Joanna Stępniewska

Oxidative Stress and Antioxidative Enzyme Activities in Chronic Kidney Disease and Different Types of Renal Replacement Therapy

The incidence and diagnosis of chronic kidney disease (CKD) is on the rise all over the world. CKD is related to ageing of the society and high morbidity due to lifestyle diseases like diabetes, atherosclerosis, and hypertension. CKD is associated with increased oxidative stress generated by uremic toxicity, chronic inflammatory state, lack of vitamins and microelements, parenteral iron administration, and dialysis procedure itself. In terms of cellular physiology, erythrocytes and blood platelets in particular have effective enzymatic and non-enzymatic antioxidative system. The most efficient enzymatic antioxidants include superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glucose-6-phosphate dehydrogenase. Glutathione is the leading non-enzymatic free radical scavenger. In CKD, antioxidative defense is impaired and the abnormal activity of the enzymes and glutathione concentration is described in literature. The imbalance between the formation of reactive oxygen species and antioxidative system efficiency takes part in the pathogenesis of cardiovascular complications. It contributes to increased morbidity and mortality in patients with CKD. The severity of these processes depends on the type of renal replacement therapy; haemodialysis (HD) is more predisposing to such disorders than peritoneal dialysis (PD), or even conservative treatment. This can influence the outcome and the possibility of kidney transplantation. Moreover, the early function of kidney allograft seems to be dependent on perioperative antioxidative ability of platelets, which can play a potential protective role in kidney transplantation.

Does Glucose in Dialysis Fluid Protect Erythrocytes in Patients with Chronic Renal Failure

Background/Aims: The aim of this study was to assess the multifaceted influence of glucose present in dialyzing fluid on erythrocytes of patients with chronic renal failure (CRF) undergoing regular hemodialysis. Methods: A group of 44 subjects with CRF undergoing regular hemodialysis was studied. Two tests were used: osmotic fragility and resistance to the hemolytic agent saponin. The total content of isoprostane 8-iso-prostaglandin F2α type III (8-iPF2α-III) in plasma and erythrocyte’s membrane were determined by the ELISA method. Results: The presence of glucose in the dialysate is associated with lower intravascular hemolysis markers and high total 8-iPF2α-III concentrations in plasma. Conclusion: The presence of glucose in dialyzing fluid could protect erythrocytes. It limits hemolysis in patients with CRF, but, on the other hand, increases the oxidative processes. This kind of treatment along with other therapeutic intervention such as administration of antioxidants (e.g. α-tocopherol, ascorbic acid, N-acetylcysteine) could improve the condition of erythrocytes and outcome in CRF.

Insulin resistance and brain-derived neurotrophic factor levels in chronic kidney disease

Introduction: Insulin resistance is a frequent abnormality in chronic kidney disease (CKD) appearing in early stages. Factors known to promote insulin resistance in CKD patients include disorders of ion and acid–base equilibrium and circulating uremia toxins. Recent research has focused on the central nervous system as the source of the brain-derived neurotrophic factor (BDNF). The aim of our work was to study plasma BDNF concentrations in stage 3 and 4 CKD patients in relationship with insulin resistance and distribution of adipose tissue. Method: Plasma BDNF concentrations were measured in a study group of 31 patients, including a subgroup of 20 non-diabetic subjects. Additionally dual-energy X-ray absorptiometry (DXA) was performed. Homeostatic model assessment of insulin resistance (HOMA-IR) and homeostatic model assessment of B-cell function (HOMA-beta) indices were calculated. Results: Two separate analyses were performed. In the first analysis performed in all 31 CKD patients, there were no correlations between BDNF and: body mass index (BMI), android, gynoid fat distribution, HOMA-IR and HOMA-beta. In the second analysis performed in 20 CKD patients without diabetes, BDNF was negatively related to gynoid fat (Rs = −0.47, P = 0.034) and women revealed significantly lower levels of BDNF than men (P = 0.046). Normotensive patients disclosed significantly higher BDNF levels than hypertensive patients in the whole CKD group (P = 0.039) and in the non-diabetic subgroup (P = 0.028). No correlations between BDNF and eGFR were found. Conclusions: Female sex and arterial hypertension are associated with lower BDNF plasma concentration in CKD patients.

Prooxidative-Antioxidative Balance of Cells in Different Types of Renal Replacement Therapy

Background: Patients suffering from chronic kidney disease (CKD) are exposed to increased oxidative stress and disturbances manifesting in the enzymatic and non-enzymatic antioxidative defence system. The object of the research was to assess the differences between conservative treatment, peritoneal dialysis and haemodialysis in moderating cellular antioxidative agents. Methods: The group examined comprised 145 patients. The activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase were obtained using kinetic methods. The spectrophotometric method established the concentrations of reduced glutathione, albumin, uric acid, glucose, total protein and lipids. Results: The type of treatment determined significant changes in antioxidative enzyme activities and concentrations of non-enzymatic antioxidative compounds. Conclusions: Peritoneal dialysis provides better antioxidant protection than other types of therapy in CKD and should be considered as first-choice treatment despite more metabolic disorders.

The association of the Klotho polymorphism rs9536314 with parameters of calcium-phosphate metabolism in patients on long-term hemodialysis

Abstract Background: Patients on long-term hemodialysis frequently suffer from complications, such as secondary hyperparathyroidism, bone fractures, and arteriosclerosis. The process of regulating Ca/P metabolism depends on factors, such as FGF23 and Klotho. This study aimed to answer the question of whether the Klotho polymorphism rs9536314 is associated with FGF23 plasma concentration. Methods: In 118 patients undergoing hemodialysis, blood was collected before and after hemodialysis. The following parameters were measured in plasma: FGF23, serum: Ca, P, PTH, HGB, and iron concentrations. The KL gene polymorphism rs9536314 was identified by PCR-RFLP. Results: The KL polymorphism rs9536314 was not associated with Ca, P, PTH, or FGF23. There was a negative correlation between FGF23 and blood HGB levels and positive correlation between FGF23 and ESA dose. Conclusions: The results obtained may indicate that there is no association between the KL polymorphism and FGF23 concentration in patients undergoing long-term.

The Role of Klotho Protein in Chronic Kidney Disease: Studies in Animals and Humans.

The identification of Klotho gene was a major discovery as the gene encodes a protein regulating multiple functions. A defect in Klotho gene expression in mice results in a phenotype of premature aging including shortened life span, growth retardation, hypogonadism, skin and muscle atrophies, vascular calcification, cognition impairment, motor neuron degeneration and others. This phenotype is associated with phosphate balance disorders and underlines the major function of Klotho in mineral metabolism. As another 2 related paralogs were discovered (beta-Klotho, which is involved in bile acid and energy metabolism, and gamma-Klotho, with a yet to be defined function), this led to the revised naming of Klotho as alpha-Klotho. Two forms of alpha-Klotho protein have been reported: a membrane-bound and a soluble one. Membrane Klotho forms a complex with fibroblast growth factor (FGF) receptors and functions as an obligate co-receptor for the FGF-23 phosphatonin in distal tubules. The soluble form of Klotho seems to function as a humoral factor and regulates glycoproteins on the cell surface including ion channels and growth factors. There is data suggesting that soluble Klotho exerts phosphaturic effects independently of FGF-23. Circulating soluble Klotho is produced either by proteolytic cleavage of the extracellular domain of the transmembrane form by two membrane-anchored proteases (ADAM10 and ADAM17) or by alternative mRNA splicing. In animal models Klotho has been shown to exert pleiotropic actions, including cytoprotection, anti-oxidation, anti-apoptosis, protection of vasculature, promotion of angiogenesis and vascularization, inhibition of fibrogenesis and preservation of stem cells. The exact diagnostic and therapeutic role of Klotho in humans is not fully known yet. The article presents the role of Klotho in physiology and different stages of chronic kidney disease (CKD).

Bioactive lipids derived from arachidonic acid metabolism in different types of renal replacement therapy

INTRODUCTION Metabolism and plasma concentration of lipids and lipid-derived compounds play an important role in kidney physiology and pathological processes. The component of membrane phospholipids - arachidonic acid (AA) and its active derivatives - eicosanoids are involved in the development of hypertension, diabetes, inflammation and may contribute to progression of chronic kidney disease (CKD). The purpose of the study was to determine, whether the type of renal replacement therapy has an effect on eicosanoids metabolism. MATERIALS AND METHODS The study included 145 patients with CKD: on conservative treatment (n=68), on peritoneal dialysis (PD) (n=23) and undergoing chronic haemodialysis (HD) (n=54). The concentrations of TXB2, 20-HETE, 8-epi-PGF2α in platelet poor plasma (PPP) were determined using the ELISA method and 5-HETE, 12-HETE, 15-HETE were measured using the RP-HPLC. RESULTS The concentrations of TXB2 in HD group, both before (2.28±0.72ng/mL) and after (1.49±0.63ng/mL) haemodialysis treatment differed significantly from PD group (57.76±6.13ng/mL). Haemodialysis session led to the significant decrease in TXB2 plasma concentration (p=0.046). 20-HETE concentrations in HD group (113.55±107.54pg/mL and 199.54±142.98pg/mL before and after haemodialysis, respectively) were significantly higher than in CKD 3-5 group (8.96±12.66pg/mL) and PD group (47.78±34.07pg/mL). The highest concentration of 12-HETE was obtained in PD patients (3.58±3.99ng/mL) and differed significantly from HD group after haemodialysis (0.97±0.28ng/mL) and CKD3-5 group (1.06±0.52ng/mL). The concentrations of 5-HETE, 15-HETE and 8-epi-PGF2α-III did not differ significantly among examined groups. CONCLUSIONS The concentrations of active AA metabolites depend on the mode of renal replacement therapy and are associated with intensity of oxidative stress. They might be considered as potential indicators of kidney damage.

Atypical Renal Presentation in Severe Leptospirosis

Michał Małecki, Edyta Gołembiewska, Anna Maria Muraszko, Beata Fiecek, Magda Lewandowska, El _ zbieta Urasi nska, Joanna Stępniewska, Maciej Fijałkowski and Kazimierz Ciechanowski Department of Nephrology, Transplantology and Internal Medicine, Pomeranian Medical University, Szczecin, Poland; Laboratory of Rickettsiae, Chlamydiae and Spirochetes, National Institute of Public Health, Warsaw, Poland; and Department of Pathology, Pomeranian Medical University, Szczecin, Poland

Platelet - derived CD154 antigen in patients with chronic kidney disease

INTRODUCTION CD154 is a surface glycoprotein present on activated platelets, lymphocytes and mast cells. It mediates the transmission of information between cells and initiates an inflammatory response. The interaction of CD154 with its receptor CD40 leads to increase in concentrations of soluble forms of both molecules (sCD154, sCD40), which has an important prognostic value in cardiovascular complications. The metabolic disorders in chronic kidney disease (CKD), chronic inflammation, increased oxidative stress and type of renal replacement therapy may influence on the balance of sCD154/sCD40 in plasma and blood platelets. The purpose of the reasearch was to analyse the concentrations of sCD154 antigen and sCD40 receptor in platelet pure plasma (PPP) and platelet rich plasma (PRP) of patients with CKD treated conservatively, haemodialysed and on petitoneal dialysis. METHODS The group examined comprised 141 patients with chronic kidney disease: in pre-dialysis stage (n = 68), haemodialysed (n = 38) and on peritoneal dialysis (n = 35). The concentrations of sCD154 and sCD40 in PRP and PPP were determined with an ELISA method. The biochemical parameters were obtained using colorimetric method. RESULTS The concentrations of sCD154 and sCD40 in PPP and PRP in examined group were significantly different depending on the method of renal replacement therapy. The haemodialysis procedure caused a significant increase in sCD40 concentration in PRP. The concentrations of sCD40 and sCD154 were correlated with lipid parameters. CONCLUSIONS The type of renal replacement therapy influences on platelet activation which may be a factor contributing to increased cardiovascular complications in patients suffering from CKD.