Nephrinuria and podocytopathies

The discovery of nephrin in 1998 has launched a new era in glomerular diseases research, emphasizing its crucial role in the structure and function of the glomerular filtration barrier. In the past 20 years, substantial advances have been made in understanding podocyte structure and function as well as the discovery of several podocyte-related proteins including nephrin. The glomerular filtration barrier is comprised of podocytes, the glomerular basement membrane and endothelial cells. Podocytes, with their specialized slit diaphragm, form the essential backbone of the glomerular filtration barrier. Nephrin is a crucial structural and functional feature of the slit diaphragm that prevents plasma protein, blood cell and macromolecule leakage into the urine. Podocyte damage results in nephrin release. Podocytopathies are kidney diseases in which podocyte damage drives proteinuria, i.e., nephrotic syndrome. Many kidney diseases involve podocytopathy including congenital nephrotic syndrome of Finnish type, diffuse mesangial sclerosis, minimal change disease, focal segmental glomerulosclerosis, collapsing glomerulonephropathy, diabetic nephropathy, lupus nephropathy, hypertensive nephropathy and preeclampsia. Recently, urinary nephrin measurement has become important in the early detection of podocytopathies. In this chapter, we elaborate the main structural and functional features of nephrin as a podocyte-specific protein, pathomechanisms of podocytopathies which result in nephrinuria, highlight the most commonly used methods for detecting urinary nephrin and investigate the diagnostic, prognostic and potential therapeutic relevance of urinary nephrin in primary and secondary proteinuric kidney diseases.

Urinary Nephrin and Podocalyxin Levels as Predictors of Pre-eclampsia in High-Risk Pregnant Women

Introduction: Pre-eclampsia (PE) is characterized by new-onset hypertension and proteinuria. Damage of podocyte cells has been reported in pre-eclamptic women, thus podocyte specific proteins such as nephrin and podocalyxin could be useful biomarkers in PE.

Aim: To investigate the role of urinary nephrin (u-nephrin) and urinary podocalyxin (u-PDX) levels in predicting PE in women with a high-risk pregnancy.

Materials and methods: We included 101 pregnant women in this study and allocated them into three groups: group 1 included pregnant women at high risk of developing PE (n=41), group 2 - pregnant women with PE (n=30), and group 3 was the controls including healthy pregnant women (n=30). The inclusion criteria for women with PE were de novo hypertension >140/90 mm Hg, proteinuria >300 mg/24 hours, and presence of edema after 20 weeks of gestation, while the exclusion criteria were a history of renal diseases and pregnant women younger than 18. Inclusion criteria for the group of women with a high-risk pregnancy was gestational week >15, a history of PE in a previous pregnancy, pre-existing diabetes type 1 or 2, pre-existing hypertension, multiple gestations, prior placental abruption, obesity women, nulliparity, maternal age >35 years, and a family history of PE. The study was conducted from March 2016 to May 2017 in the Medical Faculty at the Institute of Medical and Experimental Biochemistry in Skopje. Urine samples were used to measure the nephrin and podocalyxin levels using immunoenzyme assay, creatinine and microalbumin. Blood samples were collected for biochemical analyses.

Results: U-nephrin levels were elevated in 96.7% of women with PE, and 73% of women with a high-risk pregnancy. U-PDX levels were elevated in 63% of the women with PE and 100% of the women with a high-risk pregnancy. U-nephrin and u-PDX levels were significantly increased in women with a high-risk pregnancy and women with PE compared with a control group (p<0.001). A significant difference was found between the subgroups of pregnant women classified according to gestational age in their u-nephrin and u-PDX levels. There was a significant positive correlation between the levels of both markers and glomerular filtration rate, and significant negative correlation between the levels of both markers and gestational age. ROC analysis revealed that the cut-off value of 304.6 ng/ml of u-nephrin had a sensitivity (Se) of 96.7%, specificity (Sp) of 96.7% (for both Se and Sp 95% confidence interval (CI) 82.8-99.9), while the cut-off value of 59.5 ng/ml of u-PDX had a sensitivity of 100% and Sp of 93.3% (Se - 95% CI 88.4-100, Sp - 95% CI 77.9-99.2), in distinguishing women with PE and healthy pregnancies. Both markers showed excellent clinical utility (CUI&ge;0.81), for u-nephrin (CUI+ and CUI&minus; is 0.934), for u-PDX (CUI+ is 0.938; CUI&minus; is 0.933).

Conclusions: U-nephrin and U-PDX levels could be useful as predictors of PE in women with a high-risk pregnancy.

Role of urinary podocalyxin in early diagnosis of diabetic nephropathy

Introduction. Podocyte injury has been reported as an early feature of DN therefore, the assessment of podocyte injury can be accomplished by estimation of podocalyxin in urine. This study aimed to estimate the urinary podocalyxin levels and to determine the sensitivity and specificity of this biomarker for early detection of DN.Materials and methods. A total of 90 patients with type 2 diabetes mellitus (T2DM) were included in this cross-sectional study. Sixty of them were without diagnosed DN, and 30 with diagnosed DN. A control group consisted of 30 healthy subjects. All patients with T2DM were divided into three subgroups according to urinary microalbumin/creatinine ratio (UM/CR): normoalbuminuric, microalbuminuric and macroalbuminuric patients. Urine samples, were used for measurement of podocalyxin by ELISA, creatinine and microalbumin. Fasting venous blood samples was collected for biochemical analyses.Results. The levels of urinary podocalyxin (u-PDX) were higher in patients with T2DM compared to control subjects and a statistically significant difference among studied subgroups regarding u-PDX was found (p < 0.05). Levels of u-PDX are increasing gradually with the degree of DN (p < 0.029). u-PDX levels were positively correlated with UM/CR (r = 0.227, p = 0.002). A cut-off level of 43.8 ng/ml u-PDX showed 73.3% sensitivity and 93.3% specificity to detect DN in early stage. A cut-off level of 30 mg/g UM/CR showed 41.5% sensitivity and 90% specificity in predicting DN. u-PDX was elevated in 48,2% of normoalbuminuric patients.Conclusion. Urinary podocalyxin be useful and more sensitive and specific marker in early detection of DN than microalbuminuria.

Patient's knowledge and awareness about the effect of the over-the-counter (OTC) drugs and dietary supplements on laboratory test results: a survey in 18 European countries

Background Nowadays over-the-counter (OTC) drugs and dietary supplements are widely used. Their use can have a significant impact on the validity of laboratory results. The aim of this multicenter European study was to determine the frequency of consumption of various dietary products and OTC drugs among patients and explore their level of knowledge and awareness about the potential impact of various products on laboratory test results. Methods Eighteen European countries participated in this study. The survey was carried out anonymously on a subsequent series of outpatients (n=200) in each participating country. Included were patients who were referred to the laboratory for blood sampling and who voluntarily agreed to participate in the study. The survey included questions about the frequency of consumption of various products, awareness of the importance of informing physicians and laboratory staff about it and information about influence of preanalytical factors in general on laboratory test results. Results In total, 68% of patients were regularly taking at least one OTC drug or dietary supplement. The frequency of patients consuming at least one OTC drug or dietary supplement differed between countries (p=0.001). Vitamins (38%), minerals (34%), cranberry juice (20%), acetylsalicylic acid (ASA) (17%) and omega fatty acids (17%) were the most commonly used in our study. Conclusions The use of various OTC drugs and dietary supplements is highly prevalent in Europe and patients are often not willing to disclose this information to the laboratory staff and ordering physician. The education of both patients and healthcare staff is needed.

Lipoprotein(a) – Link between Atherogenesis and Thrombosis

Lipoprotein(a) – Lp(a) – is an independent risk factor for cardiovascular disease (CVD). Indeed, individuals with plasma concentrations of Lp(a) > 200 mg/l carry an increased risk of developing CVD. Circulating levels of Lp(a) are remarkably resistant to common lipid lowering therapies, currently available treatment for reduction of Lp(a) is plasma apheresis, which is costly and labour intensive. The Lp(a) molecule is composed of two parts: LDL/apoB-100 core and glycoprotein, apolipoprotein(a) – Apo(a), both of them can interact with components of the coagulation cascade, inflammatory pathways and blood vessel cells (smooth muscle cells and endothelial cells). Therefore, it is very important to determine the molecular pathways by which Lp(a) affect the vascular system in order to design therapeutics for targeting the Lp(a) cellular effects. This paper summarises the cellular effects and molecular mechanisms by which Lp(a) participate in atherogenesis, thrombogenesis, inflammation and development of cardiovascular diseases.

Nephrin and Podocalyxin - New Podocyte Proteins for Early Detection of Secondary Nephropathies

In the last two decades a great progress was observed in understanding of podocytes, their specific structure and function identifying many specific podocyte proteins, such as nephrin and podocalyxin. Podocytes form the final barrier to plasma proteins leakage. Nephrin as a main component of the filtration diaphragm forms a physical barrier while podocalyxin as sialoglycoprotein forms an electrostatic barrier. Podocyte damage, i.e. podocytopathies and their loss through urine-podocyturia, are crucial in pathogenesis and progression of nephropathies with proteinuria as main clinical manifestation. In podocytopathies, nephrin and podocalyxin appear in the urine before proteinuria and microalbuminuria which were previously considered as earliest markers of nephropathies. Nephrinuria and podocalyxuria indicate damage of the podocytes on glomerular level and/or presence of apoptotic and necrotic podocytes in urine. These urinary markers are also important in early diagnosis of secondary nephropathies such as diabetic, lupus and hypertensive nephropathy as the most common causes of end-stage renal failure (ESRF). These markers are also important in the prediction of preeclampsia, which is the most common complication in pregnancy. In this review we elaborate in dept the main structural and functional features of podocytes and their specific proteins, nephrin and podocalyxin, summarizing the recent literature data on their importance in the early diagnosis of the most common secondary nephropathies.

Cholesteryl ester transfer protein, low density lipoprotein particle size and intima media thickness in patients with coronary heart disease

Cholesteryl ester transfer protein (CETP) plays a key role in reverse cholesterol transport and high density lipoprotein (HDL) metabolism. Predominance of small, dense LDL particles is associated with an increased risk of atherosclerosis and coronary heart disease (CHD).The aim of the study was to determine the potential relationship between the CETP concentration and low density lipoprotein (LDL) particle size and their association with intima media thickness (IMT) in patients with CHD. Lipid parameters, CETP concentration and LDL particle size were determined in 100 healthy subjects (control group) and in 100 patients with CHD, aged 43 to 77 years. Plasma CETP concentrations were measured by an enzyme-linked immuno-sorbent assay with two different monoclonal antibodies. LDL subclasses were separated by nondenaturing polyacrilamide 3-31% gradient gel electrophoresis. CETP concentration was higher in patients compared to controls (2.02 ± 0.75 mg/ml vs. 1.74 ± 0.63 mg/ml, p<0.01). Mean LDL particle size (nm) was significantly smaller in patients than in controls (24.5 ± 1.1 vs. 26.1 ± 0.9; p<0.001). There was no relation between LDL particle size and CETP concentration (r=-0.1807, p=0.072). Age, diastolic blood pressure, CETP concentration and LDL particle size were independent factors for determing IMT by multiple linear regression analysis. They accounted for 35.2 % of the observed variability in IMT. CETP is not an independent contributor of LDL particle size. CETP might play a role in determining lipoprotein distributions, but did not seem to be the sole factor in the formation of small LDL particles.

Effect of clofibrate on the enzymes associated with oxidative stress in Wistar rat liver

BACKGROUND

A diversity of endogenous and exogenous compounds have been demonstrated to cause proliferation of peroxisomes and variety of associated effects in rodents. The aim of our study was to see the effect of clofibrate on the enzymes associated with oxidative stress.

METHODS

Male Wistar rats weighting 250-350 g were treated with clofibrate in a dose of 250 mg/1000 g/ 24 h for 12 days. Whole liver homogenates and subsequent subcellular fractions wrere proceeded for enzyme measurements by spectrophotometric methods.

RESULTS

The activity of hydrogen producing enzymes D-aminoacid oxidase, Urate oxidase and Palmitoyl CoA oxidase was statistically significantly increased in the treated group in comparison with the control one. On the contrary to the massive increase of the Palmitoyl CoA oxidase--a marker enzyme for peroxisomal proliferation, there was only a limited increase of catalase (which inactivates hydrogen peroxide) activity. On the other hand superoxide dismutase and glutathione peroxidase activities in experimental group were down regulated in the treated group.

CONCLUSION

Our results support the hypothesis that clofibrate (peroxisomal proliferators) application might produce oxidative stress in rat livers (Tab. 2, Fig. 8, Ref. 56) Full Text (Free, PDF) www.bmj.sk.

Lipoprotein (a) and apolipoprotein (a) phenotypes in healthy Macedonian children

BACKGROUND

Plasma levels of lipoprotein(a) [Lp(a)] are determined largely by genetic variation in the gene encoding apolipoprotein(a) [apo(a)], the unique protein component of Lp(a). High plasma levels of Lp(a) increase the risk of premature atherosclerosis. However, the association of apo(a) phenotypes with the development of these diseases remains largely unexplored.

OBJECTIVES

Determination of Lp(a) levels and apo(a) isoforms (phenotypes) in 100 (51 boys, 49 girls) Macedonian healthy children aged 9-18.

METHODS

We used 3-15 % gradient SDS-PAGE for separation of apo(a) isoforms. According to the different apo(a) electrophoretic mobilities, Apo(a) was classified into five single and respective double-band phenotypes.

RESULTS

Each individual expressed a single (homozygotic), double-band (heterozygotic) or no band (null phenotype). The apo(a) phenotype frequencies revealed that the frequency of single-band phenotype expression (64 %) was higher than that of double bands (32 %) and that the frequency of phenotypes representative of low molecular weight was very low (4%). The most frequent phenotype was S4 (42.65%). The distribution of plasma Lp(a) levels was skewed, with the highest frequencies at low levels. The mean Lp(a) concentration was 11.95 (SD of 5.98 and median of 9.62 mg/dL). We did not find differences in the mean and median plasma Lp(a) levels between boys and girls (p > 0.05). A strong inverse relationship was found between the apparent molecular weight of apo(a) phenotypes and plasma Lp(a) concentration (r = -0.4257).

CONCLUSIONS

Determination of Lp(a) levels and apo(a) phenotypes in children, may help in preventing and reducing the risk of atherosclerotic development (Tab. 6, Ref 32). Full Text (Free, PDF) www.bmj.sk.

Erythrocyte antioxidant enzymes in patients with alcohol dependence syndrome

BACKGROUND

The role of free radicals and hydrogen peroxides in the metabolism and toxicity of alcohol is supported by many studies, therefore, many autors have tried to use the enzymes, metabolizing highly reactive chemical compounds as biological markers of alcoholism.

METHODS

Erythrocyte antioxidant enzymes were measured in 37 male patients with alcohol dependence syndrome, without severe liver disease, aged between 18 and 59 years, with different duration (years) of alcohol abuse.

RESULTS

Superoxide dismutase (SOD) activity was statistically significantly increased in alcoholics. Glutathione peroxidase (GPX) activity has shown no significant difference in alcoholics compared to the control group. Catalase (CAT) activity was significantly decreased in alcoholics. Specific activity of CAT was positively correlated with the duration of alcohol abuse (years).

CONCLUSIONS

Catalase activity has shown statistically significant decrease in patients with alcohol dependence syndrom. (Tab. 3, Fig. 4, Ref: 31.)

Distribution of low density lipoprotein subclasses in Macedonian children

BACKGROUND

Current reports claim that small and dense LDL particles are more atherogenic than larger LDL particles. There are many studies presenting LDL subclass distribution in adults, but there is not enough data regarding children in the literature on this problem. The aim of our study was to examine LDL subclass distribution in healthy children in the Republic of Macedonia.

MATERIALS/METHODS

Plasma LDL subclasses in 100 children aged 9-18 years were analyzed using non-denaturing polyacrilamide gradient (3-31%) gel electrophoresis. Conventional plasma lipid and apoprotein parameters thought to be related to LDL size were determined as well.

RESULTS

The results obtained showed the prevalence of large LDL subclasses (phenotype A) in 89% of the children, whereas small LDL subclasses (phenotype B) were observed in 11%. The mean LDL size was 26.37 +/- 0.68 nm, and there was no difference between gender groups. No association was noted between LDL size and plasma lipid and apoprotein levels, age, or BMI.

CONCLUSIONS

LDL size and distribution is not gender- or age-dependent, or influenced by plasma lipid and apoprotein concentrations in childhood. This suggests that analysis of LDL subclass phenotype may provide better information on the risk of atherosclerosis development in adulthood.

Reference intervals of Apo A-1 , Apo B and Apo B/Apo A-1 ratio in sample of macedonian population

The disorders of serum concentration of Apolipoproteins A-1 and B (Apo A-1 and Apo B), as well as of Apolipoprotein B/Apoliporotein A-1 ratio (Apo B/ Apo A-1) are considered to be independent risk factors for coronary heart disease. It is recommended that each laboratory should asign its own reference intervals for Apo A-1 and Apo B, as well as for Apo B/Apo A-1 ratio, as these depend on the geographical location. For this purpose we determined the serum concentration of Apo A-1 and Apo B and we calculated the Apo B/Apo A-1 ratio in 122 healthy individuals from Macedonian population (70 women and 52 men), aged 18-60 years. We used commercial, standardized manual immunoturbidimetric assay (Randox). The obtained concentrations (x ± SD) were: Apo A-1 = 1.39 ± 0.28 g/l in the female population and 1.42 ± 0.27 g/l in the male population, Apo B = 0.95 ± 0.24 g/l in the female and 1.00 ± 0.23 g/l in the male population. The calculated Apo B/Apo A-1 ratio was 0.70 ± 0.17 in the female subgroup and 0.72 ± 0.18 in the male subgroup. Student's t-test detected no significant difference (p>0.05) in mean values for Apolipoproteins A-1 and B and for Apo B/Apo A-1 ratio between female and male subgroups, which lead to the conclusion that division according to sex is not necessary from diagnostic point of view. The Apo A-1 and Apo B concentrations estimated for the mixed group (N=122) were 1.40 ± 0.28 g/l and 0.97 ± 0.23 g/l. The Apo B/Apo A-1 ratio estimated for whole group was 0.71 ± 0.17. The type of distribution of values for Apo A-1, Apo B and Apo B/A-1 ratio was tested by calculating the values of coefficient of asymetry (Skewness), coefficient of flatness (Kurtosis) and standard deviations of these coefficients. The distribution of values was according to Gaussian curve for all three parameters. Therefore, according to the normal distribution reference intervals for Apo A-1, Apo B and Apo B/Apo A-1 ratio was estimated parametrically (mean ± 2 standard deviations). Reference intervals for Apo A-1 were 0.84 - 1.96 g/l, 0.51 - 1.43 g/l for Apo B and 0.37- 1.05 for Apo B/Apo A-1 ratio.