Circulating suPAR levels are affected by glomerular filtration rate and proteinuria in primary and secondary glomerulonephritis

Intestinal homeostasis in the gut-lung-kidney axis: a prospective therapeutic target in immune-related chronic kidney diseases

In recent years, the role of intestinal homeostasis in health has received increasing interest, significantly improving our understanding of the complex pathophysiological interactions of the gut with other organs. Microbiota dysbiosis, impaired intestinal barrier, and aberrant intestinal immunity appear to contribute to the pathogenesis of immune-related chronic kidney diseases (CKD). Meanwhile, the relationship between the pathological changes in the respiratory tract (e.g., infection, fibrosis, granuloma) and immune-related CKD cannot be ignored. The present review aimed to elucidate the new underlying mechanism of immune-related CKD. The lungs may affect kidney function through intestinal mediation. Communication is believed to exist between the gut and lung microbiota across long physiological distances. Following the inhalation of various pathogenic factors (e.g., particulate matter 2.5 mum or less in diameter, pathogen) in the air through the mouth and nose, considering the anatomical connection between the nasopharynx and lungs, gut microbiome regulates oxidative stress and inflammatory states in the lungs and kidneys. Meanwhile, the intestine participates in the differentiation of T cells and promotes the migration of various immune cells to specific organs. This better explain the occurrence and progression of CKD caused by upper respiratory tract precursor infection and suggests the relationship between the lungs and kidney complications in some autoimmune diseases (e.g., anti-neutrophil cytoplasm antibodies -associated vasculitis, systemic lupus erythematosus). CKD can also affect the progression of lung diseases (e.g., acute respiratory distress syndrome and chronic obstructive pulmonary disease). We conclude that damage to the gut barrier appears to contribute to the development of immune-related CKD through gut-lung-kidney interplay, leading us to establish the gut-lung-kidney axis hypothesis. Further, we discuss possible therapeutic interventions and targets. For example, using prebiotics, probiotics, and laxatives (e.g., Rhubarb officinale) to regulate the gut ecology to alleviate oxidative stress, as well as improve the local immune system of the intestine and immune communication with the lungs and kidneys.

Evaluation of plasma soluble urokinase plasminogen activator receptor (SuPAR) levels in ulcerative colitis

BACKGROUND AND STUDY AIM

Soluble urokinase plasminogen activator receptor (SuPAR), a soluble form of the urokinase-type plasminogen activator receptor, is a biomarker produced by macrophages, monocytes, neutrophils, active T cells, endothelial cells, and circulating tumor cells. SuPAR is a novel biomarker showing altered inflammation in many inflammatory diseases. This study aims to investigate the SuPAR level in ulcerative colitis (UC) patients, and to evaluate the SuPAR level in active, and remission patients.

PATIENTS AND METHODS

Patient and healthy control SuPAR levels were analyzed by immunoassay method. SuPAR levels between UC patients and control group were compared. The difference between SuPAR levels in patients with active UC and UC in remission was analyzed. The relationship between C-reactive protein level, Total Mayo score, Mayo Endoscopic score used to predict disease activity, and amount of SuPAR were evaluated.

RESULTS

SuPAR levels were determined in the UC patient group (2170,3 ± 121,0 pg/ml), and healthy controls (2130,7 ± 164,8 pg/ml) (p = 0. 805). Median SuPAR levels were determined in moderate UC (2479 pg/ml), mild UC (1944 pg/ml), and patients in remission (1774 pg/ml) (p = 0,207). There were no significant relationships between SuPAR levels and CRP levels, Total Mayo score, disease duration in the UC group (r = 0.177, r = 0.267, and r = 0,007; respectively p > 0.05). A slightly positive correlation was found between Mayo Endoscopic Score and SuPAR level (r = 0.303; p = 0.031).

CONCLUSION

SuPAR is of limited value in the diagnosis of ulcerative colitis and in the assessment of disease activation.

Serum soluble urokinase plasminogen activator receptor as a potential biomarker of renal impairment severity in diabetic nephropathy

AIMS

To investigate serum soluble form of urokinase-type plasminogen activator receptor (suPAR) in patients with diabetic kidney disease (DKD) and biopsy-proven diabetic nephropathy (DN), its correlation with histological parameters and its capacity as a biomarker for renal impairment severity.

METHODS

We conducted a cross-sectional study on 75 patients with diabetes mellitus (DM) and DKD, among whom 28 had biopsy-proven DN.

RESULTS

Among the 75 patients, 9 (12%) had type 1 and 66 (88%) type 2 DM. The median value of the serum suPAR level was 2857.2 pg/mL (1916.4-3700) in the entire cohort and 2472.1 pg/mL (1782.6-3745.8) in the biopsy-proven DN subgroup, respectively. suPAR was significantly correlated with diabetes duration, diabetic retinopathy, anti-proteinuric treatment, albuminuria, kidney function, DN class, interstitial fibrosis and tubular atrophy (IFTA) score and with interstitial inflammation score. suPAR had a good accuracy for the association with chronic kidney disease (CKD) stages G3b-5, macroalbuminuria, DN class IV, IFTA score 3 and interstitial inflammation score 2.

CONCLUSIONS

Serum suPAR was increased in DN patients and was associated with DM duration, diabetic retinopathy, renoprotective treatment, kidney function, proteinuria, DN class, IFTA and interstitial inflammation scores. Also, suPAR had a good capacity as a biomarker for advanced renal impairment and severe histological lesions of DN.

Targeting the Urokinase-Type Plasminogen Activator Receptor (uPAR) in Human Diseases With a View to Non-invasive Imaging and Therapeutic Intervention

The interaction between the serine protease urokinase-type plasminogen activator (uPA) and its glycolipid-anchored receptor (uPAR) focalizes plasminogen activation to cell surfaces, thereby regulating extravascular fibrinolysis, cell adhesion, and migration. uPAR belongs to the Ly6/uPAR (LU) gene superfamily and the high-affinity binding site for uPA is assembled by a dynamic association of its three consecutive LU domains. In most human solid cancers, uPAR is expressed at the invasive areas of the tumor-stromal microenvironment. High levels of uPAR in resected tumors or shed to the plasma of cancer patients are robustly associated with poor prognosis and increased risk of relapse and metastasis. Over the years, a plethora of different strategies to inhibit uPA and uPAR function have been designed and investigated in vitro and in vivo in mouse models, but so far none have been implemented in the clinics. In recent years, uPAR-targeting with the intent of cytotoxic eradication of uPAR-expressing cells have nonetheless gained increasing momentum. Another avenue that is currently being explored is non-invasive imaging with specific uPAR-targeted reporter-molecules containing positron emitting radionuclides or near-infrared (NIR) florescence probes with the overarching aim of being able to: (i) localize disease dissemination using positron emission tomography (PET) and (ii) assist fluorescence guided surgery using optical imaging. In this review, we will discuss these advancements with special emphasis on applications using a small 9-mer peptide antagonist that targets uPAR with high affinity.

Prognostic value of suPAR and hsCRP on acute kidney injury after cardiac surgery

Background

Acute kidney injury (AKI) represents a serious complication following cardiac surgery. Adverse outcome after cardiac surgery has been observed in the presence of elevated levels of soluble urokinase-type plasminogen activator receptor (suPAR) and high-sensitivity C-Reactive Protein (hsCRP). The aim of study was (i) to investigate the relationship between preoperative elevated levels of suPAR and hsCRP and postoperative AKI in unselected cardiac surgery patients and (ii) to assess whether the concentration of the biomarkers reflected severity of AKI.

Methods

In a retrospective observational study, biobank blood plasma samples (n = 924) from patients admitted for elective on-pump cardiac surgery were analysed for suPAR and hsCRP levels. The relation between suPAR and hsCRP-values and AKI (any stage), defined by the KDIGO (Kidney Disease: Improving Global Outcomes) criteria, was assessed using adjusted logistic regression. Further, the association between biomarkers and severity (KDIGO 1, KDIGO 2–3 and renal replacement therapy (RRT)) was assessed using adjusted logistic regression.

Results

Postoperative AKI (any stage) was observed in 327 patients (35.4 %). A doubling of preoperative suPAR corresponded to an adjusted odds ratio (OR) for postoperative AKI (any stage) of 1.62 (95 % CI 1.26–2.09, p < 0.001). Furthermore, a doubling of suPAR had an adjusted OR of 1.50 (95 % CI 1.16–1.93, p = 0.002), 2.44 (95 % CI 1.56–3.82, p < 0.001) and 1.92 (95 % CI 1.15–3.23, p = 0.002), for KDIGO 1, KDIGO 2–3 and need for RRT, respectively. No significant association was found between elevated levels of hsCRP and any degree of AKI.

Conclusions

Increasing levels of suPAR, but not hsCRP, were associated with development and severity of AKI following on-pump cardiac surgery.

Validation of suPAR turbidimetric assay on Cobas® (c502 and c702) and comparison to suPAR ELISA

suPAR is a plasma marker of chronic inflammation, and an elevated suPAR is consistently associated with worse outcome in a variety of clinical conditions. Quantification of suPAR is useful for determining patient risk in triage, but there is no fast automatized method for quick determination of suPAR. We developed and validated a rapid latex particle-enhanced turbidimetric immunoassay for quantification of plasma suPAR on the c502 and the c702 Roche Cobas® 8000 measurment systems. The turbidimetric assay was validated against the suPARnostic® ELISA (ViroGates, Denmark). This validation demonstrates suPAR can be analysed by turbidimetry giving very similar results (<15% difference) compared to the ELISA method and the observed correlations (n = 103) were strong, r > 0.95. Roche Cobas® 8000 instruments demonstrated repeatability and repoducibility, CV % at 3.4-4.1 and 5.7-11.4, respectively. The estimated limit of detection was 1.30 µg/L and 1.31 µg/L for the Cobas® c502 and c702, respectively. Dilution tests showed linearity of suPAR from 1.8 to 26.5 μg/L. The acceptable concentrations of Bilirubin, Intralipid and Hemoglobin, were 350 µmol/L, 3.3 g/L and 1.4 g/L, respectively. suPAR can be quantified reproducibly within 10 min using a turbidimetry assay. This assay is faster than ELISA with similar results, making it suitable for clinical routine analysis.

Idiopathic nephrotic syndrome and serum permeability factors: a molecular jigsaw puzzle

Nephrotic syndrome is traditionally defined using the triad of edema, hypoalbuminemia, and proteinuria, but this syndrome is very heterogeneous and difficult to clarify. Its idiopathic form (INS) is probably the most harmful and essentially comprises two entities: minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS). We will consider some hypotheses regarding the mechanisms underlying INS: (i) the presence of several glomerular permeability factors in the sera of patients that alter the morphology and function of podocytes leading to proteinuria, (ii) the putative role of immune cells. Thanks to recent data, our understanding of these disorders is evolving towards a more multifactorial origin. In this context, circulating factors may be associated according to sequential kinetic mechanisms or micro-environmental changes that need to be determined. In addition, the resulting proteinuria may trigger more proteinuria enhancing the glomerular destabilization.

Association between Soluble Urokinase-Type Plasminogen Activator Receptor Levels and Chronic Kidney Disease: A Systematic Review and Meta-Analysis

Background

Chronic kidney disease (CKD) has become a global public health problem with a high prevalence and mortality. There is no sensitive and effective markers for chronic kidney disease. Previous studies proposed suPAR as an early predict biomarker for chronic kidney disease, but the results are controversial. Therefore, the purpose of the current meta-analysis is to evaluate the association between suPAR and CKD.

Methods

We searched the PubMed, Embase, Cochrane Library databases, and Web of Science before May 1, 2019. The search was based on the key words including suPAR and CKD. Data are extracted independently according to standard format, and quality analysis is performed. We extracted the concentration of suPAR and hazard rate (HR) values of mortality, cardiovascular disease, and end-stage renal disease.

Results

There were 14 studies fulfilling the criteria. The concentration of suPAR was higher in patients with CKD than that in the control group (P < 0.001; SMD: −2.17; 95% CI: −2.71, −1.63; I² = 67.4%). SuPAR had a higher risk of mortality (P=0.001; HR: 1.72; 95% CI: 1.24, 2.39; I² = 68.0%). The higher suPAR level increased the risk of cardiovascular disease (P < 0.001; HR: 3.06; 95% CI: 2.21, 4.22; I² = 0.0%) and the risk of end-stage renal disease (P < 0.001; HR: 1.40; 95% CI: 1.22, 1.60; I² = 0.0%).

Conclusions

Monitoring suPAR concentrations may be used for early diagnosis and prognosis for patients with CKD, and the higher suPAR increased the risk of mortality, cardiovascular events, and end-stage renal disease.

Expression of Urokinase-type Plasminogen Activator Receptor and its Soluble Form in Type 2 Diabetic Kidney Disease

BACKGROUND

Urokinase-type plasminogen activator receptor (uPAR) and its soluble form (suPAR) are new injury biomarkers that have been recently suggested to play a vital role in renal diseases.

AIM AND METHODS

We evaluated the expression of uPAR and the serum concentration of suPAR in type 2 diabetes (T₂DM) patients with diabetic kidney disease (DKD) to determine the role of this molecule as a biomarker in DKD. The uPAR immunohistochemical staining was performed in biopsy-confirmed DKD renal tissues. Meanwhile, the serum suPAR, Interleukin-18 (IL-18) and C-reactive protein (CRP) levels of 70 diabetic patients with or without DKD and 15 healthy controls were measured.

RESULTS

The uPAR expression in DKD patients was significantly increased compared to that in healthy controls and was widely colocalized with the podocyte marker WT1. Meanwhile, serum suPAR and IL-18 levels gradually increased as DKD progressed to the advanced stage. Moreover, serum suPAR and IL-18 levels were negatively correlated with eGFR (ρ = ‒0.734, ρ = ‒0.462, p <0.01) and positively correlated with the urine protein to creatinine ratio (UP/CR) (ρ = 0.730, ρ = 0.440, p <0.01). The suPAR AUC performed better than the IL-18 AUC for the diagnosis of proteinuria (0.845 vs. 0.753, p <0.01) and the decline of renal function (0.895 vs. 0.796, p <0.01).

CONCLUSIONS

The uPAR expressed in the renal tissues of DKD patients. The soluble form of uPAR, suPAR, can be detected in the serum of DKD patients and has a better diagnostic efficiency in the diagnosis of proteinuria and renal dysfunction in patients with T₂DM than that of IL-18.

Clinical value of soluble urokinase type plasminogen activator receptors in chronic kidney disease

Chronic kidney disease (CKD) will progress to end stage without treatment, the decline off renal function may not linear. A sensitive marker such as soluble urokinase-type plasminogen activator receptors (suPARs) may allow potential intervention and treatment in earlier stages of CKD.

OBJECTIVES

This study was designed to measure plasma (suPAR) in patients with CKD with different stages and to find its correlation with the disease severity.

METHODS

This study was conducted on 114 subjects, 84 were patients with different stages and different causes of CKD, and 30 healthy subjects as controls. Blood urea, serum creatinine, serum high-sensitive C-reactive protein, estimated glomerular filtration rate, and 24 hours proteinuria were measured, renal biopsy was done for all patients, and plasma (suPAR) was measured using enzyme-linked immunosorbent assay.

RESULTS

suPAR plasma levels were significantly higher in patients with CKD (7.9 ± 3.82 ng/mL) than controls (1.76 ± 0.77 ng/mL, P < .001). suPAR correlated with the disease severity. In stage 1 to 2 group, it was 3.7 ± 1.5 ng/mL, in stage 3 to 4, it was 10.10 ± 1.22 ng/mL, and in stage 5 group, it was 12.34 ± 0.88 ng/mL; the difference between the 3 groups was highly significant (P < .001). A cutoff point 2.5 ng/mL of suPAR was found between controls and stage 1 group. According to the cause of CKD, although patients with obstructive cause and those with focal glomerulosclerosis had the higher levels 9.11 ± 3.32 ng/mL and 8.73 ± 3.19 ng/mL, respectively, but there was no significant difference between patients with CKD according to the cause of the CKD.

CONCLUSION

Plasma (suPAR) increased in patients with CKD and correlated with disease severity.

Increased Serum Soluble Urokinase-Type Plasminogen Activator Receptor (suPAR) Levels in FSGS: A Meta-Analysis

Introduction

The soluble urokinase-type plasminogen activator receptor (suPAR) has been found to be elevated in primary focal segmental glomerulosclerosis (pFSGS). However, its usefulness as a biomarker for FSGS remains controversial. We conducted a meta-analysis aiming at investigating the significance of suPAR in diagnosing pFSGS.

Methods

Electronic databases (PubMed and EMBASE) were searched to identify studies comparing suPAR levels in FSGS patients and controls, from the earliest available date to May 1, 2018. A random-effects model with standardized mean difference (SMD) was used for meta-analyses. Risk of bias was assessed using the Newcastle-Ottawa quality assessment scale.

Results

A total of 187 articles were screened, and the final analysis included 13 articles. In comparison to healthy controls, serum suPAR levels were significantly increased in pFSGS patients (SMD, 1.07, 95% confidence interval (CI) 0.65 to 1.48; participants = 814; studies = 9, I ² = 85%). Higher suPAR levels were also found in patients with pFSGS compared to those with minimal change disease (SMD 0.53, 95% CI 0.22 to 0.84). Of note, such a difference was not found in pediatric groups (SMD 0.42, 95% CI -0.13 to 0.96) while it was more evidently noted in adult patients (SMD 1.32, 95% CI 0.90 to 1.74). Serum suPAR levels did not differ between pFSGS patients in remission compared to those in active proteinuric state (SMD 0.29, 95% CI -0.30 to 0.88). Comparison with membranous nephropathy and IgA nephropathy showed no significant difference.

Conclusions

Our meta-analysis demonstrated that, in comparison to both healthy controls and controls with minimal change disease, suPAR levels were significantly higher in adult patients with pFSGS. suPAR levels did not differ between pFSGS patients during the initial period of diagnosis and those in remission.

SuPAR, an emerging biomarker in kidney and inflammatory diseases

Soluble urokinase plasminogen activator receptor (suPAR) is a circulating form of a physiological and pathophysiological important cell surface receptor, implicated in inflammation. Recent studies showed that suPAR is a promising biomarker, useful for diagnosis, assessment and prognosis of several diseases. This review summarises the majority of preliminary studies and analyses the significance and the clinical application of suPAR in various clinical conditions. SuPAR seems to have a significant value in the diagnosis as well as prognosis of many diseases; nonetheless, it merits large-scale studies to set cut-off values that help physicians in following up their patients and accordingly tailor their treatment plans.

Soluble Urokinase-Type Plasminogen Activator Receptor in Black Americans with CKD

BACKGROUND AND OBJECTIVES

Black Americans with and without APOL1 kidney disease risk variants face high risk of ESKD. Soluble urokinase-type plasminogen activator receptor (suPAR), a circulating signaling protein and marker of immune activation, constitutes a promising biomarker of CKD-associated risks. We aimed to quantify the associations between serum suPAR concentration and adverse outcomes in Black Americans with and without APOL1 kidney disease risk variants, over and above iodine-125 iothalamate measured GFR and proteinuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using data from the African-American Study of Kidney Disease and Hypertension, a multicenter clinical trial followed by a cohort phase with a median total follow-up of 9.7 years (interquartile range, 6.5-10.9 years), we examined the associations of suPAR with CKD progression (defined as doubling of serum creatinine or ESKD), ESKD, worsening proteinuria (defined as pre-ESKD doubling of 24-hour urine protein-to-creatinine ratio to ≥220 mg/g), and all-cause death.

RESULTS

At baseline, the median suPAR was 4462 pg/ml, mean measured GFR was 46 ml/min per 1.73 m2, and median 24-hour urine protein-to-creatinine ratio was 80 mg/g. After controlling for baseline demographics, randomization arm, GFR, proteinuria, APOL1 risk status, and clinical risk factors, there was a 1.26-times higher risk for CKD progression per SD higher baseline log-transformed suPAR (hazard ratio [HR], 1.26; 95% confidence interval [95% CI], 1.11 to 1.43; P<0.001). Higher suPAR was also independently associated with risk of ESKD (HR, 1.36; 95% CI, 1.17 to 1.58; P<0.001) and death (HR, 1.25; 95% CI, 1.08 to 1.45; P=0.003). suPAR was only associated with worsening proteinuria in patients with two APOLI risk alleles (HR, 1.46; 95% CI, 1.08 to 1.99; P=0.02).

CONCLUSIONS

Higher suPAR was associated with various adverse outcomes in Black Americans with CKD, with and without APOL1 kidney disease risk variants, independently of proteinuria and GFR.

Soluble Urokinase Plasminogen Activator Receptor and Outcomes in Patients with Diabetes on Hemodialysis

BACKGROUND AND OBJECTIVES

Soluble urokinase plasminogen activator receptor is a novel biomarker strongly predictive of cardiovascular outcomes implicated in the pathogenesis of kidney disease. Soluble urokinase plasminogen activator receptor levels, however, correlate with declining kidney function. It is unclear whether soluble urokinase plasminogen activator receptor levels remain associated with outcomes in patients with ESRD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We measured plasma soluble urokinase plasminogen activator receptor levels in 1175 patients (mean age =66±8 years old, 54% men) with type 2 diabetes mellitus on hemodialysis participating in the German Diabetes and Dialysis Study followed for a median of 4 years for outcomes including all-cause death, cardiovascular events, and infection-related mortality. Survival analysis was performed using stepwise Cox proportional hazards models adjusted for potential confounders. Also, adjustments were made for inflammatory markers (C-reactive protein and leukocyte count) and the oxidative stress marker asymmetric dimethyl arginine to investigate potential mediators of the relationship between soluble urokinase plasminogen activator receptor and outcomes.

RESULTS

Median soluble urokinase plasminogen activator receptor levels were 10,521 pg/ml (interquartile range, 9105-12,543 pg/ml). When stratified by tertiles, patients with soluble urokinase plasminogen activator receptor >11,633 pg/ml (third tertile) had adjusted 1.6-fold higher mortality (hazard ratio, 1.60; 95% confidence interval, 1.27 to 2.03) compared with those with low soluble urokinase plasminogen activator receptor <9599 pg/ml (first tertile). Risks of sudden death and stroke were higher (adjusted hazard ratio, 1.98; 95% confidence interval, 1.27 to 3.09 and adjusted hazard ratio, 1.74; 95% confidence interval, 1.05 to 2.90, respectively), together accounting for higher incidence of cardiovascular events (adjusted hazard ratio, 1.48; 95% confidence interval, 1.15 to 1.89). Associations with outcomes persisted after adjusting for C-reactive protein, leukocyte count, and asymmetric dimethyl arginine. Addition of soluble urokinase plasminogen activator receptor to a risk factor model modestly improved risk discrimination for all-cause death (ΔC statistic, 0.02; 95% confidence interval, 0.00 to 0.03) and cardiovascular events (ΔC statistic, 0.02; 95% confidence interval, 0.00 to 0.05).

CONCLUSIONS

The association of soluble urokinase plasminogen activator receptor levels with outcomes persists in patients on hemodialysis. Additional study is warranted to characterize the underlying pathways of that association, which may yield opportunities to develop new therapeutic strategies.

suPAR and chronic kidney disease-a podocyte story

The soluble urokinase-type plasminogen activator receptor (suPAR) is a circulating signaling molecule derived from immature myeloid cells. Elevated levels of suPAR have been linked to the pathogenesis of the kidney disease focal and segmental glomerulosclerosis. Here, suPAR acts on podocytes by activating αvβ3 integrins. Large observational studies showed that suPAR also predicts chronic kidney disease incidence and progression by predating the disease by several years prior to any other known marker of renal dysfunction. suPAR is rapidly developing into a prime target for pharmacotherapy as its neutralization is forecasted to be feasible and safe.

A high-protein diet during hospitalization is associated with an accelerated decrease in soluble urokinase plasminogen activator receptor levels in acutely ill elderly medical patients with SIRS

Acute illness and hospitalization in elderly individuals are often accompanied by the systemic inflammatory response syndrome (SIRS) and malnutrition, both associated with wasting and mortality. Nutritional support and resistance training were shown to increase muscle anabolism and reduce inflammation in healthy elderly. We hypothesized that nutritional support and resistance training would accelerate the resolution of inflammation in hospitalized elderly patients with SIRS. Acutely admitted patients aged >65 years with SIRS were randomized to an intervention consisting of a high-protein diet (1.7 g/kg per day) during hospitalization, and daily protein supplement (18.8 g) and 3 weekly resistance training sessions for 12 weeks after discharge (Intervention, n=14), or to standard-care (Control, n=15). Plasma levels of the inflammatory biomarkers soluble urokinase plasminogen activator receptor (suPAR), interleukin-6, C-reactive protein (CRP), and albumin were measured at admission, discharge, and 4 and 13 weeks after discharge. The Intervention group had an earlier decrease in suPAR levels than the Control group: -15.4% vs. +14.5%, P=.007 during hospitalization, and -2.4% vs. -28.6%, P=.007 between discharge and 4 weeks. There were no significant effects of the intervention on the other biomarkers. All biomarkers improved significantly between admission and 13 weeks, although with different kinetics (suPAR: -22%, interleukin-6: -86%, CRP: -89%, albumin: +11%). Nutritional support during hospitalization was associated with an accelerated decrease in suPAR levels, whereas the combined nutrition and resistance training intervention after discharge did not appear to affect the inflammatory state. Our results indicate that improved nutritional care during hospitalization may accelerate recovery in acutely ill elderly medical patients.

Soluble Urokinase Receptors in Focal Segmental Glomerulosclerosis: A Review on the Scientific Point of View

Focal segmental glomerulosclerosis (FSGS) is one of the primary glomerular disorders in both children and adults which can progress to end-stage renal failure. Although there are genetic and secondary causes, circulating factors have also been regarded as an important factor in the pathogenesis of FSGS, because about 40% of the patients with FSGS have recurrence after renal transplantation. Soluble urokinase-type plasminogen activator receptor (suPAR) is a soluble form of uPAR, which is a membrane-bound protein linked to GPI in various immunologically active cells, including podocytes. It has recently been suggested as a potential circulating factor in FSGS by in vitro podocyte experiments, in vivo mice models, and human studies. However, there have also been controversies on this issue, because subsequent studies showed conflicting results. suPAR levels were also increased in patients with other glomerular diseases and were inversely correlated with estimated glomerular filtration rate. Nevertheless, there has been no balanced review on this issue. In this review, we compare the conflicting data on the involvement of suPAR in the pathogenesis of FSGS and shed light on interpretation by taking into account many points and the potential variables and confounders influencing serum suPAR levels.

FSGS: from pathogenesis to the histological lesion

Focal and segmental glomerulosclerosis (FSGS) is a generic term that in the current terminology can be appropriate for identifying two conditions. First, a morphological pattern of injury characterized by the occlusion of a single or group of glomerular capillary loops by sclerotic material, indicating a precise histological lesion but with a wide range of etiological interpretations. Second, a pauci-immune renal disease called idiopathic or primary FSGS, which is a podocytopathy triggered by an endogenous cytotoxin that recognizes the podocyte as its sole target. Based on the current and past literature, we do not possess practical tools to easily provide a precise classification of an FSGS lesion, although some clues may be of help in everyday clinical practice. Reactive forms, genetic forms, adaptive forms, forms associated with a deregulation of the proliferation and forms secondary to local glomerular inflammation are the etiological classes known to be associated with the development of an FSGS lesion. However, diagnosing each single case based on clinical, serological and histological criteria is still far from easy and mostly depends on the experience of the renal team, which should involve skilled nephrologists and pathologists.

Plasma Soluble Urokinase Receptor Level Is Correlated with Podocytes Damage in Patients with IgA Nephropathy

Background

Focal segmental glomerulosclerosis (FSGS) lesions are similar in characteristics to S lesions of the Oxford classification of IgA nephropathy (IgAN) and may predict poor prognosis. In the present study, we aimed to explore the association between plasma soluble urokinase receptor (suPAR) levels and S lesions and podocytes damage in IgAN patients.

Methods

We enrolled 569 IgAN patients with follow-up data and detected plasma suPAR levels at renal biopsy by enzyme-linked immunosorbent assay.

Results

Plasma suPAR levels in IgAN patients with or without S lesions did not differ significantly (P = 0.411). However, suPAR levels were positively correlated with proteinuria (r = 0.202, P < 0.001), and negatively correlated with estimated glomerular filtration rate (eGFR, r = –0.236, P < 0.001). In the partial correlation to adjust for eGFR, plasma suPAR levels remained positively correlated with proteinuria (r = 0.112, P = 0.023). In a Cox proportional hazards model, higher levels of plasma suPAR were not associated with poor renal outcome. Plasma suPAR levels of IgAN and primary FSGS patients with nephrotic syndrome were not significantly different (P = 0.306). Plasma suPAR levels in patients with extensive effacement of the epithelial cell foot processes of glomerular podocytes were significantly higher than those with segmental effacement on the basis of comparable eGFR (P = 0.036).

Conclusions

In IgAN patients, plasma suPAR levels were not associated with S lesions. However, they were positively associated with proteinuria and negatively associated with eGFR. In addition, plasma suPAR levels were positively associated with the effacement degree of the foot processes, which might partially contribute to the development of proteinuria in patients with IgAN.

Soluble urokinase plasminogen activator receptor--a valuable biomarker in systemic lupus erythematosus?

Systemic lupus erythematosus (SLE) is a potentially severe autoimmune condition with an unpredictable disease course, often with fluctuations in disease activity over time. Long term inflammation and drug-related side-effects may subsequently lead to permanent organ damage, a consequence which is intimately connected to decreased quality of life and mortality. New lupus biomarkers that convey information regarding inflammation and/or organ damage are thus warranted. Today, there is no clinical biomarker that indicates the risk of damage accrual. Herein we highlight the urokinase plasminogen activator receptor (uPAR) and especially its soluble form (suPAR) that besides having biological functions in e.g. proteolysis, cell migration and tissue homeostasis, recently has emerged as a promising biomarker of inflammation and prognosis of several disorders. A strong association between suPAR and organ damage in SLE was recently demonstrated, and preliminary data (presented in this review) suggests the possibility of a predictive value of suPAR blood levels. The involvement of suPAR in the pathogenesis of SLE remains obscure, but its effects in leukocyte recruitment, phagocytic uptake of dying cells (efferocytosis) and complement regulation suggests that the central parts of the SLE pathogenesis could be regulated by suPAR, and vice versa.