Effects of L-glutamine of acetylsalicylic acid or taurocholic acid-induced gastric lesions and secretory changes in pylorus-ligated rats under normal or stress conditions

Thirteen-Week Oral Toxicity Study of l-Glutamine in Rats

l-Glutamine (Gln) is a semiessential amino acid used in enteral feeding in critically ill patients, and is contained in numerous dietary supplements available to the general public. This study evaluated toxicological effects of Gln in male and female Sprague-Dawley rats. Gln produced by Ajinomoto Co. (Tokyo, Japan) was incorporated into a standard diet at doses equal to 1.25%, 2.5%, and 5.0% ( w/ w), respectivelly. A control group of rats received only a standard diet. All diets were administered ad libitum for 13 consecutive weeks. To examine recoverability of any potential effects, the administration period was followed by a 5-week recovery period, during which only the standard diet was provided to all animals. Throughout the administration and recovery periods, no deaths were observed, and no changes in diet consumption, ophthalmologic findings, gross pathology, and histopathology were detected. Several changes in urine parameters (total protein, urine pH, and a positive incidence (±) of ketone bodies) were observed in the 2.5% and 5.0% groups at the end of the administration period. Minor increases were found in hematology parameters for the 5.0% group (platelet count, γ-globulin, lactate dehydrogenase [LDH]), but all changes were within physiological range. No effects of administration were observed in the 1.25% group. The no-observed-adverse-effect level (NOAEL) for Gln was estimated at 1.25% for both genders (males 0.83 ± 0.01 g/kg/day; females, 0.96 ± 0.06 g/kg/day).

New therapeutic strategy for amino acid medicine: prophylactic and healing promoting effect of monosodium glutamate against NSAID-induced enteropathy

We reviewed the effect of monosodium glutamate (MSG) on the development and healing of nonsteroidal anti-inflammatory drug (NSAID)-induced small intestinal lesions in rats. Loxoprofen (60 mg/kg, p.o.) induced lesions in the small intestine within 24 h, accompanied by a decrease of Muc2 expression and an increase in enterobacterial invasion and inducible nitric oxide synthase (iNOS) expression. These lesions were prevented when MSG was given as a mixture of powdered food for 5 days before the loxoprofen treatment. This effect of MSG was accompanied by an increase in Muc2 expression / mucus secretion as well as the suppression of bacterial invasion and iNOS expression. These intestinal lesions healed spontaneously within 6 days, but the process was impaired by the repeated administration of low-dose loxoprofen (30 mg/kg) for 5 days after the ulceration, with the decrease of vascular endothelial derived growth factor (VEGF) expression and angiogenesis. The healing-impairing effect of loxoprofen was prevented by feeding 5% MSG for 5 days after the ulceration. These results suggest that MSG not only prevents loxoprofen-induced small intestinal damage but also promotes a healing of these lesions; the former is functionally associated with the increase in Muc2 expression / mucus secretion and the suppression of bacterial invasion and iNOS expression, while the latter is associated with the stimulation of VEGF expression/angiogenesis.

New frontiers in gut nutrient sensor research: prophylactic effect of glutamine against Helicobacter pylori-induced gastric diseases in Mongolian gerbils

Ammonia is one of the important toxins produced by Helicobacter pylori (H. pylori), the major cause of peptic ulcer diseases. We examined whether glutamine or marzulene (a gastroprotective drug containing 1% sodium azulene and 99% glutamine) protects the gastric mucosa against H. pylori in vivo and investigated the mechanism underlying glutamine-induced mucosal protection against ammonia in gastric epithelial cells in vitro. Mongolian gerbils were fed for 3 months with a diet containing glutamine (2%-20%) or marzulene (20%) starting from 2 weeks or 2 years after H. pylori infection. Then, gastric mucosal changes were evaluated both macro- and microscopically. Cultured gastric epithelial cells were incubated in the presence of ammonia, with or without glutamine; and cell viability, ammonia accumulation, and chemokine production were determined. Gerbils exhibited edema, congestion, and erosion after 3-month infection; and after 2-year infection, they showed cancer-like changes in the gastric mucosa. Glutamine and marzulene significantly suppressed these pathological changes caused in the gastric mucosa by H. pylori infection. Ammonia was accumulated in the cells, resulting in an increase in chemokine production and a decrease in cell viability. These pathological responses were prevented by glutamine. In addition, glutamine decreased chemokine production and cell death through inhibition of cellular accumulation of ammonia, resulting in the prevention of H. pylori-induced gastric diseases in vivo. These results suggest that glutamine/marzulene would be useful for prophylactic treatment of H. pylori-induced gastric diseases in patients.

Relative contribution of bile and pancreatic juice duodenogastric reflux in gastric ulcer disease and cholelithiasis

Bile acid concentrations, phospholipase A2 activity and pH in the stomach were measured in the fasting state and for 2 h after a fat-containing test meal in patients with an active gastric ulcer (GU), in patients with gallstones before and after cholecystectomy and in normal subjects. Fasting and peak postprandial bile acid concentrations in the stomach were low in all normal controls. Although high concentrations were found in many patients with GU (P less than 0.01), similar concentrations were found in many patients with radiologically non-functioning gallbladders containing gallstones (NFG) (P less than 0.01) and also after cholecystectomy (AC) (P less than 0.01). Fasting intragastric phospholipase A2 activities were similar, and very high in GU and NFG patients compared with control subjects (P less than 0.01). High values were not found after cholecystectomy. There was no difference in pH profile or in postprandial phospholipase A2 between patient groups. Since patients with cholelithiasis or after cholecystectomy are not known to have an increased incidence of gastric ulceration, the significance of duodenogastric reflux in the aetiology of gastric ulcers must be questioned. If reflux does produce ulcers in GU patients then factors in addition to bile acid are probably involved. However, neither patterns of phospholipase A2 reflux nor pH profiles can explain the absence of gastric ulceration in those patients with gallstones who reflux large quantities of bile acid.

Restraint stress in biomedical research: a review

The use of restraint or immobilization for investigations of animal physiology, pathology and pharmacology has an extensive history. The major use of this technique has been as a "stressor" for the induction of stress response syndromes in animals. Many such syndromes have been characterized from the behavioral level to the neurochemical concomitants of stress. As a consequence of this particular use of the restraint procedure, much information concerning drug effects on stress response syndromes has been obtained. Indeed, many researchers in the area of gastrointestinal drugs routinely screen their new compounds in a restraint model of gastric stress ulcer. The purpose of this review is to present for researchers, a summary of the methods for, the parameters of, and known drug effects on, restraint-induced pathology. In our experience, this technique has proven to be a very useful one for the examination of both central and peripheral mechanisms of stress-related disorders, as well as for studying drug effects upon these disorders.

Effects of cholestyramine and synthetic hydrotalcite on acute gastric or intestinal lesion formation in rats and dogs

Cholestyramine, a bile-binding agent, markedly inhibited the development of gastric lesions induced by water-immersion stress in rats and of gastric and intestinal lesions induced by indomethacin in rats and dogs with an intact pylorus. However, cholestyramine had no effect on gastric lesions induced by stress in pylorus-ligated rats and on aspirin-induced gastric lesions in rats and dogs with or without pylorus ligation. Hydrotalcite, a potent antacid, significantly inhibited the gastric lesions induced by stress and aspirin in rats and dogs with or without pylorus ligation. Hydrotalcite also inhibited the gastric lesions induced by a single administration of indomethacin in rats with an intact pylorus. In contrast, the agent had no effect on gastric and intestinal lesions induced by repeated administration of indomethacin to rats and dogs with an intact pylorus. These results suggest that while bile probably plays an important role in the pathogenesis of stress-induced gastric lesions and of indomethacin-induced gastric and intestinal lesions, bile does not appear to play a role in the pathogenesis of aspirin-induced gastric lesions.