Basics of blood sugar regulation

The body has a complicated system to keep the sugar (glucose) in the body at a constant level. This is necessary to provide the cells with a sufficient supply of energy. However, the glucose level in the blood should not be too high, as this can lead to vascular damage and metabolic imbalances. The body regulates sugar levels mainly with the help of two hormones that are released in the pancreas.

‍

Insulin

Insulin is released from the pancreas after carbohydrate-rich meals and ensures that glucose is absorbed into the cells. This makes it available to the cells for energy production. The hormone also has an anabolic effect. This means that the body stores excess energy in the form of larger molecules such as proteins/fat/glycogen. This means that alternative energy sources are available in the event of a sugar deficiency. Insulin is produced in the beta cells of the pancreas and released into the blood from there.

‍

Glucagon

Glucagon is the antagonist of insulin and ensures the release of sugar from the stores (especially from the glycogen in the liver). This happens, for example, when you are hungry. Glycogen can be imagined as a chain of sugar molecules strung together. When sugar is needed for energy production, the sugar molecules can be split off and released into the blood. The blood carries the sugar to where it is needed, e.g. to the brain or the muscles.

In diabetes mellitus, either the production of insulin (type 1) or its effect on the target cells (type 2) is defective. As a result, the glucose concentration in the blood cannot be properly regulated. Complications of impaired glucose concentration include nerve damage, kidney damage, retinal damage and arterial occlusive disease.

‍

But what does all this have to do with COVID-19?

‍

‍

Interactions between diabetes and Long Covid

Existing diabetes can influence the course of a Covid-19 infection. At the same time, a Covid-19 disease can influence and trigger diabetes:

‍

Covid-19 in diabetes: a risk factor for severe progression

In Germany, there are around 372,000 patients with type 2 diabetes and around 11,000,000 patients with type 1 diabetes. These patient groups are particularly at risk of Covid-19 disease:

Data sets from England, Scotland and Sweden have shown that the risk of severe courses is increased. The risk of intensive care treatment and the risk of death is around two to four times higher in type 1 diabetics and two to five times higher in type 2 diabetics than in comparable patients without diabetes. In type 2 diabetics, the risk increases particularly in younger patients, while in type 1 diabetics the risk increases with increasing age and progression of the disease. This risk is particularly increased in patients with elevated HbA1c levels, obesity, a history of blood glucose derailment, poorer kidney function and microvascular and macrovascular damage [1]. According to Prof. Naveed Sattar from the University of Glasgow, diabetes is “a far greater risk factor for the progression of Covid-19 disease than cardiovascular disease.”

In addition to vaccination protection, it is important to follow an optimal diabetes therapy. This also includes lifestyle measures such as sufficient exercise and a healthy and balanced diet. In the acute case of an infection, rapid normalization of hyperglycaemia offers protection against severe courses.

‍

Diabetes caused by Covid-19: An overview

Some research results suggest that Covid-19 disease can cause diabetes. We present some of these studies here.

‍

SARS-CoV-2 in the human organism

A group of researchers at Stanford University has taken pancreatic samples from deceased Covid-19 patients and examined them. Coronaviruses were detected in the beta cells of the pancreas. Coronaviruses normally enter the cells via the so-called ACE-2 receptor. This receptor is mainly present in the lungs. In contrast, it is rarely found in pancreatic cells. However, pancreatic cells do express neuropilin-1 on their surface. In the next step, the researchers attempted to simulate the infection of the beta cells in the laboratory. They found that the cells produced significantly less insulin under the influence of coronaviruses and some of them died. Observations that can also be made in type 1 diabetes mellitus. If neuropilin-1 is blocked, the viruses are less able to penetrate the cells [2].

Researchers at the University of Ulm were also able to achieve similar results. They were able to detect coronaviruses in the pancreatic cells of four autopsied patients, even when virus particles were no longer detectable in the lungs. Viruses were also detected in other areas of the pancreas that are relevant for digestion. The effects of this are still unclear. However, the strong immune reaction that can accompany a corona infection may also derail an already impaired metabolism.In some patients, the damage to the pancreatic cells can still be detected months after the infection. The extent to which this impairment persists in the long term or whether patients can fully recover has not yet been clarified [3].

‍

‍

Covid-19 and increased risk of type 2 diabetes

‍A study from St. Louis, USA, examined the incidence of type 2 diabetes mellitus in 181.280 patients who had experienced a Covid-19 infection and were alive 30 days after the positive test result. A distinction was also made according to the severity of the course (non-hospitalized, hospitalized, treated in the intensive care unit).

The Covid-19 group was compared with a control group of around 4 million patients. This showed a 40% increase in the risk of type 2 diabetes mellitus in the COVID-19 group. If the results are broken down according to the severity of the Covid-19 course, the diabetes risk is linked to the respective course. Non-hospitalized patients had an approx. 1.2-fold risk, hospitalized patients had an approx. 2.6-fold risk and patients treated with intensive care had an approx. 3.6-fold risk compared to the control group [4].

‍

A meta-analysis of studies with around 3.700 patients, i.e. a comprehensive analysis of many individual studies, showed that 14.4% of the patients examined and hospitalized with Covid-19 developed diabetes mellitus after the illness [5].

However, there were confounding factors in the data collection that could distort the results of the study: An inactive lifestyle with little exercise/sport is one of the most important risk factors for developing type 2 diabetes mellitus. During the pandemic, many people have been forced to live a more inactive lifestyle. Working from home, closed sports facilities and few opportunities to exercise could also explain an increase in diabetes cases after Covid.

The study from St. Louis examined US veterans. These were mostly older, white men who often had high blood pressure or were overweight. These factors generally increase the risk of diabetes. The average age of the population is significantly lower.

It is also possible that the people in the control group have also been infected with Covid-19 without realizing it, thus distorting the evaluation.

It should also be noted that some of the Covid-19 patients were treated with glucocorticoids, which can also have a diabolic effect. This means that the blood glucose level rises when glucocorticoids (e.g. cortisone) are administered. The medication could therefore also be a reason for the increased risk of diabetes in Covid-19 patients.

‍