OBJECTIVE: To determine the contribution of total gluconeogenesis to glucose production in preterm infants receiving total parenteral nutrition (TPN) providing glucose exceeding normal infant glucose turnover rates. STUDY DESIGN: Eight infants (0.955+/-0.066 kg, 26.5+/-0.5 weeks, 4+/-1 days) were studied while receiving routine TPN. The glucose appearance rate (the sum of rates of glucose infusion and residual glucose production) and gluconeogenesis were measured by stable isotope-gas chromatography-mass spectrometry techniques using deuterated water and applying the Chacko and Landau methods. RESULTS: Blood glucose ranged from 5.2 to 14.3 mmol/l (94-257 mg/dl) and the glucose infusion rate from 7.4 to 11.4 mg/kg per min, thus exceeding the normal glucose production rates (GPR) of newborn infants in most of the babies. The glucose appearance rate was 12.4+/-0.6 and GPR 2.1+/-0.3 mg/kg per min. Gluconeogenesis as a fraction of the glucose appearance rate was 11.2+/-1.1% (Chacko) and 10.5+/-1.2% (Landau) (NS) and the rate of gluconeogenesis was 1.35+/-0.15 mg/kg per min (Chacko) and 1.29+/-0.14 mg/kg per min (Landau) (NS). Gluconeogenesis accounted for 73+/-11% and 68+/-10 (NS) of the GPR for the two methods, respectively. Gluconeogenesis and glycogenolysis were not affected by the total glucose infusion rate, glucose concentration, gestational age or birth weight. Glucose concentration correlated with the total glucose infusion rate and gestational age (combined R(2)=0.79, p=0.02). CONCLUSIONS: Gluconeogenesis is sustained in preterm infants receiving routine TPN providing glucose at rates exceeding normal infant glucose turnover rates and accounts for the major part of residual glucose production. Gluconeogenesis is not affected by the glucose infusion rate or blood glucose concentration.
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