Endothelial Cell and Platelet Bioenergetics: Effect of Glucose and Nutrient Composition

Abstract

It has been suggested that cells that are independent of insulin for glucose uptake, when exposed to high glucose or other nutrient concentrations, manifest enhanced mitochondrial substrate oxidation with consequent enhanced potential and generation of reactive oxygen species (ROS); a paradigm that could predispose to vascular complications of diabetes. Here we exposed bovine aortic endothelial (BAE) cells and human platelets to variable glucose and fatty acid concentrations. We then examined oxygen consumption and acidification rates using recently available technology in the form of an extracellular oxygen and proton flux analyzer. Acute or overnight exposure of confluent BAE cells to glucose concentrations from 5.5 to 25 mM did not enhance or change the rate of oxygen consumption (OCR) under basal conditions, during ATP synthesis, or under uncoupled conditions. Glucose also did not alter OCR in sub-confluent cells, in cells exposed to low serum, or in cells treated with added pyruvate. Likewise, overnight exposure to fatty acids of varying saturation had no such effects. Overnight exposure of BAE cells to low glucose concentration decreased maximal uncoupled respiration, but not basal or ATP related oxygen consumption. Labeled glucose oxidation to CO 2 increased, but only marginally after high glucose exposure while oleate oxidation to CO 2 decreased. Overnight exposure to linolenic acid, but not oleic or linoleic acid increased extracellular acidification consistent with enhanced glycolytic metabolism. We were unable to detect an increase in production of reactive oxygen species (ROS) from BAE cells exposed to high medium glucose. Like BAE cells, exposure of human platelets to glucose did not increase oxygen consumption. As opposed to BAE cells, platelet mitochondria demonstrate less respiratory reserve capacity (beyond that needed for basal metabolism). Our data do not support the concept that exposure to high glucose or fatty acids accelerates mitochondrial oxidative metabolism in endothelial cells or platelets.

Prevailing vitamin D status influences mitochondrial and glycolytic bioenergetics in peripheral blood mononuclear cells obtained from adults

“…Numerous studies have harnessed PBMC's as a potential tool to determine the inflammatory and metabolic status in a variety of different disease states, including sepsis [19], neurodegeneration [20], rheumatic disease [21], obesity [22], [23], cardiovascular disease [24], diabetes mellitus [25], [26], and anorexia nervosa [27], all of which have been linked to mitochondrial dysfunction or altered bioenergetics. These studies in immune cells are consistent with a large body of work suggesting altered mitochondrial respiratory capacity and function in tissues classically studied such as skeletal muscle, liver, islet cells, and the myocardium [28], [29], [30], [31]. Recently, the concept of a bioenergetic health index (BHI) has been proposed as a novel prognostic or diagnostic biomarker of disease [32].…”

Deletion of GLUT1 and GLUT3 Reveals Multiple Roles for Glucose Metabolism in Platelet and Megakaryocyte Function

“…Platelet bioenergetics were evaluated by Seahorse XF24 Analyzer (Agilent Technologies, Santa Clara, CA) as previously described (Fink et al, 2012). Leukocytes and red blood cells were depleted using Terr119 and CD45 micro beads and data are normalized to platelet counts.…”

Platelet bioenergetic screen in sickle cell patients reveals mitochondrial complex V inhibition, which contributes to platelet activation

“…6,22,23 Herein, we further validate XF analysis and couple this technology with biochemical measures of mitochondrial ROS generation and platelet thrombotic function to screen SCD patients for bioenergetic dysfunction and simultaneously determine the contribution of the mitochondrial ETC to platelet activation in this population. We identify a specific bioenergetic alteration in SCD patients and provide in vivo and in vitro evidence that this specific alteration in the mitochondrial ETC may mechanistically underlie augmented platelet activation in this population.…”