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Energy substrate utilization in infants receiving total parenteral nutrition with different glucose to fat ratios
J L Bresson1, P Narcy, G Putet
1Department of Pediatrics, Hôpital des Enfants Malades, Paris, France.
Insights
Understanding how infants utilize glucose and lipids during total parenteral nutrition (TPN) is crucial. This study found that excessive glucose infusion leads to fat storage, while optimal fat oxidation occurs at specific glucose infusion rates in infants receiving TPN.
Area of Science:
- Metabolism
- Pediatrics
- Nutritional Science
Background:
- The metabolic fate of glucose and lipids during total parenteral nutrition (TPN) in infants is not fully understood.
- Infants receiving TPN require careful management of energy substrates to optimize growth and prevent complications.
Purpose of the Study:
- To assess energy substrate oxidation in infants receiving continuous TPN with varying glucose and lipid compositions.
- To determine the optimal balance of glucose and lipids for energy substrate utilization in infants on TPN.
Main Methods:
- 36 infants on continuous TPN were studied using open-circuit indirect calorimetry.
- Infants received isocaloric feeding regimens with varying nonprotein energy intakes, ranging from glucose alone to 70% fat.
- Glucose and fat oxidation rates were measured after at least 6 days of the assigned feeding regimen.
Main Results:
- Oxidative glucose disposal reached a maximum rate of 12.6 mg/kg.min (17.9 g/kg.d), with excess glucose being stored as fat.
- Increased glucose infusion rates paralleled increased energy expenditure.
- Net fat oxidation was observed only when glucose infusion rates were below 18.3 g/kg.d, with no further increase in fat oxidation at higher fat intakes, indicating increased fat deposition.
Conclusions:
- Fat infusion for energy coverage in infants on TPN is effective only when glucose infusion rates are at or below the maximal oxidative glucose disposal rate (approximately 18 g/kg.d).
- Excessive glucose infusion during TPN in infants leads to significant fat deposition.
- Optimizing TPN composition requires careful consideration of glucose and lipid balance to ensure adequate energy substrate oxidation and minimize fat accumulation.
Abstract:
As the fate of glucose and lipids infused during total parenteral nutrition is not well known in infants, we assessed energy substrate oxidation in 36 patients (mean age: 5.8 +/- 3.6 mo) on continuous total parenteral nutrition. The infants received isocaloric feeding regimens with nonprotein energy intakes either based on glucose alone (group 1) or on glucose-lipid mixtures providing 15% (group 2), 35% (group 3), 50% (group 4), or 70% (group 5) energy as fat for at least 6 d before glucose and fat oxidation rates were measured by open-circuit indirect calorimetry. Oxidative glucose disposal reached a maximal rate of 12.6 +/- 1.2 mg/kg.min (17.9 +/- 1.7 g/kg.d) in patients with the higher glucose infusion rates. Glucose infused in excess of maximal oxidative disposal was stored, mainly as fat. The increase in glucose infusion rate was paralleled by an increase in energy expenditure amounting to 16% of the energy value of infused glucose. Net fat oxidation was only observed in group 3 (1.6 +/- 0.7 g/kg.d), 4 (3.4 +/- 0.6 g/kg.d), and 5 (3.9 +/- 0.4 g/kg.d) patients, with glucose infusion rates lower than 18.3 g/kg.d. However, there was no further increase in fat oxidation in group 5 as compared to group 4 patients, despite a further increase in fat intake, which only resulted in increasing fat deposition. Thus, fat infusion aiming at a significant contribution to coverage of energy expenditure requires that glucose oxidation be equal to or lower than maximal oxidative glucose disposal, hence that glucose infusion rates be lower than 18 g/kg.d.(ABSTRACT TRUNCATED AT 250 WORDS)