Effect of Exercise on β-Endorphin and Its Receptors in Myasthenia Gravis Patients

This is a prospective observational study evaluating the change in β-endorphin (BE) and its receptors following exercise in patients with myasthenia gravis (MG) and their association with clinical improvement. Fifteen patients with mild to moderate MG, aged 16–70 years, who were able to do 6-Minute Walk Test (6-MWT) and had MG Quality of Life-15 (MGQoL-15) ≤ 45 without any contraindication for exercise were included. The patients walked 30 min daily for 3 months. The primary outcome at 3 months was > 50% improvement in MGQoL-15 from the baseline, and the secondary outcomes were MG Activities of Daily Living (MGADL), Hospital Anxiety and Depression Scale (HADS), number of steps, and distance covered on 6-MWT and adverse events. Plasma BE level, μ-opioid receptor (MOR), and δ-opioid receptor (DOR) were measured on admission and at 1 and 3 months. Twelve age- and gender-matched healthy controls who were not on regular exercise were included for comparison of BE, MOR, and DOR levels. Plasma BE level ( P = 0.007) and DOR expression ( P = 0.001) were lower in MG patients compared to the healthy controls. After 3 months of exercise, 6 patients improved. Plasma BE, MOR, and DOR levels increased in the first and decreased in the third month. MGQoL-15 ( P < 0.001), HADS ( P < 0.0001), number of steps ( P < 0.007), distance ( P = 0.030), and MGADL ( P < 0.001) significantly improved compared to baseline. At 3 months, MGQoL-15 was associated with HADS score ( P = 0.001), reduced depression ( P = 0.013), MGADL ( P = 0.035), and distance travelled on the 6-WMW test ( P = 0.050). The improvement in depression was associated with higher BE level. Graphical Abstract