Effects of vitamin E on oxidative stress and membrane fluidity in brain of streptozotocin-induced diabetic rats.

BACKGROUND: Diabetics and experimental animal models exhibit high oxidative stress due to persistent and chronic hyperglycemia, thereby deplete the activity of the antioxidative defense system and thereby promote the generation of free radicals. The current study examined the effects of vitamin E on oxidative stress and membrane fluidity in the brain of diabetes-induced rats. METHODS: Sprague-Dawley male rats were randomly assigned to normal and streptozotocin (STZ)-induced diabetic groups. The diabetic groups were fed a vitamin E-free diet, 40 mg vitamin E/kg diet, or 400 mg vitamin E/kg diet. Diabetes was induced with STZ after 3 weeks of the experimental diet, then the rats were sacrificed 9 days later to determine the oxidative stress and cell membrane fluidity in the brain. RESULTS: Dietary vitamin E strengthened the antioxidative defense system with an increased activity of the antioxidant enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) and increased vitamin E content, in the brain of the diabetes-induced experimental rats. Accordingly, vitamin E was found to reduce the accumulation of reactive oxygen species (ROS), such as superoxide radical decrease the generation of oxidative damage substances, such as the carbonyl value, increase the membrane fluidity lowered by oxidative damage, and significantly improve the lipid composition. CONCLUSIONS: Vitamin E was found to be excellent for strengthening the antioxidative defense system, reducing the generation of ROS and damaging oxidative substances, and maintaining membrane fluidity in the brain of diabetes-induced rats.

Effects of manufactured soluble dietary fiber from Quercus mongolica on hepatic HMG-CoA reductase and lipoprotein lipase activities in epididymal adipose tissue of rats fed high cholesterol diets.

This study investigated the effect of a manufactured soluble dietary fiber on lipid metabolism in rats fed high cholesterol diets. Soluble dietary fiber was prepared from wood chips of oak (Quercus mongolica). Male Sprague-Dawley rats weighing 100 +/- 10 g were randomly assigned to either a normal diet or five high cholesterol diets containing 1% cholesterol and different fiber supplements. The high cholesterol groups were subdivided into fiber-free diet (FF), 5% pectin (5P), 10% pectin (10P), 5% manufactured soluble dietary fiber (5QM), and 10% manufactured soluble dietary fiber (10QM) groups. Total serum cholesterol concentrations in all soluble dietary fiber-supplemented groups were lower than in the FF group. The high-density lipoprotein-cholesterol concentration in the FF group was significantly lower, compared with the normal group, but was increased in groups supplemented with soluble dietary fiber. Low-density lipoprotein-cholesterol levels and the atherogenic index had the same tendency as total cholesterol concentration. Compared with the FF group, in the 5P, 5QM, 10P, and 10QM groups hepatic triglyceride concentrations were 12%, 16%, 20%, and 24% lower, respectively, and hepatic cholesterol concentrations were 48%, 52%, 52%, and 58% lower, respectively. Hepatic 3-hydroxy-3-methylglutaryl-CoA reductase activity in the soluble fiber groups was significantly higher than in the FF groups, but lower than the normal group. When hepatic tissue was observed under a light microscope, the FF group had completely formed lipomas in the hepatic tissue, which led to fat deposits and then a fatty liver. The size and number of lipomas were lower in the soluble dietary fiber-fed groups, as compared with the group not fed dietary fiber. In conclusion, improvements in lipid metabolism were observed as a result of the manufactured soluble dietary fiber from the oak chips, and were similar to that seen for pectin. The preparation method for the soluble dietary fiber from oak chips successfully produced a functional soluble fiber.

Green tea catechin improves microsomal phospholipase A2 activity and the arachidonic acid cascade system in the kidney of diabetic rats.

The purpose of this study was to investigate the effects of green tea catechin on the microsomal phospholipase A2 activity and arachidonic acid cascade in the kidneys of streptozotocin-induced diabetic rats. Sprague-Dawley male rats weighing 100 +/- 10 g were assigned randomly to one normal and three streptozotocin-induced diabetic groups. The diabetic groups were the DM-0C group (n = 10), fed a catechin-free diet, the DM-0.25C group (n = 10), fed a 0.25 g catechin per 100 g diet, and the DM-0.5C group (n = 10), fed a 0.5 g catechin per 100 g diet. The kidney microsomal phospholipase A2 activity was higher in the diabetic groups than in the normal group, while it was lower in the DM-0.25C and DM-0.5C groups than in the DM-OC group. The percentage of phosphatidylcholine hydrolysed in the kidney microsomes was not significantly different between any of the four groups. The percentage of phosphatidylethanolamine hydrolysed in the kidney microsomes was progressively higher in the DM-0.5C, DM-0.25C and DM-OC groups, respectively, compared to the normal group. The formation of thromboxane A2 was significantly higher while the formation of prostacyclin was lower in kidney microsomes of the streptozotocin-induced diabetic groups compared with the normal group, but this condition was improved by catechin supplementation. Kidney microsomal vitamin E concentrations were progressively lower in the DM-0.5C, DM-0.25C, and DM-0C groups, respectively, compared to the normal group. The kidney thiobarbituric acid reactive substance (TBARS) contents became higher in the DM-0C and DM-0.25C groups as compared with the normal group, whereas the DM-0.5C group did not differ from the normal group. Kidney function appears to be improved by green tea catechin supplementation due to its antithrombus action, which in turn controls the arachidonic acid cascade system.