Dynamics of the vitamin D C3-epimer levels in preterm infants

Abstract

Objectives The primary objective was to determine levels of C3-epi-25(OH)D in very low birth weight infants. The secondary objective was to evaluate the possible influence of preterm birth, intrauterine growth restriction (IUGR), and season of birth on the production of C3-epimers. Methods A total of 127 infants with birth weight less than 1,500 g met the inclusion criteria of the study. We examined 25-hydroxyvitamin-D [25(OH)D] levels and C3-epi-25(OH)D in maternal serum before labor, and in cord blood and infants’ serum on days 14 and 28, and at discharge. Results The mean levels (±SD) of C3-epi-25(OH)D of the cord, on day 14, on day 28, and at discharge were 2.2 (2.9), 7.7 (5.5), 11.7 (7.6) and 14.9 (11.7) nmol/L respectively. The proportion of total 25(OH)D as the C3-epimer was 6.9% (cord), 16.3% (day 14), 22.4% (day 28) and 23.3% (discharge). A statistically significant correlation between 25(OH)D and C3-epi-25(OH)D can be demonstrated from birth. The severity of immaturity and IUGR did not affect the production of C3-epimers. In summer/autumn vs. winter/spring, the mean (SD) percentage of total 25(OH)D as the C3-epimer significantly differs only in maternal serum samples and umbilical cord samples (p value <0.001). Conclusions The production of C3-epi-25(OH)D is functional even in the most immature newborns, has fetal origins, and is largely dependent on circulating 25(OH)D. At the end of the first month of life, C3-epimers make up more than 20% of 25(OH)D.

Is 25OH Vitamin D Excess before 36 Weeks Corrected Age an Independent Risk Factor for Bronchopulmonary Dysplasia or Death?

“…The next factor that could explain the discrepancy between the results observed in the animal model reported by Chen et al [14] and the present study is that in this animal study the active form of vitamin D, namely 1,25(OH) 2 D, was used, whereas native vitamin D was used herein, according to clinical practice. Using 1,25(OH) 2 D, the physiological regulation of the production of 1,25(OH) 2 D is circumvented, even though the limiting factor of this synthesis as classically described is the availability of 25(OH)D in preterm infants [40], but the regulation in extremely and very preterm infants and in particular the function of the C3 epimers are still not fully elucidated [41,42]. The results of the studies reported by Wang et al and Mandell et al in rodent pups exposed to hyperoxia receiving native vitamin D demonstrated improved lung histology but 25(OH)D was measured at low and normal levels, not allowing conclusions on supraphysiological doses [3,43].…”