Microbiota-gut-brain axis as a regulator of reward processes

Standard rodent diets differentially impact alcohol consumption, preference, and gut microbiome diversity

Alcohol use disorder (AUD) is a complex and widespread disease with limited pharmacotherapies. Preclinical animal models of AUD use a variety of voluntary alcohol consumption procedures to recapitulate different phases of AUD, including binge alcohol consumption and dependence. However, voluntary alcohol consumption in mice is widely variable, making it difficult to reproduce results across labs. Accumulating evidence indicates that different brands of commercially available rodent chow can profoundly influence alcohol intake. In this study, we investigated the effects of three commercially available and widely used rodent diet formulations on alcohol consumption and preference in C57BL/6 J mice using the 24 h intermittent access procedure. The three brands of chow tested were LabDiet 5,001 (LD5001), LabDiet 5,053 (LD5053), and Teklad 2019S (TL2019S) from two companies (Research Diets and Envigo, respectively). Mice fed LD5001 and LD5053 displayed higher levels of alcohol consumption and preference compared to mice fed TL2019S. We also found that alcohol consumption and preference could be rapidly switched by changing the diet 48 h prior to alcohol administration. Sucrose, saccharin, and quinine preferences were not altered, suggesting that the diets did not alter sweet and bitter taste perception. We also found that mice fed LD5001 displayed increased quinine-resistant alcohol intake compared to mice fed TL2019S, suggesting that diets could influence the development of compulsive behaviors such as alcohol consumption. We profiled the gut microbiome of water- and alcohol-drinking mice that were maintained on different diets and found significant differences in bacterial alpha- and beta-diversities, which could impact the gut-brain axis signaling and alcohol consumption.

A gut (microbiome) feeling about addiction: Interactions with stress and social systems

In recent years, an increasing attention has given to the intricate and diverse connection of microorganisms residing in our gut and their impact on brain health and central nervous system disease. There has been a shift in mindset to understand that drug addiction is not merely a condition that affects the brain, it is now being recognized as a disorder that also involves external factors such as the intestinal microbiota, which could influence vulnerability and the development of addictive behaviors. Furthermore, stress and social interactions, which are closely linked to the intestinal microbiota, are powerful modulators of addiction. This review delves into the mechanisms through which the microbiota-stress-immune axis may shape drug addiction and social behaviors. This work integrates preclinical and clinical evidence that demonstrate the bidirectional communication between stress, social behaviors, substance use disorders and the gut microbiota, suggesting that gut microbes might modulate social stress having a significance in drug addiction.

Cholinergic interneurons in the nucleus accumbens are a site of cellular convergence for corticotropin release factor and estrogen regulation

Cholinergic interneurons (ChIs) act as master regulators of striatal output, finely tuning neurotransmission to control motivated behaviors. ChIs are a cellular target of many peptide and hormonal neuromodulators, including corticotropin releasing factor, opioids, insulin and leptin, which can influence an animal's behavior by signaling stress, pleasure, pain and nutritional status. However, little is known about how sex hormones via estrogen receptors influence the function of these other neuromodulators. Here, we performed in situ hybridization on mouse striatal tissue to characterize the effect of sex and sex hormones on choline acetyltransferase ( Chat ), estrogen receptor alpha ( Esr1 ), and corticotropin releasing factor type 1 receptor ( Crhr1 ) expression. Although we did not detect sex differences in ChAT protein levels in the striatum, we found that female mice have more Chat mRNA-expressing neurons than males. At the population level, we observed a sexually dimorphic distribution of Esr1 - and Crhr1 -expressing ChIs in the ventral striatum that demonstrates an antagonistic correlational relationship, which is abolished by ovariectomy. Only in the NAc did we find a significant population of ChIs that co-express Crhr1 and Esr1 . At the cellular level, Crhr1 and Esr1 transcript levels were negatively correlated only during estrus, indicating that changes in sex hormones levels can modulate the interaction between Crhr1 and Esr1 mRNA levels. Together, these data provide evidence for the unique expression and interaction of Esr1 and Crhr1 in ventral striatal ChIs, warranting further investigation into how these transcriptomic patterns might underlie important functions for ChIs at the intersection of stress and reproductive behaviors.

Standard rodent diets differentially impact alcohol consumption and preference and gut microbiome diversity

Alcohol Use Disorder (AUD) is a complex and widespread disease with limited pharmacotherapies. Preclinical animal models of AUD use a variety of voluntary alcohol consumption procedures to recapitulate different phases of AUD including binge alcohol consumption and dependence. However, voluntary alcohol consumption in mice is widely variable rendering it difficult to reproduce results across labs. Accumulating evidence indicates that different brands of commercially available rodent chow can profoundly influence alcohol intake. In this study, we investigated the effects of three commercially available and widely used rodent diet formulations on alcohol consumption and preference in C57BL/6J mice using the 24h intermittent access procedure. The three brands of chow tested were LabDiet 5001 (LD 5001), LabDiet 5053 (LD 5053), and Teklad 2019S (TL2019S) from two companies (Research Diets and Envigo respectively). Mice fed LD5001 displayed the highest levels of alcohol consumption and preference followed by LD5053 and TL2019S. We also found that alcohol consumption and preference could be rapidly switched by changing the diet 48h prior to alcohol administration. Sucrose, saccharin, and quinine preference were not altered suggesting that the diets did not alter taste perception. We also found that mice fed LD5001 displayed increased quinine-resistant alcohol intake compared to mice fed TL2019S, suggesting that diets could influence the development of "compulsive" like alcohol consumption. We profiled the gut microbiome of water and alcohol drinking mice that were maintained on different diets and found significant differences in bacterial alpha and beta diversity, which could impact gut-brain axis signaling and alcohol consumption.

Glymphatic System Pathology and Neuroinflammation as Two Risk Factors of Neurodegeneration

The key to the effective treatment of neurodegenerative disorders is a thorough understanding of their pathomechanism. Neurodegeneration and neuroinflammation are mutually propelling brain processes. An impairment of glymphatic system function in neurodegeneration contributes to the progression of pathological processes. The question arises as to how neuroinflammation and the glymphatic system are related. This review highlights the direct and indirect influence of these two seemingly independent processes. Protein aggregates, a characteristic feature of neurodegeneration, are correlated with glymphatic clearance and neuroinflammation. Glial cells cannot be overlooked when considering the neuroinflammatory processes. Astrocytes are essential for the effective functioning of the glymphatic system and play a crucial role in the inflammatory responses in the central nervous system. It is imperative to acknowledge the significance of AQP4, a protein that exhibits a high degree of polarization in astrocytes and is crucial for the functioning of the glymphatic system. AQP4 influences inflammatory processes that have not yet been clearly delineated. Another interesting issue is the gut-brain axis and microbiome, which potentially impact the discussed processes. A discussion of the correlation between the functioning of the glymphatic system and neuroinflammation may contribute to exploring the pathomechanism of neurodegeneration.

Associations between impulsivity and fecal microbiota in individuals abstaining from methamphetamine

INTRODUCTION

Methamphetamine (MA) abuse is a major public problem, and impulsivity is both a prominent risk factor and a consequence of addiction. Hence, clarifying the biological mechanism of impulsivity may facilitate the understanding of addiction to MA. The microbiota-gut-brain axis was suggested to underlie a biological mechanism of impulsivity induced by MA.

METHODS

We therefore recruited 62 MA addicts and 50 healthy controls (HCs) to investigate the alterations in impulsivity and fecal microbiota and the associations between them in the MA group. Thereafter, 25 MA abusers who abstained from MA for less than 3 months were followed up for 2 months to investigate the relationship between impulsivity and microbiota as abstinence became longer. 16S rRNA sequencing was conducted for microbiota identification.

RESULTS

Elevated impulsivity and dysbiosis characterized by an increase in opportunistic pathogens and a decrease in probiotics were identified in MA abusers, and both the increased impulsivity and disrupted microbiota tended to recover after longer abstinence from MA. Impulsivity was related to microbiota, and the effect of MA abuse on impulsivity was mediated by microbiota.

CONCLUSION

Our findings potentially highlighted the importance of abstention and implicated the significant role of the microbiota-gut-brain axis in the interrelationship between microbiota and behaviors, as well as the potential of microbiota as a target for intervention of impulsivity.

Adolescent alcohol drinking interaction with the gut microbiome: implications for adult alcohol use disorder

Reciprocal communication between the gut microbiota and the brain, commonly referred to as the "gut-brain-axis" is crucial in maintaining overall physiological homeostasis. Gut microbiota development and brain maturation (neuronal connectivity and plasticity) appear to be synchronized and to follow the same timeline during childhood (immature), adolescence (expansion) and adulthood (completion). It is important to note that the mesolimbic reward circuitry develops early on, whereas the maturation of the inhibitory frontal cortical neurons is delayed. This imbalance can lead to increased acquirement of reward-seeking and risk-taking behaviors during adolescence, and consequently eventuate in heightened risk for substance abuse. Thus, there is high initiation of alcohol drinking in early adolescence that significantly increases the risk of alcohol use disorder (AUD) in adulthood. The underlying causes for heightened AUD risk are not well understood. It is suggested that alcohol-associated gut microbiota impairment during adolescence plays a key role in AUD neurodevelopment in adulthood. Furthermore, alcohol-induced dysregulation of microglia, either directly or indirectly through interaction with gut microbiota, may be a critical neuroinflammatory pathway leading to neurodevelopmental impairments and AUD. In this review article, we highlight the influence of adolescent alcohol drinking on gut microbiota, gut-brain axis and microglia, and eventual manifestation of AUD. Furthermore, novel therapeutic interventions via gut microbiota manipulations are discussed briefly.

Restraint stress-associated gastrointestinal injury and implications from the Evans blue-fed restraint stress mouse model

The association between stress and gastrointestinal (GI) tract diseases is well established, while the exact mechanism remains elusive. As a result, it is urgent to establish mouse models to investigate restraint stress-associated GI leakage, but current models have their limitations. A new Evans blue-fed restraint mouse model has recently been developed that allows researchers to study restraint stress-associated GI leakage in live animals. This review article will focus on this model, including its mechanisms, clinical implications, and applications for studying restraint stress-associated GI injury. Recent findings from studies using this model will also be highlighted, along with their potential for diagnosis and treatment. The article aims to discuss about current research and provide recommendations for further study, ultimately improving our understanding of the link between stress and GI injury and improving patient outcomes.

Noxious ramifications of cosmetic pollutants on gastrointestinal microbiome: A pathway to neurological disorders

On exposure to cosmetic pollutants, gastrointestinal dysbiosis, which is characterised by a disturbance in the gut microbiota, has come into focus as a possible contributor to the occurrence of neurotoxic consequences. It is normal practice to use personal care products that include parabens, phthalates, sulphates, triclosans/triclocarbans and micro/nano plastics. These substances have been found in a variety of bodily fluids and tissues, demonstrating their systemic dispersion. Being exposed to these cosmetic pollutants has been linked in recent research to neurotoxicity, including cognitive decline and neurodevelopmental problems. A vital part of sustaining gut health and general well-being is the gut flora. Increased intestinal permeability, persistent inflammation, and impaired metabolism may result from disruption of the gut microbial environment, which may in turn contribute to neurotoxicity. The link between gastrointestinal dysbiosis and the neurotoxic effects brought on by cosmetic pollutants may be explained by a number of processes, primarily the gut-brain axis. For the purpose of creating preventative and therapeutic measures, it is crucial to comprehend the intricate interactions involving cosmetic pollutants, gastrointestinal dysbiosis, and neurotoxicity. This review provides an in-depth understanding of the various hazardous cosmetic pollutants and its potential role in the occurrence of neurological disorders via gastrointestinal dysbiosis, providing insights into various described and hypothetical mechanisms regarding the complex toxic effects of these industrial pollutants.

Intestinal microbiome dysbiosis in alcohol-dependent patients and its effect on rat behaviors

IMPORTANCE

Intestinal microbiome dysbiosis is associated with psychiatric disease through the "microbiota-gut-brain" axis. Here, we revealed that there was obvious intestinal microbiome (including bacterial and fungal) dysbiosis in alcohol-dependent patients. Alcohol consumption seriously disturbs the gut equilibrium between bacteria and fungi, reduces the interactions among bacterial-fungal trans-kingdom, and increases intestinal permeability. Gut microbiota should be considered as a whole to study the development of alcohol dependence. The gut microbiome of alcohol-dependent patients increased the anxiety- and depression-like behavior in rats. The gut microbiota dysbiosis may promote the development of alcohol dependence by regulating the endogenous cholecystokinin (CCK) and related receptors. Hence, regulating the balance of gut microbiota and the endogenous CCK may be a potential strategy for reducing the risk of relapse in alcohol addiction patients.

The microbiome-gut-brain axis in nutritional neuroscience

Emerging evidence is highlighting the microbiome as a key regulator of the effect of nutrition on gut-brain axis signaling. Nevertheless, it is not yet clear whether the impact of nutrition is moderating the microbiota-gut-brain interaction or if diet has a mediating role on microbiota composition and function to influence central nervous system function, brain phenotypes and behavior. Mechanistic evidence from cell-based in vitro studies, animal models and preclinical intervention studies are linking the gut microbiota to the effects of diet on brain function, but they have had limited translation to human intervention studies. While increasing evidence demonstrates the triangulating relationship between diet, microbiota, and brain function across the lifespan, future mechanistic and translational studies in the field of microbiota and nutritional neuroscience are warranted to inform potential strategies for prevention and management of several neurological, neurodevelopmental, neurodegenerative, and psychiatric disorders. This brief primer provides an overview of the most recent advances in the nutritional neuroscience - microbiome field, highlighting significant opportunities for future research.

Olive oil-derived endocannabinoid-like mediators inhibit palatable food-induced reward and obesity

N-oleoylglycine (OlGly), a lipid derived from the basic component of olive oil, oleic acid, and N-oleoylalanine (OlAla) are endocannabinoid-like mediators. We report that OlGly and OlAla, by activating the peroxisome proliferator-activated receptor alpha (PPARα), reduce the rewarding properties of a highly palatable food, dopamine neuron firing in the ventral tegmental area, and the obesogenic effect of a high-fat diet rich in lard (HFD-L). An isocaloric olive oil HFD (HFD-O) reduced body weight gain compared to the HFD-L, in a manner reversed by PPARα antagonism, and enhanced brain and intestinal OlGly levels and gut microbial diversity. OlGly or OlAla treatment of HFD-L mice resulted in gut microbiota taxonomic changes partly similar to those induced by HFD-O. We suggest that OlGly and OlAla control body weight by counteracting highly palatable food overconsumption, and possibly rebalancing the gut microbiota, and provide a potential new mechanism of action for the obeso-preventive effects of olive oil-rich diets.

Beyond the symptom: the biology of fatigue

A workshop titled "Beyond the Symptom: The Biology of Fatigue" was held virtually September 27-28, 2021. It was jointly organized by the Sleep Research Society and the Neurobiology of Fatigue Working Group of the NIH Blueprint Neuroscience Research Program. For access to the presentations and video recordings, see: https://neuroscienceblueprint.nih.gov/about/event/beyond-symptom-biology-fatigue. The goals of this workshop were to bring together clinicians and scientists who use a variety of research approaches to understand fatigue in multiple conditions and to identify key gaps in our understanding of the biology of fatigue. This workshop summary distills key issues discussed in this workshop and provides a list of promising directions for future research on this topic. We do not attempt to provide a comprehensive review of the state of our understanding of fatigue, nor to provide a comprehensive reprise of the many excellent presentations. Rather, our goal is to highlight key advances and to focus on questions and future approaches to answering them.

Microbes, oxytocin and stress: Converging players regulating eating behavior

Oxytocin is a peptide-hormone extensively studied for its multifaceted biological functions and has recently gained attention for its role in eating behavior, through its action as an anorexigenic neuropeptide. Moreover, the gut microbiota is involved in oxytocinergic signaling through the brain-gut axis, specifically in the regulation of social behavior. The gut microbiota is also implicated in appetite regulation and is postulated to play a role in central regulation of hedonic eating. In this review, we provide an overview on oxytocin and its individual links with the microbiome, the homeostatic and non-homeostatic regulation of eating behavior as well as social behavior and stress.

Gut microbiota metabolites mediate the interplay between childhood maltreatment and psychopathology in patients with eating disorders

Eating disorders (EDs) are syndromes with a multifactorial etiopathogenesis, involving childhood traumatic experiences, as well as biological factors. Human microbiome has been hypothesised to play a fundamental role, impacting on emotion regulation, as well as with eating behaviours through its metabolites such as short chain fatty acids (SCFAs). The present study investigated the interactions between psychopathology of EDs, the gut microbiome and SCFAs resulting from bacterial community metabolic activities in a population of 47 patients with Anorexia Nervosa, Bulimia Nervosa, and Binge Eating Disorder and in healthy controls (HCs). Bacterial gut microbiota composition differences were found between subjects with EDs and HCs, especially in association with different pathological behaviours (binge-purge vs restricting). A mediation model of early trauma and ED-specific psychopathology linked reduction of microbial diversity to a typical microbiota-derived metabolite such as butyric acid. A possible interpretation for this model might be that childhood trauma represents a risk factor for gut dysbiosis and for a stable modification of mechanisms responsible for SCFAs production, and that this dysfunctional community is inherited in the passage from childhood to adulthood. These findings might open the way to novel interventions of butyric acid-like compounds as well as faecal transplant.

The Neurobiology of Eating Behavior in Obesity: Mechanisms and Therapeutic Targets: A Report from the 23rd Annual Harvard Nutrition Obesity Symposium

Obesity is increasing at an alarming rate. The effectiveness of currently available strategies for the treatment of obesity (including pharmacologic, surgical, and behavioral interventions) is limited. Understanding the neurobiology of appetite and the important drivers of energy intake (EI) can lead to the development of more effective strategies for the prevention and treatment of obesity. Appetite regulation is complex and is influenced by genetic, social, and environmental factors. It is intricately regulated by a complex interplay of endocrine, gastrointestinal, and neural systems. Hormonal and neural signals generated in response to the energy state of the organism and the quality of food eaten are communicated by paracrine, endocrine, and gastrointestinal signals to the nervous system. The central nervous system integrates homeostatic and hedonic signals to regulate appetite. Although there has been an enormous amount of research over many decades regarding the regulation of EI and body weight, research is only now yielding potentially effective treatment strategies for obesity. The purpose of this article is to summarize the key findings presented in June 2022 at the 23rd annual Harvard Nutrition Obesity Symposium entitled "The Neurobiology of Eating Behavior in Obesity: Mechanisms and Therapeutic Targets." Findings presented at the symposium, sponsored by NIH P30 Nutrition Obesity Research Center at Harvard, enhance our current understanding of appetite biology, including innovative techniques used to assess and systematically manipulate critical hedonic processes, which will shape future research and the development of therapeutics for obesity prevention and treatment.

Oral and fecal microbiota perturbance in cocaine users: Can rTMS-induced cocaine abstinence support eubiosis restoration?

The effects of cocaine on microbiota have been scarcely explored. Here, we investigated the gut (GM) and oral (OM) microbiota composition of cocaine use disorder (CUD) patients and the effects of repetitive transcranial magnetic stimulation (rTMS). 16S rRNA sequencing was used to characterize GM and OM, whereas PICRUST2 assessed functional changes in microbial communities, and gas-chromatography was used to evaluate fecal short and medium chain fatty acids. CUD patients reported a significant decrease in alpha diversity and modification of the abundances of several taxa in both GM and OM. Furthermore, many predicted metabolic pathways were differentially expressed in CUD patients' stool and saliva samples, as well as reduced levels of butyric acid that appear restored to normal amounts after rTMS treatment. In conclusion, CUD patients showed a profound dysbiotic fecal and oral microbiota composition and function and rTMS-induced cocaine abstinence determined the restoration of eubiotic microbiota.

Impact of the gut microbiome on nicotine's motivational effects and glial cells in the ventral tegmental area in male mice

A link between gut dysbiosis and the pathogenesis of brain disorders has been identified. A role for gut bacteria in drug reward and addiction has been suggested but very few studies have investigated their impact on brain and behavioral responses to addictive drugs so far. In particular, their influence on nicotine's addiction-like processes remains unknown. In addition, evidence shows that glial cells shape the neuronal activity of the mesolimbic system but their regulation, within this system, by the gut microbiome is not established. We demonstrate that a lack of gut microbiota in male mice potentiates the nicotine-induced activation of sub-regions of the mesolimbic system. We further show that gut microbiota depletion enhances the response to nicotine of dopaminergic neurons of the posterior ventral tegmental area (pVTA), and alters nicotine's rewarding and aversive effects in an intra-VTA self-administration procedure. These effects were not associated with gross behavioral alterations and the nicotine withdrawal syndrome was not impacted. We further show that depletion of the gut microbiome modulates the glial cells of the mesolimbic system. Notably, it increases the number of astrocytes selectively in the pVTA, and the expression of postsynaptic density protein 95 in both VTA sub-regions, without altering the density of the astrocytic glutamatergic transporter GLT1. Finally, we identify several sub-populations of microglia in the VTA that differ between its anterior and posterior sub-parts, and show that they are re-organized in conditions of gut microbiota depletion. The present study paves the way for refining our understanding of the pathophysiology of nicotine addiction.

Seeking the Psilocybiome: Psychedelics meet the microbiota-gut-brain axis

Moving towards a systems psychiatry paradigm embraces the inherent complex interactions across all levels from micro to macro and necessitates an integrated approach to treatment. Cortical 5-HT2A receptors are key primary targets for the effects of serotonergic psychedelics. However, the therapeutic mechanisms underlying psychedelic therapy are complex and traverse molecular, cellular, and network levels, under the influence of biofeedback signals from the periphery and the environment. At the interface between the individual and the environment, the gut microbiome, via the gut-brain axis, plays an important role in the unconscious parallel processing systems regulating host neurophysiology. While psychedelic and microbial signalling systems operate over different timescales, the microbiota-gut-brain (MGB) axis, as a convergence hub between multiple biofeedback systems may play a role in the preparatory phase, the acute administration phase, and the integration phase of psychedelic therapy. In keeping with an interconnected systems-based approach, this review will discuss the gut microbiome and mycobiome and pathways of the MGB axis, and then explore the potential interaction between psychedelic therapy and the MGB axis and how this might influence mechanism of action and treatment response. Finally, we will discuss the possible implications for a precision medicine-based psychedelic therapy paradigm.

The Microbiome-Gut-Brain axis regulates social cognition & craving in young binge drinkers

BACKGROUND

Binge drinking is the consumption of an excessive amount of alcohol in a short period of time. This pattern of consumption is highly prevalent during the crucial developmental period of adolescence. Recently, the severity of alcohol use disorders (AUDs) has been linked with microbiome alterations suggesting a role for the gut microbiome in its development. Furthermore, a strong link has emerged too between microbiome composition and socio-emotional functioning across different disorders including AUD. The aim of this study was to investigate the potential link (and its predictive value) between alcohol-related altered microbial profile, social cognition, impulsivity and craving.

METHODS

Young people (N = 71) aged 18-25 reported their alcohol use and underwent a neuropsychological evaluation. Craving was measured at baseline and three months later. Diet was controlled for. Blood, saliva and hair samples were taken for inflammatory, kynurenine and cortisol analysis. Stool samples were provided for shotgun metagenomic sequencing and short-chain fatty acids (SCFAs) were measured.

FINDINGS

Binge drinking was associated with distinct microbiome alterations and emotional recognition difficulties. Associations were found for several microbiome species with emotional processing and impulsivity. Craving showed a strong link with alterations in microbiome composition and neuroactive potential over time.

INTERPRETATION

In conclusion, this research demonstrates alterations in the gut microbiome of young binge drinkers (BDs) and identifies early biomarkers of craving. Associations between emotional processing and microbiome composition further support the growing literature on the gut microbiome as a regulator of social cognition. These findings are of relevance for new gut-derived interventions directed at improving early alcohol-related alterations during the vulnerability period of adolescence.

FUNDING

C.C. and R.G-C. received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 754535. APC Microbiome Ireland is a research centre funded by Science Foundation Ireland (SFI), through the Irish Government's National Development Plan [grant no. SFI/12/RC/2273_P2]. J.F.C has research support from Cremo, Pharmavite, DuPont and Nutricia. He has spoken at meetings sponsored by food and pharmaceutical companies. G.C. has received honoraria from Janssen, Probi, and Apsen as an invited speaker; is in receipt of research funding from Pharmavite, Fonterra, Nestle and Reckitt; and is a paid consultant for Yakult, Zentiva and Heel pharmaceuticals. All the authors declare no competing interests.

Effects of Dietary Supplementation of L-Carnitine and Mannan-Oligosaccharides on Growth Performance, Selected Carcass Traits, Content of Basic and Mineral Components in Liver and Muscle Tissues, and Bone Quality in Turkeys

The study aimed to determine the effect of L-carnitine and Bio-Mos administration on selected production performance, slaughter parameters, elemental and mineral content of liver, breast and thigh muscles, and physical, morphometric, strength and bone mineral composition parameters of turkeys. The experiment was conducted on 360 six-week-old Big-6 turkey females, randomly divided into three groups of 120 birds each (six replicates of 20 birds). The turkeys of the control group were fed standard feed without additives; group II was fed with drinking water, a preparation containing L-carnitine at a dose of 0.83 mL/L, while group III was provided mixed feed with 0.5% Bio-Mos. The addition of L-carnitine and Bio-Mos increased body weight at 16 weeks (p = 0.047) and reduced the proportion of fat in the breast muscle (p = 0.029) and liver (p = 0.027). It also modified the content of some minerals in breast muscle, thigh muscle, liver, and bone. Furthermore, the addition of L-carnitine and Bio-Mos increased bone mass and length and modified the value of selected morphometric and strength parameters. The results indicate a positive effect of the applied feed additives on selected rearing indices and carcass quality while improving the elasticity and fracture toughness of the femur. There is a need for further research to determine optimal doses of L-carnitine and Bio-Mos in poultry nutrition.

Effects of Broad-Spectrum Antibiotic Treatment or Germ-Free Status on Endurance Performance and Exercise Adaptations in Mice

PURPOSE

Endurance exercise alters the gut microbiome independently of diet. The extent to which gut microbes are responsible for physiologic adaptations to exercise training is unknown. The purpose of these experiments was to determine the role of gut microbes in performance and muscle adaptation to 6 wk of voluntary wheel running (VWR) in mice.

METHODS

We depleted microbes with broad-spectrum antibiotic (ABX) treatment and used germ-free (GF) mice to determine effects on adaptations to VWR. Male and female C57Bl/6 mice ( n = 56) were assigned to daily VWR or sedentary conditions. After the intervention, treadmill endurance and glucose tolerance were assessed, and gastrocnemius and soleus tissues were harvested and analyzed for citrate synthase (CS) enzyme activity and expression of exercise training-sensitive genes.

RESULTS

ABX treatment and GF status resulted in VWR volumes ~22% and 26% lower than controls, respectively. Analysis of variance revealed that, although VWR increased treadmill endurance, ABX had no effect. GF status significantly reduced treadmill performance in trained GF mice after training. VWR increased gastrocnemius CS enzyme activity in all groups, and ABX and GF status did not reduce the VWR effect. VWR also increased muscle expression of PGC1a, but this was not affected by ABX treatment.

CONCLUSIONS

ABX treatment and GF status reduced VWR behavior but did not affect VWR-induced adaptations in endurance capacity, CS activity, or expression of muscle metabolic genes. However, GF status reduced endurance capacity. These data indicated that reducing microbes in adulthood does not inhibit endurance training adaptations in C57Bl/6 mice, but that GF mice possess a reduced responsiveness to endurance exercise training, perhaps because of a developmental defect associated with lack of microbes from birth.

Effects of molecular hydrogen intervention on the gut microbiome in methamphetamine abusers with mental disorder

Methamphetamine (METH) is a potent and highly addictive psychostimulant and one of the most widely used illicit drugs, the abuse of which has become a severe public health problem worldwide. A growing amount of evidence has indicated potential connections between gut microbiota and mental disorders induced by METH and associations with neural and metabolic pathways. The present study aimed to explore the relationship between fecal microbial alterations and neuropsychiatric diseases in METH addictions. Thus, mental disorders and gut microbial alterations were analyzed by self-rating depression (SDS) and anxiety (SAS) scales and 16 S rRNA gene sequencing, respectively. Our results showed that increased SDS and SAS indices and decreased alpha diversity indicated more serious mental disorders and lower bacterial diversity in METH users than in the age-matched healthy control group. The gut microbial composition in female METH users was also significantly altered, with reductions in hydrogen-producing bacteria, including Bacteroides and Roseburia. Molecular hydrogen (H₂) is spontaneously produced by intestinal bacteria in the process of anaerobic metabolism, which is the main pathway for H₂ production in vivo. Numerous studies have shown that hydrogen intervention can significantly improve neuropsychiatric diseases, including Alzheimer's disease and Parkinson's disease. Our results showed that hydrogen intervention, including drinking and inhaling, significantly alleviated mental disorders induced by METH abuse, and the inhalation of hydrogen also altered gut microbiota profiles in the METH abusers. These results suggest that hydrogen intervention has potential therapeutic applicability in the treatment of mental disorders in METH abusers.

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.

The gut microbiota alone and in combination with a social stimulus regulates cocaine reward in the mouse

The gut microbiota is a key factor in the maintenance of physiological homeostasis and immunity. Correlational studies have demonstrated that alterations in microbiota composition have been associated with addiction. Moreover, animal studies have confirmed a link between reward and social processes, which may be shaped by the gut microbiota thus influencing neurodevelopment and the programming of social behaviors across diverse animal species. However, whether there is an interaction between the microbiota and social reward processes in the context of drug reward remains unclear. To this end, we explored the influence of gut microbiota in regulating behaviourally conditioned responses to different rewards (cocaine and social interactions). Depletion of the intestinal microbiota resulted in differential reward responses to both drug and social stimuli with an attenuation of the former and enhancement of the latter independent of concomitant immune changes. Moreover, the combination of depleting the gut microbiota in the presence of a positive social stimulus attenuates cocaine reward. Together these data suggest that the two-pronged approach of targeting the microbiota and enhancing social behaviour could constitute a valuable component in reducing harm in drug use by altering the salient effects of cocaine.

Diet and the microbiota - gut - brain-axis: a primer for clinical nutrition

PURPOSE OF REVIEW

Diet is an essential modulator of the microbiota - gut - brain communication in health and disease. Consequently, diet-induced microbiome states can impact brain health and behaviour. The integration of microbiome into clinical nutrition perspectives of brain health is sparse. This review will thus focus on emerging evidence of microbiome-targeted dietary approaches with the potential to improve brain disorders.

RECENT FINDINGS

Research in this field is evolving toward randomized controlled trials using dietary interventions with the potential to modulate pathways of the microbiota - gut - brain-axis. Although most studies included small cohorts, the beneficial effects of Mediterranean-like diets on symptoms of depression or fermented foods on the immune function of healthy individuals shed light on how this research line can grow. With a clinical nutrition lens, we highlight several methodological limitations and knowledge gaps, including the quality of dietary intake information, the design of dietary interventions, and missing behavioural outcomes.

SUMMARY

Findings in diet - microbiome - brain studies can have groundbreaking implications in clinical nutrition practice and research. Modulating brain processes through diet via the gut microbiota raises numerous possibilities. Novel dietary interventions targeting the microbiota - gut - brain-axis can offer various options to prevent and treat health problems such as mental disorders. Furthermore, knowledge in this field will improve current nutritional guidelines for disease prevention.

Gut-microbiota-brain axis in the vulnerability to psychosis in adulthood after repeated cannabis exposure during adolescence

Increasing epidemiological evidence shows that the use of cannabis during adolescence could increase the risk for psychosis in adulthood. However, the precise mechanisms underlying long-lasting cannabis-induced risk for psychosis remain unclear. Accumulating evidence suggests the role of gut microbiota in the pathogenesis of psychiatric disorders. Here, we examined whether gut microbiota plays a role in the risk for psychosis of adult after exposure of cannabinoid (CB) receptor agonist WIN55,212-2 during adolescence. Repeated administration of WIN55,212-2 (2 mg/kg/day) during adolescence (P35-P45) significantly increased the expression of Iba1 (ionized calcium-binding adapter molecule 1) in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc) of adult mice after administration of lipopolysaccharide (LPS: 0.5 mg/kg). In contrast, there were no changes in blood levels of pro-inflammatory cytokines between the two groups. Although alpha-diversity and beta-diversity of gut microbiota were no differences between the two groups, there were several microbes altered between the two groups. Interestingly, there were significant correlations between the relative abundance of microbiota and Iba1 expression in the mPFC and NAc. Furthermore, there were also significant correlations between the relative abundance of microbiota and several metabolites in the blood. These findings suggest that gut microbiota may play a role in the microglial activation in the mPFC and NAc of adult mice after repeated WIN55,212-2 exposure during adolescence. Therefore, it is likely that gut-microbiota-microglia crosstalk might play a role in increased risk for psychosis in adults with cannabis use during adolescence.

Through the Looking-Glass: Psychoneuroimmunology and the Microbiome-Gut-Brain Axis in the Modern Antiretroviral Therapy Era

OBJECTIVE

Depression, substance use disorders, and other neuropsychiatric comorbidities are common in people with HIV (PWH), but the underlying mechanisms are not sufficiently understood. HIV-induced damage to the gastrointestinal tract potentiates residual immune dysregulation in PWH receiving effective antiretroviral therapy. However, few studies among PWH have examined the relevance of microbiome-gut-brain axis: bidirectional crosstalk between the gastrointestinal tract, immune system, and central nervous system.

METHODS

A narrative review was conducted to integrate findings from 159 articles relevant to psychoneuroimmunology (PNI) and microbiome-gut-brain axis research in PWH.

RESULTS

Early PNI studies demonstrated that neuroendocrine signaling via the hypothalamic-pituitary-adrenal axis and autonomic nervous system could partially account for the associations of psychological factors with clinical HIV progression. This review highlights the need for PNI studies examining the mechanistic relevance of the gut microbiota for residual immune dysregulation, tryptophan catabolism, and oxytocin release as key biological determinants of neuropsychiatric comorbidities in PWH (i.e., body-to-mind pathways). It also underscores the continued relevance of neuroendocrine signaling via the hypothalamic-pituitary-adrenal axis, autonomic nervous system, and oxytocin release in modifying microbiome-gut-brain axis functioning (i.e., mind-to-body pathways).

CONCLUSIONS

Advancing our understanding of PNI and microbiome-gut-brain axis pathways relevant to depression, substance use disorders, and other neuropsychiatric comorbidities in PWH can guide the development of novel biobehavioral interventions to optimize health outcomes. Recommendations are provided for biobehavioral and neurobehavioral research investigating bidirectional PNI and microbiome-gut-brain axis pathways among PWH in the modern antiretroviral therapy era.

Effects of Chronic Bifidobacteria Administration in Adult Male Rats on Plasma Metabolites: A Preliminary Metabolomic Study

Probiotics are live microorganisms distributed in the gastrointestinal tract that confer health benefits to the host when administered in adequate amounts. Bifidobacteria have been widely tested as a therapeutic strategy in the prevention and treatment of a broad spectrum of gastrointestinal disorders as well as in the regulation of the “microbiota-gut-brain axis”. Metabolomic techniques can provide details in the study of molecular metabolic mechanisms involved in Bifidobacteria function through the analysis of metabolites that positively contribute to human health. This study was focused on the effects of the chronic assumption of a mixture of Bifidobacteria in adult male rats using a metabolomic approach. Plasma samples were collected at the end of treatment and analyzed with a gas chromatography-mass spectrometry (GC-MS) platform. Partial least square discriminant analysis (PLS-DA) was performed to compare the metabolic pattern in control and probiotic-treated rats. Our results show, in probiotic-treated animals, an increase in metabolites involved in the energetic cycle, such as glucose, erythrose, creatinine, taurine and glycolic acid, as well as 3-hydroxybutyric acid. This is an important metabolite of short-chain fatty acids (SCFA) with multitasking roles in energy circuit balance, and it has also been proposed to have a key role in the prevention and treatment of neurodegenerative diseases.

Food Reward Alterations during Obesity Are Associated with Inflammation in the Striatum in Mice: Beneficial Effects of Akkermansia muciniphila

The reward system involved in hedonic food intake presents neuronal and behavioral dysregulations during obesity. Moreover, gut microbiota dysbiosis during obesity promotes low-grade inflammation in peripheral organs and in the brain contributing to metabolic alterations. The mechanisms underlying reward dysregulations during obesity remain unclear. We investigated if inflammation affects the striatum during obesity using a cohort of control-fed or diet-induced obese (DIO) male mice. We tested the potential effects of specific gut bacteria on the reward system during obesity by administrating Akkermansia muciniphila daily or a placebo to DIO male mice. We showed that dysregulations of the food reward are associated with inflammation and alterations in the blood–brain barrier in the striatum of obese mice. We identified Akkermansia muciniphila as a novel actor able to improve the dysregulated reward behaviors associated with obesity, potentially through a decreased activation of inflammatory pathways and lipid-sensing ability in the striatum. These results open a new field of research and suggest that gut microbes can be considered as an innovative therapeutic approach to attenuate reward alterations in obesity. This study provides substance for further investigations of Akkermansia muciniphila-mediated behavioral improvements in other inflammatory neuropsychiatric disorders.

Gut-brain mechanisms underlying changes in disordered eating behaviour after bariatric surgery: a review

Bariatric surgery results in long-term weight loss and an improved metabolic phenotype due to changes in the gut-brain axis regulating appetite and glycaemia. Neuroendocrine alterations associated with bariatric surgery may also influence hedonic aspects of eating by inducing changes in taste preferences and central reward reactivity towards palatable food. However, the impact of bariatric surgery on disordered eating behaviours (e.g.: binge eating, loss-of-control eating, emotional eating and 'addictive eating'), which are commonly present in people with obesity are not well understood. Increasing evidence suggests gut-derived signals, such as appetitive hormones, bile acid profiles, microbiota concentrations and associated neuromodulatory metabolites, can influence pathways in the brain implicated in food intake, including brain areas involved in sensorimotor, reward-motivational, emotional-arousal and executive control components of food intake. As disordered eating prevalence is a key mediator of weight-loss success and patient well-being after bariatric surgery, understanding how changes in the gut-brain axis contribute to disordered eating incidence and severity after bariatric surgery is crucial to better improve treatment outcomes in people with obesity.

Alterations in gut microbiota affect behavioral and inflammatory responses to methamphetamine in mice

RATIONALE AND OBJECTIVES

Methamphetamine (METH) is a highly addictive and widely abused drug that causes severe neuroinflammation in the human brain. The gut microbiota has a tremendous impact on the core symptoms of neuropsychiatric disorders via the microbiota-gut-brain (MGB) axis. However, it is not clear whether alterations in the gut microbiota are involved in METH exposure.

METHODS

We established a mouse model with chronic, escalating doses of METH exposure. Intervene in gut microbiota with antibiotics to observe the changes of locomotor activity caused by METH exposure in mice. qPCR and 16S rRNA gene sequencing were used to analyze the gut microbiota profiles. In addition, we tested the levels of inflammatory factors in the nucleus accumbens (NAc), prefrontal cortex (mPFC), hippocampus (HIp), and spleen. Finally, short-chain fatty acids (SCFAs) were supplemented to determine the interaction between behavior changes and the structure of gut microbiota.

RESULTS

In this research, METH increased the locomotor activity of mice, while antibiotics changed the effect. Antibiotics enhanced the expression of pro-inflammatory cytokines in mPFC, HIp, and spleen of METH-exposed mice. METH altered the gut microbiota of mice after antibiotic treatment, such as Butyricicoccus and Roseburia, which are related to butyrate metabolism. Supplementation with SCFAs changed the behavior of METH-exposed mice and decreased Parabacteroides and increased Lactobacillus in METH-exposed mice gut.

CONCLUSIONS

This research showed that antibiotics affected the behavior of METH-exposed mice and promoted inflammation. Our findings suggest that SCFAs might regulate METH-induced gut microbiota changes and behavior.

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.

Probing the Skin–Brain Axis: New Vistas Using Mouse Models

Inflammatory diseases of the skin, including atopic dermatitis and psoriasis, have gained increasing attention with rising incidences in developed countries over the past decades. While bodily properties, such as immunological responses of the skin, have been described in some detail, interactions with the brain via different routes are less well studied. The suggested routes of the skin–brain axis comprise the immune system, HPA axis, and the peripheral and central nervous system, including microglia responses and structural changes. They provide starting points to investigate the molecular mechanisms of neuropsychiatric comorbidities in AD and psoriasis. To this end, mouse models exist for AD and psoriasis that could be tested for relevant behavioral entities. In this review, we provide an overview of the current mouse models and assays. By combining an extensive behavioral characterization and state-of-the-art genetic interventions with the investigation of underlying molecular pathways, insights into the mechanisms of the skin–brain axis in inflammatory cutaneous diseases are examined, which will spark further research in humans and drive the development of novel therapeutic strategies.

Dose- and Sex-Dependent Bidirectional Relationship between Intravenous Fentanyl Self-Administration and Gut Microbiota

Gut bacteria influence neural circuits in addiction-related behaviors. Given the association between opioid use, gastrointestinal distress, and microbial dysbiosis in humans and mice, we test the hypothesis that interactions between gut bacteria and the brain mediate the rewarding and reinforcing properties of fentanyl. We implant rats with intravenous catheters in preparation for fentanyl intravenous self-administration (IVSA) on an escalating schedule of reinforcement to determine factors that influence fentanyl intake, including sex, dose, and gut microbiota. Our data show the impact of fentanyl IVSA on gut microbiota diversity, as well as the role of gut microbiota on fentanyl IVSA, in Sprague Dawley rats in a sex- and dose-dependent manner (n = 10–16/group). We found that the diversity of gut microbiota within females dose-dependently predicts progressive but not fixed ratio schedules of fentanyl IVSA. Depending on sex and fentanyl dose, alpha diversity (richness and evenness measured with Shannon index) is either increased or decreased following fentanyl IVSA and predicts progressive ratio breakpoint. Our findings collectively suggest a role of gut bacteria in drug-related behavior, including motivation and reinforcement. This work provides feasibility for an intravenous fentanyl self-administration model and uncovers potential factors mediating drug use, which may lead to the development of effective addiction interventions.

Viewing Bacterial Colonization through the Lens of Systems Biology

The gastrointestinal ecosystem is formed from interactions between the host, indigenous gut microbiota, and external world. When colonizing the gut, bacteria must overcome barriers imposed by the intestinal environment, such as host immune responses and microbiota-mediated nutrient limitation. Thus, understanding bacterial colonization requires determining how the gut landscape interacts with microbes attempting to establish within the ecosystem. However, the complicated network of interactions between elements of the intestinal environment makes it challenging to uncover emergent properties of the system using only reductionist methods. A systems biology approach, which aims to investigate complex systems by examining the behavior and relationships of all elements of the system, may afford a more holistic perspective of the colonization process. Here, we examine the confluence between the gut landscape and bacterial colonization through the lens of systems biology. We offer an overview of the conceptual and methodological underpinnings of systems biology, followed by a discussion of key elements of the gut ecosystem as they pertain to bacterial establishment and growth. We conclude by reintegrating these elements to guide future comprehensive investigations of the ecosystem in the context of bacterial intestinal colonization.

Early Life Social Stress Causes Sex- and Region-Dependent Dopaminergic Changes that Are Prevented by Minocycline

Early life stress (ELS) is known to modify trajectories of brain dopaminergic development, but the mechanisms underlying have not been determined. ELS perturbs immune system and microglia reactivity, and inflammation and microglia influence dopaminergic transmission and development. Whether microglia mediate the effects of ELS on dopamine (DA) system development is still unknown. We explored the effects of repeated early social stress on development of the dopaminergic system in male and female mice through histological, electrophysiological, and transcriptomic analyses. Furthermore, we tested whether these effects could be mediated by ELS-induced altered microglia/immune activity through a pharmacological approach. We found that social stress in early life altered DA neurons morphology, reduced dopamine transporter (DAT) and tyrosine hydroxylase expression, and lowered DAT-mediated currents in the ventral tegmental area but not substantia nigra of male mice only. Notably, stress-induced DA alterations were prevented by minocycline, an inhibitor of microglia activation. Transcriptome analysis in the developing male ventral tegmental area revealed that ELS caused downregulation of dopaminergic transmission and alteration in hormonal and peptide signaling pathways. Results from this study offer new insight into the mechanisms of stress response and altered brain dopaminergic maturation after ELS, providing evidence of neuroimmune interaction, sex differences, and regional specificity.

The Impact of Probiotic Bacillus subtilis on Injurious Behavior in Laying Hens

Simple Summary

Injurious behavior prevention is a critical issue in the poultry industry due to increasing social stress, leading to negative effects on bird production and survivability, consequently enhancing gut microbiota dysbiosis and neuroinflammation via the microbiota–gut–brain axis. Probiotics have been used as potential therapeutic psychobiotics to treat or improve neuropsychiatric disorders or symptoms by boosting cognitive and behavioral processes and reducing stress reactions in humans and various experimental animals. The current data will first report that probiotic Bacillus subtilis reduces stress-induced injurious behavior in laying hens via regulating microbiota–gut–brain function with the potential to be an alternative to beak trimming during poultry egg production.

Abstract

Intestinal microbiota functions such as an endocrine organ to regulate host physiological homeostasis and behavioral exhibition in stress responses via regulating the gut–brain axis in humans and other mammals. In humans, stress-induced dysbiosis of the gut microbiota leads to intestinal permeability, subsequently affecting the clinical course of neuropsychiatric disorders, increasing the frequency of aggression and related violent behaviors. Probiotics, as direct-fed microorganism, have been used as dietary supplements or functional foods to target gut microbiota (microbiome) for the prevention or therapeutic treatment of mental diseases including social stress-induced psychiatric disorders such as depression, anxiety, impulsivity, and schizophrenia. Similar function of the probiotics may present in laying hens due to the intestinal microbiota having a similar function between avian and mammals. In laying hens, some management practices such as hens reared in conventional cages or at a high stocking density may cause stress, leading to injurious behaviors such as aggressive pecking, severe feather pecking, and cannibalism, which is a critical issue facing the poultry industry due to negative effects on hen health and welfare with devastating economic consequences. We discuss the current development of using probiotic Bacillus subtilis to prevent or reduce injurious behavior in laying hens.

Satiety Associated with Calorie Restriction and Time-Restricted Feeding: Central Neuroendocrine Integration

This review focuses on summarizing current knowledge on how time-restricted feeding (TRF) and continuous caloric restriction (CR) affect central neuroendocrine systems involved in regulating satiety. Several interconnected regions of the hypothalamus, brainstem, and cortical areas of the brain are involved in the regulation of satiety. Following CR and TRF, the increase in hunger and reduction in satiety signals of the melanocortin system [neuropeptide Y (NPY), proopiomelanocortin (POMC), and agouti-related peptide (AgRP)] appear similar between CR and TRF protocols, as do the dopaminergic responses in the mesocorticolimbic circuit. However, ghrelin and leptin signaling via the melanocortin system appears to improve energy balance signals and reduce hyperphagia following TRF, which has not been reported in CR. In addition to satiety systems, CR and TRF also influence circadian rhythms. CR influences the suprachiasmatic nucleus (SCN) or the primary circadian clock as seen by increased clock gene expression. In contrast, TRF appears to affect both the SCN and the peripheral clocks, as seen by phasic changes in the non-SCN (potentially the elusive food entrainable oscillator) and metabolic clocks. The peripheral clocks are influenced by the primary circadian clock but are also entrained by food timing, sleep timing, and other lifestyle parameters, which can supersede the metabolic processes that are regulated by the primary circadian clock. Taken together, TRF influences hunger/satiety, energy balance systems, and circadian rhythms, suggesting a role for adherence to CR in the long run if implemented using the TRF approach. However, these suggestions are based on only a few studies, and future investigations that use standardized protocols for the evaluation of the effect of these diet patterns (time, duration, meal composition, sufficiently powered) are necessary to verify these preliminary observations.

Role of the nuclear receptor subfamily 4a in mast cells in the development of irritable bowel syndrome

The activation of mast cells (MCs) and mediator release are closely related to the pathophysiology of irritable bowel syndrome (IBS). However, the exact underlying mechanisms are still not completely understood. The nuclear receptor subfamily 4a (Nr4a) is a family of orphan nuclear receptors implicated in regulating MC activation, degranulation, cytokine/chemokine synthesis and release. Acute and chronic stress trigger hypothalamic–pituitaryadrenal axis (HPA) activation to induce the release of corticotropin-releasing hormone (CRH), resulting in MC activation and induction of the Nr4a family. Our newest data showed that Nr4a members were specially over-expressed in colonic MCs of the chronic water-avoidance stress (WAS)-induced visceral hyperalgesia mice, suggesting that Nr4a members might be involved in the pathophysiology of visceral hypersensitivity. In this review, we highlight the present knowledge on roles of Nr4a members in the activation of MCs and the pathophysiology of IBS, and discuss signaling pathways that modulate the activation of Nr4a family members. We propose that a better understanding of Nr4a members and their modulators may facilitate the development of more selective and effective therapies to treat IBS patients.

Potential roles of the gut microbiota in the manifestations of drug use disorders

Drug use disorders (DUDs) not only cause serious harm to users but also cause huge economic, security, and public health burdens to families and society. Recently, several studies have shown that gut microbiota (GM) can affect the central nervous system and brain functions. In this review, we focus on the potential role of the GM in the different stages of DUDs. First, the GM may induce individuals to seek novel substances. Second, the gut microbiota is involved in the decomposition and absorption of drugs. Symptoms of individuals who suffer from DUDs are also related to intestinal microorganisms. Third, the effects of the GM and its metabolites on drug relapse are mainly reflected in the reward effect and drug memory. In conclusion, recent studies have preliminarily explored the relationship between GM and DUDs. This review deepens our understanding of the mechanisms of DUDs and provides important information for the future development of clinical treatment for DUDs.

Microbiota and body weight control: Weight watchers within?

Background

Despite several decades of research, managing body weight remains an unsolved clinical problem. Health problems associated with dysregulated body weight, such as obesity and cachexia, exhibit several gut microbiota alterations. There is an increased interest in utilising the gut microbiota for body weight control, as it responds to intervention and plays an important role in energy extraction from food, as well as biotransformation of nutrients.

Scope of the review

This review provides an overview of the role of the gut microbiota in the physiological and metabolic alterations observed in two body weight dysregulation-related disorders, namely obesity and cachexia. Second, we assess the available evidence for different strategies, including caloric restriction, intermittent fasting, ketogenic diet, bariatric surgery, probiotics, prebiotics, synbiotics, high-fibre diet, and fermented foods – effects on body weight and gut microbiota composition. This approach was used to give insights into the possible link between body weight control and gut microbiota configuration.

Major conclusions

Despite extensive associations between body weight and gut microbiota composition, limited success could be achieved in the translation of microbiota-related interventions for body weight control in humans. Manipulation of the gut microbiota alone is insufficient to alter body weight and future research is needed with a combination of strategies to enhance the effects of lifestyle interventions.

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The gut microbiota is involved in the control of nutrient availability, appetite, and body weight.

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Both obesity and cachexia are associated with altered gut microbiota.

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Specific dietary and surgical approaches positively impact body weight and gut microbiota.

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Manipulation of the gut microbiota alone is insufficient to alter body weight in humans.

Sodium Butyrate Protects Against Ethanol-Induced Toxicity in SH-SY5Y Cell Line

Alcohol use disorder (AUD), brought about by excessive alcohol use, is associated with damages to several organs including the brain. Chronic excessive use of alcohol can compromise intestinal integrity, leading to changes in gut microbiota (GM) composition known as dysbiosis. Dysbiosis, by disruption of the gut-brain axis (GBA), further exacerbates the deleterious effects of alcohol. One of the fermentation by-products of GM is butyrate (BUT), a short-chain fatty acid (SCFA) that plays an important role in maintaining homeostasis of the GBA. Alcohol metabolism results in formation of acetaldehyde, a highly reactive compound that reacts with dopamine in the brain to form toxic adducts such as salsolinol. Recent studies indicate potential neuro-protective effects of BUT against various toxicants including salsolinol. Here, we sought to investigate whether BUT can also protect against alcohol toxicity. Pretreatment of neuroblastoma-derived SH-SY5Y cells with 500 mM ethanol (ETOH) for 24 h resulted in approximately 40% reduction in cell viability, which was totally blocked by 10 µM of either BUT or AR 420,626 (AR), a selective fatty acid 3 receptor (FA3R) agonist. The neuro-protective effects of both BUT and AR were significantly (80%) attenuated by beta-hydroxy butyrate (BHB), a selective FA3R antagonist. Interestingly, combination of BUT and AR resulted in synergistic protection against ETOH, which was totally blocked by BHB. These findings suggest potential utility of butyrate and/or FA3R agonists against ETOH-induced toxicity.

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.

The Microbiome-Gut-Brain Axis, a Potential Therapeutic Target for Substance-Related Disorders

Substance addiction is a complex worldwide public health problem. It endangers both personal life and social stability, causing great loss on economy. Substance-related disorder is considered to be a complicated chronic brain disorder. It resulted from interactions among pharmacological properties of addictive substances, individual susceptibility, and social–environmental factors. Unfortunately, there is still no ideal treatment for this disorder. Recent lines of evidence suggest that gut microbiome may play an important role in the pathogenesis of neuropsychiatric disorders, including substance-related disorders. This review summarizes the research on the relationship between gut microbiome and substance-related disorders, including different types of substance, different individual susceptibility, and the occurrence and development of substance-induced mental disorders. We also discuss the potentiation of gut microbiome in the treatment of substance-related disorders, especially in the treatment of substance-induced mental disorders and manipulation on individuals’ responsiveness to addictive substances.

Drugs and bugs: Negative affect, psychostimulant use and withdrawal, and the microbiome

BACKGROUND AND OBJECTIVES

A growing body of literature demonstrates that the human microbiota plays a crucial role in health and disease states, as well as in the body's response to stress. In addition, the microbiome plays a role in psychological well-being and regulating negative affect. Regulation of negative affect is a factor in psychostimulant abuse disorders. We propose a risk chain in which stress leads to negative affect that places an individual at risk to develop or relapse to psychostimulant abuse disorder. Stress, negative affect, and psychostimulant use all alter the gut microbiome.

METHODS

This review brings together the literature on affective disorders, stress, and psychostimulant abuse disorders to assess possible modulatory actions of the gut-brain axis to regulate these conditions.

RESULTS

Studies reviewed across the various disciplines suggest that the dysbiosis resulting from drug use, drug withdrawal, or stress may cause an individual to be more susceptible to addiction and relapse. Probiotics and prebiotics reduce stress and negative affect.

SCIENTIFIC SIGNIFICANCE

Treatment during the withdrawal phase of psychostimulant abuse disorder, when the microbiome is altered, may ameliorate the symptoms of stress and negative affect leading to a reduced risk of relapse to psychostimulant use.

Decoding the Role of Gut-Microbiome in the Food Addiction Paradigm

Eating behaviour is characterised by a solid balance between homeostatic and hedonic regulatory mechanisms at the central level and highly influenced by peripheral signals. Among these signals, those generated by the gut microbiota have achieved relevance in recent years. Despite this complex regulation, under certain circumstances eating behaviour can be deregulated becoming addictive. Although there is still an ongoing debate about the food addiction concept, studies agree that patients with eating addictive behaviour present similar symptoms to those experienced by drug addicts, by affecting central areas involved in the control of motivated behaviour. In this context, this review tries to summarise the main data regarding the role of the gut microbiome in eating behaviour and how a gut dysbiosis can be responsible for a maladaptive behaviour such as “food addiction”.