Infusion of donor feces affects the gut-brain axis in humans with metabolic syndrome

The Involvement of Serotonin in the Obesity Pathway-A Last Decade Systematic Review of the Literature

Obesity represents a complex, multifactorial syndrome that represents a high burden for public health systems worldwide. Serotonin is an important factor in feeding behavior and weight regulation and their interplay implies multiple mechanisms that could explain the correlation with obesity, so understanding these interconnections is essential for developing targeted therapeutic strategies. A systematic review of the literature was conducted using PubMed and Scopus databases, using articles published between 1 January 2015 and 1 December 2024, based on predefined inclusion and exclusion criteria. After the selection process, 22 studies were selected for detailed analysis, focusing on the role of serotonin in obesity. Serotonin significantly influences appetite control and energy homeostasis through multiples pathways, including insulin resistance, high-fat diets, gut microbiota, low-grade inflammation, interferences with tryptophan metabolism, psychiatric modifications, genetic alterations of serotonin receptors, serotonin implications in eating behavior, and neurohormonal regulation of appetite. This review highlights the multidimensional characteristics of the serotonin-obesity association, along with its significance in metabolic and psychiatric pathologies. In order to develop more efficient methods for managing obesity, future studies should concentrate on serotonergic regulation and complex management strategies involving the neurohormonal axis.

Therapeutic Strategies to Modulate Gut Microbial Health: Approaches for Chronic Metabolic Disorder Management

Numerous recent studies have suggested that the composition of the intestinal microbiota can trigger metabolic disorders, such as diabetes, prediabetes, obesity, metabolic syndrome, sarcopenia, dyslipidemia, hyperhomocysteinemia, and non-alcoholic fatty liver disease. Since then, considerable effort has been made to understand the link between the composition of intestinal microbiota and metabolic disorders, as well as the role of probiotics in the modulation of the intestinal microbiota. The aim of this review was to summarize the reviews and individual articles on the state of the art regarding ideal therapy with probiotics and prebiotics in order to obtain the reversion of dysbiosis (alteration in microbiota) to eubiosis during metabolic diseases, such as diabetes, prediabetes, obesity, hyperhomocysteinemia, dyslipidemia, sarcopenia, and non-alcoholic fatty liver diseases. This review includes 245 eligible studies. In conclusion, a condition of dysbiosis, or in general, alteration of the intestinal microbiota, could be implicated in the development of metabolic disorders through different mechanisms, mainly linked to the release of pro-inflammatory factors. Several studies have already demonstrated the potential of using probiotics and prebiotics in the treatment of this condition, detecting significant improvements in the specific symptoms of metabolic diseases. These findings reinforce the hypothesis that a condition of dysbiosis can lead to a generalized inflammatory picture with negative consequences on different organs and systems. Moreover, this review confirms that the beneficial effects of probiotics on metabolic diseases are promising, but more research is needed to determine the optimal probiotic strains, doses, and administration forms for specific metabolic conditions.

Therapeutic targeting of obesity-induced neuroinflammation and neurodegeneration

Obesity is a major modifiable risk factor leading to neuroinflammation and neurodegeneration. Excessive fat storage in obesity promotes the progressive infiltration of immune cells into adipose tissue, resulting in the release of pro-inflammatory factors such as cytokines and adipokines. These inflammatory mediators circulate through the bloodstream, propagating inflammation both in the periphery and in the central nervous system. Gut dysbiosis, which results in a leaky intestinal barrier, exacerbates inflammation and plays a significant role in linking obesity to the pathogenesis of neuroinflammation and neurodegeneration through the gut-brain/gut-brain-liver axis. Inflammatory states within the brain can lead to insulin resistance, mitochondrial dysfunction, autolysosomal dysfunction, and increased oxidative stress. These disruptions impair normal neuronal function and subsequently lead to cognitive decline and motor deficits, similar to the pathologies observed in major neurodegenerative diseases, including Alzheimer's disease, multiple sclerosis, and Parkinson's disease. Understanding the underlying disease mechanisms is crucial for developing therapeutic strategies to address defects in these inflammatory and metabolic pathways. In this review, we summarize and provide insights into different therapeutic strategies, including methods to alter gut dysbiosis, lifestyle changes, dietary supplementation, as well as pharmacological agents derived from natural sources, that target obesity-induced neuroinflammation and neurodegeneration.

Butyrate: A potential mediator of obesity and microbiome via different mechanisms of actions

Butyrate, a short-chain fatty acid, is a crucial product of gut microbial fermentation with significant implications for various metabolic and physiological processes. Dietary sources of butyrate are limited, primarily derived from the fermentation of dietary fibers by butyrate-producing gut bacteria. Butyrate exerts its effects primarily as a histone deacetylase (HDAC) inhibitor and through signaling pathways involving G protein-coupled receptors (GPCRs). Its diverse benefits include promoting gut health, enhancing energy metabolism, and potentially alleviating complications associated with obesity. However, the exact role of butyrate in obesity is still under investigation, with a limited number of human trials necessitating further research to determine its efficacy and safety profile. Moreover, butyrate impact on the gut-brain axis and its modulation of microbiome effect on behavior highlight its broader importance in regulating host physiology. A thorough understanding of the metabolic pathways and mechanisms of butyrate is essential for developing targeted interventions for metabolic disorders. Continued research is crucial to fully realize its therapeutic potential and optimize its clinical applications in human health. In summary, this review illuminates the multifaceted role of butyrate as a potential mediator of obesity and related metabolic changes.

Exploring Gut Microbiota Imbalance in Irritable Bowel Syndrome: Potential Therapeutic Effects of Probiotics and Their Metabolites

Irritable bowel syndrome is a common functional gastrointestinal disorder characterized by recurrent abdominal discomfort, bloating, cramping, flatulence, and changes in bowel movements. The pathophysiology of IBS involves a complex interaction between motor, sensory, microbiological, immunological, and psychological factors. Diversity, stability, and metabolic activity of the gut microbiota are frequently altered in IBS, thus leading to a situation of gut dysbiosis. Therefore, the use of probiotics and probiotic-derived metabolites may be helpful in balancing the gut microbiota and alleviating irritable bowel syndrome symptoms. This review aimed to report and consolidate recent progress in understanding the role of gut dysbiosis in the pathophysiology of IBS, as well as the current studies that have focused on the use of probiotics and their metabolites, providing a foundation for their potential beneficial effects as a complementary and alternative therapeutic strategy for this condition due to the current absence of effective and safe treatments.

The role of fecal microbiota transplantation in type 2 diabetes mellitus treatment

In contemporary microbial research, the exploration of interactions between microorganisms and multicellular hosts constitutes a burgeoning field. The gut microbiota is increasingly acknowledged as a pivotal contributor to various disorders within the endocrine system, encompassing conditions such as diabetes and thyroid diseases. A surge in research activities has been witnessed in recent years, elucidating the intricate interplay between the gut microbiota and disorders of the endocrine system. Simultaneously, fecal microbiota transplantation (FMT) has emerged as a focal point, garnering substantial attention in both biomedical and clinical spheres. Research endeavors have uncovered the remarkable therapeutic efficacy of FMT across diverse diseases, with particular emphasis on its application in addressing type 2 diabetes mellitus (T2DM) and associated com-plications. Consequently, this manuscript accentuates the intimate connection between the gut microbiota and disorders within the endocrine system, with a specific focus on exploring the potential of FMT as an intervention in the therapeutic landscape of T2DM and its complications. Furthermore, the article scrutinizes concerns inherent in treatment modalities centered around the gut microbiota, proposing viable solutions to address these issues.

Biospecimens in the HEALthy Brain and Child Development (HBCD) Study: Rationale and protocol

The HEALthy Brain and Child Development (HBCD) Study, a multi-site prospective longitudinal cohort study, will examine human brain, cognitive, behavioral, social, and emotional development beginning prenatally and planned through early childhood. The longitudinal collection of biological samples from over 7000 birthing parents and their children within the HBCD study enables research on pre- and postnatal exposures (e.g., substance use, toxicants, nutrition), and biological processes (e.g., genetics, epigenetic signatures, proteins, metabolites) on neurobehavioral developmental outcomes. The following biosamples are collected from the birthing parent: 1) blood (i.e., whole blood, serum, plasma, buffy coat, and dried blood spots) during pregnancy, 2) nail clippings during pregnancy and one month postpartum, 3) urine during pregnancy, and 4) saliva during pregnancy and at in-person postnatal assessments. The following samples are collected from the child at in-person study assessments: 1) saliva, 2) stool, and 3) urine. Additionally, placenta tissue, cord blood, and cord tissue are collected by a subset of HBCD sites. Here, we describe the rationale for the collection of these biospecimens, their current and potential future uses, the collection protocol, and collection success rates during piloting. This information will assist research teams in the planning of future studies utilizing this collection of biological samples.

Impact of gut microbiota on metabolic syndrome and its comprising traits: a two-sample mendelian randomization study

BACKGROUND

The prevalence of metabolic syndrome is on the rise globally. Understanding the etiology and discovering potential treatment target have become a priority. Observational data have linked gut microbiota with metabolic syndrome and its comprising traits. However, whether these relations underlie causal effects remains unclear.

METHODS

Using Inver Variance Weighted (IVW) as primary analysis method, we performed two-sample Mendelian Randomization (MR) analyses to explore the causal relationship between gut microbiota and metabolic syndrome with its comprising traits. Methods including MR-Egger regression, MR Pleiotropy RESidual Sum and Outlier (MR-PRESSO), Weighted Mode, and Weighted Median were chosen for additional MR analysis to test the robustness of MR results. Cochran's IVW Q test and leave-one-out IVW analysis tested the heterogeneity among instrumental variables (IVs). Steiger filtering was utilized to exclude all IVs with reverse causality. Genome-wide association study (GWAS) data used in this study were all from the largest respective GWAS studies available.

RESULTS

Out of 1172 tests, a total of 16 associations with evidence of causality were identified after sensitivity analyses, but only 3 remained after multiple testing correction. Class Melainabacteria (β = 0.02, adjusted P = 0.01) with affiliated order Gastranaerophilales (β = 0.02, adjusted P = 1.20*10- 3) and genus Eubacterium hallii (β = 0.03, adjusted P = 0.03) showed a positive effect on abdominal obesity. All effect sizes were small (abs(β) < 0.1). All causal relationships identified were unidirectional.

CONCLUSIONS

Given the study's limitations, we found little evidence supporting a large causal effect, i.e. absolute effect size > 0.1, of gut microbial taxa abundance on metabolic syndrome and its comprising traits. This study also suggests that previously reported associations between gut microbiota and metabolic syndrome with its comprising traits may not necessarily lead to causal relations.

CLINICAL TRIAL NUMBER

Not applicable.

Causal relationships between gut microbiota and polycystic ovarian syndrome: A bidirectional Mendelian randomization study

INTRODUCTION

Previous studies have established a link between gut microbiota and polycystic ovary syndrome (PCOS), but little is known about their precise causal relationship. Therefore, this study aims to explore whether there are precise causal relationships between gut microbiota and PCOS.

MATERIAL AND METHODS

We performed a bidirectional two-sample Mendelian randomization (MR) analysis. Datasets were from the largest published meta-analysis on gut microbiota composition and the FinnGen cohort of the IEU Open Genome-Wide Association Study Project database. Inverse variance weighted (IVW), MR-Egger, constrained maximum likelihood-based Mendelian randomization, weighted median, weighted mode, and simple mode were used. Cochran's Q and MR-Egger intercept tests were employed to measure the heterogeneity.

RESULTS

A total of 211 gut microbiota taxa were identified in MR analysis. Nine taxa of bacteria, including Alphaproteobacteria (0.55, 0.30-0.99, p = 0.04), Bacilli (1.76, 1.07-2.91, p = 0.03), Bilophila (0.42, 0.23-0.77, p < 0.01), Blautia (0.16, 0.03-0.79, p = 0.02), Burkholderiales (2.37, 1.22-4.62, p = 0.01), Candidatus Soleaferrea (0.65, 0.43-0.98, p = 0.04), Cyanobacteria (0.51, 0.31-0.83, p = 0.01), Holdemania (0.53, 0.35-0.81, p < 0.01), and Lachnospiraceae (1.86, 1.04-3.35, p = 0.03), were found to be associated with PCOS in the above MR methods included at least IVW method. Cochran's Q statistics and MR-Egger intercept test suggested no significant heterogeneity. In addition, 69 taxa were shown significant for at least the IVW method in reverse MR analysis, of these, 25 had a positive correlation, and 37 had a negative correlation. Additionally, Alphaproteobacteria and Lachnospiraceae (0.95, 0.91-0.98, p < 0.01; 0.97, 0.94-0.99, p = 0.02, respectively) were shown a bidirected causally association with PCOS.

CONCLUSIONS

Our study provides evidence of the bidirectional causal association between gut microbiota and PCOS from a genetic perspective.

Christensenella minuta mitigates behavioral and cardiometabolic hallmarks of social defeat stress

Psychological stress during early development and adolescence may increase the risk of psychiatric and cardiometabolic comorbidities in adulthood. The gut microbiota has been associated with mental health problems such as depression and anxiety and with cardiometabolic disease, but the potential role of the gut microbiota in their comorbidity is not well understood. We investigated the effects and mode of action of the intestinal bacterium Christensenella minuta DSM 32891 on stress-induced mental health and cardiometabolic disturbances in a mouse model of social defeat stress. We demonstrate that administered C. minuta alleviates chronic stress-induced depressive, anxiogenic and antisocial behavior. These effects are attributed to the bacterium's ability to modulate the hypothalamic-pituitary-adrenal axis, which mediates the stress response. This included the oversecretion of corticosterone and the overexpression of its receptors, as well as the metabolism of dopamine (DA) and the expression of its receptors (D1, D2L and D2S). Additionally, C. minuta administration reduced chronically induced inflammation in plasma, spleen and some brain areas, which likely contribute to the recovery of physical and behavioral function. Furthermore, C. minuta administration prevented chronic stress-induced cardiovascular damage by regulating key enzymes mediating liver fibrosis and oxidative stress. Finally, C. minuta increased the abundance of bacteria associated with mental health. Overall, our study highlights the potential of microbiota-directed interventions to alleviate both the physical and mental effects of chronic stress.

The Impact of Prevotella on Neurobiology in Aging: Deciphering Dendritic Cell Activity and Inflammatory Dynamics

Prevotella species, notably Prevotella copri, significantly populate the human gut. In particular, P. copri is prevalent among non-Western populations with diets high in fiber. These species show complex relationships with diverse health aspects, associating with beneficial outcomes, including reduced visceral fat and improved glucose tolerance. Studies implicate various Prevotella species in specific diseases. Prevotella nigrescens and Porphyromonas gingivalis were linked to periodontal disease, promoting immune responses and influencing T helper type 17 (Th17) cells. Prevotella bivia was associated with bacterial vaginosis and a specific increase in activated cells in the vaginal mucosa. In contrast, they have shown substantial potential for inducing connective tissue degradation and alveolar bone resorption. Prevotella's role in neuroinflammatory disorders and autoinflammatory conditions such as Alzheimer's disease and Parkinson's disease has also been noted. The complex relationship between Prevotella and age-related conditions further extends to neurobiological changes in aging, with varying associations with Alzheimer's, Parkinson's, and other inflammatory conditions. Studies have also identified Prevotella to be implicated in cognitive decline in middle aged and the elderly. Future directions in this research area are anticipated to explore Prevotella-associated inflammatory mechanisms and therapeutic interventions. Investigating specific drug targets and immunomodulatory measures could lead to novel therapeutic strategies. Understanding how Prevotella-induced inflammation interacts with aging diseases would offer promising insights for treatments and interventions. This review urges ongoing research to discover therapeutic targets and mechanisms for moderating Prevotella-associated inflammation to further enhance our understanding and improve health outcomes.

Unveiling the causal effects of gut microbiome on trimethylamine N-oxide: evidence from Mendelian randomization

Objective

The relationship between gut microbiome and trimethylamine oxide (TMAO) has not been fully elucidated. We aimed to assess the causal effects of different gut microbes on TMAO using Mendelian randomization (MR).

Methods

Gut microbiome and TMAO datasets were acquired from genome-wide association studies and screened for single nucleotide polymorphisms according to the basic assumptions of MR. Inverse variance weighted was used as the main method in MR analysis to assess the causal relationship between the gut microbiome and TMAO. Finally, the MR-Egger intercept, Cochran's Q test, and leave-one-out sensitivity analysis were used to assess the horizontal pleiotropy, heterogeneity, and robustness of the results, respectively.

Results

MR analysis revealed that the species Bacteroides finegoldii (odds ratio [OR] 1.064, 95% confidence interval [CI] 1.003 to 1.128, p = 0.039), family Sutterellaceae (OR 1.188, 95% CI 1.003 to 1.407, p = 0.047), and phylum Pseudomonadota (OR 1.205, 95% CI 1.036 to 1.401, p = 0.016), as well as the species Bacteroides uniformis (OR 1.263, 95% CI 1.039 to 1.535, p = 0.019), were positively associated with increased genetic susceptibility to TMAO. In contrast, the species Bacteroides thetaiotaomicron (OR 0.813, 95% CI 0.696 to 0.950, p = 0.009) and Bilophila wadsworthia (OR 0.828, 95% CI 0.690 to 0.995, p = 0.044) were associated with reduced genetic susceptibility to TMAO. Additionally, the MR-Egger intercept indicated no horizontal pleiotropy (p ≥ 0.05), and Cochran's Q test and sensitivity analysis demonstrated that the results were not heterogeneous (p ≥ 0.05) and were robust.

Conclusion

Our findings revealed the role of the phylum Pseudomonadota, family Sutterellaceae, species Bacteroides finegoldii, and Bacteroides uniformis in increasing TMAO, as well as the species Bacteroides thetaiotaomicron and Bilophila wadsworthia in decreasing TMAO. This study provides new insights into the relationship between the gut microbiome and TMAO levels.

Safety and efficacy of fecal microbiota transplantation for viral diseases: A systematic review of clinical trials

BACKGROUND

Gut microbiota play important roles in several diseases like viral infections. In this systematic review, our objective was to assess the efficacy and safety of fecal microbiota transplantation (FMT) in treating various viral diseases.

METHODS

We conducted searches on databases including PubMed, Web of Science, Scopus, and Google Scholar until November 2023. Clinical trials reported outcomes related to safety of FMT or its efficacy in patients with viral diseases were included. We excluded other types of studies that enrolled healthy individuals or patients with other disorders and did not use FMT. The assessment of bias risk was conducted using the National Institutes of Health (NIH) study quality evaluation tool.

RESULTS

Eight studies with total 196 participants were included. Viral diseases were human immunodeficiency virus (HIV), hepatitis B, COVID-19 and Clostridioides difficile coinfection, and cytomegalovirus colitis. In hepatitis B cases, HBeAg clearance was significant in those received FMT (p<0.01), while it was not significant in another one (p = 0.19). A clinical response was noted in 37.5% of patients with cytomegalovirus colitis, with an equal percentage achieving clinical remission post-FMT. There was a significant reduction in Clostridioides difficile relapse rate in FMT group than controls in coinfection of Clostridioides difficile and COVID-19 (2.17% vs. 42.5%, p<0.05). In patients with HIV, partial engraftment of the donor microbiome and increases in alpha diversity were observed after FMT. No severe adverse events were reported. Most studies had fair or good qualities.

CONCLUSIONS

Our findings revealed FMT as a promising, safe treatment for some viral diseases. It improved viral clearance, clinical outcomes, and inflammation. However, the varying responses and small sample sizes call for more trials on FMT in viral diseases.

Gut microbiota causally impacts adrenal function: a two-sample mendelian randomization study

Some studies have reported that the gut microbiota can influence adrenal-related hormone levels. However, the causal effects of the gut microbiota on adrenal function remain unknown. Therefore, we employed a two-sample Mendelian randomization (MR) study to systematically investigate the impact of gut microbiota on the function of different regions of the adrenal gland. The summary statistics for gut microbiota and adrenal-related hormones used in the two-sample MR analysis were derived from publicly available genome-wide association studies (GWAS). In the MR analysis, inverse variance weighting (IVW) was used as the primary method, with MR-Egger, weighted median, and cML-MA serving as supplementary methods for causal inference. Sensitivity analyses such as the MR-Egger intercept test, Cochran's Q test, and leave-one-out analysis were used to assess pleiotropy and heterogeneity. We identified 27 causal relationships between 23 gut microbiota and adrenal function using the IVW method. Among these, Sellimonas enhanced the function of the adrenal cortex reticularis zone (beta = 0.008, 95% CI: 0.002-0.013, P = 0.0057). The cML-MA method supported our estimate (beta = 0.009, 95% CI: 0.004-0.013, P = 2 × 10- 4). Parasutterella, Sutterella, and Anaerofilum affect the functioning of different regions of the adrenal gland. Notably, pleiotropy was not observed. Our findings revealed that the gut microbiota is causally associated with adrenal function. This enhances our understanding of the gut-microbiota-brain axis and provides assistance in the early diagnosis and treatment of adrenal-related diseases in clinical practice.

Understanding the role of the human gut microbiome in overweight and obesity

The gut microbiome may be related to the prevalence of overweight and obesity, but high interindividual variability of the human microbiome complicates our understanding. Obesity often occurs concomitantly with micronutrient deficiencies that impair energy metabolism. Microbiota composition is affected by diet. Host-microbiota interactions are bidirectional. We propose three pathways whereby these interactions may modulate the gut microbiome and obesity: (1) ingested compounds or derivatives affecting small intestinal transit, endogenous secretions, digestion, absorption, microbiome balance, and gut barrier function directly affect host metabolism; (2) substrate availability affecting colonic microbial composition and contact with the gut barrier; and (3) microbial end products affecting host metabolism. The quantity/concentration, duration, and/or frequency (circadian rhythm) of changes in these pathways can alter the gut microbiome, disrupt the gut barrier, alter host immunity, and increase the risk of and progression to overweight and obesity. Host-specific characteristics (e.g., genetic variations) may further affect individual sensitivity and/or resilience to diet- and microbiome-associated perturbations in the colonic environment. In this narrative review, the effects of selected interventions, including fecal microbiota transplantation, dietary calorie restriction, dietary fibers and prebiotics, probiotics and synbiotics, vitamins, minerals, and fatty acids, on the gut microbiome, body weight, and/or adiposity are summarized to help identify mechanisms of action and research opportunities.

Gut microbiota modulates neurotransmitter and gut-brain signaling

Neurotransmitters, including 5-hydroxytryptamine (5-HT), dopamine (DA), gamma-aminobutyric acid (GABA), and glutamate, are essential transductors in the Gut-Brain Axis (GBA), playing critical roles both peripherally and centrally. Accumulating evidence suggests that the gut microbiota modulates intestinal neurotransmitter metabolism and gut-to-brain signaling, shedding light on the crucial role of the gut microbiota in brain function and the pathogenesis of various neuropsychiatric diseases, such as major depression disorder (MDD), anxiety, addiction and Parkinson's disease (PD). Despite the exciting findings, the mechanisms underlying the modulation of neurotransmitter metabolism and function by the gut microbiota are still being elucidated. In this review, we aim to provide a comprehensive overview of the existing knowledge about the role of the gut microbiota in neurotransmitter metabolism and function in animal and clinical experiments. Moreover, we will discuss the potential mechanisms through which gut microbiota-derived neurotransmitters contribute to the pathogenesis of neuropsychiatric diseases, thus highlighting a novel therapeutic target for these conditions.

Mendelian randomization study reveals causal effects of specific gut microbiota on the risk of interstitial cystitis/bladder pain syndrome (IC/BPS)

Evidence from previous studies have demonstrated that gut microbiota are closely associated with occurrence of interstitial cystitis/bladder pain syndrome (IC/BPS), yet the causal link between the two is not well known. In this study, we performed a two-sample Mendelian randomization (MR) analysis to determine the possible causal association between gut microbiota with IC/BPS. Gut microbiota summary level data were derived from the genome-wide association study (GWAS) conducted by MiBioGen and the IC/BPS GWAS summary level data were obtained from the GWAS Catalog. Next, we performed an MR study to investigate the causal link between gut microbiota and IC/BPS. The primary method for causal analysis was the inverse variance weighted (IVW), and the MR results were validated through multiple sensitivity analyses. A positive association was found between IC/BPS and eight gut microbial taxa, including genus Bacteroides, genus Haemophilus, genus Veillonella, genus Coprococcus1, genus Butyricimonas, family Bacteroidaceae, family Christensenellaceae, and order Lactobacillales. Sensitivity analysis revealed lack of significant pleiotropy or heterogeneity in the obtained results. This MR analysis reveals that a causal association exists between some gut microbiota with IC/BPS. This finding may is expected to guide future research and development of IC/BPS preventions and treatments based on the bladder-gut axis. However, given the clinical complexity and diagnostic challenges of IC/BPS, along with the limitations of using large-scale GWAS summary data for analysis, our MR results require further validation through additional research.

Fecal microbiota transplantation in autoimmune diseases - An extensive paper on a pathogenetic therapy

The role of infections in the pathogenesis of autoimmune diseases has long been recognized and reported. In addition to infectious agents, the internal composition of the "friendly" living bacteria, (microbiome) and its correlation to immune balance and dysregulation have drawn the attention of researchers for decades. Nevertheless, only recently, scientific papers regarding the potential role of transferring microbiome from healthy donor subjects to patients with autoimmune diseases has been proposed. Fecal microbiota transplantation or FMT, carries the logic of transferring microorganisms responsible for immune balance from healthy donors to individuals with immune dysregulation or more accurately for our paper, autoimmune diseases. Viewing the microbiome as a pathogenetic player allows us to consider FMT as a pathogenetic-based treatment. Promising results alongside improved outcomes have been demonstrated in patients with different autoimmune diseases following FMT. Therefore, in our current extensive review, we aimed to highlight the implication of FMT in various autoimmune diseases, such as inflammatory bowel disease, autoimmune thyroid and liver diseases, systemic lupus erythematosus, and type 1 diabetes mellitus, among others. Presenting all the aspects of FMT in more than 12 autoimmune diseases in one paper, to the best of our knowledge, is the first time presented in medical literature. Viewing FMT as such could contribute to better understanding and newer application of the model in the therapy of autoimmune diseases, indeed.

Exploring the nigrostriatal and digestive interplays in Parkinson's disease using dynamic total-body [11C]CFT PET/CT

PURPOSE

Dynamic total-body imaging enables new perspectives to investigate the potential relationship between the central and peripheral regions. Employing uEXPLORER dynamic [11C]CFT PET/CT imaging with voxel-wise simplified reference tissue model (SRTM) kinetic modeling and semi-quantitative measures, we explored how the correlation pattern between nigrostriatal and digestive regions differed between the healthy participants as controls (HC) and patients with Parkinson's disease (PD).

METHODS

Eleven participants (six HCs and five PDs) underwent 75-min dynamic [11C]CFT scans on a total-body PET/CT scanner (uEXPLORER, United Imaging Healthcare) were retrospectively enrolled. Time activity curves for four nigrostriatal nuclei (caudate, putamen, pallidum, and substantia nigra) and three digestive organs (pancreas, stomach, and duodenum) were obtained. Total-body parametric images of relative transporter rate constant (R1) and distribution volume ratio (DVR) were generated using the SRTM with occipital lobe as the reference tissue and a linear regression with spatial-constraint algorithm. Standardized uptake value ratio (SUVR) at early (1-3 min, SUVREP) and late (60-75 min, SUVRLP) phases were calculated as the semi-quantitative substitutes for R1 and DVR, respectively.

RESULTS

Significant differences in estimates between the HC and PD groups were identified in DVR and SUVRLP of putamen (DVR: 4.82 ± 1.58 vs. 2.58 ± 0.53; SUVRLP: 4.65 ± 1.36 vs. 2.84 ± 0.67; for HC and PD, respectively, both p < 0.05) and SUVREP of stomach (1.12 ± 0.27 vs. 2.27 ± 0.65 for HC and PD, respectively; p < 0.01). In the HC group, negative correlations were observed between stomach and substantia nigra in both the R1 and SUVREP values (r=-0.83, p < 0.05 for R1; r=-0.94, p < 0.01 for SUVREP). Positive correlations were identified between pancreas and putamen in both DVR and SUVRLP values (r = 0.94, p < 0.01 for DVR; r = 1.00, p < 0.001 for SUVRLP). By contrast, in the PD group, no correlations were found between the aforementioned target nigrostriatal and digestive areas.

CONCLUSIONS

The parametric images of R1 and DVR generated from the SRTM model, along with SUVREP and SUVRLP, were proposed to quantify dynamic total-body [11C]CFT PET/CT in HC and PD groups. The distinction in correlation patterns of nigrostriatal and digestive regions between HC and PD groups identified by R1 and DVR, or SUVRs, may provide new insights into the disease mechanism.

Gut Microbiota Profiles in Myopes and Nonmyopes

Purpose

To identify compositional differences in the gut microbiome of nonmyopes (NM) and myopes using 16S ribosomal RNA sequencing and to investigate whether the microbiome may contribute to the onset or progression of the condition.

Methods

Faecal samples were collected from 52 adult participants, of whom 23 were NM, 8 were progressive myopes (PM), and 21 were stable myopes (SM). The composition of the gut microbiota in each group was analysed using 16S ribosomal RNA gene sequencing.

Results

There were no significant differences in alpha and beta diversity between the three groups (NM, PM, and SM). However, the distributions of Bifidobacterium, Bacteroides, Megamonas, Faecalibacterium, Coprococcus, Dorea, Roseburia, and Blautia were significantly higher in the myopes (SM and PM combined) when compared with emmetropes. The myopes exhibited significantly greater abundance of bacteria that are linked to the regulation of dopaminergic signalling, such as Clostridium, Ruminococcus, Bifidobacterium, and Bacteroides. Individuals with stable myopia were found to have a significantly higher proportion of Prevotella copri than those with progressive myopia. Bifidobacterium adolescentis, a gamma-aminobutyric acid (GABA)-producing bacterium, was significantly higher in all myopes than in NM and, in the comparison between SM and PM, it is significantly higher in SM. B. uniformis and B. fragilis, both GABA-producing Bacteroides, were present in relatively high abundance in all myopes and in SM compared with PM, respectively.

Conclusions

The presence of bacteria related to dopamine effect and GABA-producing bacteria in the gut microbiome of myopes may suggest a role of these microorganisms in the onset and progression of myopia.

Influence of Bariatric Surgery on Gut Microbiota Composition and Its Implication on Brain and Peripheral Targets

Obesity remains a significant global health challenge, with bariatric surgery remaining as one of the most effective treatments for severe obesity and its related comorbidities. This review highlights the multifaceted impact of bariatric surgery beyond mere physical restriction or nutrient malabsorption, underscoring the importance of the gut microbiome and neurohormonal signals in mediating the profound effects on weight loss and behavior modification. The various bariatric surgery procedures, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), act through distinct mechanisms to alter the gut microbiome, subsequently impacting metabolic health, energy balance, and food reward behaviors. Emerging evidence has shown that bariatric surgery induces profound changes in the composition of the gut microbiome, notably altering the Firmicutes/Bacteroidetes ratio and enhancing populations of beneficial bacteria such as Akkermansia. These microbiota shifts have far-reaching effects beyond gut health, influencing dopamine-mediated reward pathways in the brain and modulating the secretion and action of key gut hormones including ghrelin, leptin, GLP-1, PYY, and CCK. The resultant changes in dopamine signaling and hormone levels contribute to reduced hedonic eating, enhanced satiety, and improved metabolic outcomes. Further, post-bariatric surgical effects on satiation targets are in part mediated by metabolic byproducts of gut microbiota like short-chain fatty acids (SCFAs) and bile acids, which play a pivotal role in modulating metabolism and energy expenditure and reducing obesity-associated inflammation, as well as influencing food reward pathways, potentially contributing to the regulation of body weight and reduction in hedonic eating behaviors. Overall, a better understanding of these mechanisms opens the door to developing non-surgical interventions that replicate the beneficial effects of bariatric surgery on the gut microbiome, dopamine signaling, and gut hormone regulation, offering new avenues for obesity treatment.

The Effect of Fecal Microbiota Transplantation on Cardiometabolic Risk Factors: A Systematic Review and Meta-Analysis

PURPOSE

Cardiometabolic disease (CMD) is increasing along with its predisposing factors and adverse consequences. As gut microbiota dysbiosis is established in these patients, fecal microbiota transplantation (FMT), which alters the bacterial composition of the intestine, supposedly can help improve cardiometabolic disturbances. We conducted a systematic review and meta-analysis evaluating the impact of FMT on the cardiometabolic parameters and gut microbiota composition of patients experiencing at least one cardiometabolic issue.

METHODS

Eligible studies were searched through the PubMed, Web of Science, and Scopus databases until December 2022. The initial search results underwent duplication removal and screening until each included study was scanned for intended data. The Cochrane risk of bias tool was used to evaluate the methodologic accuracy of studies and the random effects model was used for conducting the meta-analysis.

FINDINGS

Eighteen of the original 2414 articles from the literature search were entered into the systematic review; of these, 11 were included in the meta-analysis. Insulin showed a significant decrease by 24.7 pmol/L (weighted mean difference [WMD], -24.77; 95% CI, -48.704 to -0.848) after short-term follow-up, and HDL increased by 0.1 mmol/l(WMD, 0.106; 95% CI, 0.027 to 0.184) and 0.12 mmol/l(WMD, 0.120; 95% CI, 0.003 to 0.237) in those using a capsule deliver mode and in short-term follow-up, respectively. No significant changes were seen in other lipid profiles, blood glucose, insulin resistance, or anthropometric indices. In addition, multiple studies reported gut microbiota alterations after the intervention, including an increase in butyrate-producing species.

IMPLICATIONS

Although some articles reported the beneficial effects of FMT on metabolic parameters, we failed to find a clinically significant alteration. Also, information regarding proper donors and the best method to induce FMT have not yet been sufficiently investigated, which should be considered along with means to prevent potential damages. PROSPERO identifier: CRD42022380705.

Human gut microbiome: Therapeutic opportunities for metabolic syndrome-Hype or hope?

Shifts in gut microbiome composition and metabolic disorders are associated with one another. Clinical studies and experimental data suggest a causal relationship, making the gut microbiome an attractive therapeutic goal. Diet, intake of probiotics or prebiotics and faecal microbiome transplantation (FMT) are methods to alter a person's microbiome composition. Although FMT may allow establishing a proof of concept to use microbiome modulation to treat metabolic disorders, studies show mixed results regarding the effects on metabolic parameters as well as on the composition of the microbiome. This review summarizes the current knowledge on diet, probiotics, prebiotics and FMT to treat metabolic diseases, focusing on studies that also report alterations in microbiome composition. Furthermore, clinical trial results on the effects of common drugs used to treat metabolic diseases are synopsized to highlight the bidirectional relationship between the microbiome and metabolic diseases. In conclusion, there is clear evidence that microbiome modulation has the potential to influence metabolic diseases; however, it is not possible to distinguish which intervention is the most successful. In addition, a clear commitment from all stakeholders is necessary to move forward in the direction of developing targeted interventions for microbiome modulation.

Disentangle beneficial effects of strain engraftment after fecal microbiota transplantation in subjects with MetSyn

Fecal Microbiota Transplantation (FMT) has emerged as a potential modality for mitigating microbiome-associated diseases. Despite this potential, the precise causal pathways by which specific gut microbiota strains induce remission remain inadequately elucidated. In this study, we aimed to discern the impact of engraftment of donor-infused strains on alterations in plasma metabolites, subsequently contributing to the amelioration of clinical parameters involved in subjects with metabolic syndrome (MetSyn) receiving an FMT. We observed that a higher fraction of donor strains engrafted in the recipient is correlated to a reduction in diastolic blood pressure and found specific strain associations through canonical correlation analysis. Integrating the metabolomics profile shows that engraftment of Collinsella aerofaciens and Fusocatenibacter saccharovorans was related to a reduction in 2-oxoarginine in plasma, which was subsequently correlated to a reduction in diastolic blood pressure. In conclusion, we applied a novel framework to elucidate on the complex and heterogenous FMT intervention, establishing a connection between engrafted microbiota and clinical outcome parameters. Our findings underscore the potential therapeutic efficacy of FMT in ameliorating MetSyn, demonstrating a potential contribution of microbial strain engraftment to the improvement of MetSyn via modulation of circulating metabolites.

Bridging the Mind and Gut: Uncovering the Intricacies of Neurotransmitters, Neuropeptides, and their Influence on Neuropsychiatric Disorders

BACKGROUND

The gut-brain axis (GBA) is a bidirectional signaling channel that facilitates communication between the gastrointestinal tract and the brain. Recent research on the gut-brain axis demonstrates that this connection enables the brain to influence gut function, which in turn influences the brain and its cognitive functioning. It is well established that malfunctioning of this axis adversely affects both systems' ability to operate effectively.

OBJECTIVE

Dysfunctions in the GBA have been associated with disorders of gut motility and permeability, intestinal inflammation, indigestion, constipation, diarrhea, IBS, and IBD, as well as neuropsychiatric and neurodegenerative disorders like depression, anxiety, schizophrenia, autism, Alzheimer's, and Parkinson's disease. Multiple research initiatives have shown that the gut microbiota, in particular, plays a crucial role in the GBA by participating in the regulation of a number of key neurochemicals that are known to have significant effects on the mental and physical well-being of an individual.

METHODS

Several studies have investigated the relationship between neuropsychiatric disorders and imbalances or disturbances in the metabolism of neurochemicals, often leading to concomitant gastrointestinal issues and modifications in gut flora composition. The interaction between neurological diseases and gut microbiota has been a focal point within this research. The novel therapeutic interventions in neuropsychiatric conditions involving interventions such as probiotics, prebiotics, and dietary modifications are outlined in this review.

RESULTS

The findings of multiple studies carried out on mice show that modulating and monitoring gut microbiota can help treat symptoms of such diseases, which raises the possibility of the use of probiotics, prebiotics, and even dietary changes as part of a new treatment strategy for neuropsychiatric disorders and their symptoms.

CONCLUSION

The bidirectional communication between the gut and the brain through the gut-brain axis has revealed profound implications for both gastrointestinal and neurological health. Malfunctions in this axis have been connected to a range of disorders affecting gut function as well as cognitive and neuropsychiatric well-being. The emerging understanding of the role of gut microbiota in regulating key neurochemicals opens up possibilities for novel treatment approaches for conditions like depression, anxiety, and neurodegenerative diseases.

The Characteristics, Mechanisms and Therapeutics: Exploring the Role of Gut Microbiota in Obesity

Presently, obesity has emerged as a significant global public health concern due to its escalating prevalence and incidence rates. The gut microbiota, being a crucial environmental factor, has emerged as a key player in the etiology of obesity. Nevertheless, the intricate and specific interactions between obesity and gut microbiota, along with the underlying mechanisms, remain incompletely understood. This review comprehensively summarizes the gut microbiota characteristics in obesity, the mechanisms by which it induces obesity, and explores targeted therapies centered on gut microbiota restoration.

Questioning the foundations of the gut microbiota and obesity

The role of the gut microbiota in determining body fatness has been a prominent area of research and has received significant public attention. Based largely on animal studies, recent attempts to translate these findings into interventions in humans have not been successful. This review will outline the key mouse research that initiated this area of study, examine whether those results warranted the initial enthusiasm and progress into human studies, and examine whether later follow-up research supported earlier conclusions. It will look at whether the absence of a gut microbiota protects germ-free mice from obesity, whether microbiota can transfer obesity into germ-free mice, the evidence for the role of immune system activation as a causal mechanism linking the gut microbiota to body weight, and consider the evidence for effects of individual bacterial species. Finally, it will examine the outcomes of randomized controlled trials of microbiota transfer in human participants that have not shown effects on body weight. With a more critical reading, early studies did not show as large an effect as first appeared and later research, including human trials, has failed to support a role of the gut microbiota in shaping body weight. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.

Implication of microbiota gut-brain axis in the manifestation of obsessive-compulsive disorder: Preclinical and clinical evidence

Recent research has highlighted the key role of gut microbiota in the development of psychiatric disorders. The adverse impact of stress, anxiety, and depression has been well documented on the commensal gut microflora. Thus, therapeutic benefits of gut microbiota-based interventions may not be avoided in central nervous system (CNS) disorders. In this review, we outline the current state of knowledge of gut microbiota with respect to obsessive-compulsive disorder (OCD). We discuss how OCD-generated changes corresponding to the key neurotransmitters, hypothalamic-pituitary-adrenal axis, and immunological and inflammatory pathways are connected with the modifications of the microbiota-gut-brain axis. Notably, administration of few probiotics such as Lactobacillus rhamnosus (ATCC 53103), Lactobacillus helveticus R0052, Bifidobacterium longum R0175, Saccharomyces boulardii, and Lactobacillus casei Shirota imparted positive effects in the management of OCD symptoms. Taken together, we suggest that the gut microbiota-directed therapeutics may open new treatment approaches for the management of OCD.

Gut-Brain Crosstalk and the Central Mechanisms of Orofacial Pain

Accumulated evidence has demonstrated that the gut microbiome can contribute to pain modulation through the microbiome-gut-brain axis. Various relevant microbiome metabolites in the gut are involved in the regulation of pain signaling in the central nervous system. In this review, we summarize recent advances in gut-brain interactions by which the microbiome metabolites modulate pain, with a focus on orofacial pain, and we further discuss the role of gut-brain crosstalk in the central mechanisms of orofacial pain whereby the gut microbiome modulates orofacial pain via the vagus nerve-mediated direct pathway and the gut metabolites/molecules-mediated indirect pathway. The direct and indirect pathways both contribute to the central regulation of orofacial pain through different brain structures (such as the nucleus tractus solitarius and the parabrachial nucleus) and signaling transmission across the blood-brain barrier, respectively. Understanding the gut microbiome-regulated pain mechanisms in the brain could help us to develop non-opioid novel therapies for orofacial pain.

The impact of the gut microbiome on tumor immunotherapy: from mechanism to application strategies

Immunotherapy is one of the fastest developing areas in the field of oncology. Many immunological treatment strategies for refractory tumors have been approved and marketed. Nevertheless, much clinical and preclinical experimental evidence has shown that the efficacy of immunotherapy in tumor treatment varies markedly among individuals. The commensal microbiome mainly colonizes the intestinal lumen in humans, is affected by a variety of factors and exhibits individual variation. Moreover, the gut is considered the largest immune organ of the body due to its influence on the immune system. In the last few decades, with the development of next-generation sequencing (NGS) techniques and in-depth research, the view that the gut microbiota intervenes in antitumor immunotherapy through the immune system has been gradually confirmed. Here, we review important studies published in recent years focusing on the influences of microbiota on immune system and the progression of malignancy. Furthermore, we discuss the mechanism by which microbiota affect tumor immunotherapy, including immune checkpoint blockade (ICB) and adoptive T-cell therapy (ACT), and strategies for modulating the microbial composition to facilitate the antitumor immune response. Finally, opportunity and some challenges are mentioned to enable a more systematic understanding of tumor treatment in the future and promote basic research and clinical application in related fields.

Acupuncture as multi-targeted therapy for the multifactorial disease obesity: a complex neuro-endocrine-immune interplay

The prevalence of obesity has reached pandemic dimensions. It is associated with multiple comorbidities and is becoming a clinical and public health threat. Obesity is a multifactorial disease with a complex pathophysiology and interplay of various systems. A strong interplay exists between the neuro-endocrine system, the immune system with systemic chronic low-grade inflammation, and microbiome dysbiosis that can lead to the development of obesity, which in turn can exacerbate each of these factors, hence creating a vicious cycle. The conventional treatment with lifestyle modifications such as diet, physical exercise, pharmacotherapy, and bariatric surgery does not always result in sufficient weight control thus paving the way for other strategies. As one such strategy, acupuncture is increasingly used worldwide to treat obesity. This narrative review outlines the evidence for this neuro-endocrine-immune interplay in the pathophysiology of obesity. Furthermore, the existing experimental and clinical evidence of acupuncture as a multi-targeted therapy for obesity is explained and future research perspectives are discussed.

Gut microbiome association with brain imaging markers, APOE genotype, calcium and vegetable intakes, and obesity in healthy aging adults

Introduction

Advanced age is a significant factor in changes to brain physiology and cognitive functions. Recent research has highlighted the critical role of the gut microbiome in modulating brain functions during aging, which can be influenced by various factors such as apolipoprotein E (APOE) genetic variance, body mass index (BMI), diabetes, and dietary intake. However, the associations between the gut microbiome and these factors, as well as brain structural, vascular, and metabolic imaging markers, have not been well explored.

Methods

We recruited 30 community dwelling older adults between age 55-85 in Kentucky. We collected the medical history from the electronic health record as well as the Dietary Screener Questionnaire. We performed APOE genotyping with an oral swab, gut microbiome analysis using metagenomics sequencing, and brain structural, vascular, and metabolic imaging using MRI.

Results

Individuals with APOE e2 and APOE e4 genotypes had distinct microbiota composition, and higher level of pro-inflammatory microbiota were associated higher BMI and diabetes. In contrast, calcium- and vegetable-rich diets were associated with microbiota that produced short chain fatty acids leading to an anti-inflammatory state. We also found that important gut microbial butyrate producers were correlated with the volume of the thalamus and corpus callosum, which are regions of the brain responsible for relaying and processing information. Additionally, putative proinflammatory species were negatively correlated with GABA production, an inhibitory neurotransmitter. Furthermore, we observed that the relative abundance of bacteria from the family Eggerthellaceae, equol producers, was correlated with white matter integrity in tracts connecting the brain regions related to language, memory, and learning.

Discussion

These findings highlight the importance of gut microbiome association with brain health in aging population and could have important implications aimed at optimizing healthy brain aging through precision prebiotic, probiotic or dietary interventions.

Overview of the Gut-Brain Axis: From Gut to Brain and Back Again

The gut-brain axis refers to a bidirectional communication pathway linking the gastrointestinal system to the central nervous system. The hardware of this multifaceted pathway takes many forms, at once structural (neurons, microglia, intestinal epithelial cell barrier), chemical (neurotransmitters, enteroendocrine hormones, bacterial metabolites), and cellular (immune signaling, inflammatory pathways). The gut-brain axis is exquisitely influenced by our environment, diet, and behaviors. Here, we will describe recent progress in understanding the gut-brain axis in neurological disease, using Parkinson's disease as a guide. We will see that each component of the gut-brain axis is heavily mediated by intestinal microbiota and learn how gut-brain communication can go awry in microbial dysbiosis.

Fecal microbiota transplantation in obesity metabolism: a META analysis and systematic review

OBJECTIVE

The effect of fecal microbiota transplantation (FMT) on microbiota engraftment in patients with metabolic syndrome remains unclear. This systematic review employed a meta-analysis of RCTs for assessment on the role of FMT in treating obesity and metabolic syndrome, and its impact on clinically relevant parameters.

METHOD

Major databases and grey literatures were searched identifying RCTs comparing FMT of lean donors with placebo in obese/metabolic syndrome patients. Studies using any form of placebo were included. Variations in the parameters before and after treatment were calculated followed by meta-analyses.

RESULT

Ten studies met the inclusion criteria and a total of 334 patients were included for further analysis. Clinically significant parameters associated with obesity and metabolic syndrome were explored and FMT was identified significantly and negatively associated with most indices of abdominal adiposity including caloric intake, fasting glucose, HOMA-IR, systolic blood pressure, diastolic blood pressure, total cholesterol, HDL, LDL, triglycerides and CRP, Obesity parameters including fasting glucose and acetic acid were increased following FMT.

CONCLUSION

FMT is more advantageous for obese patients with elevated blood pressure, disordered glucose and insulin metabolism, and elevated blood lipids. The study of metabolic factors in obese patients will be our starting point in the future.

Effects of Fructose and Palmitic Acid on Gene Expression in Drosophila melanogaster Larvae: Implications for Neurodegenerative Diseases

One of the largest health problems worldwide is the development of chronic noncommunicable diseases due to the consumption of hypercaloric diets. Among the most common alterations are cardiovascular diseases, and a high correlation between overnutrition and neurodegenerative diseases has also been found. The urgency in the study of specific damage to tissues such as the brain and intestine led us to use Drosophila melanogaster to study the metabolic effects caused by the consumption of fructose and palmitic acid in specific tissues. Thus, third instar larvae (96 ± 4 h) of the wild Canton-S strain of D. melanogaster were used to perform transcriptomic profiling in brain and midgut tissues to test for the potential metabolic effects of a diet supplemented with fructose and palmitic acid. Our data infer that this diet can alter the biosynthesis of proteins at the mRNA level that participate in the synthesis of amino acids, as well as fundamental enzymes for the dopaminergic and GABAergic systems in the midgut and brain. These also demonstrated alterations in the tissues of flies that may help explain the development of various reported human diseases associated with the consumption of fructose and palmitic acid in humans. These studies will not only help to better understand the mechanisms by which the consumption of these alimentary products is related to the development of neuronal diseases but may also contribute to the prevention of these conditions.

Microbiome–Metabolome Reveals the Contribution of the Gut–Testis Axis to Sperm Motility in Sheep (Ovis aries)

A close association exists among testicular function, gut microbiota regulation, and organismal metabolism. In this study, serum and seminal plasma metabolomes, and the rumen microbiome of sheep with significant differences in sperm viability, were explored. Serum and seminal plasma metabolomes differed significantly between high-motility (HM) and low-motility (LM) groups of sheep, and 39 differential metabolites closely related to sperm motility in sheep were found in seminal plasma metabolomes, while 35 were found in serum samples. A 16S rRNA sequence analysis showed that the relative abundance of HM and LM rumen microorganisms, such as Ruminococcus and Quinella, was significantly higher in the HM group, whereas genera such as Rikenellaceae_RC9_gut_group and Lactobacillus were enriched in the mid-LM group. Serum hormone assays revealed that serum follicle-stimulating hormone (FSH) and MT levels were significantly lower in the LM group than in the HM group, whereas serum glucocorticoid (GC) levels were higher in the LM group than in the HM group, and they all affected sperm motility in sheep. Ruminococcus and other rumen microorganisms were positively correlated with sperm motility, whereas Lactobacillus was negatively correlated with FSH and GCs levels. Our findings suggest that rumen microbial activity can influence the host metabolism and hormone levels associated with fertility in sheep.

Trust the gut: outcomes of gut microbiota transplant in metabolic and cognitive disorders

Type 2 diabetes mellitus (T2DM) is a main public health concern, with increasing prevalence and growingly premature onset in children, in spite of emerging and successful therapeutic options. T2DM promotes brain aging, and younger age at onset is associated with a higher risk of subsequent dementia. Preventive strategies should address predisposing conditions, like obesity and metabolic syndrome, and be started from very early and even prenatal life. Gut microbiota is an emerging target in obesity, diabetes and neurocognitive diseases, which could be safely modulated since pregnancy and infancy. Many correlative studies have supported its involvement in disease pathophysiology. Faecal material transplantation (FMT) studies have been conducted in clinical and preclinical settings to deliver cause-effect proof and mechanistic insights. This review provides a comprehensive overview of studies in which FMT was used to cure or cause obesity, metabolic syndrome, T2DM, cognitive decline and Alzheimer's disease, including the evidence available in early life. Findings were analysed to dissect consolidated from controversial results, highlighting gaps and possible future directions.

Regulation of body weight: Lessons learned from bariatric surgery

BACKGROUND

Bariatric or weight loss surgery is currently the most effective treatment for obesity and metabolic disease. Unlike dieting and pharmacology, its beneficial effects are sustained over decades in most patients, and mortality is among the lowest for major surgery. Because there are not nearly enough surgeons to implement bariatric surgery on a global scale, intensive research efforts have begun to identify its mechanisms of action on a molecular level in order to replace surgery with targeted behavioral or pharmacological treatments. To date, however, there is no consensus as to the critical mechanisms involved.

SCOPE OF REVIEW

The purpose of this non-systematic review is to evaluate the existing evidence for specific molecular and inter-organ signaling pathways that play major roles in bariatric surgery-induced weight loss and metabolic benefits, with a focus on Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), in both humans and rodents.

MAJOR CONCLUSIONS

Gut-brain communication and its brain targets of food intake control and energy balance regulation are complex and redundant. Although the relatively young science of bariatric surgery has generated a number of hypotheses, no clear and unique mechanism has yet emerged. It seems increasingly likely that the broad physiological and behavioral effects produced by bariatric surgery do not involve a single mechanism, but rather multiple signaling pathways. Besides a need to improve and better validate surgeries in animals, advanced techniques, including inducible, tissue-specific knockout models, and the use of humanized physiological traits will be necessary. State-of-the-art genetically-guided neural identification techniques should be used to more selectively manipulate function-specific pathways.

Liver-Gut-Interaction: Role of Microbiome Transplantation in the Future Treatment of Metabolic Disease

The association between shifts in gut microbiome composition and metabolic disorders is a well-recognized phenomenon. Clinical studies and experimental data suggest a causal relationship, making the gut microbiome an attractive therapeutic goal. Fecal microbiome transplantation (FMT) is a method to alter a person's microbiome composition. Although this method allowed for the establishment of proof of concept for using microbiome modulation to treat metabolic disorders, the method is not yet ready for broad application. It is a resource-intensive method that also carries some procedural risks and whose effects are not always reproducible. This review summarizes the current knowledge on FMT to treat metabolic diseases and gives an outlook on open research questions. Further research is undoubtedly required to find applications that are less resource-intensive, such as oral encapsulated formulations, and have strong and predictable results. Furthermore, a clear commitment from all stakeholders is necessary to move forward in the direction of developing live microbial agents, next-generation probiotics, and targeted dietary interventions.

The gut microbiota in obesity and weight management: microbes as friends or foe?

Obesity is caused by a long-term difference between energy intake and expenditure - an imbalance that is seemingly easily restored by increasing exercise and reducing caloric consumption. However, as simple as this solution appears, for many people, losing excess weight is difficult to achieve and even more difficult to maintain. The reason for this difficulty is that energy intake and expenditure, and by extension body weight, are regulated through complex hormonal, neural and metabolic mechanisms that are under the influence of many environmental factors and internal responses. Adding to this complexity, the microorganisms (microbes) that comprise the gut microbiota exert direct effects on the digestion, absorption and metabolism of food. Furthermore, the gut microbiota exerts a miscellany of protective, structural and metabolic effects both on the intestinal milieu and peripheral tissues, thus affecting body weight by modulating metabolism, appetite, bile acid metabolism, and the hormonal and immune systems. In this Review, we outline historical and recent advances in understanding how the gut microbiota is involved in regulating body weight homeostasis. We also discuss the opportunities, limitations and challenges of using gut microbiota-related approaches as a means to achieve and maintain a healthy body weight.

Gut Microbial-Derived Short Chain Fatty Acids: Impact on Adipose Tissue Physiology

Obesity is a global public health issue and major risk factor for pathological conditions, including type 2 diabetes, dyslipidemia, coronary artery disease, hepatic steatosis, and certain types of cancer. These metabolic complications result from a combination of genetics and environmental influences, thus contributing to impact whole-body homeostasis. Mechanistic animal and human studies have indicated that an altered gut microbiota can mediate the development of obesity, leading to inflammation beyond the intestine. Moreover, prior research suggests an interaction between gut microbiota and peripheral organs such as adipose tissue via different signaling pathways; yet, to what degree and in exactly what ways this inter-organ crosstalk modulates obesity remains elusive. This review emphasizes the influence of circulating gut-derived short chain fatty acids (SCFAs) i.e., acetate, propionate, and butyrate, on adipose tissue metabolism in the scope of obesity, with an emphasis on adipocyte physiology in vitro and in vivo. Furthermore, we discuss some of the well-established mechanisms via which microbial SCFAs exert a role as a prominent host energy source, hence regulating overall energy balance and health. Collectively, exploring the mechanisms via which SCFAs impact adipose tissue metabolism appears to be a promising avenue to improve metabolic conditions related to obesity.

Butyrate and hexanoate-enriched triglycerides increase postprandrial systemic butyrate and hexanoate in men with overweight/obesity: A double-blind placebo-controlled randomized crossover trial

Background

Short chain fatty acids (SCFA) are increasingly recognized for their potential ability to alleviate obesity-associated chronic low-grade inflammation and disturbed energy homeostasis. Evidence suggests that an increase in circulating SCFA might be necessary to induce beneficial alterations in energy metabolism.

Objective

To compare the bioaccessibility of two different SCFA-enriched triglycerides: Akovita SCT (butyrate and hexanoate esterified with long chain fatty acids) and tributyrin/caproin (solely butyrate and hexanoate) and investigate whether the SCFA from orally administrated Akovita SCT reach the circulation and affect postprandial metabolism in men with overweight/obesity.

Methods

The site, speed, and amount of SCFA release from Akovita SCT and tributyrin/caproin were assessed in a validated In vitro Model of the stomach and small intestine (TIM-1). Subsequently, a double-blind placebo-controlled randomized crossover study was conducted at Maastricht University with fourteen men with overweight/obesity (BMI 25-35 kg/m²) of which twelve men finished all testdays and were included for analysis. The participants received a liquid high fat mixed meal test containing either a low (650 mg), medium (1,325 mg), or high dose (2,000 mg) of Akovita SCT or a placebo (sunflower oil) in randomized order. Blood was sampled at baseline and after ingestion for 6 h for the primary outcome plasma butyrate and hexanoate concentration. Secondary outcomes included hydrogen breath, appetite, gastrointestinal complaints, circulating glucagon-like peptide 1, free fatty acids, glucose, triglycerides, insulin, and cytokines concentrations.

Results

In TIM-1, tributyrin/caproin was rapidly cleaved in the gastric compartment whereas the release of SCFA from Akovita SCT occurred predominantly in the small intestine. In vivo, all doses were well-tolerated. The medium dose increased (P < 0.05) and the high dose tended to increase (P < 0.10) postprandial circulating butyrate and both doses increased circulating hexanoate (P < 0.05) compared to placebo. Nevertheless, Akovita SCT supplementation did not affect any secondary outcomes compared to placebo.

Conclusion

Esterifying SCFA-enriched triglycerides with long chain fatty acids delayed SCFA release from the glycerol backbone. Akovita SCT increased postprandial circulating butyrate and hexanoate without changing metabolic parameters in men with overweight/obesity. Future randomized clinical trials should investigate whether long-term Akovita SCT supplementation can aid in the treatment or prevention of metabolic disorders.

Clinical trial registration

www.ClinicalTrials.gov, identifier: NCT04662411.

Alterations in glycine metabolism in obesity and chronic metabolic diseases - an update on new advances

PURPOSE OF REVIEW

The metabolic signature associated with obesity is characterized by a decrease in plasma glycine concentration, a feature closely associated with insulin resistance and highly predictive of the risk of developing chronic metabolic diseases. This review presents recent advances in understanding the causes of decreased glycine availability and in targeting strategies to replenish the glycine pool and especially to improve insulin resistance.

RECENT RESULTS

Recent literature has made progress in understanding host and gut microbiota mechanisms in determining circulating glycine levels. It has also explored new clinical pathways to restore circulating glycine levels and insulin resistance in obesity-related metabolic diseases.

SUMMARY

Recent findings suggest that glycine metabolism must now be considered in close interaction with branched-chain amino acid (BCAA) metabolism. Thus, strategies that decrease BCAAs seem to be the best to restore glycine. Furthermore, recent literature has confirmed that lifestyle strategies aimed at inducing weight loss are effective in replenishing the glycine pool. It also confirms that correcting the dysbiosis of the gut microbiota associated with obesity may be a valuable means of achieving this goal. However, it remains unclear whether dietary glycine is an effective strategy for correcting cardiometabolic disorders in obesity.

Immunology and microbiome: Implications for motor systems

Immune-inflammatory mechanisms seem to play a relevant role in neurodegenerative disorders affecting motor systems, particularly Parkinson's disease, where activity changes in inflammatory cells and evidence of neuroinflammation in experimental models and patients is available. Amyotrophic lateral sclerosis is also characterized by neuroinflammatory changes that involve primarily glial cells, both microglia and astrocytes, as well as systemic immune dysregulation associated with more rapid progression. Similarly, the exploration of gut dysbiosis in these two prototypical neurodegenerative motor disorders is advancing rapidly. Altered composition of gut microbial constituents and related metabolic and putative functional pathways is supporting a pathophysiological link that is currently explored in preclinical, germ-free animal models. Less compelling, but still intriguing, evidence suggests that motor neurodevelopmental disorders, e.g., Tourette syndrome, are associated with abnormal trajectories of maturation that include also immune system development. Microglia has a key role also in these disorders, and new therapeutic avenues aiming at its modulation are exciting prospects. Preclinical and clinical research on the role of gut dysbiosis in Tourette syndrome and related behavioral disorders is still in its infancy, but early findings support the rationale to delve deeper into its contribution to neural and immune maturation abnormalities in its spectrum.

Fecal microbiota transplantation in non-communicable diseases: Recent advances and protocols

Fecal microbiota transplant (FMT) is a therapeutic method that aims to restore normal gut microbial composition in recipients. Currently, FMT is approved in the USA to treat recurrent and refractory Clostridioides difficile infection and has been shown to have great efficacy. As such, significant research has been directed toward understanding the potential role of FMT in other conditions associated with gut microbiota dysbiosis such as obesity, type 2 diabetes mellitus, metabolic syndrome, neuropsychiatric disorders, inflammatory bowel disease, irritable bowel syndrome, decompensated cirrhosis, cancers and graft-versus-host disease. This review examines current updates and efficacy of FMT in treating conditions other than Clostridioides difficile infection. Further, protocols for administration of FMT are also discussed including storage of fecal samples in stool banks, inclusion/exclusion criteria for donors, fecal sample preparation and methods of treatment administration. Overall, understanding the mechanisms by which FMT can manipulate gut microbiota to provide therapeutic benefit as well as identifying potential adverse effects is an important step in clarifying its long-term safety and efficacy in treating multiple conditions in the future.

Emerging insights between gut microbiome dysbiosis and Parkinson's disease: Pathogenic and clinical relevance

Parkinson's disease (PD) is a complicated neurodegenerative disease, of which gastrointestinal disturbance appears prior to motor symptoms. Numerous studies have shed light on the roles of gastrointestinal tract and its neural connection to brain in PD pathology. In the past decades, the fields of microbiology and neuroscience have become ever more entwined. The emergence of gut microbiome has been considered as one of the key regulators of gut-brain function. With the advent of multi-omics sequencing techniques, gut microbiome of PD patients has been shown unique characteristics. The resident gut microbiota can exert considerable effects in PD and there are suggestions of a link between gut microbiome dysbiosis and PD progression. In this review, we summarize the latest progresses of gut microbiome dysbiosis in PD pathogenesis, further highlight the clinical relevance of gut microbiota and its metabolites in both the non-motor and motor symptoms of PD. Furthermore, we draw attention to the complex interplay between gut microbiota and PD drugs, with the purpose of improving drug efficacy and prescription accordingly. Further studies at specific strain level and longitudinal prospective clinical trials using optimized methods are still needed for the development of diagnostic markers and novel therapeutic regimens for PD.

Fecal microbiota transplantation treatment of autoimmune-mediated type 1 diabetes: A systematic review

There is a strong link between fecal microbiota and the development of type 1 diabetes. As an emerging therapeutic modality, fecal microbiota transplantation has been shown to be safe and effective in the treatment of many intestinal and extraintestinal diseases. Various studies have found that fecal microbiota transplantation can treat diseases by correcting patients' immune disorders. Besides, many studies have found that fecal microbiota transplantation can improve glycemic control and insulin resistance in diabetic patients. Therefore, this paper reviews the mechanism of action of fecal microbiota transplantation on autoimmune-mediated T1DM and the current research progress, feasibility, and issues that need to be addressed in the future development of fecal microbiota transplantation in the treatment of autoimmune-mediated T1DM.

Protective role of butyrate in obesity and diabetes: New insights

Studies in human microbiota dysbiosis have shown that short-chain fatty acids (SCFAs) like propionate, acetate, and particularly butyrate, positively affect energy homeostasis, behavior, and inflammation. This positive effect can be demonstrated in the reduction of butyrate-producing bacteria observed in the gut microbiota of individuals with type 2 diabetes (T2DM) and other energy-associated metabolic alterations. Butyrate is the major end product of dietary fiber bacterial fermentation in the large intestine and serves as the primary energy source for colonocytes. In addition, it plays a key role in reducing glycemia and improving body weight control and insulin sensitivity. The major mechanisms involved in butyrate regulation include key signaling pathways such as AMPK, p38, HDAC inhibition, and cAMP production/signaling. Treatment strategies using butyrate aim to increase its intestine levels, bioavailability, and improvement in delivery either through direct supplementation or by increasing dietary fiber in the diet, which ultimately generates a higher production of butyrate in the gut. In the final part of this review, we present a summary of the most relevant studies currently being carried out in humans.

Diet-Related Changes of Short-Chain Fatty Acids in Blood and Feces in Obesity and Metabolic Syndrome

Obesity-related illnesses are one of the leading causes of death worldwide. Metabolic syndrome has been associated with numerous health issues. Short-chain fatty acids (SCFAs) have been shown to have multiple effects throughout the body, both directly as well as through specific G protein-coupled receptors. The main SCFAs produced by the gut microbiota are acetate, propionate, and butyrate, which are absorbed in varying degrees from the large intestine, with some acting mainly locally and others systemically. Diet has the potential to influence the gut microbial composition, as well as the type and amount of SCFAs produced. High fiber-containing foods and supplements increase the production of SCFAs and SCFA-producing bacteria in the gut and have been shown to have bodyweight-lowering effects. Dietary supplements, which increase SCFA production, could open the way for novel approaches to weight loss interventions. The aim of this review is to analyze the variations of fecal and blood SCFAs in obesity and metabolic syndrome through a systematic search and analysis of existing literature.

Butyrate to combat obesity and obesity-associated metabolic disorders: Current status and future implications for therapeutic use

Evidence is increasing that disturbances in the gut microbiome may play a significant role in the etiology of obesity and type 2 diabetes. The short chain fatty acid butyrate, a major end product of the bacterial fermentation of indigestible carbohydrates, is reputed to have anti-inflammatory properties and positive effects on body weight control and insulin sensitivity. However, whether butyrate has therapeutic potential for the treatment and prevention of obesity and obesity-related complications remains to be elucidated. Overall, animal studies strongly indicate that butyrate administered via various routes (e.g., orally) positively affects adipose tissue metabolism and functioning, energy and substrate metabolism, systemic and tissue-specific inflammation, and insulin sensitivity and body weight control. A limited number of human studies demonstrated interindividual differences in clinical effectiveness suggesting that outcomes may depend on the metabolic, microbial, and lifestyle-related characteristics of the target population. Hence, despite abundant evidence from animal data, support of human data is urgently required for the implementation of evidence-based oral and gut-derived butyrate interventions. To increase the efficacy of butyrate-focused interventions, future research should investigate which factors impact treatment outcomes including baseline gut microbial activity and functionality, thereby optimizing targeted-interventions and identifying individuals that merit most from such interventions.