Submitted to: Pediatric Research
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2001
Publication Date: 4/1/2001
Citation: SUNEHAG, A., HAYMOND, M., SCHANLER, R.J., BIER, D.M. GLUCONEOGENIC SUBSTRATE AVAILABILITY IS IMPORTANT FOR MAINTAINING GLUCOSE PRODUCTION IN PREMATURELY BORN INFANTS. PEDIATRIC RESEARCH. 2001. Interpretive Summary: Not required.
Technical Abstract: Background: We have reported that preterm infants receiving IV glucose at half normal glucose turnover rate during parenteral nutrition (TPN) maintain normoglycemia mainly via gluconeogenesis (GNG), use glycerol as an important gluconeogenic substrate and support GNG more effectively with exogenous lipids than with amino acids. Objective: To test the hypotheses that substrate availability limits glucose production (GPR) when TPN glucose supply is reduced and both lipids and amino acids are withdrawn from the solution for 10 h, and that normoglycemia is maintained because glucose utilization is decreased. Design/Methods: 8 infants (1039 ± 68 g, 28 ± 1 wks) received parenteral glucose alone at the rate of 17 micromol/kg min for 10 h on day 4 ± 1 of life. GPR, GNG, glycogenolysis, glucose utilization, lipolysis, (glycerol flux) and proteolysis (leucine flux) were measured using appropriate stable isotopically labeled tracers. The results were compared to corresponding data obtained by us previously in 8 matched infants receiving TPN providing glucose at 17 micromol/kg min plus Intralipid® (2g/kg d) plus TrophAmine® (3 g/kg d) for 10 h. Results: When parenteral glucose was given alone, normoglycemia was maintained (3.8 ± 0.3) at 10 h vs. 4.1 ±0.3 mM at 4 h (ns) (mean ± SE), while GPR declined (p < 0.01) from 13.0 ± 1.1 (4 h) to 7.4 ± 0.8 micromol/kg min (10 h). Glucose utilization also declined (P < 0.01) from 29.5 ± 1.1 (4 h) to 24.8 ± 1.1 micromol/kg min (10 h) as did glycogenolysis from 7.8 ± 1.0 (4 h) to 1.7 ± 0.7 micromol/kg min (10 h) (p < 0.001). There was no change in GNG (5.1 ± 0.6 vs 5.7 ± 0.3 micromol/kg min) (ns) or glycerol flux (7.8 ± 1.7 vs 9.3 ± 1.9 micromol/kg min) (ns). Leucine flux declined slightly (p < 0.05) from 3.6 ± 0.1 (4 h) to 3.0 ± 0.2 micromol/kg min (10h). On the other hand, after 10 h of TPN, matched infants maintained GPR of 9.9±0.7 micromol/kg min (p < 0.05 vs glucose alone group) and glucose utilization (26.8 ± 0.7 micromol/kg min; p < 0.05) with a higher GNG rate (9.4 ± 0.9 micromol/kg min; p < 0.01). Glycogenolytic rate did not differ. Conclusions: Very premature infants receiving parenteral glucose at half normal glucose turnover rates have activated GNG during the first days of extrauterine life and utilize both endogenous and exogenous substrate to maintain GPR via GNG. When limited lipid and amino acid substrate are available, normoglycemia is supported by reducing glucose utilization.