Plasma 3‐epi‐25‐hydroxyvitamin D3 in Very Low Birth Weight Preterm Infants in Canada During the First Five Weeks After Birth

Vitamin D status during infancy is important for skeletal growth and development. Response to vitamin D 3 supplementation is complicated by the presence of 3‐epi‐25‐hydroxyvitamin D 3 (3‐epi‐25‐OH‐D 3 ). We undertook a small prospective study to simultaneously examine changes in 25‐OH‐D 3 , 3‐epi‐25‐OH‐D 3 and 24,25‐dihydroxyvitamin D 3 (24,25‐(OH) 2 D 3 ) in preterm infants over the first five weeks after birth. Nineteen infants from Manitoba, born before 32 weeks of gestation and <1500 g, were included in the study. Plasma samples were obtained at the end of the first (wk1) and fifth (wk5) week after birth.Vitamin D metabolites were analyzed in triplicate using LC‐MS/MS. Differences over time were tested using ANOVA and Bonferroni post hoc test, p<0.05. Mean gestational age at birth was 29.0 ± 1.5 weeks and birth weight 1144.5 ± 244.4 g. Total vitamin D intake increased over time (Table). Increases were observed in vitamin D status based on plasma 25‐OH‐D 3 concentration over the first 5 weeks (wk1: 18.1 ± 7.1 vs wk5: 25.3 ± 10.6 ng/ml, p=0.02) as well as in 3‐epi‐25‐OH‐D 3 (wk1: 5.1 ± 4.2 vs wk5: 20.0 ± 15.9 ng/ml, p<0.0001). Over the same time‐period 24,25‐(OH) 2 D 3 (wk1: 0.9 ± 0.5 vs wk5: 0.7 ± 0.5 ng/ml, p=0.13) was not significantly changed.This work showed that 3‐epi‐25‐OH‐D 3 increased over the first 5 weeks in parallel with increases of 25‐OH‐D 3 while 24,25‐(OH) 2 D 3 was relatively stable suggesting the CYP24A1 activity does not readily mature during 5 weeks postnatally in prematurely born infants.Vitamin D intake from all sources (IU/day) Mean SD Min Max Week 1 202.8 a 115.9 4.5 400.7 Week 2 189.3 a 118.0 54.9 442.8 Week 3 250.8 a 155.7 65.0 551.9 Week 4 366.2 b 163.6 42.5 626.3 Week 5 489.3 c 186.9 93.1 736.7 Week 6 515.9 c 192.5 177.7 779.6Means with different superscript letters are different, p<0.05