Katsurada A, Iritani N, Fukuda H, Matsumura Y, Nishimoto N, Noguchi T, Tanaka T
Tezukayama Gakuin College, Osaka, Japan.
Eur J Biochem. 1990 Jun 20;190(2):435-41. doi: 10.1111/j.1432-1033.1990.tb15593.x.
The effects of nutrients and hormones on transcriptional and post-transcriptional regulation of acetyl-CoA carboxylase in rat liver were investigated following a cDNA cloning. After refeeding a carbohydrate/protein diet to fasted rats, the transcriptional rate was increased 2.5-fold in only 1 h. The mRNA concentration reached a maximal level of 9-12-fold increase in 8-16 h, and the enzyme induction increased 10-fold in 48 h. By a carbohydrate diet without protein, the transcriptional rate, mRNA concentration and enzyme induction were similarly increased to the levels in the carbohydrate/protein diet. It appears that protein feeding is not necessary to induce acetyl-CoA carboxylase. Corn oil feeding decreased the transcriptional rate. In diabetic rats, the transcriptional rate, mRNA concentration and enzyme induction were very low in comparison with the normal. After insulin treatment, the transcriptional rate was increased 2-fold (the normal level) in 2 h in diabetic rats. By fructose feeding to diabetic rats, the transcriptional rate and mRNA concentration were increased similarly to the levels reached by insulin treatment, while the enzyme induction was increased by only 60%. Thus, it is suggested that insulin is importantly involved in the transcription and also translation of acetyl-CoA carboxylase. On the other hand, triiodothyronine treatment increased the mRNA and enzyme levels in diabetic and normal rats, and somewhat increased the transcriptional rate only in diabetic rats. Triiodothyronine appears to stabilize the mRNA besides having an insulin-like action in acetyl-CoA carboxylase transcription.
在完成乙酰辅酶A羧化酶cDNA克隆后，研究了营养物质和激素对大鼠肝脏中该酶转录及转录后调控的影响。给禁食大鼠重新喂食碳水化合物/蛋白质饮食后，转录速率在仅1小时内就增加了2.5倍。mRNA浓度在8 - 16小时内达到最大水平，增加了9 - 12倍，酶的诱导在48小时内增加了10倍。通过喂食不含蛋白质的碳水化合物饮食，转录速率、mRNA浓度和酶的诱导也同样增加到碳水化合物/蛋白质饮食中的水平。看来诱导乙酰辅酶A羧化酶并不需要蛋白质。喂食玉米油会降低转录速率。与正常大鼠相比，糖尿病大鼠的转录速率、mRNA浓度和酶的诱导都非常低。糖尿病大鼠经胰岛素治疗后，2小时内转录速率增加了2倍（达到正常水平）。给糖尿病大鼠喂食果糖后，转录速率和mRNA浓度的增加与胰岛素治疗达到的水平相似，而酶的诱导仅增加了60%。因此，提示胰岛素在乙酰辅酶A羧化酶的转录和翻译中都起着重要作用。另一方面，三碘甲状腺原氨酸处理增加了糖尿病大鼠和正常大鼠的mRNA及酶水平，且仅在糖尿病大鼠中略微增加了转录速率。三碘甲状腺原氨酸除了在乙酰辅酶A羧化酶转录中具有类似胰岛素的作用外，似乎还能稳定mRNA。
