Early changes of fecal short-chain fatty acid levels in patients with mild cognitive impairments

Diagnostic Accuracy of Machine Learning-Assisted MRI for Mild Cognitive Impairment in Parkinson's Disease: A Systematic Review and Meta-Analysis

To evaluate the diagnostic accuracy of machine learning-assisted magnetic resonance imaging (MRI) in detecting cognitive impairment among Parkinson's disease (PD) patients through a systematic review and meta-analysis. We systematically searched for studies that applied machine learning algorithms to MRI data for diagnosing PD with mild cognitive impairment (PD-MCI). Data were extracted and synthesized to calculate pooled sensitivity, specificity, positive likelihood ratio (PLR) and negative diagnostic likelihood ratio (NLR), and diagnostic odds ratios (DOR). A bivariate random-effects model and summary receiver operating characteristic (SROC) curves were employed for statistical analysis. The quality of studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) instrument. The publication bias was investigated through Deeks' funnel plot. All statistical analyses were conducted using Stata 14.0. The pooled sensitivity and specificity for diagnosing PD-MCI using machine learning-assisted MRI were 0.82 (95% CI: 0.75-0.87) and 0.81 (95% CI: 0.73-0.87), respectively. The PLR was 4.28 (95% CI: 2.93-6.27), and the NLR was 0.23 (95% CI: 0.16-0.32), indicating a high diagnostic accuracy. The area under the curve (AUC) for the SROC was 0.85 (95% CI: 0.82-0.88). Quality assessment using the QUADAS-2 tool showed a predominantly low risk of bias among the studies, and the Deeks' funnel plot suggested no significant publication bias (p=0.30). In summary, the MRI combined with machine learning for diagnosing PD-MCI achieved high accuracy with the pooled sensitivity of 82% and specificity of 81%.

Linking oxysterols and different stages of mild cognitive impairment: insights from gut metabolites and N6-methyladenosine

BACKGROUND

Oxysterols, gut metabolites, and N6-methyladenosine (m6A) are extensively implicated in the pathogenesis of cognitive dysfunction, while their alterations in different stages of mild cognitive impairment (MCI) have not been elucidated. Therefore, this study was conducted to explore the associations of oxysterols, gut metabolites, and m6A methylation profiles in early MCI (EMCI) and late MCI (LMCI) individuals.

METHODS

Liquid chromatography-mass spectrometry, untargeted metabolomic analysis, and m6A mRNA Epitranscriptomic Microarray were used to detect the characteristics of serum oxysterols (n = 35/group), fecal gut metabolites (n = 30/group), and m6A in whole blood (n = 4/group) respectively. The concentration of serum β-amyloid (Aβ) was detected with ELISA (n = 25/group). The gene expression of amyloid precursor protein (APP) and its key enzyme β-secretase (BACE1) in whole blood were measured by quantitative real-time PCR (n = 25/group).

RESULTS

EMCIs and LMCIs, especially LMCIs, exhibited poorer performance in almost all global and multidimensional cognitive tests. Serum 27-hydroxycholesterol (27-OHC) and 24S-hydroxycholesterol (24S-OHC) were elevated in EMCI and LMCI groups. Changes in gut metabolites occurred mainly in the EMCI group, in which several gut metabolites, including Procyanidin dimer B7 and Phorbol myristate, were significantly decreased. The m6A methylation landscape of EMCIs and LMCIs obviously differed from Controls. Hypomethylated mRNAs accounted for the majority and were mainly accompanied by downregulated mRNAs, which was consistent with the downregulated expression of the m6A writer methyltransferase-like 4 (METTL4). 27-OHC and 24S-OHC combined with various gut metabolites significantly distinguished between MCI subgroups from healthy controls (EMCI/Control: AUC = 0.877; LMCI/Control: AUC = 0.952). Heatmap revealed the correlation between Phorbol myristate and differentially m6A-methylated mRNAs. Differentially expressed gut metabolites and methylated mRNAs were commonly enriched in 34 KEGG metabolic pathways, including cholesterol metabolism and neurodegenerative disease-related pathways.

CONCLUSIONS

Our study explored the altered oxysterols, gut metabolites, and m6A methylation and their associations in different stages of MCI. The potential function of aberrant gut metabolites in oxysterols and m6A methylation driving MCI progression warrants further mechanistic investigation.

Butyrate: a key mediator of gut-brain communication in Alzheimer's disease

Alzheimer's disease (AD), a prevalent neurodegenerative disorder, represents a significant global health challenge, characterized by cognitive decline and neuroinflammation. Recent investigations have highlighted the critical role of the gut-brain axis in the pathogenesis of AD, particularly focusing on the influence of short-chain fatty acids (SCFAs), metabolites produced by the gut microbiota through the fermentation of dietary fiber. Among SCFAs, butyrate has emerged as a crucial mediator, positively impacting various pathological processes associated with AD, including epigenetic regulation, neuroinflammation modulation, maintenance of the blood-brain barrier (BBB), enhanced intestinal integrity, regulation of brain metabolism, and interference with amyloid protein formation as well as tau protein hyperphosphorylation. Furthermore, distinctions in butyrate profile and microbial communities have been observed between AD patients and healthy individuals, underscoring the importance of gut microbiota in AD progression. This review summarizes the current understanding of the many functions of butyrate in reducing the consequences of AD and emphasizes the possibility of addressing the gut microbiota as a therapeutic approach to managing AD.

Conversion Reaction of Stable-Isotope Oxygen Labeling of Carboxylic Acids for Accurate Screening LC-MS/MS Assay: Application of Behavioral Changes of Short-Chain Fatty Acids in Sports Athletes under Exercise Loading

Short-chain fatty acids (SCFAs) have attracted considerable interest as potential biomarkers, therapeutic targets, and nutritional factors in athletic training. SCFAs are typically produced by the intestinal microbiome and exhibit various structural forms, including linear- and branched-chain types. In particular, branched-chain SCFAs have been associated with muscle metabolism during exercise loading. Consequently, accurate and efficient analytical methods are essential for identifying these biomarkers. Liquid chromatography-tandem mass spectrometry is a suitable and accurate technique for SCFA analysis; however, stable isotope calibrations are required for all analytes. Because of technological limitations, the available species are restricted to certain types of SCFAs. To address this issue, this study performed a simple conversion reaction involving the incorporation of 18O into the carboxyl group. Specifically, oxygen atoms in the carboxyl groups were substituted with 18O sourced from commercially available H218O. An SCFA mixture standard solution was successfully labeled under optimized conditions, and the SIL purity and amount were sufficient for isotope dilution (95.2-96.9%, 250 assays using 10 μL of H218O). Moreover, no reversion to 16O was observed during storage or analysis. Analytical validation was performed in human serum using the substituted isotopic standard mixture, achieving good accuracy (90-110%) and precision (<10% relative standard deviation) across three concentration levels. Finally, changes in SCFA patterns were examined in athletes during exercise loading.

Time-restricted feeding mitigates Alzheimer's disease-associated cognitive impairments via a B. pseudolongum-propionic acid-FFAR3 axis

Time-restricted feeding (TRF) holds promise for alleviating cognitive decline in aging, albeit the precise mechanism via the gut-brain axis remains elusive. In a clinical trial, we observed, for the first time, that a 4-month TRF ameliorated cognitive impairments among Alzheimer's disease (AD) patients. Experiments in 5xFAD mice corroborated the gut microbiota-dependent effect of TRF on mitigating cognitive dysfunction, amyloid-beta deposition, and neuroinflammation. Multi-omics integration linked Bifidobacterium pseudolongum (B. pseudolongum) and propionic acid (PA) with key genes in AD pathogenesis. Oral supplementation of B. pseudolongum or PA mimicked TRF's protective effects. Positron emission tomography imaging confirmed PA's blood-brain barrier penetration, while knockdown of the free fatty acid receptor 3 (FFAR3) diminished TRF's cognitive benefits. Notably, we observed a positive correlation between fecal PA and improved cognitive function in an AD cohort, further indicating that TRF enhanced PA production. These findings highlight the microbiota-metabolites-brain axis as pivotal in TRF's cognitive benefits, proposing B. pseudolongum or PA as potential AD therapies.

Ginger Extract Improves Cognitive Dysfunction via Modulation of Gut Microbiota-Derived Short-Chain Fatty Acids in D-Galactose/Ovariectomy-Induced Alzheimer-Like Disease

Alzheimer's disease (AD) is the most common form of dementia with complex causes and limited treatment options. Recent research has suggested a connection between the progression of AD and the activity of gut microbiota. Ginger, a plant known for its anti-inflammatory, antioxidant, and neuroprotective properties, has gained attention as a potential treatment for alleviating AD symptoms. In this study, we induced an AD model in female rats through ovariectomy and D-galactose injection and then investigated the protective effects of oral administration of ginger ethanolic extract. We assessed changes in short-chain fatty acids (SCFAs), learning and memory abilities, neuroinflammatory markers in plasma, and the hippocampus, as well as histological changes in the intestine and hippocampus in sham-operated, diseased, and treatment groups. Oral administration of ginger ethanolic extract improved gut microbiota activity, increased SCFA levels, and enhanced the expression of tight junction proteins. Additionally, ginger extract reduced the concentrations of TNF-α and IL-1β in both plasma and the hippocampus. Furthermore, it significantly reduced cell death and amyloid plaque deposition in the hippocampal tissue. These physiological changes resulted in improved performance in learning and memory tasks in rats treated with ginger compared with the disease group. These findings provide compelling evidence for the beneficial effects of ginger on the gut-brain axis, leading to improvements in learning and memory through the reduction of neuroinflammation.

Gut Microbiota Mediates Neuroinflammation in Alzheimer's Disease: Unraveling Key Factors and Mechanistic Insights

The gut microbiota, the complex community of microorganisms that inhabit the gastrointestinal tract, has emerged as a key player in the pathogenesis of neurodegenerative disorders, including Alzheimer's disease (AD). AD is characterized by progressive cognitive decline and neuronal loss, associated with the accumulation of amyloid-β plaques, neurofibrillary tangles, and neuroinflammation in the brain. Increasing evidence suggests that alterations in the composition and function of the gut microbiota, known as dysbiosis, may contribute to the development and progression of AD by modulating neuroinflammation, a chronic and maladaptive immune response in the central nervous system. This review aims to comprehensively analyze the current role of the gut microbiota in regulating neuroinflammation and glial cell function in AD. Its objective is to deepen our understanding of the pathogenesis of AD and to discuss the potential advantages and challenges of using gut microbiota modulation as a novel approach for the diagnosis, treatment, and prevention of AD.

Association between plasma short-chain fatty acids and inflammation in human immunodeficiency virus-associated neurocognitive disorder: a pilot study

BACKGROUND AND AIMS

Short-chain fatty acids (SCFAs), key metabolites produced by gut microbiota, have neuroprotective effects in neurodegenerative diseases by modulating immune responses. However, their role in human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) remains largely unexplored.

METHODS

We recruited HAND patients, HIV Control, and healthy controls (HC). Plasma SCFAs and SCFA-producing gut microbiota were quantified via gas chromatography-mass spectrometry and fecal metagenomic analysis. Inflammatory cytokine levels were measured using liquid chromatography. Receiver operating characteristic (ROC) curves were generated to evaluate the predictive accuracy of SCFAs for HAND.

RESULTS

Plasma SCFAs were significantly reduced in HAND patients, correlating with a decrease in SCFA-producing gut bacteria, such as Prevotella and its related species. Reduced SCFAs were positively correlated with pro-inflammatory cytokines and cognitive impairment, while being negatively correlated with anti-inflammatory cytokines. ROC curve analysis demonstrated that several SCFAs exhibited strong predictive accuracy for HAND status.

CONCLUSIONS

SCFAs may influence cognitive function by modulating inflammatory responses, and identifies plasma SCFAs as potential biomarkers and therapeutic targets for HAND. Further investigation is needed to delineate the mechanisms that SCFAs influence HAND pathology.

Microbiota-Gut-Brain Axis in Age-Related Neurodegenerative Diseases

BACKGROUND

Age-related neurodegenerative diseases (NDs) pose a formidable challenge to healthcare systems worldwide due to their complex pathogenesis, significant morbidity, and mortality. Scope and Approach: This comprehensive review aims to elucidate the central role of the microbiotagut- brain axis (MGBA) in ND pathogenesis. Specifically, it delves into the perturbations within the gut microbiota and its metabolomic landscape, as well as the structural and functional transformations of the gastrointestinal and blood-brain barrier interfaces in ND patients. Additionally, it provides a comprehensive overview of the recent advancements in medicinal and dietary interventions tailored to modulate the MGBA for ND therapy.

CONCLUSION

Accumulating evidence underscores the pivotal role of the gut microbiota in ND pathogenesis through the MGBA. Dysbiosis of the gut microbiota and associated metabolites instigate structural modifications and augmented permeability of both the gastrointestinal barrier and the blood-brain barrier (BBB). These alterations facilitate the transit of microbial molecules from the gut to the brain via neural, endocrine, and immune pathways, potentially contributing to the etiology of NDs. Numerous investigational strategies, encompassing prebiotic and probiotic interventions, pharmaceutical trials, and dietary adaptations, are actively explored to harness the microbiota for ND treatment. This work endeavors to enhance our comprehension of the intricate mechanisms underpinning ND pathogenesis, offering valuable insights for the development of innovative therapeutic modalities targeting these debilitating disorders.

Liuweizhiji Gegen-Sangshen beverage protects against alcoholic liver disease in mice through the gut microbiota mediated SCFAs/GPR43/GLP-1 pathway

Introduction

Alcoholic liver disease (ALD) is a pathological state of the liver caused by longterm alcohol consumption. Recent studies have shown that the modulation of the gut microbiota and its metabolic products, specifically the short-chain fatty acids (SCFAs), exert a critical role in the evolution and progression of ALD. The Liuweizhiji Gegen-Sangshen beverage (LGS), as a functional beverage in China, is derived from a traditional Chinese herbal formula and has been clinically applied for ALD treatment, demonstrating significant efficacy. However, the underlying mechanisms of LGS for alleviating ALD involving gut microbiota regulation remain unknown.

Methods

In this study, an ALD murine model based on the National Institute on Alcohol Abuse and Alcoholism (NIAAA) method was established.

Results

The results showed that oral LGS treatment dose-dependently alleviated alcoholinduced liver injury and inflammation in mice through decreasing levels of ALT, AST and proinflammatory cytokines (TNF-α, IL-6, IL-1β). LGS significantly improved liver steatosis, enhanced activities of alcohol metabolizing enzymes (ALDH and ADH), and reduced the CYP2E1 activity. Notably, regarding most detected indices, the effect of LGS (particularly at medium and high dose) was comparable to the positive drug MTDX. Moreover, LGS had a favorable effect on maintaining intestinal barrier function through reducing epithelial injury and increasing expression of occludin. 16S rRNA sequencing results showed that LGS remarkably modulated gut microbiota structure in ALD mice via recovering alcohol-induced microbial changes and specifically mediating enrichment of several bacterial genera (Alloprevotella, Monoglobus, Erysipelatoclostridium Parasutterella, Harryflintia and unclassified_c_Clostridia). Further study revealed that LGS increased production of SCFAs of hexanoic acid in cecum, promoted alcohol-mediated reduction of GRP43 expression in ileum, and increased serum GLP-1 level.

Discussion

Overall, LGS exerts a remarkable protective effect on ALD mice through the gut microbiota mediated specific hexanoic acid production and GPR43/GLP-1 pathway.

Prevention and Treatment of Alzheimer's Disease Via the Regulation of the Gut Microbiota With Traditional Chinese Medicine

Alzheimer's disease (AD) is caused by a variety of factors, and one of the most important factors is gut microbiota dysbiosis. An imbalance in the gut mincrobiota have been shown to change the concentrations of lipopolysaccharide and short-chain fatty acids. These microorganisms synthesize substances that can influence the levels of a variety of metabolites and cause multiple diseases through the immune response, fatty acid metabolism, and amino acid metabolism pathways. Furthermore, these metabolic changes promote the formation of β-amyloid plaques and neurofibrillary tangles. Thus, the microbiota-gut-brain axis plays an important role in AD development. In addition to traditional therapeutic drugs such as donepezil and memantine, traditional Chinese medicines (TCMs) have also showed to significantly decrease the severity of AD symptoms and suppress the underlying related mechanisms. We searched for studies on the effects of different herbal monomers, single herbs, and polyherbal formulas on the gut microbiota of AD patients and identified the relevant pathways through which the gut microbiota affected AD. We conclude that improvements in the gut microbiota not only decrease the occurrence of inflammatory reactions but also reduce the deposition of central pathological products. Herbal monomers have a stronger effect on improving of central pathology. Polyherbal formulas have the most extensive effect on the gut microbiota in patients with AD. Among the effects of formulas, the anti-inflammatory effect is the most essential and is also the main concern regarding the use of TCMs in treating AD from the viewpoint of the gut microbiota. We hope that this review will be helpful for providing new ideas for the clinical application of TCMs in the treatment of AD.

The Gut Microbiota Modulates Neuroinflammation in Alzheimer's Disease: Elucidating Crucial Factors and Mechanistic Underpinnings

BACKGROUND AND PURPOSE

Alzheimer's disease (AD) is characterized by progressive cognitive decline and neuronal loss, commonly linked to amyloid-β plaques, neurofibrillary tangles, and neuroinflammation. Recent research highlights the gut microbiota as a key player in modulating neuroinflammation, a critical pathological feature of AD. Understanding the role of the gut microbiota in this process is essential for uncovering new therapeutic avenues and gaining deeper insights into AD pathogenesis.

METHODS

This review provides a comprehensive analysis of how gut microbiota influences neuroinflammation and glial cell function in AD. A systematic literature search was conducted, covering studies from 2014 to 2024, including reviews, clinical trials, and animal studies. Keywords such as "gut microbiota," "Alzheimer's disease," "neuroinflammation," and "blood-brain barrier" were used.

RESULTS

Dysbiosis, or the imbalance in gut microbiota composition, has been implicated in the modulation of key AD-related mechanisms, including neuroinflammation, blood-brain barrier integrity, and neurotransmitter regulation. These disruptions may accelerate the onset and progression of AD. Additionally, therapeutic strategies targeting gut microbiota, such as probiotics, prebiotics, and fecal microbiota transplantation, show promise in modulating AD pathology.

CONCLUSIONS

The gut microbiota is a pivotal factor in AD pathogenesis, influencing neuroinflammation and disease progression. Understanding the role of gut microbiota in AD opens avenues for innovative diagnostic, preventive, and therapeutic strategies.

Cutting-Edge iPSC-Based Approaches in Studying Host-Microbe Interactions in Neuropsychiatric Disorders

Gut microbiota (GM), together with its metabolites (such as SCFA, tryptophan, dopamine, GABA, etc.), plays an important role in the functioning of the central nervous system. Various neurological and psychiatric disorders are associated with changes in the composition of GM and their metabolites, which puts them in the foreground as a potential adjuvant therapy. However, the molecular mechanisms behind this relationship are not clear enough. Therefore, before considering beneficial microbes and/or their metabolites as potential therapeutics for brain disorders, the mechanisms underlying microbiota-host interactions must be identified and characterized in detail. In this review, we summarize the current knowledge of GM alterations observed in prevalent neurological and psychiatric disorders, multiple sclerosis, major depressive disorder, Alzheimer's disease, and autism spectrum disorders, together with experimental evidence of their potential to improve patients' quality of life. We further discuss the main obstacles in the study of GM-host interactions and describe the state-of-the-art solution and trends in this field, namely "culturomics" which enables the culture and identification of novel bacteria that inhabit the human gut, and models of the gut and blood-brain barrier as well as the gut-brain axis based on induced pluripotent stem cells (iPSCs) and iPSC derivatives, thus pursuing a personalized medicine agenda for neuropsychiatric disorders.

Microbiota and Resveratrol: How Are They Linked to Osteoporosis?

Osteoporosis (OP), which is characterized by a decrease in bone density and increased susceptibility to fractures, is closely linked to the gut microbiota (GM). It is increasingly realized that the GM plays a key role in the maintenance of the functioning of multiple organs, including bone, by producing bioactive metabolites such as short-chain fatty acids (SCFA). Consequently, imbalances in the GM, referred to as dysbiosis, have been identified with a significant reduction in beneficial metabolites, such as decreased SCFA associated with increased chronic inflammatory processes, including the activation of NF-κB at the epigenetic level, which is recognized as the main cause of many chronic diseases, including OP. Furthermore, regular or long-term medications such as antibiotics and many non-antibiotics such as proton pump inhibitors, chemotherapy, and NSAIDs, have been found to contribute to the development of dysbiosis, highlighting an urgent need for new treatment approaches. A promising preventive and adjuvant approach is to combat dysbiosis with natural polyphenols such as resveratrol, which have prebiotic functions and ensure an optimal microenvironment for beneficial GM. Resveratrol offers a range of benefits, including anti-inflammatory, anti-oxidant, analgesic, and prebiotic effects. In particular, the GM has been shown to convert resveratrol, into highly metabolically active molecules with even more potent beneficial properties, supporting a synergistic polyphenol-GM axis. This review addresses the question of how the GM can enhance the effects of resveratrol and how resveratrol, as an epigenetic modulator, can promote the growth and diversity of beneficial GM, thus providing important insights for the prevention and co-treatment of OP.

Gut Microbiota Metabolite Messengers in Brain Function and Pathology at a View of Cell Type-Based Receptor and Enzyme Reaction

The human gastrointestinal (GI) tract houses a diverse microbial community, known as the gut microbiome comprising bacteria, viruses, fungi, and protozoa. The gut microbiome plays a crucial role in maintaining the body's equilibrium and has recently been discovered to influence the functioning of the central nervous system (CNS). The communication between the nervous system and the GI tract occurs through a two-way network called the gut-brain axis. The nervous system and the GI tract can modulate each other through activated neuronal cells, the immune system, and metabolites produced by the gut microbiome. Extensive research both in preclinical and clinical realms, has highlighted the complex relationship between the gut and diseases associated with the CNS, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. This review aims to delineate receptor and target enzymes linked with gut microbiota metabolites and explore their specific roles within the brain, particularly their impact on CNS-related diseases.

Modulating the Gut Microbiota and Metabolites with Traditional Chinese Medicines: An Emerging Therapy for Type 2 Diabetes Mellitus and Its Complications

Currently, an estimated 537 million individuals are affected by type 2 diabetes mellitus (T2DM), the occurrence of which is invariably associated with complications. Glucose-lowering therapy remains the main treatment for alleviating T2DM. However, conventional antidiabetic agents are fraught with numerous adverse effects, notably elevations in blood pressure and lipid levels. Recently, the use of traditional Chinese medicines (TCMs) and their constituents has emerged as a preferred management strategy aimed at curtailing the progression of diabetes and its associated complications with fewer adverse effects. Increasing evidence indicates that gut microbiome disturbances are involved in the development of T2DM and its complications. This regulation depends on various metabolites produced by gut microbes and their interactions with host organs. TCMs' interventions have demonstrated the ability to modulate the intestinal bacterial microbiota, thereby restoring host homeostasis and ameliorating metabolic disorders. This review delves into the alterations in the gut microbiota and metabolites in T2DM patients and how TCMs treatment regulates the gut microbiota, facilitating the management of T2DM and its complications. Additionally, we also discuss prospective avenues for research on natural products to advance diabetes therapy.

Microbiota-gut-brain axis and its therapeutic applications in neurodegenerative diseases

The human gastrointestinal tract is populated with a diverse microbial community. The vast genetic and metabolic potential of the gut microbiome underpins its ubiquity in nearly every aspect of human biology, including health maintenance, development, aging, and disease. The advent of new sequencing technologies and culture-independent methods has allowed researchers to move beyond correlative studies toward mechanistic explorations to shed light on microbiome-host interactions. Evidence has unveiled the bidirectional communication between the gut microbiome and the central nervous system, referred to as the "microbiota-gut-brain axis". The microbiota-gut-brain axis represents an important regulator of glial functions, making it an actionable target to ameliorate the development and progression of neurodegenerative diseases. In this review, we discuss the mechanisms of the microbiota-gut-brain axis in neurodegenerative diseases. As the gut microbiome provides essential cues to microglia, astrocytes, and oligodendrocytes, we examine the communications between gut microbiota and these glial cells during healthy states and neurodegenerative diseases. Subsequently, we discuss the mechanisms of the microbiota-gut-brain axis in neurodegenerative diseases using a metabolite-centric approach, while also examining the role of gut microbiota-related neurotransmitters and gut hormones. Next, we examine the potential of targeting the intestinal barrier, blood-brain barrier, meninges, and peripheral immune system to counteract glial dysfunction in neurodegeneration. Finally, we conclude by assessing the pre-clinical and clinical evidence of probiotics, prebiotics, and fecal microbiota transplantation in neurodegenerative diseases. A thorough comprehension of the microbiota-gut-brain axis will foster the development of effective therapeutic interventions for the management of neurodegenerative diseases.

The Gut-Brain Axis in Alzheimer's and Parkinson's Diseases: The Catalytic Role of Mitochondria

Accumulating evidence suggests that gut inflammation is implicated in neuroinflammation in Alzheimer's and Parkinson's diseases. Despite the numerous connections it remains unclear how the gut and the brain communicate and whether gut dysbiosis is the cause or consequence of these pathologies. Importantly, several reports highlight the importance of mitochondria in the gut-brain axis, as well as in mechanisms like gut epithelium self-renewal, differentiation, and homeostasis. Herein we comprehensively address the important role of mitochondria as a cellular hub in infection and inflammation and as a link between inflammation and neurodegeneration in the gut-brain axis. The role of mitochondria in gut homeostasis and as well the crosstalk between mitochondria and gut microbiota is discussed. Significantly, we also review studies highlighting how gut microbiota can ultimately affect the central nervous system. Overall, this review summarizes novel findings regarding this cross-talk where the mitochondria has a main role in the pathophysiology of both Alzheimer's and Parkinson's disease strengthen by cellular, animal and clinical studies.