Abstract Body: Background: Inhaled molecular hydrogen gas (H₂) has been shown to improve outcomes in both animal models and patients of cardiac arrest (CA). Although the molecular mechanisms of H2 have been studied, the impacts of H₂ on metabolic alterations following CA remain to be elucidated.
Methods: Rats were subjected to 10 minutes of asphyxial CA followed by CPR to achieve a return of spontaneous circulation (ROSC). Ten minutes after achieving ROSC, rats were mechanically ventilated with 21% O₂ (Air group) or with 21% O₂ plus 1.3% H₂ (H₂ group). Whole-brain and plasma samples were obtained 2 h post-ROSC in each group (n = 5 for each). Unbiased GC/MS analysis was performed and the data were analyzed using MetaboAnalyst 6.0.
Results: In brain, a total of 117 metabolites were analyzed. In H₂ group, 15 were significantly increased and 3 were decreased metabolites in comparison with Air group (raw P < 0.05, Fold Change (FC > 1.2 or < 0.8). By using metabolites with the variable importance in projection score > 1.0 based on partial least squares discriminant analysis, pathway enrichment analysis (PEA) was conducted. PEA identified specific metabolic pathways that are significantly changed in the brain following H₂ inhalation, including “Alanine, aspartate and glutamate metabolism”, “Glycine, serine and threonine metabolism”, “Arginine biosynthesis,” and “Arginine and proline metabolism” (all FDR < 0.01). These pathways are integral to cellular processes such as neurotransmitter synthesis, energy production, and cell signaling, highlighting the potential neuroprotective mechanisms of H₂. In plasma, a total of 123 metabolites were analyzed. The H₂ group had 2 increased and 3 decreased metabolites compared to the Air group (raw P < 0.05, FC > 1.2 or < 0.8). PEA identified the “Valine, leucine and isoleucine biosynthesis” pathway (FDR < 0.01), suggesting the involvement of branched-chain amino acid metabolism, which plays a critical role in energy homeostasis and protein synthesis. These findings emphasize the systemic impact of H₂ inhalation on post-CA metabolic regulation.
Conclusion: Our analysis reveals that inhaled H₂ induces significant metabolic alterations in both brain and plasma post-CA. The data highlight the broad metabolic impacts of H₂ in modulating several pathways crucial for cellular recovery and protection. Further research is warranted to elucidate biomolecular mechanisms and clinical applications of H₂ therapy in CA patients.