The contribution of visceral adipose tissue to splanchnic cortisol production in healthy humans

The Metabolic Syndrome, a Human Disease

This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.

11β-Hydroxysteroid dehydrogenase and the brain: Not (yet) lost in translation

11-beta-hydroxysteroid dehydrogenases (11β-HSDs) catalyse the conversion of active 11-hydroxy glucocorticoids (cortisol, corticosterone) and their inert 11-keto forms (cortisone, 11-dehydrocorticosterone). They were first reported in the body and brain 70 years ago, but only recently have they become of interest. 11β-HSD2 is a dehydrogenase, potently inactivating glucocorticoids. In the kidney, 11β-HSD2 generates the aldosterone-specificity of intrinsically non-selective mineralocorticoid receptors. 11β-HSD2 also protects the developing foetal brain and body from premature glucocorticoid exposure, which otherwise engenders the programming of neuropsychiatric and cardio-metabolic disease risks. In the adult CNS, 11β-HSD2 is confined to a part of the brain stem where it generates aldosterone-specific central control of salt appetite and perhaps blood pressure. 11β-HSD1 is a reductase, amplifying active glucocorticoid levels within brain cells, notably in the cortex, hippocampus and amygdala, paralleling its metabolic functions in peripheral tissues. 11β-HSD1 is elevated in the ageing rodent and, less certainly, human forebrain. Transgenic models show this rise contributes to age-related cognitive decline, at least in mice. 11β-HSD1 inhibition robustly improves memory in healthy and pathological ageing rodent models and is showing initial promising results in phase II studies of healthy elderly people. Larger trials are needed to confirm and clarify the magnitude of effect and define target populations. The next decade will be crucial in determining how this tale ends - in new treatments or disappointment.

Non-invasive in vivo assessment of 11β-hydroxysteroid dehydrogenase type 1 activity by 19F-Magnetic Resonance Spectroscopy

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) amplifies tissue glucocorticoid levels and is a pharmaceutical target in diabetes and cognitive decline. Clinical translation of inhibitors is hampered by lack of in vivo pharmacodynamic biomarkers. Our goal was to monitor substrates and products of 11β-HSD1 non-invasively in liver via ¹⁹Fluorine magnetic resonance spectroscopy (¹⁹F-MRS). Interconversion of mono/poly-fluorinated substrate/product pairs was studied in Wistar rats (male, n = 6) and healthy men (n = 3) using 7T and 3T MRI scanners, respectively. Here we show that the in vitro limit of detection, as absolute fluorine content, was 0.625 μmole in blood. Mono-fluorinated steroids, dexamethasone and 11-dehydrodexamethasone, were detected in phantoms but not in vivo in human liver following oral dosing. A non-steroidal polyfluorinated tracer, 2-(phenylsulfonyl)-1-(4-(trifluoromethyl)phenyl)ethanone and its metabolic product were detected in vivo in rat liver after oral administration of the keto-substrate, reading out reductase activity. Administration of a selective 11β-HSD1 inhibitor in vivo in rats altered total liver ¹⁹F-MRS signal. We conclude that there is insufficient sensitivity to measure mono-fluorinated tracers in vivo in man with current dosage regimens and clinical scanners. However, since reductase activity was observed in rats using poly-fluorinated tracers, this concept could be pursued for translation to man with further development.

Increased systemic and adipose 11β-HSD1 activity in idiopathic intracranial hypertension

Context

Idiopathic intracranial hypertension (IIH) is a disease of raised intracranial pressure (ICP) of unknown etiology. Reductions in glucocorticoid metabolism are associated with improvements in IIH disease activity. The basal IIH glucocorticoid metabolism is yet to be assessed.

Objective

The objective of this study was to determine the basal glucocorticoid phenotype in IIH and assess the effects of weight loss on the IIH glucocorticoid phenotype.

Design

A retrospective case-control study and a separate exploratory analysis of a prospective randomized intervention study were carried out.

Methods

The case-control study compared female IIH patients to BMI, age, and sex-matched controls. In the randomized intervention study, different IIH patients were randomized to either a community weight management intervention or bariatric surgery, with patients assessed at baseline and 12 months. Glucocorticoid levels were determined utilizing 24-h urinary steroid profiles alongside the measurement of adipose tissue 11β-HSD1 activity.

Results

Compared to control subjects, patients with active IIH had increased systemic 11β-hydroxysteroid dehydrogenase (11β-HSD1) and 5α-reductase activity. The intervention study demonstrated that weight loss following bariatric surgery reduced systemic 11β-HSD1 and 5α-reductase activity. Reductions in these were associated with reduced ICP. Subcutaneous adipose tissue explants demonstrated elevated 11β-HSD1 activity compared to samples from matched controls.

Conclusion

The study demonstrates that in IIH, there is a phenotype of elevated systemic and adipose 11β-HSD1 activity in excess to that mediated by obesity. Bariatric surgery to induce weight loss was associated with reductions in 11β-HSD1 activity and decreased ICP. These data reflect new insights into the IIH phenotype and further point toward metabolic dysregulation as a feature of IIH.

Translating PUFA omega 6:3 ratios from wild to captive hibernators (Urocitellus parryii) enhances sex-dependent mass-gain without increasing physiological stress indicators

Omega 3 polyunsaturated fatty acids (PUFAs) are well-documented for their influence on health and weight loss. Recent studies indicate omega 3 PUFAs may exert a negative impact on cellular stress and physiology in some hibernators. We asked if physiological stress indicators, lipid peroxidation and mass gain in Arctic Ground Squirrels (AGS) were negatively influenced by naturally occurring dietary omega 3 PUFA levels compared to omega 3 PUFA levels found in common laboratory diets. We found plasma fatty acid profiles of free-ranging AGS to be high in omega 3 PUFAs with balanced omega 6:3 ratios, while standard laboratory diets and plasma of captive AGS are high in omega 6 and low in omega 3 PUFAs with higher omega 6:3 ratios. Subsequently, we designed a diet to mimick free-range AGS omega 6:3 ratios in captive AGS. Groups of wild-caught juvenile AGS were either fed: (1) Mazuri Rodent Chow (Standard Rodent chow, 4.95 omega 6:3 ratio), or (2) balanced omega 6:3 chow (Balanced Diet, 1.38 omega 6:3). AGS fed the Balanced Diet had plasma omega 6:3 ratios that mimicked plasma profiles of wild AGS. Balanced Diet increased female body mass before hibernation, but did not influence levels of cortisol in plasma or levels of the lipid peroxidation product 4-HNE in brown adipose tissue. Overall, as the mass gain is critical during pre-hibernation for obligate hibernators, the results show that mimicking a fatty acid profile of wild AGS facilitates sex-dependent mass accumulation without increasing stress indicators.

Transient expansion of the expression region of Hsd11b1, encoding 11β-hydroxysteroid dehydrogenase type 1, in the developing mouse neocortex

Corticosteroids are stress-related hormones that maintain homeostasis. The most effective corticosteroids are corticosterone (CORT) in rodents and cortisol in primates. 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1; EC 1.1.1.146), encoded by Hsd11b1, is a key regulator of the local concentration of CORT/cortisol. Hsd11b1 expression in layer 5 of the primary somatosensory cortex has been shown in adult mice. However, its localization in the entire neocortex, especially during development, has not been fully addressed. Here, we established robust and dynamic expression profiles of Hsd11b1 in the developing mouse neocortex. Hsd11b1 was found mostly in pyramidal neurons. By retrograde tracing, we observed that some Hsd11b1-positive cells were projection neurons, indicating that at least some were excitatory. At postnatal day 0 (P0), Hsd11b1 was expressed in the deep layer of the somatosensory cortex. Then, from P3 to P8, the expression area expanded broadly; it was observed in layers 4 and 5, spanning the whole neocortex, including the primary motor cortex (M1) and the primary visual cortex (V1). The positive region gradually narrowed from P14 onwards and was ultimately limited to layer 5 of the somatosensory cortex at P26 and later. Furthermore, we administered CORT to nursing dams to increase the systemic CORT level of their pups. Here, we observed a reduced number of Hsd11b1-positive cells in the neocortex of these pups. Our observation suggests that Hsd11b1 expression in the developing neocortex is affected by systemic CORT levels. It is possible that stress on mothers influences the neocortical development of their children.

Effects of Obesity and Insulin on Tissue-Specific Recycling Between Cortisol and Cortisone in Men

CONTEXT

11β-Hydroxysteroid dehydrogenase 1 (11βHSD1) reduces inert cortisone into active cortisol but also catalyzes reverse dehydrogenase activity. Drivers of cortisol/cortisone equilibrium are unclear. With obesity, 11βHSD1 transcripts are more abundant in adipose, but the consequences for oxidation vs reduction remain unknown.

OBJECTIVE

This work aimed to determine whether 11βHSD1 equilibrium in metabolic tissues is regulated by insulin and obesity.

METHODS

A 2-phase, randomized, crossover, single-blinded study in a clinical research facility was conducted of 10 lean and obese healthy men. 11β-Reductase and 11β-dehydrogenase activities were measured during infusion of 9,11,12,12-[2H]4-cortisol and 1,2-[2H]2-cortisone, respectively, on 2 occasions: once during saline infusion and once during a hyperinsulinemic-euglycemic clamp. Arterialized and venous samples were obtained across forearm skeletal muscle and abdominal subcutaneous adipose. Steroids were quantified by liquid chromatography-tandem mass spectrometry and adipose tissue transcripts by quantitative polymerase chain reaction.

RESULTS

Neither whole-body nor tissue-specific rates of production of cortisol or cortisone differed between lean and obese men, however insulin attenuated the diurnal decrease. Whole-body 11β-HSD1 reductase activity tended to be higher in obesity (~ 10%) and was further increased by insulin. Across adipose tissue, 11β-reductase activity was detected in obese individuals only and increased in the presence of insulin (18.99 ± 9.62 vs placebo 11.68 ± 3.63 pmol/100 g/minute; P < .05). Across skeletal muscle, 11β-dehydrogenase activity was reduced by insulin in lean men only (2.55 ± 0.90 vs 4.50 ± 1.42 pmol/100 g/minute, P < .05).

CONCLUSIONS

Regeneration of cortisol is upregulated by insulin in adipose tissue but not skeletal muscle. In obesity, the equilibrium between 11β-reductase and 11β-dehydrogenase activities likely promotes cortisol accumulation in adipose, which may lead to adverse metabolic consequences.

Multifaceted Control of GR Signaling and Its Impact on Hepatic Transcriptional Networks and Metabolism

Glucocorticoids (GCs) and the glucocorticoid receptor (GR) are important regulators of development, inflammation, stress response and metabolism, demonstrated in various diseases including Addison's disease, Cushing's syndrome and by the many side effects of prolonged clinical administration of GCs. These conditions include severe metabolic challenges in key metabolic organs like the liver. In the liver, GR is known to regulate the transcription of key enzymes in glucose and lipid metabolism and contribute to the regulation of circadian-expressed genes. Insights to the modes of GR regulation and the underlying functional mechanisms are key for understanding diseases and for the development of improved clinical uses of GCs. The activity and function of GR is regulated at numerous levels including ligand availability, interaction with heat shock protein (HSP) complexes, expression of GR isoforms and posttranslational modifications. Moreover, recent genomics studies show functional interaction with multiple transcription factors (TF) and coregulators in complex transcriptional networks controlling cell type-specific gene expression by GCs. In this review we describe the different regulatory steps important for GR activity and discuss how different TF interaction partners of GR selectively control hepatic gene transcription and metabolism.

Association of Estradiol and Visceral Fat With Structural Brain Networks and Memory Performance in Adults

IMPORTANCE

Changes in estradiol during aging are associated with increased dementia risk. It remains unclear how estradiol supports cognitive health and whether risk factors, such as midlife obesity, are exacerbated by estrogen loss.

OBJECTIVES

To assess whether visceral adipose tissue (VAT) moderates the association between age and brain network structure and to investigate whether estradiol moderates the association between VAT and brain network structure.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study of data from 974 cognitively healthy adults in Germany who participated in the Health Study of the Leipzig Research Centre for Civilization Diseases, a previously described population-based cohort study. Two moderation analyses were performed, including VAT as the moderator variable between age and brain network structure and estradiol as the moderator variable between VAT and brain network structure. The study was conducted from August 1, 2011, to November 23, 2014. Analyses were conducted from August 2017 to September 2018.

EXPOSURES

Serum estradiol levels from fasting blood and visceral adipose tissue volume from T1-weighted magnetic resonance imaging (MRI).

MAIN OUTCOMES AND MEASURES

Brain network covariance (individual loading on structural network derived from T1-weighted MRI) and memory performance (composite score from the Consortium to Establish a Registry for Alzheimer Disease [CERAD] verbal episodic memory test on learning [score range, 0-30], recall [score range, 0-10], and recognition [score range, 0-20]).

RESULTS

Final analyses included data from 473 women (mean [SD] age, 50.10 [15.63] years) and 501 men (mean [SD] age, 51.24 [15.67] years). Visceral adipose tissue was associated with an exacerbation of the negative association of aging with network covariance for women (interaction term β = -0.02; 95% bias-corrected bootstrap CI, -0.03 to -0.01; P = .001) and men (interaction term β = -0.02; 95% bias-corrected bootstrap CI, -0.03 to -0.01; P < .001). Estradiol level was associated with a reduction in the negative association of VAT with network covariance in women (interaction term β = 0.63; 95% bias-corrected bootstrap CI, 0.14-1.12; P = .01), with no significant association in men. In the female midlife subgroup (age range, 35-55 years, when menopause transition occurs), low estradiol levels were associated with lower memory network covariance (Cohen d = 0.61; t80 = 2.76; P = .007) and worse memory performance (Cohen d = 0.63; t76 = 2.76; P = .007).

CONCLUSIONS AND RELEVANCE

This study reports a novel association between VAT, estradiol, and structural brain networks as a potential mechanism underlying cognitive decline in women. These findings appear to highlight the need for sex-specific strategies, including VAT and hormonal screening during midlife, to support healthy cognitive aging.

Fructose-induced inflammation and increased cortisol: A new mechanism for how sugar induces visceral adiposity

Traditionally, the leading hypothesis regarding the development of obesity involves caloric imbalance, whereby the amount of calories consumed exceeds the amount of calories burned which causes obesity. Another hypothesis for why we get fat has surfaced in the last decade which is the idea that the overconsumption of added sugars and refined carbohydrates induce insulin resistance and high insulin levels causing obesity. While insulin is a fat-storing hormone, this hypothesis does not explain visceral adiposity, or why certain people are found to have fat stored in and around their organs. We propose a new mechanism for body fattening, particular visceral adiposity. This hypothesis involves the overconsumption of fructose, which leads to inflammation in all cells that metabolize it rapidly. When fructose is metabolized in subcutaneous adipocytes, the subsequent inflammation leads to an increase in intracellular cortisol in order to help squelch the inflammation. Unfortunately, the increase in intracellular cortisol leads to an increased flux of fatty acids out of the subcutaneous adipocytes allowing more substrate for fat storage into visceral fat tissue. Moreover fructose-induced inflammation in the liver also leads to increased intracellular cortisol via an upregulation of 11-B hydroxysteroid dehydrogenase type 1 causing increased fat storage in the liver (i.e., fatty liver). In essence, the fructose-induced inflammatory cortisol response causes "thin on the outside, fat on the inside" (TOFI). Furthermore, fructose in the brain, either from fructose uptake via the blood brain barrier or endogenous formation from glucose via the polyol pathway stimulates an increased release of cortisol causing hepatic gluconeogenesis leading to overall insulin resistance and further body fattening. This review paper will discuss in detail the hypothesis that fructose-induced inflammation and cortisol activation causes visceral adiposity.

Systemic overexpression of the 11β‑HSD1 promotes endoplasmic reticulum stress in multiple tissues and the development of metabolic syndrome in mice

Glucocorticoids are associated with lipid metabolism and their abnormal expression has an important function in the development of metabolic syndrome. The 11β‑hydroxysteroid dehydrogenase type 1 (11β‑HSD1) is a metabolic enzyme of glucocorticoids and may be a potential drug target for the treatment of metabolic syndrome. However, the association between the systemic expression of 11β‑HSD1 and metabolic syndrome remains to be elucidated. The present study used a cytomegalovirus promoter to obtain mice that systemically overexpressed the 11β‑HSD1 gene. The transgenic mice and negative control groups received a high‑fat diet at the age of 10 weeks in order to induce metabolic syndrome and this diet was continued for 12 weeks. Several indicators, including body weight, blood glucose, glucose tolerance and insulin resistance, were monitored in vivo. In addition, the protein expression levels of 11β‑HSD1 and DNA damage inducible transcript 3 were detected and the histopathology of important tissues for metabolic syndrome were analyzed. The current findings revealed that the body weights of transgenic mice were significantly higher compared with the control group before and during the periods of high fat diet induction. Transgenic mice also exhibited significantly impaired glucose tolerance, insulin resistance, endoplasmic reticulum stress and increased metabolic syndrome‑associated biochemical indicators in the blood and severely impaired liver and kidney functions. The present study successfully established a 11β‑HSD1 systemic overexpression mouse model that exhibited typical characteristics of metabolic syndrome and may be useful for future studies of metabolic syndrome.

Characterization of Cortisol Secretion Rate in Secondary Adrenal Insufficiency

Context:

In secondary adrenal insufficiency (SAI), chronic deficiency of adrenocorticotropin (ACTH) is believed to result in secondary changes in adrenocortical function, causing an altered dose-response relationship between ACTH concentration and cortisol secretion rate (CSR).

Objective:

We sought to characterize maximal cortisol secretion rate (CSR_max) and free cortisol half-life in patients with SAI, compare results with those of age-matched healthy controls, and examine the influence of predictor variables on ACTH-stimulated cortisol concentrations.

Design:

CSR_max was estimated from ACTH_1-24 (250 μg)_–stimulated cortisol time-concentration data. Estimates for CSR_max and free cortisol half-life were obtained for both dexamethasone (DEX) and placebo pretreatment conditions for all subjects.

Setting:

Single academic medical center.

Patients:

Patients with SAI (n = 10) compared with age-matched healthy controls (n = 21).

Interventions:

The order of DEX vs placebo pretreatment was randomized and double-blind. Cortisol concentrations were obtained at baseline and at intervals for 120 minutes after ACTH_1-24.

Main Outcome Measures:

CSR_max and free cortisol half-life were obtained by numerical modeling analysis. Predictors of stimulated cortisol concentrations were evaluated using a multivariate model.

Results:

CSR_max was significantly (P < 0.001) reduced in patients with SAI compared with controls for both placebo (0.17 ± 0.09 vs 0.46 ± 0.14 nM/s) and DEX (0.18 ± 0.13 vs 0.43 ± 0.13 nM/s) conditions. Significant predictors of ACTH_1-24–stimulated total cortisol concentrations included CSR_max, free cortisol half-life, and baseline total cortisol, corticosteroid-binding globulin, and albumin concentrations (all P < 0.05).

Conclusions:

Our finding of significantly decreased CSR_max confirms that SAI is associated with alterations in the CSR-ACTH dose-response curve. Decreased CSR_max contributes importantly to the laboratory diagnosis of SAI.

Mass spectrometry and its evolving role in assessing tissue specific steroid metabolism

Glucocorticoid hormones play vital roles in regulating diverse biological processes in health and disease. Tissue levels are regulated by enzymes which activate and inactivate hormones. The enzyme, 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), in particular, has been identified as a potential drug target; inhibiting this enzyme attenuates glucocorticoid action by lowering local levels of active hormone. A variety of mass spectrometric approaches have been developed to characterize this enzymein vivo Endogenous glucocorticoids and their metabolites can be profiled in urine by GC-MS and circulating steroids are now more commonly quantified by liquid chromatography tandem mass spectrometry. Tracer dilution studies have allowed rates of generation of glucocorticoids by the enzyme to be distinguished from hormone generated directly by the adrenal glands and, in combination with arterio-venous (AV) sampling, rates of production by specific tissues have been quantified. This has allowed the contribution of liver, adipose, muscle and brain to cortisol production in metabolic disease and hence prioritized drug targets. Most recently MS imaging in combination with on-tissue derivatization has been developed to profile oxo-steroids in tissue sections, allowing molecular maps to be generated across complex tissues, where regional functions are important. The review provides a synopsis of how measurement of steroids by MS has evolved with technological advances and this has provided insight into the dynamic turnover of glucocorticoidsin vivo, highlighting the milestones that have advanced the field and identifying the remaining challenges for researchers, in terms of analytical chemistry and endocrine physiology and biochemistry.

Metformin Increases Cortisol Regeneration by 11βHSD1 in Obese Men With and Without Type 2 Diabetes Mellitus

CONTEXT

The mechanism of action of metformin remains unclear. Given the regulation of the cortisol-regenerating enzyme 11βhydroxysteroid dehydrogenase 1 (11βHSD1) by insulin and the limited efficacy of selective 11βHSD1 inhibitors to lower blood glucose when co-prescribed with metformin, we hypothesized that metformin reduces 11βHSD1 activity.

OBJECTIVE

To determine whether metformin regulates 11βHSD1 activity in vivo in obese men with and without type 2 diabetes mellitus.

DESIGN

Double-blind, randomized, placebo-controlled, crossover study.

SETTING

A hospital clinical research facility.

PARTICIPANTS

Eight obese nondiabetic (OND) men and eight obese men with type 2 diabetes (ODM).

INTERVENTION

Participants received 28 days of metformin (1 g twice daily), placebo, or (in the ODM group) gliclazide (80 mg twice daily) in random order. A deuterated cortisol infusion at the end of each phase measured cortisol regeneration by 11βHSD1. Oral cortisone was given to measure hepatic 11βHSD1 activity in the ODM group. The effect of metformin on 11βHSD1 was also assessed in human hepatocytes and Simpson-Golabi-Behmel syndrome adipocytes.

MAIN OUTCOME MEASURES

The effect of metformin on whole-body and hepatic 11βHSD1 activity.

RESULTS

Whole-body 11βHSD1 activity was approximately 25% higher in the ODM group than the OND group. Metformin increased whole-body cortisol regeneration by 11βHSD1 in both groups compared with placebo and gliclazide and tended to increase hepatic 11βHSD1 activity. In vitro, metformin did not increase 11βHSD1 activity in hepatocytes or adipocytes.

CONCLUSIONS

Metformin increases whole-body cortisol generation by 11βHSD1 probably through an indirect mechanism, potentially offsetting other metabolic benefits of metformin. Co-prescription with metformin should provide a greater target for selective 11βHSD1 inhibitors.

Cortisol promotes endoplasmic glucose production via pyridine nucleotide redox

Both increased adrenal and peripheral cortisol production, the latter governed by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), contribute to the maintenance of fasting blood glucose. In the endoplasmic reticulum (ER), the pyridine nucleotide redox state (NADP/NADPH) is dictated by the concentration of glucose-6-phosphate (G6P) and the coordinated activities of two enzymes, hexose-6-phosphate dehydrogenase (H6PDH) and 11β-HSD1. However, luminal G6P may similarly serve as a substrate for hepatic glucose-6-phophatase (G6Pase). A tacit belief is that the G6P pool in the ER is equally accessible to both H6PDH and G6Pase. Based on our inhibition studies and kinetic analysis in isolated rat liver microsomes, these two aforesaid luminal enzymes do share the G6P pool in the ER, but not equally. Based on the kinetic modeling of G6P flux, the ER transporter for G6P (T1) preferentially delivers this substrate to G6Pase; hence, the luminal enzymes do not share G6P equally. Moreover, cortisol, acting through 11β-HSD1, begets a more reduced pyridine redox ratio. By altering this luminal redox ratio, G6P flux through H6PDH is restrained, allowing more G6P for the competing enzyme G6Pase. And, at low G6P concentrations in the ER lumen, which occur during fasting, this acute cortisol-induced redox adjustment promotes glucose production. This reproducible cortisol-driven mechanism has been heretofore unrecognized.

The direct and indirect effects of corticosterone and primary adipose tissue on MCF7 breast cancer cell cycle progression

BACKGROUND

Breast cancer is the second leading cause of cancer-related mortality in women. Glucocorticoids (GCs) have the potential to directly affect breast cancer or indirectly via changes to the tumor growth microenvironment a breast cancer is exposed to. The role of GCs in breast cancer progression by direct and indirect means are not fully understood.

AIM

To study the direct and indirect effects of GCs on breast cancer cell cycle regulation.

METHODS

MCF7 breast cancer cells were incubated with increasing concentrations of corticosterone (CORT) to investigate the direct effects. In addition, MCF7 cells were cultured in conditioned media (CM) from primary adipose tissue excised from CORT-supplemented lean and obese male rats.

RESULTS

CORT alone resulted in dose-dependent increases in p27 and hypophosphorylated retinoblastoma protein (Rb) which was accompanied by a reduction in the number of cells in S-phase. CM prepared from adipose tissue overrode these direct CORT effects, suggesting that the tumor growth microenvironment created in the CM dominates MCF7 cell cycle regulation.

CONCLUSIONS

The direct inhibitory effects of CORT on cancer cell cycle progression are largely limited by the hormone's effects on adipose tissue biology.

The role and regulation of 11β-hydroxysteroid dehydrogenase type 1 in obesity and the metabolic syndrome

The cortisol regenerating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) amplifies tissue glucocorticoid levels, particularly in the liver and adipose tissue. The importance of this enzyme in causing metabolic disease was highlighted by transgenic mice which over- or under-expressed 11β-HSD1; consequently, selective 11β-HSD1 inhibitors have been widely developed as novel agents to treat obesity and type 2 diabetes mellitus (T2DM). This review focuses on the importance of 11β-HSD1 in humans which has been more difficult to ascertain. The recent development of a deuterated cortisol tracer has allowed us to quantify in vivo cortisol production by 11β-HSD1. These results have been surprising, as cortisol production rates by 11β-HSD1 are at least equivalent to that of the adrenal glands. The vast majority of this production is by the liver (>90%) with a smaller contribution from subcutaneous adipose tissue and possibly skeletal muscle, but with no detectable production from visceral adipose tissue. This tracer has also allowed us to quantify the tissue-specific regulation of 11β-HSD1 observed in obesity and obesity-associated T2DM, determine the likely basis for this dysregulation, and identify obese patients with T2DM as the group most likely to benefit from selective inhibition of 11β-HSD1. Some of these inhibitors have now reached Phase II clinical development, demonstrating efficacy in the treatment of T2DM. We review these results and discuss whether selective 11β-HSD1 inhibitors are likely to be an important new therapy for metabolic disease.

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.

11β-Hydroxysteroid dehydrogenase activity in the brain does not contribute to systemic interconversion of cortisol and cortisone in healthy men

CONTEXT AND OBJECTIVE

11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) catalyses regeneration of cortisol in liver, adipose tissue, and skeletal muscle, making a substantial contribution to circulating cortisol as demonstrated in humans by combining stable isotope tracer infusion with arteriovenous sampling. In the brain, 11βHSD1 is a potential therapeutic target implicated in age-associated cognitive dysfunction. We aimed to quantify brain 11βHSD1 activity, both to assess its contribution to systemic cortisol/cortisone turnover and to develop a tool for measuring 11βHSD1 in dementia and following administration of 11βHSD1 inhibitors.

DESIGN, SETTING, AND PARTICIPANTS

With ethical approval and informed consent, 8 healthy men aged 38.1 years (sd 16.5) underwent an ECG-gated phase-contrast magnetic resonance scan to quantify internal jugular vein blood flow and were infused with 1,2 [(2)H]2-cortisone and 9,11,12,12 [(2)H]4-cortisol for 3 h before samples were obtained from the internal jugular vein and an arterialized hand vein. Steroids were quantified by liquid chromatography-tandem mass spectrometry.

MAIN OUTCOME MEASURES AND RESULTS

Steady state tracer enrichments were achieved and systemic indices of cortisol/cortisone interconversion were consistent with previous studies in healthy men. However, there was no measurable release or production of cortisol, 9,12,12 [(2)H]3-cortisol or cortisone into the internal jugular vein.

CONCLUSIONS

Although cerebral 11βHSD1 reductase activity may be greater in cognitively impaired patients, in healthy men any contribution of 11βHSD1 in the brain to systemic cortisol/cortisone turnover is negligible. The influence of 11βHSD1 in the brain is likely confined to subregions, notably the hippocampus. Alternative approaches are required to quantify pharmacodynamics effects of 11βHSD1 inhibitors in the human brain.

Metabolic fate of fructose in human adipocytes: a targeted 13C tracer fate association study

The development of obesity is becoming an international problem and the role of fructose is unclear. Studies using liver tissue and hepatocytes have contributed to the understanding of fructose metabolism. Excess fructose consumption also affects extra hepatic tissues including adipose tissue. The effects of fructose on human adipocytes are not yet fully characterized, although in vivo studies have noted increased adiposity and weight gain in response to fructose sweetened-beverages. In order to understand and predict the metabolic responses of adipocytes to fructose, this study examined differentiating and differentiated human adipocytes in culture, exposed to a range of fructose concentrations equivalent to that reported in blood after consuming fructose. A stable isotope based dynamic profiling method using [U-¹³C₆]-d-fructose tracer was used to examine the metabolism and fate of fructose. A targeted stable isotope tracer fate association method was used to analyze metabolic fluxes and flux surrogates with exposure to escalating fructose concentration. This study demonstrated that fructose stimulates anabolic processes in adipocytes robustly, including glutamate and de novo fatty acid synthesis. Furthermore, fructose also augments the release of free palmitate from fully differentiated adipocytes. These results imply that in the presence of fructose, the metabolic response of adipocytes in culture is altered in a dose dependent manner, particularly favoring increased glutamate and fatty acid synthesis and release, warranting further in vivo studies.

Tissue-specific dysregulation of 11β-hydroxysteroid dehydrogenase type 1 in overweight/obese women with polycystic ovary syndrome compared with weight-matched controls

CONTEXT

Abnormal cortisol metabolism in polycystic ovary syndrome (PCOS) has been invoked as a cause of secondary activation of the hypothalamic-pituitary-adrenal axis and hence androgen excess. However, this is based on urinary excretion of cortisol metabolites, which cannot detect tissue-specific changes in metabolism and may be confounded by obesity.

OBJECTIVE

To assess cortisol clearance and whole-body and tissue-specific activities of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1 (HSD11B1)) in PCOS.

DESIGN

Case-control study.

SETTING

Medical center.

PATIENTS

A total of 20 overweight-obese unmedicated Caucasian women with PCOS, aged 18-45 years, and 20 Caucasian controls matched for age, BMI, body fat distribution, and HSD11B1 genotypes (rs846910 and rs12086634).

MAIN OUTCOME MEASURES

Cortisol metabolites were measured in 24 h urine. During steady-state 9,11,12,12-[(2)H]4-cortisol infusion, cortisol clearance was calculated and whole-body HSD11B1 activity was assessed as the rate of appearance of 9,12,12-(2)H3-cortisol (d3-cortisol). Hepatic HSD11B1 activity was quantified as the generation of plasma cortisol following an oral dose of cortisone. Subcutaneous adipose HSD11B1 activity and HSD11B1 mRNA were measured, ex vivo, in biopsies.

RESULTS

Urinary cortisol metabolite excretion, deuterated cortisol clearance, and the rate of appearance of d3-cortisol did not differ between patients with PCOS and controls. However, hepatic HSD11B1 conversion of oral cortisone to cortisol was impaired (P<0.05), whereas subcutaneous abdominal adipose tissue HSD11B1 mRNA levels and activity were increased (P<0.05) in women with PCOS when compared with controls.

CONCLUSIONS

Tissue-specific dysregulation of HSD11B1 is a feature of PCOS, over and above obesity, whereas increased clearance of cortisol may result from obesity rather than PCOS.

Hepatic 11β-hydroxysteroid dehydrogenase type 1 activity in obesity and type 2 diabetes using a novel triple tracer cortisol technique

AIMS/HYPOTHESIS

Dysregulation of 11β-hydroxysteroid dehydrogenase (11β-HSD) enzyme activities are implicated in the pathogenesis of obesity and insulin resistance. The aim of the study was to determine whether hepatic 11β-HSD type 1 (11β-HSD-1) enzyme activity differs in people with and without obesity and type 2 diabetes.

METHODS

We measured hepatic 11β-HSD-1 activity in the overnight fasted state in 20 lean non-diabetic participants (LND), 21 overweight/obese non-diabetic participants (OND) and 20 overweight/obese participants with type 2 diabetes (ODM) using a non-invasive approach. One mg doses of [9,12,12-(2)H3]cortisol (D cortisol) and [4-(13)C]cortisone ([(13)C]cortisone) were ingested, while [1,2,6,7-(3)H]cortisol ([(3)H] cortisol) was infused intravenously to enable concurrent measurements of first-pass hepatic extraction of ingested D cortisol and hepatic conversion of ingested [(13)C]cortisone to C13 cortisol derived from the ingested cortisone (a measure of 11β-HSD-1 activity in the liver) using an isotope dilution technique. One-way ANOVA models and Kruskal-Wallis tests were used to test the hypothesis.

RESULTS

Plasma D cortisol and C13 cortisol concentrations were lower in OND than in LND (p < 0.05) over 6 h of the study. There was no difference (p = 0.15) in C13 and D cortisol concentrations between OND and ODM and between LND and ODM for the same study period. Hepatic conversion of [(13)C]cortisone to C13 cortisol was similar between groups.

CONCLUSIONS/INTERPRETATION

Hepatic conversion of [(13)C]cortisone to C13 cortisol did not differ between the groups studied. We conclude that hepatic 11β-HSD-1 activity is similar in individuals who are overweight/obese or who have type 2 diabetes.

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

Cushing's syndrome, caused by increased production of cortisol, leads to metabolic dysfunction including visceral adiposity, hypertension, hyperlipidaemia and type 2 diabetes. The similarities with the metabolic syndrome are striking and major efforts have been made to find obesity-associated changes in the regulation of glucocorticoid action and synthesis, both at a systemic level and tissue level. Obesity is associated with tissue-specific alterations in glucocorticoid metabolism, with increased activity of the glucocorticoid-regenerating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) in subcutaneous adipose tissue and decreased conversion of cortisone to cortisol, interpreted as decreased 11βHSD1 activity, in the liver. In addition, genetic manipulation of 11βHSD1 activity in rodents can either induce (by overexpression of Hsd11b1, the gene encoding 11βHSD1) or prevent (by knocking out Hsd11b1) obesity and metabolic dysfunction. Taken together with earlier evidence that non-selective inhibitors of 11βHSD1 enhance insulin sensitivity, these results led to the hypothesis that inhibition of 11βHSD1 might be a promising target for treatment of the metabolic syndrome. Several selective 11βHSD1 inhibitors have now been developed and shown to improve metabolic dysfunction in patients with type 2 diabetes, but the small magnitude of the glucose-lowering effect has precluded their further commercial development.This review focuses on the role of 11βHSD1 as a tissue-specific regulator of cortisol exposure in obesity and type 2 diabetes in humans. We consider the potential of inhibition of 11βHSD1 as a therapeutic strategy that might address multiple complications in patients with type 2 diabetes, and provide our thoughts on future directions in this field.

Increased aldosterone: mechanism of hypertension in obesity

The prevalence of both obesity and hypertension are increasing worldwide. Hypertension is a common consequence of obesity. Increased central adiposity is associated with increased aldosterone levels and blood pressure in human beings. A number of small studies have shown an association between obesity-mediated hypertension and mechanisms directly linked to increased levels of aldosterone. These studies have shown a trend toward relatively greater blood pressure reduction using aldosterone-receptor blockers compared with other classes of antihypertensive agents. Other than treatment for weight loss, treatment of hypertension with specific antihypertensive medications that block or reduce aldosterone action are appropriate in obese patients. Further research is needed to understand the exact role of the adipocyte in obesity-mediated hypertension.

11β-HSD1 inhibitors for the treatment of type 2 diabetes and cardiovascular disease

Inhibition of the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) has been proposed as a novel therapeutic target for the treatment of type 2 diabetes mellitus. Over 170 new compounds targeting 11β-HSD1 have been developed. This article reviews the current published literature on compounds that have reached phase II clinical trials in patients with type 2 diabetes, and summarises the preclinical evidence that such agents may be useful for associated conditions, including peripheral vascular disease, coronary artery disease and cognitive decline. In clinical trials, 11β-HSD1 inhibitors have been well tolerated and have improved glycaemic control, lipid profile and blood pressure, and induced modest weight loss. The magnitude of the effects are small relative to other agents, so that further development of 11β-HSD1 inhibitors for the primary therapeutic indication of type 2 diabetes has stalled. Ongoing programmes are focused on additional benefits for cognitive function and other cardiovascular risk factors.

Displacement of cortisol from human heart by acute administration of a mineralocorticoid receptor antagonist

CONTEXT

Mineralocorticoid receptor (MR) antagonists have beneficial effects in patients with heart failure and myocardial infarction, often attributed to blocking aldosterone action in the myocardium. However, binding of aldosterone to MR requires local activity of the enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), which inactivates cortisol to cortisone and thereby prevents receptor occupancy by cortisol. In vivo activity of 11β-HSD2 and potential occupancy of MR by cortisol in human heart have not been quantified.

OBJECTIVE

This study aimed to measure in vivo activity of 11β-HSD2 and to establish whether cortisol binds MR in human heart.

PARTICIPANTS AND INTERVENTIONS

Nine patients without heart failure undergoing diagnostic coronary angiography were infused to steady state with the stable isotope tracers 9,11,12,12-[(2)H]4-cortisol and 1,2-[(2)H]2-cortisone to quantify cortisol and cortisone production. Samples were obtained from the femoral artery and coronary sinus before and for 40 minutes after bolus iv administration of an MR antagonist, potassium canrenoate. Coronary sinus blood flow was measured by venography and Doppler flow wire.

RESULTS

There was no detectable production of cortisol or cortisone across the myocardium. After potassium canrenoate administration, plasma aldosterone concentrations increased substantially but aldosterone was not detectably released from the myocardium. In contrast, plasma cortisol concentrations did not change in the systemic circulation but tissue-bound cortisol was released transiently from the myocardium after potassium canrenoate administration.

CONCLUSIONS

Human cardiac 11β-HSD2 activity appears too low to inactivate cortisol to cortisone. Cortisol is displaced acutely from the myocardium by MR antagonists and may contribute to adverse MR activation in human heart.

The postprandial rise in plasma cortisol in men is mediated by macronutrient-specific stimulation of adrenal and extra-adrenal cortisol production

CONTEXT

Circadian variation is a fundamental characteristic of plasma glucocorticoids, with a postprandial rise in cortisol an important feature. The diurnal rhythm is presumed to reflect alterations in hypothalamic-pituitary-adrenal axis activity; however, cortisol is produced not only by the adrenal glands but also by regeneration from cortisone by the enzyme 11β-hydroxysteroid dehydrogenase type 1, mainly in liver and adipose tissue.

OBJECTIVE

We tested the contribution of peripheral cortisol regeneration to macronutrient-induced circadian variation of plasma cortisol in humans.

DESIGN

This was a randomized, single-blinded, crossover study.

SETTING

The study was conducted at a hospital research facility.

PARTICIPANTS

Eight normal-weight healthy men participated in the study.

INTERVENTIONS

Subjects were given isocaloric energy isodense flavor-matched liquid meals composed of carbohydrate, protein, fat, or low-calorie placebo during infusion of the stable isotope tracer 9,11,12,12-[2H]4-cortisol.

OUTCOME MEASURES AND RESULTS

Plasma cortisol increased similarly after all macronutrient meals (by ∼90 nmol/L) compared with placebo. Carbohydrate stimulated adrenal secretion and extra-adrenal regeneration of cortisol to a similar degree. Protein and fat meals stimulated adrenal cortisol secretion to a greater degree than extra-adrenal cortisol regeneration. The increase in cortisol production by 11β-hydroxysteroid dehydrogenase type 1 was in proportion to the increase in insulin. The postprandial cortisol rise was not accounted for by decreased cortisol clearance.

CONCLUSIONS

Food-induced circadian variation in plasma cortisol is mediated by adrenal secretion and extra-adrenal regeneration of cortisol. Given that the latter has the more potent effect on tissue cortisol concentrations and that effects on adrenal and extra-adrenal cortisol production are macronutrient specific, this novel mechanism may contribute to the physiological interplay between insulin and glucocorticoids and the contrasting effects of certain diets on postprandial metabolism.

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.

Peripheral and central nervous system inhibition of 11β-hydroxysteroid dehydrogenase type 1 in man by the novel inhibitor ABT-384

ABT-384 is a potent, selective inhibitor of 11-beta-hydroxysteroid dehydrogenase type 1 (HSD-1). One milligram of ABT-384 daily fully inhibited hepatic HSD-1. Establishing the dose that fully inhibits central nervous system (CNS) HSD-1 would enable definitive clinical studies in potential CNS indications. [9,11,12,12-(2)H4] cortisol (D4 cortisol), a stable labeled tracer, was used to characterize HSD-1 inhibition by ABT-384. D4 cortisol and its products were measured in the plasma and cerebrospinal fluid (CSF) of healthy male volunteers during D4 cortisol infusions, for up to 40 h after five daily doses of 1-50 mg ABT-384. Similar procedures were conducted in control subjects who received no ABT-384. Peripheral HSD-1 inhibition was calculated from plasma levels of D4 cortisol and its products. CNS HSD-1 inhibition was characterized from plasma and CSF levels of D4 cortisol and its products. ABT-384 regimens ≥2 mg daily maintained peripheral HSD-1 inhibition ≥88%. ABT-384 1 mg daily maintained peripheral HSD-1 inhibition ≥81%. No CNS formation of D3 cortisol (the mass-labeled product of HSD-1) was detected following ABT-384 ≥2 mg daily, indicating full CNS HSD-1 inhibition by these regimens. Partial CNS HSD-1 inhibition was associated with 1 mg ABT-384 daily. CNS HSD-1 inhibition was characterized by strong hysteresis and increased with maximum post-dose plasma concentration of ABT-384 and its active metabolites. ABT-384 has a wide potential therapeutic window for potential indications including Alzheimer's disease and major depressive disorder. Stable labeled substrates may be viable tools for measuring CNS effect during new drug development for other enzyme targets.

Reduced cortisol metabolism during critical illness

BACKGROUND

Critical illness is often accompanied by hypercortisolemia, which has been attributed to stress-induced activation of the hypothalamic-pituitary-adrenal axis. However, low corticotropin levels have also been reported in critically ill patients, which may be due to reduced cortisol metabolism.

METHODS

In a total of 158 patients in the intensive care unit and 64 matched controls, we tested five aspects of cortisol metabolism: daily levels of corticotropin and cortisol; plasma cortisol clearance, metabolism, and production during infusion of deuterium-labeled steroid hormones as tracers; plasma clearance of 100 mg of hydrocortisone; levels of urinary cortisol metabolites; and levels of messenger RNA and protein in liver and adipose tissue, to assess major cortisol-metabolizing enzymes.

RESULTS

Total and free circulating cortisol levels were consistently higher in the patients than in controls, whereas corticotropin levels were lower (P<0.001 for both comparisons). Cortisol production was 83% higher in the patients (P=0.02). There was a reduction of more than 50% in cortisol clearance during tracer infusion and after the administration of 100 mg of hydrocortisone in the patients (P≤0.03 for both comparisons). All these factors accounted for an increase by a factor of 3.5 in plasma cortisol levels in the patients, as compared with controls (P<0.001). Impaired cortisol clearance also correlated with a lower cortisol response to corticotropin stimulation. Reduced cortisol metabolism was associated with reduced inactivation of cortisol in the liver and kidney, as suggested by urinary steroid ratios, tracer kinetics, and assessment of liver-biopsy samples (P≤0.004 for all comparisons).

CONCLUSIONS

During critical illness, reduced cortisol breakdown, related to suppressed expression and activity of cortisol-metabolizing enzymes, contributed to hypercortisolemia and hence corticotropin suppression. The diagnostic and therapeutic implications for critically ill patients are unknown. (Funded by the Belgian Fund for Scientific Research and others; ClinicalTrials.gov numbers, NCT00512122 and NCT00115479; and Current Controlled Trials numbers, ISRCTN49433936, ISRCTN49306926, and ISRCTN08083905.).

Clinical Safety, Pharmacokinetics, and Pharmacodynamics of the 11β-Hydroxysteroid Dehydrogenase Type 1 Inhibitor ABT-384 in Healthy Volunteers and Elderly Adults

ABT-384 is a potent and selective inhibitor of 11β-hydroxysteroid dehydrogenase type 1 (HSD-1), the enzyme that regenerates cortisol in several tissues. Two clinical studies of ABT-384 were undertaken to assess its safety, pharmacokinetics, target engagement, and pharmacologic effects in healthy subjects. Single doses from 1 to 240 mg, and multiple doses from 1 to 100 mg once daily for 7-14 days, were administered to healthy adults. Multiple doses from 10 to 100 mg once daily for 21 days were administered to elderly subjects. A total of 103 subjects received at least 1 dose of ABT-384. A maximum-tolerated dose was not defined in either study. The pharmacokinetic profiles of ABT-384 and its active metabolite support once daily dosing. Analysis of urine cortisol metabolites demonstrated full hepatic HSD-1 inhibition with regimens from 1 mg daily, and confirmed in vitro target selectivity. Pharmacologic effects included increases of adrenocorticotrophic hormone levels, cortisol production and androgen and estradiol levels. ABT-384 has a wide therapeutic index relative to full hepatic target engagement which is relevant for indications such as diabetes and metabolic syndrome. Its therapeutic index for other potential indications such as Alzheimer's disease remains to be established.

Recycling between cortisol and cortisone in human splanchnic, subcutaneous adipose, and skeletal muscle tissues in vivo

11β-Hydroxysteroid dehydrogenase type 1 (11βHSD1) is a therapeutic target in metabolic syndrome because it catalyses reductase regeneration of cortisol from cortisone in adipose and liver. 11βHSD1 can also catalyze the reverse dehydrogenase reaction in vitro (e.g., if cofactor is limited). We used stable isotope tracers to test the hypothesis that both 11βHSD1-reductase and -dehydrogenase activities occur in human metabolic tissues in vivo. 1,2-[(2)H](2)-Cortisone (d2-cortisone) was validated as a tracer for 11β-dehydrogenase activity and its inhibition by licorice. d2-Cortisone and 9,11,12,12-[(2)H](4)-cortisol (d4-cortisol) (to measure 11β-reductase activity) were coinfused and venous samples obtained from skeletal muscle, subcutaneous adipose (n = 6), and liver (n = 4). Steroids were measured by liquid chromatography-tandem mass spectrometry and arteriovenous differences adjusted for blood flow. Data are means ± SEM. 11β-Reductase and -dehydrogenase activities were detected in muscle (cortisol release 19.7 ± 4.1 pmol/100 mL/min, d3-cortisol 5.9 ± 1.8 pmol/100 mL/min, and cortisone 15.2 ± 5.8 pmol/100 mL/min) and splanchnic (cortisol 64.0 ± 11.4 nmol/min, d3-cortisol 12.9 ± 2.1 nmol/min, and cortisone 19.5 ± 2.8 nmol/min) circulations. In adipose, dehydrogenase was more readily detected than reductase (cortisone release 38.7 ± 5.8 pmol/100 g/min). Active recycling between cortisol and cortisone in metabolic tissues in vivo may facilitate dynamic control of intracellular cortisol but makes consequences of dysregulation of 11βHSD1 transcription in obesity and diabetes unpredictable. Disappointing efficacy of 11βHSD1 inhibitors in phase II studies could be explained by lack of selectivity for 11β-reductase.

Estimation of maximal cortisol secretion rate in healthy humans

CONTEXT

Cortisol secretion is related to ACTH concentration by a sigmoidal dose-response curve, in which high ACTH concentrations drive maximal cortisol secretion rates (CSR(max)).

OBJECTIVE

We sought to estimate CSR(max) and free cortisol half-life in healthy humans (n = 21) using numerical methods applied to data acquired during cosyntropin (250 μg) stimulation. We also evaluated the effect of overnight dexamethasone (DEX; 1 mg) vs. placebo on estimates of CSR(max) and free cortisol half-life.

DESIGN

This study was a double-blind, placebo-controlled, randomized order of overnight DEX vs. placebo, cosyntropin (250 μg) stimulation with frequent serum cortisol sampling and computer-assisted numerical analysis.

SETTING

The study was conducted at a single academic medical center.

PARTICIPANTS

Twenty-one healthy adult subjects (15 females and six males), mean aged 46 yr, participated in the study.

INTERVENTION

Intervention in the study included DEX vs. placebo pretreatment, cosyntropin (250 μg) iv with frequent cortisol sampling.

MAIN OUTCOME MEASURES

CSR(max) and free cortisol half-life estimates, R² for goodness of fit, were measured.

RESULTS

Mean ± sd CSR(max) was 0.44 ± 0.13 nm/second, with free cortisol half-life of 2.2 ± 1.1 min. DEX did not significantly affect estimates of CSR(max) or free cortisol half-life. Our model accounts for most of the variability of measured cortisol concentrations (overall R² = 90.9 ±11.0%) and was more accurate (P = 0.004) during DEX suppression (R² = 94.6 ± 4.6%) compared with placebo (R² = 87.2 ± 8.7%).

CONCLUSIONS

Application of a mass-action model under conditions of cosyntropin stimulation provides a relatively simple method for estimation CSR(max) that accurately predicts measured cortisol concentrations. DEX administration did not significantly affect estimates of CSR(max) or free cortisol half-life.

Minireview: Stress-related psychiatric disorders with low cortisol levels: a metabolic hypothesis

Several stress-associated neuropsychiatric disorders, notably posttraumatic stress disorder and chronic pain and fatigue syndromes, paradoxically exhibit somewhat low plasma levels of the stress hormone cortisol. The effects appear greatest in those initially traumatized in early life, implying a degree of developmental programming, perhaps of both lower cortisol and vulnerability to psychopathology. In these conditions, lowered cortisol is not due to any adrenal or pituitary insufficiency. Instead, two processes appear involved. First, there is increased target cell sensitivity to glucocorticoid action, notably negative feedback upon the hypothalamic-pituitary-adrenal (stress) axis. Altered density of the glucocorticoid receptor is inferred, squaring with much preclinical data showing early life challenges can permanently program glucocorticoid receptors in a tissue-specific manner. These effects involve epigenetic mechanisms. Second, early life trauma/starvation induces long-lasting lowering of glucocorticoid catabolism, specifically by 5α-reductase type 1 (predominantly a liver enzyme) and 11β-hydroxysteroid dehydrogenase type 2 (in kidney), an effect also seen in model systems. These changes reflect a plausible early-life adaptation to increase the persistence of active cortisol in liver (to maximize fuel output) and kidney (to increase salt retention) without elevation of circulating levels, thus avoiding their deleterious effects on brain and muscle. Modestly lowered circulating cortisol and increased vulnerability to stress-associated disorders may be the outcome. This notion implies a vulnerable early-life phenotype may be discernable and indicates potential therapy by modest glucocorticoid replacement. Indeed, early clinical trials with cortisol have shown a modicum of promise.

A combination of polymorphisms in HSD11B1 associates with in vivo 11{beta}-HSD1 activity and metabolic syndrome in women with and without polycystic ovary syndrome

OBJECTIVE

Regeneration of cortisol by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) within liver and adipose tissue may be of pathophysiological importance in obesity and the metabolic syndrome. single nucleotide polymorphisms (SNPs) in HSD11B1, the gene encoding 11β-HSD1, have been associated with type 2 diabetes and hypertension in population-based cohort studies, and with hyperandrogenism in patients with the polycystic ovary syndrome (PCOS). However, the functional consequences of these SNPs for in vivo 11β-HSD1 expression and activity are unknown.

METHODS

We explored associations of well-characterised hormonal and metabolic phenotypes with two common SNPs (rs846910 and rs12086634) in HSD11B1 in 600 women (300 with PCOS) and investigated 11β-HSD1 expression and activity in a nested study of 40 women from this cohort.

RESULTS

HSD11B1 genotypes (as single SNPs and as the combination of the two minor allele SNPs) were not associated with PCOS. Women who were heterozygous for rs846910 A and homozygous for rs12086634 T (GA, TT genotype) had a higher risk of metabolic syndrome, regardless of the diagnosis of PCOS (odds ratio in the whole cohort=2.77 (95% confidence interval (CI) 1.16-6.67), P=0.023). In the nested cohort, women with the GA, TT genotype had higher HSD11B1 mRNA levels in adipose tissue, and higher rates of appearance of cortisol and d3-cortisol (16.1±0.7 nmol/min versus 12.1±1.1, P=0.044) during 9,11,12,12-2H4-cortisol (d4-cortisol) steady-state infusion.

CONCLUSIONS

We conclude that, in a population of Southern European Caucasian women with and without PCOS, alleles of HSD11B1 containing the two SNPs rs846910 A and rs12086634 T confer increased 11β-HSD1 expression and activity, which associates with the metabolic syndrome.

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.

11β-hydroxysteroid dehydrogenase type 1, brain atrophy and cognitive decline

Excess cortisol levels are linked with brain atrophy and cognitive decline in older people. 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) potently amplifies intracellular glucocorticoid action by converting inert cortisone to active cortisol, but any causal importance in brain aging is unexplored. We tested the hypotheses that higher systemic 11β-HSD1 activity predicts brain atrophy and cognitive decline in older men. In a longitudinal study of 41 men (65-70 years old at baseline) we measured baseline systemic 11β-HSD1 activity, the urinary 5alpha- and 5beta-tetrahydrocortisol to tetrahydrocortisone ratio (ratio of tetrahydrometabolites of cortisol (THFs)/ratio of tetrahydrometabolites of cortisol (THE)), and assessed change in brain atrophy, white matter lesions and cognitive function over 6 years. Baseline THFs/THE correlated negatively with baseline hippocampal volumes (left: r = -0.37; right: r = -0.34; p < 0.05) and positively with ventricular volumes (r = 0.43, p = 0.006) and periventricular white matter lesions (rho = 0.31, p = 0.047). Importantly, baseline THFs/THE but not cortisol predicted increase in ventricular volumes (r = 0.33, p = 0.037) and decline in processing speed (r = -0.55, p = 0.0002) over 6 years. The predictive link between systemic 11β-HSD1 activity and progressive brain atrophy and cognitive decline suggests 11β-HSD1 inhibition as a plausible therapy for brain aging.

Glucocorticoids turn over slowly in human adipose tissue in vivo

CONTEXT

Lipophilic plasma glucocorticoids are thought to gain rapid access to intracellular compartments in adipose tissue. In other organs, transport can be regulated in a steroid- and tissue-specific manner. Moreover, 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) generates additional cortisol within adipose.

AIM

The aim was to measure the rate of exchange of cortisol between plasma and adipose for comparison with rates of intracellular cortisol generation by 11βHSD1.

PARTICIPANTS AND INTERVENTIONS

With ethical approval, otherwise healthy females (n = 6) undergoing hysterectomy for benign indications were infused with tracer 9,11,12,12-[(2)H](4)cortisol (d4-cortisol). Adipose biopsies and peripheral venous samples were obtained during surgery after 3.9-5.5 h of infusion. Glucocorticoids were quantified using liquid chromatography tandem mass spectrometry.

RESULTS

In plasma, d4-cortisol concentrations and appearance rates of cortisol and d3-cortisol (reflecting 11βHSD1 activity) did not change during surgery. In both omental and sc adipose, cortisol concentrations were lower than in plasma, consistent with differences in corticosteroid binding globulin, and enrichment with d4-cortisol was low (sc, 7.2 ± 0.6%; omental, 7.4 ± 0.7%; vs. plasma, 15.5 ± 1.0%). The rate of accumulation of d4-cortisol in adipose depots was 0.5 ± 0.1 (sc) and 0.4 ± 0.1 (omental) nmol/kg · h, and the proportion of intraadipose cortisol replaced each hour only 10.7 ± 1.0 and 10.4 ± 0.7%, respectively. The contribution of 11βHSD1 to this turnover could not be quantified because very little substrate d3-cortisone accumulated in adipose during infusion.

CONCLUSIONS

Slow turnover of the adipose glucocorticoid pool suggests that rapid acute fluctuations in circulating cortisol are not reflected in adipose, so that 11βHSD1 activity (previously estimated to generate 9 nmol cortisol/kg · h in sc adipose) may play a relatively important role in modulating activation of glucocorticoid receptors.

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.

Visceral adipose tissue in children and adolescents: a review

Research conducted among adults has mainly shown that visceral adipose tissue (VAT) is strongly linked to insulin resistance, type 2 diabetes, hypertension and dyslipidaemia, leading to increased risk of CVD or the metabolic syndrome. However, little is known about the aetiology, determinants and consequences of VAT in children. The present article reviews the current literature relating to the factors influencing visceral fat accumulation in children and adolescents. The literature used in the present study was collected by searching a PubMed database, in which studies up to 2008 exploring the factors influencing accumulation of visceral fat among children and youth were found on the basis of appropriate keywords. Further studies concerning different factors influencing deposition of VAT among children and youth should first of all concentrate on: carrying out long-term analyses among children of different ethnical groups, which should begin in the period of prepuberty and which should cover the whole period of puberty till adulthood; drawing up norms specifying the amount of VAT among healthy children; identification of anthropometric indicators which will help to determine the VAT:subcutaneous adipose tissue ratio in the most precise way; broader studies of the influence of eating habits on developing VAT deposit among children and youth.

Lack of regulation of 11beta-hydroxysteroid dehydrogenase type 1 during short-term manipulation of GH in patients with hypopituitarism

OBJECTIVE

Evidence from long-term clinical studies measuring urinary steroid ratios, and from in vitro studies, suggests that GH administered for longer than 2 months down-regulates 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), thereby reducing cortisol regeneration in liver and adipose tissue. We aimed to measure acute effects of GH on 11beta-HSD1 in liver and adipose tissue in vivo, including using a stable isotope tracer.

DESIGN

Observational studies of GH withdrawal and reintroduction in patients with hypopituitarism.

METHODS

Twelve men with benign pituitary disease causing GH and ACTH deficiency on stable replacement therapy for >6 months were studied after GH withdrawal for 3 weeks, and after either placebo or GH injections were reintroduced for another 3 weeks. We measured cortisol kinetics during 9,11,12,12-(2)H(4)-cortisol (d4-cortisol) infusion, urinary cortisol/cortisone metabolite ratios, liver 11beta-HSD1 by appearance of plasma cortisol after oral cortisone, and 11beta-HSD1 mRNA levels in subcutaneous adipose biopsies.

RESULTS

GH withdrawal and reintroduction had no effect on 9,12,12-[(2)H](3)-cortisol (d3-cortisol) appearance, urinary cortisol/cortisone metabolite ratios, initial appearance of cortisol after oral cortisone, or adipose 11beta-HSD1 mRNA. GH withdrawal increased plasma cortisol 30-180 min after oral cortisone, increased d4-cortisol clearance, and decreased relative excretion of 5alpha-reduced cortisol metabolites.

CONCLUSIONS

In this setting, GH did not regulate 11beta-HSD1 rapidly in vivo in humans. Altered cortisol metabolism with longer term changes in GH may reflect indirect effects on 11beta-HSD1. These data do not suggest that glucocorticoid replacement doses need to be increased immediately after introducing GH therapy to compensate for reduced 11beta-HSD1 activity, although dose adjustment may be required in the longer term.

Expression of cortisol metabolism-related genes shows circadian rhythmic patterns in human adipose tissue

OBJECTIVE

To analyze, in morbid obese patients, the expression of several human genes regulating cortisol metabolism, such as glucocorticoid receptor (GR), 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1), 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2), stearoyl-acute regulatory protein (StAR), 5alpha-reductase type I (5alpha-R) and peroxisome proliferator-activated receptor-gamma (PPARgamma) in two different adipose depots. A second objective was to characterize the circadian rhythmicity of these genes in both adipose tissue (AT) regions.

DESIGN

Visceral and subcutaneous abdominal AT biopsies were obtained from obese patients (body mass index >or=40 kg m(-2)). To carry out rhythmic expression analysis, AT explants were cultured for 24 h and gene expression at times (T) 0, 6, 12 and 18 h, was performed with quantitative real-time PCR.

RESULT

GR, 11betaHSD1 and PPARgamma genes were highly expressed in both subcutaneous and visceral depots. StAR and 5alpha-R genes were detected at lower levels. The expression of 11betaHSD2 was quantified in both AT depots with a higher expression in the visceral depot (P=0.032). Both sexes had similar gene expression levels, except for 5alpha-R (P=0.002). The genes studied showed circadian rhythmicity being more robust in visceral than in subcutaneous AT. Genes ranged in anti-phase between both depots (P=0.002). This rhythmicity was maintained in an AT culture.

CONCLUSION

We have shown for the first time circadian rhythmicity in glucocorticoid-related gene expression in human AT ex vivo. These results may have potential therapeutic implications with respect to the pathogenesis and treatment of diseases, such as obesity, type 2 diabetes and cardiovascular diseases.

Cortisol release from adipose tissue by 11beta-hydroxysteroid dehydrogenase type 1 in humans

OBJECTIVE

11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1) regenerates cortisol from cortisone. 11beta-HSD1 mRNA and activity are increased in vitro in subcutaneous adipose tissue from obese patients. Inhibition of 11beta-HSD1 is a promising therapeutic approach in type 2 diabetes. However, release of cortisol by 11beta-HSD1 from adipose tissue and its effect on portal vein cortisol concentrations have not been quantified in vivo.

RESEARCH DESIGN AND METHODS

Six healthy men underwent 9,11,12,12-[(2)H](4)-cortisol infusions with simultaneous sampling of arterialized and superficial epigastric vein blood sampling. Four men with stable chronic liver disease and a transjugular intrahepatic porto-systemic shunt in situ underwent tracer infusion with simultaneous sampling from the portal vein, hepatic vein, and an arterialized peripheral vein.

RESULTS

Significant cortisol and 9,12,12-[(2)H](3)-cortisol release were observed from subcutaneous adipose tissue (15.0 [95% CI 0.4-29.5] and 8.7 [0.2-17.2] pmol . min(-1) . 100 g(-1) adipose tissue, respectively). Splanchnic release of cortisol and 9,12,12-[(2)H](3)-cortisol (13.5 [3.6-23.5] and 8.0 [2.6-13.5] nmol/min, respectively) was accounted for entirely by the liver; release of cortisol from visceral tissues into portal vein was not detected.

CONCLUSIONS

Cortisol is released from subcutaneous adipose tissue by 11beta-HSD1 in humans, and increased enzyme expression in obesity is likely to increase local glucocorticoid signaling and contribute to whole-body cortisol regeneration. However, visceral adipose 11beta-HSD1 activity is insufficient to increase portal vein cortisol concentrations and hence to influence intrahepatic glucocorticoid signaling.

Liver is the site of splanchnic cortisol production in obese nondiabetic humans

OBJECTIVE

To determine the contribution of liver and viscera to splanchnic cortisol production in humans.

RESEARCH DESIGN AND METHODS

D4 cortisol was infused intravenously; arterial, portal venous, and hepatic venous blood was sampled; and liver and visceral fat were biopsied in subjects undergoing bariatric surgery.

RESULTS

Ratios of arterial and portal vein D4 cortisol/cortisol(total) (0.06 +/- 0.01 vs. 0.06 +/- 0.01) and D4 cortisol/D3 cortisol (1.80 +/- 0.14 vs. 1.84 +/- 0.14) did not differ, indicating that no visceral cortisol production or conversion of D4 cortisol to D3 cortisol via 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1) occurred. Conversely, ratios of both D4 cortisol to cortisol(total) (0.05 +/- 0.01; P < 0.05) and D4 cortisol to D3 cortisol (1.33 +/- 0.11; P < 0.001) were lower in the hepatic vein than in the portal vein, indicating production of both cortisol and D3 cortisol by the liver. The viscera did not produce either cortisol (-8.1 +/- 2.6 microg/min) or D3 cortisol (-0.2 +/- 0.1 microg/min). In contrast, the liver produced both cortisol (22.7 +/- 3.90 microg/min) and D3 cortisol (1.9 +/- 0.4 microg/min) and accounted for all splanchnic cortisol and D3 cortisol production. Additionally, 11beta-HSD-1 mRNA was approximately ninefold higher (P < 0.01) in liver than in visceral fat. Although 11beta-HSD-2 gene expression was very low in visceral fat, the viscera released cortisone (P < 0.001) and D3 cortisone (P < 0.01) into the portal vein.

CONCLUSIONS

The liver accounts for all splanchnic cortisol production in obese nondiabetic humans. In contrast, the viscera releases cortisone into the portal vein, thereby providing substrate for intrahepatic cortisol production.