Differential Gut Microbiota Compositions Related With the Severity of Major Depressive Disorder

Integration of Gut Microbiota, Serum Metabolomic, and Network Pharmacology to Reveal the Anti Insomnia Mechanism of Mongolian Medicine Sugemule-4 Decoction on Insomnia Model Rats

Objective

To explored the potential molecular mechanism of Sugemule-4 decoction (MMS-4D) in treating insomnia.

Methods

DL-4-chlorophenylalanine (PCPA) + chronic unpredictable mild stress stimulation (CUMS) was used to induce an insomnia model in rats. After the model was successfully established, MMS-4D was intervened at low, medium, and high doses for 7 days. The open-field test (OFT) was used to preliminarily evaluate the efficacy. The potential mechanism of MMS-4D in treating insomnia was investigated using gut microbiota, serum metabolomics, and network pharmacology (NP). Experimental validation of the main components of the key pathways was carried out using ELISA and Western blot.

Results

The weights of the insomnia-model rats were significantly raised (p ≤ 0.05), the total exercise distance in the OFT increased (p ≤ 0.05), the rest time shortened, and the number of standing times increased (p ≤ 0.05), after treatment with MMS-4D. Moreover, there was a substantial recovery in the 5-HT, DA, GABA, and Glu levels in the hypothalamus tissue and the 5-HT and GABA levels in the colon tissue of rats. The expression of DAT and DRD1 proteins in the hippocampus of insomnia rats reduced after drug treatment. MMS-4D may treat insomnia by regulating different crucial pathways including 5-HT -, DA -, GABA -, and Glu-mediated neuroactive light receiver interaction, cAMP signaling pathway, serotonergic, glutamatergic, dopaminergic, and GABAergic synapses.

Conclusion

This study revealed that MMS-4D can improve the general state and behavioral changes of insomnia model rats. Its mechanism may be related to the reversal of abnormal pathways mediated by 5-HT, DA, GABA, and Glu, such as Serotonergic synapse, Dopaminergic synapse, Glutamatergic synapse, and GABAergic synapse.

A Narrative Review of Intestinal Microbiota's Impact on Migraine with Psychopathologies

Migraine is a common and debilitating neurological disorder characterized by the recurrent attack of pulsating headaches typically localized on one side of the head associated with other disabling symptoms, such as nausea, increased sensitivity to light, sound and smell and mood changes. Various clinical factors, including the excessive use of migraine medication, inadequate acute treatment and stressful events, can contribute to the worsening of the condition, which may evolve to chronic migraine, that is, a headache present on >15 days/month for at least 3 months. Chronic migraine is frequently associated with various comorbidities, including anxiety and mood disorders, particularly depression, which complicate the prognosis, response to treatment and overall clinical outcomes. Emerging research indicates a connection between alterations in the composition of the gut microbiota and mental health conditions, particularly anxiety and depression, which are considered disorders of the gut-brain axis. This underscores the potential of modulating the gut microbiota as a new avenue for managing these conditions. In this context, it is interesting to investigate whether migraine, particularly in its chronic form, exhibits a dysbiosis profile similar to that observed in individuals with anxiety and depression. This could pave the way for interventions aimed at modulating the gut microbiota for treating difficult-to-manage migraines.

Raspberry Ketone Prevents LPS-Induced Depression-Like Behaviors in Mice by Inhibiting TLR-4/NF-κB Signaling Pathway via the Gut-Brain Axis

SCOPE

Depression, a prevalent mental disorder, has significantly impacted the lives of 350 million people, yet it holds promise for amelioration through food-derived phenolics. Raspberries, renowned globally for their delectable flavor, harbor a phenolic compound known as raspberry ketone (RK). However, the impact of RK on depressive symptoms remains ambiguous. This study aims to investigate the impact of RK on lipopolysaccharide (LPS)-induced depressed mice and elucidates its potential mechanisms, focusing on the gut-brain axis.

METHODS AND RESULTS

Through behavioral tests, RK exerts a notable preventive effect on LPS-induced depression-like behaviors in mice. RK proves capable of attenuating gut inflammation, repairing gut barrier impairment, modulating the composition of the gut microbiome (Muribaculaceae, Streptococcus, Lachnospiraceae, and Akkermansia), and promoting the production of short-chain fatty acids. Furthermore, RK alleviates neuroinflammation by suppressing the TLR-4/NF-κB pathway and bolsters synaptic function by elevating levels of neurotrophic factors and synapse-associated proteins.

CONCLUSION

The current study provides compelling evidence that RK effectively inhibits the TLR-4/NF-κB pathway via the gut-brain axis, leading to the improvement of LPS-induced depression-like behaviors in mice. This study addresses the research gap in understanding the antidepressant effects of RK and illuminates the potential of utilizing RK as a functional food for preventing depression.

Role of Inflammatory Mechanisms in Major Depressive Disorder: From Etiology to Potential Pharmacological Targets

The involvement of central and peripheral inflammation in the pathogenesis and prognosis of major depressive disorder (MDD) has been demonstrated. The increase of pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, IL-18, and TNF-α) in individuals with depression may elicit neuroinflammatory processes and peripheral inflammation, mechanisms that, in turn, can contribute to gut microbiota dysbiosis. Together, neuroinflammation and gut dysbiosis induce alterations in tryptophan metabolism, culminating in decreased serotonin synthesis, impairments in neuroplasticity-related mechanisms, and glutamate-mediated excitotoxicity. This review aims to highlight the inflammatory mechanisms (neuroinflammation, peripheral inflammation, and gut dysbiosis) involved in the pathophysiology of MDD and to explore novel anti-inflammatory therapeutic approaches for this psychiatric disturbance. Several lines of evidence have indicated that in addition to antidepressants, physical exercise, probiotics, and nutraceuticals (agmatine, ascorbic acid, and vitamin D) possess anti-inflammatory effects that may contribute to their antidepressant properties. Further studies are necessary to explore the therapeutic benefits of these alternative therapies for MDD.

Inferior social hierarchy is vulnerable to anxiety-like behavior in chronic pain mice: Potential role of gut microbiota and metabolites

Social dominance is a universal phenomenon among grouped animals that profoundly affects survival, health, and reproductive success by determining access to resources, and exerting a powerful influence on subsequent behavior. However, the understanding of pain and anxiety comorbidities in dominant or subordinate animals suffering from chronic pain is not well-defined. Here, we provide evidence that subordinate mice are more susceptible to pain-induced anxiety compared to dominant mice. We propose that the gut microbiota may play a mediating role in this mechanism. Our findings demonstrate that transplantation of fecal microbiota from subordinate mice with chronic inflammatory pain, but not dominant mice, into antibiotics-treated pseudo-germ-free mice significantly amplifies anxiety-like phenotypes, highlighting the critical involvement of gut microbiota in this behavioral response. Using chronic inflammatory pain model, we carried out 16S rRNA sequencing and untargeted metabolomic analyses to explore the relationship between microbiota and metabolites in a stable social hierarchy of mice. Interestingly, anxiety-like behaviors were directly associated with some microbial genera and metabolites, especially bile acid metabolism. Overall, we have demonstrated a close relationship between social status and anxiety susceptibility, highlighting the contributions of gut microbiota and the associated metabolites in the high-anxiety state of subordinate mice with chronic inflammatory pain.

Dietary fibre confers therapeutic effects in a preclinical model of Huntington's disease

Huntington's disease (HD) is a neurodegenerative disorder involving psychiatric, cognitive and motor deficits, as well as peripheral symptoms, including gastrointestinal dysfunction. The R6/1 HD mouse model expresses a mutant human huntingtin transgene and has been shown to provide an accurate disease model. Recent evidence of gut microbiome disruption was shown in preclinical and clinical HD. Therefore, we aimed to assess the potential role of gut microbial modulation in the treatment of HD. The R6/1 HD mice and wild-type littermate controls were randomised to receive diets containing different amounts of fibre: high-fibre (10 % fibre), control (5 % fibre), or zero-fibre (0 % fibre), from 6 to 20 weeks of age. We characterized the onset and progression of motor, cognitive and affective deficits, as well as gastrointestinal function and gut morphological changes. Faeces were collected for gut microbiome profiling using 16S rRNA sequencing, at 14 and 20 weeks of age. When compared to the control diet, high-fibre diet improved the performance of HD mice in behavioral tests of cognitive and affective function, as well as the gastrointestinal function of both HD and wild-type mice. While the diets changed the beta diversity of wild-type mice, no statistical significance was observed at 14 or 20 weeks of age within the HD mice. Analysis of Composition of Microbiomes with Bias Correction (ANCOM-BC) models were performed to evaluate microbiota composition, which identified differences, including a decreased relative abundance of the phyla Actinobacteriota, Campylobacterota and Proteobacteria and an increased relative abundance of the families Bacteroidaceae, Oscillospiraceae and Ruminococcaceae in HD mice when compared to wild-type mice after receiving high-fibre diet. PICRUSt2 revealed that high-fibre diet also decreased potentially pathogenic functional pathways in HD. In conclusion, high-fibre intake was effective in enhancing gastrointestinal function, cognition and affective behaviors in HD mice. These findings indicate that dietary fibre interventions may have therapeutic potential in Huntington's disease to delay clinical onset, and have implications for related disorders exhibiting dysfunction of the gut-brain axis.

Oral D-ribose causes depressive-like behavior by altering glycerophospholipid metabolism via the gut-brain axis

Our previous work has shown that D-ribose (RIB)-induced depressive-like behaviors in mice. However, the relationship between variations in RIB levels and depression as well as potential RIB participation in depressive disorder is yet unknown. Here, a reanalysis of metabonomics data from depressed patients and depression model rats is performed to clarify whether the increased RIB level is positively correlated with the severity of depression. Moreover, we characterize intestinal epithelial barrier damage, gut microbial composition and function, and microbiota-gut-brain metabolic signatures in RIB-fed mice using colonic histomorphology, 16 S rRNA gene sequencing, and untargeted metabolomics analysis. The results show that RIB caused intestinal epithelial barrier impairment and microbiota-gut-brain axis dysbiosis. These microbial and metabolic modules are consistently enriched in peripheral (fecal, colon wall, and serum) and central (hippocampus) glycerophospholipid metabolism. In addition, three differential genera (Lachnospiraceae_UCG-006, Turicibacter, and Akkermansia) and two types of glycerophospholipids (phosphatidylcholine and phosphatidylethanolamine) have greater contributions to the overall correlations between differential genera and glycerophospholipids. These findings suggest that the disturbances of gut microbiota by RIB may contribute to the onset of depressive-like behaviors via regulating glycerophospholipid metabolism, and providing new insight for understanding the function of microbiota-gut-brain axis in depression.

The involvement of the gut microbiota in postoperative cognitive dysfunction based on integrated metagenomic and metabolomics analysis

IMPORTANCE

As the population ages and medical technology advances, anesthesia procedures for elderly patients are becoming more common, leading to an increased prevalence of postoperative cognitive dysfunction. However, the etiology and correlation between the gut microbiota and cognitive dysfunction are poorly understood, and research in this area is limited. In this study, mice with postoperative cognitive dysfunction were found to have reduced levels of fatty acid production and anti-inflammatory flora in the gut, and Bacteroides was associated with increased depression, leading to cognitive dysfunction and depression. Furthermore, more specific microbial species were identified in the disease model, suggesting that modulation of host metabolism through gut microbes may be a potential avenue for preventing postoperative cognitive dysfunction.

Diversity and community composition of strictly anaerobic and culturable bacteria from the feces of Styrofoam-fed Tenebrio molitor larvae: a culturomics-based study

Introduction

In recent years, researchers have been exploring the plastic-degrading abilities of bacteria residing in the guts of Styrofoam-eating Tenebrio molitor larvae. However, none of the reported strains have displayed highly efficient plastic degradation capabilities, and it's noteworthy that none of the existing studies have focused on strictly anaerobic microbes.

Methods

In this study, we exclusively fed Styrofoam to T. molitor larvae and examined how this dietary change influence the gut's bacterial community composition, as observed through fecal bacteria using bacterial 16S rRNA gene amplicon sequencing and the small-scale culturomics method with 20 types of anaerobic media under four different conditions.

Results

The results revealed a significant shift in the dominant phylogroup from Lactococcus (37.8%) to Escherichia-Shigella (54.7%) when comparing the feces of larvae fed with bran and Styrofoam, as analyzing through the bacterial 16S rRNA gene amplicon sequencing. For small-scale culturomics method, a total of 226 strains of anaerobic bacteria were isolated and purified using the rolling-tube/strictly anaerobic technique. Among them, 226 strains were classified into 3 phyla, 7 classes, 9 orders, 17 families, 29 genera, 42 known species and 34 potential novel species.

Discussion

Interestingly, 24 genera in total, identified through the culturomics method, were not found in the results obtained from amplicon sequencing. Here, we present a collection of culturable anaerobic bacteria from the feces of T. molitor larvae, which might be a promising avenue for investigating the biodegradability of plastics by combining specific strains, either randomly or intentionally, while considering the abundance ratio of the microbial community composition.

Gut microbiota from sigma-1 receptor knockout mice induces depression-like behaviors and modulates the cAMP/CREB/BDNF signaling pathway

Introduction

Depression is a common mental disorder that affects approximately 350 million people worldwide. Much remains unknown about the molecular mechanisms underlying this complex disorder. Sigma-1 receptor (Sig-1R) is expressed at high levels in the central nervous system. Increasing evidence has demonstrated a close association between the Sig-1R and depression. Recently, research has suggested that the gut microbiota may play a crucial role in the development of depression.

Methods

Male Sig-1R knockout (Sig-1R KO) and wild-type (WT) mice were used for this study. All transgenic mice were of a pure C57BL/6J background. Mice received a daily gavage of vancomycin (100 mg/kg), neomycin sulfate (200 mg/kg), metronidazole (200 mg/kg), and ampicillin (200 mg/kg) for one week to deplete gut microbiota. Fecal microbiota transplantation (FMT) was conducted to assess the effects of gut microbiota. Depression-like behaviors was evaluated by tail suspension test (TST), forced swimming test (FST) and sucrose preference test (SPT). Gut microbiota was analyzed by 16s rRNA and hippocampal transcriptome changes were assessed by RNA-seq.

Results

We found that Sig-1R knockout induced depression-like behaviors in mice, including a significant reduction in immobility time and an increase in latency to immobility in the FST and TST, which was reversed upon clearance of gut microbiota with antibiotic treatment. Sig-1R knockout significantly altered the composition of the gut microbiota. At the genus level, the abundance of Alistipes, Alloprevotella, and Lleibacterium decreased significantly. Gut microbiota dysfunction and depression-like phenotypes in Sig-1R knockout mice could be reproduced through FMT experiments. Additionally, hippocampal RNA sequencing identified multiple KEGG pathways that are associated with depression. We also discovered that the cAMP/CREB/BDNF signaling pathway is inhibited in the Sig-1R KO group along with lower expression of neurotrophic factors including CTNF, TGF-α and NGF. Fecal bacteria transplantation from Sig-1R KO mice also inhibited cAMP/CREB/BDNF signaling pathway.

Discussion

In our study, we found that the gut-brain axis may be a potential mechanism through which Sig-1R regulates depression-like behaviors. Our study provides new insights into the mechanisms by which Sig-1R regulates depression and further supports the concept of the gut-brain axis.

The Effect of a Diet Enriched with Jerusalem artichoke, Inulin, and Fluoxetine on Cognitive Functions, Neurogenesis, and the Composition of the Intestinal Microbiota in Mice

The aim of the study was to assess the effect of long-term administration of natural prebiotics: Jerusalem artichoke (topinambur, TPB) and inulin (INU) as well as one of the most popular antidepressants, fluoxetine (FLU), on the proliferation of neural stem cells, learning and memory functions, and the composition of the intestinal microbiota in mice. Cognitive functions were assessed using the Morris Water Maze (MWM)Test. Cells were counted using a confocal microscope and ImageJ software. We performed 16S rRNA sequencing to assess changes in the gut microbiome of the mice. The obtained results showed that the 10-week supplementation with TPB (250 mg/kg) and INU (66 mg/kg) stimulates the growth of probiotic bacteria, does not affect the learning and memory process, and does not disturb the proliferation of neural stem cells in the tested animals. Based on this data, we can assume that both TPB and INU seem to be safe for the proper course of neurogenesis. However, 2-week administration of FLU confirmed an inhibitory impact on Lactobacillus growth and negatively affected behavioral function and neurogenesis in healthy animals. The above studies suggest that the natural prebiotics TPB and INU, as natural supplements, may have the potential to enrich the diversity of intestinal microbiota, which may be beneficial for the BGM axis, cognitive functions, and neurogenesis.

Tryptophan metabolism as bridge between gut microbiota and brain in chronic social defeat stress-induced depression mice

Backgrounds

Gut microbiota plays a critical role in the onset and development of depression, but the underlying molecular mechanisms are unclear. This study was conducted to explore the relationships between gut microbiota and host's metabolism in depression.

Methods

Chronic social defeat stress (CSDS) model of depression was established using C57BL/6 male mice. Fecal samples were collected from CSDS group and control group to measure gut microbiota and microbial metabolites. Meanwhile, tryptophan metabolism-related metabolites in hippocampus were also analyzed.

Results

CSDS successfully induced depressive-like behaviors in CSDS group. The 24 differential bacterial taxa between the two groups were identified, and 14 (60.87%) differential bacterial taxa belonged to phylum Firmicutes. Functional analysis showed that tryptophan metabolism was significantly affected in CSDS mice. Meanwhile, 120 differential microbial metabolites were identified, and two key tryptophan metabolism-related metabolites (tryptophan and 5-hydroxytryptophan (5-HTP)) were significantly decreased in feces of CSDS mice. The correlation analysis found the significant relationships between tryptophan and differential bacterial taxa under Firmicutes, especially genus Lactobacillus (r=0.801, p=0.0002). In addition, the significantly decreased 5-hydroxytryptamine (5-HT) in hippocampus of depressed mice was also observed.

Conclusions

Our results showed that tryptophan metabolism might have an important role in the crosstalk between gut microbioa and brain in depression, and phylum Firmicutes, especially genus Lactobacillus, might be involved in the onset of depression through regulating tryptophan metabolism.

The microbiota-gut-brain axis in stress and depression

Humans and animals are evolved to have instinctive physiological responses to threats. The perception of threat by the brain triggers a multitude of changes across the brain and body. A large body of research have demonstrated that our hardwired survival instinct, the stress response, can become maladaptive and promote major depressive disorders and other neuropsychiatric impairments. However, gaps in our understanding of how chronic stress contributes to depression and mental disorders suggest that we also need to consider factors beyond the biology of the host. The unravelling of the structure and function of microorganisms that humans and animals are host to have driven a paradigm shift in understanding the individual as a collective network composed of the host plus microbes. Well over 90% of bacteria in the body reside in the large intestines, and these microbes in the lower gut function almost like an organ in the body in the way it interacts with the host. Importantly, bidirectional interactions between the gut microbiota and the brain (i.e., the two-way microbiota-gut-brain axis) have been implicated in the pathophysiology of mental disorders including depression. Here, in summarizing the emerging literature, we envisage that further research particularly on the efferent brain-gut-microbiota axis will uncover transformative links in the biology of stress and depression.

Depression Pathophysiology: Astrocyte Mitochondrial Melatonergic Pathway as Crucial Hub

Major depressive disorder (MDD) is widely accepted as having a heterogenous pathophysiology involving a complex mixture of systemic and CNS processes. A developmental etiology coupled to genetic and epigenetic risk factors as well as lifestyle and social process influences add further to the complexity. Consequently, antidepressant treatment is generally regarded as open to improvement, undoubtedly as a consequence of inappropriately targeted pathophysiological processes. This article reviews the diverse array of pathophysiological processes linked to MDD, and integrates these within a perspective that emphasizes alterations in mitochondrial function, both centrally and systemically. It is proposed that the long-standing association of MDD with suppressed serotonin availability is reflective of the role of serotonin as a precursor for the mitochondrial melatonergic pathway. Astrocytes, and the astrocyte mitochondrial melatonergic pathway, are highlighted as crucial hubs in the integration of the wide array of biological underpinnings of MDD, including gut dysbiosis and permeability, as well as developmental and social stressors, which can act to suppress the capacity of mitochondria to upregulate the melatonergic pathway, with consequences for oxidant-induced changes in patterned microRNAs and subsequent patterned gene responses. This is placed within a development context, including how social processes, such as discrimination, can physiologically regulate a susceptibility to MDD. Future research directions and treatment implications are derived from this.

Reviewing the role of gut microbiota in the pathogenesis of depression and exploring new therapeutic options

The relationship between gut microbiota (GM) and mental health is one of the focuses of psychobiology research. In recent years, the microbial-gut-brain axis (MGBA) concept has gradually formed about this bidirectional communication between gut and brain. But how the GM is involved in regulating brain function and how they affect emotional disorders these mechanisms are tenuous and limited to animal research, and often controversial. Therefore, in this review, we attempt to summarize and categorize the latest advances in current research on the mechanisms of GM and depression to provide valid information for future diagnoses and therapy of mental disorders. Finally, we introduced some antidepressant regimens that can help restore gut dysbiosis, including classic antidepressants, Chinese materia medica (CMM), diet, and exogenous strains. These studies provide further insight into GM's role and potential pathways in emotion-related diseases, which holds essential possible clinical outcomes for people with depression or related psychiatric disorders. Future research should focus on clarifying the causal role of GM in disease and developing microbial targets, applying these findings to the prevention and treatment of depression.