GDF6 Alleviates Pathological Cardiac Hypertrophy via AMPKα Signaling Pathway

<b>Objective:</b> Cardiac hypertrophy, a key feature and predisposing factor of heart failure, is mainly controlled by complex signaling cascades. Growth differentiation factor 6 (GDF6) plays critical roles in cell growth and cardiovascular homeostasis; however, its role and underlying mechanisms in cardiac hypertrophy remain unclear. <b>Methods:</b> Mice were intravenously injected with adeno-associated virus serotype 9 to overexpress and knock down GDF6 in murine hearts and then exposed to transverse aortic constriction (TAC) surgery to generate pressure overload-induced cardiac hypertrophy. Echocardiographic, histological, and molecular analyses were performed to decipher the alterations to cardiac hypertrophy. In addition, neonatal rat ventricular myocytes (NRVMs) were isolated and stimulated with phenylephrine (PE) to further validate its involvement in hypertrophic growth of cardiomyocytes. <b>Results:</b> GDF6 expression was elevated in murine hearts and NRVMs by ROS production under hypertrophic stimuli. GDF6 knockdown aggravated, while GDF6 overexpression attenuated, pressure overload-induced cardiac hypertrophy, inflammation, and dysfunction in vivo. Meanwhile, we found that GDF6 also prevented PE-induced hypertrophic growth of NRVMs in vitro. Mechanistically, GDF6 activated AMPKα to exert cardioprotective effects, and AMPKα inhibition significantly blocked the anti-hypertrophic effects of GDF6. Further studies showed that GDF6 activated AMPKα through the cAMP/Epac1 pathway, and that Epac1 knockdown abolished the protective effects of GDF6 against TAC- or PE-induced cardiac hypertrophy in vivo and in vitro. <b>Conclusions:</b> In general, our findings, for the first time, define GDF6 as a negative regulator of cardiac hypertrophy and show that supplementation of GDF6 may be of great therapeutic interest for heart failure.