FNDC5 and relapsing-remitting multiple sclerosis: The aim of the present study is to contribute to the existing literature by assessing serum irisin and nesfatin-1 levels, both known to have similar anti-inflammatory, antioxidant and antiapoptotic effects and to determine whether serum irisin and nesfatin-1 levels may be used as a biomarker for making MS diagnosis, and evaluating course of disease and responses to relapsing-remitting MS (RRMS) treatment.