Associations of Angiopoietin 2 and Vascular Endothelial Growth Factor-A Concentrations with Clinical End Points

BACKGROUND

Angiopoietin 2 regulates endothelial function partially mediated by vascular endothelial growth factor-A (VEGF-A) and may play a role in diabetic kidney disease (DKD). We assessed the association of angiopoietin 2 and VEGF-A with cardiorenal outcomes and investigated the effect of canagliflozin on angiopoietin 2 and VEGF-A concentrations.

METHODS

Two thousand five hundred sixty-five study participants with DKD and available plasma samples treated with canagliflozin or placebo in the Canagliflozin and Kidney Events in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE) trial were included. Angiopoietin 2 and VEGF-A concentrations were measured at baseline, year 1, and year 3. The primary composite end point of the trial was a composite of kidney failure, doubling of the serum creatinine level, and kidney or cardiovascular death.

RESULTS

Patients with the highest baseline quartile of angiopoietin 2, but not VEGF-A, concentration had the highest risk clinical profile. Treatment with canagliflozin significantly lowered concentrations of angiopoietin 2 (adjusted geometric mean ratio: 0.94; 95% confidence interval, 0.92 to 0.95; P < 0.001), but not VEGF-A. In multivariable-adjusted modeling, each 50% increment in log baseline angiopoietin 2 concentrations was associated with a higher risk of primary composite outcome (hazard ratio, 1.27; 95% confidence interval, 1.13 to 1.43). Angiopoietin 2 change at year 1 compared with baseline explained 10% of the effect of canagliflozin on the primary composite outcome. VEGF-A concentrations were not associated with outcomes, alone or in combination with angiopoietin 2.

CONCLUSIONS

Higher angiopoietin 2 levels were associated with cardiorenal risk among individuals with DKD independent of VEGF-A. Canagliflozin lowered angiopoietin 2 concentrations.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Evaluation of the Effects of Canagliflozin on Renal and Cardiovascular Outcomes in Participants With Diabetic Nephropathy, NCT02065791 .

Endothelial activation and damage as a common pathological substrate in different pathologies and cell therapy complications

The endothelium is a biologically active interface with multiple functions, some of them common throughout the vascular tree, and others that depend on its anatomical location. Endothelial cells are continually exposed to cellular and humoral factors, and to all those elements (biological, chemical, or hemodynamic) that circulate in blood at a certain time. It can adapt to different stimuli but this capability may be lost if the stimuli are strong enough and/or persistent in time. If the endothelium loses its adaptability it may become dysfunctional, becoming a potential real danger to the host. Endothelial dysfunction is present in multiple clinical conditions, such as chronic kidney disease, obesity, major depression, pregnancy-related complications, septic syndromes, COVID-19, and thrombotic microangiopathies, among other pathologies, but also in association with cell therapies, such as hematopoietic stem cell transplantation and treatment with chimeric antigen receptor T cells. In these diverse conditions, evidence suggests that the presence and severity of endothelial dysfunction correlate with the severity of the associated disease. More importantly, endothelial dysfunction has a strong diagnostic and prognostic value for the development of critical complications that, although may differ according to the underlying disease, have a vascular background in common. Our multidisciplinary team of women has devoted many years to exploring the role of the endothelium in association with the mentioned diseases and conditions. Our research group has characterized some of the mechanisms and also proposed biomarkers of endothelial damage. A better knowledge would provide therapeutic strategies either to prevent or to treat endothelial dysfunction.

Impact of Angiopoietin-2 on Kidney Diseases

Background

Angiopoietins (Ang) are essential angiogenic factors involved in angiogenesis, vascular maturation, and inflammation. The most studied angiopoietins, angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2), behave antagonistically to each other in vivo to sustain vascular endothelium homeostasis. While Ang-1 typically acts as the endothelium-protective mediator, its context-dependent antagonist Ang-2 can promote endothelium permeability and vascular destabilization, hence contributing to a poor outcome in vascular diseases via endothelial injury, vascular dysfunction, and microinflammation. The pathogenesis of kidney diseases is associated with endothelial dysfunction and chronic inflammation in renal diseases.

Summary

Several preclinical studies report overexpression of Ang-2 in renal tissues of certain kidney disease models; additionally, clinical studies show increased levels of circulating Ang-2 in the course of chronic kidney disease, implying that Ang-2 may serve as a useful biomarker in these patients. However, the exact mechanisms of Ang-2 action in renal diseases remain unclear.

Key Messages

We summarized the recent findings on Ang-2 in kidney diseases, including preclinical studies and clinical studies, aiming to provide a systematic understanding of the role of Ang-2 in these diseases.

Association between angiopoietin-2 and functional cardiac remodeling in hemodialysis patients with normal left ventricular ejection

Cardiac remodeling is the initial process in heart failure development. The aim of this study is to evaluate the association between endothelium-related biomarkers and cardiac remodeling in hemodialysis (HD) patients and how the presence of high blood pressure and diabetes mellitus modulates these associations. This was a cross-sectional study with adult HD and normal left ventricular (LV) ejection fraction-LVEF-patients. The authors correlated several endothelium-related biomarkers with echocardiographic indices-LV mass index (LVMi), LVEF, global longitudinal strain, mitral E/e', and aortic root diameter. Seventy-one patients were included, with 37 women (52.1%) and mean age of 54.3 ± 16.8 years. Angiopoietin-2 (AGPT2) was inversely correlated with global longitudinal strain (r = -.374, p = .001) and directly with E/e' (r = .265, p = .025). After adjustment, only AGPT2 was significantly associated with global longitudinal strain. blood pressure and diabetes mellitus were independent moderators for the AGPT2 and global longitudinal strain association. The conditional association was significant only when the mean pre-HD blood pressure was above 97.5 mmHg or in diabetes mellitus patients. Finally, there was an interaction between diabetes mellitus and blood pressure when moderating the conditional effect of AGPT2 on global longitudinal strain. While in non-diabetic patients, the association between AGPT2 with global longitudinal strain was significant only with pre-HD blood pressure levels as high as 110 mmHg, in diabetic patients, this association was significant with pre-HD blood pressure as low as 90 mmHg. Higher levels of AGPT2 were associated with worse cardiac function as determined by lower global longitudinal strain values. This association was moderated by blood pressure and diabetes mellitus, suggesting that the effects of AGPT2 on cardiac remodeling is dependent of such circumstances.

Angiopoietin-2 predicts all-cause mortality in male but not female end-stage kidney disease patients on hemodialysis

Background

Angiopoietin-2 (Ang-2) plays a pivotal role in pathological vascular remodeling and angiogenesis. Both vascular mechanisms are active in patients with end-stage renal disease (ESRD) and may contribute to the high mortality in these patients. The aim of this multicenter prospective cohort study was to investigate baseline serum Ang-2 concentrations in ESRD patients on hemodialysis (HD) for their ability to predict all-cause mortality.

Methods

We conducted a prospective cohort study in 340 stable HD patients from different chronic dialysis centers in Berlin, Germany. The primary endpoint was all-cause mortality during a 5-year follow-up period. Blood samples and clinical data were collected at baseline. Serum Ang-2 was measured with a validated enzyme-linked immunosorbent assay (Biomedica, Vienna, Austria).

Results

A total of 313 HD patients (206 men and 107 women) were finally included in the study. Receiver operating characteristic (ROC) analysis of Ang-2 concentrations yielded an area under the curve (AUC) of 0.65 (P < 0.0001) for predicting all-cause mortality in the entire study population and was used to determine the optimal cut-off (111.0 pmol/L) for all-cause mortality. Kaplan–Meier survival analysis indicated that male but not female end-stage kidney disease patients on HD with higher Ang-2 concentrations had a significantly lower survival (log-rank test, P < 0.0001 and P = 0.380 for male and female patients, respectively). Multivariable Cox regression analyses adjusted for age, comorbidity, smoking, dialysis vintage, serum creatinine, hemoglobin, C-reactive protein, serum albumin, intact parathyroid hormone (iPTH), low-density lipoprotein (LDL) and Kt/V likewise indicated that elevated Ang-2 concentrations are associated with all-cause mortality in male {hazard ratio [HR] 3.294 [95% confidence interval (CI) 1.768–6.138]; P = 0.0002} but not in female end-stage kidney disease patients on HD [HR 1.084 (95% CI 0.476–2.467); P = 0.847].

Conclusion

Ang-2 at baseline is independently associated with all-cause mortality in male ESRD patients on HD.

Effect of HIV-1 Infection on Angiopoietin 1 and 2 Levels and Measures of Microvascular and Macrovascular Endothelial Dysfunction

Background Individuals infected with HIV have an increased risk of developing cardiovascular disease; yet, the underlying mechanisms remain unknown. Recent evidence has implicated the Tie-2 tyrosine kinase receptor system and its associated ligands ANG1 (angiopoietin 1) and ANG2 (angiopoietin 2) in maintaining vascular homeostasis. In the general population, lower ANG1 levels and higher ANG2 levels are strongly correlated with the development of cardiovascular disease. In this study, we aim to investigate the associations of HIV infection with angiopoietin levels and endothelial dysfunction. Methods and Results In this cross-sectional study, we compared measures of ANG1, ANG2, and endothelial dysfunction using flow-mediated vasodilation of the brachial artery in 39 untreated subjects infected with HIV, 47 treated subjects infected with HIV, and 46 uninfected subjects from the SCOPE (Observational Study of the Consequences of the Protease Inhibitor Era) cohort. Compared with uninfected controls, treated individuals infected with HIV had 53.1% lower mean ANG1 levels (P<0.01) and similar ANG2 levels. On the other hand, untreated individuals infected with HIV had similar ANG1 levels, and 29.2% had higher ANG2 levels (P<0.01) compared with uninfected controls. When compared with individuals with untreated HIV infection, those with treated HIV infection had 56% lower ANG1 levels (P<0.01) and 22% lower ANG2 levels (P<0.01).Both treated and untreated HIV infection were associated with significant impairment in hyperemic velocity, a key measure of microvascular dysfunction (median 61 versus 72 cm/s, P<0.01), compared with uninfected controls (median 73 cm/s). This difference persisted after adjustment for ANG1 and ANG2 levels. Interestingly, when compared with untreated individuals infected with HIV, treated individuals infected with HIV had worse hyperemic velocity (-12.35 cm/s, P=0.05). In contrast, HIV status, ANG1 levels, and ANG2 levels were not associated with macrovascular dysfunction as measured by flow-mediated dilatation and brachial artery diameter, 2 other measures of vascular homeostasis. Conclusions HIV infection affects the balance between levels of ANG1 and ANG2 and may disturb endothelial homeostasis through disruption of vascular homeostasis. Individuals with treated HIV had decreased ANG1 levels and similar ANG2 levels, whereas individuals with untreated HIV had similar ANG1 levels and increased ANG2 levels, suggesting that treatment status may alter the balance between ANG1 and ANG2. HIV also promotes endothelial dysfunction via impairment of microvascular dysfunction, independent of the Tie-2 receptor system; the finding of worse microvascular dysfunction in the setting of treated HIV infection may reflect the impact of viral persistence on the microvasculature or toxicities of specific antiretroviral regimens. Further research to clarify the mechanism of HIV-mediated endothelial dysfunction is necessary to advance treatment of cardiovascular complications of HIV infection.

Syndecan-1 and Free Indoxyl Sulfate Levels Are Associated with miR-126 in Chronic Kidney Disease

Chronic kidney disease (CKD) is a major cause of death worldwide and is associated with a high risk for cardiovascular and all-cause mortality. In CKD, endothelial dysfunction occurs and uremic toxins accumulate in the blood. miR-126 is a regulator of endothelial dysfunction and its blood level is decreased in CKD patients. In order to obtain a better understanding of the physiopathology of the disease, we correlated the levels of miR-126 with several markers of endothelial dysfunction, as well as the representative uremic toxins, in a large cohort of CKD patients at all stages of the disease. Using a univariate analysis, we found a correlation between eGFR and most markers of endothelial dysfunction markers evaluated in this study. An association of miR-126 with all the evaluated uremic toxins was also found, while uremic toxins were not associated with the internal control, specifically cel-miR-39. The correlation between the expression of endothelial dysfunction biomarker Syndecan-1, free indoxyl sulfate, and total p-cresyl glucuronide on one side, and miR-126 on the other side was confirmed using multivariate analysis. As CKD is associated with reduced endothelial glycocalyx (eGC), our results justify further evaluation of the role of correlated parameters in the pathophysiology of CKD.

Endothelial Activation, Acute Kidney Injury, and Cognitive Impairment in Pediatric Severe Malaria

OBJECTIVES

Evaluate the relationship between endothelial activation, malaria complications, and long-term cognitive outcomes in severe malaria survivors.

DESIGN

Prospectively cohort study of children with cerebral malaria, severe malarial anemia, or community children.

SETTING

Mulago National Referral Hospital in Kampala, Uganda.

SUBJECTS

Children 18 months to 12 years old with severe malaria (cerebral malaria, n = 253 or severe malarial anemia, n = 211) or community children (n = 206) were followed for 24 months.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Children underwent neurocognitive evaluation at enrollment (community children) or a week following hospital discharge (severe malaria) and 6, 12, and 24 months follow-up. Endothelial activation was assessed at admission on plasma samples (von Willebrand factor, angiopoietin-1 and angiopoietin-2, soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1, soluble E-Selectin, and P-Selectin). False discovery rate was used to adjust for multiple comparisons. Severe malaria was associated with widespread endothelial activation compared with community children (p < 0.0001 for all markers). Acute kidney injury was independently associated with changes in von Willebrand factor, soluble intercellular adhesion molecule-1, soluble E-Selectin, P-Selectin, and angiopoietin-2 (p < 0.0001 for all). A log10 increase in angiopoietin-2 was associated with lower cognitive z scores across age groups (children < 5, β -0.42, 95% CI, -0.69 to -0.15, p = 0.002; children ≥ 5, β -0.39, 95% CI, -0.67 to -0.11, p = 0.007) independent of disease severity (coma, number of seizures, acute kidney injury) and sociodemographic factors. Angiopoietin-2 was associated with hemolysis (lactate dehydrogenase, total bilirubin) and inflammation (tumor necrosis factor-α, interleukin-10). In children with cerebral malaria who had a lumbar puncture performed, angiopoietin-2 was associated with blood-brain barrier dysfunction, and markers of neuroinflammation and injury in the cerebrospinal fluid (tumor necrosis factor-α, kynurenic acid, tau).

CONCLUSIONS

These data support angiopoietin-2 as a measure of disease severity and a risk factor for long-term cognitive injury in children with severe malaria.

Circulating angiopoietin-2 and angiogenic microRNAs associate with cerebral small vessel disease and cognitive decline in older patients reaching end stage renal disease

BACKGROUND

The prevalence of end-stage renal disease (ESRD) is increasing worldwide, with the majority of new ESRD cases diagnosed in patients aged >60 years. These older patients are at increased risk for impaired cognitive functioning, potentially through cerebral small vessel disease (SVD). Novel markers of vascular integrity may be of clinical value for identifying patients at high risk for cognitive impairment.

METHODS

We aimed to associate the levels of Angiopoietin-2 (Ang-2), asymmetric dimethylarginine (ADMA), and a selection of eight circulating angiogenic miRNAs with SVD and cognitive impairment in older patients reaching ESRD that did not initiate renal replacement therapy yet (n = 129; mean age 75.3 years; mean eGFR 16.4 mL/min). We assessed brain MRI changes of SVD (white matter hyperintensity volume, microbleeds and presence of lacunes) and measures of cognition in domains of memory, psychomotor speed and executive function, comprised in a neuropsychological test battery.

RESULTS

Older patients reaching ESRD showed an unfavorable angiogenic profile, as indicated by aberrant levels of Ang-2 and five angiogenic miRNAs (miR-27a, miR-126, miR-132, miR-223, miR-326), compared to healthy persons and patients with diabetic nephropathy. Moreover, Ang-2 associated with SVD and with the domains of psychomotor speed and executive function, while miR-223 and miR-29a associated with memory function.

CONCLUSIONS

Taken together, these novel angiogenic markers might serve to identify older patients with ESRD at risk of cognitive decline, as well as give insight into the underlying (vascular) pathophysiology.

Higher serum angiopoietin 2 levels are independently associated with coronary microvascular dysfunction in patients with angina in the absence of obstructive coronary artery disease

Background

Angiopoietin-2 (Ang-2) is a type of endothelial growth factor involved in angiogenesis and vascular remodeling. Circulating Ang-2 levels are elevated in patients with obstructive coronary artery disease (CAD). This study aimed to evaluate the association between serum Ang-2 levels and coronary microvascular dysfunction in patients without obstructive CAD.

Methods

A total of 125 patients with angina in the absence of obstructive CAD were included in this cross-sectional study. Coronary flow reserve (CFR) was measured in the distal left anterior descending coronary artery by trans-thoracic Doppler echocardiography. The patients were divided into the following two sub-groups according to CFR: the impaired CFR group with CFR values <2.5 and the preserved CFR group with CFR values ≥2.5. Serum Ang-2 levels were determined using enzyme-linked immunosorbent assay. Independent predictors for impaired CFR were identified by binary logistic regression analysis. The receiver-operating characteristic curve was determined to evaluate the ability of serum Ang-2 in predicting impaired CFR.

Results

We found that age, percentage of female sex, N-terminal pro-B-type natriuretic peptide levels, Ang-2 levels (763.3 ± 264.9 vs. 579.7 ± 169.3 pg/mL, P < 0.001), and the left atrial volume index were significantly higher in patients with impaired CFR than in patients with preserved CFR. Serum Ang-2 levels were negatively correlated with CFR (r = −0.386, P < 0.001). Binary logistic regression analysis showed that Ang-2 (odds ratio: 1.004, 95% confidence interval [CI]: 1.001–1.006, P = 0.003) and age (odds ratio: 1.088, 95% CI: 1.023–1.156, P = 0.007) were independently associated with impaired CFR. Furthermore, Ang-2 was a significant predictor of impaired CFR on the receiver-operating characteristic curve (P < 0.001). The area under the curve was 0.712 (95% CI: 0.612–0.813).

Conclusions

High serum Ang-2 levels are independently associated with impaired CFR in patients with angina in the absence of obstructive CAD.

Endothelial Damage, Inflammation and Immunity in Chronic Kidney Disease

Chronic kidney disease (CKD) patients have an accelerated atherosclerosis, increased risk of thrombotic-ischemic complications, and excessive mortality rates when compared with the general population. There is also evidence of an endothelial damage in which the proinflammatory state, the enhanced oxidative stress, or the accumulation of toxins due to their reduced renal clearance in uremia play a role. Further, there is evidence that uremic endothelial cells are both involved in and victims of the activation of the innate immunity. Uremic endothelial cells produce danger associated molecular patterns (DAMPS), which by binding to specific pattern recognition receptors expressed in multiple cells, including endothelial cells, induce the expression of adhesion molecules, the production of proinflammatory cytokines and an enhanced production of reactive oxygen species in endothelial cells, which constitute a link between immunity and inflammation. The connection between endothelial damage, inflammation and defective immunity in uremia will be reviewed here.

Association between serum angiopoietin-2 concentrations and periprocedural myocardial injury in patients undergoing elective percutaneous coronary intervention

Angiopoietin-2 (Ang-2) is a proangiogenic factor that mediates inflammation and atherosclerosis. We evaluated the predictive value of circulating Ang-2 levels for periprocedural myocardial injury (PMI) in 145 patients undergoing elective percutaneous coronary intervention (PCI), and investigated whether post-PCI Ang-2 levels are influenced by PMI. PMI was defined as a post-procedural troponin elevation above the 5×99^th percentile upper reference limit. Blood samples for Ang-2 analysis were collected at admission and on postoperative days 1 and 3. PMI occurred in 40 patients (28%). At baseline, there was no difference in Ang-2 levels between PMI and non-PMI patients (P=0.554). However, a significant interaction effect between PMI occurrence and time on Ang-2 levels was observed (interaction P=0.036). Although serum Ang-2 levels in non-PMI patients gradually decreased, Ang-2 levels in PMI patients did not change between different time-points. Multiple logistic regression analysis revealed that age, total stent length, and serum levels of N-terminal pro-brain natriuretic peptide were independent PMI predictors. These findings indicate that pre-procedural Ang-2 levels do not impact PMI occurrence after elective PCI. However, changes in Ang-2 levels after the procedure are closely related to PMI.

Angiopoietin-2 as a Marker of Retinopathy in Children and Adolescents With Sickle Cell Disease: Relation to Subclinical Atherosclerosis

OBJECTIVES

Angiopoietin-2 (Ang-2) is a multifaceted cytokine that functions in both angiogenesis and inflammation. A proangiogenic state has been found in adults with sickle cell disease (SCD), mainly because of elevated Ang-2 levels. We determined Ang-2 level in 40 children and adolescents with SCD compared with 40 healthy controls and assessed its relation to retinopathy as well as carotid intimamedia thickness (CIMT).

METHODS

Hematologic profile, serum ferritin, and serum Ang-2 were measured. CIMT was assessed using high-resolution ultrasound. Fundus examination was performed followed by fundus fluorescein angiography. Optical coherence tomography angiography (OCTA) was used to find small vascular changes not clinically manifested.

RESULTS

Ang-2 levels and CIMT were significantly higher in SCD patients compared with controls. The incidence of nonproliferative retinopathy was 45%. SCD patients with retinopathy were older in age with a history of sickling crisis of >3 attacks per year and had a higher incidence of sickle cell anemia than sickle β-thalassemia. Ang-2 cutoff value 9000 pg/mL could significantly detect the presence of retinopathy among SCD patients with 100% sensitivity and specificity. Serum Ang-2 levels were positively correlated with HbS and CIMT. Logistic regression analysis revealed that Ang-2 and HbS significantly contribute to retinopathy among patients with SCD.

CONCLUSIONS

Elevated Ang-2 highlights the role of angiogenesis in the pathophysiology of SCD and may be considered a promising marker for screening of patients at risk of sickle retinopathy and vascular dysfunction.

Targeting VE-PTP phosphatase protects the kidney from diabetic injury

Diabetic nephropathy is a leading cause of kidney failure. VE-PTP phosphatase expression is increased in the endothelium of rodents with diabetes and hypertension. Genetic deletion of VE-PTP reduces kidney injury in diabetic mice, suggesting it may be a therapeutic target.

Diabetic nephropathy is a leading cause of end-stage kidney failure. Reduced angiopoietin-TIE2 receptor tyrosine kinase signaling in the vasculature leads to increased vascular permeability, inflammation, and endothelial cell loss and is associated with the development of diabetic complications. Here, we identified a mechanism to explain how TIE2 signaling is attenuated in diabetic animals. Expression of vascular endothelial protein tyrosine phosphatase VE-PTP (also known as PTPRB), which dephosphorylates TIE2, is robustly up-regulated in the renal microvasculature of diabetic rodents, thereby reducing TIE2 activity. Increased VE-PTP expression was dependent on hypoxia-inducible factor transcriptional activity in vivo. Genetic deletion of VE-PTP restored TIE2 activity independent of ligand availability and protected kidney structure and function in a mouse model of severe diabetic nephropathy. Mechanistically, inhibition of VE-PTP activated endothelial nitric oxide synthase and led to nuclear exclusion of the FOXO1 transcription factor, reducing expression of pro-inflammatory and pro-fibrotic gene targets. In sum, we identify inhibition of VE-PTP as a promising therapeutic target to protect the kidney from diabetic injury.

Study of Angiopoietin-2 and vascular endothelial growth factor as markers of diabetic nephropathy onset in Egyptians diabetic patients with non-albuminuric state

BACKGROUND

Vascular endothelial growth factor (VEGF) and angiopoietin (Ang-2) systems have a central role in vasculogenesis and neoangiogenesis during glomerular development. disruption, their levels are associated with alterations in the glomerular filtration barrier and proteinuria as in diabetic nephropathy. Aim of this study to assess the validity of blood Ang-2 and VEGF as biomarkers for early detection of diabetic nephropathy as well as to study the relation between them and inflammation in diabetic nephropathy patients.

SUBJECTS AND METHODS

Cross-sectional study included 180 diabetic nephropathy patients. Patients were classified to non-albuminuric, microalbuminuria and macroalbuminuria patients. Patients with macroalbuminuria complicated to renal impairment and ESRD on top of diabetic nephropathy. Ang-2 and VEGF were measured beside urinary albumin creatinine ratio (UACR).

RESULTS

Significant increase of Ang-2 and VEGF levels among patients with normoalbuminuric state compared to control but there is no significant difference of UACR between both groups. Ang-2 and VEGF concentrations were significantly higher in patients with microalbuminuria and macroalbuminuria compared to healthy. Ang-2 and VEGF levels increase with the progression of albuminuria. There were significant positive correlation between CRP and Ang-2 in addition to VEGF. Significant negative correlation between eGFR, Ang-2 and VEGF.

CONCLUSION

VEGF and Ang-2 were significantly elevated in diabetic nephropathy patients without albuminuria, their levels steadily increase with the progress of albuminuria, So can use them as markers for diagnosis of diabetic nephropathy onset and progression specially in patients without an increase in albumin excretion.

Serum angiopoietin-2 concentrations of post-PCI are correlated with the parameters of renal function in patients with coronary artery disease

Patients with coronary artery disease (CAD) frequently have comorbidity of chronic kidney disease (CKD). Their renal function may deteriorate because of the use of contrast agent after percutaneous coronary intervention (PCI). Angiopoietin-2 (Ang-2), which is highly expressed in the site of angiogenesis, plays an important role in both CAD and CKD. This study aimed to investigate the relation of serum Ang-2 concentrations with the renal function after PCI.This study enrolled 57 patients with CAD undergoing PCI. Blood samples for Ang-2 were collected in the first morning after admission and within 24 to 48 h after PCI. The parameters of renal function (serum creatinine, cystatin C and eGFR) were tested on the first day after admission and within 72 h after PCI.Overall, serum Ang-2 levels of post-PCI were significantly lower than those of pre-PCI [median, 1733 (IQR, 1100-2568) vs median, 2523 (IQR, 1702-3640) pg/mL; P < .001]. However, in patients with CKD (eGFR < 60 mL/min/1.73 m), there was no significant difference between serum Ang-2 levels of post-PCI and those of pre-PCI [median, 2851 (IQR, 1720-4286) vs. median, 2492 (IQR, 1434-4994) pg/mL; P = .925]. In addition, serum Ang-2 levels of post-PCI, but not pre-PCI, were significantly correlated with the post-PCI parameters of renal function.Serum Ang-2 concentrations of post-PCI are closely related to renal function in patients with CAD. It may have potential to be the early biomarker of contrast-induced nephropathy in the future.

Proteomic analysis of heart failure hospitalization among patients with chronic kidney disease: The Heart and Soul Study

Background

Patients with chronic kidney disease (CKD) are at increased risk for heart failure (HF). We aimed to investigate differences in proteins associated with HF hospitalizations among patients with and without CKD in the Heart and Soul Study.

Methods and results

We measured 1068 unique plasma proteins from baseline samples of 974 participants in The Heart and Soul Study who were followed for HF hospitalization over a median of 7 years. We sequentially applied forest regression and Cox survival analyses to select prognostic proteins. Among participants with CKD, four proteins were associated with HF at Bonferroni-level significance (p<2.5x10^-4): Angiopoietin-2 (HR[95%CI] 1.45[1.33, 1.59]), Spondin-1 (HR[95%CI] 1.13 [1.06, 1.20]), tartrate-resistant acid phosphatase type 5 (HR[95%CI] 0.65[0.53, 0.78]) and neurogenis locus notch homolog protein 1 (NOTCH1) (HR[95%CI] 0.67[0.55, 0.80]). These associations persisted at p<0.01 after adjustment for age, estimated glomerular filtration and history of HF. CKD was a significant interaction term in the associations of NOTCH1 and Spondin-1 with HF. Pathway analysis showed a trend for higher representation of the Cardiac Hypertrophy and Complement/Coagulation pathways among proteins prognostic of HF in the CKD sub-group.

Conclusions

These results suggest that markers of heart failure differ between patients with and without CKD. Further research is needed to validate novel markers in cohorts of patients with CKD and adjudicated HF events.

Association of serum angiopoietin-2 with malnutrition, inflammation, atherosclerosis and valvular calcification syndrome and outcome in peritoneal dialysis patients: a prospective cohort study

Background

To examine serum angiopoietin-2 (Angpt-2) in relation to malnutrition, inflammation, atherosclerosis and cardiac valvular calcification, so-called MIAC syndrome and its predictive role in outcomes of peritoneal dialysis (PD) patients.

Methods

A prospective observational study was conducted in 324 chronic PD patients. Biochemical analysis was performed at baseline for serum angiopoietins, albumin and high sensitive C-reactive protein (hs-CRP) and echocardiography was done to detect cardiac valvular calcification. Primary study end points were fatal or nonfatal cardiovascular events and mortality.

Results

The median of serum Angpt-2 levels was 5.44 ng/mL (interquartile range, 3.41–7.85). Across the three tertiles of serum Angpt-2, a significant trend effect was observed for body mass index, normalized protein catabolic rate, calcium × phosphorus product, hs-CRP, brain natriuretic peptide, lower-density lipoprotein cholesterol, left ventricular ejection fraction, total weekly urea clearance and residual renal function (all p < 0.05). Serum Angpt-2 showed a significant increase across the four groups of patients with increasing components of MIAC syndrome (p < 0.001). There were 77 deaths and 57 cardiovascular events. High serum Angpt-2 was an independent predictor of fatal and nonfatal cardiovascular events in PD patients (p = 0.02), however serum Angpt-2 was not an independent predictor of all-cause mortality (p = 0.3).

Conclusions

Serum Angpt-2 showed close association with valvular calcification, atherosclerosis, inflammation and malnutrition, having significant independent prognostic value and is useful for cardiovascular event stratification in chronic PD patients. Angpt-2 might be a potential mediator of increased cardiovascular risk in patients undergoing PD treatment.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1687-0) contains supplementary material, which is available to authorized users.

Non-neutralizing antibodies increase endogenous circulating Ang1 levels

Ang1 is a soluble ligand to receptor Tie2, and increasing the circulating Ang1 level may improve vascular stabilization under certain disease conditions. Here, we found that the circulating Ang1 level was significantly increased in cynomolgus monkeys treated with non-neutralizing anti-Ang1 antibodies. Improving the antibodies’ pharmacokinetic properties by IgG Fc mutations further increased the circulating Ang1 level. However, the mutations decreased the thermal stability of the molecules, which may limit their use as therapeutic antibodies. Nevertheless, we showed that non-neutralizing antibodies may have therapeutic potential by increasing the level of a target molecule in the circulation.

Angiopoietin-2: A Potential Mediator of the Glycocalyx Injury in Adult Nephrotic Patients

Introduction: Glomerulopathy is a group of diseases that affect mainly young adults between the ages of 20 and 40 years. Recently, it has been demonstrated that syndecan-1, a biomarker of endothelial glycocalyx damage, is increased in nephrotic patients with near-normal renal function and it is important to endothelial dysfunction in these patients. Angiopoietin-2 (AGPT2) is an endothelial growth factor that promotes cell derangement. Here we evaluated AGPT2 levels in patients with nephrotic syndrome, near-normal renal function and the possible interaction of AGPT2 with endothelial glycocalyx derangement. Methods: This was a cross-sectional study performed from January through November 2017. Adult patients (age > 18 years) with nephrotic syndrome and without immunosuppression were included. Blood samples were drawn after a 12 h fast for later measurement of syndecan-1 and AGPT2. Mediation analyses were performed to assess the hypothesized associations of nephrotic syndrome features and AGPT2 with syndecan-1. Results: We included 65 patients, 37 (56.9%) of them female, with primary glomerular disease. Syndecan-1 in nephrotic patients was higher than in control individuals (102.8 ± 36.2 vs. 28.2 ± 9.8 ng/mL, p < 0.001). Correlation of syndecan-1 with the main features of nephrotic syndrome after adjustment for age and estmmated glomerular filtration rate (eGFR) demonstrated that syndecan-1 was significantly associated with 24-h urinary protein excretion, total cholesterol, LDL (low density lipoprotein)-cholesterol, HDL (high-density lipoprotein)-cholesterol, and triglycerides. Angiopoietin-2 was independently associated with serum albumin, 24 h urinary protein excretion, total cholesterol, and LDL-cholesterol, in addition to being strongly associated with syndecan-1 (0.461, p < 0.001). The results of the mediation analyses showed that the direct association between LDL-cholesterol and syndecan-1 was no longer significant after AGPT-2 was included in the mediation analysis. AGPT2 explained 56% of the total observed association between LDL-cholesterol and syndecan-1. Conclusion: The association between LDL-cholesterol and glycocalyx derangement in nephrotic patients is possibly mediated by AGPT2.

Biomarker Profiling in Stage 5 Chronic Kidney Disease Identifies the Relationship between Angiopoietin-2 and Atrial Fibrillation

Atrial fibrillation (AF) is prevalent in nearly 27% of patients with stage 5 chronic kidney disease on hemodialysis (CKD5-HD), suggesting a strong association between these 2 pathologies. It is hypothesized that the relationship between these 2 diseases may be mediated by inflammation. Angiopoietin-2 (Ang-2), a pro-inflammatory biomarker of endothelial instability, inflammation, and vascular remodeling, is elevated in CKD5-HD and AF, yet has not been evaluated in patients with concomitant AF and CKD5-HD. The aim of this study is to analyze circulating levels of inflammatory and thrombotic biomarkers in patients with concomitant AF and CKD5-HD. Plasma levels of Ang-2 were measured via sandwich enzyme-linked immunosorbent assay method in CKD5-HD patients (n = 96), patients with AF (n = 38), and controls (n = 50). Angiopoietin-2 was markedly elevated in CKD5-HD with comorbid AF as compared to CKD5-HD alone, and AF alone, respectively (13.05 ± 1.56 vs 9.57 ± 0.71 ng/mL; P = .00169; vs 2.48 ± 0.57 ng/mL; P < .0001). The results of this study suggest an additive effect of Ang-2 with coexistence of AF and CKD5-HD, which may be useful in the detection of AF within this patient population.

The association of serum angiogenic growth factors with renal structure and function in patients with adult autosomal dominant polycystic kidney disease

PURPOSE

Autosomal dominant polycystic kidney disease (ADPKD) is a common congenital chronic kidney disease (CKD). We report here the relationship of serum angiopoietin-1 (Ang-1), Ang-2, and vascular endothelial growth factor (VEGF) with total kidney volume (TKV), total cyst volume (TCV), and renal failure in adult ADPKD patients at various stages of CKD.

METHODS

This cross-sectional study was conducted with 50 patients diagnosed with ADPKD and a control group of 45 age-matched healthy volunteers. In patient group, TKV and TCV were determined with upper abdominal magnetic resonance imaging, whereas in controls, TKV was determined with ultrasonography according to ellipsoid formula. Renal function was assessed with serum creatinine, estimated glomerular filtration rate (eGFR), and spot urinary protein/creatinine ratio (UPCR). Ang-1, Ang-2, and VEGF were measured using enzyme-linked immunosorbent assay.

RESULTS

Patients with ADPKD had significantly higher TKV (p < 0.001) and UPCR (p < 0.001), and lower eGFR (p ≤ 0.001) compared to the controls. Log₁₀Ang-2 was found to be higher in ADPKD patients at all CKD stages. Multiple linear regression analysis showed that there was no association between log₁₀Ang-1, log₁₀Ang-2, or log₁₀VEGF and creatinine, eGFR, UPCR, log₁₀TKV (p > 0.05).

CONCLUSION

There was no association of serum angiogenic growth factors with TKV or renal failure in ADPKD patients. Increased serum Ang-2 observed in stages 1-2 CKD suggests that angiogenesis plays a role in the progression of early stage ADPKD, but not at later stages of the disease. This may be explained by possible cessation of angiogenesis in advanced stages of CKD due to the increased number of sclerotic glomeruli.

Angiopoietin-1 deficiency increases renal capillary rarefaction and tubulointerstitial fibrosis in mice

Presence of tubulointerstitial fibrosis is predictive of progressive decline in kidney function, independent of its underlying cause. Injury to the renal microvasculature is a major factor in the progression of fibrosis and identification of factors that regulate endothelium in fibrosis is desirable as they might be candidate targets for treatment of kidney diseases. The current study investigates how loss of Angipoietin-1 (Angpt1), a ligand for endothelial tyrosine-kinase receptor Tek (also called Tie2), affects tubulointerstitial fibrosis and renal microvasculature. Inducible Angpt1 knockout mice were subjected to unilateral ureteral obstruction (UUO) to induce fibrosis, and kidneys were collected at different time points up to 10 days after obstruction. Staining for aSMA showed that Angpt1 deficient kidneys had significantly more fibrosis compared to wildtype mice 3, 6, and 10 days after UUO. Further investigation 3 days after UUO showed a significant increase of Col1a1 and vimentin in Angpt1 deficient mice, as well as increased gene expression of Tgfb1, Col1a1, Fn1, and CD44. Kidney injury molecule 1 (Kim1/Havcr1) was significantly more increased in Angpt1 deficient mice 1 and 3 days after UUO, suggesting a more severe injury early in the fibrotic process in Angpt1 deficient mice. Staining for endomucin showed that capillary rarefaction was evident 3 days after UUO and Angpt1 deficient mice had significantly less capillaries 6 and 10 days after UUO compared to UUO kidneys in wildtype mice. RNA sequencing revealed downregulation of several markers for endothelial cells 3 days after UUO, and that Angpt1 deficient mice had a further downregulation of Emcn, Plvap, Pecam1, Erg, and Tek. Our results suggest that loss of Angpt1 is central in capillary rarefaction and fibrogenesis and propose that manipulations to maintain Angpt1 levels may slow down fibrosis progression.

Friends Turned Foes: Angiogenic Growth Factors beyond Angiogenesis

Angiogenesis, the formation of new blood vessels from pre-existing ones is a biological process that ensures an adequate blood flow is maintained to provide the cells with a sufficient supply of nutrients and oxygen within the body. Numerous soluble growth factors and inhibitors, cytokines, proteases as well as extracellular matrix proteins and adhesion molecules stringently regulate the multi-factorial process of angiogenesis. The properties and interactions of key angiogenic molecules such as vascular endothelial growth factors (VEGFs), fibroblast growth factors (FGFs) and angiopoietins have been investigated in great detail with respect to their molecular impact on angiogenesis. Since the discovery of angiogenic growth factors, much research has been focused on their biological actions and their potential use as therapeutic targets for angiogenic or anti-angiogenic strategies in a context-dependent manner depending on the pathologies. It is generally accepted that these factors play an indispensable role in angiogenesis. However, it is becoming increasingly evident that this is not their only role and it is likely that the angiogenic factors have important functions in a wider range of biological and pathological processes. The additional roles played by these molecules in numerous pathologies and biological processes beyond angiogenesis are discussed in this review.

High Circulating Levels of ANGPTL2: Beyond a Clinical Marker of Systemic Inflammation

Angiopoietin-like 2 (ANGPTL2) is a proinflammatory protein belonging to the angiopoietin-like family. ANGPTL2 is secreted and detected in the systemic circulation. Different observational clinical studies reported that circulating levels of ANGPTL2 increase significantly in various chronic inflammatory diseases and showed associations between ANGPTL2 levels and diagnosis and/or prognosis of cardiovascular diseases, diabetes, chronic kidney disease, and various types of cancers. However, these studies did not address the following questions: (a) what are the sources of circulating ANGPTL2? (b) How and by which mechanisms an increase in circulating ANGPTL2 contributes to the pathogenesis of chronic inflammatory diseases? (c) Does an increase in circulating levels of ANGPTL2 measured in a well-defined chronic medical condition originate from a specific cell type? Mechanistic hypotheses have been proposed based on studies performed in mice and cultured cells, and proinflammatory, prooxidative, proangiogenic, proliferative, and antiapoptotic properties of ANGPTL2 have been reported. The aim of this review is to propose answers concerning the potential sources of circulating ANGPTL2 and its common pathological properties associated with various chronic inflammatory diseases and death in humans. We believe that high circulating ANGPTL2 levels are more than an inflammatory marker and may reflect the senescent cellular load of an individual.

Levels of Angiopoietin-Like-2 Are Positively Associated With Aortic Stiffness and Mortality After Kidney Transplantation

BACKGROUND

Angiopoietin-like-2 (ANGPTL2) is a secreted proinflammatory glycoprotein that promotes endothelial dysfunction, atherosclerosis, and cardiovascular disease (CVD). Circulating ANGPTL2 is increased in chronic kidney disease (CKD), where the risk of CVD is amplified. The objectives of the present study were to (i) examine whether kidney transplantation (KTx) reduces ANGPTL2 levels, (ii) identify the determinants of ANGPTL2 after KTx, (iii) study the association of ANGPTL2 with aortic stiffness, and (iv) assess the impact of ANGPTL2 on mortality after KTx.

METHODS

In 75 patients, serum ANGPTL2 levels were measured at baseline and 3 months after KTx. Aortic stiffness was determined by carotid-femoral pulse wave velocity, glomerular filtration rate was estimated by CKD-EPI formula, and serum cytokines and endothlin-1 levels were determined 3 months after KTx. Survival analysis was performed using Kaplan-Meier and Cox regression after a median follow-up of 90 months.

RESULTS

After 3 months of KTx, ANGPTL2 levels decreased from 71 ng/ml (53-95) to 11 ng/ml (9-15) (P < 0.001). In multivariate analysis, age, lower renal function, and endothelin-1 were independently associated with higher post-KTx ANGPTL2 levels. ANGPTL2 was positively associated with aortic stiffness after KTx, even when adjusted for mean blood pressure (standardized β = 0.314; P = 0.008). During follow-up, 13 deaths occurred. The group of patients with higher post-KTx ANGPTL2 levels had a hazard ratio for mortality of 3.9 (95% confidence interval: 1.07-14.4; P = 0.039).

CONCLUSION

KTx significantly reduced serum ANGPTL2 levels. The positive association between post-KTx ANGPTL2, aortic stiffness and mortality, suggests that ANGPTL2 may play a biological role in CKD-related CVD.

Angiopoietin-2, Angiopoietin-1 and subclinical cardiovascular disease in Chronic Kidney Disease

Angiopoietins (Angpt) and vascular endothelial growth factor (VEGF) have been associated with cardiovascular disease. The study enrolled 270 pre-dialysis stage 3–5 CKD patients to assess the link between circulating Angpt2, Angpt1 and VEGF-A and subclinical measures of cardiovascular structure and function. Serum markers of angiogenesis were measured using commercial enzyme-linked immunosorbent assays. Cardiac structure and function were examined by echocardiography. Brachial-ankle pulse wave velocity (baPWV) was measured by the ankle-brachial index. The adjusted mean of left ventricular mass index (LVMI) was 2.05 in patients of Angpt2 quartile 4 and 1.99 in those of Angpt2 quartile 1 (P = 0.04). Angpt2 was significantly associated with LV hypertrophy (LVH) (Angpt2 quartile 4 compared with Angpt2 quartile 1: adjusted OR: 2.68, 95% CI: 1.15–6.20). Angpt1 was negatively correlated with left atrial diameter (adjusted mean of LAD: 3.59 in Angpt1 quartile 4, 3.92 in Angpt1 quartile 1, P = 0.03). A positive and significant correlation was found between Angpt2 level and baPWV in spearman’s correlation, but not in adjusted model. In conclusion, high Angpt2 and low Angpt1 levels were positively associated with abnormal cardiac structure in stages 3–5 CKD patients, which is compatible with the viewpoint that angiopoietins participates in cardiovascular burdens.

Circulating Angiopoietin-2 and Its Soluble Receptor Tie-2 Concentrations Are Related to Renal Function in Two Population-Based Cohorts

Background

An intact angiopoietin/Tie-2 ligand receptor system is indispensable for life. High circulating angiopoietin-2 (Ang-2) concentrations are strongly associated with kidney disease involving the progressive loss of glomerular filtration. The aim of our study was to investigate the associations between renal function and serum Ang-2 or serum Tie-2 concentrations in the general population.

Methods

Data of 3081 and 4088 subjects from two population-based studies, the Study of Health in Pomerania (SHIP-1) and SHIP-Trend, were used. Renal function was assessed by serum creatinine, cystatin C concentration, creatinine-based estimated glomerular filtration rate [eGFR(crea)], cystatin C-based eGFR [eGFR(cys)] and urinary albumin-to-creatinine ratio (uACR). Analyses of variance and linear regression models were calculated.

Results

In both cohorts, strong positive associations between serum cystatin C concentrations and serum Ang-2 or Tie-2 concentrations as well as inverse associations between eGFR(cys) and serum Ang-2 or Tie-2 concentrations were found. These relations were also present in a subpopulation without hypertension or diabetes mellitus type 2. Furthermore, we detected weak U-shaped associations between serum creatinine concentrations or eGFR(crea) and serum Ang-2 concentrations. With respect to uACR a strong positive association with serum Ang-2 concentrations was revealed.

Conclusion

Serum Ang-2 concentrations are strongly associated with sensitive parameters of renal impairment like serum cystatin C, uACR and eGFR(cys). These findings persisted even after exclusion of subjects with hypertension or diabetes mellitus type 2, conditions that predispose to chronic renal disease and are associated with increased Ang-2 concentrations. Interestingly, we did not detect the same strong relations between serum creatinine and eGFR(crea) with serum Ang-2 concentration. Additionally, significant association of serum Tie-2 concentrations with cystatin C and eGFR(cys) were detected.

Reduced Microvascular Density in Omental Biopsies of Children with Chronic Kidney Disease

BACKGROUND

Endothelial dysfunction is an early manifestation of cardiovascular disease (CVD) and consistently observed in patients with chronic kidney disease (CKD). We hypothesized that CKD is associated with systemic damage to the microcirculation, preceding macrovascular pathology. To assess the degree of "uremic microangiopathy", we have measured microvascular density in biopsies of the omentum of children with CKD.

PATIENTS AND METHODS

Omental tissue was collected from 32 healthy children (0-18 years) undergoing elective abdominal surgery and from 23 age-matched cases with stage 5 CKD at the time of catheter insertion for initiation of peritoneal dialysis. Biopsies were analyzed by independent observers using either a manual or an automated imaging system for the assessment of microvascular density. Quantitative immunohistochemistry was performed for markers of autophagy and apoptosis, and for the abundance of the angiogenesis-regulating proteins VEGF-A, VEGF-R2, Angpt1 and Angpt2.

RESULTS

Microvascular density was significantly reduced in uremic children compared to healthy controls, both by manual imaging with a digital microscope (median surface area 0.61% vs. 0.95%, p<0.0021 and by automated quantification (total microvascular surface area 0.89% vs. 1.17% p = 0.01). Density measured by manual imaging was significantly associated with age, height, weight and body surface area in CKD patients and healthy controls. In multivariate analysis, age and serum creatinine level were the only independent, significant predictors of microvascular density (r2 = 0.73). There was no immunohistochemical evidence for apoptosis or autophagy. Quantitative staining showed similar expression levels of the angiogenesis regulators VEGF-A, VEGF-receptor 2 and Angpt1 (p = 0.11), but Angpt2 was significantly lower in CKD children (p = 0.01).

CONCLUSIONS

Microvascular density is profoundly reduced in omental biopsies of children with stage 5 CKD and associated with diminished Angpt2 signaling. Microvascular rarefaction could be an early systemic manifestation of CKD-induced cardiovascular disease.

Circulating angiogenic factors in diabetes patients in a tertiary hospital in Ghana

Background

Impaired angiogenesis is amongst the underlining mechanisms of organ damage in diabetes and hypertensive patients. In diabetes and hypertensive patients without proteinuria and overt CVDs, we studied the levels of angiogenic growth factors, angiopoietin (Ang)-1, Ang-2 and vascular endothelial growth factor (VEGF), and the relationship between these angiogenic growth factors and renal function, measured as estimated glomerular filtration rate (eGFR).

Method

In a case control design, 107 type 2 diabetes (T2DM) patients and 93 non-diabetes controls were recruited into the study. Levels of plasma glucose, lipids, creatinine and angiogenic growth factors; Ang-1, Ang-2 and VEGF measured from fasting blood samples. Estimated glomerular filtration rate (eGFR) was computed using Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) algorithm and eGFR < 60 ml/min/1.73 m² was considered to be low. Multivariable logistic regression was used to assess the odds of change in angiogenic growth factors among patients with diabetes and hypertension, and patients with low eGFR, compared to those without these conditions.

Results

In a total of 200 participants with 49 % females and mean age of 54.1 ± 10.2 years, 22.7 % of T2DM patients and 13.3 % of non-diabetes participant had low eGFR. The levels of Ang-1 and Ang-2 were highest in hypertensive T2DM patients, followed by patients with either T2DM or hypertension alone, with the controls having the lowest levels. The odds of change in circulating Ang-2 levels increased in patients with both diabetes and hypertension [11.76 (7.97–16.63), p < 0.01] compared to patients with either diabetes [5.45 (3.31–9.71), p = 0.02] or hypertension [5.45 (3.31–9.71), p = 0.02] alone. Compared to those with normal eGFR, the odds of change in serum Ang-2 levels were increased in patients with low eGFR in both the crude [1.26 (1.08–2.110), p = 0.023] and adjusted [1.14 (1.03–2.34), p = 0.043] regression models.

Conclusion

In our study population, having diabetes and hypertension increased the levels of Ang-1 and Ang-2. Also, low eGFR status was associated with increased levels of Ang-2 after adjustment for other risk factors.

Circulating angiopoietin-2 levels in children and adolescents with type 1 diabetes mellitus: relation to carotid and aortic intima-media thickness

BACKGROUND

Angiopoietin-2 is a growth factor involved in the pathophysiology of vascular and inflammatory diseases such as arteriosclerosis. Carotid or aortic scans provide noninvasive screening tools for assessment of preclinical atherosclerosis in high-risk children.

AIM

We assessed serum angiopoietin-2 in children and adolescents with type 1 diabetes mellitus as a potential marker for vascular complications in relation to glycemic control, inflammation and vascular structure.

METHODS

Sixty patients with type 1 diabetes were divided into 2 groups according to the presence of micro-vascular complications and compared with 30 healthy controls. High-sensitivity C-reactive protein (hs-CRP), hemoglobin A1c (HbA1c), urinary albumin/creatinine ratio, serum angiopoietin-2, carotid and aortic intima-media thickness (CIMT and AIMT) were measured.

RESULTS

CIMT, AIMT and serum angiopoietin-2 levels were significantly increased in patients with and without micro-vascular complications compared with controls, and the highest levels were in patients with complications (p < 0.001). Angiopoietin-2 was higher in patients with microalbuminuria than normoalbuminuric group (p < 0.001). Fasting blood glucose, HbA1c, hs-CRP, CIMT and AIMT were independently related to angiopoietin-2 in multiple regression analysis. Disease duration, hyperglycemia, poor glycemic control, hypercholesterolemia, inflammation and angiopoietin-2 were independent factors contributing to atherosclerosis risk.

CONCLUSION

The relation between angiopoietin-2 and assessed parameters of vascular structure in type 1 diabetes reflects a state of endothelial injury and highlights the role of disturbed angiogenesis and vascular inflammation in the occurrence of diabetic complications.

Angiopoietin/Tie2 Dysbalance Is Associated with Acute Kidney Injury after Cardiac Surgery Assisted by Cardiopulmonary Bypass

INTRODUCTION

The pathophysiology of acute kidney injury (AKI) after cardiac surgery is not completely understood. Recent evidence suggests a pivotal role for the endothelium in AKI. In experimental models of AKI, the endothelial specific receptor Tie2 with its ligands Angiopoietin (Ang) 1 and Ang2 are deranged. This study investigates their status after cardiac surgery, and a possible relation between angiopoietins and AKI.

METHODS

From a cohort of 541 patients that underwent cardiac surgery, blood and urine was collected at 5 predefined time points. From this cohort we identified 21 patients who had at least 50% post-operative serum creatinine increase (AKI). We constructed a control group (n = 21) using propensity matching. Systemic levels of Ang1, Ang2, and sTie2 were measured in plasma and the AKI markers albumin, kidney injury molecule-1 (KIM-1) and N-acetyl-beta-D-glucosaminidase (NAG) were measured in the urine.

RESULTS

Ang2 plasma levels increased over time in AKI (from 4.2 to 11.6 ng/ml) and control patients (from 3.0 to 6.7 ng/ml). Ang2 levels increased 1.7-fold more in patients who developed AKI after cardiac surgery compared to matched control patients. Plasma levels of sTie2 decreased 1.6-fold and Ang1 decreased 3-fold over time in both groups, but were not different between AKI and controls (Ang1 P = 0.583 and sTie2 P = 0.679). Moreover, we found a positive correlation between plasma levels of Ang2 and urinary levels of NAG.

CONCLUSIONS

The endothelial Ang/Tie2 system is in dysbalance in patients that develop AKI after cardiac surgery compared to matched control patients.

Angiopoietin-2 as a Prognostic Biomarker of Major Adverse Cardiovascular Events and All-Cause Mortality in Chronic Kidney Disease

Background

Chronic kidney disease (CKD) patients have higher prevalence of major adverse cardiovascular events (MACE) and all-cause mortality. Endothelial damage and dysfunction have been regarded as early portents of MACE in CKD patients. Angiopoietin-2 (Ang-2) impairs endothelial function and promotes aberrant neovascularization. The aim of the study was to assess the relationship between circulating Ang-2 and MACE or all-cause mortality in a CKD cohort.

Methods

A total of 621 pre-dialysis stage 3–5 CKD patients were enrolled from January 2006 to December 2011 and were followed up till October 2014. Plasma Ang-2 was measured in duplicate using commercial enzyme-linked immunosorbent assays (ELISA). Clinical outcomes included MACE or all-cause mortality

Results

Of all patients, 122 (19.8%) reached MACE or all-cause mortality. Seventy-two had MACE, 79 died, and 29 had both MACE and all-cause mortality during the follow-up period of 41.5±28.3 months. Ang-2 quintile was divided at 1405.0, 1730.0, 2160.9, and 2829.9 pg/ml. The adjusted HR of MACE or all-cause mortality for every single higher log Ang-2 was 5.69 (95% CI: 2.00–16.20, P = 0.001). The adjusted HR of MACE or all-cause mortality was 2.48 (95% CI: 1.25–4.90) for patients of quintile 5 compared with those of quintile 1. A longitudinal association between MACE or all-cause mortality and stepwise increases in Ang-2 levels was found (P-trend = 0.008).

Conclusions

Ang-2 is an independent predictor of MACE or all-cause mortality in CKD patients. Additional study is necessary in order to explore the mechanism of the association of Ang-2 with adverse outcomes in patients with CKD.

Early systemic microvascular damage in pigs with atherogenic diabetes mellitus coincides with renal angiopoietin dysbalance

Background

Diabetes mellitus (DM) is associated with a range of microvascular complications including diabetic nephropathy (DN). Microvascular abnormalities in the kidneys are common histopathologic findings in DN, which represent one manifestation of ongoing systemic microvascular damage. Recently, sidestream dark-field (SDF) imaging has emerged as a noninvasive tool that enables one to visualize the microcirculation. In this study, we investigated whether changes in the systemic microvasculature induced by DM and an atherogenic diet correlated spatiotemporally with renal damage.

Methods

Atherosclerotic lesion development was triggered in streptozotocin-induced DM pigs (140 mg/kg body weight) by administering an atherogenic diet for approximately 11 months. Fifteen months following induction of DM, microvascular morphology was visualized in control pigs (n = 7), non-diabetic pigs fed an atherogenic diet (ATH, n = 5), and DM pigs fed an atherogenic diet (DM+ATH, n = 5) using SDF imaging of oral mucosal tissue. Subsequently, kidneys were harvested from anethesized pigs and the expression levels of well-established markers for microvascular integrity, such as Angiopoietin-1 (Angpt1) and Angiopoietin-2 (Angpt2) were determined immunohistochemically, while endothelial cell (EC) abundance was determined by immunostaining for von Willebrand factor (vWF).

Results

Our study revealed an increase in the capillary tortuosity index in DM+ATH pigs (2.31±0.17) as compared to the control groups (Controls 0.89±0.08 and ATH 1.55±0.11; p<0.05). Kidney biopsies showed marked glomerular lesions consisting of mesangial expansion and podocyte lesions. Furthermore, we observed a disturbed Angpt2/ Angpt1balance in the cortex of the kidney, as evidenced by increased expression of Angpt2 in DM+ATH pigs as compared to Control pigs (p<0.05).

Conclusion

In the setting of DM, atherogenesis leads to the augmentation of mucosal capillary tortuosity, indicative of systemic microvascular damage. Concomitantly, a dysbalance in renal angiopoietins was correlated with the development of diabetic nephropathy. As such, our studies strongly suggest that defects in the systemic microvasculature mirror the accumulation of microvascular damage in the kidney.

Plasma angiopoietin 2 concentrations are related to impaired lung function and organ failure in a clinical cohort receiving high-dose interleukin 2 therapy

INTRODUCTION

The pathophysiology and therapeutic options in sepsis-induced lung injury remain elusive. High-dose interleukin 2 therapy (HDIL-2) is an important protocol for advanced malignancies but is limited by systemic inflammation and pulmonary edema that is indistinguishable from sepsis. In preclinical models, IL-2 stimulates angiopoietin 2 (AngP-2) secretion, which increases endothelial permeability and causes pulmonary edema. However, these relationships have not been fully elucidated in humans. Furthermore, the relevance of plasma AngP-2 to organ function is not clear. We hypothesized that plasma AngP-2 concentrations increase during HDIL-2 and are relevant to clinical pathophysiology.

METHODS

We enrolled 13 subjects with metastatic melanoma or renal cell carcinoma admitted to receive HDIL-2 and collected blood and spirometry data daily. The plasma concentrations of AngP-2 and IL-6 were measured with enzyme-linked immunosorbent assay.

RESULTS

At baseline, the mean AngP-2 concentration was 2.5 (SD, 1.0) ng/mL. Angiopoietin 2 concentrations increased during treatment: the mean concentration on the penultimate day was 16.0 (SD, 4.5) ng/mL and increased further to 18.6 (SD, 4.9) ng/mL (P < 0.05 vs. penultimate) during the last day of therapy. The forced expiratory volume in 1 s decreased during treatment. Interestingly, plasma AngP-2 concentrations correlated negatively with forced expiratory volume in 1 s (Spearman r = -0.78, P < 0.0001). Plasma AngP-2 concentrations also correlated with plasma IL-6 concentrations (r = 0.61, P < 0.0001) and Sequential Organ Failure Assessment scores (r = 0.68, P < 0.0001).

CONCLUSIONS

Plasma AngP-2 concentrations increase during HDIL-2 administration and correlate with pulmonary dysfunction. High-dose IL-2 may serve as a clinical model of sepsis and acute lung injury. Further investigation is warranted.

Urinary angiopoietin-2 is associated with albuminuria in patients with type 2 diabetes mellitus

Aims. To evaluate the levels of angiopoietin-1 (Ang-1), Ang-2, and vascular endothelial growth factor (VEGF) in serum and urine, and their association with albuminuria in patients with type 2 diabetes mellitus. Methods. In 113 type 2 diabetic patients with normoalbuminuria, microalbuminuria, and macroalbuminuria and 30 healthy controls, the levels of Ang-1, Ang-2, and VEGF in serum and urine were measured by enzyme-linked immunosorbent assay (ELISA). Results. Urinary and serum levels of Ang-2 were significantly higher in diabetic patients with normoalbuminuria than in healthy controls. Increased urinary Ang-2 level was positively associated with the degree of albuminuria. Urinary Ang-1 levels were significantly higher in normoalbuminuria patients and lower in macroalbuminuria patients than in controls. The levels of urinary VEGF increased in the albuminuria subgroup, though serum levels of Ang-1 and VEGF did not change. Urinary Ang-2 levels were correlated positively with albuminuria and negatively with glomerular filtration rate (GFR). Stepwise multiple regression analysis identified albuminuria (P < 0.001) and GFR (P = 0.001) as significant predictors of urinary Ang-2. Conclusions. Our data suggest that urinary Ang-2 is stepwise increased with renal damage in patients with type 2 diabetes mellitus and is associated with albuminuria.

Markers of endothelial function in migraine patients: Results from a bi-center prospective study

Background

Numerous studies suggest an increased vascular risk in patients with migraine, in particular in those with aura. A possible link between both conditions might be a dysfunction of the vascular endothelium. This observational study analyzed the endothelial markers angiopoietin-1, angiopoietin-2, Tie-2, sFlt-1 and NT-proBNP for the first time in migraineurs, patients with other primary headache disorders and healthy controls.

Methods

Patients with episodic migraine with and without aura, episodic cluster headache, tension-type headache and healthy controls were included. Blood samples were obtained during migraine attacks and headache-free periods in migraineurs, in and out of bout in cluster headache and during headache-free periods in tension-type headache and healthy individuals to analyze markers of endothelial function.

Results

No significant difference in endothelial markers between migraine, other headache disorders and healthy controls was detected. There was no significant difference between migraine attacks and headache-free intervals. Additionally, no distinction could be found between migraine with and without aura.

Discussion

The endothelial markers analyzed do not display a characteristic pattern in different headache disorders especially migraine compared to healthy controls. The novel findings of our study indicate that factors other than endothelial dysfunction seem to be responsible for the at least statistical association of migraine with vascular disease.

Association of angiopoietin-2 with renal outcome in chronic kidney disease

Background

The pathophysiological mechanisms of renal function progression in chronic kidney disease (CKD) have still not been completely explored. In addition to well-known traditional risk factors, non-traditional risk factors, such as endothelial dysfunction, have gradually attracted physicians' attention. Angiopoietin-2 (Ang-2) impairs endothelial function through preventing angiopoietin-1 from binding to Tie2 receptor. Whether Ang-2 is associated with renal function progression in CKD is unknown.

Methods

This study enrolled 621 patients with stages 3–5 CKD to assess the association of circulating Ang-2 with commencing dialysis, doubling creatinine and rapid decline in renal function (the slope of estimated glomerular filtration rate (eGFR) greater than 5 ml/min per 1.73 m²/y) over follow-up of more than 3 years.

Results

Of all patients, 224 patients (36.1%) progressed to commencing dialysis and 165 (26.6%) reached doubling creatinine. 85 subjects (13.9%) had rapid decline in renal function. Ang-2 quartile was divided at 1494.1, 1948.8, and 2593.1 pg/ml. The adjusted HR of composite outcomes, either commencing dialysis or doubling creatinine was 1.53 (95% CI: 1.06–2.23) for subjects of quartile 4 compared with those of quartile 1. The adjusted OR for rapid decline in renal function was 2.96 (95% CI: 1.13–7.76) for subjects of quartile 4 compared with those of quartile 1. The linear mixed-effects model shows a more rapid decrease in eGFR over time in patients with quartile 3 or more of Ang-2 than those with the lowest quartile of Ang-2.

Conclusions

Ang-2 is an independent predictor of adverse renal outcome in CKD. Further study is needed to identify the pathogenic role of Ang-2 in CKD progression.

Increased concentration of circulating angiogenesis and nitric oxide inhibitors induces endothelial to mesenchymal transition and myocardial fibrosis in patients with chronic kidney disease

BACKGROUND

Sudden cardiovascular death is increased in chronic kidney disease (CKD). Experimental CKD models suggest that angiogenesis and nitric oxide (NO) inhibitors induce myocardial fibrosis and microvascular dropout thereby facilitating arrhythmogenesis. We undertook this study to characterize associations of CKD with human myocardial pathology, NO-related circulating angiogenesis inhibitors, and endothelial cell behavior.

METHODS

We compared heart (n=54) and serum (n=162) samples from individuals with and without CKD, and assessed effects of serum on human coronary artery endothelial cells (HCAECs) in vitro. Left ventricular fibrosis and capillary density were quantified in post-mortem samples. Endothelial to mesenchymal transition (EndMT) was assessed by immunostaining of post-mortem samples and RNA expression in heart tissue obtained during cardiac surgery. Circulating asymmetric dimethylarginine (ADMA), endostatin (END), angiopoietin-2 (ANG), and thrombospondin-2 (TSP) were measured, and the effect of these factors and of subject serum on proliferation, apoptosis, and EndMT of HCAEC was analyzed.

RESULTS

Cardiac fibrosis increased 12% and 77% in stage 3-4 CKD and ESRD and microvascular density decreased 12% and 16% vs. preserved renal function. EndMT-derived fibroblast proportion was 17% higher in stage 3-4 CKD and ESRD (P trend = 0.02). ADMA, ANG, TSP, and END concentrations increased in CKD. Both individual factors and CKD serum increased HCAEC apoptosis (P=0.02), decreased proliferation (P=0.03), and induced EndMT.

CONCLUSIONS

CKD is associated with an increase in circulating angiogenesis and NO inhibitors, which impact proliferation and apoptosis of cardiac endothelial cells and promote EndMT, leading to cardiac fibrosis and capillary rarefaction. These processes may play key roles in CKD-associated CV disease.

Circulating Angiopoietin-2 levels predict mortality in kidney transplant recipients: a 4-year prospective case-cohort study

Angiopoietin 2 (Angpt2) impairs endothelial function by preventing angiopoietin 1 from binding to their common endothelial-specific receptor Tie2. Here, we examined whether circulating Angpt2 predicts outcome in kidney transplant recipients. For this case-cohort study, we selected 130 kidney transplant recipients who had died or returned to dialysis within the first 2 years of follow-up of our cohort study, as well as 130 age- and gender-matched kidney transplant recipients without an event (controls) from a total of 993 kidney transplant recipients. The total of 260 selected patients were followed in median 4 years. Serum Angpt2 at baseline was measured using an in-house immunoluminometric assay. Median Angpt2 concentrations were significantly higher in patients who died [median (interquartile range--IQR) 3.6 (2.8-5.9) ng/ml] as compared to patients who did not die during the study period [2.8 (2.1-4.1) ng/ml; P < 0.001]. Ln (natural log) Angpt2 levels correlated positively with C-reactive protein levels (r = 0.315, P < 0.001) and the Charlson Comorbidity Index (r = 0.188, P = 0.002) and were inversely associated with eGFR (r = -0.301, P < 0.001) hemoglobin (r = -0.269, P < 0.001), and serum albumin concentrations (r = -0.382, P < 0.001). On multivariate analyses, baseline Angpt2 levels independently predicted all-cause mortality (multivariable-adjusted hazard ratio associated with one natural log unit higher Angpt2 level: 1.70 (95% confidence interval: 1.10-2.61)). In our analysis, circulating Angpt2 was an independent predictor of all-cause mortality in stable, prevalent kidney transplant recipients.

Angiopoietin-2-induced arterial stiffness in CKD

The mechanism of vascular calcification in CKD is not understood fully, but may involve collagen deposition in the arterial wall upon osteo/chondrocytic transformation of vascular smooth muscle cells (VSMCs). Increased levels of circulating angiopoietin-2 correlate with markers of CKD progression and angiopoietin-2 regulate inflammatory responses, including intercellular and vascular adhesion and recruitment of VSMCs. Here, we investigate the potential role of angiopoietin-2 in the pathogenesis of arterial stiffness associated with CKD. In a cohort of 416 patients with CKD, the plasma level of angiopoietin-2 correlated independently with the severity of arterial stiffness assessed by pulse wave velocity. In mice subjected to 5/6 subtotal nephrectomy or unilateral ureteral obstruction, plasma levels of angiopoietin-2 also increased. Angiopoietin-2 expression markedly increased in tubular epithelial cells of fibrotic kidneys but decreased in other tissues, including aorta and lung, after 5/6 subtotal nephrectomy. Expression of collagen and profibrotic genes in aortic VSMCs increased in mice after 5/6 subtotal nephrectomy and in mice producing human angiopoietin-2. Angiopoietin-2 stimulated endothelial expression of chemokines and adhesion molecules for monocytes, increased Ly6C(low) macrophages in aorta, and increased the expression of the profibrotic cytokine TGF-β1 in aortic endothelial cells and Ly6C(low) macrophages. Angiopoietin-2 blockade attenuated expression of monocyte chemokines, profibrotic cytokines, and collagen in aorta of mice after 5/6 subtotal nephrectomy. This study identifies angiopoietin-2 as a link between kidney fibrosis and arterial stiffness. Targeting angiopoietin-2 to attenuate inflammation and collagen expression may provide a novel therapy for cardiovascular disease in CKD.

Microvascular damage in type 1 diabetic patients is reversed in the first year after simultaneous pancreas-kidney transplantation

Simultaneous pancreas-kidney transplantation (SPK) is an advanced treatment option for type 1 diabetes mellitus (DM) patients with microvascular disease including nephropathy. Sidestreamdarkfield (SDF) imaging has emerged as a noninvasive tool to visualize the human microcirculation. This study assessed the effect of SPK in diabetic nephropathy (DN) patients on microvascular alterations using SDF and correlated this with markers for endothelial dysfunction. Microvascular morphology was visualized using SDF of the oral mucosa in DN (n = 26) and SPK patients (n = 38), healthy controls (n = 20), DM1 patients (n = 15, DM ≥ 40 mL/min) and DN patients with a kidney transplant (KTx, n = 15). Furthermore, 21 DN patients were studied longitudinally up to 12 months after SPK. Circulating levels of angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and soluble thrombomodulin (sTM) were measured using ELISA. Capillary tortuosity in the DN (1.83 ± 0.42) and DM ≥ 40 mL/min (1.55 ± 0.1) group was increased and showed reversal after SPK (1.31 ± 0.3, p < 0.001), but not after KTx (1.64 ± 0.1). sTM levels were increased in DN patients and reduced in SPK and KTx recipients (p < 0.05), while the Ang-2/Ang-1 ratio was normalized after SPK and not after KTx alone (from 0.16 ± 0.04 to 0.08 ± 0.02, p < 0.05). Interestingly, in the longitudinal study, reversal of capillary tortuosity and decrease in Ang-2/Ang-1 ratio and sTM was observed within 12 months after SPK. SPK is effective in reversing the systemic microvascular structural abnormalities in DN patients in the first year after transplantation.

Angiopoietin-2 is associated with albuminuria and microinflammation in chronic kidney disease

Although cardiovascular disease (CVD) is the leading cause of mortality in patients with chronic kidney disease (CKD), the pathophysiology is not thoroughly understood. Given that elevated albuminuria or circulating angiopoietin-2 associates with CVD and mortality in CKD patients, we were intrigued by the relationship between albuminuria and angiopoietin-2. A total of 416 patients with CKD stages 3 to 5 were stratified by urine albumin-creatinine ratio as normoalbuminuria (<30 mg/g), microalbuminuria (30–300 mg/g), or macroalbuminuria (>300 mg/g). The levels of plasma angiopoietin-2 and vascular endothelial growth factor (VEGF) increased, and soluble Tie-2 decreased in the subgroups of albuminuria; whereas angiopoietin-1 did not change. Linear regression showed a positive correlation between urine albumin-creatinine ratio (ACR) and plasma angiopoietin-2 (correlation coefficient r = 0.301, 95% confidence interval 0.211–0.386, P<0.0001), but not between ACR and VEGF or soluble Tie-2. Multivariate linear regression analysis showed that plasma angiopoietin-2 was independently associated with ACR (P = 0.025). Furthermore, plasma angiopoietin-2 was positively correlated with high sensitive C-reactive protein (r = 0.114, 95% confidence interval 0.018–0.208, P = 0.020). In conclusion, plasma angiopoietin-2 was associated with albuminuria and markers of systemic microinflammation in CKD patients. Although previous evidence has shown that angiopoietin-2 destabilizes vasculature and induces inflammation in different scenarios, further study will be required to delineate the role of angiopoietin-2 in albuminuria and microinflammation in CKD patients.

Circulating angiopoietin-2 is a marker for early cardiovascular disease in children on chronic dialysis

Cardiovascular disease (CVD) is increasingly recognised as a complication of childhood chronic kidney disease (CKD) even in the absence of diabetes and hypertension. We hypothesized that an alteration in angiopoietin-1 and -2, growth factors which regulate endothelial and vascular function could be involved. We report that the endothelial survival factor, angiopoietin-1 is low in children with pre-dialysis CKD whereas the pro-inflammatory angiopoietin-2 is elevated in children on dialysis. In dialysis patients, angiopoietin-2 positively correlated with time on dialysis, systolic blood pressure, and carotid artery intima media thickness. Elevated angiopoietin-2 levels in dialysis versus pre-dialysis CKD patients were also associated with an anti-angiogenic (high soluble VEGFR-1 and low VEGF-A) and pro-inflammatory (high urate, E-selectin, P-selectin and VCAM-1) milieu. Ang-2 was immunodetected in arterial biopsy samples whilst the expression of VEGF-A was significantly downregulated in dialysis patients. Serum urate correlated with angiopoietin-2 levels in dialysis patients and addition of uric acid was able to induce rapid release of angiopoietin-2 from cultured endothelial cells. Thus, angiopoietin-2 is a marker for cardiovascular disease in children on chronic dialysis and may act as an anti-angiogenic and pro-inflammatory effector in this context. The possibility that the release of angiopoietin-2 from endothelia is mediated by urate should be explored further.