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Osteocalcin, skeletal alkaline phosphatase, and bone mineral content in very low birth weight infants: a longitudinal
W B Pittard1, K M Geddes, T C Hulsey
1Department of Pediatrics, Medical University of South Carolina, Charleston 29425.
Insights
Serum osteocalcin (Gla) and skeletal alkaline phosphatase (SAP) reflect bone formation. In premature infants, changes in bone mineral content (BMC) did not correlate with Gla or SAP levels, despite vitamin D correlations.
Area of Science:
- Pediatrics
- Biochemistry
- Bone Metabolism
Background:
- Osteocalcin (Gla) and skeletal alkaline phosphatase (SAP) are key markers of osteoblast activity.
- Assessing bone formation in premature infants is crucial for their long-term health.
Purpose of the Study:
- To investigate the relationship between bone mineral content (BMC) changes and serum Gla and SAP concentrations in very low birth weight infants.
- To monitor key biochemical markers related to bone metabolism in premature infants.
Main Methods:
- Longitudinal measurement of BMC using photon absorptiometry in 20 very low birth weight infants from birth to 16 weeks.
- Serial measurements of serum Gla, SAP, total calcium, phosphorus, parathyroid hormone, and vitamin D metabolites.
- Maternal serum values at delivery and cord blood were also analyzed.
Main Results:
- Cord blood Gla levels were significantly higher than maternal levels and increased significantly by 1 week of age.
- Serum Gla increases from birth to 1 week correlated significantly with 1,25-dihydroxyvitamin D increases.
- No significant correlation was found between changes in BMC and serum Gla or SAP concentrations over the first 4 months.
- A significant negative correlation between serum Gla and SAP concentrations was observed at 4 weeks.
Conclusions:
- While vitamin D influences early osteocalcin levels in premature infants, serum Gla and SAP do not reliably predict bone mineral content changes in the first four months.
- Further research is needed to understand the complex interplay of factors affecting bone development in preterm infants.
Abstract:
Serum osteocalcin (Gla) and skeletal alkaline phosphatase (SAP) concentration both reflect osteoblast activity in the dynamic process of bone formation. To assess the relation in premature infants between change in bone mineral content (BMC) and both Gla and SAP serum concentration, we longitudinally measured BMC via photon absorptiometry and serum Gla and SAP concentration from birth to 16 wk in 20 very low birth weight infants. Serum total calcium, phosphorus, parathyroid hormone, and vitamin D metabolite concentrations were also monitored. All serum values were measured in the 20 mothers at delivery. Cord blood Gla concentrations were significantly (p less than 0.03) greater than maternal levels, and by 1 wk had significantly (p less than 0.001) increased from birth values. Total calcium, parathyroid hormone, phosphorus, and vitamin D concentrations remained in the normal range throughout the study. The increase in serum Gla concentrations, birth to 1 wk, were significantly correlated with the simultaneous increase in 1,25-dihydroxyvitamin D concentrations. The correlation between the change in BMC, however, over the first 4 mo of life and both Gla and SAP serum concentrations failed to reach statistical significance. Finally, a significant (p less than 0.003) negative correlation was measured between serum Gla and SAP concentrations at wk 4, and, although not significant, a consistently negative correlation was measured from 1-16 wk of age.(ABSTRACT TRUNCATED AT 250 WORDS)