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In order to determine whether cardiac mTORC1 activation modulated by Sestrin2 is impaired in aging that sensitizes heart to hypertrophy.
C57BL/6J young WT (4-6 months) and aged WT mice (24-26 months), and young Sestrin2 knockout mice (4-6 months) were subjected to transverse aortic constriction (TAC) for pressure overload. The ex vivo working heart perfusion was used for measuring substrate metabolism.
The protein levels of cardiac Sestrin2 were decreased with aging. There are no phenotypic differences in young WT, aged WT and Sesn2 KO mice under normal physiology, while aged WT and Sesn2 KO versus young WT mice exhibit bigger hearts after 4 weeks of TAC surgery. The echocardiography showed an impaired cardiac function of aged WT and Sesn2 KO hearts by pressure overload. The pressure overload-induced phosphorylation of mTOR and mTORC1 downstream effectors 4E-BP1 and p70S6K were augmented in aged WT and Sesn2 KO versusyoung WT hearts. The swollen mitochondria with severely disrupted cristae and higher levels of redox markers pShc66 and 4-hydroxynonenal were observed in aged WT and Sesn2 KO versus young WT hearts by pressure overload. The rate of glucose oxidation and fatty acid oxidation were impaired in the aged WT and Sesn2 KO versus young WT hearts by pressure overload. Intriguingly, pressure overload induced an interaction between Sestrin2 and GATOR2, a complex of unknown function that positively regulates mTORC1. Moreover, the binding affinity between Sestrin2 and GATOR2 is impaired in the aged WT hearts (p<0.05 vs. young WT). Furthermore, Adeno-associated virus 9 (AAV9)-Sestrin2 were delivered into the aged WT and Sesn2 KO hearts viaa coronary delivery approach that rescued the protein levels of Sestrin2, attenuated mTORC1 activation and increased the tolerance of both aged WT and Sesn2 KO hearts to pressure overload.
Cardiac Sestrin2 is a sensor for mTORC1 pathway in response to pressure overload. Sestrin2 deficiency in aging could be a reason for an increased sensitivity to hypertrophy in the elderly.