Probiotics modulate the microbiota-gut-brain axis and improve memory deficits in aged SAMP8 mice

Unveiling the role of gut-brain axis in regulating neurodegenerative diseases: A comprehensive review

Emerging evidence have shown the importance of gut microbiota in regulating brain functions. The diverse molecular mechanisms involved in cross-talk between gut and brain provide insight into importance of this communication in maintenance of brain homeostasis. It has also been observed that disturbed gut microbiota contributes to neurological diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis and aging. Recently, gut microbiome-derived exosomes have also been reported to play an essential role in the development and progression of neurodegenerative diseases and could thereby act as a therapeutic target. Further, pharmacological interventions including antibiotics, prebiotics and probiotics can influence gut microbiome-mediated management of neurological diseases. However, extensive research is warranted to better comprehend this interconnection in maintenance of brain homeostasis and its implication in neurological diseases. Thus, the present review is aimed to provide a detailed understanding of gut-brain axis followed by possibilities to target the gut microbiome for improving neurological health.

Prebiotics modulate the microbiota-gut-brain axis and ameliorate cognitive impairment in APP/PS1 mice

PURPOSE

Prebiotics, including fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS), stimulate beneficial gut bacteria and may be helpful for patients with Alzheimer's disease (AD). This study aimed to compare the effects of FOS and GOS, alone or in combination, on AD mice and to identify their underlying mechanisms.

METHODS

Six-month-old APP/PS1 mice and wild-type mice were orally administered FOS, GOS, FOS + GOS or water by gavage for 6 weeks and then subjected to relative assays, including behavioral tests, biochemical assays and 16S rRNA sequencing.

RESULTS

Through behavioral tests, we found that GOS had the best effect on reversing cognitive impairment in APP/PS1 mice, followed by FOS + GOS, while FOS had no effect. Through biochemical techniques, we found that GOS and FOS + GOS had effects on multiple targets, including diminishing Aβ burden and proinflammatory IL-1β and IL-6 levels, and changing the concentrations of neurotransmitters GABA and 5-HT in the brain. In contrast, FOS had only a slight anti-inflammatory effect. Moreover, through 16S rRNA sequencing, we found that prebiotics changed composition of gut microbiota. Notably, GOS increased relative abundance of Lactobacillus, FOS increased that of Bifidobacterium, and FOS + GOS increased that of both. Furthermore, prebiotics downregulated the expression levels of proteins of the TLR4-Myd88-NF-κB pathway in the colons and cortexes, suggesting the involvement of gut-brain mechanism in alleviating neuroinflammation.

CONCLUSION

Among the three prebiotics, GOS was the optimal one to alleviate cognitive impairment in APP/PS1 mice and the mechanism was attributed to its multi-target role in alleviating Aβ pathology and neuroinflammation, changing neurotransmitter concentrations, and modulating gut microbiota.

The role of Lactobacillus in inflammatory bowel disease: from actualities to prospects

Inflammatory Bowel Disease (IBD), a chronic nonspecific intestinal inflammatory disease, is comprised of Ulcerative Colitis (UC) and Crohn's Disease (CD). IBD is closely related to a systemic inflammatory reaction and affects the progression of many intestinal and extraintestinal diseases. As one of the representative bacteria for probiotic-assisted therapy in IBD, multiple strains of Lactobacillus have been proven to alleviate intestinal damage and strengthen the intestinal immunological barrier, epithelial cell barrier, and mucus barrier. Lactobacillus also spares no effort in the alleviation of IBD-related diseases such as Colitis-associated Colorectal cancer (CAC), Alzheimer's Disease (AD), Depression, Anxiety, Autoimmune Hepatitis (AIH), and so on via gut-brain axis and gut-liver axis. This article aims to discuss the role of Lactobacillus in IBD and IBD-related diseases, including its underlying mechanisms and related curative strategies from the present to the future.

Blood-spinal cord barrier disruption in degenerative cervical myelopathy

Degenerative cervical myelopathy (DCM) is the most prevalent cause of spinal cord dysfunction in the aging population. Significant neurological deficits may result from a delayed diagnosis as well as inadequate neurological recovery following surgical decompression. Here, we review the pathophysiology of DCM with an emphasis on how blood-spinal cord barrier (BSCB) disruption is a critical yet neglected pathological feature affecting prognosis. In patients suffering from DCM, compromise of the BSCB is evidenced by elevated cerebrospinal fluid (CSF) to serum protein ratios and abnormal contrast-enhancement upon magnetic resonance imaging (MRI). In animal model correlates, there is histological evidence of increased extravasation of tissue dyes and serum contents, and pathological changes to the neurovascular unit. BSCB dysfunction is the likely culprit for ischemia-reperfusion injury following surgical decompression, which can result in devastating neurological sequelae. As there are currently no therapeutic approaches specifically targeting BSCB reconstitution, we conclude the review by discussing potential interventions harnessed for this purpose.

Analysis of an Individualised Stepwise Approach to Non-Pharmacological Therapy in COVID-19

BACKGROUND

Early intubation versus use of conventional or high-flow nasal cannula oxygen therapy (COT/HFNC), continuous positive airway pressure (CPAP), and non-invasive ventilation (NIV) has been debated throughout the COVID-19 pandemic. Our centre followed a stepwise approach, in concordance with German national guidelines, escalating non-invasive modalities prior to invasive mechanical ventilation (IMV) or extracorporeal membrane oxygenation (ECMO), rather than early or late intubation.

OBJECTIVES

The aims of the study were to investigate the real-life usage of these modalities and analyse patient characteristics and survival.

METHOD

A retrospective monocentric observation was conducted of all consecutive COVID-19 hospital admissions between March 2020 and December 2021 at a university-affiliated pulmonary centre in Germany. Anthropometric data, therapy, and survival status were descriptively analysed.

RESULTS

From 1,052 COVID-19-related admissions, 835 patients were included (54% male, median 58 years). Maximum therapy was as follows: 34% (n = 284) no therapy, 40% (n = 337) COT, 3% (n = 22) HFNC, 9% (n = 73) CPAP, 7% (n = 56) NIV, 4% (n = 34) IMV, and 3% (n = 29) ECMO. Of 551 patients treated with at least COT, 12.3% required intubation. Overall, 183 patients required intensive unit care, and 106 (13%) died. Of the 68 patients who received IMV/ECMO, 48 died (74%). The strategy for non-pharmacological therapy was individual but remained consistent throughout the studied period.

CONCLUSIONS

This study provides valuable insight into COVID-19 care in Germany and shows how the majority of patients could be treated with the maximum treatment required according to disease severity following the national algorithm. Escalation of therapy modality is interlinked with disease severity and thus associated with mortality.

Improving intestinal inflammaging to delay aging? A new perspective

Greying population is becoming an increasingly critical issue for social development. In advanced aging context, organismal multiple tissues and organs experience a progressive deterioration, initially presenting with functional decline, followed by structural disruption and eventually organ failure. The aging of the gut is one of the key links. Decreased gut function leads to reduced nutrient absorption and can perturb systemic metabolic rates. The degeneration of the intestinal structure causes the migration of harmful components such as pathogens and toxins, inducing pathophysiological changes in other organs through the "brain-gut axis" and "liver-gut axis". There is no accepted singular underlying mechanism of aged gut. While the inflamm-aging theory was first proposed in 2000, the mutual promotion of chronic inflammation and aging has attracted much attention. Numerous studies have established that gut microbiome composition, gut immune function, and gut barrier integrity are involved in the formation of inflammaging in the aging gut. Remarkably, inflammaging additionally drives the development of aging-like phenotypes, such as microbiota dysbiosis and impaired intestinal barrier, via a broad array of inflammatory mediators. Here we demonstrate the mechanisms of inflammaging in the gut and explore whether aging-like phenotypes in the gut can be negated by improving gut inflammaging.

Fecal Microbiota Transplantation from Aged Mice Render Recipient Mice Resistant to MPTP-Induced Nigrostriatal Degeneration Via a Neurogenesis-Dependent but Inflammation-Independent Manner

Accumulating data support a crucial role of gut microbiota in Parkinson's disease (PD). However, gut microbiota vary with age and, thus, will affect PD in an age-dependent, but unknown manner. We examined the effects of fecal microbiota transplantation (FMT) pretreatment, using fecal microbiota from young (7 weeks) or aged mice (23 months), on MPTP-induced PD model. Motor function, pathological changes, striatal neurotransmitters, neuroinflammation, gut inflammation and gut permeability were examined. Gut microbiota composition and metabolites, namely short-chain fatty acids (SCFAs), were analyzed. Neurogenesis was also evaluated by measuring the number of doublecortin-positive (DCX+) neurons and Ki67-positive (Ki67+) cells in the hippocampus. Expression of Cd133 mRNA, a cellular stemness marker, in the hippocampus was also examined. Mice who received FMT from young mice showed MPTP-induced motor dysfunction, and reduction of striatal dopamine (DA), dopaminergic neurons and striatal tyrosine hydroxylase (TH) levels. Interestingly and unexpectedly, mice that received FMT from aged mice showed recovery of motor function and rescue of dopaminergic neurons and striatal 5-hydroxytryptamine (5-HT), as well as decreased DA metabolism after MPTP challenge. Further, they showed improved metabolic profiling and a decreased amount of fecal SCFAs. High-throughput sequencing revealed that FMT remarkably reshaped the gut microbiota of recipient mice. For instance, levels of genus Akkermansia and Candidatus Saccharimonas were elevated in fecal samples of recipient mice receiving aged microbiota (AM + MPTP mice) than YM + MPTP mice. Intriguingly, both young microbiota and aged microbiota had no effect on neuroinflammation, gut inflammation or gut permeability. Notably, AM + MPTP mice showed a marked increase in DCX+ neurons, as well as Ki67+ cells and Cd133 expression in the hippocampal dentate gyrus (DG) compared to YM + MPTP mice. These results suggest that FMT from aged mice augments neurogenesis, improves motor function and restores dopaminergic neurons and neurotransmitters in PD model mice, possibly through increasing neurogenesis.

Pterostilbene could alleviate diabetic cognitive impairment by suppressing TLR4/NF-кB pathway through microbiota-gut-brain axis

Diabetic cognitive impairment (DCI) is a serious neurodegenerative disorder caused by diabetes, with chronic inflammation being a crucial factor in its pathogenesis. Pterostilbene is a well-known natural stilbene derivative that has excellent anti-inflammatory activity, suggesting its potential medicinal advantages for treating DCI. Therefore, this study is to explore the beneficial effects of pterostilbene for improving cognitive dysfunction in DCI mice. A diabetic model was induced by a high-fat diet plus streptozotocin (40 mg·kg-1 ) for consecutive 5 days. After the animals were confirmed to be in a diabetic state, they were treated with pterostilbene (20 or 60 mg·kg-1 , i.g.) for 10 weeks. Pharmacological evaluation showed pterostilbene could ameliorate cognitive dysfunction, regulate glycolipid metabolism disorders, improve neuronal damage, and reduce the accumulation of β-amyloid in DCI mice. Pterostilbene alleviated neuroinflammation by suppressing oxidative stress and carbonyl stress damage, astrocyte and microglia activation, and dopaminergic neuronal loss. Further investigations showed that pterostilbene reduced the level of lipopolysaccharide, modulated colon and brain TLR4/NF-κB signaling pathways, and decreased the release of inflammatory factors, which in turn inhibited intestinal inflammation and neuroinflammation. Furthermore, pterostilbene could also improve the homeostasis of intestinal microbiota, increase the levels of short-chain fatty acids and their receptors, and suppress the loss of intestinal tight junction proteins. In addition, the results of plasma non-targeted metabolomics revealed that pterostilbene could modulate differential metabolites and metabolic pathways associated with inflammation, thereby suppressing systemic inflammation in DCI mice. Collectively, our study found for the first time that pterostilbene could alleviate diabetic cognitive dysfunction by inhibiting the TLR4/NF-κB pathway through the microbiota-gut-brain axis, which may be one of the potential mechanisms for its neuroprotective effects.

Association between Nonfood Pre- or Probiotic Use and Cognitive Function: Results from NHANES 2011-2014

In this study, we collected data from the National Health and Nutrition Examination Survey (NHANES) for the years 2011-2014. Multiple linear regression and logistic regression were used to analyse the association between nonfood pro- or prebiotic use and cognitive function among elderly Americans. To estimate the potential unobserved results, propensity score matching (PSM) was used to analyse the causal effect. Nonfood pro- or prebiotic use was analysed through the Dietary Supplement Use 30-Day Study. Cognitive function was evaluated by the Digit Symbol Substitution Test (DSST), the Animal Fluency Test (AFT), the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), and a composite Z-score calculated by summing the Z-scores of three tests. Male participants who used nonfood pro- or prebiotics tended to have higher comprehensive cognitive function (sum.z) with a β-coefficient of 0.64 (95% CI: 0.08-1.19). Probiotics or prebiotics may be a protective factor against cognitive impairment in males, with an odds ratio of 0.08 (95% CI: 0.02-0.29). Furthermore, the average treatment effect for the treated (ATT) with nonfood pro- or prebiotics (0.555) on sum.z in males was statistically significant (p < 0.05). Our research revealed that nonfood pre- or probiotic use was an effective method to improve cognitive function in elderly men from the USA.

The Role of Bifidobacterium bifidum novaBBF7, Bifidobacterium longum novaBLG2 and Lactobacillus paracasei TJB8 to Improve Mechanisms Linked to Neuronal Cells Protection against Oxidative Condition in a Gut-Brain Axis Model

Despite the identification of several innovative targets for avoiding cognitive decline, there has yet to be a widely accepted approach that deals with minimising the deterioration of cognitive function. In this light, recent studies suggest that regulating the gut-brain axis with probiotics is a potential therapeutic strategy to support brain health. For this reason, in vitro models were used to examine the efficacy of different probiotic combinations to enhance intestinal homeostasis and positively affect the brain. Therefore, the new formulation has been evaluated for its capacity to modify intestinal barrier functions in a 3D in vitro model without any adverse effects and directly impact the mechanisms underlying cognitive function in a gut-brain axis model. According to our findings, B. bifidum novaBBF7 10 mg/mL, B. longum novaBLG2 5 mg/mL and L. paracasei TJB8 10 mg/mL may successfully modify the intestinal barrier and improve SCFA production. Successively, the probiotics studied caused no harm at the neuronal level, as demonstrated by iNOS, mitochondrial potential, and cell viability tests, confirming their safety features and enhancing antioxidant mechanisms and antineuroinflammation activity. Additionally, the damage caused by oxidative stress was also healed, and critical pathways that result in cognitive impairment were changed by synergetic action, supporting the hypothesis that brain ageing and neurodegeneration are slowed down. All these findings demonstrate the ability of probiotics to affect cognitive processes and their ability to sustain the mechanisms underlying cognitive function by acting on intestinal function.

Microbiome Alterations and Alzheimer's Disease: Modeling Strategies with Transgenic Mice

In the last decade, the role of the microbiota-gut-brain axis has been gaining momentum in the context of many neurodegenerative and metabolic disorders, including Alzheimer's disease (AD) and diabetes, respectively. Notably, a balanced gut microbiota contributes to the epithelial intestinal barrier maintenance, modulates the host immune system, and releases neurotransmitters and/or neuroprotective short-chain fatty acids. However, dysbiosis may provoke immune dysregulation, impacting neuroinflammation through peripheral-central immune communication. Moreover, lipopolysaccharide or detrimental microbial end-products can cross the blood-brain barrier and induce or at least potentiate the neuropathological progression of AD. Thus, after repeated failure to find a cure for this dementia, a necessary paradigmatic shift towards considering AD as a systemic disorder has occurred. Here, we present an overview of the use of germ-free and/or transgenic animal models as valid tools to unravel the connection between dysbiosis, metabolic diseases, and AD, and to investigate novel therapeutical targets. Given the high impact of dietary habits, not only on the microbiota but also on other well-established AD risk factors such as diabetes or obesity, consistent changes of lifestyle along with microbiome-based therapies should be considered as complementary approaches.

Lonicera japonica polysaccharides alleviate D-galactose-induced oxidative stress and restore gut microbiota in ICR mice

Lonicera japonica polysaccharides (LJPs) exhibit anti-aging effect in nematodes. Here, we further studied the function of LJPs on aging-related disorders in D-galactose (D-gal)-induced ICR mice. Four groups of mice including the control group, the D-gal-treated group, the intervening groups with low and high dose of LJPs (50 and 100 mg/kg/day) were raised for 8 weeks. The results showed that intragastric administration with LJPs improved the organ indexes of D-gal-treated mice. Moreover, LJPs improved the activity of superoxide dismutase (SOD), catalase (CAT) as well as glutathione peroxidase (GSH-Px) and decreasing the malondialdehyde (MDA) level in serum, liver and brain. Meanwhile, LJPs restored the content of acetylcholinesterase (AChE) in the brain. Further, LJPs reversed the liver tissue damages in aging mice. Mechanistically, LJPs alleviate oxidative stress at least partially through regulating Nrf2 signaling. Additionally, LJPs restored the gut microbiota composition of D-gal-treated mice by adjusting the Firmicutes/Bacteroidetes ratio at the phylum level and upregulating the relative abundances of Lactobacillaceae and Bifidobacteriacesa. Notably, the KEGG pathways involved in hazardous substances degradation and flavone and flavonol biosynthesis were significantly enhanced by LJPs treatment. Overall, our study uncovers the role of LJPs in modulating oxidative stress and gut microbiota in the D-gal-induced aging mice.

Targeting gut-brain axis by dietary flavonoids ameliorate aging-related cognition decline: Evidences and mechanisms

Aging-related cognitive impairment, mainly Alzheimer's disease (AD), has been widely studied. However, effective prevention and treatment methods are still lacking. In recent years, researchers have observed beneficial effects of plant-based supplements, such as flavonoids, on cognitive protection. This provides a new clue for the prevention of cognitive dysfunction. Studies have shown that dietary flavonoids have neuroprotective effects, but the mechanism is not clear. In this review, we systematically reviewed the research progress on the effects of dietary flavonoids on gut microbes and their metabolites, and concluded that flavonoids could improve cognitive function through the gut-brain axis. Flavonoids can be absorbed through the intestine, cross the blood-brain barrier, and enter the brain tissue. Flavonoids can inhibit the expression and secretion of inflammatory factors in brain tissue, reduce the damage caused by oxidative stress, clear neural damage proteins and inhibit neuronal apoptosis, thereby ameliorating age-related cognitive disorders. Future work will continue to explore the gut-brain axis and target genes regulated by flavonoids. In addition, clinical research and its mechanisms need to be further explored to provide solutions or advise for patients with cognitive impairment.

Tris(2-chloroethyl) Phosphate Exerts Hepatotoxic Impacts on Zebrafish by Disrupting Hypothalamic-Pituitary-Thyroid and Gut-Liver Axes

The ubiquitous environmental presence of tris(2-chloroethyl) phosphate (TCEP) poses a potential threat to animals; however, little is known about its hepatotoxicity. In this study, the effects of TCEP exposure (0.5 and 5.0 μg/L for 28 days) on liver health and the potential underlying toxification mechanisms were investigated in zebrafish. Our results demonstrated that TCEP exposure led to hepatic tissue lesions and resulted in significant alterations in liver-injury-specific markers. Moreover, TCEP-exposed fish had significantly lower levels of thyrotropin-releasing hormone and thyroid-stimulating hormone in the brain, evidently less triiodothyronine whereas more thyroxine in plasma, and markedly altered expressions of genes from the hypothalamic-pituitary-thyroid (HPT) axis in the brain or liver. In addition, a significantly higher proportion of Bacteroidetes in the gut microbiota, an elevated bacterial source endotoxin lipopolysaccharide (LPS) in the plasma, upregulated expression of LPS-binding protein and Toll-like receptor 4 in the liver, and higher levels of proinflammatory cytokines in the liver were detected in TCEP-exposed zebrafish. Furthermore, TCEP-exposed fish also suffered severe oxidative damage, possibly due to disruption of the antioxidant system. These findings suggest that TCEP may exert hepatotoxic effects on zebrafish by disrupting the HPT and gut-liver axes and thereafter inducing hepatic inflammation and oxidative stress.

Neurodegenerative and Neurodevelopmental Diseases and the Gut-Brain Axis: The Potential of Therapeutic Targeting of the Microbiome

The human gut microbiome contains the largest number of bacteria in the body and has the potential to greatly influence metabolism, not only locally but also systemically. There is an established link between a healthy, balanced, and diverse microbiome and overall health. When the gut microbiome becomes unbalanced (dysbiosis) through dietary changes, medication use, lifestyle choices, environmental factors, and ageing, this has a profound effect on our health and is linked to many diseases, including lifestyle diseases, metabolic diseases, inflammatory diseases, and neurological diseases. While this link in humans is largely an association of dysbiosis with disease, in animal models, a causative link can be demonstrated. The link between the gut and the brain is particularly important in maintaining brain health, with a strong association between dysbiosis in the gut and neurodegenerative and neurodevelopmental diseases. This link suggests not only that the gut microbiota composition can be used to make an early diagnosis of neurodegenerative and neurodevelopmental diseases but also that modifying the gut microbiome to influence the microbiome-gut-brain axis might present a therapeutic target for diseases that have proved intractable, with the aim of altering the trajectory of neurodegenerative and neurodevelopmental diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, autism spectrum disorder, and attention-deficit hyperactivity disorder, among others. There is also a microbiome-gut-brain link to other potentially reversible neurological diseases, such as migraine, post-operative cognitive dysfunction, and long COVID, which might be considered models of therapy for neurodegenerative disease. The role of traditional methods in altering the microbiome, as well as newer, more novel treatments such as faecal microbiome transplants and photobiomodulation, are discussed.

Effects of gut microbiota on neurodegenerative diseases

A progressive degradation of the brain's structure and function, which results in a reduction in cognitive and motor skills, characterizes neurodegenerative diseases (NDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). The morbidity linked to NDs is growing, which poses a severe threat to human being's mental and physical ability to live well. The gut-brain axis (GBA) is now known to have a crucial role in the emergence of NDs. The gut microbiota is a conduit for the GBA, a two-way communication system between the gut and the brain. The myriad microorganisms that make up the gut microbiota can affect brain physiology by transmitting numerous microbial chemicals from the gut to the brain via the GBA or neurological system. The synthesis of neurotransmitters, the immunological response, and the metabolism of lipids and glucose have all been demonstrated to be impacted by alterations in the gut microbiota, such as an imbalance of helpful and harmful bacteria. In order to develop innovative interventions and clinical therapies for NDs, it is crucial to comprehend the participation of the gut microbiota in these conditions. In addition to using antibiotics and other drugs to target particular bacterial species that may be a factor in NDs, this also includes using probiotics and other fecal microbiota transplantation to maintain a healthy gut microbiota. In conclusion, the examination of the GBA can aid in understanding the etiology and development of NDs, which may benefit the improvement of clinical treatments for these disorders and ND interventions. This review indicates existing knowledge about the involvement of microbiota present in the gut in NDs and potential treatment options.

Effect of Probiotic Yogurt Supplementation(Bifidobacterium animalis ssp. lactis BB-12) on Gut Microbiota of Female Taekwondo Athletes and Its Relationship with Exercise-Related Psychological Fatigue

OBJECTIVE

The gut microbiota plays a critical role in regulating human health and athletic performance. Probiotic supplementation has been shown to modulate gut microbiota composition and improve exercise performance. This study aimed to investigate the effect of probiotic yogurt supplementation on gut microbiota and its relationship with exercise-related psychological fatigue in female taekwondo athletes.

METHODS

Twenty female taekwondo athletes were randomly assigned to either a dietary intervention group (DK) or a control group (CK). The athletes' exercise-related psychological fatigue was measured using the Athlete Burnout Questionnaire (ABQ) before and after an 8-week intervention. High-throughput sequencing was used to profile the gut microbiota, and functional prediction of the microbial community was performed. The effect of the dietary intervention on the athletes' exercise-related psychological fatigue clearance rate and its relationship with the gut microbiota were explored.

RESULTS

(1) The probiotic supplementation of Bifidobacterium animalis ssp. lactis BB-12 for 8 weeks significantly increased the ABQ scores of the DK group compared to the CK group (p < 0.05). (2) The abundances of Bifidobacterium, Bacteroides, Lachnospiraceae, family _Lactobacillaceae, and genus _Lactobacillus were significantly higher in the DK group than in the CK group after probiotic supplementation, while Escherichia coli was significantly lower in the DK group than in the CK group. (3) The ABQa scores were positively correlated with Proteus; ABQb scores were positively correlated with Streptococcus and Enterococcus; and ABQc scores were positively correlated with Klebsiella, Bacteroides, and Streptomyces. (4) The DK group had significantly higher levels of L-arginine biosynthesis I (via L-ornithine), fatty acid biosynthesis and oxidation, and L-isoleucine biosynthesis III pathways compared to the CK group. Tyrosine degradation I (via 2,3-dihydroxyphenylpropionate) was significantly lower in the DK group than in the CK group.

CONCLUSIONS

Probiotic yogurt supplementation of Bifidobacterium animalis ssp. lactis can promote the clearance of exercise-related psychological fatigue in female taekwondo athletes by upregulating beneficial gut microbiota, inhibiting harmful gut microbiota, and regulating relevant metabolic pathways.

Exploring the Relationship between the Gut Microbiota and Ageing: A Possible Age Modulator

The gut microbiota (GM) has been the subject of intense research in recent years. Therefore, numerous factors affecting its composition have been thoroughly examined, and with them, their function and role in the individual's systems. The gut microbiota's taxonomical composition dramatically impacts older adults' health status. In this regard, it could either extend their life expectancy via the modulation of metabolic processes and the immune system or, in the case of dysbiosis, predispose them to age-related diseases, including bowel inflammatory and musculoskeletal diseases and metabolic and neurological disorders. In general, the microbiome of the elderly tends to present taxonomic and functional changes, which can function as a target to modulate the microbiota and improve the health of this population. The GM of centenarians is unique, with the faculty-promoting metabolic pathways capable of preventing and counteracting the different processes associated with age-related diseases. The molecular mechanisms by which the microbiota can exhibit anti-ageing properties are mainly based on anti-inflammatory and antioxidant actions. This review focuses on analysing the current knowledge of gut microbiota characteristics and modifiers, its relationship with ageing, and the GM-modulating approaches to increase life expectancy.

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.

Chaihu Shugan San ameliorated cognitive deficits through regulating gut microbiota in senescence-accelerated mouse prone 8

Background: Traditional Chinese medicines exhibit promising preventive effects on Alzheimer's disease. Chaihu Shugan San (CSS) is a well-known traditional herbal formula whose several kinds of ingredients have the potential of ameliorating Alzheimer's disease. The present study aimed to evaluate the effects of CSS on the microbiota-gut-brain axis and cognitive deficits of senescence-accelerated mouse prone 8 (SAMP8) mice as well as investigate the underlying mechanisms. Methods: Thirty 5-month-old SAMP8 mice were randomly divided into the model group (SAMP8), CSS low-dose treatment group (CSSL), and CSS high-dose treatment group (CSSH). Ten SAMR1 mice were used as the normal control, and ten SAMP8 mice treated with donepezil were used as the positive control of cognitive function. CSS was orally administrated to SAMP8 mice for 8 weeks. The Morris water maze test was used to evaluate cognitive function. Histological staining was used to observe neuronal injury and Aβ deposition. Transmission electron microscopy was used to observe the synaptic ultrastructure. 16S rRNA gene analysis was performed to measure the changes in intestinal microbiota. Results: The results showed that CSS significantly improved the learning function and memory deficits of aged SAMP8 mice in the Morris water maze examination. CSS ameliorated neuronal injury, synaptic injuries, and Aβ deposition in the brain of SAMP8 mice. In addition, CSS also significantly improved microbiota composition in terms of elevating Lactobacillus reuteri and decreasing Staphylococcus xylosus in the feces of aged SAMP8 mice. Conclusion: These findings suggested that CSS might have a preventive potential for cognitive deficits in aging through regulating gut microbiota, which paved the way for the application of CSS for prevention and therapeutic purposes for mild cognitive impairment as well as Alzheimer's disease.

Probiotics therapy show significant improvement in obesity and neurobehavioral disorders symptoms

Obesity is a complex metabolic disease, with cognitive impairment being an essential complication. Gut microbiota differs markedly between individuals with and without obesity. The microbial-gut-brain axis is an important pathway through which metabolic factors, such as obesity, affect the brain. Probiotics have been shown to alleviate symptoms associated with obesity and neurobehavioral disorders. In this review, we evaluated previously published studies on the effectiveness of probiotic interventions in reducing cognitive impairment, depression, and anxiety associated with obesity or a high-fat diet. Most of the probiotics studied have beneficial health effects on obesity-induced cognitive impairment and anxiety. They positively affect immune regulation, the hypothalamic-pituitary-adrenal axis, hippocampal function, intestinal mucosa protection, and glucolipid metabolism regulation. Probiotics can influence changes in the composition of the gut microbiota and the ratio between various flora. However, probiotics should be used with caution, particularly in healthy individuals. Future research should further explore the mechanisms underlying the gut-brain axis, obesity, and cognitive function while overcoming the significant variation in study design and high risk of bias in the current evidence.

Early life adversity as a risk factor for cognitive impairment and Alzheimer's disease

Neurological conditions, including cognitive impairment and Alzheimer's disease (AD), impose a huge burden on society, affecting millions of people globally. In addition to genetic factors, recent studies indicate that environmental and experiential factors may contribute to the pathogenesis of these diseases. Early life adversity (ELA) has a profound impact on brain function and health later in life. In rodent models, exposure to ELA results in specific cognitive deficits and aggravated AD pathology. Extensive concerns have been raised regarding the higher risk of developing cognitive impairments in people with a history of ELA. In this review, we scrutinize findings from human and animal studies focusing on the connection of ELA with cognitive impairment and AD. These discoveries suggest that ELA, especially at early postnatal stages, increases susceptibility to cognitive impairment and AD later in life. In terms of mechanisms, ELA could lead to dysregulation of the hypothalamus-pituitary-adrenal axis, altered gut microbiome, persistent inflammation, oligodendrocyte dysfunction, hypomyelination, and aberrant adult hippocampal neurogenesis. Crosstalks among these events may synergistically contribute to cognitive impairment later in life. Additionally, we discuss several interventions that may alleviate adverse consequences of ELA. Further investigation into this crucial area will help improve ELA management and reduce the burden of related neurological conditions.

Lactic Acid Bacteria (LAB) and Neuroprotection, What Is New? An Up-To-Date Systematic Review

BACKGROUND

In recent years, the potential role of probiotics has become prominent in the discoveries of neurotherapy against neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Lactic acid bacteria (LAB) exhibit neuroprotective properties and exert their effects via various mechanisms of actions. This review aimed to evaluate the effects of LAB on neuroprotection reported in the literature.

METHODS

A database search on Google Scholar, PubMed, and Science Direct revealed a total of 467 references, of which 25 were included in this review based on inclusion criteria which comprises 7 in vitro, 16 in vivo, and 2 clinical studies.

RESULTS

From the studies, LAB treatment alone or in probiotics formulations demonstrated significant neuroprotective activities. In animals and humans, LAB probiotics supplementation has improved memory and cognitive performance mainly via antioxidant and anti-inflammatory pathways.

CONCLUSIONS

Despite promising findings, due to limited studies available in the literature, further studies still need to be explored regarding synergistic effects, efficacy, and optimum dosage of LAB oral bacteriotherapy as treatment or prevention against neurodegenerative diseases.

Gut Dysbiosis and Blood-Brain Barrier Alteration in Hepatic Encephalopathy: From Gut to Brain

A common neuropsychiatric complication of advanced liver disease, hepatic encephalopathy (HE), impacts the quality of life and length of hospital stays. There is new evidence that gut microbiota plays a significant role in brain development and cerebral homeostasis. Microbiota metabolites are providing a new avenue of therapeutic options for several neurological-related disorders. For instance, the gut microbiota composition and blood-brain barrier (BBB) integrity are altered in HE in a variety of clinical and experimental studies. Furthermore, probiotics, prebiotics, antibiotics, and fecal microbiota transplantation have been shown to positively affect BBB integrity in disease models that are potentially extendable to HE by targeting gut microbiota. However, the mechanisms that underlie microbiota dysbiosis and its effects on the BBB are still unclear in HE. To this end, the aim of this review was to summarize the clinical and experimental evidence of gut dysbiosis and BBB disruption in HE and a possible mechanism.

Microbiota-gut-brain axis and related therapeutics in Alzheimer's disease: prospects for multitherapy and inflammation control

Alzheimer's disease (AD) is the most common type of dementia in the elderly and causes neurodegeneration, leading to memory loss, behavioral disorder, and psychiatric impairment. One potential mechanism contributing to the pathogenesis of AD may be the imbalance in gut microbiota, local and systemic inflammation, and dysregulation of the microbiota-gut-brain axis (MGBA). Most of the AD drugs approved for clinical use today are symptomatic treatments that do not improve AD pathologic changes. As a result, researchers are exploring novel therapeutic modalities. Treatments involving the MGBA include antibiotics, probiotics, transplantation of fecal microbiota, botanical products, and others. However, single-treatment modalities are not as effective as expected, and a combination therapy is gaining momentum. The purpose of this review is to summarize recent advances in MGBA-related pathological mechanisms and treatment modalities in AD and to propose a new concept of combination therapy. "MGBA-based multitherapy" is an emerging view of treatment in which classic symptomatic treatments and MGBA-based therapeutic modalities are used in combination. Donepezil and memantine are two commonly used drugs in AD treatment. On the basis of the single/combined use of these two drugs, two/more additional drugs and treatment modalities that target the MGBA are chosen based on the characteristics of the patient's condition as an adjuvant treatment, as well as the maintenance of good lifestyle habits. "MGBA-based multitherapy" offers new insights for the treatment of cognitive impairment in AD patients and is expected to show good therapeutic results.

Identification of the Genetic Influence of SARS-CoV-2 Infections on IgA Nephropathy Based on Bioinformatics Method

INTRODUCTION

Coronavirus disease-2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. It was initially detected in Wuhan, China, in December 2019. In March 2020, the World Health Organization (WHO) declared COVID-19 a global pandemic. Compared to healthy individuals, patients with IgA nephropathy (IgAN) are at a higher risk of SARS-CoV-2 infection. However, the potential mechanisms remain unclear. This study explores the underlying molecular mechanisms and therapeutic agents for the management of IgAN and COVID-19 using the bioinformatics and system biology way.

METHODS

We first downloaded GSE73953 and GSE164805 from the Gene Expression Omnibus (GEO) database to obtain common differentially expressed genes (DEGs). Then, we performed the functional enrichment analysis, pathway analysis, protein-protein interaction (PPI) analysis, gene regulatory networks analysis, and potential drug analysis on these common DEGs.

RESULTS

We acquired 312 common DEGs from the IgAN and COVID-19 datasets and used various bioinformatics tools and statistical analyses to construct the PPI network to extract hub genes. Besides, we performed gene ontology (GO) and pathway analyses to reveal the common correlation between IgAN and COVID-19. Finally, on the basis of common DEGs, we determined the interactions between DEGs-miRNAs, the transcription factor-genes (TFs-genes), protein-drug, and gene-disease networks.

CONCLUSION

We successfully identified hub genes that may act as biomarkers of COVID-19 and IgAN and also screened out some potential drugs to provide new ideas for COVID-19 and IgAN treatment.

Extracellular vesicles: Critical bilateral communicators in periphery-brain crosstalk in central nervous system disorders

Growing evidence shows that there is a comorbid mechanism between the central nervous system (CNS) and the peripheral organs. The bilateral transmission of signal molecules in periphery-brain crosstalk plays an important role in the underlying mechanism, which result from complex networks of neurohumoral circuits. Secreted by almost all cells and considered innovative information transport systems, extracellular vesicles (EVs) encapsulate and deliver nucleic acids, proteins, lipids, and various other bioactive regulators. Moreover, EVs can cross the blood-brain barrier (BBB), they are also identified primarily as essential communicators between the periphery and the CNS. In addition to transporting molecules under physiological or pathological conditions, EVs also show novel potential in targeted drug delivery. In this review, we discuss the mechanisms implicated in the transport of EVs in crosstalk between the peripheral and the central immune systems as well as in crosstalk between the peripheral organs and the brain in CNS disorders, especially in neurodegenerative diseases, stroke, and trauma. This work will help in elucidating the contributions of EVs to brain health and disorders, and promote the development of new strategies for minimally invasive treatment.

Probiotic supplementation improved cognitive function in cognitively impaired and healthy older adults: a systematic review of recent trials

INTRODUCTION

Recent evidence suggests that there is clear association between microbiota and cognitive functioning, which is known as microbiome-gut-brain axis. Probiotic bacteria consumption can alter human microbiota; therefore, probiotic supplementation might affect the gut microbiota dynamics and influence cognitive function.

METHODS

Three electronic databases including PubMed, ProQuest, and EBSCOHost databases were utilized. Manual hand search of article was also done. We selected randomized controlled trial articles that measure cognitive function (as the primary outcome) after intervention with probiotic supplementation on older adult population with AD, MCI, or healthy condition. The following terms and its variant were used: "probiotic," "cognitive function," "mild cognitive impairment," "dementia," and "Alzheimer's disease."

RESULT

Nine of 10 included studies (AD, MCI, or healthy cognition population) showed cognitive function was improved significantly after probiotic supplementation, compared to control group. One study that included severe AD did not show significant changes.

CONCLUSION

Most studies involving AD, MCI, or healthy older adults showed cognitive improvement in subjects treated with probiotics for 12-24 weeks.

Impact of Pesticide Residues on the Gut-Microbiota–Blood–Brain Barrier Axis: A Narrative Review

Accumulating evidence indicates that chronic exposure to a low level of pesticides found in diet affects the human gut-microbiota–blood–brain barrier (BBB) axis. This axis describes the physiological and bidirectional connection between the microbiota, the intestinal barrier (IB), and the BBB. Preclinical observations reported a gut microbial alteration induced by pesticides, also known as dysbiosis, a condition associated not only with gastrointestinal disorders but also with diseases affecting other distal organs, such as the BBB. However, the interplay between pesticides, microbiota, the IB, and the BBB is still not fully explored. In this review, we first consider the similarities/differences between these two physiological barriers and the different pathways that link the gut microbiota and the BBB to better understand the dialogue between bacteria and the brain. We then discuss the effects of chronic oral pesticide exposure on the gut-microbiota-BBB axis and raise awareness of the danger of chronic exposure, especially during the perinatal period (pregnant women and offspring).

Narrative Review: The Effect of Vitamin A Deficiency on Gut Microbiota and Their Link with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders defined by a lack of social behaviors, repetitive behaviors and nonverbal interactions, such as limited eye contact, facial expression, and body gesturing. It is not a single condition, but rather a multi-factorial disorder caused by hereditary and non-genetic risk factors, as well as their interaction. According to several studies, the gut microbiota may have a role in the pathophysiology of autism spectrum disorder. Various studies have found differences in the composition of the gastrointestinal (GI) microbiota in children with ASD compared to unaffected siblings and/or healthy unrelated controls. The processes that relate the gut microbiota to brain dysfunctions (the gut-brain axis) in ASD are yet to be fully understood. However, the differences in the gastrointestinal composition might be due to vitamin A deficiency because vitamin A (VA) plays a role in the regulation of the intestinal microbiota. This narrative review discusses the impact of vitamin A deficiency on the gut microbiota composition and tries to understand how this may contribute for the development and severity of ASD.

Obeticholic acid protects against methamphetamine-induced anxiety-like behavior by ameliorating microbiota-mediated intestinal barrier impairment

Methamphetamine (Meth) abuse can cause severe anxiety disorder and interfere with gut homeostasis. Obeticholic acid (OCA) has emerged as a protective agent against diet-related anxiety that improves gut homeostasis. The potential for OCA to ameliorate Meth-induced anxiety, and the microbial mechanisms involved, remain obscure. Here, C57/BL6 mice were intraperitoneally injected with Meth (15 mg/kg) to induce anxiety-like behavior. 16 S rRNA sequence analysis and fecal microbiome transplantation (FMT) were used to profile the gut microbiome and evaluate its effects, respectively. Orally administered OCA was investigated for protection against Meth-induced anxiety. Results indicated that Meth mediated anxiety-like behavior, aroused hippocampal neuroinflammation through activation of the TLR4/MyD88/NF-κB pathway, weakened intestinal barrier and disturbed the gut microbiome. Specifically, abundance of anxiety-related Rikenella was increased. FMT from Meth-administrated mice also weakened intestinal barrier and elevated serum LPS, inducing hippocampal neuroinflammation and anxiety-like behavior in recipient mice. Finally, OCA pretreatment ameliorated Meth-induced impairment of gut homeostasis by reshaping the microbial composition and improving the intestinal barrier. Meth-induced anxiety-like behavior and hippocampal neuroinflammation were also ameliorated by OCA pretreatment. These preliminary findings reveal the crucial role of gut microbiota in Meth-induced anxiety-like behavior and neuroinflammation, highlighting OCA as a potential candidate for the prevention of Meth-induced anxiety.

The Gut-Organ-Axis Concept: Advances the Application of Gut-on-Chip Technology

The intestine is considered to be a vital digestive organ to absorb nutrients and is the largest immune organ, while numerous microorganisms coexist with the host. It is well known that the complex interactions between the gut microbiota and the host's immune system inevitably affect the function of other organs, creating an "axis" between them. During the past few years, a new technique based mainly on microfluidics and cell biology has been developed to emulate the structure, function, and microenvironment of the human gut, called the "gut-on-chip". This microfluidic chip provides insight into key aspects of gut function in health and disease, such as the gut-brain axis, gut-liver axis, gut-kidney axis, and gut-lung axis. In this review, we first describe the basic theory of the gut axis and the various composition and parameter monitoring of the gut microarray systems, as well as summarize the development and emerging advances in the gut-organ-on-chip, with a focus on the host-gut flora and nutrient metabolism, and highlight their role in pathophysiological studies. In addition, this paper discusses the challenges and prospects for the current development and further use of the gut-organ-on-chip platform.

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.

Gut-brain axis through the lens of gut microbiota and their relationships with Alzheimer's disease pathology: Review and recommendations

Alzheimer's disease (AD) is a neurodegenerative disorder that affects millions of people worldwide. Growing evidence suggests that the gut microbiome (GM) plays a pivotal role in the pathogenesis of AD through the microbiota-gut-brain axis (MGB). Alterations in GM composition and diversity have been observed in both animal models and in human patients with AD. GM dysbiosis has been implicated in increased intestinal permeability, blood-brain barrier (BBB) impairment, neuroinflammation and the development of hallmarks of AD. Further elucidation of the role of GM in AD could pave way for the development of holistic predictive methods for determining AD risk and progression of disease. Furthermore, accumulating evidence suggests that GM modulation could alleviate adverse symptoms of AD or serve as a preventive measure. In addition, increasing evidence shows that Type 2 Diabetes Mellitus (T2DM) is often comorbid with AD, with common GM alterations and inflammatory response, which could chart the development of GM-related treatment interventions for both diseases. We conclude by exploring the therapeutic potential of GM in alleviating symptoms of AD and in reducing risk. Furthermore, we also propose future directions in AD research, namely fecal microbiota transplantation (FMT) and precision medicine.

Dietary flavonoids: a novel strategy for the amelioration of cognitive impairment through intestinal microbiota

The chances of people suffering from cognitive impairments increase gradually with age. Diet and lifestyle are closely related to the occurrence and development of cognitive function. Dietary flavonoid supplementation has been shown to be one of the protective factors against cognitive decline. Flavonoids belong to a class of polyphenols that have been proposed for the treatment of cognitive decline. Recent evidence has shown that intestinal flora in the human body can interact with flavonoids. Intestinal microbiota can modify the chemical structure of flavonoids, producing new metabolites, the pharmacological activities of which may be different from those of the parent; meanwhile, flavonoids and their metabolites can, in turn, regulate the composition and structure of intestinal flora. Notably, intestinal flora affect host nervous system activity through the gut-brain axis, ultimately causing changes in cognitive function. This review therefore summarizes the interaction of dietary flavonoids and intestinal flora, and their protective effect against cognitive decline through the gut-brain axis, indicating that dietary flavonoids may ameliorate cognitive impairment through their interaction with intestinal microbiota. © 2022 Society of Chemical Industry.

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

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

Microbiota-Gut-Brain Axis: Pathophysiological Mechanism in Neuropsychiatric Disorders

Gut microbiota influence human behavior. The immunological, metabolic, and endocrine systems are involved in bidirectional communication between the gut and the brain, which is regulated by microbes through the microbiota-derived neurochemicals and metabolites. Gut microbiota have certain effects on neurodevelopment and maturation of immunity. However, gut dysbiosis can lead to neuropsychiatric disorders. Animal research and clinical case-control studies have demonstrated that gut dysbiosis has an adverse effect on human behavior through a variety of mechanisms. Recent meta-analysis on clinical studies confirmed gut dysbiosis in several major neuropsychiatric disorders. Microbiota-targeted intervention has recently been in the spotlight and meta-analyses have confirmed its effectiveness. In this chapter, we summarize the evidence for the interactions between microbiota and brain-gut network, as well as the potential pathophysiological mechanisms involved.

The intestinal barrier in disorders of the central nervous system

The intestinal barrier, which primarily consists of a mucus layer, an epithelial barrier, and a gut vascular barrier, has a crucial role in health and disease by facilitating nutrient absorption and preventing the entry of pathogens. The intestinal barrier is in close contact with gut microbiota on its luminal side and with enteric neurons and glial cells on its tissue side. Mounting evidence now suggests that the intestinal barrier is compromised not only in digestive disorders, but also in disorders of the central nervous system (CNS), such as Parkinson's disease, autism spectrum disorder, depression, multiple sclerosis, and Alzheimer's disease. After providing an overview of the structure and functions of the intestinal barrier, we review existing preclinical and clinical studies supporting the notion that intestinal barrier dysfunction is present in neurological, neurodevelopmental, and psychiatric disorders. On the basis of this evidence, we discuss the mechanisms that possibly link gut barrier dysfunction and CNS disorders and the potential impact that evaluating enteric barriers in brain disorders could have on clinical practice, in terms of novel diagnostic and therapeutic strategies, in the near future.

Modulation of the gut-brain axis via the gut microbiota: a new era in treatment of amyotrophic lateral sclerosis

There are trillions of different microorganisms in the human digestive system. These gut microbes are involved in the digestion of food and its conversion into the nutrients required by the body. In addition, the gut microbiota communicates with other parts of the body to maintain overall health. The connection between the gut microbiota and the brain is known as the gut-brain axis (GBA), and involves connections via the central nervous system (CNS), the enteric nervous system (ENS), and endocrine and immune pathways. The gut microbiota regulates the central nervous system bottom-up through the GBA, which has prompted researchers to pay considerable attention to the potential pathways by which the gut microbiota might play a role in the prevention and treatment of amyotrophic lateral sclerosis (ALS). Studies with animal models of ALS have shown that dysregulation of the gut ecology leads to dysregulation of brain-gut signaling. This, in turn, induces changes in the intestinal barrier, endotoxemia, and systemic inflammation, which contribute to the development of ALS. Through the use of antibiotics, probiotic supplementation, phage therapy, and other methods of inducing changes in the intestinal microbiota that can inhibit inflammation and delay neuronal degeneration, the clinical symptoms of ALS can be alleviated, and the progression of the disease can be delayed. Therefore, the gut microbiota may be a key target for effective management and treatment of ALS.

Research progress on perioperative blood-brain barrier damage and its potential mechanism

The blood-brain barrier (BBB) is an important barrier separating the central nervous system from the periphery. The composition includes endothelial cells, pericytes, astrocytes, synapses and tight junction proteins. During the perioperative period, anesthesia and surgical operations are also a kind of stress to the body, which may be accompanied by blood-brain barrier damage and brain metabolism dysfunction. Perioperative blood-brain barrier destruction is closely associated with cognitive impairment and may increase the risk of postoperative mortality, which is not conducive to enhanced recovery after surgery. However, the potential pathophysiological process and specific mechanism of blood-brain barrier damage during the perioperative period have not been fully elucidated. Changes in blood-brain barrier permeability, inflammation and neuroinflammation, oxidative stress, ferroptosis, and intestinal dysbiosis may be involved in blood-brain barrier damage. We aim to review the research progress of perioperative blood-brain barrier damage and its potential adverse effects and potential molecular mechanisms, and provide ideas for the study of homeostasis maintenance of brain function and precision anesthesia.

A randomized controlled trial into the effects of probiotics on electroencephalography in preschoolers with autism

LAY ABSTRACT

This study investigates the effects of a probiotic on preschoolers' brain electrical activity with autism spectrum disorder. Autism is a disorder with an increasing prevalence characterized by an enormous individual, family, and social cost. Although the etiology of autism spectrum disorder is unknown, an interaction between genetic and environmental factors is implicated, converging in altered brain synaptogenesis and, therefore, connectivity. Besides deepening the knowledge on the resting brain electrical activity that characterizes this disorder, this study allows analyzing the positive central effects of a 6-month therapy with a probiotic through a randomized, double-blind placebo-controlled study and the correlations between electroencephalography activity and biochemical and clinical parameters. In subjects treated with probiotics, we observed a decrease of power in frontopolar regions in beta and gamma bands, and increased coherence in the same bands together with a shift in frontal asymmetry, which suggests a modification toward a typical brain activity. Electroencephalography measures were significantly correlated with clinical and biochemical measures. These findings support the importance of further investigations on probiotics' benefits in autism spectrum disorder to better elucidate mechanistic links between probiotics supplementation and changes in brain activity.

Pubertal consumption of R. badensis subspecies acadiensis modulates LPS-induced immune responses and gut microbiome dysbiosis in a sex-specific manner

Puberty is a critical period of development characterized by significant brain remodeling and increased vulnerability to immune challenges. Exposure to an immune challenge such as LPS during puberty can result in inflammation and gut dysbiosis which may lead to altered brain functioning and psychiatric illnesses later in life. However, treatment with probiotics during puberty has been found to mitigate LPS-induced peripheral and central inflammation, prevent LPS-induced changes to the gut microbiota and protect against enduring behavioural disorders in a sex-specific manner. Recent findings from our laboratory revealed that pubertal R. badensis subspecies acadiensis (R. badensis subsp. acadiensis) treatment prevents LPS-induced depression-like behavior and alterations in 5HT1A receptor expression in a sex-specific manner. However, the underlying mechanism remains unclear. Thus, the aim of this study was to gain mechanistic insights and to investigate the ability of R. badensis subsp. acadiensis consumption during puberty to mitigate the effects of LPS treatment on the immune system and the gut microbiome. Our results revealed that pubertal treatment with R. badensis subsp. acadiensis reduced sickness behaviors in females more than males in a time-specific manner. It also mitigated LPS-induced increases in pro-inflammatory cytokines in the blood and in TNFα mRNA expression in the prefrontal cortex and the hippocampus of female mice. There were sex-dependent differences in microbiome composition that persisted after LPS injection or R. badensis subsp. acadiensis consumption. R. badensis subsp. acadiensis had greater impact on the microbiota of male mice but female microbiota's were more responsive to LPS treatment. This suggested that female mice microbiota's may be more prone to modulation by this probiotic. These findings emphasize the sex-specific effects of probiotic use during puberty on the structure of the gut microbiome and the immune system and highlight the critical role of gut colonization with probiotics during adolescence on immunomodulation and prevention of the enduring effects of infections.

ALZHEIMER'S DISEASE AND ITS RELATIONSHIP WITH THE MICROBIOTA-GUT-BRAIN AXIS

BACKGROUND

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disease, characterized by the accumulation of amyloid plaques and neurofibrillary tangles in the brain. Several pathways enable bidirectional communication between the central nervous system (CNS), the intestine and its microbiota, constituting the microbiota-gut-brain axis.

OBJECTIVE

Review the pathophysiology of AD, relate it to the microbiota-gut-brain axis and discuss the possibility of using probiotics in the treatment and/or prevention of this disease.

METHODS

Search of articles from the PubMed database published in the last 5 years (2017 to 2022) structure the narrative review.

RESULTS

The composition of the gut microbiota influences the CNS, resulting in changes in host behavior and may be related to the development of neurodegenerative diseases. Some metabolites produced by the intestinal microbiota, such as trimethylamine N-oxide (TMAO), may be involved in the pathogenesis of AD, while other compounds produced by the microbiota during the fermentation of food in the intestine, such as D-glutamate and fatty acids short chain, are beneficial in cognitive function. The consumption of live microorganisms beneficial to health, known as probiotics, has been tested in laboratory animals and humans to evaluate the effect on AD.

CONCLUSION

Although there are few clinical trials evaluating the effect of probiotic consumption in humans with AD, the results to date indicate a beneficial contribution of the use of probiotics in this disease.

The Gut Microbiome and Alzheimer's Disease: A Growing Relationship

Evidence that the gut microbiota plays a key role in the pathogenesis of Alzheimer's disease is already un-ravelling. The microbiota-gut-brain axis is a bidirectional communication system that is not fully understood but includes neural, immune, endocrine, and metabolic pathways. The progression of Alzheimer's disease is supported by mechanisms related to the imbalance in the gut microbiota and the development of amyloid plaques in the brain, which are at the origin of Alzheimer's disease. Alterations in the composition of the gut microbiome led to dysregulation in the pathways governing this system. This leads to neurodegeneration through neuroinflammation and neurotransmitter dysregulation. Neurodegeneration and disruption of the blood-brain barrier are frontiers at the origin of Alzheimer's disease. Furthermore, bacteria populating the gut microbiota can secrete large amounts of amyloid proteins and lipopolysaccharides, which modulate signaling pathways and alter the production of proinflammatory cytokines associated with the pathogenesis of Alz-heimer's disease. Importantly, through molecular mimicry, bacterial amyloids may elicit cross-seeding of misfolding and induce microglial priming at different levels of the brain-gut-microbiota axis. The potential mechanisms of amyloid spreading include neuron-to-neuron or distal neuron spreading, direct blood-brain barrier crossing, or via other cells such as astrocytes, fibroblasts, microglia, and immune system cells. Gut microbiota metabolites, including short-chain fatty acids, pro-inflammatory factors, and neurotransmitters may also affect AD pathogenesis and associated cognitive decline. The purpose of this review is to summarize and discuss the current findings that may elucidate the role of gut microbiota in the development of Alzheimer's disease. Understanding the underlying mechanisms may provide new insights into novel therapeutic strategies for Alzheimer's disease, such as probiotics and targeted oligosaccharides.

Probiotic Bifidobacterium longum BB68S Improves Cognitive Functions in Healthy Older Adults: A Randomized, Double-Blind, Placebo-Controlled Trial

Probiotics could improve cognitive functions in patients with neurological disorders such as Alzheimer’s disease, but the effects on cognitive function in healthy older adults without cognitive impairment need further study. The purpose of this study was to investigate the effect of Bifidobacterium longum BB68S (BB68S) on cognitive functions among healthy older adults without cognitive impairment. A randomized, double-blind, placebo-controlled trial was conducted with 60 healthy older adults without cognitive impairment who were divided into probiotic or placebo groups and required to consume either a sachet of probiotic (BB68S, 5 × 1010 CFU/sachet) or placebo once daily for 8 weeks. The Montreal Cognitive Assessment (MoCA) was used as an inclusion screening tool to screen elderly participants with healthy cognitive function in our study, and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was used to assess cognitive function in subjects before and after intervention as an assessment tool. BB68S significantly improved subjects’ cognitive functions (total RBANS score increased by 18.89 points after intervention, p < 0.0001), especially immediate memory, visuospatial/constructional, attention, and delayed memory domains. BB68S intervention increased the relative abundances of beneficial bacteria Lachnospira, Bifidobacterium, Dorea, and Cellulosilyticum, while decreasing those of bacteria related to cognition impairment, such as Collinsella, Parabacteroides, Tyzzerella, Bilophila, unclassified_c_Negativicutes, Epulopiscium, Porphyromonas, and Granulicatella. In conclusion, BB68S could improve cognitive functions in healthy elderly adults without cognitive impairment, along with having beneficial regulatory effects on their gut microbiota. This study supports probiotics as a strategy to promote healthy aging and advances cognitive aging research.

Structural Alteration of Gut Microbiota During the Amelioration of Chronic Psychological Stress-Aggravated Diabetes-Associated Cognitive Decline by a Traditional Chinese Herbal Formula, ZiBu PiYin Recipe

BACKGROUND

Chronic psychological stress (PS) hinders the treatment of diabetes-associated cognitive decline (DACD). However, the impact of chronic PS on the risk of developing DACD remains unclear. There is growing evidence that gut flora interventions are promising targets for treating stress-related diseases.

OBJECTIVE

We examined whether chronic PS triggers or exacerbates the onset of DACD in rats and aimed to elucidate whether ZiBuPiYin recipe (ZBPYR) prevents and treats chronic PS-aggravated DACD by dynamically maintaining the components of the gut microbiota.

METHODS

We performed chronic PS (restraint, rotation, and congestion) on ZDF rats to establish a model. Cognitive function was evaluated by behavioral experiments, and activation of the hypothalamic-pituitary-adrenal axis was detected by ELISA. Weekly feces from rats were collected for 16 S RNA sequencing.

RESULTS

We found that chronic PS promoted cognitive abnormalities and exacerbated DACD phenotypes. Additionally, chronic PS altered intestinal flora diversity, dynamically elevating the abundance of Alistipes and Coprococcus; enriching Module 1 (Dorea, Blautia, Ruminococcus) and Module 48 (Blautia); and inhibiting Module 20 (Lactobacillus, SMB53), and Module 42 (Akkermansia). ZBPYR significantly alleviated hyperglycemia and cognitive impairment in chronic PS-aggravated DACD rats and dynamically reduced the abundance of Alistipes and Coprococcus; significantly enriched Module 3 (Ruminococcus) and Module 45 (Lactobacillus, Coprococcus, SMB53); and suppressed Module 2 (Lactobacillus), Module 16 (Turicibacter, Trichococcus, Lactobacillus, 02d06, Clostridium), Module 23 (Bifidobacterium), and Module 43 (Clostridium).

CONCLUSION

ZBPYR might prevent and treat chronic PS-aggravated DACD by dynamically regulating Lactobacillus, Alistipes, and Coprococcus.

Berberine ameliorates chronic kidney disease through inhibiting the production of gut-derived uremic toxins in the gut microbiota

At present, clinical interventions for chronic kidney disease are very limited, and most patients rely on dialysis to sustain their lives for a long time. However, studies on the gut-kidney axis have shown that the gut microbiota is a potentially effective target for correcting or controlling chronic kidney disease. This study showed that berberine, a natural drug with low oral availability, significantly ameliorated chronic kidney disease by altering the composition of the gut microbiota and inhibiting the production of gut-derived uremic toxins, including p-cresol. Furthermore, berberine reduced the content of p-cresol sulfate in plasma mainly by lowering the abundance of g_Clostridium_sensu_stricto_1 and inhibiting the tyrosine-p-cresol pathway of the intestinal flora. Meanwhile, berberine increased the butyric acid producing bacteria and the butyric acid content in feces, while decreased the renal toxic trimethylamine N-oxide. These findings suggest that berberine may be a therapeutic drug with significant potential to ameliorate chronic kidney disease through the gut-kidney axis.