Association Between Luminal Bile Salt Content and Duodenal Mucosal Integrity in Functional Dyspepsia
Condition: Functional Dyspepsia
MeSH terms: Dyspepsia
Study type: Interventional

Summary: 
      Functional dyspepsia (FD) is an extremely common disorder of gastrointestinal function.
      Recently, impaired duodenal mucosal integrity was reported as a potential pathophysiological
      mechanism in FD. However, the factors controlling duodenal mucosal integrity remain unknown.
      In this study, we evaluated whether the luminal bile salt content could play a role in
      impaired duodenal permeability in FD.

      Duodenal biopsies were obtained from 25 healthy volunteers (HV) and 25 FD patients. Biopsies
      were mounted in Ussing chambers to measure transepithelial resistance (TEER) and paracellular
      permeability using fluorescein isothiocyanate dextran (FITC-dx4, MW 4kDa). Expression of bile
      acid-sensing receptors (TGR5, VDR, PXR, FXR and CAR) in duodenal biopsies was measured by
      western blot and real time RT-PCR. Immunohistochemistry was used to evaluate eosinophil and
      mastcell infiltration in duodenal biopsies of FD patients and HV. Duodenal fluid aspirates
      were collected at fixed time points during 1 hour in fasted state and 1.5 hours after a
      liquid meal (Nutridrink, 200ml). Concentration and composition of the bile salt pool
      (including glycocholic acid (GC), taurocholic acid (TC), glycochenodeoxycholic acid (GCDC),
      taurochenodeoxycholic acid (TCDC), glycodeoxycholic acid (GDC), taurodeoxycholic acid (TDC),
      glycoursodeoxycholic acid (GUDC) and tauroursodeoxycholic acid (TUDC)) in these aspirates was
      evaluated by liquid chromatography-mass spectrometry-selected ion monitoring analysis
      (LC-MS/MS).
    

Detailed description: 
      The Rome III criteria defined functional dyspepsia (FD) as the presence of symptoms thought
      to originate in the gastroduodenal region, in the absence of any organic, systemic or
      metabolic disease that readily explains the complaints. FD is extremely common, affecting up
      to 15-20% of the population and is associated with significantly decreased quality of life
      and substantial healthcare costs. The available treatment options for FD are of limited
      effectiveness, which reflects the poorly understood pathogenesis. Studies indicate that FD is
      a heterogeneous disorder, in which different pathophysiological mechanisms underlie specific
      symptom patterns. Traditionally, gastric abnormalities such as impaired accommodation,
      delayed emptying and hypersensitivity have been believed to be involved in the
      pathophysiology of FD. More recent studies have suggested that also a number of duodenal
      abnormalities can be responsible for the generation of symptoms, like increased sensitivity
      to duodenal acid, increased sensitivity to duodenal lipids and low-grade mucosal
      inflammation.

      The investigators recently showed that FD patients display impaired duodenal mucosal
      integrity. The trigger of increased permeability is unknown, but it is possible that
      increased exposure to duodenal bile acids or an altered composition of bile acids leads to
      impairment of the intestinal barrier. This sustained enhancement of paracellular permeability
      could facilitate the constant passage of luminal antigens through the mucosa and lead to
      local mucosal immune responses that manifest as inflammation and finally result in generation
      of dyspeptic symptoms.

      The investigators hypothesized that increased duodenal bile acid exposure or a change in the
      composition of bile acids lead to impaired duodenal mucosal integrity in FD, allowing luminal
      substances to pass through the mucosa and result in immune responses and finally in dyspeptic
      symptom generation. The general aim of this project is to assess if FD patients display
      increased endogenous duodenal bile acid exposure and a different bile acid composition. In
      addition, it will be tested whether duodenal mucosal permeability of FD patients with an
      endogenous duodenal bile acid exposure above the normal range and an altered bile acid
      composition is higher than in FD patients with a normal endogenous duodenal acid exposure and
      composition.

      Participants will be expected on the department endoscopy of the UZ Gasthuisberg after they
      have fasted overnight. Before the study, they are asked to fill in a bundle of questionnaires
      concerning physical complaints, depression, anxiety (disturbances), pain/disease,
      body/interoceptive awareness, trauma/abuse and personality.

      Gastroduodenoscopy will be performed by an experienced endoscopist (Jan Tack). Hereby, 12
      duodenal biopsies (2 biopsies at a time) (Radial Jaw™3 with needle; outside diameter 2.2mm;
      Boston Scientific, 302 Parkway, Global Park, Heredia, Costa Rica) will be obtained. To
      measure the in vitro transepithelial resistance, 4 biopsies will be examined using an adapted
      mini-Ussing chambers system. After equilibration, the mucosal side of the tissue will be
      exposed to 4kDa FITC-dextran as a measure of paracellular permeability. A sample will be
      taken from the serosal side during 2h at 30min interval. The concentration of fluorescein
      will then be measured using a fluorescence plate reader. Also, 2 biopsies will be used for
      mRNA extraction and subsequent cDNA synthesis. This cDNA will be used to measure the gene
      expression of cell-to-cell adhesion proteins and acid-sensing receptors by means of real-time
      PCR. In addition, 2 biopsies will be prepared for immunofluorescence and immunohistochemistry
      and 2 will be used for western blot to measure changes in distribution/expression of the
      cell-to-cell adhesion proteins and of bile acid-sensitive receptors. Two biopsies will be
      obtained to study ultrastructural alterations by transmission electron microscopy.

      After recovery, a catheter will be introduced in the second duodenum via the nose and the
      position of the catheter will be checked fluoroscopically. This catheter allows collection of
      intestinal fluids by means of a syringe to collect duodenal fluid aspirates and
      characterization of the bile acid composition of those samples (8). After 30 minutes, the
      participants will be given a specified amount of water (250 mL) (fasted state) and another 30
      minutes later a nutritional drink (fed state). Intestinal fluids will be sampled every 15 min
      for a period of 1 h before the liquid meal intake and until 90 minutes after the liquid meal
      intake. So, after the total collection period, 7 fractions for the fed state and 4 fractions
      for the fasted state will be obtained per participant in a time frame of 2 hours and a half.
      The composition of bile acids of the intestinal samples will be determined by GC-MS-selected
      ion monitoring analysis.
    

Intervention name(s): Duodenogastroscopy; Duodenal aspiration catheter; Nutri drink
Intervention type(s): Procedure; Device; Dietary Supplement
Intervention description(s): Catheter goes through the mouth in the duodenum to take duodenal biopsies.; Catheter goes through the nose in the duodenum to aspirate duodenal fluid in fasted and fed state.; Liquid meal of 200 ml.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science