Gastric emptying and duodenal motility upon intake of a liquid meal with monosodium glutamate in healthy subjects

Comparison of gut toxicity and microbiome effects in zebrafish exposed to polypropylene microplastics: Interesting effects of UV-weathering on microbiome

Weathered microplastics (MPs) exhibit different physicochemical properties compared to pristine MPs, thus, their effects on the environment and living organisms may also differ. In the present study, we investigated the gut-toxic effects of virgin polypropylene MPs (PP) and UV-weathered PP MPs (UV-PP) on zebrafish. The zebrafish were exposed to the two types of PP MPs at a concentration of 50 mg/L each for 14 days. After exposure, MPs accumulated primarily within the gastrointestinal tract, with UV-PP exhibiting a higher accumulation than PP. The ingestion of PP and UV-PP induced gut damage in zebrafish and increased the gene expression and levels of enzymes related to oxidative stress and inflammation, with no significant differences between the two MPs. Analysis of the microbial community confirmed alterations in the abundance and diversity of zebrafish gut microorganisms in the PP and UV-PP groups, with more pronounced changes in the PP-exposed group. Moreover, the Kyoto Encyclopedia of Genes and Genomes pathway analysis confirmed the association between changes in the gut microorganisms at the phylum and genus levels with cellular responses, such as oxidative stress, inflammation, and tissue damage. This study provides valuable insights regarding the environmental impact of MPs on organisms.

Effects of vincristine and monosodium glutamate on gastrointestinal motility and visceral sensitivity

BACKGROUND

Chemotherapy-induced adverse effects are an unresolved nightmare. In preclinical studies in rats, the food additive monosodium glutamate (MSG) improved some of the side effects caused by cisplatin, but its effects in other models of chemotherapy-treated animals are not well known. The aim of this study was to test if MSG may improve some of the adverse effects induced by vincristine in rats.

METHODS

Young male Wistar rats were exposed or not to MSG (4 g L-1 ) in drinking water from week 0 till 1 week after treatment (week 3). Rats received two cycles of five daily intraperitoneal (ip) injections (Monday to Friday, weeks 1 and 2) of either saline (2 mL kg-1 ) or vincristine (0.1 mg kg-1 ). Gastrointestinal motility was measured in vivo by radiological methods after the first and tenth ip administrations. On week 3, the threshold for mechanical somatic and colorectal sensitivity was recorded using Von Frey filaments applied to the paws and an intracolonic balloon, respectively. Finally, samples of the terminal ileum and distal colon were histologically evaluated in sections.

KEY RESULTS

Vincristine reduced body weight gain, food intake, and upper gastrointestinal transit, caused somatic (but not visceral) hypersensitivity and increased the thickness of the submucosal and muscle layers of the small intestine. In vincristine-treated animals, MSG partially prevented gastrointestinal dysmotility and reduced visceral sensitivity but did not improve structural alterations of the small intestine.

CONCLUSIONS & INFERENCES

MSG could be used as an adjuvant to conventional treatments to improve some gastrointestinal dysfunctions caused by chemotherapy.

Effects of the food additive monosodium glutamate on cisplatin-induced gastrointestinal dysmotility and peripheral neuropathy in the rat

BACKGROUND

Cisplatin is an antineoplastic drug known to produce intense vomiting, gastric dysmotility, and peripheral neuropathy. Monosodium glutamate (MSG) is a flavor enhancer with prokinetic properties potentially useful for cancer patients under chemotherapy. Our aim was to test whether MSG may improve gastrointestinal motor dysfunction and other adverse effects induced by repeated cisplatin in rats.

METHODS

Male Wistar rats were exposed or not to MSG (4 g L^-1 ) in drinking water from week 0 to 1 week after treatment. On the first day of weeks 1-5, rats were treated with saline or cisplatin (2 mg kg^-1  week^-1 , ip). Gastrointestinal motility was measured by radiological methods after first and fifth administrations, as well as 1 week after treatment finalization. One week after treatment, the threshold for mechanical somatic sensitivity was recorded. Finally, samples of stomach, terminal ileum and kidneys were evaluated in sections using conventional histology. The myenteric plexus was immunohistochemically evaluated on distal colon whole-mount preparations.

KEY RESULTS

Monosodium glutamate prevented the development of cisplatin-induced neuropathy and partially improved intestinal transit after the fifth cisplatin administration with little impact on gastric dysmotility. MSG did not improve the histological damage of gut wall, but prevented the changes induced by cisplatin in the colonic myenteric plexus.

CONCLUSION AND INFERENCES

Our results suggest that MSG can improve some dysfunctions caused by anticancer chemotherapy in the gut and other systems, associated, at least partially, with neuroprotectant effects. The potentially useful adjuvant role of this food additive to reduce chemotherapy-induced sequelae warrants further evaluation.

Assessment of abdominal organ motion using cine magnetic resonance imaging in different gastric motilities: a comparison between fasting and postprandial states

This study assessed abdominal organ motion induced by gastroduodenal motilities in volunteers during fasting and postprandial states, using cine magnetic resonance imaging (cine-MRI). Thirty-five volunteers underwent cine-MRI while holding their breath in the fasting and postprandial states. Gastric motility was quantified by the amplitude and velocity of antral peristaltic waves. Duodenal motility was evaluated as the change of duodenal diameter. Abdominal organ motion was measured in the liver, pancreas and kidneys. Motion was quantified by calculating maximal organ displacement in the left-right, antero-posterior and caudal-cranial directions. Median antral amplitude and velocity in the fasting and postprandial states were 7.7 and 15.1 mm (P < 0.01), and 1.3 and 2.5 mm/s (P < 0.01), respectively. Duodenal motility did not change. Median displacement for all organs ranged from 0.9 to 2.9 mm in the fasting state and from 1.0 to 2.9 mm in the postprandial state. Significant increases in abdominal organ displacement in the postprandial state were observed in the right lobe of the liver, pancreatic head and both kidneys. Differences in the median displacement of these organs between the two states were all <1 mm. Although the motion of several abdominal organs increased in the postprandial state, the difference between the two states was quite small. Thus, our study suggests that treatment planning and irradiation need not include strict management of gastric conditions, nor the addition of excess margins to compensate for differences in the intra-fractional abdominal organ motion under different gastric motilities in the fasting and postprandial states.

Glycaemic, gastrointestinal and appetite responses to breakfast porridges from ancient cereal grains: A MRI pilot study in healthy humans

Cereal grain based porridges are commonly consumed throughout the world. Whilst some data are available for varieties that are popular in the Western world such as oats and rye, other 'ancient' grains used in the East and in Africa such as millets are thought to have beneficial health effects, such as a suppression of post prandial hunger and circulating glucose levels. These grains, a sustainable food source due to their tolerance of extreme weather and growing conditions, are commonly found throughout Asia and Africa. However, knowledge of the physiological responses to these grain varieties is very limited. This study aimed to collect initial pilot data on the physiological and gastrointestinal responses to breakfast porridges made with two millet varieties and oats and rye grains. A total of n=15 completed the oats and rye, n=9 the finger millet n=12 the pearl millet meals. MRI scans were undertaken at baseline, immediately after consumption and then hourly postprandially. Blood glucose was measured at baseline, immediately after consumption and then every 15min until t=80min, then every 20min until t=120min, followed on each occasion by completion of VAS. Seven participants completed the entire protocol and were included in the final analysis. A subgroup analysis with the n=10 paired comparison between the same individuals that completed the oats, rye and pearl millet was also considered. The gastric volume AUC was higher for pearl millet than oats and rye (n=10, p<0.001). The incremental area under the curve (iAUC) for blood glucose was not significantly different between the meals although this showed a trend to be lower for pearl millet. Hunger was lower for pearl millet compared to oats and rye (n=10, p=0.01). There was a significant correlation between total gastric volume AUC and average appetite AUC r=-0.47, p<0.010. Isoenergetic breakfast porridges from 'ancient' varieties of millet grains showed physiological responses that were comparable with those from common Western varieties known to have beneficial health effects. Pearl millet appeared to induce lower postprandial blood glucose response and appetite scores though the differences were not conclusive compared with the other porridges and further work is needed. Improved knowledge of the effects of different cereal grains could help direct dietary advice and ultimately improve health outcomes in the general population worldwide.

L-Arginine L-Glutamate Enhances Gastric Motor Function in Rats and Dogs and Improves Delayed Gastric Emptying in Dogs

Amino acids are not only constituents of proteins, but also have multiple physiologic functions. Recent findings have revealed that ingested amino acids either activate luminal receptors or are metabolized, causing physiologic reactions in the gastrointestinal (GI) tract. We examined the effect of oral L-arginine L-glutamate (ArgGlu), a pharmaceutical amino acid salt used i.v. for the treatment of hyperammonemia, on gastric motor function in rats and dogs. Gastric emptying was determined using phenol red and ¹³C-breath test methods, whereas gastric relaxation was determined using the barostat method. ArgGlu (10-30 mg/kg, p.o.) dose-dependently promoted gastric emptying in rats. This effect was dependent on vagus nerve activation and comparable to that of the prokinetic mosapride. Intragastric ArgGlu (3-30 mg/kg intragastrically) also dose-dependently enhanced adaptive relaxation of rat stomachs, which was negated not by vagotomy of gastric branches, but by pretreatment with N omega-nitro-L-arginine methyl ester (20 mg/kg i.v.), a nitric oxide synthase inhibitor. Its relaxing effect on the stomach was also confirmed in dogs and was equally as efficacious as treatment with sumatriptan (1-3 mg/kg s.c.). ArgGlu (30 mg/kg p.o.) significantly reduced the half gastric emptying time in clonidine-induced delayed gastric emptying of solids in dogs, and its effect was comparable to that of cisapride (3 mg/kg p.o.). This study demonstrated that the pharmaceutical ingredient ArgGlu, currently used i.v., enhanced gastric motor function when administered orally, suggesting that it could be a new oral medicine indicated for treatment of upper GI hypofunction or dysfunction like functional dyspepsia.

Overview on gastroretentive drug delivery systems for improving drug bioavailability

In recent decades, many efforts have been made in order to improve drug bioavailability after oral administration. Gastroretentive drug delivery systems are a good example; they emerged to enhance the bioavailability and effectiveness of drugs with a narrow absorption window in the upper gastrointestinal tract and/or to promote local activity in the stomach and duodenum. Several strategies are used to increase the gastric residence time, namely bioadhesive or mucoadhesive systems, expandable systems, high-density systems, floating systems, superporous hydrogels and magnetic systems. The present review highlights some of the drugs that can benefit from gastroretentive strategies, such as the factors that influence gastric retention time and the mechanism of action of gastroretentive systems, as well as their classification into single and multiple unit systems.

Effects of chronic dietary exposure to monosodium glutamate on feeding behavior, adiposity, gastrointestinal motility, and cardiovascular function in healthy adult rats

BACKGROUND

Monosodium glutamate (MSG) is a flavor-enhancer widely used as a food additive. However, its safe dietary concentration and its toxicity, including its possible implication in the recent metabolic syndrome pandemia, is still a controversial issue. Therefore, a deep knowledge of its effects upon regular dietary use is needed. Our aim was to evaluate the effects of chronic exposure to MSG on feeding behavior, abdominal fat, gastrointestinal motility, and cardiovascular function in rats.

METHODS

Two groups of adult male Wistar rats were used: control and treated with MSG (4 g/L in drinking water) for 6 weeks. Different functional parameters were determined and the histological structure was analyzed in tissues of interest.

KEY RESULTS

Compared to control animals, chronic MSG increased water intake but did not modify food ingestion or body weight gain. Neither the abdominal fat volume nor the fat fraction, measured by magnetic resonance imaging, was modified by MSG. Monosodium glutamate did not alter general gastrointestinal motility, but significantly increased the colonic response to mechanical stimulation. It slightly reduced endothelium-dependent relaxation in aorta, without significantly modifying any other cardiovascular parameters. No significant histological alterations were detected in salivary glands, intestinal wall, aorta, heart, and kidney.

CONCLUSIONS & INFERENCES

Chronic treatment with MSG in the adult rat increased water intake. This supports its potential to improve acceptance of low-fat regimens and to increase hydration in the elderly and sportspeople, often at risk of dehydration. Changes in colonic contractility and cardiovascular function could have some long-term repercussions warranting further research.