Intestinal Hypoxia Research Articles

Hypoxia protects the gut.

Antibiotic-induced loss of intestinal hypoxia boosts the growth of C. albicans in mice.

Elimination of Intestinal Hypoxia in Complex Treatment of Intestinal Failure (Case Report)

INTRODUCTION: Currently, various approaches to the treatment of intestinal failure (IF) are considered. In search for pathogenetically justified therapy, it is possible to use oxygenated saline enteral solution (OSES). АIM: To demonstrate, by gas analysis of the introduced oxygenated saline enteral solution and the excreted intestinal fluid, the possibility of gas exchange in the intestine with increased oxygen extraction under hypoxic conditions. An 8-year-old child with burdened premorbid history and severe community–acquired bilateral pleuropneumonia kept on mechanical ventilation, had signs of IF (disorder in passage, absence of independent defecation for more than two days). During treatment and observation of the child, enteral feeding was attempted with pharmacological stimulation with prokinetics, and introduction of laxative sorbent with prebiotic effect (lactulose). Because of non-effectiveness of these measures, it was decided to perform intestinal lavage with OSES introduced through the nasogastral tube. In 30 minites after start of OSES introduction, the gastrointestinal tract motility notably enhanced, in 1.5 hour from the beginning of the procedure, fractional passage of a significant amount of thick fecal masses was noted, after which intestinate — liquid stool stained yellow with bile, was obtained. During the procedure, a comparative analysis of the gas composition of the introduced OSES and excreted intestinate was done. In the excreted solution, 97-fold decrease of рО2 from 659 to 6.8 mm Hg, and 3.6-fold increase in CO2 tension from 23 to 85.7 mm Hg, were noted. CONCLUSION: Oxygenation of the enteral environment by barbotage of a saline enteral solution introduced through a tube is an effective component of intensive therapy for intestinal failure syndrome, taking into account the ability of the gastrointestinal tract tissues to actively participate in gas exchange: extract oxygen and release carbon dioxide.

Effects and mechanisms of Gegen Qinlian Decoction in inhibiting M1 polarization of macrophages under inflammatory hypoxia microenvironment

To explore the effect and mechanism of Gegen Qinlian Decoction(GQD) in inhibiting M1 polarization of macrophages under inflammatory hypoxia by simulating intestinal hypoxia microenvironment in vitro. A tri-gas incubator was used to simulate normal physiological hypoxia of the colon and inflammatory hypoxia microenvironments of ulcerative colitis(UC). RAW264.7 macrophages were divided into 18.5% O_(2 )(normoxia group), 4% O_2(physiological hypoxia group), and 1% O_2(inflammatory hypoxia group), and they were induced by lipopolysaccharide(LPS) for 24 h. M1 polarization was detected by flow cytometry. Under the condition of 1% inflammatory hypoxia, they were divided into blank group, model group, and GQD-containing serum low, medium, and high dose groups. Flow cytometry was used to detect M1 polarization marker CD86, and ELISA was used to detect the expression of tumor necrosis factor-α(TNF-α) and interleukin-1β(IL-1β) in cell supernatant. The mRNA expression of hypoxia-inducible factor-1α(HIF-1α), TNF-α, and IL-1β was detected by qRT-PCR. Western blot was used to detect the expression of HIF-1α/nuclear transcription factor-κB(NF-κB) signaling pathway-related proteins. The nuclear translocation of NF-κB p65 was detected by immunofluorescence. The results showed that the positive rate of CD86 in the 1% O_2 group was the highest. Under the condition of 1% inflammatory hypoxia, compared with the blank group, the expression of CD86, TNF-α, IL-1β, and HIF-1α in the model group increased. Compared with the model group, each group of GQD could reduce the expression of CD86, TNF-α, IL-1β, and HIF-1α. Compared with the blank group, the protein expression of HIF-1α, NF-κB p65, p-IKKα/β, and p-IκBα in the model group increased. Compared with the model group, the protein expression of HIF-1α, NF-κB p65, p-IKKα/β, and p-IκBα in GQD groups was significantly decreased. Compared with the blank group, NF-κB p65 in the model group entered the nucleus significantly. Compared with the model group, the nuclear expression of NF-κB p65 was decreased in each GQD group. Studies have shown that GQD may protect the intestine by down-regulating the HIF-1α/NF-κB signaling pathway to inhibit M1 polarization of macrophages and secretion of related inflammatory factors under 1% inflammatory hypoxia.

Intersection of the microbiome and immune metabolism in lupus.

Systemic lupus erythematosus is a complex autoimmune disease resulting from a dysregulation of the immune system that involves gut dysbiosis and an altered host cellular metabolism. This review highlights novel insights and expands on the interactions between the gut microbiome and the host immune metabolism in lupus. Pathobionts, invasive pathogens, and even commensal microbes, when in dysbiosis, can all trigger and modulate immune responses through metabolic reprogramming. Changes in the microbiota's global composition or individual taxa may trigger a cascade of metabolic changes in immune cells that may, in turn, reprogram their functions. Factors contributing to dysbiosis include changes in intestinal hypoxia, competition for glucose, and limited availability of essential nutrients, such as tryptophan and metal ions, all of which can be driven by host metabolism changes. Conversely, the accumulation of some host metabolites, such as itaconate, succinate, and free fatty acids, could further influence the microbial composition and immune responses. Overall, mounting evidence supports a bidirectional relationship between host immunometabolism and the microbiota in lupus pathogenesis.

Heat shock protein 90 and prolyl hydroxylase 2 co-regulate hypoxia-inducible factor-1α expression in porcine small intestinal epithelial cells under heat stress

Heat stress (HS) poses a substantial threat to animal growth and development, resulting in declining performance and economic losses. The intestinal system is susceptible to HS and undergoes intestinal hyperthermia and pathological hypoxia. Hypoxia-inducible factor-1α (HIF-1α), a key player in cellular hypoxic adaptation, is influenced by prolyl-4-hydroxylase 2 (PHD2) and heat shock protein 90 (HSP90). However, the comprehensive regulation of HIF-1α in the HS intestine remains unclear. This study aims to explore the impact of HS on pig intestinal mucosa and the regulatory mechanism of HIF-1α. Twenty-four Congjiang Xiang pigs were divided into the control and five HS-treated groups (6, 12, 24, 48, and 72 h). Ambient temperature and humidity were maintained in a thermally-neutral state (temperature–humidity index (THI) < 74) in the control group, whereas the HS group experienced moderate HS (78 < THI <84). Histological examination revealed villus exfoliation after 12 h of HS in the duodenum, jejunum, and ileum, with increasing damage as HS duration extended. The villus height to crypt depth ratio (V/C) decreased and goblet cell number increased with prolonged HS. Quantitative real-time PCR, Western blot, and immunohistochemistry analysis indicated increased expression of HIF-1α and HSP90 in the small intestine with prolonged HS, whereas PHD2 expression decreased. Further investigation in IPEC-J2 cells subjected to HS revealed that overexpressing PHD2 increased PHD2 mRNA and protein expression, while it decreases HIF-1α. Conversely, interfering with HSP90 expression substantially decreased both HSP90 and HIF-1α mRNA and protein levels. These results suggest that HS induces intestinal hypoxia with concomitant small intestinal mucosal damage. The expression of HIF-1α in HS-treated intestinal epithelial cells may be co-regulated by HSP90 and PHD2 and is possibly linked to intestinal hyperthermia and hypoxia.

Hypoxia-inducible factor 1α inhibits heat stress-induced pig intestinal epithelial cell apoptosis through eif2α/ATF4/CHOP signaling

Unstoppable global warming and increased frequency of extreme heat leads to human and animals easier to suffer from heat stress (HS), with gastrointestinal abnormalities as one of the initial clinical symptoms. HS induces intestinal mucosal damage owing to intestinal hypoxia and hyperthermia. Hypoxia-inducible factor 1α (HIF-1α) activates numerous genes to mediate cell hypoxic responses; however, its role in HS-treated intestinal mucosa is unknown. This work aimed to explore HIF-1α function and regulatory mechanisms in HS-treated pig intestines. We assigned 10 pigs to control and moderate HS groups. Physical signs, stress, and antioxidant levels were detected, and the intestines were harvested after 72 h of HS treatment to study histological changes and HIF-1α, heat shock protein 90 (HSP90), and prolyl-4-hydroxylase 2 (PHD-2) expression. In addition, porcine intestinal columnar epithelial cells (IPEC-J2) underwent HS treatment (42 °C, 5 % O2) to further explore the functions and regulatory mechanism of HIF-1α. The results of histological examination revealed HS caused intestinal villi damage and increased apoptotic epithelial cell; the expression of HIF-1α and HSP90 increased while PHD-2 showed and opposite trend. Transcriptome sequencing analysis revealed that HS activated HIF-1 signaling. To further explore the role of HIF-1α on HS induced IPEC-J2 apoptosis, the HIF-1α was interfered and overexpression respectively, and the result confirmed that HIF-1α could inhibited cell apoptosis under HS. Furthermore, HS-induced apoptosis depends on eukaryotic initiation factor 2 alpha (eif2α)/activating transcription factor 4 (ATF4)/CCAAT-enhancer-binding protein homologous protein (CHOP) pathway, and HIF-1α can inhibit this pathway to alleviate IPEC-J2 cell apoptosis. In conclusion, this study suggests that HS can promote intestinal epithelial cell apoptosis and cause pig intestinal mucosal barrier damage; the HIF-1α can alleviate cell apoptosis by inhibiting eif2α/ATF4/CHOP signaling. These results indicate that HIF-1α plays a protective role in HS, and offers a potential target for HS prevention and mitigation.

Acute gastrointestinal permeability after traumatic brain injury in mice precedes a bloom in Akkermansia muciniphila supported by intestinal hypoxia

Traumatic brain injury (TBI) increases gastrointestinal morbidity and associated mortality. Clinical and preclinical studies implicate gut dysbiosis as a consequence of TBI and an amplifier of brain damage. However, little is known about the association of gut dysbiosis with structural and functional changes of the gastrointestinal tract after an isolated TBI. To assess gastrointestinal dysfunction, mice received a controlled cortical impact or sham brain injury and intestinal permeability was assessed at 4 h, 8 h, 1 d, and 3 d after injury by oral administration of 4 kDa FITC Dextran prior to euthanasia. Quantification of serum fluorescence revealed an acute, short-lived increase in permeability 4 h after TBI. Despite transient intestinal dysfunction, no overt morphological changes were evident in the ileum or colon across timepoints from 4 h to 4 wks post-injury. To elucidate the timeline of microbiome changes after TBI, 16 s gene sequencing was performed on DNA extracted from fecal samples collected prior to and over the first month after TBI. Differential abundance analysis revealed that the phylum Verrucomicrobiota was increased at 1, 2, and 3 d after TBI. The Verrucomicrobiota species was identified by qPCR as Akkermansia muciniphila, an obligate anaerobe that resides in the intestinal mucus bilayer and produces short chain fatty acids (e.g. butyrate) utilized by intestinal epithelial cells. We postulated that TBI promotes intestinal changes favorable for the bloom of A. muciniphila. Consistent with this premise, the relative area of mucus-producing goblet cells in the medial colon was significantly increased at 1 d after injury, while colon hypoxia was significantly increased at 3 d. Our findings reveal acute gastrointestinal functional changes coupled with an increase of beneficial bacteria suggesting a potential compensatory response to systemic stress after TBI.

Outcome of stress on G protein-coupled receptors and hypoxia inducible factor-1α.

Stress drives neuroendocrine signals with detrimental effects to the intestinal homeostasis. The aim of this study was to evaluate the effect of stress on intestinal hypoxia response elements, including G protein-coupled receptor 41 (GPR41), GPR43, and hypoxia inducible factor (HIF)-1α. Groups of five BALB/c mice were subjected to acute (2 h per day) and chronic (2 h per day for 4 days) stress induced by restraint, and the results were compared to those of an unstressed control group. Whole mucosal samples from the colon were collected to evaluate the expression of GPR41, GPR43 and HIF-1α using Western blot chemiluminescent analysis. Compared to the control group, in the chronic stress group the expression of GPR43 (P = 0.0092) and HIF-1α (P < 0.0001) were significantly lower and the expression of GPR41 was similar (P = 0.9184); acute stress significantly increased HIF-1α expression (P = 0.0030) and increased GPR41 expression (P = 0.0937), without affecting GPR43 (P = 0.9184). These findings offer insights into the modulation of hypoxia response elements under stress conditions and their pharmacological implications for developing drugs that mitigate the effects of stress on intestinal homeostasis.

A compound of paraprobiotic and postbiotic derived from autochthonous microorganisms improved growth performance, epidermal mucus, liver and gut health and gut microbiota of common carp (Cyprinus carpio)

High-density intensive farming is the development trend of modern aquaculture, which is characterized by high density culture environment and feeding of high-fat diet. The use of high-fat diet can increase the weight gain rate of some fish species, but it affects the health of fish. In this study, we investigated the beneficial effects of a compound of paraprobiotic and postbiotic (CPP) derived from autochthonous microorganisms supplemented diet on growth performance, epidermal mucus, liver and gut health, and gut microbiota profile of common carp (Cyprinus carpio). Common carp were fed with diets supplemented with 0, 1, 2 or 3 g/kg of CPP in the control diet for 14 weeks, with four replications in each group and 20 fish in each repetition. The results showed that fish fed with diet supplemented with CPP significantly decreased the hepatosomatic index (p < 0.05), even though no significant effects were observed in the growth performance of the fish. In the CPP1.0 and CPP2.0 groups the level of complement 4 and superoxide dismutase (SOD) activity in the epidermal mucus were significantly increased compared to the control group (p < 0.05). No significant values were recorded among the treatment groups in the level of Lysozyme activity and total antioxidant capacity (T-AOC) (p > 0.05). For liver health, dietary CPP2.0 were significantly decreased the Triacylglycerol content in the liver, compared with the control (p < 0.05). Furthermore, fish groups fed with CPP1.0 and CPP2.0 showed significant decreased in the number of vacuoles representing lipid droplets and the liver damage scores (p < 0.05), compared with the control group. The CPP2.0 group significantly decreased serum alanine aminotransferase (Alt) and aspartate aminotransferase (Ast) levels, and significantly increased liver antioxidant (total antioxidant capacity, superoxide dismutase and catalase (CAT)) levels compared to the control group (p < 0.05). The level of liver malondialdehyde (MDA) was significantly reduced in the CPP groups compared to the control (p < 0.05). Dietary CPP supplementation were significantly down-regulated the relative expression of pro-inflammatory cytokines (nf-κb p65 and tnf-α) and up-regulated anti-inflammatory cytokines (il-1β, il-10 and tgf-β), compared to the control group (p < 0.05). Similarly, intestinal hypoxia inducible factor 1 subunit alpha (hif-1α) expression was significantly increased in the CPP1.0 and 2.0 groups, compared with then control (p < 0.05). Combined with intestinal HE staining and inflammatory gene expression, it was found that the intestinal inflammatory cytokines (nf-κb p65, il-1β, il-10 and tgf-β) in the CPP2.0 supplemented group were significantly higher than the control group (p < 0.05), and the intestinal villi were more orderly arranged. In the CPP3.0 group, the expression of nf-κb p65, il-1β, il-10 were significantly higher compared with the control (p < 0.05). Furthermore, remarkably lower intestinal injury scores were recorded in the CPP groups verses the control (p < 0.05). The gut microbiota diversity index data showed that lower diversity index values were observed in the CPP2.0 group compared with the control (p < 0.05). The relative abundances of Fusobacteria and Cetobacterium in the CPP2.0 and 3.0 groups were significantly higher than those in the control group (p < 0.05). In conclusion, dietary CPP supplementation could enhance non-specific immunity and antioxidant levels, reduce liver lipid deposition, alleviate liver and intestinal damage and inflammation, and improve gut microbiota abundance and diversity in common carp fed with high-fat diet. The best positive effect was observed in common carp fed with diet supplemented at a level of 2 g/kg of basal diet.

The mechanism of colon tissue damage mediated by HIF-1α/NF-κB/STAT1 in high-altitude environment.

The high-altitude environment damages the intestinal mucosal barrier, leading to a high incidence of intestinal diseases and seriously affects the working ability of people at high altitude. However, how high altitude induces intestinal mucosal barrier injury has not been well defined. The purpose of this study was to investigate the mechanism of colonic tissue injury induced by the influence of the high-altitude environment on the colonic microenvironment. Forty-eight SPF C57BL/6J mice were randomly divided into four groups: the control group and three other that were high-altitude exposure groups (Yushu, Qinghai; elevation: 4,010 m; 12 h, 24 h, 48 h). First, HE staining was used to observe the effect of the high-altitude environment on colon histomorphology of mice. The protein expression levels of claudin-1, occludin, and ZO-1 were analyzed by molecular biological methods. We found that altitude caused inflammatory damage to colon tissue. Intestinal hypoxia was measured with the hypoxic probe pimonidazole (PMDZ). Interestingly, we observed a decrease in the concentration of oxygen in the microenvironment in the colonic lumen. We sought to explore the mechanism of colonic mucosal barrier damage at different times when entering high altitude. The expression levels of hypoxia-inducible factors: HIF-1α, STAT1, and NF-κB and of inflammatory factors: IFN-γ, TNF-α, and IL-6 were significantly increased. This work highlights that the high-altitude environment leads to a reduction in the concentration of oxygen in the microenvironment of the colonic lumen, which disrupts the colonic mucosal barrier and ultimately induces and exacerbates intestinal injury.

Growth performance, hepatic enzymes, and gut health status of common carp (Cyprinus carpio) in response to dietary Cetobacterium somerae fermentation product

Intensive aquaculture practices compromise the health of fish. Probiotics especially those isolated from aquatic animals play important roles in improving fish health. The aim of the study was to evaluate the effects of stabilized fermentation product of Cetobacterium somerae (XMX-1) on the growth performance, gut and liver health of common carp. A total of 300 carps (initial weight of 2.32 ± 0.02 g) were divided into the control (fed a basal diet) and XMX-1 groups (fed a basal diet with 2 g/kg, 3 g/kg, 4 g/kg or 5 g/kg XMX-1 diet). After 8-week feeding, growth performance, serum lipopolysaccharide (LPS), diamine oxidase activity (DAO), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were evaluated. The intestinal total superoxide dismutase (SOD) activity, the expression of gut health related genes was tested. In addition, the liver triacylglycerol (TAG) and the expression of liver lipid metabolism related genes were conducted. Results showed that XMX-1 addition had no effect on the growth performance of carps at a supplementation level up to 5 g/kg (P > 0.05). However, dietary XMX-1 at addition levels ranging from 2 g/kg to 5 g/kg reduced serum LPS and DAO. Furthermore, all XMX-1 additions significantly increased total SOD activity compared with the control group (P < 0.05). In contrast, dietary 3 g/kg XMX-1 significantly increased the expression of intestinal hypoxia inducible factor 1 subunit alpha (HIF1α), Occludin, Hepcidin and zonula occludens (ZO)-1 (P < 0.05). Dietary 2 g/kg XMX-1 significantly increased the expression of intestinal Hepcidin and ZO-1 (P < 0.05). Moreover, dietary XMX-1 decreased the level of serum ALT (P ≤ 0.37) and liver TAG (P ≤ 0.07). Furthermore, we found that dietary XMX-1 significantly reduced the expression of genes related to lipid synthesis including sterol regulatory element-binding protein (SREBP1c) and peroxisome proliferator-activated receptor gamma (PPARγ) (P < 0.05). Meanwhile, dietary 3 g/kg XMX-1 significantly increased the expression of carnitine palmitoyltransferase 1 (CPT1) and peroxisome proliferator-activated receptor alpha (PPARα) compared with the control group (P < 0.05). Together, our findings suggest that XMX-1 additions of 3 g/kg had the best effect on fish health.

Vertical sleeve gastrectomy increases duodenal Lactobacillus spp. richness associated with the activation of intestinal HIF2α signaling and metabolic benefits

ObjectiveVertical Sleeve Gastrectomy (VSG) is one of the most efficacious treatments for obesity and its comorbidities. Although a range of evidence suggests that alterations of the microbiota in the distal gut following VSG are pivotal to these metabolic improvements, the effect of surgery to alter the microbiota of the proximal intestine and its effect on host physiology remain largely unknown. As the main bacteria in the upper small intestine, Lactobacillus subspecies have been appreciated as important regulators of gut function. These bacteria also regulate intestinal Hypoxia- Inducible Factor 2α (HIF2α) signaling that plays an integral role in gut physiology and iron absorption. In the present study, we sought to determine the impact of VSG on Lactobacillus spp. in the small intestine and potential downstream impacts of Lactobacillus spp. on HIF2α, specifically in the duodenum. MethodsTo determine the effects of VSG on the microbiota and HIF2α signaling in the duodenum, VSG surgeries were performed on diet-induced obese mice. To further probe the relationship between Lactobacillus spp. and HIF2α signaling in the duodenum, we applied a customized high-fat but iron-deficient diet on mice to increase duodenal HIF2α signaling and determined alterations of gut bacteria. To explore the causal role of Lactobacillus spp. in duodenal HIF2α signaling activation, we chronically administered probiotics containing Lactobacillus spp. to high-fat-fed obese mice. Lastly, we studied the effect of lactate, the major metabolite of Lactobacilli, on HIF2α in ex vivo duodenal organoids. ResultsThere were pronounced increases in the abundance of Lactobacillus spp. in samples isolated from duodenal epithelium in VSG-operated mice as compared to sham-operated mice. This was accompanied by an increase in the expression of genes that are targets of HIF2α in the duodenum of VSG-treated mice. Activating HIF2α signaling with a high-fat but iron-deficient diet resulted in weight loss, improvements in glucose regulation, and increased Lactobacillus spp. richness in the duodenum as compared to mice on an iron-replete diet. Chronic administration of probiotics containing Lactobacillus spp. not only increased HIF2α signaling in the duodenum such as occurs after VSG but also resulted in reduced weight gain and improved glucose tolerance in high-fat-fed mice. Furthermore, lactate was able to activate HIF2α in ex vivo duodenal organoids. ConclusionsThese results support a model whereby VSG increases duodenal Lactobacillus richness and potentially stimulates intestinal HIF2α signaling via increased lactate production.

The Low-density Lipoprotein Receptor-related Protein 6 Pathway in the Treatment of Intestinal Barrier Dysfunction Induced by Hypoxia and Intestinal Microbiota through the Wnt/β-catenin Pathway

Our study is to explore the key molecular of Low-density lipoprotein receptor-related protein 6 (LRP6) and the related Wnt/β-catenin pathway regulated by LRP6 during the intestinal barrier dysfunction. Colorectal protein profile analysis showed that LRP6 expression was decreased in dextran sulfate sodium (DSS)-induced colitis mice, and mice received fecal bacteria transplantation from stroke patients. Mice with intestinal hypoxia and intestinal epithelial cells cultured in hypoxia showed decreased expression of LRP6. Overexpression of LPR6 or its N-terminus rescued the Wnt/β-catenin signaling pathway which was inhibited by hypoxia and endoplasmic reticulum stress. In mice overexpressing of LRP6, the expression of β-catenin and DKK1 increased, Bcl2 decreased, and Bax increased. Mice with LRP6 knockout showed an opposite trend, and the expression of Claudin2, Occludin and ZO-1 decreased. Two drugs, curcumin and auranofin could alleviate intestinal barrier damage in DSS-induced colitis mice by targeting LRP-6. Therefore, gut microbiota dysbiosis and hypoxia can inhibit the LRP6 and Wnt/β-catenin pathway, and drugs targeting LRP6 can protect the intestinal barrier.

Некротизирующий энтероколит у новорожденных с врожденными пороками сердца: частота и факторы риска

Necrotizing enterocolitis (NEC) is a serious complication in newborns with critical congenital heart disease (CHD), prolonging hospital stay, worsening neurological prognosis, and increasing mortality. The leading role in the pathogenesis of NEC in these infants is the violation of mesenteric perfusion. A decrease in arterial blood oxygenation may be an additional risk factor for intestinal hypoxia. Objective. To assess the incidence and risk factors for NEC in full-term newborns with CHD born in 2019–2021 at the Perinatal Center of Almazov National Research Medical Center. Patients and methods. The article presents an analysis of the frequency and risk factors of NEC in children with CHD born at the Almazov National Medical Research Centre in 2019–2021. In the group of critical and duct-dependent CHD (n = 264), the overall incidence of NEC was 15.9% (42 cases). The frequency of surgical stages of NEC (IIIA) was 1.1% (3 cases). In the preoperative period, there was a trend towards a higher frequency of inotropic therapy in a subgroup of children who subsequently developed NEC. NEC in newborns with duct-dependent CHD developed mainly in the early postoperative period after cardiac surgery. In children with duct-dependent pulmonary blood flow, a higher incidence of NEC after surgery was noted compared to children with duct-dependent systemic blood flow. Conclusion. Risk factors for NEC in the postoperative period were arterial hypotension and hemodynamically significant cardiac arrhythmias. Dysbiosis of the gut microbiota and changes in microbial metabolism may be additional risk factors for NEC in children with CHD. Key words: necrotizing enterocolitis, risk factors, congenital heart disease, cardiopulmonary bypass, intestinal microbiome, metabolomics

HIF-Dependent NFATC1 Activation Upregulates ITGA5 and PLAUR in Intestinal Epithelium in Inflammatory Bowel Disease.

Intestinal epithelial cells exist in physiological hypoxia, leading to hypoxia-inducible factor (HIF) activation and supporting barrier function and cell metabolism of the intestinal epithelium. In contrast, pathological hypoxia is a common feature of some chronic disorders, including inflammatory bowel disease (IBD). This work was aimed at studying HIF-associated changes in the intestinal epithelium in IBD. In the first step, a list of genes responding to chemical activation of hypoxia was obtained in an in vitro intestinal cell model with RNA sequencing. Cobalt (II) chloride and oxyquinoline treatment of both undifferentiated and differentiated Caco-2 cells activate the HIF-signaling pathway according to gene set enrichment analysis. The core gene set responding to chemical hypoxia stimulation in the intestinal model included 115 upregulated and 69 downregulated genes. Of this set, protein product was detected for 32 genes, and fold changes in proteome and RNA sequencing significantly correlate. Analysis of publicly available RNA sequencing set of the intestinal epithelial cells of patients with IBD confirmed HIF-1 signaling pathway activation in sigmoid colon of patients with ulcerative colitis and terminal ileum of patients with Crohn’s disease. Of the core gene set from the gut hypoxia model, expression activation of ITGA5 and PLAUR genes encoding integrin α5 and urokinase-type plasminogen activator receptor (uPAR) was detected in IBD specimens. The interaction of these molecules can activate cell migration and regenerative processes in the epithelium. Transcription factor analysis with the previously developed miRGTF tool revealed the possible role of HIF1A and NFATC1 in the regulation of ITGA5 and PLAUR gene expression. Detected genes can serve as markers of IBD progression and intestinal hypoxia.

Splanchnic oxygen saturation during reoxygenation with 21% or 100% O2 in newborn piglets.

Increasing evidence recognizes the harm of excess oxygen to lungs, eyes, and brain of preterm infants, but not yet to the intestine. We assessed changes in splanchnic oxygenation during reoxygenation with 21% compared to 100% O2 in a newborn piglet model of perinatal asphyxia. We randomized 25 piglets to control or intervention. Intervention groups underwent global hypoxia until acidosis and hypotension occurred. Piglets were reoxygenated for 30 min with 21% or 100% O2 and observed for 9 h. We continuously measured regional splanchnic oxygen saturation (rsSO2) using near-infrared spectroscopy (NIRS). We calculated mean rsSO2 and rsCoVar (as SD/mean). We measured PaO2 and SaO2, sampled from the right carotid artery. Reoxygenation after global hypoxia restored rsSO2. Reoxygenation with 100% O2 increased rsSO2 to values significantly higher than baseline. In intervention groups, rsCoVar decreased during observation compared to baseline. We found a correlation between rsSO2 and PaO2 (r = 0.420, P < 0.001) and between rsSO2 and SaO2 (r = 0.648, P < 0.001) in pooled data from the entire experiment. Reoxygenation after global hypoxia improves splanchnic oxygenation, but is associated with reduced variability of rsSO2. Reoxygenation with 100% O2 exposes the intestine to hyperoxia. Splanchnic NIRS is able to detect intestinal hypoxia and hyperoxia. Splanchnic oxygenation improves during reoxygenation after global hypoxia, though reoxygenation with 100% O2 exposes the intestine to hyperoxia. Decreased variability of splanchnic oxygenation several hours after hypoxia and reoxygenation seems to be independent of the resuscitation strategy, and may indicate intestinal injury. Splanchnic NIRS monitoring was able to detect intestinal hypoxia and exposure to hyperoxia, as evidenced by a strong correlation between splanchnic oxygenation and arterial oxygen content.

New role for ceramide in hypoxia and insulin resistance.

Ceramides are significant metabolic products of sphingolipids in lipid metabolism and are associated with insulin resistance and hepatic steatosis. In chronic inflammatory pathological conditions, hypoxia occurs, the metabolism of ceramide changes, and insulin resistance arises. Hypoxia-inducible factors (HIFs) are a family of transcription factors activated by hypoxia. In hypoxic adipocytes, HIF-1α upregulates pla2g16 (a novel HIF-1α target gene) gene expression to activate the NLRP3 inflammasome pathway and stimulate insulin resistance, and adipocyte-specific Hif1a knockout can ameliorate homocysteine-induced insulin resistance in mice. The study on the HIF-2α—NEU3—ceramide pathway also reveals the role of ceramide in hypoxia and insulin resistance in obese mice. Under obesity-induced intestinal hypoxia, HIF-2α increases the production of ceramide by promoting the expression of the gene Neu3 encoding sialidase 3, which is a key enzyme in ceramide synthesis, resulting in insulin resistance in high-fat diet-induced obese mice. Moreover, genetic and pathophysiologic inhibition of the HIF-2α—NEU3—ceramide pathway can alleviate insulin resistance, suggesting that these could be potential drug targets for the treatment of metabolic diseases. Herein, the effects of hypoxia and ceramide, especially in the intestine, on metabolic diseases are summarized.

Effect of Pravastatin Pretreatment and Hypercapnia on Intestinal Microvascular Oxygenation and Blood Flow During Sepsis.

In septic patients, adequate microvascular oxygenation (μHBO2) of the intestine is vital for their outcome. Recent studies suggest that statins can ameliorate septic microcirculation in a variety of tissues. However, the effect on intestinal microvascular oxygenation and blood flow is largely unknown. Furthermore, there are indications that statin therapy might not be beneficial in the presence of hypercapnia, as observed in septic acute respiratory distress syndrome (ARDS) patients. Therefore, the present study explores the effect of pravastatin with and without additional moderate acute hypercapnia on intestinal microvascular oxygenation and blood flow in experimental sepsis. Forty male Wistar rats were randomized into four groups. Half of the animals received 0.2 mg • kg pravastatin s.c., the other half received the same volume as vehicle (NaCl 0.9%). After 18 h, colon ascendens stent peritonitis surgery was conducted in all animals to induce sepsis. Twenty-four hours after surgery, baseline was established and the animals were subjected to either 120 min of normocapnic (pCO2 40 ± 6 mm Hg) or moderate hypercapnic (pCO2 72 ± 10 mm Hg) ventilation. Microcirculatory oxygenation (μHBO2) and perfusion (μflow) of the colon were continuously recorded using tissue reflectance spectrophotometry and laser Doppler, respectively. In normocapnic septic animals μHBO2 decreased over time (-8.4 ± 8.7%; P < 0.05 vs. baseline), whereas after pravastatin pretreatment μHBO2 remained constant (-1.9 ± 5.7% vs. baseline). However, in hypercapnic septic animals pretreated with pravastatin μHBO2 declined significantly over time (-8.9 ± 11.8%; P < 0.05 vs. baseline) and was significantly lower compared with normocapnic pravastatin-pretreated animals. μflow did not change over time in any group. Pravastatin pretreatment ameliorates the intestinal microvascular oxygenation in sepsis and thus seems to prevent intestinal hypoxia. Furthermore, we demonstrated that additional hypercapnia abolishes this effect, indicating why septic ARDS patients might not benefit from pravastatin therapy.

First person – Yong Chen

ABSTRACTFirst Person is a series of interviews with the first authors of a selection of papers published in Disease Models & Mechanisms (DMM), helping early-career researchers promote themselves alongside their papers. Yong Chen is first author on ‘Formula feeding and immature gut microcirculation promote intestinal hypoxia, leading to necrotizing enterocolitis’, published in DMM. Yong conducted the research described in this article while a research fellow in Agostino Pierro's lab at The Hospital for Sick Children, Toronto, Canada. He is now a staff physician in the Department of Pediatric Surgery at KK Women's and Children's Hospital, as well as adjunct assistant professor at Duke-NUS Medical School, Singapore, investigating the aetiology, treatment and prevention of necrotizing enterocolitis.

The gut microbiota modulator berberine ameliorates collagen‐induced arthritis in rats by facilitating the generation of butyrate and adjusting the intestinal hypoxia and nitrate supply

The commensal microbiota is one of the environmental triggers of rheumatoid arthritis (RA). Recent studies have identified the characteristics of the gut microbiota in patients with RA. However, it is still unclear how the microbiota can be modulated to slow down disease progression. In the present study, berberine, a modulator of gut microbiota with substantial anti-RA effect, was chosen to explore the mechanisms by which the microbiota modulators ameliorate RA. The results showed that oral administration of berberine alleviated collagen-induced arthritis (CIA) in rats in a gut microbiota-dependent manner. Berberine down-regulated the diversity and richness of the gut bacteria, reduced the abundance of Prevotella, and elevated the abundance of butyrate-producing bacteria in CIA rats as determined by the 16S rRNA gene sequence, which might function through limiting the generation of nitrate and stabilizing the physiologic hypoxia in the intestine. Moreover, berberine treatment significantly increased the intestinal butyrate level and promoted the expression and activity of butyryl-CoA:acetate-CoA transferase (BUT). The coadministration of a BUT inhibitor largely diminished the adjustment of intestinal environment and the antiarthritic effect of berberine. In conclusion, modulators of the gut microbiota might serve as therapeutic agents for RA by inducing the butyrate generation through promoting the expression and activity of BUT.-Yue, M., Tao, Y., Fang, Y., Lian, X., Zhang, Q., Xia, Y., Wei, Z., Dai, Y. The gut microbiota modulator berberine ameliorates collagen-induced arthritis in rats by facilitating the generation of butyrate and adjusting the intestinal hypoxia and nitrate supply.