Plasma Free Fatty Acids Profile As A Diagnostic Tool For Acute Ischemic Stroke

Ischemic stroke is the third leading cause of death and the leading cause of long-term
disability in the United States. Immediate treatment can play a major role in the outcome of
ischemic stroke and can help improve prognosis in many cases. One of the factors effecting
immediate treatment is a rapid and accurate diagnostics of ischemic stroke.

Although imaging techniques remain to be the primary diagnostic instrumental tool, advanced
imaging studies can slow management decisions and are sometimes unavailable. In addition,
imaging studies often cannot discriminate between pre-existing lesions and acute or ongoing
processes. Thus, additional diagnostic and prognosis tools such as plasma biomarkers will be
beneficial for the early management of ischemic stroke. Importantly, the only FDA approved
therapeutic treatment for ischemic stroke is tPA administration within 3-4.5 hours of stroke
onset. Thus, the ideal biomarker for ischemic stroke would be readily detectible within this
window for intravenous thrombolysis.

To date, the majority of potential stroke biomarkers studied are of peptide/protein nature
and do not meet this requirement. One of the reasons is that hydrophilic substrates including
peptides and proteins do not readily cross blood-brain barrier (BBB). Thus, brain specific
peptides/proteins are unlikely to be significantly increased in plasma within the therapeutic
windows of acute stroke conditions, but rather will be slowly increased during progression of
stroke associated with BBB integrity loss. As a result, the most commonly utilized
brain-specific protein biomarkers, including S100b and neuron specific enolase, do not
increase in plasma before 10-18 hours, and do not correlate with infarct volume prior to 24
hours after injury. Many other brain-specific proteins studied have similar limitations,
while proteins such as copeptin found elevated under acute stroke conditions are highly
non-specific for the brain and may serve as a more general marker of physiologic stress.
Another promising approach is utilization of blood gene expression analysis to identify the
etiology of acute ischemic stroke. However, the timing of RNA expression measurement, as well
as dynamics for RNA expression may add limitations to this approach to meet "the ideal
ischemic stroke biomarker" requirement.

Alternatively, lipid biomarkers may overcome these limitations. Lipids are hydrophobic and
readily cross the BBB, are very abounded accounting for about 10% of brain wet weight, have a
brain specific profile, and alterations in brain lipids develop immediately upon ischemic
injury. Recently, using a targeted quantification, a brain specific sphingolipid was
identified as a promising biomarker for acute brain damage, demonstrating a feasibility of
using lipid biomarkers to diagnose stroke.

In the current project, the investigators propose a novel approach of using plasma free fatty
acid profiling as a biomarker for ischemic stroke. This novel approach is based on well
documented features of brain lipid composition and metabolism under acute ischemia
conditions. First, the brain has a unique signature of phospholipid fatty acid composition
that is different from plasma and other tissues with one of the highest arachidonic,
docosahexaenoic, and adrenic acid concentrations, that make up to 20% of fatty acids in the
mammalian brain. These polyunsaturated fatty acids are mainly esterified in the sn-2 position
on phospholipids and are released by a phospholipase of the A2 family. Secondly, lipids
constitute more than half of the dry weight in human brain, making it the second greatest
lipid containing organ in the body after adipose tissue, thus representing a significant
potential source for fatty acids. Third, upon acute ischemic injury, brain phospholipases
(predominantly A2 family) are immediately activated, leading to a rapid (within minutes)
release of polyunsaturated fatty acids from sn-2 position from phospholipids in the free
form. Because of the hydrophobicity of fatty acids, they are readily permeable for BBB and
are expected to be found in plasma. Forth, dietary fatty acids are circulated in the
esterified form, while released from adipose tissue free fatty acids have a different fatty
acid profile, making brain free fatty acids distinguishable from other fatty acid pools in
plasma.

The only FDA approved treatment for ischemic strokes is tissue plasminogen activator (tPA,
also known as IV rtPA, given through an IV in the arm), administered within 3-4.5 hours of
stroke onset. tPA works by dissolving the clot and improving blood flow to the part of the
brain being deprived of blood flow. Although imaging techniques remain to be the primary
diagnostic instrumental tool, advanced imaging studies can slow management decisions and are
sometimes unavailable. In addition, imaging studies often cannot discriminate between
pre-existing lesions and acute or ongoing processes. Thus, additional diagnostic and
prognosis tools such as plasma biomarkers will be beneficial for the early management of
ischemic stroke.

This study will not involve children, neonates, pregnant women or prisoners.

Inclusion Criteria:

- Have onset of symptoms within 24-hours of presentation (AIS and Brain ?Trauma arms
only).

- 18-years old and older.

- Able to offer informed consent after passing the MMSE with score ≥18 or able to obtain
consent from legally authorized representative if MMSE score is ≤17.

- Participants must be admitted to the hospital and stay for at least 24 hours.

- Present with a traumatic or non AIS-related brain injury (non-AIS brain injury arm
only).

- Diagnosed with non-neurological pathology (non-neurological pathology arm only).

Exclusion Criteria:

- Have onset of symptoms more than 24-hours before presentation (AIS and Brain Trauma
arms).

- Less than 18-years old.

- Patients unwilling to provide consent with MMSE score of 18 or greater.

- Legally authorized representative unable or unwilling to provide consent for patients
with an MMSE score of 17 or less.

- If they leave the hospital within 24 hours after being admitted.

- No longer meeting the eligibility criteria.