In vivo CYP3A4 heteroactivation is a possible mechanism for the drug interaction between felbamate and carbamazepine

Atypical (non-Michaelis-Menten) kinetics are commonly observed with CYP3A4 substrates in vitro. If relevant in vivo, cytochrome P450 heteroactivation could give rise to increased drug clearance. To test the possible in vivo relevance of atypical cytochrome P450 kinetics, we investigated the role of heteroactivation in the therapeutically relevant drug interaction between the anti-epileptics felbamate and carbamazepine. Felbamate heteroactivates CYP3A4-mediated formation of carbamazepine-10,11-epoxide (carbamazepine-ep), the major metabolite of carbamazepine, in human liver microsomes and recombinant CYP3A4 at relevant in vivo concentrations of both drugs (maximum activation 98% at 10 microM carbamazepine, 1 mM felbamate). Felbamate (50-500 microM) did not induce CYP3A4, as based on mRNA measurements in human liver slices. The further metabolism of carbamazepine-ep was inhibited (38% by 500 microM felbamate) in human liver slices. We propose a methodology to predict changes in steady-state plasma concentrations (Css) of parent drug and metabolite from in vitro heteroactivation and inhibition data, including prediction of the increase in fraction metabolized. A meta-analysis of reported in vivo effects of felbamate on Csscarbamazepine was performed to allow evaluation of this approach. The predicted effect of in vitro heteroactivation on Csscarbamazepine corresponds well to that observed in vivo. Combining the effect of heteroactivation on the fraction metabolized to carbamazepine-ep, and inhibition of its further metabolism, predicts a change in Csscarbamazepine-ep that falls within the range observed in vivo. Our results strongly suggest that in vivo heteroactivation of CYP3A4 is a possible mechanism of the clinically observed drug interaction between felbamate and carbamazepine.     

Generation and evaluation of a CYP2C9 heteroactivation pharmacophore

Positive cooperativity (auto- and heteroactivation) of drug oxidation, a potential cause of drug interactions, is well established in vitro for cytochrome P450 (P450) 3A4 but to a much lesser extent for other drug-metabolizing P450 isoforms. Using a high throughput fluorescent-based CYP2C9 effector assay, we identified >30 heteroactivators from a set of 1504 structurally diverse compounds. Several potent heteroactivators of CYP2C9-mediated 7-methoxy-4-trifluoromethyl-coumarin metabolism are marketed drugs or endogenous compounds (amiodarone, niclosamide, liothyronine, meclofenemate, zafirlukast, estropipate, and dichlorphenamide, yielding 150% control reaction velocity at 0.04, 0.09, 0.5, 1, 1.2, 1.5, and 2.5 microM, respectively). Some heteroactivators are also known CYP2C9 substrates or inhibitors, suggesting potential multiple binding sites and substrate-dependent effects. v(150%), the concentration of effector giving 150% of control reaction velocity, was used as pharmacophore modeling parameter based on enzyme kinetic assumptions. The generated pharmacophore (training set: n = 36, v(150%) 0.04-150 microM) contains one hydrogen bond acceptor, one aromatic ring, and two hydrophobes. v(150%) values for 94% of the training set heteroactivators were predicted within 1 log unit for the residual (r [log observed v(150%)] versus [log predicted v(150%)] = 0.71; r2 0.50). The model also correctly identifies close to 70% of potent inhibitors (IC50 < 1 microM) as high-affinity CYP2C9 binders, suggesting that heteroactivators and inhibitors share some common structural CYP2C9 binding features, supporting the previously suggested hypothesis that CYP2C9 heteroactivators can bind within the active site.     

Evaluation of new enzyme-linked immunosorbent assay based on a supernatant containing Staphylococcus aureus alpha-toxin produced by Bacillus subtilis.

The gene encoding alpha-toxin from Staphylococcus aureus was cloned into a Bacillus subtilis expression vector (pEF 231/alpha-Tox). The protease-deficient B. subtilis strain DB 104 transformed with pEF 231/alpha-Tox expressed and secreted 5 mg of alpha-toxin per liter into the growth medium. The alpha-toxin-containing supernatant was diluted 200-fold and used as coating antigen in an enzyme-linked immunosorbent assay (ELISA) for serodiagnosis of septicemia and endocarditis caused by S. aureus. Paired sera from patients in acute and convalescent stages of S. aureus and non-S. aureus infections were used to evaluate this ELISA. To evaluate the effectiveness of the crude preparation, the results were compared with those of an ELISA based on a commercially available alpha-toxin. Similar rises in serum titers were obtained with either type of alpha-toxin preparation. This is the first time a crude supernatant without any further purification has been used as an ELISA coating antigen. We therefore conclude that B. subtilis is a suitable host organism for cheap and simple production of prokaryotic recombinant antigens to be used in serodiagnosis.     

Correction to: Objective understanding of the Nutri-score front-of-pack label by European consumers and its effect on food choices: an online experimental study

There is increasing concern about the time people spend in sedentary behaviour, including screen time, leisure and occupational sitting. The number of both primary research studies (published trials) and reviews has been growing rapidly in this research area. A summary of the highest level of evidence that provides a broader quantitative synthesis of diverse types of interventions is needed. This research is to articulate the evidence of efficacy of sedentary behaviour interventions to inform interventions to reduce sitting time. The umbrella review, therefore, synthesised systematic reviews that conducted meta-analyses of interventions aiming at reducing sedentary behaviour outcomes across all age group and settings. A systematic search was conducted on six databases (MEDLINE Complete, PsycINFO, CINAHL, Global Health via EBSCOhost platform, EMBASE, and Cochrane Central Register of Systematic Reviews). Included articles were systematic reviews with meta-analysis of interventions aiming at reducing sedentary behaviour (screen time, sitting time or sedentary time) in the general population across all age group. Seventeen reviews met the inclusion criteria (7 in children and adolescent, 10 in adults). All reviews of sedentary behaviour interventions in children and adolescents investigated intervention effectiveness in reducing screen time. Six out of 11 meta-analyses (reported in 7 reviews) showed small but significant changes in viewing time. All reviews of sedentary behaviour interventions in office workplaces indicated substantial reduction in occupational sitting time (range: 39.6 to 100 min per 8-h workday). Sub-group analyses reported a trend favouring environmental change components such as sit-stand desks, active permissive workstations etc. Meta-analyses indicated that sedentary behaviour interventions were superior to physical activity alone interventions or combined physical activity and sedentary behaviour interventions in reducing sitting time. The current systematic reviews and meta-analyses supported sedentary behaviour interventions for reducing occupational sitting time in particular, with small changes seen in screen time in children and adolescents. Future research should explore approaches to maintaining behaviour change beyond the intervention period and investigate the potential of sedentary behaviour reduction interventions in older age groups in non-occupational settings.     

Jejunostomy Enteral Feeding in Children

Background: The aim of this study was to report on the clinical outcome and safety of jejunostomy tube feeding used in our clinical setting for more than 14 years. Material and Methods: A retrospective study of all children who underwent a surgical catheter jejunostomy placement between July 1996 and March 2010 was conducted. Data were collected regarding the outcome and complications. Results: Thirty‐three children (14 girls) were included. The median age at the time of primary surgery was 1.43 years (range, 0.15–17.7 years), and the median time of follow‐up was 2.34 years (range, 0.27–12.6 years). Seventeen children were severely neurologically impaired (NI). Surgical insertion of a jejunostomy tube was performed due to 1 or more of the following indications: gastroesophageal reflux disease (GERD), failure to thrive, recurrent pneumonia, esophageal disease, or oral feeding difficulties. The effect of the indications showed a reduction in GERD and pneumonia. Feeding difficulties also decreased. Weaning was possible in 12 of 16 children without NI but in only 2 of 17 with NI. Major complications requiring surgical reoperation affected 8 children. No mortality was related to the jejunostomy feeding catheter. Conclusion: In selected cases, surgically placed jejunostomy tubes for feeding in children is an effective and safe method to overcome GERD, feeding difficulties, or recurrent pneumonia without major surgery.