Nudix hydrolase 23 post-translationally regulates carotenoid biosynthesis in plants.

Carotenoids are essential for photosynthesis and photoprotection. Plants must evolve multifaceted regulatory mechanisms to control carotenoid biosynthesis. However, the regulatory mechanisms and the regulators conserved among plant species remain elusive. Phytoene synthase (PSY) catalyzes the highly regulated step of carotenogenesis and geranylgeranyl diphosphate synthase (GGPPS) acts as a hub to interact with GGPP-utilizing enzymes for the synthesis of specific downstream isoprenoids. Here, we report a function of Nudix hydrolase 23 (NUDX23), a Nudix domain-containing protein, in post-translational regulation of PSY and GGPPS for carotenoid biosynthesis. NUDX23 expresses highly in Arabidopsis (Arabidopsis thaliana) leaves. Overexpression of NUDX23 significantly increases PSY and GGPPS protein levels and carotenoid production, whereas knockout of NUDX23 dramatically reduces their abundances and carotenoid accumulation in Arabidopsis. NUDX23 regulates carotenoid biosynthesis via direct interactions with PSY and GGPPS in chloroplasts, which enhances PSY and GGPPS protein stability in a large PSY-GGPPS enzyme complex. NUDX23 was found to co-migrate with PSY and GGPPS proteins and to be required for the enzyme complex assembly. Our findings uncover a regulatory mechanism underlying carotenoid biosynthesis in plants and offer promising genetic tools for developing carotenoid-enriched food crops.

Corrigendum: The computational implementation of a platform of relative identity-by-descent scores algorithm for introgressive mapping.

[This corrects the article DOI: 10.3389/fgene.2022.1028662.].

BCH1 expression pattern contributes to the fruit carotenoid diversity between peach and apricot.

Peach (Prunus persica L. Batsch) and apricot (Prunus armeniaca L.) are two species of economic importance for fruit production in the genus Prunus. Peach and apricot fruits exhibit significant differences in carotenoid levels and profiles. HPLC-PAD analysis showed that a greater content of ß-carotene in mature apricot fruits is primarily responsible for orange color, while peach fruits showed a prominent accumulation of xanthophylls (violaxanthin and cryptoxanthin) with yellow color. There are two ß-carotene hydroxylase genes in both peach and apricot genomes. Transcriptional analysis revealed that BCH1 expresses highly in peach but lowly in apricot fruit, showing a correlation with peach and apricot fruit carotenoid profiles. By using a carotenoid engineered bacterial system, it was demonstrated that there was no difference in the BCH1 enzymatic activity between peach and apricot. Comparative analysis about the putative cis-acting regulatory elements between peach and apricot BCH1 promoters provided important information for our understanding of the differences in promoter activity of the BCH1 genes in peach and apricot. Therefore, we investigated the promoter activity of BCH1 gene through a GUS detection system, and confirmed that the difference in the transcription level of the BCH1 gene resulted from the difference of the promoter function. This study provides important perspective to understanding the diversity of carotenoid accumulation in Prunus fruits such as peach and apricot. In particular, BCH1 gene is proposed as a main predictor for ß-carotene content in peach and apricot fruits during the ripening process.

The role of exosomes and exosomal microRNA in diabetic cardiomyopathy.

Diabetic cardiomyopathy, a formidable cardiovascular complication linked to diabetes, is witnessing a relentless surge in its incidence. Despite extensive research efforts, the primary pathogenic mechanisms underlying this condition remain elusive. Consequently, a critical research imperative lies in identifying a sensitive and dependable marker for early diagnosis and treatment, thereby mitigating the onset and progression of diabetic cardiomyopathy (DCM). Exosomes (EXOs), minute vesicles enclosed within bilayer lipid membranes, have emerged as a fascinating frontier in this quest, capable of transporting a diverse cargo that mirrors the physiological and pathological states of their parent cells. These exosomes play an active role in the intercellular communication network of the cardiovascular system. Within the realm of exosomes, MicroRNA (miRNA) stands as a pivotal molecular player, revealing its profound influence on the progression of DCM. This comprehensive review aims to offer an introductory exploration of exosome structure and function, followed by a detailed examination of the intricate role played by exosome-associated miRNA in diabetic cardiomyopathy. Our ultimate objective is to bolster our comprehension of DCM diagnosis and treatment strategies, thereby facilitating timely intervention and improved outcomes.

The computational implementation of a platform of relative identity-by-descent scores algorithm for introgressive mapping.

With the development of genotyping and sequencing technology, researchers working in the area of conservation genetics are able to obtain the genotypes or even the sequences of a representative sample of individuals from the population. It is of great importance to examine the genomic variants and genes that are highly preferred or pruned during the process of adaptive introgression or long-term hybridization. To the best of our knowledge, we are the first to develop a platform with computational integration of a relative identity-by-descent (rIBD) scores algorithm for introgressive mapping. The rIBD algorithm is designed for mapping the fine-scaled genomic regions under adaptive introgression between the source breeds and the admixed breed. Our rIBD calculation platform provides compact functions including reading input information and uploading of files, rIBD calculation, and presentation of the rIBD scores. We analyzed the simulated data using the rIBD calculation platform and calculated the average IBD score of 0.061 with a standard deviation of 0.124. The rIBD scores generally follow a normal distribution, and a cut-off of 0.432 and -0.310 for both positive and negative rIBD scores is derived to enable the identification of genomic regions showing significant introgression signals from the source breed to the admixed breed. A list of genomic regions with detailed calculated rIBD scores is reported, and all the rIBD scores for each of the considered windows are presented in plots on the rIBD calculation platform. Our rIBD calculation platform provides a user-friendly tool for the calculation of fine-scaled rIBD scores for each of the genomic regions to map possible functional genomic variants due to adaptive introgression or long-term hybridization.

Double NCED isozymes control ABA biosynthesis for ripening and senescent regulation in peach fruits.

During ripening, peach fruits (Prunus persica L. Batsch) rapidly progress to the senescent stage, resulting in a brief shelf life. Abscisic acid (ABA) plays an important role in regulating the ripening process, both in climacteric and non-climacteric fruits. A key enzyme for ABA biosynthesis in higher plants is 9-cis-epoxycarotenoid dioxygenase (NCED). In this study, two NCED isozymes, PpNCED1 and PpNCED5, were identified in peach fruits. While both NCED genes had similar transcriptional patterns (up-regulation) at the beginning of peach ripening, PpNCED5 showed a consistently lower expression level than PpNCED1. During the post-harvest stage, gene expression of PpNCED1 declined, while PpNCED5 expression increased relative to PpNCED1 expression. Considering the dynamic process of ABA accumulation during fruit ripening and senescence in peach, this study indicates that both NCED genes cooperatively control ABA biosynthesis in peach fruits. Moreover, spatio-temporal expression and transcriptional response to hormone and abiotic stress suggested that there is functional divergence between PpNCED1 and PpNCED5 genes in peach. A carotenoid-rich callus system was used to verify the function of PpNCED1 and PpNCED5. In the transgenic callus system, both PpNCED1 and PpNCED5 isozymes promoted ABA biosynthesis, which likely accelerated cell senescence through activating ROS signals. The results from this study provide evidence supporting an ABA biosynthetic regulation process via the two NCED genes in peach fruit, and suggest a mechanism of ABA-induced fruit ripening and senescence.

Yield-Maturity Relationships of Summer Maize from 2003 to 2017 in the Huanghuaihai Plain of China.

Information on yield-maturity relationships is important for maize breeding and cultivation, but it is seldom available in geographic zones where there are limited heat resources for summer maize. Two novel systematic crop yield models were put forward in terms of production efficiency. These models as well as three other conventional models were used to analyze the crop yield and maturity dataset of 23,691 records that were collected from the annual reports for the national summer maize zonal trials conducted in the Huanghuaihai Plain of China during 2003 to 2017. (1) Crop yield increases were usually below 14.5 kg/666.7 m2 due to longer maturity days, varying from 1 d to 15 d increments. Maize hybrids with later maturity fell into five categories: statistically significantly less, not significantly less, the same, not significantly more, or statistically significantly more output than their earlier counterparts. (2) Three yield components acted on crop yield gaps in the order of descending effects as kernel number per ear ≈ 1000-kernel weight > ear number per unit land area. (3) Space production efficiency was more important than canopy volume to crop yield. (4) Time production efficiency was dominant and maturity was negligible in crop yield formation. The findings provide insights into yield-maturity relationships in maize and useful information for summer maize breeding and cultivation strategies.

A Neighboring Aromatic-Aromatic Amino Acid Combination Governs Activity Divergence between Tomato Phytoene Synthases.

Carotenoids exert multifaceted roles to plants and are critically important to humans. Phytoene synthase (PSY) is a major rate-limiting enzyme in the carotenoid biosynthetic pathway. PSY in plants is normally found as a small enzyme family with up to three members. However, knowledge of PSY isoforms in relation to their respective enzyme activities and amino acid residues that are important for PSY activity is limited. In this study, we focused on two tomato (Solanum lycopersicum) PSY isoforms, PSY1 and PSY2, and investigated their abilities to catalyze carotenogenesis via heterologous expression in transgenic Arabidopsis (Arabidopsis thaliana) and bacterial systems. We found that the fruit-specific PSY1 was less effective in promoting carotenoid biosynthesis than the green tissue-specific PSY2. Examination of the PSY proteins by site-directed mutagenesis analysis and three-dimensional structure modeling revealed two key amino acid residues responsible for this activity difference and identified a neighboring aromatic-aromatic combination in one of the PSY core structures as being crucial for high PSY activity. Remarkably, this neighboring aromatic-aromatic combination is evolutionarily conserved among land plant PSYs except PSY1 of tomato and potato (Solanum tuberosum). Strong transcription of tomato PSY1 likely evolved as compensation for its weak enzyme activity to allow for the massive carotenoid biosynthesis in ripe fruit. This study provides insights into the functional divergence of PSY isoforms and highlights the potential to rationally design PSY for the effective development of carotenoid-enriched crops.

Natural Variation in CCD4 Promoter Underpins Species-Specific Evolution of Red Coloration in Citrus Peel.

Carotenoids and apocarotenoids act as phytohormones and volatile precursors that influence plant development and confer aesthetic and nutritional value critical to consumer preference. Citrus fruits display considerable natural variation in carotenoid and apocarotenoid pigments. In this study, using an integrated genetic approach we revealed that a 5' cis-regulatory change at CCD4b encoding CAROTENOID CLEAVAGE DIOXYGENASE 4b is a major genetic determinant of natural variation in C30 apocarotenoids responsible for red coloration of citrus peel. Functional analyses demonstrated that in addition the known role in synthesizing ß-citraurin, CCD4b is also responsible for the production of another important C30 apocarotenoid pigment, ß-citraurinene. Furthermore, analyses of the CCD4b promoter and transcripts from various citrus germplasm accessions established a tight correlation between the presence of a putative 5' cis-regulatory enhancer within an MITE transposon and the enhanced allelic expression of CCD4b in C30 apocarotenoid-rich red-peeled accessions. Phylogenetic analysis provided further evidence that functional diversification of CCD4b and naturally occurring variation of the CCD4b promoter resulted in the stepwise evolution of red peels in mandarins and their hybrids. Taken together, our findings provide new insights into the genetic and evolutionary basis of apocarotenoid diversity in plants, and would facilitate breeding efforts that aim to improve the nutritional and aesthetic value of citrus and perhaps other fruit crops.

Carotenoid Metabolism in Plants: The Role of Plastids.

Carotenoids are indispensable to plants and critical in human diets. Plastids are the organelles for carotenoid biosynthesis and storage in plant cells. They exist in various types, which include proplastids, etioplasts, chloroplasts, amyloplasts, and chromoplasts. These plastids have dramatic differences in their capacity to synthesize and sequester carotenoids. Clearly, plastids play a central role in governing carotenogenic activity, carotenoid stability, and pigment diversity. Understanding of carotenoid metabolism and accumulation in various plastids expands our view on the multifaceted regulation of carotenogenesis and facilitates our efforts toward developing nutrient-enriched food crops. In this review, we provide a comprehensive overview of the impact of various types of plastids on carotenoid biosynthesis and accumulation, and discuss recent advances in our understanding of the regulatory control of carotenogenesis and metabolic engineering of carotenoids in light of plastid types in plants.

Naoxuekang, Xinnaoshutong and Xuesaitong capsules for treating stroke: a protocol for a randomised controlled trial.

INTRODUCTION: After stroke, hemiplegia, dysphasia and facial paralysis can manifest during the convalescent period. Currently, no Chinese patent medicine (CPM) is previously reported to cure each of these symptoms primarily, and thus, there are no relevant instructions for the use of CPM. This study presents a new approach based on comparative effectiveness research to distinguish the curative effects of three CPMs that are often used in stroke convalescence to determine the ideal medicine for the treatment of each symptom. METHODS AND ANALYSIS: In this multicentre and double-blind clinical trial, stratified randomisation is used to group the patients according to their primary symptoms (hemiplegia, dysphasia and facial paralysis). Three strata will be enrolled, with 80 eligible participants included in each stratum. Each stratum will be randomly and equally divided into four groups, and each group will receive one of the following treatments: Naoxuekang, Xinnaoshutong (XNST), Xuesaitong (XST) or placebo. This study will include two stages: the initial treatment period (30 days) and a follow-up period (180 days). Three replicates for each data point will be completed during this trial. The first visit will occur on day 0 after enrolment, the second visit on day 30±2 and the third visit on day 210±5. The Delphi technique is adopted to achieve index weighting, which ensures that the evaluation outcome is patient oriented. The weighted index value will be computed as the final measurement index of the outcome. ETHICS AND DISSEMINATION: This study has been approved by the Medical Ethics Committee of Tianjin University of Traditional Chinese Medicine (registration number TJUTCM-EC20160007). The results will be offered for publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: This trial was registered with the Chinese Clinical Trial Registry (ChiCTR-IOR-17010397). The date of registration was 11 January 2017.

JinqiJiangtang tablets for pre-diabetes: A randomized, double-blind and placebo-controlled clinical trial.

This study observed the efficacy and safety of JinqiJiangtang tablets (JQJT tablets, a traditional Chinese patent medicine) for pre-diabetes. Four hundred patients with pre-diabetes at five centres were treated for 12months and followed for an additional 12months to investigate the preventative effects of JQJT tablets (Registration ID: ChiCTR-PRC-09000401). The incidence rate of diabetes mellitus was the primary endpoint. The risk of converting from pre-diabetes to diabetes was 0.58-fold less in the JQJT tablets group than in the placebo group [HR (95% CI): 0.58 (0.384, 0.876), P = 0.010]. Furthermore, the probability of achieving normalized blood glucose was 1.41-fold greater in the JQJT tablets group than in the placebo group [HR (95% CI): 1.41 (1.002, 1.996), P = 0.0049]. ITT analysis revealed that the incidence of diabetes upon treatment completion was 16.5% in the JQJT tablets group compared with 28.9% in the control group. The percentage of patients with normalized blood glucose upon 12-month intervention was 41.8% in the JQJT tablets group compared with 27.8% in the control group. JQJT tablets could be an effective intervention for preventative treatment of Type 2 diabetes mellitus.

Practice of Comparative Effectiveness Research to Identify Treatment Characteristics of Similar Chinese Patent Medicine for Angina Pectoris.

OBJECTIVE: Individualized application of TCM is not easy and may lead to undesirable results, such as poor effect or even adverse reactions. This trial aims to compare two common Chinese patent medicines with similar effects. BACKGROUND OF THE RESEARCH: Four hospitals carried out the test at the same time in Tianjin city of China. PARTICIPANTS: 144 patients were involved in this study; all patients must meet the diagnostic criteria. INTERVENTIONS: Qishen Yiqi pills, compound danshen pills, and their placebos; an efficacy analysis was conducted after the first medication and after crossover medication. PRIMARY OUTCOME MEASURES: The primary index of end point includes Seattle Angina Questionnaire score-7 and score of 7-point Likert Scale; the curative effect was compared with minimal clinically important differences value. RESULT: Two drugs have their respective advantages in treating SAP. In practical application, the two drugs shall be discriminated in use based on patients' specific symptoms. TRIAL REGISTRATION: Chinese clinical trials register is ChiCTR-TTRCC-14004406 (registered 23 March 2014).

Dynamic changes in methylome and transcriptome patterns in response to methyltransferase inhibitor 5-azacytidine treatment in citrus.

DNA methylation is known to play an important role in various developmental processes in plants. However, there is a general lack of understanding about the possible functions of DNA methylation in fruit trees. Using callus as a model, methylome, transcriptome and metabolite changes were assessed after treatment with the DNA methyltransferase inhibitor 5-azacytidine (5azaC). Genome-wide methylome analysis revealed the demethylation of a diverse of genes, including many genes encoding transcription factors (TFs), genes involved in biological processes, and the up-regulation of a wide range of transposable elements (TEs). Combined with the RNA-seq data, we observed no obvious genome-wide correlation between the changes in methylation status and expression levels. Furthermore, 5azaC treatment induced carotenoid degradation along with strong activation of carotenoid cleavage dioxygenases 1 (CpCCD1). Functional complementation analysis in bacterial system showed that CpCCD1 exhibited strong catalytic activities toward zeaxanthin, ß-carotene and lycopene. In summary, 5azaC treatments induced carotenoid degradation by CpCCD1 activation and led to a genome-wide demethylation effect.

Reporting of core items in hierarchical Bayesian analysis for aggregating N-of-1 trials to estimate population treatment effects is suboptimal.

OBJECTIVES: N-of-1 trials can be aggregated to estimate population treatment effects using hierarchical Bayesian models. It is very important to report core items in hierarchical Bayesian analysis. In this study, we assessed reporting of items in hierarchical Bayesian analysis for aggregating N-of-1 trials to estimate population treatment effects. STUDY DESIGN AND SETTING: This was a systematic literature review of aggregating N-of-1 trials by hierarchical Bayesian models to estimate population treatment effects. A comprehensive search was performed to collect eligible articles. Pilot studies, formal N-of-1 trials and reports in which the data were reanalyzed using hierarchical Bayesian methods, were included. The information of reported items related with hierarchical Bayesian analysis was extracted by two independent reviewers. The guideline "ROBUST," developed for reporting Bayesian analysis of clinical studies, was published in Journal of Clinical Epidemiology in 2005. We assessed the included reports using ROBUST criteria and 18 other important items. RESULTS: After careful screening, 11 studies were identified to be eligible for inclusion. There were three pilot studies, four formal trials, and four reports in which the data were reanalyzed using hierarchical Bayesian methods. The number of reported items in ROBUST criteria ranged from six to seven, with a median number of six. Five of eleven included articles reported all items of the ROBUST criteria. But for justification and sensitivity analysis in prior distribution items, other items were reported in all of the included articles. Software and analysis data set items were reported the most frequently in additional items excluded from the ROBUST criteria. Less than half of the studies reported the other additional items. CONCLUSION: Reporting of core items in hierarchical Bayesian analysis for aggregating N-of-1 trials to estimate population treatment effects is suboptimal. A PRISMA-like guidance on reviews of Bayesian N-of-1 trials may be required in the future.

Carotenoid accumulation affects redox status, starch metabolism, and flavonoid/anthocyanin accumulation in citrus.

BACKGROUND: Carotenoids are indispensable plant secondary metabolites that are involved in photosynthesis, antioxidation, and phytohormone biosynthesis. Carotenoids are likely involved in other biological functions that have yet to be discovered. In this study, we integrated genomic, biochemical, and cellular studies to gain deep insight into carotenoid-related biological processes in citrus calli overexpressing CrtB (phytoene synthase from Pantoea agglomerans). Fortunella hindsii Swingle (a citrus relative) and Malus hupehensis (a wild apple) calli were also utilized as supporting systems to investigate the effect of altered carotenoid accumulation on carotenoid-related biological processes. RESULTS: Transcriptomic analysis provided deep insight into the carotenoid-related biological processes of redox status, starch metabolism, and flavonoid/anthocyanin accumulation. By applying biochemical and cytological analyses, we determined that the altered redox status was associated with variations in O2 (-) and H2O2 levels. We also ascertained a decline in starch accumulation in carotenoid-rich calli. Furthermore, via an extensive cellular investigation of the newly constructed CrtB overexpressing Fortunella hindsii Swingle, we demonstrated that starch level reducation occurred in parallel with significant carotenoid accumulation. Moreover, studying anthocyanin-rich Malus hupehensis calli showed a negative effect of carotenoids on anthocyanin accumulation. CONCLUSIONS: In citrus, altered carotenoid accumulation resulted in dramatic effects on metabolic processes involved in redox modification, starch degradation, and flavonoid/anthocyanin biosynthesis. These findings provided new perspectives to understand the biological importance of carotenogenesis and of the developmental processes associated with the nutritional and sensory qualities of agricultural products that accumulate carotenoids.

CUPID: a protocol of a randomised controlled trial to identify characteristics of similar Chinese patent medicines.

INTRODUCTION: Traditional Chinese medicine (TCM) has accumulated some experience in curing stable angina pectoris (SAP) and efficacy has been demonstrated. Chinese patent medicines, known as modern dosage forms of TCM, can attain the desired effect in clinical application only with the guidance of TCM syndrome theory. However, due to their use by a large number of persons with little knowledge of TCM theories and practices, their efficacy and reputation have been seriously affected. METHOD AND ANALYSIS: Two common syndrome types of SAP in TCM, 'qi deficiency and blood stasis' and 'qi stagnation and blood stasis', will be studied in 144 subjects from four TCM hospitals in Tianjin in China using a partial crossover design. The two syndromes will be broken down into six symptom combinations; patients will select a combination of the most distressing to them, and then will be randomised into two groups. Each group, on the basis of routine medication, will be administered one kind of Chinese patent drug: Qishenyiqi Dripping Pills or Compound Danshen Dripping Pills. The treatment characteristics of the two medicines will be evaluated with the COME-PIO method developed by our research team. ETHICS AND DISSEMINATION: This protocol has been approved by the medical ethics committee of Tianjin University of TCM (registration number TJUTCM-EC20130005). The study is safe and reliable. TRIAL REGISTRATION NUMBER: Chinese clinical trials register ChiCTR-TTRCC-14004406.

Use of comparative effectiveness research for similar Chinese patent medicine for angina pectoris of coronary heart disease: a new approach based on patient-important outcomes.

BACKGROUND: The practice of traditional Chinese medicine (TCM) has a profound history in many Asian countries. TCM syndrome is a set of characteristic physical signs and symptoms shared by a group of patients. Syndrome diagnosis and treatment assignment according to the identified TCM syndrome is a long-held practice of Chinese medicine. Owing to its distinctive way of interpreting illness and administering care, medical practitioners not well educated in TCM theories and practices are generally incapable of giving out prescriptions for Chinese patent drugs. Currently, the existence of a multitude of Chinese patent drugs marked with largely identical indications is further complicating this situation. METHODS: In this multicenter, randomized, controlled, double-blind, double-dummy clinical trial, in which we will use the comparative effectiveness research method, we will compare the efficacy of two commonly used Chinese patent medicines for angina patients diagnosed with qi deficiency and blood stasis syndrome. A total of 160 patients will be recruited and randomly assigned to receive either (1) QiShenYiQi dripping pills, Tongxinluo placebo and routine medication or (2) Tongxinluo capsules, QiShenYiQi placebo and routine medication. These treatment regimens will be carried out for 4 weeks, followed by a 10-day washout period and a 4-week crossover phase in which the treatments in the two patient groups will be exchanged. Patients will be allowed to choose symptoms that matter most to them and will be grouped accordingly. Patient-reported outcomes such as the Seattle Angina Questionnaire score and the 15-point Likert scale score will be measured and reported. The minimally clinical important difference will be calculated and used for efficacy assessment, and correspondence analysis will be performed to identify the best indications for each drug. DISCUSSION: The goal of the study is to establish a methodology for the precise identification of the characteristic indications for which a Chinese patent drug is most effective. The findings of this study will inform the practicality of the proposed evaluation method. TRIAL REGISTRATION: Chinese clinical trials register Chi CTRTTRCC13003732.

Internal challenge to clinical trial project management: strategies for managing investigator compliance.

BACKGROUND: Managing compliance in a clinical research, especially in a multi-centre randomized clinical trial (MRCT) is vital. We now feel the need to take a look at the once overlooked area of investigator compliance as it may provide resources necessary for producing satisfactory trial outcomes. OBJECTIVES: To analyze investigator performance and examine their adherence behavior using data collected and information gained from the MISPS-TCM, a Chinese national research project. METHODS: Four researchers were responsible for collecting relevant information and investigating the compliance behavior of participants in MISPS-TCM. The Data Management Committee of MISPS-TCM offered us the number of withdrawal at each site and other site information. Reports on investigator compliance events were provided by the Monitoring Committee. Records of any misconduct of or errors made by the investigator were collected from the Center's daily management diary. Other information sources included trial managers and investigators at the Center or at different sites of the study. RESULTS: Investigator compliance can be an important determinant of trial outcomes and the degree of compliance may have detrimental effects on the reliability of findings of an MRCT, directly or indirectly. CONCLUSIONS: Trial managers of future MRCTs should take a firm grip on investigator compliance from the following aspects. First, physicians should be provided with more opportunities. Second, we created and recommended the 'Five Step Method' for evaluating investigators. Third, measures must be taken to secure investigator compliance. Fourth, evaluation of investigator compliance in an MRCT needs to be made.