Diabetes mellitus is a chronic metabolic disease characterized by high levels of glucose (sugar) in the blood. Known as the silent killer, it is increasing at an alarming rate worldwide. In the US it is estimated that it affects more than 34 million citizens, while almost 1.5 million new cases of diabetes are recorded each year, a number that is shocking and alarming.

In our country it concerns 10-12% of the general population, translating into the alarming number of 1-1.2 million of our fellow citizens. If we add people with prediabetes, then the numbers jump to close to 2 million. In simple numbers, in every family of five over the age of 45, at least one person suffers from diabetes.

“But the worst thing is that a large number of people with pre-diabetes do not know it, since diabetes mellitus for a whole decade from its onset may not manifest any serious symptoms to be diagnosed in time”, emphasizes Mr. Antonios Lepouras MDSpecialist Pathologist-Diabetologist Director of Pathology-Diabetology Clinic & Diabetes Center Metropolitan General.

“Diabetes not only affects the heart, kidneys and brain, but also has a prolonged and devastating effect on the immune system. Uncontrolled, long-term diabetes weakens the immune system and increases susceptibility to disease and infection.

It is also proven with the recent experience from COVID-19, that both good sugar regulation (euglycemia), and above all good regulation in the first days of the infection, play a very important role in the favorable outcome of the disease.

A weakened immune system makes infections dangerous for people with diabetes, and unfortunately the slightest infection affects them adversely, increasing hospitalization-mortality rates and prolonging recovery time”, points out the diabetologist who lists the ways in which the diabetes has a negative effect on the immune system.

The 5 mechanisms by which diabetes affects the immune system and leads to immunosuppression:

1. Diabetes mellitus reduces the ability of the defense mechanism and white blood cells to reach the site of infection sufficiently.

Diabetes is known to increase the risk of atherosclerosis – a disease in which inflammation within the blood vessels and arteries creates lesions known as “atherosclerotic plaque” – which in turn leads to hardening and narrowing of the blood vessels, which significantly affects the body’s defense ability and white blood cells (the cells that fight germs and viruses) to reach the site of infection in time and stay there. This leads to a delayed, anti-inflammatory response, reduced wound healing and increased vulnerability to subsequent infections.

2. Chronic hyperglycemia (elevated blood sugar) slows the diffusion of blood through blood vessels increasing the risk of complications from injuries.

Due to the pathological thickening of the blood vessel wall, a decrease in blood flow is observed at the site of the injury. Less blood flow then results in less nutrients, defenses and other healthy cells reaching the site of injury and initiating a repair mechanism.
This delays wound healing and allows bacteria to easily enter the body and cause infection. The skin, which is nourished by small capillaries and is a key factor in providing innate immunity, is no longer capable enough to provide protection against infections, resulting in infections and inflammation.

3. High glucose levels limit and dysregulate the synthesis of defensive white neutrophil cells.

Neutrophils are cells of the immune system that play an important role in mediating the host’s immune response to bacterial infections. They are the first white blood cells to arrive at the infected area and fight the infection. But high glucose levels limit and dysregulate the synthesis of neutrophils in the body.
Uncontrolled diabetes impairs the production and maturation of neutrophils in the bone marrow, leading to a decrease in the number of neutrophils in the blood. High blood sugar also inhibits the ability of white blood cells to mobilize and reach the site of infection adequately and in a timely manner.

4. Diabetes mellitus leads to a reduced response of complement, an important factor in the body’s defense mechanism.

The complement system is an integral part of the immune system. It enhances the ability of antibodies and phagocytic cells to fight disease-causing germs and viruses and eliminate them from our body. However, hyperglycemia or high blood sugar causes defects in the complement receptors and impairs their ability to induce phagocytosis.
This disruption of phagocytosis, in turn, leads to increased microbial activity in the body and enhances susceptibility to infections.

5. High blood sugar provides bacteria with the perfect environment to thrive and grow.

Hyperglycemia promotes the production of AGEs in the body, which interfere with the body’s natural defense mechanism and limit its ability to fight infection and inflammation.

The weakened defense mechanism makes room for more serious bacterial and viral infections, when they find a portal of entry into the body (eg injuries – wounds, respiratory system – infections, digestive system with gastroenteritis, genitourinary, etc.). Also, increased sugar promotes the use of fat for energy resulting in increased levels of “ketone” bodies, which lead to increased acidity in the blood creating the perfect environment for microbes to thrive unchecked.

What can be done to strengthen immunity?

“For people with diabetes, the best way to stay protected is to:

Euglycemia: That is, controlling their blood sugar levels and keeping them well within the limits. It is the easiest way together with a Mediterranean healthy and balanced diet and good physical condition (fitness) to prevent problems.

Quitting smoking: Equally important and necessary.

Pay attention to the weight: Obesity, or excess body weight, puts you at high risk for insulin resistance and uncontrolled diabetes while damaging the immune system, increasing the risk of more severe inflammation and worsening infections and other chronic conditions. Recent experience with COVID-19 showed that obese individuals had the highest risk of complications and mortality, even in the absence of diabetes mellitus.

Excercise: Regular physical activity helps the body to use insulin effectively, helping to reduce blood sugar levels, while at the same time significantly improving the immune system and mental well-being,” concludes Mr. Lepouras.