Glycogen levels and peripheral mechanisms of glucose-induced spppression of feeding

Rabbits deprived of food for 0, 2, 4, 6, 8, 16, and 24 h were assessed for glucose-induced feeding suppression, refeeding after deprivation, and liver glycogen. In previous research, we hypothesized a relationship between liver glycogen and the transition from duodenal to hepatic glucose suppression. In duodenally cannulated rabbits, the infusion of 10 ml of isotonic glucose in awake, free-feeding animals significantly suppressed food intake but did not do so in those food deprived for 2, 4, 6, 8, or 24 h. In hepatic-cannulated rabbits, similar amounts of glucose significantly suppressed food intake in 4-, 6-, 16-, and 24-h-deprived animals. Also, refeeding after deprivation increased as a function of continued deprivation until 6 or 8 h, when refeeding reached asymptote, or decreased through 24-h deprivations. In agreement with these observations, liver glycogen showed a sharp decline between 4, 6, and 8 h of deprivation (depending on circadian cycle). It is proposed that liver glycogen depletion, or some correlate, alters liver glucostatic regulation and determines refeeding after deprivation.