Feeding state and age dependent changes in melanin-concentrating hormone expression in the hypothalamus of broiler chickens
We aimed to quantify the gene expression changes of the potent orexigenic melanin concentrating hormone (MCH) in chicken (Gallus gallus) hypothalamus with quantitative real-time polymerase chain reaction (qPCR), and for the first time determine peptide concentrations with a novel radioimmunoassay (RIA) under different feeding status. Three different experimental conditions, namely ad libitum fed, fasting for 24h, fasting for 24h then refed for 2h were applied to study the changes of the aforementioned target and its receptor (MCHR4) gene expression to different nutritional states. The relative changes of MCH and MCHR4 were also studied from 7 to 35 days of age. Expression of PMCH and MCHR4 along the gastrointestinal tract (GIT) was also investigated. We found that both targets expression are restricted to the hypothalamus, only weak expression was detected along the GIT. Different nutritional states did not affect the PMCH and MCHR4 mRNA levels. However, fasting for 24h significantly increased MCH-like immunoreactivity with 25.65%. Fasting for 24h then refed for 2h further significantly increased MCH peptide concentration by 32.51% compared to ad libitum state. Decreasing trend with age was observable both for PMCH and MCHR4 mRNA levels and also for MCH-like immunoreactivity. Correlation analysis did not result significant correlation between MCH peptide concentration and abdominal fat mass in ad libitum fed birds. In conclusion, MCH peptide concentration altered with different feeding states, which indicated that this peptide takes part in feed intake regulation (short-term signalization of feed intake) of broiler chickens in a same manner as in mammals.