Nutrient Regulation of Amino Acid Transporters in Aging Human Skeletal Muscle

Inclusion criteria

1 . Age between 18-35 and 60-75 yrs 2. Ability to sign informed consent 3. Mini-mental state exam score >26 4. Free-living, prior to admission

Exclusion criteria

• Cardiac abnormalities considered exclusionary by the study physician (e.g., CHF, CAD, right-to-left shunt)
• Uncontrolled endocrine or metabolic disease (e.g., hypo/hyperthyroidism, diabetes)
• GFR <65 mL/min/1.73m2 or evidence of kidney disease or failure
• Vascular disease or risk factors of peripheral atherosclerosis. (e.g., uncontrolled hypertension, obesity, diabetes, hypercholesterolemia > 250 mg/dl, claudication or evidence of venous or arterial insufficiency upon palpitation of femoral, popliteal and pedal arteries)
• Risk of DVT including family history of thrombophilia, DVT, pulmonary emboli, myeloproliferative diseases including polycythemia (Hb>18 g/dL) or thrombocytosis (platelets>400x103/mL), and connective tissue diseases (positive lupus anticoagulant), hyperhomocysteinemia, deficiencies of factor V Leiden, proteins S and C, and antithrombin III
• Use of anticoagulant therapy. (e.g., Coumadin, heparin)
• Prior history of Heparin-Induced Thrombocytopenia (HIT)
• Elevated systolic pressure >150 or a diastolic blood pressure > 100
• Implanted electronic devices (e.g., pacemakers, electronic infusion pumps, stimulators)
• Cancer or history of successfully treated cancer (less than 1 year) other than basal cell carcinoma
• Currently on a weight-loss diet or body mass index > 30 kg/m2
• Inability to abstain from smoking for duration of study
• A history of > 20 pack per year smoking
• HIV or hepatitis B or C*
• Recent anabolic or corticosteroids use (within 3 months)
• Subjects with hemoglobin or hematocrit lower than accepted lab values
• Agitation/aggression disorder (by psychiatric history and exam)
• History of stroke with motor disability
• A recent history (<12 months) of GI bleed
• Pregnancy as determined by a pregnancy test
• Depression [>5 on the 15 items Geriatric Depression Scale (GDS)]
• Alcohol or drug abuse
• Exercise training (>1 session of moderate to high intensity aerobic or resistance exercise/week)
• Liver disease (AST/ALT 2 times above the normal limit, hyperbilirubinemia)
• Respiratory disease (acute upper respiratory infection, history of chronic lung disease with resting oxygen saturation <97% on room air)
• Any other condition or event considered exclusionary by the PI and faculty physician