Magazine article Science News

Muscles Can Remember Past Glory: Nuclei Made in Training Survive Disuse, Making Regrowth Easier

Magazine article Science News

Muscles Can Remember Past Glory: Nuclei Made in Training Survive Disuse, Making Regrowth Easier

Article excerpt

Pumping up is easier for people who have been buffbefore, and now scientists think they know why--muscles retain a memory of their former fitness even as they wither from lack of use.

That memory is stored as DNA-containing nuclei, which proliferate when a muscle is exercised. Contrary to previous thinking, those nuclei aren't lost when muscles atrophy, researchers report online August 16 in the Proceedings of the National Academy of Sciences. The extra nuclei form a type of muscle memory that allows the muscle to bounce back quickly when retrained.

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The findings suggest that exercise early in life could help fend off frailness in the elderly, says study leader Kristian Gundersen, a physiologist at the University of Oslo in Norway.

Because muscle cells are huge, more than one nucleus is needed to supply the DNA templates for making large amounts of the proteins that give the tissue its strength. Previous research has demonstrated that with exercise, muscle cells get even bigger by merging with stem cells called satellite cells, which are nestled between muscle fiber cells. Researchers had previously thought that when muscles atrophy, the extra cell nuclei are killed by a cell death program called apoptosis.

In the new study, Gundersen's team simulated the effect of working out by making a muscle that helps lift the toes work harder in mice. As the muscle worked, the number of nuclei increased, starting on day six. …

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