Expression of Irisin and PGC-1α in Selected Organs of Rats Subjected to Running Training at Different Intensities

Background: Physical exercise induces a number of beneficial adaptive changes in the body. One of the adaptive mechanisms involves the expression of irisin and PGC-1α. Despite numerous studies describing the stimulation of their synthesis in response to exercise, there remains a lack of data on the local expression of these proteins in organs that maintain homeostasis and play important regulatory roles during physical exercise. The aim of our study was to assess changes in the expression of irisin and PGC-1α in the kidneys, liver, and lungs of rats in response to physical training. Methods: Sprague–Dawley rats underwent 12 weeks of training at different intensities. The rats were divided into four groups: a control group—rats remaining in their cages (SC), and three training groups performing running exercise at low (LIT), moderate (MIT), and high (HIT) intensity 5 times/week. Following completion of the training protocols, the organs were collected, and histological specimens of the kidneys, liver, and lungs were prepared, on which immunohistochemical staining was performed to assess the expression of irisin and PGC-1α. Results: In the SC group, irisin expression was highest in the renal cortex and medulla and lowest in the liver and lungs. Similarly, the highest expression of PGC-1α was observed in the renal cortex, while the lowest was observed in the lungs. Among the training groups, the greatest effect on irisin expression was observed following LIT and MIT, which stimulated irisin expression, but only in the kidneys and liver, with no effect on its expression in the lungs. HIT did not stimulate irisin expression in any of the organs examined. In the case of PGC-1α, an increase in expression was observed only in the lungs of rats from the LIT group. No changes in PGC-1α expression were observed in any of the other organs following MIT and HIT. Conclusions: Both LIT and MIT were associated with increased irisin expression, whereas increased PGC-1α expression was observed only in the LIT group. No statistically significant changes in the expression of either irisin or PGC-1α were detected in the HIT group.