Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA.
Dis Model Mech. 2013 Jan;6(1):84-94. doi: 10.1242/dmm.010207. Epub 2012 Jul 5.
Classic galactosemia is a genetic disorder that results from profound loss of galactose-1P-uridylyltransferase (GALT). Affected infants experience a rapid escalation of potentially lethal acute symptoms following exposure to milk. Dietary restriction of galactose prevents or resolves the acute sequelae; however, many patients experience profound long-term complications. Despite decades of research, the mechanisms that underlie pathophysiology in classic galactosemia remain unclear. Recently, we developed a Drosophila melanogaster model of classic galactosemia and demonstrated that, like patients, GALT-null Drosophila succumb in development if exposed to galactose but live if maintained on a galactose-restricted diet. Prior models of experimental galactosemia have implicated a possible association between galactose exposure and oxidative stress. Here we describe application of our fly genetic model of galactosemia to the question of whether oxidative stress contributes to the acute galactose sensitivity of GALT-null animals. Our first approach tested the impact of pro- and antioxidant food supplements on the survival of GALT-null and control larvae. We observed a clear pattern: the oxidants paraquat and DMSO each had a negative impact on the survival of mutant but not control animals exposed to galactose, and the antioxidants vitamin C and α-mangostin each had the opposite effect. Biochemical markers also confirmed that galactose and paraquat synergistically increased oxidative stress on all cohorts tested but, interestingly, the mutant animals showed a decreased response relative to controls. Finally, we tested the expression levels of two transcripts responsive to oxidative stress, GSTD6 and GSTE7, in mutant and control larvae exposed to galactose and found that both genes were induced, one by more than 40-fold. Combined, these results implicate oxidative stress and response as contributing factors in the acute galactose sensitivity of GALT-null Drosophila and, by extension, suggest that reactive oxygen species might also contribute to the acute pathophysiology in classic galactosemia.
经典型半乳糖血症是一种遗传性疾病，由半乳糖-1-P-尿苷酰转移酶（GALT）严重缺失引起。受影响的婴儿在接触牛奶后会迅速出现潜在致命的急性症状。限制半乳糖的饮食可以预防或解决急性后遗症；然而，许多患者会经历严重的长期并发症。尽管经过几十年的研究，经典型半乳糖血症的病理生理学机制仍不清楚。最近，我们开发了一种经典型半乳糖血症的黑腹果蝇模型，并证明与患者一样，如果 GALT 缺失的果蝇暴露于半乳糖中，它们在发育过程中会死亡，但如果维持在半乳糖限制饮食中则可以存活。先前的实验性半乳糖血症模型暗示了半乳糖暴露与氧化应激之间可能存在关联。在这里，我们描述了我们的半乳糖血症果蝇遗传模型在以下问题上的应用，即氧化应激是否对半乳糖敏感的 GALT 缺失动物的急性半乳糖敏感性有影响。我们的第一个方法测试了抗氧化剂和氧化剂食品补充剂对 GALT 缺失和对照幼虫存活的影响。我们观察到一个明显的模式：氧化剂百草枯和 DMSO 都对半乳糖暴露的突变体而不是对照动物的存活有负面影响，而抗氧化剂维生素 C 和 α-倒捻子素则有相反的效果。生化标志物还证实，半乳糖和百草枯协同增加了所有测试队列的氧化应激，但有趣的是，与对照相比，突变体动物的反应降低了。最后，我们测试了暴露于半乳糖的突变体和对照幼虫中两种对氧化应激有反应的转录本 GSTD6 和 GSTE7 的表达水平，发现这两种基因都被诱导，一种基因的诱导倍数超过 40 倍。综上所述，这些结果表明氧化应激和反应是 GALT 缺失的果蝇对半乳糖急性敏感性的重要因素，并暗示活性氧也可能对半乳糖血症的急性病理生理学有贡献。
