Altered bile acid metabolism in patients with constipation-predominant irritable bowel syndrome and functional constipation.

OBJECTIVE

Bile acids are derived from cholesterol and are potent physiological laxatives. The aim of this study was to investigate whether bile acid synthesis is altered in constipation.

MATERIAL AND METHODS

Female patients with constipation (23 IBS-C, 4 functional constipation (FC)) were studied and compared with non-constipated subjects (16 IBS-D, 20 healthy women). Body mass index (BMI), blood lipids, lanosterol, sitosterol, colonic transit (oro-anal transit time (OATT), reference < or =4.3 days) and stool frequency were measured. C4 (7-alpha-hydroxy-4-cholesten-3-one) levels reflecting bile acid synthesis were measured at 0800 h and 1300 h.

RESULTS

When all the groups of constipated and non-constipated subjects were compared, it was found that only stool frequency and OATT differed between groups (p <0.001). When constipated patients were categorized according to OATT, absence of the usual C4 increase at lunchtime was noted in 82% of patients with delayed OATT compared with 17% in subjects with normal OATT (p <0.001). Symptom severity did not differ between groups. A subset of the patients with severely delayed OATT had markedly elevated C4 levels.

CONCLUSIONS

Patients with IBS-C and FC have marked changes in bile acid synthesis in relation to colonic transit. The diurnal rhythm is altered in the slow transit colon when there is no C4 peak at lunchtime. Alterations in bile acid metabolism may be implicated in the pathophysiology of constipation.