Inclusion criteria:  Healthy, 20-70 years, BMI 20-30 kg/m^2  Exclusion criteria:  Diabetes mellitus, symptoms of acute infection, cardiac arrhythmias, active malignancy, clinical signs or symptoms of cardiovascular disease (coronary artery disease, lower extremity artery disease, cerebrovascular disease): angina pectoris, dyspnea, palpitation, syncope, claudication, active vasoactive medication.