Association between Bone Turnover Markers, Leptin and Nutritional Status in Girls with Adolescent Idiopathic Scoliosis (AIS)

The link between scoliotic deformity and bone metabolism in adolescent idiopathic scoliosis (AIS) has not been well researched. Moreover, the data concerning the cross-talk between fat tissue content/hormonal activity and bone markers in this group of patients are lacking. The objective of this study was to correlate the extent of scoliotic-curve severity with the bone turnover vs. leptin level and nutritional status in girls with AIS. The study encompassed 77 AIS girls, aged 14.7 ± 2.17 years. Scoliotic curve severity assessed by Cobb’s angle was categorized as mild (10-19o) moderate (20-39º) or severe (≥40º). Corrected height, weight, waist and hip circumferences were measured and body mass index (BMI), corrected height Z-score, BMI Z-score and waist/height ratio (WHtR) were calculated for the entire group. Body composition parameters: fat mass (FAT), fat-free mass (FFM) and predicted muscle mass (PMM) were determined using a bioelectrical impedance analyzer. Bone turnover markers (osteocalcin (OC) and amino terminal of collagen cross-links NTx) and leptin levels were assessed in serum. Multiple regression analysis showed that, OC, NTx (negatively with p<0.05) and leptin (positively with p<0.01) were significantly associated with curve severity in AIS girls. Moreover, Cobb’s angle was positively correlated with W/HtR (p<0.01)and FAT (p<0.05). One-way analysis of variance (ANOVA) revealed significant differences in leptin (p<0.05 vs. mild only), OC (p<0.05 vs. mild and moderate)) and W/HtR (p<0.01 and p<0.05 vs. mild and moderate respectively) between the three AIS severity subgroups. OC was significantly lower in the severe AIS subgroup, while leptin and W/HtR were significantly higher. Significant correlations between leptin and anthropometrical parameters as BMI z-score and W/HtR were shown. Leptin level correlated also significantly with BMI z score (p<0.001), W/HtR (p<0.0001) and body composition parameters (p<0.000001). Moreover, there was a significant negative correlation between NTx and leptin level (p<0.05). Bone metabolism in AIS girls seems to be altered and significantly related to the scoliotic curve severity. Leptin may be a crucial link in the cross-talk between bone turnover and body composition in this group of patients. Further studies concerning this topic are needed.