Urinary ACE2 is associated with urinary L-FABP and albuminuria in patients with chronic kidney disease

Urinary angiotensin-converting enzyme 2 and its activity in cats with chronic kidney disease

Introduction

Angiotensin-converting enzyme 2 (ACE2) played an important role in the renin-angiotensin-aldosterone system (RAAS) and it was proved to be renoprotective in renal disease. Urinary angiotensin-converting enzyme 2 (uACE2) has been shown to reflect renal injury in human and experimental studies, but its role in feline kidney disease remains unknown.

Aims

Our objectives involve comparing uACE2 concentrations and activities in cats across CKD stages with healthy controls, investigating the relationship between uACE2 concentrations, activities, and clinicopathological data in feline CKD patients, and assessing the predictive abilities of both for CKD progression.

Methods

A retrospective, case-control study. The concentration and activity of uACE2 were measured by commercial ELISA and fluorometric assay kits, respectively. The concentration was adjusted to give uACE2 concentration-to-creatinine ratios (UACCRs).

Results

In total, 67 cats consisting of 24 control and 43 chronic kidney disease (CKD), including 24 early-stage CKD and 19 late-stage CKD, were enrolled in this study. UACCR values were significantly higher in both early-stage (2.100 [1.142-4.242] x 10-6) and late-stage feline CKD (4.343 [2.992-5.0.71] x 10-6) compared to healthy controls (0.894 [0.610-1.076] x 10-6; p < 0.001), and there was also significant difference between-early stage group and late-stage group (p = 0.026). Urinary ACE2 activity (UAA) was significantly lower in CKD cats (1.338 [0.644-2.755] x pmol/min/ml) compared to the healthy cats (7.989 [3.711-15.903] x pmol/min/ml; p < 0.001). UACCR demonstrated an independent, positive correlation with BUN (p < 0.001), and UAA exhibited an independent, negative correlation with plasma creatinine (p < 0.001). Both UACCR and UAA did not yield significant results in predicting CKD progression based on the ROC curve analysis.

Conclusion and clinical importance

uACE2 concentration and activity exhibit varying changes as renal function declines, particularly in advanced CKD cats.

A comprehensive guide to the pharmacologic regulation of angiotensin converting enzyme 2 (ACE2), the SARS-CoV-2 entry receptor

The recent emergence of coronavirus disease-2019 (COVID-19) as a global pandemic has prompted scientists to address an urgent need for defining mechanisms of disease pathology and treatment. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent for COVID-19, employs angiotensin converting enzyme 2 (ACE2) as its primary target for cell surface attachment and likely entry into the host cell. Thus, understanding factors that may regulate the expression and function of ACE2 in the healthy and diseased body is critical for clinical intervention. Over 66% of all adults in the United States are currently using a prescription drug and while earlier findings have focused on possible upregulation of ACE2 expression through the use of renin angiotensin system (RAS) inhibitors, mounting evidence suggests that various other widely administered drugs used in the treatment of hypertension, heart failure, diabetes mellitus, hyperlipidemias, coagulation disorders, and pulmonary disease may also present a varied risk for COVID-19. Specifically, we summarize mechanisms on how heparin, statins, steroids and phytochemicals, besides their established therapeutic effects, may also interfere with SARS-CoV-2 viral entry into cells. We also describe evidence on the effect of several vitamins, phytochemicals, and naturally occurring compounds on ACE2 expression and activity in various tissues and disease models. This comprehensive review aims to provide a timely compendium on the potential impact of commonly prescribed drugs and pharmacologically active compounds on COVID-19 pathology and risk through regulation of ACE2 and RAS signaling.

Twenty years of progress in angiotensin converting enzyme 2 and its link to SARS-CoV-2 disease

The virulence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the aggressive nature of the disease has transformed the universal pace of research in the desperate attempt to seek effective therapies to halt the morbidity and mortality of this pandemic. The rapid sequencing of the SARS-CoV-2 virus facilitated identification of the receptor for angiotensin converting enzyme 2 (ACE2) as the high affinity binding site that allows virus endocytosis. Parallel evidence that coronavirus disease 2019 (COVID-19) disease evolution shows greater lethality in patients with antecedent cardiovascular disease, diabetes, or even obesity questioned the potential unfavorable contribution of angiotensin converting enzyme (ACE) inhibitors or angiotensin II (Ang II) receptor blockers as facilitators of adverse outcomes due to the ability of these therapies to augment the transcription of Ace2 with consequent increase in protein formation and enzymatic activity. We review, here, the specific studies that support a role of these agents in altering the expression and activity of ACE2 and underscore that the robustness of the experimental data is associated with weak clinical long-term studies of the existence of a similar regulation of tissue or plasma ACE2 in human subjects.

Assessment of the Diagnostic Validities of Serum NGAL, KIM-1, and L-FABP in Patients With Chronic Kidney Disease

Introduction: Chronic kidney disease (CKD) is one of the most threatening and important disorders worldwide in both industrial and developing nations. In addition, neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty acid-binding protein (L-FABP), and kidney injury molecule-1 (KIM-1) are three factors suggested as diagnostic and prognostic biomarkers in CKDs. Considering the lack of enough efficiency of the creatinine in the prognosis of the CKD, the present study aimed to assess the relationship between these three factors and CKD occurrence and determine if they could be considered valid biomarkers in this regard. Materials and Methods: The present case-control study was designed enrolling 42 patients with confirmed CKD referring to the Imam Khomeini hospital of Kangan. The participants were 42 years old and gender-matched healthy counterparts. Blood samples were obtained, and then NGAL, KIM-1, and L-FABP were determined by the enzyme-linked immunosorbent assay using commercial kits (Bioassay Technology Laboratory). Finally, the serum creatinine was detected by applying Jaffe’s method. Results: Based on the results, significant differences were found in the serum levels of all four factors between CKD patients and the control group. More precisely, the serum levels of NGAL (P < 0.0001, specificity: 87.6%, sensitivity: 79.3%, and the area under the curve, AUC: 0.89), L-FABP (P < 0.0001, specificity: 83.3%, sensitivity: 78.3%, and AUC: 0.86), KIM-1 (P < 0.0001, specificity: 85.7%, sensitivity: 78.6%, and AUC: 0.88), and creatinine (P < 0.0001) were significantly higher in individuals with CKDs in comparison with controls. Eventually, the serum levels of NGAL, L-FABP, and KIM-1 were significantly correlated with each other in both patient and control groups (P < 0.0001). Conclusion: In general, NGAL, L-FABP, KIM-1, and creatinine could be used as independent biomarkers for the diagnosis of CKD. Moreover, the measurement of NGAL, L-FABP, and KIM-1 altogether could be a valid assessment for the diagnosis of CKD.

A review of urinary angiotensin converting enzyme 2 in diabetes and diabetic nephropathy

Urinary angiotensin converting enzyme 2 (ACE2) is significantly increased in diabetes and diabetic nephropathy. While studies on its clinical significance are still underway, its urinary expression, association with metabolic and renal parameters has been in the recent past considerably studied. The recent studies have demystified urine ACE2 in many ways and suggested the roles it could play in the management of diabetic nephropathy. In all studies the expression of urinary ACE2 was determined by enzyme activity assay and/with the quantification of ACE2 protein and mRNA by methods whose reliability are yet to be evaluated. This review summarizes recent findings on expression of urinary ACE2, examines its relationship with clinical parameters and highlights possible applications in management of diabetic nephropathy.

Changes in the urinary extracellular vesicle proteome are associated with nephronophthisis-related ciliopathies

Nephronophthisis is one of the leading genetic causes of end-stage renal disease in childhood. Early diagnostics and prognostics for nephronophthisis are currently limited. We aimed to identify non-invasive protein biomarkers for nephronophthisis in urinary extracellular vesicles. Extracellular vesicles were isolated from urine of 12 patients with a nephronophthisis-related ciliopathy and 12 age- and gender-matched controls, followed by in-depth label-free LC-MS/MS proteomics analysis of gel fractionated extracellular vesicle proteins. Supervised cluster analysis of proteomic profiles separated patients from controls. We identified 156 differentially expressed proteins with fold change ≥4 in patients compared to controls (P < .05). Importantly, expression levels of discriminating proteins were correlated with chronic kidney disease stage, suggesting possible applications for urinary extracellular vesicle biomarkers in prognostics for nephronophthisis. Enrichment analysis of gene ontology terms revealed GO terms including signaling, actin cytoskeleton and endocytosis among the downregulated proteins in patients, whereas terms related to response to wounding and extracellular matrix organization were enriched among upregulated proteins. Our findings represent the first step towards a non-invasive diagnostic test for nephronophthisis. Further research is needed to determine specificity of the candidate biomarkers. In conclusion, proteomic profiles of urinary extracellular vesicles differentiate nephronophthisis-related ciliopathy patients from healthy controls. SIGNIFICANCE: Nephronophthisis is an important cause of end-stage renal disease in children and is associated with an average diagnostic delay of 3.5 years. This is the first study investigating candidate biomarkers for nephronophthisis using global proteomics analysis of urinary extracellular vesicles in patients with nephronophthisis compared to control individuals. We show that measuring protein markers in urinary extracellular vesicles is a promising approach for non-invasive early diagnostics of nephronophthisis.

Intrarenal Angiotensin-Converting Enzyme: the Old and the New

PURPOSE OF REVIEW

The intrarenal renin-angiotensin-aldosterone system (RAS) is an independent paracrine hormonal system with an increasingly prominent role in hypertension and renal disease. Two enzyme components of this system are angiotensin-converting enzyme (ACE) and more recently discovered ACE2. The purpose of this review is to describe recent discoveries regarding the roles of intrarenal ACE and ACE2 and their interaction.

RECENT FINDINGS

Renal tubular ACE contributes to salt-sensitive hypertension. Additionally, the relative expression and activity of intrarenal ACE and ACE2 are central to promoting or inhibiting different renal pathologies including renovascular hypertension, diabetic nephropathy, and renal fibrosis. Renal ACE and ACE2 represent two opposing axes within the intrarenal RAS system whose interaction determines the progression of several common disease processes. While this relationship remains complex and incompletely understood, further investigations hold the potential for creating novel approaches to treating hypertension and kidney disease.

Serum protease activity in chronic kidney disease patients: The GANI_MED renal cohort

Serum or plasma proteases have been associated with various diseases including cancer, inflammation, or reno-cardiovascular diseases. We aimed to investigate whether the enzymatic activities of serum proteases are associated with the estimated glomerular filtration rate (eGFR) in patients with different stages of chronic kidney disease (CKD). Our study population comprised 268 participants of the "Greifswald Approach to Individualized Medicine" (GANI_MED) cohort. Enzymatic activity of aminopeptidase A, aminopeptidase B, alanyl (membrane) aminopeptidase, insulin-regulated aminopeptidase, puromycin-sensitive aminopeptidase, leucine aminopeptidase 3, prolyl-endopeptidase (PEP), dipeptidyl peptidase 4 (DPP4), angiotensin I-converting enzyme, and angiotensin I-converting enzyme 2 (ACE2) proteases was measured in serum. Linear regression of the respective protease was performed on kidney function adjusted for age and sex. Kidney function was modeled either by the continuous Modification of Diet in Renal Disease (MDRD)-based eGFR or dichotomized by eGFR < 15 mL/min/1.73 m² or <45 mL/min/1.73 m², respectively. Results with a false discovery rate below 0.05 were deemed statistically significant. Among the 10 proteases investigated, only the activities of ACE2 and DPP4 were correlated with eGFR. Patients with lowest eGFR exhibited highest DPP4 and ACE2 activities. DPP4 and PEP were correlated with age, but all other serum protease activities showed no associations with age or sex. Our data indicate that ACE2 and DPP4 enzymatic activity are associated with the eGFR in patients with CKD. This finding distinguishes ACE2 and DPP4 from other serum peptidases analyzed and clearly indicates that further analyses are warranted to identify the precise role of these serum ectopeptidases in the pathogenesis of CKD and to fully elucidate underlying molecular mechanisms. Impact statement • Renal and cardiac diseases are very common and often occur concomitantly, resulting in increased morbidity and mortality. Understanding of molecular mechanisms linking both diseases is limited, available fragmentary data point to a role of the renin-angiotensin system (RAS) and, in particular, Ras-related peptidases. • Here, a comprehensive analysis of serum peptidase activities in patients with different stages of chronic kidney disease (CKD) is presented, with special emphasis given to RAS peptidases • The serum activities of the peptidases angiotensin I-converting enzyme 2 and dipeptidyl peptidase 4 were identified as closely associated with kidney function, specifically with the estimated glomerular filtration rate. The findings are discussed in the context of available data suggesting protective roles for both enzymes in reno-cardiac diseases. • The data add to our understanding of pathomechanisms underlying development and progression of CKD and indicate that both enzymes might represent potential pharmacological targets for the preservation of renal function.