Aging and circadian clock gene expression in peripheral tissues in rats

Aging is associated with alterations of the circadian rhythms (shortened amplitude and phase-advance). We studied by quantitative RT-PCR the influence of aging on the expression of circadian clock genes (Clock, Bmal1, Cryl,2, Per1-3) in peripheral tissues (liver and heart) of middle-aged(13 months) and old (27 months)rats of the Wag/Rij strain exposed to a 12 hours light/12 hours dark cycle. Rats were killed at the light-dark transition (8 am and 8 pm). In the liver, Per Cry et Bmal1 genes showed a morning/evening difference of expression; in addition, old rats exhibited a significant decrease of Per gene expression in the evening vs middle-aged rats. The heart showed similar profiles with only a tendency toward a decrease of Per expression and an increased Bmal1 expression in the evening in old rats. These results show that aging is associated with circadian gene expression changes. (c) 2005 Elsevier SAS. Tons droits reserves.