Breast milk microRNA profile is influenced by mother’s dietary polyphenol intake

Epidemiological studies suggest that a high dietary intake of polyphenols (PPs) is associated with decreased risk of diseases development. Nowadays, it is commonly accepted that most of the physiological effects of PPs are being mediated by their capacity to modulate the expression of genes, including microRNAs (miRNA) genes. MiRNAs are small noncoding RNAs involved in the regulation of numerous biological processes, including infant development. Maternal dietary intake partially influences the PP concentrations of human milk as well as other milk component including miRNA. The objective of this pilot study is to evaluate the influence of maternal PP intake on miRNAs in milk, still largely unknown, that could impact babies’ health.

Human breast colostrum (days 1-5 postpartum; n=10) and mature milk (>21 days postpartum; n=10) were collected from women at the Human Milk Bank at Hospital das Clínicas and Hospital Universitário, São Paulo, Brazil. The food consumption was

assessed using 24-hour food recalls conducted on two non-consecutive days. The identification and quantification of phenolic compounds will be performed by LC-MS/MS. Total RNAs were extracted from 200 L of colostrum (n=6) and mature milk (n=7) using RNeasy kit with TriZol LS. Small-RNA-sequencing and bioinformatics analysis were performed at BMKGenomics. Pearson correlation between miRNA expression levels and major PP intake was calculated using SRplot.

Preliminary data showed that total PP intake was higher in the immediate postpartum period (637.12±203.67 mg/day) than at 1-2 months postpartum (365.70± 144.57 mg/day), although a high overlap between the two periods was observed. RNA extraction yield from mature milk (267.9 ng/mL) was ca. 58% higher than the one obtained from colostrum (157.2 ng/mL). RNA-sequencing allowed to determine the miRNA profile (miRNomes) in both colostrum and mature milk. Ongoing analyses have identified a correlation between abundant miRNAs and the amount of PPs consumed by mothers. For example, two abundant miRNAs in milk, let-7g and miR-26a contents are correlated with the consumption of phenolic acids and proanthocyanidins, respectively. The results indicate that the PP consumption may impact miRNAs levels in breast milk. Further bioinformatic analysis will allow us to assess the impact of food source PP on miRNAs with potential roles in infant health. 

In conclusion, to the best of our knowledge, this is the first study to evaluate the influence of maternal PP intake on miRNA profiles in colostrum and mature milk. The analysis identified the breast milk miRNomes and changes in miRNAs levels associated with variations in PP intake. Given the potential role of milk miRNAs in infant development, these findings suggest that PP consumption by breastfeeding mothers may confer additional benefits for infants.