Adenosine monophosphate deaminase in the endoplasmic reticulum–mitochondria interface promotes mitochondrial Ca2+ overload in type 2 diabetes rat hearts

Abstract

AbstractAims/IntroductionWe previously showed that upregulation of myocardial adenosine monophosphate deaminase (AMPD) is associated with pressure overload‐induced diastolic dysfunction in type 2 diabetes hearts. Here, we examined involvement of AMPD localized in the endoplasmic reticulum–mitochondria interface in mitochondrial Ca2+ overload and its pathological significance.Materials and MethodsWe used type 2 diabetes Otsuka Long–Evans Tokushima Fatty rats (OLETF) and non‐diabetes Long–Evans Tokushima Otsuka Fatty rats (LETO) as well as AMPD3‐overexpressing H9c2 cells and human embryonic kidney 293 cells.ResultsOLETF, but not LETO, showed diastolic dysfunction under the condition of phenylephrine‐induced pressure overload. The levels of 90‐kDa AMPD3 in outer mitochondrial membranes/endoplasmic reticulum and mitochondria‐associated endoplasmic reticulum membrane (MAM) fractions were significantly higher in OLETF than in LETO. The area of the MAM quantified by electron microscopic analysis was 57% larger, mitochondrial Ca2+ level under the condition of pressure overload was 47% higher and Ca2+ retention capacity in MAM‐containing crude mitochondria isolated before the pressure overloading was 21% lower in OLETF than in LETO (all P‐values <0.05). Transfection of FLAG‐AMPD3 in cells resulted in significant enlargement of the MAM area, and impairment in pyruvate/malate‐driven adenosine triphosphate‐stimulated and uncoupler‐stimulated mitochondrial respiration compared with those in control cells.ConclusionsThe findings suggest that 90‐kDa AMPD3 localized in the endoplasmic reticulum–mitochondria interface promotes formation of the MAM, inducing mitochondrial Ca2+ overload and dysfunction in type 2 diabetes hearts.