Tissue-specific dysregulation of cortisol regeneration by 11βHSD1 in obesity: has it promised too much?

The Role of microRNA in the Regulation of Cortisol Metabolism in the Adipose Tissue in the Course of Obesity

The similarity of the clinical picture of metabolic syndrome and hypercortisolemia supports the hypothesis that obesity may be associated with impaired expression of genes related to cortisol action and metabolism in adipose tissue. The expression of genes encoding the glucocorticoid receptor alpha (GR), cortisol metabolizing enzymes (HSD11B1, HSD11B2, H6PDH), and adipokines, as well as selected microRNAs, was measured by real-time PCR in adipose tissue from 75 patients with obesity, 19 patients following metabolic surgery, and 25 normal-weight subjects. Cortisol levels were analyzed by LC-MS/MS in 30 pairs of tissues. The mRNA levels of all genes studied were significantly (p < 0.05) decreased in the visceral adipose tissue (VAT) of patients with obesity and normalized by weight loss. In the subcutaneous adipose tissue (SAT), GR and HSD11B2 were affected by this phenomenon. Negative correlations were observed between the mRNA levels of the investigated genes and selected miRNAs (hsa-miR-142-3p, hsa-miR-561, and hsa-miR-579). However, the observed changes did not translate into differences in tissue cortisol concentrations, although levels of this hormone in the SAT of patients with obesity correlated negatively with mRNA levels for adiponectin. In conclusion, although the expression of genes related to cortisol action and metabolism in adipose tissue is altered in obesity and miRNAs may be involved in this process, these changes do not affect tissue cortisol concentrations.

Age-related increase in the expression of 11β-hydroxysteroid dehydrogenase type 1 in the hippocampus of male rhesus macaques

Introduction

The hippocampus is especially susceptible to age-associated neuronal pathologies, and there is concern that the age-associated rise in cortisol secretion from the adrenal gland may contribute to their etiology. Furthermore, because 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1) catalyzes the reduction of cortisone to the active hormone cortisol, it is plausible that an increase in the expression of this enzyme enhances the deleterious impact of cortisol in the hippocampus and contributes to the neuronal pathologies that underlie cognitive decline in the elderly.

Methods

Rhesus macaques were used as a translational animal model of human aging, to examine age-related changes in gene and protein expressions of (HSD11B1/HSD11B1) in the hippocampus, a region of the brain that plays a crucial role in learning and memory.

Results

Older animals showed significantly (p < 0.01) higher base-line cortisol levels in the circulation. In addition, they showed significantly (p < 0.05) higher hippocampal expression of HSD11B1 but not NR3C1 and NR3C2 (i.e., two receptor-encoding genes through which cortisol exerts its physiological actions). A similar age-related significant (p < 0.05) increase in the expression of the HSD11B1 was revealed at the protein level by western blot analysis.

Discussion

The data suggest that an age-related increase in the expression of hippocampal HSD11B1 is likely to raise cortisol concentrations in this cognitive brain area, and thereby contribute to the etiology of neuropathologies that ultimately lead to neuronal loss and dementia. Targeting this enzyme pharmacologically may help to reduce the negative impact of elevated cortisol concentrations within glucocorticoid-sensitive brain areas and thereby afford neuronal protection.

Editorial: Liver hypercortisolism as a potential target for MASH treatment

This article is linked to Kim et al papers. To view these articles, visit https://doi.org/10.1111/apt.17726 and https://doi.org/10.1111/apt.17780

Assessment of steroid enzymes action in children and adolescents with obesity

Rising prevalence of obesity has become an important impulse to investigate basic mechanisms involved in regulating the energy balance. It is widely accepted that steroids are potent factors affecting glucose, fat, and protein metabolism. Our study was aimed to analyze differences in the total amount of selected enzymes implicated in steroid metabolism in a group of children suffering from obesity and those with normal weight, further subdivided according to sex and pubertal stage. Data were obtained from 187 Caucasian children and adolescents, including 113 patients (63 girls, 50 boys) with obesity and 74 (34 girls, 40 boys) normal weight volunteers. Standard clinical examinations were performed in both groups. To evaluate the impact of puberty, preadolescent children and those with advanced puberty were assessed separately. Urine steroid excretion profiles were analyzed using gas chromatography/mass spectrometry method. Children with obesity revealed several changes in in the total amount of steroid enzymes as assessed by the relevant metabolite proportions, compared to their norm weight peers. Girls showed a significant increase in the activity of 11βHSD1, while boys demonstrated a relevant elevation in 20αHSD action. Regardless of sex, children with obesity showed an increase in the activity of 5β-reductase + 3αHSD complex and a decrease in the involvement of 11βOH-lase. The effect is attenuated when consider pre- and pubertal subgroups. We hypothesize that changes in the activity levels of selected enzymes may be a compensatory mechanism to limit the glucocorticoid exposure of key target tissues as well as to improve metabolic control and reduce long-term complications of obesity.

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.

High-resolution daily profiles of tissue adrenal steroids by portable automated collection

Rhythms are intrinsic to endocrine systems, and disruption of these hormone oscillations occurs at very early stages of the disease. Because adrenal hormones are secreted with both circadian and ultradian periods, conventional single-time point measurements provide limited information about rhythmicity and, crucially, do not provide information during sleep, when many hormones fluctuate from nadir to peak concentrations. If blood sampling is attempted overnight, then this necessitates admission to a clinical research unit, can be stressful, and disturbs sleep. To overcome this problem and to measure free hormones within their target tissues, we used microdialysis, an ambulatory fraction collector, and liquid chromatography-tandem mass spectrometry to obtain high-resolution profiles of tissue adrenal steroids over 24 hours in 214 healthy volunteers. For validation, we compared tissue against plasma measurements in a further seven healthy volunteers. Sample collection from subcutaneous tissue was safe, well tolerated, and allowed most normal activities to continue. In addition to cortisol, we identified daily and ultradian variation in free cortisone, corticosterone, 18-hydroxycortisol, aldosterone, tetrahydrocortisol and allo-tetrahydrocortisol, and the presence of dehydroepiandrosterone sulfate. We used mathematical and computational methods to quantify the interindividual variability of hormones at different times of the day and develop "dynamic markers" of normality in healthy individuals stratified by sex, age, and body mass index. Our results provide insight into the dynamics of adrenal steroids in tissue in real-world settings and may serve as a normative reference for biomarkers of endocrine disorders (ULTRADIAN, NCT02934399).

Safety, tolerability, pharmacodynamics and pharmacokinetics following once-daily doses of BI 187004, an inhibitor of 11 beta-hydroxysteroid dehydrogenase-1, over 28 days in patients with type 2 diabetes mellitus and overweight or obesity

AIMS

To study the oral 11 beta-hydroxysteroid dehydrogenase-1 (11β-HSD1) inhibitor BI 187004 (NCT02150824), as monotherapy and in combination with metformin, versus placebo in patients with type 2 diabetes mellitus (T2DM) affected by overweight or obesity.

MATERIALS AND METHODS

This Phase II, randomized controlled trial investigated multiple rising doses of BI 187004 as monotherapy (Arm 1: 20, 80 or 240 mg) and in combination with metformin (Arm 2: 240 mg), in adults with T2DM and a body mass index of 28-40 kg/m² .

RESULTS

In total, 103 patients (Arm 1: n = 62, Arm 2: n = 41) were included in this study. BI 187004 was rapidly absorbed and exposure increased approximately dose-dependently. Target engagement of 11β-HSD1 was observed with near-full inhibition of 11β-HSD1 in the liver [decreased (5α-tetrahydrocortisol + 5β-tetrahydrocortisol)/tetrahydrocortisone ratio]; hypothalamic-pituitary-adrenal axis activation was also seen (increased total urinary corticosteroids). No clinically relevant changes from baseline with BI 187004 treatment were observed for bodyweight or meal tolerance test parameters, or in most efficacy endpoints testing glucose and lipid metabolism; a significant increase was observed in weighted mean plasma glucose (p < .05 for 80 and 240 mg BI 187004) but not fasting plasma glucose. Drug-related adverse events were reported for 14 patients (22.6%) in Arm 1 and 10 patients (24.4%) in Arm 2, most frequently headache, diarrhoea, flushing and dizziness. A dose-dependent increase in heart rate was seen with BI 187004 treatment.

CONCLUSIONS

BI 187004 was generally well tolerated in patients with T2DM. Despite complete 11β-HSD1 inhibition, no clinically relevant effects were observed with BI 187004.

Selective Inhibition of 11beta-Hydroxysteroiddehydrogenase-1 with BI 187004 in Patients with Type 2 Diabetes and Overweight or Obesity: Safety, Pharmacokinetics, and Pharmacodynamics After Multiple Dosing Over 14 Days

OBJECTIVE

To assess safety, tolerability, pharmacokinetics, and pharmacodynamics of treatment with the selective 11beta-hydroxysteroid dehydrogenase-1 (11beta-HSD1) inhibitor BI 187004 in male and female patients with type 2 diabetes and overweight or obesity.

METHODS

Randomized, double-blind, parallel-group, placebo-controlled multiple rising dose study, with 10-360 mg BI 187004 once daily over 14 days in 71 patients. Assessments included 11beta-HSD1 inhibition in the liver and subcutaneous adipose tissue ex vivo (clinical trial registry number NCT01874483).

RESULTS

BI 187004 was well tolerated and safe in all tested dose groups. The incidence of drug-related adverse events was 51.8% (n=29) for BI 187004 and 35.7% (n=5) for placebo. There were no clinically relevant deviations in laboratory or electrocardiogram parameters besides one patient on 360 mg discontinuing treatment due to moderate supraventricular tachycardia.BI 187004 was rapidly absorbed within 2 h; exposure increased non-proportionally. The oral clearance was low, apparent volume of distribution was moderate to large, and terminal half-life with 106-124 h was rather long. Urinary tetrahydrocortisol/tetrahydrocortisone ratio decreased, indicating liver 11beta-HSD1 inhibition. Median inhibition of 11beta-HSD1 in subcutaneous adipose tissue biopsies was 87.9-99.4% immediately after the second dose and 73.8-97.5% 24 h after the last dose of BI 187004.

CONCLUSIONS

BI 187004 was safe and well tolerated over 14 days and could be dosed once daily. Targeted 11beta-HSD1 enzyme inhibition of≥80% could be shown for BI 187004 doses≥40 mg. This dose should be targeted in further studies to test blood glucose lowering in patients with type 2 diabetes and overweight or obesity.

Vertical sleeve gastrectomy normalizes circulating glucocorticoid levels and lowers glucocorticoid action tissue-selectively in mice

Objectives

Glucocorticoids produced by the adrenal cortex are essential for the maintenance of metabolic homeostasis. Glucocorticoid activation is catalysed by 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1). Excess glucocorticoids are associated with insulin resistance and hyperglycaemia. A small number of studies have demonstrated effects on glucocorticoid metabolism of bariatric surgery, a group of gastrointestinal procedures known to improve insulin sensitivity and secretion, which were assumed to result from weight loss. In this study, we hypothesize that a reduction in glucocorticoid action following bariatric surgery contributes to the widely observed euglycemic effects of the treatment.

Methods

Glucose and insulin tolerance tests were performed at ten weeks post operatively and circulating corticosterone was measured. Liver and adipose tissues were harvested from fed mice and 11β-HSD1 levels were measured by quantitative RT-PCR or Western (immuno-) blotting, respectively. 11β-HSD1 null mice (Hsd11b1 -/-) were generated using CRISPR/Cas9 genome editing. Wild type and littermate Hsd11b1 -/- mice underwent Vertical Sleeve Gastrectomy (VSG) or sham surgery.

Results

Under the conditions used, no differences in weight loss were observed between VSG treated and sham operated mice. However, both lean and obese WT VSG mice displayed significantly improved glucose clearance and insulin sensitivity. Remarkably, VSG restored physiological corticosterone production in HFD mice and reduced 11β-HSD1 expression in liver and adipose tissue post-surgery. Elimination of the 11β-HSD1/Hsd11b1 gene by CRISPR/Cas9 mimicked the effects of VSG on body weight and tolerance to 1g/kg glucose challenge. However, at higher glucose loads, the euglycemic effect of VSG was superior to Hsd11b1 elimination.

Conclusions

Bariatric surgery improves insulin sensitivity and reduces glucocorticoid activation at the tissular level, under physiological and pathophysiological (obesity) conditions, irrespective of weight loss. These findings point towards a physiologically relevant gut-glucocorticoid axis, and suggest that lowered glucocorticoid exposure may represent an additional contribution to the health benefits of bariatric surgery.

Zebrafish: A New Promise to Study the Impact of Metabolic Disorders on the Brain

Zebrafish has become a popular model to study many physiological and pathophysiological processes in humans. In recent years, it has rapidly emerged in the study of metabolic disorders, namely, obesity and diabetes, as the regulatory mechanisms and metabolic pathways of glucose and lipid homeostasis are highly conserved between fish and mammals. Zebrafish is also widely used in the field of neurosciences to study brain plasticity and regenerative mechanisms due to the high maintenance and activity of neural stem cells during adulthood. Recently, a large body of evidence has established that metabolic disorders can alter brain homeostasis, leading to neuro-inflammation and oxidative stress and causing decreased neurogenesis. To date, these pathological metabolic conditions are also risk factors for the development of cognitive dysfunctions and neurodegenerative diseases. In this review, we first aim to describe the main metabolic models established in zebrafish to demonstrate their similarities with their respective mammalian/human counterparts. Then, in the second part, we report the impact of metabolic disorders (obesity and diabetes) on brain homeostasis with a particular focus on the blood-brain barrier, neuro-inflammation, oxidative stress, cognitive functions and brain plasticity. Finally, we propose interesting signaling pathways and regulatory mechanisms to be explored in order to better understand how metabolic disorders can negatively impact neural stem cell activity.

Inhibition of 11β-Hydroxysteroid dehydrogenase-1 with AZD4017 in patients with nonalcoholic steatohepatitis or nonalcoholic fatty liver disease: A randomized, double-blind, placebo-controlled, phase II study

AIM

To evaluate whether short-term treatment with a selective 11β-Hydroxysteroid dehydrogenase-1 (11β-HSD1) inhibitor, AZD4017, would block hepatic cortisol production and thereby decrease hepatic fat in patients with nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH), with or without type 2 diabetes (T2D).

MATERIALS AND METHODS

This was a randomized, double-blind, placebo-controlled, phase 2 study conducted at two sites. Key inclusion criteria were the presence of NAFLD or NASH on magnetic resonance imaging (MRI) or recent biopsy positive for NASH. Enrolled patients were randomly assigned (1:1) to AZD4017 or placebo for 12 weeks. Primary outcomes were between-group differences in mean change from baseline to week 12 in liver fat fraction (LFF) and conversion of ¹³ C cortisone to ¹³ C cortisol in the liver.

RESULTS

A total of 93 patients were randomized; 85 patients completed treatment. The mean (standard deviation [SD]) change in LFF was -0.667 (5.246) and 0.139 (4.323) in the AZD4017 and placebo groups (P = 0.441). For patients with NASH and T2D, the mean (SD) change in LFF was significantly improved in the AZD4017 versus the placebo group (-1.087 [5.374] vs. 1.675 [3.318]; P = 0.033). Conversion of ¹³ C cortisone to ¹³ C cortisol was blocked in all patients in the AZD4017 group. There were no significant between-group differences (AZD4017 vs. placebo) in changes in fibrosis, weight, levels of liver enzymes or lipids, or insulin sensitivity.

CONCLUSION

Although the study did not meet one of the primary outcomes, AZD4017 blocked the conversion of ¹³ C cortisone to ¹³ C cortisol in the liver in all patients who received the drug. In patients with NASH and T2D, AZD4017 improved liver steatosis versus placebo.

Safety, tolerability, pharmacokinetics and pharmacodynamics of single oral doses of BI 187004, an inhibitor of 11beta-hydroxysteroid dehydrogenase-1, in healthy male volunteers with overweight or obesity

BACKGROUND

The study characterizes safety, tolerability, pharmacokinetic and pharmacodynamic profiles of single rising doses of the 11beta-hydroxysteroid dehydrogenase-1 (11beta-HSD1) inhibitor BI 187004 in healthy men with overweight or obesity.

METHODS

This was a randomized, double-blind, parallel group, placebo-controlled study with administration of 2.5-360 mg BI 187004 or placebo once daily as single dose in 72 healthy male volunteers with overweight or obesity. Assessments included 11beta-HSD1 inhibition in the liver (assessed indirectly by urinary tetrahydrocortisol/tetrahydrocortisone ratio) and in subcutaneous adipose tissue ex vivo and determination of hypothalamus-pituitary-adrenal axis hormones.

RESULTS

BI 187004 was well tolerated and safe in all tested dose groups. The incidence of drug-related adverse events was 16.7% (n = 9) for all 9 BI 187004 dose groups and 5.9% (n = 1) for placebo. All treatment groups were similar concerning kind and intensity of adverse events. No clinically relevant deviations in clinical laboratory or ECG parameters were reported. Exposure of BI 187004 increased non-proportionally over the entire dose range tested. The geometric mean apparent terminal half-life decreased from 33.5 h (5 mg) to 14.5 h (160 mg) remaining stable up to 360 mg. Renal excretion of BI 187004 was low (3-5%). Urinary tetrahydrocortisol/tetrahydrocortisone ratio decreased, indicating liver 11beta-HSD1 inhibition. Median inhibition of 11beta-HSD1 in subcutaneous adipose tissue biopsies following single dosing ranged from 86.8% (10 mg) to 99.5% (360 mg) after 10 h and from 59.4% (10 mg) to 98.6% (360 mg) after 24 h.

CONCLUSIONS

BI 187004 as single dose was safe and well tolerated and is suitable for once daily dosing. There was significant, sustained 11beta-HSD1 inhibition in liver and adipose tissue.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01587417 , registered on 26-Apr-2012.

Novel 2-(Adamantan-1-ylamino)Thiazol-4(5H)-One Derivatives and Their Inhibitory Activity towards 11β-HSD1-Synthesis, Molecular Docking and In Vitro Studies

A common mechanism in which glucocorticoids participate is suggested in the pathogenesis of such metabolic diseases as obesity, metabolic syndrome, or Cushing’s syndrome. The enzyme involved in the control of the availability of cortisol, the active form of the glucocorticoid for the glucocorticoid receptor, is 11β-HSD1. Inhibition of 11β-HSD1 activity may bring beneficial results for the alleviation of the course of metabolic diseases such as metabolic syndrome, Cushing’s syndrome or type 2 diabetes. In this work, we obtained 10 novel 2-(adamantan-1-ylamino)thiazol-4(5H)-one derivatives containing different substituents at C-5 of thiazole ring and tested their activity towards inhibition of two 11β-HSD isoforms. For most of them, over 50% inhibition of 11β-HSD1 and less than 45% inhibition of 11β-HSD2 activity at the concentration of 10 µM was observed. The binding energies found during docking simulations for 11β-HSD1 correctly reproduced the experimental IC₅₀ values for analyzed compounds. The most active compound 2-(adamantan-1-ylamino)-1-thia-3-azaspiro[4.5]dec-2-en-4-one (3i) inhibits the activity of isoform 1 by 82.82%. This value is comparable to the known inhibitor-carbenoxolone. The IC₅₀ value is twice the value determined by us for carbenoxolone, however inhibition of the enzyme isoform 2 to a lesser extent makes it an excellent material for further tests.

Variants in HSD11B1 gene modulate susceptibility to diabetes kidney disease and to insulin resistance in type 1 diabetes

BACKGROUND AND AIM

11β-Hydroxysteroid dehydrogenase 1 has been implicated in insulin resistance (IR) in the setting of metabolic disorders, and single nucleotide polymorphisms (SNPs) in its encoding gene (HSD11B1) have been associated with type 2 diabetes and metabolic syndrome. In type 1 diabetes (T1D), IR has been related to the development of chronic complications. We investigated the association of HSD11B1 SNPs with microvascular complications and with IR in a Brazilian cohort of T1D individuals.

MATERIALS AND METHODS

Five SNPs were genotyped in 466 T1D individuals (57% women; median of 37 years old, diabetes duration of 25 years and HbA1c of 8.4%).

RESULTS

The minor allele T of rs11799643 was nominally associated with diabetic retinopathy (OR = 0.52; confidence interval [CI] 95% = 0.28-0.96; P = .036). The minor allele C of rs17389016 was nominally associated with overt diabetic kidney disease (DKD) (OR = 1.90; CI 95% = 1.07-3.37; P = .028). A follow-up study revealed that 29% of the individuals lost ≥5 mL min^-1 × 1.73 m² per year of the estimated glomerular filtration rate (eGFR). In these individuals (eGFR decliners), C allele of rs17389016 was more frequent than in non-decliners (OR = 2.10; CI 95% = 1.14-3.89; P = .018). Finally, minor allele T of rs846906 associated with higher prevalence of arterial hypertension, higher body mass index and waist circumference, thus conferring risk to a lower estimated glucose disposal rate, a surrogate marker of insulin sensitivity (OR = 1.23; CI 95% = 1.06-1.42; P = .004).

CONCLUSION

SNPs in the HSD11B1 gene may confer susceptibility to DKD and to IR in T1D individuals.

Exploring the Temporal Relation between Body Mass Index and Corticosteroid Metabolite Excretion in Childhood

Childhood obesity is associated with alterations in hypothalamus–pituitary–adrenal (HPA) axis activity. However, it is unknown whether these alterations are a cause or a consequence of obesity. This study aimed to explore the temporal relationship between cortisol production and metabolism, and body mass index (BMI). This prospective follow-up study included 218 children (of whom 50% were male), born between 1995 and 1996, who were assessed at the ages of 9, 12 and 17 years. Morning urine samples were collected for assessment of cortisol metabolites by gas chromatography-tandem mass spectrometry, enabling the calculation of cortisol metabolite excretion rate and cortisol metabolic pathways. A cross-lagged regression model was used to determine whether BMI at various ages during childhood predicted later cortisol production and metabolism parameters, or vice versa. The cross-lagged regression coefficients showed that BMI positively predicted cortisol metabolite excretion (p = 0.03), and not vice versa (p = 0.33). In addition, BMI predicted the later balance of 11β-hydroxysteroid dehydrogenase (HSD) activities (p = 0.07), and not vice versa (p = 0.55). Finally, cytochrome P450 3A4 activity positively predicted later BMI (p = 0.01). Our study suggests that changes in BMI across the normal range predict alterations in HPA axis activity. Therefore, the alterations in HPA axis activity as observed in earlier studies among children with obesity may be a consequence rather than a cause of increased BMI.

Diet-induced weight loss alters hepatic glucocorticoid metabolism in type 2 diabetes mellitus

CONTEXT

Altered tissue-specific glucocorticoid metabolism has been described in uncomplicated obesity and type 2 diabetes. We hypothesized that weight loss induced by diet and exercise, which has previously been shown to reverse abnormal cortisol metabolism in uncomplicated obesity, also normalizes cortisol metabolism in patients with type 2 diabetes.

OBJECTIVE

Test the effects of a diet intervention with added exercise on glucocorticoid metabolism.

DESIGN

Two groups followed a Paleolithic diet (PD) for 12 weeks with added 180 min of structured aerobic and resistance exercise per week in one randomized group (PDEX).

SETTING

Umeå University Hospital.

PARTICIPANTS

Men and women with type 2 diabetes treated with lifestyle modification ± metformin were included. Twenty-eight participants (PD, n = 15; PDEX, n = 13) completed measurements of glucocorticoid metabolism.

MAIN OUTCOME MEASURES

Changes in glucocorticoid metabolite levels in 24-h urine samples, expression of HSD11B1 mRNA in s.c. adipose tissue and conversion of orally administered cortisone to cortisol measured in plasma. Body composition and insulin sensitivity were measured using a hyperinsulinemic-euglycemic clamp, and liver fat was measured by magnetic resonance spectroscopy.

RESULTS

Both groups lost weight and improved insulin sensitivity. Conversion of orally taken cortisone to plasma cortisol and the ratio of 5α-THF + 5β-THF/THE in urine increased in both groups.

CONCLUSIONS

These interventions caused weight loss and improved insulin sensitivity with concomitant increases in the conversion of cortisone to cortisol, which is an estimate of hepatic HSD11B1 activity. This suggests that dysregulation of liver glucocorticoid metabolism in these patients is a consequence rather than a cause of metabolic dysfunction.

Glucocorticoid Metabolism in Obesity and Following Weight Loss

Glucocorticoids are steroid hormones produced by the adrenal cortex and are essential for the maintenance of various metabolic and homeostatic functions. Their function is regulated at the tissue level by 11β-hydroxysteroid dehydrogenases and they signal through the glucocorticoid receptor, a ligand-dependent transcription factor. Clinical observations have linked excess glucocorticoid levels with profound metabolic disturbances of intermediate metabolism resulting in abdominal obesity, insulin resistance and dyslipidaemia. In this review, we discuss the physiological mechanisms of glucocorticoid secretion, regulation and function, and survey the metabolic consequences of excess glucocorticoid action resulting from elevated release and activation or up-regulated signaling. Finally, we summarize the reported impact of weight loss by diet, exercise, or bariatric surgery on circulating and tissue-specific glucocorticoid levels and examine the therapeutic possibility of reversing glucocorticoid-associated metabolic disorders.

Steroid Hormones in Cord Blood Mediate the Association Between Maternal Prepregnancy BMI and Birth Weight

OBJECTIVE

Maternal overweight has been associated with increasing offspring birth weight, but epidemiological data on potential biological mechanisms are limited. This study aimed to examine whether steroid hormones mediate the association between maternal prepregnancy BMI (pre-BMI) and birth weight.

METHODS

This study involving 2,039 participants was conducted from an ongoing cohort study in Wuhan, China. Mediation analysis was used to identify the extent to which steroid hormones mediated associations.

RESULTS

Each one-unit increase in pre-BMI was significantly associated with lower log₂ -transformed cord blood levels of cortisol and corticosterone. Levels of cortisol and corticosterone were also negatively associated with birth weight. It was estimated that corticosterone mediated 3.48% of the association between pre-BMI and birth weight, and no significant mediation effect was observed in cortisol. After stratification by maternal gestational weight gain (GWG; within or in excess of the Institute of Medicine [IOM] guidelines), the associations of pre-BMI with cortisol and corticosterone levels were significant in the women with GWG > IOM but not in women with GWG ≤ IOM. When the mediation analysis in the women with GWG > IOM was limited, the mediation effects of cord blood cortisol and corticosterone were both significant (P < 0.05).

CONCLUSIONS

Cord blood cortisol and corticosterone partially mediate the association of increased maternal pre-BMI with higher birth weight.

Carbenoxolone enhances peripheral insulin sensitivity and GLUT4 expression in skeletal muscle of obese rats: Potential participation of UBC9 protein

AIM

This study investigates the insulin sensitizer effect of carbenoxolone (CBX) and potentially involved peripheral mechanisms.

MAIN METHODS

Taking glucose transporter 4 (GLUT4) as a marker of glucose disposal, we investigated the CBX effects on whole-body insulin sensitivity and solute carrier 2a4 (Slc2a4)/GLUT4 expression in visceral (VAT) and subcutaneous (SAT) adipose tissues and soleus muscle of monosodium glutamate (MSG)-induced obese rats. Sterol regulatory element binding protein (SREBP1), an enhancer of Slc2a4 expression was analyzed through mRNA content and SREBP1-binding to Slc2a4 promoter. Finally, the small ubiquitin-modifier conjugating enzyme 9 (UBC9), whose low content indicates accelerated GLUT4 degradation was analyzed in soleus.

KEY FINDINGS

Hypercorticosteronemia, hyperinsulinemia and low glucose decay rate in the insulin tolerance test of obese rats were restored by CBX (P < 0.05). Slc2a4/GLUT4 increased in SAT (P < 0.05) and decreased in VAT (P < 0.01) of obese rats. In soleus, obesity increased Slc2a4 but decreased GLUT4 (P < 0.01), possibly by accelerating GLUT4 degradation, as suggested by decreased UBC9 (P < 0.01). CBX restored both UBC9 and GLUT4 contents. SREBP1 did not participate in the Slc2a4 transcriptional regulation.

SIGNIFICANCE

The insulin sensitizer effect of CBX involves the increase of GLUT4 expression in soleus, indicating an increased glucose disposal in skeletal muscle. This observation reinforces the skeletal muscle as the main site of insulin-induced glucose uptake and sheds new light on the metabolic effects of 11βHSD1 inhibitors, since most of the studies so far have focused on its effects on liver and adipose tissues.

Alterations of Cortisol Metabolism in Human Disorders

The interconversion of active and inactive corticosteroids - cortisol and cortisone, respectively, in humans - is modulated by isozymes of 11β-hydroxysteroid dehydrogenase (11-HSD). Studies of this process have provided crucial insights into glucocorticoid effects in a wide variety of tissues. The 11-HSD1 isozyme functions mainly as an oxoreductase (cortisone to cortisol) and is expressed at high levels in the liver and other glucocorticoid target tissues. Because it is required for full physiological effects of cortisol, it has emerged as a drug target for metabolic syndrome and type 2 diabetes. Mutations in the corresponding HSD11B1 gene, or in the H6PD gene encoding hexose-6-phosphate dehydrogenase (which supplies the NADPH required for the oxoreductase activity of 11-HSD1), cause apparent cortisone reductase deficiency, a rare syndrome of adrenocortical hyperactivity and hyperandrogenism. In contrast, the 11-HSD2 isozyme functions as a dehydrogenase (cortisol to cortisone) and is expressed mainly in mineralocorticoid target tissues, where it bars access of cortisol to the mineralocorticoid receptor. Mutations in the HSD11B2 gene encoding 11-HSD2 cause the syndrome of apparent mineralocorticoid excess, a severe form of familial hypertension. The role of this enzyme in the pathogenesis of common forms of low-renin hypertension remains uncertain.

Copeptin and insulin resistance: effect modification by age and 11 β-HSD2 activity in a population-based study

PURPOSE

Arginine vasopressin (AVP) may be involved in metabolic syndrome (MetS) by altering liver glycogenolysis, insulin and glucagon secretion, and pituitary ACTH release. Moreover, AVP stimulates the expression of 11β-hydroxysteroid-dehydrogenase-type 2 (11β-HSD2) in mineralocorticosteroid cells. We explored whether apparent 11β-HSD2 activity, estimated using urinary cortisol-to-cortisone ratio, modulates the association between plasma copeptin, as AVP surrogate, and insulin resistance/MetS in the general adult population.

METHODS

This was a multicentric, family-based, cross-sectional sample of 1089 subjects, aged 18-90 years, 47% men, 13.4% MetS, in Switzerland. Mixed multivariable linear and logistic regression models were built to investigate the association of insulin resistance (HOMA-IR)/fasting glucose and MetS/Type 2 Diabetes with copeptin, while considering potential confounders or effect modifiers into account. Stratified results by age and 11β-HSD2 activity were presented as appropriate.

RESULTS

Plasma copeptin was higher in men [median 5.2, IQR (3.7-7.8) pmol/L] than in women [median 3.0, IQR (2.2-4.3) pmol/L], P < 0.0001. HOMA-IR was positively associated with copeptin after full adjustment if 11β-HSD2 activity was high [β (95% CI) = 0.32 (0.17-0.46), P < 0.001] or if age was high [β (95% CI) = 0.34 (0.20-0.48), P < 0.001], but not if either 11β-HSD2 activity or age was low. There was a positive association of type 2 diabetes with copeptin [OR (95% CI) = 2.07 (1.10-3.89), P = 0.024), but not for MetS (OR (95% CI) = 1.12 (0.74-1.69), P = 0.605), after full adjustment.

CONCLUSIONS

Our data suggest that age and apparent 11β-HSD2 activity modulate the association of copeptin with insulin resistance at the population level but not MeTS or diabetes. Further research is needed to corroborate these results and to understand the mechanisms underlying these findings.

Drug-induced obesity and its metabolic consequences: a review with a focus on mechanisms and possible therapeutic options

Weight gain is a common side effect of many widely used drugs. Weight gain of a few kilograms to an increase of 10% or more of initial body weight has been described. Not only the weight gain as such puts a burden on the health risks of the involved patients, the accompanying increase in the incidence of the metabolic syndrome, type 2 diabetes mellitus, and cardiovascular risk factors urges the caregiver to identify and to closely monitor the patients at risk. In this review, the different classes of drugs with significant weight gaining properties and the metabolic consequences are described. Specific attention is given to pathogenetic mechanisms underlying the metabolic effects and to potential therapeutic measures to prevent them.

In obese mice, exercise training increases 11β-HSD1 expression, contributing to glucocorticoid activation and suppression of pulmonary inflammation

Exercise training is advocated for treating chronic inflammation and obesity-related metabolic syndromes. Glucocorticoids (GCs), the anti-inflammatory hormones, are synthesized or metabolized in extra-adrenal organs. This study aims to examine whether exercise training affects obesity-associated pulmonary inflammation by regulating local GC synthesis or metabolism. We found that sedentary obese (ob/ob) mice exhibited increased levels of interleukin (IL)-1β, IL-18, monocyte chemotactic protein (MCP)-1, and leukocyte infiltration in lung tissues compared with lean mice, which was alleviated by 6 wk of exercise training. Pulmonary corticosterone levels were decreased in ob/ob mice. Exercise training increased pulmonary corticosterone levels in both lean and ob/ob mice. Pulmonary corticosterone levels were negatively correlated with IL-1β, IL-18, and MCP-1. Immunohistochemical staining of the adult mouse lung sections revealed positive immunoreactivities for the steroidogenic acute regulatory protein, the cholesterol side-chain cleavage enzyme (CYP11A1), the steroid 21-hydroxylase (CYP21), 3β-hydroxysteroid dehydrogenase (3β-HSD), and type 1 and type 2 11β-hydroxysteroid dehydrogenase (11β-HSD) but not for 11β-hydroxylase (CYP11B1). Exercise training significantly increased pulmonary 11β-HSD1 expression in both lean and ob/ob mice. In contrast, exercise training per se had no effect on pulmonary 11β-HSD2 expression, although pulmonary 11β-HSD2 levels in ob/ob mice were significantly higher than in lean mice. RU486, a glucocorticoid receptor antagonist, blocked the anti-inflammatory effects of exercise training in lung tissues of obese mice and increased inflammatory cytokines in lean exercised mice. These findings indicate that exercise training increases pulmonary expression of 11β-HSD1, thus contributing to local GC activation and suppression of pulmonary inflammation in obese mice.NEW & NOTEWORTHY Treadmill training leads to a significant increase in pulmonary corticosterone levels in ob/ob mice, which is in parallel with the favorable effects of exercise on obesity-associated pulmonary inflammation. Exercise training increases pulmonary 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) expression but has no significant effect on 11β-HSD2 expression in both lean and ob/ob mice. These findings indicate that exercise training increases pulmonary expression of 11β-HSD1, thus contributing to local glucocorticoid activation and suppression of pulmonary inflammation in obese mice.

A post-weaning fish oil dietary intervention reverses adverse metabolic outcomes and 11β-hydroxysteroid dehydrogenase type 1 expression in postnatal overfed rats

Early life is considered a critical period for determining long-term metabolic health. Postnatal over-nutrition may alter glucocorticoid (GC) metabolism and increase the risk of developing obesity and metabolic disorders in adulthood. Our aim was to assess the effects of the dose and timing of a fish oil diet on obesity and the expression of GC-activated enzyme 11β-hydroxysteroid dehydrogenase type 1 (HSD1) in postnatal overfed rats. Litter sizes were adjusted to three (small litter (SL)) or ten (normal litter) rats on postnatal day 3 to induce overfeeding or normal feeding. The SL rats were divided into three groups after weaning: high-dose fish oil (HFO), low-dose fish oil (LFO) and standard-diet groups. After 10 weeks, the HFO diet reduced body weight gain (16 %, P0·05). In conclusion, the post-weaning HFO diet could reverse adverse outcomes and decrease tissue GC activity in postnatal overfed rats.

Obesity and the dysregulation of fatty acid metabolism: implications for healthy aging

The population of the world is aging. In 2010, an estimated 524 million people were aged 65 years or older representing eight percent of the global population. By 2050, this number is expected to nearly triple to approximately 1.5 billion, 16 percent of the world's population. Although people are living longer, the quality of their lives are often compromised due to ill-health. Areas covered: Of the conditions which compromise health as we age, obesity is at the forefront. Over half of the global older population were overweight or obese in 2010, significantly increasing the risk of a range of metabolic diseases. Although, it is well recognised excessive calorie intake is a fundamental driver of adipose tissue dysfunction, the relationship between obesity; intrinsic aging; and fat metabolism is less understood. In this review we discuss the intersection between obesity, aging and the factors which contribute to the dysregulation of whole-body fat metabolism. Expert commentary: Being obese disrupts an array of physiological systems and there is significant crosstalk among these. Moreover it is imperative to acknowledge the contribution intrinsic aging makes to the dysregulation of these systems and the onset of disease.

Safety, pharmacokinetics and pharmacodynamics of BI 135585, a selective 11β-hydroxysteroid dehydrogenase-1 (HSD1) inhibitor in humans: liver and adipose tissue 11β-HSD1 inhibition after acute and multiple administrations over 2 weeks

AIMS

To assess the safety and pharmacokinetic and pharmacodynamic characteristics of BI 135585, a selective 11β-hydroxysteroid dehydrogenase-1 (11β-HSD1) inhibitor, after single- and repeated-dose administration.

METHODS

The single-dose study included open-label administration of 200 mg BI 135585 in healthy volunteers, while in the multiple-dose study, we carried out randomized, double-blind administration of 5-200 mg BI 135585 or placebo once daily over 14 days in patients with type 2 diabetes (T2DM). Assessments included 11β-HSD1 inhibition in the liver (urinary tetrahydrocortisol (THF)/tetrahydrocotisone (THE) ratio) and in subcutaneous adipose tissue (AT) ex vivo and determination of hypothalamus-pituitary-adrenal (HPA) axis hormone levels.

RESULTS

No major safety issues occurred with BI 135585 administration. The HPA axis was mildly activated with slightly increased, but still normal adrenocorticotropic hormone levels, increased total urinary corticoid excretion but unchanged plasma cortisol levels. After multiple doses of 5-200 mg BI 135585, exposure (area under the curve) increased dose-proportionally and half-life was 55-65 h. The urinary THF/THE ratio decreased, indicating liver 11β-HSD1 inhibition. Median 11β-HSD1 enzyme inhibition in the AT reached 90% after a single dose of BI 135585, but was low (31% or lower) after 14 days of continuous treatment.

CONCLUSIONS

BI 135585 was safe and well tolerated over 14 days and can be dosed once daily. Future studies are required to clarify the therapeutic potential of BI 135585 in view of its effects on 11β-HSD1 inhibition in AT after single and multiple doses. Enzyme inhibition in the AT was not adequately predicted by the urinary THF/THE ratio.

Decreased expression of the glucocorticoid receptor-GILZ pathway in Kupffer cells promotes liver inflammation in obese mice

BACKGROUND & AIMS

Kupffer cells (KC) play a key role in the onset of inflammation in non-alcoholic steatohepatitis (NASH). The glucocorticoid receptor (GR) induces glucocorticoid-induced leucine zipper (GILZ) expression in monocytes/macrophages and is involved in several inflammatory processes. We hypothesized that the GR-GILZ axis in KC may contribute to the pathophysiology of obesity-induced liver inflammation.

METHODS

By using a combination of primary cell culture, pharmacological experiments, mice deficient for the Gr specifically in macrophages and transgenic mice overexpressing Gilz in macrophages, we explored the involvement of the Gr-Gilz axis in KC in the pathophysiology of obesity-induced liver inflammation.

RESULTS

Obesity was associated with a downregulation of the Gr and Gilz, and an impairment of Gilz induction by lipopolysaccharide (LPS) and dexamethasone (DEX) in KC. Inhibition of Gilz expression in isolated KC transfected with Gilz siRNA demonstrated that Gilz downregulation was sufficient to sensitize KC to LPS. Conversely, liver inflammation was decreased in obese transgenic mice specifically overexpressing Gilz in macrophages. Pharmacological inhibition of the Gr showed that impairment of Gilz induction in KC by LPS and DEX in obesity was driven by a downregulation of the Gr. In mice specifically deficient for Gr in macrophages, Gilz expression was low, leading to an exacerbation of obesity-induced liver inflammation.

CONCLUSIONS

Obesity is associated with a downregulation of the Gr-Gilz axis in KC, which promotes liver inflammation. The Gr-Gilz axis in KC is an important target for the regulation of liver inflammation in obesity.

Aldosterone and the Mineralocorticoid Receptor: Risk Factors for Cardiometabolic Disorders

Preclinical studies have convincingly demonstrated a role for the mineralocorticoid receptor (MR) in adipose tissue physiology. These studies show that increased MR activation causes adipocyte dysfunction leading to decreased production of insulin-sensitizing products and increased production of inflammatory factors, creating an environment conducive to metabolic and cardiovascular disease. Accumulating data also suggest that MR activation may be an important link between obesity and metabolic syndrome. Moreover, MR activation may mediate the pathogenic consequences of metabolic syndrome. Recent attempts at reversing cardiometabolic damage in patients with type 2 diabetes using MR antagonists have shown promising results. MR antagonists are already used to treat heart failure where their use decreases mortality and morbidity over and above the use of traditional therapies alone. However, more data are needed to establish the benefits of MR antagonists in diabetes, obesity, and metabolic syndrome.

Hypothalamic-pituitary-adrenal axis dysregulation and cortisol activity in obesity: A systematic review

BACKGROUND

Although there is substantial evidence of differential hypothalamic-pituitary-adrenal (HPA) axis activity in both generalized and abdominal obesity, consistent trends in obesity-related HPA axis perturbations have yet to be identified.

OBJECTIVES

To systematically review the existing literature on HPA activity in obesity, identify possible explanations for inconsistencies in the literature, and suggest methodological improvements for future study.

DATA SOURCES

Included papers used Pubmed, Google Scholar, and the University of California Library search engines with search terms body mass index (BMI), waist-to-hip ratio (WHR), waist circumference, sagittal diameter, abdominal versus peripheral body fat distribution, body fat percentage, DEXA, abdominal obesity, and cortisol with terms awakening response, slope, total daily output, reactivity, feedback sensitivity, long-term output, and 11β-HSD expression.

STUDY ELIGIBILITY CRITERIA

Empirical research papers were eligible provided that they included at least one type of obesity (general or abdominal), measured at least one relevant cortisol parameter, and a priori tested for a relationship between obesity and cortisol.

RESULTS

A general pattern of findings emerged where greater abdominal fat is associated with greater responsivity of the HPA axis, reflected in morning awakening and acute stress reactivity, but some studies did show underresponsiveness. When examined in adipocytes, there is a clear upregulation of cortisol output (due to greater expression of 11β-HSD1), but in hepatic tissue this cortisol is downregulated. Overall obesity (BMI) appears to also be related to a hyperresponsive HPA axis in many but not all studies, such as when acute reactivity is examined.

LIMITATIONS

The reviewed literature contains numerous inconsistencies and contradictions in research methodologies, sample characteristics, and results, which partially precluded the development of clear and reliable patterns of dysregulation in each investigated cortisol parameter.

CONCLUSIONS AND IMPLICATIONS

The literature to date is inconclusive, which may well arise from differential effects of generalized obesity vs. abdominal obesity or from modulators such as sex, sex hormones, and chronic stress. While the relationship between obesity and adipocyte cortisol seems to be clear, further research is warranted to understand how adipocyte cortisol metabolism influences circulating cortisol levels and to establish consistent patterns of perturbations in adrenal cortisol activity in both generalized and abdominal obesity.

Glucocorticoid Excess Increases Hepatic 11β-HSD-1 Activity in Humans: Implications in Steroid-Induced Diabetes

CONTEXT

Animal studies indicate that glucocorticoids increase hepatic 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1) expression and activity.

OBJECTIVE

Our goal was to determine whether glucocorticoid excess increases cortisol production in the liver via 11β-HSD-1 enzyme pathway in humans.

DESIGN

A total of 1 mg each [4-(13)C] cortisone and [9,12,12-(2)H3] cortisol were ingested, and [1,2,6,7-(3)H] cortisol was infused to measure C13 cortisol (derived from ingested [4-(13)C] cortisone) turnover using the triple tracer technique, whereas glucose turnover was measured using isotope dilution technique following [6-6(2)H2] glucose infusion during a saline clamp.

SETTING

This study took place at the Mayo Clinic Clinical Research Unit.

PARTICIPANTS

Thirty nondiabetic healthy subjects participated.

INTERVENTION

Subjects were randomized to hydrocortisone (n = 15) or placebo 50 mg twice daily (n = 15) for 1 week.

OUTCOME MEASURES

Hepatic cortisol production and endogenous glucose production were measured.

RESULTS

Plasma cortisol concentrations were higher throughout the study period in hydrocortisone group. Rates of appearance of C13 cortisol and hepatic C13 cortisol production were higher in hydrocortisone vs placebo group, indicating increased hepatic 11β-HSD-1 activity. Higher plasma cortisol and presumably higher intrahepatic cortisol was associated with impaired suppression of endogenous glucose production in hydrocortisone vs placebo group.

CONCLUSION

Chronic glucocorticoid excess increases intrahepatic cortisone to cortisol conversion via the 11β-HSD-1 pathway. The extent to which this causes or exacerbates steroid induced hepatic insulin resistance remains to be determined.

Cortisol dysregulation in obesity-related metabolic disorders

PURPOSE OF REVIEW

The present review highlights recent investigations in the prior 18 months focusing on the role of dysregulated cortisol physiology in obesity as a potential modifiable mechanism in the pathogenesis of obesity-related cardiometabolic disorders.

RECENT FINDINGS

Given the clinical resemblance of obesity-related metabolic disorders with the Cushing's syndrome, new studies have investigated the intracellular regulation and metabolism of cortisol, new measurements of cortisol in scalp hair as a tool for long-term exposure to cortisol, and the cortisol-mineralocorticoid receptor pathway. Thus, current and future pharmacological interventions in obesity may include specific inhibition of steroidogenic and regulatory enzymes as well as antagonists of the mineralocorticoid and glucocorticoid receptors.

SUMMARY

The understanding of how adrenal function is challenged by the interplay of our genetic and environmental milieu has highlighted the importance of inappropriate cortisol regulation in cardiometabolic disorders. Increased adipose tissue in obesity is associated with hypothalamic-pituitary-adrenal axis overactivation, increased cortisol production at the local tissue level, and probably higher mineralocorticoid receptor activation in certain tissues.

11β-hydroxysteroid dehydrogenase types 1 and 2 activity in subcutaneous adipose tissue in humans: implications in obesity and diabetes

CONTEXT

The role of 11β-hydroxysteroid dehydrogenase types 1 (11β-HSD-1) and 2 (11β-HSD-2) enzymes in sc adipose tissue is controversial.

OBJECTIVE

The objective of the study was to determine the activity of 11β-HSD-1 and -2 enzymes in the abdominal and leg sc adipose tissue in obesity and diabetes.

DESIGN

11β-HSD-1 and -2 enzyme activities in abdominal and leg sc adipose tissue were measured by infusing [2,2,4,6,6,12,12-(2)H7] cortisone (D7 cortisone) and [9,12,12-(2)H3] cortisol (D3 cortisol) via microdialysis catheters placed in sc fat depots.

SETTING

The study was conducted at the Mayo Clinic Clinical Research Unit.

PARTICIPANTS

Lean nondiabetic (n = 13), overweight/obese nondiabetic (n = 15), and overweight/obese participants with type 2 diabetes mellitus (n = 15) participated in the study.

MAIN OUTCOME MEASURES

The conversion of infused D7 cortisone to D7 cortisol (via 11β-HSD reductase activity) and D3 cortisol to D3 cortisone (via 11β-HSD dehydrogenase activity) in sc adipose tissue.

RESULTS

Enrichment of D7 cortisone and D3 cortisol were similar in the effluents from both sites in all groups. D3 cortisone enrichment did not differ in the three cohorts, indicating that 11β-HSD-2 enzyme activity (conversion of cortisol to cortisone) occurs equally in all groups. However, D7 cortisol enrichment was detectable in abdominal sc fat of overweight/obese participants with type 2 diabetes mellitus only, implying 11β-HSD-1 reductase activity (conversion of cortisone to cortisol) occurs in obese subjects with type 2 diabetes.

CONCLUSIONS

There is conversion of cortisone to cortisol via the 11β-HSD-1 enzyme pathway in abdominal sc fat depots in overweight/obese participants with type 2 diabetes mellitus. This observation has significant implications for developing tissue-specific 11β-HSD-1 inhibitors in type 2 diabetes mellitus.