Sibel Özyazgan

Effect of Glucagon-Like Peptide-1(7–36) and Exendin-4 on the Vascular Reactivity in Streptozotocin/Nicotinamide-Induced Diabetic Rats

We investigated the vascular effects of glucagon-like peptide-1 (GLP-1) and Exendin-4 in type 2 diabetic rat aortae. Studies were performed in a normal control group (NC) (0.2 ml i.p. saline, n = 10), streptozotocin (STZ)/nicotinamide diabetic control group (DC) (a single dose of 80 mg/kg STZ i.p. injection 15 min after administration of 230 mg/kg nicotinamide i.p.), GLP-1 (GLPC) control group (1 µg/kg twice daily i.p. for 1 month, n = 10), Exendin-4 control group (EXC) (0.1 µg/kg twice daily i.p. for 1 month, n = 10), GLP-1-treated diabetic group (GLPT) (1 µg/kg twice daily i.p. for 1 month, n = 10), and Exendin-4-treated diabetic group (EXT) (0.1 µg/kg twice daily i.p. for 1 month, n = 10). One month of GLP-1 and Exendin-4 treatment significantly decreased the blood glucose levels of diabetic rats (113 ± 2 mg/dl, p < 0.001, and 117 ± 1 mg/dl, p < 0.001, respectively versus 181 ± 9 mg/dl in the DC group). Sensitivity (pD2) and maximum response (% Max. Relax) of acetylcholine-stimulated relaxations in the DC group (pD2: 6.73 ± 0.12 and 55 ± 6, respectively) were decreased compared with the non-diabetic NC group (pD2: 7.41 ± 0.25, p < 0.05, and 87 ± 4, p < 0.01). Treating diabetic rats with GLP-1, pD2 values and with Exendin-4, Max. Relax %values of aortic strips to acetylcholine returned to near non-diabetic NC values (pD2: 7.47 ± 0.15, p < 0.05, and 87 ± 3, p < 0.01, respectively). Maximal contractile responses (Emax) to noradrenaline in aortic strips from the diabetic DC group (341 ± 27 mg tension/mg wet weight) were significantly decreased compared with the non-diabetic NC (540 ± 66 mg tension/mg wet weight, p < 0.001) and the GLPT group (490 ± 25 mg tension/mg wet weight, p < 0.05). There were no significant differences in pD2 values of aortic strips to noradrenaline from all groups. Emax to KCl in aortic strips from the DC group (247 ± 10 mg tension/mg wet weight, p < 0.01) was significantly decreased compared with non-diabetic NC group (327 ± 26 mg tension/mg wet weight). Treating diabetic rats with GLP-1 (GLPT), Emax values of aortic strips to KCl returned to near non-diabetic NC values (271 ± 12 mg tension/mg wet weight). GLP-1 and (partially) Exendin-4 treatment could improve the increased blood glucose level and normalize the altered vascular tone in type 2 diabetic rats.

The effects of alpha lipoic acid on liver cells damages and apoptosis induced by polyunsaturated fatty acids.

We studied the effect of alpha-lipoic acid (ALA) on the liver cell damages and apoptosis by n-6 polyunsaturated fatty acids (PUFA) rich diet in young rats. 24 Wistar rats were divided into four groups. During the study, 12 of them (control) were fed with standard chow and other 12 (n-6) were fed with the food containing high-fat n-6 for 8 weeks. At the end of the fourth week, control and n-6 groups were randomly divided into two groups and then, 4 weeks, 35 mg/kg ALA are injected. Groups; control, control+ALA, n-6, n-6+ALA. The liver tissue glutathione (GSH) activity was determined. Immunohistochemistry for caspase-3 and TUNEL method for apoptosis were performed. The GSH levels have significantly decreased (p<0,001), and vacuolization in the hepatocytes, infiltration and the collagen accumulation around the central vein, hepatic stellate cells in the sinusoids have increased in n-6 group compared with the other groups. TUNEL (p<0,001) and caspase-3 (p<0,001) positive cells increased in n-6 group whereas all degenerative observations decreased in n-6+ALA group. Our results demonstrate that the feeding with n-6 PUFA causes fatty liver, fibrosis development, inflammations and apoptosis in the liver of young rats. ALA has a beneficial effects on these degenerative effects.

The effect of agmatine on the vascular reactivity in streptozotocin-diabetic rats

AIM We investigated the vascular effects of agmatine (decarboxylated arginine=AGM), an endogenous ligand for alpha(2)-adrenoceptors and imidazoline receptors, present in endothelium and smooth muscle, using the diabetic rat aortae. MATERIALS AND METHODS Studies were performed in control group (0.2 ml i.p. saline, n=10), streptozotocin (STZ)-diabetic control group (60 mg kg(-1) STZ i.p., n=10), agmatine (AGM)-control group (5 mg kg(-1)day(-1) i.p. AGM for 1 month, n=10), citrate-control group (0.2 ml 0.01 M, n=10), insulin-treated diabetic group ((3 U kg(-1) NPH+1 U kg(-1) regular insulin) twice per day, for 1 month, n=10) and AGM-treated diabetic group (5 mg kg(-1)day(-1) i.p. for 1 month, n=10). All values are expressed as means+/-S.E.M. Statistical analysis of the data was performed using ANOVA followed by Tukey multiple comparisons test. RESULTS One-month AGM-treatment significantly decreased the blood glucose levels of diabetic rats (502+/-44 mg dl(-1) to 343+/-31 mg dl(-1), P<0.001). Fast, slow and total components of responses to noradrenaline in all the experimental groups were not significantly affected by AGM-treatment. AGM reversed the decreased responses of acetylcholine (pD(2) and Inh.%, P<0.001 and P<0.05) in diabetic rats although it did not affect the responses of sodium nitroprusside in all groups. The contraction values of KCl in all groups were not affected by AGM-treatment. CONCLUSION AGM-treatment could improve the increased blood glucose level, reverse the endothelial dysfunction and normalize the endothelium-dependent relaxation responses in STZ-diabetic rats.

Impaired Relaxation in Aorta from Streptozotocin-diabetic Rats: Effect of Aminoguanidine (AMNG) Treatment

Aim The effect of 8 weeks′ streptozotocin (STZ)- induced diabetes and aminoguanidine (AMNG), the inhibitor of advanced glycosylation reaction, treatment on arteriolar reactivity to vasoactive substances was investigated in vitro. Materials and Methods Studies were performed in untreated control rats (n = 10), STZ-induced (60 mg/kg i.v.) diabetic rats (n = 10), AMNG-treated (600 mg/l given in drinking water throughout 8 weeks) control rats (n = 10) and AMNG-treated (600 mg/l given in drinking water, beginning at 72h after STZ and throughout 8 weeks of diabetes) diabetic rats (n = 10). Results are expressed as the mean ±s.e. Relaxant responses are expressed as a percentage (%) relaxation of noradrenaline-induced tone. Statistical comparisons were made by one-way analysis of variance (ANOVA) followed by Tukey–Kramer multiple comparisons test. Results 1. The decreased body weights (205 ± 6 g) and increased blood glucose levels (583 ± 8 mg/dl) of diabetic rats were partially restored by treatment of aminoguanidine (253 ± 6 g, p < 0.05 and 480 ± 14 mg/dl, p < 0.001, respectively). 2. Diabetes caused a 71% deficit in maximal endothelium-dependent relaxation to acetylcholine for noradrenaline precontracted aortas (p < 0.001). AMNG treatment prevented the diabetes-induced impairment in endothelium dependent relaxation (58 ± 8%) to acetylcholine, maximum relaxation remaining in the non-diabetic range (78 ± 4%). 3. Neither diabetes nor treatment affected endothelium-independent relaxation (pD2 and max. Relax.) to sodium nitroprusside. 4. Vasoconstrictor responses (pD2 and Max. Contraction) to noradrenaline and KCl were not influenced by the diabetic state and treatment. Conclusion Our data suggest that 8 weeks of experimental diabetes is associated with a decreased endothelium-dependent vasodilatation. AMNG treatment may prevent diabetes-induced endothelial dysfunction. This may be mediated via the prevention of advanced glycosylation end product formation, the enhanced release of vasodilator substances such as prostacyclin, the increased elasticity of blood vessels, the antioxidant activity and inhibitor activity of enzyme aldose-reductase by AMNG.

The Effects of Potassium Channels in Human Internal Mammary Artery

Background: Structural and functional changes in potassium channels of vascular smooth muscle cells may contribute to the development of diseases such as hypertension. We aim to investigate the vascular effects of potassium channel openers and blockers in human internal mammary artery (HIMA). Methods: Remaining segments of HIMA from 18 consecutive patients undergoing coronary artery bypass surgery were obtained to examine the vascular effects of various potassium channel openers (staurosporine, hydrochlorothiazide and cromakalim) and potassium channel blockers (4-aminopyridin [4-AP], charybdotoxin [CTX] and glibenclamide [GLBC]). Results: Noradrenaline (NA)-induced maximal contractions were inhibited by all 3 K+-channel blockers but only fully inhibited by 4-AP (95.6%). Only NA-induced contractions were reversed by CTX. Only K+-induced maximal contractions were significantly inhibited by 4-AP (95.6%, p < 0.05). Only acetylcholine-induced relaxation was fully inhibited by CTX. Only sodium nitroprusside-induced relaxations in potassium chloride-precontracted strips could be reversed by GLBC. Conclusions: Drugs affecting potassium channels may be useful in the treatment of hypertension and management of perioperative vasospasm during the coronary artery bypass surgery.

Elevated serum gamma-glutamyltransferase levels in patients with dilated ascending aorta

OBJECTIVE This study aimed to evaluate the serum gamma-glutamyltransferase (GGT) levels as an indirect marker of elevated oxidative stress in patients with dilated ascending aorta. METHODS The study was designed as an observational cross-sectional controlled study. One hundred consecutive patients with dilated ascending aorta and 50 consecutive controls with normal ascending aorta diameter were selected for the study by comprehensive transthoracic echocardiography (TTE). The aortic dilatation group was divided into two subgroups, according to the literature as the ectasia group (3.8-4.3 cm, 53 patients, 24 male and 29 female, mean age: 62.9±10.9 years) and the aneurysm group (≥4.4 cm, 47 patients, 18 male and 29 female, mean age: 65.5±11.1 years). The control group consisted of patients demonstrating no ascending aorta dilatation (≤3.7 cm, 50 patients, 24 male and 26 female, mean age: 62.7±9.2 years). ANOVA, Mann-Whitney U test, Pearsons correlation analysis, multivariate logistic regression analysis, and receiver-operator curve analysis were used for statistical analysis. RESULTS Regarding the comparison of laboratory parameters between the patient and control groups, serum gamma-glutamyltransferase (GGT) levels were found to be statistically significantly higher in both of the aortic dilatation subgroups than in the control group (p<0.001). In the correlation analysis between the ascending aorta diameter and GGT, a statistically significant positive correlation was found (r=0.282, p<0.001). The multivariate regression analysis revealed a significant relationship between GGT and the proximal ascending aorta diameter (β=0.131, odds ratio: 1.140, 95% CI: 1.060-1.225, p<0.001). CONCLUSION GGT as a marker of oxidative stress may play a role in the pathogenesis of aneurysm of the ascending aorta.

Investigation of MTHFR gene C677T polymorphism in cardiac syndrome X patients

Definition of Cardiac Syndrome X (CSX) refers to groups of patients with positive exercise stress test and normal epicardial coronary arteries on coronary angiography accompanied by chest pain. Although the etiology of CSX is not completely understood, there is a common consensus that its pathophysiology may be associated with endothelial dysfunction resulting in impaired coronary flow. Some polymorphisms observed on the MTHFR gene cause inactivation of the MTHFR enzyme, leading to hyperhomocysteinemia and homocysteinuria, which are prominent risk factors of cardiovascular and cerebrovascular diseases. It was aimed to explain the association of the endothelial dysfunction, which is thought to play a role in the pathophysiology of CSX, with C677T polymorphism on MTHFR gene based on genetic basis.

Plasma Betatrophin Levels of Subjects Classified with Normal, Impaired, and Diabetic Glucose Tolerance, and Subjects with Impaired Fasting Glucose

This study was aimed to investigate whether betatrophin shows glucose intolerance or not. To access the plasma betatrophin levels after basal and glucose load, groups were classified as normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and diabetic glucose tolerance (DGT) according to WHO 2012 criteria. An oral glucose tolerance test was performed on age-matched subjects (n=220) with a body mass index (BMI)<27 kg/m2. Subjects were categorized as normoglycemic (n=55), IFG (n=50), IGT (n=60), and DM (n=55) according to the WHO criteria. Baseline betatrophin levels in DGT are significantly higher than in NGT (p<0.005), IFG (p<0.004), and IGT (p<0.001). Male subjects have significantly higher betatrophin levels than female subjects (p<0.01). In DGT, betatrophin of male subjects was found to be significantly higher than the betatrophin of male subjects in NGT (p<0.04), IFG (p<0.01), and IGT (p<0.01). Significant relationship between betatrophin and both ages and HbA1c in all groups were observed. When ages were accepted as an independent factor, significant correlation between betatrophin and ages were found. Betatrophin is increased and associated with age and HbA1c in DGT. Males had higher betatrophin levels compared with females in DGT group. As no obvious betatrophin deficiency to substitute in IFG and IGT individuals were observed, betatrophin levels appeared to be related to the pathogenesis of the diabetic stages rather than prediabetic stages.

Does Inflammation Have a Role in the Pathogenesis of Cardiac Syndrome X? A Genetic-Based Clinical Study With Assessment of Multiple Cytokine Levels

We compared Turkish patients with cardiac syndrome X (CSX) and controls with respect to serum pro- and anti-inflammatory cytokine levels, as well as the single-nucleotide polymorphisms located in the promoter regions of their related genes. This study included 111 consecutive patients angiographically diagnosed with CSX and 111 healthy controls with similar demographic characteristics. Serum interleukin (IL) 6, tumor necrosis factor α (TNF-α), and IL-10 levels were measured, and the genotypes of the patients and controls were determined using standard methods. Serum IL-6 and IL-10 levels were significantly higher in the CSX group than in the control group (P < .01, respectively). Serum TNF-α level was lower in the CSX group than in the control group (P < .001). On the other hand, participants with CSX and healthy controls were not significantly different with respect to the genotype distributions of IL-6, TNF-α, and IL-10 genes. As a result of our study, both pro-inflammatory and anti-inflammatory cytokines may play a role in the pathogenesis of CSX. In contrast, the studied gene polymorphisms did not influence CSX pathogenesis.

Role of Bombesin and Cholecystokinin Receptors in Gastric Injury Induced by Hemorrhagic Shock in the Rat

Bombesin has been shown to have trophic effects on the gastrointestinal tissue. Bombesin has direct mitogenic effects besides stimulating release of gastric hormones. The aim of this study was to investigate the effect of bombesin in hemorrhagic shock-induced stress ulcers in rats, and the role of cholecystokinin (CCK) receptors in this activity. Hemorrhagic shock was created by withdrawing 3 ml blood/200 g b.w. of rats. At the end of the 1-hour hypovolemic shock period, histological analysis, gastric ulcer index, gastric myeloperoxidase activity and gastric protein oxidation levels were determined. When given before the hemorrhage, subcutaneous bombesin (10 µg/kg) reduced macroscopically gastric ulcer index (p < 0.05). Blockade of CCK-A receptors with intraperitoneal MK-329 (1 mg/kg) did not reverse bombesin-induced gastroprotection. Blockade of CCK-B receptors with intraperitoneal L-365,260 (25 mg/kg) reversed bombesin-induced gastroprotection. Blockade of the two receptors resulted in no gastroprotection at all. It is concluded that bombesin treatment attenuated hemorrhagic shock-induced stress ulcers in rats via CCK receptors.