Researchers have discovered that the coronavirus infects both adipose cells and certain immune cells within body fat.
Since the beginning of the pandemic, the coronavirus seemed to be targeting people with extra kilos. Overweight or obese patients were more likely to develop severe COVID-19 and were more likely to die.
Although these patients often have health problems such as diabetes that increase their risk, scientists are increasingly convinced that their vulnerability is related to obesity itself.
Now researchers have discovered that the coronavirus infects both fat cells and certain immune cells within body fat, causing a damaging defensive response in the body.
“The bottom line is, ‘Oh my gosh, indeed, the virus can directly infect fat cells,'” said Philipp Scherer, a scientist who studies fat cells at UT Southwestern Medical Center in Dallas, who was not involved in the research.
“What happens in fat does not stay in fat,” he added. “It also affects the surrounding tissues.”
The research has not yet been peer-reviewed or published in a scientific journal, but it was published online in October. If the results hold up, they could not only why overweight patients are vulnerable to the virus, but also why some young adults with no other risks get so sick.
The study authors suggested that the evidence could point to new COVID-19 treatments targeting body fat.
“Maybe that’s the Achilles heel that the virus uses to evade our protective immune responses, hiding in this place,” said Vishwa Deep Dixit, professor of comparative medicine and immunology at Yale School of Medicine.
The finding is especially relevant for the United States, which has one of the highest obesity rates in the world. Most American adults are overweight, and 42 percent are obese. Blacks, Hispanics, American Indians, and Alaska Natives have higher obesity rates than white adults and Asian Americans; They have also been disproportionately affected by the pandemic, with death rates nearly double those of white Americans.
“This may be contributing to a serious illness,” said Catherine Blish, a professor at Stanford University Medical Center and one of the report’s two lead authors. “We are seeing the same inflammatory cytokines present in the blood of very ill patients being produced in response to the infection of those issues.”
Before it was thought that body fat was inert, a kind of storage, but now scientists know that tissue is biologically active, as it produces hormones and proteins of the immune system that act on other cells, promoting a state of persistent low-grade inflammation even when there is no infection.
Inflammation is the body’s response to an invader and is sometimes so vigorous that it is more damaging than the infection that triggered it.
Adipose tissue is mainly made up of adipose cells or adipocytes. It also contains preadipocytes, which mature into fat cells, and a variety of immune cells, including a type called adipose tissue macrophages.
Blish, along with colleagues from Stanford and Germany, and Switzerland, conducted experiments to test whether adipose tissue obtained from patients undergoing bariatric surgery could be infected with the coronavirus, and followed the response of various cell types.
The scientists discovered that the fat cells themselves could become infected, but did not become overly inflamed, however, certain immune cells called macrophages are also susceptible to infection and develop a strong inflammatory response.
What is weirder is that the preadipocytes did not become infected, but contributed to the inflammatory response. (The scientists did not analyze whether certain variants were more destructive in this regard than others.)
The research team also obtained adipose tissue from the bodies of European patients who had died from COVID-19 and discovered the coronavirus in fat near various organs.
The idea that adipose tissue can serve as a reservoir for pathogens is not new, Dixit said. Body fat is known to harbor several of them, such as HIV and the influenza virus.
The virus takes up residence in fat
The coronavirus appears to be able to evade the immune defenses of body fat, which are limited and unable to fight it effectively, and in obese people there can be a lot of body fat.
A man whose ideal weight is 77 kilograms but weighs 113 is loading a substantial amount of fat in which the virus can hang out, replicate and trigger a destructive immune system response, David Kass noted, Professor of Cardiology at Johns Hopkins.
“If you are very obese, fat is the largest organ in your body,” Kass said.
The coronavirus “can infect that tissue and live there,” he said. “It doesn’t matter if he hurts him, kills him or, at best, uses it to amplify himself. It becomes a kind of deposit ”.
As the inflammatory response snowballs, the cytokines trigger even more inflammation and the release of more cytokines. “It’s like a perfect storm,” Kass said.
Blish and her colleagues speculated that infected body fat may even contribute to the development of prolonged COVID-19, a disease that features bothersome symptoms, such as fatigue, that persist for weeks to months after recovery from an acute episode.
The data also suggests that COVID-19 vaccines and treatments should take into account the weight and fat stores of the patient.
“This work is another wake-up call for the medical profession and public health to take a closer look at the problems of people who are overweight and obese, and the treatments and vaccines we are administering to them,” said Barry Popkin, professor of nutrition at the University of North Carolina at Chapel Hill, who has studied the elevated risk posed by COVID-19 for people with obesity.