PPARA and COVID-19: Specifically, in COVID-19 patients, mono-CD14+, and mono-CD14+CD16+ cells showed higher levels of glycolysis, fatty acid synthesis, TCA cycle activity, OXPHOS, and pentose phosphate pathway (PPP) activity with PPAR and HIF-1 signaling pathway activation than those in HCs, and these cells showed the highest PPP activity in patients with severe cases (Figure 2A).