Insulin is produced by beta cells of the pancreas. It is called anabolic because it promotes synthesis - synthesis of glycogen, protein and triglycerides.

Regulation of insulin secretion in the body :

Glucose - After ingestion of carbohydrate rich diet, there will be increased levels of glucose in the blood. Beta cells sense this increase and release insulin.

Amino acids - Ingestion of protein leads to an increase in aminoacids in the blood. This is also a stimulus for insulin release.

Hormones produced in the intestines (like secretin) - These hormones are released into our blood when we eat food. And these raise the levels of insulin well before the actual glucose increases in the blood.

These factors all increase insulin secretion after eating, while during fasting insulin secretion is inhibited. We need fuel in fasting states, so epinephrine (a stress induced hormone) inhibits insulin secretion and mobilizes glucose from liver and fatty acids from fat stores. These glucose and fatty acids are used as fuel in a starving state.

How insulin acts in the body :

• In muscle and fat, insulin increases glucose uptake by increasing the number of transporters in the cell membrane.
• In the liver, insulin decreases the breakdown of glycogen (glucose storage form) to glucose.
• In the liver, insulin inhibits glucose synthesis.
• In fat stores, insulin inhibits release of fatty acids in to the blood.
• Insulin increases uptake of amino acids by cells leading to protein synthesis.

Types of insulin preparations :

Rapid-acting insulin - Action will be within 20 minutes. Convenient for taking before meals as you don’t have to wait 60 minutes as with regular insulin. But the diabetic patient is instructed to eat carbohydrates first.

Short-acting insulin - Effect occurs with in 30 minutes after subcutaneous injection and lasts for around 6 hours. Used after hyperglycemic episodes and emergencies and insulin changing needs like after a surgery.

Intermediate-acting insulin - Example is Lente insulin. Action starts within 2 hours and extends up to 18 - 24 hours. Two doses per day are needed for this reason. Used for regular daily maintanence of blood sugar.

Long-acting insulin - These actions are prolonged more than 24 hours. Daily dose is used in two divided doses.

Most important thing to follow when using insulins is the careful monitoring of blood glucose at home and recording it in a dairy. Follow your doctor’s instructions carefully regarding when and how much to take. Any deviation from your original healthy state should be shared with your doctor for further checking.