Extracellular vesicles (EVs) in milk harbor a variety of compounds, including lipids, proteins, noncoding RNAs, and mRNAs. Among the various classes of EVs, exosomes are of particular interest, because cargo sorting in exosomes is a regulated, nonrandom process and exosomes play essential roles in cell-to-cell communication. Encapsulation in exosomes confers protection against enzymatic and nonenzymatic degradation of cargos and provides a pathway for cellular uptake of cargos by endocytosis of exosomes. Compelling evidence suggests that exosomes in bovine milk are transported by intestinal cells, vascular endothelial cells, and macrophages in human and rodent cell cultures, and bovine-milk exosomes are delivered to peripheral tissues in mice. Evidence also suggests that cargos in bovine-milk exosomes, in particular RNAs, are delivered to circulating immune cells in humans. Some microRNAs and mRNAs in bovine-milk exosomes may regulate the expression of human genes and be translated into protein, respectively. Some exosome cargos are quantitatively minor in the diet compared with endogenous synthesis. However, noncanonical pathways have been identified through which low concentrations of dietary microRNAs may alter gene expression, such as the accumulation of exosomes in the immune cell microenvironment and the binding of microRNAs to Toll-like receptors. Phenotypes observed in infant-feeding studies include higher Mental Developmental Index, Psychomotor Development Index, and Preschool Language Scale-3 scores in breastfed infants than in those fed various formulas. In mice, supplementation with plant-derived MIR-2911 improved the antiviral response compared with controls. Porcine-milk exosomes promote the proliferation of intestinal cells in mice. This article discusses the above-mentioned advances in research concerning milk exosomes and their cargos in human nutrition. Implications for infant nutrition are emphasized, where permitted, but data in infants are limited.

Encapsulation of microRNAs in exosomes confers protection against degradation and a vehicle for shuttling of microRNAs between cells and tissues, and cellular uptake by endocytosis. Exosomes can be found in foods including milk. Humans absorb cow's milk exosomes and deliver the microRNA cargo to peripheral tissues, consistent with gene regulation by dietary nucleic acids across species boundaries. Here, we tested the hypothesis that human vascular endothelial cells transport milk exosomes by endocytosis, constituting a step crucial for the delivery of dietary exosomes and their cargo to peripheral tissues. We tested this hypothesis by using human umbilical vein endothelial cells and fluorophore-labeled exosomes isolated from cow's milk. Exosome uptake followed Michaelis-Menten kinetics (Vmax = 0.057 ± 0.004 ng exosome protein × 40,000 cells/h; Km = 17.97 ± 3.84 μg exosomal protein/200 μl media) and decreased by 80% when the incubation temperature was lowered from 37°C to 4°C. When exosome surface proteins were removed by treatment with proteinase K, or transport was measured in the presence of the carbohydrate competitor d-galactose or measured in the presence of excess unlabeled exosomes, transport rates decreased by 45% to 80% compared with controls. Treatment with an inhibitor of endocytosis, cytochalasin D, caused a 50% decrease in transport. When fluorophore-labeled exosomes were administered retro-orbitally, exosomes accumulated in liver, spleen, and lungs in mice. We conclude that human vascular endothelial cells transport bovine exosomes by endocytosis and propose that this is an important step in the delivery of dietary exosomes and their cargo to peripheral tissues.

Exosomes are natural nanoparticles that play an important role in cell-to-cell communication. Communication is achieved through the transfer of cargos, such as microRNAs, from donor to recipient cells and binding of exosomes to cell surface receptors. Exosomes and their cargos are also obtained from dietary sources, such as milk. Exosome and cell glycoproteins are crucial for intestinal uptake. A large fraction of milk exosomes accumulates in the brain, whereas the tissue distribution of microRNA cargos varies among distinct species of microRNA. The fraction of milk exosomes that escapes absorption elicits changes in microbial communities in the gut. Dietary depletion of exosomes and their cargos causes a loss of circulating microRNAs and elicits phenotypes such as loss of cognitive performance, increase in purine metabolites, loss of fecundity, and changes in the immune response. Milk exosomes meet the definition of bioactive food compounds.

Human milk contains large amounts of small extracellular vesicles (sEVs) and their microRNA cargos, whereas infant formulas contain only trace amounts of sEVs and microRNAs. We assessed the transport of sEVs across the blood-brain barrier (BBB) and sEV accumulation in distinct regions of the brain in brain endothelial cells and suckling mice. We further assessed sEV-dependent gene expression profiles and effects on the dendritic complexity of hippocampal granule cells and phenotypes of EV depletion in neonate, juvenile and adult mice. The transfer of sEVs across the BBB was assessed by using fluorophore-labeled bovine sEVs in brain endothelial bEnd.3 monolayers and dual chamber systems, and in wild-type newborn pups fostered to sEV and cargo tracking (ECT) dams that express sEVs labeled with a CD63-eGFP fusion protein for subsequent analysis by serial two-photon tomography and staining with anti-eGFP antibodies. Effects of EVs on gene expression and dendritic architecture of granule cells was analyzed in hippocampi from juvenile mice fed sEV and RNA-depleted (ERD) and sEV and RNA-sufficient (ERS) diets by using RNA-sequencing analysis and Golgi-Cox staining followed by integrated neuronal tracing and morphological analysis of neuronal dendrites, respectively. Spatial learning and severity of kainic acid-induced seizures were assessed in mice fed ERD and ERS diets. bEnd.3 cells internalized sEVs by using a saturable transport mechanism and secreted miR-34a across the basal membrane. sEVs penetrated the entire brain in fostering experiments; major regions of accumulation included the hippocampus, cortex and cerebellum. Two hundred ninety-five genes were differentially expressed in hippocampi from mice fed ERD and ERS diets; high-confidence gene networks included pathways implicated in axon guidance and calcium signaling. Juvenile pups fed the ERD diet had reduced dendritic complexity of dentate granule cells in the hippocampus, scored nine-fold lower in the Barnes maze test of spatial learning and memory, and the severity of seizures was 5-fold higher following kainic acid administration in adult mice fed the ERD diet compared to mice fed the ERS diet. We conclude that sEVs cross the BBB and contribute toward optimal neuronal development, spatial learning and memory, and resistance to kainic acid-induced seizures in mice.

Objectives Exosomes are natural nanoparticles that can be found in most body fluids including milk. Bovine milk exosomes (BME) are bioavailable and transfer cargos such as RNAs, lipids and proteins across species boundaries. Previous competitor studies implicated galactose-modifications in exosome surface proteins in exosome transport. The objectiveof our study was to assess the importance of glycan modifications in BME surface glycoproteins for BME uptake and distribution in human intestinal cells (FHs cells) and mice. Methods BME were isolated from milk by differential centrifugation (Fig. 1). Putative glycan binding sites on the surfaces of BME were identified by LC/MS-MS and bioinformatics protocols and confirmed by eastern blotting. Surface glycans were altered using proteases, glycosidases and blocking of glycans with lectins for subsequent transport and distribution studies (Table 1). The uptake of BME by FHs cells was assessed using membrane and RNA cargo-labeled BME. The distribution of BME in mice was assessed using BME transfected with fluorophore (IRDye)-labeled synthetic miR-320a in C57BL/6 mice and MGAT-1 tamoxifen inducible conditional knockout (CKO) mice ages 5–8 weeks. One-way ANOVA and Bonferroni's multiple comparison were used for statistical analyses; P < 0.05 was considered significant. Results We identified 49 (N), 13 (O) and 13 (C) putative glycan binding sites on the BME surface, and confirmed the presence of mannose, galactose, N-acetylgalactose, fucose and neuraminate (Fig. 2). Galactose and N-acetylgalactosamine residues on the surface of BME were of particular importance for their uptake by FHs cells, whereas N-acetylglucosamine on the surface of FHs cells was more important than other glycans for BME uptake (Fig. 3). Enzymatic and genetic removal of glycans in BME and MGAT-1 CKO, respectively, caused a loss of BME accumulation in murine livers and pancreas (Fig. 4). Conclusions Distinct glycan features are essential for the uptake of BME in mice. The study laid a foundation to assess the importance of glycan modifications in infant formulas and the homing of drug-loaded exosomes to sites of disease. Funding Sources NIFA, NIH, Bill & Melinda Gates Foundation, PureTech Health, and USDA Hatch & Multistate. J.Z. is a consultant for PureTech. Supporting Tables, Images and/or Graphs

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Background Bovine milk exosomes (BMEs) harbor regulatory proteins, lipids and microRNAs. Consumption of an exosome and RNA-depleted (ERD) diet elicited phenotypes compared to controls fed an exosome and RNA-sufficient (ERS) diet in mice. All other ingredients were identical in the diets. ERD and ERS diets were prepared by substituting ultrasonicated and non-ultrasonicated milk, respectively, for casein in the AIN-93G formulation. Objective The objective of this study was to assess the effect of ultrasonication of milk on exosome content and bioavailability, and cargo content. Methods Bovine milk was ultrasonicated and exosomes were isolated by ultracentrifugation (USE); controls were not ultrasonicated (NSE). Exosome count, size and morphology were assessed using a nanoparticle tracker and electron microscopy. RNAs, lipids and proteins were analyzed by RNA-sequencing and mass spectrometry. Intestinal transport, bioavailability and distribution were measured by using fluorophore-labeled USEs and NSEs in Caco-2 cells, FHs 74 Int cells and C57BL/6J mice (n = 3; age 6 - 8 weeks). Results The exosome count was 76 ± 22% lower in USE compared to NSE (P &lt; 0.05). Ultrasonication caused a degradation of up to 100% of microRNAs. USE and NSE contained 145 and 332 unique lipid signatures, respectively (P &lt; 0.05). We detected total of 525 and 484 proteins in USE and NSE. The uptake of USEs decreased by 46 ± 30% and 40 ± 27% compared to NSEs in Caco-2 and FHs 74 Int cells, respectively (P &lt; 0.05). The hepatic accumulation of USEs was 48% ± 28% lower than the accumulation of NSEs in mice (P &lt; 0.05). Conclusions Ultrasonication of milk depletes bioavailable BMEs in studies of Caco-2 cells, FHs 74 Int cells and C57BL/6J mice and causes a near-complete degradation of microRNA cargos.

Objectives Exosomes are endogenous nanoparticles that participate in cell-to-cell communication through the transfer of cargos such RNAs, lipids and proteins from donor cells to recipient cells. Previously, we showed that mammals absorb exosomes from milk. Ultrasonication causes a transient disruption of the exosome membranes, leading to loss of microRNAs. When mice were fed diets based on the AIN-93G formulation, modified to contain a physiological amount of milk exosomes (exosome and RNA-sufficient diet, ERS) or sonicated exosomes (exosome and RNA-depleted diet, ERD), we observed a loss of circulating and tissue microRNAs and phenotypes such as aberrant purine metabolism. The objective of this study was to conduct a comprehensive analysis ofthe effects of sonication on exosomes cargos and bioavailability, thereby generating insights into mechanisms through which ERD elicits phenotypes. Methods Exosomes were isolated from ultrasonicated (USE) and non-sonicated (NSE) bovine milk by ultracentrifugation and authenticated following guidelines of the International Society for Extracellular Vesicles. MicroRNAs were analyzed by small RNA-sequencing. Lipids and proteins were analyzed by LC/MS-MS. Intestinal transport was assessed using FM 4-64-labeled exosomes in primary human small intestine cells (FHs cells). Bioavailability of exosomes transfected with IRDye-labeled miR-320a was assessed using oral gavage in C57BL/6 mice.The unpaired t-test was used for statistical analysis P < 0.05 was considered statistically significant. Results Ultrasonication affected the vesicle count and exosome morphology. Western blot analysis detected marker proteins only in NSE. The content of microRNAs was about 93% lower in USE than NSE. Significant difference was noted for lipid and protein identities between NSE and USE. Reduced uptake of USE by intestinal cells and loss of cargo accumulation in murine livers and pancreas for USE compared to NSE (Fig. 1-5). Conclusions Ultrasonication causesa loss of microRNAs in milk exosomes. The unique patterns of proteins and lipids likely is due to an exchangeof membranes between exosomes and other vesicles during ultrasonication, which might explain the lower bioavailability of USE compared to NSE. We currently test the exchange of lipids during ultrasonication. Funding Sources NIFA, NIH, Gates Foundation, PureTech, Inc. and USDA Hatch and Multistate. J.Z. is a consultant for PureTech. Supporting Tables, Images and/or Graphs