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How does type 2 diabetes develop?

Scientific support: Dr. Theresia Sarabhai

Type 2 diabetes develops over a long period of time and usually without the person affected noticing any signs of the disease. Scientists are working hard to investigate precisely what leads to type 2 diabetes and how and why. As well as a genetic predisposition, an unhealthy lifestyle with overweight and too little exercise have a role to play.

What increases the risk of type 2 diabetes?

A range of factors makes it more likely for someone to develop type 2 diabetes:

  • High incidence of type 2 diabetes in the family
  • Old age
  • Overweight, high blood pressure and high blood lipid levels (such as cholesterol)
  • Unhealthy lifestyle
    • Smoking
    • Lack of physical exercise
    • A low-fiber and/or high-fat diet
  • Diabetes in pregnancy
  • Drugs that impair glucose metabolism (such as cortisone)
  • Other hormonal diseases (such as polycystic ovary syndrome)

Which processes in the body are impaired by type 2 diabetes?

With type 2 diabetes, insulin does not work properly on the cells of the body. Insulin is an essential hormone in the body. It is developed in the beta cells of the islets of Langerhans of the pancreas. The pancreas is in the upper abdomen behind the stomach.

After a meal, the pancreas excretes insulin into the blood. Insulin ensures that the sugar (or more precisely: glucose) from food passes into the cells of the various organs, for example into the liver, the muscles or the fatty tissue. The glucose helps deliver essential energy into the cells.

In type 2 diabetes, 2 processes of insulin effect are impaired, which causes blood glucose to rise:

  1. Insulin can only have a weak or insufficient effect on the cells of various organs. This means that the cells cannot take in the glucose and it remains in the blood. The medical term for this is insulin resistance.
     
  2. Because the body cells only respond weakly to insulin, the pancreas produces more insulin to lower the blood glucose levels. This strain means that the beta cells in the pancreas become more and more exhausted. They no longer produce enough insulin and so too little insulin enters the bloodstream. This results in an insulin deficiency. Experts also refer to a relative insulin deficiency, because the pancreas is still actually producing enough insulin. The amount is, however, not sufficient for the insulin-resistant cells in the body to absorb the glucose from the blood.

What is prediabetes? The quiet development of type 2 diabetes

Type 2 diabetes develops gradually over a long period of time. Before people develop it, most have had a precursor of type 2 diabetes - prediabetes - for some time beforehand. People with prediabetes often have elevated blood glucose levels. The values are not quite high enough to qualify as diabetes. Experts also call this impaired glucose tolerance or abnormal fasting blood glucose.

Good to know:

The precursor to type 2 diabetes is called prediabetes.

The elevated blood glucose levels put people with prediabetes at a much greater risk of developing type 2 diabetes. People with prediabetes can, however, often still prevent the development of type 2 diabetes with more exercise and weight loss.

Find out more about the diagnosis of type 2 diabetes here!

What exactly is insulin resistance?

Long before people develop type 2 diabetes or prediabetes, they already have insulin resistance. Insulin resistance causes the cells, especially in the muscles, liver, and fatty tissue, to no longer sufficiently respond to the hormone insulin. This means that the insulin can no longer effectively transport glucose from the blood into the cells.

It often takes several years to decades to go from insulin resistance to developing a high glucose level. In this phase, the changes to the functions in glucose metabolism are initially very mild or often imperceptible.

Insulin resistance increases the risk not only of type 2 diabetes but also of high blood pressure, cardiovascular diseases, lipid metabolism disorders and overweight. If someone has all of these, experts refer to this as “metabolic syndrome”.

How does insulin resistance develop?

Genetic predisposition plays an important role in the development of insulin resistance. But there are also certain habits that can make it more likely to develop. Important risk factors are

  • Lack of physical exercise
  • Poor diet and
  • Overweight.

How exactly being overweight and not exercising enough increase insulin resistance is not completely clear. In people with insulin resistance, studies have shown that the fatty tissue cells, especially in the abdominal area, no longer work as they do in people who do not have insulin resistance.

These cells in the fatty tissue absorb too little glucose from and release more fats into the blood. Researchers suspect that there is also a change in the way messenger substances are released from the fatty tissue. These messenger substances enter the body in a kind of inflammatory state, which may also be responsible for the reduced effect of the insulin in the body cells in the muscles, liver and fatty tissue.

Click here for more information on overweight and obesity!

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Sources:

American Diabetes Association: Standards of Medical Care in Diabetes - 2019. In: Diabetes Care, 2019, 42: S1-S193
Bundesärztekammer et al.: Nationale Versorgungsleitlinie Therapie des Typ-2-Diabetes. Langfassung. 1. Auflage. Version 4. 2014 (Gültigkeit abgelaufen, in Überarbeitung)
Bundesärztekammer et al.: Patientenleitlinie zur Nationalen Versorgungsleitlinie Therapie des Typ-2-Diabetes. 1. Auflage. Version 1. 2015
Hanefeld, M. & Pistrosch, F.: Metabolisches Syndrom und Insulinresistenz. In: Gastroenterologe, 2017, 12: 300-304
International Diabetes Federation: The IDF consensus worldwide definition of the metabolic syndrome. 2006 (Letzter Abruf: 15.10.2019)
Landgraf, R. et al.: Therapie des Typ-2-Diabetes. In: Diabetologie, 2018, 13: S144-S165
McCracken, E. et al.: Pathophysiology of the metabolic syndrome. In: Clin Dermatol, 2018, 36: 14-20
As of: 31.10.2019