The trace aminergic system: a gender-sensitive therapeutic target for IBS?

Functional Analysis of TAAR1 Expression in the Intestine Wall and the Effect of Its Gene Knockout on the Gut Microbiota in Mice

Currently, the TAAR1 receptor has been identified in various cell groups in the intestinal wall. It recognizes biogenic amine compounds like phenylethylamine or tyramine, which are products of decarboxylation of phenylalanine and tyrosine by endogenous or bacterial decarboxylases. Since several gut bacteria produce these amines, TAAR1 is suggested to be involved in the interaction between the host and gut microbiota. The purpose of this present study was to clarify the TAAR1 function in the intestinal wall and estimate the TAAR1 gene knockout effect on gut microbiota composition. By analyzing public transcriptomic data of the GEO repository, we identified TAAR1 expression in enterocytes, enteroendocrine cells, tuft cells, and myenteric neurons in mice. The analysis of genes co-expressed with TAAR1 in enteroendocrine cells allows us to suggest the TAAR1 involvement in enteroendocrine cell maturation. Also, in myenteric neurons, we identified the co-expression of TAAR1 with calbindin, which is specific for sensory neurons. The 16S rRNA gene-based analysis of fecal microbiota revealed a slight but significant impact of TAAR1 gene knockout in mice on the gut microbial community, which manifests in the higher diversity, accompanied by low between-sample variability and reorganization of the microbial co-occurrence network.

Effect of Chronic Dolutegravir Administration on the Trace Amine Profile in Wistar Rats

BACKGROUND

Dolutegravir (DTG), an integrase strand inhibitor, is currently used as the first-line treatment for HIV. Despite relatively poor tissue penetration, the risk of adverse effects in metabolic and excretory systems should be considered. The trace aminergic system and trace amines are emerging as relevant role players in many chronic diseases that are commonly diagnosed but poorly understood. Trace amines are biogenic amines that are endogenously produced and can also be ingested by the intake of trace amine-rich food. Trace amines are known to differentially regulate inflammatory and neurological outcome.

OBJECTIVE

This study investigated the effects of DTG on the trace amine profile in a wistar rat model.

METHODS

A total of 24 healthy wistar rats were randomly divided into four experimental groups: male and female controls and male and female DTG-treated. Blood and tissue samples were collected following a 12-week DTG administration study. Liquid chromatography-tandem mass spectroscopy (LC-MS/MS) was used to determine trace amine concentrations in urine, plasma, brain, and gastrointestinal tissue.

RESULTS

Current data illustrate that polyamines differ significantly (p < 0.05) between males and females in various matrices. DTG significantly (p < 0.05) reduced jejunal tyramine and urinary synephrine levels.

CONCLUSION

Data do not raise major concerns about DTG in the context of the trace amine profile. However, given the importance of the dysregulated trace amine profile in various diseased states, including HIV, current data warrant clinical investigation to further evaluate the significance of DTG-associated effects on the trace amine profile.

Psychedelic therapy in depression and substance use disorders

Psychoactive substances obtained from botanicals have been applied for a wide variety of purposes in the rituals of different cultures for thousands of years. Classical psychedelics from N,N'-dimethyltryptamine, psilocybin, mescaline and various lysergamides cause specific alterations in perception, emotion and cognition by acting through serotonin 5-HT2A receptor activation. Lysergic acid diethylamide, the first famous breakthrough in the field, was discovered by chance by Albert Hoffman in the Zurich Sandoz laboratory in 1943, and studies on its psychoactive effects began to take place in the literature. Studies in this area were blocked after the legislation controlling the use and research of psychedelic drugs came into force in 1967, but since the 1990s, it has started to be a matter of scientific curiosity again by various research groups. In particular, with the crucial reports of psychotherapy-assisted psilocybin applications for life-threatening cancer-related anxiety and depression, a new avenues have been opened in the treatment of psychiatric diseases such as treatment-resistant depression and substance addictions. An increasing number of studies show that psychedelics have a very promising potential in the treatment of neuropsychiatric diseases where the desired efficiency cannot be achieved with conventional treatment methods. In this context, we discuss psychedelic therapy, encompassing its historical development, therapeutic applications and potential treatment effects-especially in depression, trauma disorders and substance use disorders-within the framework of ethical considerations.

Exploring the serotonin-probiotics-gut health axis: A review of current evidence and potential mechanisms

Modulatory effects of serotonin (5-Hydroxytryptamine [5-HT]) have been seen in hepatic, neurological/psychiatric, and gastrointestinal (GI) disorders. Probiotics are live microorganisms that confer health benefits to their host. Recent research has suggested that probiotics can promote serotonin signaling, a crucial pathway in the regulation of mood, cognition, and other physiological processes. Reviewing the literature, we find that peripheral serotonin increases nutrient uptake and storage, regulates the composition of the gut microbiota, and is involved in mediating neuronal disorders. This review explores the mechanisms underlying the probiotic-mediated increase in serotonin signaling, highlighting the role of gut microbiota in the regulation of serotonin production and the modulation of neurotransmitter receptors. Additionally, this review discusses the potential clinical implications of probiotics as a therapeutic strategy for disorders associated with altered serotonin signaling, such as GI and neurological disorders. Overall, this review demonstrates the potential of probiotics as a promising avenue for the treatment of serotonin-related disorders and signaling of serotonin.

Trace Amine-Associated Receptors and Monoamine-Mediated Regulation of Insulin Secretion in Pancreatic Islets

Currently, metabolic syndrome treatment includes predominantly pharmacological symptom relief and complex lifestyle changes. Trace amines and their receptor systems modulate signaling pathways of dopamine, norepinephrine, and serotonin, which are involved in the pathogenesis of this disorder. Trace amine-associated receptor 1 (TAAR1) is expressed in endocrine organs, and it was revealed that TAAR1 may regulate insulin secretion in pancreatic islet β-cells. For instance, accumulating data demonstrate the positive effect of TAAR1 agonists on the dynamics of metabolic syndrome progression and MetS-associated disease development. The role of other TAARs (TAAR2, TAAR5, TAAR6, TAAR8, and TAAR9) in the islet's function is much less studied. In this review, we summarize the evidence of TAARs' contribution to the metabolic syndrome pathogenesis and regulation of insulin secretion in pancreatic islets. Additionally, by the analysis of public transcriptomic data, we demonstrate that TAAR1 and other TAAR receptors are expressed in the pancreatic islets. We also explore associations between the expression of TAARs mRNA and other genes in studied samples and demonstrate the deregulation of TAARs' functional associations in patients with metabolic diseases compared to healthy donors.

Potential of bone morphogenetic protein-7 in treatment of lupus nephritis: addressing the hurdles to implementation

Up to 50% of systemic lupus erythematosus (SLE) patients world-wide develop lupus nephritis (LN). In low to middle income countries and in particular in sub-Saharan Africa, where SLE is prevalent with a more aggressive course, LN and end stage renal disease is a major cause of mortality. While developed countries have the funding to invest in SLE and LN research, patients of African descent are often underrepresented in clinical trials. Thus, the complex influence of ethnicity and genetic background on outcome of LN and SLE as a whole, is not fully understood. Several pathophysiological mechanisms including major role players driving LN have been identified. A large body of literature suggest that prevention of fibrosis-which contributes to chronicity of LN-may significantly improve long-term prognosis. Bone morphogenetic protein-7 (BMP-7) was first identified as a therapeutic option in this context decades ago and evidence of its benefit in various conditions, including LN, is ever-increasing. Despite these facts, BMP-7 is not being implemented as therapy in the context of renal disease. With this review, we briefly summarise current understanding of LN pathology and discuss the evidence in support of therapeutic potential of BMP-7 in this context. Lastly, we address the obstacles that need to be overcome, before BMP-7 may become available as LN treatment.

Delayed gut microbiota maturation in the first year of life is a hallmark of pediatric allergic disease

Allergic diseases affect millions of people worldwide. An increase in their prevalence has been associated with alterations in the gut microbiome, i.e., the microorganisms and their genes within the gastrointestinal tract. Maturation of the infant immune system and gut microbiota occur in parallel; thus, the conformation of the microbiome may determine if tolerant immune programming arises within the infant. Here we show, using deeply phenotyped participants in the CHILD birth cohort (n = 1115), that there are early-life influences and microbiome features which are uniformly associated with four distinct allergic diagnoses at 5 years: atopic dermatitis (AD, n = 367), asthma (As, n = 165), food allergy (FA, n = 136), and allergic rhinitis (AR, n = 187). In a subset with shotgun metagenomic and metabolomic profiling (n = 589), we discover that impaired 1-year microbiota maturation may be universal to pediatric allergies (AD p = 0.000014; As p = 0.0073; FA p = 0.00083; and AR p = 0.0021). Extending this, we find a core set of functional and metabolic imbalances characterized by compromised mucous integrity, elevated oxidative activity, decreased secondary fermentation, and elevated trace amines, to be a significant mediator between microbiota maturation at age 1 year and allergic diagnoses at age 5 years (βindirect = -2.28; p = 0.0020). Microbiota maturation thus provides a focal point to identify deviations from normative development to predict and prevent allergic disease.

Tyramine-induced gastrointestinal dysregulation is attenuated via estradiol associated mechanisms in a zebrafish larval model

Development of targeted therapeutics to alleviate gastrointestinal (GI) inflammation and its debilitating consequences are required. In this context, the trace aminergic system may link together sex, diet and inflammation. Utilising a zebrafish larval model of GI inflammation, the current study aimed to investigate mechanisms by which excess amounts of trace amines (TAs) may influence GI health. In addition, we probed the potential role of 17β-estradiol (E2) and its receptors, given the known female-predominance of many GI disorders. To assess GI functionality and integrity, live imaging techniques (neutral red staining) and post-mortem immunofluorescent staining of tight junction proteins (occludin and ZO-1) were analyzed respectively. In addition, behavioural assays, as an indication of overall wellbeing, as well as whole body H₂O₂ and prostaglandin E2 assays were performed to inform on oxidative and inflammatory status. Excess β-phenethylamine (PEA), tryptamine (TRP) and ρ-tyramine (TYR) resulted in adverse GI and systemic effects. In this regard, clear beneficial effects of E2 to modulate the effects of PEA, TRP and TYR was evident. Moreover, agmatine displayed potential protective effects on GI epithelium and whole body oxidative status, however, potential to induce systemic inflammation suggests the importance of dosage and administration optimisation. Taken together, TYR seems like the most prominent TA to have damaging GI effects, feasibly exacerbating GI inflammation. In this context, the relative lack of E2 may provide mechanistic insights into the reported female-predominance of GI disorders. Moreover, an effective therapeutic in this context may be required to maintain GI TA load despite fluctuating E2 levels.

Bifico relieves irritable bowel syndrome by regulating gut microbiota dysbiosis and inflammatory cytokines

PURPOSE

Gut microbiota dysbiosis, a core pathophysiology of irritable bowel syndrome (IBS), is closely related to immunological and metabolic functions. Gut microbiota-based therapeutics have been recently explored in several studies. Bifico is a probiotic cocktail widely used in gastrointestinal disorders which relate to the imbalance of gut microbiota. However, the efficacy and potential mechanisms of Bifico treatment in IBS remains incompletely understood.

METHODS

Adopting a wrap restraint stress (WRS) -induced IBS mice model. Protective effect of Bifico in IBS mice was examined through abdominal withdrawal reflex (AWR) scores. 16S rDNA, ¹H nuclear magnetic resonance (¹H-NMR) and western blot assays were performed to analyze alterations of gut microbiota, microbiome metabolites and inflammatory cytokines, respectively.

RESULTS

Bifico could decrease intestinal visceral hypersensitivity. Although gut microbiota diversity did not increase, composition of gut microbiota was changed after treatment of Bifico, which were characterized by an increase of Proteobacteria phylum and Actinobacteria phylum, Muribaculum genus, Bifidobacterium genus and a decrease of Parabacteroides genus, Sutterella genus and Lactobacillus genus. Moreover, Bifico elevated the concentration of short-chain fatty acids (SCFAs) and reduced protein levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). From further Spearman's correlation analysis, Bifidobacterium genus were positively correlated with SCFAs including propionate, butyrate, valerate and negatively correlated with IL-6 and TNF-α.

CONCLUSION

Bifico could alleviate symptoms of IBS mice through regulation of the gut microbiota, elevating production of SCFAs and reducing the colonic inflammatory response.

Gut microbiota plays a role in irritable bowel syndrome by regulating 5-HT metabolism

Irritable bowel syndrome (IBS) is a common chronic functional gastrointestinal disorder. Brain-gut-microbiota axis dysfunction is an important pathogenic factor for IBS, in which neurotransmitters and gut microbes play key roles. The gastrointestinal tract contains large amounts of serotonin (5-hydroxytryptamine, 5-HT), a neurotransmitter that has been strongly linked to IBS-related symptoms. More than 90% of serotonin is synthesized in the gut by enterochromaffin cells (ECs), and certain intestinal flora can affect the occurrence and development of IBS by regulating 5-HT and its metabolism. In this review, we will discuss the role of gut microbiota in IBS by regulating 5-HT.

Rooibos (Aspalathus linearis) alters secretome trace amine profile of probiotic and commensal microbes in vitro

ETHNOPHARMACOLOGY RELEVANCE

Aspalathus linearis (Burm.f.) R. Dahlgren (rooibos) tea is anecdotally renowned for its calming effect in the context of gastrointestinal discomfort, but little scientific support is available to elucidate potential mechanisms of action. Enhancement of dietary polyphenol content to improve gut health via prebiotic-like modulation of the gut microbiota has gained significant research interest. Given the known high polyphenol content of rooibos, rooibos tea may potentially exert a prebiotic effect in the gut to facilitate an improvement in chronic inflammatory gastrointestinal conditions.

AIM OF THE STUDY

This study aimed to determine the prebiotic or health-modulating potential of rooibos tea in terms of its effect on gut microbial growth and secretome trace amine composition, as well as to determine how differential rooibos processing alters this activity.

METHODS

Three rooibos preparations (green and fermented leave aqueous extracts, as well as a green leaf ethanol extract) were compared in terms of their phenolic composition (qTOF-LC/MS). Moreover, the effect of rooibos exposure on growth and secretome trace amine levels of probiotic and commensal microbes were assessed (LC/MS). In addition, given the known female bias prevalent for many gastrointestinal disorders, experiments were conducted in the absence and presence of estradiol.

RESULTS

Polyphenolic composition of rooibos was drastically reduced by fermentation. Aqueous extracts of both green and fermented rooibos improved microbial growth, although fermented rooibos had the most pronounced effect (p < 0.01). In terms of secretome trace amine profile, both aqueous extracts of rooibos seemed to facilitate increased putrescine secretion (p < 0.0001) and decreased tryptamine production (p < 0.0001). Estradiol seemed to suppress trace amine secretion by bacteria (Lactobacillus plantarum, Lactobacillus reuteri and Enterococcus mundtii) but increased it in yeast (Saccharomyces boulardii).

CONCLUSION

Rooibos altered gut probiotic and commensal microbial growth and secretome trace amine profiles in vitro, suggesting it has potential to modulate gut microbial composition and functionality as a prebiotic. Current data suggest that these effects are highly dependent on raw material processing. Finally, rooibos may be able to prevent estradiol-associated alterations in trace amine profile, which may have important implications for patient management in female-predominant gastrointestinal disorders.

Neonatal antibiotics have long term sex-dependent effects on the enteric nervous system

Infants and young children receive the highest exposures to antibiotics globally. Although there is building evidence that early life exposure to antibiotics increases susceptibility to various diseases including gut disorders later in life, the lasting impact of early life antibiotics on the physiology of the gut and its enteric nervous system (ENS) remains unclear. We treated neonatal mice with the antibiotic vancomycin during their first 10 postnatal days, then examined potential lasting effects of the antibiotic treatment on their colons during young adulthood (6 weeks old). We found that neonatal vancomycin treatment disrupted the gut functions of young adult female and male mice differently. Antibiotic-exposed females had significantly longer whole gut transit while antibiotic-treated males had significantly lower faecal weights compared to controls. Both male and female antibiotic-treated mice had greater percentages of faecal water content. Neonatal vancomycin treatment also had sexually dimorphic impacts on the neurochemistry and Ca2+ activity of young adult myenteric and submucosal neurons. Myenteric neurons of male mice were more disrupted than those of females, while opposing changes in submucosal neurons were seen in each sex. Neonatal vancomycin also induced sustained changes in colonic microbiota and lasting depletion of mucosal serotonin (5-HT) levels. Antibiotic impacts on microbiota and mucosal 5-HT were not sex-dependent, but we propose that the responses of the host to these changes are sex-specific. This first demonstration of long-term impacts of neonatal antibiotics on the ENS, gut microbiota and mucosal 5-HT has important implications for gut function and other physiological systems of the host. KEY POINTS: Early life exposure to antibiotics can increase susceptibility to diseases including functional gastrointestinal (GI) disorders later in life. Yet, the lasting impact of this common therapy on the gut and its enteric nervous system (ENS) remains unclear. We investigated the long-term impact of neonatal antibiotic treatment by treating mice with the antibiotic vancomycin during their neonatal period, then examining their colons during young adulthood. Adolescent female mice given neonatal vancomycin treatment had significantly longer whole gut transit times, while adolescent male and female mice treated with neonatal antibiotics had significantly wetter stools. Effects of neonatal vancomycin treatment on the neurochemistry and Ca2+ activity of myenteric and submucosal neurons were sexually dimorphic. Neonatal vancomycin also had lasting effects on the colonic microbiome and mucosal serotonin biosynthesis that were not sex-dependent. Different male and female responses to antibiotic-induced disruptions of the ENS, microbiota and mucosal serotonin biosynthesis can lead to sex-specific impacts on gut function.

Aspalathus linearis (Rooibos) and Agmatine May Act Synergistically to Beneficially Modulate Intestinal Tight Junction Integrity and Inflammatory Profile

In order to promote gastrointestinal health, significant increases in the prevalence of gastrointestinal disorders should be paralleled by similar surges in therapeutics research. Nutraceutical interventions may play a significant role in patient management. The current study aimed to determine the potential of Aspalathus linearis (rooibos) to prevent gastrointestinal dysregulation resulting from high-dose trace-amine (TA) exposure. Considering the substantial female bias in functional gastrointestinal disorders, and the suggested phytoestrogenicity of rooibos, the study design allowed for a comparison between the effects of an ethanol extract of green rooibos and 17β-estradiol (E2). High levels of ρ-tyramine (TYR) and agmatine (AGM), but not β-phenethylamine (PEA) or tryptamine (TRP), resulted in prostaglandin E2 (PGE2) hypersecretion, increased tight-junction protein (TJP; occludin and ZO-1) secretion and (dissimilarly) disrupted the TJP cellular distribution profile. Modulating benefits of rooibos and E2 were TA-specific. Rooibos pre-treatment generally reduced IL-8 secretion across all TA conditions and prevented PGE2 hypersecretion after exposure to both TYR and AGM, but was only able to normalise TJP levels and the distribution profile in AGM-exposed cells. In contrast, E2 pre-treatment prevented only TYR-associated PGE2 hypersecretion and TJP dysregulation. Together, the data suggest that the antioxidant and anti-inflammatory effects of rooibos, rather than phytoestrogenicity, affect benefits illustrated for rooibos.

Non-alcoholic fatty liver is associated with increased risk of irritable bowel syndrome: a prospective cohort study

BACKGROUND

The relationship between non-alcoholic fatty liver degree as well as non-alcoholic fatty liver disease (NAFLD) and irritable bowel syndrome (IBS) remains poorly understood. We aimed to investigate the prospective association of non-alcoholic fatty liver degree as well as NAFLD with incident IBS in a large-scale population-based cohort.

METHODS

Participants free of IBS, coeliac disease, inflammatory bowel disease, alcoholic liver disease, and any cancer at baseline from the UK Biobank were included. Non-alcoholic fatty liver degree was measured by a well-validated fatty liver index (FLI), with FLI ≥ 60 as an indicator of NAFLD. Primary outcome was incident IBS. Cox proportional hazard model was used to investigate the associated risk of incident IBS.

RESULTS

Among 396,838 participants (mean FLI was 48.29 ± 30.07), 153,203(38.6%) were with NAFLD diagnosis at baseline. During a median of 12.4-year follow-up, 7129 cases of incident IBS were identified. Compared with non-NAFLD, NAFLD patients showed a 13% higher risk of developing IBS (HR = 1.13, 95%CI: 1.05-1.17) after multivariable adjustment. Compared with the lowest, the highest FLI quartile was associated with a significantly increased risk of IBS (HR_{Q4 VS Q1} = 1.21, 1.13-1.30, P_trend < 0.001). Specifically, the positive association between non-alcoholic fatty liver degree and IBS was also observed by per SD change of FLI (adjusted HR = 1.08, 1.05-1.10). Further sensitivity analysis and subgroup analysis indicated similar results, with the positive association particularly observed in females, but not in males.

CONCLUSIONS

High degree of non-alcoholic fatty liver as well as non-alcoholic fatty liver disease is associated with increased risk of incident IBS. Further studies are warranted to confirm the findings and elucidate the underlying biological mechanisms.

Shedding light on biological sex differences and microbiota-gut-brain axis: a comprehensive review of its roles in neuropsychiatric disorders

Women and men are suggested to have differences in vulnerability to neuropsychiatric disorders, including major depressive disorder (MDD), generalized anxiety disorder (GAD), schizophrenia, eating disorders, including anorexia nervosa, and bulimia nervosa, neurodevelopmental disorders, such as autism spectrum disorder (ASD), and neurodegenerative disorders including Alzheimer’s disease, Parkinson’s disease. Genetic factors and sex hormones are apparently the main mediators of these differences. Recent evidence uncovers that reciprocal interactions between sex-related features (e.g., sex hormones and sex differences in the brain) and gut microbiota could play a role in the development of neuropsychiatric disorders via influencing the gut–brain axis. It is increasingly evident that sex–microbiota–brain interactions take part in the occurrence of neurologic and psychiatric disorders. Accordingly, integrating the existing evidence might help to enlighten the fundamental roles of these interactions in the pathogenesis of neuropsychiatric disorders. In addition, an increased understanding of the biological sex differences on the microbiota–brain may lead to advances in the treatment of neuropsychiatric disorders and increase the potential for precision medicine. This review discusses the effects of sex differences on the brain and gut microbiota and the putative underlying mechanisms of action. Additionally, we discuss the consequences of interactions between sex differences and gut microbiota on the emergence of particular neuropsychiatric disorders.

The human microbiome is a unique set of organisms affecting health via the gut–brain axis.

Neuropsychiatric disorders, eating disorders, neurodevelopmental disorders, and neurodegenerative disorders are regulated by the microbiota–gut–brain axis in a sex-specific manner.

Understanding the role of the microbiota–gut–brain axis and its sex differences in various diseases can lead to better therapeutic methods.

Mycotherapy: Potential of Fungal Bioactives for the Treatment of Mental Health Disorders and Morbidities of Chronic Pain

Mushrooms have been used as traditional medicine for millennia, fungi are the main natural source of psychedelic compounds. There is now increasing interest in using fungal active compounds such as psychedelics for alleviating symptoms of mental health disorders including major depressive disorder, anxiety, and addiction. The anxiolytic, antidepressant and anti-addictive effect of these compounds has raised awareness stimulating neuropharmacological investigations. Micro-dosing or acute dosing with psychedelics including Lysergic acid diethylamide (LSD) and psilocybin may offer patients treatment options which are unmet by current therapeutic options. Studies suggest that either dosing regimen produces a rapid and long-lasting effect on the patient post administration with a good safety profile. Psychedelics can also modulate immune systems including pro-inflammatory cytokines suggesting a potential in the treatment of auto-immune and other chronic pain conditions. This literature review aims to explore recent evidence relating to the application of fungal bioactives in treating chronic mental health and chronic pain morbidities.

Alterations to microbial secretome by estrogen may contribute to sex bias in irritable bowel syndrome

INTRODUCTION

Irritable bowel syndrome (IBS) is a female predominant functional gastrointestinal disorder, underpinned by microbial dysbiosis and microinflammation. We suggest that changes in trace amine (TA) load and metabolism may link together diet, inflammation and sex in this context.

METHODS

The effect of E2 treatment on microbial growth and TA generation was assessed using liquid chromatography and tandem mass spectrometry methodology. To investigate the effects of TAs on the gut, WST-1, prostaglandin E2 and tight junction protein dynamics were investigated in TA treated (HT-29) colon epithelial monolayer cultures.

RESULTS

Differential E2-dependent alterations of the TA production capabilities of microbes were observed. Significantly, E2 treatment resulted in a 50% increase in tryptamine secretion from a probiotic microbe (p < 0.0001). Moreover, in vitro experiments indicated that TA treatment exerted type-specific effects in the gut, e.g., reducing mitochondrial functionality, even at low doses of tryptamine (p < 0.0001) and ρ-tyramine (p < 0.001). Additionally, prostaglandin E2 levels were significantly increased following ρ-tyramine and agmatine treatment (p < 0.05). In terms of functionality, all investigated TAs resulted in occludin redistribution and loss of zona occludens-1 and occludin co-localization.

CONCLUSION

Increases in the gastrointestinal TA load may contribute to a relatively pro-inflammatory outcome in the intestine, along with tight junction protein disruption. Additionally, fluctuating levels of endogenous E2 may modulate microbially-derived TA levels, potentially explaining exaggerating gastrointestinal symptomology in females during low E2 phases. Thus, current data warrants subsequent investigations in appropriate in vivo models to fully elucidate the role of the trace aminergic system in the sex bias observed in IBS.

Colonization resistance: metabolic warfare as a strategy against pathogenic Enterobacteriaceae

The intestine is home to a large and complex bacterial ecosystem (microbiota), which performs multiple beneficial functions for the host, including immune education, nutrition, and protection against invasion by enteric pathogens (colonization resistance). The host and microbiome symbiotic interactions occur in part through metabolic crosstalk. Thus, microbiota members have evolved highly diverse metabolic pathways to inhibit pathogen colonization via activation of protective immune responses and nutrient acquisition and utilization. Conversely, pathogenic Enterobacteriaceae actively induce an inflammation-dependent disruption of the gut microbial ecosystem (dysbiosis) to gain a competitive metabolic advantage against the resident microbiota. This review discusses the recent findings on the crucial role of microbiota metabolites in colonization resistance regulation. Additionally, we summarize metabolic mechanisms used by pathogenic Enterobacteriaceae to outcompete commensal microbes and cause disease.

Trace Amine-Associated Receptor 1 Contributes to Diverse Functional Actions of O-Phenyl-Iodotyramine in Mice but Not to the Effects of Monoamine-Based Antidepressants

Trace Amine-Associated Receptor 1 (TAAR1) is a potential target for the treatment of depression and other CNS disorders. However, the precise functional roles of TAAR1 to the actions of clinically used antidepressants remains unclear. Herein, we addressed these issues employing the TAAR1 agonist, o-phenyl-iodotyramine (o-PIT), together with TAAR1-knockout (KO) mice. Irrespective of genotype, systemic administration of o-PIT led to a similar increase in mouse brain concentrations. Consistent with the observation of a high density of TAAR1 in the medial preoptic area, o-PIT-induced hypothermia was significantly reduced in TAAR1-KO mice. Furthermore, the inhibition of a prepulse inhibition response by o-PIT, as well as its induction of striatal tyrosine hydroxylase phosphorylation and elevation of extracellular DA in prefrontal cortex, were all reduced in TAAR1-KO compared to wildtype mice. O-PIT was active in both forced-swim and marble-burying tests, and its effects were significantly blunted in TAAR1-KO mice. Conversely, the actions on behaviour and prefrontal cortex dialysis of a broad suite of clinically used antidepressants were unaffected in TAAR1-KO mice. In conclusion, o-PIT is a useful tool for exploring the hypothermic and other functional antidepressant roles of TAAR1. By contrast, clinically used antidepressants do not require TAAR1 for expression of their antidepressant properties.