Aged endothelial cells exhibit a metabolic shift from anaerobic glycolysis to oxidative phosphorylation

Abstract

Endothelial dysfunction is a hallmark of vascular aging and is associated with increased arterial oxidative stress. Mitochondria, via the electron transport chain, are thought to be an important source of cellular superoxide that suppresses endothelial function in older humans but surprisingly little is understood about the effect of aging on endothelial cell metabolic activity. Young, normally functioning endothelial cells typically utilize anaerobic glycolytic metabolism but with aging a shift toward a greater reliance on oxidative metabolism could explain enhanced superoxide production via the electron transport chain. Here we aimed to determine the impact of aging on endothelial cell metabolism. To do so, we utilized SeahorseTM technology to assess mitochondrial oxygen consumption and extracellular acidification rate as measures of oxidative and anaerobic glycolytic metabolism in primary lung endothelial cells (ECs) isolated from young (4–6M) and old (16–18M) C57BL/6 mice, as well as in early (P3) and late (P16) passage human umbilical vein endothelial cells (HUVECs), a cell culture model of aging. We found that old primary ECs demonstrate a 37% higher rate of oxygen consumption (p<0.01), 74% higher spare respiration (p<0.01) and 92% higher proton leak (p<0.01) compared with young primary ECs. In contrast, ATP production was 27% lower in old compared with young primary ECs (p<0.01). Total extracellular acidification rate (glycolytic shift) was 47% (p<0.01) lower and maximal glycolytic rate was 22% lower (p<0.01) in old compared with young primary ECs, indicating reduced glycolysis and increased oxidative phosphorylation in old ECs. Next, we assessed mitochondrial membrane potential, pyruvate kinase (PK) activity, lactate dehydrogenase (LDH) activity, as well as the expression of mitochondrial membrane complexes by western blot. Interestingly, we observed 62% lower mitochondrial membrane potential (p<0.05), and reduced expression of mitochondrial membrane complex II (34%, p<0.05), III (65%, p<0.01), IV (87%, p<0.01) and V (56%, p<0.01) in old compared with young ECs. PK activity was increased by 62% (p<0.01) and LDH activity was decreased by 72% (p<0.01) in old compared with young ECs. Similar differences were observed between early and late passage HUVECs. Taken together, these findings suggest that aging results in a shift away from anaerobic glycolysis and towards a greater reliance on oxidative phosphorylation in old ECs. This is despite less efficient mitochondrial coupling and lower protein expression of mitochondrial electron transport chain proteins. Overall, these results suggest that this age related metabolic shift in ECs may contribute to increased mitochondrial superoxide production and subsequent endothelial dysfunction.Support or Funding InformationSupported by awards from the National Institute of Health (R01 AG040297, R01 AG048366, K02 AG045339) and US Department of Veterans Affairs (1I01BX002151).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.