Abstract 16069: O-linked Glycosylation is Implicated in Mitochondrial Fission and Low Glucose-induced Endothelial Dysfunction
Introduction: Attempts to improve cardiovascular complications associated with Type 2 Diabetes Mellitus through intensive glycemic therapy have been ineffective and result in increased incidence of hypoglycemia. Prior data examining the impact of low glucose (LG) on endothelial cells (ECs) and human arterioles demonstrated impaired endothelial function associated with altered mitochondrial dynamics involving the fission regulatory protein, Drp1. Published work regarding fission regulation suggests a role for O-linked glycosylation (O-GlcNAcylation).
Hypothesis: We propose that O-GlcNAcylation is responsible for transducing the LG environment into an intracellular signal capable of inducing mitochondrial fission and subsequent endothelial dysfunction.
Methods: Quantification of mitochondrial fission in human ECs was performed utilizing confocal microscopy to examine mitochondrial structures. Cells were analyzed following incubation in physiologic LG (40 mg/dL) or normal glucose (NG, 90 mg/dL) environments for 2 hours. The impact of O-GlcNAcylation was evaluated by targeting the O-glycosylation transferase (OGT) using an inhibitor, ST-060266 (ST-06), or siRNA knockdown. Video microscopy was employed to measure the vasoactivity of human adipose arterioles, subjected to LG or NG ±ST-06, in a dose-response manner to acetylcholine.
Results: ECs exposed to LG exhibited increased mitochondrial fission in comparison to NG (0.68±0.03 vs 0.36±0.09, N=5, P<0.05) and addition of ST-06 decreased LG-induced fragmentation (0.29±0.08, N=5, P<0.05). Knockdown of OGT expression during LG exposure also abrogated the mitochondrial fission response (Scramble vs siRNA, 0.48±0.05 vs 0.36±0.06, N=5, P<0.05). Human arterioles treated with ST-06 displayed improved endothelial-dependent vasodilation in comparison to LG alone (N=3, P<0.05).
Conclusions: Altered mitochondrial dynamics exhibited by ECs during LG can be prevented through targeted inhibition of modification by O-GlcNAcylation. Similarly, this approach also improved endothelial function in human arterioles exposed to LG. O-GlcNAcylation may provide the mechanistic link between glucose, endothelial impairment and adverse vascular events associated with hypoglycemia.
Author Disclosures: M.J. Tanner: None. J. Wang: None. R. Ying: None. M. Shahreyar: None. V. Puppala: None. A. Branum: None. M.E. Widlansky: Research Grant; Significant; Merck Sharp & Dohme Corp., Everist Health.
- © 2016 by American Heart Association, Inc.