Editors' ChoiceCARDIAC AGING

Young at Heart

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Science Translational Medicine  22 May 2013:
Vol. 5, Issue 186, pp. 186ec87
DOI: 10.1126/scitranslmed.3006569

You can’t teach an old dog new tricks; but, what if you can teach an old heart to feel young again? As we age, our hearts can grow larger—known as hypertrophy—causing the chambers of the heart to pump blood less efficiently. Being able to stop this aging process would reduce the number of cardiac-related deaths in the elderly. Rather than looking into new drugs to stop this enlargement, in the most recent issue of Cell, Loffredo et al. asked, What keeps the young heart young? By physically joining young and old mice, they identified a protein in the blood of young mice that could reverse such age-related effects on the heart.

In a process called parabiosis, the authors stitched together mice in different pairs: old with old (O/O), young with young (Y/Y), and old with young (O/Y). These pairs ate, slept, and exercised together. More importantly, the mice shared a circulatory system: Cells and proteins in the blood could move freely between the mice. After 4 weeks, Loffredo et al. saw that hearts from old mice exposed to a young circulation (O/Y) were smaller than hearts from old mice paired with another old mouse (O/O) as well as from old, nonparabiotic control animals. Individual heart cells (myocytes) in the old mice from O/Y pairs were as small as those from the paired Y/Y animals. These results suggest that regression of cardiac hypertrophy in old mice was linked to something circulating in the blood of young mice.

After ruling out factors such as blood pressure and behavior, Loffredo et al. discovered in the young mice a blood-borne protein, called growth differentiation factor 11 (GDF11), that reversed age-related cardiac hypertrophy in old mice. Although GDF11 may be the secret ingredient in the fountain of youth, the role of this protein in the aging human heart is yet unknown. Future studies will look at the possibility of translating GDF11 for therapeutic use.

F. S. Loffredo et al., Growth differentiation factor 11 is a circulating factor that reverses age-related cardiac hypertrophy. Cell 153, 828–839 (2013). [Abstract]

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