UTILITY OF ALPHA CTX AS AN INDEX OF VELOCITY OF SKELETAL GROWTH IN PREPUBERAL CHILDREN.

ZENI SN; PELLEGRINI GG; LINARI M; PIAZZA N; SOMOZA J; RIO ME

5-9 mayo de 2007. Copenhagen, Denmark

Congreso; 34th. European symposium on Calcified Tissues; 2007

European Calcifief Tissues Society

Degradation products of collagen type I can be measured by CrossLaps (CTX) immunoassays, providing an index of bone resorption. The CTX epitope EKAHDGGR comprises a DG-motif susceptible to post-translational modifications. In newly synthesized collagen this motif is in the -CTX form, but during aging of bone it is isomerized to -CTX form. Both CTX reflects metabolic activity and rate of bone remodelling but as -CTX arises from new bone, it could be associated with bone modelling at childhood. In the present work -CTX was measured in children attending public schools of Vicente Lopez to assess if there were differences in -CTX levels related to the usual calcium intake. In 48 normal healthy children, aged 6.2 to 9.2 years, calcium (Ca) (atomic absorptiometry), -CTX (ELISA, Nordic Bioscience Diag. A/S) and creatinine (C) (modified Jaffé method) levels were performed on second morning void samples. The calcaneous ultrasound (QUI) was also measured (Sahara-Olohi). Ca and -CTX were expressed as ratio to C excretion. Results: In normal healthy children, a biochemical nutritional index of usual Ca intake is Ca/C ratio determined in the second morning void which ranged between 0.07 and 0.15 when Ca intake is adequate. Results: As expected, according to food intake records, usual Ca intake which is necessary for skeletal growth was low in 37 of 48 studied children (77%). Levels of -CTX correlated with both Ca/C and QUI values (r=0.52; p<0.001 and r= -0.43; p<0.003, respectively). When children were divided according to their range of Ca/C:lower than 0.07(0.036±0.018a); 0.07-0.15(0.096±0.024b)and higher than 0.150(0.222±0.06c), the -CTX levels (mean±SD) were: 0.73±0.21a (n=37); 0.93±0.26b (n=11)and 1.19±0.38b (n=5), respectively (different letters: p<0.04)Conclusion: Bone metabolic activity during growth could be estimated by -CTX since it correlated with both, nutritional and bone density parameters. Although future studies are necessary, -CTX seems to be a promissory index of skeletal growth and bone modelling to be used in cross-sectional screening studies of growth velocity. Supported by UBACyT, B703. SU Project