Relationship of MicroRNA according to Immune Components of Breast Milk in Korean Lactating Mothers

Human breast milk (HBM) contains immune components that produced and delivered from the mother along with nutrients necessary for the baby. MicroRNA (miRNA) is a small noncoding RNA molecule, that is used as an ideal biomarker for diagnosis and prognosis of various diseases and are more abundant in HBM. We analyzed and compared the immune components and miRNAs of HBM.

HBM were collected from 20 healthy breastfeeding mothers. We measured the amount of lactoferrin, lysozyme, and immunoglobulin A (IgA) and extracted the miRNAs from each breast milk samples. Next, the top 5 and bottom 5 expressed miRNAs were compared and analyzed based on the amounts of the 3 immune components.

The mean levels and ranges of lactoferrin, lysozyme, and IgA were 6.33 (2.24-14.77)×10⁶ ng/mL, 9.90 (1.42-17.59)×10⁷ pg/mL, and 6.64 (0.48-20.01)×10⁵ ng/mL, respectively. The miRNAs concentration per 1 mL of skim milk was 40.54 (14.95-110.01) ng/μL. Comparing the bottom 5 and top 5 groups of each immune component, 19 miRNAs were significantly upregulated (6, 9, and 4 targeting lactoferrin, lysozyme, and IgA, respectively) and 21 were significantly downregulated (4, 9, and 8 targeting lactoferrin, lysozyme, and IgA, respectively). There were no miRNAs that were expressed significantly higher or lower in common to all 3 components. However, 2 and 3 miRNAs were commonly overexpressed and underexpressed, in the top 5 groups of lysozyme and IgA concentrations.

We identified the immune components and miRNAs in breast milk and found that each individual has different ingredients.