| It is well-known that insulin resistance is not only the main pathophysiology characteristic of type 2 diabetes mellitus, but also the independent risk factor of hypertension, coronary heart disease, obesity, dyslipidemia and atherosclerosis.More and more people are tending to prevent diseases through diet modification along with the advance of lifestyle changes. Tea is widely accepted for its good taste and high bioactivity as a daily drink. Chinese tea culture has a long long history; the tea culture is highly diverse in China as a result of the rich biological, ethnic and cultural diversity. Except for Camellia sinensis, various plants are known to be used as drinking tea locally in different part of China, for example, Vine Tea (Ampelopsis grossedentata), Large-leaved bitter tea (Ilex latifolia, I.kudingcha), Small-leaved bitter tea (Ligustrum robustum), sweet tea (Rubus suavissimus, Lithocarpus polystachys) and Hawks tea (Litsea coreana), etc. Therefore, we define as "non-Camellia Teas" those plants that (1) do not belong to Theaceae Camellia, (2) have been long and widely used to as drinking tea with a history of at least 500 years within an area spanning a minimum of a few counties and within an ethnic group, and (3) are being actively used nowadays and are readily available on the market. Previous researches reported that the "non-Camellia Teas" have the biological effects on lipid decreasing, reducing blood glucose and anti-oxidation.In this study, insulin resistance cells model was induced by high concentration of glucose to evalue the hypoglycemic effects of non-Camellia teas. Different fractions from seven non-Camellia teas on improving HepG2 cells insulin resistance were also been studied. Vine tea showed a high activity on improving insulin resistance of HepG2 cells and was choosed for the further research. Further, we also investigated the influence of the main compounds from Ampelopsis grossedentata on ROS, MAD, SOD, CAT, LA and ATP in insulin-resistant HepG2 cells.To determine the activity of Ampelopsis grossedentata further, type 2 diabetic rat model was induced by high fat diet. The concentrations of TC, TG, LDL-C, HDL-C and the level of fast insulin were detected. The insulin sensitivity index (ISI) and HOME-IR were calculated to evaluate insulin resistance. The results indicated that vine tea can improve insulin resistance in type 2 diabetic rats.Finally, we studied the hypoglycemic effects of different composition vine tea by insulin resistance cells model, the best proportion is Ampelopsis grossedentata: Cyclocarya paliurus:Green tea(Camellia sinensis)=2:1:1.The brewing conditions on the antioxidant activity of compound vine tea were optimized, different extraction parameters such as temperature, solid-liquid ratio; time and frequency, kind of water on the DPPH radical scavenging rate of compound vine tea were investigated by Box-Behnken design-response surface method. The results showed that the optimum brewing conditions for vine tea were as follows:temperature 80℃,time 10.7 min and so lid-liquid ratio 1:58 (g/mL), then the DPPH radical-scavenging activity of compound vine tea reached the best. The research provides theoretical guidance and reference for scientific drinking way of compound vine tea.In summary, this thesis mainly focus on the hypoglycemic effects on insulin resistance of non-Camellia Teas on cell levels. Futhermore we studied the effects on improving insulin resistance of vine tea in vivo and in vitro.Application research mainly about the best proportion and the best brewing conditions of composition vine tea. To provide theoretical evidence for the further development of the medicinal value in vine tea, and also be useful for the rational utilization of this herbal medicine resource. |
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