Insulin and its Mechanism

Insulin

Insulin is a hormone that makes our body's cells absorbs glucose from the blood.  Glucose is stored in the liver and muscle as glycogen and stops the body from using fat as a source of energy.

When there is very little insulin in the blood or none at all, then glucose is not taken up by most body cells. When this happens our body uses fat as a source of energy. Insulin is also a control signal to other body systems, such as amino acid uptake by body cell. Insulin is not identical in all animals their levels of strength vary.

Porcine insulin that found from pig, is the most similar to human insulin. Humans can receive animal insulin. Though  genetic engineering has allowed us to synthetically produce 'human' insulin.

Background

Insulin has been available since 1925. It was initially extracted from beef and pork pancreases. In early 1980’s, technology became available to produce human insulin synthetically. Synthetic human insulin has replaced beef and pork insulin in the US. And now, insulin analogs are replacing human insulin.

Insulin chemistry and etymology

Insulin is a protein chain or peptide hormone. There are 51 amino acids in an insulin molecule.  It has a molecular weight of 5808 Da.

Insulin is produced in the islets of Langerhans in the pancreas.  The name insulin comes from the Latin ''insula'' for "island" from the cells that produce the hormone in the pancreas.

Insulin's structure varies slightly between species of animal. Porcine (from pigs) and bovine (from cows) both insulin are similar to human insulin but porcine insulin resembles human insulin more closely.

Insulin Basics

• There are different types of insulin depending on how quickly they work , when they peak and how long they last.
• Insulin is available in different strength, the most common is U-100.
• All insulin available in the United States is manufactured in a laboratory,  but animal insulin can still be imported for personal use.

Inside the pancreas, Beta cells make the hormone insulin.  With each meal, beta cells release insulin to help the body use or store the blood glucose it gets from food.

In people with type 1 diabetes, pancreas no longer makes insulin. Beta cells have been destroyed and they need insulin shots to use glucose from meals.

People with type 2 diabetes make insulin, though their bodies don't respond well to it. People with type 2 diabetes need diabetes pills or insulin shots to help their bodies use glucose for energy.

Insulin cannot be taken as a pill because it would be broken down during digestion just like the protein in food. This must be injected into the fat under the skin for it to get into blood.

 

Characteristics of Insulin

Insulin has 3 characteristics-

• Onset is the length of time before insulin reaches the bloodstream and begins lowering blood glucose.
• Peaktime is the time during which insulin is at maximum strength in terms of lowering blood glucose.
• Duration is how long insulin continues to lower blood glucose.
• Concentration-Insulins sold in the U.S. have a concentration of 100 units per ml or U100. And in other countries, some additional concentrations are available.
• Route of delivery-whether they are injected under the skin or given intravenously.

Reason for  prescribing insulin 

Insulin injection is used to control blood sugar in people who have type 1 diabetes (condition in which the body does not make insulin and therefore cannot control the amount of sugar in the blood) or in people who have type 2 diabetes (condition in which the blood sugar is too high because the body does not produce or use insulin normally) that cannot be controlled with oral medications alone. Insulin injection is in a class of medications called hormone. Insulin injection is used to take the place of insulin that is normally produced by the body. This works by helping move sugar from the blood into other body tissues where it is used for energy. It stops the liver from producing more sugar. All types of insulin that are available work in this way. 

Mechanism of action

Insulin is a naturally occurring hormone secreted by the pancreas. It is required by the cells of the body in order for them to remove and use glucose from the blood. The cells produce the energy from glucose that they need to carry out their functions. Patient with diabetes mellitus has a reduced ability to take up and use glucose from the blood and therefore the glucose level in the blood rise. In case of type 1 diabetes, the pancreas cannot produce enough insulin. So, insulin therapy is needed. In case of type 2 diabetes, patients produce insulin, though cells throughout the body do not respond normally to the insulin. It may be used in type 2 diabetes to overcome the resistance of the cells to insulin. By increasing the uptake of glucose by cells and reducing the concentration of glucose in the blood, it prevents or reduces the long-term complications of diabetes, damage to the blood vessels, eyes, kidneys, and nerve. Insulin is administered by injection under the skin (subcutaneously). Subcutaneous tissue of the abdomen is preferred because absorption of the insulin is more consistent from this location than subcutaneous tissues in other locations.

Insulin has several broad actions including:

• It causes the cells in the liver, muscle, and fat tissue to take up glucose from blood and convert it to glycogen that can be stored in the liver and muscle.
• Insulin also prevents the utilization of fat as an energy source. Absence of insulin or in conditions where insulin is low glucose is not taken up by body cell and the body begins to use fat as an energy source.
• Insulin also controls other body systems and regulates the amino acid uptake by body cell.
• It has several other anabolic effects throughout the body.

 

Action of Insulin in different parts of body