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In this post we have to learn all about the Insulin for academic and medical competitive examination point of view.

Insulin-Sugar Love Story

Insulin is a polypeptide or protein hormone synthesizes and secretes by the beta cells of the pancreas and released directly into the bloodstream.

Insulin hormone controls the Levels of blood glucose or sugar in the body.

You must have probably heard this word that a some one person suffers from sugar or someone is suffering from diabetes.

You are frequently heard that don’t take too much sweet otherwise you face sugar issues.

But all these things depend on the imbalance in the body due to the defective sugar metabolism.

This is because of the same hormone which we called insulin.

Today in this post we will discuss in briefly about the insulin hormone.

Pancreas-Mixed Gland

The cells that make insulin hormone are present in the pancreas.

Pancreas is the mixed or heterocrine gland.it means Pancreas work both as Endocrine and Exocrine gland.

Pancreatic exocrine part is called pancreatic acini. The Acinar cells synthesized & secrete pancreatic Enzymes and the endocrine part secretes many important hormones.

The Endocrine part of Pancreas contains groups of cells called Islets of Langerhans.

The Islets of Langerhans are the endocrine part of the pancreas that Synthesized and secretes hormones.

This group of cells was first discovered by a Langerhans. Hence it is called Islets of Langerhans.

However, most of the portions of pancreas is exocrine in function and is called pancreatic acini.

This part manufactures and secretes pancreatic enzymes.

While only a small part of the pancreas functions as an endocrine, it is called the islets of Langerhans.

The cells found here and some of the hormones released from them are as follows.

• Alpha cells Synthesized and secretes Glucagon hormone.
• Beta cells Synthesized and secretes hormone Insulin.
• Delta cells secrete hormone Somatostatin.
• PP (pancreatic polypeptide) cells synthesized and secretes Pancreatic Polypeptide.

What is Insulin?

It is a polypeptide or protein hormone made up of two polypeptide chains.

One chain is called alpha or A-polypeptide chain and the other peptide chain is called beta or B-polypeptide chain.

Fully matured and finished insulin contains 51 amino acids. Out of which 21 amino acids are present in alpha or A-polypeptide chain, the remaining 30 amino acids are present in beta or B-polypeptide chain.

Hence the beta or B-polypeptide chain is longer. Both the polypeptide chains are linked by disulfide bonds.

Disulfide bonds are formed between two Cysteine ​​amino acids (amino acids containing sulfur).

If we look the structure of insulin hormone, there are three disulfides is present, although the initial insulin that is made and released is non functional and immature called Proinsulin.

In Proinsulin an additional C-polypeptide chain is present, but this chain is removed when insulin is processed.

Genes that make Insulin

Insulin is made by beta cells of the pancreas and the gene present on chromosome number 11 of these cells.

Here you will be surprised to know, the genes that make insulin are present in every cell of the body except RBC.

But no cell of the body is able to make insulin; this question will surely come in the mind, why?  Why only beta cells of the pancreas are able to synthesize insulin?

All cells will have a nucleus and 23 pairs of chromosomes are present in that nucleus, then the 11th chromosome will also be there. Then why other cells not able to produce insulin hormone.

Leave this question as the same question, you will understand in detail in some other post or if you know then comment us.

Functions of insulin

Insulin controls the amount of blood sugar in our body.

Whenever we eat carbohydrate or glucose-rich food, beta cells start secreting insulin into the blood.

Insulin increases the absorption of glucose into the cells of the body, thereby controlling the amount of sugar in the blood.

If seen in normal condition, empty stomach means fasting plasma glucose in the blood is 70-100dl in the blood and 100-140dl after two hours of meals.

If there is too much change in the amount of sugar given above, then there may be a risk of diabetes.

Insulin enhances the absorption and utilization of glucose mainly in the adipose tissue cells or adipocytes of the liver cells or hepatocytes.

Insulin also stimulates glycogenesis (the conversion of glucose into glycogen) in hepatocytes and muscle cells.  Apart from this, it also controls Lipogenesis.

In this way, insulin is also called hypoglycemic factor or factor, which maintains the homeostasis of glucose in the blood.

Mode of working of Insulin

Because insulin increases the absorption of glucose in liver cells and muscle cells.

Therefore, its target cells are also the same. Receptors for insulin are present in these cells, and insulin binds to these receptors.

These receptors are called GLUT-4 (glucose transporter).

These receptors are present on the plasma membrane of these cells, and are chemically made of proteins.

When insulin binds to these receptors, the plasma membrane of these cells changes to make them more permeable to glucose.

Due to which the glucose present in the blood enters them rapidly, as a result the amount of glucose in the blood remains under control.

Receptors for insulin are also present in other cells of the body that have different names.

Deficiency of Insulin

When there is a lack of insulin hormone in the body or the cells of the body do not show any sensitivity to insulin, then the amount of glucose in the blood increases.

When this condition persists for a long time, the chances of developing diabetes or diabetes increases.

The amount of sugar in the blood of such a person becomes more than normal.  So they have to buy insulin from outside.

You can read more information about diabetes by clicking here.

Genetically Engineered Insulin 

Initially, the insulin given to diabetic patients was insulin derived from other animals.

Since it showed allergic or other side effects after entering the body of patients due to lack of human insulin.

So insulin was made inside bacteria, similar to man-made insulin.

Artificial insulin is also called recombinant insulin.  Which was first created by Biotechnology or Genetic Engineering methodology?

This work was first time done by an American company Eli-Lilly in 1983. The insulin-producing genes were first isolated from beta cells.  It was then cloned with the help of a vector.

After this, the genes are introduced in E. coli bacteria with the help of plasmid vector. Where these genes became active and started coding for insulin and the production of insulin started.

This insulin was named Recombinant Insulin or Humulin.

We will discuss this in detail in a series of posts on Biotechnology or Genetic Engineering.

In today’s time, insulin of many pharmaceutical companies is available in the market. Which should be used only after consulting a doctor?

Conclusion

Overall we can say that insulin hormone controls the metabolism of glucose or carbohydrates.

This is the short discussion about the Insulin hormone. Hope you have to understand basic knowledge about this important hormone.

If any suggestion or updating require from your side please comment us.

Thanks for reading the Post.