Exploring the effect of vitamin D and DHA supplementation on the urine metabolome of preterm infants by 1H NMR-based metabolomics

Background and objectives: Vitamin D and docosahexaenoic acid (DHA) insufficiency and deficiency could potentially have a great impact on health outcomes in preterm infant. Due to the importance of early nutrition intervention in this population and given the lack of metabolomic studies concerning the supplementations effect on the metabolome of preterm infants, 44 premature infants were studied, divided in two groups, one receiving only vitamin D (DS) and the second both vitamin D and DHA (D-DHAS) supplementation. Two were the main objectives of the study: 1) to look at changes over time in the urinary metabolic profiles of infants before and over two months of supplementation; 2) to compare the urinary metabolome of the two groups after supplementation. Methods: 1H NMR-based metabolomics approach was used to analyze urine samples obtained from preterm newborns at three different time points: at the time of hospital discharge and before supplementation (T0), 1 month (T1) and 2 months (T2) after the beginning of supplementation. Results: A clear temporal dynamics of the urinary metabolic profiles of preterm infants was highlighted by OPLS analysis. Both groups were characterized by growing levels of betaine, N,N-dimethylglycine, creatinine, creatine and guanidinoacetate and diminishing levels of myo-inositol and hydroxyproline with increasing postmenstrual age (PMA). Additionally, for D-DHAS citrate and dimethylamine increased, while lactate decreased over time. OPLS-DA clearly discriminated the two groups after two months of supplementation. Compared to DS, D-DHAS group was characterized by higher levels of betaine, N,N-dimethylglycine, creatinine and dimethylamine and lower amounts of lactate and myo-inositol. Conclusions: Metabolomic analysis of urine from the neonatal period could be a useful tool to understand metabolic processes linked to early nutrition and supplementation. According to our results, vitamin D supplementation exerts in preterm newborns positive effects evaluated with urinary metabolomics. Moreover, it seems that the supplementation with vitamin D and DHA exerts a higher antioxidant and protective action on newborns, and it could also positively affect the body fat composition.