| BackgroundWith the rising level of living standard and change of people's dietary structure, the prevalence of type 2 diabetics (DM) and metabolic syndrome(MS) is increasing year by year. The complications of these two deseases have great dangers to people's health. The health benefits of tea has been identified in a lot of researches. It's lipid regulating and hypoglycemic activities had received more and more attentions in recent years. It had been suggested that tea polysaccharide and tea polyphenols are the main active component of tea in glucolipid regulation.Tea is one of the special products in China and Chinese people have tradition of tea drinking. It may bring great benefits to patients with type 2 diabetics or metabolic syndrome if these agents can be extracted and used in clinic.ObjectiveThe purpose of this study is to make a rat model of metabolic syndrome by induction of high sucrose and high lipid diet,to observe the lipid regulating, hypoglycemic and insulin sensitivity improving effect of tea polysaccharide on MS rat,to study the mechanism of the lipid regulating and hypoglycemic activity,which provide the theoretical base for clinical treatment of MS.Method1. Establish the model of metabolic syndrome rat by induction of high sucrose and high lipid diet for 4 months. After that we calculate the model-forming rate of MS rats.2. To investigate the effect of tea polysaccharide on modulating the glycolipid metabolism in rats with metabolic syndrome. The SD rats were divided to 3 groups:group A (tea polysaccharide intervention group), group B(MS control group), group C(normal control group). We observed the change of blood glucose, blood fat, blood pressure, Lee's index, the level of insulin and free fatty acid, insulin resistance index in rats with metabolic syndrome after treatment of tea polysaccharide.3. To study the molecular mechanism of tea polysaccharide on metabolic syndrome,we detected the gene and protein expression of interleukin-1β(IL-1β), tumor necrosis factor-a(TNF-a), interferon-y(IFN-γ) and inducible nitric oxide synthase(iNOS) in pancreatic tissue of SD rats. We both detected the gene and protein expression of peroxisome proliferator-activated receptor-y (PPAR-y), adiponcetin (APN), nuclear factor-kappa B (NF-κ) and intercellular adhesion molecule-1 (ICAM-1)to investigate whether tea polysaccharide participate in regulating the expression of these cytokines.4. We used immunohistochemisty staining assay to observe the expression of PPAR-y in adipose tissue of experimental rats.5. We used electron microscope to observe the ultrastructural changes of islet (3 cells and skeletal muscle fiber.Result1. The prevalence of obesity, hypertriglyceridemia, hyperglycemia, low HDL-C concentration and hypertension in rats model induced by high sucrose and high lipid diet was 81.3%,62.5%, 50% and 37.5%, respectively. MS group began to be more obese than NC group since the 10th weak and the mean weight of MS group was 18% more than NC group(P<0.05) Fasting glucose and caudal arterial pressure of MS rat raised in week 14 and 16, respectively (P＜0.05). At 16th week, the mean weight, Lee's index, fasting glucose, fasting insulin, cholesterol, TG, LDL-C and free fatty acid of MS group were significantly higher than those of NC group, and the level of HDL-C of MS group was significantly lower than that of NC group (P＜0.05)2. After the intervention of tea polysaccharide,there were no significant change in mean length and caudal arterial pressure, rats showed slower weight gain tendency in TPS group than in MS group, but there was no significant difference(p>0.05). Since the 8th week of TPS treatment, level of fasting blood glucose in TPS group began to decreased, the difference had statistical significance (P＜0.05), meanwhile the level of insulin and HOMA-IR index also decreased significantly (P＜0.05). The levels of FFA,TG, CHO and LDL-C in TPS group decreased significantly while the level of HDL-C increased significantly after the treatment of TPS for 10 weeks. 3. The gene and protein expression of TNF-a,iNOS and iNOS in the pancreatic tissue of MS rats was decreased after the intervention of tea polysaccharide (p<0.05). The expression of IFN-y had on significant different in each group (p>0.05)4. The gene and protein expression of ICAM-1 and NF-κB in adipose tissue decreased significantly while the expression of adiponectin and PPAR-yincreased significantly after the intervention of tea polysaccharide(p<0.05).We furiously confirmed by immunohistochemisty staining assay that the expression of PPAR-yreality increased in omentum adipose tissue.lt suggest that tea polysaccharide improve the glucolipid metabolism through the mechanism of relieving insulin resistance.5. Electron microscope observation indicated that the secretory granules of islet Pcells increased and the destroy of organelle structures were reduced, the glycogen granules in skeletal muscle fiber of MS rats significantly decreased which suggested that tea polysaccharide might decrease the glucose level though the mechanism of reducing the inflammatory damage of isletβcells and improving insulin resistance in peripheral tissue.Conclusions1. The animal model of metabolic syndrome rat can be successfully established by induction of high sucrose and high lipid diet.2. Tea polysaccharide can improve the disorders of glucolipid metabolism and relieving insulin resistance in MS rats.3. The mechanism of relieving insulin resistance by tea polysaccharide may due to the decreased level of FFA and the regulation of relent cytosine expressions. |
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