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.