Do adipocytes serve as a reservoir for SARS-CoV-2?

Obesity is associated with a higher risk of severe COVID-19 and increased mortality. In the current study, we have investigated the expression of ACE2, NRP1, and HMGB1, known to facilitate SARS-CoV-2 cell entry, in adipose tissue from non-COVID-19 control patients with normal weight, overweight and obesity. All factors were expressed, but no significant differences between the groups were observed. Furthermore, diabetes status and medications did not affect the expression of ACE2. Only in obese men, the expression of ACE2 in adipose tissue was higher than in obese women. In adipose tissue from patients that died from COVID-19, SARS-CoV-2 was detected in the adipocytes even though the patients died more than three weeks after the acute infection. This suggests that adipocytes may act as reservoirs for the virus. In COVID-19 patients, the expression of NRP1 was increased in COVID-19 patients with overweight and obesity. Furthermore, we observed an increased infiltration with macrophages in the COVID-19 adipose tissues compared to control adipose tissue. In addition, crown-like structures of dying adipocytes surrounded by macrophages were observed in the adipose tissue from COVID-19 patients. These data suggest that in obese individuals, in addition to an increased mass of adipose tissue that could potentially be infected, increased macrophage infiltration due to direct infection with SARS-CoV-2 and sustained viral shedding, rather than preinfection ACE2 receptor expression, may be responsible for the increased severity and mortality of COVID-19 in patients with obesity.