Vascular Dysfunction in Diabetes: Genes and Hormones

The investigators are very excited that the National Institutes of Health are sponsoring us
to investigate why patients with diabetes are more likely to develop high blood pressure,
atherosclerosis (hardening of the arteries), and heart disease. There are two parts of our
research program. The first part is a screening visit. At this visit you will be given a
brief physical exam and will be asked questions concerning your medical history. During the
same visit you will have your blood drawn for routine screening and to prepare DNA for
genetic testing. You will also be asked to collect a urine sample for routine screening.

If the doctor finds that you are a healthy candidate you will be invited to participate in
the second part of the study. During Phase II the investigators will perform physiologic
tests after you are placed on a low salt diet and again after you are placed on a high salt
diet. All of the food that you will eat during the two diets will be provided to you by the
hospital. If you are on blood pressure medication, it may be necessary to discontinue taking
your present medication for up to three months before beginning the study. Patients
discontinuing their current blood pressure medication may be placed on a different blood
pressure medication during this washout period if necessary to maintain blood pressure at
pre-study levels. The investigators will take you off all medications, except cholesterol
medications two weeks prior to your scheduled in-patient study. However, if you are currently
on medication to control your diabetes you will remain on this throughout the entire study.

Once your blood pressure medications are discontinued, you will be closely monitored to make
sure you do not encounter any difficulty. If you do not own a home blood pressure monitor,
the investigators will provide one for to use during the study so that you can keep a daily
record of your blood pressure readings. The investigators will ask you to call us every three
days to report your blood pressure readings. Less than 20% of patients with hypertension have
any significant increase in their blood pressure during this short time off therapy. After
you have been off your medication for nine days the dieticians will give you low salt meals
to eat at home for six days. On the sixth day of the low salt diet, you will be asked to
begin a 24-hour urine collection. You will also be required to come to the Ambulatory
Clinical Center (221 Longwood Ave.) for a one-hour test. You will return that evening to the
inpatient Clinical Research Center where you will be admitted for your first study that will
occur the next morning. On the morning of your low salt study you will have three naturally
occurring hormones administered and blood samples drawn from an intravenous needle. The
investigators will also take ultrasound pictures of your heart to see how salt and hormones
affect the way the heart functions. These tests will last approximately five hours and you
will be discharged around 12:00 p.m. The dieticians will then give you your meals for the
next week to take home. Each of these meals will have a high salt content. After six days of
your high salt diet, on the morning of your second admission to the hospital, you will be
asked to begin a final 24-hour urine collection. The same study that was done for the low
salt study will be repeated for the high salt study. You will be discharged around 3:00 p.m.
This study will determine if you are salt-sensitive. A high salt diet has been found to lead
to higher blood pressure and weight gain. In addition, the investigators hope to learn more
about the hormones that regulate your blood pressure and the genes responsible for regulating
those hormones.

You will be placed back on your initial blood pressure medication (if you are on any) and
returned to your regular physician for care. The investigators will provide clinically
relevant information to you and your physician.