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Diabetic gastroparesis.

Our understanding of gastric motility disorder--diabetic gastroparesis has advanced in the last ten to fifteen years, but the published data regarding pathogenesis are confusing and show conflicting results. The pathogenesis is sometimes linked with hyperglycemia, autonomic neuropathy, gastrointestinal hormone or myogenic mechanism. Antral hypomotility is often associated with hyperglycemia which is often accompanied by reduction in duodenal waves. Varying level of motilin, a gastrokinetic hormone has been reported. However none of the mechanism could explain the exact pathogenesis. The relationship of this mortality disorder with clinical symptoms is not always established, however nausea and vomiting lasting for days or weeks are the prominent symptoms. Other symptoms are post-prandial fullness, early satiety, bloating, belching, and vague abdominal discomfort. In a few cases, it may be the cause of poor nutrition, uncontrolled diabetes and recurrent ketoacidosis. Last one or two decades have seen some advancement in the investigational procedures like scintigraphy, radio-opaque markers, breath test, electrogastrography and MRI. Which can lead to a proper diagnosis. Such objective assessment is all the more important as nearly half of the patients do not have any symptom. Symptomatic improvement of gastroparetic patients should be the aim and in asymptomatic patients, treatment is often not recommended. Some dietary advice and prokinetic agents like metoclopramide, cisapride etc. are often prescribed but much needs to be further known as management is not always uniformly rewarding.

Diabetes Complications↗

Orocecal transit during mild exercise in women.

Little is known of the influence of exercise on movement of ingested food through the alimentary tract or of the association of several gastrointestinal hormones with transit rate in exercise. In this study, orocecal transit during mild exercise was measured in 21 women by detecting a rise in expired H2 after ingestion of 20 g lactulose in a 350-ml (360 kcal) liquid meal. Motilin, gastrin, and cortisol were measured in peripheral venous blood when, as evidenced by a breath H2 rise, the first portion of the meal arrived at the cecum. Comparison was made between seated rest and a treadmill walk at 5.6 km/h up a 2% grade. The walk predictably elevated heart rate, O2 uptake, and rectal temperature and also reduced transit time from 98 min at rest to 75 min during exercise (P less than 0.001). Faster transit in exercise was associated with a significant rise in cortisol, while gastrin and motilin levels were both unchanged. In conclusion, in women mild concurrent exercise accelerates orocecal transit rate of at least the first portion of nonabsorbable carbohydrate in a liquid meal. Although the mechanism for the effect remains unknown, it may be secondary to some aspect of the stress response to physical activity.

Adult↗

Antroduodenal motility in chronic pancreatitis: are abnormalities related to exocrine insufficiency?

In patients with chronic pancreatitis (CP) the relation among exocrine pancreatic secretion, gastrointestinal hormone release, and motility is disturbed. We studied digestive and interdigestive antroduodenal motility and postprandial gut hormone release in 26 patients with CP. Fifteen of these patients had pancreatic insufficiency (PI) established by urinary para-aminobenzoic acid test and fecal fat excretion. Antroduodenal motility was recorded after ingestion of a mixed liquid meal. The effect of pancreatic enzyme supplementation was studied in 8 of the 15 CP patients with PI. The duration of the postprandial antroduodenal motor pattern was significantly (P < 0.01) prolonged in CP patients (324 +/- 20 min) compared with controls (215 +/- 19 min). Antral motility indexes in the first hour after meal ingestion were significantly reduced in CP patients. The interdigestive migrating motor complex cycle length was significantly (P < 0.01) shorter in CP patients (90 +/- 8 min) compared with controls (129 +/- 8 min). These abnormalities were more pronounced in CP patients with exocrine PI. After supplementation of pancreatic enzymes, these alterations in motility reverted toward normal. Digestive and interdigestive antroduodenal motility are abnormal in patients with CP but significantly different from controls only in those with exocrine PI. These abnormalities in antroduodenal motility in CP are related to maldigestion.

Adult↗

Response to exogenous cholecystokinin of six human gastrointestinal cancers xenografted in nude mice.

Gastrointestinal hormones regulate growth of cancers as well as normal tissues. We investigated whether long-term cholecystokinin (CCK) administration might affect growth or metabolism of human tumors xenografted in nude mice. In each experiment, approximately 20 nude mice bearing subcutaneous xenografts of the particular cancer line being studied were used. Half received CCK and half received saline solution intraperitoneally twice daily for 14 days. Tumor volume and body weight were measured every 3 days. If the tumors produced marker substances, these were measured in nude mouse serum and also in the xenografts. Tumor growth was significantly retarded by CCK in two of the six cancers studied. In each case, DNA, RNA, and protein reflected tumor volumes. In one of these tumors (SLU 077), serum carcinoembryonic antigen (CEA) levels paralleled the tumor volumes. In another tumor (SLU 132), serum CEA levels and tumor immunolabeling for CEA and pancreatic oncofetal antigen increased in response to CCK administration, whereas tumor volumes did not. These findings suggest that exogenous highdose CCK altered the growth and metabolism in two of six human cancers studied.

Animals↗

Effects of psychological stress on small intestinal motility and expression of cholecystokinin and vasoactive intestinal polypeptide in plasma and small intestine in mice.

AIM: To investigate the effects of psychological stress on small intestinal motility and expression of cholecystokinin (CCK) and vasoactive intestinal polypeptide (VIP) in plasma and small intestine, and to explore the relationship between small intestinal motor disorders and gastrointestinal hormones under psychological stress. METHODS: Thirty-six mice were randomly divided into psychological stress group and control group. A mouse model with psychological stress was established by housing the mice with a hungry cat in separate layers of a two-layer cage. A semi-solid colored marker (carbon-ink) was used for monitoring small intestinal transit. CCK and VIP levels in plasma and small intestine in mice were measured by radioimmunoassay (RIA). RESULTS: Small intestinal transit was inhibited (52.18+/-19.15% vs 70.19+/-17.79%, P<0.01) in mice after psychological stress, compared to the controls. Small intestinal CCK levels in psychological stress mice were significantly lower than those in the control group (0.75+/-0.53 microg/g vs 1.98+/-1.17 microg/g, P<0.01), whereas plasma CCK concentrations were not different between the groups. VIP levels in small intestine were significantly higher in psychological stress mice than those in the control group (8.45+/-1.09 microg/g vs 7.03+/-2.36 microg/g, P<0.01), while there was no significant difference in plasma VIP levels between the two groups. CONCLUSION: Psychological stress inhibits the small intestinal transit, probably by down-regulating CCK and up-regulating VIP expression in small intestine.

Animals↗

GLP-1/GIP chimeric peptides define the structural requirements for specific ligand-receptor interaction of GLP-1.

The gastrointestinal hormones glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) strongly stimulate insulin release. Despite their high N-terminal sequence similarity, GLP-1 does not bind to the GIP receptor and vice versa. To characterize the domains required for interaction of the peptide ligands with their specific receptors, we performed displacement studies with various synthetic GLP-1/GIP hybrid peptides on RINm5F insulinoma cells. Displacement of 125I-GIP and 125I-GLP-1 was measured using GLP-1/GIP chimeras which comprised GIP and GLP-1 sequences at different positions. The binding affinity to the GLP-1 receptor was found to be sensitive to GIP-like exchanges in the N-terminal 22 amino acids as well as in positions 13 and 15 (loss of affinity 280-fold to more than 1000-fold). C-terminal substitution of the GLP-1 sequence by GIP diminished the affinity towards the GLP-1 receptor only 20-fold. All hybrid peptides investigated showed minimal binding affinity for the GIP receptor, indicating that the entire GIP-sequence (1-31) is important for receptor recognition. These findings provide insight into the structural requirements for the specific interaction of two important insulinotropic peptides with their specific receptors.

Amino Acid Sequence↗

Erythromycin improves glycaemic control in patients with Type II diabetes mellitus.

AIMS/HYPOTHESIS: Erythromycin mimics the effect of the gastrointestinal hormone motilin by binding to its receptor and acting as a motilin agonist. We recently found that motilin stimulates insulin secretion at lower doses than doses required to stimulate gastric contractile activity. We studied the effects of erythromycin on insulin secretion and glycaemic control in patients with diabetes mellitus. METHODS: Inpatients (n = 34) with Type II (non-insulin-dependent) diabetes mellitus were randomly assigned to receive either erythromycin (400 mg orally three times a day, n = 19) or a placebo (n = 15) for 1 week (first study). Another 34 outpatients with Type II diabetes were also treated with erythromycin (200 mg orally three times a day, n = 17) or a placebo (n = 17) for 4 weeks (second study). Finally, nine inpatients with Type II diabetes and eight normal control subjects received intravenous erythromycin (10 mg x kg(-1) x h(-1)) or saline infusion and insulin secretion was examined (third study). RESULTS: Erythromycin lowered fasting blood glucose and fructosamine concentrations (p < 0.01) and increased basal as well as glucose-stimulated insulin secretion (p <0.05-0.01) (first study). Low doses of erythromycin treatment for 4 weeks also significantly improved glycaemic control in Type II diabetic patients (second study). Erythromycin infusion significantly increased plasma insulin and decreased glucose concentrations in Type II diabetic and control subjects and greatly potentiated glucose-induced insulin secretion in the latter (third study). CONCLUSION/INTERPRETATION: These results indicate that erythromycin given orally has an antidiabetogenic effect and therefore erythromycin derivatives that lack the antibacterial activity could have a therapeutic value in Type II diabetic patients.

Blood Glucose↗

Direct inhibitory effect of erythromycin on the gallbladder muscle.

Erythromycin, a macrolide antibiotic, stimulates motor activity in various parts of the gastrointestinal tract in humans and animals. This effect of erythromycin resembles that of motilin, a gastrointestinal hormone, in evoking contractions similar to phase 3 activity of the migrating motor complex. Motilin induces contractions in the canine gallbladder but fails to evoke any response, either in vivo or in vitro, in the human gallbladder. Surprisingly, erythromycin stimulates human gallbladder emptying in healthy volunteers and in persons with diabetic autonomic neuropathy. In the present study we examined the effect of erythromycin on chemically and electrically evoked contractions of isolated gallbladders from guinea pigs and humans by use of isometric force measurements. Carbachol, a muscarinic cholinergic agonist, evoked gallbladder contractions that were diminished by erythromycin in a concentration-dependent manner: at 200 micromol/L the contractions were 86% +/- 20% of the control response, at 500 micromol/L they were 63% +/- 21% of control, and at 1000 micromol/L they were 41% +/- 20% of control (P <0.05, N = 10, mean +/- standard deviation). Electrically evoked gallbladder contractions were reduced to 68% +/- 18% of the control response with the addition of 500 micromol/L of erythromycin and to 56% +/- 19% of control after the addition of 1000 micromol/L (P <0.05, N = 8). Guinea pig but not human gallbladders contracted after stimulation with the alpha-adrenergic agonist phenylephrine. Erythromycin reduced these contractions in a concentration-dependent manner but had no effect on gallbladder contractions induced by bradykinin. In human gallbladder strips, erythromycin at 500 micromol/L reduced the contractile response to electrical stimulation to 71% +/- 16% of the control value (N = 10 [5 patients], P <0.01) and the carbachol-evoked contractions to 53% +/- 24% (P <0.01, N = 32). The inhibitory effect of erythromycin persisted in the presence of the nerve blocker tetrodotoxin at 1 micromol/L. It is concluded that erythromycin has a direct inhibitory effect on guinea pig and human gallbladder contractions.

Adrenergic alpha-Agonists↗

Serum calcium responses to exogenous secretin.

Increasing attention is being focused on the relationship between gastrointestinal hormones and calcium metabolism. While it is apparent that some relationship does exist, the exact nature and significance is as yet undefined. Information regarding the effect of secretin on serum calcium has been both sparse and contradictory. Boot's secretin, 3 units/kg, was given to a group of 44 patients consisting of normal controls and patients with duodenal, gastric, and marginal ulcers; primary hyperparathyroidism; and pernicious anemia. Six serial serum specimens were obtained from each patient at ten-minute intervals for calcium determination by atomic absorption spectrophotometry. Using two-way analysis of variance, no significant changes in postsecretin serum calcium values were observed. It is unlikely that physiologic levels of secretin exert any effect on serum calcium.

Anemia, Pernicious↗

Delayed gastric emptying occurs following acarbose administration and is a further mechanism for its anti-hyperglycaemic effect.

The therapeutic effect of acarbose is generally attributed to inhibition of amylase and brush border glucosidases and consequent impaired digestion and absorption of carbohydrates. We have investigated the possibility that acarbose may also influence the rate of gastric emptying by comparing plasma glucose and gastrointestinal hormone responses to an oral sucrose load with and without acarbose in 11 healthy subjects. Gastric emptying was assessed indirectly by measuring circulating paracetamol concentrations following administration of paracetamol along with the sucrose load. Peak plasma glucose, insulin, and glucose-dependent insulinotropic polypeptide (GIP) responses were reduced when sucrose was given with acarbose. There was a significant reduction in post-sucrose paracetamol levels with acarbose suggestive of a significant delay in gastric emptying. The failure of acarbose to induce change in circulating paracetamol concentrations until after 60 min is indicative of a delay in gastric emptying rather than an osmotic malabsorption. The exaggerated and sustained release of glucagon-like peptide-1 (7-36)amide (GLP-1) seen when sucrose was given with acarbose may play a part in the inhibition of gastric emptying. This study indicates that a significant delay in gastric emptying may be an added mechanism contributing to the therapeutic effect of acarbose.

Acarbose↗

Gastrointestinal carcinoid tumors and second primary malignancies.

The development of second primary malignancies (SPM) in patients with gastrointestinal carcinoid tumors is a well-described phenomenon, with reported rates as high as 55%. There is a predilection for gastrointestinal and genitourinary adenocarcinomas, but a variety of other malignancies have been reported as well. The etiology of this malignant predisposition may be rooted in the tumorigenic properties of the various neuroendocrine peptides elaborated and secreted by neuroendocrine cells. Peptides such as secretin, gastrin, bombesin, cholecystokinin (CCK), and vasoactive intestinal peptide (VIP) are believed to promote the growth of tumor cells. As many as 30 peptides and amines identified in neuroendocrine cells may have similar properties. This review of the literature on carcinoid-associated second primary malignancies is accompanied by a case report of metastatic carcinoid identified during surgical exploration for a perforating colon adenocarcinoma.

Adenocarcinoma, Mucinous↗

Role of colonic cytochrome P-450 in large bowel carcinogenesis.

Rat colon mucosa microsomes contain a competent mixed function oxidase system that hydroxylates the N-methyl drugs benzphetamine and ethylmorphine, the O-alkyl drugs p-nitroanisole and p-nitrophenetole and the polycyclic carcinogen benzo[alpha]pyrene. The colon system's hydroxylation activities can be selectively induced by pretreatment with phenobarbital or beta-naphthoflavone and can be selectively inhibited by SKF-525A or 7,8-benzoflavone. The colon microsomal system has been solubilized with the non-ionic detergent Renex 690 and resolved by column chromatography into its components cytochrome P-450 and cytochrome P-450 reductase. Colon cytochrome P-450 and cytochrome P-450 reductase can be recombined to reconstitute hydroxylation activity. The colon system is also able to activate carcinogens to mutagenic metabolites as demonstrated in the Ames test system. In addition, the activity of the colon system is markedly increased by pretreatment with gastrointestinal hormones.

Animals↗

Growth-promoting action of gastrin on human colonic and gastric tumour cells cultured in vitro.

The gastrointestinal hormone, gastrin, was examined for its trophic effect on the growth of colorectal and gastric tumour cells. All of the freshly disaggregated colorectal and gastric human adenocarcinomas responded to pentagastrin in 24 h cultures in vitro. Two newly established adenocarcinoma cell lines showed a response to pentagastrin at passage 2 but not at passage 6. Long-established cell lines did not respond to pentagastrin; however, upon synchronization of the human gastric cell line, MKN45, a trophic growth response with gastrin-17 was observed. This response was enhanced when the same cell line was grown as a xenograft in nude mice and then examined in vitro for gastrin dependence; this dependence was gradually reduced on further in vitro passaging. These results indicate that trophic responses to gastrin are lost during in vitro culture and may be underestimated by using long-established tumour cell lines. However, as all of the early cultures of colorectal and gastric tumours respond trophically to gastrin, perhaps gastrin-receptor blockers may be an important therapeutic modality for these patients.

Adenocarcinoma↗

Stimulation of hepatocyte DNA synthesis by neurotensin.

Epidermal growth factor and transforming growth factor alpha stimulated DNA synthesis in primary cultures of adult rat hepatocytes. Neurotensin amplified epidermal growth factor-stimulated or transforming growth factor alpha-stimulated DNA synthesis by three- to eightfold. Neurotensin by itself did not stimulate DNA synthesis. Amplification of DNA synthesis by neurotensin was observed as low as 10(-10) M, and it was increased in a dose-dependent manner with maximal effects at 10(-8) M. These results were obtained when hepatocytes were cultured in Williams' medium E, but not in Leibovitz L-15 medium, suggesting that a minor component(s) in the medium is required for hepatocytes to fully respond to neurotensin. Neurotensin effect on DNA synthesis was observed not only in normal rat hepatocytes but also in partially hepatectomized rat hepatocytes, although its effect was stronger in normal hepatocytes. Amplified DNA synthesis was inhibited by transforming growth factor beta. Secondary mitogens (co-mitogens) such as insulin, vasopressin, or angiotensin II interacted additively with low concentrations of epidermal growth factor as well as with neurotensin. Neurotensin-related peptides such as kinetensin or neuromedin-N, which was released from blood plasma by pepsin digestion, did not have this amplifying effect on DNA synthesis at any concentrations tested. Neurotensin mRNA was found in several organs including brain and intestine, but not liver. These results suggest that neurotensin can be regarded as a new secondary mitogen and that it may be involved in cell proliferation, including regenerating liver as a gastrointestinal hormone and/or a neurotransmitter.

Animals↗

Bombesin stimulates the in vitro growth of a human gastric cancer cell line.

Bombesin (BBS) and its mammalian equivalent, gastrin-releasing peptide (GRP), exhibit diverse biological functions, including that of a neurotransmitter, a regulator of gastrointestinal hormone release, and a trophic factor for various normal and neoplastic tissues. Bombesin stimulates the growth of normal cells of the stomach, pancreas, and bronchial epithelium as well as cells in breast cancer, gastrinoma, and small cell lung cancer. The purpose of this study was to determine whether BBS regulates the growth of a human gastric cancer cell line (SIIA) in vitro, and if so, to examine the mechanisms of signal-transduction that are involved. We found that BBS stimulated the growth of SIIA cells in vitro. The GRP receptor antagonists, BIM 26189 and BIM 26226, had no effect on growth of SIIA cells. Although these antagonists blocked the BBS-induced increase of [Ca2+]i, they failed to block the growth-stimulatory effect of BBS. BBS stimulated intracellular tyrosine phosphorylation of multiple proteins, with a predominant protein of apparent molecular weight of 125 kDa. Inhibition of intracellular tyrosine kinases by tyrphostin blocked the growth-stimulatory effect of BBS on SIIA cells. These results indicate that BBS exerts its trophic effect on SIIA cells through a receptor(s) linked to tyrosine kinase pathway, but not to the phospholipase C (PLC) pathway.

Adenocarcinoma↗

Topological mimicry and epitope duplication in the guanylyl cyclase C receptor.

Guanylyl cyclase C (GCC) is the receptor for the gastrointestinal hormones, guanylin, and uroguanylin, in addition to the bacterial heat-stable enterotoxins, which are one of the major causes of watery diarrhea the world over. GCC is expressed in intestinal cells, colorectal tumor tissue and tumors originating from metastasis of the colorectal carcinoma. We have earlier generated a monoclonal antibody to human GCC, GCC:B10, which was useful for the immunohistochemical localization of the receptor in the rat intestine (Nandi A et al., 1997, J Cell Biochem 66:500-511), and identified its epitope to a 63-amino acid stretch in the intracellular domain of GCC. In view of the potential that this antibody has for the identification of colorectal tumors, we have characterized the epitope for GCC:B10 in this study. Overlapping peptide synthesis indicated that the epitope was contained in the sequence HIPPENIFPLE. This sequence was unique to GCC, and despite a short stretch of homology with serum amyloid protein and pertussis toxin, no cross reactivity was detected. The core epitope was delineated using a random hexameric phage display library, and two categories of sequences were identified, containing either a single, or two adjacent proline residues. No sequence identified by phage display was identical to the epitope present in GCC, indicating that phage sequences represented mimotopes of the native epitope. Alignment of these sequences with HIPPENIFPLE suggested duplication of the recognition motif, which was confirmed by peptide synthesis. These studies allowed us not only to define the requirements of epitope recognition by GCC:B10 monoclonal antibody, but also to describe a novel means of epitope recognition involving topological mimicry and probable duplication of the cognate epitope in the native guanylyl cyclase C receptor sequence.

Amino Acid Sequence↗