Injection Of Glucagon-like Peptide-1 Research Articles

Influence of fasting and neuropeptide Y on the suppressive food intake induced by intracerebroventricular injection of glucagon-like peptide-1 in the neonatal chick

Recently, we have reported that central administration of glucagon-like peptide-1 (GLP-1) strongly decreased food intake of chicks. The aim of the present study was to elucidate whether suppressed food intake by central injection of GLP-1 would be modified by an appetite stimulant such as fasting and neuropeptide Y (NPY). Birds (2 days old) were starved for 3 or 6 h and then GLP-1 (0.03 μg/10 μl) or saline was injected by the intracerebroventricular (i.c.v.) route. Birds starved for 6 h ate significantly more food than those starved for 3 h, while irrespective of the time for fasting GLP-1 strongly inhibited food intake as rapidly as 10 min after i.c.v injection. The suppressive effect on food intake continued until 4 h after injection. Central administration of NPY (2.5 μg/10 μl) greatly enhanced food intake, but co-injection of GLP-1 (0.01, 0.02 or 0.03 μg/10 μl) decreased food intake in a dose-dependent fashion. Under GLP-1 (0.03 μg/10 μl) treatment, whether NPY modifies food intake of chicks in a dose-dependent manner was investigated by co-injection of graded levels of NPY (0.4, 1.0 and 2.5 μg/10 μl). GLP-1 completely inhibited the effect of NPY on food intake without a dose response. These results suggest that central GLP-1 may interact with NPY and may be the most potent inhibitor of food intake in the chicken.

Intracerebroventricular injection of mammalian and chicken glucagon-like peptide-1 inhibits food intake of the neonatal chick

Glucagon-like peptide-1 (GLP-1), structurally similar to glucagon, is synthesized from a larger precursor, preproglucagon, and has been postulated to be a novel incretin. Recently, it was reported that central administration of GLP-1 decreased food intake in rats. The amino acid sequences of GLP-1 are identical in all mammals, and chicken GLP-1 exhibits a high homology with mammalian GLP-1. The aim of this study was to elucidate whether central injection of mammalian or chicken GLP-1 inhibits food intake in the chick, and to compare their effects. Intracerebroventricular administration of mammalian and chicken GLP-1 strongly inhibited food intake of chicks. However, the suppressive effect of both GLP-1 on food intake was similar. These results show that GLP-1 with a variety of amino acid sequences may be the most potent inhibitor of food intake in the chicken.

Effects of truncated glucagon-like peptide-1 on pancreatic hormone release in normal conscious dogs

The effects of truncated glucagon-like peptide-1 (GLP-1) on insulin and glucagon release were examined in unanesthetized normal dogs. A bolus injection of GLP-1(7-36)amide elicited a transient increase in the plasma insulin level, which brought about a decrease in the plasma glucose level. The degree of increase in plasma insulin levels with GLP-1(7-35)OH or GLP-1(7-37)OH was less than that induced by GLP-1(7-36)amide. The plasma glucagon level did not increase in spite of mild hypoglycemia. The infusion of graded doses of GLP-1(7-36)amide (6, 36, 120 ng.kg-1.min-1 every 30 min) did not change the plasma glucose, insulin or glucagon levels significantly. The degree of increase in the plasma glucose level induced by iv glucose infusion (12 mg.kg-1.min-1) was reduced by coinfusion of GLP-1(7-36)amide (6 ng.kg-1.min-1), although the degree of increase in the plasma insulin level was the same as that in a control experiment (coinfusion of the vehicle). Coinfusion of GLP-1(7-36)amide (60 ng.kg-1.min-1) caused an augmented increase in the plasma insulin level and a reduced increase in the plasma glucose level during iv glucose infusion (17 mg.kg-1.min-1) compared with the control experiment. The degree of decrease in the plasma glucagon level during iv glucose infusion was not affected by the coinfusion. The degree of increase in the plasma glucagon level induced by insulin hypoglycemia and the profile of the plasma glucose level at that time were not affected by the infusion of GLP-1(7-36)amide.(ABSTRACT TRUNCATED AT 250 WORDS)