The effects of different types of calorie restrictions on epigenetic modifications of age-related genes in aging mouse brain.

The effects of calorie restriction (CR) on age-related epigenetic modifications have recently been exposed, yet there is a road ahead in explaining the effects of CR on the epigenetic regulations. Although the exact mechanism(s) underlying the beneficial effects of CR on healthy brain aging is still unclear, increasing evidence suggests that epigenetic modifications are promising regulators that may be involved in this phenomenon. Here, we assessed the long-term effects of two different types of CR on DNA methylation levels of nutrient and aging related Igf1r, Adipor1, and Foxo1 genes in aging mice brains. Mice underwent different types of CR-application for up to 72 weeks: Ad-libitum (AL), chronic CR (CCR, 15% CR), and intermittent CR (ICR) alternating one week 60% CR (ICR-R) with three weeks AL feeding (ICR-RF) cyclically. DNA methylation levels were analyzed by pyrosequencing. Expressions of mRNA levels were measured by RT-PCR. Pyrosequencing results revealed that the methylation levels of CpG1 in Igf1r and CpG2-5-68 in Foxo1 were significantly changed by age in different dietary groups. Average DNA methylation levels were similar in calorie-restricted groups for all genes of interest. The gene expression level of only Igf1r was correlated with the average DNA methylation. In addition, there was a significant negative correlation between CpG5 methylation and Igf1r expression. These findings report that CR may exert its preventive effects on the regulation of nutrient sensing and aging related genes, Igf1r, Adipor1, and Foxo1, by modulating the methylation levels of specific CpG sites rather than altering overall methylation levels.