tissue (Chub-S7 cell line and primary cultures of human subcutaneous (sc) and omental (om) adipocytes. Across adipocyte differentiation, lipogenesis increased whilst β-oxidation decreased. GC treatment decreased lipogenesis but did not alter rates of β-oxidation in Chub-S7 cells, whilst insulin increased lipogenesis in all adipocyte cell models. Low dose Dexamethasone pre-treatment (5 nM) of Chub-S7 cells augmented the ability of insulin to stimulate lipogenesis and there was no evidence of adipose tissue insulin resistance in primary sc cells. Both cortisol and cortisone decreased lipogenesis; selective 11β-HSD1 inhibition completely abolished cortisone-mediated repression of lipogenesis. GCs have potent actions upon lipid homeostasis and these effects are dependent upon interactions with insulin. These in vitro data suggest that manipulation of GC availability through selective 11β-HSD1 inhibition modifies lipid homeostasis in human adipocytes.

Dietary manipulation reveals an unexpected inverse relationship between fat mass and adipose 11β-hydroxysteroid dehydrogenase type 1

Increased dietary fat intake is associated with obesity, insulin resistance, and metabolic disease. In transgenic mice, adipose tissue-specific overexpression of the glucocorticoid-amplifying enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) exacerbates high-fat (HF) diet-induced visceral obesity and diabetes, whereas 11β-HSD1 gene knockout ameliorates this, favoring accumulation of fat in nonvisceral depots. Paradoxically, in normal mice HF diet-induced obesity (DIO) is associated with marked downregulation of adipose tissue 11β-HSD1 levels. To identify the specific dietary fats that regulate adipose 11β-HSD1 and thereby impact upon metabolic disease, we either fed mice diets enriched (45% calories as fat) in saturated (stearate), monounsaturated (oleate), or polyunsaturated (safflower oil) fats ad libitum or we pair fed them a low-fat (11%) control diet for 4 wk. Adipose and liver mass and glucocorticoid receptor and 11β-HSD1 mRNA and activity levels were determined. Stearate caused weight loss and hypoinsulinemia, partly due to malabsorption, and this markedly increased plasma corticosterone levels and adipose 11β-HSD1 activity. Oleate induced pronounced weight gain and hyperinsulinemia in association with markedly low plasma corticosterone and adipose 11β-HSD1 activity. Weight gain and hyperinsulinemia was less pronounced with safflower compared with oleate despite comparable suppression of plasma corticosterone and adipose 11β-HSD1. However, with pair feeding, safflower caused a selective reduction in visceral fat mass and relative insulin sensitization without affecting plasma corticosterone or adipose 11β-HSD1. The dynamic depot-selective relationship between adipose 11β-HSD1 and fat mass strongly implicates a dominant physiological role for local tissue glucocorticoid reactivation in fat mobilization.

Functional variability in corticosteroid receptors is a major component of strain differences in fat deposition and metabolic consequences of enriched diets in rat

We aimed to distinguish mineralocorticoid (MR) from glucocorticoid receptor (GR) actions in the nutritional differences between the Fischer 344 (F344) and LOU/C (LOU) rat strains. The decrease of urinary Na+/K+ ratio induced via MR activation by aldosterone and decrease of circulating lymphocyte counts exerted via GR activation by dexamethasone revealed a higher efficiency of corticosteroid receptor in LOU than in F344 rats. Afterward, we submitted F344 and LOU male rats to adrenalectomy and to substitution treatments with agonists of MR or GR under 3 successive diets--standard, free choice between chow and pork lard, and an imposed high-fat/high-sugar diet--to explore the involvement of the interactions between activation of corticosteroid receptors and diet on food intake, body composition, and metabolic blood parameters in these rats. Lastly, we measured energy expenditure and substrate oxidization in various experimental conditions in LOU and F344 rats by indirect calorimetry. In LOU rats, we showed greater basal and MR-induced energy expenditure, diet-induced thermogenesis, and lipid oxidization. We showed that the F344 rat strain constitutes a relevant model of the unfavorable effects exerted by glucocorticoids via GR on food preference for high-calorie diets, abdominal fat deposition, diabetes, and other deleterious consequences of visceral obesity. Contrary to F344 rats, the LOU rats did not exhibit the expected visceral fat deposition linked to GR activation. This strain is therefore a relevant model of resistance to diet-induced obesity and to the deleterious effects exerted by glucocorticoids on metabolism.

High fructose diets increase 11β-hydroxysteroid dehydrogenase type 1 in liver and visceral adipose in rats within 24-h exposure

The increased prevalence of overweight and obesity in the United States during the past three decades coincides with a trend of increased sugar intake, especially fructose, leading to speculation that the two trends may be linked. The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), that regulates intracellular tissue-specific glucocorticoid levels, is increased in adipose and suppressed in liver of obese humans and animals. Hexose-6-phosphate dehydrogenase (H6PDH) is colocalized with 11β-HSD1 and generates nicotinamide adenosine dinucleotide phosphate, the required cofactor for 11β-HSD1 reductase activity that converts inert glucocorticoid metabolite into active hormone. We examined the acute effects of ad lib access to 16% solutions of sucrose, fructose, or glucose and chow and water. Diets high in fructose, but not glucose or sucrose increased 11β-HSD1 mRNA within 24 h in liver and adipose by greater than two- and threefold, respectively (P ≤ 0.05). After 1 week, hepatic 11β-HSD1 mRNA and protein were suppressed by >60% in all sugar-fed groups, a phenomenon not previously reported in the absence of obesity. Sucrose- and fructose-fed rats had higher plasma triglycerides than did control or glucose-fed rats at both 24 h and 1 week (P ≤ 0.02), consistent with previously reported effects of fructose on lipid metabolism. We conclude that high-sugar diets initiate glucocorticoid dysregulation associated with obesity prior to the onset of phenotypic changes, and that high fructose diets specifically induce changes in 11β-HSD1 within 24-h exposure.

Novel fat depot-specific mechanisms underlie resistance to visceral obesity and inflammation in 11 β-hydroxysteroid dehydrogenase type 1-deficient mice

OBJECTIVE

The study objective was to determine the key early mechanisms underlying the beneficial redistribution, function, and inflammatory profile of adipose tissue in 11β-hydroxysteroid dehydrogenase type 1 knockout (11β-HSD1(-/-)) mice fed a high-fat (HF) diet.

RESEARCH DESIGN AND METHODS

By focusing on the earliest divergence in visceral adiposity, subcutaneous and visceral fat depots from 11β-HSD1(-/-) and C57Bl/6J control mice fed an HF diet for 4 weeks were used for comparative microarray analysis of gene expression, and differences were validated with real-time PCR. Key changes in metabolic signaling pathways were confirmed using Western blotting/immunoprecipitation, and fat cell size was compared with the respective chow-fed control groups. Altered adipose inflammatory cell content and function after 4 weeks (early) and 18 weeks (chronic) of HF feeding was investigated using fluorescence (and magnetic)-activated cell sorting analysis, immunohistochemistry, and in situ hybridization.

RESULTS

In subcutaneous fat, HF-fed 11β-HSD1(-/-) mice showed evidence of enhanced insulin and β-adrenergic signaling associated with accretion of smaller metabolically active adipocytes. In contrast, reduced 11β-HSD1(-/-) visceral fat accumulation was characterized by maintained AMP kinase activation, not insulin sensitization, and higher adipocyte interleukin-6 release. Intracellular glucocorticoid deficiency was unexpectedly associated with suppressed inflammatory signaling and lower adipocyte monocyte chemoattractant protein-1 secretion with strikingly reduced cytotoxic T-cell and macrophage infiltration, predominantly in visceral fat.

CONCLUSIONS

Our data define for the first time the novel and distinct depot-specific mechanisms driving healthier fat patterning and function as a result of reduced intra-adipose glucocorticoid levels.

Increased whole-body and sustained liver cortisol regeneration by 11beta-hydroxysteroid dehydrogenase type 1 in obese men with type 2 diabetes provides a target for enzyme inhibition

OBJECTIVE

The cortisol-regenerating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) amplifies glucocorticoid levels in liver and adipose tissue. 11β-HSD1 inhibitors are being developed to treat type 2 diabetes. In obesity, 11β-HSD1 is increased in adipose tissue but decreased in liver. The benefits of pharmacological inhibition may be reduced if hepatic 11β-HSD1 is similarly decreased in obese patients with type 2 diabetes. To examine this, we quantified in vivo whole-body, splanchnic, and hepatic 11β-HSD1 activity in obese type 2 diabetic subjects.

RESEARCH DESIGN AND METHODS

Ten obese men with type 2 diabetes and seven normal-weight control subjects were infused with 9,11,12,12-[(2)H](4)cortisol (40%) and cortisol (60%) at 1.74 mg/h. Adrenal cortisol secretion was suppressed with dexamethasone. Samples were obtained from the hepatic vein and an arterialized hand vein at steady state and after oral administration of cortisone (5 mg) to estimate whole-body and liver 11β-HSD1 activity using tracer dilution.

RESULTS

In obese type 2 diabetic subjects, the appearance rate of 9,12,12-[(2)H](3)cortisol in arterialized blood was increased (35 ± 2 vs. 29 ± 1 nmol/min, P < 0.05), splanchnic 9,12,12-[(2)H](3)cortisol production was not reduced (29 ± 6 vs. 29 ± 6 nmol/min), and cortisol appearance in the hepatic vein after oral cortisone was unchanged.

CONCLUSIONS

Whole-body 11β-HSD1 activity is increased in obese men with type 2 diabetes, whereas liver 11β-HSD1 activity is sustained, unlike in euglycemic obesity. This supports the concept that inhibitors of 11β-HSD1 are likely to be most effective in obese type 2 diabetic subjects.

11beta-hydroxysteroid dehydrogenase type 1 inhibitors for the treatment of type 2 diabetes

IMPORTANCE OF THE FIELD

The prevalence of obesity and type 2 diabetes is rising and reaching pandemic proportions. For this reason, identification of novel therapeutic targets is urgently needed.

AREAS COVERED IN THIS REVIEW

The endoluminal enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) catalyzes glucocorticoid activation in key metabolic tissues including skeletal muscle, liver and adipose tissue, and is strongly implicated in the pathogenesis of obesity, type 2 diabetes and the metabolic syndrome. Selective 11beta-HSD1 inhibitors limit local glucocorticoid availability and improve insulin sensitivity, glucose tolerance, lipid profiles and atherosclerosis. To date, there is a paucity of clinical studies using selective 11beta-HSD1 inhibitors; however, early indications show that these compounds have great therapeutic potential.

WHAT THE READER WILL GAIN

We present a comprehensive overview of the background to the development of selective 11beta-HSD1 inhibitors, the preclinical data supporting 11beta-HSD1 as a therapeutic target, and the current status of clinical trials of these agents.

TAKE HOME MESSAGE

Selective 11beta-HSD1 inhibitors have the potential to improve insulin sensitivity and may ultimately add to the treatment options available for patients with type 2 diabetes. However, further clinical studies are urgently required.

Inhibitors of 11β-hydroxysteroid dehydrogenase type 1 in antidiabetic therapy

Glucocorticoid action is mediated by glucocorticoid receptor (GR), which upon cortisol binding is activated and regulates the transcriptional expression of target genes and downstream physiological functions. 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyzes the conversion of inactive cortisone to active cortisol. Since cortisol is also produced through biosynthesis in the adrenal glands, the total cortisol level in a given tissue is determined by both the circulating cortisol concentration and the local 11β-HSD1 activity. 11β-HSD1 is expressed in liver, adipose, brain, and placenta. Since it contributes to the local cortisol levels in these tissues, 11β-HSD1 plays a critical role in glucocorticoid action. The metabolic symptoms caused by glucocorticoid excess in Cushing's syndrome overlap with the characteristics of the metabolic syndrome, suggesting that increased glucocorticoid activity may play a role in the etiology of the metabolic syndrome. Consistent with this notion, elevated adipose expression of 11β-HSD1 induced metabolic syndrome-like phenotypes in mice. Thus, 11β-HSD1 is a proposed therapeutic target to normalize glucocorticoid excess in a tissue-specific manner and mitigate obesity and insulin resistance. Selective inhibitors of 11β-HSD1 are under development for the treatment of type 2 diabetes and other components of the metabolic syndrome.

Thermogenesis and related metabolic targets in anti-diabetic therapy

Exercise, together with a low-energy diet, is the first-line treatment for type 2 diabetes type 2 diabetes . Exercise improves insulin sensitivity insulin sensitivity by increasing the number or function of muscle mitochondria mitochondria and the capacity for aerobic metabolism, all of which are low in many insulin-resistant subjects. Cannabinoid 1-receptor antagonists and β-adrenoceptor agonists improve insulin sensitivity in humans and promote fat oxidation in rodents independently of reduced food intake. Current drugs for the treatment of diabetes are not, however, noted for their ability to increase fat oxidation, although the thiazolidinediones increase the capacity for fat oxidation in skeletal muscle, whilst paradoxically increasing weight gain.There are a number of targets for anti-diabetic drugs that may improve insulin sensitivity insulin sensitivity by increasing the capacity for fat oxidation. Their mechanisms of action are linked, notably through AMP-activated protein kinase, adiponectin, and the sympathetic nervous system. If ligands for these targets have obvious acute thermogenic activity, it is often because they increase sympathetic activity. This promotes fuel mobilisation, as well as fuel oxidation. When thermogenesis thermogenesis is not obvious, researchers often argue that it has occurred by using the inappropriate device of treating animals for days or weeks until there is weight (mainly fat) loss and then expressing energy expenditure energy expenditure relative to body weight. In reality, thermogenesis may have occurred, but it is too small to detect, and this device distracts us from really appreciating why insulin sensitivity has improved. This is that by increasing fatty acid oxidation fatty acid oxidation more than fatty acid supply, drugs lower the concentrations of fatty acid metabolites that cause insulin resistance. Insulin sensitivity improves long before any anti-obesity effect can be detected.

Targeting the pre-receptor metabolism of cortisol as a novel therapy in obesity and diabetes

Due to its impact upon health and the economy, the mechanisms that contribute to the pathogenesis of obesity and the metabolic syndrome are under intense scrutiny. In addition to understanding the pathogenesis of disease it is important to design and trial novel therapies. Patients with cortisol excess, Cushing's syndrome, have a phenotype similar to that of the metabolic syndrome and as a result there is much interest the manipulation of glucocorticoid (GC) action as a therapeutic strategy. Intracellular GC levels are regulated by 11β-hydroxysteroid dehydrogenase (11β-HSD1) which converts inactive cortisone to cortisol, thereby increasing local GC action. There is an abundance of data implicating 11β-HSD1 in the pathogenesis of obesity, type 2 diabetes and the metabolic syndrome and 11β-HSD1 is an attractive therapeutic target. Selective 11β-HSD1 inhibitors, which do not act upon 11β-HSD2 (which inactivates cortisol to cortisone) are in development. So far studies have primarily been carried out in rodents, with results showing improvements in metabolic profile. Data are now beginning to emerge from human studies and the results are promising.

Will treating diabetes with 11β-HSD1 inhibitors affect the HPA axis?

Inhibitors of 11β-HSD1 are in clinical trials for the treatment of type 2 diabetes. These compounds act by decreasing the cortisol generated in liver and adipose tissue, and therefore reducing tissue-specific gluconeogenesis and fatty acid metabolism. However, there is concern that reduction in tissue-regenerated cortisol might decrease feedback to the hypothalamic-pituitary-adrenal (HPA) axis, resulting in upregulation of cortisol from the adrenal gland. This review considers evidence from 11β-HSD1 knockout and transgenic mice, inhibitor studies and results from clinical trials evaluating HPA axis biomarkers. It is clear that analysis of the HPA axis is not sufficiently detailed, and there is a need to understand the subtle changes in the axis associated with pulsatility, diurnal rhythm and stress.

The 11-beta-hydroxysteroid dehydrogenase type 1 inhibitor INCB13739 improves hyperglycemia in patients with type 2 diabetes inadequately controlled by metformin monotherapy

OBJECTIVE

11-Beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) converts inactive cortisone into active cortisol, thereby amplifying intracellular glucocorticoid action. The efficacy and safety of the 11betaHSD1 inhibitor INCB13739 were assessed when added to ongoing metformin monotherapy in patients with type 2 diabetes exhibiting inadequate glycemic control (A1C 7-11%).

RESEARCH DESIGN AND METHODS

This double-blind placebo-controlled paralleled study randomized 302 patients with type 2 diabetes (mean A1C 8.3%) on metformin monotherapy (mean 1.5 g/day) to receive one of five INCB13739 doses or placebo once daily for 12 weeks. The primary end point was the change in A1C at study end. Other end points included changes in fasting glucose, lipids, weight, adverse events, and safety.

RESULTS

After 12 weeks, 200 mg of INCB13739 resulted in significant reductions in A1C (-0.6%), fasting plasma glucose (-24 mg/dl), and homeostasis model assessment-insulin resistance (HOMA-IR) (-24%) compared with placebo. Total cholesterol, LDL cholesterol, and triglycerides were all significantly decreased in hyperlipidemic patients. Body weight decreased relative to placebo after INCB13739 therapy. A reversible dose-dependent elevation in adrenocorticotrophic hormone, generally within the normal reference range, was observed. Basal cortisol homeostasis, testosterone in men, and free androgen index in women were unchanged by INCB13739. Adverse events were similar across all treatment groups.

CONCLUSIONS

INCB13739 added to ongoing metformin therapy was efficacious and well tolerated in patients with type 2 diabetes who had inadequate glycemic control with metformin alone. 11BetaHSD1 inhibition offers a new potential approach to control glucose and cardiovascular risk factors in type 2 diabetes.

Weight loss after gastric bypass surgery in women is followed by a metabolically favorable decrease in 11beta-hydroxysteroid dehydrogenase 1 expression in subcutaneous adipose tissue

BACKGROUND AND AIMS

The role of 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1) in the pathogenesis of obesity has been elucidated in humans and in various rodent models. Obesity is accompanied by disturbances in glucocorticoid metabolism, circulating adipokine levels, and fatty acid (FA) reesterification. This study was undertaken to evaluate glucocorticoid metabolism in sc fat before and after weight loss and to explore putative associations between 11beta-HSD1 and leptin, adiponectin, and FA recycling.

SUBJECTS AND METHODS

Twenty-seven obese (mean body mass index 44.4 + or - 4.4 kg/m(2)) women underwent gastric bypass surgery. Subcutaneous fat biopsies were collected before and 2 yr after surgery. The expression of 11beta-HSD1, leptin, adiponectin, and phosphoenolpyruvate carboxykinase (PEPCK) mRNA was evaluated with real-time PCR. Serum leptin and adiponectin protein levels were estimated by ELISA.

RESULTS

Two years after gastric bypass surgery, significant reductions were observed in the mean body mass index (from 44.4 to 30.8 kg/m(2)) and mean waist circumference (from 121.9 to 90.6 cm). After weight loss, 11beta-HSD1 mRNA expression decreased 4-fold (P < 0.001). Both leptin and adiponectin mRNA expression decreased, with concomitantly decreased circulating leptin and increased circulating adiponectin levels. PEPCK mRNA expression did not change.

CONCLUSION

Weight loss after gastric bypass surgery was followed by metabolically favorable changes in insulin sensitivity, circulating leptin and adiponectin, and peripheral glucocorticoid metabolism. A significant reduction in 11beta-HSD1 expression was observed in sc adipose tissue after weight loss. This suggests that up-regulation of 11beta-HSD1 is a consequence, rather than a cause, of obesity.

Chronic rapamycin treatment causes glucose intolerance and hyperlipidemia by upregulating hepatic gluconeogenesis and impairing lipid deposition in adipose tissue

OBJECTIVE

The mammalian target of rapamycin (mTOR)/p70 S6 kinase 1 (S6K1) pathway is a critical signaling component in the development of obesity-linked insulin resistance and operates a nutrient-sensing negative feedback loop toward the phosphatidylinositol 3-kinase (PI 3-kinase)/Akt pathway. Whereas acute treatment of insulin target cells with the mTOR complex 1 (mTORC1) inhibitor rapamycin prevents nutrient-induced insulin resistance, the chronic effect of rapamycin on insulin sensitivity and glucose metabolism in vivo remains elusive.

RESEARCH DESIGN AND METHODS

To assess the metabolic effects of chronic inhibition of the mTORC1/S6K1 pathway, rats were treated with rapamycin (2 mg/kg/day) or vehicle for 15 days before metabolic phenotyping.

RESULTS

Chronic rapamycin treatment reduced adiposity and fat cell number, which was associated with a coordinated downregulation of genes involved in both lipid uptake and output. Rapamycin treatment also promoted insulin resistance, severe glucose intolerance, and increased gluconeogenesis. The latter was associated with elevated expression of hepatic gluconeogenic master genes, PEPCK and G6Pase, and increased expression of the transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) as well as enhanced nuclear recruitment of FoxO1, CRTC2, and CREB. These changes were observed despite normal activation of the insulin receptor substrate/PI 3-kinase/Akt axis in liver of rapamycin-treated rats, as expected from the blockade of the mTORC1/S6K1 negative feedback loop.

CONCLUSIONS

These findings unravel a novel mechanism by which mTORC1/S6K1 controls gluconeogenesis through modulation of several key transcriptional factors. The robust induction of the gluconeogenic program in liver of rapamycin-treated rats underlies the development of severe glucose intolerance even in the face of preserved hepatic insulin signaling to Akt and despite a modest reduction in adiposity.

Aryl hydrocarbon receptor (AHR)-regulated transcriptomic changes in rats sensitive or resistant to major dioxin toxicities

BACKGROUND

The major toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) appear to result from dysregulation of mRNA levels mediated by the aryl hydrocarbon receptor (AHR). Dioxin-like chemicals alter expression of numerous genes in liver, but it remains unknown which lie in pathways leading to major toxicities such as hepatotoxicity, wasting and lethality. To identify genes involved in these responses we exploited a rat genetic model. Rats expressing an AHR splice-variant lacking a portion of the transactivation domain are highly resistant to dioxin-induced toxicities. We examined changes in hepatic mRNA abundances 19 hours after TCDD treatment in two dioxin-resistant rat strains/lines and two dioxin-sensitive rat strains/lines.

RESULTS

Resistant rat strains/lines exhibited fewer transcriptional changes in response to TCDD than did rats with wildtype AHR. However, well-known AHR-regulated and dioxin-inducible genes such as CYP1A1, CYP1A2, and CYP1B1 remained fully responsive to TCDD in all strains/lines. Pathway analysis indicated that the genes which respond differently to TCDD between sensitive and resistant rats are mainly involved in lipid metabolism, cellular membrane function and energy metabolism. These pathways previously have been shown to respond differently to dioxin treatment in dioxin-sensitive versus dioxin-resistant rats at a biochemical level and in the differential phenotype of toxicologic responses.

CONCLUSION

The transactivation-domain deletion in dioxin-resistant rats does not abolish global AHR transactivational activity but selectively interferes with expression of subsets of genes that are candidates to mediate or protect from major dioxin toxicities such as hepatotoxicity, wasting and death.

Obesity and corticosteroids: 11beta-hydroxysteroid type 1 as a cause and therapeutic target in metabolic disease

The metabolic abnormalities found associated with high blood glucocorticoid levels (e.g. rare Cushing's syndrome) include insulin-resistance, visceral obesity, hypertension, dyslipidaemia and an increased risk of cardiovascular diseases. The same constellation of abnormalities is found in the highly prevalent idiopathic obesity/insulin-resistance (metabolic)-syndrome. It is now apparent that tissue-specific changes in cortisol metabolism explain these parallels rather than altered blood cortisol levels. Primary among these changes is increased intracellular glucocorticoid reactivation, catalysed by the enzyme 11beta-hydroxysteroid dehydrogenase type (HSD)-1 in obese adipose tissue. Liver, skeletal muscle, endocrine pancreas, blood vessels and leukocytes express 11beta-HSD1 and their potential role in metabolic disease is discussed. The weight of evidence, much of it gained from animal models, suggests that therapeutic inhibition of 11beta-HSD1 will be beneficial in most cellular contexts, with clinical trials supportive of this concept.

11beta-hydroxysteroid dehydrogenase type 1 regulates glucocorticoid-induced insulin resistance in skeletal muscle

OBJECTIVE

Glucocorticoid excess is characterized by increased adiposity, skeletal myopathy, and insulin resistance, but the precise molecular mechanisms are unknown. Within skeletal muscle, 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) converts cortisone (11-dehydrocorticosterone in rodents) to active cortisol (corticosterone in rodents). We aimed to determine the mechanisms underpinning glucocorticoid-induced insulin resistance in skeletal muscle and indentify how 11beta-HSD1 inhibitors improve insulin sensitivity.

RESEARCH DESIGN AND METHODS

Rodent and human cell cultures, whole-tissue explants, and animal models were used to determine the impact of glucocorticoids and selective 11beta-HSD1 inhibition upon insulin signaling and action.

RESULTS

Dexamethasone decreased insulin-stimulated glucose uptake, decreased IRS1 mRNA and protein expression, and increased inactivating pSer(307) insulin receptor substrate (IRS)-1. 11beta-HSD1 activity and expression were observed in human and rodent myotubes and muscle explants. Activity was predominantly oxo-reductase, generating active glucocorticoid. A1 (selective 11beta-HSD1 inhibitor) abolished enzyme activity and blocked the increase in pSer(307) IRS1 and reduction in total IRS1 protein after treatment with 11DHC but not corticosterone. In C57Bl6/J mice, the selective 11beta-HSD1 inhibitor, A2, decreased fasting blood glucose levels and improved insulin sensitivity. In KK mice treated with A2, skeletal muscle pSer(307) IRS1 decreased and pThr(308) Akt/PKB increased. In addition, A2 decreased both lipogenic and lipolytic gene expression.

CONCLUSIONS

Prereceptor facilitation of glucocorticoid action via 11beta-HSD1 increases pSer(307) IRS1 and may be crucial in mediating insulin resistance in skeletal muscle. Selective 11beta-HSD1 inhibition decreases pSer(307) IRS1, increases pThr(308) Akt/PKB, and decreases lipogenic and lipolytic gene expression that may represent an important mechanism underpinning their insulin-sensitizing action.

Obesity is accompanied by disturbances in peripheral glucocorticoid metabolism and changes in FA recycling

The glucocorticoid activating enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) is of major interest in obesity-related morbidity. Alterations in tissue-specific cortisol levels may influence lipogenetic and gluco/glyceroneogenetic pathways in fat and liver. We analyzed the expression and activity of 11betaHSD1 as well as the expression of phosphoenolpyruvate carboxykinase (PEPCK), sterol regulatory element binding protein (SREBP), and fatty acid synthase (FAS) in adipose and liver and investigated putative associations between 11betaHSD1 and energy metabolism genes. A total of 33 obese women (mean BMI 44.6) undergoing gastric bypass surgery were enrolled. Subcutaneous adipose tissue (SAT), omental fat (omental adipose tissue (OmAT)), and liver biopsies were collected during the surgery. 11betaHSD1 gene expression was higher in SAT vs. OmAT (P = 0.013), whereas the activity was higher in OmAT (P = 0.009). The SAT 11betaHSD1 correlated with waist circumference (P = 0.045) and was an independent predictor for the OmAT area in a linear regression model. Energy metabolism genes had AT depot-specific expression; higher leptin and SREBP in SAT than OmAT, but higher PEPCK in OmAT than SAT. The expression of 11betaHSD1 correlated with PEPCK in both AT depots (P = 0.05 for SAT and P = 0.0001 for OmAT). Hepatic 11betaHSD1 activity correlated negatively with abdominal adipose area (P = 0.002) and expression positively with PEPCK (P = 0.003). In human obesity, glucocorticoid regeneration in the SAT is associated with central fat accumulation indicating that the importance of this specific fat depot is underestimated. Central fat accumulation is negatively associated with hepatic 11betaHSD1 activity. A disturbance in peripheral glucocorticoid metabolism is associated with changes in genes involved in fatty acid (FA) recycling in adipose tissue (AT).

Antidiabetic effects of 11beta-HSD1 inhibition in a mouse model of combined diabetes, dyslipidaemia and atherosclerosis

AIM

11 beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) is considered to contribute to the aetiology of the metabolic syndrome, and specific inhibitors have begun to emerge as treatments for insulin resistance and other facets of the syndrome, including atherosclerosis. Given the role of glucocorticoids and 11beta-HSD1 in the anti-inflammatory response and the involvement of inflammation in the development of atherosclerosis, 11beta-HSD1 inhibition may exacerbate atherosclerosis. Our aim was to investigate in vivo the effects of a specific 11beta-HSD1 inhibitor (2922) on atherosclerosis while assessing glucose homeostasis.

METHODS

We conducted a 12-week study administering 2922 (at three doses, 3, 10 and 100 mg/kg body weight) in Ldlr 3KO (Ldlr(-/-)Apob(100/100)Lep(ob/ob)) mice, a genetic model of obesity, insulin resistance, dyslipidaemia and atherosclerosis. Rosiglitazone and simvastatin were used to test the responsiveness of our model in both types of therapy.

RESULTS

2922 was effective in reducing 11beta-HSD1 activity in inguinal adipose tissue (>90% for 100 mg/kg) and was efficacious in improving glucose homeostasis at doses > or =10 mg/kg. Plasma insulin, blood glucose, glucose tolerance and homeostatic model assessment indices were all improved in mice treated with 2922 (100 mg/kg) compared with control animals. Despite an improvement in these parameters, no differences were observed in body weight, adipose or lean tissue masses in the 2922-treated mice. Interestingly, circulating lipids, proinflammatory cytokines and atherosclerosis were unaltered in response to 2922, although a small reduction in LDL cholesterol was detected.

CONCLUSIONS

Importantly, 11beta-HSD1 inhibition leads to improved glucose metabolism and does not result in a worsening of atherosclerotic lesion area, yet retained antidiabetic potential in the face of multiple severe metabolic aberrations. This study reinforces the potential use of 11beta-HSD1 inhibitors in patients with the metabolic syndrome without negatively impacting atherosclerosis.

Therapeutic manipulation of glucocorticoid metabolism in cardiovascular disease

The therapeutic potential for manipulation of glucocorticoid metabolism in cardiovascular disease was revolutionized by the recognition that access of glucocorticoids to their receptors is regulated in a tissue-specific manner by the isozymes of 11beta-hydroxysteroid dehydrogenase. Selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 have been shown recently to ameliorate cardiovascular risk factors and inhibit the development of atherosclerosis. This article addresses the possibility that inhibition of 11beta-hydroxsteroid dehydrogenase type 1 activity in cells of the cardiovascular system contributes to this beneficial action. The link between glucocorticoids and cardiovascular disease is complex as glucocorticoid excess is linked with increased cardiovascular events but glucocorticoid administration can reduce atherogenesis and restenosis in animal models. There is considerable evidence that glucocorticoids can interact directly with cells of the cardiovascular system to alter their function and structure and the inflammatory response to injury. These actions may be regulated by glucocorticoid and/or mineralocorticoid receptors but are also dependent on the 11beta-hydroxysteroid dehydrogenases which may be expressed in cardiac, vascular (endothelial, smooth muscle) and inflammatory (macrophages, neutrophils) cells. The activity of 11beta-hydroxysteroid dehydrogenases in these cells is dependent upon differentiation state, the action of pro-inflammaotory cytokines and the influence of endogenous inhibitors (oxysterols, bile acids). Further investigations are required to clarify the link between glucocorticoid excess and cardiovascular events and to determine the mechanism through which glucocorticoid treatment inhibits atherosclerosis/restenosis. This will provide greater insights into the potential benefit of selective 11beta-hydroxysteroid dehydrogenase inhibitors in treatment of cardiovascular disease.

Tissue-specific postprandial clearance is the major determinant of PPARgamma-induced triglyceride lowering in the rat

Peroxisome proliferator-activated receptor-gamma (PPARgamma) agonism potently reduces circulating triglycerides (TG) in rodents and more modestly so in humans. This study aimed to quantify in vivo the relative contribution of hepatic VLDL-TG secretion and tissue-specific TG clearance to such action. Rats were fed an obesogenic diet, treated with the PPARgamma full agonist COOH (30 mg.kg(-1).day(-1)) for 3 wk, and studied in both the fasted and refed (fat-free) states. Hepatic VLDL-TG secretion rate was not affected by chronic COOH in the fasted state and was only modestly decreased (-30%) in refed rats. In contrast, postprandial VLDL-TG clearance was increased 2.6-fold by COOH, which concomitantly stimulated adipose tissue TG-derived lipid uptake and one of its major determinants, lipoprotein lipase (LPL) activity, in a highly depot-specific manner. TG-derived lipid uptake and LPL were indeed strongly increased in subcutaneous inguinal white adipose tissue and in brown adipose tissue, independently of the nutritional state, whereas of the three visceral fat depots examined (epididymal, retroperitoneal, mesenteric) only the latter responded consistently to COOH. Robust correlations (0.5 < r < 0.9) were observed between TG-derived lipid uptake and LPL in adipose tissues. The agonist did not increase LPL in muscle, and its enhancing action on postprandial muscle lipid uptake appeared to be mediated by post-LPL processes involving increased expression of fatty acid binding/transport proteins (aP2, likely in infiltrated adipocytes, FAT/CD36, and FATP-1). The study establishes in a diet-induced obesity model the major contribution of lipid uptake by specific, metabolically safe adipose depots to the postprandial hypotriglyceridemic action of PPARgamma agonism, and suggests a key role for LPL therein.

Impaired glucose tolerance and insulin resistance are associated with increased adipose 11beta-hydroxysteroid dehydrogenase type 1 expression and elevated hepatic 5alpha-reductase activity

OBJECTIVE

The precise molecular mechanisms contributing to the development of insulin resistance, impaired glucose tolerance (IGT), and type 2 diabetes are largely unknown. Altered endogenous glucocorticoid metabolism, including 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), which generates active cortisol from cortisone, and 5alpha-reductase (5alphaR), which inactivates cortisol, has been implicated.

RESEARCH DESIGN AND METHODS

A total of 101 obese patients (mean age 48 +/- 7 years, BMI 34.4 +/- 4.3 kg/m(2), 66 women, 35 men) underwent 75-g oral glucose tolerance testing (OGTT), body composition analysis (dual-energy X-ray absorptiometry), assessment of glucocorticoid metabolism (24-h urine steroid metabolite analysis by gas chromatography/mass spectrometry), and subcutaneous abdominal adipose tissue biopsies.

RESULTS

A total of 22.7% of women had IGT compared with 34.2% of men. Two women and five men were diagnosed with type 2 diabetes. In women, adipose 11beta-HSD1 expression was increased in patients with IGT and correlated with glucose levels across the OGTT (R = 0.44, P < 0.001) but was independent of fat mass. Total glucocorticoid secretion was higher in men with and without IGT (normal 13,743 +/- 863 vs. 7,453 +/- 469 microg/24 h, P < 0.001; IGT 16,871 +/- 2,113 vs. 10,133 +/- 1,488 microg/24 h, P < 0.05), and in women, it was higher in those with IGT (7,453 +/- 469 vs. 10,133 +/- 1,488 microg/24 h, P < 0.001). In both sexes, 5alphaR activity correlated with fasting insulin (men R = 0.53, P = 0.003; women R = 0.33, P = 0.02), insulin secretion across an OGTT (men R = 0.46, P = 0.01; women R = 0.40, P = 0.004), and homeostasis model assessment of insulin resistance (men R = 0.52, P = 0.004; women R = 0.33, P = 0.02).

CONCLUSIONS

Increased adipose 11beta-HSD1 expression in women may contribute to glucose intolerance. Enhanced 5alphaR activity in both sexes is associated with insulin resistance but not body composition. Augmented glucocorticoid inactivation may serve as a compensatory, protective mechanism to preserve insulin sensitivity.

Reduced glucocorticoid production rate, decreased 5alpha-reductase activity, and adipose tissue insulin sensitization after weight loss

OBJECTIVE

The epidemics of obesity, insulin resistance, and type 2 diabetes have heightened the need to understand mechanisms that contribute to their pathogenesis. Increased endogenous glucocorticoid production has been implicated based on parallels with Cushing's syndrome. We have assessed the impact of weight loss on glucocorticoid secretion and metabolism (notably 11beta-hydroxysteroid dehydrogenase type 1 and 5alpha-reductase [5alphaR] activity) and insulin sensitivity.

RESEARCH DESIGN AND METHODS

Twenty obese volunteers were investigated before and after weight loss. Patients underwent hyperinsulinemic-euglycemic clamps with simultaneous adipose microdialysis and oral cortisone acetate administration. Changes in glucocorticoid secretion and metabolism were assessed using 24-h urine collections.

RESULTS

Before weight loss, fat mass correlated with glucocorticoid secretion rate (total fat, r = 0.46, P < 0.05; trunk fat, r = 0.52, P < 0.05); however, glucocorticoid secretion rate was inversely related to insulin sensitivity (r = -0.51, P < 0.05). Hyperinsulinemia failed to suppress adipose tissue interstitial fluid glycerol release (180 +/- 50 micromol [basal] vs. 153 +/- 10 micromol [steady state], NS). After oral cortisone (25 mg), cortisol concentrations within adipose interstitial fluid increased (4.3 +/- 1.1 vs. 14.2 +/- 2.6 nmol/l, P < 0.01), but glycerol concentrations did not change. After weight loss, insulin sensitivity increased. Consistent with insulin sensitization, adipose tissue interstitial fluid glycerol concentrations fell under hyperinsulinemic conditions (186 +/- 16 vs. 117 +/- 9 micromol, P < 0.05). Glucocorticoid secretion decreased (11,751 +/- 1,520 vs. 7,464 +/- 937 microg/24 h, P < 0.05) as did 5alphaR activity (5alpha-tetrahydrocortisol-to-tetrahydrocortisol ratio 1.41 +/- 0.16 vs. 1.12 +/- 0.17, P < 0.005).

CONCLUSIONS

Obesity is associated with insulin resistance within adipose tissue and increased cortisol secretion rates; both are reversed with weight loss. Reduced 5alphaR activity after weight loss may decrease hypothalamo-pituitary-adrenal axis activation and reduce glucocorticoid metabolite production.