Eser Yildirim Sözmen

Catalase/Superoxide Dismutase (SOD) and Catalase/Paraoxonase (PON) Ratios May Implicate Poor Glycemic Control

BACKGROUND Previous studies suggest that elevated oxidative stress implicates poor glycemic control resulting in the development of diabetic complications. By evaluating the relationship between paraoxonase (PON) and antioxidant enzyme activities and glycemic control in diabetic patients with and without complications, we investigated whether there is a role of PON and/or antioxidant status in glycemic control. METHODS A total of 107 patients with type 2 diabetes mellitus (DM) was included in the study. Seventy-five patients had complications including microangiopathy, proliferative retinopathy, and/or nephropathy while 32 had no complications. The control group consisted of 29 age- and sex-matched healthy persons. Serum superoxide dismutase (SOD) and catalase activities were measured according to Sun and Goth, respectively. Basal and salt-stimulated paraoxonase activities and arylesterase activity were determined using the method of Eckerson et al. RESULTS There was an increase in the catalase activity and a decrease in the basal and salt-stimulated PON activity of patients when compared with controls, while no significant difference was observed in SOD activity. PON phenotypes had no effect on any parameter in patient and control groups. The ratio of catalase/SOD was 2.44 +/- 7.10 and 0.17 +/- 0.09 in diabetics and controls, respectively (p = 0.004); this was associated with an elevation in HbA1c levels. On the other hand, catalase/PON ratio was also enhanced in diabetic patients (2.8 +/- 5.2), showing a relationship with HbA1c levels compared to controls (0.29 +/- 0.3, p = 0.000). CONCLUSIONS The data of this study reveal that enhanced catalase/SOD and catalase /PON ratios that are correlated with HbA1c levels are observed in diabetic patients; thus, these ratios may be used as markers of poor glycemic control and as risk factors in the development of diabetic complications.

Sex differences in nitrite/nitrate levels and antioxidant defense in rat brain.

THIS study assessed sex differences in stable metabolites of nitric oxide and major enzymes involved in antioxidant defense in various regions of rat brain. Nitrite/ nitrate levels and activities of superoxide dismutase and catalase were determined in cortex, hippocampus, corpus striatum, midbrain and cerebellum of adult male and female Sprague–Dawley rats. Nitrite/nitrate levels were significantly higher in the cortex and the hippocampus of male than female rats, while catalase activity was higher in the cortex of females than in males. These sex differences may have significant effects on brain function in health and disease.

Effect of organophosphate intoxication on human serum paraoxonase.

Recently, interindividual variations in serum paraoxonase (PON1) activity and the differences in its metabolic activity towards different organophosphates (OPs) caused by the coding region polymorphisms L55M and Q192R have been found to be important risk factors in susceptibility to OP poisoning. In this study, we investigated the effect of PON1 on the outcome of acute OP intoxication and the effect of acute OP intoxication on PON1. Twenty-eight OP-poisoned patients and 66 healthy volunteers were studied. Patients were evaluated for the clinical manifestations of OP intoxication as well as PON1 activity, PON1 mass and PON1 polymorphisms. Butyrylcholine-esterase (BChE) activity was 50% lower (2276±738 U/L versus 5037±1553 U/L, P<0.01) while PON1 activity was 30% lower (114.2±67.4 nmol/mL/min versus 152.9±78.9 nmol/mL/ min, P<0.05) in patients than in controls. We observed that the PON1 and BChE activities of eight of the original subjects returned to normal levels when they were reinvestigated six months after exposure. The frequency of the PON192Q allele was significantly higher in patients than controls (85.7% versus 59.7%, χ 2=6.745, P=0.034). QQ/MM individuals had the lowest activity towards paraoxon, while RR/LL individuals had the highest activity. Our data indicate that interindividual differences in PON1 activity and the PON1-55 and-192 polymorphisms are important risk factors in susceptibility to acute OP poisoning; therefore, identifying an individuals PON1 alloenzymes may play an important role in the treatment of patients suffering from OP intoxication.

Fenofibrate Treatment Enhances Antioxidant Status and Attenuates Endothelial Dysfunction in Streptozotocin-Induced Diabetic Rats

Diabetic endothelial dysfunction is accompanied by increased oxidative stress and upregulated proinflammatory and inflammatory mediators in the vasculature. Activation of peroxisome proliferator-activated receptor-alpha (PPAR-α) results in antioxidant and anti-inflammatory effects. This study was designed to investigate the effect of fenofibrate, a PPAR-α activator, on the endothelial dysfunction, oxidative stress, and inflammation in streptozotocin diabetic rats. Diabetic rats received fenofibrate (150 mg kg−1 day−1) for 4 weeks. Fenofibrate treatment restored the impaired endothelium-dependent relaxation and increased basal nitric oxide availability in diabetic aorta, enhanced erythrocyte/liver superoxide dismutase and catalase levels, ameliorated the abnormal serum/aortic thiobarbituric acid reactive substances, and prevented the increased aortic myeloperoxidase without a significant change in serum total cholesterol and triglyceride levels. It did not affect the decreased total homocysteine level and the increased tumor necrosis factor-α level in the serum of diabetic rats. Fenofibrate-induced prevention of the endothelial function seems to be related to its potential antioxidant and antiinflammatory activity.

PON1 activities and oxidative markers of LDL in patients with angiographically proven coronary artery disease

BACKGROUND There is growing evidence that ox-LDL plays an important role during the atherosclerosis process and PON1 can significantly inhibit generation of lipid peroxidation during LDL oxidation and thus play a role in the in vivo protection by HDL against atherosclerosis. METHODS Twenty-four healthy volunteers and one-hundred and one patients were taken into study, sixty-eight patients had coronary artery disease which was confirmed by coronary angiography. Serum PON1, erythrocyte superoxide dismutase and catalase activities, oxidative markers of LDL were determined along with the routine biochemical parameters in all groups. RESULTS The indicators of oxidative stress were higher in the patients compared with the controls. No statistically significant difference in any of parameters were observed between the patients who had obstruction with different degrees except for erythrocyte TBARS [24.5 nM/g Hb in patients with one vessel disease (VD) (n=22), 29.6 nM/g Hb in patients with two VD (n=26) and 33.5 nM/g Hb in patients with three VD (n=20)]. Basal and stimulated diene levels were higher in patients who had more diseased vessels than those who had less. CONCLUSION The increase in erythrocyte TBARS and CRP levels with the severity of disease supports the reports that showed the inflammatory and oxidative nature of atherosclerosis. In the light of the fact that the well-known classical risk factors for atherosclerosis are closely associated with increased oxidative stress, we propose that the elevation in TBARS levels might be a more marked indicator for the degree of atherosclerosis than the insufficiency in antioxidant enzymes such as SOD and PON1.

The Effects of Estrogen and Raloxifene Treatment on Antioxidant Enzymes in Brain and Liver of Ovarectomized Female Rats

Recent studies documented that estrogen have antioxidant properties in‐vitro, there are conflicting results on the effect of estrogen in vivo. We aimed to investigate the effects of estradiol and Raloxifene on the antioxidant enzyme [superoxide dismutase (SOD) and catalase (CAT)] activities and MDA levels in brain and liver homogenates of ovariectomized female rats. Twelve weeks after ovariectomy, female Sprague–Dawley rats (n = 26) were divided into three groups: (1) Ovariectomized placebo group (n = 6) was given physiologic saline. (2) Estrogen group (n = 10) was given Ethynyl estradiol, 0.1 mg/kg sc. (3) Raloxifene group (n = 10) was given raloxifene, 1 mg/kg sc during 8 weeks. Ten rats were used as naive controls without any treatment (Sham operated group, n = 10). Ovariectomy lead to an increase in the CAT activities in liver tissue samples compared to the sham group ( p = 0.056, Mann–Whitney test). While estrogen treatment reversed to normal levels of CAT activities, raloxifene remained as ineffective. Superoxide dismutase activities and MDA levels in liver were remained unchanged in all groups. There was no significant change in the brain tissue SOD and CAT activities between the control, ovariectomy, estrogen treated, and raloxifen treated groups. We determined an increase in MDA levels in brain of ovariectomised rat ( p = 0.02). While raloxifene treatment reversed to normal levels of MDA ( p = 0.008), estrogen treatment failed. Our data showed that estrogen may play a role in regulation of CAT and SOD activities in liver due to its antioxidative effects. We can suggest that estrogen and raloxifene exert their antioxidative effects in brain rather than liver. Since Raloxifenes effect is more clear than estradiol, raloxifene may be suggested primarily for treatment and/or prevention of diseases which can be resulted from oxidative stress in postmenopausal women.

CATALASE AND PARAOXONASE IN HYPERTENSIVE TYPE 2 DIABETES MELLITUS : CORRELATION WITH GLYCEMIC CONTROL

OBJECTIVES Type 2 diabetes mellitus (DM) is well recognized as being associated with increased prevalence of hypertension. Experimental and epidemiologic studies have shown that oxygen-free radicals are elevated because antioxidant enzyme activities are altered both in uncontrolled essential hypertension and DM itself. Recently paraoxonase (PON) has been recognized as an antioxidant enzyme that hydrolyzes lipid peroxides. The aim of this study is to evaluate simultaneously PON activities and antioxidant status in hypertensive type 2 DM cases and to establish any possible relationship between these parameters and duration of hypertension or diabetes, hemoglobin (Hb) A1c levels, and lipid parameters. DESIGN AND METHODS Nineteen normotensive subjects with type 2 DM, 37 hypertensive (diastolic blood pressure 90 mm Hg or more) subjects with type 2 DM, and 25 normotensive control subjects with normal glucose tolerance were selected for this study. Superoxide dismutase (SOD), catalase, and basal-stimulated PON activities were measured by the methods of Sun et al.; Goth; and Eckerson, Wyte, and La Du, respectively; other lipid parameters were determined using an autoanalyzer. RESULTS Catalase activities of either hypertensive patients with type 2 DM or type 2 DM patients without complication were found to be higher than controls (p<0.01), although no significant difference in SOD and basal-stimulated PON activities was observed between these groups. A significant elevation in catalase activity (p = 0.004) of patients with high HbA1c levels (>7.0%) (n = 37) compared with patients with low HbA1c levels (<7.0%) (n = 19) was detected. There was also a positive correlation between the catalase activities and fasting glucose levels and HbA1c concentrations in hypertensive patients with type 2 DM (r = 0.4567, p<0.05 and r = 0.3686, p<0.05, respectively). An increase in catalase activity of patients with B and/or AB phenotype compared with patients with A phenotype was also noted. CONCLUSION Poor glycemic control in diabetes is strongly associated with an increase in free radicals and consequent diabetic complications. Uncontrolled glucose metabolism may also be the cause of alterations in antioxidant enzymes. Among these, catalase correlates best with poor glycemic control. The current data reveal that B allele carriers of PON are more susceptible to oxidant stress.

Antioxidant enzymes and paraoxonase show a co-activity in preserving low-density lipoprotein from oxidation.

Abstract Oxidative modification of low-density lipoprotein in the artery wall plays a crucial role in the development of atherosclerosis. This physiopathological mechanism is clearly inhibited by high-density lipoprotein possibly via paraoxonase enzyme activity, present in high-density lipoprotein. In this study we determined the in vitro susceptibility of low-density lipoprotein to oxidation and the effect of various factors, such as paraoxonase phenotypes, on this process. Low-density lipoprotein from healthy volunteers (n=66) was isolated using the precipitant reagent and the oxidation was evaluated by measuring the malonyl dialdehyde and diene levels. Low-density lipoprotein cholesterol and phospholipid, vitamin E, serum cholesterol, high-density lipoprotein and low-density lipoprotein cholesterol levels, and erythrocyte antioxidant enzymes were also determined. There was no difference among the parameters with regard to gender. Low-density lipoprotein samples obtained from subjects with the AA allele were more prone to oxidation, as observed by their higher stimulated conjugated diene (P=0.041) and thiobarbituric acid-related substance (P=0.042) levels, than samples from subjects with AB or BB alleles. The subjects with the BB allele had higher superoxide dismutase (P=0.021) and catalase (insignificant increase) activities, while their conjugated diene (P=0.000) levels were lower. In conclusion, our results revealed that the high low-density lipoprotein oxidation is related to the high low-density lipoprotein cholesterol content and low phospholipid content. The present study demonstrated an increase in superoxide dismutase and catalase activities, asl well as PON1 activities, in subjects with the BB allele. Since these enzymes all show activity against low-density lipoprotein oxidation, we propose that future investigations on atherosclerotic processes should address PON1 polymorphism as well as PON1 and other antioxidant enzymes.

The effects of estrogen and raloxifene treatment on the antioxidant enzymes and nitrite-nitrate levels in brain cortex of ovariectomized rats

Number of studies indicate that the female gonadal hormone estrogen protects women against several neurodegenerative diseases and cerebral ischemia via various mechanisms. The possible protective effects of estrogen are mediated mainly by three ways; the activation of steroid receptors and/or modulation of a neurotransmitter and/or direct antioxidative action. Therefore we aimed to investigate the effects of estradiol and raloxifene on levels of nitric oxide (NO) and antioxidant enzymes in brain cortex of ovariectomized female rats. Ten Sprague-Dawley rats were used as naive controls while 32 rats were ovariectomized at 120-140 days of age. Twelve weeks after ovariectomy: (1). Ovariectomized Placebo group (n=11), was given physiologic saline. (2). Estrogen group (n=10) was given Ethynyl estradiol, 0.1 mg/kg sc. (3). Raloxifene group (n=10) was given raloxifene, 1 mg/kg sc. At the end of the treatment period (8 weeks), rats were decapitated and cortex samples were dissected. Results showed that ovariectomy caused a decrease in total nitrite-nitrate levels. The NO levels of both the estrogen and the raloxifene group were higher than the placebo group. Catalase activities did not show any significant difference between the groups, while superoxide dismutase (SOD) activities were elevated via ovariectomy. Estradiol and Raloxifene treatment had no statistically significant effect on SOD activity.

Insulin-Like Growth Factor Attenuates Apoptosis and Mucosal Damage in Hypoxia/Reoxygenation-Induced Intestinal Injury

Objective: Necrotizing enterocolitis (NEC) is a potentially lethal disease among premature infants. The aim of the present study was to investigate whether hypoxia-reoxygenation (H/R)-induced intestinal injury was due to increased apoptosis of the intestinal mucosa in young mice and whether pre-treatment of the animals with recombinant human insulin-like growth factor-I (IGF-I), a known anti-apoptotic factor, could protect the intestinal cells from H/R-induced apoptosis or intestinal injury. Study Design: Young mice were divided into three groups: group 1 mice (H/R) were hypoxia-reoxygenation; group 2 mice (H/R + IGF-I) were treated with recombinant human IGF-I by intraperitoneal injection (1 µg/g b.w. once daily) for 7 days, and group 3 mice served as control. Hypoxia was induced by placing young mice in a Plexiglas chamber consisting of 10% oxygen for 60 min. After hypoxia, the young mice were reoxygenated for 10 min with 100% oxygen. Intestinal generation of substances reactive to thiobarbituric acid (TBARS) and active caspase-3 were measured in H/R-induced intestinal injury. Results: Increased numbers of apoptotic cells (apoptotic index) across the villi in young mice subjected to H/R were observed with the TUNEL reaction whereas few apoptotic cells existed in the control animals. In addition, H/R-induced intestinal damage in the H/R + IGF-I group was greatly attenuated, with necrosis limited partially to the mucosa. Tissue-active caspase-3 levels in the H/R group were found to be significantly higher when compared with that of the H/R + IGF-I group of mice and control. However, TBARS concentrations in the intestine were similar in H/R groups when compared to the intestine of control animals. Conclusion: The present study suggests that both necrosis and apoptosis, via mechanisms occurring due to oxygen-derived free radicals and activation of caspase-3, play a role in the pathogenesis of H/R-induced bowel injury. We also show that IGF-I protect intestinal mucosa from necrosis and apoptosis from intestinal H/R injury.