Diurnal variation and age differences in the biochemical markers of bone turnover in horses.

Abstract

Biochemical markers of bone turnover provide sensitive, rapid, and noninvasive monitoring of bone resorption and formation. Serum concentrations of osteocalcin (OC) reflect rates of bone formation, and urinary concentrations of the pyridinium crosslinks pyridinoline (Pyd) and deoxypyridinoline (Dpd) are specific and sensitive markers of bone resorption. These markers are age-dependent and are used to detect and monitor changes in the rates of bone turnover in a variety of orthopedic diseases in humans and may prove to have similar application in horses. This study examined age differences and diurnal variation in OC, Pyd, and Dpd in eight adult geldings and seven weanling colts. Blood and urine were collected at regular intervals over 24 h. Serum OC and cortisol, and urinary Pyd and Dpd were analyzed. Mean 24-h concentrations of cortisol and all three markers were higher (P<.003) in weanlings than adults. Significant 24-h variation was observed in adult gelding OC, Pyd, and Dpd concentrations (P< .02). Adult OC concentrations were highest between 2400 and 0900; Pyd and Dpd peaked between 0200 and 0800. Similar patterns of bone turnover were observed in weanling values, but they were not significant (P>.17) owing to greater variability between individuals. Cortisol secretion varied (P<.001) over 24 h in both adults and weanlings and, thus, did not seem to be responsible for greater variability in markers of bone turnover between weanlings. These data demonstrate that diurnal rhythms exist for serum OC and urinary Pyd and Dpd in adult horses, as reported in humans, and that sample timing is an important consideration in future equine studies using these markers.

Diagnostic Importance of Deoxypyridinoline and Osteocalcine in Equine Osteoarthritis

“…However, in this study, the general indication of a lack of increase of osteocalcin suggests that either most of the horses were at an early stage in osteoarthritis or that bone synthesis is impaired in equine OA, possibly as a result of the effects of circulating cytokines; it is well established that both IL-1β and TNFα inhibit bone formation (Poole and Dieppe 1994). Black et al (1999) has shown that diurnal rhytms exist for serum OC in adult horses. Therefore, sample timing is an important consideration in equine studies.…”

“…The overlap between groups, however, made further analysis and interpretation difficult. There was no correlation between radiographic evidence of cartilage/bone damage and deoxpyridinoline/creatinine ratios (Black et al 1999).…”

Clinical Usefulness of the Measurement of Bone Mineral Content by Radiographic Absorptiometry in the Young Thoroughbred

“…The levels of the bone metabolism markers OC [4,6], PICP [32], and ICTP [21] are known to decrease progressively after birth. In Thoroughbreds, these bone metabolism markers decrease mostly between the ages of 0 months to 6 months but continued to decrease until the age of 18 months [33].…”

The influence of mineral supplementation on skeleton formation and growth in Lusitano foals

“…Girth and cannon circumference (midsection of the third metacarpus) were assessed with a measuring tape. Blood samples were also collected periodically (0, 35, 70, 105 and 140 days), between 09:00 and 11:00 a.m., in order to reduce the possible influence of diurnal rhythms on markers levels (Black et al, 1999). Samples (10 ml) were collected from the jugular vein into heparinized tubes (MonovettesR-Sarstedt) 1 and transported on ice to the laboratory.…”

“…Previous experimental research in the horse has shown the metabolic activity of the osteoblasts can be assessed by biochemical markers like bone alkaline phosphatase (BALP) or osteocalcin (OC) (Lepage et al, 1990(Lepage et al, , 1991(Lepage et al, , 1997(Lepage et al, , 1998Price et al, 1995Price et al, , 2001Black et al, 1999).…”