The renin-angiotensin system and its vasoactive metabolite angiotensin-(1-7) in the mechanism of the healing of preexisting gastric ulcers. The involvement of Mas receptors, nitric oxide, prostaglandins and proinflammatory cytokines.

The inhibition of angiotensin-converting enzyme (ACE) or the blockade of angiotensin (Ang) AT-1 receptors affords protection against acute gastric mucosal injury, but whether the major metabolite of renin-angiotensin system (RAS), Ang-(1-7), accelerates the healing process of preexisting gastric ulcers remains unknown. Previous studies documented that Ang-(1-7) acting via its own Mas receptor exerts vascular responses opposing those of Ang II. We studied the effects of the Ang-(1-7)/Mas receptor axis on the healing rate of acetic-acid-induced gastric ulcers with or without the blockade of Mas receptors by A 779 and compared it with the effects of activation and blockade of the AT-1 receptor by the treatment with Ang II and losartan, respectively, the inhibition of ACE by lisinopril, the NO/cNOS inhibition by L-NAME and inhibition of prostaglandin/COX system by indomethacin in the presence of Ang-(1-7). Additionally, ex vivo metabolism of Ang I in gastric tissue was assessed by LC/MS method. At day 9 after ulcer induction, the area of these ulcers and the accompanying changes in total gastric blood flow (GBF) were determined as were gastric mucosal blood flow (GMBF) at ulcer margin and gastric oxygen uptake (GVO2). The gastric mucosal expression of mRNAs for constitutive nitric oxide synthase (cNOS), superoxide dismutase (SOD), and pro-inflammatory cytokines interleukin 1ß (IL-1ß) and tumor necrosis factor alpha (TNF-α) and plasma level of both cytokines were determined by RT-PCR and ELISA. The 9 days treatment with Ang II dose-dependently increased the area of gastric ulcers and this effect was accompanied by a significant fall in the GBF, GVO2 and GMBF at ulcer margin. In contrast, treatment with Ang-(1-7) which produced a significant rise in the luminal content of NO significantly reduced the area of gastric ulcer and significantly increased the GBF, GVO2 and the GMBF at ulcer margin. Similar GMBF changes and significant reduction the area of gastric ulcer was observed in rats with gastric ulcers treated with the agonist of Mas receptor, AVE 0991. These effects of Ang-(1-7) and AVE 0991 were eliminated by blockade of the Mas receptor with A779. Similarly to Ang-(1-7), treatment with losartan or lisinopril significantly reduced the area of gastric ulcers and the accompanying increase in the GMBF at ulcer margin and these effects were significantly attenuated by a concomitant administration of L-NAME and indomethacin. The rate of healing of ulcers was associated with a decrease in ex vivo Ang-(1-7) formation and this effect was attenuated by lisinopril. The treatment with Ang-(1- 7) or AVE 0991 increased the expression of mRNA for cNOS and SOD and downregulated that of IL-1ß and TNF-α followed by the decrease in the plasma IL-1ß and TNF-α levels. We conclude that the Ang-(1-7)/Mas receptor system accelerates the healing of preexisting gastric ulcers via an increase in the gastric macro- and microcirculations, and an increase in gastric tissue oxygenation. These effects are mediated by PG and NO derived from overexpression of cNOS, an increase in the expression of antioxidizing enzyme SOD 2 and an anti-inflammatory action involving the inhibition of expression and release of pro-inflammatory cytokines IL-1ß and TNF-α. Our results seem to underlie the importance of the Ang-(1-7), AT-1 and Mas receptors in the regulation of local vascular and metabolic effects associated with mechanism of gastric ulcer healing.

Emerging role of fecal microbiota therapy in the treatment of gastrointestinal and extra-gastrointestinal diseases.

In the recent decade our understanding of the role of the human gut microbiome has been revolutionized by advances in development of molecular methods. Approximately, up to 100 trillion (10(14)) microorganisms per human body colonize the intestinal tract making an additional acquired organ that provides many vital functions to the host. A healthy gut microbiome can be defined by the presence of the various classes of microbes that enhance metabolism, resistance to infection and inflammation, prevention against cancer and autoimmunity and that positively influence so called braingut axis. Diet represents one of the most important driving forces that besides environmental and genetic factors, can define and influence the microbial composition of the gut. Aging process due to different changes in gut physiology (i.e. gastric hypochlorhydria, motility disorders, use of drugs, degenerative changes in enteric nervous system) has a profound effect on the composition, diversity and functional features of gut microbiota. A perturbed aged gut microbiome has been associated with the increasing number of gastrointestinal (e.g. Clostridium difficile infection - CDI) and non-gastrointestinal diseases (metabolic syndrome, diabetes mellitus, fatty liver disease, atherosclerosis etc.). Fecal microbiota transplantation (FMT) is a highly effective method in the treatment of refractory CDI. FMT is the term used when stool is taken from a healthy individual and instilled during endoscopy (colonoscopy or enteroscopy) into a gut of the sick person to cure certain disease. FMT represents an effective therapy in patient with recurrent CDI and the effectiveness of FMT in the prevention of CDI recurrence had reached approx. 90%. There is also an increasing evidence that the manipulation of gut microbiota by FMT represents a promising therapeutic method in patients with inflammatory bowel disease and irritable bowel syndrome. There is also an increased interest in the role of FMT for the treatment of metabolic syndrome and obesity which collectively present the greatest health challenge in the developed world nowadays. Targeting of gut microbiota by FMT represents an exciting new frontier in the prevention and management of gastrointestinal and non-gastrointestinal diseases that awaits further studies in preclinical and clinical settings.

Effects of treatment with melatonin and tryptophan on liver enzymes, parameters of fat metabolism and plasma levels of cytokines in patients with non-alcoholic fatty liver disease--14 months follow up.

Non-alcoholic fatty liver disease (NAFLD), most common chronic hepatic pathology, that occurs in the developed countries is estimated at 1/3 of the population. Amongst the numerous pathogenetic factors, oxidative stress and apoptosis of hepatocytes initiate many inflammatory processes and are involved in the progression of disease, particularly in transformation of non-alcoholic steatohepatitis (NASH) to cirrhosis. The aim of our study was to determine the effects of tryptophan and melatonin on the selected biochemical parameters in patients with NAFLD, and additionally, to evaluate the effects of tryptophan and melatonin in improvement of liver tissue in selected NAFLD patients. Seventy four patients with NAFLD confirmed by histopathological examination of liver biopsy samples, were admitted to the study. They were randomly assigned to three groups. Group I received the preparation Essentiale forte in the dose of 3 x 1 tablet per day and tryptophan 2 x 500 mg/day over the period of 14 months, group II received Essentiale forte and melatonin 2 x 5 mg/day over 14 months and group III received only Essentiale over the period of 14 months. In nine patients of groups I, II, and III, the liver biopsy was performed after 14-months of treatment period. Out of nine patients whom biopsy was performed, three of them were from group I, four from group II and two of them were from group III, respectively. After the 14-month treatment period, gamma-glutamyl transferase (GGPT) activity and levels of triglycerides and LDL-cholesterol were found to be significantly reduced in group I and II. The level of melatonin after the therapy was significantly elevated in group I and II and did not change in group III. Statistically significantly lower levels of IL-1, IL-6 and TNF-α were observed in patients receiving melatonin and tryptophan, comparing with group III treated with Essentiale forte only. These study findings demonstrate that melatonin and tryptophan substantially reduce the levels of pro-inflammatory cytokines and improve some parameters of fat metabolism in patients with NAFLD. In few patients with NASH melatonin and tryptophan reduced the inflammation in liver. We conclude that melatonin is worth considering for the therapy of NAFLD, particularly in patients with impaired fat metabolism accompanied by hypertriglyceridemia and hyper-LDL cholesterolemia.

Esophagoprotective activity of angiotensin-(1-7) in experimental model of acute reflux esophagitis. Evidence for the role of nitric oxide, sensory nerves, hypoxia-inducible factor-1alpha and proinflammatory cytokines.

Gastroesophageal reflux disease (GERD) is a global disease rapidly increasing among world population. The pathogenesis of reflux esophagitis which is considered as the early stage of GERD is complex, resulting from an imbalance between aggressive factors damaging the esophagus and a number of the natural defense mechanisms. The esophageal mucosa is in a state of continuous exposure to potentially damaging endogenous and exogenous factors. Important aggressive components of gastric refluxate include acid and pepsin and also pancreatic enzymes and bile. Among aggressive factors of exogenous origin, cigarette smoking, non-steroidal anti-inflammatory drugs (NSAID), and steroids are of the utmost importance. The basic level of esophageal defense against acid-pepsin damage consists of the anti-reflux mechanisms such as the luminal acid clearance and removal of the esophageal contents and neutralization of luminal acidity. In addition the esophageal mucosal protection includes the presence of pre-epithelial, epithelial and post-epithelial cellular and functional components. Recently, the progress have been made in the understanding of role of the heptapeptide member of the renin-angiotensin system (RAS), angiotensin-(1-7) (Ang-(1-7)) in the control of gastrointestinal functions. It has been shown that all components of local RAS including Ang-(1-7) are detectable in the gastrointestinal wall including not only the stomach but also the esophagus. Previous studies revealed that Ang-(1-7), which is an important component of the RAS, exerts vasodilatory, anti-inflammatory and antioxidant activities in the stomach. Ang-(1-7) was recently implicated in gastroprotection, but its effects on esophageal mucosa in a rodent model of reflux esophagitis and in human subjects presenting GERD symptoms have not been explored. The present study was aimed to evaluate the possible protective effects of Ang-(1-7) and Mas-receptors upon esophageal mucosal damage in acute reflux esophagitis (RE) induced in anesthetized rats by ligating the pylorus and the limiting ridge (a transitional region between the forestomach and the corpus of stomach). Consequently, the total gastric reservoir to store gastric juice was greatly diminished, resulting in the reflux of this juice into the esophagus. Because Mas receptors are functionally linked to nitric oxide (NO) formation, we also studied involvement of endogenous NO in the mediation of protective and circulatory effects of exogenous Ang-(1-7). Moreover, an attempt was made to assess the possible role of sensory neurons in the modulation of the protective effects exerted by Ang-(1-7)/Mas receptor system. Six series of rats were pretreated 30 min before induction of RE with 1) vehicle (saline), 2) Ang-(1-7) (5-50 µg/kg i.p.), 3) A779 (50 µg/kg i.p.), the selective Mas receptor antagonist applied alone, 4) Ang-(1-7) (50 µg/kg i.p.) combined with A779, 5) L-NNA (20 mg/kg i.p.) administered alone, and 6) Ang-(1-7) (50 µg/kg i.p.) combined with L-NNA. In separate group of rats, capsaicin (total dosage of 125 mg/kg within three days) was administered s.c. 2 weeks before the induction of RE to induce functional ablation of sensory nerves. Rats with intact sensory nerves and those with capsaicin-induced sensory denervation received vehicle (saline) or Ang-(1-7) (50 µg/kg i.p.) to determine whether this vasoactive metabolite of angiotensin I could be also effective in rats with capsaicin-induced impairment of the synthesis and release of sensory neuropeptides such as CGRP. Four hours after induction of RE, the mucosal damage was graded with mucosal lesion index (LI) from 0 to 6, the esophageal microcirculatory blood flow (EBF) was determined by H2-gas clearance technique and plasma level of pro-inflammatory cytokines interleukin-1b (IL-1ß), and tumor necrosis factor-α (TNF-α) was determined by ELISA. The expression of proinflammatory factors including COX-2, cytokine IL-1ß and hypoxia inducible factor 1alpha (Hif1α) was analyzed in the esophageal mucosal biopsies. In rats with RE, the esophageal LI was significantly elevated comparing its value observed in intact rats, and the EBF was significantly decreased as compared with intact mucosa. Pretreatment with Ang-(1-7) of control rats without esophagitis induced increase in EBF by about 25% without any macroscopic changes in the esophageal mucosa or in the plasma level of cytokines. In animals with RE, pretreatment with Ang-(1-7) significantly reduced gross and histological esophageal mucosal injury and significantly increased EBF in comparison to vehicle-pretreated animals. The observed gross and histologic esophagoprotective effect of Ang-(1-7) was totally abolished by A779 so in rats with combined treatment of A779 with Ang-(1-7), the LI was identical with this observed in control RE and the EBF was decreased in these animals by about 39%. Inhibition of NO synthase by L-NNA significantly reduced the LI and the rise in EBF caused by Ang-(1-7). Similarly, the capsaicin denervation also significantly attenuated the vasodilatory and the esophagoprotective effects of Ang-(1-7). The expression of proinflammatory factors COX-2, Hif1α and IL-1ß which was negligible in intact esophageal mucosa, was upregulated in esophageal mucosa of rats with RE. In contrast, the administration of Ang-(1-7) resulted in a downregulation of mRNA for COX-2, Hif1 and IL-1ß in esophageal mucosa an this effect was abolished in A779-dependent manner. The Ang-(1-7) significantly decreased the RE-induced elevation of plasma levels of IL-1ß and TNF-α, and this effect was also reversed by pretreatment with A779, and significantly attenuated by pretreatment with L-NNA and capsaicin-induced sensory denervation. The present study indicates that the protective effect of Ang-(1-7) observed in the esophageal mucosa during early acute stage of gastroesophageal reflux depends upon the enhancement of esophageal microcirculatory blood flow via the activation of Mas receptor possibly due to NO synthase/NO system activation, stimulation of sensory nerves, the inhibition of expression of pro-inflammatory factors including COX-2, Hif1α and IL-1ß and release of proinflammatory cytokines IL-1ß and TNF-α.

Expression and release of leptin and proinflammatory cytokines in patients with ulcerative colitis and infectious diarrhea.

Leptin plays not only an important role in regulation of food intake, but also in the mechanism of inflammation. The universal presence of leptin in the cells of immune system and its secretion by these cells caused increasing interest in the role of this hormone in ulcerative colitis (UC). We determined the role of leptin in 80 patients, aged from 18 to 69 years, including 50 patients with active UC and 30 patients with infectious diarrhea. The tests were performed within 48 hours of the first symptoms, in the period of remission of UC and 8 weeks after resolution of infectious diarrhea. Endoscopy was performed in each patient, and the biopsy samples were taken for the assessments of expression of mRNA for leptin, IL-1ß, IL-6 and TNF-α by RT-PCR and Western blot. Blood tests included concentrations of leptin, IL-1ß, IL-6 and TNF-α. In addition, the plasma levels of leptin, IL-1ß, IL-6 and TNF-α were assessed by ELISA. Serum concentrations of leptin was significantly increased in patients with exacerbation of UC over that in patients with UC in remission. The serum leptin concentration was significantly higher in patients with infectious diarrhea, than the patients that recovered from infectious diarrhea. The leptin protein was overexpressed in the biopsy samples of the mucosa of large intestine compared to those with exacerbation of UC, and in patients after successful recovery from infectious diarrhea. The leptin mRNA was overexpressed in patients with infectious diarrhea compared with that in the group of patients after successful recovery from this condition. Serum concentrations of leptin failed to correlate with severity of exacerbation of UC and with extent of intestinal inflammatory lesions in patients with UC. However, the correlation was observed between serum concentrations of leptin in patients with exacerbation of UC and serum concentrations of proinflammatory cytokines IL-1ß and TNF-α. We conclude that 1) the increased leptin in exacerbated UC is related to the increased serum proinflammatory cytokines IL-1ß, TNF-α and IL-6 levels; 2) In patients with infectious diarrhea, the concentrations of leptin in intestinal mucosa correlates with serum concentrations of cytokines IL-1ß, IL-6 and TNF-α and with an increased expression of leptin mRNA in intestinal mucosa but not with alterations in serum levels of this hormone; 3) leptin may serve as useful predictive marker of inflammation in inflammatory bowel disease (IBD).

Asymmetric dimethylarginine, an endogenous inhibitor of nitric oxide synthase, interacts with gastric oxidative metabolism and enhances stress-induced gastric lesions.

Asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of nitric oxide (NO) synthase known to exert vasoconstriction of vascular bed. The elevation of ADMA has been considered as the cardiovascular risk factor associated with hyperlipidemia, hypercholesterolemia and metabolic syndrome. ADMA is produced by the action of dimethylarginine dimethylaminohydrolase (DDAH), which hydrolyzes ADMA to L-citrulline and dimethylamine. Previous studies have shown that endogenous NO plays an important role in the mechanism of gastric mucosal defense, but the role of ADMA in the pathogenesis of serious clinical entity, such as the acute gastric mucosal injury induced by stress has been little studied. In present study, we determined the effect of intragastric (i.g.) pretreatment with ADMA applied in graded doses ranging from 0.1 up to 20 mg/kg on gastric mucosal lesions induced by 3.5 h of water immersion and restraint stress (WRS). The number of gastric lesions was determined by planimetry and the gastric blood flow (GBF) was assessed by laser Doppler technique. The malondialdehyde and 4-hydroxynonenal (MDA+4-HNE) concentration, as an index of oxygen radical-lipid peroxidation was assessed in the gastric mucosa in rats exposed to WRS with or without ADMA administration. Proinflammatory cytokines IL-1ß, TNF-α, superoxide dismutase (SOD) and glutathione peroxidase (GPx) mRNAs in the gastric mucosa and plasma levels of ADMA, IL-1ß and TNF-α were analyzed by RT-PCR and ELISA, respectively. The exposure of rats to WRS for 3.5 h produced acute gastric lesions accompanied by a significant rise in the plasma ADMA levels and a significant fall in the GBF, an increase in MDA+4-HNE concentrations and the significant increase in the expression and release of IL-1ß and TNF-α. The pretreatment with ADMA, applied i.g. 30 min before WRS dose-dependently, aggravated WRS damage and this effect was accompanied by a further significant fall in the GBF. The ADMA induced exacerbation of WRS lesions and the accompanying rise in the plasma ADMA levels and the fall in GBF were significantly attenuated by concurrent treatment with glyceryl trinitrate (GTN) (10 mg/kg i.g.) in the presence of ADMA. Administration of ADMA resulted in a significant decrease in the expression of SOD and GPx mRNAs and the up-regulation of mRNA for IL-1ß and TNF-α followed by an increase in these plasma cytokine levels as compared to respective values observed in vehicle-pretreated animals. We conclude that 1) ADMA could be implicated in the mechanism of WRS-induced ulcerogenesis, 2) ADMA exacerbates WRS-induced gastric lesions due to enhancement in neutrophil dependent lipid peroxidation and overexpression and release of proinflammatory cytokines IL-1ß and TNF-α and a potent depletion of antioxidative enzymes SOD and GPx expression and activity.

Interaction between selective cyclooxygenase inhibitors and capsaicin-sensitive afferent sensory nerves in pathogenesis of stress-induced gastric lesions. Role of oxidative stress.

Gastric microcirculation plays an important role in the maintenance of the mucosal gastric integrity and the mechanism of injury as well as providing protection to the gastric mucosa. Disturbances in the blood perfusion, through the microcapillaries within the gastric mucosa may result in the formation of mucosal damage. Acute gastric mucosal lesions constitute an important clinical problem. Originally, one of the essential component of maintaining the gastric mucosal integrity was the biosynthesis of prostaglandins (PGs), an issue that has captured the attention of numerous investigations. PGs form due to the activity of cyclooxygenase (COX), an enzyme which is divided into 2 isoforms: constitutive (COX-1) and inducible (COX-2) ones. The inhibition of COX-1 by SC-560, or COX-2 by rofecoxib, reduces gastric blood flow (GBF) and impairs gastric mucosal integrity. Another detrimental effect on the gastric mucosal barrier results from the ablation of sensory afferent nerves by neurotoxic doses of capsaicin. Functional ablation of the sensory afferent nerves by capsaicin attenuates GBF and also renders the gastric mucosa more susceptible to gastric mucosal damage induced by ethanol, aspirin and stress. However, the role of reactive oxygen species (ROS) in the interaction between COX specific inhibitors and afferent sensory nerves has not been extensively studied. The aim of our present study was to determine the participation of ROS in pathogenesis of stress-induced gastric lesions in rats administered with SC-560 or rofecoxib, with or without ablation of the sensory afferent nerves. ROS were estimated by measuring the gastric mucosal tissue level of MDA and 4-HNE, the products of lipid peroxidation by ROS as well as the SOD activity and reduced glutathione (GSH) levels, both considered to be scavengers of ROS. It was demonstrated that exposure to 3.5 h of WRS resulted in gastric lesions, causing a significant increase of MDA and 4-HNE in the gastric mucosa, accompanied by a decrease of SOD activity and mucosal GSH level. Pretreatment with COX-1 and COX-2 inhibitors (SC-560 and rofecoxib, respectively) aggravated the number of gastric lesions, decreased GBF, attenuated GSH level without further significant changes in MDA and 4-HNE tissue levels and SOD activity. Furthermore, the capsaicin--nactivation of sensory nerves resulted in exaggeration of gastric mucosal damage induced by WRS and this was further augmented by rofecoxib. We conclude that oxidative stress, as reflected by an increase of MDA and 4-HNE tissue concentrations (an index of lipid peroxidation), as well as decrease of SOD activity and the fall in GSH tissue level, may play an important role in the mechanism of interaction between the inhibition of COX activity and afferent sensory nerves releasing vasoactive neuropeptides. This is supported by the fact that the addition of specific COX-1 or COX-2 inhibitors to animals with capsaicin denervation led to exacerbation of gastric lesions, and further fall in the antioxidizing status of gastric mucosa exposed to stress.

The effects of long-term melatonin treatment on plasma liver enzymes levels and plasma concentrations of lipids and melatonin in patients with nonalcoholic steatohepatitis: a pilot study.

The present study represents the follow-up of our initial observations designed to investigate whether in patients with nonalcoholic steatohepatitis (NASH) the beneficial effect of 12-week course of melatonin (MT) on liver enzymes could be maintained with prolonged period of treatment and to analyze whether biochemical treatment responses could be sustainable after melatonin discontinuation. Forty two patients with histologically proven NASH (30 treated with melatonin 2x5 mg daily, 12 controls receiving placebo) enrolled to our previous 3-month study agreed to take part of subsequent 12 weeks treatment followed by 12-week follow-up period. Enrolled patients had biochemical determinations every six weeks during the melatonin treatment period and again after 12 weeks of follow-up. Significant reduction in median alanine aminotransferase (ALT) levels between baseline and week 18, week 24 and follow-up was observed in both MT-treated and control group: 43% and 31%, 42% and 33%, 32% and 31%. Aspartate aminotransferase (AST) and gamma-glutamyl transpeptidase (GGT) levels decrease significantly only in MT-treated group. In MT-treated group mean percentage change in AST level below baseline at week 18, at week 24 and at follow-up was 45%, 33% (p<0.05) and 8% (ns), respectively. The evolution of GGT levels was as follows: the mean percentage reduction in GGT below baseline level at week 18, 24 and follow-up was: 48%, 52% and 38% (p<0.05), respectively. In both MT-treated and control group plasma cholesterol, triglicerydes and glucose concentrations as well as plasma alkaline phosphatase persisted within normal values during the prolonged study period. Plasma concentration of melatonin (pg/ml) in MT-treated group averaged 7.5±3.5 at baseline and increased to 52.5±17.5 at 24th week. The results of our study demonstrating beneficial effect of melatonin on liver enzymes in patients with NASH would seem to encourage further controlled trials of melatonin given over a longer period of time with liver histology as end point.

Novel concept in the mechanism of injury and protection of gastric mucosa: role of renin-angiotensin system and active metabolites of angiotensin.

The term cytoprotection pioneered by Robert and colleagues has been introduced to describe the remarkable ability of endogenous and exogenous prostaglandins (PGs) to prevent acute gastric hemorrhagic lesions induced by noxious stimuli such as ethanol, bile acids, hiperosmolar solutions and nonsteroidal anti-inflammatory agents such as aspirin. Since that time many factors were implicated to possess gastroprotective properties such as growth factors including epidermal growth factor (EGF) and transforming factor alpha (TGFα), vasodilatory mediators such as nitric oxide (NO) and calcitonin gene related peptide (CGRP) as well as appetite gut hormones including gastrin and cholecystokinin (CCK), leptin and recently ghrelin. This protective action of gut peptides has been attributed to the release of PG but question remains whether another peptide angiotensin, the classic component of the systemic and local renin-angiotensin system (RAS) could be involved in the mechanism of gastric integrity and gastroprotection. After renin stimulation, the circulating angiotensin I is converted to angiotensin II (ANG II) by the activity of the Angiotensin Converting Enzyme (ACE). The ANG II acting via its binding to two major receptor subtypes the ANG type 1 (AT1) and type 2 (AT2) has been shown be activated during stress and to contribute to the pathogenesis of cold stress- and ischemia-reperfusion-induced gastric lesions. All bioactive angiotensin peptides can be generated not only in systemic circulation, but also locally in several tissues and organs. Recently the new functional components of RAS, such as Ang-(1-7), Ang IV, Ang-(1-12) and novel pathways ACE2 have been described suggesting the gastroprotective role for the novel ANG II metabolite, Ang-(1-7). The fact that Ang-(1-7) is produced in excessive amounts in the gastric mucosa of rodents and that pretreatment by Ang-(1-7) exhibits a potent gastroprotective activity against the gastric lesions induced by cold-restraint stress suggests that this and possibly other vasoactive metabolites of ANG II pathway could be involved in the mechanism of gastric integrity and gastroprotection. This review summarizes the novel gastroprotective factors and mechanisms associated with metabolic fate of systemic and local RAS activation with major focus to recent advancement in the angiotensin pathways in the gut integrity.

Effects of melatonin and tryptophan on healing of gastric and duodenal ulcers with Helicobacter pylori infection in humans.

Melatonin (MT) and its precursor L-tryptophan (TRP) are implicated in the protection of gastric mucosa against aspirin-induced lesions and in the acceleration of healing of idiopathic gastro-duodenal ulcers, but no information is available whether these agents are also effective in healing of gastroduodenal ulcers accompanied by Helicobacter pylori (H. pylori) infection. In this study three groups A, B and C, each including 7 H. pylori-positive patients with gastric ulcers and 7 H. pylori-positive patients with duodenal ulcers, aging 28-50 years, were randomly assigned for the treatment with omeprazole 20 mg twice daily combined with placebo (group A), MT administered in a dose of 5 mg twice daily (group B) or TRP applied in a dose of 250 mg twice daily (group C). All patients underwent routine endoscopy at day 0 during which the gastric mucosa was evaluated and gastric biopsies were taken for the presence of H. pylori and histopathological evaluation. The rate of ulcer healing was determined by gastroduodenoscopy at day 0, 7, 14 and 21 after the initiation of the therapy. Plasma MT, gastrin, ghrelin and leptin were measured by specific RIA. At day 21, all ulcers were healed in patients of groups B and C but only 3 out of 7 in group A of gastric ulcers and 3 out of 7 in duodenal ulcers. Initial plasma MT showed similar low levels in all three groups but it increased several folds above initial values in ulcer patients at day 7, 14 and 21. Plasma gastrin and leptin levels showed a significant rise over initial values in patients treated with omeprazole and placebo, MT or TRP while plasma ghrelin levels were not significantly affected by these treatments. We conclude that MT or TRP added to omeprazole treatment, significantly accelerates healing rate of H. pylori infected chronic gastroduodenal ulcers over that obtained with omeprazole alone and this likely depends upon the significant rise in plasma MT and possibly also in leptin levels, both hormones involved in the mechanism of gastroprotection and ulcer healing.

Effects of peripherally and centrally applied ghrelin in the pathogenesis of ischemia-reperfusion induced injury of the small intestine.

Ghrelin is an important hormone involved in the control of the human appetite center. Recently, protective properties of this hormone have been recognized in various models of impairment of the gastric mucosa, including stress, ischemia and reperfusion (I/R). Ghrelin is predominantly secreted by the gastric mucosa of stomach, but there are other sources of ghrelin, for example in the hypothalamus and various parts of the central nervous system (CNS) that should be taken into consideration. This hormone exerts biological effects via the activation of growth hormone secretagogue receptor (GHSR), the presence of which was confirmed in different parts of the gastrointestinal (GI) tract and midbrain structures. Although substantial evidence of the divergent biological effects of ghrelin and the mechanism of its action has been emphasized, the precise mechanisms of ghrelin which affords GI protection is still unclear. Particularly, there is a sparse amount of evidence concerning its action on the GI system. The major aim of the present study was to evaluate the importance of peripherally and centrally administered ghrelin at different times of the ischemia and reperfusion (I/R period in the modulation of resistance of the intestinal mucosa to the injury induced by ischemia and subsequent reperfusion. Secondly, we wanted to evaluate the possible mechanism of the action of ghrelin with a particular focus on its influence on the intestinal blood flow. Male Wistar rats were divided into 4 series (A-D) of the experimental groups (n=7). In series A the importance of peripherally administered ghrelin at different time of I/R period was studied. In series B the importance of centrally administered ghrelin at different time of I/R period was evaluated. In series C and D, the mechanisms of peripherally and centrally administered hormone were examined, respectively. Two models of the I/R period were selected: short lasting (30/60 min) and long lasting (60/120 min). The following drugs were used: ghrelin (50 µg/kg i.p. or 1 nmol in 10 µl i.c.v.), 6 hydroxy dopamine (50 mg/kg i.p.), nadolol (0.5 mg/kg i.p.), calcitonin gene related peptide fragment (CGRP(8-37), 100 µg /kg i.p.), capsaicin (5-10 mg/100 ml solution s.c.). The mesenteric blood flow (MBF-ml/min), the intestinal microcirculatory blood flow (LDBF-PU), the arterio-venous oxygen difference (AVO(2)-ml/O(2)/100 ml blood), and the intestinal oxygen uptake (VO(2)) in ml O(2)/min were measured. Mucosal impairment was assessed planimetrically with the use of a digital photo analyzer (LA) and histologically with the use of the six-point Park/Chiu scale. Peripheral administration of ghrelin evoked marked increase of MBF and LDBF by 42% and 48%, respectively, with significant reduction of LA by 38%. When ghrelin was administered at the beginning of the reperfusion period during the short I/R period or prior to the long lasting I/R period, the vascular reactions and protective effects were reduced, but not completely abolished. The central administration of ghrelin before the short I/R period significantly increased the MBF and LDBF by about 32% and 35%, respectively, as well as LA reduction by about 20% in comparison to the control group. However, when ghrelin was administered prior to the long I/R period or after the onset of completed ischemia, neither vascular nor protective effects were noticed. Sensory denervation and the blockade of the CGRP1 receptors totally blocked the protective and hyperemic effects of the peripherally administered ghrelin. Selective blockade of the adrenergic system or blunting of the vagal nerves (vagotomy) significantly but not totally eliminated the effects of centrally applied ghrelin, which were abolished when both adrenergic and parasympathetic pathways were ablated. These results indicate that ghrelin applied centrally or peripherally markedly increases resistance of the intestinal tissue during the I/R period induced mucosal and hyperemic impairment evoked by I/R. Ghrelin is an important mediator of the increase in the intestinal microcirculation and elevation of the intestinal metabolism, which seems to be, at least in part, responsible for the observed protection of the intestine subjected to I/R. Impairment of this microvasculature response due to I/R seems to be responsible for a markedly observed weaker effect of ghrelin when this hormone was administered after the ischemic period. The lack of a protective effect observed after central administration of this peptide against a long lasting I/R period is probably due to damage of neural pathways caused by I/R. Finally, the peripheral activity of ghrelin in the intestine is mediated by the sensory neurons with a prominent role of CGRP released from their endings. However, this peripheral action of ghrelin depends upon the proper functioning of both the sympathetic and parasympathetic system.

The photoperiod, circadian regulation and chronodisruption: the requisite interplay between the suprachiasmatic nuclei and the pineal and gut melatonin.

The current scientific literature is replete with investigations providing information on the molecular mechanisms governing the regulation of circadian rhythms by neurons in the suprachiasmatic nucleus (SCN), the master circadian generator. Virtually every function in an organism changes in a highly regular manner during every 24-hour period. These rhythms are believed to be a consequence of the SCN, via neural and humoral means, regulating the intrinsic clocks that perhaps all cells in organisms possess. These rhythms optimize the functions of cells and thereby prevent or lower the incidence of pathologies. Since these cyclic events are essential for improved cellular physiology, it is imperative that the SCN provide the peripheral cellular oscillators with the appropriate time cues. Inasmuch as the 24-hour light:dark cycle is a primary input to the central circadian clock, it is obvious that disturbances in the photoperiodic environment, e.g., light exposure at night, would cause disruption in the function of the SCN which would then pass this inappropriate information to cells in the periphery. One circadian rhythm that transfers time of day information to the organism is the melatonin cycle which is always at low levels in the blood during the day and at high levels during darkness. With light exposure at night the amount of melatonin produced is compromised and this important rhythm is disturbed. Another important source of melatonin is the gastrointestinal tract (GIT) that also influences the circulating melatonin is the generation of this hormone by the entero-endocrine (EE) cells in the gut following ingestion of tryptophan-containing meal. The consequences of the altered melatonin cycle with the chronodisruption as well as the alterations of GIT melatonin that have been linked to a variety of pathologies, including those of the gastrointestinal tract.

Antibiotic treatment with ampicillin accelerates the healing of colonic damage impaired by aspirin and coxib in the experimental colitis. Importance of intestinal bacteria, colonic microcirculation and proinflammatory cytokines.

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for their anti-inflammatory, analgesic and antipyretic effects, however their use is associated with the broad spectrum of side effects observed in human as well as the experimental animals. Despite damaging activity of NSAIDs in upper gastrointestinal (GI) tract, these drugs exert deleterious influence in lower GI tract, including colon. The role of GI microflora in the pathogenesis of NSAIDs-induced experimental colonic damage is not completely understood. The aim of this study was 1) to evaluate the relative importance of the GI microflora on the experimental colonic damage in the presence of caused by NSAID, and 2) to assess the efficacy of antibiotic treatment with ampicillin on the process of healing of colitis. We compared the effect of vehicle, ASA applied 40 mg/kg intragastrically (i.g.) or the selective cyclooxygenase (COX)-2 inhibitor, celecoxib (25 mg/kg i.g.) without or with ampicillin treatment (800 mg/kg i.g.) administered throughout the period of 10 days, on the intensity of TNBS-induced colitis in rats. The severity of colonic damage, the alterations in the colonic blood flow (CBF) and myeloperoxidase (MPO) activity, the mucosal expression of TNF-α, IL-1ß, COX-2, VEGF and iNOS and the plasma concentration of TNF-α and IL-1ß were assessed. In all rats, the faeces samples as well as those from the colonic mucosa, blood, liver and spleen underwent microbiological evaluation for intestinal bacterial species including Escherichia coli and Enterococcus spp. The administration of TNBS resulted in macroscopic and microscopic lesions accompanied by the significant fall in the CBF, an increase in tissue weight and 4-5-fold rise in the MPO activity and a significant increase in the plasma IL-1ß and TNF-α levels. ASA or celecoxib significantly increased the area of colonic lesions, enhanced MPO activity and caused the marked increase in colonic tissue weight and plasma IL-1ß and TNF-α levels, as well as an overexpression of mRNA for IL-1ß and TNF-α, COX-2, VEGF and iNOS in the colonic tissue. ASA and coxib also resulted also in a significant increase of E. coli counts in the stool at day 3 and day 10 day of the observation compared with the intact rats. Moreover, E. coli translocation from the colon to the blood and extraintestinal organs such as liver and spleen in the group of rats treated without or with ASA and coxib. E. coli was the most common bacteria isolated from these organs. Treatment with ampicillin significantly attenuated the ASA- or celecoxib-induced increase in plasma levels of IL-1ß and TNF-α and suppressed the mucosal mRNA expression for IL-1ß and TNF-ß, COX-2, iNOS and VEGF in the colonic mucosa. Ampicillin administration caused a significant fall in the number of E. coli in the faeces at day 3 and day 10 of observation in ASA- and coxib-treated rats with colitis. Antibiotic therapy markedly reduced bacterial translocation to the colonic tissue and the extraintestinal organs such as the liver and spleen. We conclude that administration of ASA and to lesser extent of celecoxib, delays the healing of experimental colitis and enhances the alterations in colonic blood flow, proinflammatory markers such as IL-1ß, TNF-α, COX-2, iNOS and VEGF and increased intestinal mucosal permeability resulting in the intestinal bacterial translocation to the blood, spleen and liver. Antibiotic treatment with ampicillin is effective in the diminishing of the severity of colonic damage, counteracts both the NSAID-induced fall in colonic microcirculation and bacterial E.coli translocation to the extraintestinal organs.

Gut clock: implication of circadian rhythms in the gastrointestinal tract.

Circadian and seasonal rhythms are a fundamental feature of all living organisms and their organelles. Biological rhythms are responsible for daily food intake; the period of hunger and satiety is controlled by the central pacemaker, which resides in the suprachiasmatic nucleus (SCN) of the hypothalamus, and communicates with tissues via bidirectional neuronal and humoral pathways. The molecular basis for circadian timing in the gastrointestinal tract (GIT) involves interlocking transcriptional/translational feedback loops which culminate in the rhythmic expression and activity of a set of clock genes and related hormones. Interestingly, it has been found that clocks in the GIT are responsible for the periodic activity (PA) of its various segments and transit along the GIT; they are localized in special interstitial cells, with unstable membrane potentials located between the longitudinal and circular muscle layers. The rhythm of slow waves is controlled in various segments of the GIT: in the stomach (about 3 cycles per min), in the duodenum (12 cycle per min), in the jejunum and ileum (from 7 to 10 cycles per min), and in the colon (12 cycles per min). The migrating motor complex (MMC) starts in the stomach and moves along the gut causing peristaltic contractions when the electrical activity spikes are superimposed on the slow waves. GIT hormones, such as motilin and ghrelin, are involved in the generation of MMCs, while others (gastrin, ghrelin, cholecystokinin, serotonin) are involved in the generation of spikes upon the slow waves, resulting in peristaltic or segmental contractions in the small (duodenum, jejunum ileum) and large bowel (colon). Additionally, melatonin, produced by neuro-endocrine cells of the GIT mucosa, plays an important role in the internal biological clock, related to food intake (hunger and satiety) and the myoelectric rhythm (produced primarily by the pineal gland during the dark period of the light-dark cycle). This appears to be an endocrine encoding of the environmental light-dark cycle, conveying photic information which is used by organisms for both circadian and seasonal organization. Motor and secretory activity, as well as the rhythm of cell proliferation in the GIT and liver, are subject to many circadian rhythms, mediated by autonomic cells and some enterohormones (gastrin, ghrelin and somatostatin). Disruption of circadian physiology, due to sleep disturbance or shift work, may result in various gastrointestinal diseases, such as irritable bowel syndrome (IBS), gastroesophageal reflux disease (GERD) or peptic ulcer disease. In addition, circadian disruption accelerates aging, and promotes tumorigenesis in the liver and GIT. Identification of the molecular basis and role of melatonin in the regulation of circadian rhythm allows researchers and clinicians to approach gastrointestinal diseases from a chronobiological perspective. Clinical studies have demonstrated that the administration of melatonin improves symptoms in patients with IBS and GERD. Moreover, our own studies indicate that melatonin significantly protects gastrointestinal mucosa, and has strong protective effects on the liver in patients with non-alcoholic steatohepatitis (NASH). Recently, it has been postulated that disruption of circadian regulation may lead to obesity by shifting food intake schedules. Future research should focus on the role of clock genes in the pathophysiology of the GIT and liver.

Professor Jerzy Kaulbersz, pioneer of Polish gastroenterology.

Jerzy Kaulbersz was undoubtedly the father of experimental gastroenterological physiology in Poland. He pioneered the neural and endocrine aspects of the mechanisms controlling gastric and pancreatic secretion by assessing the influence on this secretion of vagal nerves and endocrine factors such as gastrin, enterogastrone, urogastrone, pituitary, adrenal, thyroid and sex hormones as well as bile, hypoxia and X-ray irradiation. He introduced various models of peptic ulcerations such as induced by pylorus-ligation (Shay ulcers) or Mann-Williamson ulcers to test the influence of neuroendocrine factors on the formation and healing of these ulcerations. This review is designed to commemorate the outstanding contribution to experimental gastroenterology of Professor Kaulbersz, who first studied biology in German universities to obtain the title of Doctor of Natural Philosophy (Ph.D.) in Freiburg in 1913 and then completed medical studies at the Medical Faculty of the Jagiellonian University in Cracow receiving the title of Doctor of Universal Medicine (MD) in 1920. He then joined Department of Physiology of Jagiellonian University in Krakow as its assistant and gradually was appointed docent and finally promoted to professor in this Department, working here as chairman from 1934 to 1964 with only 7 years interruption when he spent the time of World War II in USA, working at various departments of experimental gastroenterology and publishing his outstanding papers in most prestigious physiology ournals such as American Journal of Physiology. He possessed comprehensive knowledge of physiology and was gifted to create and organize Cracow Department of Physiology. Moreover he became co-founder of the of Polish Physiological Society, the honorary member of American Physiological Association, honorary member of Polish Society of Gastroenterology and Physiology and received the diploma of Doctor Honoris Causa of Medical Academy in Cracow. This ad memoriam note commemorates his achievements at one hundred twenty anniversary of Prof. Kaulbersz birth with intention to bring his fundamental discoveries to younger physiologists and pharmacologists.

Melatonin and aging: prospects for human treatment.

Human life span, with or without modern medicine is around 85-95 years. All living creatures have their inner clock that measures their daily (circadian) and their seasonal (circannual) time. These time changes are mediated by the alteration of levels of melatonin, an evolutionary ancient hormone, which is produced in many body tissues, including the pineal gland, retina and the gastrointestinal tract (GIT). Light is blocking the production of melatonin in the pineal gland, darkness is stimulating it. So, the diurnal changes of light intensity of melatonin, provide a "daily clock" and the seasonal changes provide a "seasonal clock". Finally, the reduction of melatonin observed with aging, may indicate the presence of an "age clock". Melatonin is a strong antioxidant (often it is called scavenger of free radicals), which protects the body from the effects of noxious compounds. Therefore it was hypothesized that the reduction of melatonin levels with age contributes to the aging process. So far, the only remedy to extend the life span was a 40% reduction in caloric intake, which prolonged the life in mice, rats, dogs and monkeys by 30-50%. A large group of people imitate these experiments performed on animals, but the results of these experiments will not be known for several decades. How is being hungry prolonging the life span? There is a connection between caloric reduction and melatonin levels in GIT. Several experiments indicate that fasting in animals substantially increased their production of GIT melatonin. Therefore, instead of being permanently hungry, a prolongation of human life could be achieved by a replacement melatonin therapy. A daily intake of melatonin before bed time might achieve the same effect as fasting e.g. an increase of body melatonin levels, which will protect the individual from the ravages of old age. That includes Parkinson's disease and Alzheimer's disease. There is a large group of people taking melatonin daily who believe that melatonin is the "fountain of youth". Those are the subjects which will one day provide an experimental evidence of the efficacy of melatonin.

Nitric oxide (NO)-releasing aspirin exhibits a potent esophagoprotection in experimental model of acute reflux esophagitis. Role of nitric oxide and proinflammatory cytokines.

The purpose of this study was to develop an acute animal model of reflux esophagitis, which would be suitable to induce the esophageal damage caused by gastric acid reflux, thus mimicking the esophageal injury of human gastroesophageal reflux disease (GERD). Global research indicates that GERD is rapidly increasing among the world's population. NSAIDs are known to induce gastrointestinal damage and low doses of aspirin (ASA) have been shown to increase the incidences of GERD in humans. Gastric acid and pepsin secretion and enhanced COX-2 expression were implicated in the pathogenesis of reflux esophagitis, but the effect of selective COX-2 inhibitors against lesions induced by the reflux of gastric acid content into esophagus has not been thoroughly studied. Here, we compared the effect of aspirin (ASA) and so called "safe" nitric oxide (NO) derivative of ASA with those of non-selective and selective cyclooxygenase (COX)-1 and COX-2 in rat model of reflux esophagitis. Reflux esophagitis was induced in anesthetized rats by ligating the pylorus and limiting ridge transitional region between the forestomach and the corpus of stomach. Subsequently, the total gastric reservoir to store gastric juice was greatly diminished, resulting in the reflux of this juice into the esophagus. Rats with esophagitis received intragastric (i.g.) pretreatment either with: 1) vehicle (saline), 2) ASA or NO-ASA (100 mg/kg); 3) the non-selective COX inhibitor, indomethacin (5 mg/kg); 4) the selective COX-1 inhibitor, SC-560 (10 mg/kg), and 5) the selective COX-2 inhibitor, celecoxib (5 mg/kg). In a separate series of rats with reflux oesophagitis, the efficacy of ASA combined with a donor of NO, glyceryl trinitrate (GTN; 10 mg/kg i.g.) to prevent esophageal mucosal injury was investigated. Four hours after induction of esophagitis the gross mucosal damage was graded with a macroscopic lesion index (LI) from 0-6. The esophageal blood flow (EBF) was determined by H2-gas clearance technique, the oesophageal mucosal and blood samples were collected for histology and analysis of the RT-PCR expression and release of proinflammatory cytokines IL-1ß, TNF-α and IL-6 using specific ELISA. The exposure of the esophagus to reflux of gastric acid time-dependently increased the esophageal LI and morphologic damage, and decreased EBF with the most significant changes observed at 4 hrs after the ligation procedure. The pretreatment with native ASA in the dose that suppressed the generation of mucosal PGE2, enhanced gross and histologic esophageal damage and produced a significant fall in EBF. NO-ASA or ASA coupled with GTN counteracted the aggravation of the damage and accompanying fall in EBF when compared with native ASA applied alone to rats with esophagitis. The proinflammatory cytokines IL-1ß and TNF-α were overexpressed in rats with esophagitis and those pretreated with ASA but this effect was significantly attenuated by NO-ASA. Plasma IL-1ß, TNF-α and IL-6 were negligible in the intact rats but significantly increased in those with esophagitis, with this effect being further enhanced by non-selective (indomethacin) and selective (SC-560, celecoxib) COX-1 and COX-2 inhibitors. We conclude that conventional NSAID such as aspirin augments esophagitis, while NO-ASA exerts the beneficial protective effect against reflux esophagitis via the enhancement of esophageal microcirculation due to NO release and an inhibitory effect on expression and release of pro-inflammatory cytokines.

Stress and the gut: pathophysiology, clinical consequences, diagnostic approach and treatment options.

Stress, which is defined as an acute threat to homeostasis, shows both short- and long-term effects on the functions of the gastrointestinal tract. Exposure to stress results in alterations of the brain-gut interactions ("brain-gut axis") ultimately leading to the development of a broad array of gastrointestinal disorders including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and other functional gastrointestinal diseases, food antigen-related adverse responses, peptic ulcer and gastroesophageal reflux disease (GERD). The major effects of stress on gut physiology include: 1) alterations in gastrointestinal motility; 2) increase in visceral perception; 3) changes in gastrointestinal secretion; 4) increase in intestinal permeability; 5) negative effects on regenerative capacity of gastrointestinal mucosa and mucosal blood flow; and 6) negative effects on intestinal microbiota. Mast cells (MC) are important effectors of brain-gut axis that translate the stress signals into the release of a wide range of neurotransmitters and proinflammatory cytokines, which may profoundly affect the gastrointestinal physiology. IBS represents the most important gastrointestinal disorder in humans, and is characterized by chronic or recurrent pain associated with altered bowel motility. The diagnostic testing for IBS patients include routine blood tests, stool tests, celiac disease serology, abdominal sonography, breath testing to rule out carbohydrate (lactose, fructose, etc.) intolerance and small intestinal bacterial overgrowth. Colonoscopy is recommended if alarming symptoms are present or to obtain colonic biopsies especially in patients with diarrhoea predominant IBS. The management of IBS is based on a multifactorial approach and includes pharmacotherapy targeted against the predominant symptom, behavioural and psychological treatment, dietary alterations, education, reassurance and effective patient-physician relationship. When evaluating for the stress-induced condition in the upper GI tract, the diagnostic testing includes mainly blood tests and gastroscopy to rule out GERD and peptic ulcer disease. The therapy for these conditions is mainly based on the inhibition of gastric acid by proton pump inhibitors and eradication of Helicobacter pylori-infection. Additionally, melatonin an important mediator of brain gut axis has been shown to exhibit important protective effects against stress-induced lesions in the gastrointestinal tract. Finally, probiotics may profoundly affect the brain-gut interactions ("microbiome-gut-brain axis") and attenuate the development of stress-induced disorders in both the upper and lower gastrointestinal tract. Further studies on the brain-gut axis are needed to open new therapeutic avenues in the future.

Brain-gut axis in the modulation of pancreatic enzyme secretion.

Pancreatic enzyme secretion is controlled by complex of neurohormonal mechanisms, activated by nutrients. Food components in the duodenum acts as the signals for activation of intestinal phase of pancreatic secretion. Direct stimulation of pancreatic exocrine function involves several hormones, which bind to the receptors on pancreatic acinar cell. Indirect mechanism depends on the activation of autonomic nervous reflexes. Brain is also implicated in the regulation of pancreatic exocrine function. Dorsal vagal complex of the brainstem (DVC) appears the center of long vago-vagal cholinergic entero-pancreatic reflex. Mucosal terminals, which initiates entro-pancreatic reflex could be stimulated by CCK, serotonin and perhaps others peptides, which are released into duodenum from the enteroendocrine (EE) cells of the gastrointestinal mucosa. Melatonin, leptin and ghrelin are released from the EE cells into the gastrointestinal lumen. These substances given intraduodenally to the rats produced dose-dependent stimulation of pancreatic enzyme secretion, but they failed to affect directly amylase release from isolated pancreatic acini. Intraluminal application of melatonin, its precursor: L-tryptophan, leptin or ghrelin dose-dependently increased plasma CCK level. Above stimulatory effects of investigated substances on CCK release were completely abolished by bilateral, subdiaphragmatic vagotomy, capsaicin-deactivation of afferent nerves as well as blockade of CCK receptors. We conclude that melatonin, leptin or ghrelin, which are released into duodenal lumen by nutrients, stimulate pancreatic enzyme secretion by activation of CCK release and activation of duodeno-pancreatic reflex.

The effects of L-tryptophan and melatonin on selected biochemical parameters in patients with steatohepatitis.

Nonalcoholic fatty liver disease is the most common chronic liver disease and nonalcocholic steatohepatitis (NASH) is its advanced form. Oxidative stress and hepatocyte apoptosis may be involved in pathogenesis of NASH and particularly in progress of NASH to liver fibrosis and cirrhosis, which are initiated by the inflammation and which promote the progress of the disease. The aim of this study was to evaluate the effects of melatonin and L-tryptophan on selected biochemical parameters of blood in patients with NASH. Forty five patients with NASH, confirmed by histopathological examination of liver biopsy samples, were admitted to the study. They were divided into three groups (I, II and III). The first group (group I, n=15) received preparation Essentiale forte 3 times a day and tryptophan 500 mg twice daily for 4 weeks. In the second group (group II, n=15), Essentiale forte three times a day was administered with melatonin 5 mg applied twice a day for 4 weeks. The third group (group III, n=15) received only Essentiale forte with placebo three times a day for 4 weeks. After four-week treatment we found statistically significant reduction in GGTP, triglycerides and proinflammatory cytokine levels in the melatonin-treated (group I) and the L-tryptophan-treated patients (group II). Plasma level of melatonin was significantly elevated in groups treated with tryptophan (group I) and melatonin (group II), but remained unchanged in placebo-treated group (group III). Among patients from the third group (treated with placebo) no statistically significant differences in the measured biochemical parameters were observed. The present study suggests that melatonin and tryptophan have the significant impact on the reduction in plasma levels of proinflammatory cytokines and may be useful in the treatment of patients with NASH.