Emina Colak

Parameters of antioxidative defense in type 2 diabetic patients with cardiovascular complications

OBJECTIVE. Diabetes‐associated oxidative stress is a consequence of both increased production of free radicals and reduced capacity of antioxidative defense. Prolonged hyperglycemia is the major factor in the pathogenesis of atherosclerosis in diabetes which can lead to cardiovascular complications. The aim of this study was to test the parameters of antioxidative defense in type 2 diabetic patients. METHODS. A total of 117 type 2 diabetics with and without cardiovascular complications were examined in order to find out the influence of hyperglycemia, type and duration of complications and duration of diabetes on the extent of disorder of antioxidative parameter values: superoxide dismutase (SOD), glutathione peroxidase (GSH‐Px), glutathione reductase (GR) and total antioxidant status (TAS). RESULTS. Compared to healthy control subjects, type 2 diabetic patients with cardiovascular complications (CVC) had significantly lower SOD (P<0.0001), GSH‐Px (P<0.0001), GR ( P = 0.0002) and TAS values (P<0.0001). In type 2 diabetic subjects with CVC, males had significantly lower SOD (778.7±103.2 U/gHb, P<0.01) and GR activities (52.2±8.9 U/L, P<0.001) compared to females (839.3±94.9 U/gHb; 58.5±9.1 U/L). Significant and positive correlation was found between glucose levels and SOD (r = 0.375 for P<0.05) and GSH‐Px (r = 0.384, P<0.05 ) activity in the group of complications‐free diabetics, while significant negative correlation between glucose and GSH‐Px values (r = −0.382, P<0.05) was found in the group of type 2 diabetics with coronary artery disease (CAD) and hypertension (HTA) and with CAD and acute myocardial infarction (AMI) (r = −0.860 P<0.05), and highly negative correlation between glucose and SOD levels (r = −0.590, P<0.05) in the group of diabetic subjects with CAD, AMI and HTA. Likewise, there was highly significant negative correlation of SOD (r = −0.949, P<0.05) and TAS (r = −0.393 for P = 0.038) with duration of diabetes in the group of diabetics with CAD and HTA. CONCLUSION. Our results confirm the hypothesis that there is reduced antioxidative defense in type 2 diabetics with prominent cardiovascular complications, which negatively correlates with glucose concentrations and duration of diabetes and cardiovascular complications.

Prothrombogenic factors and reduced antioxidative defense in children and adolescents with pre-metabolic and metabolic syndrome.

Abstract Background: The aim of this study was to examine prothrombogenic factors and antioxidative defense in obese children and adolescents with pre-metabolic and metabolic syndrome, and to analyze insulin secretion and resistance, early glycoregulation disorders and lipid status. Methods: Insulin sensitivity was determined using the homeostasis model assessment for insulin resistance (HOMA-IR), while insulin secretion was determined using the homeostasis model assessment β (HOMA-β). Prothrombogenic factors analyzed were plasma plasminogen activator inhibitor-1 (PAI-1) and fibrinogen. Superoxide dismutase and glutathione peroxidase were measured as markers of antioxidative defense. Results: Patients with metabolic syndrome were characterized with increased body mass index (BMI), waist circumference, and HOMA-IR and HOMA-β levels, and all had increased blood pressure and triglyceride levels, low high-density lipoprotein cholesterol levels, increased PAI-1 levels and reduced antioxidative defense levels. Patients with pre-metabolic syndrome had higher levels of basal and mean insulinemia during an oral glucose tolerance test, higher levels of HOMA-β and lower levels of antioxidative defense compared to patients with metabolic syndrome. Conclusions: Negative correlations between antioxidative defense parameters and BMI, abdominal obesity, insulin secretion, systolic blood pressure and atherogenic lipid factors, as well as correlations between PAI-1 and insulin resistance and basal glycemia in the metabolic syndrome group contribute to accelerated atherosclerosis. Positive correlations between PAI-1 and waist circumference and BMI, and negative correlations between BMI and antioxidative defense in the pre-metabolic syndrome patients show that this early stage preceding the metabolic syndrome is also characterized by atherosclerotic complication risks and evident hyperinsulinism and insulin resistance. Clin Chem Lab Med 2007;45:1140–4.

The role of CRP and inflammation in the pathogenesis of age-related macular degeneration.

Age-related macular degeneration (AMD) is a complex, degenerative and progressive disease involving the multiple genetic and environmental factors that can result in severe visual loss. The etiology of AMD is not well understood. Many theories exist and feature mechanisms of oxidative stress, atherosclerotic-like changes, genetic predisposition and inflammation. The most recent clinical studies appointed to a great role of inflammation and C-reactive protein (CRP) in the pathogenesis of AMD. There is a large body of evidence indicating the association of CRP with endothelial dysfunction, oxidative stress and production of reactive oxygen species (ROS), as well as with lipid status disorder in AMD patients. According to recent studies, CRP is definitely not only the inflammatory marker but also a mediator of development of the vascular disorders in the retinal circulation. The results obtained from the present studies may help our understanding the pathogenesis of the retinal vascular disease associated with high levels of CRP.

The association of lipoprotein parameters and C-reactive protein in patients with age-related macular degeneration.

Background: Age-related macular degeneration (AMD) is the most common cause of visual impairment in individuals over 50 years of age, with the prevalence of 0.05% before the age of 50 rising to 30% after 74 years of age. An elevated concentration of plasma lipoproteins is considered to be one of the risk factors of AMD development. The aim of our study was to analyze the concentration of serum lipoproteins – total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), non-LDL cholesterol and triglycerides – as well as apolipoproteins – apoA1, apoB and Lp(a) – along with C-reactive protein (CRP) in patients with AMD in order to explore the possible association of lipid and inflammatory parameters with the pathogenesis of AMD. Material and Methods: In the cross-sectional study in the University clinical setting, 79 patients with AMD, aged 71.47 ± 7.02 years, and 84 aged-matched control subjects were included. The patients underwent complete ophthalmological examination including visual acuity assessment, color fundus photography and fluorescein angiography. Results: Statistical processing data revealed significantly higher total (p = 0.0002), LDL (p = 0.023), non-HDL cholesterol (p = 0.0014) and CRP (p = 0.049) values in AMD patients compared to control subjects. Conclusions: Based on the obtained results, it may be concluded that lipid status disorder and inflammation could play an important role in the development of AMD in elderly people.

New Markers of Oxidative Damage to Macromolecules

New Markers of Oxidative Damage to Macromolecules The presence of free radicals in biological material has been discovered some 50 years ago. In physiological conditions, free radicals, in the first place the ones of oxygen and nitrogen, are continuously synthesized and involved in the regulation of a series of physiological processes. The excess of free radicals is efficiently eliminated from the body in order to prevent their toxic effects. Toxic effects of free radicals may be classified into three groups: a) change of intracellular redox potential, b) oxidative modification of lipids, proteins and DNA, and c) gene activation. Lipid peroxidation involving cell membranes, lipoproteins and other molecules leads to the production of primary high-reactive intermediaries (alkyl radicals, conjugated dienes, peroxy- and alkoxyl radicals and lipid hydroperoxide), whose further breakdown generates the secondary products of lipid peroxidation: short-chain evaporable hydrocarbons, aldehydes and final products of lipid peroxidation: isoprostanes, MDA, 4-hydroxy-2, 3-transnonenal and 4,5-dihydroxydecenal which are important mediators of atherosclerosis, coronary disease, acute myocardial infarction, rheumatoid arthritis, systemic sclerosis and lupus erythematodes. Oxidative modification of proteins is manifested by changes in their primary, secondary and tertiary structures. Proteins have a specific biological function, and therefore their modification results in unique functional consequences. The nature of protein modification may provide valid information on the type of oxidants causing the damage. Chlorotyrosyl is a specific marker of oxidative damage to tyrosine caused by HOCl action, which most commonly reflects the involvement of neutrophils and monocytes in oxidative stress, while nitrotyrosyl indicates the presence of higher peroxy-nitrite synthesis. Methyonin and cysteine are the amino acids most sensitive to oxidative stress, carbonyl groups are markers of severe damage caused by free radicals, and di-tyrosyl is the most significant and sensitive marker of oxidative modification made by γ rays. >Carbonyl stress< is an important form of the secondary oxidation of proteins, where reducing sugars non-enzymatically react with amino groups of proteins and lipids and give rise to the production of covalent compounds known as advanced glycosylated end products (AGE-products). A hydroxyl radical damages the DNA, leading to a loss of base and the formation of abasic sites (AP sites), break of DNA chain and sugar modification. Final lipid peroxidation products (MDA) may covalently bind to DNA, producing the >DNA radicals< which are responsible for mutations. Measurement of an adequate oxidative stress biomarker may not only point to an early onset of disease, its progression and assessment of therapy effectiveness, but can also help in the clarification of the pathophysiological mechanisms of tissue damage caused by oxidative stress, prediction of disease prognosis and choice of appropriate treatment in the early stages of disease. Novi Markeri Oksidativnog Oštećenja Makromolekula Prisustvo slobodnih radikala u biološkim materijalima je otkriveno pre nešto više od 50 godina. U fiziološkim uslovima, slobodni radikali, pre svega kiseonika i azota, stalno se sintetišu i pri tom učestvuju u regulaciji niza fizioloških procesa. Višak slobodnih radikala se efikasno uklanja iz organizma u cilju sprečavanja njihovih toksičnih efekata. Toksični efekti delovanja slobodnih radikala se mogu podeliti u tri grupe: a) pomeranje intraćelijskog redoks stanja, b) oksidativna modifikacija lipida, proteina i DNK i c) aktivacija gena. Lipidna peroksidacija koja zahvata ćelijske membrane, lipoproteine i druge molekule dovodi do stvaranja primarnih visokoreaktivnih intermedijera (alkil radikala, konjugovanih diena, peroksi i alkoksi radikala i lipidnih hidroperoksida), koji daljom razgradnjom daju sekundarne produkte lipidne peroksidacije: kratkolančane isparljive ugljovodonike, aldehide i krajnje proizvode lipidne peroksidacije: izoprostane, MDA (malondialdehid), 4-hidroksi-2,3-transnonenal i 4,5-dihidroksidecenal, koji su značajni medijatori ateroskleroze, koronarne bolesti, akutnog infarkta miokarda, reumatoidnog artritisa, sistemske skleroze, lupusa eritematodesa. Oksidativna modifikacija proteina manifestuje se promenama njihove primarne, sekundarne i tercijarne strukture. Proteini imaju specifičnu biološku funkciju, stoga njihova izmena ima jedinstvene funkcionalne posledice. Priroda proteinske modifikacije može nam dati validan podatak o vrsti oksidansa koji je doveo do oštećenja. Hlorotirozil je specifičan marker oksidativnog oštećenja tirozina dejstvom hipohlorita (HOCl), koji najčešće reflektuje učešće neutrofila i monocita u oksidativnom stresu, dok nitrotirozil ukazuje na prisustvo povećane sinteze peroksinitrita. Metionin i cistein su najosetljivije aminokiseline na dejstvo oksidativnog stresa, karbonilne grupe su markeri teškog oštećenja slobodnim radikalima, dok je di-tirozil najznačajniji i najosetljiviji marker oksidativne modifikacije dejstvom γ-zraka. >Karbonilni stres< je značajan vid sekundarne oksidacije proteina u kojem redukujući šećeri neenzimski reaguju sa amino grupama proteina i lipida dovodeći do stvaranja kovalentnih jedinjenja poznatih kao uznapredovani proizvodi glikozilacije ili AGE-proizvodi (advanced glycosylated end products). Hidroksilni radikal oštećuje i molekul DNK dovodeći do gubitka baze i stvaranja abazičnih mesta (AP site-ova), cepanja lanca DNK i modifikacije šećera. Krajnji proizvodi lipidne peroksidacije (MDA) mogu se kovalentno vezivati za DNK, stvarajući >DNK radikale< koji su odgovorni za nastanak mutacija. Merenje adekvatnog biomarkera oksidativnog stresa može nam ukazati ne samo na ranu pojavu bolesti, njenu progresiju i procenu efikasnosti terapije, već i pomoći u rasvetljavanju patofizioloških mehanizama oštećenja tkiva dejstvom oksidativnog stresa, u predikciji prognoze bolesti i izboru adekvatnog lečenja u ranim stadijumima bolesti.

Homocysteine is a marker for metabolic syndrome and atherosclerosis.

BACKGROUND It has been documented that patients with metabolic syndrome (MS) and vascular complications have higher homocysteine levels. Hyperhomocysteinemia correlates with IR, increasing oxidative stress, which causes lesions of vascular endothelium leading to endothelial dysfunction, hypertension and atherosclerosis. OBJECTIVE The objectives of the study were to examine homocysteine values, along with cardiovascular risk factors (lipid and apolipoprotein status, CRP, blood pressure), indicators of renal function (microalbuminuria/24h), glucose regulation and insulin resistance (glucose and insulin level, HbA1c, HOMA-IR, uric acid) and anthropometric parameters (BMI, WC, HC, WHR) in patients with and without MS as a correlation between homocysteine and MS factors. METHODS The study included obese and overweight individuals, aged of 30-75 yrs. classified into two groups: with MS (n=35) and without MS (n=41). RESULTS Patients with MS had increased WC, BMI, BP, glycaemia, HOMA-IR, TG, CRP, microalbuminuria, homocysteine and decreased HDL-C (p<0.05). Statistically significant difference between groups was found for WC, BMI, sBP and dBP, TG, HDL-C (p<0.01) and glycaemia, CRP, Apo B, HOMA-IR (p<0.05). Significant positive correlations were found between homocysteine and sBP (p=0.036), dBP (p=0.04), Apo B (p=0.038) and hyperlipoproteinemia (type IIa, type IIb and type IV) (p=0.04). CONCLUSION Patients with MS had increased abdominal obesity, hypertension, hypertriglyceridemia, inflammation factors, IR, homocysteine and microalbuminuria as markers of endothelial dysfunction. A correlation between homocysteine and hypertension and hyperlipoproteinemia showed that homocysteine could be used as a potential marker for atherosclerosis progression.

The impact of inflammation to the antioxidant defense parameters in AMD patients

Background and aims: Oxidative stress and inflammation are postulated to be involved in the pathogenesis of the age-related macular degeneration (AMD) although the mechanism linking the oxidation and inflammation is still unknown. The aim of this study was the analysis of the antioxidant capacity measured by levels of the antioxidant enzymes: superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and total antioxidant status (TAS) along with the inflammatory markers such as Creactive protein (CRP), interleukin-6 (IL-6) and fibrinogen in AMD patients in order to analyze the relationship of the inflammatory markers with the antioxidant parameters and their association with AMD. Methods: The cross-sectional study, carried out in the University clinical setting, included 84 patients with the age-related macular degeneration, aged 71.25±7.14 years and 84 aged-matched control subjects (CG). Results: Statistical analysis revealed significantly lower GR (p=0.007) and TAS (p<0.000) values in the group of AMD patients compared to the controls. Logistic regression analysis showed that higher values of inflammatory markers (CRP>3 mg/L, IL>4.9 pg/mL, fibrinogen>3.8 g/L) and lower values of antioxidative parameters (SOD<900 U/gHb, GR<55 U/L and TAS<1.15 mmol/L) were significantly associated with AMD (ORCRP: 1.29, 95% CI 0.54-3.12, p<0.05; ORIL-6: 3.53, 95% CI 1.16–10.75, p=0.024; ORFIB: 3.06, 95% CI 1.78–7.92, p=0.019; ORSOD: 2.39, 95% CI 0.78–7.35, p<0.05; ORGR: 4.04, 95% CI 1.28–12.73, p=0.013; ORTAS: 2.9, 95% CI 1.4–6.3, p=0.032). Conclusions: Based on the results obtained, it may be concluded that the antioxidant defense system was significantly reduced in patients with AMD and the probability to develop AMD was higher in older individuals with lower values of antioxidant parameters and higher values of inflammatory markers.

The effect of Hyperglycemia and Oxidative Stress on the Development and Progress of Vascular Complications in Type 2 Diabetes

The effect of Hyperglycemia and Oxidative Stress on the Development and Progress of Vascular Complications in Type 2 Diabetes Oxidative stress is the result of increased production of free radicals, which impair the cell function and cause many pathological conditions and diseases. The development of diabetes, its course and complications are closely associated with an imbalance in pro-antioxidative cell state and change of redox potential. Prolonged exposure to hyperglycemia is currently considered the major factor of the pathogenesis of atherosclerosis in diabetes. Atherosclerosis is the cause of about 80% of mortality in diabetics, and over 75% of all hospitalized diabetic patients have associated cardiovascular complications. Hyperglycemia induces different vascular tissue damage at the cellular level, which potentially accelerates the atherosclerotic processes. The most significant mechanisms responsible for acceleration of atherosclerotic processes in diabetic patients are: a) non-enzymatic protein and lipid glycosylation which interferes with normal function, in the way that it deranges molecular conformation, impairs enzymatic function, reduces the capacity of breakdown and interferes with recognition of protein structures by receptors; b) interaction of glycosylated proteins with their receptors resulting in induction of oxidative stress and pro-inflammatory reactions; c) polyol pathway; d) hexosamine pathway and e) activation of protein kinase C and impaired growth factor expression. Uticaj Hiperglikemije I Oksidativnog Stresa na Nastanak I Razvoj Vaskularnih Komplikacija U Dijabetesu Tipa 2 Oksidativni stres nastaje kao posledica prekomerne produkcije slobodnih radikala, koji oštećuju ćelijsku funkciju i dovode do nastanka mnogih patoloških stanja i bolesti. Nastanak dijabetesa, tok i razvoj kompli-kacija, usko su povezani sa disbalansom pro-antioksidativnog stanja ćelije i promenom redoks potencijala. Prolongirana izloženost hiperglikemiji danas se smatra glavnim faktorom u patogenezi ateroskleroze u dijabetesu. Atero-skleroza je uzrok oko 80% smrtnosti u dijabetičara, a više od 75% hospitalizovanih dijabetičara imaju i prateće kardiovaskularne komplikacije. Hiperglikemija indukuje veliki broj oštećenja vaskularnog tkiva na ćelijskom nivou koji potencijalno ubrzavaju aterosklerotske procese. Istraživanja na ljudima i životinjama rasvetlila su nekoliko mehanizama koja obuhvataju većinu patoloških oštećenja u vaskulaturi: a) neenzimska glikozilacija proteina i lipida koja interferira sa normalnom funkcijom, tako što remeti molekularnu konformaciju, oštećuje enzimsku funkciju, smanjuje kapacitet razgradnje i interferira sa prepoznavanjem proteinskih struktura od strane receptora; b) interakcija glikoziliranih proteina sa njihovim receptorima rezultuje indukcijom oksidativnog stresa i proinflamatornim reakcijama; c) put poliola; d) put heksozamina; i e) aktivacija protein kinaze C i poremećaj ekspresije faktora rasta.

Structural myocardial alterations in diabetes and hypertension: the role of galectin-3.

Abstract Background: Galectin-3 is a protein widely distributed in the heart, brain and blood vessels, and has a regulatory role in inflammation, immunology and cancer. Many studies demonstrated that the increased level of galectin-3 is associated with progressive fibrosis and stiffening of the myocardium. The aim of this study was to investigate the role of galectin-3 in patients with type 2 diabetes (T2D) and/or arterial hypertension (HT). Methods: Study population included 189 patients, with no coronary artery disease, divided into three groups: group 1 (T2D), group 2 (T2D+HT), and group 3 (HT). All subjects underwent routine laboratory tests, as well as specific biomarkers assessment [galectin-3, glycosylated hemoglobin (HbA1c), N- terminal fragment B-type natriuretic peptide (NT-proBNP)]. Cardiological evaluation included physical examination, transthoracic tissue Doppler echocardiography and stress echocardiography. Results: The results of this study demonstrated significantly increased levels of galectin-3, blood glucose, and HbA1c in group 2. Also, echocardiographicaly, left ventricular (LV) diameters and IVS thickness were increased in this group of patients. Furthermore, in the same cohort a positive correlation between galectin-3 and NT-pro BNP, and galectin-3 and LV mass were demonstrated. In addition, a negative correlation between galectin-3 and LV end-diastolic diameter was revealed. Conclusions: This study revealed that levels of galectin-3 were higher in patients with both T2D and HT, and correlated with LV mass, indicating the potential role of this biomarker for early detection of myocardial structural and functional alterations.

Allopurinol and Enalapril Failed to Conserve Urinary NOx and Sodium in Ischemic Acute Renal Failure in Spontaneously Hypertensive Rats

Background: Ischemia-reperfusion-induced acute renal failure (ARF) is associated with a high mortality in patients with hypertension and with an unfavorable outcome of kidney transplants from marginal donors. Aim: The influence of allopurinol and enalapril on urinary nitrate/nitrite (UNOx), glomerular filtration rate, plasma and urinary sodium, and hemodynamic parameters was examined in spontaneously hypertensive rats (SHR) with ARF. Methods: ARF was induced by right-kidney removal and clamping the left renal artery for 40 min in 50 male 26-week-old SHR weighing 300 ± 23 g. The rats were randomly allocated to five groups: (1) sham operated; (2) ARF; (3) ARF after pretreatment with 40 mg/kg allopurinol; (4) ARF after pretreatment with 40 mg/kg enalapril, and (5) ARF after pretreatment with 40 mg/kg allopurinol and 40 mg/kg enalapril. Creatinine clearance, UNOx (Griess reaction), cardiac output (dye dilution technique), mean arterial blood pressure, and renal blood flow were measured 24 h after reperfusion. Total vascular resistance and renal vascular resistance were calculated and compared between the groups. Results: A nonsignificant decrease was found in both daily UNOx excretion and creatinine clearance when pretreated ARF groups and the ARF group without pretreatment were compared (p > 0.05). Significantly lower plasma sodium values (139.5 ± 4.86 mmol/l) in the allopurinol-pretreated ARF group were found than in the ARF group without pretreatment, in the ARF group pretreated with enalapril, and in the sham SHR group (p = 0.029). The urinary sodium loss was greater in the enalapril-pretreated than in the allopurinol-pretreated ARF group (p = 0.047). Allopurinol and/or enalapril pretreatment decreased total vascular resistance (p = 0.003) in comparison with the sham SHR group. Conclusion: Neither allopurinol nor enalapril nor both were protective against ischemia-reperfusion injury in SHR, nor altered glomerular filtration rate and UNOx in a favorable direction.