Plasma concentrations of cholecystokinin and neurotensin in patients with cystic fibrosis

Pathophysiological role of cholecystokinin in humans

Cholecystokinin (CCK) is a major gastrointestinal hormone that plays an important role in stimulation of pancreatic secretion and gall-bladder contraction, regulation of gastrointestinal motility and induction of satiety. Ingestion of fat and protein induces significant increases in plasma CCK. Intraluminal mediators of CCK secretion, luminal CCK releasing factor and diazepam-binding inhibitor, were purified from rat intestinal secretion. These CCK-releasing factors (RF) are secreted tonically by the small intestine and stimulate CCK release. Another kind of CCK-RF named 'monitor peptide' was purified from the rat pancreatic juice that stimulates CCK secretion when introduced into rat intestine. Bile exclusion from the duodenum causes an increase in basal CCK and enhances stimulated plasma CCK release, and bile salt replacement reverses these effects. Thus, the CCK-RF are spontaneously secreted into the intestinal lumen in humans, while the CCK-producing cells are under constant suppression by intraduodenal bile acids. In acute pancreatitis, plasma CCK levels are high in patients with gallstone pancreatitis, but not in patients with pancreatitis from other causes, such as alcoholic and idiopathic pancreatitis. A transient disturbance of bile flow into the duodenum by stones or oedema of the pancreas together with impairment of pancreatic exocrine function might cause the increase in plasma CCK release in gallstone pancreatitis. Patients with chronic pancreatitis with mild to moderate impairment of exocrine function and abdominal pain, had significantly higher plasma CCK concentrations, whereas patients with pancreatic insufficiency had a significantly lower plasma CCK response to a test meal than the healthy subjects. The increased CCK may further aggravate pancreatitis and worsen the prognosis of pancreatitis by stimulating the injured pancreas, resulting in the vicious circle via endogenous CCK release. The CCK-A receptor antagonist might be therapeutically useful in acute pancreatitis by stopping the vicious circle.

Comparison of fecal elastase-1 determination with the secretin-cholecystokinin test in patients with cystic fibrosis

BACKGROUND

The secretin-cholecystokinin (CCK) test is the gold standard in the evaluation of exocrine pancreatic insufficiency. Because of its invasive character, it is of limited value in cystic fibrosis (CF) patients, especially in those with severe respiratory disease. The aim of the study was to evaluate the sensitivity of fecal elastase-1 in relation to the secretin-CCK test and quantitative fecal fat excretion in CF patients.

METHODS

The study comprised 28 patients (11 females and 17 males) aged 4 to 20 years. In all patients the secretin-CCK test and determination of fecal elastase-1 concentration (with enzyme-linked immunosorbent assay) and fecal fat excretion were performed.

RESULTS

The range of fecal elastase-1 was from undetectable to 485 microg/g (mean, 84.6+/-119.9 microg/g) and of fecal fat excretion from 1.0 to 55.1 g/day (mean, 15.0+/-12.2 g/day). On the basis of the results of the secretin-CCK test (and fecal fat analysis) exocrine pancreatic insufficiency was divided into three subgroups: mild (I), moderate (II), and severe (III). Four patients were classified in subgroup I, 4 in II and 20 in III. Fecal elastase (elastase-1) results were 332.0+/-124.9 microg/g in subgroup I, 96.9+/-45.7 microg/g in subgroup II, and 32.1+/-41.2 microg/g in subgroup III. The fecal elastase-1 sensitivity with a cut-off point of 200 microg/g was 89.3% for all patients, 100% for patients in subgroups II and III, but only 25.0% for patients in subgroup I; the specificity was 96.4%. Linear regression analysis showed a statistically significant correlation between fecal elastase (elastase-1) and duodenal volume, bicarbonate, amylase, lipase, and trypsin secretion (in all cases P < 0.001).

CONCLUSIONS

Measurement of fecal elastase-1 is simple and very useful for assessing the exocrine pancreatic function in CF patients. Elastase is highly specific in severe and moderate exocrine pancreatic insufficiency, but it is rather unspecific for milder forms of pancreatic insufficiency.