Association of Irisin Serum Concentration and Muscle Strength in Normal-Weight and Overweight Young Women.

Background: Irisin is a muscle-contraction-induced myokine. In previous studies, it has been related to exercise type, fitness and physical activity; however, evidence is not consistent. Thus, the aim of this study was to research the association between health-related fitness and irisin in young women. Methods: The study was designed as a prospective cross-sectional one. Young, healthy, nonsmoking women were enlisted. The sample comprised 40 overweight (OW) and 40 normal-weight (NW) individuals. The average age was 18.63 ± 0.63 and 18.78 ± 0.73 years, respectively. Components of health-related fitness, metabolic parameters, serum irisin and body composition were analyzed. Results: Statistically significant differences were found in physical tests between NW and OW groups for one-leg standing, hand grip strength, vertical jump, modified push-up, fitness index and maximal oxygen uptake (VO2MAX). There were no differences in concentrations of serum irisin between the groups. We found a positive correlation between irisin and hand grip strength (r = 0.374, p = 0.023). In a multivariate analysis adjusted by body fat, a significant association between irisin and hand grip strength was observed in OW group (ß = 0.380, p = 0.026); as well, a positive association between irisin and one-leg standing test in NW group (ß = 0.311, p = 0.044) was found. Conclusions: According to our findings, hand grip strength could be linked to irisin concentration in overweight young women.

Irisin a Novel Metabolic Biomarker: Present Knowledge and Future Directions.

The rising prevalence of chronic diseases such as type 2 diabetes and cardiovascular diseases owing to fat mass excess has been described. In recent years, muscle function/dysfunction has become relevant in metabolic homeostasis. Irisin was described as an exercise-induced myokine. It is the product of type I membrane protein cleavage encoded by the fibronectin type III domain containing 5 (FNDC5) gene. The main beneficial function attributable to irisin is the change of subcutaneous and visceral adipose tissue into brown adipose tissue, with a consequential increase in thermogenesis. Irisin has also been described as a hormone that may have a key role in glucose homeostasis. The way the association of type 2 diabetes with obesity occurs is not fully understood. In recent years, the possible pathways through which irisin could interact with other organs such as the brain or bone have been described. The present paper intends to review the new findings and possible new directions in irisin research.