AAV9-cTNT-Null

Heart failure due to sustained pressure overload is a major public health problem. PKM (Pyruvate Kinase M) is the rate-limiting enzyme of glycolysis. The alternative splicing product of PKM, PKM2 (pyruvate kinase M2), plays complex roles in a variety of biological processes and diseases. Here, cardiomyocyte‐specific Pkm2 knockout mice were generated by crossing the floxed Pkm2 mice with α‐MHC (myosin heavy chain)‐Cre transgenic mice, and cardiac specific Pkm2 overexpression mice were established by injecting adeno‐associated virus serotype 9 system. The results showed that cardiomyocyte-specific deletion of Pkm2 led to significant deterioration of cardiac function under pressure overload, while overexpression of Pkm2 alleviated cardiac hypertrophy caused by aortic coarctation and improved cardiac function. Mechanistically, these studies demonstrate that PKM2 is a protein kinase, rather than pyruvate kinase, which inhibited the activation of RAC1 (rho family, small GTP binding protein)‐MAPK (mitogen‐activated protein kinase) signaling pathway by phosphorylating RAC1 in the progress of heart failure. Furthermore, blocking RAC1 by NSC23766, a specific RAC1 inhibitor, attenuated pathological cardiac remodeling in Pkm2-deficient mice treated with transverse aortic coarctation.

One week after TAC surgery, 1×10¹¹ virus particles/mouse AAV9-cTnT-null or AAV9-cTnT-mPkm2 virus was injected through the tail vein. At the same time, cardiac function was monitored by echocardiography once a week during the 8-week experimental period (Figure 1A). Echocardiography examination showed that the cardiac systolic function of mice injected with AAV9-cTnT-mPkm2 after TAC surgery was improved, and the heart rate was not affected (Figure 1B through 1D). Compared with sham surgery, the hearts of TAC mice were significantly enlarged and the degree of fibrosis was more severe, and the degree of fibrosis was reduced after injection of AAV9-cTnT-mPkm2 (Figure 1B, 1E, and 1F). At the same time, there was no significant difference in the heart weight/body weight ratio between sham-operated and Pkm2-overexpressing TAC-operated mice (Figure 1G). Furthermore, β‐MHC expression was significantly reduced in Pkm2 overexpressing hearts compared with TAC mice treated with AAV9‐cTnT‐null (Figure 1H). In contrast to Pkm2 knockout, Pkm2 overexpression inhibited the hyperactivation of MAPK signaling pathway in TAC mouse hearts (Figure 1H). Taken together, these findings suggest that maintaining higher PKM2 expression may protect the heart from pressure overload-induced hypertrophy and HF.

Figure 1. Cardiomyocyte‐specific overexpression of PKM2 (pyruvate kinase M2) ameliorated pressure overload‐induced heart failure. (Ni L, et al., 2022)