Leili S, Scanes C G
Department of Animal Sciences, Rutgers: The State University of New Jersey, New Brunswick 08903, USA.
Proc Soc Exp Biol Med. 1998 Sep;218(4):322-8. doi: 10.3181/00379727-218-44299.
The effect of dietary protein restriction (5% and 10% compared to control 20%) on circulating concentrations of insulin-like growth factor (IGF)-1 and IGF binding proteins (IGFBPs) was examined in young (18-day-old) chickens during a 2-week period. Reductions in dietary protein caused progressive growth retardation as evidenced by decreased body-weight gain and reduced bone growth. The decrease in plasma concentrations of IGF-I appeared to be directly related to dietary protein levels (i.e., the lower the amount of dietary protein, the greater the reduction in the circulating concentrations of this growth factor). Three IGFBPs with MWs of 30, 36, and 40 kDa were detected by radioligand assay following separation by SDS-electrophoresis. Binding activity of the 30-kDa IGFBP was transiently increased on Day 3 by protein restriction (both 5% and 10%). The 36-kDa IGFBP was also affected by protein restriction with binding activity of this IGFBP decreased throughout the study. The binding activity of the 40-kDa IGFBP was transiently increased on Days 3 and 7 but subsequently decreased on Days 10 and 14 in the 10% protein group. In the 5% protein group, binding activity of the 40-kDa IGFBP was decreased throughout the study. The decrease in circulating concentrations of IGF-I appeared to be inversely related to the initial increase in the binding activity of the 30-kDa IGFBP on Day 3 (5% and 10% protein) and to the increased binding activity of the 40-kDa IGFBP on Days 3 and 7 (10% protein). This may suggest that bioavailability of plasma IGF-I is decreased initially due to increased binding with these IGFBPs. However, binding activity of all three IGFBPs then decreased in a manner directly related to the decreasing IGF-I plasma concentrations for the remainder of the experiment. The initial increase in binding activity observed with the 30-kDa IGFBP is similar to that observed with IGFBP-1 in mammals in that both of these IGFBPs respond rapidly to nutritional deprivation. Decreased protein intake would certainly have an impact on the amount of available proteins required for the synthesis of these growth factors.
在为期2周的时间里，研究了饮食蛋白质限制（与20%的对照相比为5%和10%）对幼龄（18日龄）鸡循环中胰岛素样生长因子（IGF）-1和IGF结合蛋白（IGFBPs）浓度的影响。饮食蛋白质减少导致渐进性生长迟缓，表现为体重增加减少和骨骼生长减缓。IGF-I血浆浓度的降低似乎与饮食蛋白质水平直接相关（即饮食蛋白质含量越低，这种生长因子循环浓度的降低幅度越大）。通过SDS电泳分离后，用放射性配体测定法检测到三种分子量分别为30、36和40 kDa的IGFBPs。蛋白质限制（5%和10%）使30-kDa IGFBP的结合活性在第3天短暂增加。36-kDa IGFBP也受到蛋白质限制的影响，在整个研究过程中该IGFBP的结合活性降低。在10%蛋白质组中，40-kDa IGFBP的结合活性在第3天和第7天短暂增加，但随后在第10天和第14天降低。在5%蛋白质组中，40-kDa IGFBP的结合活性在整个研究过程中降低。IGF-I循环浓度的降低似乎与第3天30-kDa IGFBP结合活性的初始增加（5%和10%蛋白质）以及第3天和第7天40-kDa IGFBP结合活性的增加（10%蛋白质）呈负相关。这可能表明，由于与这些IGFBPs的结合增加，血浆IGF-I的生物利用度最初会降低。然而，在实验的剩余时间里，所有三种IGFBPs的结合活性随后以与IGF-I血浆浓度降低直接相关的方式降低。在30-kDa IGFBP中观察到的结合活性的初始增加与在哺乳动物中IGFBP-1中观察到的相似，因为这两种IGFBPs对营养剥夺都有快速反应。蛋白质摄入量的减少肯定会对合成这些生长因子所需的可用蛋白质数量产生影响。
