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.

Biomedical Research Centre University Hospital Hradec Kralove Hradec Kralove Czech Republic

Department of Paediatrics 48234 University Hospital Hradec Kralove Hradec Kralove Czech Republic

Department of Paediatrics Faculty of Medicine Hradec Kralove Charles University Prague Hradec Kralove Czech Republic

Institute of Clinical Biochemistry and Diagnostics Faculty of Medicine Hradec Kralove Hradec Kralove Czech Republic

Institute of Clinical Biochemistry and Diagnostics University Hospital Hradec Kralove Hradec Kralove Czech Republic

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