FNDC4 and FNDC5 reduce SARS-CoV-2 entry points and spike glycoprotein S1-induced pyroptosis, apoptosis, and necroptosis in human adipocytes

A sedentary lifestyle and obesity are important risk factors for severe COVID-19 complications and death[1,2].Excessive adipose tissue(AT)might contribute to more extensive viral spread with increased shedding,immune activation,and cytokine amplification[3].Several factors secreted by contracting muscle,termed myokines,mediate the beneficial effects of exercise in a wide range of diseases,including obesity[4].Thus,we conducted a study to explore the potential role of myokines of the fibronectin type III domain-containing family,FNDC4 and FNDC5,in mechanisms underlying the increased susceptibility to COVID-19 complications in obesity.