Brian R Walker

The University of Edinburgh, Edinburgh, Scotland, United Kingdom

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Publications (265)1337.07 Total impact

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    ABSTRACT: 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.
    Diabetologia 04/2014; · 6.49 Impact Factor
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    ABSTRACT: Context: Mineralocorticoid receptors (MR) contribute to negative feedback of the hypothalamic-pituitary-adrenal (HPA) axis in rodents. Studies with MR antagonists suggest a similar role in humans. Objective: To establish whether loss-of-function mutations in NR3C2, encoding MR, cause activation of the HPA axis. Design and Setting: A case-control study in members of pedigrees from the PHA1.NET cohort, comprising patients with pseudohypoaldosteronism type 1 (PHA1) who are heterozygous for loss-of-function mutations in NR3C2 and healthy controls who are unaffected family members. Participants: 12 adult patients with PHA1 (6 men, 6 women) and 20 age-matched healthy controls (7 men, 13 women). Results: Patients with PHA1 had higher morning plasma cortisol (816 ± 85 vs 586 ± 50 nmol/L, p=0.02) and increased 24h urinary excretion of cortisol metabolites (985 ± 150 vs 640 ± 46 μ g/mmol creatinine, p=0.03), independently of gender. After adjustment for gender, age, PHA1 diagnosis and percentage body fat, higher plasma cortisol was associated with higher plasma renin, lower serum HDL-cholesterol and higher waist circumference, but not with blood pressure, carotid intima-media thickness or echocardiographic parameters. Conclusions: Haploinsufficiency of MR in PHA1 causes HPA axis activation, providing genetic evidence that MR contributes to negative feedback in the human HPA axis. With limited sample size, initial indications suggest the resulting hypercortisolaemia is related to the severity of MR deficiency and has adverse effects mediated by glucocorticoid receptors on liver lipid metabolism and adipose tissue distribution, but does not adversely affect cardiac and vascular remodelling in the absence of normal signalling through MR.
    The Journal of clinical endocrinology and metabolism 04/2014; · 6.50 Impact Factor
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    ABSTRACT: Fuelled by the obesity epidemic, there is considerable interest in the developmental origins of white adipose tissue (WAT) and the stem and progenitor cells from which it arises. Whereas increased visceral fat mass is associated with metabolic dysfunction, increased subcutaneous WAT is protective. There are six visceral fat depots: perirenal, gonadal, epicardial, retroperitoneal, omental and mesenteric, and it is a subject of much debate whether these have a common developmental origin and whether this differs from that for subcutaneous WAT. Here we show that all six visceral WAT depots receive a significant contribution from cells expressing Wt1 late in gestation. Conversely, no subcutaneous WAT or brown adipose tissue arises from Wt1-expressing cells. Postnatally, a subset of visceral WAT continues to arise from Wt1-expressing cells, consistent with the finding that Wt1 marks a proportion of cell populations enriched in WAT progenitors. We show that all visceral fat depots have a mesothelial layer like the visceral organs with which they are associated, and provide several lines of evidence that Wt1-expressing mesothelium can produce adipocytes. These results reveal a major ontogenetic difference between visceral and subcutaneous WAT, and pinpoint the lateral plate mesoderm as a major source of visceral WAT. They also support the notion that visceral WAT progenitors are heterogeneous, and suggest that mesothelium is a source of adipocytes.
    Nature Cell Biology 03/2014; · 20.76 Impact Factor
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    ABSTRACT: Insulin resistance and associated metabolic sequelae are common in chronic kidney disease (CKD) and are positively and independently associated with increased cardiovascular mortality. However, the pathogenesis has yet to be fully elucidated. 11β-Hydroxysteroid dehydrogenase type 1 (11βHSD1) catalyzes intracellular regeneration of active glucocorticoids, promoting insulin resistance in liver and other metabolic tissues. Using two experimental rat models of CKD (subtotal nephrectomy and adenine diet) which show early insulin resistance, we found that 11βHSD1 mRNA and protein increase in hepatic and adipose tissue, together with increased hepatic 11βHSD1 activity. This was associated with intrahepatic but not circulating glucocorticoid excess, and increased hepatic gluconeogenesis and lipogenesis. Oral administration of the 11βHSD inhibitor carbenoxolone to uremic rats for 2 wk improved glucose tolerance and insulin sensitivity, improved insulin signaling, and reduced hepatic expression of gluconeogenic and lipogenic genes. Furthermore, 11βHSD1(-/-) mice and rats treated with a specific 11βHSD1 inhibitor (UE2316) were protected from metabolic disturbances despite similar renal dysfunction following adenine experimental uremia. Therefore, we demonstrate that elevated hepatic 11βHSD1 is an important contributor to early insulin resistance and dyslipidemia in uremia. Specific 11βHSD1 inhibitors potentially represent a novel therapeutic approach for management of insulin resistance in patients with CKD.
    Proceedings of the National Academy of Sciences 02/2014; · 9.74 Impact Factor
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    ABSTRACT: 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyzes intracellular regeneration of corticosterone and cortisol, thereby enhancing glucocorticoid action. Inhibition of 11β-HSD1 reverses the deficits in cognition with ageing, a state of elevated glucocorticoid levels. However, any impact of 11β-HSD1 inhibition during high glucocorticoid states in younger animals is unknown. Here we examined whether a single injection of the selective 11β-HSD1 inhibitor UE2316 modifies the effect of stress on hippocampal long-term potentiation and fear conditioning, a learning paradigm that is strongly modulated by glucocorticoids. We found that novelty stress suppresses hippocampal synaptic potentiation. This effect was completely prevented by administration of UE2316 one hour before stress exposure. A single injection of UE2316 also impaired contextual, but not tone-cue-fear conditioning. These observations suggest that local metabolism of glucocorticoids is relevant for the outcome of stress effects on hippocampal synaptic plasticity and contextual fear conditioning. Selective 11β-HSD1 inhibitors may be an interesting new approach to the prevention of trauma-associated psychopathology.
    Neuropharmacology 02/2014; · 4.11 Impact Factor
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    ABSTRACT: An unhealthy lifestyle is thought to contribute to the metabolic syndrome in subjects with psychoses. In the present study we aimed to study whether life stress or cortisol measures may influence dietary patterns in subjects with early stages of psychoses. We studied 81 subjects with early psychoses (65 subjects with a psychotic disorder [PD] and <5 years of illness; 16 subjects at risk for psychosis [high-risk, HR]) and a control group of 25 healthy subjects (HS). Dietary habits were examined by a dietician, who registered food intake (24h recall). Physical activity was assessed by validated questionnaire. Life stress was assessed with Holmes-Rahe Social Readjustment Scale. Fasting morning salivary and plasma cortisol levels were determined. We found that PD and HR reported an unhealthier lifestyle with more smoking, reduced physical activity and poorer dietary habits. HR reported increased intake of calories and saturated fatty acids and reduced protein consumption, when compared to HS. Life stress was a predictor of these adverse behaviours, although we found opposite associations in HR and PD. Life stress was associated with increased intake of refined sugar in PD and decreased intake in HR and HS. Salivary cortisol was related to increased intake of saturated fat only in HR subjects, but cortisol levels in plasma or saliva were not associated with other dietary habits or obesity measures (BMI, waist circumference). Our study suggests that unhealthy diet in early psychoses is influenced by stress, but our data do not support this effect being mediated by hypercortisolism. Future preventive interventions in psychosis may target dietary habits, particularly for those who are at risk for psychosis.
    Psychoneuroendocrinology 01/2014; 39:1-10. · 5.14 Impact Factor
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    ABSTRACT: An unhealthy lifestyle is thought to contribute to the metabolic syndrome in subjects with psychoses. In the present study we aimed to study whether life stress or cortisol measures may influence dietary patterns in subjects with early stages of psychoses. We studied 81 subjects with early psychoses (65 subjects with a psychotic disorder [PD] and <5 years of illness; 16 subjects at risk for psychosis [high-risk, HR]) and a control group of 25 healthy subjects (HS). Dietary habits were examined by a dietician, who registered food intake (24 h recall). Physical activity was assessed by validated questionnaire. Life stress was assessed with Holmes–Rahe Social Readjustment Scale. Fasting morning salivary and plasma cortisol levels were determined. We found that PD and HR reported an unhealthier lifestyle with more smoking, reduced physical activity and poorer dietary habits. HR reported increased intake of calories and saturated fatty acids and reduced protein consumption, when compared to HS. Life stress was a predictor of these adverse behaviours, although we found opposite associations in HR and PD. Life stress was associated with increased intake of refined sugar in PD and decreased intake in HR and HS. Salivary cortisol was related to increased intake of saturated fat only in HR subjects, but cortisol levels in plasma or saliva were not associated with other dietary habits or obesity measures (BMI, waist circumference). Our study suggests that unhealthy diet in early psychoses is influenced by stress, but our data do not support this effect being mediated by hypercortisolism. Future preventive interventions in psychosis may target dietary habits, particularly for those who are at risk for psychosis.
    Psychoneuroendocrinology 01/2014; 39:1–10. · 5.14 Impact Factor
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    ABSTRACT: Congenital adrenal hyperplasia (CAH) is a genetic disorder caused by defective steroidogenesis that results in glucocorticoid deficiency; the most common underlying mutation is in the gene that encodes 21-hydroxylase. Life-saving glucocorticoid treatment was introduced in the 1950s, and the number of adult patients is now growing; however, no consensus has been reached on the management of CAH beyond childhood. Adult patients are prescribed a variety of glucocorticoids, including hydrocortisone, prednisone, prednisolone, dexamethasone and combinations of these drugs taken in either a circadian or reverse circadian regimen. Despite these personalized treatments, biochemical control of CAH is only achieved in approximately one-third of patients. Some patients have a poor health status, with an increased incidence of obesity and osteoporosis, and impaired fertility and quality of life. The majority of poor health outcomes seem to relate to inadequate treatment rather than the genotype of the patient. Patients receiving high doses of glucocorticoids and the more potent synthetic long-acting glucocorticoids are at an increased risk of obesity, insulin resistance and a reduced quality of life. Further research is required to optimize the treatment of adult patients with CAH and improve health outcomes.
    Nature Reviews Endocrinology 12/2013; · 11.03 Impact Factor
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    ABSTRACT: The University of Edinburgh is currently inviting applications for a unique training programme intended to develop a new generation of veterinary researchers, who are able to conduct internationally competitive research while still being grounded in clinical practice. Modelled on the Edinburgh Clinical Academic Track (ECAT) programme for medical trainees, the ECAT-V programme will allow successful applicants to develop both their clinical and research skills. Here, David Argyle, head of the Royal (Dick) School of Veterinary Studies, and his medical colleagues, John Iredale, Andrew Jackson and Brian Walker, describe the initiative and explain why it is important.
    The Veterinary record. 10/2013; 173(15):364-5.
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    ABSTRACT: Steroid concentrations within tissues are modulated by intracellular enzymes. Such 'steroid intracrinology' influences hormone-dependent cancers and obesity, and provides targets for pharmacological inhibition. However, no high resolution methods exist to quantify steroids within target tissues. We developed mass spectrometry imaging (MSI), combining matrix assisted laser desorption ionization with on-tissue derivatization with Girard T and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, to quantify substrate and product (11-dehydrocorticosterone and corticosterone) of the glucocorticoid-amplifying enzyme 11β-HSD1. Regional steroid distribution was imaged at 150-200μm resolution in rat adrenal gland and mouse brain sections, and confirmed with collision induced dissociation/liquid extraction surface analysis. In brains of mice with 11ß-HSD1 deficiency or inhibition, MSI quantified changes in sub-regional corticosterone/11-dehydrocorticosterone ratio, distribution of inhibitor, and accumulation of alternative 11ß-HSD1 substrate 7-ketocholesterol. MSI data correlated well with LC-MS/MS in whole brain homogenates. MSI with derivatization is a powerful new tool to investigate steroid biology within tissues.
    Analytical Chemistry 10/2013; · 5.70 Impact Factor
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    ABSTRACT: Context:Circadian variation is a fundamental characteristic of plasma glucocorticoids, with a post-prandial 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 (11β-HSD1), 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:Randomised single-blinded crossover studySetting:Hospital Research FacilityParticipants:Eight normal weight healthy menInterventions:Subjects were given isocaloric energy isodense flavour-matched liquid meals composed of either carbohydrate, protein, fat or low calorie placebo during infusion of the stable isotope tracer 9,11,12,12-[(2)H]4-cortisol.Outcome Measures and Results:Plasma cortisol increased similarly after all macronutrient meals (by ∼90nmol/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-HSD1 was in proportion to the increase in insulin. The post-prandial 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 post-prandial metabolism.
    The Journal of clinical endocrinology and metabolism 10/2013; · 6.50 Impact Factor
  • Anna Anderson, Brian R Walker
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    ABSTRACT: 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.
    Drugs 08/2013; · 4.63 Impact Factor
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    ABSTRACT: AIMS/HYPOTHESIS: We have previously reported a high prevalence of non-alcoholic fatty liver disease (NAFLD) among women with previous gestational diabetes mellitus (pGDM). We wanted to confirm that intrahepatocellular lipid (IHCL) is associated with pGDM independently of adiposity and determine: (1) if VLDL metabolism is dysregulated; and (2) the extent to which NAFLD and IHCL account for the dysmetabolic phenotype in pGDM. METHODS: We analysed data from a cohort of 234 women (114 with pGDM) and identified effects of pGDM on lipid and glucoregulation that were independent of ultrasound-diagnosed NAFLD. We then measured IHCL by MR spectroscopy in a representative subgroup (n = 36) and conducted detailed metabolic studies (IVGTT, VLDL apolipoprotein B [apoB] kinetics and palmitate turnover) and measurement of regional body fat by MRI to demonstrate effects of IHCL that were independent of a history of pGDM. RESULTS: pGDM was associated with increased IHCL (p = 0.04) after adjustment for adiposity. Independently of IHCL, pGDM was associated with a lower IVGTT disposition index (p = 0.02) and acute insulin response to glucose (pGDM+/NAFLD-, 50% lower; pGDM+/NAFLD+, 36% lower; effect of pGDM, p = 0.03), increased VLDL apoB pool size (pGDM+/NAFLD-, 3.1-fold higher; pGDM+/NAFLD+, 1.2-fold higher; effect of pGDM, p = 0.02) and, at borderline significance (p = 0.05), increased rate of VLDL apoB synthesis. CONCLUSIONS/INTERPRETATION: pGDM is associated with increased IHCL independently of adiposity. The increased liver fat contributes to the phenotype, but pGDM status is independently associated with diminished insulin secretion and (shown for the first time) augmented VLDL metabolism. IHCL with pGDM may compound a dysmetabolic phenotype.
    Diabetologia 06/2013; · 6.49 Impact Factor
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    ABSTRACT: Maternal obesity during pregnancy has been linked to an increased risk of obesity and cardiometabolic disease in the offspring, a phenomenon attributed to developmental programming. Programming effects may be transmissible across generations through both maternal and paternal inheritance, although the mechanisms remain unclear. Using a mouse model, we explored the effects of moderate maternal diet-induced obesity (DIO) on weight gain and glucose-insulin homeostasis in first-generation (F1) and second-generation (F2) offspring. DIO was associated with insulin resistance, hyperglycemia and dyslipidemia before pregnancy. Birth weight was reduced in female offspring of DIO mothers (by 6%, P = .039), and DIO offspring were heavier than controls at weaning (males by 47%, females by 27%), however there were no differences in glucose tolerance, plasma lipids, or hepatic gene expression at 6 months. Despite the relative lack of effects in the F1 generation, we found clear fetal growth restriction and persistent metabolic changes in otherwise unmanipulated F2 offspring with effects on birth weight, insulin levels, and hepatic gene expression that were transmitted through both maternal and paternal lines. This suggests that the consequences of the current dietary obesity epidemic may also have an impact on the descendants of obese individuals, even when the phenotype of the first generation appears largely unaffected.
    Endocrinology 05/2013; · 4.72 Impact Factor
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    ABSTRACT: A simple, sensitive and robust method to extract tamsulosin from human serum, and quantify by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed and validated and is applicable as a measure of compliance in clinical research. Tamsulosin was extracted from human serum (100μL) via liquid-liquid extraction with methyl tert-butyl ether (2mL) following dilution with 0.1M ammonium hydroxide (100μL), achieving 99.9% analyte recovery. Internal standard, d9-finasteride, was synthesised in-house. Analyte and internal standard were separated on an Ascentis(®) Express C18 (100mm×3mm, 2.7μm) column using a gradient elution with mobile phases methanol and 2mM aqueous ammonium acetate (5:95, v/v). Total run-time was 6min. Tamsulosin was quantified using a triple quadrupole mass spectrometer operated in multi-reaction-monitoring (MRM) mode using positive electrospray ionisation. Mass transitions monitored for quantitation were: tamsulosin m/z 409→228 and d9-finasteride m/z 382→318, with the structural formulae of ions confirmed by Fourier transform ion cyclotron resonance mass spectrometry (within 10ppm). The limit of quantitation was 0.2ng/mL, and the method was validated in the linear range 0.2-50ng/mL with acceptable inter- and intra-assay precision and accuracy and stability suitable for routine laboratory practice. The method was successfully applied to samples taken from research volunteers in a clinical study of benign prostatic hyperplasia.
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 04/2013; 930C:121-128. · 2.78 Impact Factor
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    ABSTRACT: CONTEXT: Quality of life (QoL) has been variously reported as normal or impaired in adults with congenital adrenal hyperplasia (CAH). To explore the reasons for this discrepancy we investigated the relationship between QoL, glucocorticoid treatment, and other health outcomes in CAH adults. METHODS: Cross-sectional analysis of 151 adults with 21-hydroxylase deficiency aged 18-69 years in whom QoL (SF-36), glucocorticoid regimen, anthropometric, and metabolic measures were recorded. Relationships were examined between QoL, type of glucocorticoid (hydrocortisone, prednisolone, and dexamethasone), and dose of glucocorticoid expressed as prednisolone dose equivalent, PreDEq. QoL was expressed as z-scores calculated from matched controls (14,430 subjects from UK population). Principal components analysis (PCA) was undertaken to identify clusters of associated clinical and biochemical features and the principal component scores used in regression analysis as predictor of QoL. RESULTS: QoL scores were associated with type of glucocorticoid treatment for vitality (P=0.002) and mental health (P=0.011), with higher z-scores indicating better QoL in patients on hydrocortisone monotherapy (P<0.05). QoL did not relate to PreDEq or mutation severity. PCA identified three principal components (PC1, disease control; PC2, adiposity and insulin resistance; PC3, blood pressure and mutations) that explained 61% of the variance in observed variables. Stepwise multiple regression analysis demonstrated that PC2, reflecting adiposity and insulin resistance (waist circumference, serum triglycerides, HOMA-IR and HDL-cholesterol), related to QoL scores, specifically impaired physical functioning, bodily pain, general health, Physical Component Summary Score (P<0.001) and vitality (P=0.002). CONCLUSIONS: Increased adiposity, insulin resistance, and use of prednisolone or dexamethasone are associated with impaired QoL in adults with CAH. Intervention trials are required to establish whether choice of glucocorticoid treatment and/or weight loss can improve QoL in CAH adults.
    European Journal of Endocrinology 03/2013; · 3.14 Impact Factor
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    ABSTRACT: 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 .).
    New England Journal of Medicine 03/2013; · 51.66 Impact Factor
  • Conference Proceeding: endocrine abstracts
    Society For Endocrinology BES 2013; 03/2013
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    ABSTRACT: 11β-Hydroxysteroid dehydrogenase 1 (11βHSD1; EC 1.1.1.146) generates active glucocorticoids from inert 11-keto metabolites. However, it can also metabolise alternative substrates, including 7β-hydroxy- and 7-keto-cholesterol (7βOHC, 7KC). This has been demonstrated in vitro but its consequences in vivo are uncertain. We used knockout mice to investigate the contribution of 11βHSD1 to the balance of circulating levels of 7KC and 7βOHC in vivo, and dissected in vitro the kinetics of the interactions between oxysterols and glucocorticoids for metabolism by the mouse enzyme. Circulating levels of 7KC and 7βOHC in mice were 91.3±22.3 and 22.6±5.7nM respectively, increasing to 1240±220 and 406±39nM in ApoE(-/-) mice receiving atherogenic western diet. Disruption of 11βHSD1 in mice increased (p<0.05) the 7KC/7βOHC ratio in plasma (by 20%) and also in isolated microsomes (2 fold). The 7KC/7βOHC ratio was similarly increased when NADPH generation was restricted by disruption of hexose-6-phosphate dehydrogenase. Reduction and oxidation of 7-oxysterols by murine 11βHSD1 proceeded more slowly and substrate affinity was lower than for glucocorticoids. In vitro 7βOHC was a competitive inhibitor of oxidation of corticosterone (Ki=0.9μM), whereas 7KC only weakly inhibited reduction of 11-dehydrocorticosterone. However supplementation of 7-oxysterols in cultured cells, secondary to cholesterol loading, preferentially slowed reduction of glucocorticoids, rather than oxidation. Thus, in mouse, 11βHSD1 influenced the abundance and balance of circulating and tissue levels of 7βOHC and 7KC, promoting reduction of 7KC. In health, 7-oxysterols are unlikely to regulate glucocorticoid metabolism. However, in hyperlipidaemia, 7-oxysterols may inhibit glucocorticoid metabolism and modulate signaling through corticosteroid receptors.
    Biochemical pharmacology 02/2013; · 4.25 Impact Factor
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    ABSTRACT: Context:In congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, a strong genotype-phenotype correlation exists in childhood. However, similar data in adults are lacking.Objective:The objective of the study was to test whether the severity of disease-causing CYP21A2 mutations influences the treatment and health status in adults with CAH.Research Design and Methods:We analyzed the genotype in correlation with treatment and health status in 153 adults with CAH from the United Kingdom Congenital adrenal Hyperplasia Adult Study Executive cohort.Results:CYP21A2 mutations were distributed similarly to previously reported case series. In 7 patients a mutation was identified on only 1 allele. Novel mutations were detected on 1.7% of alleles (5 of 306). Rare mutations were found on 2.3% of alleles (7 of 306). For further analysis, patients were categorized into CYP21A2 mutation groups according to predicted residual enzyme function: null (n = 34), A (n = 42), B (n = 36), C (n = 34), and D (n = 7). Daily glucocorticoid dose was highest in group null and lowest in group C. Fludrocortisone was used more frequently in patients with more severe genotypes. Except for lower female height in group B, no statistically significant associations between genotype and clinical parameters were found. Androgens, blood pressure, lipids, blood glucose, and homeostasis model assessment of insulin resistance were not different between groups. Subjective health status was similarly impaired across groups.Conclusions:In adults with classic CAH and women with nonclassic CAH, there was a weak association between genotype and treatment, but health outcomes were not associated with genotype. The underrepresentation of males with nonclassic CAH may reflect that milder genotypes result in a milder condition that is neither diagnosed nor followed up in adulthood. Overall, our results suggest that the impaired health status of adults with CAH coming to medical attention is acquired rather than genetically determined and therefore could potentially be improved through modification of treatment.
    The Journal of clinical endocrinology and metabolism 01/2013; · 6.50 Impact Factor

Publication Stats

8k Citations
1,337.07 Total Impact Points

Institutions

  • 1991–2014
    • The University of Edinburgh
      • • Queen's Medical Research Institute
      • • MRC Centre for Regenerative Medicine
      • • Centre for Cardiovascular Science
      • • School of Clinical Sciences and Community Health
      • • Medical Genetics Unit
      Edinburgh, Scotland, United Kingdom
  • 2013
    • University College London
      Londinium, England, United Kingdom
  • 2011
    • University of Bologna
      • Division of Endocrinology
      Bologna, Emilia-Romagna, Italy
  • 2010
    • University of Birmingham
      • School of Clinical and Experimental Medicine
      Birmingham, ENG, United Kingdom
  • 2009
    • University of Gothenburg
      Goeteborg, Västra Götaland, Sweden
  • 2002–2009
    • Umeå University
      • Department of Public Health and Clinical Medicine
      Umeå, Vaesterbotten, Sweden
  • 2006
    • University of Cape Town
      • MRC/UCT Research Unit for Exercise Science & Sports Medicine (ESSM)
      Cape Town, Province of the Western Cape, South Africa
    • Policlinico S.Orsola-Malpighi
      Bolonia, Emilia-Romagna, Italy
  • 2003
    • University of Helsinki
      • Department of Oral Medicine
      Helsinki, Province of Southern Finland, Finland
    • National Institutes of Health
      • National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
      Bethesda, MD, United States
  • 1993–2003
    • Western General Hospital
      Edinburgh, Scotland, United Kingdom
  • 1998–2001
    • University of Southampton
      • Developmental Origins of Health and Disease
      Southampton, ENG, United Kingdom
  • 1994
    • The Queen Elizabeth Hospital
      Tarndarnya, South Australia, Australia