Are Circulating Fibroblast Growth Factor 21 and N-Terminal Prohormone of Brain Natriuretic Peptide Promising Novel Biomarkers in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome?

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a chronic, disabling, and complex multisystem illness of unknown etiology. The protein fibroblast growth factor 21 (FGF21) regulates glucose homeostasis and lipid metabolism, and the protein N-terminal prohormone of brain natriuretic peptide (NT-proBNP) is strongly associated with an elevated cardiovascular risk; however, little is known about their role in ME/CFS patients. To address this gap, we explored the association between FGF21 and NT-proBNP and oxidative stress and inflammatory markers in ME/CFS. Twenty-one ME/CFS patients and 20 matched healthy controls were included in the study. Participants filled out validated self-reported questionnaires on their current health status covering demographic and clinical characteristics. Plasma showed significantly decreased total antioxidant capacity and increased lipoperoxide levels ( = 0.009 and  = 0.021, respectively) in ME/CFS. These ME/CFS patients also had significantly increased levels of inflammatory cytokines (interleukin [IL]-1β, IL-6, IL-10, TNF-α, and C-reactive protein) ( < 0.05 for all) but not for IL-8 ( = 0.833), indicating low-grade systemic inflammation status. Circulating FGF21 and NT-proBNP levels were significantly higher ( < 0.0001 and  = 0.005, respectively) in ME/CFS patients than in healthy controls. Significantly positive correlations were found between NT-proBNP levels and IL-1β and IL-6 ( = 0.04 and  = 0.01) in ME/CFS patients but not between FGF21 and these cytokines. In contrast, no significant correlations were found for either FGF21 or NT-proBNP in controls. These findings lead to the hypothesis that elevated FGF21 and NT-proBNP levels and the association between NT-proBNP and inflammation may be promising novel diagnostic and therapeutic targets in ME/CFS. 34, 1420-1427.