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

Abstract

The aim of the present study was to evaluate the effect of a chronic oral γ-conglutin treatment in male Sprague-Dawley rats in which hyperglycaemia had been induced by supplying 10 % d-glucose in drinking-water. A γ-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 γ-conglutin attenuated the rise in plasma glucose (1•9-fold) and insulin (1•8-fold) levels in the glucose-fed rats (P < 0•05). Fasting insulin and homeostasis model of insulin resistance were decreased by 34 and 48 % (P < 0•05), respectively, in the γ-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 μmol/l γ-conglutin with or without 10 mmol/l metformin or 100 nmol/l insulin. γ-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 γ-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 γ-conglutin in the control of glycaemia. © 2011 The Authors.