Evaluation of irisin levels in plasma, skeletal muscle, and brain tissues after voluntary or regular exercise in adolescent male rats exposed to chronic social isolation.

Irisin is a myokine secreted by various tissues in response to exercise and plays a role in neuroplasticity and energy metabolism. This study investigated the effects of voluntary and regular exercise on irisin levels in plasma, prefrontal cortex (PFC), hippocampus, and skeletal muscle of socially isolated adolescent male rats. Forty-two Sprague-Dawley rats were used, groups: control (C), social isolation (SI), voluntary exercise (VE), regular exercise (RE), social isolation + voluntary exercise (SI-VE), social isolation + regular exercise (SI-RE). Rats underwent 4-week isolation and exercise protocols. Irisin levels in the hippocampus, PFC, plasma, and gastrocnemius were measured using ELISA. Hippocampal irisin levels were increased in SI-RE; prefrontal irisin levels were increased in RE; and gastrocnemius irisin levels were increased in SI-RE and SI-VE. No significant differences were observed in plasma irisin levels. The elevated hippocampal irisin levels observed in SI-RE may indicate that irisin plays a protective role in reducing the negative effects of social isolation-induced stress on learning and memory, potentially promoting neuroplasticity. The increase in prefrontal cortical irisin in RE suggests a possible role for irisin in mood regulation. The elevated irisin levels in the gastrocnemius in SI-VE, SI-RE support the idea that irisin is an important muscle-derived hormone regulated not only by physical activity but also by stress responses. Overall, this study suggests that irisin interacts with both the central nervous system and skeletal muscle tissues in the context of social isolation, stress, and exercise, and that regular physical exercise may play a role in reducing the negative neurobiological effects of chronic stress.