Tülay Akçay
Istanbul University
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Tülay Akçay.
Experimental Gerontology | 2001
Ufuk Çakatay; Aysegul Telci; Refik Kayali; Fatma Tekeli; Tülay Akçay; Ahmet Sivas
An increase in oxidative stress may contribute to the development of oxidative protein damage in the aging rat brain. In the present study, we investigated the relation between nitrotyrosine levels and other oxidative protein damage parameters such as protein carbonyl and protein thiol, as well as oxidative stress parameters such as total thiol, nonprotein thiol, and lipid hydroperoxides in the brain tissue of young, adult, and old Wistar rats. Brain nitrotyrosine levels of old rats were significantly decreased compared with those of young rats. Young and adult rats were not significantly different as far as these parameters were concerned, however, brain protein carbonyl and lipid hydroperoxide levels of old rats were significantly increased compared with those of young and adult rats. On the other hand, brain tissue total thiol, nonprotein thiol, and protein thiol levels of old rats were significantly decreased compared with those of young and adult rats. The strong correlation we found between protein carbonyl and lipid hydroperoxide levels indicates a striking relation between protein oxidation and lipid peroxidation in the aging brain tissue. The results of this study suggest that protein carbonyl formation is both a sensitive and a specific marker of brain aging. However, decreased nitrotyrosine levels in old rats, in contradiction to the expected, may be due to mechanisms other than oxidative protein damage in the aging rat brain.
Mutation Research | 2002
Yildiz Dincer; Tülay Akçay; Zeynep Alademir; Hasan Ilkova
The first aim of the present study was to examine the relationship between reduced glutathione (GSH) level, a powerful cellular antioxidant, and oxidative damage to DNA; and secondly, to see the effect of glycemic control on oxidative DNA damage in type 2 diabetics. We determined GSH level and, using the comet assay, formamidopyrimidine DNA glycosylase (Fpg)-sensitive sites which indicates oxidised guanine in freshly isolated blood from age-matched type 2 diabetics and controls. We found significant differences between men and women in the control group for both GSH and Fpg-sensitive sites. Therefore, we compared the controls and type 2 diabetics separately in men and women. GSH level of whole blood was found to be lower, Fpg-sensitive sites in leukocytes was found to be higher in the both type 2 diabetic men and women, as compared with their respective controls. When the diabetic group was divided into two groups as well-controlled diabetics and poorly-controlled diabetics with respect to glycosylated haemoglobine levels, it was found that Fpg-sensitive sites was significantly higher in the poorly-controlled diabetics than in the well-controlled diabetics in both the men and women. GSH level was lower in the poorly-controlled diabetics but not significantly. Fpg-sensitive sites were found to be moderately correlated with both glycosylated haemoglobine and GSH, and weakly correlated with glucose. Data indicate that decreased GSH level may be a contributory factor for enhanced oxidative DNA damage in type 2 diabetics; and chronic hyperglycemia derived from poorly-controlled diabetic conditions may induce oxidative DNA damage in these patients.
Clinical Biochemistry | 2003
Ufuk Çakatay; Aysegul Telci; Refik Kayali; Fatma Tekeli; Tülay Akçay; Ahmet Sivas
OBJECTIVES An increase in oxidative stress may contribute to the development of oxidative protein damage in the aging rat skeletal muscle. Our aim was to reveal protein carbonyl (PCO), advanced oxidation protein products (AOPP), a novel marker of oxidative stress, and protein thiol (P-SH) levels as markers of protein oxidation, as well as lipid hydroperoxide (LHP) levels as a marker of lipid peroxidation, and relation of nitrotyrosine (NT) levels with these markers in skeletal muscle tissue of young, adult, and old male Wistar rats. DESIGN AND METHODS In the present study, we investigated the relation between aging and oxidative protein damage parameters such as PCO, NT, AOPP, and P-SH, as well as oxidative stress parameters such as total thiol, nonprotein thiol, and LHP in the skeletal muscle tissue of young, adult, and old Wistar rats. RESULTS PCO and NT levels of old rats were significantly increased compared with those of young and adult rats. Skeletal muscle AOPP levels were significantly increased in old rats compared with those of adult rats. P-SH levels were significantly decreased in old rats compared with those of young rats. CONCLUSIONS The finding that the increase in PCO levels of young vs. old group was more significant than that of adult vs. old group may suggest that PCO formation is an early specific marker of aging process in skeletal muscle. In addition, increased levels of nitrotyrosine in the skeletal muscle of the old rat group may be a novel specific marker of oxidative protein damage in the aging muscle. The absence of correlation between oxidative protein damage markers mentioned above and LHP levels may indicate that protein oxidation and lipid peroxidation in the aging rat skeletal tissue are two distinct mechanisms.
Clinical Biochemistry | 2002
Yildiz Dincer; Zeynep Alademir; Hasan Ilkova; Tülay Akçay
OBJECTIVES The aim of the present study was to examine the susceptibility of glutathione (GSH) and glutathione related antioxidant enzymes to oxidation in type 2 diabetic patients with and without glycemic control. DESIGN AND METHODS Erythrocyte glutathione level and activities of glutathione peroxidase (G-Px), glutathione reductase (G-Red) and glutathione S-transferase (GST) in controls, well controlled and poorly controlled type 2 diabetics were measured by spectrophotometric assays before and after the incubation in vitro with H2O2. RESULTS GSH level, G-Px and G-Red activities decreased but GST activity increased in the erythrocytes from all the groups after the incubation with H2O2. Percentage of decrease in GSH was independent from glycemic control, whereas the percentage of decreases in G-Px and G-Red was related to glycemic control. The percentage of increase in GST was found to be independent from diabetes. CONCLUSIONS GSH and GSH-related antioxidant enzymes in human erythrocytes are susceptible to oxidation, particularly, G-Px and G-Red which were found to be more susceptible to oxidation in erythrocytes from poorly controlled type 2 diabetic patients.
Gynecologic and Obstetric Investigation | 2001
Serap Arıkan; Dildar Konukoglu; Çağan Arıkan; Tülay Akçay; İnci Davas
The present study was undertaken to determine the change of blood lipid peroxide and antioxidant status in healthy nonpregnant women (n = 20), pregnant women in the third trimester (n = 20), pregnant women during delivery (n = 26) and fetal cord blood. Plasma and erythrocyte malondialdehyde (MDA) levels were found to be significantly higher and erythrocyte glutathione (GSH) levels were significantly lower in pregnant women in the third trimester than in nonpregnant women (p < 0.02, p < 0.03 and p < 0.001, respectively). The highest plasma and erythrocyte MDA levels and the lowest GSH levels were obtained from the pregnant women during delivery (6.99 ± 2.35 nmol/ml, 283.20 ± 43.81 nmol/g Hb, 6.73 ± 2.34 µmol/g Hb, respectively). Erythrocyte glutathione peroxidase (GSH-P) and glutathione reductase (GSH-R) activities were not different between the groups. Maternal plasma and erythrocyte MDA levels were significantly correlated with cord blood plasma and erythrocyte MDA levels (r = 0.63, p < 0.001, and r = 0.41, p < 0.001, respectively). There was a significant positive correlation in GSH-R and in GSH-P activities between maternal and cord blood erythrocytes (r = 0.81, p < 0.001, and r = 0.79, p < 0.001, respectively). A significant correlation was found between maternal erythrocyte GSH-P and both cord blood erythrocyte GSH-R activities (r = 0.74, p < 0.001) and cord erythrocyte GSH levels (r = 0.73, p < 0.001). There was also a significant negative correlation between maternal erythrocyte MDA and cord erythrocyte GSH-R levels (r = –0.9, p < 0.001). Our results suggest that lipid peroxidation and antioxidant status may be changed during delivery, and these changes may affect the fetus by creating oxidative stress.
Mutation Research | 2003
Yildiz Dincer; Tülay Akçay; Hasan Ilkova; Zeynep Alademir; Gulsen Ozbay
We determined relationship among DNA damage, nitric oxide (NO) and antioxidant defense in leukocytes of patients with Type 1 DM. DNA damage was evaluated as strand breakage and formamidopyrimidine DNA glycosylase (Fpg)-sensitive sites by the comet assay in DNA from leukocytes of the subjects. Nitrite level, as a product of NO, superoxide dismutase (SOD) activity and glutathione peroxidase (G-Px) activity of the leukocytes were measured by spectrophotometric kits. Serum glucose level and glycosylated haemoglobin (HbA(1c)) were higher in the patients, as expected. Differences in measured parameters between controls and patients were assessed in men and women separately. There was no significant difference between patient and control groups in neither men nor women for nitrite level. Strand breakage and Fpg-sensitive sites were found to be increased, SOD and G-Px activities of the leukocytes were found to be decreased in both men and women of patient group as compared to their respective controls. Significant correlations were determined between strand breakage and HbA(1c) (r = 0.37, P<0.05); Fpg-sensitive sites and HbA(1c) (r = 0.59, P<0.01); Fpg-sensitive sites and glucose (r = 0.45, P<0.02); Fpg-sensitive sites and SOD (r = -0.48, P<0.02); HbA(1c) and SOD (r = -0.50, P<0.02). In conclusion, impaired antioxidant defense in leukocytes of patients with Type 1 DM may be one of the responsible mechanisms for increased DNA damage in those patients.
Clinical and Experimental Pharmacology and Physiology | 2002
Yildiz Dincer; Aysegul Telci; Refik Kayali; İlker Aydın Yilmaz; Ufuk Çakatay; Tülay Akçay
1. Oxidative damage has been suggested to be a contributory factor in the development and complications of diabetes. Recently, α‐lipoic acid (ALA) has gained considerable interest as an anti‐oxidant. Various studies have indicated the anti‐ oxidant effects of ALA and its reduced form dihydrolipoic acid. Therefore, it appears that these compounds have important therapeutic potential in conditions where oxidative stress is involved. The aim of the present study was to investigate the effect of ALA supplementation on lipid peroxidation and anti‐oxidant enzyme activities in various tissues in diabetic rats.
International Urology and Nephrology | 2003
İlker Aydın Yilmaz; Tülay Akçay; Ufuk Çakatay; Aysegul Telci; Süleyman Ataus; Veli Yalcin
DNA, protein oxidation and lipid peroxidation possess a major impact in carcinogenesis. Also, inflammatory and oxidative events have remarkable importance in bladder cancer. Thus, in this study total protein, protein carbonyl, nitrotyrosine, thiol residues, non-protein thiols, lipid peroxidation, and also, because of their relations to the above parameters, iron and iron binding levels have been investigated in patients with bladder cancer and in control group. Statistical evaluation of the results demonstrated significantly lower plasma protein levels in the patients with bladder cancer, as compared to the healthy control group. Serumiron levels in patients with invasive bladdercancer were found to be significantly lowerwhen compared with non-invasive group. Proteincarbonyl groups were remarkably higher inbladder cancer patients than in healthycontrols. Patients with bladder cancer weredemonstrated to have significantly lower levelsof total thiol groups and protein-bound thiolgroups as compared to healthy controls.Protein-bound thiol groups in patients withinvasive bladder cancer revealed a moresignificant decline, than in non-invasivegroup.
Urologia Internationalis | 2003
Tülay Akçay; Ilker Saygılı; Gülnur Andican; Veli Yalcin
Introduction: Reactive oxygen species-induced damage to DNA plays a major role in carcinogenesis. Methods: In order to estimate the level of oxidative damage in bladder cancer, 8-hydroxy-2′-deoxyguanosine (8-OHdG) was determined in DNA isolated from peripheral blood leukocytes of healthy adults and patients with superficial transitional cell carcinoma. Patients with transitional cell carcinoma of the bladder and control individuals were similar in age. In this study, the level of 8-OHdG in DNA in male subjects was measured by the high-performance liquid chromatography-electrochemical detector method. Results: The 8-OHdG levels in DNA from leukocytes of bladder cancer patients were significantly higher than those in controls. Conclusion: Reduction of oxidative stress is thought to be a very important measure for primary prevention of bladder cancer.
Journal of Toxicology and Environmental Health | 2000
Tülay Akçay; Yildiz Dincer; Refik Kayali; Umur Colgar; Engrin Oral; Ufuk Çakatay
A short-term evaluation of 6 months of estrogen therapy on oxidant status in 38 postmenopausal women was conducted. The levels of serum lipid peroxidation products, glutathione (GSH) status, and glutathione-related enzymes were evaluated before and after 6 months of hormone replacement therapy. After 6 months of estrogen treatment there was a significantly increased concentration of thiobarbituric acid-reactive substances (TBARS), which are an end product of lipid peroxidation. This was accompanied by a significant increase in the activity of glutathione peroxidase (GSH-Px). However, the activities of glutathione reductase (GSSG-R) and superoxide dismutase (SOD) were significantly decreased and total protein thiols were reduced. Data suggest that hormone replacement therapy in postmenopausal women is associated with oxidant mechanisms.