Profile of Nucleotides and Nucleosides in Taiwanese Human Milk

BackgroundHuman milk–borne nucleotides and their related metabolic products have been reported to have important physiological roles in breast-fed infants. The purpose of this study was to measure the concentrations of free nucleotides and nucleosides in human milk from Taiwanese women.MethodsA total of 24 individual milk specimens were collected from women in Taipei and Kaohsiung, at four stages of lactation. Vegetarian or non-vegetarian dietary patterns were recorded. The samples were analyzed for nucleotides and nucleosides by high-performance liquid chromatography.ResultsThe mean (±standard deviation) free nucleotide and nucleoside concentrations in Taiwanese human milk were 213.13 ± 76.26 μmol/L and 16.38 ± 7.11 μmol/L. The predominant nucleotide was cytidine diphosphate for almost all samples, regardless of the location, stage of lactation, or dietary status of the subjects. Overall, the mean concentrations of cytidine diphosphate, cytidine monophosphate, uridine monophosphate, guanosine monophosphate, adenosine monophosphate, and inosine monophosphate, in milk samples were 129.86 μmol/L, 49.10 μmol/L, 5.60 μmol/L, 0.82 μmol/L, 2.96 μmol/L, and 25.25 μmol/L, respectively (equivalent to 61.0%, 23.1%, 2.6%, 0.4%, 1.0%, and 11.9% of free nucleotide composition). In free nucleosides, cytidine and uridine were predominant during all stages of lactation. The average concentrations of cytidine, uridine, adenosine, guanosine, and inosine, in milk samples were 9.25 μmol/L, 6.33 μmol/L, 0.18 μmol/L, 0.36 μmol/L, and 0.23 μmol/L, respectively (equivalent to 56.5%, 38.7%, 1.1%, 2.2%, and 1.4% of free nucleoside composition). Comparing vegetarian and non-vegetarian statuses, it was found that the total free nucleotide concentration was high in the vegetarian group (p = 0.037).ConclusionOur data showed a wide range of concentrations of individual nucleotides and nucleosides in Taiwanese human milk. Unique dietary status could affect the nucleotide and nucleoside levels in human milk, especially the nucleotides in our study. However, the mechanism of modulation of nucleotide and nucleoside levels in human milk is not clear.