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The physiological consequences of stress often manifest in the gastrointestinal tract. Traumatic or chronic stress is associated with widespread maladaptive changes throughout the gut, although comparatively little is known about the effects of acute stress. Furthermore, these stress-induced changes in the gut may increase susceptibility to gastrointestinal disorders and infection, and impact critical features of the neural and behavioural consequences of the stress response by impairing gut-brain axis communication. Understanding the mechanisms behind changes in enteric nervous system circuitry, visceral sensitivity, gut barrier function, permeability, and the gut microbiota following stress is an important research objective with pathophysiological implications in both neurogastroenterology and psychiatry. Moreover, the gut microbiota has emerged as a key aspect of physiology sensitive to the effects of stress. In this review, we focus on different aspects of the gastrointestinal tract including gut barrier function as well as the immune, humoral and neuronal elements involved in gut-brain communication. Furthermore, we discuss the evidence for a role of stress in gastrointestinal disorders. Existing gaps in the current literature are highlighted, and possible avenues for future research with an integrated physiological perspective have been suggested. A more complete understanding of the spatial and temporal dynamics of the integrated host and microbial response to different kinds of stressors in the gastrointestinal tract will enable full exploitation of the diagnostic and therapeutic potential in the fast-evolving field of host-microbiome interactions.
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Visceral hypersensitivity, a hallmark of disorders of the gut-brain axis, is associated with exposure to early-life stress (ELS). Activation of neuronal ß3-adrenoceptors (AR) has been shown to alter central and peripheral levels of tryptophan and reduce visceral hypersensitivity. In this study, we aimed to determine the potential of a ß3-AR agonist in reducing ELS-induced visceral hypersensitivity and possible underlying mechanisms. Here, ELS was induced using the maternal separation (MS) model, where Sprague Dawley rat pups were separated from their mother in early life (postnatal day 2-12). Visceral hypersensitivity was confirmed in adult offspring using colorectal distension (CRD). CL-316243, a ß3-AR agonist, was administered to determine anti-nociceptive effects against CRD. Distension-induced enteric neuronal activation as well as colonic secretomotor function were assessed. Tryptophan metabolism was determined both centrally and peripherally. For the first time, we showed that CL-316243 significantly ameliorated MS-induced visceral hypersensitivity. Furthermore, MS altered plasma tryptophan metabolism and colonic adrenergic tone, while CL-316243 reduced both central and peripheral levels of tryptophan and affected secretomotor activity in the presence of tetrodotoxin. This study supports the beneficial role of CL-316243 in reducing ELS-induced visceral hypersensitivity, and suggests that targeting the ß3-AR can significantly influence gut-brain axis activity through modulation of enteric neuronal activation, tryptophan metabolism, and colonic secretomotor activity which may synergistically contribute to offsetting the effects of ELS.
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The metabolism of dietary tryptophan occurs locally in the gut primarily via host enzymes, with ~ 5% metabolized by gut microbes. Three major tryptophan metabolic pathways are serotonin (beyond the scope of this review), indole, kynurenine and related derivatives. We introduce the gut microbiome, dietary tryptophan and the potential interplay of host and bacterial enzymes in tryptophan metabolism. Examples of bacterial transformation to indole and its derivative indole-3 propionic acid demonstrate associations with human metabolic disease and gut permeability, although causality remains to be determined. This review will focus on less well-known data, suggestive of local generation and functional significance in the gut, where kynurenine is converted to kynurenic acid and xanthurenic acid via enzymatic action present in both host and bacteria. Our functional data demonstrate a limited effect on intestinal epithelial cell monolayer permeability and on healthy mouse ileum. Other data suggest a modulatory effect on the microbiome, potentially in pathophysiology. Supportive of this, we found that the expression of mRNA for three kynurenine pathway enzymes were increased in colon from high-fat-fed mice, suggesting that this host pathway is perturbed in metabolic disease. These data, along with that from bacterial genomic analysis and germ-free mice, confirms expression and functional machinery of enzymes in this pathway. Therefore, the host and microbiota may play a significant dual role in either the production or regulation of these kynurenine metabolites which, in turn, can influence both host and microbiome, especially in the context of obesity and intestinal permeability.
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Microbioma Gastrointestinal , Animales , Microbioma Gastrointestinal/fisiología , Intestinos , Quinurenina/metabolismo , Ratones , Obesidad/metabolismo , Triptófano/metabolismoRESUMEN
The microbiome plays a key role in health and disease, and there has been considerable interest in therapeutic targeting of the microbiome as well as mining this rich resource in drug discovery efforts. However, a growing body of evidence suggests that the gut microbiota can itself influence the actions of a range of xenobiotics, in both beneficial and potentially harmful ways. Traditionally, clinical studies evaluating the pharmacokinetics of new drugs have mostly ignored the important direct and indirect effects of the gut microbiome on drug metabolism and efficacy. Despite some important observations from xenobiotic metabolism in general, there is only an incomplete understanding of the scope of influence of the microbiome specifically on drug metabolism and absorption, and how this might influence systemic concentrations of parent compounds and toxic metabolites. The significance of both microbial metabolism of xenobiotics and the impact of the gut microbiome on host hepatic enzyme systems is nonetheless gaining traction and presents a further challenge in drug discovery efforts, with implications for improving treatment outcomes or counteracting adverse drug reactions. Microbial factors must now be considered when determining drug pharmacokinetics and the impact that an evolving and dynamic microbiome could have in this regard. In this review, we aim to integrate the contribution of the gut microbiome in health and disease to xenobiotic metabolism focusing on therapeutic interventions, pharmacological drug action, and chemical biotransformations that collectively will have implications for the future practice of precision medicine.
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Microbioma Gastrointestinal/fisiología , Microbiota , Xenobióticos/metabolismo , Animales , Descubrimiento de Drogas/métodos , Efectos Colaterales y Reacciones Adversas Relacionados con Medicamentos/epidemiología , Humanos , Medicina de Precisión/métodos , Xenobióticos/efectos adversos , Xenobióticos/farmacologíaRESUMEN
The gastrointestinal tract houses a reservoir of bacterial-derived enzymes that can directly catalyze the metabolism of drugs, dietary elements and endogenous molecules. Both host and environmental factors may influence this enzymatic activity, with the potential to dictate the availability of the biologically-active form of endogenous molecules in the gut and influence inter-individual variation in drug metabolism. We aimed to investigate the influence of the microbiota, and the modulation of its composition, on fecal enzymatic activity. Intrinsic factors related to the host, including age, sex and genetic background, were also explored. Fecalase, a cell-free extract of feces, was prepared and used in a colorimetric-based assay to quantify enzymatic activity. To demonstrate the functional effects of fecal enzymatic activity, we examined ß-glucuronidase-mediated cleavage of serotonin ß-d-glucuronide (5-HT-GLU) and the resultant production of free 5-HT by HPLC. As expected, ß-glucuronidase and ß-glucosidase activity were absent in germ-free mice. Enzymatic activity was significantly influenced by mouse strain and animal species. Sex and age significantly altered metabolic activity with implications for free 5-HT. ß-Glucuronidase and ß-glucosidase activity remained at reduced levels for nearly two weeks after cessation of antibiotic administration. This effect on fecalase corresponded to significantly lower 5-HT levels as compared with incubation with pre-antibiotic fecalase from the same mice. Dietary targeting of the microbiota using prebiotics did not alter ß-glucuronidase or ß-glucosidase activity. Our data demonstrate that multiple factors influence the activity of bacterial-derived enzymes which may have potential clinical implications for drug metabolism and the deconjugation of host-produced glucuronides in the gut.NEW & NOTEWORTHY This article explores a comprehensive range of host and environmental factors that introduce variability in the expression of bacterial-derived metabolic enzymes. Our results demonstrate that altered ß-glucuronidase activity has implications for the bioavailability of luminal serotonin. The experimental approach employed, fecalase, provides a mechanistic basis and translational platform to further delineate the functional outputs of altered metabolic activity, and the associated physiological effects of microbiota-targeted interventions on host response to drugs and host-produced glucuronides.
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Heces/química , Glucuronidasa/metabolismo , Serotonina/metabolismo , beta-Glucosidasa/metabolismo , Animales , Antibacterianos , Caspasa 1/genética , Caspasa 1/metabolismo , Femenino , Microbioma Gastrointestinal/efectos de los fármacos , Regulación Enzimológica de la Expresión Génica , Vida Libre de Gérmenes , Glucuronidasa/química , Glucuronidasa/genética , Interleucina-10/genética , Interleucina-10/metabolismo , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Noqueados , Prebióticos , Ratas , Ratas Sprague-Dawley , Serotonina/química , Factores Sexuales , Porcinos , beta-Glucosidasa/química , beta-Glucosidasa/genéticaRESUMEN
Colonic inflammation is associated with decreased tissue oxygenation, significantly affecting gut homeostasis. However, the crosstalk between O2 consumption and supply in the inflamed tissue are not fully understood. Using a murine model of colitis, we analysed O2 in freshly prepared samples of healthy and inflamed colon tissue. We developed protocols for efficient ex vivo staining of mouse distal colon mucosa with a cell-penetrating O2 sensitive probe Pt-Glc and high-resolution imaging of O2 concentration in live tissue by confocal phosphorescence lifetime-imaging microscopy (PLIM). Microscopy analysis revealed that Pt-Glc stained mostly the top 50-60 µm layer of the mucosa, with high phosphorescence intensity in epithelial cells. Measured O2 values in normal mouse tissue ranged between 5 and 35 µM (4-28 Torr), tending to decrease in the deeper tissue areas. Four-day treatment with dextran sulphate sodium (DSS) triggered colon inflammation, as evidenced by an increase in local IL6 and mKC mRNA levels, but did not affect the gross architecture of colonic epithelium. We further observed an increase in oxygenation, partial activation of hypoxia inducible factor (HIF) 1 signalling, and negative trends in pyruvate dehydrogenase activity and O2 consumption rate in the colitis mucosa, suggesting a decrease in mitochondrial respiration, which is known to be regulated via HIF-1 signalling and pyruvate oxidation rate. These results along with efficient staining with Pt-Glc of rat and human colonic mucosa reveal high potential of PLIM platform as a powerful tool for the high-resolution analysis of the intestinal tissue oxygenation in patients with inflammatory bowel disease and other pathologies, affecting tissue respiration.
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Colitis/patología , Colon/patología , Mucosa Intestinal/patología , Oxígeno/análisis , Animales , Células CACO-2 , Colitis/inmunología , Colon/inmunología , Humanos , Mucosa Intestinal/inmunología , Mediciones Luminiscentes , Masculino , Ratones Endogámicos C57BL , Microscopía Confocal , Imagen Óptica , Oxígeno/inmunología , Ratas Sprague-Dawley , Coloración y EtiquetadoRESUMEN
The enteric nervous system (ENS), considered a separate branch of the autonomic nervous system, is located throughout the length of the gastrointestinal (GI) tract as a series of interconnected ganglionated plexi. Given the proximity of the intestinal microbiota to the ENS, it is perhaps not surprising that the gut microbiota can influence its development and function. However, these interactions are complex and may be either direct or indirect, often involving signalling initiated by microbe-derived components, metabolites or host-derived intermediaries which subsequently affect enteric nerve excitability and GI function. Individual microbes and strains can differentially influence ENS activity and neurochemistry. In this review we will briefly summarise the role of the microbiota on ENS development, and, in some more detail, explore the mechanisms by which the microbiota can influence ENS activity and function.
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Sistema Nervioso Entérico/metabolismo , Microbioma Gastrointestinal/fisiología , Tracto Gastrointestinal/inervación , Tracto Gastrointestinal/microbiología , Animales , Vida Libre de Gérmenes , Humanos , Ratones , Neurogénesis/fisiología , Probióticos/farmacología , Transducción de Señal/fisiologíaRESUMEN
NEW FINDINGS: What is the central question of this study? Does crosstalk exist between leptin and interleukin-6 in colonic enteric neurons, and is this a contributory factor in gastrointestinal dysfunction associated with irritable bowel syndrome? What is the main finding and its importance? Leptin ameliorates the prosecretory and prokinetic effects of the pro-inflammatory cytokine interleukin-6 on rat colon. Leptin also suppresses the neurostimulatory effects of irritable bowel syndrome plasma, which has elevated concentrations of interleukin-6, on enteric neurons. This may indicate a regulatory role for leptin in immune-mediated bowel dysfunction. In addition to its role in regulating energy homeostasis, the adipokine leptin modifies gastrointestinal (GI) function. Indeed, leptin-resistant obese humans and leptin-deficient obese mice exhibit altered GI motility. In the functional GI disorder irritable bowel syndrome (IBS), circulating leptin concentrations are reported to differ from those of healthy control subjects. Additionally, IBS patients display altered cytokine profiles, including elevated circulating concentrations of the pro-inflammatory cytokine interleukin-6 (IL-6), which bears structural homology and similarities in intracellular signalling to leptin. This study aimed to investigate interactions between leptin and IL-6 in colonic neurons and their possible contribution to IBS pathophysiology. The functional effects of leptin and IL-6 on colonic contractility and absorptosecretory function were assessed in organ baths and Ussing chambers in Sprague-Dawley rat colon. Calcium imaging and immunohistochemical techniques were used to investigate the neural regulation of GI function by these signalling molecules. Our findings provide a neuromodulatory role for leptin in submucosal neurons, where it inhibited the stimulatory effects of IL-6. Functionally, this translated to suppression of IL-6-evoked potentiation of veratridine-induced secretory currents. Leptin also attenuated IL-6-induced colonic contractions, although it had little direct effect on myenteric neurons. Calcium responses evoked by IBS plasma in both myenteric and submucosal neurons were also suppressed by leptin, possibly through interactions with IL-6, which is elevated in IBS plasma. As leptin has the capacity to ameliorate the neurostimulatory effects of soluble mediators in IBS plasma and modulated IL-6-evoked changes in bowel function, leptin may have a role in immune-mediated bowel dysfunction in IBS patients.
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Colon/efectos de los fármacos , Colon/metabolismo , Citocinas/metabolismo , Interleucina-6/metabolismo , Leptina/farmacología , Adolescente , Adulto , Anciano , Animales , Motilidad Gastrointestinal/efectos de los fármacos , Humanos , Síndrome del Colon Irritable/metabolismo , Masculino , Persona de Mediana Edad , Neuronas/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Adulto JovenRESUMEN
Evidence has grown to support the efficacy of probiotics in the management of gastrointestinal disorders, many of which are associated with dysregulated fluid and electrolyte transport. A growing body of evidence now suggests that the host microbiota and probiotics can influence intestinal ion transport and that these effects often occur in a strain-dependent manner. In this study, we sought to investigate the effects of two therapeutically relevant organisms, Bifidobacterium infantis 35,624 and Lactobacillus salivarius UCC118, on small intestinal transit, fecal output and water content, transepithelial resistance (TER), and colonic secretomotor function. Mice fed either strain displayed significantly reduced small intestinal transit in vivo, though neither strain influenced fecal pellet output or water content. Colon from mice fed both organisms displayed increased colonic TER, without a concomitant change in the gene expression of the tight junction proteins claudin 1 and occludin. However, L. salivarius UCC118 selectively inhibited neurally evoked ion secretion in tissues from animals fed this particular probiotic. Consistent with this finding, the neurotoxin tetrodotoxin (TTx) significantly inhibited the short-circuit current response induced by L. salivarius UCC118 following addition to colonic preparations in Ussing chambers. Responses to B. infantis 35,624 also displayed sensitivity to TTx, although to a significantly lesser degree than L. salivarius UCC118. Both strains similarly inhibited cholinergic-induced ion transport after addition to Ussing chambers. Taken together, these data suggest that B. infantis 35,624 and L. salivarius UCC118 may be indicated in disorders associated with increased small intestinal transit, and, in particular for L. salivarius UCC118, neurally mediated diarrhea.
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Bifidobacterium/crecimiento & desarrollo , Colon/microbiología , Intestino Delgado/microbiología , Lactobacillus/crecimiento & desarrollo , Probióticos , Animales , Claudina-1/metabolismo , Colon/efectos de los fármacos , Colon/metabolismo , Defecación , Impedancia Eléctrica , Heces/química , Heces/microbiología , Tránsito Gastrointestinal , Humanos , Secreciones Intestinales/metabolismo , Intestino Delgado/efectos de los fármacos , Intestino Delgado/metabolismo , Masculino , Ratones , Ocludina/metabolismo , Tetrodotoxina/farmacología , Factores de Tiempo , Agua/metabolismoRESUMEN
Although classically recognized as a neurotransmitter, gamma aminobutyric acid (GABA) has also been identified in colonic tumors. Moreover, the gut microbiome represents another potential source of GABA. Both GABAA and GABAB receptors have been implicated in contributing to the effects of GABA in colorectal cancer, with both pro- and anti-tumorigenic functions identified. However, their subunit composition is often overlooked. Studies to date have not addressed whether the GABA-producing potential of the microbiome changes over the course of colon tumor development or whether receptor subunit expression patterns are altered in colon cancer. Therefore, we investigated the clusters of orthologous group frequencies of glutamate decarboxylase (GAD) in feces from two murine models of colon cancer and found that the frequency of microbial GAD was significantly decreased early in the tumorigenic process. We also determined that microbial-derived GABA inhibited proliferation of colon cancer cells in vitro and that this effect of GABA on SW480 cells involved both GABAA and GABAB receptors. GABA also inhibited prostaglandin E2 (PGE2)-induced proliferation and interleukin-6 (IL-6) expression in these cells. Gene expression correlations were assessed using the "Cancer Exploration" suite of the TIMER2.0 web tool and identified that GABA receptor subunits were differentially expressed in human colon cancer. Moreover, GABAA receptor subunits were predominantly positively associated with PGE2 synthase, cyclooxygenase-2 and IL-6. Collectively, these data demonstrate decreased potential of the microbiome to produce GABA during tumorigenesis, a novel anti-tumorigenic pathway for GABA, and that GABA receptor subunit expression adds a further layer of complexity to GABAergic signaling in colon cancer.
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Proliferación Celular , Neoplasias del Colon , Microbioma Gastrointestinal , Receptores de GABA-A , Receptores de GABA-B , Transducción de Señal , Ácido gamma-Aminobutírico , Animales , Neoplasias del Colon/metabolismo , Neoplasias del Colon/microbiología , Neoplasias del Colon/patología , Ácido gamma-Aminobutírico/metabolismo , Humanos , Ratones , Línea Celular Tumoral , Receptores de GABA-A/metabolismo , Receptores de GABA-A/genética , Receptores de GABA-B/metabolismo , Dinoprostona/metabolismo , Glutamato Descarboxilasa/metabolismo , Interleucina-6/metabolismo , Ciclooxigenasa 2/metabolismo , Ciclooxigenasa 2/genética , Carcinogénesis , Heces/microbiología , Receptores de GABA/metabolismo , Receptores de GABA/genética , Masculino , Ratones Endogámicos C57BL , FemeninoRESUMEN
Host-microbe interactions have gained considerable attention in recent years with regards to their role in various organic disorders and diseases. In particular, research efforts have focused on the intestinal microbiota, where the largest and most diverse populations not only co-exist with the host, but also directly influence the state and function of the gastrointestinal (GI) tract. Moreover, both human and animal studies alike are now beginning to show a positive influence of probiotic bacteria on GI disorders associated with diarrhoea or constipation. Diarrheagenic GI diseases, such as those caused by Vibreo cholera or enterpathogenic Eschericia coli, have well-characterised interactions with the host that explain much of the observed symptoms, in particular severe diarrhoea. However, the mechanisms of action of nonpathogenic bacteria or probiotics on host physiology are less clearly understood. In the context of defining the mechanisms of action of probiotics in vitro, the Ussing chamber has proven to be a particularly useful tool. Here, we will present data from several studies that have defined molecular targets for microbes and putative probiotics in the regulation of intestinal secretory and absorptive function, and we will discuss these in the context of their application in pathogen- or inflammation-induced alterations in intestinal ion transport.
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Cámaras de Difusión de Cultivos , Enfermedades Gastrointestinales/terapia , Mucosa Intestinal/metabolismo , Mucosa Intestinal/microbiología , Intestinos/microbiología , Proteínas de Transporte de Membrana/metabolismo , Probióticos , Animales , Enfermedades Gastrointestinales/metabolismo , Enfermedades Gastrointestinales/microbiología , Interacciones Huésped-Patógeno , Humanos , Absorción Intestinal , Secreciones Intestinales/metabolismo , Transporte Iónico , Transducción de SeñalRESUMEN
Human aging is characterized by gut microbiome alteration and differential loss of gut commensal species associated with the onset of frailty. The administration of cultured commensal strains to replenish lost taxa could potentially promote healthy aging. To investigate the interaction of whole microbiomes and administered strains, we transplanted gut microbiota from a frail or healthy elderly subject into germ-free mice. We supplemented the frail-donor recipient group with a defined consortium of taxa (the "S7") that we identified by analyzing healthy aging subjects in our previous studies and whose abundance correlated with health-promoting dietary intervention. Inoculation with a frail or a healthy donor microbiome resulted in differential microbiota compositions in murine recipients 5 weeks post-transplantation. Fecal acetate levels were significantly higher in healthy donor recipient mice than in frail donor recipient mice after 4 weeks. However, the frailty-related phenotype was not replicated in recipient mice with single-dose microbiota transplantation from a healthy and a frail donor. Five S7 species colonized successfully in germ-free mice, with a relatively high abundance of Barnesiella intestinihominis and Eubacterium rectale. The engraftment of five S7 species in germ-free mice increased fecal acetate levels and reduced colon permeability and plasma TNF-É concentration. Supplementation with the S7 in frail-microbiota recipient mice did not increase alpha-diversity but significantly increased the abundance of Barnesiella intestinihominis. S7 supplementation showed the potential for improving spatial reference memory in frail-microbiota recipient mice. Collectively, these data highlight the challenge of elderly microbiota engraftment in the germ-free mouse model but show promise for modulating the gut microbiome of frail elderly subjects by administering an artificial gut microbe consortium associated with healthy aging.
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Fragilidad , Microbioma Gastrointestinal , Humanos , Animales , Ratones , Anciano , Microbioma Gastrointestinal/genética , Bacteroidetes , Heces/microbiología , Trasplante de Microbiota Fecal , AcetatosRESUMEN
Background/Aims: Chronic psychological stress affects gastrointestinal physiology which may underpin alterations in the immune response and epithelial transport, both functions are partly regulated by enteric nervous system. However, its effects on enteric neuroplasticity are still unclear. This study aims to investigate the effects of chronic unpredictable psychological stress on intestinal motility and prominent markers of enteric function. Methods: Adult male C57BL/6J mice were exposed to 19 day of unpredictable stress protocol schedule of social defeat and overcrowding. We investigated the effects on plasma corticosterone, food intake, and body weight. In vivo gastrointestinal motility was assessed by fecal pellet output and by whole-gastrointestinal transit (using the carmine red method). Tissue monoamine level, neural and glial markers, neurotrophic factors, monoamine signaling, and Toll-like receptor expression in the proximal and distal colon, and terminal ileum were also assessed. Results: Following chronic unpredictable psychological stress, stressed mice showed increased food intake and body weight gain (P < 0.001), and reduced corticosterone levels (P < 0.05) compared to control mice. Stressed mice had reduced stool output without differences in water content, and showed a delayed gastrointestinal transit compared to control mice (P < 0.05). Stressed mice exhibited decreased mRNA expression of tyrosine hydroxylase (Th), brain-derived neurotrophic factor (Bdnf) and glial cell-derived neurotrophic factor (Gdnf), as well as Toll-like receptor 2 (Tlr2) compared to control (P < 0.05), only proximal colon. These molecular changes in proximal colon were associated with higher levels of monoamines in tissue. Conclusion: Unpredictable psychological chronic stress induces region-specific impairment in monoamine levels and neuroplasticity markers that may relate to delayed intestinal transit.
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The gut microbiome can produce metabolic products that exert diverse activities, including effects on the host. Short chain fatty acids and amino acid derivatives have been the focus of many studies, but given the high microbial density in the gastrointestinal tract, other bacterial products such as those released as part of quorum sensing are likely to play an important role for health and disease. In this review, we provide of an overview on quorum sensing (QS) in the gastrointestinal tract and summarise what is known regarding the role of QS molecules such as auto-inducing peptides (AIP) and acyl-homoserine lactones (AHL) from commensal, probiotic, and pathogenic bacteria in intestinal health and disease. QS regulates the expression of numerous genes including biofilm formation, bacteriocin and toxin secretion, and metabolism. QS has also been shown to play an important role in the bacteria-host interaction. We conclude that the mechanisms of action of QS at the intestinal neuro-immune interface need to be further investigated.
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Microbioma Gastrointestinal , Percepción de Quorum , Acil-Butirolactonas/química , Acil-Butirolactonas/metabolismo , Bacterias/metabolismo , Percepción de Quorum/genética , SimbiosisRESUMEN
Irritable bowel syndrome (IBS) is characterized by episodic bouts of abdominal pain, bloating, and altered bowel habit. Accumulating evidence has linked immune activation with IBS, including reports of increases in circulating levels of the proinflammatory cytokine interleukin (IL)-6. However, it is unknown whether IL-6 contributes directly to disease manifestation. As enteric nervous activity mediates motility and secretory function, the aims of this study were to determine the effects of IL-6 on submucosal neurons and related gastrointestinal (GI) function. In these studies, we examined the colons of maternally separated (MS) rats, which exhibit elevated circulating levels of IL-6 in addition to GI dysfunction. To our knowledge, these studies are the first to provide evidence of the sensitivity of submucosal neurons to colonic secretions from MS rats (n = 50, P < 0.05), thus recapitulating clinical biopsy data. Moreover, we demonstrated that the excitatory action is IL-6 dependent. Thereafter, the impact of IL-6 on neuronal and glial activation and absorpto/secretory function was pharmacologically characterized. Other proinflammatory cytokines including IL-8 (n = 30, P > 0.05), IL-1ß (n = 56, P > 0.05), and TNF-α (n = 56, P > 0.05) excited fewer neurons. Both muscarinic and nicotinic cholinergic receptors participate in the effect and cause downstream activation of ERK, JAK-STAT, and NF-κB signaling cascades. Functionally, IL-6 increases transepithelial resistance and enhances neurally and cholinergically mediated ion transport. These data provide a role for IL-6 in colonic secretory functions and relate these effects to GI dysfunction in an animal model of IBS, thereby elucidating a potential relationship between circulating levels of IL-6 and aberrant GI function.
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Colon/inervación , Colon/fisiopatología , Interleucina-6/metabolismo , Síndrome del Colon Irritable/fisiopatología , Privación Materna , Neuronas , Plexo Submucoso/fisiopatología , Acetilcolina/metabolismo , Animales , Agonistas Colinérgicos/metabolismo , Femenino , Ganglios/fisiopatología , Técnicas In Vitro , Interleucina-1beta/farmacología , Interleucina-6/sangre , Interleucina-6/farmacología , Interleucina-8/farmacología , Síndrome del Colon Irritable/etiología , Masculino , Proteínas Quinasas Activadas por Mitógenos/metabolismo , FN-kappa B/metabolismo , Neuronas/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Receptores de Interleucina-6/metabolismo , Proteínas Recombinantes/farmacología , Factor de Transcripción STAT3/metabolismo , Transducción de Señal/efectos de los fármacos , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
Aquamin is a calcium-rich multi-mineral supplement derived from the red marine algae, Lithothamnion species. Calcium supplementation has been shown to exert a prebiotic-like effect on the gut microbiota and has been associated with distinct changes in lactate and short chain fatty acid (SCFA) production. Irritable bowel syndrome (IBS) subtype is associated with changes in SCFA levels compared with healthy controls. Using an ex vivo simulation model, and a fecal inoculum from a patient diagnosed with IBS, we evaluated the effects of Aquamin (at 6 and 30 mg/mL) on SCFAs and lactate production, pH and gas production, and human microbiota composition. Our results demonstrate that Aquamin increased SCFA production (acetate and propionate by 8% and 24%, respectively, at 30 mg/mL dose), significantly decreased lactate production (30 mg/mL), and increased colonic fluid pH without inducing changes in colonic gas production or gastrointestinal (GI) microbiota composition. These results indicate that Aquamin may play a role in optimizing GI microbial function in an ex vivo setting.
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Microbioma Gastrointestinal , Síndrome del Colon Irritable , Ácidos Grasos Volátiles , Heces , Fermentación , Humanos , MineralesRESUMEN
BACKGROUND: The role of the gut microbiome in the biotransformation of drugs has recently come under scrutiny. It remains unclear whether the gut microbiome directly influences the extent of drug absorbed after oral administration and thus potentially alters clinical pharmacokinetics. METHODS: In this study, we evaluated whether changes in the gut microbiota of male Sprague Dawley rats, as a result of either antibiotic or probiotic administration, influenced the oral bioavailability of two commonly prescribed antipsychotics, olanzapine and risperidone. FINDINGS: The bioavailability of olanzapine, was significantly increased (1.8-fold) in rats that had undergone antibiotic-induced depletion of gut microbiota, whereas the bioavailability of risperidone was unchanged. There was no direct effect of microbiota depletion on the expression of major CYP450 enzymes involved in the metabolism of either drug. However, the expression of UGT1A3 in the duodenum was significantly downregulated. The reduction in faecal enzymatic activity, observed during and after antibiotic administration, did not alter the ex vivo metabolism of olanzapine or risperidone. The relative abundance of Alistipes significantly correlated with the AUC of olanzapine but not risperidone. INTERPRETATION: Alistipes may play a role in the observed alterations in olanzapine pharmacokinetics. The gut microbiome might be an important variable determining the systemic bioavailability of orally administered olanzapine. Additional research exploring the potential implication of the gut microbiota on the clinical pharmacokinetics of olanzapine in humans is warranted. FUNDING: This research is supported by APC Microbiome Ireland, a research centre funded by Science Foundation Ireland (SFI), through the Irish Government's National Development Plan (grant no. 12/RC/2273 P2) and by Nature Research-Yakult (The Global Grants for Gut Health; Ref No. 626891).
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Microbioma Gastrointestinal , Olanzapina/farmacocinética , Inhibidores Selectivos de la Recaptación de Serotonina/farmacocinética , Administración Oral , Animales , Antibacterianos/farmacología , Biodiversidad , Disponibilidad Biológica , Cromatografía Líquida de Alta Presión , Monitoreo de Drogas , Heces/microbiología , Masculino , Estructura Molecular , Olanzapina/administración & dosificación , Olanzapina/química , Probióticos , Ratas , Inhibidores Selectivos de la Recaptación de Serotonina/administración & dosificación , Inhibidores Selectivos de la Recaptación de Serotonina/químicaRESUMEN
OBJECTIVES: Our objective was to demonstrate microbial regulation of hepatic genes implicated in drug metabolism and transport using germ-free (GF) mice and to explore the impact of a microbial metabolite, butyrate, and a prebiotic dietary intervention on hepatic gene expression in mice. METHODS: Using reverse-transcriptase PCR, we investigated cytochrome P450 (CYP) and multidrug-resistance protein 1 (MDR1) expression in conventional, GF and colonised GF mice. To investigate the effects of butyrate, sodium butyrate (3 g/l) was administered for 21 days to conventional or GF mice. In the prebiotic study, young adult and middle-aged mice received diet enriched with 10% fructo-oligosaccharide (FOS)-inulin for 14 weeks. KEY FINDINGS: Colonisation of GF animals normalised expression of Cyp3a11 and Mdr1b to conventional levels. Butyrate upregulated Cyp2b10 in conventional mice (P < 0.05) but overall did not induce widespread changes in hepatic genes. FOS-inulin increased Cyp3a13 expression and had the opposite effect on Mdr1a expression in young adult mice (P < 0.05). Age, on the other hand, influenced the prebiotic effect on Cyp2a4 expression (P < 0.01). CONCLUSION: The expression of hepatic genes implicated in drug metabolism and transport displays sensitivity to the microbiome, microbiome-derived metabolites and a microbial-targeted intervention. Our study may provide the impetus to explore microbiota-targeted interventions in normalising host metabolic activity and reducing inter-individual variability in drug pharmacokinetics.
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Subfamilia B de Transportador de Casetes de Unión a ATP/metabolismo , Bacterias/efectos de los fármacos , Butiratos/farmacología , Sistema Enzimático del Citocromo P-450/metabolismo , Microbioma Gastrointestinal/efectos de los fármacos , Intestinos/efectos de los fármacos , Inulina/farmacología , Hígado/efectos de los fármacos , Oligosacáridos/farmacología , Prebióticos , Subfamilia B de Transportador de Casetes de Unión a ATP/genética , Factores de Edad , Animales , Bacterias/metabolismo , Sistema Enzimático del Citocromo P-450/genética , Regulación Enzimológica de la Expresión Génica , Vida Libre de Gérmenes , Intestinos/microbiología , Isoenzimas , Hígado/enzimología , Masculino , Ratones Endogámicos C57BL , Miembro 4 de la Subfamilia B de Casete de Unión a ATPRESUMEN
BACKGROUND: A hallmark feature of Parkinson's disease (PD) is the build-up of α-synuclein protein aggregates throughout the brain; however α-synuclein is also expressed in enteric neurons. Gastrointestinal (GI) symptoms and pathology are frequently reported in PD, including constipation, increased intestinal permeability, glial pathology, and alterations to gut microbiota composition. α-synuclein can propagate through neuronal systems but the site of origin of α-synuclein pathology, whether it be the gut or the brain, is still unknown. Physical exercise is associated with alleviating symptoms of PD and with altering the composition of the gut microbiota. METHODS: This study investigated the effects of bilateral nigral injection of adeno-associated virus (AAV)-α-synuclein on enteric neurons, glia and neurochemistry, the gut microbiome, and bile acid metabolism in rats, some of whom were exposed to voluntary exercise. KEY RESULTS: Nigral overexpression of α-synuclein resulted in significant neuronal loss in the ileal submucosal plexus with no change in enteric glia. In contrast, the myenteric plexus showed a significant increase in glial expression, while neuronal numbers were maintained. Concomitant alterations were observed in the gut microbiome and related bile acid metabolism. Voluntary running protected against neuronal loss, increased enteric glial expression, and modified gut microbiome composition in the brain-injected AAV-α-synuclein PD model. CONCLUSIONS AND INFERENCES: These results show that developing nigral α-synuclein pathology in this PD model exerts significant alterations on the enteric nervous system (ENS) and gut microbiome that are receptive to modification by exercise. This highlights brain to gut communication as an important mechanism in PD pathology.
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Sistema Nervioso Entérico/patología , Microbioma Gastrointestinal , Trastornos Parkinsonianos , Sustancia Negra/metabolismo , alfa-Sinucleína/toxicidad , Animales , Vectores Genéticos , Humanos , Inyecciones Intraventriculares , Masculino , Ratas , Ratas Sprague-Dawley , Ratas Transgénicas , Transfección , alfa-Sinucleína/administración & dosificaciónRESUMEN
GABA(B) receptors are the G-protein-coupled receptors for the neurotransmitter gamma-aminobutyric acid (GABA). Receptor subtypes are based on the subunit isoforms GABA(B1a) and GABA(B1b), which combine with GABA(B2) subunits to form heteromeric receptors. Here, we used a modified bacterial artificial chromosome (BAC) containing the GABA(B1) gene to generate transgenic mice expressing GABA(B1a) and GABA(B1b) subunits fused to the enhanced green fluorescence protein (eGFP). We demonstrate that the GABA(B1)-eGFP fusion proteins reproduce the cellular expression patterns of endogenous GABA(B1) proteins in the brain and in peripheral tissue. Crossing the GABA(B1)-eGFP BAC transgene into the GABA(B1) (-/-) background restores pre and postsynaptic GABA(B) functions, showing that the GABA(B1)-eGFP fusion proteins substitute for the lack of endogenous GABA(B1) proteins. Finally, we demonstrate that the GABA(B1)-eGFP fusion proteins replicate the temporal expression patterns of native GABA(B) receptors in cultured neurons. These transgenic mice therefore provide a validated tool for direct visualization of native GABA(B) receptors.