Kouda Katsuyasu, Kohno Hirao, Nakamura Harunobu, Ha-Kawa Sang K, Sonoda Yoshiaki, Iki Masayuki
Department of Public Health, Kinki University School of Medicine, 377-2 Ono-Higashi, Osaka-Sayama 589-8511, Japan.
Ann Nucl Med. 2009 Feb;23(2):123-9. doi: 10.1007/s12149-008-0217-1. Epub 2009 Feb 19.
Dietary restriction (DR) without malnutrition is widely acknowledged to prolong lifespan in laboratory animals. Evidence suggests that DR retards age-related decline in protein turnover of most organs. However, there has been no report about hepatic serum glycoprotein catabolism under DR. In the current study, we evaluate the hepatic uptake of asialoglycoprotein in ICR mice with DR by measuring the plasma clearance of technetium-99m galactosyl human serum albumin (Tc-GSA).
The amount of food supplied to the restricted mice was 70% of that consumed by the mice fed ad libitum (AL). The regimen was initiated at the age of 7 weeks and terminated after the age of 44 weeks. The plasma clearance of Tc-GSA was measured at the age of 7 weeks, 14 weeks, 28 weeks, and 42 weeks.
The restricted animals showed a marked decrease in their body and liver weight, and hepatic uptake of Tc-GSA per liver weight in the restricted mice was greater than that in the mice fed AL. On the other hand, the Tc-GSA plasma clearance in the mice fed AL was stable during the study period, and that in the restricted mice showed no change with age either, and those in the two groups were similar. In addition to the receptor function, there was no difference in the expression of mRNAs of the asialoglycoprotein receptor between the two groups. Serum concentrations of cholinesterase and hepatic mRNAs of glutamine synthetase in the restricted mice were higher than those in the mice fed AL. Serum levels of amino acids in the restricted mice were lower than those in the mice fed AL.
The data presented here show that the DR did not affect the capacity of hepatic serum glycoprotein catabolism, whereas several protein metabolic pathways were affected.
无营养不良的饮食限制（DR）可延长实验动物的寿命，这一点已得到广泛认可。有证据表明，DR可延缓大多数器官与年龄相关的蛋白质周转下降。然而，尚无关于DR条件下肝脏血清糖蛋白分解代谢的报道。在本研究中，我们通过测量99m锝半乳糖基人血清白蛋白（Tc-GSA）的血浆清除率，评估了DR条件下ICR小鼠肝脏对去唾液酸糖蛋白的摄取情况。
限制饮食组小鼠的食物供应量为自由摄食（AL）小鼠消耗量的70%。该方案于7周龄开始，44周龄结束。在7周龄、14周龄、28周龄和42周龄时测量Tc-GSA的血浆清除率。
限制饮食组动物的体重和肝脏重量显著降低，限制饮食组小鼠每单位肝脏重量对Tc-GSA的肝脏摄取量高于自由摄食组小鼠。另一方面，自由摄食组小鼠的Tc-GSA血浆清除率在研究期间保持稳定，限制饮食组小鼠的Tc-GSA血浆清除率也不随年龄变化，两组的清除率相似。除了受体功能外，两组去唾液酸糖蛋白受体的mRNA表达没有差异。限制饮食组小鼠的胆碱酯酶血清浓度和谷氨酰胺合成酶的肝脏mRNA水平高于自由摄食组小鼠。限制饮食组小鼠的血清氨基酸水平低于自由摄食组小鼠。
本文提供的数据表明，DR不影响肝脏血清糖蛋白的分解代谢能力，而一些蛋白质代谢途径受到了影响。
