What is insulin and how does insulin work?
Insulin is a hormone that is produced in the pancreas. The medical name of the pancreas is pancreas. The name insulin comes from the Latin insula which means island. The cells that make insulin are called beta cells and these cells are located in the islets of Langerhans (in the pancreas). The pancreas contains many such islands, and in these islands there are the beta cells that make the hormone. The following picture shows the pancreas, the islets of Langerhans and the beta cells.
Thus, insulin is a hormone made by the beta cells of the pancreas. These beta cells are located in the Langerhans Islands. The hormone has many functions in the body and the most important functions are as follows:
- Insulin regulates our turnover of sugar (glucose) and other carbohydrates
- Insulin affects our turnover of Fat
- Insulin affects our turnover of protein
This text is aimed at those who have diabetes, overweight or obesity. People with type 2 diabetes often need (but far from always) insulin syringes to regulate their blood sugar (glucose). This has two explanations:
- Type 2 diabetes is due to the inferior effect of insulin in the body, and more insulin is needed to regulate the circulation of sugar, fat and protein.
- Type 2 diabetes gradually leads to the failure of beta cells and thus make less insulin. Then you need to inject insulin via syringes.
For type 1 diabetes, the situation is different. People with type 1 diabetes do not have functioning beta cells and therefore do not have their own production of the hormone. Therefore, all people with type 1 diabetes must supply insulin via syringes in order to survive.
In this chapter, we will review what effects insulin has in your body and how this affects your health. We will also discuss when and why insulin should be administered via syringes, and how this should be handled.
How and when insulin is released in the body
Insulin is thus released from the beta cells of the pancreas. These cells release the hormone to the blood in the following situations:
- When blood sugar rises (sugar, namely, stimulates the beta cells so that they release the hormone).
- When the level of amino acids (protein) increases in the blood.
- When the level of certain hormones (especially GLP-1 and GIP) increases in the blood. These hormones are called “incretins”.
When you eat food, all three of these happen at the same time! Food often contains a lot of carbohydrates, in all its forms (glucose, fruit sugar, milk sugar, malt sugar, starch, etc.). All carbohydrates (except fiber) turn into glucose (glucose) in the body! Food also contains proteins and when the proteins enter the intestine, they break down into amino acids that the intestine takes up. These amino acids also get into the blood and can stimulate beta cells to release insulin. Last but not least, GLP-1 and GIP are released when from the small intestine when we eat food. GLP-1 and GIP strongly stimulate beta cells, which leads to the release of insulin.
Abstract: beta cells release the hormone to the blood when we eat food. The more carbohydrates you eat, the more they are released into the blood.
Effects of insulin in the body
Insulin affects many organs and cells. Most clearly, the effect of the hormone on the metabolism of carbohydrates (sugar, blood sugar), fat and protein. Let’s look at these effects in detail.
Effect of insulin on carbohydrates (sugar)
- Insulin stimulates the organs (especially the liver, fat and muscles) to absorb sugar (glucose) from the blood. This reduces blood sugar and tissues can use glucose as a fuel.
- Insulin affects the liver so that it stops producing glucose (sugar) and continues to store glucose in the form of glycogen (glycogen is a storage form for glucose in the body). Insulin ensures that the liver does not release glucose (sugar) to the blood and, in addition, stores more glucose in the form of glycogen.
- In muscles, the hormone leads to the fact that the muscles absorb glucose and store the excess in the form of glycogen.
Abstract: insulin causes the cells of the body to take up sugar and use it as a fuel. In addition, in the liver and muscles, glucose (sugar) can be stored in the form of glycogen.
Effect of insulin on fat (lipids)
- Insulin reduces the breakdown of fat in adipose tissue. This means that when we eat food, insulin is released which prevents the breakdown of fat.
- Instead, insulin stimulates fat tissue to produce more fat (triglycerides). Part of the new fat comes from the fat content of the food, and the rest comes from the fact that sugar can be converted into fat inside the fat tissue.
Abstract: Insulin causes us to make and store more fat.
Effect of insulin on protein
Insulin leads to the fact that most cells absorb amino acids used to manufacture proteins.
Insulin on acts mainly fat, liver and muscle. Insulin causes blood sugar to fall because these three tissues take up sugar (glucose) from the blood when stimulated by insulin. Insulin makes the liver less sugar and instead stores sugar. Insulin affects the fat tissue so that the breakdown of fat decreases and instead increases the production and storage of fat. In muscles, insulin leads to increased absorption of sugar and, in addition, sugar can be stored (like glycogen).
Insulin is therefore a hormone that leads to the body getting ready. Sugar is absorbed, and excess sugar is stored in the form of glycogen. Amino acids are absorbed and used to produce proteins. Likewise increases the production and storage of fat. Hormones with such effects are called anabolic hormones, which are aimed at the body “equipping itself”.
What happens between meals, or during fasting? Between meals and during fasting, the level of insulin in the blood drops and this makes all these processes go in the other direction. In other words, the following happens:
- This leads to the liver breaking down glycogen to glucose (sugar) and this glucose is sent out to the body. In this way, we can continue to have a normal blood sugar even in fasting and between meals.
- Fat tissue stops producing fat.
- The fat tissue instead begins to break down fat, which can then be used as fuel in the body.
- In the liver and kidneys, fatty acids (which come from the breakdown of fat) and amino acids (such as comes from the breakdown of protein) used to manufacture new sugar (glucose).
Between meals and wonder fasting, the level of insulin in the blood drops. This leads to the liver breaking down glycogen to glucose (sugar) and this glucose is sent out to the body. The fat tissue stops producing fat and instead begins to break down fat, which can then be used as fuel in the body.
It means that low levels of insulin lead to the breakdown of fat and also the breakdown of protein. This always occurs during fasting and between meals. The hormone glucagon is very important for our metabolism during fasting (between meals).
What is glucagon and what effects does that hormone have?
In the island of Langerhans there are also alpha-cells that produce glucagon. This happens when blood sugar drops and glucagon has exactly opposite effects to insulin. This means that glucagon leads to an increase in blood sugar through the production of new sugar and the breakdown of glycogen.
Glucagon is a hormone released by alpha cells, which are also found in the islets of Langerhans! Alpha cells release glucagon when blood sugar drops, that is, between meals and during fasting. Glucagon has opposite effects to insulin. This means that glucagon raises blood sugar! With the help of glucagon we can therefore continue to have normal blood sugar even during fasting and between meals.
Thus, in the body there is a balance between insulin and glucagon. When we eat food, the level of insulin in the blood increases. Between meals and during fasting, the level of insulin drops and instead glucagon in the blood increases.
Type 1 diabetes: lack of insulin
In type 1 diabetes, something extremely unfortunate occurs. The body’s immune system attacks the beta cells and destroys them. Today, no one knows why this is happening, but we know with great certainty that it is the immune system that attacks and kills the beta cells. Once the beta cells have died, there is no longer any production of insulin and this leads to very seriously ill and death within one or a few weeks unless you add insulin from outside. People with type 1 diabetes are therefore completely dependent on administering insulin using insulin pens. Type 1 diabetes is therefore an autoimmune disease, which means that the disease is caused by the immune system attacking the body’s own cells.
Type 2 diabetes: reduced effect of insulin
People with type 2 diabetes initially have fully functioning beta cells that can make insulin. The problem in type 2 diabetes is that the body responds less to insulin. This means that fat, muscles and the liver do not react as strongly to insulin and therefore insulin has a lesser effect. This is called insulin resistance. The pancreas tries to compensate for this by making even more insulin. This means that people with type 2 diabetes often have high levels of the hormone in the blood. Unfortunately, the situation usually gets worse and insulin resistance increases to the point that blood sugar begins to rise. The pancreas tries to compensate, but it does not succeed. In addition, after a few years, the function of beta cells is deteriorating and may eventually become so exhausted that they stop producing insulin.
People with type 2 diabetes usually do not need insulin at the beginning of the disease. However, after a few years, insulin may become topical. You can see that if your blood sugar rises even though you do your treatment. This is a sign that its own production of insulin is beginning to subside.
How is insulin produced in the form of medicines?
Insulin has been produced since 1921, when it was learned to extract insulin from the pancreas in dogs, pigs and cows. That way you could save the lives of people with type 1 diabetes. The explanation for taking the hormone from animals and giving to humans is simple: human and animal insulin is very similar. Unfortunately, two tons of pigs are required to make 300 grams of insulin. In addition, the effect of the hormone from animals tends to subside over time and this is because the human immune system detects that insulin is not “real” and therefore interprets it as foreign. The immune system can attack insulin from other animal species and this makes the insulin worse and worse.
In the 1980s, the big breakthrough came. A technique was developed which allowed the insertion of the human insulin gene (the gene describing how to make insulin) into bacteria. This means that the human gene for insulin was pasted into the bacteria’s DNA and it was then able to stimulate the bacteria to produce human insulin. This was done the first time with the bacterium E. coli. You can then start with a single bacterium that has the insulin in it and get that bacterium to split over and over again. Every two hours the number of bacteria doubles and it won’t be long before you have a whole basin of insulin-producing E. coli. So the hormone is manufactured today.
Insulin analogues: modified versions of insulin
It was not long before scientists came to the conclusion that they would modify the human insulin gene so that the insulin acquired new properties. The gene for insulin is actually a code that describes what insulin should look like (insulin is a protein). You can modify that code and it changes the properties of insulin. Researchers have experimented tremendously with this over the years and thus created insulin analogues, which are modified versions of insulin. Insulin analogues may have a faster or slower effect than normal human insulin. These modifications allow people with diabetes to receive several types of insulin, which facilitates the management of blood sugar.