Stimulation of gastric inhibitory polypeptide release in ob/ob mice by oral administration of sugars and their analogues.

The effect of oral administration of sugars and their analogues (glucose, galactose, fructose, mannose, sucrose, N-acetylglucosamine, 2-deoxyglucose, 3-O-methylglucose and alpha-methyl-glucoside) on plasma gastric inhibitory polypeptide (GIP) concentration was examined in 18-h fasted ob/ob mice. Administration of sucrose (5.52 mol/kg body wt), or the monosaccharides (11.04 mol/kg body wt) glucose, galactose or fructose, elicited prompt GIP responses that peaked at 30 min. Similar effects were induced by 3-O-methylglucose or alpha-methyl-glucoside, but the stimulatory action of 2-deoxyglucose was delayed. In contrast to the other sugars, N-acetylglucosamine decreased plasma GIP concentration, while mannose exerted no effect. The results suggest that sugars using the Na+ glucose contransporter at the luminal brush border stimulate GIP release without the necessity of being metabolized or removed from the cell by the glucose transporter at the basolateral membrane. The ability of fructose to stimulate GIP release in ob/ob mice suggests that the Na+-glucose contransporter does not represent an exclusive trigger for sugar-induced GIP secretion.