Goal: To identify small molecules with anti-aging effects, that will be used as a prototypic medicine for treatment of age-associated metabolic disorders to increase health- and, ultimately, lifespan.
Calorie restriction – the reduction in calorie intake without malnutrition - is a dietary paradigm known to increase health- and lifespan. In humans, calorie restriction has a strong beneficial effect on metabolism and cardiovascular physiology. Therefore, there is a great interest in finding “calorie restriction mimetics” – medicine-like compounds that could produce effects similar to the beneficial effects of calorie restriction; however, effective mimetics of calorie restriction have not been created yet. We developed an approach to override a key set of major limitations of previous studies. Our laboratory pioneered the circadian clocks- and rhythms-based approach to study aging and mechanisms of calorie restriction. The circadian clock is an internal time-keeping system that generates 24-hour rhythms in behavior and physiology. In the human body literally all physiological systems are under control of the circadian clock. In order to develop potential anti-aging medicine, we decided to combine the advantages of dietary, circadian and microRNA approaches by comparing the changes in the circadian rhythms of micoRNA expression. MicroRNAs are small regulatory RNAs that regulate the expression of target genes through sequence-specific interaction with mRNAs of target genes. MicroRNAs are almost ready-to-use therapeutic agents. Indeed, microRNAs are relatively small, they can be synthesized and purified in large amounts in vitro; finally, methods of microRNAs delivery into the organism have been developed and are continuously improved. Many microRNA demonstrate pronounced rhythmic changes in their expression across the day; thus, measuring microRNA at one randomly selected time point of the day inevitably produces misleading results. The circadian approach allows to override this problem. We used microarrays to analyze the expression of about 1000 microRNAs in the liver of calorie-restricted and control mice at six different time points of the day. Interestingly, although many microRNAs demonstrated some changes in the expression upon calorie restriction, for the majority of them the difference was detected only at a single time point. Only for a few microRNAs the expression was affected by calorie restriction at many time points across the day, which suggests that these microRNAs are main candidates to be the mediators of the effects of calorie restriction. We analyzed the expression of several downstream targets of the selected microRNAs and found changes in the expression of these targets that correlated with changes in microRNA expression, which confirms that changes in microRNA expression induced by calorie restriction are biologically significant.
Thus, by combining calorie restriction and circadian approaches, we have overridden the previous limitations and identified several microRNAs that are candidate calorie restriction mimetics. Essentially, the selected microRNAs are conserved between mice and humans, therefore, if they work in mice, there is a high chance that they will also work in humans.
We plan to test physiological activity of the selected microRNAs in an animal model.
Step I. To assay short-term effects (2 months) of calorie restriction mimetics on metabolism in order to identify primary candidates for the long-term study. Estimated duration of the step I is 1.5 – 2 years.
Step II: To investigate the kinetics of action of microRNA mimetics in order to determine the frequency/dosage of administration of microRNA mimetics to achieve desirable therapeutic effects. Estimated duration of step II is 6-8 months.
Step III: Long-term anti-aging effects of microRNA administration and the effect on longevity.
Estimated duration of step III is 2-3 years.