Fucoidan Therapy for Extraintestinal Diseases: Targeting the Microbiota–Gut–Organ Axes

The microbiota-gut-organ axis is widely recognized as a pivotal mediator of systemic health, primarily through gut-derived immune, metabolic, and inflammatory signaling. Fucoidans, a class of fucose-containing sulfated polysaccharides predominantly composed of L-fucose and exclusively found in brown seaweeds, have been demonstrated to modulate gut microbiota composition and function, resulting in the enrichment of beneficial bacteria and the suppression of harmful species. They enhance the production of beneficial metabolites, such as short-chain fatty acids and specific bile acids, while suppressing harmful metabolites, including lipopolysaccharide, thereby ameliorating organ damage via key mechanisms such as the mitigation of oxidative stress and inhibition of inflammatory responses. Furthermore, fucoidan supplementation was found to restore intestinal barrier integrity. Using disease models including Parkinson's disease, alcoholic liver disease, diabetic kidney disease, and obesity, the mechanisms through which fucoidans ameliorate extraintestinal diseases via the microbiota-gut-organ axis were elucidated. Microbiota-dependent mechanisms have been confirmed via experimental approaches such as fecal microbiota transplantation and specific bacterial strain supplementation. Fucoidans represent promising prebiotic agents for the restoration of microbial ecology and the treatment of extraintestinal diseases, highlighting the need for further clinical investigation.