To determine whether HD-induced mitochondrial apoptosis via the PI3K/Akt/Bad signaling pathway, effects of IGF-1 (a PI3K-specific agonist) on the expression levels of Akt, p-Akt, Bad and p-Bad proteins were tested in VSC4.1 cells exposed to HD (Figure 4A,B). Here, IGF1 is linked to Huntington disease.