Effect of different cold acclimation methods on the exercise capacity of mice in low-temperature environments.

Objective: This study aimed to evaluate the effects of different cold acclimation strategies on exercise performance in male mice exposed to low-temperature environments.

Methods: Male mice were subjected to five distinct acclimation regimens over 8 weeks: immersion at 10 °C (10 °CI) or 20 °C (20 °CI), swimming at 10 °C (10 °CS), 20 °C (20 °CS), or 34 °C (34 °CS). During the first 2 weeks, the acclimation time progressively decreased from 30 min to 3 min per day, and the water temperatures were lowered from 34 °C to the target levels, followed by 6 weeks of consistent exposure. Body weight, food intake, and rectal temperature were monitored throughout the study. Post-acclimation assessments included low-temperature exhaustion exercise ability testing; 16 S rDNA sequencing of gut microbiota; and quantification of gene expression related to brown adipose thermogenesis, skeletal muscle synthesis, and degradation.

Results: (1) After 8 weeks of acclimation, neither serum adrenaline nor angiotensin II levels significantly increased in mice exposed to 10 °C or 20 °C water. (2) Cold acclimation extended the endurance time under low-temperature conditions, notably in the 20 °CI, 10 °CS, and 20 °CS groups. (3) Compared with the control (C) group, the 20 °CI and 10 °CS groups showed significantly increased UCP1, IGF-1, AKT, and mTOR gene expression levels (P < 0.05). The expression levels of MAFbx and MuRF1 genes in the 10 °CS and 20 °CS groups significantly decreased compared with those in the C group (P < 0.05). (4) Compared with the C group, the 20 °CI, 10 °CS, and 20 °CS groups demonstrated significant changes in intestinal microbiota diversity. Specifically, the abundance of Akkermansia strains significantly increased in the 20 °CI and 10 °C S groups. The abundance of Ruminococcus and Prevotellaceae_UCG-001 significantly increased in the 20 °C S group.

Conclusion: Exercise in cold environments can activate genes related to heat production and skeletal muscle synthesis and increase the abundance of beneficial bacteria producing short-chain fatty acids, thereby modulating host metabolism, accelerating the formation of cold acclimation, and enhancing exercise capacity in low-temperature environments.