Lupin seed γ-conglutin lowers blood glucose in hyperglycaemic rats and increases glucose consumption of HepG2 cells

The aim of the present study was to evaluate the effect of a chronic oral gamma-conglutin treatment in male Sprague-Dawley rats in which hyperglycaemia had been induced by supplying 10% D-glucose in drinking-water. A gamma-conglutin dosage of 28 mg/kg body weight was daily administered to animals for 21 d. Plasma glucose, insulin and glucose overloading were monitored. Chronic administration of glucose resulted in a statistically significant (P<0.05) increase in fasting blood glucose (2.5-fold) and insulin (2.7-fold) v. the values recorded in control rats. Simultaneous treatment with gamma-conglutin attenuated the rise in plasma glucose (1.9-fold) and insulin (1.8-fold) levels in the glucose-fed rats (P<005). Fasting insulin and homeostasis model of insulin resistance were decreased by 34 and 48% (P<005), respectively, in the gamma-conglutin-treated rats v. the values found in pair-fed animals. To confirm these results with a different approach, HepG2 cells, grown for 24 and 48 h in Dulbecco's minimum essential medium containing different glucose concentrations (5.5, 11.1 and 16-5 mmol/l), were exposed to 10 mu mol/l gamma-conglutin with or without 10 mmol/l metformin or 100 nmol/l insulin. gamma-Conglutin increased glucose consumption (from 1.5- to 2.5-fold) in HepG2 cells, under all experimental conditions; this effect was more evident after 48 h incubation. Moreover, in this in vitro model, the addition of gamma-conglutin potentiated the activity of insulin and metformin in cell glucose consumption. These findings extend the previous ones and suggest the potential use of lupin gamma-conglutin in the control of glycaemia.