Effects of Agaricus blazei and its liquid fermentation product on plasma glucose in rats
|Keywords:||糖尿病;代謝症候群;巴西洋菇;口服葡萄糖耐受性試驗;Diabetes mellitus;metabolic syndrome;Agaricus blazei;oral glucose tolerance test||Issue Date:||2007||Abstract:||
糖尿病已成為一個重要的全球性健康議題。近年研究發現，包含高血壓、高胰島素血症、胰島素阻抗、血脂代謝異常和肥胖等諸多病症的代謝症候群 (metabolic syndrome)，與糖尿病及心血管疾病關係密切，已成為各國研究及預防的重點。巴西洋菇（Agaricus blazei）具有抗腫瘤、抗氧化、增強免疫力及護肝等功效，但是對抗糖尿病之探討較少；此外，人工栽培巴西洋菇成本高、產量低且品質不穩，故以液態深層發酵 (submerged fermentation) 生產巴西洋菇被認為是值得開發的生產方式，其保健功效如何則有待進一步評估。
急性試驗結果顯示，在正常鼠之口服葡萄糖耐受性試驗中，給予0.56 g/kg BW 的液態發酵產物熱水萃出物之大鼠，在灌糖後第 30 分鐘的血糖值顯著較對照組為低 (p<0.05)，在第 120 分鐘時則明顯高於對照組 (p<0.01)，顯示液態發酵產物熱水萃出物能有效減緩血糖上升；但在代謝症候群鼠則以 0.28 g/kg BW 的劑量在第 90 分鐘顯著降低血糖值 (p<0.05)；糖尿病鼠方面，也是給予 0.28 g/kg BW 的液態發酵產物熱水萃出物能在第 30 分鐘展現降血糖功效 (p<0.05)。另一方面，巴西洋菇子實體熱水萃出物在三種動物模式之口服葡萄糖耐受性試驗中，不論是給予 0.28 g/kg BW 或 0.56 g/kg BW 的劑量皆無法影響血糖變化。因此選用液態發酵產物熱水萃出物進入第二階段實驗。由第二階段結果發現，液態發酵產物熱水萃出物的確具有減少血糖上升的效果，且效果與關華豆膠 (0.0375 g/kg BW) 相比，兩者效果相當，皆能延緩血糖的上升。
長效性試驗結果顯示，飼料中添加 10 % 巴西洋菇子實體時，可改善由高果糖飲食所誘發之高血壓、高三酸甘油酯血症、高血糖及高胰島素血症等現象，在口服葡萄糖耐受性試驗中亦可顯著降低血糖及提升胰島素敏感性，且明顯降低肝中三酸甘油酯、總膽固醇及 TBARS 之濃度，顯示巴西洋菇子實體具有減輕代謝症候群諸多症狀的效果。飼料中添加 5 % 液態發酵產物時，亦具有改善高三酸甘油酯血症及高血壓之效果，並能減少肝中三酸甘油酯與總膽固醇的堆積，但在口服葡萄糖耐受性試驗中，降低血糖及提升胰島素敏感性的效果則不如巴西洋菇子實體。
Diabetes mellitus (DM) has become a major global health problem. Recent research finding have demonstrated that there is a strong association among metabolic syndrome, DM and cardiovascular disease (CVD). Metabolic syndrome is a cluster of metabolic abnormalities including hypertension, hyperinsulinemia, insulin resistance, dyslipidemia and obesity. Therefore, prevention of metabolic syndrome is an important public health issune in many countries. Agaricus blazei has been shown to possess many beneficial health effects, including antitumor activity, antioxidation, immune enhancement and liver protection. But little is known about its antidiabetic activity. The prime cost of cultivating A.blazei is high and the yield is low with unstable quality. Therefore, using submerged fermentation technology to produce A. Blazei has been considered to be a method worth developing. Its health protection effect, however, needs to be confirmed.
The purpose of this study was to investigate the effects of A. Blazei and its liquid fermentation product on plasma glucose in rats. The study contains two parts, the acute and the long term experiments. At the first stage of the acute experiment, we used hot water extracts of A. Blazei (AB-hw) and its liquid fermentation product (ABFP-hw) in the oral glucose tolerance test (OGTT) to normal rats, metabolic syndrome rats and diabetic rats in order to evaluate the hypoglycemic effects of these two kinds of hot water extracts and find out the more effective one and its dose. At the second stage, the hypoglycemic effect of the chosen one was compared with guar gum which was designed as the positive control group. In the long term experiment, we investigated the effect of the fruiting body of A. Blazei and its liquid fermentation product on the symptoms of metabolic syndrome in rats which were induced by high fructose diet.
Results of the acute experiment showed that plasma glucose levels of the normal Sprague-Dawley rats administered 0.56 g/kg BW of ABFP-hw were lower than the control group after 30 minutes of glucose ingestion (p<0.05) but were higher than the control group after 120 minutes (p<0.01). This indicated that ABFP-hw could effectively delay the rise of plasma glucose. In metabolic syndrome rats and diabetic rats, 0.28 g/kg BW ABFP-hw administration significantly reduced plasma glucose after 90 minutes (p<0.05) and 30 minutes (p<0.05) of glucose ingestion. On the other hand, AB-hw had no effect on plasma glucose changes of OGTT for all these animal models. Therefore, we chose ABFP-hw for further study. In the second stage, ABFP-hw was found again to have hypoglycemic effect which was similar to the effect of gaur gum. Both of them could delay the elevation of plasma glucose on OGTT.
In the long term experiment, we found that rats fed with 10% A.Blazei could ameliorate the hypertension, hypertriglyceridemia, hyperglycemia and hyperinsulinemia induced by high fructose diet. A.Blazei added at 10% level in the deit could also reduce plasma glucose, increase insulin sensitivity in the OGTT test and decrease the concentrations of triglyceride, total cholesterol and TBARS in rat liver. These results indicated that A.Blazei could ameliorate the metabolic syndrome. Liquid fermentation product of A.blazei (ABFP) added at 5% level in the deit also had effects on ameliorating hypertriglyceridemia and hypertention and could also decrease the accumulation of liver triglyceride and total cholesterol. Comparing with the fruiting bodies of A.blazei, the liquid fermentation product had less efficacy in reducing plasma glucose and increasing insulin sensitivity on OGTT.
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