Mucin secretion is modulated by luminal factors in the isolated vascularly perfused rat colon

BACKGROUND

Mucins play an important protective role in the colonic mucosa. Luminal factors modulating colonic mucus release have been not fully identified.

AIM

To determine the effect of some dietary compounds on mucus discharge in rat colon.

METHODS

An isolated vascularly perfused rat colon model was used. Mucus secretion was induced by a variety of luminal factors administered as a bolus of 1 ml for 30 minutes in the colonic loop. Mucin release was evaluated using a sandwich enzyme linked immunosorbent assay supported by histological analysis.

RESULTS

The three dietary fibres tested in this study (pectin, gum arabic, and cellulose) did not provoke mucus secretion. Luminal administration of sodium alginate (an algal polysaccharide used as a food additive) or ulvan (a sulphated algal polymer) induced a dose dependent increase in mucin discharge over the concentration range 1-25 mg/l (p<0.05 for 25 mg/l alginate and p<0.05 for 10 and 25 mg/l ulvan). Glucuronic acid and galacturonic acid, which are major constituents of a variety of fibres, produced significant mucin secretion (p<0.05). Hydrogen sulphide and mercaptoacetate, two sulphides produced in the colonic lumen by microbial fermentation of sulphated polysaccharides, did not modify mucin secretion. Among the short chain fatty acids, acetate (5-100 mM) induced a dose dependent release of mucus (p<0.05 for 100 mM acetate). Interestingly, butyrate at a concentration of 5 mM produced colonic mucin secretion (p<0.05), but increasing its concentration to 100 mM provoked a gradual decrease in mucus discharge. Propionate (5-100 mM) did not induce mucin release. Several dietary phenolic compounds (quercetin, epicatechin, resveratrol) did not provoke mucus discharge.

CONCLUSIONS

Two algal polysaccharides (alginate and ulvan), two uronic acids (glucuronic acid and galacturonic acid), and the short chain fatty acids acetate and butyrate induce mucin secretion in rat colon. Taken together, these data suggest that some food constituents and their fermentation products may regulate the secretory function of colonic goblet cells.

Treatment of the carcinoid syndrome with the longacting somatostatin analogue lanreotide: a prospective study in 39 patients

BACKGROUND

Somatostatin analogues effectively control flushing and diarrhoea in patients with the carcinoid syndrome. The octapeptide lanreotide is available in slow release form, which could eliminate the necessity of twice a day injections as with octreotide.

PATIENTS AND METHODS

39 patients with carcinoid syndrome were included in a prospective multicentre study. Patients received lanreotide 30 mg intramuscularly every 14 days for six months. The number and intensity of flushing episodes and bowel movements, urinary 5 hydroxy-indolacetic acid (5 HIAA) concentrations, and variations of tumour mass were recorded.

RESULTS

After one month of treatment, flushing episodes (median (range)) decreased significantly (3 (0.3-24) episodes per day v 1 (0-15), p = 0.04) and completely resolved in 39% of the patients. A significant decrease was seen in the number of bowel movements and discomfort related to diarrhoea. Urinary 5 HIAA concentrations were unchanged in 57% of the patients and decreased in 18%. After six months of treatment, the actuarial proportions of patients with at least a 50% decrease in the number of flushing episodes and bowel movements were 54% and 56%, respectively. Forty two per cent of the patients who were treated for six months had at least a 50% reduction in 5 HIAA values. No clear signs of regression of tumours were seen in any of the patients. Lanreotide was well tolerated despite transient mild pain or erythema at the injection site in 25% of the patients. Biliary lithiasis appeared in two patients after six months of lanreotide.

CONCLUSION

Lanreotide, 30 mg intramuscularly every other week, is an effective and convenient treatment in patients with the carcinoid syndrome.

Food-dependent Cushing's syndrome mediated by aberrant adrenal sensitivity to gastric inhibitory polypeptide

BACKGROUND

Some patients with Cushing's syndrome have nodular adrenal hyperplasia. In most the disease is corticotropin-dependent, but in others it is corticotropin-independent. The cause of the adrenal hyperplasia in the latter patients is not known.

METHODS

We studied a 49-year-old woman with Cushing's syndrome and nodular adrenal hyperplasia in whom food stimulated cortisol secretion. Plasma cortisol concentrations were measured in response to the ingestion of mixed meals, glucose, protein, and fat and after the administration of various gastrointestinal and other types of hormones. We also studied the ability of the long-acting somatostatin analogue octreotide to prevent the food-induced increase in plasma cortisol concentrations and to ameliorate the clinical manifestations of Cushing's syndrome in this patient.

RESULTS

The patient's fasting plasma cortisol concentrations were subnormal, ranging from 3.0 to 7.5 micrograms per deciliter (83 to 207 nmol per liter), and they increased to as high as 16.5 micrograms per deciliter (455 nmol per liter) after a mixed meal. Her urinary cortisol excretion ranged from 164 to 250 micrograms per day (453 to 690 nmol per day) and could not be suppressed by a large dose of dexamethasone. Plasma corticotropin concentrations were virtually undetectable at all times. The ingestion of glucose, protein, and fat increased plasma cortisol concentrations to 3.6, 2.2, and 4 times the base-line value, respectively; the meal-induced and glucose-induced increases were inhibited by octreotide. The infusion of gastric inhibitory polypeptide (GIP) increased the patient's plasma cortisol concentration to 3.7 times the base-line value, but had no effect in normal subjects. The patient's fasting plasma GIP concentrations were normal both before and after a meal, and there was a close correlation between her plasma cortisol and GIP concentrations. Treatment with octreotide decreased urinary cortisol excretion and ameliorated the clinical manifestations of Cushing's syndrome.

CONCLUSIONS

The development of aberrant adrenal sensitivity to GIP can result in food-dependent adrenal hyperplasia and therefore in Cushing's syndrome.

The antitumoral effect of the long-acting somatostatin analog lanreotide in neuroendocrine tumors

OBJECTIVE

Somatostatin analogs are the first-line drugs for controlling hormone-mediated symptoms of carcinoid tumors. Prospective and retrospective studies have suggested that somatostatin analogs also have antiproliferative activity. The octapeptide lanreotide is available in sustained-release form, obviating the need for daily injections.

METHODS

A total of 46 patients were enrolled in this open, prospective, phase II trial. They received lanreotide 30 mg i.m. every 14 days for 6 months when they had symptomatic carcinoid tumors, and lanreotide 30 mg i.m. every 10 days if they had nonsymptomatic tumors. Nonsymptomatic tumors were progressive before the start of the study. Tumor size was assessed every 3 months by means of computed tomography. The assessment was centralized and was made by an external panel.

RESULTS

In all, 30 patients had symptomatic neuroendocrine tumors and 16 had asymptomatic neuroendocrine tumors. Five patients in the group with symptomatic tumors and two in the group with nonsymptomatic tumors were considered not to be evaluable. The mean duration of treatment was 12 months in the group with symptomatic tumors and 13 months in the other group. Among the 39 evaluable patients, two objective responses were obtained, giving an objective response rate of 5% (one in the group with symptomatic tumors and one in the other group). Nineteen patients had no significant increase in their tumor size for a mean of 9.5 months.

CONCLUSIONS

Lanreotide is safe and well tolerated in patients with carcinoid tumors. It seems to have both symptomatic and antitumoral effects in this setting.

Contrast-enhanced harmonic endoscopic ultrasound in solid lesions of the pancreas: results of a pilot study

BACKGROUND AND STUDY AIMS

Distinguishing pancreatic adenocarcinoma from other pancreatic masses remains challenging with current imaging techniques. This prospective study aimed to evaluate the accuracy of a new procedure, imaging the microcirculation pattern of the pancreas by contrast-enhanced harmonic endoscopic ultrasound (CEH-EUS) with a new Olympus prototype echo endoscope.

PATIENTS AND METHODS

35 patients presenting with solid pancreatic lesions were prospectively enrolled. All patients had conventional B mode and power Doppler EUS. After an intravenous bolus injection of 2.4 ml of a second-generation ultrasound contrast agent (SonoVue) CEH-EUS was then performed with a new Olympus prototype echo endoscope (xGF-UCT 180). The microvascular pattern was compared with the final diagnosis based on the pathological examination of specimens from surgery or EUS-guided fine-needle aspiration (EUS-FNA) or on follow-up for at least 12 months.

RESULTS

The final diagnoses were: 18 adenocarcinomas, 9 neuroendocrine tumors, 7 chronic pancreatitis, and 1 stromal tumor. Power Doppler failed to display microcirculation, whereas harmonic imaging demonstrated it in all cases. Out of 18 lesions with a hypointense signal on CEH-EUS, 16 were adenocarcinomas. The sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy of hypointensity for diagnosing pancreatic adenocarcinoma were 89 %, 88 %, 88 %, 89 %, and 88.5 %, compared with corresponding values of 72 %, 100 %, 77 %, 100 %, and 86 % for EUS-FNA. Of five adenocarcinomas with false-negative results at EUS-FNA, four had a hypointense echo signal at CEH-EUS.

CONCLUSIONS

CEH-EUS with the new Olympus prototype device successfully visualizes the microvascular pattern in pancreatic solid lesions, and may be useful for distinguishing adenocarcinomas from other pancreatic masses.

Severe portal hypertensive gastropathy and antral vascular ectasia are distinct entities in patients with cirrhosis

BACKGROUND/AIMS

Whereas severe portal hypertensive gastropathy and gastric antral vascular ectasia (GAVE) have been separately defined in patients with cirrhosis, there is much confusion in the literature because they are both characterized by red spots at endoscopy. This prospective study compared clinical, biochemical, and pathological features of these syndromes.

METHODS

Three groups of patients with cirrhosis and either GAVE (n = 14), severe portal hypertensive gastropathy (n = 14), or no gastric features at endoscopy (controls; n = 10) were included.

RESULTS

No difference was found between patients with gastropathy and controls. Patients with GAVE presented with the following significant differences compared with other patients: a higher Child-Pugh score, a lower blood level of hemoglobin and gastrin, and a higher intestinal blood loss. At pathological examination, these patients more frequently had vascular ectasia (P = 0.04), spindle cell proliferation (P < 0.01), fibrohyalinosis (P = 0.004), and Gilliam's score of > or = 2 (P < 0.05); thrombi were encountered only in patients with GAVE (P = 0.006). Using discriminant analysis, spindle cell proliferation and fibrohyalinosis were the only significant variables yielding a diagnostic accuracy of 85% for GAVE and gastropathy.

CONCLUSIONS

GAVE and severe portal hypertensive gastropathy are two distinct entities.

Peptones stimulate both the secretion of the incretin hormone glucagon-like peptide 1 and the transcription of the proglucagon gene

Truncated glucagon-like peptide (GLP)-1 is a potent incretin. Its synthesis and secretion are modulated by food, but the influence of individual nutrients remains to be established. The hypothesis that protein hydrolysates (peptones) can directly regulate both GLP-1 secretion and proglucagon (PG) gene transcription was tested in this study, ex vivo in the isolated vascularly perfused rat intestine and in vitro in the murine enteroendocrine cell line STC-1. Peptones were albumin egg hydrolysate (AEH) and meat hydrolysate (MH). We demonstrate in these two models that peptones dose-dependently stimulate GLP-1 release, whereas isocaloric quantities of bovine serum albumin or of an amino acid mixture had no stimulatory effect. A strong and rapid increase of PG RNA level was observed in STC-1 cells treated with peptones (14-fold and 7-fold increase after 4 h of incubation with 3% wt/vol MH and AEH, respectively). Peptones also increased the PG RNA level in the colonic PG-expressing cell line GLUTag. In contrast, peptones did not modify the PG RNA level in two pancreatic glucagon-producing cell lines, namely, the RINm5F and INR1G9 cells. The peptone effect in STC-1 cells was completely abolished by blocking transcription before MH treatment. The stability of proglugacon transcripts was not modified by MH treatment, but nascent transcripts were more abundant in STC-1 cells preincubated with MH. Finally, MH treatment strongly stimulated (15-fold stimulation) the transcriptional activity of two PG gene promoter fragments (-1100 and -350 base pair) linked to the CAT reporter gene transiently transfected in STC-1 cells. Overall, peptones evoke an as yet undescribed release of GLP-1 when brought into contact with native intestinal L-cells or with STC-1 enteroendocrine cells. The increased transcription of the glucagon gene in the latter system suggests an important role of protein hydrolysates in the control of not only the secretion but also the synthesis of the incretin hormone.

Olmesartan-associated enteropathy: results of a national survey

BACKGROUND

Recently, a new enteropathy has been described: olmesartan-associated enteropathy. However, the association has been questioned: a phase 3 trial and a cohort study found no association between gastrointestinal events and olmesartan.

AIM

To collect French cases of sartan-associated enteropathy to describe further this entity, confirm or refute causality, and determine if the association exists with other sartans.

METHODS

French gastroenterologists were invited to report cases of sartan-associated enteropathy and collect clinical, biological and histological data. Patients with diarrhoea and histological duodenal abnormalities were included.

RESULTS

Thirty-six patients with olmesartan-associated enteropathy were reported, including 32 with villous atrophy and four without. There was only one patient with irbesartan-associated enteropathy. None of the patients died. Patients with villous atrophy had diarrhoea, vomiting, renal failure, hypokalaemia, body weight loss and hypoalbuminaemia. Thirty-one patients were hospitalised; four required intensive care. Anti-transglutaminase and anti-enterocyte antibodies were negative; anti-nuclear antibodies were positive (9/11). Endoscopic duodenal biopsies showed villous atrophy (32/32) and polyclonal intra-epithelial CD3+CD8+ lymphocytosis (11/11). Exactly, 14/15 patients responded to steroids and/or immunosuppressants, prescribed because of suspected autoimmune enteropathy. Ten olmesartan interruptions were followed by reintroductions before steroids or immunosuppressants. Interruptions were followed by remissions (9/10), but reintroductions were followed by relapses (9/9). Twenty-nine patients were in remission since olmesartan interruption, including 26 without immunosuppressants. Patients with normal villi had similar clinical characteristics, but mild histological abnormalities (intra-epithelial lymphocytosis and lamina propria lymphocytic infiltration).

CONCLUSIONS

Olmesartan causes a severe and immune-mediated enteropathy, with or without villous atrophy. Enteropathy associated with other sartans seems to be very rare.

Cystic endocrine tumors of the pancreas: clinical, radiologic, and histopathologic features in 13 cases

Cystic endocrine tumors of the pancreas are rare and raise difficult clinical problems. Our aims were to reevaluate the diagnostic and therapeutic strategy and to assess their histopathologic characteristics. Thirteen cystic endocrine tumors diagnosed in 10 patients were included. Clinical, radiologic, and pathologic data were reviewed. There were 6 male and 4 female patients (median age, 46 yrs). Six patients had evidence of multiple endocrine neoplasia type 1 (MEN1) disease. Four had a functional endocrine syndrome. Ten tumors were visible on imaging studies. The most suggestive radiologic features were the existence of a peripheral hypervascular rim (10 cases) and images of cyst into cyst (two cases). On gross and histologic examinations, two distinct types were present. Macrocystic tumors (six cases) were unilocular and limited by a thick wall containing nests of tumor cells. Microcystic tumors (seven cases) were characterized by the presence of multiple cystic spaces directly lined by tumor cells. Surgical resection was performed in all cases. Three patients had lymph node metastases at the time of diagnosis. One patient is dead with metastatic dissemination. The others are alive without recurrence or metastasis. The diagnosis of endocrine tumor must be considered for any pancreatic cyst discovered in a patient with a history of MEN1 syndrome or with clinical features suggestive of this syndrome. Cystic pancreatic endocrine tumors must be treated by surgical resection because of their possible malignant evolution.

Erythromycin enhances fasting and postprandial proximal gastric tone in humans

BACKGROUND & AIMS

Low doses of erythromycin induce antral contractions and accelerate gastric emptying. However, the effect of erythromycin on the proximal stomach remains unknown. The aim of this study was to assess the effect and mechanism(s) of action of erythromycin on proximal gastric tone in humans.

METHODS

Gastric tone was measured using an electronic barostat in two groups of 6 subjects both in the fasting state and after a 200-kcal meal. On different occasions, subjects received saline, atropine alone (6 micrograms.kg-1.h-1 for 30 minutes), erythromycin alone (1.5 mg/kg in the fasting state and 1.5 and 3.0 mg/kg in the postprandial state), and erythromycin plus atropine.

RESULTS

Low-dose (1.5 mg/kg) erythromycin enhanced fasting gastric tone, but only the 3.0-mg/kg dose reduced the duration of meal-induced relaxation (37 +/- 14 vs. 105 +/- 20 minutes; P < 0.01). Atropine did not change the fasting or postprandial gastric tone as well as the erythromycin-induced responses. Plasma motilin levels were unaffected by erythromycin infusion. No correlation was observed between gastric tone and plasma motilin or erythromycin levels.

CONCLUSIONS

Erythromycin enhances fasting and postprandial proximal gastric tone in humans by a mechanism that does not seem to involve endogenous motilin release or a cholinergic pathway.

Effect of somatostatin on diarrhea and on small intestinal water and electrolyte transport in a patient with pancreatic cholera

The effects of somatostatin on diarrhea and on small intestinal flow of water and electrolytes (slow-marker perfusion technique) in a patient with pancreatic cholera are reported. Continuous intravenous infusion of somatostatin (8 micrograms/kg/hr) suppressed the diarrhea, but a rebound was observed after somatostatin. Infusion of somatostatin at the same dosage decreased the ileal fluid flow rate to within control values. This effect was mainly due to a sharp reduction in the rate fluid entered the jejunum, but was also due to a suppression of the abnormal water and electrolyte secretion in the proximal jejunum. Secretion in the rest of the small bowel remained unchanged. Somatostatin did not noticeably alter the high preinfusion plasma level of prostaglandin E1, but decreased the initially high plasma concentration of vasoactive intestinal peptide to normal values. These results suggest that long-acting somatostatin analogs could be of value in the symptomatic treatment of diarrhea in pancreatic cholera.

Localization of substance P- and enkephalin-like immunoreactivity in relation to catecholamine-containing cell bodies in the cat dorsolateral pontine tegmentum: an immunofluorescence study

The distribution of tyrosine hydroxylase-, substance P- and enkephalin-immunoreactive neurons in the cat dorsolateral pons was studied using the indirect immunofluorescence method of Coons. To allow for the visualization of substance P- and enkephalin-immunoreactive cell bodies, colchicine was injected either in the ventricular space or in the cerebral tissue. The distribution of the tyrosine hydroxylase-immunoreactive cell bodies corresponded with the well-known distribution of catecholamine cells in this area of the brain. The observation of adjacent sections treated separately with tyrosine hydroxylase- and enkephalin-antiserum revealed that most catecholaminergic cells contain enkephalin-immunoreactivity. In addition to this catecholamine-enkephalin cell population, a moderate number of substance P-immunoreactive cell bodies was found in dorsolateral pons. The peribrachial nuclei were found to be densely supplied with substance P- and enkephalin-immunoreactive fibers, whereas the medial subdivisions, which contain the majority of the catecholamine cells in the dorsolateral pons, display a moderate number of immunoreactive fibers. These results are suggestive of interactions between peptide-containing and catecholaminergic neurons and also between-peptide-containing and non-catecholamine-containing neurons in the cat dorsolateral pons.

Distribution of substance P-like immunoreactivity in the spinal cord and dorsal root ganglia of the human foetus and infant

Using the indirect immunofluorescence method, the distribution of substance P-like-immunoreactivity was studied in spinal cord and dorsal root ganglia of 25 human foetuses ranging from 12 to 29 weeks of gestational age. The spinal cord and dorsal root ganglia of three infants (1 day-, 2 and 4 month-old) were also investigated as a post-natal reference. On the whole, the substance P distribution patterns seen in infants were already visible throughout most of foetal life. The highest density of substance P-like-immunoreactive fibres was localized over the superficial layers of the dorsal grey horn. Punctiform immunofluorescence was often found over the white matter especially in the funiculi dorsalis et lateralis. In the ventral horn, substance P immunoreactive fibres were few and far between in the grey matter and were only detected from foetal stage 16 weeks. In addition, longitudino-frontal sections through the dorsal regions revealed repetitive arrangements of substance P-like-immunoreactive fibres along the whole spinal cord. In dorsal root ganglia only a few immunoreactive cells were observed. These findings demonstrate the wide and early occurrence of substance P-like-immunoreactivity in the human foetus spinal cord and dorsal root ganglia. They suggest that the development of the substance P neuronal system begins early in ontogenesis and is regionally differentiated.

Luminal peptide YY-releasing factors in the isolated vascularly perfused rat colon

Peptide YY (PYY) is produced in endocrine L cells primarily localized in the distal bowel. These open-type L cells make contact with the intestinal chyme which may thus affect their secretory activity. The aim of the present study was to examine a large variety of luminal compounds found in colonic contents for their potential as PYY-releasing factors, using the isolated vascularly perfused rat colon. The release of PYY into the portal effluent was measured by a specific RIA. Luminal administration of 5 mM glucose or 0.5% (w/v) starch for 30 min did not induce significant release of PYY. Oleic acid (10 and 100 mM) also did not significantly increase PYY secretion. A pharmacological concentration of glucose (250 mM) and a mixture of amino acids (total concentration 250 mM) both induced PYY secretion (200% of basal). Pectin, a poly-galacturonic acid, evoked dose-dependent secretion of PYY-like immunoreactivity over the range 0.1-0.5% (w/v). The maximal response was observed after infusion of 0.5% pectin which induced a prompt and sustained release of PYY (300% of basal). Galacturonic acid itself (5%) produced marked PYY secretion. Gum arabic (0.5%) induced a gradual increase in portal PYY concentration (maximal response 250% of the basal value) whereas cellulose (0.5%) did not elicit PYY secretion. Luminal n-butyrate over the range 0.5-5 mM produced a dose-dependent release of PYY (maximal response 300% of the basal value with 5 mM n-butyrate). Increasing the concentration of n-butyrate to 100 mM provoked a gradual decrease in PYY secretion. Propionate was a less potent stimulant than n-butyrate, and acetate did not increase PYY secretion above the basal value. At a concentration of 2 or 20 mM, taurocholate, cholate and deoxycholate brought about PYY secretion while hyodeoxycholate was without effect. In conclusion, glucose and amino acids may mediate PYY release but only when they are present at high supraphysiological concentrations in the colon while oleic acid does not produce any PYY secretion. Physiological concentrations of fibers (pectin, gum arabic), short-chain fatty acids (n-butyrate, propionate) and bile salts (taurocholate, cholate, deoxycholate) are all potent stimulants of PYY release. Whether the release of PYY by luminal factors is coupled to water and electrolyte transfer via a local/paracrine pathway remains an open question which requires additional work with the isolated vascularly perfused colon preparation.

Effect of ethanol ingestion on postprandial gastric emptying and secretion, biliopancreatic secretions, and duodenal absorption in man

Although abdominal complaints are frequent in both acute and chronic alcoholism, little is known of the effect of ingestion of ethanol with a meal on the function of the upper digestive tract. We have studied the effects of oral ethanol (1 g/kg body wt) taken with food on the gastric emptying rate of a solid-liquid meal as measured by a dual radioisotope technique in six normal subjects; and the gastric response (emptying and secretion), biliopancreatic secretions, and duodenal nutrient absorption after an homogenized meal, as evaluated by a gastroduodenal intubation-marker perfusion technique on seven healthy volunteers. In the latter experiments, radioimmunoassays of gastrin, secretin, cholecystokinin, pancreatic polypeptide, motilin, somatostatin, gastric inhibitory polypeptide, and vasoactive intestinal polypeptide were performed serially. As compared with the control experiment, alcohol induced the following effects: marked delay of gastric emptying of solids, smaller slowing effect on gastric emptying of the liquid phase of the solid-liquid meal and of the homogenized meal; no significant change in gastric acid secretion; no change in the overall postprandial pancreatic enzyme outputs, but a delay of lipase secretion; no change in the early bile salt postprandial output, but a reduced bile salt secretion from the second postprandial hour onwards; no significant change in carbohydrate and lipid duodenal absorption; and a significantly greater postcibal gastrin release. The mechanisms for these effects of alcohol on upper digestive tract function remain to be clarified.

Luminal glucagon-like peptide-1(7-36) amide-releasing factors in the isolated vascularly perfused rat colon

Glucagon-like peptide-1 (GLP-1) is released from endocrine cells of the distal part of the gut after ingestion of a meal. GLP-1 secretion is, in part, under the control of hormonal and/or neural mechanisms. However, stimulation of the colonic L cells may also occur directly by the luminal contents. This was examined in the present study, using an isolated vascularly perfused rat colon. GLP-1 immunoreactivity was measured in the portal effluent after luminal infusion of a variety of compounds which are found in colonic contents (nutrients, fibers, bile acids, short-chain fatty acids (SCFAs)). Oleic acid (100 mM) or a mixture of amino acids (total concentration 250 mM), or starch (0.5%, w/v) did not increase GLP-1 secretion over basal value. A pharmacological concentration of glucose (250 mM) elicited a marked release of GLP-1 which was maximal at the end of infusion (400% of basal), while 5 mM glucose was without effect on secretion. Pectin evoked a dose-dependent release of GLP-1 over the range 0.1-0.5% (w/v) with a maximal response at 360% of basal when 0.5% pectin was infused. Cellulose or gum arabic (0.5%) did not modify GLP-1 secretion. The SCFAs acetate, propionate or butyrate (5, 20 and 100 mM) did not induce a significant release of GLP-1. Among the four bile acids tested, namely taurocholate, cholate, deoxycholate and hyodeoxycholate, the last one was the most potent at eliciting a GLP-1 response with a maximal release at 300% and 400% of the basal value when 2 and 20 mM bile acid were administered respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Peptones stimulate cholecystokinin secretion and gene transcription in the intestinal cell line STC-1

In rats, protein hydrolysates (peptones) stimulate cholecystokinin (CCK) release both in vivo and in a model of isolated vascularly perfused duodeno-jejunum. However, the mechanisms involved in peptone-induced stimulation of CCK cells are not well understood. In particular, the possibility that peptones may directly interact with CCK-producing cells to stimulate CCK release and gene transcription has not yet been examined. To test this hypothesis, we used the enteroendocrine cell line STC-1. Incubation of STC-1 cells for 2 h with albumin egg hydrolysate over the concentration range 0.01-1% (wt/ vol) caused a dose-dependent release of CCK, with a maximal increase at 1420% of the control value. In contrast, BSA (1%, wt/vol) or a mixture of amino acids (1%, wt/vol) induced a modest rise in CCK secretion. A dose-dependent, hydrolysate-specific, increase in the CCK steady state RNA level was also observed. It was detectable by 2-4 h of peptone treatment and sustained until 24-48 h. Peptones did not increase the CCK RNA level in the colonic CCK-producing cell line GLUTag or in nonintestinal CCK-expressing cell lines, namely the pancreatic cell line RINm5F and the medullar thyroid carcinoma cell line CA77. The peptone-induced increase in the CCK RNA level resulted from enhanced gene transcription, because labeled CCK transcripts from nuclear run-on incubations increased 3-fold when cells were incubated with peptones, whereas the level of beta-actin transcripts was not modified. Finally, peptones dose-dependently stimulated the transcriptional activity of an 800-bp fragment of CCK gene promoter transfected in STC-1 cells. These studies indicate that peptones specifically stimulate CCK secretion and gene transcription in the intestinal cell line STC-1, and that cis-acting elements conferring peptone inducibility are located in the first 800 bp of the 5'-flanking region of the CCK gene.

Ultrastructural evidence for endogenous substance-P-like immunoreactivity in the rat pituitary gland

Substance P (SP) is known to act on pituitary hormone release either at the hypothalamic level or directly at the pituitary level. In order to investigate whether SP is present in the pituitary gland and to localize the peptide at the cellular and subcellular levels, the immunocytological method was used. Rat pituitaries were fixed and frozen. Ultrathin sections, obtained by cryoultramicrotomy, were incubated with anti-SP serum. The antigen-antibody reaction was detected by 4-chloro-1-naphtol. SP immunoreactivity was observed both in the prolactin and in the gonadotropic cells, but not in the somatotropic, corticotropic and thyrotropic cells. In reactive cells, SP immunoreactivity was observed in the secretory granules, in the cytoplasm, and in the nucleus distributed all over the euchromatin near to the heterochromatin regions. No immunoreactivity was observed when nonimmune serum or anti-SP serum incubated with SP was used. No modification of the immunocytochemical reaction was observed when anti-SP serum incubated with somatostatin, gonado- or thyroliberin was used. These data (1) provide immunocytological evidence for the presence of SP in the pituitary gland; (2) indicate the presence of SP peptide in the gonadotropic and prolactin cells only. They support previous findings indicating that SP could have a direct effect at the pituitary level.

Regulation of glucagon-like peptide-1-(7-36) amide, peptide YY, and neurotensin secretion by neurotransmitters and gut hormones in the isolated vascularly perfused rat ileum

Neurotensin (NT), peptide YY (PYY), and several peptides derived from proglucagon are promptly released from endocrine cells of the distal part of the gut after oral ingestion of a meal, thus suggesting that release of these peptides is partly under neural and/or hormonal control. Our previous studies conducted with a model of isolated vascularly perfused rat colon showed that colonic L cells are highly responsive to several transmitters of the gut and to the hormonal peptide GIP. To test the possibility that hormones produced by the proximal small intestine or transmitters of the enteric nervous system may also modulate the secretory activity of the ileal L cells, various intestinal regulatory peptides and neurotransmitters were administered intraarterially for 30 min in the isolated vascularly perfused rat ileum preparation. The secretory activity of the ileal N cells was comparatively assessed. The release of NT, PYY, and glucagon-like peptide-1 (GLP-1) in the portal effluent was measured with specific RIAs. The muscarinic cholinergic agonist bethanechol at a concentration of 10(-4) M provoked a biphasic release of PYY, GLP-1, and NT, consisting of an early peak followed by a sustained response. Similarly, bombesin (10(-7) M) induced a marked biphasic release of PYY and GLP-1. In contrast, the NT response was essentially monophasic, characterized by an early peak secretion. Tetrodotoxin did not modify the bombesin-induced release of PYY, GLP-1, and NT. The beta-adrenergic agonist isoproterenol at a concentration of 10(-6) M induced a transient rise in portal PYY and GLP-1 concentrations, whereas the effect on NT release was clearly biphasic. Calcitonin gene-related peptide (5 x 10(-8) M) induced a dramatic rise in PYY, GLP-1, and NT immunoreactivities in the portal effluent (peaks at 600%, 500%, and 550% of the basal values, respectively, 4 mi n after the start of infusion). Intraarterial infusion of GIP over the concentration range (0.5-3 nM) evoked a significant increase in portal concentration of the three peptides only at the threshold concentration of 3 nM. Secretin (50 pM) or cholecystokinin (50 pM) did not affect the release of ileal hormones. In conclusion, ileal L and N cells respond to a variety of transmitters of the gut. The pattern of peptide release depends on the cell type studied. The two cosynthesized peptides, PYY and GLP-1, appear to be cosecreted in the conditions of the present study.

Thirteen-month registration of patients with gastroenteropancreatic endocrine tumours in France

The prevalence, clinical profiles and management of gastroenteropancreatic endocrine tumours (GEP) in France are not known. From August 1, 2001 to September 1, 2002, standardized records on patients with GEP were prospectively completed in 87 participating centres. The total group amounted to 668 patients (median age: 56 years, range: 12-89). WHO performance status was 0/1 for 80.2% of patients. The primary sites were the small bowel and colon (288), pancreas (211), unknown (77), stomach (33), non-digestive primary sites (24), appendix (20), rectum-anus (12), and oesophagus or cardia (3). GEP were functional in 260 patients (39%). Most pancreatic tumours were non-functional (72%). Metastatic disease was observed in 73.4% of cases. Most tumours (85.8%) were well or moderately differentiated. Somatostatin receptor scintigraphy was performed in only 55% of patients. The following treatment modalities were employed: resection of primary tumour: 66%; systemic chemotherapy: 41%; somatostatin analogues: 44 and 26% for GEP of small intestine and pancreas, respectively; interferon: 12%, and intra-arterial hepatic (chemo)embolization in 23 and 15% of GEP arising from the midgut and pancreas, respectively. Despite their low prevalence, well-differentiated GEP represent a significant and heterogeneous clinical group, which warrants improved medical education, referral to expert centres at an early stage, and the design of prospective therapeutic trials.

Gut regulatory peptides in young cattle and sheep

This review summarizes recent advances on blood plasma patterns, receptors, secondary messengers and metabolism of gut regulatory peptides (i.e. gastrin, secretin, somatostatin, cholecystokinin, vasoactive intestinal polypeptide, pancreatic polypeptide, gastric inhibitory polypeptide, motilin), in young ruminants during fetal and perinatal stages, during the preruminant stage and at weaning. It also deals with their role in the digestive tract function and postabsorptive changes. Some pathological situations in young ruminants are considered. Recent molecular aspects of digestive enzyme synthesis are also reported.

Stimulation of glucagon-like peptide-1 secretion by muscarinic agonist in a murine intestinal endocrine cell line

Studies on the cholinergic regulation of intestinal L-cells have been focused on the release of enteroglucagon, but the signal transduction pathways were not defined. These were here investigated by using as index the release of immunoreactive glucagon-like peptide-1 (GLP-1) from the endocrine cell line STC-1, that has been shown to contain proglucagon mRNA transcripts. Abundant GLP-1 immunoreactivity was revealed in STC-1 cells at immunocytochemistry and by RIA. The cell content was 4927 +/- 689 pg/10(6) cells, as measured with antiserum 199D that recognizes specifically the C-terminal amidated forms of GLP-1. The secretion of GLP-1 over a 2-h incubation period amounted to 1.4 +/- 0.3% of the total GLP-1 cell content and was significantly increased by 10 microM forskolin and 100 nM 12-O-tetradecanoylphorbol 13-acetate to 206% and 574% of control values, respectively. The cholinergic agonist carbachol stimulated GLP-1 secretion in a concentration-dependent manner, maximal release was observed at 1 mM carbachol (228% of the control value). Binding of the muscarinic antagonist [N-methyl-]scopolamine ([3H]NMS) on cell homogenates was time dependent, specific, and saturable. Scatchard analysis revealed one class of receptors (Kd, 14 pM; binding capacity, 20 fmol/mg protein). Carbachol (0.1 microM to 1 mM) dose dependently displaced [3H] NMS binding and increased the intracellular calcium concentration without modification of adenylate cyclase activity. The order of potency of different antagonists, showing a preferential affinity for M1, M2, and M3 muscarinic receptor subtypes, to inhibit [3H]NMS binding, the carbachol-induced increase in intracellular calcium, and carbachol-stimulated GLP-1 secretion, was as follows: atropine (nonselective) > 4-diphenylacetoxy-N-methylpiperidine methiodide (M3) > pirenzepine (M1) > AF-DX 116 (M2). The results of the present study, therefore, demonstrate that secretion of GLP-1 induced by cholinergic agonist depends on muscarinic M3-subtype receptors in the endocrine intestinal cell line STC-1. This system may prove useful to study the cellular mechanisms of GLP-1 secretion.

Multihormonal carcinoid tumor of the pancreas. Secreting growth hormone-releasing factor as a cause of acromegaly

This report describes the histologic, immunocytochemical, and ultrastructural study of a multihormonal carcinoid tumor of the pancreas, secreting a growth hormone releasing factor (GRF) which provoked acromegaly. The patient presented a nonfamilial multiple endocrine neoplasia, type 1. The absence of radiologic signs of a pituitary adenoma in conjunction with elevated plasma levels of pancreatic polypeptide, glucagon, somatostatin, as well as growth hormone (GH), led to the discovery of the tumor. Its surgical excision produced a rapid disappearance of most of the clinical and biologic disorders. No immunoreactive GH was found in the tumor using radioimmunoassay and immunocytochemistry. In contrast, three peptides with GH-releasing activity were extracted and characterized. Immunocytochemistry showed that the GRF-reactive cells, together with rare somatostatin-storing cells, made up areas which demonstrated a medullary pattern of growth with extracellular amyloid deposits. Under electron microscopic examination, actively secreting cells were observed which carried endocrine granules of 100 to 150 nm in diameter. The other regions of the tumor presented a different type of growth and were composed of pancreatic polypeptide-, glucagon-, or somatostatin-reacting cells. Cells immunostained with antisera raised against beta-endorphin were also noted. These data suggest that GRF may be a new biologic marker for pancreatic endocrine tumors.