How do mitochondrial defects affect energy production in muscle cells?

Mitochondrial defects impair the electron transport chain (ETC), which is the primary apparatus responsible for generating adenosine triphosphate (ATP), the essential energy currency of muscle cells. When these defects occur, the cell's ability to produce energy through oxidative metabolism is compromised.12

The consequences of this dysfunction include:

• Reduced ATP Production: A deficiency in the proteins that constitute the ETC prevents the efficient conversion of chemical energy into ATP, leading to an energy deficit in highly dependent tissues like skeletal muscle.31
• Lactic Acid Accumulation: To compensate for the failure of oxidative energy production, muscle cells rely on the nonoxidative breakdown of stored glycogen. This process frequently results in the generation of large amounts of lactic acid.2
• Cellular Damage: Dysfunction often leads to the production of toxic reactive oxygen species (ROS), which cause oxidative stress and damage cellular molecules. Furthermore, damaged mitochondria may release apoptotic factors that signal the cell to undergo death.31
• Metabolic By-products: The buildup of unused intermediate molecules from sugar and fat metabolism can lead to the formation of additional damaging by-products.1