Abstract 516: Altered Autophagy Contributes to Endothelial Dysfunction in Human Diabetes Mellitus
Diabetes is associated with increased oxidative stress and decreased nitric oxide (NO) bioactivity in the vasculature. Autophagy is a critical multistep pathway that eliminates oxidatively damaged proteins and organelles from the cell. Emerging evidence implicates impaired autophagy in a variety of non-vascular tissues that contributes to the pathogenesis of diabetes in experimental models. We hypothesized that impaired autophagy contributes to endothelial dysfunction associated with type 2 diabetes mellitus in humans. We measured vascular function and markers of autophagy in freshly isolated endothelial cells from patients with diabetes (n=41) and non-diabetic controls (n=41). Diabetes was associated with endothelial dysfunction characterized by lower brachial artery flow-mediated dilation. Endothelial cells from diabetic patients displayed no differences in LC3 puncta compared to those from controls but had higher levels of endothelial p62 (p=0.004), a protein that accumulates with reduced autophagic flux. In endothelial cells from controls, the autophagy inhibitor bafilomycin impaired eNOS activation, confirming that intact autophagy is necessary for NO signaling. Global activation of autophagy with spermidine reversed endothelial dysfunction in cultured endothelial cells exposed to high glucose (p=0.007). In regard to mechanism of impairment, the autophagy initiator rapamycin failed to improve eNOS activation in endothelial cells from diabetics. Further, expression of beclin-1, a key contributor to autophagosome formation, was similar in diabetics and controls, arguing against impaired initiation of autophagy. In endothelial cells from diabetics, blocking the terminal step of autophagy with bafilomycin led to a further accumulation of p62 (P=0.01), suggesting intact but insufficient levels of autophagy. Lamp2a, which facilitates the merger of autophagosomes and lysosomes, was higher in diabetic cells, possibly reflecting a compensatory response to reduced flux. Collectively, these findings provide evidence for inadequate autophagic flux in endothelial cells from diabetic patients that contributes to endothelial dysfunction and may be a target for therapy of diabetic vascular disease.
Author Disclosures: J.L. Fetterman: None. N. Flint: None. M. Holbrook: None. E.A. Linder: None. B.D. Berk: None. B. Feng: None. M.A. Duess: None. M.G. Farb: None. N. Gokce: None. O.S. Shirihai: None. N.M. Hamburg: None. J.A. Vita: None.
- © 2014 by American Heart Association, Inc.