Excitability and Synaptic Transmission in the Enteric Nervous System: Does Diet Play a Role?

GLP-1 and IL-6 regulates obesity in the gut and brain

Obesity is a chronic metabolic disease characterized by excessive nutrient intake leading to increased subcutaneous or visceral fat, resulting in pathological and physiological changes. The incidence rate of obesity, an important form of metabolic syndrome, is increasing worldwide. Excess appetite is a key pathogenesis of obesity, and the inflammatory response induced by obesity has received increasing attention. This review focuses on the role of appetite-regulating factor (Glucogan-like peptide 1) and inflammatory factor (Interleukin-6) in the gut and brain in individuals with obesity and draws insights from the current literature.

Regulating the Enteric Nervous System against Obesity in Mice by Electroacupuncture

BACKGROUND AND OBJECTIVES

The enteric nervous system (ENS) dominates the onset of obesity and has been shown to regulate nutrient absorption and energy metabolism.

METHODS AND STUDY DESIGN

This study was performed to investigate the role of electroacupuncture in regulating ENS function in obese mice. Obese mice were obtained by high-fat diet. 16S rRNA pyrosequencing, Western blotting, quantitative PCR, and neurotransmitter analysis were used for this purpose.

RESULTS

Body weight, Lee index, serum lipid, leptin, and adiponectin levels, and other basic indices were significantly ameliorated after electroacupuncture intervention. The pathological ENS scores, serum neurotransmitter levels, and intestinal transit rate were markedly changed in obese mice. Moreover, electroacupuncture promoted the diversity of gut microbiota. No significant differences were observed 21 and 28 days after electroacupuncture.

CONCLUSIONS

These results suggested ENS may be a new treatment approach to obesity.

Neurochemical characterization of nerve fibers in the porcine gallbladder wall under physiological conditions and after the administration of Salmonella enteritidis lipopolysaccharides (LPS)

Lipopolysaccharides (LPS, bacterial endotoxin) are a component of the cellular membrane of Gram-negative bacteria, which is known as an important pathological factor. In spite of many previous studies describing multidirectional negative effects of LPS on living organisms, the knowledge concerning the influence of bacterial endotoxins on the gallbladder innervation is extremely scarce. The present study, based on the immunofluorescence technique, describes the changes in the neurochemical characterization of nerves within various parts of the porcine gallbladder (neck, body and fundus) after the administration of low doses of LPS. The obtained results show that even low doses of bacterial endotoxins affect the nerve structures within the gallbladder wall and the intensity of fluctuations in immunoreactivity to particular substances clearly depends on the part of the investigated organ. The most evident changes were observed in the case of fibers exhibiting the presence of neuropeptide Y (an increase from 7.84 ± 0.17 to 14.66 ± 0.37) in the neck, substance P (an increase from 0.88 ± 0.1 to 8.4 ± 0.3) in the body and the vesicular acetylocholine transporter in the gallbladder's fundus (an increase from 4.29 ± 0.18 to 11.01 ± 0.26). The mechanisms of the observed changes still remain unclear, but probably they are connected with the pro-inflammatory and/or neurodegenerative activity of LPS.

Modulation of the main porcine enteric neuropeptides by a single low-dose of lipopolysaccharide (LPS) Salmonella Enteritidis

Background

The present research was conducted to investigate the influence of a low, single dose of LPS, which does not result in any clinical symptoms of intoxication on the expression of selected neuropeptides within the intestines of the domestic pig.

Methods

This experiment was conducted on immature female pigs of the Pitrain × Duroc breed (n = five per group). Seven days after the intravenous injection of 10 mL saline solution for control animals and 5 μg/kg b.w. (in 10 mL saline solution) LPS Salmonella Enteritidis for the experimental group, the excised segments of duodenum, jejunum, ileum, ileocecal valve, caecum, descending colon, transverse colon, ascending colon and rectum were prepared to extract the main enteric neuropeptides, including GAL, NPY, SOM, SP, VIP.

Results

The results of this research indicate that single low-dose LPS S. Enteritidis produced changes in the content of the selected neuropeptides of the porcine intestine. The most visible changes were observed in the transverse colon, where LPS induced the increase of GAL expression from 19.41 ± 7.121 to 92.92 ± 11.447 ng/g tissue.

Conclusion

The exact functions of the substances studied and mechanisms of responses to LPS action depend on the sections of the intestines. The mechanisms of observed changes are not fully understood, but fluctuations in neuronal active substance levels may be connected with neurodegenerative and/or pro-inflammatory activity of LPS.

Antibiotic-induced dysbiosis of the microbiota impairs gut neuromuscular function in juvenile mice

BACKGROUND AND PURPOSE

Gut microbiota is essential for the development of the gastrointestinal system, including the enteric nervous system (ENS). Perturbations of gut microbiota in early life have the potential to alter neurodevelopment leading to functional bowel disorders later in life. We examined the hypothesis that gut dysbiosis impairs the structural and functional integrity of the ENS, leading to gut dysmotility in juvenile mice.

EXPERIMENTAL APPROACH

To induce gut dysbiosis, broad-spectrum antibiotics were administered by gavage to juvenile (3weeks old) male C57Bl/6 mice for 14 days. Bile acid composition in the intestinal lumen was analysed by liquid chromatography-mass spectrometry. Changes in intestinal motility were evaluated by stool frequency, transit of a fluorescent-labelled marker and isometric muscle responses of ileal full-thickness preparations to receptor and non-receptor-mediated stimuli. Alterations in ENS integrity were assessed by immunohistochemistry and Western blot analysis.

KEY RESULTS

Antibiotic treatment altered gastrointestinal transit, luminal bile acid metabolism and bowel architecture. Gut dysbiosis resulted in distorted glial network, loss of myenteric plexus neurons, altered cholinergic, tachykininergic and nitrergic neurotransmission associated with reduced number of nNOS neurons and different ileal distribution of the toll-like receptor TLR2. Functional defects were partly reversed by activation of TLR2 signalling.

CONCLUSIONS AND IMPLICATIONS

Gut dysbiosis caused complex morpho-functional neuromuscular rearrangements, characterized by structural defects of the ENS and increased tachykininergic neurotransmission. Altogether, our findings support the beneficial role of enteric microbiota for ENS homeostasis instrumental in ensuring proper gut neuromuscular function during critical stages of development.