GDF11 has anti-ageing effects in flies as well. Flies that express more of the fly version of GDF11, called myoglianin, live longer than normal flies. They also keep their muscle strength for longer. Flies, like humans, lose muscle strength as they age. This shows up in old flies as an inability to climb. Old flies that over-expressed myoglianin could still climb. In the opposite experiment, flies with less myoglianin had shorter lifespans and lost their ability to climb at a younger age.
The amazing thing is that these flies were genetically engineered to have more or less myoglianin only in their muscles. More myoglianin in muscles only had anti-ageing effects on their whole body. This result helps answer the questions: What is role of muscles in causing ageing? How can one organ affect how other organs age? What is the crosstalk between organs as we age?
It turns out that myoglianin acts like a hormone. It is secreted from muscle cells and can travel to other organs. Myoglianin can control a specialised part of the nucleus called the nucleolus in fat cells (adipocytes). Flies with more myoglianin have smaller nucleoli in their fat cells, and flies with less myoglianin have larger fat cell nucleoli. Nucleoli make ribosomes which are the cell’s protein factories. Other anti-ageing genes like AMPK also partially inhibit the nucleolus. The flies that over-expressed myoglianin had less active ribosomes in their entire body. This shows a specific mechanism by which ageing muscles can affect the whole body.
The concept of myokines might also explain in some part how exercise can help delay the effects of ageing (more on that in a future post).
The Scientific Paper (free open access – woohoo):
Demontis et al. Intertissue Control of the Nucleolus via a Myokine-Dependent Longevity Pathway. Cell Rep. 2014.