Caloric restriction recovered cerebellar motor and cognitive abilities in aged rats

Abstract

The beneficial effects of CR would work through epigenetic processes, but this is largely unexplored. Here, we examine the hypothesis that CR recovers learning and motor coordination associated to changes in Bdnf and TrkB DNA methylation, in old rats. For that, male Holtzman rats -young (3-mo-old, n=8), old (22-mo-old, n=9), both fed ad-libitum, and 18-mo-old rats fed a 40% calorie restricted diet for 3 months (n=4)- were kept under 12h-light: 12h-dark, 22-24 °C and water ad-libitum. Performing the Single Reaching Pellet test, we observed that the percentage of the total success rate and the quality of the first attempt during performance are significantly lower in the old compared to the young and old rats with CR (p <0.05). As a control the olfactory sense and mood of the animals, the Buried Food Pellet and Corner Test were performed respectively. Samples (n=6) of cerebellar DNA from the three groups, were examined by bisulfite sequencing at CpG sites in regulatory regions in exons 3 and 9 of Bdnf and exon 1 of TrkB genes, to measure methylation with base-specificity. We observed 89 to 100% methylation at the CpG site in exon 9 of Bdnf gene, with no significant differences between groups. Methylations were not detected at the CpG sites in exon 3 of Bdnf nor exon 1 of TrkB gene, in any of the experimental groups. Our results show there is no association between cognitive CR benefits and CpG methylation of cerebellar Bdnf and TrkB genes in the studied exons.