Oxylipin Responses during the Yukon Arctic Ultra: The Longest and Coldest Ultramarathon in the World

Aerobic exercise and cold exposure modulate lipid mediator production, which may optimize physiological resilience. The Yukon Arctic Ultra (YAU), a 692-km self-provisioned multiday endurance event, offers a unique opportunity to examine lipidomic adaptations to nutrients and environmental and physical stress. This study aimed to identify lipid mediators responsive in YAU athletes compared to control participants.

Nine athletes and six controls were recruited from the 2017 and 2019 YAU events. Targeted liquid chromatography-tandem mass spectrometry/mass spectrometry-based signaling lipidomic analysis was conducted on serum samples collected from participants at pre-event, during the event, and post-event time points.

Athletes and controls did not differ significantly in age, body mass index (BMI), fat mass index (FMI), or fat-free mass index. During the event, athletes exhibited significant reductions in BMI, fat mass, and FMI, whereas no changes were observed in controls. Athletes showed higher baseline levels of anti-inflammatory oxylipins, including resolvin D2 and lipoxin A4 (LXA4), and lower levels of the pro-inflammatory leukotriene E4 compared to controls. Linoleic acid- and α-linolenic acid-derived oxylipins were also elevated in athletes. Notably, these anti-inflammatory lipids remained elevated throughout the event. Certain hydroxy-eicosapentaenoic acids demonstrated a declining trend during the event in athletes.

YAU athletes exhibit a distinct lipidomic signature marked by persistently elevated anti-inflammatory oxylipins, likely reflecting a complex interplay between adipose tissue and skeletal muscle. Overall, the oxylipin shifts point to anti-inflammatory and thermogenic adaptations that support physiological resilience during physical, nutrient, and environmental stress in austere circumstances.