Randomised Controlled Trials May Underestimate Drug Effects: Balanced Placebo Trial Design

Background

It is an inherent assumption in randomised controlled trials that the drug effect can be estimated by subtracting the response during placebo from the response during active drug treatment.

Objective

To test the assumption of additivity. The primary hypothesis was that the total treatment effect is smaller than the sum of the drug effect and the placebo effect. The secondary hypothesis was that non-additivity was most pronounced in participants with large placebo effects.

Methods

We used a within-subject randomised blinded balanced placebo design and included 48 healthy volunteers (50% males), mean (SD) age 23.4 (6.2) years. Experimental pain was induced by injections of hypertonic saline into the masseter muscle. Participants received four injections with hypertonic saline along with lidocaine or matching placebo in randomised order: A: received hypertonic saline/told hypertonic saline; B: received hypertonic saline+lidocaine/told hypertonic saline; C: received hypertonic saline+placebo/told hypertonic saline+pain killer; D: received hypertonic saline+lidocaine/told hypertonic saline+pain killer. The primary outcome measure was the area under the curve (AUC, mm²) of pain intensity during injections.

Results

There was a significant difference between the sum of the drug effect and the placebo effect (mean AUC 6279 mm² (95% CI, 4936–7622)) and the total treatment effect (mean AUC 5455 mm² (95% CI, 4585–6324)) (P = 0.049). This difference was larger for participants with large versus small placebo effects (P = 0.015), and the difference correlated significantly with the size of the placebo effect (r = 0.65, P = 0.006).

Conclusion

Although this study examined placebo effects and not the whole placebo response as in randomised controlled trials, it does suggest that the additivity assumption may be incorrect, and that the estimated drug effects in randomised controlled trials may be underestimated, particularly in studies reporting large placebo responses. The implications for randomised controlled trials and systematic reviews need to be discussed.     

Purification and partial characterization of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase from Streptomyces clavuligerus.

delta-(L-alpha-Aminoadipyl)-L-cysteinyl-D-valine synthetase (ACVS) was purified from Streptomyces clavuligerus by a combination of salt precipitation, ultrafiltration, and anion-exchange chromatography. The final purified material gave two protein bands with molecular weights of 283,000 and 32,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Electrophoresis in nondenaturing gels gave a single protein band with an estimated molecular weight of 560,000. These results suggest that ACVS is a multimer composed of nonidentical subunits.     

Are cultured human myotubes far from home?

Satellite cells can be isolated from skeletal muscle biopsies, activated to proliferating myoblasts and differentiated into multinuclear myotubes in culture. These cell cultures represent a model system for intact human skeletal muscle and can be modulated ex vivo. The advantages of this system are that the most relevant genetic background is available for the investigation of human disease (as opposed to rodent cell cultures), the extracellular environment can be precisely controlled and the cells are not immortalized, thereby offering the possibility of studying innate characteristics of the donor. Limitations in differentiation status (fiber type) of the cells and energy metabolism can be improved by proper treatment, such as electrical pulse stimulation to mimic exercise. This review focuses on the way that human myotubes can be employed as a tool for studying metabolism in skeletal muscles, with special attention to changes in muscle energy metabolism in obesity and type 2 diabetes.     

The Trypanosoma brucei Life Cycle Switch TbPTP1 Is Structurally Conserved and Dephosphorylates the Nucleolar Protein NOPP44/46

Trypanosoma brucei adapts to changing environments as it cycles through arrested and proliferating stages in the human and tsetse fly hosts. Changes in protein tyrosine phosphorylation of several proteins, including NOPP44/46, accompany T. brucei development. Moreover, inactivation of T. brucei protein-tyrosine phosphatase 1 (TbPTP1) triggers differentiation of bloodstream stumpy forms into tsetse procyclic forms through unknown downstream effects. Here, we link these events by showing that NOPP44/46 is a major substrate of TbPTP1. TbPTP1 substrate-trapping mutants selectively enrich NOPP44/46 from procyclic stage cell lysates, and TbPTP1 efficiently and selectively dephosphorylates NOPP44/46 in vitro. To provide insights into the mechanism of NOPP44/46 recognition, we determined the crystal structure of TbPTP1. The TbPTP1 structure, the first of a kinetoplastid protein-tyrosine phosphatase (PTP), emphasizes the conservation of the PTP fold, extending to one of the most diverged eukaryotes. The structure reveals surfaces that may mediate substrate specificity and affords a template for the design of selective inhibitors to interfere with T. brucei transmission.     

An Entangled Model for Sustainability Indicators

Nowadays the challenge for humanity is to find pathways towards sustainable development. Decision makers require a set of sustainability indicators to know if the sustainability strategies are following those pathways. There are more than one hundred sustainability indicators but they differ on their relative importance according to the size of the locality and change on time. The resources needed to follow these sustainability indicators are scarce and in some instances finite, especially in smaller regions. Therefore strategies to select set of these indicators are useful for decision makers responsible for monitoring sustainability. In this paper we propose a model for the identification and selection of a set of sustainability indicators that adequately represents human systems. In developing this model, we applied evolutionary dynamics in a space where sustainability indicators are fundamental entities interconnected by an interaction matrix. we used a fixed interaction that simulates the current context for the city of Cuernavaca, México as an example. We were able to identify and define relevant sets indicators for the system by using the Pareto principle. In this case we identified a set of sixteen sustainability indicators with more than 80% of the total strength. This set presents resilience to perturbations. For the Tangled Nature framework we provided a manner of treating different contexts (i.e., cities, counties, states, regions, countries, continents or the whole planet), dealing with small dimensions. This model provides decision makers with a valuable tool to select sustainability indicators set for towns, cities, regions, countries, continents or the entire planet according to a coevolutionary framework. The social legitimacy can arise from the fact that each individual indicator must be selected from those that are most important for the subject community.     

The trehalose utilization gene thuA ortholog in Mesorhizobium loti does not influence competitiveness for nodulation on Lotus spp.

Competitiveness for nodulation is a desirable trait in rhizobia strains used as inoculant. In Sinorhizobium meliloti 1021 mutation in either of the trehalose utilization genes thuA or thuB influences its competitiveness for root colonization and nodule occupancy depending on the interacting host. We have therefore investigated whether mutation in the thuA ortholog in Mesorhizobium loti MAFF303099 also leads to a similar competitive phenotype on its hosts. The results show that M. loti thuA mutant Ml7023 was symbiotically effective and was as competitive as the wild type in colonization and nodule occupancy on Lotus corniculatus and Lotus japonicus. The thuA gene in M. loti was not induced during root colonization or in the infection threads unlike in S. meliloti, despite its induction by trehalose and high osmolarity in in vitro assays.