This project aims to assess coronary vessel response to isometric handgrip exercise (IHE) during magnetic resonance imaging (MRI) in children with T1D children and healthy controls. The investigators will compare the groups in terms of surrogate markers of intima media alteration and arterial stiffness, i.e. carotid intima media thickness (CIMT) and aortic pulse wave velocity (PWV).

Background Type 1 diabetes mellitus (T1D) in children and adolescents is associated with significant cardiovascular morbidity and mortality. Early detection of vascular dysfunction is key to management yet assessment is invasive - which is particularly challenging when considering pediatric patient populations. Recently, a novel approach using isometric handgrip exercise (IHE) during magnetic resonance imaging (MRI) has been developed to evaluate coronary endothelial function in adults.

This project aims to assess coronary vessel response to IHE using MRI in children with T1D children and healthy controls. In addition, the investigators will compare the groups in terms of surrogate markers of intima media alteration and arterial stiffness, i.e. carotid intima media thickness (CIMT) and aortic pulse wave velocity (PWV).

Community-dwelling healthy volunteers (<18 years-old) and children with type 1 diabetes mellitus (disease duration ≥ 5 years) are recruited. IHE-MRI studies are conducted and measurements are recorded at rest (baseline) and under stress (IHE at 30% maximal effort). Carotic Ultrasound and Sphygmocor CPV System are used to assess CIMT and PWV respectively. Student's T-tests are used to compare results between groups.

Inclusion Criteria:

• Type 1 Diabetes mellitus or
• Healthy community-dwelling children on no medications

Exclusion Criteria:

• smoking
• obesity (BMI >97th percentile)
• systolic or diastolic hypertension (>90th percentile)
• inflammatory process.