Department of Physiology, Keimyung University School of Medicine, Daegu, Korea.
Diabetes Metab J. 2013 Jun;37(3):196-206. doi: 10.4093/dmj.2013.37.3.196. Epub 2013 Jun 14.
The increasing prevalence of type 2 diabetes mellitus (T2DM) is associated with the rapid spread of obesity. Obesity induces insulin resistance, resulting in β-cell dysfunction and thus T2DM. Green tea extract (GTE) has been known to prevent obesity and T2DM, but this effect is still being debated. Our previous results suggested that circulating green tea gallated catechins (GCs) hinders postprandial blood glucose lowering, regardless of reducing glucose and cholesterol absorption when GCs are present in the intestinal lumen. This study aimed to compare the effect of GTE with that of GTE coadministered with poly-γ-glutamic acid (γ-PGA), which is likely to inhibit the intestinal absorption of GCs.
The db/db mice and age-matched nondiabetic mice were provided with normal chow diet containing GTE (1%), γ-PGA (0.1%), or GTE+γ-PGA (1%:0.1%) for 4 weeks.
In nondiabetic mice, none of the drugs showed any effects after 4 weeks. In db/db mice, however, weight gain and body fat gain were significantly reduced in the GTE+γ-PGA group compared to nondrug-treated db/db control mice without the corresponding changes in food intake and appetite. Glucose intolerance was also ameliorated in the GTE+γ-PGA group. Histopathological analyses showed that GTE+γ-PGA-treated db/db mice had a significantly reduced incidence of fatty liver and decreased pancreatic islet size. Neither GTE nor γ-PGA treatment showed any significant results.
These results suggest that GTE+γ-PGA treatment than GTE or γ-PGA alone may be a useful tool for preventing both obesity and obesity-induced T2DM.
2 型糖尿病（T2DM）的患病率不断上升与肥胖的迅速传播有关。肥胖会引起胰岛素抵抗，导致β细胞功能障碍，从而引发 T2DM。绿茶提取物（GTE）已被证明可预防肥胖和 T2DM，但这种效果仍存在争议。我们之前的研究结果表明，循环中的绿茶没食子儿茶素（GCs）会阻碍餐后血糖降低，而不管 GCs 存在于肠腔中时是否会降低葡萄糖和胆固醇的吸收。本研究旨在比较 GTE 与 GTE 与聚γ-谷氨酸（γ-PGA）联合使用的效果，γ-PGA 可能会抑制 GCs 的肠道吸收。
给予 db/db 小鼠和年龄匹配的非糖尿病小鼠正常的含 GTE（1%）、γ-PGA（0.1%）或 GTE+γ-PGA（1%：0.1%）的饮食 4 周。
在非糖尿病小鼠中，4 周后，没有一种药物有任何效果。然而，在 db/db 小鼠中，与未接受药物治疗的 db/db 对照组相比，GTE+γ-PGA 组的体重增加和体脂肪增加明显减少，而食物摄入量和食欲没有相应变化。葡萄糖耐量也得到了改善。组织病理学分析表明，GTE+γ-PGA 治疗的 db/db 小鼠的脂肪肝发生率明显降低，胰岛体积减小。GTE 或 γ-PGA 单独治疗均未显示出任何显著结果。
这些结果表明，GTE+γ-PGA 治疗可能比 GTE 或 γ-PGA 单独治疗更有助于预防肥胖和肥胖引起的 T2DM。
