Shared CI-linked bioenergetic dysfunction and muscle-specific lipid/redox stress in skeletal muscle of male cardiometabolic HFpEF mice

Abstract

Exercise intolerance is a hallmark of heart failure with preserved ejection fraction (HFpEF), particularly in its cardiometabolic form, where obesity, metabolic dysfunction, and impaired peripheral oxygen utilization contribute to functional limitation. Skeletal muscle mitochondrial dysfunction is a recognized contributor to this phenotype, yet whether it is shared across muscles with contrasting oxidative profiles, or accompanied by muscle-specific stress responses, has been little explored. We therefore examined gastrocnemius and soleus from male cardiometabolic HFpEF mice using a descriptive and integrative approach. Male C57BL/6J mice received a 60% high-fat diet plus L-NAME for 12 weeks (n = 32); controls received standard chow (n = 29). Gastrocnemius and soleus were assessed for muscle mass, fiber-size distribution, atrogene expression, triglycerides, lipid peroxidation, oxidative DNA damage, high-resolution respirometry, mitochondrial membrane potential (ΔΨm), TMRE-based intermyofibrillar (IMF) mitochondrial signal density and spatial organization by confocal microscopy, and transcripts related to mitochondrial remodeling and stress signaling. HFpEF mice developed obesity, impaired glucose tolerance, diastolic dysfunction, and reduced exercise capacity. Muscle mass, mean fiber area, mean fiber diameter, and canonical atrogenes were unchanged, whereas fiber-size distributions shifted in both muscles, indicating myofiber remodeling before overt wasting. Gastrocnemius showed increased triglycerides, lipid peroxidation, and 8-OHdG, whereas soleus was relatively preserved from these lipid/redox stress markers. Despite this muscle-specific profile, CI-linked LEAK respiration was reduced to a similar extent in both muscles, together with lower ΔΨm, while ADP-stimulated CI-linked and succinate-supported CII-linked OXPHOS capacities were relatively preserved. TMRE-based IMF mitochondrial signal density and spatial organization showed no detectable large-scale remodeling under basal conditions. Biogenesis and dynamics transcripts were unchanged; however, Parkin mRNA was reduced in gastrocnemius and increased in soleus, and Ampk transcripts were increased in gastrocnemius. Early cardiometabolic HFpEF is associated with impaired exercise capacity and a skeletal muscle phenotype in which a shared CI-linked bioenergetic dysfunction and ΔΨm loss coexist with muscle-specific lipid/redox stress and myofiber redistribution. Divergent Parkin and Ampk transcript patterns highlight mitochondrial quality-control and energetic stress pathways as candidate regulators of muscle-specific stress adaptation. Future studies should test whether modulating these pathways improves mitochondrial function and exercise tolerance.