Double transcranial direct current stimulation of the brain increases cerebral energy levels and systemic glucose tolerance in men

Abstract

Transcranial direct current stimulation (tDCS) is a neuromodulatory method, which has been experimentally tested and is already used as an adjuvant therapeutic option to treat a number of neurological disorders and neuropsychiatric diseases. Beyond its well‐known local effects within the brain, tDCS also transiently promotes systemic glucose uptake and reduces the activity of the neurohormonal stress axes. We aimed to test if the effects of a single tDCS application could be replicated upon double stimulation to persistently improve systemic glucose tolerance and stress axes activity in humans. In a single‐blinded crossover study, we examined 15 healthy male volunteers. Anodal tDCS vs. sham was applied twice in series. Systemic glucose tolerance was investigated by the standard hyperinsulinaemic‐euglycaemic glucose clamp procedure and parameters of neurohormonal stress axes activity were measured. Because tDCS‐induced brain energy consumption has been shown to be part of the mechanism underlying the assumed effects, we monitored the cerebral high‐energy phosphates adenosinetriphosphate (ATP) and phosphocreatine (PCr) by ³¹phosphorus magnetic resonance spectroscopy (³¹P‐MRS). As hypothesized, analyses revealed that double anodal tDCS persistently increases glucose tolerance compared with sham. Moreover, we observed a significant rise in cerebral high‐energy phosphate content upon double tDCS. Accordingly, activity of the neurohormonal stress axes was reduced upon tDCS compared with sham. Our data demonstrate that double tDCS promotes systemic glucose uptake and reduces stress axes activity in healthy humans. These effects raise hope that repetitive tDCS may be a future non‐pharmacological option to combat glucose intolerance in type 2 diabetes patients.

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