NMR-BASED MUSCLE METABOLOMICS IN INFLAMMATORY MYOSITIS- UNDERSTANDING CHANGES IN SERUM AS A REFLECTION OF THE MUSCLE

Background: Systemic Sclerosis (SSc) is an autoinmune disease that can affect several organs and its mortality is fundamentally related to its pulmonary involvement. It is mandatory to seek for biomarkers that help us with early diagnosis and that are also useful for predicting organic involvement, so that we can adjust the diagnostic and therapeutic approach. Objectives: Our aim was to check if the presence of CXCL4, CXCL8 and GDF-15 is greater in the disease than in healthy population, and also their involvement in organic damage. Methods: Observational and cross-sectional study, with a prospectively performed protocol, of patients diagnosed of SSc according to ACR/EULAR 2013 criteria. Demographic, clinical, analytical, activity (EUSTAR index), severity (Medsger scale and modified Rodnan index), health perception (SF36) and disability (HAQ and Cochin test) variables were collected. Moreover, Videocapillaroscopy (VCL) and Respiratory Function Test were made, as well High Resolution Lung Tomography and Echocardiography in order to describe pulmonary features. Serum levels of CXCL4, CXCL8 and GDF-15 were measured in SSc patients and in healthy controls. Results: A total of 42 patients (95.4% women) were included, with an average age of 59.2 years. The median of years since diagnosis was 4, by 6 since the first non-Raynaud symptom. 20 patients were diagnosed with limited SSc, 20 patients diffusely and 2 patients with SSc without scleroderma. 42 healthy controls were also included. We found significantly higher levels of GDF-15 in patients with SSc (P The presence of GDF-15 was associated with diffuse SSc (P=0.009), pulmonary arterial hypertension (P=0.038), interstitial lung disease (P=0.004), decreased forced vital capacity (FVC), (P=0.002), high serum titles of antiScl70 (P=0.006), increased disease activity measured by EUSTAR index (P=0.001), as with capillary dilations in Capillaroscopy (P=0.015). Moreover, we found an association between CXCL4 levels and the consumption of complement C3 fraction (P=0.008) and skin involvement (higher Rodnan modified score), (P = 0.001); not finding association with lung involvement or other features (spirometric or analytical changes, capillaroscopy or functional tests). Attending to CXCL8, it was associated to consumption of the C4 fraction of complement (P=0.013) and the presence of tortuosities in capillaroscopy (P=0.02) with no other significant findings. Conclusion: The presence of GDF-15 is associated with diffuse SSc, lung impairment, disease activity and changes in capillaroscopy. In addition, CXCL4 was only associated with skin involvement, while CXCL8 was not related to any organic damage in our patients. Disclosure of Interests: None declared