Lactate as a metabolic-epigenetic signal linking high-intensity interval training (HIIT) to miRNA-Centered remodeling of the skeletal muscle methylome and transcriptome.

BACKGROUND: Lactate, a key exercise-derived metabolite and exerkine, is increasingly recognized as a metabolic-epigenetic signal, yet whether lactate and its transport directly shape skeletal-muscle epigenetic and transcriptional adaptations to exercise remains unclear. METHODS: Young male mice underwent six-week interventions: Control, lactate administration, high intensity interval training (HIIT), monocarboxylate transporter isoforms 1 and 2 (MCT1/2) inhibition, or HIIT plus inhibition. Gastrocnemius muscle was profiled by DNA methylation arrays, mRNA and miRNA-seq, together with analyses of signaling proteins, metabolites, and running performance. RESULTS: Exogenous lactate and HIIT each elicited broad, site-specific remodeling of the skeletal muscle methylome and transcriptome with substantial overlap at promoter CpGs and differentially expressed genes. Promoter methylation changes showed weak coupling to steady-state mRNA, whereas integrative analyses revealed robust anti-directional miRNA-mRNA networks and included numerous chromatin and epigenetic regulators, identifying a lactate-driven, miRNA-centered axis. At the protein level, lactate increased TET2/DNMT3A and activated signaling involved in satellite-cell activation, angiogenesis, and AKT-S6 axis, accompanied by reciprocal miRNA-mRNA pairs. HIIT increased TET1/2 and DNMT3A, reduced DNMT3B, and uniquely enhanced mitochondrial/antioxidant signaling. Pharmacologic MCT1/2 blockade abrogated HIIT-induced methylome and miRNA remodeling and blunted transcriptomic and protein adaptations, demonstrating that intact lactate flux is required for exercise-induced epigenetic reprogramming. Despite molecular convergence, chronic lactate did not improve running performance, suggesting that lactate is necessary, but not sufficient for the full physiological benefits of HIIT. CONCLUSIONS: These data support a lactate-miRNA-transcriptome/epigenome interplay that links metabolic perturbation to gene regulation in skeletal muscle. Using an integrated multi-omics approach, we propose a mechanistic framework for future studies targeting metabolic-epigenetic signaling in both physiology and pathology.