Casein Protein and Leucine Supplementation in Chronic Obstructive Pulmonary Disease (COPD)

Weight loss commonly occurs in patients with COPD, negatively influencing their quality of life, treatment response and survival. Loss of muscle protein is generally a central component of this weight loss and independently increases mortality. This study will provide relevant clinical information in regards to the anabolic properties of specific dietary substrates and their co-active anabolic effects. Hypotheses: 1) That supplementation of a hydrolyzed casein-based protein meal with the addition of carbohydrates is more anabolic than a hydrolyzed casein-based protein meal without carbohydrates in COPD patients and healthy older adults; 2) That leucine addition to a hydrolyzed casein-based protein meal only enhances the protein anabolic response in COPD patients and healthy older adults when carbohydrates are not added to the protein meal; 3) That COPD patients have a more efficient protein anabolic response to a hydrolyzed casein-based protein meal than healthy older adults. A fifth study day was added to measure protein requirements of included individuals to be able to interpret their response to the other interventions on the other study days, and to test the hypothesis that subjects with lower protein requirements respond less to intervention with leucine and/or carbohydrates. For the 5th additional test day we will first approach the 10 COPD and 10 healthy subjects who already completed the first 4 study days (and signed the re-contact form) to come back for this extra test day. We will (pre-)screen these subjects by phone for eligibility and check for changes in their recent medical history (with help of the (pre-)screening questionnaires in CRF). If all inclusion criteria are still met, these subjects will be asked to provide a written re-consent. If necessary, we will recruit new subjects who will complete only one of the four test days (i.e. the test day on which the hydrolyzed casein-based protein meal with carbohydrates is provided) and the additional 5