Bone Abstracts

Objectives: The skeleton and adipose tissue interact. Our aim was to evaluate the interactions between adipokines and bone metabolism, and their association with disease-related factors in patients with severe juvenile idiopathic arthritis (JIA).

Methods: The study included 49 patients (median age 14.8 years, median disease duration 10.2 years) with refractory polyarticular JIA and 89 sex- and age-matched healthy controls. The subjects underwent clinical examination, body composition measurement with DXA and analyses for leptin, adiponectin and bone turnover markers.

Results: Patients with JIA were shorter and more often overweight (P=0.001) or obese (P<0.001) than controls. They had significantly higher leptin levels, even when adjusted for fat mass (P<0.001), and similar adiponectin but slightly lower adiponectin-to-fat mass ratio (P=0.073) than controls. Concentrations of bone formation markers were similar, but the level of carboxyterminal telopeptide of type I collagen (ICTP) (P=0.006) and the ratios of ICTP to osteocalcin or alkaline phosphatase were higher in the patients, indicating increased bone resorption. In controls, the inverse association between leptin and bone turnover markers was largely dependent of fat mass. Conversely, in patients the inverse association between leptin and bone formation markers was strengthened and became significant when adjusted for fat mass. Leptin, adiponectin or bone markers did not associate with disease duration or activity. Adiponectin associated inversely with ICTP in the controls.

Conclusions: We observed high adiposity and thus increased risk for metabolic complications in a cohort of patients with severe JIA. This was accompanied with increased bone resorption. Serum leptin was higher in patients, even when adjusted for fat mass. In patients leptin tended to associate inversely with bone formation markers but it did not associate with disease activity.