Gönül Şahin

Oxidative stress and nitric oxide related parameters in type II diabetes mellitus: effects of glycemic control

OBJECTIVES The aim of this study is to investigate the status of oxidative stress and nitric oxide related parameters in type II diabetes mellitus (DM) patients in which heart disease, atherosclerosis, retinopathy, and nephropathy commonly occur, and also to determine the effect of glycemic control on these parameters. DESIGN AND METHODS Erythrocyte copper zinc-superoxide dismutase (CuZn-SOD), erythrocyte and plasma selenium dependent glutathione peroxidase (Se-GPx), erythrocyte catalase (CAT) activities, erythrocyte and plasma thiobarbituric acid reactive substances (TBARS) levels; nitrite/nitrate (NO(2)(-)/NO(3)(-)), cyclic guanosine monophosphate (cGMP) and nitrotyrosine levels in plasma of type II DM patients were measured. RESULTS Erythrocyte CuZn-SOD activities in type II DM were significantly higher than those of the control subjects (p < 0.05). TBARS levels in type II DM were significantly higher than the control subjects (p < 0.001). Plasma NO(2)(-)/NO(3)(-) levels in type II DM patients both during poor glycemic control and after three months of oral antidiabetic treatment were significantly higher than those of the control subjects (p < 0.001). Plasma cGMP levels in type II DM patients during poor glycemic control were significantly lower than those of control subjects (p < 0.001). CONCLUSION These results indicate that oxidative status and nitric oxide metabolism are affected in type II DM patients. We found high CuZn-SOD activity in type II DM patients. This increased activity could not protect the patients against the reactive oxygen species (ROS), since lipid peroxidation (defined by erythrocyte and plasma TBARS levels) still occurs in DM patients. After the therapy with oral antidiabetic agents for three months, erythrocyte SE-GPx and CAT activities were found to be decreased below the control values. Our results suggested that the low cGMP levels in the study may be a good marker of endothelium dysfunction in DM.

Effects of some probable antioxidants on selenite-induced cataract formation and oxidative stress-related parameters in rats

The effect of several natural and synthetic compounds on selenite-induced cataract was investigated in rat pups. Simultaneous determination of glutathione S-transferase (GST), selenium dependent glutathione peroxidase (Se-GPx), catalase (CAT), superoxide dismutase (SOD) activities and malondialdehyde (MDA) levels were carried out in the lens, erythrocyte and plasma. The results showed that propolis, diclofenac, vitamin C (Vit-C) and quercetin prevented cataract formation to the extent of 70, 60, 58.4, and 40%, respectively. Standardized extract of Ginkgo biloba (Egb 761) did not affect the cataract formation. Selenite treatment caused a significant decrease in the activity of erythrocyte SOD. This was accompanied by a simultaneous increase in the levels of MDA either in lens and in plasma. A significant increase was shown in erythrocyte GST (substrate ethacrynic acid; eaa), and GPx activities and lens GST (substrate chlorodinitro benzene; cdnb) activity. Antioxidant treatment caused significant changes in enzyme activities and MDA levels. There was no effect of selenite and antioxidants on total body weight increase during the course of the study. Blood parameters did not correlate to lens parameters following selenite treatment. Our results suggest that antioxidant supplementation following selenite exposure may prevent the cataract formation and may enhance antioxidant defence of blood and lens.

Exposure of newborns to aflatoxin M1 and B1 from mothers' breast milk in Ankara, Turkey

Aflatoxins (AFs) are important risks for human health due to their widespread presence in foods and environment. However, contamination risk of breast milk with different pollutants including AFs is high in todays life conditions. Since breast milk is a major nutrient for infants, feeding of infants with safe milk is essential. Therefore, the objective of this study was to determine the levels of AF M(1) and B(1) in breast milk samples collected from 75 mothers in Ankara, Turkey. AF M(1) and B(1) levels were investigated by high performance liquid chromatography (HPLC) with a fluorescence detector following an extraction procedure. The limit of detection was found to be 5 ng/l. Both AFs were detected in diverse degrees in all breast milk samples: The level of AF M(1) were in the ranges of 60.90-299.99 ng/l, and AF B(1) were in the ranges of 94.50-4123.80 ng/l. These results pointed out the exposure of mothers and neonates to AF M(1) and B(1), and the necessity of further research on mycotoxin contamination both in foods and biological fluids as well as protection strategies.

In vitro effects of NSAIDS and paracetamolon oxidative stress-related parameters of human erythrocytes

In vitro effects of widely used nonsteroidal antiinflammatory drugs (NSAIDs) and paracetamol were studied on oxidative stress-related parameters of human red blood cells (RBC). Membrane lipid integrity, activity of erythrocyte antioxidant enzymes; i.e. glutathione S-transferase (GST), selenium dependent-glutathione peroxidase (Se-GPx), and catalase (CAT), and hemolytic/stabilizing action of the drugs on erythrocyte membrane were assessed. Diclofenac, indomethacin and paracetamol at the therapeutic and higher concentrations, and dipyrone at the high concentration exerted a statistically significant inhibition on H2O2 forced erythrocytic membrane lipid peroxidation (EMLP). Increased hemolysis was observed by Na-salicylate, naproxen and ketorolac at therapeutic and higher concentrations, and by diclofenac and tiaprofenic acid at high concentrations, while the others seemed to stabilize the membrane at the same conditions. Na-salicylate inhibited GST activity at the therapeutic dose, however activated the same enzyme at high concentrations. Naproxen, tiaprofenic acid and piroxicam caused a decrease in GST activity at therapeutic doses. Paracetamol caused an activation at a high dose. Tiaprofenic acid, ketorolac, naproxen and piroxicam caused a significant Se-GPx inhibition. Erythrocyte CAT activity was increased by Na-salicylate, acemetacin, and tenoxicam at the therapeutic, and by dipyrone at the high concentration. Our results suggest that NSAIDs and paracetamol may be involved in oxidative/antioxidative processes of human erythrocytes. Also, the in vitro EMLP method can be considered as a simple test for evaluating possible antioxidant potency of chemicals.

Urinary neopterin excretion and dihydropteridine reductase activity in rheumatoid arthritis

Abstract Neopterin and biopterin are two products of the pteridine pathway. Even though their roles and interrelationships have not been exactly clarified, neopterin is known as a biomarker of cell-mediated immunity. In this case, the highly elevated neopterin levels are parallel to the slightly elevated biopterin levels. On the otherhand, the reduced form of biopterin-tetrahydrobiopterin is an essential cofactor of aromatic monoxygenases that leads to synthesis of tyrosine, tryptophan and dopamine neurotransmitters and its concentration in body fluids and tissues is maintained by the enzyme dihydropteridine reductase (DHPR). Increased numbers of activated lymphocytes can be found in peripheral blood, in the synovial fluid and synovial membranes or patients with rheumatoid arthritis (RA). Since the present study was undertaken to evaluate the role of the pteridine pathway in RA, we measured urine neopterin levels and dried blood DHPR activities in 36 patients with RA and in 20 healthy volunteers, in parallel with other clinical parameters. We found that neopterin excretion was significantly increased in RA patients compared with controls. The means were 433±216, 153±43 and 111±34 μmol/mol creatinine for patients in active stage, in remission and controls, respectively. Our results suggest that urine neopterin levels were strongly dependent on the stage and activity of RA. Either as an effect of the disease itself or of drug administration, slightly reduced DHPR activities were detected (3.484± 0.304 for control, 2.974±0.255 in active stage RA, and 3.048±0.302 red cytochrome C/min/5 mm disc in remission).

Determination of seasonal variations in serum ochratoxin A levels in healthy population living in some regions of Turkey by enzyme-linked immunosorbent assay.

This study has been undertaken to investigate the regional and seasonal variability in ochratoxin A (OTA) exposure of healthy population living in Black Sea and Mediterranean regions of Turkey by measuring serum OTA concentrations. The mean serum concentrations of OTA were determined to be 0.137 ng/mL (0.0306-0.887 ng/mL) and 0.312 ng/mL (0.028-1.496 ng/mL) in all samples for winter and summer, respectively by enzyme-linked immunosorbent assay (ELISA). The differences between mean values of OTA in all serum samples collected in summer and winter were statistically significant. The highest OTA concentration was determined in the children living in Black Sea Region in summer. The mean daily intake levels of OTA in all samples were estimated as 0.182 ng/kg b.w./day and 0.408 ng/kg b.w./day in winter and summer, respectively. The results showed that the mean serum concentrations of OTA in healthy population in both regions were found not to be exceeded 1 ng/mL in agreement with the distribution reported in most European countries and that the daily intake levels of OTA were calculated below the tolerable daily intake levels given by regulatory authorities. However, overall results suggest that Turkish population living in these regions is continuously exposed to OTA and that the exposure levels are also elevated in summer period compared to winter.

Aflatoxin M1 levels in commonly consumed cheese and yogurt samples in Ankara, Turkey

The potential hazardous human exposure to aflatoxin M1 via consumption of milk and milk products has been demonstrated by several workers. Considering its risk to human health, determination of aflatoxin M1 levels in dairy products is important. Since there are limited data available on the occurrence of aflatoxin M1 levels in dairy products in Turkey, the aim of the present study was to investigate the presence of this toxin in various types of commonly consumed cheese and yogurt samples in the capital city of Turkey—Ankara. For this purpose, 39 samples of cheese and 40 samples of yogurt were randomly collected from supermarkets in Ankara. Aflatoxin M1 levels were determined by a competitive enzyme-linked immunosorbent assay (ELISA) kit. Aflatoxin M1 was detected in 11 cheese samples ranging from 78.20 to 188.44 ng/kg. Thirty-two of the 40 yogurt samples had aflatoxin M1 levels between 61.61 and 365.64 ng/kg. The results of this study indicated the importance of continuous surveillance of commonly consumed cheese and yogurt samples for aflatoxin M1 contamination in Turkey.

The in vitro effects of new non-steroidal antiinflammatory compounds on antioxidant system of human erythrocytes.

It has been reported by our group that some benzoxazolone and benzothiazolone derivatives showed significant antinociceptive and anti-inflammatory activity [DOGRUER et al. 1997]. It has been speculated that nonsteroidal anti-inflammatory drugs (NSAIDs) can act as the free radical scavengers and possess antioxidant activity. It is also well documented that oxidative stress can play an important role in the side effects of many xenobiotics including NSAIDs. Therefore, in the present study, the effects of six of the above mentioned benzoxazolone and benzothiazolone derivatives bearing 2-pyridylaminocarbonylmetyl moiety at the position 3 (I) on the antioxidant system-related parameters of human erythrocytes have been investigated. Diclofenac and nimesulid were also tested in the same systems as the control, because they are commonly used as NSAIDs. Our results showed that these compounds made significant changes in the antioxidant system of human erythrocyte.

Spot analyses of serum neopterin, tryptophan and kynurenine levels in a random group of blood donor population

Abstract In transfusions, safety measures are used for the health of both receivers and donors. In this regard, early and sensitive markers are strongly needed. The aim of this study was to evaluate neopterin profile and tryptophan degradation in a group of Turkish blood donors. The effect of age, gender, blood type and Rh factor were also assessed. Neopterin was measured by ELISA kits. Serum tryptophan and kynurenine were determined by high performance liquid chromatography. Kynurenine/tryptophan (kyn/trp) was calculated to estimate tryptophan degradation. Tryptophan, kynurenine and kyn/trp levels were found to be higher in males compared with females (all p<0.05). Neopterin and kynurenine levels tended to increase with age in age subgroups (all p<0.05). On the contrary, smoking, Rh factor and blood types were all observed to have no effect on measured parameters (all p>0.05). In routine analysis, early and reliable biomarkers are needed. In parallel with current markers, neopterin can be used to select safe donors and to maintain the safety of transfusion. In the face of our results, we recommend that donations with neopterin levels above 19 nmol/L should be excluded from the program because increased neopterin levels indicate activation of the cellular immune system.

Evaluation of dihydropteridine reductase activities in patients with kidney failure

Abstract End-stage renal disease (ESRD) is the inability of the kidneys to remove waste products from the blood. The most important factors causing ESRD that require hemodialysis are diabetes and hypertension. There are limited numbers of studies to evaluate tetrahydrobiopterin pathway in these patients. The aim of the study was to evaluate tetrahydrobiopterin pathway by measuring its important components, biopterin to creatinine concentrations and dihydropteridine reductase activities in diabetes and hypertension patients treated with/without hemodialysis. The patients undergoing hemodialysis were classified as diabetic nephropathy (n=21), hypertensive nephropathy (n=20) and others (n=30), while the controls consisted of healthy subjects (n=21), diabetic subjects (n=23) and hypertensive subjects (n=22) without any renal disorder. It was found that urinary biopterin to creatinine concentrations significantly increased in kidney failure patients undergoing hemodialysis compared to the healthy control group (p<0.05). Additionally, there were significant differences in urinary biopterin to creatinine concentrations between diabetes or hypertension patients and their hypertensive or diabetic control counterparts (both p<0.05). Our results indicated an alteration in tetrahydrobiopterin pathway in ESRD, and in the presence of secondary pathologies such as diabetes and hypertension in the patients undergoing hemodialysis, more considerable changes are observed in the pathway.