Globin digest and its constituent peptides promote skeletal muscle hypertrophy and enhance physical performance

Globin digest (GD), an acidic protease hydrolysate of hemoglobin, has been recognized for its anti-obesity and glucose-modulating effects; however, its direct anabolic potential in skeletal muscle remains uncharacterized. We evaluated the effects of GD and its constituent peptides on muscle hypertrophy and motor function using zebrafish, mice, and C2C12 myoblasts. Adult zebrafish administered GD (400 mg/kg BW/d) for 1 week showed significantly increased swimming distance ( p < 0.05). Similarly, oral administration of GD (1 g/kg BW/d) to C57BL/6J mice for 4 weeks enhanced grip strength and rotarod performance, accompanied by a 1.5-fold increase in myofiber diameter and upregulation of fast-twitch Myh1 (1.9-fold) and Myh2 (1.8-fold) mRNA levels. In vitro , GD dose-dependently (1–100 μg/mL) stimulated C2C12 differentiation and MyHC accumulation. Notably, GD did not merely serve as a nutritional nitrogen source; instead, it functioned as a signaling modulator via a specific “relay-like” peptide orchestration. Among six identified sequences, Peptides 3 (WTQR) and 5 (WGK) primarily initiated early-stage commitment by upregulating MyoD and Myf5 , whereas Peptides 2 (VVYP) and 6 (FES) accelerated mid-stage maturation. This stage-specific synergy achieved robust myotube hypertrophy that exceeded the efficacy of individual components. These findings demonstrate that GD promotes skeletal muscle hypertrophy and motor function through direct myogenic signaling, establishing a novel foundation for precision sports nutrition to optimize muscle maintenance and physical performance.