The relationships between physical activity, fitness, and serum biomarkers of brain damage and repair among individuals with Multiple Sclerosis

Background: Multiple sclerosis (MS) is the most common demyelinating, inflammatory and neurodegenerative disease that impacts the central nervous system (CNS) and can cause significant physical and cognitive disability. Physical activity and cardiorespiratory fitness may influence potential biomarkers such as brain-derived neurotrophic factor (BDNF), neurofilament light chain (NfL), and interleukin-6 (IL-6). I investigated whether fitness and self-reported physical activity were related to blood biomarkers of neuroinflammation and repair in individuals with MS. Methods: Blood samples were obtained from twenty-four patients with Relapsing-Remitting and Progressive MS (18 women and 6 men) before completing a maximal graded exercise test on a recumbent stepper. Participants reported moderate to vigorous physical activity (MVPA) in the previous 24 hours using the adapted International Physical Activity Questionnaire. Serum levels of BDNF, NfL, and IL-6 were analyzed using enzyme-linked immunosorbent assay (ELISA). Results: I evaluated the relationships between MVPA, fitness (VO₂ₚₑₐₖ), age, weight and biomarkers (BDNF, IL-6, NfL, and BDNF/IL-6 ratio). Results showed that only serum NfL, weight and VO₂ₚₑₐₖ were significantly correlated (r= -0.435, p= 0.034, and r= 0.436, p= 0.033), and that the other biomarkers did not correlate with MVPA, fitness, age, or weight (p > 0.05). Conclusion: Higher serum NfL levels, a neuronal damage biomarker, are associated with lower body weight and better physical fitness. Most of the remaining biomarkers show a sensitivity that is not specific enough to differentiate the relationship of fitness to MVPA. This reflects one of the limitations of my study and shall further be elaborated on in the discussion regarding the limitations of my findings.