Enlargement of the heart—cardiac hypertrophy—occurs with aging and is thought to contribute to diastolic heart failure, a common form of heart failure in the elderly. Richard Lee and his colleagues now identify the cytokine GDF11 as a circulating anti-hypertrophic factor in mice whose levels decrease with age (Cell 153, 828–839).

In parabiosis experiments, in which the blood circulations of an old mouse and a young mouse are connected, the researchers found that cardiac hypertrophy in the old mouse was reversed after 4 weeks. The authors found a number of proteins whose abundance differed between blood plasma from young versus old mice. One of these was GDF11, which showed widespread tissue expression, with the highest levels in the spleen, and whose levels in both blood and spleen were higher in young mice as compared to old mice The researchers carried out functional studies to show that GDF11 inhibits cardiac hypertrophy of cultured cardiomyocytes and reverses cardiac hypertrophy in old mice. Raising the levels of GDF11 in the blood might therefore be beneficial for the aged heart.