Gastrointestinal enhanced insulin release in response to glucose in newborn infants.

The purpose of this investigation was to determine whether or not gastrointestinal (GI) enhanced insulin response occurs in newborn infants soon after birth. Glucose infusion by intravenous or orogastric routes was given to infants during the first 4 days of life, aiming at achieving similar plasma glucose concentrations. Their plasma insulin responses were then compared. Thirty term, newborn infants (10 appropriate for gestational age, 8 small for gestational age, 6 large for gestational age, and 6 infants of diabetic mothers) were studied. With intravenous glucose infusions of 8 mg/kg/min or orogastric infusion of 16 mg/kg/min, the plasma glucose concentrations achieved were similar and approximated 110 mg/dl. Plasma insulin responses were greater in infants receiving glucose via the GI route. The finding was in contrast to our previous data, in which no GI enhancement of insulin response was demonstrated. The present data suggest that in the term newborn infant, GI enhanced insulin release occurs only when a threshold of plasma glucose concentration has been exceeded. It appears that the enteroinsular axis is functional in newborns soon after birth.