Sodium-hydrogen Exchange Inhibition Research Articles

Antiarrhythmic Effect of SGLT-2 Inhibitors in high-degree AV Block Caused by Heart Failure: A Case Report

Highlights: 1. The antiarrhythmic effect of SGLT-2 inhibitors, particularly empagliflozin, is a very interesting topic to discuss further. 2. In patients with high degree AV block due to HF in rural areas, the use of SGLT-2 inhibitors is quite rare in Indonesia. - Background: According to WHO's Top 10 Global Health Threats, non-communicable diseases such as heart failure contribute to more than 70% of all deaths worldwide. Several studies have shown that SGLT-2 inhibitors can considerably reduce HF. As research progresses, SGLT-2 inhibitors may lessen the risk of arrhythmias in HF patients. Case Summary: A 57-year-old female with uncontrolled hypertension came to the ED after collapsing at home. The vital signs and physical examination are normal. The preliminary ECG showed a high degree AV Block with multiple multifocal PVC. Early laboratory revealed mild hypokalemia. The patient experienced a seizure the next day, and an ECG showed total AV block with a non-sustained VT episode with PVC R on T. Following critical cardiac care and stabilization, the patient underwent echocardiography, which showed mild MR and AR with a reduced ejection fraction (47.7%). Once the patient's condition has stabilized, the patient is given 1x10mg Empagliflozin PO. Discussion: SGLT-2 inhibitors are beneficial in the treatment of heart failure and arrhythmia. SGLT-2 inhibitors have antiarrhythmic effects through a variety of pathways, such as lowering preload and afterload, inhibition of sodium-hydrogen exchange in myocardial cells, and suppression of the sympathetic nervous system.

Effect of an NHE3 inhibitor in combination with an NPT2b inhibitor on gastrointestinal phosphate absorption in Rodent models.

Many of the pathological consequences of chronic kidney disease can be attributed to an elevation in serum phosphate levels. Current therapies focused on decreasing intestinal phosphate absorption to treat hyperphosphatemia are inadequate. The most effective therapeutic strategy may be to target multiple absorptive pathways. In this study, the ability of a novel inhibitor of the intestinal sodium hydrogen exchanger 3 (NHE3), LY3304000, which inhibits paracellular, diffusional uptake of phosphate, to work in combination with an inhibitor of the active transporter, sodium dependent phosphate cotransporter 2b (NPT2b), LY3358966, was explored. LY3304000 modestly inhibited the acute uptake of phosphate into plasma of rats, while surprisingly, it doubled the rate of phosphate uptake in mice, an animal model dominated by NPT2b mediated acute phosphate uptake. In rats, LY3004000 and LY3358966 work in concert to inhibit acute phosphate uptake. On top of LY3358966, LY3304000 further decreased the acute uptake of phosphate into plasma. Studies measuring the recovery of radiolabeled phosphate in the intestine demonstrated LY3304000 and LY3358966 synergistically inhibited the absorption of phosphate in rats. We hypothesize the synergism is because the NHE3 inhibitor, LY3304000, has two opposing effects on intestinal phosphate absorption in rats, first it decreases diffusion mediated paracellular phosphate absorption, while second, it simultaneously increases phosphate absorption through the NPT2b pathway. NHE3 inhibition decreases proton export from enterocytes and raises the cell surface pH. In vitro, NPT2b mediated phosphate transport is increased at higher pHs. The increased NPT2b mediated transport induced by NHE3 inhibition is masked in rats which have relatively low levels of NPT2b mediated phosphate transport, by the more robust inhibition of diffusion mediated phosphate absorption. Thus, the inhibition of NPT2b mediated phosphate transport in rats in the presence of NHE3 inhibition has an effect that exceeds its effect in the absence of NHE3 inhibition, leading to the observed synergism on phosphate absorption between NPT2b and NHE3 inhibition.

Empagliflozin prevents oxidative stress in human coronary artery endothelial cells via the NHE/PKC/NOX axis

BackgroundEmpagliflozin (EMPA) ameliorates reactive oxygen species (ROS) generation in human endothelial cells (ECs) exposed to 10 % stretch, but the underlying mechanisms are still unclear. Pathological stretch is supposed to stimulate protein kinase C (PKC) by increasing intracellular calcium (Ca2+), therefore activating nicotinamide adenine dinucleotide phosphate oxidase (NOX) and promoting ROS production in human ECs. We hypothesized that EMPA inhibits stretch-induced NOX activation and ROS generation through preventing PKC activation. MethodsHuman coronary artery endothelial cells (HCAECs) were pre-incubated for 2 h before exposure to cyclic stretch (5 % or 10 %) with either vehicle, EMPA or the PKC inhibitor LY-333531 or PKC siRNA. PKC activity, NOX activity and ROS production were detected after 24 h. Furthermore, the Ca2+ chelator BAPTA-AM, NCX inhibitor ORM-10962 or NCX siRNA, sodium/potassium pump inhibitor ouabain and sodium hydrogen exchanger (NHE) inhibitor cariporide were applied to explore the involvement of the NHE/Na+/NCX/Ca2+ in the ROS inhibitory capacity of EMPA. ResultsCompared to 5 % stretch, 10 % significantly increased PKC activity, which was reduced by EMPA and PKC inhibitor LY-333531. EMPA and LY-333531 showed a similar inhibitory capacity on NOX activity and ROS generation induced by 10 % stretch, which was not augmented by combined treatment with both drugs. PKC-β knockdown inhibits the NOX activation induced by Ca2+ and 10 % stretch. BAPTA, pharmacologic or genetic NCX inhibition and cariporide reduced Ca2+ in static HCAECs and prevented the activation of PKC and NOX in 10%-stretched cells. Ouabain increased ROS generation in cells exposed to 5 % stretch. ConclusionEMPA reduced NOX activity via attenuation of the NHE/Na+/NCX/Ca2+/PKC axis, leading to less ROS generation in HCAECs exposed to 10 % stretch.

Empagliflozin suppressed cardiac fibrogenesis through sodium-hydrogen exchanger inhibition and modulation of the calcium homeostasis

BackgroundThe novel sodium-glucose co-transporter 2 inhibitor (SGLT2i) potentially ameliorates heart failure and reduces cardiac arrhythmia. Cardiac fibrosis plays a pivotal role in the pathophysiology of HF and atrial myopathy, but the effect of SGLT2i on fibrogenesis remains to be elucidated. This study investigated whether SGLT2i directly modulates fibroblast activities and its underlying mechanisms.Methods and resultsMigration, proliferation analyses, intracellular pH assay, intracellular inositol triphosphate (IP3) assay, Ca2+ fluorescence imaging, and Western blotting were applied to human atrial fibroblasts. Empagliflozin (an SGLT2i, 1, or 5 μmol/L) reduced migration capability and collagen type I, and III production. Compared with control cells, empagliflozin (1 μmol/L)- treated atrial fibroblasts exhibited lower endoplasmic reticulum (ER) Ca2+ leakage, Ca2+ entry, inositol trisphosphate (IP3), lower expression of phosphorylated phospholipase C (PLC), and lower intracellular pH. In the presence of cariporide (an Na+-H+ exchanger (NHE) inhibitor, 10 μmol/L), control and empagliflozin (1 μmol/L)-treated atrial fibroblasts revealed similar intracellular pH, ER Ca2+ leakage, Ca2+ entry, phosphorylated PLC, pro-collagen type I, type III protein expression, and migration capability. Moreover, empagliflozin (10 mg/kg/day orally for 28 consecutive days) significantly increased left ventricle systolic function, ß-hydroxybutyrate and decreased atrial fibrosis, in isoproterenol (100 mg/kg, subcutaneous injection)-induced HF rats.ConclusionsBy inhibiting NHE, empagliflozin decreases the expression of phosphorylated PLC and IP3 production, thereby reducing ER Ca2+ release, extracellular Ca2+ entry and the profibrotic activities of atrial fibroblasts.

Sodium-glucose Cotransporter Type 2 Inhibitors: A New Insight into the Molecular Mechanisms of Diabetic Nephropathy.

Diabetic nephropathy is one of the chronic microvascular complications of diabetes and is a leading cause of end-stage renal disease. Fortunately, clinical trials have demonstrated that sodium-glucose cotransporter type 2 inhibitors could decrease proteinuria and improve renal endpoints and are promising agents for the treatment of diabetic nephropathy. The renoprotective effects of sodium-glucose cotransporter type 2 inhibitors cannot be simply attributed to their advantages in aspects of metabolic benefits, such as glycemic control, lowering blood pressure, and control of serum uric acid, or improving hemodynamics associated with decreased glomerular filtration pressure. Some preclinical evidence suggests that sodium-glucose cotransporter type 2 inhibitors exert their renoprotective effects by multiple mechanisms, including attenuation of oxidative and endoplasmic reticulum stresses, anti-fibrosis and anti-inflammation, protection of podocytes, suppression of megalin function, improvement of renal hypoxia, restored mitochondrial dysfunction and autophagy, as well as inhibition of sodium-hydrogen exchanger 3. In the present study, the detailed molecular mechanisms of sodium-glucose cotransporter type 2 inhibitors with the actions of diabetic nephropathy were reviewed, with the purpose of providing the basis for drug selection for the treatment of diabetic nephropathy.

Therapeutic Inhibition of Acid-Sensing Ion Channel 1a Recovers Heart Function After Ischemia-Reperfusion Injury.

Ischemia-reperfusion injury (IRI) is one of the major risk factors implicated in morbidity and mortality associated with cardiovascular disease. During cardiac ischemia, the buildup of acidic metabolites results in decreased intracellular and extracellular pH, which can reach as low as 6.0 to 6.5. The resulting tissue acidosis exacerbates ischemic injury and significantly affects cardiac function. We used genetic and pharmacologic methods to investigate the role of acid-sensing ion channel 1a (ASIC1a) in cardiac IRI at the cellular and whole-organ level. Human induced pluripotent stem cell-derived cardiomyocytes as well as ex vivo and in vivo models of IRI were used to test the efficacy of ASIC1a inhibitors as pre- and postconditioning therapeutic agents. Analysis of human complex trait genetics indicates that variants in the ASIC1 genetic locus are significantly associated with cardiac and cerebrovascular ischemic injuries. Using human induced pluripotent stem cell-derived cardiomyocytes in vitro and murine ex vivo heart models, we demonstrate that genetic ablation of ASIC1a improves cardiomyocyte viability after acute IRI. Therapeutic blockade of ASIC1a using specific and potent pharmacologic inhibitors recapitulates this cardioprotective effect. We used an in vivo model of myocardial infarction and 2 models of ex vivo donor heart procurement and storage as clinical models to show that ASIC1a inhibition improves post-IRI cardiac viability. Use of ASIC1a inhibitors as preconditioning or postconditioning agents provided equivalent cardioprotection to benchmark drugs, including the sodium-hydrogen exchange inhibitor zoniporide. At the cellular and whole organ level, we show that acute exposure to ASIC1a inhibitors has no effect on cardiac ion channels regulating baseline electromechanical coupling and physiologic performance. Our data provide compelling evidence for a novel pharmacologic strategy involving ASIC1a blockade as a cardioprotective therapy to improve the viability of hearts subjected to IRI.

A naturally occurring mutation in ATP synthase subunit c is associated with increased damage following hypoxia/reoxygenation in STEMI patients.

Preclinical models of ischemia/reperfusion injury (RI) demonstrate the deleterious effects of permeability transition pore complex (PTPC) opening in the first minutes upon revascularization of the occluded vessel. The ATP synthase c subunit (Csub) influences PTPC activity in cells, thus impacting tissue injury. A conserved glycine-rich domain in Csub is classified as critical because, when mutated, it modifies ATP synthase properties, protein interaction with the mitochondrial calcium (Ca2+) uniporter complex, and the conductance of the PTPC. Here, we document the role of a naturally occurring mutation in the Csub-encoding ATP5G1 gene at the G87 position found in two ST-segment elevation myocardial infarction (STEMI) patients and how PTPC opening is related to RI in patients affected by the same disease. We report a link between the expression of ATP5G1G87E and the response to hypoxia/reoxygenation of human cardiomyocytes, which worsen when compared to those expressing the wild-type protein, and a positive correlation between PTPC and RI.

Might proton pump or sodium-hydrogen exchanger inhibitors be of value to ameliorate SARs-CoV-2 pathophysiology?

Discovering therapeutics for COVID‐19 is a priority. Besides high‐throughput screening of compounds, candidates might be identified based on their known mechanisms of action and current understanding of the SARs‐CoV‐2 life cycle. Using this approach, proton pump (PPIs) and sodium‐hydrogen exchanger inhibitors (NHEIs) emerged, because of their potential to inhibit the release of extracellular vesicles (EVs; exosomes and/or microvesicles) that could promote disease progression, and to directly disrupt SARs‐CoV‐2 pathogenesis. If EVs exacerbate SARs‐CoV‐2 infection as suggested for other viruses, then inhibiting EV release by PPIs/NHEIs should be beneficial. Mechanisms underlying inhibition of EV release by these drugs remain uncertain, but may involve perturbing endosomal pH especially of multivesicular bodies where intraluminal vesicles (nascent exosomes) are formed. Additionally, PPIs might inhibit the endosomal sorting complex for transport machinery involved in EV biogenesis. Through perturbing endocytic vesicle pH, PPIs/NHEIs could also impede cleavage of SARs‐CoV‐2 spike protein by cathepsins necessary for viral fusion with the endosomal membrane. Although pulmonary epithelial cells may rely mainly on plasma membrane serine protease TMPRSS2 for cell entry, PPIs/NHEIs might be efficacious in ACE2‐expressing cells where viral endocytosis is the major or a contributing entry pathway. These pharmaceutics might also perturb pH in the endoplasmic reticulum‐Golgi intermediate and Golgi compartments, thereby potentially disrupting viral assembly and glycosylation of spike protein/ACE2, respectively. A caveat, however, is that facilitation not inhibition of avian infectious bronchitis CoV pathogenesis was reported in one study after increasing Golgi pH. Envelope protein‐derived viroporins contributed to pulmonary edema formation in mice infected with SARs‐CoV. If similar pathogenesis occurs with SARs‐CoV‐2, then blocking these channels with NHEIs could ameliorate disease pathogenesis. To ascertain their potential efficacy, PPIs/NHEIs need evaluation in cell and animal models at various phases of SARs‐CoV‐2 infection. If they prove to be therapeutic, the greatest benefit might be realized with the administration before the onset of severe cytokine release syndrome.

Sodium-glucose cotransporter 2 inhibitors' mechanisms of action in heart failure.

Three major cardiovascular outcome trials (CVOTs) with a new class of antidiabetic drugs - sodium-glucose cotransporter 2 (SGLT2) inhibitors (EMPA-REG OUTCOME trial with empagliflozin, CANVAS Program with canagliflozin, DECLARE-TIMI 58 with dapagliflozin) unexpectedly showed that cardiovascular outcomes could be improved possibly due to a reduction in heart failure risk, which seems to be the most sensitive outcome of SGLT2 inhibition. No other CVOT to date has shown any significant benefit on heart failure events. Even more impressive findings came recently from the DAPA-HF trial in patients with confirmed and well-treated heart failure: Dapagliflozin was shown to reduce heart failure risk for patients with heart failure with reduced ejection fraction regardless of diabetes status. Nevertheless, despite their possible wide clinical implications, there is much doubt about the mechanisms of action and a lot of questions to unravel, especially now when their benefits translated to non-diabetic patients, rising doubts about the validity of some current mechanistic assumptions.The time frame of their cardiovascular benefits excludes glucose-lowering and antiatherosclerotic-mediated effects and multiple other mechanisms, direct cardiac as well as systemic, are suggested to explain their early cardiorenal benefits. These are: Anti-inflammatory, antifibrotic, antioxidative, antiapoptotic properties, then renoprotective and hemodynamic effects, attenuation of glucotoxicity, reduction of uric acid levels and epicardial adipose tissue, modification of neurohumoral system and cardiac fuel energetics, sodium-hydrogen exchange inhibition. The most logic explanation seems that SGLT2 inhibitors timely target various mechanisms underpinning heart failure pathogenesis. All the proposed mechanisms of their action could interfere with evolution of heart failure and are discussed separately within the main text.

Empagliflozin Improves Cardiac Functional Recovery after Prolonged Cold Storage of Donor Hearts in an Isolated Working Rat Heart Model

Many donor hearts are unsuitable for transplantation after prolonged cold storage or donation after circulatory death. Improved donor heart recovery is observed after supplementation of preservation solutions with sodium-hydrogen exchange inhibitors (NHEI) cariporide/zoniporide (Gao et al, 2010, BJP; Cropper et al, 2003, JHLT). NHEI are not clinically used due to neurotoxicity observed in cariporide clinical trials however the search for suitable NHEI alternatives continues. One promising alternative is the sodium-glucose cotransporter 2 inhibitor Empagliflozin (Empa) - the first anti-diabetic drug to yield positive cardiovascular outcomes. Studies have shown Empa mimics NHEI and slows pH recovery in cardiomyocytes following an acidic load. This study tests the cardioprotective efficacy of Empa-supplementation in cardiac preservation solution during prolonged cold storage of donor hearts. Wistar rat (320-420g; n=5-7) hearts were perfused ex-vivo and baseline hemodynamic measurements acquired. Hearts were arrested and stored in Celsior±0.3-10µM Empa, or zoniporide (1µM) (6h, 4°C) then reperfused (37°C, Langendorff 15min, working 30min). Post-reperfusion aortic flow (AF) and cardiac output (CO) were expressed as a percentage of baseline measurements. Coronary effluent (pre-storage, 15, 30, and 45 min reperfusion) was assessed for lactate dehydrogenase (LDH) release. Donor hearts supplemented with Empa during cold storage showed a dose-dependent improvement in cardiac functional recovery. Compared to unsupplemented control hearts, 10µM Empa-supplemented hearts showed significantly improved AF (54±11% vs 10±7%, p=0.006) and CO (55±12 vs 16±8, p=0.03) recovery. Hearts supplemented with 1µM zoniporide also showed significantly improved AF (63±7%, p=0.002 vs control) and CO (65±9%, p=0.01) recovery. A trend for reduced LDH efflux was observed in hearts supplemented with 1-10µM Empa or zoniporide compared to control hearts. Supplementation of cardiac preservation solution with 10µM Empa yields significantly improved functional recovery after prolonged cold storage, with similar cardioprotective efficacy to the NHEI zoniporide. Given the approved clinical use of Empa, this study highlights its potential as a suitable alternative for NHEI in donor heart preservation.

Placebo and Nocebo Responses in Randomized, Controlled Trials of Medications for ADHD: A Systematic Review and Meta-Analysis

Background: The nature and magnitude of placebo and nocebo responses to ADHD medications is unclear. The extent to which response to active medications and placebo are inter-correlated has not been explored. Methods: We searched scientific literature until June 26, 2019 for published/unpublished double-blind, randomised placebo-controlled trials (RCTs) of ADHD medications in children, adolescents and adults. Authors and drug manufacturers were contacted for additional information. We assessed placebo effects on efficacy and nocebo effects on tolerability outcomes using aggregate data from trials and random-effects meta-analysis. We assessed the association of study design and patient features with placebo/nocebo response. Findings: We analysed 128 RCTs and found significant and heterogenous placebo effects for all efficacy outcomes, with no publication bias. We found nocebo effects on some tolerability outcomes. Apart from self-ratings, efficacy outcomes from other raters showed significant positive correlations between the baseline to endpoint placebo effects and the baseline to endpoint drug effects, suggesting that response to placebo and ADHD medications are influenced by similar non-specific factors. Baseline severity and type of rating scale influenced the magnitude of placebo response. Interpretation: Placebo effects are highly significant and response to placebo and ADHD medications are correlated, suggesting that shared non-specific factors influence response to both placebo and active medication. Although ADHD medications are superior to placebo, and placebo treatment in clinical practice is not feasible, clinicians should attempt to incorporate factors associated with placebo effects into clinical care, and future studies should explore how such effects influence response to medication treatment. Funding Statement: This was not a funded study. Declaration of Interests: In the past year, Dr. Faraone received income, potential income, travel expenses continuing education support and/or research support from Takeda, OnDosis, Tris, Otsuka, Arbor, Ironshore, Rhodes, Akili Interactive Labs, Enzymotec, Sunovion, Supernus and Genomind. With his institution, he has US patent US20130217707 A1 for the use of sodium-hydrogen exchange inhibitors in the treatment of ADHD. He also receives royalties from books published by Guilford Press: Straight Talk about Your Child’s Mental Health, Oxford University Press: Schizophrenia: The Facts and Elsevier: ADHD: Non-Pharmacologic Interventions. He is Program Director of www.adhdinadults.com. In the past year, Dr. Newcorn is/has been an advisor and/or consultant for Adlon Therapeutics, Arbor, Eisai, NLS, OnDosis, Rhodes, Shire/Takeda, and Supernus. He was a DSMB member for Pfizer and Sunovion, and received research funds from Otsuka, Shire and Supernus. He also has received speaker fees from Shire/Takeda for disease-state presentations and served as a consultant for the US National Football League. Dr. Cipriani has received research and consultancy fees from INCiPiT (Italian Network for Paediatric Trials), CARIPLO Foundation and Angelini Pharma. Dr. Brandeis serves as an unpaid scientific consultant for an EUfunded neurofeedback trial. Anna Kaiser reports has no financial disclosures. Sarah Hohmann has no financial disclosures. Dr. Hage received conference support, speaker´s fee and/or served in an advisory role for Shire/Takeda and Lily. He was involved as investigator in clinical trials by Shire, Janssen-Cilag, Otsuka, Sunovion, Servier, Lundbeck, Takeda,Nuvelution, Gedeon Richter, and Emalex. The present work is unrelated to the above relationships. Dr. Cortese declares reimbursement for travel and accommodation expenses from the Association for Child and Adolescent Central Health (ACAMH) in relation to lectures delivered for ACAMH, Canadian ADHD Resource Alliance (CADDRA), British Association of Psychopharmacology (BAP), and from Healthcare Convention for educational activity on ADHD.

Development of a Novel Sodium-Hydrogen Exchanger Inhibitor for Heart Failure

This study was designed to determine the potential therapeutic effects of a new sodium-hydrogen exchanger (NHE-1) inhibitor in the rat coronary artery ligation model of chronic heart failure. After the induction of acute myocardial infarction, rats were entered into a randomly designed pilot dose study from 0.3 mg/kg, 1.0 mg/kg, and 3.0 mg/kg. Solid state micrometer hemodynamics, echocardiographic, and pressure-volume relationships were measured after 6 weeks of treatment. Treatment with this NHE-¬1 inhibitor at 3 mg/kg increased (P<0.05) ejection fraction from 23±3% (N=6) to 33±2% (N=13), while the 1 mg/kg dose decreased (P<0.05) the infarct size in CHF rats from 21.7±1.4% (N=7) to 15.9±0.7% (N=3) and prevented (P<0.05) dilata¬tion of the left ventricle in CHF rats in diastole (1.0±0.1 cm, N=6) to 0.9±0.1 cm, N=10) and in systole (0.9±0.1 cm, N=6) to 0.8±0.1, N=10). These study results suggest that this new NHE-1 inhibitor may be potentially useful in treating CHF with an improvement in maladaptive left ventricle remodeling. Because the mechanism of action of this agent is entirely different than the currently applied approach in treating CHF that focuses on aggressive neuro-hormonal blockade and because this agent does not adversely affect important hemodynamic variables, further investigations with this agent may be warranted.

Trefoil factor 2 activation of CXCR4 requires calcium mobilization to drive epithelial repair in gastric organoids.

Determining the signalling cascade of epithelial repair, using murine gastric organoids, allows definition of regulatory processes intrinsic to epithelial cells, at the same time as validating and dissecting the signalling cascade with more precision than is possible in vivo Following single cell damage, intracellular calcium selectively increases within cells adjacent to the damage site and is essential for promoting repair. Trefoil factor 2 (TFF2) acts via chemokine C-X-C receptor 4 and epidermal growth factor receptor signalling, including extracellular signal-regulated kinase activation, to drive calcium mobilization and promote gastric repair. Sodium hydrogen exchanger 2, although essential for repair, acts downstream of TFF2 and calcium mobilization. The gastric mucosa of the stomach is continually exposed to environmental and physiological stress factors that can cause local epithelial damage. Although much is known about the complex nature of gastric wound repair, the stepwise process that characterizes epithelial restitution remains poorly defined. The present study aimed to determine the effectors that drive gastric epithelial repair using a reductionist culture model. To determine the role of trefoil factor 2 (TFF2) and intracellular calcium (Ca2+ ) mobilization in gastric restitution, gastric organoids were derived from TFF2 knockout (KO) mice and yellow Cameleon-Nano15 (fluorescent calcium reporter) transgenic mice, respectively. Inhibitors and recombinant protein were used to determine the upstream and downstream effectors of gastric restitution following photodamage (PD) to single cells within the gastric organoids. Single cell PD resulted in parallel events of dead cell exfoliation and migration of intact neighbouring cells to restore a continuous epithelium in the damage site. Under normal conditions following PD, Ca2+ levels increased within neighbour migrating cells, peaking at ∼1min, suggesting localized Ca2+ mobilization at the site of cell protrusion/migration. TFF2 KO organoids exhibit delayed repair; however, this delay can be rescued by the addition of exogenous TFF2. Inhibition of epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK)1/2 or a TFF2 receptor, chemokine C-X-C receptor 4 (CXCR4), resulted in significant delay and dampened Ca2+ mobilization. Inhibition of sodium hydrogen exchanger 2 (NHE2) caused significant delay but did not affect Ca2+ mobilization. A similar delay was observed in NHE2 KO organoids. In TFF2 KO gastric organoids, the addition of exogenous TFF2 in the presence of EGFR or CXCR4 inhibition was unable to rescue repair. The present study demonstrates that intracellular Ca2+ mobilization occurs within gastric epithelial cells adjacent to the damage site to promote repair by mechanisms that involve TFF2 signalling via CXCR4, as well as activation of EGFR and ERK1/2. Furthermore NHE2 is shown to be important for efficient repair and to operate via a mechanism either downstream or independent of calcium mobilization.

Intestinal phosphate absorption: The paracellular pathway predominates?

This review summarizes the work on transcellular intestinal phosphate absorption, arguing why this pathway is not the predominant pathway in humans consuming a "Western" diet. We then highlight the recent evidence which is strongly consistent with paracellular intestinal phosphate absorption mediating the bulk of intestinal phosphate absorption in humans.

Potential mechanisms underlying the cardiovascular benefits of sodium glucose cotransporter 2 inhibitors: a systematic review of data from preclinical studies.

There is growing evidence from Phase III randomized clinical trials of the cardiovascular benefits of sodium glucose cotransporter 2 (SGLT2) inhibitors in patients with diabetes mellitus. It is hypothesized that these benefits are mediated by mechanisms other than glucose control. To address this, we performed a systematic review of data from preclinical studies examining the direct cardioprotective effects of SGLT2 inhibitors. Medline, EMBASE, CINAHL, and International Pharmaceutical Abstracts databases were searched for preclinical studies that examined the potential cardioprotective effects of SGLT2 inhibitors. Submission documents to the US Food and Drug Administration, European Medicines Agency, and Japanese Pharmaceutical and Medical Devices Agency for the registration of SGLT2 inhibitors were also reviewed. A total of 36 reports were included in the final analysis. The potential direct cardiovascular benefits of SGLT2 inhibitors include: augmentation of signal transducer and activator of transcription 3; inhibition of sodium hydrogen exchange; reduction of atherosclerosis; modulation of natriuretic peptides; vasodilation; modulation of sympathetic tone; and reduction of inflammation, oxidative stress, endoplasmic reticulum stress, and cardiac glucose uptake via down-regulation of SGLT1 expression. There are a number of mechanisms by which SGLT2 inhibitors may exert cardiovascular benefits beyond glycaemic control.

Empagliflozin effects on ischemic contracture and I/R injury in isolated mouse hearts perfused with or without insulin

IntroductionThe kidney‐targeted Empagliflozin (EMPA) has shown large unexpected cardiovascular benefits, which cannot be explained by general cardiovascular risk factors. We recently reported that EMPA has sodium hydrogen exchanger (NHE) inhibition properties in isolated cardiomyocytes. Classic NHE inhibitors such as Cariporide (CARI) delay ischemic contracture onset and reduce ischemia reperfusion (I/R) injury in the heart. Here we examined whether EMPA delays contracture onset and reduces I/R injury. Both normal‐ and low‐glycogen hearts were used, because the rate of glycogen depletion during ischemia affects contracture onset and IR injury.Methods/ResultsIsolated mouse hearts were perfused with and without 50 mU/L insulin, to create normal‐ and low‐glycogen hearts respectively, and subjected to 25 min I and 120 min R. 1μM EMPA, 10μM cariporide (CARI; positive control) or vehicle was administered prior to ischemia until 10 minutes post‐reperfusion. In normal‐glycogen hearts, EMPA and CARI did not change ischemic contracture (in seconds, vehicle 1056±56, EMPA 900±44, CARI 880±84) and IR injury (infarct size (%): vehicle 59±6, Empa 62±10, Cari 68±4), however in low‐glycogen hearts, both EMPA and CARI delayed ischemic contracture onset (vehicle 459±25, EMPA 559±22, CARI 588±31). Higher EMPA concentration further delayed contracture onset. Only CARI reduced I/R injury (from 51±6 to 34±5). The presence of insulin (same concentration used) did not alter NHE activity, nor the ability of CARI or EMPA to inhibit NHE, in isolated cardiomyocytes. The increased IR injury in normal‐glycogen hearts was associated with increased end‐ischemic lactate and glucose‐6‐phosphate accumulation, and consequently decreased mitochondrial hexokinase ll.ConclusionEMPA does not protect against I/R injury in isolated hearts, yet EMPA delayed ischemic contracture onset in low‐glycogen hearts, suggesting a direct cardiac, ATP preserving, effect of EMPA during ischemia. Cardiac glycogen content interferes with the effects of NHE inhibitors on I/R injury in isolated hearts. These data indicate that empagliflozin and cariporide may inhibit NHE in different manners.Support or Funding InformationNone.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Sodium-hydrogen exchange inhibition attenuates glycoside-induced hypertrophy in rat ventricular myocytes.

Sodium-hydrogen exchange inhibition attenuates glycoside-induced hypertrophy in rat ventricular myocytes.

Does Neprilysin Inhibition Potentiate or Minimize the Adverse Effects of Glucagon-Like Peptide-1 Receptor Agonists in Chronic Heart Failure?

Heart failure and diabetes commonly coexist, and therefore, drugs that favorably influence the natural history of each of these two disorders are likely to be prescribed together. 1 Packer M. Activation and inhibition of sodium-hydrogen exchanger is a mechanism that links the pathophysiology and treatment of diabetes mellitus with that of heart failure. Circulation. 2017; 136: 1548-1559 Crossref PubMed Scopus (138) Google Scholar In patients with type 2 diabetes, glucagon-like peptide-1 (GLP-1) receptor agonists decrease the risk of major adverse cardiovascular events, 2 Marso S.P. Daniels G.H. Brown-Frandsen K. Kristensen P. Mann J.F. Nauck M.A. et al. Liraglutide and cardiovascular outcomes in type 2 diabetes. N Engl J Med. 2016; 375: 311-322 Crossref PubMed Scopus (4190) Google Scholar , 3 Marso S.P. Bain S.C. Consoli A. Eliaschewitz F.G. Jódar E. Leiter L.A. et al. Semaglutide and cardiovascular outcomes in patients with type 2 diabetes. N Engl J Med. 2016; 375: 1834-1844 Crossref PubMed Scopus (2977) Google Scholar and liraglutide is approved to reduce cardiovascular death, nonfatal myocardial infarction and nonfatal stroke. 4 Tucker M.E. FDA grants liraglutide cardiovascular events indication. https://www.medscape.com/viewarticle/884726Date: 2017 Date accessed: November 12, 2017 Google Scholar Analogously, in patients with chronic heart failure and a reduced ejection fraction, neprilysin inhibition has been shown to decrease the risk of cardiovascular death and hospitalization for heart failure, 5 McMurray J.J. Packer M. Desai A.S. Gong J. Lefkowitz M.P. Rizkala A.R. et al. Angiotensin-neprilysin inhibition versus enalapril in heart failure. N Engl J Med. 2014; 371: 993-1004 Crossref PubMed Scopus (3899) Google Scholar and sacubitril/valsartan is approved to reduce cardiovascular morbidity and mortality. Since the shared goal of treating diabetes and heart failure is to minimize the occurrence of life-threatening cardiovascular events, it is likely that physicians will be prescribing GLP-1 receptor agonists and neprilysin inhibitors concurrently in the same patients.

Activation and Inhibition of Sodium-Hydrogen Exchanger Is a Mechanism That Links the Pathophysiology and Treatment of Diabetes Mellitus With That of Heart Failure.

The mechanisms underlying the progression of diabetes mellitus and heart failure are closely intertwined, such that worsening of one condition is frequently accompanied by worsening of the other; the degree of clinical acceleration is marked when the 2 coexist. Activation of the sodium-hydrogen exchanger in the heart and vasculature (NHE1 isoform) and the kidneys (NHE3 isoform) may serve as a common mechanism that links both disorders and may underlie their interplay. Insulin insensitivity and adipokine abnormalities (the hallmarks of type 2 diabetes mellitus) are characteristic features of heart failure; conversely, neurohormonal systems activated in heart failure (norepinephrine, angiotensin II, aldosterone, and neprilysin) impair insulin sensitivity and contribute to microvascular disease in diabetes mellitus. Each of these neurohormonal derangements may act through increased activity of both NHE1 and NHE3. Drugs used to treat diabetes mellitus may favorably affect the pathophysiological mechanisms of heart failure by inhibiting either or both NHE isoforms, and drugs used to treat heart failure may have beneficial effects on glucose tolerance and the complications of diabetes mellitus by interfering with the actions of NHE1 and NHE3. The efficacy of NHE inhibitors on the risk of cardiovascular events may be enhanced when heart failure and glucose intolerance coexist and may be attenuated when drugs with NHE inhibitory actions are given concomitantly. Therefore, the sodium-hydrogen exchanger may play a central role in the interplay of diabetes mellitus and heart failure, contribute to the physiological and clinical progression of both diseases, and explain certain drug-drug and drug-disease interactions that have been reported in large-scale randomized clinical trials.

Effects of Sodium-Glucose Cotransporter 2 Inhibitors for the Treatment of Patients With Heart Failure

ImportanceOnly 1 class of glucose-lowering agents—sodium-glucose cotransporter 2 (SGLT2) inhibitors—has been reported to decrease the risk of cardiovascular events primarily by reducing the risk of the development or progression of heart failure. In a landmark trial called Empagliflozin, Cardiovascular Outcomes, and Mortality in Type 2 Diabetes [EMPA-REG Outcomes], long-term treatment with empagliflozin prevented fatal and nonfatal heart failure events but did not reduce the risk of myocardial infarction or stroke in diabetic patients.ObservationsThe beneficial effect of SGLT2 inhibitors on heart failure cannot be explained by their actions on glycemic control or as osmotic diuretics. Instead, in the kidneys, SGLT2 functionally interacts with the sodium-hydrogen exchanger, which is responsible for the majority of sodium tubular reuptake following filtration. The activity of sodium-hydrogen exchanger is markedly increased in patients with heart failure and may be responsible for both resistance to diuretics and to endogenous natriuretic peptides. In addition, in the heart, empagliflozin appears to inhibit sodium-hydrogen exchange, which may in turn lead to a reduction in cardiac injury, hypertrophy, fibrosis, remodeling, and systolic dysfunction. Furthermore, the major pathophysiological derangements of heart failure and a preserved ejection fraction may be mitigated by the actions of SGLT2 inhibitors to reduce blood pressure, body weight, and fluid retention as well as to improve renal function. The benefits of spironolactone in patients with heart failure with either a reduced or a preserved ejection fraction may also be attributable to the actions of the drug to inhibit the sodium-hydrogen exchange mechanism.Conclusions and RelevanceThe benefits of SGLT2 inhibitors in heart failure may be mediated by the inhibition of sodium-hydrogen exchange rather than the effect on glucose reabsorption. This hypothesis has important implications for the design and analysis of large-scale outcomes trials involving diabetic or nondiabetic patients with chronic heart failure.