Western diet triggers cardiac dysfunction in heterozygous Mybpc3-targeted knock-in mice: A two-hit model of hypertrophic cardiomyopathy

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Phenotypic expression of hypertrophic cardiomyopathy (HCM) and disease course are associated with unfavorable metabolic health. We investigated if Western diet (WD) feeding is sufficient to trigger cardiac hypertrophy and dysfunction in heterozygous (HET) Mybpc3 c.772G>A knock-in mice. Wild-type (WT) and HET mice (3-months-old) were fed a WD or normal chow (NC) for 8weeks. Metabolomic analyses on serum revealed systemic metabolic derailment in WD-fed WT and HET mice. Strikingly, only WD-fed HET mice developed cardiac hypertrophy and dysfunction, which was not driven by aggravated cardiac myosin binding protein-C haploinsufficiency. WD reduced oxidative phosphorylation and increased toxic lipids in the heart irrespective of genotype. Cardiac proteomic analyses revealed higher abundance of proteins involved in fatty acid oxidation in WD-fed mice, however this increase was blunted in HET compared to WT mice. Accordingly, cardiac metabolomic and lipidomic analyses showed accumulation of acylcarnitines in WD-fed HET vs WT mice. WD feeding triggered cardiac dysfunction and hypertrophy in otherwise phenotype-negative HET Mybpc3 c.772G>A mice. We propose that the presence of a HCM mutation predisposes the heart to metabolic inflexibility when subjected to systemic metabolic stress. Our study represents a novel approach to study the interplay between unfavorable metabolic health and mutation-induced defects in HCM disease development.