Altered profiles of fecal metabolites correlate with visceral hypersensitivity and may contribute to symptom severity of diarrhea-predominant irritable bowel syndrome

Figure 1 Visceral sensation thresholds to rectal distension stimulation. A: The first sensation threshold showed no significant difference between the two groups (P = 0.315). B: The score of the defecating sensation threshold was significantly decreased in the patients (P = 0.032). C: The maximum tolerable threshold was also lower in patients with irritable bowel syndrome with predominant diarrhea than in controls (P < 0.001). Box means the interquartile range; line inside the boxes indicates the median; the two whiskers indicate the 5^th percentile and 95^th percentile of the data. ^aP < 0.05 vs healthy control (HC); ^bP < 0.01 vs HC. IBS-D: Irritable bowel syndrome with predominant diarrhea; HC: Healthy control.

Figure 2 Correlation of fecal microbial metabolites with irritable bowel syndrome symptom severity scale score or maximum tolerable threshold. A: Correlation of fecal microbial metabolites with irritable bowel syndrome symptom severity scale score in irritable bowel syndrome with predominant diarrhea (IBS-D) patients (R²_Adjusted = 0.693, P < 0.001). The composite index was the sum of score based on linear combination of metabolites using the coefficients listed in Table 4. B: Correlation of metabolites with maximum tolerable threshold in IBS-D patients (R²_Adjusted = 0.255, P = 0.007); The composite index was the sum of scores based on linear combination of isovalerate and valerate using the coefficients listed in Table 6. C: Correlation of metabolites with maximum tolerable threshold in all subjects (R²_Adjusted = 0.079, P = 0.034).