Abstract
BackgroundMilk-derived microRNAs (miRNAs), including hsa-miR-148a-3p (miR-148a) and hsa-miR-125b-5p (miR-125b), have been shown to be beneficial to the gastrointestinal function in infants. Here, we investigated their expression during lactation in humans and determined whether the infant formulae available in Japan contain these miRNAs.MethodsHealthy Japanese women (n = 16) who gave birth vaginally or by cesarean section at the Teine Keijinkai Hospital between 1 September 2020, and 31 April 2021 were included in this study. Breast milk was collected by nurses on days 4 or 5 after delivery (hereinafter, transition milk) and on day 30 of postpartum (hereinafter, mature milk). The levels of miR-148a and miR-125b in breastmilk and six commercially available infant formulae were compared and evaluated using quantitative reverse transcription-polymerase chain reaction.ResultsIn all participants, the miR-148a level in mature breastmilk was significantly lower than that in the transition milk. The changes in miR-125b expression during lactation showed similar trends to the changes in miR-148a expression. The miR-148a and miR-125b levels in all analyzed infant formulae were lower than 1/500th and 1/100th of those in mature breastmilk, respectively.ConclusionsThe levels of both miR-148a and miR-125b in human breast milk decreased on day 30 postpartum compared with those in the transition milk. Additionally, the expression of these miRNAs in infant formulae available in Japan was very low. Further studies with larger populations are required to understand precisely the lactational changes in the expression of miR148a and miR-125b in breast milk.
Highlights
Milk-derived microRNAs, including hsa-miR-148a-3p and hsa-miR-125b-5p, have been shown to be beneficial to the gastrointestinal function in infants
Several hundred of miRNAs have been detected in breast milk, most of which are synthesized by mammary epithelial cells [8,9,10,11]
Patient characteristics In this study, we aimed to investigate the changes in miR-148a and miR-125b levels during lactation and compare them with those in six infant formulae commercially available in Japan
Summary
Milk-derived microRNAs (miRNAs), including hsa-miR-148a-3p (miR-148a) and hsa-miR-125b-5p (miR125b), have been shown to be beneficial to the gastrointestinal function in infants. MicroRNAs (miRNA) are short (approximately 22 nucleotides long), non-coding RNAs found in various body fluids, such as the blood, saliva, urine, and milk. They control several biological processes in cells, including cell growth, differentiation, and apoptosis [7]. When fluorescence-labeled bovine milk-derived exosomes were orally administered to mice, the exosomes were detected in the brain, liver, lung, and spleen of the mice [15] These observations show that milk exosomes and milkderived miRNAs reach some tissues in infants via general circulation
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