Nuclear AGO2 exacerbates heart failure with preserved ejection fraction through myocardial ketogenesis

BACKGROUND AND AIMS: With the prevalence of Western-style high-fat diet (HFD), the incidence of heart failure with preserved ejection fraction (HFpEF) is gradually increasing. Recent studies suggested that microRNAs (miRNAs) located in different subcellular organelles could regulate lipid metabolism and cardiac function. However, the functional property of subcellular argonaute 2 (AGO2), the core member of miRNA machinery, remained elusive in HFD-related HFpEF. METHODS: The causal role of nuclear AGO2 in inducing cardiac dysfunction was revealed with a recombinant adeno-associated virus (serotype 9) vector. The underlying mechanisms were explored with echocardiography, catheter manometer system, proteomics analyses, chromatin immunoprecipitation assays, luciferase assays, Western blotting, immunofluorescence, seahorse assays, β-hydroxybutyrate (β-OHB), and ATP measurements. RESULTS: Knockdown of AGO2 attenuated HFD-induced cardiac dysfunction. Mechanistically, AGO2 could activate the transcription of HMGCS2. Knockdown of either cardiac AGO2 or HMGCS2 protected against HFD-induced cardiac dysfunction. Subsequent high-through profiling further identified ATP5MG and UQCR10 as the key downstream targets for AGO2/HMGCS2 mediated β-OHB over-production, and a feed forward loop involving lipo-toxicity and ketone-toxicity was discovered. Furthermore, a PKCα-ERK-EGR1-AGO2-HMGCS2 axis in the initiation of fatty acid-induced cardiomyocyte dysfunction was revealed. Importantly, overexpressing of nuclear AGO2 rather than cytosolic AGO2 exacerbated the HFD-induced cardiac dysfunction in mice. CONCLUSIONS: These findings uncover that long-term Western-style HFD treatment captures some critical characteristics of HFpEF, characterized by diastolic dysfunction with left ventricular ejection fraction >50%. AGO2/HMGCS2 pathway links lipo-toxicity to ketone-toxicity in the heart, which provides new mechanistic insights and suggests a potential strategy to develop treatments against metabolism disorder-related HFpEF.