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Rationale: Growth differentiation factor 11 (GDF11) and GDF8 are members of the transforming growth factor-β superfamily sharing 89% protein sequence homology. We have previously shown that circulating GDF11 levels decrease with age in mice. However, a recent study by Egerman et al reported that GDF11/8 levels increase with age in mouse serum. Objective: Here, we clarify the direction of change of circulating GDF11/8 levels with age and investigate the effects of GDF11 administration on the murine heart. Methods and Results: We validated our previous finding that circulating levels of GDF11/8 decline with age in mice, rats, horses, and sheep. Furthermore, we showed by Western analysis that the apparent age-dependent increase in GDF11 levels, as reported by Egerman et al, is attributable to cross-reactivity of the anti-GDF11 antibody with immunoglobulin, which is known to increase with age. GDF11 administration in mice rapidly activated SMAD2 and SMAD3 signaling in myocardium in vivo and decreased cardiac mass in both young (2-month-old) and old (22-month-old) mice in a dose-dependent manner after only 9 days. Conclusions: Our study confirms an age-dependent decline in serum GDF11/8 levels in multiple mammalian species and that exogenous GDF11 rapidly activates SMAD signaling and reduces cardiomyocyte size. Unraveling the molecular basis for the age-dependent decline in GDF11/8 could yield insight into age-dependent cardiac pathologies.

Age-related diastolic dysfunction is a major factor in the epidemic of heart failure. In patients hospitalized with heart failure, HFpEF is now as common as heart failure with reduced ejection fraction. We now have many successful treatments for heart failure with reduced ejection fraction, while specific treatment options for HFpEF patients remain elusive. The lack of treatments for HFpEF reflects our very incomplete understanding of this constellation of diseases. There are many pathophysiological factors in HFpEF, but aging appears to play an important role. Here, we propose that aging of the myocardium is itself a specific pathophysiological process. New insights into the aging heart, including hormonal controls and specific molecular pathways, such as microRNAs, are pointing to myocardial aging as a potentially reversible process. While the overall process of aging remains mysterious, understanding the molecular pathways of myocardial aging has never been more important. Unraveling these pathways could lead to new therapies for the enormous and growing problem of HFpEF. © 2014 American Heart Association, Inc.

Aging is a major factor in many cardiovascular diseases. The molecular factors that regulate age-related changes in cardiac physiology and contribute to the increased cardiovascular risk in the elderly are not fully understood. A study recently published in Nature suggests a specific role for microRNAs (miRNAs) in regulating cardiac aging and function, challenging the concept that aging is an inevitable process in the heart. Aging is an evolutionarily conserved yet poorly understood process that leads to deterioration of many physiological functions during the lifespan of an organism.1 Aging increases the risk of cardiovascular diseases and leads to worse clinical outcomes.2 Elderly patients have an increased risk of acute myocardial infarction (MI) and an increase in both in-hospital and postdischarge mortality.3 The capability of the adult mammalian heart to replenish its cardiomyocyte pool both during physiological aging and in response to injury has now been definitively established.4,5 However, cardiomyocyte refreshment occurs at a low rate (≈1%/y) even in youth and seems to slow with advancing age.4 Recent evidence suggests that some of the aging hallmarks, like age-related cardiac hypertrophy, are regulated by hormones and can be reversed.6 The molecular mechanisms that regulate cardiac aging are complex and not yet completely understood. In the March 31, 2013, issue of Nature , Boon et al7 describe a new molecular pathway that regulates cardiac aging. Using a microarray approach, the authors identified several miRNAs, including miR-34a, that change with age. miR-34a increases with age and acts as a regulator of telomere shortening, DNA damage, and apoptosis in cardiomyocytes, whereas its inhibition improves functional recovery after acute MI (Figure). miRNAs …

SummaryThe most common form of heart failure occurs with normal systolic function and often involves cardiac hypertrophy in the elderly. To clarify the biological mechanisms that drive cardiac hypertrophy in aging, we tested the influence of circulating factors using heterochronic parabiosis, a surgical technique in which joining of animals of different ages leads to a shared circulation. After 4 weeks of exposure to the circulation of young mice, cardiac hypertrophy in old mice dramatically regressed, accompanied by reduced cardiomyocyte size and molecular remodeling. Reversal of age-related hypertrophy was not attributable to hemodynamic or behavioral effects of parabiosis, implicating a blood-borne factor. Using modified aptamer-based proteomics, we identified the TGF-β superfamily member GDF11 as a circulating factor in young mice that declines with age. Treatment of old mice to restore GDF11 to youthful levels recapitulated the effects of parabiosis and reversed age-related hypertrophy, revealing a therapeutic opportunity for cardiac aging.PaperFlick