Abstract Body (Do not enter title and authors here): Background: Skeletal muscle (SKM) dysfunction is a critical determinant of exercise intolerance and frailty in heart failure with preserved ejection fraction (HFpEF). Perturbed SKM metabolism and mitochondrial dysfunction are considered to be major components of SKM dysfunction, but the mechanisms and pathways are understudied and poorly defined. Molecular elucidation of dysregulated metabolism in SKM in HFpEF is essential to determine viable targets for the treatment of exercise intolerance in HFpEF.
Methods: 26-week-old Male ZSF1 Obese rats (HFpEF) and WKY lean normotensive controls. Gastrocnemius was subjected to bulk RNA-seq, proteomics, and metabolomics analysis. Limma was used to determine significant differential expression of genes and proteins, with an adjusted p-value (FDR) of <0.1. Pathway enrichment analysis was performed on transcriptomics and proteomics datasets via the fGSEA package in R. Differentially expressed metabolites were also identified via limma with a cutoff of nominal p-value <0.01 for statistical significance, and metabolites of interest were mapped onto KEGG pathways.
Results: Pathway level analysis of the Wikipathways database for transcriptomics and proteomics revealed significant downregulation of oxidative phosphorylation (NES -2.1, p<0.005), ETC (NES -2.0 p<0.005), and TCA cycle (-1.8, p<0.05) in HFpEF. The most upregulated pathways were PPAR signaling (NES 2.2, p<0.001), tryptophan metabolism (NES 1.8, P<0.005), and amino acid oxidation (NES 1.8, p<0.005) pathways. Metabolomics revealed an accumulation of TCA cycle intermediates (isocitrate, 2.4 FC), and phosphate reduction (0.9 FC). Branched-chain amino acids were significantly increased in HFpEF whereas amino acids related to tryptophan metabolism (kynurenine, 0.3 FC) were reduced and shifted towards increased serotonin (1.8 FC) accumulation. Phospholipid species were differentially regulated with increased palmitoylated phosphatidylcholines (~1.6 FC) but reduced arachidonoyl-PC species (~0.7). Phosphatidylethanolamines (PE) species (16:0/16:1-18:0/18:2) were increased (2.2 FC) in HFpEF.
Conclusion: Our multi-omics analysis of skeletal muscle in HFpEF revealed severe mitochondrial dysfunction characterized by the slowing of TCA cycle flux with accelerated lipid influx. The accumulation of lipids results in a shift in membrane phospholipid accumulation. Reduced BCAA oxidation and dysregulation of tryptophan metabolism are key features of SKM dysfunction in HFpEF.