Decreased Mitochondrial Pyruvate Transport Activity in the Diabetic Heart

Abstract

Alterations in mitochondrial function contribute to diabetic cardiomyopathy. We have previously shown that heart mitochondrial proteins are hyperacetylated in OVE26 mice, a transgenic model of type 1 diabetes. However, the universality of this modification and its functional consequences are not well established. In this study, we demonstrate that Akita type 1 diabetic mice exhibit hyperacetylation. Functionally, isolated Akita heart mitochondria have significantly impaired maximal (state 3) respiration with physiological pyruvate (0.1 mm) but not with 1.0 mm pyruvate. In contrast, pyruvate dehydrogenase activity is significantly decreased regardless of the pyruvate concentration. We found that there is a 70% decrease in the rate of pyruvate transport in Akita heart mitochondria but no decrease in the mitochondrial pyruvate carriers 1 and 2 (MPC1 and MPC2). The potential role of hyperacetylation in mediating this impaired pyruvate uptake was examined. The treatment of control mitochondria with the acetylating agent acetic anhydride inhibits pyruvate uptake and pyruvate-supported respiration in a similar manner to the pyruvate transport inhibitor α-cyano-4-hydroxycinnamate. A mass spectrometry selective reactive monitoring assay was developed and used to determine that acetylation of lysines 19 and 26 of MPC2 is enhanced in Akita heart mitochondria. Expression of a double acetylation mimic of MPC2 (K19Q/K26Q) in H9c2 cells was sufficient to decrease the maximal cellular oxygen consumption rate. This study supports the conclusion that deficient pyruvate transport activity, mediated in part by acetylation of MPC2, is a contributor to metabolic inflexibility in the diabetic heart.

Glucagon up‐regulates hepatic mitochondrial pyruvate carrier 1 through cAMP‐responsive element‐binding protein; inhibition of hepatic gluconeogenesis by ginsenoside Rb1

“…In cardiomyocytes and cancer cells, deacetylation modification increases MPC protein induction by improving its stability (Liang, Li, Huang, Li, & Li, 2015;Vadvalkar et al, 2017). Pyruvate load also increases MPC expression by preventing degradation, a process which occurs at 8 hr after MPC1 induction (Li et al, 2018).…”

Cardiac Insulin Signaling Regulates Glycolysis Through Phosphofructokinase 2 Content and Activity

“…Heart samples were prepared on the basis of our standard targeted proteomics approach 19, 20, 21, 22. Whole heart homogenates were used for the analysis.…”

“…18 Heart samples were prepared on the basis of our standard targeted proteomics approach. [19][20][21][22] Whole heart homogenates were used for the analysis. Total proteins (50-µg amounts) were taken for analysis, and 8 pmol BSA was added as an internal standard.…”

The yeast mitochondrial pyruvate carrier is a hetero‐dimer in its functional state

“…As the mitochondrial pyruvate carrier is central for cellular homeostasis, the identification of the MPC proteins intensified efforts to understand their role in cancer (Schell et al , , ; Yang et al , ; Zhong et al , ; Li et al , , ; Corbet et al , ; Ohashi et al , ; Bader et al , ), diabetes (Colca et al , ; Divakaruni et al , ; Vigueira et al , ; Gray et al , ; McCommis et al , , ; Vadvalkar et al , ) and neurodegeneration (Ghosh et al , ; Divakaruni et al , ; Quansah et al , ). Moreover, pathogenic mutations in the mpc1 gene were found in rare but severe metabolic syndromes, further enhancing the clinical relevance of this transporter (Bricker et al , ).…”