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The present study aimed to determine the primary sequence of ovine xenin and clarify the mRNA expression and peptide localization of xenin in the gastrointestinal tract in sheep. The colocalization of xenin and glucose-dependent insulinotropic polypeptide was also compared in the antrum and duodenum. Analysis of the nucleotide sequence of ovine xenin revealed a high degree (97.9%) of sequence homology of the sequence between sheep and cattle, and the amino acids sequence determined for ovine xenin coincided (100%) with that of other mammalian species. Real-time quantitative PCR for ovine xenin did not show regional difference in the mRNA expression ratio of xenin. In contrast to the real-time quantitative PCR results, anti-xenin positive cells were abundantly localized in the abomasal antrum (P < 0.01) and at a lesser amount in the duodenum, but no antixenin positive cells were observed in the other regions. Anti-xenin single-positive cells were in a majority in the abomasal antrum, whereas anti-xenin single-positive cells, and anti-GIP single-positive cells, and double-positive cells were even colocalized in the duodenum. These results suggest that abomasal antrum is a major source of xenin in the ovine gastrointestinal tract., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Ethnopharmacological Relevance: Semen Arecae (SA) is one of the most commonly used Traditional Chinese Medicine. Charred Semen Arecae (CSA) is the processed product of SA. Alkaloids are considered as pharmacological mechanisms of SA and CSA on gastrointestinal motility. Recent studies have shown alkaloids decreased quickly after procession. However, the promoting on gastrointestinal motility were not decreased. Is gastrointestinal motility related to alkaloids of CSA? This study explored the effects of SA, CSA, Semen Arecae-Removal (SA-R), and Charred Semen Arecae-Removal (CSA-R) on gastrointestinal motility, Gastric Inhibitory Polypeptide (GIP), Glucagon Like Peptide-1 (GLP-1), gastric juice and bile in rats., Material and Methods: Rats were randomly divided into six groups, including the Control group, SA group, CSA group, SA-R group, CSA-R group, and Positive drug group (Mosapride). Alkaloids of samples were knocked out by using the "target constituent removal" strategy. Gastric residue and intestinal propulsion rate were evaluated in rats. Serum levels of GIP and GLP-1 were measured by Enzyme-Linked Immunosorbent Assay (ELISA). Gastric juice and bile were examined, respectively., Results: CSA-R and SA-R have been investigated by the Preparative Thin-layer Chromatography (PTLC) method. Intestinal propulsion and gastric residue assessments confirmed the effectiveness of CSA and CSA-R. CSA-R was higher than SA-R in the GLP-1, pepsin activity, the secretion of bile, Bilirubin (BIL), and Cholesterol (CHO). The statistical comparison demonstrated that there is no difference between the CSA group and CSA-R group., Conclusions: After processing, the promoting gastrointestinal motility might be not related to alkaloids. Maillard reaction could be produced to promote the secretion of GLP-1, bile, and CHO for gastrointestinal motility. Our findings provide a pharmacological reference for the clinical application of SA and CSA in the treatment of digestive diseases., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The short-form glucose-dependent insulinotropic polypeptide (GIP) (1-30) is released from islet alpha cells and promotes insulin secretion in a paracrine manner in vitro. However, it is not well elucidated how GIP (1-30) is involved in glucose metabolism in vivo, since a specific assay system for GIP (1-30) has not yet been established. We first developed a sandwich enzyme-linked immunosorbent assay (ELISA) specific for GIP (1-30) by combining a novel antibody specific to the GIP (1-30) C terminus with the common antibody against GIP N terminus. Then, we explored cross-reactivities with incretins and glucagon-related peptides in this ELISA. GIP (1-30) amide, but not GIP (1-42), GLP-1, or glucagon increased absorbance in a dose-dependent manner. We next measured plasma GIP (1-30) concentrations in nondiabetic participants (ND) during a 75-g oral glucose tolerance test or cookie meal test (carbohydrates 75 g, lipids 28.5 g, proteins 8.5 g). Both glucose and cookie load increased GIP (1-30) concentrations in ND, but the increases were much lower than those of GIP (1-42). Furthermore, the DPP-4 inhibitor significantly increased GIP (1-30) concentrations similarly to GIP (1-42) in ND. In conclusion, we for the first time developed an ELISA specific for GIP (1-30) and revealed its secretion in ND., (© 2020 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)

The incretin hormones glucagon-like peptide-1 (GLP1) and glucose-dependent insulinotropic polypeptide (GIP) are secreted from intestinal endocrine cells, the so-called L- and K-cells. The cells are derived from a common precursor and are highly related, and co-expression of the two hormones in so-called L/K-cells has been reported. To investigate the relationship between the GLP1- and GIP-producing cells more closely, we generated a transgenic mouse model expressing a fluorescent marker in GIP-positive cells. In combination with a mouse strain with fluorescent GLP1 cells, we were able to estimate the overlap between the two cell types. Furthermore, we used primary cultured intestinal cells and isolated perfused mouse intestine to measure the secretion of GIP and GLP1 in response to different stimuli. Overlapping GLP1 and GIP cells were rare (∼5%). KCl, glucose and forskolin+IBMX increased the secretion of both GLP1 and GIP, whereas bombesin/neuromedin C only stimulated GLP1 secretion. Expression analysis showed high expression of the bombesin 2 receptor in GLP1 positive cells, but no expression in GIP-positive cells. These data indicate both expressional and functional differences between the GLP1-producing 'L-cell' and the GIP-producing 'K-cell'., (© 2016 Society for Endocrinology.)

The two incretin hormones, glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP), are secreted from the gastrointestinal tract in response to meals and contribute to the regulation of glucose homeostasis by increasing insulin secretion. Assessment of plasma concentrations of GLP-1 and GIP is often an important endpoint in both clinical and preclinical studies and, therefore, accurate measurement of these hormones is important. Here, we provide an overview of current approaches for the measurement of the incretin hormones, with particular focus on immunological methods., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Glucose-dependent insulinotropic peptide (GIP), glucagon-like peptide (GLP)-1 and GLP-2 are hormones secreted from specialized K cells (GIP) and L cells (GLP-1, GLP-2) in the intestinal mucosa. These hormones play major roles in health and disease by modulating insulin secretion, satiety, and multiple intestinal functions. The aim of this study was to describe the distribution of K cells and L cells in the intestines of healthy cats. Samples of duodenum, mid-jejunum, ileum, cecum, and colon were collected from 5 cats that were euthanized for reasons unrelated to this study and had no gross or histologic evidence of gastrointestinal disease. Samples stained with rabbit-anti-porcine GIP, mouse-anti-(all mammals) GLP-1, or rabbit-anti-(all mammals) GLP-2 antibodies were used to determine the number of cells in 15 randomly selected 400× microscopic fields. In contrast to other mammals (eg, dogs) in which K cells are not present in the ileum and aborally, GIP-expressing cells are abundant throughout the intestines in cats (>6/high-power field in the ileum). Cells expressing GLP-1 or GLP-2 were most abundant in the ileum (>9/high-power field) as in other mammals, but, although GLP-1-expressing cells were abundant throughout the intestines, GLP-2-expressing cells were rarely found in the duodenum. In conclusion, the distribution of GIP-secreting K cells in cats is different from the distribution of K cells that is described in other mammals. The difference in distribution of GLP-2- and GLP-1-expressing cells suggests that more than 1 distinct population of L cells is present in cats., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The presence and distribution of glucose-dependent insulinotropic polypeptide or gastric inhibitory polypeptide (GIP), gastric-releasing peptide (GRP) and glucagon immunoreactivity were studied in the small intestine of the New Hampshire chicken using immunohistochemistry. This is the first report of the presence of GIP-immunoreactive (ir) cells in avian small intestine. GIP, GRP and glucagon immunoreactivity was localized in the epithelium of the villi and crypts of the duodenum, jejunum and ileum. In particular, both in the duodenum and in the jejunum immunoreactive endocrine cells to GIP, GRP and glucagon were observed. In the ileum, we noticed GIP-ir and glucagon-ir cells. GRP-ir was found in nerve fibres of all three segments of the small intestine. The distribution of these bioactive agents in the intestinal tract of the chicken suggests that GIP and glucagon may play a role in the enteropancreatic axis in which intestinal peptides modulate pancreas secretion., (© 2010 Blackwell Verlag GmbH.)

Ezetimibe is a potent inhibitor of cholesterol absorption by enterocytes. Although ezetimibe minimally affects the absorption of triglyceride, it is unknown whether ezetimibe affects the secretion of the incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). It has been shown that ezetimibe-treated mice are protected from diet-induced insulin resistance. Since GIP and GLP-1 promote the actions of insulin, we hypothesized that ezetimibe may affect the secretion of GIP and GLP-1 by enteroendocrine cells into lymph in response to the intestinal absorption of a mixed meal (Ensure). To test this hypothesis, we used the lymph fistula rat model to determine GIP and GLP-1 concentrations in lymph during the 2 h after the infusion of Ensure. Ezetimibe significantly reduced lymphatic cholesterol output during fasting, without coincident decreases in glucose, protein, and triglyceride outputs. However, ezetimibe did not influence cholesterol output after infusion of Ensure. Interestingly, ezetimibe significantly reduced the secretion of both GIP and GLP-1 into lymph after the infusion of Ensure. Therefore, the inhibitory effect of ezetimibe on GIP and GLP-1 secretion by enteroendocrine cells occurs outside of the effects of glucose, protein, or triglyceride secretion by the intestine.

Background: Enteroendocrine K cells secrete the incretin hormone glucose-dependent insulinotropic peptide (GIP) and are predominately located in the duodenum. GIP levels should decrease after gastric bypass due to duodenal exclusion; however, studies have found conflicting data regarding the changes in GIP secretion after gastric bypass and duodenal-jejunal bypass (DJB)., Methods: We performed a DJB or Sham surgery on Wistar rats followed by an oral glucose tolerance test on postoperative (post-op) day 12 and superior mesenteric lymphatic cannulation on post-op day 14. We measured meal-stimulated GIP concentrations and small bowel GIP and GLP-1 protein content after DJB or Sham surgery., Results: There was no difference in glucose tolerance by 12 days post-op. We found no difference in lymphatic GIP concentration area under the curve between DJB and Sham rats (15,240 pg/ml min +/- 2,651 vs. 17,201 pg/ml min +/- 2,763, respectively, p = 0.62). GIP and GLP-1 protein contents were both significantly increased only in the midjejunum in DJB rats compared to Sham rats (p = 0.009 and p = 0.01, respectively)., Conclusions: Plasma and lymphatic GIP concentrations did not significantly change after DJB in Wistar rats. DJB increased GIP protein content in the midjejunum at the new site of nutrient absorption, but this was surprisingly not countered by a decrease in GIP protein content in the bypassed duodenum. Further studies are needed to determine the mechanisms that account for the discrepancy in GIP production and subsequent secretion after DJB as well as what role GIP plays in the effect of gastrointestinal surgery on glucose homeostasis.

The measurement of the incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), using immunologically based assays is made difficult by the fact that the processing of the precursor molecules gives rise to a number of different peptides which cross-react with antisera raised against the two hormones. For GLP-1, the picture is further complicated because of the necessity to differentiate between the intestinal and pancreatic proglucagon products. Finally, once secreted, both incretins are rapidly degraded by the enzyme dipeptidyl peptidase-4 (DPP-4) to generate metabolites which have lost their insulinotropic activities. These metabolites are the major circulating forms of the incretins, accounting for 60-80% of total immunoreactive GLP-1 and GIP in the peripheral plasma, while concentrations of the intact forms can be very low and, in some cases, barely detectable. The use of highly specific assays using well-characterised antisera and careful sample handling is therefore required for a reliable determination of incretin hormone concentrations.

The distribution and relative frequency of neuroendocrine cells in the small and large intestines of one-humped camel were studied using antisera against 5-hydroxytryptamine (5-HT), cholecystokinin (CCK-8), somatostatin (SOM), peptide tyrosine tyrosine (PYY), gastric inhibitory polypeptide (GIP), neuronal nitric oxide synthase (nNOS), gastrin releasing peptide (GRP), substance P (SP), and neurokinin A (NKA). Among these cell types, CCK-8 immunoreactive (IR) cells were uniformly distributed in the mucosa, while others showed varied distribution in the villi or crypts of the small intestine. Immunoreactive cells like 5HT, CCK-8, and SOM showed peak density in the villi and crypts of the small intestine and in the colonic glands of the large intestine, while cells containing SP were discerned predominately in the crypts. 5-HT, CCK-8 and SOM cells were mainly flask-shaped and of the open-variety, while PYY and SP immunoreactive cells were mainly rounded or basket-shaped and of the closed variety. Basically the distribution pattern of the endocrine cells in the duodenum, jejunum and colon of the one-humped camel is similar to that of other mammals. Finally, the distribution of these bioactive agents may give clues as to how these agents aid in the function of the intestinal tract of this desert animal.

Intestinal metaplasia has been investigated extensively as a possible premalignant condition for stomach cancer but its pathogenesis is still not fully understood. In the present study, we examined the relationship between endocrine and mucous cell marker expression periodically after Helicobacter pylori infection in the Mongolian gerbil model. The numbers of chromogranin A (CgA)-positive, gastrin-positive and gastric inhibitory polypeptide (GIP)-positive cells in H. pylori-infected groups was increased significantly compared with the non-infected case. However, CgA-positive and gastrin-positive cells then decreased from 50 through 100 experimental weeks after H. pylori infection, whereas GIP-positive cells increased. Coexistence of gastrin-positive and GIP-positive cells was detected in the same gastric and intestinal mixed phenotypic glandular-type glands. In conclusion, the endocrine cell phenotype is in line with that of the mucous counterpart in the glands of H. pylori-infected Mongolian gerbil stomach, supporting the concept that development of intestinal metaplasia is due to the abnormal differentiation of a stem cell.

Intestinal metaplasia (IM) in the human stomach has previously been classified into a gastric and intestinal mixed (GI-IM) and a solely intestinal phenotype (I-IM). The phenotypes of mucous and endocrine cells were evaluated in 3034 glandular ducts associated with chronic gastritis. In the pyloric region, the relative expression of gastric endocrine cell markers, such as gastrin and somatostatin, decreased gradually from glandular ducts with only gastric mucous cell phenotype (G type) to GI-IM toward I-IM, while that of the intestinal endocrine cell markers, glicentin, gastric inhibitory polypeptide (GIP), and glucagon-like peptide-1 (GLP-1) was inversely correlated. In the fundic region, gastrin-positive cells emerged in the pseudo-pyloric and GI-IM glands, whereas I-IM glands did not possess any gastrin-positive cells, suggesting the presence of a distinct pathway of intestinalization. Double staining revealed coexistence of gastrin- and GLP-1-positive cells in the same gland and occasionally in the same cell in GI-IM glands. These results suggest that the phenotypes of endocrine cells are in line with those for mucous counterparts and support the concept that all of the different types of mucous and endocrine cells in normal and IM glands might be derived from a single progenitor cell in each gland.

Stereological methods were used to quantify secretin and gastric inhibitory peptide (GIP)-immunoreactivity (GIP-IR) in paraffin sections of the duodenum, jejunum and ileum of fetal and neonatal piglets. In addition, sections were processed for GLP-1-immunohistochemistry. The volume density of the tunica mucosa increased after birth, giving rise to a decreased volume density of the tela submucosa and tunica muscularis. Generally known region-specific morphological distinctions were reflected in differing volume densities of the various layers. The highest volume density of GIP-IR epithelial cells was observed in the jejunum of the neonate. In contrast, the volume density of secretin-IR epithelial cells was highest in the duodenum of both fetal and neonatal piglets. The volume occupied by GIP-IR and secretin-IR epithelial cells increased in the jejunum after birth. Additionally, ileal secretin-IR epithelial cells were more numerous in the neonatal piglet. In conclusion, the quantitative and qualitative presence of GIP-IR and secretin-IR epithelial cells agree with earlier reports of their presence and co-localization between GIP-IR and GLP-1-IR, in the pig small intestine. Furthermore, the differences suggest that age- and region-related functional demands are temporally and probably causally related with the morphological diversification of the intestine and its endocrine cells.

Objective: To evaluate the early effect of Roux-en-Y (RYGB) gastric bypass on hormones involved in body weight regulation and glucose metabolism. SIGNIFICANT BACKGROUND DATA: The RYGB is an effective bariatric procedure for which the mechanism of action has not been elucidated yet. Reports of hormonal changes after RYGB suggest a possible endocrine effect of the operation; however, it is unknown whether these changes are the cause or rather the effect of surgically induced weight loss. We speculated that if the mechanism of action of the RYGB involves an endocrine effect, then hormonal changes should occur early after surgery, prior to substantial body weight changes., Methods: Ten patients with a mean preoperative body mass index (BMI) of 46.2 kg/m (40-53 kg/m) underwent laparoscopic RYGB. Six patients had type 2 diabetes treated by oral hypoglycemic agents. Preoperatively and 3 weeks following surgery, all patients were tested for fasting glucose, insulin, glucagon, insulin-like growth factor 1 (IGF-1), leptin, gastric inhibitory polypeptide (GIP), glucagon-like peptide-1 (GLP-1), cholecystokinin (CCK), adrenocorticotropic hormone (ACTH), corticosterone, and neuropeptide Y (NPY)., Results: Changes in mean BMI were rather minimal (43.2 kg/m; P = not significant), but there was a significant decrease in blood glucose (P = 0.005), insulin (P = 0.02), IGF-1 (P < 0.05), leptin (P = 0.001), and an increase in ACTH levels (P = 0.01). The other hormones were not significantly changed by surgery. All the 6 diabetic patients had normal glucose and insulin levels and did not require medications after surgery. The RYGB reduced GIP levels in diabetic patients (P < 0.01), whereas no changes in GIP levels were found in nondiabetics., Conclusions: Roux-en-Y gastric bypass determines considerable hormonal changes before significant BMI changes take place. These results support the hypothesis of an endocrine effect as the possible mechanism of action of RYGB.

Gastrointestinal peptides, including insulin, glucagon and glucose-dependent insulinotropic polypeptide (GIP) have previously been reported in salivary glands. Recent evidence has suggested they might influence postprandial macronutrient metabolism. This study therefore investigated and compared postprandial hormone concentrations in saliva and plasma to determine whether their secretion was influenced by oral food stimuli. In a within-subject randomised cross-over comparison of hormone concentrations in plasma and saliva following a mixed meal, 12 subjects were given two 1708 kJ mixed meals. On one occasion the meal was chewed and swallowed (swallowed meal), on the other it was chewed and expectorated (sham-fed meal). Salivary and plasma levels of immunoreactive insulin, GIP and glucagon-like peptide-1 (GLP-1), total protein, alpha-amylase, glucose and non-esterified fatty acid were measured before and for 90 min following the meals. Saliva total protein and alpha-amylase rose following both meals, indicating that the stimulus for salivary protein release is related to the presence of food in the mouth. GLP-1 was not detected in saliva. Fasting salivary insulin levels were lower in saliva than plasma (28+/-6 vs 40+/-25 pmol/l respectively). Both increased following the swallowed meal but the rise in saliva was slower and less marked than in plasma (peak levels 96+/-18 and 270+/-66 pmol/l for saliva and plasma respectively, P<0.01). Both were unchanged following the sham-fed meal. GIP was detected in saliva. Fasting GIP levels were significantly higher in saliva than plasma (183+/-23 compared with 20+/-7 pmol/l, P<0.01). They decreased in saliva following both swallowed and sham-fed meals to nadirs of 117+/-17 and 71+/-12 pmol/l respectively, but rose following the swallowed meal to peak levels of 268+/-66 pmol/l. These findings are consistent with insulin in saliva being an ultrafiltrate of that circulating in blood, but GIP in saliva being the product of local salivary gland synthesis, whose secretion is influenced, directly or indirectly, by oral stimuli. The function of salivary GIP is unknown, but we speculate that it may play a role in the regulation of gastric acid secretion in the fasting state.

Gastric inhibitory polypeptide (GIP) is produced within endocrine cells of the small intestine and released into the circulation upon nutrient ingestion. This study has quantified the levels of this insulinotropic peptide in the intestines of lean and diabetic obese ob/ob mice and estimated the proportion that is glycated. The total intestinal GIP concentration and content of the diabetic mice were significantly greater (p < 0.01) than that of control animals. Affinity chromatographic separation and side-viewing GIP radioimmunoassay demonstrated that approx 20% of the GIP extracted from intestines of ob/ob mice was present in glycated form. Less than 2% of intestinal GIP was glycated in lean mice. In conclusion substantial quantities of glycated GIP exist within the intestines of diabetic ob/ob mice, suggesting that this may be a contributing factor to the physiological disarray of this syndrome.

To establish indirect in-situ PCR for the detection of intestinal peptide hormones, rat intestine and a murine intestinal tumor cell line, STC 1, were used. The results exhibited intensive staining of GIP-producing K-cells. Paraformaldehyde-fixed cryostat sections yielded the best results in signal to background ratio with RT-PCR in-situ hybridization. Moreover, it was possible to elevate the positive staining signal and to reduce background staining. Digoxigenin-labeled in-situ hybridization served as a control for specificity and sensitivity of GIP (glucose-dependent insulinotropic peptide) mRNA expression on cryostat as well as paraffin sections. In conclusion, this RT-PCR in-situ hybridization protocol proves to be a specific, sensitive and reliable non-radioactive technique for the detection of intestinal peptide hormone mRNA, especially in tissues or tumor cells where the application of ISH is limited.

The regional distribution and relative frequency of endocrine cells in the gastrointestinal tract of the camel, Camelus bactrianus, were investigated using immunohistochemical methods. Ten types of immunoreactive (IR) endocrine cells were identified in this study. Among these cell types, only serotonin- and somatostatin-IR cells were detected in almost all regions of the gastrointestinal tract. Most of the cell types showed peak density in the pyloric gland region. The others showed restricted distribution: gastrin, cholecystokinin (CCK), motilin, bovine pancreatic polypeptide (BPP), and (gastric) substance P in the stomach; gastrin, CCK, BPP, gastric inhibitory polypeptide (GIP), glucagon, peptide tyrosine tyrosine (PYY) and substance P in the small intestine; and CCK, motilin, BPP, and PYY in the large intestine. Fundamentally the distribution pattern of endocrine cells in the gastrointestinal tract of the camel is similar to that of cattle. The distribution and frequency of endocrine cells in the glandular sac region are the same as those of the cardiac gland.

The endocrine cells in the duodenum of pre-diabetic and diabetic female non-obese diabetic (NOD) mice aged 22-24 weeks were studied by means of immunohistochemistry and computed image analysis as well as by radioimmunoassays of tissue extracts. As controls, 12 female BALB/cJ mice of the same age as NOD mice were used. The number of secretin-immunoreactive cells increased in diabetic but not in pre-diabetic NOD mice. The level of extractable secretin was higher in both pre-diabetic and diabetic NOD mice. The number of GIP-, CCK/gastrin-, and serotonin-immunoreactive cells was significantly reduced in both pre-diabetic and diabetic NOD mice. There was no statistical difference in the number of somatostatin-immunoreactive cells between the NOD mice and controls. The level of GIP was higher and gastrin was lower in NOD mice compared to controls. There was no statistical difference in the somatostatin level between the NOD mice and controls. The cell secretory index was elevated in all the endocrine cell types except CCK/gastrin cells. It has been suggested that some of the changes in the duodenal endocrine cells could be attributed to the diabetes state, but most of the changes seem to take place before the onset of diabetes. The abnormalities in the duodenal endocrine cells observed here in an animal model for diabetes type I might have relevance for the gastrointestinal dysfunction displayed in human diabetes.

Several gastrointestinal hormones appear to play an important developmental role in the newborn, particularly in preterm neonates. Although the cells producing these peptides develop towards the end of the first trimester, fetal secretion of these regulatory peptides has not hitherto been demonstrated. Using samples collected by fetoscopy at 19-21 weeks of gestation we have measured concentrations of several gastrointestinal and pancreatic hormones. Maternal venous and amniotic fluid hormone concentrations were measured simultaneously. Concentrations of the pancreatic hormones, insulin, glucagon and pancreatic polypeptide (PP) were similar in fetal and maternal blood. Gastrin and motilin were present in the fetal circulation but at about 30% (p < 0.05) and 60% (p < 0.01) of the maternal levels, respectively. In contrast, enteroglucagon concentrations were more than twofold higher in the fetal circulation compared with maternal levels (p < 0.05). Concentrations of gastric inhibitory polypeptide (GIP) in fetal blood were higher than levels in maternal blood but not significantly. Concentrations of GIP (p < 0.001) were higher in the amniotic fluid than the fetal circulation. Gastrin and glucagon levels were similar in amniotic fluid and fetal blood. In contrast, PP and motilin were present in amniotic fluid, but at lower concentrations than in fetal blood. Enteroglucagon was not detectable in amniotic fluid. In conclusion, several alimentary hormones are secreted in the fetus at midterm. Since these peptides have trophic, secretory and motor effects on the gut, it is likely that these regulatory peptides are involved in the functional development of the fetal intestine.

Glucose-dependent insulinotropic peptide (GIP) enhances insulin secretion by pancreatic beta-islet cells. Its release has been demonstrated predominantly after the ingestion of carbohydrate and fat. We have recently cloned a rat intestinal GIP cDNA and in the present studies have used this cDNA as a probe for measuring rat duodenal GIP mRNA after nutrient administration. Rats were fasted overnight, after which they were permitted to drink water or 10% glucose. The duodenum was then removed, GIP mRNA was measured by Northern hybridization analysis, and duodenal mucosa and serum GIP levels were determined by radioimmunoassay. In response to oral 10% glucose, duodenal mucosal GIP mRNA concentrations increased from 2 to 4 h, and at the end of 4 h a threefold increase was detected. Serum and mucosal GIP concentrations increased earlier, starting at 60 min, and levels remained elevated at 4 h. In separate studies, nuclear run-on assays were performed to compare the effects of glucose and water ingestion on transcription of the GIP gene. Whereas no increase in GIP gene transcription was detected in rats ingesting water, the rate of transcription doubled in glucose-fed rats. Actin gene transcription was nearly identical in both groups, indicating genomic specificity. The results of these studies indicate that duodenal GIP gene expression is stimulated at both the pre- and posttranslational levels by glucose-containing meals. These studies further suggest that the release of GIP from cellular storage granules might account for the initial increase in serum GIP levels after oral glucose ingestion.

The aim of the experiment was to test the theory that accustoming pigs to a high-fat diet causes exaggerated gastric inhibitory polypeptide (GIP) secretion in response to a high-fat meal, and to determine whether hypersecretion of GIP could be related to an increase in the GIP content of the small intestine. Twenty-four pigs were fed one of three dietary regimens for 11 weeks: a high-carbohydrate diet (CL), or a high-fat diet (FL), both fed at 1.46 MJ gross energy (GE)/kg live weight0.75 per d, or a high-fat diet (FH) fed at 2.10 MJ GE/kg live weight0.75 per d. At the end of the period two acute tests were performed. For acute test 1 the accustomed meal (diets CL, FL and FH) and for acute test 2 a standard high-fat meal (diet FL) were given; blood samples were taken during the next 5 h and analysed for GIP, insulin and glucose. Integrated increases in hormone and glucose levels were compared by analysis of variance (0-300 min). In acute test 1 there were significantly different plasma GIP concentrations between groups (CL greater than FH greater than FL; P less than 0.05). Plasma insulin concentrations were significantly higher in group CL compared with groups FL and FH (P less than 0.002). There were no differences in glucose levels. In acute test 2 integrated increases in plasma GIP (0-300 min) concentrations were not significantly different; however, GIP (0-45 min) concentrations were significantly higher in group FH than in groups CL and FL (P less than 0.05). There were no differences in plasma insulin concentrations. Plasma glucose (0-300 min) concentrations were significantly higher in groups FL and FH compared with group CL (P less than 0.05). The GIP content of tissue samples taken at the end of the experiment from the duodenum, jejunum, upper and lower ileum decreased significantly in a proximal to distal direction (P less than 0.001). Diet FH significantly increased the average GIP content of the small intestine compared with diets CL and FL (P less than 0.05). It is concluded that fat meal-stimulated GIP secretion was enhanced by increased feeding level during a pre-treatment phase, possibly due to an increase in GIP synthesis in the small intestine. The high-fat diet caused glucose intolerance after a high-fat meal. This may be due in part to the action of dietary fat on glucose transport and metabolism.

There is a marked difference in insulin secretion between the ob+/ob+ obese mouse and its non-obese littermate. Numerous peptides have been implicated in the modification of postprandial insulin secretion. In this study, the morphological and immunohistochemical studies of the genetically obese mouse (ob+/ob+) pancreata were compared with control littermates. Additionally, the distribution of gastric inhibitory polypeptide, somatostatin, glucagon, and insulin immunoreactive cells was also quantitated. Hyperglycemia and hyperinsulinemia were verified in the obese mice. The control animals had some islets and ductules with mononuclear infiltrations of a possible immune character. The obese individuals had a marked increase in both number and size of the islets of Langerhans compared with lean controls. The insulin immunocytochemical reaction in the obese pancreatic beta-cells was weaker than that of controls, as was the aldehyde-fuchsin reaction. The glucagon, gastric inhibitory polypeptide, and somatostatin containing cells were intermingled with the beta-cells. In contrast, the control animals showed a peripheral localization of these cell types. The morphometric analysis of the obese pancreas showed a decreased proportion of non-beta cells within the islets but not in total pancreatic volume in comparison with controls. The obese mouse also had cavities filled with eosin-stained material among numerous beta-cells. No complete epithelial lining distinguished these formations from the surrounding islet cells. The content of the cavities was not stained by any of the immunocytochemical reactions applied. In conclusion, the pancreatic islets of the ob+/ob+ mouse show marked differences in both morphological and immunocytochemical characteristics if compared with control littermates. These differences in architecture may be related to the eventual development of diabetes mellitus in the ob+/ob+ mouse.

Concentrations of gastrointestinal neuropeptides in serial human milk samples from 28 women were determined over the first 6 postpartum mo. All gut neuropeptides were present during the first postpartum week. Gastric inhibitory peptide (GIP) concentration remained constant but the others decreased by 6 wk. Bombesin concentration in breast milk was threefold greater than concurrent plasma concentration (p less than 0.001); all other neuropeptides were at the same or lower concentrations in milk than in plasma. At 36 wk gestation plasma concentrations of GIP were lower and concentrations of vasoactive intestinal peptide were higher than concentrations in age-matched control subjects. Concentrations of gastrin and cholecystokinin, bombesin, peptide histidine methionine, peptide YY, and neurotensin in plasma were similar in pregnant and nonpregnant women. These gut neuropeptides in milk may be important for growth and maturation of the gastrointestinal system in neonates. Bombesin may contribute to neonatal hypergastrinemia.

The Mastomys (Praomys natalensis) species are a unique natural model in which the bioactivity of gastric carcinoids may be studied. Several investigators have previously demonstrated that these tumors contain large amounts of histamine. In this study we investigated the presence of peptides associated with the neoplasm. The levels and location of gastrin, gastric inhibitory peptide (GIP), neurotensin, peptide YY (PYY), pancreatic polypeptide (PP), glucagon, bombesin, vasoactive intestinal peptide (VIP) and somatostatin (SRIF) were investigated by radioimmunoassay and immunocytochemistry. In addition the distribution of these peptides were evaluated in the gastrointestinal tract of young and old animals to investigate possible age-related changes. PYY and enteroglucagon (EG) were significantly (P less than 0.001) elevated in both tumor tissue (676 +/- 152, 551 +/- 164 pmol/g) and plasma (620 +/- 160, 500 +/- 147 pmol/l) of tumor-bearing animals. Immunocytochemistry revealed PYY- and EG-like immunoreactivity in 20-30% of tumor cells. A significant decrease (P less than 0.05) in bombesin was noted in older animals, but no changes in gastric tissue content of PYY or EG could be detected between young and old animals. Gastrin was not detected in tumors and there were no significant changes in tissue or plasma levels with age. Small bowel concentrations of VIP and PYY were higher in the older mastomys (P less than 0.05). In contrast, colonic levels of bombesin, VIP, somatostatin and PYY were significantly lower (P less than 0.05) in older mastomys compared with young. The age-related changes in several peptides may reflect an adaptive response to acid hypersecretion. The multi-hormonal character of these neoplasms suggests that these tumors develop from a pluripotential stem cell.

Methanol extracted skins from 84 species of amphibia were screened, measuring by RIAs: gastrin-CCK, VIP, calcitonin, GIP, PP and motilin. G-CCK-like immunoreactivity was found in 97.6%; VIP-like immunoreactivity in 41%; CT-like immunoreactivity in 34%; GIP-like immunoreactivity in 10%; PP-like immunoreactivity in 40% and MT-like immunoreactivity in 60% of the samples. The use of a sequence-specific radioimmunoassay and of gel-chromatography confirmed the caerulein-CCK-8-like nature of the immunoreactive material. Detected amounts of the other peptides (VIP, CT, GIP, PP, MT) were too low for bioassay or chromatographic studies, thus leaving the question open if they are due to some kind of unspecific interferences or, most likely, to species-specificity differences of the used antisera.

Existing methods for the histochemical demonstration of gastrointestinal cells are somewhat limited. Chromogranin represents a family of proteins that coexist with catecholamines in the secretory vesicles of adrenal medulla cells. In the present study, immunocytochemistry was used to test whether chromogranin is a marker for gut endocrine cells. Serial sections of each area of human gut were immunostained for chromogranin and for the amine and each of the peptides known to be present in mucosal endocrine cells. Chromogranin was immunostained in large numbers of endocrine cells in all tissues examined. All identified endocrine cell types were found, in serial sections or by sequential silver impregnations, to be chromogranin immunoreactive. However, the possibility exists that some chromogranin-immunoreactive cells contain a yet to be discovered endocrine substance. Immunostaining of chromogranin thus appears to provide a means for demonstrating all gastrointestinal mucosal endocrine cells identifiable by the methods described in this study.

The polypeptide hormone GIP has been localized ultrastructurally by using specific, monoclonal GIP antibodies and an immunogold technique on aldehyde-osmium fixed specimens of dog duodenal mucosa. A single type of cell showing round, homogeneous, fairly osmiophilic granules with closely applied membrane and a mean size of 188 nm +/- 34 SD has been identified as the GIP cell.

The distribution of the postulated glucagon precursor, glicentin, as well as of the gastrointestinal hormone GIP (gastric inhibitory polypeptide), has been studied by immunocytochemistry and radioimmunoassay. Our results show that GIP antisera may contain a population of antibodies recognizing an immunoreactant common to glicentin and GIP. The occurrence of such common immunoreactants makes immunological distinction between the two hormones difficult and may explain previous results indicating that GIP is stored by glucagon cells. The present results indicate that GIP is produced by endocrine cells of the duodenum and jejunem and is absent from the pancreas, stomach, and large intestine. Glicentin-like immunoreactivity is displayed by A cells of the pancreas and by oxyntic A cells of the stomach, as well as by numerous glucagon-like immunoreactant (GLI) cells of the ileum and colon. Use of glucagon ad glicentin antisera of differing specificities indicates that the processing of this putative prohormone differs between A cells and GLI cells. Studies on the ontogeny of pancreatic A cells also reveal differences in the reactivity pattern of glicentin-like immunoreactivity between fetal and adult rats. Ultraimmunocytochemical studies show that glicentin-like immunoreactivity is mainly, stored in the cytoplasmic granules of pancreatic A cells.

The localization and distribution of regulatory peptides was studied in separated epithelium, lamina propria, submucosa, and external muscular layer from 16 specimens of human bowel. Immunoreactive enteroglucagon, gastric inhibitory polypeptide, and neurotensin were almost confined to the epithelial fraction (97.5 +/- 2.2%, 97.5 +/- 4.2%, and 99.3 +/- 1.1% of their respective total content, mean +/- SEM) and were only localized in endocrine cells. Vasoactive intestinal polypeptide-, substance P-, and bombesinlike peptides were virtually restricted to the nonepithelial layers (99.6 +/- 0.2%, 99.6 +/- 0.2%, and 100%) and were demonstrated exclusively in nerves. A particularly rich vasoactive intestinal polypeptide- and substance P-immunoreactive nerve supply was seen in the nonepithelial mucosa, which contained the highest concentrations of these peptides, while bombesin was mainly recovered from the external muscle (87.7 +/- 2.7%). Somatostatin, measured with an antiserum highly specific for somatostatin-14, was found throughout the wall, mainly in the epithelium (39.9 +/- 5.2%) and lamina propria (29.5 +/- 5.9%), but could be immunostained only in endocrine cells.

Clinical applications of analyses of hormones in amniotic fluid (AF) have recently been increased. In diabetic pregnancy, determinations of insulin and C-peptide in AF have been suggested as good indicators of the status of the foetus. We have investigated the pancreatic alpha and beta cell function by measuring insulin (IRI), C-peptide (CPR), glucagon (IRG), somatostatin (SLI), and gastric inhibitory polypeptide (GIP) in amniotic fluid collected during basal conditions or 2 h after an arginine test in 92 diabetic and 32 non-diabetic pregnant women. During basal conditions, in diabetic pregnant women, IRI, CPR and the insulin: glucagon molar ratio (I/G) were all significantly higher while amniotic fluid-IRG was significantly lower than in the controls. After arginine stimulation, IRI increased in AF of the diabetic pregnant women but not in AF of the controls while no differences were observed in AF-GIP and AF-SLI concentrations. Higher IRI and CPR, as well as lower IRG values were significantly related to poor maternal metabolic control. The occurrence of neonatal morbidity including macrosomia was significantly associated with increased AF, IRI and CPR concentrations after an arginine challenge and these factors were the most sensitive predictors of neonatal morbidity in infants of diabetic mothers. Increased AF glucose concentrations and I/G ratios were related to neonatal hypoglycaemia; jaundice and respiratory distress syndrome were associated to low concentrations of SF-IRG.

Reliable and specific radioimmunoassays have been developed for the gut hormones secretin, gastrin, cholecystokinin, pancreatic glucagon, VIP, GIP, motilin, and enteroglucagon. Using these assays, the relative pattern of distribution of the gut hormones has been determined using the same bowel extracts for all measurements. VIP occurred in high concentration in all regions of the bowel, whereas secretin, GIP, motilin, and CCK were predominantly localised in the proximal small intestine. Pancreatic glucagon was almost exclusively confined to the pancreas. Like VIP, enteroglucagon also exhibited a wide pattern of distribution but was maximal in the ileum. The acid ethanol extraction method that was used was found to be unsuitable for gastrin. On gel chromatography of the extracts, motilin and VIP eluted as single molecular species in identical position to the pure porcine peptides. CCK, pancreatic glucagon, enteroglucagon and GIP were all multiform.

A systematic approach is outlined for the preparation of a whole series of immunoreactive 125I-labeled gastrointestinal regulatory peptides with high specific radioactivities. In our hands, the theoretically superior Iodo-gen method has no more to offer than the harsher chloramine-T method in the iodination of secretin, vasoactive intestinal polypeptide, gastric inhibitory polypeptide, and motilin; whereas the gentler Iodo-gen method has to be used to obtain fully immunoreactive cholecystokinin39 (CCK39) and Tyr1-somatostatin tracers. By applying the iodination mixtures on a Sephadex G-15 or a Sephadex G-10 column followed by an SP Sephadex C-25 column--being eluted under so-called 'finite adsorption equilibrium' between the peptides to be purified and the adsorbent--highly purified tracers are obtained with unusually high specific radioactivities. Stored at -20 degrees C in diluted aliquots of from 200 to 500 microliter, these tracers can be used for radioimmunoassay purposes without rechromatography for at least 60 days.

Duodenal juice was collected before and after an intragastric infusion of 300 ml 25% glucose in five healthy subjects. After extraction with 95% ethanol, IR-GIP in duodenal juice was determined by radioimmunoassay and found to increase from mean basal level of 63 pmol/l to a mean peak of 354 pmol/l after the glucose infusion. The elution diagrams of IR-GIP in glucose-stimulated duodenal juice and the corresponding plasma from a 16 X 400 mm Sephadex G-50 Fine column were similar, and the radioimmunoassay dilution curves of porcine GIP and duodenal juice IR-GIP were superimposable.

The occurrence of gastrin and gastric inhibitory polypeptide (GIP) was investigated immunocytochemically in 17 foetal and neonatal human pancreata of gestational ages ranging from 12-41 weeks. GIP immunoreactive cells were observed in the pancreas of five foetuses with gestational ages of 18-20 weeks. These cells were located in islet-like cell clusters, at the base of tubular structures and among the exocrine-like acini. They were sometimes seen to emit a single long protrusion. The controls used, including preincubation of the antisera with anticomplement Clq, emphasized the specificity of the observed immunoreaction. No gastrin-immunoreactive cells were seen in any of the foetal or neonatal pancreata examined.

Several studies report that placenta and amniotic fluid (AF) may be a source of many peptide hormones. Although the presence of gastric inhibitory polypeptide (GIP) in amniotic fluid has not been described, it is present in the fetal gut. In this study we report the presence of insulin and GIP in human AF of normal and diabetic pregnancies. GIP concentrations in the AF collected two hours after an arginine tolerance test (ATT), at 34-36 weeks of gestation, were evaluated in 8 normal and 53 diabetic pregnant women. GIP was found in all samples of AF. The mean AF-GIP concentrations were 133 +/- 19 pmol/l in controls and 111 +/- 6 pmol/l in the diabetics, being the GIP values of the diabetics belonging to White Class B significantly lower than those of normals (99 +/- 10 vs 133 +/- 19 pmol/l). The GIP/IRI molar ratio was significantly lower in the diabetics than in controls (1.2 +/- 0.2 vs 2.5 +/- 0.4); moreover the GIP/IRI molar ratio was significantly higher in AF collected from diabetic pregnant women who delivered overweight infants than in AF of normal weight infants or controls. This finding would suggest a negative feedback mechanism between GIP and insulin in fetus.

In this study we have investigated the mucin profile and the endocrine cell population in gastric endoscopic biopsies from 22 patients affected by chronic gastritis and intestinal metaplasia and in five surgical specimens of stomachs removed because of intestinal-type carcinoma (4) or peptic ulcer (1). High iron diamine-Alcian blue (HID-Ab) staining and peptide immunocytochemistry (peroxidase anti-peroxidase technique) were used. Forty-one foci of intestinal metaplasia were detected, 15 produced sulphomucins and 26 sialomucins. Of the endocrine cells investigated, gastrin and somatostatin cells were the most frequently observed, while cholecystokinin, glucose-dependent insulinotropic peptide-, secretin- and enteroglucagon-containing cells were also found in the metaplastic areas, but less frequently. No significant correlation was found between the type of mucin and the types of endocrine cells present, the latter usually resembling those normally found in the small intestine. On the basis of these results we conclude that intestinal metaplasia involves mucin- and peptide-producing cells of the stomach in a variable manner, with no correlation between the two.

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.

The effect of total parenteral nutrition (TPN) in rats on a number of enteroendocrine cells was investigated. The rats were given a continuous intravenous infusion of basal TPN solution for 7 days. Samples from duodenum, jejunum and ileum were collected, immunostained and the immunoreactive cells quantified using a computerised morphometrics system. The endocrine cells containing somatostatin, cholecystokinin (CCK), gastric inhibitory polypeptide (GIP), neurotensin and enteroglucagon were investigated. The results demonstrated a significant reduction in the number of CCK cells in the duodenum and jejunum. In the ileum the neurotensin-immunoreactive cells were significantly increased in number (P less than 0.02). No change was seen in the number of cells immunostained for somatostatin, GIP or enteroglucagon. These data indicate that short term TPN has a definite effect on the enteroendocrine cell population which may be linked to the side effects of TPN seen in man.

Gastric inhibitory polypeptide (GIP) is a 42-amino-acid hormone which may have a role in the regulation of insulin secretion. The characterization of cDNA clones encoding this hormone indicates that it is derived by proteolytic processing of a 153-amino-acid precursor. The human gene coding for the human GIP precursor spans approximately 10 kilobase pairs and consists of six exons. Similar to genes encoding other members of the glucagon superfamily, each exon appears to encode a distinct region of the GIP precursor or its mRNA. The promoter region of the human GIP gene contains potential binding sites for a number of transcriptional factors including Sp 1, AP-1, and AP-2. The human GIP gene has been assigned to chromosome 17q21.3----q22.