Human Milk Cells and Lipids Conserve Numerous Known and Novel miRNAs, Some of Which Are Differentially Expressed during Lactation

Abstract

Human milk (HM) is rich in miRNAs, which are thought to contribute to infant protection and development. We used deep sequencing to profile miRNAs in the cell and lipid fractions of HM obtained post-feeding from 10 lactating women in months 2, 4, and 6 postpartum. In both HM fractions, 1,195 mature known miRNAs were identified, which were positively associated with the cell (p = 0.048) and lipid (p = 0.010) content of HM. An additional 5,167 novel miRNA species were predicted, of which 235 were high-confidence miRNAs. HM cells contained more known miRNAs than HM lipids (1,136 and 835 respectively, p<0.001). Although the profile of the novel miRNAs was very different between cells and lipids, with the majority conserved in the cell fraction and being mother-specific, 2/3 of the known miRNAs common between cells and lipids were similarly expressed (p>0.05). Great similarities between the two HM fractions were also found in the profile of the top 20 known miRNAs. These were largely similar also between the three lactation stages examined, as were the total miRNA concentration, and the number and expression of the known miRNAs common between cells and lipids (p>0.05). Yet, approximately a third of all known miRNAs were differentially expressed during the first 6 months of lactation (p<0.05), with more pronounced miRNA upregulation seen in month 4. These findings indicate that although the total miRNA concentration of HM cells and lipids provided to the infant does not change in first 6 months of lactation, the miRNA composition is altered, particularly in month 4 compared to months 2 and 6. This may reflect the remodeling of the gland in response to infant feeding patterns, which usually change after exclusive breastfeeding, suggesting adaptation to the infant’s needs.

Cafeteria Diet Consumption during Lactation in Rats, Rather than Obesity Per Se, alters miR‐222, miR‐200a, and miR‐26a Levels in Milk

“…Several specific miRNAs are endogenously produced in the mammary gland and are involved in the synthesis and regulation of milk components such as fatty acids, triacylglycerol, lactose, and others, supporting the involvement of miRNA in the normal function of the lactating mammary gland . The miRNAs expression pattern in breast tissue changes in the different periods of mammary gland development, including the lactating period . Some of these miRNAs are related to milk fat metabolic activity in mammary gland development and lactation .…”

Milk MicroRNAs in Health and Disease

“…Differences in protocols and milks used for these studies, including milk processing or the use of purified milk EVs, might underline the discrepancies observed for milk microRNA resistance towards degradative conditions. Raw and processed milk have indeed different microRNA profiles (Alsaweed, Hepworth, et al., , , ; Alsaweed, Lai, Hartmann, Geddes, & Kakulas, ), with possibly more free microRNAs in raw milk (Tome‐Carneiro et al., ). In the view of these data, it seems that processing might act as a selective pressure discarding most fragile milk EVs, and associated microRNAs or unprotected microRNAs,although keeping the most robust form of these two entities (Benmoussa et al., , ; Golan‐Gerstl et al., ; Kirchner et al., ; Melnik et al., , , ).…”

“…The majority of studies have only investigated this matter in silico using microRNA‐target identification tools and associated pathways/gene ontology analysis (Alsaweed et al., , ; Cai et al., , ; Carney et al., ; Chen et al., , , ; Chokeshaiusaha, Sananmuang, Puthier, & Nguyen, ; Do, Li, Dudemaine, & Ibeagha‐Awemu, ; Golan‐Gerstl, Elbaum Shiff, et al., ; Gu et al., , ; Hou et al., ; Kang et al., ; Li et al., , ; Liao et al., ; Liu et al., ; Lukasik & Zielenkiewicz, ; Modepalli et al., ; Munch et al., ; Shen et al., ; Simpson et al., ; Sun et al., ; Wang et al., ; Zhang et al., ; Zhou et al., ).…”

Roles of MicroRNA across Prenatal and Postnatal Periods

“…Using a model GI tract, bovine milk exosomes have been shown to withstand the harsh conditions of the gut [79]. There are a number of known and unknown miRNAs conserved in human milk cells and lipids that are differentially expressed during lactation [80]. Exogenous food-derived miRNAs appear to be stable in the oral cavity and in the GI tract and are transferred to the blood of adults, thought to influence gene expression in different tissues [81,82,83].…”