Fig. 1. Treatment of YAC128 mice with ethyl-EPA results in a mild improvement in motor function but is unable to prevent neuropathology. YAC128 and WT mice were treated with 1% ethyl-EPA in chow from 7 to 12 months of age. (A) Longitudinal analysis of open-field activity reveals significant hypoactivity in YAC128 mice compared to WT mice which is reduced by treatment with EPA. *Significant difference between untreated YAC128 and WT mice. ^#Significant difference between untreated and EPA-treated YAC128 mice. (B) At 12 months of age, EPA-treated YAC128 mice are significantly more active than untreated YAC128 mice and not significantly different from WT mice. (C) Longitudinal analysis of performance on the accelerating rotarod reveals that YAC128 mice show significant impairment compared to WT mice beginning prior to 7 months of age. While the performance of EPA-treated and untreated YAC128 mice is equal from 7 to 10 months of age, EPA-treated YAC128 mice perform better at 11 and 12 months. *Significant difference between untreated YAC128 and WT mice. ^#Significant difference between untreated and EPA-treated YAC128 mice. (D) At 12 months of age, the difference in rotarod performance between EPA-treated YAC128 mice and untreated YAC128 mice is significant. (E) To demonstrate delivery of EPA to the treated animals, red blood cell membranes were isolated and the percentage of EPA in blood was determined. In both WT and YAC128 mice, oral administration of ethyl-EPA in food resulted in increased levels of EPA in RBC membranes indicating that the treatment was successfully delivered. (F) Analysis of striatal volume revealed that YAC128 mice show a significant decrease in striatal volume at 12 months which was not improved by treatment with ethyl-EPA. N = 5 WT, 4 WT-EPA treated, 7 YAC128, 8 YAC128-EPA treated. Error bars show SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ^#P < 0.05, ^##P < 0.01.

Fig. 2. YAC128 mice show down-regulation of striatal DARPP-32 expression that is not affected by treatment with ethyl-EPA. (A–D) Photographs of representative DARPP-32-stained sections from WT (A, C) and YAC128 (B, D) mice show a clear reduction in DARPP-32 immunoreactivity in the YAC128 mice compared to WT mice. Photographs A and B were taken using the 2.5× objective (scale bar indicates 500 μm). Photographs C and D were taken using the 100× objective (scale bar indicates 20 μm). (E) Quantification of the average staining intensity in the striatum of 12-month-old mice confirms the decreased expression of DARPP-32 in YAC128 mice compared to WT mice. N = 10 WT, 10 YAC128. (F) Similarly, measurement of DARPP-32 levels by ELISA reveals a significant decrease in DARPP-32 expression in 12-month-old YAC128 mice compared to WT mice. (G) Assessment of striatal DARPP-32 expression in the ethyl-EPA therapeutic trial confirms that DARPP-32 is down-regulated in YAC128 mice compared to WT mice and shows that treatment with ethyl-EPA is unable to improve the level of DARPP-32 expression in YAC128 mice. N = 5 WT, 4 WT-EPA treated, 7 YAC128, 8 YAC128-EPA treated. Error bars show SEM. **P < 0.01, ***P < 0.001.