SIRT4 and familial dilated cardiomyopathy: There was a significant decrease in the mRNA and protein levels of SIRT2, but not SIRT4, in the cardiac tissues of the STZ/HFD-fed mice compared with those of the NCD control mice (Fig. 1L, M and Supplementary Fig. 2), so we focused on investigating the potential role of SIRT2 in the regulation of DCM.