Association Between Human Milk-Targeted Metabolites and Maternal Characteristics: Targeted Metabolomic Profiling of...

Background/Objectives: Human milk (HM) is recognized as the optimal source of infant nutrition, particularly during the first six months of life. While its nutritional aspects and bioactive components are well studied, the HM metabolome remains less understood, particularly in low- and middle-income countries. This study utilized targeted metabolomics for HM profiling and investigated associations of the HM metabolome with maternal and infant characteristics. Methods: In total, 267 HM samples and demographic data from mothers participating in the Maternal and environmental Impact assessment on Neurodevelopment in Early childhood years (MINE) study were collected during enrolment (up to 6-months postpartum) and analyzed using the MxP^® Quant 500 targeted metabolomics kit from Biocrates. Results: A total of 440 metabolites were quantified, mostly lipids such as triglycerides (59.73%), phosphatidylcholines (14.25%), and diglycerides (8.49%), and small molecules including amino acids (26.67%), amino acid-related compounds (21.33%), hexosylceramides (17.33%), and fatty acids (14.67%). Maternal age was positively correlated with a wide range of metabolites, mainly cholesteryl esters, sphingomyelins, triglycerides, and acylcarnitines, while child age was associated with metabolites belonging to acylcarnitine, phosphatidyl-choline, ceramide, diacylglycerol, sphingomyelin, and triglyceride classes. Child's gender was associated with metabolites, including ceramides, phosphatidylcholines, and sphingomyelins. Pathway enrichment analysis revealed that the metabolites were significantly enriched in valine, leucine, and isoleucine biosynthesis; arginine biosynthesis; phenylalanine, tyrosine, and tryptophan biosynthesis; and glutathione metabolism; however, these reflect annotation-based clustering rather than evidence of active metabolic processes in HM. Conclusions: The HM metabolome varies with maternal and infant characteristics, particularly infant age, reflecting cross-sectional differences in milk composition among mother-infant dyads. Enrichment of metabolites annotated to amino acid and antioxidant-related pathways highlights coordinated representation of nutritionally relevant compounds. These findings provide new insight into the factors shaping HM composition in a low- and middle-income populations.