DiabetesNCT00071526
Urinary Vitamin C Loss in Diabetic Subjects
An observational study of Diabetes, run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) at 1 site in United States.
Trial 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… Read more about this study
- Who is it for?
- Ages 18 to 65 yearsHealthy volunteers can take part
- Conditions the study is for
- Diabetes
- How many people
- 5,000 participants
- Where
- 1 siteUnited States
- Study dates
- 11 Apr 2006to not given
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Study population: Community sample.
Who may be able to join
- 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
Who cannot join
- 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
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
National Institutes of Health Clinical Center
Bethesda, Maryland, 20892
About this study
Official title: Urinary Vitamin C Loss in Subjects With and Without Diabetes
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.
Read the 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.
- Conditions
- Diabetes
- Keywords
- Renal Threshold, Diabetes Mellitus, Proteinuria, Plasma Concentrations, Healthy Volunteer
- Medical subject headings
- Diabetes Mellitus, Proteinuria
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
| Study group | Role | What they receive |
|---|---|---|
| Diabetes Type I | Subjects with Type I diabetes mellitus | |
| Diabetes Type II | Subjects with Type II diabetes mellitus | |
| Healthy Volunteers | Healthy Volunteers |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: end of study
Secondary outcomes (2)
Urinary vitamin C concentration
Measurements of urinary vitamin c concentrations in diabetic subjects as compared to healthy controls.
Measured: end of study
Determine the renal threshold and relative bioavailability for vitamin C
Calculate renal threshold of vitamin C in diabetic subjects as compared to healthy controls.
Measured: end of study
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted28 Oct 2003 (estimated)
- Study start11 Apr 2006
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (4)Papers the sponsor has linked to this study.
- Other trials for DiabetesStudies of the same condition, open and under way.
- More trials run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)The sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Prospective
- Enrolment
- 5,000 participants (estimated)
Sponsor and investigators
- Sponsor type
- US National Institutes of Health
- Responsible party
- Sponsor
- Investigators
- Ifechukwude C Ebenuwa, M.D., Principal investigator, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT00071526
- Sponsor's protocol ID
- 040021
- Other IDs
- 04-DK-0021
- Status last verified
- 26 Aug 2026
- First submitted
- 27 Oct 2003
- Last updated
- 29 Oct 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Publications
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.
PubMed 3513016Goodwin 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.
PubMed 6842805Fata 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.
PubMed 8554224Ebenuwa 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.
PubMed 39425096
Study at a glance
From the registry record, last updated by the sponsor on 29 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Urinary Vitamin C Loss in Subjects With and Without Diabetes
- ClinicalTrials.gov ID
- NCT00071526
- Acronym / sponsor ID
- 040021
- Conditions
- Diabetes
- Keywords
- Renal Threshold, Diabetes Mellitus, Proteinuria, Plasma Concentrations, Healthy Volunteer
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 5,000 participants (estimated)
- Lead sponsor
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)US National Institutes of Health
- Study start
- 11 Apr 2006 (actual)
- First posted
- 28 Oct 2003 (estimated)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
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.
Study design
- Observational model
- Cohort
- Time perspective
- Prospective
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| Diabetes Type I | – | –Subjects with Type I diabetes mellitus |
| Diabetes Type II | – | –Subjects with Type II diabetes mellitus |
| Healthy Volunteers | – | –Healthy Volunteers |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
- Study population
- Community sample.
Key inclusion criteria (5 listed)
- Aged 18-65 years.
- Either:
Key exclusion criteria (7 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Primary outcome
Plasma, neutrophil and RBC Vitamin C concentrates
Time frame: end of study
Measurements of plasma, neutrophil and red blood cell vitamin c concentrations in diabetic subjects as compared to healthy controls.
2 secondary outcomes
Urinary vitamin C concentration
Time frame: end of study
Determine the renal threshold and relative bioavailability for vitamin C
Time frame: end of study
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 29 Oct 2026.
- Background: PubMed 3513016Levine 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.
- Background: PubMed 6842805Goodwin 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.
- Background: PubMed 8554224Fata 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.
- Derived from this study: PubMed 39425096Ebenuwa 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.
- NIH Clinical Center Detailed Web PageLink provided by the sponsor.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Ifechukwude C Ebenuwa, M.D. principal investigator
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Diabetes, run by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 29 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Razi S Berman, C.R.N.P. ((301) 827-5757, razi.berman@nih.gov), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Plasma, neutrophil and RBC Vitamin C concentrates (time frame: end of study). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT00071526, which also lists 4 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 29 Oct 2026.