Short-term ingestion of Ginkgo biloba extract does not alter whole body insulin sensitivity in non-diabetic, pre-diabetic or type 2 diabetic subjects--a randomized double-blind placebo-controlled crossover study

BACKGROUND & AIMS: Ingestion of Ginkgo biloba Extract (EGb 761) may increase pancreatic beta-cell function in both healthy subjects with normal glucose tolerance (NGT) as well as patients with Type 2 Diabetes mellitus (T2DM). Since hyperinsulinemia is a hallmark of T2DM, it is important to verify that increased insulin production is not due to increased insulin resistance. METHOD: NGT subjects (n = 10; age, 44.2 +/- 13.9 years old), impaired glucose tolerance (IGT) (n = 8; age 51.3 +/- 6.6 years old) and T2DM subjects (n = 8, 51.6 +/- 15.2 years old) completed a randomized, double-blind, placebo-controlled crossover study. After ingesting either EGb 761 (120 mg/day as a single dose) or placebo during each 3-month arm, a 2-step euglycemic insulin clamp was performed. RESULTS: At the low insulin infusion rate (10 mU/m2/min) the glucose metabolic rates (M values) were 3.5 +/- 1.5 vs. 3.0 +/- 0.5 mg/kg (P = 0.16), 3.0 +/- 0.4 vs. 2.8 +/- 0.8 mg/kg (P = 0.19) and 2.6 +/- 0.7 vs. 2.4 +/- 0.5 mg/kg (P = 0.09) for the placebo and EGb 761 cycles, in the NGT, IGT and T2DM subjects, respectively. At the high insulin infusion rate (40 mU/m2/min) the M values were 7.3+/-2.3 vs. 8.1 +/- 2.5mg/kg (P = 0.07), 6.2 +/- 1.6 vs. 6.5 +/- 2.1 mg/kg (P = 0.32) and 3.6 +/- 1.6 vs. 3.5 +/- 1.0 mg/kg (P = 0.34) for placebo vs. EGb 761 cycles, in the NGT, IGT and T2DM subjects, respectively. CONCLUSION: The ingestion of 120 mg of EGb 761 as a single for 3 months did not produce insulin resistance in the non-diabetic or pre-diabetic subjects or exacerbate the disease in the T2DM subjects.