Extracellular vesicle microRNAs in breastmilk of mothers with overweight and obesity: a systematic review.

Breastmilk (BM) is the optimal nutrition source that supports both short- and long-term health in the growing infant. Breastfeeding also has direct implications for maternal health, with breastfeeding mothers shown to have reduced risk of developing certain diseases including diabetes, some cancers and protection from postpartum depression. BM contains numerous biologically active substances, with milk-borne microRNAs (miRNAs) reported to be associated with a range of physiological processes and health outcomes. BM is an abundant source of miRNAs that present as either free molecules or packaged inside extracellular vesicles (EVs). EVs are lipid-bound vesicles that transport bioactive molecules to recipient cells. miRNAs enclosed in EVs (EV-miRNAs) can survive the digestive environment of an infant's gut and enter the bloodstream, whereby they travel to distant organs and regulate their function. This systematic review provides an overview of EV-miRNAs that have been characterised in the BM of mothers who are overweight or obese, and the associations between these miRNAs and maternal and infant health outcomes in this specific population group. IMPACT: This systematic review provides an overview of extracellular vesicle (EV)-miRNAs that have been characterised in the breastmilk of mothers with overweight and obesity and the associations between these microRNAs with maternal and infant health outcomes. Breastmilk EV research is emerging, with limited number of studies, particularly in mothers with overweight and obesity, making it difficult to fully understand how maternal metabolic status influences EV-miRNAs and its potential effects on infant health. The lack of standardised protocols to isolate and analyse EV-miRNAs and maternal and infant outcome measures reported in clinical studies makes data synthesis challenging, thus preventing conclusive results.