Soluble Urokinase Receptor and Acute Kidney Injury

Clinical value of soluble urokinase-type plasminogen activator receptor in predicting sepsis-associated acute kidney injury

BACKGROUND

Sepsis-associated acute kidney injury (S-AKI) is a critical illness and is often associated with high morbidity and mortality rates. The soluble urokinase-type plasminogen activator receptor (suPAR) is an important immune mediator and is involved in kidney injury. However, its diagnostic value in S-AKI patients remains unclear. Therefore, we assessed the early predictive value of suPAR for S-AKI patients.

METHODS

We prospectively enrolled adult patients, immediately after fulfilling the sepsis-3 criteria. Plasma suPAR levels at 0-, 12-, 24-, and 48-h post-sepsis diagnosis were measured. S-AKI development was the primary outcome. S-AKI risk factors were analyzed using logistic regression, and the value of plasma suPAR for early S-AKI diagnosis was assessed using receiver operating characteristic (ROC) curves.

RESULTS

Of 179 sepsis patients, 63 (35.2%) developed AKI during hospitalization. At 12-, 24-, and 48-h post-sepsis diagnosis, plasma suPAR levels were significantly higher in patients with S-AKI than in patients without S-AKI (p < 0.05). The plasma suPAR had the highest area under the ROC curve of 0.700 (95% confidence interval (CI), 0.621-0.779) at 24-h post-sepsis diagnosis, at which the best discrimination ability for S-AKI was achieved with suPAR of ≥6.31 ng/mL (sensitivity 61.9% and specificity 71.6%). Logistic regression analysis showed that suPAR at 24-h post-sepsis diagnosis remained an independent S-AKI risk factor after adjusting for mechanical ventilation, blood urea nitrogen, and pH.

CONCLUSIONS

The findings suggest that plasma suPAR may be a potential biomarker for early S-AKI diagnosis.

Elevated Serum KIM-1 in Sepsis Correlates with Kidney Dysfunction and the Severity of Multi-Organ Critical Illness

The kidney injury molecule (KIM)-1 is shed from proximal tubular cells in acute kidney injury (AKI), relaying tubular epithelial proliferation. Additionally, KIM-1 portends complex immunoregulation and is elevated after exposure to lipopolysaccharides. It thus may represent a biomarker in critical illness, sepsis, and sepsis-associated AKI (SA-AKI). To characterise and compare KIM-1 in these settings, we analysed KIM-1 serum concentrations in 192 critically ill patients admitted to the intensive care unit. Irrespective of kidney dysfunction, KIM-1 serum levels were significantly higher in patients with sepsis compared with other critical illnesses (191.6 vs. 132.2 pg/mL, p = 0.019) and were highest in patients with urogenital sepsis, followed by liver failure. Furthermore, KIM-1 levels were significantly elevated in critically ill patients who developed AKI within 48 h (273.3 vs. 125.8 pg/mL, p = 0.026) or later received renal replacement therapy (RRT) (299.7 vs. 146.3 pg/mL, p < 0.001). KIM-1 correlated with markers of renal function, inflammatory parameters, hematopoietic function, and cholangiocellular injury. Among subcomponents of the SOFA score, KIM-1 was elevated in patients with hyperbilirubinaemia (>2 mg/dL, p < 0.001) and thrombocytopenia (<150/nL, p = 0.018). In univariate and multivariate regression analyses, KIM-1 predicted sepsis, the need for RRT, and multi-organ dysfunction (MOD, SOFA > 12 and APACHE II ≥ 20) on the day of admission, adjusting for relevant comorbidities, bilirubin, and platelet count. Additionally, KIM-1 in multivariate regression was able to predict sepsis in patients without prior (CKD) or present (AKI) kidney injury. Our study suggests that next to its established role as a biomarker in kidney dysfunction, KIM-1 is associated with sepsis, biliary injury, and critical illness severity. It thus may offer aid for risk stratification in these patients.

suPAR in cardiovascular disease

Soluble urokinase plasminogen activator receptor (suPAR), the soluble counterpart of urokinase plasminogen activator receptor, is found in the circulation at various levels. suPAR and its parent molecule, cell surface uPAR, exhibit similar structure and extracellular functional roles facilitating fibrinolysis, cellular adhesion, and migration. Studies have assessed the correlation between suPAR in cardiovascular disease (CVD). It is postulated that suPAR may serve as an indicator of inflammatory activation and burden during CVD progression. Increased suPAR independently predicts poorer outcomes in acute coronary syndromes, in heart failure, as well as in coronary artery disease and atherosclerosis. To guide translation into clinical utization, suPAR has been assessed in numerous CVD settings for improved risk discrimination independently or in association with established traditional risk factors. Whilst the involvement of suPAR has been explored in other diseases such as kidney diseases and cancer, there is only emerging evidence of suPAR's mechanistic involvement in cardiovascular disease. In this review, we provide a background into suPAR and its potential role as a biomarker in CVD.

Soluble urokinase Plasminogen Activator Receptor (suPAR) mediates the effect of a lower education level on adverse outcomes in patients with coronary artery disease

AIMS

To investigate whether the adverse impact of lower educational attainment on mortality risk in patients with coronary artery disease (CAD) is mediated by the activation of inflammatory and immune pathways, estimated as elevated soluble urokinase plasminogen activator receptor levels.

METHODS AND RESULTS

In 3164 patients undergoing coronary angiography, we investigated multivariable associations between suPAR and educational attainment and assessed the relationship between a lower educational level (defined as a high-school degree or less as the highest educational qualification) and outcomes using Cox proportional hazard and Fine and Gray's subdistribution competing risk models. The potential mediating effect through suPAR and high-sensitivity C-reactive protein (hs-CRP) was assessed using mediation analysis. A total of 1814 patients (57.3%) had achieved a higher (≥college) education level and 1350 patients (42.7%) a lower (≤high school) education level. Soluble urokinase plasminogen activator receptor levels were 9.0% [95% confidence interval (CI) 6.3-11.8, P ≤ 0.0001] higher in patients with lower educational qualifications than in those with higher educational qualifications after covariate adjustment. Lower educational attainment was associated with a higher risk of cardiovascular death after adjustment for demographic, clinical, and behavioural covariates, including CAD severity and heart failure history, medication use, and hs-CRP levels [hazard ratio 1.26 (95% CI 1.02-1.55, P = 0.03)]. However, after adjustment for suPAR levels, the effect of a lower educational level on cardiovascular death became insignificant. Values were similar for all-cause death. Soluble urokinase plasminogen activator receptor levels mediated 49% and hs-CRP levels 17% of the cardiovascular death risk attributable to lower educational attainment.

CONCLUSION

Circulating suPAR levels importantly mediate the effects of lower educational attainment on mortality, indicating the importance of systemic inflammation and immune dysregulation as biologic mediators of adverse social determinants of health.

Prognostic Biomarkers and AKI: Potential to Enhance the Identification of Post-Operative Patients at Risk of Loss of Renal Function

Acute kidney injury (AKI) is a common complication after surgery and the more complex the surgery, the greater the risk. During surgery, patients are exposed to a combination of factors all of which are associated with the development of AKI. These include hypotension and hypovolaemia, sepsis, systemic inflammation, the use of nephrotoxic agents, tissue injury, the infusion of blood or blood products, ischaemia, oxidative stress and reperfusion injury. Given the risks of AKI, it would seem logical to conclude that early identification of patients at risk of AKI would translate into benefit. The conventional markers of AKI, namely serum creatinine and urine output are the mainstay of defining chronic kidney disease but are less suited to the acute phase. Such concerns are compounded in surgical patients given they often have significantly reduced mobility, suboptimal levels of nutrition and reduced muscle bulk. Many patients may also have misleadingly low serum creatinine and high urine output due to aggressive fluid resuscitation, particularly in intensive care units. Over the last two decades, considerable information has accrued with regard to the performance of what was termed "novel" biomarkers of AKI, and here, we discuss the most examined molecules and performance in surgical settings. We also discuss the application of biomarkers to guide patients' postoperative care.

A Pilot Investigation of the Association Between Vpr Amino Acid Substitutions and Peripheral Immune Marker Levels in People With Human Immunodeficiency Virus: Implications for Neurocognitive Impairment

Background

Subtype-specific amino acid variations in viral proteins of human immunodeficiency virus type 1 (HIV-1) influence disease progression. Furthermore, Vpr sequence variation correlates with chronic inflammation, a central mechanism in HIV-1 (neuro)pathogenesis. Nevertheless, no clinical study has investigated the link between Vpr sequence variation and peripheral inflammation in people with HIV (PWH). The aim of this pilot study was to ascertain whether specific Vpr amino acid variants were associated with immune markers in PWH.

Methods

We included a unique cohort of 48 treatment-naive South African PWH to determine the association between blood-derived Vpr sequence variation and peripheral immune marker levels using Sanger sequencing and enzyme-linked immunosorbent assay analysis, respectively.

Results

Our findings indicate that among the many neuropathogenic Vpr amino acid variants and immune markers examined, after applying Bonferroni corrections (P = .05/3) and adjusting for sex and locality, soluble urokinase plasminogen activator receptor (suPAR) was nearing significance for higher levels in participants with the G41 amino acid variant compared to those with the S41 variant (P = .035). Furthermore, amino acid variations at position 41 (between G41 and S41) exhibited a significant association with suPAR (adjusted R2 = 0.089, β = .386 [95% confidence interval, .125-3.251]; P = .035).

Conclusions

These findings suggest that Vpr amino acid sequence variations might contribute to dysregulated inflammation, which could explain the observed association between specific Vpr variants and HIV-1 (neuro)pathogenesis found in prior research. These Vpr variants merit further investigation to fully understand their roles in HIV-1 pathogenesis and neuropathogenesis.

Comprehensive strategy for identifying extracellular vesicle surface proteins as biomarkers for chronic kidney disease

Chronic kidney disease (CKD) poses a significant health burden worldwide. Especially, obesity-induced chronic kidney disease (OCKD) is associated with a lack of accuracy in disease diagnostic methods. The identification of reliable biomarkers for the early diagnosis and monitoring of CKD and OCKD is crucial for improving patient outcomes. Extracellular vesicles (EVs) have emerged as potential biomarkers in the context of CKD. In this review, we focused on the role of EVs as potential biomarkers in CKD and OCKD and developed a comprehensive list of EV membrane proteins that could aid in the diagnosis and monitoring of the disease. To assemble our list, we employed a multi-step strategy. Initially, we conducted a thorough review of the literature on EV protein biomarkers in kidney diseases. Additionally, we explored papers investigating circulating proteins as biomarkers in kidney diseases. To further refine our list, we utilized the EV database Vesiclepedia.org to evaluate the qualifications of each identified protein. Furthermore, we consulted the Human Protein Atlas to assess the localization of these candidates, with a particular focus on membrane proteins. By integrating the information from the reviewed literature, Vesiclepedia.org, and the Human Protein Atlas, we compiled a comprehensive list of potential EV membrane protein biomarkers for CKD and OCKD. Overall, our review underscores the potential of EVs as biomarkers in the field of CKD research, providing a foundation for future studies aimed at improving CKD and OCKD diagnosis and treatment.

Soluble urokinase plasminogen activator receptor (suPAR) in bronchoalveolar fluid and blood in critically ill patients-a prospective cohort study

INTRODUCTION

Soluble urokinase plasminogen activator receptor (suPAR) is a biologically active protein and increased levels are associated with worse outcomes in critically ill patients. suPAR in bronchoalveolar fluid (BALF) may be helpful to differentiate between types of acute respiratory distress syndrome (ARDS) and may have potential for early detection of fungal infection.

METHODS

We prospectively investigated levels of suPAR in BALF and serum in critically ill patients who underwent bronchoscopy for any reason at the ICU of the Department of Internal Medicine, Medical University of Graz, Graz, Austria.

RESULTS

Seventy-five patients were available for analyses. Median age was 60 [25th-75th percentile: 50-69] years, 27% were female, and median SOFA score was 12 [11-14] points. Serum suPAR levels were significantly associated with ICU mortality in univariable logistic regression analysis. There was no correlation between BALF and serum suPAR. Serum suPAR was higher in ARDS patients at 11.2 [8.0-17.2] ng/mL compared to those without ARDS at 7.1 [3.7-10.1] (p < 0.001). BALF-suPAR was significantly higher in patients with evidence of fungal lung infection compared to patients without fungal infection both in the general cohort (7.6 [3.2-9.4] vs 2.5 [1.1-5.3], p = 0.013) and in the subgroup of ARDS (7.2 [3.1-39.2] vs 2.5 [1.0-5.2], p = 0.022). All patients were classified as putative/probable invasive aspergillosis.

CONCLUSION

We found significant higher levels of serum suPAR in ARDS patients compared to those not fulfilling ARDS criteria. Serum and BALF-suPAR were significantly higher in those patients with evidence for invasive pulmonary aspergillosis. These findings may suggest testing this biomarker for early diagnosis of fungal infection in a greater cohort.

Urinary biomarkers associated with podocyte injury in lupus nephritis

The most prevalent and devastating form of organ damage in systemic lupus erythematosus (SLE) is lupus nephritis (LN). LN is characterized by glomerular injury, inflammation, cell proliferation, and necrosis, leading to podocyte injury and tubular epithelial cell damage. Assays for urine biomarkers have demonstrated significant promise in the early detection of LN, evaluation of disease activity, and tracking of reaction to therapy. This is because they are non-invasive, allow for frequent monitoring and easy self-collection, transport and storage. Podocyte injury is believed to be a essential factor in LN. The extent and type of podocyte injury could be connected to the severity of proteinuria, making podocyte-derived cellular debris and injury-related urinary proteins potential markers for the diagnosis and monitoring of LN. This article focuses on studies examining urinary biomarkers associated with podocyte injury in LN, offering fresh perspectives on the application of biomarkers in the early detection and management of LN.

Role of Formyl Peptide Receptors and β-Arrestin-1 in suPAR Signal Transduction in Mouse Podocytes: Interactions with αVβ3-Integrin

The soluble urokinase plasminogen activator receptor (suPAR) has been implicated in a wide range of pathological conditions including primary nephrotic syndromes and acute kidney injuries. suPAR can trigger transduction cascades in podocytes by outside-in activation of αVβ3-integrin, but there is evidence that the functional cell surface response element is actually a complex of different types of receptors, which may also include the receptor for advanced glycation end-products (RAGE) and formyl peptide receptors (FPRs). Here we observed that ROS accumulation and Src activation could be evoked by continuous 24 h exposure to either suPAR or the FPR agonist fMLF. Responses to suPAR and fMLF were completely blocked by either the FPR antagonist WRW4 or by the αV-integrin inhibitor cilengitide. Moreover, endogenous podocyte mouse Fpr1 co-immunoprecipitates with β3-integrin, suggesting that these receptors occur as a complex on the cell surface. suPAR- and fMLF-evoked activation of Src and ROS differed in time course. Thus, robust pertussis toxin (PTX)-sensitive responses were evoked by 60 min exposures to fMLF but not to suPAR. By contrast, responses to 24 h exposures to either suPAR or fMLF were PTX-resistant and were instead abolished by knockdown of β-arrestin-1 (BAR1). FPRs, integrins, and RAGE (along with various Toll-like receptors) can all function as pattern-recognition receptors that respond to "danger signals" associated with infections and tissue injury. The fact that podocytes express such a wide array of pattern-recognition receptors suggests that the glomerular filter is designed to change its function under certain conditions, possibly to facilitate clearance of toxic macromolecules.

New biomarkers in acute kidney injury

Acute kidney injury (AKI) is a commonly encountered clinical syndrome. Although it often complicates community acquired illness, it is more common in hospitalized patients, particularly those who are critically ill or who have undergone major surgery. Approximately 20% of hospitalized adult patients develop an AKI during their hospital care, and this rises to nearly 60% in the critically ill, depending on the population being considered. In general, AKI is more common in older adults, in those with preexisting chronic kidney disease and in those with known risk factors for AKI (including diabetes and hypertension). The development of AKI is associated with an increase in both mortality and morbidity, including the development of post-AKI chronic kidney disease. Currently, AKI is defined by a rise in serum creatinine from either a known or derived baseline value and/or oliguria or anuria. However, clinicians may fail to recognize the initial development of AKI because of a delay in the rise of serum creatinine or because of inaccurate urine output monitoring. This, in turn, delays any putative measures to treat AKI or to limit its degree. Consequently, efforts have focused on new biomarkers associated with AKI that may allow early recognition of this syndrome with the intent that this will translate into improved patient outcomes. Here we outline current biomarkers associated with AKI and explore their potential in aiding diagnosis, understanding the pathophysiology and directing therapy.

SuPAR, biomarkers of inflammation, and severe outcomes in patients hospitalized for COVID-19: The International Study of Inflammation in COVID-19

Severe coronavirus disease 2019 (COVID-19) is a hyperinflammatory syndrome. The biomarkers of inflammation best suited to triage patients with COVID-19 are unknown. We conducted a prospective multicenter observational study of adult patients hospitalized specifically for COVID-19 from February 1, 2020 to October 19, 2022. Biomarkers measured included soluble urokinase plasminogen activator receptor (suPAR), C-reactive protein, interleukin-6, procalcitonin, ferritin, and D-dimer. In-hospital outcomes examined include death and the need for mechanical ventilation. Patients admitted in the United States (US, n = 1962) were used to compute area under the curves (AUCs) and identify biomarker cutoffs. The combined European cohorts (n = 1137) were used to validate the biomarker cutoffs. In the US cohort, 356 patients met the composite outcome of death (n = 197) or need for mechanical ventilation (n = 290). SuPAR was the most important predictor of the composite outcome and had the highest AUC (0.712) followed by CRP (0.642), ferritin (0.619), IL-6 (0.614), D-dimer (0.606), and lastly procalcitonin (0.596). Inclusion of other biomarkers did not improve discrimination. A suPAR cutoff of 4.0 ng/mL demonstrated a sensitivity of 95.4% (95% CI: 92.4%-98.0%) and negative predictive value (NPV) of 92.5% (95% CI: 87.5%-96.9%) for the composite outcome. Patients with suPAR < 4.0 ng/mL comprised 10.6% of the cohort and had a 0.8% probability of the composite outcome. Applying this cutoff to the validation cohort yielded a sensitivity of 93.8% (90.4%-96.7%) and NPV of 95.5% (93.1%-97.8%) for the composite outcome. Among commonly measured biomarkers, suPAR offered stronger discriminatory ability and may be useful in triaging low-risk patients with COVID-19.

Soluble Urokinase-Type Plasminogen Activator Receptor (suPAR) and Growth Differentiation Factor-15 (GDF-15) Levels Are Significantly Associated with Endothelial Injury Indices in Adult Allogeneic Hematopoietic Cell Transplantation Recipients

Hematopoietic stem cell transplantation-associated thrombotic microangiopathy (HSCT-TMA) and graft-versus-host disease (GvHD) represent life-threatening syndromes after allogeneic hematopoietic stem cell transplantation (allo-HSCT). In both conditions, endothelial dysfunction is a common denominator, and development of relevant biomarkers is of high importance for both diagnosis and prognosis. Despite the fact that soluble urokinase plasminogen activator receptor (suPAR) and growth differentiation factor-15 (GDF-15) have been determined as endothelial injury indices in various clinical settings, their role in HSCT-related complications remains unexplored. In this context, we used immunoenzymatic methods to measure suPAR and GDF-15 levels in HSCT-TMA, acute and/or chronic GVHD, control HSCT recipients, and apparently healthy individuals of similar age and gender. We found considerably greater SuPAR and GDF-15 levels in HSCT-TMA and GVHD patients compared to allo-HSCT and healthy patients. Both GDF-15 and suPAR concentrations were linked to EASIX at day 100 and last follow-up. SuPAR was associated with creatinine and platelets at day 100 and last follow-up, while GDF-15 was associated only with platelets, suggesting that laboratory values do not drive EASIX. SuPAR, but not GDF-15, was related to soluble C5b-9 levels, a sign of increased HSCT-TMA risk. Our study shows for the first time that suPAR and GDF-15 indicate endothelial damage in allo-HSCT recipients. Rigorous validation of these biomarkers in many cohorts may provide utility for their usefulness in identifying and stratifying allo-HSCT recipients with endothelial cell impairment.

Detection of Inflammatory Biomarker suPAR in COVID-19 Disease With CHORUS TRIO Instrument

Background

Deregulation in the urokinase-type plasminogen activator receptor (uPA/uPAR) system is reported in many diseases where the immune system is activated. During SARS-CoV-2 infection, a rise in soluble uPAR (suPAR) levels has been detected and its concentration above 6 µg/L predicts worsening to severe respiratory failure 14 days earlier, with a positive predictive value of 85.9%, and was the prerequisite for a treatment with anakinra, a recombinant IL-1 receptor antagonist that blocks the activity of both IL-1α and IL-1β.

Objectives

To compare suPAR concentrations measured by CHORUS suPAR on CHORUS TRIO instrument of DIESSE with the commercially available suPARnostic (ViroGates) ELISA assay.

Design

A single-centre, non-pharmacological, diagnostic study was performed.

Results

A total of 522 serum samples from patients with COVID-19 were tested for suPAR. CHORUS suPAR resulted accurate and reliable, with a high grade of specificity (97.9%), accuracy (97.3%) and sensitivity (96.9%). The median concentration of suPAR, as determined with CHORUS suPAR, was 6.8 µg/L (interquartile range 4.5-9.7) in patients with moderate disease (n = 465) and 8.5 µg/L (interquartile range 5.4-10.6) in patients with severe disease. Among patients with moderate and severe disease, 60.6% and 71.9%, respectively, reached the cut-off concentration of suPAR ⩾6 µg/L, defining their illness severity and suggesting eligibility to anakinra treatment.

Conclusion

CHORUS suPAR kit resulted as sensitive, specific, accurate and able to quantify suPAR concentrations in patients with moderate and severe COVID-19.

Role of soluble urokinase type plasminogen activator receptor (suPAR) in predicting mortality, readmission, length of stay and discharge in emergency patients: A systematic review and meta analysis

BACKGROUND

Soluble urokinase plasminogen activator receptor (suPAR) is an inflammatory biomarker that is used to predict mortality, readmission, early discharge, and LOS, thus, serves as a useful tool for ED physicians. Our study aims to analyze the efficacy of suPAR in predicting these prognostic markers in ED.

METHODS

We performed a comprehensive search on 6 databases from the inception to 30th November 2022, to select the following eligibility criteria; a) observation or triage trial studies investigating the role of suPAR levels in predicting: 30 day and 90-day mortality, 30-day readmission, early discharge (within 24hr), and LOS in patients coming to AMU.

RESULTS

A total of 13 studies were included, with a population size of 35,178, of which 52.9% were female with a mean age of 62.93 years. Increased risk of 30-day mortality (RR = 10.52; 95% CI = 4.82-22.95; I2 = 38%; P < .00001), and risk of 90-day mortality (RR = 5.76; 95% CI = 3.35-9.91; I2 = 36%; P < .00001) was observed in high suPAR patients. However, a slightly increased risk was observed for 30-day readmission (RR = 1.50; 95% CI = 1.16-1.94; I2 = 54%; P = .002). More people were discharged within 24hr in the low suPAR level group compared to high suPAR group (RR = 0.46; 95% CI = 0.40-0.53; I2 = 41%; P < .00001). LOS was thrice as long in high suPAR level patients than in patients with low suPAR (WMD = 3.20; 95% CI = 1.84-4.56; I2 = 99%; P < .00001).

CONCLUSION

suPAR is proven to be a significant marker in predicting 30-day and 90-day mortality in ED patients.

Gut Microbiota and Its Role in the Brain-Gut-Kidney Axis in Hypertension

PURPOSE OF REVIEW

The role of the gut microbiota in modulating blood pressure is increasingly being recognized, currently. The purpose of this review is to summarize recent findings about the mechanisms involved in hypertension with regard to the phenomenon of "gut dysbiosis."

RECENT FINDINGS

Gut dysbiosis, i.e., the imbalance between the gut microbiota and the host, is characterized by a disruption of the tight junction proteins, such as occludins, claudins, and JAMs (junctional adhesion molecules), resulting in increased gut permeability or the so called "leaky gut." Due to the influence of genetic as well as environmental factors, various metabolites produced by the gut microbiota, such as indole and p-cresol, are increased. Thereby, uremic toxins, such as indoxyl sulfates and p-cresol sulfates, accumulate in the blood and the urine, causing damage in the podocytes and the tubular cells. In addition, immunological mechanisms are implicated as well. In particular, a switch from M2 macrophages to M1 macrophages, which produce pro-inflammatory cytokines, occurs. Moreover, a higher level of Th17 cells, releasing large amounts of interleukin-17 (IL-17), has been reported, when a diet rich in salt is consumed. Therefore, apart from the aggravation of uremic toxins, which may account for direct harmful effects on the kidney, there is inflammation not only in the gut, but in the kidneys as well. This crosstalk between the gut and the kidney is suggested to play a crucial role in hypertension. Notably, the brain is also implicated, with an increasing sympathetic output. The brain-gut-kidney axis seems to be deeply involved in the development of hypertension and chronic kidney disease (CKD). The notion that, by modulating the gut microbiota, we could regulate blood pressure is strongly supported by the current evidence. A healthy diet, low in animal protein and fat, and low in salt, together with the utilization of probiotics, prebiotics, synbiotics, or postbiotics, may contribute to our fight against hypertension.

Overall and inter-individual effect of four different drug classes on soluble urokinase plasminogen activator receptor in type 1 and type 2 diabetes

AIM

To evaluate the effect of four different drug classes on soluble urokinase plasminogen activator receptor (suPAR), a biomarker active in multiple inflammatory processes and a risk factor for complications, in people with type 1 and type 2 diabetes.

METHODS

We conducted post hoc analyses of a randomized, open-label, crossover trial including 26 adults with type 1 and 40 with type 2 diabetes with urinary albumin-creatinine ratio ≥30 and ≤500 mg/g assigned to 4-week treatments with telmisartan 80 mg, empagliflozin 10 mg, linagliptin 5 mg and baricitinib 2 mg, separated by 4-week washouts. Plasma suPAR was measured before and after each treatment. SuPAR change after each treatment was calculated and, for each individual, the best suPAR-reducing drug was identified. Subsequently, the effect of the best individual drug was compared against the mean of the other three drugs. Repeated-measures linear mixed-effects models were employed.

RESULTS

The baseline median (interquartile range) plasma suPAR was 3.5 (2.9, 4.3) ng/mL. No overall effect on suPAR levels was observed for any one drug. The individual best-performing drug varied, with baricitinib being selected for 20 participants (30%), followed by empagliflozin for 19 (29%), linagliptin for 16 (24%) and telmisartan for 11 (17%). The individual best-performing drug reduced suPAR by 13.3% (95% confidence interval [CI] 3.7, 22.8; P = 0.007). The difference in suPAR response between the individual best-performing drug and the other three was -19.7% (95% CI -23.1, -16.3; P < 0.001).

CONCLUSIONS

We demonstrated no overall effect of 4-week treatment with telmisartan, empagliflozin, linagliptin or baricitinib on suPAR. However, individualization of treatment might significantly reduce suPAR levels.

Prospective Cohort Study of Soluble Urokinase Plasminogen Activation Receptor and Cardiovascular Events in Patients With CKD

Introduction

Soluble urokinase plasminogen activation receptor (suPAR) is an immune-derived pathogenic factor for kidney and atherosclerotic disease. Whether the association between suPAR and cardiovascular (CV) outcomes is dependent on the severity of underlying kidney disease is unclear.

Methods

We measured serum suPAR levels in 4994 participants (mean age 60 years; 60% men; 36% with diabetes mellitus; mean estimated glomerular filtration rate (eGFR) 49 ml/min per 1.73 m2, SD 18) of the German Chronic Kidney Disease (GCKD) cohort and examined its association with all-cause death, CV death, and major CV events (MACE) across the range of eGFR and urine albumin-to-creatinine ratio (UACR).

Results

The median suPAR level was 1771 pg/ml (interquartile range [IQR] 1447-2254 pg/ml). SuPAR levels were positively and independently correlated with age, eGFR, UACR, and parathyroid hormone levels. There were 573 deaths, including 190 CV deaths and 683 MACE events at a follow-up time of 6.5 years. In multivariable analyses, suPAR levels (log2) were associated with all-cause death (hazard ratio [HR] 1.36, 95% confidence interval [CI] 1.21-1.53), CV death (HR 1.27, 95% CI 1.03-1.57), and MACE (HR 1.13, 95% CI 1.00-1.28), and were not found to differ according to diabetes mellitus status, baseline eGFR, UACR, or parathyroid hormone levels. In mediation analysis, suPAR's direct effect on all-cause death, CV death, and MACE accounted for 77%, 67%, and 60% of the total effect, respectively; whereas the effect mediated through eGFR accounted for 23%, 34%, and 40%, respectively.

Conclusion

In a large cohort of individuals with chronic kidney disease (CKD), suPAR levels were associated with mortality and CV outcomes independently of indices of kidney function, consistent with its independent role in the pathogenesis of atherosclerosis.

Update on persistent acute kidney injury in critical illnesses

Acute kidney injury (AKI) affects about half of patients admitted to the intensive care unit (ICU), and worsens their short- and long-term outcomes. Apparently self-limiting AKI episodes initiate a progression toward chronic kidney disease (CKD) through cellular and molecular mechanisms that are yet to be explained. In particular, persistent AKI, defined in 2016 by the Acute Dialysis Quality Initiative as an AKI which lasts more than 48 h from its onset, has been correlated with higher morbidity and mortality, and with a higher progression to acute kidney disease (AKD) and CKD than transient AKI (i.e. AKI with a reversal within 48 h). This classification has been also used in the setting of solid organ transplantation, demonstrating similar outcomes. Due to its incidence and poor prognosis and because prompt interventions seem to change its course, persistent AKI should be recognized early and followed-up also after its recovery. However, while AKI and CKD are well-described syndromes, persistent AKI and AKD are relatively new entities. The purpose of this review is to highlight the key phases of persistent AKI in ICU patients in terms of both clinical and mechanistic features in order to offer to clinicians and researchers an updated basis from which to start improving patients' care and direct future research.

Cardiac surgery-Associated acute kidney injury - A narrative review

Cardiac Surgery-Associated Acute Kidney Injury (CSA-AKI) is a serious complication seen in approximately 20-30% of cardiac surgery patients. The underlying pathophysiology is complex, often involving both patient- and procedure related risk factors. In contrast to AKI occurring after other types of major surgery, the use of cardiopulmonary bypass comprises both additional advantages and challenges, including non-pulsatile flow, targeted blood flow and pressure as well as the ability to manipulate central venous pressure (congestion). With an increasing focus on the impact of CSA-AKI on both short and long-term mortality, early identification and management of high-risk patients for CSA-AKI has evolved. The present narrative review gives an up-to-date summary on definition, diagnosis, underlying pathophysiology, monitoring and implications of CSA-AKI, including potential preventive interventions. The review will provide the reader with an in-depth understanding of how to identify, support and provide a more personalized and tailored perioperative management to avoid development of CSA-AKI.

The Protective Pathways Activated in Kidneys of αMUPA Transgenic Mice Following Ischemia\Reperfusion-Induced Acute Kidney Injury

Despite the high prevalence of acute kidney injury (AKI), the therapeutic approaches for AKI are disappointing. This deficiency stems from the poor understanding of the pathogenesis of AKI. Recent studies demonstrate that αMUPA, alpha murine urokinase-type plasminogen activator (uPA) transgenic mice, display a cardioprotective pathway following myocardial ischemia. We hypothesize that these mice also possess protective renal pathways. Male and female αMUPA mice and their wild type were subjected to 30 min of bilateral ischemic AKI. Blood samples and kidneys were harvested 48 h following AKI for biomarkers of kidney function, renal injury, inflammatory response, and intracellular pathways sensing or responding to AKI. αMUPA mice, especially females, exhibited attenuated renal damage in response to AKI, as was evident from lower SCr and BUN, normal renal histology, and attenuated expression of NGAL and KIM-1. Notably, αMUPA females did not show a significant change in renal inflammatory and fibrotic markers following AKI as compared with wild-type (WT) mice and αMUPA males. Moreover, αMUPA female mice exhibited the lowest levels of renal apoptotic and autophagy markers during normal conditions and following AKI. αMUPA mice, especially the females, showed remarkable expression of PGC1α and eNOS following AKI. Furthermore, MUPA mice showed a significant elevation in renal leptin expression before and following AKI. Pretreatment of αMUPA with leptin-neutralizing antibodies prior to AKI abolished their resistance to AKI. Collectively, the kidneys of αMUPA mice, especially those of females, are less susceptible to ischemic I/R injury compared to WT mice, and this is due to nephroprotective actions mediated by the upregulation of leptin, eNOS, ACE2, and PGC1α along with impaired inflammatory, fibrotic, and autophagy processes.

Targeted imaging of uPAR expression in vivo with cyclic AE105 variants

A comprehensive literature reports on the correlation between elevated levels of urokinase-type plasminogen activator receptor (uPAR) and the severity of diseases with chronic inflammation including solid cancers. Molecular imaging is widely used as a non-invasive method to locate disease dissemination via full body scans and to stratify patients for targeted treatment. To date, the only imaging probe targeting uPAR that has reached clinical phase-II testing relies on a high-affinity 9-mer peptide (AE105), and several studies by positron emission tomography (PET) scanning or near-infra red (NIR) fluorescence imaging have validated its utility and specificity in vivo. While our previous studies focused on applying various reporter groups, the current study aims to improve uPAR-targeting properties of AE105. We successfully stabilized the small uPAR-targeting core of AE105 by constraining its conformational landscape by disulfide-mediated cyclization. Importantly, this modification mitigated the penalty on uPAR-affinity typically observed after conjugation to macrocyclic chelators. Cyclization did not impair tumor targeting efficiency of AE105 in vivo as assessed by PET imaging and a trend towards increased tracer uptake was observed. In future studies, we predict that this knowledge will aid development of new fluorescent AE105 derivatives with a view to optical imaging of uPAR to assist precision guided cancer surgery.

The D2D3 form of uPAR acts as an immunotoxin and may cause diabetes and kidney disease

Soluble urokinase plasminogen activator receptor (suPAR) is a risk factor for kidney diseases. In addition to suPAR, proteolysis of membrane-bound uPAR results in circulating D1 and D2D3 proteins. We showed that when exposed to a high-fat diet, transgenic mice expressing D2D3 protein developed progressive kidney disease marked by microalbuminuria, elevated serum creatinine, and glomerular hypertrophy. D2D3 transgenic mice also exhibited insulin-dependent diabetes mellitus evidenced by decreased levels of insulin and C-peptide, impaired glucose-stimulated insulin secretion, decreased pancreatic β cell mass, and high fasting blood glucose. Injection of anti-uPAR antibody restored β cell mass and function in D2D3 transgenic mice. At the cellular level, the D2D3 protein impaired β cell proliferation and inhibited the bioenergetics of β cells, leading to dysregulated cytoskeletal dynamics and subsequent impairment in the maturation and trafficking of insulin granules. D2D3 protein was predominantly detected in the sera of patients with nephropathy and insulin-dependent diabetes mellitus. These sera inhibited glucose-stimulated insulin release from human islets in a D2D3-dependent manner. Our study showed that D2D3 injures the kidney and pancreas and suggests that targeting this protein could provide a therapy for kidney diseases and insulin-dependent diabetes mellitus.

Aggregate Clinical and Biomarker-Based Model Predicts Adverse Outcomes in Patients With Coronary Artery Disease

Despite guideline-based therapy, patients with coronary artery disease (CAD) are at widely variable risk for cardiovascular events. This variability demands a more individualized risk assessment. Herein, we evaluate the prognostic value of 6 biomarkers: high-sensitivity C-reactive protein, heat shock protein-70, fibrin degradation products, soluble urokinase plasminogen activator receptor, high-sensitivity troponin I, and B-type natriuretic peptide. We then develop a multi-biomarker-based cardiovascular event prediction model for patients with stable CAD. In total, 3,115 subjects with stable CAD who underwent cardiac catheterization at Emory (mean age 62.8 years, 17% Black, 35% female, 57% obstructive CAD, 31% diabetes mellitus) were randomized into a training cohort to identify biomarker cutoff values and a validation cohort for prediction assessment. Main outcomes included (1) all-cause death and (2) a composite of cardiovascular death and nonfatal myocardial infarction (MI) within 5 years. Elevation of each biomarker level was associated with higher event rates in the training cohort. A biomarker risk score was created using optimal cutoffs, ranging from 0 to 6 for each biomarker exceeding its cutoff. In the validation cohort, each unit increase in the biomarker risk score was independently associated with all-cause death (hazard ratio 1.62, 95% confidence interval [CI] 1.45 to 1.80) and cardiovascular death/MI (hazard ratio 1.52, 95% CI 1.35 to 1.71). A biomarker risk prediction model for cardiovascular death/MI improved the c-statistic (∆ 6.4%, 95% CI 3.9 to 8.8) and net reclassification index by 31.1% (95% CI 24 to 37), compared with clinical risk factors alone. Integrating multiple biomarkers with clinical variables refines cardiovascular risk assessment in patients with CAD.

Validation of a Contemporary Acute Kidney Injury Risk Score in Patients With Acute Coronary Syndrome

BACKGROUND

A simple, contemporary risk score for the prediction of contrast-associated acute kidney injury (CA-AKI) after percutaneous coronary intervention (PCI) was recently updated, although its external validation is lacking.

OBJECTIVES

The aim of this study was to validate the updated CA-AKI risk score in a large cohort of acute coronary syndrome patients from the MATRIX (Minimizing Adverse Haemorrhagic Events by Transradial Access Site and Systemic Implementation of angioX) trial.

METHODS

The risk score identifies 4 risk categories for CA-AKI. The primary endpoint was to appraise the receiver-operating characteristics of an 8-component and a 12-component CA-AKI model. Independent predictors of Kidney Disease Improving Global Outcomes-based acute kidney injury and the impact of CA-AKI on 1-year mortality and bleeding were also investigated.

RESULTS

The MATRIX trial included 8,201 patients with complete creatinine values and no end-stage renal disease. CA-AKI occurred in 5.5% of the patients, with a stepwise increase of CA-AKI rates from the lowest to the highest of the 4 risk categories. The receiver-operating characteristic area under the curve was 0.67 (95% CI: 0.64-0.70) with model 1 and 0.71 (95% CI: 0.68-0.74) with model 2. CA-AKI risk was systematically overestimated with both models (Hosmer-Lemeshow goodness-of-fit test: P < 0.05). The 1-year risks of all-cause mortality and bleeding were higher in CA-AKI patients (HR: 7.03 [95% CI: 5.47-9.05] and HR: 3.20 [95% CI: 2.56-3.99]; respectively). There was a gradual risk increase for mortality and bleeding as a function of the CA-AKI risk category for both models.

CONCLUSIONS

The updated CA-AKI risk score identifies patients at incremental risks of acute kidney injury, bleeding, and mortality. (Minimizing Adverse Haemorrhagic Events by Transradial Access Site and Systemic Implementation of angioX [MATRIX]; NCT01433627).

SuPAR mediates viral response proteinuria by rapidly changing podocyte function

Elevation in soluble urokinase receptor (suPAR) and proteinuria are common signs in patients with moderate to severe coronavirus disease 2019 (COVID-19). Here we characterize a new type of proteinuria originating as part of a viral response. Inoculation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes increased suPAR levels and glomerulopathy in African green monkeys. Using an engineered mouse model with high suPAR expression, inhaled variants of SARS-CoV-2 spike S1 protein elicite proteinuria that could be blocked by either suPAR antibody or SARS-CoV-2 vaccination. In a cohort of 1991 COVID-19 patients, suPAR levels exhibit a stepwise association with proteinuria in non-Omicron, but not in Omicron infections, supporting our findings of biophysical and functional differences between variants of SARS-CoV-2 spike S1 protein and their binding to podocyte integrins. These insights are not limited to SARS-CoV-2 and define viral response proteinuria (VRP) as an innate immune mechanism and co-activation of podocyte integrins.

Liquid Biopsy at the Frontier of Kidney Diseases: Application of Exosomes in Diagnostics and Therapeutics

In the era of precision medicine, liquid biopsy techniques, especially the use of urine analysis, represent a paradigm shift in the identification of biomarkers, with considerable implications for clinical practice in the field of nephrology. In kidney diseases, the use of this non-invasive tool to identify specific and sensitive biomarkers other than plasma creatinine and the glomerular filtration rate is becoming crucial for the diagnosis and assessment of a patient's condition. In recent years, studies have drawn attention to the importance of exosomes for diagnostic and therapeutic purposes in kidney diseases. Exosomes are nano-sized extracellular vesicles with a lipid bilayer structure, composed of a variety of biologically active substances. In the context of kidney diseases, studies have demonstrated that exosomes are valuable carriers of information and are delivery vectors, rendering them appealing candidates as biomarkers and drug delivery vehicles with beneficial therapeutic outcomes for kidney diseases. This review summarizes the applications of exosomes in kidney diseases, emphasizing the current biomarkers of renal diseases identified from urinary exosomes and the therapeutic applications of exosomes with reference to drug delivery and immunomodulation. Finally, we discuss the challenges encountered when using exosomes for therapeutic purposes and how these may affect its clinical applications.

Longitudinal links between early adolescent temperament and inflammation among young black adults

A large body of research demonstrates that inflammation is involved in physical health problems that cause substantial morbidity and early mortality. Given inflammation's role in the etiology of chronic diseases, pediatric scientists have begun to study childhood factors that presage elevation of inflammatory biomarkers later in life. The purpose of this study was to test hypotheses designed to determine whether early adolescent emotionally intense and low attention temperaments forecast (a) inflammation at ages 25 and 29 years and (b) worsening levels of inflammation between these two data points. Toward this end, 307 Black children from the rural southeastern United States participated in an 18-year longitudinal study (mean age at baseline, 11.2 years) to determine whether and how early adolescent's behavioral styles or emotionally intense and low attention temperaments may be associated with absolute and worsening levels of inflammation in young adulthood. When children were 11-13 years of age, different teachers at each age provided assessments of emotionally intense and low attention temperaments. Thus, multiple measures of the same temperament constructs were obtained across 3 years for each participant. At age 25, participants provided data on their self-regulation abilities. Peripheral blood was collected at ages 25 and 29 years from which inflammation was quantified, using soluble urokinase plasminogen activator (suPAR), the proinflammatory cytokines interleukin (IL) IL-6, IL-10, and tumor necrosis factor-alpha (TNF-α). Covariates associated with inflammation in prior studies were also assessed; these included socioeconomic risk, gender, cigarette smoking, body mass index (BMI), adverse childhood experiences (ACEs), depressive symptoms, and medication use. An early adolescent emotionally intense temperament was associated directly with higher suPAR and cytokine levels at age 29, and with worsening cytokine levels between ages 25 and 29. A low attention temperament was associated with suPAR levels at age 29. Collectively, these observations highlight pathways that could underlie health risks associated with early adolescent temperaments. The findings suggest that emotionally intense and low-attention early adolescent temperaments forecast higher and worsening inflammation levels across young adulthood.

Association of Kidney Tubule Biomarkers With Cardiac Structure and Function in the Multiethnic Study of Atherosclerosis

Markers of glomerular disease, estimated glomerular filtration rate (eGFR) and albuminuria, are associated with cardiac structural abnormalities and incident cardiovascular disease (CVD). We aimed to determine whether biomarkers of kidney tubule injury, function, and systemic inflammation are associated with cardiac structural abnormalities. Among 393 Multi-Ethnic Study of Atherosclerosis participants without diabetes, CVD, or chronic kidney disease, we assessed the association of 12 biomarkers of kidney tubule injury, function, and systemic inflammation with the left ventricular mass/volume ratio (LVmvr) and left ventricular ejection fraction (LVEF) on cardiac magnetic resonance imaging using linear regression. The average age was 60 ± 10 years; 48% were men; mean eGFR was 96±16 ml/min/1.73 m2; mean LVmvr was 0.93±0.18 g/ml, and mean LVEF was 62±6%. Each twofold greater concentration of plasma soluble urokinase plasminogen activator receptor was associated with a 0.04 g/ml (95% confidence interval [CI] 0.01 to 0.08 g/ml) higher LVmvr and 2.1% (95% CI 0.6 to 3.5%) lower LVEF, independent of risk factors for CVD, eGFR, and albuminuria. Each twofold greater plasma monocyte chemoattractant protein 1 was associated with higher LVmvr with a similar coefficient to that of plasma soluble urokinase plasminogen activator receptor. Each twofold greater concentration of plasma chitinase-3-like protein 1 and urine alpha-1-microglobulin was associated with a 1.1% (95% CI 0.4 to 1.7%) and 1.2% (95% CI 0.2 to 2.2%) lower LVEF, respectively. In conclusion, abnormal kidney tubule health may lead to cardiac dysfunction above and beyond eGFR and albuminuria.

Prediction of urinary dickkopf-3 for AKI, sepsis-associated AKI, and PICU mortality in children

BACKGROUND

Preoperative urinary dickkopf-3 (DKK3) is proposed as an early biomarker for the prediction of acute kidney injury (AKI) in patients undergoing cardiac surgery. We explored the clinical utility of urinary DKK3 for the early predictive value for AKI, sepsis-associated AKI (SA-AKI), and pediatric intensive care unit (PICU) mortality in critically ill children.

METHODS

Urine samples were collected during the first 24 h after admission for measurement of DKK3. AKI diagnosis was based on serum creatinine and urine output using the KDIGO criteria. SA-AKI was defined as AKI that occurred in children who met the sepsis criteria in accordance with the surviving sepsis campaign international guidelines for children.

RESULTS

Of the 420 children, 73 developed AKI, including 24 with SA-AKI, and 30 died during the PICU stay. The urinary DKK3 level was significantly associated with AKI, SA-AKI, and PICU mortality, even after adjustment for confounders. The area under the receiver operating characteristic curve of urinary DKK3 for the discrimination of AKI, SA-AKI, and PICU mortality was 0.70, 0.80, and 0.78, respectively.

CONCLUSION

Urinary DKK3 was independently associated with an increased risk for AKI, SA-AKI, and PICU mortality and may be predictive of the aforementioned issues in critically ill children.

IMPACT

Urinary dickkopf-3 (DKK3) has been identified as a preoperative biomarker for the prediction of acute kidney injury (AKI) following cardiac surgery or coronary angiography in adult patients. However, little is known about the clinical utility of urinary DKK3 in pediatric cohorts. This study demonstrated that urinary DKK3 is capable of early predicting AKI and pediatric intensive care unit (PICU) mortality and discriminating sepsis-associated AKI (SA-AKI) from other types of AKI. Urinary DKK3 may be an early biomarker for predicting AKI, SA-AKI, and PICU mortality in critically ill children.

Circulating Soluble Urokinase Plasminogen Activator Receptor as a Predictive Indicator for COVID-19-Associated Acute Kidney Injury and Mortality: Clinical and Bioinformatics Analysis

Urokinase receptors regulate the interplay between inflammation, immunity, and blood clotting. The soluble urokinase plasminogen activator system is an immunologic regulator affecting endothelial function and its related receptor; the soluble urokinase plasminogen activator receptor (suPAR) has been reported to impact kidney injury. This work aims to measure serum levels of suPAR in COVID-19 patients and correlate the measurements with variable clinicolaboratory parameters and patient outcomes. In this prospective cohort study, 150 COVID-19 patients and 50 controls were included. The circulating suPAR levels were quantified by Enzyme-linked immunosorbent assay (ELISA). Routine COVID-19 laboratory assessments, including CBC, CRP, LDH, serum creatinine, and estimated glomerular filtration rates, were performed. The need for oxygen therapy, CO-RAD score, and survival rates was assessed. Bioinformatic analysis and molecular docking were run to explore the urokinase receptor structure/function and to characterize molecules as potential anti-suPAR therapeutic targets, respectively. We found higher circulating suPAR levels in COVID-19 patients vs. controls (p < 0.001). Circulating suPAR levels positively correlated with COVID-19 severity, the need for O₂ therapy, the total leukocytes count, and the neutrophils to lymphocyte ratio, while they were negatively correlated with the O₂ saturation level, albumin, blood calcium, lymphocytic count, and GFR. In addition, the suPAR levels were associated with poor prognostic outcomes such as a high incidence of acute kidney injury (AKI) and mortality rate. Kaplan-Meier curves showed a lower survival rate with higher suPAR levels. The logistic regression analysis confirmed the significant association of suPAR levels with the occurrence of AKI related to COVID-19 and with increased mortality probability within three months of COVID-19 follow-up. Some compounds that can act similarly to uPAR were discovered and tested by molecular docking to identify the possible ligand-protein interactions. In conclusion, higher circulating suPAR levels were associated with COVID-19 severity and could be considered a putative predictor of AKI development and mortality.

suPAR links a dysregulated immune response to tissue inflammation and sepsis-induced acute kidney injury

Acute kidney injury (AKI) secondary to sepsis results in poor outcomes and conventional kidney function indicators lack diagnostic value. Soluble urokinase plasminogen activator receptor (suPAR) is an innate immune-derived molecule implicated in inflammatory organ damage. We characterized the diagnostic ability of longitudinal serum suPAR levels to discriminate severity and course of sepsis-induced AKI (SI-AKI) in 200 critically ill patients meeting Sepsis-3 criteria. The pathophysiologic relevance of varying suPAR levels in SI-AKI was explored in a polymicrobial sepsis model in WT, (s)uPAR-knockout, and transgenic suPAR-overexpressing mice. At all time points studied, suPAR provided a robust classification of SI-AKI disease severity, with improved prediction of renal replacement therapy (RRT) and mortality compared with established kidney biomarkers. Patients with suPAR levels of greater than 12.7 ng/mL were at highest risk for RRT or death, with an adjusted odds ratio of 7.48 (95% CI, 3.00-18.63). suPAR deficiency protected mice against SI-AKI. suPAR-overexpressing mice exhibited greater kidney damage and poorer survival through inflamed kidneys, accompanied by local upregulation of potent chemoattractants and pronounced kidney T cell infiltration. Hence, suPAR allows for an innate immune-derived and kidney function-independent staging of SI-AKI and offers improved longitudinal risk stratification. suPAR promotes T cell-based kidney inflammation, while suPAR deficiency improves SI-AKI.

BIOMARKERS: CAN THEY REALLY GUIDE OUR DAILY PRACTICE?

ABSTRACT

Optimal management of septic patients requires accurate assessment of both current severity status and prognosis. Since the 1990s, substantial advances have been made in the use of circulating biomarkers for such assessments. This summary of the session on "Biomarkers: can they really use guide our daily practice?" presented at the 2021 WEB-CONFERENCE OF THE EUROPEAN SHOCK SOCIETY, 6 November 2021. These biomarkers include ultrasensitive detection of bacteremia, circulating soluble urokina-type plasminogen activator receptor (suPAR), C-reactive protein (CRP) and ferritin and procalcitonin. In addition, the potential application of novel multiwavelength optical biosensor technology allows noninvasive monitoring of multiple metabolites that can be used to assess severity and prognosis in septic patients. The application these biomarkers and improved technologies provide the potential for improved personalized management of septic patients.

Soluble Urokinase Plasminogen Activator Receptor Levels and Outcomes in Patients with Heart Failure

BACKGROUND

Soluble urokinase-type plasminogen activator receptor (suPAR) is a marker of immune activation and pathogenic factor for kidney disease shown to predict cardiovascular outcomes including heart failure (HF) in various populations. We characterized suPAR levels in patients with HF and compared its ability to discriminate risk to that of B-type natriuretic peptide (BNP).

METHODS AND RESULTS

We measured plasma suPAR and BNP levels in 3,437 patients undergoing coronary angiogram and followed for a median of 6.2 years. We performed survival analyses for the following outcomes: all-cause death, cardiovascular death, and hospitalization for HF. We then assessed suPAR's ability to discriminate risk for the aforementioned outcomes. We identified 1116 patients with HF (age 65±12, 67.2% male, 20.0% Black, 67% with reduced ejection fraction). The median suPAR level was higher in HF compared to those without HF (3370 [IQR 2610-4371] vs. 2880 [IQR 2270-3670] pg/mL, respectively, P<0.001). In patients with HF, suPAR levels (log-base 2) were associated with outcomes including all-cause death (adjusted hazard ratio aHR 2.30, 95%CI[1.90-2.77]), cardiovascular death (aHR 2.33 95%CI[1.81-2.99]) and HF hospitalization (aHR 1.96, 95%CI[1.06-1.25]) independently of clinical characteristics and BNP levels. The association persisted across subgroups and did not differ between patients with reduced or preserved ejection fraction, or those with ischemic or non-ischemic cardiomyopathy. Addition of suPAR to a model including BNP levels significantly improved the C-statistic for death (Δ0.027), cardiovascular death (Δ0.017) and hospitalization for HF (Δ0.017).

CONCLUSIONS

SuPAR levels are higher in HF compared to non-HF, are strongly predictive of outcomes, and combined with BNP, significantly improved risk prediction.

LAY SUMMARY

Soluble urokinase plasminogen activator receptor and survival in elective cardiac surgery

BACKGROUND

The study investigated the prognostic value of soluble urokinase plasminogen activator receptor (suPAR) in patients undergoing cardiac surgery and calculated a simplified biomarker score comprising suPAR, N-terminal pro B-type natriuretic peptide (NT-proBNP) and age.

METHODS AND RESULTS

Biomarkers were assessed in a cohort of 478 patients undergoing elective cardiac surgery. After a median follow-up of 4.2 years, a total of 72 (15.1%) patients died. SuPAR, NT-proBNP and age were independent prognosticators of mortality in a multivariable Cox regression model after adjustment for EuroScoreII. We then calculated a simplified biomarker score comprising age, suPAR and NT-proBNP, which had a superior prognostic value compared to EuroScoreII (Harrel's C of 0.76 vs. 0.72; P for difference = 0.02). Besides long-term mortality, the biomarker score had an excellent performance predicting one-year mortality and hospitalization due to heart failure.

CONCLUSION

The biomarker suPAR and NT-proBNP were strongly and independently associated with mortality in patients undergoing cardiac surgery. A simplified biomarker score comprising only three variables (age, suPAR and NT-proBNP) performed better than the established EuroScoreII with respect to intermediate and long-term outcome as well as hospitalization due to heart failure. As such, integration of established and upcoming biomarkers in clinical practice may provide improved decision support in cardiac surgery.

Predictive value of suPAR in AKI: a systematic review and meta-analysis

BACKGROUND

Some clinical trials have shown that soluble urokinase-type plasminogen activator receptor (suPAR) has good predictive value for acute kidney injury (AKI), but there is still a lack of evidence-based proof. Therefore, we conducted this systematic review and meta-analysis to evaluate the predictive value of suPAR for AKI.

METHODS

Pubmed, EMBASE, Cochrane Library, and Web of Science databases were searched until December 2021 to obtain the literature on the prediction of suPAR for AKI. The quality of the included studies was assessed using the QUADAS-2 scoring system, and a bivariate random-effect model was used for the meta-analysis. The present study has been registered on PROSPERO (Registration No. CRD42022324978).

RESULTS

Seven articles were included, involving 2,319 patients, 635 of whom were AKI patients. The meta-analysis results showed that the combined sensitivity of suPAR in predicting AKI was 0.77 (95% CI 0.67-0.84); the specificity was 0.64 (95% CI 0.53-0.75); the odds ratio of diagnosis was 6 (95% CI 3-10); the pooled positive likelihood ratio was 2.2 (95% CI 1.6-2.9); the pooled negative likelihood ratio was 0.36 (95% CI 0.26-0.52); and the area under the summary receiver-operating characteristic (SROC) curve was 0.77 (95% CI 0.12~0.99). Deek's funnel plot suggested no potential publication bias among included studies.

CONCLUSION

suPAR is a valuable biomarker for the prediction of AKI with relatively high predictive accuracy, but its clinical application needs improvements. SuPAR should be considered as an indicator in the subsequent development of more effective predictive tools for AKI.

Increased soluble urokinase plasminogen activator levels modulate monocyte function to promote atherosclerosis

People with kidney disease are disproportionately affected by atherosclerosis for unclear reasons. Soluble urokinase plasminogen activator receptor (suPAR) is an immune-derived mediator of kidney disease, levels of which are strongly associated with cardiovascular outcomes. We assessed suPAR's pathogenic involvement in atherosclerosis using epidemiologic, genetic, and experimental approaches. We found serum suPAR levels to be predictive of coronary artery calcification and cardiovascular events in 5,406 participants without known coronary disease. In a genome-wide association meta-analysis including over 25,000 individuals, we identified a missense variant in the plasminogen activator, urokinase receptor (PLAUR) gene (rs4760), confirmed experimentally to lead to higher suPAR levels. Mendelian randomization analysis in the UK Biobank using rs4760 indicated a causal association between genetically predicted suPAR levels and atherosclerotic phenotypes. In an experimental model of atherosclerosis, proprotein convertase subtilisin/kexin-9 (Pcsk9) transfection in mice overexpressing suPAR (suPARTg) led to substantially increased atherosclerotic plaques with necrotic cores and macrophage infiltration compared with those in WT mice, despite similar cholesterol levels. Prior to induction of atherosclerosis, aortas of suPARTg mice excreted higher levels of CCL2 and had higher monocyte counts compared with WT aortas. Aortic and circulating suPARTg monocytes exhibited a proinflammatory profile and enhanced chemotaxis. These findings characterize suPAR as a pathogenic factor for atherosclerosis acting at least partially through modulation of monocyte function.

Soluble urokinase plasminogen activator receptor: from biomarker to active participant in atherosclerosis and cardiovascular disease

Atherosclerosis contributes to the majority of deaths related to cardiovascular disease (CVD). Recently, the nonspecific inflammatory biomarker soluble urokinase plasminogen activator receptor (suPAR) has shown prognostic value in patients with CVD; however, it remains unclear whether suPAR participates in the disease process. In this issue of the JCI, Hindy and colleagues report on their evaluation of a multi-ethnic cohort of over 5,000 participants without known CVD. High suPAR levels correlated with incident CVD and atherosclerosis. Genetic analysis revealed two variants associated with the suPAR-encoding gene (PLAUR) with higher plasma suPAR levels. Notably, a mouse model with high suPAR levels possessed aortic tissue with a proinflammatory phenotype, including monocytes with enhanced chemotaxis similar to that seen in atherogenesis. These findings suggest a causal relationship between suPAR and coronary artery calcification and have clinical implications that extend to inflammatory disorders beyond CVD.

Exosomal transfer of microRNA-590-3p between renal tubular epithelial cells after renal ischemia-reperfusion injury regulates autophagy by targeting TRAF6

BACKGROUND

Acute kidney injury (AKI) is a common complication in patients, especially elderly patients, who undergo cardiac surgery with cardiopulmonary bypass. Studies have indicated a protective role of autophagy in AKI. However, the mechanisms underlying the regulatory effect of autophagy in AKI among patients undergoing cardiac surgeries are poorly understood. In this study, we aimed to test the hypothesis that exosomal microRNAs (miRNAs) regulate autophagy in tubular epithelial cells after AKI.

METHODS

Plasma exosomal RNA was extracted from young and elderly AKI patients undergoing cardiac surgery, and the miRNAs expression during the perioperative period were analyzed using next-generation sequencing. The screened miRNAs and their target genes were subjected to gene oncology function and Kyoto Encyclopedia of Genes and Genome enrichment analyses. Renal tubular epithelial cell line (HK-2 cells) was cultured and hypoxia/reoxygenation (H/R) model was established, which is an in vitro renal ischemia/reperfusion (I/R) model. We used Western blot analysis, cell viability assay, transfection, luciferase assay to investigate the mechanisms underlying the observed increases in the levels of renal I/R injury-mediated exosomal miRNAs and their roles in regulating HK-2 cells autophagy.

RESULTS

miR-590-3p was highly enriched in the plasma exosomes of young AKI patients after cardiac surgery. Increased levels of miR-590-3p led to the increases in the expression of autophagy marker proteins, including Beclin-1 and microtubule associated protein 1 light chain 3 beta (LC3II), and prolonged the autophagic response in HK-2 cells after H/R treatment. These effects were achieved mainly via increases in the exosomal miR-590-3p levels, and the tumor necrosis factor receptor-associated factor 6 protein was shown to play a key role in I/R injury-mediated autophagy induction.

CONCLUSION

Exosomes released from HK-2 cells after renal I/R injury regulate autophagy by transferring miR-590-3p in a paracrine manner, which suggests that increasing the miR-590-3p levels in HK-2 cell-derived exosomes may increase autophagy and protect against kidney injury after renal I/R injury.

Soluble Urokinase Plasminogen Activator Receptor and Venous Thromboembolism in COVID-19

Background Venous thromboembolism (VTE) contributes significantly to COVID-19 morbidity and mortality. The urokinase receptor system is involved in the regulation of coagulation. Levels of soluble urokinase plasminogen activator receptor (suPAR) reflect hyperinflammation and are strongly predictive of outcomes in COVID-19. Whether suPAR levels identify patients with COVID-19 at risk for VTE is unclear. Methods and Results We leveraged a multinational observational study of patients hospitalized for COVID-19 with suPAR and D-dimer levels measured on admission. In 1960 patients (mean age, 58 years; 57% men; 20% Black race), we assessed the association between suPAR and incident VTE (defined as pulmonary embolism or deep vein thrombosis) using logistic regression and Fine-Gray modeling, accounting for the competing risk of death. VTE occurred in 163 (8%) patients and was associated with higher suPAR and D-dimer levels. There was a positive association between suPAR and D-dimer (β=7.34; P=0.002). Adjusted for clinical covariables, including D-dimer, the odds of VTE were 168% higher comparing the third with first suPAR tertiles (adjusted odds ratio, 2.68 [95% CI, 1.51-4.75]; P<0.001). Findings were consistent when stratified by D-dimer levels and in survival analysis accounting for death as a competing risk. On the basis of predicted probabilities from random forest, a decision tree found the combined D-dimer <1 mg/L and suPAR <11 ng/mL cutoffs, identifying 41% of patients with only 3.6% VTE probability. Conclusions Higher suPAR was associated with incident VTE independently of D-dimer in patients hospitalized for COVID-19. Combining suPAR and D-dimer identified patients at low VTE risk. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT04818866.

The Perspective of Vitamin D on suPAR-Related AKI in COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has claimed the lives of millions of people around the world. Severe vitamin D deficiency can increase the risk of death in people with COVID-19. There is growing evidence that acute kidney injury (AKI) is common in COVID-19 patients and is associated with poorer clinical outcomes. The kidney effects of SARS-CoV-2 are directly mediated by angiotensin 2-converting enzyme (ACE2) receptors. AKI is also caused by indirect causes such as the hypercoagulable state and microvascular thrombosis. The increased release of soluble urokinase-type plasminogen activator receptor (suPAR) from immature myeloid cells reduces plasminogen activation by the competitive inhibition of urokinase-type plasminogen activator, which results in low plasmin levels and a fibrinolytic state in COVID-19. Frequent hypercoagulability in critically ill patients with COVID-19 may exacerbate the severity of thrombosis. Versican expression in proximal tubular cells leads to the proliferation of interstitial fibroblasts through the C3a and suPAR pathways. Vitamin D attenuates the local expression of podocyte uPAR and decreases elevated circulating suPAR levels caused by systemic inflammation. This decrease preserves the function and structure of the glomerular barrier, thereby maintaining renal function. The attenuated hyperinflammatory state reduces complement activation, resulting in lower serum C3a levels. Vitamin D can also protect against COVID-19 by modulating innate and adaptive immunity, increasing ACE2 expression, and inhibiting the renin–angiotensin–aldosterone system. We hypothesized that by reducing suPAR levels, appropriate vitamin D supplementation could prevent the progression and reduce the severity of AKI in COVID-19 patients, although the data available require further elucidation.

Integrating basic science with translational research: the 13th International Podocyte Conference 2021

The 13th International Podocyte Conference was held in Manchester, UK, and online from July 28 to 30, 2021. Originally planned for 2020, this biannual meeting was postponed by a year because of the coronavirus disease 2019 (COVID-19) pandemic and proceeded as an innovative hybrid meeting. In addition to in-person attendance, online registration was offered, and this attracted 490 conference registrations in total. As a Podocyte Conference first, a day for early-career researchers was introduced. This premeeting included talks from graduate students and postdoctoral researchers. It gave early career researchers the opportunity to ask a panel, comprising academic leaders and journal editors, about career pathways and the future for podocyte research. The main meeting over 3 days included a keynote talk and 4 focused sessions each day incorporating invited talks, followed by selected abstract presentations, and an open panel discussion. The conference concluded with a Patient Day, which brought together patients, clinicians, researchers, and industry representatives. The Patient Day was an interactive and diverse day. As well as updates on improving diagnosis and potential new therapies, the Patient Day included a PodoArt competition, exercise and cooking classes with practical nutrition advice, and inspirational stories from patients and family members. This review summarizes the exciting science presented during the 13th International Podocyte Conference and demonstrates the resilience of researchers during a global pandemic.

Soluble urokinase-type plasminogen activator receptor improves early risk stratification in cardiogenic shock

AIMS

Soluble urokinase-type plasminogen activator receptor (suPAR) is a biomarker reflecting the level of immune activation. It has been shown to have prognostic value in acute coronary syndrome and heart failure as well as in critical illness. Considering the complex pathophysiology of cardiogenic shock (CS), we hypothesized suPAR might have prognostic properties in CS as well. The aim of this study was to assess the kinetics and prognostic utility of suPAR in CS.

METHODS AND RESULTS

SuPAR levels were determined in serial plasma samples (0-96 h) from 161 CS patients in the prospective, observational, multicentre CardShock study. Kinetics of suPAR, its association with 90-day mortality, and additional value in risk-stratification were investigated. The median suPAR-level at baseline was 4.4 [interquartile range (IQR) 3.2-6.6)] ng/mL. SuPAR levels above median were associated with underlying comorbidities, biomarkers reflecting renal and cardiac dysfunction, and higher 90-day mortality (49% vs. 31%; P = 0.02). Serial measurements showed that survivors had significantly lower suPAR levels at all time points compared with nonsurvivors. For risk stratification, suPAR at 12 h (suPAR12h) with a cut-off of 4.4 ng/mL was strongly associated with mortality independently of established risk factors in CS: OR 5.6 (95% CI 2.0-15.5); P = 0.001) for death by 90 days. Adding suPAR12h > 4.4 ng/mL to the CardShock risk score improved discrimination identifying high-risk patients originally categorized in the intermediate-risk category.

CONCLUSION

SuPAR associates with mortality and improves risk stratification independently of other previously known risk factors in CS patients.

RAGE pathway activation and function in chronic kidney disease and COVID-19

The multi-ligand receptor for advanced glycation end-products (RAGE) and its ligands are contributing factors in autoimmunity, cancers, and infectious disease. RAGE activation is increased in chronic kidney disease (CKD) and coronavirus disease 2019 (COVID-19). CKD may increase the risk of COVID-19 severity and may also develop in the form of long COVID. RAGE is expressed in essentially all kidney cell types. Increased production of RAGE isoforms and RAGE ligands during CKD and COVID-19 promotes RAGE activity. The downstream effects include cellular dysfunction, tissue injury, fibrosis, and inflammation, which in turn contribute to a decline in kidney function, hypertension, thrombotic disorders, and cognitive impairment. In this review, we discuss the forms and mechanisms of RAGE and RAGE ligands in the kidney and COVID-19. Because various small molecules antagonize RAGE activity in animal models, targeting RAGE, its co-receptors, or its ligands may offer novel therapeutic approaches to slowing or halting progressive kidney disease, for which current therapies are often inadequate.

Biomarkers for early detection and predicting outcomes in acute kidney injury

The current diagnosis of acute kidney injury relies on the measurement of serum creatinine levels and urine output. However, both measures are subject to considerable limitations; for example, change in serum creatinine levels ideally requires a knowledge of baseline function that is often not available. Furthermore, creatinine levels are influenced by many factors including diet, drug therapy, muscle mass, gender and ethnicity, which may lead to underestimation of the extent of renal dysfunction. Similarly, urine output lacks both specificity and sensitivity as a marker of acute kidney injury given that oliguria may be an appropriate physiological response to a multitude of stressors and that output may be maintained until significant renal damage has already occurred.

Given the well-documented consequences of acute kidney injury and the considerable burden associated with its development, much attention has focused on early identification of patients at high risk to try and improve outcomes. Many studies have focused on the identification of candidate molecules that may enable the early detection of individuals at risk of developing acute kidney injury, including constitutive proteins associated with kidney damage, as well as molecules upregulated in response to injury, non-renal products that may be filtered, reabsorbed or secreted by the kidney, and markers of renal stress. Such biomarkers may also aid stratification for adverse events, such as the need for kidney replacement therapy or progression to chronic kidney disease and end-stage kidney disease. This article discusses some of these novel biomarkers and assesses the role they may have in the understanding, management, diagnosis and prognostication of acute kidney injury.

Soluble urokinase Plasminogen Activator Receptor (suPAR) levels are predictive of COVID-19 severity: An Italian experience

Background

The soluble urokinase Plasminogen Activator Receptor (suPAR) has been identified as a reliable marker of COVID-19 severity, helping in personalizing COVID-19 therapy. This study aims to evaluate the correlation between suPAR levels and COVID-19 severity, in relation to the traditional inflammatory markers.

Methods

Sera from 71 COVID-19 patients were tested for suPAR levels using Chorus suPAR assay (Diesse Diagnostica Senese SpA, Italy). suPAR levels were compared with other inflammatory markers: IL-1β, IL-6, TNF-α, circulating calprotectin, neutrophil and lymphocyte counts, and Neutrophil/Lymphocytes Ratio (NLR). Respiratory failure, expressed as P/F ratio, and mortality rate were used as indicators of disease severity.

Results

A positive correlation of suPAR levels with IL-6 (r = 0.479, p = 0.000), TNF-α (r = 0.348, p = 0.003), circulating calprotectin (r = 0.369, p = 0.002), neutrophil counts (r = 0.447, p = 0.001), NLR (r = 0.492, p = 0.001) has been shown. Stratifying COVID-19 population by suPAR concentration above and below 6 ng/mL, we observed higher levels of circulating calprotectin (10.1 μg/mL, SD 7.9 versus 6.4 μg/mL, SD 7.5, p < 0.001), higher levels of P/F ratio (207.5 IQR 188.3 vs 312.0 IQR 127.8, p = 0.013) and higher mortality rate. Median levels of suPAR were increased in all COVID-19 patients requiring additional respiratory support (Nasal Cannula, Venturi Mask, BPAP and CPAP) (6.5 IQR = 4.9) compared to the group at room air (4.6 IQR = 4.2).

Conclusion

suPAR levels correlate with disease severity and survival rate of COVID-19 patients, representing a promising prognostic biomarker for the risk assessment of the disease.