Gynostemma pentaphyllum Tea Improves Insulin Sensitivity in Type 2 Diabetic Patients

Aims. To evaluate the effect of the traditional Vietnamese herb Gynostemma pentaphyllum tea on insulin sensitivity in drug-naïve 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), HbA(1C), 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 (P < 0.001). The levels of FPG in the control group were slightly reduced to 0.2 ± 1.5 versus 1.9 ± 1.0 mmol/L in GP group (P < 0.001), 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.

Antidiabetic effect of Gynostemma pentaphyllum tea in randomly assigned type 2 diabetic patients

The aim of the study was to investigate the antidiabetic effect of the traditional Vietnamese herb Gynostemma pentaphyllum in 24 drug-naïve type 2 diabetic patients. All patients were randomized to authenticated Gynostemma pentaphyllum tea or placebo tea, 6 g daily, during twelve weeks and received information regarding diet and exercise. Fasting plasma glucose, insulin levels, and glycosylated hemoglobin (HbA(1C)) were measured before, during, and after the treatment. Oral glucose tolerance tests were performed every four weeks. After 12-week treatment, fasting plasma glucose levels totally decreased to an extent of 3.0+/-1.8 mmol/l in the Gynostemma pentaphyllum tea group as compared to a decrease of 0.6+/-2.2 mmol/l in the control group (p<0.01). HbA(1C) levels after 12 weeks decreased approximately 2% units in the Gynostemma pentaphyllum group compared to 0.2% unit in the controls (p<0.001). Change in Homeostasis Model Assessment-Insulin Resistance between baseline and twelfth week indicated that insulin resistance decreased significantly in the Gynostemma pentaphyllum group (-2.1+/-3.0) compared with that (+1.1+/-3.3) in the control group (p<0.05). There were no hypoglycemias, or adverse effects regarding kidney and liver parameters or gastrointestinal function. In addition, lipid profiles, glucagon, cortisol levels, body measurements, and blood pressure were not different between the groups. This study shows a prompt improvement of glycemia and insulin sensitivity, and thereby provides a basis for a novel, effective, and safe approach, using Gynostemma pentaphyllum tea, to treat type 2 diabetic patients.

Screening of the hypoglycemic effect of eight Vietnamese herbal drugs

The prevalence of type 2 diabetes in developing countries is increasing. In Vietnam, several plants are thought to be useful for the treatment of type 2 diabetes. This study has been performed to screen the hypoglycemic effects of eight Vietnamese herbs used in traditional medicine for the treatment of diabetes. Blood glucose levels were measured before and several times after oral or i.p. administration of the ethanol-based plant extracts in normal mice. The extracts that reduced blood glucose both orally and i.p. were also studied in glucose tolerance tests in mice. Gynostemma pentaphyllum Makino (Cucurbitaceae) at doses of 200 and 300 mg/kg i.p. or 1500 mg/kg orally reduced blood glucose in mice (P < 0.001 for all compared to control group using NaCl 0.9%). Similarly, Anemarrhena asphodeloides Bunge (Liliaceae) at 200 and 300 mg/kg i.p. (P < 0.001 vs. control group) and 1500 mg/kg orally reduced blood glucose 4 h after administration (P < 0.001). Angiopteris evecta Forst. Hoffn. (Marattiaceae) 300 mg/kg i.p. and 1500 mg/kg orally strongly reduced blood glucose levels (P < 0.001 vs. control groups). All three extracts when dosed at 1000 mg/kg orally suppressed the rise in blood glucose in normal mice during a glucose tolerance test. We have found three herbs that reduced blood glucose and inhibited increases in blood glucose after a glucose challenge in normal mice.

Insulin Secretion is Stimulated by Ethanol Extract of Anemarrhena asphodeloides in Isolated Islet of Healthy Wistar and Diabetic Goto-Kakizaki Rats

BACKGROUND

The hypoglycemic effect of extract of Anemarrhena asphodeloides has been accounted for by the substance mangiferin which increases insulin sensitivity. The present study aimed to investigate whether an ethanol extract of Anemarrhena asphodeloides would stimulate insulin secretion and if so, further elucidate the mechanism behind this effect.

METHODS

Isolated pancreatic islets of normal Wistar rats and spontaneously diabetic Goto-Kakizaki (GK) rats were batch incubated or perifused to study effect of Anemarrhena asphodeloides extract (TH2) on insulin release.

RESULTS

At 3.3 mM glucose, 2, 4, and 8 mg/ml TH2 increased the insulin release of Wistar rat islets 2.5-, 4.1-, and 5.7-fold, respectively (p < 0.05) and of GK rat islets 1.7-, 3.0-, and 6.3-fold, respectively (p < 0.01). Similarly at 16.7 mM glucose, 2, 4 and 8 mg/ml TH2 increased insulin release of Wistar rat islets 1.5-, 2.2-, and 3.8-fold, respectively (p < 0.05) and of GK rat 2.5-, 4.2-, and 11.9-fold, respectively (p < 0.01). In perifusions of islets, TH2 also increased insulin secretion that returned to basal levels when TH2 was omitted from the perifusate. Mangiferin had no effect on insulin secretion of islets. In islets depolarized by 30 mM KCl and B-cell K-ATP channels kept open by 0.25 mM diazoxide, TH2 (8 mg/ml) further enhanced insulin secretion at 3.3 but not at 16.7 mM glucose. Pertussis toxin suppressed the insulin stimulating effect of 2 and 8 mg/ml TH2 by 35 % and 47 % (p < 0.05 and p < 0.001, respectively).

CONCLUSIONS

Ethanol extract of the roots of Anemarrhena asphodeloides contains a substance, TH2, that stimulates insulin secretion both at 3.3 and 16.7 mM glucose in islets of normal Wistar and diabetic GK rats. The mechanism behind TH2-stimulated insulin secretion involves an effect on the exocytotic machinery of the B-cell, mediated via pertussis toxin-sensitive Gi- (or Ge-) proteins.