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How can the liver make glucose from amino acids, pyruvate, and lactate?

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A biochemical flowchart shows the metabolic pathways for carbohydrate utilization, including glycolysis, the pentose phosphate pathway, and the tricarboxylic acid (TCA) cycle. The diagram traces the conversion of glucose, fructose, and glycerol through various intermediates, leading to energy production, carbon dioxide release, and biosynthesis of amino acids and porphyrins. Key steps and branches are labeled, with colored boxes highlighting biosynthetic outputs. — Carbohydrate Pathways for the utilization of carbohydrates.

The liver produces glucose from noncarbohydrate precursors—including lactate, pyruvate, and certain amino acids—through a metabolic process called gluconeogenesis.

The Process of Gluconeogenesis

While many steps in this pathway are the reverse of glycolysis, the liver bypasses three virtually irreversible steps of glucose catabolism using alternative enzymatic reactions that drive the process toward glucose synthesis.12

Lactate and Pyruvate: The synthesis of glucose from lactate is particularly active in the liver during recovery from intense physical exertion.12
Amino Acids: The liver converts glucogenic amino acids into intermediates of the tricarboxylic acid cycle, which are subsequently transformed into glucose.2

Hormonal Regulation

This process is tightly controlled by the balance of hormones, primarily insulin and glucagon, as well as cortisol. During fasting, decreased insulin and increased glucagon levels stimulate the liver to mobilize these precursors to maintain blood glucose concentrations, ensuring a steady energy supply for the brain.3