To Discover The Relationship Between Gut Microbiota And Over-Ingestion Of Energy Based On High Dietary-Fiber Diets

Gut microbes have been found to be related with the hosts’ energy intake, and they are believed to be associated with the formation of obesity. This article researched on the effect of high-dietary-fiber(HDF) diets, including the high-soybean-fiber(HSF) diet and the high-fructooligosaccharide(HFOS) diet, on the hosts’ growth and gut microbiota. In this study, the diet-induced normal and obese rats were fed HDF diets for 8 weeks. Rats’ body weight(BW) were recorded weekly, the level of lipopolysaccharides(LPS) and leptin in plasma were detected, the concentration of short-chain fatty acids(SCFAs) in feces was detected, and gut microbiota was analyzed by 16 S r DNA sequencing. The results showed that:1) Normal rats gained more BW than obese ones from both the HSF and HFOS diet(P<0.01), and microbial diversity of normal rats was elevated(P<0.01) with a significant increase in Bacteroidetes(P<0.05); however, no significant variation in obese rats’ gut microbiota was detected. Thus, the gut microbiota of obese rats could not help harvest more energy from the HDF diets; HDF diets caused the increase of Bacterioidetes that have better polysaccharides-degrading capacity, as well as the increase of the microbiota diversity in lean rats, which might make primary contribution to the hosts’ increased energy intake.2) The ingestion of HSF diet caused the decrease in Lactobacillus abundance(P<0.05) in normal rats, as well as unchanged gut Bifidobacterium(P>0.05); the abundances of Bifidobacterium and Lactobacillus in obese rats all declined, but the alteration of Bifidobacterium was not statistically significant. In both normal and obese rats, HFOS diet could stimulate the growth of gut Bifidobacterium(P<0.05), but the abundance of Bifidobacterium was decreased to a small level in the end(P<0.05); the abundance of Lactobacillus was increased in normal rats(P<0.05), but decreased in obese rats(P<0.05). So the alteration of Bifidobacterium and Lactobacillus was not related to the variation of energy ingestion.3) The level of plasma leptin was elevated when rats’ BW gain increased, and the ratio of Firmicutes to Bacteroidetes was decreased when rats BW increased; higher concentration of fecal SCFAs was found in the groups of rats with higher abundance of Bacteroidetes, and higher level of plasma LPS was found in the groups of rats with higher abundance of gram-negative bacteria. The increase in plasma leptin provided evidence for the elevated level of energy harvesting of normal rats; the augment of fecal SCFAs also suggested the increased energy release from HDF diets; besides, the relationship between plasma LPS and energy harvest was not significant in this study.In conclusion, this study indicated that the alteration of gut microbiota was modulated by the diet composition and its energy content; that is, the microbial shift was the result of obesity, but not the reason of obesity. In addition, when the rats continuously ingested HFOS diet, the abundance of gut Bifidobacterium could not keep in high level.