Iritani N, Nishimoto N, Katsurada A, Fukuda H
Tezukayama Gakuin College, Osaka, Japan.
J Nutr. 1992 Jan;122(1):28-36. doi: 10.1093/jn/122.1.28.
This investigation concerns the effects of the level of intake of a high carbohydrate diet on transcriptional rate, mRNA concentration and enzyme induction for lipogenic enzymes in rat liver. Six hours after refeeding fasted rats, the transcriptional rates in livers reached low maximum levels with small quantities of diet, but the mRNA concentrations continued to increase as diet intake increased. Greater diet intake primarily increased transcriptional rates and mRNA concentrations of lipogenic enzymes. After refeeding for 16 h, the mRNA concentrations were sigmoidly increased relative to the diet quantity and reached maximum levels of 20-, 110-, 22- and 16-fold above each fasted level for acetyl-CoA carboxylase, fatty acid synthase, malic enzyme and glucose-6-phosphate dehydrogenase, respectively. After 3 d of refeeding (in a steady state of lipogenic enzyme activities), however, the transcriptional rates, mRNA concentrations and activity inductions of all the enzymes were sigmoidly increased relative to diet quantity, but were not different among the enzymes. Consequently, fatty acid synthesis and triglyceride levels in the liver were not increased by feeding less than 70% of ad libitum intake but were greatly increased by feeding greater than 70% of ad libitum intake.
本研究关注高碳水化合物饮食的摄入量对大鼠肝脏中脂肪生成酶的转录速率、mRNA浓度及酶诱导作用的影响。禁食大鼠重新喂食6小时后，肝脏中的转录速率在摄入少量食物时达到较低的最高水平，但mRNA浓度随着食物摄入量的增加而持续上升。更多的食物摄入主要增加了脂肪生成酶的转录速率和mRNA浓度。重新喂食16小时后，mRNA浓度相对于食物量呈S形增加，相对于禁食水平，乙酰辅酶A羧化酶、脂肪酸合酶、苹果酸酶和葡萄糖-6-磷酸脱氢酶的mRNA浓度分别达到最高水平，比各自的禁食水平高出20倍、110倍、22倍和16倍。然而，重新喂食3天（处于脂肪生成酶活性的稳定状态）后，所有酶的转录速率、mRNA浓度和活性诱导相对于食物量呈S形增加，但各酶之间没有差异。因此，喂食量低于自由摄入量的70%时，肝脏中的脂肪酸合成和甘油三酯水平不会增加，但喂食量超过自由摄入量的70%时则会大幅增加。
