Association between Human Milk Fatty Acid Esters of Hydroxy Fatty Acids and Maternal Body Mass Index and Early Infant Growth: A Longitudinal Study

Background: Fatty acid esters of hydroxy fatty acids (FAHFAs) are a novel class of endogenous lipids with biologically active functions in human. Objectives: Our objective was to determine the role of maternal body mass index (BMI) in breast milk (BM) FAHFA composition and delineate the association between these BM fatty acids and infant growth during the first 6 mo postpartum. Methods: We recruited 65 healthy singleton pregnant females from the obstetric clinic. Regular mother-child follow-up was performed at 3 d (V1), 42 d (V2), 3 mo (V3), 4 mo (V4), and 6 mo (V5) after birth. High-throughput targeted metabolomics was used to detect the content of 9 representative FAHFA isomers in BM. Multivariate linear mixed models were conducted. The Holm-Bonferroni stepdown procedure was utilized to control the type I error rate in multiple comparisons. Results: As compared with the normal-weight mothers, the mothers with obesity/overweight had higher contents of 5-palmitic acid esters of hydroxy stearic acid (PAHSA) in colostrum (V1) and 9-stearic acid esters of hydroxy stearic acid (SAHSA) in mature milk (V2) (corrected P = 0.013 and 0.044, respectively), and lower contents of 13-linoleic acid esters of hydroxy linoleic acid (LAHLA in mature milk (V2 and V3) (corrected P = 0.028 and 0.005, respectively). The mean concentrations of 9-PAHSA in mature milk (V2 and V3) showed positive correlations with children's fat-free mass index ( FFMI), whereas those of 5-PAHSA, 10-oleic acid esters of hydroxy stearic acid (OAHSA), and 9-palmitic acid esters of hydroxy palmitic acid (PAHPA) were negatively correlated with children's fat mass index (FMI) (corrected P < 0.05 for all). Conclusions: Higher maternal BMI was associated with higher concentrations of 2 saturated FAHFAs (5-PAHSA and 9-SAHSA) and a lower concentration of 1 polyunsaturated FAHFA (13-LAHLA) in BM. Specific FAHFA isomers were associated with growth and body composition development in exclusively breastfed infants during early infancy. Expanding the sample size and conducting further research is necessary to explore the mechanisms of action in the future.