Sirtuin 4 accelerates heart failure development by enhancing reactive oxygen species-mediated profibrotic transcriptional signaling

Sirtuin 4 (SIRT4) is a mitochondrially-localized stress-responsive NAD+-dependent deacylase predominantly regulating energy metabolism and ROS homeostasis. While SIRT4 has been implicated in pathological cardiac hypertrophy, underlying mechanisms remain incompletely understood. Here, we show that myocardial expression of SIRT4 was decreased in individuals with severe dilated cardiomyopathy (-73%) but was relatively higher in subjects with concomitant type 2 diabetes (T2D; +56%). To evaluate consequences and mechanisms of altered myocardial SIRT4 expression, mice with global Sirt4 deletion (Sirt4-/-) or cardiomyocyte-specific Sirt4 overexpression (cSirt4-Tg) underwent transverse aortic constriction (TAC) or sham procedures. Cardiac structure and function were similar in Sirt4-/- and WT mice 12 weeks following TAC, whereas cSirt4-Tg mice displayed aggravated cardiac dilation, dysfunction, and fibrosis following TAC. Transcriptional analysis using RNA sequencing revealed synergistic upregulation of collagens and profibrotic regulators in TAC-treated cSirt4-Tg mice, including transforming growth factor beta (TGF), connective tissue growth factor (CTGF), or follistatin-like 1 (Fstl1). These alterations were reversed by mitochondria-targeted antioxidant treatment using MitoQ, along with attenuation of cardiac dysfunction and remodeling, and reversal of tissue fibrosis. SIRT4 overexpression may drive oxidative stress and fibrotic signaling via synergistically increased NOX4 expression (> 7-fold), and/or direct modulation of SIRT4 targets newly identified by protoarray experiments, including calcitonin gene-related peptide (CGRP) receptor component protein (RCP), cyclophilin A, and interleukin-2 receptor β. Thus, SIRT4 overexpression aggravates cardiac remodeling and dysfunction in response to chronic pressure overload by ROS-mediated enhancement of profibrotic transcriptional signaling, suggesting that relatively higher SIRT4 expression may aggravate heart failure development in individuals with concomitant T2D.