Corticotroph axis sensitivity after exercise: comparison between elite athletes and sedentary subjects

Heart Rate Variability and Cortisol Levels Before and After a Brief Anaerobic Exercise in Handball Players

ABSTRACT

Kayacan, Y, Makaracı, Y, Ucar, C, Amonette, WE, and Yıldız, S. Heart rate variability and cortisol levels before and after a brief anaerobic exercise in handball players. J Strength Cond Res 37(7): 1479-1485, 2023-Evaluating stress in athletes is important for monitoring overall physiologic load and is a core practice for sport performance teams. This study examined relationships between 2 metrics of training stress, heart rate variability (HRV) and cortisol, before and after intense anaerobic power testing. Electrocardiogram recordings and saliva samples were collected before and immediately after a Wingate anaerobic power test (WAnT-30) from professional handball players ( n = 20) and sedentary controls ( n = 18). Between-group differences and correlations were computed to assess study hypotheses. No differences were observed in HRV frequency-dependent parameters between groups, but in athletes, Min. R-R ( p < 0.01) and Avg.R-R ( p = 0.03) before WAnT-30 and the percentage of successive normal cardiac beat intervals greater than 50 milliseconds (i.e., pNN50; p = 0.03) after WAnT-30 were elevated. A high positive correlation was detected between the pretest and post-test cortisol levels in athletes ( p = 0.0001; r = 0.87) but not in sedentary individuals. No correlations were observed between the cortisol levels and WAnT-30 power parameters in either group. Relationships were evident in the standard deviation of RR intervals ( p = 0.02, r = -0.53), square root of the mean squared difference of successive RR intervals ( p = 0.043, r = -0.46), very low frequency ( p = 0.032; r = -0.480), high-frequency ( p = 0.02; r = -0.52) variables, and pretesting cortisol in athletes. These findings suggest that HRV analysis is a valuable tool for examining cardiovascular regulation, independent of cortisol; the data may provide valuable information for performance teams in evaluating acute stress.

Can a single session of noninvasive brain stimulation applied over the prefrontal cortex prevent stress-induced cortisol release?

INTRODUCTION

A better understanding of how the hypothalamic-pituitary-adrenal (HPA) axis can be externally regulated is of major importance, especially because hyperreactivity to stress has been proposed as a key factor in the onset and maintenance of many psychiatric conditions. Over the past decades, numerous studies have investigated whether non-invasive brain stimulation (NIBS) can regulate HPA axis reactivity in acute stress situation. As the current results did not allow us to draw clear conclusions, we decided to conduct a systematic review of the literature investigating the effect of a single NIBS session on stress-induced cortisol release.

METHODS

We searched MEDLINE and Web Of Science for articles indexed through December 2021. Among the 246 articles identified, 15 fulfilled our inclusion criteria with a quality estimated between 52 and 93%.

RESULTS

Of the different NIBS used and targeted brain regions, stimulating the left dorsolateral prefrontal cortex, with either high frequency repetitive transcranial magnetic stimulation or anodal transcranial direct current stimulation, seems to be the most appropriate for reducing cortisol release in acute stress situations.

CONCLUSIONS

Despite the heterogeneity of the stimulation parameters, the characteristics of participants, the modalities of cortisol collection, the timing of the NIBS session in relation to the stressor exposure, and methodological considerations, stimulating the left dorsolateral prefrontal cortex can be efficient to modulate stress-induced cortisol release.

Biomarkers of post-match recovery in semi-professional and professional football (soccer)

High-level football (soccer) players face intense physical demands that result in acute and residual fatigue, impairing their physical performance in subsequent matches. Further, top-class players are frequently exposed to match-congested periods where sufficient recovery times are not achievable. To evaluate training and recovery strategies, the monitoring of players' recovery profiles is crucial. Along with performance and neuro-mechanical impairments, match-induced fatigue causes metabolic disturbances denoted by changes in chemical analytes that can be quantified in different body fluids such as blood, saliva, and urine, thus acting as biomarkers. The monitoring of these molecules might supplement performance, neuromuscular and cognitive measurements to guide coaches and trainers during the recovery period. The present narrative review aims to comprehensively review the scientific literature on biomarkers of post-match recovery in semi-professional and professional football players as well as provide an outlook on the role that metabolomic studies might play in this field of research. Overall, no single gold-standard biomarker of match-induced fatigue exists, and a range of metabolites are available to assess different aspects of post-match recovery. The use of biomarker panels might be suitable to simultaneously monitoring these broad physiological processes, yet further research on fluctuations of different analytes throughout post-match recovery is warranted. Although important efforts have been made to address the high interindividual heterogeneity of available markers, limitations inherent to these markers might compromise the information they provide to guide recovery protocols. Further research on metabolomics might benefit from evaluating the long-term recovery period from a high-level football match to shed light upon new biomarkers of post-match recovery.

Stressor-Induced Temporal Cortisol Deficiency as a Primary Trigger for Adaptation to Stress

BACKGROUND

Inconsistencies in measurements of cortisol response to stress have caused disagreements in the direction of the change in cortisol concentrations immediately after the onset of stress. Researchers typically observe increased cortisol levels in response to a stressor, perceiving occasional decreases as a sign of possible disorders. Reports indicate the relative ease of standardizing a physical stressor compared with a mental stressor, and cross-stressor adaptation is observable only in elite athletes.

METHODS

We investigated the cortisol response to top-intensity physical exertion by analyzing the course of the cortisol response, the changes in this response resulting from adaptation to intense exercise, and the possible convergence between the cortisol changes and body fat content. We examined 16 male athletes, members of the Polish National Rowing Team, competing in the World Rowing Championships, in top form, of an average training experience of seven years. The measurements were performed before and after the training camp preparatory to the Championships. We performed the measurements before and after the training camp preparatory to the Championships.

RESULTS

Before the camp, the athletes consistently reacted to the exertion test with a decrease in cortisol concentration and elevated cortisol levels after rest compared with baseline. After the camp, the post-exertion cortisol decrease as well as the post-rest cortisol elevation was much smaller and less consistent.

CONCLUSIONS

The transient decrease in cortisol concentration at the onset of stress thus represents a physiological reaction, and the stress response counteracts the resulting cortisol deficiency to support cortisol availability during stress. Adaptation to stress enhanced this counteracting effect by (1) increasing the baseline cortisol concentration and (2) speeding up the response to its decline. This enhanced effect was boosted by adipose tissue.

Adrenal, Gonadal and Peripherally Steroid Changes in Response to Extreme Physical Stress for Characterizing Load Capacity in Athletes

Athletes are often exposed to extreme physical stress during training or competitions. The consequent activation of the hypothalamus–hypophysis–adrenal (HPA) axis results in intensified steroid hormone production in the adrenal cortex. We determined the impact of an acute extreme physical stress on adrenal and gonadal steroidogenesis in healthy male professional athletes (n = 40). The subjects underwent an extreme physical load test until total voluntary fatigue between 14:00 and 18:00 when the hormone levels are relatively stable. Blood was taken before the start (baseline), at the peak load (peak), and 30 min following completion of the exercise (recovery). The vital parameters, lactate levels, and blood levels of the 14 steroid hormones were recorded. The multivariate statistical analysis of the results revealed that all monitored hormone levels increased upon stress. Significant changes in steroid concentrations were detected at peak versus baseline, peak versus recovery, and at baseline versus recovery. The mineralocorticoid (including aldosterone and corticosterone), glucocorticoid (11-deoxycortisol and cortisol), and androgen (androstenedione, dehydroepiandrosterone, and dehydroepiandrosterone sulfate) pathways, as well as gonadal testosterone synthesis are activated simultaneously under extreme physical load. The profiling of adrenal and gonadal steroid biosynthesis in athletes may help the characterization of their loading capacity.

The importance of physical fitness for the relationship of BDNF with obesity measures in young normal-weight adults

Aims

Brain derived neurotrophic factor (BDNF) is essential for cognitive function. It is also found in non-neuronal tissues with various regulatory actions, including metabolic. Physical fitness (PF) is associated with improved synthesis and secretion of BDNF and reduced obesity. However, the importance of PF for the relationship of BDNF with obesity has not been investigated. This study aims at examining the relationship of PF with BDNF and obesity in 174 young (age = 25.30 ± 9.2 years) healthy adults.

Main methods

Serum BDNF was evaluated using ELISA while obesity was determined using body weight (BW), BMI, and waist circumference (WC). Six minute walk distance (6MWD) test was used to estimate PF.

Key findings

Serum BDNF was greater (p = 0.000) in the participants with high (Hi6MWD) versus low (Lw6MWD) PF group. Additionally, 6MWD explained 6.8% of serum BDNF. Obesity measures were greater (p < 0.05) in the participants with low versus high BDNF. In regression analyses, serum BDNF explained 4.7% of BW (p = 0.004), 3.8% of BMI (p = 0.011), and 6.2% of WC (p = 0.001). However, when the participants were divided into Hi6MWD and Lw6MWD, BDNF explained 8.2% of BW (p = 0.009), 6.0% of BMI (p = 0.03), and 7.0% of WC (p = 0.013), only in the Hi6MWD, but not in the Lw6MWD (p > 0.05) groups.

Significance

The finding confirms the relationship of BDNF with obesity. Additionally, it further suggests the importance of PF level to this relationship among young adults. Future studies are needed to confirm these findings.

The impact of an exercise training intervention on cortisol levels and post-traumatic stress disorder in juveniles from an Ugandan refugee settlement: study protocol for a randomized control trial

Background

Latest research demonstrates a significant improvement in stress-related symptoms in psychological disorders as a result of exercise training (ET). Controlled clinical trials further validate the significance of ET by demonstrating lower salivary cortisol levels in patients with post-traumatic stress disorder (PTSD) after intervention. A significant change in cortisol and dehydroepiandrosterone (DHEA) levels can already be found after an 8–12-week ET program. The proposed study aims to investigate the impact of an 8-week ET on PTSD symptoms and changes in cortisol levels in a juvenile refugee sample from the Democratic Republic of the Congo (DRC) at an Ugandan refugee settlement. It is the first to implement an ET intervention in a resource-poor, post-conflict setting.

Methods/design

In a randomized controlled trial, 198 adolescent participants aged 13–16 years from the DRC who, suffer from PTSD, will be investigated. The participants are based at the Nakivale refugee settlement, an official refugee camp in Uganda, Africa, which is among the largest in the world. The participants will be randomized into an Exercise Training (ET) group with a maximum heart rate (HR_max) of > 60%, an Alternative Intervention (AI) group with low-level exercises, and a Waiting-list Control (WC) group. After the 8-week interventional phase, changes in cortisol awakening response (CAR) and DHEA in the ET group that correspond to an improvement in PTSD symptoms are expected that remain at follow-up after 3 months.

Discussion

To date, there is no controlled and reliable longitudinal study examining the effects of an ET program on symptom severity in individuals with PTSD that can be explained with a harmonization of cortisol secretion. The presented study design introduces an intervention that can be implemented with little expenditure. It aims to provide a promising low-threshold and cost-effective treatment approach for the application in resource-poor settings.

Trial registration

German Trials Register, ID: DRKS00014280. Registered prospectively on 15 March 2018.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2753-x) contains supplementary material, which is available to authorized users.

Biochemical stress evaluation after medial parapatellar and subvastus approach in total knee replacement

INTRODUCTION

Even if different surgical approaches for total knee arthroplasty are well known since decades, the standard medial parapatellar incision remains the most common one; general agreement about significant advantages with minimally invasive techniques is lacking. Furthermore, the surgical stress effect on the organism has always been analyzed through blood inflammatory parameters. This study aim was to compare the standard and subvastus approaches, using the salivary cortisol in particular as measure for systemic surgery-related stress.

METHODS

Fifteen operations were performed in a consecutive series; clinical (Knee Society Knee Scoring System., a questionnaire score, range of motion, tourniquet time, intra-operative bleeding) and biochemical factors (salivary and hematic cortisol, C-reactive protein, muscular creatine phosphokinase levels) were evaluated. The final follow-up was at two months after the operation.

RESULTS

No significant differences were observed in most of the parameters; however, the subvastus group had a sharper and earlier functional improvement trend than the standard one. On the other side, it increased the CPK levels significantly.

CONCLUSIONS

In our experience, the medial subvastus approach, firstly associated with greater surgical stress, has then been characterized by a more favorable functional improvement trend. Moreover, the salivary cortisol measurement has proved to be a non-invasive and reliable method to evaluate the systemic surgery-related stress.

Sport and male sexuality

The relationships between sport and sexuality in males are of great social and clinical interest, because of sports and motor activities that highly promote social and sexual relationships. Even if few literature exist, two main questions should be taken into account: whether and how physical exercise and sport positively or negatively influence sexual health and behavior and/or whether and how sexual behavior may affect a sub-sequent sport performance. Physical exercise and sport per se can influence, positively or negatively, the hypothalamic-pituitary-testicular axis function and, consequently, the individual's reproductive and/or sexual health. This depends on individual factors such as genetic and epigenetic ones and on different variables involved in the practice of sport activities (type of sport, intensity and duration of training, doping and drug use and abuse, nutrition, supplements, psychological stress, allostatic load, etc.). If well conducted, motor and sport activities could have beneficial effects on sexual health in males. Among different lifestyle changes, influencing sexual health, regular physical activity is fundamental to antagonize the onset of erectile dysfunction (ED). However, competitive sport can lead both reproductive and/or sexual tract damages and dysfunctions, transient (genital pain, hypoesthesia of the genitalia, hypogonadism, DE, altered sexual drive, etc.) or permanent (hypogonadism, DE, etc.), by acting directly (traumas of the external genitalia, saddle-related disorders in cyclists, etc.) or indirectly (exercise-related hypogonadism, drug abuse, doping, stress, etc.). Sexual activities shortly performed before a sport competition could differently influence sport performance. Due to the few existing data, it is advisable to avoid an absolute pre-competition sexual abstinence.

Attenuated salivary cortisol response after exercise test in children with asthma

OBJECTIVE

The clinical relevance of lower basal cortisol levels in children with asthma is unclear. We compared the salivary cortisol response after a standardized exercise test in children with asthma versus the salivary cortisol response in healthy children.

METHODS

Nineteen prepubertal children with asthma and 20 prepubertal healthy children performed a standardized exercise test twice. Salivary cortisol levels were determined before exercise and immediately and 15 min after exercise. Morning salivary cortisol levels were determined from saliva collected at home.

RESULTS

Salivary cortisol levels increased in 84.2% of the healthy children compared to 35.0% in children with asthma after the 20-m shuttle-run test. Median increase in salivary cortisol levels was 200.3% [95% confidence interval (CI), 141.8-346.1] in healthy children compared to 89.8% (95% CI, 56.9-181.6) in children with asthma. The response was not related to the morning salivary cortisol level or maintenance dose of inhaled corticosteroids. The mean time to exhaustion of both shuttle-run tests was significantly shorter in children with asthma (mean difference 1.4 min; 95% CI, 0.7-2.3). None of the children had to stop because of dyspnea.

CONCLUSION

Our study demonstrates that children with asthma using a maintenance dose of inhaled corticosteroids (ICS) have an attenuated salivary cortisol response compared with healthy children.

DHEA, physical exercise and doping

The dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S) concentrations during acute and chronic exercise (training) have been investigated only fairly recently. DHEA is generally preferred to DHEA-S for exploring the acute exercise repercussions in laboratory or field tests because of its shorter elimination half-life. Conversely, DHEA-S is preferred to estimate chronic adaptations. Both can be measured noninvasively in saliva, and it is therefore possible to follow these hormone responses in elite athletes during competitive events and in healthy and pathological populations, without imposing additional stress. Indeed, the correlation between saliva and serum concentrations is high for steroid hormones, both at rest and during exercise. In this review, we will first summarize the current knowledge on the DHEA/DHEA-S responses to exercise and examine the potential modulating factors: exercise intensity, gender, age, and training. We will then discuss the ergogenic effects that athletes expect from the exogenous administration of DHEA and the antidoping methods of analysis currently used to detect this abuse.

Acute effects of physical exercise and phosphodiesterase's type 5 inhibition on serum 11β-hydroxysteroid dehydrogenases related glucocorticoids metabolites: a pilot study

Endogenous glucocorticoids (GC) rapidly increase after acute exercise, and the phosphodiesterase's type 5 inhibitor (PDE5i) tadalafil influences this physiological adaptation. No data exist on acute effects of both acute exercise and PDE5i administration on 11β-hydroxysteroid dehydrogenases (11β-HSDs)-related GC metabolites. We aimed to investigate the rapid effects of exercise on serum GC metabolites, with and without tadalafil administration. A double blind crossover study was performed in eleven healthy male volunteers. After the volunteers randomly received a short-term administration of placebo or tadalafil (20 mg/die for 2 days), a maximal exercise test to exhaustion on cycle ergometer was performed. Then, after a 2-week washout period, the volunteers were crossed over. Blood samples were collected before starting exercise and at 5 and 30 min of recovery (+5-Rec, +30-Rec). Serum ACTH, corticosterone (Cn), cortisol (F), cortisone (E), tetrahydrocortisol (THF), tetrahydrocortisone (THE), cortols, cortolones and respective ratios were evaluated. Pre-Ex THF was higher after tadalafil. Exercise increased ACTH, Cn, F, E, THE, cortols and cortolones after both placebo and tadalafil, and THF after placebo. The F/E ratio increased at +5-Rec and decreased at +30-Rec after placebo. Compared to placebo, after tadalafil lower ACTH, F and Cn, higher THF/F and THE/E, and not E (at +5-Rec) and F/E modifications were observed. Acute exercise rapidly influences serum GC metabolites concentrations. Tadalafil influences both GC adaptation and 11β-HSDs activity during acute exercise. Additional researches on the effects of both exercise and PDE5i on tissue-specific 11β-HSDs activity at rest and during physiological adaptation are warranted.

How does stress possibly affect cardiac remodeling?

The aim of this study was to evaluate the predictive value of adrenocorticotropic hormone (ACTH), cortisol and ACTH receptor polymorphism (ACTHRP) for left ventricular (LV) remodeling. Thirty-six elite male athletes, as chronic stress adaptation models, and twenty sedentary age and sex-mached subjects emabarked on standard and tissue Doppler echocardiography to assess cardiac parameters at rest. They performed maximal cardiopulmonary test, which was used as an acute stress model. ACTH and cortisol were measured at rest (10min before test), at beginning, at maximal effort, at 3rd min of recovery, using radioimmunometric and radioimmunoassey techniques, respectively. Promoter region of ACTHR gene (18p11.2) was analysed from blood samples using reverse polymerization reaction with the analysis of restriction fragment length polimorphisam by SacI restriction enzyme. Normal genotype was CTC/CTC, heterozygot for ACTHRP CTC/CCC and homozygot CCC/CCC. In all participants, ACTH and cortisol increased during acute stress, whereas in recovery ACTH increased and cortisol remained unchanged. 49/56 examiners manifested CTC/CTC, 7/56 CTC/CCC and 0/56 CCC/CCC. There was no difference in ACTHRP frequency between groups (χ(1)(2)=0.178, p=0.67). LV mass (LVM) and LV end-diastolic volume (LVVd) were higher in athletes than in controls (p<0.01) and lower in CTC/CTC than in CTC/CCC genotype (219.43±46.59(SD)g vs. 276.34±48.86(SD)g, p=0.004; 141.24±24.46(SD)ml vs. 175.29±37.07(SD)ml, p=0.002; respectively). In all participants, predictors of LVM and LVVd were ACTH at rest (B=-1.00,-0.44; β=-0.30,-0.31; p=0.026,0.012, respectively) and ACTHRP (B=56.63,34; β=0.37,0.40; p=0.003,0.001, respectively). These results demonstrate that ACTH and ACTHRP strongly predict cardiac morphology suggesting possible regulatory role of stress system activity and sensitivity in cardiac remodeling.

Testosterone responses to standardized short-term sub-maximal and maximal endurance exercises: issues on the dynamic adaptive role of the hypothalamic-pituitary-testicular axis

BACKGROUND

Few and conflicting data on the acute adaptive role of the hypothalamic-pituitary-testicular (HPT) axis to sub-maximal endurance exercise exist.

AIMS

To investigate the acute HPT axis responses to standardized endurance exercises in a laboratory setting and the correlations between testosterone and classic adaptive hormones variations.

SUBJECTS AND METHODS

12 healthy male volunteers were recruited for this experimental study. Serum PRL, GH, ACTH, LH, cortisol, DHEAS, testosterone [total (TT), calculated free (cFT) and bioavailable (cBioT)], SHBG, and respective ratios, were evaluated before and after a 30-min sub-maximal exercise on cycle ergometer at individual anaerobic threshold (IAT) and a maximal exercise until exhaustion. Blood samples were collected before exercise (30, 15 min and immediately before), immediately after and at different time points during recovery (+15, +30 and +60 min) for hormones assays. Oxygen consumption and lactate concentration were evaluated.

RESULTS

Testosterone (TT, cFT and cBioT) acutely increased in all volunteers after both exercises. Testosterone increased in parallel to GH after both exercises and to cortisol only after maximal exercise. Differently from other increased hormones, testosterone increases were not correlated to exercise-intensity-related variables. The anabolic/catabolic steroids ratios were higher after sub-maximal exercise, compared to maximal.

CONCLUSIONS

A 30-min sub-maximal endurance exercise acutely increased serum testosterone similarly to maximal exercise, but without cortisol increases. Exercise-related testosterone peaks should be considered adaptive phenomena, but few data on their short- and long-term effects exist. Investigations on the mechanisms of adaptation to exercise in active individuals with physiological or pathological hypo-testosteronemia are warranted.

The interface of hypothalamic-pituitary-adrenocortical axis and circulating brain natriuretic peptide in prediction of cardiopulmonary performance during physical stress

Brain natriuretic peptide (NT-pro-BNP) was implicated in the regulation of hypothalamic-pituitary-adrenocortical (HPA) responses to psychological stressors. However, HPA axis activation in different physical stress models and its interface with NT-pro-BNP in the prediction of cardiopulmonary performance is unclear. Cardiopulmonary test on a treadmill was used to assess cardiopulmonary parameters in 16 elite male wrestlers (W), 21 water polo player (WP) and 20 sedentary age-matched subjects (C). Plasma levels of NT-pro-BNP, cortisol and adrenocorticotropic hormone (ACTH) were measured using immunoassay sandwich technique, radioimmunoassay and radioimmunometric techniques, respectively, 10min before test (1), at beginning (2), at maximal effort (3), at 3rdmin of recovery (4). In all groups, NT-pro-BNP decreased between 1 and 2; increased from 2 to 3; and remained unchanged until 4. ACTH increased from 1 to 4, whereas cortisol increased from 1 to 3 and stayed elevated at 4. In all groups together, ΔNT-pro-BNP2/1 predicted peak oxygen consumption (B=37.40, r=0.38, p=0.007); cortisol at 3 predicted heart rate increase between 2 and 3 (r=-0.38,B=-0.06, p=0.005); cortisol at 2 predicted peak carbon-dioxide output (B=2.27, r=0.35, p<0.001); ΔACTH3/2 predicted peak ventilatory equivalent for carbon-dioxide (B=0.03, r=0.33, p=0.003). The relation of cortisol at 1 with NT-pro-BNP at 1 and 3 was demonstrated using logistic function in all the participants together (for 1/cortisol at 1 B=63.40, 58.52; r=0.41, 0.34; p=0.003, 0.013, respectively). ΔNT-pro-BNP2/1 linearly correlated with ΔACTH4/3 in WP and W (r=-0.45, -0.48; p=0.04, 0.04, respectively). These results demonstrate for the first time that HPA axis and NT-pro-BNP interface in physical stress probably contribute to integrative regulation of cardiopulmonary performance.

The phosphodiesterases type 5 inhibitor tadalafil reduces the activation of the hypothalamus-pituitary-adrenal axis in men during cycle ergometric exercise

Phosphodiesterase type 5 inhibitors may influence human physiology, health, and performance by also modulating endocrine pathways. We evaluated the effects of a 2-day tadalafil administration on adenohypophyseal and adrenal hormone adaptation to exercise in humans. Fourteen healthy males were included in a double-blind crossover trial. Each volunteer randomly received two tablets of placebo or tadalafil (20 mg/day with a 36-h interval) before a maximal exercise was performed. After a 2-wk washout, the volunteers were crossed over. Blood samples were collected at -30 and -15 min and immediately before exercise, immediately after, and during recovery (+15, +30, +60, and +90 min) for adrenocorticotropin (ACTH), β-endorphin, growth hormone (GH), prolactin, cortisol (C), corticosterone, dehydroepiandrosterone-sulfate (DHEAS), and cortisol binding globulin (CBG) assays. C-to-CBG (free cortisol index, FCI) and DHEAS-to-C ratios were calculated. Exercise intensity, perceived exertion rate, O₂ consumption, and CO₂ and blood lactate concentration were evaluated. ACTH, GH, C, corticosterone, and CBG absolute concentrations and/or areas under the curve (AUC) increased after exercise after both placebo and tadalafil. Exercise increased DHEAS only after placebo. Compared with placebo, tadalafil administration reduced the ACTH, C, corticosterone, and FCI responses to exercise and was associated with higher β-endorphin AUC and DHEAS-to-C ratio during recovery, without influencing cardiorespiratory and performance parameters. Tadalafil reduced the activation of the hypothalamus-pituitary-adrenal axis during exercise by probably influencing the brain's nitric oxide- and cGMP-mediated pathways. Further studies are necessary to confirm our results and to identify the involved mechanisms, possible health risks, and potential clinical uses.

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.

Prolonged ingestion of prehydrolyzed whey protein induces little or no change in digestive enzymes, but decreases glutaminase activity in exercising rats

Because consumption of whey protein hydrolysates is on the increase, the possibility that prolonged ingestion of whey protein hydrolysates affect the digestive system of mammals has prompted us to evaluate the enzymatic activities of pepsin, leucine-aminopeptidase, chymotrypsin, trypsin, and glutaminase in male Wistar rats fed diets containing either a commercial whey isolate or a whey protein hydrolysate with medium degree of hydrolysis and to compare the results with those produced by physical training (sedentary, sedentary-exhausted, trained, and trained-exhausted) in the treadmill for 4 weeks. The enzymatic activities were determined by classical procedures in all groups. No effect due to the form of the whey protein in the diet was seen in the activities of pepsin, trypsin, chymotrypsin, and leucine-aminopeptidase. Training tended to increase the activity of glutaminase, but exhaustion promoted a decrease in the trained animals, and consumption of the hydrolysate decreased it even further. The results are consistent with the conclusion that chronic consumption of a whey protein hydrolysate brings little or no modification of the proteolytic digestive system and that the lowering of glutaminase activity may be associated with an antistress effect, counteracting the effect induced by training in the rat.

Hormonal responses to physical and cognitive stress in a school setting

Little is known about the influence of physical and cognitive stress on the concentration of steroid hormones (SHs) in a school setting. Forty high school students from the 9th grade were randomly assigned to two intervention groups: physical and cognitive stress. Saliva collection took place before (pre-test) and after (post-test) 12 min of high intensity exercise in a defined heart rate (HR) interval (70-85% HR (max); n=19) and cognitive testing (Letter Digit Span and d2-test, n=21), respectively. Saliva was analyzed for testosterone (T) and cortisol (C). Results indicated a significant increase of T and C due to a physical but not cognitive stressor. Thus, only the physical stressor was capable of activating the hypothalamic-pituitary-adrenal (HPA) and the hypothalamic-pituitary-gonadal (HPG) axis.

Glucocorticoid receptor mRNA expression in peripheral blood mononuclear cells in high trained compared to low trained athletes and untrained subjects

BACKGROUND

Physiological needs during prolonged exercise are a potent stimulus for the hypothalamic-pituitary-adrenal (HPA) axis. Hence, athletes undergoing daily endurance training sessions may have frequent and prolonged phases of endogenous hypercortisolism. Since chronic glucocorticoids treatment leads to down-regulation of glucocorticoid receptor alpha (GR-alpha) mRNA expression, endurance training could lead to modulation of GR expression.

AIM

The aim of the study was to evaluate GR-alpha and GR-beta mRNA expressions in peripheral blood mononuclear cells and plasma cortisol, ACTH and cortisol binding globulin (CBG) concentrations at rest in subjects undergoing different training regimes.

SUBJECTS AND METHODS

Nine high trained (HT) swimmers (training volume: 21.6+/-1.7 hours/week in 10-12 sessions) were compared with two age-matched control groups represented by 8 low trained (LT) runners (training volume: 6.4+/-2.6 h/week in 3-5 sessions) and 9 untrained subjects. Expression of GR was determined by RT-PCR of total RNA. Hormone levels were determined by radioimmunoassay methods.

RESULTS

HT athletes showed 10 times less GR-alpha mRNA expression than the untrained subjects, while LT athletes exhibited values about twofold less than the untrained subjects. GR-beta mRNA expression was undetectable in all subjects. No differences were observed among the three groups in hormone levels.

CONCLUSIONS

GR- alpha mRNA expression is repressed in proportion to the amount and frequency of the stressful stimuli due to training. Hence, this down-regulation may be a consequence of the frequent and prolonged exposure to cortisol acute elevations induced by training. GR-beta did not play an important role in inducing the down-regulation of GR-alpha mRNA expression observed.

Effect of exercise on glutamine synthesis and transport in skeletal muscle from rats

1. Reductions in plasma glutamine are observed after prolonged exercise. Three hypotheses can explain such a decrease: (i) high demand by the liver and kidney; (ii) impaired release from muscles; and (iii) decreased synthesis in skeletal muscle. The present study investigated the effects of exercise on glutamine synthesis and transport in rat skeletal muscle. 2. Rats were divided into three groups: (i) sedentary (SED; n = 12); (ii) rats killed 1 h after the last exercise bout (EX-1; n = 15); and (iii) rats killed 24 h after the last exercise bout (EX-24; n = 15). Rats in the trained groups swam 1 h/day, 5 days/week for 6 weeks with a load equivalent to 5.5% of their bodyweight. 3. Plasma glutamine and insulin were lower and corticosterone was higher in EX-1 compared with SED rats (P < 0.05 and P < 0.01, respectively). Twenty-four hours after exercise (EX-24), plasma glutamine was restored to levels seen in SED rats, whereas insulin levels were higher (P < 0.001) and corticosterone levels were lower (P < 0.01) than in EX-1. In the soleus, ammonia levels were lower in EX-1 than in SED rats (P < 0.001). After 24 h, glutamine, glutamate and ammonia levels were lower in EX-24 than in SED and EX-1 rats (P < 0.001). Soleus glutamine synthetase (GS) activity was increased in EX-1 and was decreased in EX-24 compared with SED rats (both P < 0.001). 4. The decrease in plasma glutamine concentration in EX-1 is not mediated by GS or glutamine transport in skeletal muscle. However, 24 h after exercise, lower GS may contribute to the decrease in glutamine concentration in muscle.

Cardio-respiratory fitness, habitual physical activity and serum brain derived neurotrophic factor (BDNF) in men and women

Short episodes of high intensity exercise transiently increase serum levels of BDNF in humans, but serum levels of BDNF at rest appear to be lower in more physically active humans with greater levels of energy expenditure. The relationship between serum BDNF concentration, cardio-respiratory fitness (Astrand-Rhyming test estimated VO2 max) and volume of long-term, regular exercise and sporting activity (Baecke Habitual Physical Activity Index) was investigated in 44 men and women between the age range of 18-57 years. In this group an inverse relationship between resting serum BDNF concentration and measures of both estimated VO2 max (r=-0.352; P<0.05) and long-term sporting activity (r=-0.428, P<0.01) was found. These results indicate that increased levels of cardio-respiratory fitness and habitual exercise are associated with lower resting levels of serum BDNF in healthy humans. This is the first study to demonstrate an inverse relationship between a physiological estimate of cardio-respiratory fitness and serum BDNF.

Transcriptional control of complement activation in an exercise model of chronic fatigue syndrome

Complement activation resulting in significant increases of C4a split product may be a marker of postexertional malaise in individuals with chronic fatigue syndrome (CFS). This study focused on identification of the transcriptional control that may contribute to the increased C4a in CFS subjects after exercise. We used quantitative reverse-transcription polymerase chain reaction to evaluate differential expression of genes in the classical and lectin pathways in peripheral blood mononuclear cells (PBMCs). Calibrated expression values were normalized to the internal reference gene peptidylpropyl isomerase B (PPIB), the external reference gene ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL), or the geometric mean (GM) of the genes ribosomal protein, large, P0 (RPLP0) and phosphoglycerate kinase 1 (PGK1). All nine genes tested, except mannose-binding lectin 2 (MBL2), were expressed in PBMCs. At 1 hour postexercise, C4, mannan-binding lectin serine protease 2 (MASP2) and ficolin 1 (FCN1) transcripts were detected at higher levels (> or = 2-fold) in at least 50% (4 of 8) of CFS subjects and were detected in 88% (7 of 8) CFS subjects when subjects with overexpression of either C4 or MASP2 were combined. Only an increase in the MASP2 transcript was statistically significant (PPIB, P = 0.001; GM, P = 0.047; rbcL, P = 0.045). This result may be due to the significant but transient downregulation of MASP2 in control subjects (PPIB, P = 0.023; rbcL, P = 0.027). By 6 hours postexercise, MASP2 expression was similar in both groups. In conclusion, lectin pathway responded to exercise differentially in CFS than in control subjects. MASP2 down-regulation may act as an antiinflammatory acute-phase response in healthy subjects, whereas its elevated level may account for increased C4a and inflammation-mediated postexertional malaise in CFS subjects.

The glucocorticoid receptor and FOXO1 synergistically activate the skeletal muscle atrophy-associated MuRF1 gene

The muscle specific ubiquitin E3 ligase MuRF1 has been implicated as a key regulator of muscle atrophy under a variety of conditions, such as during synthetic glucocorticoid treatment. FOXO class transcription factors have been proposed as important regulators of MuRF1 expression, but its regulation by glucocorticoids is not well understood. The MuRF1 promoter contains a near-perfect palindromic glucocorticoid response element (GRE) 200 base pairs upstream of the transcription start site. The GRE is highly conserved in the mouse, rat, and human genes along with a directly adjacent FOXO binding element (FBE). Transient transfection assays in HepG2 cells and C(2)C(12) myotubes demonstrate that the MuRF1 promoter is responsive to both the dexamethasone (DEX)-activated glucocorticoid receptor (GR) and FOXO1, whereas coexpression of GR and FOXO1 leads to a dramatic synergistic increase in reporter gene activity. Mutation of either the GRE or the FBE significantly impairs activation of the MuRF1 promoter. Consistent with these findings, DEX-induced upregulation of MuRF1 is significantly attenuated in mice expressing a homodimerization-deficient GR despite no effect on the degree of muscle loss in these mice vs. their wild-type counterparts. Finally, chromatin immunoprecipitation analysis reveals that both GR and FOXO1 bind to the endogenous MuRF1 promoter in C(2)C(12) myotubes, and IGF-I inhibition of DEX-induced MuRF1 expression correlates with the loss of FOXO1 binding. These findings present new insights into the role of the GR and FOXO family of transcription factors in the transcriptional regulation of the MuRF1 gene, a direct target of the GR in skeletal muscle.