Abstract
Inulin (INU) is a non-digestible carbohydrate, known for its beneficial properties in metabolic disorders. However, whether and how gut microbiota in its regulation contributes to host metabolism has yet to be investigated. We conduct this study to examine the possible associations between the gut microbiota and circulating gut microbiota–host co-metabolites induced by inulin interventions. Plasma and intestinal site samples were collected from the pigs that have consumed inulin diet for 60 days. High-throughput sequencing was adopted for microbial composition, and the GC-TOF-MS-based metabolomics were used to characterize featured plasma metabolites upon inulin intervention. Integrated multi-omics analyses were carried out to establish microbiota–host interaction. Inulin consumption decreased the total cholesterol (p = 0.04) and glucose (p = 0.03) level in serum. Greater β-diversity was observed in the cecum and colon of inulin-fed versus that of control-fed pigs (p < 0.05). No differences were observed in the ileum. In the cecum, 18 genera were altered by inulin, followed by 17 in the colon and 6 in the ileum. Inulin increased propionate, and isobutyrate concentrations but decreased the ratio of acetate to propionate in the cecum, and increased total short fatty acids, valerate, and isobutyrate concentrations in the colon. Metabolomic analysis reveals that indole-3-propionic acid (IPA) was significantly higher, and the branched-chain amino acids (BCAA), L-valine, L-isoleucine, and L-leucine are significantly lower in the inulin groups. Mantel test and integrative analysis revealed associations between plasma metabolites (e.g., IPA, BCAA, L-tryptophan) and inulin-responsive cecal microbial genera. These results indicate that the inulin has regional effects on the intestine microbiome in pigs, with the most pronounced effects occurring in the cecum. Moreover, cecum microbiota plays a pivotal role in the modulation of circulating host metabolites upon inulin intervention
Highlights
A plethora of studies suggest that the dietary fibers, such as inulin, confer health benefits to host metabolism; protect against the metabolic disorder; and reduces the risk of inflammatory bowel diseases [1], cardiovascular diseases [2], obesity [3], and type 2 diabetes mellitus (T2D) [4] in human
After being fed with the experimental diets, the body weight of pigs was not affected by inulin feeding (p = 0.50, Figure 1A)
Plasma metabolomics analysis revealed that branched-chain amino acids (BCAA), tryptophan, and indole-3-propionic acid (IPA) featured in inulin-fed pigs only correlated with gut bacteria in cecum, suggesting that the cecum was the primary region for host–microbe interplay upon inulin intervention
Summary
A plethora of studies suggest that the dietary fibers, such as inulin, confer health benefits to host metabolism; protect against the metabolic disorder; and reduces the risk of inflammatory bowel diseases [1], cardiovascular diseases [2], obesity [3], and type 2 diabetes mellitus (T2D) [4] in human. Inulin encompasses all β (2→1) linear fructans of varying chain lengths. It has generally been recognized as safety status in many countries and is extensively employed in formula foods. Inulin influences directly on the gut, including prebiotic effects, improvement of bowel function and glycolipid metabolism in the host, secretion of satiety hormone and increased short fatty acids (SCFAs) production [5,6,7,8]. Unique contributions of the gut microbiota at each site to overall host health are not yet fully clarified but are likely dependent on diet ingredients and overall health of the host [12]. Inulin-associated alterations in the composition of the gut microbiota are well documented. Inulin promotes the growth of genera Prevotella, Blautia, Veillonella, and Faecalibacterium [16,17,18], which produced more SCFAs
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