Impaired immunoreactive secretin release in coeliac disease

Gut endocrine cell population in coeliac disease estimated by immunocytochemistry using a monoclonal antibody to chromogranin

Abnormalities of gut endocrine responses, as well as changes in the number of different endocrine cell types, have been reported convincingly in coeliac patients. Nevertheless, no estimation of total numbers of gut endocrine cells has yet been made in well defined groups of coeliacs. In this study, we have visualised all endocrine cell types in jejunal biopsies from coeliac patients with active and quiescent disease as well as in controls, using a monoclonal antibody to chromogranin. This protein was purified originally from bovine adrenal medulla and is known to be a reliable marker for all endocrine cells of the gut. The following groups were considered: (a) nine coeliacs with active illness, (b) 10 coeliacs under gluten-free diet, (c) eight coeliacs receiving gluten challenge, (d) five non-coeliacs (controls). Histological (haematoxylin and eosin) and immunocytochemical (peroxidase anti-peroxidase) stains were applied to 3 micron paraffin sections. Quantitative estimation of endocrine cell density was made using four different methods in order to evaluate the results fully (number of cells/mm2, number of cells/visual field, number of cells/8 crypts-villi, number of cells/unit of length of muscularis mucosae). In patient groups (a) and (c), coeliacs with active disease and coeliacs on gluten challenge diet respectively, a significantly higher number of endocrine cells was observed in comparison with normal controls (group d). In group (b) patients, coeliacs on gluten-free diet, no significant changes in the number of endocrine cells were observed in comparison with controls. Our results show that a significant increase in endocrine cell density exists in coeliacs with active illness (groups a and c), in comparison with controls. This condition is resolved in coeliacs receiving a gluten-free diet (group b).

Gastrointestinal regulatory peptide storage granule abnormalities in jejunal mucosal diseases

The mucosal concentrations of seven regulatory peptides and the density properties and integrity of their storage granules have been studied in mucosal biopsies from the human jejunum in eight gastrointestinal disease states and compared with normal controls. In diseases with associated mucosal inflammation (coeliac disease, Crohn's disease with jejunal involvement, postinfective tropical malabsorption, and common variable immunodeficiency) there was a selective increase in fragility of the gastric inhibitory polypeptide (GIP) and somatostatin storage granules. The gastrin, motilin, enteroglucagon, secretin, and vasoactive intestinal polypeptide granules had normal properties in these conditions. In diseases in which diarrhoea occurred in the absence of changes in jejunal mucosal histology (irritable bowel syndrome, pancreatic insufficiency, jejuno-ileal bypass for morbid obesity, and purgative abuse) there were no abnormalities of the storage granules. Increased mucosal concentrations of all peptides except vasoactive intestinal polypeptide (VIP) were found in coeliac disease and selective increases of VIP found in Crohn's disease, motilin in the irritable bowel syndrome and gastrin and GIP in pancreatic insufficiency. It is suggested that the storage granule abnormalities in the diseases with abnormal mucosal histology are secondary to the inflammatory changes.

Secretin release in coeliac disease. Plasma secretin concentration and bicarbonate output to the duodenum after intraduodenal acid infusion in coeliac patients before and after treatment

Infusion of 40 ml 0.1 mol/l HCl into the duodenum in eight untreated coeliac patients was followed by an increase of the plasma immunoreactive secretin (IRS) concentration from 1.6 +/- 0.2 pmol/l to a peak level of 2.4 +/- 0.3 pmol/l (p less than 0.05). After treatment with a gluten-free diet, the same patients showed an increase from 1.4 +/- 0.3 pmol/l to a peak level of 5.5 +/- 0.9 pmol/l after intraduodenal acid infusion, which was significantly higher than before treatment (p less than 0.01). In control subjects, intraduodenal acid infusion was followed by an increase from 1.4 +/- 0.2 pmol/l to 6.7 +/- 1.1 pmol/l, which was significantly higher than in untreated coeliac disease (p less than 0.01) but did not differ from what was found in treated coeliac patients. Significant differences in pH, volume, or bicarbonate content of the duodenal aspirates or the basal IRS levels were not found.

Plasma secretin concentrations and gastric pH in healthy subjects and patients with digestive diseases

Plasma secretin concentrations were determined in healthy subjects and patients with duodenal ulcer, achlorhydria, and celiac sprue. Mean fasting plasma secretin concentrations in 26 healthy subjects and 26 duodenal ulcer patients were 6.7 +/- 0.5 and 10.2 +/- 1.2 pg/ml, respectively, and were significantly different (P less than 0.02). After ingestion of a standard meat meal, pyloric pH decreased to less than 4.5 within 15 min and plasma secretin concentrations significantly increased in all 52 subjects. In 14 subjects (seven healthy subjects and seven patients with duodenal ulcer), no significant rise in plasma secretin concentration occurred when pyloric pH was maintained at greater than 5.0 by intravenous cimetidine (600 mg) and intragastric antacid. In 10 achlorhydric patients, intragastric pH remained greater than 5.0 after the meal and plasma secretin concentrations did not change. However, plasma secretin concentrations increased significantly when 0.1 N HCl was infused in the stomach (25 mEq/hr) during the postprandial period. In all eight adult patients with celiac disease (seven untreated, one partially treated), pyloric pH remained less than 4.0 after a meal. Postprandial secretin concentrations did not increase significantly in six and showed a transient rise in two. These studies show that (1) plasma secretin concentration increases significantly after meals in healthy subjects and patients with duodenal ulcer; (2) neutralization of gastric acid and the achlorhydric state show no significant postprandial rise in plasma secretin concentration; (3) achlorhydric patients do not have a defect in secretin release in response to acid; and (4) failure of postprandial rise in plasma secretin in patients with celiac disease is attributed to impaired release of secretin and in achlorhydric patients it is attributed to lack of acid secretion.

Changes in N-terminal glucagon-like immunoreactivity and insulin during short-term gluten challenge in childhood coeliac disease

Sixteen patients (aged 3.5-14.3 years) with normal jejunal mucosa, originally diagnosed as having coeliac disease at least 18 months before, were started on gluten challenge. The 'end point' of challenge was significant deterioration in jejunal mucosa morphologically and morphometrically. Studies carried out both before and after challenge included intestinal absorption of D-xylose and glucose, and release of insulin and N-terminal glucagon-like immunoreactivity (N-GLI). After gluten challenge, there were significant increases in plasma N-GLI at both 45 (P less than 0.05) and 120 minutes (P less than 0.03) after oral glucose. Significant reduction occurred in glucose absorption at 45 minutes (P less than 0.04), in one-hour D-xylose absorption (P less than 0.01) and fasting serum cholesterol (P less than 0.01). Plasma N-GLI showed significant negative correlations with D-xylose absorption (P less than 0.003) and serum cholesterol (P less than 0.004).

Pathophysiology of gastrointestinal hormones. Implications for paediatrics

Gastrointestinal hormones (GI hormones) have received growing interest in endocrinology, gastroenterology and neuroendocrinology. Because of new methodological techniques, they can be measured in plasma and therefore be related to different pathophysiological conditions. In childhood, our present knowledge is as yet limited to the physiological rôle of gastrin at different ages and in some diseases (gastrinoma; Verner-Morrison syndrome) caused by humoral dysfunction. The present review relates the clinical important GI hormones to chemically classified families. The diagnostic value of determining endogenous hormone concentration in plasma and the validity of function tests carried out by administration of exogenous hormones are pointed out. Particular emphasis is given to the trophic action of GI hormones in the development and function of the gastrointestinal tract during childhood. More speculatively, GI hormones are involved in the complex function of the central nervous system, thus making food intake a trophotropic action in a broader sense.

Radioimmunoassay of secretin. A critical review and current status

The radioimmunoassay methods of secretin are reviewed with respect to production of antibody, preparation of radioactive tracers, and effect of plasma interference. The major difference in the secretin assay methods resides in handling plasma interference. Thus the assay sensitivity decreased markedly when the assay was conducted by diluting plasma samples. When the assay was conducted by compensating for plasma interference with homologous hormone-free plasma, the effect of plasma interference was greatly reduced, leading to a more sensitive assay. However, this method probably can not obtain consistent results with plasma samples collected under various experimental conditions. The method is still subject to considerable desensitization and assay variation. On the other hand, the elimination of plasma interference before assay results in the most sensitive secretin assays capable of detecting consistently a significant postprandial rise in plasma secretin level. It is concluded that a sensitive, validated secretin radioimmunoassay should be one that is capable of detecting increments of plasma secretin in response to doses of intraduodenal acid at 0.055 mEq/min or lower and intravenous administration of exogenous secretin at 0.03 CU/kg/hr with concomitant stimulation of pancreatic bicarbonate and water secretion. With a sensitive and accurate radioimmunoassay for secretin, it is now possible to further investigate the physiology and pathophysiology of secretin.

Impairment of secretin release in celiac sprue

Plasma secretin concentrations and pH in the second portion of duodenum were measured in the fasting state and during duodenal infusion of HCl in five patients with untreated celiac sprue, five celiac sprue patients after gluten-free diets, and five normal subjects. Mean fasting plasma secretin concentrations were insignificantly lower in untreated sprue patients (4.1 +/- 1.4 pg/ml) than in normal subjects (5.7 +/- 0.59 pg/ml). During 30-min intraduodenal infusions of 0.1 N HCl at 0.20 mEqH+/min, mean plasma secretin concentrations were significantly lower in untreated sprue patients (5.8 +/- 1.8 pg/ml) than in normal subjects (25.4 +/- 1.60 pg/ml, P less than 0.01). The increases in mean secretin concentrations over fasting were 2.1 +/- 0.82 pg/ml in untreated sprue patients compared to 19.7 +/- 1.47 pg/ml in normal subjects (P less than 0.01), a ninefold difference. The results indicate that endogenous release of secretin in response to duodenal acidification is impaired in patients with celiac sprue.

Gut-hormone profile in coeliac disease

Patients with coeliac disease have a highly significant reduction in the release of secretin and gastric inhibitory polypeptide from the upper small intestine, but a greatly increased release of enteroglucagon, and also of neurotensin, from the lower part of the small intestine. The release of gastrin and pancreatic polypeptide, from the antrum and pancreas respectively, is, however, normal. Thus the pattern of hormone release reflects the location of the mucosal lesion. The gut-hormone profile may also help to characterise other gastrointestinal diseases.