Table 1.

Suggested mechanisms to explain the possible positive effects of metformin on COVID-19 outcomes.

Mechanisms	References
Improved glucose control	Ceriello et al. [5], [6]
Reduction in body weight	El-Arabey and Abdalla [20]
Reduction in insulin resistance	Penlioglou et al. [16] Sharma et al. [17]
AMPK activation leads to phosphorylation of ACE2, thereby inhibition of virus penetration	Sharma et al. [17]
Inhibition of mTOR pathway and prevention of immune hyperactivation	Sharma et al. [17] Bolourian and Mojtahedi [21] Lehrer [22]
Action on endosomal Na+/H+ exchanger, thereby increasing cellular pH and interference with viral endocytic cycle	Esam [23]
Anti-inflammatory properties	Kumar Singh and Singh [18]
Reduction in neutrophils	Dalan [24]
Inhibition of mitochondrial complex 1, suppression of mitochondrial reactive oxygen species (ROS) signalling, ROS prevention: CRAC-mediated interleukin-6 release	Menendez [25]

AMPK: AMP-activated protein kinase; ACE2: angiotensin-converting enzyme 2; mTOR: mammalian target of rapamycin; CRAC: Ca²⁺ release-activated Ca²⁺ channels.