Impact of Acute Exercise on Vascular Insulin Sensitivity in Metabolic Syndrome

Inclusion Criteria: * Males and females, ages 40-70 years * Never diagnosed with type 2 diabetes and/or cardiovascular disease * Not currently engaged in \> 60 min/wk of exercise * Inclusion criteria specific to health obese vs. metabolic syndrome potential participants: * Healthy Obese: (BMI ≥ 30 kg/m2 but ≤ 45 kg/m2) and no other metabolic syndrome risk factors, excluding waist circumference. * Metabolic Syndrome: (BMI ≥ 30 kg/m2 but ≤ 45 kg/m2) and must meet at least 3 out of 5 National Cholesterol Education Adult Treatment Panel III Metabolic Syndrome Criteria: Increased waist circumference (≥102 cm in men; ≥88 cm in women) Elevated triglycerides (≥150 mg/dl) or currently taking medication (Rx) Reduced HDL-cholesterol (\<40mg/dl in men, \<50 mg/dl in women) or currently taking medication (Rx) High blood pressure (≥130 mmHg systolic or ≥85mmHg diastolic) or currently taking medication (Rx) Elevated fasting glucose (≥100 mg/dl) Subject may participate if on the following drugs: * Diuretics, ace-inhibitors and ARBs for treatment of hypertension * Statins Exclusion Criteria: * Morbidly obese patients (BMI \>45 kg/m2) and overweight/lean patients (BMI \<30 kg/m2). * Subjects who have not been weight stable (\>2kg weight change in past 3 months). * Currently participating in a regular exercise training program ( \>30 min. of physical activity per day, \>2 days/week) * Medication or food supplement that is known to affect insulin sensitivity or endothelial function (TZDs, sulfonylureas, biguanides, alpha-glucosidase inhibitors, phosphodiesterase inhibitors, beta-blockers, alpha-blockers, fibrates, glucocorticoids, fish oil, allopurinol) * Subjects with abnormal estimated glomerular filtration rate (eGFR). * Hypertriglyceridemic (\>400 mg/dl) subjects. * Hypertensive (\>160/100 mmHg) * Subjects taking vasoactive medications also known to affect heart rate and rhythm (i.e. Ca++ channel blockers, nitrates, alpha- or beta-blockers). * Subjects with a history of significant metabolic, cardiac, congestive heart failure, cerebrovascular, hematological, pulmonary, gastrointestinal, liver, renal, or endocrine disease or cancer that in the investigator's opinion would interfere with or alter the outcome measures, or impact subject safety. * Smoking presently or in the past 1 year. * HbA1c ≥ 6.5 * Subjects currently taking Metformin or any active weight suppression medication (e.g. phentermine, orlistat, lorcaserin, naltrexone-bupropion in combination, liraglutide, benzphetamine, diethylpropion, phendimetrazine) * Pregnant (as evidenced by positive pregnancy test) or breastfeeding * Subjects with contraindications to participation in an exercise program * Known hypersensitivity to perflutren (contained in Definity)