Abstract
The endothelium is considered to be relatively independent of the mitochondrial energy supply. The goals of this study were to examine mitochondrial respiratory functions in endothelial cells and isolated mitochondria and to assess the influence of chronic high glucose exposure on the aerobic metabolism of these cells. A procedure to isolate of bioenergetically active endothelial mitochondria was elaborated. Human umbilical vein endothelial cells (EA.hy926 line) were grown in medium containing either 5.5 or 25 mM glucose. The respiratory response to elevated glucose was observed in cells grown in 25 mM glucose for at least 6 days or longer. In EA.hy926 cells, growth in high glucose induced considerably lower mitochondrial respiration with glycolytic fuels, less pronounced with glutamine, and higher respiration with palmitate. The Crabtree effect was observed in both types of cells. High glucose conditions produced elevated levels of cellular Q10, increased ROS generation, increased hexokinase I, lactate dehydrogenase, acyl-CoA dehydrogenase, uncoupling protein 2 (UCP2), and superoxide dismutase 2 expression, and decreased E3-binding protein of pyruvate dehydrogenase expression. In isolated mitochondria, hyperglycaemia induced an increase in the oxidation of palmitoylcarnitine and glycerol-3-phosphate (lipid-derived fuels) and a decrease in the oxidation of pyruvate (a mitochondrial fuel); in addition, increased UCP2 activity was observed. Our results demonstrate that primarily glycolytic endothelial cells possess highly active mitochondria with a functioning energy-dissipating pathway (UCP2). High-glucose exposure induces a shift of the endothelial aerobic metabolism towards the oxidation of lipids and amino acids.Electronic supplementary materialThe online version of this article (doi:10.1007/s00424-012-1156-1) contains supplementary material, which is available to authorized users.
Highlights
Mitochondria are found in most human cells; the synthesis of ATP in endothelial cells occurs primarily via a glycolytic pathway
The comparison between the mitochondrial respiratory functions of EA.hy926 cells cultured in medium with either high or normal glucose demonstrated that chronic highglucose conditions induced a reduction in mitochondrial respiration with carbohydrate catabolism intermediates and glutamine, whereas OCR with palmitate was increased
These results indicate that hyperglycaemia lowers the contribution of carbohydrate oxidation to the aerobic metabolism of EA.hy926 cells, whereas the contributions of amino acid oxidation and lipid oxidation increase
Summary
Mitochondria are found in most human cells; the synthesis of ATP in endothelial cells occurs primarily via a glycolytic pathway. The relatively slight dependence of endothelial cells on oxidative phosphorylation has created the perception that mitochondria play no significant role in the endothelium and has thereby resulted in the neglect of their study in this context. Several recent observations challenge this view by suggesting that mitochondria can contribute to ATP generation and are centrally involved in maintaining the fine regulatory balance among mitochondrial calcium concentrations, reactive oxygen species (ROS) production, and NO [4, 5, 13]. There is emerging evidence that mitochondrial ROS are important signalling molecules in vascular endothelial cells [30]. Endothelial mitochondria may play a central role in the development of many cardiovascular diseases. The oxidative stress induced by hyperglycaemia is an important aspect of diabetic
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
