In Vitro Effect of Fenugreek Extracts on Intestinal Sodium-dependent Glucose Uptake and Hepatic Glycogen Phosphorylase A

Fenugreek (Trigonella foenum-graecum L. seed) is a food with traditional medicinal use in diabetes. Beneficial effects have been demonstrated in diabetic animals and both insulin-dependent and non-insulin-dependent diabetic subjects. Effects of a lipid extract A, crude ethanolic extract B, further sub-fractions of B (saponin-free C, saponin D and sapogenin E) and a gum fibre fraction F on intestinal sodium-dependent glucose uptake were investigated in vitro using rabbit intestinal brush border membrane vesicles. All fractions except A inhibited glucose-uptake at 0.33 and/or 3.3mg/mL (p < 0.001). Greatest inhibition was observed with fractions D and E. Diosgenin and trigonelline (compounds reported in fenugreek)also inhibited glucose-uptake ((50)C values approximately 3mg/ ml, equivalent to 8mM and 19mM respectively) but did not account for the activity of the crude extracts. Fenugreek extracts had no effect on basal levels of glycogen phosphorylase a (HGPa) activity in rat hepatocyte suspensions. However fractions C and E caused a marginal but statistically significant inhibition (18.9 and 15.1% respectively, p < 0.05) of glucagon induction of this enzyme suggesting a glucagon-antagonist effect. Diosgenin (1.65mg/ml; 4mM) inhibited glucagon-induced HGPa activity by 20% (p < 0.05), and was more effective than trigonelline (non significant inhibition of 9.4% at 1.65mg/ml, 10mM).