Ketogenic Dietary Therapies and β-Hydroxybutyrate as Modulators of Mitochondrial Function: From Molecular Mechanisms to Clinical Translation.

Ketogenic dietary therapies (KDTs) have been used for a century in drug-resistant epilepsy, and β-hydroxybutyrate (BHB), the major ketone body, is recognized as a signaling metabolite. This review examines how KDTs and BHB modulate mitochondrial function and evaluates evidence supporting these mechanisms. BHB is oxidized through D-β-hydroxybutyrate dehydrogenase 1 and succinyl-CoA:3-oxoacid-CoA transferase and alters redox balance and oxidative phosphorylation. It also inhibits class I histone deacetylases, serves as the substrate for lysine β-hydroxybutyrylation, activates hydroxycarboxylic acid receptor 2, and blocks the NLR family pyrin domain-containing 3 inflammasome. These pathways influence redox defense, organelle quality, and inflammation. However, ketogenic feeding suppresses mitochondrial one-carbon metabolism and some signaling effects occur only at BHB concentrations exceeding those typically achieved through dietary ketosis. Clinical benefits are best established in drug-resistant epilepsy and appear genotype-dependent in primary mitochondrial disease, with potential benefit in mitochondrial DNA (mtDNA) variant carriers but possible harm in DNA polymerase gamma-related disease and mtDNA deletion myopathy. Outside neurology, human evidence includes a hemodynamic response to infused 3-hydroxybutyrate in heart failure, sustained glycemic improvement in non-randomized diabetes cohorts, and small trials in psychiatric and oncological populations. Most clinical studies have not directly measured mitochondrial outcomes. Proposed mitochondrial mechanisms of KDTs and BHB remain plausible but are not established explanations for clinical benefit. Genotype-stratified trials, ketone exposure assessment, and direct measurement of mitochondrial variables in patients are needed.