Impaired Gut Barrier Function Research Articles

Deletion of ghrelin alters tryptophan metabolism and exacerbates experimental ulcerative colitis in aged mice.

A major component of aging is chronic, low-grade inflammation, attributable in part by impaired gut barrier function. We previously reported that deletion of ghrelin, a peptidergic hormone released mainly from the gut, exacerbates experimental muscle atrophy in aged mice. In addition, ghrelin has been shown to ameliorate colitis in experimental models of inflammatory bowel disease (IBD), although the role of endogenous ghrelin in host-microbe interactions is less clear. Here, we showed that 22-month-old global ghrelin knockout (Ghrl-/-) mice exhibited significantly increased depressive-like behaviors, while anxiety levels and working memory were similar to littermate wild-type (WT) mice. Furthermore, old Ghrl-/- mice showed significantly increased intestinal permeability to fluorescein isothiocyanate (FITC)-dextran, significantly higher colonic interleukin (IL-1β) levels, and trends for higher colonic IL-6 and tumor necrosis factor-α (TNF-α) compared to WT mice. Interestingly, young Ghrl-/- and WT mice showed comparable depressive-like behavior and gut permeability, suggesting age-dependent exacerbation in gut barrier dysfunction in Ghrl-/- mice. While fecal short-chain fatty acids levels were comparable between old Ghrl-/- and WT mice, serum metabolome revealed alterations in metabolic cascades including tryptophan metabolism. Specifically, tryptophan and its microbial derivatives indole-3-acetic acid and indole-3-lactic acid were significantly reduced in old Ghrl-/-mice. Furthermore, in an experimental model of dextran sulfate sodium (DSS)-induced colitis, Ghrl-/- mice showed exacerbated disease symptoms, and higher levels of chemoattractant and pro-inflammatory cytokines in the colon. Overall, these data demonstrated that ghrelin deficiency is associated with gut barrier dysfunction, alterations in microbially derived tryptophan metabolites, and increased susceptibility to colitis. These data suggested that endogenous ghrelin contributes to maintaining a healthy host-microbe environment, ultimately impacting on brain function.

Amelioratory Effect of Resistant Starch on Non-alcoholic Fatty Liver Disease via the Gut-Liver Axis.

Non-alcoholic fatty liver disease (NAFLD) is a hepatic manifestation of metabolic syndrome with a global prevalence. Impaired gut barrier function caused by an unhealthy diet plays a key role in disrupting the immune-metabolic homeostasis of the gut-liver axis (GLA), leading to NAFLD. Therefore, dietary interventions have been studied as feasible alternative therapeutic approaches to ameliorate NAFLD. Resistant starches (RSs) are prebiotics that reduce systemic inflammation in patients with metabolic syndrome. The present review aimed to elucidate the mechanisms of the GLA in alleviating NAFLD and provide insights into how dietary RSs counteract diet-induced inflammation in the GLA. Emerging evidence suggests that RS intake alters gut microbiota structure, enhances mucosal immune tolerance, and promotes the production of microbial metabolites such as short-chain fatty acids (SCFAs) and secondary bile acids. These metabolites directly stimulate the growth of intestinal epithelial cells and elicit GPR41/GPR43, FXR, and TGR5 signaling cascades to sustain immune-metabolic homeostasis in the GLA. The literature also revealed the dietary-immune-metabolic interplay by which RSs exert their regulatory effect on the immune-metabolic crosstalk of the GLA and the related molecular basis, suggesting that dietary intervention with RSs may be a promising alternative therapeutic strategy against diet-induced dysfunction of the GLA and, ultimately, the risk of developing NAFLD.

Can periodontitis affect colorectal cancer by altering microbiota balance?

Emerging evidence suggests that, along with dietary, genetic and environmental factors, gut microbiota plays a role in the progress of colorectal cancer. Dysbiosis of oral flora in patients with periodontitis affects the composition of microbial community in the gut, impairs gut barrier function, and induces a proinflammatory microenvironment, all of which contribute to the progression of colorectal cancer. In view of the influences by microbiota dysbiosis, this article reviews the role of periodontitis in affecting the occurrence and development of colorectal cancer.

Antibiotics and High‐Fat‐Diet Induced Gut Inflammation and Impaired Gut Permeability are Improved by Dietary Blueberries Possibly Through NFκB Signaling

BackgroundEvidence indicates that a high fat diet can promote gut inflammation and increase gut permeability. The use of antibiotics further exacerbates these complications and can lead to the development of inflammatory bowel disease. Blueberries are rich in bioactive components such as anthocyanins. We recently reported the vascular and prebiotic effects of dietary blueberries. However, the effects of blueberries on gut inflammation and permeability are unknown. In the present study, we tested the hypothesis that blueberries improve antibiotics and high‐fat‐diet (HFD) induced gut inflammation and impaired gut barrier function in C57BL/6J mice.Methods7‐week‐old male mice (Jackson Lab) consumed standard diet (10% kcal fat) (CON) or HFD (60% kcal fat) with antibiotic cocktail (ampicillin, vancomycin, neomycin sulfate and metronidazole) in drinking water (HFA) or 3.7% freeze‐dried blueberry powder supplemented HFD with antibiotic cocktail in drinking water (HFA+BB) for 12 weeks. Body weight and body composition were assessed at the end of the experiment. Inflammation and permeability of the colon were assessed by the mRNA expression of inflammatory markers (IL‐1β, IL‐6, iNOS, MCP‐1); gut barrier markers (MUC‐2, cldn‐1 and TJP‐10); and markers of NFκB signaling (p65, IKK‐ β and IκBα) by qPCR using specific primers and SYBR green.ResultsHFA mice had an increased body weight, reduced lean body mass, and increased body fat compared to CON mice. Blueberry supplementation did not alter these metabolic parameters in HFA+BB vs HFA mice. mRNA expression of inflammatory markers (IL‐1β, iNOS, MCP‐1); gut barrier marker MUC‐2; and markers of NFκB signaling (p65 and IκBα) were increased in HFA vs CON mice. However, blueberry supplementation improved inflammation and permeability of the colon as shown by a reduced colonic expression of IL‐1β, iNOS, MCP‐1 and MUC‐2 in HFA+BB vs HFA mice. Further, a reduced mRNA expression of p65 and IκBα in HFA+BB vs HFA mice indicates that the protective effect of blueberry on the colon could be mediated through NFκB signaling.ConclusionBlueberry supplementation suppresses colon inflammation and ameliorates colon permeability possibly through NFκB Signaling. Consumption of blueberry is a potential dietary approach to improve gut health.

Front Cover: Isoliquiritigenin Attenuates Adipose Tissue Inflammation and Metabolic Syndrome by Modifying Gut Bacteria Composition in Mice

Mol. Nutr. Food Res. 2022, 66, 202101119 DOI: 10.1002/mnfr.202101119 Isoliquiritigenin (ILG), a flavonoid with a chalcone structure derived from Glycyrrhiza uralensis, beneficially modified gut microbiota by increasing the abundance of Akkermansia muciniphila and Parabacteroides goldsteinii. The altered composition of the gut bacteria by ILG restored impaired gut barrier function and prevented metabolic disorder in high fat diet-fed mice. This is reported by Riko Ishibashi and co-workers in article number 2101119.

Cigarette smoke promotes colorectal cancer through modulation of gut microbiota and related metabolites

ObjectiveCigarette smoking is a major risk factor for colorectal cancer (CRC). We aimed to investigate whether cigarette smoke promotes CRC by altering the gut microbiota and related metabolites.DesignAzoxymethane-treated C57BL/6 mice...

Squalene epoxidase drives cancer cell proliferation and promotes gut dysbiosis to accelerate colorectal carcinogenesis

ObjectiveAberrant lipid metabolism is a hallmark of colorectal cancer (CRC). Squalene epoxidase (SQLE), a rate-limiting enzyme in cholesterol biosynthesis, is upregulated in CRC. Here, we aim to determine oncogenic function...

Gut Microbial Dysbiosis Associated with Type 2 Diabetes Aggravates Acute Ischemic Stroke.

ABSTRACTType 2 diabetes (T2D) is an independent risk factor for acute ischemic stroke (AIS), but the underlying mechanisms remain elusive. Because the gut microbiota plays a causal role in both T2D and AIS, we wondered whether gut dysbiosis in T2D aggravates stroke progression. We recruited 35 T2D, 90 AIS, 60 AIS with T2D (AIS_T2D) patients, and 55 healthy controls and found that AIS and T2D had an additive effect on AIS_T2D patient gut dysbiosis by exhibiting the largest difference from the heathy controls. In addition, we found that the degree of gut dysbiosis associated with T2D was positively correlated with the National Institutes of Health Stroke Scale (NIHSS), modified Rankin score (mRS), and Essen stroke risk score in patients with AIS, including AIS and AIS_T2D patients. Compared with mice colonized with gut microbiota from healthy controls poststroke modeling, germfree (GF) mice colonized with gut microbiota from T2D patients showed exacerbated cerebral injury and impaired gut barrier function. Specifically, exacerbated brain injury and gut barrier dysfunction in T2D-treated GF mice were significantly associated with a reduction in short-chain fatty acid (SCFA)-producing bacteria. Our study showed that T2D and AIS have an additive effect on AIS_T2D patient gut microbiota dysbiosis. T2D-associated gut microbiota dysbiosis is associated with stroke severity in AIS patients and aggravates stroke progression in mice.IMPORTANCE We demonstrated an additive effect of type 2 diabetes (T2D) and acute ischemic stroke (AIS) on AIS with T2D (AIS_T2D) patient gut microbiota dysbiosis, and gut dysbiosis associated with T2D was positively correlated with stroke severity in AIS patients. Through animal experiments, we found that cerebral injury was exacerbated by fecal microbiota transplantation from T2D patients compared with that from healthy controls, which was associated with a reduction in short-chain fatty acid (SCFA)-producing bacteria. This study provided a novel view that links T2D and AIS through gut microbial dysbiosis.

Metabolic endotoxemia is dictated by the type of lipopolysaccharide.

Lipopolysaccharides (LPSs) can promote metabolic endotoxemia, which is considered inflammatory and metabolically detrimental based on Toll-like receptor (TLR)4 agonists, such as Escherichia coli-derived LPS. LPSs from certain bacteria antagonize TLR4 yet contribute to endotoxemia measured by endotoxin units (EUs). We found that E.coli LPS impairs gut barrier function and worsens glycemic control in mice, but equal doses of LPSs from other bacteria do not. Matching the LPS dose from R.sphaeroides and E.coli by EUs reveals that only E.coli LPS promotes dysglycemia and adipose inflammation, delays intestinal glucose absorption, and augments insulin and glucagon-like peptide (GLP)-1 secretion. Metabolically beneficial endotoxemia promoted by R.sphaeroides LPS counteracts dysglycemia caused by an equal dose of E.coli LPS and improves glucose control in obese mice. The concept of metabolic endotoxemia should be expanded beyond LPS load to include LPS characteristics, such as lipid A acylation, which dictates the effect of metabolic endotoxemia.

High-Fat Diet Promotes Colorectal Tumorigenesis Through Modulating Gut Microbiota and Metabolites

Dietary fat intake is associated with increased risk of colorectal cancer (CRC). We examined the role of high-fat diet (HFD) in driving CRC through modulating gut microbiota and metabolites. HFD or control diet was fed to mice littermates in CRC mouse models of an azoxymethane (AOM) model and Apcmin/+ model, with or without antibiotics cocktail treatment. Germ-free mice for fecal microbiota transplantation were used for validation. Gut microbiota and metabolites were detected using metagenomic sequencing and high-performance liquid chromatography-mass spectrometry, respectively. Gut barrier function was determined using lipopolysaccharides level and transmission electron microscopy. HFD promoted colorectal tumorigenesis in both AOM-treated mice and Apcmin/+ mice compared with control diet-fed mice. Gut microbiota depletion using antibiotics attenuated colon tumor formation in HFD-fed mice. A significant shift of gut microbiota composition with increased pathogenic bacteria Alistipessp.Marseille-P5997 and Alistipessp.5CPEGH6, and depleted probiotic Parabacteroides distasonis, along with impaired gut barrier function was exhibited in HFD-fed mice. Moreover, HFD-modulated gut microbiota promotes colorectal tumorigenesis in AOM-treated germ-free mice, indicating gut microbiota was essential in HFD-associated colorectal tumorigenesis. Gut metabolites alteration, including elevated lysophosphatidic acid, which was confirmed to promote CRC cell proliferation and impair cell junction, was also observed in HFD-fed mice. Moreover, transfer of stools from HFD-fed mice to germ-free mice without interference increased colonic cell proliferation, impaired gut barrier function, and induced oncogenic genes expression. HFD drives colorectal tumorigenesis through inducing gut microbial dysbiosis, metabolomic dysregulation with elevated lysophosphatidic acid, and gut barrier dysfunction in mice.

Therapeutic Applications of Resveratrol in Hepatic Encephalopathy through Its Regulation of the Microbiota, Brain Edema, and Inflammation.

Hepatic encephalopathy is a common complication in patients with liver cirrhosis and portosystemic shunting. Patients with hepatic encephalopathy present a variety of clinical features, including neuropsychiatric manifestations, cognitive dysfunction, impaired gut barrier function, hyperammonemia, and chronic neuroinflammation. These pathogeneses have been linked to various factors, including ammonia-induced oxidative stress, neuronal cell death, alterations in the gut microbiome, astrocyte swelling, and blood-brain barrier disruptions. Many researchers have focused on identifying novel therapeutics and prebiotics in the hope of improving the treatment of these conditions. Resveratrol is a natural polyphenic compound and is known to exert several pharmacological effects, including antioxidant, anti-inflammatory, and neuroprotective activities. Recent studies suggest that resveratrol contributes to improving the neuropathogenic effects of liver failure. Here, we review the current evidence describing resveratrol’s effects in neuropathogenesis and its impact on the gut-liver axis relating to hepatic encephalopathy. We highlight the hypothesis that resveratrol exerts diverse effects in hepatic encephalopathy and suggest that these effects are likely mediated by changes to the gut microbiota, brain edema, and neuroinflammation.

Salmonella-induced changes of the rat intestinal microbiota

The gut microbiome profoundly affects the body functioning: it participates in host protection against pathogenic microorganisms, metabolic events, inhibition of inflammatory responses, formation of innate and adaptive immune response in the intestinal mucosa. One of the causes altering microbiota community is due to antibiotics. Therefore, the processes of antibiotics interaction together with Salmonella enteritidis and Salmonella typhimurium with representatives of normal intestinal microflora are of particular interest. Materials and methods. The quantitative and qualitative analysis of the wall microbiota composition in rats was evaluated by bacteriological method, the statistical data analysis was performed using the software StatSoft Statistica v.12. Results and discussion. Inoculation of vancomycin and S. enteritidis, S. typhimurium in groups II, III, IV resulted in quantitatively decreased E. coli level by 10-, 7- and 110-fold, respectively (p ≤ 0.05). The count of P. aeruginosa decreased markedly only in the group III (p ≤ 0.05). The count of Bacteroides spp. members was profoundly decreased by several thousand times (group II) as well as 70- and 87-fold (groups III and IV), respectively (p ≤ 0.05). The count of E. faecalis and E. faecium decreased by 861-, 6- and several thousand times (groups II, III, IV), respectively (p ≤ 0.05). The count of Proteus spp. markedly decreased in group II by 27-fold and rapidly increased in group IV (p ≤ 0.05). Group III revealed a sharp decline in level of Enterobacter spp. and Klebsiella spp. by 847- and 150-fold, whereas in group II they were increased by 7- and 46-fold, respectively (p ≤ 0.05). The count of Staphylococcus spp. decreased by 10-fold only in group II. The level of Clostridium spp. decreased by several thousand times (group II) and by 5,500 times (group IV) (p ≤ 0.05). The count of Lactobacillus spp. decreased by several thousand times (group II). The count of Bifidobacterium spp. members significantly decreased by 10.9-fold and by several thousand times (groups III, IV). The level of Peptostreptococcus anaerobius profoundly decreased in all three study groups (p ≤ 0.05). The level of Salmonella spp. increased in group II by 49 times, but markedly increased in groups III and IV (p ≤ 0.05). Inoculation of Salmonella after vancomycin pretreatment caused dramatic change in the microbiota composition in groups V and VI, namely: increased count of E. coli by 65- and 105-fold, markedly increased level of P. aeruginosa in group V and VI — by 3-fold. In addition, these groups also showed decreased level of Bacteroides spp. by 9- and 10-fold (p ≤ 0.05). The count of E. faecalis and E. faecium decreased dramatically only in group V (p ≤ 0.05). The count of Proteus spp. decreased by 17 times in group V as well as in group VI (p ≤ 0.05). A sharp increase in level of Enterobacter spp. and Klebsiella spp. members was observed in groups V and VI (p ≤ 0.05). However, representatives of Peptostreptococcus anaerobius in groups V and VI decreased by 20 and 9 times, respectively (p ≤ 0.05). The count of Salmonella spp. decreased only in group V by 7 times (p ≤ 0,05). Inoculating experimental animals with B. fragilis conditioned with S. enteritidis, S. typhimurium and pretreated with vancomycin resulted in markedly decreased level of E. coli in group VII and VIII by 538 times (p ≤ 0.05). The count of P. aeruginosa in groups VII and VIII decreased profoundly, whereas level of Bacteroides spp. members was reciprocally increased (p ≤ 0.05). The level of Lactobacillus spp. decreased by 10.3 times only in group VI. The count of E. faecalis and E. faecium increased by 10 and 19 times in groups VII and VIII, respectively, whereas level of Proteus spp. decreased only in group VII by 322 times (p ≤ 0.05). In addition, a sharp decrease in level of Enterobacter spp. and Klebsiella spp. members (p ≤ 0.05) was found in groups VII and VIII. The count of Peptostreptococcus anaerobius and Lactobacillus spp. members was markedly increased by 7-, 12-, several thousand-fold and 40 times (groups VII and VIII, respectively) (p ≤ 0.05). The count of S. enteritidis and S. typhimurium in groups VII and VIII decreased rapidly (p ≤ 0.05). Conclusion. Inoculation of B. fragilis can be used in treatment of inflammatory bowel diseases or disorders with impaired gut barrier function.

LRRC19 Promotes Permeability of the Gut Epithelial Barrier Through Degrading PKC-ζ and PKCι/λ to Reduce Expression of ZO1, ZO3, and Occludin.

A dysfunctional gut epithelial barrier allows the augmented permeation of endotoxins, luminal antigens, and bacteria into the bloodstream, causing disease. The maintenance of gut epithelial barrier integrity may be regulated by multiple factors. Herein we analyze the role of leucine-rich repeat-containing protein 19 (LRRC19) in regulating the permeability of the gut epithelial barrier. We utilized Lrrc19 knockout (KO) mice and clinical samples through transmission electron, intestinal permeability assay, Western blot, and immunofluorescence staining to characterize the role of LRRC19 in the permeability of the gut epithelial barrier. We found that LRRC19, which is expressed in gut epithelial cells, impairs gut barrier function. Transmission electron micrographs revealed a tighter junction and narrower gaps in the colon epithelium cells in LRRC19 KO mice. There were lower levels of serum lipopolysaccharide and 4 kDa-fluorescein isothiocyanate-dextran after gavage in LRRC19 KO mice than in wild-type mice. We found that LRRC19 could reduce the expression of zonula occludens (ZO)-1, ZO-3, and occludin in the colonic epithelial cells. The decreased expression of ZO-1, ZO-3, and occludin was dependent on degrading protein kinase C (PKC) ζ and PKCι/λ through K48 ubiquitination by LRRC19. The expression of LRRC19 was also negatively correlated with ZO-1, ZO-3, occludin, PKCζ, and PKCι/λ in human colorectal cancers. The protein LRRC19 can promote the permeability of the gut epithelial barrier through degrading PKC ζ and PKCι/λ to reduce the expression of ZO-1, ZO-3, and occludin.

Punicalagin Prevents Hepatic Steatosis through Improving Lipid Homeostasis and Inflammation in Liver and Adipose Tissue and Modulating Gut Microbiota in Western Diet-Fed Mice.

Punicalagin (PU)-rich pomegranate peel extract has been shown before to exert protective effects against high fat-induced hepatic damage. The aim of this study is to explore whether and how PU antagonizes hepatic steatosis in Western diet-fed (WD) mice. Mice are fed either chow diet, WD (containing 42% fat, 15% protein, and 43% carbohydrates), or WD supplemented with PU (50mg kg-1 body weight/day) for 13 weeks. Weight gain, hepatic fat content, and inflammation in the liver and adipose tissues are measured. Compared to the WD group, PU-treated mice have lower fat content, decreased levels of alanine transaminase, and inflammation in liver. PU also changed the transcriptional expression of important genes in fatty acid oxidation pathway and alleviated glucose intolerance. Furthermore, PU improved adiponectin signaling and lipid metabolism in visceral adipose tissue. Moreover, PU improved gut microbiota dysbiosis induced by WD and enhanced gut barrier function. The findings suggest that PU improves hepatic steatosis induced by WD, in part through regulating lipid homeostasis and inflammation in liver and adipose tissue and restoring microbiota shift and impaired gut barrier function. Thus, PU can be potentially developed as a potential prevention strategy in combating nonalcoholic fatty liver disease.

Constant Light Exposure Alters Gut Microbiota and Promotes the Progression of Steatohepatitis in High Fat Diet Rats

BackgroundNon-alcoholic fatty liver disease (NAFLD) poses a significant health concern worldwide. With the progression of urbanization, light pollution may be a previously unrecognized risk factor for NAFLD/NASH development. However, the role of light pollution on NAFLD is insufficiently understood, and the underlying mechanism remains unclear. Interestingly, recent studies indicate the gut microbiota affects NAFLD/NASH development. Therefore, the present study explored effects of constant light exposure on NAFLD and its related microbiotic mechanisms.Materials and MethodsTwenty-eight SD male rats were divided into four groups (n = 7 each): rats fed a normal chow diet, and exposed to standard light-dark cycle (ND-LD); rats fed a normal chow diet, and exposed to constant light (ND-LL); rats fed a high fat diet, and exposed to standard light-dark cycle (HFD-LD); and rats on a high fat diet, and exposed to constant light (HFD-LL). Body weight, hepatic pathophysiology, gut microbiota, and short/medium chain fatty acids in colon contents, serum lipopolysaccharide (LPS), and liver LPS-binding protein (LBP) mRNA expression were documented post intervention and compared among groups.ResultIn normal chow fed groups, rats exposed to constant light displayed glucose abnormalities and dyslipidemia. In HFD-fed rats, constant light exposure exacerbated glucose abnormalities, insulin resistance, inflammation, and liver steatohepatitis. Constant light exposure altered composition of gut microbiota in both normal chow and HFD fed rats. Compared with HFD-LD group, HFD-LL rats displayed less Butyricicoccus, Clostridium, and Turicibacter, butyrate levels in colon contents, decreased colon expression of occludin-1 and zonula occluden−1 (ZO-1), and increased serum LPS and liver LBP mRNA expression.ConclusionConstant light exposure impacts gut microbiota and its metabolic products, impairs gut barrier function and gut-liver axis, promotes NAFLD/NASH progression in HFD rats.

Elevated trefoil factor 3 plasma levels in critically ill patients with abdominal sepsis or non-infectious abdominal illness

Trefoil factor 3 (TFF3) is a small peptide secreted mainly by goblet cells in the gut, where it plays a key role in gastrointestinal defence and repair. Plasma TFF3 has been reported as a biomarker of intestinal injury and as such it has been evaluated as a marker of disease activity in colitis. Impaired gut barrier function has been postulated as the “motor” of critical illness. We here sought to determine the temporal dynamics of plasma TFF3 in adult patients admitted to intensive care unit with abdominal sepsis or after major abdominal surgery for a non-infectious condition (post-op GI patients). TFF3 was measured in plasma obtained from 143 patients with abdominal sepsis and 98 post-op GI patients on admission to the intensive care (day 0) and at days 2 and 4 thereafter. Abdominal sepsis patients showed sustained elevated plasma TFF3 levels from day 0 to 4 relative to healthy control values, while in post-op GI patients admission TFF3 levels were not increased, only rising at day 2 and 4. In both patient groups, the presence of shock was associated with higher TFF3 levels. Moreover, patients with 3 or more organs failing had higher plasma TFF3 concentrations. While plasma TFF3 was higher in sepsis patients who did not survive until day 30, TFF3 levels were not independently associated with 30-day mortality in a Cox regression analysis. These results could support the theory that intestinal injury contributes to the pathogenesis of critical illness. Future studies are needed to elucidate whether the proposed gut dysfunction precedes or supersedes organ dysfunction in time.

1936-P: The Role of Adipose Tissue in Intestinal Functions

Introduction: Adipokines regulate whole-body energy homeostasis, insulin sensitivity and immunity by mediating the crosstalk between adipose tissues and multiple tissues, including liver, skeletal muscle, brain, pancreas and intestines. Recent studies revealed that intestines also exhibit insulin resistance and dysregulated immune homeostasis in obese condition. On the other hand, several adipokines including adiponectin and adipocyte fatty acid binding protein have been shown to regulate intestinal function. Here, we aim to investigate the relationship between the adipose tissue and gut homeostasis using lipodystrophy animal models. Methods: We employed our recently developed lipodystrophic mouse model, in which adipocyte MDM2 is genetically deleted (so-called Adipo-MDM2-KO mice). In fat transplantation experiment, subcutaneous fat form their wild type (WT) littermates was transplanted to the Adipo-MDM2-KO mice for 8 weeks. To assess gut permeability, Adipo-MDM2-KO mice and their wild type (WT) littermates were orally gavaged with DX-4000-FITC for 1 hour. Circulating LPS level were measured using the endotoxin assays, which reflects gut permeability and endotoxemia. For assessment of gut morphology, ileum isolated from Adipo-MDM2-KO mice and their WT littermates were subjected to Haemotoxylin and Eosin (H and E) staining. Results and Conclusion: Adipo-MDM2-KO mice exhibited impaired gut barrier function and altered gut microbiota composition when compared with the WT littermates. A higher level of DX-4000-FITC in the serum of Adipo-MDM2-KO mice were detected. In addition, circulating level of LPS was significantly increased in Adipo-MDM2-KO mice. H and E staining showed a change in gut morphology and an increased number of inflammatory cells in the ileum of Adipo-MDM2-KO mice. These results demonstrated that fat loss leads to intestinal dysfunction, therefore, the adipose tissue is required for gut homeostasis. Disclosure K. Long: None. Funding National Natural Science Foundation of China (91857119)

Serum Citrulline As a Biomarker for Blood Stream Infections in Pediatric Hematopoietic Stem Cell Transplant Patients

Background: Invasive microbial infections remain a major cause of morbidity and mortality in hematopoietic stem cell transplant (HSCT) patients. Microbes residing in the GI tract are believed to be the source of mucosal barrier injury-associated blood stream infections (mBSI) in HSCT and cancer patients. Three host factors are critical for preventing microbial translocation from the gut: neutrophils, intact gut barrier function, and gut microbiota homeostasis. Currently there are no reliable biomarkers that can identify patients who will develop mBSIs. Objectives/Hypothesis: Since all HSCT patients develop severe neutropenia (ANC<100), we hypothesized that HSCT patients who develop mBSI will have more impaired gut barrier function and a greater imbalance in gut microbiota populations (as evidenced by depletion of beneficial obligate anaerobe commensals) compared to counterparts who do not develop mBSI. Methods: We designed a prospective, non-randomized, case control pilot study for HSCT patients < 20 years of age. Serum citrulline, which has been used as a surrogate to measure overall gut function, was obtained 1-2 times weekly. Bacterial genomic DNA was isolated from stool samples collected every 7 days. Amplicons (16S rRNA V4 variable region) were generated and sequenced using the Illumina MiSeq platform. Microbial taxonomic assignments were determined using QIIME software and further characterized into relative abundances of obligate (beneficial commensal) versus facultative (pathogenic) anaerobes. Clinical characteristics were recorded. Results: Of the 78 HSCT patients enrolled on the study, 27% (21 patients) developed BSI. Of the patients with confirmed blood stream infections, 16 patients were categorized as mBSI, and ultimately 11 patients were included in our analysis. 48 patients did not develop a BSI and had evaluable citrulline levels and constituted our control group. Patients with mBSI had a more significant decline in citrulline levels during the period from the start of conditioning to the development of mBSIs (linear mixed effect model, p = 0.048, likelihood ratio test) compared to counterparts without mBSI. We found no significant association between levels of facultative (pathogenic) anaerobes and the development of mBSI in this cohort. Conclusions: Decreased citrulline levels, which suggest impaired gut epithelial function, are associated with the development of severe, invasive bacterial infections. These data suggest that measuring citrulline may have utility as a biomarker for predicting mBSI in HSCT patients. Disclosures Koh: Merck: Consultancy.

Food Allergies and Ageing.

All over the world, there is an increase in the overall survival of the population and the number of elderly people. The incidence of allergic reactions is also rising worldwide. Until recently, allergies, and in particular food allergies (FAs), was regarded as a pediatric problem, since some of them start in early childhood and may spontaneously disappear in adulthood. It is being discovered that, on the contrary, these problems are increasingly affecting even the elderly. Along with other diseases that are considered characteristics of advanced age, such as cardiovascular, dysmetabolic, autoimmune, neurodegenerative, and oncological diseases, even FAs are increasingly frequent in the elderly. An FA is a pleiomorphic and multifactorial disease, characterized by an abnormal immune response and an impaired gut barrier function. The elderly exhibit distinct FA phenotypes, and diagnosis is difficult due to frequent co-morbidities and uncertainty in the interpretation of in vitro and in vivo tests. Several factors render the elderly susceptible to FAs, including the physiological changes of aging, a decline in gut barrier function, the skewing of adaptive immunity to a Th2 response, dysregulation of innate immune cells, and age-related changes of gut microbiota. Aging is accompanied by a progressive remodeling of immune system functions, leading to an increased pro-inflammatory status where type 1 cytokines are quantitatively dominant. However, serum Immunoglobulin E (IgE) levels and T helper type 2 (Th2 cytokine production have also been found to be increased in the elderly, suggesting that the type 2 cytokine pattern is not necessarily defective in older age. Dysfunctional dendritic cells in the gut, defects in secretory IgA, and decreased T regulatory function in the elderly also play important roles in FA development. We address herein the main immunologic aspects of aging according to the presence of FAs.

Exploiting the Zonulin Mouse Model to Establish the Role of Primary Impaired Gut Barrier Function on Microbiota Composition and Immune Profiles.

The balanced interplay between epithelial barrier, immune system, and microbiota maintains gut homeostasis, while disruption of this interplay may lead to inflammation. Paracellular permeability is governed by intercellular tight-junctions (TJs). Zonulin is, to date, the only known physiological regulator of intestinal TJs. We used a zonulin transgenic mouse (Ztm) model characterized by increased small intestinal permeability to elucidate the role of a primary impaired gut barrier on microbiome composition and/or immune profile. Ztm exhibit an altered gene expression profile of TJs in the gut compared to wild-type mice (WT): Claudin-15, Claudin-5, Jam-3, and Myosin-1C are decreased in the male duodenum whereas Claudin-15, Claudin-7, and ZO-2 are reduced in the female colon. These results are compatible with loss of gut barrier function and are paralleled by an altered microbiota composition with reduced abundance of the genus Akkermansia, known to have positive effects on gut barrier integrity and strengthening, and an increased abundance of the Rikenella genus, associated to low-grade inflammatory conditions. Immune profile analysis shows a subtly skewed distribution of immune cell subsets toward a pro-inflammatory phenotype with more IL-17 producing adaptive and innate-like T cells in Ztm. Interestingly, microbiota “normalization” involving the transfer of WT microbiota into Ztm, did not rescue the altered immune profile. Our data suggest that a primary impaired gut barrier causing an uncontrolled trafficking of microbial products leads to a latent pro-inflammatory status, with a skewed microbiota composition and immune profile that, in the presence of an environmental trigger, as we have previously described (1), might promote the onset of overt inflammation and an increased risk of chronic disease.