Effects of age and dietary restriction on animal model SAMP8 mice with learning and memory impairments

This study was to investigate a hypothesis that dietary restriction (DR) suppresses learning and memory impairments in dementia animal model SAMP8 mice. Four-week-old female SAMP8 mice were fed either ad libitum (AL) or fed restricted (40% of the food consumed by AL). Results showed that acetylcholine (ACh) levels in hippocampus at aged 12 months of age were 12% higher in DR than that of AL group. Dopamine (DA) and norepinephrine (NE) levels in cerebellum at 8 and 12 months of age were significantly higher (26~94% and 34~43%, respectively) in DR group than those in AL group. Serotonin (5-HT) levels in cerebellum at aged 12 months of age were markedly increased (~53%) in DR group. Homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA) levels in cerebellum at 8 and 12 months of age were significantly increased (28~41% and 24~64%, respectively) in DR group compared with AL group. In addition, neurotransmitter-related enzymes, choline acetyltransferase (ChAT) and acetylchoinesterase (AChE) activities at 8 and 12 months of age were elevated (6~8% and 5~7%, respectively) in DR group. Monoamine oxidase-B (MAO-B) that catalyzes oxidative deamination in brain were suppressed by 7~10% in DR group. At aged 12 months of age, the generation of basal and induced reactive oxygen species (ROS) in brain significantly decreased by 20% in DR group compared with AL group. These results suggest that inhibitory effect of oxidative stress by DR may play a pivotal role in attenuating the age-related changes observed in dementia animal model SAMP8.