| Selenium play important roles in maintaining normal pancreatic function and pancreas was the target organ which was susceptible to selenium deficiency, selenium deficiency can affect the development and function of pancreas and induced the occurrence of pancreatic degeneration, necrosis, atrophy and fibrosis in chickens. However the effect of supranutritional supplement of selenium on development and secretion of pancreas is still unclear.Insulin is mainly secreted by the pancreas and selenium is reported to have the insulin mimic function, which may exert its insulin mimic function through affecting insulin metabolism in target tissues. Selenium exerts its biological function mainly through selenoproteins, while the effects of supranutritional selenium on the expression of selenoprotein genes and insulin signal-related genes in insulin target tissues of chicken were still unclear.Our objective was to investigate the effects of supranutritional selenium on growth performance, oxidative stress measures, mRNA expression of selenoprotein gene and insulin signal-related gene expression in chickens. And explore how the incidences were related to selenogenome expression in three major tissues pancreas, liver and muscle.Our results may provide clues for exploration the biological roles of selenium involving in insulin function maintenance and metabolism.Totally 160 one-day-old Cobb male broilers of average body weight (44.30±0.49)g were randomly allocated into two groups, each of 4 replicates with 20 birds. The birds were fed a se-deficient corn-soybean basal diet (BD) supplemented with 0.3, and 3.0 mg/kg sodium selenite for 6 weeks, respectively. The basal diet (BD) was formulated for better meeting nutrient requirements of broiler. The experiment lasted for 6 wk. Birds were weighted at biweekly intervals and growth performance was recorded. At the end of the 2, 4 and 6 wk, birds were fasted for 8 h overnight, and then four birds with average body weight per group were selected out and killed by decapitation to collect blood, liver, pectoral muscle and pancreas for determination of selenium content, antioxidant measures, plasma biochemical measures and mRNA abundances of selenoprotein and insulin signal-related genes.The results are as follows:1. Growth performance and biochemical measuresDietary high-Se supplement negative affected growth performance of chickens. Compared to the control group (0.3mg Se/kg), high-Se diet intake decrease ADG of broiler at 2,4 wk and full period 0-6 wk (P<0.05), also ADFI at 4 wk and 0-6 wk were significantly decreased (P<0.05). FCR was not affected by the high Se diet in any periods of experiment(P>0.05).High-Se diet significantly increased selenium concentration in plasma and liver of chickens in each period (P<0.01) and liver had a higher selenium deposit than plasma.Compared to 0.3 mg Se/kg group, high Se diet improved Plasma GSH-Px by 37%(P<0.01) and decreased plasma MDA concentration by about 35% (P<0.01) at 4wk.In liver, SOD and MDA were increased in high-Se group at 4wk (P<0.05), whereas T-AOC was decreased by 8% in high-Se group at 4wk compared to 0.3mg Se/kg group (P<0.05).High Se intake increased GSH-Px activities by about 1.8,2.2 and 2.8-fold in muscle at 2,4 and 6 wk (P<0.01), respectively. The SOD activities in muscle were also increased in broiler fed high-Se diet than that of in control group at 2 wk (P<0.05).At 2 wk, High-Se diet result in a higher GSH-Px, T-AOC and MDA activities or concentration (P<0.05) in pancreas compared to the 0.3mg Se/kg group. The effect of high-Se on pancreas SOD last to 4 wk of age, which showed a 2.7-fold higher (P<0.05) compared to the 0.3mg Se/kg group.Chicken fed 3.0mg/kg Se (high Se group) exhibited a lower fasted plasma glucose concentration and a higher plasma insulin concentration at 2 wk compared to the control group (0.3mg/kg Se) (P<0.05).High-Se diet result in a higher plasma TG concentration at 2 and 4 wk (P<0.05) and increased plasma TCH concentration at 6 wk.2. Abundances of selenoprotein mRNAAt 4 wk, high-Se diet up-regulated the mRNA level of two slenoprotein genes (Seli and Selx) in liver, and five slenoprotein genes (GPx3,TR1,Dio3,Selm and Seli) in pancreas of the chickens; at the same time down-regulated the mRNA level of two slenoprotein genes (Diol and Selt) in liver, three slenoprotein genes (Diol,Seli and Selp) in muscle and Sephs2 in pancreas.At 6 wk, compared with those of supplementation Se at 0.3 mg/kg, dietary high-Se (3.0mg Se/kg) resulted in up-regulated (P<0.05 or as indicated) mRNA expression of 7 selenoprotein genes (TR1, TR3, Selm, Seli, Sepxl, Selpn1 and Sephs2) in liver,12 selenoprotein genes (GPx1, GPx2, TR1, TR3, Dio2, Selk, Selo, Selu, Seli, Sepnl,Selw,and Sephs2) in muscle, and Sephs2 in pancreas. At the same times down-regulated 3 genes (Diol,Selm and Selp) in muscle,4 seleniprotein genes (GPx1,Selu,Selk and Selw) in liver, and 7 selenoprotein genes (Selm,GPx1,GPx3, GPx4, Dio3, Selk and Selp) in pancreas. The numbers of affected selenoprotein genes increased with the duration of high Se supplementation.3. mRNA levels of insulin signal-related genesAt 4 wk, high-Se diet up-regulated the mRNA level of two insulin signal-related genes (Hnf4A and Ucp) in liver, Pdxl in muscle, Hnf4A and Irsl in pancreas; down-regulated the mRNA level of Irsl and slc2A in muscle, and HnflA in pancreas.Among the 13 insulin signal-related genes assayed, six genes in three tissues were up-regulated by high-Se diet at 6 wk (P<0.05). These included Foxol, Hnf4A, Irs2 and Pi3k in muscle, GCG, Hnf4A and Slc2A2 in liver, Hnf4A and Irs2 in pancreas. Hnf4A was up-regulated in three tissues investigated and Irs2 was up-regulate in 2 tissues (pancreas and muscle). In contrast,8 genes were down-regulated (P<0.05 or as indicated) in 2 tissues. These changes included 5 genes(Akt1, Foxo2, Ins, Pi3k and Ucp) in pancreas, three genes (Aktl, GCG and Ir) in muscle.Conclusion:Supranutritional selenium supplement decreased growth performance of chickens and increased selenium deposition in plasma and liver. High-Se diet significantly influenced antioxidant activity in plasma and tissues, and increase plasma insulin,TG and TCH concentration, decrease plasma glusose. The results of qPCR showed the dietary high Se affected mRNA profiles of selenoprotein genes in pancreas,liver and muscle of chickens and the numbers of the affected gene increased with the increased duration of high Se supplementation. Corresponding the supranutritional selenium supplement also affected insulin signal-related genes expression in these issues, and the affected gene increased with the age of high Se supplementation. Our results indicated dietary selenium play important roles in insulin function regulation.and selenium may exert its insulin-like roles through regulate slenoprotein genes expression in corresponding target tissues. |
PDF Full Text Request