Inhibitory Effects and the Potential Mechanism of Phloretin on Animal Fatty Acid Synthase

Fatty acid synthase (FASN), a critical enzyme involved in lipid biosynthesis, is highly expressed in adipocytes and exhibits aberrant activity in diverse human cancers. Phloretin, a natural dihydrochalcone abundant in apple peels, crabapples, strawberries, and pears, has emerged as a potential modulator of FASN activity. This study investigates phloretin's inhibitory effects on FASN and the underlying mechanisms. Biochemical assays revealed that phloretin inhibited FASN in a dose-dependent manner, with a half-maximal inhibitory concentration (IC₅₀) of 4.90 ± 0.66 μM. Kinetic analysis demonstrated distinct inhibition patterns: competitive inhibition against acetyl-CoA, mixed competitive/noncompetitive inhibition toward malonyl-CoA, and uncompetitive inhibition relative to NADPH. Molecular docking simulations further indicated that phloretin binds to the β-ketoacyl synthase (KS) domain of FASN, suggesting a mechanism distinct from that of typical flavonoid inhibitors. Notably, phloretin exhibited irreversible inhibition of FASN, in contrast with the inhibition observed for other flavonoids. To validate the cellular relevance, we demonstrated that phloretin suppressed FASN expression and enzymatic activity in breast cancer cells, concomitant with significant reductions in intracellular triglyceride (TG) accumulation and cancer cell viability. Although adipocytes were not studied in this work due to the long differentiation period required, future studies are planned to investigate FASN inhibition in adipogenesis models. Given FASN's dual role as a therapeutic target in obesity and oncogenesis, these findings highlight phloretin's translational potential as a multitarget agent for metabolic and neoplastic disorders. The well-characterized inhibition mechanism of phloretin, combined with its dual capacity to suppress lipogenesis and inhibit proliferation, establishes this natural compound as a compelling candidate for advanced preclinical evaluation in therapeutics for metabolic disorders.