Intestinal Permeability Defects: Is It Time to Treat?
01 Sep 2013-Clinical Gastroenterology and Hepatology (NIH Public Access)-Vol. 11, Iss: 9, pp 1075-1083
TL;DR: The correlation between increased intestinal permeability and disease has caught the attention of the public, leading to a rise in popularity of the diagnosis of "leaky gut syndrome," which encompasses a range of systemic disorders.
About: This article is published in Clinical Gastroenterology and Hepatology.The article was published on 2013-09-01 and is currently open access. It has received 268 citations till now. The article focuses on the topics: Intestinal mucosa & Intestinal permeability.
Citations
More filters
TL;DR: Mechanisms of intestinal barrier loss and the role of intestinal epithelial barrier function in pathogenesis of both intestinal and systemic diseases are reviewed and a discussion of potential strategies to restore the epithelium is discussed.
Abstract: A fundamental function of the intestinal epithelium is to act as a barrier that limits interactions between luminal contents such as the intestinal microbiota, the underlying immune system and the remainder of the body, while supporting vectorial transport of nutrients, water and waste products. Epithelial barrier function requires a contiguous layer of cells as well as the junctions that seal the paracellular space between epithelial cells. Compromised intestinal barrier function has been associated with a number of disease states, both intestinal and systemic. Unfortunately, most current clinical data are correlative, making it difficult to separate cause from effect in interpreting the importance of barrier loss. Some data from experimental animal models suggest that compromised epithelial integrity might have a pathogenic role in specific gastrointestinal diseases, but no FDA-approved agents that target the epithelial barrier are presently available. To develop such therapies, a deeper understanding of both disease pathogenesis and mechanisms of barrier regulation must be reached. Here, we review and discuss mechanisms of intestinal barrier loss and the role of intestinal epithelial barrier function in pathogenesis of both intestinal and systemic diseases. We conclude with a discussion of potential strategies to restore the epithelial barrier.
658 citations
TL;DR: Clinicians are to discuss the components of the intestinal barrier, the diverse measurements of intestinal permeability, their perturbation in non-inflammatory ‘stressed states’ and the impact of treatment with dietary factors.
Abstract: The objectives of this review on 'leaky gut' for clinicians are to discuss the components of the intestinal barrier, the diverse measurements of intestinal permeability, their perturbation in non-inflammatory 'stressed states' and the impact of treatment with dietary factors. Information on 'healthy' or 'leaky' gut in the public domain requires confirmation before endorsing dietary exclusions, replacement with non-irritating foods (such as fermented foods) or use of supplements to repair the damage. The intestinal barrier includes surface mucus, epithelial layer and immune defences. Epithelial permeability results from increased paracellular transport, apoptosis or transcellular permeability. Barrier function can be tested in vivo using orally administered probe molecules or in vitro using mucosal biopsies from humans, exposing the colonic mucosa from rats or mice or cell layers to extracts of colonic mucosa or stool from human patients. Assessment of intestinal barrier requires measurements beyond the epithelial layer. 'Stress' disorders such as endurance exercise, non-steroidal anti-inflammatory drugs administration, pregnancy and surfactants (such as bile acids and dietary factors such as emulsifiers) increase permeability. Dietary factors can reverse intestinal leakiness and mucosal damage in the 'stress' disorders. Whereas inflammatory or ulcerating intestinal diseases result in leaky gut, no such disease can be cured by simply normalising intestinal barrier function. It is still unproven that restoring barrier function can ameliorate clinical manifestations in GI or systemic diseases. Clinicians should be aware of the potential of barrier dysfunction in GI diseases and of the barrier as a target for future therapy.
458 citations
TL;DR: Results imply that AmEVs may act as a functional moiety for controlling gut permeability and that the regulation of intestinal barrier integrity can improve metabolic functions in HFD-fed mice.
Abstract: The gut microbiota has an important role in the gut barrier, inflammation and metabolic functions. Studies have identified a close association between the intestinal barrier and metabolic diseases, including obesity and type 2 diabetes (T2D). Recently, Akkermansia muciniphila has been reported as a beneficial bacterium that reduces gut barrier disruption and insulin resistance. Here we evaluated the role of A. muciniphila-derived extracellular vesicles (AmEVs) in the regulation of gut permeability. We found that there are more AmEVs in the fecal samples of healthy controls compared with those of patients with T2D. In addition, AmEV administration enhanced tight junction function, reduced body weight gain and improved glucose tolerance in high-fat diet (HFD)-induced diabetic mice. To test the direct effect of AmEVs on human epithelial cells, cultured Caco-2 cells were treated with these vesicles. AmEVs decreased the gut permeability of lipopolysaccharide-treated Caco-2 cells, whereas Escherichia coli-derived EVs had no significant effect. Interestingly, the expression of occludin was increased by AmEV treatment. Overall, these results imply that AmEVs may act as a functional moiety for controlling gut permeability and that the regulation of intestinal barrier integrity can improve metabolic functions in HFD-fed mice.
394 citations
TL;DR: It is hypothesized that modulating the gut microbiota can serve as a potential method for regulating intestinal permeability and may help to alter the course of autoimmune diseases in susceptible individuals.
Abstract: The intestinal epithelial lining, together with factors secreted from it, forms a barrier that separates the host from the environment. In pathologic conditions, the permeability of the epithelial lining may be compromised allowing the passage of toxins, antigens, and bacteria in the lumen to enter the blood stream creating a “leaky gut.” In individuals with a genetic predisposition, a leaky gut may allow environmental factors to enter the body and trigger the initiation and development of autoimmune disease. Growing evidence shows that the gut microbiota is important in supporting the epithelial barrier and therefore plays a key role in the regulation of environmental factors that enter the body. Several recent reports have shown that probiotics can reverse the leaky gut by enhancing the production of tight junction proteins; however, additional and longer-term studies are still required. Conversely, pathogenic bacteria that can facilitate a leaky gut and induce autoimmune symptoms can be ameliorated with the use of antibiotic treatment. Therefore, it is hypothesized that modulating the gut microbiota can serve as a potential method for regulating intestinal permeability and may help to alter the course of autoimmune diseases in susceptible individuals.
345 citations
Cites background from "Intestinal Permeability Defects: Is..."
...Some argue that the leaky gut is only an outcome of disease progression rather than an initiator or exacerbator of disease (109), but this should not be the case for T1D....
[...]
TL;DR: Evidence is provided for the gut microbiota as a key factor mediating the link between diet and depressive illness and promise is suggested in the development of interventions targeting the Gut microbiota for the prevention and treatment of common mental health disorders.
Abstract: With depressive disorders the leading source of disability globally, the identification of new targets for prevention and management is imperative. A rapidly emerging field of research suggests that the microbiome-gut-brain axis is of substantial relevance to mood and behaviour. Similarly, unhealthy diet has recently emerged as a significant correlate of and risk factor for depression. This review provides evidence for the gut microbiota as a key factor mediating the link between diet and depressive illness.
292 citations
Cites background from "Intestinal Permeability Defects: Is..."
...Unau 0951-7367 2014 Wolters Kluwer Health | Lippincott Williams & Wilk disorders, asthma, IBD and, speculatively, to mental health [65,66], although it is important to note that most data are correlational at this stage [67]....
[...]
References
More filters
TL;DR: It is shown that increased lipopolysaccharide is bioactive in vivo and correlates with measures of innate and adaptive immune activation, which establish a mechanism for chronic immune activation in the context of a compromised gastrointestinal mucosal surface and provide new directions for therapeutic interventions that modify the consequences of acute HIV infection.
Abstract: Chronic activation of the immune system is a hallmark of progressive HIV infection and better predicts disease outcome than plasma viral load, yet its etiology remains obscure. Here we show that circulating microbial products, probably derived from the gastrointestinal tract, are a cause of HIV-related systemic immune activation. Circulating lipopolysaccharide, which we used as an indicator of microbial translocation, was significantly increased in chronically HIV-infected individuals and in simian immunodeficiency virus (SIV)-infected rhesus macaques (P
3,049 citations
TL;DR: Recent advances have uncovered mechanisms by which the intestinal mucosal barrier is regulated in response to physiological and immunological stimuli, along with evidence that this regulation shapes mucosal immune responses in the gut and, when dysfunctional, may contribute to disease.
Abstract: Mucosal surfaces are lined by epithelial cells. These cells establish a barrier between sometimes hostile external environments and the internal milieu. However, mucosae are also responsible for nutrient absorption and waste secretion, which require a selectively permeable barrier. These functions place the mucosal epithelium at the centre of interactions between the mucosal immune system and luminal contents, including dietary antigens and microbial products. Recent advances have uncovered mechanisms by which the intestinal mucosal barrier is regulated in response to physiological and immunological stimuli. Here I discuss these discoveries along with evidence that this regulation shapes mucosal immune responses in the gut and, when dysfunctional, may contribute to disease.
2,795 citations
"Intestinal Permeability Defects: Is..." refers background in this paper
...122 Aepithelium, is to form a barrier that prevents potentially noxious contents of the intestinal lumen, including the microbiota, from accessing internal sites and the systemic circulation.(1) Barrier defects have been reliably associated with a variety of human diseases, including those primarily affecting the gut, eg, inflammatory bowel disease (IBD), celiac disease, and irritable bowel syndrome (IBS), as well as systemic diseases or diseases involving other organ systems, eg, type I diabetes, graft-versushost disease (GVHD), human immunodeficiency virus, multiple sclerosis, rheumatoid arthritis, and autism....
[...]
...Indeed, data from some mouse studies indicate that mild permeability increases may activate immunoregulatory pathways that can limit colitis on subsequent challenge.(1,43) 688...
[...]
...These have been termed pore and leak pathways and refer to high capacity, sizeselective and charge-selective routes and low capacity, nonselective routes, respectively.(1,10) IL-13 specifically increases flux across the pore pathway by up-regulating expression of the tight junction protein claudin-2, which forms a paracellular cation and water channel....
[...]
...Together with high-resolution in vitro analyses of tight junction size selectivity, this has led to a model in which there are at least 2 distinct routes of paracellular flux across the tight junction.(1,6,10) These have been termed pore and leak pathways and refer to high capacity, sizeselective and charge-selective routes and low capacity, nonselective routes, respectively....
[...]
TL;DR: It is shown that circulating microbial products, probably derived from the gastrointestinal tract, are a cause of HIV-related systemic immune activation and increased lipopolysaccharide is bioactive in vivo and correlates with measures of innate and adaptive immune activation.
Abstract: Chronic activation of the immune system is a hallmark of progressive HIV infection and better predicts disease outcome than plasma viral load, yet its etiology remains obscure. Here, we show that circulating microbial products, likely derived from the gastrointestinal tract, are a primary cause of HIV-related systemic immune activation. Circulating lipopolysaccharide, an indicator of microbial translocation, is significantly increased in chronically HIV-infected individuals and SIV-infected rhesus macaques. We show that monocytes are chronically stimulated in vivo by increased lipopolysaccharide, which also correlates with measures of innate and adaptive immune activation. Effective antiretroviral therapy appears to reduce microbial translocation. Furthermore, in non-pathogenic SIV infection of sooty mangabeys, microbial translocation does not seem to occur. These data establish a mechanism for chronic immune activation in the context of a compromised gastrointestinal mucosal surface and provide novel directions for therapeutic interventions that modify the consequences of acute HIV infection.
1,984 citations
"Intestinal Permeability Defects: Is..." refers background in this paper
...Bacterial translocation has been postulated to cause immune activation.(67) Yes (in patients)(68)...
[...]
TL;DR: Findings show that the Muc2 mucin can build a mucus barrier that separates bacteria from the colon epithelia and suggest that defects in this mucus can cause colon inflammation.
Abstract: We normally live in symbiosis with approximately 10(13) bacteria present in the colon. Among the several mechanisms maintaining the bacteria/host balance, there is limited understanding of the structure, function, and properties of intestinal mucus. We now demonstrate that the mouse colonic mucus consists of two layers extending 150 mum above the epithelial cells. Proteomics revealed that both of these layers have similar protein composition, with the large gel-forming mucin Muc2 as the major structural component. The inner layer is densely packed, firmly attached to the epithelium, and devoid of bacteria. In contrast, the outer layer is movable, has an expanded volume due to proteolytic cleavages of the Muc2 mucin, and is colonized by bacteria. Muc2(-/-) mice have bacteria in direct contact with the epithelial cells and far down in the crypts, explaining the inflammation and cancer development observed in these animals. These findings show that the Muc2 mucin can build a mucus barrier that separates bacteria from the colon epithelia and suggest that defects in this mucus can cause colon inflammation.
1,868 citations
TL;DR: It is found that MyD88 deficiency changes the composition of the distal gut microbiota, and that exposure to the microbiota of specific pathogen-free MyD 88-negative NOD donors attenuates T1D in germ-free NOD recipients.
Abstract: Type 1 diabetes (T1D) is a debilitating autoimmune disease that results from T-cell-mediated destruction of insulin-producing beta-cells. Its incidence has increased during the past several decades in developed countries, suggesting that changes in the environment (including the human microbial environment) may influence disease pathogenesis. The incidence of spontaneous T1D in non-obese diabetic (NOD) mice can be affected by the microbial environment in the animal housing facility or by exposure to microbial stimuli, such as injection with mycobacteria or various microbial products. Here we show that specific pathogen-free NOD mice lacking MyD88 protein (an adaptor for multiple innate immune receptors that recognize microbial stimuli) do not develop T1D. The effect is dependent on commensal microbes because germ-free MyD88-negative NOD mice develop robust diabetes, whereas colonization of these germ-free MyD88-negative NOD mice with a defined microbial consortium (representing bacterial phyla normally present in human gut) attenuates T1D. We also find that MyD88 deficiency changes the composition of the distal gut microbiota, and that exposure to the microbiota of specific pathogen-free MyD88-negative NOD donors attenuates T1D in germ-free NOD recipients. Together, these findings indicate that interaction of the intestinal microbes with the innate immune system is a critical epigenetic factor modifying T1D predisposition.
1,795 citations
"Intestinal Permeability Defects: Is..." refers background in this paper
...Type I diabetes Increased in pre-diabetic and diabetic patients(61) Yes(62) Unknown Changes in microbiome modify incidence of experimental disease.(63,64) Unknown...
[...]