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日粮对雏鸡不同组织中IGFBP-2基因表达变化的影响。各处理组均未检测到肝脏IGFBP-2mRNA的表达。饲喂5%大豆日粮的雏鸡，脑IGFBP-2的mRNA水平低于饲喂20%大豆日粮添加必需氨基酸的雏鸡。在肌胃中，添加必需氨基酸的20%大豆日粮组的IGFBP-2mRNA水平显著低于其他组。各处理组大鼠肾脏IGFBP-2基因表达差异无统计学意义。这些结果表明，饲料蛋白质含量的差异影响IGFBP-2基因在脑和胃中的表达，而饲料蛋白质质量的差异只影响胃的IGFBP-2基因的表达。IGFBP-2基因的表达对日粮蛋白质质量差异的反应可能不如对日粮蛋白质含量的反应。禁食2天后，肝脏IGFBP-2基因的表达显著增加，再饲喂6小时后，IGFBP-2基因的表达显著降低，胰岛素可将禁食刺激的肝脏IGFBP-2基因的表达降低到饲喂鸡的水平。禁食2天后，肌胃中IGFBP-2基因的表达水平显著升高，再饲喂6 h后，IGFBP-2基因的表达有下降趋势，但胰岛素处理组肌胃IGFBP-2基因的表达低于饲喂鸡。各处理组脑、肾组织中IGFBP-2mRNA的表达差异无统计学意义。这些结果表明，禁食和再喂养引起的肝脏和肌胃IGFBP-2基因表达的变化可能部分是通过血浆胰岛素浓度的变化来调节的。

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.