RESUMO
Diabetes mellitus is a chronic disease associated with serious complications that may be linked to increased lipid peroxidation. This study investigated the effects of dietary supplementation of sea tangle on lipid peroxidation and antioxidant systems in streptozotocin (STZ)-induced diabetes. Forty Sprague-Dawley rats were divided into four groups (n = 10 each) fed AIN76-based diets with either sea tangle powder, water extract of sea tangle, or sodium alginate, or a control diet with no supplement. On day 21 after beginning the diets, rats received intramuscular injections of STZ (45 mg/kg of body weight) to induce diabetes. Experimental diet feeding was continued for 3 more weeks. Dietary supplementation with water extract of sea tangle resulted in lower plasma glucose compared with the control and sodium alginate groups. There was no significant difference in plasma and hepatic lipid peroxides among the groups. Sea tangle and sodium alginate did not affect activities of catalase and glutathione peroxidase; however, supplementation of water extract of sea tangle resulted in higher superoxide dismutase activity as compared with the control and sodium alginate groups. The plasma concentration of alpha-tocopherol increased in the sea tangle water extract group, but the hepatic concentration of alpha-tocopherol was not affected by dietary supplementation. Plasma retinol was not different among experimental groups. In conclusion, our results showed that water extract of sea tangle reduces plasma glucose and protects the antioxidant system in diabetic rats. These results suggest that water extract of sea tangle contains unknown physiologically active components, other than alginic acid, that may exert a protective effect against diabetes.