Impact of Inosine on Chronic Unpredictable Mild Stress-Induced Depressive and Anxiety-Like Behaviors With the Alteration of Gut Microbiota

Dorsal CA3 overactivation mediates witnessing stress-induced recognition memory deficits in adolescent male mice

Witnessing violent or traumatic events is common during childhood and adolescence and could cause detrimental effects such as increased risks of psychiatric disorders. This stressor could be modeled in adolescent laboratory animals using the chronic witnessing social defeat (CWSD) paradigm, but the behavioral consequences of CWSD in adolescent animals remain to be validated for cognitive, anxiety-like, and depression-like behaviors and, more importantly, the underlying neural mechanisms remain to be uncovered. In this study, we first established the CWSD model in adolescent male mice and found that CWSD impaired cognitive function and increased anxiety levels and that these behavioral deficits persisted into adulthood. Based on the dorsal-ventral functional division in hippocampus, we employed immediate early gene c-fos immunostaining after behavioral tasks and found that CWSD-induced cognition deficits were associated with dorsal CA3 overactivation and anxiety-like behaviors were associated with ventral CA3 activity reduction. Indeed, chemogenetic activation and inhibition of dorsal CA3 neurons mimicked and reversed CWSD-induced recognition memory deficits (not anxiety-like behaviors), respectively, whereas both inhibition and activation of ventral CA3 neurons increased anxiety-like behaviors in adolescent mice. Finally, chronic administration of vortioxetine (a novel multimodal antidepressant) successfully restored the overactivation of dorsal CA3 neurons and the cognitive deficits in CWSD mice. Together, our findings suggest that dorsal CA3 overactivation mediates CWSD-induced recognition memory deficits in adolescent male mice, shedding light on the pathophysiology of adolescent CWSD-induced adverse effects and providing preclinical evidence for early treatment of stress-induced cognitive deficits.

Christensenella minuta mitigates behavioral and cardiometabolic hallmarks of social defeat stress

Psychological stress during early development and adolescence may increase the risk of psychiatric and cardiometabolic comorbidities in adulthood. The gut microbiota has been associated with mental health problems such as depression and anxiety and with cardiometabolic disease, but the potential role of the gut microbiota in their comorbidity is not well understood. We investigated the effects and mode of action of the intestinal bacterium Christensenella minuta DSM 32891 on stress-induced mental health and cardiometabolic disturbances in a mouse model of social defeat stress. We demonstrate that administered C. minuta alleviates chronic stress-induced depressive, anxiogenic and antisocial behavior. These effects are attributed to the bacterium's ability to modulate the hypothalamic-pituitary-adrenal axis, which mediates the stress response. This included the oversecretion of corticosterone and the overexpression of its receptors, as well as the metabolism of dopamine (DA) and the expression of its receptors (D1, D2L and D2S). Additionally, C. minuta administration reduced chronically induced inflammation in plasma, spleen and some brain areas, which likely contribute to the recovery of physical and behavioral function. Furthermore, C. minuta administration prevented chronic stress-induced cardiovascular damage by regulating key enzymes mediating liver fibrosis and oxidative stress. Finally, C. minuta increased the abundance of bacteria associated with mental health. Overall, our study highlights the potential of microbiota-directed interventions to alleviate both the physical and mental effects of chronic stress.

Treatment response of venlafaxine induced alterations of gut microbiota and metabolites in a mouse model of depression

Antidepressants remain the first-line treatment for depression. However, the factors influencing medication response are still unclear. Accumulating evidence implicates an association between alterations in gut microbiota and antidepressant response. Therefore, the aim of this study is to investigate the role of the gut microbiota-brain axis in the treatment response of venlafaxine. After chronic social defeat stress and venlafaxine treatment, mice were divided into responders and non-responders groups. We compared the composition of gut microbiota using 16 S ribosomal RNA sequencing. Meanwhile, we quantified metabolomic alterations in serum and hippocampus, as well as hippocampal neurotransmitter levels using liquid chromatography-mass spectrometry. We found that the abundances of 29 amplicon sequence variants (ASVs) were significantly altered between the responders and non-responders groups. These ASVs belonged to 8 different families, particularly Muribaculaceae. Additionally, we identified 38 and 39 differential metabolites in serum and hippocampus between the responders and non-responders groups, respectively. Lipid, amino acid, and purine metabolisms were enriched in both serum and hippocampus. In hippocampus, the concentrations of tryptophan, phenylalanine, gamma-aminobutyric acid, glutamic acid, and glutamine were increased, while the level of succinic acid was decreased in the responders group, compared with the non-responders group. Our findings suggest that the gut microbiota may play a role in the antidepressant effect of venlafaxine by modulating metabolic processes in the central and peripheral tissues. This provides a novel microbial and metabolic framework for understanding the impact of the gut microbiota-brain axis on antidepressant response.

Inosine pretreatment of pregnant rats ameliorates maternal inflammation-mediated hypomyelination in pups via microglia polarization switch

Periventricular leukomalacia (PVL) is a neurological condition observed in premature infants, characterized by hypomyelination and activation of microglia. Maternal inflammation-induced brain injury in offspring significantly contributes to the development of PVL. Currently, there are no clinical pharmaceutical interventions available for pregnant women to prevent maternal inflammation-mediated brain injury in their offspring. Inosine has been shown to modulate the immune response in diverse stressful circumstances, such as injury, ischemia, and inflammation. The aim of this investigation was to examine the potential prophylactic impact of inosine on offspring PVL induced by maternal inflammation. This was accomplished by administering a 1 mg/ml inosine solution (40 ml daily) to pregnant Sprague-Dawley (SD) rats for 16 consecutive days prior to their intraperitoneal injection of lipopolysaccharide (350 µg/kg, once a day, for two days). The results showed that maternal inosine pretreatment significantly reversed the reduction in MBP and CNPase (myelin-related markers), CC-1 and Olig2 (oligodendrocyte-related markers) in their PVL pups (P7), suggesting that inosine administration during pregnancy could improve hypomyelination and enhance the differentiation of oligodendrocyte precursor cells (OPCs) in their PVL pups. Furthermore, the protective mechanism of inosine against PVL is closely associated with the activation and polarization of microglia. This is evidenced by a notable reduction in the quantity of IBA 1-positive microglia, a decrease in the level of CD86 (a marker for M1 microglia), an increase in the level of Arg 1 (a marker for M2 microglia), as well as a decrease in the level of pro-inflammatory factors TNF-α, IL-1β, and IL-6, and an increase in the level of anti-inflammatory factors IL-4 and IL-10 in the brain of PVL pups following maternal inosine pretreatment. Taken together, inosine pretreatment of pregnant rats can improve hypomyelination in their PVL offspring by triggering the M1/M2 switch of microglia.

Differential effect of chronic mild stress on anxiety and depressive-like behaviors in three strains of male and female laboratory mice

Major depressive disorder is the most common psychiatric disorder worldwide. To understand mechanisms and search for new approaches to treating depression, animal models are crucial. Chronic mild stress (CMS) is the most used animal model of depression. Although CMS is considered a robust model of depression, conflicting results have been reported for emotion-related behaviors, which the intrinsic characteristics of each rodent strain could explain. To further shed light on the impact of genetic background on the relevant parameters commonly addressed in depression, we examined the effect of 4-weeks CMS on anxiety and depression-related behaviors and body weight gain in three strain mice (BALB/c, C57BL/6, and CD1) of both sexes. CMS reduced body weight gain in C57BL/6NCrl and CD1 male mice. C57BL/6 animals exhibited a more pronounced anxious-like behavior than CD1 and BALB/c mice in the light-dark box (LDB) and the elevated plus maze (EPM) tests, whereas BALB/c animals exhibited the more robust depressive-like phenotype in the splash test (ST), tail suspension test (TST) and forced-swimming test (FST). Under CMS, exposure did not affect anxiety-related behaviors in any strain but induced depression-like behaviors strain-dependently. CMS C57BL/6 and CD1 mice of both sexes showed depression-like behaviors, and CMS BALB/c male mice exhibited reduced depressive behaviors in the FST. These results suggest a differential effect of stress, with the C57BL/6 strain being more vulnerable to stress than the CD1 and BALB/c strain mice. Furthermore, our findings emphasize the need for researchers to consider mouse strains and behavioral tests in their CMS experimental designs.

The gut microbiota regulates the depressive-type behaviors and inflammatory processes after severe burn injuries in mice

An emerging number of studies have recently revealed the correlation between burn injuries and psychological disorders. Gut microbiota and inflammatory factors may play a vital role in this process. Nevertheless, there are few studies conducted to disclose the potential mechanism of the gut microbiota between depression and burn injuries. In this study, we constructed a burn model of C57BL/6 mice, which showed that the symptom of depression became more and more severe with the burn of mice lasted longer. Meanwhile, there are significant differences of composition of gut microbiota among mice before and after burn. Then, we tested the inflammatory factors in the brain and peripheral blood, which showed an increased expression of Iba1, VWF, TNF-α and IL-6, and a decreased expression of IL-10 in burn mice. In addition, the expression of zonula occludens-1 (ZO-1) in cecum showed a down-regulation in burn mice, which indicated impaired intestinal barrier function. Lastly, the crossing fecal microbiota transplantation (FMT) and cohousing experiment were conducted to determine the functions of cross-transplantation of fecal microbiota on the depressive-type behaviours in burned mice. According to the score of Tail suspension test (TST), the burn mice were divided into two groups: Resilient mice (no-depressed mice) and Abnormal mice (depressed mice). After abnormal mice were transplanted with fecal microbiota of resilient mice, the symptom of depression was improved, and the expression of TNF-α, IL-6 and IL-10 return to normal levels (P < 0.05). On the contrary, after resilient mice were transplanted with fecal microbiota of abnormal mice both the TST scores and inflammatory factor developed depressive-type changes. In conclusion, our study demonstrated the changes of gut microbiota and inflammatory factors in depressed burn mice and non-depressed burn mice. The gut microbiota dysbiosis could impaired intestinal barrier function and lead to neuroinflammation, and this phenomenon could be significantly mitigated by FMT.

Regulation of miRNA expression in the prefrontal cortex by fecal microbiota transplantation in anxiety-like mice

Background

The gut-brain axis and gut microbiota have emerged as key players in emotional disorders. Recent studies suggest that alterations in gut microbiota may impact psychiatric symptoms through brain miRNA along the gut-brain axis. However, direct evidence linking gut microbiota to the pathophysiology of generalized anxiety disorder (GAD) via brain miRNA is limited. In this study, we explored the effects of fecal microbiota transplantation (FMT) from GAD donors on gut microbiota and prefrontal cortex miRNA in recipient mice, aiming to understand the relationship between these two factors.

Methods

Anxiety scores and gut microbiota composition were assessed in GAD patients, and their fecal samples were utilized for FMT in C57BL/6J mice. Anxiety-like behavior in mice was evaluated using open field and elevated plus maze tests. High-throughput sequencing of gut microbiota 16S rRNA and prefrontal cortex miRNA was performed.

Results

The fecal microbiota of GAD patients exhibited a distinct microbial structure compared to the healthy group, characterized by a significant decrease in Verrucomicrobia and Akkermansia, and a significant increase in Actinobacteria and Bacteroides. Subsequent FMT from GAD patients to mice induced anxiety-like behavior in recipients. Detailed analysis of gut microbiota composition revealed lower abundances of Verrucomicrobia, Akkermansia, Bifidobacterium, and Butyricimonas, and higher abundances of Deferribacteres, Allobaculum, Bacteroides, and Clostridium in mice that received FMT from GAD patients. MiRNA analysis identified five key miRNAs affecting GAD pathogenesis, including mmu-miR-10a-5p, mmu-miR-1224-5p, mmu-miR-218-5p, mmu-miR-10b-5p, and mmu-miR-488-3p. Notably, mmu-miR-488-3p showed a strong negative correlation with Verrucomicrobia and Akkermansia.

Conclusion

This study demonstrates that anxiety-like behavior induced by human FMT can be transmitted through gut microbiota and is associated with miRNA expression in the prefrontal cortex. It is inferred that the reduction of Akkermansia caused by FMT from GAD patients leads to the upregulation of mmu-miR-488-3p expression, resulting in the downregulation of its downstream target gene Creb1 and interference with its related signaling pathway. These findings highlight the gut microbiota's crucial role in the GAD pathophysiology.

Choline metabolism in regulating inflammatory bowel disease-linked anxiety disorders: A multi-omics exploration of the gut-brain axis

Anxiety and depression caused by inflammatory bowel disease (IBD) negatively affect the mental health of patients. Emerging studies have demonstrated that the gut-brain axis (GBA) mediates IBD-induced mood disorders, but the underlying mechanisms of these findings remain unknown. Therefore, it's vital to conduct comprehensive research on the GBA in IBD. Multi-omics studies can provide an understanding of the pathological mechanisms of the GBA in the development of IBD, helping to uncover the mechanisms underlying the onset and progression of the disease. Thus, we analyzed the prefrontal cortex (PFC) of Dextran Sulfate Sodium Salt (DSS)-induced IBD mice using transcriptomics and metabolomics. We observed increased mRNA related to acetylcholine synthesis and secretion, along with decreased phosphatidylcholine (PC) levels in the PFC of DSS group compared to the control group. Fecal metagenomics also revealed abnormalities in the microbiome and lipid metabolism in the DSS group. Since both acetylcholine and PC are choline metabolites, we posited that the DSS group may experience choline deficiency and choline metabolism disorders. Subsequently, when we supplemented CDP-choline, IBD mice exhibited improvements, including decreased anxiety-like behaviors, reduced PC degradation, and increased acetylcholine synthesis in the PFC. In addition, administration of CDP-choline can restore imbalances in the gut microbiome and disruptions in lipid metabolism caused by DSS treatment. This study provides compelling evidence to suggest that choline metabolism plays a crucial role in the development and treatment of mood disorders in IBD. Choline and its metabolites appear to have a significant role in maintaining the stability of the GBA.

Dietary inulin alleviated constipation induced depression and anxiety-like behaviors: Involvement of gut microbiota and microbial metabolite short-chain fatty acid

Chronic constipation has been associated with depression-like behavior. Previous study identified the crucial role of gut microbiota in the development of constipation and depression. Dietary inulin (INU) could regulate gut microbiota. Whether INU treatment could ameliorate constipation induced depression was not clear. For this purpose, male CD-1 mice were administered diphenoxylate (20 mg/kg body weight/day) to induce constipation. We found that INU (10 % in standard diet) alleviated the diphenoxylate-induced constipation, manifested as the increase weight and moisture content of feces. Furthermore, the associated depression and anxiety-like behavior disorders were improved by inhibiting neuro-inflammation and preventing synaptic ultrastructure damage under INU treatment. Moreover, INU pretreatment improved the diphenoxylate-induced gut barrier damage by upregulating tight junction protein expression. INU also reshaped gut microbiota in constipation mice by increasing the relative abundance of Bacteroides and Proteobacteria and downregulating the abundance of Muribacalum and Melaminabacteria. The effects of INU on diphenoxylate-induced depression were abolished by gut microbiota depletion via antibiotic treatment. In addition, INU increased the concentration of short chain fatty acids (SCFAs) in feces contents. Meanwhile, supplementation of SCFAs could also partly improve diphenoxylate-induced depression. In conclusion, INU intake was a potential nutritional intervention strategy to prevent constipation induced depression via microbiota-gut-SCFAs axis.

Analysis of the Efficacy of Diet and Short-Term Probiotic Intervention on Depressive Symptoms in Patients after Bariatric Surgery: A Randomized Double-Blind Placebo Controlled Pilot Study

(1) Background: studies have shown that some patients experience mental deterioration after bariatric surgery. (2) Methods: We examined whether the use of probiotics and improved eating habits can improve the mental health of people who suffered from mood disorders after bariatric surgery. We also analyzed patients' mental states, eating habits and microbiota. (3) Results: Depressive symptoms were observed in 45% of 200 bariatric patients. After 5 weeks, we noted an improvement in patients' mental functioning (reduction in BDI and HRSD), but it was not related to the probiotic used. The consumption of vegetables and whole grain cereals increased (DQI-I adequacy), the consumption of simple sugars and SFA decreased (moderation DQI-I), and the consumption of monounsaturated fatty acids increased it. In the feces of patients after RYGB, there was a significantly higher abundance of two members of the Muribaculaceae family, namely Veillonella and Roseburia, while those after SG had more Christensenellaceae R-7 group, Subdoligranulum, Oscillibacter, and UCG-005. (4) Conclusions: the noted differences in the composition of the gut microbiota (RYGB vs. SG) may be one of the determinants of the proper functioning of the gut-brain microbiota axis, although there is currently a need for further research into this topic using a larger group of patients and different probiotic doses.

rTMS ameliorates depressive-like behaviors and regulates the gut microbiome and medium- and long-chain fatty acids in mice exposed to chronic unpredictable mild stress

INTRODUCTION

Repetitive transcranial magnetic stimulation (rTMS) is a clinically useful therapy for depression. However, the effects of rTMS on the metabolism of fatty acids (FAs) and the composition of gut microbiota in depression are not well established.

METHODS

Mice received rTMS (15 Hz, 1.26 T) for seven consecutive days after exposure to chronic unpredictable mild stress (CUMS). The subsequent depressive-like behaviors, the composition of gut microbiota of stool samples, as well as medium- and long-chain fatty acids (MLCFAs) in the plasma, prefrontal cortex (PFC), and hippocampus (HPC) were evaluated.

RESULTS

CUMS induced remarkable changes in gut microbiotas and fatty acids, specifically in community diversity of gut microbiotas and PUFAs in the brain. 15 Hz rTMS treatment alleviates depressive-like behaviors and partially normalized CUMS induced alterations of microbiotas and MLCFAs, especially the abundance of Cyanobacteria, Actinobacteriota, and levels of polyunsaturated fatty acids (PUFAs) in the hippocampus and PFC.

CONCLUSION

These findings revealed that the modulation of gut microbiotas and PUFAs metabolism might partly contribute to the antidepressant effect of rTMS.

Disordered gut microbiota and changes in short-chain fatty acids and inflammatory processes in stress-vulnerable mice

Long-term exposure to chronic stress increases the incidence of depression. However, chronic stress is an associated risk factor in only a subset of individuals. Inflammation has been identified as a putative mechanism promoting stress vulnerability. Because of the gut microbiota's potential role as a source of inflammatory substances, short-chain fatty acids (SCFAs) may exert their influence on inflammation, emotional states, and cognition via the gut-brain axis. In this study, Classic behavioral tests were used to categorize C57BL/6 J mice into a CUMS-vulnerable and a CUMS-resilient group after they were exposed to chronic unpredictable mild stress (CUMS). We compared the 16S ribosomal RNA (rRNA) gene sequences retrieved from fecal samples between control, CUMS-vulnerable, and CUMS-resilient mice. SCFAs in fecal samples were detected by liquid chromatography and gas chromatography-mass spectrometry. Hippocampal cytokine production and TLR4/MYD88/NF-κB inflammatory pathway activation were evaluated using enzyme-linked immunosorbent assays (ELISAs) and western blotting. Then, we supplemented SCFAs in CUMS mice. we observed depression-like behavior and the expression of TLR4/MYD88/NF-κB inflammatory pathway in hippocampus of SCFAs supplementation mice. Susceptible mice to CUMS showed more severe symptoms of depression and anxiety, α diversity was significantly different, as well as higher expression of interleukin (IL)-1β and TLR4/MYD88/NF-κB inflammatory pathway components in the hippocampus. SCFA levels in the feces were significantly higher in CUMS-resilient mice than in control mice. Depressive behavior was reversed in CUMS-SCFAs group, and the protein level of TLR4/MYD88/NF-κB in hippocampus was decreased. Overall, these results provide new light on the possible involvement of the microbiome in the gut-brain axis development in depressive disorder and provide a theoretical basis for identifying novel therapeutic targets.

The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective

The physiological consequences of stress often manifest in the gastrointestinal tract. Traumatic or chronic stress is associated with widespread maladaptive changes throughout the gut, although comparatively little is known about the effects of acute stress. Furthermore, these stress-induced changes in the gut may increase susceptibility to gastrointestinal disorders and infection, and impact critical features of the neural and behavioural consequences of the stress response by impairing gut-brain axis communication. Understanding the mechanisms behind changes in enteric nervous system circuitry, visceral sensitivity, gut barrier function, permeability, and the gut microbiota following stress is an important research objective with pathophysiological implications in both neurogastroenterology and psychiatry. Moreover, the gut microbiota has emerged as a key aspect of physiology sensitive to the effects of stress. In this review, we focus on different aspects of the gastrointestinal tract including gut barrier function as well as the immune, humoral and neuronal elements involved in gut-brain communication. Furthermore, we discuss the evidence for a role of stress in gastrointestinal disorders. Existing gaps in the current literature are highlighted, and possible avenues for future research with an integrated physiological perspective have been suggested. A more complete understanding of the spatial and temporal dynamics of the integrated host and microbial response to different kinds of stressors in the gastrointestinal tract will enable full exploitation of the diagnostic and therapeutic potential in the fast-evolving field of host-microbiome interactions.

Intergenerational association of gut microbiota and metabolism with perinatal folate metabolism and neural tube defects

Disorders of folic acid metabolism during pregnancy lead to fetal neural tube defects (NTDs). However, the mechanisms still require further investigation. Here, we aim to analyze the brain metabolic profiles of 30 NTDs and 30 healthy fetuses. Our results indicated that low-folate diet during early life played a causal role in cerebral metabolism, especially in lipometabolic disturbance, highlighting the importance of folate in modulating brain development and metabolism. Next, we established a mouse model of NTDs. Interestingly, the differential metabolites are mainly involved in glycerophospholipid metabolism and biosynthesis of unsaturated fatty acids both in human and mice fetal brain. Since intestinal microbes could critically regulate neurofunction via the intestinal-brain axis, we further found the abundances of Firmicutes and Bacteroidetes in the gut of pregnant mice were correlated with the abundances of lipid metabolism related metabolites in the fetal brain. This finding probably reflects the intergenerational microbial-metabolism biomarkers of NTDs.

Disturbances of purine and lipid metabolism in the microbiota-gut-brain axis in male adolescent nonhuman primates with depressive-like behaviors

INTRODUCTION

Major depressive disorder (MDD) in adolescents is a widespread and growing global public health concern with unique characteristics and pathophysiological mechanisms that are distinct from MDD in adults.

OBJECTIVE

The purpose of our work was to address this knowledge gap about the unique characteristics and pathophysiological mechanisms of adolescent depression from a microbiota-gut-brain (MGB) axis perspective.

METHOD

Ten healthy male cynomolgus macaques (Macaca fascicularis) were paired into five pairs based on age and body weight, and two cynomolgus macaques from each pair were randomly allocated to chronic unpredictable mild stress group, or unstressed control group. At endpoint, microbe composition from cecum, ascending colon, transverse colon, and descending colon were analyzed by metagenome sequencing, and the metabolite profiles of MGB axis including central (prefrontal cortex, hippocampus and amygdala) and peripheral (plasma, gut and feces of cecum, ascending colon, transverse colon and descending colon) samples were analyzed by metabolomic profiling. Then, we compare the gut microbiome and metabolic signatures in MGB axis between adolescent and adult depressed macaques.

RESULTS

The microbial composition and gut-brain metabolic signatures were widely divergent between adolescent and adult depressed macaques, though the phylum Firmicutes and lipid metabolism pathways were persistently altered in both populations. Purine and arginine biosynthesis metabolism were a specific hallmark of adolescent depressed macaques, while fatty acyl metabolism was specially altered in adult. These differential metabolic pathways in adolescent and adult depressed macaques were mainly mapped into the prefrontal cortex and hippocampus, respectively. Notably, the genus Clostridium and Haemophilus, characteristically disturbed in adolescent depressed macaques but not in adult, were also significantly associated with the majority of purine metabolites in MGB axis.

CONCLUSION

These findings provide a new framework describing divergent pathophysiological mechanisms between adolescent and adult depression, and may open new windows for more effective treatment strategies of adolescent depression.

Protective Effects of Kefir Against Unpredictable Chronic Stress Alterations in Mice Central Nervous System, Heart, and Kidney

Kefir is a probiotic mixture with anxiolytic and antioxidant properties. Chronic stress can lead to anxiety disorders and increase oxidative damage in organs such as the heart and kidney. In this study, we examined whether kefir ameliorates the anxiety-like behavior of mice submitted to chronic unpredictable stress (CUS) by modulating brain-derived neurotrophic factor (BDNF) and corticosterone levels and whether kefir modifies the oxidative parameters in the heart and kidney of mice. Male Swiss mice received kefir (0.3 mL/100 g/day) or milk for 30 days (gavage). On the 10th day, the mice were submitted to CUS. Behavioral analysis was performed using the elevated plus maze and forced swimming tests. BDNF levels were analyzed in brain tissues. Heart and kidney superoxide dismutase (SOD), catalase, glutathione (GSH), thiobarbituric acid reactive substances (TBARS), 3-nitrotyrosine, metalloproteinase-2 (MMP-2), and plasma corticosterone were evaluated. Kefir reverted the CUS-induced decrease in the time spent in the open arms, the increase in grooming frequency, and decrease in the head dipping frequency, but not the reduced immobility time. CUS decreased the cerebellum BDNF levels and increased corticosterone levels, which were restored by Kefir. Neither catalase and SOD activities nor GSH, TBARS, 3-nitrotyrosine, and MMP-2 were modified by CUS in the heart. In the kidney, CUS increased 3-nitrotyrosine and MMP-2. Kefir increased the antioxidant defense in the heart and kidney of control and CUS mice. These results suggest that kefir ameliorated CUS-induced anxiety-like behavior by modulating brain BDNF and corticosterone levels. Kefir also increased the antioxidant defense of mice heart and kidney.

Microplastic-induced gut microbiota and serum metabolic disruption in Sprague-Dawley rats

Toxic effects of exposure to microplastics (MPs) on living organisms and humans have attracted global concern. However, most previous studies exposed animals to only one type of MP (mainly polystyrene) to assess the health risk of MPs for animals. Therefore, we conducted a laboratory gavage experiment on rats based on the types and concentration of MPs to which humans are exposed in their daily life. The purpose of this study is to use Sprague-Dawley (SD) rat models to assess the potential health risks in mammals from co-exposure to various MPs. In the present study, SD rats were exposed to 12 mg/kg bw/day mixed-MPs (containing 10 types of MPs) for 42 days, and then examined the alteration of gut microbes and serum metabolites. The results showed that 6 gut microbes at the family level (f_Muribaculaceae, f_Oscillospiraceae, f_Bacteroidaceae, f_Neisseriaceae, f_Prevotellaceae, and f_Veillonellaceae) were significantly perturbed (t-test, p < 0.05) in rats after MP exposure. After MP intervention, 47 metabolites significantly regulated in SD rat serum, mainly including lipids and lipid-like molecules (e.g., fatty acids), organic acids and derivatives (e.g., phosphoric acids), and isoflavonoids (e.g., daidzein). These findings contribute to assessing the health risks of various MP co-exposure in mammals in the actual environment and provide a novel insight into the toxicity mechanism of MPs.

Cuscutae semen alleviates CUS-induced depression-like behaviors in mice via the gut microbiota-neuroinflammation axis

Introduction: Major depressive disorder is a mental disease with complex pathogenesis and treatment mechanisms involving changes in both the gut microbiota and neuroinflammation. Cuscutae Semen (CS), also known as Chinese Dodder seed, is a medicinal herb that exerts several pharmacological effects. These include neuroprotection, anti-neuroinflammation, the repair of synaptic damage, and the alleviation of oxidative stress. However, whether CuscutaeSemen exerts an antidepressant effect remains unknown. Methods: In this study, we evaluated the effect of CS on chronic unpredictable stress (CUS)-induced depression-like behaviors in mice by observing changes in several inflammatory markers, including proinflammatory cytokines, inflammatory proteins, and gliocyte activation. Meanwhile, changes in the gut microbiota were analyzed based on 16 S rRNA sequencing results. Moreover, the effect of CS on the synaptic ultrastructure was detected by transmission electron microscopy. Results: We found that the CS extract was rich in chlorogenic acid and hypericin. And CS relieved depression-like behaviors in mice exposed to CUS. Increased levels of cytokines (IL-1β and TNF-α) and inflammatory proteins (NLRP3, NF-κB, and COX-2) induced by CUS were reversed after CS administration. The number of astrocytes and microglia increased after CUS exposure, whereas they decreased after CS treatment. Meanwhile, CS could change the structure of the gut microbiota and increase the relative abundance of Lactobacillus. Moreover, there was a significant relationship between several Lactobacilli and indicators of depression-like behaviors and inflammation. There was a decrease in postsynaptic density after exposure to CUS, and this change was alleviated after CS treatme. Conclusion: This study found that CS treatment ameliorated CUS-induced depression-like behaviors and synaptic structural defects in mice via the gut microbiota-neuroinflammation axis. And chlorogenic acid and hypericin may be the main active substances for CS to exert antidepressant effects.

Comparative analysis of gut microbiota and fecal metabolome features among multiple depressive animal models

BACKGROUNDS

Emerging studies reported that gut microbiota and fecal metabolites take part in major depressive disorder (MDD) pathogenesis. However, the conclusions based on a single depressive animal model seem inconsistent or even controversial.

METHODS

Multiple depression rat models, including chronic unpredictable mild stress, chronic restraint stress, social defeat, and learned helplessness, were used. Then, the 16S ribosomal RNA gene sequencing and liquid chromatography-mass spectrometry analysis determined the alteration of gut microbiota and fecal metabolites.

RESULTS

The results of sucrose preference test and forced swimming test suggested that each model successfully established depression-like behavior. A total of 179 discriminative amplicon sequence variants (ASVs) were identified among four models. The overall discriminative ASVs mainly belonged to the family Lachnospiraceae, Muribaculaceae, and Oscillospiraceae. Moreover, the fecal metabolomic analysis identified 468 differential expressed metabolites. Among all the differential metabolites, 11 specific pathways significantly altered, which were mainly belonged to lipid and amino acid metabolism. Finally, co-occurrence network analysis suggested that target differential metabolites were associated with discriminative ASVs mainly assigned to family taxon Lachnospiraceae, Muribaculaceae, and Oscillospiraceae.

LIMITATIONS

The heterogeneity of MDD in humans cannot be totally imitated by animal models.

CONCLUSIONS

In multiple depression models, the alterations of family Lachnospiraceae, Muribaculaceae, and Oscillospiraceae with the dysbiosis of lipid and amino acid metabolism were gut microbiota and fecal metabolome features. The findings of our research may help us to have a comprehensive understanding of gut microbiota and fecal metabolome in depression.

Role of sirtuin1 in impairments of emotion-related behaviors in mice with chronic mild unpredictable stress during adolescence

Long-term exposure to physical and/or psychosocial stress during early life and/or adolescence increases the risk of psychiatric disorders such as major depressive disorder and anxiety disorders. However, the molecular mechanisms underlying early stress-induced brain dysfunction are poorly understood. In the present study, mice at 4 weeks old were subjected to chronic mild unpredictable stress (CMUS) for 4 weeks, and subsequently to assays of emotion-related behaviors. Thereafter, they were sacrificed and their brains were collected for real-time quantitative polymerase chain reaction (RT-qPCR). Mice with CMUS during adolescence showed despair behavior, anxiety-like behavior, social behavior deficits, and anhedonia in forced-swim, marble-burying, social interaction, and sucrose preference tests, respectively. Additionally, RT-qPCR revealed that the expression levels of sirtuin1 (SIRT1), a NAD⁺-dependent deacetylase that mediates stress responses, were down-regulated in the prefrontal cortex and hippocampus of mice with CMUS compared with control mice. Next, to investigate the pathophysiological role of decreased Sirt1 expression levels in stress-induced behavioral deficits, we assessed the effects of resveratrol, a pharmacological activator of SIRT1, in mice exposed to CMUS. Chronic treatment with resveratrol prevented -induced social behavior deficits and depression-like behaviors. These results suggest that CMUS during adolescence decreases Sirt1 expression in the brain, leading to deficits in emotional behavior. Accordingly, SIRT1 activators, such as resveratrol, may be preventive agents against abnormalities in emotional behavior following stress during an immature period.

Modulation of the gut microbiota and glycometabolism by a probiotic to alleviate amyloid accumulation and cognitive impairments in AD rats

SCOPE

Regulating the gut microecology by probiotics is an efficient strategy to rational prevention and treatment of Alzheimer's disease (AD). However, there is currently a lack of well-known probiotic species in the protection against AD, and the involved mechanism has not been clearly interpreted.

METHODS AND RESULTS

Herein, Lactobacillus plantarum MA2 (MA2), a functional probiotic isolated from traditional Chinese Tibetan kefir grains, was demonstrated to improve the cognitive deficits and anxiety-like behaviors in the D-galactose/AlCl₃ induced AD rats, and attenuate the neuronal degeneration and Aβ accumulation in the brain. Moreover, we found MA2 could alleviate the intestinal mucosal impairments, and impede the activation of microglia and neuroinflammation through TLR4/MYD88/NLRP3 signaling pathway. 16S rRNA sequencing and metabolomic analysis indicated that MA2 reshaped the gut microbiota structure and composition, and remarkably modulated the glycometabolism. In that case, the EPS (exopolysaccharides) that derived from MA2 was furtherly proved with inhibitory effects on the Aβ42 aggregation and amyloid-induced cytotoxicity.

CONCLUSION

MA2 or MA2 EPS may be used as functional food and nutritional supplement for regulating the gut microbiota and metabolism disorders in AD. This study is of great significance to develop new intervention and therapeutic strategy on AD using probiotics and their metabolites. This article is protected by copyright. All rights reserved.

Associations Between Disordered Microbial Metabolites and Changes of Neurotransmitters in Depressed Mice

Backgrounds

Many pieces of evidence demonstrated that there were close relationships between gut microbiota and depression. However, the specific molecular mechanisms were still unknown. Here, using targeted metabolomics, this study was conducted to explore the relationships between microbial metabolites in feces and neurotransmitters in prefrontal cortex of depressed mice.

Methods

Chronic unpredictable mild stress (CUMS) model of depression was built in this study. Targeted liquid chromatography-mass spectrometry analysis was used to detect the microbial metabolites in feces and neurotransmitters in prefrontal cortex of mice. Both univariate and multivariate statistical analyses were applied to identify the differential microbial metabolites and neurotransmitters and explore relationships between them.

Results

Ninety-eight differential microbial metabolites (mainly belonged to amino acids, fatty acids, and bile acids) and 11 differential neurotransmitters (belonged to tryptophan pathway, GABAergic pathway, and catecholaminergic pathway) were identified. Five affected amino acid-related metabolic pathways were found in depressed mice. The 19 differential microbial metabolites and 10 differential neurotransmitters were found to be significantly correlated with depressive-like behaviors. The two differential neurotransmitters (tyrosine and glutamate) and differential microbial metabolites belonged to amino acids had greater contributions to the overall correlations between microbial metabolites and neurotransmitters. In addition, the significantly decreased L-tyrosine as microbial metabolites and tyrosine as neurotransmitter had the significantly positive correlation (r = 0.681, p = 0.0009).

Conclusions

These results indicated that CUMS-induced disturbances of microbial metabolites (especially amino acids) might affect the levels of neurotransmitters in prefrontal cortex and then caused the onset of depression. Our findings could broaden the understanding of how gut microbiota was involved in the onset of depression.

Gut Microbiota-Related Inflammation Factors as a Potential Biomarker for Diagnosing Major Depressive Disorder

Objective

Although many works have been done, the objectively measured diagnostic biomarkers are not available. Thus, we conducted this study to identify potential biomarkers for objectively diagnosing depression and explore the role of gut microbiota in the onset of depression.

Methods

Major depressive disorder (MDD) patients (n=56) and demographic data-matched healthy controls (HCs) (n=56) were included in this study. The gut microbiota in fecal samples and inflammation-related factors in serum were measured. Both univariate and multivariate statistical analyses were performed to identify the differential gut microbiota and inflammation-related factors.

Results

Finally, 46 differential operational taxonomic units (OTUs) (60.9% OTUs belonging to Firmicutes) and ten differential inflammation-related factors were identified. Correlation analysis showed that there were significant correlations between 14 differential OTUs (9 OTUs belonging to Firmicutes and 5 OTUs belonging to family Lachnospiraceae under Firmicutes) and seven differential inflammation-related factors. Meanwhile, 14 differential OTUs (9 OTUs belonging to Firmicutes and 5 OTUs belonging to family Lachnospiraceae under Firmicutes) and five differential inflammation-related factors (adiponectin, apolipoprotein A1, alpha 1-antitrypsin, neutrophilicgranulocyte count/white blood cell count and basophil count) were significantly correlated to depression severity. A panel consisting of these five differential inflammation-related factors could effectively diagnose MDD patients from HCs.

Conclusions

Our results suggested that Firmicutes, especially family Lachnospiraceae, might play a role in the onset of depression via affecting the inflammation levels of host, and these five differential inflammation-related factors could be potential biomarkers for objectively diagnosing MDD.