Irisin increases the expression of anorexigenic and neurotrophic genes in mouse brain

Irisin, a newly discovered muscle-derived hormone, acts in different organs and tissues, improving energy homeostasis. In this study, we assessed, for the first time, the effects of intraperitoneal irisin injections on circulating levels of leptin and ghrelin, mRNA expression of the major hypothalamic appetite regulators and brain neurotrophic factors, as well as feeding behaviour in healthy mice.

Twelve male 6-week-old C57BL/6 mice were randomized into two groups and intraperitoneally injected daily with irisin (0.5 μg/g body weight) or vehicle (phosphate-buffered saline [PBS]) for 14 days. On the last day of observation, leptin and ghrelin levels were measured with an enzyme-linked immunosorbent assay (ELISA). mRNA levels of genes of interest were analysed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) in brain extracts.

Irisin administration did not change leptin or ghrelin serum concentrations. However, irisin injection increased CART, POMC, NPY, and BDNF mRNA levels, without affecting the mRNA expression of AgRP, orexin, PMCH, and UCP2. Finally, over the time frame of irisin treatment, body weight and feeding behaviour were unaltered.

These results suggest that intraperitoneal injection of irisin, although without effects on feeding behaviour and body weight, can increase the expression of anorexigenic and neurotrophic genes in mouse brain.