Bone disease in β-thalassemia major (βTM) remains poorly understood. Receptor activator of nuclear factor-κβ ligand (RANKL) regulates osteoclast formation and function. RANKL activity is balanced by interaction with its receptor (RANK) and binding to osteoprotegerin (OPG). L-Carnitine (LC) enhances osteoblastic activity by furnishing fuel. This study hypothesized that abnormal bone metabolism in βTM involves imbalanced RANKL/OPG and LC/free fatty acids (FFAs) metabolism. Sixty-nine transfusion-dependent βTM patients and 15 healthy controls were enrolled. One group of patients (n=34) received desferrioxamine (DFO) and the other (n=35) did not. Serum OPG, soluble RANKL (sRANKL), FFAs, LC [total LC (TC), free LC (FC), and esterified LC (EC)], calcium, and inorganic phosphate were measured by specific immuno and colorimetric assays; bone mineral density was examined by dual x-ray absorptiometry. Patients showed lower levels of OPG, TC, FC, EC and higher levels of sRANKL, sRANKL/OPG ratio, and FFAs than controls. Patients on DFO showed lower levels of OPG, TC, FC and higher levels of sRANKL, sRANKL/OPG ratio, and FFAs than those without chelation. In patients, sRANKL correlated negatively with TC and OPG and FC correlated positively with OPG and negatively with sRANKL, sRANKL/OPG ratio, and FFAs. In conclusion, altered bone metabolism owing to imbalanced osteoclastic bone resorption versus constructive osteoblastic activities in βTM pediatric patients could be due to abnormal sRANKL-OPG and LC-FFAs systems that were worsened by DFO.
Departments of *Physiology
‡Medical Biochemistry, Faculty of Medicine, Assiut University, Assiut, Egypt
Reprints: Enas A. Hamed, MD, Department of Physiology, Faculty of Medicine, Assiut University, 71526 Assiut, Egypt (e-mail: firstname.lastname@example.org).
Received for publication August 5, 2009; accepted January 13, 2010