Covid-19 can infect insulin-producing cells in the pancreas and alter their function, potentially explaining why some previously healthy people develop diabetes after catching the virus.
Doctors are increasingly concerned about the growing number of patients who have developed diabetes either while they were infected with the coronavirus or shortly after recovering from it.
Different theories have been put forward to explain this increase. The first is that the virus infects pancreatic cells via the same ACE2 receptor found on the surface of lung cells, and interferes with their ability to produce insulin – a hormone that helps the body regulate blood glucose levels. ; alternatively, an overly exuberant antibody response to the virus could accidentally damage pancreatic cells, or inflammation elsewhere in the body can make tissues less sensitive to insulin.
To investigate, Professor Shuibing Chen of Weill Cornell Medicine in New York City examined various cells and organoids – laboratory-grown clumps of cells that mimic organ function – to identify those that could be infected with Covid. The results suggest that organoids in the lungs, colon, heart, liver and pancreas could all be infected, as could dopamine-producing brain cells.
Other experiments found that the insulin-producing beta cells in the pancreas were also sensitive and that when infected these cells produced less insulin, as well as hormones usually made by different pancreatic cells.
“We call it transdifferentiation,” said Chen, who presented the results at the annual meeting of the European Association for the Study of Diabetes on Wednesday. “They basically change their cell fate, so instead of being hardcore beta cells that secrete a lot of insulin, they start mixing different hormones. This could provide additional information on the pathological mechanisms of Covid-19. “
Scientists have observed a similar phenomenon in some people with type 2 diabetes, although the disease is more strongly associated with body tissues becoming less sensitive to insulin.
It is not yet clear whether the changes triggered by the Covid infection are sustainable. “However, we do know that some patients who had very unstable blood sugar levels when they were in the intensive care unit and recovered from Covid-19, some of them also recovered [glucose control], suggesting that not all patients will be permanent, ”Chen said.
Separate research by Professor Francesco Dotta of the University of Siena in Italy and his colleagues confirmed that Covid attacks pancreatic cells by targeting the angiotensin converting enzyme protein 2 (ACE2) on their surface, and that the cells Beta insulin producers express particularly high levels of this protein.
They also showed that ACE2 levels were increased under inflammatory conditions, which is important because people with type 2 diabetes may already have inflammation in their pancreas. “This means that these insulin-producing beta cells could be even more susceptible to viral infections when inflamed,” Dotta said.
This could imply that people with existing diabetes or prediabetes are at greater risk of pancreatic dysfunction if they catch Covid-19 – something he now plans to investigate. “Diabetic patients in general are not more susceptible to Covid-19 infection in terms of frequency, but once infected they develop more serious complications and a serious metabolic disorder,” Dotta said.
Professor Francesco Rubino, president of metabolic surgery at King’s College London, said: ‘These studies appear to be consistent in supporting a biological rationale for the idea that Covid-19 may increase the risk of developing diabetes in people who are there. are predisposed, or even potentially completely from scratch.
He is co-leading an international effort to establish a global database of diabetes cases linked to Covid-19, to better understand whether the infection can cause a new form of diabetes or trigger a stress response that leads to diabetes. type 1 or type 2.
“Whether such changes are enough to allow this virus to cause diabetes is a question these studies do not answer, but it gives us another reason to believe it is a possibility,” he said. .
However, this may not be the only way the virus increases the risk of diabetes. “At least clinically, one of the things we are seeing is that in some cases, patients who already had type 1 diabetes started expressing severe insulin resistance, which is a typical feature of diabetes. type 2, ”said Rubino. It may involve an issue with how cells elsewhere in the body respond to insulin after infection with Covid-19.
Dr Lucy Chambers, Head of Research Communications at Diabetes UK, said: ‘People with diabetes have been disproportionately affected by Covid-19, and many people with the disease have tragically died as a result. Diabetes is a well-established risk factor for serious illness from Covid-19, and there is new evidence that Covid-19 could trigger new cases of diabetes, but how these two conditions are biologically related is not still well understood.
“This research deepens our understanding of how diabetes and Covid 19 can biologically interact. This will help the development of new, effective ways to treat people at risk for – or living with – diabetes who have Covid-19. Taking the Covid-19 vaccination, including a booster when offered, remains the best form of protection against the virus. “