PROJECT SUMMARY/ABSTRACT
Despite being a leading cause of death and morbidity in the U.S., ischemic stroke still has limited therapeutic
options. In recent years, the protective potential of pre-conditioning has attracted much attention, though given
the difficulty in predicting when stroke will occur, its application to preventing stroke in the general population is
somewhat limited. However, there are several clinical scenarios where for a period of time, the risk of stroke is
dramatically increased, including cardiac/vascular surgery, and recent history of stroke or transient ischemic
attack. In these common scenarios, short-term protection conferred by pre-conditioning may offer considerable
clinical potential. While the benefit of hypoxic pre-conditioning against stroke has been known for many years,
only recently has the neuroprotective effect of a ketogenic diet been demonstrated. While this neuroprotection
has largely been attributed to improving metabolic efficiency, thus far, no-one has examined the vascular
contribution to this protection. In this R21 application, we hypothesize that a ketogenic diet protects against
ischemic stroke by promoting blood-brain barrier (BBB) integrity via increased expression of
endothelial tight junction proteins and the vasculo-protective integrin a6ß4. This hypothesis is supported
by several observations. First, like mild hypoxia, a ketogenic diet promotes profound angiogenic remodeling in
the brain, along with increased expression of key BBB transporter molecules. Second, also like mild hypoxia, a
ketogenic diet activates hypoxia-inducible factor (HIF)-1a signaling, suggesting that these two stimuli may
achieve neuroprotection via common downstream mechanisms. Third, mild hypoxia upregulates endothelial
expression of tight junction proteins, implying that one mode of action of these pre-conditioning stimuli is to
promote BBB integrity. Last, we have shown that the endothelial extracellular matrix integrin receptor a6ß4 is
upregulated during hypoxic conditioning, and appears to enhance BBB integrity. To test our hypothesis, we
propose three specific aims: (1) demonstrate that a ketogenic diet promotes cerebral angiogenesis and
increased endothelial expression of vascular remodeling integrins and tight junction proteins, (2) demonstrate
that ketogenic-conditioned mice are resistant to ischemic stroke due to enhanced BBB integrity through
upregulation of endothelial tight junction proteins and a6ß4 integrin, and (3) define the roles of the angiogenic
(a5ß1) and stabilizing (a6ß4) integrins in mediating vascular remodeling in response to a ketogenic diet.
These studies will characterize for the first time, the cerebrovascular remodeling events induced by a
ketogenic diet and define the contribution of this remodeling to protection from ischemic stroke. We expect to
demonstrate that a ketogenic diet promotes robust cerebrovascular remodeling and that ketogenic-conditioned
mice will be resistant to ischemic stroke, in part due to enhanced BBB integrity via increased endothelial
expression of the vasculo-protective integrin a6ß4 and tight junction proteins. Successful completion of these
studies could lead to the development of a novel approach for preventing ischemic stroke in high-risk patients.
