Clinical Research Directory

Venous Thrombosis Biomarkers in Sickle Cell Disease and Sickle Cell Trait

Background: Venous thromboembolism (VTE) includes the abnormal clotting of blood in a deep vein of the upper or lower limbs (deep vein thrombosis) that may travel to and block a blood vessel in the lung (pulmonary embolism). Some people with sickle cell disease (SCD)-a red blood cell disorder-seem to be at greater risk for developing these blood clots. Researchers want to study the blood of people with SCD and VTE as well as healthy people to develop better treatments to prevent blood clots. Objective: To study blood clotting in SCD because it is the most common cause of vascular death after a heart attack or stroke. Eligibility: People ages 18-80 who have SCD (with or without a history of blood clots) or the trait for SCD, and healthy volunteers Design: Participants will be screened with medical history, physical exam, and medical records review. They will give blood samples. Participants will have phone calls either every 3 months or once a year, for 2 years. They will give updates on their health. They may give additional medical records. The phone calls may last up to 30 minutes. If participants have a VTE or pain crisis episode, they may visit the Clinical Center. These visits may last up to 4 hours. They will repeat the screening tests and give blood samples. Some participants may be invited to take part in blood studies. After 2 years, some participants will have a follow-up visit at the Clinical Center. Participation will last for about 2 years.

Effects of Sweetener Consumption on Risk Factors for Heart Disease in Prediabetic Subjects

The aim of this prospective interventional study is to investigate the metabolic effects of consuming artificial and natural sweeteners in persons with prediabetes. Prediabetes is a condition characterized by blood sugar levels that are elevated above normal but not yet meeting the criteria for type 2 diabetes. This condition markedly increases the risk of progressing to type 2 diabetes, which in turn can lead to complications including cardiovascular diseases. Artificial sweeteners such as saccharin and sucralose, as well as natural sugar substitutes like erythritol, are increasingly used as alternatives to sugar and are recommended for individuals at cardiometabolic risk - including overweight individuals, patients with prediabetes, or diabetics - to help reduce caloric intake. Recent literature has reported possible negative associations between artificial sweeteners and blood sugar regulation in healthy subjects (1). Additionally, effects on various blood cells have been observed. For example, erythritol has been shown to alter platelet function leading to increased reactivity in healthy study participants following consumption (2). However, the impact of alternative sweeteners on metabolic processes and their effects on blood coagulation in patients with prediabetes-a population at increased risk-has not been systematically studied. In this planned interventional study, 80 patients meeting laboratory criteria for prediabetes will be randomly assigned to one of four groups, each receiving a different intervention for two weeks: saccharin, sucralose, erythritol, or a control group receiving water. The doses reflect the acceptable daily intake or known doses that are considered safe. After enrollment, participants will visit the study center 2 times: before starting the intervention and after completing the intervention. During these visits, biological samples such as blood, urine, and stool will be collected to study metabolism, gut bacteria, immune and blood cell function. Tests will include an oral glucose tolerance test, coagulation tests, and additional blood analyses. Additionally, participants will wear a glucose monitor to track blood sugar fluctuations during the intervention. The investigators hypothesize that consumption of alternative sweeteners negatively affects blood sugar regulation and insulin sensitivity in patients with prediabetes. Furthermore, this study will explore how the candidate sweeteners influence the gut microbiome, blood cells and other metabolic factors in this population.