Anti-apoptotic PI3K/Akt signaling by sodium/glucose transporter 1 reduces epithelial barrier damage and bacterial translocation in intestinal ischemia

To study whether over-starvation aggravates intestinal mucosal injury and promotes bacterial and endotoxin translocation in a high-altitude hypoxic environment. Sprague-Dawley rats were exposed to hypobaric hypoxia at a simulated altitude of 7000 m for 72 h. Lanthanum nitrate was used as a tracer to detect intestinal injury. Epithelial apoptosis was observed with terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Serum levels of diamino oxidase (DAO), malondialdehyde (MDA), glutamine (Gln), superoxide dismutase (SOD) and endotoxin were measured in intestinal mucosa. Bacterial translocation was detected in blood culture and intestinal homogenates. In addition, rats were given Gln intragastrically to observe its protective effect on intestinal injury. Apoptotic epithelial cells, exfoliated villi and inflammatory cells in intestine were increased with edema in the lamina propria accompanying effusion of red blood cells. Lanthanum particles were found in the intercellular space and intracellular compartment. Bacterial translocation to mesenteric lymph nodes (MLN) and spleen was evident. The serum endotoxin, DAO and MDA levels were significantly higher while the serum SOD, DAO and Gln levels were lower in intestine (P < 0.05). The bacterial translocation number was lower in the high altitude hypoxic group than in the high altitude starvation group (0.47 ± 0.83 vs 2.38 ± 1.45, P < 0.05). The bacterial translocation was found in each organ, especially in MLN and spleen but not in peripheral blood. The bacterial and endotoxin translocations were both markedly improved in rats after treatment with Gln. High-altitude hypoxia and starvation cause severe intestinal mucosal injury and increase bacterial and endotoxin translocation, which can be treated with Gln.

Contribution of SGLT1 in cardiac glucose transport

Neutrophil priming by hypoxic preconditioning protects against epithelial barrier damage and enteric bacterial translocation in intestinal ischemia/reperfusion

Contribution of SGLT1 in cardiac glucose uptake

Bacterial translocation (BT) may be a normal physiologic process that is important for mucosal antigen sampling in the gut. However, physiologic insults such as endotoxemia, hemorrhagic shock, or necrotizing enterocolitis (NEC) may lead to pathologic BT and thus contribute to the pathogenesis of nosocomial infection. The mechanism may involve accelerated enterocyte apoptosis at the intestinal villus apex resulting, at least transiently, in a "bare area" at the villus tip where bacteria can attach and traverse the epithelium. Evidence suggests that sustained upregulation of the inducible isoform of nitric oxide synthase (NOS-2) co-localizes with enterocyte apoptosis and immunoreactivity to 3-nitrotyrosine, the footprint of peroxynitrite (ONOO-), a potent oxidant formed by the reaction of nitric oxide (NO) with superoxide. We propose that the bare area at the villus apex is caused by apoptosis of enterocytes that have migrated from the base of the crypts to the villus apex and are shed into the intestinal lumen. These bare areas, and thus the degree of BT, may be the result of an imbalance between enterocyte proliferation and apoptosis. We postulate that normal enterocyte apoptosis is mediated by the caspase cascade, whereas enterocyte proliferation and differentiation in the crypt may be regulated by tyrosine kinase-dependent signaling pathways. Both of these cellular pathways may be influenced by overproduction of NO and its metabolite ONOO-. Therefore, sustained NO production and ONOO- formation occurring in inflammatory states may differentially accelerate apoptosis in the villus apex and/or inhibit proliferation at the base of the crypts resulting in expanded extrusion zones at the villus tip and accelerated BT.

Introduction: Diabetes is the leading cause of microvascular disorders such as diabetic retinopathy (DR). There are no treatments for DR and finding new drug targets is of considerable interest. SGLT2 inhibitors, a newer class of antidiabetics are promising in the management of diabetes, however, the potential role of SGLT2 in diabetic retinal microvasculature remains unknown. We hypothesized that diabetes will lead to an increase in SGLT2 in the retina and that its inhibition will be beneficial in protecting retinal vasculature from the insult of diabetes milieu. Methods: The retinal sections of diabetic (db/db; an animal model of type 2 diabetes) and control (db/m) mice were analyzed for SGLT2 expression using confocal microscopy. In parallel, the mRNA levels of SGLT2 were determined using qRT-PCR. Human retinal endothelial cells (HRECs) were treated with the SGLT2 inhibitor dapagliflozin (0.1, 1, 10 nM) to perform a glucose uptake assay and to determine its effects on mRNA levels of SGLT2. Results: The mRNA levels of SGLT2 were significantly higher (p&amp;lt;0.05) in the retina of db/db mice, 1.1 ± 0.46, n=5, when compared to db/m retinas, 0.06 ± 0.02, n=4. The confocal microscopy revealed SGLT2 expression throughout the retina and around the retinal blood vessels, brighter fluorescence was observed in the db/db retina. Treatment of HRECs with 10 nM dapagliflozin led to a significant decrease in SGLT2 mRNA (p&amp;lt;0.05); dapagliflozin: 7.95 ± 4.7, n=4; vehicle: 26 ± 3.6, n=8. The dapagliflozin inhibition demonstrated a profound decrease in glucose uptake in HRECs at all concentrations. Untreated: 2012 ± 388, n=3; 0.1 nM: 545.7 ± 296, 1 nM: 358.2 ± 241.5, 10 nM: 70.67 ± 138.9; p&amp;lt;0.01 as compared to untreated; n=6. Conclusion: Our studies suggest that SGLT2 is significantly upregulated in the retina during diabetes and that SGLT2 potentially plays a critical role in retinal glucose transport. In future, SGLT2 inhibition could be a useful treatment option to slow down or prevent the onset of diabetic retinopathy. Disclosure S.P. Leley: None. Q. Luo: None. A.L. Alex: None. A.D. Bhatwadekar: None. Funding National Eye Institute; Indiana University Center for Diabetes and Metabolic Diseases

Verbascoside as a potential SGLT2 inhibitor in diabetic nephropathy: Targeting AMPK activation to suppress NOX4/NF-κB signaling and attenuate inflammation and fibrosis.

27. Induction of Diurnal Expression of Intestinal Hexose Transporter SGLT1 in Rat Ileum After Massive Small Bowel Resection

Swertisin, a novel SGLT2 inhibitor, with improved glucose homeostasis for effective diabetes therapy

Mechanism of SGLT1-Dependent Translocation of GLUT2 to the Apical Membrane of Enterocytes

Increased expression of sodium-glucose cotransporter 2 and O-GlcNAcylation in hepatocytes drives non-alcoholic steatohepatitis

P2.11-39 Multimodal Monitoring of Patient-Derived Early-Stage Lung Adenocarcinoma with the Chicken Chorioallantoic Membrane System

Restricted Feeding Phase Shifts Clock Gene and Sodium Glucose Cotransporter 1 (SGLT1) Expression in Rats1–4

Our group has previously shown that the intestinal epithelium exhibits increased postburn barrier permeability and bacterial translocation associated with deranged neutrophil activity. The purpose of this investigation is to explore possible underlying intestinal structural mechanisms, leading to those functional changes with emphasis on (1) neutrophil influx and extravasation in the intestinal lamina propria 1-3 days after burn and (2) enterocyte proliferation, migration, apoptosis, and E-cadherin junctional epithelium levels 3 days after burn. Freshly isolated ileum specimens were quick frozen, then cut by a cryostat into 30-micron-thick sections. Sections from day 1 postburn rats were immunostained with (1) anti-granulocyte or anti-elastase antibodies to assess neutrophil influx or (2) combined anti-granulocyte and anti-von Willebrand factor double immunolabeling to compare levels of neutrophil extravasation. Sections from day 3 postburn rats were immunostained with (1) bromodeoxyuridine immunohistochemistry 1, 3, 6, or 18 hrs after bromodeoxyuridine injection to assess enterocyte proliferation and migration, (2) cytokeratin-18 M30-immunohistochemistry to compare levels of enterocyte apoptosis, and (3) E-cadherin immunohistochemistry to compare junctional E-cadherin integrity. Ileal myeloperoxidase activity and bacterial translocation of Enterococcus faecalis were assessed biochemically and by E. faecalis-specific bacterial cultures, respectively, in day 3 postburn rats. : Research laboratories in a medical center and an academic institution. Male Sprague-Dawley rats given sham treatment or treatment as a burn model with full-thickness skin scald over 30% total body surface area. We report (1) increased levels of neutrophil influx and extravasation in villi lamina propriae, including elastase-positive cells (postburn day 1), (2) heightened levels of intestinal myeloperoxidase activity (postburn day 3), (3) decreased levels of epithelial cell proliferation, migration, and E-cadherin (postburn day 3), and (4) increased enterocyte apoptosis and E. faecalis bacterial translocation (postburn day 3). Based on these structural and functional abnormalities, we propose a mechanism for burn injury-related intestinal barrier dysfunction that includes increased trans- and para-cellular leakage caused by impaired enterocyte renewal and decreased junctional E-cadherin levels subsequent to increased neutrophil influx and extravasation within the villus lamina propria microenvironment.

Bacterial translocation in cirrhosis can trigger infection and hepatic decompensation, leading to systemic inflammation, organ failure and increased mortality. These infections often originate from the gastrointestinal tract after bacteria breach the intestinal barrier and disseminate to systemic sites. In this study, we explore the mechanisms underlying intestinal barrier dysfunction in cirrhosis using an experimental cirrhosis model and patient-derived intestinal biopsies. We developed a murine model of cirrhosis through chronic administration of carbon tetrachloride for up to 20 weeks. We investigated both the intestinal epithelial and vascular compartments and performed single-cell transcriptomic profiling of myeloid cells isolated from cirrhotic mice and from individuals with compensated and decompensated cirrhosis. Our findings indicate that bacterial translocation in cirrhosis is the result of failure at multiple checkpoints, including aberrant epithelial cell death, vascular barrier damage and dysfunction of gut-vascular macrophages. In a preclinical model of cirrhosis, macrophages exhibited increased levels of monocyte-attracting chemokines, reduced bacterial clearance and impaired interactions with blood vessels. Importantly, depleting vascular-lining macrophages resulted in bacterial translocation to systemic sites, even in the absence of experimental liver disease. Transcriptional profiling of macrophages from duodenal biopsies of patients with cirrhosis indicated similar dysregulation of pathways supporting blood vessels and elevated expression of chemokines. This study emphasises the critical role of intestinal macrophages in preventing the dissemination of luminal bacteria and highlights the multifaceted breakdown of the intestinal barrier in cirrhosis and the importance of the gut-vascular barrier.