植食性哺乳動物消化道之代謝體學研究

Abstract

食葉性哺乳動物為一有效利用能量及與消化道微生物共生適應的植食性哺乳動物，其以富含纖維素的成熟葉子為食。大赤鼯鼠（Petaurista philippensis grandis）和白面鼯鼠（P. alborufus lena）是台灣典型的食葉性哺乳動物，膨大及延長的盲腸是與其他後腸發酵動物共通的消化道結構，且為提供共生微生物進行厭氧代謝之處。代謝產物為代謝過程中的產物，即反映動物的生理和代謝狀態及消化道的化學環境。本研究透過液相層析質譜儀非標的性之代謝體分析大鼠和飛鼠消化道內容物的代謝產物，比較馴養之實驗大鼠，在餵食一般飼料或高纖維飼料者，與食葉性飛鼠的消化道代謝產物組成差異和代謝途徑之生化反應動態的代謝體學。主成份分析配合K-means分群法發現大鼠和飛鼠的消化道內容物代謝產物組成與消化道的解剖結構、位置分佈相關，且消化的時間會減少代謝產物組成的變異程度。而五碳糖磷酸途徑可能為飛鼠後腸高度表現的代謝途徑，推測與提供脂肪酸等植物性食物來源缺乏之養分的生合成有關。

Folivorous mammals, which consume mature leaves, are able to extract energy from leave cellulose, with the aid from microbes inhabiting in their guts. Two flying squirrels in Taiwan, red-giant flying squirrel (Petaurista philippensis grandis) and white-faced flying squirrel (P. alborufus lena) that contain enlarged caeca (where microbial fermentation happens) are typical folivorous mammals. Metabolites are the products of metabolism and reflect physiological status and gastrointestinal chemical environment of an animal. We analyzed untargeted gut metabolic substance of the flying squirrels by liquid chromatography-mass spectrometry (LC-MS). Specifically, we compare flying squirrel with laboratory rats to reveal the difference between wild folivores (flying squirrel) and domesticated laboratory rats, especially to highlight the uniqueness of hindgut metabolome of flying squirrels. We found that metabolite composition corresponds to gut anatomical structures with metabolite groups revealed by principle component analysis (PCA) coupled with K-means cluster analysis. Variation of metabolite composition also relates to digestive time. In addition, Pentose phosphate pathway (PPP) might be a highly expressed pathway in flying squirrels’ hindguts. PPP in flying squirrel hindgut might relate to biosynthesis of certain essential nutrients (e.g. fatty acids which lack in leaves).