請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/19891
標題: | 透過飲食調節的生長加速及脂肪儲存 Diet Dependent Regulation of Developmental Acceleration and Fat Storage |
作者: | Mao-Yen Huang 黃楙硯 |
指導教授: | 吳益群 |
關鍵字: | 飲食,線蟲,發育,脂肪, diet,C. elegans,development,fat, |
出版年 : | 2015 |
學位: | 碩士 |
摘要: | 食物的營養素,像蛋白質、脂肪、碳水化合物、維他命、礦物質等,能夠提供生物體生存所需的能量及維持生物體內的恆定,同時也已經被證實能夠影響生物體的生活史如生長、生殖、壽命等。一般飲食的組成是由不同物質以不同比例加以混和,因此各個物質如何對於生物體產生影響目前仍未完全了解。先前研究發現餵食線蟲Comamonas sp. DA1877比餵食Escherichia coli OP50會使線蟲有更快的生長速度。利用Escherichia coli OP50和Comamonas sp. DA1877這兩種食物,我們研究不同食物對生長速度及脂肪含量的影響與其背後的分子機制。首先我們先比較線蟲在餵食這兩種食物後生長速度的差異,觀察到不只正在食用DA1877的親代會生長加速,子代即使換回食用OP50也還是有生長加速的現象,此現象同時也出現在可以受食物DA1877影響,而抑制螢光表現的轉錄報導線蟲(Pacdh-1::gfp transgenic worms)子代當中。同時我們也透過實驗,確認了影響子代生長速度的因子需要透過卵子傳送,而非透過食物的分泌物或濾液等因素導致。有其他研究指出DA1877中的vitamin B12 是造成生長加速的關鍵因子,因此我們也在食物中補充vitamin B12來觀察子代生長情況,結果發現vitamin B12果然和DA1877食物一般,使線蟲生長加速,並抑制轉錄報導線蟲的螢光表現,其影響也確實能夠傳遞到子代,因此可推論出影響到子代生長的因子很可能就是B12。Vitamin B12是細胞中甲基轉移作用(Trans-methylation)的重要調控因子,酵母菌的研究中發現,酵母菌的生長速度可經由蛋白質protein phosphatase 2(PP2A)的甲基化修飾來調控,因此我們進一步推測DA1877食物中的B12可能藉由調控蛋白質PP2A的甲基化修飾,來影響線蟲生長。實驗結果顯示加入甲基移轉作用的反應物methionine和SAM (S-adenolsylmethionine)於食物中,皆造成線蟲生長加速,而加入methionine造成的生長速度改變,則在甲基移轉作用反應酶(S-adenolsylmethionine synthetase)的突變株和PP2A的突變株中受到抑制。此外,在PP2A的突變株中也觀察到vitamin B12造成的生長速度影響受到抑制。另一方面由於甲基移轉作用也被發現調控脂肪代謝,我們發現食用DA1877的線蟲表現顯著的脂肪儲存量下降,同樣的現象也發生在食物補充 vitamin B12, SAM,或methionine的線蟲中。我們的研究顯示: 食物中的微量營養素(micronutrient) Vitamin B12 會透過促進甲基移轉作用,來降低脂肪儲存量,並經由調控PP2A的甲基化修飾來增進生長速度。接下來我們將針對PP2A甲基化,脂肪儲存量和生長速度間的相互關聯進行深入研究,並探討甲基移轉作用是否仍調控其他反應,而造成生長速度的改變。 The nutrients of diet, such as proteins, fats, carbohydrates, vitamins, and minerals, are essential for development and homeostasis of organisms. Different diets has been shown to alternate organismal life-history, such as development and reproduction, and affect lifespan. However, mechanisms by which the nutrients in complex dietary compositions regulate lifespan and life-history of organism are poorly understood. Here we used Caenorhabditis elegans as a model organism to study this issue. Previous studies have shown that C. elegans fed Comamonas sp. DA1877 has faster developmental rate than those fed Escherichia coli OP50. Using Escherichia coli OP50 or Comamonas sp. DA1877, we investigated how the two diets affect developmental rate differently and the underlying molecular mechanisms. Our results showed that parental worms fed DA1877 produce progeny that grow faster than those fed OP50, the effect of parental diet is also observed in the transcription acetyl-CoA dehydrogenase acdh-1, whose expression is greatly suppressed by DA1877 diet, in the progeny. Next we crossed the transgenic worms fed with different diets and demonstrated that such inherited growth acceleration is mediated by hermaphroditic oocytes. We further tested if the developmental acceleration by DA1877 is caused by the volatile or secreted substances from the bacteria diets. The data indicated that neither the volatiles nor secreted substances from the bacteria diets affect worm developmental rate. Vitamin B12 has been shown recently the key substance in the DA1877 diet for developmental acceleration of C. elegans. To examine whether vitamin B12 is also the cause for developmental acceleration in the progeny, we added vitamin B12 in the parental OP50 diet and tested the expression of acdh-1 in the progeny. Our data showed that the expression of acdh-1 is suppressed both in the parents and the progeny, suggesting vitamin B12 is also the key substance of DA1877 that accelerates the developmental rate in the progeny. Vitamin B12 plays an important role in transmethylation reaction. In budding yeast, methylation of PP2Ac (protein phosphatase 2A catalytic subunit) promotes growth. We tested whether vitamin B12 in DA1877 may activate transmethylation reaction, resulting in the methylation of PP2Ac which in turn accelerates developmental rate in the worms. Our results showed that methionine and S-adenosylmethionine (SAM) supplement, like vitamin B12, increase developmental rate and that the accelerated development is blocked by a mutation of SAM synthesase, sams-1, or PP2Ac RNAi. Moreover, PP2Ac RNAi also suppress the developmental acceleration induced by vitamin B12. In addition, transmethylation reactions are involved in lipid metabolism. We found that not only DA1877 diet but also vitamin B12, SAM, methionine supplements result in decreased lipid droplets in the worms. Together, based on these data, we proposed that vitamin B12 from theDA1877 diet regulates the fat storage and the methylation of PP2Ac through transmethylation reaction to promote developmental rate in C. elegans. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/19891 |
全文授權: | 未授權 |
顯示於系所單位: | 分子與細胞生物學研究所 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-104-1.pdf 目前未授權公開取用 | 6.16 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。