Takahashi Keita, Kishimoto Yuki, Konishi Tomokazu, Fujita Yasunori, Ito Masafumi, Shimokado Kentaro, Maruyama Naoki, Ishigami Akihito
Molecular Regulation of Aging, Tokyo Metropolitan Institute of Gerontology, Tokyo 173-0015, Japan; Department of Geriatrics and Vascular Medicine, Tokyo Medical and Dental University, Tokyo 113-8510, Japan.
Faculty of Bioresource Sciences, Akita Prefectural University, Akita 010-0195, Japan.
Biochim Biophys Acta. 2014 Jul;1840(7):2289-98. doi: 10.1016/j.bbagen.2014.03.019. Epub 2014 Apr 3.
We sought to elucidate the effect of an ascorbic acid (AA) deficiency on gene expression, because the water soluble antioxidant AA is an important bioactive substance in vivo.
We performed microarray analyses of the transcriptome in the liver from senescence marker protein-30 (SMP30)/gluconolactonase (GNL) knockout (KO) mice, which are unable to synthesize AA in vivo.
Our microarray analysis revealed that the AA deficiency increased gene expression related to the oxidation-reduction process, i.e., the nuclear factor, erythroid derived 2, like 2 (Nrf2) gene, which is a reactive oxygen species-sensitive transcriptional factor. Moreover, this AA deficiency increased the expression of genes for lipid metabolism including the cytochrome P450, family 7, subfamily a, polypeptide 1 (Cyp7a1), which is a late-limiting enzyme of the primary bile acid biosynthesis pathway. Although an AA deficiency increased the Cyp7a1 protein level, bile acid levels in the liver and gallbladder decreased. Since Cyp7a1 has a heme iron at the active site, AA must function as a reductant of the iron required for the continuous activation of Cyp7a1.
This experimental evidence strongly supports a role for AA in the physiologic oxidation-reduction process and lipid metabolism including bile acid biosynthesis.
Although many effects of AA supplementation have been reported, no microarray analysis of AA deficiency in vivo is available. Results from using this unique model of AA deficiency, the SMP30/GNL-KO mouse, now provide new information about formerly unknown AA functions that will implement further study of AA in vivo.
我们试图阐明抗坏血酸（AA）缺乏对基因表达的影响，因为水溶性抗氧化剂AA是体内一种重要的生物活性物质。
我们对衰老标志物蛋白-30（SMP30）/葡糖酸内酯酶（GNL）基因敲除（KO）小鼠肝脏中的转录组进行了微阵列分析，这些小鼠在体内无法合成AA。
我们的微阵列分析显示，AA缺乏增加了与氧化还原过程相关的基因表达，即核因子红细胞衍生2样2（Nrf2）基因，它是一种对活性氧敏感的转录因子。此外，这种AA缺乏增加了脂质代谢相关基因的表达，包括细胞色素P450家族7亚家族a多肽1（Cyp7a1），它是初级胆汁酸生物合成途径中的一种限速酶。虽然AA缺乏增加了Cyp7a1蛋白水平，但肝脏和胆囊中的胆汁酸水平却下降了。由于Cyp7a1在活性位点有一个血红素铁，AA必须作为Cyp7a1持续激活所需铁的还原剂发挥作用。
这一实验证据有力地支持了AA在生理氧化还原过程和脂质代谢（包括胆汁酸生物合成）中的作用。
虽然已经报道了补充AA的许多作用，但尚无关于体内AA缺乏的微阵列分析。使用这种独特的AA缺乏模型，即SMP30/GNL-KO小鼠，所得到的结果现在提供了关于以前未知的AA功能的新信息，这将推动对AA在体内的进一步研究。
