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| INSULIN THERAPY
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Physiological
Secretion and Functions of Insulin
The body's homeostatic system maintains a uniform blood glucose
level between meal times and fasting periods. Basal insulin secretion
maintains a balance against high blood sugar during the resting
state.
Insulin
Sources
The insulins available for routine clinical use are derived from
three sources beef, pork and human (recombinant).
Types
of Insulin
The insulins available now are the "pure" varieties
and contain negligible risks of immunogenicity. These are of four
types - beef, porcine, mixed and human insulin
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Beef insulin differs from human insulin in three amino acids,
namely A8, A 10 and B 30.
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Porcine insulin differs from human insulin in only one amino
acid i.e. B30 position. Thus, porcine insulin is less immunogenic
than beef insulin.
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Mixed insulin contains a mixture of bovine and porcine insulin
and it is more antigenic than single species
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Human insulin is pure and has the same amino acid structure
as that of native insulin. They are made by genetic engineering
or by transformation from porcine insulin by substituting alanine
with threonine in the B30 position.
Classification
and Types of Insulin
In a normal person without diabetes, insulin is secreted throughout
the day and thus there is a basal level and peaks of insulin secretion
are seen following meals when the blood glucose rises (Fig 2).
Fig 2: Physiological Secretion of Insulin.
Last
updated on 13-12-2002
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