Alterations in fecal short-chain fatty acids in patients with irritable bowel syndrome: A systematic review and meta-analysis

Abstract

Background: Recent studies indicate that gut microbiota disorders potentially contribute to the pathogenesis of irritable bowel syndrome (IBS), which can be partly reflected by fecal short-chain fatty acids (SCFAs) generated from gut microbiota. Previous studies on SCFA alterations in patients with IBS have yielded conflicting results. No prior systematic review has been conducted on the alterations in fecal SCFAs in IBS patients.

Aims: We performed a meta-analysis to explore and clarify alterations in fecal SCFAs in IBS patients.

Methods: Case-control studies, randomized controlled trials (RCTs), and self-controlled studies were identified through electronic database searches. The standardized mean difference (SMD) with 95% confidence interval (CI) in fecal SCFA levels between different groups was calculated.

Results: The proportion of fecal propionate in patients with IBS was significantly higher than in healthy controls (HCs) (SMD = 0.44, 95% CI = 0.12, 0.76). A subgroup analysis showed that the concentration of fecal propionate (SMD = -0.91, 95% CI = -1.41, -0.41) and butyrate (SMD = -0.53, 95% CI = -1.01, -0.04) in patients with constipation-predominant IBS (IBS-C) was significantly lower than that in HCs, and the concentration of fecal butyrate in patients with diarrhea-predominant IBS (IBS-D) was higher than that in HCs (SMD = 0.34, 95% CI = 0.00, 0.67). Finally, we found that restricted diets correlated with fecal butyrate reduction in IBS (SMD = -0.26, 95% CI = -0.51, -0.01).

Conclusions: In terms of fecal SCFAs, there were differences between patients with IBS and HCs. In IBS-C patients, propionate and butyrate were reduced, whereas butyrate was increased in IBS-D patients in comparison to HCs. Propionate and butyrate could be used as biomarkers for IBS diagnosis.

Figure 1

Flowchart of study selection. HC = healthy control, IBS = irritable bowel syndrome, RCT = randomized controlled trial, SCFA = short-chain fatty acids, SD = standard deviation.

Figure 2

Forest plots of alterations of fecal short-chain fatty acids in patients with irritable bowel syndrome versus healthy controls: (A-1) concentration of acetate, (A-2) proportion of acetate, (B-1) concentration of propionate, (B-2) proportion of propionate, (C-1) concentration of butyrate, (C-2) proportion of butyrate, (D-1) concentration of iso-butyrate, (D-2) proportion of iso-butyrate, (E-1) concentration of valerate, (E-2) proportion of valerate, (F-1) concentration of iso-valerate, and (F-2) proportion of iso-valerate. CI = confidence interval, SMD = standardized mean difference.

Figure 3

Forest plots of alterations of fecal short-chain fatty acids concentration in patients with different subtypes of irritable bowel syndrome (IBS) versus healthy controls (HC): (A-1) acetate in constipation-predominant irritable bowel syndrome (IBS-C) vs HC, (A-2) acetate in diarrhea-predominant irritable bowel syndrome (IBS-D) vs HC, (B-1) propionate in IBS-C vs HC, (B-2) propionate in IBS-D vs HC, (C-1) butyrate in IBS-C vs HC, and (C-2) butyrate in IBS-D vs HC. CI = confidence interval, SMD = standardized mean difference

Figure 4

Forest plots of alterations of fecal short-chain fatty acids concentration in patients with irritable bowel syndrome after different treatments: (A-1) acetate after restricted diet, (A-2) acetate after probiotics treatment, (B-1) propionate after restricted diet, (B-2) propionate after probiotics treatment, (C-1) butyrate after restricted diet, (C-2) butyrate after probiotics treatment, (D-1) iso-butyrate after restricted diet, (D-2) iso-butyrate after probiotics treatment, (E-1) valerate after restricted diet, (E-2) valerate after probiotics treatment, (F-1) iso-valerate after restricted diet, and (F-2) iso-valerate after probiotics treatment. CI = confidence interval, SMD = standardized mean difference.

Figure 5

Funnel plots of included studies analyzing the concentration of fecal short-chain fatty acids from patients with irritable bowel syndrome versus healthy controls: (A) acetate, (B) propionate, (C) butyrate. SE = standard error, SMD = standardized mean difference.