Ketogenic and lipolytic effects of glucagon on liver

Abstract

The glycogenolytic effect of glucagon on liver has been extensively investigated. Increased glycogen breakdown and glucose production are apparent after both in vivo and in vitro administration, depending on the activation of phosphorylase, mediated by the formation of adenosine-3′5′-phosphate (cyclic AMP) by the adenyl cyclase system. In addition, glucagon has been shown to stimulate gluconeogenesis in livers of fasted rats ( Struck et al., 1965; Garcia et al., 1966). Other actions of glucagon on the liver include inhibition of incorporation of acetate into fatty acids and cholesterol ( Berthet, 1960) and increased ketogenesis. The ketogenic effect of glucagon is apparent in vivo ( Foa and Weinstein, 1951) and in vitro ( Haugaard and Haugaard, 1954; Berthet 1958). The present communication reports further experiments on increased ketogenesis due to glucagon, and suggests that the likely mechanism of this effect is activation of hepatic lipase, thus increasing the supply of fatty acids for β-oxidation within the liver.