Age-dependent tissue expression patterns of Sirt1 in senescence-accelerated mice

Sirtuin 1 (Sirt1) has a range of molecular functions and has emerged as an important protein in aging and metabolic regulations. Studies have reported a correlation between disturbance of Sirt1 activity and the onset of aging- or obesity-associated diseases, including diabetes, cardiovascular disease and neurodegenerative disorders. However, a systematic investigation to examine the changes of Sirt1 expression in a wide range of ages and to what degree it changes has yet to be performed. To assess the effects of aging on the changes of Sirt1 expression, an in vivo model of aging, senescence-accelerated mouse prone 8 (SAM-P8) and a control counterpart strain, senescence-accelerated mouse resistant 1 (SAM-R1) was used. The mRNA and protein expression levels of Sirt1 were detected in four different tissues, including brain, liver, skeletal muscle and white adipose tissue, in both strains at different ages (1-, 4-, 8- and 12-month old). Therefore, different life stages, including young age prior to maturation, adult, middle age and old age were examined. The results identified that Sirt1 expression declined with age at the transcriptional and translational levels in the brain, liver, skeletal muscle and white adipose tissue in SAM-P8 and SAM-R1. The Sirt1 expression level was lower in SAM-P8 than in SAM-R1, particularly at old age. Among the four tissues, it was most significantly reduced in the brain.