Supplement of dietary fibers (DF) is regarded as one of the most effective way to prevent and relieve chronic diseases caused by long-term intake of a high-fat diet in the current society. The health benefits of soluble dietary fibers (SDF) have been widely researched and applied, whereas the insoluble dietary fibers (IDF), which represent a higher proportion in plant food, were mistakenly thought to have effects only in fecal bulking. In this article, we proved the anti-obesity and glucose homeostasis improvement effects of IDF from pear pomace at first, and then the mechanisms responsible for these effects were analyzed. The preliminary study by real-time PCR and ELISA showed that this kind of IDF caused more changes in the gut microbiota compared with in satiety hormone or in hepatic metabolism. Further analysis of the gut microbiota by high-throughput amplicon sequencing showed IDF from pear pomace obviously improved the structure of the gut microbiota. Specifically, it promoted the growth of Bacteroidetes and inhibited the growth of Firmicutes. These results are coincident with previous hypothesis that the ratio of Bacteroidetes/Firmicutes is negatively related with obesity. In conclusion, our results demonstrated IDF from pear pomace could prevent high-fat diet-induced obesity in rats mainly by improving the structure of the gut microbiota.

Rabbit neutrophils peptide-1 (NP-1) is a type of defensin that possesses a broad spectrum of antimicrobial activity. Chlorella ellipsoidea is a new eukaryotic expression system for exogenously producing NP-1. The NP-1 transgenic C. ellipsoidea can be directly added into feed as antimicrobial agent without any purification procedure for the NP-1 peptide. However, the effects of C. ellipsoidea and NP-1 on the host gut microbiota should be explored before application. In this study, diets containing different concentrations (1.25, 2.5, and 5%) of C. ellipsoidea and NP-1 transgenic C. ellipsoidea were administered to male Sprague-Dawley rats. Compared with the chow diet control group, none of the experimental groups showed any significant differences in their growth indices, and no histopathological damage was observed. The phylotypes of gut microbiota in the control group, the 5% C. ellipsoidea diet group and the 5% NP-1 transgenic C. ellipsoidea diet group were determined by 16S rRNA sequencing. The results showed that both 5% experimental groups had shifted community memberships of gut microbiota. In particular, the 5% NP-1 transgenic C. ellipsoidea diet exhibited an increased abundance of most Gram-positive bacterial taxa and a reduced abundance of most Gram-negative bacterial taxa, and it promoted the growth of some lactic acid bacterial genera. Lactic acid bacteria, especially the Bifidobacterium and Lactobacillus, have been widely reported to be benefic effects on the host. Thus NP-1 transgenic C. ellipsoidea is promising feed additive and gut regulator, as it have the potential to increase the abundance of Bifidobacterium and Lactobacillus in gut microbiota of animal.