Tryptophan-kynurenine metabolism: a link between the gut and brain for depression in inflammatory bowel disease
TL;DR: In this paper, the relationship between depression and the tryptophan-kynurenine metabolic pathway is overviewed in the light of recent publications, among which kynerunic acid (KYNA) and quinolinic acid (QUIN) are molecules of great interest in recent studies on the mechanisms of inflammationinduced depression.
Abstract: Inflammatory bowel disease (IBD), which mainly includes ulcerative colitis (UC) and Crohn's disease (CD), is a group of chronic bowel diseases that are characterized by abdominal pain, diarrhea, and bloody stools. IBD is strongly associated with depression, and its patients have a higher incidence of depression than the general population. Depression also adversely affects the quality of life and disease prognosis of patients with IBD. The tryptophan-kynurenine metabolic pathway degrades more than 90% of tryptophan (TRP) throughout the body, with indoleamine 2,3-dioxygenase (IDO), the key metabolic enzyme, being activated in the inflammatory environment. A series of metabolites of the pathway are neurologically active, among which kynerunic acid (KYNA) and quinolinic acid (QUIN) are molecules of great interest in recent studies on the mechanisms of inflammation-induced depression. In this review, the relationship between depression in IBD and the tryptophan-kynurenine metabolic pathway is overviewed in the light of recent publications.
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TL;DR: In this paper , the brain-gut-microbiota axis was found to play a crucial role in susceptibility versus resilience in rodents exposed to stress, suggesting that the vagus nerve influences depression through the braingut microbiota.
75 citations
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TL;DR: In this article , a review mechanistically provides an overview of the neuropathological roles of sustained neuroinflammatory response in the development of depression and elucidates the therapeutic potential of flavonoid and non-flavonoid polyphenols in modulating inflammatory mediators and signaling cascades as well as promoting other neurophysiological and neuroprotective functions underlying inflammation-associated depressive symptoms.
29 citations
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TL;DR: This review provides scientific bases for the correlation of indoles with diseases moreover highlights several directions for subsequent indoles-related studies.
Abstract: Endogenous indole and its derivatives (indoles), considered as promising N-substituted heterocyclic compounds, are tryptophan metabolites derived from intestinal microbiota and exhibit a range of biological activities. Recent studies indicate that indoles contribute to maintaining the biological barrier of the human intestine, which exert the anti-inflammatory activities mainly through activating AhR and PXR receptors to affect the immune system’s function, significantly improving intestinal health (inflammatory bowel disease, hemorrhagic colitis, colorectal cancer) and further promote human health (diabetes mellitus, central system inflammation, and vascular regulation). However, the revealed toxic influences cannot be ignored. Indoxyl sulfate, an indole derivative, performs nephrotoxicity and cardiovascular toxicity. We addressed the interaction between indoles and intestinal microbiota and the indoles’ effects on human health as double-edged swords. This review provides scientific bases for the correlation of indoles with diseases moreover highlights several directions for subsequent indoles-related studies.
19 citations
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TL;DR: In this paper , it is believed that heightened intestinal inflammation and dysfunction of the enteric nervous system contribute to impaired intestinal permeability, which facilitates the translocation of intestinal enterotoxins into the blood circulation.
Abstract: Patients with inflammatory bowel disease (IBD) suffer from depression at higher rates than the general population. An etiological trigger of depressive symptoms is theorised to be inflammation within the central nervous system. It is believed that heightened intestinal inflammation and dysfunction of the enteric nervous system (ENS) contribute to impaired intestinal permeability, which facilitates the translocation of intestinal enterotoxins into the blood circulation. Consequently, these may compromise the immunological and physiological functioning of distant non-intestinal tissues such as the brain. In vivo models of colitis provide evidence of increased blood-brain barrier permeability and enhanced central nervous system (CNS) immune activity triggered by intestinal enterotoxins and blood-borne inflammatory mediators. Understanding the immunological, physiological, and structural changes associated with IBD and neuroinflammation may aid in the development of more tailored and suitable pharmaceutical treatment for IBD-associated depression.
16 citations
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TL;DR: In this paper , it is believed that heightened intestinal inflammation and dysfunction of the enteric nervous system contribute to impaired intestinal permeability, which facilitates the translocation of intestinal enterotoxins into the blood circulation.
Abstract: Patients with inflammatory bowel disease (IBD) suffer from depression at higher rates than the general population. An etiological trigger of depressive symptoms is theorised to be inflammation within the central nervous system. It is believed that heightened intestinal inflammation and dysfunction of the enteric nervous system (ENS) contribute to impaired intestinal permeability, which facilitates the translocation of intestinal enterotoxins into the blood circulation. Consequently, these may compromise the immunological and physiological functioning of distant non-intestinal tissues such as the brain. In vivo models of colitis provide evidence of increased blood-brain barrier permeability and enhanced central nervous system (CNS) immune activity triggered by intestinal enterotoxins and blood-borne inflammatory mediators. Understanding the immunological, physiological, and structural changes associated with IBD and neuroinflammation may aid in the development of more tailored and suitable pharmaceutical treatment for IBD-associated depression.
15 citations
References
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TL;DR: The goal of this article is to establish the current epidemiology of IBD in the Western world, contrast it with the increase in IBD on health-care systems in newly industrialized countries and forecast the global effects of I BD in 2025.
Abstract: Over 1 million residents in the USA and 2.5 million in Europe are estimated to have IBD, with substantial costs for health care. These estimates do not factor in the 'real' price of IBD, which can impede career aspirations, instil social stigma and impair quality of life in patients. The majority of patients are diagnosed early in life and the incidence continues to rise; therefore, the effect of IBD on health-care systems will rise exponentially. Moreover, IBD has emerged in newly industrialized countries in Asia, South America and Middle East and has evolved into a global disease with rising prevalence in every continent. Understanding the worldwide epidemiological patterns of IBD will prepare us to manage the burden of IBD over time. The goal of this article is to establish the current epidemiology of IBD in the Western world, contrast it with the increase in IBD in newly industrialized countries and forecast the global effects of IBD in 2025.
1,488 citations
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TL;DR: It is demonstrated that dysbiosis of the gut microbiome may have a causal role in the development of depressive-like behaviors, in a pathway that is mediated through the host’s metabolism.
Abstract: Major depressive disorder (MDD) is the result of complex gene-environment interactions. According to the World Health Organization, MDD is the leading cause of disability worldwide, and it is a major contributor to the overall global burden of disease. However, the definitive environmental mechanisms underlying the pathophysiology of MDD remain elusive. The gut microbiome is an increasingly recognized environmental factor that can shape the brain through the microbiota-gut-brain axis. We show here that the absence of gut microbiota in germ-free (GF) mice resulted in decreased immobility time in the forced swimming test relative to conventionally raised healthy control mice. Moreover, from clinical sampling, the gut microbiotic compositions of MDD patients and healthy controls were significantly different with MDD patients characterized by significant changes in the relative abundance of Firmicutes, Actinobacteria and Bacteroidetes. Fecal microbiota transplantation of GF mice with 'depression microbiota' derived from MDD patients resulted in depression-like behaviors compared with colonization with 'healthy microbiota' derived from healthy control individuals. Mice harboring 'depression microbiota' primarily exhibited disturbances of microbial genes and host metabolites involved in carbohydrate and amino acid metabolism. This study demonstrates that dysbiosis of the gut microbiome may have a causal role in the development of depressive-like behaviors, in a pathway that is mediated through the host's metabolism.
1,224 citations
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TL;DR: Therapeutic targeting of the gut microbiota might be a viable treatment strategy for serotonin-related brain-gut axis disorders.
1,201 citations
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TL;DR: This review gathers the most recent advances concerning the central role of Trp metabolism in microbiota-host crosstalk in health and disease and aims to facilitate a better understanding of the pathogenesis of human diseases and open therapeutic opportunities.
1,172 citations
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TL;DR: Data support an association between smoking and Crohn's disease whereas smoking cessation, but not current smoking, is associated with an increased risk of ulcerative colitis.
Abstract: IBD, comprising Crohn's disease and ulcerative colitis, is a chronic immunologically mediated disease at the intersection of complex interactions between genetics, environment and gut microbiota. Established high-prevalence populations of IBD in North America and Europe experienced the steepest increase in incidence towards the second half of the twentieth century. Furthermore, populations previously considered 'low risk' (such as in Japan and India) are witnessing an increase in incidence. Potentially relevant environmental influences span the spectrum of life from mode of childbirth and early-life exposures (including breastfeeding and antibiotic exposure in infancy) to exposures later on in adulthood (including smoking, major life stressors, diet and lifestyle). Data support an association between smoking and Crohn's disease whereas smoking cessation, but not current smoking, is associated with an increased risk of ulcerative colitis. Dietary fibre (particularly fruits and vegetables), saturated fats, depression and impaired sleep, and low vitamin D levels have all been associated with incident IBD. Interventional studies assessing the effects of modifying these risk factors on natural history and patient outcomes are an important unmet need. In this Review, the changing epidemiology of IBD, mechanisms behind various environmental associations and interventional studies to modify risk factors and disease course are discussed.
1,125 citations