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VOLUNTARY EXERCISE ENHANCES CIRCADAIN RHYTHMS AND CLOCK GENE EXPRESSION IN MICE

Abstract

Circadian rhythms are endogenous 24-hour cycles, regulated by clock genes throughout the body and synchronized by the suprachiasmatic nucleus (SCN). Disruptions to this rhythm have been shown to increase the risk of chronic diseases, making it essential to understand ways to reset or maintain a consistent circadian rhythm. Various periodic cues such as light stimuli have been shown to reset/entrain this rhythm, but less is known about the effects of exercise on the circadian clock. PURPOSE: To investigate the effect of voluntary wheel-running exercise on circadian rhythm, METHODS: this study used young adult male mice (4 months old; n=4) and aged male mice (18 months old; n=3). Over nine days, the activity of each mouse on its running wheel was monitored, and their circadian rhythms were subsequently analyzed and charted using ClockLab software. RESULTS: As expected, the young adult mice expressed stronger, more consolidated rhythms (amplitude =7800) as compared to aged males ( amplitude = 4000) when using the average periodogram amplitude as a metric of internal circadian strength. The younger mice also ran more, averaging ~4.2 km/day, while the older mice ran ~1 km/day. Brain samples were taken from each mouse, and immunohistochemistry was used to view clock gene expression in the SCN. The markers specifically analyzed for clock gene expression were arginine, cFOS, vasopressin and neuro-peptide Y. CONCLUSION: Results showed that clock gene expression in the SCN increased, suggesting that voluntary exercise enhances circadian rhythms in mice. Future studies will focus on the underlying mechanisms by which exercise affects circadian rhythm. Financial Support: 2P20GM121310-06 COBRE SENSORY BIOLOGY

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