High glucose induces mitochondrial dysfunction independently of protein O-GlcNAcylation

Abstract

Diabetes is characterized by hyperglycaemia and perturbations in intermediary metabolism. In particular, diabetes can augment flux through accessory pathways of glucose metabolism, such as the hexosamine biosynthetic pathway (HBP), which produces the sugar donor for the β-O-linked-N-acetylglucosamine (O-GlcNAc) post-translational modification of proteins. Diabetes also promotes mitochondrial dysfunction. Nevertheless, the relationships among diabetes, hyperglycaemia, mitochondrial dysfunction and O-GlcNAc modifications remain unclear. In the present study, we tested whether high-induced increases in O-GlcNAc modifications directly regulate mitochondrial function in isolated cardiomyocytes. Augmentation of O-GlcNAcylation with high glucose (33 mM) was associated with diminished basal and maximal cardiomyocyte respiration, a decreased mitochondrial reserve capacity and lower Complex II-dependent respiration (P < 0.05); however, pharmacological or genetic modulation of O-GlcNAc modifications under normal or high glucose conditions showed few significant effects on mitochondrial respiration, suggesting that O-GlcNAc does not play a major role in regulating cardiomyocyte mitochondrial function. Furthermore, an osmotic control recapitulated high-glucose-induced changes to mitochondrial metabolism (P < 0.05) without increasing O-GlcNAcylation. Thus, increased O-GlcNAcylation is neither sufficient nor necessary for high-glucose-induced suppression of mitochondrial metabolism in isolated cardiomyocytes.

Cardiomyocyte Ogt limits ventricular dysfunction in mice following pressure overload without affecting hypertrophy

“…Neonatal rat cardiomyocytes were isolated from 1–2-day-old Sprague–Dawley rats as previously described [1, 5, 6, 12, 18–21, 29, 30, 33]. NRCMs were plated at a density of 850,000 cells per ml.…”

“…For gene transfer experiments, NRCMs were serum-starved overnight and then transduced with 100 multiplicity of infection (MOI) of replication-deficient adenoviruses carrying OGA gene (Ad-OGA; Vector Biolabs, Malvern, PA, USA), or null virus (Ad-Null; 1240, Vector Biolabs, Malvern, PA, USA) in serum free medium for 5 h as previously described [5, 6, 18–21, 42]. Following virus treatment, NRCMs were returned to complete medium.…”

Redox biology and the interface between bioenergetics, autophagy and circadian control of metabolism

“…Mitochondrial dysfunction associated with increased O-GlcNAc levels has also been linked to O-GlcNAcylation of VDAC2 [79]. It should be noted however that there remains some controversy whether the adverse effects of hyperglycemia on mitochondrial function are mediated via increased O-GlcNAcylation [80]. On the other hand OGT has been shown to interact directly with complex IV in cardiac mitochondria from normal rats and this interaction is markedly decreased in mitochondria from diabetic rats [81].…”

The regulatory roles ofO-GlcNAcylation in mitochondrial homeostasis and metabolic syndrome

“…Also, they further found that heart mitochondrial respiratory chain proteins were differently O -GlcNAcylated under diabetic condition, and those changes in O -GlcNAcylation seemed to be closely related to changes in mitochondrial function, in particular respiration and ROS generation. However, there're also studies concluding that change of myocardial mitochondrial respiration induced by hyperglycemia is not related to O -GlcNAcylation [47]. …”