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Serum bone gamma-carboxyglutamic acid protein in a longitudinal study of infants: lower values in formula-fed infants
K F Michaelsen1, J S Johansen, G Samuelson
1Research Department of Human Nutrition, Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
Insights
Serum bone gamma-carboxyglutamic acid protein (BGP) levels are significantly higher in breast-fed infants compared to formula-fed infants, suggesting differences in bone formation. These elevated BGP levels correlate with breast milk intake but not linear growth velocity.
Area of Science:
- Pediatrics
- Biochemistry
- Nutrition Science
Background:
- Bone gamma-carboxyglutamic acid protein (BGP), also known as osteocalcin, is synthesized by osteoblasts and incorporated into the bone matrix.
- Serum BGP is a recognized indicator of bone formation, mirroring growth velocity during childhood and adolescence.
- Infant nutrition significantly influences growth and development, with breast milk and formula representing distinct nutritional sources.
Purpose of the Study:
- To investigate the relationship between infant feeding methods (breast milk vs. formula) and serum BGP levels.
- To assess the correlation between serum BGP concentrations and breast milk intake.
- To explore potential differences in bone metabolism between breast-fed and formula-fed infants.
Main Methods:
- A cohort study involving 91 healthy infants was conducted.
- Serum BGP levels were measured at 2, 6, and 9 months of age.
- Breast milk intake was quantified using test-weighing at 2 and 9 months; linear growth velocity was also monitored.
Main Results:
- Significantly higher serum BGP levels were observed in exclusively breast-fed infants compared to formula-fed infants at 2, 6, and 9 months (p < 0.001).
- Serum BGP levels showed a positive correlation with breast milk intake at 2 months (r = 0.59, p < 0.001) and 9 months (r = 0.41, p = 0.06).
- Elevated BGP concentrations decreased when breast-feeding ceased, and no significant differences in linear growth velocity were found between feeding groups.
Conclusions:
- Breast-feeding is associated with significantly higher serum BGP levels in infants, indicating potentially enhanced bone formation.
- The findings suggest that a component in human milk or its mineral content may influence BGP levels.
- Higher BGP values in breast-fed infants may imply differences in bone remodeling or mineralization compared to formula-fed infants, despite similar linear growth.
Abstract:
Bone gamma-carboxyglutamic acid protein [BGP (osteocalcin)] is a protein synthesized by osteoblasts and incorporated in the bone matrix. Serum BGP is a sensitive marker of bone formation, and it parallels the growth velocity curve during childhood and adolescence. Serum BGP was measured at the age of 2, 6, and 9 mo in a cohort study of nutrition and growth in 91 healthy infants. At 2 mo, the mean BGP value (+/- SD) was 275 +/- 87 ng/mL in infants exclusively breast-fed, and 80 +/- 44 ng/mL in formula-fed infants. At 6 mo, the values were 142 +/- 58 ng/mL and 55 +/- 30 ng/mL, and at 9 mo 75 +/- 39 ng/mL and 45 +/- 19 ng/mL in partially breast-fed and formula-fed infants, respectively. The differences were significant (p less than 0.001) at all three ages. At 2 and 9 mo, breast-milk intake was measured by test-weighing. Serum BGP was positively correlated to breast milk intake (mL/kg body wt) at 2 mo (r = 0.59, p less than 0.001) and 9 mo (r = 0.41, p = 0.06). When breast-feeding was stopped, the high BGP concentrations were not sustained. There were no significant differences in linear growth velocity between breast-fed and formula-fed infants and no correlation between BGP values and linear growth velocity. We speculate that either a factor in human milk or the level of minerals in human milk causes the high BGP values. Moreover, if the higher values are associated with increased osteoblast activity, then the remodeling or the mineralization of bone might be different in infants not being breast-fed.