Aims. To evaluate the effect of the traditional Vietnamese herb Gynostemma pentaphyllum tea on insulin sensitivity in drug-na？ve type 2 diabetic patients. Methods. Patients received GP or placebo tea 6？g daily for four weeks and vice versa with a 2-week wash-out period. At the end of each period, a somatostatin-insulin-glucose infusion test (SIGIT) was performed to evaluate the insulin sensitivity. Fasting plasma glucose (FPG), , and oral glucose tolerance tests and insulin levels were measured before, during, and after the treatment. Results. FPG and steady-state plasma glucose (SIGIT mean) were lower after GP treatment compared to placebo treatment ( ). The levels of FPG in the control group were slightly reduced to versus ？mmol/L in GP group ( ), and the effect on FPG was reversed after exchanging treatments. The glycometabolic improvements were achieved without any major change of circulating insulin levels. There were no changes in lipids, body measurements, blood pressure, and no reported hypoglycemias or acute adverse effects regarding kidney and liver parameters. Conclusion. The results of this study suggested that the GP tea exerted antidiabetic effect by improving insulin sensitivity. 1. Introduction Type 2 diabetes mellitus (T2D) is a global health problem and is predicted to become more prevalent in the coming decades [1, 2]. Many currently available antidiabetic drugs improve the impaired insulin secretion or decreased insulin sensitivity seen in T2D. However, they exhibit a number of limitations such as side effects and high rates of secondary failure and, in the case of novel drugs, rather high treatment costs [3–5]. Thus, diabetic patients and healthcare professionals are considering complementary and alternative approaches, including the use of herbal medicine with antidiabetic properties. Traditional herbal medicines have played a major role in the management of diabetes in Vietnam and many Asian countries for centuries [6]. Gynostemma pentaphyllum Makino (family Cucurbitaceae) is a perennial creeping herb growing wild in the mountain regions of Vietnam, China, and some other Asian countries. It has been used widely in Southeast Asian countries as a herbal medicine and being beneficial for the prevention and treatment of diabetes [7–9]. We have previously presented evidence that GP tea possesses antidiabetic effect, both as a single treatment and as an add-on therapy to sulfonylureas with good safety data in newly diagnosed T2D patients [10, 11]. In addition, the extract of GP has been shown to reduce both hyperglycemia and
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