İlknur Bingül

Effect of blueberry pretreatment on diethylnitrosamine-induced oxidative stress and liver injury in rats.

Diethylnitrosamine (DEN) treatment increases the generation of reactive oxygen species (ROS), apoptosis, necrosis and proliferation in the liver. Blueberries (BB; Vaccinium corymbosum L.) contain polyphenols and other active components and have high antioxidant capacities. We investigated the effect of BB pretreatment on DEN-induced liver injury and oxidative and nitrosative stress in male rats. Rats were fed with 5% and 10% BB containing diet for six weeks and DEN (200mg/kg; i.p.) was applied two days before the end of this period. Liver function tests were determined in serum and histopathological evaluation was performed in the liver tissue. Apoptosis-related proteins, Bax and B cell lymphoma-2 (Bcl-2) and proliferating cell nuclear antigen (PCNA) expressions were also examined. Oxidative and nitrosative stress were evaluated in the liver by measuring thiobarbituric acid reactive substances, diene conjugate, protein carbonyl and nitrotyrosine levels, and glutathione levels and glutathione peroxidase, superoxide dismutase and glutathione transferase (GST) activities. Pretreatment with high dose of BB reduced apoptotic, necrotic and proliferative changes in the liver induced by DEN. Dietary BB also decreased hepatic lipid peroxidation, protein oxidation and nitrotyrosine levels together with increased GST activity. In conclusion, BB may have an inhibiting effect on acute liver injury by reducing apoptosis, necrosis, proliferation, oxidative and nitrosative stress in DEN-treated rats.

Betaine treatment decreased oxidative stress, inflammation, and stellate cell activation in rats with alcoholic liver fibrosis

The aim of this study was to investigate the effect of betaine (BET) on alcoholic liver fibrosis in rats. Fibrosis was experimentally generated with ethanol plus carbon tetrachloride (ETH+CCl4) treatment. Rats were treated with ETH (5% v/v in drinking water) for 14 weeks. CCl4 was administered intraperitoneally (i.p.) 0.2mL/kg twice a week to rats in the last 6 weeks with/without commercial food containing BET (2% w/w). Serum hepatic damage markers, tumor necrosis factor-α, hepatic triglyceride (TG) and hydroxyproline (HYP) levels, and oxidative stress parameters were measured together with histopathologic observations. In addition, α-smooth muscle-actin (α-SMA), transforming growth factor-β1 (TGF-β1) and type I collagen (COL1A1) protein expressions were assayed immunohistochemically to evaluate stellate cell (HSC) activation. mRNA expressions of matrix metalloproteinase-2 (MMP-2) and its inhibitors (TIMP-1 and TIMP-2) were also determined. BET treatment diminished TG and HYP levels; prooxidant status and fibrotic changes; α-SMA, COL1A1 and TGF-β protein expressions; MMP-2, TIMP-1 and TIMP-2 mRNA expressions in the liver of fibrotic rats. In conclusion, these results indicate that the antifibrotic effect of BET may be related to its suppressive effects on oxidant and inflammatory processes together with HSC activation in alcoholic liver fibrosis.

Olive leaf extract decreases age-induced oxidative stress in major organs of aged rats.

Olive leaf (Olea europaea L.) extract (OLE) is a powerful anti‐oxidant rich in polyphenols. As oxidative stress plays an important role in aging, we investigated the effect of OLE on oxidative stress in the liver, heart and brain of aged rats.

Analysis of vitamin D receptor gene polymorphisms in vitiligo.

Background: Vitiligo is a progressive depigmenting disorder characterized by the loss of functional melanocytes from the epidermis. The etiopathogenesis of vitiligo is still unclear. Vitamin D has both stimulatory and protective effects on melanocytes and acts through its nuclear vitamin D receptor (VDR) on target cells. Aim: The aim of this study was to investigate the association between VDR gene polymorphisms and susceptibility to vitiligo. Methods: 98 patients with vitiligo and 216 age- and sex-matched controls recruited from dermatology outpatients attending the same department were included in the study. Genomic DNA was extracted from peripheral blood leukocytes using a DNA isolation kit. The VDR polymorphisms of BsmI, ApaI, TaqI, FokI and Cdx2 were investigated by rapid capillary PCR with melting curve analysis. Differences in genotype distributions and allele frequencies in vitiligo cases versus controls were compared for statistical significance using χ2 test. Results: Subjects with TaqI polymorphism had a 2.23-fold increased risk of developing vitiligo. Furthermore, a haplotype analysis showed that BsmI/ApaI/TaqI/FokI/Cdx2 GCCCG was significantly overrepresented in the vitiligo patients in comparison with controls (p = 0.031). Conclusion: This study showed that VDR TaqI gene polymorphism and the haplotype BsmI/ApaI/ TaqI/FokI/Cdx2 GCCCG may be considered as novel risk factors in vitiligo.

Effects of carnosine, taurine, and betaine pretreatments on diethylnitrosamine-induced oxidative stress and tissue injury in rat liver.

Several chemicals such as N-diethylnitrosamine (DEN) promote hepatocellular cancer in rodents and induce hepatocyte injury. DEN affects the initiation stage of carcinogenesis together with enhanced cell proliferation accompanied by hepatocellular necrosis. DEN-induced hepatocellular necrosis is reported to be related to enhanced generation of reactive oxygen species. Carnosine (CAR), taurine (TAU), and betaine (BET) are known to have powerful antioxidant properties. We aimed to investigate the effects of CAR, TAU, and BET pretreatments on DEN-induced oxidative stress and liver injury in male rats. Rats were given CAR (2 g L−1 in drinking water), TAU (2.5% in chow), and BET (2.5% in chow) for 6 weeks and DEN (200 mg kg−1 intraperitoneally) was given 2 days before the end of this period. Serum alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and γ-glutamyl transferase activities were determined and a histopathologic evaluation was performed on the liver tissue. Oxidative stress was detected in the liver by measuring malondialdehyde, diene conjugate, protein carbonyl and nitrotyrosine levels, glutathione and glutathione peroxidase levels, and superoxide dismutase and glutathione transferase activities. Pretreatments with CAR, TAU, and BET decreased liver prooxidant status without remarkable changes in antioxidant parameters in DEN-treated rats. Pretreatments with TAU and BET, but not CAR, were also found to be effective to reduce liver damage in DEN-treated rats. In conclusion, TAU, BET, and possibly CAR may have an ameliorating effect on DEN-induced hepatic injury by reducing oxidative stress in rats.

High-fat diet plus carbon tetrachloride-induced liver fibrosis is alleviated by betaine treatment in rats.

Steatosis, the first lesion in non-alcoholic fatty liver disease (NAFLD), may progress to fibrosis, cirrhosis, and hepatocellular carcinoma. Steatosis predisposes the liver to oxidative stress, inflammation, and cytokines. Betaine (BET) has antioxidant, antiinflammatory and hepatoprotective effects. However, the effects of BET on liver fibrosis development are unknown. Rats were treated with high-fat diet (60% of total calories from fat) for 14weeks. Carbon tetrachloride (0.2mL/kg; two times per week; i.p.) was administered to rats in the last 6weeks with/without commercial food containing BET (2%; w/w). Serum liver function tests and tumor necrosis factor-α, insulin resistance, hepatic triglyceride (TG) and hydroxyproline (HYP) levels and oxidative stress parameters were determined along with histopathologic observations. Alpha-smooth muscle-actin (α-SMA), transforming growth factor-β1 (TGF-β1) and type I collagen (COL1A1) protein expressions and mRNA expressions of matrix metalloproteinase-2 (MMP-2) and its inhibitors (TIMP-1 and TIMP-2) were evaluated. BET decreased TG and HYP levels, prooxidant status and fibrotic changes in the liver. α-SMA, COL1A1 and TGF-β1 protein expressions, MMP-2, TIMP-1, and TIMP-2 mRNA expressions diminished due to BET treatment. BET has an antifibrotic effect and this effect may be related to its antioxidant and antiinflammatory actions together with suppression on HSC activation.

Carnosine decreased oxidation and glycation products in serum and liver of high-fat diet and low-dose streptozotocin-induced diabetic rats

High‐fat diet (HFD) and low‐dose streptozotocin (STZ)‐treated rats provide useful animal model for type II diabetes mellitus. Oxidative stress and advanced glycation end products (AGEs) play a role in the development of diabetic complications. Carnosine (CAR) has anti‐oxidant and anti‐glycating properties. We investigated the effects of CAR on oxidation and glycation products in HFD+STZ rats. Rats were fed with HFD (60% of total calories from fat) for 4 weeks, and then a single dose of STZ (40 mg/kg; i.p.) was applied. Rats with blood glucose levels above 200 mg/dl were fed with HFD until the end of the 12th week. CAR (250 mg/kg body weight; i.p.; five times a week) was administered to the rats for the last four weeks. CAR significantly decreased serum triglyceride (TG) (57.7%), cholesterol (35.6%) levels and hepatic marker enzyme activities of HFD+STZ rats. It significantly reduced serum reactive oxygen species (ROS) (23.7%), AGEs (13.4%) and advanced oxidized protein products (AOPP) (35.9%) and hepatic TG (59%), ROS (26%), malondialdehyde (MDA) (11.5%), protein carbonyl (PC) (19.2%) and AGE (20.2%) levels. Liver steatosis and hepatocyte ballooning were also significantly reduced. However, CAR treatment did not alter serum glucose and blood glycated haemoglobin and hepatic anti‐oxidant enzyme activities/mRNA expressions in HFD+STZ rats. Our results indicate that CAR decreased accumulation of oxidation and glycation products, such as MDA, AGE, AOPP and PC in the serum and liver and ameliorated hepatic dysfunction in HFD+STZ rats. This effect may be related to its anti‐oxidative, anti‐glycating, and anti‐lipogenic potential.

Effect of Carnosine on Renal Function, Oxidation and Glycation Products in the Kidneys of High-Fat Diet/Streptozotocin-Induced Diabetic Rats

High fat diet (HFD) and low dose of streptozotocin (STZ)-treated rats provide an animal model for type 2 Diabetes Mellitus (T2DM). Oxidative stress plays a role in the development of diabetic complications. Carnosine (CAR) has antioxidant and antiglycating properties. We investigated effects of CAR on renal function, oxidation and glycation products in HFD+STZ-rats. Rats were fed with HFD (60% of total calories from fat) for 4 weeks and then a single dose STZ (40 mg/kg; i.p.) was applied. Rats with blood glucose levels above 200 mg/dL were fed with HFD until the end of the 12th week. CAR (250 mg/kg body weight; i.p.; 5 times a week) was administered to rats for the last 4 weeks. Glycated hemoglobin (HbA1c), glucose, lipids, and andrenal function tests in serum as well as reactive oxygen species, malondialdehyde, protein carbonyl, advanced oxidation protein products, advanced glycation end products (AGEs), antioxidant power, and antioxidant enzyme activities and their mRNA expressions in kidneys were determined. CAR treatment did not alter glucose and HbA1c, but it decreased serum lipids, creatinine, and urea levels in HFD+STZ rats. Oxidation products of lipids and proteins and AGEs levels decreased, but antioxidant enzyme activities and their mRNA expressions remained unchanged due to CAR treatment. Our results indicate that CAR treatment alleviated renal function and decreased accumulation of oxidation and glycation products in kidneys in HFD+STZ-rats.

Blueberry treatment attenuated cirrhotic and preneoplastic lesions and oxidative stress in the liver of diethylnitrosamine-treated rats.

Diethylnitrosamine (DEN)-induced liver cancer normally develops in stages that progress from cirrhosis and carcinoma. Increased oxidative stress is suggested to play a role in DEN-induced carcinogenicity. Blueberries (BB) contain high antioxidant capacity. We investigated the effect of BB supplementation on development of DEN-induced cirrhosis and neoplastic lesions in the liver. Rats were injected with DEN (200 mg/kg; i.p.) three times with an interval of 15 days at 4, 6, and 8 weeks and sacrificed 8 weeks after the last DEN injection. They were also fed on 8% BB (w/w) containing chow for 16 weeks. Hepatic damage markers in serum were determined together with hepatic histopathological examinations. Hydroxyproline (HYP), malondialdehyde (MDA), diene conjugate (DC), protein carbonyl (PC), and glutathione (GSH) levels, and CuZn-superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities, and their mRNA expressions were measured. Protein and mRNA expressions of glutathione transferase-pi (GST-pi) were evaluated as a marker of preneoplastic lesions. BB supplementation decreased hepatic damage markers in serum and hepatic MDA, DC, and PC levels, but SOD, CAT, and GSH-Px activities and their mRNA expressions remained unchanged in DEN-treated rats. BB attenuated cirrhotic changes and decreased hepatic HYP levels and GST-pi expressions. Our results indicate that BB is effective in decreasing development of DEN-induced hepatic cirrhosis and preneoplastic lesions by acting as an antioxidant (radical scavenger) itself without affecting activities and mRNA expressions of antioxidant enzymes.

Vascular endothelial growth factor G+405C polymorphism may contribute to the risk of developing papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy. Vascular endothelial growth factor (VEGF) is a mediator implicated with cell proliferation, differentiation and migration, and monocyte/macrophage chemotaxis. In present study, we aimed to investigate the relationship between VEGF gene polymorphisms (G+405C, T‐460C, and A‐2578C) and PTC susceptibility.