Type 1 Diabetes Impacts of Semaglutide on Cardiovascular Outcomes

Inclusion Criteria: * Age 18-49 years * 1\) T1D diagnosis defined as positive T1D-associated antibody(ies) or 2) a clinical diagnosis of T1D plus insulin requirement since diagnosis * Insulin pump or automated insulin delivery systems * Estimated glomerular filtration rate (eGFR) ≥ 45 ml/min/1.73m2 * Stable doses of drugs altering cardiovascular and renal function (e.g., Angiotensin-Converting Enzyme Inhibitor (ACEi), Angiotensin Receptor Blocker (ARB), statins, diuretics) * BMI 20-45 kg/m2 * Adequate contraceptive method for females Exclusion Criteria: * HbA1c \>9%, recent diabetic ketoacidosis (DKA) or hospitalization * Major congenital heart disease, anemia, severe non-proliferative retinopathy, proliferative retinopathy * History/family history of medullary thyroid carcinoma, multiple endocrine neoplasia type 2 (MEN2), pancreatitis * Current/planned pregnancy or nursing * Uncontrolled thyroid disease or hypertension (HTN) (≥ 160/100 mm Hg despite optimal therapy) * Use of other non-insulin diabetes medications, insulin sensitizing medications, or systemic steroids in past 3 months * Use of atypical antipsychotics * Significant systemic illness such as cancer * Shellfish/iodine allergy (only exclusionary to iohexol clearance procedure) * MRI or PAH contraindications (only exclusionary to MRI and PAH procedures), GLP-1RA allergy