Global research trends in microbiome-gut-brain axis during 2009-2018: a bibliometric and visualized study

An examination of global research trends for exploring the associations between the gut microbiota and nonalcoholic fatty liver disease through bibliometric and visualization analysis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as a significant health issue. Emerging research has focused on the role of the gut microbiota in NAFLD, emphasizing the gut-liver axis. This study aimed to identify key research trends and guide future investigations in this evolving area.

METHODS

This bibliometric study utilized Scopus to analyze global research on the link between the gut microbiota and NAFLD. The method involved a search strategy focusing on relevant keywords in article titles, refined by including only peer-reviewed journal articles. The data analysis included bibliometric indicators such as publication counts and trends, which were visualized using VOSviewer software version 1.6.20 for network and co-occurrence analysis, highlighting key research clusters and emerging topics.

RESULTS

Among the 479 publications on the gut microbiota and NAFLD, the majority were original articles (n = 338; 70.56%), followed by reviews (n = 119; 24.84%). The annual publication count increased from 1 in 2010 to 118 in 2022, with a significant growth phase starting in 2017 (R2 = 0.9025, p < 0.001). The research was globally distributed and dominated by China (n = 231; 48.23%) and the United States (n = 90; 18.79%). The University of California, San Diego, led institutional contributions (n = 18; 3.76%). Funding was prominent, with 62.8% of the articles supported, especially by the National Natural Science Foundation of China (n = 118; 24.63%). The average citation count was 43.23, with an h-index of 70 and a citation range of 0 to 1058 per article. Research hotspots shifted their focus post-2020 toward the impact of high-fat diets on NAFLD incidence.

CONCLUSIONS

This study has effectively mapped the growing body of research on the gut microbiota-NAFLD relationship, revealing a significant increase in publications since 2017. There is significant interest in gut microbiota and NAFLD research, mainly led by China and the United States, with diverse areas of focus. Recently, the field has moved toward exploring the interconnections among diet, lifestyle, and the gut-liver axis. We hypothesize that with advanced technologies, new opportunities for personalized medicine and a holistic understanding of NAFLD will emerge.

The global state of research in stem cells therapy for spinal cord injury (2003-2022): a visualized analysis

Objective

Our study aimed to visualize the global status and frontiers in stem cell therapy for spinal cord injury by using bibliometric methodology.

Methods

Publication citation information related to stem cell therapy for spinal cord injury (SCI) studies between 2003 and 2022 was retrieved from the Web of Science Core Collection database. For the visualized study, VOS viewer software and Graph Pad Prism 9.5 were used to perform bibliometric analysis of included data and publication number statistics in stem cell therapy for the SCI domain.

Results

A total of 6,686 publications were retrieved. The USA and China made the highest contributions to global research with the highest number of citations and link strength. The journal Experimental Neurology ranks as the top journal, combining the publication amount and bibliometrics results. The University of Toronto, based in Canada, was the first-ranking institution. The directions of the current study could be divided into five clusters. The research of Transplantation and Regenerative Medicine and Neurosciences Mechanism Research may be the emerging frontiers in this domain.

Conclusion

In summary, stem cell therapy for spinal cord injuries is poised for more valuable advances.

Trends in Brain Research: A Bibliometric Analysis

BACKGROUND

Bibliometrics methods have allowed researchers to assess the popularity of brain research through the ever-growing number of brain-related research papers. While many topics of brain research have been covered by previous studies, there is no comprehensive overview of the evolution of brain research and its various specialties and funding practices over a long period of time.

OBJECTIVE

This paper aims to (1) determine how brain research has evolved over time in terms of number of papers, (2) countries' relative and absolute positioning in terms of papers and impact, and (3) how those various trends vary by area.

METHODS

Using a list of validated keywords, we extracted brain-related articles and journals indexed in the Web of Science over the 1991-2020 period, for a total of 2,467,708 papers. We used three indicators to perform: number of papers, specialization, and research impact.

RESULTS

Our results show that over the past 30 years, the number of brain-related papers has grown at a faster pace than science in general, with China being at the forefront of this growth. Different patterns of specialization among countries and funders were also underlined. Finally, the NIH, the European Commission, the National Natural Science Foundation of China, the UK Medical Research Council, and the German Research Foundation were found to be among the top funders.

CONCLUSION

Despite data-related limitations, our findings provide a large-scope snapshot of the evolution of brain research and its funding, which may be used as a baseline for future studies on these topics.

Gut microbiota and autism spectrum disorders: where do we stand?

BACKGROUND

Children with autism spectrum disorder (ASD) often have digestive problems and microbial imbalances in their guts, suggesting that these conditions may play a role in the development of the disorder. Scopus-based research on the gut microbiota and ASD was examined in this bibliometric analysis to shed light on the current state of research and identify potential hotspots for future work in this area.

METHODS

We searched documents from the Scopus database and reference citation analysis to collect published data on the gut microbiota and ASD from 2003 to 2022. The downloaded document records were exported to VOSviewer v.1.6.19 to examine and visualize the collaboration between countries and determine the research hotspots.

RESULTS

The search yielded 958 articles specifically dedicated to gut microbiota and ASD. The number of publications in this field increased rapidly after 2013, with a peak in 2022. The United States (n = 267; 27.87%) was the most active country, followed by China (n = 171; 17.85%) and Italy (n = 96; 10.02). International collaboration was observed, with the USA playing a central role. University College Cork, Ireland, was the most productive institution (n = 24; 2.51%). The National Natural Science Foundation of China was the most active funding agency (n = 76; 7.93%). Nutrients journal had the highest number of publications (n = 28; 2.92%). The articles related to gut microbiota and ASD were highly cited, with an h-index of 108. The research themes identified focused on the modulation of gut microbiota as a potential therapy for children with ASD and gut-brain axis dysfunction in ASD.

CONCLUSIONS

In recent years, the study of gut microbiota and its association with ASD has garnered considerable interest as an emergent field of study. The results of this study substantially enhance our current understanding of the knowledge landscape in this field and illuminate potential avenues for future research. It is essential to emphasize the significance of devoting more resources to the newest and most promising research areas, such as investigating the potential therapeutic benefits of modulating the intestinal microbiota in children with ASD. This research has enormous potential and merits intensified focus and investigation.

Unveiling the hidden world of gut health: Exploring cutting-edge research through visualizing randomized controlled trials on the gut microbiota

BACKGROUND

The gut microbiota plays a crucial role in gastrointestinal and overall health. Randomized clinical trials (RCTs) play a crucial role in advancing our knowledge and evaluating the efficacy of therapeutic interventions targeting the gut microbiota.

AIM

To conduct a comprehensive bibliometric analysis of the literature on RCTs involving the gut microbiota.

METHODS

Using bibliometric tools, a descriptive cross-sectional investigation was conducted on scholarly publications concentrated on RCTs related to gut microbiota, spanning the years 2003 to 2022. The study used VOSviewer version 1.6.9 to examine collaboration networks between different countries and evaluate the frequently employed terms in the titles and abstracts of the retrieved publications. The primary objective of this analysis was to identify key research areas and focal points associated with RCTs involving the gut microbiota.

RESULTS

A total of 1061 relevant articles were identified from the 24758 research articles published between 2003 and 2022. The number of publications showed a notable increase over time, with a positive correlation (R2 = 0.978, P < 0.001). China (n = 276, 26.01%), the United States (n = 254, 23.94%), and the United Kingdom (n = 97, 9.14%) were the leading contributing countries. Københavns Universitet (n = 38, 3.58%) and Dankook University (n = 35, 3.30%) were the top active institutions. The co-occurrence analysis shows current gut microbiota research trends and important topics, such as obesity interventions targeting the gut microbiota, the efficacy and safety of fecal microbiota transplantation, and the effects of dietary interventions on humans.

CONCLUSION

The study highlights the rapid growth and importance of research on RCTs that involve the gut microbiota. This study provides valuable insight into research trends, identifies key players, and outlines potential future directions in this field. Additionally, the co-occurrence analysis identified important topics that play a critical role in the advancement of science and provided insights into future research directions in this field.

Project portfolio risk management. Bibliometry and collaboration Scientometric domain analysis

Purpose

''Project Portfolio Risk Management" is approached through a bibliometry and collaboration networks study determining its dynamics and development as a formal domain that links Project, Risk Management and Portfolio concepts.

Design/methodology/approach

To facilitate replicability, a scientometric study under a PRISMA structure is carried out: i) Identification or domain structuring, as well as keywording accuracy; ii) Screening: Search string refinement and outputs review; iii) Eligibility: Several criteria applied to a content analysis, and iv) Inclusion: Consolidation of domain analytics through bibliometry and collaboration networks.

Originality and findings

Assessing the field as a formal knowledge domain is novel, contributing to a synthesis of its trends and evolution: For first time, descriptive statistics show increasing attention based on the growing citation scores, participation, H index and productivity of its main journals. Project Portfolio Selection is established as hot topic, the main authors are identified, as well as key concepts such as optimization, mathematical programming, multi-objective optimization, stochastic programming, and robust optimization. Three main research themes are obtained: Incorporation of Risk Assessment into Project Portfolio Selection problem, Risk Management as a Project Portfolio Management process, and Risk Analysis considering social and environmental issues. An accurate match is found in the contrast of the domain's behavior with some bibliometric and linguistic laws.

Practical implications

Theoretical richness is achieved in the conjunction of the three terms, presenting dynamics and tendencies and thus contributing to focus related research processes on a unified field for the use of both scholars' and practitioners' perspectives.

The Top 100 Cited Articles on Acupuncture in the Last 20 Years: A Bibliometric Analysis

BACKGROUND

Acupuncture has gained increasing international attention in recent decades. The act of incorporating acupuncture treatment into the routine treatment of COVID-19 in China drove us to review the 100 most influential articles of the last 20 years to learn about the current status and trends of acupuncture.

METHOD

Articles related to acupuncture from January 1, 2001, to July 4, 2022, were searched in the Clarivate Analytics Web of Science Core Collection database. The top 100 most cited publications were selected, and information was extracted. Software such as VOSviewer, GraphPad Prism, Scimago Graphica, and CiteSpace were used to visualize and analyze the extracted data.

RESULT

The 100 most cited articles were identified, with an average of 218 citations (range: 131-625). The majority of the top 100 articles were from the USA (n = 53). The institution that published the most highly cited papers was Harvard University (n = 16). The most influential team was Klaus Linde's group. Pain was the top-ranked journal in terms of the number of publications. The largest clusters for co-occurrence keyword analysis focused on acupuncture and electroacupuncture analgesia and brain imaging responses to acupuncture stimulation via functional MRI. The two highest strength burst keywords were "randomized controlled trials" and "osteoarthritis," with "randomized controlled trials" being a consistent burst keyword from 2011 to the present.

CONCLUSION

This study provides insight into articles of historical significance in the field of acupuncture through bibliometric analysis. These data should provide clinicians and researchers with insight into future directions related to acupuncture.

Hintergrund

Die Akupunktur hat in den vergangenen Jahrzehnten zunehmend die internationale Aufmerksamkeit auf sich gezogen. Die Einbeziehung der Akupunktur in die Routinebehandlung von COVID-19 in China hat uns dazu veranlasst, die 100 einflussreichsten Artikel der letzten 20 Jahre zu überprüfen, um etwas über den aktuellen Stand und die Trends in der Akupunktur zu erfahren.

Methode

Artikel mit Bezug zu Akupunktur vom 1. Januar 2001 bis 4. Juli 2022 wurden in der Clarivate Analytics Web of Science Core Collection Datenbank gesucht. Die 100 am häufigsten zitierten Veröffentlichungen wurden ausgewählt und die Informationen wurden extrahiert. Visualisierung und Analyse der extrahierten Daten erfolgten mithilfe der Software VOSviewer, GraphPad Prism, Scimago Graphica und CiteSpace.

Ergebnis

Es wurden die 100 am häufigsten zitierten Artikel ermittelt mit durchschnittlich 218 Zitierungen (Spanne: 131 bis 625). Der Großteil der 100 meistzitierten Artikel stammte aus den Vereinigten Staaten (n = 53). Die Institution, die die meisten zitierten Artikel veröffentlichte, war die Harvard-Universität (n = 16). Das einflussreichste Team war die Gruppe von Klaus Linde. Was die Zahl der Veröffentlichungen betrifft, war Pain die am häufigsten zitierte Zeitschrift. Bei der Analyse der Koinzidenz von Schlüsselwörtern lag der Fokus der größten Cluster auf Akupunktur-und Elektroakupunktur-Analgesie sowie auf den Reaktionen auf Akupunkturstimulation in den bildgebenden Untersuchungen des Gehirns mittels funktioneller MRT. Die beiden stärksten Burst-Schlüsselwörter waren “randomisierte kontrollierte Studien” und “Osteoarthritis,” wobei “randomisierte kontrollierte Studien” von 2011 bis heute durchgängig ein Burst-Schlüsselwort ist.

Schlussfolgerung

Diese Studie bietet einen Einblick in historisch bedeutsame Artikel auf dem Gebiet der Akupunktur mittels bibliometrischer analyse. Diese Daten sollen Klinikern und Forschern einen Einblick in zukünftige Richtungen im Zusammenhang mit Akupunktur geben.

Emerging trends and focus on the link between gut microbiota and type 1 diabetes: A bibliometric and visualization analysis

Objective

To conduct the first thorough bibliometric analysis to evaluate and quantify global research regarding to the gut microbiota and type 1 diabetes (T1D).

Methods

A literature search for research studies on gut microbiota and T1D was conducted using the Web of Science Core Collection (WoSCC) database on 24 September 2022. VOSviewer software and the packages Bibliometrix R and ggplot used in RStudio were applied to perform the bibliometric and visualization analysis.

Results

A total of 639 publications was extracted using the terms "gut microbiota" and "type 1 diabetes" (and their synonyms in MeSH). Ultimately, 324 articles were included in the bibliometric analysis. The United States and European countries are the main contributors to this field, and the top 10 most influential institutions are all based in the United States, Finland and Denmark. The three most influential researchers in this field are Li Wen, Jorma Ilonen and Mikael Knip. Historical direct citation analysis showed the evolution of the most cited papers in the field of T1D and gut microbiota. Clustering analysis defined seven clusters, covering the current main topics in both basic and clinical research on T1D and gut microbiota. The most commonly found high-frequency keywords in the period from 2018 to 2021 were "metagenomics," "neutrophils" and "machine learning."

Conclusion

The application of multi-omics and machine learning approaches will be a necessary future step for better understanding gut microbiota in T1D. Finally, the future outlook for customized therapy toward reshaping gut microbiota of T1D patients remains promising.

Research trends in the field of the gut-brain interaction: Functional dyspepsia in the spotlight – An integrated bibliometric and science mapping approach

Objectives

This study aims to perform a bibliometric analysis of functional dyspepsia (FD), which includes visualizing bibliographic information, in order to identify prevailing study themes, topics of interest, contributing journals, countries, institutions, and authors as well as co-citation patterns.

Methods

The Web of Science™ Core Collection Database was used to retrieve all peer-reviewed scientific publications related to FD research. The validated search terms were entered into the “title” and “author keywords” fields, and the results were sorted by publication year from 2006 to 2022. There were no restrictions on language. On 12 February 2023, a manual export of the complete metadata for each original publication and review article was performed. CiteSpace was used to reveal co-authorship, publication, and co-citation patterns to find prominent authors, organizations, countries, and journals in FD research as well as to identify author keywords with strong citation bursts, which could indicate an emerging research area. VOSviewer was used to build the co-occurrence indicator (co-word) to identify the main author keywords on which previous studies focused and to induce clustered scientific landscape for two consecutive periods to identify intriguing areas for future research.

Results

A search of the database retrieved 2,957 documents. There was a wave-like pattern in the number of publications until 2017, after which there was a spike in publication volume. The USA, China, and Japan provided the majority of contributions. In terms of institution, Mayo Clin, Univ Newcastle, and Katholieke Univ Leuven were found to be the prolific institutions. Additionally, the results indicate that eastern Asian researchers contributed significantly to the global knowledge of literature that led other countries; however, Canada, the USA, Australia, England, and Germany were found to have the highest degree of betweenness centrality. Nicholas J. Talley, Jan Tack, Gerald Holtmann, Michael Camilleri, Ken Haruma, and Paul Moayyedi occupied the top positions based on productivity and centrality indicators. Six thematic clusters emerged (Helicobacter pylori infection; pathophysiological mechanisms of FD; extraintestinal co-morbidities and overlap syndromes associated with FD; herbal medicine in FD; diabetic gastroparesis; and dietary factors in FD). “Acupuncture,” “duodenal eosinophilia,” “gut microbiota,” and others were among the author keywords with rising prevalence.

Conclusion

In FD research, eastern Asian countries have established themselves as major contributors with the highest publishing productivity; however, research has primarily been driven by North America, Europe, and Australia, where cooperation is generally more active and highly influential scientific results are produced. Our analysis suggests that increased investments, training of human resources, improved infrastructures, and expanded collaborations are essential to improving the quality of FD research in Asia. The emerging author keyword analysis suggests that eosinophil-mast cell axis, gut microbiota, mental disorders, and acupuncture are the key areas that attract researchers’ attention as future research boulevards. There is a highly skewed distribution of research output across Asia, with most focus on complementary and alternative medicine (CAM) coming from Chinese, Japanese, and South Korean centers. However, CAM remains an underexplored area of research in the context of FD, and it deserves greater research efforts in order to obtain quality scientific evidence. Furthermore, we propose that the research framework of CAM should not be limited to dysmotility; rather, it could be interpreted within a more holistic context that includes the brain-gut-microbiota axis, as well as novel concepts such as duodenitis, increased mucosal permeability, and infiltration and activation of eosinophils and mast cells, among others. Overall, we provided bibliometrics-based overviews of relevant literature to researchers from different backgrounds and healthcare professionals to provide an in-depth overview of major trends in FD research.

Brain-gut axis and psychiatric disorders: A perspective from bibliometric and visual analysis

BACKGROUND

The Brain-Gut Axis, a bidirectional signaling pathway that connects the intestinal and central nervous systems, plays an important role in the development of psychiatric disorders. However, the overall research trends in this field are unclear. This study explored the patterns of research on the brain-gut axis and psychiatric disorders from a bibliometric perspective.

METHODS

Relevant data were retrieved from the Web of Science Core Collection, with search terms on psychiatric disorders and the brain-gut axis. R (version 4.2.0), VOSviewer (version 1.6.17), CiteSpace software, and the online bibliometric platform were used in the data analysis.

RESULTS

A total of 2,298 articles published between 1993 and 2022 were identified, showing an increasing trend over time. China (1,859; 20.70%) was the country that contributed the most publications. The journal Nutrients (95; 4.13%) published the most publications. Cryan JF (153; H-index=73) and University College Cork (559; 22.54%) were the most influential author and the most productive institution, respectively. The high-frequency keywords were clustered into six themes, including neurodegenerative diseases, stress-related diseases, immune, brain behavior, depression, and probiotic-related topics; of which, depression (880; 2019), anxiety (207; 2018) and autism (191; 2019) were the most studied psychiatric disorders in the past 5 years. "Depressive symptom" (2019-2020) and "probiotic treatment" (2019-2020) were the main areas addressed in recent years.

CONCLUSION

Research on the brain-gut axis and psychiatric disorders has attracted increasing attention in the past decade, with most publications originating from high-income level countries. This study provides a useful perspective on understanding the research trends, key hot topics, and research gaps in this expanding field.

Current global research landscape on COVID-19 and cancer: Bibliometric and visualization analysis

BACKGROUND

Cancer is a severe public health issue that seriously jeopardizes global health. In individuals with coronavirus disease 2019 (COVID-19), cancer is considered an independent risk factor for severe illness and increased mortality.

AIM

To identify research hotspots and prospects, we used bibliometrics to examine the global production of COVID-19 literature published in the field of oncology.

METHODS

Data on publication output were identified based on the Scopus database between January 1, 2020, and June 21, 2022. This study used VOSviewer to analyze collaboration networks among countries and assess the terms most often used in the titles and abstracts of retrieved publications to determine research hotspots linked to cancer and COVID-19. The Impact Index Per Article for the top 10 high-cited papers collected from Reference Citation Analysis (RCA) are presented.

RESULTS

A total of 7015 publications were retrieved from the database. The United States published the greatest number of articles (2025; 28.87%), followed by Italy (964; 13.74%), the United Kingdom (839; 11.96%), and China (538; 7.67%). The University of Texas MD Anderson Cancer Center (n = 205, 2.92%) ranked first, followed by the Memorial Sloan-Kettering Cancer Center (n = 176, 2.51%). The European Journal of Cancer (n = 106, 1.51%) ranked first, followed by the Frontiers in Oncology (n = 104, 1.48%), Cancers (n = 102, 1.45%), and Pediatric Blood and Cancer (n = 95; 1.35%). The hot topics were stratified into “cancer care management during the COVID-19 pandemic”; and “COVID-19 vaccines in cancer patients”.

CONCLUSION

This is the first bibliometric analysis to determine the present state and upcoming hot themes related to cancer and COVID-19 and vice versa using VOSviewer during the early stages of the pandemic. The emergence of hot themes related to cancer and COVID-19 may aid researchers in identifying new research areas in this field.

Global research trends on the links between the gut microbiota and diabetes between 2001 and 2021: A bibliometrics and visualized study

Background

Over the past 20 years, evidence has suggested that gut microbiota plays an important role in metabolic homeostasis. The relationship between gut microbiota and diabetes has become the focus of considerable scientific interest. With the sharp increase in publications in this area, it is imperative to analyze the relevant articles using bibliometrics methods.

Methods

Publications on “the gut microbiota and diabetes” were retrieved and downloaded from the Web of Science Core Collection database. Microsoft Excel 2020, VOSviewer, CiteSpace 5.8.R3 and Co-Occurrence 9.94 software were used for data analysis and visualization. Country/academic institution, journal, author, subject category, keyword and reference were analyzed thoroughly. The cutting-edge directions in this field were also determined by analyzing keywords and key articles.

Results

A total of 2,342 documents were included in the analysis; the number of articles in this field has increased yearly, particularly after 2010. China and the University of Copenhagen are the country and research institution associated with the largest number of publications. Nutrients have published 191 articles in this field, ranking first among highly productive journals in the number of publications. The researcher Cani PD affiliated with the University of Leuven, Belgium, published the greatest number of articles in this field between 2001 and 2021 and was also ranked as the first co-cited author and the largest contributor of highly cited papers in this field. Endocrinology &amp; Metabolism was the most common subject category. Three of the most frequently found keywords, besides terms related to “microbiota” and “diabetes,” were “obesity,” “probiotics,” and “inflammation.” Akkermansia muciniphila, Faecalibacterium prausnitzii, trimethylamine n-oxide and branched-chain amino acids are intestinal bacteria or metabolites that have attracted more attention in recent years. Natural products represented by Chinese herbal medicine and some protein receptors or signaling pathways such as aryl hydrocarbon receptor, farnesoid X receptor and AMP-activated protein kinase were frontiers in this field.

Conclusion

Over the past two decades, the rapid development of research on the gut microbiota has deepened the understanding of the physiology and pathology of diabetes, providing new insights into different approaches to treatment. In the future, further interdisciplinary innovation, clinical transformation, and application may receive more attention.

Global trends in research on irritable bowel syndrome and the brain–gut axis: Bibliometrics and visualization analysis

Irritable bowel syndrome (IBS) is a gastrointestinal disorder with no structural damage, and its pathogenesis remains unclear. Studies have shown that the brain–gut axis is closely related to the occurrence of IBS. However, studies of IBS related to the brain–gut axis have not been systematically analyzed by bibliometrics and visual analysis. This study is based on 631 publications in the Web of Science Core Collection (WoSCC) to analyze hot spots and trends in this field. The collaborations between different authors, institutions, countries, and keywords were bibliometrically analyzed by CiteSpace software. Meanwhile, VOSviewer analyzed the references. The results show that since 2012, the number of publications has been growing rapidly. According to the collaborative network analysis, the United States, the National University of Ireland, Cork, and J.F. Cryan are the countries, institutions, and authors contributing the most, respectively. Through keywords and literature analysis, mechanisms and therapy associated with IBS and the brain–gut axis have still been a research focus in recent years. Furthermore, the physiological and pathological mechanisms of the brain–gut axis influencing IBS (related to gastrointestinal dysfunction, vagus nerve, visceral pain, intestinal flora, serotonin, tryptophan metabolism, stress, brain-derived neurotrophic factor (BDNF), and malonyldialdehyde) are the future research trends, especially the mechanisms related to intestinal flora. This is the first bibliometric and visualization analysis of IBS and brain–gut axis-related literature to explore research hotspots and trends.

Global research trends in extracellular vesicles based on stem cells from 1991 to 2021: A bibliometric and visualized study

Objective: With the development of extracellular vesicles (EVs) based on stem cells research all over the world, our present study was aiming to discover the global trends in this field.

Methods: All publications related to EVs based on stem cells from 1991 to 2021 were collected from the Science Citation Index-Expanded of Web of Science Subsequently, the data were evaluated using the bibliometric methodology. In terms of visualized study, the VOS viewer software was performed to investigate the bibliographic coupling, co-citation, co-authorship, and co-occurrence trends, and last for the publication’s trends involved in the field of EVs based on stem cells.

Results: A total of 8,208 publications were retrieved and the relative number of global publications and research interests were increasing every year especially in recent 5 years. China rank top one in terms of total publications, prolific authors, and funds, whereas the USA made the greatest contributions with the most total citations and highest H-index to the global research. Stem cell research therapy contributed the highest publications, whereas the journal of PLOS ONE showed the best total link strength. The Shanghai Jiao Tong University, University of California System, and Harvard University were the most contributive institutions. The global studies could be divided into six clusters as follows: cancer research, musculoskeletal system research, respiratory system research, urinary system and endocrine system research, nerve system research, and cardiovascular system research. All the directions were predicted to still hotspots in near future researches in this field.

Conclusion: The total number of publications about EVs based stem cells would be increasing according to the current global trends. China and the USA was the largest contributors in this field. Further efforts should be put in the directions of cancer research, musculoskeletal system research, respiratory system research, urinary system and endocrine system research, nerve system research, as well was cardiovascular system research in this field of EVs based stem cells.

Global research on Clostridium difficile-associated diarrhoea: A visualized study

BACKGROUND

Clostridioides (Clostridium) difficile (C. difficile) is still the most common cause of healthcare-associated diarrhoea and is increasing in prevalence as a community-acquired infection. In addition, the emergence of antibiotic resistance in C. difficile can increase the likelihood of the disease developing and/or spreading.

AIM

To provide an up-to-date picture of the trends in publications related to C. difficile infection, together with specific insights into hot-button issues in this field.

METHODS

Publications on C. difficile infections in the field of microbiology between 2001 and 2020 were identified from the Scopus database and Reference Citation Analysis. Bibliometric indicators were determined, including the number and type of publications, countries, affiliations, funding agencies, journals and citation patterns. VOSviewer was used to determine research areas and hot-button issues by identifying recurring terms with a high relative occurrence in the title and abstract.

RESULTS

A total of 8127 documents on ‘C. difficile-associated diarrhoea’ published between 2001 and 2020 were retrieved from the Scopus database. In the last decade, there has been a significant almost fourfold increase in the number of published papers on this topic. The United States was among the countries (44.11%) with the most publications, and the most involved institution was the University of Leeds in the United Kingdom (2.50%). Three clusters of research were identified and included ‘illness spectrum and severity, as well as the signs, symptoms and clinical pathogenesis of C. difficile’; ‘laboratory diagnosis and characterization of C. difficile’ and ‘risk factors for C. difficile infection’.

CONCLUSION

This study contains the most up-to-date and comprehensive data ever compiled in this field. More international research and cross-institutional collaborations are needed to address more global C. difficile concerns and to benefit from greater sharing of expertise, which will result in higher quality or more effective studies in the future. Promising research avenues in the near future may draw the attention of relevant scientists and funding organizations and open up novel C. difficile infection–based diagnosis and treatment approaches.

A Bibliometric Analysis of Research on the Links Between Gut Microbiota and Atherosclerosis

Background

Emerging evidence has linked gut microbiota (GM) and its related metabolites to atherosclerosis (AS). This study aimed to analyze the evolution of GM in AS in the past decades, and provide valuable insights in this field.

Methods

Web of Science Core Collection (WoSCC) was applied to retrieve the publications related to GM in AS from their inception until 2 December 2021, and the data was analyzed in Microsoft Excel, Scimago Graphica, CiteSpace, and VOSviewer.

Results

In total, 560 documents were extracted from the WoSCC databases. The publications have shown rapid growth since 2008. China and Cleveland Clin were the most prolific country and institution, respectively. The journal with the most publications is Nutrients, and Nature was the most co-cited journal. Among 3556 related authors, Hazen, Stanley L., Tang, W. H. Wilson, and Wang, Zeneng were the top 3 contributing authors in this field. Aside from “gut microbiota,” “atherosclerosis,” the terms “TMAO,” “metabolite,” “obesity,” and “phosphatidylcholine” were frequently occurred in the abstract and title of articles. Burst detection of keywords indicated that “metabolic syndrome,” “acid,” and “bile acid” were hot topics in recent years. According to the co-citation analysis of references, the research focus in this area has changed over time, and recent researches focus on choline, hypertension, butyrate, and berberine.

Conclusion

Our study showed that the researches of GM in AS have been flourishing, and the content themes were constantly deepened. Human GM is critical to atherosclerotic diseases, and this hot topic is still worthy of more focus in the future.

A 10-Year Bibliometric Analysis of Global Research on Gut Microbiota and Parkinson's Disease: Characteristics, Impact, and Trends

Objective

To perform a bibliometric analysis of scientific production related to gut microbiota and Parkinson's disease between 2011 and 2020.

Methods

A descriptive, retrospective, cross-sectional, and bibliometric study was carried out. The Scopus database was used as a source to evaluate the worldwide scientific production on intestinal microbiota and its relationship with Parkinson's disease. Data were extracted from Scopus using a formula developed with thesaurus terms MeSH (Medline) and Emtree (Embase).

Results

A total of 591 documents were found. The retrieved manuscripts received an average of 41.9 citations per document. Four of the 10 most productive authors were Italian. The University of Helsinki (Finland) was the institution with the highest scientific production (19 papers) and the highest impact (5921 citations). In terms of productivity and impact, Movement Disorders ranked first with 38 papers and 2782 citations, and those papers published in Q1 quartile journals exceeded the sum of the remaining quartiles. Papers with international collaboration were the most cited. Keyword analysis showed that the terms Parkinson Disease, Disease, and Intestine Flora were the most frequent.

Conclusion

The number of papers on Parkinson's disease and gut microbiota has been increasing; however, high-quality journals maintain the same high publication rate. International collaboration from high-income countries played an important role in the impact generated by the publications.

The Efficacy of S-Adenosyl Methionine and Probiotic Supplementation on Depression: A Synergistic Approach

Depression is a common and serious health issue affecting around 280 million people around the world. Suicidal ideation more frequently occurs in people with moderate to severe depression. Psychotherapy and pharmacological drugs are the mainstay of available treatment options for depressive disorders. However, pharmacological options do not offer complete cure, especially in moderate to severe depression, and are often seen with a range of adverse events. S-adenosyl methionine (SAMe) supplementation has been widely studied, and an impressive collection of literature published over the last few decades suggests its antidepressant efficacy. Probiotics have gained significant attention due to their wide array of clinical uses, and multiple studies have explored the link between probiotic species and mood disorders. Gut dysbiosis is one of the risk factors in depression by inducing systemic inflammation accompanied by an imbalance in neurotransmitter production. Thus, concomitant administration of probiotics may be an effective treatment strategy in patients with depressed mood, particularly in resistant cases, as these can aid in dysbiosis, possibly resulting in the attenuation of systemic inflammatory processes and the improvement of the therapeutic efficacy of SAMe. The current review highlights the therapeutic roles of SAMe and probiotics in depression, their mechanistic targets, and their possible synergistic effects and may help in the development of food supplements consisting of a combination of SAMe and probiotics with new dosage forms that may improve their bioavailability.

Knowledge Mapping of the Links Between the Gut Microbiota and Heart Failure: A Scientometric Investigation (2006–2021)

Background

There is considerable research value and extensive application perspectives to explore the link between gut microbiota and heart failure. The purpose of this study is to provide an overview of overall characteristics, evolutionary pathways, frontier research hotspots, and future trends in this field.

Methods

Research datasets were acquired from the Web of Science Core Collection (WoSCC) between January 1, 2006 and December 31, 2021. Three different analysis tools including one online platform, VOS viewer V1.6.17.0, and CiteSpace V5.8.R2 software were used in order to conduct collaboration network analysis, co-cited analysis, co-occurring analysis, and citation burst detection.

Results

A total of 873 publications in the WoSCC database met the requirement. The overall characteristics analysis showed that a steady growth trend in the number of publications and citations, with the predominant literature type being articles and the most frequent subject category being cardiac cardiovascular systems. The United States was the most prolific country and the center of national collaboration. Cleveland Clinic and Nathalie M. Delzenne provided the leading influence with publications, the cooperation between the institutes and authors were relatively weak. Moreover, gut microbiota, heart failure, risk factor, obesity, and inflammation were the keywords that appeared more frequently in the clustering analysis of reference co-citation and keyword co-occurrence. Burst detection analysis of top keywords showed that trimethylamine N-oxide (TMAO), bile acid, blood pressure, hypertension, and fermentation were the new research foci on the association between gut microbiota and heart failure. Strategies to improve gut microbiota hold promise as a new approach to treat heart failure.

Conclusion

The comprehensive bibliometric study indicates that the structured information may be helpful in understanding research trends in the link between gut microbiota and heart failure, and locating research hotspots and gaps in this domain, especially further advances in this field will lead to significant breakthroughs in the development of novel therapeutic tools for metabolic modulation of heart failure.

Global research trends on the links between the gut microbiome and cancer: a visualization analysis

BACKGROUND

Significant links between the microbiota and human health have emerged in the last 20 years. A correlation has recently been demonstrated between changes in the gut microbiota and the development of cancer. This study aimed to use bibliometric analysis of the published gut microbiome and cancer literature to present the research status and summarize the hotspots for frontier studies.

METHODS

A literature search for research on the gut microbiome and cancer research from 2001 to 2020 was conducted using the Scopus database on 20 March 2021. VOSviewer software (version 1.6.16) was used to perform the visualization analysis.

RESULTS

From 2001 to 2020, a total of 2061 publications were retrieved. Annual publication output grew from 10 in 2001 to 486 in 2020. The USA had the largest number of publications, making the largest contribution to the field (n  = 566, 27.46%). Before 2016, most studies focused on the 'effect of probiotics on cancer'. The latest trends showed that 'microbiota composition and gene expression' and 'host-microbiome interaction in cancer immunotherapy' would be more concerned more widely in the future.

CONCLUSIONS

Research on 'microbiota composition and gene expression' and 'host-microbiome interaction in cancer immunotherapy' will continue to be the hotspot. Therefore, this study provides the trend and characteristics of the literature on the gut microbiota and cancer literature, which provided a useful bibliometric analysis for researchers to conduct further research.

Global Research Trends on the Use of Nanotechnology to Boost Meat Production: A Scientometric Analysis

Meat production plays a vital socioeconomic role for sustainable development and for promoting food security in most countries. However, not much is known about research agendas done globally and the advancement of knowledge-generating networks in this area of study. The present study aims to reveal and analyze scientific research outputs on meat production linked with recent nanotechnology research work done till date. A compilation of research advancement and development within the sphere was realized through a scientometric study to comprehend the trend of research outputs, scientific impacts, authors' involvement, collaboration networks, and the advancement of knowledge gaps for future research endeavors on the current subject matter. Scholarly published articles were retrieved from the web of science (WOS) and Scopus databases from 1985 to 2020 and they were merged together using bibliometric package in R studio. All duplicated articles (438) from both data bases were excluded. A combination of terms (nano* AND (livestock* OR meat* OR beef* OR mutton* OR pork* OR chevon* OR chicken* OR turkey*)), and conversely analyzed for scientometric indices. A collection of 656 peer-reviewed, research articles were retrieved for the study period and authored by 2,133 researchers with a collaboration index of 3.31. The research outputs were highest in the year 2020 with total research outputs of 140 articles. The topmost three authors' keywords commonly used by authors were nanoparticles, meat, and chitosan with a respective frequency of 75, 62, and 57. China, Iran, and India ranked top in terms of meat production research outputs linked to nanotechnology and total citation with respective article productivity (total citations) of 160 (3,193), 111 (1,765), and 37 (552). Our findings revealed an increasing trend in research (with an annual growth rate of 25.18%) tending toward advancing meat production with the use of nanotechnology. Likewise, there is an increasing pointer to the fact that research work on nanotechnology and meat production has the prospect to influence positively, decision-making on research direction, and collaborations, hereby increasing the production of meat and its products in the future.

Comprehensive Bibliometric Analysis of the Kynurenine Pathway in Mood Disorders: Focus on Gut Microbiota Research

Background: Emerging evidence implicates the dysregulated kynurenine pathway (KP), an immune-inflammatory pathway, in the pathophysiology of mood disorders (MD), including depression and bipolar disorder characterized by a low-grade chronic pro-inflammatory state. The metabolites of the KP, an important part of the microbiota-gut-brain axis, serve as immune system modulators linking the gut microbiota (GM) with the host central nervous system.

Aim: This bibliometric analysis aimed to provide a first glimpse into the KP in MD, with a focus on GM research in this field, to guide future research and promote the development of this field.

Methods: Publications relating to the KP in MD between the years 2000 and 2020 were retrieved from the Scopus and Web of Science Core Collection (WoSCC), and analyzed in CiteSpace (5.7 R5W), biblioshiny (using R-Studio), and VOSviewer (1.6.16).

Results: In total, 1,064 and 948 documents were extracted from the Scopus and WoSCC databases, respectively. The publications have shown rapid growth since 2006, partly owing to the largest research hotspot appearing since then, “quinolinic acid.” All the top five most relevant journals were in the neuropsychiatry field, such as Brain Behavior and Immunity. The United States and Innsbruck Medical University were the most influential country and institute, respectively. Journal co-citation analysis showed a strong tendency toward co-citation of research in the psychiatry field. Reference co-citation analysis revealed that the top four most important research focuses were “kynurenine pathway,” “psychoneuroimmunology,” “indoleamine 2,3-dioxygenase,” and “proinflammatory cytokines,” and the most recent focus was “gut-brain axis,” thus indicating the role of the KP in bridging the GM and the host immune system, and together reflecting the field’s research foundations. Overlap analysis between the thematic map of keywords and the keyword burst analysis revealed that the topics “Alzheimer’s disease,” “prefrontal cortex,” and “acid,” were research frontiers.

Conclusion: This comprehensive bibliometric study provides an updated perspective on research associated with the KP in MD, with a focus on the current status of GM research in this field. This perspective may benefit researchers in choosing suitable journals and collaborators, and aid in the further understanding of the field’s hotspots and frontiers, thus facilitating future research.

Global research trends in the microbiome related to irritable bowel syndrome: A bibliometric and visualized study

BACKGROUND

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder. Dysregulation of the gut–brain axis plays a central role in the pathophysiology of IBS. It is increasingly clear that the microbiome plays a key role in the development and normal functioning of the gut–brain axis.

AIM

To facilitate the identification of specific areas of focus that may be of relevance to future research. This study represents a bibliometric analysis of the literature pertaining to the microbiome in IBS to understand the development of this field.

METHODS

The data used in our bibliometric analysis were retrieved from the Scopus database. The terms related to IBS and microbiome were searched in titles or abstracts within the period of 2000–2019. VOSviewer software was used for data visualization.

RESULTS

A total of 13055 documents related to IBS were retrieved at the global level. There were 1872 scientific publications focused on the microbiome in IBS. There was a strong positive correlation between publication productivity related to IBS in all fields and productivity related to the microbiome in IBS (r = 0.951, P < 0.001). The United States was the most prolific country with 449 (24%) publications, followed by the United Kingdom (n = 176, 9.4%), China (n = 154, 8.2%), and Italy (n = 151, 8.1%). The h-index for all retrieved publications related to the microbiome in IBS was 138. The hot topics were stratified into four clusters: (1) The gut–brain axis related to IBS; (2) Clinical trials related to IBS and the microbiome; (3) Drug-mediated manipulation of the gut microbiome; and (4) The role of the altered composition of intestinal microbiota in IBS prevention.

CONCLUSION

This is the first study to evaluate and quantify global research productivity pertaining to the microbiome in IBS. The number of publications regarding the gut microbiota in IBS has continuously grown since 2013. This finding suggests that the future outlook for interventions targeting the gut microbiota in IBS remains promising.

COVID-19 vaccine research focusses on safety, efficacy, immunoinformatics, and vaccine production and delivery: a bibliometric analysis based on VOSviewer

Coronavirus Disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has affected tens of millions of people globally since it was declared a pandemic by the World Health Organization (WHO) on March 11, 2020. There is an urgent need for safe and effective preventive vaccines to curb this pandemic. A growing amount of related research has been published. This study aimed to provide the current status of COVID-19 vaccine using bibliometric analysis. We searched Embase.com and MEDLINE comprehensively and included articles, articles in press, reviews, short surveys, conference abstracts and conference papers about COVID-19 vaccine. VOSviewer1.6.11 (Leiden University, Leiden, Netherlands) was applied to perform the bibliometric analysis of these papers. A total of 1,312 papers were finally included. The BMJ has been the most popular journal in this field. The United States maintained a top position worldwide and has provided a pivotal influence, followed by China, India and United Kingdom. Among all the institutions, Harvard University was regarded as a leader for research collaboration. We analyzed the keywords and identified seven COVID-19 vaccine research hotspot clusters. COVID-19 vaccine research hotspots focus on clinical trials on vaccine safety and efficacy, research on vaccine immunology and immunoinformatics, and vaccine hesitancy. Our analysis results demonstrated that cooperation between countries, institutions, and authors were insufficient. The results suggested that clinical trials on vaccine safety, efficacy, immunology, immunoinformatics, production and delivery are research hotspots. Furthermore, we can predict that there will be a lot of research focusing on vaccine adverse reactions.

Neurodevelopmental Outcomes and Gut Bifidobacteria in Term Infants Fed an Infant Formula Containing High sn-2 Palmitate: A Cluster Randomized Clinical Trial

A few studies suggested high stereo-specifically numbered (sn)-2 palmitate in a formula might favor the gut Bifidobacteria of infants. The initial colonization and subsequent development of gut microbiota in early life might be associated with development and later life functions of the central nervous system via the microbiota–gut–brain axis, such as children with autism. This study aims to assess the hypothesized effect of increasing the amount of palmitic acid esterified in the sn-2 position in infant formula on neurodevelopment in healthy full-term infants and to explore the association of this effect with the altered gut Bifidobacteria. One hundred and ninety-nine infants were enrolled in this cluster randomized clinical trial: 66 breast-fed (BF group) and 133 formula-fed infants who were clustered and randomly assigned to receive formula containing high sn-2 palmitate (sn-2 group, n = 66) or low sn-2 palmitate (control group, n = 67), where 46.3% and 10.3% of the palmitic acid (PA) was sn-2-palmitate, respectively. Infants’ neurodevelopmental outcomes were measured by the Ages and Stages Questionnaire, third edition (ASQ-3). Stool samples were collected for the analysis of Bifidobacteria (Trial registration number: ChiCTR1800014479). At week 16, the risk of scoring close to the threshold for fine motor skills (reference: scoring above the typical development threshold) was significantly lower in the sn-2 group than the control group after adjustment for the maternal education level (p = 0.036) but did not differ significantly versus the BF group (p = 0.513). At week 16 and week 24, the sn-2 group (week 16: 15.7% and week 24: 15.6%) had a significantly higher relative abundance of fecal Bifidobacteria than the control group (week 16: 6.6%, p = 0.001 and week 24:11.2%, p = 0.028) and did not differ from the BF group (week 16: 14.4%, p = 0.674 and week 24: 14.9%, p = 0.749). At week 16, a higher relative abundance of Bifidobacteria was associated with the decreased odds of only one domain scoring close to the threshold in the formula-fed infants group (odds ratio (OR), 95% confidence interval (CI): 0.947 (0.901–0.996)). Elevating the sn-2 palmitate level in the formula improved infants’ development of fine motor skills, and the beneficial effects of high sn-2 palmitate on infant neurodevelopment was associated with the increased gut Bifidobacteria level.

COVID-19 research progress: Bibliometrics and visualization analysis

Background: Coronavirus primarily targets the human respiratory system, COVID-19 (Coronavirus disease 2019) triggered in China in the late 2019. In March 2020, WHO announced the COVID-19 pandemic. This study aims to analyze and visualize the scientific structure of the COVID-19 publications using co-citation and co-authorship. Methods: This is a scientometric study. Web of Science Core Collection (WoSCC) was searched for all documents regarding COVID-19, MERS-Cov, and SARS-Cov from the beginning to 2020. An Excel spreadsheet was applied to gather and analyze the data and the CiteSpace was used to visualize and analyze the data. Results: A total of 5159 records were retrieved in WoSCC. The structure of the network indicated that the network mean silhouette was low (0.1444), implying that the network clusters' identity is not identifiable with high confidence. The network modularity was 0.7309. The cluster analysis of the co-citation network on documents from 2003 to 2020 provided 188 clusters. The largest cluster entitled, "the Middle East respiratory syndrome coronavirus" had 255 nodes. The coauthorship network illustrated that the most prolific countries, USA, China, and Saudi Arabia, have focused on a specific field and have formed separate clusters. Conclusion: The present study identified the important topics of research in the field of COVID-19 based on co-citation networks as well as the analysis of clusters of countries' collaborations. Despite the similarities in the production behavior in prolific countries, their thematic focus varies so that a country like China plays a role in "Quantitative Detection" cluster, while USA is the leading country in the "Biological Evaluation" cluster.

Mapping research trends in diabetic retinopathy from 2010 to 2019: A bibliometric analysis

Background:

Although many publications in diabetic retinopathy (DR) have been reported, there is no bibliometric analysis.

Purpose:

To perform a bibliometric analysis in the field of diabetic retinopathy (DR) research, to characterize the current international status of DR research, to identify the most effective factors involved in this field, and to explore research hotspots in DR research.

Methods:

Based on the Web of Science Core Collection (WoSCC), a bibliometric analysis was conducted to investigate the publication trends in research related to DR. Knowledge maps were constructed by VOSviewer v.1.6.10 to visualize the publications, the distribution of countries, international collaborations, author productivity, source journals, cited references and keywords, and research hotspots in this field.

Results:

In total, 11,839 peer-reviewed papers were retrieved on DR from 2010 to 2019, and the annual research output increased with time. The United States ranks highest among countries with the most publications. The most active institution is the University of Melbourne. Wong, TY contributed the largest number of publications in this field. Investigative Ophthalmology & Visual Science was the most prolific journal in DR research. The top-cited references mainly investigated the use of anti-vascular endothelial growth factor (VEGF) medications in the management of DR, and the keywords formed 6 clusters:

Discussion:

With the improvement of living standard, DR has gradually become one of the important causes of blindness, and has become a hot spot of public health research in many countries. The application of deep learning and artificial intelligence in diabetes screening and anti-VEGF medications in the management of DR have been the research hotspots in recent 10 years.

Conclusions:

Based on data extracted from the WoSCC, this study provides a broad view of the current status and trends in DR research and may provide clinicians and researchers with insight into DR research and valuable information to identify potential collaborators and partner institutions and better predict their dynamic directions.

The global state of research in pain management of osteoarthritis (2000-2019): A 20-year visualized analysis

There has been a highly active area in the pain management of osteoarthritis (OA) over the past 2 decades. The study aims to unmask the global status and trends in this field.Publications on pain management of OA from 2000 to 2019 were retrieved from the Web of Science (WOS) database. The data were analyzed using bibliometric statistical methodology. The software VOS viewer was used for bibliographic coupling, co-authorship, co-citation, co-occurrence analysis and to investigate the publication trends in pain management of OA.A total of 8207 researches in amount were included. The relative research interests and number of publications indicated a rising trend. The USA made the greatest contribution to this field, with the most publications, total citations and the highest H-index, while Sweden had the highest average citation per publication. The most contributive organization was Boston University. The journal OA and Cartilage published the most relative articles. Researches could be grouped into 5 clusters based on co-occurrence network map: Health and Epidemiology; Sport Medicine; Clinical Study; Mechanism Research and Medical Technology and Science. Medical Technology and Science was predicted as the next research topic in this field.The number of publications about pain management of OA would be increasing based on current global trends. The USA made the largest contribution to this field. The development of Medical Technology and Science may be the next popular topics in the pain management of OA research.

Vaccination and Immunotherapy for Major Depression

Depression is a very common disease with increasing incidence resulting from complex interactions of genetic, environmental, and immunological processes. To this day, the etiopathogenesis and treatment of depression unfortunately seem to be stuck in the synaptic gap. Despite highly potent antidepressants, the treatment rate cannot reach 100%, the treatment resistant group cannot be eliminated, and relapse cannot be prevented. These problems lead researchers to further and different research to understand and treat psychopathology. Immune dysfunction and neuroinflammation have been one of the main issues that psychiatry has focused on in recent years and helps us to understand depression. Extraneuronal components of all neuropsychiatric disorders, especially depression, have begun to be revealed in detail thanks to a better understanding of the immune system and an increase in experimental and technological possibilities. There is increasing evidence of a causal relationship between the etiopathogenesis of major depression and low-level chronic neuroinflammation. In this article, the role of neuroinflammation in the etiopathogenesis of depression and the possibilities of vaccination and immunotherapy are discussed.

Exposure to greenspaces could reduce the high global burden of pain

Painful conditions are among the leading causes of years lived with disability, and may increase following the coronavirus pandemic, which has led to temporary closure of some healthcare services for people with chronic pain. To reduce this burden, novel, cost-effective and accessible interventions are required. We propose that greenspace exposure may be one such intervention. Drawing on evidence from neuroscience, physiology, microbiology, and psychology, we articulate how and why exposure to greenspaces could improve pain outcomes and reduce the high global burden of pain. Greenspace exposure potentially provides opportunities to benefit from known or proposed health-enhancing components of nature, such as environmental microbiomes, phytoncides, negative air ions, sunlight, and the sights and sounds of nature itself. We review the established and potential links between these specific exposures and pain outcomes. While further research is required to determine possible causal links between greenspace exposure and pain outcomes, we suggest that there is already sufficient evidence to help reduce the global burden of pain by improving access and exposure to quality greenspaces.

Mapping the situation of research on coronavirus disease-19 (COVID-19): a preliminary bibliometric analysis during the early stage of the outbreak

BACKGROUND

The novel coronavirus, named as 2019-nCoV or coronavirus disease 2019 (COVID-19), has recently appeared in China and has spread worldwide, presenting a health threat to the global community. Therefore, it is important to understand the global scientific output of COVID-19 research during the early stage of the outbreak. Thus, to track the current hotspots, and highlight future directions, we performed a bibliometric analysis to obtain an approximate scenario of COVID-19 to date.

METHODS

Relevant studies to COVID-19 were obtained from the Scopus database during the early stage of the outbreak. We then analysed the data by using well-established bibliometric indices: document type, country, collaboration patterns, affiliation, journal name, and citation patterns. VOSviewer was applied to map and determine hot topics in this field.

RESULTS

The bibliometric analysis indicated that there were 19,044 publications on Scopus published on COVID-19 during the early stage of the outbreak (December 2019 up until June 19, 2020). Of all these publications, 9140 (48.0%) were articles; 4192 (22.0%) were letters; 1797 (9.4%) were reviews; 1754 (9.2%) were editorials; 1728 (9.1%) were notes; and 433 (2.3%) were others. The USA published the largest number of publications on COVID-19 (4479; 23.4%), followed by China (3310; 17.4%), Italy, (2314; 12.2%), and the UK (1981; 10.4%). British Medical Journal was the most productive. The Huazhong University of Science and Technology, Tongji Medical, and Harvard Medical School were the institutions that published the largest number of COVID-19 research. The most prevalent topics of research in COVID-19 include "clinical features studies", "pathological findings and therapeutic design", "care facilities preparation and infection control", and "maternal, perinatal and neonatal outcomes".

CONCLUSIONS

This bibliometric study may reflect rapidly emerging topics on COVID-19 research, where substantial research activity has already begun extensively during the early stage of the outbreak. The findings reported here shed new light on the major progress in the near future for hot topics on COVID-19 research including clinical features studies, pathological findings and therapeutic design, care facilities preparation and infection control, and maternal, perinatal and neonatal outcomes.

Role of Gut Microbiota in Neuroendocrine Regulation of Carbohydrate and Lipid Metabolism via the Microbiota-Gut-Brain-Liver Axis

Gut microbiota play an important role in maintaining intestinal health and are involved in the metabolism of carbohydrates, lipids, and amino acids. Recent studies have shown that the central nervous system (CNS) and enteric nervous system (ENS) can interact with gut microbiota to regulate nutrient metabolism. The vagal nerve system communicates between the CNS and ENS to control gastrointestinal tract functions and feeding behavior. Vagal afferent neurons also express receptors for gut peptides that are secreted from enteroendocrine cells (EECs), such as cholecystokinin (CCK), ghrelin, leptin, peptide tyrosine tyrosine (PYY), glucagon-like peptide-1 (GLP-1), and 5-hydroxytryptamine (5-HT; serotonin). Gut microbiota can regulate levels of these gut peptides to influence the vagal afferent pathway and thus regulate intestinal metabolism via the microbiota-gut-brain axis. In addition, bile acids, short-chain fatty acids (SCFAs), trimethylamine-N-oxide (TMAO), and Immunoglobulin A (IgA) can also exert metabolic control through the microbiota-gut-liver axis. This review is mainly focused on the role of gut microbiota in neuroendocrine regulation of nutrient metabolism via the microbiota-gut-brain-liver axis.

Trends in chronic hepatitis B treatment-related research from 1973 to 2018: a bibliometric and visual analysis

OBJECTIVE

Chronic hepatitis B (CHB) is a worldwide disease and the most common cause of liver cancer. This study aimed to identify specific areas of research activity concerning CHB treatment between 1973 and 2018 and to aid in identifying new areas for future development.

METHODS

The literature was searched from the GoPubMed and Web of Science databases using terms related to CHB treatment, analyzed with bibliometric methods and visualized using VOSviewer.

RESULTS

A total of 9486 and 5883 papers were collected from PubMed and Web of science, respectively. The studies focused on two clusters of topics: antiviral therapy for CHB and progressive diseases, and drug resistance. Studies related to antiviral drugs concentrated on lamivudine (n = 788), entecavir (n = 390), and adefovir dipivoxil (n = 376). Studies addressing conditions developing from CHB highlighted hepatocellular carcinoma (n = 403) and cirrhosis (n = 223). China (n = 1978) contributed the most publications. The 10 most quantitatively prolific organizations were in France. All 20 of the most cited papers investigated antiviral treatments for CHB or CHB-associated cirrhosis.

CONCLUSIONS

Research on CHB treatment over the past 45 years has concentrated on antiviral therapy, CHB-associated progressive conditions, drug resistance and immunization. Although work on CHB treatment has made considerable progress, new approaches must be explored.

Bibliometric Analysis of Dendritic Epidermal T Cell (DETC) Research From 1983 to 2019

Dendritic epidermal T cells (DETC) are a group of immune cells expressing canonical γδ TCR in the murine epidermis. Similar to γδ T cells in the human epidermis, DETC serve an important barrier cell in the skin and participate in skin immune surveillance, immune regulation, skin homeostasis, tissue protection, and other activities. Since its discovery in 1983, research on DETC has grown rapidly and unevenly. To evaluate DETC research trends and map the DETC knowledge structure, we have applied bibliometric methods and techniques. A total of 384 DETC-related articles obtained from the Scopus database published between 1983 and 2019 were analyzed using indicators of publication and citation metrics, country and international cooperation, author and co-authorship, and keyword co-occurrence cluster. The present research status, the emerging global trends and the future development direction are also visualized and discussed. In summary, this study provides novel and useful data for the DETC research scientific community, and will help researchers explore DETC more intuitively and effectively.

Bibliometric and Visual Analysis of Research on the Links Between the Gut Microbiota and Depression From 1999 to 2019

Background: There is a crucial link between the gut microbiota and the host central nervous system, and the communication between them occurs via a bidirectional pathway termed the "microbiota-gut-brain axis." The gut microbiome in the modern environment has markedly changed in response to environmental factors. These changes may affect a broad range of host psychiatric disorders, such as depression, by interacting with the host through metabolic, immune, neural, and endocrine pathways. Nevertheless, the general aspects of the links between the gut microbiota and depression have not been systematically investigated through bibliometric analysis. Aim: This study aimed to analyze the current status and developing trends in gut microbiota research in the depression field through bibliometric and visual analysis. Methods: A total of 1,962 publications published between 1999 and 2019 were retrieved from the Web of Science Core Collection. CiteSpace (5.6 R5) was used to perform collaboration network analysis, co-citation analysis, co-occurrence analysis, and citation burst detection. Results: The number of publications has been rapidly growing since 2010. The collaboration network analysis revealed that the USA, University College Cork, and John F. Cryan were the most influential country, institute, and scholar, respectively. The most productive and co-cited journals were Brain Behavior and Immunity and Proceedings of the National Academy of Sciences of the United States of America, respectively. The co-citation analysis of references revealed that the most recent research focus was in the largest theme cluster, "cytokines," thus reflecting the important research foundation in this field. The co-occurrence analysis of keywords revealed that "fecal microbiota" and "microbiome" have become the top two research hotspots since 2013. The citation burst detection for keywords identified several keywords, including "Parkinson's disease," "microbiota-gut-brain axis," "microbiome," "dysbiosis," "bipolar disorder," "impact," "C reactive protein," and "immune system," as new research frontiers, which have currently ongoing bursts. Conclusions: These results provide an instructive perspective on the current research and future directions in the study of the links between the gut microbiota and depression, which may help researchers choose suitable cooperators or journals, and promote their research illustrating the underlying molecular mechanisms of depression, including its etiology, prevention, and treatment.