Protocol Details

Urinary Vitamin C Loss in Subjects with and without Diabetes

This study is currently recruiting participants.

Summary | Eligibility | Citations | Contacts

Summary

Number	04-DK-0021
Sponsoring Institute	National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Recruitment Detail	Type: Participants currently recruited/enrolled Gender: Male & Female Min Age: 18 Years Max Age: 65 Years
Referral Letter Required	No
Population Exclusion(s)	Children
Keywords	Renal Threshold; Diabetes Mellitus; Proteinuria; Plasma Concentrations; Healthy Volunteer
Recruitment Keyword(s)	None
Condition(s)	Diabetes
Investigational Drug(s)	None
Investigational Device(s)	None
Intervention(s)	None
Supporting Site	National Institute of Diabetes and Digestive and Kidney Diseases

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.

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Eligibility

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

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Citations:

Levine M. New concepts in the biology and biochemistry of ascorbic acid. N Engl J Med. 1986 Apr 3;314(14):892-902.

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.

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Contacts:

Principal Investigator	Referral Contact	For more information:
Ifechukwude C. Ebenuwa, M.D. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) NIHBC 10 - CLINICAL CENTER BG RM 4D51 10 CENTER DR BETHESDA MD 20892 (301) 435-6582 ifechukwude.ebenuwa@nih.gov	Irene T. Rozga, R.N. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) National Institutes of Health Building 10 Room 6C432B 10 Center Drive Bethesda, Maryland 20892 (301) 496-1069 irene.rozga@nih.gov	Office of Patient Recruitment National Institutes of Health Clinical Center (CC) Building 61, 10 Cloister Court Bethesda, Maryland 20892 Toll Free: 1-800-411-1222 Local Phone: 301-451-4383 TTY: TTY Users Dial 7-1-1 ccopr@nih.gov

Clinical Trials Number:

NCT00071526

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