FNDC5 and obesity due to melanocortin 4 receptor deficiency: The effects of FNDC4 and FNDC5 on S1-induced inflammatory responses were evaluated in vitro using human visceral adipocytes and THP-1-derived macrophages.<h4>Results</h4>Obesity was associated with higher circulating ACE2 and increased expression of SARS-CoV-2 entry receptors (ACE2, CD147, DPP4 and neuropilin-1) in VAT, whereas plasma FNDC4 and FNDC5 levels were reduced.