Donepezil improves skeletal muscle insulin resistance in obese mice via the AMPK/FGF21-mediated suppression of inflammation and ferroptosis

Donepezil has traditionally been used in Alzheimer's disease treatment and is known for its ability to alleviate neural inflammation and apoptosis. However, its impact on insulin signaling remains unexplored. This study sought to elucidate the novel role of donepezil in mitigating skeletal muscle insulin resistance under hyperlipidemic conditions. Western blot analysis was used to assess the expression of various proteins of interest, whereas a glucose uptake assay was performed in skeletal muscle cells via commercially available kits. An in vitro model of obesity was developed using palmitate. These in vitro findings were corroborated in vivo via insulin resistance models established through high-fat diet (HFD) feeding in mice. Intraperitoneal glucose tolerance tests and insulin tolerance tests were performed on the experimental mice. The results revealed that donepezil treatment improved insulin signaling and inflammation in palmitate-treated C2C12 myocytes and the skeletal muscle of HFD-fed mice. Notably, donepezil treatment augmented FGF21 expression and AMPK phosphorylation in the myocytes and skeletal muscle of HFD-fed mice. Knockdown of FGF21 or AMPK via siRNA reversed the effects of donepezil on insulin signaling and inflammation in cultured myocytes. We also found that donepezil ameliorated skeletal muscle insulin resistance via the FGF21-mediated suppression of ferroptosis under hyperlipidemic conditions. These findings suggest that donepezil enhances the FGF21/AMPK axis, thereby mitigating inflammation and insulin resistance in skeletal muscle. This study introduces a novel therapeutic approach for treating Alzheimer's disease patients with insulin resistance.