Associations of Fecal Short Chain Fatty Acids With Colonic Transit, Fecal Bile Acid, and Food Intake in Irritable Bowel Syndrome

INTRODUCTION: Short-chain fatty acids (SCFAs) correlatewith colonic transit time (CTT) andmay influence irritable bowel syndrome (IBS) pathophysiology. However, the clinical significance of fecal SCFAs, relationships between SCFAs and other metabolites (bile acids [BAs]), and real-time diet effects on SCFAs in IBS are uncertain. The aim was to evaluate fecal SCFA associations with IBS phenotype and mechanisms and explore effects of real-time diet. METHODS: We conducted a prospective observational study of fecal SCFA, BAs, and CTT in healthy controls (HCs) and participants with IBS. We compared study end points across groups, analyzed relationships between end points, and evaluated the discriminative ability of SCFAs. Diet effects were explored in participants with dietary data. RESULTS: Among 21 HCs and 43 participants with IBS, fecal SCFAs (total, individual) were inversely correlated with overall (allP< 0.01) andsegmental (allP< 0.05) CTT; similar associationswere observed withinHCand IBS groups. The acetate-to-butyrate ratio correlated with slower overall and left CTT in all and in HCs (both P < 0.01). SCFAs (total, acetate) correlated with BAs (total,% primary) in all participants and in those with IBS with diarrhea. Logistic regression analyses demonstrated associations of acetate with slower transit (odds ratio 5 0.988, P 5 0.002) and BA diarrhea (BAD; odds ratio 5 1.014, P 5 0.001). Acetate accurately predicted delayed CTT (area under the receiving operating characteristic curve50.84) andBAD (area under the receiver operating characteristic curve50.79). Adjusting for diet strengthened correlations of total SCFAs with overall CTT (R 5 [20.46], P 5 0.04) and SCFAs with transverse CTT (all P < 0.05). DISCUSSION: Fecal SCFAs correlate with CTT and fecal BAs and reliably exclude delayed CTT and BAD. Accounting for diet strengthens SCFA associations with transit.

Automated summary

Short-chain fatty acids are associated with colonic transit time and bile acids, and can reliably exclude delayed transit and bile acid diarrhea. Real-time diet can affect the levels of short-chain fatty acids.