Reversing Glucose and Lipid-mediated Vascular Dysfunction

Inclusion Criteria: * Lean: BMI \< 25 kg/m * Normal insulin sensitivity: (calculation based on fasting glucose and insulin concentrations in blood) * Middle-aged: 18-79 years * Blood pressure: \< 140 (systolic) and \< 90 mmHg (diastolic * Weight stable (+/- 5 lbs) for the previous 3 months * Participants must be willing and able to discontinue taking any vitamin C or E supplements or omega-3 fatty acids beginning 2 weeks prior. * Able and willing to provide written informed consent Exclusion Criteria: * Diabetes mellitus Type I or Type II: fasting glucose \< 126 mg/dL and/or HbA1c \< 6.5% * Current smoker or History of smoking in the past 3 months. * Hyperlipidemia: Fasting triglycerides \< 250 mg/dL * Hypertension: \>130/80 mmHg * History of heart disease (e.g., myocardial infarction, stent, heart attack, stroke, heart failure, valvular heart disease, cardiomyopathy) * History of vascular disease (e.g., bypass, stroke)