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.
“It’s very possible that this is contributing to the serious complications,” Blish said. “We are seeing the same inflammatory cytokines present in the blood of very ill patients being produced in response to infection of those tissues.”
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. “The more fat, and particularly visceral fat, the worse the inflammatory response,” McLaughlin said, referring to the abdominal fat that surrounds internal organs.
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.
McLaughlin and Blish, along with their colleagues, conducted experiments to see if adipose tissue obtained from patients undergoing bariatric surgery could be infected with the coronavirus, and they 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 developed a strong inflammatory response.
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