MYOD1 and sarcopenia: RBP4 correlates with the presence and severity of aging sarcopenia. Knockdown of RBP4 attenuated denervation-induced fat infiltration and skeletal muscle atrophy while decreasing expression of the atrophy markers Atrogin-1 and MuRF1 and increasing expression of the myogenesis regulators MyoD and myoglobin. Lowering RBP4 levels may represent a promising therapeutic strategy for the prevention and treatment of muscle atrophy.