Insulin: hormone structure, production, and regulation

Insulin as a peptide hormone

Insulin is a peptide hormone produced by pancreatic beta cells in the islets of Langerhans. Encoded by the human INS gene, it is the body’s main anabolic hormone, regulating metabolism of carbohydrates, fats, and proteins. Insulin promotes glucose uptake into liver, fat, and skeletal muscle cells and supports conversion of absorbed glucose into glycogen and fats, while high circulating insulin strongly inhibits liver glucose production. It is secreted in response to elevated blood glucose and suppressed when glucose is low, helping maintain glucose homeostasis alongside glucagon. Structurally, human insulin is a heterodimer made of an A-chain and a B-chain linked by disulfide bonds (with an additional intrachain disulfide bond in the A-chain). It is synthesized as an inactive precursor, preproinsulin, then processed to proinsulin and cleaved to remove the C-peptide, producing mature insulin that is stored in secretory granules and released upon metabolic signals. Insulin is released from beta cells in two phases (a rapid first phase and a sustained second phase), and its deficiency or impaired activity leads to diabetes (type 1 from autoimmune beta-cell destruction and type 2 from less pronounced beta-cell dysfunction plus insulin resistance).

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Insulin gene encoding and chromosomal location

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