GCN5L1 impairs diastolic function in mice exposed to a high fat diet by restricting cardiac pyruvate oxidation

Abstract

Left ventricular diastolic dysfunction is a structural and functional condition that precedes the development of heart failure with preserved ejection fraction (HFpEF). The etiology of diastolic dysfunction includes alterations in fuel substrate metabolism that negatively impact cardiac bioenergetics, and may precipitate the eventual transition to heart failure. To date, the molecular mechanisms that regulate early changes in fuel metabolism leading to diastolic dysfunction remain unclear. In this report, we use a diet-induced obesity model in aged mice to show that inhibitory lysine acetylation of the pyruvate dehydrogenase (PDH) complex promotes energetic deficits that may contribute to the development of diastolic dysfunction in mouse hearts. Cardiomyocyte-specific deletion of the mitochondrial lysine acetylation regulatory protein GCN5L1 prevented hyperacetylation of the PDH complex subunit PDHA1, allowing aged obese mice to continue using pyruvate as a bioenergetic substrate in the heart. Our findings suggest that changes in mitochondrial protein lysine acetylation represent a key metabolic component of diastolic dysfunction that precedes the development of heart failure.

Keywords: acetylation; diastolic dysfunction; heart failure; mitochondria; pyruvate dehydrogenase.

FIGURE 1

GCN5L1 inhibits cardiac pyruvate oxidation in obese mice. (a–f) oxygen consumption in cardiac tissues from HFD‐fed WT and KO mice was measured in response to either pyruvate‐malate‐ADP (a–c) or palmitate‐malate‐ADP (d–f) using Oroboros respirometry. N = 6; t‐test; *p < 0.05.

FIGURE 2

GCN5L1 promotes PDHA1 acetylation and inhibits pyruvate dehydrogenase activity. (a, b) PDHA1 phosphorylation (S293) and lysine acetylation in WT and KO mice following LFD or HFD. N = 3–5; two‐way ANOVA; *p < 0.05 relative to WT LFD, ^# p < 0.05 to WT HFD (c) PDH activity in WT and KO mice following LFD or HFD. N = 3–5; two‐way ANOVA; *p < 0.05 relative to WT LFD, ^# p < 0.05 to WT HFD. (d) Linear regression of PDH activity and acetylation levels in WT and KO mice following LFD or HFD.

FIGURE 3

GCN5L1 expression correlates with reduced PDH activity in cardiac cells. (a–f) Total PDH acetylation and enzymatic activity was measured in stable control shRNA or GCN5L1 shRNA knockdown (KD) human cardiac AC16 cells. N = 3; t‐test; *p < 0.05 relative to WT.

FIGURE 4

Acetylation of PDHA1 directly reduces its enzymatic activity. (a) Schematic of human PDHA1 showing published lysine acetylation sites. (b, c) GCN5L1 KD AC16 cells were transfected with Myc‐tagged wildtype PDHA1 (WT‐Myc), a non‐acetylated PDHA1 mimic in which lysines K18/K39/K244/K321/K336 were replaced with arginine (5KR‐Myc), and an acetylated PDHA1 mimic where lysines K18/K39/K244/K321/K336 were replaced with glutamine (5KQ‐Myc). N = 6; one‐way ANOVA; *p < 0.05 relative to WT, ^# p < 0.05 to 5KR.

FIGURE 5

Schematic of proposed PDH regulation by GCN5L1. A combination of nutrient excess and aging leads to increased GCN5L1 expression (Thapa et al., ; Thapa, Manning, Stoner, et al., 2020), which results in significantly increased PDHA1 lysine acetylation. Increased PDHA1 acetylation results in decreased PDH enzymatic activity, which contributes to the diastolic dysfunction observed in obese, aged mice.