Proximal Sodium Research Articles

Antihypertensive Effect of Sodium-Glucose Cotransporter 2 Inhibitors and Glucagon-like Peptide 1 Receptor Agonists

An increasing body of evidence shows that new antidiabetic drugs—particularly sodium-glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 (GLP-1) receptor agonists—have a beneficial effect on cardiovascular outcome. The majority of these studies have been performed in patients with heart failure and the results have shown first positive effect on blood pressure (BP) reduction. These effects are more pronounced with SGLT2 inhibitors than with GLP-1 receptor agonists. However, the reasons and mechanisms of action inducing BP reduction are still not sufficiently clear. Proposed mechanisms of SGLT2 inhibitors involve the natriuretic effect, modification of the renin-angiotensin-aldosterone system, and/or the reduction in the sympathetic nervous system. GLP-1 receptor agonists have several mechanisms that are related to glycemic, weight, and BP control. Current data show that SGLT2 inhibitors have a stronger antihypertensive effect than GLP-1 receptor agonists, which is mainly related to their renal effect. Briefly, SGLT2 inhibitors increase the response to diuretics and decrease the meal-related antinatriuretic pressure by lowering post-prandial hyperglycemia and hyperinsulinemia and prevent proximal sodium reabsorption. SGLT2 inhibitors can be used as second-line therapy in patients with diabetes mellitus or heart disease and concomitant hypertension. This article aims to summarize current knowledge regarding the antihypertensive effect of SGLT2 inhibitors and GLP-1 receptor agonists.

Critical Analysis of the Effects of SGLT2 Inhibitors on Renal Tubular Sodium, Water and Chloride Homeostasis and Their Role in Influencing Heart Failure Outcomes.

SGLT2 (sodium-glucose cotransporter 2) inhibitors interfere with the reabsorption of glucose and sodium in the early proximal renal tubule, but the magnitude and duration of any ensuing natriuretic or diuretic effect are the result of an interplay between the degree of upregulation of SGLT2 and sodium-hydrogen exchanger 3, the extent to which downstream compensatory tubular mechanisms are activated, and (potentially) the volume set point in individual patients. A comprehensive review and synthesis of available studies reveals several renal response patterns with substantial variation across studies and clinical settings. However, the common observation is an absence of a large acute or chronic diuresis or natriuresis with these agents, either when given alone or combined with other diuretics. This limited response results from the fact that renal compensation to these drugs is rapid and nearly complete within a few days or weeks, preventing progressive volume losses. Nevertheless, the finding that fractional excretion of glucose and lithium (the latter being a marker of proximal sodium reabsorption) persists during long-term treatment with SGLT2 inhibitors indicates that pharmacological tolerance to the effects of these drugs at the level of the proximal tubule does not meaningfully occur. This persistent proximal tubular effect of SGLT2 inhibitors can be hypothesized to produce a durable improvement in the internal set point for volume homeostasis, which may become clinically important during times of fluid expansion. However, it is difficult to know whether a treatment-related change in the volume set point actually occurs or contributes to the effect of these drugs to reduce the risk of major heart failure events. SGLT2 inhibitors exert cardioprotective effects by a direct effect on cardiomyocytes that is independent of the presence of or binding to SGLT2 or the actions of these drugs on the proximal renal tubule. Nevertheless, changes in the volume set point mediated by SGLT2 inhibitors might potentially act cooperatively with the direct favorable molecular and cellular effects of these drugs on cardiomyocytes to mediate their benefits on the development and clinical course of heart failure.

Abstract P248: Estrogen Replacement Mitigated Blood Pressure Elevation Via Suppression Of Sodium Cotransporter In Angiotensin Ii-infused Ovariectomized Female Rats

Introduction: Female rats with lower proximal sodium transporters are known to excrete natriuresis faster than male rats. However, it is not sure whether the protective effect would be conserved in menopausal rats. Hypothesis: We assessed the hypothesis that ovariectomy would change renal sodium transporters in female rats and the estrogen supplementation could reverse angiotensin II (ANGII)-induced changes in renal sodium transporters and natriuresis. Methods: Six-week female Sprague Dawley rats (n=22) were ovariectomized, and half of them (n=11) were treated with estradiol 2 weeks later for 4 weeks, and then ANGII (n=14) or vehicle (n=8) was infused via osmotic minipumps for 2 weeks. Blood pressure (BP) was measured by the tail-cuff sphygmomanometer. Blood, urine, and kidney samples were collected. Results: The ANGII induced significant BP elevation in ovariectomized (OVX) and OVX with estradiol (OVX+E) rats. OVX affected elevating BP even in the sham rats. Albuminuria significantly increased in ANGII-infused OVX rats and did not change in ANGII-infused OVX+E rats. Urine sodium was significantly decreased in ANGII-infused OVX rats, while it increased in ANGII-infused OVX+E rats. Sodium transporters in the proximal tubule (sodium-hydrogen exchange 3, sodium phosphate cotransporter) were not different between OVX and OVX+E irrespective of ANGII infusion. Among the distal tubule transporters (α/β/γ-epithelial sodium channel (α/β/γENaC), sodium chloride cotransporter (NCC), phosphorylated NCC (pNCC)), pNCC were markedly augmented in ANGII-infused OVX rats, whereas not changed in ANGII-infused OVX+E rats. ANGII infusion affected increasing ANGII type 2 receptor (AT 2 R) in OVX+E rats but did not influence AT 2 R levels in OVX rats. Conclusions: Estradiol has the protective effect from elevating BP in ANGII-infused OVX rats. It was achieved via augmentation of natriuresis, which was connected to the suppression of NCC.

Renal and Vascular Effects of Combined SGLT2 and Angiotensin-Converting Enzyme Inhibition.

Background:The cardiorenal effects of sodium-glucose cotransporter 2 inhibition (empagliflozin 25 mg QD) combined with angiotensin-converting enzyme inhibition (ramipril 10 mg QD) were assessed in this mechanistic study in patients with type 1 diabetes with potential renal hyperfiltration.Methods:Thirty patients (out of 31 randomized) completed this double-blind, placebo-controlled, crossover trial. Recruitment was stopped early because of an unexpectedly low proportion of patients with hyperfiltration. Measurements were obtained after each of the 6 treatment phases over 19 weeks: (1) baseline without treatment, (2) 4-week run-in with ramipril treatment alone, (3) 4-week combined empagliflozin-ramipril treatment, (4) a 4-week washout, (5) 4-week combined placebo-ramipril treatment, and (6) 1-week follow-up. The primary end point was glomerular filtration rate (GFR) after combination treatment with empagliflozin-ramipril compared with placebo-ramipril. GFR was corrected for ramipril treatment alone before randomization. At the end of study phase, the following outcomes were measured under clamped euglycemia (4 to 6 mmol/L): inulin (GFR) and para-aminohippurate (effective renal plasma flow) clearances, tubular sodium handling, ambulatory blood pressure, arterial stiffness, heart rate variability, noninvasive cardiac output monitoring, plasma and urine biochemistry, markers of the renin-angiotensin-aldosterone system, and oxidative stress.Results:Combination treatment with empagliflozin-ramipril resulted in an 8 mL/min/1.73 m2 lower GFR compared with placebo-ramipril treatment (P=0.0061) without significant changes to effective renal plasma flow. GFR decrease was accompanied by a 21.3 mL/min lower absolute proximal fluid reabsorption rate (P=0.0092), a 3.1 mmol/min lower absolute proximal sodium reabsorption rate (P=0.0056), and a 194 ng/mmol creatinine lower urinary 8-isoprostane level (P=0.0084) relative to placebo-ramipril combination treatment. Sodium-glucose cotransporter 2 inhibitor/angiotensin-converting enzyme inhibitor combination treatment resulted in additive blood pressure–lowering effects (clinic systolic blood pressure lower by 4 mm Hg [P=0.0112]; diastolic blood pressure lower by 3 mm Hg [P=0.0032]) in conjunction with a 94.5 dynes × sex/cm5 lower total peripheral resistance (P=0.0368). There were no significant changes observed to ambulatory blood pressure, arterial stiffness, heart rate variability, or cardiac output with the addition of empagliflozin.Conclusions:Adding sodium-glucose cotransporter 2 inhibitor treatment to angiotensin-converting enzyme inhibitor resulted in an expected GFR dip, suppression of oxidative stress markers, additive declines in blood pressure and total peripheral resistance. These changes are consistent with a protective physiologic profile characterized by the lowering of intraglomerular pressure and related cardiorenal risk when adding a sodium-glucose cotransporter 2 inhibitor to conservative therapy.Registration:URL: https://www.clinicaltrials.gov; Unique identifier: NCT02632747.

20-OR: The Renal and Vascular Effects of Combined SGLT2 and Angiotensin Converting Enzyme Inhibition

The goal of this mechanistic trial was to determine the kidney and cardiovascular effects of combined treatment with an SGLT2i (empagliflozin 25mg QD) and an ACEi (ramipril 10mg QD) for 4 weeks in patients at risk of renal hyperfiltration. In this randomized, double-blind, placebo-controlled, cross-over trial, measurements were obtained following each of the 4 treatment phases: 1) no treatment, 2) 4-week ramipril treatment alone, 3) 4-week empagliflozin-ramipril combination treatment, and 4) 4-week placebo-ramipril combination treatment. The primary endpoint was GFR after empagliflozin-ramipril treatment compared to placebo-ramipril. At the end of each study phase the following measurements were performed under clamped euglycemia (4-6 mmol/L) : inulin (GFR) and paraaminohippurate (effective renal plasma flow, ERPF) clearances, tubular sodium handling, ambulatory blood pressure, arterial stiffness, heart rate variability, non-invasive cardiac output monitoring, plasma and urine biochemistry. Empagliflozin-ramipril treatment resulted in an 8ml/min/1.73m2 lower GFR (p=0.0061) , lower absolute proximal fluid reabsorption rate (p=0.0092) , lower absolute proximal sodium reabsorption rate (p=0.0056) , and lower urinary 8-isoprostane (p=0.0084) relative to placebo-ramipril treatment. Empagliflozin-ramipril treatment resulted in additive blood pressure lowering effects (SBP p=0.0112; DBP p=0.0032) and a lower total peripheral resistance (p=0.0368) . There were no other significant changes observed with the addition of empagliflozin. SGLT2i-ACEi combination treatment resulted in an expected GFR “dip”, suppression of oxidative stress markers, and additive declines in blood pressure and total peripheral resistance in this mechanistic study. These changes are consistent with a protective physiological profile characterized by the lowering of intraglomerular pressure and related cardiorenal risk when adding an SGLT2i to conservative therapy. Disclosure Y. Lytvyn: None. K. Kimura: Employee; 3Boehringer Ingelheim Canada Ltd./Ltée. N. Peter: Employee; Boehringer Ingelheim Pharma GmbH & Co.KG. V.S. Lai: Advisory Panel; Baxter. J. Tse: None. L. Cham: None. B.A. Perkins: Advisory Panel; Abbott Diabetes, Insulet Corporation, Sanofi. Board Member; Novo Nordisk. Research Support; BMO Bank of Montreal, Novo Nordisk. Other Relationship; Abbott Diabetes, Insulet Corporation, Medtronic, Novo Nordisk. N. Soleymanlou: Employee; Boehringer Ingelheim Pharmaceuticals Inc., Boehringer Ingelheim Pharmaceuticals Inc. D. Cherney: Research Support; Boehringer Ingelheim-Lilly, Merck, Janssen, Sanofi, AstraZeneca and Novo-Nordisk. Other Relationship; AbbVie Inc., AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Janssen Research & Development, LLC, Lilly, Maze, BMS, CSL-Behring, Merck, Otsuka, Novartis and Novo-Nordisk, Mitsubishi Tanabe Pharma Corporation, Sanofi. Funding Boehringer Ingelheim and CIHR, Diabetes Canada and the Heart and Stroke Richard Lewar Centre of Excellence and the Heart and Stroke Foundation of Canada

Twenty-Four Hour Blood Pressure Response to Empagliflozin and Its Determinants in Normotensive Non-diabetic Subjects.

BackgroundSodium–glucose co-transport 2 inhibitors (SGLT2i) lower blood pressure (BP) in normotensive subjects and in hypertensive and normotensive diabetic and non-diabetic patients. However, the mechanisms of these BP changes are not fully understood. Therefore, we examined the clinical and biochemical determinants of the BP response to empagliflozin based on 24-h ambulatory BP monitoring.MethodsIn this post-hoc analysis of a double-blind, randomized, placebo-controlled study examining the renal effects of empagliflozin 10 mg vs. placebo in untreated normotensive non-diabetic subjects, the 1-month changes in 24 h ambulatory BP were analyzed in 39 subjects (13 placebo/26 empagliflozin) in regard to changes in biochemical and hormonal parameters.ResultsAt 1 month, empagliflozin 10 mg decreased 24-h systolic (SBP) and diastolic (DBP) BP significantly by −5 ± 7 mmHg (p < 0.001) and −2 ± 6 mmHg (p = 0.03). The effect on SBP and DBP was more pronounced during nighttime (resp. −6 ± 11 mmHg, p = 0.004; −4 ± 7 mmHg, p = 0.007). The main determinants of daytime and nighttime SBP and DBP responses were baseline BP levels (for daytime SBP: coefficient −0.5; adj. R2: 0.36; p = 0.0007; for night-time SBP: coefficient −0.6; adj. R2: 0.33; p = 0.001). Although empaglifozin induced significant biochemical changes, none correlated with blood pressure changes including urinary sodium, lithium, glucose and urate excretion and free water clearance. Plasma renin activity and plasma aldosterone levels increased significantly at 1 month suggesting plasma volume contraction, while plasma metanephrine and copeptin levels remained the same. Renal resistive indexes did not change with empagliflozin.ConclusionSGLT2 inhibition lowers daytime and nighttime ambulatory systolic and diastolic BP in normotensive non-diabetic subjects. Twenty-four jour changes are pronounced and comparable to those described in diabetic or hypertensive subjects. Baseline ambulatory BP was the only identified determinant of systolic and diastolic BP response. This suggests that still other factors than sustained glycosuria or proximal sodium excretion may contribute to the resetting to lower blood pressure levels with SGLT2 inhibition.Clinical Trial Registration:[https://www.clinicaltrials.gov], identifier [NCT03093103].

Efficacy and Safety of Dapagliflozin in Children With Inherited Proteinuric Kidney Disease: A Pilot Study

Efficacy and Safety of Dapagliflozin in Children With Inherited Proteinuric Kidney Disease: A Pilot Study

Clinic and ambulatory blood pressure in relation to the interaction between plasma advanced glycation end products and sodium dietary intake and renal handling.

Advanced glycation end product (AGE) clearance may cause renal tubular injuries, such as changes in sodium reabsorption. We hypothesize that AGEs interact with sodium metabolism to influence blood pressure (BP). The study participants were outpatients who were suspected of having hypertension but had not been treated with antihypertensive medication. Clinic and ambulatory blood pressures were measured at baseline (n = 989) and during follow-up (median, 4.4 years, n = 293). Plasma AGE concentrations were measured by enzyme-linked immunosorbent assay. Twenty-four-hour urine was collected for measurements of creatinine, sodium and lithium. In a cross-sectional analysis (n = 989), subjects in the top quintile versus quintiles 1-4 of plasma AGE concentration had significantly (P ≤ 0.004) lower fractional excretion of lithium (18.3% vs. 21.6%) and fractional distal reabsorption rate of sodium (95.0% vs. 95.8%) but similar BP (P ≥ 0.25). However, there was an interaction between plasma AGE concentration and urinary sodium excretion in relation to diastolic BP (P ≤ 0.058). Only in participants with low urinary sodium chloride excretion (≤6 grams/day, n = 189), clinic (84.3 vs. 80.2 mmHg), 24-h (83.9 vs. 80.4 mmHg), daytime (87.8 vs. 84.8 mmHg) and nighttime (75.1 vs. 72.1 mmHg) diastolic BP at baseline were higher (P ≤ 0.05) in the top quintile than in quintiles 1-4 of plasma AGE concentration. In the longitudinal study (n = 383), similar trends were observed, with significant (P ≤ 0.05) differences in the increment in daytime diastolic BP (6.8 vs. -1.7 mmHg) and incidence of ambulatory and treated hypertension (hazard ratio 3.73) during follow-up. In conclusion, AGEs were associated with high BP, probably via enhanced proximal sodium handling and on low dietary sodium intake.

Fetal Undernutrition Programming, Sympathetic Nerve Activity, and Arterial Hypertension Development.

A wealth of evidence showed that low birth weight is associated with environmental disruption during gestation, triggering embryotic or fetal adaptations and increasing the susceptibility of progeny to non-communicable diseases, including metabolic and cardiovascular diseases, obesity, and arterial hypertension. In addition, dietary disturbance during pregnancy in animal models has highlighted mechanisms that involve the genesis of arterial hypertension, particularly severe maternal low-protein intake (LP). Functional studies demonstrated that maternal low-protein intake leads to the renal decrease of sodium excretion and the dysfunction of the renin-angiotensin-aldosterone system signaling of LP offspring. The antinatriuretic effect is accentuated by a reduced number of nephron units and glomerulosclerosis, which are critical in establishing arterial hypertension phenotype. Also, in this way, studies have shown that the overactivity of the central and peripheral sympathetic nervous system occurs due to reduced sensory (afferent) renal nerve activity. As a result of this reciprocal and abnormal renorenal reflex, there is an enhanced tubule sodium proximal sodium reabsorption, which, at least in part, contributes directly to arterial hypertension development in some of the programmed models. A recent study has observed that significant changes in adrenal medulla secretion could be involved in the pathophysiological process of increasing blood pressure. Thus, this review aims to compile studies that link the central and peripheral sympathetic system activity mechanisms on water and salt handle and blood pressure control in the maternal protein-restricted offspring. Besides, these pathophysiological mechanisms mainly may involve the modulation of neurokinins and catecholamines pathways.

Pathogenetical aspects of tubulointerstitial syndrome development in alloxan-induced experimental diabetes mellitus

Annotation. The aim of our study was to explore the pathogenetical aspects of tubulointerstitial syndrome development in alloxan-induced experimental diabetes mellitus. The experiments were carried out on 20 white non-linear mature male rats, 10 with experimental diabetes mellitus (EDМ) induced by intraperitoneal administration of alloxan at a dose of 160 mg/kg of body weight, 10 intact rats served as the control group. 25 days after administration of the diabetogenic substance, the animals were withdrawn from the experiment. The concentration of sodium and potassium ions in urine and blood plasma samples was determined, followed by calculation (considering water-induced 2-hour diuresis and endogenous creatinine clearance) of glomerular filtration rate, electrolyte excretion, their filtration rate, absolute and relative reabsorption, clearance, their proximal and distal renal transport. Removed after decapitation rats’ kidneys were dissected to 3 parts – renal cortex, medulla and papilla, sodium and potassium content was determined in water-extract of the corresponding part of the renal parenchyma, and papillary-cortical, papillary-medullar and medullary-cortical concentration ion gradients were calculated. Significant suppression of papillary-medullar and papillary-cortical concentration sodium gradients, as well as a slight limitation of its medullary-cortical gradient were established. The concentration potassium gradients were significantly reduced. Statistical processing of the obtained data was carried out with the determination of the average value, standard deviations. To assess the probability of the difference between the study groups used non-parametric Mann-Whitney ranking criterion according to the algorithms implemented in the computer program “Statistica for Windows”, “Version 8.0”. There was a decrease of the sodium-potassium ratio in urine, enhanced urinary excretion of potassium and an increase of its content in urine, as well as intensification of absolute transtubular sodium transport due to equivalent augmentation of the filtration charge of this cation, increase of proximal sodium reabsorption and, to a lesser degree, – of distal one. The distal and proximal sodium reabsorption, reduced to a unit of active nephrons, was found to be decreased, and the relative reabsorption of the cation significantly exceeded the control values, contributing to the limitation of natriuresis. The results of the study suggest that in 26-day alloxan-induced experimental diabetes hemodynamic-hyperperfusion overload on the tubular apparatus of the kidney causes the development of relative insufficiency of the proximal and distal tubules, disorders of hormone-dependent reabsorption of cations, limitation of regulatory influence of aldosterone and ADH with further tubulointerstitial disturbances that unable adequate osmotic concentration of urine.

Dynamics of proximal and distal transport of sodium in case of bilateral gonadectomy and the efficacy of hormonal replacement therapy

Introduction. The characteristic feature of current trauma in Ukraine and in the world is the prevalence of highly energetic skeletal trauma which is followed by the appearance of combined and multiple injuries with the formation of multiorgan dysfunction and failure. Because of the increase of life duration, the high interest of current traumatology is the investigation process of trauma course in older people. Among them the high interest is given to females in postmenopausal period. The decrease of estrogen level causes very unfavorable ground for the trauma course. However, the influence of severe trauma on changes in proximal and distal transport of sodium in case of hypoestrogenic state is not fully investigated. There is no available data concerning the effectiveness of hormonal replacement therapy in this condition.The goal of the study: is to investigate the influence of cranioskeletal injury on the dynamics of proximal and distal sodium transport in rats with bilateral ovariectomy in the period of late changes of traumatic disease and evaluate the effectiveness of hormonal replacement therapy. Materials and methods. Experiments were performed on 42 non-linear white female rats with the weight of 200-220 g. The model of hypoestrogenic state was performed via surgical removal of the ovaries. 1 month after the gonadectomy in rats skeletal trauma was performed. As a treatment option in one subgroup of rats with gonadectomy and cranioskeletal injury we performed hormonal replacement therapy. The control groups were formed by intact rats and osteoporotic rats 1 month after gonadectomy which were not injured. In control groups and after 1 and 2 months of posttraumatic period we were investigating the functional state of kidneys by performing the water upload method. Afterwards we performed the laboratory checkup of creatinine and sodium levels in serum and urine and additionally calculated the values of proximal and distal sodium transport. Results and its discussion. It was found that the level of proximal and distal sodium transport depends on the estrogen level, the decrease of its secretion leads to the decrease of sodium reabsorption in tubules and the increase in secretion. These changes were more prevalent in proximal tubules. In the course of trauma 1 month after posttraumatic period the value was decreasing in both research groups. However, in rats with gonadectomy the changes were much bigger and stayed at the same level until the 2nd month of the experiment. In rats without gonadectomy these values were achieving the same levels as control group until 2nd month. The use of combined hormonal replacement therapy caused the increase of proximal and distal sodium transport in comparison to the group without receiving treatment. The results that we got though was not achieving the level of rats without gonadectomy, but it showed the perspective for the use of combined hormonal replacement therapy in case of hypoestrogenic state for the decrease of renal dysfunction. Conclusions: Bilateral ovariectomy in female rats after 1 month shows the decrease of proximal and distal sodium levels comparing to rats with preserved gonads. The cranioskeletal injury that happened 1 month after bilateral ovariectomy causes the much bigger decrease of proximal and distal sodium transport comparing to rats with preserved gonads. The use of combined hormonal replacement therapy caused lower changes in proximal and distal sodium transport comparing to rats without this treatment.

Acute and Chronic Effects of SGLT2 Inhibitor Empagliflozin on Renal Oxygenation and Blood Pressure Control in Nondiabetic Normotensive Subjects: A Randomized, Placebo-Controlled Trial.

BackgroundThe sodium/glucose cotransporter 2 inhibitor empagliflozin has cardiorenal protective properties through mechanisms beyond glucose control. In this study we assessed whether empagliflozin modifies renal oxygenation as a possible mechanism of renal protection, and determined the metabolic, renal, and hemodynamic effects of empagliflozin in nondiabetic subjects.Methods and ResultsIn this double‐blind, randomized, placebo‐controlled study, 45 healthy volunteers underwent blood and urine sampling, renal ultrasound, and blood‐oxygenation‐level–dependent magnetic resonance imaging before and 180 minutes after administration of 10 mg empagliflozin (n=30) or placebo (n=15). These examinations were repeated after 1 month of daily intake. Cortical and medullary renal oxygenation were not affected by the acute or chronic administration of empagliflozin, as determined by 148 renal blood‐oxygenation‐level–dependent magnetic resonance imaging examinations. Empagliflozin increased glucosuria (24‐hour glucosuria at 1 month: +50.1±16.3 g). The acute decrease in proximal sodium reabsorption, as determined by endogenous fractional excretion of lithium (−34.6% versus placebo), was compensated at 1 month by a rise in plasma renin activity (+28.6%) and aldosterone (+55.7%). The 24‐hour systolic and diastolic ambulatory blood pressures decreased significantly after 1 month of empagliflozin administration (−5.1 and −2.0 mm Hg, respectively). Serum uric acid levels decreased (−28.4%), hemoglobin increased (+1.7%), and erythropoietin remained the same.ConclusionsEmpagliflozin has a rapid and significant effect on tubular function, with sustained glucosuria and transient natriuresis in nondiabetic normotensive subjects. These effects favor blood pressure reduction. No acute or sustained changes were found in renal cortical or medullary tissue oxygenation. It remains to be determined whether this is the case in nondiabetic or diabetic patients with congestive heart failure or kidney disease. REGISTRATION: URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT03093103.

Bothrops alternatus Snake Venom Induces Cytokine Expression and Oxidative Stress on Renal Function.

Envenomation caused by Bothrops alternatus is common in Southern Brazil. Acute Kidney Injury occurs after Bothrops snakebite and more information is necessaryrequired to understand its mechanism. The objective was to evaluate the effect of Bothrops alternatus venom (BaV) on renal cells and rat isolated kidney function. Wistar rats (n = 6, weighing 260-320 g) were perfused with a Krebs-Henseleit solution containing 6 g 100 mL-1 of bovine serum albumin. After 30 minutes, the kidneys were perfused with BaV to a final concentration of 1 and 3 μgmL-1; and subsequently were evaluated for Perfusion Pressure (PP), Renal Vascular Resistance (RVR), Urinary Flow (UF), Glomerular Filtration Rate (GFR), and percentage of electrolyte tubular transport. Renal histological analysis, cytokine release, oxidative stress and cytotoxicity in renal proximal tubular cells were assessed. BaV reduced PP, RVR, GFR, UF, total and proximal sodium transport (%TNa+), and chloride (%TCl-) in the isolated kidney perfusion model. Histological analysis of perfused kidneys disclosed the presence of proteinaceous material in the glomeruli and renal tubules, vacuolar tubular epithelial cell degeneration, Bowman's capsule degeneration, swelling of glomerular epithelial cells, glomerular atrophy and degeneration, and the presence of intratubular protein. Cytokine release (TNF-α, IL-1β, IL-10) and oxidative stress were increased in the kidneys. The viability of LLC-MK2 cells (IC50: 221.3 μg/mL) was decreased by BaV and necrosis was involved in cell death. These findings indicate that BaV modifies functional parameters in an isolated perfused kidney model and has cytotoxic effects on renal lineage cells.

Abstract P2038: A Nobel I551F Mutant of Sodium Handling Transporter NBCe1 Has Cytosolic Retention and Diminishes Transport Activity

The electrogenic Na + /HCO 3 - cotransporter NBCe1 is expressed in many organs and controls sodium handling. NBCe1 homozygous mutation causes not only severe hypotension but also proximal renal tubular acidosis in human and rodents. Here we shows the functional significance of the mutations reported from NCBI database on NBCe1 function. We identified 14 mutations in NBCe1 variant A(kidney type), resulting in the single amino acid substitutions, A425T, F461L, A465S, L494F, N503H, A518T, A518G, I523V, V533D, Y535H, I551F, Y554H, M753V, and L785I. Immunocytological analysis with confocal microscopy revealed only I551F mutant was expressed predominantly in the cytoplasm of HEK 293 cells and MDCK cells. Functional analysis using Xenopus oocytes revealed that I551F mutant had a significantly reduced activity corresponding to 52% of that of wild-type (p&lt;0.01). Whole and biotinylated western blotting in HEK293 cells confirmed that the surface expression of I551F mutant was significantly reduced. Deglycosylation study revealed that I551F has impaired N-glycosylation. To examine the role of I551 in more detail, we also examined the properties of artificial mutants I551A, I551P, I551K, I551R, I551D and I551E in HEK293 and MDCK cells. All of artificial mutants were properly expressed in the plasma membrane. By contrast, only I551F mutant was predominantly expressed in cytoplasmic regions. These results indicate that I551F mutation inactivates the NBCe1 function with cytoplasmic retention. Because NBCe1 plays a major role in renal proximal sodium and bicarbonate reabsorption, I551F mutation may be associated with the disturbance in systemic acid-base balance or the changes in blood pressure.

Insulin Resistance and Renal Sodium Handling Influence Arterial Stiffness in Hypertensive Patients with Prevailing Sodium Intake.

Insulin resistance and renal tubular sodium handling influence arterial structure and function and play an essential role in salt-sensitive forms of hypertension. In a population with prevailing sodium consumption, we assessed the relationship between cardiovascular phenotypes (peripheral and central blood pressures, elastic properties of large arteries, the left ventricular structure) and sodium handling parameters (daily urinary sodium excretion, fractional urinary lithium excretion in proximal-FELi and distal tubules), as a function of insulin sensitivity-measured by homeostasis model assessment-insulin resistance (HOMA-IR), leptin-to-adiponectin (L/A) ratio, and homeostasis model assessment-adiponectin (HOMA-AD). In patients with FELi below the median value (corresponding to the group with increased proximal sodium reabsorption) and higher insulin resistance as measured by HOMA-IR, pulse wave augmentation indexes were significantly higher-AIxP (99.4% vs. 86.2%; P = 0.007), AIxC1 (159.4% vs. 144.2%; P = 0.04), and AIxC2 (36.1% vs. 28.3%; P = 0.02), than in patients with lower insulin resistance. The same trend was observed in relation to L/A ratio-AIxP (98.7% vs. 87.1%; P = 0.005), AIxC1 (158.6% vs. 144.5%; P = 0.02), and AIxC2 (35.6% vs. 28.5%; P = 0.01) and HOMA-AD-AIxP (99.7% vs. 83.8%; P = 0.001), AIxC1 (160.5% vs. 140.3%; P = 0.007), and AIxC2 (36.6% vs. 26.3%; P = 0.003). Such relationships were not observed in patients with FELi above the median value. In the hypertensive population with prevailing sodium intake, insulin resistance and increased sodium reabsorption in proximal tubules may affect arterial wall function.

Acetazolamide Administration Restores the Blood Pressure Lowering Effect of Tempol in Female SHR

The mechanisms responsible for the sex differences in blood pressure (BP) in humans are not clear. Over the past several years, we have studied the spontaneously hypertensive rat (SHR) as a model of sex differences in BP control. Oxidative stress (OS) plays a major role in BP regulation in preclinical studies. There is a sex difference in the BP responses to pro‐oxidants and antioxidants in the SHR. In contrast to males, BP in female SHR does not decrease in response to Tempol or Apocynin. Acetazolamide (Aceta) inhibits proximal tubular sodium reabsorption, increasing sodium delivery to the distal tubule which increases distal tubule OS. We tested the hypothesis that an increase in sodium delivery in the distal tubule will restore the BP lowering effects of Tempol in female SHR.Materials and MethodsFemale SHR, aged twenty weeks, were implanted with radiotelemetry transmitters and following a two week recovery period, baseline mean arterial pressure (MAP) was measured 24 hrs per day. All rats were then given Aceta (100 mg/kg/day sc) for 14 days (n=14). After this period, a group of rats were randomized to receive Tempol (1mmol/L) in drinking water for an additional two weeks (Aceta + Tempol) (n=7/grp) and BP was compared to controls who received Aceta only (n=7/grp). MAP was measured continuously throughout the treatment periods.ResultsAt baseline, MAP was similar in both groups of female SHR (144 ± 1 vs. 145 ± 1 mmHg). Aceta administration for two weeks caused a 10 mmHg reduction in MAP, which was similar in both group of rats (132 ± 1 vs. 131 ± 1 mmHg, p=0.43). Tempol administration significantly lowered MAP in presence of Aceta (138 ± 1vs. 122 ± 1 mmHg, p&lt;0.0001). Body weight was similar between Aceta and Aceta + Tempol groups (200.3 ± 2.0g vs. 192.2 ± 4.0 g).In conclusion, our data suggest that there are sex differences in proximal sodium reabsorption that may impact OS in SHR. By increasing sodium delivery to the distal nephron with acetazolamide, the BP lowering effect of Tempol is restored in female SHR. These data suggest that different mechanisms may control oxidative stress and blood pressure in male and female SHR.Support or Funding InformationThis project was funded by NIH R01 HL135089, P20 GM12334, &amp; PO1HL51971This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Superabsorbent Poly(isoprenecarboxylate) Hydrogels from Glucose

Isoprenecarboxylic acid (ICA-H), available from glucose via one of its major metabolites mevalonate, has been converted to cross-linked networks by radical polymerization. Monomer feeds comprising various ratios of ICA-H and its sodium salt (ICA-Na) were used to give hydrogels that show attractive performance in comparison with (nonbioderived) poly(acrylate) hydrogels. In particular, these new materials show increasing levels of water uptake (i.e., swelling ratio) across the entire range of ionization (10–90 %Na). This behavior is attributed to the larger distance between carboxylate moieties in the hydrogels, a feature that reduces the average amount of charge repulsion between proximal sodium carboxylate ion pairs (counterion condensation).

HIGH SODIUM INTAKE IS ASSOCIATED WITH MASKED HYPERTENSION IN THE GENERAL POPULATION

Objective: We investigated the association between office (OBP) and daytime ambulatory blood pressure (ABP) and sodium dietary intake and renal handling, as assessed by 24-hour urinary sodium excretion (24hUVNa) and endogenous lithium clearance (FELi), respectively. Design and method: We recruited from general population 192 individuals, never treated with antihypertensive medications. We administered standardized questionnaires to obtain information on subjects’ medical history and life style. SpaceLab 90207 monitors were programmed to measure blood pressure each 15 min during daytime (6:00–22:00) and each 30 min night-time. In adjusted categorical analyses, normotension was the referent group (OBP < 140/90 and daytime ABP < 135/85 mmHg). White-coat hypertension was defined as OBP > = 140/90 and daytime ABP < 135/85 mmHg; masked hypertension as OBP < 140/90 and daytime ABP > = 135/85 mmHg; and sustained hypertension as OBP > = 140/90 and daytime ABP > = 135/85 mmHg. Blood and 24-hour urine samples were collected. We calculated fractional excretion of lithium (FELi) as the marker of proximal sodium handling. A higher FELi indicates that less sodium and water is reabsorbed in the proximal tubule. Results: The study group included 87 men and 105 women, mean age 40.5 years, office BP 124.3/84.0 mm Hg, 24hUVNa 160 mmol/24 h, 128 (66.7%) normotensives, 29 (15.1%) sustained hypertensives, 8 (4.2%) individuals with masked hypertension, 27 (14.0%) subjects with white coat hypertension. In adjusted analyses, we did not find any associations between office or daytime ambulatory BP and 24hUVNa (P > = 0.24) or FE Li (P > = 0.30). However, in categorical multivariate analyses, individuals with masked hypertension had higher 24hUVNa as compared to normotensives (197 vs 153 mmol/24 h; P = 0.04). There were no differences in 24hUVNa between white-coat hypertensives (P = 0.59) or sustained hypertensives (P = 0.44) and normotensive reference group. None of BP categories differed from normotensives in terms of FELi (P > = 0.19). Conclusions: Excessive sodium intake may play a part in the genesis of masked hypertension in the general population.

Signaling pathways involved in the rapid biphasic effect of aldosterone on Na+/H+ exchanger in rat proximal tubule cells

The receptors and signaling pathways for nongenomic effects of aldosterone (Aldo) on the proximal Na+/H+ exchanger are still unknown; therefore, the aim of this study was to investigate the mineralocorticoid receptor (MR) and/or glucocorticoid receptor (GR) participation in rapid Aldo effects on NHE1 (basolateral Na+/H+ exchanger isoform) and cytosolic calcium concentration ([Ca2+]i). In addition, phospholipase C (PLC), protein kinase C (PKC), and mitogen-activated protein kinase kinase (MEK) involvement in signaling pathways of such effects was evaluated, using immortalized proximal tubule cells of rat (IRPTC) as an experimental model. MR and GR expression was investigated using reverse transcription polymerase chain reaction and immunoblotting. The intracellular pH recovery rate (after acid loading) and [Ca2+]i were determined by the probes BCECF-AM and FURA 2-AM, respectively. Aldo (10−12 M) promoted a moderate increase in [Ca2+]i and stimulation of NHE1, whereas Aldo (10−6 M) greatly increased the [Ca2+]i, but inhibited the NHE1. BAPTA-AM (a calcium chelator), GR antagonism and inhibition of PLC, PKC and MEK pathway abolished the biphasic and dose-dependent effect of Aldo on NHE1 and decreased the [Ca2+]i; whereas MR do not appear to participate in this rapid signaling in IRPTC cells. The reduction of GR content, by gene silencing, abolished the Aldo effect on NHE1, in low concentration, confirming the importance of this receptor in the rapid modulation of proximal sodium and hydrogen transports.

MEXIDOL EFFECT ON THE MORPHOFUNCTIONAL STATE OF KIDNEYS DURING PROGRESSION OF FIRST FEVER STAGE

Structural-functional state of kidneys under conditions of aseptic fever development, induced by pyrogenal (25 mg/kg) injection, was studied in the experiment on 36 white non-linear male rats weighting 0.16-0.2 kg, maintained on hypo-sodium diet. The identified changes included reduction of glomerular filtration rate and proximal sodium reabsorption, increase of protein excretion, vacuolar epithelial dystrophy of the proximal tubules, and focal character of changes in protein properties with the shift of colouring to red colour during the first fever stage. Determined modifications reflect the intensification of the compensatory reactions, directed on the providing of body temperature rise during the first fever stage through increasing of heat production and limitation of heat loss. A significant protective effect of mexidol on the structural-functional state of kidneys during the progression of first fever stage is demonstrated.