Nina Hojs

Biomarkers of Renal Disease and Progression in Patients with Diabetes

Diabetes prevalence is increasing worldwide, mainly due to the increase in type 2 diabetes. Diabetic nephropathy occurs in up to 40% of people with type 1 or type 2 diabetes. It is important to identify patients at risk of diabetic nephropathy and those who will progress to end stage renal disease. In clinical practice, most commonly used markers of renal disease and progression are serum creatinine, estimated glomerular filtration rate and proteinuria or albuminuria. Unfortunately, they are all insensitive. This review summarizes the evidence regarding the prognostic value and benefits of targeting some novel risk markers for development of diabetic nephropathy and its progression. It is focused mainly on tubular biomarkers (neutrophil-gelatinase associated lipocalin, kidney injury molecule 1, liver-fatty acid-binding protein, N-acetyl-beta-d-glucosaminidase), markers of inflammation (pro-inflammatory cytokines, tumour necrosis factor-α and tumour necrosis factor-α receptors, adhesion molecules, chemokines) and markers of oxidative stress. Despite the promise of some of these new biomarkers, further large, multicenter prospective studies are still needed before they can be used in everyday clinical practice.

Albuminuria is Associated With Subendocardial Viability Ratio in Chronic Kidney Disease Patients.

Background/Aims: Albuminuria is a well-established marker of subclinical organ damage. Pulse-wave analysis (PWA) employs the technique of applanation tonometry to obtain a peripheral pulse pressure waveform, from which central hemodynamic data are derived by application of the transfer function. Using PWA we can measure the subendocardial viability ratio (SEVR) and ejection duration (ED). SEVR or the Buckberg index is a non-invasive estimate of myocardial workload, oxygen supply and perfusion and a measure of the ability of the arterial system to meet the heart`s energy requirements. ED is the duration of ventricular ejection. The objective of this study was to evaluate the relationship between albuminuria and PWA parameters in chronic kidney disease (CKD) patients. Methods: We studied 86 CKD patients aged 59.8±13.5 years, 56 (65.1%) were male. PWA analysis and 24-hour ambulatory blood pressure (24hABP) monitoring were performed. The following parameters were calculated: (1) aortic augmentation index with and without correction for a heart rate of 75 (Aix and AIx@ HR75), (2) SEVR, calculated as the ratio of the diastolic pressure time index and the systolic pressure time index, (3) ED, (4) estimated central aortic systolic and diastolic pressure and (5) central aortic pulse pressure calculated as the difference between estimated aortic systolic and diastolic BP. Blood samples and urine albumin-to-creatinine ratio (UACR) were analyzed; UACR values were natural log transformed (lnUACR). Results: Using CKD-EPI creatinine-cystatin C formula the eGFR in patients was 7-130 ml/min/1.73m2 (mean 32.6; SD±24.6). We found statistically significant correlation between lnUACR and cystatin C (r=0.308; P=0.004), eGFR (r=-0.219; P=0.04), hemoglobin (r=-0.255; P=0.02), phosphorus (r=0.222; P=0.04), iPTH (r=0.268; P=0.01), SEVR (r=-0.254; P=0.02) and ED (r=0.315; P=0.003). No statistically significant correlations between lnUACR and cardiac biomarkers TnI, NT-proBNP, central aortic BP and 24h ABP values were found. Using multiple regression analysis statistically significant association was found between SEVR as dependent variable and lnUACR (β=-0.223, P=0.039), sex (β=-0.216, P=0.035), and diabetes (β=0.332, P=0.001). Multiple regression analysis with ED as dependent variable has shown statistically significant association with lnUACR (β=0.242, P=0.031) and diabetes (β=-0.275, P=0.01). Patients were stratified into tertiles according to the lnUACR. Statistically significant differences in serum creatinine (P=0.001), cystatin C (P=0.012), hemoglobin (P=0.03), calcium (P=0.036), iPTH (P=0.008), SEVR (P=0.007) and ED (P=0.004) were found between tertiles. In post hoc analysis we found statistically significant differences between first and third tertile in SEVR (P=0.002; 95% CI:10.5-45) and in ED (P=0.001; 95% CI:-6.89-(-1.87)). Conclusions: Nondialysis CKD patients with higher levels of albuminuria have lower SEVR and higher ED and our results have shown the importance of central hemodynamic parameters like are SEVR and ED as a better or earlier noninvasive hemodynamic indexes in these patients.

Markers of Inflammation and Oxidative Stress in the Development and Progression of Renal Disease in Diabetic Patients.

The prevalence of diabetes is increasing and has already reached pandemic proportions. Diabetes is a well-known risk factor for chronic kidney disease. Diabetic kidney disease (DKD) occurs in up to 40% of people with type 1 or 2 diabetes and is nowadays the leading cause of end-stage renal disease (ESRD). Among several factors involved in the development and progression of DKD are also inflammation and oxidative stress. Unfortunately, there is a paucity of sensitive and specific biomarkers for the early prediction of patients who will develop DKD or will progress to ESRD. This review summarizes the evidence regarding the prognostic value and benefits of targeting markers of inflammation (pro-inflammatory cytokines, tumour necrosis factor-α (TNF-α) and TNF-α receptors, adhesion molecules, chemokines) and markers of oxidative stress. Some of these biomarkers are promising, but further studies are needed before they can be used in clinical practice.

Testosterone and Hemoglobin in Hemodialysis Male and Female Patients

It has been speculated that testosterone stimulates erythropoiesis. We hypothesized that hemoglobin levels in hemodialysis (HD) patients are associated with serum testosterone concentrations. Testosterone, hemoglobin, and other biochemical parameters were measured in a representative sample of 98 chronic HD patients (50 male, 48 female; age 30-90 years, mean 65±13.9 years). We investigated relations among serum testosterone concentration, hemoglobin, ferritin, albumin, body mass index, lean body mass, total cholesterol, low-density lipoprotein and high-density lipoprotein cholesterol, triglycerides, high-sensitivity C-reactive protein (hsCRP), calcium (Ca), P, intact parathyroid hormone, N-terminal pro-brain natriuretic peptide, Karnofsky performance status, and blood pressure (BP) before and after HD. A statistically significant positive correlation between testosterone and hemoglobin was found in all patients (r=0.25, P<0.01), men (r=0.34, P<0.02), but not in women (r=0.27, P=0.07). Multiple regression analysis for all patients has shown statistically significant association between hemoglobin and testosterone (P<0.001), hsCRP (P<0.005), lean body mass (P<0.05), post-HD systolic (P<0.04), and diastolic BP (P<0.005). Multiple regression analysis in men has shown an association between hemoglobin and testosterone (P<0.04) and post-HD diastolic BP (P<0.04) and in women association between hemoglobin and testosterone (P<0.04), Ca (P<0.03), and post-HD diastolic BP (P<0.03). We found an association between serum testosterone concentration and hemoglobin in male and female HD patients.

Paricalcitol reduces proteinuria in non-dialysis chronic kidney disease patients.

Existing treatment of proteinuria is not sufficient to halt the chronic kidney disease (CKD) epidemic. Therefore the aim of our study was to evaluate the effect of paricalcitol on proteinuria in non‐dialysis CKD patients with secondary hyperparathyroidism treated according to Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. Forty‐one non‐dialysis CKD patients with secondary hyperparathyroidism (iPTH >65 pg/mL), serum calcium <2.6 mmol/L, serum phosphate <1.8 mmol/L and proteinuria (>150 mg/day) were treated with paricalcitol 1 μg/day. Most were treated for 6 months, with the exception of three patients having iPTH <30 pg/mL after 3 months, in whom therapy was stopped. All patients were followed for 6 months. 24‐h ambulatory blood pressure (24hABP) monitoring was performed at 0 and 6 months. Fixed doses of ACE inhibitors and/or ARBs and/or statins were kept for 3 months before and during the study. Forty‐one patients (30 men, 11 women; age 62.44 ± 11.93 years) with different primary causes of CKD were enrolled in the study. Urinary albumin/creatinine ratio (UACR), 24‐h urinary albuminuria (24hUA) and 24‐h urinary quantitative proteinuria (24hUQP) were measured. Values at 0 and 6 months of these parameters were log‐transformed for statistical analysis. After treatment with paricalcitol, statistically significant reduction (paired t‐test) in 24hUA (P < 0.011) and 24hUQP (P < 0.0001) were found. The reduction of UACR was not significant (P = 0.074). In the observational period no statistically significant reduction in 24hABP was found. Treatment with 1 μg paricalcitol daily according to clinical practice in non‐dialysis CKD patients with secondary hyperparathyroidism and proteinuria significantly reduces 24hUA and 24hUQP without significant change in 24hABP.

Ankle-brachial index and cardiovascular mortality in nondiabetic hemodialysis patients.

Atherosclerosis is a leading cause of morbidity and mortality in hemodialysis (HD) patients. Low (<0.90) and high (>1.40) ankle‐brachial index (ABI) is known as a non‐invasive diagnostic marker for generalized atherosclerosis associated with higher cardiovascular (CV) mortality in the general population. Less is known about associations between ABI and CV mortality in HD patients. The aim of our study was to determine the impact of the ABI on CV mortality in nondiabetic HD patients. Fifty‐two nondiabetic HD patients (mean age 59 years, range 22 – 76 years) were enrolled in our study. Twenty‐three (44%) were women and 29 (56%) men. The ABI was determined using an automated, non‐invasive, waveform analysis device. All patients were divided according to the ABI into three groups: low ABI (<0.9), normal ABI (0.9–1.4) and high ABI (>1.4). The presence of arterial hypertension and smoking was established. Serum cholesterol (HDL and LDL) and triglycerides were measured by routine laboratory methods. Survival rates were analyzed using Kaplan–Meier survival curves. The Cox regression model was used to assess the influence of the ABI on CV outcomes. The model was adjusted for age, arterial hypertension, smoking, cholesterol and triglycerides. Mean ABI value was 1.2 ± 0.3 (range 0.2–2.2). Patients were observed from the date of the ABI measurement until their death or maximally up to 1620 days. Kaplan–Meier survival analysis showed that the risk for CV death was higher for HD patients with low and high ABI compared to normal ABI (log rank test: P < 0.006; P < 0.0001). In the adjusted Cox multivariable regression model low and high ABI (P < 0.011; P < 0.003) remained predictors of mortality in our patients. The results indicate a U‐shaped association between the ABI and CV mortality in nondiabetic HD patients and showed that low and high ABI were directly associated with higher mortality of our patients.

Estimation of Glomerular Filtration Rate in Elderly Chronic Kidney Disease Patients: Comparison of Three Novel Sophisticated Equations and Simple Cystatin C Equation: Estimation of GFR in Elderly CKD Patients

Estimating glomerular filtration rate (GFR) in elderly patients is a problem, since they are poorly represented in studies developing GFR equations. Serum cystatin C is a better indicator of GFR than serum creatinine in elderly patients. Therefore the aim of our study was to compare frequently used serum cystatin C based GFR equations with a gold standard (51CrEDTA clearance) in elderly chronic kidney disease (CKD) patients. 106 adult Caucasian patients, older than 65 years (58 women, 48 men; mean age 72.5 years), were included. In each patient 51CrEDTA clearance, serum creatinine (IDMS traceable method) and serum cystatin C (immunonephelometric method) were determined. GFR was estimated using the Simple cystatin C, CKD‐EPI cystatin C, CKD‐EPI creatinine‐cystatin C and BIS2 equation. Mean serum creatinine of our patients was 141.4 ± 41.5 μmol/L, mean serum cystatin C 1.79 ± 0.6 mg/L, mean 51CrEDTA clearance was 52.2 ± 15.9 mL/min per 1.73 m2. Statistically significant correlations between 51CrEDTA clearance and all formulas were found (P < 0.0001). In the receiver operating characteristic (ROC) curve analysis (cut‐off for GFR 45 mL/min per 1.73 m2) no significant differences in diagnostic accuracy between all the before mentioned equations were found. Bland‐Altman analysis for the same cut‐off showed that CKD‐EPI creatinine‐cystatin C and BIS2 equation underestimated and CKD‐EPI cystatin C and Simple cystatin C equation overestimated measured GFR. All equations lacked precision. Analysis of ability to correctly predict patients GFR below or above 45 mL/min per 1.73 m2 showed similar ability for all equations (P = 0.24–0.89). All equations are equally accurate for estimating GFR in elderly Caucasian CKD patients. For daily practice Simple cystatin C equation is most practical.

Ankle‐Brachial Index and Long‐Term (10 Years) Survival of Nondiabetic Hemodialysis Patients

Low (<0.9) and high (>1.4) ankle brachial index (ABI) is associated with a higher cardiovascular (CV) mortality in the general and hemodialysis (HD) population. The aim of our study was to determine the impact of ABI on long‐term survival of 52 non‐diabetic HD patients. The ABI was determined using an automated, non‐invasive waveform analysis device. Patients were divided into three groups: low (<0.9), normal (0.9–1.4) and high (>1.4) ABI. Patients were observed from the date of ABI measurement until their death or ten years. Survival analysis showed higher risk for CV death in HD patients with high ABI compared to normal ABI (log rank test P < 0.027). In Cox regression model adjusted for arterial hypertension, smoking, serum cholesterol and triglycerides, high ABI (P < 0.049) remained a predictor of mortality. The results indicate an association between ABI and long‐term survival of non‐diabetic HD patients and only high ABI was associated with higher CV mortality.

Cystatin C as a predictor of mortality in elderly patients with chronic kidney disease

Abstract Background: The prevalence of chronic kidney disease (CKD) in the elderly is high. Serum cystatin C is an accurate marker of kidney function and it also has prognostic utility in CKD patients. The aim of our study was to determine the prediction of serum cystatin C and other markers of kidney function on long-term survival in elderly CKD patients. Methods: Fifty eight adult Caucasian patients, older than 65 years, without known malignancy, thyroid disease and/or not on steroid therapy were enrolled in the study. In each patient, 51CrEDTA clearance, serum creatinine, serum cystatin C, and estimated glomerular filtration rate using different equations were determined on the same day and patients were then followed for 11 years or until their death. Results: The means are as follows: 51CrEDTA clearance 53.3 ± 17.4 ml/min/1.73 m2, serum creatinine 1.62 ± 0.5 mg/dl, serum cystatin C 1.79 ± 0.5 mg/l, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation 40.1 ± 14 ml/min/1.73 m2, Berlin Initiative Study 2 (BIS2) equation 38.9 ± 10.7 ml/min/1.73 m2, full age spectrum (FAS) creatinine equation 43.8 ± 13.8 ml/min/1.73 m2, FAS cystatin C equation 40.1 ± 11.7 ml/min/1.73 m2. In the follow up period, 47 (81%) patients died. Cox regression analysis showed different hazard ratios (HRs) for death: for 51CrEDTA clearance HR 1.022 (95% CI 1.004–1.042; p = .015), serum creatinine HR 1.013 (95% CI 1.006–1.019; p = .001), serum cystatin C HR 2.028 (95% CI 1.267–3.241; p = .003), CKD-EPI creatinine equation HR 1.048 (95% CI 1.019–1.076; p = .001), BIS2 equation HR 1.055 (95% CI 1.021–1.088; p = .001), FAS creatinine equation HR 1.046 (95% CI 1.017–1.074; p = .001), FAS cystatin C equation HR 1.039 (95% CI 1.010–1.071; p = .009). Conclusions: Our results showed the highest HR for serum cystatin C among kidney function markers for prediction of outcome in elderly CKD patients.

Subendocardial Viability Ratio Is Impaired in Highly Proteinuric Chronic Kidney Disease Patients With Low Estimated Glomerular Filtration Rate

Proteinuria and estimated glomerular filtration rate (eGFR) are markers of chronic kidney disease (CKD) and cardiovascular disease. With applanation tonometry, pulse wave analysis and many hemodynamic data are available. One of them is the subendocardial viability ratio (SEVR) which represents a non‐invasive measure of myocardial perfusion related to the work of the heart. The aim of our study was to investigate the importance of SEVR in proteinuric CKD patients and healthy subjects. We performed a cross‐sectional study in a cohort of 90 non‐dialysis CKD patients and 39 healthy controls. SEVR was assessed by radial applanation tonometry (SphygmoCor, Atcor, Australia). Blood samples and urine albumin‐to‐creatinine ratio (UACR) were analyzed. CKD patients were divided in four groups according to the UACR and eGFR: CKD group 1: UACR > 1000 mg/g and eGFR < 30 mL/min; CKD group 2: UACR > 1000 mg/g and eGFR >30 mL/min; CKD group 3: UACR <1000 mg/g and eGFR < 30 mL/min and CKD group 4: UACR < 1000 mg/g and eGFR >30 mL/min. Using one‐way ANOVA, we found a statistically significant difference in SEVR only between CKD group 1 and all other CKD groups and healthy control group (P < 0.022). Results of our study show that only CKD patients with UACR more than 1000 mg/g and eGFR below 30 mL/min have significantly lower SEVR.