Marein protects against methylglyoxal-induced apoptosis by activating the AMPK pathway in PC12 cells.

Diabetic encephalopathy, which is characterized by cognitive decline and dementia, commonly occurs in patients with long-standing diabetes. Previous studies have suggested that methylglyoxal (MG), an endogenous toxic compound, plays an important role in diabetic complications such as cognitive impairment. MG induces neuronal apoptosis. To clarify whether marein, a major compound from the hypoglycemic plant Coreopsis tinctoria, prevents PC12 cell damage induced by MG, we cultured PC12 cells in the presence of MG and marein. Marein attenuated MG-induced changes in the mitochondrial membrane potential (ΔΨm), mitochondrial permeability transition pores (mPTPs), intracellular Ca2+  levels, the production of reactive oxygen species (ROS), glutathione (GSH)/glutathione disulfide (GSSG) and adenosine triphosphate (ATP), and the increase in the percentage of apoptotic cells. Marein also increased glyoxalase I (Glo1) activity, phospho-AMPKα (Thr172) and Bcl-2 expression and diminished the activation of Bax, caspase-3 and inhibitor of caspase-activated deoxyribonuclease (ICAD). Importantly, pretreatment of cells with marein diminished the compound C-induced inactivation of p-AMPK. Molecular docking simulation showed that marein interacted with the γ subunit of AMPK. In conclusion, we found for the first time that the neuroprotective effect of marein is due to a reduction of damage to mitochondria function and activation of the AMPK signal pathway. These results indicate that marein may be a potent compound for preventing/counteracting diabetic encephalopathy.