Bone and exercise outcomes in healthy children and children with chronic inflammatory disease.

Background: Chronic inflammatory diseases, such as juvenile idiopathic arthritis (JIA) and Crohn's disease (CD), are characterized by pro-inflammatory status, which can alter bone metabolism. This predisposes children with JIA and CD to low bone mineral content and higher risk of bone fracture. Exercise is an effective approach to strengthen bone and increase bone accrual in healthy and children with inflammatory conditions. This may be linked to mechanical loading or delayed anti-inflammatory effects of exercise, which can trigger bone turnover. The aim of this study was to utilize an in vitro model to examine the effects of exercise and inflammation on osteoblast proliferation. Methods: Serum samples from 30 youth (JIA n=8,13.36 ± 2.37 years; CD n=9,14.08 ± 2.44 years; and Controls n=13,14.10 ± 2.52 years) that participated in a previous exercise study were analyzed using in vitro experiments. The exercise protocol consisted of two 30-minute bouts of cycling at 50% of their peak mechanical power. Blood samples were collected at rest, immediately post-exercise, and at 1 hour of recovery. Inflammatory status was assessed by measuring cytokines IL-6 and tumor necrosis factor-α (TNF-α) in resting serum using high-sensitivity ELISA kits. Serum samples were also used to incubate MC3T3E1 osteoblasts in vitro for 48-hours. Osteoblast proliferation was measured using an MTS assay. Effects of exercise and inflammation were analyzed using one-way and two-way ANOVA while relationships between osteoblast proliferation and inflammatory status and aerobic fitness were analyzed using Pearson correlation. Results: There was no significant difference in osteoblast proliferation between JIA, CD, and healthy controls at rest (F=0.967, p=0.392). Exercise did not cause any significant effects on osteoblast proliferation between groups (F=0.0377, p=0.578,). Furthermore, osteoblast proliferation was not related to inflammatory status at rest (r = -0.149-0.243, p>0.05) or aerobic fitness (r=-0.164, p=0.412).Discussion: Exercise and chronic disease did not present any significant effects on in vitro osteoblast proliferation. This may be attributed to a delayed osteoblast response, which may be preceded by upstream signaling molecules of osteoblast proliferation, as well as effective disease management in JIA and CD patients, which may have attenuated inflammatory status. Further investigation is required. [ABSTRACT FROM AUTHOR]