Metabolic Responses to the Yukon Arctic Ultra: Longest and Coldest in the World.
The Yukon Arctic Ultra is considered the longest and coldest ultraendurance event in the world. Cold exposure and exercise has been reported to influence circulating levels of myokines, adipokines, and hepatokines that may influence considerable alterations in the regulation of metabolism. The purpose of the study was to evaluate the influence of the Yukon Arctic Ultra (430-mile event) on potential activators of brown fat, metabolites, and body composition in healthy individuals.



Eight male and female participants (mean ± SEM: age, 44 ± 3 yr; body mass index, 23.4 ± 0.9) were recruited for participation. Blood samples were collected at pre-event, mid-event, and post-event checkpoints.



The temperature during the event ranged from -45°C to -8°C. Because of these extremely challenging conditions, 50% of the participants withdrew from competition by the 300-mile mark, and those that surpassed 300 miles lost a significant (P = 0.002; P = 0.01) amount of body weight (76 ± 5 kg to 73 ± 4 kg) and fat mass (13 ± 1 kg to 12 ± 3 kg), respectively. With respect to serum irisin, there was a trend (P = 0.06) toward significance from pre-event (1033 ± 88 ng·mL), mid-event (1265 ± 23 ng·mL) to post-event (1289 ± 24 ng·mL). Serum meteorin-like and fibroblast growth factor-21 remained stable throughout the event. There were no changes in creatinine, acetoacetate, acetate, and valine. Serum lactate decreased (P = 0.04) during the event.



The influence of cold exposure and extreme physical exertion may promote substantial increases in serum irisin, and specific alterations in substrate metabolism that largely preserve skeletal muscle and physiological resilience.
1Institute of Arctic Biology, University of Alaska-Fairbanks, Fairbanks, AK; 2Molecular Imaging Facility, University of Alaska-Fairbanks, Fairbanks, AK; and 3Center for Space Medicine and Extreme Environments, Berlin, GERMANY.
Robert H
RH
Coker
Alyssa N
AN
Weaver
Melynda S
MS
Coker
Carl J
CJ
Murphy
Hanns-Christian
HC
Gunga
Mathias
M
Steinach
D002001:Adipose Tissue, Brown / Q000378:metabolism; D000328:Adult; D001823:Body Composition; D050218:Body Fat Distribution; D003081:Cold Climate; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005346:Fibroblast Growth Factors / Q000097:blood; D005353:Fibronectins / Q000097:blood; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood; D008297:Male; D009419:Nerve Tissue Proteins / Q000097:blood; D010807:Physical Endurance / Q000502:physiology*; D013177:Sports / Q000502:physiology*; D015431:Weight Loss; D015874:Yukon Territory
C577593:FNDC5 protein, human; D005353:Fibronectins; D036341:Intercellular Signaling Peptides and Proteins; C502097:METRN protein, human; D009419:Nerve Tissue Proteins; C414620:fibroblast growth factor 21; D005346:Fibroblast Growth Factors
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