New research further corroborates that adipose tissue -- a storehouse of fats -- acts as a reservoir for SARS-CoV-2, making it severe for obese patients.
Researchers in their study also speculated that during infection fat cells release into the bloodstream substances that boost the inflammatory reaction triggered by the virus in the organism.
These hypotheses are being investigated by researchers at the University of São Paulo's Medical School (FM-USP) in Brazil.
"A cytokine storm resulting in systemic inflammation similar to sepsis occurs in some severe Covid-19 patients. We believe these inflammatory factors come from adipose tissue. It's been shown that when adipocytes expand too much, they can cause inflammation throughout the body, even in the brain," Marilia Cerqueira Leite Seelaender, a professor in the Department of Clinical Surgery told Agência FAPESP.
For the study, the researchers analyzed samples of adipose tissue obtained from autopsies of people who died from Covid-19, and also from patients infected with SARS-CoV-2 who had to be submitted to emergency surgery.
Preliminary results confirmed that the virus can be found in fat cells, whose membranes are rich in ACE-2, the main receptor used by the virus to invade human cells.
Seelaender said: "It's worth noting that visceral adipocytes [located deep in the abdomen and around internal organs] have much more ACE2 than subcutaneous adipose tissue. In addition, they're much more inflammatory. As a result, visceral obesity tends to be even more harmful as far as Covid-19 is concerned."
In the analysis, Seelaender and the team noted how nutritional status can influence a patient's response to Covid-19.
According to the authors, both obesity and malnutrition - including cachexia and sarcopenia (loss of skeletal muscle mass associated with aging) - can impair the immune response and prevent the organism from combating viral infection.
She explained: "Fat can be a problem when it's excessive or insufficient. However paradoxical it may seem, both extremes are dangerous. Adipose tissue secretes leptin, a hormone that regulates T-lymphocyte metabolism. Leptin signaling falls in a body with very low fat. Excessively high fat makes cells less sensitive to leptin, so the amount of leptin released rises sharply."