Discovery of myokines has emphasized the role of muscle as an important source of exercise-induced hormones to communicate information and interact with other tissues, including fat, the liver, and the pancreas, to alter metabolism ¹.

Metabolic diseases such as obesity and diabetes are undoubtedly some of the most challenging health issues of our times ². The prevalence of obesity and type 2 diabetes is escalating at an alarming rate in many developed as well as developing countries and is basically a consequence of imbalance between energy intake and energy expenditure ^{3, 4}. Obesity on itself could be the source of other disease like type2 diabetes. The prevalence of obesity among the women is more than the men that may be because of the lowest knowledge and lack of exercise and sport facilities in some countries ^{5, 6}. The health benefits of regular exercise are undisputed, thereby reduce the risk of lifestyle-related diseases, such as obesity but the molecular mechanisms are not completely understood ⁷.

Irisin is a novel muscle and adipose drived chemokine that is, proteolytically processed from the product of the FNDC5 (fibronectin type ш domain containing 5) gene. Both exercise and the PGC1α (peroxisome proliferator-activated receptor gamma coactivator 1 α) induce irisin expression. Irisin induces the browning of adipocytes and thermogenesis by increasing of UCP1 (uncoupling protein 1) level ^{8, 9, 10, 11, 12}. It is mentioned that irisin could orchestrate many metabolic pathways ^{13, 14, 15, 16, 17, 18}, for example irisin has gained great interest as a potential new target to combat obesity and its associated disorders, such as type 2 diabetes mellitus ¹⁰.

Although circulating irisin was shown to increase in humans in response to exercise ⁸, but relevance of irisin in human physiology is not fully understood under effect of endurance, strength and in particular concurrent training obscure, and conflicting data in humans have recently emerged, thereby more researches are needed. It has been shown that although circulating irisin is associated with signs of metabolic syndrome and insulin resistance but it is differently regulated by training in normal versus overweight subjects ^{19, 20, 21, 22, 23, 24, 25, 26}. Some mechanism have suggested about the effect of irisin role in glucose uptake and lipid homeostasis ^{15, 16, 27, 28, 29}. In diabetic mice, persistent subcutaneous perfusion of irisin improved the insulin sensitivity, reduced fasting blood glucose, increased GSK3 and Akt phosphorylation, glycogen content and irisin level, and suppressed GS phosphorylation, PEPCK and G6Pase expressions in liver. Irisin improves glucose homeostasis by reducing gluconeogenesis via PI3K/Akt/FOXO1-mediated PEPCK and G6Pase down-regulation and increasing glycogenesis via PI3K/Akt/GSK3-mediated GS activation. Irisin may be taken as a novel therapeutic strategy for insulin resistance and type 2 diabetes ¹⁶. But it is necessary to investigate it in different population and under different conditions like exercise, Then in this study it is tried to explore the effect of three kind of isocaloric exercise (Endurance, Resistance and concurrent) on irisin circulation in obese sedentary women.

This study was carried out during the three month (July to August) in the Northwest of Iran, in the capital city of East-Azerbaijan, Tabriz. At first near the 200 obese women were enrolled by public announcement from different big sectors of the city. Finally according to inclusion criteria and the property of exercise program in many stages by cluster sampling method, all the remained women randomly assigned into endurance, resistance and concurrent exercise training groups on base of obesity. Some of subjects failed during the study and could not complete it. Lastly 33 obese and sedentary women participate in this study (endurance n=10, resistance n=12 and concurrent n=11). Subject characteristics are shown in Table 1. The inclusion criteria required a BMI>25 kg/m² or a body fat percentage ≥ 30%. Subjects with a history of disease such as major cardiovascular disease, hemodialysis, asthma and other problems were excluded. This study was approved by the ethics committee of IR. TBZMED. REC. 1395. 927. Informed written consent was obtained from each subject. Participants were evaluated before and after the exercise training in all of the measurement (physiologic like irisin, insulin, glucose, HOMA-IR and anthropometric like BMI, Fat% and etc.). BMI (kg/m²)and body composition was determined. Bio-impedance body composition analyzer was used. Also skeletal observed indicated that circulating irisin correlated positively with increased risk of metabolic syndrome and insulin resistance as assessed with these kinds of findings it has been observed higher levels of irisin in overweight pre-diabetes subjects compared with healthy controls ^{4, 30}. Many recent studies in obese patients have shown that irisin decreases with weight reduction. Moreno et al found that irisin was higher in subjects with low activity than in those with average or high activity ³⁷. Huh et al showed that irisin was highest in obese prediabetic patients, followed by obese patients and non-obese individuals, and lowest in athletes ¹⁰. The higher irisin in obese persons is due to compensation for metabolic homeostasis, and this suggests that irisin should be decreased by body weight reduction due to discontinuation of compensatory action ¹⁴. Due to the difference in metabolism in obese and non-obese individuals, there are disturbances and differences in the signaling processes and intramuscular stimuli of these individuals. Recent investigates suggested that probably irisin has effects on gluconeogenesis and glycogenesis via PI3K/ populations. Irisin secretion in response to adipose and insulin resistance probably enhanced metabolic homeostasis in a compensatory way by altering lipid metabolism via browning of white adiposities ³⁷. Therefore, with regard to one of the important sources of irisin secretion, the adipose tissue, it seems that in this study, the high levels of irisin in obese individuals who did not have a metabolic disorder would have a protective and supportive role in obstructing the complications of obesity, so obese people are less likely to suffer from obesity. In these people, physical activity could decrease the complications of obesity by improving the glucose signaling pathways and other routes, as well as the higher body fat intake, thus reducing Irisin by the end of the period. In general, the present study did not show a significant difference in the effect of different types of training on the Irisin of sedentary and obese women.

This study is not without limitations. We did not any lean control group, however all subjects completed the study in random order then served as their own controls. Also by finding of receptor(s) of irisin in different part of body would open the door to better understand of its role and its mechanisms. Additional researches are needed to elucidate the potential and hidden interaction of irisin and exercise by different intensity and duration in several populations.

Figure 1. Irisin in different groups

Figure 2. Glucose in different groups

Figure 3. Insulin in different groups

Figure 4. HOMA-IR in different groups

With regard to one of the important sources of irisin secretion, the adipose tissue, it seems that in this study, the high levels of irisin in obese individuals who did not have a metabolic disorder would have a protective and supportive role in obstructing the complications of obesity, so obese people are less likely to suffer from obesity. In these people, physical activity could decrease the complications of obesity by improving the glucose signaling pathways and other routes, as well as the higher body fat intake, thus reducing Irisin by the end of the period. In general, the present study did not show a significant difference in the effect of different types of training on the Irisin of sedentary and obese women.