2.2  Metformin-mTOR-Coronavirus
The mammalian target of rapamycin (mTOR) signalling plays an important role in the pathogenesis of influenza, besides modulating antibody response for cross-protective immunity against infective influenza viruses. Metformin activates AMPK via liver kinase B1 (LKB1), inhibiting the mTOR pathway. It also indirectly attenuates AKT activation through phosphorylation of insulin receptor substrate 1 (IRS-1) resulting in inhibition of the mTOR signalling cascade [11]. Other biguanide molecules, buformin and phenformin have been associated with better survival outcomes in animal models of influenza [12], [13]. Further, the PI3K/AKT/mTOR pathway plays major roles in MERS‑CoV infection [14]. Since metformin inhibits the same pathway, it would be interesting to decipher its role against SARS-CoV-2.