Obtainment and characterization of digestive aspartic proteases from the fish Caranx hippos (Linnaeus, 1766) / Obtenção e caracterização de proteases aspárticas digestórias do peixe Caranx hippos (Linnaeus, 1766)

This work aimed to obtain aspartic proteases of industrial and biotechnological interest from the stomach of the crevalle jack fish (Caranx hippos). In order to do so, a crude extract (CE) of the stomach was obtained and subjected to a partial purification by salting-out, which resulted in the enzyme extract (EE) obtainment. EE proteases were characterized physicochemically and by means of zymogram. In addition, the effect of chemical agents on their activity was also assessed. By means of salting-out it was possible to obtain a purification of 1.6 times with a yield of 49.4%. Two acid proteases present in the EE were observed in zymogram. The optimum temperature and thermal stability for EE acidic proteases were 55 ºC and 45 °C, respectively. The optimum pH and pH stability found for these enzymes were pH 1.5 and 7.0, respectively. Total inhibition of EE acid proteolytic activity was observed in the presence of pepstatin A. dithiothreitol (DTT) and Ca2+ did not promote a significant effect on enzyme activity. In the presence of heavy metals, such as Al3+, Cd2+ and Hg2+, EE acidic proteases showed more than 70% of their enzymatic activity. The results show that it is possible to obtain, from the stomach of C. hippos, aspartic proteases with high proteolytic activity and characteristics that demonstrate potential for industrial and biotechnological applications.

Este trabalho objetivou obter proteases aspárticas de interesse industrial e biotecnológico a partir do estômago do peixe xaréu (Caranx hippos). Para isso, foi obtido um extrato bruto do estômago, o qual foi submetido a uma purificação parcial por salting-out onde se obteve o extrato enzimático (EE). As proteases do EE foram caracterizadas físico-quimicamente e através de zimograma. Além disso, o efeito de agentes químicos sobre sua atividade também foi avaliado. Através de salting-out foi possível obter uma purificação de 1,6 vezes com rendimento de 49,4%. Foram observadas duas proteases ácidas presentes no EE através de zimograma. A temperatura ótima e a estabilidade térmica para as proteases ácidas do EE foram de 55 ºC e 45 °C, respectivamente. O pH ótimo e a estabilidade ao pH encontrados para estas enzimas foram o pH 1,5 e 7,0, respectivamente. Observou-se a inibição total da atividade proteolítica ácida do EE na presença de pepstatina A. O ditiotreitol (DTT) e o Ca2+ não promoveram efeito significativo na atividade enzimática. Na presença de metais pesados, como Al3+, Cd2+ e Hg2+, o EE manteve mais de 70% de atividade enzimática do EE. Os resultados mostram que é possível obter, a partir do estômago de C. hippos, proteases aspárticas com alta atividade proteolítica e características que demonstram potencial para aplicações industriais e biotecnológicas.

Toxic effects of hexavalent chromium (Cr6+) on bioaccumulation, apoptosis, oxidative damage and inflammatory response in Channa asiatica.

The objective of this study was to evaluate the toxic effects of Cr6+ on bioaccumulation, digestion, immunity, oxidative stress, apoptosis and inflammation-related genes in Channa asiatica. The fish was exposed to waterborne Cr6+ concentrations (0, 0.5, 1.0 and 2.0 mg/L) for 28 and 56 days. Our results demonstrated that the accumulation of Cr6+ in tissues increased in a concentration-dependent manner, and the content in tissue was liver > gill > gut > muscle. Meanwhile, Cr6+ exposure led to a remarkable suppression of digestion, immunity and antioxidant capacity in C. asiatica. Inversely, MDA and PC content were positively correlated with Cr6+ exposure concentration. Furthermore, the expression of genes went up with the increase of waterborne Cr6+ concentration. Among them, HSP90, NF-κB and TNF-α have a sharp increase. These results elucidate that waterborne Cr6+ exposure may induce bioaccumulation, inhibit digestion and immunity, promote oxidative stress and up-regulate the expression of apoptosis and inflammation-related genes in C. asiatica.

Piglets can secrete acidic mammalian chitinase from the pre weaning stage.

Fishmeal substitutes (such as insect-based feeds) in pig diets can promote sustainable pork production. Insect powders contain chitin, a nitrogen-containing indigestible material, and pigs must have the capacity to secrete chitin-degrading enzymes to benefit from these diets. The chitin-degrading enzyme (acidic mammalian chitinase; AMCase) and its gene expression have been detected in the stomach tissue of approximately 6-month-old fattening pigs; however, it remains unclear from which stage chitin-degrading enzymes are secreted. In the present study, the stomach tissue of piglets was collected from the suckling stage (14 d old) to 56 d to evaluate chitin-degrading enzymes and associated gene expression. AMCase mRNA and protein expression was detected in the stomach tissue of all piglets from days 14 to 56. AMCase secretion might increase with the increase in stomach tissue weight as piglets grow. Insect powders can therefore be used in the diets of pre-weaning piglets. The gastric AMCase level was approximately 30% that of fattening pigs. The appropriate inclusion of insect meals in the diets of pigs at different growth stages still needs to be determined.

Stability of tuna trypsin-loaded alginate-chitosan beads in acidic stomach fluid and the release of active enzyme in a simulated intestinal tract environment.

Encapsulation properties of trypsin from tonggol tuna (Thunnus tonggol) spleen using different materials including alginate (AG), low and high molecular weight chitosan (LC and HC, respectively), and soy lecithin (SL) were studied. The highest encapsulation efficiency and greatest relative activity were found in AG/LC beads after simulated gastric phase (p < .05). AG/LC encapsulated trypsin was used in simulated in vitro gastrointestinal tract for hydrolysis of sodium caseinate, soy protein isolate and fish mince, in which all protein samples were hydrolyzed as indicated by the increased α-amino group content (p < .05). Higher degradation was attained when beads containing trypsin were added. When AG/LC beads packed in blister pack were stored for 8 weeks at refrigerated temperature, a 26% decrease in activity occurred. Therefore, encapsulated tonggol tuna spleen trypsin can be prepared using AG/LC to withstand structural breakdown in stomach, but be released as an active protease within intestinal tract. PRACTICAL APPLICATION: Spleen from tonggol tuna is a by-product, which can be used as a source of trypsin, a proteolytic enzyme. The trypsin that was encapsulated within alginate and low molecular weight chitosan beads was released in the intestinal phase and was retained proteolytic activity. Therefore, this encapsulated trypsin can be packaged in capsules and taken as a supplement to aid protein digestion in the gastrointestinal tract, especially for people that need such digestive aids.

Reduce, Reuse and Recycle in Protein Chromatography: Development of an Affinity Adsorbent from Waste Paper and Its Application for the Purification of Proteases from Fish By-Products.

In the present study, we report the development of a cellulose-based affinity adsorbent and its application for the purification of proteases from fish by-products. The affinity adsorbent was synthesized using cellulose microfibers as the matrix, isolated from recycled newspapers using the acid precipitation method. As an affinity ligand, the triazine dye Cibacron Blue 3GA (CB3GA) was used and immobilized directly onto the cellulose microfibers. Absorption equilibrium studies and frontal affinity chromatography were employed to evaluate the chromatographic performance of the adsorbent using as model proteins bovine serum albumin (BSA) and lysozyme (LYS). Absorption equilibrium studies suggest that the adsorption of both proteins obeys the Langmuir isotherm model. The kinetics of adsorption obey the pseudo-second-order model. The affinity adsorbent was applied for the development of a purification procedure for proteases from Sparus aurata by-products (stomach and pancreas). A single-step purification protocol for trypsin and chymotrypsin was developed and optimized. The protocol afforded enzymes with high yields suitable for technical and industrial purposes.

Effects of simulated saliva-gastrointestinal digestion on the physicochemical properties and bioactivities of okra polysaccharides.

This study was to investigate the effects of in vitro simulated saliva-gastrointestinal digestion on the physicochemical properties and bioactivities of okra polysaccharides (OPS). Results showed that the digestibilities of OPS were about 5.1%, 37.5%, and 41.3% after saliva digestion (SD), saliva-gastric digestion (SGD), and saliva-gastrointestinal digestion (SGID), respectively. The SGID significantly changed the physicochemical properties of OPS, such as total uronic acids, total flavonoids, monosaccharide composition, rheological properties, and molecular weights (Mw). Especially, Mw changes resulted in the breakdown of glycosidic bonds during SGD, and the degradation of OPS during SGID was mainly caused by disrupting aggregates. Furthermore, the bioactivities of OPS were also affected by SGID. After SGID, OPS still possessed strong antioxidant activities, binding capacities, and prebiotic activities, but the α-glucosidase inhibitory effect was obviously decreased. Overall, results can provide valuable and scientific support on the oral administration of OPS as functional foods and medicines in the future.

Association of cagA+ Helicobacter pylori strains with high urease activity and dyspepsia in Mexican adults. / Asociación de cepas de Helicobater pylori cagA+ con alta actividad de ureasa y dispepsia en adultos mexicanos.

INTRODUCTION AND AIMS: Helicobacter pylori (H. pylori) is associated with a higher risk of peptic ulcer and gastric cancer. The sole presence of the bacterium is not a determinant of clinical outcome, but rather the interaction of strain type and host factors determines the risk of disease. Our aim was to study the association between bacterial load, strain type, and gastric symptoms in H. pylori-positive subjects. MATERIALS AND METHODS: In a community survey, a diagnostic 13C-urea breath test for H. pylori was performed on 302 volunteers that were not taking antibiotics, antacids, or proton pump inhibitors one month prior to the test. The breath test produced 25 H. pylori-positive subjects, between 25-74 years of age, who then took a gastric symptoms survey and were tested for the presence of the cagA genotype in gastric juice, using the Entero-test®. Bacterial load was determined as a measure of urease activity, utilizing the delta over baseline value, obtained in the 13C-urea breath test. RESULTS: A total of 48% of the H. pylori-positive subjects were cagA+. A positive association was found between cagA status and high gastric urease activity (P<.0001) and the latter was significantly associated with the presence of symptoms (P<.0001). CONCLUSION: Gastric urease activity was strongly associated with dyspeptic symptoms and cagA+ H. pylori. Elevated 13C-delta over baseline values could be used as indicators of a higher risk for gastric disease.

Effect of Single-Dose, Oral Enzymatic Porcine Placental Extract on Pharmacokinetics of Alcohol and Liver Function in Rats.

BACKGROUND: Human placenta extract (HPE) has been used to treat a number of liver diseases. Porcine placenta is relatively safe and has been reported to have similar immune effects to HPE and used as its alternative. This study evaluates the effect of enzymatic porcine placental extract (EPPE, Uni-Placenta®) on alcohol pharmacokinetics in rat. METHODS: This study was designed to determine the effect of single-dose EPPE on the pharmacokinetics of alcohol and liver function. Results were based on serum alcohol and acetaldehyde concentrations and activities of hepatic and gastric ADH and ALDH in rats. RESULTS: The hepatic ADH in alcohol group was significantly increased and it may be enzyme-induction by alcohol. The hepatic ALDH and gastric ADH were not changed, but gastric ALDH was significantly decreased only in the high-dose EPPE group. In the alcohol pharmacokinetics parameters, the AUC was 44.5 mM∙h in the alcohol group. Otherwise, AUCs of low, middle, high, and silymarin groups were significantly decreased. Cmax was reached at 1 hour and then gradually decreased to 63% and 43% in the middle and high groups at 3 hours, respectively, and to 92% in the low groups. The pharmacokinetics and serum concentrations of acetaldehyde showed no differences between EPPE groups except the silymarin group. No histologic changes were seen in any group. CONCLUSIONS: The single-dose EPPE (0.5 to 2.5 g/kg) suppressed absorption of alcohol in the gastrointestinal tract. This may be useful in preventing hangover effects and toxicity after drinking alcohol and may also preserve liver health after alcohol ingestion.

Appraisal of different levels of soybean meal in diets on growth, digestive enzyme activity, antioxidation, and gut histology of tilapia (Oreochromis niloticus).

This study was designed to determine the effect of fishmeal (FM) replacement with soybean meal (SBM) in the diet of tilapia (Oreochromis niloticus). Growth, digestive enzyme activity, antioxidation, and gut histomorphology were assessed in the fish fed with five different formulated diets that increasingly replaced FM. The SBM0 contained 100% FM, followed by 25% (SBM25), 50% (SBM50), 75% (SBM75), and 100% (SBM100). Juvenile tilapia having weight and length of 6.6 ± 0.1 g and 5.4 ± 0.2 cm, respectively, were randomly divided into five treatment groups. Each group had 40 individual fish and fed to visual satiation for 90 days. Body weight gain and specific growth rate in fish fed with 25-75% SBM increased significantly (P < 0.01) compared with those in fish fed with SBM100. Fish having the same weight fed with diets SBM50, SBM75, and SBM100 showed a significantly (P < 0.01) longer intestine compared with those fed with SBM0 and SBM25. Villus height of the stomach and intestine was significantly (P < 0.01) greater in the fish fed with the diets SBM0, SBM25, and SBM50 compared with SBM75 and SBM100. Muscular thickness was inversely related with the increasing villus height. Protease activity increased significantly (P < 0.01) in the stomach, anterior intestine, and posterior intestine of fish fed with SBM0 compared with SBM100. In the stomach and anterior and posterior segments of the intestine, significantly (P < 0.01) higher lipase activity was observed in fish fed with the diets SBM0 and SBM25 compared with diet SBM100. In the stomach, anterior intestine, and posterior intestine, amylase activity was also significantly (P < 0.01) greater in SBM0 compared with SBM100. The antioxidant enzymes including superoxide dismutase and catalase of the liver were significantly (P < 0.01) higher in fish fed SBM100 compared with SBM0. These results suggest that the replacement of FM up to 75% with SBM could be possible considering the growth performances, gut health, and activities of digestive enzymes and antioxidant enzymes in O. niloticus.

Helicobacter Pylori Targets the EPHA2 Receptor Tyrosine Kinase in Gastric Cells Modulating Key Cellular Functions.

Helicobacter pylori, a stomach-colonizing Gram-negative bacterium, is the main etiological factor of various gastroduodenal diseases, including gastric adenocarcinoma. By establishing a life-long infection of the gastric mucosa, H. pylori continuously activates host-signaling pathways, in particular those associated with receptor tyrosine kinases. Using two different gastric epithelial cell lines, we show that H. pylori targets the receptor tyrosine kinase EPHA2. For long periods of time post-infection, H. pylori induces EPHA2 protein downregulation without affecting its mRNA levels, an effect preceded by receptor activation via phosphorylation. EPHA2 receptor downregulation occurs via the lysosomal degradation pathway and is independent of the H.pylori virulence factors CagA, VacA, and T4SS. Using small interfering RNA, we show that EPHA2 knockdown affects cell-cell and cell-matrix adhesion, invasion, and angiogenesis, which are critical cellular processes in early gastric lesions and carcinogenesis mediated by the bacteria. This work contributes to the unraveling of the underlying mechanisms of H. pylori-host interactions and associated diseases. Additionally, it raises awareness for potential interference between H. pylori infection and the efficacy of gastric cancer therapies targeting receptors tyrosine kinases, given that infection affects the steady-state levels and dynamics of some receptor tyrosine kinases (RTKs) and their signaling pathways.

Physico-chemical behaviors of human and bovine milk membrane extracts and their influence on gastric lipase adsorption.

Milk fat globule membrane conditions the reactivity and enzymatic susceptibility of milk lipids. The use of bovine membrane extracts to make infant formulas more biomimetic of human milk has been suggested recently. A comparison of the physico-chemical behavior of human and bovine milk membrane extracts and their interaction with gastric lipase is here undertaken using biophysical tools. Milk membrane extracts (70% of polar lipids) were obtained either pooling of mature human milk (n = 5) or bovine buttermilk. Human extract contained more anionic glycerophospholipids, less phosphatidylethanolamine and more unsaturated fatty acids (57% versus 46%) than bovine extract. Human extract presented a higher compressibility, with slower increase of surface pressure, than bovine extract. Micronic liquid condensed (LC) domains were evidenced in both extracts at 10 mN/m, but the evolution differs upon compression. Upon gastric lipase addition, an adsorption preference for liquid expanded phase (LE) was observed for both extracts. However, insertion was more homogeneous in terms of height level in human extract and impacted less its lipid lateral organization than in bovine extract. Both membrane extracts share close physico-chemical properties, however human membrane higher compressibility may favour gastric lipase insertion and higher interfacial reactivity in gastric conditions.

INOS-mediated acute stomach injury and recovery in mice after oral exposure to halloysite nanotubes.

Natural halloysite nanotubes (HNTs) with a hollow lumen are already applied in numerous fields and enter the environment in increasing quantities, which may have effects on animal and human health. However their in vivo toxicity in mammals is still largely unclear. The aim of this study is to assess acute oral toxicity of HNTs in the stomach of mice and recovery. Oral HNTs at low dose (5 mg HNTs/kg BW) for 30 days increased in daily food and water intake and promoted mouse growth with no obvious adverse effect on the stomach. The promotive effect on mouse growth disappeared after cessation of oral administration of the nanotubes. Oral HNTs for 30 days at high dose (50 mg HNTs/kg BW) induced Si and Al accumulation in the stomach, which caused oxidative stress, inflammation and iNOS-mediated damage in the organ. The damage in the stomach led to slight atrophic gastritis and reduced mouse growth. Oral HNTs-induced changes at high dose were not observed after a 30-days recovery period. The findings provided the evidence that oral HNTs-induced acute toxicity in the stomach was reversible. More importantly, this research showed that Al and Si were cleared out of the mice by hepatic excretion and renal excretion, respectively, during the recovery period. The results suggest that HNTs at low concentration in environments have no adverse effect on mice, while there are health risks to mice under severe contamination by HNTs.

Gastrin secretion in normal subjects and diabetes patients is inhibited by glucagon-like peptide 1: a role in the gastric side effects of GLP-1-derived drugs?

Background: Randomized and controlled trials of glucagon-like peptide-1 (GLP-1) derived drugs have shown that the most frequent adverse symptoms are gastrointestinal. Some of the side effects such as dyspepsia, nausea and upper abdominal pain may well be of gastric origin. Since the antral hormone gastrin regulates gastric secretion of acid and enzymes and contributes to the regulation of gastric motility, we examined the effect of GLP-1 on the secretion of gastrin in normal subjects and diabetes patients.Method: Plasma was sampled from ten healthy subjects and ten patients with diabetes mellitus type 1 with glucose clamped between 6 and 9 mM. GLP-1 or saline were infused for 4 h during and after a meal. Plasma concentrations of gastrin and GLP-1 were measured using specific radioimmunoassays.Results: Basal plasma concentrations of gastrin were similar in controls and patients. After the meal, the gastrin concentrations rose significantly during saline infusion, whereas the GLP-1 infusion suppressed the secretion of gastrin significantly, most pronounced in the diabetes patients.Conclusions: The results show that GLP-1 infusion suppresses the postprandial secretion of gastrin in normal subjects and even more so in the diabetes patients. The results may therefore shed further light on the upper gastrointestinal side effects of GLP-1-derived drugs in diabetic patients.

Protective effects of Weipixiao decoction against MNNG-induced gastric precancerous lesions in rats.

Gastric cancer is recognized as one of the most common cancer. In-depth research of gastric precancerous lesions (GPL) plays an important role in preventing the occurrence of gastric cancer. Meanwhile, traditional treatment provides a novel sight in the prevention of occurrence and development of gastric cancer. The current study was designed to assess the effects of therapy with Weipixiao (WPX) decoction on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced GPL rats and the underlying molecular mechanisms. After 10-weeks treatment, all rats were sacrificed. Histopathological changes of gastric tissue were assessed via hematoxylin-eosin (HE) and High-iron diamine-Alcian blue-Periodic acid-Schiff (HID-AB-PAS) staining. To be fully evidenced, RT-qPCR, Western blot and immunohistochemistry were used to detect the expressions of LDHA, CD147, HIF-1α, MCT4, PI3K, AKT, mTOR and miRNA-34a, which were crucial factors for evaluating GPL in the aspect of glycolysis pathogenesis. According to the results of HE and HID-AB-PAS staining, it could be confirmed that MNNG-induced GPL rats were obviously reversed by WPX decoction. Additionally, the increased gene levels of LDHA, CD147, MCT4, PI3K, AKT, mTOR and HIF-1α in model group were down-regulated by WPX decoction, while miRNA-34a expression was decreased and up-regulated by WPX decoction. The significantly increased protein levels of LDHA, CD147, MCT4, PI3K, AKT, mTOR and HIF-1α induced by MNNG were attenuated in rats treated with WPX decoction. In brief, the findings of this study imply that abnormal glycolysis in MNNG-induced GPL rats was relieved by WPX decoction via regulation of the expressions of LDHA, CD147, HIF-1α, MCT4, PI3K, AKT, mTOR and miRNA-34a.

Enzyme activity and histological analysis of Clarias gariepinus fed on Imbrasia belina meal used for partial replacement of fishmeal.

An experiment was carried out to assess the effect of replacing fishmeal with mopane worm meal in the diet of Clarias gariepinus. Juvenile C. gariepinus weighing 67.04 ± 3 g were stocked in 15 rectangular concrete tanks connected to a recirculating system. Five diets denoted D1, D2, D3, D4 and D5 were formulated to replace fishmeal with mopane worm meal at 0, 10, 20, 40 and 60%. Triplicate groups of C. gariepinus were randomly assigned to each diet at a stocking density of 100 fish per tank. The fish were fed to apparent satiation twice daily for 51 days. All growth performance indices declined with higher mopane worm inclusion levels. Specific growth rate (SGR) declined from 1.85%/day in the control diet to 1.43%/day in diet 5. Protein efficiency ratio (PER) also declined from 25.27% in the control diet to 19.30% in diet 5. Apparent digestibility coefficient (ADC) followed a similar pattern declining from 92.2% in the control diet to 87.1% in diet 5. Both amylase and protease activity in the stomach increased with higher mopane worm inclusion levels. Despite the increased enzyme activity in the stomach, SGR declined. The decline in SGR was attributed to high acid detergent fibre (ADF 58.4 g/kg) and chitin in the mopane worm diets. Lipase and chitinase did not show any discernible pattern with high mopane worm inclusion levels in the stomach. In the intestines, protease, lipase and chitinase did not show any discernible pattern with high mopane worm inclusion levels. Consequently, the relationship between SGR and all these enzymes was weak. However, amylase activity declined with higher mopane worm inclusion levels in the intestines, and this resulted in decreased SGR (r2 = 0.6722). The negative effects of mopane worm meal were further confirmed by the increase in liver degradation scores at high mopane worm inclusion levels. The liver degradation score increased from 1.12 in the control to 2.46 in diet 5.

INFOGEST static in vitro simulation of gastrointestinal food digestion.

Developing a mechanistic understanding of the impact of food structure and composition on human health has increasingly involved simulating digestion in the upper gastrointestinal tract. These simulations have used a wide range of different conditions that often have very little physiological relevance, and this impedes the meaningful comparison of results. The standardized protocol presented here is based on an international consensus developed by the COST INFOGEST network. The method is designed to be used with standard laboratory equipment and requires limited experience to encourage a wide range of researchers to adopt it. It is a static digestion method that uses constant ratios of meal to digestive fluids and a constant pH for each step of digestion. This makes the method simple to use but not suitable for simulating digestion kinetics. Using this method, food samples are subjected to sequential oral, gastric and intestinal digestion while parameters such as electrolytes, enzymes, bile, dilution, pH and time of digestion are based on available physiological data. This amended and improved digestion method (INFOGEST 2.0) avoids challenges associated with the original method, such as the inclusion of the oral phase and the use of gastric lipase. The method can be used to assess the endpoints resulting from digestion of foods by analyzing the digestion products (e.g., peptides/amino acids, fatty acids, simple sugars) and evaluating the release of micronutrients from the food matrix. The whole protocol can be completed in ~7 d, including ~5 d required for the determination of enzyme activities.

Effects of Tegoprazan, a Novel Potassium-Competitive Acid Blocker, on Rat Models of Gastric Acid-Related Disease.

Tegoprazan, a novel potassium-competitive acid blocker (P-CAB), is a next-generation therapeutics developed for the treatment of acid-related gastrointestinal diseases such as gastroesophageal reflux disease (GERD) and peptic ulcers. In the present study, the in vitro and in vivo pharmacological properties of tegoprazan were compared with those of esomeprazole, a representative proton pump inhibitor. In vitro enzyme assays were performed using ion-leaky vesicles containing gastric H+/K+-ATPases isolated from pigs. The in vivo efficacies of tegoprazan were evaluated in rat models of GERD and peptic ulcer. Tegoprazan inhibited the activity of porcine H+/K+-ATPase with an IC50 value of 0.53 µM in a reversible manner, whereas esomeprazole showed weak and irreversible inhibition with an IC50 value of 42.52 µM. In a GERD model, tegoprazan showed dose-dependent efficacy in inhibiting esophageal injury and gastric acid secretion with an ED50 of 2.0 mg/kg, which was 15-fold more potent than that of esomeprazole. In peptic ulcer models, tegoprazan exhibited superior antiulcer activity compared with esomeprazole. The ED50 of tegoprazan in the naproxen-, ethanol-, and water-immersion restraint stress-induced peptic ulcer models were 0.1, 1.4, and 0.1 mg/kg, respectively. In the acetic acid-induced peptic ulcer model, the curative ratio of tegoprazan at 10 mg/kg was higher than that of esomeprazole at 30 mg/kg (44.2% vs. 32.7%, respectively), after 5 days of repeated oral administration. Thus, tegoprazan is a novel P-CAB that shows potent and reversible inhibition of gastric H+/K+-ATPase and may provide stronger efficacy compared with previous proton pump inhibitors.

High expression of acidic chitinase and chitin digestibility in the stomach of common marmoset (Callithrix jacchus), an insectivorous nonhuman primate.

Chitin is a polymer of N-acetyl-D-glucosamine (GlcNAc) and a main constituent of insects' exoskeleton. Insects are rich in protein with high energy conversion efficiency. Recently, we have reported that acidic chitinases (Chia) act as digestive enzymes in mouse, pig and chicken (omnivorous) but not in dog (carnivorous) and bovine (herbivorous), indicating that feeding behavior affects Chia expression levels, and determines chitin digestibility in the particular animals. Common marmoset (Callithrix jacchus) belongs to New World monkey family and provides a potential bridge between mouse models and human diseases. Common marmoset is an insectivorous nonhuman primate with unknown expression levels and enzymatic functions of the Chia homologue, CHIA. Here, we report that common marmoset highly expresses pepsin-, trypsin- and chymotrypsin-resistant CHIA in the stomach. We show that CHIA is most active at pH 2.0 and degrades chitin and mealworm shells into GlcNAc dimers under gastrointestinal conditions. Although common marmoset and crab-eating monkey (Old World monkey) have two CHIA genes in their genomes, they primarily express one gene in the stomach. Thus, this study is the first to investigate expression levels and enzymatic functions of CHIA in a New World primate, contributing to the understanding of dietary adaptation and digestion in this taxon.

Identification of a new natural gastric lipase inhibitor from star anise.

The identification and isolation of bioactive compounds are of great interest in the drug delivery field, despite being a difficult task. We describe here an innovative strategy for the identification of a new gastric lipase inhibitor from star anise for the treatment of obesity. After plant screening assays for gastric lipase inhibition, star anise was selected and investigated by bioactivity guided fractionation. MALDI-TOF mass spectrometry and peptide mass fingerprinting allowed the detection of an inhibitor covalently bound to the catalytic serine of gastric lipase. A mass-directed screening approach using UPLC-HRMS and accurate mass determination searching identified the flavonoid myricitrin-5-methyl ether (M5ME) as a lipase inhibitor. The inhibitory activity was rationalized based on molecular docking, showing that M5ME is susceptible to nucleophilic attack by gastric lipase. Overall, our data suggest that M5ME may be considered as a potential candidate for future application as a gastric lipase inhibitor for the treatment of obesity.

The CAT-262 C>T, MnSOD Ala16Val, GPX1 Pro198Leu Polymorphisms Related to Oxidative Stress and the Presence of Gastric Lesions.

BACKGROUND AND AIMS: The increased oxidative stress plays an important role in gastro-duodenal ulcers and gastric cancer occurrence. We investigated the association between the genetic polymorphisms of genes encoding the antioxidative enzymes CAT, GPX and SOD and the occurrence of gastric lesions, considering also the environmental risk factors such as H. pylori infection, drug exposure, smoking and alcohol consumption. METHODS: We included 373 patients who underwent endoscopy for symptoms, anemia or bleeding investigation. A complete set of demographical, clinical and pathological data was recorded. All patients were successfully genotyped. RESULTS: In the multivariate logistic regression model, the patients having Pro/Pro genotype of GPX1 gene polymorphism had more severe gastric lesions as compared with patients with the Leu/Pro or Leu/Leu genotype (OR= 1.89, 95%CI: 0.99-3.57, p=0.051). The GPX1 Pro198Leu and the MnSOD Ala16Val gene polymorphism could be independent risk factors for reactive gastropathy changes, as shown by their association very close to statistical significance (p=0.059 and p=0.054, respectively). Consumption of anticoagulants was a significant independent predictor (p=0.023, OR:0.43 95%CI:0.21-0.89) for the absence of active gastritis, while low-dose aspirin consumption was a risk factor for active gastritis in biopsy samples (p=0.025, OR:1.71, 95%CI:1.07-2.74). CONCLUSION: The variant genotype of GPX1Pro198Leu was associated with an increased risk for reactive gastropathy changes in gastric biopsies and with less severe endoscopic lesions, while MnSODAla16Val variant genotype (Val/Val or Val/Ala) seems to be related to the reactive gastropathy. However, none of them were associated with inflammatory or premalignant gastric lesions.