Differential expression of appetite-regulating genes in avian models of anorexia and obesity

Abstract

Chickens from lines that have been selected for low (LWS) or high (HWS) juvenile body weight for more than 57 generations provide a unique model to research appetite regulation. The LWS display different severities of anorexia while all HWS become obese. Herein we measured mRNA abundance of various factors in appetite-associated nuclei in the hypothalamus. The lateral hypothalamus (LHA), paraventricular nucleus (PVN), ventromedial hypothalamus (VMH), dorsomedial nucleus (DMN), and arcuate nucleus (ARC) were collected from 5 day-old chicks that were fasted for 180 minutes or provided continuous access to food. Fasting increased neuropeptide Y receptor sub-type 1 (NPYR1) mRNA in the LHA and c-Fos in the VMH, while decreasing c-Fos in the LHA, NPYR5 and ghrelin in the PVN and NPYR2 in the ARC. Fasting increased melanocortin receptor sub-type 3 (MC3R) expression in the DMN and NPY in the ARC of LWS but not HWS chicks. Expression of NPY was greater in LWS than HWS in the DMN. NPYR5 mRNA was greater in LWS than HWS in the LHA, PVN, and ARC. Expression of orexin was greater in LWS than HWS in the LHA. There was greater expression of NPYR1, MC4R, and cocaine- and amphetamine-regulated transcript in HWS than LWS and mesotocin in LWS than HWS in the PVN. In the ARC, agouti-related peptide and MC3R were greater in LWS than HWS and in the VMH, orexin receptor 2 and leptin receptor were greater in LWS than HWS. Greater MT in the PVN, orexin in the LHA, and ORXR2 in the VMH of LWS may contribute to their increased sympathetic tone and anorexic phenotype. Results also suggest that there is increased hypothalamic anorexigenic tone in the LWS that overrides orexigenic factors such as NPY and AgRP that were more highly expressed in LWS than HWS in several nuclei.

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