New research found that COVID-19 is specifically more aggressive to fatty tissues and immune cells found within body fat, causing poor immune response and contributing to the worsening of the disease. The research could help better understand the reasons for the increased risk for overweight and obese patients from coronavirus.
The study, published in October, is in the revision phase, but it seems to confirm the trend of serious illness and death in overweight and obese patients.
Although it is true that some comorbidities such as hypertension or diabetes regularly coexist in a large part of patients with severe disease, scientists believe that obesity plays a large role on its own.
This finding is an important step in the future treatment of the disease, with a new focus on the development of therapeutic procedures, vaccines, and drugs.
If the findings hold up, they may shed light not only on why overweight patients are vulnerable to the virus but also on why certain younger adults with no other risks get so sick.
“Maybe that’s the Achilles heel that the virus uses to evade our protective immune responses, by hiding in this place,” said Dr. Vishwa Deep Dixit, professor of comparative medicine and immunology at Yale School of Medicine.
Obesity now affects 8 out of 10 Mexicans, raising the risks of hypertension and other cardiovascular diseases, diabetes, and some types of cancer, which in turn were, together with COVID-19, the main causes of death in Mexico in 2020.
“This could well be contributing to a serious illness,” said Dr. 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 that I see in the blood of really sick patients that are produced in response to infection of those tissues.”
Body fat used to be considered inert, a form of storage. But scientists now know that tissue is biologically active and produces hormones and immune system proteins that act on other cells, promoting a persistent low-grade inflammation state even when there is no infection.
Inflammation is the body’s response to an invader and can sometimes be so vigorous that it is more damaging than the infection that triggered it.
Fat tissue is mainly made up of fat 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.
Tissue studies: fat becomes infected
Dr. Blish, with colleagues at Stanford and in Germany and Switzerland, conducted experiments to see whether fatty tissue obtained from bariatric surgery patients could be infected with the coronavirus and tracked how various cell types responded.
The scientists found that the fat cells themselves could become infected, but they didn’t get too swollen. But certain immune cells called macrophages could also become infected and develop a strong inflammatory response. Even stranger, the preadipocytes did not become infected but contributed to the inflammatory response.
The research team also obtained fat tissue from the bodies of European patients who had died of COVID and discovered the coronavirus in fat near various organs.
The idea that adipose tissue could serve as a reservoir for pathogens is not new, Dr. Dixit said. Body fat is known to harbor a number of them, including HIV and the influenza virus.
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 80 kilograms but who weighs 110 kilograms has a substantial amount of fat on which the virus can “hang”, replicate, and trigger a destructive immune system response, said Dr. David Kass, professor of cardiology at Johns Hopkins.
“If you really are very obese, fat is the largest organ in your body,” Dr. Kass said.
The coronavirus “can infect that tissue and actually reside there,” he said. “Whether it hurts him, kills him or, at best, it’s a place to amplify himself, it doesn’t matter. It becomes a kind of deposit ”.
As the inflammatory response increases, cytokines trigger even more inflammation and the release of additional cytokines. “It’s like a perfect storm,” he said.
Dr. Blish and her colleagues speculated that infected body fat may even contribute to “prolonged COVID,” a condition that describes uncomfortable symptoms such as fatigue that persists for weeks or months after recovery from an acute episode.
The data also suggests that coronavirus vaccines and treatments may need to take into account a patient’s weight and fat stores.