Association between fecal short-chain fatty acid levels and constipation severity in subjects with slow transit constipation

Objective We measured the fecal levels of short-chain fatty acids (SCFAs) in subjects with slow transit constipation (STC) and assessed the correlation between SCFA levels and disease severity as well as quality of life. Methods We isolated the supernatant from fecal samples of healthy and STC subjects and measured the SCFA levels. To assess the correlation between fecal SCFA levels and disease severity as well as quality of life, we used the Constipation Scoring System, Patient Assessment of Constipation Symptoms, and Patient Assessment of Constipation Quality of Life questionnaires. Results 16 STC subjects and 16 healthy controls were enrolled. STC subjects had lower SCFA levels, but the difference was not statistically significant (475.85 ± 251.68 vs. 639.77 ± 213.97 µg/ml, P = 0.056). Additionally, STC subjects had lower acetic and propionic acid levels (149.06 ± 88.54 vs. 261.33 ± 109.75 µg/ml and 100.60 ± 60.62 vs. 157.34 ± 66.37 µg/ml, respectively, P < 0.05) and higher isobutyric and isovaleric acid levels (27.21 ± 15.06 vs. 18.16 ± 8.65 µg/ml and 31.78 ± 18.81 vs. 16.90 ± 10.05 µg/ml, respectively, P < 0.05). At 252.21 µg/ml acetic acid, the specificity and sensitivity to distinguish healthy from STC subjects were 93.7% and 56.3%, respectively. In STC subjects, there were significant negative correlations between acetic and propionic acid levels and Constipation Scoring System scores. Conclusion Fecal SCFA, acetic acid, and propionic acid levels decreased in STC subjects. There were significant negative correlations between the levels of the two acids and constipation severity.