Hypoglycemic Effect Of Selenium-enriched Compound SOD Green Tea In Diabetic Rats

Objectives:Diabetes mellitus (DM) is one of the most commonly metabolic diseases which have an adversely effect on the human being's healthy. Oxidative damage is an importantly causative agent contributes to the pathogenesis of the DM. It is demonstrated that progressive disfunction of insulin secretion by the beta cell of islet, which probably promoted by the free radical reaction and oxidative stress damage, is a significant character in the natural process of DM. In view of the multiple elements such as tea polyphenols, tea polysaccharide, etc. have hypoglycemic effects and the antioxygen function by SOD and selenium (Se), the current study was designed to investigate the hypoglycemic effect of selenium-enriched compound SOD green tea in diabetic rats.Methods:1. Protection StudyEighty adult Wister rats were randomly divided into control group (A), DM group (B),green tea group (C) and selenium-enriched compound SOD green tea group (D). Besides a basic bait vessel for each group, A and B were treated with intragastric administration of distilled water,while 10% green tea and 10% selenium-enriched compound SOD green tea were administrated for C and D respectively (intake:1g/kg.d). Then the diabetic models were induced by alloxan (50mg/k.w) after 30 feeding days, and control group were injected with iso-osmia normal sodium. Five days later, the death rate and fasting plasma glucose (FPG) of suvivral rats in each group were evaluated. Next day, the arterial blood levels of SOD, malondialdehyde (MDA), triglyeride (TG), cholesterol (CHOL), creatinine (Cr) and urea nitrogen (BUN) of ten randomly rats in each group were measured.2. Therapeutic StudyControl group (A), ten rats were randomly selected from sixty adult Wister rats, were intravenously injected with iso-osmia normal sodium (3.3ml/k.w), and the others were administrated with alloxan (50mg/k.w). Concentrations of FPG wer determined in each group after 5 days, and diabetic models were classified according to the FPG concentration more than 16mmol/L. Thirty rats of the diabetic models were randomly divided into DM group (B), green tea group (C) and selenium-enriched compound SOD green tea group (D). Besides a basic bait vessel for each group, A and B were treated with intragastric administration of distilled water,while 10% green tea and 10% selenium-enriched compound SOD green tea were administrated for C and D respectively (intake:1g/kg.d-1). The value of FPG in every group was investigated after 30, 60 and 90 feeding days. Then, oral glucose tolerance test (OGTT) was determined before 1 day prior to the termination of the experiment. Furthermore, the arterial blood levels of insulin (INS), C-peptide (C-P), glycosylated serum protein (GSP), SOD, malondialdehyde (MDA), CHOL and TG, the contents of SOD and MDA in liver tissues were evaluated next day.Results:1. If rats were injected with alloxan before feeding on green tea and selenium-enriched compound SOD green tea for 30 days, the death rate of B, C and D group were 25%, 20% and 15% respectively. Moreover, the FPG concentrations of the above three groups were all significantly higher than that of control group (p<0.01), and there were no differences between B, C and D groups. Compared with A group, the activity of SOD was obviously lower (p<0.01) and the contents of MDA were significantly heightened (p<0.01) in the three other groups. However, the level of SOD in D group was higher than that in B and C group (p<0.05), but the content of MDA was decreased or significantly decreased than the other groups (p<0.05, p<0.01). Additionally, there were no statistically significant differences of the serum concentrations of CHOL, TG, Cr and BUN between each group.2. Results of hypoglycemic effect of selenium-enriched compound SOD green tea in diabetic models.2.1 Rats were continuously feeding after the diabetic models were successfully induced. Compared with B group, the concentration of FPG in C group were markedly step down on feeding 60 and 90 days (p<0.05, p<0.01). Notably, the FPG concentrations in D group were obviously cut down not only than that in B group (p<0.01), but also than C group (p<0.05, p<0.01) on feeding 30, 60 and 90 days. In addition, data of OGTT suggested that the levels of 1.5h and 2h-blood glucose in C group were degraded or significantly degraded than that in B group (p<0.05, p<0.01), and the values of 0.5h, 1.0h, 1.5h and 2.0h-blood glucose in D group were obviously decreased than that in both B and C groups (p<0.05, p<0.01). Furthermore, the concentration of GSP in C group was significantly lower than that in B group (p<0.05). Meanwhile, there were statistically significant differences of the GSP concentration between D and B group or between D and C group (p<0.05, p<0.01).2.2 Compared with C or D group, the activity of SOD was obviously increased in A group (p<0.01), but decreased or markedly decreased in B group (p<0.05, p<0.01). Interestingly, the SOD activity of D group was significantly increased than that of C group. Moreover, there were significant differences of the MDA levels between D and B group or between D and C group (p<0.05, p<0.01). Although the level in C group was reduced than that in B group, the difference was no statistic significance. Additionally, D group had much higher level of SOD (p<0.05, p<0.01) and much lower level of MDA (p<0.01) in liver tissues than B and C groups, between which there was, however, no statistically significant difference.2.3 After 92 feeding days, the serum concentrations of TG and CHOL in C group were cut down than that in B group, but there was statistically significant difference merely on CHOL (p<0.05). Nevertheless, these levels in D group were markedly lower than that in both B and C groups (p<0.01).2.4 The serum concentrations of INS in D group were obviously set up than that in B or C group (p<0.05, p<0.01), and the level in C group was higher than that in B group (p<0.05). Moreover, there was statistically significant differences of the C-P concentration between D and B group (p<0.05).2.5 Rats in B, C and D group presented with different degree symptoms in the process of the study, including polydipsia, polyphagia, hyperdiuresis and worse glossiness of fur, which were obvious in former two groups. Moreover, there were 5 and 3 rats presented with cataract in B and C group respectively, and there was no one, however, in D group.Conclusion:1. The level of oxidative damage and death rate of diabetic rats induced by alloxan can be step down by pre-intake of selenium-enriched compound SOD green tea, which has no effect on FBG, blood lipid and renal function. 2. Selenium-enriched compound SOD green tea can more effectively relieve the lipid peroxidation damage of diabetic model rats than that by green tea. Moreover, the former contributes to improvement of lipid metabolism of diabetic models.3. Both selenium-enriched compound SOD green tea and common green tea have an effectual regulation on the glycometabolic disturbance of diabetic rats. However, the former's effect is more significant and obvious than the latter's. The synthetic action induced by multiple ingredients, such as selenium and SOD, may contributes to the difference.