Changes in tea exosome-like nanoparticles fermented by Aspergillus cristatus and the preventive effects on non-alcoholic fatty liver disease.

Research on dark tea-derived exosome-like nanoparticles (TELNs) and microbial fermentation-mediated modifications of TELNs remains limited. To comprehensively explore the fermentation-induced alterations in TELNs' physical properties, metabolic composition, and biological functions, a systematic investigation was conducted in this study. Particle size distribution, zeta potential, protein content, and particle concentration of TELNs were characterized and compared before and after Aspergillus cristatus (AC) fermentation using nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), and bicinchoninic acid assay (BCA), respectively. Untargeted metabolomics was employed to profile metabolic changes, while functional assessment was performed in a non-alcoholic fatty liver disease (NAFLD) mouse model. As a result, AC fermentation significantly reduced the particle size of TELNs and increased their yield. It altered the overall metabolite profile of TELNs, and a total of 30 differential metabolites were tentatively identified, mainly including flavonoids, alkaloids, and lipids. Meanwhile, AC fermentation enhanced the blood-lipid-lowering and anti-inflammatory abilities of TELNs in NAFLD mice. This study deepened the understanding of the molecular-level changes during tea fermentation, and offered a new perspective on the applications of dark tea or TELNs in the fields of food science and medical healthcare.