Body weight at young adulthood and association with epigenetic aging and lifespan in the BXD murine family

DNA methylation (DNAm) is shaped by genetic and environmental factors and modulated by aging. Here, we examine interrelations between epigenetic aging, body weight (BW), and lifespan in 12 inbred mouse strains from the BXD panel that exhibit over two-fold variation in longevity. Genome-wide DNAm was assayed in 70 liver specimens from mice ranging in age from 6 to 25 months that were maintained on normal chow or high fat diet (HFD). We defined subsets of CpG regions associated with age, BW at young adulthood, and strain-by-diet dependent life expectancy. The age associated differentially methylated CpG regions (age-DMRs) featured distinct genomic characteristics, with DNAm gains over time occurring in sites with high CpG density and low average methylation. CpG regions associated with BW were enriched in introns and generally showed lower methylation in mice with higher BW, and inversely correlated with gene expression such that mRNA was higher in mice with higher BW. Lifespan-associated regions featured no distinct genomic characteristics but were linked to genes involved in lifespan regulation, including the telomerase reverse transcriptase gene, Tert, which showed lower methylation and higher gene expression in long-lived strains. An epigenetic clock defined from the age-DMRs conveyed accelerated aging in mice belonging to strains with shorter lifespans. Both higher BW at young adulthood and HFD were associated with accelerated epigenetic aging. Our results highlight the age-accelerating effect of heavier body weight. Furthermore, the study demonstrates that the measure of epigenetic aging derived from age-DMRs can predict strain and diet-induced differences in lifespan.