The association between endostatin and kidney disease and mortality in patients with type 2 diabetes

Endostatin, soluble tumour necrosis factor receptor 1 and soluble tumour necrosis factor receptor 2 cannot predict new onset of microalbuminuria in patients with type 2 diabetes

AIMS

Inflammation and angiogenesis play an important role in the development of early diabetic kidney disease. We investigated the association of soluble Tumour Necrosis Factor Receptor 1 (sTNF-R1), sTNF-R2 and endostatin with new onset microalbuminuria in normoalbuminuric patients with diabetes mellitus type 2.

METHODS

We conducted a case control study to assess serum levels of sTNF-R1, sTNF-R2 and endostatin in 169 patients with new onset microalbuminuria and in 188 matched normoalbuminuric, diabetic controls. Baseline serum samples from participants of the ROADMAP (Randomized Olmesartan and Diabetes Microalbuminuria Prevention) and observational follow-up (ROADMAP-OFU) studies were used.

RESULTS

Endostatin and sTNF-R1 but not sTNF-R2 were increased at baseline in patients with future microalbuminuria. In the multivariate analysis, each log2 increment in endostatin levels was associated with an increase of only 6% in the risk of development of microalbuminuria (adjusted HR (95% CI) 1.006 (1.001-1011). sTNF-R1 and sTNF-R2 levels were conversely associated with microalbuminuria, but the results did not reach statistical significance. The respective adjusted HRs (95% CI) were 1.305 (0.928-1.774) and 0.874 (0.711-1.074).

CONCLUSIONS

sTNF-R1 and sTNF-R2 failed to predict the occurrence of microalbuminuria in normoalbuminuric patients with type 2 diabetes. Likewise, the utility of endostatin in predicting new onset proteinuria is limited.

Biomarkers of the End-Stage Renal Disease Progression: Beyond the GFR

Chronic kidney disease can progress to the end-stage renal disease (ESRD) characterized by a high risk of morbidity and mortality. ESRD requires immediate therapy or even dialysis or kidney transplantation, therefore, its timely diagnostics is critical for many patients. ESRD is associated with pathological changes, such as inflammation, fibrosis, endocrine disorders, and epigenetic changes in various cells, which could serve as ESRD markers. The review summarizes information on conventional and new ESRD biomarkers that can be assessed in kidney tissue, blood, and urine. Some biomarkers are specific to a particular pathology, while others are more universal. Here, we suggest several universal inflammatory, fibrotic, hormonal, and epigenetic markers indicative of severe deterioration of renal function and ESRD progression for improvement of ESRD diagnostics.

Molecular Mechanisms of Diabetic Kidney Disease

The inflammatory component of diabetic kidney disease has become of great interest in recent years, with genetic and epigenetic variants playing a fundamental role in the initiation and progression of the disease. Cells of the innate immune system play a major role in the pathogenesis of diabetic kidney disease, with a lesser contribution from the adaptive immune cells. Other components such as the complement system also play a role, as well as specific cytokines and chemokines. The inflammatory component of diabetic kidney disease is of great interest and is an active research field, with the hope to find potential innovative therapeutic targets.

Serum VEGF-D level is correlated with renal dysfunction and proteinuria in patients with diabetic chronic kidney disease

Biomarkers associated with chronic kidney disease (CKD) may play a crucial role in the early diagnosis of diabetic kidney disease. However, there have been few reports published on serum vascular endothelial cell growth factor (VEGF)-D in patients with diabetic CKD. We divided patients with diabetic CKD into two groups: CKD 3-4 and CKD 5. In total, 42 patients with diabetic kidney disease and seven healthy controls without diabetes mellitus were enrolled in this study. An observational study was conducted to evaluate the serum VEGF-D levels and other clinical parameters in each group and to assess the relationship among these factors. The serum levels of VEGF-D were higher in the CKD 3-4 group and CKD 5 group than in the control group. However, there was no significant difference in serum levels of VEGF-D between CKD stage 3-4 group and CKD stage 5 group. Correlation analysis showed that serum VEGF-D was negatively correlated with estimated glomerular filtration rate but positively correlated with serum creatinine, urine albumin-to-creatinine ratio, and urine protein-to-creatinine ratio. Serum VEGF-D was a good biomarker in receiver operating characteristic analysis and independently associated with CKD stages in multiple linear regression analysis. Circulating VEGF-D was positively correlated with blood growth/differentiation factor-15, endostatin, and chemokine (C-X-C motif) ligand 16 levels. Serum VEGF-D levels were correlated with renal dysfunction, albuminuria, and proteinuria in patients with diabetic kidney disease. Elucidation of the role of VEGF-D as a biomarker requires further study.

Endostatin in Renal and Cardiovascular Diseases

Endostatin, a protein derived from the cleavage of collagen XVIII by the action of proteases, is an endogenous inhibitor known for its ability to inhibit proliferation and migration of endothelial cells, angiogenesis, and tumor growth. Angiogenesis is defined as the formation of new blood vessels from pre-existing vasculature, which is crucial in many physiological processes, such as embryogenesis, tissue regeneration, and neoplasia.

SUMMARY

Increasing evidence shows that dysregulation of angiogenesis is crucial for the pathogenesis of renal and cardiovascular diseases. Endostatin plays a pivotal role in the regulation of angiogenesis. Recent studies have provided evidence that circulating endostatin increases significantly in patients with kidney and heart failure and may also contribute to disease progression.

KEY MESSAGE

In the current review, we summarize the latest findings on preclinical and clinical studies analyzing the impact of endostatin on renal and cardiovascular diseases.

Effect of Lisinopril and Verapamil on Angiopoietin 2 and Endostatin in Hypertensive Diabetic Patients with Nephropathy: A Randomized Trial

Angiogenesis is a multistep process implicated in the pathophysiology and progression of diabetic nephropathy (DN). Angiotensin-converting enzyme inhibitors (ACEI) and calcium channel blockers (CCB) have an important role in DN. We performed a randomized-controlled trial of lisinopril alone (an ACEI) or in combination with verapamil (a CCB) as a therapy for DN in type 2 diabetes mellitus (T2DM) patients with hypertension (HTN) and urinary albumin creatinine ratio (UACR) (30-300 mg/g) also to evaluate their effect on UACR, the angiogenic proteins: Angiopoietin 2 (Ang-2) and Endostatin (EST). Forty T2DM patients with microalbuminuria, aged 45-65 years were included. Patients were randomly assigned into group 1 receiving oral lisinopril and group 2 receiving oral lisinopril and verapamil once daily. After 3 months follow-up fasting blood glucose (FPG), HbA1c, lipid profile, UACR, serum urea and creatinine levels were assessed. EST and Ang-2 were measured using ELISA technique. Baseline Ang-2 and EST levels were elevated in both groups compared with controls (p<0.001). After follow-up, group 2 had significantly decreased FPG, HbA1c, UACR, EST and Ang-2 compared with their baseline levels (p<0.001 for all comparisons) and with group 1 (p<0.001). No adverse reactions were reported. Baseline EST and Ang-2 were positively correlated to UACR (r=0.753, p<0.001) (r=0.685, p<0.001). Lisinopril/verapamil combination enhanced glycemic control and kidney function via diminishing EST and Ang-2. This combination can be considered as a safe and effective approach for early stage nephropathy therapy in T2DM.

Diabetic kidney disease in type 2 diabetes: a review of pathogenic mechanisms, patient-related factors and therapeutic options

The global prevalence of diabetic kidney disease is rapidly accelerating due to an increasing number of people living with type 2 diabetes. It has become a significant global problem, increasing human and financial pressures on already overburdened healthcare systems. Interest in diabetic kidney disease has increased over the last decade and progress has been made in determining the pathogenic mechanisms and patient-related factors involved in the development and pathogenesis of this disease. A greater understanding of these factors will catalyse the development of novel treatments and influence current practice. This review summarises the latest evidence for the factors involved in the development and progression of diabetic kidney disease, which will inform better management strategies targeting such factors to improve therapeutic outcomes in patients living with diabetes.

Urinary chemokine C-X-C motif ligand 16 and endostatin as predictors of tubulointerstitial fibrosis in patients with advanced diabetic kidney disease

BACKGROUND

Interstitial fibrosis and tubular atrophy (IFTA) is a well-recognized risk factor for poor renal outcome in patients with diabetic kidney disease (DKD). However, a noninvasive biomarker for IFTA is currently lacking. The purpose of this study was to identify urinary markers of IFTA and to determine their clinical relevance as predictors of renal prognosis.

METHODS

Seventy patients with biopsy-proven isolated DKD were enrolled in this study. We measured multiple urinary inflammatory cytokines and chemokines by multiplex enzyme-linked immunosorbent assay in these patients and evaluated their association with various pathologic features and renal outcomes.

RESULTS

Patients enrolled in this study exhibited advanced DKD at the time of renal biopsy, characterized by moderate to severe renal dysfunction [mean estimated glomerular filtration rate (eGFR) 36.1 mL/min/1.73 m2] and heavy proteinuria (mean urinary protein:creatinine ratio 7.8 g/g creatinine). Clinicopathologic analysis revealed that higher IFTA scores were associated with worse baseline eGFR (P < 0.001) and poor renal outcome (P = 0.002), whereas glomerular injury scores were not. Among measured urinary inflammatory markers, C-X-C motif ligand 16 (CXCL16) and endostatin showed strong correlations with IFTA scores (P = 0.001 and P < 0.001, respectively), and patients with higher levels of urinary CXCL16 and/or endostatin experienced significantly rapid renal progression compared with other patients (P < 0.001). Finally, increased urinary CXCL16 and endostatin were independent risk factors for poor renal outcome after multivariate adjustments (95% confidence interval 1.070-3.455, P = 0.029).

CONCLUSIONS

Urinary CXCL16 and endostatin could reflect the degree of IFTA and serve as biomarkers of renal outcome in patients with advanced DKD.

Antiangiogenic therapy in diabetic nephropathy: A double‑edged sword (Review)

Diabetes and the associated complications are becoming a serious global threat and an increasing burden to human health and the healthcare systems. Diabetic nephropathy (DN) is the primary cause of end-stage kidney disease. Abnormal angiogenesis is well established to be implicated in the morphology and pathophysiology of DN. Factors that promote or inhibit angiogenesis serve an important role in DN. In the present review, the current issues associated with the vascular disease in DN are highlighted, and the challenges in the development of treatments are discussed.

Endothelial Basement Membrane Components and Their Products, Matrikines: Active Drivers of Pulmonary Hypertension?

Pulmonary arterial hypertension (PAH) is a vascular disease that is characterized by elevated pulmonary arterial pressure (PAP) due to progressive vascular remodeling. Extracellular matrix (ECM) deposition in pulmonary arteries (PA) is one of the key features of vascular remodeling. Emerging evidence indicates that the basement membrane (BM), a specialized cluster of ECM proteins underlying the endothelium, may be actively involved in the progression of vascular remodeling. The BM and its steady turnover are pivotal for maintaining appropriate vascular functions. However, the pathologically elevated turnover of BM components leads to an increased release of biologically active short fragments, which are called matrikines. Both BM components and their matrikines can interfere with pivotal biological processes, such as survival, proliferation, adhesion, and migration and thus may actively contribute to endothelial dysfunction. Therefore, in this review, we summarize the emerging role of the BM and its matrikines on the vascular endothelium and further discuss its implications on lung vascular remodeling in pulmonary hypertension.

Endostatin as a novel prognostic biomarker in acute ischemic stroke

BACKGROUND AND AIMS

Endostatin is implicated in the atherosclerosis process and serves as a promising cardiovascular biomarker, while its clinical significance in ischemic stroke patients remains unclear. We aimed to examine the association between endostatin and mortality and disability after ischemic stroke.

METHODS

A total of 3463 acute ischemic stroke patients with measured plasma endostatin from the China Antihypertensive Trial in Acute Ischemic Stroke were included in this study. The primary outcome was death or severe disability (modified Rankin scale score of 4-6), and secondary outcomes included death and vascular events.

RESULTS

After 3-month follow-up, 402 (11.61%) participants experienced severe disability or died. Compared with the lowest quartile of endostatin, odds ratios or hazard ratios (95% confidence intervals) for the highest quartile were 1.47 (1.04-2.09) for the primary outcome, and 2.36 (1.23-4.54) for death after adjustment for multiple covariates, including age, sex, admission NIH Stroke Scale score and systolic blood pressure. Each 1-SD higher log-transformed endostatin was associated with a 20% (6%-36%) increased risk for primary outcome. Adding plasma endostatin to the basic model constructed with conventional factors significantly improved risk stratification of primary outcome, as observed by the category-free net reclassification index of 20.5% (95% CI 10.1%-30.8%; p < 0.001) and integrated discrimination improvement of 0.3% (95% CI 0.01%-0.6%; p = 0.04).

CONCLUSIONS

Increased baseline plasma endostatin levels in acute ischemic stroke were associated with increased risk of mortality and severe disability at 3 months. Plasma endostatin may serve as an important prognostic marker for risk stratification in patients with ischemic stroke.

Endostatin predicts mortality in patients with acute dyspnea - A cohort study of patients seeking care in emergency departments

BACKGROUND

Increased levels of circulating endostatin predicts cardiovascular morbidity and impaired kidney function in the general population. The utility of endostatin as a risk marker for mortality in the emergency department (ED) has not been reported.

AIM

Our main aim was to study the association between plasma endostatin and 90-day mortality in an unselected cohort of patients admitted to the ED for acute dyspnea. Design Circulating endostatin was analyzed in plasma from 1710 adults and related to 90-day mortality in Cox proportional hazard models adjusted for age, sex, body mass index, oxygen saturation, respiratory rate, body temperature, C-reactive protein, lactate, creatinine and medical priority according to the Medical Emergency Triage and Treatment System-Adult score (METTS-A). The predictive value of endostatin for mortality was evaluated with receiver operating characteristic (ROC) analysis and compared with the clinical triage scoring system and age.

RESULTS

Each one standard deviation increment of endostatin was associated with a HR of 2.12 (95% CI 1.31-3.44 p < 0.01) for 90-day mortality after full adjustment. Levels of endostatin were significantly increased in the group of patients with highest METTS-A (p < 0.001). When tested for the outcome 90-day mortality, the area under the ROC curve (AUC) was 0.616 for METTS-A, 0.701 for endostatin, 0.708 for METTS -A and age and 0.738 for METTS-A, age and levels of endostatin.

CONCLUSIONS

In an unselected cohort of patients admitted to the ED with acute dyspnea, endostatin had a string association to 90-day mortality and improved prediction of 90-day mortality in the ED beyond the clinical triage scoring system and age with 3%.

Validation of an enzyme-linked immunosorbent assay (ELISA) for quantification of endostatin levels in mice as a biomarker of developing glomerulonephritis

Endostatin, the C-terminal fragment of type XVIII collagen, was shown to be one of the most potent endothelial cell-specific inhibitors of angiogenesis. As altered circulating endostatin concentration is associated with impaired kidney function, new tools for measuring endostatin in rodents may be helpful to further investigate and understand its role within kidney disease progression. A novel and commercially available ELISA for the quantification of mouse and rat endostatin was developed and validated according to international quality guidelines including the parameters specificity, robustness, accuracy, dilution linearity, precision, limit of detection (LOD) and lower limit of quantification (LLOQ). Endostatin and blood urea nitrogen (BUN) concentration were measured in mice with a glomerulonephritis phenotype. The validation revealed that within the range of 0.5–32 nmol/L the immunoassay is robust and highly specific for the measurement of rodent endostatin with high sensitivity (LOD 0.24 nmol/L, LLOQ 0.5 nmol/L) and good reproducibility (intra- and inter-assay CV <10%). Also accuracy and dilution linearity were within the range of acceptance. BCL2 transgenic and ETV6/RUNX1;BCL2 double transgenic mice develop a glomerulonephritis phenotype over time, which was displayed by staining of kidney sections. Even before full manifestation of disease serum endostatin concentration rises significantly, whereas BUN levels just slightly increase. This newly developed and commercially available ELISA provides a reliable and accurate tool for the quantification of mouse and rat endostatin and may give new perspectives in the investigation of the role of endostatin as an important and early biomarker for reduced kidney function. Measurement of endostatin concentration is recommended to be used as a superior biomarker for chronic kidney disease compared to BUN.

Circulating endostatin as a risk factor for cardiovascular events in patients with stable coronary heart disease: A CLARICOR trial sub-study

BACKGROUND AND AIMS

Raised levels of serum endostatin, a biologically active fragment of collagen XVIII, have been observed in patients with ischemic heart disease but association with incident cardiovascular events in patients with stable coronary heart disease is uncertain.

METHODS

The CLARICOR-trial is a randomized, placebo-controlled trial of stable coronary heart disease patients evaluating 14-day treatment with clarithromycin. The primary outcome was a composite of acute myocardial infarction, unstable angina pectoris, cerebrovascular disease or all-cause mortality. In the present sub-study using 10-year follow-up data, we investigated associations between serum endostatin at entry (randomization) and the composite outcome and its components during follow-up. The placebo group was used as discovery sample (1204 events, n = 1998) and the clarithromycin-treated group as replication sample (1220 events, n = 1979).

RESULTS

In Cox regression models adjusting for cardiovascular risk factors, glomerular filtration rate, and current pharmacological treatment, higher serum endostatin was associated with an increased risk of the composite outcome in the discovery sample (hazard ratio per standard deviation increase 1.11, 95% CI 1.03-1.19, p = 0.004), but slightly weaker and not statistically significant in the replication sample (hazard ratio 1.06, 95% CI 1.00-1.14, p = 0.06). In contrast, strong and consistent associations were found between endostatin and cardiovascular and all-cause mortality in all multivariable models and sub-samples. Addition of endostatin to a model with established cardiovascular risk factors provided no substantial improvement of risk prediction (<1%).

CONCLUSIONS

Raised levels of serum endostatin might be associated with cardiovascular events in patients with stable coronary heart disease. The clinical utility of endostatin measurements remains to be established.

Plasma endostatin predicts kidney outcomes in patients with type 2 diabetes

Novel biomarkers are needed to predict kidney function decline in patients with type 2 diabetes, especially those with preserved glomerular filtration rate (GFR). There are limited data on the association of markers of endothelial dysfunction with longitudinal GFR decline. We used banked specimens from a nested case-control study in the Action to Control Cardiovascular Disease (ACCORD) trial (n=187 cases: 187 controls) and from a diverse contemporary cohort of type 2 diabetic patients from the Mount Sinai BioMe Biobank (n=871) to assess the association of plasma endostatin and kidney outcomes. We measured plasma endostatin at enrollment and examined its association with a composite kidney outcome of sustained 40% decline in estimated GFR or end-stage renal disease. Baseline plasma endostatin levels were higher in participants with the composite outcome. Each log2 increment in plasma endostatin was associated with approximately 2.5-fold higher risk of the kidney outcome (adjusted odds ratio [OR] 2.5; 95% confidence interval [CI] 1.5-4.3 in ACCORD and adjusted hazard ratio [HR] 2.6; 95% CI 1.8-3.8 in BioMe). Participants in the highest vs. lowest quartile of plasma endostatin had approximately four-fold higher risk for the kidney outcome (adjusted OR 3.6; 95% CI 1.8-7.3 in ACCORD and adjusted HR 4.4; 95% CI 2.3-8.5 in BioMe). The AUC for the kidney outcome improved from 0.74 to 0.77 in BioMe with the addition of endostatin to a base clinical model. Plasma endostatin was strongly associated with kidney outcomes in type 2 diabetics with preserved eGFR and improved risk discrimination over traditional predictors.

New Insights into the Role of Basement Membrane-Derived Matricryptins in the Heart

The extracellular matrix (ECM), which contributes to structural homeostasis as well as to the regulation of cellular function, is enzymatically cleaved by proteases, such as matrix metalloproteinases and cathepsins, in the normal and diseased heart. During the past two decades, matricryptins have been defined as fragments of ECM with a biologically active cryptic site, namely the 'matricryptic site,' and their biological activities have been initially identified and clarified, including anti-angiogenic and anti-tumor effects. Thus, matricryptins are expected to be novel anti-tumor drugs, and thus widely investigated. Although there are a smaller number of studies on the expression and function of matricryptins in fields other than cancer research, some matricryptins have been recently clarified to have biological functions beyond an anti-angiogenic effect in heart. This review particularly focuses on the expression and function of basement membrane-derived matricryptins, including arresten, canstatin, tumstatin, endostatin and endorepellin, during cardiac diseases leading to heart failure such as cardiac hypertrophy and myocardial infarction.

Endogenous Antiangiogenic Factors in Chronic Kidney Disease: Potential Biomarkers of Progression

Chronic kidney disease (CKD) is a major global health problem. Unless intensive intervention is initiated, some patients can rapidly progress to end-stage kidney disease. However, it is often difficult to predict renal outcomes using conventional laboratory tests in individuals with CKD. Therefore, many researchers have been searching for novel biomarkers to predict the progression of CKD. Angiogenesis is involved in physiological and pathological processes in the kidney and is regulated by the balance between a proangiogenic factor, vascular endothelial growth factor (VEGF)-A, and various endogenous antiangiogenic factors. In recent reports using genetically engineered mice, the roles of these antiangiogenic factors in the pathogenesis of kidney disease have become increasingly clear. In addition, recent clinical studies have demonstrated associations between circulating levels of antiangiogenic factors and renal dysfunction in CKD patients. In this review, we summarize recent advances in the study of representative endogenous antiangiogenic factors, including soluble fms-related tyrosine kinase 1, soluble endoglin, pigment epithelium-derived factor, VEGF-A₁₆₅b, endostatin, and vasohibin-1, in associations with kidney diseases and discuss their predictive potentials as biomarkers of progression of CKD.

Circulating endostatin and the incidence of heart failure

OBJECTIVE

Circulating levels of endostatin are elevated in many underlying conditions leading to heart failure such as hypertension, diabetes, chronic kidney disease and ischemic heart disease. Yet, the association between endostatin and the incidence of heart failure has not been reported previously in the community.

DESIGN

We investigated the longitudinal association between serum endostatin levels and incident heart failure in two community-based cohorts of elderly: Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS, n = 966; mean age 70 years, 51% women, 81 events, mean follow-up 10 years) and Uppsala Longitudinal Study of Adult Men (ULSAM, n = 747 men; mean age 78 years, 98 heart failure events, mean follow-up 8 years). We also investigated the cross-sectional association between endostatin and echocardiographic left ventricular systolic function and diastolic function (ejection fraction and E/A-ratio, respectively).

RESULTS

Higher serum endostatin was associated with an increased risk for heart failure in both cohorts after adjustment for established heart failure risk factors, glomerular filtration rate and N-terminal pro-brain natriuretic peptide (NT-proBNP) (PIVUS: multivariable hazard ratio (HR) per 1-standard deviation (SD) increase, HR 1.46 (95%CI, 1.17-1.82, p < .001); ULSAM: HR 1.29 (95%CI, 1.00-1.68, p < .05). In cross-sectional analyses at baseline, higher endostatin was significantly associated with both worsened left ventricular systolic and diastolic function in both cohorts. Conclusion Higher serum endostatin was associated with left ventricular dysfunction and an increased heart failure risk in two community-based cohorts of elderly. Our findings encourage further experimental studies that investigate the role of endostatin in the development of heart failure.

Difference in Serum Endostatin Levels in Diabetic Patients with Critical Limb Ischemia Treated by Autologous Cell Therapy or Percutaneous Transluminal Angioplasty

The aim of this study was to compare the serum levels of the anti-angiogenic factor endostatin (S-endostatin) as a potential marker of vasculogenesis after autologous cell therapy (ACT) versus percutaneous transluminal angioplasty (PTA) in diabetic patients with critical limb ischemia (CLI). A total of 25 diabetic patients with CLI treated in our foot clinic during the period 2008–2014 with ACT generating potential vasculogenesis were consecutively included in the study; 14 diabetic patients with CLI who underwent PTA during the same period were included in a control group in which no vasculogenesis had occurred. S-endostatin was measured before revascularization and at 1, 3, and 6 months after the procedure. The effect of ACT and PTA on tissue ischemia was confirmed by transcutaneous oxygen pressure (TcPO₂) measurement at the same intervals. While S-endostatin levels increased significantly at 1 and 3 months after ACT (both P < 0.001), no significant change of S-endostatin after PTA was observed. Elevation of S-endostatin levels significantly correlated with an increase in TcPO₂ at 1 month after ACT (r = 0.557; P < 0.001). Our study showed that endostatin might be a potential marker of vasculogenesis because of its significant increase after ACT in diabetic patients with CLI in contrast to those undergoing PTA. This increase may be a sign of a protective feedback mechanism of this anti-angiogenic factor.

Biomarkers of diabetic kidney disease

Diabetic kidney disease (DKD) remains one of the leading causes of reduced lifespan in diabetes. The quest for both prognostic and surrogate endpoint biomarkers for advanced DKD and end-stage renal disease has received major investment and interest in recent years. However, at present no novel biomarkers are in routine use in the clinic or in trials. This review focuses on the current status of prognostic biomarkers. First, we emphasise that albuminuria and eGFR, with other routine clinical data, show at least modest prediction of future renal status if properly used. Indeed, a major limitation of many current biomarker studies is that they do not properly evaluate the marginal increase in prediction on top of these routinely available clinical data. Second, we emphasise that many of the candidate biomarkers for which there are numerous sporadic reports in the literature are tightly correlated with each other. Despite this, few studies have attempted to evaluate a wide range of biomarkers simultaneously to define the most useful among these correlated biomarkers. We also review the potential of high-dimensional panels of lipids, metabolites and proteins to advance the field, and point to some of the analytical and post-analytical challenges of taking initial studies using these and candidate approaches through to actual clinical biomarker use.

The association between circulating endostatin and a disturbed circadian blood pressure pattern in patients with type 2 diabetes

BACKGROUND

Endostatin, cleaved from collagen XVIII in the extracellular matrix, is a promising circulating biomarker for cardiovascular damage. It possesses anti-angiogenic and anti-fibrotic functions and has even been suggested to be involved in blood pressure regulation. Less is known if endostatin levels relate to circadian blood pressure patterns. In the present paper we studied the association between circulating levels of endostatin and nocturnal dipping in blood pressure.

METHODS

We used the CARDIPP-study, a cohort of middle aged, type 2 diabetics (n = 593, 32% women), with data on both 24-hour and office blood pressure, serum-endostatin, cardiovascular risk factors, and incident major cardiovascular events. Nocturnal dipping was defined as a >10% difference between day- and night-time blood pressures.

RESULTS

Two-hundred four participants (34%) were classified as non-dippers. The mean endostatin levels were significantly higher in non-dippers compared to dippers (mean ± standard deviation: 62.6 ± 1.8 µg/l vs. 58.7 ± 1.6 µg/l, respectively, p = .007). Higher serum levels of endostatin were associated with a diminished decline in nocturnal blood pressure adjusted for age, sex, HbA1c, mean systolic day blood pressure, hypertension treatment, glomerular filtration rate, and prevalent cardiovascular disease (regression coefficient per SD increase of endostatin -0.01, 95% CI, -0.02-(-0.001), p = .03). Structural equation modelling analyses suggest that endostatin mediates 7% of the association between non-dipping and major cardiovascular events.

CONCLUSION

We found an independent association between higher circulating levels of endostatin and a reduced difference between day- and night-time systolic blood pressure in patients with type 2 diabetes. Yet endostatin mediated only a small portion of the association between non-dipping and cardiovascular events arguing against a clinical utility of our findings.

Association of the Serum Endostatin Level, Renal Function, and Carotid Atherosclerosis of Healthy Residents of Japan: Results from the Kyushu and Okinawa Population Study (KOPS)

Aim: To analyze associations among the serum endostatin level, renal function, and carotid atherosclerosis of healthy residents of Japan.

Methods: Among 1,057 Japanese residents who attended free public physical examinations between 2010 and 2011, we evaluated the data of 648 healthy residents (200 men and 448 women, age 24 to 84 years) for whom the serum endostatin level and common carotid intima-media thickness (IMT) were measured. Renal function was assessed by estimated glomerular filtration rate (eGFR). Multiple linear regression analysis was done to determine the association of eGFR and serum endostatin level after adjustment for known covariates. Mediation analysis was done using Baron and Kenny's regression approach.

Results: The median endostatin level was 63.7 ng/mL (interquartile range: 49.7–93.2). The mean eGFR was 78.4 ± 14.8 mL/min/1.73m². Univariate analysis showed that age (r = −0.37, P < 0.01), non current smoking (85.8 ± 13.0 vs. 77.5 ± 14.8 mL/min/1.73 m², P < 0.01), hemoglobin A1c (r = −0.08, P = 0.05), low-density lipoprotein-cholesterol (r = −0.13, P < 0.01), uric acid (r = −0.15, P < 0.01), carotid IMT (r = −0.11, P < 0.01), and log-transformed endostatin (r = −0.36, P < 0.01) were significantly associated with eGFR. In multiple linear regression analysis, log-transformed endostatin was significantly associated with eGFR (beta = −0.24, P < 0.01). While, carotid IMT was no longer significant. Mediation analysis showed serum endostatin level to be a mediator in the association between carotid IMT and eGFR.

Conclusions: The association between carotid IMT and eGFR is mediated by the serum endostatin level of healthy individuals.

Biomarker for early renal microvascular and diabetic kidney diseases

Recognition of early stage of diabetic kidney disease, under common practice using biomarkers, namely microalbuminuria, serum creatinine level above 1 mg/dL and accepted definition of diabetic kidney disease associated with creatinine clearance value below 60 mL/min/1.73 m2, is unlikely. This would lead to delay treatment associated with therapeutic resistance to vasodilator due to a defective vascular homoeostasis. Other alternative biomarkers related to the state of microalbuminuria is not sensitive to screen for early diabetic kidney disease (stages I, II). In this regard, a better diagnostic markers to serve for this purpose are creatinine clearance, fractional excretion of magnesium (FE Mg), cystatin C. Recently, renal microvascular disease and renal ischemia have been demonstrated to correlate indirectly with the development of diabetic kidney disease and its function. Among these are angiogenic and anti-angiogenic factors, namely VEGF, VEGF receptors, angiopoietins and endostatin. With respect to therapeutic prevention, implementation of treatment at early stage of diabetic and nondiabetic kidney disease is able to restore renal perfusion and function.

Identification of Novel Circulating Biomarkers Predicting Rapid Decline in Renal Function in Type 2 Diabetes: The Fremantle Diabetes Study Phase II

OBJECTIVE

To assess the ability of plasma apolipoprotein (apo) A-IV (apoA4), apo C-III, CD5 antigen-like (CD5L), complement C1q subcomponent subunit B (C1QB), complement factor H-related protein 2, and insulin-like growth factor binding protein 3 (IBP3) to predict rapid decline in estimated glomerular filtration rate (eGFR) in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Mass spectrometry was used to measure baseline biomarkers in 345 community-based patients (mean age 67.0 years, 51.9% males) from the Fremantle Diabetes Study Phase II (FDS2). Multiple logistic regression was used to determine clinical predictors of rapid eGFR decline trajectory defined by semiparametric group-based modeling over a 4-year follow-up period. The incremental benefit of each biomarker was then assessed. Similar analyses were performed for a ≥30% eGFR fall, incident chronic kidney disease (eGFR <60 mL/min/1.73 m²), and eGFR decline of ≥5 mL/min/1.73 m²/year.

RESULTS

Based on eGFR trajectory analysis, 35 participants (10.1%) were defined as "rapid decliners" (mean decrease 2.9 mL/min/1.73 m²/year). After adjustment for clinical predictors, apoA4, CD5L, and C1QB independently predicted rapid decline (odds ratio 2.40 [95% CI 1.24-4.61], 0.52 [0.29-0.93], and 2.41 [1.14-5.11], respectively) and improved model performance and fit (P < 0.001), discrimination (area under the curve 0.75-0.82, P = 0.039), and reclassification (net reclassification index 0.76 [0.63-0.89]; integrated discrimination improvement 6.3% [2.1-10.4%]). These biomarkers and IBP3 contributed to improved model performance in predicting other indices of rapid eGFR decline.

CONCLUSIONS

The current study has identified novel plasma biomarkers (apoA4, CD5L, C1QB, and IBP3) that may improve the prediction of rapid decline in renal function independently of recognized clinical risk factors in type 2 diabetes.

Endostatin: a promising biomarker in the cardiovascular continuum?

The current review article aims to provide an up-to-date summary of previous studies in humans that have reported the association between circulating endostatin levels and different cardiovascular phenotypes. We also aim to provide suggestions for future directions of future research evaluating endostatin as a clinically relevant cardiovascular biomarker. With a few exceptions, higher circulating levels of endostatin seem to reflect vascular and myocardial damage, and a worsened prognosis for cardiovascular events or mortality in individuals with hypertension, diabetes, kidney disease, cardiovascular disease, as well as in the general population. Circulating endostatin seems to be a promising biomarker for cardiovascular pathology, but there is not enough evidence to date to support the use of endostatin measurements in clinical practice.

Antiangiogenic Therapy for Diabetic Nephropathy

Angiogenesis has been shown to be a potential therapeutic target for early stages of diabetic nephropathy in a number of animal experiments. Vascular endothelial growth factor (VEGF) is the main mediator for abnormal angiogenesis in diabetic glomeruli. Although beneficial effects of anti-VEGF antibodies have previously been demonstrated in diabetic animal experiments, recent basic and clinical evidence has revealed that the blockade of VEGF signaling resulted in proteinuria and renal thrombotic microangiopathy, suggesting the importance of maintaining normal levels of VEGF in the kidneys. Therefore, antiangiogenic therapy for diabetic nephropathy should eliminate excessive glomerular angiogenic response without accelerating endothelial injury. Some endogenous antiangiogenic factors such as endostatin and tumstatin inhibit overactivation of endothelial cells but do not specifically block VEGF signaling. In addition, the novel endothelium-derived antiangiogenic factor vasohibin-1 enhances stress tolerance and survival of the endothelial cells, while inhibiting excess angiogenesis. These factors have been demonstrated to suppress albuminuria and glomerular alterations in a diabetic mouse model. Thus, antiangiogenic therapy with promising candidates will possibly improve renal prognosis in patients with early stages of diabetic nephropathy.

Collagen XVIII in tissue homeostasis and dysregulation - Lessons learned from model organisms and human patients

Collagen XVIII is a ubiquitous basement membrane (BM) proteoglycan produced in three tissue-specific isoforms that differ in their N-terminal non-collagenous sequences, but share collagenous and C-terminal non-collagenous domains. The collagenous domain provides flexibility to the large collagen XVIII molecules on account of multiple interruptions in collagenous sequences. Each isoform has a complex multi-domain structure that endows it with an ability to perform various biological functions. The long isoform contains a frizzled-like (Fz) domain with Wnt-inhibiting activity and a unique domain of unknown function (DUF959), which is also present in the medium isoform. All three isoforms share an N-terminal laminin-G-like/thrombospondin-1 sequence whose specific functions still remain unconfirmed. The proteoglycan nature of the isoforms further increases the functional diversity of collagen XVIII. An anti-angiogenic domain termed endostatin resides in the C-terminus of collagen XVIII and is proteolytically cleaved from the parental molecule during the BM breakdown for example in the process of tumour progression. Recombinant endostatin can efficiently reduce tumour angiogenesis and growth in experimental models by inhibiting endothelial cell migration and proliferation or by inducing their death, but its efficacy against human cancers is still a subject of debate. Mutations in the COL18A1 gene result in Knobloch syndrome, a genetic disorder characterised mainly by severe eye defects and encephalocele and, occasionally, other symptoms. Studies with gene-modified mice have elucidated some aspects of this rare disease, highlighting in particular the importance of collagen XVIII in the development of the eye. Research with model organisms have also helped in determining other structural and biological functions of collagen XVIII, such as its requirement in the maintenance of BM integrity and its emerging roles in regulating cell survival, stem or progenitor cell maintenance and differentiation and inflammation. In this review, we summarise current knowledge on the properties and endogenous functions of collagen XVIII in normal situations and tissue dysregulation. When data is available, we discuss the functions of the distinct isoforms and their specific domains.