2. Let’s look at,
Sources of insulin
Actions of insulin
Uses
Preparations of insulin
Insulin regimens
Injection technique
Adverse effects
3. Sources of Insulin
Synthesised & stored in granules in the beta islet cells of the pancreas.
Daily secretion is about 25% of total pancreatic insulin content.
Principal factor evoking insulin secretion is high blood glucose
concentration.
Insulin is a polypeptide with 2 chains.
Insulin receptors are present on the surface of target cells such as liver,
muscle & fat.
4. Actions of insulin
Reduction in blood glucose by increased glucose uptake in peripheral
tissues (oxidise glucose or convert into glycogen or fat)
Reduction in hepatic output of glucose (diminished breakdown/increased
synthesis of glycogen & diminish gluconeogenesis)
Other metabolic effects : anabolic hormone enhancing protein synthesis,
inhibits both breakdown of fat (lipolysis) & ketogenesis.
Stimulate potassium uptake into cells & renal sodium retention. (anti
natriureteric)
May have actions to stimulate memory & act as a nutritional signal to help
control appetite/food intake.
5. Uses
Diabetes mellitus is the main indication.
Hyperkalaemia – promotes the passage of potassium into cells by
stimulating cell surface Na/K ATPase action.
Insulin induced hypoglycaemia can be used as a stress test of anterior
pituitary function. (growth hormone & corticotropin)
6. Preparations of Insulin
Short duration of action
Intermediate duration of action
Longer duration of action
A biphasic mixture
7. Short acting insulin
Soluble insulin (neutral or regular insulin)
Recent additions – lispro, aspart & glulisine modified human insulins
with changes in the beta chain resulting in more rapid absorption after
subcutaneous injection.
8. Intermediate acting insulin
Modified physically by combination with protamine or zinc
Given subcutaneously & slowly dissociate to release insulin in it’s soluble
form
Isophane (NPH) insulin is widely used
9. Long acting insulin
Newer analogues glargine & determir, widely used especially in type 1
diabetes
Small changes in the amino acid structure of glargine result in a significant
slowing of absorption from subcutaneous depots
After absorption determir is bound to albumin which delays it’s action
13. Insulin regimens
Basal bolus therapy : multiple injections of short acting insulin are given during the
day to mimic prandial secretion of insulin by the pancreas, combined with once or
twice daily intermediate or long acting insulin to provide the background insulin. This
approach aims to mimic the non diabetic pattern of insulin release.
Twice daily therapy : involves 2 injections of biphasic insulin. Simpler with fewer
insulin injections. Most commonly used is 30:70 (soluble:NPH). Typically half to 2/3 of
the daily dose may be given in the morning before breakfast & half to 1/3 before
evening meal.
Background or prandial insulin alone : sufficient in type 2 diabetes patients when
progress from oral therapy to insulin. Here, oral therapy is usually combined with
insulin.
