Screening of biomarkers in autoimmune thyroid diseases (AITDs): preliminary study based on Raman spectroscopy and MALDI-ToF mass spectrometry.

Hashimoto's thyroiditis (HT) and Graves' disease (GD), autoimmune thyroid diseases (AITDs), are among the most commonly reported autoimmune disorders. Early and unambiguous diagnosis and monitoring of the disease development are crucial to obtain the most effective treatment results. Matrix-assisted laser desorption/ionization with a time-of-flight analyzer mass spectrometry (MALDI-ToF MS) and Raman spectroscopy are promising analytical methods in this regard. These non-invasive and sensitive techniques provide information on specific features of proteins, including their post-translational modifications and the level of a wide range of biomolecules in the bloodstream, which are useful for assessing the health status of patients. This study screened for potential biomarkers in AITDs using both methods. Sera from HT patients at two stages of disease progression and GD patients before and after normalization of thyrotropic hormone following immunosuppressive treatment were used in the study. Serum biomolecule changes were analyzed using Raman spectroscopy. N-glycans released from serum glycoproteins were detected by MALDI-ToF mass spectrometry. We observed that the levels of phenylalanine, carotenoids, and phospholipids in HT sera correlate with increased inflammation accompanying this disease. The GD group showed a lower amount of serum collagen compared to the HT patients. Quantitative comparison of N-glycans revealed several differences between the study groups and healthy donors. The higher galactosylation and α2,6-sialylation of serum proteins in HT2 relative to GD patients are the main differences in N-glycan profiles of AITDs. The obtained preliminary results demonstrate that these analytical techniques have potential in diagnosing and monitoring AITDs, and can be a good alternative to the currently used methods. Analysis of a larger number of samples, as well as a more detailed MS methodology for precise decoding of glycan structures, is necessary for further research.