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Immunoregulatory effect of metformin in monocytes exposed to SARS-CoV-2 spike protein subunit 1

Maurmann RM, Davis K, Mosalmanzadeh N, Schmitt BL, Pence BD

bioRxiv : the preprint server for biology, 2025

Abstract

BACKGROUND: Severe COVID-19 is characterized by a hyperinflammatory state associated with an exacerbated inflammatory activation of monocytes and macrophages in the respiratory tract. Metformin has been identified as a potent monocyte inflammatory suppressor, and it has been demonstrated to attenuate inflammation in COVID-19. The mechanisms underlying metformin anti-inflammatory effects are, however, unclear. We thus sought to investigate metformin's main interactions and their respective isolated effects in modulating monocyte inflammatory response to SARS-CoV-2 stimulation.

METHODS: Classical human monocytes were isolated from healthy 18-40-year-old individuals and stimulated in vitro with recombinant spike protein subunit 1 (rS1) to assess glycolytic and oxidative metabolic responses by Seahorse extracellular flux analysis, and inflammatory gene expression by qPCR. Stimulated monocytes were either pre-treated with metformin, rotenone, S1QEL, or A769662.

RESULTS: Monocytes stimulated in vitro with rS1 showed an increased glycolytic response associated with production of pro-inflammatory cytokines. Metformin pre-treatment reduced glycolytic activation while partially suppressing inflammation. Rotenone-dependent mitochondrial complex I inhibition was not able to replicate the same effect, and neither complex I specific ROS scavenging. Conversely, A769662 induced AMPK activation led to suppressed glycolytic inflammatory response and cytokine expression pattern similar to…

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