Yavuz Taga

Resveratrol: French Paradox Revisited

Resveratrol is a polyphenol that plays a potentially important role in many disorders and has been studied in different diseases. The research on this chemical started through the “French paradox,” which describes improved cardiovascular outcomes despite a high-fat diet in French people. Since then, resveratrol has been broadly studied and shown to have antioxidant, anti-inflammatory, anti-proliferative, and anti-angiogenic effects, with those on oxidative stress possibly being most important and underlying some of the others, but many signaling pathways are among the molecular targets of resveratrol. In concert they may be beneficial in many disorders, particularly in diseases where oxidative stress plays an important role. The main focus of this review will be the pathways affected by resveratrol. Based on these mechanistic considerations, the involvement of resveratrol especially in cardiovascular diseases, cancer, neurodegenerative diseases, and possibly in longevity will be is addressed.

Increased erythrocyte susceptibility to lipid peroxidation in human Parkinson's disease

Recent evidence suggests that among the factors that lead to neurodegenerative changes in Parkinsons disease are stimulation of lipid peroxidation and deficiency of glutathione and glutathione peroxidase in substantia nigra. We have investigated the effect of neurodegenerative changes on plasma and erythrocytes of patients with Parkinsons disease and compared the results with those of age-matched controls. Both plasma lipid peroxide levels and erythrocyte susceptibility to lipid peroxidation were significantly increased in Parkinsons disease. Erythrocyte fragility tests revealed that in 35% of the patients there was increased fragility. In addition, erythrocyte catalase activities were not changed whereas glutathione levels and glutathione peroxidase activities were decreased in Parkinsons disease. Our results suggest that erythrocyte membrane integrity may be impaired in Parkinsons disease.

The effect of vitamin E therapy on plasma and erythrocyte lipid peroxidation in chronic hemodialysis patients.

The effect of vitamin E therapy on plasma and erythrocyte (RBC) lipid peroxidation was investigated in patients undergoing chronic hemodialysis. Before vitamin E therapy, both plasma and RBC lipid peroxidation values of chronic hemodialysis patients were significantly higher than those of healthy controls. Treatment with vitamin E (300 mg/day) for 1 month resulted in a significant decrease of lipid peroxidation. Vitamin E therapy may be a promising approach to prevent peroxidation of membrane lipids in chronic renal failure.

Effect of zinc supplementation on growth hormone secretion, IGF-I, IGFBP-3, somatomedin generation, alkaline phosphatase, osteocalcin and growth in prepubertal children with idiopathic short stature

Controversy exists about the effect of zinc on growth and the GH-IGF system. Zinc supplementation has been shown to stimulate linear growth in zinc-deficient children. However the mechanism of this effect has not been well characterized. Furthermore, the effect of zinc supplementation on non-zinc-deficient short children is unknown. We investigated the effect of zinc supplementation on endogenous GH secretion, serum IGF-I and IGFBP-3 concentrations, IGF-I and IGFBP-3 generation in response to exogenous GH, bone formation markers, and linear growth of non-zinc-deficient children with idiopathic short stature. We analyzed prospectively serum zinc, IGF-I, IGFBP-3, alkaline phosphatase, osteocalcin, and GH response to clonidine test, and performed a somatomedin generation test before and 6 weeks after zinc supplementation in 22 (16 M, 6 F) prepubertal children with idiopathic short stature. Serum IGF-I increased from 67.4+/-70.6 to 98.2+/-77.3 ng/ml (p <0.001), IGFBP-3 from 2326+/-770 to 2758+/-826 ng/ml (p <0.001), alkaline phosphatase from 525+/-136 to 666+/-197 U/l (p <0.0001), and osteocalcin from 16.8+/-10.6 to 25.8+/-12.8 ng/ml (p <0.05) after zinc supplementation despite there being no difference in GH response to clonidine after zinc supplementation (peak GH 11.6+/-6.9 vs 13.4+/-7.8 ng/ml, GH area under the curve during clonidine test 689+/-395 vs 761+/-468, NS). Percent change in IGF-I and IGFBP-3 during the somatomedin generation test was not significantly affected by zinc supplementation (118% vs 136% and 57% vs 44%, respectively). There was no significant correlation between percentage increase in zinc levels and percentage increase in parameters tested. Height SDS or weight SDS did not improve significantly in 17 patients who continued on zinc supplementation for at least 6 months (6-12 months) (-2.59 vs -2.53 SDS and -1.80 vs -1.67 SDS, respectively). Zinc supplementation increased basal IGF-I, IGFBP-3, alkaline phosphatase and osteocalcin without changing GH response to clonidine. Zinc supplementation did not affect sensitivity to exogenous GH as tested by IGF-I and IGFBP-3 generation test. These results suggest a direct stimulatory effect of zinc on serum IGF-IGFBP-3, alkaline phosphatase and osteocalcin. Despite improvements in the above parameters, zinc supplementation to children with idiopathic short stature with normal serum zinc levels did not significantly change height or weight SDS during 6-12 months follow-up.

Effects of ACE inhibition and angiotensin II receptor blockade on glomerular basement membrane protein excretion and charge selectivity in type 2 diabetic patients.

Angiotensin-converting enzyme (ACE) inhibitors may reduce urinary albumin excretion (UAE) by decreasing glomerular pressure and increasing glomerular charge selectivity through preservation of glycosaminoglycans. The effect of Angiotensin II antagonism on glomerular charge selectivity remains to be determined. The aim of this study was to compare the effects of an AT1 blocker losartan and an ACE inhibitor (ACE-I) enalapril on UAE, extracellular matrix proteins, glycosaminoglycan excretion (UGAG) and red blood cell anionic charge (RBCCh) which are the indirect markers of glomerular basement membrane anionic content in hypertensive Type 2 diabetic patients. Twenty-four patients were randomised into two groups and received either enalapril (5—20 mg/d) or losartan (50—100 mg/d). All parameters were measured at baseline and after six months of treatment. At the end of six months, systolic and diastolic blood pressures (BP), UAE rates, UGAG excretion and RBCCh were significantly and equally reduced in both treatment groups compared with baseline. RBCCh was negatively correlated with UAE (r=-0. O 57, p<0.0001) and UGAG excretion (r=-0.57, Rp<0.0001); UAE was correlated with UGAG excretion (r=0.58, p<0.0001). In conclusion, enalapril and losartan treatment were equally effective in reducing BP, UAE as well as UGAG excretion and preserving RBCCh in hypertensive Type 2 diabetic patients. ACE inhibition and AT1-receptor blockade may have favourable effects on preserving glomerular anionic content in hypertensive diabetic patients.

Apolipoprotein E Genotyping in Turkish Myocardial Infarction Survivors and Healthy Controls.

The apolipoprotein (Apo) E gene is known to be polymorphic. Three common alleles determine six phenotypes which can easily be detected by restriction fragment length polymorphism. We performed apo E genotyping in myocardial infarction survivors and healthy controls for the first time in the Turkish population. DNA was amplified by polymerase chain reaction (PCR) and the PCR product was digested with restriction enzymes HhaI to detect apo E2, E3, E4 and with TaqI to detect apo E1. Relative allele frequency for the patient group was found to be 0.91 for E3, 0.07 for E2, 0.02 for E4 and for the control group 0.875 for E3, 0.067 for E2, 0.058 for E4. Copyright 1995 S. Karger AG, Basel

Hyperglycemia induced by intracerebroventricular choline: involvement of the sympatho-adrenal system.

Intracerebroventricular (i.c.v.) injection of choline (75-300 microg) produced a dose-dependent increase in blood glucose levels. Pre-treatment with the nicotinic acetylcholine receptor antagonist, mecamylamine (50 microg, i.c.v.) blocked the hyperglycemia induced by choline (150 microg, i.c.v.), but the response was not affected by pre-treatment with the muscarinic acetylcholine receptor antagonist, atropine (10 microg, i.c.v.). Pre-treatment with the neuronal choline uptake inhibitor, hemicholinium-3 (20 microg, i.c.v.), attenuated the hyperglycemia induced by choline. The hyperglycemic response to choline was associated increased plasma levels of adrenaline and noradrenaline. The hyperglycemia elicited by choline was greatly attenuated by bilateral adrenalectomy, and entirely blocked by either surgical transection of the splanchnic nerves or by pre-treatment with the alpha-adrenoceptor antagonist, phentolamine. These data show that choline, a precursor of acetylcholine, increases blood glucose and this effect is mediated by central nicotinic acetylcholine receptor activation. An increase in sympatho-adrenal activity appears to be involved in the hyperglycemic effect of choline.

INTERACTION OF 3H-DEFIBROTIDE WITH CULTURED HUMAN UMBILICAL VEIN ENDOTHELIAL CELLS

Defibrotide is a profibrinolytic and antithrombotic drug which seems to modulate endothelial cell function. In this study, a method for radioactive labeling of the drug and its interaction with cultured endothelial cells is proposed. 3H-Acetic anhydride was used to label defibrotide. Endothelial cells obtained by collagenase treatment of human umbilical cord veins were cultured in 24-welled plastic culture dishes. Binding experiments were carried out by incubating cell cultures with media containing various concentrations of labeled defibrotide. Our results showed that labeled defibrotide has a KL value of 4.2 micrograms/ml for endothelial cells. Although the presence of a specific transporter is possible, the high molecular weight of the fraction used suggests that the interaction is binding to a specific receptor.

Quercetin-Induced Cell Death in Human Papillary Thyroid Cancer (B-CPAP) Cells

In this study, we have investigated the antiproliferative effect of quercetin on human papillary thyroid cancer cells and determined the apoptotic mechanisms underlying its actions. We have used different concentrations of quercetin to induce apoptosis and measured cell viability. Apoptosis and cell cycle analysis was determined by flow cytometry using Annexin V and propidium iodide. Finally, we have measured changes in caspase-3 and cleaved poly(ADP-ribose) polymerase (PARP) protein expression levels as hallmarks of apoptosis and Hsp90 protein expression level as a marker of proteasome activity in treated and control cells. Quercetin treatment of human papillary thyroid cancer cells resulted in decreased cell proliferation and increased rate of apoptosis by caspase activation. Furthermore, it was demonstrated that quercetin induces cancer cell apoptosis by downregulating the levels of Hsp90. In conclusion, we have shown that quercetin induces downregulation of Hsp90 expression that may be involved in the decrease of chymotrypsin-like proteasome activity which, in order, induces inhibition of growth and causes cell death in thyroid cancer cells. Thus, quercetin appears to be a promising candidate drug for Hsp90 downregulation and apoptosis of thyroid cancer cells.

The effect of resveratrol on signal transduction pathways and the role of pro-apoptotic Bax protein on apoptosis in HCT- 116 colon carcinoma cell lines.

Colon carcinoma is the third among the cancer related deaths. The role of pro-apoptotic Bax protein on the resveratrol related apoptosis, mitochondrial membrane potential and signal pathways has not been identified in colon carcinoma cells. In this direction, HCT-116 bax positive and HCT-116 negative cell lines were utilized to detect the apoptotic effect and I?B, MEK1 and STAT 3 signal transduction pathways of resveratrol. The impact on the cell viability and IC50 value of resveratrol has been determined via WST-1 viability assay. The ratio of apoptosis has been evaluated via flow cytometry following Annexin V/Propidium iodide (PI) double staining. Changes in the mitochondrial membrane potential have been analyzed by flow cytometry and JC-1 fluorometric staining. IkB, MEK1 and STAT3 molecules were measured by Enspire device. Data showed the IC50 value for resveratrol as 50M. According to the flow cytometry, apoptosis ratio has been determined as 29.65% in the experimental group of bax positive cells, as 13.98% in the experimental group of bax negative cells. Changes in the membrane potential has been established as 8.62% in the experimental group of bax positive cells, as 97.98% in the experimental group of bax negative cells. When the obtained data from Enspire device was reviewed; bax positive cells I?B phosphorylations were found as as 5.22 for experimental groups; MEK1 phosphorylations were found as and as 1.15 for experimental groups; STAT 3 phosphorylations were found as and as 2.52 for experimental groups. In HCT-116 bax negative cells, I?B phosphorylation were and 2.71 in experimental groups; MEK1 phosphorylation were 1.18 in experimental groups; STAT 3 phosphorylation were 1.54 in experimental groups. Our data show that Bax protein plays role in the apoptotic effect of resveratrol by altering mitochondrial membrane potential and mitochondrial membrane permeability, signal transduction and the absence of Bax increase the sensitivity of HCT-116 colon carcinoma cells to apoptosis.