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The coronavirus infects fat cells and certain immune cells within body fat, creating an immune response that could lead to major damage, according to a recent preprint study.
The finding could explain why those who are overweight or obese face higher risks for severe illness and death from COVID-19. The study hasn't yet been peer-reviewed or published in a journal, but it offers insight into why some patients are vulnerable, even if they don't have any other risks or conditions.
"The bottom line is, 'Oh my God, indeed, the virus can infect fat cells directly,' " Philipp Scherer, PhD, a scientist who studies fat cells at UT Southwestern Medical Center in Dallas, told The New York Times.
"Whatever happens in fat doesn't stay in fat," he said. "It affects the neighboring tissues as well."
In the study, researchers from the Stanford University School of Medicine tested fat tissue from bariatric surgery patients to understand whether they could become infected with the coronavirus. They looked at different types of cells — adipocytes, or fat cells, as well as pre-adipocytes that become fat cells and immune cells called adipose tissue macrophages.
The research team found that the adipocytes could become infected, though they didn't become overly inflamed. But certain immune cell macrophages could be infected and have a major inflammatory response. Beyond that, the pre-adipocytes weren't infected, but they added to the inflammatory response.
The researchers also looked at fat tissue from the bodies of European patients who died from COVID-19 and found the coronavirus in fat around various organs, including the heart and intestines. That could be linked with the organ damage seen in severe COVID-19 patients, they wrote.
The coronavirus appears to evade the body's immune defenses and "hang out" in fat tissue, which allows it to replicate and trigger a severe immune response, David Kass, MD, a professor of cardiology at Johns Hopkins Medicine, told the Times.
"If you really are very obese, fat is the biggest single organ in your body," he said.
The coronavirus "can infect that tissue and actually reside there," he continued. "Whether it hurts it, kills it, or at best, it's a place to amplify it — it doesn't matter. It becomes kind of a reservoir."
The infected body fat could contribute to "long COVID," which has led to symptoms that last for weeks or months after someone has recovered from a coronavirus infection, the study authors wrote.
The findings could open avenues for new COVID-19 treatments that target body fat, they said. Drugs that ease inflammation of the adipose tissue in obese patients could help COVID-19 patients, they wrote.
What's more, the study may show that health care professionals should consider a patient's weight and body fat when giving COVID-19 vaccines and treatments, the Times reported.
"This paper is another wake-up call for the medical profession and public health to look more deeply into the issues of overweight and obese individuals, and the treatments and vaccines we're giving them," Barry Popkin, PhD, an obesity researcher at the University of North Carolina at Chapel Hill who has studied COVID-19 risks for overweight and obese patients, told the newspaper.
"We keep documenting the risk that they have, but we still aren't addressing it," he said.
BioRxiv: "SARS-CoV-2 infects human adipose tissue and elicits an inflammatory response consistent with severe COVID-19."
The New York Times: "The Coronavirus Attacks Fat Tissue, Scientists Find."
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Cite this: Coronavirus Attacks Fat Tissue, Study Says - Medscape - Dec 09, 2021.