OBJECTIVE To compare serum concentrations of biomarkers of cartilage and bone metabolism between racehorses with a carpal or metacarpophalangeal or metatarsophalangeal (ie, fetlock) joint injury and matched uninjured control horses, determine changes in biomarker concentrations following joint injury, and establish the biomarkers’ diagnostic test performance.
ANIMALS 50 Thoroughbred racehorses with a carpal or fetlock joint injury and 50 matched uninjured horses (control horses).
PROCEDURES Serum concentrations of 2 cartilage synthesis biomarkers (carboxy-terminal propeptide of type II collagen [CPII] and chondroitin sulfate epitope 846 [CS846]), 2 cartilage degradation biomarkers (neoepitope generated by collagenase cleavage of type II collagen [C2C] and cross-linked carboxy-terminal telopeptide fragments of type II collagen [CTX-II]), and serum activity of a bone formation marker (bone-specific alkaline phosphatase [BAP]) were measured around the time of injury diagnosis and monthly thereafter for as long as possible.
RESULTS Injured horses as a group and horses specifically with fetlock joint injuries had significantly lower serum CPII concentrations and significantly higher serum BAP activities than matched control horses. Concentrations of CTX-II were decreased between 2 and 4 months following joint injury. Measurement of CPII concentration at baseline could distinguish between injured horses and control horses with a sensitivity of 82% and specificity of 50%.
CONCLUSIONS AND CLINICAL RELEVANCE Although significant differences in specific biomarker concentrations between horses with carpal and fetlock joint injuries and matched control horses were identified, there was no convincing evidence of the suitability of these biomarkers as diagnostic or prognostic tools in a clinical setting.
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. (Am J Vet Res 2003;64:1549–1556)
Objective—To investigate the relationship between stage of estrous cycle and bone cell activity in Thoroughbreds.
Sample Population—Blood samples collected from forty-seven 2-year-old Thoroughbred mares in training for racing.
Procedures—Blood samples were collected monthly (in April through September) from the mares. Stage of estrus was determined by assessing serum progesterone concentration. Bone cell activity was determined by measuring concentrations of 2 markers of bone formation (osteocalcin and the carboxy-terminal propeptide of type I collagen [PICP]) and a marker of bone resorption (the cross-linked carboxy-terminal telopeptide of type I collagen [ICTP]) in sera.
Results—When the relationship between stage of the estrous cycle and markers of bone cell activity was examined, serum concentrations of both osteocalcin and ICTP were significantly higher in mares that were in the luteal phase, compared with mares that were at other stages of the estrous cycle. Stage of estrus did not affect serum PICP concentration.
Conclusions and Clinical Relevance—Results indicate that bone cell activity in Thoroughbred mares fluctuates during the estrous cycle; serum concentrations of markers of bone formation and bone resorption are increased during the luteal phase. Further studies are required to determine whether these changes are of clinical importance and increase the risk of injury for mares in training during the breeding season. As in humans, stage of estrus must be considered as a source of uncontrollable variability in serum bone marker concentrations in horses.