Lactate kinetics in human tissues at rest and during exercise

Area of Science:

• Exercise Physiology
• Biochemistry
• Human Metabolism

Background:

• Lactate's role in skeletal muscle has been debated for centuries, initially linked to fatigue and hypoxia.
• Early research viewed skeletal muscle primarily as a lactate producer during exercise.
• The Copenhagen School in the 1930s highlighted skeletal muscle's role in lactate clearance, renewing interest in its metabolic functions.

Purpose of the Study:

• To review in vivo human skeletal muscle lactate metabolism at rest and during exercise.
• To propose explanations for the observed simultaneous lactate uptake and release in muscle.
• To discuss lactate metabolism in other key human tissues.

Main Methods:

• Review of existing literature on human lactate kinetics and oxidation.
• Analysis of studies utilizing lactate isotopes to track metabolic pathways.
• Synthesis of findings on lactate turnover in various physiological states.

Main Results:

• Skeletal muscle exhibits simultaneous lactate uptake and release, challenging earlier views.
• Lactate kinetics and oxidation can be effectively studied using isotopic tracers.
• Lactate plays a metabolic role beyond anaerobic glycolysis in multiple human tissues.

Conclusions:

• Skeletal muscle lactate metabolism is dynamic, involving both production and clearance.
• Simultaneous lactate flux requires further investigation to fully elucidate its mechanisms.
• Lactate's metabolic significance extends to organs including the heart, liver, kidneys, brain, adipose tissue, and lungs.