Effect Of 30 Or 11.5 Volts Of Pulse Stimulation On Mitochondrial Density In Vitro

Abstract

We have previously shown an increase in mitochondrial density using an exercise mimetic electrical pulse stimulation (EPS) (30V; single bipolar pulses of 2ms and 1Hz continuously) applied to an in vitro human primary cell culture model. PURPOSE: To determine if continuous EPS of 11.5V, 2ms single bipolar pulses at 1Hz is a valid in vitro exercise mimetic to effectively increase mitochondrial density and insulin action of human primary myotubes. METHODS: Primary cultures were established from myoblast extracted from 5 healthy lean Caucasian male donors (23 ± 1.9 y; BMI 24.2 ± 0.6 kg/m2). Myoblasts were pooled, grown and differentiated into myotubes. EPS was applied to fully differentiated myotubes at either 11.5V or 30V, using single bipolar pulses of 2ms and 1Hz continuously for 24 hours. Control groups were maintained without stimulation. Protein was extracted from EPS stimulated and unstimulated (control) myotubes for western immunobloting of mitochondrial density measured by total OXPHOS, and insulin action measured by Akt phosphorylation. RESULTS: 24 hours of EPS at 30V resulted in ~1.7 fold greater OXPHOS content compared to the unstimulated control, while 11.5V resulted in 0.82 fold lesser OXPHOS content compared to control. After 24 hours of EPS, there was a 0.9 fold and 0.5 fold difference in the Akt phosphorylation using 30V and 11.5V respectively, compared to corresponding unstimulated control cells. CONCLUSION: 30V of EPS resulted in a greater mitochondrial density, an evident adaptation to regular physical activity, and greater Akt phosphorylation compared to 11.5V stimulation, suggesting electrical pulse stimulation of continuous single bipolar pulses of 2ms at 30V and 1Hz, is a more effective exercise mimetic model for in vitro human myotubes than 11.5V.