Ascorbic acid supplementation effects during refeeding in musculature of pacus subjected to a fasting period

Fasting periods commonly occur throughout the fish’s life. During this condition, there is an increase in muscle degradation and reactive oxygen species (ROS) production, which can cause cell disturbances. Antioxidants, such as ascorbic acid (AA), can neutralize and prevent ROS’s damage. Thus, we aimed to evaluate the AA supplementation impacts in the skeletal muscle of pacu after a fasting period. Pacu juvenile were grouped in Control (C; continuous feeding - 200 mg/kg of AA), Fasting (F; 15 days of fasting) and three refeeding groups after fasting: Low (L-AA; 100 mg/kg of AA), Balanced (B-AA; 200 mg/kg of AA) and High-supplementation (H-AA; 400 mg/kg of AA). Muscle samples were collected after fasting (15 days) and refeeding (6 hours, 15 and 30 days). Muscle fibers were measured and grouped in diameter classes. Biochemistry analyses were performed to evaluate antioxidant enzymes activity. Genes related to anabolism, catabolism, myogenesis and oxidative metabolism were analyzed by RT-qPCR. Besides, in vitro analyzes were performed to evaluate the direct AA effect’s in muscle cells. After fasting, a decrease in fiber diameter and anabolic genes expression, besides an increase in catabolic genes was observed in F group. In the first moment after refeeding (6 hours), the anabolic and myogenic genes expression increased in the H-AA. After 15 days, the L-AA group presented a general decrease in gene expression, while the H-AA had an increase in myogenic genes expression and recovered fiber diameter. After 30 days, the H-AA presented an increase in the expression of genes related to myogenesis and oxidative metabolism combined with a recovery in fiber diameters. Besides, the AA supplementation promoted a decrease in catalase activity through time in this same group. Our data indicate that the low AA level may have impaired muscle metabolism resumption, while the higher supplementation may have contributed to a faster recovery of muscle growth, possibly providing a beneficial microenvironment for energetic production. Moreover, our in vitro results indicate a possible direct AA effect on muscle cells. These findings may present a strategy to minimize the loss of aquaculture profits, promoting faster muscle recovery after fasting and stressful situations. (AU)