Fecal Short Chain Fatty Acids and Dietary Intake in Italian Women With Restrictive Anorexia Nervosa: A Pilot Study

Relationship of Genetic Polymorphisms and Microbial Composition with Binge Eating Disorder: A Systematic Review

Humans are the result of an evolutionary process, and because of this, many biological processes are interconnected with each other. The intestine-brain axis consists of an intricately connected neuronal-neuroendocrine circuit that regulates the sensation of hunger and satiety. Genetic variations and the consumption of unnatural diets (ultra-processed foods, high contents of sugars, etc.) can override this circuit and cause addiction to certain foods and/or the inability to feel satiety in certain situations. The patients who come to consultations (mainly psychology or nutrition) in an attempt to resolve this problem sometimes fail, which leads to them looking for new strategies based on biological predisposition. This investigation aims to evaluate the genetic studies regarding the microbiota carried out in the last 12 years in humans to try to determine which genes and microbes that have been recently studied are related to patients diagnosed with binge eating disorder or compulsive eating (presenting obesity or not). The protocol followed the PRISMA statement, and the following databases were searched from 2012 until the present day: PubMed, PsycINFO, SCOPUS, and Web of Science. Twenty-four international articles were analyzed, including cross-sectional or exploratory studies; five of them referred to the microbial composition, and in nineteen, the existence of genetic polymorphisms present in binge eating disorder or in compulsive eating could be observed: DRD2, OPRM1, COMT, MC4R, BNDF, FTO, SLC6A3, GHRL, CARTPT, MCHR2, and LRP11. Even though there is still much to investigate on the subject, it must be highlighted that, in the last 4 years, a two-fold increase has been observed in potential markers and in studies related to the matter, also highlighting the importance of different analyses in relation to psychosocial factors and their interaction with the genetic and microbial factors, for which research on the matter must be continued.

The Microbiome in Child and Adolescent Psychiatry

Recent research has increasingly emphasized the function of the microbiome in human health. The gut microbiome is essential for digesting food and seems to play a vital role in mental health as well. This review briefly overviews the gut microbiome and its interplay with the central nervous system. We then summarize some of the latest findings on the possible role of the microbiome in psychiatric disorders in children and adolescents. In particular, we focus on autism spectrum disorder, attention-deficit/hyperactivity disorder, anorexia nervosa, bipolar disorder, and major depressive disorder. Although the role of microbiota in mental development and health still needs to be researched intensively, it has become increasingly apparent that the impact of microbiota must be considered to better understand psychiatric disorders.

Probiotic and prebiotic interventions in eating disorders: A narrative review

AIMS

The review aimed to summarise and discuss findings focused on therapeutic probiotic and prebiotic interventions in eating disorders (ED).

METHODS

Using PubMed/MEDLINE, Cochrane Library, and Web of Science all published studies were retrieved until February 2023, following PRISMA guidelines. From the 111 initial studies, 5 met the inclusion criteria for this review.

RESULTS

All studies included in this narrative review were focused on anorexia nervosa (AN). Three longitudinal, randomised, controlled trials aimed to evaluate interventions with probiotics (Lactobacillus reuteri, yoghurt with Lactobacillus, and Streptococcus) in children and adolescents. These studies primarily emphasised medical outcomes and anthropometric measures following the administration of probiotics. However, the findings yielded mixed results in terms of short-term weight gain or alterations in specific immunological parameters. With a lower level of evidence, supplementation with synbiotics (probiotic + prebiotic) has been associated with improvements in microbiota diversity and attenuation of inflammatory responses.

CONCLUSIONS

Research on probiotics and prebiotics in ED is limited, primarily focussing on anorexia nervosa (AN). Their use in AN regarding medical and anthropometric outcomes needs further confirmation and future research should be warranted to assess their impact on psychological and ED symptomatology, where there is a notable gap in the existing literature.

The role of short-chain fatty acids (SCFAs) in regulating stress responses, eating behavior, and nutritional state in anorexia nervosa: protocol for a randomized controlled trial

OBJECTIVE

This protocol proposes investigating the effects of short-chain fatty acids (SCFAs)-namely acetate, propionate, and butyrate-as mediators of microbiota-gut-brain interactions on the acute stress response, eating behavior, and nutritional state in malnourished patients with anorexia nervosa (AN). SCFAs are produced by bacterial fermentation of dietary fiber in the gut and have recently been proposed as crucial mediators of the gut microbiota's effects on the host. Emerging evidence suggests that SCFAs impact human psychobiology through endocrine, neural, and immune pathways and may regulate stress responses and eating behavior.

METHOD

We will conduct a randomized, triple-blind, placebo-controlled trial in 92 patients with AN. Patients will receive either a placebo or a mixture of SCFAs (acetate propionate, butyrate) using pH-dependent colon-delivery capsules for six weeks. This clinical trial is an add-on to the standard inpatient psychotherapeutic program focusing on nutritional rehabilitation.

HYPOTHESES

We hypothesize that colonic SCFAs delivery will modulate neuroendocrine, cardiovascular, and subjective responses to an acute laboratory psychosocial stress task. As secondary outcome measures, we will assess alterations in restrictive eating behavior and nutritional status, as reflected by changes in body mass index. Additionally, we will explore changes in microbiota composition, gastrointestinal symptoms, eating disorder psychopathology, and related comorbidities.

DISCUSSION

The findings of this study would enhance our understanding of how gut microbiota-affiliated metabolites, particularly SCFAs, impact the stress response and eating behavior of individuals with AN. It has the potential to provide essential insights into the complex interplay between the gut, stress system, and eating behavior and facilitate new therapeutic targets for stress-related psychiatric disorders. This protocol is prospectively registered with ClinicalTrials.gov, with trial registration number NCT06064201.

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 Impact of Anorexia Nervosa and the Basis for Non-Pharmacological Interventions

Anorexia nervosa is a psychiatric disorder with an unknown etiology that is characterized by an individual's preoccupation with their weight and body structure while denying the severity of their low body weight. Due to the fact that anorexia nervosa is multifaceted and may indicate the coexistence of genetic, social, hormonal, and psychiatric disorders, a description of non-pharmacological interventions can be used to ameliorate or reduce the symptoms of this condition. Consequently, the purpose of the present narrative review is to describe the profile's context in the anorexic person as well as the support they would require from their family and environment. In addition, it is aimed at examining preventative and non-pharmacological interventions, such as nutritional interventions, physical activity interventions, psychological interventions, psychosocial interventions, and physical therapy interventions. To reach the narrative review aims, a critical review was conducted utilizing both primary sources, such as scientific publications, and secondary sources, such as bibliographic indexes, web pages, and databases. Nutritional interventions include nutritional education and an individualized treatment for each patient, physical activity interventions include allowing patients to perform controlled physical activity, psychological interventions include family therapy and evaluation of the existence of other psychological disorders, psychosocial interventions include management of the relationship between the patient and social media and physical therapy interventions include relaxation massages and exercises to relieve pain. All these non-pharmacological interventions need to be individualized based on each patient's needs.

Novel ketamine and zinc treatment for anorexia nervosa and the potential beneficial interactions with the gut microbiome

Anorexia nervosa (AN) is a severe illness with diverse aetiological and maintaining contributors including neurobiological, metabolic, psychological, and social determining factors. In addition to nutritional recovery, multiple psychological and pharmacological therapies and brain-based stimulations have been explored; however, existing treatments have limited efficacy. This paper outlines a neurobiological model of glutamatergic and γ-aminobutyric acid (GABA)-ergic dysfunction, exacerbated by chronic gut microbiome dysbiosis and zinc depletion at a brain and gut level. The gut microbiome is established early in development, and early exposure to stress and adversity contribute to gut microbial disturbance in AN, early dysregulation to glutamatergic and GABAergic networks, interoceptive impairment, and inhibited caloric harvest from food (e.g., zinc malabsorption, competition for zinc ions between gut bacteria and host). Zinc is a key part of glutamatergic and GABAergic networks, and also affects leptin and gut microbial function; systems dysregulated in AN. Low doses of ketamine in conjunction with zinc, could provide an efficacious combination to act on NMDA receptors and normalise glutamatergic, GABAergic and gut function in AN.

Gut microbiome-brain interactions in anorexia nervosa: Potential mechanisms and regulatory strategies

Anorexia nervosa (AN) is a psychiatric disorder characterised by malnutrition, fear of weight gain, and body image disturbances. The aetiology of AN is complex, and may involve environmental factors, genetic factors, and biochemical factors, with the latter meaning that AN may be closely associated with neurons, neurotransmitters, and hormones related to appetite and emotional regulation. In addition, an increasing number of studies have shown there is a link between the intestinal microbiota and psychiatric disorders, such as depression. However, few studies and reviews have focused on AN and gut microbes. Accordingly, in this review, we examine the potential pathogenesis of AN in terms of changes in the gut microbiota and its metabolites, and their effects on AN. The neurobiological function of the nervous system in relation to AN are also been mentioned. Furthermore, we suggest future research directions for this field, and note that probiotics may be developed for use as dietary supplements to help alleviate AN in patients.

Associations of disordered eating with the intestinal microbiota and short-chain fatty acids among young adults with type 1 diabetes

BACKGROUND AND AIMS

Disordered eating (DE) in type 1 diabetes (T1D) includes insulin restriction for weight loss with serious complications. Gut microbiota-derived short chain fatty acids (SCFA) may benefit host metabolism but are reduced in T1D. We evaluated the hypothesis that DE and insulin restriction were associated with reduced SCFA-producing gut microbes, SCFA, and intestinal microbial diversity in adults with T1D.

METHODS AND RESULTS

We collected stool samples at four timepoints in a hypothesis-generating gut microbiome pilot study ancillary to a weight management pilot in young adults with T1D. 16S ribosomal RNA gene sequencing measured the normalized abundance of SCFA-producing intestinal microbes. Gas-chromatography mass-spectrometry measured SCFA (total, acetate, butyrate, and propionate). The Diabetes Eating Problem Survey-Revised (DEPS-R) assessed DE and insulin restriction. Covariate-adjusted and Bonferroni-corrected generalized estimating equations modeled the associations. COVID-19 interrupted data collection, so models were repeated restricted to pre-COVID-19 data. Data were available for 45 participants at 109 visits, which included 42 participants at 65 visits pre-COVID-19. Participants reported restricting insulin "At least sometimes" at 53.3% of visits. Pre-COVID-19, each 5-point DEPS-R increase was associated with a -0.34 (95% CI -0.56, -0.13, p = 0.07) lower normalized abundance of genus Anaerostipes; and the normalized abundance of Lachnospira genus was -0.94 (95% CI -1.5, -0.42), p = 0.02 lower when insulin restriction was reported "At least sometimes" compared to "Rarely or Never".

CONCLUSION

DE and insulin restriction were associated with a reduced abundance of SCFA-producing gut microbes pre-COVID-19. Additional studies are needed to confirm these associations to inform microbiota-based therapies in T1D.

Anorexia nervosa and gut microbiome: implications for weight change and novel treatments

INTRODUCTION

Host-microbiota interactions may be involved in many physical and psychological functions ranging from the digestion of food, maintenance of immune homeostasis, to the regulation of mood and cognition. Microbiome dysbiosis has been consistently described in many diseases. The pathogenesis and weight regulation mechanism in anorexia nervosa (AN) also seem to be implicated in the dynamic bidirectional adjustment of the microbiota-gut-brain axis. This review aims at elucidating this relationship.

AREA COVERED

This review starts with a description of pathogenic gut-brain pathways. Next, we focus on the latest research on the associations between gut microbiota and weight change in the condition of AN. The strategies to alter the intestinal microbiome for the treatment of this disorder are discussed, including dietary, probiotics, prebiotics, synbiotics, and fecal microbiota transplantation.

EXPERT OPINION

Gut microbiome is inextricably linked to AN. It may regulate weight gain in the process of refeeding via the microbiota-gut-brain axis, while the specific mechanism has yet to be clearly established. In the future, a better understanding of gut microbiome could have implications for developing microbiome-based prevention, diagnostics and therapies.

An In Vitro Approach to Studying the Microbial Community and Impact of Pre and Probiotics under Anorexia Nervosa Related Dietary Restrictions

Individuals with anorexia nervosa (AN) often suffer psychological and gastrointestinal problems consistent with a dysregulated gut microbial community. Psychobiotics have been postulated to modify microbiota and improve mental well-being and gut symptoms, but there is currently a lack of evidence for such approaches in AN. The aim of this study was to use an in vitro colonic model to evaluate the impact of dietary restrictions associated with AN on the intestinal ecosystem and to assess the impact of pre and probiotic intervention. Bacteriology was quantified using flow cytometry combined with fluorescence in situ hybridisation and metabolic end products (including neurotransmitters) by gas chromatography and liquid chromatography mass spectrometry Consistent with previous research, the nutritional changes significantly reduced total microbiota and metabolites compared with healthy conditions. Pre and probiotic supplementation on restricted conditions enhanced the microbial community and modulated metabolic activity to resemble that of a healthy diet. The model system indicates that nutritional changes associated with AN can impact the microbial community, and that these changes can, at least in part, be restored through the use of pre and probiotic interventions.

[The Gut Microbiome and Its Clinical Implications in Anorexia Nervosa]

The Gut Microbiome and Its Clinical Implications in Anorexia Nervosa Abstract. The diverse interactions of the gut microbiome with the metabolism, the immune system, and the brain of the host are increasingly becoming to the forefront of relevant research. Studies suggest a connection between an altered intestinal microbiome and somatic diseases, such as colitis ulcerosa, Crohn's disease, and diabetes, as well as mental illnesses such as anxiety and depression. Patients with anorexia nervosa (AN) also show significant changes in their gut microbiome which seem to be associated, among other things, with a different energy uptake from food, immunological and inflammatory processes, genetic predisposition, hormonal changes, and possibly increased intestinal permeability. In rats, stool transplantation from patients with AN resulted in decreased appetite and weight as well as anxious and compulsive behavior. In this review, we summarize the possible mechanisms of interaction between the microbiome and the host, and present initial findings on the microbiome in AN. Research on nutritional interventions, for example, with prebiotics and probiotics or nutritional supplements such as omega-3 fatty acids, which aim to positively influence the intestinal microbiome, could lead to additional treatment options in the therapy of patients with AN.

Progress in understanding of relationship between short chain fatty acids and irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional intestinal disease whose pathogenesis has not yet been fully defined. The main clinical manifestations of IBS are irregular abdominal pain, abdominal distension, and changes in stool character and defecation habits. As one of the pathogeneses of IBS, intestinal flora imbalance plays an important role in the development of IBS. The vast majorities of short chain fatty acids (SCFAs) are produced through the interaction of intestinal flora with host diet in the colon. As one of the main metabolites of intestinal flora, SCFAs have the effects of intestinal barrier protection, immune regulation, anti-inflammation, and regulation of visceral sensitivity in the intestine. In recent years, with the increasing attention to SCFAs, studies on the relationship between SCFAs and IBS are emerging. This review summarizes the progress in the understanding of the relationship between SCFAs and IBS in recent five years.

Gut Microbiota in Psychiatric Disorders: A Systematic Review

OBJECTIVE

This systematic review sought to comprehensively summarize gut microbiota research in psychiatric disorders following PRISMA guidelines.

METHODS

Literature searches were performed on databases using keywords involving gut microbiota and psychiatric disorders. Articles in English with human participants up until February 13, 2020, were reviewed. Risk of bias was assessed using a modified Newcastle-Ottawa Scale for microbiota studies.

RESULTS

Sixty-nine of 4231 identified studies met the inclusion criteria for extraction. In most studies, gut microbiota composition differed between individuals with psychiatric disorders and healthy controls; however, limited consistency was observed in the taxonomic profiles. At the genus level, the most replicated findings were higher abundance of Bifidobacterium and lower abundance of Roseburia and Faecalibacterium among patients with psychiatric disorders.

CONCLUSIONS

Gut bacteria that produce short-chain fatty acids, such as Roseburia and Faecalibacterium, could be less abundant in patients with psychiatric disorders, whereas commensal genera, for example, Bifidobacterium, might be more abundant compared with healthy controls. However, most included studies were hampered by methodological shortcomings including small sample size, unclear diagnostics, failure to address confounding factors, and inadequate bioinformatic processing, which might contribute to inconsistent results. Based on our findings, we provide recommendations to improve quality and comparability of future microbiota studies in psychiatry.

A systematic review on the role of microbiota in the pathogenesis and treatment of eating disorders

Background

There is growing interest in new factors contributing to the genesis of eating disorders (EDs). Research recently focused on the study of microbiota. Dysbiosis, associated with a specific genetic susceptibility, may contribute to the development of anorexia nervosa (AN), bulimia nervosa, or binge eating disorder, and several putative mechanisms have already been identified. Diet seems to have an impact not only on modification of the gut microbiota, facilitating dysbiosis, but also on its recovery in patients with EDs.

Methods

This systematic review based on the PICO strategy searching into PubMed, EMBASE, PsychINFO, and Cochrane Library examined the literature on the role of altered microbiota in the pathogenesis and treatment of EDs.

Results

Sixteen studies were included, mostly regarding AN. Alpha diversity and short-chain fatty acid (SCFA) levels were lower in patients with AN, and affective symptoms and ED psychopathology seem related to changes in gut microbiota. Microbiota-derived proteins stimulated the autoimmune system, altering neuroendocrine control of mood and satiety in EDs. Microbial richness increased in AN after weight regain on fecal microbiota transplantation.

Conclusions

Microbiota homeostasis seems essential for a healthy communication network between gut and brain. Dysbiosis may promote intestinal inflammation, alter gut permeability, and trigger immune reactions in the hunger/satiety regulation center contributing to the pathophysiological development of EDs. A restored microbial balance may be a possible treatment target for EDs. A better and more in-depth characterization of gut microbiota and gut–brain crosstalk is required. Future studies may deepen the therapeutic and preventive role of microbiota in EDs.

The Gut Microbiome in Anorexia Nervosa: Friend or Foe?

The human gut microbiome is emerging as a key modulator of homeostasis, with far-reaching implications for various multifactorial diseases, including anorexia nervosa (AN). Despite significant morbidity and mortality, the underlying mechanisms of this eating disorder are poorly understood, but the classical view defining AN as a purely psychiatric condition is increasingly being challenged. Accumulating evidence from comparative studies of AN and healthy fecal microbial composition reveals considerable low divergence and altered taxonomic abundance of the AN gut microbiome. When integrated with preclinical data, these findings point to a significant role of the gut microbiome in AN pathophysiology, via effects on host energy metabolism, intestinal permeability, immune function, appetite, and behavior. While complex causal relationships between genetic risk factors, dietary patterns and microbiome, and their relevance for AN onset and perpetuation have not been fully elucidated, preliminary clinical studies support the use of microbiome-based interventions such as fecal microbiota transplants and probiotics as adjuvants to standard AN therapies. Future research should aim to move from observational to mechanistic, as dissecting how specific microbial taxa interact with the host to impact the development of AN could help design novel therapeutic approaches that more effectively address the severe comorbidities and high relapse rate of this serious disorder.

Reconceptualizing anorexia nervosa

Anorexia nervosa (AN) has one of the highest mortality rates of any psychiatric disorder. Treatments are often ineffective and relapse is common. Most research attempting to understand the underlying causes and maintenance factors of AN has focused on environmental contributions, yet there is much to be explored in terms of biological risk and maintenance factors. In this paper, we focus primarily on AN research related to genetics and the complex microbial community in the gut (intestinal microbiota), and how these impact our conceptualization of this disorder. Emerging research identifying significant negative genetic correlations between AN and obesity suggests that the conditions may represent 'metabolic bookends'. The identification of underlying biological mechanisms may provide both insight into extreme weight dysregulation on both ends of the spectrum and new possible points of entry for AN treatment. Additionally, the reported microbial imbalance (dysbiosis) in the gut microbiota in AN patients, potentially due to a nutrient- and energy-deprived gut environment, implies alterations in functional and metabolic capacity of the gut microbiome. The extent to which AN and obesity can also be considered to be 'microbiome bookends' requires further investigation. Finally, we discuss ongoing and future AN projects exploring the interplay between host genomics, the environment, and cumulative microbial genomes (microbiome) as well as interventions at the microbial and gut level.

Alterations in fecal short-chain fatty acids in patients with irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND

Recent studies indicate that gut microbiota disorders potentially contribute to the pathogenesis of irritable bowel syndrome (IBS), which can be partly reflected by fecal short-chain fatty acids (SCFAs) generated from gut microbiota. Previous studies on SCFA alterations in patients with IBS have yielded conflicting results. No prior systematic review has been conducted on the alterations in fecal SCFAs in IBS patients.

AIMS

We performed a meta-analysis to explore and clarify alterations in fecal SCFAs in IBS patients.

METHODS

Case-control studies, randomized controlled trials (RCTs), and self-controlled studies were identified through electronic database searches. The standardized mean difference (SMD) with 95% confidence interval (CI) in fecal SCFA levels between different groups was calculated.

RESULTS

The proportion of fecal propionate in patients with IBS was significantly higher than in healthy controls (HCs) (SMD = 0.44, 95% CI = 0.12, 0.76). A subgroup analysis showed that the concentration of fecal propionate (SMD = -0.91, 95% CI = -1.41, -0.41) and butyrate (SMD = -0.53, 95% CI = -1.01, -0.04) in patients with constipation-predominant IBS (IBS-C) was significantly lower than that in HCs, and the concentration of fecal butyrate in patients with diarrhea-predominant IBS (IBS-D) was higher than that in HCs (SMD = 0.34, 95% CI = 0.00, 0.67). Finally, we found that restricted diets correlated with fecal butyrate reduction in IBS (SMD = -0.26, 95% CI = -0.51, -0.01).

CONCLUSIONS

In terms of fecal SCFAs, there were differences between patients with IBS and HCs. In IBS-C patients, propionate and butyrate were reduced, whereas butyrate was increased in IBS-D patients in comparison to HCs. Propionate and butyrate could be used as biomarkers for IBS diagnosis.