Why does Covid-19 increase the risk of diabetes in some people?

Recent studies show that coronavirus infection can lead to type 2 diabetes or, more rarely, type 1 diabetes. By what mechanisms? The explanations of Pr Eric Renard, head of the diabetology department at the University Hospital of Montpellier and Dr Joseph Bigirimana , Legal representative of the association  Initiative for the Promotion of Rural Health and Development ( IPROSARUDE )

Scientists have, in recent months, drawn attention to the risk of developing diabetes after an infection with Sars-Cov2.  Published on March 21, 2022, an American study of 200,000 people shows that diabetes is a possible sequela of the infection. Another research study, conducted by a German team and published in the journal Diabetologia on March 16, 2022, compares two groups of patients after their consultation with a general practitioner: the first infected with Covid, the second with a respiratory infection due to a virus other than coronavirus. Results: the risk of type 2 diabetes is increased by 28% in the first group compared to the second.

These results are of concern to the diabetes community. For Pr Eric Renard, vice-president of the French-speaking Society of Diabetes, it is necessary to distinguish two situations: on the one hand the type 2 diabetes occurring without real surprise in predisposed patients, on the other hand the more unexpected cases of type 1 diabetes in children, teenagers or, sometimes, adults.

An increased risk in patients predisposed to type 2 diabetes

The vast majority of diabetes cases that occur after a Covid are “type 2”.

What is type 2 diabetes?

According to Dr. Joseph Bigirimana, Legal Representative of IROSARUDE (Initiative for the Promotion of Rural Health and Development), this disease generally occurs around the age of 50, in overweight and sedentary people, or those with a family history of diabetes. Gradually, their blood sugar level (glycemia) starts to rise. Their bodies are resistant to insulin, the hormone that regulates blood sugar throughout the day. In these people, the beta cells in the pancreas that secrete insulin are not destroyed. They continue to function, but with limits.

This type 2 diabetes evolves without symptoms. Only blood glucose tests can reveal it. The person begins by developing pre-diabetes, characterized by a fasting blood sugar level measured repeatedly between 1 and 1.25 grams per liter (g/l). “It is estimated that currently in Burundi, between 500,000 and 1 million people have pre-diabetes,” says Dr. Joseph Bigirimana. The diagnosis of diabetes is made when this fasting blood glucose level is measured at least twice above 1.26 g/l.

What happens in case of Sars-Cov2 infection?

The virus enters the body, especially the beta cells of the pancreas. This infection triggers an inflammatory reaction which, in turn, induces insulin resistance. As a result, blood sugar levels rise.

In people with a healthy pancreas, insulin secretion will increase to overcome the resistance, and blood glucose levels will remain normal. But in people whose pancreas has limited capacity to adapt, even moderate Covid can lead to type 2 diabetes.

Professor Renard: “Many of the patients concerned were pre-diabetic or were starting diabetes without knowing it. The inflammatory reaction due to the coronavirus infection created insulin resistance in people whose pancreas was already failing.

For Dr. Joseph, in the most severe cases, the inflammatory response is so violent that it causes very high blood sugar levels. The patient must then be put on insulin. Most of the time, this treatment is transient. When the blood sugar is back under control and the infection is cured, the patient returns to the usual management of type 2 diabetes: weight loss, balanced diet, regular physical activity and, if necessary, prescription of medication other than insulin.

On the other hand, according to the same researchers, when inflammation persists for several months, insulin injections must be continued as long as necessary.

More rarely, Covid-19 can reveal type 1 diabetes

In much rarer cases, mainly affecting children, adolescents or young adults, the infection by the coronavirus reveals type 1 diabetes even though these patients had no apparent risk factors.

What is type 1 diabetes?

In this form of the disease, the beta cells of the pancreas are irreversibly destroyed by the body’s own defenses (this is why it is called an autoimmune disease) and no longer produce insulin. In order to control blood sugar, the patient must receive daily insulin injections, either by self-injection or with the help of a pump.

What happens after Sars-cov2 infection?

The mechanism is less clear than for type 2 diabetes after a Covid. Nevertheless, one hypothesis prevails: “The coronavirus would modify the beta cells after having infected them, which could trigger an auto-immune reaction in predisposed subjects. In this case, the patient’s body destroys its own cells because it considers them abnormal,” explains Professor Eric Renard. The only possible treatment is insulin, for life.

Is it necessary to systematically screen for diabetes after a Covid?

There is no need to rush to perform a blood glucose test after an infectious episode. “A Covid alone is not enough to justify blood glucose monitoring,” says Dr. Joseph.

This monitoring is justified, however, in people who have risk factors for diabetes (obesity, overweight, family history …). It is, in any case, recommended even outside the Covid context.

The only real emergency is the appearance of symptoms suggesting diabetes after a Covid, such as very intense thirst or frequent urination. In this case, rapid screening for diabetes is necessary.

Other viruses and stress may be involved

The Covid epidemic has highlighted the links between coronavirus and diabetes. But Sars-Cov2 is not the only virus involved. “There are other diabetogenic viruses such as coxsackie viruses (notably the cause of hand-foot-and-mouth syndrome, editor’s note), rubella viruses and mumps viruses that can induce type 1 diabetes,” says Dr. Joseph Bigirimana.

In many of the more common viral infections, such as influenza, inflammation can also reveal type 2 diabetes, using the same mechanism as with Sars-Cov2.

But this process can also start after a particularly stressful event, such as a car accident or a serious heart problem. “After a heart attack, one third of patients discover that they have diabetes and did not know it. The heart attack induces intense stress that raises blood sugar levels,” explains the diabetologist.

The cases of diabetes that occurred during the Covid-19 pandemic did not surprise diabetologists. “What surprised us was the violence of the inflammatory reaction that triggered a sharp rise in blood sugar levels,” says Professor Eric Renard, head of the diabetology department at Montpellier University Hospital.

It should be recalled that in all the polyclinics of Iprosarude, Polyclinique Espoir of Gitega, Polyclinique Espoir of Kayanza, Mwaro and Makamba, rapid tests for diabetes are available.

                                                                                           E.Allickan Niragira