Insulin -Yuan peptide

Insulin

Product Description

Insulin is the only peptide hormone secreted by pancreatic β-cells in the human body that directly lowers blood glucose, and it is also a core drug for the treatment of diabetes.

I. Basic Structure and Origin

Structure: Composed of an A-chain (21 amino acids) and a B-chain (30 amino acids) linked by two disulfide bonds, with a total of 51 amino acid residues.

Synthesis: Within pancreatic islet β-cells, preproinsulin is first synthesized, which is cleaved to form proinsulin, and then enzymatically digested into insulin and C-peptide (C-peptide can reflect the level of endogenous insulin secretion).

Nomenclature: Derived from the Latin word insula (island), as it is secreted by the islets of Langerhans.

II. Core Physiological Functions

Insulin is the major anabolic hormone in the body, regulating the metabolism of the three major nutrients:

Glucose Metabolism (Blood Glucose Lowering)

Promotes glucose uptake by muscle, adipose tissue, and the liver.

Stimulates the synthesis of hepatic glycogen and muscle glycogen, inhibits glycogenolysis and gluconeogenesis in the liver, thereby rapidly lowering blood glucose.

Lipid Metabolism

Promotes fat synthesis, inhibits lipolysis, and reduces ketone body production.

Protein Metabolism

Enhances amino acid uptake and protein synthesis, suppresses protein breakdown, and facilitates tissue repair.

III. Regulation of Secretion

Major stimulants: Elevated blood glucose (the most direct stimulus), gastrointestinal hormones after meals (such as GLP‑1, GIP), and vagus nerve activation.

Inhibitory factors: Decreased blood glucose, sympathetic nerve activation, glucagon, epinephrine, etc.

Secretory pattern: Sustained basal secretion + large postprandial pulsatile secretion to maintain blood glucose homeostasis.

IV. Classification of Clinical Preparations (by Duration of Action)

1. Ultrarapid / Rapid-Acting Insulin Analogues

Representatives: Insulin aspart, insulin lispro, insulin glulisine.

Characteristics: Rapid onset (10–15 minutes), high peak effect, short duration (3–5 hours).

Usage: Injected immediately before meals to control postprandial blood glucose.

2. Short-Acting / Regular Insulin (Human Insulin)

Representative: Regular (neutral) human insulin.

Characteristics: Onset 30 minutes after subcutaneous injection, peak at 1–3 hours, duration 4–8 hours.

Usage: Injected 15–30 minutes before meals; may be administered intravenously for diabetic ketoacidosis and hyperosmolar coma.

3. Intermediate-Acting Insulin

Representative: Isophane insulin (NPH).

Characteristics: Onset in 1–2 hours, peak at 4–12 hours, duration 18–24 hours.

Usage: Administered once or twice daily to provide basal insulin and control fasting blood glucose.

4. Long-Acting Insulin Analogues

Representatives: Insulin glargine, insulin detemir, insulin degludec.

Characteristics: Stable and peakless action, duration of 24 hours (up to 42 hours for insulin degludec).

Usage: Injected once daily at a fixed time for basal blood glucose control with low risk of hypoglycemia.

5. Premixed Insulin

Representatives: Insulin aspart 30/50, insulin lispro 25/50, human insulin 30R/50R.

Characteristics: A fixed ratio mixture of rapid-acting and intermediate-acting insulin, covering both postprandial and basal blood glucose control.

Usage: Injected once or twice daily before meals; must be thoroughly mixed before use.

V. Clinical Applications

Type 1 diabetes mellitus: Lifelong dependence on exogenous insulin (absolute deficiency).

Type 2 diabetes mellitus

Failure of oral antidiabetic drugs and poor glycemic control.
Acute complications (diabetic ketoacidosis, hyperosmolar coma).
Stress conditions such as severe infection, surgery, and trauma.
Gestational diabetes, impaired hepatic or renal function, and contraindications to oral medications.

Other uses: Correction of intracellular potassium deficiency (in combination with glucose and potassium chloride), diabetes caused by certain pancreatic diseases.

VI. Administration Routes

Subcutaneous injection: Abdomen, thigh, upper arm, buttocks (rotate injection sites to prevent lipohypertrophy / lipoatrophy).

Intravenous injection: Only short-acting insulin is used for emergency conditions (e.g., diabetic ketoacidosis).

Insulin pump: Continuous subcutaneous infusion to simulate physiological secretion, suitable for patients requiring precise glycemic control.

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