Sato Yasunori, Amano Akiko, Kishimoto Yuki, Takahashi Keita, Handa Setsuko, Maruyama Naoki, Ishigami Akihito
Molecular Regulation of Aging, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.
Geriatr Gerontol Int. 2014 Oct;14(4):989-95. doi: 10.1111/ggi.12162. Epub 2013 Oct 10.
Senescence marker protein-30 (SMP30)/gluconolactonase (GNL) knockout (KO) mice are incapable of synthesizing L-ascorbic acid (AA) in vivo. As AA is known to be a water-soluble anti-oxidant, we assessed protein oxidation levels in livers from SMP30/GNL KO mice maintained in an AA-insufficient condition.
Livers were collected from male SMP30/GNL KO mice at the ages of 3, 6 and 12 months, and wild-type (WT) mice at the ages of 3, 6, 12 and 24 months. To assess protein oxidation, we measured the content of protein carbonyl, which is a major protein oxidation marker. AA levels were measured by 2,4-dinitrophenylhydrazine method using high-performance liquid chromatography.
Livers of SMP30/GNL KO mice had just ∼5% as much AA as those of WT mice from 3 to 12 months-of-age. Protein carbonyl levels in livers from SMP30/GNL KO mice were a significant 1.8- to 2.3-fold higher than those from age-atched WT mice. To establish that the AA-insufficiency caused this difference, we added AA to some drinking water, and examined the effect on AA and protein carbonyl levels in livers from SMP30/GNL KO and WT mice. Livers from SMP30/GNL KO mice given extra AA had a significantly higher content than those from their deprived counterparts. Furthermore, protein carbonyl levels in livers from AA-supplemented SMP30/GNL KO mice were significantly lower than those from the SMP30/GNL KO mice without AA supplementation. However, added AA did not affect the protein carbonyl levels in WT mice.
These results strongly suggest that AA plays an important role in preventing protein oxidation in vivo, thus enhancing overall health.
衰老标记蛋白30（SMP30）/葡萄糖酸内酯酶（GNL）基因敲除（KO）小鼠无法在体内合成L-抗坏血酸（AA）。由于已知AA是一种水溶性抗氧化剂，我们评估了处于AA不足状态下的SMP30/GNL KO小鼠肝脏中的蛋白质氧化水平。
从3、6和12月龄的雄性SMP30/GNL KO小鼠以及3、6、12和24月龄的野生型（WT）小鼠中采集肝脏。为了评估蛋白质氧化，我们测量了蛋白质羰基的含量，其是主要的蛋白质氧化标记物。使用高效液相色谱法通过2,4-二硝基苯肼法测量AA水平。
3至12月龄的SMP30/GNL KO小鼠肝脏中的AA含量仅为WT小鼠的约5%。SMP30/GNL KO小鼠肝脏中的蛋白质羰基水平比同龄WT小鼠显著高出1.8至2.3倍。为了确定AA不足导致了这种差异，我们在一些饮用水中添加了AA，并检查了对SMP30/GNL KO和WT小鼠肝脏中AA和蛋白质羰基水平的影响。给予额外AA的SMP30/GNL KO小鼠肝脏中的含量显著高于未给予的同类小鼠。此外，补充AA的SMP30/GNL KO小鼠肝脏中的蛋白质羰基水平显著低于未补充AA的SMP30/GNL KO小鼠。然而，添加AA对WT小鼠的蛋白质羰基水平没有影响。
这些结果有力地表明，AA在体内预防蛋白质氧化中起重要作用，从而增强整体健康。
