Neonatal lipid utilization increases with injury severity: recombinant human growth hormone versus placebo

Abstract

Increased lipid oxidation has been observed in injured adult and pediatric patients who receive growth hormone (GH). In infants, whose bodies make fat more readily (de novo lipogenesis), this effect has not been tested. After surgery for necrotizing enterocolitis or gastroschisis, 22 neonates (average gestational age, 35 weeks; average postnatal age, 7 days) were provided basal protein-calorie parenteral repletion, and were prospectively randomized to receive either recombinant human GH (rhGH, 0.2 mg/kg/d) or placebo for 6 days. Injury severity was established by serial serum C-reactive protein (CRP) levels (high v low stress: CRP > or = 6.0 mg/dL v < 6.0 mg/dL). Indirect calorimetry was used to measure energy expenditure (MEE), respiratory quotient (RQ), net lipid oxidation (Fe), and lipid oxidative O2 consumption (VO2f). Among the GH+ group, MEE, Fe, and VO2f were significantly higher for the high-stress patients (MEE: 52.87 +/- 13.35 v 42.57 +/- 9.47 kcal/kg/d; P < .03: Fe; 18.32 +/- 27.74 v 0.81 +/- 13.47 kcal/kg/d; P < .02; VO2f: 7.21 +/- 9.86 v 0.01 +/- 7.42 L/d, P < .02), and RQnp was significantly lower in the high-stress patients (RQnp: 0.93 +/- 0.14 v 1.05 +/- 0.11; P < .02). In addition, Fe and RQnp were directly proportional to carbohydrate intake (CHO) in the high-stress patients (CHO to Fe: Pearson r = -.701; CHO to RQnp: Pearson r = .714; P < .05). Lipid oxidation was directly proportional to stress severity, was higher in the GH group (18.32 v 11.91 kcal/kg/d for the placebo group), and was depressed in response to increased CHO intake in all groups. Lipid is an important energy source in acutely injured, especially severely stressed neonates. Lipid substrate utilization is improved with GH supplementation during acute metabolic stress. In addition, excess carbohydrate delivery reduces the amount of lipid utilized for energy metabolism. An appropriately balanced, mixed-fuel formula should be used for caloric repletion in this infant population.