Previous epidemiological studies have shown that methylglyoxal (MGO) levels are highly regulated in diabetic cardiovascular diseases. We have also previously reported that MGO mediates ER stress and apoptosis in cardiomyocytes. Furthermore, activated protein C (APC) has recently been shown to play a protective role against ER stress, as well as a cardioprotective role against ischemia and reperfusion injury by augmenting the AMP-activated protein kinase (AMPK) signaling pathway. Therefore, we hypothesized that APC protects against MGO-induced cardiomyocyte apoptosis through the inhibition of ER stress. Our results showed that APC inhibited MGO-induced cardiomyocyte apoptosis and ER stress related gene expression. Additionally, APC inhibited MGO-induced Ca2+ mobilization and the generation of reactive oxygen species. In contrast, inhibitors of AMPK signaling abolished the cytoprotective effects of APC. Collectively, these data depict a pivotal role for AMPK signaling in inhibiting ER stress responses via the activation of APC during MGO-induced cardiomyocyte apoptosis. Thus, APC may be a potential novel therapeutic target for the management of diabetic cardiovascular complications such as diabetic cardiomyopathy. (C) 2016 Elsevier Inc. All rights reserved.