Lyophilized Royal Jelly Enhances Antioxidant Enzyme Signaling and Autonomic Adaptation to HIIT Through Glutathione Metabolism Pathways

Royal jelly (RJ) is a bioactive substance produced by honeybees, rich in 10-hydroxy-2-decenoic acid (10-HDA), with well-documented antioxidant and immunomodulatory properties. However, its capacity to modulate redox homeostasis during high-intensity interval training (HIIT) in trained human athletes remains unexplored. This randomized, double-blind, placebo-controlled trial investigated the effects of 4-week supplementation with 1,000 mg/day of lyophilized RJ (n=12) versus placebo (n=11) on biochemical and physiological responses to three repeated HIIT sessions (T0=acute, T1=2 weeks, T2=4 weeks) in trained male cyclists. Blood samples were collected pre-, post-, and 1h-post each session. Univariate analysis (Mann-Whitney U / independent t-test) revealed significant between-group differences in Catalase (CAT) activity at T0 (Pre: p=0.003, Post: p=0.032) and T1 (Post: p=0.001), Superoxide Dismutase (SOD) at T2 (Pre: p=0.038), Glutathione Reductase (GR) at T1 (Pre: p=0.031), and Reduced Glutathione (GSH) at T0 (Pre: p=0.002), with large effect sizes (Cohen's d range: 0.88–1.76). Principal Component Analysis (PCA) demonstrated clear multivariate separation between groups (PC1+PC2 explaining 27.8+13.2% of total variance). SHAP analysis identified CAT T0 Post, CAT T1 Post, GSH T1 Post as the primary drivers of group discrimination. These findings suggest that lyophilized RJ modulates the glutathione metabolism pathway and enzymatic antioxidant signaling, rather than acting as a direct ROS scavenger, representing a novel mechanism for nutritional support of exercise adaptation.