Indicator Of Glomerular Filtration Rate Research Articles

Arg-liposome-amplified colorimetric immunoassay for selective and sensitive detection of cystatin C to predict acute kidney injury

Cystatin C (Cys C) has been considered as a novel biomarker of kidney disease, which is thought to be a better indicator of glomerular filtration rate than creatinine (Scr) in the prediction of acute kidney injury (AKI). Hence, there is strong need to develop a precise, rapid and simple detection method for Cys C. Here we reported a Arg-liposome-amplified colorimetric immunoassay for the detection of Cys C to predict AKI. Cys C antibodies are conjugated on the surface of magnetic beads (MBs) and arginine (Arg)-loaded liposomes to form Ab1-MBs and Ab2-Arg-liposomes, respectively. When Ab1-MBs captured Cys C, Ab2-Arg-liposomes are added and incubated to form the immuno-sandwich complex. After magnetic separation, the surfactant Triton ×100 is added to damage the liposomes, leading to the release of Arg which can induce the gold nanoparticles aggregation. Therefore, the discoloration can be used for visual and quantitative detection of Cys C. Notably, the method has a linear relation in the range of 10–100 μg/L for Cys C with a limit of detection 4.32 μg/L, which is lower than some of the previous reports. In addition, the AKI mice serum samples were tested by the developed method, which were in good agreement with ELISA results. More intriguingly, the results of cisplatin induced acute kidney injury in mice showed that the method could be used to evaluate the protective effect of astragalus membranaceus (AM) on AKI by detecting Cys C in serum, providing a new strategy for screening renal protective drugs. Accordingly, a rapid and highly sensitive Cys C detection system was established with great potential for clinical diagnostics.

Serum symmetric dimethylarginine concentration in healthy neonatal Thoroughbred foals.

Symmetric dimethylarginine (SDMA) is widely used in other species as a marker of renal dysfunction and is considered a more sensitive indicator of glomerular filtration rate than creatinine. Reference ranges are established in healthy adult horses (≤14μg/dL) and concentrations are increased in horses with acute kidney injury (median 32μg/dL; range 15-92). To establish the normal range of SDMA concentrations in neonatal Thoroughbreds. Cross-sectional. Blood samples were collected from Thoroughbred foals <36h old deemed healthy by physical examination. Exclusion criteria included foals from mares undergoing treatment for placentitis and foals that developed clinical disease or died/euthanised <2weeks from birth. Biochemistry and serum SDMA concentrations were obtained. Subjects included 120 foals. Median age was 13.5h (range 1.0-34.0). Median and 95% confidence interval for SDMA concentration was 69.0µg/dL (63.0, 75.0; range 35.0-376.0). A cut-off value of 168µg/dL would include 95% of individuals and is therefore suggested. Serum SDMA concentration was correlated with age (R=-.3, P=.003), creatinine concentration (R=.6, P≤.001) and urea concentration (R=.3, P=.002). Limitations include a small sample size, no consideration of subclinical disease and a short follow-up period. In equine neonates, SDMA concentration is higher than in adult horses, older foals and adults with acute kidney injury. Therefore, currently SDMA cannot be used as a marker of renal dysfunction in this age group. Further work is required to assess whether SDMA concentration is increased in neonates with renal disease and, if so, what cut-off should be used.

Dependence of renal filtration capacity on the phenotype of chronic heart failure, indicators of systolic and diastolic heart function

The issue of changes in the filtration capacity of the kidneys depending on the structural-geometric and functional remodeling of the heart in different phenotypes of chronic heart failure, disorders of systolic and diastolic function of the left ventricle remains insufficiently studied. The aim of this work: to investigate the relationship between changes in the filtration capacity of the kidneys in patients with chronic heart failure of ischemic genesis depending on the phenotype, indicators of systolic and diastolic cardiac function. Materials and methods. After an informed consent was signed, 87 patients (men – n = 45, women – n = 42) with CHF of ischemic genesis with sinus rhythm, stage II A–B, II–IV functional class NYHA, who were divided into 2 groups, were involved in the study. Group 1 included patients with reduced (&lt;45 %) left ventricular ejection fraction (HFrEF) (n = 57; 59.6 % men), group 2 – patients with CHF with preserved left ventricular ejection fraction (HFpEF) (n = 30; 36.6 % men). Patient groups were comparable in terms of age, sex, height, weight, and body surface area. Doppler echocardiographic examination was performed using the Esaote MyLab Eight (Italy). Glomerular filtration rate (GFR) was assessed using the CKD-EPI, MDRD, and Cockcroft-Gault formulas. Results. Renal dysfunction was registered in patients with CHF in 72 % of cases when calculated using the CKD-EPI formula, 66.7 % using the MDRD formula and 52.6 % using the Cockcroft-Gault formula. Only indicators of blood creatinine level (P = 0.011) and the calculated indicator of glomerular filtration rate according to Cockcroft-Gault (p = 0.047) depended on the types of CHF. GFR for all applied formulas (СKD-EPI, MDRD, Cockcroft-Gault) depended on age (r = -0.42; P = 0.001), height (r = 0.28; P = 0.08), weight (r = 0.31; P = 0.004), body surface area (r = 0.33; P = 0.002). A direct correlation between the creatinine level and the LV myocardial mass index, calculated using the Penn Convention formula, was established, however, the dependence of the creatinine level and GFR on the types of LV geometry was not revealed. The presence of an inverse correlation between LVEF and blood creatinine level (r = -0.3172; P = 0.003), between creatinine content and S lat (r = -0.531; Р = 0.006), a direct correlation between S lat and CKD-EPI (r = 0.5586; P = 0.004), MDRD (r = 0.6254; P = 0.001), Cockcroft-Gault (r = 0.4043; P = 0.045). Conclusions. In chronic heart failure of ischemic genesis with reduced left ventricular ejection fraction, a more pronounced impairment of the filtration capacity of the kidneys than in chronic heart failure patients with preserved left ventricular ejection fraction is observed. An inverse correlation was established between the LV EF and the blood creatinine level (r = -0.3172; P = 0.003). A decrease in the systolic velocity of movement of the lateral annulus fibrosus of the mitral valve is associated with a decrease in the filtration capacity of the kidneys in terms of creatinine level (r = -0.531; P = 0.006), GFR according to the CKD-EPI (r = 0.5586; P = 0.004), MDRD (r = 0.6254; P = 0.001), Cockcroft-Gault (r = 0.4043; P = 0.045) in patients with CHF of ischemic genesis of both phenotypes. In patients with CHF of ischemic genesis of both phenotypes, the myocardial mass index, calculated according to the Penn Convention, correlates with the blood creatinine content (r = 0.95; P = 0.003). In patients with CHF of ischemic genesis, the restrictive type of diastolic filling of the left ventricle is associated with a significant increase in blood creatinine levels by 14 % (P = 0.03) compared with patients with diastolic LV dysfunction by the type of relaxation disorder.

Development of an Approach of High Sensitive Chemiluminescent Assay for Cystatin C Using a Nanoparticle Carrier.

Cystatin C is an important cysteine protease inhibitor in the human body and is proposed as a new indicator of glomerular filtration rate for the detection of kidney damage. In this article, we report an ultra-sensitive, simple, and rapid chemiluminescence immunoassay method for cystatin C detection using functionalized mesoporous silica nanoparticles. After a three step hydrolysis, the amino-functionalized MSN encapsulating dye resulted in a hydrophobic environment for fixing the dye and amino groups for biological modification. The NaIO4 immobilization method maintained the activity of the antibody notably well. The sandwich immunoassay using two monoclonal antibodies was chosen for its selectivity. The analysis demonstrated that the detection upper was 0.0029 ng/mL and linear relationship within the range of 0.0035–0.5 ng/mL (R2 = 0.9936). The relative standard deviation (RSD) for 11 parallel measurements of 0.25 ng/mL CysC was 4.7%. The automated chemiluminescence analyzer could detect 96 wells continuously. The results demonstrated that this method is ultra-sensitive, simple, and rapid for detecting cystatin C.

Changes in Novel AKI Biomarkers after Exercise. A Systematic Review.

More than 100 substances have been identified as biomarkers of acute kidney injury. These markers can help to diagnose acute kidney injury (AKI) in its early phase, when the creatinine level is not increased. The two markers most frequently studied in plasma and serum are cystatin C and neutrophil gelatinase-associated lipocalin (NGAL). The former is a marker of kidney function and the latter is a marker of kidney damage. Some other promising serum markers, such as osteopontin and netrin-1, have also been proposed and studied. The list of promising urinary markers is much longer and includes cystatin C, NGAL, kidney injury molecule-1 (KIM-1), liver-type fatty-acid-binding protein (L-FABP), interleukin 18, insulin-like growth factor binding protein 7 (IGFBP-7), tissue inhibitor of metalloproteinases-2 (TIMP-2) and many others. Although these markers are increased in urine for no longer than a few hours after nephrotoxic agent action, they are not widely used in clinical practice. Only combined IGFBP-7/TIMP-2 measurement was approved in some countries as a marker of AKI. Several studies have shown that the levels of urinary AKI biomarkers are increased after physical exercise. This systematic review focuses on studies concerning changes in new AKI biomarkers in healthy adults after single exercise. Twenty-seven papers were identified and analyzed in this review. The interpretation of results from different studies was difficult because of the variety of study groups, designs and methodology. The most convincing data concern cystatin C. There is evidence that cystatin C is a better indicator of glomerular filtration rate (GFR) in athletes after exercise than creatinine and also at rest in athletes with a lean mass lower or higher than average. Serum and plasma NGAL are increased after prolonged exercise, but the level also depends on inflammation and hypoxia; therefore, it seems that in physical exercise, it is too sensitive for AKI diagnosis. It may, however, help to diagnose subclinical kidney injury, e.g., in rhabdomyolysis. Urinary biomarkers are increased after many types of exercise. Increases in NGAL, KIM-1, cystatin-C, L-FABP and interleukin 18 are common, but the levels of most urinary AKI biomarkers decrease rapidly after exercise. The importance of this short-term increase in AKI biomarkers after exercise is doubtful. It is not clear if it is a sign of mild kidney injury or physiological metabolic adaptation to exercise.

Association between breed and renal biomarkers of glomerular filtration rate in dogs

BackgroundKidney disease, especially chronic kidney disease (CKD), is common in older dogs. The biomarkers symmetric dimethylarginine (SDMA) and creatinine (Cr) are indicators of glomerular filtration rate (GFR). This retrospective study...

Evaluation of serum biomarkers and proteinuria for the early detection of renal damage in dogs with heartworm (Dirofilaria immitis)

Glomerulonephropathy associated with Dirofilaria immitis (heartworm) is relatively frequent in infected dogs. Given the importance and the scarcity of studies focused on its prevalence and diagnosis, the objective was to determine the prevalence of proteinuria and functional indicators of glomerular filtration rate in dogs with heartworm disease and discuss its utility in the detection of renal impairment. Sera and urine from 47 infected dogs were analyzed in a reference laboratory. Urea, creatinine, plasma proteins and serum symmetric dimethylarginine (SDMA) were analyzed in sera, while the UPC ratio was performed in urine. Dogs were further evaluated for the presence/absence of microfilariae, pulmonary and systemic hypertension, and the parasite burden was assessed. The results showed that 19.1 % of dogs showed proteinuria (UPC > 0.5) and 17 % showed borderline proteinuria (UPC 0.2−0.5). Creatinine and SDMA were high (>1.8 mg/dl and ≥18 μg/dl, respectively) in 4.2 % of dogs. UPC ratio was significantly increased in dogs with high parasite burden and in dogs with microfilariemia (p < 0.05). Dogs with pulmonary hypertension showed higher increases in proteinuria as well, which was probably due to the chronicity of the infection. No significant differences were found in serum and urine values regarding systemic blood pressure. Despite the limitations of this study, proteinuria/borderline proteinuria was present in 36.2 % of dogs with heartworm disease, and this may be due to glomerular disease. Therefore, the detection of proteinuria, along with other renal biomarkers in the diagnostic protocols, could help identify kidney alterations or risk of renal damage in heartworm disease.

Effects of Jwagwieum on Renal Dysfunction in Ischemia/Reperfusion‐induced Acute Renal Failure in Rats

Jwagwieum ( , JGE), a Korean traditional medicine, has been used for treatment of kidney‐yin deficient ( ) syndrome. However, there is no pharmacological study of JGE on ischemia/reperfusion‐induced acute renal failure (ARF). Therefore, the objective of this study was to evaluate whether JGE ameliorates renal function and its related mechanism in acute kidney injury‐induced by ischemia/reperfusion in rats. In this experiment, 5‐week‐old male Sprague Dawley (SD) rats were used under 12 h light and dark cycle. After a week of adaptation, they were randomly divided into following groups. 1) Cont. (Control), 2) ischemia/reperfusion injury (ARF), 3) ARF + JGE100 (100 mg/kg/day), 4) ARF + JGE200 (200 mg/kg/day). The ARF group was subjected to reperfusion after inserting a clip into the renal artery for 45 min. ARF + JGE100 group was orally administered with JGE 100 mg/kg/day after ischemia/reperfusion surgery, and ARF + JGE200 group was orally administered with JGE 200 mg/kg/day for 4 days, respectively. As a result, JGE suppressed the increase of kidney size in the acute renal failure animal model and alleviated polyuria symptoms. In addition, solute‐free water reabsorption (TcH2O) and creatinine clearance (Ccr), indicators of glomerular filtration rate, were significantly increased in JGE group compared with those of ARF rats. In ARF group, blood urea nitrogen (BUN)/creatinine (Cr) and lactate dehydrogenase (LDH) were significantly increased compared to the control group, respectively, while they were significantly decreased in JGE group. The present results also showed that JGE improved the morphological aspects of renal tissue and ameliorated fibrosis in ARF group. Inflammation is one of the main causes of ischemic acute kidney injury and was inhibited by JGE, which was confirmed by the NLRP3 inflammasome decline.The present results showed that JGE has protective effects against inflammatory process via inhibition of NLRP3 signal pathway, which is associated with improvement of renal function in rats with ARF. These results suggest that JGE has a therapeutic effect on acute kidney injury‐induced by ischemia/reperfusion in rats.Support or Funding InformationThis work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (2017R1A5A2015805)(2015M3A9A5030620)(2017R1A2B4009884).

Activity of lysosomal urine enzymes in children after acute kidney injury

The importance of the problem of acute kidney injury in children is due to the high risk of developing chronic kidney disease as a consequence. Lysosomal enzymes of β-galactosidase (GAL) and N-acetyl-β-D-hexozoaminidase (NAG) in urine are considered to be informative markers of renal parenchyma damage. The objective of this study - to determine the activity of lysosomal enzymes in urine as markers of progression of interstitial nephritis in children after acute kidney injury.&#x0D; Methods. 41 children were examined after acute kidney injury, achievement of self-diuresis and improvement. Group I included 22 patients with a disease period of up to 2 years after acute kidney injury, group II - 19 patients with a disease period of 2 years or more. The control (reference) group consisted of 28 children who were conditionally healthy, without kidney disease, as well as without acute diseases and severe metabolic disorders and anatomical defects.&#x0D; Results. NAG and GAL activity were found to exceed 8 and 3 times parameters in the reference group of healthy children, respectively, in patients who had acute kidney injury during the year (p &lt;0.001). In patients with a history of 2 years or more, enzyme levels decreased, but remained higher than normal up to 4 times (p &lt;0.001). The highest level of NAG activity was observed in patients of group 1 with the combination of hemolytic-uremic syndrome with hemolytic anemia, and the lowest - in children with toxic kidney.&#x0D; Determination of the activity of lysosomal enzymes NAG and GAL is a more informative marker of torpid course of interstitial nephritis with a progressive decrease in renal function than indicators of glomerular filtration rate. In twelve months after acute kidney damage in 75% of children, the level of NAG and GAL activity remained significantly elevated at normal glomerular filtration rate. A correlation between glomerular filtration rate and NAG activity (r = -0.473) and GAL (r = -0.333) and a direct correlation between NAG and GAL activity (r = 0.845) were observed.&#x0D; Conclusions. The levels of lysosomal enzymes of NAG and GAL were found to be 8 and 3 times higher than normal, respectively, in patients who suffered acute kidney injury during the year, and in patients with a history of 2 years or more, enzyme activity levels decreased, but remained higher than normal 4-fold (p &lt;0.001). In a year after acute kidney damage in 75% of children, the level of NAG and GAL activity remained significantly elevated despite of normal glomerular filtration rate. Therefore, the detection of NAG and β-galactosidase in the urine of children after acute kidney injury are informative markers of renal parenchyma damage, which may serve as objective criteria for progressive decline in renal functional status, and the lack of normalization of their levels is not a sign of progression of interstitial nephritis in corresponding group of children.

Serum Cystatin C as a Useful Marker for Evaluation of Renal Function at Birth: A Pilot Study

Background: Serum creatinine (SCr) is widely used to test renal function. SCr at birth is strongly affected by maternal SCr and does not reflect the renal function of the neonate. Serum cystatin C (CysC) has been used as an indicator of glomerular filtration rate in adults and children. However, CysC has not been widely used to evaluate kidney function in neonates until now. Methods: The renal function of neonates admitted to our neonatal intensive care unit was evaluated by analyzing cord blood CysC levels at birth using a latex immunoturbidimetric assay. Results: The cord blood CysC and SCr of ten neonates was measured at birth. The CysC levels of four patients without impaired renal function were between 1.26 and 1.53 mg/L. The CysC level in one case whose mother was diagnosed with chronic kidney disease was not elevated (1.60 mg/L), although the patient’s SCr level was elevated (2.25 mg/dL). The CysC levels of three patients with acute kidney injury due to asphyxia were slightly higher (1.78 to 2.17 mg/L) than those in patients without acute kidney disease. The CysC levels of two patients diagnosed with renal failure were substantially higher (4.09 and 7.07 mg/L) than those of patients without renal failure. Conclusion: CysC shows potential as a useful marker to evaluate the kidney function of neonates at birth, as CysC is not affected by maternal CysC.

Hepatoprotective and Renoprotective Potentials of the Aqueous Extract of Bixa orellana on Streptozotocin Induced Diabetic Rats

Objective: The present study was undertaken to evaluate the effects of the aqueous extract of Bixa orellana on the liver enzymes such as AST, ALT and ALP and also to evaluate the efficacy of the extract for the protection of the renal function in streptozotocin induced diabetic rats. Methods: Diabetes was induced by administering streptozotocin dissolved in saline while the normal control group was given propylene glycol. Diabetes induced animals were randomly assigned into different groups. Blood samples were collected from all the control and experimental group. Estimation of urea, uric acid and creatinine as well as the liver enzymes such as AST, ALT and ALP were assayed. These estimations were carried out on day 30 only. Results: The 30 days treatment with the aqueous extract (200 mg/kg body weight) showed no statistical significance with respect to urea and uric acid but there was statistical significance in the levels of creatinine which is an indicator of glomerular filtration rate. The alteration in the levels of ALT and ALP were highly significant statistically but no changes observed in the level of AST. Conclusion: The employed dose of the extract is nontoxic to the kidney and it even caused a significant decrease in level of liver enzymes when diabetic induced rat subjected to treatment hence this may indicate the hepatoprotective properties of this extract.

Biochemical Markers of Renal Function.

Kidney damage can be induced by ischemia, autoimmune diseases, hypertension, allograft rejection, metabolic or genetic disorders, infections or toxins. The influence of these factors could result in acute kidney injury (AKI) defined as an unexpected decrease in urine output or renal function, or encourage the development of chronic kidney disease (CKD). Biomarkers of renal function, measured in urine and serum, are in increasing use in order to estimate the severity and nature of kidney injury, and consequently apply appropriate therapy and improve patient management. The determined values of biomarkers can suggest the potential risk of kidney disease and the type of renal injury, predict the disease progression, as well as be helpful for assessing the response to an applied therapy. Although novel biomarkers are in practical use, serum creatinine, the indicator of glomerular filtration rate is still the most frequently used biomarker of renal function despite its known limitations. In recent decades, numerous studies resulted in discovering urinary and serum proteins that can serve as biomarkers for early and accurate detection of AKI and its development, as well as the identification of CKD. This review gives an overview of the most important renal biomarkers investigated in kidney diseases, classified in following types: functional biomarkers, up-regulated proteins, enzymes, and cycle arrest biomarkers. It describes their properties, physiological roles, and discusses the utility of these molecules in different clinical settings.

The association of plasma cystatin C proteoforms with diabetic chronic kidney disease.

BackgroundCystatin C (CysC) is an endogenous cysteine protease inhibitor that can be used to assess the progression of kidney function. Recent studies demonstrate that CysC is a more specific indicator of glomerular filtration rate (GFR) than creatinine. CysC in plasma exists in multiple proteoforms. The goal of this study was to clarify the association of native CysC, CysC missing N-terminal Serine (CysC des-S), and CysC without three N-terminal residues (CysC des-SSP) with diabetic chronic kidney disease (CKD).ResultsUsing mass spectrometric immunoassay, the plasma concentrations of native CysC and the two CysC truncation proteoforms were examined in 111 individuals from three groups: 33 non-diabetic controls, 34 participants with type 2 diabetes (DM) and without CKD and 44 participants with diabetic CKD. Native CysC concentrations were 1.4 fold greater in CKD compared to DM group (p = 0.02) and 1.5 fold greater in CKD compared to the control group (p = 0.001). CysC des-S concentrations were 1.55 fold greater in CKD compared to the DM group (p = 0.002) and 1.9 fold greater in CKD compared to the control group (p = 0.0002). CysC des-SSP concentrations were 1.8 fold greater in CKD compared to the DM group (p = 0.008) and 1.52 fold greater in CKD compared to the control group (p = 0.002). In addition, the concentrations of CysC proteoforms were greater in the setting of albuminuria. The truncated CysC proteoform concentrations were associated with estimated GFR independent of native CysC concentrations.ConclusionOur findings demonstrate a greater amount of CysC proteoforms in diabetic CKD. We therefore suggest assessing the role of cystatin C proteoforms in the progression of CKD.Electronic supplementary materialThe online version of this article (doi:10.1186/s12953-016-0096-7) contains supplementary material, which is available to authorized users.

Pretransplant renal function according to CKD‐EPI cystatin C equation is a prognostic factor of death after liver transplantation

In patients with cirrhosis, cystatin C (CystC) based equations may be more accurate indicators of glomerular filtration rate (GFR) than creatinine (Pcr) based equations. Renal function before liver transplantation (LT) is thought to impact survival after LT. We aimed at assessing pretransplant creatinine and CystC based equations with respect to their predictive value on long-term survival after LT. From 2001 to 2011, CystC was determined at pre-LT evaluation in 682 patients together with GFR assessed using MDRD-4, MDRD-6, CKD-EPI-cystatin C, CKD-EPI-creatinine and CKD-EPI-creatinine-cystatin C equations. Patients were classified according to the Kidney Disease Outcomes Quality Initiative classification (KDOQI). Median age at LT was 55 [49-60] years with a median MELD score of 13.5 [8.3-19.2] and a median post-transplant follow-up of 60 [26-89] months. Using CKD-EPI Cystatin C and the KDOQI classification, 21.1% of patients were stage 1, 43.1% stage 2, 29.1% stage 3 and 6.5% stage 4. Kaplan-Meier survival estimates were significantly different between KDOQI stages when determined using the CKD-EPI-CystatinC equation. This was not the case when using the other equations. At multivariate analysis, GFR and KDOQI estimated using the CKD-EPI-CystatinC equation were significantly associated with death (HR: 0.992; CI95%: 0.986-0.999 and 1.24; CI95%: 1.02-1.50 respectively). When assessed using the MDRD-4, MDRD-6, CKD-EPI-Creatinine-CystatinC and CKD-EPI-Creatinine equations GFR was not significantly associated with death. Estimated pre-LT renal function is predictive of post-LT survival only when assessed using the CKD-EPI cystatin C equation. This supports the use of Cystatine C and of its related equation for the assessment of renal function before liver transplantation.

Cystatin C: a kidney function biomarker.

Renal function is essential for homeostasis. The kidneys play important pleiotropic roles including removal of metabolic waste products and maintenance of water-electrolyte balance and blood pressure. Early diagnosis of renal dysfunction and institution of appropriate therapy are vital to survival. Unfortunately, common indicators of renal function lack necessary sensitivity and specificity. Recent evidence has, however, suggested that cystatin C (cysC) may be useful as a marker for glomerular filtration. CysC is a protein belonging to a group of cysteine proteases inhibitors produced primarily by nucleated cells. Due to low molecular weight and positive pI, it is easily filtered. Moreover, its serum concentration is independent of gender, age, or muscle mass, i.e., typical confounders in assessing glomerular filtration rate (GFR). This chapter discusses the structure and biologic function of cysC, its role as an indicator of GFR, and the most frequently used methods for its determination.

Serum cystatin‐C levels correlate with endothelial dysfunction in patients with the metabolic syndrome

Serum cystatin‐C levels correlate with endothelial dysfunction in patients with the metabolic syndrome

Creatinine Estimation and Interference

Sir, Creatinine is one of the most common analyte used as the indicator of glomerular filtration rate (GFR) and kidney function. In 1886, Jaffe reported a reaction of creatinine and picric acid in an alkaline medium forming complex having absorbance maxima at 520 nm. The reaction has been brought to use for the measurement of creatinine by Folin and Wu in 1919. Since then, Jaffe’s reaction has been used for estimation of creatinine in serum and urine sample. For more than 90 years, this method is in use for the measurement of creatinine concentration due to its simplicity and low cost. Creatinine is produced as the byproduct of creatine metabolism and is transported through bloodstream to the kidneys for excretion. Malfunctioning of kidney is reflected by lowering of the amount of creatinine in urine and rise of its level in blood. Creatinine levels in blood and urine also indicate the creatinine clearance, accounting for GFR. Creatinine readings indicate the total kidney GFR which is the sum of filtration rates of all functional nephrons. Early structural damage to the renal cells involving reduction in functional nephron number may not affect an individual’s total GFR as remaining renal units may perform compensatory function, enabling the kidneys to maintain kidney function temporarily even after the loss of functional tissue. Thus, creatinine/GFR may not indicate the early damage to kidney tissue. Jaffe also elaborated the interference in alkaline picrate reaction by number of organic compounds (e.g. acetone, glucose) which has been described as pseudochromogens. Still, creatinine remains the gold standard for measuring the glomerular filtration rate and kidney functioning. And Jaffe method remains the default method for estimation of creatinine. In last century, many caveats in this method were reported which we have indicated in brief in this article. Recently we have reported an interference by streptomycin (an aminoglycoside) in high doses which act as false positive in Jaffe reaction [1]. It is known from literature that aminoglycosides can be nephrotoxic and may potentially affect kidney function. If it is so, then, nephrotoxicity due to high dose of aminoglycosides (say streptomycin) can never be correctly estimated as defect in excreting out creatinine would be masked by the false positive Jaffe reaction given by streptomycin. Antibiotics like cephapirin, cefazolin, cefamandole, cephalothin, and cefoxitin have been shown to interfere with creatinine determination at various concentrations [1, 2]. Phenacemide and cephalothin may interfere either positively or negatively with the determination of creatinine by the Jaffe reaction [3] . Cephalosporin antibiotics have been shown to form non-creatinine chromogen with alkaline picrate reagent and produce false positive results for creatinine. Serum creatinine and creatinine clearance values are positively interfered by cefoxitin in the Jaffe reaction, the routine laboratory method of creatinine measurement. Both invitro and invivo analysis suggest the same [4]. Many biomolecules like bilirubin, glucose, acetone etc. are also known to interfere with the Jaffe method of creatinine estimation and therefore the method has gone through modifications [5]. To overcome the effect of interference specific enzymatic method of creatinine estimation has been also developed [6]. But in-spite of various modification of the Jaffe method and development of the specific enzymatic method for creatinine estimation, the classical alkaline picrate method remains popular in India.

Use of Serum Cystatin C in Assessment of Early Deterioration of Renal Function in Type 2 Diabetic Industrial Workers in Port Harcourt, Nigeria

Early detection of deterioration or impairment in renal function is critical in management of diabetic patients. Serum cystatin C may be the most sensitive indicator of glomerular filtration rate (GFR) in a clinical environment. We compared cystatin C with creatinine, the Cockcroft-Gault (C-G) formular, and the Modification of Diet in Renal Disease (MDRD) equation for the assessment of early decreased renal function in 50 type 2 diabetic patients with and without significant renal impairment (GFR; 8-205 ml/min/1.73m 2 ).Relationships of cystatin C, creatinine, and iohexol clearance were linearized using simple regression model and diagnostic efficiency calculated. In our study population, cystatin C (P<0.001) was better correlated with glomerular filtration rate (GFR) (r=0.922) than were creatinine (r=743), Cockcroft-Gault (C-G)formular (r=0.755) and Modification of Diet in Renal Disease (MDRD) equation (r=0.818). Mean cystatin C concentrations showed step wise statistically significant increases as GFR reduces, allowing very early identification of reduction in renal function. At 90ml/min/1.73m 2 and 75ml/min/1.73m 2 cut-points, diagnostic efficiencies of cystatin C (90% and 93%) were better than those of the other variables (80%-84% and 86%-89%, respectively; P = 0.01). All data supported the value of serum cystatin C compared with conventional estimates based on serum creatinine measurement for detecting very early reduction of renal function. Use of cystatin C to measure renal function will make for early detection, prevention, and treatment of diabetic nephropathy in type 2 diabetics.

Effects of Tepoxalin and Medetomidine on Glomerular Filtration Rate in Dogs

The objective of this study was to evaluate glomerular filtration rate (GFR) and the cardiovascular effects of the combination of tepoxalin (TPX) and medetomidine (MED) in dogs. Six healthy dogs of either sex (5 males and 1 female), aged 2.5 ± 2.2 years and weighing 14.7 ± 4.4 kg, were studied. Each dog received four randomized treatments with a minimum of 1 week between treatments: no medication as the control group (C); MED (750 μg/m(2), intravenously [IV]); TPX (10 mg/kg orally for 3 days); and MT (TPX 10 mg/kg orally for 3 days plus MED 750 μg/m(2), IV). Iohexol (300 mg iodine/kg, IV) was injected in all dogs in each treatment as an indicator of GFR. Blood samples for serum iohexol clearance analysis were collected before and 1, 2, 5, 10, 15, 20, 60, 120, 240 and 360 min after the iohexol administration. Rectal temperature, heart rate, respiratory rate and direct arterial pressure (AP) were obtained before and 5, 10, 15, 20, 60, 120, 240 and 360 min after the iohexol injection. GFR did not differ between treatments. Heart rate was significantly lower in the MED and MT groups than in C or TPX. Mean AP was significantly higher with MT than TPX, but only at 5 min after the iohexol injection. TPX, MED and the combination of these two drugs do not alter GFR. The combination has minimal effect on cardiovascular variables at these doses in healthy dogs.

Quantification of creatinine in biological samples based on the pseudoenzyme activity of copper–creatinine complex

Glomerular filtration rate (GFR), the marker of chronic kidney disease can be analyzed by the concentration of cystatin C or creatinine and its clearance in human urine and serum samples. The determination of cystatin C alone as an indicator of GFR does not provide high accuracy, and is more expensive, thus measurement of creatinine has an important role in estimating GFR. We have made an attempt to quantify creatinine based on its pseudoenzyme activity of creatinine in the presence of copper. Creatinine in the presence of copper oxidizes paraphenylenediamine dihydrochloride (PPDD) which couples with dimethylamino benzoicacid (DMAB) giving green colored chromogenic product with maximum absorbance at 710nm. Kinetic parameters relating this reaction were evaluated. Analytical curves of creatinine by fixed time and rate methods were linear at 8.8–530μmolL−1 and 0.221–2.65mmolL−1, respectively. Recovery of creatinine varied from 97.8 to 107.8%. Limit of detection and limit of quantification were 2.55 and 8.52μmolL−1 respectively whereas Sandell's sensitivity and molar absorption coefficient values were 0.0407μgcm−2 and 0.1427×104Lmol−1cm−1 respectively. Precision studies showed that within day imprecision was 0.745–1.26% and day-to-day imprecision was 1.55–3.65%. The proposed method was applied to human urine and serum samples and results were validated in accordance with modified Jaffe's procedure. Wide linearity ranges with good recovery, less tolerance from excipients and application of the method to serum and urine samples are the claims which ascertain much advantage to this method.