A diet-induced gut microbiota component and related plasma metabolites are associated with depressive-like behaviour in rats

An Updated Bio-Behavioral Profile of the Flinders Sensitive Line Rat: Reviewing the Findings of the Past Decade

The Flinders sensitive line (FSL) rat is an accepted rodent model for depression that presents with strong face, construct, and predictive validity, thereby making it suitable to investigate novel antidepressant mechanisms. Despite the translatability of this model, available literature on this model has not been reviewed for more than ten years. The PubMed, ScienceDirect and Web of Science databases were searched for relevant articles between 2013 and 2024, with keywords relating to the Flinders line rat, and all findings relevant to treatment naïve animals, included. Following screening, 77 studies were included and used to create behavioral reference standards and calculate FSL favor ratios for the various behavioral parameters. The GRADE and SYRCLE risk of bias tools were used to scale the quality of these studies. Based on these results, FSL rats display reliable and reproducible depressive-like behavior in the forced swim test, together with hyperlocomotor activity across various behavioral tests. Despite reports of increased anhedonia, anxiety-like behavior, and cognitive dysfunction, the reviewed findings indicate that these parameters are comparable between strains. For the various neuro- and biological constructs, oxidative stress, energy production, and glutamatergic, noradrenergic and serotonergic neurotransmission received the most support for strain differences. Taken together, the FSL remains a reliable, popular, and translatable rodent model of depression, with strong face and construct validity. As for predictive validity, similar review approaches should be considered to establish whether the mentioned behavioral aspects and neurochemical constructs may be more sensitive (or resistant) to certain antidepressant strategies.

Ultrasonic vocalisations in the Flinders Sensitive Line rat, a genetic animal model of depression

OBJECTIVE

Ultrasonic vocalisations (USVs) emitted by rats may reflect affective states. Specifically, 50 kHz calls emitted during juvenile playing are associated with positive affect. Given that depression is characterised by profound alterations in this domain, we proposed that USV calls may configure a suitable tool for assessing depressive-like states. Utilising the Flinders Sensitive Line (FSL), a well-established animal model of depression, we assessed USV calls emitted by rats during tickling, a procedure based on juvenile rats' rough-and-tumble play.

METHODS

Juvenile FSL rats and their control counterparts, the Flinders Resistant Line (FRL) and Sprague Dawley, were submitted to tickling sessions to imitate rats playing behaviour. The rats were tickled daily for 6 weeks starting at PND21. Tickling sessions were recorded for further acoustic analysis of 50 kHz calls.

RESULTS

Tickling increased 50 kHz calls in all the strains. FSL rats emitted more calls than control strains and exhibited a higher number of flat-trill combination calls.

CONCLUSION

Tickling is a robust method for inducing 50 kHz USV calls. Analysing USV calls emitted during tickling configurates a suitable method for studying affective states relevant to depression. FSL rats did not present anhedonia but rather higher reward sensitivity, which may underlie their stress vulnerability.

Relationship Between Depression and Epigallocatechin Gallate from the Perspective of Gut Microbiota: A Systematic Review

Depression, a serious mental illness, is characterized by high risk, high incidence, persistence, and tendency to relapse, posing a significant burden on global health. The connection between depression and gut microbiota is an emerging field of study in psychiatry and neuroscience. Understanding the gut-brain axis is pivotal for understanding the pathogenesis and treatment of depression. Gut microbes influence depression-like behaviors by impacting the hypothalamic-pituitary-adrenal axis (HPA), monoamine neurotransmitters, immune responses, cell signaling, and metabolic pathways. Tea, widely used in clinical practice to improve neuropsychiatric disorders, contains Epigallocatechin gallate (EGCG), a major ingredient of green tea, which effectively regulates intestinal flora. This review examined the risks and causes of depression, the complications associated with intestinal flora, their role in the development and treatment of depression, and how EGCG may alleviate depression through interactions with gut microbiota and other mechanisms.

Therapeutic modulation of the kynurenine pathway in severe mental illness and comorbidities: A potential role for serotonergic psychedelics

Mounting evidence points towards a crucial role of the kynurenine pathway (KP) in the altered gut-brain axis (GBA) balance in severe mental illness (SMI, namely depression, bipolar disorder, and schizophrenia) and cardiometabolic comorbidities. Preliminary evidence shows that serotonergic psychedelics and their analogues may hold therapeutic potential in addressing the altered KP in the dysregulated GBA in SMI and comorbidities. In fact, aside from their effects on mood, psychedelics elicit therapeutic improvement in preclinical models of obesity, metabolic syndrome, and vascular inflammation, which are highly comorbid with SMI. Here, we review the literature on the therapeutic modulation of the KP in the dysregulated GBA in SMI and comorbidities, and the potential application of psychedelics to address the altered KP in the brain and systemic dysfunction underlying SMI and comorbidities. Psychedelics might therapeutically modulate the KP in the altered GBA in SMI and comorbidities either directly, via altering the metabolic pathway by influencing the rate-limiting enzymes of the KP and affecting the levels of available tryptophan, or indirectly, by affecting the gut microbiome, gut metabolome, metabolism, and the immune system. Despite promising preliminary evidence, the mechanisms and outcomes of the KP modulation with psychedelics in SMI and systemic comorbidities remain largely unknown and require further investigation. Several concerns are discussed surrounding the potential side effects of this approach in specific cohorts of individuals with SMI and systemic comorbidities.

An Analysis of the Intestinal Microbiome Combined with Metabolomics to Explore the Mechanism of How Jasmine Tea Improves Depression in CUMS-Treated Rats

Recently, research has confirmed that jasmine tea may help improve the depressive symptoms that are associated with psychiatric disorders. Our team previously found that jasmine tea improved the depressive-like behavior that is induced by chronic unpredictable mild stress (CUMS) in Sprague Dawley (SD) rats. We hypothesized that the metabolic disorder component of depression may be related to the gut microbiota, which may be reflected in the metabolome in plasma. The influence of jasmine tea on gut microbiota composition and the association with depressive-related indexes were explored. Furthermore, the metabolites in plasma that are related to the gut microbiota were identified. SD rats were treated with control or CUMS and administrated jasmine tea for 8 weeks. The 16S rRNA gene amplicon sequencing was used to analyze the gut microbiota in feces samples, and untargeted metabolomics was used to analyze the metabolites in plasma. The results found that jasmine tea significantly ameliorated the depressive behavior induced by CUMS, significantly improved the neurotransmitter concentration (BDNF and 5-HT), and decreased the pro-inflammation levels (TNF-α and NF-κB). The intervention of jasmine tea also alleviated the dysbiosis caused by CUMS; increased the relative abundance of Bacteroides, Blautia, Clostridium, and Lactobacillus; and decreased Ruminococcus and Butyrivibrio in the CUMS-treated rats. Furthermore, the serum metabolites of the CUMS-treated rats were reversed after the jasmine tea intervention, i.e., 22 were up-regulated and 18 were down-regulated, which may have a close relationship with glycerophospholipid metabolism pathways, glycine serine and threonine metabolism pathways, and nicotinate and nicotinamide metabolism pathways. Finally, there were 30 genera of gut microbiota related to the depressive-related indexes, and 30 metabolites in the plasma had a strong predictive ability for depressive behavior. Potentially, our research implies that the intervention of jasmine tea can ameliorate the depression induced by CUMS via controlling the gut flora and the host's metabolism, which is an innovative approach for the prevention and management of depression.

Antidepressant-like Effects of Representative Types of Food and Their Possible Mechanisms

Depression is a mental disorder characterized by low mood, lack of motivation, negative cognitive outlook, and sleep problems. Suicide may occur in severe cases, although suicidal thoughts are not seen in all cases. Globally, an estimated 350 million individuals grapple with depression, as reported by the World Health Organization. At present, drug and psychological treatments are the main treatments, but they produce insufficient responses in many patients and fail to work at all in many others. Consequently, treating depression has long been an important topic in society. Given the escalating prevalence of depression, a comprehensive strategy for managing its symptoms and impacts has garnered significant attention. In this context, nutritional psychiatry emerges as a promising avenue. Extensive research has underscored the potential benefits of a well-rounded diet rich in fruits, vegetables, fish, and meat in alleviating depressive symptoms. However, the intricate mechanisms linking dietary interventions to brain function alterations remain largely unexplored. This review delves into the intricate relationship between dietary patterns and depression, while exploring the plausible mechanisms underlying the impact of dietary interventions on depression management. As we endeavor to unveil the pathways through which nutrition influences mental well-being, a holistic perspective that encompasses multidisciplinary strategies gains prominence, potentially reshaping how we approach and address depression.

Molecular Mechanisms and Pathophysiological Pathways of High-Fat Diets and Caloric Restriction Dietary Patterns on Pain

Pain perception provides evolutionary advantages by enhancing the probability of survival, but chronic pain continues to be a significant global health concern in modern society. Various factors are associated with pain alteration. Accumulating evidence has revealed that obesity correlates with enhanced pain perception, especially in chronic pain individuals. Existing dietary patterns related to obesity are primarily high-fat diets (HFD) and calorie restriction (CR) diets, which induce or alleviate obesity separately. HFD has been shown to enhance nociception while CR tends to alleviate pain when measuring pain outcomes. Herein, this review mainly summarizes the current knowledge of the effects of HFD and CR on pain responses and underlying molecular mechanisms of the immunological factors, metabolic regulation, inflammatory processes, Schwann cell (SC) autophagy, gut microbiome, and other pathophysiological signaling pathways involved. This review would help to provide insights on potential nonpharmacological strategies of dietary patterns in relieving pain.

Seeking the Psilocybiome: Psychedelics meet the microbiota-gut-brain axis

Moving towards a systems psychiatry paradigm embraces the inherent complex interactions across all levels from micro to macro and necessitates an integrated approach to treatment. Cortical 5-HT2A receptors are key primary targets for the effects of serotonergic psychedelics. However, the therapeutic mechanisms underlying psychedelic therapy are complex and traverse molecular, cellular, and network levels, under the influence of biofeedback signals from the periphery and the environment. At the interface between the individual and the environment, the gut microbiome, via the gut-brain axis, plays an important role in the unconscious parallel processing systems regulating host neurophysiology. While psychedelic and microbial signalling systems operate over different timescales, the microbiota-gut-brain (MGB) axis, as a convergence hub between multiple biofeedback systems may play a role in the preparatory phase, the acute administration phase, and the integration phase of psychedelic therapy. In keeping with an interconnected systems-based approach, this review will discuss the gut microbiome and mycobiome and pathways of the MGB axis, and then explore the potential interaction between psychedelic therapy and the MGB axis and how this might influence mechanism of action and treatment response. Finally, we will discuss the possible implications for a precision medicine-based psychedelic therapy paradigm.

Antioxidant and Anti-Inflammatory Effects of Carotenoids in Mood Disorders: An Overview

Depression has a multifactorial etiology comprising family history and unemployment. This review aims to summarize the evidence available for the antioxidant and anti-inflammatory effects of carotenoids in mood disorders. This review article’s methodologies were based on a search of the PubMed database for all linked published papers. Epidemiological studies indicate that a diet rich in vegetables, fruits, nuts, fish, and olive oil may prevent the development of depression. Antioxidant supplementation has been found to combat various stress-induced psychiatric disorders, including depression and anxiety. A growing body of evidence indicates that carotenoids have both antioxidant and anti-inflammatory. Studies also suggest that poor dietary intake, particularly low intakes of fruit and vegetables and high intakes of fast food and other convenience foods, may increase the risk of developing depression. Thus, dietary interventions have the potential to help mitigate the risk of mental health decline in both the general population and those with mood disorders. Considering that carotenoids have both antioxidant and anti-inflammatory effects, it is expected that they might exert a promising antidepressant effect. Nevertheless, further studies (including interventional and mechanistic studies) assessing the effect of carotenoids on preventing and alleviating depression symptoms are needed.

Feed your microbes to deal with stress: a psychobiotic diet impacts microbial stability and perceived stress in a healthy adult population

The impact of diet on the microbiota composition and the role of diet in supporting optimal mental health have received much attention in the last decade. However, whether whole dietary approaches can exert psychobiotic effects is largely understudied. Thus, we investigated the influence of a psychobiotic diet (high in prebiotic and fermented foods) on the microbial profile and function as well as on mental health outcomes in a healthy human population. Forty-five adults were randomized into either a psychobiotic (n = 24) or control (n = 21) diet for 4 weeks. Fecal microbiota composition and function was characterized using shotgun sequencing. Stress, overall health and diet were assessed using validated questionnaires. Metabolic profiling of plasma, urine and fecal samples was performed. Intervention with a psychobiotic diet resulted in reductions of perceived stress (32% in diet vs. 17% in control group), but not between groups. Similarly, biological marker of stress were not affected. Additionally, higher adherence to the diet resulted in stronger decreases in perceived stress. While the dietary intervention elicited only subtle changes in microbial composition and function, significant changes in the level of 40 specific fecal lipids and urinary tryptophan metabolites were observed. Lastly, microbial volatility was linked to greater changes in perceived stress scores in those on the psychobiotic diet. These results highlight that dietary approaches can be used to reduce perceived stress in a human cohort. Using microbiota-targeted diets to positively modulate gut-brain communication holds possibilities for the reduction of stress and stress-associated disorders, but additional research is warranted to investigate underlying mechanisms, including the role of the microbiota.

Antidepression of Xingpijieyu formula targets gut microbiota derived from depressive disorder

OBJECTIVE

This investigation aims to determine the antidepressant role of Xingpijieyu formula (XPJYF) mediated via gut microbiota (GM)-brain axis.

METHODS

We collected fecal microbiota from patients with depressive disorder (DD) and cultured microbiota in vitro. Some of microbiota were transplanted into germ-free rats with the intragastric administration of XPJYF grain at the dose of 1.533 g/kg/day. The behaviors were studied by forced swimming test, open field test, sucrose preference test, and body weight. Products of hypothalamus-pituitary-adrenocortical (HPA) axis, neurotransmitter, and serum cytokines were investigated by enzyme linked immunosorbent assay. Glial fibrillary acidic protein (GFAP), a biomarker of astrocyte, was quantified using immunofluorescence. Microbiota culturing in vitro after XPJYF treatment was analyze by 16 s RNA sequencing technology. We used lipopolysaccharide (LPS) to mimic activated rat primary astrocyte in vitro. Brain-derived neurotrophic factor (BDNF), cytokines, and oxidative stress factors were determined by western blotting, and glycometabolism in astrocyte was investigated by 2-deoxy-D-glucose (2-DG) uptake, adenosine triphosphate (ATP), and glucose-1-phosphate (G1P) kits.

RESULTS

Microbiota composition during 8 mg/ml of XPJYF (H12-8) for 12 h showed the more consistency. Lactococcus is enriched in DD-derived microbiota composition, and Biffdobacterium and Lactobacillus in H12-8 group. GLUCOSE1PMETAB-PWY and PWY-7328 of which biofunctions were dominantly encoded by Biffdobacterium were the top two of altered pathways. XPJYF improved behaviors and repressed astrocyte activation in depression rats. XPJYF elevated 2-DG uptake, ATP, glucose-1-phosphate, and brain-derived neurotrophic factor (BDNF), and inhibited cytokines and oxidative stress in LPS-induced astrocyte.

CONCLUSION

XPJYF treatment targets inflammation, activation, and glycometabolim in astrocyte via gut microbiota modulation, thereby improve animal behaviors, HPA axis dysfunction, and neurotransmitter synthesis in depression rats.

The antidepressant effects and serum metabonomics of bifid triple viable capsule in a rat model of chronic unpredictable mild stress

Background

Probiotics have shown potential antidepressant effects. This study evaluated the effect and probable mechanisms of bifid triple viable capsules (BTVCs) on a rat model of chronic unpredictable mild stress (CUMS).

Materials and methods

Rats were randomly divided into Normal, CUMS model, fluoxetine hydrochloride (FLX), BTVCs, and FLX+BTVCs groups. Depressive-like behaviours, pathological changes in the hippocampus, changes in serum metabolites and potential biomarkers, and metabolic pathways were detected via behavioural tests, haematoxylin-eosin staining, nissl staining, non-targetted metabolomics, and ingenuity pathway analysis (IPA).

Results

The rats displayed depressive-like behaviours after CUMS exposure, but BTVCs ameliorated the depressive-like behaviours. In addition, the pathological results showed that the hippocampal tissue was damaged in rats after CUMS exposure and that the damage was effectively alleviated by treatment with BTVCs. A total of 20 potential biomarkers were identified. Treatment with BTVCs regulated D-phenylalanine, methoxyeugenol, (±)-myristoylcarnitine, 18:3 (6Z, 9Z, 12Z) /P-18:1 (11Z), propionyl-L-carnitine, and arachidonic acid (AA) concentrations, all compounds that are involved with biosynthesis of unsaturated fatty acids, glycerophospholipid metabolism, linoleic acid metabolism and AA metabolism. The IPA demonstrated that endothelin-1 signalling and cyclic adenosine monophosphate response element binding protein (CREB) signalling in neurons may be involved in the development of depression.

Conclusion

Our findings suggest that BTVCs can alleviate depressive-like behaviours, restore damage to the hippocampus in CUMS rats and regulate serum metabolism, which may be related to endothelin-1 signalling or CREB signalling in neurons.

The Role of Psychobiotics in Supporting the Treatment of Disturbances in the Functioning of the Nervous System-A Systematic Review

Stress and anxiety are common phenomena that contribute to many nervous system dysfunctions. More and more research has been focusing on the importance of the gut-brain axis in the course and treatment of many diseases, including nervous system disorders. This review aims to present current knowledge on the influence of psychobiotics on the gut-brain axis based on selected diseases, i.e., Alzheimer's disease, Parkinson's disease, depression, and autism spectrum disorders. Analyses of the available research results have shown that selected probiotic bacteria affect the gut-brain axis in healthy people and people with selected diseases. Furthermore, supplementation with probiotic bacteria can decrease depressive symptoms. There is no doubt that proper supplementation improves the well-being of patients. Therefore, it can be concluded that the intestinal microbiota play a relevant role in disorders of the nervous system. The microbiota-gut-brain axis may represent a new target in the prevention and treatment of neuropsychiatric disorders. However, this topic needs more research. Such research could help find effective treatments via the modulation of the intestinal microbiome.

Jasmine Tea Attenuates Chronic Unpredictable Mild Stress-Induced Depressive-like Behavior in Rats via the Gut-Brain Axis

The number of depressed people has increased worldwide. Dysfunction of the gut microbiota has been closely related to depression. The mechanism by which jasmine tea ameliorates depression via the brain-gut-microbiome (BGM) axis remains unclear. Here, the effects of jasmine tea on rats with depressive-like symptoms via the gut microbiome were investigated. We first established a chronic unpredictable mild stress (CUMS) rat model to induce depressive symptoms and measured the changes in depression-related indicators. Simultaneously, the changes in gut microbiota were investigated by 16S rRNA sequencing. Jasmine tea treatment improved depressive-like behaviors and neurotransmitters in CUMS rats. Jasmine tea increased the gut microbiota diversity and richness of depressed rats induced by CUMS. Spearman’s analysis showed correlations between the differential microbiota (Patescibacteria, Firmicutes, Bacteroidetes, Spirochaetes, Elusimicrobia, and Proteobacteria) and depressive-related indicators (BDNF, GLP-1, and 5-HT in the hippocampus and cerebral cortex). Combined with the correlation analysis of gut microbiota, the result indicated that jasmine tea could attenuate depression in rats via the brain- gut-microbiome axis.

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.

Microbiota-brain interactions: Moving toward mechanisms in model organisms

Changes in the microbiota are associated with alterations in nervous system structure-function and behavior and have been implicated in the etiology of neuropsychiatric and neurodegenerative disorders. Most of these studies have centered on mammalian models due to their phylogenetic proximity to humans. Indeed, the germ-free mouse has been a particularly useful model organism for investigating microbiota-brain interactions. However, microbiota-brain axis research on simpler genetic model organisms with a vast and diverse scientific toolkit (zebrafish, Drosophila melanogaster, and Caenorhabditis elegans) is now also coming of age. In this review, we summarize the current state of microbiota-brain axis research in rodents and humans, and then we elaborate and discuss recent research on the neurobiological and behavioral effects of the microbiota in the model systems of fish, flies, and worms. We propose that a cross-species, holistic and mechanistic approach to unravel the microbiota-brain communication is an essential step toward rational microbiota-based therapeutics to combat brain disorders.

The Impact of Host Genotype, Intestinal Sites and Probiotics Supplementation on the Gut Microbiota Composition and Diversity in Sheep

Three sampling strategies with a 16s rRNA high-throughput sequencing and gene expression assay (by RT-PCR) were designed, to better understand the host and probiotics effect on gut microbiota in sheep. Sampling: (1) colon contents and back-fat tissues from small-tailed Han sheep (SHS), big-tailed Hulun Buir sheep (BHBS), and short-tailed Steppe sheep (SHBS) (n = 12, 14, 12); (2) jejunum, cecum and colon contents, and feces from Tan sheep (TS, n = 6); (3) feces from TS at 4 time points (nonfeeding, 30 and 60 feeding days, and stop feeding 30 days) with probiotics supplementation (n = 7). The results indicated SHS had the highest Firmicutes abundance, the thinnest back-fat, and the lowest expression of C/EBPβ, C/EBPδ, ATGL, CFD, and SREBP1. Some bacteria orders and families could be potential biomarkers for sheep breeds with a distinct distribution of bacterial abundance, implying the host genotype is predominant in shaping unique microbiota under a shared environment. The microbiota diversity and Bifidobacterial populations significantly changed after 60 days of feeding but restored to its initial state, with mostly colonies, after 30 days ceased. The microbiota composition was greatly different between the small and large intestines, but somewhat different between the large intestine and feces; feces may be reliable for studying large intestinal microbiota in ruminants.