Nondigestible carbohydrates and mineral bioavailability

Generally, fiber and compounds associated with fiber in cereal products (e.g., phytates) have been found to reduce the apparent absorption of minerals (such as calcium, magnesium, zinc and manganese) in humans, livestock and animal models. The effects of "soluble" forms of fiber (specifically pectins, gums, resistant starches, lactulose, oligofructose and inulin) on mineral absorption are more difficult to characterize. The addition of these soluble forms of fiber has been found in various studies to add viscosity to the gut contents, promote fermentation and the production of volatile fatty acids in the cecum, have a trophic effect on the ceca of animals and increase serum enteroglucagon concentrations. Thus it is not surprising that the addition of soluble forms of fiber to diets often has been found to improve absorption of minerals. This may reflect absorption of electrolytes from the large intestine. Future work should address the mechanisms by which ingestion of nondigestible carbohydrates improves mineral absorption in humans.

Gastrointestinal responses to a panel of lectins in rats maintained on total parenteral nutrition

Total parenteral nutrition (TPN) causes atrophy of gastrointestinal epithelia, so we asked whether lectins that stimulate epithelial proliferation can reverse this effect of TPN. Two lectins stimulate pancreatic proliferation by releasing CCK, so we asked whether lectins that stimulate gastrointestinal proliferation also release hormones that might mediate their effects. Six rats per group received continuous infusion of TPN and a once daily bolus dose of purified lectin (25 mg. rat-1. day-1) or vehicle alone (control group) for 4 days via an intragastric cannula. Proliferation rates were estimated by metaphase arrest, and hormones were measured by RIAs. Phytohemagglutinin (PHA) increased proliferation by 90% in the gastric fundus (P < 0.05), doubled proliferation in the small intestine (P < 0.001), and had a small effect in the midcolon (P < 0.05). Peanut agglutinin (PNA) had a minor trophic effect in the proximal small intestine (P < 0.05) and increased proliferation by 166% in the proximal colon (P < 0.001) and by 40% in the midcolon (P < 0.001). PNA elevated circulating gastrin and CCK by 97 (P < 0.05) and 81% (P < 0.01), respectively, and PHA elevated plasma enteroglucagon by 69% and CCK by 60% (both P < 0.05). Only wheat germ agglutinin increased the release of glucagon-like peptide-1 by 100% (P < 0.05). PHA and PNA consistently reverse the fall in gastrointestinal and pancreatic growth associated with TPN in rats. Both lectins stimulated the release of specific hormones that may have been responsible for the trophic effects. It is suggested that lectins could be used to prevent gastrointestinal atrophy during TPN. Their hormone-releasing effects might be involved.

Circulating oxyntomodulin-like immunoreactivity in healthy children and children with celiac disease

BACKGROUND

The aim of the study was to evaluate the new hormonal entity oxyntomodulin-like immunoreactivity in malabsorption states, and to assess its potential in celiac disease management.

METHODS

We measured basal and postprandial oxyntomodulin-like immunoreactivity values in 35 children divided into 3 groups: group 1 was composed of 13 children with celiac disease, either under a gluten-free diet (8 patients) or normal diet (5 patients); group 2 was composed of 8 children hospitalized for gastroenteritis or chronic diarrhea, without biological evidence of malabsorption nor abnormal jejunal mucosa; group 3 was composed of 22 control subjects.

RESULTS

Fasting and meal-stimulated levels in the control group were 71+/-10 and 130+/-26 pmol/l, respectively. Mean concentrations were elevated in patients with celiac disease (basal = 349+/-254 pmol/l, postprandial = 446+/-332 pmol/l) and in the group 2 (basal = 139+/-58 pmol/l, postprandial = 218+/-85 pmol/l), but the difference with control subjects did not reach statistical significance. In children with celiac disease, basal and stimulated values correlated with the degree of malabsorption as assessed by hemoglobin (p = 0.006 and p = 0.01, respectively) and serum folate concentrations (p = 0.03 and p = 0.02, respectively).

CONCLUSIONS

Oxyntomodulin-like immunoreactivity is noticeably higher in healthy children than previously measured in healthy adult subjects. This hormonal parameter is not an adequate diagnostic tool in celiac disease. Nevertheless, in the context of celiac disease, its elevation reflects the degree of malabsorption and may provide a quantitative approach of the extent of mucosal damage.

Fermentable dietary fibre, intestinal microflora and plasma hormones in the rat

1. Conventional and germ-free rats were fed a fibre-free elemental diet with or without the addition of fermentable dietary fibres. We have previously reported that fibre was associated with greatly increased epithelial cell proliferation, but only in the conventional group, implying that it is the breakdown of fibre by the colonic microflora that is the main determinant of mucosal proliferation in the hind gut. The relationship of these changes to various plasma hormones implicated in intestinal growth control are described in this paper. 2. The most dramatic finding was that plasma levels of enteroglucagon and peptide YY were greatly increased in the germ-free groups. The response of these rats to fibre differed in that fibre decreased levels of enteroglucagon and peptide YY in the germ-free animals, but increased them in the conventional rats. Gastrin and insulin levels were significantly lowered in the fibre-supplemented groups, but were not affected by the microflora. 3. These results corroborate our previous findings that the effects of fibre and its fermentation are dynamically complex, and demonstrate that, like proliferation, direct effects and indirect fermentation-derived effects on plasma hormones also coexist.

Effect of ageing on pancreatic hyperplasia after 90% proximal small bowel resection

The present study was performed to examine the effect of ageing on pancreatic hyperplasia observed after proximal small bowel resection (PSBR). Young and old Wistar rats were randomly assigned to two groups, which underwent either an approximate 90% PSBR or a jejunal and ileal transection (TRC). One week after the operation, the pancreatic wet weight and the protein, DNA and RNA content of the pancreas were all significantly higher in young PSBR rats than in young TRC rats. However, no differences were seen in the old rat groups. Plasma enteroglucagon levels were elevated in both young and old PSBR rats, but the ratio of increase between the PSBR and TRC groups was significantly higher in young rats. Plasma cholecystokinin and gastrin levels did not increase after PSBR in either the young or old rats. These findings suggest that pancreatic hyperplasia observed after PSBR is attenuated by ageing, probably due to an insufficient increase in plasma enteroglucagon levels.

Colonic fermentation and proximal gastric tone in humans

BACKGROUND & AIMS

Some carbohydrates escape small intestinal absorption, and their presence in the ileum can affect proximal gut motility. Carbohydrates reaching the colon can inhibit gastric and pancreatic secretions. The hypothesis of this study was that colonic fermentation products of carbohydrates (short-chain fatty acids [SCFAs]) affect proximal gut motility and especially gastric tone.

METHODS

Healthy volunteers were studied after oral administration of 20 g lactulose (n = 6) and intracolonic infusions of 20 g lactose (n = 7) and SCFAs (54 mmol/180 mL and 90 mmol/180 mL, respectively). Gastric tone (electronic barostat) and H2 concentrations in exhaled air were simultaneously monitored, and peripheral intestinal peptide levels were measured by specific radioimmunoassays.

RESULTS

After oral lactulose administration (but not after saline), a significant decrease in gastric tone was observed, which rapidly followed the increase in H2 concentrations. Gastric tone also decreased after intracolonic infusions of both lactose and SCFAs; the most marked effect occurred after the highest SCFA dose. No significant changes in the level of plasma oxyntomodulin-like immunoreactivity and glucagon-like peptide 1 were found, whereas the level of peptide YY increased significantly over time, but not differently after saline and test solutions.

CONCLUSIONS

Colonic fermentation of undigestible carbohydrates can inhibit gastric tone, and SCFAs may be responsible for this colonic brake. The role of intestinal peptides, if any, was not identified.

Fermentable carbohydrate modulates postprandial enteroglucagon and gastrin release in rats

We studied the effects of a fermentable sugar-alcohol (lactitol) on the concentrations of enteroglucagon and gastrin in the blood of rats for 7.5 h after feeding. The control and treatment groups were fed on semi-purified diets containing either non-fermentable cellulose or lactitol respectively, at 100 g/kg. Compared with the cellulose-fed group, the animals fed with lactitol had higher levels of enteroglucagon (5-10 times higher than control; P < 0.05) and lower serum gastrin (70-80% of control; P < 0.05) for several hours after the withdrawal of feed. In contrast, varying the level of dietary lipid (maize oil) over a range of 8-120 g/kg had no effect on the release of either peptide. These results suggest that poorly absorbed fermentable dietary carbohydrate stimulates postprandial plasma enteroglucagon and inhibits serum gastrin release in the rat. The mechanism is uncertain but an endocrine response by the colon to fermentation products seems probable.

Increased ileal proglucagon expression after jejunectomy is not suppressed by inhibition of bowel growth

After jejunectomy, a rapid and sustained increase in the abundance of proglucagon mRNA occurs in residual ileum and is accompanied by increases in plasma intestinal proglucagon-derived peptides. This response may be a component of adaptive growth, or proglucagon-derived peptides may regulate adaptive growth. To distinguish these possibilities, rats were treated with difluoromethylornithine, blocking ornithine decarboxylase activity and thereby adaptive bowel growth. Three groups fed ad libitum were compared: (1) resect: rats with 80% proximal small bowel resection; (2) resect + difluoromethylornithine: resected rats given difluoromethylornithine in drinking water; and (3) transect: transected controls. Six days after surgery, the resect + difluoromethylornithine group demonstrated inhibition of adaptive bowel growth. Abundance of ileal proglucagon mRNA in resect and resect + difluoromethylornithine groups was double that in the transect group (P < 0.02), whereas ornithine decarboxylase mRNA levels did not differ. Plasma enteroglucagon and glucagon-like peptide-I levels were greater in resect than transect groups (P < 0.002) and did not differ between resect and resect + difluoromethylornithine groups. The rise in ileal proglucagon mRNA after proximal small bowel resection is not inhibited by difluoromethylornithine despite blocking bowel growth and, therefore, is not merely a component of adaptive growth. Proglucagon-derived peptides are possible modulators of adaptive bowel but cannot stimulate growth when ornithine decarboxylase activity is inhibited.

Fermentable carbohydrates elevate plasma enteroglucagon but high viscosity is also necessary to stimulate small bowel mucosal cell proliferation in rats

Enteroglucagon is a collective term for a small family of peptides derived from proglucagon by post-translational processing in the L-cells of the distal small intestine and colon. There is evidence that it inhibits gastric secretion, and high levels of enteroglucagon occur in plasma during intestinal adaptation, which suggests that it may also function as a trophic factor for the intestine. Certain types of soluble non-starch polysaccharide (dietary fiber) stimulate the release of enteroglucagon in rats but the mechanism is unknown. In this study we explored the importance of the viscosity and fermentability of nonabsorbed carbohydrates as determinants of plasma enteroglucagon and mucosal cell proliferation in the distal ileum of rats. Replacement of cellulose (10 g/kg) with guar gum in a semisynthetic diet led to a prompt and sustained rise in plasma enteroglucagon concentrations. Our initial hypothesis that this was a consequence of delayed nutrient absorption was disproven by the fact that hydroxypropylmethylcellulose (HPMC), a viscous but nonfermentable polysaccharide, had no effect on plasma enteroglucagon under the same conditions. In contrast, the nondigestible disaccharide lactitol led to a prolonged rise in plasma enteroglucagon, similar to that observed with guar gum. Lactitol is nonviscous, but highly fermentable, and we conclude that fermentable carbohydrate is an important stimulus for the release of enteroglucagon under our experimental conditions. There was no evidence that enteroglucagon released by this mechanism exerted trophic effects on the distal small intestinal mucosa.

Release of vasodilator, but not vasoconstrictor, neuropeptides and of enteroglucagon by intestinal ischaemia/reperfusion in the rat

Reperfusion of ischaemic intestine is characterised by an initial hyperaemia with ensuing mucosal repair. This study investigated possible roles for gut vasoactive neuropeptides and trophic peptides in these phenomena. Groups of rats were monitored during superior mesenteric artery occlusion for five or 20 minutes, with or without subsequent reperfusion for five minutes. Peptide concentrations (fmol/ml) in arterial blood, were measured using specific radioimmunoassays. Intestinal ischaemia alone did not cause haemodynamic disturbance or peptide release. Reperfusion, after five minutes of ischaemia, resulted in arterial hypotension and a rise in plasma vasoactive intestinal polypeptide (mean (SEM)) (37 (3), control 11 (4), p < 0.001). After 20 minutes of ischaemia, reperfusion resulted in greater hypotension (p < 0.05) and release of both vasoactive intestinal polypeptide (31 (3), p < 0.05 v control) and the more potent vasodilator beta-calcitonin gene related peptide (49 (3), control 23 (1), p < 0.001). By contrast, the vasodilators alpha-calcitonin gene related peptide and substance P and the vasoconstrictors neuropeptide Y, peptide YY, and somatostatin were not released. Bombesin, a stimulatory neuropeptide, was released after 20 minutes of ischaemia/reperfusion (13 (2), control 7 (3), p < 0.05). Plasma enteroglucagon rose from control (51 (4)) to 110 (16) (p < 0.001) and to 158 (27) (p < 0.005) after five and 20 minutes of ischaemia/reperfusion. The potent enteric vasodilators vasoactive intestinal polypeptide and beta-calcitonin gene related peptide, unopposed by vasoconstrictors, may promote post-ischaemic intestinal hyperaemia. The rise in plasma enteroglucagon may point to diffuse mucosal injury and is consistent with the putative trophic role of this peptide.

Enteroglucagon, but not CCK, plays an important role in pancreatic hyperplasia after proximal small bowel resection

The present study was performed to examine the role played by pancreatotrophic factors, especially enteroglucagon and cholecystokinin (CCK), in the compensatory pancreatic hyperplasia observed after proximal small bowel resection (PSBR). Male Wistar rats were randomized into two groups, receiving either PSBR or transection (TRC). Five animals from each group were randomly selected for treatment with FK-480, a novel CCK antagonist. Four weeks after the operation, plasma levels of gastrin, CCK and enteroglucagon were measured. Pancreatic wet weight and protein, DNA, RNA and enzyme content were also determined. The wet weight and content of protein, DNA and RNA were significantly higher in PSBR rats than in TRC rats, regardless of whether they received FK-480. FK-480 had no suppressive effects on adaptive pancreatic growth after PSBR. Plasma enteroglucagon levels rose significantly in PSBR rats, and there were positive correlations between plasma enteroglucagon levels and pancreatic protein, DNA and RNA content. These findings demonstrated that plasma CCK was not the major trophic factor operating in the pancreas after PSBR, and showed that enteroglucagon plays an important role in the pancreatic hyperplasia that occurs after PSBR.

Enteroglucagon. A putative humoral factor inducing pancreatic hyperplasia after proximal small bowel resection

The present study evaluated pancreatotrophic factors after massive small bowel resection. Specifically, we examined the role of enteroglucagon in compensatory pancreatic hyperplasia after proximal small bowel resection (PSBR) by using rats fed a fiber-free elemental diet or an elemental diet containing pectin. PSBR increased the net pancreatic weight as well as the protein, DNA, RNA, and amylase contents, and elevated plasma enteroglucagon levels. Pectin addition to the diet provoked a further increase in these parameters and significant positive correlations were found between the plasma enteroglucagon levels and the protein, DNA, and RNA contents of the pancreas. Plasma gastrin and CCK levels were not affected by the small bowel resection. These results indicate that enteroglucagon may exert a potent trophic effect on the pancreas after PSBR.

Effect of ileal oleate on interdigestive intestinal motility of the dog

To determine the effect of ileal oleate on fasting intestinal motility, pairs of duodenal and ileal catheters and bipolar duodenal and jejunal seromuscular electrodes were surgically implanted in six dogs. The ileum was perfused with either normal saline (154 mM NaCl) or oleic acid emulsion (152 mM), while intestinal myoelectric activity was continuously monitored. For transit studies, a bolus of [3H]PEG was injected into the duodenum, and jejunal and ileal alliquots were collected every 15 min for a 6-hr study period. Plasma samples were collected for radioimmunoassays of peptide YY and enteroglucagon. Ileal oleate infusion increased the MMC cycle length and decreased the number of MMCs (P < 0.001) and the myoelectric spike-burst frequency/10 min in the duodenum (P < 0.05). Both duodenal-jejunal (P < 0.05) and duodenal-ileal transit (P < 0.01) were delayed markedly by ileal perfusion with oleic acid emulsion as compared to control studies. Ileal oleate increased plasma levels of peptide YY (P < 0.01) and enteroglucagon (P < 0.01). Ileal perfusion with oleate therefore activated the so-called "ileal brake," diminishing duodenal myoelectric spike bursts and slowing intestinal transit while concurrently increasing plasma levels of peptide YY and enteroglucagon.

Polyunsaturated fatty acids of the n - 3 series influence intestinal crypt cell production in rats

The effects of saturated and polyunsaturated dietary lipids on intestinal mucosal cell proliferation were investigated in rats. Animals were randomly allocated to three groups of 10, and fed fibre-free diets containing lipid in the form of lard, corn oil or fish oil at a level of 80 g/kg. Total energy intake was kept constant by pair-feeding. After 14 days the crypt cell production rates (CCPR) at two sites in the small intestine, one site in the caecum and two sites in the colon were determined by the metaphase arrest technique, together with circulating levels of enteroglucagon and gastrin and parameters of mucosal morphology. Consumption of fish oil led to lower CCPR compared to corn oil at all sampling positions except the caecum (Treatment approximately 50% of control values; P < 0.05). In animals fed lard the CCPR in the small bowel was not significantly different to that of animals fed corn oil but their rates were lower in the colon. Post-prandial enteroglucagon and gastrin levels were lower in animals fed fish oil compared to the other two groups. These results suggest that polyunsaturated fatty acids of the n - 3 series may support a relatively low rate of crypt cell proliferation in some regions of the alimentary tract and might thereby tend to suppress the progression of colorectal neoplasms.

Activity of oxyntomodulin on gastric acid secretion induced by histamine or a meal in the rat

Conscious rats with chronic gastric fistula were trained for drinking a 14-ml milk meal. The activity of an intestinal hormone, oxyntomodulin (OXM), was studied in this model and compared to that observed when histamine was the stimulus. Under histamine (0.25 mg.kg-1.h-1) stimulation, OXM at doses (60-120 pmol.kg-1.h-1) that induced physiological circulating levels inhibited gastric acid secretion up to 50%. Under meal stimulation, OXM reduced up to 29% acid secretion at doses (1-1.5 nmol.kg-1.h-1) inducing supraphysiological levels. We conclude that at physiological concentrations OXM cannot counteract the complex processes triggered by a meal. OXM would be a component of enterogastrone, a combination of several intestinal hormones acting in synergy. The OXM action is related to pathways recognizing the C-terminal 19-37 moiety of the molecule.

Plasma enteroglucagon levels in different models of intestinal resection in the rat

To assess the influence of the different intestinal segments on the plasma enteroglucagon level, three models of intestinal resection in the rat were studied (jejunal, ileal, 90%). The basal values for this peptide and those obtained after an infusion of intraduodenal glucose were compared. The results obtained in basal/post-glucose infusion were: 50% proximal (jejunum): 220/728 pg/ml; 50% distal (ileum): 10/233 pg/ml; and the middle 90%: 108/297 pg/ml. The glucose infusion produced a maximal response, permitting a better evaluation of the differences among the three resection models. The highest levels corresponded to the group in which the entire ileum was conserved.

Hormonal enteroinsular axis in newborn infants of insulin-treated diabetic mothers

To study whether the increased glucose levels in the amniotic fluid during diabetic pregnancies induce an early maturation of the hormonal enteroinsular axis, we measured blood glucose levels and plasma concentrations of C-peptide, pancreatic glucagon, enteroglucagon, and gastric inhibitory polypeptide (GIP) in cord blood from 18 newborn infants of insulin-treated diabetic mothers (IDM) and 18 infants of nondiabetic mothers. In addition, we studied the same parameters in 20 IDM and 12 control infants before and after their first feed comprising human milk (5 mL/kg), given by nasogastric tube at the age of 2 h. The IDM had significantly higher blood glucose levels and plasma C-peptide concentrations in their cord blood than the control infants, which was followed postnatally by a substantial fall in these levels, whereas a more modest decrease could be seen in the control infants. Circulating enteroglucagon and GIP concentrations at the age of 2 h were significantly higher than those observed in cord blood in both the IDM and the control infants, but the IDM had significantly lower blood glucose levels, higher plasma C-peptide, and lower enteroglucagon concentrations before the first feed. There was a significant increase in blood glucose levels after the feed in both the IDM and the control infants, and the concentrations 2 h after feeding were of the same magnitude in the two groups. No significant C-peptide response could be observed in either group, but the IDM continuously had higher C-peptide concentrations. A significant enteroglucagon and GIP response could be seen in the IDM, whereas the controls exhibited only a GIP response. However, no significant differences were found between the two groups in the absolute postprandial plasma concentrations of these hormones. Our results show rapid, substantial postnatal changes in circulating concentrations of enteroinsular hormones in both IDM and control infants. Enteral feeding with human milk corrects early postnatal hypoglycemia within 2 h in most IDM without causing any exacerbation of their hyperinsulinemia. The absence of any C-peptide response to the first feed and of any observed differences between IDM and normal infants in absolute concentrations of enteroglucagon and GIP after the first feed suggests that the enteroinsular axis matures postnatally in both groups of infants.

Diurnal profile of oxyntomodulin-like immunoreactivity in duodenal ulcer patients

Plasma concentrations of oxyntomodulin-like immunoreactivity, a group of intestinal peptides capable of mediating an enterogastrone signal, were measured during a 24-h period in 6 duodenal ulcer patients and compared with those of 16 age-matched controls. Each subject was submitted to 18 oxyntomodulin-like immunoreactivity determinations. Four standardized meals were given during the test. Furthermore, each patient was evaluated for peak acid output after pentagastrin stimulation. The values of the duodenal ulcer subjects were predominantly within normal acid secretion limits. Fasting levels, meal-induced variations, and nocturnal production of oxyntomodulin-like immunoreactivity were similar in the two groups. A negative correlation was observed between peak acid output and oxyntomodulin-like immunoreactivity evaluated either as nocturnal production or as maximum nyctohemeral concentration. We conclude that, taken as a whole, duodenal ulcer disease is not caused by a defect in oxyntomodulin-like immunoreactivity secretion. However, this study does not rule out the possibility of a selective deficiency of these peptides in some duodenal ulcer subgroups such as hypersecretory patients.

Fat-induced ileal brake in humans: a dose-dependent phenomenon correlated to the plasma levels of peptide YY

BACKGROUND

Upper gastrointestinal motility is regulated by the presence of nutrients in the distal gut. The present study evaluated whether lipid-induced ileal brake on gastric emptying (1) can be elicited by low fat concentrations; (2) is a dose-dependent phenomenon; and (3) is related to gastrointestinal peptide release.

METHODS

Seven patients were studied in the defunctionalized stage of total colectomy, on three separate occasions. On each study day, patients ate a meal labeled in the solid component; 30 minutes later, one of the following solutions was randomly infused into the ileal pouch: 0.9% saline, 2% oleic acid, and 20% oleic acid. Plasma concentrations of peptide YY (PYY), enteroglucagon, neurotensin, and motilin were measured.

RESULTS

Both oleic acid solutions slowed gastric emptying compared with saline (P < 0.001), the effect being dose dependent (P < 0.001). Ileal infusions did not modify neurotensin and enteroglucagon levels but induced a dose-dependent increase of PYY (P < 0.01) and a borderline decrease of motilin (P = 0.05) levels. Slower rates of gastric emptying were related to increased plasma concentrations of PYY (r = 0.615; P < 0.05).

CONCLUSIONS

This study shows that (1) the ileal brake on gastric emptying can be evoked by low doses of lipids in the distal ileum; (2) the delay of gastric emptying is related to the release of PYY; and (3) both phenomena are dose dependent.

Bile salt inhibition of motility in the isolated perfused rabbit terminal ileum

The effects of bile on small bowel motility were studied in isolated, perfused rabbit terminal ileum. It was proposed that bile delivery into the distal ileum would inhibit ileal motor activity, by peptide YY (PYY) release and therefore the effect of luminal bile on motor activity was examined and PYY release measured. Luminal bile and taurocheodeoxycholic acid (10 mmol) inhibited ileal motor activity. Arterial infusion of venous effluents from a bile inhibited ileum suppressed motor activity in a second isolated ileum. This shows the presence of a humoral inhibitor of ileal motor activity. Luminal bile increased venous PYY concentrations (42.5 (8.5) to 502 (46.2) pmol/l; p < 0.01) and increased bile salt values (1.7 (0.36) to 88.6 (5.6) 10 mumol/l/l; p < 0.005). Arterial infusion of taurocheodeoxycholic acid at concentrations found in the venous effluent (100 mumol/l/l) suppressed motility (p < 0.001) but infusion of PYY at concentrations in the venous effluent (500.0 pmol/l) failed to inhibit motility. Furthermore, PYY antagonist, PYX 1, failed to reverse the bile induced inhibition of motility. Luminal bile salts inhibit terminal ileal motility and this is independent of PYY release. By slowing motility, bile salts may participate in their own absorption by the 'ileal pump' and in the 'ileal brake' mechanism.

Pancreas and gut hormone responses to oral glucose and intravenous glucagon in cystic fibrosis patients with normal, impaired, and diabetic glucose tolerance

Pancreatic and gut hormone responses to oral glucose, and insulin sensitivity were studied in cystic fibrosis patients with normal (N = 14), impaired (N = 4), and diabetic (N = 12) glucose tolerance, and in 10 control subjects, and beta cell responses to oral glucose and intravenous glucagon were compared. Compared to control subjects, initial insulin and C-peptide responses to oral glucose were lower in all patient groups, and decreased with decreasing glucose tolerance. Insulin sensitivity in patients with impaired and diabetic glucose tolerance was lower than in control subjects. The 6 min post-glucagon C-peptide concentration was positively correlated with the initial insulin response to oral glucose. Fasting levels of pancreatic polypeptide, pancreatic glucagon, total glucagon, glucagon-like peptide-1 7-36 amide, and gastric inhibitory polypeptide were normal in all patient groups. Following oral glucose, pancreatic polypeptide responses were absent in all patients, suppressibility of pancreatic glucagon secretion was increasingly impaired with decreasing glucose tolerance, and gut hormone levels were normal. In conclusion, at cystic fibrosis (a) insulin secretion is impaired even when glucose tolerance and insulin sensitivity are within the normal range, (b) the glucagon test gives valid estimates of residual beta cell function, (c) pancreatic polypeptide response to oral glucose is absent, (d) glucagon suppressibility decreases with decreasing glucose tolerance, and (e) the enteroinsular axis is intact.

[Oxyntomodulin, a new hormonal marker of intestinal malabsorption syndromes]

Plasma oxyntomodulin-like immunoreactivity (OLI) concentrations were found to be significantly elevated in 6 patients with coeliac disease when compared with those observed in 38 healthy subjects. Furthermore, OLI hypersecretion is related to the degree of malabsorption. This marker could be used as a test for detection and follow-up of patients with malabsorptive disorders.

Dietary corn oil and guar gum stimulate intestinal crypt cell proliferation in rats by independent but potentially synergistic mechanisms

The effects of corn oil, guar gum and cellulose on mucosal proliferation were investigated in rats. Animals were allocated to three groups and fed a fiber-free diet or diets containing 100 g/kg of cellulose or guar gum. Each group was subdivided to receive corn oil at 40 or 80 g/kg. The crypt cell production rate (CCPR) was determined after 28 d. Consumption of guar gum or corn oil led to greater CCPR in the ileum and cecum. In a second experiment, animals were allocated to two groups and fed diets containing either cellulose or guar gum (100 g/kg). Each group was again subdivided to receive either corn oil (80 g/kg) or minimal lipid (linolenic acid, 10 g/kg). The trophic effect of guar gum occurred even in the low lipid-fed group, indicating that guar gum exerts a positive effect on cell turnover independently of any interaction with luminal lipid. However, the highest CCPR occurred in animals fed guar gum and corn oil. Postprandial enteroglucagon and gastrin concentrations were highest in animals fed both guar gum and corn oil. Thus, corn oil and guar gum exert independent trophic effects on the intestinal mucosa. The combination of effects led to a three- to four-fold increase in colon mucosal CCPR.

An experimental study on the gastric acid and gut hormone secretion after pylorus preserving duodenectomy in dogs

To clarify changes in gastric acid and gut hormone secretion after pylorus-preserving pancreaticoduodenectomy (PPPD), an experimental study was performed using a model of pylorus-preserving duodenectomy in dogs previously provided with Heidenhain pouch (HP). The duodenectomy involves resection of the duodenum and 10 cm of the proximal jejunum preserving 2 cm of juxtapyloric duodenum and round-shaped duodenal wall around pancreatic papilla. Reconstruction was done by anastomosing the rho-shaped jejunal loop to gallbladder, juxtapyloric duodenum and peripapillar round-shaped duodenal wall with ligation of the common bile duct. For these dogs, intravenous glucose tolerance test (IVGTT), oral glucose tolerance test (OGTT), meal ingestion test (TM) and histological studies of pancreatic specimen obtained at autopsy were performed investigating pancreatic, gastric acid and gut hormone secretion. Preservation of endocrine and exocrine pancreatic secretion after operation demonstrated our experimental model to be adequate for evaluation of the factor of duodenectomy in PPPD on gastric acid and gut hormone secretion avoiding the influences of changes in pancreatic secretion. Postprandial gastric acid secretion from HP did not change significantly after operation. Postprandial secretion of gastrin, glucagon, GIP and enteroglucagon did not alter significantly after operation. These results indicated that in the clinical PPPD procedure, preservation of more than 2 cm of duodenum from the pylorus produced neither postprandial gastric acid hypersecretion, which might be cause of postoperative stomal ulcer, nor any change of related gut hormone secretion.