Serum orexin-A levels are associated with disease progression and motor impairment in multiple sclerosis

Diencephalon is frequently affected in multiple sclerosis (MS), and lesions of this region are associated with increased disability. Orexin-A and melatonin, two foremost mediators of diencephalon, modulate cognitive and motor functions through several pathways including the brain-derived neurotrophic factor (BDNF)-cAMP response element-binding protein (CREB) signaling pathway. In this pilot study, our aim was to investigate the prognostic value of these factors in progression of cognitive and physical disability.

Levels of BDNF, melatonin, CREB, and orexin-A were determined by ELISA in sera of 25 relapsing remitting MS (RRMS) patients, 15 secondary progressive MS (SPMS) patients, and 20 healthy controls. Cognitive and motor functions were assessed by a neuropsychological test battery, timed 25-ft walk (T25-FW) and 9-hole peg (9-HP) tests.

MS patients had significantly lower serum levels of orexin-A and BDNF than healthy controls, and SPMS patients had significantly lower levels of melatonin and orexin-A than RRMS patients. Serum orexin-A levels were negatively correlated with 9-HP, T25-FW test scores, and progression index in RRMS patients. BDNF, CREB, and melatonin levels did not show any significant correlation with clinical features including EDSS and cognitive/motor performance of the patients.

Our results suggest that orexin-A levels are decreased in parallel to disease progression and motor system deterioration in the earlier stages of the disease. Thus, orexin-A might be used as a potential biomarker of physical disability.