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Öğe The association between HbA1c levels and cardiovascular diseases in non-diabetic peritoneal dialysis patients(Oxford Univ Press, 2007) Dheir, Hamad; Toz, Huseyin; Asci, Gulay; Duman, Soner; Ertilav, Muhittin; Kircelli, Fatih; Sevinc, Ebru Gunay; Sipahi, Savas; Sezis, Meltem; Kose, Timur; Ok, Ercan; Ozkahya, MehmetÖğe Association of insulin resistance with arterial stiffness in nondiabetic peritoneal dialysis patients(Springer, 2012) Tatar, Erhan; Demirci, Meltem Sezis; Kircelli, Fatih; Gungor, Ozkan; Turan, Mehmet Nuri; Sevinc Ok, Ebru; Asci, Gulay; Ozkahya, Mehmet; Ok, ErcanInsulin resistance is a risk factor for cardiovascular morbidity and mortality in the general and end-stage renal disease populations. In this study, we investigated the association between insulin resistance and arterial stiffness in nondiabetic peritoneal dialysis (PD) patients. Fifty-three patients were enrolled. Patients were divided into 2 groups as homeostasis model assessment of insulin resistance (HOMA-IR) a parts per thousand currency sign2.97 (low) and > 2.97 (high). Carotid-femoral pulse wave velocity (c-f PWV) analysis and intima-media thickness of the carotid artery were measured. Mean age was 46 +/- A 12 years and HOMA-IR was 2.97 +/- A 1.77 (0.77-8.88). Mean c-f PWV was 7.6 +/- A 1.7 m/s. HOMA-IR was positively correlated with age, body mass index, and c-f PWV and negatively with serum HDL cholesterol and parathormone. In linear regression analysis, age and mean arterial pressure were predictors for c-f PWV. When patients were divided into 2 groups according to median age as a parts per thousand currency sign49 and > 50, mean arterial pressure, male gender, and age were predictors for c-f PWV in patients aged a parts per thousand currency sign49, whereas HOMA-IR was the only predictor for c-f PWV in patients aged > 50 years. Insulin resistance is an independent risk factor for arterial stiffness in PD patients older than 50 years. IR is not associated with carotid intima-media thickness.Öğe Associations of Triiodothyronine Levels with Carotid Atherosclerosis and Arterial Stiffness in Hemodialysis Patients(Amer Soc Nephrology, 2011) Tatar, Erhan; Kircelli, Fatih; Asci, Gulay; Carrero, Juan Jesus; Gungor, Ozkan; Demirci, Metem Sezis; Ozbek, Suha Sureyya; Ceylan, Naim; Ozkahya, Mehmet; Toz, Huseyin; Ok, ErcanBackground and objectives End-stage renal disease is linked to alterations in thyroid hormone levels and/or metabolism, resulting in a high prevalence of subclinical hypothyroidism and low triiodothyronine (T3) levels. These alterations are involved in endothelial damage, cardiac abnormalities, and inflammation, but the exact mechanisms are unclear. In this study, we investigated the relationship between serum free-T3 (fT3) and carotid artery atherosclerosis, arterial stiffness, and vascular calcification in prevalent patients on conventional hemodialysis. Design, setting, participants, & measurements 137 patients were included. Thyroid-hormone levels were determined by chemiluminescent immunoassay, carotid artery intima media thickness (CA-IMT) by Doppler ultrasonography, carotid-femoral pulse wave velocity (c-f PWV), and augmentation index by Sphygrnocor device, and coronary artery calcification (CAC) scores by multi-slice computerized tomography. Results Mean fT3 level was 3.70 +/- 1.23 pmol/L. Across decreasing fT3 tertiles, c-f PWV and CA-IMT values were incrementally higher, whereas CACs were not different. In adjusted ordinal logistic regression analysis, fT3 level (odds ratio, 0.81; 95% confidence interval, 0.68 to 0.97), age, and interdialytic weight gain were significantly associated with CA-IMT. fT3 level was associated with c-f PWV in nondiabetics but not in diabetics. In nondiabetics (11 = 113), c-f PWV was positively associated with age and systolic BP but negatively with fT3 levels (odds ratio = 0.57, 95% confidence interval 0.39 to 0.83). Conclusions fT3 levels are inversely associated with carotid atherosclerosis but not with CAC in hemodialysis patients. Also, fT3 levels are inversely associated with surrogates of arterial stiffness in nondiabetics. Clin J Am Soc Nephrol 6: 2240-2246, 2011. doi:10.2215/CJN.02540311Öğe Atorvastatin ameliorates morphological changes in encapsulated peritoneal sclerosis rat models(Oxford Univ Press, 2006) Sipahi, Savas; Sezak, Murat; Duman, Soner; Ozkan, Sultan; Sen, Sait; Ok, ErcanÖğe The benefit of salt restriction in the treatment of end-stage renal disease by haemodialysis(Oxford Univ Press, 2009) Kayikcioglu, Meral; Tumuklu, Murat; Ozkahya, Mehmet; Ozdogan, Oner; Asci, Gulay; Duman, Soner; Toz, Huseyin; Can, Levent H.; Basci, Ali; Ok, ErcanBackground. Most haemodialysis (HD) centres use anti-hypertensive drugs for the management of hypertension, whereas some centres apply dietary salt restriction strategy. In this retrospective cross-sectional study, we assessed the effectiveness and cardiac consequences of these two strategies. Methods. We enrolled all patients from two dialysis centres, who had been on a standard HD programme at the same centre for at least 1 year. All patients underwent echocardiographic evaluation. Clinical data were obtained from patients' charts. Centre A (n = 190) practiced 'salt restriction' strategy and Centre B (n = 204) practiced anti-hypertensive-based strategy. Salt restriction was defined as managing high blood pressure (BP) via lowering dry weight by strict salt restriction and insistent ultrafiltration without using anti-hypertensive drugs. Results. There was no difference regarding age, gender, diabetes, history of cardiovascular disease and efficiency of dialysis between centres. Antihypertensive drugs were used in 7% of the patients in Centre A and 42% in Centre B (P < 0.01); interdialytic weight gain was significantly lower in Centre A (2.29 +/- 0.83 kgversus 3.31 +/- 1.12 kg, P < 0.001). Mean systolic and diastolic blood pressures were similar in the two centres. However, Centre A had lower left ventricular (LV) mass (indexed for height(2.7): 59 +/- 16 versus 74 +/- 27 g/m(2.7), P < 0.0001). The frequency of LV hypertrophy was lower in Centre A (74% versus 88%, P < 0.001). Diastolic and systolic functions were better preserved in Centre A. Intradialytic hypotension (hypotensive episodes/100 patient sessions) was more frequent in Centre B (11 versus 27, P < 0.01). Conclusions. This cross-sectional study suggests that salt restriction and reduced prescription of antihypertensive drugs may limit LV hypertrophy, better preserve LV functions and reduce intradialytic hypotension in HD patients.Öğe Can strict volume control be the key for treatment and prevention of posterior reversible encephalopathy syndrome in hemodialysis patients?(Wiley-Blackwell, 2013) Gungor, Ozkan; Kircelli, Fatih; Kitis, Omer; Asci, Gulay; Toz, Huseyin; Ok, ErcanPosterior reversible encephalopathy syndrome (PRES) is a rare but if diagnosed late an irreversible disease. The majority of the patients present with severe hypertension, and effective blood pressure control is the mainstay of therapy. In this case report, we present three cases with PRES, treated successfully with strict volume control policy and propose that strict volume control policy may be a key element for the treatment of PRES.Öğe Can strict volume control be the key for treatment and prevention of posterior reversible encephalopathy syndrome in hemodialysis patients?(Wiley-Blackwell, 2013) Gungor, Ozkan; Kircelli, Fatih; Kitis, Omer; Asci, Gulay; Toz, Huseyin; Ok, ErcanPosterior reversible encephalopathy syndrome (PRES) is a rare but if diagnosed late an irreversible disease. The majority of the patients present with severe hypertension, and effective blood pressure control is the mainstay of therapy. In this case report, we present three cases with PRES, treated successfully with strict volume control policy and propose that strict volume control policy may be a key element for the treatment of PRES.Öğe Carbamylated LDL but not oxidized LDL is associated with atherosclerosis in uremic patients(Oxford Univ Press, 2006) Basnakian, Alexei G.; Apostolov, Eugene O.; Ok, Ercan; Yin, Xiaoyan; Altunel, Ekrem; Shah, Sudhir V.Öğe Carbamylated low-density lipoprotein induces monocyte adhesion to endothelial cells through intercellular adhesion molecule-1 and vascular cell adhesion molecule-1(Lippincott Williams & Wilkins, 2007) Apostolov, Eugene O.; Shah, Sudhir V.; Ok, Ercan; Basnakian, Alexei G.Objective - Carbamylated low-density lipoprotein (LDL), the most abundant modified LDL isoform in human blood, has been recently implicated in causing the atherosclerosis-prone injuries to endothelial cells in vitro and atherosclerosis in humans. This study was aimed at testing the hypothesis that carbamylated LDL acts via inducing monocyte adhesion to endothelial cells and determining the adhesion molecules responsible for the recruitment of monocytes. Methods and Results - Exposure of human coronary artery endothelial cells with carbamylated LDL but not native LDL caused U937 monocyte adhesion and the induction of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 adhesion molecules as measured by cell enzyme-linked immunosorbent assay. Silencing of intercellular adhesion molecule-1 by siRNA or its inhibition using neutralizing antibody resulted in decreased monocyte adhesion to the endothelial cells. Similar silencing or neutralizing of vascular cell adhesion molecule-1 alone did not have an effect but was shown to contribute to intercellular adhesion molecule-1 when tested simultaneously. Conclusions - Taken together, these data provide evidence that intercellular adhesion molecule-1 in cooperation with vascular cell adhesion molecule-1 are essential for monocyte adhesion by carbamylated low-density lipoprotein-activated human vascular endothelial cells in vitro.Öğe Carbamylated Low-Density Lipoprotein: Nontraditional Risk Factor for Cardiovascular Events in Patients With Chronic Kidney Disease(W B Saunders Co-Elsevier Inc, 2012) Apostolov, Eugene O.; Basnakian, Alexei G.; Ok, Ercan; Shah, Sudhir V.The high cardiovascular morbidity and mortality associated with chronic kidney disease (CKD) cannot be explained entirely by traditional risk factors. Urea spontaneously dissociates to form cyanate, which modifies proteins in a process referred to as carbamylation. Carbamylated low-density lipoprotein (cLDL) has been shown to have all of the major biological effects relevant to atherosclerosis, including endothelial cell injury, increased expression of cell adhesion molecules, and vascular smooth muscle cell proliferation. Recent studies indicate that cLDL leads to endonuclease G activation, which participates in cellular injury. In addition, cLDL has been shown to enhance generation of oxidants. Limited human data have demonstrated high levels of cLDL in hemodialysis patients, with the highest levels in patients who have atherosclerosis. In 2 separate clinical studies, plasma levels of carbamylated protein independently predicted an increased risk of coronary artery disease, future myocardial infarction, stroke, and death. Future prospective studies to examine the association and/or predictive value of cLDL and studies to establish cause-effect relationship in patients with CKD are needed. Published by the National Kidney Foundation, Inc.Öğe Carbamylated-Oxidized LDL: Proatherosclerotic Effects on Endothelial Cells and Macrophages(Japan Atherosclerosis Soc, 2013) Apostolov, Eugene O.; Ok, Ercan; Burns, Samuel; Nawaz, Safia; Savenka, Alena; Shah, Sudhir V.; Basnakian, Alexei G.Aim: Both oxidized LDL and carbamylated LDL are considered important for initiating atherosclerosis in patients with end-stage kidney disease through vascular endothelial cell dysfunction or injury. However their effects on each other and their relationship related to pro-atherosclerotic effects on endothelial cells and macrophages have not been investigated. In this study, we analyzed the competition between LDL carbamylation and oxidation, tested biological effects of carbamylated-oxidized LDL (coxLDL) toward the endothelial cells, assessed its ability to cause foam cell development, and determined the roles of scavenger receptors in this process. Methods: Cross-competition between carbamylation and oxidation of LDL particles was tested using cell-free fluorescent ligand-receptor assay. Pro-atherogenic properties (cell proliferation, cytotoxicity, and foam cell formation) of all LDL isoforms were tested in vitro and ex vivo using endothelial cells and peritoneal macrophages. In addition, coxLDL was assessed in human sera and in vivo atherosclerotic plaques which were developed in mouse model of uremia-induced atherosclerosis. Results: Our data suggest that there is potential competition between carbamylation and oxidation of LDL, and that oxidation is a much stronger inhibitor of carbamylation than vice versa. coxLDL is highly cytotoxic to endothelial cells and strongly induce their proliferation measured by DNA synthesis. All three tested LDL isoforms demonstrated strong ability for transformation of primary mouse peritoneal macrophages to foam cells using predominantly CD36 scavenger receptor. coxLDL was the most potent inducer of foam cell development and macrophages/foam cell injury assessed by cell count and TUNEL, respectively. Finally, LDL particles modified by oxidation and carbamylation were detected in blood and shown to co-localize in atherosclerotic plaques in mice. Conclusion: Our study demonstrated that LDL particles can be simultaneously carbamylated and oxidized and modifications are likely coexisting in the same LDL particle. We also demonstrated proatherosclerotic properties of coxLDL and proposed its role in atherosclerosis.Öğe Carbamylated-Oxidized LDL: Proatherosclerotic Effects on Endothelial Cells and Macrophages(Japan Atherosclerosis Soc, 2013) Apostolov, Eugene O.; Ok, Ercan; Burns, Samuel; Nawaz, Safia; Savenka, Alena; Shah, Sudhir V.; Basnakian, Alexei G.Aim: Both oxidized LDL and carbamylated LDL are considered important for initiating atherosclerosis in patients with end-stage kidney disease through vascular endothelial cell dysfunction or injury. However their effects on each other and their relationship related to pro-atherosclerotic effects on endothelial cells and macrophages have not been investigated. In this study, we analyzed the competition between LDL carbamylation and oxidation, tested biological effects of carbamylated-oxidized LDL (coxLDL) toward the endothelial cells, assessed its ability to cause foam cell development, and determined the roles of scavenger receptors in this process. Methods: Cross-competition between carbamylation and oxidation of LDL particles was tested using cell-free fluorescent ligand-receptor assay. Pro-atherogenic properties (cell proliferation, cytotoxicity, and foam cell formation) of all LDL isoforms were tested in vitro and ex vivo using endothelial cells and peritoneal macrophages. In addition, coxLDL was assessed in human sera and in vivo atherosclerotic plaques which were developed in mouse model of uremia-induced atherosclerosis. Results: Our data suggest that there is potential competition between carbamylation and oxidation of LDL, and that oxidation is a much stronger inhibitor of carbamylation than vice versa. coxLDL is highly cytotoxic to endothelial cells and strongly induce their proliferation measured by DNA synthesis. All three tested LDL isoforms demonstrated strong ability for transformation of primary mouse peritoneal macrophages to foam cells using predominantly CD36 scavenger receptor. coxLDL was the most potent inducer of foam cell development and macrophages/foam cell injury assessed by cell count and TUNEL, respectively. Finally, LDL particles modified by oxidation and carbamylation were detected in blood and shown to co-localize in atherosclerotic plaques in mice. Conclusion: Our study demonstrated that LDL particles can be simultaneously carbamylated and oxidized and modifications are likely coexisting in the same LDL particle. We also demonstrated proatherosclerotic properties of coxLDL and proposed its role in atherosclerosis.Öğe The change of mean platelet volume and mean platelet volume to platelet count ratio one year after iniation of peritoneal dialysis(2022) Özkahya, Mehmet; Ok, Ercan; Alataş, Zalal; Çeltik, Aygül; Seziş, Meltem; Aşçı, Gülay; Yılmaz, MümtazAim: Cardiovascular diseases are the most common cause of mortality in patients undergoing peritoneal dialysis. Thrombocyte indices which are indicators of platelet activation are predictors of cardiovascular events. We aim to examine the change in platelet count, mean platelet volume, and mean platelet volume to platelet count ratio one year after initiation of peritoneal dialysis in patients with end-stage renal disease. Materials and Methods: This retrospective study included 28 patients. Demographic and clinical characteristics of the patients at the time of initiation of peritoneal dialysis were recorded from the patient files. Laboratory data within the last month before the initiation of peritoneal dialysis and in the first year were recorded from the patient files. The mean platelet volume to platelet count ratio was calculated as mean platelet volume (femtolitres) divided by platelet count (number of thousand platelets/microliter). Results: The mean age was 51.1 ± 14.6 years, and 42.8% of the patients were male. Diabetic nephropathy and hypertensive nephropathy were the most common causes of end-stage renal disease. One year after the initiation of peritoneal dialysis, the urea level decreased significantly, and C-reactive protein level increased significantly. Platelet count increased from 240 ± 55 x10 3 /µL to 274 ± 53 x10 3 /µL (p=0.003) and mean platelet volume decreased from 10.7 ± 1.0 fl to 10.2 ± 0.8 fl (p<0.001). There was a significant decrease in mean platelet volume to platelet count ratio (p=0.001). Conclusion: Mean platelet volume and mean platelet volume to platelet count ratio, which are risk factors for cardiovascular diseases, decreases one year after initiation of peritoneal dialysis. This finding may be associated with the improvement of the uremic environment.Öğe Comparison of 4- and 8-h dialysis sessions in thrice-weekly in-centre haemodialysis(Oxford Univ Press, 2011) Ok, Ercan; Duman, Soner; Asci, Gulay; Tumuklu, Murat; Sertoz, Ozen Onen; Kayikcioglu, Meral; Toz, Huseyin; Adam, Siddik M.; Yilmaz, Mumtaz; Tonbul, Halil Zeki; Ozkahya, MehmetBackground. Longer dialysis sessions may improve outcome in haemodialysis (HD) patients. We compared the clinical and laboratory outcomes of 8- and 4-h thrice-weekly HD. Methods. Two-hundred and forty-seven HD patients who agreed to participate in a thrice-weekly 8-h in-centre nocturnal HD (NHD) treatment and 247 age-, sex-, diabetes status-and HD duration-matched control cases to 4-h conventional HD (CHD) were enrolled in this prospective controlled study. Echocardiography and psychometric measurements were performed at baseline and at the 12th month. The primary outcome was 1-year overall mortality. Results. Overall mortality rates were 1.77 (NHD) and 6.23 (CHD) per 100 patient-years (P = 0.01) during a mean 11.3 +/- 4.7 months of follow-up. NHD treatment was associated with a 72% risk reduction for overall mortality compared to the CHD treatment (hazard ratio = 0.28, 95% confidence interval 0.09-0.85, P = 0.02). Hospitalization rate was lower in the NHD arm. Post-HD body weight and serum albumin levels increased in the NHD group. Use of antihypertensive medications and erythropoietin declined in the NHD group. In the NHD group, left atrium and left ventricular end-diastolic diameters decreased and left ventricular mass index regressed. Both use of phosphate binders and serum phosphate level decreased in the NHD group. Cognitive functions improved in the NHD group, and quality of life scores deteriorated in the CHD group. Conclusions. Eight-hour thrice-weekly in-centre NHD provides morbidity and possibly mortality benefits compared to conventional 4-h HD.Öğe Comparison of biochemical nutritional parameters and bioimpedance indexes in hemodialysis patients(Oxford Univ Press, 2007) Demirci, Cenk; Adam, Siddik Momin; Ok, Ercan; Colak, Taskin; Caliskan, Nalan; Ulas, Hasibe; Sagdic, Alfert; Caliskan, Sihli; Kaplan, Hakan; Gurgen, Umit; Isik, Nurdan; Kircelli, Fatih; Ozkahya, MehmetÖğe Comparison of dialysates with and without glucose in hemodialysis patients(Oxford Univ Press, 2007) Asci, Gulay; Toz, Huseyin; Duman, Soner; Ozkahya, Mehmet; Sayin, Kerime; Kircelli, Fatih; Gunay, Ebru; Boydak, Can; Sipahi, Savas; Basci, Ali; Sever, Mehmet S.; Ok, ErcanÖğe Comparison of Turkish and US haemodialysis patient mortality rates: an observational cohort study(Oxford Univ Press, 2016) Asci, Gulay; Marcelli, Daniele; Celtik, Aygul; Grassmann, Aileen; Gunestepe, Kutay; Yaprak, Mustafa; Tamer, Abdulkerim Furkan; Turan, Mehmet Nuri; Sever, Mehmet Sukru; Ok, ErcanBackground: There are significant differences between countries in the mortality rates of haemodialysis (HD) patients. The extent of these differences and possible contributing factors are worthy of investigation. Methods: As of March 2009, all patients undergoing HD or haemodiafiltration for >3 months (n = 4041) in the Turkish clinics of the NephroCare network were enrolled. Data were prospectively collected for 2 years through the European Clinical Dialysis Database. Mean age +/- standard deviation was 58.7 +/- 14.7 years, 45.9% were female and 22.9% were diabetic. Comparison with US data was performed by applying an indirect standardization technique, using specific mortality rates for patients on HD by age, gender, race and primary diagnosis as provided by the 2012 US Renal Data System Annual Data Report as reference. Results: The crude mortality rate in Turkey was 95.1 per 1000 patient-years. Compared with the US reference population, the annual mortality rate for Turkey was significantly lower, irrespective of gender, age and diabetes. After adjustments for age, gender and diabetes, the mortality risk in the Turkish cohort was 50% lower than US whites [95% confidence interval (CI) 0.46-0.54, P < 0.001], 44% lower than US African-Americans (95% CI 0.52-0.61, P < 0.001) and 20% lower than Asian-Americans (95% CI 0.74-0.86, P < 0.05). Conclusions: The annual mortality rate of prevalent HD patients was found to be significantly lower in the studied Turkish cohort compared with that published by the US Renal Data System Annual Data Report. Differences in practice patterns may contribute to the divergence.Öğe The contribution of thyroid dysfunction on cardiovascular disease in patients with chronic kidney disease(Elsevier Ireland Ltd, 2013) Tatar, Erhan; Kircelli, Fatih; Ok, ErcanAccelerated atherosclerosis and arterial stiffness are the two leading causes of increased cardiovascular disease in patients with chronic kidney disease. Dysfunctional thyroid hormone metabolism has been suggested to play a role in atherosclerosis and arterial stiffness. Changes in cardiac contractility and output, myocardial oxygen demand, systemic and peripheral vascular resistance, blood pressure and lipid profile, increased inflammatory burden and endothelial dysfunction may be responsible for thyroid hormone-related cardiovascular disease. This article focuses on the mechanistic insights of this association and provides a concise review of the current literature. (C) 2012 Elsevier Ireland Ltd. All rights reserved.Öğe The contribution of thyroid dysfunction on cardiovascular disease in patients with chronic kidney disease(Elsevier Ireland Ltd, 2013) Tatar, Erhan; Kircelli, Fatih; Ok, ErcanAccelerated atherosclerosis and arterial stiffness are the two leading causes of increased cardiovascular disease in patients with chronic kidney disease. Dysfunctional thyroid hormone metabolism has been suggested to play a role in atherosclerosis and arterial stiffness. Changes in cardiac contractility and output, myocardial oxygen demand, systemic and peripheral vascular resistance, blood pressure and lipid profile, increased inflammatory burden and endothelial dysfunction may be responsible for thyroid hormone-related cardiovascular disease. This article focuses on the mechanistic insights of this association and provides a concise review of the current literature. (C) 2012 Elsevier Ireland Ltd. All rights reserved.Öğe Controversies and problems of volume control and hypertension in haemodialysis(Elsevier Science Inc, 2016) Ok, Ercan; Asci, Gulay; Chazot, Charles; Ozkahya, Mehmet; Mees, Evert J. DorhoutExtracellular volume overload and hypertension are important contributors to the high risk of cardiovascular mortality in patients undergoing haemodialysis. Hypertension is present in more than 90% of patients at the initiation of haemodialysis and persists in more than two-thirds, despite use of several antihypertensive medications. High blood pressure is a risk factor for the development of left ventricular hypertrophy, heart failure, and mortality, although there are controversies with some study findings showing poor survival with low-but not high-blood pressure. The most frequent cause of hypertension in patients undergoing haemodialysis is volume overload, which is associated with poor cardiovascular outcomes itself independent of blood pressure. Although antihypertensive medications might not be successful to control blood pressure, extracellular volume reduction by persistent ultrafiltration and dietary salt restriction can produce favourable results with good blood pressure control. More frequent or longer haemodialysis can facilitate volume and blood pressure control. However, successful volume and blood pressure control is also possible in patients undergoing conventional haemodialysis.