Caloric restriction transiently improves motor performance but hastens clinical onset of disease in the Cu/Zn-superoxide dismutase mutant G93A mouse
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Caloric restriction (CR) prolongs lifespan in insects, rodents, and nonhuman primates, a process attributed to a reduction in oxidative stress. Transgenic mice that overexpress the mutant human Cu/Zn-superoxide dismutase (SOD1) gene (G93A mice) are an animal model of amyotrophic lateral sclerosis showing progressively lower motor neuron weakness and increased oxidative stress. We investigated the effect of CR on motor performance, clinical onset, disease progression, and lifespan in G93A mice. Starting at 40 days of age, 14 separately caged G93A mice were randomly divided into two groups: ad libitum (AL; n = 6) and calorie-restricted (CR; n = 8) with a diet equal to 60% of AL. The CR mice (mean +/- SEM: 14.0 +/- 0.7 g) weighed 31% less than the AL mice (20.3 +/- 1.0 g) (P = 0.0002). From 74 to 93 days of age, the CR mice performed better on the rotarod than the AL mice: fall time, P = 0.039; fall speed, P = 0.009. The CR mice had a faster rate of reaching clinical onset than the AL mice (hazard ratio = 4.3, P = 0.0006). The CR and AL mice reached clinical onset of disease at age 99 +/- 1 and 110 +/- 2 days, respectively (P = 0.0003), with no significant difference in disease progression. The CR mice tended to reach endpoint sooner than the AL mice (age-specific death: 125 +/- 3 vs. 133 +/- 3 days, respectively, P = 0.09). We conclude that CR diet transiently improves motor performance but hastens clinical onset of disease in G93A mice. These results suggest that CR diet is not a protective strategy for patients with amyotrophic lateral sclerosis (ALS) and hence is contraindicated.
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