Murine microRNAs implicated in liver functions and aging process.

Small non-coding microRNAs (miRNAs) are involved in gene regulation in various cellular and developmental processes, including mechanisms of aging. Here, the mouse liver was used as a paradigm for the study of miRNAs implicated in the aging process in mammals. Expression profiling of 367 murine miRNAs (Sanger Version 8.2) was assessed in livers from 4 to 33 months old mice, and their predicted targets were compared with proteomic profiling data generated from the same animals. Gradual increases in the levels of miR-669c and miR-709 were observed from mid-age of 18-33 months, while miR-93 and miR-214 were significantly up-regulated only in extremely old liver. In contrast, we did not identify any miRNAs showing significant down-regulation with age. Interestingly, the up-regulated miRNAs' targets are associated with detoxification activity and regeneration capacity functions known to decline in old liver. In particular, three up-regulated miRNAs may contribute to the aging-related decline in oxidative defense by targeting various classes of glutathione S-transferases. Other proteins in decline in old liver and targeted by the up-regulated miRNAs are involved in mitochondrial functions or maintenance. Taken together, we identified the up-regulation of key miRNAs that may participate in the decline of regeneration and oxidative defense mechanisms in aging liver.