| Abstrakt: |
Background:An epimeric form of 25-hydroxyvitamin D3(25(OH)D3) has recently been detected in clinical samples, with relatively high levels in infants. Little is known on 3-epi-25(OH)D3formation and physiological function. Our objective was to study dynamics of 3-epi-25(OH)D3formation during infancy.Methods:25(OH)D3and 3-epi-25(OH)D3levels were measured by liquid chromatography-tandem mass spectrometry in 22 preterm (aged 34–37?wk), 15 early preterm (aged <34?wk), and 118 term infants up to 2 y of age. All infants were prescribed vitamin D 400 IU/day after the first week of life.Results:At birth, 3-epi-25(OH)D3levels were 3 (1–7) nmol/l, <10% of total 25(OH)D3. From the second week to 3 mo of age, both 25(OH)D3and 3-epi-25(OH)D3increased, with highest 3-epi-25(OH)D3contribution in early preterm infants (up to 55% of total 25(OH)D3vs. 36% in term infants, P < 0.0001). After 3 mo of age, 3-epi-25(OH)D3normalized to <10% in all infants.Conclusions:At birth, all infants showed low contribution of 3-epi-25(OH)D3, increasing the week after starting vitamin D supplementation, until 3 mo of age. Highest levels of 3-epi-25(OH)D3were found in early preterm infants, supporting the hypothesis that hepatic immaturity plays a role in 3-epi-25(OH)D3formation. |
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