Melatonin Enhances Metabolic Recovery After Endurance Exercise: Time-Dependent Modulation of Glycogen and Triglyceride Levels in Skeletal Muscle and Liver

Abstract Purpose This study investigated the time-dependent effects of melatonin administration on recovery following physical exercise, focusing on key tissues involved in energy metabolism and serum markers of skeletal muscle damage. Methods Sixty male Wistar rats were subjected to a 60-min swimming session at 90% of the maximal aerobic capacity and then received melatonin (10 mg/kg) or vehicle, being euthanized at 6, 12 or 48 h post-exercise. Data were analyzed using two-way ANOVA with post hoc tests. Effect sizes and multivariate approaches (Integrated Biomarker Response (IBR) and Principal Component Analysis (PCA)) were applied to assess treatment and time effects. Results Melatonin significantly enhanced glycogen resynthesis in the soleus, red and white gastrocnemius, gluteus maximus, and liver ( P < 0.01), and concurrently reduced triglyceride content in the soleus, white gastrocnemius, gluteus maximus, and liver ( P < 0.01). Serum glucose, triglyceride, creatine kinase (CK), and lactate dehydrogenase (LDH) levels were significantly attenuated in melatonin-treated animals, indicating reduced muscle damage. IBR analysis revealed the most pronounced metabolic modulation at 12 h post-exercise, while PCA showed distinct clustering of melatonin-treated groups, particularly at 6 h, supporting a temporally dynamic effect. Conclusion These findings suggest that melatonin improved substrate restoration and enhanced metabolic recovery in a tissue and time-specific manner, likely through mechanisms involving improved glucose uptake, lipid oxidation, and protection against skeletal muscle damage induced by exercise.