| Pancreas was the target organ which was susceptible to selenium(Se) deficiency, and long-term Se deficiency can induced the occurrence of pancreatic degeneration and atrophy in chickens, which indicated Seplay important roles in maintaining normal pancreatic function. However, whetherSe deficiency has negative effects on insulin synthesis and metabolismremain unclear.Pancreas is the organ responsible for the secretion of insulin, and liver and muscle are two important insulin target tissues. Se exert its biological via selenoprotein,however the effects of Se deficiency on selenoprotein genes and insulin metabolism-related genes expression in those tissues of chickenarestill unclear.Therefore, our objective was to exploration the effects of Se deficiency on growth performance, physiological and biochemical measures, tissues mRNA expression of selenoprotein genes and insulin metabolism-related genes in chickens.Our results may provide clues for exploration the biological roles of Seinvolving in insulin metabolism.In this experiment, corn and soybean derived from severe Se-deficient area of Sichuan (Hanyuan Mountain) were adopted to formulate the corn-soybean basal diet (Se<0.02mg Se/kg) and effects of dietary Se deficiency on expression of selenoprotein genes in insulin synthesis and target tissues in chicken were investigated.Totally 120 one-day-old Cobb male broilers of average body weight (44.30±0.49)g were randomly allocated into two groups. The birds were fed a Se-deficient corn-soybean basal diet (BD) supplemented with 0, and 0.3 mg/kg sodium selenite for 5 weeks, respectively.Birds were weighted weekly and growth performance was recorded, exudative diathesis (ED) and other classical Se-deficient diseases and mortality of broilerswere recorded.At the end of the 5 wk. birds (n=6/group) were killed by decapitation to collect blood, liver, pectoral muscle and pancreas for Secontent, antioxidant and biochemical measures assayed,also the effects of dietary Se deficiency on 23 selenoprotein genes and 17 insulin metabolism-related genes expression in liver, muscle and pancreas were investigated by RT-qPCR.The results are as follows:1. Effects of dietary Se deficiency on pathology. growth performance and tissues Se deposition of chickenThe dietary Se deficiency induced the appearance of ED. pancreatic atrophy dyskinesia, and otherSe deficiency symptoms in chicken. The birds with Se deficiency has shown high incidence rate of Se deficiency symptoms (90%) and mortality (62%). At the same time dietary Se deficiency negative affected growth performance of chickens. Compared to the control group (0.3mg Se/kg), dietanry Se deficiency decrease average body weight of broiler at 14 to 35 days of age (P<0.05). Compared to 0.3 mg Se/kg group, dietary Se deficiency decrease serum (?) selenium concentration by 80% and 73%(P<0.01)2.Effects of dietary Se deficiency on biochemical measure of chickenDietary Se deficiency decreased (P<0.05) serum insulin concentration, TG, TCH by 32%,61%andby 45%, and increased (P<0.05) serum glucose concentration, interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α) by 233.3%,40% and 23%. Compared with control group, serum glutathione peroxidase (GSH-Px) and total antioxidant capacity (T-AOC) decreased by 76% and 57%(P<0.05) in Se deficiency group; Dietary Se deficiency decreased (P<0.05) GSH-Px and superoxide dismutase (SOD) activities by 66% and 24%, respectively, and increasedmalondialdehyde(MDA) concentration by 63% (P<0.05) in liver; In muscle onlythe GSH-Px activities was affected by dietary Se deficiency and decreased by 48%(P<0.05); Se-deficient result in a lower GSH-Px and SOD activities (P<0.05) in pancreas, which were decreased by 32%(P<0.05)3. Effects of dietary Se deficiency onexpression ofselenoprotein genes in tissues of chickenCompared with control group, dietary Se deficiency down-regulated (P<0.05) 9 selenoprotein genes (Gpx2,Gpx3,Dio1,Dio3,Txnrdl,Selk,Seli,Selm,Selo,Sels,Selt,Sepn1,Sepp1 and Selx) expression and up-regulated (P<0.05) 2 selenoprotein genes (Txnrdl and Sels) in liver.Dietary Se deficiency also down-regulated(P<0.05) mRNA profiles of 14 selenoprotein genes (Gpx2.Gpx3.Dio1,Dio3,Txnrd1,Selk,Seli,Selm,Selo,Sels.Selt,Sepn1, Sepp1 and Selx) in muscle.Compared to liver and muscle, the pancreas has more selenoprotein genes affected by dietary Se deficiency, among 23 selenoprotein genes investigated,18 selenoprotein genes (Gpx2,Gpx3,Gpx4,Txnrd1, Txnrd3,Selk,Seli,Selm,Selo,Sels,Selu,Seli,Sep15,Sepn1,Sepp1,Sepw1,Selx and Sephs2) were down-regulated(P<0.05).4.Effects of dietary Se deficiency onexpression of insulin metabolism related genes in tissues of chickenAt 5 week, dietary Se deficiency down-regulated (P<0.05) the mRNA levels of 5 insulin metabolism-related genes (Irs2,Ins,Pdxl,Ptpnl and Slc2A2) and up-regulated (P<0.05) the mRNA level of three insulin metabolism-rel(?) genes (Foxa2、Gcg and Irsl) in liver of chicken.Dietary Se deficiency also depressed (P<0.05 or 0.01) expression of 14(Irsl,Ins,Neurodl,Slc2A2,Aktl,Braf,Foxo1,Foxa2,Ir,Irs2,Ptpn,Pi3kand Ucp) and 6 (Aktl,Foxa2,Hnf1A,Hnf4A,IrandPdx1) insulin metabolism-related genes in muscle and pancreas, in respectively.Conclusion:Dietary Se deficiency depressed growth performance of broilers, increased the incidence rate of Se deficiencysymptoms (90%) and mortality (62%),anddecreased serum and liver selenium deposition in birds. Also Se-deficient diet significantly influenced antioxidant activity in blood and three insulin target tissues, impaired insulinsynthesis, and induced hyperglycemia anddyslipidemia in chicken.The results of qPCR showed dietary Se deficiency globally affected mRNA profiles of selenoprotein genes in pancreas,liver and muscle of broilers.And the pancreas had the most number of affected selenoprotein genes, followed by muscle and liver. Among the three tissues investigated, only the liver had up-regulated selenoprotein genes subject to Se deficiency.At the same time dietary Sedeficiency also affected expression of insulin metabolism-related genes in those three tissues, and the muscle had the most affected genes, followed by liver and pancreas, and most affected genes were down-regulated. Our results shows dietary Se deficiency depressed expression of selenoprotein genes and insulin metabolism-related genes in pancreas, liver and muscle, caused dyslipidemiaand induced hyposinculimia and hyperglycemia in chicken.Our results indicated dietary Seplay important roles in maintaininginsulin function and Semay exert its insulin-like roles through regulate selenoprotein genes expression in corresponding target tissues. |
