A230 ISOMALTODEXTRIN DOSE-DEPENDENTLY REDUCES COLITIS DEVELOPMENT IN HLA-B27 RAT COLITIS MODEL WITH ASSOCIATED CHANGES TO GUT MICROBIOME COMPOSITION AND SHORT CHAIN FATTY ACID PRODUCTION

Abstract

Abstract Background Inflammatory bowel disease (IBD) is characterized by altered intestinal microbiome (i.e. dysbiosis), described by reduced strict butyrate-producing anaerobes versus increased facultative anaerobes. Data from preclinical studies and clinical trials show prebiotic inulin-type fibers can prevent and reduce colitis. However, other dietary fibers (e.g. resistant starches, RS) are understudied and it is unknown if RS-induced microbial shifts are protective in experimental colitis. Aims Assess efficacy of isomaltodextrin (IMD), a novel RS, to reduce intestinal inflammation in HLA-B27 transgenic (TG) rat colitis model and identify protective mechanisms associated with gut microbial composition and function. Methods 4 week old HLA-B27 TG rats were fed standard chow supplemented with: 7.5% IMD (low dose, LD), 15% IMD (high dose, HD), negative control (15% cellulose, NC), or positive control (15% fructooligosaccharides, PC) for 12 weeks. Body weight and food intake were measured. Cecal and colonic inflammation assessed by weight/length ratio, macroscopic scoring and mucosal IL-1β secretion. Changes in microbial energy metabolism evaluated by measuring short chain fatty acid (SCFA) production in stool and cecal contents. Endpoint fecal and cecal microbiota composition differences assessed by 16S rRNA gene sequencing (Illumina MiSeq platform). Results IMD showed dose-dependent effect on cecal inflammation, measured by macroscopic tissue scoring, weight/length ratio and IL-1β secretion. HD rats had significantly lower cecum IL-1β concentration compared to NC (q=0.01), while LD showed only a trend (q=0.09). HD had significantly higher cecal amounts of Bacteroidaceae and Allobaculum spp. and lower amounts of Peptostreptococcaceae, Eubacterium and Barnesiella spp. versus the LD and NC. HD was associated with significantly higher total SCFA compared to NC (q<0.01) and showed a trend of higher total SCFA than LD (q=0.06). Analysis of SCFAs revealed propionate, isobutyrate and valerate ratios were significantly lower in HD than LD and NC. HD showed a trend of higher ratio of butyrate + acetate compared to NC. This suggests increased carbohydrate fermentation by acetate-producing and -converting microbial groups. Correlation analysis confirmed IL-1β concentrations were positively associated with isobutyrate (r=0.52, q<0.01), valerate (r=0.54, q<0.01), and propionate (r=0.48, q<0.01), suggesting their use as chronic inflammation markers in HLA-B27 models. Conclusions IMD was dose-dependently effective in reducing chronic cecal inflammation in experimental colitis. Benefits were associated with specific shifts in gut microbiome composition and SCFA production. Results from this preclinical study warrant future microbiota-altering intervention trials using IMD in clinical IBD. Funding Agencies Hayashibara Co., Ltd.