Blood from active mice sharpened the memory of lazy ones

Researchers at the University of California, San Francisco let aged mice run on wheels for six weeks, then drew their blood plasma and injected it into sedentary aged mice that had never exercised at all, to see whether the benefit could travel through blood alone.

The sedentary mice that received plasma from runners performed better on memory tasks and grew more new neurons in the hippocampus than mice given plasma from other sedentary mice, and the team traced much of the effect to a single liver-made protein, Gpld1, that rose in the blood after running.

Raising Gpld1 on its own, without any running at all, reproduced much of the cognitive benefit, pointing to the liver, not only the brain or muscle, as a source of exercise's reach into memory. The result came entirely from aged mice and injected plasma, not pills or exercise substitutes for people, and it has opened a search for similar blood factors that might be harnessed more directly.

Borrowed blood, borrowed sharpness.