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 aim of the study was to assess whether there exists a significant relationship between the severity of AIS and bone turnover markers and leptin levels. The study group was consisted of 77 AIS girls, aged 14.7 +/- 2.17 years. Scoliotic curve severity assessed by Cobb's angle was categorized as mild (10-19 degrees), moderate (20-39 degrees), or severe (>= 40 degrees). Corrected height, weight, and 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 withp< 0.05), and leptin (positively withp< 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 andp< 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 interrelationship between nutritional status and bone metabolism in patients with AIS are warranted.