Exercise Training Attenuates the Muscle Mitochondria Genomic Response to Bed Rest

Area of Science:

• Space physiology
• Molecular biology
• Genomics

Background:

• Prolonged bed rest induces significant physiological deconditioning.
• Exercise countermeasures are known to mitigate some negative effects of bed rest.
• Understanding the molecular basis of these adaptations is crucial for astronaut health.

Purpose of the Study:

• To investigate the genomic and microRNA response in vastus lateralis muscle during 70-day bed rest.
• To compare the effects of different exercise training modalities (standard vs. flywheel) as countermeasures.
• To identify molecular pathways affected by bed rest and exercise.

Main Methods:

• Randomized controlled trial with 22 healthy males in three groups: bed rest only, bed rest with standard exercise, and bed rest with flywheel exercise.
• Gene and microRNA expression analysis of vastus lateralis muscle biopsies.
• Statistical analysis including interaction analysis and enrichment analysis.

Main Results:

• Bed rest altered the expression of over 2100 genes, with a predominant downregulation in the bed rest-only group.
• Exercise training attenuated or reversed the bed rest-induced gene expression changes in 511 genes, with no significant difference between exercise types.
• Mitochondrial-related genes and pathways were significantly affected, and 12 microRNAs known to regulate these genes were altered.

Conclusions:

• Mitochondrial gene expression is a key molecular component of the response to long-term bed rest.
• Exercise countermeasures partially mitigate but do not fully reverse all molecular consequences of bed rest.
• Both standard and flywheel exercise modalities demonstrated similar efficacy in attenuating gene expression changes.