Pathway thermodynamic analysis postulates change in glutamate metabolism as a key factor in modulating immune responses.

Background: Temperature, as seen during fever, plays a pivotal role in modulating immune responses and maintaining cellular homeostasis. Shifts in temperature influence the thermodynamic feasibility of metabolic reactions, with Gibbs free energy (ΔG) serving as a key indicator of the spontaneity of reactions under specific conditions. By altering ΔG in response to temperature changes across various metabolite concentrations and cell types, we can gain insights into the thermodynamic properties of metabolic pathways and identify critical factors involved in metabolism and immune function. Using Max-min Driving Force (MDF) analysis, we can assess changes in ΔG by varying temperature and metabolite concentrations, allowing for a detailed examination of thermodynamic feasibility at both the pathway and individual reaction levels. Method: Minimum driving force analysis was conducted to estimate the thermodynamic feasibility of metabolic pathways, including glycolysis, gluconeogenesis, oxidative phosphorylation, the pentose phosphate pathway, the tricarboxylic acid cycle, arginine and proline metabolism, amino sugar and nucleotide sugar metabolism (collectively referred to as amino sugar metabolism), leukotriene metabolism, and other amino acid pathways. The analysis was performed across a temperature range of 310.15 to 314.15 K. In addition, the ΔG for each reaction was calculated using standard Gibbs free energy values obtained from the equilibrator. Results: In this study, MDF analysis is applied to measure the changes in the driving force of pathways and the ΔG of each reaction at normal human core temperature (310.15 K) and elevated temperatures (up to 314.15 K). Additionally, we explore how shifts in the thermodynamic feasibility of reactions under immune activation, compared with normal physiological conditions, highlight key metabolic intermediates, such as fructose-1,6-bisphosphate, glucose-6-phosphate, and several steps in glutamate utilization, as important regulators of metabolic processes and immune responses. Conclusion: In conclusion, this study demonstrates that MDF-based thermodynamic analysis effectively captures temperature-dependent shifts in metabolic pathway feasibility and highlights glutamate metabolism as a key regulator of immune function. These findings underscore the utility of thermodynamic frameworks in advancing system-level understanding of human metabolism and immune regulation.