Serum levels of metabolism of type I collagen in relation to physical growth of AGA newborns

The most interest indicators of bone turn-over are the metabolites of type I collagen, which makes up 90% of bone matrix. C-terminal propeptide type I procollagen (PICP) which is removed from procollagen during extracellular process of collagen fibres formation is known as marker of bone formation. Marker of bone resorption is C-telopeptide alfa 1-chain of type I collagen (Cross-laps) which is removed from collagen during process of degradation. It is known that intensive turn-over of bone tissue take place during developmental periods and is proportional to velocity of child's growth. The aim of the study was to assess correlation between bone formation and resorption and physical development of AGA newborns. Clinical material consisted of 47 newborns born from 26 and 41 weeks of gestation with development appropriate for gestational age (AGA); 28 of them were full-terms and 19 were preterms Physical status at birth was assessed by measuring basic anthropometric parameters of newborns. Biochemical investigations were performed in all newborns between 1st and 2nd week of chronological age. Serum level of PICP (ng/ml) and Cross-laps (pM/I) were assessed using Elisa method. Statistical analysis was performed with the t-Student and Pearson correlation test. Mean level of PICP in newborns' serum was 2073.8 +/- 555.1 ng/ml and mean level of Cross-laps was: 17413.8 +/- 5932.5 pM/l. There were no statistical differences in the level of PICP and Cross-laps in boys and girls, as well as in full-terms and preterms (p > 0.05). Serum level of PICP correlated negatively with gestational age and birth weight of newborns (p < 0.05). Positive correlations were detected for serum level of Cross-laps, gestational and chronological age of newborns (p < 0.05) as well as for serum level of Cross-laps and anthropometric parameters of newborns. There was no statistical correlation between PICP and Cross-laps in newborns serum. The authors suggest that serum level of metabolites of type I collagen may not reflect only bone turn-over but may be dependent on overall physical growth.