DietarEffects on Human Fecal Microbiota.

摘要

The establishment of microbial populations in the gastrointestinal (GI)-tract is a complex process, involving microbial and host interactions eventually resulting in a dense and stable population. Recently, the identification of microbial species from fecal samples has become more accurate with the use of 16S RNA gene-based methods. However, although these molecular-based detection methods have apparent benefits over culture-based techniques, they involve potential pitfalls that should be taken into consideration when studying the fecal microbiota, such as the storage conditions and deoxyribonucleic acid (DNA)-extraction. Therefore, the effects of different storage conditions and DNA-extraction protocols on fecal samples were evaluated in this study. Whereas the DNA-extraction protocol did not affect the numbers of Bacteroides spp., the abundance of this group showed significant decrease after one week’s storage at -20°C. Furthermore, the numbers of predominant bacteria, Eubacterium rectal group, Clostridium leptum group, bactericidal and Atopobium group, were significantly higher in samples stored at-70°C after mechanical DNA-extraction than after enzymatic DNA-extraction as detected with real-time PCR (qPCR). These results indicate that rigorous mechanically sis leads to the detection of higher bacterial numbers from human fecal samples than enzymatic DNA-extraction. Therefore, the use of different DNA extraction protocols may partly explain contradictory results reported in previous studies.The composition of the human intestinal microbiota is influenced by host specific factors such as age, genetics and physical and chemical conditions encountered in the GI-tract. On the other hand, it is modulated by environmental factors with impact on the host during the lifespan, such as diet. The impact of dieton the gut microbiota has usually been assessed by subjecting people to the same controlled diet, and thereafter following the shifts in the microbiota. In the presentstudy, the habitual dietary intake of monozygotic twins was associated with the fecal microbiota composition, which was analyses using qPCR and Denaturing Gradient Gel Electrophoresis (DGGE). The effect of diet on the numbers of the bacteria was described using a hierarchical linear mixed model that included the twin individuals, stratified by body mass index, and their families as random effects.The abundance and diversity of the bacterial groups studied did not differ between normal weight, overweight, and obese individuals with the techniques used. However, intakes of energy, monounsaturated fat, (n-3) polyunsaturated fat, (n-6)polyunsaturated fat and soluble fiber had significant associations with the fecal bacterial numbers.