Associations Between Neuromuscular Fatigue, Anxiety, and Peripheral Biomarkers of Neuronal Injury, Inflammation, and Mitochondrial Dysfunction in Treatment-Naïve Relapsing-Remitting Multiple Sclerosis.

OBJECTIVE: To investigate whether neuromuscular fatigue and anxiety are associated with a peripheral biological signature involving inflammation, oxidative stress, mitochondrial homeostasis, neurotrophic support, and neuronal/glial injury markers in treatment-naïve patients with relapsing-remitting multiple sclerosis (RRMS). METHOD: This cross-sectional case-control study included 20 newly diagnosed, treatment-naïve patients with RRMS and 20 age- and sex-matched healthy controls. Anxiety symptoms were assessed using the Beck Anxiety Inventory, while fatigue was evaluated using the Modified Fatigue Impact Scale and the Fatigue Severity Scale. Peripheral blood samples were collected before the initiation of multiple sclerosis-specific therapy. Cytokines, neurotrophic factors, neuronal/glial injury markers, vitamin D, oxidative damage parameters, mitochondrial reactive oxygen species, mitochondrial DNA damage, inflammasome-related proteins, apoptotic markers, and mitochondrial homeostasis-related genes were analyzed in serum using ELISA, biochemical assays, Western blotting, and RT-PCR. RESULTS: Compared with healthy controls, patients with RRMS showed higher anxiety and fatigue scores, increased circulating IL-1β, IL-18, and TNF-α levels, and increased NLRP3 inflammasome expression. These alterations were accompanied by increased oxidative damage, higher mitochondrial reactive oxygen species production, increased mitochondrial 8-oxoG levels, increased Bax expression, reduced Bcl-2 expression, decreased TFAM expression, and increased Pink-1 and Parkin expression. In addition, patients exhibited increased serum levels of S100β and neuron-specific enolase, along with reduced brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) levels. Exploratory correlation analyses suggested biologically plausible associations among neurotrophic signaling, mitochondrial biogenesis, inflammatory activation, oxidative stress, and markers of neuronal/glial injury. CONCLUSION: These findings suggest that treatment-naïve RRMS is characterized by a peripheral inflammatory-mitochondrial imbalance associated with fatigue, anxiety, increased neuronal/glial injury markers, and reduced neurotrophic support. Peripheral biomarkers such as S100β, neuron-specific enolase, BDNF, and mitochondrial homeostasis-related markers may represent accessible candidate indicators of disease-related biological alterations.