The effects of exercise on irisin and short-chain fatty acids concentrations in rats and their transferability through fecal microbiota transplantation

Yildirim E. Aydın Adnan Menderes University, Health Sciences Institute, Veterinary Physiology Program, Doctorate Thesis, Aydın, 2025. Objective: We aimed to evaluate the effects of exercise on irisin and short-chain fatty acid concentrations (SCFA) in rats and the transferability of possible effects by fecal microbiota transplantation (FMT). Material and Methods: In this study, which consists of two experiments, a total of 34, 4-6 months old Wistar albino male rats were used. In the first experiment, rats were divided into 2 groups: Control (n=8) and Exercise (n=10). The rats in the exercise group were given moderate swimming exercise for 1 hour, 5 days a week for 6 weeks. The control group rats were kept in shallow water for 30 minutes on the same days. In the last week of the experiment, the feces that would be used for FMT in experiment 2 were collected and frozen. In the second experiment, two groups were formed as control FMT (n=8) and exercise FMT (n=8). Feces collected from the control group rats of the first experiment were transferred to the rats in the control FMT group, and those from the exercise group rats of the first experiment were transferred to the rats in the exercise FMT group. FMT was administered at dose of 1ml/100g intragastrically a total of 6 times on Mondays of each week. In both experiments, irisin concentrations were determined in serum and gastrocnemius muscle samples and the SCFA concentrations in cecal and colonic contents at the end of the 6th week. During the experiments the body weights were recorded. Analysis of variance for repeated measurements was used to evaluate body weight data. Irisin and SCFA concentrations data were evaluated using the t test for independent groups or Mann-Whitney U test. Results: In both experiments, while the time-dependent change in body weight was significant (p<0.001), there was no significant difference between the groups. In the first experiment, muscle and serum irisin concentrations were found to be higher in the exercise group than in the control group (p<0.05 and p<0.001, respectively). Similarly, in the second experiment, irisin concentrations in muscle and serum were higher in the exercise FMT group than in the control FMT group (p<0.05 and p<0.01, respectively). In both experiments, there was no significant difference in SCFA concentrations between the groups. Conclusion: Swimming exercise increased muscle and serum irisin concentrations, and this exercise-induced effect was transferred to intact rats with FMT. Exercise did not cause a significant change in the concentrations of SCFA in the intestinal content. While the transfer of the exercise-induced increase in irisin concentrations with FMT supports the interaction between the microbiota-muscle axis, the interaction between the microbiota composition and metabolites, the host's metabolic, inflammatory and myokine panel needs to be evaluated in more detail to clarify this interaction. Keywords: Exercise, Fecal Microbiota Transplantation, Irisin, Microbiota, Short Chain Fatty Acids