Plasma secretin concentrations and gastric pH in healthy subjects and patients with digestive diseases

Pancreatic Enzyme Replacement Therapy in Patients with Non-pancreatic Digestive Conditions: A Nationwide Claims Analysis

BACKGROUND AND AIMS

Pancreatic enzyme replacement therapy (PERT) is most commonly used to treat exocrine insufficiency related to pancreatic diseases, but can be used for non-pancreatic digestive conditions (NPDC). We aimed to determine the prevalence of PERT use and describe prescription patterns in individuals with NPDC.

METHODS

A nationally representative claims database of 48.6 million enrollees was used to identify individuals who received PERT prescription(s) in the absence of any pancreas-related diagnosis. Data on demographics, enrolment, comorbidities, exocrine function testing, treatment and potential indications for PERT were retrieved, and compared with individuals who received PERT for primary diagnosis of chronic pancreatitis (CP).

RESULTS

A total of 29,234 individuals (64.1% female, mean age 52.4 ± 16.5 years) received PERT for NPDC. The overall estimated US population prevalence rate for PERT use for NDPC was 60.2/100,000 persons. Rates increased significantly with age and were higher in women in all age groups except 1-20 years old. When compared with CP, individuals with NPDC receiving PERT were more likely to be older (52.4 vs. 50.1 years), female (64.1% vs. 51.0%), have lower prevalence of alcoholism (3.6% vs. 25.0%), tobacco abuse (8.4% vs. 30.1%), and received PERT for shorter mean duration (5.3 vs. 8.2 months) (all p < 0.001). Median dose of PERT in individuals with NPDC was 2880 lipase units/day.

CONCLUSIONS

Although proportionally low, a sizable population receives PERT for NPDC. PERT for NPDC is usually prescribed at a low dose and for shorter duration, suggesting it is used mostly as a trial for or until resolution of symptoms.

Exploring the Effect of Esomeprazole on Gastric and Duodenal Fluid Volumes and Absorption of Ritonavir

Proton-pump inhibitors (PPIs), frequently prescribed to lower gastric acid secretion, often exert an effect on the absorption of co-medicated drug products. A previous study showed decreased plasma levels of the lipophilic drug ritonavir after co-administration with the PPI Nexium (40 mg esomeprazole), even though duodenal concentrations were not affected. The present study explored if a PPI-induced decrease in gastrointestinal (GI) fluid volume might contribute to the reduced absorption of ritonavir. In an exploratory cross-over study, five volunteers were given a Norvir tablet (100 mg ritonavir) orally, once without PPI pre-treatment and once after a three-day pre-treatment with the PPI esomeprazole. Blood samples were collected for eight hours to assess ritonavir absorption and magnetic resonance imaging (MRI) was used to determine the gastric and duodenal fluid volumes during the first three hours after administration of the tablet. The results confirmed that PPI intake reduced ritonavir plasma concentrations by 40%. The gastric residual volume and gastric fluid volume decreased by 41% and 44% respectively, while the duodenal fluid volume was reduced by 33%. These data suggest that the PPI esomeprazole lowers the available fluid volume for dissolution, which may limit the amount of ritonavir that can be absorbed. Although additional factors may play a role, the effect of PPI intake on the GI fluid volume should be considered when simulating the absorption of poorly soluble drugs like ritonavir in real-life conditions.

The physiological roles of secretin and its receptor

Secretin is secreted by S cells in the small intestine and affects the function of a number of organ systems. Secretin receptors (SR) are expressed in the basolateral domain of several cell types. In addition to regulating the secretion of a number of epithelia (e.g., in the pancreas and biliary epithelium in the liver), secretin exerts trophic effects in several cell types. In this article, we will provide a comprehensive review on the multiple roles of secretin and SR signaling in the regulation of epithelial functions in various organ systems with particular emphasis in the liver. We will discuss the role of secretin and its receptor in health and biliary disease pathogenesis. Finally, we propose future areas of research for the further evaluation of the secretin/secretin receptor axis in liver pathophysiology.

Anti-acid medication as a risk factor for food allergy

An important feature for oral allergens is their digestion-resistance during gastrointestinal transit. For some oral allergens, digestion stability is an innate feature, whereas digestion-labile antigens may only persist in times of impairment of the digestive system. In this review, we collect evidence from mouse and human studies that besides the inherent molecular characteristics of a food protein, the stomach function is decisive for the allergenic potential. Gastric acid levels determine the activation of gastric pepsin and also the release of pancreatic enzymes. When anti-ulcer drugs inhibit or neutralize gastric acid, they allow persistence of intact food allergens and protein-bound oral drugs with enhanced capacity to sensitize and elicit allergic reactions via the oral route. Mouse studies further suggest that maternal food allergy arising from co-application of a food protein with anti-acid drugs results in a Th2-biased immune response in the offspring. Especially, anti-ulcer drugs containing aluminum compounds act as Th2 adjuvants. Proton pump inhibitors act on proton secretion but also on expression of the morphogen Sonic hedgehog, which has been related to the development of atrophic gastritis. On the other hand, atrophic gastritis and resulting hypoacidity have previously been correlated with enhanced sensitization risk to food allergens in elderly patients. In summary, impairment of gastric function is a documented risk factor for sensitization against oral proteins and drugs.

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.

Duodenal acidification and secretin, but not intraduodenal fat, inhibit human gastric acid secretion via prostaglandins

BACKGROUND/AIMS

Acid and fat in the duodenum inhibit gastric acid secretion and increase plasma secretin. The role of prostaglandins and secretin in the inhibition of gastric acid secretion by duodenal infusion of hydrochloric acid and fat in healthy human volunteers was studied.

METHODS

Gastric acid secretion was submaximally stimulated with intravenous pentagastrin followed by duodenal infusion of 0.1N hydrochloric acid, oleic acid, or intravenous secretin. To inhibit endogenous prostaglandins, the protocol was then repeated after indomethacin treatment.

RESULTS

Duodenal fat infusion inhibited acid secretion 80% +/- 5% and was unaffected by indomethacin treatment. Intraduodenal acidification inhibited acid secretion by 43% +/- 8% and was reduced by indomethacin treatment to 15% +/- 4% (P < 0.01). Similarly, intravenous secretin inhibited acid secretion by 34% +/- 3%, which was decreased to 13% +/- 6% by indomethacin treatment (P < 0.01). The increase in plasma secretin levels after intraduodenal hydrochloric acid treatment was significantly greater than that observed with intravenous secretin or introduodenal oleic acid treatment; all were within the physiological range. Acid in the duodenum releases secretin, which inhibits gastric acid secretion at least in part via prostaglandins. In contrast, fat in the duodenum strongly inhibits gastric acid secretion via a nonprostaglandin pathway.

CONCLUSIONS

Secretin is the predominant mediator for the inhibition of human gastric acid secretion induced by the presence of acid, but not fat, in the duodenum.

Role of vasoactive intestinal polypeptide (VIP), secretin and gastrin in the genesis of the late exocrine pancreatic hypersecretion, food intake dependent in conscious dogs

Plasma levels of vasoactive intestinal polypeptide (VIP), secretin and gastrin were studied in four saphenous vein-catheterized dogs during the first 12 h after ingestion of a standard solid meal. Under these conditions we found significant postprandial increases in secretion only, which rose from a basal value of 219 +/- 27 pg/ml to 449 +/- 66 pg/ml 60 min postprandial (p < 0.001), and remained elevated until 4 h after food intake. However, no increase was seen from 8 to 12 h in any of the hormones studied, indicating that they are not directly involved in the enhancement of exocrine pancreatic secretion during this period.

Postprandial modifications of plasma secretin levels during pancreatic secretion in dogs

In dogs with a direct pancreatic fistula, a duodenal cannula and a catheter in a saphenous vein, plasma secretin levels, changes in the flow, bicarbonate and chloride concentrations of the exocrine pancreatic secretion as well as in the pH of intraduodenal content have been studied 12 hours after the ingestion of a standard diet. Under these conditions the pancreatic secretion showed a biphasic response with a maximum flow and bicarbonate concentration during the 0-4 and 8-12 h postprandial periods. This coincided with a marked decrease of pH in the intraduodenal content, with values close to 4.5. On the other hand, during the first postprandial hour, plasma secretin values increased from basal ones (218.66 +/- 27 pg/ml) to 448.94 +/- 66 pg/ml, remaining elevated for four hours after the meal ingestion. However, no increase occurred between 8-12 h when intraduodenal pH reached values below 4.5. This study indicated that: 1) plasma secretin levels increased significantly (P less than 0.05) after the ingestion of a standard solid diet, and 2) determinants liberating secretin were not only the presence of a duodenal pH below 4.5, but probably the presence of some macronutrients from the meal.

Plaunotol inhibits postprandial gastrin release by its unique secretin-releasing action in humans

Plaunotol, an acrylic diterpene alcohol, is a new antiulcer agent derived from the "plau-noi" plant and has been reported to stimulate the release of endogenous secretin in humans. We investigated the effect of plaunotol on postprandial gastrin release, comparing it to the effect of exogenous secretin in a physiological dose in eight healthy volunteers. Four sets of experiments were performed in each volunteer: (1) meal alone, (2) meal after intravenous ranitidine (50 mg), (3) meal after oral administration of plaunotol (320 mg) in addition to ranitidine, and (4) meal after ranitidine with simultaneous intravenous infusion of secretin (0.03 CU/kg/hr). The postprandial increase in plasma secretin concentration was significantly reduced by ranitidine, while postprandial gastrin release was markedly exaggerated. Plaunotol in combination with ranitidine significantly increased secretin release and inhibited gastrin release after a meal. Intravenous infusion of secretin resulted in significant suppression of postprandial gastrin release exaggerated by ranitidine. The present study indicates that plaunotol inhibits postprandial gastrin release by its unique secretin-releasing action.

Secretin is an enterogastrone in humans

We studied in humans the effect of exogenous secretin in a physiological dose on gastric acid secretion stimulated by pentagastrin and postprandial plasma gastrin concentration. Two doses of pentagastrin, 80 and 160 pmol/kg/hr were used to stimulate gastric acid secretion. Secretin in two doses, 2.8 and 5.6 pmol/kg/hr were tried to study the response on stimulated gastric acid secretion. Intravenous secretin in a dose of 5.6 pmol/kg/hr significantly inhibited the gastric acid output stimulated by intravenous pentagastrin in a dose of 160 pmol/kg/hr, from 11.25 +/- 1.5 to 5.99 +/- 1.34 meq/hr while lower dose of intravenous secretin (2.8 pmol/kg/hr) failed to inhibit the gastric acid output stimulated by the same dose of pentagastrin. However, the lower dose of intravenous secretin (2.8 pmol/kg/hr) inhibited the gastric acid output significantly from 8.78 +/- 1.21 to 6.37 +/- 1.62 meq/hr when gastric secretion was stimulated by the lower dose of pentagastrin (80 pmol/kg/hr). The plasma concentrations of secretin during intravenous secretin in a dose of 2.8 pmol/kg/hr was similar to postprandial plasma concentrations of secretin as previously reported. Doubling the dose of intravenous secretin resulted in almost twofold higher plasma concentrations than postprandial plasma concentrations. In addition, the low dose of secretin (2.8 pmol/kg/hr) suppressed the integrated postprandial gastrin response from 13.9 +/- 3.7 to 11.2 +/- 2.8 ng/min/ml (P = 0.05) when endogenous release of secretin was blocked by intravenous cimetidine. Since the dose of pentagastrin and secretin employed in this study fell in a physiologic range, the inhibitory effect of secretin on stimulated gastric acid secretion appears to be a physiologic action in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal aspects of the pathophysiology of human ulcer disease

In this paper, a peptic ulcer is considered from the perspective that it is representative of a heterogeneous group of multifactorial determined or influenced disorders having a common pathomorphologic expression. This heterogeneity involves pathophysiological attributes, including both functional (including secretory and motility events and their respective driving mechanisms) and morphologic alterations that relate to mucosal resistance. Patients with duodenal ulcer (DU) have been observed to exhibit alterations, in comparison to normal subjects, in the circadian rhythm characteristics of several gastrointestinal functions. Prominent among these are altered amplitudes of several circadian-organized gastric variables, such as intragastric pH, gastrin, pepsinogen and gastric mitotic index. With respect to any given variable, a reduced group amplitude (a measure of one-half the peak-trough difference of a 24-hr rhythm) could signify an increased dispersion of acrophases (the location of the peak of a circadian rhythm along the 24-hr time scale) reflecting interindividual variation in synchronization schedules, sleep-wake patterns, or chronobiologic alterations. A reduced interindividual amplitude further supports the concept of the heterogeneity of peptic disease. A decrease in the intraindividual amplitude of certain gastric rhythms implies an altered temporal pattern over the 24 hr. This is consistent with the hypothesis of a decrease in the amount of time available for recovery of a given function or set of integrated functions, and hence, increased susceptibility to mucosal injury. Normal high-amplitude variation in gastrointestinal functioning over the 24 hr appears to be required for natural restoration of the gut.

Release of cholecystokinin and exocrine pancreatic secretion in response to an elemental diet in human subjects

We investigated in human volunteers the effects of an elemental diet (ED) containing amino acids on release of endogenous cholecystokinin (CCK) using a highly sensitive and specific radioimmunoassay of CCK and exocrine pancreatic secretion using a dye dilution technique with polyethylene glycol 4000 as a nonabsorbable marker. Intrajejunal administration of ED at three different infusion rates (12.5, 25, and 50 ml/30 min) resulted in a significant increase in plasma CCK concentration in a dose-related manner. Plasma concentrations of gastrin or secretin, however, did not change. Pancreatic secretion of protein, amylase, and bicarbonate also increased significantly. The change in pancreatic secretion of protein, amylase, and bicarbonate output paralleled that of the circulating CCK level but not that of plasma secretin. Thus, the dose of amino acid contained in ED recommended for clinical use can significantly stimulate the release of CCK from the upper small intestine, raising the plasma concentration of CCK. This level can evoke a significant increase in exocrine pancreatic secretion.

The effect of cyclic nucleotides on secretin secretion in canine duodenal mucosa in vitro

We examined the effects of cyclic nucleotides and calcium on secretin release from canine duodenal mucosal explants incubated in organ culture media. Time course studies revealed that at pH 7.4, 5 and 10 mM dibutyryl cyclic adenosine monophosphate (DBcAMP) increased secretin release progressively, reaching a peak at 2 hours. Two mM of DBcAMP at pH 7.4 did not increase secretin release but at pH 4.5, all 3 doses potentiated secretin release. DBcAMP-stimulated secretin release was not dependent on the influx of extracellular calcium. Graded doses of 3-isobutyl-1-methylxanthine (IBMX) did not stimulate secretin secretion but 1 mM IBMX with 2 mM DBcAMP increased secretin secretion significantly. Dibutyryl cyclic guanosine monophosphate, cholera toxin and 5'-guanylyl-imidodiphosphate (GPP(NH)p) did not stimulate basal secretion release. The release of secretin from our explants incubated at pH 7.4 was not due to specific leakage because all of our viability studies revealed that our explants were functionally intact at the end of 2 hours. Our observations suggest that cyclic nucleotides may participate in the intracellular regulation of secretin secretion.

Neurohormonal regulation of secretin secretion in canine duodenal mucosa in vitro

We examined the effects of cholinergic, peptidergic and GABAergic agents on secretin secretion from canine duodenal mucosal explants incubated in organ culture media. Carbachol (10(-12) to 10(-4) M), atropine (10(-6) to 10(-4) M), hexamethonium (10(-6) to 10(-4) M), and somatostatin did not alter basal secretion of secretin. Somatostatin (10(-7) to 10(-8) M) inhibited secretin secretion stimulated by pH 4.5. Met, Leu and their D-ala2-analogs inhibited both basal and pH 4.5-stimulated secretin. Naloxone reversed the inhibition caused by met-enkephalin at pH 7.4. GABA (10(-9) to 10(-6) M) stimulated both basal and pH 4.5-stimulated secretin secretion. GABA-stimulated secretin secretion was neuronal in nature, bicuculline sensitive and was mediated via post ganglionic cholinergic neurons. GABA-stimulated secretin secretion was inhibited by both somatostatin and metenkephalin, suggesting that GABA-stimulated secretin secretion may be under the inhibitory control of peptidergic agents as well.

Plasma secretin in response to pure bile salts and endogenous bile in man

The effect of exogenous bile salts on plasma concentrations of secretin was studied by infusion of chenodeoxycholate, cholate, glycocholate, and taurocholate into the duodenum of normal subjects. The effect of endogenous bile on plasma secretin was studied by ingestion of a liquid test meal, by reinfusion of postprandial duodenal aspirates with known contents of bile salts, and by stimulation of gallbladder contraction by cholecystokinin. Each experiment was performed in groups of seven subjects. The relative secretin-releasing potencies of glycocholate, cholate, taurocholate and chenodeoxycholate (2.25 mmol) were 1.0:1.3:1.9:3.2. Hydrochloric acid (0.5 mmol) was, on a molar basis, approximately ten times more potent than sodium cholate. The effect of taurocholate was diminished when a liquid meal was used as vehicle instead of saline. Endogenous bile did, in no circumstance, elicit release of secretin. It is concluded that although bile salts have the ability to stimulate secretin release, endogenous secretin release is of minor, if any, importance for secretin release when physiological conditions are approached.

Role of endogenous secretin in acid-induced inhibition of human gastric function

The role of secretin in the inhibition of gastric acid secretion that occurs during acidification of the gastric lumen was studied in nine healthy men. Gastric acid secretion was stimulated by 500-ml meals of 8% peptone solution, and the pH of the stomach was maintained at 5.5, 2.5, or 2.0 by intragastric titration. The increase in plasma secretin was measured, after extraction, by a new secretin radioimmunoassay. After determining the intravenous dose of secretin required to reproduce plasma secretin concentrations achieved during pH 2.5 and 2.0 meals, similar doses were given during administration of a pH 5.5 peptone meal. The doses of secretin led to plasma secretin concentrations that averaged 3.4 pM, not different from the 3.2 and 3.9 pM concentrations achieved during acidified meals. However, exogenous secretin infusion failed to inhibit acid secretion or gastrin response to peptone, although significant inhibitions occurred in both during peptone meals given at pH 2.5 or 2.0. When secretin infusions were given at fivefold higher rates, plasma gastrin responses again failed to demonstrate significant inhibition. Gastric emptying was inhibited significantly by both acidified peptone meals but only slightly (P = 0.053) during exogenous infusion of physiologic secretin doses. The decrease in acid secretion could be explained by decreased gastrin release, but neither of these findings could be explained by circulating secretin concentrations. These results cast strong doubt on a physiological role of secretin in inhibition of acid secretion in man.

Plasma secretion and pancreatic secretion in response to liver extract meal with varied pH and exogenous secretin in the dog

1. In dogs with chronic gastric and pancreatic fistulas, a liver extract meal adjusted to various pH levels ranging from 7.0 to 2.0, was introduced into the stomach and the increments in plasma secretin levels were correlated with the pH of the liver extract meal and pancreatic bicarbonate outputs. 2. The pH threshold for both bicarbonate secretion and secretin release was found to be about 4.5. With a stepwise decrease in the pH of the meal below pH 4.5, there were stepwise increments in the plasma secretin concentrations and pancreatic bicarbonate outputs. 3. Exogenous secretin, given in graded doses ranging from 0.03 to 2.0 clinical unit/kg per hr, increased the plasma secretin concentrations and bicarbonate secretion in a dose-dependent fashion. 4. These results indicate that the pH threshold for release of endogenous secretin is 4.5 and suggests that, at pH levels below 4.5, pancreatic bicarbonate secretion depends upon the duodenal acid load and is linearly correlated to an increment in plasma secretin concentrations. 5. It is concluded that endogenous secretin is a major determinant of pancreatic bicarbonate secretion after a meal. 6. Pancreatic protein secretion by intragastric liver extract meal was greatly increased both in experiments with liver extract meal, pH 4.0 or below, and I.V. infusion of secretin at a dose of 0.12 u./kg per hr. It is questioned, however, whether this effect of secretin is physiological.