Blood Vessel Study

According to the CDC, heart disease is the leading cause of death for both men and women of
most racial/ethnic groups in the United States, including African Americans, Hispanics, and
whites. About 610,000 people die of cardiovascular disease (CVD) every year, accounting for 1
in every 4 deaths (41). Because many known risk factors for heart disease are hereditary,
understanding the connection between genetics, particularly heritable polymorphisms, and
cardiovascular disease risk is of great importance. This is a cross-sectional, controlled
study designed to investigate the association of two single nucleotide polymorphisms (SNPs) -
a cytochrome P450 (CYP) epoxygenase gene CYP2J2 SNP, CYP2J2 7, and a soluble epoxide
hydrolase (sEH) gene EPHX2 SNP encoding a K55R variant - with altered endothelial function in
humans. Healthy adults, aged 18-65 years, who are either carriers of CYP2J2 7 or EPHX2 K55R,
or who are wild type (WT) with respect to either SNP will be recruited into a total of five
genotype groups. Potential participants will be identified from the Environmental
Polymorphisms Registry, mailed an informational letter, contacted by phone and/or email, and
pre-screened for eligibility. As participants are recruited, demographic characteristics
(i.e., age, gender, and race/ethnicity) will be compared between the groups, and, if
necessary, recruitment will be targeted to achieve an approximate match in demographic
characteristics across the groups. Pre-screened individuals will provide verbal consent to
refrain from taking certain as needed supplements/medications that could alter endothelial
function and recreational drugs (such as marijuana, cocaine and amphetamines) prior to the
study visit, and will be mailed an informed consent form, medical history form, a urine
collection cup, and pre-visit instructions. Participants will attend a single study visit
that will take place at the NIEHS Clinical Research Unit. During this visit, written informed
consent will be obtained, and there will be a final screening and eligibility determination
including medical history review, assessment of vital signs, physical examination, carbon
monoxide measurement, pregnancy test (if applicable), and electrocardiogram (ECG). In
eligible participants, a lipid panel will be performed and endothelial function will be
assessed non-invasively by brachial artery ultrasound (i.e., flow-mediated dilation) and
digital peripheral arterial tonometry. Blood and urine (first void) samples will be collected
for biomarker analyses, which will be conducted in the Zeldin laboratory at NIEHS. The
primary objective of the study is to determine whether individuals who are homozygous or
heterozygous for the CYP2J2 7 or EPHX2 K55R SNPs exhibit altered endothelial function
compared with individuals who are WT for that SNP. As a secondary objective, the impact of
these two SNPs on inflammatory and CYP epoxygenase pathway biomarkers will be examined.

- INCLUSION CRITERIA:

- Participant of the Environmental Polymorphisms Registry and current contact
information available

- Genotype information available for relevant CYP2J2 and EPHX2 polymorphisms, which
indicates:

- WT for EPHX2 K55R and WT for CYP2J2 7

- WT for EPHX2 K55R and heterozygous for CYP2J2 7

- WT for EPHX2 K55R and homozygous for CYP2J2 7

- WT for CYP2J2 7 and heterozygous for EPHX2 K55R (N=30)

- WT for CYP2J2 7 and homozygous for EPHX2 K55R (N=30)

- Age 18-70 years

- Willing and able to provide informed consent

- Able to comply with all protocol procedures

EXCLUSION CRITERIA:

- Currently pregnant or breast feeding

- Hospitalized for a cardiovascular disease or stroke event within the previous 3 months

- Current use of long-acting nitrates (e.g., isosorbide mononitrate, isosorbide
dinitrate)

- Current use of medications taken for hypertension.

- For participants with current daily or chronic use of NSAIDs; unable or unwilling to
refrain from taking NSAIDs for 7 days prior to enrollment visit.

- Current use of insulin for Type I Diabetes

- Presence of a pacemaker or implanted cardioverter-defibrillator

- Presence of an irregular heart rhythm (atrial fibrillation) at the study visit

- Current resting heart rate <40 or >125 beats per minute

- Current systolic blood pressure <90 or >180 mmHg, or diastolic blood pressure >110
mmHg

- Skin sensitivity precluding use of ECG electrodes

- History of hypersensitivity to nitroglycerin or other nitrates or nitrites

- History of infection within the preceding 1 week or temperature >38 degrees C

- Unwilling or unable to:

- Fast (including alcohol and caffeine-containing products) and discontinue tobacco
use for 12 hours prior to Visit 1

- Withhold all prescribed and over-the-counter medications and supplements the
morning of Visit 1, until after the visit is completed

- Refrain from taking the following, as needed, medications for 7 days prior to
Visit 1:

- Vasoactive agents, such as decongestants (e.g., pseudoephedrine)

- Recreational drugs such as marijuana, cocaine, and amphetamines

- Anti-inflammatory agents (NSAIDs), such as ibuprofen, naproxen or aspirin

- Sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis)

Exclusion of Pregnant and Breast Feeding Women: Any woman who is pregnant or breast feeding
will be excluded from this study because nitroglycerin, administered as part of the study,
is category C, and it is unknown whether nitroglycerin can cause fetal harm when
administered to a pregnant woman or whether it can affect reproductive capacity; it is also
unknown whether nitroglycerin is excreted in human milk. Also, hormonal changes associated
with pregnancy can significantly influence the proposed measures of endothelial function.
Females will have a urine pregnancy test prior to undergoing study procedures.