Su1196 THE ROLE OF THE SMALL INTESTINAL MUCOSAL MICROBIOME IN MODULATING SYMPTOMS OF LACTOSE INTOLERANCE

Background:The gut microbiome plays a vital role in symptom generation in lactose intolerance (LI).Bacterial fermentation of undigested lactose that enters the large intestine leads to increased gas production.While this phenomenon is well described, there is a paucity of data describing the upstream impact of the small intestine mucosal microbiome in LI pathogenesis.The objective of this study was to investigate the association between the small intestine mucosal microbiome and symptoms of LI in adults.Methods: We evaluated 19 patients who underwent esophagogastroduodenoscopy with duodenal biopsies to assess small intestinal mucosal microbiota composition.Eligibility was confirmed by medical history and medication review.Data on severity and frequency of gastrointestinal symptoms after consuming dairy products were collected using a self-administered questionnaire.Small intestinal mucosal microbiota were characterized by 16S rRNA-based sequencing on an Illumina MiSeq instrument.We examined associations of overall microbial composition and individual taxa with self-reported LI and with severity and frequency of LI symptoms using the Wilcoxon rank sum test, Spearman correlation, and permutational multivariate analysis of variance.Results: Among 12 patients with self-reported LI and 7 patients without LI, mean ± SD age was 45.4 ± 14.9 years; mean body mass index was 30.5 ± 9.5 kg/m 2 ; 15 (78%) were female; and 18 (95%) were Caucasian.No participants were on probiotics at the time of study participation.Analysis of 16S rRNA-based microbial community composition of the small intestinal mucosa at the amplicon sequence variant level revealed significant associations of small intestinal mucosal microbiome beta diversity ( Figure 1) with stool consistency (p=0.03,weighted UniFrac), age (p=0.02,unweighted UniFrac), and sex (p= 0.03, weighted UniFrac).There were no significant associations between small intestinal mucosal microbiome alpha diversity and LI symptom assessments (total symptom score, frequency of bowel urgency, number of bowel movements, stool consistency).Comparisons between patients with and without self-reported LI showed no significant differences in small intestinal mucosal microbiome alpha (Figure 2) or beta diversity.Analysis of individual microbial taxa identified a total of 369 unique genera.Univariate genus-level analyses showed no significant associations of the relative abundance of individual genera with LI group or with LI symptom assessments after adjusting for false discovery rate.Conclusions: Existing literature clearly links LI with the colonic microbiome.In our pilot study, we observed associations between community composition of the small intestinal mucosal microbiota and stool consistency after consuming dairy products to suggest that the small intestine mucosal microbiome participates in LI.