Caloric restriction (CR) is the best known approach to extend organism’s lifespan. It works remarkably well in various living beings, from yeast to mice. It is likely also to work in primates and humans. If an animal lives under CR, essentially semi-starving, one may think that it will try to preserve its energy by reducing physical activity. Apparently, this is not the case. For example, mice in reality move more and demonstrate increased foraging activity while on a restricted diet. This does make sense as far as individual’s survival is concerned. In the wild, mice confronted with food shortage are more likely to find more food when they try to search for it than if they simply sit there hoping for a piece of cheese to appear out of thin air.

I have recently written about Sir2, a gene critical for longevity in different organisms. Sir2 is multi-facet gene and may have opposite roles as far as longevity is concerned in different cell types. In the paper published this week in Science the authors add another evidence for Sir2 role in CR induced longevity in mammals. Sir2 homologue from mice, Sirt1, turns out to be needed for the increased activity induced by calorie restrictions in mice. The mice lacking Sirt1 demonstrate various biochemical changes triggered by CR (for example, reduction

Ok, calorie restricted mice demonstrate enhanced physical activity. But what about their sex lives? Are they as sexually active as their relatives who enjoy fuller plates? Could CR mice be in fact more sexually active just as they are more physically active? My guess is that most likely CR mice are less sexually active than their well-fed brothers and sisters. The reason for this is that while the mouse may not able to compromise its foraging activity when threatened with looming starvation, it can more easily forgo sexual activities to preserve the limited energy that is critically needed to hunt for food.

Reference:
Science 9 December 2005:
Vol. 310. no. 5754, p. 1641
DOI: 10.1126/science.1118357
Increase in Activity During Calorie Restriction Requires Sirt1
Danica Chen, Andrew D. Steele, Susan Lindquist, Leonard Guarente

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