Response of serum biochemical markers of bone metabolism totraining in the juvenile racehorse

Clodronate disodium does not produce measurable effects on bone metabolism in an exercising, juvenile, large animal model

Bisphosphonates are commonly used to treat and prevent bone loss, but their effects in active, juvenile populations are unknown. This study examined the effects of intramuscular clodronate disodium (CLO) on bone turnover, serum bone biomarkers (SBB), bone mineral density (BMD), bone microstructure, biomechanical testing (BT), and cartilage glycosaminoglycan content (GAG) over 165 days. Forty juvenile sheep (253 ± 6 days of age) were divided into four groups: Control (saline), T0 (0.6 mg/kg CLO on day 0), T84 (0.6 mg/kg CLO on day 84), and T0+84 (0.6 mg/kg CLO on days 0 and 84). Sheep were exercised 4 days/week and underwent physical and lameness examinations every 14 days. Blood samples were collected for SBB every 28 days. Microstructure and BMD were calculated from tuber coxae (TC) biopsies (days 84 and 165) and bone healing was assessed by examining the prior biopsy site. BT and GAG were evaluated postmortem. Data, except lameness data, were analyzed using a mixed-effects model; lameness data were analyzed as ordinal data using a cumulative logistic model. CLO did not have any measurable effects on the skeleton of sheep. SBB showed changes over time (p ≤ 0.03), with increases in bone formation and decreases in some bone resorption markers. TC biopsies showed increasing bone volume fraction, trabecular spacing and thickness, and reduced trabecular number on day 165 versus day 84 (p ≤ 0.04). These changes may be attributed to exercise or growth. The absence of a treatment effect may be explained by the lower CLO dose used in large animals compared to humans. Further research is needed to examine whether low doses of bisphosphonates may be used in active juvenile populations for analgesia without evidence of bone changes.

The Effect of a Moderate Exercise Program on Serum Markers of Bone Metabolism in Dogs

Simple Summary

In this article, we investigate the long-term (four months) effects of a 25 min moderate-intensity treadmill exercise, three times per week, on serum markers of bone metabolism (bone alkaline phosphatase and osteocalcin as bone formation markers and C-terminal telopeptide as bone resorption marker) in dogs. Twenty healthy dogs (Labrador and Golden Retrievers), median age 16.2 (11.7–24.4) months underwent the exercise program. Blood samples were collected as a baseline, mid-term (after two months) and at the end of the study. The values of bone formation markers significantly decreased following two months of exercise program; after which, bone alkaline phosphatase increased while osteocalcin concentration continued to decrease towards the end of the study. Bone resorption marker did not significantly change through the exercise duration. In overall, moderate exercise resulted in no change in bone resorption, and a mild bone formation in young developing dogs.

Abstract

The beneficial effect of physical activity on the musculoskeletal health in dogs is well recognized, but the level of intensity, duration, and frequency of exercise is not fully described. Measurement of serum markers of bone metabolism (bone alkaline phosphatase and osteocalcin as bone formation markers and C-terminal telopeptide as bone resorption marker) during four months of organized moderate-intensity physical training in Labrador retriever and Golden retriever dogs aged between 11.7–24.4 months, showed variations of bone metabolism. Dogs were included in treadmill running sessions for 25 min, three times per week. Blood samples were taken at the beginning of the program (baseline), after two months (mid-term) and at the end of the study after four months. The values of bone alkaline phosphatase and osteocalcin significantly decreased following two months of exercise program. Bone alkaline phosphatase increased by the end of four-month training cycle, but did not reach baseline value. Osteocalcin levels continued to decrease towards the end of the study. C-terminal telopeptide concentrations did not significantly change throughout the study duration. The results of this study show that aerobic exercise of moderate-intensity caused an initial decrease in bone formation followed by an increase of bone alkaline phosphatase and a further decrease of osteocalcin concentration. The response of two formation markers can be explained by the different stage of osteoblast activity that they express. In summary, moderate exercise resulted in no change in bone resorption, and a mild bone formation in young developing dogs.

Revisiting predictive biomarkers of musculoskeletal injury in thoroughbred racehorses: longitudinal study in polish population

BACKGROUND

High prevalence of musculoskeletal disorders in racehorses and its impact on horse welfare and racing economics call for improved measures of injury diagnosis and prevention. Serum biomarkers of bone and cartilage metabolism have previously shown promise in prediction of musculoskeletal injuries in horses. This study aimed to re-evaluate usability of the predictive serum biomarkers identified in North American Thoroughbred racehorses in a geographically distinct group of Polish Thoroughbreds.

RESULTS

Serum concentrations of bone and cartilage biomarkers: osteocalcin, c-terminal telopeptide of type I collagen, total glycosaminoglycans (GAG), chondroitin sulfate epitope and c-propeptide of type II procollagen (CPII) were evaluated in the beginning and the next 3 months of one racing season in a cohort of twenty-six 2-year-old Polish racehorses. Exit criteria were diagnosis of musculoskeletal injury, leading to > 5 days off training (n = 8), or completion of 3 study months with no training interruptions (n = 18). Normalized results and matching archival data from 35 2-year-old North American racehorses was used for logistic regression analysis to identify universal predictors of injury. Mean GAG and CPII levels were lower in injured group comparing to control, which is consistent with previous findings in racehorses. These biomarkers were also identified as predictors of injury in the mixed population model. Population origin had no significant effect on predictive value of evaluated biomarkers (Wald test p = 0.137). Decreased osteocalcin and increased c-terminal telopeptide of type I collagen levels in injured horses comparing to controls were specific for Polish population and signalized disruption in bone turnover homeostasis.

CONCLUSIONS

Changes in serum GAG and CPII in racehorses at risk of injury appear to be similar across distinct populations while dynamics of serum bone marker is more population-specific.

Biochemical markers of bone metabolism and risk of dorsal metacarpal disease in 2-year-old Thoroughbreds

REASONS FOR PERFORMING STUDY

Dorsal metacarpal disease (DMD) is a common problem in 2-year-old racehorses and results in loss of a significant number of days from training. Biochemical markers of bone cell activity measured early in the training season could have value for identifying 2-year-old Thoroughbred racehorses that develop DMD.

OBJECTIVES

To determine the association between serum concentrations of osteocalcin, the carboxyterminal propeptide of type I collagen (PICP) and the carboxyterminal cross-linked telopeptide of type I collagen (ICTP) measured early in the training season and the risk of DMD.

METHODS

Blood samples were collected from 165 two-year-old Thoroughbreds during late November/early December. Osteocalcin and PICP were measured as markers of bone formation, and ICTP as a marker of bone resorption. Training and veterinary records for each horse were monitored over the following training/racing season (10 months). Cases were defined as an episode where signs of DMD were sufficiently severe for a horse to miss at least 5 consecutive days of training. Classification tree and logistic regression analysis were used to identify the most important factors suitable for prediction of DMD risk.

RESULTS

There were 24 cases of DMD during the season (14.6% cumulative incidence), with an average time to recognition of approximately 6 months (May). The earliest recognised case was in February and the latest in September. Osteocalcin and ICTP concentrations in the early stages of the training season were significantly higher in horses that subsequently developed DMD (P = 0.017 and 0.019, respectively). DMD cases were also significantly older compared to noncases (21.04 vs. 20.44 months, P = 0.023). Using a multivariable logistic regression model, it was possible to postulate a set of diagnostic rules to predict the likelihood of DMD injury during the season. This suggested that horses with ICTP concentrations above 12365 ug/l and older than 20.5 months are 2.6 times more likely to develop DMD.

CONCLUSIONS

The measurement of the bone resorption marker ICTP could be useful for identification of 2-year-olds at increased risk of developing DMD.

POTENTIAL RELEVANCE

These findings, together with other strategies such as modification of training regimens, e.g. early introduction of short distances of high-speed exercise into the training programme, could help reduce the days lost to training as a result of DMD.

Response of biochemical markers of bone metabolism to exercise intensity in thoroughbred horses

We studied the response of biochemical markers of bone metabolism to exercise intensity in horses. Four horses were walked on a mechanical walker for one week (pre-exercise). Then they performed low-speed exercise on a high-speed treadmill in the first week and medium-speed exercise in the second week and high-speed exercise in the third week of training. We measured two indices of bone resorption, serum hydroxyproline concentration and the urinary deoxypyridinoline/creatinine ratio, and serum osteocalcin (OC) concentration as an index of bone formation. Both indices of bone resorption gradually decreased during the experiment. Serum OC concentration did not change in the first week but was significantly lower in the second and the third weeks compared to in the pre-exercise period and in the first week. These results suggest that the low-speed exercise decreased bone resorption but did not affect bone formation, which possibly results in increasing bone mineral content and strengthening of bones. The high-speed exercise decreased bone formation and bone resorption, i.e., bone turnover was suppressed. The low-speed exercise may be preferable for increasing bone mineral content.

Changes in synovial fluid and serum biomarkers with exercise and early osteoarthritis in horses

OBJECTIVE

To discriminate between changes in biomarkers with exercise compared to changes in biomarkers with osteoarthritis (OA) in exercising horses.

METHOD

Sixteen, 2-year-old horses were randomly assigned either to an exercise-alone (n=8) or OA-affected (also exercised) (n=8) group. All horses had both mid-carpal joints arthroscoped and OA induced in one mid-carpal joint in the OA-affected joints of OA-affected horses. Two weeks after surgery all horses commenced a strenuous exercise program on a high-speed treadmill. Clinical outcomes and synovial fluid and serum biomarkers, were evaluated weekly. Synovial and serum biomarkers evaluated were epitope CS846 (CS846), epitope CPII (CPII), glycosaminoglycans (GAGs), epitope Col CEQ (Col CEQ) (a marker of type II collagen degradation), type I and II collagen degradation fragments (C1,2C), osteocalcin, C-terminal of bone type I collagen (CTX1), type I collagen (Col I) and (synovial fluid only of cartilage) prostaglandin E2 (PGE2) levels. Horses were euthanized at day 91 and their joints assessed grossly, histopathologically, and histochemically.

RESULTS

Exercise induced a significant increase in synovial fluid CS846, CPII, GAG, Col CEQ, C1,2C, osteocalcin and Col I concentrations. There was a significant increase in synovial fluid CS846, CPII, Col CEQ, C1,2C, osteocalcin, Col I and PGE2 concentrations in OA-affected joints compared to exercise-alone joints. The concentration of serum CS846, CPII, GAG, osteocalcin, C1,2C and Col I increased with exercise. For each of these biomarkers there was also a statistically significant increase in serum biomarker levels in OA-affected horses compared to exercise-alone horses.

CONCLUSIONS

Six synovial fluid and serum biomarkers were useful in separating early experimental OA from exercise alone but synovial fluid CTX1 and serum Col CEQ and CTX1 were not.

High-intensity exercise induces structural, compositional and metabolic changes in cuboidal bones--findings from an equine athlete model

Fatigue fracture of cuboidal bones occurs in the human foot as well as the equine carpus. The racehorse provides a naturally-occurring model to study the effects of high-intensity exercise on the morphology and metabolism of cuboidal bones. We studied both the mineral and the collagenous matrix of the third (C(3)) and radial (C(r)) carpal bones of raced and non-raced Thoroughbred (TB) horses. We hypothesised that racehorses would show increases in the mineral component of these bones and post-translational modifications of the collagenous matrix alongside changes in markers of collagen remodelling and bone formation. C(3) and C(r) carpal bones were retrieved from raced TB horses (n=14) and non-raced TB horses (n=11). Standardised proximal-distal sections were taken from each bone and these were sliced transversely to study the proximal-distal differences in bone metabolism from the subchondral plate through to trabecular bone. Histomorphometry and bone mineral density measurements were performed in parallel with biochemical analyses including total collagen, collagen synthesis and cross-links, matrix metalloproteinases-2 and 9 and their inhibitors, calcium and phosphate, and bone alkaline phosphatase. The results of this study show that, while there is a net increase in bone formation in the racehorses, there is additionally an increase in bone collagen synthesis and remodelling, particularly within the trabecular regions of the bone. The increase in bone density would lead to greater stiffness, particularly in the cortical bone, and failure of this 'stiffer' cortical bone may result from its lack of support from the rapidly remodelling and structurally weakened underlying trabecular bone.

Serum osteocalcin and CTX-MMP concentration in young exercising thoroughbred racehorses

Bone responds to exercise with changes in bone (re-)modelling, which might be monitored non-invasively with biochemical bone markers. The aim of this study was to evaluate the influence of exercise on serum osteocalcin and serum carboxy-terminal cross-linked telopeptide of type I collagen generated by matrix metalloproteinases (CTX-MMP) concentration in young racehorses. Seventy-one 2 to 4-year-old Thoroughbreds were included in this prospective infield study. Blood sampling was performed six times (i.e. six sampling cycles) during a 9-month period. Serum samples were analysed with commercial osteocalcin and CTX-MMP radioimmunoassays. Two-year-old racehorses had higher serum osteocalcin and CTX-MMP values than 3-year-old horses. Gender and training amplitude did not significantly influence serum osteocalcin and CTX-MMP values. Two-year-old horses showed an increase in osteocalcin values between cycles 2 and 3 and an increase in serum CTX-MMP values between cycles 1 and 2. Serum osteocalcin and CTX-MMP concentrations decreased between cycles 4 and 5, and 5 and 6. Three-year-old horses showed an increase in serum osteocalcin levels between cycles 3 and 4 and an increase in serum CTX-MMP concentrations between cycles 1 and 2, and 3 and 4. Serum osteocalcin levels decreased between cycles 5 and 6, whereas serum CTX-MMP levels decreased between cycles 4 and 5, and 5 and 6. Two- and three-year-old horses showed a decreased osteocalcin/CTX-MMP ratio between cycles 1 and 2. Moreover, 2-year-old horses showed an increase in the osteocalcin/CTX-MMP ratio between cycles 2 and 3. Sore shin formation did not significantly influence serum osteocalcin and CTX-MMP values. Serum osteocalcin and CTX-MMP are promising bone markers for monitoring exercise induced changes in equine bone metabolism.

Evaluation of serum concentrations of biochemical markers of bone metabolism and insulin-like growth factor I associated with treadmill exercise in young horses

OBJECTIVE

To evaluate changes in serum concentrations of biochemical markers of bone metabolism and insulin-like growth factor I (IGF-I) associated with treadmill exercise in young horses.

ANIMALS

12 two-year-old Thoroughbred mares.

PROCEDURE

During a 20-week study period, 6 horses were exercised on a treadmill 3 times a week (exercise group) and 6 horses received walking exercise 6 days a week (controls). Serum concentrations or activity of biochemical markers and IGF-I were assessed biweekly. Bone mineral density and content of the first phalanx were measured by dual-energy X-ray absorbiometry (DEXA) on completion of the study.

RESULTS

Compared with values in controls, bone mineral density and content were higher and serum concentrations of osteocalcin (a marker of bone formation) and the carboxy-terminal telopeptide of type I collagen (a marker of bone resorption; ICTP) were lower in exercised horses. Serum concentration and activity of the bone formation markers carboxy-terminal propeptide of type I collagen and bone-specific alkaline phosphatase (BAP) were not different between the 2 groups. Serum IGF-I concentration was lower in the exercise group, compared with control values; there was a significant correlation between change in IGF-I values and changes in osteocalcin, ICTP, and BAP values at the end of the study.

CONCLUSIONS AND CLINICAL RELEVANCE

Treadmill exercise over 20 weeks induced adaptive changes in bones of 2-year-old Thoroughbreds; training appears to increase bone mineral density, thereby enhancing mechanical strength of bone, but decreases bone turnover. Results indicated an association between changes in serum IGF-I concentration and bone cell activity in horses.

Biochemical markers of bone activity in young standardbred horses during different types of exercise and training

Seven untrained Standardbred horses were used in a training programme of 6 weeks to evaluate the effects of exercise and training on bone metabolism. The horses were exercised on a treadmill according to a standardized exercise test (SET 1: six incremental steps, 5 min duration each; start 5 m/s, increase 1 m/s). SET 1 was followed by a training programme of 6 weeks. In alternating order: high-speed exercise (HSE): 15 min duration, start at VLa4, continuous increase in speed every 60 s by 0.3 m/s (14 incremental steps); low-speed exercise (LSE): constant velocity at VLa2.5, duration: approximately 60-90 min (total training programme: eight HSE and eight LSE sessions). SET 2 finished the training programme and a deconditioning period of 12 weeks followed. Blood samples for lactate, total plasma protein (TPP), osteocalcin, and ICTP (cross-linked C-telopeptide of type I collagen) were collected. ICTP increased during SET 1 and SET 2, whereas osteocalcin decreased to below resting concentration 24 h after SET 1. A rise in ICTP was observed during LSE 1 and LSE 8, which was followed by a drop 24 h after exercise. No changes in osteocalcin were noted during LSE 1, but 24 h after LSE 1 osteocalcin dropped to below pre-exercise levels. LSE 8 resulted in an increase in osteocalcin, followed by a drop 24 h after LSE 8. Osteocalcin and ICTP were not affected by HSE. Baseline osteocalcin levels dropped during the course of training. The acute response of biochemical bone markers indicates a direct influence of a single bout of exercise on bone metabolism.