Gastrointestinal Metabolomic Study of Herbivorous Mammals

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).