Date of Award

2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Regulatory Biology

Department

Biological, Geological and Environmental Sciences

First Advisor

Kondratov, Roman

Subject Headings

Biology, Molecular Biology

Abstract

Calorie Restriction (CR) is a powerful paradigm known to delay aging and thus increase longevity in several organisms, from yeast to non-human primates. Many molecular pathways have been proposed to mediate the beneficial effects of CR, however, the mechanism is still unknown. Circadian clock which is an internal time keeping system is regulated by feeding. Thus our aim was to study the effect of CR on the circadian clock. Here we show that CR significantly affects the expression of circadian clock genes in mice at the mRNA and protein levels, suggesting that CR reprograms the clocks at the transcriptional and post-transcriptional level. CR also affected the circadian output through up- or down-regulation of the expression of several clock-controlled transcriptional factors and the longevity candidate genes. CR-dependent effects on some clock gene expression were impaired in the liver of mice deficient for BMAL1, suggesting importance of this transcriptional factor for the transcriptional reprogramming of the clock, however, BMAL1-independent mechanisms exist too. We have shown that Bmal1 deficient mice develop premature aging phenotype and have a shortened lifespan. We decided to apply 30%CR to these mice and found that CR did not increase the lifespan of these Bmal1 mutants, further suggesting that BMAL1 is necessary for full benefits of CR. We also analyzed the plasma levels of IGF-1 and insulin, which were found to be impaired in Bmal1 deficient mice on 30%CR. We propose that CR recruits biological clocks as a natural mechanism of metabolic optimization and synchronization of the several downstream pathways under limited nutrient conditions.

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