Plasma Leptin Association with Body Composition and Energy Expenditure in Sickle Cell Disease

Plasma Leptin Association with Body Composition and Energy Expenditure in Sickle Cell Disease

Maciej S. Buchowski, PhD^,, Lorenza A. Simmons, BS, Kong Y. Chen, PhD, Paul J. Flakoll, PhD, FACN, Beverly G. Mellen, PhD and Ernest A. Turner, MD

Center for Nutrition (M.S.B., L.A.S.) at Meharry Medical College, 1005 D.B. Todd Blvd., 21st Avenue South, Nashville, Tennessee
Comprehensive Sickle Cell Center (E.A.T.) at Meharry Medical College, 1005 D.B. Todd Blvd., 21st Avenue South, Nashville, Tennessee
Department of Medicine (K.Y.C., M.S.B.) at Vanderbilt University Medical Center, 21st Avenue South, Nashville, Tennessee
Department of Surgery (P.J.F.) at Vanderbilt University Medical Center, 21st Avenue South, Nashville, Tennessee
Department of Preventive Medicine (B.G.M.) at Vanderbilt University Medical Center, 21st Avenue South, Nashville, Tennessee

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Fig. 1. Regressions of log plasma leptin (nanograms per milliliter) vs. FM (kilograms)

a.No significant differences were noted between regression lines generated for males (SCD versus non-SCD controls). Thus, these groups are presented together. Although log plasma leptin was found to be 0.174 units lower on average with each 10-year increase in age (adjusting for SCD, gender and FM; see Table 2), for ease of presentation, age was excluded from the model in this graph and in graph 1b. No interactions involving age were significant. The regression equation for 18-year-old males is log [leptin]=1.019+0.038*SCD+0.382*(FM-15)/10.

b.Log plasma leptin concentrations were significantly greater in non-SCD control females versus males (adjusting for FM and age; p<0.0001) and significantly lower in females with SCD versus non-SCD controls (adjusting for FM and age; p<0.0001). The regression equation for 18-year-old females is log [leptin]=2.569-0.863*SCD+0.699*(FM-15)/10.

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Fig. 2. Residual-residual plots. Each plot shows the relationship between REE and log leptin after both have been adjusted for the effects of FFM using linear regression. The adjusted variables are labeled "Residual REE" and "Residual log leptin," respectively.

a.In males, a positive linear relationship was observed between log leptin and REE in control subjects, after adjusting for FFM (see Table 3 for corresponding analysis; regression coefficient=1.01). This relationship was not observed in SCD patients.

b.In females, no consistent relationship between log leptin and REE was observed after adjusting for FFM, though REE was higher on average in SCD females those in control females (see Table 3 for corresponding analysis; regression coefficient=0.901).