Metformin has been shown to ameliorate
diabetic cardiomyopathy. In the present research we investigated whether
metformin would reduce cardiomyocyte apoptosis that was induced by high-
glucose stimulation in vitro via activation of PP2A. Primary human and rat cardiomyocytes were subject to high-
glucose stimulation.
Okadaic acid was used to inhibit PP2A activity. Cell viability and apoptosis was assessed using
CCK-8 and by flow cytometry, respectively. Release of
HMGB1, TNFα or
IL-6 was analyzed by ELISA. Oxidative stress was evaluated by measuring cellular ROS and mitochondrial
superoxide level. PP2A activity was evaluated by
Serine/ Threonine phosphatase assay system or analyzing Y307 phosphorylation level of PP2A catalytic domain (PP2Ac) by Western blot and the association between PP2Ac and α4 by co-immunoprecipitation. Activation of the NF-κB signaling pathway was assessed by detecting Ser32 phosphorylation level of IκBα as well as nuclear entry of p65
protein by Western blot. Activation of the GSK3β/MCL1 signaling pathway was assessed by detecting Ser9 phosphorylation level of GSK3 β and
protein level of MCL1. We found
Metformin pre-treatment attenuated human and rat cardiomyocytes apoptosis,
HMGB1, TNFα and
IL-6 release and ROS production that were induced by high-
glucose stimulation, and these effects of
metformin could be blocked by
okadaic acid treatment.
Metformin reduced the upregulation of PP2Ac pY307 and the PP2Ac-a4 association, which was not affected by
okadaic acid treatment.
Metformin pre-treatment reduced NF-κB activation in human and rat cardiomyocytes apoptosis that was elicited by high-
glucose stimulation, and this effect of
metformin could be blocked by
okadaic acid treatment. GSK3 β/MCL1 is not part of
metformin activating PP2A induced myocardial cell death inhibition. In conclusion,
metformin reduced apoptosis, ROS production and inflammatory response in primary human and rat cardiomyocytes in vitro in a PP2A dependent manner.