In this protocol, 60 subjects with DM1 will be studied at baseline, after 12 weeks of MCR blockade or 12 weeks of exercise, and again after an additional 12 weeks of MCR blockade, exercise or the combination of both interventions. Investigators will assess function in conduit (pulse wave velocity-PWV, flow-mediated dilation-FMD and augmentation index-AI), resistance (post-ischemic flow velocity-PIFV) and heart and skeletal muscle microvascular (contrast enhanced ultrasound-CEU) vessels before and after 2 hrs of a euglycemic insulin clamp.