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Sponsored by: |
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) |
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Information provided by: | National Institutes of Health Clinical Center (CC) |
ClinicalTrials.gov Identifier: | NCT00071526 |
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 vitamin C concentrations in patients with type 1 and type 2 diabetes and in matched healthy research subjects. Vitamin C concentrations in plasma, neutrophils (as a proxy for tissue concentrations) and in urine will be measured in outpatients. In those willing to be admitted to the Clinical Center, we will measure 24-hour urinary excretion of vitamin C while on a vitamin C free diet, and creatinine clearance, a measure of glomerular filtration rate. On day 2 of the inpatient study, subjects will receive a single 200mg dose of oral vitamin C and we will measure vitamin C concentrations in frequent blood and urine samples to determine the renal threshold and relative bioavailability for vitamin C. Single nucleotide polymorphisms (SNPs) will be determined in genomic DNA responsible for the two proteins mediating sodium-dependent vitamin C transport, SVCT1 and SVCT2. If low plasma and high urine vitamin C concentrations are found in diabetic subjects, further studies will be needed to explore mechanisms and to determine recommended dietary allowances for this patient population.
Condition |
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Diabetes Mellitus |
Study Type: | Observational |
Official Title: | Urinary Vitamin C Loss in Subjects With and Without Diabetes |
Estimated Enrollment: | 150 |
Study Start Date: | October 2003 |
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 vitamin C concentrations in patients with type 1 and type 2 diabetes and in matched healthy research subjects. Vitamin C concentrations in plasma, neutrophils (as a proxy for tissue concentrations) and in urine will be measured in outpatients. In those willing to be admitted to the Clinical Center, we will measure 24-hour urinary excretion of vitamin C while on a vitamin C free diet, and creatinine clearance, a measure of glomerular filtration rate. On day 2 of the inpatient study, subjects will receive a single 200mg dose of oral vitamin C and we will measure vitamin C concentrations in frequent blood and urine samples to determine the renal threshold and relative bioavailability for vitamin C. Single nucleotide polymorphisms (SNPs) will be determined in genomic DNA responsible for the two proteins mediating sodium-dependent vitamin C transport, SVCT1 and SVCT2. If low plasma and high urine vitamin C concentrations are found in diabetic subjects, further studies will be needed to explore mechanisms and to determine recommended dietary allowances for this patient population.
Ages Eligible for Study: | 18 Years to 65 Years |
Genders Eligible for Study: | Both |
Accepts Healthy Volunteers: | Yes |
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:
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:
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.
Contact: Patient Recruitment and Public Liaison Office | (800) 411-1222 | prpl@mail.cc.nih.gov |
Contact: TTY | 1-866-411-1010 |
United States, Maryland | |
National Institutes of Health Clinical Center, 9000 Rockville Pike | Recruiting |
Bethesda, Maryland, United States, 20892 |
Study ID Numbers: | 040021, 04-DK-0021 |
Study First Received: | October 27, 2003 |
Last Updated: | April 24, 2009 |
ClinicalTrials.gov Identifier: | NCT00071526 History of Changes |
Health Authority: | United States: Federal Government |
Vitamin C Diabetes Mellitus Proteinuria Plasma Concentrations Renal Threshold |
Diabetes Type II Diabetes Type I Healthy Volunteer HV |
Metabolic Diseases Antioxidants Diabetes Mellitus Endocrine System Diseases Trace Elements Healthy Proteinuria |
Vitamins Diabetes Mellitus, Type 2 Micronutrients Endocrinopathy Glucose Metabolism Disorders Metabolic Disorder Ascorbic Acid |
Metabolic Diseases Antioxidants Molecular Mechanisms of Pharmacological Action Growth Substances Physiological Effects of Drugs Diabetes Mellitus Endocrine System Diseases |
Protective Agents Pharmacologic Actions Vitamins Micronutrients Glucose Metabolism Disorders Ascorbic Acid |