Acute metformin preconditioning confers neuroprotection against focal cerebral ischaemia by pre‐activation of AMPK‐dependent autophagy

Abstract

BACKGROUND AND PURPOSERecent clinical trials report that metformin, an activator of AMP-activated protein kinase (AMPK) used to treat type 2 diabetes, significantly reduces the risk of stroke by actions that are independent of its glucose-lowering effects. However, the underlying molecular mechanisms are not known. Here, we tested the possibility that acute metformin preconditioning confers neuroprotection by pre-activation of AMPK-dependent autophagy in a rat model of permanent middle cerebral artery occlusion (pMCAO). EXPERIMENTAL APPROACHMale Sprague-Dawley rats were pretreated with either vehicle, an AMPK inhibitor, Compound C, or an autophagy inhibitor, 3-methyladenine, and were injected with a single dose of metformin (10 mg kg −1 , i.p.). Then, AMPK activity and autophagy biomarkers in the brain were assessed. At 24 h after metformin treatment, rats were subjected to pMCAO; infarct volume, neurological deficits and cell apoptosis were evaluated 24 and 96 h later. KEY RESULTSA single dose of metformin significantly activated AMPK and induced autophagy in the brain. The enhanced autophagic activity was inhibited by Compound C pretreatment. Furthermore, acute metformin preconditioning significantly reduced infarct volume, neurological deficits and cell apoptosis during a subsequent focal cerebral ischaemia. The neuroprotection mediated by metformin preconditioning was fully abolished by Compound C and partially inhibited by 3-methyladenine. CONCLUSIONS AND IMPLICATIONSThese results provide the first evidence that acute metformin preconditioning induces autophagy by activation of brain AMPK, which confers neuroprotection against subsequent cerebral ischaemia. This suggests that metformin, a well-known hypoglycaemic drug, may have a practical clinical use for stroke prevention.

Metformin Improves Neurologic Outcome Via AMP‐Activated Protein Kinase–Mediated Autophagy Activation in a Rat Model of Cardiac Arrest and Resuscitation

“…In addition to the preventive effect of metformin, we also found that daily administration of metformin for 7 days after CA occurs significantly attenuated brain injury induced by CA/CPR, which further supports metformin as a neuroprotective agent on CA/CPR‐induced brain injury. In addition, short‐term intervention of metformin has been shown to be neuroprotective in focal cerebral ischemia and reperfusion46 however, further study is required to determine whether and to what extent short‐term metformin administration is effective in reducing brain injury under CA condition.…”

Pre-treatment with metformin activates Nrf2 antioxidant pathways and inhibits inflammatory responses through induction of AMPK after transient global cerebral ischemia

“…It has been shown that during ischemia metformin induces AMPK phosphorylation and improves cellular ATP depletion (Manwani and McCullough 2013). Moreover, metformin can help cells to survive against ischemia/reperfusion (I/R) injury by induction of some proteins within the protective pathways such as autophagy (Jiang et al 2014) and mitochondrial biogenesis (Ashabi et al 2014) in the brain under different cerebral ischemic conditions. Our previous study also confirmed that inducing AMPK by metformin protected neurons against I/R injury (Ashabi et al 2014).…”

Metformin improves anxiety-like behaviors through AMPK-dependent regulation of autophagy following transient forebrain ischemia

“…Conversion of Light chain-3 (LC3) protein from LC3-I to LC3-II initiates autophagy and consequently increases autophagic related proteins (Atgs) such as Atg7, Atg12 and beclin-1 (Wang et al 2011). It was demonstrated that autophagy can be regulated by AMPK under both normal and stressful situations (Jiang et al 2014;Meijer and Codogno 2007). AMPK initiates autophagy against focal cerebral ischemia and hence improves ischemia related cell death (Jiang et al 2014).…”

“…It was demonstrated that autophagy can be regulated by AMPK under both normal and stressful situations (Jiang et al 2014;Meijer and Codogno 2007). AMPK initiates autophagy against focal cerebral ischemia and hence improves ischemia related cell death (Jiang et al 2014). In addition, associations between autophagy and behavioral amendment have been speculated in recent years (Rodriguez-Navarro et al 2010).…”