Metformin regulates LKB1/AMPK/HIF-1α pathways in early stress response to promote angiogenesis and reduce brain damage occasioned by cerebral ischemia

Abstract Purpose As a difficult-to-treat neurological condition, cerebral ischemia is currently limited to treatments such as intravenous recombinant tissue plasminogen activator thrombolysis and thrombectomy. Metformin, a potent antidiabetic drug, has been reported to have an independent function in enhancing the prognosis of stroke patients, in addition to its glucose-lowering effects. However, the mechanism of metformin in this context remains unclear. Methods In vivo, a middle cerebral artery occlusion model was established to measure the infarct area by TTC staining after administering a low dose of 10.5mg/mL metformin, and blood flow in the rat’s cerebral cortex was measured using a Laser Doppler imaging assay. In vitro, the study established human umbilical vein endothelial cells treated with cobalt chloride. Immunofluorescence, immunohistochemistry, and Western blot experiments were performed to observe the expression of angiogenic factors, tight junction proteins, and apoptotic factors. A TUNEL assay was utilized to appraise apoptosis production. A tube formation assay and scratch assay were conducted to determine the endothelial neovascularization status. Results Animal experiments have revealed that the administration of the AMPK activator metformin significantly reduced the infarct area, promoted the expression of angiogenic factors, and maintained the stability of tight junction proteins in endothelial cells. Moreover, metformin affects the expression of apoptosis protein in brain tissues through the HIF-1α pathway and reduces the apoptosis of brain cells. In vitro, the LKB1/AMPK signaling pathway is activated after hypoxic stimulation, attaining its peak within the early stages of hypoxia (1–12 hours) and gradually weakening thereafter. The administration of AMPK pharmacological agonists (between 36 and 48 hours) can enhance AMPK activity, which can lead to the expression of angiogenic factors, maintain the stability of tight-junction proteins in endothelial cells, and facilitate endothelial cell migration and vascular structure formation. Conversely, the AMPK inhibitors exert the opposite effects. Conclusion The early activation of the LKB1/AMPK/HIF-1α signaling pathway by metformin in cerebral ischemia contributes to angiogenesis, promotes tissue repair in the injured area, and enhances neurologically functional symptoms.