Protein metabolism in glucocorticoid excess: study in Cushing's syndrome and the effect of treatment

Whole-body metabolic fate of branched-chain amino acids

Oxidation of branched-chain amino acids (BCAAs) is tightly regulated in mammals. We review here the distribution and regulation of whole-body BCAA oxidation. Phosphorylation and dephosphorylation of the rate-limiting enzyme, branched-chain α-ketoacid dehydrogenase complex directly regulates BCAA oxidation, and various other indirect mechanisms of regulation also exist. Most tissues throughout the body are capable of BCAA oxidation, and the flux of oxidative BCAA disposal in each tissue is influenced by three key factors: 1. tissue-specific preference for BCAA oxidation relative to other fuels, 2. the overall oxidative activity of mitochondria within a tissue, and 3. total tissue mass. Perturbations in BCAA oxidation have been implicated in many disease contexts, underscoring the importance of BCAA homeostasis in overall health.

Fully automated method for quantitative determination of steroids in serum: An approach to evaluate steroidogenesis

Steroidogenesis is a set of metabolic reactions where the enzymes play a key role to control the physiological levels of steroids. A deficiency in steroidogenesis induces an accumulation and/or insufficiency of steroids in human blood and can lead to different pathologies. This issue added to the low levels of steroids (pg mL^-1 to ng mL^-1) in this biofluid make of their determination an analytical challenge. In this research, we present a high-throughtput and fully automated method based on solid-phase extraction on-line coupled to liquid chromatography with tandem mass spectrometry detection (SPE-LC-MS/MS) to quantify estrogens (estrone and estradiol), androgens (testosterone, androstenedione, dihydrotestosterone and dehydroepiandrosterone), progestogens (progesterone, pregnenolone, 17-hydroxyprogesterone and 17-hydroxypregnenolone), glucocorticoids (21-hydroxyprogesterone, 11-deoxycortisol, cortisone, corticosterone and cortisol) and one mineralocorticoid (aldosterone) in human serum. The performance of the SPE step and the multiple reaction monitoring (MRM) mode allowed reaching a high sensitivity and selectivity levels without any derivatization reaction. The fragmentation mechanisms of the steroids were complementary studied by LC-MS/MS in high-resolution mode to confirm the MRM transitions. The method was characterized with two SPE sorbents with similar physico-chemical properties. Thus, limits of quantification were at pg mL^-1 levels, the variability was below 25% (except for pregnenolone and cortisone), and the accuracy, expressed as bias, was always within ±25%. The proposed method was tested in human serum from ten volunteers, who reported levels for the sixteen target steroids that were satisfactorily in agreement with the physiological ranges reported in the literature.

Thigh Muscle Fat Infiltration Is Associated With Impaired Physical Performance Despite Remission in Cushing's Syndrome

CONTEXT

Muscle weakness is common in patients with Cushing's syndrome (CS) and may persist after the resolution of hypercortisolism. Intramuscular fatty infiltration has been associated with the deterioration of muscle performance in several conditions.

OBJECTIVES

To quantify the degree of fatty infiltration in the thigh muscles of "cured" CS patients and evaluate the relationship between intramuscular fatty infiltration and physical performance.

DESIGN

This was a cross-sectional study.

SETTING

Tertiary referral center.

PATIENTS

Thirty-six women with CS in remission, and 36 controls matched for age, BMI, menopausal status, and level of physical activity.

MAIN OUTCOME MEASURES

We analyzed the percentage fat fraction (FF) of the thigh muscles in the anterior, posterior, and combined anterior and posterior compartments using MRI and 2-point Dixon sequence. We assessed muscle function and strength using the following tests: gait speed (GS), timed up and go (TUG), 30-second chair stand, and hand grip strength.

RESULTS

Fat fraction in all the compartments analyzed was increased in patients as compared with controls. The performance on TUG, 30-second chair stand, and GS was more impaired in CS patients versus controls. In patients, greater FF was negatively associated with performance on functional tests. Fat fraction in the combined anterior and posterior compartments predicted performance on TUG (ß 0.626, P < 0.000) and GS (ß -0.461, P = 0.007), after adjusting for age, BMI, menopausal status, and muscle mass.

CONCLUSIONS

Thigh muscle fatty infiltration is increased in "cured" CS patients and is associated with poorer muscle performance. Future studies are needed to establish therapeutic strategies to improve muscle weakness in these patients.

Mechanistic inferences on metabolic dysfunction in posttraumatic stress disorder from an integrated model and multiomic analysis: role of glucocorticoid receptor sensitivity

Posttraumatic stress disorder (PTSD) is associated with neuroendocrine alterations and metabolic abnormalities; however, how metabolism is affected by neuroendocrine disturbances is unclear. The data from combat-exposed veterans with PTSD show increased glycolysis to lactate flux, reduced TCA cycle flux, impaired amino acid and lipid metabolism, insulin resistance, inflammation, and hypersensitive hypothalamic-pituitary-adrenal (HPA) axis. To analyze whether the co-occurrence of multiple metabolic abnormalities is independent or arises from an underlying regulatory defect, we employed a systems biological approach using an integrated mathematical model and multiomic analysis. The models for hepatic metabolism, HPA axis, inflammation, and regulatory signaling were integrated to perform metabolic control analysis (MCA) with respect to the observations from our clinical data. We combined the metabolomics, neuroendocrine, clinical laboratory, and cytokine data from combat-exposed veterans with and without PTSD to characterize the differences in regulatory effects. MCA revealed mechanistic association of the HPA axis and inflammation with metabolic dysfunction consistent with PTSD. This was supported by the data using correlational and causal analysis that revealed significant associations between cortisol suppression, high-sensitivity C-reactive protein, homeostatic model assessment of insulin resistance, γ-glutamyltransferase, hypoxanthine, and several metabolites. Causal mediation analysis indicates that the effects of enhanced glucocorticoid receptor sensitivity (GRS) on glycolytic pathway, gluconeogenic and branched-chain amino acids, triglycerides, and hepatic function are jointly mediated by inflammation, insulin resistance, oxidative stress, and energy deficit. Our analysis suggests that the interventions to normalize GRS and inflammation may help to manage features of metabolic dysfunction in PTSD.

Modern Management of Mild Autonomous Cortisol Secretion

Incidentally discovered adrenal tumors are reported in ~ 5% of adults undergoing cross-sectional imaging. Mild autonomous cortisol secretion (MACS) from the adrenal mass is demonstrated in 5-48% of patients with adrenal tumors. The diagnosis of MACS represents a challenge due to limitations of the currently used diagnostic tests, differences in the definitions of the clinically relevant MACS, and heterogeneity in an individual's susceptibility to abnormal cortisol secretion from the adrenal mass. Patients with MACS present with increased risk of cardiovascular risk factors, cardiovascular events, metabolic bone disease, and mortality. Adrenalectomy improves or reverses MACS-associated comorbidities in selected patients. The current review will address diagnostic and management challenges in the care of patients with MACS, discuss data on emerging biomarkers, and suggest future directions in the field of MACS.

Effects of Prednisolone on Serum and Tissue Fluid IGF-I Receptor Activation and Post-Receptor Signaling in Humans

CONTEXT

Short-term glucocorticoid exposure increases serum insulinlike growth factor I (IGF-I) concentrations but antagonizes IGF-I tissue signaling. The underlying mechanisms remain unknown.

OBJECTIVE

To identify at which levels glucocorticoid inhibits IGF-I signaling.

DESIGN AND METHODS

Nineteen healthy males received prednisolone (37.5 mg/d) and placebo for 5 days in a randomized, double-blinded, placebo-controlled crossover study. Serum was collected on days 1, 3, and 5, and abdominal skin suction blister fluid (SBF; ~interstitial fluid) was taken on day 5 (n = 9) together with muscle biopsy specimens (n = 19). The ability of serum and SBF to activate the IGF-I receptor (IGF-IR) (bioactive IGF) and its downstream signaling proteins was assessed using IGF-IR-transfected cells.

RESULTS

Prednisolone increased IGF-I concentrations and bioactive IGF in serum (P ≤ 0.001) but not in SBF, which, compared with serum, contained less bioactive IGF (~28%) after prednisolone (P < 0.05). This observation was unexplained by SBF concentrations of IGFs and IGF-binding proteins (IGFBPs) 1 to 4. However, following prednisolone treatment, SBF contained less IGFBP-4 fragments (P < 0.05) generated by pregnancy-associated plasma protein A (PAPP-A). Concomitantly, prednisolone increased SBF levels of stanniocalcin 2 (STC2) (P = 0.02) compared with serum. STC2 blocks PAPP-A from cleaving IGFBP-4. Finally, prednisolone suppressed post-IGF-IR signaling pathways at the level of insulin receptor substrate 1 (P < 0.05) but did not change skeletal muscle IGF-IR, IGF-I, or STC2 messenger RNA.

CONCLUSION

Prednisolone increased IGF-I concentrations and IGF bioactivity in serum but not in tissue fluid. The latter may relate to a STC2-mediated inhibition of PAPP-A in tissue fluids. Furthermore, prednisolone induced post-IGF-IR resistance. Thus, glucocorticoid may exert distinct, compartment-specific effects on IGF action.

Glucose Metabolism Abnormalities in Cushing Syndrome: From Molecular Basis to Clinical Management

An impaired glucose metabolism, which often leads to the onset of diabetes mellitus (DM), is a common complication of chronic exposure to exogenous and endogenous glucocorticoid (GC) excess and plays an important part in contributing to morbidity and mortality in patients with Cushing syndrome (CS). This article reviews the pathogenesis, epidemiology, diagnosis, and management of changes in glucose metabolism associated with hypercortisolism, addressing both the pathophysiological aspects and the clinical and therapeutic implications. Chronic hypercortisolism may have pleiotropic effects on all major peripheral tissues governing glucose homeostasis. Adding further complexity, both genomic and nongenomic mechanisms are directly induced by GCs in a context-specific and cell-/organ-dependent manner. In this paper, the discussion focuses on established and potential pathologic molecular mechanisms that are induced by chronically excessive circulating levels of GCs and affect glucose homeostasis in various tissues. The management of patients with CS and DM includes treating their hyperglycemia and correcting their GC excess. The effects on glycemic control of various medical therapies for CS are reviewed in this paper. The association between DM and subclinical CS and the role of screening for CS in diabetic patients are also discussed.

Effects of prednisolone on energy and fat metabolism in patients with rheumatoid arthritis: tissue-specific insulin resistance with commonly used prednisolone doses

OBJECTIVE

Glucocorticoids can cause postprandial hyperglycaemia, but the effects on postprandial energy and fat metabolism are uncertain. We investigated the effects of acute and chronic low-dose prednisolone on fasting and postprandial energy expenditure and substrate metabolism.

DESIGN

An open interventional and cross-sectional study was undertaken.

PATIENTS AND MEASUREMENTS

Eighteen patients who had not taken oral glucocorticoids for ≥6 months were studied before and after 7 days prednisolone (6 mg/day) to assess the acute effects of prednisolone. Baseline data from patients, not on glucocorticoids, were compared with 18 patients on long-term prednisolone (6·5 ± 1·8 mg/day for >6 months) to assess the chronic effects. Energy expenditure and substrate oxidation were measured using indirect calorimetry before and after a mixed meal. Adipocyte insulin resistance index and insulin-mediated suppression of NEFA were calculated from fasting and postprandial insulin and NEFA concentrations.

RESULTS

There were no significant differences in resting energy expenditure or diet-induced thermogenesis with prednisolone. Acute (-2·1 ± 6·2 vs -16·3 ± 4·8 mg/min, P = 0·01) and chronic (-1·4 ± 2·8 vs -16·3 ± 4·8 mg/min, P = 0·01) prednisolone attenuated postprandial suppression of fat oxidation. Chronic (31·6 ± 3·8 vs 17·0 ± 3·3, P = 0·007), but not acute, prednisolone increased adipocyte insulin resistance index. However, insulin-mediated suppression of NEFA was not significantly different after acute or chronic prednisolone.

CONCLUSIONS

Prednisolone does not alter energy expenditure. However, even at low doses, prednisolone exerts adverse effects on fat metabolism, which could exacerbate insulin resistance and increase cardiovascular risk. Attenuated postprandial suppression of fat oxidation, but not lipolysis, suggests that prednisolone causes greater insulin resistance in skeletal muscle than in adipocytes.

Energy expenditure and nutritional complications of metabolic syndrome and rheumatoid cachexia in rheumatoid arthritis: an observational study using calorimetry and actimetry

OBJECTIVE

Altered energy expenditure may contribute to the nutritional complications of RA, metabolic syndrome (MS) and rheumatoid cachexia (RC). The main aim of this study was to evaluate whether the altered resting energy expenditure (REE) and physical activity (PA)-related energy expenditure (EE) are related to the duration of RA and inflammatory activity and nutritional complications in RA.

METHODS

Among patients with well-characterized RA (duration, activity: DAS28 ESR), we measured REE by indirect calorimetry, and PA-EE by actimetry (SenseWear Armband). MS was defined according to the International Diabetes Federation criteria and RC from DXA body composition analysis. The relations between the characteristics and nutritional complications, and EE were analysed by linear regression.

RESULTS

Fifty-seven patients were included [73% women, age 57 (10) years] with a wide range of disease duration: 3.8 (3.0) years, and DAS28 ESR: 3.9 (1.4). The mean REE was 1486 (256) kcal/day, associated with the DAS28 ESR (β = +0.21, P = 0.02 after adjusting for gender and fat free mass). The prevalence of MS and RC was, respectively, 24 and 18%, and they were unrelated to each other. The patients with MS and/or RC had double the longstanding RA score (P < 0.05), twice the homeostasis model assessment of insulin resistance values (P = 0.052) and halved levels of PA (P < 0.05 for metabolic equivalent tasks (METs) and number of steps/day). Two modifiable factors were associated with the presence of MS and/or RC: a low level of PA as METs [exp(B) = 0.03, P = 0.009] and the use of glucocorticoids [exp(B) = 4.08, P = 0.046].

CONCLUSION

Low levels of PA and treatment by glucocorticoids are associated with the nutritional complications of RA, suggesting the potential for therapeutic interventions.

Formoterol, a highly β2-selective agonist, induces gender-dimorphic whole body leucine metabolism in humans

OBJECTIVE

Formoterol is a β(2)-selective agonist that enhances protein anabolism in rodents. Whether formoterol imparts anabolic benefits in humans is unknown. The objective of the study was to investigate the effects of formoterol on whole body protein rates of turnover, oxidative loss and synthesis.

DESIGN

Open label intervention study.

PATIENTS

Fifteen healthy adults (8 men).

MEASUREMENTS

Volunteers were treated with oral formoterol 160 μg/day for one week. Changes in leucine turnover (LRa; index of protein breakdown), oxidation (Lox; irreversible protein loss) and incorporation into protein (LIP; index of protein synthesis) were assessed using the whole body 1-[(13)C]leucine turnover technique before/after treatment.

RESULTS

LRa, Lox and LIP correlated significantly with lean body mass (LBM). LRa, adjusted for LBM was significantly higher (P<0.05, 160±6 vs 109±3 μmol/min) in men but not fractional Lox and LIP (expressed as a proportion of LRa). Formoterol reduced LRa (-9±4%) in men but stimulated LRa (9±3%) in women. Formoterol significantly reduced (P<0.05) fractional Lox, an effect greater in women (-4±1 vs -1±1 %). It stimulated fractional LIP in women (∆4±1%, P<0.05) but not in men (∆1±1%). Formoterol induced an absolute anabolic effect that was greater in women (30 vs 8%). Heart rate, systolic and diastolic blood pressures were unaffected.

CONCLUSION

In a therapeutic dose, formoterol stimulates protein anabolism in humans. It induced gender-dimorphic effects on protein turnover and on the partitioning of amino acids from oxidative loss toward protein synthesis, effects that are greater in women than in men. Formoterol holds promise as a treatment for sarcopenia.

Body composition and bone mineral density in women with Cushing's syndrome in remission and the association with common genetic variants influencing glucocorticoid sensitivity

OBJECTIVE

Adverse body compositional features and low bone mineral density (BMD) are the characteristic of patients with active Cushing's syndrome (CS). The aim of this study was to evaluate body composition and BMD in women with CS in long-term remission and the influence of polymorphisms in genes affecting glucocorticoid (GC) sensitivity on these end-points.

DESIGN, PATIENTS AND METHODS

This was a cross-sectional, case-controlled study, including 50 women previously treated for CS and 50 age and gender-matched controls. Median (interquartile range) remission time was 13 (5-19) years. Body composition and BMD were measured with dual-energy X-ray absorptiometry. Five polymorphisms in four genes associated with GC sensitivity were analysed using TaqMan or Sequenom single-nucleotide polymorphism genotyping.

RESULTS

Patients with CS in remission had increased abdominal fat mass (P<0.01), whereas BMD was not significantly different at any site between patients and controls. In patients, the NR3C1 Bcl1 polymorphism was associated with reduced total (P<0.05) and femur neck BMD (P<0.05). The polymorphism rs1045642 in the ABCB1 gene was associated with increased abdominal fat mass (P<0.05) and decreased appendicular skeletal muscle mass (P<0.05). GC replacement was associated with reduced total BMD (P<0.01), BMD at lumbar spine (P<0.05) and increased abdominal fat (P<0.01).

CONCLUSION

Ongoing GC replacement therapy together with polymorphisms in two genes related with GC sensitivity is associated with abdominal obesity and adverse skeletal health in patients with CS in long-term remission.

Whole-body phenylalanine kinetics and skeletal muscle protein signaling in horses with pituitary pars intermedia dysfunction

OBJECTIVE

To compare whole-body phenylalanine kinetics and the abundance of factors in signaling pathways associated with skeletal muscle protein synthesis and protein breakdown between horses with pituitary pars intermedia dysfunction (PPID) and age-matched control horses without PPID.

ANIMALS

12 aged horses (6 horses with PPID and 6 control horses; mean age, 25.0 and 25.7 years, respectively).

PROCEDURES

Plasma glucose, insulin, and amino acids concentrations were determined before and 90 minutes after feeding. Gluteal muscle biopsy samples were obtained from horses 90 minutes after feeding, and the abundance and activation of factors involved in signaling pathways of muscle protein synthesis and breakdown were determined. The next day, horses received a priming dose and 2 hours of a constant rate infusion of (13)C sodium bicarbonate followed by a priming dose and 4 hours of a constant rate infusion of 1-(13)C phenylalanine IV; whole-body protein synthesis was determined.

RESULTS

Plasma glucose and insulin concentrations were higher after feeding than they were before feeding for both groups of horses; however, no significant postprandial increase in plasma amino acids concentrations was detected for either group. Phenylalanine flux, oxidation, release from protein breakdown, and nonoxidative disposal were not significantly different between groups. No significant effect of PPID status was detected on the abundance or activation of positive or negative regulators of protein synthesis or positive regulators of protein breakdown.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study suggested that whole-body phenylalanine kinetics and the postprandial activation of signaling pathways that regulate protein synthesis and breakdown in muscles were not affected by PPID status alone in aged horses.

Chronic glucocorticoid treatment enhances lipogenic activity in visceral adipocytes of male Wistar rats

AIM

Glucocorticoid (GC) in excess promotes the redistribution of adipose tissue from peripheral to central sites of the body. In this study, we characterized an experimental condition of prolonged GC excess and investigated its effect on the lipogenic metabolism in white adipose tissue.

METHODS

Twenty male Wistar rats were divided into control (CON) and dexamethasone-treated (DEX) groups. DEX group received dexamethasone (0.25 mg kg(-1) day(-1) ) during 4 weeks, while CON group received saline. Animals were killed and subcutaneous (SC), retroperitoneal (RP) and mesenteric (MS) fat pads were excised, weighed and processed for adipocyte isolation, morphometric cell analysis and incorporation of glucose into lipids.

RESULTS

The treatment effectively blocked hypothalamic-pituitary-adrenal axis, as verified by a 58% decrease in plasma corticosterone levels and 19% atrophy in adrenal glands in DEX group. Animals from DEX group presented insulin resistance, glucose intolerance, dyslipidaemia and increased insulin and leptin plasma levels and hypertrophied adipocytes. They showed increased lipogenesis in RP and MS depots, with increased incorporation of glucose into fatty acids of triacylglycerol. Increased activity of lipogenic enzymes ATP-citrate lyase, fatty acid synthase, glucose-6-phosphate dehydrogenase and malic was only seen in the MS depot in DEX group, while gene expression of these enzymes was enhanced in SC and MS fat depots.

CONCLUSION

The adaptations promoted by GC treatment in adipose metabolism seemed to be mainly due to the increased activity of enzymes that supply the NADPH required for lipogenesis than to the increase in enzymes that more directly deal with fatty acid synthesis itself.

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

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

Glycated albumin is set lower in relation to plasma glucose levels in patients with Cushing's syndrome

BACKGROUND

Glycated albumin (GA) is an indicator of glycemic control, which has some specific characters in comparison with HbA1c. Since glucocorticoids (GC) promote protein catabolism including serum albumin, GC excess state would influence GA levels. We therefore investigated GA levels in patients with Cushing's syndrome.

METHODS

We studied 16 patients with Cushing's syndrome (8 patients had diabetes mellitus and the remaining 8 patients were non-diabetic). Thirty-two patients with type 2 diabetes mellitus and 32 non-diabetic subjects matched for age, sex and BMI were used as controls.

RESULTS

In the patients with Cushing's syndrome, GA was significantly correlated with HbA1c, but the regression line shifted downwards as compared with the controls. The GA/HbA1c ratio in the patients with Cushing's syndrome was also significantly lower than the controls. HbA1c in the non-diabetic patients with Cushing's syndrome was not different from the non-diabetic controls, whereas GA was significantly lower. In 7 patients with Cushing's syndrome who performed self-monitoring of blood glucose, the measured HbA1c was matched with HbA1c estimated from mean blood glucose, whereas the measured GA was significantly lower than the estimated GA.

CONCLUSIONS

We clarified that GA is set lower in relation to plasma glucose levels in patients with Cushing's syndrome.

Modulation in Wistar rats of blood corticosterone compartmentation by sex and a cafeteria diet

In the metabolic syndrome, glucocorticoid activity is increased, but circulating levels show little change. Most of blood glucocorticoids are bound to corticosteroid-binding globulin (CBG), which liver expression and circulating levels are higher in females than in males. Since blood hormones are also bound to blood cells, and the size of this compartment is considerable for androgens and estrogens, we analyzed whether sex or eating a cafeteria diet altered the compartmentation of corticosterone in rat blood. The main corticosterone compartment in rat blood is that specifically bound to plasma proteins, with smaller compartments bound to blood cells or free. Cafeteria diet increased the expression of liver CBG gene, binding plasma capacity and the proportion of blood cell-bound corticosterone. There were marked sex differences in blood corticosterone compartmentation in rats, which were unrelated to testosterone. The use of a monoclonal antibody ELISA and a polyclonal Western blot for plasma CBG compared with both specific plasma binding of corticosterone and CBG gene expression suggested the existence of different forms of CBG, with varying affinities for corticosterone in males and females, since ELISA data showed higher plasma CBG for males, but binding and Western blot analyses (plus liver gene expression) and higher physiological effectiveness for females. Good cross- reactivity to the antigen for polyclonal CBG antibody suggests that in all cases we were measuring CBG.The different immunoreactivity and binding affinity may help explain the marked sex-related differences in plasma hormone binding as sex-linked different proportions of CBG forms.

Effect of short-term GH and testosterone administration on body composition and glucose homoeostasis in men receiving chronic glucocorticoid therapy

OBJECTIVE

Long-term pharmacological glucocorticoid (GC) therapy leads to skeletal muscle atrophy and weakness. The objective of this study was to investigate whether short-term treatment with GH and testosterone (T) can increase lean mass without major impairment of glucose homoeostasis in patients on GC therapy.

DESIGN, MATERIALS AND METHODS

This was a prospective, open-label, randomised, crossover study. Twelve men (age 74±6 years) on chronic GC treatment participated. The effects of 2 weeks' treatment with GH, testosterone and the combination of both on lean body mass (LBM), appendicular skeletal muscle mass (ASMM), extracellular water (ECW), body cell mass (BCM) and plasma glucose concentrations were investigated.

RESULTS

LBM increased significantly after GH (Δ1.7±1.4 kg; P=0.007) and GH+testosterone (Δ2.4±1.1 kg; P=0.003), but not testosterone alone. ASMM increased after all three treatment periods; by 1.0±0.8 kg after GH (P=0.005), 1.7±0.4 kg after GH+testosterone (P=0.002) and 0.8±1.0 kg after testosterone (P=0.018). The increase in ASMM was larger with combined treatment than either GH or testosterone alone (P<0.05). ECW increased significantly after GH+testosterone by 1.5±2.6 l (P=0.038) but not after GH or testosterone alone. BCM increased slightly after single and combined treatments, but the changes were not significant. Fasting glucose increased significantly after GH (Δ0.4±0.4 mmol/l, P=0.006) while both fasting (Δ0.2±0.3 mmol/l, P=0.045) and post glucose-load (Δ1.8±2.3 mmol/l, P=0.023) plasma glucose concentrations increased after GH+testosterone.

CONCLUSIONS

GH and testosterone induce favourable and additive body compositional changes in men on chronic, low-dose GC treatment. In the doses used, combination therapy increases fasting and postprandial glucose concentration.

Corticosteroids increase protein breakdown and loss in newly diagnosed pediatric Crohn disease

Children with Crohn disease have altered growth and body composition. Previous studies have demonstrated decreased protein breakdown after either corticosteroid or anti-TNF-α therapy. The aim of this study was to evaluate whole body protein metabolism during corticosteroid therapy in children with newly diagnosed Crohn disease. Children with suspected Crohn disease and children with abdominal symptoms not consistent with Crohn disease underwent outpatient metabolic assessment. Patients diagnosed with Crohn disease and prescribed corticosteroid therapy returned in 2 wk for repeat metabolic assessment. Using the stable isotopes [d5] phenylalanine, [1-(13)C] leucine, and [(15)N(2)] urea, protein kinetics were determined in the fasting state. Thirty-one children (18 controls and 13 newly diagnosed with Crohn disease) completed the study. There were no significant differences in protein breakdown or loss between patients with Crohn disease at diagnosis and controls. After corticosteroid therapy in patients with Crohn disease, the rates of appearance of phenylalanine (32%) and leucine (26%) increased significantly, reflecting increased protein breakdown, and the rate of appearance of urea also increased significantly (273%), reflecting increased protein loss. Whole body protein breakdown and loss increased significantly after 2 wk of corticosteroid therapy in children with newly diagnosed Crohn disease, which may have profound effects on body composition.

Short-term prednisone use antagonizes insulin's anabolic effect on muscle protein and glucose metabolism in young healthy people

Glucocorticoids cause muscle atrophy and weakness, but the mechanisms for these effects are unclear. The purpose of this study was to test a hypothesis that prednisone (Pred) counteracts insulin's anabolic effects on muscle. A randomized, double-blind cross-over design was used to test the effects of 6 days either Pred (0.8 mg x kg(-1) x day(-1)) or placebo use in seven healthy young volunteers. Protein dynamics were measured across the leg using stable isotope tracers of leucine (Leu) and phenylalanine (Phe) after overnight fast and during a hyperinsulinemic (1.5 microU x min(-1) x kg FFM(-1)) euglycemic clamp with amino acid replacement. Fasting glucose, amino acids, insulin, and glucagon were higher (P < 0.01) on Pred vs. placebo, whereas leg blood flow was 18% lower. However, basal whole body and leg kinetics of Leu and Phe were unaltered by Pred. Insulin infusion increased leg glucose uptake in both trials but was 65% lower with Pred than with placebo. Insulin in both trials similarly suppressed whole body flux of Leu and Phe. Importantly, insulin increased net Leu and Phe balance across the leg and the balance between muscle protein synthesis and breakdown, but these changes were 45-140% lower (P < 0.03) in Pred than in placebo. The present study demonstrates that short-term Pred use in healthy people does not alter whole body or leg muscle protein metabolism during the postaborptive state but causes muscle insulin resistance for both glucose and amino acid metabolism, with a blunted protein anabolism. This interactive effect may lead to muscle atrophy with continued use of glucocorticoids.

Impact of growth hormone and dehydroepiandrosterone on protein metabolism in glucocorticoid-treated patients

CONTEXT

Chronic pharmacological glucocorticoid (GC) use causes substantial morbidity from protein wasting. GH and androgens are anabolic agents that may potentially reverse GC-induced protein loss.

OBJECTIVE

Our objective was to assess the effect of GH and dehydroepiandrosterone (DHEA) on protein metabolism in subjects on long-term GC therapy.

DESIGN

This was an open, stepwise GH dose-finding study (study 1), followed by a randomized cross-over intervention study (study 2).

SETTING

The studies were performed at a clinical research facility.

PATIENTS AND INTERVENTION

In study 1, six subjects (age 69+/-4 yr) treated with long-term (>6 months) GCs (prednisone dose 8.3+/-0.8 mg/d) were studied before and after two sequential GH doses (0.8 and 1.6 mg/d) for 2 wk each. In study 2, 10 women (age 71+/-3 yr) treated with long-term GCs (prednisone dose 5.4+/-0.5 mg/d) were studied at baseline and after 2-wk treatment with GH 0.8 mg/d, DHEA 50 mg/d, or GH and DHEA (combination treatment).

MAIN OUTCOME MEASURE

Changes in whole body protein metabolism were assessed using a 3-h primed constant infusion of 1-[13C]leucine, from which rates of leucine appearance, leucine oxidation, and leucine incorporation into protein were estimated.

RESULTS

In study 1, GH 0.8 and 1.6 mg/d significantly reduced leucine oxidation by 19% (P=0.03) and 31% (P=0.02), and increased leucine incorporation into protein by 10% (P=0.13) and 19% (P=0.04), respectively. The lower GH dose did not cause hyperglycemia, whereas GH 1.6 mg/d resulted in fasting hyperglycemia in two of six subjects. In study 2, DHEA did not significantly change leucine metabolism alone or when combined with GH. Blood glucose was not affected by DHEA.

CONCLUSION

GH, at a modest supraphysiological dose of 0.8 mg/d, induces protein anabolism in chronic GC users without causing diabetes. DHEA 50 mg/d does not enhance the effect of GH. GH may safely prevent or reverse protein loss induced by chronic GC therapy.

The growth hormone/insulin-like growth factor-I axis in exercise and sport

The syndrome of adult GH deficiency and the effects of GH replacement therapy provide a useful model with which to study the effects of the GH/IGF-I axis on exercise physiology. Measures of exercise performance including maximal oxygen uptake and ventilatory threshold are impaired in adult GH deficiency and improved by GH replacement, probably through some combination of increased oxygen delivery to exercising muscle, increased fatty acid availability with glycogen sparing, increased muscle strength, improved body composition, and improved thermoregulation. In normal subjects, in addition to the long-term effects of GH/IGF-I status, there is evidence that the acute GH response to exercise is important in regulating substrate metabolism after exercise. Administration of supraphysiological doses of GH to athletes increases fatty acid availability and reduces oxidative protein loss, particularly during exercise, and increases lean body mass. Despite a lack of evidence that these metabolic effects translate to improved performance, GH abuse by athletes is widespread. Tests to detect GH abuse have been developed based on measurement in serum of 1) indirect markers of GH action, and 2) the relative proportions of the two major naturally occurring isoforms (20 and 22kDa) of GH. There is evidence that exercise performance and strength are improved by administration of GH and testosterone in combination to elderly subjects. The potential benefits of GH in these situations must be weighed against potential adverse effects.

Impact of acute and chronic low-dose glucocorticoids on protein metabolism

CONTEXT

High-dose glucocorticoids cause acute protein loss by increasing protein breakdown and oxidation. Whether lower glucocorticoid doses, typical of therapeutic use, induce sustained catabolism has not been studied.

OBJECTIVE

Our objective was to assess the effect of acute and chronic therapeutic glucocorticoid doses on protein metabolism.

DESIGN AND SETTING

We conducted an open longitudinal and a cross-sectional study at a clinical research facility.

PATIENTS AND INTERVENTION

Ten healthy subjects were studied before and after a short course of prednisolone (5 and 10 mg/d sequentially for 7 d each). Twelve subjects with inactive polymyalgia rheumatica receiving chronic (>12 months) prednisone (mean = 5.0 +/- 0.8 mg/d) were compared with 12 age- and gender-matched normal subjects.

MAIN OUTCOME MEASURE

Whole-body protein metabolism was assessed using a 3-h primed constant infusion of 1-[(13)C]leucine, from which rates of leucine appearance (leucine Ra, an index of protein breakdown), leucine oxidation (Lox, index of protein oxidation) and leucine incorporation into protein (LIP, index of protein synthesis) were estimated.

RESULTS

Prednisolone induced an acute significant increase in Lox (P = 0.008) and a fall in LIP (P = 0.08) but did not affect leucine Ra. There was no significant difference between the effects of the 5- and 10-mg prednisolone doses on leucine metabolism. In subjects receiving chronic prednisone therapy, leucine Ra, Lox, and LIP were not significantly different from normal subjects.

CONCLUSION

Glucocorticoids stimulate protein oxidation after acute but not chronic administration. This time-related change suggests that glucocorticoid-induced stimulation of protein oxidation does not persist but that a metabolic adaptation occurs to limit protein loss.