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Urinary Vitamin C Loss in Diabetic Subjects
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) 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,1 expand

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.

Type: Observational

Start Date: Apr 2006

open study
Collection of Human Biospecimens for Basic and Clinical Research Into Globin Variants
National Institute of Allergy and Infectious Diseases (NIAID) Alpha and Beta Thalassemia Sickle Cell Disease Malaria Human Physiology
Background: Blood disorders like sickle cell disease and malaria affect many people around the world. Researchers want to learn more about blood disorders. To do this, they need to collect biological samples from people with blood disorders. They also need to collect samples from healthy people.1 expand

Background: Blood disorders like sickle cell disease and malaria affect many people around the world. Researchers want to learn more about blood disorders. To do this, they need to collect biological samples from people with blood disorders. They also need to collect samples from healthy people. Objective: To collect samples to use for research on blood disorders. Eligibility: People ages 18-70 who have blood disorders. Healthy volunteers without blood disorders are also needed. Design: Participants will be screened with a medical history, physical exam, and blood and urine tests. Participants will give one or more samples. They will give them over 5 years. They can choose not to give any of the samples: Saliva: Participants will spit into a tube. They may also have the inside of their mouth swabbed. Urine: Participants will urinate into a cup. Blood and blood waste products: Blood will be taken through a needle in the participant s arm. Fat samples: An area on the participant s belly or buttock will be numbed. A small cut will be made into the skin and a small piece of fat removed. Mucus and cells from the lungs: The participant will be sedated. A flexible tube will be inserted through the nose or mouth into the lung airways. These participants will also have a physical exam, chest x-ray, and heart tests after the procedure. ...

Type: Observational

Start Date: Sep 2019

open study