Background/objectives: Specific microRNAs (miRNAs) that are known to have roles in various physiological and pathological processes in mammals are found in human breast milk, but the impact of maternal status on miRNA levels in milk is not fully understood. The objective of this study was to explore maternal and infant factors that can potentially influence the levels of let-7a (MIMAT0000062), miRNA-30B (MIMAT0000420) and miRNA-378 (MIMAT0000732) in human milk, all of which are known to participate in adipogenesis.
Subjects/methods: Colostrum from 86 mothers and mature milk from 33 mothers were collected. The miRNA levels in these samples were determined using real-time PCR. Correlations between the levels of these miRNAs and lactation duration, maternal weight/BMI before and late in the pregnancy, maternal age, gestational weeks and infant gender were analysed.
Results: The levels of let-7a (2.58±0.67) and miRNA-378 (4.64±0.69) in colostrum were higher than those in mature milk (2.39±0.62, 3.62±0.77, P<0.01). Conversely, the level of miRNA-30B was higher in mature milk (4.92±0.57) than in colostrum (4.05±0.61, P<0.01). The levels of miRNA-30B, let-7a and miRNA-378 in colostrum were negatively correlated with maternal pre-pregnancy BMI (P<0.01), and, in mature milk, let-7a was negatively correlated with maternal weight late in the pregnancy (P<0.05). Moreover, miRNA-30B and miRNA-378 were higher in the colostrum received by girls than in that received by boys (P<0.01). This pattern held for miRNA-378 when controlling for maternal pre-pregnancy BMI.
Conclusions: Adipogenesis miRNAs were expressed in both colostrum and mature milk and were related to maternal weight and infant gender. The miRNAs in human milk determined in this study provide a basis for future studies of their biological functions in infants.