Cerebrovascular O-GlcNAcylation Worsens Diabetes-associated Neurovascular Injury and Recovery Post-stroke

PROJECT SUMMARY Diabetes affects more than 463 million people worldwide and significantly increases the risk of stroke, as well causing greater neurovascular injury in response to ischemia and compromising recovery. Cerebral vascular integrity is critical for preventing stroke and ameliorating the lasting effects of brain ischemia, should it

unfortunately occur. Nonetheless, a critical barrier to our progress in reducing the morbidity and mortality of diabetics is our lack of understanding of the mechanisms that predispose them to increased stroke risk, exacerbated neurovascular injury, and impaired recovery. Mechanisms that underlie the vascular damage in

diabetes vary widely, but the O-linked β-N-acetylglucosamine (O-GlcNAc) modification (O-GlcNAcylation) is significant given the perpetual state of hyperglycemia that is hallmark of the disease. O-GlcNAcylation is a ubiquitous post-translational modification that alters target protein function, activity, subcellular localization, and

stability, and is executed by two enzymes: O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), which add and remove O-GlcNAc, respectively. Acutely, O-GlcNAcylation serves as a form of stress signaling. On the other hand, chronic O-GlcNAc modifications are harmful to vascular function and have been reported in the

vasculature from wide range of pathological conditions including diabetes and obesity. Importantly, it has been reported that a high fat diet augments basilar artery O-GlcNAc expression and this is associated with increased neurovascular injury after middle cerebral artery occlusion. However, it is unknown whether cerebrovascular O-

GlcNAcylation, and the two O-GlcNAc enzymes, have a causal role in (i) predisposing diabetics to stroke, (ii) worsening the stroke-induced neurovascular injury, and (iii) impairing functional recovery after stroke. To address this gap in the literature, we have composed this Stephen Katz ESI R01 with the central hypothesis that

deficiency of OGT will protect against pre-stroke parenchymal arteriole dysfunction, post-stroke neurovascular injury, and improve chronic recovery. On the other hand, insufficiency of OGA will exacerbate pre-stroke parenchymal arteriole dysfunction, post-stroke neurovascular injury, and worsen chronic recovery. We will test

this hypothesis by executing the following approaches: In vitro we will culture primary cerebral microvascular endothelial and vascular smooth muscle cells with high glucose and palmitate. In vivo we will predominantly use a high-fat diet/low-dose streptozotocin model of diabetes, and stroke will be induced via thromboembolization of

the middle cerebral artery. Measurements of cerebrovascular integrity, neurovascular injury, and behavior will be executed pre-stroke and post-stroke. Some mice will also be maintained long-term after stroke to evaluate chronic recovery. In summary, while this Stephen Katz ESI R01 application represents new research directions

for our lab, our fresh insights and rigorous application (including an excellent support team of co-investigators and significant contributors) could potentially transform the fields of diabetes and stroke research by revealing cerebrovascular O-GlcNAcylation as a causal mechanism and novel therapeutic target.