Dietary αKG inhibits SARS CoV-2 infection and rescues inflamed lungs to restore normal O2 saturation in animals
Our recent works described the rescue effect of -ketoglutarate (KG, a metabolite of Krebs cycle) on thrombosis and inflammation in animals. KG augments activity of prolyl hydroxylase 2 (PHD2), which in turn degrades proline residues of substrates like phosphorylated Akt (pAkt) and hypoxia inducible factor (HIF). Here we describe the inhibitory effect of octyl KG on pAkt as well as on HIF1/HIF2, and in turn decreasing SARS CoV-2 replication in Vero E6 cells. KG failed to inhibit the viral replication and Akt phosphorylation in PHD2-knockdown U937 cells transiently expressing ACE2. Contrastingly, triciribine (TCN, an Akt-inhibitor) inhibited viral replication alongside a downmodulation of pAkt in PHD2-KD cells. Dietary KG significantly inhibited viral infection and rescued hamsters from thrombus formation and inflammation in lungs, the known causes of acute respiratory distress syndrome (ARDS) in COVID-19. KG supplementation also reduced the apoptotic death of lung tissues in infected animals, alongside a downmodulation of pAkt and HIF2. KG supplementation neither affected IgG levels against SARS CoV-2 RBD protein nor altered the neutralization antibody response against SARS CoV-2. It did not interfere with the percentage of interferon-{gamma} positive (IFN{gamma}+) CD4+ and IFN{gamma}+CD8+ T cells in infected animals. The extended work in balb/c mice transiently expressing ACE2 showed a similar effect of KG in reducing accumulation of inflammatory immune cells and cytokines, including IL6, IL1{beta} and TNF, in lungs as well as in circulation of infected animals. Pro-thrombotic markers like platelet microparticles and platelet-leukocyte aggregates were reduced significantly in infected mice after KG supplementation. Importantly, KG supplementation restored the O2 saturation (SpO2) in circulation of SARS CoV-2 infected hamsters and mice, suggesting a potential therapeutic role of this metabolite in COVID-19 treatment.