Motilin stimulates pepsinogen secretion in Suncus murinus

Piezo1/2 regulates gastric pepsinogen secretion of mandarin fish

Pepsinogen plays a crucial role in the gastric digestion of carnivorous fish. Piezo signals in the stomach, which are typically associated with digestion through mechanical forces resulting from food intake, have been extensively investigated in mammals but have received comparatively limited attention in fish. To explore the physiological characteristics of gastric digestion and the regulatory mechanism of pepsinogen and piezo secretion in carnivorous fish, we investigated the gastric contents of juvenile mandarin fish (5.83 ± 1.32 g, 6.60 ± 0.46 cm) following feeding and developed a mathematical model for gastric emptying (feeding live baits at 26 °C) to briefly describe changes in gastric pressure. The expression patterns of piezo1/2 and pepsinogens were examined under normal feeding and water gavage (only gastric pressure) conditions. The results indicated that the weight of gastric contents gradually decreased over time, and the most appropriate model describing this trend was the square root model with a fitted equation of Y = - 0.0006t2 - 0.0130t + 0.6163 (R2 = 0.9599) of mandarin fish. The percentage of wet weight decreased significantly after 6 hpf (hour post-feeding) (P < 0.05), meaning that the stomach pressure decreased significantly at 6 hpf. During gastric digestion, there was a significant increase in piezo1/2 expression at 6 hpf (P < 0.05), followed by a gradual plateau (P > 0.05). Pepsinogen (PG A and PG C) content exhibited a similar trend to piezo1/2, showing a rising trend and peaking at 6 hpf (P < 0.05). The relative expression levels of gas, pg a1/2, pg c, and hk α demonstrated an "upward and then downward" trajectory and peak levels at 6 hpf (P < 0.05). In the water gavage group, piezo1/2 increased significantly (P < 0.05) and peaked at 1-2 h. Similarly, the rises in PG A and PG C contents, gas, pg a2, and hk α mRNA relative expression levels were also observed with a peak at 1-2 h (P < 0.05), while no distinct peaks of piezo and pepsinogen were observed in the starved group. Our results suggested that piezo1/2 is activated by intragastric pressure and up-regulated the pepsinogen expression in juvenile mandarin fish (5.83 ± 1.32 g, 6.60 ± 0.46 cm).

Molecular characterization and distribution of motilin and motilin receptor in the Japanese medaka Oryzias latipes

Motilin (MLN) is a peptide hormone originally isolated from the mucosa of the porcine intestine. Its orthologs have been identified in various vertebrates. Although MLN regulates gastrointestinal motility in tetrapods from amphibians to mammals, recent studies indicate that MLN is not involved in the regulation of isolated intestinal motility in zebrafish, at least in vitro. To determine the unknown function of MLN in teleosts, we examined the expression of MLN and the MLN receptor (MLNR) at the cellular level in Japanese medaka (Oryzias latipes). Quantitative PCR revealed that mln mRNA was limitedly expressed in the gut, whereas mlnr mRNA was not detected in the gut but was expressed in the brain and kidney. By in situ hybridization and immunohistochemistry, mlnr mRNA was detected in the dopaminergic neurons of the area postrema in the brain and the noradrenaline-producing cells in the interrenal gland of the kidney. Furthermore, we observed efferent projections of mlnr-expressing dopaminergic neurons in the lobus vagi (XL) and nucleus motorius nervi vagi (NXm) of the medulla oblongata by establishing a transgenic medaka expressing the enhanced green fluorescence protein driven by the mlnr promoter. The expression of dopamine receptor mRNAs in the XL and cholinergic neurons in NXm was confirmed by in situ hybridization. These results indicate novel sites of MLN activity other than the gastrointestinal tract. MLN may exert central and peripheral actions through the regulation of catecholamine release in medaka.

Motilin Comparative Study: Structure, Distribution, Receptors, and Gastrointestinal Motility

Motilin, produced in endocrine cells in the mucosa of the upper intestine, is an important regulator of gastrointestinal (GI) motility and mediates the phase III of interdigestive migrating motor complex (MMC) in the stomach of humans, dogs and house musk shrews through the specific motilin receptor (MLN-R). Motilin-induced MMC contributes to the maintenance of normal GI functions and transmits a hunger signal from the stomach to the brain. Motilin has been identified in various mammals, but the physiological roles of motilin in regulating GI motility in these mammals are well not understood due to inconsistencies between studies conducted on different species using a range of experimental conditions. Motilin orthologs have been identified in non-mammalian vertebrates, and the sequence of avian motilin is relatively close to that of mammals, but reptile, amphibian and fish motilins show distinctive different sequences. The MLN-R has also been identified in mammals and non-mammalian vertebrates, and can be divided into two main groups: mammal/bird/reptile/amphibian clade and fish clade. Almost 50 years have passed since discovery of motilin, here we reviewed the structure, distribution, receptor and the GI motility regulatory function of motilin in vertebrates from fish to mammals.

Effect of Bacillus velezensis to substitute in-feed antibiotics on the production, blood biochemistry and egg quality indices of laying hens

BACKGROUND

The excessive use of antibiotics in the livestock feed industry caused inevitable side effects of microbial resistance. Besides this residual antibiotics in animal-derived foodstuff imposed serious health problems for humans. So this study aimed to investigate the potential use of Bacillus velezensis to substitute antibiotics for poultry production. A total of 468, 49-week-old Hy-Line Brown chickens, were randomly divided into four groups the control group (regular diet), experiment group I (0.1% B. veleznesis), experiment group II (0.2% B. veleznesis), and antibiotic group (50 mg/kg flavomycin), with three replicates per group and trial period consisted on 42 days.

RESULTS

The results showed that, compared with the control group, the average egg production rate and daily feed intake of experimental groups I and II increased significantly (P < 0.05), while the average egg weight was increased in experimental group II as compared to (I) (P < 0.01). The feed conversion ratio was decreased (P > 0.05) in group (II) Egg quality parameters such as yolk weight of the experimental group II was increased, but that of the antibiotic group and experiment group I was decreased, neither significant (P > 0.05). Moreover, the eggshell strength, yolk color, albumen height, and Haugh unit were significantly increased (P < 0.05). Compared with the control group, probiotic groups can increase the progesterone and motilin (P > 0.05) but decrease the secretin and cholecystokinin in the blood plasma (P > 0.05).

CONCLUSIONS

This study suggested that B. velezensis can substitute in-feed-antibiotics and improved most of the study parameters significantly. Which suggested that B. velezensis has potential future application value to replace the feed antibiotics.