Coronavirus attacks fat tissue, scientists find
From the start of the pandemic, the coronavirus seemed to target people carrying extra pounds. Patients who were overweight or obese were more likely to develop severe COVID-19 and die.
Although these patients often have health conditions such as diabetes that increase their risk, scientists have become increasingly convinced that their vulnerability has something to do with obesity itself.
“The bottom line is, ‘Oh my god, actually, the virus can directly infect fat cells,'” said Dr. Philip Scherer, a scientist who studies fat cells at UT Southwestern Medical Center in Dallas, who is involved in the research. was not. ,
“Whatever is in the fat doesn’t stay in the fat,” he said. “It also affects neighboring tissues.”The research has yet to be peer-reviewed or published in a scientific journal, but it was posted online in October. If the findings hold, they could shed light not only on why overweight patients are vulnerable to the virus, but also why some young adults become so ill with no other exposure.
The study authors suggested that the evidence may point to newer COVID treatments that target body fat.
“Maybe it’s the Achilles heel that the virus uses to evade our protective immune responses – lurking in this space,” said Dr. Vishwa Deep Dixit, professor of comparative medicine and immunology at Yale School of Medicine.
The finding is particularly relevant to the United States, which has one of the highest rates of obesity in the world. Most American adults are overweight, and 42 percent are obese. Black, Hispanic, Native American, and Alaska Native people in the US have higher rates of obesity than white adults and Asian Americans; They have also been disproportionately affected by the pandemic, with the death rate nearly twice that of white Americans.
“It can contribute to serious illness,” Dr. Katherine Blish, a professor at Stanford University Medical Center and one of the report’s two senior authors. “We’re seeing the same inflammatory cytokines that I’m seeing in the blood of really sick patients that are being produced in response to infection of those tissues.”
Body fat was considered inactive, a form of storage. But scientists now know that the tissue is biologically active, producing hormones and immune-system proteins that act on other cells, promoting conditions that reduce low-grade inflammation even when there is no infection.
Inflammation is the body’s response to an invader, and sometimes it can be so strong that it is more harmful than the infection that triggered it.
Adipose tissue is composed mostly of fat cells, or adipocytes. It also contains pre-adipocytes, which mature into fat cells, and various types of immune cells, including a type called adipose tissue macrophages.
Dr. Blish conducted experiments with Stanford and his colleagues in Germany and Switzerland to see if adipose tissue obtained from bariatric surgery patients could be infected with the coronavirus, and to find out how different cell types responded. .
The fat cells themselves may have become infected, the scientists found, yet didn’t cause much inflammation. But some immune cells called macrophages can also become infected, and they developed a strong inflammatory response.
Stranger as well, pre-adipocytes were not infected but contributed to the inflammatory response. (The scientists did not investigate whether particular types were more destructive than others in this regard.)
The research team also obtained adipose 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 can serve as a reservoir for pathogens is not new, Dr. Dixit said. Body fat is known to harbor many of them, including those of the HIV and influenza viruses.
The coronavirus appears to be able to evade the immune defenses of body fat, which are limited and unable to fight effectively. And people who are obese can have a lot of body fat.
A man whose ideal weight is 170 pounds but who weighs 250 pounds has a substantial amount of fat in which the virus can “hang out,” replicate and trigger a devastating immune system response, Dr. David Kass, professor of cardiology. Johns Hopkins.
“If you’re really very fat, fat is the biggest single organ in your body,” Dr. Kaas said.
The coronavirus “can infect that tissue and actually stay there,” he said. “Whether it hurts it, kills it, or at best, it’s a place to amplify itself—it doesn’t matter. It becomes a kind of reservoir.”
As the inflammatory response snowballs, cytokines trigger even more inflammation and the release of additional cytokines. “It’s like a perfect storm,” he said.
Dr. Blish and colleagues speculate that infected body fat may also contribute to “long covid”, a condition that describes distressing symptoms such as fatigue that occur weeks or months after recovery from an acute episode. Lasts till
The data also suggests that COVID vaccines and treatments may need to take into account the patient’s weight and fat stores.
Professor of Nutrition Barry Popkin said, “This paper is another wake-up call for the medical profession and public health to look more deeply at the issues of overweight and obese individuals, and the treatments and vaccines we are giving them.” ” The University of North Carolina at Chapel Hill, who studied the increased risk for obese people from Covid.
“We keep documenting their risk, but we are still not addressing it,” Dr. Popkin said.