Bone-muscle unit activity, salivary steroid hormones profile, and physical effort over a 3-week stage race

Non-specific and ski-specific performance development in peri-pubertal cross-country skiers

PURPOSE

To evaluate non-specific and ski-specific performance development in male (M) and female (F) peri-pubertal cross-country skiers and to evaluate their relationship with cross-country skiing (XCS) performance and biological maturation within each age category and sex.

METHODS

Twenty-one and 19 athletes under 14 and 16 years old, respectively (U14 and U16), were tested for biological maturation; non-specific speed, agility, strength, endurance, and balance; ski-specific speed, agility, and endurance. XCS index was considered as average percentage time-gap from the winner in four official races. Sex and age-category effects were verified and a model predicting XCS index was extrapolated for each group.

RESULTS

Performance capacities raised across age categories (p < 0.05) except for non-specific speed, agility, balance, and relative arm strength (p > 0.05). F showed advanced biological maturation and greater balance than M (p < 0.05), while M showed higher performance capacities (p < 0.05). XCS index was not related to biological maturation within each group (p > 0.05); its variance was explained by non-specific speed and ski-specific upper-body endurance in M-U14 (p = 0.014), lower-limb strength and ski-specific agility in M-U16 and F-U14 (both p = 0.001), ski-specific upper-body endurance in F-U16 (p = 0.002).

CONCLUSION

Ski-specific performance capacities still develop during peri-puberty, with peri-pubertal M overperforming with respect to F of comparable performance level. XCS index was not influenced by biological maturation withing each age category, but it was rather explained by specific parameters that commonly undergo the "adolescent spurts", accordingly to the average biological maturation level of M and F athletes of each age category.

Effects of running a marathon on sclerostin and parathyroid hormone concentration in males aged over 50

The aim of our study was to verify whether running a marathon (32nd Wroclaw Marathon) was associated with changes in sclerostin and intact PTH (iPTH) concentration in middle-aged males. We enrolled 33 males who completed the marathon race. Blood samples were taken 60 minutes before (V1), immediately after (V2), and 7 days after the run (V3). The mean serum sclerostin concentration was 42.4 ± 10.8 pmol/L at V1, increased to 62.9 ± 12.6 pmol/L at V2 (t= -11.206; p < 0.001) and returned to baseline in V3 (t = 8.344; p < 0.001, V3 vs. V2). A similar trend was recorded for iPTH (t= -7.440; p < 0.001, for V2 vs. V1; t = 6.229; p < 0.001, for V3 vs. V2), at V3, iPTH levels remained significantly higher than V1 (t= -2.759; p = 0.010). The results of our study suggest that, in middle-aged males, running a marathon affects skeletal metabolism by activating two counteracting mechanisms, although temporarily overlapping: first, by a sudden inhibition of bone formation, through induction sclerostin expression and, secondly, by a long-lasting induction of PTH, which also guarantees the maintenance of adequate circulating levels of calcium. The net effect would be the maintenance of adequately high levels of circulating calcium to be used for neuromuscular activity and muscle contraction.

Sclerostin as a biomarker of physical exercise in osteoporosis: A narrative review

Osteoporosis, a disease of low bone mass, is characterized by reduced bone mineral density (BMD) through abnormalities in the microarchitecture of bone tissue. It affects both the social and economic areas, therefore it has been considered a lifestyle disease for many years. Bone tissue is a dynamic structure exhibiting sensitivity to various stimuli, including mechanical ones, which are a regulator of tissue sclerostin levels. Sclerostin is a protein involved in bone remodeling, showing an anti-anabolic effect on bone density. Moderate to vigorous physical activity inhibits secretion of this protein and promotes increased bone mineral density. Appropriate exercise has been shown to have an osteogenic effect. The effectiveness of osteogenic training depends on the type, intensity, regularity and frequency of exercise and the number of body parts involved. The greatest osteogenic activity is demonstrated by exercises affecting bone with high ground reaction forces (GRF) and high forces exerted by contracting muscles (JFR). The purpose of this study was to review the literature for the effects of various forms of exercise on sclerostin secretion.

Serum concentrations of oxytocin, DHEA and follistatin are associated with osteoporosis or sarcopenia in community-dwelling postmenopausal women

Background

Osteoporosis and sarcopenia are major health issues in postmenopausal women due to their high prevalence and association with several adverse outcomes. However, no biomarkers may be used for screening and diagnosis. The current study investigated potential biomarkers for osteoporosis and/or sarcopenia in postmenopausal women.

Methods

A cross-sectional study on 478 healthy community-dwelling postmenopausal women aged 50–90 years was performed. Osteoporosis and sarcopenia were defined according to the World Health Organization (WHO) and Asian Working Group for Sarcopenia (AWGS).

Results

Dehydroepiandrosterone (DHEA) was related to muscle strength (β = 0.19, p = 0.041) and function (β = 0.58, p = 0.004). Follistatin (β = − 0.27, p = 0.01) was related to muscle mass. Oxytocin (β = 0.59, p = 0.044) and DHEA (β = 0.51, p = 0.017) were related to bone mass. After adjusting for age, oxytocin (odds ratio (OR) 0.75; 95% confidence intervals (CI) 0.63–0.98; p = 0.019) was associated with osteoporosis, and DHEA (OR 0.73; 95% CI 0.51–0.96; p = 0.032) and follistatin (OR 1.66; 95% CI 1.19–3.57; p = 0.022) were associated with sarcopenia.

Conclusions

Postmenopausal women with sarcopenia were more likely to have lower DHEA levels and higher follistatin levels, and postmenopausal women with osteoporosis were more likely to have lower oxytocin levels.

Serum sclerostin concentration is associated with specific adipose, muscle and bone tissue markers in lean adolescent females with increased physical activity

OBJECTIVES

Sclerostin is an important regulator of bone mass involving the Wnt/β-catenin signalling pathway. Relatively few studies have investigated the relationships of circulating sclerostin levels with adiposity-related and muscle-related biochemical factors in individuals with increased energy metabolism. The aim of this study was to investigate the associations of circulating sclerostin with adipokines, myokines, osteokines and body composition values in lean adolescent females with increased physical activity.

METHODS

A total of 73 adolescent females who were physically active and aged 14-18 years old participated in the study. Sclerostin, leptin, resistin, tumour necrosis factor (TNF)-α, interleukin (IL)-6, irisin, osteocalcin, C-terminal telopeptide of type I collagen (CTx), insulin-like growth factor (IGF)-1 and insulin were obtained from fasting blood samples. Body composition was measured by dual-energy X-ray absorptiometry (DXA) and analyzed for body fat mass, lean body mass, bone mineral content and muscle mass.

RESULTS

Serum sclerostin (117.9 ± 60.3 pg/mL) was correlated with age, age at menarche, body fat, muscle mass, training activity, leptin, TNF-α, irisin, osteocalcin, CTx and IGF-1. Multivariate linear regression analysis demonstrated that fat mass (β = 0.434; p = 0.001), leptin (β = -0.308; p = 0.015), irisin (β = 0.227; p = 0.024) and CTx (β = 0.290; p = 0.031) were the most important predictors of serum sclerostin concentration.

CONCLUSIONS

Bone-derived sclerostin is associated with specific adipokine, myokine and osteokine values in lean adolescent females with increased physical activity. These results suggest that the interactions between bone, adipose and muscle tissues could also be associated with circulating sclerostin concentrations.

Bone-to-Brain: A Round Trip in the Adaptation to Mechanical Stimuli

Besides the classical ones (support/protection, hematopoiesis, storage for calcium, and phosphate) multiple roles emerged for bone tissue, definitively making it an organ. Particularly, the endocrine function, and in more general terms, the capability to sense and integrate different stimuli and to send signals to other tissues, has highlighted the importance of bone in homeostasis. Bone is highly innervated and hosts all nervous system branches; bone cells are sensitive to most of neurotransmitters, neuropeptides, and neurohormones that directly affect their metabolic activity and sensitivity to mechanical stimuli. Indeed, bone is the principal mechanosensitive organ. Thanks to the mechanosensing resident cells, and particularly osteocytes, mechanical stimulation induces metabolic responses in bone forming (osteoblasts) and bone resorbing (osteoclasts) cells that allow the adaptation of the affected bony segment to the changing environment. Once stimulated, bone cells express and secrete, or liberate from the entrapping matrix, several mediators (osteokines) that induce responses on distant targets. Brain is a target of some of these mediator [e.g., osteocalcin, lipocalin2, sclerostin, Dickkopf-related protein 1 (Dkk1), and fibroblast growth factor 23], as most of them can cross the blood-brain barrier. For others, a role in brain has been hypothesized, but not yet demonstrated. As exercise effectively modifies the release and the circulating levels of these osteokines, it has been hypothesized that some of the beneficial effects of exercise on brain functions may be associated to such a bone-to-brain communication. This hypothesis hides an interesting clinical clue: may well-addressed physical activities support the treatment of neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases?

Mountain Bike Racing Stimulates Osteogenic Bone Signaling and Ingesting Carbohydrate-Protein Compared With Carbohydrate-Only Prevents Acute Recovery Bone Resorption Dominance

ABSTRACT

Oosthuyse, T, Bosch, AN, Kariem, N, and Millen, AME. Mountain bike racing stimulates osteogenic bone signaling and ingesting carbohydrate-protein compared with carbohydrate-only prevents acute recovery bone resorption dominance. J Strength Cond Res 35(2): 292-299, 2021-Mountain biking, unlike road cycling, includes vibrational accelerations but whether it stimulates osteogenic signaling remains unknown. Furthermore, exercise nutrition influences bone turnover, and the effect of ingesting protein during multiday racing was investigated. We measured plasma bone turnover markers, C-terminal telopeptide of type1-collagen (β-CTX) and N-terminal propeptides of type1-procollagen (P1NP), and osteocyte mechanosensory signaling factor, sclerostin (SOST), corrected for plasma volume change, before (pre-day 1) and 20-60 minutes after (post-day 3) a multiday mountain bike race in 18 male cyclists randomly assigned to ingest carbohydrate-only (CHO-only) or carbohydrate-with-casein protein hydrolysate (CHO-PRO) during racing. Fourteen cyclists (n = 7 per group) completed the race, and data were analyzed with p < 0.05 accepted as significant. Plasma SOST decreased similarly in both groups (mean ± SD, CHO-only: 877 ± 451 to 628 ± 473 pg·ml-1, p = 0.004; CHO-PRO: 888 ± 411 to 650 ± 443 pg·ml-1, p = 0.003), suggesting that osteocytes sense mountain biking as mechanical loading. However, the bone formation marker, P1NP, remained unchanged in both groups, whereas the bone resorption marker, β-CTX, increased in CHO-only (0.19 ± 0.034 to 0.31 ± 0.074 ng·ml-1, p = 0.0036) but remained unchanged in CHO-PRO (0.25 ± 0.079 to 0.26 ± 0.074 ng·ml-1, p = 0.95). Mountain bike racing does stimulate osteogenic bone signaling but bone formation is not increased acutely after multiday mountain biking; investigation for a delayed effect is warranted. The acute recovery increase in bone resorption with CHO-only is prevented by ingesting CHO-PRO during racing.

Laboratory medicine: health evaluation in elite athletes

The need to evaluate the health status of an athlete represents a crucial aim in preventive and protective sports science in order to identify the best diagnostic strategy to improve performance and reduce risks related to physical exercise. In the present review we aim to define the main biochemical and haematological markers that vary significantly during and after sports training to identify risk factors, at competitive and professional levels and to highlight the set up of a specific parameter's panel for elite athletes. Moreover, we also intend to consider additional biomarkers, still under investigation, which could further contribute to laboratory sports medicine and provide reliable data that can be used by athlete's competent staff in order to establish personal attitudes and prevent sports injuries.

Effects of High-Intensity Interval Running Versus Cycling on Sclerostin, and Markers of Bone Turnover and Oxidative Stress in Young Men

This study compared sclerostin's response to impact versus no-impact high-intensity interval exercise in young men and examined the association between exercise-induced changes in sclerostin and markers of bone turnover and oxidative stress. Twenty healthy men (22.3 ± 2.3 years) performed two high-intensity interval exercise trials (crossover design); running on treadmill and cycling on cycle ergometer. Trials consisted of eight 1 min running or cycling intervals at ≥ 90% of maximal heart rate, separated by 1 min passive recovery intervals. Blood samples were collected at rest (pre-exercise), and 5 min, 1 h, 24 h, and 48 h following each trial. Serum levels of sclerostin, cross-linked telopeptide of type I collagen (CTXI), procollagen type I amino-terminal propeptide (PINP), thiobarbituric acid reactive substances (TBARS), and protein carbonyls (PC) were measured. There was no significant time or exercise mode effect for PINP and PC. A significant time effect was found for sclerostin, CTXI, and TBARS with no significant exercise mode effect and no significant time-by-mode interaction. Sclerostin increased from pre- to 5 min post-exercise (47%, p < 0.05) and returned to baseline within 1 h following the exercise. CTXI increased from pre- to 5 min post-exercise (28%, p < 0.05), then gradually returned to baseline by 48 h. TBARS did not increase significantly from pre- to 5 min post-exercise but significantly decreased from 5 min to 48 h post-exercise. There were no significant correlations between exercise-induced changes in sclerostin and any other marker. In young men, sclerostin's response to high-intensity interval exercise is independent of impact and is not related to changes in bone turnover and oxidative stress markers.

Effect of ingesting carbohydrate only or carbohydrate plus casein protein hydrolysate during a multiday cycling race on left ventricular function, plasma volume expansion and cardiac biomarkers

PURPOSE

Multiday racing causes mild left ventricular (LV) dysfunction from day 1 that persists on successive days. We evaluated ingesting casein protein hydrolysate-carbohydrate (PRO) compared with carbohydrate-only (CHO) during a 3-day mountain bike race.

METHODS

Eighteen male cyclists were randomly assigned to ingest 6.7% carbohydrate without (CHO) or with 1.3% casein hydrolysate (PRO) during racing (~ 4-5 h/day; 68/71/71 km). Conventional LV echocardiography, plasma albumin content, plasma volume (PV) and blood biomarkers were measured before day 1 and post race on day 3.

RESULTS

Fourteen cyclists (n = 7 per group) completed the race. PV increased in CHO (mean increase (95% CI), 10.2% (0.1 to 20.2)%, p = 0.045) but not in PRO (0.4% (- 6.1 to 6.9)%). Early diastolic transmitral blood flow (E) was unchanged but deceleration time from peak E increased post race (CHO: 46.7 (11.8 to 81.6) ms, p = 0.019; PRO: 24.2 (- 0.5 to 48.9) ms, p = 0.054), suggesting impaired LV relaxation. Tissue Doppler mitral annular velocity was unchanged in CHO, but in PRO septal early-to-late diastolic ratio decreased (p = 0.016) and was compensated by increased lateral early (p = 0.034) and late (p = 0.012) velocities. Systolic function was preserved in both groups; with increased systolic lateral wall velocity in PRO (p = 0.002). Effect size increase in serum creatine kinase (CK) activity, CK-MB and C-reactive protein concentrations was less in PRO than CHO (Cohen's d mean ± SD, PRO: 2.91 ± 2.07; CHO: 7.56 ± 4.81, p = 0.046).

CONCLUSION

Ingesting casein hydrolysate with carbohydrate during a 3-day race prevented secondary hypervolemia and failed to curb impaired LV relaxation despite reducing tissue damage and inflammatory biomarkers. Without PV expansion, systolic function was preserved by lateral wall compensating for septal wall dysfunction.

Response of Sclerostin and Bone Turnover Markers to High Intensity Interval Exercise in Young Women: Does Impact Matter?

This study examined potential exercise-induced changes in sclerostin and in bone turnover markers in young women following two modes of high intensity interval exercise that involve impact (running) or no-impact (cycling). Healthy, recreationally active, females (n=20; 22.5±2.7 years) performed two exercise trials in random order: high intensity interval running (HIIR) on a treadmill and high intensity interval cycling (HIIC) on a cycle ergometer. Trials consisted of eight 1 min running or cycling intervals at ≥90% of maximal heart rate, separated by 1 min passive recovery intervals. Blood samples were collected at rest (pre-exercise) and 5 min, 1h, 24h, and 48h following each exercise trial. Serum was analyzed for sclerostin, cross linked telopeptide of type I collagen (CTXI), and procollagen type I amino-terminal propeptide (PINP). A significant time effect was found for sclerostin, which increased from pre-exercise to 5 min after exercise in both trials (100.2 to 131.6 pg/ml in HIIR; 102.3 to 135.8 pg/ml in HIIC, p<0.001) and returned to baseline levels by 1h, with no difference between exercise modes and no exercise mode-by-time interaction. CTXI did not significantly change following either trial. PINP showed an overall time effect following HIIR, but none of the post hoc pairwise comparisons were statistically significant. In young women, a single bout of high intensity exercise induces an increase in serum sclerostin, irrespective of exercise mode (impact versus no-impact), but this response is not accompanied by a response in either bone formation or resorption markers.

Physiological implications of DHEAS-induced non-classical steroid hormone signaling

In the spermatogenic cell line GC-2, dehydroepiandrosterone sulfate (DHEAS), activates the Src/Ras/c-Raf/Erk1/2/CREB(ATF-1) signaling cascade. Since DHEAS is present in the gonads, and since spermatogenesis and maturation of spermatogonia to haploid spermatozoa requires activation of Erk1/2, the triggering of these signaling events by DHEAS might have physiological relevance. In the Sertoli cell line TM4, DHEAS-induces activation of Erk1/2, CREB, and ATF-1, stimulates expression of claudin-3 and claudin-5 and augments transepithelial resistance, indicating the formation of tight junctions between adjacent Sertoli cells. Thus, by influencing the formation and dynamics of tight junctions at the blood-testis barrier, which protects germ cells from cells of the immune system, DHEAS might play a crucial role in the regulation and maintenance of male fertility. In bEnd.3 brain-derived endothelial cells, DHEAS stimulates the expression of zonula occludens-1 and claudin-3 and promotes tight junction formation between neighboring cells, which at the blood-brain barrier protects the brain from harmful factors and cells. If DHEAS supports the integrity of the blood-brain barrier also in vivo, the current findings might lead to new strategies for the prevention or treatment of neurological disorders associated with barrier defects.

Effects of repeated sprints training on fracture risk-associated miRNA

Repeated-sprint training (RS, short-duration sprints at supramaximal intensities interspersed with brief recoveries) is a time-saving metabolically effective strategy whose effects on bone are unknown. Bone metabolism is a finely regulated process profoundly affected by exercise as assayable by studying specific systemic (e.g., hormones, cytokines) and bone-derived molecules (e.g., bone markers, miRNAs). Aim of this study was to determine the effect of a 8-week repeated-sprint on circulating levels of fracture risk-associated miRNA. Blood was collected from 9 subjects performing RS 3 times/week (EXP) and 9 age-matched inactive controls (CTRL) before the start of the protocol (T0) and after 4 (T1) and 8 weeks (T2). The relative expression of miR-21-5p, miR-23a-3p, miR-24-3p, miR93-5p, miR-100-5p, miR-122-5p, miR-124-3p, miR-125b-5p, miR-148a-3p, miR-637 was assayed by real-time PCR by the 2^−ΔΔCT method (housekeeping: miR-425-5p, miR-484). Serum concentrations of bone markers (DKK1, sclerostin, osteoprotegerin, osteocalcin, osteopontin), cytokines (IL-1β, TNFα), and metabolic hormones (leptin, insulin, PTH) were assayed by multiplex assay. miR-637 and miR-124-3p were undetectable. In CTRL miRNA levels remained unchanged. In EXP miR-21-5p remained unchanged. Compared to T0 miR-23a-3p and miR-24-3p were significantly decreased at T1 and T2, also compared to CTRL, miR-100 was significantly decreased at T2, miR-122-5p, miR-125-5p, and miR148a-3p were significantly decreased at T1, while miR-93-5p was significantly increased at T1. None of the metabolic hormones was affected by the intervention while, among the bone markers, DKK1, osteocalcin and sclerostin were slightly but significantly decreased. In conclusion, an 8-week repeated-sprint training downregulates the expression of circulating miRNA associated with fracture risk.

Bone adaptation in response to treadmill exercise in young and adult mice

Exercise is a key determinate of fracture risk and provides a clinical means to promote bone formation. However, the efficacy of exercise to increase bone mass declines with age. The purpose of this study was to identify age-related differences in the anabolic response to exercise at the cellular and tissue level. To this end, young (8-weeks of age) and adult (36-weeks of age) male mice were subjected to a moderate exercise regimen of running on a treadmill. As a result, exercise had a significant effect on PTHrP and SOST gene expression during the first week that was dependent upon age. In particular, young mice displayed an increase in PTHrP expression and decrease in SOST expression, both of which remained unaffected by exercise in the adult mice. After 5-weeks of exercise, a significant decrease in the percentage of osteocytes expressing sclerostin at the protein level was found in young mice, but not adult mice. Mechanical testing of the tibia found exercise to have a significant influence on tissue-level mechanical properties, specifically ultimate-stress and modulus that was dependent on age. Adult mice in particular experienced a significant decrease in modulus despite an increase in cortical area and cortical thickness compared to sedentary controls. Altogether, this study demonstrates a shift in the cellular response to exercise with age, and that gains in bone mass at the adult stage fail to improve bone strength.

Novel bone metabolism-associated hormones: the importance of the pre-analytical phase for understanding their physiological roles

The endocrine function of bone is now a recognized feature of this tissue. Bone-derived hormones that modulate whole-body homeostasis, are being discovered as for the effects on bone of novel and classic hormones produced by other tissues become known. Often, however, the data regarding these last generation bone-derived or bone-targeting hormones do not give about a clear picture of their physiological roles or concentration ranges. A certain degree of uncertainty could stem from differences in the pre-analytical management of biological samples. The pre-analytical phase comprises a series of decisions and actions (i.e., choice of sample matrix, methods of collection, transportation, treatment and storage) preceding analysis. Errors arising in this phase will inevitably be carried over to the analytical phase where they can reduce the measurement accuracy, ultimately, leading discrepant results. While the pre-analytical phase is all important, in routine laboratory medicine, it is often not given due consideration in research and clinical trials. This is particularly true for novel molecules, such as the hormones regulating the endocrine function of bone. In this review we discuss the importance of the pre-analytical variables affecting the measurement of last generation bone-associated hormones and describe their, often debated and rarely clear physiological roles.

Bone turnover response is linked to both acute and established metabolic changes in ultra-marathon runners

Bone and energy metabolisms regulation depends on a two-way street aimed at regulating energy utilization. Mountain ultra-marathons are highly demanding aerobic performances that deeply affect the whole body homeostasis. In this study we aimed to investigate and characterize the metabolic profile (in terms of hormones involved in energy metabolism), the inflammatory adipokines, and the bone turnover; in particular the osteocalcin-mediated response has been compared in experienced mountain ultra-marathons runners versus control subjects. Serum concentrations of specific markers of bone turnover (pro-collagen type I N-terminal propeptide, carboxylated/undercarboxylated osteocalcin), measured by enzyme-linked immunosorbent assay, and metabolic hormones (C-peptide, insulin, glucagon, glucagon-like peptide, gastric-inhibitory peptide, ghrelin, leptin, resistin, and visfatin), measured by fluorescent-based multiplex assay, were compared before and after a 65 km mountain ultra-marathons in 17 trained runners and 12 age-matched controls characterized by a low physical activity profile. After the mountain ultra-marathons, runners experienced a reduction in pro-collagen type I N-terminal propeptide, though it remained higher than in controls; while carboxylated osteocalcin remained unchanged. Among the metabolic hormones, only glucagon and leptin were different between runners and controls at rest. C-peptide and leptin decreased after the mountain ultra-marathons in runners; while glucagon, glucagon-like peptide 1, resistin, and visfatin were all increased. Uncarboxylated osteocalcin (and uncarboxylated/carboxylated osteocalcin ratio) was decreased and this highly correlated with insulin and C-peptide levels. In conditions of high energy expenditure, homeostasis is maintained at expenses of bone metabolism. Changes in the uncarboxylated osteocalcin clearly mark the global energy needs of the body.

Serum sclerostin decreases following 12months of resistance- or jump-training in men with low bone mass

PURPOSE

We previously reported that 12months of resistance training (RT, 2×/wk, N=19) or jump training (JUMP, 3×/wk, N=19) increased whole body and lumbar spine BMD and increased serum bone formation markers relative to resorption in physically active (≥4h/wk) men (mean age: 44±2y; median: 44y) with osteopenia of the hip or spine. The purpose of this secondary analysis was to examine the effects of the RT or JUMP intervention on potential endocrine mediators of the exercise effects on bone, specifically IGF-I, PTH and sclerostin.

METHODS

Fasting blood samples were collected after a 24-h period of no exercise at baseline and after 12months of RT or JUMP. IGF-I, PTH and sclerostin were measured in serum by ELISA. The effects of RT or JUMP on IGF-I, PTH and sclerostin were evaluated using 2×2 repeated measures ANOVA (time, group). This study was conducted in accordance with the Declaration of Helsinki and was approved by the University of Missouri IRB.

RESULTS

Sclerostin concentrations in serum significantly decreased and IGF-I significantly increased after 12months of RT or JUMP; while PTH remained unchanged.

CONCLUSION

The beneficial effects of long-term, progressive-intensity RT or JUMP on BMD in moderately active men with low bone mass are associated with decreased sclerostin and increased IGF-I.

Implications of exercise-induced adipo-myokines in bone metabolism

Physical inactivity has been recognized, by the World Health Organization as the fourth cause of death (5.5 % worldwide). On the contrary, physical activity (PA) has been associated with improved quality of life and decreased risk of several diseases (i.e., stroke, hypertension, myocardial infarction, obesity, malignancies). Bone turnover is profoundly affected from PA both directly (load degree is the key determinant for BMD) and indirectly through the activation of several endocrine axes. Several molecules, secreted by muscle (myokines) and adipose tissues (adipokines) in response to exercise, are involved in the fine regulation of bone metabolism in response to the energy availability. Furthermore, bone regulates energy metabolism by communicating its energetic needs thanks to osteocalcin which acts on pancreatic β-cells and adipocytes. The beneficial effects of exercise on bone metabolism depends on the intermittent exposure to myokines (i.e., irisin, IL-6, LIF, IGF-I) which, instead, act as inflammatory/pro-resorptive mediators when chronically elevated; on the other hand, the reduction in the circulating levels of adipokines (i.e., leptin, visfatin, adiponectin, resistin) sustains these effects as well as improves the whole-body metabolic status. The aim of this review is to highlight the newest findings about the exercise-dependent regulation of these molecules and their role in the fine regulation of bone metabolism.

Sclerostin as a novel marker of bone turnover in athletes

Sclerostin is a protein secreted by osteocytes that acts as an inhibitor of bone formation. It has been shown that physical activity affects sclerostin concentration and thus bone remodelling. The aim of the study was to evaluate serum concentrations of sclerostin, selected bone turnover markers (PTH, P1NP), 25(OH)D3 and the intake of calcium and vitamin D in physically active versus sedentary men. A total of 59 healthy men aged 17-37 were enrolled in the study (43 athletes and 16 non-athletes). The mean sclerostin concentration in the group of athletes (A) was significantly higher than in non-athletes (NA) (35.3±8.9 vs 28.0±5.6 pmol·l^-1, p= 0.004). A compared with NA had higher concentrations of P1NP (145.6±77.5 vs 61.2±22.3 ng·ml^-1, p= <0.0001) and 25(OH)D3 (16.9±8.4 vs 10.3±4.3 ng·ml^-1, p= 0.004) and lower concentrations of PTH (25.8±8.3 vs 38.2±11.5 pg·ml^-1, p= <0.0001). Vitamin D deficiency was found in 77% of A and 100% of NA. A and NA had similar daily energy intake. They did not differ as to the intake of calcium and vitamin D. We observed a negative correlation between the serum concentrations of sclerostin and calcium in the studied subjects. Our results suggest that regular, long-lasting physical training may be associated with higher concentration of sclerostin. It seems that increased sclerostin is not related to other bone turnover markers (PTH, P1NP).

Changes in urinary amino acids excretion in relationship with muscle activity markers over a professional cycling stage race: in search of fatigue markers

The aim of this study was to identify the relationship between metabolic effort, muscular damage/activity indices, and urinary amino acids profile over the course of a strenuous prolonged endurance activity, as a cycling stage race is, in order to identify possible fatigue markers. Nine professional cyclists belonging to a single team, competing in the Giro d'Italia cycling stage race, were anthropometrically characterized and sampled for blood and urine the day before the race started, and on days 12 and 23 of the race. Diet was kept the same over the race, and power output and energy expenditure were recorded. Sera were assayed for muscle markers (lactate dehydrogenase, aspartate aminotransferase, and creatine kinase activities, and blood urea nitrogen), and creatinine, all corrected for plasma volume changes. Urines were profiled for amino acid concentrations, normalized on creatinine excretion. Renal function, in terms of glomerular filtration rate, was monitored by MDRD equation corrected on body surface area. Creatine kinase activity and blood urea were increased during the race as did serum creatinine while kidney function remained stable. Among the amino acids, taurine, glycine, cysteine, leucine, carnosine, 1-methyl histidine, and 3-methyl histidine showed a net decreased, while homocysteine was increased. Taurine and the dipeptide carnosine (β-alanyl-L-histidine) were significantly correlated with the muscle activity markers and the indices of effort. In conclusion, the metabolic profile is modified strikingly due to the effort. Urinary taurine and carnosine seem useful tools to evaluate the muscle damage and possibly the fatigue status on a long-term basis.

Osteocartilaginous metabolic markers change over a 3-week stage race in pro-cyclists

Evidence suggests that endurance and even recreational cycling may stimulate bone resorption; however, little is known about cartilage response to endurance cycling exercise. We investigated effort-dependent changes in bone turnover and cartilage biomarkers in blood and urine samples from elite cyclists during a 3-week stage race. Whole blood and urine samples were collected the day before the start of the race, at mid and end-race for serum and urinary CTx-I, NTx-I, PINP, COMP (only in serum), and CTx-II analysis by enzyme-linked immunosorbent assay. The values were corrected for plasma volume or creatinine excretion, respectively, and correlated with power output (corrected for body weight) and net energy expenditure. Bone marker concentrations in both serum and urine were slightly but significantly decreased. Among the cartilage degradation markers, only CTx-II was decreased, while COMP remained unchanged. The changes in bone and cartilage turnover indexes were correlated with the indexes of physical effort and energy consumption. Strenuous physical effort, in the absence of mechanical loading, slows bone metabolism and only minimally affects cartilage turnover. Since changes in plasma and urine volume, which normally occur in exercising athletes, can mask these effects, biomarker concentrations need to be corrected for shifts in plasma volume and urinary creatinine for correct interpretation of the data.