Mol. inflammation in liver. Pharmacologic inhibition of fermentation or depletion of fermenting bacteria markedly reduced intestinal SCFA and prevented HCC. Intervening with cholestyramine to prevent reabsorption of bile acids also conferred protection against such HCC. Thus, its benefits notwithstanding, enrichment of foods with fermentable fiber should be approached with great caution as it may increase risk of HCC. Graphical Abstract In Brief Dysregulated fermentation of dietary soluble fibers by gut microbiota induces cholestasis, hepatic inflammation, and liver cancer in mice. INTRODUCTION Societal changes associated Zotarolimus with industrialization have resulted in increased consumption of processed foods rich in sugars and fats and decreased consumption of grains, fruits, and vegetables, which are naturally rich in fiber. Such dietary changes have ushered a well-documented increase in the prevalence of obesity and related metabolic diseases. Yet, engineering and effective marketing of low-fat and fat-free foods have not slowed the obesity epidemic. One seemingly logical and practical approach to counter some of Zotarolimus the unhealthy effects of western diets might be to enrich processed foods with plant-derived fibers. Dietary fiber can be broadly categorized as insoluble or soluble, while the former resists fermentation, the latter is readily metabolized by gut bacteria. One such prebiotic fiber is inulin, which is fermented by gut microbiota into short-chain fatty acids (SCFA) acetate, butyrate, and propionate in the colon (Gill et al., 2006). SCFA play important roles in mammalian physiology, including serving as an energy source for gut epithelia (Donohoe et al., 2011) and promoting the differentiation of anti-inflammatory regulatory T cells (Arpaia et al., 2013; Furusawa et al., 2013; Smith et al., 2013). Such effects likely contribute to inulins beneficial metabolic effects, which include reducing adiposity (Cani et al., 2007) and improving glycemic control (Dewulf et al., 2013). Metabolism of dietary fibers into valuable nutrients is among the prime benefits gut microbiota provide to their host. However, the inability to properly manage gut microbiota can be detrimental to the host and result in chronic inflammation. For example, we demonstrated that mice deficient in Toll-like receptor 5 (TLR5; a receptor for flagellin) are prone to developing overt microbiota-dependent colitis (Vijay-Kumar et al., 2007) and low-grade inflammation associated with metabolic syndrome (Vijay-Kumar et al., 2010). Ablation of microbiota in TLR5-deficient (and were substantially elevated in HB mice, whereas only a modest increasing trend was observed for and (Figure S2F). Expression of inflammatory mediators such as was upregulated only in HB mice, although was elevated in both HB and NB mice (Figure S2G). Spontaneous inflammation in in double knockout (DKO) GPM6A mice fed ICD was indistinguishable from the HCC observed in confer any protection as ICD-fed predominantly distinguished HB from the other groups (Figures 3H and ?and3I).3I). members (phylum Firmicutes) comprise a constellation of fiber-fermenting bacteria, particularly the Clostridium cluster XIVa, which are the main producers of butyrate and secondary bile acids (Van den Abbeele et al., 2013). In addition, the phylum Proteobacteria was also found to be strongly associated with H-bili. Overgrowth of Proteobacteria was noteworthy as it occurs in a spectrum of disease states and is implicated in hepatocarcinogenesis in humans (Gr?t et al., 2016). Furthermore, metagenome prediction analysis identified enrichment in genes encoding for fatty acid/lipid biosynthesis as well as motility/secretion (data not shown) in HB mice. These results correlated with the increased Zotarolimus microbiota byproducts (i.e., LPS, flagellin) in the gut of HB mice and the markers of their systemic dissemination (Figures 3JC3N). Open in a separate window Figure 3. proteins (arrows showing new bands/increased intensity in and (classical pathway) but reduced and (alternate pathway) (Figures 6C and ?and6D).6D). Such impaired expression of genes required for bile acid uptake into hepatocytes, as well as genes encoding canalicular and basolateral exporters, in HB mice (Figures 6C and ?and6D)6D) implied that their elevated serum.