Effects of oral glucose and protein load on plasma glucagon and insulin concentrations in small for gestational age infants

Abstract

This paper reports portal and peripheral blood glucose, insulin, and glucagon levels in small for gestational age (SGA) and appropriate for gestational age (AGA) newborns during the first 48 hr of life. These parameters were studied after an oral glucose and protein load (1 g/kg of each) after a 4 hr fast. In AGA and SGA infants, mean fasting blood glucose level was significantly higher in the portal vein than in the aorta (P < 0.05). After the load, mean blood glucose level rose significantly in both vessels. The mean fasting plasma insulin level was low and was similar in both vessels. After the load in the AGA group mean plasma insulin level rose significantly at 45 min in both vessels (P < 0.05) (52.1 ± 37.2 μU/ml in aorta and 91.8 ± 75.3 μU/ml in portal vein). In the SGA group, the insulin response was minimal in the aorta and in the portal vein; the increase was significant only in the portal vein (P < 0.05) at 180 min (47.1 ± 25.3 μU/m). The mean fasting plasma glucagon level was higher in the portal vein than in the aorta in both groups (P < 0.05). After the load in AGA infants plasma glucagon rose significantly from 193 ± 55 pg/ml at zero time to 290 ± 76.8 pg/ml at 180 min (P < 0.01) in the aorta but not in the portal vein. In the SGA group, the mean plasma glucagon did not rise significantly in the aorta or in the portal vein (from 231.2 ± 54.3 pg/ml at zero time to 293.7 ± 123.5 pg/ml at 180 min in the portal vein). The molar ratio of insulin to glucagon (I/G) rose significantly after the load in the portal vein in both groups of infants (AGA 2.48 ± 2.06 at zero time to 5.08 ± 4.06 at 180 min; SGA infants from 2.2 ± 1.98 at zero time to 4.16 ± 2.59 at 180 min). When both groups of infants were compared there was no significant difference either in the aorta or in the portal vein in mean blood glucose, mean plasma level, and plasma glucagon level. It is concluded that SGA and AGA premature infants are similar in regard to secretion of both pancreatic hormones in the first day of life.