Hypoxia and Thermogenesis Constrain Peak V̇o₂ in Exercising Naked Mole Rats

Area of Science:

• Comparative physiology
• Animal adaptation
• Metabolic regulation

Background:

• Naked mole rats (NMRs) exhibit remarkable hypoxia tolerance, reducing metabolic rate by over 85% and switching to carbohydrate metabolism.
• Previous studies focused on resting NMRs, leaving the impact of exercise on their metabolic strategies under hypoxia unknown.

Purpose of the Study:

• To investigate how interactions between hypoxia and intense exercise affect metabolic rate (V̇o₂), aerobic scope, and fuel utilization in NMRs.
• To determine the relative influence of hypoxia, exercise intensity, and ambient temperature on NMR metabolism.

Main Methods:

• Measured oxygen consumption rate (V̇o₂) and assessed fuel usage in NMRs.
• Exposed animals to normoxia and hypoxia (7% O₂) at two temperatures (22°C and 30°C).
• Evaluated metabolic responses during both stationary-wheel activity and forced intense exercise.

Main Results:

• Hypoxia significantly reduced both resting and peak V̇o₂, constraining metabolic scope for exercise.
• Exercising V̇o₂ and peak V̇o₂ did not increase from stationary-wheel levels in hypoxia, indicating exercise capacity is limited.
• Metabolic rate was unaffected by temperature in hypoxic conditions.
• Hypoxia, independent of exercise or temperature, induced a shift towards carbohydrate metabolism.

Conclusions:

• Environmental hypoxia is the primary factor limiting V̇o₂ and dictating fuel use in exercising NMRs.
• Hypoxic hypometabolism is prioritized over thermoregulatory and activity-related energy demands in NMRs.
• This metabolic strategy supports NMR ecophysiology, balancing energy needs in varying burrow conditions.