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Neonatal lipid utilization increases with injury severity: recombinant human growth hormone versus placebo
R W Letton1, W J Chwals, A Jamie
1Department of Surgery, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC, USA.
Insights
Growth hormone (GH) increases lipid oxidation in injured neonates, especially under high stress. Supplementation improves lipid utilization, but excess carbohydrates reduce its use for energy.
Area of Science:
- Biochemistry
- Pediatric Metabolism
- Endocrinology
Background:
- Increased lipid oxidation is noted in injured adults and children receiving growth hormone (GH).
- The effect of GH on lipid metabolism in neonates, who readily synthesize fat, has not been previously studied.
- Neonates undergoing surgery for gastrointestinal conditions face significant metabolic stress.
Purpose of the Study:
- To investigate the impact of recombinant human growth hormone (rhGH) on lipid oxidation in neonates recovering from surgery.
- To assess the influence of injury severity and carbohydrate intake on lipid metabolism in these infants.
- To determine if GH supplementation enhances lipid substrate utilization during acute metabolic stress in neonates.
Main Methods:
- A randomized controlled trial involving 22 neonates (average gestational age 35 weeks) post-surgery.
- Participants received either rhGH (0.2 mg/kg/d) or placebo for 6 days alongside parenteral nutrition.
- Indirect calorimetry measured energy expenditure, respiratory quotient, and lipid oxidation rates, with injury severity assessed by C-reactive protein levels.
Main Results:
- GH supplementation significantly increased energy expenditure, net lipid oxidation (Fe), and oxygen consumption for lipid oxidation (VO2f) in high-stress neonates.
- High-stress neonates exhibited lower respiratory quotient (RQnp) values, indicating greater reliance on fat oxidation.
- Lipid oxidation was directly proportional to stress severity and GH treatment, but inversely related to carbohydrate intake.
Conclusions:
- Lipid is a crucial energy source for acutely injured neonates, particularly those with severe stress.
- GH supplementation improves lipid substrate utilization in neonates experiencing acute metabolic stress.
- Optimizing caloric repletion requires a balanced formula, as excessive carbohydrate intake can suppress lipid utilization.
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.