Influence of stimulation frequency on brain-derived neurotrophic factor and cathepsin-B production in healthy young adults

Abstract

Electrical muscle stimulation (EMS) has been shown to stimulate the production of myokines (i.e., brain-derived neurotrophic factor (BDNF)), but the most effective EMS parameters for myokine production have not been fully elucidated. The purpose of this study was to quantify the optimal EMS frequency for stimulating myokine production. This study included sixteen young adults (male, n = 13, age = 27.3 ± 5.5 years). Participants underwent four EMS interventions (20 min each) with the following conditions: (1) 4 Hz, (2) 20 Hz, (3) 80 Hz, and (4) control (no intervention). Blood samples were obtained before and immediately after EMS. For the control condition, blood samples were taken before and after 20 min of quiet sitting. BDNF and cathepsin-B levels were analyzed in serum. Compared to preintervention levels, stimulation at 20 Hz resulted in significantly greater postintervention cathepsin-B and BDNF levels (p < 0.01). On the other hand, the control condition did not result in a significant change between pre- and posttreatment. Furthermore, stimulation at 20 Hz caused significantly larger increases in cathepsin-B and BDNF levels than stimulation at 4-80 Hz or the control condition (p < 0.05). In conclusion, stimulation at 20 Hz effectively causes a robust cathepsin-B and BDNF response. Based on these results, we suggest a new strategy for rehabilitation of people with neurological disorders.

Keywords: Brain-derived neurotrophic factor, cathepsin-B; Electrical muscle stimulation; Myokine.

Fig. 1

Position of electrodes and protocol of electrical muscle stimulation In the seated position, the electrodes were positioned at the midpoints of the bilateral femurs and the soles of the feet of the participants (A). The protocol of electrical muscle stimulation (B). The repetition time of pulse series varied between 12.5 ms (80 Hz), 50 ms (20 Hz), and 250 ms (4 Hz)

Fig. 2

Comparison of pre- and postintervention cathepsin-B and BDNF levels between conditions The 20 Hz intervention resulted in significantly higher cathepsin-B (A) and BDNF (B) levels at postintervention than at preintervention. However, the other interventions and the control did not result in significant pre-post differences * p < 0.05, ** p < 0.01

Fig. 3

Comparison of changes in cathepsin-B and BDNF levels among groups The 20 Hz condition resulted in significantly higher changes in cathepsin-B (A) and BDNF (B) levels than the other interventions and the control condition * p < 0.05, ** p < 0.01, *** p < 0.001