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

Background: Researchers use mixed meal tolerance tests (MMTTs) to look at how people s bodies respond to eating a meal. However, researchers do not agree on how to decide the number of calories to give in each meal. Some use fixed meals, which are the same size for everyone, and some use adjusted meals, based on the size of the person s body. Researchers want to know which MMTT is best to use for future research. Objective: To learn how fixed vs adjusted meals affect blood glucose levels in healthy people. Eligibility: Healthy people aged 18 years or older. Design: Participants will have 3 or 4 clinic visits of up to 8 hours in 8 weeks. Participants will have baseline tests: Their height, weight, and waist size will be measured. They will have an oral glucose tolerance test: A needle attached to a tube (IV) will be inserted into a vein in the arm. They will have a sugary drink. Blood samples will be taken from the tube at intervals up to 3 hours after the drink. They will have a body scan. Participants will have 2 MMTT visits. One will include a fixed meal and one will include an adjusted meal. They will have tests at both visits: Resting metabolic rate: A clear hood will be placed over the participant s head while they rest for 20 minutes. This will measure the oxygen they breathe in and out. MMTT. Participants will have 5 minutes to drink a liquid meal. Blood samples will be taken at intervals for the next 4 hours....

Type: Interventional

Start Date: Aug 2024

open study

Latino caregivers of individuals with Alzheimer's disease and related dementias experience high levels of stress burden and depressive symptoms and are underrepresented in caregiver intervention research. Tele Savvy is an evidence based caregiver education program that focuses on developing caregiver mastery skills. This study aims to culturally adapt the Tele Savvy intervention for Latino caregivers and evaluate its preliminary efficacy in a Stage 1b single arm clinical trial. The intervention is delivered remotely and includes weekly group sessions and asynchronous instructional videos. Primary outcomes focus on caregiver mastery with secondary outcomes including stress burden depressive symptoms and self efficacy.

Type: Interventional

Start Date: Apr 2026

open study

The purpose of the study is to learn about how effective, safe, and tolerable the Clostridioides difficile (C. difficile) vaccine is in decreasing the number of C. difficile infections (pCDI) in adults 65 years of age or older. The participants will receive either the C. difficile vaccine or placebo (saline). A placebo does not contain any active ingredients. The vaccines will be given as a shot into the upper arm muscle. This study looks at the number of diarrhea (loose stools) events related to a C. difficile infection, so the length of the study can change. If these events happen quickly, the study may finish sooner; if they happen slowly, it could take longer. Sometimes, the study might stop early if the vaccine clearly works or clearly doesn't. Participants will stay in the study until enough events have occurred to answer the main question. On average, each person is expected to take part for up to about three and a half years. During this time, participants will have 3 planned clinical visits and 3 planned phone visits. After these visits, more scheduled clinic visits will happen every year until the end of study. Besides the scheduled study visits, if at any time during the study a participant has 3 or more loose stools in 24 hours, they will be asked to save the next one (the fourth or later) and contact the study site. The study site will check to see if it could be a C. difficile infection. This check may happen at the clinic or through a phone or video call.

Type: Interventional

Start Date: Dec 2025

open study

A Basket Trial of Refractory Rheumatoid Arthritis (RA), Sjögren's Disease (SjD), Idiopathic Inflammatory Myopathies (IIMs) and Systemic Sclerosis (SSc) subjects to evaluate the safety and efficacy of AlloNK, a non-genetically modified allogeneic NK cell, in combination with rituximab.

Type: Interventional

Start Date: Jul 2025

open study

Chronic tics are a disabling neuropsychiatric symptom associated with multiple child-onset mental disorders. Chronic tics affect 1-3% of youth 1 and are associated with impaired functioning, emotional and behavioral problems, physical pain, diminished quality of life, peer victimization, and a fourfold increased risk of suicide compared to the general population. Large randomized trials have demonstrated the superiority of CBIT over supportive therapy in child and adult patients. However, in these trials, only 52% of children and 38% of adults showed clinically meaningful tic improvement, meaning that 50-60% of patients do not benefit from CBIT. CBIT success relies on an ability to suppress tics that many youth lack. The central aim of CBIT is to enhance voluntary tic suppression. Better tic suppression ability drives CBIT improvement 10 and predicts lower tic burden over the course of illness. During the core CBIT procedure, competing response training, patients learn to inhibit tics by engaging in a competing motor action. However, research shows that many youth lack this fundamental tic suppression ability that CBIT aspires to enhance. This study will examine the clinical and neural effects of a treatment combining Comprehensive Behavioral Intervention for Tics (CBIT) and transcranial magnetic stimulation (TMS) to the supplementary motor area (SMA) in young people with tic disorder.

Type: Interventional

Start Date: Feb 2025

open study

This research study is investigating whether people with Alzheimer's disease (AD) experience more changes to swallowing than their healthy age-matched peers. The prevalence of swallowing impairments in moderate-severe AD is high (85-93%), yet little is known about how swallow function evolves throughout the disease course in people with AD. The overall objective of this study is to evaluate swallowing function in adults with and without Alzheimer's disease. The investigator will also be involving the primary caregivers of individuals with Alzheimer's that are enrolled in the study to better understand the impact of swallowing impairments on the primary caregivers of those with Alzheimer's Disease. Healthy adults and individuals with Alzheimer's disease will: - undergo tests of cough and swallow function - undergo tests of grip and tongue strength - complete questionnaires Caregivers of individuals with Alzheimer's disease will also complete questionnaires.

Type: Observational

Start Date: Apr 2025

open study

This study aims to identify how enhanced allopregnanolone activity (via pregnenolone) affects behavior and neurobiology that may underlie perimenopausal depression.

Type: Interventional

Start Date: May 2024

open study

This will be a multi-center, single arm, open-label study of Ovaprene, a non-hormonal intravaginal ring, to investigate the contraceptive effectiveness, safety and acceptability of Ovaprene.

Type: Interventional

Start Date: Dec 2023

open study