The Gibbs free energy landscape based on liver metabolome revealed thermodynamic robustness against fasting and obesity

Summary: Mammalian liver metabolism shifts substantially during fasting, yet the Gibbs free energy change of reaction (Δ r G ′), a fundamental thermodynamic quantity that defines reaction driving force and constrains metabolic directionality, remains poorly characterized in intact organs. Here, we mapped the Δ r G ′ landscape of mouse liver glucose metabolism during fasting using absolute metabolite concentrations and GLEAM (Gibbs free energy of reaction landscape estimation from metabolome assisted by variance-covariance matrix), a computational method developed here. Despite metabolite fluctuations, Δ r G ′ landscapes remained robust, changing only modestly, even for reactions reversing direction between glycolysis and gluconeogenesis. Thermodynamically inferred potential rate-limiting steps were maintained during fasting. Enzyme-cost analysis further suggested a trade-off between thermodynamic robustness and enzyme requirements during glycolytic switching. Obese mouse liver also showed thermodynamic robustness despite metabolic disruption. Our framework provides a novel thermodynamic perspective on intact organ metabolism, revealing preservation of key thermodynamic characteristics across fasting and obesity.