Compressed residual green tea extract prevents capillary regression by inhibiting slow-to-fast muscle fiber transformation in the atrophied skeletal muscle

Disuse induces capillary regression in skeletal muscle, which is associated with excessive production of reactive oxygen species (ROS), impaired mitochondrial oxidative capacity, and a shift from slow- to fast-twitch muscle fibers. Green tea is rich in catechins with potent antioxidant properties. We hypothesized that compressed residual green tea extract, a byproduct of green tea manufacturing, may attenuate capillary regression during muscle disuse. Twenty female Wistar rats were randomly assigned to four groups: control (CON), compressed residual green tea supplementation (GTs), hindlimb unloading (HU), and hindlimb unloading with compressed residual green tea supplementation (HU+GTs). Hindlimb unloading was performed for 2 weeks. Compressed residual green tea extract (850 mg/kg/day) or distilled water was administered orally. HU induced significant reductions in soleus muscle mass, capillary-to-fiber (C/F) ratio, slow-twitch fiber proportion, and succinate dehydrogenase (SDH) activity, along with increased ROS production. Compressed residual green tea supplementation significantly attenuated capillary regression, preserved slow fiber composition, restored SDH activity, and suppressed ROS overproduction under unloaded conditions. These findings suggest that compressed residual green tea may serve as a practical nutritional strategy to maintain skeletal muscle capillarity during disuse by preserving oxidative fiber phenotype and mitochondrial function.