Cori cycle

The Cori cycle transfers lactate produced by working muscle to the liver, where it is converted back into glucose and returned to the circulation.

Anaerobic glycolysis: The breakdown of glucose to pyruvate without oxygen as the final electron acceptor, yielding ATP and often lactate. Working muscle can sustain glycolysis by converting pyruvate to lactate when oxygen delivery cannot meet demand.
Skeletal muscle: Contractile tissue composed of muscle fibers that generate force and consume energy for voluntary movement. Active skeletal muscle is a major source of the lactate carried through the cycle.
Glucose–alanine cycle: A metabolic exchange in which muscle sends alanine to the liver for glucose production and nitrogen disposal. It also links muscle metabolism to liver gluconeogenesis, but transports nitrogen as alanine rather than carbon as lactate.
Exercise physiology: The study of how the body responds and adapts to physical activity and exercise. Exercise increases muscle glycolysis and reveals how lactate and glucose circulate between tissues.
Lactate dehydrogenase: An enzyme that reversibly interconverts pyruvate and lactate while transferring electrons to or from NADH. It links muscle pyruvate production to lactate formation and enables the liver’s reverse conversion.
Liver: A large metabolic organ that processes nutrients, stores fuel, and synthesizes or breaks down circulating molecules. The liver takes up lactate and supplies newly synthesized glucose to the blood.
Lactate shuttle: The movement and use of lactate among cells and tissues as a transferable metabolic fuel and carbon source. Unlike the Cori cycle’s liver-centered glucose return, lactate shuttling includes oxidation by other tissues.
Lactic acidosis: A metabolic acidosis associated with elevated blood lactate, arising when lactate production and clearance are imbalanced. Lactate clearance through liver metabolism is relevant to understanding elevated lactate, though the cycle alone does not explain acidosis.
Gluconeogenesis: The metabolic synthesis of glucose from non-carbohydrate precursors such as lactate, glycerol, and amino acids. The liver uses this pathway to turn circulating lactate back into glucose.
Monocarboxylate transporter: A membrane transport protein that carries lactate and other monocarboxylates across cell membranes with protons. Lactate movement between tissues and into cells depends on membrane transport.

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