A Novel Acidic Polysaccharide from <i>Eurotium cristatum</i>-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 <i>Eurotium cristatum</i>, focusing on its dual immunomodulatory and prebiotic effects. Structural characterization revealed that FOFTP2 primarily consists of →4)-α-D-Gal<i>p</i>A-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 (<i>Bifidobacterium</i>, <i>Romboutsia</i>) while suppressing inflammation-associated genera (<i>Adlercreutzia</i>, <i>Dubosiella</i>). Multiomics analyses show that FOFTP2 mitigates adipose inflammation and gut dysbiosis, linked to the upregulation of lipid catabolism genes (<i>Acot4</i>, <i>Sphk</i>, <i>Lcn2</i>) and modulation of immune signaling pathways (<i>Itgam</i>, <i>Ccr2</i>, <i>Tlr8</i>). 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.