Investigation of the effects of irisin hormone on the hypothalamic control of feeding

Aim: Hypothalamus undertakes important roles in the control of feeding, and in this center, taking active roles of leptin, ghrelin, neuropeptide Y (NPY), proopiomelanocortin (POMC) and many other peptides controlling feeding behavior is known. Boström et al. identified irisin as a myokine in 2012. This study intends to clarify possible effects of the irisin on feeding behavior with gene expression of NPY, POMC UCP2 and their protein levels. Material and Method: In this study, 240-325 g in weight of 40 male Wistar-Albino rats were used. Rats were evenly separated into four groups (n=10). Osmotic mini-pumps were implanted to lateral ventricule and artificial cerebrospinal fluid (vehicle; sham group), 10 and 100 nM concentrations of irisin were infused for 7 days. Throughout the experimental period, the rats were kept in individual cages, and body weight, food and water consumption of the animals were daily recorded. At the end of the seven day infusion the animals were killed, and the brain tissue and blood samples were collected. Serum leptin and ghrelin levels of the groups were measured from blood samples by ELISA method and metabolic parameters (glucose, cholesterol, triglycerides, HDL, LDL) using a photometric method. UCP2, POMC and NPY mRNA levels from brains tissues (hypothalamus) and the protein analysis of these genes were determined by Real Time-PCR and Western blot methods, respectively. Results: All concentrations of irisin (10 and 100 nM) increased the daily food intake of the rats (p<0.05); but they did not cause a significant change in body weight and water consumption. Irisin reduced the levels of serum leptin (p<0.05), and it increased ghrelin levels (p<0.05). Administration of irisin increased NPY and UCP2 levels while it decreased POMC levels (p<0.05). In addition, although irisin decreased the levels of serum glucose and HDL, it increased LDL, cholesterol and TG levels (p<0.05). Conclusion: All these findings indicated that irisin increased the appetite, however it did not change body weight despite increasing feed consumption.