This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. CF patients with impaired glucose tolerance due to defective insulin secretion are not routinely treated with exogenous insulin since fasting glucose and hemoglobin Alc levels are normal. This practice ignores the potentially detrimental effects of insulin deficiency on protein metabolism. We hypothesize that chronic treatment with either insulin or an oral hypoglycemic agent will lead to improved protein anabolism in insulin-deficient, non-diabetic CF adults. A multicenter, prospective, placebo-controlled, double-blinded intervention trail will be undertaken to treat glucose intolerant adult CF patients for six months with one of three agents: insulin, glipizide, troglitazone or placebo. We will evaluate the effects of these agents on protein synthesis and breakdown, pulmonary function, and body composition.