Fig 1: Evaluation of the activity of complex I of the respiratory chain. Aged human hippocampal neurons were incubated with culture medium only (control cells) or GPE (5, 50 and 500 μM), or choline alphoscerate (500 μM) for 21 days. At the end of the treatments, the mitochondria were isolated by centrifugation, and the activity of complex I of the respiratory chain was evaluated by an in vitro ELISA (MitoTox Complex I OXPHOS activity assay, Abcam ab109903). The data are expressed as a percentage with respect to the control (set at 100%) and represent the mean ± SEM of three separate experiments, executed in triplicate. *p < 0.05, ***p < 0.001 versus aged cells; ## p < 0.01 versus choline alphoscerate