Effects of aging on central and peripheral mammalian clocks.
Circadian organization changes with age, but we do not know the extent to which age-related changes are the result of alterations in the central pacemakers, the peripheral oscillators, or the coupling mechanisms that hold the system together. By using transgenic rats with a luciferase (luc) reporter, we assessed the effects of aging on the rhythm of expression of the Period 1 (Per1) gene in the suprachiasmatic nucleus (SCN) and in peripheral tissues. Young (2 months) and aged (24-26 months) Per1-luc transgenic rats, entrained to light-dark cycles, were killed, and tissues were removed and cultured. Per1-luc expression was measured from 10 tissues. In the SCN, the central mammalian pacemaker, Per1-luc expression was robustly rhythmic for more than 7 weeks in culture. The only difference between SCN rhythmicity in young and old rats was a small but significant age-related shortening of the free-running period. Circadian rhythmicity in some peripheral tissues was unaffected by aging, whereas rhythmicity in other tissues was either phase advanced relative to the light cycle or absent. Those tissues that were arrhythmic could be induced to oscillate by application of forskolin, suggesting that they retained the capacity to oscillate but were not being appropriately driven in vivo. Overall, the results provide new insights into the effects of aging on the mammalian circadian system. Aging seems to affect rhythms in some but not in all tissues and may act primarily on interactions among circadian oscillators, perhaps attenuating the ability of the SCN to drive damped oscillators in the periphery.
Yamazaki
Shin
S
National Science Foundation Center for Biological Timing and Department of Biology, University of Virginia, Charlottesville, VA 22904-4328, USA.
Straume
Marty
M
Tei
Hajime
H
Sakaki
Yoshiyuki
Y
Menaker
Michael
M
Block
Gene D
GD
D000375:Aging / Q000378:metabolism*; D000818:Animals; D030801:Animals, Genetically Modified; D001683:Biological Clocks / Q000502:physiology*; D018797:Cell Cycle Proteins; D002490:Central Nervous System / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D003315:Cornea / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism; D056950:Period Circadian Proteins; D010870:Pineal Gland / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism; D051381:Rats; D013493:Suprachiasmatic Nucleus / Q000378:metabolism
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C539024:Per1 protein, rat; D056950:Period Circadian Proteins
Non-programmatic