Reductions in anti-inflammatory gut bacteria are associated with depression in a sample of young adults

Role of the Intestinal Microbiota in the Genesis of Major Depression and the Response to Antidepressant Drug Therapy: A Narrative Review

A major depressive disorder is a serious mental illness characterized by a pervasive low mood that negatively concerns personal life, work life, or education, affecting millions of people worldwide. To date, due to the complexity of the disease, the most common and effective treatments consist of a multi-therapy approach, including psychological, social, and pharmacological support with antidepressant drugs. In general, antidepressants are effective in correcting chemical imbalances of neurotransmitters in the brain, but recent evidence has underlined the pivotal role of gut microbiota (GM) also in the regulation of their pharmacokinetics/pharmacodynamics, through indirect or direct mechanisms. The study of these complex interactions between GM and drugs is currently under the spotlight, and it has been recently named "pharmacomicrobiomics". Hence, the purpose of this review is to summarize the contribution of GM and its metabolites in depression, as well as their role in the metabolism and activity of antidepressant drugs, in order to pave the way for the personalized administration of antidepressant therapies.

Neuroprotective effects of polysaccharide from Sparassis crispa on Alzheimer's disease-like mice: Involvement of microbiota-gut-brain axis

Alzheimer's disease (AD) is an irreversible neurodegenerative disease that may cause neurotoxicity and imbalance in gut microbiota. A polysaccharide derived from Sparassis crispa-1 (SCP-1) acts as a neuroprotective agent in vitro. There is, however, no clarity on the mechanism responsible for SCP-1's neuroprotective effects against AD. In this study, C57BL/6J male mice were treated with D-galactose and AlCl₃ to establish an animal model of AD, followed by treatment with SCP-1. As evidenced by behavioral tests and brain pathology, SCP-1 treatment ameliorated learning deficits and defective spatial recognition, reduced amyloidogenesis, and modulated the neurotransmitter levels (γ-aminobutyric acid, glutamate, and acetylcholine) in the brain of AD mice. The results of 16S rRNA sequencing revealed that SCP-1 reshaped the gut microbiota composition, especially by promoting the proliferation of butyrate-producing genera, such as Intestinaimonas, [Eubacterium] ventriosum group, Lachnospiraceae_UCG_010, and Lachnospiraceae_UCG_001, and suppressing the growth of inflammation-related bacteria (i.e., Escherichia/Shigella). Furthermore, SCP-1 significantly attenuated inflammation by reducing the levels of inflammatory cytokines, maintaining intestinal barrier function, inhibiting glial activation, and decreasing the expression of toll-like receptor 4 (TLR4) and nuclear factor-κB (NF-κB). Collectively, our findings suggest that SCP-1 may prevent the development of AD via modulation of gut microbiota and suppression of inflammation, for a potential application in preventing or managing AD.

Safety and feasibility of faecal microbiota transplant for major depressive disorder: study protocol for a pilot randomised controlled trial

BACKGROUND

Mental disorders, including major depressive disorder (MDD), are a leading cause of non-fatal burden of disease globally. Current conventional treatments for depression have significant limitations, and there have been few new treatments in decades. The microbiota-gut-brain-axis is now recognised as playing a role in mental and brain health, and promising preclinical and clinical data suggest Faecal Microbiota Transplants (FMT) may be efficacious for treating a range of mental illnesses. However, there are no existing published studies in humans evaluating the efficacy of FMT for MDD.

METHODS AND DESIGN

This protocol describes an 8-week, triple-blind, 2:1 parallel group, randomised controlled pilot trial (n = 15), of enema-delivered FMT treatment (n = 10) compared with a placebo enema (n = 5) in adults with moderate-to-severe MDD. There will be a further 26-week follow-up to monitor longer-term safety. Participants will receive four FMT or placebo enemas over four consecutive days. The primary aims of the study are to evaluate feasibility and safety of FMT as an adjunctive treatment for MDD in adults. Changes in gut microbiota will be assessed as a secondary outcome. Other data will be collected, including changes in depression and anxiety symptoms, and safety parameters.

DISCUSSION

Modification of the microbiota-gut-brain axis via FMT is a promising potential treatment for MDD, but there are no published rigorous clinical trials evaluating its use. If this study finds that our FMT strategy is safe and feasible, a larger fully powered RCT is planned. Further high-quality research in this field is urgently needed to address unmet need.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry: ACTRN12621000932864.

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.

Association between Fecal Microbiota, SCFA, Gut Integrity Markers and Depressive Symptoms in Patients Treated in the Past with Bariatric Surgery-The Cross-Sectional Study

(1) Background: Depressive symptoms often appear after surgical treatment. (2) Methods: We involved 41 adults who underwent bariatric surgery a minimum of 6 months before the study and had the Beck scale ≥12. We analysed patients' mental state, gut barrier markers, faecal short chain fatty acids, and microbiota. (3) Results: Gut microbiota composition differed significantly among patients undergoing two different types of surgery (F = 1.64, p = 0.00002). Additionally, we discovered an association between short chain fatty acids and the Beck scale (F = 1.22, p = 0.058). The rearrangement of bacterial metabolites may be due to the patients' use of increased dietary protein, with insufficient intake of products containing vegetable fiber (Diet Quality Index (DQI-I )adequacy 22.55 (±3.46) points). (4) Conclusions: Bariatric surgery affects the gut microbiota, which may play an important role in the development of depressive and gastrointestinal symptoms in patients after bariatric surgery. Low fiber consumption and increased levels of faecal isobutyric acid may lead to intestinal inflammation. There is a need for further research on this topic including a larger sample size.

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.

Gut microbiome-wide association study of depressive symptoms

Depression is one of the most poorly understood diseases due to its elusive pathogenesis. There is an urgency to identify molecular and biological mechanisms underlying depression and the gut microbiome is a novel area of interest. Here we investigate the relation of fecal microbiome diversity and composition with depressive symptoms in 1,054 participants from the Rotterdam Study cohort and validate these findings in the Amsterdam HELIUS cohort in 1,539 subjects. We identify association of thirteen microbial taxa, including genera Eggerthella, Subdoligranulum, Coprococcus, Sellimonas, Lachnoclostridium, Hungatella, Ruminococcaceae (UCG002, UCG003 and UCG005), LachnospiraceaeUCG001, Eubacterium ventriosum and Ruminococcusgauvreauiigroup, and family Ruminococcaceae with depressive symptoms. These bacteria are known to be involved in the synthesis of glutamate, butyrate, serotonin and gamma amino butyric acid (GABA), which are key neurotransmitters for depression. Our study suggests that the gut microbiome composition may play a key role in depression.

Toward a Deeper Understanding of Gut Microbiome in Depression: The Promise of Clinical Applicability

The emergence of the coronavirus disease 2019 pandemic has dramatically increased the global prevalence of depression. Unfortunately, antidepressant drugs benefit only a small minority of patients. Thus, there is an urgent need to develop new interventions. Accumulating evidence supports a causal relationship between gut microbiota dysbiosis and depression. To advance microbiota-based diagnostics and therapeutics of depression, a comprehensive overview of microbial alterations in depression is presented to identify effector microbial biomarkers. This procedure generated 215 bacterial taxa from humans and 312 from animal models. Compared to controls, depression shows significant differences in β-diversity, but no changes in microbial richness and diversity. Additionally, species-specific microbial changes are identified like increased Eggerthella in humans and decreased Acetatifactor in rodent models. Moreover, a disrupted microbiome balance and functional changes, characterized by an enrichment of pro-inflammatory bacteria (e.g., Desulfovibrio and Escherichia/Shigella) and depletion of anti-inflammatory butyrate-producing bacteria (e.g., Bifidobacterium and Faecalibacterium) are consistently shared across species. Confounding effects of geographical region, depression type, and intestinal segments are also investigated. Ultimately, a total of 178 species and subspecies probiotics are identified to alleviate the depressive phenotypes. Current findings provide a foundation for developing microbiota-based diagnostics and therapeutics and advancing microbiota-oriented precision medicine for depression.

Association between Depression, Anxiety Symptoms and Gut Microbiota in Chinese Elderly with Functional Constipation

This study aimed to investigate the relationship between anxiety, depression, and gut microbiota in elderly patients with FC.

METHODS

in this cross-sectional study, a total of 198 elderly participants (85 male and 113 female) aged over 60 years were recruited. The study was conducted in Changsha city, China. The participants completed an online questionnaire, including The Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), The Patient Assessment of Symptoms (PAC-SYM), and The Patient Assessment of Quality of Life (PAC-QoL). We selected the 16S rDNA V3 + V4 region as the amplification region and sequenced the gut microbiota using the Illumina Novaseq PE250 high-throughput sequencing platform.

RESULTS

in total, 30.3% of patients with constipation had depression, while 21.3% had anxiety. The relative abundance of intestinal microbiota in the normal group was higher than that in the anxiety and depression group. According to LEfSe analysis, the relative abundance of g_Peptoniphilus and g_Geobacter in the people without depression and anxiety was higher. The relative abundance of g_Pseudoramibacter-Eubacterium and g_Candidatus-Solibacter in the depression group was lower, and the relative abundance of g_Bacteroides and g_Paraprevotella, g_Cc_115 in the anxiety group was higher. In addition, according to the correlation analysis, g_Aquicella and g_Limnohabitans were negatively correlated with constipation symptoms, anxiety, and depression.

CONCLUSIONS

this study found that gut microbiota composition may be associated with a higher incidence of anxiety and depression in patients with FC, thus providing insight into the mechanisms that ameliorate mood disorders in patients with FC.

Vagus Nerve and Underlying Impact on the Gut Microbiota-Brain Axis in Behavior and Neurodegenerative Diseases

The gut microbiota is the most abundant and diverse microbiota in the human body and the vagus nerve is the most widely distributed and complex nerve in the body, both of them are essential in maintaining homeostasis. The most important phenomenon is how they coordinate to regulate functions, which has attracted the great attention of scientists. The academic literature on the correlation with a host of intestinal diseases and even systemic diseases has revealed the bidirectional communication between the gut microbiota and the brain, which can be carried out via multiple patterns. In the review, firstly, we have a general overview of the gut microbiota and the gut microbiota-brain axis. Secondly, according to the distribution characteristics of the vagus nerve, we analyzed and summarized its function in the intestinal tract. At the same time, we have summarized the underlying mechanism of some behavior changes such as depressive and anxiety-like behaviors and related neurodegenerative diseases caused by the vagus nerve and intestinal microecological environment disorders, and then we also analyzed inconsistency of the experimental evidence in order to propose novel strategies for the clinical practice.

Depression and fatigue in active IBD from a microbiome perspective-a Bayesian approach to faecal metagenomics

BACKGROUND

Extraintestinal symptoms are common in inflammatory bowel diseases (IBD) and include depression and fatigue. These are highly prevalent especially in active disease, potentially due to inflammation-mediated changes in the microbiota-gut-brain axis. The aim of this study was to investigate the associations between structural and functional microbiota characteristics and severity of fatigue and depressive symptoms in patients with active IBD.

METHODS

We included clinical data of 62 prospectively enrolled patients with IBD in an active disease state. Patients supplied stool samples and completed the questionnaires regarding depression and fatigue symptoms. Based on taxonomic and functional metagenomic profiles of faecal gut microbiota, we used Bayesian statistics to investigate the associative networks and triangle motifs between bacterial genera, functional modules and symptom severity of self-reported fatigue and depression.

RESULTS

Associations with moderate to strong evidence were found for 3 genera (Odoribacter, Anaerotruncus and Alistipes) and 3 functional modules (pectin, glycosaminoglycan and central carbohydrate metabolism) with regard to depression and for 4 genera (Intestinimonas, Anaerotruncus, Eubacterium and Clostridiales g.i.s) and 2 functional modules implicating amino acid and central carbohydrate metabolism with regard to fatigue.

CONCLUSIONS

This study provides the first evidence of association triplets between microbiota composition, function and extraintestinal symptoms in active IBD. Depression and fatigue were associated with lower abundances of short-chain fatty acid producers and distinct pathways implicating glycan, carbohydrate and amino acid metabolism. Our results suggest that microbiota-directed therapeutic approaches may reduce fatigue and depression in IBD and should be investigated in future research.

Interactions between central nervous system and peripheral metabolic organs

According to Descartes, minds and bodies are distinct kinds of "substance", and they cannot have causal interactions. However, in neuroscience, the two-way interaction between the brain and peripheral organs is an emerging field of research. Several lines of evidence highlight the importance of such interactions. For example, the peripheral metabolic systems are overwhelmingly regulated by the mind (brain), and anxiety and depression greatly affect the functioning of these systems. Also, psychological stress can cause a variety of physical symptoms, such as bone loss. Moreover, the gut microbiota appears to play a key role in neuropsychiatric and neurodegenerative diseases. Mechanistically, as the command center of the body, the brain can regulate our internal organs and glands through the autonomic nervous system and neuroendocrine system, although it is generally considered to be outside the realm of voluntary control. The autonomic nervous system itself can be further subdivided into the sympathetic and parasympathetic systems. The sympathetic division functions a bit like the accelerator pedal on a car, and the parasympathetic division functions as the brake. The high center of the autonomic nervous system and the neuroendocrine system is the hypothalamus, which contains several subnuclei that control several basic physiological functions, such as the digestion of food and regulation of body temperature. Also, numerous peripheral signals contribute to the regulation of brain functions. Gastrointestinal (GI) hormones, insulin, and leptin are transported into the brain, where they regulate innate behaviors such as feeding, and they are also involved in emotional and cognitive functions. The brain can recognize peripheral inflammatory cytokines and induce a transient syndrome called sick behavior (SB), characterized by fatigue, reduced physical and social activity, and cognitive impairment. In summary, knowledge of the biological basis of the interactions between the central nervous system and peripheral organs will promote the full understanding of how our body works and the rational treatment of disorders. Thus, we summarize current development in our understanding of five types of central-peripheral interactions, including neural control of adipose tissues, energy expenditure, bone metabolism, feeding involving the brain-gut axis and gut microbiota. These interactions are essential for maintaining vital bodily functions, which result in homeostasis, i.e., a natural balance in the body's systems.

The effects of different stress on intestinal mucosal barrier and intestinal microecology were discussed based on three typical animal models

Recent studies have revealed that the effect of intestinal microecological disorders on organismal physiology is not limited to the digestive system, which provides new perspectives for microecological studies and new ideas for clinical diagnosis and prevention of microecology-related diseases. Stress triggers impairment of intestinal mucosal barrier function, which could be duplicated by animal models. In this paper, pathological animal models with high prevalence and typical stressors—corresponding to three major stressors of external environmental factors, internal environmental factors, and social psychological factors, respectively exemplified by burns, intestinal ischemia-reperfusion injury (IIRI), and depression models—were selected. We summarized the construction and evaluation of these typical animal models and the effects of stress on the organism and intestinal barrier, as well as systematically discussed the effects of different stresses on the intestinal mucosal barrier and intestinal microecology.

In vitro fermentation of Bangia fusco-purpurea polysaccharide by human gut microbiota and the protective effects of the resultant products on Caco-2 cells from lipopolysaccharide-induced injury

Polysaccharide extracted from red seaweed Bangia fusco-purpurea (BFP) is a novel sulfated galactan, differed from agarans and carrageenans in fine structure. In this study, in vitro fermentation characteristics of BFP by human gut microbiota and its protective effect on lipopolysaccharide (LPS)-induced injury in Caco-2 cells were investigated. Our results showed that BFP was mainly degraded at transverse colon for 18 h fermentation by gut microbiota with reduced molecular weight. Meanwhile, BFP fermentation was associated with increased short-chain fatty acids (SCFAs) as compared to control group, especially acetic acid was increased to 129.53 ± 0.24 from 82.14 ± 0.23 mmol/L, and butyric acid was up to 1.56 ± 0.004 from 0.62 ± 0.01 mmol/L. Furthermore, BFP promoted abundances of Bacteroidetes and Firmicutes, while decreased numbers of Proteobacteria. The up-regrated beneficial differential metabolites were SCFAs, L-proline, arginine, folic acid, pyridoxamine, thiamine, etc. (p < 0.05), and their related metabolic pathways mainly included mTOR, arginine biosynthesis, and vitamin metabolism. Notably, BFP fermentation products at transverse colon significantly restored cell viability of LPS-treated Caco-2 cells from 73.79 ± 0.48 % to 93.79-99.64 %, which might be caused by increased beneficial differential metabolites (e.g., SCFAs). Our findings suggest that BFP has prebiotic potential and can enhance gut health.

Depression-like behaviors in mouse model of Sjögren's syndrome: A role of gut-microbiota-brain axis

Depression is a common psychiatric symptom in patients with Sjögren's syndrome (SS). Prevalence of depression in SS patients is significantly higher than that in the general population. Increasing evidence suggests a crucial role of gut-microbiota-brain axis in depression. In this study, we investigated whether non-obese diabetic (NOD) mice, a widely used animal model of SS, exhibit depression-like phenotypes and abnormal composition of gut microbiota. Eleven-week-old NOD mice spontaneously exhibited SS-related symptoms without pancreatic destruction. NOD mice displayed depression-like behaviors, decreased expression of synaptic proteins in the prefrontal cortex (PFC), and abnormal composition of gut microbiota. Interestingly, SS-related proinflammatory factors in the submandibular gland (SMG) and autoantibodies (anti-SSA and anti-SSB) in the plasma were correlated with the expression of synaptic proteins in the PFC or depression-like behaviors. In addition, there were correlations between the relative abundance of microbiota and SS-related symptoms (or depression-related phenotypes). These data suggest that SS-related symptoms and abnormal composition of gut microbiota may play a role in depression-like phenotypes in NOD mice through gut-microbiota-brain axis.

The involvement of gut microbiota in the anti-tumor effect of carnosic acid via IL-17 suppression in colorectal cancer

Colorectal cancer (CRC) is a malignant tumor that threatens human health worldwide. Disturbance of the gut microbiota caused by various external factors is one of the leading causes. Carnosic acid (CA) is a phenolic diterpene compound, mainly isolated from rosemary plants, with anti-inflammatory and anti-tumor properties. In this study, we aimed to investigate the role of CA in CRC development and its underlying mechanisms in B6/JGpt-Apc^em1Cin(min)/Gpt (Apc^Min/+) mice based on the analysis of gut microbiota, serum metabolomics, and tumor proteomics. Enzyme-linked immunosorbent assay (ELISA) and Western blot were performed to confirm the changes in cytokine and protein levels related to inflammation after CA administration. CA regulated the abundance of the gut microbiota, which further caused changes in the production of dl-lactic acid. CA suppressed the inflammatory response by reducing the levels of IL-1β, -6, and -17A. Overall, CA showed anti-CRC properties via modulation of gut microbiota and serum metabolites through NF-κB/STAT3 signaling to inhibit IL-17 expression in Apc^Min/+ mice. These results provide experimental evidence for the future treatment of CRC with CA.

Associations of maternal prenatal emotional symptoms with neurodevelopment of children and the neonatal meconium microbiota: A prospective cohort study

BACKGROUND

Maternal emotional symptoms during pregnancy increase the risk of neurodevelopmental problems in offspring, and microbiota have been shown to be a potential mechanism underlying the link. However, the associations among maternal prenatal emotional symptoms, the meconium microbiota, and offspring neurodevelopment have yet to be fully elucidated. The aim of this prospective cohort study was to assess the relationship between maternal prenatal emotional symptoms and neurodevelopment of the child at 24 months of age, and to investigate the potential role of the neonatal meconium microbiota in the relationship.

METHODS

A total of 410 mother-child pairs (152 women in the Symptoms group vs. 258 women in the No-symptoms group) were recruited from the ongoing Shanghai Maternal-Child Pairs Cohort. This study included a subgroup of women who were assessed for maternal anxiety and depressive symptoms at 32-36 weeks of gestation. Neonatal meconium samples were collected after birth for 16 S sequencing. Children's neurodevelopment was measured using the Ages and Stages Questionnaire, Third Edition (ASQ-3) and Strengths and Difficulties Questionnaire (SDQ) at 24 months postnatally (n = 287).

RESULTS

Compared with the No-symptoms group, children in the Symptoms group had a higher degree of hyperactivity and total difficulties at 24 months of age. Increases in alpha diversity, distinct overall composition, enriched relative abundance of Proteobacteria, and different predicted microbial functions were observed in the meconium of neonates exposed to maternal prenatal emotional symptoms. The neonatal gut microbiota alpha diversity and relative abundance of genera from the Proteobacteria phylum and Lactobacillus were negatively correlated with children's degree of prosocial behavior, tendency toward hyperactivity, and poor fine motor development. In addition, mediating effects of neonatal meconium microbial richness and the relative abundance of Lactobacillus were observed between maternal emotional symptoms and children's prosocial behavior.

CONCLUSIONS

Maternal prenatal emotional symptoms are associated with alterations in the offspring meconium microbiota and children's neurodevelopment at 24 months of age, and the microbial richness indices and Lactobacillus may play a mediating role. Future research is needed to identify and understand the biological pathways and metabolisms linking the relationships among maternal emotional symptoms, meconium microbiota, and neurodevelopment of children.

The Many Ages of Microbiome–Gut–Brain Axis

Frailty during aging is an increasing problem associated with locomotor and cognitive decline, implicated in poor quality of life and adverse health consequences. Considering the microbiome–gut–brain axis, we investigated, in a longitudinal study, whether and how physiological aging affects gut microbiome composition in wild-type male mice, and if and how cognitive frailty is related to gut microbiome composition. To assess these points, we monitored mice during aging at five selected experimental time points, from adulthood to senescence. At all selected experimental times, we monitored cognitive performance using novel object recognition and emergence tests and measured the corresponding Cognitive Frailty Index. Parallelly, murine fecal samples were collected and analyzed to determine the respective alpha and beta diversities, as well as the relative abundance of different bacterial taxa. We demonstrated that physiological aging significantly affected the overall gut microbiome composition, as well as the relative abundance of specific bacterial taxa, including Deferribacterota, Akkermansia, Muribaculaceae, Alistipes, and Clostridia VadinBB60. We also revealed that 218 amplicon sequence variants were significantly associated to the Cognitive Frailty Index. We speculated that some of them may guide the microbiome toward maladaptive and dysbiotic conditions, while others may compensate with changes toward adaptive and eubiotic conditions.

Probiotics: Protecting Our Health from the Gut

The gut microbiota (GM) comprises billions of microorganisms in the human gastrointestinal tract. This microbial community exerts numerous physiological functions. Prominent among these functions is the effect on host immunity through the uptake of nutrients that strengthen intestinal cells and cells involved in the immune response. The physiological functions of the GM are not limited to the gut, but bidirectional interactions between the gut microbiota and various extraintestinal organs have been identified. These interactions have been termed interorganic axes by several authors, among which the gut–brain, gut–skin, gut–lung, gut–heart, and gut–metabolism axes stand out. It has been shown that an organism is healthy or in homeostasis when the GM is in balance. However, altered GM or dysbiosis represents a critical factor in the pathogenesis of many local and systemic diseases. Therefore, probiotics intervene in this context, which, according to various published studies, allows balance to be maintained in the GM, leading to an individual’s good health.

Abnormal gut microbiota and bile acids in patients with first-episode major depressive disorder and correlation analysis

AIM

Gut microbiota and its metabolite bile acids may play a significant role in the occurrence and development of major depressive disorder (MDD). Therefore, this study analyzes gut microbiota and bile acids, as well as their correlation in patients.

METHODS

Thirty-one patients with MDD and 29 healthy controls (HCs) were enrolled in this study. We collected their both blood and feces. Plasma bile acid content was determined by liquid chromatography-mass spectrometry and gut microbiota was detected by 16SrRNA gene sequencing and subsequently analyzed. We also analyzed the correlation between different gut microbiota, bile acids, and Hamilton Depression (HAMD) score.

RESULTS

The α-diversity analysis found that Simpson and Pielou evenness index was much higher in HCs than in the patients with MDD. The β-diversity of the two groups were differences by nonmetric multidimensional scaling analysis. Linear discriminant analysis effect size analysis identified 16 different strains. Bile acids detection showed that 23-nordeoxycholic acid in patients with MDD was significantly higher than in HCs, whereas taurolithocholic acid (TLCA), glycolithocholic acid (GLCA), and lithocholic acid 3-sulfate were significantly lower. Spearman correlation analysis showed that Turicibacteraceae, Turicibacterales, and Turicibacter were positively related with TLCA, GLCA, glycodeoxycholic acid (GDCA), and taurodeoxycholic acid, and were negatively correlated with HAMD score. At the same time, TLCA, GLCA, and GDCA were negatively correlated with HAMD score.

CONCLUSIONS

Gut microbiota and bile acids metabolism are disturbances in MDD, and there exists a correlation between gut microbiota and bile acids metabolism. Moreover, their interaction may be related to the pathophysiological mechanism of MDD.

Overlapping Mechanisms of Action of Brain-Active Bacteria and Bacterial Metabolites in the Pathogenesis of Common Brain Diseases

The involvement of the gut microbiota and the metabolites of colon-residing bacteria in brain disease pathogenesis has been covered in a growing number of studies, but comparative literature is scarce. To fill this gap, we explored the contribution of the microbiota–gut–brain axis to the pathophysiology of seven brain-related diseases (attention deficit hyperactivity disorder, autism spectrum disorder, schizophrenia, Alzheimer’s disease, Parkinson’s disease, major depressive disorder, and bipolar disorder). In this article, we discussed changes in bacterial abundance and the metabolic implications of these changes on disease development and progression. Our central findings indicate that, mechanistically, all seven diseases are associated with a leaky gut, neuroinflammation, and over-activated microglial cells, to which gut-residing bacteria and their metabolites are important contributors. Patients show a pro-inflammatory shift in their colon microbiota, harbouring more Gram-negative bacteria containing immune-triggering lipopolysaccharides (LPS) in their cell walls. In addition, bacteria with pro-inflammatory properties (Alistipes, Eggerthella, Flavonifractor) are found in higher abundances, whereas lower abundances of anti-inflammatory bacteria (Bifidobacterium, Coprococcus, Eucbacterium, Eubacterium rectale, Faecalibacterium, Faecalibacterium prasunitzii, Lactobacillus, Prevotella, Roseburia) are reported, when compared to healthy controls. On the metabolite level, aberrant levels of short-chain fatty acids (SCFAs) are involved in disease pathogenesis and are mostly found in lower quantities. Moreover, bacterial metabolites such as neurotransmitters (acetylcholine, dopamine, noradrenaline, GABA, glutamate, serotonin) or amino acids (phenylalanine, tryptophan) also play an important role. In the future, defined aberrations in the abundance of bacteria strains and altered bacterial metabolite levels could likely be possible markers for disease diagnostics and follow-ups. Moreover, they could help to identify novel treatment options, underlining the necessity for a deeper understanding of the microbiota–gut–brain axis.

Taxonomic and Metabolic Signatures of Gut Microbiota for Assessing the Severity of Depression and Anxiety in Major Depressive Disorder Patients

Major depressive disorder (MDD) is a heterogeneous mental disorder for which the precise assessment of symptom severity remains challenging. Studies have consistently found that the microbiota-gut-brain (MGB) axis is profoundly altered in MDD, but whether MGB-relevant clinical parameters are applicable to depression subphenotyping remains largely unexplored. In this prospective study, we assessed the taxonomic and metabolic signatures of fecal microbiota from 45 unmedicated MDD patients and explored their associations with the severity of depression and anxiety symptoms as measured by Hamilton depression scale-17 (HAMD-17) and Hamilton anxiety scale-14 (HAMA-14), respectively. The global microbial compositions of MDD patients with mild, moderate and severe symptoms were largely similar. Nevertheless, multiple discriminative bacterial taxa could be identified among the subgroups across the genus to species level. The abundance of fecal Streptococcus was highly correlated with both HAMD and HAMA scores. Patients with severe depression symptoms showed significantly higher abundance of Phascolarctobacterium and Akkermansia, while enrichment of Akkermansia, Coprococcus and Streptococcus were observed with severe anxiety symptoms. In addition, fecal microbial metabolite indole-3-carboxyaldehyde proved useful to discriminate the severity of depression or anxiety symptoms. Together, our results support the utility of microbial taxa and metabolites as potential MGB-based biomarker panel for stratifying the symptom severity of MDD patients.

Characteristics and Mediating Effect of Gut Microbiota With Experience of Childhood Maltreatment in Major Depressive Disorder

Gut microbiota and childhood maltreatment are closely related to depressive symptoms. This study aimed to analyze the characteristics of gut microbiota in major depressive disorder (MDD) patients with childhood maltreatment experience and explore the correlation between gut microbiota, childhood maltreatment, and depressive symptoms. A total of 37 healthy controls (HCs) and 53 patients with MDD were enrolled, including 18 MDD patients without childhood maltreatment experience and 35 MDD patients with childhood maltreatment experience. The Hamilton’s Depression Scale (HAMD-24) and Childhood Trauma Questionnaire-Short Form (CTQ-SF) were used to evaluate their depressive symptoms and childhood maltreatment experience, respectively. The composition of gut microbiota was evaluated using 16S rRNA sequencing. Spearman’s correlation analysis was used to evaluate the correlation between different gut microbiota, depressive symptoms and childhood maltreatment. The mediation analysis was used to evaluate the mediating effect of gut microbiota. In the α-diversity analysis, we found that the Simpson index and Pielou’s Evenness index differed significantly between MDD patients without childhood maltreatment experience and HCs. In the β-diversity analysis, principal coordinate analysis (PCoA) showed significant differences between MDD patients without childhood maltreatment experience, MDD patients with childhood maltreatment experience and HCs. Twenty-seven different bacteria were identified through Linear discriminant analysis effect size (LEfSe) analysis at different levels of classification. The analysis of the correlation showed that Blautia, Bifidobacterium, Bacteroides, Roseburia, and Phascolarctobacterium were significantly correlated with HAMD and CTQ-SF scores. The mediation analysis showed that childhood maltreatment had a significant direct effect on the patients’ depressive symptoms, and Blautia, Bifidobacterium, Roseburia had a significant mediating effect. The findings of this study suggested that MDD patients with childhood maltreatment experience had different gut microbiota, which might have a mediating effect on the influence of childhood maltreatment on depressive symptoms.

Fecal microbiota transplantation from patients with rheumatoid arthritis causes depression-like behaviors in mice through abnormal T cells activation

Depression is common in patients with rheumatoid arthritis (RA); however, the precise mechanisms underlying a link between depression and RA remain unclear. Accumulating evidence suggests the role of gut-microbiota-brain axis in depression. In this study, we investigated whether collagen-induced arthritis (CIA) mice produce depression-like behaviors and abnormal composition of gut microbiota. Furthermore, we investigated whether fecal microbiota transplantation (FMT) from RA patients causes depression-like phenotypes in antibiotic cocktail (ABX)-treated mice. CIA mice displayed depression-like behaviors, increased blood levels of pro-inflammatory cytokine interleukin-6 (IL-6), decreased expression of synaptic proteins in the prefrontal cortex (PFC), and abnormal composition of gut microbiota. Furthermore, FMT from RA patients caused depression-like phenotypes, alterations of gut microbiota composition, increased levels of IL-6 and tumor necrosis factor-α (TNF-α), and downregulation of synaptic proteins in the PFC compared to FMT from healthy controls. There were correlations between relative abundance of microbiota and plasma cytokines, expression of synaptic proteins in the PFC or depression-like behaviors. Interestingly, FMT from RA patients induced T cells differentiation in Peyer's patches and spleen. Reduced percentage of Treg cells with an increase of Th1/Th2 index was observed in the mice after FMT from RA patients. These findings suggest that CIA mice exhibit depression-like behaviors, systemic inflammation, and abnormal composition of gut microbiota, and that FMT from RA patients produces depression-like behaviors in ABX-treated mice via T cells differentiation. Therefore, abnormalities in gut microbiota in RA patients may contribute to depression via gut-microbiota-brain axis.

Fecal microbiota in pediatric depression and its relation to bowel habits

Although gut microbiota dysbiosis has been observed in the fecal samples of depressive adult patients, the detailed structure and composition of microbiota in pediatric depression remain unclear. To enhance our understanding of gut microbiota structure in depressive children, as well as the relationship between gut microbiota and bowel habits, we performed 16S rRNA sequencing to evaluate the gut microbial population in a cohort of 171 children (101 depressive patients and 70 controls) aged 12-18 years. Further analysis consisting of 30 drug-naive patients and 23 controls was performed to validate the results. Compared to controls, we found markedly decreased microbial richness and diversity, a distinct metagenomic composition with reduced short-chain fatty acid-producing bacteria (associated with healthy status), and overgrowth of bacteria such as Escherichia-Shigella and Flavonifractor in pediatric depression. Further analyses limited to drug-naive patients found similar results. Notably, we also observed that several taxa may be involved in the pathogenesis of disordered bowel habits in pediatric depression. Our findings suggest could inform future pediatric depression interventions specifically targeting the bacteria associated with bowel movements.

Role of the gut microbiome in three major psychiatric disorders

Major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia-spectrum disorders (SSD) are heterogeneous psychiatric disorders, which place significant burden on patient's well-being and global health. Disruptions in the gut-microbiome may play a role in these psychiatric disorders. This review presents current data on composition of the human gastrointestinal microbiota, and its interaction mechanisms in the gut-brain axis in MDD, BD and SSD. Diversity metrics and microbial relative abundance differed across studies. More studies reported inconsistent findings (n = 7) or no differences (n = 8) than studies who reported lower α-diversity in these psychiatric disorders (n = 5). The most consistent findings across studies were higher relative abundances of the genera Streptococcus, Lactobacillus, and Eggerthella and lower relative abundance of the butyrate producing Faecalibacterium in patients with psychiatric disorders. All three increased genera were associated with higher symptom severity. Confounders, such as medication use and life style have not been accounted for. So far, the results of probiotics trials have been inconsistent. Most traditional and widely used probiotics (consisting of Bifidobacterium spp. and Lactobacillus spp.) are safe, however, they do not correct potential microbiota disbalances in these disorders. Findings on prebiotics and faecal microbiota transplantation (FMT) are too limited to draw definitive conclusions. Disease-specific pro/prebiotic treatment or even FMT could be auspicious interventions for prevention and therapy for psychiatric disorders and should be investigated in future trials.

Resilience or susceptibility to traumatic stress: Potential influence of the microbiome

Exposure to traumatic stress is a major risk factor for development of neuropsychiatric disorders in a sub-population of individuals, while others remain resilient. The mechanisms and contributing factors differentiating between these phenotypes are still unclear. We hypothesize that inter-individual differences in the microbial composition and function contribute to host resilience or susceptibility to stress-induced psychopathologies. The current study aimed to characterize gut microbial community before and after exposure to traumatic stress in an animal model of PTSD. Sprague-Dawley male rats were randomly divided into unstressed controls and experimental group subjected to Single Prolonged Stress (SPS). After 14 days, behavioral analyses were performed using Open Field, Social Interaction and Elevated Plus Maze tests. Based on the anxiety measures, the SPS group was further subdivided into resilient (SPS-R) and susceptible (SPS–S) cohorts. The animals were sacrificed after the last behavioral test and cecum, colon, hippocampus, and medial prefrontal cortex were dissected. Prior to SPS and immediately after Open Field test, fecal samples were collected from each rat for 16S V3–V4 ribosomal DNA sequencing, whereas urine samples were collected before SPS, 90 min into immobilization and on the day of sacrifice to measure epinephrine and norepinephrine levels. Analyses of the fecal microbiota revealed significant differences in microbial communities and in their predictive functionality among the groups before and after SPS stressors. Before SPS, the SPS-S subgroup harbored microbiota with an overall pro-inflammatory phenotype, whereas SPS-R subgroup had microbiota with an overall anti-inflammatory phenotype, with predictive functional pathways enriched in carbohydrate and lipid metabolism and decreased in amino acid metabolism and neurodegenerative diseases. After SPS, the gut microbial communities and their predictive functionality shifted especially in SPS cohorts, with volatility at the genus level correlating inversely with Anxiety Index. In line with the alterations seen in the gut microbiota, the levels of cecal short chain fatty acids were also altered, with SPS-S subgroup having significantly lower levels of acetate, valerate and caproate. The levels of acetate inversely correlated with Anxiety Index. Interestingly, urinary epinephrine and norepinephrine levels were also higher in the SPS-S subgroup at baseline and during stress, indicative of an altered sympathoadrenal stress axis. Finally, shorter colon (marker of intestinal inflammation) and a lower claudin-5 protein expression (marker for increased blood brain barrier permeability) were observed in the SPS-S subgroup. Taken together, our results suggest microbiota is a potential factor in predisposing subjects either to stress susceptibility or resilience. Moreover, SPS triggered significant shifts in the gut microbiota, their metabolites and brain permeability. These findings could lead to new therapeutic directions for PTSD possibly through the controlled manipulation of gut microbiota. It may enable early identification of individuals more likely to develop prolonged anxiogenic symptoms following traumatic stress.

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Preexisting individual differences in microbiome relate to host's stress response.

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Shift in the microbial composition differs in SPS-R and SPS-S subgroups after SPS.

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Cecal levels of acetate in SPS subgroups correlate inversely with anxiety index.

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Basal and stress-induced urinary catecholamine levels are higher in SPS-S subgroup.

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SPS-S subgroup has shorter colon, less cecal SCFA and lower brain TJ protein.

The Gut Microbiome in Depression and Potential Benefit of Prebiotics, Probiotics and Synbiotics: A Systematic Review of Clinical Trials and Observational Studies

An emerging body of literature demonstrates differences in the gut microbiome (GMB) of patients with major depressive disorder (MDD) compared to healthy controls (HC), as well as the potential benefits of prebiotic, probiotic, and synbiotic treatment. We conducted a systematic review of 24 observational studies (n = 2817), and 19 interventional trials (n = 1119). We assessed alpha diversity, beta diversity, and taxa abundance changes in patients with MDD relative to HC, as well as the effect of prebiotics, probiotics, and synbiotics on depressive symptoms in individuals with clinical or subclinical depression. We observed no significant differences in alpha diversity but a significant difference in beta diversity between patients with MDD and HC. There were fluctuations in the abundance of specific taxa in patients with MDD relative to HC. Probiotic and synbiotic, but not prebiotic, treatment showed a modest benefit in reducing depressive symptoms in patients with MDD over four to nine weeks. The GMB profiles of patients with MDD differ significantly from HC, but further studies are needed to elucidate the benefits of prebiotic, probiotic and synbiotic treatments relative to antidepressants and over longer follow-up before these therapies are implemented into clinical practice.

Mechanistic Insights into the Link between Gut Dysbiosis and Major Depression: An Extensive Review

Depression is a highly common mental disorder, which is often multifactorial with sex, genetic, environmental, and/or psychological causes. Recent advancements in biomedical research have demonstrated a clear correlation between gut dysbiosis (GD) or gut microbial dysbiosis and the development of anxiety or depressive behaviors. The gut microbiome communicates with the brain through the neural, immune, and metabolic pathways, either directly (via vagal nerves) or indirectly (via gut- and microbial-derived metabolites as well as gut hormones and endocrine peptides, including peptide YY, pancreatic polypeptide, neuropeptide Y, cholecystokinin, corticotropin-releasing factor, glucagon-like peptide, oxytocin, and ghrelin). Maintaining healthy gut microbiota (GM) is now being recognized as important for brain health through the use of probiotics, prebiotics, synbiotics, fecal microbial transplantation (FMT), etc. A few approaches exert antidepressant effects via restoring GM and hypothalamus–pituitary–adrenal (HPA) axis functions. In this review, we have summarized the etiopathogenic link between gut dysbiosis and depression with preclinical and clinical evidence. In addition, we have collated information on the recent therapies and supplements, such as probiotics, prebiotics, short-chain fatty acids, and vitamin B12, omega-3 fatty acids, etc., which target the gut–brain axis (GBA) for the effective management of depressive behavior and anxiety.

Gut Microbiome Alterations Affect Glioma Development and Foxp3 Expression in Tumor Microenvironment in Mice

Glioma is the most common malignant tumor of the central nervous system (CNS), with high degree of malignancy and poor prognosis. The gut microbiome (GM) is composed of microorganisms with different properties and functions, which play an important role in human physiology and biological activities. It has been proved that GM can affect the development of glioma through natural immunity, but whether GM can affect glioma through adaptive immunity and whether there are some microorganisms in the GM that may affect glioma growth still remain unclear. In our study, we evaluated the relationship between GM and glioma. We proved that (I) glioma growth can induce structural changes of mouse GM, including the decreased abundance of Bacteroidia and increased abundance of Firmicutes. (II) GM dysbiosis can downregulate Foxp3 expression in the brain and promote glioma growth. A balanced environment of GM can upregulate the expression of Foxp3 in the brain and delay the development of glioma. (III) The increased abundance of Bacteroidia is associated with accelerated glioma progression, while its decreased abundance is associated with delayed glioma progression, which may be one of the key microorganisms affecting glioma growth. This study is helpful to reveal the relationship between GM and glioma development and provide new ideas for adjuvant therapy of glioma.

The Role of Gut Microbiota in Neuropsychiatric Diseases – Creation of An Atlas-Based on Quantified Evidence

There is a growing body of evidence highlighting the significant role of gut microbiota in various pathologies. We performed a systematic review to review the different microbiota involved in neuropsychiatric diseases. 50 studies (23 studies for autism spectrum disorders, 18 for major depression, and 9 for schizophrenia), representing 2,137 patients and 2,844 controls. Concerning the microbiota, the genera Prevotella, Clostridium, Bacteroides, Bifidobacterium, Ruminococcus, Megamonas, and Faecalbacterium were the ones detected with the most frequent variation of their relatives abundance. We also assess the overlap between the different pathologies. This study provides new insights into the complex relationship between the brain and the gut and the implications in neuropsychiatric pathologies. The identification of unique signatures in neuropsychiatric diseases suggests new possibilities in targeted anti or probiotic treatment.

Influence of dietary supplementation of short-chain fatty acid sodium propionate in people living with HIV (PLHIV)

BACKGROUND

Non-AIDS associated chronic diseases in HIV+ patients have been on the rise since the advent of antiretroviral therapy. Especially cardiovascular diseases and disruption in the gastrointestinal tract have limited health-related quality of life (QoL). Several of those complications have been associated with chronic systemic inflammation. Short chain fatty-acids (SCFA), with propionate as one of the major compounds, have been described as an important link between gut microbiota and the immune system, defining the pro- and the anti-inflammatory milieu through direct and indirect regulation of T-cell homeostasis. The effects of dietary supplementation of sodium propionate (SP) in people living with HIV (PLHIV) have not yet been investigated prior to this study.

OBJECTIVES

To investigate the impact of SP uptake among PLHIV and its relevance to improve QoL, the study aimed to investigate metabolic, immunological, microbiome and patient-reported QoL related changes post SP-supplementation with follow up.  METHODS: A prospective, non-randomized, controlled, monocentric interventional study was conducted in WIR, Center for Sexual Health and Medicine, in Bochum, Germany. 32 HIV+ patients with unaltered ART-regimen in the last three months were included. Participants were given SP for a duration of 12 weeks in the form of daily oral supplementation and were additionally followed-up for another 12 weeks.

RESULTS

The supplementation of SP was well tolerated. We found an improvement in lipid profiles and long-term blood glucose levels. A decrease in pro-inflammatory cytokines and a depletion of effector T-Cells was observed. Regulatory T-Cells and IL-10 decreased. Furthermore, changes in taxonomic composition of the microbiome during follow-up were observed and improvement of items of self-reported life-quality assessment.  CONCLUSION: Taken together, the beneficial impact of SP in PLHIV reflects its potential in improving metabolic parameters and modulating pro-inflammatory immune responses. Thus possibly reducing the risk of cardiovascular disorders and facilitating long-term improvement of the gut flora.

Gut Microbiome Composition Linked to Inflammatory Factors and Cognitive Functions in First-Episode, Drug-Naive Major Depressive Disorder Patients

Objective

The microbiota–gut–brain axis, especially the inflammatory pathway, may play a critical role in the pathogenesis of cognitive impairment in major depressive disorder (MDD). However, studies on the microbiota-inflammatory-cognitive function axis in MDD are lacking. The aim of the present study was to analyze the gut microbiota composition and explore the correlation between gut microbiota and inflammatory factors, cognitive function in MDD patients.

Method

Study participants included 66 first-episode, drug naïve MDD patients as well as 43 healthy subjects (HCs). The composition of fecal microbiota was evaluated using16S rRNA sequencing and bioinformatics analysis. The cytokines such as hs-CRP, IL-1β, IL-6, IL-10, and TNF-α in peripheral blood were detected via enzyme linked immunosorbent assay (ELISA); assessment of cognitive functions was performed using the Color Trail Test (CTT), The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and the Stroop Color-Word Test (SCWT).

Results

We found that compared with HCs, MDD patients had cognitive impairments and showed different α-diversity and β-diversity of gut microbiota composition. LDA effect size (LEfSe) analysis found MDD have higher Deinococcaceae and lower Bacteroidaceae, Turicibacteraceae, Clostridiaceae and Barnesiellaceae at family level. Deinococcus and Odoribacter was higher in the MDD group, however, Bacteroides, Alistipes, Turicibacter, Clostridium, Roseburia, and Enterobacter were lower at genus level. Furthermore, In MDD patients, the Bacteroidaceae and Bacteroides were both positively correlated with hsCRP, CCT1, CCT2. Alistipes was positively correlated with IL-6, Word time, Color time, Word-Color time, Color-Word time and negatively correlated with Delayed Memory, Total score and Standardized score. Turicibacteraceae and Turicibacter were both negatively correlated with IL-1β and IL-6.

Conclusion

The present findings confirm that the gut microbiota in MDD patients have altered gut microbes that are closely associated with inflammatory factors and cognitive function in MDD patients.

The Future Potential of Biosensors to Investigate the Gut-Brain Axis

The multifaceted and heterogeneous nature of depression presents challenges in pinpointing treatments. Among these contributions are the interconnections between the gut microbiome and neurological function termed the gut-brain axis. A diverse range of microbiome-produced metabolites interact with host signaling and metabolic pathways through this gut-brain axis relationship. Therefore, biosensor detection of gut metabolites offers the potential to quantify the microbiome's contributions to depression. Herein we review synthetic biology strategies to detect signals that indicate gut-brain axis dysregulation that may contribute to depression. We also highlight future challenges in developing living diagnostics of microbiome conditions influencing depression.

CUMS and dexamethasone induce depression-like phenotypes in mice by differentially altering gut microbiota and triggering macroglia activation

Background

Although the link between gut microbiota and depression has been suggested, changes of gut microbiota vary largely among individuals with depression.

Aims

Explore the heterogeneity of microbiota–gut–brain axis and new pathogenic characteristics in murine models of depression.

Methods

Adolescent female mice were randomly divided into control (CON) group (n=10), chronic unexpected mild stress (CUMS) group (n=15) and dexamethasone (DEX) group (n=15). Mice in the DEX group were gavaged twice a day with 0.2 mg/kg of DEX for 5 weeks, whereas CON mice were given the same amount of solvent. Mice in the CUMS group were exposed to stressors. After behavioural evaluations, all mice were sacrificed for harvesting tissues and blood samples. Enzyme-linked immunosorbent assay (ELISA) was conducted for measuring levels of corticosterone (CORT) and interleukin-1β (IL-1β) in sera, whereas levels of protein expression in colon and hippocampal tissues were examined by western blot. Faecal microbial communities were analysed by sequencing 16S rDNAs.

Results

Mice in CUMS and DEX groups exhibited severe depression-like behaviours. Compared with CON mice, CUMS-exposed mice showed a significant increase in both α and β diversity. Prevotellaceae and Desulfovibrio were enriched, whereas Bacilli were decreased in the faeces of mice in the CUMS group. DEX-treated mice had a decrease in the abundance of Clostridium XVIII. Levels of occludin in colon tissue of DEX-treated mice were reduced. Relative to mice in the CON and CUMS groups, DEX-treated mice contained higher serum levels of CORT and IL-1β. Compared with CON mice, mice in the DEX and CUMS groups had higher levels of IL-1β in sera and lower levels of glial fibrillary acidic protein (GFAP), Nestin, Synapsin-1 and P2Y12 receptor in the hippocampus.

Conclusions

Changes of gut microbiota diversity, intestinal integrity and neuroinflammation in the brain contribute to CUMS-induced depression, whereas pathobionts and excessive immunosuppression with damaged neuronal synapses is a basis of the DEX-induced depression.

Preoperative Status of Gut Microbiota Predicts Postoperative Delirium in Patients With Gastric Cancer

INTRODUCTION

Post-operative delirium (POD) is a serious complication which occurs after surgery, especially in the elderly undergoing abdominal surgery. Increasing evidence has revealed an association between the gut microbiota and psychological disorders involving the "brain-gut" axis. However, the association between the pathogenesis of POD after abdominal surgery in aging and composition of the gut microbiota remains unclear.

METHODS

Forty patients (≥65 years old) who underwent abdominal surgery were included in the study. Twenty patients had POD, whereas 20 patients did not. POD was diagnosed and assessed using the confusion assessment method (CAM) during the postoperative period. Total DNA fractions were extracted from all fecal samples of patients. 16S rRNA sequencing was performed to determine the composition of the gut microbiota. The quality of the samples was determined by calculating the α- and β-diversities.

RESULTS

The α- and β-diversities indicated that the samples were eligible for detection and comparison. We observed multiple differentially abundant bacteria in patients with and without POD. Generally, Proteobacteria, Enterbacteriaceae, Escherichia shigella, Klebsiella, Ruminococcus, Roseburia, Blautia, Holdemanella, Anaerostipes, Burkholderiaceae, Peptococcus, Lactobacillus, and Dorea were abundant in the POD cohort, whereas Streptococcus equinus and Blautia hominis were abundant in the control cohort. The results of receiver operating characteristic (ROC) curve analysis showed that the area under the curve (AUC) of Escherichia shigella was 0.75. Phenotype prediction showed that the gut microbiota may influence POD by altering the tolerance to oxidative stress.

CONCLUSION

There were significant associations between the pathogenesis of POD and composition of the gut microbiota. Escherichia shigella are promising diagnostic bacterial species for predicting POD onset after abdominal surgery in elderly people.

CLINICAL TRIAL REGISTRATION

http://www.chictr.org.cn/index.aspx, Chinese Clinical Trial Registry ChiCTR200030131.

Strategies for circadian rhythm disturbances and related psychiatric disorders: A new cue based on plant polysaccharides and intestinal microbiota

Circadian rhythm is essential to human physiological homeostasis and health. The oscillation of host circadian rhythm affects the composition and function of intestinal microbiota, meanwhile, the normal operation of host...

A systematic review of gut microbiota composition in observational studies of major depressive disorder, bipolar disorder and schizophrenia

The emerging understanding of gut microbiota as 'metabolic machinery' influencing many aspects of physiology has gained substantial attention in the field of psychiatry. This is largely due to the many overlapping pathophysiological mechanisms associated with both the potential functionality of the gut microbiota and the biological mechanisms thought to be underpinning mental disorders. In this systematic review, we synthesised the current literature investigating differences in gut microbiota composition in people with the major psychiatric disorders, major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ), compared to 'healthy' controls. We also explored gut microbiota composition across disorders in an attempt to elucidate potential commonalities in the microbial signatures associated with these mental disorders. Following the PRISMA guidelines, databases were searched from inception through to December 2021. We identified 44 studies (including a total of 2510 psychiatric cases and 2407 controls) that met inclusion criteria, of which 24 investigated gut microbiota composition in MDD, seven investigated gut microbiota composition in BD, and 15 investigated gut microbiota composition in SZ. Our syntheses provide no strong evidence for a difference in the number or distribution (α-diversity) of bacteria in those with a mental disorder compared to controls. However, studies were relatively consistent in reporting differences in overall community composition (β-diversity) in people with and without mental disorders. Our syntheses also identified specific bacterial taxa commonly associated with mental disorders, including lower levels of bacterial genera that produce short-chain fatty acids (e.g. butyrate), higher levels of lactic acid-producing bacteria, and higher levels of bacteria associated with glutamate and GABA metabolism. We also observed substantial heterogeneity across studies with regards to methodologies and reporting. Further prospective and experimental research using new tools and robust guidelines hold promise for improving our understanding of the role of the gut microbiota in mental and brain health and the development of interventions based on modification of gut microbiota.

The Role of the Gut Microbiota in the Development and Progression of Major Depressive and Bipolar Disorder

A growing number of studies in rodents indicate a connection between the intestinal microbiota and the brain, but comprehensive human data is scarce. Here, we systematically reviewed human studies examining the connection between the intestinal microbiota and major depressive and bipolar disorder. In this review we discuss various changes in bacterial abundance, particularly on low taxonomic levels, in terms of a connection with the pathophysiology of major depressive and bipolar disorder, their use as a diagnostic and treatment response parameter, their health-promoting potential, as well as novel adjunctive treatment options. The diversity of the intestinal microbiota is mostly decreased in depressed subjects. A consistent elevation of phylum Actinobacteria, family Bifidobacteriaceae, and genus Bacteroides, and a reduction of family Ruminococcaceae, genus Faecalibacterium, and genus Roseburia was reported. Probiotics containing Bifidobacterium and/or Lactobacillus spp. seemed to improve depressive symptoms, and novel approaches with different probiotics and synbiotics showed promising results. Comparing twin studies, we report here that already with an elevated risk of developing depression, microbial changes towards a “depression-like” microbiota were found. Overall, these findings highlight the importance of the microbiota and the necessity for a better understanding of its changes contributing to depressive symptoms, potentially leading to new approaches to alleviate depressive symptoms via alterations of the gut microbiota.

Metformin inhibits tumor growth and affects intestinal flora in diabetic tumor-bearing mice

Many studies have found that diabetes increases the risk of some cancers such as hepatocellular carcinoma. However, there are few studies on the relationship between the two diseases and their effects on intestinal flora. Therefore, we used streptozotocin and high-fat diet to establish a mouse model of type 2 diabetes, and then inoculated the Huh-7 hepatocellular carcinoma cells to obtain mouse diabetic tumor model. Mice inoculated with Huh-7 cells alone served as control. The tumor size in the diabetic tumor group was significantly higher than that in the tumor group. Our study also showed that the expression levels of inflammation-related factors (TNFα, IL-1β, IL-6, TLR4 and MCP1) in the diabetic tumor group were significantly higher than that in the tumor group. We found that metformin alleviated blood glucose level, reduced the expressions of inflammation-related factors and retarded xenograft tumor growth in the diabetic tumor group, but it couldn't reduce the tumor growth in the tumor group. Subsequent studies found that the content of some short chain fatty acids (SCFAs) including acetic acid, propionic acid and isobutyric acid decreased significantly in diabetic tumor group. Metformin increased short chain fatty acid levels (acetic acid, butyic acid and valeric acid) and enriched the abundance of SCFA-producing bacterial genera such as Ruminococcaceae, Clostridiales, Anaerovorax, Odoribacter and Marvinbryantia. In conclusion, type 2 diabetes could promote the growth of hepatoma cells in mice. Metformin could inhibit the growth of tumor under the condition of diabetes and play a role in the intestinal homeostasis in mice.

Perturbations in Gut Microbiota Composition in Psychiatric Disorders: A Review and Meta-analysis

Importance

Evidence of gut microbiota perturbations has accumulated for multiple psychiatric disorders, with microbiota signatures proposed as potential biomarkers. However, no attempts have been made to evaluate the specificity of these across the range of psychiatric conditions.

Objective

To conduct an umbrella and updated meta-analysis of gut microbiota alterations in general adult psychiatric populations and perform a within- and between-diagnostic comparison.

Data Sources

Cochrane Library, PubMed, PsycINFO, and Embase were searched up to February 2, 2021, for systematic reviews, meta-analyses, and original evidence.

Study Selection

A total of 59 case-control studies evaluating diversity or abundance of gut microbes in adult populations with major depressive disorder, bipolar disorder, psychosis and schizophrenia, anorexia nervosa, anxiety, obsessive compulsive disorder, posttraumatic stress disorder, or attention-deficit/hyperactivity disorder were included.

Data Extraction and Synthesis

Between-group comparisons of relative abundance of gut microbes and beta diversity indices were extracted and summarized qualitatively. Random-effects meta-analyses on standardized mean difference (SMD) were performed for alpha diversity indices.

Main Outcomes and Measures

Alpha and beta diversity and relative abundance of gut microbes.

Results

A total of 34 studies provided data and were included in alpha diversity meta-analyses (n = 1519 patients, n = 1429 control participants). Significant decrease in microbial richness in patients compared with control participants were found (observed species SMD = -0.26; 95% CI, -0.47 to -0.06; Chao1 SMD = -0.5; 95% CI, -0.79 to -0.21); however, this was consistently decreased only in bipolar disorder when individual diagnoses were examined. There was a small decrease in phylogenetic diversity (SMD = -0.24; 95% CI, -0.47 to -0.001) and no significant differences in Shannon and Simpson indices. Differences in beta diversity were consistently observed only for major depressive disorder and psychosis and schizophrenia. Regarding relative abundance, little evidence of disorder specificity was found. Instead, a transdiagnostic pattern of microbiota signatures was found. Depleted levels of Faecalibacterium and Coprococcus and enriched levels of Eggerthella were consistently shared between major depressive disorder, bipolar disorder, psychosis and schizophrenia, and anxiety, suggesting these disorders are characterized by a reduction of anti-inflammatory butyrate-producing bacteria, while pro-inflammatory genera are enriched. The confounding associations of region and medication were also evaluated.

Conclusions and Relevance

This systematic review and meta-analysis found that gut microbiota perturbations were associated with a transdiagnostic pattern with a depletion of certain anti-inflammatory butyrate-producing bacteria and an enrichment of pro-inflammatory bacteria in patients with depression, bipolar disorder, schizophrenia, and anxiety.

Gut Microbiota and Fecal Metabolites Associated With Neurocognitive Impairment in HIV-Infected Population

Gut microbiota dysbiosis has been associated with many neurological diseases. However, how microbiota composition and metabolism relate to neurocognitive impairment (NCI) in HIV-infected individuals is largely unknown. In this study, a total of 102 HIV infected participants were classified into two groups—those with NCI and those without—using the global deficit score (GDS). Fecal samples were collected from the participants for 16S rRNA gene sequencing and untargeted metabolomics. The plasma level of 25 hydroxy-vitamin D (25(OH)D) was also evaluated. Although α-diversity and β-diversity were comparable, the HIV patients with NCI were significantly different from those without NCI in terms of abundance of several gut microbiota. The decreased abundance of butyrate-producing bacteria (BPB) and increased abundance of Klebsiella were related with NCI and carotid intima-media thickness (CIMT). Significant differences in fecal metabolites were also found between individuals with versus without NCI, including increased bile acids and bioactive lipids, decreased vitamin D, terpenoids, and resolvin D1 in the NCI group. Furthermore, the perturbed metabolic profile was closely related to BPB and Klebsiella. In addition, a low level of vitamin D was associated with NCI and CIMT. Both fecal and plasma vitamin D were positively correlated with BPB. Our results show that BPB and Klebsiella and the associated metabolites are associated with NCI in people with HIV. In addition, vitamin D, both in feces and blood, was associated with NCI and BPB, suggesting a protective effect of vitamin D on NCI.

Faecal microbiota transplantation from patients with depression or healthy individuals into rats modulates mood-related behaviour

Differences in gut microbiota composition have been observed in patients with major depressive disorder (MDD) compared to healthy individuals. Here, we investigated if faecal microbiota transplantation (FMT) from patients with MDD into rats could induce a depressive-like phenotype. We performed FMT from patients with MDD (FMT-MDD) and healthy individuals (FMT-Healthy) into male Flinders Sensitive Line (FSL) and Flinders Resistant Line (FRL) rats and assessed depressive-like behaviour. No behavioural differences were observed in the FSL rats. In FRL rats, the FMT-Healthy group displayed significantly less depressive-like behaviour than the FMT-MDD group. However, there was no difference in behaviour between FMT-MDD FRL rats and negative controls, indicating that FMT-Healthy FRL rats received beneficial bacteria. We additionally found different taxa between the FMT-MDD and the FMT-Healthy FRL rats, which could be traced to the donors. Four taxa, three belonging to the family Ruminococcaceae and the genus Lachnospira, were significantly elevated in relative abundance in FMT-MDD rats, while the genus Coprococcus was depleted. In this study, the FMT-MDD group was different from the FMT-Healthy group based on behaviour and intestinal taxa.

Abnormalities of the composition of the gut microbiota and short-chain fatty acids in mice after splenectomy

The brain–gut–microbiota axis is a complex multi-organ bidirectional signaling system between the brain and microbiota that participates in the host immune system. The spleen, as the largest immune organ in the body, has a key role in the brain–gut–microbiota axis. Here, we investigated whether splenectomy could affect depression-like phenotypes and the composition of the gut microbiota in adult mice. In behavioral tests, splenectomy did not cause depression-like behaviors in mice. Conversely, splenectomy led to significant alterations in the diversity of gut microbes compared with the findings in control (no surgery) and sham-operated mice. In an unweighted UniFrac distance analysis, the boxplots representing the splenectomy group were distant from those representing the other two groups. We found differences in abundance for several bacteria in the splenectomy group at the taxonomic level compared with the other two groups. Finally, splenectomy induced significant changes in lactic acid and n-butyric acid levels compared with those in the other groups. Interestingly, there were significant correlations between the counts of certain bacteria and lactic acid (or n-butyric acid) levels in all groups. These data suggest that splenectomy leads to an abnormal composition of the gut microbiota. It is likely that the spleen–gut–microbiota axis plays a crucial role in the composition of the gut microbiota by regulating immune homeostasis.

Assessing the effect of interaction between C-reactive protein and gut microbiome on the risks of anxiety and depression

Cumulative evidence shows that gut microbiome can influence brain function and behavior via the inflammatory processes. However, the role of interaction between gut dysbiosis and C-reactive protein (CRP) in the development of anxiety and depression remains to be elucidated. In this study, a total of 3321 independent single nucleotide polymorphism (SNP) loci associated with gut microbiome were driven from genome-wide association study (GWAS). Using individual level genotype data from UK Biobank, we then calculated the polygenetic risk scoring (PRS) of 114 gut microbiome related traits. Moreover, regression analysis was conducted to evaluate the possible effect of interaction between gut microbiome and CRP on the risks of Patient Health Questionnaire-9 (PHQ-9) (N = 113,693) and Generalized Anxiety Disorder-7 (GAD-7) (N = 114,219). At last, 11 candidate CRP × gut microbiome interaction with suggestive significance was detected for PHQ-9 score, such as F_Ruminococcaceae (β = - 0.009, P = 2.2 × 10^-3), G_Akkermansia (β = - 0.008, P = 7.60 × 10^-3), F_Acidaminococcaceae (β = 0.008, P = 1.22 × 10^-2), G_Holdemanella (β = - 0.007, P = 1.39 × 10^-2) and O_Lactobacillales (β = 0.006, P = 1.79× 10^-2). 16 candidate CRP × gut microbiome interaction with suggestive significance was detected for GAD-7 score, such as O_Bacteroidales (β = 0.010, P = 4.00×  10^-4), O_Selenomonadales (β = - 0.010, P = 1.20 × 10^-3), O_Clostridiales (β = 0.009, P = 2.70 × 10^-3) and G_Holdemanella (β = - 0.008, P = 4.20 × 10^-3). Our results support the significant effect of interaction between CRP and gut microbiome on the risks of anxiety and depression, and identified several candidate gut microbiomes for them.

The association between serum microbial DNA composition and symptoms of depression and anxiety in mood disorders

There is increasing evidence supporting the association between gut microbiome composition and mood disorders; however, studies on the circulating microbiome are scarce. This study aimed to analyze the association of the serum microbial DNA composition with depressive and anxiety symptoms in patients with mood disorders. The sera of 69 patients with mood disorders, aged from 19 to 60, were analyzed. Bacterial DNA was isolated from extracellular membrane vesicles and, subsequently, amplified and quantified with specific primers for the V3-V4 hypervariable region of the 16S rDNA gene. Sequence reads were clustered into Operational Taxonomic Units and classified using the SILVA database. There were no significant associations between alpha diversity measures and the total Hamilton depression rating scale (HAM-D) or Beck anxiety inventory (BAI) scores. Only the weighted UniFrac distance was associated with the total HAM-D score (F = 1.57, p = 0.045). The Bacteroidaceae family and Bacteroides genus were negatively associated with the total HAM-D score (β =  - 0.016, p < 0.001, q = 0.08 and β =  - 0.016, p < 0.001, q = 0.15, respectively). The Desulfovibrionaceae family and Clostridiales Family XIII were positively associated with the total BAI score (β = 1.8 × 10-3, p < 0.001, q = 0.04 and β = 1.3 × 10-3, p < 0.001, q = 0.24, respectively). Further studies with larger sample sizes and longitudinal designs are warranted.