Increase in carbohydrate utilization in high-altitude Andean mice

Area of Science:

• Physiology
• Evolutionary Biology
• Mammalian Metabolism

Background:

• High altitude presents a significant physiological stressor due to low oxygen levels (hypoxia).
• Mammals living at high altitudes are hypothesized to adapt by increasing carbohydrate utilization for aerobic activities.
• Carbohydrate metabolism offers a more oxygen-efficient ATP yield compared to lipid metabolism, suggesting an evolutionary advantage.

Purpose of the Study:

• To investigate in vivo whole-body fuel utilization patterns during exercise in high-altitude mammals.
• To test the hypothesis that high-altitude mammals rely more on carbohydrates than their lowland counterparts.
• To examine cardiac oxidative capacities as an indicator of metabolic adaptation.

Main Methods:

• A multispecies comparative approach was employed using native high-altitude and low-altitude rodent species.
• Wild-caught Phyllotis mice from the Peruvian Andes at different altitudes were studied.
• Fuel use patterns and cardiac muscle oxidative capacities were analyzed.

Main Results:

• High-altitude Phyllotis mice (4,000-4,500 m) exhibited a higher proportion of carbohydrate utilization compared to low-altitude counterparts (100-300 m).
• Cardiac muscles of highland mice showed higher oxidative capacities.
• These findings indicate a distinct metabolic adaptation to high-altitude conditions.

Conclusions:

• Highland Phyllotis mice have evolved a metabolic strategy to conserve oxygen during strenuous activities at high altitudes.
• Adjustments in fuel substrate utilization represent a key adaptation to survive high-altitude hypoxia in mammals.
• This study provides strong evidence for evolved metabolic adjustments in response to environmental oxygen availability.