The importance of determining cystatin C for assessment of glomerular filtration disturbance

Zbog značaja koji bubreg ima u organizmu važno je rano prepoznati poremećaj njegove funkcije. Do oštećenja bubrega i do poremećaja funkcije mogu da dovedu različiti uzroci. Za procenu stanja bubrega najčešće se u kliničkoj praksi koristi kreatinin koji zavisi od pola, starosne dobi i rase, pa je zato nepouzdana za preciznu procenu JGF i to naročito kod početnih oštećenja bubrežne funkcije, a neki od ovih nedostataka mogu da budu prevaziđeni upotrebom renalnog klirensa kreatinina. Pored klirensa kreatinina primenjuje se i klirens supstanci obeleženih radioakivnim elementima, kao 99mTc-DTPA. Izotopske metode su reproducibilne i u visokoj korelaciji sa klirensom inulina kao zlatnim standardom za određivanje JGF. Postoji široko naučno interesovanje za utvrđivanje primenljivosti cistatina C za određivanje jačine glomerulske filtracije, kojom se u prvom redu procenjuju filtracioni procesi u glomerulu, ali se ipak nameće kao mera za praćenje najvećeg broja promena u funkciji bubrega i progresije njihovog oštećenja. Zbog male molekulske mase cistatin C se lako filtrira kroz bazalnu membranu glomerula i na taj način skoro se potpuno eliminiše iz cirkulacije posle čega se u tubulima u potpunosti kataboliše i ne vraća se u cirkulaciju, što znači da njegova koncentarcija u serumu prvenstveno zavisi od jačine glomerulske filtracije. Ispitano je u studiji preseka koja je trajala 4 godine i obuhvatila 337 ispitanika, 62 bubrežna bolesnika, 109 zdravih trudnica, 33 trudnica sa hipertenzijom izazvanom trudnoćom, 57 bolesnika sa endemskom nefropatijom, 30 bolesnika sa nefrotskim sindromom i 15 zdravih ispitanika kao i 31 bolesnik sa šećernom bolešću. Ispitivanje je sprovedeno u Kliničkom centru Srbije uz saglasnost bolesnika u skladu sa Helsinškom deklaracijom o medicinskim istraživanjima i uz odobrenje Etičkog komiteta Medicinskog fakulteta u Beogradu. Laboratorijska ispitivanja su urađena u laboratorijama Centra za medicinsku biohemiju Kliničkog centra Srbije iz preostalih alikvota krvi korišćene za rutinske laboratorijske analize. Za sva ispitivanja uzorci krvi i mokraće uzimani su ujutru. Uzorak 24h urina sakupljan je od 6h ujutro prvog dana do 6h ujutro narednog dana. Uzorci venske krvi su sakupljani u vakutajnerima (BD) bez aditiva, centrifugirani na 3500 rpm, (≈2000 g) i posle separacije serum je čuvan na minus 80 oC do određivanja. Cistatin C u serumu je određivan PENIA metodom (Particle-Enhancesd Nephelometric Immuno-Assay) testovima firme Dade Behring (Marburg, Germany) na laserskom nefelometru (BN II Dade Behring). Cilj rada je bio da se utvrdi da li je cistatin C pouzdan pokazatelj: 1) jačine glomerulske filtracije (JGF), tj. u kakvoj je vezi sa klirensom 99mTc-DTPA; 2) da se utvrdi u kakvoj je on vezi sa kreatininom u serumu i klirensom kreatinina; 3) da se utvrdi kako životna dob utiče na nivo cistatina C; 4) početnog oštećenja JGF i da li je pouzdaniji od kreatinina; 5) JGF kod obolelih od nefrotskog sindroma i kako proteinurija i životna dob bolesnika utiče na nivo cistatina C u serumu; 6) JGF kod osoba sa endemskom nefropatijom; 7) JGF kod obolelih od dijabetesa tipa 2; 8) kako gestacioni periodi trudnica sa normalnim bubrežnom funkcijom utiču na nivo cistatina C; 9) kako životna dob trudnica utiče na nivo cistatina C; 10) odnos nivoa cistatina C, serumskog kreatinina i klirensa kreatinina u različitim gestacionim periodima u normalnoj i u trudnoći komplikovanoj trudnoćom izazavanom hipertenzijom, da li cistatin C u ovoj grupi može da se koristi kao marker JGF. Da bi se ustanovilo da li cistatin C može da se primeni za procenu JGF određivan je klirens 99mTc-DTPA, zlatni standard za procenu JGF, serumski kreatinin i cistatin C kod bolesnika sa različitim bolestima bubrega. Za razliku od kreatinina, cistatin C i klirens 99mTc-DTPA ne zavise od pola bolesnika a cistatin C ne zavisi ni od starosne dobi bolesnika. Ustanovljeno je visoko slaganje vrednosti klirensa 99mTc-DTPA i cistatina C, što potvrđuje da je cistatin C pouzdan pokazatelj jačine glomerulske filtracije...mainstay for detecting impaired kidney function is serum creatinine. Unfortunately, serum creatinine is an insensitive marker of kidney injury, since it depends on sex, age and race. Furthermore, it does not reflect mildly diminshed renal function. Some of these shortcomings can be overcome by the creatinine clearance. However, creatinine clearance may be inaccurate because of tubular creatinine secretion and errors in specimen collection. Measurements of the renal clearance of infused tracers such as 99mTc-DTPA provide accurate measurements of GFR and correlates well with inulin clearance, which is the gold standard for determining GFR. There has been an ongoing search for improved markers for impaired renal function or injury. Cystatin C seems to be a promising candidate to assess GFR, but also other functional chnages in the kidney and their progression. It is produced by all nucleated cells and is small enough to be freely filtered at the glomerulus and completely removed from blood. It is then fully catabolized in the tubules, meaning that its serum concentration depends mainly on GFR. In this cross-sectional study we aimed to: 1) determine is cystatin C reliable marker of GFR, by determinig its correlation with 99mTc-DTPA clearance; 2) determine the relationship between serum cystatin C concentration, serum creatinine and creatinine clearance; 3) determine the correlation between serum cystatin C and age; 4) determine is cystatin C a reliable marker of mildly diminshed renal function; 5) determine is serum cystatin C a reliable marker of GFR in nephrotic syndrome and how proteinuria and age influence its serum concentration; 6) determine if serum cystatin C is a reliable marker of renal function in nedemic nephropathy; 7) determine is serum cystatin C a reliable marker of renla function in nephropathy caused by type 2 diabetes; 8) determine correlation between serum cystatin C and gestational period in healthy pregnant women; 9) determine correlation between age and serum cystatin C in healthy pregnant women and 10) assess relationship between cystatin C, creatinine and creatinine clearance in different gestational period in normal and hypertensive pregnancies. Over the period of 4 years we investigated 337 persons: 62 renal failure patients, 109 healthy pregnant women, 33 preagnant women with pregnancy induced hypertension (PIH), 57 patients with Balkan endemic nephropathy (BEN), 30 patients with nephrotic syndrome, 31 patients with type 2 diabetes and 15 healthy subjects. All individuals gave their informed consent for participation the study, accordnig to the Declaration of Helsinki. The study was approved by the Ethical Commitee of University School of Medicine in Belgrade and conducted in the Clinical Center of Serbia. Laboratory investigations were performed in the Center for Medical Biochemistry at the Clinical Center of Serbia from the remaining aliquotes of blood used for routine analyses. All blood and urine samples were taken in the morning. The 24-hour udine was collected between 6 A.M. one day and 6 A.M. the next day. Venous blood samples were collected in vacutainers (BD) without aditives, centrifuged at 3500 rpm (≈2000 g) and preserved at 80°C after separation. Cystatin C serum concentration was determined by the PENIA method (Particle-Enhancesd Nephelometric Immuno-Assay), using the Dade Behring (Marburg, Germany) tests, on a laser nephelometer (BN II Dade Behring). In order to determine if cystatin C can be used as a marker of GFR, its correlation with 99mTc- DTPA clearance and serum creatinine was determined in patients with different renal diseases. Unlike creatinine, cystatin C and 99mTc-DTPA clearance do not depend on sex, and cystatin C also does not depend on patients age. Serum creatinine is significantly inversely correlated with 9mTc-DTPA clearance (p<0,001) and significantly correlated with serum cystatin C concentration (p<,0001)..

Role of cystatin C and renal resistive index in assessment of renal function in patients with liver cirrhosis

AIM: To evaluate the clinical significance of cystatin C and renal resistive index for the determination of renal function in patients with liver cirrhosis. METHODS: We conducted a study of 63 patients with liver cirrhosis. A control group comprised of 30 age and gender-matched healthy persons. Serum cystatin C was determined in all study subjects and renal Doppler ultrasonography was made. Estimated glomerular filtration rate from serum creatinine (GFR(Cr)) and cystatin C (GFR(Cys)) was calculated. RESULTS: We confirmed significant differences in values of cystatin C between patients with different stages of liver cirrhosis according to Child-Pugh (P = 0.01), and a significant correlation with model of end stage liver disease (MELD) score (r(s) = 0.527, P lt 0.001). More patients with decreased glomerular filtration rate were identified based on GFR(Cys) than on GFR(Cr) (P lt 0.001). Significantly higher renal resistive index was noted in Child-Pugh C than in A (P lt 0.001) and B stage (P = 0.001). Also, a significant correlation between renal resistive index and MELD score was observed (r(s) = 0.607, P lt 0.001). Renal resistive index correlated significantly with cystatin C (r(s) = 0.283, P = 0.028) and showed a negative correlation with GFR(Cys) (r(s) = -0.31, P = 0.016). CONCLUSION: Cystatin C may be a more reliable marker for assessment of liver insufficiency. Additionally, cystatin C and renal resistive index represent sensitive indicators of renal dysfunction in patients with liver cirrhosis

The Clinical Importance of Cystatin C and Hepatic Artery Resistive Index in Liver Cirrhosis

Background: Data suggest cystatin C (CysC) levels and hepatic artery resistive index (HARI) correspond to the progression of chronic liver disease. We aimed to evaluate the clinical significance of these parameters in assessment of fibrosis in patients with liver cirrhosis. Methods: The cross-sectional study included 63 patients with liver cirrhosis. A control group consisted of 30 age- and gender-matched healthy persons. Results: We confirmed significantly higher values of CysC in patients with cirrhosis compared to control group (p = 0.036). Average value of HARI in the examined group was increased (0.72 +/- 0.06) and there was the statistically significant difference compared to controls (0.66 +/- 0.03) (p lt 0.001). We found statistically significant correlation between HARI and CysC in the study group. Analyzing the possibility of distinguishing healthy subjects from patients with fibrosis, we have found that the area under the curve is far greater in the HARI index than CysC. Comparison of CysC among Child-Pugh stages and correlation with a model for end-stage liver disease (MELD) score showed statistically significant results. Conclusion: We confirmed HARI is a more accurate parameter than CysC in discriminating healthy subjects from patients with fibrosis, while CysC could be a better indicator of the stage of liver cirrhosis

Damage of tubule cells in diabetic nephropathy type 2: Urinary N-acetyl-β-D-glucosaminidasis and γ-glutamil-transferasis

Background/Aim. A damage of tubular epithelial cells is followed by the release of cell enzymes and production of proinflammatory compounds, which lead to the tubulointerstitial damage. The aim of this study was to examine the function of renal tubules in the patients with diabetes mellitus type 2 (DM type 2) and the various proteinuria degrees, to establish the damage of the proximal tubule cells caused by DM type 2 by determining urinary N-acetyl-β-D-glucosaminidasis (β-NAG) and γ- glutamil-transferasis (γ-GT) activity in urine, as well as to compare the obtained results in the examined groups of patients with the values in the healthy examinees. Methods. A complete examination of renal function and selective enzymuria was performed in 37 patients with DM type 2, and 14 healthy examinees as the controls. The patients were divided in three groups according to the degree of proteinuria. The first group consisted of the patients with diabetes without microalbuminuria; the second one consisted of the patients with proteinuria of &lt; 300 mg/24 h, and microalbuminuria of &gt;20 mg/24 h, while the third one included the patients with proteinuria of &gt;300 mg/24 h. Results. In the patients with DM type 2 and the preserved global renal function, fractional excretion of sodium, potassium and phosphates, as well as renal threshold of phosphates concentration, were not sensitive parameters for discovering the damage of the renal tubule function. The determination of β-NAG activity proved to be the most sensitive parameter for early discovering of tubule cells damages. The difference among the examined groups was statistically highly significant. Conclusion. The increased presence of β-NAG in the urine of DM type 2 patients, pointed out an early tubular disorder and damage of cells, while γ-GT was a less sensitive indicator of this damage

Influence of proteinuria on the lipoprotein (a) metabolism disorder

Background/Aim. Proteinuria causes lipid metabolism abnormalities. The aim of the present study was to examine the influence of proteinuria on the lipoprotein (a) metabolism disorder. Methods. The study included 60 patients of the male-famele ratio (M : F = 32 : 28), mean age 37.15±9.85 years with, the average endogenous creatinine clearance 86.27±19.81 ml/min, and the average body mass index (BMI) 24.18±2.23 kg/m2. Regarding the level of glomerular proteinuria, the patients were divided into four groups. The first (control) group, with proteinuria levels less than 0.25 g/24h, included 15 patients (M : F = 6 : 9), mean age 34.66±4.82 years, the mean clearance of endogenous creatinine 99.70±12.94 ml/min, and mean BMI 23.28±3.50 kg/m2. The second group, with proteinuria between 0.25 and 1.0 g/24 h, includ 15 patients (M : F = 9 : 6) with primary glomerulonephritis, mean age 37.87±9.65 years, the mean clearance of endogenous creatinine 82.85±18.48 ml/min, and mean BMI 23.83±1.57 kg/m2. The third group include 15 patients (M : F = 8 : 7) with primary glomerulonephritis, with proteinuria between 1.0 and 3.0 g/24 h, mean age 35.67±13.29 years, the mean clearance of endogenous creatinine 82.85±18.48 ml/min, and mean BMI 23.83±1.57 kg/m2. The fourth group, with proteinuria higher than 3.0 g/24 h, included 15 patients (M : F = 9 : 6) with primary glomerulonephritis, mean age 40.40±9.75 years, the mean clearance of endogenous creatinine 80.16±20.80 ml/min, and mean BMI 24.83±1.44 kg/m2. In order to assess the influence of proteinuria on the lipoprotein (a) metabolism abnormalities we investigated 24-hour proteinuria, the colloid osmotic pressure (COP) of plasma, and the serum concentration of lipoprotein (a). The results were statistically analyzed using ANOVA, Kruscal-Wallis test, Mann-Whitney U test, χ2 test and Spearman test. Results. Statistically, the patients with proteinuria over 3.0 g/24 h had the significantly higher values of lipoprotein (a) in serum as compared to the control group, and the patients with proteinuria about 0.25-1.0 g/24 h. The patients with proteinuria between 1.0-3.0 g/24 h had the statistically significantly higher values of lipoprotein (a) in serum than the control group (proteinuria &lt; 0.25 g/24 h). There was a highly statistically significant negative correlation between serum albumin concentration, COP and the concentration of lipoprotein (a) in serum. There was a highly statistically significant positive correlation between 24-hour proteinuria and the concentration of lipoprotein (a) in serum. Conclusion. Proteinuria leads to the deterioration of lipoprotein (a) abnormalities

The influence of proteinuria on tubular transport of Na+, K+, CL

Functional and structural damages of tubulointerstitium are caused by proteinuria. The aim of this study was to assess the influence of different proteinuria levels on Na+, K+, Cl tubular transport. We examined 50 patients (24 males, 26 females), mean age 46.50 ± 13.08 years, with mean creati-nine clearence of 87.29 ± 31.17 mL/min. They were separated in three groups depending on proteinuria value. The first group with proteinuria less than 0.3 g/24h included 19 persons (7 males, 12 females), mean age 45.12 ± 13.28 years, with mean creatinine clearance of 94.27 ± 34.70 mL/min. The second group of 18 patients (8 males, 10 females), mean age 45.39 ± 12.64 years had proteinuria of 0.3-3,0 g/24h and mean creatinine clearance of 90.07 ± 31.89 mL/min. The third group had proteinuria level higher than 3.0g/24h and mean creatinine clearance of 73.25 ± 20.44 mL/min. It included 13 patients (9 males, 4 females), mean age 50.08 ± 13.73 years. As a parameter of proteinuria influence on tubular transport of Na+, K+ and Cl-, fractional excretion of these electrolytes, was studied. Student's T test, Mann Whitney U test and c2 test were used for statistical analysis. No statistically significant influence of proteinuria was found on Na+, K+ and Cl tubular transport

Effect of Long-term Topiramate Therapy on Serum Bicarbonate and Potassium Levels in Adult Epileptic Patients

Background: Topiramate (TPM) is a sulfamate-substituted monosaccharide that is structurally different from other antiepileptic drugs. TPM inhibits carbonic anhydrase activity, which is associated with loss of bicarbonate from the kidney and consequently metabolic acidosis or electrolyte imbalance. Objective: The objectives of the study were to investigate the influence of TPM therapy on bicarbonate and potassium levels in adult epileptic patients. Methods: Data were collected from 59 adult patients on monotherapy or co-therapy of TPM and other antiepileptic drugs. Serum bicarbonate and potassium levels were available from all patients. Steady-state TPM trough concentrations were determined in blood samples by high-performance liquid chromatography. Data analysis was performed by SPSS software (version 17, Chicago, IL). Results: Patients were divided into group A (duration of therapy shorter than or equal to 5 years) and group B (duration of therapy longer than 5 years). Significant difference (P lt 0.05) in serum bicarbonate levels was observed between these 2 groups. Bicarbonate levels were linearly related to the TPM therapy duration. No correlation was found between the TPM dose or patient age and bicarbonate or potassium levels, as well as between therapy duration and potassium level. Linear regression analysis showed no significant association among 54 available TPM trough concentrations and bicarbonate or potassium levels. Conclusions: Results highlight the frequent occurrence of lower bicarbonate level associated with prolonged TPM therapy. Monitoring bicarbonate levels in patients on long-term TPM therapy might be useful

Effect of Long-term Topiramate Therapy on Serum Bicarbonate and Potassium Levels in Adult Epileptic Patients

Background: Topiramate (TPM) is a sulfamate-substituted monosaccharide that is structurally different from other antiepileptic drugs. TPM inhibits carbonic anhydrase activity, which is associated with loss of bicarbonate from the kidney and consequently metabolic acidosis or electrolyte imbalance. Objective: The objectives of the study were to investigate the influence of TPM therapy on bicarbonate and potassium levels in adult epileptic patients. Methods: Data were collected from 59 adult patients on monotherapy or co-therapy of TPM and other antiepileptic drugs. Serum bicarbonate and potassium levels were available from all patients. Steady-state TPM trough concentrations were determined in blood samples by high-performance liquid chromatography. Data analysis was performed by SPSS software (version 17, Chicago, IL). Results: Patients were divided into group A (duration of therapy shorter than or equal to 5 years) and group B (duration of therapy longer than 5 years). Significant difference (P lt 0.05) in serum bicarbonate levels was observed between these 2 groups. Bicarbonate levels were linearly related to the TPM therapy duration. No correlation was found between the TPM dose or patient age and bicarbonate or potassium levels, as well as between therapy duration and potassium level. Linear regression analysis showed no significant association among 54 available TPM trough concentrations and bicarbonate or potassium levels. Conclusions: Results highlight the frequent occurrence of lower bicarbonate level associated with prolonged TPM therapy. Monitoring bicarbonate levels in patients on long-term TPM therapy might be useful

Vitamin D Is Inversely Related to Obesity: Cross-Sectional Study in a Small Cohort of Serbian Adults

Objective: Vitamin D (vitD) mediates numerous health conditions other than bone health and mineralization. Its role in cardiometabolic condition is still inconclusive. Methods: We conducted a cross-sectional study in 87 apparently healthy Serbian adults. We assessed their dietary intake, anthropometric and biochemical parameters, blood pressure, and vitD status (as serum 25-hydroxyvitamin D, 25(OH)D). Unexpectedly, the status was significantly higher in January than in July. Therefore, we pooled the data from two time points, to enhance the statistical power for carrying out association analyses. We employed linear regression models to evaluate the associations between vitD status and the obesity biomarkers of serum lipids and blood pressure. Results: Mean vitD intake of 3.85 +/- 4.71 mu g in the cohort was below recommended. Of the subjects in the pooled cohort, 60.58% were vitD deficient (with serum 25(OH)D below 50 nmol/L), with the majority of them being women who were overweight. VitD status tended to be inversely related to percent body fat and waist/height ratio in the crude regression model. After age and gender adjustment, the status was significantly related to waist circumference, waist/height ratio, and waist/hip ratio (beta = -0.116, 95% confidence interval [CI]: -0.206, -0.025, beta = -0.001, 95% CI: -0.001, 0.000, and beta = -0.001, 95% CI: -0.001, 0.000, respectively). These associations remained only within women. Fully adjusted models supported the notion of vitD being independently associated with central adiposity, regardless of age, gender, and total obesity. Conclusions: In apparently healthy adults with low vitD intake, vitD status was inversely associated with obesity parameters, pronouncedly in women. Our data support the need for development and implementation of public health policies on increasing vitD intake also as part of obesity management strategies