TNF and COVID-19: In addition, this cytokine storm could be involved with changes in nitrogen metabolism, once a metabolome study in COVID-19 patients showed a positive correlation between asparagine, isoleucine, leucine, and valine with TNF-α, proline with IL-17 A and IL-17RA, threonine with IL-26, and a negative correlation of tryptophan with IL-26 (Caterino et al., 2021).