Análise de biomarcadores salivares por espectroscopia ATR-FTIR e expressão de microRNAs plasmáticos em indivíduos treinados frente a diferentes protocolos de exercício físico

Abstract

Introduction: Analysis of the alterations in the different biological fluids induced by exercise can lead to the discovery of new biomarkers, that can enhance our understanding of the mechanisms related to the training status and performance of athletes. In this way, the Fourier Transform Infrared Spectroscopy (FTIR) technique has been widely applied for the determination of new salivary markers, since this analytical method allows the characterization of different molecules with high sensitivity and cost-effectiveness. In addition, molecular studies involving the analysis of microRNAs (miRNAs) (small non-coding RNA molecules involved in the process of post-transcriptional regulation of gene expression), have gained prominence in sports medicine, since their plasmatic levels can change in response to acute exercise and training, making these molecules classified as mediators of adaptive exercise responses. However, it is not clear how the levels of these markers change according to the type, duration and intensity of exercise. Objective: To determine biomarkers through the analysis of alterations in the vibrational modes of salivary samples and expression of plasmatic miRNAs in trained individuals following different protocols of physical exercise. Material and methods: Saliva and blood samples were collected from male individuals at the moments: pre-exercise, post-exercise and 3 hours post-exercise. Protocols included acute bouts of continuous exercise (CE), high-intensity interval exercise (HIIE), and resistance exercise (RE). Salivary samples were analyzed by ATR- FTIR and the RT-qPCR technique was used to determine the expression of different miRNAs. Results: It was observed through the ATR-FTIR analysis that the salivary biochemical components were altered according to the exercise protocol performed, suggesting some specific spectral peaks as their biomarkers. CE showed a salivary spectrum pattern similar to HIIE, while RE showed minor changes. An algorithm capable of determining a spectrum range related to the determination of exercise intensity was also developed. Regarding the expression of the different analyzed miRNAs, an increase in miR-23a levels was observed following CE. Conclusion: to our knowledge, the present work is the first to evaluate miR-23a expression in plasma samples after continuous exercise, contributing to a better understanding of this modality in relation to circulating miRNAs and possible effects on mitochondrial pathways, since this miRNA targets peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Regarding the results obtained with FTIR, this is the first study that compared changes in salivary spectra after different exercise protocols, suggesting spectrum peaks as biomarkers and the first to develop the referred algorithm. Therefore, we highlight infrared spectroscopy as a useful, fast and efficient tool to evaluate the metabolic alterations promoted by exercise, allowing the use of saliva as a cost-effective alternative for studying the state of training and performance of athletes.