Green Tea Polyphenols Alleviate Autophagy Inhibition Induced by High Glucose in Endothelial Cells.

Bovine aortic endothelial cells (BAECs) were cultured with high glucose (33 mmol/L), 4 mg/L green tea polyphenols (GTPs) or 4 mg/L GTPs co-treatment with high glucose for 24 h in the presence or absence of Bafilomycin-A1 (BAF). We observed that high glucose increased the accumulation of LC3-II. Treatment with BAF did not further increase the accumulation of LC3-II. Results also showed an increased level of p62 and decreased Beclin-1. However, GTPs showed inversed trends of those proteins. Furthermore, GTPs co-treatment with high glucose decreased the level of LC3-II and a much higher accumulation of LC3-II was observed in the presence of BAF in comparison with high glucose alone. Results also showed a decreased p62 and increased Beclin-1. The results demonstrated that GTPs alleviated autophagy inhibition induced by high glucose, which may be involved in the endothelial protective effects of green tea against hyperglycemia.

Analysis of trans-resveratrol and trans-piceid in vegetable foods using high-performance liquid chromatography.

Trans-resveratrol and resveratrol glucoside are natural phenolic compounds existed in a wide variety of plant species, which are extensively consumed in many countries. The existing studies excessively focused on grapes and their products, and little about daily vegetable foods. Actually, in much more countries, vegetable foods are residents' principal food and nutrient origins. This study was to investigate the levels of trans-resveratrol and trans-piceid in daily vegetable foods of China using high-performance liquid chromatography (HPLC) method with fluorescence detection (FLD). Trans-piceid was the major form existing in most vegetable foods, and most of the samples contained higher trans-piceid than trans-resveratrol. The contents of trans-resveratrol and trans-piceid in different varieties and regions were different. Moreover, peculiar vegetable foods to some region were also one of the most important sources of trans-resveratrol and trans-piceid. Therefore, vegetable foods were other significant sources of trans-resveratrol and trans-piceid except the foods published.

Green Tea Polyphenols Attenuate High-Fat Diet-Induced Renal Oxidative Stress through SIRT3-Dependent Deacetylation.

Fifty male Wistar rats were fed a standard chow diet or a high-fat (HF) diet, and different concentrations of green tea polyphenols (GTPs) (0.8, 1.6, and 3.2 g/L) were administered in the drinking water. We found that the malondialdehyde (MDA) level in the HF diet group was significantly higher than that in the control (CON) group (P<0.05). Decreased peroxisome proliferator-activated receptor (PPAR)-α and sirtuin 3 (SIRT3) expression, and increased manganese superoxide dismutase (MnSOD) acetylation levels were also detected in the HF diet group (P<0.05). GTP treatment upregulated SIRT3 and PPARα expression, increased the pparα mRNA level, reduced the MnSOD acetylation level, and decreased MDA production in rats fed a HF diet (P<0.05). No significant differences in total renal MnSOD and PPAR-γ coactivator-1α (PGC1-α) expression were detected. The reduced oxidative stress detected in kidney tissues after GTP treatment was partly due to the higher SIRT3 expression, which was likely mediated by PPARα.

Resveratrol ameliorates high glucose and high-fat/sucrose diet-induced vascular hyperpermeability involving Cav-1/eNOS regulation.

Vascular endothelial hyperpermeability is one of the manifestations of endothelial dysfunction. Resveratrol (Res) is considered to be beneficial in protecting endothelial function. However, currently, the exact protective effect and involved mechanisms of Res on endothelial dysfunction-hyperpermeability have not been completely clarified. The aim of present study is to investigate the effects of Res on amelioration of endothelial hyperpermeability and the role of caveolin-1 (Cav-1)/endothelial nitric oxide synthase (eNOS) pathway. Adult male Wistar rats were treated with a normal or high-fat/sucrose diet (HFS) with or without Res for 13 weeks. HFS and in vitro treatment with high glucose increased hyperpermeability in rat aorta, heart, liver and kidney and cultured bovine aortic endothelial cells (BAECs), respectively, which was attenuated by Res treatment. Application of Res reversed the changes in eNOS and Cav-1 expressions in aorta and heart of rats fed HFS and in BAECs incubated with high glucose. Res stimulated the formation of NO inhibited by high glucose in BAECs. Beta-Cyclodextrin (ß-CD), caveolae inhibitor, showed the better beneficial effect than Res alone to up-regulate eNOS phosphorylative levels, while NG-Nitro-77 L-arginine methyl ester (L-NAME), eNOS inhibitor, had no effect on Cav-1 expression. Our studies suggested that HFS and in vitro treatment with high glucose caused endothelial hyperpermeability, which were ameliorated by Res at least involving Cav-1/eNOS regulation.

Dose and time-dependent hypercholesterolemic effects of iodine excess via TRbeta1-mediated down regulation of hepatic LDLr gene expression.

BACKGROUND: With the global improvement of iodine nutrition, iodine excess is emerging as a new concern. AIM OF STUDY: The aim of this study is to illustrate the physiological effects and potential molecular mechanisms of excessive iodine intake on lipid metabolism. METHODS: Balb/c mice were given drinking water containing different levels of iodine for 1 month and treated with 1.2 microg/mL iodine for different periods of time, respectively. Plasma lipid parameters and serum thyroid hormones were measured. Expressions of hepatic genes were detected by real-time polymerase chain reactions and Western blot. RESULTS: Dose-dependent hypercholesterolemic effects were detected in mice (TC, r = 0.615; p < 0.01). Drinking 1.2 microg/mL iodine water for 1 month had no significant effect on serum lipid metabolism, while prolonged exposure induced an increase of serum cholesterol. Serum thyroid hormones were not affected by iodine throughout the study. At the molecular level, we detected a dose-dependent attenuation of hepatic low density lipoprotein receptor (LDLr) and thyroid hormone receptor beta1 (TRbeta1) expression in parallel to the change of serum cholesterol. Treatment with 1.2 microg/mL iodine water for 1 month did not affect LDLr and TRbeta1 expression, while 3 or 6 months exposure resulted in a decrease of their expression. CONCLUSION: Present findings demonstrated dose- and time-dependent hypercholesterolemic effects of iodine excess. Furthermore, our data suggests that TRbeta1-mediated down regulation of hepatic LDLr gene may play a critical role in iodine excess-induced hypercholesterolemic effects.

The diabetogenic effects of excessive ethanol: reducing beta-cell mass, decreasing phosphatidylinositol 3-kinase activity and GLUT-4 expression in rats.

The diabetogenic impact of ethanol remains as a focal point of basic and clinical investigations. In this study, Wistar rats were subjected to daily intragastric ethanol administration (10 ml/kg body weight injection with 0 (control), 10, 20 and 33 % (v/v) ethanol in the injections, respectively) for 19 weeks. At the end of the administration, we found that the fasting plasma glucose level of the 33 % (v/v) ethanol-loaded group was 18 % higher than the control. Insulin sensitivity was decreased in a dose-dependent manner in all the ethanol-loaded groups (r - 0.842, P < 0.001) during intraperitoneal insulin tolerance test. Necrotic/haemorrhagic injury was detected in the pancreas and islet beta-cell mass was significantly reduced in the 33 % (v/v) ethanol-loaded rats by immunohistochemical and morphometric analysis. At the molecular level, we detected a dose-dependent attenuation of phosphatidylinositol 3-kinase activity (r - 0.956, P < 0.001) and GLUT-4 expression (GLUT-4 mRNA, r - 0.899, P < 0.001; GLUT-4 protein, r - 0.964, P < 0.001) in skeletal muscle. These results demonstrated that drinking is a conditional aetiological factor for diabetes and excessive ethanol intake is negatively associated with both insulin sensitivity and beta-cell mass. The whole-body insulin resistance might result from the ethanol-induced insulin signalling defects in muscle.

The role of cytochrome p-450 in salt-sensitive stroke in stroke-prone spontaneously hypertensive rats.

Stroke-prone spontaneously hypertensive rats (SHRSP/Izm) are salt sensitive: they develop severe hypertension and die of stroke within a short time after salt loading. We studied the role of cytochrome P-450 (CYP) isoforms in the brain and the effect of clofibrate to investigate the mechanism of salt sensitive stroke-proneness in SHRSP/Izm. Male SHRSP/Izm at 9 weeks of age were fed a regular diet with or without 0.25% clofibrate and given a 1% NaCl solution for drinking water for 10 d. The expression levels of CYP4A1, 2C11, and 2C23 were measured by Western blotting. Cerebral blood flow was measured with a laser Doppler method and blood vessel diameters were measured under microscopic observation. SHRSP/Izm died within 60 d after salt loading; however, clofibrate prolonged the survival (mean life span, 33+/-7 vs. 215+/-23 d, p<0.0001) without significant attenuation of the severe hypertension. CYP4A1 and CYP2C11 expression levels were lower in SHRSP/Izm than those in age-matched male spontaneously hypertensive rats (SHR/Izm) in the cerebral cortex (p<0.05). Salt loading down-regulated CYP2C11 expression in the cerebral cortex of SHRSP/Izm (p<0.05). No obvious change in cerebral CYP4A1 was observed in either salt-loaded SHRSP/Izm or SHR/Izm. Clofibrate significantly up-regulated the expression of cerebral CYP2C11 and significantly attenuated its salt-induced suppression (p<0.05). Additionally, clofibrate significantly increased blood vessel diameters (p<0.01) and cerebral blood flow (p<0.0001). CYP2C11 plays an important role in regulating cerebral blood flow and, as a result, in preventing stroke in the salt-sensitive stroke-prone SHRSP/Izm.

[Oxidative damage and apoptosis in NIT-1 cells induced by ethanol].

OBJECTIVE: To decide whether ethanol induce apoptosis in mouse insulinoma cells (NIT-1) and the potential mechanism involved. METHODS: After NIT-1 cells were exposed to various concentrations of ethanol, agarose gel electrophoresis was used to detected DNA fragmentation. malondialdehyde (MDA) content, glutathione (GSH) level, superoxide dismutase(SOD) and glutathione peroxidase (GSH-Px) were measured in NIT-1 cells to evaluate the oxidative damage degree. Caspase-3 relative activity was determined by colorimetric assay. RESULTS: The results showed a "DNA ladder" pattern after treated with ethanol in NIT-1 cells. The MDA content was higher, the SOD activity, GSH-Px activity and GSH content were lower in ethanol group than those of control group. Ethanol increased the caspase-3 activity by a dose and time dependent manner. CONCLUSION: Higher concentration of ethanol induces imbalance of oxidation and antioxidative ability in NIT-1 cells, and oxidative stress further leads to apoptosis which may be related to the increased caspase-3 activity.

[Influence of alcohol on insulin sensitivity and insulin receptor substrate-1 mRNA expression in rat skeletal muscle].

OBJECTIVE: To investigate the molecular mechanism of the effect of alcohol on insulin sensitivity. METHODS: Four groups of Wistar rats were used, i.e. control (C) group, and low (L), moderate (M) and high (H) alcohol group. Alcohol doses of each group were 0, 0.6, 1.8 and 3.0 ml.(kg.bw)(-1).day(-1). Each group was comprised of 10 male and 10 female rats. Alcohol was given to rats by gastric intubation. Thirteen weeks later, serum was collected for testing of fasting plasma glucose and insulin. HOMA-IR index of each group were calculated. Total muscle RNA was extracted using Trizol Reagent (Promega). The expression level of IRS-1 mRNA in muscle was detected by RT-PCR. RESULTS: In female rats, the fasting plasma glucose of group (8.36 +/- 0.57) mmol/L was higher and the fasting plasma insulin (15.25 +/- 3.32) was lower than those of group C (7.56 +/- 0.85, 20.80 +/- 3.25). The HOMA-IR of group L (1.775 3 +/- 0.138 1) was lower than that of group C (1.982 6 +/- 0.124 6) (P < 0.05), while IRS-1 mRNA (0.766 1 +/- 0.076 9) was up-regulated (P < 0.05); HOMA-IR of group M (2.202 2 +/- 0.271 0) was higher than that of group C (P < 0.01), while IRS-1 mRNA (0.501 8 +/- 0.049 2) was suppressed (P < 0.01); HOMA-IR of group H (1.850 1 +/- 0.162 8) was not significantly changed as compared with that of group C (1.982 6 +/- 0.124 6) (P > 0.05), while IRS-1 mRNA (0.418 1 +/- 0.049 1) was significantly suppressed (P < 0.01). In male rats, the fasting plasma glucose and insulin had the similar change as those of female rats. The HOMA-IR of group M (1.878 5 +/- 0.250 2) was lower than that of C group (2.147 3 +/- 0.330 8) (P < 0.05), IRS-1 mRNA was up-regulated (0.824 9 +/- 0.064 7) (P < 0.05). CONCLUSIONS: The present study showed that low-to-moderate dose of alcohol could increase insulin sensitivity; while alcohol abuse could decrease insulin sensitivity. Sex difference in this effect was found. Changes of IRS-1 mRNA expression may be involved in the molecular mechanism of the effects of alcohol on insulin sensitivity.

ROS-related enzyme expressions in endothelial cells regulated by tea polyphenols.

OBJECTIVE: Elevation of reactive oxygen species (ROS), especially the level of superoxide is a key event in many forms of cardiovascular diseases. To study the mechanism of tea polyphenols against cardiovascular diseases, we observed the expressions of ROS-related enzymes in endothelial cells. METHODS: Tea polyphenols were co-incubated with bovine carotid artery endothelial cells (BCAECs) in vitro and intracellular NADPH oxidase subunits p22phox and p67phox, SOD-1, and catalase protein were detected using Western blot method. RESULTS: Tea polyphenols of 0.4 microg/mL and 4.0 microg/mL (from either green tea or black tea) down-regulated NADPH oxidase p22phox and p67phox expressions in a dose-negative manner (P < 0.05), and up-regulated the expressions of catalase (P < 0.05). CONCLUSIONS: Tea polyphenols regulate the enzymes involved in ROS production and elimination in endothelial cells, and may be beneficial to the prevention of endothelial cell dysfunction and the development of cardiovascular diseases.

Tea polyphenols regulate nicotinamide adenine dinucleotide phosphate oxidase subunit expression and ameliorate angiotensin II-induced hyperpermeability in endothelial cells.

Out-of-control reactive oxygen species (ROS) signaling is one of the key events in the pathogenesis of endothelial dysfunction and essential hypertension. We observed that tea polyphenols decreased the production of ROS via regulation of the protein expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in bovine carotid artery endothelial cells (BCAECs). Both green tea polyphenols (GTP) and black tea polyphenols (BTP) down-regulated the expression of NADPH oxidase subunits p22phox and p67phox while up-regulating catalase expression (p < 0.05, respectively). Pre-treatment with GTP or BTP for 24 h significantly decreased the superoxide anion level (p < 0.05) and permeable fluorescence intensities in Ang II-stimulated BCAECs. A decrease in cell permeability was also observed by pre-treatment with diphenylene iodonium chloride (DPI) or vitamin E (p < 0.05, respectively). The result demonstrates that tea polyphenols alleviate angiotensin (Ang) II-induced hyperpermeability mainly by decreasing ROS production. Our results suggest that tea polyphenols regulate ROS-related protein expression and may be beneficial in preventing endothelial cell dysfunction and development of cardiovascular diseases, including hypertension.