“I did the experiment again and again to make sure that it was right. But it became clear that some circulating factor in the blood is able to change the level of Tet2 in the brain.”
Tet2 – or ten eleven translocation methylcytosine dioxygenase 2 – is known to play a role in epigenetically regulating activity in a number of genes. As we age, mutations in the gene for this enzyme accumulate, leading to an increased risk of cancer, stroke, and cardiovascular disease.
https://www.sciencealert.com/mice-hippocampus-enzyme-discovery-anti-aging-therapy