Are Volumetric Bone Mineral Density and Bone Micro-Architecture Associated with Leptin and Soluble Leptin Receptor Levels in Adolescent Idiopathic Scoliosis? – A Case-Control Study

BACKGROUND Adolescent idiopathic scoliosis (AIS) is associated with low bone mineral density (BMD). The underlying etiology and how it may relate to the development of osteopenia remains unknown. Leptin has been postulated as one of the etiologic factors of AIS because of its profound effects on bone metabolism and pubertal growth. Its modulator, soluble leptin receptor (sOB-R), may affect leptin bioavailability and signaling. This study aimed to investigate whether serum leptin and sOB-R levels may be associated with bone quality, and whether these relationships may differ between young adolescent girls with and without AIS. METHODS This was a case-control study involving 94 newly diagnosed AIS girls (Cobb angle 12-48°) aged 12 to 14 years old and 87 age and gender-matched normal controls. Subjects with BMI>23.0 Kg/m(2) were excluded. Anthropometric measurements including body weight, height, arm span and sitting height were taken. Serum total leptin and sOB-R were assayed with ELISA. Non-dominant distal radius was scanned with High Resolution pQCT for assessing bone quality in terms of bone morphometry, volumetric BMD (vBMD) and trabecular bone micro-architecture. RESULTS Compared with normal controls, AIS girls had numerically higher sOB-R (p = 0.006), lower average vBMD (p = 0.048), lower cortical vBMD (p = 0.029), higher cortical bone perimeter (p = 0.014) and higher trabecular area (p = 0.027), but none remained statistically significant after the Hochberg-Benjamini procedure. Correlation analysis on serum leptin level indicated that distinctive correlations with trabecular bone parameters occurred only in AIS. CONCLUSION This study showed that bone quality in AIS girls was deranged as compared with controls. In addition, the distinct differences in correlation pattern between leptin and trabecular bone parameters indicated possible abnormalities in bone metabolism and dysfunction of the leptin signaling pathway in AIS.