The Gut-Brain Axis, BDNF, NMDA and CNS Disorders

Synergistic effects of tilapia head protein hydrolysate and walnut protein hydrolysate on the amelioration of cognitive impairment in mice

BACKGROUND

Cognitive impairment (CI) is a significant public health concern, and bioactive peptides have shown potential as therapeutic agents. However, information about their synergistic effects on cognitive function is still limited. Here, we investigated the synergistic effects of tilapia head protein hydrolysate (THPH) and walnut protein hydrolysate (WPH) in mitigating CI induced by scopolamine in mice.

RESULTS

The results showed that the combined supplementation of THPH and WPH (mass ratio, 1:1) was superior to either individual supplement in enhancing spatial memory and object recognition abilities in CI mice, and significantly lessened brain injury in CI mice by alleviating neuronal damage, reducing oxidative stress and stabilizing the cholinergic system. In addition, the combined supplementation was found to be more conducive to remodeling the gut microbiota structure in CI mice by not only remarkably reducing the ratio of Firmicutes to Bacteroidota, but also specifically enriching the genus Roseburia. On the other hand, the combined supplementation regulated the disorders of sphingolipid and amino acid metabolism in CI mice, particularly upregulating glutathione and histidine metabolism, and displayed a stronger ability to increase the expression of genes and proteins related to the brain-derived neurotrophic factor (BDNF)/TrkB/CrEB signaling pathway in the brain.

CONCLUSION

These findings demonstrate that tilapia head and walnut-derived protein hydrolysates exerted synergistic effects in ameliorating CI, which was achieved through modulation of gut microbiota, serum metabolic pathways and BDNF signaling pathways. © 2024 Society of Chemical Industry.

Effect of time restricted feeding on anthropometric measures, eating behavior, stress, serum levels of BDNF and LBP in overweight/obese women with food addiction: a randomized clinical trial

BACKGROUND & AIM

Food addiction (FA) as a specific food-related behavior may play an essential role in the pathogenesis of obesity. Brain-derived neurotrophic factor (BDNF) and gut microbiota (GM) alterations probably through fasting are closely related to brain function, affecting eating behaviors and body weight management. This study aimed to evaluate the effect of time-restricted feeding (TRF) on serum BDNF levels and eating behaviors in overweight and obese women with FA.

METHODS AND DESIGN

This clinical trial was performed with a 2-month follow-up on 56 obese and overweight women with FA. Participants were randomly divided into two groups receiving a low-calorie diet (n = 27) and a group receiving a low-calorie diet with TRF (n = 29). Anthropometric measurements, biochemical markers, eating behavior, and stress were assessed during the study period.

RESULTS

The reductions in weight, body mass index (BMI), waist circumference, and body fat mass were significantly higher in the TRF group compared to the control group at week 8 (P = 0.018, P = 0.015. P = 0.03, and P = 0.036, respectively). The cognitive restriction score was higher in the TRF as compared with the control group (P = 0.002). The food addiction criteria score was significantly reduced in both groups (P < 0.001). Serum levels of BDNF were significantly increased in the TRF group (P < 0.001). In addition, BDNF levels had a positive and significant correlation with the cognitive restriction score (r = 0.468 and P < 0.001), While the correlation with FA was not significant (β = 0.588 and P = 0.618). Lipopolysaccharide binding protein decreased significantly in both groups, but this decrease was significantly higher in the TRF group than in the control group (P < 0.001).

CONCLUSION

The results of this study showed that a low-calorie diet with TRF is more effective in weight management than a low-calorie diet alone, probably through further modulating the GM and improving BDNF levels. More effective weight loss in the TRF is probably related to better management of eating behavior than FA.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials identifier: IRCT20131228015968N7.

Mechanism Explanation on Improved Cognitive Ability of D-Gal Inducing Aged Mice Model by Lactiplantibacillus plantarum MWFLp-182 via the Microbiota-Gut-Brain Axis

Gut microbiota can influence cognitive ability via the gut-brain axis. Lactiplantibacillus plantarum MWFLp-182 (L. plantarum MWFLp-182) was obtained from feces of long-living individuals and could exert marked antioxidant ability. Interestingly, this strain reduced the D-galactose-induced impaired cognitive ability in BALB/c mice. To comprehensively elucidate the underlying mechanism, we evaluated the colonization, antioxidant, and anti-inflammatory activities of L. plantarum MWFLp-182, along with the expression of potential genes associated with cognitive ability influenced and gut microbiota. L. plantarum MWFLp-182 enhanced the expression of anti-inflammatory cytokines, reduced the expression of proinflammatory cytokines, and increased tight junction protein expression in the colon. Moreover, L. plantarum MWFLp-182 could modify the gut microbiota. Notably, treatment with L. plantarum MWFLp-182 upregulated the expression of postsynaptic density protein-95, nuclear factor erythroid 2-related factor, nerve growth factor, superoxide dismutase, and brain-derived neurotrophic factor/neuronal nuclei, while downregulating the expression of bcl-2-associated X and malondialdehyde in the hippocampus and upregulating short-chain fatty acids against D-galactose-induced mouse brain deficits. Accordingly, L. plantarum MWFLp-182 could improve cognitive ability in a D-galactose-inducing mouse model.

Can essential fatty acids (EFAs) prevent and ameliorate post-COVID-19 long haul manifestations?

It is hypothesized that COVID-19, post-COVID and post-mRNA COVID-19 (and other related) vaccine manifestations including "long haul syndrome" are due to deficiency of essential fatty acids (EFAs) and dysregulation of their metabolism. This proposal is based on the observation that EFAs and their metabolites can modulate the swift immunostimulatory response of SARS-CoV-2 and similar enveloped viruses, suppress inappropriate cytokine release, possess cytoprotective action, modulate serotonin and bradykinin production and other neurotransmitters, inhibit NF-kB activation, regulate cGAS-STING pathway, modulate gut microbiota, inhibit platelet activation, regulate macrophage and leukocyte function, enhance wound healing and facilitate tissue regeneration and restore homeostasis. This implies that administration of EFAs could be of benefit in the prevention and management of COVID-19 and its associated complications.

Kynurenines, Neuronal Excitotoxicity, and Mitochondrial Oxidative Stress: Role of the Intestinal Flora

The intestinal flora has been the focus of numerous investigations recently, with inquiries not just into the gastrointestinal aspects but also the pathomechanism of other diseases such as nervous system disorders and mitochondrial diseases. Mitochondrial disorders are the most common type of inheritable metabolic illness caused by mutations of mitochondrial and nuclear DNA. Despite the intensive research, its diagnosis is usually difficult, and unfortunately, treating it challenges physicians. Metabolites of the kynurenine pathway are linked to many disorders, such as depression, schizophrenia, migraine, and also diseases associated with impaired mitochondrial function. The kynurenine pathway includes many substances, for instance kynurenic acid and quinolinic acid. In this review, we would like to show a possible link between the metabolites of the kynurenine pathway and mitochondrial stress in the context of intestinal flora. Furthermore, we summarize the possible markers of and future therapeutic options for the kynurenine pathway in excitotoxicity and mitochondrial oxidative stress.

Gut-Brain Axis Deregulation and Its Possible Contribution to Neurodegenerative Disorders

The gut-brain axis is an essential communication pathway between the central nervous system (CNS) and the gastrointestinal tract. The human microbiota is composed of a diverse and abundant microbial community that compasses more than 100 trillion microorganisms that participate in relevant physiological functions such as host nutrient metabolism, structural integrity, maintenance of the gut mucosal barrier, and immunomodulation. Recent evidence in animal models has been instrumental in demonstrating the possible role of the microbiota in neurodevelopment, neuroinflammation, and behavior. Furthermore, clinical studies suggested that adverse changes in the microbiota can be considered a susceptibility factor for neurological disorders (NDs), such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). In this review, we will discuss evidence describing the role of gut microbes in health and disease as a relevant risk factor in the pathogenesis of neurodegenerative disorders, including AD, PD, HD, and ALS.

Olfactory Three-Needle Electroacupuncture Improved Synaptic Plasticity and Gut Microbiota of SAMP8 Mice by Stimulating Olfactory Nerve

OBJECTIVE

To investigate the effects and mechanisms of olfactory three-needle (OTN) electroacupuncture (EA) stimulation of the olfactory system on cognitive dysfunction, synaptic plasticity, and the gut microbiota in senescence-accelerated mouse prone 8 (SAMP8) mice.

METHODS

Thirty-six SAMP8 mice were randomly divided into the SAMP8 (P8), SAMP8+OTN (P8-OT), and SAMP8+nerve transection+OTN (P8-N-OT) groups according to a random number table (n=12 per group), and 12 accelerated senescence-resistant (SAMR1) mice were used as the control (R1) group. EA was performed at the Yintang (GV 29) and bilateral Yingxiang (LI 20) acupoints of SAMP8 mice for 4 weeks. The Morris water maze test, transmission electron microscopy, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining, Nissl staining, Golgi staining, Western blot, and 16S rRNA sequencing were performed, respectively.

RESULTS

Compared with the P8 group, OTN improved the cognitive behavior of SAMP8 mice, inhibited neuronal apoptosis, increased neuronal activity, and attenuated hippocampal synaptic dysfunction (P<0.05 or P<0.01). Moreover, the expression levels of synaptic plasticity-related proteins N-methyl-D-aspartate receptor 1 (NMDAR1), NMDAR2B, synaptophysin (SYN), and postsynaptic density protein-95 (PSD95) in hippocampus were increased by OTN treatment (P<0.05 or P<0.01). Furthermore, OTN greatly enhanced the brain-derived neurotrophic factor (BDNF)/cAMP-response element binding (CREB) signaling and phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling compared with the P8 group (P<0.05 or P<0.01). However, the neuroprotective effect of OTN was attenuated by olfactory nerve truncation. Compared with the P8 group, OTN had a very limited effect on the fecal microbial structure and composition of SAMP8 mice, while specifically increased the genera Oscillospira and Sutterella (P<0.05). Interestingly, the P8-N-OT group showed an abnormal fecal microbiota with higher microbial α-diversity, Firmicutes/Bacteroidetes ratio and pathogenic bacteria (P<0.05 or P<0.01).

CONCLUSIONS

OTN improved cognitive deficits and hippocampal synaptic plasticity by stimulating the olfactory nerve and activating the BDNF/CREB and PI3K/AKT/mTOR signaling pathways. Although the gut microbiota was not the main therapeutic target of OTN for Alzheimer's disease, the olfactory nerve was essential to maintain the homeostasis of gut microbiota.

Antidepressant properties of voluntary exercise mediated by gut microbiota

Although regular exercise has been reported to prevent depression, it has not been clarified whether the gut microbiota is involved in the factors that prevent depression through exercise. We investigated the effects of voluntary exercise on the gut microbiota and the prevention of depression-like behaviors using mice. C57BL/6 J male mice were subjected to 10 weeks of sedentary control or wheel running, then they were subjected to social defeat stress (SDS). Exercise attenuated that sucrose drinking was decreased by SDS treatment. Exercise increased the expression of Bdnf and decreased expression of Zo-1 and Claudin5 in the brain. Fecal Turicibacter, Allobaculum, and Clostridium sensu stricto, and propionate in the cecum were decreased by the exercise. Voluntary exercise-induced antidepressant properties might be partially caused by suppression of serotonin uptake into gut microbiota and increase the permeability of the blood-brain barrier via reduced propionate production.

Probiotics supplementation and brain-derived neurotrophic factor (BDNF): a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

An emerging body of evidence has demonstrated the beneficial effects of probiotics on various mental health conditions. In this systematic review and meta-analysis, we sought to examine the effects of probiotics supplementation on brain-derived neurotrophic factor (BDNF) in adults.

METHODS

PubMed, Scopus, ISI Web of Science, and the Cochrane Library were searched, from database inception to April 2021, for eligible randomized controlled trials (RCTs). We pooled mean differences and standard deviations from RCTs using random-effect models.

RESULTS

Overall, meta-analysis of 11 trials (n = 648 participants) showed no significant changes in serum level of BDNF following probiotics. However, subgroup analysis revealed that probiotics increased BDNF levels in individuals suffering from neurological disorders (n = 214 participants; WMD = 3.08 ng/mL, 95% CI: 1.83, 4.34; P = 0.001; I2 = 7.5%; P-heterogeneity 0.34), or depression (n = 268 participants; WMD = 0.77 ng/mL, 95% CI: 0.07, 1.47; P = 0.032; I2 = 88.4%; P-heterogeneity < 0.001). Furthermore, a significant increase in BDNF levels was found in studies that administered the mixture of Lactobacillus and Bifidobacterium genera, and were conducted in Asia .

CONCLUSION

Our main findings suggest that probiotics may be effective in elevating BDNF levels in patients with depression and neurological disorders, and a mixed of Lactobacillus and Bifidobacterium appear to show greater efficacy than the single genus supplement. The low quality of evidence reduces clinical advocacy, and indicates that more large-scale, high-quality, RCTs are needed to facilitate reliable conclusions.

Tumor-mediated microbiota alteration impairs synaptic tagging/capture in the hippocampal CA1 area via IL-1β production

Cancer patients often experience impairments in cognitive function. However, the evidence for tumor-mediated neurological impairment and detailed mechanisms are still lacking. Gut microbiota has been demonstrated to be involved in the immune system homeostasis and brain functions. Here we find that hepatocellular carcinoma (HCC) growth alters the gut microbiota and impedes the cognitive functions. The synaptic tagging and capture (STC), an associative cellular mechanism for the formation of associative memory, is impaired in the tumor-bearing mice. STC expression is rescued after microbiota sterilization. Transplantation of microbiota from HCC tumor-bearing mice induces similar STC impairment in wide type mice. Mechanistic study reveals that HCC growth significantly elevates the serum and hippocampus IL-1β levels. IL-1β depletion in the HCC tumor-bearing mice restores the STC. Taken together, these results demonstrate that gut microbiota plays a crucial role in mediating the tumor-induced impairment of the cognitive function via upregulating IL-1β production.

Small fish, big discoveries: zebrafish shed light on microbial biomarkers for neuro-immune-cardiovascular health

Zebrafish (Danio rerio) have emerged as a powerful model to study the gut microbiome in the context of human conditions, including hypertension, cardiovascular disease, neurological disorders, and immune dysfunction. Here, we highlight zebrafish as a tool to bridge the gap in knowledge in linking the gut microbiome and physiological homeostasis of cardiovascular, neural, and immune systems, both independently and as an integrated axis. Drawing on zebrafish studies to date, we discuss challenges in microbiota transplant techniques and gnotobiotic husbandry practices. We present advantages and current limitations in zebrafish microbiome research and discuss the use of zebrafish in identification of microbial enterotypes in health and disease. We also highlight the versatility of zebrafish studies to further explore the function of human conditions relevant to gut dysbiosis and reveal novel therapeutic targets.

Gut microbiota decreased inflammation induced by chronic unpredictable mild stress through affecting NLRP3 inflammasome

Dysbiosis of the gut microbiota is associated with the development of depression, but the underlying mechanism remains unclear. The aim of this study was to determine the relationship between microbiota and NLRP3 inflammasome induced by chronic unpredictable mild stress (CUMS). Fecal transplantation (FMT) experiment was conducted to elucidate the potential mechanism. Levels of NLRP3 inflammasome, microbiota, inflammatory factors and tight junction proteins were measured. CUMS stimulation significantly increased the levels of NLRP3, Caspase-1 and ASC in brain and colon(p<0.05), decreased the levels of tight junction proteins Occludin and ZO-1 (p<0.05). Interestingly, increased NLRP3 inflammasome and inflammatory cytokines and decreased tight junction proteins were found in antibiotic-treated (Abx) rats received CUMS rat fecal microbiota transplantation. Furthermore, fecal microbiota transplantation altered the microbiota in Abx rats, which partially overlapped with that of the donor rats. Importantly, probiotic administration amended the alteration of microbiota induced by CUMS treatment, then reduced the levels of NLRP3 inflammasome and inflammatory factors. In conclusion, these findings suggested that depression-like behaviors induced by CUMS stimulation were related to altered gut microbiota, broke the intestinal barrier, promoted the expression of NLRP3 inflammasome and elevated inflammation. Therefore, improving the composition of microbiota via probiotic can attenuate inflammation by amending the microbiota and suppressing the activation of NLRP3 inflammasome, which is considered as a novel therapeutic strategy for depression.

Role of microbial dysbiosis in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is the leading cause of dementia in the elderly and detected during the advanced stages where the chances of reversal are minimum. The gut-brain axis mediates a bidirectional communication between the gut and brain, which is dependent on bacterial products such as short chain fatty acids (SCFA) and neurotransmitters. Accumulating lines of evidence suggests that AD is associated with significant alteration in the composition of gut microbiota. Furthermore, transfer of gut microbiota from healthy individuals to patients can reshape the gut microbiota structure and thus holds the potential to be exploited for the treatment of various neurodegenerative disease. Moreover, AD-associated gut dysbiosis can be partially reversed by using probiotics, prebiotics, natural compounds and dietary modifications, but need further validations. Reversal of AD associated gut dysbiosis alleviate AD-associated pathological feature and therefore can be explored as a therapeutic approach in the future. The current review article will describe various studies suggesting that AD dysbiosis occurs with AD and highlights the causal role by focussing on the interventions that hold the potential to reverse the gut dysbiosis partially.

Probiotics for the treatment of depression and its comorbidities: A systemic review

Depression is one of the most common psychiatric conditions, characterized by significant and persistent depressed mood and diminished interest, and often coexists with various comorbidities. The underlying mechanism of depression remain elusive, evidenced by the lack of an appreciate therapy. Recent abundant clinical trials and animal studies support the new notion that the gut microbiota has emerged as a novel actor in the pathophysiology of depression, which partakes in bidirectional communication between the gut and the brain through the neuroendocrine, nervous, and immune signaling pathways, collectively known as the microbiota-gut-brain (MGB) axis. Alterations in the gut microbiota can trigger the changes in neurotransmitters, neuroinflammation, and behaviors. With the transition of human microbiome research from studying associations to investigating mechanistic causality, the MGB axis has emerged as a novel therapeutic target in depression and its comorbidities. These novel insights have fueled idea that targeting on the gut microbiota may open new windows for efficient treatment of depression and its comorbidities. Probiotics, live beneficial microorganisms, can be used to modulate gut dysbiosis into a new eubiosis and modify the occurrence and development of depression and its comorbidities. In present review, we summarize recent findings regarding the MGB axis in depression and discuss the potential therapeutic effects of probiotics on depression and its comorbidities.

A review of probiotics in the treatment of autism spectrum disorders: Perspectives from the gut–brain axis

Autism spectrum disorders (ASD) are a class of neurodevelopmental conditions with a large societal impact. Despite existing evidence suggesting a link between ASD pathogenesis and gut–brain axis dysregulation, there is no systematic review of the treatment of probiotics on ASD and its associated gastrointestinal abnormalities based on the gut–brain axis. Therefore, we performed an analysis for ASD based on preclinical and clinical research to give a comprehensive synthesis of published evidence of a potential mechanism for ASD. On the one hand, this review aims to elucidate the link between gastrointestinal abnormalities and ASD. Accordingly, we discuss gut microbiota dysbiosis regarding gut–brain axis dysfunction. On the other hand, this review suggests that probiotic administration to regulate the gut–brain axis might improve gastrointestinal symptoms, restore ASD-related behavioral symptoms, restore gut microbiota composition, reduce inflammation, and restore intestinal barrier function in human and animal models. This review suggests that targeting the microbiota through agents such as probiotics may represent an approach for treating subsets of individuals with ASD.

Novel ketamine and zinc treatment for anorexia nervosa and the potential beneficial interactions with the gut microbiome

Anorexia nervosa (AN) is a severe illness with diverse aetiological and maintaining contributors including neurobiological, metabolic, psychological, and social determining factors. In addition to nutritional recovery, multiple psychological and pharmacological therapies and brain-based stimulations have been explored; however, existing treatments have limited efficacy. This paper outlines a neurobiological model of glutamatergic and γ-aminobutyric acid (GABA)-ergic dysfunction, exacerbated by chronic gut microbiome dysbiosis and zinc depletion at a brain and gut level. The gut microbiome is established early in development, and early exposure to stress and adversity contribute to gut microbial disturbance in AN, early dysregulation to glutamatergic and GABAergic networks, interoceptive impairment, and inhibited caloric harvest from food (e.g., zinc malabsorption, competition for zinc ions between gut bacteria and host). Zinc is a key part of glutamatergic and GABAergic networks, and also affects leptin and gut microbial function; systems dysregulated in AN. Low doses of ketamine in conjunction with zinc, could provide an efficacious combination to act on NMDA receptors and normalise glutamatergic, GABAergic and gut function in AN.

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

ETHNIC PHARMACOLOGICAL RELEVANCE

The causes of depression are complex. Many factors are involved in its pathogenesis, including the individual's biological and social environment. Although numerous studies have reported that the gut microbiota plays a significant role in depression, drugs that regulate the gut microbiota to treat depression have not yet been comprehensively reviewed. At the same time, more and more attention has been paid to the characteristics of traditional Chinese medicine (TCM) in improving depression by regulating gut microbiota. In ancient times, fecal microbiota transplantation was recorded in TCM for the treatment of severe diseases. There are also records in Chinese ancient books about the use of TCM to adjust gut microbiota to treat diseases, which has opened up a unique research field in TCM. Therefore, this article focuses on the pharmacological effects, targets, and mechanisms of TCM in improving depression by mediating the influence of gut microbiota.

AIM OF THIS REVIEW

To summarize the role the gut microbiota plays in depression, highlight potential regulatory targets, and elucidate the anti-depression mechanisms of TCMs through regulation of the gut microbiota.

METHODS

A systematic review of 256 clinical trials and pharmaceutical studies published until June 2022 was conducted in eight electronic databases (Web of Science, PubMed, SciFinder, Research Gate, ScienceDirect, Google Scholar, Scopus, and China Knowledge Infrastructure), according to the implemented PRISMA criteria, using the search terms "traditional Chinese medicine," "depression," and "gut microbiota."

RESULTS

Numerous studies reported the effects of different gut bacteria on depression and that antidepressants work through the gut microbiota. TCM preparations based on compound Chinese medicine, the Chinese Materia Medica, and major bioactive components exerted antidepressant-like effects by improving levels of neurotransmitters, short-chain fatty acids, brain-derived neurotrophic factor, kynurenine, and cytokines via regulation of the gut microbiota.

CONCLUSION

This review summarized the anti-depression effects of TCM on the gut microbiota, providing evidence that TCMs are safe and effective in the treatment of depression and may provide a new therapeutic approach.

Beyond the classical amyloid hypothesis in Alzheimer's disease: Molecular insights into current concepts of pathogenesis, therapeutic targets, and study models

Alzheimer's disease (AD) is one of the progressive neurodegenerative disorders and the most common cause of dementia in the elderly worldwide causing difficulties in the daily life of the patient. AD is characterized by the aberrant accumulation of β-amyloid plaques and tau protein-containing neurofibrillary tangles (NFTs) in the brain giving rise to neuroinflammation, oxidative stress, synaptic failure, and eventual neuronal cell death. The total cost of care in AD treatment and related health care activities is enormous and pharmaceutical drugs approved by Food and Drug Administration have not manifested sufficient efficacy in protection and therapy. In recent years, there are growing studies that contribute a fundamental understanding to AD pathogenesis, AD-associated risk factors, and pharmacological intervention. However, greater molecular process-oriented research in company with suitable experimental models is still of the essence to enhance the prospects for AD therapy and cell lines as a disease model are still the major part of this milestone. In this review, we provide an insight into molecular mechanisms, particularly the recent concept in gut-brain axis, vascular dysfunction and autophagy, and current models used in the study of AD. Here, we emphasized the importance of therapeutic strategy targeting multiple mechanisms together with utilizing appropriate models for the discovery of novel effective AD therapy. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology.

Alleviation of Porphyromonas gingivalis or Its Extracellular Vesicles Provoked Periodontitis and Cognitive Impairment by Lactobacillus pentosus NK357 and Bifidobacterium bifidum NK391

Porphyromonas gingivalis (PG) is closely involved in the outbreak of periodontitis and cognitive impairment (CI). Herein, we examined the effects of anti-inflammatory Lactobacillus pentosus NK357 and Bifidobacterium bifidum NK391 on PG- or its extracellular vesicles (pEVs)-induced periodontitis and CI in mice. Oral administration of NK357 or NK391 significantly decreased PG-induced tumor necrosis factor (TNF)-α, receptor activator of nuclear factors κB (RANK), and RANK ligand (RANKL) expression, gingipain (GP)⁺lipopolysaccharide (LPS)⁺ and NF-κB⁺CD11c⁺ populations, and PG 16S rDNA level in the periodontal tissue. Their treatments also suppressed PG-induced CI -like behaviors, TNF-α expression and NF-κB-positive immune cells in the hippocampus and colon, while PG-suppressed hippocampal BDNF and N-methyl-D-aspartate receptor (NMDAR) expression increased. The combination of NK357 and NK391 additively alleviated PG- or pEVs-induced periodontitis, neuroinflammation, CI-like behaviors, colitis, and gut microbiota dysbiosis and increased PG- or pEVs-suppressed BDNF and NMDAR expression in the hippocampus. In conclusion, NK357 and NK391 may alleviate periodontitis and dementia by regulating NF-κB, RANKL/RANK, and BDNF-NMDAR signaling and gut microbiota.

The Prevention of Inflammation and the Maintenance of Iron and Hepcidin Homeostasis in the Gut, Liver, and Brain Pathologies

The human gut microbiome consists of a variety of microorganisms that inhabit the intestinal tract. This flora has recently been shown to play an important role in human disease. The crosstalk between the gut and brain axis has been investigated through hepcidin, derived from both hepatocytes and dendritic cells. Hepcidin could potentially play an anti-inflammatory role in the process of gut dysbiosis through a means of either a localized approach of nutritional immunity, or a systemic approach. Like hepcidin, mBDNF and IL-6 are part of the gut-brain axis: gut microbiota affects their levels of expression, and this relationship is thought to play a role in cognitive function and decline, which could ultimately lead to a number of neurodegenerative diseases such as Alzheimer's disease. This review will focus on the interplay between gut dysbiosis and the crosstalk between the gut, liver, and brain and how this is mediated by hepcidin through different mechanisms including the vagus nerve and several different biomolecules. This overview will also focus on the gut microbiota-induced dysbiotic state on a systemic level, and how gut dysbiosis can contribute to beginnings and the progression of Alzheimer's disease and neuroinflammation.

Lactobacillus gasseri NK109 and Its Supplement Alleviate Cognitive Impairment in Mice by Modulating NF-κB Activation, BDNF Expression, and Gut Microbiota Composition

Aging-related gut microbiota dysbiosis initiates gut inflammation and microbiota dysbiosis, which induce the occurrence of psychiatric disorders including dementia. The alleviation of gut microbiota dysbiosis by probiotics is suggested to be able to alleviate psychiatric disorders including cognitive impairment (CI). Therefore, to understand how probiotics could alleviate CI, we examined the effects of anti-inflammatory Lactobacillus gasseri NK109 and its supplement (NS, mixture of NK109 and soybean embryo ethanol extract) on cognitive function in aged (Ag), 5XFAD transgenic (Tg), or mildly cognition-impaired adult fecal microbiota (MCF)-transplanted mice. Oral administration of NK109 or NS decreased CI-like behaviors in Ag mice. Their treatments suppressed TNF-α and p16 expression and NF-κB-activated cell populations in the hippocampus and colon, while BDNF expression was induced. Moreover, they partially shifted the β-diversity of gut microbiota in Ag mice to those of young mice: they decreased Bifidobacteriaceae, Lactobacillaceae, and Helicobacteriaceae populations and increased Rikenellaceae and Prevotellaceae populations. Oral administration of NK109 or NS also reduced CI-like behaviors in Tg mice. Their treatments induced BDNF expression in the hippocampus, decreased hippocampal TNF-α and Aβ expression and hippocampal and colonic NF-κB-activated cell populations. NK109 and NS partially shifted the β-diversity of gut microbiota in Tg mice: they decreased Muribaculaceae and Rhodospiraceae populations and increased Helicobacteriaceae population. Oral administration of NK109 or NS decreased MCF transplantation-induced CI-like behaviors in mice. NK109 and NS increased hippocampal BDNF expression, while hippocampal and colonic TNF-α expression and NF-κB-activated cell populations decreased. These findings suggest that dementia can fluctuate the gut microbiota composition and NK109 and its supplement NS can alleviate CI with systemic inflammation by inducing BDNF expression and suppressing NF-κB activation and gut microbiota dysbiosis.

Canagliflozin attenuates chronic unpredictable mild stress induced neuroinflammation via modulating AMPK/mTOR autophagic signaling

Although vast progress has been made to understand the pathogenesis of depression, existing antidepressant remedies, with several adverse effects, are not fully adequate. Interestingly, new emerging theories implicating an altered HPA-axis, tryptophan metabolism, neuroinflammation and altered gut integrity were proposed to further identify novel therapeutic targets. Along these lines, canagliflozin (CAN), a novel antidiabetic medication with anti-inflammatory and neuroprotective activity may present an effective treatment for depression; nevertheless, no studies have explored its effect on depressive disorder yet. To this end, this study aimed to investigate the possible antidepressant activity of CAN in CUMS and the mechanisms underlying its action on the gut-brain inflammation axis as well as the alteration in the TRY/KYN pathway in addition to its role in modulating the autophagic signaling cascade. Interestingly, CAN successfully attenuated the CUMS-induced elevations in despair and anhedonic behaviors as well as the elevated serum CORT. Furthermore, it enhanced gut integrity via hampering the CUMS-induced colonic inflammation and amending colonic tight junction proteins. The enhanced gut integrity was further corroborated by a notable anti-inflammatory and neuroprotective activity manifested via the observed mitigation of immune cell activation in addition to IDO hippocampal protein content and promotion of the autophagy cascade. Our findings postulate the possible anti-inflammatory and neuroprotective effects of CAN and the implication of TRY/KYN and AMPK/mTOR signaling pathways in the CUMS-induced MDD. Hence, this study shed light to the promising role of CAN in the augmentation of the current antidepressant treatments.

Anxiolytic- and antidepressant-like effects of Bacillus coagulans Unique IS-2 mediate via reshaping of microbiome gut-brain axis in rats

BACKGROUND

Due to the rising cases of treatment-refractory affective disorders, the discovery of newer therapeutic approaches is needed. In recent times, probiotics have garnered notable attention in managing stress-related disorders. Herein, we examined the effect of Bacillus coagulans Unique IS-2® probiotic on anxiety- and depression-like phenotypes employing maternal separation (MS) and chronic-unpredictable mild stress (CUMS) model in rats.

METHODS

Both male and female Sprague-Dawley rats were subjected to MS + CUMS. Probiotic treatment was provided for 6 weeks via drinking water. Anxiety- and depression-like phenotypes were assessed using sucrose-preference test (SPT), forced-swimming test (FST), elevated-plus maze test (EPM), and open-field test (OFT). Blood, brain, intestine, and fecal samples were obtained for biochemical and molecular studies.

RESULTS

Stress-exposed rats drank less sucrose solution, showed increased passivity, and explored less in open-arms in SPT, FST, and EPM, respectively. These stress-generated neurobehavioral aberrations were alleviated by 6-week of Bacillus coagulans Unique IS-2 treatment. The overall locomotor activity in OFT remained unchanged. The decreased levels of BDNF and serotonin and increased levels of C-reactive protein, TNF-α, IL-1β, and dopamine, in the hippocampus and/or frontal cortex of stress-exposed rats were reversed following probiotic treatment. Administration of probiotic also restored the systemic levels of L-tryptophan, L-kynurenine, kynurenic-acid, and 3-hydroxyanthranilic acid, villi/crypt ratio, goblet-cell count, Firmicutes to Bacteroides ratio, and levels of acetate, propionate, and butyrate in fecal samples. These results indicate remodeling of the microbiome gut-brain axis in Bacillus coagulans Unique IS-2 recipient rats. However, protein levels of doublecortin, GFAP, and zona occludens in the hippocampus and occludin-immunoreactivity in the intestine remained unchanged. No prominent sex-specific changes were noted.

CONCLUSION

Anxiolytic- and antidepressant-like effects of Bacillus coagulans Unique IS-2 in MS + CUMS rat model may be mediated via reshaping the microbiome gut-brain axis.

Gut as the target tissue of mercury and the extraintestinal effects

Mercury (Hg) is harmful to the environment and human health. The gut plays important roles as the biological, chemical, mechanical, and immune barriers in animals and human beings. It has been known that Hg can be absorbed and methylated/demethylated in the gut, on the other hand, the impacts of Hg to the gut (especially the gut microbiota) is less studied. This review paper summarizes the impacts of inorganic Hg (IHg) and methyl Hg (MeHg) on gut barriers and the extraintestinal effects (damage to other organs such as the liver and brain). Both IHg and MeHg were found to cause intestinal microbial disorders, abnormal metabolites production, tight junction damage, and immune responses in the gut. The damage to the gut also contributed to the extraintestinal effects like the hepatotoxicity by IHg and the neurotoxicity by MeHg. In all, it is proposed that the gut should be considered as an important target tissue of Hg exposure, and the regulation of gut microbiota may have the potential for the prevention and control of the toxicity of Hg.

Microbiota-Gut-Brain Axis in Major Depression: A New Therapeutic Approach

Major depression is impacted by the disruption of gut microbiota. Defects in gut microbiota can lead to microbiota-gut-brain axis dysfunction and increased vulnerability to major depression. While traditional chemotherapeutic approaches, such as antidepressant use, produce an overall partial therapeutic effect on depression, the gut microbiome has emerged as an effective target for better therapeutic outcomes. Recent representative studies on the microbiota hypothesis to explore the association between gut pathophysiology and major depression have indicated that restoring gut microbiota and microbiota-gut-brain axis could alleviate depression. We reviewed studies that supported the gut microbiota hypothesis to better understand the pathophysiology of depression; we also explored reports suggesting that gut microbiota restoration is an effective approach for improving depression. These findings indicate that gut microbiota and microbiota-gut-brain axis are appropriate new therapeutic targets for major depression.

Efficacy of Bifidobacterium longum alone or in multi-strain probiotic formulations during early life and beyond

The significance of Bifidobacterium to human health can be appreciated from its early colonization of the neonatal gut, where Bifidobacterium longum represents the most abundant species. While its relative abundance declines with age, it is further reduced in several diseases. Research into the beneficial properties of B. longum has unveiled a range of mechanisms, including the production of bioactive molecules, such as short-chain fatty acids, polysaccharides, and serine protease inhibitors. From its intestinal niche, B. longum can have far-reaching effects in the body influencing immune responses in the lungs and even skin, as well as influencing brain activity. In this review, we present the biological and clinical impacts of this species on a range of human conditions beginning in neonatal life and beyond. The available scientific evidence reveals a strong rationale for continued research and further clinical trials that investigate the ability of B. longum to treat or prevent a range of diseases across the human lifespan.

Roles of gut microbiome in epilepsy risk: A Mendelian randomization study

Background

Recent studies have suggested an association between gut microbiomes (GMs) and epilepsy. However, the GM taxa identified in different studies are variable. In addition, observational studies cannot indicate causality. Therefore, our study aimed to explore the causal association of GMs with epilepsy and identify the most influential GM taxa.

Methods

We conducted a Mendelian randomization (MR) study using summary statistics from genome-wide association studies (GWAS) of 211 GM taxa and epilepsy. The GWAS summary statistics for 211 GM taxa (from phylum to genus level) were generated by the MiBioGen consortium, while the FinnGen consortium provided the GWAS summary statistics for epilepsy. The primary analytical method to assess causality was the inverse-variance weighted (IVW) approach. To complement the IVW method, we also applied four additional MR methods: MR-Egger, weighted median, simple mode, and weighted. In addition, we conducted sensitivity analyses using Cochrane's Q-test, MR-Egger intercept test, MR-PRESSO global test, and leave-one-out analysis.

Results

We evaluated the causal effect of 211 GM taxa (from phylum to genus level) on epilepsy, generalized epilepsy, and focal epilepsy. After using the Bonferroni method for multiple testing correction, Class Betaproteobacteria [odds ratio (OR) = 1.357, 95% confidence interval (CI): 1.126-1.635, p = 0.001] and Order Burkholderiales (OR = 1.336, 95% CI: 1.112-1.606, p = 0.002). In addition, 21 nominally significant causal relationships were also identified. Further, the MR-Egger intercept test and MR-PRESSO global test suggested that our MR analysis was unaffected by horizontal pleiotropy (p > 0.05). Finally, the leave-one-out analysis suggested the robustness of the results.

Conclusion

Through the MR study, we analyzed the causal relationship of 211 GM taxa with epilepsy and determined the specific intestinal flora associated with increased epilepsy risk. Our findings may provide helpful biomarkers for disease progression and potential candidate therapeutic targets for epilepsy. In addition, in-depth analysis of large-scale microbiome GWAS datasets based on metagenomics sequencing is necessary for future studies.

Interlink between the gut microbiota and inflammation in the context of oxidative stress in Alzheimer's disease progression

The microbiota-gut-brain axis is an important pathway of communication and may dynamically contribute to Alzheimer's disease (AD) pathogenesis. Pathological commensal gut microbiota alterations, termed as dysbiosis, can influence intestinal permeability and break the blood-brain barrier which may trigger AD pathogenesis via redox signaling, neuronal, immune, and metabolic pathways. Dysbiosis increases the oxidative stress. Oxidants affect the innate immune system through recognizing microbial-derived pathogens by Toll-like receptors and initiating the inflammatory process. Most of the gut microbiome research work highlights the relationship between the gut microbiota and AD, but the contributory connection between precise bacteria and brain dysfunction in AD pathology cannot be fully demonstrated. Here, we summarize the current information of the fundamental connections between oxidative stress, inflammation, and gut dysbiosis in AD. This review emphasizes on the involvement of gut microbiota in the regulation of oxidative stress, inflammation, immune responses including central and peripheral cross-talk. It provides insights for novel preventative and therapeutic approaches in AD.

Fermented maize slurry (Ogi) and its supernatant (Omidun) mitigate elevated intraocular pressure by modulating BDNF expression and glial plasticity in the retina-gut axis of glaucomatous rats

OBJECTIVES

Growing interest has been reported on the health benefits of fermented foods, which includes cognition enhancement and inflammation attenuation. BDNF is a known protectant against retinal degeneration, however, therapies that target this neurotrophic factor has been limited. Therefore, we assessed the reaction of BDNF and glial cells in glaucomatous rats and their response to treatment with fermented maize products.

METHODS

Thirty male adult rats were either injected via the episcleral vein with hypertonic saline to elevate intraocular pressure (IOP) or treated with fermented maize slurry (Ogi) or its supernatant (Omidun). Following sacrifice, the retina and duodenum were studied by immunohistochemical analysis using antibodies directed against GFAP, AIF-1 and BDNF.

RESULTS

Hypertonic saline injection produced hypertrophy of the Müller cells and increased GFAP and AIF-1 expression in the retina and gut when compared to the control. Treatment with Ogi and Omidun produced varying degrees of reduction of gliosis, protection against hypertonic saline-induced retinal ganglion cell loss, and reduced intraocular pressure. BDNF expression was downregulated following the hypertonic saline assault, while Omidun and Ogi treatment abrogated its reduction following the hypertonic saline assault.

CONCLUSIONS

Collectively, our findings suggest that acute elevation of IOP alters crosstalk between gut and retina with consequent aberrant activation of glial cells; and that probiotic bacteria like the lactic acid bacteria rich in fermented foods including Ogi and Omidun may offer neuroprotection to the ganglionic cells by attenuating the retinal glial reaction and improving BDNF activity.

Mucosal Immunity and the Gut-Microbiota-Brain-Axis in Neuroimmune Disease

Recent advances in next-generation sequencing (NGS) technologies have opened the door to a wellspring of information regarding the composition of the gut microbiota. Leveraging NGS technology, early metagenomic studies revealed that several diseases, such as Alzheimer's disease, Parkinson's disease, autism, and myalgic encephalomyelitis, are characterized by alterations in the diversity of gut-associated microbes. More recently, interest has shifted toward understanding how these microbes impact their host, with a special emphasis on their interactions with the brain. Such interactions typically occur either systemically, through the production of small molecules in the gut that are released into circulation, or through signaling via the vagus nerves which directly connect the enteric nervous system to the central nervous system. Collectively, this system of communication is now commonly referred to as the gut-microbiota-brain axis. While equally important, little attention has focused on the causes of the alterations in the composition of gut microbiota. Although several factors can contribute, mucosal immunity plays a significant role in shaping the microbiota in both healthy individuals and in association with several diseases. The purpose of this review is to provide a brief overview of the components of mucosal immunity that impact the gut microbiota and then discuss how altered immunological conditions may shape the gut microbiota and consequently affect neuroimmune diseases, using a select group of common neuroimmune diseases as examples.

Altered gut microbiota and its metabolites correlate with plasma cytokines in schizophrenia inpatients with aggression

BACKGROUND

The pathophysiological mechanisms of aggression are manifold and they may closely interconnect. Current study aimed to determine the gut microbiota and its metabolites, and clarify their correlations with inflammation, oxidation, leaky gut and clinical profiles underlying aggression in schizophrenia (ScZ).

METHODS

Serum and stool specimens from ScZ inpatients with (ScZ-Ag, 25 cases) and without aggression (NScZ-Ag, 25 cases) were collected. Systemic inflammation, oxidation and leaky gut biomarkers were determined by ELISA, gut microbiota by 16S rRNA sequencing, short-chain fatty acids (SCFAs) by gas chromatography-mass spectrometry analysis and neurotransmitters by liquid chromatograph mass spectrometry analysis.

RESULTS

Significantly higher systemic pro-inflammation, pro-oxidation and leaky gut biomarkers were observed in ScZ-Ag than NScZ-Ag group (all P<0.001). Compared to NScZ-Ag group, the alpha-diversity and evenness of fecal bacterial community were much lower, the abundance of fecal genera Prevotella was significantly increased, while that Bacteroides, Faecalibacterium, Blautia, Bifidobacterium,Collinsella and Eubacterium_coprostanoligenes were remarkably reduced in ScZ-Ag group (all corrected P<0.001). Meanwhile, 6 SCFAs and 6 neurotransmitters were much lower in ScZ-Ag group (all P<0.05). Finally, a few strongly positive or negative correlations among altered gut microbiota, SCFAs, systemic pro-inflammation, leaky gut, pro-oxidation and aggression severity were detected.

CONCLUSIONS

These results demonstrate that pro-inflammation, pro-oxidation and leaky gut phenotypes relating to enteric dysbacteriosis and microbial SCFAs feature the aggression onset or severity in ScZ individuals.

Dysbiosis and Migraine Headaches in Adults With Celiac Disease

One of the most significant illnesses associated with gluten is celiac disease, which encompasses many conditions. It is generally recognized that neurological manifestations can occur either at the time of the disease onset or as the illness continues to develop. One of the main clinical presentations of celiac disease is headache, either in the form of migraine or in an unspecific form. Migraine pathophysiology is intricate and still poorly understood. Several mechanisms involving the gut-brain axis have been proposed to explain this association. These include the interaction of chronic inflammation with inflammatory and vasoactive mediators, the modulation of the intestinal immune environment of the microbiota, and the dysfunction of the autonomic nervous system. However, further research is required to fully comprehend the fundamental mechanisms and pathways at play. This review aims to give a narrative summary of the literature on celiac disease's neurological symptoms, particularly migraines, and to assess any potential associations to dysbiosis, an imbalance in the microbiome.

Dietary Fiber Intake is Associated with Cognitive Function in Older Adults: Data from the National Health and Nutrition Examination Survey

BACKGROUND

Aging is a global health challenge that is associated with a decline in cognitive function. In the United States, most older adults (≥50 years) do not meet the recommended daily fiber intake, although preliminary evidence suggests that dietary fiber consumption could elicit clinical benefits on cognitive function. We investigated the associations between dietary fiber intake and cognitive function in older adults.

METHODS

We analyzed data from the US National Health and Nutrition Examination Survey (NHANES) between 2011 and 2014, with a study cohort of 1070 older adults (≥60 years). Cognitive function was assessed using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word Learning Test (WLT), Word Recall Test (WRT) and their Intrusion Word Count Tests (WLT-IC and WRT-IC), the Animal Fluency Test (AFT), and the Digit Symbol Substitution Test (DSST). Multiple linear regression and cubic spline analyses were employed to examine the association between dietary fiber intake and cognitive performance on a test-by-test basis, after covariates adjustment (ie, age, sex, race, socioeconomic status, educational level, medical history, body mass index, alcohol, and energy intake).

RESULTS

Participants had a mean age of 69.2 years and were primarily non-Hispanic white of middle-high socioeconomic status with a college degree at minimum. The mean dietary fiber intake was 17.3 g/d. The analysis showed that dietary fiber intake was positively associated with DSST (P = .031). No associations with CERAD WLT (P = .41), WRT (P = .68), WLT-IC (P = .07), and WRT-IC (P = .28), and AFT (P = .40) scores were observed. A plateau in DSST score was revealed at a dietary fiber intake of 34 g/d.

CONCLUSIONS

Higher dietary fiber intake is associated with improved specific components of cognitive function in older adults aged 60 years and older. Public health interventions that target a recommended dietary fiber intake may provide a promising strategy to combat cognitive decline in high-risk groups of older adults.

Gut microbiota dysbiosis: The potential mechanisms by which alcohol disrupts gut and brain functions

Alcohol use disorder (AUD) is a high-risk psychiatric disorder and a key cause of death and disability in individuals. In the development of AUD, there is a connection known as the microbiota-gut-brain axis, where alcohol use disrupts the gut barrier, resulting in changes in intestinal permeability as well as the gut microbiota composition, which in turn impairs brain function and worsens the patient’s mental status and gut activity. Potential mechanisms are explored by which alcohol alters gut and brain function through the effects of the gut microbiota and their metabolites on immune and inflammatory pathways. Alcohol and microbiota dysregulation regulating neurotransmitter release, including DA, 5-HT, and GABA, are also discussed. Thus, based on the above discussion, it is possible to speculate on the gut microbiota as an underlying target for the treatment of diseases associated with alcohol addiction. This review will focus more on how alcohol and gut microbiota affect the structure and function of the gut and brain, specific changes in the composition of the gut microbiota, and some measures to mitigate the changes caused by alcohol exposure. This leads to a potential intervention for alcohol addiction through fecal microbiota transplantation, which could normalize the disruption of gut microbiota after AUD.

Effect of time restricted feeding on anthropometric measures, eating behavior, stress, and brain-derived neurotrophic factor (BDNF) and lipopolysaccharide-binding protein (LBP) levels in women with overweight/obesity and food addiction: a study protocol for a randomized clinical trial

Background

Food addiction is one of the behavioral factors that play an important role in the pathogenesis of obesity. Much evidence is available suggesting intestinal microbiomes can play a role in eating behavior, body composition, and BDNF levels, and they can be modified by time-restricted feeding (TRF). So, this study will aim to evaluate the effect of TRF on anthropometric measures, eating behavior, stress, and serum BDNF and LBP levels in women with overweight/obesity and food addiction.

Methods

We will carry out a randomized clinical trial for 8 weeks to evaluate the effect of a TRF on anthropometric measures, eating behavior, stress level, serum BDNF and LBP levels in women with overweight/obesity and food addiction.

Discussion

Given the effect of BDNF on regulating eating behavior and body weight and the effect of dietary restrictions on BDNF and the gut microbiome, the TRF diet could possibly be a new way to successfully manage weight through modifying BDNF in people with eating disorders, including food addiction.

Trial registration

Iranian Registry of Clinical Trials IRCT20131228015968N7. Registered on 25 October 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06439-x.

Alteration in peritoneal cells with the chemokine CX3CL1 reverses age-associated impairment of recognition memory

Cognitive function progressively declines with advancing age. The aging process can be promoted by obesity and attenuated by exercise. Both conditions affect levels of the chemokine CX3CL1 in peripheral tissues; however, its role in cognitive aging is unknown. In the current study, we administered CX3CL1 into the peritoneal cavity of aged mice to investigate its impact on the aging process. In the peritoneal cavity, CX3CL1 not only reversed the age-associated accumulation of cells expressing the senescence marker p16^INK4a but also increased peritoneal phagocytic activity, indicating that CX3CL1 affected the phenotypes of peritoneal cells. In the hippocampus of aged mice, intraperitoneal administration of CX3CL1 increased the number of Type-2 neural stem cells and promoted brain-derived neurotrophic factor (BDNF) expression. This treatment, furthermore, improved novel object recognition memory impaired with advancing age. Intraperitoneal transplantation of peritoneal cells from CX3CL1-treated aged mice improved novel object recognition memory in recipient aged mice. It indicates that peritoneal cells have a critical role in the CX3CL1-induced improvement of recognition memory in aged mice. Vagotomy inhibited the CX3CL1-induced increase in BDNF expression, demonstrating that the vagus nerve is involved in the hippocampal BDNF expression induced by intraperitoneal administration of CX3CL1. Thus, our results demonstrate that a novel connection among the peritoneal cells, the vagus nerve, and the hippocampus can reverse the age-associated decline in recognition memory.

Novel probiotic treatment of autism spectrum disorder associated social behavioral symptoms in two rodent models

The prevalence of autism spectrum disorder (ASD) has rapidly increased in the past decades, and several studies report about the escalating use of antibiotics and the consequent disruption of the gastrointestinal microbiome leading to the development of neurobehavioral symptoms resembling to those of ASD. The primary purpose of this study was to investigate whether depletion of the gastrointestinal microbiome via antibiotics treatment could induce ASD-like behavioral symptoms in adulthood. To reliably evaluate that, validated valproic acid (VPA) ASD animal model was introduced. At last, we intended to demonstrate the assessed potential benefits of a probiotic mixture (PM) developed by our research team. Male Wistar rats were used to create antibiotics treated; antibiotics and PM treated; PM treated, VPA treated; VPA and PM treated; and control groups. In all investigations we focused on social behavioral disturbances. Antibiotics-induced microbiome alterations during adulthood triggered severe deficits in social behavior similar to those observed in the VPA model. Furthermore, it is highlighted that our PM proved to attenuate both the antibiotics- and the VPA-generated antisocial behavioral symptoms. The present findings underline potential capacity of our PM to improve social behavioral alterations thus, indicate its promising therapeutic power to attenuate the social-affective disturbances of ASD.

Emerging Evidence for the Widespread Role of Glutamatergic Dysfunction in Neuropsychiatric Diseases

The monoamine model of depression has long formed the basis of drug development but fails to explain treatment resistance or associations with stress or inflammation. Recent animal research, clinical trials of ketamine (a glutamate receptor antagonist), neuroimaging research, and microbiome studies provide increasing evidence of glutamatergic dysfunction in depression and other disorders. Glutamatergic involvement across diverse neuropathologies including psychoses, neurodevelopmental, neurodegenerative conditions, and brain injury forms the rationale for this review. Glutamate is the brain's principal excitatory neurotransmitter (NT), a metabolic and synthesis substrate, and an immune mediator. These overlapping roles and multiple glutamate NT receptor types complicate research into glutamate neurotransmission. The glutamate microcircuit comprises excitatory glutamatergic neurons, astrocytes controlling synaptic space levels, through glutamate reuptake, and inhibitory GABA interneurons. Astroglia generate and respond to inflammatory mediators. Glutamatergic microcircuits also act at the brain/body interface via the microbiome, kynurenine pathway, and hypothalamus-pituitary-adrenal axis. Disruption of excitatory/inhibitory homeostasis causing neuro-excitotoxicity, with neuronal impairment, causes depression and cognition symptoms via limbic and prefrontal regions, respectively. Persistent dysfunction reduces neuronal plasticity and growth causing neuronal death and tissue atrophy in neurodegenerative diseases. A conceptual overview of brain glutamatergic activity and peripheral interfacing is presented, including the common mechanisms that diverse diseases share when glutamate homeostasis is disrupted.

Gut Microbiota Dysbiosis in Acute Ischemic Stroke Associated With 3-Month Unfavorable Outcome

Background

Alterations in the gut microbiota after ischemic stroke have been demonstrated, whereas the effect on stroke outcome remains to be established.

Methods

A total of 132 consecutive patients with acute ischemic stroke were prospectively enrolled. Their gut microbiomes within 24 h of admission were profiled using 16S ribosomal RNA (rRNA) gene (V3–V4 region) sequencing. Microbiota comparisons were made between groups with good outcome (n = 105) and poor outcome (n = 27) based on 3-month modified Rankin Scale scores of 0–2 and 3–6. Propensity score-matching (PSM) analysis was conducted to assess the robustness of our findings. The functional potential was predicted using the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt).

Results

Patients in the poor outcome group were characterized by a significant reduction in the alpha diversity (Shannon index, p = 0.025; Simpson index, p = 0.010), an increase in the pathogenic bacteria (e.g., Enterococcaceae and Enterococcus), and a decrease in the short-chain fatty acids (SCFAs)-producing bacteria (e.g., Bacteroidaceae, Ruminococcaceae, and Faecalibacterium) to those with good outcome group (all p < 0.05). Similar results of microbial composition were obtained after PSM. The PICRUSt revealed that the pathway for membrane transport was relatively dominant in patients with poor outcome (p < 0.05).

Conclusion

This study demonstrated that stroke patients with 3-month poor outcome had baseline gut microbiota dysbiosis featured by increased pathogenic bacteria and decreased SCFAs-producing bacteria.

Brain-derived neurotrophic factor in Alzheimer's disease and its pharmaceutical potential

Synaptic abnormalities are a cardinal feature of Alzheimer's disease (AD) that are known to arise as the disease progresses. A growing body of evidence suggests that pathological alterations to neuronal circuits and synapses may provide a mechanistic link between amyloid β (Aβ) and tau pathology and thus may serve as an obligatory relay of the cognitive impairment in AD. Brain-derived neurotrophic factors (BDNFs) play an important role in maintaining synaptic plasticity in learning and memory. Considering AD as a synaptic disorder, BDNF has attracted increasing attention as a potential diagnostic biomarker and a therapeutical molecule for AD. Although depletion of BDNF has been linked with Aβ accumulation, tau phosphorylation, neuroinflammation and neuronal apoptosis, the exact mechanisms underlying the effect of impaired BDNF signaling on AD are still unknown. Here, we present an overview of how BDNF genomic structure is connected to factors that regulate BDNF signaling. We then discuss the role of BDNF in AD and the potential of BDNF-targeting therapeutics for AD.

Using integrated meta-omics to appreciate the role of the gut microbiota in epilepsy

The way the human microbiota may modulate neurological pathologies is a fascinating matter of research. Epilepsy is a common neurological disorder, which has been largely investigated in correlation with microbiota health and function. However, the mechanisms that regulate this apparent connection are scarcely defined, and extensive effort has been conducted to understand the role of microbiota in preventing and reducing epileptic seizures. Intestinal bacteria seem to modulate the seizure frequency mainly by releasing neurotransmitters and inflammatory mediators. In order to elucidate the complex microbial contribution to epilepsy pathophysiology, integrated meta-omics could be pivotal. In fact, the combination of two or more meta-omics approaches allows a multifactorial study of microbial activity within the frame of disease or drug treatments. In this review, we provide information depicting and supporting the use of multi-omics to study the microbiota-epilepsy connection. We described different meta-omics analyses (metagenomics, metatranscriptomics, metaproteomics and metabolomics), focusing on current technical challenges in stool collection procedures, sample extraction methods and data processing. We further discussed the current advantages and limitations of using the integrative approach of multi-omics in epilepsy investigations.

The Effect of Pro-/Synbiotic Supplementation on Brain-Derived Neurotrophic Factor: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

There is a growing interest in supplementation with pro-/synbiotics for brain and mental health. Animal studies have reported that pro-/synbiotic administration can increase brain-derived neurotrophic factor (BDNF), a key regulator...

The Gut Microbiota-Brain Axis: A New Frontier on Neuropsychiatric Disorders

Alzheimer's disease (AD) is a progressive and incurable neurodegenerative disorder of integrative areas of the brain, characterized by cognitive decline and disability resulting in negative impacts on the family of the patients and the health care services worldwide. AD involves oxidative stress, neuroinflammation and accelerated apoptosis, accompanied by deposition of amyloid-β peptide plaques and tau protein-based neurofibrillary tangles in the central nervous system. Among the multiple factors that contribute to the onset and evolution of this disease, aging stands out. That is why the prevalence of this disease has increased due to the constant increase in life expectancy. In the hope of finding new, more effective methods to slow the progression of this disease, over the last two decades, researchers have promoted "omics"-based approaches that include the gut microbiota and their reciprocal interactions with different targets in the body. This scientific advance has also led to a better understanding of brain compartments and the mechanisms that affect the integrity of the blood-brain barrier. This review aims to discuss recent advances related to the gut-brain-microbiota axis in AD. Furthermore, considering that AD involves psychiatric symptoms, this review also focuses on the psychiatric factors that interact with this axis (an issue that has not yet been sufficiently addressed in the literature).

Effects of gut microbiota and probiotics on Alzheimer’s disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disease with high morbidity, disability, and fatality rate, significantly increasing the global burden of public health. The failure in drug discovery over the past decades has stressed the urgency and importance of seeking new perspectives. Recently, gut microbiome (GM), with the ability to communicate with the brain bidirectionally through the microbiome–gut–brain axis, has attracted much attention in AD-related studies, owing to their strong associations with amyloids, systematic and focal inflammation, impairment of vascular homeostasis and gut barrier, mitochondrial dysfunction, etc., making the regulation of GM, specifically supplementation of probiotics a promising candidate for AD treatment. This article aims to review the leading-edge knowledge concerning potential roles of GM in AD pathogenesis and of probiotics in its treatment and prevention.

Gut microorganisms and neurological disease perspectives

The gastrointestinal tract of every healthy human consists of a unique set of gut microbiota that collectively harbors a diverse and complex community of over 100 trillion microorganisms, including bacteria, viruses, archaea, protozoa and fungi. Gut microbes have a symbiotic relationship with our body. The composition of the microbiota is shaped early in life by gut maturation, which is influenced by several factors. Intestinal bacteria are crucial in maintaining immune and metabolic homeostasis and protecting against pathogens. Dysbiosis of gut microbiota is associated not only with intestinal disorders but also with extraintestinal diseases such as metabolic and neurological disorders. In this review, the authors examine different studies that have revealed the possible hypotheses and links in the development of neurological disorders associated with the gut microbiome.

Exploring the Impact of the Microbiome on Neuroactive Steroid Levels in Germ-Free Animals

Steroid hormones are essential biomolecules for human physiology as they modulate the endocrine system, nervous function and behaviour. Recent studies have shown that the gut microbiota is directly involved in the production and metabolism of steroid hormones in the periphery. However, the influence of the gut microbiota on levels of steroids acting and present in the brain (i.e., neuroactive steroids) is not fully understood. Therefore, using liquid chromatography–tandem mass spectrometry, we assessed the levels of several neuroactive steroids in various brain areas and the plasma of germ-free (GF) male mice and conventionally colonized controls. The data obtained indicate an increase in allopregnanolone levels associated with a decrease in those of 5α-androstane-3α, 17β-diol (3α-diol) in the plasma of GF mice. Moreover, an increase of dihydroprogesterone and isoallopregnanolone in the hippocampus, cerebellum, and cerebral cortex was also reported. Changes in dihydrotestosterone and 3α-diol levels were also observed in the hippocampus of GF mice. In addition, an increase in dehydroepiandrosterone was associated with a decrease in testosterone levels in the hypothalamus of GF mice. Our findings suggest that the absence of microbes affects the neuroactive steroids in the periphery and the brain, supporting the evidence of a microbiota-mediated modulation of neuroendocrine pathways involved in preserving host brain functioning.

Effect of probiotics combined with applied behavior analysis in the treatment of children with autism spectrum disorder: a prospective randomized controlled trial

OBJECTIVES

To study the effect of probiotics combined with applied behavior analysis (ABA) in the treatment of children with autism spectrum disorder (ASD).

METHODS

A total of 41 children with ASD who attended the Affiliated Hospital of Jiangsu University from May 2019 to December 2020 were enrolled and randomly divided into an observation group with 21 children and a control group with 20 children. The children in the observation group were given oral probiotics combined with ABA intervention, while those in the control group were given ABA intervention alone. The treatment outcomes were compared between the two groups. Autism Treatment Evaluation Checklist (ATEC) was used to evaluate the severity of behavioral symptoms in both groups before intervention and at 3 months after intervention. The fecal samples were collected to analyze the difference in intestinal flora between the two groups based on 16s rRNA high-throughput sequencing.

RESULTS

Before intervention, there was no significant difference in the ATEC score between the observation and control groups (P>0.05). At 3 months after intervention, both groups had a significant reduction in the ATEC score, and the observation group had a significantly lower ATEC score than the control group (P<0.05). Before intervention, there was no significant difference in the composition of intestinal flora between the observation and control groups. At 3 months after intervention, there was a significant difference in the composition of intestinal flora between the observation and control groups. Compared with the control group, the observation group had significantly higher relative abundances of Bifidobacterium, Lactobacillus, Coprobacillus, Ruminococcus, Prevotella, and Blautia (P<0.05) and significantly lower relative abundances of Shigella and Clostridium (P<0.05).

CONCLUSIONS

Probiotics may improve the effect of conventional ABA intervention in children with ASD by regulating intestinal flora.

The Impact of Gut Microbiota-Derived Metabolites in Autism Spectrum Disorders

Autism Spectrum Disorder (ASD) is a set of neurodevelopmental disorders characterised by behavioural impairment and deficiencies in social interaction and communication. A recent study estimated that 1 in 89 children have developed some form of ASD in European countries. Moreover, there is no specific treatment and since ASD is not a single clinical entity, the identification of molecular biomarkers for diagnosis remains challenging. Besides behavioural deficiencies, individuals with ASD often develop comorbid medical conditions including intestinal problems, which may reflect aberrations in the bidirectional communication between the brain and the gut. The impact of faecal microbial composition in brain development and behavioural functions has been repeatedly linked to ASD, as well as changes in the metabolic profile of individuals affected by ASD. Since metabolism is one of the major drivers of microbiome-host interactions, this review aims to report emerging literature showing shifts in gut microbiota metabolic function in ASD. Additionally, we discuss how these changes may be involved in and/or perpetuate ASD pathology. These valuable insights can help us to better comprehend ASD pathogenesis and may provide relevant biomarkers for improving diagnosis and identifying new therapeutic targets.

Polyphenols as adjunctive treatments in psychiatric and neurodegenerative disorders: Efficacy, mechanisms of action, and factors influencing inter-individual response

The pathophysiology of psychiatric and neurodegenerative disorders is complex and multifactorial. Polyphenols possess a range of potentially beneficial mechanisms of action that relate to the implicated pathways in psychiatric and neurodegenerative disorders. The aim of this review is to highlight the emerging clinical trial and preclinical efficacy data regarding the role of polyphenols in mental and brain health, elucidate novel mechanisms of action including the gut microbiome and gene expression, and discuss the factors that may be responsible for the mixed clinical results; namely, the role of interindividual differences in treatment response and the potentially pro-oxidant effects of some polyphenols. Further clarification as part of larger, well conducted randomized controlled trials that incorporate precision medicine methods are required to inform clinical efficacy and optimal dosing regimens.