NUTRITIONAL REGUILATION OF INSULIN-LIKE GROWTH FACTOR BINDING PROTEIN-2 GENE EXPRESSION IN THE CHICKEN

研究了饲喂不同蛋白质含量和质量的试验日粮对雏鸡各组织IGFBP-2基因表达变化的影响。肝脏IGFBP-2 mRNA在所有处理组中均未检测到。当鸡饲喂5%的大豆饲料，脑IGFBP-2的mRNA水平低于饲喂20%的大豆饲料补充必需氨基酸的鸡。在砂囊中，添加20%必需氨基酸组IGFBP-2 mRNA表达量显著低于其他组。各处理组肾脏IGFBP-2基因表达无显著差异。这些结果表明，饲料蛋白质量的差异影响IGFBP-2基因在脑和砂囊中的表达，而饲料蛋白质质量的差异只影响IGFBP-2基因在砂囊中的表达。IGFBP-2基因的表达可能对日粮蛋白质质量的反应比对日粮蛋白质量的反应更小。肝脏IGFBP-2 mRNA在禁食2 d后显著升高，再进食6 h后显著降低。胰岛素给药也降低了肝脏IGFBP-2基因表达的水平，禁食刺激再喂食鸡。禁食2 d后，肌胃IGFBP-2 mRNA表达显著增加，再喂食6 h后，IGFBP-2 mRNA表达呈下降趋势。胰岛素处理降低了砂囊IGFBP-2基因的表达，低于饲喂鸡的水平。各处理组脑、肾组织IGFBP-2 mRNA表达差异无统计学意义。这些结果表明，IGFBP-2基因表达的变化，在肝脏和砂囊禁食和再喂养可能部分调节血浆胰岛素浓度的变化。

The influence of feeding with experimental diets containing different dietary protein quantity and quality on changes in IGFBP-2 gene expression in various tissues of young chickens was examined. The hepatic IGFBP-2 mRNA was not detected among all treatments. When chickens fed a 5% soybean diet, brain IGFBP-2 mRNA level was lower than that of chickens fed a 20% soybean diets supplemented with essential amino acids. In the gizzard, IGFBP-2 mRNA in the group of a 20% soybean diets supplemented with essential amino acids was significantly lower than other groups. There was no significant difference in IGFBP-2 gene expression in the kidney among all treatments. These results suggest that the difference in dietary protein quantity affect IGFBP-2 gene expression in brain and gizzard, and that the difference in dietary protein quality affects IGFBP-2 gene expression in only gizzard. The expression of IGFBP-2 gene might be less responsive to the difference in dietary protein quality than that in dietary protein quantity.The changes in tissue IGFBP-2 gene expression of young fasted chickens followed by refeeding a commercial diet or by administrating bovine insulin was examined. Hepatic IGFBP-2 mRNA was significantly increased by fasting for 2 days and decreased by refeeding for 6 h. Insulin administration also decreased hepatic IGFBP-2 gene expression stimulated by fasting to the level of refed chickens. IGFBP-2 mRNA in the gizzard was significantly increased by fasting for 2 days and tended to decrease by refeeding for 6 h. Insulin administration decreased gizzard IGFBP-2 gene expression lower than the level of refed chickens. There was no significant difference in IGFBP-2 mRNA in the brain and kidney among all treatments. These results suggest that the changes in IGFBP-2 gene expression in the liver and gizzard by fasting and refeeding might be partly regulated by the alteration in plasma insulin concentration.