Background: Yoga is a representative mind-body therapy. Our previous studies have demonstrated that isometric yoga (i.e. yoga programs that we developed so individuals can practice yoga poses with a self-adjustable isometric load) reduces the fatigue of patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS); however, the underlying mechanisms remain unclear. Several studies have suggested that the micro-ribonucleic acid (miRNA) expression of ME/CFS patients is different from that of healthy subjects. However, it has not to date been determined if the practice of isometric yoga can affect miRNA expression. Therefore, we sought to investigate if isometric yoga is associated with changes in the expression levels of serum miRNA of patients with ME/CFS. Methods: The study included nine patients with ME/CFS who failed to show satisfactory improvement after at least 6 months of treatment administered at our hospital. Patients practiced recumbent isometric yoga for 3 months; they met with a yoga instructor every 2 to 4 weeks and participated in daily in-home sessions. The effect of recumbent isometric yoga on fatigue was assessed by comparing pre- and post-intervention scores on the Japanese version of the 11-item Chalder fatigue scale (CFQ 11). Patient blood samples were drawn pre- and post-intervention, just prior to practicing recumbent isometric yoga with an instructor. The serum was used for miRNA array analysis with known human miRNAs. Results: The average CFQ 11 score decreased significantly (from 25.3 ± 5.5 to 17.0 ± 5.8, p < 0.0001) after practicing recumbent isometric yoga for 3 months. The miRNA microarray analysis revealed that four miRNAs were significantly upregulated, and 42 were downregulated after the intervention period. Conclusions: This explorative pilot study is the first to demonstrate changes in the serum levels of several miRNAs after regular practice of recumbent isometric yoga. These miRNAs might represent biomarkers for the fatigue-relieving effects of isometric yoga of patients with ME/CFS. Trial registration: University Hospital Medical Information Network (UMIN CTR) 000023472. Registered Aug 4, 2016.
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