Siculella L, Damiano F, Sabetta S, Gnoni G V
Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Laboratorio di Biochimica, Università di Lecce, I-73100 Lecce, Italy.
J Lipid Res. 2004 Jul;45(7):1333-40. doi: 10.1194/jlr.M400061-JLR200. Epub 2004 Apr 1.
The tricarboxylate (citrate) carrier (TCC), a protein of the mitochondrial inner membrane, is an obligatory component of the shuttle system by which mitochondrial acetyl-CoA is transported into the cytosol, where lipogenesis occurs. The aim of this study was to investigate the molecular basis for the regulation of TCC gene expression by a high-fat, n-6 PUFA-enriched diet. Rats received for up to 4 weeks a diet enriched with 15% safflower oil (SO), which is high in linoleic acid (70.4%). We found a gradual decrease of TCC activity and a parallel decline in the abundance of TCC mRNA, the maximum effect occurring after 4 weeks of treatment. At this time, the estimated half-life of TCC mRNA was the same in the hepatocytes from rats on both diets, whereas the transcriptional rate of TCC mRNA, tested by nuclear run-on assay, was reduced by approximately 38% in the rats on the SO-enriched diet. The RNase protection assay showed that the ratio of mature to precursor RNA, measured in the nuclei, decreased with the change to the n-6 PUFA diet. These results suggest that administration of n-6 PUFAs to rats leads to changes not only in the transcriptional rate of the TCC gene but also in the processing of the nuclear precursor for TCC RNA.
三羧酸（柠檬酸）载体（TCC）是线粒体内膜的一种蛋白质，是线粒体乙酰辅酶A转运至胞质溶胶（发生脂肪生成的部位）的穿梭系统的必需组成部分。本研究的目的是探究高脂、富含n-6多不饱和脂肪酸（PUFA）的饮食对TCC基因表达调控的分子基础。大鼠连续4周摄入富含15%红花油（SO）的饮食，红花油富含亚油酸（70.4%）。我们发现TCC活性逐渐降低，TCC mRNA丰度也相应下降，在治疗4周后出现最大效应。此时，两种饮食喂养的大鼠肝细胞中TCC mRNA的估计半衰期相同，而通过核转录分析检测，富含SO饮食喂养的大鼠中TCC mRNA的转录率降低了约38%。核糖核酸酶保护分析表明，在细胞核中测得的成熟RNA与前体RNA的比率随n-6 PUFA饮食的改变而降低。这些结果表明，给大鼠喂食n-6 PUFAs不仅会导致TCC基因转录率的变化，还会导致TCC RNA核前体加工过程的变化。
