Melahat Dirican

Exercise-induced oxidative stress and muscle performance in healthy women: role of vitamin E supplementation and endogenous oestradiol.

Abstract The purpose of this study was to investigate the individual and combined antioxidant effects of menstrual cycle phase-related alterations in blood serum oestradiol concentrations and of dietary vitamin E supplementation on exercise-induced oxidative stress and muscle performance. A group of 18 sedentary women, aged 19–35 years, were given supplements of 300 mg α-tocopherol (n=10) or placebo (n=8) daily during the course of two menstrual cycles. The subjects exercised the knee isokinetically to exhaustion after cycling submaximally at 50% maximal oxygen uptake during the menstrual and preovulatory phases of their menstrual cycles. Blood samples were taken before and after the exercise, to evaluate haematocrit, plasma lactic acid and malondialdehyde concentrations, erythrocyte antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities and apolipoprotein B containing lipoprotein (non-high density lipoprotein, HDL, fraction) oxidation. Serum vitamin E, follicle stimulating hormone, luteinizing hormone and oestradiol concentrations were measured in pre-exercise blood samples. Neither vitamin E supplementation nor oestradiol concentrations influenced SOD and GPx activities or the susceptibility of the non-HDL fraction to oxidation while at rest. Plasma malondialdehyde concentration was unaffected by exercise, however significant reductions in erythrocyte SOD and GPx activities and increased susceptibility of the non-HDL fraction to oxidation were noted after exercise. Exercise-induced changes were reduced when oestradiol concentration was high in the preovulatory phase, independent of the serum vitamin E concentrations. In addition, both pre- (r=0.58, P < 0.05) and post-exercise (r=0.73, P < 0.001) GPx activities in placebo administered subjects were positively correlated with oestradiol concentrations. In conclusion, these findings suggest a better protective role of oestradiol against oxidative injury, compared to vitamin E. Exhausting muscle performance was, however, not influenced by vitamin E supplementation and/or cycle-phase related changes in oestradiol concentrations.

Oxidation of apolipoprotein B-containing lipoproteins and serum paraoxonase/arylesterase activities in major depressive disorder

Major depressive disorder (MDD) is blaimed to play a role in the onset of coronary artery disease (CAD). The aim of the present study was to investigate serum paraoxonase/arylesterase activities and oxidation of apolipoprotein B-containing lipoproteins in patients with MDD. Oxidation of lipoproteins plays an important role in atherogenesis and the enzyme paraoxonase, has been shown to prevent lipoprotein oxidation. Furthermore, low paraoxonase activity was suggested to predict CAD. Eighty-six patients who fully met the fourth Diagnostic and Statistical Manual of Mental Disorders criteria for MDD and 36 healthy control subjects were included in the study. Serum paraoxonase and arylesterase activities were determined spectrophotometrically. Malondialdehyde (MDA) levels of apolipoprotein B-containing lipoproteins were determined before (basal) and after incubation with copper-sulphate, that yielded basal- and Delta-MDA values, respectively. Serum paraoxonase/arylesterase activities were significantly reduced in the post-treatment group compared with the pre-treatment group. Basal-MDA (MDA) level was significantly higher in the MDD group compared with the control group. Delta-MDA level of the severe MDD group was significantly higher than that of the control group. There was a positive correlation between the oxidizability of apolipoprotein B-containing lipoproteins and the severity of the disease. Total cholesterol, HDL-cholesterol, LDL-cholesterol, apolipoprotein B levels were significantly higher and apolipoprotein AI levels were significantly lower in the MDD group compared with those of the control group. The findings of the present study suggest that: 1) antidepressant treatment might reduce serum paraoxonase activity/mass; 2) oxidation and oxidizability of apolipoprotein B-containing lipoproteins seem to be increased in MDD.

Effects of red wine consumption on serum paraoxonase/arylesterase activities and on lipoprotein oxidizability in healthy-men

Although there is a general consensus concerning the lower risk for cardiovascular disease in moderate drinkers, the mechanisms responsible for the cardioprotective effect of red wine remain unknown. It has been proposed that increased serum paraoxonase activity may be a mechanism of action underlying reduced cardiovascular disease risk in moderate drinkers, since paraoxonase inhibits lipoprotein oxidation. The aim of this study was to investigate the effects of red wine consumption on serum paraoxonase/arylesterase activities and on lipoprotein oxidizability in healthy-men. Fourteen healthy-men were included in the study. The subjects consumed 0.375 g alcohol / kg body weight for 3 weeks. Paraoxonase and arylesterase activities were studied spectrophotometrically. Oxidizability of apolipoprotein B-containing lipoproteins were determined, after separating them with precipitation method, by incubating with copper-sulfate. Paraoxonase activity did not change, however arylesterase activity significantly decreased after red wine consumption (P < 0.01). There was a reduced susceptibility of apolipoprotein B-containing lipoproteins to copper-sulfate induced oxidation after red wine consumption (P < 0.01). Our results support that red wine protects lipoproteins against oxidation, however there was not any significant change in serum paraoxonase activity after red wine consumption.

A multicenter nationwide reference intervals study for common biochemical analytes in Turkey using Abbott analyzers

Abstract Background: A nationwide multicenter study was organized to establish reference intervals (RIs) in the Turkish population for 25 commonly tested biochemical analytes and to explore sources of variation in reference values, including regionality. Methods: Blood samples were collected nationwide in 28 laboratories from the seven regions (≥400 samples/region, 3066 in all). The sera were collectively analyzed in Uludag University in Bursa using Abbott reagents and analyzer. Reference materials were used for standardization of test results. After secondary exclusion using the latent abnormal values exclusion method, RIs were derived by a parametric method employing the modified Box-Cox formula and compared with the RIs by the non-parametric method. Three-level nested ANOVA was used to evaluate variations among sexes, ages and regions. Associations between test results and age, body mass index (BMI) and region were determined by multiple regression analysis (MRA). Results: By ANOVA, differences of reference values among seven regions were significant in none of the 25 analytes. Significant sex-related and age-related differences were observed for 10 and seven analytes, respectively. MRA revealed BMI-related changes in results for uric acid, glucose, triglycerides, high-density lipoprotein (HDL)-cholesterol, alanine aminotransferase, and γ-glutamyltransferase. Their RIs were thus derived by applying stricter criteria excluding individuals with BMI >28 kg/m2. Ranges of RIs by non-parametric method were wider than those by parametric method especially for those analytes affected by BMI. Conclusions: With the lack of regional differences and the well-standardized status of test results, the RIs derived from this nationwide study can be used for the entire Turkish population.

High-dose taurine supplementation increases serum paraoxonase and arylesterase activities in experimental hypothyroidism.

1 Hypothyroidism is accompanied by hyperlipidaemia and oxidative stress and is associated with several complications, such as atherosclerosis. Paraoxonase activity has been reported to decrease in several situations associated with atherosclerosis and oxidative stress. In the present study, the effects of different doses of taurine on serum paraoxonase and arylesterase activities, as well as on the serum lipid profile, were investigated in hypothyroid rats. 2 Forty male Sprague‐Dawley rats were randomly divided into five groups as follows: Group 1, rats received normal rat chow and tap water; Group 2, rats received standard rat chow + 0.05% propylthiouracil (PTU) in the drinking water; and Groups 3–5, taurine‐supplemented PTU groups (standard rat chow + 0.5, 2 or 3% taurine in the drinking water, respectively, in addition to PTU). Paraoxon or phenylacetate were used as substrates to measure paraoxonase and arylesterase activity, respectively. Plasma and tissue malondialdehyde (MDA) levels, indicators of lipid peroxidation, were determined using the thiobarbituric‐acid reactive substances method. Serum triglyceride, total cholesterol and high‐density lipoprotein–cholesterol (following precipitation with dextran sulphate–magnesium chloride) were determined using enzymatic methods. 3 Serum paraoxonase and arylesterase activities were increased and plasma and tissue MDA levels and serum triglyceride levels were reduced in a dose‐dependent manner in taurine‐treated hypothyroid rats. Taurine concentrations were positively correlated with enzyme activities and negatively correlated with MDA and triglyceride levels. 4 Further studies are needed to investigate the role of taurine supplementation in hypothyroidism in human subjects.

Ulva rigida improves carbohydrate metabolism, hyperlipidemia and oxidative stress in streptozotocin‐induced diabetic rats

This study was designed to investigate the effects of Ulva rigida, one of the green algae, on the lipid profile and oxidative–antioxidative systems in streptozotocin‐induced diabetic rats. Forty Wistar rats randomly divided into four groups: control (C), control + U. rigida extract (C + URE), diabetes (D) and diabetes + U. rigida extract (D + URE). U. rigida (2%) was administered in drinking water for 5 weeks after the induction of diabetes. U. rigida reduced the blood glucose, serum total cholesterol, triglyceride levels and plasma and tissue malondialdehyde (MDA) levels in the D + URE group. Insulin levels were significantly higher in the D + URE than those of the D group. Serum total cholesterol and tissue MDA levels were reduced in the C + URE group. Whole blood glutathione peroxidase and erythrocyte superoxide dismutase activities were higher in the D and C + URE groups compared with the C group. Paraoxonase and arylesterase activities were lower in the D group while U. rigida increased paraoxonase activities in C + URE and D + URE groups. This is the first study which showed U. rigida has antidiabetic and antihyperlipidemic effects and improves oxidative stress in diabetic rats. We conclude that U. rigida might have a potential use as a protective and/or therapeutic agent in diabetes mellitus. Copyright

Oxidizability of apolipoprotein B-containing lipoproteins, levels of lipid peroxidation products and antioxidants in normal pregnancy

ObjectThe object was to assess oxidizability of apolipoprotein B-containing lipoproteins, levels of lipid peroxidation products and antioxidants in normal pregnancy.MethodSerum malondialdehyde, vitamin E, carotenoids, albumin, uric acid, bilirubin, triglyceride, total cholesterol levels and in vitro copper-induced oxidation of apolipoprotein B-containing lipoproteins were investigated in 21 healthy pregnant and 22 nonpregnant women. Mann-Whitney U test was used for the statistical analyses.ResultsSerum malondialdehyde, vitamin E, triglyceride and total cholesterol levels were significantly higher; albumin and uric acid levels and vitamin E/triglyceride + total cholesterol and carotenoids/triglyceride + total cholesterol ratios were significantly lower in the pregnant group. Basal malondialdehyde concentrations of apolipoprotein B-containing lipoprotein fraction and Δ-malondialdehyde values determined at 30, 60, 90, 120, 150 and 180th minutes of incubation were significantly lower in the pregnant group compared to those in the non-pregnant group.ConclusionAlthough greater lipid peroxidation product levels reflect an enhanced lipid peroxidation status in normal pregnancy, apolipoprotein B-containing lipoprotein fraction of normal pregnant women compared with the nonpregnant subjects seems to be protected from oxidation.

The relationship of serum ferritin with malondialdehyde concentration in patients with coronary artery disease: Ferritin and oxidative stress in CAD

It has been suggested that the risk of coronary heart disease increased with increasing body iron stores. Free iron catalyzes the generation of free radicals and free radicals promote the oxidation of lipids. The aim of this study was to determine the association of serum ferritin levels with coronary artery disease (CAD) and to establish the relation of ferritin to the lipid peroxidation product malondialdehyde (MDA). The study included 188 patients. Thirty-eight patients (mean age: 55±9 years) had angiographically normal coronary arteries and 150 patients (mean age: 54±10 years) had significant stenosis at least in one coronary artery. Serum ferritin, total iron binding capacity (TIBC), MDA levels, lipoprotein variables and CAD risk factors were determined in all patients. Serum ferritin levels were significantly higher in patients with CAD compared with control groups (105±65 ng/ml versus 83±71 ng/ml) (p<0.01). TIBC was lower in patients with CAD (333±62 µg/dl) versus 348±48 µg/dl), (p<0.05). In patients with CAD, serum MDA levels were significantly higher when compared with control groups (8.1±2 nmol/ml versus 5.9±1.8 nmol/ml), (p<0.001). There were positive correlation between ferritin and MDA levels (r=0.20, p=0.02) and negative correlation between TIBC and MDA levels (r=0.22, p=0.001). These findings support the concept that iron, being an important transition metal, might contribute to atherogenesis, along with the classic risk factors. The results are also in agreement with the concept that iron overload would elevate the risk of CAD by promoting the lipid peroxidation.

Paraoxonase Activity in Glomerulonephritic Patients

Background. Cardiovascular disease is the most common cause of morbidity and mortality in patients with chronic renal failure. Glomerulonephritic patients have an increased risk for cardiovascular disease, but its etiology is unclear. It is known that an increase in oxidizability of apolipoprotein B-containing lipoproteins has a key role in the initiation of atherosclerosis, and paraoxonase enzyme activity particularly has a preventive role against atherosclerosis. The aim of the present study was to evaluate the oxidizability of apolipoprotein B-containing lipoproteins, serum, and urinary paraoxonase/arylesterase activities in glomerulonephritis patients who had normal lipid parameters and creatinine levels. Methods. Thirty-two patients with glomerulonephritis and 22 healthy controls were included in this study. A total of 32 patients (including nine with membranous GN, eight with immunoglobulin A nephropathy, eight with mesangial proliferative GN, five with focal-segmental glomerulosclerosis, one with diffuse proliferative GN, and one with minimal chance disease having biopsy proven GN) were enrolled into the study. We compared serum and urinary paraoxonase, arylesterase, serum lipids, urea, creatinine, hemoglobin, total protein and albumin values between groups. Results. Serum urea, creatinine, total protein, albumin, uric acid, hemoglobin, and lipid parameters were similar in the glomerulonephritis and control groups (p > 0.05). PON1 activity was significantly lower in GN group than controls, but there was no statistically significant difference on arylesterase activity between groups. Oxidizability of apolipoprotein B-containing lipoproteins was significantly higher in GN group than controls. Conclusion. Our study shows that the findings of normal serum levels of creatinine, lipids, and proteins increased the oxidizability of apolipoprotein B-containing lipoproteins, and any decrease in PON1 activity in patients diagnosed with GN should be considered important. Hence, the immediate commencement of preventive as well as curative treatment in other to avoid the risk of cardiovascular and renal problems would be a correct approach.

Adiponectin, leptin, nitric oxide, and C-reactive protein levels in kidney transplant recipients: comparison with the hemodialysis and chronic renal failure

Abstract Background: Cardiovascular disease (CVD) is the leading cause of mortality and morbidity in patients with chronic kidney disease (CKD) including kidney transplant recipients (KTR). Secondary lipid metabolism disorders, endothelial dysfunction, and inflammation enhance the risk of CVD development in these patients. The aim of the present study was to investigate the lipid profile, adiponectin, leptin, nitric oxide (NO), and high sensitivity C-reactive protein (hs-CRP) levels in KTR and to compare these parameters with those of the patients with chronic renal failure (CRF), hemodialysis (HD) patients, and healthy controls. Methods: Serum adiponectin and leptin levels were measured by radioimmunoassay; hs-CRP was determined immunoturbidimetrically. Determination of NO was based on the Griess reaction. Results: Compared with the control group, serum NO and adiponectin levels were significantly higher in the KTR, CRF, and HD groups; hs-CRP levels were significantly higher in the KTR and HD groups; leptin levels were significantly higher in the KTR. In addition, serum NO level was significantly higher in the KTR compared to CRF cases. Adiponectin correlated positively with high density lipoprotein-cholesterol in the control and patient groups. A positive correlation was observed between hs-CRP and NO in the KTR and the patients with CRF. Serum adiponectin levels were inversely correlated with hs-CRP and leptin in the HD group. Conclusion: KTR suffer from inflammation and accompanying changes in levels of adipocytokines and NO which contribute to the increased risk of CVD in these patients.