Long-term multi-species Lactobacillus and Bifidobacterium dietary supplement enhances memory and changes regional brain metabolites in middle-aged rats

Exploring animal protein sources against prevent age-related short-term memory decline in mice: Dietary fish (Alaska Pollock) protein exhibits superior protective effects

Dietary factors, particularly proteins, have been extensively explored to combat cognitive impairment. We have previously reported that dietary fish (Alaska Pollock) protein (APP) is more effective than casein (CAS) or fish oil in maintaining short-term memory in senescence-accelerated mice prone 10 (SAMP10). To examine the specificity of the protective effect of APP intakes against short-term memory decline, we assessed the impact of various dietary animal proteins, including APP, CAS, chicken breast protein (CP), and whey protein (WP), against age-related cognitive function in SAMP10 mice. After feeding the experimental diets for 5 months, memory was assessed using the Y-maze. The APP group exhibited a significant increase in spontaneous alternation behavior as an indicator of working memory when group compared with groups fed with other protein source. Additionally, the APP group displayed significantly higher neurofilament heavy chain positivity than the CAS and CP groups, as evidenced immunohistochemical analysis. Gut microbiota analysis indicated that dietary APP significantly enhanced the relative abundance of Lactobacillus, which positively correlated with spontaneous alternation behavior. Collectively, these findings suggest that dietary APP is more effective than CAS, CP, or WP in preventing age-related short-term memory decline and morphological abnormalities in the hippocampal axons of SAMP10 mice. Moreover, APP-mediated improvements in cognitive deficits may be associated with changes in microbiota diversity. PRACTICAL APPLICATION: This research suggests that dietary fish protein from Alaska Pollock may be more efficient in prevention short-term memory decline in mice, compared to other animal proteins. This finding has practical implications for nutritional optimization, developing the new health food products, and elucidating the relationship between the impact of specific proteins on gut microbiota and prevention of age-related cognitive decline.

Microbiota-Gut-Brain Axis Dysregulation in Alzheimer's Disease: Multi-Pathway Effects and Therapeutic Potential

An essential regulator of neurodegenerative conditions like Alzheimer's disease (AD) is the gut microbiota. Alterations in intestinal permeability brought on by gut microbiota dysregulation encourage neuroinflammation, central immune dysregulation, and peripheral immunological dysregulation in AD, as well as hasten aberrant protein aggregation and neuronal death in the brain. However, it is unclear how the gut microbiota transmits information to the brain and how it influences brain cognition and function. In this review, we summarized the multiple pathways involved in the gut microbiome in AD and provided detailed treatment strategies based on the gut microbiome. Based on these observations, this review also discusses the problems, challenges, and strategies to address current therapeutic strategies.

A double-blind, randomized, placebo-controlled study assessing the impact of probiotic supplementation on the symptoms of irritable bowel syndrome in females

BACKGROUND

A previous exploratory study demonstrated the ability of the Lab4 probiotic to alleviate the symptoms of IBS, and post hoc data analysis indicated greatest improvements in the female subgroup. The aim of this study is to confirm the impact of this multistrain probiotic on IBS symptom severity in females.

METHODS

An 8-week, single-center, randomized, double-blinded, placebo-controlled, superiority study in 70 females with Rome IV-diagnosed irritable bowel syndrome (IBS) receiving the Lab4 probiotic (25 billion colony-forming units) daily or a matched placebo. Changes from baseline in the IBS-symptom severity score (IBS-SSS), daily bowel habits, anxiety, depression, IBS-related control, and avoidance behavior, executive function, and the fecal microbiota composition were assessed. The study was prospectively registered: ISRCTN 14866272 (registration date 20/07/22).

KEY RESULTS

At the end of the study, there were significant between-group reductions in IBS-SSS (-85.0, p < 0.0001), anxiety and depression scores (-1.9, p = 0.0002 and -2.4, p < 0.0001, respectively), and the IBS-related control and avoidance behavior score (-7.5, p = 0.0002), all favoring the probiotic group. A higher proportion of the participants in the probiotic group had normal stool form (p = 0.0106) and/or fewer defecations with loose stool form (p = 0.0311). There was little impact on the overall diversity of the fecal microbiota but there were significant differences in Roseburia, Holdemanella, Blautia, Agathobacter, Ruminococcus, Prevotella, Bacteroides, and Anaerostipes between the probiotic and placebo groups at the end of the study.

CONCLUSIONS & INFERENCES

Daily supplementation with this probiotic may represent an option to be considered in the management of IBS.

Bifidobacterium animalis subsp. lactis A6 attenuates hippocampal damage and memory impairments in an ADHD rat model

Attention deficit hyperactivity disorder (ADHD) is commonly accompanied by learning and memory deficits. This study aimed to demonstrate the effects of probiotic Bifidobacterium animalis subsp. lactis A6 (BAA6) on behaviour and memory function in spontaneously hypertensive rats (SHRs). The results showed that BAA6 treatment ameliorated spatial working memory deficits and inhibited hippocampal neuron loss in SHRs. The levels of neurotransmitters such as acetylcholine, dopamine, and norepinephrine, and the brain derived neurotrophic factor increased and that of glutamate decreased in the brain tissue of SHRs after BAA6 administration. Moreover, BAA6 reduced the levels of pro-inflammatory cytokines TNF-α and IL-1β, and increased the levels of anti-inflammatory IL-10 and antioxidant glutathione in SHRs. 16S rRNA high-throughput sequencing showed that BAA6 treatment changed the gut microbiota composition. BAA6 promoted beneficial Lactobacillus, Romboutsia, Blautia, and Turicibacter, and decreased the enrichment of bacterial genera such as Dietzia, Sporosarcina, Brevibacterium, NK4A214_group, Atopostipes, and Facklamia negatively associated with neurotransmitter release and anti-inflammatory effects in SHRs. Together, these results suggested that BAA6 improved memory function by ameliorating hippocampal damage, abnormal neurotransmitter release and cerebral inflammation by reshaping the gut microbiota in SHRs. This study provides a scientific basis for the development and application of BAA6 as a promising dietary intervention to reduce the risk of ADHD.

Acupuncture modulates the gut microbiota in Alzheimer's disease: current evidence, challenges, and future opportunities

Alzheimer's disease, one of the most severe and common neurodegenerative diseases, has no effective cure. Therefore it is crucial to explore novel and effective therapeutic targets. The gut microbiota - brain axis has been found to play a role in Alzheimer's disease by regulating the neuro-immune and endocrine systems. At the same time, acupuncture can modulate the gut microbiota and may impact the course of Alzheimer's disease. In this Review, we discuss recent studies on the role of acupuncture on the gut microbiota as well current challenges and future opportunities of acupuncture as potential treatment for the prevention and treatment of Alzheimer's disease.

The Causal Relationships Between Gut Microbiota, Brain Volume, and Intelligence: A Two-Step Mendelian Randomization Analysis

BACKGROUND

Growing evidence indicates that dynamic changes in gut microbiome can affect intelligence; however, whether these relationships are causal remains elusive. We aimed to disentangle the poorly understood causal relationship between gut microbiota and intelligence.

METHODS

We performed a 2-sample Mendelian randomization (MR) analysis using genetic variants from the largest available genome-wide association studies of gut microbiota (N = 18,340) and intelligence (N = 269,867). The inverse-variance weighted method was used to conduct the MR analyses complemented by a range of sensitivity analyses to validate the robustness of the results. Considering the close relationship between brain volume and intelligence, we applied 2-step MR to evaluate whether the identified effect was mediated by regulating brain volume (N = 47,316).

RESULTS

We found a risk effect of the genus Oxalobacter on intelligence (odds ratio = 0.968 change in intelligence per standard deviation increase in taxa; 95% CI, 0.952-0.985; p = 1.88 × 10-4) and a protective effect of the genus Fusicatenibacter on intelligence (odds ratio = 1.053; 95% CI, 1.024-1.082; p = 3.03 × 10-4). The 2-step MR analysis further showed that the effect of genus Fusicatenibacter on intelligence was partially mediated by regulating brain volume, with a mediated proportion of 33.6% (95% CI, 6.8%-60.4%; p = .014).

CONCLUSIONS

Our results provide causal evidence indicating the role of the microbiome in intelligence. Our findings may help reshape our understanding of the microbiota-gut-brain axis and development of novel intervention approaches for preventing cognitive impairment.

Repeated (S)-ketamine administration ameliorates the spatial working memory impairment in mice with chronic pain: role of the gut microbiota-brain axis

Chronic pain is commonly linked with diminished working memory. This study explores the impact of the anesthetic (S)-ketamine on spatial working memory in a chronic constriction injury (CCI) mouse model, focusing on gut microbiome. We found that multiple doses of (S)-ketamine, unlike a single dose, counteracted the reduced spontaneous alteration percentage (%SA) in the Y-maze spatial working memory test, without affecting mechanical or thermal pain sensitivity. Additionally, repeated (S)-ketamine treatments improved the abnormal composition of the gut microbiome (β-diversity), as indicated by fecal 16S rRNA analysis, and increased levels of butyrate, a key gut - brain axis mediator. Protein analysis showed that these treatments also corrected the upregulated histone deacetylase 2 (HDAC2) and downregulated brain-derived neurotrophic factor (BDNF) in the hippocampi of CCI mice. Remarkably, fecal microbiota transplantation from mice treated repeatedly with (S)-ketamine to CCI mice restored %SA and hippocampal BDNF levels in CCI mice. Butyrate supplementation alone also improved %SA, BDNF, and HDAC2 levels in CCI mice. Furthermore, the TrkB receptor antagonist ANA-12 negated the beneficial effects of repeated (S)-ketamine on spatial working memory impairment in CCI mice. These results indicate that repeated (S)-ketamine administration ameliorates spatial working memory impairment in CCI mice, mediated by a gut microbiota - brain axis, primarily through the enhancement of hippocampal BDNF - TrkB signaling by butyrate.

Efficacy of Probiotic Supplements on Brain-Derived Neurotrophic Factor, Inflammatory Biomarkers, Oxidative Stress and Cognitive Function in Patients with Alzheimer's Dementia: A 12-Week Randomized, Double-Blind Active-Controlled Study

The role of neurotrophic factors, oxidative stress, and inflammation in the pathogenesis of Alzheimer's disease (AD) has been explored. Animal studies have reported the positive effects of probiotics on these factors. Some clinical studies also support the potential role of probiotics in improving cognitive function via the gut-brain axis in older adults. However, clinical experimental studies evaluating the efficacy of probiotics targeting the neurotrophic factors and inflammatory biomarkers, particularly among AD patients, remain very limited. In this randomized, double-blinded, active-controlled trial, we used multi-strain probiotic supplements, including Bifidobacterium longum subsp. infantis BLI-02, B. breve Bv-889, B. animalis subsp. lactis CP-9, B. bifidum VDD088, and Lactobacillus plantarum PL-02 as the intervention. Participants were divided into an active control group (received probiotic supplements containing 5 × 107 colony-forming units per day, CFU/day) and a treatment group (1 × 1010 CFU/day). Student's t test was applied as the main method of statistical analysis. After 12 weeks of intervention, the treatment group demonstrated a 36% increase in serum brain-derived neurotrophic factor (BDNF) (* p = 0.005), a reduction in IL-1β (* p = 0.041), and an increase in antioxidant superoxide dismutase (SOD) (* p = 0.012). No significant change was found in the active control group. A trend toward less cognitive deterioration was observed, but not statistically significant. In conclusion, this study presents evidence supporting the benefits of multi-strain probiotics in enhancing BDNF, ameliorating inflammation and oxidative stress in AD patients.

Clostridium butyricum Alleviates DEHP Plasticizer-Induced Learning and Memory Impairment in Mice via Gut-Brain Axis

Di-(2-ethylhexyl) phthalate (DEHP) plasticizer, a well-known environmental and food pollutant, has neurotoxicity. However, it is unknown whether DEHP leads to learning and memory impairment through gut-brain axis and whether Clostridium butyricum can alleviate this impairment. Here, C57BL/6 mice were exposed to DEHP and treated with C. butyricum. Learning and memory abilities were evaluated through the Morris water maze. The levels of synaptic proteins, inflammatory cytokines, and 5-hydroxytryptamine (5-HT) were detected by immunohistochemistry or ELISA. Gut microbiota were analyzed through 16S rRNA sequencing. C. butyricum alleviated DEHP-induced learning and memory impairment and restored synaptic proteins. It significantly relieved DEHP-induced inflammation and recovered 5-HT levels. C. butyricum recovered the richness of the gut microbiota decreased by DEHP, with the Bifidobacterium genus increasing the most. Overall, C. butyricum alleviated DEHP-induced learning and memory impairment due to reduced inflammation and increased 5-HT secretion, which was partly attributed to the recovery of gut microbiota.

Torreya grandis oil attenuates cognitive impairment in scopolamine-induced mice

The oil of Torreya grandis (TGO), a common nut in China, is considered to be a bioactive edible oil and has a great value in functional food development. In this study, the neuroprotective effects of TGO were investigated on a scopolamine (SCOP)-induced C57BL/6J mouse model. The mice were pretreated with TGO for 30 days (1000 mg per kg per day and 3000 mg per kg per day, i.g.). Behavioral tests showed that the supplementation of TGO could prevent the cognitive deficits induced by SCOP. TGO rebalanced the disorder of the cholinergic system by upgrading the level of acetylcholine. TGO also alleviated the over-activation of microglia and inhibited neuroinflammation and oxidative stress. Additionally, TGO could regulate the composition of gut microbiota, increase the production of short-chain fatty acids, and decrease the content of lipopolysaccharides in the serum. In conclusion, TGO has the potential to prevent loss of memory and impairment of cognition, which may be related to its regulation of the gut microbiota-metabolite-brain axis.

Insights into the Current and Possible Future Use of Opioid Antagonists in Relation to Opioid-Induced Constipation and Dysbiosis

Opioid receptor agonists, particularly those that activate µ-opioid receptors (MORs), are essential analgesic agents for acute or chronic mild to severe pain treatment. However, their use has raised concerns including, among others, intestinal dysbiosis. In addition, growing data on constipation-evoked intestinal dysbiosis have been reported. Opioid-induced constipation (OIC) creates an obstacle to continuing treatment with opioid analgesics. When non-opioid therapies fail to overcome the OIC, opioid antagonists with peripheral, fast first-pass metabolism, and gastrointestinal localized effects remain the drug of choice for OIC, which are discussed here. At first glance, their use seems to only be restricted to constipation, however, recent data on OIC-related dysbiosis and its contribution to the appearance of several opioid side effects has garnered a great of attention from researchers. Peripheral MORs have also been considered as a future target for opioid analgesics with limited central side effects. The properties of MOR antagonists counteracting OIC, and with limited influence on central and possibly peripheral MOR-mediated antinociception, will be highlighted. A new concept is also proposed for developing gut-selective MOR antagonists to treat or restore OIC while keeping peripheral antinociception unaffected. The impact of opioid antagonists on OIC in relation to changes in the gut microbiome is included.

Potential Effects of Alpha-Glycosyl Isoquercitrin on Memory by Altering the Gut Microbiota-Blood-Brain Axis in Mice

Alpha-glycosyl isoquercitrin (AGIQ), composed of isoquercitrin and glycosylated quercetin, has multiple biological effects. Here, we further examined the influence of AGIQ on brain function and provided its potential mechanism. Male C57BL/6 mice were treated with 0, 0.005, and 0.05% AGIQ in drinking water for 4 weeks prior to behavioral testing. Behavior tests showed that 0.05% AGIQ treatment significantly improved learning and memory function without affecting emotion. In the hippocampus, the gene expression of antioxidative defense enzymes was upregulated after 0.05% AGIQ treatment. In contrast, AGIQ caused significant alterations in the microbial abundance of genera Akkermansia, Bifidobacterium, and Alistipes associated with memory function. Metabolomics analysis identified that taurine concentration was significantly increased in serum and hippocampus from AGIQ-treated mice. The correlation analysis suggested that elevated serum taurine levels were closely related to the abundance of Akkermansia, indicating the underlying crosstalk of gut microbiota and serum metabolites. In vitro fecal culture further demonstrated that AGIQ could increase the level of Akkermansia. Taurine could exert antioxidant activity in SH-SY5Y neuroblastoma cell lines in vitro. Finally, vancomycin-induced alterations of gut microbiota attenuated the taurine increases in the serum and the antioxidant gene level in the hippocampus by AGIQ. Taken together, it is likely that AGIQ could increase genus Akkermansia abundance and ultimately increase taurine levels in serum and hippocampus to improve learning and memory function, relying on the gut microbiota-blood-brain axis. Our results supply a new view for understanding effects of AGIQ on brain function.

Gut microbiota is associated with spatial memory and seed-hoarding behavior of South China field mice (Apodemus draco)

Background

Scatter-hoarding animals store food in multiple locations within their home range and rely on spatial memory for subsequent localization and retrieval. The relationship between memory and scatter-hoarding behavior has been widely demonstrated, but the association of gut microbiota with spatial memory and seed-hoarding behavior of animals remains unclear.

Methods

In this study, by using enclosure behavior tests, memory tests including an object location test (OLT) and a novel object recognition test (NORT), and fecal microbiota transplantation (FMT) experiment, we evaluated the role of gut microbiota in affecting the memory and seed-hoarding behavior of rodents. According to their scatter-hoarding intensity, South China field mice (Apodemus draco) were divided into scatter-hoarding group (SG) and non-scatter-hoarding group (NG).

Results

We found that the SG performed better than the NG in the NORT. FMT from SG donor mice altered the NG recipient mice's gut microbiota structure. Further tests demonstrated FMT from SG donor mice increased memory of NG recipient mice in laboratory tests and seed larder hoarding intensity of NG recipient mice in enclosures.

Conclusion

Our results suggest gut microbiota could modulate the memory and seed-hoarding behavior of animals.

Short-chain fatty and carboxylic acid changes associated with fecal microbiota transplant communally influence microglial inflammation

The intestinal microbiota has been proposed to influence human mental health and cognition through the gut-brain axis. Individuals experiencing recurrent Clostridioides difficile infection (rCDI) frequently report depressive symptoms, which are improved after fecal microbiota transplantation (FMT); however, mechanisms underlying this association are poorly understood. Short-chain fatty acids and carboxylic acids (SCCA) produced by the intestinal microbiota cross the blood brain barrier and have been proposed to contribute to gut-brain communication. We hypothesized that changes in serum SCCA measured before and after successful FMT for rCDI influences the inflammatory response of microglia, the resident immune cells of the central nervous system. Serum SCCA were quantified using gas chromatography-mass spectroscopy from 38 patients who participated in a randomized trial comparing oral capsule-vs colonoscopy-delivered FMT for rCDI, and quality of life was assessed by SF-36 at baseline, 4, and 12 weeks after FMT treatment. Successful FMT was associated with improvements in mental and physical health, as well as significant changes in a number of circulating SCCA, including increased butyrate, 2-methylbutyrate, valerate, and isovalerate, and decreased 2-hydroxybutyrate. Primary cultured microglia were treated with SCCA and the response to a pro-inflammatory stimulus was measured. Treatment with a combination of SCCA based on the post-FMT serum profile, but not single SCCA species, resulted in significantly reduced inflammatory response including reduced cytokine release, reduced nitric oxide release, and accumulation of intracellular lipid droplets. This suggests that both levels and diversity of SCCA may be an important contributor to gut-brain communication.

When the microbiome helps the brain-current evidence

The gut microbiota-brain axis has been recognized as a network of connections that provides communication between the gut microflora and both central and autonomic nervous system. The gut microbiota alteration has been targeted for therapy in various neurodegenerative and psychiatric disbalances. Psychobiotics are probiotics that contribute beneficially to the brain function and the host mental health as a result of an interaction with the commensal gut bacteria, although their mechanism of action has not been completely revealed. In this state-of-art review, the findings about the potential therapeutic effects of the psychobiotics alone or in combination with conventional medicine in the treatment of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease, as well as in some psychiatric diseases like depression, schizophrenia, and bipolar disorder, have been summarized. The evidence of the psychobiotics therapeutic outcomes obtained in preclinical and clinical trials have been given respectively for the observed neurodegenerative and psychiatric disorders.

Gut Microbiome-Brain Alliance: A Landscape View into Mental and Gastrointestinal Health and Disorders

Gut microbiota includes a vast collection of microorganisms residing within the gastrointestinal tract. It is broadly recognized that the gut and brain are in constant bidirectional communication, of which gut microbiota and its metabolic production are a major component, and form the so-called gut microbiome-brain axis. Disturbances of microbiota homeostasis caused by imbalance in their functional composition and metabolic activities, known as dysbiosis, cause dysregulation of these pathways and trigger changes in the blood-brain barrier permeability, thereby causing pathological malfunctions, including neurological and functional gastrointestinal disorders. In turn, the brain can affect the structure and function of gut microbiota through the autonomic nervous system by regulating gut motility, intestinal transit and secretion, and gut permeability. Here, we examine data from the CAS Content Collection, the largest collection of published scientific information, and analyze the publication landscape of recent research. We review the advances in knowledge related to the human gut microbiome, its complexity and functionality, its communication with the central nervous system, and the effect of the gut microbiome-brain axis on mental and gut health. We discuss correlations between gut microbiota composition and various diseases, specifically gastrointestinal and mental disorders. We also explore gut microbiota metabolites with regard to their impact on the brain and gut function and associated diseases. Finally, we assess clinical applications of gut-microbiota-related substances and metabolites with their development pipelines. We hope this review can serve as a useful resource in understanding the current knowledge on this emerging field in an effort to further solving of the remaining challenges and fulfilling its potential.

A review of neuroendocrine immune system abnormalities in IBS based on the brain–gut axis and research progress of acupuncture intervention

Irritable bowel syndrome (IBS) is a common digestive disorder observed in clinics. Current studies suggest that the pathogenesis of the disease is closely related to abnormal brain–gut interactions, hypokinesia, visceral sensory hypersensitivity in the gastrointestinal tract, and alterations in the intestinal microenvironment. However, it is difficult for a single factor to explain the heterogeneity of symptoms. The Rome IV criteria emphasized the holistic biologic-psycho-social model of IBS, suggesting that symptoms of the disease are closely related to neurogastroenterology and various abnormalities in brain–gut interaction. This study comprehensively reviewed the relationship between the brain–gut axis and IBS, the structure of the brain–gut axis, and the relationship between the brain–gut axis and intestinal microenvironment, and discussed the relationship between the abnormal regulation of the nervous system, endocrine system, and immune system and the incidence of IBS on the basis of brain–gut axis. In terms of treatment, acupuncture therapy can regulate the neuroendocrine-immune system of the body and improve the intestinal microenvironment, and it has the advantages of safety, economy, and effectiveness. We study the pathogenesis of IBS from local to global and micro to macro, and review the use of acupuncture to treat the disease as a whole so as to provide new ideas for the treatment of the disease.

Assessment of Lab4P Probiotic Effects on Cognition in 3xTg-AD Alzheimer's Disease Model Mice and the SH-SY5Y Neuronal Cell Line

Aging and metabolic syndrome are associated with neurodegenerative pathologies including Alzheimer's disease (AD) and there is growing interest in the prophylactic potential of probiotic bacteria in this area. In this study, we assessed the neuroprotective potential of the Lab4P probiotic consortium in both age and metabolically challenged 3xTg-AD mice and in human SH-SY5Y cell culture models of neurodegeneration. In mice, supplementation prevented disease-associated deteriorations in novel object recognition, hippocampal neurone spine density (particularly thin spines) and mRNA expression in hippocampal tissue implying an anti-inflammatory impact of the probiotic, more notably in the metabolically challenged setting. In differentiated human SH-SY5Y neurones challenged with β-Amyloid, probiotic metabolites elicited a neuroprotective capability. Taken together, the results highlight Lab4P as a potential neuroprotective agent and provide compelling support for additional studies in animal models of other neurodegenerative conditions and human studies.

Gut Microbiota and Alzheimer's Disease: How to Study and Apply Their Relationship

Gut microbiota (GM), the microorganisms in the gastrointestinal tract, contribute to the regulation of brain homeostasis through bidirectional communication between the gut and the brain. GM disturbance has been discovered to be related to various neurological disorders, including Alzheimer's disease (AD). Recently, the microbiota-gut-brain axis (MGBA) has emerged as an enticing subject not only to understand AD pathology but also to provide novel therapeutic strategies for AD. In this review, the general concept of the MGBA and its impacts on the development and progression of AD are described. Then, diverse experimental approaches for studying the roles of GM in AD pathogenesis are presented. Finally, the MGBA-based therapeutic strategies for AD are discussed. This review provides concise guidance for those who wish to obtain a conceptual and methodological understanding of the GM and AD relationship with an emphasis on its practical application.

Probiotic has prophylactic effect on spatial memory deficits by modulating gut microbiota characterized by the inhibitory growth of Escherichia coli

Background: The aim of this study is to interrogate the prophylactic effect of probiotic on the lead-induced spatial memory impairment, as well as the underlying mechanisms based on gut microbiota. Methods: Rats were exposed postnatally to 100 ppm of lead acetate during lactation (from postnatal day 1 to 21), to establish the memory deficits model. A probiotic bacterium, namely Lacticaseibacillus rhamnosus, was administered by drinking into pregnant rats with a dosage of 10⁹ CFU/rat/day till birth. At postnatal week 8 (PNW8), the rats were subjected to Morris water maze and Y-maze test, with fecal samples collected for 16S rRNA sequencing. Besides, the inhibitory effect of Lb. rhamnosus on Escherichia coli was carried out in bacterial co-culture. Results: Female rats prenatally exposed to probiotic improved their performances in the behavioral test, indicating that probiotic could protect rats from memory deficits caused by postnatal lead exposure. This bioremediation activity varies depending on the intervention paradigm used. As revealed by microbiome analysis, although administered in a distinct period from lead exposure, Lb. rhamnosus further changed the microbial structure disrupted by lead exposure, suggesting an effective transgenerational intervention. Of note, gut microbiota, represented by Bacteroidota, varied greatly depending on the intervention paradigm as well as the developmental stage. The concerted alterations were revealed between some keystone taxa and behavioral abnormality, including lactobacillus and E. coli. To this end, an in vitro co-culture was created to demonstrate that Lb. rhamnosus could inhibit the growth of E. coli with direct contact, which is dependent on the growth condition under study. In addition, in vivo infection of E. coli O157 aggravated memory dysfunction, which could also be rescued by probiotic colonization. Conclusions: Early probiotic intervention could prevent organisms from lead-induced memory decline in later life through reprogramming gut microbiota and inhibiting E. coli, providing a promising approach to ameliorate the cognitive damage with environmental origins.

Improving the effectiveness of anti-aging modalities by using the constrained disorder principle-based management algorithms

Aging is a complex biological process with multifactorial nature underlined by genetic, environmental, and social factors. In the present paper, we review several mechanisms of aging and the pre-clinically and clinically studied anti-aging therapies. Variability characterizes biological processes from the genome to cellular organelles, biochemical processes, and whole organs' function. Aging is associated with alterations in the degrees of variability and complexity of systems. The constrained disorder principle defines living organisms based on their inherent disorder within arbitrary boundaries and defines aging as having a lower variability or moving outside the boundaries of variability. We focus on associations between variability and hallmarks of aging and discuss the roles of disorder and variability of systems in the pathogenesis of aging. The paper presents the concept of implementing the constrained disease principle-based second-generation artificial intelligence systems for improving anti-aging modalities. The platform uses constrained noise to enhance systems' efficiency and slow the aging process. Described is the potential use of second-generation artificial intelligence systems in patients with chronic disease and its implications for the aged population.

Normative cognition and the effects of a probiotic food intervention in first grade children in Côte d'Ivoire

The cognitive skills critical for success have largely been studied in Western populations, despite the fact that children in low- and middle-income countries are at risk to not reach their full developmental potential. Moreover, scientists should leverage recent discovery to explore means of boosting cognition in at-risk populations. This semi-randomized controlled trial examined normative cognitive development and whether it could be enhanced by consumption of a probiotic food in a sample of 251 4- to 7-year-old children in urban schools in Côte d'Ivoire. Participants completed executive functioning measures at baseline (T1) and 5 months later (T2). After T1, children in one school received a probiotic (N = 74) or placebo (N = 79) fermented dairy food every day they were in school for one semester; children in the other school (N = 98) continued their diet as usual. Children improved on all tests across time (Cohen's d = 0.08-0.30). The effects of probiotic ingestion were inconclusive and are interpreted with caution due to socio-political factors affecting daily administration. Given the general feasibility of the study, we hope that it will serve as an inspiration for future research into child development and sustainable (health-promoting) interventions for school children in developing nations.

Microbiota-derived metabolites as drivers of gut-brain communication

Alterations in the gut microbiota composition have been associated with a range of neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. The gut microbes transform and metabolize dietary- and host-derived molecules generating a diverse group of metabolites with local and systemic effects. The bi-directional communication between brain and the microbes residing in the gut, the so-called gut-brain axis, consists of a network of immunological, neuronal, and endocrine signaling pathways. Although the full variety of mechanisms of the gut-brain crosstalk is yet to be established, the existing data demonstrates that a single metabolite or its derivatives are likely among the key inductors within the gut-brain axis communication. However, more research is needed to understand the molecular mechanisms underlying how gut microbiota associated metabolites alter brain functions, and to examine if different interventional approaches targeting the gut microbiota could be used in prevention and treatment of neurological disorders, as reviewed herein.Abbreviations:4-EPS 4-ethylphenylsulfate; 5-AVA(B) 5-aminovaleric acid (betaine); Aβ Amyloid beta protein; AhR Aryl hydrocarbon receptor; ASD Autism spectrum disorder; BBB Blood-brain barrier; BDNF Brain-derived neurotrophic factor; CNS Central nervous system; GABA ɣ-aminobutyric acid; GF Germ-free; MIA Maternal immune activation; SCFA Short-chain fatty acid; 3M-4-TMAB 3-methyl-4-(trimethylammonio)butanoate; 4-TMAP 4-(trimethylammonio)pentanoate; TMA(O) Trimethylamine(-N-oxide); TUDCA Tauroursodeoxycholic acid; ZO Zonula occludens proteins.

The Gut Microbiome-Brain Crosstalk in Neurodegenerative Diseases

The gut–brain axis (GBA) is a complex interactive network linking the gut to the brain. It involves the bidirectional communication between the gastrointestinal and the central nervous system, mediated by endocrinological, immunological, and neural signals. Perturbations of the GBA have been reported in many neurodegenerative diseases, suggesting a possible role in disease pathogenesis, making it a potential therapeutic target. The gut microbiome is a pivotal component of the GBA, and alterations in its composition have been linked to GBA dysfunction and CNS inflammation and degeneration. The gut microbiome might influence the homeostasis of the central nervous system homeostasis through the modulation of the immune system and, more directly, the production of molecules and metabolites. Small clinical and preclinical trials, in which microbial composition was manipulated using dietary changes, fecal microbiome transplantation, and probiotic supplements, have provided promising outcomes. However, results are not always consistent, and large-scale randomized control trials are lacking. Here, we give an overview of how the gut microbiome influences the GBA and could contribute to disease pathogenesis in neurodegenerative diseases.

The Impact of Probiotic Supplementation on Cognitive, Pathological and Metabolic Markers in a Transgenic Mouse Model of Alzheimer's Disease

Brain degenerative disorders such as Alzheimer’s disease (AD) can be exacerbated by aberrant metabolism. Supplementation with probiotic bacteria is emerging as a promising preventative strategy for both neurodegeneration and metabolic syndrome. In this study, we assess the impact of the Lab4b probiotic consortium on (i) cognitive and pathological markers of AD progression and (ii) metabolic status in 3xTg-AD mice subjected to metabolic challenge with a high fat diet. The group receiving the probiotic performed better in the novel object recognition test and displayed higher hippocampal neuronal spine density than the control group at the end of the 12 weeks intervention period. These changes were accompanied by differences in localised (brain) and systemic anti-inflammatory responses that favoured the Probiotic group together with the prevention of diet induced weight gain and hypercholesterolaemia and the modulation of liver function. Compositional differences between the faecal microbiotas of the study groups included a lower Firmicutes:Bacteroidetes ratio and less numbers of viable yeast in the Probiotic group compared to the Control. The results illustrate the potential of the Lab4b probiotic as a neuroprotective agent and encourage further studies with human participants.

Effects of a multi-strain probiotic on hippocampal structure and function, cognition, and emotional well-being in healthy individuals: a double-blind randomised-controlled trial

BACKGROUND

Animal studies have shown beneficial effects of probiotic supplementation on the hippocampus (HC) and cognitive performance. Evidence in humans is scarce. It was hypothesised that probiotic supplementation is associated with enhanced hippocampal (HC) regional grey matter volume (rGMV), as well as HC functional connectivity (FC). Relatedly improvements in mnestic and navigational performance, or emotional well-being, were expected to be observed in healthy human volunteers.

METHODS

A randomised-controlled, double-blind trial (RCT) was conducted in N = 59 volunteers (age Mean = 27.1, s.d. = 6.7), applying a multi-strain probiotic (Vivomixx®) v. non-probiotic milk-powder placebo, each with 4.4 g/day, for 4 weeks. Volumetric data was extracted from 3T structural magnetic resonance images of total HC and -subfields. Voxel-based morphometry (VBM) and FreeSurfer-based analyses were performed. Potential neuroplastic change beyond HC was explored using whole-brain-VBM for white- and GMV. Seed-based FC was calculated based on HC. Cognitive tests included visual, map-based, object-location, and verbal memory, and spatial navigation. Mental health status (stress, anxiety, depression, and emotion-regulation) was assessed using self-reports.

RESULTS

There were no changes in HC-total, -subfield GMV, or FC, through probiotics. VBM revealed no changes at a whole-brain-level. There were no effects on cognitive performance or mental health. Evidence in favor of the null-hypothesis, using Bayesian statistics, was consistent.

CONCLUSIONS

The applied multi-strain probiotic did not elicit any effects concerning hippocampal structural plasticity, cognition, or mental well-being in young, healthy adults. For future studies, longer application/observation RCTs, perhaps in stressed, otherwise psychologically/ cognitively vulnerable, or ageing groups, with well-founded strain selection and investigation of mechanism, are advised.

Effect of dendrobium mixture in alleviating diabetic cognitive impairment associated with regulating gut microbiota

Dendrobium mixture (DM) is a patent Chinese herbal formulation consisting of Dendrobii Caulis, Astragali Radix, Rehmanniae Radix as the main ingredients. DM has been shown to alleviate diabetic related symptoms attributed to its anti-hyperglycaemic and anti-inflammatory activities. However, the effect on diabetic induced cognitive dysfunction has not been investigated. This study aims to investigate the effect of DM in improving diabetic cognitive impairment and associated mechanisms. Our study confirmed the anti-hyperglycaemic effect of DM and showed its capacity to restore the cognitive and memory function in high fat/high glucose and streptozotocin-induced diabetic rats. The neuroprotective effect was manifested as improved learning and memory behaviours, restored blood-brain barrier tight junction, and enhanced expressions of neuronal survival related biomarkers. DM protected the colon tight junction, and effectively lowered the circulated proinflammatory mediators including tumour necrosis factor-α, interleukin-6 and lipopolysaccharides. In the gut microbiota, DM corrected the increase in the abundance of Firmicutes, the increase in the ratio of Firmicutes/Bacteroidetes, and the decrease in the abundance of Bacteroidetes in diabetic rats. It also reversed the abundance of Lactobacillus, Ruminococcus and Allobaculum genera. Short chain fatty acids, isobutyric acid and ethylmethylacetic acid, were negatively and significantly correlated to Ruminococcus and Allobaculum. Isovaleric acid was positively and significantly correlated with Lactobacillus, which all contributing to the improvement in glucose level, systemic inflammation and cognitive function in diabetic rats. Our results demonstrated the potential of DM as a promising therapeutic agent in treating diabetic cognitive impairment and the underlying mechanism may be associated with regulating gut microbiota.

Psychoactive Effects of Lactobacillus johnsonii BS15 on Preventing Memory Dysfunction Induced by Acute Ethanol Exposure Through Modulating Intestinal Microenvironment and Improving Alcohol Metabolic Level

The negative effects of ethanol (EtOH) abuse on the body have been widely reported in recent years. Building on the microbiota-gut-brain axis hypothesis, our study aimed to demonstrate the potential psychobiotic role of Lactobacillus johnsonii BS15 in the preventive effects of acute EtOH intake on memory impairment. We also determined whether L. johnsonii BS15 intake could effectively improve resistance to acute drinking and alleviate the adverse effects of EtOH. Male mice were fed L. johnsonii BS15 orally with (Probiotic group) or without (Control and Alcohol groups) daily dose of 0.2 × 109 CFU/ml per mouse for 28 days. Gavage with L. johnsonii BS15 significantly modified the ileal microbial ecosystem (assessed by 16S rRNA gene sequencing) in favor of Firmicutes and Lactobacillus, indicating the ability of BS15 to restore the gut microbiota. The acute EtOH exposure model (7 g/kg EtOH per mice) was established by gavage, which was administered to the alcohol and probiotic groups on day 28 of the experiment. The L. johnsonii BS15 intake effectively reduced alcohol unconsciousness time, blood alcohol concentration, and serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. Meanwhile, the improvement of ethanol resistance time and the activities of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) in the liver were shown by BS15 in acute alcohol-induced mice. We found that acute EtOH exposure reduced the exploration ratio (assessed by the novel object recognition test), escape latency, number of errors (assessed by passive avoidance test), and spontaneous exploration (assessed by T-maze test) in mice, which were obviously improved by L. johnsonii BS15. In the hippocampus, L. johnsonii BS15 significantly reversed the decrease in antioxidant capacity of superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH) and mRNA expression of memory-related functional proteins of brain-derived neurotrophic factor (BDNF) and cyclic ampresponse element binding protein (CREB) in the hippocampal tissue after acute EtOH exposure. In conclusion, L. johnsonii BS15 intake appears as a promising psychoactive therapy to ameliorate alcohol-mediated memory impairment by increasing EtOH metabolic levels.

The Potential Role of Gut Microbiota in Alzheimer’s Disease: from Diagnosis to Treatment

Gut microbiota is emerging as a key regulator of many disease conditions and its dysregulation is implicated in the pathogenesis of several gastrointestinal and extraintestinal disorders. More recently, gut microbiome alterations have been linked to neurodegeneration through the increasingly defined gut microbiota brain axis, opening the possibility for new microbiota-based therapeutic options. Although several studies have been conducted to unravel the possible relationship between Alzheimer’s Disease (AD) pathogenesis and progression, the diagnostic and therapeutic potential of approaches aiming at restoring gut microbiota eubiosis remain to be fully addressed. In this narrative review, we briefly summarize the role of gut microbiota homeostasis in brain health and disease, and we present evidence for its dysregulation in AD patients. Based on these observations, we then discuss how dysbiosis might be exploited as a new diagnostic tool in early and advanced disease stages, and we examine the potential of prebiotics, probiotics, fecal microbiota transplantation, and diets as complementary therapeutic interventions on disease pathogenesis and progression, thus offering new insights into the diagnosis and treatment of this devastating and progressive disease.

The role of the gut microbiota and nutrition on spatial learning and spatial memory: a mini review based on animal studies

The gut-brain axis is believed to constitute a bidirectional communication mechanism that affects both mental and digestive processes. Recently, the role of the gut microbiota in cognitive performance has been the focus of much research. In this paper, we discuss the effects of gut microbiota and nutrition on spatial memory and learning. Studies have shown the influence of diet on cognitive capabilities such as spatial learning and memory. It has been reported that a high-fat diet can alter gut microbiota which subsequently leads to changes in spatial learning and memory. Some microorganisms in the gut that can significantly affect spatial learning and memory are Akkermansia muciniphila, Bifidobacterium, Lactobacillus, Firmicutes, Bacteroidetes, and Helicobacter pylori. For example, a reduction in the amount of A. muciniphila in the gut leads to increased intestinal permeability and induces immune response in the brain which then negatively affects cognitive performances. We suggest that more studies should be carried out regarding the indirect effects of nutrition on cognitive activities via alteration in gut microbiota.

Integrated Multi-Omics for Novel Aging Biomarkers and Antiaging Targets

Aging is closely related to the occurrence of human diseases; however, its exact biological mechanism is unclear. Advancements in high-throughput technology provide new opportunities for omics research to understand the pathological process of various complex human diseases. However, single-omics technologies only provide limited insights into the biological mechanisms of diseases. DNA, RNA, protein, metabolites, and microorganisms usually play complementary roles and perform certain biological functions together. In this review, we summarize multi-omics methods based on the most relevant biomarkers in single-omics to better understand molecular functions and disease causes. The integration of multi-omics technologies can systematically reveal the interactions among aging molecules from a multidimensional perspective. Our review provides new insights regarding the discovery of aging biomarkers, mechanism of aging, and identification of novel antiaging targets. Overall, data from genomics, transcriptomics, proteomics, metabolomics, integromics, microbiomics, and systems biology contribute to the identification of new candidate biomarkers for aging and novel targets for antiaging interventions.

Probiotics for Alzheimer's Disease: A Systematic Review

Alzheimer’s disease (AD) is the most common form of neurodegenerative disorders affecting mostly the elderly. It is characterized by the presence of Aβ and neurofibrillary tangles (NFT), resulting in cognitive and memory impairment. Research shows that alteration in gut microbial diversity and defects in gut brain axis are linked to AD. Probiotics are known to be one of the best preventative measures against cognitive decline in AD. Numerous in vivo trials and recent clinical trials have proven the effectiveness of selected bacterial strains in slowing down the progression of AD. It is proven that probiotics modulate the inflammatory process, counteract with oxidative stress, and modify gut microbiota. Thus, this review summarizes the current evidence, diversity of bacterial strains, defects of gut brain axis in AD, harmful bacterial for AD, and the mechanism of action of probiotics in preventing AD. A literature search on selected databases such as PubMed, Semantic Scholar, Nature, and Springer link have identified potentially relevant articles to this topic. However, upon consideration of inclusion criteria and the limitation of publication year, only 22 articles have been selected to be further reviewed. The search query includes few sets of keywords as follows. (1) Probiotics OR gut microbiome OR microbes AND (2) Alzheimer OR cognitive OR aging OR dementia AND (3) clinical trial OR in vivo OR animal study. The results evidenced in this study help to clearly illustrate the relationship between probiotic supplementation and AD. Thus, this systematic review will help identify novel therapeutic strategies in the future as probiotics are free from triggering any adverse effects in human body.

Etiology and management of Alzheimer's disease: Potential role of gut microbiota modulation with probiotics supplementation

Alzheimer's disease (AD) is the leading type of dementia in aging people and is a progressive condition that causes neurodegeneration, resulting in confusion, memory loss, and deterioration of mental functions. AD happens because of abnormal twisting of the microtubule tau protein in neurons into a tangled neurofibrillary structure. Different factors responsible for AD pathogenesis include heavy metals, aging, cardiovascular disease, and environmental and genetic factors. Market available drugs for AD have several side effects that include hepato-toxicity, accelerated cognitive decline, worsened neuropsychiatric symptoms, and triggered suicidal ideation. Therefore, an emerging alternative therapeutic approach is probiotics, which can improve AD by modulating the gut-brain axis. Probiotics modulate different neurochemical pathways by regulating the signalling pathways associated with inflammation, histone deacetylation, and microglial cell activation and maturation. In addition, probiotics-derived metabolites (i.e., short-chain fatty acid, neurotransmitters, and antioxidants) have shown ameliorative effects against AD. Probiotics also modulate gut microbiota, with a beneficial impact on neural signalling and cognitive activity, which can attenuate AD progression. Therefore, the current review describes the etiology and mechanism of AD progression as well as various treatment options with a focus on the use of probiotics. PRACTICAL APPLICATIONS: In an aging population, dementia concerns are quite prevalent globally. AD is one of the most commonly occurring cognition disorders, which is linked to diminished brain functions. Scientific evidence supports the findings that probiotics and gut microbiota can regulate/modulate brain functions, one of the finest strategies to alleviate such disorders through the gut-brain axis. Thus, gut microbiota modulation, especially through probiotic supplementation, could become an effective solution to ameliorate AD.

CCL01, a novel formulation composed of Cuscuta seeds and Lactobacillus paracasei NK112, enhances memory function via nerve growth factor-mediated neurogenesis

Memory decline occurs due to various factors, including stress, depression, and aging, and lowers the quality of life. Several nutritional supplements and probiotics have been used to enhance memory function, and efforts have been made to develop mixed supplements with maximized efficacy. In this study, we aimed to examine whether a novel formulation composed of Cuscuta seeds and Lactobacillus paracasei NK112, CCL01, enhances memory function and induces neurogenesis via nerve growth factor (NGF) induction. Firstly, we orally administered CCL01 to normal mice and assessed their memory function 4 weeks after the first administration by performing a step-through passive avoidance test. We found that CCL01 at 100 mg kg^-1 treatment enhanced the fear-based memory function. By analyzing the expression of Ki-67 and doublecortin, which are the markers of proliferating cells and immature neurons, respectively, we observed that CCL01 induced neuronal proliferation and differentiation in the hippocampus of the mice. Additionally, we found that the expression of synaptic markers increased in the hippocampus of CCL01-treated mice. We measured the NGF expression in the supernatant of C6 cells after CCL01 treatment and found that CCL01 increased NGF release. Furthermore, treatment of CCL01-conditioned glial media on N2a cells increased neuronal differentiation via the TrkA/ERK/CREB signaling pathway and neurotrophic factor expression. Moreover, when CCL01 was administered and scopolamine was injected, CCL01 ameliorated memory decline. These results suggest that CCL01 is an effective enhancer of memory function and can be applied to various age groups requiring memory improvement.

A Novel Probiotic Formula, BIOCG, Protects Against Alzheimer's-Related Cognitive Deficits via Regulation of Dendritic Spine Dynamics

BACKGROUND

The brain-gut-microbiome axis has emerged as an important pathway through which perturbations in the gut and/or microbial microenvironment can impact neurological function. Such alterations have been implicated in a variety of neuropsychiatric disorders, includ- ing depression, anxiety, and Alzheimer's Disease (AD) and the use of probiotics as therapy for th- ese diseases remains promising. However, the mechanisms underlying the gut microenvironment's influence on disease pathogenesis and therapy remain unclear.

OBJECTIVE

The objective of this study is to investigate the effect of a novel probiotic formula, BIOCG, on cognitive function and pathobiological mechanisms, including amyloid processing and dendritic spine dynamics, in a mouse model of AD.

METHODS

BIOCG was administered for 3 months to 3xTg or 3xTg; Thy1-YFP AD mice and func- tional outcomes were assessed via behavioral testing and electrophysiology. Mechanisms relevant to AD pathogenesis including dendritic spine morphology and turnover, Amyloid Precursor Pro- tein (APP) processing and microglial phenotype were also evaluated. Finally, we sequenced fecal samples following probiotic treatment to assess the impact on gut microbial composition and corre- late the changes with the above described measures.

RESULTS

Mice treated with BIOCG demonstrated preserved cognitive abilities and stronger Long- Term Potentiation (LTP), spontaneous Excitatory Postsynaptic Currents (sEPSC), and glutamate-in- duced LTPs, indicative of functional and electrophysiological effects. Moreover, we observed atten- uated AD pathogenesis, including reduced Amyloid Beta (Aβ) burden, as well as more mature den- dritic spines in the BIOCG-treated. Our finding of changes in microglial number and phenotype in the treatment group suggests that this formulation may mediate its effects via attenuation of neu- roinflammation. Sequencing data confirmed that the gut microbiome in treated mice was more varied and harbored a greater proportion of "beneficial" bacteria.

CONCLUSION

Overall, our results indicate that treatment with BIOCG enhances microbial diversity and, through gut-brain axis interactions, attenuates neuroinflammation to produce histologic and functional improvement in AD pathogenesis.

Probiotics-Based Treatment as an Integral Approach for Alcohol Use Disorder in Alcoholic Liver Disease

Alcoholic liver disease (ALD) is one of the leading causes of morbidity among adults with alcohol use disorder (AUD) worldwide. Its clinical course ranges from steatosis to alcoholic hepatitis, progressing to more severe forms of liver damage, such as cirrhosis and hepatocellular carcinoma. The pathogenesis of ALD is complex and diverse elements are involved in its development, including environmental factors, genetic predisposition, the immune response, and the gut-liver axis interaction. Chronic alcohol consumption induces changes in gut microbiota that are associated with a loss of intestinal barrier function and inflammatory responses which reinforce a liver damage progression triggered by alcohol. Alcohol metabolites such as acetaldehyde, lipid peroxidation-derived aldehyde malondialdehyde (MDA), and protein-adducts act as liver-damaging hepatotoxins and potentiate systemic inflammation. Additionally, ethanol causes direct damage to the central nervous system (CNS) by crossing the blood-brain barrier (BBB), provoking oxidative stress contributing to neuroinflammation. Overall, these processes have been associated with susceptibility to depression, anxiety, and alcohol craving in ALD. Recent evidence has shown that probiotics can reverse alcohol-induced changes of the microbiota and prevent ALD progression by restoring gut microbial composition. However, the impact of probiotics on alcohol consumption behavior has been less explored. Probiotics have been used to treat various conditions by restoring microbiota and decreasing systemic and CNS inflammation. The results of some studies suggest that probiotics might improve mental function in Alzheimer’s, autism spectrum disorder, and attenuated morphine analgesic tolerance. In this sense, it has been observed that gut microbiota composition alterations, as well as its modulation using probiotics, elicit changes in neurotransmitter signals in the brain, especially in the dopamine reward circuit. Consequently, it is not difficult to imagine that a probiotics-based complementary treatment to ALD might reduce disease progression mediated by lower alcohol consumption. This review aims to present an update of the pathophysiologic mechanism underlying the microbiota-gut-liver-brain axis in ALD, as well as to provide evidence supporting probiotic use as a complementary therapy to address alcohol consumption disorder and its consequences on liver damage.

Lactobacillus plantarum PS128 prevents cognitive dysfunction in Alzheimer's disease mice by modulating propionic acid levels, glycogen synthase kinase 3 beta activity, and gliosis

Background

According to recent evidence, psychobiotics exert beneficial effects on central nervous system-related diseases, such as mental disorders. Lactobacillus plantarum PS128 (PS128), a novel psychobiotic strain, improves motor function, depression, and anxiety behaviors. However, the psychobiotic effects and mechanisms of PS128 in Alzheimer’s disease (AD) remain to be explored.

Objectives

The goal of the current study was to evaluate the beneficial effects of PS128 and to further elucidate its mechanism in AD mice.

Methods

PS128 (10¹⁰ colony-forming unit (CFU)/ml) was administered via oral gavage (o.g.) to 6-month-old male wild-type B6 and 3 × Tg-AD mice (harboring the PS1M146V, APPswe and TauP30IL transgenes) that received an intracerebroventricular injection of streptozotocin (icv-STZ, 3 mg/kg) or vehicle (saline) for 33 days. After serial behavioral tests, fecal short-chain fatty acid levels and AD-related pathology were assessed in these mice.

Results

Our findings show that intracerebroventricular injection of streptozotocin accelerated cognitive dysfunction associated with increasing levels of glycogen synthase kinase 3 beta (GSK3β) activity, tau protein phosphorylation at the T231 site (pT231), amyloid-β (Aβ) deposition, amyloid-β protein precursor (AβPP), β-site AβPP-cleaving enzyme (BACE1), gliosis, fecal propionic acid (PPA) levels and cognition-related neuronal loss and decreasing postsynaptic density protein 95 (PSD95) levels in 3 × Tg-AD mice. PS128 supplementation effectively prevented the damage induced by intracerebroventricular injection of streptozotocin in 3 × Tg-AD mice.

Conclusions

Based on the experimental results, intracerebroventricular injection of streptozotocin accelerates the progression of AD in the 3 × Tg-AD mice, primarily by increasing the levels of gliosis, which were mediated by the propionic acid and glycogen synthase kinase 3 beta pathways. PS128 supplementation prevents damage induced by intracerebroventricular injection of streptozotocin by regulating the propionic acid levels, glycogen synthase kinase 3 beta activity, and gliosis in 3 × Tg-AD mice. Therefore, we suggest that PS128 supplementation is a potential strategy to prevent and/or delay the progression of AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03426-8.

Does the application of acetylcholinesterase inhibitors in the treatment of Alzheimer's disease lead to depression?

Introduction: Alzheimer's disease and depression are health conditions affecting millions of people around the world. Both are strongly related to the level of the neurotransmitter acetylcholine. Since cholinergic deficit is characteristic of Alzheimer's disease, acetylcholinesterase inhibitors are applied as relevant drugs for the treatment of this disease, elevating the level of acetylcholine. On the other hand, a high level of acetylcholine is found to be associated with the symptoms of clinical depression.Areas covered: This article aims to discuss if acetylcholinesterase inhibitors used as anti-Alzheimer's drugs could be the cause of the symptoms of clinical depression often linked to this neurological disorder. Emphasis will be put on drugs currently in use and on newly investigated natural products, which can inhibit AChE activity.Expert opinion: Currently, it is not proven that the patient treated for Alzheimer's disease is prone to increased risk for depression due to the acetylcholinesterase inhibition, but there are strong indications. The level of acetylcholine is not the only factor in highly complicated diseases like AD and depression. Still, it needs to be considered isolated, keeping in mind the nature of presently available therapy, especially during a rational drug design process.

Interplay of Good Bacteria and Central Nervous System: Cognitive Aspects and Mechanistic Considerations

The human gastrointestinal tract hosts trillions of microorganisms that is called “gut microbiota.” The gut microbiota is involved in a wide variety of physiological features and functions of the body. Thus, it is not surprising that any damage to the gut microbiota is associated with disorders in different body systems. Probiotics, defined as living microorganisms with health benefits for the host, can support or restore the composition of the gut microbiota. Numerous investigations have proved a relationship between the gut microbiota with normal brain function as well as many brain diseases, in which cognitive dysfunction is a common clinical problem. On the other hand, increasing evidence suggests that the existence of a healthy gut microbiota is crucial for normal cognitive processing. In this regard, interplay of the gut microbiota and cognition has been under focus of recent researches. In the present paper, I review findings of the studies considering beneficial effects of either gut microbiota or probiotic bacteria on the brain cognitive function in the healthy and disease statuses.

The impact of the gut microbiome on memory and sleep in Drosophila

The gut microbiome has been proposed to influence diverse behavioral traits of animals, although the experimental evidence is limited and often contradictory. Here, we made use of the tractability of Drosophila melanogaster for both behavioral analyses and microbiome studies to test how elimination of microorganisms affects a number of behavioral traits. Relative to conventional flies (i.e. with unaltered microbiome), microbiologically sterile (axenic) flies displayed a moderate reduction in memory performance in olfactory appetitive conditioning and courtship assays. The microbiological status of the flies had a small or no effect on anxiety-like behavior (centrophobism) or circadian rhythmicity of locomotor activity, but axenic flies tended to sleep for longer and displayed reduced sleep rebound after sleep deprivation. These last two effects were robust for most tests conducted on both wild-type Canton S and w1118 strains, as well for tests using an isogenized panel of flies with mutations in the period gene, which causes altered circadian rhythmicity. Interestingly, the effect of absence of microbiota on a few behavioral features, most notably instantaneous locomotor activity speed, varied among wild-type strains. Taken together, our findings demonstrate that the microbiome can have subtle but significant effects on specific aspects of Drosophila behavior, some of which are dependent on genetic background.

Gut Microbiota at the Intersection of Alcohol, Brain, and the Liver

Over the last decade, increased research into the cognizance of the gut-liver-brain axis in medicine has yielded powerful evidence suggesting a strong association between alcoholic liver diseases (ALD) and the brain, including hepatic encephalopathy or other similar brain disorders. In the gut-brain axis, chronic, alcohol-drinking-induced, low-grade systemic inflammation is suggested to be the main pathophysiology of cognitive dysfunctions in patients with ALD. However, the role of gut microbiota and its metabolites have remained unclear. Eubiosis of the gut microbiome is crucial as dysbiosis between autochthonous bacteria and pathobionts leads to intestinal insult, liver injury, and neuroinflammation. Restoring dysbiosis using modulating factors such as alcohol abstinence, promoting commensal bacterial abundance, maintaining short-chain fatty acids in the gut, or vagus nerve stimulation could be beneficial in alleviating disease progression. In this review, we summarize the pathogenic mechanisms linked with the gut-liver-brain axis in the development and progression of brain disorders associated with ALD in both experimental models and humans. Further, we discuss the therapeutic potential and future research directions as they relate to the gut-liver-brain axis.

The impact of the microbiota-gut-brain axis on Alzheimer's disease pathophysiology

The gut microbiota is a complex ecosystem that comprises of more than 100 trillion symbiotic microbial cells. The microbiota, the gut, and the brain form an association, 'the microbiota-gut-brain axis,' and synchronize the gut with the central nervous system and modify the behavior and brain immune homeostasis. The bidirectional communication between gut and brain occurs via the immune system, the vagus nerve, the enteric nervous system, and microbial metabolites, including short-chain fatty acids (SCFAs), proteins, and tryptophan metabolites. Recent studies have implicated the gut microbiota in many neurodegenerative diseases, including Alzheimer's disease (AD). In this review, we present an overview of gut microbiota, including Firmicutes, Bacteroidetes, SCFA, tryptophan, bacterial composition, besides age-related changes in gut microbiota composition, the microbiota-gut-brain axis pathways, the role of gut metabolites in amyloid-beta clearance, and gut microbiota modulation from experimental and clinical AD models. Understanding the role of the microbiota may provide new targets for treatment to delay the onset, progression, or reverse AD, and may help in reducing the prevalence of AD.

Roles of Gut Microbiota in the Regulation of Hippocampal Plasticity, Inflammation, and Hippocampus-Dependent Behaviors

The study of the gut microbiota-brain axis has become an intriguing field, attracting attention from both gastroenterologists and neurobiologists. The hippocampus is the center of learning and memory, and plays a pivotal role in neurodegenerative diseases, such as Alzheimer’s disease (AD). Previous studies using diet administration, antibiotics, probiotics, prebiotics, germ-free mice, and fecal analysis of normal and specific pathogen-free animals have shown that the structure and function of the hippocampus are affected by the gut microbiota. Furthermore, hippocampal pathologies in AD are positively correlated with changes in specific microbiota. Genomic and neurochemical analyses revealed significant alterations in genes and amino acids in the hippocampus of AD subjects following a remarkable shift in the gut microbiota. In a recent study, when young animals were transplanted with fecal microbiota derived from AD patients, the recipients showed significant impairment of cognitive behaviors, AD pathologies, and changes in neuronal plasticity and cytokines. Other studies have demonstrated the side effects of antibiotic administration along with the beneficial effects of probiotics, prebiotics, and specific diets on the composition of the gut microbiota and hippocampal functions, but these have been mostly preliminary with unclear mechanisms. Since some specific gut bacteria are positively or negatively correlated to the structure and function of the hippocampus, it is expected that specific gut bacteria administration and other microbiota-based interventions could be potentially applied to prevent or treat hippocampus-based memory impairment and neuropsychiatric disorders such as AD.

Gut Microbiota Alteration and Its Time Course in a Tauopathy Mouse Model

Emerging evidence suggests that gut microbiota dysbiosis plays a role in neurodegenerative disorders. However, whether the composition and diversity of the gut microbiota are altered in tauopathies remains largely unknown. This study was aimed to examine the diversity and composition of the gut microbiota in tauopathies, as well as the correlation with pathological changes in the brain. We collected fecal samples from 32 P301L tau transgenic mice and 32 age- and gender-matched littermate mice at different ages. The 16S ribosomal RNA sequencing technique was used to analyze the microbiota composition in feces. Brain tau pathology levels were measured by immunohistochemistry. The diversity and composition of the gut microbiota significantly changed with aging. At the phylum level, the relative abundance of Bacteroidetes was increased, while Firmicutes were decreased in P301L mice compared with that in Wt mice after 3 months of age. In addition, Actinobacteria was decreased in P301L mice at 3 and 6 months of age, meanwhile Tenericutes was decreased in P301L mice at 10 months of age. Moreover, several specific macrobiota were highly associated with the levels of AT8-tau or pT231-tau protein in the brain. Our findings suggest that gut microbiota changed with aging, as well as in the tauopathy mice model. Modulation of the gut microbiota may be a potential strategy for treatment of tauopathy.

The relationship between epigenetics and microbiota in neuropsychiatric diseases

Microbiota might be considered as a pool for environmental epigenetic factors. Evidence is accumulating that environmental exposures - including microbes, diet, drugs - play a role in the pathogenesis of many neuropsychiatric disorders. Underlying mechanisms are complex, involving the sensitive interplay of genetics with epigenetics, neuroinflammation and the innate immune system. Modifications of microbiota affect neurogenesis and the maturation of microglia, influencing social behavior, stress-related responses and fear learning mechanisms. The excitatory neurons in the medial prefrontal cortex appear to play a key role. The mechanisms through which antibiotics administration may modulate microbiota and, therefore, behavior and neuropsychiatric disorders, may be influenced by several variables such as pre-existing gastrointestinal inflammation, the baseline microbiota composition, diet and stress perception. Probiotics, individualized diet, antibiotics and fecal transplantation could positively modulate the effects of epigenetic factors on neuropsychiatric disorders.

Depletion of gut microbiota is associated with improved neurologic outcome following traumatic brain injury

Signaling between intestinal microbiota and the brain influences neurologic outcome in multiple forms of brain injury. The impact of gut microbiota following traumatic brain injury (TBI) has not been well established. Our objective was to compare TBI outcomes in specific pathogen-free mice with or without depletion of intestinal bacteria. Adult male C57BL6/J SPF mice (n = 6/group) were randomized to standard drinking water or ampicillin (1 g/L), metronidazole (1 g/L), neomycin (1 g/L), and vancomycin (0.5 g/L) (AMNV) containing drinking water 14 days prior to controlled cortical impact (CCI) model of TBI. 16S rRNA gene sequencing of fecal pellets was performed and alpha and beta diversity determined. Hippocampal neuronal density and microglial activation was assessed 72 h post-injury by immunohistochemistry. In addition, mice (n = 8-12/group) were randomized to AMNV or no treatment initiated immediately after CCI and memory acquisition (fear conditioning) and lesion volume assessed. Mice receiving AMNV had significantly reduced alpha diversity (p < 0.05) and altered microbiota community composition compared to untreated mice (PERMANOVA: p < 0.01). Mice receiving AMNV prior to TBI had increased CA1 hippocampal neuronal density (15.2 ± 1.4 vs. 8.8 ± 2.1 cells/0.1 mm; p < 0.05) and a 26.6 ± 6.6% reduction in Iba-1 positive cells (p < 0.05) at 72 h. Mice randomized to AMNV immediately after CCI had attenuated associative learning deficit on fear conditioning test (%freeze Cue: 63.7 ± 2.7% vs. 41.0 ± 5.1%, p < 0.05) and decreased lesion volume (27.2 ± 0.8 vs. 24.6 ± 0.7 mm³, p < 0.05). In conclusion, depletion of intestinal microbiota was consistent with a neuroprotective effect whether initiated before or after injury in a murine model of TBI. Further investigations of the role of gut microbiota in TBI are warranted.

Time to test antibacterial therapy in Alzheimer's disease

Alzheimer's disease is associated with cerebral accumulation of amyloid-β peptide and hyperphosphorylated tau. In the past 28 years, huge efforts have been made in attempting to treat the disease by reducing brain accumulation of amyloid-β in patients with Alzheimer's disease, with no success. While anti-amyloid-β therapies continue to be tested in prodromal patients with Alzheimer's disease and in subjects at risk of developing Alzheimer's disease, there is an urgent need to provide therapeutic support to patients with established Alzheimer's disease for whom current symptomatic treatment (acetylcholinesterase inhibitors and N-methyl d-aspartate antagonist) provide limited help. The possibility of an infectious aetiology for Alzheimer's disease has been repeatedly postulated over the past three decades. Infiltration of the brain by pathogens may act as a trigger or co-factor for Alzheimer's disease, with Herpes simplex virus type 1, Chlamydia pneumoniae, and Porphyromonas gingivalis being most frequently implicated. These pathogens may directly cross a weakened blood-brain barrier, reach the CNS and cause neurological damage by eliciting neuroinflammation. Alternatively, pathogens may cross a weakened intestinal barrier, reach vascular circulation and then cross blood-brain barrier or cause low grade chronic inflammation and subsequent neuroinflammation from the periphery. The gut microbiota comprises a complex community of microorganisms. Increased permeability of the gut and blood-brain barrier induced by microbiota dysbiosis may impact Alzheimer's disease pathogenesis. Inflammatory microorganisms in gut microbiota are associated with peripheral inflammation and brain amyloid-β deposition in subjects with cognitive impairment. Oral microbiota may also influence Alzheimer's disease risk through circulatory or neural access to the brain. At least two possibilities can be envisaged to explain the association of suspected pathogens and Alzheimer's disease. One is that patients with Alzheimer's disease are particularly prone to microbial infections. The other is that microbial infection is a contributing cause of Alzheimer's disease. Therapeutic trials with antivirals and/or antibacterials could resolve this dilemma. Indeed, antiviral agents are being tested in patients with Alzheimer's disease in double-blind placebo-controlled studies. Although combined antibiotic therapy was found to be effective in animal models of Alzheimer's disease, antibacterial drugs are not being widely investigated in patients with Alzheimer's disease. This is because it is not clear which bacterial populations in the gut of patients with Alzheimer's disease are overexpressed and if safe, selective antibacterials are available for them. On the other hand, a bacterial protease inhibitor targeting P. gingivalis toxins is now being tested in patients with Alzheimer's disease. Clinical studies are needed to test if countering bacterial infection may be beneficial in patients with established Alzheimer's disease.

Genetic and metabolic links between the murine microbiome and memory

BACKGROUND

Recent evidence has linked the gut microbiome to host behavior via the gut-brain axis [1-3]; however, the underlying mechanisms remain unexplored. Here, we determined the links between host genetics, the gut microbiome and memory using the genetically defined Collaborative Cross (CC) mouse cohort, complemented with microbiome and metabolomic analyses in conventional and germ-free (GF) mice.

RESULTS

A genome-wide association analysis (GWAS) identified 715 of 76,080 single-nucleotide polymorphisms (SNPs) that were significantly associated with short-term memory using the passive avoidance model. The identified SNPs were enriched in genes known to be involved in learning and memory functions. By 16S rRNA gene sequencing of the gut microbial community in the same CC cohort, we identified specific microorganisms that were significantly correlated with longer latencies in our retention test, including a positive correlation with Lactobacillus. Inoculation of GF mice with individual species of Lactobacillus (L. reuteri F275, L. plantarum BDGP2 or L. brevis BDGP6) resulted in significantly improved memory compared to uninoculated or E. coli DH10B inoculated controls. Untargeted metabolomics analysis revealed significantly higher levels of several metabolites, including lactate, in the stools of Lactobacillus-colonized mice, when compared to GF control mice. Moreover, we demonstrate that dietary lactate treatment alone boosted memory in conventional mice. Mechanistically, we show that both inoculation with Lactobacillus or lactate treatment significantly increased the levels of the neurotransmitter, gamma-aminobutyric acid (GABA), in the hippocampus of the mice.

CONCLUSION

Together, this study provides new evidence for a link between Lactobacillus and memory and our results open possible new avenues for treating memory impairment disorders using specific gut microbial inoculants and/or metabolites. Video Abstract.