Insulin

Infectious diseases were the epicenter of the last millennium , metabolic issues are said to be dominant of the present era.

First recipient of insulin was a 14 year old boy from Canada, 11th Jan 1922.

Isolated in crystalline form by Abel in 1930.

Human Insulin is produced by recombinant DNA technology,  structural alterations at one or more amino acid residues modify its physical and pharmacological characteristics. It is coded for on chromosome 11 and synthesized in the beta cells of the pancreatic islets.

There are two chains, that is chain A which contains 21 amino acid molecule and chain B which contains 30 amino acid molecules linked by disulphide bridges.  It is coded on chromosome 11 and synthesized in the beta cells of the pancreatic islets.  

Source

Animal Insulin

  • Bovine Insulin- single amino acid difference from human insulin
  • Porcine insulin- three amino acid difference from human insulin
  • Combination of bovine and porcine

Human Insulin

  • Produced biosynthetically or semisynthetically

The molecular structure of insulin

Classifications

A. Purity

1. Conventional (recrystallized)

2. Highly Purified (by gel chromatography)

3. Monocomponent (by gel + ion exchanged chromatography)

B. Action profile    Onset of action  Peak Action      Duration of Action

  • Rapid acting        < half n hr          0.5 -2.5 hr         3-4.5 hr
  • Short acting         ¼ -1hr                   1- 4hrs                 4- 8hrs
  • Intermediate       1-3 hrs                   3- 8 hrs              7- 14 hrs
  • Long acting          2- 4hrs                   6- 12 hrs            12- 30 hrs
  • Ultra long acting    1- 2 hrs                  none                    24 hrs

C. Source – which is previously mentioned, based on from where insulin is extracted.

Actions of Insulin

Based on different parts of the body, Insulin can have different physiological effects, some of the most important effects can be as follows:-

On the Skeletal Muscle – Increases glucose uptake , increases glycogen synthesis & deposition

Decreases lipolysis, and increases amino acid transport into the cell. Protein synthesis is increased and breakdown is decreased.

On the liver:- Increases glycogen synthesis storage, decreases glycogenolysis & gluconeogenesis ( formation of glucose from non carbohydrate substrates )

Adverse Effects

  1. Hypoglycemia- Unmonitored dosing and carelessness can cause insulin shock and bring down the glucose levels to lethal levels.
  2. Insulin allergy- local inflammation , General inflammation- rare
  3. Lipohypertrophy- overuse of a single injection site due to lipogenic property of insulin, can occur with any type insulin.
  4. Lipoatrophy- local allergic response due to conventional insulin preparation
  5. Weight gain
  6. Insulin resistance- seen in obesity
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