Alterations of bile acid metabolism in patients with functional bowel disorders: a case-control study

Introduction
It is assumed that up to 50% of patients with functional bowel disorders with diarrhoea may suffer from bile acid (BA) malabsorption, which is considered as an underrecognized cause of chronic diarrhoea.

Aim
To evaluate the indicators of BA metabolism in patients with irritable bowel syndrome (IBS).

Material and methods
The study population included 28 healthy adults (control group), 108 patients with IBS with diarrhoea (IBS-D) and 37 with constipation (IBS-C), aged 18–44 years. All participants were assessed by symptoms questionnaires: VSI and FBDSI. High-performance liquid chromatography – mass spectrometry (HPLC-MS) was used to measure serum and faecal BA (sBA and fBA). Ultra-performance liquid chromatography – mass spectrometry (UPLC-MS) was used to evaluate the relative activity (RA) of gut bacterial bile salt hydrolase (BSH).

Results
Primary sBA in absolute and percentages, total fBA, and primary fBA in absolute and percentages were higher, and secondary sBA and fBA in percentages were lower in the IBS-D group compared to the control and IBS-C groups (p < 0.01). The RA of gut bacterial BSH was lower in IBS-D compared to the control and IBS-C groups (p < 0.01). RA of gut bacterial BSH, secondary sBA and fBA correlated negatively with abdominal pain, bloating, stool frequency, Bristol scale, VSI, and FBDSI (p < 0.05 in all). Total fBA, primary sBA, and fBA correlated positively with the same clinical parameters (p < 0.05 in all).

Conclusions
IBS-D patients had altered parameters of BA metabolism that were associated with the severity of clinical symptoms, disease severity, visceral sensitivity, and stool appearance and frequency.