Novel Methodology to Measure Protein Accumulation

Inclusion criteria

• Age 18-30 years
• Age greater than 65 years

Exclusion criteria

• Active or uncontrolled cardiovascular disease
• Chronic kidney disease with serum creatinine ≥ 1.4 mg/dL for women and ≥ 1.5 mg/dL for men
• Chronic liver disease (elevation in serum transaminases ≥ 3 times the upper limit of normal)
• Any debilitating chronic illness, including malignancy
• Significant malabsorptive state, including prior gastric bypass surgery or inflammatory bowel disease
• Diabetes mellitus (types 1 or 2) or glucose ≥ 110 mg/dL.
• Obesity (BMI ≥ 31 kg/m2)
• Anticoagulant therapy (warfarin or heparin) or bleeding disorder that increases risk of bleeding during a muscle biopsy.
• Anemia (hemoglobin ≤ 11 g/dL)
• Use of medications known to modulate protein synthesis, mitochondrial function, and/or glucose homeostasis (including β-blockers and corticosteroids).
• Participation in another study where the 13CPhe was administered during the past 6 months.
• Moderate or high level of structured exercise (on average, ≥ 30 minutes per day and ≥ 2 days per week)
• Pregnancy
• Daily use of tobacco products (smoking or chewing); or smoking ≥7 cigarettes per week, on average. Abstinence from tobacco for ≥3 months is required before enrollment in the study.