Urinary Vitamin C Loss in Diabetic Subjects
Purpose
Several studies have reported that diabetic subjects have lower plasma vitamin C concentrations than non-diabetic subjects. Although urinary vitamin C loss in diabetic subjects was reported to be increased in two studies, these are difficult to interpret due to lack of controlled vitamin C intake, inadequate sampling, lack of control subjects, or methodology uncertainties in vitamin C assay and sample processing. Consequently, it is unclear whether diabetic subjects truly have both low plasma and high urine vitamin C concentrations. We propose that low plasma vitamin C concentrations in diabetic subjects are due in part to inappropriate renal loss of vitamin C in these subjects but not in healthy controls. We will study nondiabetic controls and cohorts with diabetes. Vitamin C concentrations in plasma, RBCs, and urine will be measured in outpatients. In those willing to be admitted to the Clinical Center, we will measure vitamin C pharmacokinetics to determine the relative bioavailability for vitamin C in individuals with and without abnormal urinary loss of vitamin C (or renal leak). Single nucleotide polymorphisms (SNPs) will be determined in genomic DNA responsible for the two proteins mediating sodium dependent vitamin C transport, SVCT1 and SVCT2. We will also explore mechanisms underlying abnormal urinary vitamin C loss....
Condition
- Diabetes
Eligibility
- Eligible Ages
- Between 18 Years and 65 Years
- Eligible Genders
- All
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
To be included in the study, study subjects should be: - Aged 18-65 years. - Either: - Have no diagnosis of diabetes: "nondiabetic controls", or - Have a diagnosis in their medical history of either Type 1 or Type 2 diabetes
Exclusion Criteria
(for outpatient study, arm 1) Exclusion criteria will include the following: - Unable or unwilling to provide a signed and dated informed consent form - Unable or unwilling to comply with study procedures and lifestyle considerations EXCLUSION CRITERIA (for inpatient studies, arms 2 and 3) Study participants interested in participating in Arms 2 and/or 3 will be excluded from this further participation if they meet any of the following: - significant organ malfunction leading to clinical instability including liver disease, pulmonary disease, ischemic heart disease, heart failure, stroke, peripheral vascular disease, and anemia at investigator discretion - other serious or chronic illness; history of serious or chronic illness; coronary artery disease, or peripheral vascular disease resulting in clinical instability - pregnancy or lactation - presence of other conditions which, in the judgment of the investigators, can influence vitamin C metabolism or vitamin C renal handling
Study Design
- Phase
- Study Type
- Observational
- Observational Model
- Cohort
- Time Perspective
- Prospective
Arm Groups
| Arm | Description | Assigned Intervention |
|---|---|---|
| Diabetes Type I | Subjects with Type I diabetes mellitus | |
| Diabetes Type II | Subjects with Type II diabetes mellitus | |
| Healthy Volunteers | Healthy Volunteers |
Recruiting Locations
Bethesda, Maryland 20892
More Details
- NCT ID
- NCT00071526
- Status
- Recruiting
- Sponsor
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Detailed Description
Several studies have reported that diabetic subjects have lower plasma vitamin C concentrations than non-diabetic subjects. Although urinary vitamin C loss in diabetic subjects was reported to be increased in two studies, these are difficult to interpret due to lack of controlled vitamin C intake, inadequate sampling, lack of control subjects, or methodology uncertainties in vitamin C assay and sample processing. Consequently, it is unclear whether diabetic subjects truly have both low plasma and high urine vitamin C concentrations. We propose that low plasma vitamin C concentrations in diabetic subjects are due in part to inappropriate renal loss of vitamin C in these subjects but not in healthy controls. We will study nondiabetic controls and cohorts with diabetes. Vitamin C concentrations in plasma, RBCs, and urine will be measured in outpatients. In those willing to be admitted to the Clinical Center, we will measure vitamin C pharmacokinetics to determine the relative bioavailability for vitamin C in individuals with and without abnormal urinary loss of vitamin C (or renal leak). Single nucleotide polymorphisms (SNPs) will be determined in genomic DNA responsible for the two proteins mediating sodium dependent vitamin C transport, SVCT1 and SVCT2. We will also explore mechanisms underlying abnormal urinary vitamin C loss.