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Chronic kidney disease (CKD) affects ~10% of the population and cardiovascular disease is its commonest complication. Despite treatment, patient outcomes remain poor and newer therapies are urgently needed. Here, we investigated the systemic and renal effects of apelin in CKD. In a randomized, double-blind, placebo-controlled, crossover study, 24 subjects (12 patients with CKD and 12 matched healthy subjects) received pyroglutamated apelin-13 ([Pyr 1 ]apelin-13, 1 nmol/min and 30 nmol/min) or matched placebo on two separate visits. Systemic and renal hemodynamics were monitored throughout. The co-primary endpoints were change in systemic vascular resistance index and renal blood flow. Secondary endpoints were change in blood pressure, cardiac output, pulse wave velocity, glomerular filtration rate, natriuresis, free water clearance and urinary protein excretion. In both health and CKD, 30 nmol/min [Pyr 1 ]apelin-13 reduced mean arterial pressure by ~4%, systemic vascular resistance by ~12%, and increased cardiac index by ~10%, compared to placebo (p < 0.05 for all). Both doses of [Pyr 1 ]apelin-13 increased renal blood flow by ~15%, natriuresis by ~20% and free water clearance by ~10%, compared to placebo (p < 0.05 for all). In patients with chronic kidney disease only, glomerular filtration rate fell by ~10%, effective filtration fraction by ~5% and proteinuria by ~25% (p < 0.01 for all). Apelin has short-term cardiovascular and renal benefits in CKD. If maintained longer-term, these should improve patient outcomes. Clinical trials of long-acting oral apelin agonists are justified in CKD and other conditions with impaired salt and water balance. Registration number at www.clinicalTrials.gov : NCT03956576. Funded by Kidney Research UK.  Despite treatment, patients with chronic kidney disease remain at high risk of kidney failure and cardiovascular disease. Here, the authors show that apelin offers potential cardiorenal protection for this high-risk patient group.

Renal fractional flow reserve (rFFR), a hemodynamic evaluation indicator for functional measurement, could be used for the detection of significant renal artery stenosis (RAS). In this study, we evaluated the correlation between color Doppler ultrasonography (CDU), angiography and rFFR in assessing RAS and to validate cut-off points of ultrasound parameters for significant RAS with rFFR<0.8. A total of 77 renal artery lesions from 58 patients with at least unilateral RAS were included into this study. All patients were participated in Fractional Flow Reserve to Determine the Appropriateness of Percutaneous Renal Artery Intervention in Atherosclerosis Renal Hypertension Patients (FAIR)-pilot study (NCT05732077). The rFFR was measured through a pressure wire after renal hyperemia induced by dopamine. Peak systolic velocity (PSV), renal-to-aortic ratio (RAR), resistive index (RI) and side-to-side differences of the intrarenal resistive indices (ΔRI) were obtained by CDU. The rFFR showed good correlation with both CDU and angiography assessment methods. Among CDU parameters, the best correlation was observed in rFFR with PSV (rho = −0.668, P  < 0.0001) and RAR (rho = −0.597, P < 0.001). With a rFFR<0.80 as cut-off value for significant RAS, we computed sensitivity, specificity, and area under the curve (AUC) of CDU parameters. The most predicting cut-off points of CDU parameters were calculated as PSV for 2.415 m/s, RAR for 4.495, RI for 0.605 and ΔRI for 0.04, respectively. A PSV > 2.415 m/s provided a sensitivity of 90%, specificity of 75%, accuracy of 81% and AUC of 0.84 for detecting RAS with rFFR<0.8.

Abstract Context Mechanisms mediating the cardiovascular and renal protection exerted by SGLT2 inhibitors are still partially unknown. We investigated whether dapagliflozin modulates systemic and renal vascular function and structure, and induces epigenetic modifications. Subjects and Methods Forty hypertensive patients with type 2 diabetes were randomly assigned to 4-week treatment with dapagliflozin 10 mg or hydrochlorothiazide (HCT) 12.5 mg. Routine analyses; plasma renin activity; aldosterone, catecholamine, and 24-hour urinary electrolyte levels; flow-mediated dilation (FMD) of the brachial artery; carotid-femoral pulse-wave velocity (PWV); augmentation index; and resistive index and dynamic renal resistive index (DRIN) were measured at baseline and after treatment. Circulating miRNAs (miRs) related to heart failure (miR30e-5p, miR199a-3p), endothelial dysfunction (miR27b and miR200b), and renal function (miR130b-3p, miR21-5p) were assessed and related to the effects of treatments. Results Dapagliflozin and HCT marginally lowered blood pressure. Fasting glucose was lowered, whereas 24-hour diuresis, glycosuria, and osmolar clearance were increased by dapagliflozin (P < 0.001 for all), without affecting sodium excretion and glomerular filtration rate. Magnesium levels significantly increased after dapagliflozin treatment (P = 0.02). Neither dapagliflozin nor HCT modified FMD or PWV. DRIN did not vary in the dapagliflozin group, whereas it increased in the HCT group (P = 0.047 for time by treatment interaction). Both treatments induced variations in the expression of some miRs; dapagliflozin, but not HCT, significantly up-regulated miR30e-5p and downregulated miR199a-3p. Conclusion A putative epigenetic regulation of the protecting cardiovascular effect exerted by SGLT2 inhibitors was found. Dapagliflozin might exert nephroprotection by preserving renal vasodilating capacity. Hemodynamic and systemic vascular effects of dapagliflozin undergo epigenetic regulation that favorably affects two miRs involved in heart failure.

Acute kidney injury (AKI) is a common complication of septic shock and together these conditions carry a high mortality risk. In septic patients who develop severe AKI, renal cortical perfusion is deficient despite normal macrovascular organ blood flow. This intra-renal perfusion abnormality may be amenable to pharmacological manipulation, which may offer mechanistic insight into the pathophysiology of septic AKI. The aim of the current study is to investigate the effects of vasopressin and angiotensin II on renal microcirculatory perfusion in a cohort of patients with septic shock. In this single centre, mechanistically focussed, randomised controlled study, 45 patients with septic shock will be randomly allocated to either of the study vasopressors (vasopressin or angiotensin II) or standard therapy (norepinephrine). Infusions will be titrated to maintain a mean arterial pressure (MAP) target set by the attending clinician. Renal microcirculatory assessment will be performed for the cortex and medulla using contrast-enhanced ultrasound (CEUS) and urinary oxygen tension (pO2), respectively. Renal macrovascular flow will be assessed via renal artery ultrasound. Measurement of systemic macrovascular flow will be performed through transthoracic echocardiography (TTE) and microvascular flow via sublingual incident dark field (IDF) video microscopy. Measures will be taken at baseline, +1 and +24hrs following infusion of the study drug commencing. Blood and urine samples will also be collected at the measurement time points. Longitudinal data will be compared between groups and over time. Vasopressors are integral to the management of patients with septic shock. This study aims to further understanding of the relationship between this therapy, renal perfusion and the development of AKI. In addition, using CEUS and urinary pO2, we hope to build a more complete picture of renal perfusion in septic shock by interrogation of the constituent parts of the kidney. Results will be published in peer-reviewed journals and presented at academic meetings. The REPERFUSE study was registered on Clinical Trials.gov (NCT06234592) on the 30th Jan 24.

Abstract Aims Renal impairment frequently coexists with heart failure (HF) and is associated with increased risk of poor clinical outcomes. This highlights the urgent need for therapies targeting both cardiac and renal dysfunction. AZD3427, a long-acting recombinant fusion protein and relaxin analogue that selectively activates the relaxin family peptide receptor 1 (RXFP1), showed trends of increased stroke volume and estimated glomerular filtration rate (eGFR) in HF patients (NCT04630067). The hypothesis is that AZD3427 may enhance GFR by expanding the functional renal cortex volume and improving renal perfusion. Methods and results The Re-PERFUSE study (NCT06611423) is a Phase 1b, randomised, double-blind, placebo-controlled trial aimed at evaluating the effects of AZD3427 on renal perfusion in patients with HF and reduced ejection fraction (HFrEF) with reduced eGFR. Patients with HF, EF ≤ 40% and an eGFR of 30 to 90 mL/min/1.73 m2, assessed by the CKD-EPI 2021, will receive a single dose of subcutaneous AZD3427 (n = 6) or placebo (n = 6). Intravenous dopamine will serve as a positive control for increased renal blood flow. Positron emission tomography (PET) imaging with [15O]-labelled water will be used to measure renal cortex blood flow pre- and post-treatment, allowing differentiation between global and focal renal blood flow changes and providing insights into potential nephron recruitment and increased filtration membrane area. Safety and tolerability will be assessed through monitoring of adverse events, clinical laboratory tests and vital signs. Conclusions This study, alongside other ongoing AZD3427 studies, aims to evaluate the dual effects of AZD3427 in improving both cardiac and renal function. These insights could guide the development of future therapeutic strategies for managing HF and renal impairment.

Terlipressin improves renal function in patients with septic shock. However, the mechanism remains unclear. Here, we aimed to evaluate the effects of terlipressin on renal perfusion in patients with septic shock. This pilot study enrolled patients with septic shock in the intensive care unit of the tertiary hospital from September 2019 to May 2020. We randomly assigned patients to terlipressin and usual care groups using a 1:1 ratio. Terlipressin was intravenously pumped at a rate of 1.3 μg/kg/hour for 24 h. We monitored renal perfusion using renal contrast-enhanced ultrasound (CEUS). The primary outcome was peak sonographic signal intensity (a renal perfusion parameter monitored by CEUS) at 24 h after enrollment. 22 patients were enrolled in this study with 10 in the terlipressin group and 12 in the usual care group. The baseline characteristics of patients between the two groups were comparable. The peak sonographic signal intensity at 24 h after enrollment in the terlipressin group (60.5 ± 8.6 dB) was significantly higher than that in the usual care group (52.4 ± 7.0 dB; mean difference, 7.1 dB; 95% CI, 0.4-13.9; adjusted p = .04). Patients in the terlipressin group had a lower time to peak, heart rates, norepinephrine dose, and a higher stroke volume at 24 h after enrollment. No significant difference in the urine output within 24 h and incidence of acute kidney injury within 28 days was found between the two groups. Terlipressin improves renal perfusion, increases stroke volume, and decreases norepinephrine dose and heart rates in patients with septic shock.

Sodium-glucose co-transporter 2 (SGLT2) inhibitors immediately reduce the glomerular filtration rate (GFR) in patients with type 2 diabetes mellitus. When given chronically, they confer benefit by markedly slowing the rate at which chronic kidney disease progresses and are the first agents to do so since the advent of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs). Salutary effects on the kidney were first demonstrated in cardiovascular outcomes trials and have now emerged from trials enriched in subjects with type 2 diabetes mellitus and chronic kidney disease. A simple model that unifies the immediate and long-term effects of SGLT2 inhibitors on kidney function is based on the assumption that diabetic hyperfiltration puts the kidney at long-term risk and evidence that hyperfiltration is an immediate response to a reduced signal for tubuloglomerular feedback, which occurs to the extent that SGLT2 activity mediates a primary increase in sodium and fluid reabsorption by the proximal tubule. This model will likely continue to serve as a useful description accounting for the beneficial effect of SGLT2 inhibitors on the diabetic kidney, similar to the hemodynamic explanation for the benefit of ACEIs and ARBs. A more complex model will be required to incorporate positive interactions between SGLT2 and sodium-hydrogen exchanger 3 in the proximal tubule and between sodium-glucose co-transporter 1 (SGLT1) and nitric oxide synthase in the macula densa. The implication of these latter nuances for day-to-day clinical medicine remains to be determined.

Early diagnosis of kidney disease remains an unmet clinical challenge, preventing timely and effective intervention. Diabetes and hypertension are two main causes of kidney disease, can often appear together, and can only be distinguished by invasive biopsy. In this study, we developed a modelling approach to simulate blood velocity, volumetric flow rate, and pressure wave propagation in arterial networks of ageing, diabetic, and hypertensive virtual populations. The model was validated by comparing our predictions for pressure, volumetric flow rate and waveform-derived indexes with in vivo data on ageing populations from the literature. The model simulated the effects of kidney disease, and was calibrated to align quantitatively with in vivo data on diabetic and hypertensive nephropathy from the literature. Our study identified some potential biomarkers extracted from renal blood flow rate and flow pulsatility. For typical patient age groups, resistive index values were 0.69 (SD 0.05) and 0.74 (SD 0.02) in the early and severe stages of diabetic nephropathy, respectively. Similar trends were observed in the same stages of hypertensive nephropathy, with a range from 0.65 (SD 0.07) to 0.73 (SD 0.05), respectively. Mean renal blood flow rate through a single diseased kidney ranged from 329 (SD 40, early) to 317 (SD 38, severe) ml/min in diabetic nephropathy and 443 (SD 54, early) to 388 (SD 47, severe) ml/min in hypertensive nephropathy, showing potential as a biomarker for early diagnosis of kidney disease. This modelling approach demonstrated its potential application in informing biomarker identification and facilitating the setup of clinical trials.

Background Although serum cystatin C (sCysC), urinary N -acetyl-β- d -glucosaminidase (uNAG), and urinary albumin/creatinine ratio (uACR) are clinically available, their optimal combination for acute kidney injury (AKI) detection and prognosis prediction remains unclear. We aimed to assess the discriminative abilities of these biomarkers and their possible combinations for AKI detection and intensive care unit (ICU) mortality prediction in critically ill adults. Methods A multicenter, prospective observational study was conducted in mixed medical-surgical ICUs at three tertiary care hospitals. One thousand eighty-four adult critically ill patients admitted to the ICUs were studied. We assessed the use of individual biomarkers (sCysC, uNAG, and uACR) measured at ICU admission and their combinations with regard to AKI detection and prognosis prediction. Results AUC-ROCs for sCysC, uNAG, and uACR were calculated for total AKI (0.738, 0.650, and 0.683, respectively), severe AKI (0.839, 0.706, and 0.771, respectively), and ICU mortality (0.727, 0.793, and 0.777, respectively). The panel of sCysC plus uNAG detected total and severe AKI with significantly higher accuracy than either individual biomarkers or the other two panels (uNAG plus uACR or sCysC plus uACR). For detecting total AKI, severe AKI, and ICU mortality at ICU admission, this panel yielded AUC-ROCs of 0.756, 0.863, and 0.811, respectively; positive predictive values of 0.71, 0.31, and 0.17, respectively; and negative predictive values of 0.81, 0.97, and 0.98, respectively. Moreover, this panel significantly contributed to the accuracy of the clinical models for AKI detection and ICU mortality prediction, as measured by the AUC-ROC, continuous net reclassification index, and incremental discrimination improvement index. The comparable performance of this panel was further confirmed with bootstrap internal validation. Conclusions The combination of a functional marker (sCysC) and a tubular damage marker (uNAG) revealed significantly superior discriminative performance for AKI detection and yielded additional prognostic information on ICU mortality.

Background Acute kidney injury (AKI) is a common and serious complication after cardiac surgery, and current strategies aimed at treating AKI have proven ineffective. Levosimendan, an inodilatating agent, has been shown to increase renal blood flow and glomerular filtration rate in uncomplicated postoperative patients and in patients with the cardiorenal syndrome. We hypothesized that levosimendan through its specific effects on renal vasculature, a preferential vasodilating effect on preglomerular resistance vessels, could improve renal function in AKI-patients with who did not have clinical indication for inotropic support. Methods In this single-center, double-blind, randomized controlled study, adult patients with postoperative AKI within 2 days after cardiac surgery, who were hemodynamically stable with a central venous oxygen saturation (ScvO 2 ) ≥ 60% without inotropic support were eligible for inclusion. After randomization, study drug infusions, levosimendan (n = 16) or placebo (n = 13) were given for 5 h. A bolus infusion of levosimendan (12 µg/kg), were given for 30 min followed by 0.1 µg/kg/min for 5 h. Renal blood flow and glomerular filtration rate were measured using infusion clearance of para-aminohippuric acid and a filtration marker, respectively. As a safety issue, norepinephrine was administered to maintain mean arterial pressure between 70–80 mmHg. Intra-group differences were tested by Mann–Whitney U-tests, and a linear mixed model was used to test time and group interaction. Results Twenty-nine patients completed the study. At inclusion, the mean serum creatinine was higher in the patients randomized to levosimendan (148 ± 29 vs 127 ± 22 µmol/L, p  = 0.030), and the estimated GFR was lower (46 ± 12 vs 57 ± 11 ml/min/1.73 m 2 , p  = 0.025). Levosimendan induced a significantly ( p  = 0.011) more pronounced increase in renal blood flow (15%) compared placebo (3%) and a more pronounced decrease in renal vascular resistance (− 18% vs. − 4%, respectively, p  = 0.043). There was a trend for a minor increase in glomerular filtration rate with levosimendan (4.5%, p  = 0.079), which did differ significantly from the placebo group ( p  = 0.440). The mean norepinephrine dose was increased by 82% in the levosimedan group and decreased by 29% in the placebo group ( p  = 0.012). Conclusions In hemodynamically stable patients with AKI after cardiac surgery, levosimendan increases renal blood flow through renal vasodilatation. Trial registration NCT02531724, prospectly registered on 08/20/2015. https://clinicaltrials.gov/ct2/show/NCT02531724?cond=AKI&cntry=SE&age=1&draw=2&rank=1