Bacteroides uniformis CECT 7771 Modulates the Brain Reward Response to Reduce Binge Eating and Anxiety-Like Behavior in Rat

Behavioural and physiological effects of binge eating: A systematic review and meta-analysis of animal models

Binge eating is defined as eating abnormally large amounts in a brief period of time. Many animal studies have examined the behavioural and physiological effects of binge eating of high-fat, high-sugar foods to model the consequences of human binge eating. The present systematic review of 199 rodent studies sought to identify the behavioural and physiological consequences of binge eating and determine whether changes were specific to binge eating or to general effects of exposure to a palatable diet. A meta-analysis of 18 rodent studies revealed that binge eating produces greater anxiety-like behaviour on the Elevated Plus-Maze with a small effect size and significant funnel plot asymmetry, suggesting that the true effect size is overestimated. A history of binge-like access generally increases progressive ratio breakpoint for the binged food, without altering 'liking' as measured by lick microstructure, suggesting that dissociable effects on 'wanting' but not 'liking' accompany binge eating behaviour and contribute to its persistence. Binge eating appears to enhance compulsive food-seeking behaviour and prevent stress-induced reductions in intake but does not appear to alter depression-like behaviour or locomotor activity. Notably, binge eating may produce comparable metabolic impairments to those observed after extended continuous exposure to a palatable diet despite no overall effects on body weight outcomes in most studies.

Serotonin signaling to regulate energy metabolism: a gut microbiota perspective

Serotonin is one of the most potent gastrointestinal, peripheral, and neuronal signaling molecules and plays a key role in regulating energy metabolism. Accumulating evidence has shown the complex interplay between gut microbiota and host energy metabolism. In this review, we summarize recent findings on the role of gut microbiota in serotonin metabolism and discuss the complicated mechanisms by which serotonin, working in conjunction with the gut microbiota, affects total body energy metabolism in the host. Gut microbiota affects serotonin synthesis, storage, release, transport, and catabolism. In addition, serotonin plays an indispensable role in regulating host energy homeostasis through organ crosstalk and microbe-host communication, particularly with a wide array of serotonergic effects mediated by diverse serotonin receptors with unique tissue specificity. This fresh perspective will help broaden the understanding of serotonergic signaling in modulating energy metabolism, thus shedding light on the design of innovative serotonin-targeting strategies to treat metabolic diseases.

Gut microbiota-related neuroinflammation at the crossroad of food reward alterations: implications for eating disorders

The link between gut microbiome and eating behaviours, especially palatable food intake, is a growing focus of scientific investigation. The complex ecosystem of microorganisms in the gut influences host metabolism, immune function and neurobehavioural signalling. This review explores the role of neuroinflammation in dysregulations of food-induced reward signalling and the potential causal role of the gut microbiota on these proinflammatory processes. Particular attention is given to eating disorders (ED, specifically anorexia nervosa, binge eating disorder and bulimia nervosa) and potential links with the gut microbiota, food reward alterations and neuroinflammation. Finally, we propose gut microbiota modulation as a promising therapeutic strategy in food reward alterations and ED.

Bifidobacterium longum CECT 30763 improves depressive- and anxiety-like behavior in a social defeat mouse model through the immune and dopaminergic systems

Adolescence is a crucial period marked by profound changes in the brain. Exposure to psychological stressors such as bullying, abuse or maltreatment during this developmental period may increase the risk of developing depression, anxiety and comorbid cardiometabolic conditions. Chronic psychological stress is associated with behavioral changes and disruption of the hypothalamic-pituitary-adrenal axis, leading to corticosterone overproduction in rodents and changes in both the immune system and the gut microbiome. Here, we demonstrate the ability of Bifidobacterium longum CECT 30763 (B. longum) to ameliorate adolescent depressive and anxiety-like behaviors in a chronic social defeat (CSD) mouse model. The mechanisms underlying this beneficial effect are related to the ability of B. longum to attenuate the inflammation and immune cell changes induced by CSD after the initial stress exposure through the induction of T regulatory cells with enduring effects that may prevent and mitigate the adverse consequences of repeated stress exposure on mental and cardiometabolic health. B. longum administration also normalized dopamine release, metabolism and signaling at the end of the intervention, which may secondarily contribute to the reversal of behavioral changes. The anti-inflammatory effects of B. longum could also explain its cardioprotective effects, which were reflected in an amelioration of the oxidative stress-induced damage in the heart and improved lipid metabolism in the liver. Overall, our findings suggest that B. longum regulates the links between the immune and dopaminergic systems from the gut to the brain, potentially underpinning its beneficial psychobiotic and physiological effects in CSD.

IUPHAR review: Eating disorders, gut microbiota dysbiosis and epigenetic aberrations

Eating disorders (EDs) are a heterogeneous class of increasing mental disorders that are characterized by disturbances in eating behaviors, body weight regulation, and associated psychological dysfunctions. These disorders create physiological imbalances that alter the diversity and composition of the gut microbiota. While evidence suggests that EDs can arise from epigenetic aberrations, alterations in gut microbial communities may also contribute to the development and/or persistence of EDs through epigenetic mechanisms. Understanding the interplay among gut microbial communities, epigenetic processes, and the risk of EDs provides opportunities for designing preventive and/or therapeutic interventions through gut microbiome modulation. This review highlights how microbiome-based therapeutics and specific dietary interventions can contribute to improving various subtypes of EDs by modulating gut microbial communities and mitigating epigenetic aberrations. First, we briefly review the literature on links between epigenetic aberrations and the pathophysiology of EDs. Second, we examine the potential role of the gut microbiome in the pathogenesis of EDs through epigenetic mechanisms. Next, we explore the associations between EDs and other psychiatric disorders, and examine the potential roles of the microbiome in their pathogenesis. Finally, we present evidence supporting the potential of microbiome-based therapeutics and specific dietary interventions to improve EDs through epigenetic modifications.

Gut Microbiota Regulates Food Intake in a Rodent Model of Intermittent Limited Access to Palatable Food

OBJECTIVE

Binge-eating disorder is characterized by recurrent episodes of consumption of large amounts of food within a short period of time, without compensatory purging behaviors. This disease is a major public health issue and is associated with numerous comorbidities, encompassing anxiety and depression. The gut microbiota has been proposed to be an important player in the onset or maintenance of eating disorders. Here, we aim to better delineate the potential role of the gut microbiota in binge-eating disorder.

METHOD

We used a model of intermittent limited access to palatable food where eight-week-old C57Bl/6 female mice had access during 2 h, every 2 days over a 10-day period, to a high-fat/high-sucrose diet. Half of the animals received antibiotics to deplete their gut microbiota. Eating behavior and other behavioral parameters were compared between groups.

RESULTS

We observed an increase in food intake as well as tachyphagia during the intermittent access to high-fat/high-sucrose diet. We demonstrate that gut microbiota depletion further increases food intake during these episodes and promotes binge-eating behavior. No impact on anxiety or depressive-like behavior was observed in animals.

DISCUSSION

These results show that the gut microbiota is involved in the control of food intake during episodes of binge-eating. This strengthens the potential role of the gut bacteria in binge-eating disorder and the interest in therapeutic strategies aiming at modulating the patients' gut microbiota to treat this eating disorder.

Anxiety-like behavior during protracted morphine withdrawal is driven by gut microbial dysbiosis and attenuated with probiotic treatment

The development of anxiety during protracted opioid withdrawal heightens the risk of relapse into the cycle of addiction. Understanding the mechanisms driving anxiety during opioid withdrawal could facilitate the development of therapeutics to prevent negative affect and promote continued abstinence. Our lab has previously established the gut microbiome as a driver of various side effects of opioid use, including analgesic tolerance and somatic withdrawal symptoms. We therefore hypothesized that the gut microbiome contributes to the development of anxiety-like behavior during protracted opioid withdrawal. In this study, we first established a mouse model of protracted morphine withdrawal, characterized by anxiety-like behavior and gut microbial dysbiosis. Next, we used fecal microbiota transplantation (FMT) to show that gut dysbiosis alone is sufficient to induce anxiety-like behavior. We further demonstrate that probiotic therapy during morphine withdrawal attenuates the onset of anxiety-like behavior, highlighting its therapeutic potential. Lastly, we examined transcriptional changes in the amygdala of morphine-withdrawn mice treated with probiotics to explore mechanisms by which the gut-brain axis mediates anxiety-like behavior. Our results support the use of probiotics as a promising therapeutic strategy to prevent gut dysbiosis and associated anxiety during opioid withdrawal, with potential implications for improving treatment outcomes in opioid recovery programs.

Probiotics and eating disorders: a systematic review of humans and animal model studies

BACKGROUND

Eating disorders are complex mental health conditions that significantly impact physical and mental well-being. Current research suggests a potential link between eating disorders and the gut microbiota, highlighting the role of gut-brain communication and its influence on nutrient absorption. Probiotics, which are beneficial bacteria, have shown promise in modulating the gut microbiota and may offer complementary interventions in the treatment of eating disorders.

METHODS

A comprehensive search was conducted in electronic databases, including PubMed/Medline, Scopus, and Web of Science, from inception to January 2024 to analyze the existing literature on the effects of probiotic supplementation in eating disorders. The search strategy included terms related to probiotics, prebiotics, eating disorders, and food addiction. The human studies were assessed for risk of bias using the Cochrane tool. The quality of animal studies was evaluated using the risk of bias (RoB) tool from the Systematic Review Centre for Laboratory Animal Experimentation.

RESULTS

Of the 417 papers, 12 eligible studies were included comprising five animal and seven clinical studies. Clinical trials ranged from 10 to 20 weeks and were randomized and parallel-arm design. The included studies varied in terms of sample characteristics, intervention types, and outcome measures. Preliminary findings suggest that probiotics may influence gut microbiota composition and may offer support in the treatment of eating disorders.

CONCLUSIONS

The reviewed studies showed that probiotic supplementation may have a role in reducing food addiction and binge eating, and enhancing satiety, regulating food intake as well as positively affecting mood. However, further studies with better quality and larger sample size are needed to further validate these findings.

TLR4-dependent neuroinflammation mediates LPS-driven food-reward alterations during high-fat exposure

BACKGROUND

Obesity has become a global pandemic, marked by significant shifts in both the homeostatic and hedonic/reward aspects of food consumption. While the precise causes are still under investigation, recent studies have identified the role of gut microbes in dysregulating the reward system within the context of obesity. Unravelling these gut-brain connections is crucial for developing effective interventions against eating and metabolic disorders, particularly in the context of obesity. This study explores the causal role of LPS, as a key relay of microbiota component-induced neuroinflammation in the dysregulation of the reward system following exposure to high-fat diet (HFD).

METHODS

Through a series of behavioural paradigms related to food-reward events and the use of pharmacological agents targeting the dopamine circuit, we investigated the mechanisms associated with the development of reward dysregulation during HFD-feeding in male mice. A Toll-like receptor 4 (TLR4) full knockout model and intraventricular lipopolysaccharide (LPS) diffusion at low doses, which mimics the obesity-associated neuroinflammatory phenotype, were used to investigate the causal roles of gut microbiota-derived components in neuroinflammation and reward dysregulation.

RESULTS

Our study revealed that short term exposure to HFD (24 h) tended to affect food-seeking behaviour, and this effect became significant after 1 week of HFD. Moreover, we found that deletion of TLR4 induced a partial protection against HFD-induced neuroinflammation and reward dysregulation. Finally, chronic brain diffusion of LPS recapitulated, at least in part, HFD-induced molecular and behavioural dysfunctions within the reward system.

CONCLUSIONS

These findings highlight a link between the neuroinflammatory processes triggered by the gut microbiota components LPS and the dysregulation of the reward system during HFD-induced obesity through the TLR4 pathway, thus paving the way for future therapeutic approaches.

Bacteroides uniformis ameliorates pro-inflammatory diet-exacerbated colitis by targeting endoplasmic reticulum stress-mediated ferroptosis

INTRODUCTION

A pro-inflammatory diet is positively associated with the risk and progression of inflammatory bowel diseases (IBD). Recently, ferroptosis has been observed in patients with different dietary patterns-associated intestinal inflammation, while the mechanisms underlying the effects of a pro-inflammatory diet and whether it mediates ferroptosis are unknown.

OBJECTIVES

This study aims to elucidate the mechanisms underlying pro-inflammatory diet-mediated colitis and explore potential intervention strategies.

METHODS

Mice were fed a dietary inflammatory index-based pro-inflammatory diet for 12 weeks. Subsequently, colitis was chemically induced using 2.5 % dextran sulfate sodium. The body weight, pathological score, immune response and mucosal barrier function were evaluated to assess intestinal inflammation. Intestine tissue transcriptomics, fecal microbiome analysis and serum metabolomics were applied to identify diet-microbe-host interactions. Additionally, the dietary inflammatory index (DII) scores and intestinal specimens of 32 patients with Crohn's disease were evaluated. The biological functions of Bacteroides uniformis were observed in vitro and in vivo.

RESULTS

Pro-inflammatory diet induces low-grade intestinal inflammation in mice and exacerbates colitis by activating glutathione peroxidase 4-associated ferroptosis in the endoplasmic reticulum stress-mediated pathway. These effects are reversed by ferrostatin-1 treatment. Additionally, the pro-inflammatory diet triggers colitis by modulating the gut microbiota and metabolites. Notably, supplementation with B. uniformis improves the pro-inflammatory diet-aggravated colitis by inhibiting endoplasmic reticulum stress-mediated ferroptosis. Moreover, B. uniformis is non-enterotoxigenic and non-enteroinvasive in co-cultures with intestinal epithelial cells.

CONCLUSIONS

Pro-inflammatory diet drives colitis by targeting endoplasmic reticulum stress-mediated ferroptosis, possibly in a gut microbiota-dependent manner. Pro-inflammatory diet restriction and microbial-based therapies may be effective strategies for preventing and treating IBD.

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.

Gut microbiota signatures of vulnerability to food addiction in mice and humans

OBJECTIVE

Food addiction is a multifactorial disorder characterised by a loss of control over food intake that may promote obesity and alter gut microbiota composition. We have investigated the potential involvement of the gut microbiota in the mechanisms underlying food addiction.

DESIGN

We used the Yale Food Addiction Scale (YFAS) 2.0 criteria to classify extreme food addiction in mouse and human subpopulations to identify gut microbiota signatures associated with vulnerability to this disorder.

RESULTS

Both animal and human cohorts showed important similarities in the gut microbiota signatures linked to food addiction. The signatures suggested possible non-beneficial effects of bacteria belonging to the Proteobacteria phylum and potential protective effects of Actinobacteria against the development of food addiction in both cohorts of humans and mice. A decreased relative abundance of the species Blautia wexlerae was observed in addicted humans and of Blautia genus in addicted mice. Administration of the non-digestible carbohydrates, lactulose and rhamnose, known to favour Blautia growth, led to increased relative abundance of Blautia in mice faeces in parallel with dramatic improvements in food addiction. A similar improvement was revealed after oral administration of Blautia wexlerae as a beneficial microbe.

CONCLUSION

By understanding the crosstalk between this behavioural alteration and gut microbiota, these findings constitute a step forward to future treatments for food addiction and related eating disorders.

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.

Dietary fiber induces a fat preference associated with the gut microbiota

Eating behavior is essential to human health. However, whether future eating behavior is subjected to the conditioning of preceding dietary composition is unknown. This study aimed to investigate the effect of dietary fiber consumption on subsequent nutrient-specific food preferences between palatable high-fat and high-sugar diets and explore its correlation with the gut microbiota. C57BL/6NJcl male mice were subjected to a 2-week dietary intervention and fed either a control (n = 6) or inulin (n = 6) diet. Afterward, all mice were subjected to a 3-day eating behavioral test to self-select from the simultaneously presented high-fat and high-sugar diets. The test diet feed intakes were recorded, and the mice's fecal samples were analyzed to evaluate the gut microbiota composition. The inulin-conditioned mice exhibited a preference for the high-fat diet over the high-sugar diet, associated with distinct gut microbiota composition profiles between the inulin-conditioned and control mice. The gut microbiota Oscillospiraceae sp., Bacteroides acidifaciens, and Clostridiales sp. positively correlated with a preference for fat. Further studies with fecal microbiota transplantation and eating behavior-related neurotransmitter analyses are warranted to establish the causal role of gut microbiota on host food preferences. Food preferences induced by dietary intervention are a novel observation, and the gut microbiome may be associated with this preference.

Sexual dimorphism in neurobehavioural phenotype and gut microbial composition upon long-term exposure to structural analogues of bisphenol-A

Bisphenol S (BPS) and Bisphenol F (BPF), the analogues of the legacy endocrine disrupting chemical, Bisphenol A (BPA) are ubiquitous in the environment and present in various consumer goods, and potentially neurotoxic. Here, we studied sex-specific responses of bisphenols on behavioural phenotypes, including their association with pro-inflammatory biomarkers and altered neurotransmitters levels, and the key gut microbial abundances. Neurobehavioural changes, using standard test battery, biochemical and molecular estimations for inflammatory cytokines, neurotransmitters, and oxido-nitrosative stress markers, gene expression analysis using qRT-PCR, H&E based histological investigations, gut permeability assays and Oxford Nanopore-based 16S-rRNA metagenomics sequencing for the gut microbial abundance estimations were performed. Bisphenol(s) exposure induces anxiety and depression-like behaviours, particularly in the male mice, with heightened pro-inflammatory cytokines levels and systemic endotoxemia, altered monoamine neurotransmitters levels/turnovers and hippocampal neuronal degeneration and inflammatory responses in the brain. They also increased gut permeability and altered microbial diversity, particularly in males. Present study provides evidence for sex-specific discrepancies in neurobehavioural phenotypes and gut microbiota, which necessitate a nuanced understanding of sex-dependent responses to bisphenols. The study contributes to ongoing discussions on the multifaceted implications of bisphenols exposure and underscores the need for tailored regulatory measures to mitigate potential health risks associated with them.

Bacteroides uniformis CECT 7771 requires adaptive immunity to improve glucose tolerance but not to prevent body weight gain in diet-induced obese mice

BACKGROUND

The metabolic disturbances of obesity can be mitigated by strategies modulating the gut microbiota. In this study, we sought to identify whether innate or adaptive immunity mediates the beneficial metabolic effects of the human intestinal bacterium Bacteroides uniformis CECT 7771 in obesity.

METHODS

We evaluated the effects of orally administered B. uniformis on energy homeostasis, intestinal immunity, hormone levels, and gut microbiota in wild-type and Rag1-deficient mice with diet-induced obesity. We also assessed whether B. uniformis needed to be viable to exert its beneficial effects in obesity and to directly induce immunoregulatory effects.

RESULTS

The administration of B. uniformis to obese mice improved glucose tolerance and insulin secretion, restored the caloric intake suppression after an oral glucose challenge, and reduced hyperglycemia. The pre- and post-prandial glucose-related benefits were associated with restoration of the anti-inflammatory tone mediated by type 2 macrophages and regulatory T cells (Tregs) in the lamina propria of the small intestine. Contrastingly, B. uniformis administration failed to improve glucose tolerance in obese Rag1-/- mice, but prevented the increased body weight gain and adiposity. Overall, the beneficial effects seemed to be independent of enteroendocrine effects and of major changes in gut microbiota composition. B. uniformis directly induced Tregs generation from naïve CD4+ T cells in vitro and was not required to be viable to improve glucose homeostasis but its viability was necessary to prevent body weight gain in diet-induced obese wild-type mice.

CONCLUSIONS

Here we demonstrate that B. uniformis modulates the energy homeostasis in diet-induced obese mice through different mechanisms. The bacterium improves oral glucose tolerance by adaptive immunity-dependent mechanisms that do not require cell viability and prevents body weight gain by adaptive immunity-independent mechanisms which require cell viability. Video Abstract.

Black rice diet alleviates colorectal cancer development through modulating tryptophan metabolism and activating AHR pathway

Consumption of dietary fiber and anthocyanin has been linked to a lower incidence of colorectal cancer (CRC). This study scrutinizes the potential antitumorigenic attributes of a black rice diet (BRD), abundantly rich in dietary fiber and anthocyanin. Our results demonstrate notable antitumorigenic effects in mice on BRD, indicated by a reduction in both the size and number of intestinal tumors and a consequent extension in life span, compared to control diet-fed counterparts. Furthermore, fecal transplants from BRD-fed mice to germ-free mice led to a decrease in colonic cell proliferation, coupled with maintained integrity of the intestinal barrier. The BRD was associated with significant shifts in gut microbiota composition, specifically an augmentation in probiotic strains Bacteroides uniformis and Lactobacillus. Noteworthy changes in gut metabolites were also documented, including the upregulation of indole-3-lactic acid and indole. These metabolites have been identified to stimulate the intestinal aryl hydrocarbon receptor pathway, inhibiting CRC cell proliferation and colorectal tumorigenesis. In summary, these findings propose that a BRD may modulate the progression of intestinal tumors by fostering protective gut microbiota and metabolite profiles. The study accentuates the potential health advantages of whole-grain foods, emphasizing the potential utility of black rice in promoting health.

Fecal microbial marker panel for aiding diagnosis of autism spectrum disorders

Accumulating evidence suggests that gut microbiota alterations influence brain function and could serve as diagnostic biomarkers and therapeutic targets. The potential of using fecal microbiota signatures to aid autism spectrum disorder (ASD) detection is still not fully explored. Here, we assessed the potential of different levels of microbial markers (taxonomy and genome) in distinguishing children with ASD from age and gender-matched typically developing peers (n = 598, ASD vs TD = 273 vs 325). A combined microbial taxa and metagenome-assembled genome (MAG) markers showed a better performance than either microbial taxa or microbial MAGs alone for detecting ASD. A machine-learning model comprising 5 bacterial taxa and 44 microbial MAG markers (2 viral MAGs and 42 bacterial MAGs) achieved an area under the receiving operator curve (AUROC) of 0.886 in the discovery cohort and 0.734 in an independent validation cohort. Furthermore, the identified biomarkers and predicted ASD risk score also significantly correlated with the core symptoms measured by the Social Responsiveness Scale-2 (SRS-2). The microbiome panel showed a superior classification performance in younger children (≤6 years old) with an AUROC of 0.845 than older children (>6 years). The model was broadly applicable to subjects across genders, with or without gastrointestinal tract symptoms (constipation and diarrhea) and with or without psychiatric comorbidities (attention deficit and hyperactivity disorder and anxiety). This study highlights the potential clinical validity of fecal microbiome to aid in ASD diagnosis and will facilitate studies to understand the association of disturbance of human gut microbiota and ASD symptom severity.

Direct and Indirect Evidence of Effects of Bacteroides spp. on Obesity and Inflammation

Metabolic disorders present a significant public health challenge globally. The intricate relationship between the gut microbiome, particularly Bacteroides spp. (BAC), and obesity, including their specific metabolic functions, remains partly unresolved. This review consolidates current research on BAC's role in obesity and lipid metabolism, with three objectives: (1) To summarize the gut microbiota's impact on obesity; (2) To assess BAC's efficacy in obesity intervention; (3) To explore BAC's mechanisms in obesity and lipid metabolism management. This review critically examines the role of BAC in obesity, integrating findings from clinical and preclinical studies. We highlight the changes in BAC diversity and concentration following successful obesity treatment and discuss the notable differences in BAC characteristics among individuals with varying obesity levels. Furthermore, we review recent preclinical studies demonstrating the potential of BAC in ameliorating obesity and related inflammatory conditions, providing detailed insights into the methodologies of these in vivo experiments. Additionally, certain BAC-derived metabolites have been shown to be involved in the regulation of host lipid metabolism-related pathways. The enhanced TNF production by dendritic cells following BAC administration, in response to LPS, also positions BAC as a potential adjunctive therapy in obesity management.

Gut microbiota aggravates neutrophil extracellular traps-induced pancreatic injury in hypertriglyceridemic pancreatitis

Hypertriglyceridemic pancreatitis (HTGP) is featured by higher incidence of complications and poor clinical outcomes. Gut microbiota dysbiosis is associated with pancreatic injury in HTGP and the mechanism remains unclear. Here, we observe lower diversity of gut microbiota and absence of beneficial bacteria in HTGP patients. In a fecal microbiota transplantation mouse model, the colonization of gut microbiota from HTGP patients recruits neutrophils and increases neutrophil extracellular traps (NETs) formation that exacerbates pancreatic injury and systemic inflammation. We find that decreased abundance of Bacteroides uniformis in gut microbiota impairs taurine production and increases IL-17 release in colon that triggers NETs formation. Moreover, Bacteroides uniformis or taurine inhibits the activation of NF-κB and IL-17 signaling pathways in neutrophils which harness NETs and alleviate pancreatic injury. Our findings establish roles of endogenous Bacteroides uniformis-derived metabolic and inflammatory products on suppressing NETs release, which provides potential insights of ameliorating HTGP through gut microbiota modulation.

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.

The gut-brain axis mediates bacterial driven modulation of reward signaling

OBJECTIVE

Our goal is to investigate if microbiota composition modulates reward signaling and assess the role of the vagus in mediating microbiota to brain communication.

METHODS

Male germ-free Fisher rats were colonized with gastrointestinal contents from chow (low fat (LF) ConvLF) or HF (ConvHF) fed rats.

RESULTS

Following colonization, ConvHF rats consumed significantly more food than ConvLF animals. ConvHF rats displayed lower feeding-induced extracellular DOPAC levels (a metabolite of dopamine) in the Nucleus Accumbens (NAc) as well as reduced motivation for HF foods compared to ConvLF rats. Dopamine receptor 2 (DDR2) expression levels in the NAc were also significantly lower in ConvHF animals. Similar deficits were observed in conventionally raised HF fed rats, showing that diet-driven alteration in reward can be initiated via microbiota. Selective gut to brain deafferentation restored DOPAC levels, DRD2 expression, and motivational drive in ConvHF rats.

CONCLUSIONS

We concluded from these data that a HF-type microbiota is sufficient to alter appetitive feeding behavior and that bacteria to reward communication is mediated by the vagus nerve.

The Gut Microbiome in Early Life Stress: A Systematic Review

Exposure to early life stress (ELS), prenatal or postnatal during childhood and adolescence, can significantly impact mental and physical health. The role of the intestinal microbiome in human health, and particularly mental health, is becoming increasingly evident. This systematic review aims to summarize the clinical data evaluating the effect of ELS on the human intestinal microbiome. The systematic review (CRD42022351092) was performed following PRISMA guidelines, with ELS considered as exposure to psychological stressors prenatally and during early life (childhood and adolescence). Thirteen articles met all inclusion criteria, and all studies reviewed found a link between ELS and the gut microbiome in both prenatal and postnatal periods. However, we failed to find consensus microbiome signatures associated with pre- or postnatal stress, or both. The inconsistency of results is likely attributed to various factors such as different experimental designs, ages examined, questionnaires, timing of sample collection and analysis methods, small population sizes, and the type of stressors. Additional studies using similar stressors and validated stress measures, as well as higher-resolution microbiome analytical approaches, are needed to draw definitive conclusions about the links between stress and the human gut microbiome.

Influence of gut microbiota on resilience and its possible mechanisms

Excessive stress leads to disruptions of the central nervous system. Individuals' responses to stress and trauma differ from person to person. Some may develop various neuropsychiatric disorders, such as post-traumatic stress disorder, major depression, and anxiety disorders, while others may successfully adapt to the same stressful events. These two neural phenotypes are called susceptibility and resilience. Previous studies have suggested resilience/susceptibility as a complex, non-specific systemic response involving central and peripheral systems. Emerging research of mechanisms underlying resilience is mostly focussing on the physiological adaptation of specific brain circuits, neurovascular impairment of the blood-brain barrier, the role of innate and adaptive factors of the immune system, and the dysbiosis of gut microbiota. In accordance with the microbiota-gut-brain axis hypothesis, the gut microbiome directly influences the interface between the brain and the periphery to affect neuronal function. This review explored several up-to-date studies on the role of gut microbiota implicated in stressful events-related resilience/susceptibility. We mainly focus on the changes in behavior and neuroimaging characteristics, involved brain regions and circuits, the blood-brain barrier, the immune system, and epigenetic modifications, which contribute to stress-induced resilience and susceptibility. The perspective of the gut-brain axis could help to understand the mechanisms underlying resilience and the discovery of biomarkers may lead to new research directions and therapeutic interventions for stress-induced neuropsychiatric disorders.

Gut microbiota suppress feeding induced by palatable foods

Feeding behaviors depend on intrinsic and extrinsic factors including genetics, food palatability, and the environment.^1,2,3,4,5 The gut microbiota is a major environmental contributor to host physiology and impacts feeding behavior.^{6,7,8,9,10,11,12} Here, we explored the hypothesis that gut bacteria influence behavioral responses to palatable foods and reveal that antibiotic depletion (ABX) of the gut microbiota in mice results in overconsumption of several palatable foods with conserved effects on feeding dynamics. Gut microbiota restoration via fecal transplant into ABX mice is sufficient to rescue overconsumption of high-sucrose pellets. Operant conditioning tests found that ABX mice exhibit intensified motivation to pursue high-sucrose rewards. Accordingly, neuronal activity in mesolimbic brain regions, which have been linked with motivation and reward-seeking behavior,³ was elevated in ABX mice after consumption of high-sucrose pellets. Differential antibiotic treatment and functional microbiota transplants identified specific gut bacterial taxa from the family S24-7 and the genus Lactobacillus whose abundances associate with suppression of high-sucrose pellet consumption. Indeed, colonization of mice with S24-7 and Lactobacillus johnsonii was sufficient to reduce overconsumption of high-sucrose pellets in an antibiotic-induced model of binge eating. These results demonstrate that extrinsic influences from the gut microbiota can suppress the behavioral response toward palatable foods in mice.

Interactions between perceived stress and microbial-host immune components: two demographically and geographically distinct pregnancy cohorts

Higher stress during pregnancy associates with negative outcomes and elevated inflammation. The gut microbiota, reflecting environment and social interactions, alongside host immune responses have the potential to better understand perceived stress and identify when stress is excessive in pregnancy. Two U.S. cohorts of 84 pregnant individuals, composed of urban women of color and suburban white women, completed the Perceived Stress Scale-10 (PSS-10) and provided fecal and blood samples at two time points. Confirmatory Factor Analysis assessed the robustness of a two-factor PSS-10 model (Emotional Distress/ED and Self-Efficacy/SE). Gut microbiota composition was measured by 16 S rRNA amplicon sequencing and the immune system activity was assessed with a panel of 21 T-cell related cytokines and chemokines. ED levels were higher in the suburban compared to the urban cohort, but levels of SE were similar. ED and SE levels were associated with distinct taxonomical signatures and the gut microbiota data improved the prediction of SE levels compared with models based on socio-demographic characteristics alone. Integration of self-reported symptoms, microbial and immune information revealed a possible mediation effect of Bacteroides uniformis between the immune system (through CXCL11) and SE. The study identified links between distinct taxonomical and immunological signatures with perceived stress. The data are congruent with a model where gut microbiome and immune factors, both impacting and reflecting factors such as close social relationships and dietary fiber, may modulate neural plasticity resulting in increased SE during pregnancy. The predictive value of these peripheral markers merit further study.

Alteration of faecal microbiota balance related to long-term deep meditation

Background

Advancements in research have confirmed that gut microbiota can influence health through the microbiota-gut-brain axis. Meditation, as an inner mental exercise, can positively impact the regulation of an individual's physical and mental health. However, few studies have comprehensively investigated faecal microbiota following long-term (several years) deep meditation. Therefore, we propose that long-term meditation may regulate gut microbiota homeostasis and, in turn, affect physical and mental health.

Aims

To investigate the effects of long-term deep meditation on the gut microbiome structure.

Methods

To examine the intestinal flora, 16S rRNA gene sequencing was performed on faecal samples of 56 Tibetan Buddhist monks and neighbouring residents. Based on the sequencing data, linear discriminant analysis effect size (LEfSe) was employed to identify differential intestinal microbial communities between the two groups. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis was used to predict the function of faecal microbiota. In addition, we evaluated biochemical indices in the plasma.

Results

The α-diversity indices of the meditation and control groups differed significantly. At the genus level, Prevotella and Bacteroides were significantly enriched in the meditation group. According to the LEfSe analysis, two beneficial bacterial genera (Megamonas and Faecalibacterium) were significantly enriched in the meditation group. Functional predictive analysis further showed that several pathways-including glycan biosynthesis, metabolism and lipopolysaccharide biosynthesis-were significantly enriched in the meditation group. Moreover, plasma levels of clinical risk factors were significantly decreased in the meditation group, including total cholesterol and apolipoprotein B.

Conclusions

Long-term traditional Tibetan Buddhist meditation may positively impact physical and mental health. We confirmed that the gut microbiota composition differed between the monks and control subjects. The microbiota enriched in monks was associated with a reduced risk of anxiety, depression and cardiovascular disease and could enhance immune function. Overall, these results suggest that meditation plays a positive role in psychosomatic conditions and well-being.

A critical analysis of eating disorders and the gut microbiome

The gut microbiota, also known as our "second brain" is an exciting frontier of research across a multitude of health domains. Gut microbes have been implicated in feeding behaviour and obesity, as well as mental health disorders including anxiety and depression, however their role in the development and maintenance of eating disorders (EDs) has only recently been considered. EDs are complex mental health conditions, shaped by a complicated interplay of factors. Perhaps due to an incomplete understanding of the etiology of EDs, treatment remains inadequate with affected individuals likely to face many relapses. The gut microbiota may be a missing piece in understanding the etiology of eating disorders, however more robust scientific inquiry is needed in the field before concrete conclusions can be made. In this spotlight paper, we critically evaluate what is known about the bi-directional relationship between gut microbes and biological processes that are implicated in the development and maintenance of EDs, including physiological functioning, hormones, neurotransmitters, the central nervous system, and the immune system. We outline limitations of current research, propose concrete steps to move the field forward and, hypothesize potential clinical implications of this research. Our gut is inhabited by millions of bacteria which have more recently been referred to as "our second brain". In fact, these microbes are thought to play a role in ED behaviour, associated anxiety and depression, and even affect our weight. Recent research has dove into this field with promising findings that have the potential to be applied clinically to improve ED recovery. The present paper discusses what is known about the gut microbiome in relation to EDs and the promising implications that leveraging this knowledge, through fecal microbiome transplants, probiotics, and microbiome-directed supplemental foods, could have on ED treatment.

Neurobiological and neuropharmacological aspects of food addiction

This review aims to draw attention to current studies on syndromes related to food eating behavior, including food addiction, and to highlight the neurobiological and neuropharmacological aspects of food addiction toward the development of new therapies. Food addiction and eating disorders are influenced by several neurobiological factors. Changes in feeding behavior, food addiction, and its pharmacological therapy are related to complex neurobiological processes in the brain. Thus, it is not surprising that there is inconsistency among various individual studies. In this review, we assessed literature including both experimental and clinical studies regarding food addiction as a feeding disorder. We selected articles from animal studies, randomized clinical trials, meta-analyses, narrative, and systemic reviews given that, crucial quantitative data with a measure of neurobiological, neuropharmacological aspects and current therapies of food addiction as an outcome. Thus, the main goal to outline here is to investigate and discuss the association between the brain reward system and feeding behavior in the frame of food addiction in the light of current literature.

Gut microbes and food reward: From the gut to the brain

Inappropriate food intake behavior is one of the main drivers for fat mass development leading to obesity. Importantly the gut microbiota-mediated signals have emerged as key actors regulating food intake acting mainly on the hypothalamus, and thereby controlling hunger or satiety/satiation feelings. However, food intake is also controlled by the hedonic and reward systems leading to food intake based on pleasure (i.e., non-homeostatic control of food intake). This review focus on both the homeostatic and the non-homeostatic controls of food intake and the implication of the gut microbiota on the control of these systems. The gut-brain axis is involved in the communications between the gut microbes and the brain to modulate host food intake behaviors through systemic and nervous pathways. Therefore, here we describe several mediators of the gut-brain axis including gastrointestinal hormones, neurotransmitters, bioactive lipids as well as bacterial metabolites and compounds. The modulation of gut-brain axis by gut microbes is deeply addressed in the context of host food intake with a specific focus on hedonic feeding. Finally, we also discuss possible gut microbiota-based therapeutic approaches that could lead to potential clinical applications to restore food reward alterations. Therapeutic applications to tackle these dysregulations is of utmost importance since most of the available solutions to treat obesity present low success rate.

Roles, molecular mechanisms, and signaling pathways of TMEMs in neurological diseases

Transmembrane protein family members (TMEMs) span the entire lipid bilayer and act as channels that allow the transport of specific substances through biofilms. The functions of most TMEMs are unexplored. Numerous studies have shown that TMEMs are involved in the pathophysiological processes of various nervous system diseases, but the specific mechanisms of TMEMs in the pathogenesis of diseases remain unclear. In this review, we discuss the expression, physiological functions, and molecular mechanisms of TMEMs in brain tumors, psychiatric disorders, abnormal motor activity, cobblestone lissencephaly, neuropathic pain, traumatic brain injury, and other disorders of the nervous system. Additionally, we propose that TMEMs may be used as prognostic markers and potential therapeutic targets in patients with various neurological diseases.

Microbiome First Approaches to Rescue Public Health and Reduce Human Suffering

The is a sequential article to an initial review suggesting that Microbiome First medical approaches to human health and wellness could both aid the fight against noncommunicable diseases and conditions (NCDs) and help to usher in sustainable healthcare. This current review article specifically focuses on public health programs and initiatives and what has been termed by medical journals as a catastrophic record of recent failures. Included in the review is a discussion of the four priority behavioral modifications (food choices, cessation of two drugs of abuse, and exercise) advocated by the World Health Organization as the way to stop the ongoing NCD epidemic. The lack of public health focus on the majority of cells and genes in the human superorganism, the microbiome, is highlighted as is the "regulatory gap" failure to protect humans, particularly the young, from a series of mass population toxic exposures (e.g., asbestos, trichloroethylene, dioxin, polychlorinated biphenyls, triclosan, bisphenol A and other plasticizers, polyfluorinated compounds, herbicides, food emulsifiers, high fructose corn syrup, certain nanoparticles, endocrine disruptors, and obesogens). The combination of early life toxicity for the microbiome and connected human physiological systems (e.g., immune, neurological), plus a lack of attention to the importance of microbial rebiosis has facilitated rather than suppressed, the NCD epidemic. This review article concludes with a call to place the microbiome first and foremost in public health initiatives as a way to both rescue public health effectiveness and reduce the human suffering connected to comorbid NCDs.