PCSK9 and liver disorder: To exclude the possibility that increased cholesterol uptake in the liver, as expected in Pcsk9-/- mice [32], could lead to a more severe liver disease in Npc1-/-, that would mask a possible neurological benefit, we evaluated Purkinje neuron survival and liver disease in Npc1-/-/Pcsk9-/- and Npc1-/-/Pcsk9ctrl mice.