Lactat

Lactat, also called lactate in English, is the conjugate base of lactic acid and a common metabolite in many tissues. At physiological pH it exists predominantly as the lactate anion. Lactate is formed from pyruvate by the enzyme lactate dehydrogenase, a reaction that consumes NADH and regenerates NAD+, allowing glycolysis to continue when mitochondrial oxidation is limited or when glycolytic flux is high.

Lactate is transported across cell membranes by monocarboxylate transporters (MCTs), enabling intercellular lactate exchange. In practice this supports the lactate shuttle: muscles and other tissues release lactate into blood, while heart, brain, and liver take it up as a fuel or to convert it to glucose.

In the liver, lactate can be converted back to glucose via gluconeogenesis, completing the Cori cycle. The heart and brain commonly oxidize lactate for energy, particularly during exercise or stress.

Clinically, blood lactate concentration is used as a marker of tissue oxygenation and metabolic state. Resting lactate levels are typically about 0.5–2.0 mmol/L; levels rise with intense exercise, shock, sepsis, liver failure, or mitochondrial disorders. Elevated lactate with acidemia is called lactic acidosis; it is categorized as type A (hypoxia/hypoperfusion) or type B (metabolic or drug-induced).

In addition to its metabolic roles, lactate is increasingly recognized as a signaling metabolite that can influence gene expression, angiogenesis, and mitochondrial function, partly through receptors such as GPR81 (HCAR1).