(A) Effects of UDCA on weight of Npc1 mice. Body weight over time shown as mean ± SD, n = 8–19 for all time points except for Npc1-/- mice on UDCA at 13 weeks where n = 4 and 14 weeks where n = 1, # denotes comparison between Npc1+/+ mice untreated and Npc1+/+ mice on UDCA, * denotes comparison between Npc1-/- mice untreated and Npc1-/- mice on UDCA, # or * p—value < 0.05, ## or ** p—value < 0.01, calculated using two-way ANOVA with Bonferroni’s multiple comparison test. (B) Effects of UDCA on motor function in Npc1-/- mice. Total rearing events counted for a period of 5 minutes in Npc1+/+ and Npc1-/- mice plus or minus UDCA treatment. Data are presented as mean ± SD, n = 8–19. * p—value < 0.05, ** p—value <0.01, *** p—value <0.001, calculated using an unpaired nonparametric test Mann-Whitney test. (C-F) Effects of UDCA on tremor in Npc1-/- mice. Tremor was monitored between 0 and 63 Hz in panels (C) and (D), and quantified at 43 Hz in (E) early symptomatic (9 weeks), (F) late symptomatic (11 weeks) time points. 43 Hz is an arbitrary point selected in the high frequency tremor range to allow a simple comparison to be made between treatment groups. The low frequency tremor range overlaps at the low end with grooming activity frequencies and so was not analysed to avoid this as a potential confounder. In both early symptomatic and late symptomatic groups, mice treated with 0.5% UDCA had significantly less tremor than untreated Npc1-/-. Data are presented as mean ± SD, n = 7–19 animals/group, * p—value < 0.05, ** p—value < 0.01, *** p—value < 0.001, **** p—value < 0.0001 calculated using one-way Anova with Bonferroni's multiple comparison test.