Quercetin modulates intestinal microbiota imbalance and relates gut-liver axis activation. It reduces the Firmicutes/Bacteroidetes ratio, inhibits endotoxemia-mediated TLR-4/NF-κB signaling, and upregulates lipid β-oxidation genes like PPAR-α and CPT-1a. The gene discussed is PPARA; the disease is serum lipopolysaccharide activity.