Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT05218018 |
| Other study ID # |
STUDY00008451 |
| Secondary ID |
1R01AG067563-01 |
| Status |
Completed |
| Phase |
N/A
|
| First received |
|
| Last updated |
|
| Start date |
March 1, 2020 |
| Est. completion date |
January 13, 2022 |
Study information
| Verified date |
January 2023 |
| Source |
University of Washington |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
|
| Study type |
Interventional
|
Clinical Trial Summary
The 'Western diet' characterized by high fat feeding (HFF) is a risk factor for Alzheimer's
disease (AD); however, little is known about mechanisms. Paradoxically, individuals who carry
the AD risk gene APOE E4 cognitively improve after HFF and show different metabolic responses
to fat intake. These responses include a more pronounced drop in systolic blood pressure and
a decrease in cerebrospinal fluid glucose and lactate levels. This proposal will further
examine the brain metabolic response to HFF using non-invasive imaging. Cerebral blood flow
(CBF) as assessed by functional MRI is increasingly utilized to investigate brain function,
given that CBF is tightly coupled to brain metabolism. Acute changes in CBF have been
described in response to carbohydrate ingestion in regions important for learning and memory;
however, no one has yet assessed CBF response to lipid. Here investigators propose to
characterize CBF changes to a high fat drink in older adults. This study will include a time
course assessment as well as analyses of global and regional change in CBF. These data would
serve as feasibility pilot data for an R01 application which would include cognitive and
peripheral metabolic data. These types of studies will provide a clearer picture of acute
brain metabolic response to HFF in older adults, including the effects of APOE.
Description:
Overview: High fat feeding (HFF) is a risk factor for AD, but this risk factor is modulated
by APOE genotype. Acute meal studies including lipid tolerance tests are increasingly being
used to understand mechanisms by which diet affects disease processes. Investigators have
consistently shown that E4 carriers respond differently to HFF in acute meal challenges; this
study will further explore this phenomenon in older adults by assessing cerebral blood flow
(CBF), given its tight coupling to brain metabolism. Here investigators propose to use
arterial spin labeling (ASL) MRI as this non-invasive imaging technique can detect small
changes in global and regional CBF, and acute ∆CBF in response to nutrients have been
demonstrated in humans. With this project investigators will determine the most optimal time
point for detecting post-lipid ∆CBF, as well as determine which regions of the brain respond
to HFF. To our knowledge, this study would be the first to assess ∆CBF using ASL; these pilot
data will then assist with future grant applications in this area.
Specific aims: 1. To determine which time point (1, 2, or 3 hours) produces the most robust
∆CBF after ingestion of a lipid drink in 30 older adults. 2. To determine which regions of
the brain respond to HFF.
Methods: Participants: All study procedures will be submitted to the UW Institutional Review
Board for approval. Investigators maintain a database of ~40-50 participants from the Meal
and Memory study who have already agreed to be contacted for future studies; investigators
will recruit 30 participants. Inclusion criteria are as follows: age 55 and older, able to
read and understand English, able to give informed consent, and able to undergo MRI and
ingest dairy products. All interested participants will undergo telephone screening to ensure
they meet inclusion criteria. If they meet criteria, they will be mailed a reminder letter
which will instruct them to fast the night before. They will also receive a copy of the
consent form to look over, and a medical history form to fill out, including an MRI safety
checklist which asks them about prior surgeries and whether they have any metal in their
body.
Study visit: Participants will fast the night prior (12 hours prior to the visit time);
medications and water are ok. They will arrive at the South Lake Union facility between 8 and
10 am. They will undergo informed consent in a quiet room from the study team (either the PI
or the study coordinator) and given plenty of opportunities to ask questions. If they choose
not to enroll in the study, they will be discharged from the unit and parking or
transportation will be reimbursed. As a part of the consent process, investigators will ask
participants to give optional written permission on the consent form to release their APOE
genotype from the Meal and Memory Study, or other Alzheimer's research study they may have
participated in. Investigators will not disclose this genotype to anyone outside the study
team including the participant.
If the participant enrolls in the study and signs a consent form and a research HIPAA form,
then the protocol will begin. Vitals will be assessed by the study team, including blood
pressure, heart rate, and height/weight and BMI calculation. Participant will be escorted to
the MRI machine by the study team, who will also bring down the lipid drink in a cooler. An
MRI technician experienced with research MRI procedures will conduct the MRI portion. First a
15 minute ASL protocol will be run, then the participant will be given the heavy cream (100
mls, or just under half a cup, which contains 370 calories, 40.4 grams of total fat, 23.6
grams of saturated fat). Investigators will encourage the participant to drink the product
over 5 minutes. Participants will then undergo 3 more 15-minute scans at 1, 2, and 3 hours
post drink. It is possible that some of the acquisition times can be slightly longer than 15
minutes. After the last MRI image acquisition, lunch will be offered (up to $15 at a nearby
restaurant), participants will receive a gift card, and parking or transportation will be
reimbursed, and be discharged.
Alternative site: UWMC will run the last 2-4 participants to ensure the MRI protocols and
sequences are similar, in order to prepare for Lipid MRI 2.0. Participants will check in at
the DISC lab and vitals will be done there including height and weight for BMI calculation.
MRI protocol: The MRI is non-invasive with no need for contrast. In addition, investigators
will not be performing a clinical MRI and these findings cannot be used to diagnose any brain
condition. For the ASL protocol, we will use pseudo-continuous arterial spin labeling to
measure CBF in ml/100g/min as a marker of perfusion for improved signal quality. In this
approach, magnetically labeled arterial blood water serves as the endogenous contrast.
Investigators will use a sequence (5.5 minutes) with long label duration = 1.8 s, long
post-labeling delay = 2 s, with labeling offset = 25-30 mm, slices = 20, spatial resolution =
3.5×3.5×5 mm3, field of view = 240×240×100 mm3, SENSE-factor = 2, TR/TE= 5000/18 ms.
Investigators will apply dual adiabatic background suppression pulses to minimize gray and
white matter tissue contamination at TI = 2.05 and 3.25 s. Finally, investigators will
acquire an equilibrium magnetization scan (M0, 1 minute), identical to the above scan, but
with TR = 10,000 ms and no labeling or background suppression. For the last 8 subjects
investigators will add a T2 multi-echo sequence (approximately 10 minutes) to detect changes
in the appearance of the hypothalamus from before to after lipid ingestion.
Analysis: Analysis will be done under the supervision of Dr. Rane and the UW Diagnostic
Imaging Sciences Center (DISC). Investigators will first apply motion correction to the
arterial spin labeling images using FSL-MCFLIRT and register them to the M0 image. Then,
investigators will perform a pair-wise subtraction between the control and null images and
apply a two-compartment model to quantify CBF. Investigators will co-register the resulting
CBF map to the T1 scan followed by a transformation to MNI space. The temporal regions such
as the entorhinal cortex, temporal lobe, hippocampus as well as the posterior cingulate and
lateral parietal lobules will be identified using standard Harvard-Oxford Cortical and
Subcortical atlas. CBF values will be compared in these regions between the 3 groups. The
region of interest approach can dilute effects that are smaller than the size of the region
of interest. Therefore, we will also perform permutations testing in FSL to evaluate
voxel-wise CBF differences between group. In order to ensure that the voxel-wise outcomes are
not mere chance, investigators will impose strict family-wise error correction for multiple
comparisons.
Statistics: From these images investigators will obtain measures on global blood flow as well
as regional blood flow in pre-defined regions. Investigators will utilize standard
statistical models to compare the 1, 2, and 3 hour ASL to the baseline ASL to ascertain what
time point produces the most robust change result. If analyses of the first few subjects
necessitate, time points can shift earlier or later, depending on what time point shows the
maximum change in CBF-the primary outcome.
