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.


METHODS
12 two-year-old Thoroughbred mares.


METHODS
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
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.
Jackson
Brendan F
BF
The Royal Veterinary College, Royal College St, London, NW1 OUT.
Goodship
Allen E
AE
Eastell
Richard
R
Price
Joanna S
JS
D015502:Absorptiometry, Photon; D000469:Alkaline Phosphatase / Q000097:blood; D000596:Amino Acids / Q000097:blood; D000818:Animals; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000502:physiology; D001842:Bone and Bones / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D024042:Collagen Type I; D005260:Female; D006736:Horses / Q000097:blood* / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D015675:Osteocalcin / Q000097:blood; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011347:Procollagen / Q000097:blood
D000596:Amino Acids; D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C042813:procollagen type I carboxy terminal peptide; D015675:Osteocalcin; D007334:Insulin-Like Growth Factor I; C036020:deoxypyridinoline; D000469:Alkaline Phosphatase