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

Hydrogen Peroxide Stimulates Dihydrotestosterone Release in C2C12 Myotubes: A New Perspective for Exercise-Related Muscle Steroidogenesis?

Skeletal muscle is a tissue that has recently been recognized for its ability to produce androgens under physiological conditions. The steroidogenesis process is known to be negatively influenced by reactive oxygen species (ROS) in reproductive Leydig and ovary cells, while their effect on muscle steroidogenesis is still an unexplored field. Muscle cells are continuously exposed to ROS, resulting from both their metabolic activity and the surrounding environment. Interestingly, the regulation of signaling pathways, induced by mild ROS levels, plays an important role in muscle fiber adaptation to exercise, in a process that also elicits a significant modulation in the hormonal response. The aim of the present study was to investigate whether ROS could influence steroidogenesis in skeletal muscle cells by evaluating the release of testosterone (T) and dihydrotestosterone (DHT), as well as the evaluation of the relative expression of the key steroidogenic enzymes 5α-reductase, 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, and aromatase. C2C12 mouse myotubes were exposed to a non-cytotoxic concentration of hydrogen peroxide (H₂O₂), a condition intended to reproduce, in vitro, one of the main stimuli linked to the process of homeostasis and adaptation induced by exercise in skeletal muscle. Moreover, the influence of tadalafil (TAD), a phosphodiesterase 5 inhibitor (PDE5i) originally used to treat erectile dysfunction but often misused among athletes as a "performance-enhancing" drug, was evaluated in a single treatment or in combination with H₂O₂. Our data showed that a mild hydrogen peroxide exposure induced the release of DHT, but not T, and modulated the expression of the enzymes involved in steroidogenesis, while TAD treatment significantly reduced the H₂O₂-induced DHT release. This study adds a new piece of information about the adaptive skeletal muscle cell response to an oxidative environment, revealing that hydrogen peroxide plays an important role in activating muscle steroidogenesis.

Effect of Tadalafil Administration on Redox Homeostasis and Polyamine Levels in Healthy Men with High Level of Physical Activity

Background: The phosphodiesterase type 5 inhibitor (PDE5I) tadalafil, in addition to its therapeutic role, has shown antioxidant effects in different in vivo models. Supplementation with antioxidants has received interest as a suitable tool for preventing or reducing exercise-related oxidative stress, possibly leading to the improvement of sport performance in athletes. However, the use/abuse of these substances must be evaluated not only within the context of amateur sport, but especially in competitions where elite athletes are more exposed to stressful physical practice. To date, very few human studies have addressed the influence of the administration of PDE5Is on redox balance in subjects with a fitness level comparable to elite athletes; therefore, the aim of this study was to investigate for the first time whether acute ingestion of tadalafil could affect plasma markers related to cellular damage, redox homeostasis, and blood polyamines levels in healthy subjects with an elevated cardiorespiratory fitness level. Methods: Healthy male volunteers (n = 12), with a VO_2max range of 40.1–56.0 mL/(kg × min), were administered with a single dose of tadalafil (20 mg). Plasma molecules related to muscle damage and redox-homeostasis, such as creatine kinase (CK), lactate dehydrogenase (LDH), total antioxidant capacity (TAC), reduced/oxidized glutathione ratio (GSH/GSSG), free thiols (FTH), antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)), as well as thiobarbituric acid reactive substances (TBARs), protein carbonyls (PrCAR), and polyamine levels (spermine (Spm) and spermidine (Spd)) were evaluated immediately before and 2, 6 and 24 hours after the acute tadalafil administration. Results: A single tadalafil administration induced an increase in CK and LDH plasma levels 24 after consumption. No effects were observed on redox homeostasis or antioxidant enzyme activities, and neither were they observed on the oxidation target molecules or polyamines levels. Conclusion: Our results show that in subjects with an elevated fitness level, a single administration of tadalafil induced a significant increase in muscle damage target without affecting plasma antioxidant status.

Dihydrotestosterone (DHT) rapidly increase after maximal aerobic exercise in healthy males: the lowering effect of phosphodiesterase's type 5 inhibitors on DHT response to exercise-related stress

PURPOSE

Few data exist on dihydrotestosterone (DHT) adaptation to exercise-related stress. The aim of the study was to investigate on serum DHT and other androgens' responses to acute aerobic exercises, and to verify if a long-acting phosphodiesterase's type 5 inhibitors could influence these responses, as previously observed for salivary testosterone.

METHODS

In a double-blind cross over study, 12 healthy trained male volunteers were submitted to both an acute sub-maximal and maximal exercise tests on cycle ergometer, after randomly receiving a two days placebo or tadalafil administration (20 mg, Cialis^®, Ely-Lilly, Indianapolis, IN, USA). Blood sample collections were performed at different time points before and after exercise. Serum DHT, total testosterone (TT), dehydroepiandrosterone sulfate (DHEAS) and luteinizing hormone (LH), were assayed.

RESULTS

Serum DHT increase in placebo treatment immediately post maximal aerobic exercise and return to basal values at 60 min of recovery whereas tadalafil administration significantly reduced the DHT increase after exercise. The values of areas under curves showed the increase of TT after acute sub-maximal and maximal exercise and of DHEAS only after acute maximal aerobic exercise independently from treatment.

CONCLUSIONS

In addition to testosterone, also DHT plays an exercise-related adaptive role during high intensity aerobic exercise, but its rapid useful effects during exercise have to be determined. We hypothesized that the increased androgens secretion during exercise could be mainly related to steroidogenic enzymes modifications in peripheral tissues (i.e., muscles). Moreover, the blunting effect of tadalafil on DHT increase support a possible role of peripheral nitric oxide/GMPc related pathways in influencing physical-stress related DHT metabolism.

Effects of sildenafil citrate on peripheral fatigue and exercise performance after exhaustive swimming exercise in rats

Sildenafil citrate is a potent and selective inhibitor of phosphodiesterase type-5 used to treat erectile dysfunction. We investigated the effects of sildenafil citrate treatment on peripheral fatigue and exercise performance after exhaustive swimming exercise in rats. The rats in the sildenafil citrate-treated groups received sildenafil citrate orally once a day for 14 consecutive days at respective dosage. On the 14 days after starting experiment, each animal was submitted to swimming test with intensity equivalent to overload. The exhaustion was defined as a state in which coordinated movements did not return to the water surface for breathing within 10 sec. Western blot for monocarboxylate transporter (MCT)1, MCT4, and neuronal nitric oxide synthase (nNOS) were performed. Exhaustive swimming exercise decreased time of exhaustion and increased lactate concentration, however, sildenafil citrate enhanced time of exhaustion and decreased lactate concentration. Exhaustive swimming exercise increased MCT1 and MCT4 expressions in the gastrocnemius muscles and sildenafil citrate further enhanced MCT1 and MCT4 expressions in the exhaustive swimming exercise rats. Exhaustive swimming exercise decreased nNOS expression in the gastrocnemius muscles and sildenafil citrate enhanced nNOS expression in the exhaustive swimming exercise rats. The most potent effect appeared in the 20-mg/kg sildenafil citrate. Sildenafil citrate might be proposed as a potential ergogenic aid through antiperipheral fatigue.

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.

Effects of chronic administration of the phosphodiesterase inhibitor vardenafil on serum levels of adrenal and testicular steroids in men with type 2 diabetes mellitus

To investigate whether long-term, chronic treatment with the phosphodiesterase-5 inhibitor vardenafil affects adrenal and testicular steroidogenesis in diabetic men, using liquid chromatography-tandem mass spectrometry. A longitudinal, prospective, investigator-started, randomized, placebo-controlled, double-blind, clinical-trial was carried out, enrolling 54 male patients affected by type 2 diabetes mellitus diagnosed within the last 5 years. In total, 26 and 28 patients were followed for 1 year and assigned to the study and placebo group, respectively. Progesterone, 17-hydroxyprogesterone, androstenedione, testosterone, dehydroepiandrosterone, dehydroepiandrosterone sulfate, corticosterone, 11-deoxycortisol and cortisol, were evaluated using liquid chromatography-tandem mass spectrometry. No differences were seen in sex testicular steroids between study and control group. As for the adrenal gland, steroids were considered according to the zona in which they are produced. No significant differences were seen in steroid produced in zona fasciculata. For the zona reticularis, dehydroepiandrosterone significantly decreased during treatment only in the study group (p = 0.007), with higher levels at visit 2 and 8 than other visits. The dehydroepiandrosterone sulfate/dehydroepiandrosterone ratio significantly increased during treatment only in the verum group. Considering the adrenal zona glomerulosa, corticosterone significantly changed among visits both in both groups (p < 0.001), with higher levels at visit 2 (p = 0.028), 8 (p = 0.003), and 10 (p = 0.044), i.e., in coincidence with the complete clinical and instrumental examination performed only at these visits according to the study protocol. Chronically administered vardenafil reduces dehydroepiandrosterone levels and increases dehydroepiandrosterone sulfate/dehydroepiandrosterone ratio as possible consequences of modulation of steroidogenic enzymes by tissue changes in cyclic adenosine monophosphate and cyclic guanosine monophosphate availability. A possibly stress-related increase in corticosterone is suggested for the first time.

Supra-physiological rhGH administration induces gender-related differences in the hypothalamus-pituitary-thyroid (HPT) axis in healthy individuals

PURPOSE

The use of recombinant human growth hormone (rhGH) is a common habit among athletes. While the effects of rhGH administration have been described with contrasting results in males, no data exist in females to date. The aim of the present study was to evaluate the effects of rhGH administration on TSH, FT₄ and FT₃ levels and the time requested to return to baseline values after treatment withdrawal.

METHODS

Twenty-one healthy trained male and female athletes were treated with 0.03 mg rhGH/kg body mass 6 days/week for 3 weeks. We collected blood samples immediately before the first daily rhGH administration, at 3, 4, 8, 15 and 21 days of treatment and at 3 and 9 days after rhGH withdrawal.

RESULTS

In males, rhGH administration induced a significant (p < 0.01) early and stable TSH decrease and IGF-I increase, and a delayed FT₄ reduction without FT₃ modification, suggesting a central regulatory mechanism. In females, rhGH administration induced a significant (p < 0.01) early and transient TSH decrease and IGF-I increase, and a transient reduction in FT₄ without any changes in FT₃ concentrations. rhGH withdrawal was associated with a prompt normalization of TSH and FT₄ levels in males, while in females the effects of rhGH treatment had already disappeared during the last period of treatment.

CONCLUSION

We suggest that rhGH inhibits TSH at central level both in males and females. The pattern of normalization was different in the two genders probably due to gonadal steroids modulation on GH-IGF-I axis.

Salivary but not plasma cortisone tracks the plasma cortisol response to exercise: effect of time of day

INTRODUCTION

The cortisol, cortisone, corticosterone, and CBG responses to exercise in the AM and PM have not been described. This study examined the response of these glucocorticoids and CBG to intense exercise in 12 endurance-trained men in plasma (Pl) and saliva (Sa).

METHODS

Each subject completed treadmill exercise in the morning and evening. Paired blood and Sa samples were obtained at rest before and after exercise.

RESULTS

Significant time effect existed for Pl-cortisol and Sa-cortisol from baseline in the AM and PM (p < 0.01). Pl-cortisone and CBG significantly increased in the PM (p < 0.01). Pl-corticosterone increased in the AM and PM (p < 0.01). Unlike Pl-cortisone, Sa-cortisone was significantly higher in the AM compared to the PM, increasing in the AM and PM (All p < 0.01). Strong associations were found between Pl-cortisol and Sa-cortisol (r = 0.81, p < 0.0001), Pl-cortisol and Sa-cortisone (r = 0.81, p < 0.0001).

CONCLUSIONS

(1) Intense EX induces a similar increase in Pl-cortisone (~90 %) and corticosterone (~200 %) in the AM and PM, whereas exercise increases CBG in the PM, but not in the AM; (2) vigorous exercise increases Sa-cortisone; (3) Sa-cortisone and cortisol are equally strongly correlated to Pl-cortisol, suggesting a significant role for Sa-cortisone as a novel marker of free cortisol during exercise.

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.

Effects of tadalafil administration on plasma markers of exercise-induced muscle damage, IL6 and antioxidant status capacity

INTRODUCTION

Physical exercise is associated with enhanced production of reactive oxygen species, which if uncontrolled can result in tissue injury. Phosphodiesterase type 5 inhibitors (PDE5i) exhibit protective effect against oxidative stress, both in animals and healthy/unhealthy humans. However, the effect of a chronic administration of PDE5i, particularly combined with physical exercise, has never been investigated.

PURPOSE

The present study was designed to evaluate the effect of the long-acting PDE5i tadalafil on oxidative status and muscle damage after exhaustive exercise in healthy males included in a double-blind crossover trial.

HYPOTHESIS

Tadalafil, having a putative antioxidant activity, may reduce oxidative damage after strenuous exercise.

METHODS

Each volunteer randomly received two tablets of placebo or tadalafil (20 mg/day) with 36 h of interval before performing exhaustive exercise. After 2 weeks of washout, the volunteers were crossed over. Blood samples were collected immediately before exercise, immediately after, and during recovery (15, 30, 60 min). Plasma total antioxidant status, glutathione homeostasis (GSH/GSSG), malondialdehyde (MDA), protein carbonyls, creatine kinase (CK), lactate dehydrogenase (LDH) and the inflammatory cytokine interleukin 6 were assessed.

RESULTS

Tadalafil administration per se affected redox homeostasis (GSH/GSSG -36%; p < 0.05), cellular (CK +75% and LDH +36%; p < 0.05) and oxidative damage (MDA +41% and protein carbonyls +50%; p < 0.05) markers. The exhaustive exercise increased all the above-reported biochemical parameters, with subjects from the tadalafil group showing significantly higher values with respect to the placebo group.

CONCLUSIONS

A prolonged exposure to tadalafil decreases antioxidant capacity at resting condition, therefore making subjects more susceptible to the oxidative stress induced by an exhaustive bout of exercise.

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.

Endogenous opiates and behavior: 2012

This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Effects of sildenafil on the gastrocnemius and cardiac muscles of rats in a model of prolonged moderate exercise training

Moderate exercise training improves energetic metabolism, tissue perfusion and induces cardiac and skeletal muscle remodeling. Sildenafil, a potent phosphodiesterase-5 inhibitor used to treat erectile dysfunction, reduces infarct size and increases tissue oxygenation in experimental models of cardiovascular disease. We have evaluated the effects of prolonged moderate exercise training and a repeat administration of sildenafil on the rat gastrocnemius and cardiac muscles. Animals were divided into two groups: sedentary and trained. Each group was subdivided into animals treated with vehicle or with two doses of sildenafil (10 or 15 mg/kg/day) during the last week of training. Physical exercise did not induce cardiac hypertrophy, whereas it increased mRNA levels of the PGC-1α, HIF-1α and VEGF genes, which are involved in mitochondrial biogenesis and angiogenesis, and reduced mRNA levels of FoxO3a, MuRF-1 and Atrogin-1. Sildenafil dose-dependently promoted both angiogenesis, as shown by increased capillary density, and muscle atrophy, as shown by muscle fibre size. These effects were more pronounced in trained animals. Our data confirm the beneficial effects of a moderate and prolonged training on cardiovascular and skeletal systems and document the positive and negative effects of sildenafil on these tissues at doses higher than those used in clinical practice. This report may impact on the use of sildenafil as a substance able to influence sports performance.

Andrological aspects of physical exercise and sport medicine

Appropriate physical activity is one of the bases of healthy lifestyle. In fact, physical exercise and playing sport may be associated with both improvements and injury to both general and reproductive health. A biologically normal testosterone secretion appears fundamental in males to guarantee both a physiological exercise adaptation and safe sport participation. The reproductive system is highly sensitive to the effects of exercise-related stress and the reproductive hormones may both increase and decrease after different acute or chronic exercises. Exercise and sport participation may positively or negatively influence andrological health status depending on the type, intensity and duration of performed physical activity and on individual health status. In addition, prohibited substances administration (e.g. androgenic-anabolic steroids, and so forth) in competitive and non-competitive athletes represents the main cause of iatrogenic andrological diseases. Preventing and treating andrological problems in active healthy and unhealthy individuals is as important as promoting a correct lifestyle. Physicians need to be educated on the relationships between the male reproductive system and sport participation and on the great role of the pre-participation physical examination in the prevention of andrological diseases.