Ambient Temperature Shapes Skeletal Muscle Growth and Fiber-Type Plasticity in Mice

Area of Science:

• Environmental physiology
• Mammalian skeletal muscle biology
• Tissue adaptation

Background:

• Environmental cues, particularly ambient temperature, critically influence mammalian growth, metabolic adaptation, and physiological homeostasis.
• Understanding the effects of varying ambient temperatures on skeletal muscle and visceral tissues is crucial for comprehending mammalian resilience.

Purpose of the Study:

• To investigate the physiological impacts of five distinct ambient temperature conditions (16°C, 20°C, 24°C, 28°C, 32°C) on skeletal muscle and visceral tissues in a mouse model.
• To elucidate how ambient temperature modulates skeletal muscle phenotype, myosin heavy chain (MyHC) isoform expression, muscle performance, and intestinal morphology.

Main Methods:

• Mice were housed under five controlled ambient temperature conditions.
• Skeletal muscle phenotype, grip strength, endurance capacity, and MyHC isoform expression were assessed.
• Histological analyses were performed on major visceral organs, including the heart, liver, spleen, lung, kidney, and intestine.

Main Results:

• Ambient temperature significantly influenced growth performance and skeletal muscle phenotype, with notable shifts in myofiber cross-sectional area distribution at 20°C.
• Cold exposure upregulated slow-twitch MyHC I, while heat stress elevated fast-twitch MyHC IIb.
• Muscle performance was impaired at thermal extremes (16°C, 28°C, 32°C), and intestinal villus height was reduced at 16°C and 32°C.

Conclusions:

• Ambient temperature is a critical environmental factor that induces multi-tissue adaptations in mammals.
• Thermal stress affects skeletal muscle characteristics, functional performance, and intestinal integrity, highlighting the complex interplay between environment and physiology.
• These findings offer insights into mammalian tissue adaptation and physiological homeostasis under varying environmental temperatures.