Physiological and Morphometric Differences in Resident Moderate-Altitude vs. Sea-Level Mice

Area of Science:

• Physiology
• Altitude Research
• Comparative Biology

Background:

• High-altitude acclimatization (>2400m) is well-documented, with known physiological adaptations.
• Acclimatization at moderate altitude (MA, 1524-2438m) remains less understood.
• This study investigates physiological differences in mice reared at MA versus sea level (SL).

Purpose of the Study:

• To investigate physiological differences in mice reared at moderate altitude (MA) compared to sea level (SL).
• To test the hypothesis that MA mice would exhibit smaller body size, reduced leanness, and lower voluntary running activity.

Main Methods:

• Comparison of C57BL/6 mice reared at MA (Laramie, WY, 2194m) with C57BL/6J mice from SL (Bar Harbor, ME, 20m).
• Quantification of body composition, exercise outputs, and cardiopulmonary morphometrics.
• Analysis of neuronal activation post-exercise in subsets of MA and SL mice.

Main Results:

• MA mice had lower body weight normalized to tibia length (1.13g·mm⁻¹ vs 1.30g·mm⁻¹).
• MA mice exhibited higher total and trunk fat percentages (41% and 39% vs 28% and 26%) but similar leg fat percentage.
• MA mice showed higher heart mass (119mg vs 100mg), lower lung mass (160mg vs 177mg), and ~40% less voluntary wheel-running activity.

Conclusions:

• Significant physiological differences exist between mice reared at moderate altitude and sea level.
• MA mice demonstrate adaptations including altered body composition and reduced physical activity.
• Further research is needed to understand the broader implications of residing at moderate altitudes.