Responses of markers of bone and collagen turnover to exercise, growth hormone (GH) administration, and GH withdrawal in trained adult males

Changes in the concentration of bone turnover markers in men after maximum intensity exercise

Background

Physical activity is an important factor in modelling the remodelling and metabolism of bone tissue. The aim of the study was to evaluate the changes in indices demonstrating bone turnover in men under the influence of maximum-intensity exercise.

Methods

The study involved 33 men aged 20-25, divided into two groups: experimental (n = 15) and control (n = 18). People training medium- and long-distance running were assigned to the experimental group, and non-training individuals to the control. Selected somatic, physiological and biochemical indices were measured. The level of aerobic fitness was determined using a progressively increasing graded test (treadmill test for subjective fatigue). Blood samples for determinations were taken before the test and 60 minutes after its completion. The concentration of selected bone turnover markers was assessed: bone fraction of alkaline phosphatase (b-ALP), osteoclacin (OC), N-terminal cross-linked telopeptide of the alpha chain of type I collagen (NTx1), N-terminal propeptide of type I progolagen (PINP), osteoprotegerin (OPG). In addition, the concentration of 25(OH)D3 prior to the stress test was determined. Additionally, pre and post exercise, the concentration of lactates in the capillary blood was determined.

Results

When comparing the two groups, significant statistical differences were found for the mean level of: 25(OH)D3 (p = 0.025), b-ALP (p < 0.001), OC (p = 0.004) and PINP (p = 0.029) prior to the test. On the other hand, within individual groups, between the values pre and post the stress test, there were statistically significant differences for the average level of: b-ALP (p < 0.001), NTx1 (p < 0.001), OPG (p = 0.001) and PINP (p = 0.002).

Conclusion

A single-session maximum physical effort can become an effective tool to initiate positive changes in bone turnover markers.

The Impact of an Adapted Physical Activity Program on Bone Turnover, Physical Performance and Fear of Falling in Osteoporotic Women with Vertebral Fractures: A Quasi-Experimental Pilot Study

Physical activity has been indicated as a potential strategy to counteract osteoporosis (OP). This study of post-menopausal women with osteoporotic vertebral fractures investigated the effect of an adapted physical activity (APA) program on two serum bone turnover biomarkers (Bone Alkaline Phosphatase, B-ALP and C-terminal telopeptide of type 1 collagen, CTX-1), functional capacity (6-Minutes Walking Test, 6MWT), and risk and fear of falls (Tinetti and Falls Efficacy scale). The APA group (n = 12) performed a 1-h group session twice per week for 6 months whereas the control group (n = 9) was asked to maintain their current lifestyle. The exercise program did not affect the serum concentrations of B-ALP and CTX-1 biomarkers measured at the baseline and after 6 months in women of the APA group. Moreover, at the end of intervention no significant differences in serum concentrations for either biomarker was observed between the two study groups. Interestingly, when compared to the control group, women in the APA group showed significant improvement in the functional capacity measures by 6MWT (p = 0.037) and a decrease of the risk and fear of falls as indicated by the Tinetti test (p = 0.043). Based on these findings, exercise could provide new perspectives for the care and management of OP.

Cross-sectional associations among P3NP, HtrA, Hsp70, Apelin and sarcopenia in Taiwanese population

BACKGROUND

Sarcopenia is a multifactorial pathophysiologic condition of skeletal muscle mass and muscle strength associated with aging. However, biomarkers for predicting the occurrence of sarcopenia are rarely discussed in recent studies. The aim of the study was to elucidate the relationship between sarcopenia and several pertinent biomarkers.

METHODS

Using the Gene Expression Omnibus (GEO) profiles of the National Center for Biotechnology Information, the associations between mRNA expression of biomarkers and sarcopenia were explored, including high temperature requirement serine protease A1 (HtrA1), procollagen type III N-terminal peptide (P3NP), apelin, and heat shock proteins 70 (Hsp72). We enrolled 408 community-dwelling adults aged 65 years and older with sarcopenia and nonsarcopenia based on the algorithm proposed by the Asian Working Group for Sarcopenia (AWGS). Muscle strength is identified by hand grip strength using an analogue isometric dynamometer. Muscle mass is estimated by skeletal mass index (SMI) using a bioelectrical impedance analysis. Physical performance is measured by gait speed using 6 m walking distance. The associations between these biomarkers and sarcopenia were determined using receiver operating characteristic (ROC) curve analysis and multivariate regression models.

RESULTS

From the GEO profiles, the sarcopenia gene set variation analysis score was correlated significantly with the mRNA expression of APLNR (p < 0.001) and HSPA2 (p < 0.001). In our study, apelin was significantly associated with decreased hand grip strength with β values of - 0.137 (95%CI: - 0.229, - 0.046) in men. P3NP and HtrA1 were significantly associated with increased SMI with β values of 0.081 (95%CI: 0.010, 0.153) and 0.005 (95%CI: 0.001, 0.009) in men, respectively. Apelin and HtrA1 were inversely associated with the presence of sarcopenia with an OR of 0.543 (95%CI: 0.397-0.743) and 0.003 (95%CI: 0.001-0.890) after full adjustment. The cutoff point of HtrA1 was associated with the presence of sarcopenia with an OR of 0.254 (95%CI: 0.083-0.778) in men. The cutoff point of apelin was negatively associated with the presence of sarcopenia with an OR of 0.254 (95%CI: 0.083-0.778).

CONCLUSION

Our study highlights that P3NP, HtrA, and apelin are useful for diagnosis of sarcopenia in the clinical setting.

Insulin-Like Growth Factor-1 (IGF-1) and Its Monitoring in Medical Diagnostic and in Sports

Insulin-like growth factor-1 (IGF-1) is the principal mediator of growth hormone (GH), plays a crucial role in promoting cell growth and differentiation in childhood and continues to have an anabolic effect in adults. IGF-1 is part of a wide network of growth factors, receptors and binding proteins involved in mediating cellular proliferation, differentiation and apoptosis. Bioavailability of IGF-1 is affected by insulin-like growth factor binding proteins (IGFBPs) which bind IGF-1 in circulation with an affinity equal to or greater than that of the IGF-1 receptor (IGF-1R). The six IGFBPs serve as carrier proteins and bind approximately 98% of all circulating IGF-1. Other proteins known to bind IGF-1 include ten IGFBP-related proteins (IGFBP-rPs), albeit with lower affinities than the IGFBPs. IGF-1 expression levels vary in a number of clinical conditions suggesting it has the potential to provide crucial information as to the state of an individual’s health. IGF-1 is also a popular doping agent in sport and has featured in many high-profile doping cases in recent years. However, the existence of IGFBPs significantly reduces the levels of immunoreactive IGF-1 in samples, requiring multiple pre-treatment steps that reduce reproducibility and complicates interpretation of IGF-1 assay results. Here we provide an overview of the IGF network of growth factors, their receptors and the entirety of the extended family of IGFBPs, IGFBP-rPs, E peptides as well as recombinant IGF-1 and their derivatives. We also discuss issues related to the detection and quantification of bioavailable IGF-1.

Interleukin-6 May Not Affect Bone Resorption Marker CTX or Bone Formation Marker P1NP in Humans

Context

Interleukin 6 (IL-6) contributes to bone remodeling in preclinical studies. Clinical trials investigating the role of IL-6 in bone remodeling are limited.

Objective

To investigate if IL-6 regulates bone remodeling in humans.

Design

Plasma concentrations of the bone resorption marker carboxy-terminal type I collagen crosslinks (CTX) and of the bone formation marker procollagen type 1 N-terminal propeptide (P1NP) were measured during a mixed-meal tolerance test (MMTT) in 3 placebo-controlled human studies.

Participants

Five healthy individuals participated in study 1; 52 obese individuals, in study 2; and 10 healthy individuals, in study 3.

Interventions

Study 1 was a single-blinded crossover study consisting of a 1-h infusion of saline (placebo) or the IL-6 receptor antibody tocilizumab followed by an exercise bout. Study 2 was a randomized, double-blinded 12-week exercise training intervention study. Participants received infusions of saline or tocilizumab. Study 3 was a randomized, double-blinded, crossover study consisting of 30 min infusion of saline or IL-6.

Main outcomes measures

Effect of IL-6 on CTX levels.

Results

CTX was significantly (P < 0.01) decreased during MMTTs in all 3 studies. Treatment with tocilizumab did not affect exercise or meal induced changes in plasma CTX or P1NP concentrations acutely (study 1) or after a 12-week treatment period (study 2). Exogenous IL-6 had no effect on CTX or P1NP plasma concentrations (study 3).

Conclusions

IL-6 may not regulate bone remodeling in humans.

Acute response of biochemical bone turnover markers and the associated ground reaction forces to high-impact exercise in postmenopausal women

The aim of the study was to examine the acute response of biochemical bone turnover markers (BTM) to high-impact jumping exercise, and to quantify the ground reaction forces (GRF) achieved during each jumping exercise, in postmenopausal women. In a randomized controlled cross-over study over three days, 29 postmenopausal women (age (mean±SD): 60.0±5.6 years) were randomly assigned to 6 x 10 repetitions of three different jumps: countermovement jump (CMJ), drop jump (DJ), diagonal drop jump (DDJ). A fourth day without jumping served as a control (CON). Blood samples were collected before (PRE), after (POST), and 2 hours after (2Hr) exercise. Bone turnover was evaluated by bone formation markers (procollagen type-1 amino-terminal propeptide (P1NP) and osteocalcin (OC)) and the bone resorption marker C-terminal telopeptide of type-1 collagen (CTX). Peak anteroposterior (Fx), mediolateral (Fy), and vertical (Fz) GRF were measured using a force platform. From PRE to POST, P1NP increased (p<0.01) by 7.7±1.8%, 9.4±1.3%, and 10.6±1.6% for CMJ, DJ, and DDJ, which were higher (p<0.01) than CON. OC increased (p<0.05) by 5.5±1.8% for DJ, which was higher (p<0.05) than CON. CTX was not significantly changed at POST. There were no significant differences in BTM Δ-values between the jumps at any time point. For the CMJ, the combined three-axis peak GRF was positively associated with the PRE to POST Δ-change in P1NP (r=0.71, p<0.05). The acute, jumping-induced increase in P1NP and OC without any rise in CTX may indicate increased bone formation. Moreover, the study shows a dose-response relationship between GRF and the acute P1NP response after countermovement jumps.

Effect of acute downhill running on bone markers in responders and non-responders

This study showed that procollagen type 1 amino-terminal pro-peptide and N-MID osteocalcin significantly increased after exercise independent of the form of muscle contraction. Thus, these preliminary results will be useful for future studies that will consider bone turnover characteristics of responders and non-responders to acute and chronic aerobic exercise.

INTRODUCTION

The aim of the current study was to compare the effects of acute flat running (FR) and downhill running (DHR) on bone turnover markers in men.

METHODS

Fourteen healthy young active men performed three exercise tests in a counterbalanced order, including rest condition, FR, and DHR, at 60% maximal aerobic capacity on a treadmill with 0 and - 12% inclines. Blood samples were taken in the pre-exercise, immediately post-exercise, and 24-h post-exercise periods, and bone markers included total procollagen type 1 amino-terminal pro-peptide (total PINP) and N-MID osteocalcin.

RESULTS

Total P1NP significantly increased after exercise independent of the form of muscle contraction (p > 0.05). N-MID osteocalcin increased after DHR by 17% compared to after pre-exercise, but the difference did not reach significance (p = 0.07; partial eta square, 0.21). Biomarker responses to exercise were dependent on the exercise form and independent of hormone type in half of the participants who were classified as responders. Physiological parameters and changes in muscle voluntary contraction did not explain the differences between responders and non-responders.

CONCLUSION

The effect of acute DHR on bone turnover is determined by biomarker type and participant characteristics. Future studies should discriminate between the characteristics of responders and those of non-responders.

Serum Sclerostin Increases After Acute Physical Activity

Physical activity has a major impact on bone density and on osteoporosis prevention. Sclerostin is produced by osteocytes and inhibits bone formation. The impact of exercise on sclerostin secretion has not been studied so far. This pilot study aimed to explore circulating sclerostin levels immediately after acute exercise. Healthy young women practicing physical activity less than 120 min per week were enrolled. The exercise was a 45-min, low-speed, treadmill running test. Blood samples were taken at rest before exercise and within 5 min after the end of exercise. We assessed serum creatinine, 25-OH vitamin D, alkaline phosphatase, C-telopeptide of type I collagen, bone-specific alkaline phosphatase, and sclerostin. Sclerostin stability at rest was also validated over the same period of time among women fulfilling the same inclusion criteria. The study included 23 participants (mean ± SD age: 22.9 ± 1.5 years) for the exercise test and 9 participants for the resting test (26.1 ± 3.1 years). There was no difference in body mass index between the two groups. Sclerostin increased after exercise in comparison to baseline (mean ± SEM: 410 ± 27 vs. 290 ± 19 pg/mL; p < 0.001) corresponding to an increase of +44.3 ±5.5%. In the resting test, sclerostin remained stable (303 ± 20 vs. 294 ± 20 pg/mL, p = 0.76). There was a substantial increase in serum sclerostin in untrained healthy young women immediately after physical activity. These results suggest the existence of an acute release of systemic sclerostin in response to physical activity.

Direct effects of physical training on markers of bone metabolism and serum sclerostin concentrations in older adults with low bone mass

Background

Both gravitational loading and the forces generated by muscle contraction have direct effects on serum markers of bone metabolism. The object of this study was to examine the direct effects of a single session of resistance exercise or walking on biochemical markers of bone metabolism in participants with low bone mass.

Methods

A total of 150 otherwise healthy female subjects (mean age = 59.1 ± 7.1 years) diagnosed with osteoporosis or osteopenia were randomly allocated to either a resistance exercise group (RG; n = 50), walking group (WG; n = 50), or control group (CG; n = 50). Changes in bone-specific alkaline phosphatase (BALP), carboxy-terminal cross-linked telopeptide of type I collagen (CTX), and serum sclerostin concentrations were measured before and immediately after a single exercise intervention.

Results

There was no significant change in BALP values in any of the groups. Sclerostin levels increased in the RG and WG, and there was significant difference between the WG and CG after the exercise intervention (P < 0.01). In contrast, the changes in CTX concentrations from baseline were significant in the RG (P < 0.01) but not in the WG (P = 0.11), and there was a significant difference between resistance exercise and walking (P < 0.01).

Conclusions

In participants with low bone mass, resistance exercise influenced the serum concentrations of CTX, a marker of bone resorption, but walking did not.

Trial registration

Current Controlled Trials ISRCTN16329455; retrospectively registered on 05/05/2016.

Age-related vascular stiffening: causes and consequences

Arterial stiffening occurs with age and is closely associated with the progression of cardiovascular disease. Stiffening is most often studied at the level of the whole vessel because increased stiffness of the large arteries can impose increased strain on the heart leading to heart failure. Interestingly, however, recent evidence suggests that the impact of increased vessel stiffening extends beyond the tissue scale and can also have deleterious microscale effects on cellular function. Altered extracellular matrix (ECM) architecture has been recognized as a key component of the pre-atherogenic state. Here, the underlying causes of age-related vessel stiffening are discussed, focusing on age-related crosslinking of the ECM proteins as well as through increased matrix deposition. Methods to measure vessel stiffening at both the macro- and microscale are described, spanning from the pulse wave velocity measurements performed clinically to microscale measurements performed largely in research laboratories. Additionally, recent work investigating how arterial stiffness and the changes in the ECM associated with stiffening contributed to endothelial dysfunction will be reviewed. We will highlight how changes in ECM protein composition contribute to atherosclerosis in the vessel wall. Lastly, we will discuss very recent work that demonstrates endothelial cells (ECs) are mechano-sensitive to arterial stiffening, where changes in stiffness can directly impact EC health. Overall, recent studies suggest that stiffening is an important clinical target not only because of potential deleterious effects on the heart but also because it promotes cellular level dysfunction in the vessel wall, contributing to a pathological atherosclerotic state.

Identification of biological markers for better characterization of older subjects with physical frailty and sarcopenia

Population aging is rapidly accelerating worldwide; however, longer life expectancy is not the only public health goal. Indeed, extended lifetime involves maintaining function and the capacity of living independently. Sarcopenia and physical frailty are both highly relevant entities with regards to functionality and autonomy of older adults. The concepts and definitions of frailty and sarcopenia have largely been revised over the years. Sarcopenia is an age-related progressive and generalized loss of skeletal muscle mass and strength. On the other hand, frailty is a state of increased vulnerability to stressors, responsible for exposing the older person to enhanced risk of adverse outcomes. Physical frailty and sarcopenia substantially overlap and several adverse outcomes of frailty are likely mediated by sarcopenia. Indeed, the concepts of sarcopenia and physical frailty can be perceived as related to the same target organ (i.e., skeletal muscle) and it may be possible to combine them into a unique definition. The biological background of such a close relationship needs to be explored and clarified as it can potentially provide novel and pivotal insights for the assessment and treatment of these conditions in old age. The aim of this paper is to indicate and discuss possible biological markers to be considered in the framing of physical frailty and sarcopenia.

Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement

Despite the high prevalence of performance-enhancing drug (PED) use, media attention has focused almost entirely on PED use by elite athletes to illicitly gain a competitive advantage in sports, and not on the health risks of PEDs. There is a widespread misperception that PED use is safe or that adverse effects are manageable. In reality, the vast majority of PED users are not athletes but rather nonathlete weightlifters, and the adverse health effects of PED use are greatly underappreciated. This scientific statement synthesizes available information on the medical consequences of PED use, identifies gaps in knowledge, and aims to focus the attention of the medical community and policymakers on PED use as an important public health problem. PED users frequently consume highly supraphysiologic doses of PEDs, combine them with other PEDs and/or other classical drugs of abuse, and display additional associated risk factors. PED use has been linked to an increased risk of death and a wide variety of cardiovascular, psychiatric, metabolic, endocrine, neurologic, infectious, hepatic, renal, and musculoskeletal disorders. Because randomized trials cannot ethically duplicate the large doses of PEDs and the many factors associated with PED use, we need observational studies to collect valid outcome data on the health risks associated with PEDs. In addition, we need studies regarding the prevalence of PED use, the mechanisms by which PEDs exert their adverse health effects, and the interactive effects of PEDs with sports injuries and other high-risk behaviors. We also need randomized trials to assess therapeutic interventions for treating the adverse effects of PEDs, such as the anabolic-androgen steroid withdrawal syndrome. Finally, we need to raise public awareness of the serious health consequences of PEDs.

Hormonal response to L-arginine supplementation in physically active individuals

Background

Nutritional supplements based on the amino acid L-arginine have been hypothesized to improve exercise performance by increasing levels of insulin and growth hormone (GH). Changes of these parameters in response to L-arginine supplementation may clarify the mechanisms underlying its putative physiological effects on physical performance.

Objective

The aim of the study was to evaluate the effect of L-arginine supplementation on serum insulin, GH, Growth Factor Insulin-like (IGF-1), and cortisol in response to exercise. Exercise performance was also evaluated.

Design

Fifteen trained runners were divided into groups supplemented with 6 g of L-arginine (ARG) or placebo (PLA). Blood samples were collected before supplementation (T0), immediately after the first exercise session (T1), after the second exercise session (T2), and after 20 min of rest (T3). The exercise consisted of two bouts of 5 km time-trial running test.

Results

There was a significant increase in serum GH (T0: 3.28±0.95 vs. 3.21±0.5 ng/mL; T1: 4.35±0.23 vs. 4.17±0.13 ng/mL; T2: 4.22±0.25 vs. 4.17±0.09 ng/mL; T3: 4.14±0.29 vs. 4.13±0.18 ng/mL) and cortisol (T0: 198.71±53.77 vs. 207.57±69.51 nmol/L; T1: 458.16±116.12 vs. 433.26±101.77 nmol/L; T2: 454.61±125.21 vs. 431.88±74.82 nmol/L; T3: 311.14±102.91 vs. 362.26±110.42 nmol/L) after T1, T2, and T3, with no significant difference between the ARG and PLA groups, respectively. There was also no significant difference observed in the variables of IGF-1, insulin, and total running time between the ARG and PLA groups.

Conclusions

The supplementation of L-arginine did not appear to stimulate the production of insulin, GH, and IGF-1 and, thus, provided no benefit in hormonal response or exercise performance in trained runners.

Detecting growth hormone misuse in athletes

Athletes have been misusing growth hormone (GH) for its anabolic and metabolic effects since the early 1980s, at least a decade before endocrinologists began to treat adults with GH deficiency. Although there is an ongoing debate about whether GH is performance enhancing, recent studies suggest that GH improves strength and sprint capacity, particularly when combined with anabolic steroids. The detection of GH misuse is challenging because it is an endogenous hormone. Two approaches have been developed to detect GH misuse; the first is based on the measurement of pituitary GH isoforms and the ratio of 22-kDa isoform to total GH. The second is based on the measurement of insulin like growth factor-I (IGF-I) and N-terminal propeptide of type III procollagen (P-III-NP) which increase in a dose-dependent manner in response to GH administration. Both methodologies have been approved by the World Anti-Doping Agency (WADA) and have led to the detection of a number of athletes misusing GH.

Multiple protein biomarker assessment for recombinant bovine somatotropin (rbST) abuse in cattle

Biomarker profiling, as a rapid screening approach for detection of hormone abuse, requires well selected candidate biomarkers and a thorough in vivo biomarker evaluation as previously done for detection of growth hormone doping in athletes. The bovine equivalent of growth hormone, called recombinant bovine somatotropin (rbST) is (il)legally administered to enhance milk production in dairy cows. In this study, first a generic sample pre-treatment and 4-plex flow cytometric immunoassay (FCIA) were developed for simultaneous measurement of four candidate biomarkers selected from literature: insulin-like growth factor 1 (IGF-1), its binding protein 2 (IGFBP2), osteocalcin and endogenously produced antibodies against rbST. Next, bovine serum samples from two extensive controlled rbST animal treatment studies were used for in vivo validation and biomarker evaluation. Finally, advanced statistic tools were tested for the assessment of biomarker combination quality aiming to correctly identify rbST-treated animals. The statistical prediction tool k-nearest neighbours using a combination of the biomarkers osteocalcin and endogenously produced antibodies against rbST proved to be very reliable and correctly predicted 95% of the treated samples starting from the second rbST injection until the end of the treatment period and even thereafter. With the same biomarker combination, only 12% of untreated animals appeared false-positive. This reliability meets the requirements of Commission Decision 2002/657/EC for screening methods in veterinary control. From the results of this multidisciplinary study, it is concluded that the osteocalcin - anti-rbST-antibodies combination represent fit-for-purpose biomarkers for screening of rbST abuse in dairy cattle and can be reliably measured in both the developed 4-plex FCIA as well as in a cost-effective 2-plex microsphere-based binding assay. This screening method can be incorporated in routine veterinary monitoring programmes: in the European Union for detection of rbST abuse and in the control of rbST-free dairy farms in the United States of America and other countries.

The Lichfield bone study: the skeletal response to exercise in healthy young men

The skeletal response to short-term exercise training remains poorly described. We thus studied the lower limb skeletal response of 723 Caucasian male army recruits to a 12-wk training regime. Femoral bone volume was assessed using magnetic resonance imaging, bone ultrastructure by quantitative ultrasound (QUS), and bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA) of the hip. Left hip BMD increased with training (mean ± SD: 0.85 ± 3.24, 2.93 ± 4.85, and 1.89 ± 2.85% for femoral neck, Ward's area, and total hip, respectively; all P < 0.001). Left calcaneal broadband ultrasound attenuation rose 3.57 ± 0.5% (P < 0.001), and left and right femoral cortical volume by 1.09 ± 4.05 and 0.71 ± 4.05%, respectively (P = 0.0001 and 0.003), largely through the rise in periosteal volume (0.78 ± 3.14 and 0.59 ± 2.58% for right and left, respectively, P < 0.001) with endosteal volumes unchanged. Before training, DXA and QUS measures were independent of limb dominance. However, the dominant femur had higher periosteal (25,991.49 vs. 2,5572 mm(3), P < 0.001), endosteal (6,063.33 vs. 5,983.12 mm(3), P = 0.001), and cortical volumes (19,928 vs. 19,589.56 mm(3), P = 0.001). Changes in DXA, QUS, and magnetic resonance imaging measures were independent of limb dominance. We show, for the first time, that short-term exercise training in young men is associated not only with a rise in human femoral BMD, but also in femoral bone volume, the latter largely through a periosteal response.

Growth hormone doping: a review

The use of growth hormone (GH) as a performance enhancing substance was first promoted in lay publications, long before scientists fully acknowledged its benefits. It is thought athletes currently use GH to enhance their athletic performance and to accelerate the healing of sporting injuries. Over recent years, a number of high profile athletes have admitted to using GH. To date, there is only limited and weak evidence for its beneficial effects on performance. Nevertheless the “hype” around its effectiveness and the lack of a foolproof detection methodology that will detect its abuse longer than 24 hours after the last injection has encouraged its widespread use. This article reviews the current evidence of the ergogenic effects of GH along with the risks associated with its use. The review also examines methodologies, both currently available and in development for detecting its abuse.

Evaluation of early biomarkers of muscle anabolic response to testosterone

BACKGROUND: Early biomarkers of skeletal muscle anabolism will facilitate the development of therapies for sarcopenia and frailty. METHODS AND RESULTS: We examined plasma type III collagen N-terminal propeptide (P3NP), skeletal muscle protein fractional synthesis rate, and gene and protein expression profiles to identify testosterone-induced changes in muscle anabolism. Two placebo-controlled studies enrolled community-dwelling men (study 1, 60-75 years; study 2, 18-40 years) with low to normal testosterone levels. Men were randomized to lower dose (study 1, 100 mg; study 2, 200 mg) or higher dose (study 1, 300 mg; study 2, 600 mg) single intramuscular testosterone or saline injection. After 1 week, testosterone acutely increased plasma P3NP levels in a dose-dependent manner and altered the expression of several skeletal muscle transcripts and proteins. Though not statistically significant, mixed muscle protein fractional synthesis rate tended to increase (1.08-fold with 100 mg testosterone, 1.12-fold with 300 mg testosterone). Testosterone exposure also increased skeletal muscle expression of the collagen type III gene that encodes P3NP. CONCLUSION: P3NP is a potentially useful early biomarker for muscle anabolic therapy. Skeletal muscle protein and RNA profiling are useful tools for the discovery of novel muscle anabolic biomarkers.

Serum prolidase activity in idiopathic and ischemic cardiomyopathy patients

Idiopathic and ischemic dilated cardiomyopathies (DCM) are the most common types of DCM, and both exhibit the same histopathological feature of fibrosis. Prolidase is an enzyme that serves a rate-limiting function in collagen turnover. Several studies have shown increased prolidase activity in fibrosis, though controversy persists. In this study, we measured prolidase enzyme activity in patients with idiopathic or ischemic DCM and in healthy controls, making this, to our knowledge, the first study to do so. What we found is that serumprolidase activity was significantly lower in both DCM groups relative to healthy volunteers and lower in ischemic DCM than idiopathic. These intriguing results could be attributed either to decreased collagen turnover in the heart tissues in which DCM develops, a result of diminished functional heart tissue, or to decreased physical activity levels among DCM patients stemming from their heart failure. Either way, further studies are needed to verify and clarify our results.

Boosting The Late Blooming Male: Use of growth promoting agents in the athlete with constitutional delay of growth and puberty

Context:

The indications for use of growth hormone have broadened with the availability of unlimited recombinant human growth hormone. The Food and Drug Administration’s approval for use of growth hormone in growth hormone–sufficient patients with idiopathic short stature includes some children with constitutional delay of growth and puberty. This is a normal growth pattern variation that includes delayed puberty and prolonged linear growth, usually leading to normal adult height. Use of recombinant human growth hormone to increase growth in short-statured children with constitutional growth delay has been challenged for its modest efficacy in increasing ultimate height, high cost, limited evidence for psychosocial benefit, and some unresolved concerns about long-term posttreatment safety. An additional controversy for the young athlete with constitutional growth delay is the concern for fairness in competition.

Evidence Acquisition:

A PubMed search of the literature from 1957 through May 2010 was conducted. Data sources were limited to peer-reviewed publications.

Results:

Recombinant human growth hormone is a safe and effective therapy for increasing growth rate in short children with constitutional growth delay, but it does not markedly increase ultimate stature nor confer a clear benefit in athletic performance.

Conclusions:

Prescribing physicians should use recombinant human growth hormone treatment responsibly to bring children disabled by short stature into just the normal range.

N-terminal propeptide of type III procollagen as a biomarker of anabolic response to recombinant human GH and testosterone

CONTEXT

Biomarkers that predict musculoskeletal response to anabolic therapies should expedite drug development. During collagen synthesis in soft lean tissue, N-terminal propeptide of type III procollagen (P3NP) is released into circulation. We investigated P3NP as a biomarker of lean body mass (LBM) and muscle strength gains in response to testosterone and GH.

DESIGN

Community-dwelling older men received GnRH agonist plus 5 or 10 g testosterone gel plus 0, 3, or 5 microg recombinant human GH daily. P3NP levels were measured at baseline and wk 4, 8, 12, and 16. LBM and appendicular skeletal muscle mass (ASM) were measured by dual-energy x-ray absorptiometry.

RESULTS

One hundred twelve men completed treatment; 106 underwent serum P3NP measurements. P3NP levels were higher at wk 4 than baseline (6.61 +/- 2.14 vs. 4.51 +/- 1.05, P < 0.0001) and reached plateau by wk 4 in men receiving testosterone alone. However, wk 8 P3NP levels were higher than wk 4 levels in men receiving testosterone plus recombinant human GH. Increases in P3NP from baseline to wk 4 and 16 were significantly associated with gains in LBM (r = 0.26, P = 0.007; r = 0.53, P < 0.001) and ASM (r = 0.17, P = 0.07; r = 0.40, P < 0.0001). Importantly, for participants receiving only testosterone, P3NP increases at wk 4 and 16 were related to muscle strength gains (r = 0.20, P = 0.056 and r = 0.36, P = 0.04). In stepwise regression, change in P3NP explained 28 and 30% of the change in ASM and LBM, respectively, whereas change in testosterone but not IGF-I and age provided only small improvements in the models.

CONCLUSION

Early changes in serum P3NP levels are associated with subsequent changes in LBM and ASM during testosterone and GH administration. Serum P3NP may be a useful early predictive biomarker of anabolic response to GH and testosterone.

Perspective: proteomic approach to detect biomarkers of human growth hormone

Several serum biomarkers for recombinant human growth hormone (rhGH) have been established, however, none alone or in combination have generate a specific, sensitive, and reproducible 'kit' for the detection of rhGH abuse. Thus, the search for additional GH specific biomarkers continues. In this review, we focus on the use of proteomics in general and two-dimensional electrophoresis (2-DE) in particular for the discovery of new GH induced serum biomarkers. Also, we review some of the protocols involved in 2-DE. Finally, the possibility of tissues other than blood for biomarker discovery is discussed.

Growth hormone, IGF-I and insulin and their abuse in sport

There is widespread anecdotal evidence that growth hormone (GH) is used by athletes for its anabolic and lipolytic properties. Although there is little evidence that GH improves performance in young healthy adults, randomized controlled studies carried out so far are inadequately designed to demonstrate this, not least because GH is often abused in combination with anabolic steroids and insulin. Some of the anabolic actions of GH are mediated through the generation of insulin-like growth factor-I (IGF-I), and it is believed that this is also being abused. Athletes are exposing themselves to potential harm by self-administering large doses of GH, IGF-I and insulin. The effects of excess GH are exemplified by acromegaly. IGF-I may mediate and cause some of these changes, but in addition, IGF-I may lead to profound hypoglycaemia, as indeed can insulin. Although GH is on the World Anti-doping Agency list of banned substances, the detection of abuse with GH is challenging. Two approaches have been developed to detect GH abuse. The first is based on an assessment of the effect of exogenous recombinant human GH on pituitary GH isoforms and the second is based on the measurement of markers of GH action. As a result, GH abuse can be detected with reasonable sensitivity and specificity. Testing for IGF-I and insulin is in its infancy, but the measurement of markers of GH action may also detect IGF-I usage, while urine mass spectroscopy has begun to identify the use of insulin analogues.

Endurance treadmill running training benefits the biomaterial quality of bone in growing male Wistar rats

This study investigated the effects of endurance running training on the bones of growing rats. Thirty-two male Wistar rats (7 weeks old) were assigned to a sedentary control group (CON, n = 10), a continuous endurance running group (CEN, n = 10), or an intermittent endurance running group (IEN, n = 12). After an 8-week training period, both exercise groups had significantly less body weight (BW) gain but higher aerobic capacity, shown by increased muscle citrate synthase (CS) activity. Bone area (BA), areal bone mineral density (aBMD), and bone mineral content (BMC) were measured by dual-energy Xray absorptiometry (DXA) in the total femur and sections of femora. Except for showing a significantly higher aBMD in total femora, the CON group was only slightly and nonsignificantly higher in other DXA measurements. In tissue weight measurements, the CON group showed a nonsignificantly higher tissue dry weight (P = 0.146), but a significantly lower tissue water content ratio (WCR, %) as compared to the exercise group. Despite having nonsignificantly lower long bone cross-sectional parameters, both exercise groups showed significantly better biomaterial properties, as measured by a three-point bending test. In extrinsic analysis, femora of the two exercise groups showed no difference in bending load and stiffness, but were significantly higher in post-yield bending energy and total ultimate bending energy (P < 0.05). Similar phenomena were revealed in tissue-level measurements; the CEN and IEN groups were significantly higher in ultimate toughness and post-yield toughness (P < 0.05). Higher post-yield energy shown by two exercise groups implied a change in bone matrix organization. In conclusion, this study demonstrated that two endurance treadmill training modes benefit bone, with subjects showing better tissue biomaterial properties without significantly increasing aBMD, BMC, or bone dimension. Further study would be valuable to investigate the effects of endurance running on other components of bone, such as organization of bone matrix and its relationship with bone biomaterial properties.

Human growth hormone doping in sport

BACKGROUND AND OBJECTIVES

Recombinant human growth hormone (rhGH) has been on the list of forbidden substances since availability of its recombinant form improved in the early 1990s. Although its effectiveness in enhancing physical performance is still unproved, the compound is likely used for its potential anabolic effect on the muscle growth, and also in combination with other products (androgens, erythropoietin, etc.). The degree of similarity between the endogenous and the recombinant forms, the pulsatile secretion and marked interindividual variability makes detection of doping difficult. Two approaches proposed to overcome this problem are: the indirect method, which measures a combination of several factors in the biological cascade affected by administration of GH; and the direct method, which measures the difference between the circulating and the recombinant (represented by the unique 22 kD molecule) forms of GH. This article gives an overview of what is presently known about hGH in relation to sport. The available methods of detection are also evaluated.

METHODS

Review of the literature on GH in relation to exercise, and its adverse effects and methods of detection when used for doping.

RESULTS AND CONCLUSION

The main effects of exercise on hGH production and the use and effects of rhGH in athletes are discussed. Difficulties encountered by laboratories to prove misuse of this substance by both indirect and direct analyses are emphasised. The direct method currently seems to have the best reliability, even though the time window of detection is too short. hGH doping is a major challenge in the fight against doping. The effect of exercise on hGH and its short half-life are still presenting difficulties during doping analysis. To date the most promising method appears to be the direct approach utilising immunoassays.

Challenges in Detecting the Abuse of Growth Hormone in Sport

Background: Growth hormone (GH) is reputed to be in widespread use in the sporting arena as a performance-enhancing agent and is on the list of banned substances published by the World Anti-Doping Agency. The detection of GH abuse poses many challenges. Unlike many substances of abuse, such as synthetic anabolic steroids, GH is a naturally occurring substance; therefore, demonstration of exogenous administration must rely on detecting concentrations in excess of an established reference interval. The purpose of this review is to discuss the methodologies being developed to detect GH abuse.

Methods: We undertook a comprehensive search using multiple electronic databases and hand searches of reference lists of articles. The data for this review reflect our academic interests and experience through work on the GH-2000 and GH-2004 projects.

Results: Two approaches have been taken to detect GH abuse. The first is based on assessment of the effect of exogenous GH on pituitary GH isoforms, and the second is based on measurement of markers of GH action. The advantages of each approach and the difficulties encountered with each technique, as well as future concepts in detection, are discussed.

Conclusion: Although there are substantial challenges for the detection of GH, methodologies now exist to detect GH abuse with reasonable sensitivity and specificity.

Response of bone metabolism related hormones to a single session of strenuous exercise in active elderly subjects

OBJECTIVE

To evaluate the effect of strenuous exercise on bone metabolism and related hormones in elderly subjects.

METHODS

Twenty one active elderly subjects (11 men and 10 women; mean age 73.3 years) showing a mean theoretical Vo2max of 151.4% participated. Concentrations of plasma ionised calcium (iCa), serum intact parathyroid hormone (iPTH), 25-hydroxyvitamin D (25(OH)D), and 1.25-dihydroxy-vitamin D3 (1.25(OH)2D3), as well as the bone biochemical markers type I collagen C-telopeptide for bone resorption and osteocalcin and bone alkaline phosphatase for bone formation, were analysed before and after a maximal incremental exercise test.

RESULTS

At basal level, iPTH was positively correlated with age (r = 0.56, p < 0.01) and negatively correlated with 25(OH)D (r = -0.50; p < 0.01) and 1.25(OH)2D3 (r = -0.47; p < 0.05). Moreover, 25(OH)D and 1.25(OH)2D3 levels were negatively correlated with age (r = -0.50, p < 0.01 and r = -0.53, p < 0.01, respectively). After exercise, iCa and 25(OH)D decreased (p < 0.001 and p = 0.01, respectively) while iPTH increased (p < 0.001). The levels of 1.25(OH)2D3, bone biochemical markers, haematocrit, and haemoglobin were unchanged. The variations in iCa and 25(OH)D were not related to age and/or sex. The iPTH variation was directly related to basal iPTH levels (p < 0.01) and indirectly related to age.

CONCLUSIONS

In active elderly subjects, strenuous exercise disturbed calcium homeostasis and bone related hormones without immediate measurable effect on bone turnover. Although an increase in iPTH could have an anabolic action on bone tissue, our findings from our short term study did not allow us to conclude that such action occurred.

Cortical bone resorption during exercise is interleukin-6 genotype-dependent

The objective of this study was to examine the relationship between the interleukin-6 (IL-6) -174 G>C promoter polymorphism and exercise-induced femoral cortical bone resorption. Skeletal response to exercise was assessed in 130 male Caucasian army recruits. Five cross-sectional magnetic resonance images of the right femur were obtained before and after a 10-week period of basic physical training, and changes in cross-sectional cortical area were calculated. Recruits were genotyped for the -174 G>C IL-6 promoter polymorphism. Genotype frequencies (GG 36%, GC 47%, CC 22.17%) were in Hardy-Weinberg equilibrium. The mean percentage change in proximal femoral cross-sectional cortical area was strongly IL-6 genotype-dependent, with GG homozygotes losing 6.8 (3.82)% in cortical area, GC gaining+5.5 (4.88)% and CC gaining+17.3 (9.46)% (P=0.007 for linear trend). These changes persisted throughout the right femur and were significant in the femur as a whole (P=0.03). This study demonstrates an association between a functional polymorphism in the IL-6 gene and femoral cortical remodelling during strenuous physical exercise. Previous studies have suggested an important role for IL-6 in the regulation of bone mass in postmenopausal women, and in the invasion of bone by metastatic tumour deposits. These data extend these observations to the regulation of bone mass in healthy males, supporting a fundamental role for IL-6 in the regulation of bone mass and bone remodelling in humans.