Metformin selectively dampens the acute inflammatory response through an AMPK-dependent mechanism

Thomas S Postler,Vincent Peng,Sankar Ghosh,Dev M Bhatt

doi:10.1038/s41598-021-97441-x

Abstract

Metformin is a first-line drug in the treatment of type-2 diabetes mellitus (T2DM). In addition to its antigluconeogenic and insulin-sensitizing properties, metformin has emerged as a potent inhibitor of the chronic inflammatory response of macrophages. In particular, metformin treatment has been shown to reduce expression of interleukin (IL-) 1β during long-term exposure to the pro-inflammatory stimulus lipopolysaccharide (LPS) through a reduction in reactive oxygen species (ROS), which decreases the levels of the hypoxia-inducible factor (HIF) 1-α, and through enhanced expression of IL-10. However, the effect of metformin on the acute inflammatory response, before significant levels of ROS accumulate in the cell, has not been explored. Here, we show that metformin alters the acute inflammatory response through its activation of AMP-activated protein kinase (AMPK), but independently of HIF1-α and IL-10, in primary macrophages and two macrophage-like cell lines. Thus, metformin changes the acute and the chronic inflammatory response through fundamentally distinct mechanisms. Furthermore, RNA-seq analysis reveals that metformin pretreatment affects the levels of a large yet selective subset of inflammatory genes, dampening the response to short-term LPS exposure and affecting a wide range of pathways and biological functions. Taken together, these findings reveal an unexpected complexity in the anti-inflammatory properties of this widely used drug.

Highlights

Metformin is a first-line drug in the treatment of type-2 diabetes mellitus (T2DM)
To ascertain whether metformin affects the acute inflammatory response, we began by determining the transcript levels of Il1b in primary bone-marrow-derived macrophages (BMDMs)
Exposure to LPS for 2 h, did not increase luciferase levels significantly, further corroborating that HIF1-α does not contribute meaningfully to the acute LPS response (Fig. 1g). This is consistent with the observation by Tannahill et al that HIF1-α does not bind to the promoter of Il1b after 2 h of LPS stimulation, but does so only after 4 h and later[26]. These results indicate that the effect of metformin on transcript levels during the acute LPS response is not mediated by HIF1-α, but instead through a mechanism that is distinct from what has been reported for chronic LPS exposure

Summary

Introduction

Metformin is a first-line drug in the treatment of type-2 diabetes mellitus (T2DM). In addition to its antigluconeogenic and insulin-sensitizing properties, metformin has emerged as a potent inhibitor of the chronic inflammatory response of macrophages. Metformin treatment has been shown to reduce expression of interleukin (IL-) 1β during long-term exposure to the pro-inflammatory stimulus lipopolysaccharide (LPS) through a reduction in reactive oxygen species (ROS), which decreases the levels of the hypoxia-inducible factor (HIF) 1-α, and through enhanced expression of IL-10. Pro-inflammatory stimuli chronically present in the tissue of T2DM patients, such as free fatty acids and the bacterial cell-wall component lipopolysaccharide (LPS), induce transcription of Il1b and other cytokine-encoding genes[17,18]. This results in synthesis of the inactive form pro-IL-1β, which must be cleaved by caspase-1 after inflammasome activation to yield the active, secreted IL-1β molecule[16]. It has been reported to contribute to long-term weight loss and may exhibit modest cardioprotective effects, along with a plethora of other advantageous properties[27,29,30,31,32,33,34,35,36,37,38,39,40]

Methods

Results

Conclusion