A Novel Acidic Polysaccharide from Eurotium cristatum-Fermented Dark Tea: Structural Characterization and Dual Modulation of Adipose Inflammation-Gut Microbiota Axis

Obesity-associated adipose inflammation and gut dysbiosis exacerbate metabolic dysfunction, yet effective therapies are scarce. This study introduces a novel acidic polysaccharide (FOFTP2) isolated from postfermented dark tea by Eurotium cristatum, focusing on its dual immunomodulatory and prebiotic effects. Structural characterization revealed that FOFTP2 primarily consists of →4)-α-D-GalpA-6-O-Me-(1→ residues, along with rhamnogalacturonan-I/II and arabinogalactan-I/II side chains. Functional analysis demonstrated that FOFTP2 effectively repolarizes pro-inflammatory M1 adipose tissue macrophages to anti-inflammatory M2 phenotypes, reduces adipocyte hypertrophy, and improves systemic dyslipidemia. Additionally, FOFTP2 enriches beneficial gut taxa (Bifidobacterium, Romboutsia) while suppressing inflammation-associated genera (Adlercreutzia, Dubosiella). Multiomics analyses show that FOFTP2 mitigates adipose inflammation and gut dysbiosis, linked to the upregulation of lipid catabolism genes (Acot4, Sphk, Lcn2) and modulation of immune signaling pathways (Itgam, Ccr2, Tlr8). These findings suggest that FOFTP2 acts as a dual-targeting prebiotic immunomodulator, offering a fermented tea-derived strategy to disrupt the gut-adipose inflammatory axis in metabolic disease.