Study of Hepatic Glucose Production and De Novo Lipogenesis in Patients With Cystic Fibrosis

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Patients undergo an oral glucose tolerance test (OGTT) in which blood is drawn from an IV in the arm 6 times over 3 hours. After the first blood draw, patients receive a beverage containing sugar and write down everything they ate and drank during the 24 hours before study entry. Patients also undergo a dual energy x-ray absorptiometry (DEXA) scan over 15 minutes.

Within 2 weeks after the OGTT, patients keep a journal of everything they ate and drank over 3 days. Patients are fed a selected meal the following evening and receive saline fluids IV overnight. During the night, patients receive 2 doses of oral doubly labeled water. The next morning, patients receive [1,2-13C]acetate IV. A liquid mixed meal (Ensure Plus) is ingested hourly throughout the day. Patients also undergo hood indirect calorimetry over 30 minutes twice to measure resting energy expenditure. All urine is collected.