日本北海道大學(xué)微生物生理學(xué)橫田篤教授領(lǐng)導(dǎo)的一個(gè)研究小組發(fā)現(xiàn),，食用多的食物會(huì)促進(jìn)更多消化液（膽汁）分泌,，進(jìn)而殺死對(duì)人體有益的細(xì)菌，對(duì)腸內(nèi)細(xì)菌平衡有著破壞作用,。消化液分泌還可能引起內(nèi)臟脂肪綜合征和大腸癌的發(fā)生,。
研究小組在大鼠的普通餌料中添加與食用高脂肪后分泌的濃度相當(dāng)?shù)哪懼B續(xù)讓大鼠食用10天,，然后觀察大鼠盲腸的細(xì)菌變化情況,。
一般情況下，大鼠的盲腸中約有1000種細(xì)菌,，但食用混合膽汁的餌料后，大鼠盲腸內(nèi)僅梭菌（Clostridium）類細(xì)菌就占了98.6%,，而正常喂養(yǎng)情況下大鼠盲腸中普遍存在的10%左右的乳酸菌幾乎找不到,。梭菌在細(xì)菌總量中超過半數(shù)這一數(shù)據(jù)，與美國肥胖病人的調(diào)查結(jié)果具有相似性,。
該研究成果發(fā)表在美國消化病學(xué)會(huì)專業(yè)期刊《腸胃病學(xué)》11月號(hào)上,。（生物谷 Bioon.com）
doi:10.1053/j.gastro.2011.07.046
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Bile Acid Is a Host Factor That Regulates the Composition of the Cecal Microbiota in Rats
K.B.M. Saiful Islam
Background & Aims Alterations in the gastrointestinal microbiota have been associated with metabolic diseases. However, little is known about host factors that induce changes in gastrointestinal bacterial populations. We investigated the role of bile acids in this process because of their strong antimicrobial activities, specifically the effects of cholic acid administration on the composition of the gut microbiota in a rat model. Methods Rats were fed diets supplemented with different concentrations of cholic acid for 10 days. We used 16S ribosomal RNA gene clone library sequencing and fluorescence in situ hybridization to characterize the composition of the cecal microbiota of the different diet groups. Bile acids in feces, organic acids in cecal contents, and some blood parameters were also analyzed. Results Administration of cholic acid induced phylum-level alterations in the composition of the gut microbiota; Firmicutes predominated at the expense of Bacteroidetes. Cholic acid feeding simplified the composition of the microbiota, with outgrowth of several bacteria in the classes Clostridia and Erysipelotrichi. Externally administered cholic acid was efficiently transformed into deoxycholic acid by a bacterial 7α-dehydroxylation reaction. Serum levels of adiponectin decreased significantly in rats given the cholic acid diet. Conclusions Cholic acid regulates the composition of gut microbiota in rats, inducing similar changes to those induced by high-fat diets. These findings improve our understanding of the relationship between metabolic diseases and the composition of the gastrointestinal microbiota.
