Structure and properties of insulin

Insulin is a peptide hormone,it is the key controlling hormone in plasma glucose homeostasis. Insulin is composed of 51 amino acid residues arranged into two peptide chains named as chain-A and chain-B. its hexamer (T6) form has highly stable and compact structural organization. The 2 Zn-insulin hexamer represents the storage form of hormone in the mature secretory granules in pancreas. Insulin is available as white crystallinshort acting insulinse powder. It is mildly soluble in water. It is almost insoluble in non-polar solvents like ether, alcohol, chloroform. It is soluble in dilute solution of mineral acids as 0.01Molar solution of hydrochloric acid. Insulin formulations can be categorized into five types based on the duration of action and components of the formulations. These can be rapid acting insulins, short acting insulins, intermediate acting insulins, long acting insulins and premixed insulin formulations. Recombinant DNA technology offers the best instrument to alter the amino acid sequence of insulin that results into formation of insulin analog which have slightly better pharmacokinetic properties than insulin. Thus, Insulin analog is the changed form of insulin which exhibit similar glucose lowering effect as the human insulin. Administration of insulin through inhalation route is considered as an alternative to subcutaneous injection of insulin. The delivery of insulin into alveoli is the most promising alternative route of insulin administration. Additionally, Transdermal delivery of insulin constitutes the minimally invasive route of drug administration. It transports insulin through the skin into the blood circulation. It is least paiful in comparison to subcutaneous route of insulin administration. Jet injection is additional transdermal route of insulin adminiteration without the need for needle. This method makes use of jet injector for creating high-speed stream of small amount of insulin that can penetrate through the skin