Endocannabinoid system and mood responses to acute aerobic exercise in adult cancer patients versus healthy controls: a pilot study

Purpose: To investigate the endocannabinoid system (ECS) and affective state responses to acute aerobic exercise in adult cancer patients versus their healthy peers. Methods: Participants engaged in 30 min of quiet rest followed by 30 min of exercise. Exercise involved 5-min warm-up/cool-down procedures and 20 min of moderate-intensity training (64–76% of age-predicted maximal heart rate) on a treadmill or cycle. Blood samples and 10 Visual Analog Scales (VAS) were collected before and after each condition. Participants were also asked after exercise: ‘Did you experience a Runner’s high’. Blood samples were analysed for endocannabinoids: N-arachidonoylethanolamine (AEA; anandamide), 2-arachidonoylglycerol (2-AG) and 1-arachidonoylglycerol (1-AG), and endocannabinoid-like lipid mediators: palmitoylethanolamide (PEA), oleoylethanolamide (OEA) and stearoylethanolamide (SEA). Results: Cancer patients had lower circulating AEA, OEA and log SEA versus controls across all timepoints (all p < 0.06). In the total cohort, exercise increased AEA, log 1-AG, OEA, PEA and log SEA (all p = 0.05) while log 2-AG did not change. Of 10 VAS, only Happiness increased with exercise in the total cohort (p = 0.02). There were no group x time effects or associations between ECS and VAS responses to exercise. Five patients per group (50%) reported experiencing a Runner’s high. Conclusions: Exercise increased endocannabinoids and endocannabinoid-like lipid mediators in the total cohort. However, cancer patients exhibited lower AEA, OEA and SEA concentrations versus their peers, indicating potential ECS dysfunction. Additional research is required to investigate the effect of various modalities and dosages of exercise on ECS markers and the clinical interpretation of these adaptations across a range of cancer populations.