Soluble urokinase plasminogen activator receptor as a prognostic marker of all-cause and cardiovascular mortality in a black population

Urokinase-Type Plasminogen Activator Receptor (uPAR) in Inflammation and Disease: A Unique Inflammatory Pathway Activator

The urokinase-type plasminogen activator receptor (uPAR) is a unique protease binding receptor, now recognized as a key regulator of inflammation. Initially, uPA/uPAR was considered thrombolytic (clot-dissolving); however, recent studies have demonstrated its predominant immunomodulatory functions in inflammation and cancer. The uPA/uPAR complex has a multifaceted central role in both normal physiological and also pathological responses. uPAR is expressed as a glycophosphatidylinositol (GPI)-linked receptor interacting with vitronectin, integrins, G protein-coupled receptors, and growth factor receptors within a large lipid raft. Through protein-to-protein interactions, cell surface uPAR modulates intracellular signaling, altering cellular adhesion and migration. The uPA/uPAR also modifies extracellular activity, activating plasminogen to form plasmin, which breaks down fibrin, dissolving clots and activating matrix metalloproteinases that lyse connective tissue, allowing immune and cancer cell invasion and releasing growth factors. uPAR is now recognized as a biomarker for inflammatory diseases and cancer; uPAR and soluble uPAR fragments (suPAR) are increased in viral sepsis (COVID-19), inflammatory bowel disease, and metastasis. Here, we provide a comprehensive overview of the structure, function, and current studies examining uPAR and suPAR as diagnostic markers and therapeutic targets. Understanding uPAR is central to developing diagnostic markers and the ongoing development of antibody, small-molecule, nanogel, and virus-derived immune-modulating treatments that target uPAR.

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.

Racial Discrimination and Metabolic Syndrome in Young Black Adults

Importance

Metabolic syndrome (MetS) is a common health condition that predisposes individuals to cardiovascular disease (CVD) and disproportionately affects Black and other racially and ethnically minoritized people. Concurrently, Black individuals also report more exposure to racial discrimination compared with White individuals; however, the role of discrimination in the development of MetS over time and associated mediators in these pathways remain underexplored.

Objective

To evaluate the association between racial discrimination and MetS in rural Black individuals transitioning from late adolescence into early adulthood and to identify potential mediating pathways.

Design, Setting, and Participants

This longitudinal cohort study included Black adolescents enrolled in the Strong African American Families Healthy Adults (SHAPE) Project between June 2009 and May 2021. Families resided in rural counties of Georgia, where poverty rates are among the highest in the nation. Analyses included 322 of the 500 participants who originally enrolled in SHAPE and who were eligible to participate. Guardians provided information about socioeconomic disadvantage. Analyses were conducted in April 2023.

Exposures

Youths reported exposure to racial discrimination annually from ages 19 to 21 years.

Main Outcomes and Measures

MetS was the main health outcome and was measured at ages 25 and 31 years. MetS was diagnosed according to the International Diabetes Federation guidelines, which requires central adiposity (ie, waist circumference ≥94 cm for males and ≥80 cm for females) and at least 2 of the 4 additional components: signs of early hypertension (ie, systolic blood pressure ≥130 mm Hg or diastolic blood pressure ≥85 mm Hg); elevated triglyceride levels (ie, >150 mg/dL); elevated fasting glucose level (ie, ≥100 mg/dL); or lowered high-density lipoprotein levels (ie, <40 mg/dL in men and <50 mg/dL in women). At age 25 years, markers of inflammatory activity (ie, soluble urokinase plasminogen activator receptor [suPAR]) and sleep problems were collected to consider as potential mediators.

Results

In 322 participants (210 [65.2%] female) ages 19 to 21 years, more frequent exposure to racial discrimination was associated with higher suPAR levels (b = 0.006; 95% CI, 0.001-0.011; P = .01) and more sleep problems at age 25 years (b = 0.062; 95% CI, 0.028-0.097; P < .001) as well as a 9.5% higher risk of MetS diagnosis at age 31 years (odds ratio [OR], 1.10; 95% CI, 1.01-1.20; P = .03). Both suPAR (b = 0.015; 95% CI, 0.002-0.037) and sleep problems (b = 0.020; 95% CI, 0.002-0.047) at age 25 years were significant indirect pathways. No significant interactions between sex and discrimination emerged.

Conclusions and Relevance

This study suggests that racial discrimination in late adolescence is associated with MetS among Black young adults through biobehavioral pathways. Thus, health interventions for MetS in Black adults will need to contend with sleep behaviors and inflammatory intermediaries as well as address and reduce exposure to racial discrimination to narrow disparities and promote health equity.

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.

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.

Circulating cytokines and risk of developing hypertension: A systematic review and meta-analysis

BACKGROUND

Immune responses play a significant role in hypertension, though the importance of key inflammatory mediators remains to be defined. We used a systematic literature review and meta-analysis to study the associations between key cytokines and incident hypertension.

METHODS

We performed a systematic search of Pubmed/Medline, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL), for peer-reviewed studies published up to August 2022. Incident hypertension was defined as systolic blood pressure ≥ 140 mmHg or diastolic blood pressure ≥ 90 mmHg and/or the use of antihypertensive medications. Random effects meta-analyses were used to calculate pooled hazard ratios (HRs)/risk ratios (RRs) and 95% confidence intervals by cytokine levels (highest vs. lowest quartile).

RESULTS

Only IL-6 and IL-1β levels have evidence allowing for quantitative evaluation concerning the onset of hypertension. Six studies (10406 participants, 2932 incident cases) examined the association of IL-6 with incident hypertension. The highest versus lowest quartile of circulating IL-6 was associated with a significant HR/RR of hypertension (1.61, 95% CI: 1.00 to 2.60; I2 =87%). After adjusting for potential confounders, including body mass index (BMI), HR/RR was no longer significant (HR/RR: 1.24; 95% CI, 0.96 to 1.61; I2 = 56%). About IL-1β, neither the crude (HR/RR: 1.03; 95% CI, 0.60 to 1.76; n = 2) nor multivariate analysis (HR/RR: 0.97, 95% CI, 0.60 to 1.56; n = 2) suggested a significant association with the risk of developing hypertension.

CONCLUSIONS

A limited number of studies suggest that higher IL-6, but not IL-1β, might be associated with the development of hypertension.

Social isolation, loneliness, and inflammation: A multi-cohort investigation in early and mid-adulthood

Social isolation and loneliness have been associated with poor health and increased risk for mortality, and inflammation might explain this link. We used data from the Danish TRIAGE Study of acutely admitted medical patients (N = 6,144, mean age 60 years), and from two population-representative birth cohorts: the New Zealand Dunedin Longitudinal Study (N = 881, age 45) and the UK Environmental Risk (E-Risk) Longitudinal Twin Study (N = 1448, age 18), to investigate associations of social isolation with three markers of systemic inflammation: C-reactive protein (CRP), interleukin-6 (IL-6), and a newer inflammation marker, soluble urokinase plasminogen activator receptor (suPAR), which is thought to index systemic chronic inflammation. In the TRIAGE Study, socially isolated patients (those living alone) had significantly higher median levels of suPAR (but not CRP or IL-6) compared with patients not living by themselves. Social isolation prospectively measured in childhood was longitudinally associated with higher CRP, IL-6, and suPAR levels in adulthood (at age 45 in the Dunedin Study and age 18 in the E-Risk Study), but only suPAR remained associated after controlling for covariates. Dunedin Study participants who reported loneliness at age 38 or age 45 had elevated suPAR at age 45. In contrast, E-Risk Study participants reporting loneliness at age 18 did not show any elevated markers of inflammation. In conclusion, social isolation was robustly associated with increased inflammation in adulthood, both in medical patients and in the general population. It was associated in particular with systemic chronic inflammation, evident from the consistently stronger associations with suPAR than other inflammation biomarkers.

Biomarkers of chronic inflammation and cognitive decline: A prospective observational study

We sought to determine whether the biomarkers of chronic inflammation predict cognitive decline in a prospective observational study. We measured baseline serum soluble urokinase plasminogen activator receptor (suPAR) and high sensitivity C-reactive protein (hs-CRP) levels in 282 participants of the University of Michigan Memory and Aging Project. Cognitive function was measured using the Montreal Cognitive Assessment (MoCA) and the Clinical Dementia Rating (CDR) scale for up to five time points. SuPAR and hs-CRP levels were not significantly higher in participants with mild cognitive impairment (n = 97) or dementia (n = 59), compared to those with normal cognitive function (n = 126). Overall, 14% of participants experienced significant cognitive decline over the study period. The change in MoCA or CDR scores over time did not differ significantly according to baseline suPAR or hs-CRP levels. Chronic systemic inflammation, as measured by serum suPAR or hs-CRP levels, is unlikely to contribute significantly to cognitive decline.

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.

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.

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

suPAR as a risk Prediction Biomarker in Extracorporeal Membrane Oxygenation

suPAR is a promising biomarker of cardiovascular diseases, as it reflects “low-grade inflammation” and is associated with lifestyle factors such as smoking, alcohol, and an inactive lifestyle. suPAR is expressed in various cells involved in the development of atherosclerosis, including macrophages, endothelial cells, and smooth muscle cells, and an accumulation of suPAR in the atheroma has also been found. suPAR plays a role in the coagulation cascade during plasminogen activation and fibrinolysis. This abstract provides description of three case series showing the utility of suPAR as a risk prediction biomarker on VA extracorporeal membrane oxygenation (ECMO). We used SUPAR in 15 patients undergoing cardiac surgery of which three went on VA ECMO. Herein, we describe in detail three such patients and discuss each with good review of the literature.

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.

Self-rated health and chronic inflammation are related and independently associated with hospitalization and long-term mortality in the general population

The subjective indicator of health self-rated health (SRH) and the chronic inflammation biomarker soluble urokinase plasminogen activator receptor (suPAR) are both robust predictors of healthcare use and mortality. However, the possible relationship between SRH and suPAR in the assessment of hospitalization and mortality risk is unknown. We used data from the Danish population-based Inter99 cohort to examine the association between SRH and suPAR and test their individual and combined associations with 2-year risk of acute hospitalization and 5- and 15-year mortality. SRH and serum suPAR levels were measured in 5490 participants (median age 45.1 years, 48.7% men). Poorer SRH was associated with elevated suPAR. In unadjusted analyses, SRH and suPAR were individually associated with higher risks of acute hospitalization and mortality, and both measures remained independently associated with higher risks of hospitalization and 15-year mortality after mutual adjustments. The association of suPAR with mortality was stronger in poorer SRH categories, and when combined, SRH and suPAR could identify different groups of individuals with increased risk of acute hospitalization and mortality. Both SRH and suPAR were independently associated with risk of acute hospitalization and mortality, and different combinations of the two measures could identify different groups of individuals at increased risk.

Discrimination and Inflammation in Adolescents of Color

Background

This study examined how experiences with discrimination relate to inflammation, a key biological pathway in mental and physical illnesses, and whether associations are moderated by gender across two samples of adolescents of color.

Methods

Study 1 was a longitudinal study of 419 African American adolescents assessed on discrimination (ages 19-20), with trajectories of biomarkers of low-grade inflammation (C-reactive protein and soluble urokinase plasminogen activator receptor) measured from ages 25 to 29. Study 2 was a cross-sectional study of 201 eighth graders of color assessed on discrimination and mechanistic indicators of a proinflammatory phenotype: 1) in vitro studies of immune cells' inflammatory cytokine responses to stimuli; 2) in vitro studies of cells' sensitivity to anti-inflammatory agents; 3) circulating numbers of classical monocytes, key cellular drivers of low-grade inflammation; and 4) a composite of six biomarkers of low-grade inflammation.

Results

Interactions of discrimination by gender were found across both studies. In study 1, African American males experiencing high discrimination showed increasing trajectories of soluble urokinase plasminogen activator receptor over time (p < .001). In study 2, adolescent boys of color experiencing greater discrimination evinced a more proinflammatory phenotype: larger cytokine responses to stimuli (p = .003), lower sensitivity to anti-inflammatory agents (p = .003), higher numbers of classical monocytes (p = .008), and more low-grade inflammation (p = .003). No such associations were found in females.

Conclusions

Discrimination is a pressing societal issue that will need to be addressed in efforts to promote health equity. This study suggests that adolescent males of color may be particularly vulnerable to its effects on mental health-relevant inflammatory processes.

Midkine release during hemodialysis is predictive of hypervolemia and associates with excess (cardiovascular) mortality in patients with end-stage renal disease: a prospective study

Background

In end-stage renal disease, a high cardiovascular risk profile and endothelial damage prevails. The heparin-binding growth factor midkine stimulates neo-angiogenesis in ischemic diseases, coordinates neutrophil influx, and raises blood pressure through stimulated angiotensin synthesis.

Methods

We determined changes of midkine serum levels during hemodialysis sessions under the assumption that endothelial cell-derived midkine is released. Periprocedural differences (∆midkine) were calculated and correlated with cardiovacular biomarkers and fluid status (clinical assessment, V. cava collapse, comet tail phenomenon), cardiovascular morbidities, mortality rates. Blood was collected before and after dialysis from hemodialysis patients (n = 171; diabetes: n = 70; hypervolemia: n = 83; both: n = 32).

Results

Baseline midkine levels were ~ fourfold elevated compared to healthy controls (n = 100). Further, on average a tenfold rise was detected during dialysis, the extent of which was partially related to non-fractionated heparin application (r² = 0.17). Inter-individual differences were highly reproducible. Hypervolemic patients responded with a less than average rise in midkine levels during dialysis (p < 0.02), this difference became more obvious with co-existing diabetes (p < 0.001 for long dialysis-free interval) and was confirmed in an independently enrolled dialysis cohort (n = 88). In Kaplan Meier survival curves, low delta midkine levels correlated with cardiovascular/overall mortality rates, similar to elevated uPAR levels, whereas other markers (NTproANP, galectin, tenascin-C) were less predictive. Following intervention with successful fluid removal in hypervolemic dialysis patients to optimize fluid homeostasis, midkine values increased (p < 0.002), which was not observed in patients that failed to decrease weight.

Conclusion

Thus, for dialysis patients inadequate periprocedural midkine upregulation is linked with hypervolemia and associates with cardiovascular events.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-022-03141-4.

Soluble Urokinase Plasminogen Activator Receptor (suPAR) as a Biomarker of Systemic Chronic Inflammation

Systemic chronic inflammation (SCI) is persistent, health-damaging, low-grade inflammation that plays a major role in immunosenescence and in development and progression of many diseases. But currently, there are no recognized standard biomarkers to assess SCI levels alone, and SCI is typically measured by combining biomarkers of acute inflammation and infection, e.g., CRP, IL-6, and TNFα. In this review, we highlight 10 properties and characteristics that are shared by the blood protein soluble urokinase plasminogen activator receptor (suPAR) and SCI, supporting the argument that suPAR is a biomarker of SCI: (1) Expression and release of suPAR is upregulated by immune activation; (2) uPAR and suPAR exert pro-inflammatory functions; (3) suPAR is associated with the amount of circulating immune cells; (4) Blood suPAR levels correlate with the levels of established inflammatory biomarkers; (5) suPAR is minimally affected by acute changes and short-term influences, in contrast to many currently used markers of systemic inflammation; (6) Like SCI, suPAR is non-specifically associated with multiple diseases; (7) suPAR and SCI both predict morbidity and mortality; (8) suPAR and SCI share the same risk factors; (9) suPAR is associated with risk factors and outcomes of inflammation above and beyond other inflammatory biomarkers; (10) The suPAR level can be reduced by anti-inflammatory interventions and treatment of disease. Assessing SCI has the potential to inform risk for morbidity and mortality. Blood suPAR is a newer biomarker which may, in fact, be a biomarker of SCI since it is stably associated with inflammation and immune activation; shares the same risk factors as many age-related diseases; is both elevated by and predicts age-related diseases. There is strong evidence that suPAR is a prognostic marker of adverse events, morbidity, and mortality. It is associated with immune activity and prognosis across diverse conditions, including kidney disease, cardiovascular disease, cancer, diabetes, and inflammatory disorders. Thus, we think it likely represents a common underlying disease-process shared by many diseases; that is, SCI. We review the supporting literature and propose a research agenda that can help test the hypothesis that suPAR indexes SCI, with the potential of becoming the new gold standard for measuring SCI.

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.

Soluble Urokinase Plasminogen Activator Receptor: Genetic Variation and Cardiovascular Disease Risk in Black Adults

BACKGROUND

suPAR (Soluble urokinase plasminogen activator receptor) has emerged as an important biomarker of coagulation, inflammation, and cardiovascular disease (CVD) risk. The contribution of suPAR to CVD risk and its genetic influence in Black populations have not been evaluated.

METHODS

We measured suPAR in 3492 Black adults from the prospective, community-based JHS (Jackson Heart Study). Cross-sectional associations of suPAR with lifestyle and CVD risk factors were assessed, whole-genome sequence data were used to evaluate genetic associations of suPAR, and relationships of suPAR with incident CVD outcomes and overall mortality were estimated over follow-up.

RESULTS

In Cox models adjusted for traditional CVD risk factors, estimated glomerular filtration rate, and CRP (C-reactive protein), each 1-SD higher suPAR was associated with a 21% to 31% increased risk of incident coronary heart disease, heart failure, stroke, and mortality. In the genome-wide association study, 2 missense (rs399145 encoding p.Thr86Ala, rs4760 encoding p.Phe272Leu) and 2 noncoding regulatory variants (rs73935023 within an enhancer element and rs4251805 within the promoter) of PLAUR on chromosome 19 were each independently associated with suPAR and together explained 14% of suPAR phenotypic variation. The allele frequencies of each of the four suPAR-associated genetic variants differ considerably across African and European populations. We further show that PLAUR rs73935023 can alter transcriptional activity in vitro. We did not find any association between genetically determined suPAR and CVD in JHS or a larger electronic medical record-based analyses of Blacks or Whites.

CONCLUSIONS

Our results demonstrate the importance of ancestry-differentiated genetic variation on suPAR levels and indicate suPAR is a CVD biomarker in Black adults.

Linking stressful life events and chronic inflammation using suPAR (soluble urokinase plasminogen activator receptor)

Stressful life events have been linked to declining health, and inflammation has been proposed as a physiological mechanism that might explain this association. Using 828 participants from the Dunedin Longitudinal Study, we tested whether people who experienced more stressful life events during adulthood would show elevated systemic inflammation when followed up in midlife, at age 45. We studied three inflammatory biomarkers: C-reactive protein (CRP), interleukin-6 (IL-6), and a newer biomarker, soluble urokinase plasminogen activator receptor (suPAR), which is thought to index systemic chronic inflammation. Stressful life events were not associated with CRP or IL-6. However, people who experienced more stressful life events from age 38 to 44 had elevated suPAR at age 45, and had significantly greater increases in suPAR from baseline to follow-up across the same period. When examining stressful life events across the lifespan, both adverse childhood experiences (ACEs) and adult stressful life events were independently associated with suPAR at age 45. ACEs moderated the association of adult stressful life events and suPAR at age 45-children with more ACEs showed higher suPAR levels after experiencing stressful life events as adults. The results suggest systemic chronic inflammation is one physiological mechanism that could link stressful life events and health, and support the use of suPAR as a useful biomarker for such research.

The glomerular filtration barrier: a structural target for novel kidney therapies

Loss of normal kidney function affects more than 10% of the population and contributes to morbidity and mortality. Kidney diseases are currently treated with immunosuppressive agents, antihypertensives and diuretics with partial but limited success. Most kidney disease is characterized by breakdown of the glomerular filtration barrier (GFB). Specialized podocyte cells maintain the GFB, and structure-function experiments and studies of intercellular communication between the podocytes and other GFB cells, combined with advances from genetics and genomics, have laid the groundwork for a new generation of therapies that directly intervene at the GFB. These include inhibitors of apolipoprotein L1 (APOL1), short transient receptor potential channels (TRPCs), soluble fms-like tyrosine kinase 1 (sFLT1; also known as soluble vascular endothelial growth factor receptor 1), roundabout homologue 2 (ROBO2), endothelin receptor A, soluble urokinase plasminogen activator surface receptor (suPAR) and substrate intermediates for coenzyme Q10 (CoQ₁₀). These molecular targets converge on two key components of GFB biology: mitochondrial function and the actin-myosin contractile machinery. This Review discusses therapies and developments focused on maintaining GFB integrity, and the emerging questions in this evolving field.

Mortality and major complications after emergency laparotomy: A pilot study of risk prediction model development by preoperative blood-based immune parameters

BACKGROUND

Emergency laparotomy is associated with high risk of postoperative complications and mortality. Preoperative identification of patients at high risk of adverse outcome is important. The immune response to conditions requiring emergency laparotomy is not understood in detail. The present study describes preoperative blood-based immune profiles and their potential value in surgical risk assessment.

METHOD

Patients (N = 100) referred for emergency laparotomy at Hvidovre Hospital were consecutively included from 3 June 2013-11 April 2014. All patients had blood samples collected before surgery and the immune parameters c-reactive protein (CRP), Interleukin-6 (IL-6), Interleukin-10 (IL-10), interferon-γ induced protein 10 kDa (IP-10), tumor necrosis factor α (TNF-α) and soluble urokinase plasminogen receptor activator (suPAR) were determined. Patients were stratified according to major postoperative complications (including death), 30- and 180-day mortality. Using logistic regression models and receiver operating characteristics curves the predictive ability of the immune parameters were estimated.

RESULTS

Major complications were recorded in 45 (45.0%) of the patients, whereas 30-day and 180-day mortalities were 17 (17.0%) and 25 (25.0%), respectively. Concentrations of suPAR and TNF-α were associated with major complications while CRP, IL-6, suPAR and TNF-α were associated with mortality. Adding the combined immune parameters to a regression model including age, sex, American Society of Anesthesiologists physical status and Eastern Cooperative Oncology Group Performance Status significantly improved the predictive ability for major complications, 30-day mortality and 180-day mortality.

CONCLUSION

In emergency laparotomy, preoperative blood-based immune parameters added predictive power to regression models and could be considered in risk prediction model development.

Soluble urokinase plasminogen activator receptor (suPAR) as a prognostic marker of mortality in healthy, general and patient populations: protocol for a systematic review and meta-analysis

INTRODUCTION

Chronic inflammation is increasingly recognised as a major contributor to disease, disability and ultimately death, but measuring the levels of chronic inflammation remains non-canonised, making it difficult to relate chronic inflammation and mortality. Soluble urokinase plasminogen activator receptor (suPAR), an emerging biomarker of chronic inflammation, has been proposed as a prognostic biomarker associated with future incidence of chronic disease and mortality in general as well as patient populations. Proper prognostic biomarkers are important as they can help improve risk stratification in clinical settings and provide guidance in treatment or lifestyle decisions as well as in the design of randomised trials. Here, we wish to summarise the evidence about the overall association of the biomarker suPAR with mortality in healthy, general and patient populations across diseases.

METHODS AND ANALYSIS

The search will be conducted using Medline, Embase and Scopus databases from their inception to 03 June 2020 to identify studies investigating 'suPAR' and 'mortality'. Observational studies and control groups from intervention studies written in English or Danish will be included. The 'Quality In Prognosis Studies' tool will be used to assess the risk of bias for the studies included. Unadjusted and adjusted mortality outcome measures (eg, risk ratios, ORs, HRs) with 95% CIs will be extracted for healthy individuals, general and patient populations. The primary outcome is all-cause mortality within any given follow-up. Subgroup analyses will be performed based on time of outcome, cause of death, population type, adjustments for conventional risk factors and inflammation markers.

ETHICS AND DISSEMINATION

This systematic review will synthesise evidence on the use of suPAR as a prognostic marker for mortality. The results will be disseminated by publication in a peer-reviewed journal. Data used will be obtained from published studies, and ethics approval is therefore not necessary for this systematic review.

TRIAL REGISTRATION NUMBER PROSPERO

CRD42020167401.

Soluble urokinase receptor as a predictor of non-cardiac mortality in patients with percutaneous coronary intervention treated ST-segment elevation myocardial infarction

BACKGROUND

Identification of patients at high risk of non-cardiac mortality following ST-segment elevation myocardial infarction (STEMI) could guide clinicians to identify patients who require attention due to serious non-cardiac conditions after the acute phase of STEMI. The purpose of this study was to evaluate if the non-specific and prognostic biomarker of inflammation and comorbidity, soluble urokinase receptor (suPAR), could predict non-cardiac mortality in a cohort of STEMI patients.

METHODS

SuPAR was measured in 1,190 STEMI patients who underwent primary percutaneous coronary intervention (pPCI). The primary endpoint was non-cardiac mortality, secondary endpoints were cardiac mortality, all-cause mortality, reinfarction and periprocedural acute kidney injury. Backwards elimination of potential confounders significantly associated with the respective outcome was used to adjust associations.

RESULTS

Patients were followed for a median of 3.0 years (interquartile range 2.5- 3.6 years). Multivariate cox regression revealed that a plasma suPAR level above 3.70 ng mL^-1 was associated with non-cardiac and cardiac mortality at hazard ratios 3.33 (95% confidence interval 1.67-6.63, p = 0.001, adjusted for age) and 0.99 (0.18-5.30, p = 0.98, adjusted for previous myocardial infarction and left ventricular ejection fraction), respectively.

CONCLUSION

In patients with pPCI treated STEMI, suPAR was an independent prognostic biomarker of non-cardiac but not cardiac mortality and may identify patients with high risk of non-cardiac mortality.

Association of Adverse Experiences and Exposure to Violence in Childhood and Adolescence With Inflammatory Burden in Young People

IMPORTANCE

Childhood stress exposure is associated with inflammation as measured by C-reactive protein (CRP) and interleukin 6 (IL-6). However, findings are inconsistent and effect sizes are small. The addition of soluble urokinase plasminogen activator receptor (suPAR), a new biomarker of chronic inflammation, may improve measurement of stress-related inflammatory burden.

OBJECTIVES

To assess whether exposure to adverse experiences, stress, and violence is associated with an increase in suPAR levels in young people and to test the hypothesis that measuring suPAR in addition to CRP or IL-6 levels improves the assessment of the inflammatory burden associated with early-life stress.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included 1391 participants from a 1994 to 1995 birth cohort of twins from the nationally representative Environmental Risk Longitudinal Twin Study in the United Kingdom. Participants were followed up until 18 years of age (93% retention). Plasma samples were analyzed in July 2018, and statistical analysis was performed from October 1, 2018, to May 31, 2019.

EXPOSURES

Adverse childhood experiences and childhood and adolescent experience of stress and violence exposure.

MAIN OUTCOMES AND MEASURES

Plasma CRP, IL-6, and suPAR levels at 18 years of age.

RESULTS

Among 1391 young people (mean [SD] age, 18.4 [0.36] years; 733 [52.7%] female), those who had been exposed to stressful experiences had elevated suPAR levels by 18 years of age after controlling for sex, body mass index, and smoking: 0.03-ng/mL (95% CI, 0.01-0.05 ng/mL) increase in suPAR per each additional adverse childhood experience, 0.09-ng/mL (95% CI, 0.01-0.17 ng/mL) increase in suPAR per each additional severe childhood experience of stress or violence, and 0.04-ng/mL (95% CI, -0.02 to 0.10 ng/mL) increase in suPAR per each additional severe adolescent experience of stress or violence. Individuals exposed to multiple types of violence in both childhood and adolescence had 0.26-ng/mL (95% CI, 0.07-0.45 ng/mL) higher suPAR levels compared with children who did not experience stress or violence. These stress-exposed young people were significantly more likely to have elevated suPAR levels at 18 years of age even if they did not have elevated CRP or IL-6 levels. Measuring suPAR in addition to CRP or IL-6 increased the association between stress exposure and inflammatory burden. For example, after adjusting for CRP and IL-6 levels, each additional adverse childhood experience was associated with a 0.05-mL (95% CI, 0.03-0.07 ng/mL) increase in suPAR, each additional severe childhood experience of stress or violence was associated with a 0.14-ng/mL (95% CI, 0.06-0.22 ng/mL) increase in suPAR, and each additional severe adolescent experience of stress or violence was associated with a 0.10-ng/mL (95% CI, 0.04-0.16 ng/mL) increase in suPAR.

CONCLUSIONS AND RELEVANCE

The results suggest that adult inflammation is associated with childhood exposure to stress. Adding information about suPAR to traditional biomarkers of inflammation may improve the measurement of inflammatory burden associated with exposure to stress and violence.

Vascular Structure and Inflammation in a South African Population: The SABPA Study

Background and Objective

Inflammation plays a role in the early onset of cardiovascular disease. However, longitudinal studies on this topic, especially in South African populations, are scant. We explored whether early changes in vascular structure are associated with changes in inflammation.

Methods

We investigated 303 South African teachers aged 20-65 years at two intervals, three years apart. Standardised methods were used to determine carotid intima-media thickness (IMT) and cross-sectional wall area (CSWA) as measures of vascular structure, as well as the inflammatory markers soluble urokinase plasminogen activator receptor (suPAR), C-reactive protein (CRP) and interleukin-6 (IL-6) at baseline and follow-up.

Results

IMT and CSWA were higher, while CRP was lower at follow-up than at baseline. After adjusting for confounding factors, percent change in IMT was inversely associated with percent change in suPAR (β = -0.12, p = 0.036; adjusted R² = 0.16) only, and only in the highest tertile of percent change in suPAR (r = -0.31; p = 0.002).

Conclusion

The early structural changes observed are not related to higher inflammatory levels in this South African population. Future studies are needed to investigate the possible protective effect of suPAR on early changes in vascular structure, especially with the focus on cardiovascular disease prevention.

Soluble Urokinase Plasminogen Activator Receptor and Decline in Kidney Function in Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Levels of soluble urokinase plasminogen activator receptor (suPAR), an inflammation marker, are strongly predictive of incident kidney disease. Patients with autosomal dominant polycystic kidney disease (ADPKD) experience progressive decline in renal function, but rates of decline and outcomes vary greatly. Whether suPAR levels are predictive of declining kidney function in patients with ADPKD is unknown.

METHODS

We assessed suPAR levels in 649 patients with ADPKD who underwent scheduled follow-up for at least 3 years, with repeated measurements of height-adjusted total kidney volume and creatinine-derived eGFR. We used linear mixed models for repeated measures and Cox proportional hazards to characterize associations between baseline suPAR levels and follow-up eGFR or incident ESRD.

RESULTS

The median suPAR level was 2.47 ng/ml and median height-adjusted total kidney volume was 778, whereas mean eGFR was 84 ml/min per 1.73 m². suPAR levels were associated with height-adjusted total kidney volume (β=0.02; 95% confidence interval, 0.01 to 0.03), independent of age, sex, race, hypertension, and eGFR. Patients in the lowest suPAR tertile (<2.18 ng/ml) had a 6.8% decline in eGFR at 3 years and 22% developed CKD stage 3, whereas those in the highest tertile (suPAR>2.83 ng/ml) had a 19.4% decline in eGFR at 3 years and 68% developed CKD stage 3. suPAR levels >2.82 ng/ml had a 3.38-fold increase in the risk of incident ESRD.

CONCLUSIONS

suPAR levels were associated with progressive decline in renal function and incident ESRD in patients with ADPKD, and may aid early identification of patients at high risk of disease progression.

Soluble urokinase plasminogen activation receptor and long-term outcomes in persons undergoing coronary angiography

Soluble urokinase plasminogen activation receptor (suPAR) is risk factor for kidney disease and biomarker for cardiovascular outcomes but long term longitudinal analyses in a large European cohort have not been perfomed. To hus, we studied suPAR in participants of the Ludwigshafen Risk and Cardiovascular Health study over a very long follow-up time of nearly 10 years. We estimated overall risk of all-cause and cardiovascular death by Cox proportional hazards regression according to quartiles of suPAR, including age, sex, use of lipid-lowering drugs, body mass index, diabetes mellitus, hypertension, smoking, lipids, as well as glomerular filtration rate (eGFR), NT-proBNP, interleukin-6 and high-sensitive CRP as covariates. A total of 2940 participants (age 62.7 ± 10.5years) having a median eGFR of 83.8 mL/min/1.73 m² were included. The median suPAR concentration was 3010 pg/mL (interquartile range, 2250–3988 pg/mL). Using the lowest quartile of suPAR as the reference, crude hazard ratio for cardiovascular mortality were 1.58 (95% CI 1.16–2.16), 1.85 (95% CI 1.37–2.52) and 2.75 (95% CI 2.03–3.71) in the second, third and fourth quartile, respectively. Adjusting for NT-proBNPeGFR or inflammation (interleukin-6 and high-sensitive CRP) confirmed results. suPAR predicts all-cause and cardiovascular death over a period of ten years in persons undergoing coronary angiography, independent of the natriuretic peptide NT-proBNP, kidney function and of markers of systemic inflammation. Future investigation into a potential causal role of suPAR in cardiovascular disease is warranted.

Serum Urokinase-Type Plasminogen Activator Receptor Does Not Outperform C-Reactive Protein and Procalcitonin as an Early Marker of Severity of Acute Pancreatitis

Severe acute pancreatitis (SAP) concerns 10–20% of acute pancreatitis (AP) patients and is associated with a poor prognosis and high mortality. An early prognosis of the unfavorable outcome, transfer to an intensive care unit (ICU) and the introduction of an adequate treatment are crucial for patients’ survival. Recently, the elevated circulating urokinase-type plasminogen activator receptor (uPAR) has been reported to predict SAP with a high diagnostic accuracy among patients in a tertiary center. The aim of the study was to compare the diagnostic utility of uPAR and other inflammatory markers as the predictors of the unfavorable course of AP in patients admitted to a secondary care hospital within the first 24 h of the onset of AP. The study included 95 patients, eight with a SAP diagnosis. Serum uPAR was measured on admission and in the two subsequent days. On admission, uPAR significantly predicted organ failure, acute cardiovascular failure, acute kidney injury, the need for intensive care, and death. The diagnostic accuracy of the admission uPAR for the prediction of SAP, organ failure, and ICU transfer or death was low to moderate and did not differ significantly from the diagnostic accuracy of interleukin-6, C-reactive protein, procalcitonin, D-dimer and soluble fms-like tyrosine kinase-1. In the secondary care hospital, where most patients with AP are initially admitted, uPAR measurements did not prove better than the currently used markers.

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 (suPAR) and All-Cause and Cardiovascular Mortality in Diverse Hemodialysis Patients

Introduction

The soluble receptor of urokinase plasminogen activator (suPAR) is an innate immunity/inflammation biomarker predicting cardiovascular (CV) and non-CV events in various conditions, including type 2 diabetic patients on dialysis. However, the relationship between suPAR and clinical outcomes in the hemodialysis population at large has not been tested.

Methods

We measured plasma suPAR levels (R&D enzyme-linked immunosorbent assay [ELISA]) in 1038 hemodialysis patients with a follow-up of 2.9 years (interquartile range = 1.7−4.2) who were enrolled in the PROGREDIRE study, a cohort study involving 35 dialysis units in 2 regions in Southern Italy.

Results

suPAR was strongly (P < 0.001) and independently related to female gender (β = −0.160), age (β = 0.216), dialysis vintage (β = 0.264), CV comorbidities (β = 0.105), alkaline phosphatase (β = 0.136), albumin (β = −0.147), and body mass index (BMI; β = 0.174) (all P < 0.006). In fully adjusted analyses, suPAR tertiles predicted the risk of all-cause mortality (third tertile vs. first tertile hazard ratio (HR) = 1.91, 95% confidence interval (CI) = 1.47 – 2.48, P < 0.001), CV mortality (HR = 1.47, 95% CI = 1.03–2.09, P = 0.03), and non-CV mortality (HR = 1.94, 95% CI = 1.28–2.93, P = 0.002); these relationships were not modified by diabetes or other risk factors. suPAR added only modest prognostic risk discrimination and reclassification power for these outcomes to parsimonious models based on simple clinical variables.

Conclusion

In conclusion, suPAR robustly predicted all-cause and both CV and non-CV mortality in a large unselected hemodialysis population. Intervention studies are needed to definitively test the hypothesis that suPAR is causally implicated in clinical outcomes in this population.

Predicting Mortality in African Americans With Type 2 Diabetes Mellitus: Soluble Urokinase Plasminogen Activator Receptor, Coronary Artery Calcium, and High-Sensitivity C-Reactive Protein

BACKGROUND

Type 2 diabetes mellitus is a major risk factor for cardiovascular disease; however, outcomes in individual patients vary. Soluble urokinase plasminogen activator receptor (suPAR) is a bone marrow-derived signaling molecule associated with adverse cardiovascular and renal outcomes in many populations. We characterized the determinants of suPAR in African Americans with type 2 diabetes mellitus and assessed whether levels were useful for predicting mortality beyond clinical characteristics, coronary artery calcium (CAC), and high-sensitivity C-reactive protein (hs-CRP).

METHODS AND RESULTS

We measured plasma suPAR levels in 500 African Americans with type 2 diabetes mellitus enrolled in the African American-Diabetes Heart Study. We used Kaplan-Meier curves and Cox proportional hazards models adjusting for clinical characteristics, CAC, and hs-CRP to examine the association between suPAR and all-cause mortality. Last, we report the change in C-statistics comparing the additive values of suPAR, hs-CRP, and CAC to clinical models for prediction of mortality. The suPAR levels were independently associated with female sex, smoking, insulin use, decreased kidney function, albuminuria, and CAC. After a median 6.8-year follow-up, a total of 68 deaths (13.6%) were recorded. In a model incorporating suPAR, CAC, and hs-CRP, only suPAR was significantly associated with mortality (hazard ratio 2.66, 95% confidence interval 1.63-4.34). Addition of suPAR to a baseline clinical model significantly improved the C-statistic for all-cause death (Δ0.05, 95% confidence interval 0.01-0.10), whereas addition of CAC or hs-CRP did not.

CONCLUSIONS

In African Americans with type 2 diabetes mellitus, suPAR was strongly associated with mortality and improved risk discrimination metrics beyond traditional risk factors, CAC and hs-CRP. Studies addressing the clinical usefulness of measuring suPAR concentrations are warranted.

Soluble Urokinase-type Plasminogen Activator Receptor Predicts All-cause 5-Year Mortality in Ischemic Stroke and TIA

AIM

We evaluated soluble urokinase-type plasminogen activator receptor (suPAR) levels in different stroke subtypes and assessed their prognostic value regarding 5-year outcomes.

MATERIALS AND METHODS

The study included 117 stroke patients (81 males; mean=age 61±11 years) with suspected cardioembolic stroke whose plasma suPAR concentration was assessed. Altogether, 20 (17.1%) patients suffered from stroke as a result of cardioembolism, 12 (10.3%) from large-artery atherosclerosis, 9 (7.7%) from small-vessel disease, 11 (9.4%) from both large-artery and cardioembolic etiology, and 65 (55.6%) had cryptogenic stroke. The mean follow-up period was 5 years.

RESULTS

suPAR concentration was higher in patients who suffered from stroke/transient ischemic attack due to large-artery atherosclerosis (3.2±0.9 ng/ml) compared to small-vessel disease (2.0±0.5 ng/ml, p<0.001). An elevated plasma suPAR concentration was associated with all-cause mortality during the follow-up period (p=0.003).

CONCLUSION

Elevated plasma suPAR concentrations predicted all-cause mortality during the 5-year follow-up after ischemic stroke. suPAR was not able to differentiate patients with cardioembolic stroke from those with other stroke types.

Soluble Urokinase Plasminogen Activator Receptor and the Risk of Coronary Artery Disease in Young Chinese Patients

Background

Soluble urokinase plasminogen activator receptor (suPAR) is a novel marker of chronic inflammation and is considered to be a risk factor for coronary artery disease (CAD) in Caucasians. This study investigated the role of suPAR in young Chinese patients with CAD.

Methods

The study involved a total of 196 consecutive young (age ≤ 55 years) patients with angiographically proven CAD and 188 age-matched non-CAD individuals as controls. Traditional risk factors were evaluated using conventional assays, and levels of suPAR were measured by sandwich enzyme-linked immunosorbent assays.

Results

Levels of suPAR were significantly correlated with age (r = 0.20, P = 0.04), smoking (r = 0.33, P = 0.008), body mass index (r = 0.21, P = 0.03), and high-sensitivity C-reactive protein (hs-CRP; r = 0.31, P = 0.01). Multivariate logistic regression analysis showed that male sex (odds ratio (OR) = 3.12; 95% confidence interval (CI) = 1.18–8.25, P = 0.02), smoking (OR = 3.41, 95% CI = 1.55–7.50, P = 0.002), triglyceride (OR = 1.89, 95% CI = 1.10–3.25, P = 0.02), high-sensitivity C-reactive protein (OR = 1.24, 95% CI = 1.02–0.03, P = 0.03), and suPAR (OR = 1.37, 95% CI = 1.09–1.72, P = 0.007) were independently associated with CAD risk in young patients.

Conclusions

SuPAR is a novel independent risk factor for CAD in young Chinese patients. Further studies evaluating the effect of anti-inflammatory treatment on the suPAR levels and the risk of CAD are needed.

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.

Cardiovascular Disease Biomarkers and suPAR in Predicting Decline in Renal Function: A Prospective Cohort Study

INTRODUCTION

Soluble urokinase-type plasminogen activator receptor (suPAR) strongly predicts outcomes and incident chronic kidney disease (CKD) in patients with cardiovascular disease (CVD). Whether the association between suPAR and CKD is a reflection of its overall association with chronic inflammation and poor CVD outcomes is unclear. We examined whether CVD biomarkers, including high-sensitivity C-reactive protein (hs-CRP), fibrin-degradation products (FDPs), heat-shock protein 70 (HSP-70), and high-sensitivity troponin I (hs-TnI) were associated with a decline in kidney function in the Emory Cardiovascular Biobank cohort, in which suPAR levels were shown to be predictive of both incident CKD and CVD outcomes.

METHODS

We measured suPAR, hs-CRP, HSP-70, FDP, and hs-TnI plasma levels in 3282 adults (mean age 63 years, 64% male, 75% estimated glomerular filtration rate [eGFR] >60 ml/min per 1.73 m2). Glomerular filtration rate was estimated using Chronic Kidney Disease-Epidemiology Collaboration (eGFR) at enrollment (n = 3282) and follow-up (n = 2672; median 3.5 years). Urine protein by dipstick at baseline was available for 1335 subjects.

RESULTS

There was a weak correlation among biomarkers (r range: 0.17-0.28). hs-CRP, FDPs, hs-TnI, and suPAR were independently associated with baseline eGFR and proteinuria. The median yearly decline in eGFR was -0.6 ml/min per 1.73 m2. hs-CRP (β: -0.04; P = 0.46), FDPs (β: -0.13; P = 0.08), HSP-70 (β: 0.05; P = 0.84), or hs-TnI (β: -0.01; P = 0.76) were associated with eGFR decline. suPAR remained predictive of eGFR decline even after adjusting for all biomarkers.

DISCUSSION

hs-CRP, FDP, HSP-70, and hs-TnI were not associated with eGFR decline. The specific association of suPAR with eGFR decline supported its involvement in pathways specific to the pathogenesis of kidney disease.

Recent advances in understanding hypertension development in sub-Saharan Africa

Consistent reports indicate that hypertension is a particularly common finding in black populations. Hypertension occurs at younger ages and is often more severe in terms of blood pressure levels and organ damage than in whites, resulting in a higher incidence of cardiovascular disease and mortality. This review provides an outline of recent advances in the pathophysiological understanding of blood pressure elevation and the consequences thereof in black populations in Africa. This is set against the backdrop of populations undergoing demanding and rapid demographic transition, where infection with the human immunodeficiency virus predominates, and where under and over-nutrition coexist. Collectively, recent findings from Africa illustrate an increased lifetime risk to hypertension from foetal life onwards. From young ages black populations display early endothelial dysfunction, increased vascular tone and reactivity, microvascular structural adaptions as well as increased aortic stiffness resulting in elevated central and brachial blood pressures during the day and night, when compared to whites. Together with knowledge on the contributions of sympathetic activation and abnormal renal sodium handling, these pathophysiological adaptations result in subclinical and clinical organ damage at younger ages. This overall enhanced understanding on the determinants of blood pressure elevation in blacks encourages (a) novel approaches to assess and manage hypertension in Africa better, (b) further scientific discovery to develop more effective prevention and treatment strategies and

Introduction of a prognostic biomarker to strengthen risk stratification of acutely admitted patients: rationale and design of the TRIAGE III cluster randomized interventional trial

Background

Several biomarkers have shown to carry prognostic value beyond current triage algorithms and may aid in initial risk stratification of patients in the emergency department (ED). It has yet to be established if information provided by biomarkers can be used to prevent serious complications or deaths. Our aim is to determine whether measurement of the blood level of the biomarker soluble urokinase plasminogen activator receptor (suPAR) can enhance early risk stratification leading to reduced mortality, lower rate of complications, and improved patient flow in acutely admitted adult patients at the ED. The main hypothesis is that the availability of suPAR can reduce all-cause mortality, assessed at least 10 months after admission, by drawing attention towards patients with an unrecognized high risk, leading to improved diagnostics and treatment.

Methods

The study is designed as a cross-over cluster randomized interventional trial. SuPAR is measured within 2 h after admission and immediately reported to the treating physicians in the ED. All ED physicians are educated in the prognostic capabilities of suPAR prior to the inclusion period. The inclusion period began January 11^th 2016 and ends June 6^th 2016. The study aims to include 10.000 patients in both the interventional and control arm. The results will be presented in 2017.

Discussion

The present article aims to describe the design and rationale of the TRIAGE III study that will investigate whether the availability of prognostic information can improve outcome in acutely admitted patients. This might have an impact on health care organization and decision-making.

Trial registration

The trial is registered at clinicaltrials.gov (ID NCT02643459, November 13, 2015) and at the Danish Data Protection agency (ID HGH-2015-042 I-Suite no. 04087).

Attenuated IGF-1 predicts all-cause and cardiovascular mortality in a Black population: A five-year prospective study

BACKGROUND

Inconsistent findings are reported on whether insulin-like growth factor-1 (IGF-1) is protective or harmful in predicting hypertension, carotid wall thickness and mortality. We determined the five-year prognostic value of IGF-1 for these outcomes in a large Black population prone to hypertension and cardiovascular disease.

DESIGN

A longitudinal study as part of the PURE (Prospective Urban and Rural Epidemiology) study, North West Province, South Africa.

METHODS

We measured IGF-1 and IGF binding protein-3 (IGFBP-3) in 1038 HIV-uninfected participants (age range 32-94 years) and assessed blood pressure, carotid intima-media thickness and mortality.

RESULTS

Over five years 116 deaths occurred. Baseline IGF-1 was similar in survivors and non-survivors (p = 0.50), but tended to be higher in survivors upon adjustment for IGFBP-3 and covariates (p = 0.061). Normotensives and hypertensives (p = 0.072), and those with carotid intima-media thickness < 0.9 mm and ≥ 0.9 mm also displayed similar baseline IGF-1 (p = 0.55). Multivariable-adjusted Cox-regression indicated high IGF-1 predicting lower risk for all-cause mortality (hazard ratio 0.45; 0.23-0.88) and cardiovascular mortality (hazard ratio 0.26; 0.08-0.83) when also adjusting for IGFBP-3. When including normo- and hypertensives at baseline, high IGF-1 was related to normotension at follow-up (hazard ratio 0.68; 0.49-0.95). We found no association with carotid intima-media thickness (hazard ratio 0.59; 0.31-1.14).

CONCLUSION

In a Black South African population with low socio-economic status and harmful health behaviours, we found a protective independent association between IGF-1 and hypertension, cardiovascular and all-cause mortality, with no association with carotid wall thickness.

Increased circulating soluble urokinase-type plasminogen activator receptor (suPAR) levels in patients with slow coronary flow

Introduction

Slow coronary flow (SCF) is an angiographic phenomenon characterized by delayed opacification of epicardial coronary arteries without an obstructive coronary disease. Serum soluble urokinase-type plasminogen activator receptor (suPAR) levels seem closely related to atherosclerosis due to increased inflammation and prothrombotic state. We studied whether circulating suPAR is related to SCF.

Material and methods

The present study was cross-sectional and observational. It included 75 individuals who underwent coronary angiography with suspected CAD and had angiographically normal coronary arteries of varying coronary flow rates. The relationship between suPAR, C-reactive protein (CRP) and SCF was investigated. Forty patients with isolated SCF (mean age: 46.0 ±4.14 years) and 35 age- and gender-matched control participants with normal coronary flow (NCF) and normal coronary arteries (NCA) (mean age: 46.0 ±5.7 years) were included in the study. We used logistic regression analysis to determine the predictors of SCF.

Results

The clinical characteristics were not statistically significantly different between SCF and NCA groups. Serum suPAR level was significantly higher in the SCF group than the control group (2.5–5.4 ng/ml vs. 0.1–1.4 ng/ml; p < 0.001). Also the serum CRP level was higher in the CSF group than the control group (1.57 ±0.43 mg/l vs. 0.53 ±0.23 mg/l; p < 0.001).

Conclusions

This study revealed significantly increased serum suPAR levels in patients with SCF. Although we cannot draw conclusions on the underlying pathological process of SCF, we believe that these findings may be pioneering for further studies investigating the specific roles of circulating suPAR in the SCF phenomenon in the coronary vasculature.