Physiological levels of bile acids increase bacterial uptake in colonic biopsies of collagenous colitis patients in remission

• Objective: Patients with collagenous colitis (CC) have an impaired mucosal barrier. Moreover CC is associated with bile acid malabsorption. Bile acids may increase bacterial mucosal uptake in humans. To elucidate the possible role of bile acids in CC pathophysiology, the mucosal barrier function was investigated by exposing colonic biopsies to physiological concentrations of chenodeoxycholic acid (CDCA) or deoxycholic acid (DCA) in Ussing chamber experiments. Patients/Interventions: The study included 33 individuals; 25 with collagenous colitis (14 in clinical remission without treatment, 11 with active disease, and 8 of these again after 6 weeks budesonide treatment); 8 healthy individuals undergoing screening colonoscopy served as controls. Endoscopic biopsies from the sigmoid colon were mounted in modified Ussing chambers and assessed for short circuit current (Isc), transepithelial resistance (TER), and transmucosal passage of chemically killed E. coli K12 after addition of 100 μmol/l CDCA or DCA. The biopsies were further investigated with confocal microscopy to asses bacterial transepithelial passage routes. Results: By adding 100μmol/l CDCA or DCA the bacterial uptake was increased by 4-fold in biopsies of patients in remission; CDCA 6.5 units [2.5-9.8] and DCA 6.2 units [2.1-22] (median [IQR]), compared with uptake in biopsies without added bile acids 1.6 units [1.1-3]; (p=0.004 and p=0.01, respectively). In active disease and in patients in remission on budesonide, bile acids had no effect on bacterial uptake. Isc and TER were unaffected by the bile acids at 100μmol/l in all groups. Confocal microscopy demonstrated transepithelial passage of E.coli K12 via the paracellular route. Conclusions: Physiological concentrations of dihydroxy-bile acids augment mucosal barrier dysfunction in colonic biopsies of patients with CC in remission. This leads to a substantially increased bacterial uptake that may contribute to relapse of inflammation. Budesonide seems to counteract the bile acid-induced mucosal impairment.

Nyckelord

Microscopic colitis

permeability

intestinal mucosa

diffusion chamber

bile acids

MEDICINE

MEDICIN

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