Regulation and limitations to fatty acid oxidation during exercise

Area of Science:

• Exercise Physiology
• Metabolic Regulation
• Biochemistry

Background:

• Fatty acids (FAs) are crucial energy sources during exercise, originating from circulation or muscle stores.
• High-intensity exercise paradoxically suppresses total FA oxidation compared to moderate-intensity exercise.
• The precise mechanisms limiting FA oxidation during intense exercise remain incompletely understood.

Purpose of the Study:

• To review the regulation of FA metabolism during exercise.
• To focus on the limitations of FA oxidation when transitioning from moderate to high-intensity exercise in humans.

Main Methods:

• Literature review of current research on FA metabolism during exercise.
• Analysis of proposed mechanisms for FA oxidation suppression.
• Synthesis of evidence regarding intra-muscular factors versus adipose tissue supply.

Main Results:

• Emerging evidence suggests intra-muscular factors play a significant role in limiting FA oxidation.
• High rates of glycolysis during intense exercise increase acetyl-CoA production.
• Increased acetyl-CoA may trap carnitine, reducing free carnitine availability for mitochondrial FA transport.

Conclusions:

• The suppression of FA oxidation during high-intensity exercise may be primarily driven by intra-muscular mechanisms.
• Carnitine availability within the muscle could be a key limiting factor for long-chain FA oxidation.
• Further research is needed to fully elucidate the complex regulation of FA metabolism during varying exercise intensities.