S. S. Poulsen

Glucagon-Like Peptide I Receptors in the Subfornical Organ and the Area Postrema Are Accessible to Circulating Glucagon-Like Peptide I

The intestinal incretin hormone glucagon-like peptide I (GLP-I) inhibits gastric motility and secretion in normal, but not in vagotomized subjects, pointing to a centrally mediated effect. Therefore, our aim was to study the availability of rat brain GLP-I receptors to peripherally injected 125I-labeled GLP-I. The specificity of the binding was tested by co-injection of excess amounts of unlabeled GLP-I. Using light microscopical autoradiography of rat brain sections, we found specific 125I-GLP-I binding exclusively in the subfornical organ and the area postrema. This binding was abolished when an excess amount of unlabeled GLP-I was co-injected with the labeled GLP-I. We conclude that cells in the subfornical organ and the area postrema could be responsive to blood-borne GLP-I. The observed binding of peripherally administered GLP-I to the subfornical organ and the area postrema, which both have close neuroanatomical connections with hypothalamic areas involved in water and appetite homeostasis, is consistent with the potential roles of circulating GLP-I in the central regulation of appetite and autonomic functions.

Pancreatic and intestinal processing of proglucagon in man.

SummaryWe developed antisera and radioimmunoassays against synthetic replicas of glucagon-like peptide-1 (1–36) and -2, predicted products of the glucagon precursor, and against glucagon-like peptide-1 (7–36) identical to the sequence of glucagon-like peptide-1, but lacking its first six N-terminal amino acids. With these tools, we studied the localisation and molecular nature of glucagon-like immunoreactivity in human pancreas, small intestine and plasma. By immunohistochemistry glucagon-like peptide-1, and glucagon-like peptide-2 immunoreactivity coexisted with glucagon in pancreatic islet cells and with enteroglucagon in small intestinal enteroglucagon-producing cells. By chromatography of tissue extracts we found that glucagon-like peptide-1 and glucagon-like peptide-2-immunoreactivities in the human pancreas (307±51 and 107±37 pmol/g tissue) were mainly contained in a large peptide, whereas in the small intestine glucagon-like peptide-1 and glucagon-like peptide-2 immunoreactivities were found in separate smaller molecules (49±21 and 77±28/g tissue). By isocratic high pressure liquid chromatography of the large pancreatic glucagon-like peptide we found that this peptide is heterogeneous. By chromatographic analysis glucagon-like peptide-1 immunoreactivity in fasting plasma was mainly found in a large peptide corresponding to the pancreatic form, while after a meal a smaller molecular form coeluting by gel filtration with glucagon-like peptide-1 predominated.

Effect of sialoadenectomy and synthetic human urogastrone on healing of chronic gastric ulcers in rats.

The effect of extirpation of the submandibular glands, an exocrine organ for epidermal growth factor/urogastrone (EGF/URO), and the effect of oral administration of synthetic human (EGF/URO) on healing of chronic gastric ulcers in rats has been investigated. Removal of the submandibular glands delayed healing of chronic gastric ulcers when examined after 50, 100, and 200 days. Oral administration of synthetic human EGF/URO stimulated gastric ulcer healing when examined after 25 and 50 days of treatment. The effect of synthetic human EGF/URO was comparable with that of cimetidine. The combined administration of synthetic human EGF/URO and cimetidine further increased healing of gastric ulcers compared with administration of each substance. Neither synthetic human EGF/URO, nor removal of the submandibular glands had any influence on gastric acid secretion. This study showed that the submandibular glands influence healing of chronic gastric ulcers and suggest that EGF/URO participate in healing of chronic gastric ulcers in rats.

Glucagon-like peptide 2 (GLP-2) accelerates the growth of colonic neoplasms in mice

Background: Glucagon-like peptide 2 (GLP-2) is an intestinotrophic mediator with therapeutic potential in conditions with compromised intestinal capacity. However, growth stimulation of the intestinal system may accelerate the growth of existing neoplasms in the intestine. Aims: In the present study, the effects of GLP-2 treatment on the growth of chemically induced colonic neoplasms were investigated. Methods: In 210 female C57bl mice, colonic tumours were initially induced with the methylating carcinogen 1,2-dimethylhydrazine (DMH) and mice were then treated with GLP-2. Two months after discontinuation of the carcinogen treatment, 135 of the mice were allocated to one of six groups which were treated twice daily with 25 μg GLP-2, 25 μg Gly2-GLP-2 (stable analogue), or phosphate buffered saline for a short (10 days) or long (one month) period. The remaining 75 mice had a treatment free period of three months and were then allocated to groups subjected to long term treatment, as above. Results: Colonic polyps developed in 100% of the mice, regardless of treatment. Survival data revealed no statistical significant differences among the different groups but histopathological analysis demonstrated a clear and significant increase in tumour load of mice treated with Gly2-GLP-2. The tumour promoting effect of native GLP-2 was less pronounced but the number of small sized polyps increased following long term treatment. Conclusions: The present results clearly indicate that GLP-2 promotes the growth of mucosal neoplasms. Our findings highlight the need for future investigations on the effects of GLP-2 in conditions needing long time treatment or with increased gastrointestinal cancer susceptibility.

Short-term Administration of Glucagon-like Peptide-2. Effects on Bone Mineral Density and Markers of Bone Turnover in Short-Bowel Patients with No Colon

Background: Glucagon-like peptide 2 (GLP-2) is a newly discovered intestinotrophic hormone. We have recently reported that a 5-week GLP-2 treatment improved the intestinal absorptive capacity of shortbowel patients with no colon. Additionally, GLP-2 treatment was associated with changes in body composition that included a significant increase in total body bone mass. This article describes the effect of GLP-2 on spinal and hip bone mineral density (BMD) and biochemical markers of bone turnover in these patients. Methods: In an open-labelled pilot study, eight short-bowel patients (3M, 5F; mean age 49 years) with small-bowel resection and no colon received 400 μg s.c. of GLP-2 twice daily for 5 weeks. Four received home parenteral nutrition (mean length of residual jejunum 83 cm) and 4 did not (mean length of ileum resected 106 cm). The outcome measures were the mean percent change from baseline in spinal and hip BMD measured by dual-energy X-ray absorptiometry, changes in four biochemical markers of bone-turnover, PTH, 25-hydroxy vitamin-D, and the intestinal absorption of calcium. Results: Mean ± s x (SEM) percent changes in spinal and hip BMD were 1.1 ± 0.4% ( P < 0.05) and 1.9 ± 0.8% ( P = 0.06), respectively. The intestinal calcium absorption increased by 2.7% ( P = 0.87). Serum ionized calcium increased in 5/8 patients with a concomitant decrease in serum PTH values. Three of the four markers of bone turnover decreased. Conclusion: A 5-week GLP-2 administration significantly increased spinal BMD in short-bowel patients with no colon. The mechanism by which GLP-2 affects bone metabolism remains unclear, but may be related to an increased mineralization of bone resulting from an improved intestinal calcium absorption.

Adrenergic effects on exocrine secretion of rat submandibular epidermal growth factor.

The present study was undertaken to investigate the effect of alpha- and beta-adrenergic agonists on secretion of epidermal growth factor (EGF) from the rat submandibular glands and to test the possibility of intestinal absorption of EGF. Alpha-adrenergic agonists increased the concentration of salivary EGF by approximately a hundred times, while the serum concentration of EGF was unchanged. The contents of EGF in the submandibular glands decreased upon administration of the alpha-adrenergic agonist noradrenaline, and this was confirmed on immunohistochemical investigation of the glands. Beta-adrenergic agonists had no effect on secretion of EGF from the submandibular glands. Intestinal absorption of EGF could not be confirmed, as stimulation by noradrenaline with free passage of saliva to the gastrointestinal tract and intrajejunal infusion of EGF had no influence on the concentration of EGF in serum. This study shows that alpha-adrenergic agonists stimulate exocrine secretion of submandibular EGF and that EGF in physiological amounts are not absorbed in the gastrointestinal tract.

Vasoactive intestinal polypeptide (VIP) in the pig pancreas: role of VIPergic nerves in control of fluid and bicarbonate secretion

Vasoactive intestinal polypeptide (VIP) in the pig pancreas is localized to nerves, many of which travel along the pancreatic ducts. VIP stimulates pancreatic fluid and bicarbonate secretion like secretin. Electrical vagal stimulation in the pig causes an atropine-resistant profuse secretion of bicarbonate-rich pancreatic juice. In an isolated perfused preparation of the pig pancreas with intact vagal nerve supply, electrical vagal stimulation caused an atropine-resistant release of VIP, which accurately parallelled the exocrine secretion of juice and bicarbonate. Perfusion of the pancreas with a potent VIP-antiserum inhibited the effect of vagal stimulation on the exocrine secretion. It is concluded, that VIP is responsible for (at least part of) the neurally controlled fluid and bicarbonate secretion from the pig pancreas.

Metabolism of oral trefoil factor 2 (TFF2) and the effect of oral and parenteral TFF2 on gastric and duodenal ulcer healing in the rat

BACKGROUND Trefoil factors (TFFs) are peptides produced by mucus-secreting cells in the gastrointestinal tract. A functional association between these peptides and mucus, leading to stabilisation of the viscoelastic gel overlying the epithelia, has been suggested. Both oral and parenteral administration of the peptides increase the resistance of the gastric mucosa. AIM To study the effect in rats of oral and parenteral porcine trefoil factor 2 (pTFF2) on the healing of gastric and duodenal ulcerations and to clarify the distribution and metabolism of orally administered pTFF2 in the gastrointestinal tract. METHODS Gastric ulcers were induced in female Sprague-Dawley rats by indomethacin and duodenal ulcers by mercaptamine. The rats were treated for up to seven days with oral or subcutaneous pTFF2. Ulcer size after treatment was assessed by stereomicroscopy after whole mount staining with periodic acid-Schiff stain. 125I-labelled pTFF2 was given orally to rats, and tissues were investigated by gamma counting of samples and by autoradiography of paraffin embedded sections. RESULTS pTFF2 accelerated gastric ulcer healing after both oral and subcutaneous administration. Duodenal ulcers were aggravated by both treatments. After oral administration of 125I-pTFF2, intact peptide was recovered from the superficial part of the mucus layer in the stomach; it passed through the small intestine but was degraded in the caecum. Only a minor part of the labelled pTFF2 entered the colon and was excreted in the faeces. Most of the label was excreted in the urine. CONCLUSIONS Oral as well as parenteral pTFF2 accelerates the healing of gastric ulceration and aggravates duodenal ulcers. Oral pTFF2 binds to the mucus layer of the stomach and the small intestine but does not reach the colonic mucosa.

Short Bowel Patients Treated for Two Years with Glucagon-Like Peptide 2: Effects on Intestinal Morphology and Absorption, Renal Function, Bone and Body Composition, and Muscle Function

Background and aims. In a short-term study, Glucagon-like peptide 2 (GLP-2) has been shown to improve intestinal absorption in short bowel syndrome (SBS) patients. This study describes longitudinal changes in relation to GLP-2 treatment for two years. Methods. GLP-2, 400 micrograms, s.c.,TID, were offered, to eleven SBS patients keeping parenteral support constant. 72-hour nutritional balance studies were performed at baseline, weeks 13, 26, 52 during two years intermitted by an 8-week washout period. In addition, mucosal morphometrics, renal function (by creatinine clearance), body composition and bone mineral density (by DEXA), biochemical markers of bone turnover (by s-CTX and osteocalcin, PTH and vitamin D), and muscle function (NMR, lungfunction, exercise test) were measured. Results. GLP-2 compliance was >93%. Three of eleven patients did not complete the study. In the remaining 8 patients, GLP-2 significantly reduced the fecal wet weight from approximately 3.0 to approximately 2.0 kg/day. This was accompanied by a decline in the oral wet weight intake, maintaining intestinal wet weight absorption and urinary weight constant. Renal function improved. No significant changes were demonstrated in energy intake or absorption, and GLP-2 did not significantly affect mucosal morphology, body composition, bone mineral density or muscle function. Conclusions. GLP-2 treatment reduces fecal weight by approximately 1000 g/d and enables SBS patients to maintain their intestinal fluid and electrolyte absorption at lower oral intakes. This was accompanied by a 28% improvement in creatinine clearance.

Cysteamine-induced Duodenal Ulcer and Acid Secretion in the Rat

Duodenal ulcers can be produced in rats within 24 h by a single subcutaneous administration of cysteamine. To determine the role of gastric acid secretion in the pathogenesis of these ulcers, secretory and pathoanatomic studies were performed in chronic fistula rats ater an ulcerogenic dose of cysteamine. A prolonged increase of acid secretion was seen after cysteamine, reaching fourfold the basal level after 5 h. The acid response lasted for 10 to 11 h. After vagotomy cysteamine-induced acid secretion was markedly reduced. Ulcer formation was prevented by vagotomy and by drainage of the gastric juice before it entered the duodenum. When a gastric acid output equivalent to that produced by the ulcerogenic dose of cysteamine was induced by repeated injections of pentagastrin, no mucosal changes were seen in the duodenum. These results indicate that, although some acid in the duodenum is required for ulcer formation, the hypersecretion of acid induced by cysteamine is not the only factor responsible for the development of duodenal ulcer.