NIH Clinical Research Studies

Protocol Number: 04-DK-0021

Active Accrual, Protocols Recruiting New Patients

Title:
Urinary Vitamin C Loss in Diabetics
Number:
04-DK-0021
Summary:
The human body absorbs vitamin C from the intestine. Many different tissues store the vitamin but it is also lost in the urine. This study will examine whether patients with diabetes have low plasma vitamin C concentrations and lose more vitamin C in their urine than healthy people do. To find if this is the case, vitamin C concentrations in blood and urine will be measured. Certain proteins allow the body to absorb and store the vitamin. Variations in these proteins can be found by testing for genetic parameters called single nucleotide polymorphisms (SNPs), which are markers of genetic variation among people. We will test blood samples for specific SNPs related to vitamin C metabolism. This will show whether participants have genetic differences in the proteins that allow them to absorb and store vitamin C.

Patients 18 to 65 years of age who are either healthy or have diabetes, have no major illnesses other than diabetes, have no serious complications of the disease and whose blood pressure is well controlled may be eligible for this study.

Participants will choose to be studied either as outpatients or inpatients. They will undergo the following tests and procedures:

-Medical history

-Physical examination.

-Blood and urine tests for complete blood count, vitamin C, various chemistries, hepatitis B, hepatitis C, HIV, cotinine and other tests.

Participants will be asked to stop taking all vitamin preparations for 2 weeks before the study. Outpatients will provide a blood and urine sample after an overnight fast. The procedure will take a little over 1 hour. Inpatients will also provide a blood and urine sample, and afterward they will be hospitalized for 24 hours and placed on a diet free of vitamin C. They will be asked to eat and drink only food and beverages given to them during those 24 hours. A 24-hour urine sample will be collected for measurement of protein, creatinine, and vitamin C. Another blood sample will be collected on the morning of the second day, along with a sample of urine for vitamin C measurement.

Sponsoring Institute:
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Recruitment Detail
Type: Active Accrual Of New Subjects
Gender: Male & Female
Referral Letter Required: No
Population Exclusion(s): None

Eligibility Criteria:
INCLUSION CRITERIA:

We propose to study 150 male and female subjects between the ages of 18 and 65. This will include 50 healthy subjects and 100 subjects with type 1 or type 2 diabetes. To be included in the study, study subjects should:

-be non smokers and be in good general health.

-have no significant illnesses other than the complications of diabetes mellitus but should not have neuropathy affecting the functioning of internal organs such as the stomach and urinary bladder.

-have serum creatinine less than 2.

-be normotensive at the time of the study, with a blood pressure less than or equal to 140/90.

Acceptable medications include insulin and ACE inhibitors or ARBs for type 1 diabetes and oral hypoglycemic agents and ACE inhibitors or ARBs in the case of type 2 diabetes. Type 1 and type 2 diabetic subjects on aspirin are also eligible provided they are not taking it for known ischemic heart disease or cerebrovascular disease. The aim of this study is to determine whether diabetic subjects lose vitamin C in the urine in their normal clinical condition (i.e while on treatment) and not in the native untreated state of uncontrolled hyperglycemia. Therefore the patients will not discontinue medication.

EXCLUSION CRITERIA:

Exclusion criteria will include the following:

-significant organ malfunction including liver disease, pulmonary disease, ischemic heart disease, heart failure, stroke, peripheral vascular disease, and anemia.

-other serious or chronic illness; history of serious or chronic illness; coronary artery disease, or peripheral vascular disease.

-pregnancy or acromegaly.

-alcohol abuse, drug addiction or the use of illegal drugs.

-use of vitamin supplements within 2 weeks prior to sample procurement.

-positive HIV or hepatitis (B or C) screening tests (subjects will be notified of these test results).

-presence of other concomitant conditions which in the judgment of the investigators can influence vitamin C metabolism or vitamin C renal handling.

For inpatient subjects, an additional exclusion criterion is consumption during the hospitalization of any foods or beverages other than those in the vitamin C free diet.

Special Instructions: Currently Not Provided
Keywords:
Vitamin C
Diabetes Mellitus
Proteinuria
Plasma Concentrations
Renal Threshold
Diabetes Type II
Diabetes Type I
Healthy Volunteer
HV
Recruitment Keywords:
None
Conditions:
Diabetes Mellitus
Investigational Drug(s):
None
Investigational Device(s):
None

Contacts:
Patient Recruitment and Public Liaison Office
Building 61
10 Cloister Court
Bethesda, Maryland 20892-4754
Toll Free: 1-800-411-1222
TTY: 301-594-9774 (local),1-866-411-1010 (toll free)
Fax: 301-480-9793

Electronic Mail:prpl@mail.cc.nih.gov

Citations:
Levine M. New concepts in the biology and biochemistry of ascorbic acid. N Engl J Med. 1986 Apr 3;314(14):892-902. Review. No abstract available.

Goodwin JS, Goodwin JM, Garry PJ. Association between nutritional status and cognitive functioning in a healthy elderly population. JAMA. 1983 Jun 3;249(21):2917-21.

Fata FT, Herzlich BC, Schiffman G, Ast AL. Impaired antibody responses to pneumococcal polysaccharide in elderly patients with low serum vitamin B12 levels. Ann Intern Med. 1996 Feb 1;124(3):299-304.

Active Accrual, Protocols Recruiting New Patients

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