转酮醇酶及磷酸戊糖旁路参与韦尼克脑病中线脑区选择性损害的病理机制

项目名称： 转酮醇酶及磷酸戊糖旁路参与韦尼克脑病中线脑区选择性损害的病理机制

项目编号： No.30870871

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 钟春玖

作者单位： 复旦大学

项目金额： 35万元

中文摘要： 硫胺素缺乏导致的学习记忆功能障碍与海马神经发生减少有关，海马转酮醇酶（TK）的mRNA表达明显高于皮层，硫胺素缺乏9天（TD9）和14天（TD14）对脑组织丙酮酸脱氢酶、α#37230;戊二酸脱氢酶活性无明显影响，而磷酸戊糖通路主要产物NADPH的含量和TK活性在TD9 和TD14均有显著下降。硫胺素拮抗剂吡啶硫胺和RNA干扰TK表达均能显著抑制体外培养的海马神经干细胞增殖。利用果蝇蘑菇体过表达TK基因模型研究发现，过表达TK能显著增大果蝇蘑菇体体积。我们的研究证明TK活性下降相关的磷酸戊糖旁路功能障碍导致的NADPH或/和核糖合成障碍可能参与了TD导致的脑中线两侧特异性脑区损害以及下调海马神经发生功能的病理损害机制。此外，我们在研究中还发现硫胺素缺乏增加小鼠脑内Aβ27785;积、tau蛋白异常磷酸化，与阿尔茨海默病发病有关。我们进一步研究了硫胺素衍生物- - 苯磷硫胺防治阿尔茨海默病的研究。结果表明，苯磷硫胺显著改善APP/PS1小鼠的认知功能、减少脑内Aβ27785;积、tau蛋白异常磷酸化，与一直GSK-3活性有关。 以上研究结果分别发表在Brain、J Neurochem等国际学术杂志。

中文关键词： 硫胺素缺乏; 转酮醇酶; 海马神经发生; 阿尔茨海默病

英文摘要： Thiamine deficiency (TD) impairs hippocampal neurogenesis. However, the mechanisms involved are not identified. In this work, TD mouse model was generated using a thiamine-depleted diet at two time points, TD9 and TD14 for 9 and 14 days of TD respectively. The activities of pyruvate dehydrogenase (PDH), αetoglutamate dehydrogenase (KGDH), glucose-6-phosphate dehydrogenase (G6PD), and transketolase (TK), as well as on the contents of NADP+ and NADPH were determined in whole mouse brain, isolated cortex, and hippocampus of TD mice model. The effects of TK silencing on the growth and migratory ability of cultured hippocampal progenitor cells (HPC), as well as on neuritogenesis of hippocampal neurons were explored. The results showed that TD specifically reduced TK activity in both cortex and hippocampus, without significantly affecting the activities of PDH, KGDH, and G6PD in TD9 and TD14 groups. The level of whole brain and hippocampal NADPH in TD14 group were significantly lower than that of control group. TK silencing significantly inhibited the proliferation, growth, and migratory abilities of cultured HPC, without affecting neuritogenesis of cultured hippocampal neurons. Taken together, these results demonstrate that decreased TK activity leads to pentose-phosphate pathway dysfunction and contributes to impaired hippocampal neurogenesis induced by TD. TK and pentose-phosphate pathway may be considered new targets to investigate hippocampal neurogenesis. In addition, we found that TD caused cerebral Aβeposition and tau hyperphosphorylation and was correlated with Alzheimer's disease. Here, We show that after a chronic 8 week treatment, benfotiamine (a thiamine derivative) dose-dependently enhanced the spatial memory of amyloid precursor protein/presenilin-1 mice in the Morris water maze test. Furthermore, benfotiamine effectively reduced both amyloid plaque numbers and phosphorylated tau levels in cortical areas of the transgenic mice brains. Most notably, benfotiamine significantly elevated the phosphorylation level of glycogen synthase kinase-3αnd -3βand reduced their enzymatic activities in the amyloid precursor protein/presenilin-1 transgenic brain. Therefore, in the animal Alzheimer's disease model, benfotiamine appears to improve the cognitive function and reduce amyloid deposition via thiamine-independent mechanisms, which are likely to include the suppression of glycogen synthase kinase-3 activities. These results suggest that, unlike many other thiamine-related drugs, benfotiamine may be beneficial for clinical Alzheimer's disease treatment.

英文关键词： Thiamine deficiency; transketolase; hippocampal neurogenesis; Alzheimer's disease