Erythropoiesis and myocardial energy requirements contribute to the hypermetabolism of childhood sickle cell anemia.
OBJECTIVE
We hypothesized that an elevated hemoglobin synthesis rate (SynHb) and myocardial oxygen consumption (MVO2) contribute to the excess protein and energy metabolism reported in children with sickle cell anemia.


METHODS
Twelve children (6-12 years old) with asymptomatic sickle cell and 9 healthy children matched for age and sex were studied. Measurements were whole-body protein turnover by [1-C]leucine, SynHb by [N]glycine, resting energy expenditure by indirect calorimetry and the systolic blood pressure-heart rate product used as an index of MVO2. Protein energy cost was calculated from protein turnover. Statistical analysis included Spearman correlations and partial correlation analyses.


RESULTS
Although body mass index was significantly lower for sickle cell versus controls (P < 0.02), children with asymptomatic sickle cell had 52% higher protein turnover (P < 0.0005). Proportional reticulocyte count, SynHb, MVO2 and resting energy expenditure were also significantly higher in children with sickle cell (P < 0.01). Protein turnover correlated significantly with both SynHb (r = 0.63, P < 0.01) and reticulocyte percentage (r = 0.83, P < 0.0001). Partial correlation of these 3 variables showed reticulocyte percentage as the only variable to be significantly associated with protein turnover, even after adjusting for sickle cell anemia (P = 0.03). Partial correlation of log resting energy expenditure on MVO2 was significant, controlling for protein energy cost, sex and age (P = 0.03).


CONCLUSIONS
These results indicate that metabolic demands of increased erythropoiesis and cardiac energy consumption account for much of the excess protein and energy metabolism in children with sickle cell anemia.
Hibbert
Jacqueline M
JM
Department of Biochemistry, Morehouse School of Medicine, Atlanta, GA, USA. jhibbert@msm.edu
Creary
Melissa S
MS
Gee
Beatrice E
BE
Buchanan
Iris D
ID
Quarshie
Alexander
A
Hsu
Lewis L
LL
D000755:Anemia, Sickle Cell / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D001481:Basal Metabolism; D001794:Blood Pressure; D002153:Calorimetry, Indirect; D002648:Child; D003430:Cross-Sectional Studies; D004734:Energy Metabolism; D004920:Erythropoiesis; D005260:Female; D006339:Heart Rate; D006454:Hemoglobins / Q000096:biosynthesis; D006801:Humans; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D017701:Reticulocyte Count
D006454:Hemoglobins