Glucose Metabolism In Diabetic Mice Research Articles

Effect of green tea on blood glucose levels and serum proteomic patterns in diabetic (db/db) mice and on glucose metabolism in healthy humans

BackgroundGreen tea is widely consumed in Asian countries and is becoming increasingly popular in Western countries. Epidemiologically, it has been suggested that green tea consumption prevents type 2 diabetes. The present study was aimed at providing evidence of improvement in glucose metabolism in diabetic mice and healthy humans upon green tea consumption.ResultsGreen tea promoted glucose metabolism in healthy human volunteers at 1.5 g/body in oral glucose tolerance tests. Green tea also lowered blood glucose levels in diabetic db+/db+ mice and streptozotocin-diabetic mice 2–6 h after administration at 300 mg/kg without affecting serum insulin level, whereas no effect was observed in control mice (+m/+m and normal ddY mice). The serum protein profiles of db+/db+ and +m/+m mice were analyzed for the first time by SELDI (surface-enhanced laser desorption/ionization)-TOF (time-of-flight)-MS (mass spectrometry), and then compared to investigate any effects of oral green tea administration on serum proteins. The protein profiles in db+/db+ mice showed that the spectral peak intensities at the mass/charge ratios (m/z) of 4119, 4203, 4206, 4211, 4579, 9311 and 18691 were >3 times lower, and those of 13075, 17406, 17407, 17418, 17622, 18431 and 26100 were >3 times higher than respective peak intensities in +m/+m mice. When green tea was administered to db+/db+ mice, the peak intensities were markedly decreased at m/z 11651 and 11863, and slightly decreased at m/z 4212. The peak intensities at 7495, 7595, 7808, 14983, 15614, 31204 were markedly increased after the administration.ConclusionThe present study provides evidence that green tea has an antidiabetic effect. Although we could not find simple reversed effect of green tea on the diabetes-induced modifications of the levels of several serum proteins, we found that the 4211 (4212) Da protein level that was decreased in the diabetic state was further decreased after green tea administration. This is the first report demonstrating that a certain serum protein may be involved in the antihyperglycemic effect of green tea. The contribution of this protein should be further studied.

Effects of a high-monounsaturated fat diet on glucose and lipid metabolisms in normal and diabetic mice.

The beneficial effects of high-monounsaturated fat (high-MUFA) diets on diabetic patients have been reported, whereas studies concerning the effects on animals have been few. Although experiments on animals should be useful in elucidating underlying mechanisms, it is not clear even whether there are benefits of a high-MUFA diet in animals. This study examined the short-term effects of a high-MUFA diet on normal and genetically diabetic mice. The high-MUFA diet supplied 38% of the total calories as fat (26% from MUFA), while a regular diet was 13% fat (3% from MUFA). Normal C5 7BL/6J and diabetic C57BL/KsJ-db/db mice were fed either the regular or the high-MUFA diet for 1 wk. Serum glucose and lipid levels were then measured. In normal mice, hepatic triglyceride production was also compared between the two dietary groups using the Triton WR1339 method. An oral glucose tolerance test was conducted on the diabetic mice. After 1 wk of feeding to normal mice, the high-MUFA diet was seen to lower serum triglyceride levels and reduce hepatic triglyceride production in comparison with the regular diet; it is suggested that the lowering of triglyceride consists of mechanisms including reduced hepatic triglyceride production. When diabetic mice were fed the high-MUFA diet with a controlled caloric intake, the serum glucose levels lowered without an accompanying deterioration in lipid metabolism and the impaired glucose tolerance was ameliorated. This study demonstrates that a high-MUFA diet can lower serum triglyceride levels in normal mice and improve disorders of glucose metabolism in diabetic mice.