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

Baicalin induces ferroptosis in bladder cancer cells by downregulating FTH1

Ferroptosis is a non-apoptotic regulated cell death caused by iron accumulation and subsequent lipid peroxidation. Currently, the therapeutic role of ferroptosis on cancer is gaining increasing interest. Baicalin an active component in Scutellaria baicalensis Georgi with anticancer potential various cancer types; however, the effects of baicalein on bladder cancer and the underlying molecular mechanisms remain largely unknown. In the study, we investigated the effect of baicalin on bladder cancer cells 5637 and KU-19-19. As a result, we show baicalin exerted its anticancer activity by inducing apoptosis and cell death in bladder cancer cells. Subsequently, we for the first time demonstrate baicalin-induced ferroptotic cell death in vitro and in vivo, accompanied by reactive oxygen species (ROS) accumulation and intracellular chelate iron enrichment. The ferroptosis inhibitor deferoxamine but not necrostatin-1, chloroquine (CQ), N-acetyl-l-cysteine, l-glutathione reduced, or carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone (Z-VAD-FMK) rescued baicalin-induced cell death, indicating ferroptosis contributed to baicalin-induced cell death. Mechanistically, we show that ferritin heavy chain 1 (FTH1) was a key determinant for baicalin-induced ferroptosis. Overexpression of FTH1 abrogated the anticancer effects of baicalin in both 5637 and KU19-19 cells. Taken together, our data for the first time suggest that the natural product baicalin exerts its anticancer activity by inducing FTH1-dependent ferroptosis, which will hopefully provide a prospective compound for bladder cancer treatment.

TMEM16A inhibits angiotensin II-induced basilar artery smooth muscle cell migration in a WNK1-dependent manner

Vascular smooth muscle cell (VSMC) migration plays a critical role in the pathogenesis of many cardiovascular diseases. We recently showed that TMEM16A is involved in hypertension-induced cerebrovascular remodeling. However, it is unclear whether this effect is related to the regulation of VSMC migration. Here, we investigated whether and how TMEM16A contributes to migration in basilar artery smooth muscle cells (BASMCs). We observed that AngII increased the migration of cultured BASMCs, which was markedly inhibited by overexpression of TMEM16A. TMEM16A overexpression inhibited AngII-induced RhoA/ROCK2 activation, and myosin light chain phosphatase (MLCP) and myosin light chain (MLC20) phosphorylation. But AngII-induced myosin light chain kinase (MLCK) activation was not affected by TMEM16A. Furthermore, a suppressed activation of integrinβ3/FAK pathway, determined by reduced integrinβ3 expression, FAK phosphorylation and F-actin rearrangement, was observed in TMEM16A-overexpressing BASMCs upon AngII stimulation. Contrary to the results of TMEM16A overexpression, silencing of TMEM16A showed the opposite effects. These in vitro results were further demonstrated in vivo in basilar arteries from VSMC-specific TMEM16A transgenic mice during AngII-induced hypertension. Moreover, we observed that the inhibitory effect of TMEM16A on BASMC migration was mediated by decreasing the activation of WNK1, a Cl--sensitive serine/threonine kinase. In conclusion, this study demonstrated that TMEM16A suppressed AngII-induced BASMC migration, thus contributing to the protection against cerebrovascular remodeling during AngII-infused hypertension. TMEM16A may exert this effect by suppressing the RhoA/ROCK2/MLCP/MLC20 and integrinβ3/FAK signaling pathways via inhibiting WNK1. Our results suggest that TMEM16A may serve as a novel therapeutic target for VSMC migration-related diseases, such as vascular remodeling.

Electroacupuncture could balance the gut microbiota and improve the learning and memory abilities of Alzheimer's disease animal model

Alzheimer’s disease (AD), as one of most common dementia, mainly affects older people from the worldwide. In this study, we intended to explore the possible mechanism of improving cognitive function and protecting the neuron effect by electroacupuncture. Method: We applied senescence-accelerated mouse prone 8 (SAMP8) mice as AD animal model, used Morris water maze, HE staining, 16S rDNA amplicon sequencing of gut microbiota and ELISA to demonstrate our hypothesis. Results: electroacupuncture improved the learning and memory abilities in SAMP8 mice (P<0.05) and could protect the frontal lobe cortex and hippocampus of SAMP8 mice; electroacupuncture significantly decreased the expression of IL-1β (P<0.01), IL-6 (P<0.01) and TNF-α (P<0.01 in hippocampus, P<0.05 in serum) in serum and hippocampus; electroacupuncture balanced the quantity and composition of gut microbiome, especially of the relative abundance in Delta-proteobacteria (P<0.05) and Epsilon-proteobacteria (P<0.05). Conclusion: electroacupuncture treatment could inhibit the peripheral and central nerve system inflammatory response by balancing the gut microbiota.

Sesamol Attenuates Amyloid Peptide Accumulation and Cognitive Deficits in APP/PS1 Mice: The Mediating Role of the Gut-Brain Axis

Alzheimer's disease (AD), a neurodegenerative disease, is the leading cause of dementia. Sesamol is a lignan extracted from sesame oil and has been found to exert neuroprotective effects. The present study aimed to investigate the neuroprotective effects of sesamol on APPswe/PS1dE9 transgenic AD mice. The AD mice were fed with a diet supplemented with sesamol (0.075 w/w %). Sesamol treatment improved spatial memory and learning ability in AD mice, improved neuronal damage, and decreased Aβ accumulation. Sesamol protected the synaptic ultrastructure and inhibited neuroinflammatory responses in the brain of AD mice. Sesamol also significantly inhibited the overactivated microglia and reduced the overexpression of TNF-α and IL-1β in the brain of AD mice. Notably, sesamol reshaped gut microbiota by significantly decreasing the relative abundance of Helicobacter hepaticus, Clostridium, and Bacillaceae, enhancing the relative abundance of Rikenellaceae and Bifidobacterium in AD mice. It has been found that sesamol protected the gut barrier integrity and prevented the LPS leakage into the serum. Importantly, sesamol remarkably enhanced the content of SCFAs, including acetate, propionate, isobutyrate, butyrate, and valerate, in AD mice. Correlation analysis indicated that there was a strong correlation between the levels of SCFAs and cognitive functions. These results demonstrated that sesamol attenuated AD-related cognitive dysfunction and neuroinflammatory responses, which could be partly explained by its role in mediating the gut microbe-SCFA-brain axis. Thus, sesamol is a promising nutritional intervention strategy to prevent AD via the microbiota-gut-brain axis.

Lactobacillus plantarum TWK10 Attenuates Aging-Associated Muscle Weakness, Bone Loss, and Cognitive Impairment by Modulating the Gut Microbiome in Mice

In humans, aging is characterized by the progressive decline in biological, physiological, and psychological functions, and is a major risk factor in the development of chronic diseases. Therefore, the development of strategies aimed at attenuating aging-related disorders and promoting healthy aging is critical. In a previous study, we have demonstrated that Lactobacillus plantarum TWK10 (TWK10), a probiotic strain isolated from Taiwanese pickled cabbage, improved muscle strength, exercise endurance, and overall body composition in healthy humans. In this study, the effect of TWK10 on the progression of age-related impairments was investigated in mice. We found that TWK10 not only enhanced muscle strength in young mice, but also prevented the aging-related loss of muscle strength in aged mice, which was accompanied by elevated muscle glycogen levels. Furthermore, TWK10 attenuated the aging-associated decline in learning and memory abilities, as well as bone mass. Further analyses of gut microbiota using next-generation sequencing (NGS) of the 16S rRNA gene showed that the pattern of gut microbial composition was clearly altered following 8 weeks of TWK10 administration. TWK10-treated mice also experienced an increase in short-chain fatty acid (SCFA)-producing bacteria and higher overall levels of gut SCFA. Furthermore, TWK10 administration to some extent reversed the aging-associated accumulation of pathogenic bacterial taxa. In conclusion, TWK10 could be viewed as a potential therapeutic agent that attenuates aging-related disorders and provides health benefits by modulating the imbalance of gut microbiota.

Gut Microbiota Regulation and Their Implication in the Development of Neurodegenerative Disease

In recent years, human gut microbiota have become one of the most promising areas of microorganism research; meanwhile, the inter-relation between the gut microbiota and various human diseases is a primary focus. As is demonstrated by the accumulating evidence, the gastrointestinal tract and central nervous system interact through the gut–brain axis, which includes neuronal, immune-mediated and metabolite-mediated pathways. Additionally, recent progress from both preclinical and clinical studies indicated that gut microbiota play a pivotal role in gut–brain interactions, whereas the imbalance of the gut microbiota composition may be associated with the pathogenesis of neurological diseases (particularly neurodegenerative diseases), the underlying mechanism of which is insufficiently studied. This review aims to highlight the relationship between gut microbiota and neurodegenerative diseases, and to contribute to our understanding of the function of gut microbiota in neurodegeneration, as well as their relevant mechanisms. Furthermore, we also discuss the current application and future prospects of microbiota-associated therapy, including probiotics and fecal microbiota transplantation (FMT), potentially shedding new light on the research of neurodegeneration.

Transplantation of gut microbiota derived from Alzheimer's disease mouse model impairs memory function and neurogenesis in C57BL/6 mice

Alzheimer's disease (AD) is a neurodegenerative disease that causes memory and cognitive decline. Although many studies have attempted to clarify the causes of AD occurrence, it is not clearly understood. Recently, the emerging role of the gut microbiota in neurodegenerative diseases, including AD, has received much attention. The gut microbiota composition of AD patients and AD mouse models is different from that of healthy controls, and these changes may affect the brain environment. However, the specific mechanisms by which gut microbiota that influence memory decline are currently unclear. In this study, we performed fecal microbiota transplantation (FMT) to clarify the role of 5xFAD mouse-derived microbiota in memory decline. We observed that FMT from 5xFAD mice into normal C57BL/6 mice (5xFAD-FMT) decreased adult hippocampal neurogenesis and brain-derived neurotrophic factor expression and increased p21 expression, resulting in memory impairment. Microglia in the hippocampus of the 5xFAD-FMT mice were activated, which caused the elevation of pro-inflammatory cytokines (tumor necrosis factor-α and interleukin-1β). Moreover, we observed that pro-inflammatory cytokines increased in the colon and plasma of 5xFAD-FMT mice. The gut microbiota composition of the 5xFAD-FMT mice was different from that of the control mice or wild type-FMT mice. Collectively, 5xFAD mouse-derived microbiota decreased neurogenesis by increasing colonic inflammation, thereby contributing to memory loss. Our findings provide further evidence concerning the role of gut microbial dysbiosis in AD pathogenesis and suggest that targeting the gut microbiota may be a useful therapeutic strategy for the development of novel candidates for the treatment of AD.

Microbiome Profiling Using Shotgun Metagenomic Sequencing Identified Unique Microorganisms in COVID-19 Patients With Altered Gut Microbiota

COVID-19 is mainly associated with respiratory distress syndrome, but a subset of patients often present gastrointestinal (GI) symptoms. Imbalances of gut microbiota have been previously linked to respiratory virus infection. Understanding how the gut–lung axis affects the progression of COVID-19 can provide a novel framework for therapies and management. In this study, we examined the gut microbiota of patients with COVID-19 (n = 47) and compared it to healthy controls (n = 19). Using shotgun metagenomic sequencing, we have identified four microorganisms unique in COVID-19 patients, namely Streptococcus thermophilus, Bacteroides oleiciplenus, Fusobacterium ulcerans, and Prevotella bivia. The abundances of Bacteroides stercoris, B. vulgatus, B. massiliensis, Bifidobacterium longum, Streptococcus thermophilus, Lachnospiraceae bacterium 5163FAA, Prevotella bivia, Erysipelotrichaceae bacterium 6145, and Erysipelotrichaceae bacterium 2244A were enriched in COVID-19 patients, whereas the abundances of Clostridium nexile, Streptococcus salivarius, Coprococcus catus, Eubacterium hallii, Enterobacter aerogenes, and Adlercreutzia equolifaciens were decreased (p < 0.05). The relative abundance of butyrate-producing Roseburia inulinivorans is evidently depleted in COVID-19 patients, while the relative abundances of Paraprevotella sp. and the probiotic Streptococcus thermophilus were increased. We further identified 30 KEGG orthology (KO) modules overrepresented, with 7 increasing and 23 decreasing modules. Notably, 15 optimal microbial markers were identified using the random forest model to have strong diagnostic potential in distinguishing COVID-19. Based on Spearman’s correlation, eight species were associated with eight clinical indices. Moreover, the increased abundance of Bacteroidetes and decreased abundance of Firmicutes were also found across clinical types of COVID-19. Our findings suggest that the alterations of gut microbiota in patients with COVID-19 may influence disease severity. Our COVID-19 classifier, which was cross-regionally verified, provides a proof of concept that a set of microbial species markers can distinguish the presence of COVID-19.

Probiotics as potential therapeutic options for Alzheimer's disease

The steadily increasing prevalence of Alzheimer's disease (AD) worldwide and the lack of effective therapeutic agent attract novel therapeutic approach in recent years. In view of the close relationships between gut microbiota and AD, probiotics have been suggested as potential therapeutic options for AD in recent years. The present review discussed the research progresses concerning the effects of probiotics administration to combat AD. A total of 35 studies, including 26 animal model studies and 9 human studies, were included herein. Among the 26 animal model studies, 24 used mice model, and 2 used Caenorhabditis elegans and Drosophila melanogaster AD models, respectively. As for probiotics, a total of 13 studies employed single-strain probiotic, and the rest studies used multi-strain probiotics (ranged from 2 to 9 probiotic strains), 4 used probiotic-fermented milk or probiotic-fermented soybean, 2 studies used engineered probiotic strain, and 4 studies focused on the combined effect of probiotics with AD drug memantine, selenium, or exercise. Bifidobacterium and Lactobacillus species were the most frequently used probiotics in the included studies. Overall, currently available studies showed that probiotic administration conferred neuroprotective benefits and could attenuate cognitive deficits and modulate gut microbiota dysbiosis, which may be related to oxidative and inflammatory pathways. Several perspectives on future studies on this topic are proposed. Thus, probiotics seem to be an attractive approach to combat AD, which deserves to be further studied by well-designed large-scale clinical studies. KEY POINTS: •We discussed the recent progresses concerning the effects of probiotics administration to combat AD. •A total of 35 associated studies consisted of 26 animal model studies and 9 human studies were included. •Most studies found that probiotic administration conferred neuroprotective benefits and could attenuate cognitive deficits.

The Role of Gut Microbiota and Gut-Brain Interplay in Selected Diseases of the Central Nervous System

The gut microbiome has attracted increasing attention from researchers in recent years. The microbiota can have a specific and complex cross-talk with the host, particularly with the central nervous system (CNS), creating the so-called “gut–brain axis”. Communication between the gut, intestinal microbiota, and the brain involves the secretion of various metabolites such as short-chain fatty acids (SCFAs), structural components of bacteria, and signaling molecules. Moreover, an imbalance in the gut microbiota composition modulates the immune system and function of tissue barriers such as the blood–brain barrier (BBB). Therefore, the aim of this literature review is to describe how the gut–brain interplay may contribute to the development of various neurological disorders, combining the fields of gastroenterology and neuroscience. We present recent findings concerning the effect of the altered microbiota on neurodegeneration and neuroinflammation, including Alzheimer’s and Parkinson’s diseases, as well as multiple sclerosis. Moreover, the impact of the pathological shift in the microbiome on selected neuropsychological disorders, i.e., major depressive disorders (MDD) and autism spectrum disorder (ASD), is also discussed. Future research on the effect of balanced gut microbiota composition on the gut–brain axis would help to identify new potential opportunities for therapeutic interventions in the presented diseases.

Novel compound FLZ alleviates rotenone-induced PD mouse model by suppressing TLR4/MyD88/NF-κB pathway through microbiota-gut-brain axis

Parkinson's disease (PD) is the second most common neurodegenerative disease, but none of the current treatments for PD can halt the progress of the disease due to the limited understanding of the pathogenesis. In PD development, the communication between the brain and the gastrointestinal system influenced by gut microbiota is known as microbiota-gut-brain axis. However, the explicit mechanisms of microbiota dysbiosis in PD development have not been well elucidated yet. FLZ, a novel squamosamide derivative, has been proved to be effective in many PD models and is undergoing the phase I clinical trial to treat PD in China. Moreover, our previous pharmacokinetic study revealed that gut microbiota could regulate the absorption of FLZ in vivo. The aims of our study were to assess the protective effects of FLZ treatment on PD and to further explore the underlying microbiota-related mechanisms of PD by using FLZ as a tool. In the current study, chronic oral administration of rotenone was utilized to induce a mouse model to mimic the pathological process of PD. Here we revealed that FLZ treatment alleviated gastrointestinal dysfunctions, motor symptoms, and dopaminergic neuron death in rotenone-challenged mice. 16S rRNA sequencing found that PD-related microbiota alterations induced by rotenone were reversed by FLZ treatment. Remarkably, FLZ administration attenuated intestinal inflammation and gut barrier destruction, which subsequently inhibited systemic inflammation. Eventually, FLZ treatment restored blood-brain barrier structure and suppressed neuroinflammation by inhibiting the activation of astrocytes and microglia in the substantia nigra (SN). Further mechanistic research demonstrated that FLZ treatment suppressed the TLR4/MyD88/NF-κB pathway both in the SN and colon. Collectively, FLZ treatment ameliorates microbiota dysbiosis to protect the PD model via inhibiting TLR4 pathway, which contributes to one of the underlying mechanisms beneath its neuroprotective effects. Our research also supports the importance of microbiota-gut-brain axis in PD pathogenesis, suggesting its potential role as a novel therapeutic target for PD treatment.

Microbiota-gut-brain axis and Alzheimer's disease: Implications of the blood-brain barrier as an intervention target

The microbiota-gut-brain axis has emerged as a focal point of biomedical research. Alterations of gut microbiota are involved in not only various immune/inflammatory disorders but also neurological disorders including Alzheimer's disease (AD). The initial stage of the involvement of gut microbiota in the pathogenesis of AD may be the dysfunction of the blood-brain barrier (BBB). Gut microbiota-derived products in the circulation can worsen the BBB integrity, easily cross the disrupted BBB and enter the brain to promote pathological changes in AD. In this review, we first summarize the current evidence of the associations among gut microbiota, AD, and BBB integrity. We then discuss the mechanism of gut microbiota on BBB dysfunction with a focus on bacteria-derived lipopolysaccharide and exosomal high-mobility group box 1. Novel insights into the modification of the BBB as an intervention approach for AD are highlighted as well.

Direct modulation of the gut microbiota as a therapeutic approach for Alzheimer's disease

Alzheimer's disease is a neurodegenerative disease characterized by a progressive decline in memory and cognitive functions. It is a multifactorial disease involving a wide range of pathological factors that are not fully understood. As supported by a growing amount of evidence in recent years, the gut microbiota plays an important role in the pathogenesis of Alzheimer's disease through the brain-gut-microbiota axis. This suggests that direct modulation of the gut microbiota can be a potential therapeutic target for Alzheimer's disease. This review summarizes recent research findings on the modulation of the gut microbiota by probiotic therapies and faecal microbiota transplantation for controlling the pathologies of Alzheimer's disease. Current limitations and future research directions of this field are also discussed.

The Roles of the Gut Microbiota and Chronic Low-Grade Inflammation in Older Adults With Frailty

Frailty is a major public issue that affects the physical health and quality of life of older adults, especially as the population ages. Chronic low-grade inflammation has been speculated to accelerate the aging process as well as the development of age-related diseases such as frailty. Intestinal homeostasis plays a crucial role in healthy aging. The interaction between the microbiome and the host regulates the inflammatory response. Emerging evidence indicates that in older adults with frailty, the diversity and composition structure of gut microbiota are altered. Age-associated changes in gut microbiota composition and in their metabolites contribute to increased gut permeability and imbalances in immune function. In this review, we aim to: identify gut microbiota changes in the aging and frail populations; summarize the role of chronic low-grade inflammation in the development of frailty; and outline how gut microbiota may be related to the pathogenesis of frailty, more specifically, in the regulation of gut-derived chronic inflammation. Although additional research is needed, the regulation of gut microbiota may represent a safe, easy, and inexpensive intervention to counteract the chronic inflammation leading to frailty.

Inflammatory pathways in Alzheimer's disease mediated by gut microbiota

In the past decade, numerous studies have demonstrated the close relationship between gut microbiota and the occurrence and development of Alzheimer's disease (AD). However, the specific mechanism is still unclear. Both the neuroinflammation and systemic inflammation serve as the key hubs to accelerate the process of AD by promoting pathology and damaging neuron. What's more, the gut microbiota is also crucial for the regulation of inflammation. Therefore, this review focused on the role of gut microbiota in AD through inflammatory pathways. Firstly, this review summarized the relationship and interaction among gut microbiota, inflammation, and AD. Secondly, the direct and indirect regulatory effects of gut microbiota on AD through inflammatory pathways were described. These effects were mainly mediated by the component of the gut microbiota (lipopolysaccharides (LPS) and amyloid peptides), the metabolites of bacteria (short-chain fatty acids, branched amino acids, and neurotransmitters) and functional by-products (bile acids). In addition, potential treatments (fecal microbiota transplantation, antibiotics, probiotics, prebiotics, and dietary interventions) for AD were also discussed through these mechanisms. Finally, according to the current research status, the key problems to be solved in the future studies were proposed.

The Effect of Probiotics on Health Outcomes in the Elderly: A Systematic Review of Randomized, Placebo-Controlled Studies

Increasing evidence suggests that probiotic supplementation may be efficacious in counteracting age-related shifts in gut microbiota composition and diversity, thereby impacting health outcomes and promoting healthy aging. However, randomized controlled trials (RCTs) with probiotics in healthy older adults have utilized a wide variety of strains and focused on several different outcomes with conflicting results. Therefore, a systematic review was conducted to determine which outcomes have been investigated in randomized controlled trials with probiotic supplementation in healthy older adults and what has been the effect of these interventions. For inclusion, studies reporting on randomized controlled trials with probiotic and synbiotic supplements in healthy older adults (defined as minimum age of 60 years) were considered. Studies reporting clinical trials in specific patient groups or unhealthy participants were excluded. In addition to assessment of eligibility and data extraction, each study was examined for risk of bias and quality assessment was performed by two independent reviewers. Due to the heterogeneity of outcomes, strains, study design, duration, and methodology, we did not perform any meta-analyses and instead provided a narrative overview of the outcomes examined. Of 1997 potentially eligible publications, 17 studies were included in this review. The risk of bias was low, although several studies failed to adequately describe random sequence generation, allocation concealment, and blinding. The overall study quality was high; however, many studies did not include sample calculations, and the majority of studies had a small sample size. The main outcomes examined in the trials included microbiota composition, immune-related measurements, digestive health, general well-being, cognitive function, and lipid and other biomarkers. The most commonly assessed outcome with the most consistent effect was microbiota composition; all but one study with this outcome showed significant effects on gut microbiota composition in healthy older adults. Overall, probiotic supplementation had modest effects on markers of humoral immunity, immune cell population levels and activity, as well as the incidence and duration of the common cold and other infections with some conflicting results. Digestive health, general-well-being, cognitive function, and lipid and other biomarkers were investigated in a very small number of studies; therefore, the impact on these outcomes remains inconclusive. Probiotics appear to be efficacious in modifying gut microbiota composition in healthy older adults and have moderate effects on immune function. However, the effect of probiotic supplementation on other health outcomes remains inconclusive, highlighting the need for more well-designed, sufficiently-powered studies to investigate if and the mechanisms by which probiotics impact healthy aging.

Roles and Mechanisms of Gut Microbiota in Patients With Alzheimer's Disease

Alzheimer’s disease (AD) is the most common age-related progressive neurodegenerative disease, characterized by a decline in cognitive function and neuronal loss, and is caused by several factors. Numerous clinical and experimental studies have suggested the involvement of gut microbiota dysbiosis in patients with AD. The altered gut microbiota can influence brain function and behavior through the microbiota–gut–brain axis via various pathways such as increased amyloid-β deposits and tau phosphorylation, neuroinflammation, metabolic dysfunctions, and chronic oxidative stress. With no current effective therapy to cure AD, gut microbiota modulation may be a promising therapeutic option to prevent or delay the onset of AD or counteract its progression. Our present review summarizes the alterations in the gut microbiota in patients with AD, the pathogenetic roles and mechanisms of gut microbiota in AD, and gut microbiota–targeted therapies for AD. Understanding the roles and mechanisms between gut microbiota and AD will help decipher the pathogenesis of AD from novel perspectives and shed light on novel therapeutic strategies for AD.

Dysbiosis and Alzheimer's Disease: A Role for Chronic Stress?

Alzheimer’s disease (AD) is an incurable, neuropsychiatric, pathological condition that deteriorates the worth of geriatric lives. AD is characterized by aggregated senile amyloid plaques, neurofibrillary tangles, neuronal loss, gliosis, oxidative stress, neurotransmitter dysfunction, and bioenergetic deficits. The changes in GIT composition and harmony have been recognized as a decisive and interesting player in neuronal pathologies including AD. Microbiota control and influence the oxidoreductase status, inflammation, immune system, and the endocrine system through which it may have an impact on the cognitive domain. The altered and malfunctioned state of microbiota is associated with minor infections to complicated illnesses that include psychosis and neurodegeneration, and several studies show that microbiota regulates neuronal plasticity and neuronal development. The altered state of microbiota (dysbiosis) may affect behavior, stress response, and cognitive functions. Chronic stress-mediated pathological progression also has a well-defined role that intermingles at various physiological levels and directly impacts the pathological advancement of AD. Chronic stress-modulated alterations affect the well-established pathological markers of AD but also affect the gut–brain axis through the mediation of various downstream signaling mechanisms that modulate the microbial commensals of GIT. The extensive literature reports that chronic stressors affect the composition, metabolic activities, and physiological role of microbiota in various capacities. The present manuscript aims to elucidate mechanistic pathways through which stress induces dysbiosis, which in turn escalates the neuropathological cascade of AD. The stress–dysbiosis axis appears a feasible zone of work in the direction of treatment of AD.

Neuroprotective effects of short-chain fatty acids in MPTP induced mice model of Parkinson's disease

Gut microbial metabolites, SCFAs, were related with the occurrence and development of Parkinson's disease (PD). But the effects of different short-chain fatty acids (SCFAs) on PD and involving mechanisms are still undefined. In this study we evaluate the effects of three dominant SCFAs (acetate, propionate and butyrate) on motor damage, dopaminergic neuronal degeneration and underlying neuroinflammation related mechanisms in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced PD mice. High (2.0 g/kg) or low doses (0.2 g/kg) of sodium acetate (NaA), sodium propionate (NaP) or sodium butyrate (NaB) were gavaged into PD mice for 6 weeks. High doses of NaA reduced the turning time of PD mice. NaB significantly reduced the turning and total time in pole test, and increased the average velocity in open field test when compared with PD mice, indicating the most effective alleviation of PD-induced motor disorder. Low and high doses of NaB significantly increased the content of tyrosine hydroxylase (TH) by 12.3% and 20.2%, while reduced α-synuclein activation by 159.4% and 132.7% in the substantia nigra pars compacta (SNpc), compared with PD groups. Butyrate reached into the midbrain SNpc and suppressed microglia over-activation. It inhibited the levels of pro-inflammatory factors (IL-6, IL-1β and TNF-α) (P < 0.01) and iNOS. Besides, butyrate inhibited the activation of NF-κB and MAPK signaling pathways in the SNpc region. Consequently, sodium butyrate could inhibit neuroinflammation and alleviate neurological damage of PD.

Impact of Gut Microbiome Manipulation in 5xFAD Mice on Alzheimer's Disease-Like Pathology

The gut brain axis seems to modulate various psychiatric and neurological disorders such as Alzheimer's disease (AD). Growing evidence has led to the assumption that the gut microbiome might contribute to or even present the nucleus of origin for these diseases. In this regard, modifiers of the microbial composition might provide attractive new therapeutics. Aim of our study was to elucidate the effect of a rigorously changed gut microbiome on pathological hallmarks of AD. 5xFAD model mice were treated by antibiotics or probiotics (L. acidophilus and L. rhamnosus) for 14 weeks. Pathogenesis was measured by nest building capability and plaque deposition. The gut microbiome was affected as expected: antibiotics significantly reduced viable commensals, while probiotics transiently increased Lactobacillaceae. Nesting score, however, was only improved in antibiotics-treated mice. These animals additionally displayed reduced plaque load in the hippocampus. While various physiological parameters were not affected, blood sugar was reduced and serum glucagon level significantly elevated in the antibiotics-treated animals together with a reduction in the receptor for advanced glycation end products RAGE-the inward transporter of Aβ peptides of the brain. Assumedly, the beneficial effect of the antibiotics was based on their anti-diabetic potential.

Alterations in the Gut-Microbial-Inflammasome-Brain Axis in a Mouse Model of Alzheimer's Disease

Alzheimer’s disease (AD), a progressive neurodegenerative disorder characterized by memory loss and cognitive decline, is a major cause of death and disability among the older population. Despite decades of scientific research, the underlying etiological triggers are unknown. Recent studies suggested that gut microbiota can influence AD progression; however, potential mechanisms linking the gut microbiota with AD pathogenesis remain obscure. In the present study, we provided a potential mechanistic link between dysbiotic gut microbiota and neuroinflammation associated with AD progression. Using a mouse model of AD, we discovered that unfavorable gut microbiota are correlated with abnormally elevated expression of gut NLRP3 and lead to peripheral inflammasome activation, which in turn exacerbates AD-associated neuroinflammation. To this end, we observe significantly altered gut microbiota compositions in young and old 5xFAD mice compared to age-matched non-transgenic mice. Moreover, 5xFAD mice demonstrated compromised gut barrier function as evident from the loss of tight junction and adherens junction proteins compared to non-transgenic mice. Concurrently, we observed increased expression of NLRP3 inflammasome and IL-1β production in the 5xFAD gut. Consistent with our hypothesis, increased gut–microbial–inflammasome activation is positively correlated with enhanced astrogliosis and microglial activation, along with higher expression of NLRP3 inflammasome and IL-1β production in the brains of 5xFAD mice. These data indicate that the elevated expression of gut–microbial–inflammasome components may be an important trigger for subsequent downstream activation of inflammatory and potentially cytotoxic mediators, and gastrointestinal NLRP3 may promote NLRP3 inflammasome-mediated neuroinflammation. Thus, modulation of the gut microbiota may be a potential strategy for the treatment of AD-related neurological disorders in genetically susceptible hosts.

Aqueous extracts of Aconite promote thermogenesis in rats with hypothermia via regulating gut microbiota and bile acid metabolism

Background

Intermittent or prolonged exposure to severe cold stress disturbs energy homeostasis and can lead to hypothermia, heart failure, Alzheimer’s disease, and so on. As the typical “hot” traditional Chinese medicine, Aconite has been widely used to treat cold-associated diseases for thousands of years, but its critical mechanisms for the promotion of thermogenesis are not fully resolved. Gut microbiota and its metabolites play a crucial role in maintaining energy homeostasis. Here, we investigated whether the aqueous extracts of Aconite (AA) can enhance thermogenesis through modulation of the composition and metabolism of gut microbiota in hypothermic rats.

Methods

The therapeutic effects of AA on body temperature, energy intake, and the histopathology of white adipose tissue and brown adipose tissue of hypothermic rats were assessed. Microbiota analysis based on 16 S rRNA and targeted metabolomics for bile acids (BAs) were used to evaluate the composition of gut microbiota and BAs pool. The antibiotic cocktail treatment was adopted to further confirm the relationship between the gut microbiota and the thermogenesis-promoting effects of AA.

Results

Our results showed a sharp drop in rectal temperature and body surface temperature in hypothermic rats. Administration of AA can significantly increase core body temperature, surface body temperature, energy intake, browning of white adipose tissue, and thermogenesis of brown adipose tissue. Importantly, these ameliorative effects of AA were accompanied by the shift of the disturbed composition of gut microbiota toward a healthier profile and the increased levels of BAs. In addition, the depletion of gut microbiota and the reduction of BAs caused by antibiotic cocktails reduced the thermogenesis-promoting effect of AA.

Conclusions

Our results demonstrated that AA promoted thermogenesis in rats with hypothermia via regulating gut microbiota and BAs metabolism. Our findings can also provide a novel solution for the treatment of thermogenesis-associated diseases such as rheumatoid arthritis, obesity, and type 2 diabetes.

Alterations in the gut microbiota and metabolite profiles in the context of neuropathic pain

The aim of this study was to explore the relationships among gut microbiota disturbances and serum and spinal cord metabolic disorders in neuropathic pain. 16S rDNA amplicon sequencing and serum and spinal cord metabolomics were used to identify alterations in the microbiota and metabolite profiles in the sham rats and the chronic constriction injury (CCI) model rats. Correlations between the abundances of gut microbiota components at the genus level, the levels of serum metabolites, and pain-related behavioural parameters were analysed. Ingenuity pathway analysis (IPA) was applied to analyse the interaction networks of the differentially expressed serum metabolites. First, we found that the composition of the gut microbiota was different between rats with CCI-induced neuropathic pain and sham controls. At the genus level, the abundances of Helicobacter, Phascolarctobacterium, Christensenella, Blautia, Streptococcus, Rothia and Lactobacillus were significantly increased, whereas the abundances of Ignatzschineria, Butyricimonas, Escherichia, AF12, and Corynebacterium were significantly decreased. Additionally, 72 significantly differentially expressed serum metabolites and 17 significantly differentially expressed spinal cord metabolites were identified between the CCI rats and the sham rats. Finally, correlation analysis showed that changes in the gut microbiota was significantly correlated with changes in serum metabolite levels, suggesting that dysbiosis of the gut microbiota is an important factor in modulating metabolic disturbances in the context of neuropathic pain. In conclusion, our research provides a novel perspective on the potential roles of the gut microbiota and related metabolites in neuropathic pain.

Preventive electroacupuncture ameliorates D-galactose-induced Alzheimer's disease-like inflammation and memory deficits, probably via modulating the microbiota-gut-brain axis

OBJECTIVES

We aimed to observe the effects of preventive electroacupuncture (EA) on the microbiota-gut-brain axis and spatial learning and memory deficits and to investigate the possible mechanism using D-galactose (D-gal)-induced aging rats.

MATERIALS AND METHODS

D-gal was intraperitoneally injected to establish the aging model. We used Morris water maze to detect spatial learning and memory function of rats. RT-PCR was applied to test targeted gut microbes. The expression of zonula occludens-1 (ZO-1) and Toll-like receptor 4 (TLR4)/nuclear factor (NF)-κB pathway proteins were detected by Western blotting. ELISA was employed to evaluate the level of lipopolysaccharides (LPS), diamine oxidase (DAO) and S-100β. Additionally, we observed ionized calcium-binding adapter molecule-1 (Iba-1) expression in the hippocampal CA1 area by immunofluorescence.

RESULTS

Morris water maze test showed decreased mean escape latency and increased target quadrant time after EA treatment. The gut microbiota composition has been modified in EA treated rats. Molecular examination indicated that expression of ZO-1 was improved and the the concentration of LPS in blood and hippocampus were reduced in EA treated rats. Further, we observed an inhibition of activated microglia and TLR4/NF-κB pathway in EA groups.

CONCLUSION

Preventive EA may alleviate the impairments of the microbiota-gut-brain axis and spatial learning and memory in aging, and the mechanism may be related to the inhibition of TLR4/NF-kB signaling pathway. The combination of acupoints GV20 and ST36 can enhance the therapeutic effect in aging rats.

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.

Selenium at the eural arriers: eview

Selenium (Se) is known to contribute to several vital physiological functions in mammals: antioxidant defense, fertility, thyroid hormone metabolism, and immune response. Growing evidence indicates the crucial role of Se and Se-containing selenoproteins in the brain and brain function. As for the other essential trace elements, dietary Se needs to reach effective concentrations in the central nervous system (CNS) to exert its functions. To do so, Se-species have to cross the blood-brain barrier (BBB) and/or blood-cerebrospinal fluid barrier (BCB) of the choroid plexus. The main interface between the general circulation of the body and the CNS is the BBB. Endothelial cells of brain capillaries forming the so-called tight junctions are the primary anatomic units of the BBB, mainly responsible for barrier function. The current review focuses on Se transport to the brain, primarily including selenoprotein P/low-density lipoprotein receptor-related protein 8 (LRP8, also known as apolipoprotein E receptor-2) dependent pathway, and supplementary transport routes of Se into the brain via low molecular weight Se-species. Additionally, the potential role of Se and selenoproteins in the BBB, BCB, and neurovascular unit (NVU) is discussed. Finally, the perspectives regarding investigating the role of Se and selenoproteins in the gut-brain axis are outlined.

Mechanistic new insights of flavonols on neurodegenerative diseases

With a large and increasing elderly population, neurodegenerative diseases such as Parkinson's disease (PD), Huntington disease (HD), Alzheimer's disease (AD), Amyotrophic lateral sclerosis (ALS) and Multiple sclerosis (MS) have become a major and growing health problem. During the past few decades, the elderly population has grown 2.5 % every year. Unfortunately, there are no specific therapeutic remedies available to slow the onset or development of these diseases. An aging brain causes many pathophysiological changes and is the major risk factor for most of the neurodegenerative disorders. Polyphenolic compounds such as flavonols have shown therapeutic potential and can contribute to the treatment of these diseases. In this review, evidence for the beneficial neuroprotective effect of multiple flavonols is discussed and their multifactorial cellular pathways for the progressions of age-associated brain changes are identified. Moreover, the animal models of these diseases support the neuroprotective effect and target the potential of flavonols in the treatment of neurodegenerative diseases.

The effects of lactobacilli (L. rhamnosus, L. reuteri, L. Plantarum) on LPS-induced memory impairment and changes in CaMKII-α and TNF-α genes expression in the hippocampus of rat

In recent years, some investigations have focused on the relationship between gut microbiota and brain function in healthy and disease conditions. Moreover, changes in the gut microbiome may affect memory, behavior, and cognition. This study aimed to evaluate the effect of lactobacilli on passive avoidance learning, hippocampal CaMKII-α, and TNF-α genes expression in one experimental model of neuroinflammtion. Male wistar rats (220-240 g) received daily oral gavage of different lactobacilli including L. rhamnosus, L. reuteri, and L. plantarum for 21 days. At the next step, behavioral test was performed and 4 hours after acute injection of LPS (1mg/kg, ip) retrieval was evaluated. Then the hippocampi were extracted and kept at _80°C. Finally CaMKII-α and TNF-α mRNA levels were evaluated by Real-time PCR. Our results showed that consumption of L. rhamnosus, L.reuteri, or L. plantarum significantly prevented LPS-induced enhancement of TNF-α mRNA and memory deterioration. Furthermore, L. rhamnosus significantly prevented changes induced by LPS on CaMKII-α mRNA levels. It seems the lactobacilli used in this study can affect brain function and memory performance by their immune-modulatory properties.

Role of Probiotics, Prebiotics, and Synbiotics in the Elderly: Insights Into Their Applications

Elderly people are an important part of the global population who suffer from the natural processes of senescence, which lead to changes in the gut microbiota composition. These modifications have a great impact on their quality of life, bringing a general putrefactive and inflammatory status as a consequence. Some of the most frequent conditions related to this status are constipation, undernutrition, neurodegenerative diseases, susceptibility to opportunistic pathogens, and metabolic disbalance, among others. For these reasons, there is an increasing interest in improving their quality of life by non-invasive treatments such as the consumption of probiotics, prebiotics, and synbiotics. The aim of the present mini-review is to describe the benefits of these functional supplements/food according to the most recent clinical and pre-clinical studies published during the last decade. In addition, insights into several aspects we consider relevant to improve the quality of future studies are provided.

Age-related cognitive decline is associated with microbiota-gut-brain axis disorders and neuroinflammation in mice

Age-related cognitive decline is associated with chronic low grade neuroinflammation that may result from a complex interplay among many factors, such as bidirectional communication between the central nervous system (CNS) and gut microbiota. The present study used 2-month-old (young group) and 15-month-old (aged group) male C57BL/6 mice to explore the potential association between age-related cognitive decline and the microbiota-gut-brain axis disorder. We observed that aged mice exhibited significant deficits in learning and memory, neuronal and synaptic function compared with young mice. Aged mice also exhibited significant dysbiosis of the gut microbiota. Disruptions of the intestinal barrier and blood-brain barrier were also observed, including increases in intestinal, low-grade systemic and cerebral inflammation. Furthermore, plasma and brain levels of lipopolysaccharide (LPS) were significantly higher in aged mice compared with young mice, with increasing expression of Toll-like receptor 4 (TLR4) and myeloid differential protein-88 (MyD88) and the nuclear translocation of nuclear factor κB (NF-κB) in intestinal and brain tissues. These findings showed that microbiota-gut-brain axis dysfunction that occurs through LPS-induced activation of the TLR4/NF-κB signaling pathway is implicated in age-related neuroinflammation and cognitive decline.

The Microbiota-Gut-Brain Axis and Alzheimer's Disease: Neuroinflammation Is to Blame?

For years, it has been reported that Alzheimer’s disease (AD) is the most common cause of dementia. Various external and internal factors may contribute to the early onset of AD. This review highlights a contribution of the disturbances in the microbiota–gut–brain (MGB) axis to the development of AD. Alteration in the gut microbiota composition is determined by increase in the permeability of the gut barrier and immune cell activation, leading to impairment in the blood–brain barrier function that promotes neuroinflammation, neuronal loss, neural injury, and ultimately AD. Numerous studies have shown that the gut microbiota plays a crucial role in brain function and changes in the behavior of individuals and the formation of bacterial amyloids. Lipopolysaccharides and bacterial amyloids synthesized by the gut microbiota can trigger the immune cells residing in the brain and can activate the immune response leading to neuroinflammation. Growing experimental and clinical data indicate the prominent role of gut dysbiosis and microbiota–host interactions in AD. Modulation of the gut microbiota with antibiotics or probiotic supplementation may create new preventive and therapeutic options in AD. Accumulating evidences affirm that research on MGB involvement in AD is necessary for new treatment targets and therapies for AD.

Gut dysbiosis and age-related neurological diseases; an innovative approach for therapeutic interventions

The gut microbiota is a complex ecosystem of bacteria, fungi, and viruses that acts as a critical regulator in microbial, metabolic, and immune responses in the host organism. Imbalances in the gut microbiota, termed "dysbiosis," often induce aberrant immune responses, which in turn disrupt the local and systemic homeostasis of the host. Emerging evidence has highlighted the importance of gut microbiota in intestinal diseases, and more recently, in age-related central nervous systems diseases, for example, stroke and Alzheimer's disease. It is now generally recognized that gut microbiota significantly influences host behaviors and modulates the interaction between microbiota, gut, and brain, via the "microbiota-gut-brain axis." Several approaches have been utilized to reduce age-related dysbiosis in experimental models and in clinical studies. These include strategies to manipulate the microbiome via fecal microbiota transplantation, administration of prebiotics and probiotics, and dietary interventions. In this review, we explore both clinical and preclinical therapies for treating age-related dysbiosis.

Gut microbiota modulation by both Lactobacillus fermentum MSK 408 and ketogenic diet in a murine model of pentylenetetrazole-induced acute seizure

PURPOSE

Seizures are a threat to the host brain and body and can even cause death in epileptic children. Ketogenic diet (KD) is suggested for children suffering from epileptic seizures and has been investigated for its anti-seizure effect. However, the relationships between KD and gut microbiota (GM) is not yet been deeply understood. Herein, we investigated the anti-seizure effect by administering KD and a lactic acid bacteria (LAB) in murine model of chemically induced seizures. We hypothesized that a single Lactobacillus fermentum MSK 408 (MSK 408) strain with or without KD may exert a neuroprotection by modulating host gut microbiota.

METHOD

We performed animal study using pentylenetetrazole (PTZ) to induce seizure. Thirty 3-week-old male Institute of Cancer research (ICR) mice were divided in six groups, Normal diet (ND), ND + PTZ, ND + PTZ + LAB, KD, KD + PTZ, and KD + PTZ. Based on our previous study, 4:1 KD and selected MSK 408 strain was orally gavaged (4 × 10⁹ CFU/mL) with both diets for 4 weeks. PTZ (40 mg/kg) was injected intraperitoneally 30 min before euthanization.

RESULTS

Compared to ND, KD significantly reduced the seizure frequency. Administration of MSK 408 with both ND and KD for 4 weeks restored serum lipid profile and tight junction protein mRNA expression of the gut and brain. Additionally, PCoA revealed that MSK 408 independently affected fecal short chain fatty acid (SCFA) content via gut microbiota (GM) modulation. PICRUSt suggested that the modulation of microbiota by KD and MSK 408 led to increased GABA (gamma-aminobutyric acid) metabolism.

SIGNIFICANCE

Our findings suggest that MSK 408 strain can be consumed with KD as supplement without interfering the anti-seizure action of KD, and may improve the serum lipid profile, and brain barrier function via gut microbiota and SCFA modulation.

An evaluation of the effects of probiotics on tumoral necrosis factor (TNF-α) signaling and gene expression

The search for functional foods containing probiotics has been growing due to numerous benefits they provide to health, such as modulation of the immune system and of the anti-inflammatory activity by inhibiting the release of pro-inflammatory cytokines, such as TNF-α. However, the mechanisms of actions of the probiotics responsible for this inhibition have not been completely explained so far. A better understanding of the interaction between probiotics and cell signaling pathways related to inflammatory processes shall help to prevent inflammatory bowel diseases. Therefore, the aim of this revision is to help understand the mechanisms of action of probiotics in cell signaling pathways that regulate TNF-α expression. Probiotics might act at different points of the MAPK pathway, on NF-kB, on proteasome activity, on Toll-like receptors, and on their regulators and stimuli. The present revision reaches the conclusion that probiotics act through multiple mechanisms, especially by inhibiting IkB phosphorylation and degradation, thus preventing the translocation of NF-kB. Effects are also shown to be strain-specific, and probiotics of the genus Lactobacillus are proved to play and essential role in anti-inflammatory activity.

Gut-Brain Axis: Role of Gut Microbiota on Neurological Disorders and How Probiotics/Prebiotics Beneficially Modulate Microbial and Immune Pathways to Improve Brain Functions

The gut microbiome acts as an integral part of the gastrointestinal tract (GIT) that has the largest and vulnerable surface with desirable features to observe foods, nutrients, and environmental factors, as well as to differentiate commensals, invading pathogens, and others. It is well-known that the gut has a strong connection with the central nervous system (CNS) in the context of health and disease. A healthy gut with diverse microbes is vital for normal brain functions and emotional behaviors. In addition, the CNS controls most aspects of the GI physiology. The molecular interaction between the gut/microbiome and CNS is complex and bidirectional, ensuring the maintenance of gut homeostasis and proper digestion. Besides this, several mechanisms have been proposed, including endocrine, neuronal, toll-like receptor, and metabolites-dependent pathways. Changes in the bidirectional relationship between the GIT and CNS are linked with the pathogenesis of gastrointestinal and neurological disorders; therefore, the microbiota/gut-and-brain axis is an emerging and widely accepted concept. In this review, we summarize the recent findings supporting the role of the gut microbiota and immune system on the maintenance of brain functions and the development of neurological disorders. In addition, we highlight the recent advances in improving of neurological diseases by probiotics/prebiotics/synbiotics and fecal microbiota transplantation via the concept of the gut-brain axis.

Microbiota modulation as preventative and therapeutic approach in Alzheimer's disease

The gut microbiota coevolves with its host, and numerous factors like diet, lifestyle, drug intake and geographical location continuously modify its composition, deeply influencing host health. Recent studies demonstrated that gut dysbiosis can alter normal brain function through the so-called gut-brain axis, a bidirectional communication network between the central nervous system and the gastrointestinal tract, thus playing a key role in the pathogenesis of neurodegenerative disorders, such as Alzheimer's disease (AD). In this perspective, in the constant search for novel treatments in AD, the rational modulation of gut microbiota composition could represent a promising approach to prevent or delay AD onset or to counteract its progression. Preclinical and human studies on microbiota modulation through oral bacteriotherapy and faecal transplantation showed anti-inflammatory and antioxidant effects, upregulation of plasma concentration of neuroprotective hormones, restoration of impaired proteolytic pathways, amelioration of energy homeostasis with consequent decrease of AD molecular hallmarks and improvement of behavioural and cognitive performances. In this review, we dissect the role of gut microbiota in AD and highlight recent advances in the development of new multitarget strategies for microbiota modulation to be used as possible preventative and therapeutic approaches in AD.

Gut Microbiota and Dysbiosis in Alzheimer's Disease: Implications for Pathogenesis and Treatment

Understanding how gut flora influences gut-brain communications has been the subject of significant research over the past decade. The broadening of the term “microbiota-gut-brain axis” from “gut-brain axis” underscores a bidirectional communication system between the gut and the brain. The microbiota-gut-brain axis involves metabolic, endocrine, neural, and immune pathways which are crucial for the maintenance of brain homeostasis. Alterations in the composition of gut microbiota are associated with multiple neuropsychiatric disorders. Although a causal relationship between gut dysbiosis and neural dysfunction remains elusive, emerging evidence indicates that gut dysbiosis may promote amyloid-beta aggregation, neuroinflammation, oxidative stress, and insulin resistance in the pathogenesis of Alzheimer’s disease (AD). Illustration of the mechanisms underlying the regulation by gut microbiota may pave the way for developing novel therapeutic strategies for AD. In this narrative review, we provide an overview of gut microbiota and their dysregulation in the pathogenesis of AD. Novel insights into the modification of gut microbiota composition as a preventive or therapeutic approach for AD are highlighted.

Gut Microbiota, Probiotics and Psychological States and Behaviors after Bariatric Surgery-A Systematic Review of Their Interrelation

The gastrointestinal (GI) microbiota plays an important role in health and disease, including brain function and behavior. Bariatric surgery (BS) has been reported to result in various changes in the GI microbiota, therefore demanding the investigation of the impact of GI microbiota on treatment success. The goal of this systematic review was to assess the effects of BS on the microbiota composition in humans and other vertebrates, whether probiotics influence postoperative health, and whether microbiota and psychological and behavioral factors interact. A search was conducted using PubMed and Web of Science to find relevant studies with respect to the GI microbiota and probiotics after BS, and later screened for psychological and behavioral parameters. Studies were classified into groups and subgroups to provide a clear overview of the outcomes. Microbiota changes were further assessed for whether they were specific to BS in humans through the comparison to sham operated controls in other vertebrate studies. Changes in alpha diversity appear not to be specific, whereas dissimilarity in overall microbial community structure, and increases in the abundance of the phylum Proteobacteria and Akkermansia spp. within the phylum Verrucomicrobia after surgery were observed in both human and other vertebrates studies and may be specific to BS in humans. Human probiotic studies differed regarding probiotic strains and dosages, however it appeared that probiotic interventions were not superior to a placebo for quality of life scores or weight loss after BS. The relationship between GI microbiota and psychological diseases in this context is unclear due to insufficient available data.

A critical review of antibiotic resistance in probiotic bacteria

Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer a health benefit upon the host. At present, probiotics are gaining popularity worldwide and are widely used in food and medicine. Consumption of probiotics is increasing with further in-depth research on the relationship between intestinal flora and host health. Most people pay more attention to the function of probiotics but ignore their potential risks, such as infection and antibiotic resistance transfer to pathogenic microbes. Physiological functions, effects and mechanisms of action of probiotics were covered in this review, as well as the antibiotic resistance phenotypes, mechanisms and genes found in probiotics. Typical cases of antibiotic resistance of probiotics were also highlighted, as well as the potential risks (including pathogenicity, infectivity and excessive immune response) and corresponding strategies (dosage, formulation, and administration route). This timely study provides an avenue for further research, development and application of probiotics.