Investigation of the acute effect of leptin on the inhibition of glycogen catabolism by insulin in rat liver perfused in situ

Leptin, a cytokine secreted by adipose tissue, has been implicated in the insulin resistance associated with obesity. Here we examined the acute influence of leptin at physiological (10 ng/mL) and supraphysiological (50 ng/mL and 100 ng/mL) concentrations on the inhibition of glycogen catabolism promoted by insulin in rat liver perfusion experiments. Perfusion of the liver with insulin (20 μU/mL) decreased the activation of glucose production (p < 0.05) and glycogenolysis by cAMP (3 μM). However, the infusion of leptin, at concentrations similar to those found in non-obese (10 ng/mL), obese (50 ng/mL), and morbidly obese (100 ng/mL) individuals did not influence the acute inhibitory effect of insulin (20 μU/mL) on glucose production and glycogenolysis stimulated by cAMP(p > 0.05).We conclude that neither physiological nor supraphysiological concentrations of leptin directly influence the inhibition of glycogen catabolism promoted by insulin in rat liver perfused in situ.