OBJECTIVES: To describe the structure of vitamin D metabolome and investigate the possible cause of high serum levels of C3 epimers of 25-(OH)D in preterm infants, we compared the vitamin D metabolites in umbilical cord blood with serum samples taken at 28 days of age. METHODS: We analysed 40 preterm infants (29+0-32+6 weeks of gestation). Cholecalciferol, 25-(OH)D, and its C3-epimers were measured using liquid chromatography. A microsomal study with human liver and kidney microsomes was conducted to assess vitamin D metabolism. Identified metabolites were then examined in cord blood and serum samples. RESULTS: Cholecalciferol, 25-(OH)D, and its C3-epimers were significantly lower in cord blood compared to serum at 28 days of age (p<0.001 for all metabolites). Conversely, metabolites from the microsomal study (monohydroxylated-, dihydroxylated-, and mono-oxylated dihydroxylated-cholecalciferol and their C3-epimers) were significantly higher in cord blood (p<0.001 for all). CONCLUSIONS: Our findings indicate that cholecalciferol, 25-(OH)D, and its C3-epimers increase during the first month of life, suggesting functional biosynthesis and postnatal accumulation of these metabolites. Conversely, based on microsomal study results, it seems that biotransformation responsible for a degradation of vitamin D during the first month of life in preterm infants is functionally impaired.

• Keywords
• LC-MS/MS, metabolome, metabolomics, microsomes, preterm infant, vitamin D,
• Publication type
• Journal Article MeSH