Skeletal Muscle Mitochondria Contain Nuclear-Encoded RNA Species Prior to and Following Adaptation to Exercise...

Area of Science:

• Exercise Physiology
• Mitochondrial Biology
• Molecular Biology

Background:

• Skeletal muscle mitochondria adapt to exercise, but the molecular regulators are not fully understood.
• Mitochondria are primarily thought to contain RNA encoded by their own genome.
• Recent studies suggest nuclear-encoded RNAs may exist within mitochondria.

Purpose of the Study:

• To investigate the presence of nuclear-encoded RNAs in rat skeletal muscle mitochondria.
• To determine if endurance exercise training affects the mitochondrial RNA population.
• To explore the potential role of these RNAs in exercise-induced mitochondrial adaptation.

Main Methods:

• Rats underwent 4 weeks of moderate-intensity treadmill exercise.
• Mitochondria were isolated from gastrocnemius skeletal muscle using immunoprecipitation.
• Resident RNA was sequenced to profile the mitochondrial transcriptome.

Main Results:

• Identified 24 nuclear-encoded coding/noncoding RNAs and 50 nuclear-encoded microRNAs (miRNAs) in purified mitochondria.
• Exercise training induced typical adaptations, including increased mitochondrial respiratory capacity.
• Exploratory analysis suggested altered abundance of 3 miRNAs in trained versus sedentary muscle mitochondria.

Conclusions:

• Nuclear-encoded RNAs, including miRNAs, are present in rat skeletal muscle mitochondria.
• Endurance exercise may influence the abundance of specific mitochondrial miRNAs.
• These findings suggest a novel mechanism for regulating mitochondrial adaptation to exercise.