New Study: Fat Cells Are a Reservoir for COVID-19 Infection

Fat Cells


The complications of obesity raise the risk of many diseases, so the association with more severe COVID-19 infection was no surprise. Obese adults have higher rates of hypertension and type 2 diabetes, which increases a patient’s chance of severe illness from the novel coronavirus.  

But scientists have suspected that obesity was its own risk factor, even without the comorbidities. As reports found that even patients under 18 who are obese had over a 3 times higher risk of hospitalization, they put their theory to the test.  

A group of researchers, primarily out of Stanford’s School of Medicine, published a study proving that SARS-CoV-2 infects human adipose or fat tissue to multiply and elicit an inflammatory response corresponding with severe COVID-19. Using fat freshly harvested from bariatric and cardiothoracic surgery patients, the group separated the composition and tested the response of each to exposure to the novel coronavirus.  

Fat tissue consists of adipocytes, which are fat cells, pre-adipocytes, and immune cells. In the lab, the fat cells became infected, yet did not show much inflammation. But the macrophage immune cells also became infected and elicited a strong inflammatory response. The pre-adipocytes, which mature into fat cells, did not become infected, yet added to the inflammatory response.  

The team also found SARS-CoV-2 in the fat tissue surrounding various organs of patients who had died of COVID-19 infection.  

“This could well be contributing to severe disease,” Dr. Catherine Blish, a professor at Stanford University Medical Center and one of the report’s two senior authors, said.  

“We’re seeing the same inflammatory cytokines that I see in the blood of the really sick patients being produced in response to infection of those tissues.” 

Body fat is not just storage, it's a biologically active tissue that affects hormones and the immune system and promotes a constant state of low inflammation. Fat tissue is a known reservoir for some pathogens like HIV and influenza. It becomes a prime target for these viruses to hang out and multiply, evading the weak immune defenses of the adipose tissue.  

The CDC reports that non-Hispanic Black adults in America have disproportionately suffered from worse outcomes of COVID-19 illness. This group also has the highest prevalence of self-reported obesity.  

Obesity is considered an epidemic in the United States and has only been worsened by the COVID-19 pandemic. As of a Harris Poll completed in February 2021, 42% of adults reported undesired weight gain with an average gain of 29 pounds. Adult obesity in the U.S. surpassed 40% for the first time ever in 2017-2018.  

The recent research report on how SARS-CoV-2 infects fat cells could provide an opportunity for personalized or targeted treatment. Current vaccines and treatments may need to consider a patient’s weight and body fat content for more effective dosing.  

Meanwhile, health professionals continue to encourage exercise and balanced nutrition to support a healthy weight and minimize the risk of a long list of obesity-related diseases and complications. Easier said than done, particularly during the holiday season. 

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