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Protein and energy metabolism in prepubertal children with sickle cell anemia
E K Salman1, M W Haymond, E Bayne
1Divisions of Hematology/Oncology, Nemours Children's Clinic, Jacksonville, Florida.
Insights
Children with sickle cell anemia (HbSS) exhibit hypermetabolism, showing increased protein turnover, energy expenditure, and glutamine utilization. These findings suggest higher nutritional requirements for affected children.
Area of Science:
- Pediatric Hematology
- Human Metabolism
- Nutritional Science
Background:
- Sickle cell anemia (HbSS) is characterized by shortened erythrocyte lifespan.
- This may increase protein demands, accelerate protein turnover, and elevate energy expenditure.
- Glutamine is a key fuel source for reticulocytes, potentially increasing its utilization in HbSS.
Purpose of the Study:
- To investigate protein turnover, energy expenditure, and glutamine utilization in children with HbSS.
- To compare these metabolic parameters between children with HbSS and healthy controls.
- To determine if children with HbSS exhibit a hypermetabolic state.
Main Methods:
- Studied eight children with HbSS and seven healthy controls in a postabsorptive state.
- Administered L-[1-(13)C]leucine infusion to assess protein synthesis and breakdown.
- Used L-[2-(15)N]glutamine infusion to measure glutamine utilization rates.
- Measured resting energy expenditure via indirect calorimetry and cardiac output via echocardiography.
Main Results:
- HbSS children showed significantly higher rates of leucine appearance and non-oxidative leucine disposal (indicators of protein turnover).
- Glutamine utilization was 47% higher in HbSS children compared to controls.
- Resting energy expenditure was 19% higher, and cardiac output was 66% higher in HbSS children.
- These findings indicate a hypermetabolic state in children with HbSS.
Conclusions:
- Children with HbSS demonstrate hypermetabolism involving protein, energy, and glutamine.
- Increased hemoglobin synthesis and cardiac workload likely contribute to elevated protein and energy utilization.
- Children with HbSS may require increased protein and energy intake compared to the general population.
Abstract:
We hypothesized that, in children with homozygous sickle cell anemia (HbSS), the shortened life-span of erythrocytes places an increased demand on protein stores, accelerates whole body protein turnover, and consequently, energy expenditure, as well as the rate of utilization of glutamine, a major fuel for reticulocytes. Eight (11.2 +/- 0.4 y old) children with HbSS who were free of infection of vaso-occlusive disease, and seven (11.3 +/- 0.4 y old) healthy black children were therefore studied in the postabsorptive state. Each received a continuous 4-h infusion of L-[1-(13)C]leucine to determine the rate of leucine oxidation, leucine rate of appearance, and nonoxidative leucine disposal, indicators of whole body protein breakdown and synthesis, respectively. Infusion of L-[2-(15)N]glutamine was used to assess rates of glutamine utilization. Resting energy expenditure and cardiac output were measured using indirect calorimetry and echocardiography, respectively. Compared with control subjects, HbSS children had a 58 and 65% higher leucine rate of appearance and nonxidative leucine disposal, respectively (both p < 0.001), 47% higher rates of whole body glutamine utilization (p < 0.01), 19% higher resting energy expenditure (p < 0.05), and 66% higher cardiac output (p < 0.01). In conclusion, children with HbSS show evidence of hypermetabolism with regard to protein, energy, and glutamine utilization. Both increased Hb synthesis and increased cardiac workload may contribute to excess protein and energy utilization. Whatever the mechanism of hypermetabolism, the data suggest that children with HbSS may have greater protein and energy requirements than the general population.