Metformin as an anti-inflammatory agent: a short review

Metformin is a biguanide drug widely used as the initial treatment of type 2 diabetes. Despite its widespread use, its precise mechanisms of action remain incompletely characterised. Its effect in lowering blood glucose is largely related to the suppression of gluconeogenesis in the liver, which is probably accomplished by partial inhibition of the mitochondrial respiratory chain complex 1 with a subsequent increase in intracellular AMP levels and activation of AMP kinase. Several local and systemic anti-inflammatory effects of metformin have been described. Many of these effects seem to be mediated by AMP kinase activation and downstream effects inhibiting mTOR and NF-κB pro-inflammatory signalling cascades. However, there are also studies describing actions independent of AMP kinase action. In this review, we summarise the currently known mechanisms of metformin on inflammatory pathways and the clinical evidence underpinning the use of metformin as a potential anti-inflammatory drug.