Phosphorylation of FoxOs at the Akt-sensitive serine/threonine residues is known to cause translocation of FoxOs from the nucleus to the cytosol, resulting in transcriptional inactivation (11, 14-17). We therefore measured the nuclear and cytosolic FoxO1 and FoxO3a in the cerebral cortex after d-fenfluramine treatment. Both immunoblots and immunostained images indicated that d-fenfluramine treatment reduced nuclear FoxO1 and FoxO3a (Figure 1f, 1g), and the effect of d-fenfluramine was statistically significant when compared to saline treatment (Figure 1f). These results suggest that d-fenfluramine can inactivate FoxO1 and FoxO3a in the brain, likely through an increase in the inhibitory phosphorylation.
