Gut microbiota: A new target for traditional Chinese medicine in the treatment of depression

Visual analysis of research hotspots and trends in traditional Chinese medicine for depression in the 21st century: A bibliometric study based on citespace and VOSviewer

Background and objectives

Depression long been a key concern for scholars worldwide; however, the field of depression has not received sufficient attention in traditional Chinese medicine. It was not until the 21st century that research into depression gradually entered a period of rapid development, with an increasing number of academic studies published in major journals. However, one limitation of this field is that no scholars have yet summarised the development process and key research issues. Therefore, the present study aimed to summarise the research trends and progress in this field, providing relevant information and presenting potential future research directions for subsequent researchers.

Methods

Literature in this field was searched from January 1, 2000 to April 20, 2024 in the Web of Science Core Collection database, to analyse the current status of the literature and publication trends. Bibliographic information, including study authors, organisations, keywords, countries, references, citations, and co-citations, was extracted using CiteSpace and VOSviewer software for quantitative analysis, visual mapping, and scientific evaluation.

Results

A total of 921 papers were included, with a significant increase in the number of publications from 2017 to 2021, and a stable number of more than 140 publications between 2022 and 2023, with publications in these two years accounting for 31.38 % of the total. The Journal of Ethnopharmacology had the highest number of publications (97) and citations (2067), as well as the highest number of co-citations (1369). China (847 publications, 13256 citations), Beijing University of Chinese Medicine (90 publications, 1232 citations), and Qin Xuemei (30 publications, 759 citations) were the most prolific and influential countries, organisations, and authors in the field, respectively. Keyword clustering co-occurrence analysis revealed nine different clusters with good homogeneity. The top three clusters were randomised controlled trials, traditional Chinese medicine, and hippocampal neurogenesis. In the timeline analysis of keywords, from 2000 to 2010, keywords in this field were concentrated on hippocampal neurology and forced swimming test as clustering axes of Traditional Chinese Medicine. From 2010 to 2020, the research hotspots focused on randomised controlled trials and hippocampal neurogenesis. After 2020, keywords became more focused on network pharmacology. In addition, the occurrence time of explosive keywords were distributed before 2010 and after 2020. Before 2010, these keywords included the forced swimming test, Tail Suspension Test, Chronic Cold Stress, Neural Regeneration, and Banxia Houpu Decoction. Conversely, network Pparmacology and Molecular Docking arose as key buzzwords starting in 2020.

Conclusions

This study comprehensively analysed and summarised the research hotspots and trends in this field of research in the 21st century from a bibliometric perspective, further generating a series of visual graphs to help researchers understand the current research status, potential collaborators, collaborating institutions, and potential future research hotspots in this field.

Ginsenoside Rg1: A Neuroprotective Natural Dammarane-Type Triterpenoid Saponin With Anti-Depressive Properties

BACKGROUND

Depression, a widespread mental disorder, presents significant risks to both physical and mental health due to its high rates of recurrence and suicide. Currently, single-target antidepressants typically alleviate depressive symptoms or delay the progression of depression rather than cure it. Ginsenoside Rg1 is one of the main ginsenosides found in Panax ginseng roots. It improves depressive symptoms through various mechanisms, suggesting its potential as a treatment for depression.

MATERIALS AND METHODS

We evaluated preclinical studies to comprehensively discuss the antidepressant mechanism of ginsenoside Rg1 and review its toxicity and medicinal value. Additionally, pharmacological network and molecular docking analyses were performed to further validate the antidepressant effects of ginsenoside Rg1.

RESULTS

The antidepressant mechanism of ginsenoside Rg1 may involve various pharmacological mechanisms and pathways, such as inhibiting neuroinflammation and over-activation of microglia, preserving nerve synapse structure, promoting neurogenesis, regulating monoamine neurotransmitter levels, inhibiting hyperfunction of the hypothalamic-pituitary-adrenal axis, and combatting antioxidative stress. Moreover, ginsenoside Rg1 preserves astrocyte gap junction function by regulating connexin43 protein biosynthesis and degradation, contributing to its antidepressant effect. Pharmacological network and molecular docking studies identified five targets (AKT1, STAT3, EGFR, PPARG, and HSP90AA1) as potential molecular regulatory sites of ginsenoside Rg1.

CONCLUSIONS

Ginsenoside Rg1 may exert its antidepressant effects via various pharmacological mechanisms. In addition, multicenter clinical case-control and molecular targeted studies are required to confirm both the clinical efficacy of ginsenoside Rg1 and its potential direct targets.

Natural products that alleviate depression: The putative role of autophagy

Major depressive disorder (MDD) is a common mental disorder that severely disrupts psychosocial function and decreases the quality of life. Although the pathophysiological mechanism underlying MDD is complex and remains unclear, emerging evidence suggests that autophagy dysfunction plays a role in MDD occurrence and progression. Natural products serve as a major source of drug discovery and exert tremendous potential in developing antidepressants. Recently published reports are paying more attention on the autophagy regulatory effect of antidepressant natural products. In this review, we comprehensively discuss the abnormal changes occurred in multiple autophagy stages in MDD patients, and animal and cell models of depression. Importantly, we emphasize the regulatory mechanism of antidepressant natural products on disturbed autophagy, including monomeric compounds, bioactive components, crude extracts, and traditional Chinese medicine formulae. Our comprehensive review suggests that enhancing autophagy might be a novel approach for MDD treatment, and natural products restore autophagy homeostasis to facilitate the renovation of mitochondria, impede neuroinflammation, and enhance neuroplasticity, thereby alleviating depression.

Modulatory effects of traditional Chinese medicines on gut microbiota and the microbiota-gut-x axis

The gut microbiota offers numerous benefits to the human body, including the promotion of nutrient absorption, participation in metabolic processes, and enhancement of immune function. Recent studies have introduced the concept of the gut-organ axis, which encompasses interactions such as the gut-brain axis, gut-liver axis, and gut-lung axis. This concept underscores the complex interplay between gut microbiota and various organs and tissues, including the brain, heart, lungs, liver, kidneys, muscles, and bones. Growing evidence indicates that gut microbiota can influence the onset and progression of multi-organ system diseases through their effects on the gut-organ axis. Traditional Chinese medicine has demonstrated significant efficacy in regulating the gastrointestinal system, leveraging its unique advantages. Considerable advancements have been made in understanding the role of gut microbiota and the gut-organ axis within the mechanisms of action of traditional Chinese medicine. This review aims to elucidate the roles of gut microbiota and the gut-organ axis in human health, explore the potential connections between traditional Chinese medicine and gut microbiota, and examine the therapeutic effects of traditional Chinese medicine on the microbiota-gut-organ axis. Furthermore, the review addresses the limitations and challenges present in current research while proposing potential directions for future investigations in this area.

Investigation of the Functional Components in Health Beverages Made from Polygonatum cyrtonema Rhizomes Provides Primary Evidence to Support Their Claimed Health Benefits

This study aims to understand the functional component compositions of traditional herbal health beverages made from Polygonatum cyrtonema rhizomes and to reveal the pharmacodynamic chemical basis for their claimed health benefits. Two traditional methods, rhizome decoction and rhizome infusion, were used to make health herbal beverages, including "Huangjin" tea and "Huangjin" wine, respectively. The secondary metabolites of "Huangjin" beverages were investigated and compared by widely targeted metabolomics. The results clearly showed that the major functional components in "Huangjin" beverages were phenolic acids, flavonoids, and alkaloids. The "Huangjin" wine has a greater variety of flavonoids and alkaloids than "Huangjin" tea, and the functional components in "Huangjin" wine were more abundant than those in "Huangjin" tea. Homoisoflavones and amide alkaloids were the dominating flavonoids and alkaloids in "Huangjin" wine, respectively. Continuous rhizome infusion could not increase the content of functional components in "Huangjin" wine. In conclusion, this study not only provides primary evidence to support the claimed health benefits of "Huangjin" beverages but also suggests that making traditional herbal beverages by rhizome infusion has superior health benefits than making them by rhizome decoction, which is attributed to the higher yields of functional components extracted by Chinese liquor than hot water. Therefore, Chinese liquor shows advantages in its use as a superior binary ethanol-water solvent in making herbal health beverages to enhance the solubility of poorly water-soluble functional components.

Co-decoction of Lilii bulbus and Radix Rehmannia Recens and its key bioactive ingredient verbascoside inhibit neuroinflammation and intestinal permeability associated with chronic stress-induced depression via the gut microbiota-brain axis

BACKGROUND

Gut microbiota plays a critical role in the pathogenesis of depression and are a therapeutic target via maintaining the homeostasis of the host through the gut microbiota-brain axis (GMBA). A co-decoction of Lilii bulbus and Radix Rehmannia Recens (LBRD), in which verbascoside is the key active ingredient, improves brain and gastrointestinal function in patients with depression. However, in depression treatment using verbascoside or LBRD, mechanisms underlying the bidirectional communication between the intestine and brain via the GMBA are still unclear.

PURPOSE

This study aimed to examine the role of verbascoside in alleviating depression via gut-brain bidirectional communication and to study the possible pathways involved in the GMBA.

METHODS

Key molecules and compounds involved in antidepressant action were identified using HPLC and transcriptomic analyses. The antidepressant effects of LBRD and verbascoside were observed in chronic stress induced depression model by behavioural test, neuronal morphology, and synaptic dendrite ultrastructure, and their neuroprotective function was measured in corticosterone (CORT)-stimulated nerve cell injury model. The causal link between the gut microbiota and the LBRD and verbascoside antidepressant efficacy was evaluate via gut microbiota composition analysis and faecal microbiota transplantation (FMT).

RESULTS

LBRD and Verbascoside administration ameliorated depression-like behaviours and synaptic damage by reversing gut microbiota disturbance and inhibiting inflammatory responses as the result of impaired intestinal permeability or blood-brain barrier leakiness. Furthermore, verbascoside exerted neuroprotective effects against CORT-induced cytotoxicity in an in vitro depression model. FMT therapy indicated that verbascoside treatment attenuated gut inflammation and central nervous system inflammatory responses, as well as eliminated neurotransmitter and brain-gut peptide deficiencies in the prefrontal cortex by modulating the composition of gut microbiota. Lactobacillus, Parabacteroides, Bifidobacterium, and Ruminococcus might play key roles in the antidepressant effects of LBRD via the GMBA.

CONCLUSION

The current study elucidates the multi-component, multi-target, and multi-pathway therapeutic effects of LBRD on depression by remodeling GMBA homeostasis and further verifies the causality between gut microbiota and the antidepressant effects of verbascoside and LBRD.

Constituents, pharmacological activities, pharmacokinetic studies, clinical applications, and safety profile on the classical prescription Kaixinsan

Kaixinsan (KXS) is a noteworthy classical prescription, which consists of four Chinese medicinal herbs, namely Polygalae Radix, Ginseng Radix et Rhizoma, Poria, and Acori Tatarinowii Rhizoma. KXS was initially documented in the Chinese ancient book Beiji Qianjin Yaofang written by Sun Simiao of the Tang Dynasty in 652 A.D. As a traditional Chinese medicine (TCM) prescription, it functions to nourish the heart and replenish Qi, calm the heart tranquilize the mind, and excrete dampness. Originally used to treat amnesia, it is now also effective in memory decline and applied to depression. Although there remains an abundance of literature investigating KXS from multiple aspects, few reviews summarize the features and research, which impedes better exploration and exploitation of KXS. This article intends to comprehensively analyze and summarize up-to-date information concerning the chemical constituents, pharmacology, pharmacokinetics, clinical applications, and safety of KXS based on the scientific literature, as well as to examine possible scientific gaps in current research and tackle issues in the next step. The chemical constituents of KXS primarily consist of saponins, xanthones, oligosaccharide esters, triterpenoids, volatile oils, and flavonoids. Of these, saponins are the predominant active ingredients, and increasing evidence has indicated that they exert therapeutic properties against mental disease. Pharmacokinetic research has illustrated that the crucial exposed substances in rat plasma after KXS administration are ginsenoside Re (GRe), ginsenoside Rb1 (GRb1), and polygalaxanthone III (POL). This article provides additional descriptions of the safety. In this review, current issues are highlighted to guide further comprehensive research of KXS and other classical prescriptions.

The regulatory effect of Angelicae Sinensis Radix on neuroendocrine-immune network and sphingolipid metabolism in CUMS-induced model of depression

ETHNOPHARMACOLOGICAL RELEVANCE

Conventional antidepressants therapy remains unsatisfactory due to the disadvantages of delayed clinical onset of action and side effects. Traditional Chinese Medicine (TCM) with good efficacy and higher safety have received much attention. Angelicae Sinensis Radix (AS), a well-known TCM, has been proved to exhibit the efficacy of antidepression recently.

AIM OF THE STUDY

The purpose of this study was to investigate the potential anti-depressant mechanisms of AS based on chronic unpredictable mild stress (CUMS) rat model.

MATERIALS AND METHODS

In this study, behavioral experiments, molecular biology techniques, and ultra performance liquid chromatography-triple-time of flight mass spectrometer (UPLC-Triple-TOF/MS) were combined to explore the potential antidepressant mechanisms of AS based on CUMS rat model.

RESULTS

The results demonstrated that AS could reduce the contents of serum hypothalamic-pituitary-adrenal (HPA) axis hormones in CUMS rats, including corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and cortisol (CORT). In addition, AS regulated the percentage of CD4+ T lymphocytes, the ratio of CD4+/CD8+, and the levels of serum cytokines such as IL-1β, IL-4, IL-6, and TNF-α in CUMS rats. Lipidomics showed that 31 lipids were related to depression and AS could regulate the lipid metabolism alteration induced by CUMS, particularly sphingolipid metabolism. Finally, the key proteins in sphingolipid metabolic pathways in hippocampus of CUMS rats could be back-regulated by AS, including serine palmitoyl transferase (SPTLC2), ceramide synthase (CerS2), sphingomyelinase (SPHK1), and neutral sphingomyelinase (nSMase).

CONCLUSION

AS could alleviate NEI network disorder and restore the levels of sphingolipid metabolites and key proteins in CUMS rats. The underlying mechanism by which AS relieved depression-like behavior in CUMS rats may be through modulation of NEI and disturbances in sphingolipid metabolism.

Zuojin pill improves chronic unpredictable stress-induced depression-like behavior and gastrointestinal dysfunction in mice via the theTPH2/5-HT pathway

BACKGROUND

The complex bidirectional communication between the gastrointestinal tract and the brain is associated with mental disorders such as depression; serotonin, as a crucial neurotransmitter in the communication system between the central nervous system and the gastrointestinal tract, has effects on regulating gastrointestinal motility and sensation and improving psychosomatic status. Zuojin pill is used as a traditional Chinese medicine formula for the treatment of gastrointestinal disorders. This study explored the effects of Zuojin pill on the improvement of depression and gastrointestinal function in CUMS mice via TPH2 and its mechanism.

PURPOSE

The aim of this study was to investigate whether Zuojin pill could improve depression and concomitant gastrointestinal dysfunction, and to reveal whether Zuojin pill could work through the regulation of the tryptophan hydroxylase 2 (TPH2) pathway.

METHODS

The CUMS model was established to observe the effects of Zuojin pill on depression-like behavior and gastrointestinal function in mice. Nissler staining and HE staining were used to observe the structure of hippocampal neurons and intestinal mucosa respectively. 5-HT levels in serum, hippocampus, and intestinal tissues were measured by ELISA, and TPH2 expression in hippocampus and intestinal nerves was observed by WB and immunofluorescence. In order to investigate the protective effect and mechanism of Zuojin pill on PC12 cells, CORT used an in vitro model to produce PC12 cell damage.

RESULTS

Our study showed that Zuojin pill ameliorated depression-like behavior and gastrointestinal dysfunction in CUMS mice, elevated BDNF, 5-HT, and TPH2 expression in the hippocampus, and restored the ratio of dopaminergic and GABAergic neurons between intestinal muscles. In vitro experiments showed that Zuojin pill exerted a protective effect on neurons by regulating TPH2 ubiquitination and thus inhibiting CORT-induced apoptosis of PC12 cells.

CONCLUSION

Zuojin pill improves chronic unpredictable stress-induced depression-like behavior and gastrointestinal dysfunction in mice via the TPH2/5-HT pathway. Therefore, TPH2 may be a potential therapeutic target for depression with gastrointestinal dysfunction.

The synergistic mechanism of action of Dajianzhong decoction in conjunction with ketamine in the treatment of depression

Depression is a multifactorial syndrome with a variety of underlying pathological mechanisms. While ketamine, an N-methyl-D-aspartate receptor (NMDAR) antagonist, exhibits a rapid antidepressant action in the central never system (CNS), the potential addiction and psychotomimetic adverse effects of ketamine limit its chronic use in clinical practice. Therefore, it is necessary to discover an additional agent that shows a synergistic antidepressant activity with ketamine to sustain its therapeutic action so as to reduce its use frequency in depression treatment. The present study indicated that Dajianzhong decoction (DJZT), an empirical herbal formula used for the clinical treatment of several inflammation-related intestinal disorders, sustains behavioral and synaptic action of ketamine in depressive mouse models. Additionally, ketamine was also demonstrated to exert a synergistic action with DJZT to alleviate the chronic unpredictable mild stress (CUMS)-induced abnormalities in gut barrier proteins and colonic histology, and subsequently to normalize the diversity and composition of gut microbiota. Furthermore, DJZT was shown to possess an anti-inflammatory activity to prevent activation of NF-κB from releasing proinflammatory cytokines, specifically through inhibiting Th17 cells/IL-17A pathway. Our results uncovered the mechanism of action of DJZT in conjunction with ketamine in depression treatment by which these agents target different pathological factors across biological systems and exert a synergistic activity through a bidirectional communication in the gut-brain axis, and also provided new insights into the systematic treatment of depression.

Acupuncture treatment for post-stroke depression: Intestinal microbiota and its role

Stroke-induced depression is a common complication and an important risk factor for disability. Besides psychiatric symptoms, depressed patients may also exhibit a variety of gastrointestinal symptoms, and even take gastrointestinal symptoms as the primary reason for medical treatment. It is well documented that stress may disrupt the balance of the gut microbiome in patients suffering from post-stroke depression (PSD), and that disruption of the gut microbiome is closely related to the severity of the condition in depressed patients. Therefore, maintaining the balance of intestinal microbiota can be the focus of research on the mechanism of acupuncture in the treatment of PSD. Furthermore, stroke can be effectively treated with acupuncture at all stages and it may act as a special microecological regulator by regulating intestinal microbiota as well. In this article, we reviewed the studies on changing intestinal microbiota after acupuncture treatment and examined the existing problems and development prospects of acupuncture, microbiome, and poststroke depression, in order to provide new ideas for future acupuncture research.