Plasma Concentrations of Cholecystokinin and Neurotensin in Patients with Cystic Fibrosis

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Abstract
Background: Regulation of pancreatic exocrine secretion is controlled by vagovagal reflexes and hormones. A negative feedback control mechanism exists between the intraduodenal protease concentration and pancreatic enzyme secretion. In man cholecystokinin (CCK) is the major regulator of postprandial pancreatic enzyme secretion. There is a 50% reduction of meal-stimulated secretion by the specific CCK receptor antagonist loxiglumide, whereas atropine completely blocks postprandial secretion. Neurotensin is released postprandially by nerval reflexes and fat. It has been claimed that both hormones are increased in patients with pancreatic insufficiency. Methods: We investigated CCK and neurotensin levels in patients with cystic fibrosis and pancreatic insufficiency. In 35 patients (2–24 years old) with cystic fibrosis with steatorrhea and in 15 patients (1.5–24 years old) with cystic fibrosis without pancreatic insufficiency pre-and post-prandial CCK and neurotensin plasma levels were measured 3 days after pancreatic enzyme therapy had been withdrawn. Nine patients (3–14 years old) who had no complaint of abdominal disease served as controls. Results: Basal and postprandial CCK plasma levels did not differ statistically in the three groups, whereas basal and postprandial neurotensin levels were significantly increased in the cystic fibrosis groups. The severity of the disease had no effect on the neurotensin levels. Conclusions: Cystic fibrosis patients with severe pancreatic insufficiency did not have increased CCK plasma levels, suggesting that a CCK-mediated feedback mechanism of pancreatic enzyme secretion does not operate in our patients. In contrast, basal and postprandial neurotensin plasma levels were significantly increased in patients with cystic fibrosis but were independent of the severity of the pancreatic insufficiency.