The Study Of NPY,MC4R Gene Expression In Hypothalamus In Different Chickens

ObjectiveThe experiment was conducted to obtain the food intake and to detect theexpression of neuropeptide Y (NPY) and Melanocortin-4receptor(MC4R) inhypothalamus at different age in hy-line variety brown,da gu chicken and ArborAcres(AA broiler). We therefore investigated the difference between NPY andMC4R,and their relation with food intake.The study provided theoretical basisfor the breeding of chicken and nutrition research.MethodsAll chicks in this experiment were obtained from Food Quality and SafetyEngineering of Liaoning Province Key Laboratory,College of Animal Husbandry&Veterinary,Liaoning Medical University.All birds had ad libitum access to foodand water during the rearing period starting at1day of age and every breed ofchicks received different foods and growth condition in accordance with differentspecies nutrition requirement. Recorded the food intake weekly and got themean food intake per day for each one.6chicks of each breed were selectedrandomly at the end of different ages (4,6, and17w).Each breed of chicks wereweighed,then were sacrificed by decapitation and their hypothalamus werecollected immediately.After being flash-frozen in liquid nitrogen.The expressionof NPY,MC4R mRNA and protein contents in rhe hypothalamus was quantifiedusing quantitative real-time PCR with SYBR Green I labeling and Westernblotting. ResultsMetabolizable energy intake per kilogram of body weight of the highlandbrown laying hens,da gu chicken and Arbor Acres(AA broiler)with weeks allshowed a trend of lower，especially, it’s significantly lower in the both highlandbrown laying hens and AA broiler chicken (P <0.01). Da gu chicken still hasstrong ability of energy intake at6weeks of age, with no significant differencethan4weeks of age(P>0.05), but were significantly higher than17weeks ofage (P <0.01).At the age of4weeks,the metabolizable energy intake inhighland brown laying hens was significantly higher than AA broiler chicken (P <0.05).Among the highland brown laying hens,da gu chicken and AA broiler,theirmetabolizable energy intake gradually decrease. At the age of6weeks,therewas no significant difference in metabolizable energy intake between highlandbrown laying hens and da gu chicken,but both of them were significant higherthan AA broiler chicken (P <0.01).While at the age of17weeks,metabolizableenergy intake of da gu chicken was significant higher than AA broiler chicken (P<0.01), for an order of metabolizable energy intake:da gu chicken,highlandbrown laying hens and AA broiler chicken.With the growth of age,the tendency of the hypothalamic NPY mRNA level inhighland brown laying hens showed high-low-high.While in Da gu chicken,high-low-low.In AA broiler chicken,the tendency keeped a high state The level ofmRNA and protein of the hypothalamic NPY had no significant relevance（R=—0.421，P=0.259）.With the growth of age,the tendency of thehypothalamic NPY protein was difference in the three kinds of chickens.thetendency show rising trend in highland brown laying hens（P＜0.01）and Da guchicken（P＜0.05）.While AA broiler chicken showed high-low-high（P＜0.01）.Atthe age of4、6、17weeks,the tendency of the hypothalamic NPY protein ofevery chicken respectively showed AA broiler chicken-Da gu chicken-highlandbrown laying hens（P＜0.01）,highland brown laying hens-Da gu chicken-AA broiler chicken（P＜0.01）,highland brown laying hens-AA broiler chicken-Da guchicken（P＞0.05）.The MC4R mRNA level of Da gu chicken of4weeks of age was extremelylower than that of6,17weeks of age（P＜0.01）.There were no significantdifferences in each period of highland brown laying hens and AA broiler chicken(P>0.05).the hypothalamic MC4R protein and MC4R mRNA showed asignificant negative correlation (r=0.822, P=0.007), the tendency ofhypothalamic,MC4R protein ofchicken of different varieties was different:inhighland brown laying hens. at the4weeks of age,the Da gu chickenhypothalamus MC4R protein was significantly higher than that of6weeks of age(P <0.05), and not significant with that of17weeks of age (P>0.05). During thesame period, different varieties of chicken hypothalamus MC4R protein has thedifference. Significant differences between the4week old chickens (P <0.01),from high to low order is Da gu chicken, highland brown laying hens and AAbroiler breeder;At the age of6weeks,3varieties had no significant difference;At the age of17weeks,Da gu chicken bone was significantly higher thanhighland brown laying hens and AA broiler breeder(P <0.01), the both laterones were not significant difference (P>0.05).The chicken metabolizable energy intake per weight and hypothalamic NPYprotein, NPY protein/MC4R protein were negatively correlated (NPY protein, r=0.876, P=0.002; NPY protein/MC4R protein, r=0.835, P=0.005). Estimatingdaily metabolizable energy intake per kilogram of body weight with Chickenhypothalamus NPY protein can get mathematical model e^(0.837-0.003x)(r=0.859, P=0.0003267); with chicken hypothalamus NPY protein/MC4Rprotein, get mathematical model e^(0.748-0.581x)(r=0.776, P=0.002).Conclusions1、Three species/strains of chicken metabolizable energy intake perkilogram of body weight decreased in overall with weeks of age. differentspecies/strains of chicken metabolizable energy intake at same age wasdifferenct. The order of deposition on the energy of the three strains from high tolow was AA broiler breeder, highland brown laying hens and Zhuanghe Dagu chicken.2、The hypothalamus NPY mRNA trend of different species have somedifferences,and there are differences in the same week age of different species.The level of mRNA and protein of the hypothalamic NPY had no significantrelevance. The general trend of NPY protein increased with age. The chickenmetabolizable energy intake per kilogram of body weight and hypothalamic NPYprotein were extremely negatively correlated,which can be used to predict thechicken metabolizable energy intake per kilogram of body weight. Dagu chickenNPY protein levels was between highland brown laying hens and AA broilerbreeder.The later was minimum. Hypothalamus NPY protein which involved inthe regulation of feed intake, can be used for indicating growth rate,feedconversion rate and feed nutritional.3、Different strains of chicken have different patterns on the aspect ofMC4R gene expression. Chicken hypothalamus MC4R protein and MC4RmRNA showed significant negative correlation. both of them and metabolizableenergy intake per kilogram of body weight had no significant correlation.Whilethe ratio of NPY protein and MC4R protein and chicken metabolizable energyintake per kilogram of body weight showed significantly negative correlation.MC4R is involved in the regulation of feed intake.MC4R mRNA or MC4R proteinand NPY protein can be used for indicating the chicken feeding ability anddietary nutrient level. Three varieties,Dagu chicken MC4R protein is higher,andthe ratio of NPY protein and MC4R protein is lower, which consistent with itscharacteristics rich in meat and eggs.