Prebiotic inulin as a treatment of obesity related nonalcoholic fatty liver disease through gut microbiota: a critical review.

The microbial-derived products, including short chain fatty acids, lipopolysaccharide and secondary bile acids, have been shown to participate in the regulation of hepatic lipid metabolism. Previous studies have demonstrated that prebiotics, such as oligosaccharide and inulin, have abilities to change the concentration of microbial-derived products through modulating the microbial community structure, thus controlling body weight and alleviating hepatic fat accumulation. However, recent evidence indicates that there are individual differences in host response upon inulin treatment due to the differences in host microbial composition before dietary intervention. Probably it is because of the multiple relationships among bacterial species (e.g., competition and mutualism), which play key roles in the degradation of inulin and the regulation of microbial structure. Thereby, analyzing the composition and function of initial gut microbiota is essential for improving the efficacy of prebiotics supplementation. Furthermore, considering that different structures of polysaccharides can be used by different microorganisms, the chemical structure of processed inulin should be tested before using prebiotic inulin to treat obesity related nonalcoholic fatty liver disease.

Effects of dietary fibres on gut microbial metabolites and liver lipid metabolism in growing pigs.

This study was conducted to investigate the effects of dietary supplementation with wheat bran fibre, inulin and their combination on growth performance, short-chain fatty acids (SCFAs) production in caecum and colon and liver lipid metabolism in growing pigs. A total of 48 Duroc × Landrace × Yorkshire cross-bred growing pigs (73 ± 2 days of age; 24.37 ± 2.86 kg) were allocated to four groups randomly, each group consisting of six pens with two pigs each. The pigs were fed a control diet (CON), a diet containing 2% wheat bran fibre (WB), a diet containing 2% inulin (IN), and a diet containing both of 1% wheat bran fibre and 1% inulin (MIX), respectively. The trial lasted for 28 days. The results showed that MIX fed pigs had a higher percentage of fat in the liver than those fed the CON (p < .05). IN, WB or MIX feeding decreased the concentrations of acetate and total SCFAs in colon compared with CON (p < .01). Feeding WB or IN also decreased the colonic butyrate concentrations compared with CON (p < .01). However, the serum level of valeric acid was elevated in the IN, WB and MIX group (p < .01). MIX fed pigs tended to have lower levels of propionate in serum than the WB fed pigs (p = .098). MIX feeding enhanced the mRNA expression of lipid synthesis-related genes in liver compared with CON (p < .05). Feeding IN decreased the expression of bile acids synthesis-related genes in liver and increased mRNA expression of SCFAs transporter SLC16A1 in colon compared with CON (p < .05). In this study, these data indicated that the combined supplementation of wheat bran fibre and inulin decreased the SCFAs concentrations in the colon, enhanced the genes FAS and HNF-4α mRNA expression in liver and induced liver lipid accumulation in growing pigs.

Effects of Different Types of Dietary Fibers on Lipid Metabolism and Bile Acids in Weaned Piglets.

The aim of this study was to investigate the effects of dietary fiber on the serum biochemistry, bile acid profile, and gut microbiota in piglets. Twenty-four pigs (initial body weight: 10.53 ± 1.23 kg) were randomly divided into three treatments with eight replicate pens of one pig per pen for 21 d. The dietary treatments consisted of the following: (1) a fiber-free diet (NS); (2) a fiber-free diet + 3% fructooligosaccharides (SI); (3) a fiber-free diet + 3% dietary fiber mixture (fructooligosaccharides, long-chain inulin, and microcrystalline cellulose at the ratio 1:1:1; MIX). The results showed that compared with the NS group, the 3% SI diet reduced the serum total cholesterol (TC) concentration of the piglets (p < 0.05). The metabolomics results showed that the 3% SI diet increased the level of taurohyocholic acid (THCA) and α-muricholic acid, and the 3% MIX diet increased the level of THCA and cholic acid (p < 0.05). The use of 3% SI or MIX decreased the glycodeoxycholic acid (GDCA) level in the bile of the piglets (p < 0.05). The correlation analysis shows that the GDCA was positively related to the TC. The 16S rRNA gene sequencing results showed that UCG-002 and Holdemanella were enriched in the SI group, while Bacteroides was enriched in the MIX group. The microbial function prediction indicated that SI supplementation tended to elevate the relative abundance of gut bacteria capable of expressing bile acid-metabolizing enzymes. To sum up, the regulatory effect of dietary fiber on lipid metabolism is related to bile acids in piglets. Compared with MIX, SI is more likely to regulate bile acids through the gut microbiota.

The Bidirectional Interactions between Resveratrol and Gut Microbiota: An Insight into Oxidative Stress and Inflammatory Bowel Disease Therapy.

Dysbiosis and oxidative stress in the gut have contributed to the progression of intestinal inflammatory bowel disease (IBD). The current study has reported that enteric bacteria mediate redox homeostasis through the regulation of reactive oxygen species (ROS) production. Resveratrol, one of the most abundant polyphenols, with poor oral bioavailability, is considered as a scavenger of ROS and other free radicals. Recent studies have shown that resveratrol effectively enhances the growth of Lactococcus lactis and inhibits the growth of Enterococcus faecalis. (1) In terms of the two-way relationship between gut microbiota and resveratrol, resveratrol modulates gut microbiota; (2) in terms of resveratrol biotransformation by gut microbiota, we speculate that gut microbiota could be a target of resveratrol to maintain gut homeostasis. Here, we reviewed the current researches about the cellular signaling pathways in intestinal epithelial cells triggered by gut microbiota in response to oxidative stress. These results suggest that the modulation of the gut microbiota through resveratrol supplementation appears as a promising potential approach for the therapy of inflammatory bowel disease.