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Inhibition of human gastric lipase secretion by glucagon-like peptide-1.

Glucagon-like peptide-1 (GLP-1) may be one of the enterogastrone hormones of the ileal brake mechanism. We therefore studied its effects on gastric lipase secretion in healthy volunteers and vagotomized patients during infusion of pentagastrin. The intestinal incretin hormone GLP-1 (glucagon-like peptide-1, 7-36 amide) was investigated because of its inhibitory effects on gastric acid secretion and motility. GLP-1 infused intravenously in amounts corresponding to the postprandial release significantly inhibited pentagastrin-stimulated gastric lipase secretion and lipolytic activity. The inhibitory effect of GLP-1 persisted in vagotomized patients, suggesting that fundic chief cells, from which gastric lipase is released, or neighboring inhibitory cells could be equipped with GLP-1 receptors. Vagotomized patients had significantly higher plasma concentrations of gastrin and secretin. No significant changes of gastrin, secretin, and CCK secretion were seen during GLP-1 infusion in the vagotomized patients, whereas secretin decreased significantly in the healthy volunteers. GLP-1 seems to be a naturally occurring inhibitor of gastric lipase secretion acting via a nonvagal mechanism. Our results indicate that gastric lipase secretion is subject to hormonal stimulatory as well as inhibitory mechanisms.

Aged↗

Post-prandial intragastric and duodenal acidity are increased in patients with chronic pancreatitis.

OBJECTIVES: Patients with chronic pancreatitis and exocrine insufficiency have lower intraduodenal pH compared to controls. It has been assumed that abnormal low intraduodenal pH in these patients not only results from impaired pancreatic bicarbonate secretion but also from an increased gastric acid load to the duodenum. METHODS: We have tested this hypothesis by combined intragastric and intraduodenal 24 h pH monitoring in nine chronic pancreatitis patients with exocrine pancreatic insufficiency and nine healthy control subjects during standardized test conditions. Postprandial gastrin and cholecystokinin release were also determined. RESULTS: Median 24-h intraduodenal pH (5.90 vs. 6.00) and intragastric pH (1.60 vs. 1.70) were not significantly different between patients and controls. However, in the 2-h postprandial periods intraduodenal pH was below five for a significantly higher percentage of time in chronic pancreatitis patients compared to controls (lunch: 14.5% vs. 0.17%, P=0.011; dinner: 24.1% vs. 5.75%, P=0.05). The post-dinner intragastric pH was below three for a significantly higher percentage of time in chronic pancreatitis patients vs. controls (72.2 vs. 48.9%, P=0.04). Postprandial gastrin release was not significantly different between the two groups. Postprandial secretion of cholecystokinin (CCK), as enterogastrone, was significantly (P < 0.01) reduced in chronic pancreatitis patients (78 +/- 13 pmol/L, 120 min) compared to controls (155 +/- 14 pmol/L, 120 min). CONCLUSIONS: Median intraduodenal and intragastric pH are not significantly decreased in patients with chronic pancreatitis and exocrine insufficiency but the postprandial time with an acidic pH in the duodenum (pH < 5) and in the stomach (pH < 3) is significantly (P </= 0.05) increased.

Adult↗

PYY and NPY: control of gastric motility via action on Y1 and Y2 receptors in the DVC.

The pancreatic polypeptide family of hormones and neurotransmitters including pancreatic polypeptide (PP), peptide YY (PYY) and neuropeptide Y (NPY) are emerging as potent central regulators of gastric function. There is, however, considerable debate concerning the mechanisms and even the direction of effects mediated by these peptides. Good evidence exists showing that PYY is the 'enterogastrone' released by the ileum after feeding which acts on vagal reflex control circuits to reduce gastric motility (i.e. the 'ileal brake'). However, equally convincing evidence is available to suggest that PYY and its close structural relative NPY may act in the same region of the brain to increase gastric motility through vagal mechanisms. We hypothesize that the confounding observations are due to agonist effects on two different receptor types-Y1 and Y2, which are both present in the dorsal vagal complex (DVC) but may be accessed differentially by peripheral humoral (PYY) vs central (NPY) pathways. In our initial approach to this problem, we studied the effects of NPY, PYY, Y1 and Y2 agonists microinjected into the DVC on gastric motility in the stimulated (by central thyrotropin-releasing hormone (TRH) and basal conditions. Our results show that Y2 agonist applied to the DVC during conditions of TRH-stimulated gastric motility mimicked the suppressive effects of PYY applied under the same conditions. Under basal conditions, Y2 agonist has no effect on motility. The DVC effect of the Y1 agonist is the opposite; Y1 agonist has no further effect to stimulate gastric motility in the TRH stimulated condition while Y1 agonist strongly stimulates motility from the basal condition. The effects of NPY depend upon the condition of study. Under TRH stimulation (maximal motility), NPY in the DVC reduces (but does not completely suppress) gastric motility while in the basal state, NPY is a strong activator of motility. These results are discussed in terms of the possible differential localization of Y1 vs Y2 receptors within the DVC and in terms of recent findings suggesting that PYY is rapidly converted to a Y2 agonist by a ubiquitous dipeptidyl aminopeptidase (DAP-IV).

Animals↗

GLP-1 and extra-islet effects.

The main target of action of glucagon-like peptide-1 (GLP-1) is the islet, where the hormone stimulates insulin secretion, promotes beta cell proliferation and neogenesis, and inhibits glucagon secretion. However, GLP-1 receptors are also expressed outside the islets, increasing the likelihood that GLP-1 also plays a role in other organs. These functions are mainly the inhibition of gastric emptying, gastric acid secretion and exocrine pancreatic secretion, indicating that the hormone acts as an enterogastrone--a hormone released from the distal portion of the small intestine that inhibits proximal gastrointestinal events. Another important action of GLP-1 is to induce satiety. Other effects of the hormone include cardioprotection, neuroprotection, induction of learning and memory, stimulation of afferent, sensory nerves, stimulation of surfactant production in the lung, dilatation of pulmonary vessels, induction of diuresis, and also under some conditions, induction of antidiabetic actions unrelated to islet function. Thus, GLP-1 clearly has several manifestations of activity. The physiological relevance of these actions and their contribution to the overall antidiabetic action of GLP-1 when used in treatment of type 2 diabetes remains to be established.

Animals↗

Xylitol vs glucose: effect on the rate of gastric emptying and motilin, insulin, and gastric inhibitory polypeptide release.

The effect of xylitol and glucose on the rate of gastric emptying and intestinal transit and on motilin, gastric inhibitory polypeptide (GIP), and insulin release were studied in human volunteers. A single oral dose of 200 mL water containing 30 g glucose or 30 g xylitol, mixed with a 99mtechnetium-tin (99mTc-Sn) colloid, was used. Similar dosing without the label was used in motilin, GIP, and insulin studies. Xylitol decreased the rate of gastric emptying but concomitantly accelerated intestinal transit compared with glucose. The half-times for gastric emptying were 77.5 +/- 4.6 and 39.8 +/- 3.4 min after ingestion of xylitol and glucose solutions, respectively. Glucose suppressed motilin and stimulated GIP secretion; xylitol stimulated motilin secretion but had no effect on GIP, which is currently the main candidate for the role of enterogastrone. The accelerated intestinal transit and increase in plasma motilin observed after xylitol ingestion were thought to be causally related to the diarrhea and gastrointestinal discomfort produced by it.

Colloids↗

Neurotensin decreases pepsin output and gastrointestinal motility in chickens.

Two experiments were conducted to determine the effect of neurotensin on gastric secretion and gastrointestinal motility in conscious chickens. Chickens were surgically fitted with a cannula to collect secretions from the proventriculus and strain gauge transducers sutured to the gizzard, duodenum, and ileum in order to detect contractions. Peripheral intravenous infusion of physiological levels of neurotensin inhibited pepsin output from the proventriculus, but had no effect on the volume or pH of gastric secretions. Neurotensin also inhibited both the frequency and strength of gastrointestinal contractions when compared to motility patterns following infusion of isotonic 0.9% (wt/vol) saline. The frequency of occurrence of small intestinal refluxes was not affected by neurotensin. These results coupled with our earlier work, which demonstrated that neurotensin is released by the presence of oleic acid in the duodenum, indicate that neurotensin may function as an enterogastrone released by lipids in the gastrointestinal tract of the chicken. This overall inhibitory effect of neurotensin on the avian gut indicates that it is involved in the postprandial regulation of digestion, especially lipid digestion.

Analysis of Variance↗

Pancreatic juice enhances fat-stimulated release of enteric hormones in dogs.

The presence of pancreatic juice in the intestinal lumen results in the hydrolysis of dietary fat. The hydrolytic products of dietary fat are potent stimulants of pancreatic exocrine secretion and potent inhibitors of gastric acid secretion. In this study, residual pancreatic enzyme activity in the intestinal lumen may account for the observed increase of triglyceride-stimulated pancreatic exocrine secretion and the release of peptides during diversion of pancreatic juice. The presence of pancreatic juice enhanced the pancreatic protein output that was stimulated by the intraduodenal administration of a triglyceride (corn oil, 2 g/kg/h) by 240% (p less than .05). The presence of pancreatic juice during the intraduodenal administration of a triglyceride nearly abolished the output of gastric acid as well as the release of gastrin (p less than .05) that had been stimulated by the intragastric placement of a 10% peptone meal. Pancreatic juice in the duodenum significantly enhanced the triglyceride-stimulated release of cholecystokinin-33/39, secretin, neurotensin, peptide YY, pancreatic polypeptide, and insulin (p less than .05) when compared with the release of these enteropancreatic hormones during the diversion of pancreatic juice. This study shows that the presence of pancreatic juice in the duodenal lumen enhances the fat-stimulated release of enteric hormones that have a stimulatory action on the enteroacinar and enteroinsular axis as well as an inhibitory action (enterogastrone-like activity) on the postprandial regulation of gastric function.

Animals↗

Oxyntomodulin: a potential hormone from the distal gut. Pharmacokinetics and effects on gastric acid and insulin secretion in man.

Synthetic oxyntomodulin, a predicted product of the glucagon gene, which is produced in the human lower intestinal mucosa, was infused in doses of 100 and 400 ng kg-1 h-1 into six volunteers to study its pharmacokinetics and effects on pentagastrin-stimulated gastric acid secretion (100 ng kg-1 h-1). The concentration of oxyntomodulin in plasma measured with a cross-reacting glucagon assay increased from 37 +/- 5 to 106 +/- 17 and 301 +/- 40 pmol l-1, respectively. The metabolic clearance rate was 5.2 +/- 0.7 ml kg-1 min-1 and the half-life in plasma was 12 +/- 1 min. Oxyntomodulin reduced the pentagastrin-stimulated acid secretion by 20 +/- 9% during the low-rate infusion (P less than 0.05) and by 76 +/- 10% during the high-rate infusion (P less than 0.05). In accordance with the homology with glucagon, there was a small, significant rise in plasma concentrations of insulin and insulin C-peptide during oxyntomodulin infusion. Oxyntomodulin may therefore be included among the potential incretins and enterogastrones in man.

Gastric Acid↗

Cholecystokinin is a physiological regulator of gastric acid secretion in man.

CCK8 is a poor stimulant of gastric acid secretion in vivo, but is equipotent to gastrin-17 (G17) in in vitro systems. To further evaluate the role of cholecystokinin (CCK) in regulating acid output in humans, dose-response curves were constructed to CCK8 or G17 (6.4-800 pmol kg-1 per h) with and without a specific CCK-A receptor antagonist (loxiglumide). During loxiglumide infusion, G17-stimulated acid output was unchanged, whereas CCK8-stimulated secretion increased significantly. Gastric somatostatin-14 release increased fivefold with CCK8 alone, but was blocked with loxiglumide administration. These data suggest that CCK8 directly stimulates acid secretion by binding to a CCK-B/gastrin receptor on parietal cells, but at the same time inhibits acid responses by stimulating gastric somatostatin release to a CCK-A receptor-mediated pathway. To test which action of CCK is relevant under physiological circumstances, the effect of loxiglumide on fasting and post-prandial acidity was measured through continuous pH-metry. After eating, gastrin levels increased fourfold compared to controls with concomitant increases in acid secretion. These results suggest that post cibum, CCK is an inhibitor of acid secretion by regulating gastrin through local somatostatin; they support the hypothesis that CCK acts as an enterogastrone.

Adult↗

Intestinal control of gastric function in the calf: the relationship of neural and endocrine factors.

1. Gastric emptying and secretion were measured in conscious calves during alkaline or acid perfusion of the duodenum with simultaneous assessment of endogenous plasma somatostatin, gastrin and blood 5-hydroxytryptamine (5-HT).2. Alkaline duodenal perfusion (isotonic NaHCO(3)) caused rapid gastric emptying and increased gastric acid secretion without any affect on basal levels of somatostatin, 5-HT or gastrin.3. Duodenal perfusion of 60 mm-HCl caused complete inhibition of gastric emptying, reduced gastric acid secretion considerably, and an associated elevation of somatostatin basal levels from 123.8 +/- 11.2 to 281.9 +/- 23.0 pg/ml. (P < 0.01) occurred.4. These effects of duodenal perfusion were unimpaired by bilateral lumbar splanchnectomy.5. On bilateral cervical vagotomy of the splanchnectomized calves, the inhibition of gastric function evoked by duodenal acidification persisted, and plasma somatostatin showed a further significant elevation to 506.9 +/- 49.9 pg/ml. (P < 0.01) but gastrin and 5-HT remained unchanged. The increased gastric function caused by alkaline duodenal function was significantly reduced following vagotomy but basal somatostatin, gastrin and 5-HT in the blood remained unaffected.6. These results suggest that the stimulatory effect on gastric emptying and acid secretion of isotonic NaHCO(3) in the duodenum may be mediated, partially at least, through the vagal nerves but not the splanchnics.7. The complete inhibition of gastric function which ensued on acidification of the duodenum and which continues after splanchnovagotomy, is not mediated by the autonomic nervous system. This inhibitory process appears to involve the endocrine system only, with somatostatin (but not gastrin or 5-HT) fulfilling a main enterogastrone role.

Animals↗

The mechanism of inhibitory action of secretin on gastric acid secretion in conscious rats.

1. Secretin has been recognized as an important enterogastrone. In order to investigate the mechanism of secretin-induced inhibition of gastric acid secretion, the effects of both anti-somatostatin antibody and indomethacin on acid secretion were examined in conscious rats with gastric cannulas. 2. Secretin given intravenously at 5.6 pmol kg-1 h-1 inhibited profoundly the acid secretion stimulated by pentagastrin at 0.3 microgram kg-1 h-1. 3. When a rabbit antisomatostatin serum was given intravenously, it not only abolished the secretin-induced inhibition on the pentagastrin-stimulated acid secretion, but also augmented both basal and pentagastrin-stimulated acid secretion. 4. Indomethacin also significantly augmented basal acid secretion, starting 45 min after the drug delivery began. It reversed the secretin-induced inhibition but it did not augment the pentagastrin-stimulated acid secretion. 5. Neither antisomatostatin serum influenced prostaglandin E2-induced inhibition of the pentagastrin-stimulated acid secretion, nor did indomethacin affect the inhibition by somatostatin, suggesting strongly that the inhibition by somatostatin is not mediated by endogenous prostaglandins, nor is that by prostaglandins E2 mediated by endogenous somatostatin. 6. It is concluded that the inhibitory action of secretin on pentagastrin-stimulated gastric acid secretion is mediated by both somatostatin and prostaglandins in conscious rats. The two inhibitors do not seem to interact endogenously for the inhibition of acid secretion. While endogenous somatostatin exerts a tonic inhibitory effect on both basal and pentagastrin-simulated acid secretion, prostaglandins augment basal acid secretion only.

Animals↗

Gastric secretion after massive small bowel resection.

This paper confirms that gastric hypersecretion can occur in man and dogs after massive intestinal resection. The assumption, made by others, that hypersecretion in the clinical situation is similar to that observed in dogs is challenged. An acute hypersecretory state occurred in eight of 19 patients after massive intestinal resection. This was apparent as an increased rate of basal secretion. It was usually transient and unrelated to the length of intestine resected. A correlation was noticed between hypersecretion and jaundice in the immediate postoperative period. Histamine release after acute hepatic injury was postulated as the cause of the hypersecretion. By contrast a chronic gastric hypersecretory state was demonstrated in dogs after massive intestinal resection. The rate of basal secretion was not significantly altered. The increased daily acid output was shown to be due to prolonged and enhanced response to food. The cause was thought to be loss of inhibitory agents, such as enterogastrone, normally released by the small intestine when in contact with food. The rationale of performing vagotomy and pyloroplasty at the same time as the intestinal resection is questioned.

Adolescent↗

Endogenous glucagon-like peptide 1 controls endocrine pancreatic secretion and antro-pyloro-duodenal motility in humans.

BACKGROUND: Exogenous use of the intestinal hormone glucagon-like peptide 1 (GLP-1) lowers glycaemia by stimulation of insulin, inhibition of glucagon, and delay of gastric emptying. AIMS: To assess the effects of endogenous GLP-1 on endocrine pancreatic secretion and antro-pyloro-duodenal motility by utilising the GLP-1 receptor antagonist exendin(9-39)amide (ex(9-39)NH2). METHODS: Nine healthy volunteers underwent four experiments each. In two experiments with and without intravenous infusion of ex(9-39)NH2 300 pmol/kg/min, a fasting period was followed by intraduodenal glucose perfusion at 1 and 2.5 kcal/min, with the higher dose stimulating GLP-1 release. Antro-pyloro-duodenal motility was measured by perfusion manometry. To calculate the incretin effect (that is, the proportion of plasma insulin stimulated by intestinal hormones) the glycaemia observed during the luminal glucose experiments was mimicked using intravenous glucose in two further experiments. RESULTS: Ex(9-39)NH2 significantly increased glycaemia during fasting and duodenal glucose. It diminished plasma insulin during duodenal glucose and significantly reduced the incretin effect by approximately 50%. Ex(9-39)NH2 raised plasma glucagon during fasting and abolished the decrease in glucagon at the high duodenal glucose load. Ex(9-39)NH2 markedly stimulated antroduodenal contractility. At low duodenal glucose it reduced the stimulation of tonic and phasic pyloric motility. At the high duodenal glucose load it abolished pyloric stimulation. CONCLUSIONS: Endogenous GLP-1 stimulates postprandial insulin release. The pancreatic alpha cell is under the tonic inhibitory control of GLP-1 thereby suppressing postprandial glucagon. GLP-1 tonically inhibits antroduodenal motility and mediates the postprandial inhibition of antral and stimulation of pyloric motility. We therefore suggest GLP-1 as a true incretin hormone and enterogastrone in humans.

Adult↗

Gastric inhibitory polypeptide does not inhibit gastric emptying in humans.

The insulinotropic gut hormone gastric inhibitory polypeptide (GIP) has been demonstrated to inhibit gastric acid secretion and was proposed to possess "enterogastrone" activity. GIP effects on gastric emptying have not yet been studied. Fifteen healthy male volunteers (23.9 +/- 3.3 yr, body mass index 23.7 +/- 2.3 kg/m(2)) were studied with the intravenous infusion of GIP (2 pmol.kg(-1).min(-1)) or placebo, each administered to the volunteers on separate occasions from -30 to 360 min in the fasting state. At 0 min, a solid test meal (250 kcal containing [(13)C]sodium octanoate) was served. Gastric emptying was calculated from the (13)CO(2) exhalation rates in breath samples collected over 360 min. Venous blood was drawn in 30-min intervals for the determination of glucose, insulin, C-peptide, and GIP (total and intact). Statistical calculations were made by use of repeated-measures ANOVA and one-way ANOVA. During the infusion, GIP rose to steady-state concentrations of 159 +/- 15 pmol/l for total and 34 +/- 4 pmol/l for intact GIP (P < 0.0001). Meal ingestion further increased GIP concentrations in both groups, reaching peak levels of 265 +/- 20 and 82 +/- 9 pmol/l for total and 67 +/- 7 and 31 +/- 9 pmol/l for intact GIP during the administration of GIP and placebo, respectively (P < 0.0001). There were no differences in glucose, insulin, and C-peptide between the experiments with the infusion of GIP or placebo. Gastric half-emptying times were 120 +/- 9 and 120 +/- 18 min (P = 1.0, with GIP and placebo, respectively). The time pattern of gastric emptying was similar in the two groups (P = 0.98). Endogenous GIP secretion, as derived from the incremental area under the curve of plasma GIP concentrations in the placebo experiments, did not correlate to gastric half-emptying times (r(2) = 0.15, P = 0.15 for intact GIP; r(2) = 0.21, P = 0.086 for total GIP). We conclude that gastric emptying does not appear to be influenced by GIP. The secretion of GIP after meal ingestion is not suppressed by its exogenous administration. The lack of effect of GIP on gastric emptying underlines the differences between GIP and the second incretin glucagon-like peptide 1.

Adult↗

Secretin inhibits gastric acid secretion via a vagal afferent pathway in rats.

Secretin is an enterogastrone that inhibits gastric acid secretion and motility. Recently, it was reported that secretin inhibited gastric emptying via a capsaicin (Cap)-sensitive vagal afferent pathway. However, a possible role of the sensory afferent pathway in secretin-inhibited acid secretion has not been clarified. We investigated whether or not the acid secretion suppressed by secretin is modulated by a vagal and/or splanchnic afferent pathway in rats. Subdiaphragmatic perivagal (PV) or periceliac ganglionic (PCG) application of Cap (10 mg/ml) or vehicle was performed in both conscious and anesthetized rats 2 wk before experiments. Bilateral vagotomy was performed in some conscious rats 5 days before studies. Pentagastrin was administered intravenously at 0.6 microg . kg-1 . h-1. Secretin (20 pmol . kg-1 . h-1 iv) or 0.03 N HCl (4.32 ml/h id) was infused in conscious rats with gastric cannulas or anesthetized rats with ligation of the pylorus, respectively. A rabbit antisecretin serum was injected in some anesthetized rats before duodenal acidification. Secretin significantly inhibited pentagastrin-stimulated acid secretion by 63% (P < 0.01), which was abolished by both vagotomy and PV treatment of Cap in conscious rats. In anesthetized rats, duodenal infusion of 0.03 N HCl suppressed pentagastrin-induced acid secretion by 59.4% (P < 0.01), which was reversed not only by antisecretin serum but also by PV application of Cap. However, PCG treatment with Cap did not influence the inhibition by secretin or duodenal acidification in either awake or anesthetized rats. These results indicate that the inhibition by secretin of pentagastrin-stimulated acid secretion is mediated by a Cap-sensitive vagal afferent pathway but not via a splanchnic afferent pathway in rats.

Afferent Pathways↗

Regulation of glucose-dependent insulinotropic polypeptide release by protein in the rat.

Glucose-dependent insulinotropic polypeptide (GIP) release has been demonstrated predominantly after ingestion of carbohydrate and fat. These studies were conducted to determine the effects of protein on GIP expression in the rat. Whereas no significant changes in duodenal mucosal GIP mRNA levels were detected in response to peptone, the duodenal GIP concentration increased from 8.4+/-1.5 to 19.8+/-3.2 ng GIP/mg protein at 120 min (P<0.01). Plasma GIP levels also increased from 95+/-5.2 pg/ml to a peak of 289+/-56.1 pg/ml at 120 min (P<0.01). To determine whether the effects of protein on GIP were due to stimulation of acid secretion, rats were pretreated with 10 mg/kg omeprazole, after which mucosal and plasma GIP concentrations were partially attenuated. To further examine the effects of luminal acid, rats were administered intraduodenal 0.1 M HCl for 120 min, which significantly enhanced GIP expression. These studies indicate that nutrient protein provides a potent stimulus for GIP expression in the rat, an effect that occurs at the posttranslational level and may be mediated in part through the acid-stimulatory properties of protein. The effects of acid on GIP are consistent with a role for GIP as an enterogastrone in the rat.

Animals↗

Lack of effect of synthetic human gastric inhibitory polypeptide and glucagon-like peptide 1 [7-36 amide] infused at near-physiological concentrations on pentagastrin-stimulated gastric acid secretion in normal human subjects.

Gastric inhibitory polypeptide (GIP) and glucagon-like peptide 1 [7-36 amide] (GLP-1) are glucose-dependent insulinotropic gut hormones. Under experimental conditions, both have been shown to reduce stimulated gastric acid secretion. To study their individual and combined effects on pentagastrin-stimulated (0.1 micrograms/kg/h from -90 to 120 min) gastric volume, acid and chloride output, on separate occasions, synthetic human GIP (1 pmol/kg/min) and/or GLP-1 [7-36 amide] (0.3 pmol/kg/min) or placebo (0.9% NaCl with 1% albumin) were infused intravenously (from -30 to 120 min) in 9 healthy volunteers. At 0 min, a glucose infusion was started that mimicked the glycemic profile after an oral glucose load of 50 g/400 ml and allowed for the glucose-dependent insulinotropic action of GIP and GLP-1 [7-36 amide]. Pentagastrin stimulated acid output significantly, but neither GIP nor GLP-1 [7-36 amide] either alone or in combination, reduced pentagastrin-stimulated gastric acid secretion. The circulating concentrations of GIP and GLP-1 [7-36 amide] obtained at steady state during exogenous administration of synthetic peptides were similar to or higher than those reached after oral glucose (endogenous secretion). In conclusion, (penta)gastrin-stimulated gastric acid secretion is not inhibited by physiological circulating concentrations of GIP or GLP-1 [7-36 amide]. Therefore, the insulinotropic action of these intestinal hormones is physiologically more important than their possible role as enterogastrone.

Adult↗

Inhibition of sham feeding-stimulated human gastric acid secretion by glucagon-like peptide-2.

Glucagon-like peptide (GLP)-2 is formed from proglucagon in the intestinal L cells and is secreted postprandially in parallel with the insulinotropic hormone GLP-1, the latter of which, in addition, acts to inhibit gastric secretion and motility by inhibiting central parasympathetic outflow. We now studied the effect of GLP-2 on gastric secretion stimulated by sham feeding to test the hypothesis that also GLP-2 acts as an enterogastrone. Eight healthy volunteers were studied twice on separate days. They were sham fed with and without GLP-2 infused iv at a rate of 0.8 pmol/kg x min. Gastric contents were aspirated continuously by a nasogastric tube for determination of acid secretion, volume, and osmolarity. Sham feeding increased gastric acid secretion nearly 5-fold. Infusion of GLP-2 reduced incremental acid secretion by 65+/-6%, compared with saline infusion (delta8.75+/-0.37 vs. delta3.04+/-0.47 mmol x 60 min; P<0.01). Plasma concentrations of GLP-2 rose from a basal mean of 3.3+/-0.9 to a mean of 115+/-8 pmol/L (range, 57-149 pmol/L) during infusion of GLP-2 and remained at basal level during saline infusion. Plasma concentrations of GLP-1, gastrin, cholecystokinin, and secretin remained low and unchanged on both study days. We conclude that GLP-2 is a powerful inhibitor of gastric acid secretion in man. Further investigations will show to what extent GLP-2 contributes to the inhibitory effects on gastric secretion exerted by hormones from the distal small intestine, under physiological circumstances.

Cholecystokinin↗