Lactate Overview

Lactate: More Than a Waste Product

  • Lactate has more important functions than just being a metabolic waste product.

Enantiomers of Lactate

  • Enantiomers are molecules that are mirror images of each other.
  • The predominant form in the human body is the L+ version.

Lactate and Exercise Intensity

  • With increasing exercise intensity, more lactate is produced through fast glycolysis.
  • Lactate threshold can be determined through:
    • Visual determination.
    • Dmax method (drawing a linear line and then looking at the perpendicular line with the greatest distance).
    • Onset of blood lactate accumulation (set at 44 mmol).

Lactate as a Signaling Molecule

  • Low Intensity Exercise:
    • Role in norepinephrine release and glucose metabolism.
    • Increase ventilation and vasodilation.
  • Moderate to High Intensity:
    • Continuing effects on norepinephrine, glucose metabolism.
    • Mimics hypoxic environments.
  • Severe Intensity:
    • Signals pain receptors.

Lactate Production Under Aerobic Conditions

  • There is some evidence that suggests small amounts of lactate are produced even under fully aerobic conditions.

Lactate Shuttle Hypothesis

  • Lactate can be uptaken by different cells and tissues because it is shuttled to them.
  • Glucose is broken down into pyruvate.
  • Pyruvate can also be converted to lactate via the enzyme lactate dehydrogenase.

Lactate Shuttling

  • Lactate can be shuttled from one muscle fibre to another and also various parts of the body.
  • Fast twitch fibres (producers of lactate) -> slow twitch muscle fibres.
  • Lactate can be shuttled into the circulation where it can travel to the lung, heart, brain, liver and kidneys.

Lactate and the Cori Cycle

  • Pyruvate and lactate formed in the muscle can circulate in the bloodstream to the liver and kidney.
  • There carboxylic acids can be synthesised to form glucose.

Lactate's Influence on Exercise-Related Adaptations

  • HIF−1HIF-1 (hypoxic inducible factor one) activates signals which favour lactate production.
  • Lactate also indirectly affects HIF−1HIF-1.
  • PGCPGC one alpha (a master switch of HIT adaptations) controls lactate transport, but lactate also affects alpha.

Lactate as a Signaling Molecule (Detailed)

  • Lactate might influence the lungs to increase pulmonary ventilation during exercise.
  • Thought to increase blood vessel formation through angiogenesis.
  • Impact on tumour cells by reducing the amount of tumor genesis or the creation of tumor cells.
  • Myokines: cytokines and other peptides that are produced, expressed and released by muscle fibres and exert either autocrine, paracrine or endocrine effects.
  • Exokines: released in response to acute or chronic exercise.