Anxiang Su

The health benefits of Flammulina filiformis polysaccharides (FFPs) are often attributed to high-molecular-weight (HMW) fractions, which act via the gut microbiota. In contrast, the direct intestinal absorption and corresponding mechanisms of low-molecular-weight (LMW) FFP fractions are less understood. This study, therefore, focused on isolating an LMW and systematically investigating its absorption and anti-inflammatory potential. Structural characterization identified the LMW-FFP as an α-glucan featuring a backbone of (1→4)- and (1→4,6)-linked α-D-Glcp residues. Transport studies using a Caco-2 cell model showed that fluorescein isothiocyanate (FITC)-labeled LMW-FFP was absorbed across the intestinal epithelium. Mechanistic evidence identified macropinocytosis as the primary pathway. In LPS-induced RAW264.7 macrophages, LMW-FFP (50 μg/mL) significantly inhibited the production of pro-inflammatory mediators (NO, TNF-α, IL-1β, IL-6). Non-targeted metabolomics further suggested that the anti-inflammatory effect was associated with the regulation of histidine and glycerophospholipid metabolism, with histamine as a potential key biomarker. These findings contribute to a more comprehensive understanding of FFP’s structure–activity relationship by highlighting the potential of LMW fractions as directly bioavailable components with anti-inflammatory properties.