Tertiary alcohols, such as tert-butyl alcohol (TBA) and tert-amyl alcohol (TAA) and higher homologues, are only slowly degraded microbially. The conversion of TBA seems to proceed via hydroxylation to 2-methylpropan-1,2-diol, which is further oxidized to 2-hydroxyisobutyric acid. By analogy, a branched pathway is expected for the degradation of TAA, as this molecule possesses several potential hydroxylation sites. In Aquincola tertiaricarbonis L108 and Methylibium petroleiphilum PM1, a likely candidate catalyst for hydroxylations is the putative tertiary alcohol monooxygenase MdpJ. However, by comparing metabolite accumulations in wild-type strains of L108 and PM1 and in two mdpJ knockout mutants of strain L108, we could clearly show that MdpJ is not hydroxylating TAA to diols but functions as a desaturase, resulting in the formation of the hemiterpene 2-methyl-3-buten-2-ol. The latter is further processed via the hemiterpenes prenol, prenal, and 3-methylcrotonic acid. Likewise, 3-methyl-3-pentanol is degraded via 3-methyl-1-penten-3-ol. Wild-type strain L108 and mdpJ knockout mutants formed isoamylene and isoprene from TAA and 2-methyl-3-buten-2-ol, respectively. It is likely that this dehydratase activity is catalyzed by a not-yet-characterized enzyme postulated for the isomerization of 2-methyl-3-buten-2-ol and prenol. The vitamin requirements of strain L108 growing on TAA and the occurrence of 3-methylcrotonic acid as a metabolite indicate that TAA and hemiterpene degradation are linked with the catabolic route of the amino acid leucine, including an involvement of the biotin-dependent 3-methylcrotonyl coenzyme A (3-methylcrotonyl-CoA) carboxylase LiuBD. Evolutionary aspects of favored desaturase versus hydroxylation pathways for TAA conversion and the possible role of MdpJ in the degradation of higher tertiary alcohols are discussed.
Background Impaired executive functions (EFs, i.e., purposeful, goal-directed behaviour) cause significant disability after paediatric acquired brain injury (pABI) warranting efficient interventions. Goal Management Training (GMT) is a metacognitive protocol proven effective for executive dysfunction in adults. This pre-registered, blinded, parallel-randomized controlled trial evaluated efficacy of a paediatric adaptation (pGMT) compared to a psychoeducative control (paediatric Brain Health Workshop, pBHW) to improve EF. Methods Children aged 10 to 17 years with pABI (e.g., traumatic brain injury, brain tumour), ≥ 1 year post-onset or ended treatment, with parent-reported EF complaints were eligible. Participants were randomized (computer-algorithm) to either group-based pGMT (n = 38) or pBHW (n = 38). The active control was tailored to keep non-specific factors constant. Thus, both treatments comprised of 7 sessions at hospitals over 3 consecutive weeks, followed by 4 weeks of telephone counselling of participants, parents, and teachers. Parent-reported daily life EF, assessed by the questionnaire Behavior Rating Inventory of Executive Function (BRIEF; Behavioral Regulation Index (BRI) and Metacognition Index (MI)), were co-primary outcomes 6 months post-intervention. Secondary outcomes included neuropsychological tests and a complex naturalistic task (Children’s Cooking Task). Results Seventy-three participants (96%) completed allocated interventions and 71 (93%) attended the 6-month follow-up. The results demonstrated no significant difference in effectiveness for the two interventions on parent-reported EF: For BRIEFBRI, mean (SD) raw score for pGMT was 42.7 (8.8) and 38.3 (9.3) for pBHW. Estimated difference was − 2.3 (95% CI − 5.1 to 0.6). For BRIEFMI, the corresponding results were 80.9 (20.4) for GMT and 75.5 (19.3) for pBHW. Estimated difference was − 1.4 (95% CI −8.5 to 5.8). In performance-based tests, pGMT was associated with improved inhibition and executive attention, while pBHW was associated with fewer errors in the naturalistic task. Conclusions In pABI, metacognitive training (pGMT) did not demonstrate additional effectiveness on parent-reported daily life EF at 6-month follow-up, when compared to a psychoeducative control. Both interventions were well-tolerated and demonstrated distinct improvements at different EF assessment levels. To conclude on pGMT efficacy, larger studies are needed, including further investigation of appropriate assessment levels and possible differences in effect related to treatment duration, developmental factors, and injury characteristics. Trial registration ClinicalTrials.gov, NCT0321534211, 11 July 2017
IntroductionCompromised integrity of the brain due to paediatric acquired brain injury (pABI) has been associated with cognitive impairment, particularly executive dysfunction, in addition to somatic and emotional symptoms and reduced everyday function. Goal Management Training (GMT) is a cognitive rehabilitation intervention for improving executive function (EF) that has received empirical support in studies of adults with ABI. The purpose of the present study is to determine the efficacy of a recently developed paediatric version of GMT (pGMT) for children and adolescents with ABI and reported executive dysfunction.Methods and analysisThis study protocol describes a parallel randomised controlled trial including allocation concealment and assessor blinding. Eighty survivors after pABI, aged 10–17 years at the time of intervention, will be recruited. Participants will be randomly allocated to either pGMT (n=40) or a psychoeducative control intervention (n=40; paediatric Brain Health Workshop). Both interventions consist of seven group sessions for participants and parents, followed by external cueing and telephone counselling. The study also includes involvement of teachers. Assessments will be performed at baseline, immediately postintervention and at 6 months’ follow-up. Primary outcome measure will be changes in daily life EF as reported by parents (The Behavior Rating Inventory of Executive Function). Secondary outcomes include other assessments of EF (neuropsychological tests and questionnaires). Furthermore, we aim to assess generalisation effects of pGMT on other cognitive functions, as well as emotional, behavioural, adaptive and family function, academic performance, fatigue and quality of life.Ethics and disseminationResults from this study will be disseminated to relevant research, clinical, health service and patient communities through publications in peer-reviewed and popular science journals, in addition to presentations at scientific conferences. The study will be conducted in accordance with the Helsinki declaration and the Ethical Research Involving Children (ChildWatch International and Unicef). In accordance to Good Clinical Practice our study includes safety and quality monitoring guarantees in compliance with research ethics and safety. The trial will be reported in accordance with the Consolidated Standards of Reporting Trials 2010 statement and Standard Protocol Items for Reporting in Trials recommendations, in addition to being registered at ClinicalTrials.gov. The study has been approved by the Regional Committees for Medical and Health Research Ethics Norway (2017/772).Trial registration numberNCT03215342.
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