Effect of cholesterol feeding or functional deletion of cholesterol trafficking-related genes on lifespan and cholesterol metabolism in the npc1^−/− mouse. A, Survival rates of npc1^−/− mice fed the 1% cholesterol diet (n = 76) from weaning compared with npc1^−/− animals fed the 0.02% low-cholesterol diet (n = 72; p > 0.05). B, Survival rates of npc1^−/−/ldlr^−/− mice (n = 111) compared with npc1^−/− animals (n = 57) when both groups were fed the low-cholesterol diet (p > 0.05). C, Survival rates of npc1^−/−/abca1^−/−mice (n = 24) compared with npc1^−/− animals (n = 32) when both groups were fed the low-cholesterol diet (p > 0.05). D, Survival rates of npc1^−/−/lxrβ ^−/− mice (n = 16) compared with npc1^−/− animals (n = 16) when both groups were fed the low-cholesterol diet (p < 0.01). E, Cholesterol concentration (mg/g wet weight) in tissues of five groups of mice 7–8 weeks of age and maintained on the low-cholesterol diet except for group 3, which was fed the 1% cholesterol diet from weaning (n = 6–24). Different letters indicate results that were significantly different at p < 0.05. F, Cholesterol synthesis (nmol of ³H₂O incorporated per hour per gram wet weight) in tissues of the animals described above in E (n = 6–18). Different letters indicate results that were significantly different at p < 0.05.