Food-derived extracellular vesicles (FEVs) are nanoscale membrane vesicles obtained from dietary materials such as breast milk, plants and probiotics. Distinct from other EVs, FEVs can survive the harsh degrading conditions in the gastrointestinal tract and reach the intestines. This unique feature allows FEVs to be promising prebiotics in health and oral nanomedicine for gut disorders, such as inflammatory bowel disease. Interestingly, therapeutic effects of FEVs have recently also been observed in non-gastrointestinal diseases. However, the mechanisms remain unclear or even mysterious. It is speculated that orally administered FEVs could enter the bloodstream, reach remote organs, and thus exert therapeutic effects therein. However, emerging evidence suggests that the amount of FEVs reaching organs beyond the gastrointestinal tract is marginal and may be insufficient to account for the significant therapeutic effects achieved regarding diseases involving remote organs such as the liver. Thus, we herein propose that FEVs primarily act locally in the intestine by modulating intestinal microenvironments such as barrier integrity and microbiota, thereby eliciting therapeutic impact remotely on the liver in non-gastrointestinal diseases via the gut-liver axis. Likewise, drugs delivered to the gastrointestinal system through FEVs may act via the gut-liver axis. As the liver is the main metabolic hub, the intestinal microenvironment may be implicated in other metabolic diseases. In fact, many patients with non-alcoholic fatty liver disease, obesity, diabetes and cardiovascular disease suffer from a leaky gut and dysbiosis. In this review, we provide an overview of the recent progress in FEVs and discuss their biomedical applications as therapeutic agents and drug delivery systems, highlighting the pivotal role of the gut-liver axis in the mechanisms of action of FEVs for the treatment of gut disorders and metabolic diseases.

Polysaccharides from natural sources can regulate the composition of intestinal flora through the \"gut-liver axis\" pathway, potentially ameliorating alcoholic liver injury. Aspalathus linearis, also known as rooibos, is one such natural product that has shown promise in this regard. This study looked at the structural properties of A. linearis polysaccharide (ALP) and how well it would work to treat acute alcoholic liver impairment. This study looks at the composition of monosaccharides, functional groups, and molecular weight (Mw) of a newly discovered water-soluble polysaccharide, named ALP. The polysaccharide is composed of pyranose rings, amide groups, and sulfate groups linked by β-glycosidic linkage. It has a relative Mw of 4.30 × 103 kDa and is composed of glucose, rhamnose, and some other monosaccharides. The study found that treating mice with the model of acute alcoholic liver disease with ALP could alleviate pathological symptoms, inhibit the release of inflammatory cytokines, and suppress indicators of oxidative stress. Experiments have shown that different doses of ALP can activate the P4502E1/Keap1-Nrf2-HO-1 signaling pathway. The regulation of inflammatory factors and downstream antioxidant enzymes occurs as a result. Based on these data, it is likely that ALP protects the liver via the \"gut-liver axis\" pathway by reducing oxidative stress-related damage, inflammation, and alcohol-related alterations to the gut microbiome. The results indicate that ALP mitigates injury caused by oxidative stress, inflammatory responses, and changes in the gut microbiota induced by alcohol through the \"gut-liver axis\" pathway, which provides protection to the liver. This provides preliminary evidence for the development of related drugs. PRACTICAL APPLICATION: Researchers extracted a polysaccharide from fresh leaves of Auricularia auricula. The polysaccharide was purified and determined to have a predominantly homogeneous molecular weight. An acute alcoholic liver damage mouse model was established, and it was concluded that the polysaccharide could ameliorate liver injury in mice through the \"gut-liver axis\" pathway. This novel polysaccharide can be used as an additive to develop functional foods with beneficial effects, which can positively impact the daily maintenance of consumers.