622 - Accurate determination of serum 3-epi-25-hydroxyvitamin D₃ in preterm infants and its relationship with gestational age

Publication Number: 1599.622

Kazumi Morisawa, Keio University School of Medicine, Nerima-ku, Tokyo, Japan; Kaori Hara-Isono, Keio University School of Medicine, Tokyo, Tokyo, Japan; Arimitsu Takeshi, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan; Hida Mariko, Saitama City Hospital, Saitama, Saitama, Japan; Kazushige Ikeda, Saitama City Hospital, Saitama City, Saitama, Japan; Shota Muramatsu, Keio University Hospital, Shinjuku-ku, Tokyo, Japan; Terumichi Nakagawa, Keio university hospital, Shinjuku-ku, Tokyo, Japan; Matsushita Hiromichi, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan; Hasegawa Tomonobu, Keio University, Nakano, Tokyo, Japan; Narumi Satoshi, Keio University, Tokyo, Tokyo, Japan

Background: 3-epi-25-hydroxyvitamin D₃ (3-epi-25(OH)D₃) is one of the major metabolites of vitamin D produced through the epimerization of Vitamin D₃ in the liver, kidney, and bone. Previous studies have reported higher levels of 3-epi-25(OH)D₃ in pregnant women, fetuses, and newborns compared with adults, suggesting its potential roles during the perinatal period. However, its physiological role and regulatory mechanism in vivo remain to be elucidated. In addition, due to the technical difficulty of measurement, previously reported serum 3-epi-25(OH)D₃ levels vary widely. We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay capable of accurately separating and quantifying 3-epi-25(OH)D₃ and 25(OH)D₃.

Objective: The aim of this study was to clarify the serum 3-epi-25(OH)D₃ levels in preterm infants and examine their association with gestational age and birthweight.

Design/Methods: We included 106 preterm infants born between 25 and 36 weeks of gestation at three hospitals in Japan from September 2023 to March 2025 who required a blood test at birth or day one of age. Using residual serum samples, we measured serum 25(OH)D₃ and 3-epi-25(OH)D₃ levels by LC-MS/MS and calculated %epi (3-epi-25(OH)D₃ / (25(OH)D₃ + 3-epi-25(OH)D₃). Correlations of 25(OH)D₃, 3-epi-25(OH)D₃, and %epi with gestational age and birth weight were evaluated using Spearman's rank correlation coefficient.

Results: The median (IQR) gestational age was 34 2/7 weeks (32 4/7, 35 5/7), and the median birth weight was 1970 g (1494, 2278). Median serum 25(OH)D₃ and 3-epi-25(OH)D₃ levels were 10.4 ng/mL (7.5, 13.8), and 0.8 ng/mL (0.6, 1.2), respectively. The median of %epi was 8.0 % (7.3, 8.7). Serum 25(OH)D₃ and 3-epi-25(OH)D₃ levels were not correlated with gestational age, whereas %epi showed a negative correlation with gestational age (r = −0.201, p = 0.0386). No correlations between the levels of 25(OH)D₃, 3-epi-25(OH)D₃, or %epi and birth weight were identified.

Conclusion(s): This study is the first to determine the accurate serum 3-epi-25(OH)D₃ levels in preterm infants and reveal a weak negative correlation between %epi and gestational age. Our findings suggest that epimerase activity tends to be elevated in infants with a shorter gestational period, indicating that the production of 3-epi-25(OH)D₃ is increased due to hepatic immaturity and that 3-epi-25(OH)D₃ may play a physiological role during the perinatal period.

Dynamics and potential functions of 3-epi-25(OH)D₃
Dynamics and potential functions of 3-epi-hydroxyvitamin D₃ (3-epi-25(OH)D₃)

25(OH)D₃, 3-epi-25(OH)D₃, and %epi vs. gestational age
25(OH)D₃, 3-epi-25(OH)D₃, and %epi vs. gestational age. %epi represents the ratio of 3-epi-25(OH)D₃ to the sum of 25(OH)D₃ and 3-epi-25(OH)D₃. 25(OH)D₃, 25-hydroxyvitamin D₃, 3-epi-25(OH)D₃, 3-epi-25-hydroxyvitamin D₃.