Exogenous insulin reduces proteolysis and protein synthesis in extremely low birth weight infants.
OBJECTIVE
To determine the effect of a continuous insulin infusion on protein and glucose metabolism in extremely low birth weight (ELBW) infants.


METHODS
We measured the rate of appearance (Ra) of the essential amino acids leucine and phenylalanine (reflecting proteolysis), utilization of phenylalanine for protein synthesis, and glucose Ra using stable isotope tracers during a basal infusion of glucose (6 mg/kg/min) and in response to a continuous infusion of insulin (0.05 U/kg/hr) by means of the euglycemic hyperinsulinemic clamp technique. Four clinically stable, euglycemic ELBW infants (26 +/- 0 weeks' gestation, 894 +/- 44 gm birth weight, 2.8 +/- 0.8 days of age) were studied.


RESULTS
In response to a greater than tenfold increase in insulin concentration (from 7 +/- 2 to 79 +/- 13 microU/ml), there was a 20% decrease in leucine Ra (Basal: 272 +/- 27 mumol/kg/hr; Insulin: 226 +/- 29 mumol/kg/hr; p < 0.01) and in phenylalanine Ra (Basal: 91 +/- 5 mumol/kg/hr; Insulin: 72 +/- 2 mumol/kg/hr; p < 0.05). Use of phenylalanine for protein synthesis also decreased by a similar magnitude (Basal: 77 +/- 4 mumol/kg/hr; Insulin: 62 +/- 1 mumol/kg/hr; p < 0.05). Glucose utilization doubled (from 8 +/- 0.9 to 15.7 +/- 1.1 mg/kg/min; p = 0.0003) and plasma lactate concentrations tripled (from 2.1 +/- 0.5 to 5.7 +/- 1.0 mmol/L; p < 0.05) during the insulin infusion.


CONCLUSIONS
During an infusion of glucose alone, pharmacologic concentrations of insulin in ELBW infants produced no net protein anabolic effect. Furthermore, euglycemic hyperinsulinemia was accompanied by development of significant metabolic acidosis.
Poindexter
B B
BB
Department of Pediatrics, Indiana University School of Medicine, Indianapolis 46202-5210, USA.
Karn
C A
CA
Denne
S C
SC
D001786:Blood Glucose / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000494:pharmacology; D015309:Glucose Clamp Technique; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007231:Infant, Newborn; D007234:Infant, Premature / Q000378:metabolism*; D019102:Infant, Very Low Birth Weight / Q000378:metabolism*; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D019344:Lactic Acid / Q000097:blood; D007930:Leucine / Q000097:blood; D008297:Male; D010649:Phenylalanine / Q000097:blood
D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D019344:Lactic Acid; D010649:Phenylalanine; D007930:Leucine; D005947:Glucose