Abstract Body (Do not enter title and authors here): Background
Ketone body metabolism, known for its multifaceted effects, is gaining attention as a potential therapeutic target for cardiovascular diseases. However, the impact of ketone bodies on cardiac hypertrophy and Heart Failure with Preserved Ejection Fraction (HFpEF) remains unclear.
Research Questions
To elucidate the effects of ketone bodies on cardiac hypertrophy.
The aim of the present research is to investigate the impact of ketone bodies on cardiac hypertrophy induced by metabolic abnormalities using organ-specific ketone body synthesis-deficient mice.
Methods
Obesity and hypertension were induced by a high-fat diet combined with NG-Nitro-L-arginine methyl ester hydrochloride (L-NAME) (Combined Stress), and the resultant cardiac hypertrophy and ketone body synthesis were evaluated. Subsequently, organ-specific knockout mice of HMG-CoA synthase 2 (Hmgcs2), a rate-limiting enzyme in ketone body synthesis, were subjected to Combined Stress to assess the impact on cardiac hypertrophy. To conduct a metabolism-focused analysis, cell type-specific nuclei were isolated and subjected to RNA sequencing (RNA-seq) and comprehensive metabolomics analysis. To evaluate the direct effects of ketone bodies, H9C2 cells, rat cardiac cells ,were treated with β-hydroxybutyrate, followed by analysis of oxygen consumption and metabolomics.
Results
Combined Stress resulted in increased myocardial cross-sectional area and enhanced ketone body synthesis in the liver and heart. Hepatocyte-specific Hmgcs2 knockout mice (Hmgcs2^ΔHep) subjected to Combined Stress exhibited exacerbated myocardial hypertrophy (cardiomyocyte cell size; Hmgcs2^flox: 322.8 ± 88.3 μm²: Hmgcs2^ΔHep: 444.0 ± 118.5 μm²; p < 0.0001). RNA-seq analysis revealed that the upregulation of glycolytic genes induced by Combined Stress did not occur in Hmgcs2^ΔHep mice, and a metabolic phenotype favoring fatty acid oxidation persisted. In the liver, hepatocyte destruction and increased serum fatty acid levels were observed. Additionally, H9C2 cells treated with β-hydroxybutyrate showed decreased fatty acid utilization and increased glucose utilization.
Conclusion
In cardiac hypertrophy induced by obesity and hypertension, ketone body synthesis mitigates fatty acid overload and promotes glucose utilization, thereby exerting an anti-hypertrophic effect.