Aminoaciduria in the prediction of ifosfamide-induced tubulopathy after childhood cancer: a feasibility study

BACKGROUND

Ifosfamide, an alkylating agent used widely in the treatment of childhood malignancy, can cause many side effects including a proximal tubulopathy. Studies suggest that aminoaciduria is seen most commonly of all the biochemical abnormalities of ifosfamide-induced tubulopathy. A recent systematic review has found a paucity of data regarding the value of early markers indicating clinically significant tubulopathy. We undertook a pilot study to determine the feasibility of examining whether patients can be risk-stratified on the basis of aminoaciduria for the development of future significant ifosfamide-induced tubulopathy, to allow the evolution of appropriate follow-up strategies. We also aimed to define accrual rates, costs and clinical demands for a future larger study.

METHODS

This observational study recruited 21 patients from the Leeds Paediatric Oncology service. The medical notes of each patient were reviewed for demographic and clinical data. Simultaneous samples of blood and urine were obtained.

RESULTS

The investigations in the feasibility study were acceptable to patients and were minimally demanding on both clinical and laboratory staff. Financially, the cost per patient was minimal. This study was not powered to detect significant associations with TmP/GFR (ratio of renal tubular maximum reabsorption rate of phosphate to glomerular filtration rate), growth and electrolyte supplementation. However, all patients with minimal aminoaciduria (≤2 elevated urinary amino acids) had normal TmP/GFR and no need for electrolyte supplementation.

CONCLUSIONS

This pilot study has shown that a larger study is feasible and may provide clinically useful data to change current practice. This should aim to establish whether the number of abnormal amino acids or the degree of abnormality is most significant in predicting clinically significant proximal tubulopathy.

Systematic review of reduced therapy regimens for children with low risk febrile neutropenia

PURPOSE

Reduced intensity therapy for children with low-risk febrile neutropenia may provide benefits to both patients and the health service. We have explored the safety of these regimens and the effect of timing of discharge.

METHODS

Multiple electronic databases, conference abstracts and reference lists were searched. Randomised controlled trials (RCT) and prospective observational cohorts examining the location of therapy and/or the route of administration of antibiotics in people younger than 18 years who developed low-risk febrile neutropenia following treatment for cancer were included. Meta-analysis using a random effects model was conducted. I (2) assessed statistical heterogeneity not due to chance.

REGISTRATION

PROSPERO (CRD42014005817).

RESULTS

Thirty-seven studies involving 3205 episodes of febrile neutropenia were included; 13 RCTs and 24 prospective observational cohorts. Four safety events (two deaths, two intensive care admissions) occurred. In the RCTs, the odds ratio for treatment failure (persistence, worsening or recurrence of fever/infecting organisms, antibiotic modification, new infections, re-admission, admission to critical care or death) with outpatient treatment was 0.98 (95% confidence interval (95%CI) 0.44-2.19, I (2) = 0 %) and with oral treatment was 1.05 (95%CI 0.74-1.48, I (2) = 0 %). The estimated risk of failure using outpatient therapy from all prospective data pooled was 11.2 % (95%CI 9.7-12.8 %, I (2) = 77.2 %) and using oral antibiotics was 10.5 % (95%CI 8.9-12.3 %, I (2) = 78.3 %). The risk of failure was higher when reduced intensity therapies were used immediately after assessment, with lower rates when these were introduced after 48 hours.

CONCLUSIONS

Reduced intensity therapy for specified groups is safe with low rates of treatment failure. Services should consider how these can be acceptably implemented.

Dynamic High-Cadence Cycling Improves Motor Symptoms in Parkinson's Disease

RATIONALE

Individuals with Parkinson's disease (PD) often have deficits in kinesthesia. There is a need for rehabilitation interventions that improve these kinesthetic deficits. Forced (tandem) cycling at a high cadence improves motor function. However, tandem cycling is difficult to implement in a rehabilitation setting.

OBJECTIVE

To construct an instrumented, motored cycle and to examine if high cadence dynamic cycling promotes improvements in motor function.

METHOD

This motored cycle had two different modes: dynamic and static cycling. In dynamic mode, the motor maintained 75-85 rpm. In static mode, the rider determined the pedaling cadence. UPDRS Motor III and Timed Up and Go (TUG) were used to assess changes in motor function after three cycling sessions.

RESULTS

Individuals in the static group showed a lower cadence but a higher power, torque and heart rate than the dynamic group. UPDRS score showed a significant 13.9% improvement in the dynamic group and only a 0.9% improvement in the static group. There was also a 16.5% improvement in TUG time in the dynamic group but only an 8% improvement in the static group.

CONCLUSION

These findings show that dynamic cycling can improve PD motor function and that activation of proprioceptors with a high cadence but variable pattern may be important for motor improvements in PD.

Nutritional support in children and young people with cancer undergoing chemotherapy

BACKGROUND

It is well documented that malnutrition is a common complication of paediatric malignancy and its treatment. Malnutrition can often be a consequence of cancer itself or a result of chemotherapy. Nutritional support aims to reverse malnutrition seen at diagnosis, prevent malnutrition associated with treatment and promote weight gain and growth. The most effective and safe forms of nutritional support in children and young people with cancer are not known.

OBJECTIVES

To determine the effects of any form of parenteral (PN) or enteral (EN) nutritional support, excluding vitamin supplementation and micronutrient supplementation, in children and young people with cancer undergoing chemotherapy and to determine the effect of the nutritional content of PN and EN. This is an update of a previous Cochrane review.

SEARCH METHODS

We searched the following databases for the initial review: CENTRAL (The Cochrane Library, Issue 2, 2009), MEDLINE (1950 to 2006), EMBASE (1974 to 2006), CINAHL (1982 to 2006), the National Research Register (2007) and Dissertations & Theses (2007). Experts in the field were also contacted for information on relevant trials. For this update, we searched the same electronic databases from 2006 to September 2013. We also scrutinised the reference lists of included articles to identify additional trials.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials comparing any form of nutritional support with another, or control, in children or young people with cancer undergoing chemotherapy.

DATA COLLECTION AND ANALYSIS

Two authors independently selected trials. At least two authors independently assessed quality and extracted data. We contacted trialists for missing information.

MAIN RESULTS

The current review included the eight trials from the initial review and six new trials which randomised 595 participants (< 21 years of age) with leukaemias or solid tumours undergoing chemotherapy. The trials were all of low quality with the exception of two of the trials looking at glutamine supplementation. One small trial found that compared to EN, PN significantly increased weight (mean difference (MD) 4.12, 95% CI 1.91 to 6.33), serum albumin levels (MD 0.70, 95% CI 0.14 to 1.26), calorie intake (MD 22.00, 95% CI 5.12 to 38.88) and protein intake (MD 0.80, 95% CI 0.45 to 1.15). One trial comparing peripheral PN and EN with central PN found that mean daily weight gain (MD -27.00, 95% CI -43.32 to -10.68) and energy intake (MD -15.00, 95% CI -26.81 to -3.19) were significantly less for the peripheral PN and EN group, whereas mean change in serum albumin was significantly greater for that group (MD 0.47, 95% CI 0.13 to 0.81, P = 0.008). Another trial with few participants found an increase in mean energy intake (% recommended daily amount) in children fed an energy dense feed compared to a standard calorie feed (MD +28%, 95% CI 17% to 39%). Three studies looked at glutamine supplementation. The evidence suggesting that glutamine reduces severity of mucositis was not statistically significant in two studies (RR 0.64, 95% CI 0.19 to 2.2 and RR 0.85, 95% CI 0.66 to 1.1) and differences in reduction of infection rates were also not significant in two studies (RR 1.0, 95% CI 0.72 to 1.4 and RR 0.98, 95% CI 0.63 to 1.51). Only one study compared olive oil based PN to standard lipid containing PN. Despite similar calorie contents in both feeds, the standard lipid formula lead to greater weight gain (MD -0.34 z-scores, 95% CI -0.68 to 0.00). A single study compared standard EN with fructooligosaccharide containing EN. There was no difference in weight gain between groups (mean difference -0.12, 95% CI -0.57 to 0.33), with adverse effects (nausea) occurring equally between the groups (RR 0.92, 95% CI 0.48 to 1.74).

AUTHORS' CONCLUSIONS

There is limited evidence from individual trials to suggest that PN is more effective than EN in well-nourished children and young people with cancer undergoing chemotherapy. The evidence for other methods of nutritional support remains unclear. Limited evidence suggests an energy dense feed increases mean daily energy intake and has a positive effect on weight gain. Evidence suggesting glutamine supplementation reduces incidence and severity of mucositis, infection rates and length of hospital stay is not statistically significant. Further research, incorporating larger sample sizes and rigorous methodology utilising valid and reliable outcome measures, is essential.

Systematic review and meta-analysis of outcomes after cardiopulmonary arrest in childhood

BACKGROUND

Cardiopulmonary arrest in children is an uncommon event, and often fatal. Resuscitation is often attempted, but at what point, and under what circumstances do continued attempts to re-establish circulation become futile? The uncertainty around these questions can lead to unintended distress to the family and to the resuscitation team.

OBJECTIVES

To define the likely outcomes of cardiopulmonary resuscitation in children, within different patient groups, related to clinical features.

DATA SOURCES

MEDLINE, MEDLINE in-Process & Other non-Indexed Citations, EMBASE, Cochrane database of systematic reviews and Cochrane central register of trials, Database of Abstracts of Reviews of Effects (DARE), the Health Technology Assessment database, along with reference lists of relevant systematic reviews and included articles.

STUDY ELIGIBILITY CRITERIA

Prospective cohort studies which derive or validate a clinical prediction model of outcome following cardiopulmonary arrest.

PARTICIPANTS AND INTERVENTIONS

Children or young people (aged 0 - 18 years) who had cardiopulmonary arrest and received an attempt at resuscitation, excluding resuscitation at birth.

STUDY APPRAISAL AND SYNTHESIS METHODS

Risk of bias assessment developed the Hayden system for non-randomised studies and QUADAS2 for decision rules. Synthesis undertaken by narrative, and random effects meta-analysis with the DerSimonian-Laird estimator.

RESULTS

More than 18,000 episodes in 16 data sets were reported. Meta-analysis was possible for survival and one neurological outcome; others were reported too inconsistently. In-hospital patients (average survival 37.2% (95% CI 23.7 to 53.0%)) have a better chance of survival following cardiopulmonary arrest than out-of-hospital arrests (5.8% (95% CI 3.9% to 8.6%)). Better neurological outcome was also seen, but data were too scarce for meta-analysis (17% to 71% 'good' outcomes, compared with 2.8% to 3.2%).

LIMITATION

Lack of consistent outcome reporting and short-term neurological outcome measures limited the strength of conclusions that can be drawn from this review.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

There is a need to collaboratively, prospectively, collect potentially predictive data on these rare events to understand more clearly the predictors of survival and long-term neurological outcome.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO 2013:CRD42013005102.

Core outcomes and definitions for pediatric fever and neutropenia research: a consensus statement from an international panel

BACKGROUND

There are no specific recommendations for the design and reporting of studies of children with fever and neutropenia (FN). As a result, there is marked heterogeneity in the variables and outcomes that are reported and new definitions continue to emerge. These inconsistencies hinder the ability of researchers and clinicians to compare, contrast and combine results. The objective was to achieve expert consensus on a core set of variables and outcomes that should be measured and reported, as a minimum, in pediatric FN studies.

PROCEDURE

The Delphi method was used to achieve consensus among an international group of clinicians, pharmacists, researchers, and patient representatives. Four surveys focusing on (i) the identification of a core set of variables and outcomes; and (ii) definitions of these variables and outcomes, were administered electronically. Consensus was predefined as more than 80% agreement on any statement.

RESULTS

There were forty-five survey participants and the response rate ranged between 84 and 96%. There was consensus on eight core variables and 10 core outcomes that should be collected and reported in all studies of children with FN. Consensus definitions were identified for all of the core outcomes.

CONCLUSION

Using the Delphi method, expert consensus on a set of core variables and outcomes, and their corresponding definitions, was achieved. These core sets represent the minimum that should be collected and reported in all studies of children with FN. This will promote collaboration and ensure consistency and comparability between studies.

Chemistry and diversity of pyridoxal-5'-phosphate dependent enzymes

Pyridoxal-5'-phosphate (PLP) is a versatile cofactor that enzymes use to catalyze a wide variety of reactions of amino acids, including transamination, decarboxylation, racemization, β- and γ-eliminations and substitutions, retro-aldol and Claisen reactions. These reactions depend on the ability of PLP to stabilize, to a varying degree, α-carbanionic intermediates. Furthermore, oxidative decarboxylations and rearrangements suggest that PLP can stabilize radical intermediates as well. The reaction mechanisms of two PLP-dependent enzymes are discussed, kynureninase and tyrosine phenol-lyase (TPL). Kynureninase catalyzes a retro-Claisen reaction of kynurenine to give anthranilate and alanine. The key step, hydration of the γ-carbonyl, is assisted by acid-base catalysis with the phosphate of the PLP, mediated by a conserved tyrosine, and an oxyanion hole. TPL catalyzes the reversible elimination of phenol, a poor leaving group, from l-tyrosine. In TPL, the Cβ-Cγ bond cleavage is accelerated by ground state strain from the bending of the substrate ring out of the plane with the Cβ-Cγ bond. This article is part of a Special Issue entitled: Cofactor-dependent proteins: evolution, chemical diversity and bio-applications.

Critical Review of Clinical Practice Guidelines for Fertility Preservation in Teenagers and Young Adults with Cancer

Purpose: The 5-year survival of teenagers and young adults (TYAs; 13-24 years old) with cancer has continued to rise, but as a result more patients experience late effects of treatment, such as infertility. Advice regarding fertility preservation in relation to cancer is provided in numerous clinical practice guidelines, but the rigor of their development is unclear. Methods: A systematic search was undertaken for clinical practice guidelines regarding fertility preservation in TYAs with cancer. All guidelines were reviewed according to the Appraisal of Guidelines for Research and Evaluation (AGREE-II) criteria. Five out of 13 identified guidelines scored over 75% in the "rigor of development" section and were further appraised. Content, scope, and consistencies between recommendations were also examined. Results: All five of the reviewed guidelines encouraged oncologists to have discussions with their patients about potential fertility issues associated with treatment and available fertility preservation methods. The cryopreservation of sperm, oocytes, and embryos were all recommended as first-line interventions in postpubertal patients. Recommendations surrounding pre- or peripubescent adolescents were few, with many techniques only recommended as part of a clinical trial. The risk of subfertility associated with different treatment regimens was poorly described. Conclusions: The methodology and development of guidelines describing fertility preservation in TYA cancer patients varied greatly. Methodological quality did not clearly influence key recommendations. Those involved with the development of guidelines are encouraged to clearly define their development methods to allow users to be confident of the quality.

Protocol for a systematic review of reductions in therapy for children with low-risk febrile neutropenia

BACKGROUND

Febrile neutropenia is a common complication of therapy in children with cancer. Some patients are at low risk of complications, and research has considered reduction in therapy for these patients. A previous systematic review broadly considered whether outpatient treatment and oral antibiotics were safe in this context and concluded that this was likely to be the case. Since that review, there has been further research in this area. Therefore, we aim to provide a more robust answer to these questions and to additionally explore whether the exact timing of discharge, including entirely outpatient treatment, has an impact on outcomes.

METHODS/DESIGN

The search will cover MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, EMBASE, CDSR, CENTRAL, LILACS, HTA and DARE. A full search strategy is provided. Key conference proceedings and reference lists of included papers will be hand searched. Prominent authors/clinicians in the field will be contacted. We will include randomised and quasi-randomised controlled trials along with prospective single-arm studies that examine the location of therapy and/or the route of administration of antibiotics in children or young adults (aged less than 18 years) who attend paediatric services with fever and neutropenia due to treatment for cancer and are assessed to be at low risk of medical complications. Studies will be screened and data extracted by one researcher and independently checked by a second. All studies will be critically appraised using tools appropriate to the study design. Data from randomised controlled trials (RCTs) will be combined to provide comparative estimates of treatment failure, safety and adequacy. Information from quasi-randomised trials and single-arm studies will provide further data on the safety and adequacy of regimes. Random effects meta-analysis will be used to combine studies. A detailed analysis plan, including assessment of heterogeneity and publication bias, is provided.

DISCUSSION

This study will aim to specifically define the features of a low-risk strategy that will maintain levels of safety and adequacy equivalent to those of traditional treatments. This will both inform the development of services and provide patients and families with data to help them make an informed decision about care.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42014005817.

Mutation of Thermoanaerobacter ethanolicus secondary alcohol dehydrogenase at Trp-110 affects stereoselectivity of aromatic ketone reduction

Alcohol dehydrogenases (ADHs) are enzymes that catalyze the reversible reduction of carbonyl compounds to their corresponding alcohols. We have been studying a thermostable, nicotinamide-adenine dinucleotide phosphate (NADP(+))-dependent, secondary ADH from Thermoanaerobacter ethanolicus (TeSADH). In the current work, we expanded our library of TeSADH and adopted the site-saturation mutagenesis approach in creating a comprehensive mutant library at W110. We used phenylacetone as a model substrate to study the effectiveness of our library because this substrate showed low enantioselectivity in our previous work when reduced using W110A TeSADH. Five of the newly designed W110 mutants reduced phenylacetone at >99.9% ee, and two of these mutants exhibit an enantiomeric ratio (E-value) of over 100. These five mutants also reduced 1-phenyl-2-butanone and 4-phenyl-2-butanone to their corresponding (S)-configured alcohols in >99.9% ee. These new mutants of TeSADH will likely have synthetic utility for reduction of aromatic ketones in the future.

A straightforward kinetic evidence for coexistence of "induced fit" and "selected fit" in the reaction mechanism of a mutant tryptophan indole lyase Y72F from Proteus vulgaris

The interaction of the mutant tryptophan indole-lyase (TIL) from Proteus vulgaris Y72F with the transition state analogue, oxindolyl-l-alanine (OIA), with the natural substrate, l-tryptophan, and with a substrate S-ethyl-l-cysteine was examined. In the case of wild-type enzyme these reactions are described by the same kinetic scheme where binding of holoenzyme with an amino acid, leading to reversible formation of an external aldimine, proceeds very fast, while following transformations, leading finally to reversible formation of a quinonoid intermediate proceed with measureable rates. Principally the same scheme ("induced fit") is realized in the case of mutant Y72F enzyme reaction with OIA. For the reaction of mutant enzyme with l-Trp at lower concentrations of the latter a principally different kinetic scheme is observed. This scheme suggests that binding of the substrate and formation of the quinonoid intermediate are at fast equilibrium, while preceding conformational changes of the holoenzyme proceed with measureable rates ("selected fit"). For the reaction with S-ethyl-l-cysteine the observed concentration dependence of kobs agrees with the realization of both kinetic schemes, the "selected fit" becoming predominant at lower concentrations of substrate, the "induced fit"- at higher ones. In the reaction with S-ethyl-l-cysteine the formation of the quinonoid intermediate proceeds slower than does catalytic α,β-elimination of ethylthiol from S-ethyl-l-cysteine, and consequently does not play a considerable role in the catalysis, which may be effected by a concerted E2 mechanism.

Symbiotic bacterial metabolites regulate gastrointestinal barrier function via the xenobiotic sensor PXR and Toll-like receptor 4

Intestinal microbial metabolites are conjectured to affect mucosal integrity through an incompletely characterized mechanism. Here we showed that microbial-specific indoles regulated intestinal barrier function through the xenobiotic sensor, pregnane X receptor (PXR). Indole 3-propionic acid (IPA), in the context of indole, is a ligand for PXR in vivo, and IPA downregulated enterocyte TNF-α while it upregulated junctional protein-coding mRNAs. PXR-deficient (Nr1i2(-/-)) mice showed a distinctly "leaky" gut physiology coupled with upregulation of the Toll-like receptor (TLR) signaling pathway. These defects in the epithelial barrier were corrected in Nr1i2(-/-)Tlr4(-/-) mice. Our results demonstrate that a direct chemical communication between the intestinal symbionts and PXR regulates mucosal integrity through a pathway that involves luminal sensing and signaling by TLR4.

The role of substrate strain in the mechanism of the carbon-carbon lyases

The carbon-carbon lyases, tryptophan indole lyase (TIL) and tyrosine phenol-lyase (TPL) are bacterial enzymes which catalyze the reversible elimination of indole and phenol from l-tryptophan and l-tyrosine, respectively. These PLP-dependent enzymes show high sequence homology (∼40% identity) and both form homotetrameric structures. Steady state kinetic studies with both enzymes show that an active site base is essential for activity, and α-deuterated substrates exhibit modest primary isotope effects on kcat and kcat/Km, suggesting that substrate deprotonation is partially rate-limiting. Pre-steady state kinetics with TPL and TIL show rapid formation of external aldimine intermediates, followed by deprotonation to give quinonoid intermediates absorbing at about 500nm. In the presence of phenol and indole analogues, 4-hydroxypyridine and benzimidazole, the quinonoid intermediates of TPL and TIL decay to aminoacrylate intermediates, with λmax at about 340nm. Surprisingly, there are significant kinetic isotope effects on both formation and subsequent decay of the quinonoid intermediates when α-deuterated substrates are used. The crystal structure of TPL with a bound competitive inhibitor, 4-hydroxyphenylpropionate, identified several essential catalytic residues: Tyr-71, Thr-124, Arg-381, and Phe-448. The active sites of TIL and TPL are highly conserved with the exceptions of these residues: Arg-381(TPL)/Ile-396 (TIL); Thr-124 (TPL)/Asp-137 (TIL), and Phe-448 (TPL)/His-463 (TIL). Mutagenesis of these residues results in dramatic decreases in catalytic activity without changing substrate specificity. The conserved tyrosine, Tyr-71 (TPL)/Tyr-74 (TIL) is essential for elimination activity with both enzymes, and likely plays a role as a proton donor to the leaving group. Mutation of Arg-381 and Thr-124 of TPL to alanine results in very low but measurable catalytic activity. Crystallography of Y71F and F448H TPL with 3-fluoro-l-tyrosine bound demonstrated that there are two quinonoid structures, relaxed and tense. In the relaxed structure, the substrate aromatic ring is in plane with the Cβ-Cγ bond, but in the tense structure, the substrate aromatic ring is about 20° out of plane with the Cβ-Cγ bond. In the tense structure, hydrogen bonds are formed between the substrate OH and the guanidinium of Arg-381 and the OH of Thr-124, and the phenyl rings of Phe-448 and 449 provide steric strain. Based on the effects of mutagenesis, the substrate strain is estimated to contribute about 10(8) to TPL catalysis. Thus, the mechanisms of TPL and TIL require both substrate strain and acid/base catalysis, and substrate strain is probably responsible for the very high substrate specificity of TPL and TIL.

Docosahexaenoic Acid and Periodontitis in Adults: A Randomized Controlled Trial

Periodontitis is a common chronic inflammatory disease initiated by bacteria, resulting in bone resorption, tooth loss, and systemic inflammation. Long-chain omega-3 fatty acids such as docosahexaenoic acid (DHA) reduce periodontitis in animals. We aimed to determine whether DHA supplementation with low-dose aspirin would reduce periodontitis in humans. We conducted a double-blind placebo-controlled parallel trial lasting 3 mo. Fifty-five adults with moderate periodontitis were randomized to 2,000 mg of DHA or identical soy/corn oil capsules. All participants received 81 mg of aspirin but received no other treatments. We analyzed the primary outcome of per-pocket change in pocket depth using mixed models among teeth with pocket depth ≥5 mm. Secondary outcomes assessed with generalized estimating equations included gingival index, plaque index, and bleeding on probing. Gingival crevicular fluid samples were analyzed for changes in high-sensitivity C-reactive protein (hsCRP) and interleukins 6 and 1β (IL-6 and IL-1β). Plasma was analyzed for changes in systemic inflammatory markers, including hsCRP. We confirmed adherence with erythrocyte fatty acid measurement. Forty-six participants completed the trial. While similar at baseline, the proportion of DHA in red blood cell plasma membranes increased from 3.6% ± 0.9% to 6.2% ± 1.6% in the intervention group but did not change among controls. DHA supplementation decreased mean pocket depth (-0.29 ± 0.13; p = .03) and gingival index (-0.26 ± 0.13; p = .04). Plaque index and bleeding on probing did not change. Significant adjusted differences were found between DHA and control for both gingival crevicular fluid hsCRP (-5.3 ng/mL, standard error [SE] = 2.4, p = .03) and IL-1β (-20.1 pg/mL, SE = 8.2, p = .02) but not IL-6 (0.02 pg/mL, SE = 0.71, p = .98) or systemic hsCRP (-1.19 mg/L, SE = 0.90, p = .20). In this randomized controlled trial, aspirin-triggered DHA supplementation significantly improved periodontal outcomes in people with periodontitis, indicating its potential therapeutic efficacy (clinicaltrials.gov NCT01976806).

The efficacy and safety of probiotics in people with cancer: a systematic review

BACKGROUND

Probiotics are living microorganisms that are generally thought of as being beneficial to the recipient. They have been shown to be effective in people with acute infectious diarrhoea, and cost-effective in antibiotic-associated diarrhoea. Probiotics may have a role in people with cancer, as various cancer treatments often lead to diarrhoea. However, as people with cancer are often immunocompromised, it is important to assess for adverse events (AEs) such as infection, which could potentially be a consequence of deliberate ingestion of living microorganisms.

DESIGN

A systematic review was carried out to collect, analyse and synthesise all available data on the efficacy and safety of probiotics in people with cancer (PROSPERO registration: CRD42012003454). Randomised, controlled trials, identified through screening multiple databases and grey literature, were included for analysing efficacy, while all studies were included for the analysis of safety of probiotics. Primary outcomes were the reduction in duration, severity and incidence of antibiotic-associated diarrhoea and chemotherapy-associated diarrhoea, and AEs, especially probiotic-associated infection. Where possible, data were combined for meta-analysis by a random-effects model, assessing causes of heterogeneity, including differences in strains, dosage and patient characteristics.

RESULTS

Eleven studies (N = 1557 participants) were included for assessing efficacy. Results show that probiotics may reduce the severity and frequency of diarrhoea in patients with cancer and may reduce the requirement for anti-diarrhoeal medication, but more studies are needed to assess the true effect. For example comparing probiotic use to control 25 groups on effect on Common Toxicity Criteria ≥2 grade diarrhoea, odds ratio (OR) = 0.32 [95% confidence interval (CI) of 0.13-0.79; P = 0.01]. Seventeen studies (N = 1530) were included in the safety analysis. Five case reports showed probiotic-related bacteraemia/fungaemia/positive blood cultures.

CONCLUSIONS

Probiotics may be a rare cause of sepsis. Further evidence needs to be collated to determine whether probiotics provide a significant overall benefit for people with cancer.

Increasing value and reducing waste in biomedical research regulation and management

After identification of an important research question and selection of an appropriate study design, waste can arise from the regulation, governance, and management of biomedical research. Obtaining regulatory and governance approval has become increasingly burdensome and disproportionate to the conceivable risks to research participants. Regulation and governance involve interventions that are assumed to be justified in the interests of patients and the public, but they can actually compromise these interests. Inefficient management of the procedural conduct of research is wasteful, especially if it results in poor recruitment and retention of participants in well designed studies addressing important questions. These sources of waste can be minimised if the following four recommendations are addressed. First, regulators should use their influence to reduce other causes of waste and inefficiency in research. Second, regulators and policy makers should work with researchers, patients, and health professionals to streamline and harmonise the laws, regulations, guidelines, and processes that govern whether and how research can be done, and ensure that they are proportionate to the plausible risks associated with the research. Third, researchers and research managers should increase the efficiency of recruitment, retention, data monitoring, and data sharing in research through use of research designs known to reduce inefficiencies, and further research should be done to learn how efficiency can be increased. Finally, everyone, particularly those responsible for health-care systems, should promote integration of research into everyday clinical practice. Regulators and researchers should monitor adherence to each of these recommendations and publish metrics.

The phosphate of pyridoxal-5'-phosphate is an acid/base catalyst in the mechanism of Pseudomonas fluorescens kynureninase

Kynureninase (L-kynurenine hydrolase, EC 3.7.1.3) catalyzes the hydrolytic cleavage of L-kynurenine to L-alanine and anthranilic acid. The proposed mechanism of the retro-Claisen reaction requires extensive acid/base catalysis. Previous crystal structures showed that Tyr226 in the Pseudomonas fluorescens enzyme (Tyr275 in the human enzyme) hydrogen bonds to the phosphate of the pyridoxal-5'-phosphate (PLP) cofactor. This Tyr residue is strictly conserved in all sequences of kynureninase. The human enzyme complexed with a competitive inhibitor, 3-hydroxyhippuric acid, showed that the ligand carbonyl O is located 3.7 Å from the phenol of Tyr275 (Lima, S., Kumar, S., Gawandi, V., Momany, C. & Phillips, R. S. (2009) J. Med. Chem. 52, 389-396). We prepared a Y226F mutant of P. fluorescens kynureninase to probe the role of this residue in catalysis. The Y226F mutant has approximately 3000-fold lower activity than wild-type, and does not show the pKa values of 6.8 on kcat and 6.5 and 8.8 on k(cat)/K(m) seen for the wild-type enzyme (Koushik, S. V., Moore, J. A. III, Sundararaju, B. & Phillips, R. S. (1998) Biochemistry 37, 1376-1382). Wild-type kynureninase shows a resonance at 4.5 ppm in (31)P-NMR, which is shifted to 5.0, 3.3 and 2.0 ppm when the potent inhibitor 5-bromodihydrokynurenine is added. However, Y226F kynureninase shows resonances at 3.6 and 2.5 ppm, and no change in the peak position is seen when 5-bromodihydrokynurenine is added. Taken together, these results suggest that Tyr226 mediates proton transfer between the substrate and the phosphate, which accelerates formation of external aldimine and gem-diol intermediates. Thus, the phosphate of PLP acts as an acid/base catalyst in the mechanism of kynureninase.

Structure and mechanism of kynureninase

The kynurenine pathway is the major pathway of l-tryptophan catabolism in eukaryotes and some bacteria. In this pathway, kynureninase catalyzes the hydrolysis of l-kynurenine (in bacteria) or 3-hydroxy-l-kynurenine (in eukaryotes) to give anthranilic acid or 3-hydroxyanthranilic acid, respectively, and l-alanine. Kynureninase is a member of the aminotransferase superfamily and contains pyridoxal-5'-phosphate (PLP) as cofactor. The enzyme is a dimer of two identical subunits, with the active site containing residues contributed from both subunits. The reaction of kynureninase is formally a retro-Claisen reaction, and thus requires extensive acid-base catalysis. The pH dependence of the reaction of Pseudomonas fluorescens kynureninase shows two pKa's, a base with 6.5 and an acid with 8.8, on kcat/Km, and one pKa of 6.8 on kcat. The effects of mutagenesis of Tyr-226 and (31)P NMR results suggest that the basic group with pKa of 6.5 is the phosphate group of the PLP, which accepts a proton from the amino acid substrate zwitterion to initiate transaldimination. The external aldimine of kynurenine and PLP is then deprotonated by the ε-amino group of Lys-227 to give a quinonoid intermediate, which is reprotonated at C-4' to give a ketimine. Addition of water to the γ-carbonyl, assisted by Lys-227, then gives a gem-diol, which undergoes Cβ-Cγ cleavage to give the first product, anthranilic acid, and an enamine intermediate. The enamine is protonated at the β-carbon, resulting in a pyruvate ketimine. Deprotonation at C-4' and reprotonation of the α-carbon gives the external aldimine of l-alanine, which releases the second product, l-alanine. The reaction specificity of kynureninases is determined in part by active site residues, Trp64, Gly281, and Thr282 in P. fluorescens, and the homologous His102, Ser332, and Asn333 in human kynureninase. Asn333 can form a hydrogen bond to the 3-OH of 3-hydroxykynurenine in the human enzyme. Halogenation of kynurenine at C-5 increases activity with both enzymes, but halogenation at C-3 only increases activity for human kynureninase. The effect of halogenation at C-5 may be due to hydrophobic or van der Waals effects, and the effect of halogenation at C-3 for the human enzyme may be due to halogen bonding.