Milk-Derived Extracellular Vesicles and microRNAs: Potential Modulators of Intestinal Homeostasis

Milk represents a complex pool of nutrients and bioactive components that are indispensable for the growth and development of the infant. The key well-established roles played by milk's bioactive components in the infant are those at the level of the infant's intestinal and immune development. Through its bioactive components, including proteins, lipids, and oligosaccharides, milk helps the infant develop a mature intestinal identity with fully active digestive, absorptive, and barrier capacity and shapes both innate and adaptive immune responses. Recent evidence points to a new class of milk bioactive components including milk extracellular vesicles (EVs) and microRNAs, which are hypothesized to take part in contributing to infant development. The potential functions of milk microRNAs and EVs in the consumer's systems are not limited to the infant as these components can also be found in bovine milk, both raw and processed. Hence, adult consumers could also be influenced by milk EVs and microRNAs, which could affect their intestinal homeostasis particularly under pathological conditions. Nonetheless, the debate regarding the stability of milk EVs and microRNAs in the digestive tract persists, and their bioavailability and bioactivity in the consumer's tissues are still arguable. In this review, we discuss the potential functions mediated by milk microRNAs and EVs in the epithelial and immune components as well as the microbiome of the intestinal mucosa in health and disease. We also discuss the bioavailability, bioaccessibility, and bioactivity of milk EVs and microRNAs in consumer's tissues.