Urinary Vitamin C Loss in Diabetic Subjects

NCT00071526 | Recruiting

• 2 other identifiers: 04002104-DK-0021
• Study Type: observational
• Target: 5,000
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Diabetes

Keywords

Renal Threshold; Diabetes Mellitus; Proteinuria; Plasma Concentrations; Healthy Volunteer

Outcome Measures

Primary Outcomes (1)

• Plasma, neutrophil and RBC Vitamin C concentrates

  Measurements of plasma, neutrophil and red blood cell vitamin c concentrations in diabetic subjects as compared to healthy controls.

  end of study

Secondary Outcomes (2)

• Urinary vitamin C concentration

  end of study

• Determine the renal threshold and relative bioavailability for vitamin C

  end of study

Study Arms (3)

Diabetes Type I

Subjects with Type I diabetes mellitus

Diabetes Type II

Subjects with Type II diabetes mellitus

Healthy Volunteers

Healthy Volunteers

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Probability Sample

Study Population

Community sample.

You may qualify if:

• 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

You may not qualify if:

• Unable or unwilling to provide a signed and dated informed consent form
• Unable or unwilling to comply with study procedures and lifestyle considerations
• 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

Sponsors & Collaborators

• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): lead

Study Sites (1)

National Institutes of Health Clinical Center

Bethesda, Maryland, 20892, United States

RECRUITING

Related Publications (4)

• Levine M. New concepts in the biology and biochemistry of ascorbic acid. N Engl J Med. 1986 Apr 3;314(14):892-902. doi: 10.1056/NEJM198604033141407. No abstract available.

  PMID: 3513016 BACKGROUND

• 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.

  PMID: 6842805 BACKGROUND

• 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. doi: 10.7326/0003-4819-124-3-199602010-00003.

  PMID: 8554224 BACKGROUND

• Ebenuwa I, Violet PC, Tu H, Lee C, Munyan N, Wang Y, Niyyati M, Patra K, Wilkins KJ, Parrow N, Levine M. Altered RBC deformability in diabetes: clinical characteristics and RBC pathophysiology. Cardiovasc Diabetol. 2024 Oct 18;23(1):370. doi: 10.1186/s12933-024-02453-2.

  PMID: 39425096 DERIVED

Related Links

• NIH Clinical Center Detailed Web Page

MeSH Terms

Conditions

Diabetes Mellitus; Proteinuria

Condition Hierarchy (Ancestors)

Glucose Metabolism Disorders; Metabolic Diseases; Nutritional and Metabolic Diseases; Endocrine System Diseases; Urination Disorders; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Urogenital Diseases; Male Urogenital Diseases; Urological Manifestations; Signs and Symptoms; Pathological Conditions, Signs and Symptoms

Study Officials

• Ifechukwude C Ebenuwa, M.D.

  National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Razi S Berman, C.R.N.P.

CONTACT

(301) 827-5757; razi.berman@nih.gov

Ifechukwude C Ebenuwa, M.D.

CONTACT

(301) 435-6582; ifechukwude.ebenuwa@nih.gov

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: PROSPECTIVE
• Sponsor Type: NIH
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: October 27, 2003
• First Posted: October 28, 2003
• Study Start: April 11, 2006
• Last Updated: May 5, 2026

Record last verified: 2026-04-28

Locations

US (1)