Effect of short-term prednisone use on blood flow, muscle protein metabolism, and function

Fasting reshapes tissue-specific niches to improve NK cell-mediated anti-tumor immunity

Fasting is associated with improved outcomes in cancer. Here, we investigated the impact of fasting on natural killer (NK) cell anti-tumor immunity. Cyclic fasting improved immunity against solid and metastatic tumors in an NK cell-dependent manner. During fasting, NK cells underwent redistribution from peripheral tissues to the bone marrow (BM). In humans, fasting also reduced circulating NK cell numbers. NK cells in the spleen of fasted mice were metabolically rewired by elevated concentrations of fatty acids and glucocorticoids, augmenting fatty acid metabolism via increased expression of the enzyme CPT1A, and Cpt1a deletion impaired NK cell survival and function in this setting. In parallel, redistribution of NK cells to the BM during fasting required the trafficking mediators S1PR5 and CXCR4. These cells were primed by an increased pool of interleukin (IL)-12-expressing BM myeloid cells, which improved IFN-γ production. Our findings identify a link between dietary restriction and optimized innate immune responses, with the potential to enhance immunotherapy strategies.

Effect of three enteral diets with different protein contents on protein metabolism in critically ill infants: a randomized controlled trial

INTRODUCTION

The optimal intake to improve protein metabolism without producing adverse effects in seriously ill infants has yet to be established. The aim of our study was to analyse whether an increased protein intake delivered through enteral nutrition would be associated with an improvement in nitrogen balance and serum protein levels in critically ill infants.

METHODS

We conducted a multicentre, prospective randomized controlled trial (December 2016-June 2019). The sample consisted of critically ill infants receiving enteral nutrition assigned randomly to 3 protein content groups: standard diet (1.7 g/dL), protein-enriched diet (2.7 g/dL) and high protein-enriched diet (5.1 g/dL). Blood and urine tests were performed, and we assessed nitrogen balance at baseline and at 3-5 days of the diet. We analysed variations in nitrogen balance and serum protein levels (total protein, albumin, transferrin, prealbumin, and retinol-binding protein) throughout the study period.

RESULTS

Ninety-nine infants (33 per group) completed the study. We did not find any differences were between groups in demographic characteristics, severity scores or prescribed medications, except for corticosteroids, administered in a higher proportion of patients in the third group. We observed significant increases in prealbumin and retinol-binding protein levels in patients receiving the protein-enriched and high protein-enriched diets at 3-5 days compared to baseline. The nitrogen balance increased in all groups, but the differences were not significant in the high protein-enriched group. There were no differences in gastrointestinal tolerance. Patients fed high protein-enriched formula had higher levels of serum urea, with a higher incidence of hyperuraemia in this group.

CONCLUSION

Enteral administration of higher amounts of protein improves serum protein levels in critically ill children. A protein intake of 2.2 g/kg/day is generally safe and well tolerated, whereas an intake of 3.4 g/kg/day may produce hyperuraemia in some patients.

Glucocorticoids and physical performance: A systematic review with meta-analysis of randomized controlled trials

Introduction

This systematic review with meta-analysis investigates the effect of glucocorticoids on maximal and submaximal performance in healthy subjects.

Methods

We searched for randomised controlled trials investigating the effect of glucocorticoids on physical performance in Web of Science, Scopus, Medline, Embase and SportDiscus in March 2021. Risk of bias was assessed with the revised Cochrane Collaboration Risk of Bias Tool (RoB2). Data from random effect models are presented as standardized difference in mean (SDM) with 95% confidence interval. We included 15 studies comprising 175 subjects.

Results

Two studies had high risk of bias. Glucocorticoids had a small positive effect on maximal physical performance compared to placebo (SDM 0.300, 95% CI 0.080 to 0.520) and the SDM for the 13 included comparisons was not heterogeneous (I2= 35%, p = 0.099). Meta regression found no difference in the effect of acute treatment vs. prolonged treatment or oral ingestion vs. inhalation (p > 0.124). In stratified analysis prolonged treatment (SDM 0.428, 95% CI 0.148 to 0.709) and oral ingestion (SDM 0.361, 95% CI 0.124 to 0.598) improved physical performance. Glucocorticoids improved aerobic performance (SDM 0.371, 95% CI 0.173 to 0.569) but not anaerobic performance (p = 0.135). Glucocorticoids did not change energy expenditure during submaximal performance (SDM 0.0.225 95% CI -0.771 to 0.112).

Discussion

This study indicates that glucocorticoids improves maximal performance and aerobic performance. Glucocorticoids did not affect the energy expenditure during submaximal performance. The conclusions are based on relatively few subjects leading to limited statistical power and uncertain estimates. Still, these results are consistent and should be of interest to WADA and anyone concerned about fair play.

Systematic Review Registration

Open Science Framework 2021-04-29 (https://osf.io/fc29t/).

Mitochondrial Stress Responses in Duchenne muscular dystrophy: Metabolic Dysfunction or Adaptive Reprogramming?

Mitochondrial stress may be a secondary contributor to muscle weakness in inherited muscular dystrophies. Duchenne muscular dystrophy has received the majority of attention whereby most discoveries suggest mitochondrial ATP synthesis may be reduced. However, not all studies support this finding. Furthermore, some studies have reported increased mitochondrial reactive oxygen species and propensity for permeability transition pore formation as an inducer of apoptosis, although divergent findings have also been described. A closer examination of the literature suggests the degree and direction of mitochondrial stress responses may depend on the progression of the disease, the muscle type examined, the mouse model employed with regards to pre-clinical research, the precise metabolic pathways in consideration, and in some cases the in vitro technique used to assess a given mitochondrial bioenergetic function. One intent of this review is to provide careful considerations for future experimental designs to resolve the heterogeneous nature of mitochondrial stress during the progression of Duchenne muscular dystrophy. Such considerations have implications for other muscular dystrophies as well which are addressed briefly herein. A renewed perspective of the term 'mitochondrial dysfunction' is presented whereby stress responses might be re-explored in future investigations as direct contributors to myopathy vs an adaptive 'reprogramming' intended to maintain homeostasis in the face of disease stressors themselves. In so doing, the prospective development of mitochondrial enhancement therapies can be driven by advances in perspectives as much as experimental approaches when resolving the precise relationships between mitochondrial remodelling and muscle weakness in Duchenne and, indeed, other muscular dystrophies.

Regulation of metabolism during hibernation in brown bears (Ursus arctos): Involvement of cortisol, PGC-1α and AMPK in adipose tissue and skeletal muscle

The purpose of this study was to investigate changes in expression of known cellular regulators of metabolism during hyperphagia (Sept) and hibernation (Jan) in skeletal muscle and adipose tissue of brown bears and determine whether signaling molecules and transcription factors known to respond to changes in cellular energy state are involved in the regulation of these metabolic adaptations. During hibernation, serum levels of cortisol, glycerol, and triglycerides were elevated, and protein expression and activation of AMPK in skeletal muscle and adipose tissue were reduced. mRNA expression of the co-activator PGC-1α was reduced in all tissues in hibernation whereas mRNA expression of the transcription factor PPAR-α was reduced in the vastus lateralis muscle and adipose tissue only. During hibernation, gene expression of ATGL and CD36 was not altered; however, HSL gene expression was reduced in adipose tissue. During hibernation gene expression of the lipogenic enzyme DGAT in all tissues and the expression of the FA oxidative enzyme LCAD in the vastus lateralis muscle were reduced. Gene and protein expression of the glucose transporter GLUT4 was decreased in adipose tissue in hibernation. Our data suggest that high cortisol levels are a key adaptation during hibernation and link cortisol to a reduced activation of the AMPK/PGC-1α/PPAR-α axis in the regulation of metabolism in skeletal muscle and adipose tissue. Moreover, our results indicate that during this phase of hibernation at a time when metabolic rate is significantly reduced metabolic adaptations in peripheral tissues seek to limit the detrimental effects of unduly large energy dissipation.

Glucocorticoid-Induced Insulin Resistance in Men Is Associated With Suppressed Undercarboxylated Osteocalcin

In mice, glucocorticoid-induced insulin resistance occurs largely through impaired osteoblast function and decreased circulating undercarboxylated osteocalcin (ucOC). Whether these mechanisms contribute to glucocorticoid-induced insulin resistance in humans has yet to be established. In addition, the effects of glucocorticoids on the exercise-induced increase in circulating ucOC and insulin sensitivity are also unknown. We hypothesized that acute glucocorticoid treatment would lead to basal and postexercise insulin resistance in part through decreased circulating ucOC and ucOC-mediated skeletal muscle protein signaling. Nine healthy men completed two separate cycling sessions 12 hours after ingesting either glucocorticoid (20 mg prednisolone) or placebo (20 mg Avicel). The homeostatic model assessment was used to assess basal insulin sensitivity and a 2-hour euglycemic-hyperinsulinemic clamp was commenced 3 hours after exercise to assess postexercise insulin sensitivity. Serum ucOC and skeletal muscle protein signaling were measured. Single-dose glucocorticoid ingestion increased fasting glucose (27%, p < 0.01) and insulin (83%, p < 0.01), and decreased basal insulin sensitivity (-47%, p < 0.01). Glucocorticoids reduced insulin sensitivity after cycling exercise (-34%, p < 0.01), reduced muscle GPRC6A protein content (16%, p < 0.05), and attenuated protein phosphorylation of mTOR^Ser2481 , Akt^Ser374 , and AS160^Thr642 (59%, 61%, and 50%, respectively; all ps < 0.05). Serum ucOC decreased (-24%, p < 0.01) which correlated with lower basal insulin sensitivity (r = 0.54, p = 0.02), lower insulin sensitivity after exercise (r = 0.72, p < 0.05), and attenuated muscle protein signaling (r = 0.48-0.71, p < 0.05). Glucocorticoid-induced basal and postexercise insulin resistance in humans is associated with the suppression of circulating ucOC and ucOC-linked protein signaling in skeletal muscle. Whether ucOC treatment can offset glucocorticoid-induced insulin resistance in human subjects requires further investigation. © 2018 American Society for Bone and Mineral Research.

Changes in body composition and muscle attenuation during taxane-based chemotherapy in patients with metastatic breast cancer

PURPOSE

Body composition parameters including low muscle mass, muscle attenuation (which reflects muscle quality) and adipose tissue measurements have emerged as prognostic factors in cancer patients. However, knowledge regarding the possibility of excessive muscle loss during specific systemic therapies is unknown. We describe the changes in body composition and muscle attenuation (MA) during taxane- and anthracycline-based regimens and its association with overall survival (OS) in metastatic breast cancer patients.

METHODS

The lumbar skeletal muscle index (LSMI) was used as marker of muscle mass. LSMI, MA, subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT) and intramuscular adipose tissue (IMAT) were measured before and after first-line treatment with paclitaxel (n = 73) or 5-fluorouracil-doxorubicin-cyclophosphamide (FAC) (n = 25) using CT-images. Determinants of the change of LSMI and MA were analyzed using multiple linear regression. OS was assessed using Cox proportional hazard models.

RESULTS

MA significantly decreased during paclitaxel treatment (- 0.9 HU, p = 0.03). LSMI (p = 0.40), SAT (p = 0.75), VAT (p = 0.84) and IMAT (p = 0.10) remained stable. No significant alterations in body composition parameters during FAC-treatment were observed. Previous (neo-)adjuvant chemotherapy contributed to larger loss of MA during the current treatment. Body composition changes during chemotherapy were not associated with OS.

CONCLUSIONS

MA decreased during treatment with paclitaxel, while muscle mass was stable. Body composition changes are not associated with survival in the absence of progressive disease.

A Single Dose of Prednisolone as a Modulator of Undercarboxylated Osteocalcin and Insulin Sensitivity Post-Exercise in Healthy Young Men: A Study Protocol

BACKGROUND

Undercarboxylated osteocalcin (ucOC) increases insulin sensitivity in mice. In humans, data are supportive, but the studies are mostly cross-sectional. Exercise increases whole-body insulin sensitivity, in part via ucOC, while acute glucocorticoid treatment suppresses ucOC in humans and mice.

OBJECTIVES

A single dose of prednisolone reduces the rise in ucOC produced by exercise, which partly accounts for the failed increase in insulin sensitivity following exercise.

METHODS

Healthy young men (n=12) aged 18 to 40 years will be recruited. Initial assessments will include analysis of fasting blood, body composition, aerobic power (VO2peak), and peak heart rate. Participants will then be randomly allocated, double-blind, to a single dose of 20 mg of prednisolone or placebo. The two experimental trials will involve 30 minutes of interval exercise (90%-95% peak heart rate), followed by 3 hours of recovery and 2 hours of euglycaemic- hyperinsulinaemic clamp (insulin clamp). Seven muscle biopsies and blood samples will be obtained at rest, following exercise and post-insulin clamps.

RESULTS

The study is funded by the National Heart Foundation of Australia and Victoria University. Enrollment has already commenced and data collection will be completed in 2016.

CONCLUSION

If the hypothesis is confirmed, the study will provide novel insights into the potential role of ucOC in insulin sensitivity in human subjects and will elucidate pathways involved in exercise-induced insulin sensitivity.

Glucocorticoids and Skeletal Muscle

Glucocorticoids are known to regulate protein metabolism in skeletal muscle, producing a catabolic effect that is opposite that of insulin. In many catabolic diseases, such as sepsis, starvation, and cancer cachexia, endogenous glucocorticoids are elevated contributing to the loss of muscle mass and function. Further, exogenous glucocorticoids are often given acutely and chronically to treat inflammatory conditions such as asthma, chronic obstructive pulmonary disease, and rheumatoid arthritis, resulting in muscle atrophy. This chapter will detail the nature of glucocorticoid-induced muscle atrophy and discuss the mechanisms thought to be responsible for the catabolic effects of glucocorticoids on muscle.

Effects of short-term oral corticosteroid intake on dietary intake, body weight and body composition in adults with asthma - a randomized controlled trial

BACKGROUND

Oral corticosteroids (OCS) are an efficacious treatment for asthma exacerbations, yet risk of adverse effects may decrease patient adherence to therapy. In particular, changes in appetite and dietary intake, which lead to weight gain and changes in body composition, are considered undesirable.

OBJECTIVE

To determine whether 10-day OCS therapy in adults with asthma causes changes in leptin, appetite, dietary intake, body weight and body composition.

METHODS

Double-blinded, placebo-controlled randomized cross-over trial of 10 days prednisolone (50 mg) in adults with stable asthma (n = 55) (ACTRN12611000562976). Pre- and post-assessment included spirometry, body weight, body composition measured by dual-energy X-ray absorptiometry and bioelectrical impedance analysis, appetite measured using a validated visual analogue scale (VAS) and dietary intake assessed using 4-day food records. Leptin was measured as a biomarker of appetite and eosinophils as an adherence biomarker. Outcomes were analysed by generalized linear mixed models.

RESULTS

Subject adherence was confirmed by a significant decrease in blood eosinophils (× 10(9) /L) following prednisolone compared to placebo [Coef. -0.29, 95% CI: (-0.39, -0.19) P < 0.001]. There was no difference in serum leptin (ng/mL) [Coef. 0.13, 95% CI: (-3.47, 3.72) P = 0.945] or appetite measured by VAS (mm) [Coef. -4.93, 95% CI: (-13.64, 3.79) P = 0.267] following prednisolone vs. placebo. There was no difference in dietary intake (kJ/day) [Coef. 255, 95% CI: (-380, 891) P = 0.431], body weight (kg) [Coef. -0.38, 95% CI: (-0.81, 0.05) P = 0.083] or body fat (%) [Coef. -0.31, 95% CI: (-0.81, 0.20) P = 0.230]. Symptoms including sleep and gastrointestinal disturbance were reported significantly more often during prednisolone vs. placebo.

CONCLUSIONS AND CLINICAL RELEVANCE

Short-term OCS in stable asthma did not induce significant changes in appetite, dietary intake, body weight or composition, although other adverse effects may require medical management. This evidence may assist in increasing medication adherence of asthmatics prescribed OCS for exacerbations.

Metabolic control through glucocorticoid hormones: an update

In the past decades, glucocorticoid (GC) hormones and their cognate, intracellular receptor, the glucocorticoid receptor (GR), have been well established as critical checkpoints in mammalian energy homeostasis. Whereas many aspects in healthy nutrient metabolism require physiological levels and/or action of GC, aberrant GC/GR signalling has been linked to severe metabolic dysfunction, including obesity, insulin resistance and type 2 diabetes. Consequently, studies of the molecular mechanisms within the GC signalling axis have become a major focus in biomedical research, up-to-date particularly focusing on systemic glucose and lipid handling. However, with the availability of novel high throughput technologies and more sophisticated metabolic phenotyping capabilities, as-yet non-appreciated, metabolic functions of GC have been recently discovered, including regulatory roles of the GC/GR axis in protein and bile acid homeostasis as well as metabolic inter-organ communication. Therefore, this review summarises recent advances in GC/GR biology, and summarises findings relevant for basic and translational metabolic research.

Metabolic Signatures of Kidney Yang Deficiency Syndrome and Protective Effects of Two Herbal Extracts in Rats Using GC/TOF MS

Kidney Yang Deficiency Syndrome (KDS-Yang), a typical condition in Chinese medicine, shares similar clinical signs of the glucocorticoid withdrawal syndrome. To date, the underlying mechanism of KDS-Yang has been remained unclear, especially at the metabolic level. In this study, we report a metabolomic profiling study on a classical model of KDS-Yang in rats induced by hydrocortisone injection to characterize the metabolic transformation using gas chromatography/time-of-flight mass spectrometry. WKY1, a polysaccharide extract from Astragalus membranaceus and Lycium barbarum, and WKY2, an aqueous extract from a similar formula containing Astragalus membranaceus, Lycium barbarum, Morinda officinalis, Taraxacum mongolicum, and Cinnamomum cassia presl, were used separately for protective treatments of KDS-Yang. The changes of serum metabolic profiles indicated that significant alterations of key metabolic pathways in response to abrupt hydrocortisone perturbation, including decreased energy metabolism (lactic acid, acetylcarnitine), lipid metabolism (free fatty acids, 1-monolinoleoylglycerol, and cholesterol), gut microbiota metabolism (indole-3-propionic acid), biosynthesis of catecholamine (norepinephrine), and elevated alanine metabolism, were attenuated or normalized with different degrees by the pretreatment of WKY1 or WKY2, which is consistent with the observations in which the two herbal agents could ameliorate biochemical markers of serum cortisone, adrenocorticotropic (ACTH), and urine 17-hydroxycorticosteroids (17-OHCS).

Potential of treatment-specific protein biomarker profiles for detection of hormone abuse in cattle

Targeted protein biomarker profiling is suggested as a fast screening approach for detection of illegal hormone treatment in meat production. The advantage of using biomarkers is that they mark the biological response and, thus, are responsive to a panel of substances with similar effects. In a preliminary feasibility study, a 4-plex protein biomarker flow cytometric immunoassay (FCIA) previously developed for the detection of recombinant bovine somatotropin (rbST) was applied to cattle treated with steroids, such as estradiol, dexamethasone, and prednisolone. Each treatment resulted in a specific plasma biomarker profile for insulin-like growth factor-1 (IGF-1), IGF binding protein 2, osteocalcin, and anti-rbST antibodies, which could be distinguished from the profile of untreated animals. In summary, the 4-plex biomarker FCIA is, apart from rbST, also capable of detecting treatment with other growth-promoting agents and therefore clearly shows the potential of biomarker profiling as a screening method in veterinary control. It is proposed to perform additional validation studies covering high numbers of treated and untreated animals to support inclusion or adaptation of protein biomarker approaches in future monitoring regulations.

Bone mineral density, bone markers, and fractures in adult males with congenital adrenal hyperplasia

OBJECTIVE

The aim of this study was to determine bone mineral density (BMD), markers of bone metabolism, fractures, and steroids reflecting hormonal control in adult males with congenital adrenal hyperplasia (CAH). SUBJECTS, METHODS, AND DESIGN: We compared CAH males with 21-hydroxylase deficiency (n=30), 19-67 years old, with age- and sex-matched controls (n=32). Subgroups of CYP21A2 genotypes, age, glucocorticoid preparation, poor control vs overtreatment, and early vs late (>36 months) diagnosis were studied. BMD measured by dual energy X-ray absorptiometry and markers of bone metabolism and androgens/17-hydroxyprogesterone levels were investigated.

RESULTS

All, including older (>30 years), CAH patients had lower BMD in all measured sites compared with control subjects. The null group demonstrated lower BMD in more locations than the other groups. Osteoporosis/osteopenia was present in 81% of CAH patients compared with 32% in controls (≥30 years). Fracture frequency was similar, osteocalcin was lower, and fewer patients than controls had vitamin D insufficiency. IGF1 was elevated in the milder genotypes. In patients, total body BMD was positively correlated to weight, BMI, total lean body mass, and triglycerides, and negatively to prolactin. Patients on prednisolone had lower BMD and osteocalcin levels than those on hydrocortisone/cortisone acetate. Patients with poor control had higher femoral neck BMD. There were no differences in BMD between patients with an early vs late diagnosis.

CONCLUSIONS

CAH males have low BMD and bone formation markers. BMD should be monitored, adequate prophylaxis and treatment established, and glucocorticoid doses optimized to minimize the risk of future fractures.

Steroid myopathy: some unresolved issues

Steroid myopathy is a non-inflammatory toxic myopathy that occurs as side effect of exogenous and endogenous glucocorticoid excess. The purpose of this review is to examine issues that limit our understanding of this myopathy with respect to nosology, etiopathogenesis, conditioning factors, and muscle fiber selectivity. We suggest that if more data were available on these issues, the understanding of steroid myopathy would be enhanced substantially, thus allowing an early detection of its occurrence (before the appearance of clinical or laboratory signs) and a proper treatment of the patients.

Evidence on ergogenic action of glucocorticoids as a doping agent risk

Systemic administration of glucocorticoids (GCs) is banned by the World Anti-Doping Agency (WADA) during competition. Few studies have examined the effects of GCs on exercise performance, but increasing evidence has shown that short-term GC intake enhances performance in animals and humans. However, there are many health risks associated with GC use. Based on the available evidence, as presented in this article, I conclude that GCs are doping agents and should remain on the WADA's list of banned products. Because of the complexity of GCs, however, determining the boundaries between their medical use and abuse (eg, in sports) is a constant challenge for the WADA.

Exploratory study on oxygen consumption on-kinetics during treadmill walking in women with systemic lupus erythematosus

OBJECTIVE

To determine whether oxygen consumption (V o(2)) on-kinetics differed between groups of women with systemic lupus erythematosus (SLE) and sedentary but otherwise healthy controls.

DESIGN

Exploratory case-control study.

SETTING

Medical school exercise physiology laboratory.

PARTICIPANTS

Convenience samples of women with SLE (n=12) and sedentary but otherwise healthy controls (n=10).

INTERVENTION

None.

MAIN OUTCOME MEASURES

V o(2) on-kinetics indices including time to steady state, rate constant, mean response time (MRT), transition constant, and oxygen deficit measured during bouts of treadmill walking at intensities of 3 and 5 metabolic equivalents (METs).

RESULTS

Time to steady state and oxygen deficit were increased and rate constant was decreased in the women with SLE compared with controls. At the 5-MET energy demand, the transition constant was lower and MRT was longer in the women with SLE than in controls. For a similar relative energy expenditure that was slightly lower than the anaerobic threshold, the transition constant was higher in controls than in women with SLE.

CONCLUSION

V o(2) on-kinetics was prolonged in women with SLE. The prolongation was concomitant with an increase in oxygen deficit and may underlie performance fatigability in women with SLE.

Muscle fiber conduction slowing and decreased levels of circulating muscle proteins after short-term dexamethasone administration in healthy subjects

CONTEXT

Glucocorticoids are known to decrease protein synthesis and impair membrane excitability of muscle fibers. However, their short-term effects on muscle structure and function of healthy subjects remain poorly understood.

OBJECTIVE

Our objective was to investigate whether steroid administration could decrease the circulating levels of muscle proteins and modify myoelectric indexes of sarcolemmal excitability and fatigability.

DESIGN

We conducted a single-blind, placebo-controlled study in 20 men randomized to receive dexamethasone (8 mg/d) or placebo for 1 wk. Blood sampling, force measurements for knee extensors and elbow flexors, and electrophysiological tests for biceps brachii, vastus lateralis and medialis, and tibialis anterior muscles were performed before and after the intervention.

RESULTS

Dexamethasone administration improved force by 6.0 +/- 6.0% (P = 0.01) for elbow flexors and by 8.5 +/- 5.5% (P < 0.01) for knee extensors, decreased levels of creatine kinase by 50.5 +/- 30.0% (P < 0.01) and myoglobin by 41.8 +/- 17.5% (P < 0.01), and impaired sarcolemmal excitability, as shown by the decline of muscle fiber conduction velocity for the four muscles (range from -6 to -10.5%, P < 0.05). Moreover, significant reductions of the myoelectric manifestations of fatigue were observed for the four muscles; the decrease in the rate of change of the mean frequency of the electromyographic power spectrum ranged from -22.6 to -43.9% (P < 0.05). In contrast, no significant changes were observed in muscle excitability and fatigability in subjects who received the placebo.

CONCLUSIONS

The demonstration that glucocorticoid-induced muscle impairments can be unraveled by means of blood sampling and noninvasive electrophysiological tests has clinical implications for the early identification of subclinical or preclinical forms of myopathy in treated patients.

Glucocorticoids: a doping agent?

Certain international sports federations are requesting that glucocorticoids (GCs) be removed from the World Antidoping Agency's list of banned products. Their arguments are based on the fact that GCs are in widespread use in sports medicine and have no demonstrated ergogenic activity. This article shows that there is scientific evidence that GCs mediate ergogenic effects in animals and humans. Moreover, the health risks of using GCs are well characterized. GCs are doping agents and should remain on the World Antidoping Agency's list of banned products.

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.

The effect of high glucocorticoid administration and food restriction on rodent skeletal muscle mitochondrial function and protein metabolism

Background

Glucocorticoids levels are high in catabolic conditions but it is unclear how much of the catabolic effects are due to negative energy balance versus glucocorticoids and whether there are distinct effects on metabolism and functions of specific muscle proteins.

Methodology/Principal Findings

We determined whether 14 days of high dose methylprednisolone (MPred, 4 mg/kg/d) Vs food restriction (FR, food intake matched to MPred) in rats had different effects on muscle mitochondrial function and protein fractional synthesis rates (FSR). Lower weight loss (15%) occurred in FR than in MPred (30%) rats, while a 15% increase occurred saline-treated Controls. The per cent muscle loss was significantly greater for MPred than FR. Mitochondrial protein FSR in MPred rats was lower in soleus (51 and 43%, respectively) and plantaris (25 and 55%) than in FR, while similar decline in protein FSR of the mixed, sarcoplasmic, and myosin heavy chain occurred. Mitochondrial enzymatic activity and ATP production were unchanged in soleus while in plantaris cytochrome c oxidase activity was lower in FR than Control, and ATP production rate with pyruvate + malate in MPred plantaris was 28% lower in MPred. Branched-chain amino acid catabolic enzyme activities were higher in both FR and MPred rats indicating enhanced amino acid oxidation capacity.

Conclusion/Significance

MPred and FR had little impact on mitochondrial function but reduction in muscle protein synthesis occurred in MPred that could be explained on the basis of reduced food intake. A greater decline in proteolysis may explain lesser muscle loss in FR than in MPred rats.

Acute responses of muscle protein metabolism to reduced blood flow reflect metabolic priorities for homeostasis

The present experiment was designed to measure the synthetic and breakdown rates of muscle protein in the hindlimb of rabbits with or without clamping the femoral artery. l-[ring-(13)C(6)]phenylalanine was infused as a tracer for measurement of muscle protein kinetics by means of an arteriovenous model, tracer incorporation, and tracee release methods. The ultrasonic flowmeter, dye dilution, and microsphere methods were used to determine the flow rates in the femoral artery, in the leg, and in muscle capillary, respectively. The femoral artery flow accounted for 65% of leg flow. A 50% reduction in the femoral artery flow reduced leg flow by 28% and nutritive flow by 26%, which did not change protein synthetic or breakdown rate in leg muscle. Full clamp of the femoral artery reduced leg flow by 42% and nutritive flow by 59%, which decreased (P < 0.05) both the fractional synthetic rate from 0.19 +/- 0.05 to 0.14 +/- 0.03%/day and fractional breakdown rate from 0.28 +/- 0.07 to 0.23 +/- 0.09%/day of muscle protein. Neither the partial nor full clamp reduced (P = 0.27-0.39) the intracellular phenylalanine concentration or net protein balance in leg muscle. We conclude that the flow threshold to cause a fall of protein turnover rate in leg muscle was a reduction of 30-40% of the leg flow. The acute responses of muscle protein kinetics to the reductions in blood flow reflected the metabolic priorities to maintain muscle homeostasis. These findings cannot be extrapolated to more chronic conditions without experimental validation.

Fractures and bone mineral density in adult women with 21-hydroxylase deficiency

CONTEXT

Patients with classical congenital adrenal hyperplasia (CAH) receive lifelong, often supraphysiological, glucocorticoid therapy. Pharmacological doses of glucocorticoids are an established risk factor for osteoporosis.

OBJECTIVE

Our objective was to evaluate bone mineral density (BMD), fracture prevalence, and markers of bone metabolism in adult females with CAH.

DESIGN

This was a cross-sectional observational study.

SETTING

Tertiary care referral centers were used in this study.

PARTICIPANTS

We studied 61 women, aged 18-63 yr, with genetically verified CAH due to 21-hydroxylase deficiency. They were patients with salt wasting (n = 27), simple virilizing (n = 28), and nonclassical 21-hydroxylase deficiency (n = 6). A total of 61 age-matched women were controls.

MAIN OUTCOME MEASURES

History of fractures was recorded. Total body, lumbar spine, and femoral neck BMD were measured by dual-energy x-ray absorptiometry. The World Health Organization criteria for osteopenia and osteoporosis were used. Serum marker of bone resorption, beta-C telopeptide was studied.

RESULTS

The mean glucocorticoid dose in hydrocortisone equivalents was 16.9 +/- 0.9 mg/m2. Patients had lower BMD than controls at all measured sites (P < 0.001). In patients younger than 30 yr old, 48% were osteopenic vs. 12% in controls (P < 0.009). In patients 30 yr or older, 73% were osteopenic or osteoporotic vs. 21% in controls (P < 0.001). BMD was similar in the two classical forms and had no obvious relationship to genotypes. beta-C-telopeptide was decreased in older patients. More fractures were reported in patients than controls (P < 0.001). The number of vertebrae and wrist fractures almost reached significance (P = 0.058).

CONCLUSIONS

Women with CAH have low BMD and increased fracture risk. BMD should be monitored, adequate prophylaxis and treatment instituted, and glucocorticoid doses optimized from puberty.

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.

Effects of cortisol on carbohydrate, lipid, and protein metabolism: studies of acute cortisol withdrawal in adrenocortical failure

CONTEXT

Cortisol is an important catabolic hormone, but little is known about the metabolic effects of acute cortisol deficiency.

OBJECTIVE

The objective of the study was to test whether clinical symptoms of weight loss, fatigue, and hypoglycemia could be explained by altered energy expenditure, protein metabolism, and insulin sensitivity during cortisol withdrawal in adrenocortical failure.

DESIGN, PARTICIPANTS, AND INTERVENTION

We studied seven women after 24-h cortisol withdrawal and during replacement control during a 3-h basal period and a 3-h glucose clamp.

RESULTS

Cortisol withdrawal generated cortisol levels close to zero, a 10% decrease in basal energy expenditure, increased TSH and T(3) levels, and increased glucose oxidation. Whole-body glucose and phenylalanine turnover were unaltered, but forearm phenylalanine turnover was increased. During the clamp glucose, infusion rates rose by 70%, glucose oxidation rates increased, and endogenous glucose production decreased. Urinary urea excretion decreased by 40% over the 6-h study period.

CONCLUSIONS

Cortisol withdrawal increased insulin sensitivity in terms of increased glucose oxidation and decreased endogenous glucose production; this may induce hypoglycemia in adrenocortical failure. Energy expenditure and urea loss decreased, indicating that weight and muscle loss in Addison's disease is caused by other mechanisms, such as decreased appetite. Increased muscle protein breakdown may amplify the loss of muscle protein.

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

How protein metabolism is perturbed during chronic glucocorticoid excess is poorly understood. The aims were to investigate the impact of chronic glucocorticoid excess and restoration of eucortisolemia in Cushing's syndrome (CS) on whole body protein metabolism. Eighteen subjects with CS and 18 normal subjects (NS) underwent assessment of body composition using DEXA and whole body protein turnover with a 3-h constant infusion of l-[(13)C]leucine, allowing calculation of rates of leucine appearance (leucine R(a)), leucine oxidation (L(ox)), and leucine incorporation into protein (LIP). Ten subjects with CS were restudied after restoration of eucortisolemia. Percentage FM was greater (43.9 +/- 1.6 vs. 33.8 +/- 2.4%, P = 0.002) and LBM lower (52.7 +/- 1.6 vs. 62.1 +/- 2.3%, P = 0.002) in CS. LBM was significantly correlated (r(2) > 0.44, P < 0.005) to leuceine R(a), L(ox), and LIP in both groups. After correcting for LBM, leucine R(a) (133 +/- 5 vs. 116 +/- 5 micromol/min, P = 0.02) and L(ox) (29 +/- 1 vs. 24 +/- 1 micromol/min, P = 0.01) were greater in CS. FM significantly correlated (r(2) = 0.23, P < 0.05) with leucine R(a) and LIP, but not L(ox) in CS. In multiple regression, LBM was an independent determinant of all three indexes of leucine turnover, FM of leucine R(a), and LIP and CS of L(ox). Following restoration of eucortisolemia, L(ox) was reduced (Delta-7.5 +/- 2.6 micromol/min, P = 0.02) and LIP increased (Delta+15.2 +/- 6.2 micromol/min, P = 0.04). In summary, whole body protein metabolism in CS is influenced by changes in body composition and glucocorticoid excess per se, which increases protein oxidation. Enhanced protein oxidation is a likely explanation for the reduced protein mass in CS. Successful treatment of CS reduces protein oxidation and increases protein synthesis to prevent ongoing protein loss.

Amino acids stimulate leg muscle protein synthesis in peripheral arterial disease

OBJECTIVE

Older patients with peripheral arterial disease (PAD) and intermittent claudication have impaired walking ability resulting from reduced lower extremity blood flow. Evidence suggests that leg muscle abnormalities may also contribute to walking intolerance in claudicants. In healthy elderly people, leg muscle protein synthesis can be augmented by nutritional supplementation with amino acids; preliminary data suggest that this increases muscle mass, walking ability, and functional status. In this study, we investigated whether amino acid supplementation would improve leg muscle protein synthesis in elderly PAD subjects, given that reduced leg blood flow might restrict the availability of amino acids to muscle.

METHODS

Two groups participated in the study: a group of 11 claudicants (mean age, 62 years; mean ankle-brachial index, 0.62; 46% male) and a group of 9 age- and sex-matched healthy controls (mean ankle-brachial index, 1.1). Both groups underwent measurement of leg blood flow by using strain gauge plethysmography, as well as measurement of baseline and amino acid-stimulated protein synthesis in leg muscle. Protein synthesis was quantified from calf muscle biopsy samples by measurement of the fractional synthetic rate (FSR) of protein, by using the incorporation of the stable isotope l-[ring-(2)H(5)]-phenylalanine into muscle protein. Total protein was extracted from muscle samples, and gas chromatography/mass spectroscopy methodology was used to measure incorporation rates. After measurement of basal FSR, all subjects were given an oral drink of 15 g of essential amino acids, and the measurements of FSR were repeated. Data are expressed as mean +/- SD; statistical analysis of differences between the two groups (with and without amino acid supplementation) was performed by using analysis of variance with repeated measures.

RESULTS

Calf blood flow was reduced in the PAD subjects compared with controls (1.44 +/- 0.53 mL/min per 100 mg of tissue vs 2.40 +/- 0.57 mL/min per 100 mg of tissue; P = .005; t test). FSR in the basal state was equivalent between the two groups (healthy, 0.060% +/- 0.025% per hour; PAD, 0.061% +/- 0.029% per hour; P = .97). Equivalent increases (P < .05) occurred in both groups in response to oral amino acid supplementation (healthy, 0.087% +/- 0.012% per hour; PAD, 0.104% +/- 0.041% per hour; P > .05; analysis of variance).

CONCLUSIONS

Despite reduced leg blood flow, elderly PAD patients synthesize calf muscle protein in the basal state in a fashion similar to that in healthy elderly people. More importantly, administration of exogenous amino acids produces a significant increase in protein synthesis in these patients that is also equivalent to that in healthy elderly people. Our goal is to use these results as the basis for an intervention study to determine whether long-term oral amino acids, by augmenting calf muscle protein synthesis, increase calf muscle mass, walking ability, and functional status in elderly claudicants.

Characterization of the metabolic phenotypes of Cushing's syndrome and growth hormone deficiency: a study of body composition and energy metabolism

OBJECTIVE

A comparison of the severity and distribution of perturbations in body composition and their relationship to energy metabolism in glucocorticoid excess and GH deficiency (GHD) has not been undertaken before. The aim of this study was to investigate the impact of Cushing's syndrome (CS) and GHD on whole and regional body composition and energy metabolism.

DESIGN

Cross-sectional study design.

PATIENTS

Eighteen subjects with CS (12 women, aged = 41.5 +/- 3.0 years, 24-h urinary free cortisol = 1601 +/- 361 nmol/day, normal < 300 nmol/day), 22 subjects with GHD (14 women, age = 42.9 +/- 2.9 years) and 18 normal subjects (11 women, age = 46.8 +/- 2.8 years).

MEASUREMENTS

Lean body mass (LBM), fat mass (FM) and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA). Resting energy expenditure (REE) and fat oxidation (Fox) were assessed by indirect calorimetry.

RESULTS

Mean percentage FM was significantly greater by 30% in CS (P = 0.002) and 22% in GH-deficient subjects (P = 0.014) than in normal subjects. LBM was significantly lower by 15% in CS (P = 0.002) and 11% in GHD (P = 0.013). In CS, the proportion of lean tissue in the limbs was 12% less than in normal (P = 0.001) and GH-deficient subjects (P = 0.0005). Truncal fat represented a greater proportion of total FM in CS (52.5 +/- 1.8%vs. 46.9 +/- 1.3%, P = 0.014) than in normal subjects, but not in GHD. REE and Fox, corrected for LBM, were significantly lower in GHD (P < 0.02 for both vs. normal) but not in CS.

CONCLUSION

FM was higher and LBM lower in both CS and GHD. However, there is a greater abnormality of regional body composition in patients with CS who exhibit a lower limb lean mass and a greater truncal fat. Reduced REE and Fox contribute to increased adiposity in GHD. As REE and Fox are not perturbed in CS, other mechanisms must explain the marked gain in truncal and total fat.

Assessment of branched-chain amino Acid status and potential for biomarkers

BCAAs are not synthesized in the body in humans, but they are crucial in protein and neurotransmitter synthesis. The protein anabolic role of BCAAs seems to be mediated not only by their important role as a promoter of the translation process (and possibly acting at the transcription level) but also by inhibition of protein degradation. Leucine may play a critical role in these signaling pathways. Supplementation with BCAAs spares lean body mass during weight loss, promotes wound healing, may decrease muscle wasting with aging, and may have beneficial effects in renal and liver disease. BCAA supplementation is extensively used in the athletic field with the assumption of improved performance and muscle mass. Measuring serum BCAAs has limited clinical utility beyond the controlled setting because levels are affected by a variety of clinical states, and optimal levels in these scenarios have not been completely elucidated. We discuss the effects diet, hormones, stress, aging, and renal or liver dysfunction have on BCAA levels and how understanding the biological effects of BCAAs may help to develop biomarkers of BCAA status. We also discuss potential biomarkers of BCAA status.

[Adrenal cortex and steroids. Supplementary therapy in the perioperative phase]

Since the publication of two case reports that are considered to represent the first clinical demonstration of iatrogenic adrenal insufficiency, it has been the generally accepted practice to cover steroid-treated patients undergoing surgery with glucocorticoids in the perioperative period. Both the inclusion criteria for the patients and the extent of the substitution pattern have been selected on an empirical rather than on a rational basis. Scientific advances over the past 50 years in the knowledge of the hypothalamic-pituitary-adrenal system's physiology and the molecular mechanism of action of its biologically active components are, for the most part, not reflected in current clinical practice and instead seem to be ignored. Clinical and experimental evidence suggests, however, that even glucocorticoid-treated patients undergoing surgery do not require maximum stress doses of hydrocortisone, which should be reserved for the treatment of sepsis. With regard to the broad spectrum of efficacy of glucocorticoids and their side effects, revision and modification of the historical regimen appear prudent.