Fatty acid binding protein 3 is associated with skeletal muscle strength in polymyositis and dermatomyositis

Objective To determine serum levels and histopathological characteristics of fatty acid binding protein 3 (FABP3) in patients with polymyositis (PM) and dermatomyositis (DM), and to evaluate the correlation between the FABP3 and muscle strength. Methods The study population included 24 subjects with PM/DM, 12 subjects with asymptomatic or minimally symptomatic hyper-creatine kinase-emia (AMSH), and 10 healthy control subjects. Muscle strength was measured by using the Manual Muscle Test (MMT8). Serum CK, myoglobin and FABP3 levels were tested. Correlations between variables were studied by using Spearman's rank and partial correlation analysis methods. Immunohistochemical and double immunofluorescent stainings of FABP3 were performed to investigate its distribution in skeletal muscle. Results PM/DM patients had significantly higher (P 0.05), −0.228 (P > 0.05) and −0.927 (P < 0.001), respectively. Immunohistochemical and double immunofluorescent staining showed that FABP3 expression increased in the skeletal muscle of PM/DM patients and was mainly distributed in slow twitch muscle fibers. Conclusion Serum levels of FABP3 in PM/DM patients were significantly increased and were mainly distributed in slow twitch muscle fibers, displaying a closer association with muscle weakness than did serum levels of CK and myoglobin. FABP3 is likely to be a useful serum biomarker in PM/DM patients.