Hepatic-portal glucose and insulin levels: relationship to glucose-induced satiety and hunger.

The hepatic-portal infusions of both smaller and larger glucose loads, which had no significant effect on food intake in chronic feeding experiments, produced only a brief dose-dependent peak-like elevation in glucose and insulin levels. In contrast, metabolic changes produced by duodenal infusions were greater and considerably longer in duration. The maximal level and duration of glucose and insulin increase further differentiated two feeding phenomena induced by duodenal infusions: 1) the metabolic satiety of smaller glucose loads associated with blunted and delayed glucose and insulin increases within normal physiological range; 2) paradoxical antiregulatory stimulation of food intake induced by larger glucose loads associated with a gradually intensified, exaggerated and prolonged insulin increase. This increase was significantly larger than corresponding preinfusion value even at the end of 3 hour test period. Present results thus demonstrate that various glucose-induced feeding phenomena are associated and apparently dependent for their expression on distinct, prolonged changes in glycemia and insulin levels.