Irisin’s Mechanism of Action and Levels in Physiological and Pathological Conditions

Background and Aims: The importance of establishing a universal baseline for irisin in healthy individuals has often been overlooked. Irisin is a recently identified adipomyokine messenger with proven diverse properties and functions in various parts of the body. In this review, published studies on irisin’s structure, mechanism of action, and quantification are summarized, with a focus on its levels in relation to physiological and pathological conditions.Materials and Methods: PubMed, ScienceDirect, and Web of Science were searched for studies on irisin’s structure, mechanism of action, quantification, and effects in various tissues (no year restriction) using the following search terms: ‘irisin’, ‘FNDC5’, and ‘PGC-1α’, along with papers that discussed the levels of irisin in relation to physiological and pathological conditions.Results: Most of the current research was found to focus on the study of irisin concentrations in fluids of individuals with various comorbidities relative to controls, for the purpose of assessing its role in disease progression and prevention. Few papers have been able to establish a reliable baseline for its levels in healthy individuals due to insufficient sample sizes, use of differing quantification methods, and factors involving racial, gender, and age variances.Conclusions: Establishing a universal reference range for circulating irisin levels in healthy individuals has proven to be challenging. Despite being a potential biomarker for predicting illness, further investigation is still needed to overcome current limitations.