Gastric cytoprotection by intracisternal interleukin-1 beta in the rat

Stable Gastric Pentadecapeptide BPC 157 May Recover Brain-Gut Axis and Gut-Brain Axis Function

Conceptually, a wide beneficial effect, both peripherally and centrally, might have been essential for the harmony of brain-gut and gut-brain axes' function. Seen from the original viewpoint of the gut peptides' significance and brain relation, the favorable stable gastric pentadecapeptide BPC 157 evidence in the brain-gut and gut-brain axes' function might have been presented as a particular interconnected network. These were the behavioral findings (interaction with main systems, anxiolytic, anticonvulsive, antidepressant effect, counteracted catalepsy, and positive and negative schizophrenia symptoms models). Muscle healing and function recovery appeared as the therapeutic effects of BPC 157 on the various muscle disabilities of a multitude of causes, both peripheral and central. Heart failure was counteracted (including arrhythmias and thrombosis), and smooth muscle function recovered. These existed as a multimodal muscle axis impact on muscle function and healing as a function of the brain-gut axis and gut-brain axis as whole. Finally, encephalopathies, acting simultaneously in both the periphery and central nervous system, BPC 157 counteracted stomach and liver lesions and various encephalopathies in NSAIDs and insulin rats. BPC 157 therapy by rapidly activated collateral pathways counteracted the vascular and multiorgan failure concomitant to major vessel occlusion and, similar to noxious procedures, reversed initiated multicausal noxious circuit of the occlusion/occlusion-like syndrome. Severe intracranial (superior sagittal sinus) hypertension, portal and caval hypertensions, and aortal hypotension were attenuated/eliminated. Counteracted were the severe lesions in the brain, lungs, liver, kidney, and gastrointestinal tract. In particular, progressing thrombosis, both peripherally and centrally, and heart arrhythmias and infarction that would consistently occur were fully counteracted and/or almost annihilated. To conclude, we suggest further BPC 157 therapy applications.

Role of nucleotide binding oligomerization domain-like receptor protein 3 inflammasome in stress-induced gastric injury

BACKGROUND AND AIM

The inflammasomes promote pro-caspase-1 cleavage, leading to processing of pro-interleukin (IL)-1β into its mature form. We investigated the role of the IL-1β and nucleotide binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in gastric injury in mice receiving water-immersion restraint stress (WIRS), focusing on the cyclooxygenase (COX)-2/prostaglandin (PG) E₂ axis.

METHODS

To induce gastric injury, the mice were placed in a restraint cage and immersed in the water bath to the level of the xiphoid process. Protein levels of mature caspase-1 and IL-1β were assessed by western blotting.

RESULTS

Water-immersion restraint stress induced gastric injury with increase in IL-1β expression by activation of NLRP3 inflammasome. Exogenous IL-1β attenuated the injury, whereas anti-IL-1β neutralizing antibody and IL-1β receptor antibody aggravated it. NLRP3^-/- and caspase-1^-/- mice enhanced the injury with reducing of mature IL-1β, and this aggravation was reduced by exogenous IL-1β supplementation. Toll-like receptor 4^-/- mice were hyporesponsive to WIRS in terms of mature IL-1β production. Rabeprazole attenuated the injury with preventing inflammasome activation. WIRS injured the stomach with promotion of COX-2 mRNA and PGE₂ production, and exogenous IL-1β enhanced these molecules, while IL-1β immunoneutralization exerted opposite effect. PGE₂ supplementation abolished the hypersensitivity in NLRP3^-/- and caspase-1^-/- mice through negative regulation of inflammatory cytokines.

CONCLUSION

These results suggest that NLRP3 inflammasome-derived IL-1β plays a protective role in stress-induced gastric injury via activation of the COX-2/PGE₂ axis. Toll-like receptor 4 signaling and gastric acid may be involved in NLRP3 inflammasome activation.

Stable Gastric Pentadecapeptide BPC 157, Robert's Stomach Cytoprotection/Adaptive Cytoprotection/Organoprotection, and Selye's Stress Coping Response: Progress, Achievements, and the Future

We reviewed again the significance of the stable gastric pentadecapeptide BPC 157 as a likely mediator of Robert's stomach cytoprotection/adaptive cytoprotection and organoprotection and as novel mediator of Selye's stress coping response to reestablish homeostasis. Specific points of BPC 157 therapy and the original concept of Robert's cytoprotection/adaptive cytoprotection/organoprotection are discussed, including the beneficial effects of BPC 157. First, BPC 157 protects stomach cells and maintains gastric integrity against various noxious agents (Robert's killing cell by contact) and is continuously present in the gastric mucosa and gastric juice. Additionally, BPC 157 protects against the adverse effects of alcohol and nonsteroidal anti-inflammatory drugs on the gastric epithelium and other epithelia, that is, skin, liver, pancreas, heart (organoprotection), and brain, thereby suggesting its use in wound healing. Additionally, BPC 157 counteracts gastric endothelial injury that precedes and induces damage to the gastric epithelium and generalizes "gastric endothelial protection" to protection of the endothelium of other vessels (thrombosis, prolonged bleeding, and thrombocytopenia). BPC 157 also has an effect on blood vessels, resulting in vessel recruitment that circumvents vessel occlusion and the development of additional shunting and rapid bypass loops to rapidly reestablish the integrity of blood flow (ischemic/reperfusion colitis, duodenal lesions, cecal perforation, and inferior vena caval occlusion). Lastly, BPC 157 counteracts tumor cachexia, muscle wasting, and increases in pro-inflammatory/procachectic cytokines, such as interleukin-6 and tumor necrosis factor-α, and significantly corrects deranged muscle proliferation and myogenesis through changes in the expression of FoxO3a, p-AKT, p-mTOR, and p-GSK-3β (mitigating cancer cachexia).

Collagen Hydrolysis Products Reduce the Formation of Stress-Induced Ulcers by Regulating Stress-Associated Activation of the Neuroendocrine and Immune Systems

We studied the effect of collagen fragments (PGP and AcPGP) on serum content of epinephrine, corticosterone, and IL-1β in rats subjected to water-immersion stress. The degree of local inflammation accompanying ulceration was assessed by IL-1β production by ln. gastricus caudalis cells. In 1 h, the sharp increase in hormone concentrations in the blood of stressed animals reflected the high stress intensity. Intranasal administration of PGP reduced the area of stress-induced ulcers by 63%, prevented the increase in the levels of stress hormones and the main proinflammatory cytokine in rat blood. The concentrations of IL-1β in cell culture from regional lymph node of experimental animals returned to normal in 24 and 48 h after the stress. Acetylation of PGP prevents with gastroprotection, but does not abrogate other properties of the peptide.

No association between IL-1β -31 C/T polymorphism and the risk of duodenal ulcer: a meta-analysis of 3793 subjects

The aim of this study was to perform a meta-analysis to investigate a more authentic association between IL-1β -31 C/T polymorphism and duodenal ulcer (DU). Systematic searches of electronic databases Embase, PubMed and Web of Science were performed. Study selection, data abstraction and study quality evaluation were independently conducted in duplicate. Statistical analyses were conducted using software Stata 11.0. The pooled odds ratios (ORs) with 95% confidence intervals (95%CIs) were applied. Publication bias was tested by Begg's funnel plot and Egger's regression test. A total of 12 studies including 1151 cases and 2642 controls were included in our final meta-analysis. There was no evidence of significant association between IL-1β -31 C/T polymorphism and DU (allelic model: OR=0.96, 95%CI=0.86-1.07; additive model: OR=0.85, 95%CI=0.67-1.07; dominant model: OR=0.95, 95%CI=0.81-1.13; and recessive model: OR=0.95, 95%CI=0.79-1.15). Significant association was found in additive model for PB subgroup (OR=0.65, 95%CI=0.44-0.96) and recessive model for non-Asian subgroup (OR=0.72, 95%CI=0.52-0.99). In conclusion, our meta-analysis suggested that there was no evidence of significant association between IL-1β -31 C/T polymorphism and DU with or without Helicobacter pylori infection in overall population, whereas significant association was found by subgroup analyses which showed protective effect of C/C genotype against DU risk.

No association between IL-1β -511 C/T polymorphism and the risk of duodenal ulcer: a meta-analysis of 4667 subjects

Epidemiological studies have evaluated the association between IL-1β -511 C/T polymorphism and duodenal ulcer (DU) risk. However, the results remain conflicting. The aim of this study was to perform a meta-analysis to investigate a more authentic association between IL-1β -511 C/T polymorphism and DU. Systematic searches of electronic databases Embase, PubMed and Web of Science as well as hand searching of the references of identified articles and the meeting abstracts were performed. Study selection, data abstraction and study quality evaluation were independently conducted in duplicate. Statistical analyses were performed using software Stata 11.0. The pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were performed. Publication bias was tested by Begg's funnel plot and Egger's regression test. A total of 14 studies including 1887 cases and 2780 controls were included in our final meta-analysis. There was no evidence of significant association between IL-1β -511 C/T polymorphism and DU (for T allele vs. C allele: OR=0.93, 95% CI=0.82-1.06; for T/T vs. C/C: OR=0.83, 95% CI=0.64-1.08; for dominant model: OR=0.93, 95% CI=0.80-1.07; and for recessive model: OR=0.87, 95% CI=0.69-1.11). Significant association was found in all genetic models for the PB subgroup and sensitivity analyses. In conclusion, our meta-analysis suggests that there was no evidence of a significant association between IL-1β -511 C/T polymorphism and DU with or without Helicobacter pylori infection, whereas a significant association was found by sensitivity analyses which showed a protective effect of the T allele against DU risk.

Association between interleukin-1 gene polymorphisms and Helicobacter pylori infection in gastric carcinogenesis in a Chinese population

BACKGROUND AND AIM

Helicobacter pylori is a major cause of chronic gastritis and peptic ulcer disease and a definite carcinogen for gastric adenocarcinoma. However, the underlying pathogenic mechanisms are not fully understood. Interleukin-1 (IL-1) is a key cytokine involved in H. pylori-induced gastric inflammation. The present study aimed to determine polymorphisms of IL-1B and IL-1 receptor antagonist (IL-1RN) genes and their association with H. pylori infection and gastroduodenal diseases in Chinese patients.

METHODS

Three hundred and ninety-nine patients with gastroduodenal diseases (129 chronic gastritis, 127 duodenal ulcer and 143 non-cardiac gastric cancer) and 264 healthy controls were genotyped for IL-1B-511 and IL-1RN gene polymorphisms by the PCR-RFLP method. H. pylori infection status was determined by a validated serological test.

RESULTS

The frequency of IL-1B-511 T allele was significantly higher in H. pylori positive patients with non-cardiac gastric cancer than in both H. pylori negative patients with non-cardiac gastric cancer (60%vs 46%, P = 0.0342, OR = 1.666, 95% confidence interval [CI]: 1.045-2.656) and in healthy controls (60%vs 48%, P = 0.0071, OR = 1.665, 95%CI: 1.149-2.412). However, the polymorphism was not associated with chronic gastritis and duodenal ulcer. Multivariate logistic regression analyses identified that IL-1B-511 T/T carrier status was an independent risk factor for non-cardiac gastric cancer in the presence of H. pylori infection (adjusted OR = 3.01, 95%CI: 1.27-7.11, P = 0.01), and the frequency of IL-1B-511 T allele was an increased risk factor for developing gastric cancer (P = 0.03, adjusted OR = 2.29, 95%CI: 1.08-4.86). There was no association between IL-1RN gene polymorphisms and H. pylori infection and other gastroduodenal diseases.

CONCLUSION

IL-1B-511 T allele is associated with H. pylori infection in non-cardiac gastric cancer in a Chinese population. The IL-1B-511 gene polymorphism appears to play an important role in gastric carcinogenesis in Chinese patients with H. pylori infection.

Association of interleukin 1 gene family polymorphisms with duodenal ulcer disease

Cytokine genes taking part in the immunological response to Helicobacter pylori infection are good candidates to study for genetic predisposition to duodenal ulcer disease (DU). Among cytokines, interleukin (IL)-1beta and its natural specific inhibitor, the interleukin-1 receptor antagonist, are cytokines that play a key role in regulating gastric acid secretion and modulating the immune response in the gastrointestinal mucosa. We aimed to investigate whether polymorphisms in the IL-1B and IL-1RN genes are involved in the susceptibility to duodenal ulcer. DNA from 131 unrelated Spanish Caucasian patients with DU and 105 ethnically matched healthy controls was typed for the IL-1B-511, IL-1B-31, and IL-1B + 3954 gene polymorphisms, and the VNTR polymorphism in intron 2 of the IL-1RN gene by polymerase chain reaction (PCR)-based methods and TaqMan assays. H. pylori status and non-steroidal anti-inflammatory drugs (NSAIDs) use was determined in all patients and controls. Logistic regression analysis identified H. pylori infection (OR: 9.74; 95%CI = 3.53-26.89) and NSAIDs use (OR: 8.82; 95%CI = 3.51-22.17) as independent risk factors for DU. In addition, the simultaneous carriage of IL-1RN*2, IL-1B-511*C, IL-1B-31*T and IL-1B + 3954*C alleles was a genetic risk factor for DU in patients with H. pylori infection (OR: 3.22; 95%CI = 1.09-9.47). No significant differences in IL-1RN and IL-1B genotypes were found when patients were categorized according to gender, age of onset, smoking habit, NSAIDs use, type of complication and positive family history. Our results provide further evidence that host genetic factors play a key role in the pathogenesis of duodenal ulcer.

Use of animal models in peptic ulcer disease

Considerable progress has been made in the understanding of the formation of gastric erosions by the use of animals. The role of gastric acid secretion in their pathogenesis has been clarified. Gastric erosions are associated with the presence of acid in the stomach and slow gastric contractions. With several different experimental procedures, the animal's body temperature falls; preventing the fall averts erosions. A fall in body temperature or exposure to cold are associated with the secretion of thyrotropin-releasing hormone (TRH), and both increased and decreased concentration of corticotropin-releasing factor (CRH) in discrete regions of rat brains. Thyrotropin-releasing hormone when injected into specific sites in the brain produces gastric erosions and increases acid secretion and slow contractions, whereas CRH has the opposite effects. One of the major sites of interaction of the two peptides is in the dorsal motor complex of the vagus nerve. Thyrotropin-releasing hormone increases serotonin (5-HT) secretion into the stomach. Serotonin counter-regulates acid secretion and slow contractions. Many other peptides injected into discrete brain sites stimulate or inhibit gastric acid secretion.

Effects of IL-1 beta on neuronal activities in the dorsal motor nucleus of the vagus in rat brain slices

Effects of recombinant human interleukin-1 beta (IL-1 beta) on the neuronal activities in the rat dorsal motor nucleus of the vagus (DMV) were investigated by extra- and intracellular recordings in slice preparations. Twelve (52%) of 23 spontaneously firing neurons recorded extracellularly, 7 of which were electrophysiologically identified as vagal motoneurons, were inhibited by a bath application of IL-1 beta at a dose of either 5.8 x 10(-8) or 5.8 x 10(-8) M. The duration of the responses ranged widely from about 10 min to more than 2 h. Two (9%) of the 23 neurons were excited, whereas the remaining 9 (39%) were not affected by IL-1 beta. Of 42 DMV neurons recorded intracellularly, 19 (45%) showed a hyperpolarization following an application of 5.8 x 10(-8) M IL-1 beta, which still persisted in a TTX-containing solution. Two (5%) displayed depolarization and 21 (50%) were unaffected. The hyperpolarization in 16 of the 19 neurons (84%) ranged from -5 to -10 mV and lasted for more than 30 min without changing the input resistance. The IL-1 beta-induced hyperpolarization was completely blocked by concurrent perfusion with sodium salicylate. The remaining three neurons showed a short-lasting (5-14 min) hyperpolarization (ranging from -6 to -15 mV) with a decrease in the input resistance. These findings indicate that IL-1 beta mainly inhibits the vagal motoneurons in the DMV, at least partly through prostaglandin synthesis. This provides a mechanism that could account for the central action of IL-1 beta on visceral processes such as the inhibition of gastric acid secretion.

Interleukin 1 beta inhibits gastric emptying in rats: mediation through prostaglandin and corticotropin-releasing factor

BACKGROUND/AIMS

Interleukin 1 beta (IL-1 beta) increases the release of corticotropin-releasing factor (CRF) in the brain through prostaglandin pathways. Because central CRF inhibits gastric motor function, the influence and mechanism of action of intracisternal injection of IL-1 beta on gastric emptying were investigated.

METHODS

The 20-minute rate of gastric emptying of a nonnutrient test meal was assessed by the phenol red methylcellulose method 30 minutes after injection of human recombinant IL-1 beta in conscious rats.

RESULTS

IL-1 beta injected intracisternally (0.01-1 ng) or intravenously (0.01-10 ng) dose-dependently decreased gastric emptying by 10%-82% and 0%-89%, respectively. The median effective dose (ED50) was 30-fold lower when IL-1 beta was injected intracisternally (0.1 ng) than intravenously (3 ng). The inhibitory effect of intracisternal IL-1 beta had a rapid onset (within 20 minutes) and was long-lasting (6 hours). Indomethacin (5 mg/kg, intraperitoneally) completely prevented the 61% inhibition induced by intracisternal IL-1 beta (0.1 ng) but had no effect on CRF-induced (600 ng) 72% inhibition of gastric emptying. The intracisternal injection of the IL-1 receptor antagonist (100 ng) or the CRF antagonist [DPhe12, [DPhe12,Nle21,38,C alpha MeLeu37]CRF12-41 (20 micrograms) prevented by 100% and 52%, respectively, the inhibition of gastric emptying evoked by intracisternal IL-1 beta (0.1 ng). The antagonists alone had no effect on basal gastric emptying.

CONCLUSIONS

IL-1 beta acts in the brain to induce a long-lasting inhibition of gastric emptying; IL-1 beta action is mediated through central IL-1 receptors and prostaglandin- and CRF-dependent mechanisms.

Restraint stress in biomedical research: an update

Since the publication of our initial review of restraint stress in 1986, much work has continued with this technique, either as a tool for the investigation of other pharmacological, physiological, or pathologic phenomena or with restraint stress itself serving as the object of the study. As we noted in 1986, the major use of restraint has been for the induction of stress responses in animals and, more specifically, for the investigation of drug effects, particularly as they affect typical stress-related pathology--gastrointestinal, neuroendocrine, and immunological agents have been extensively studied. In compiling this update on restraint stress and its effects, we noted an increasing emphasis on central nervous system mechanisms in peripheral disease, especially gastrointestinal disease. In particular, many CNS-active agents have been tested for their effects on gastric and duodenal lesion formation and gastric secretion, including antidepressants, antipsychotics, anxiolytics, noradrenergic, serotonergic, dopaminergic, and peptidergic compounds. Some of these agents are especially active in the gastrointestinal tract even when administered centrally, further solidifying the concept of a brain-gut axis. The present update includes studies of: methods and procedures, pre-restraint manipulations, post-restraint/healing effects, and drug effects. In addition, a current bibliography of reports that have employed restraint is included.

The effect of interleukin 1 alpha on acetaminophen-induced hepatotoxicity

The protective effect of interleukin 1 alpha (IL-1 alpha) in mice with acetaminophen (AAP)-induced hepatitis was investigated. IL-1 alpha had a significant protective effect if given 2 or more hours (up to 24 hours) before AAP; it significantly reduced mortality of mice and decreased serum transaminase level. The maximal effect was obtained with the dose of 1000 U (166 ng/kg) IL-1 alpha. Pretreatment with IL-1 significantly increased the synthesis of prostaglandin E2 (PGE2) in samples of liver tissue from AAP-treated mice, but had no effect on the synthesis of leukotriene C4 (LTC4). Pretreatment with indomethacin (IMC) did not abrogate significantly the protective effect of IL-1. Thus, the hepatoprotective effect of IL-1 alpha can not be entirely explained by the stimulation of prostaglandin (PG) synthesis.

Potent inhibition of gastric acid secretion and ulcer formation by centrally and peripherally administered interleukin-1

IL-1 beta is one of the most potent centrally acting inhibitors of gastric acid secretion in rats. Sites of action have been located in the anterior/preoptic area and paraventricular nucleus of the hypothalamus where other biological activities of IL-1 have also been described. IL-1 beta action is, so far, quite unique to this cytokine and its action is not reproduced by IL-2 or TNF alpha. The IL-1 effect involves prostaglandin pathways and is unrelated to CRF. Similarly, systemic injection of IL-1 induces a long lasting inhibition of acid secretion through prostaglandin-dependent mechanisms. Several findings support the possibility that the effect of systemic IL-1 can be CNS-mediated and/or exerted at the periphery through local release of PG in the stomach. Exogenous IL-1 given into either the circulation or the cerebrospinal fluid also inhibits gastric injury induced by a variety of experimental models (stress, aspirin, ethanol). Such a protective effect is mediated through the inhibition of acid secretion and prostaglandin release, although other mechanisms may also contribute. Whether endogenously released IL-1 beta exerts a protective role in the gastric mucosa is still to be investigated.

Intraperitoneal administration of recombinant human interleukin-1 beta inhibits osmotic thirst in the rat

Decrease in water intake after intraperitoneal injection of interleukin-1 beta (IL-1 beta) was studied in the rat. Administration of IL-1 beta at a dose of 20 micrograms/kg attenuated osmotic thirst induced by intraperitoneal injection of hypertonic saline, but did not affect hypovolemic thirst induced by subcutaneous injection of either polyethylene glycol or angiotensin II. Interleukin-1 beta also decreased spontaneous intake of water but not that of 1.8% saline. The results suggest that the decrease in water intake by IL-1 beta is caused, at least in part, by suppression of osmotic thirst but not by general suppression of behavior. The effects of IL-1 beta were not secondary responses accompanied by feeding behavior, since food supply was removed during the experiments. Pretreatment with indomethacin blocked the decrease in water intake by IL-1 beta, suggesting the involvement of production of prostaglandins.

Central thyrotropin-releasing factor analog prevents ethanol-induced gastric damage through prostaglandins in rats

The effects of intracisternal injection of the stable thyrotropin-releasing factor (TRH) analog RX 77368 on gastric lesions induced by 60% ethanol and gastric prostaglandin E2 (PGE2) release were studied in rats. RX 77368 (1.0 and 1.5 ng) injected intracisternally inhibited (by 58% and 78%, respectively) macroscopic gastric damage induced by ethanol. Higher doses (3 and 300 ng) inhibited ethanol-induced gastric injury only in rats pretreated with omeprazole (20 mg/kg SC). Gastric acid output measured in conscious rats 2 hours after pylorus ligation was not modified by intracisternal injection of RX 77368 at 1.5 ng but was significantly increased by 54% at the 3-ng dose. The protective effect of TRH analog (1.5 ng) was completely abolished by indomethacin (5 mg/kg IP) and atropine (2 mg/kg SC) pretreatment. In pylorus-ligated rats, intracisternal RX 77368 (1.5 ng) inhibited ethanol-induced gastric lesions by 64%. Intracisternal injection of RX 77368 (1.5 ng) increased PGE2 levels measured in the effluent of dialysis fibers implanted into the corpus submucosa of urethane-anesthetized rats. Peripheral administration of omeprazole, atropine, indomethacin, or RX 77368 (1.5 ng IV) did not influence gastric damage induced by ethanol. These data show that the stable TRH analog, RX 77368, injected intracisternally at low non-secretory doses acts in the brain to protect against ethanol lesions through prostaglandin and cholinergic pathways. These findings suggest that central vagal activation induced by TRH may play a role in the control of mucosal integrity against ethanol through cholinergic prostaglandin release.

Potent inhibition of gastric acid secretion by intravenous interleukin-1 beta and -1 alpha in rats

The influence of human and rat recombinant interleukin-1 (hIL-1 beta and -1 alpha and rIL-1 beta) on acid secretion was investigated in conscious pylorus-ligated rats. Intravenous injection of either hIL-1 beta, hIL-1 alpha or rIL-1 beta dose dependently inhibited gastric acid output with an ED50 of 0.05 microgram, 0.5 microgram and 2.2 micrograms, respectively. The antisecretory action of IL-1 beta was associated with an increase in circulating levels of gastrin. hIL-1 beta-induced inhibition of acid secretion was dose dependently reversed by peripheral injection of the IL-1 receptor antagonist, IL-RA, with a dose ratio of 1:10(3) for complete reversal. The inhibitory effect of hIL-1 beta was blocked by indomethacin and was not modified by IV injections of the CRF receptor antagonist, alpha-helical CRF(9-41), or the monoclonal somatostatin antibody CURE.S6, or by systemic capsaicin pretreatment. These results show that systemic hIL-1 beta-induced inhibition of gastric acid secretion is mediated through IL-1 receptors and prostaglandin pathways, and does not involves CRF receptors, afferent fibers, or changes in circulating gastrin or somatostatin levels.