Effect of electrical stimulation on lipolysis of human white adipocytes

The goal of the present study was to investigate the effect of 30 min of electrical stimulation on the activation of lipolysis in human white adipocytes. Two stimulation protocols (S1, S2) were conducted in vitro on isolated human white adipocytes. Subcutaneous adipose tissue was obtained from female subjects undergoing abdominal adipose tissue reduction. Adipose tissue of 10 female subjects (mean age, 38.7 ± 9.1 years) and 6 female subjects (mean age, 37.2 ± 11.3 years) was obtained for S1 and S2, respectively. All subjects fasted overnight before tissue removal. The control conditions were a basal and a β-adrenergic stimulation (isoproterenol (ISO), 10(-6) mol·L(-1)) of lipolysis. For S1, the 3 electrostimulation conditions consisted of a monopolar square-wave pulse current for 30 min at intensities of 4, 8, and 20 mA, respectively. In S2, the 2 electrostimulation conditions consisted of a bipolar square-wave alternating current for 30 min at intensities of 4 and 6 mA, respectively. Fat cell lipolysis was measured by quantifying the release of glycerol from adipocytes for 3 trials in each experimental condition. For S1, 4 mA significantly increased lipolysis 1.5 times over basal values (p ≤ 0.01), 8 mA and 20 mA did not increase lipolysis significantly, and no significant difference (p > 0.05) was found between ISO and 4 mA. For S2, 4 mA (p ≤ 0.05) and 6 mA (p ≤ 0.01) significantly increased lipolysis by 1.8 and 2.3 times above basal, respectively. Our results demonstrate that both monopolar (4 mA) and bipolar (4 and 6 mA) electrical stimulations significantly activated in vitro lipolysis. Our findings suggest the existence of a new lipolytic pathway that may involve K(v) channels shown to exist in human white adipocytes.