Humoral response to Clostridium difficile in inflammatory bowel disease, including correlation with immunomodulatory treatment

Background and Aim: An abnormal immune response to intestinal bacteria has been observed in Crohn’s disease (CD). Clostridium difficile infection incidence and severity are increased in CD, but reports on the humoral response have provided conflicting results. We aimed to shed light on the possible role of C. difficile in CD pathogenesis by paying attention to the influence of immunomodulatory treatment on the humoral response. Methods: A total of 71 consecutive outpatients with CD, 67 with ulcerative colitis (UC), and 121 healthy controls were analyzed for serum IgA and IgG to C. difficile toxins A and B. Results: IgA levels were similar in all study groups. IgG to toxin A was increased similarly in CD and UC (P = 0.02 for both). In contrast, IgG to toxin B was elevated only in CD patients not receiving disease-modifying anti-inflammatory bowel disease drugs (DMAID) (n = 16) (P = 0.0001), while the CD medication subgroup (n = 47) had a level similar to healthy controls. The UC results were not influenced by DMAID treatment. Conclusion: Our findings add support to the idea of a disturbed interaction between intestinal cells and the microbiota being part of the CD disease mechanism. An abnormal immune response to C. difficile toxin B may be a critical component of this interaction.publishedVersio

The Pharmacokinetics and Hepatic Disposition of Repaglinide in Pigs: Mechanistic Modeling of Metabolism and Transport

The predictive power of using in vitro systems in combination with physiologically based pharmacokinetic (PBPK) modeling to elucidate the relative importance of metabolism and carrier-mediated transport for the pharmacokinetics was evaluated using repaglinide as a model compound and pig as the test system. Repaglinide was chosen as model drug as previous studies in humans have shown that repaglinide is subject to both carrier-mediated influx to the liver cells and extensive hepatic metabolism. A multiple sampling site model in pig was chosen since it provides detailed in vivo information about the liver disposition. The underlying assumption was that both metabolism and carrier-mediated transport are also important for the hepatic disposition of repaglinide in pigs. Microsomes and primary hepatocytes were used for in vitro evaluation of enzyme kinetics and cellular disposition, respectively. In vitro data were generated both with and without metabolism inhibitors (ketoconazole, bezafibrate and trimethoprim) and transport inhibitors (diclofenac and quinine) providing input into a semi-PBPK model. In vivo data were also generated with and without the same enzyme and transporter inhibitors, alone and in combination. The pigs were given repaglinide as intravenous infusions with and without inhibitors in a sequential manner, i.e., a control phase and a test phase. Parameters describing the passive and carrier-mediated flux as well as metabolism were estimated in the control phase. The result from test phase was used to gain further knowledge of the findings from the control phase. The in vivo pig model enabled simultaneous sampling from plasma (pre- and postliver and peripheral) as well as from bile and urine. A semi-PBPK model consisting of 11 compartments (6 tissues + 5 sampling sites) was constructed for the mechanistic elucidation of the liver disposition, in vitro based in vivo predictions, sensitivity analyses and estimations of individual pharmacokinetic parameters. Both in vitro and in vivo results showed that carrier-mediated influx was important for the liver disposition. The in vivo findings were supported by the result from the test phase where hepatic clearance (4.3 mL min^–1 kg^–1) was decreased by 29% (metabolism inhibition), 43% (transport inhibition) and 57% (metabolism + transport inhibition). These effects were in good agreement with predicted levels. This study suggests that both metabolism and carrier-mediated uptake are of significant importance for the liver disposition of repaglinide in pigs