Distribution and characterisation of CCK containing enteroendocrine cells of the mouse small and large intestine

Research advances in understanding crosstalk between organs and pancreatic β-cell dysfunction

Obesity has increased dramatically worldwide. Being overweight or obese can lead to various conditions, including dyslipidaemia, hypertension, glucose intolerance and metabolic syndrome (MetS), which may further lead to type 2 diabetes mellitus (T2DM). Previous studies have identified a link between β-cell dysfunction and the severity of MetS, with multiple organs and tissues affected. Identifying the associations between pancreatic β-cell dysfunction and organs is critical. Research has focused on the interaction between the liver, gut and pancreatic β-cells. However, the mechanisms and related core targets are still not perfectly elucidated. The aims of this review were to summarize the mechanisms of β-cell dysfunction and to explore the potential pathogenic pathways and targets that connect the liver, gut, adipose tissue, muscle, and brain to pancreatic β-cell dysfunction.

Linking serotonin homeostasis to gut function: Nutrition, gut microbiota and beyond

Serotonin (5-HT) produced by enterochromaffin (EC) cells in the digestive tract is crucial for maintaining gut function and homeostasis. Nutritional and non-nutritional stimuli in the gut lumen can modulate the ability of EC cells to produce 5-HT in a temporal- and spatial-specific manner that toning gut physiology and immune response. Of particular interest, the interactions between dietary factors and the gut microbiota exert distinct impacts on gut 5-HT homeostasis and signaling in metabolism and the gut immune response. However, the underlying mechanisms need to be unraveled. This review aims to summarize and discuss the importance of gut 5-HT homeostasis and its regulation in maintaining gut metabolism and immune function in health and disease with special emphasis on different types of nutrients, dietary supplements, processing, and gut microbiota. Cutting-edge discoveries in this area will provide the basis for the development of new nutritional and pharmaceutical strategies for the prevention and treatment of serotonin homeostasis-related gut and systematic disorders and diseases.

Microbiota influence on behavior: Integrative analysis of serotonin metabolism and behavioral profile in germ-free mice

Previous studies on germ-free (GF) animals have described altered anxiety-like and social behaviors together with dysregulations in brain serotonin (5-HT) metabolism. Alterations in circulating 5-HT levels and gut 5-HT metabolism have also been reported in GF mice. In this study, we conducted an integrative analysis of various behaviors as well as markers of 5-HT metabolism in the brain and along the GI tract of GF male mice compared with conventional (CV) ones. We found a strong decrease in locomotor activity, accompanied by some signs of increased anxiety-like behavior in GF mice compared with CV mice. Brain gene expression analysis showed no differences in HTR1A and TPH2 genes. In the gut, we found decreased TPH1 expression in the colon of GF mice, while it was increased in the cecum. HTR1A expression was dramatically decreased in the colon, while HTR4 expression was increased both in the cecum and colon of GF mice compared with CV mice. Finally, SLC6A4 expression was increased in the ileum and colon of GF mice compared with CV mice. Our results add to the evidence that the microbiota is involved in regulation of behavior, although heterogeneity among studies suggests a strong impact of genetic and environmental factors on this microbiota-mediated regulation. While no impact of GF status on brain 5-HT was observed, substantial differences in gut 5-HT metabolism were noted, with tissue-dependent results indicating a varying role of microbiota along the GI tract.

The cckOMA syndrome and its relation to the Zollinger-Ellison syndrome: a diagnostic challenge

OBJECTIVE

Among patients with enteropancreatic neuroendocrine tumor syndromes only one case with a cholecystokinin (CCK) secreting tumor has been reported. She had significant hyperCCKemia leading to a specific syndrome of severe diarrheas, weight loss, repeated duodenal ulcers and a permanently contracted gallbladder with gallstones. There are, however, reasons to believe that further CCKomas exist, for instance among Zollinger-Ellison patients with normal plasma gastrin concentrations. The present review is a call to gastroenterologists for awareness of such CCKoma patients.

METHOD

After a short case report, the normal endocrine and oncological biology of CCK is described. Subsequently, the CCKoma symptoms are discussed with particular reference to the partly overlapping symptoms of the Zollinger-Ellison syndrome. In this context, the diagnostic use of truly specific CCK and gastrin assays are emphasized. The discussion also entails the problem of access to accurate CCK measurements.

CONCLUSION

Obviously, the clinical awareness about the CCKoma syndrome is limited. Moreover, it is also likely that the knowledge about the necessary specificity demands of diagnostic gastrin and CCK assays have obscured proper diagnosis of the CCKoma syndromes in man.

Identification and target of action of cholecystokinin-releasing peptides from simulated digestion hydrolysate of wheat protein

BACKGROUND

Wheat protein intake leads to improved appetite control. However, the active components causing appetite in wheat have not been fully clarified. Gut cholecystokinin (CCK) plays a vital role in appetite control. This study aimed to investigate the ability of wheat protein digest (WPD) to stimulate CCK secretion and clarify the active components and target of action.

RESULTS

WPD was prepared by a simulated gastrointestinal digestion model. WPD treatment with a concentration of 5 mg mL-1 significantly stimulated CCK secretion in enteroendocrine STC-1 cells (P < 0.05). Furthermore, oral gavage with WPD in mice significantly increased plasma CCK level at 60 min (P < 0.01). Preparative C18 column separation was used to isolate peptide fractions associated with CCK secretion and peptide sequences were identified by liquid chromatography-tandem mass spectrometry. A new CCK-releasing peptide, RYIVPL, that potently stimulated CCK secretion was successfully identified. After pretreatment with a specific calcium-sensing receptor (CaSR) antagonist, NPS 2143, CCK secretion induced by WPD or RYIVPL was greatly suppressed, suggesting that CaSR was involved in WPD- or RYIVPL-induced CCK secretion.

CONCLUSION

The present study demonstrated that WPD has an ability to stimulate CCK secretion in vitro and in vivo, and determined that peptide RYIVPL in WPD could stimulate CCK secretion through CaSR. © 2023 Society of Chemical Industry.

Regional Growth Velocity and Incidence of Pancreatic Neuroendocrine Neoplasias in Multiple Endocrine Neoplasia Type 1

OBJECTIVES

Pancreatic neuroendocrine neoplasias (pNENs) in multiple endocrine neoplasia type 1 are predominantly found in the dorsal anlage. Whether their growth velocity and incidence might be related to their location in the pancreas has not been investigated yet.

METHODS

We studied 117 patients using endoscopic ultrasound.

RESULTS

Growth velocity could be calculated for 389 pNENs. Increase of largest tumor diameter (% per month) was 0.67 (standard deviation [SD], 2.04) in the pancreatic tail (n = 138), 1.12 (SD, 3.00) in the pancreatic body (n = 100), 0.58 (SD, 1.19) in the pancreatic head/uncinate process-dorsal anlage (n = 130), and 0.68 (SD, 0.77) in the pancreatic head/uncinate process-ventral anlage (n = 12). Comparing growth velocity of all pNENs in the dorsal (n = 368, 0.76 [SD, 2.13]) versus ventral anlage, no significant difference was detected. Annual tumor incidence rate was 0.21 in the pancreatic tail, 0.13 in the pancreatic body, 0.17 in the pancreatic head/uncinate process-dorsal anlage, 0.51 dorsal anlage together, and 0.02 in the pancreatic head/uncinate process-ventral anlage.

CONCLUSIONS

Multiple endocrine neoplasia type 1 pNENs are unequally distributed between ventral (low prevalence and incidence) and dorsal anlage. However, there are no regional differences in growth behavior.

Identification of key genes and pathways revealing the central regulatory mechanism of brain-derived glucagon-like peptide-1 on obesity using bioinformatics analysis

Objective

Central glucagon-like peptide-1 (GLP-1) is a target in treating obesity due to its effect on suppressing appetite, but the possible downstream key genes that GLP-1 regulated have not been studied in depth. This study intends to screen out the downstream feeding regulation genes of central GLP-1 neurons through bioinformatics analysis and verify them by chemical genetics, which may provide insights for future research.

Materials and methods

GSE135862 genetic expression profiles were extracted from the Gene Expression Omnibus (GEO) database. The gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were carried out. STRING database and Cytoscape software were used to map the protein-protein interaction (PPI) network of the differentially expressed genes (DEGs). After bioinformatics analysis, we applied chemogenetic methods to modulate the activities of GLP-1 neurons in the nucleus tractus solitarius (NTS) and observed the alterations of screened differential genes and their protein expressions in the hypothalamus under different excitatory conditions of GLP-1 neurons.

Results

A total of 49 DEGs were discovered, including 38 downregulated genes and 11 upregulated genes. The two genes with the highest expression scores were biglycan (Bgn) and mitogen-activated protein kinase activated protein kinase 3 (Mapkapk3). The results of GO analysis showed that there were 10 molecular functions of differential genes. Differential genes were mainly localized in seven regions around the cells, and enriched in 10 biology processes. The results of the KEGG signaling pathway enrichment analysis showed that differential genes played an important role in seven pathways. The top 15 genes selected according to the Cytoscape software included Bgn and Mapkapk3. Chemogenetic activation of GLP-1 in NTS induced a decrease in food intake and body mass, while chemogenetic inhibition induced the opposite effect. The gene and protein expression of GLP-1 were upregulated in NTS when activated by chemogenetics. In addition, the expression of Bgn was upregulated and that of Mapkapk3 was downregulated in the hypothalamus.

Conclusion

Our data showed that GLP-1 could modulate the protein expression of Bgn and Mapkapk3. Our findings elucidated the regulatory network in GLP-1 to obesity and might provide a novel diagnostic and therapeutic target for obesity.

Weight Loss and Gastrointestinal Hormone Variation Caused by Gastric Artery Embolization: An Updated Analysis Study

OBJECTIVE

Many gastric artery embolizations (GAE) have been performed in recent years. We try to determine whether GAE caused weight loss by decreasing gastrointestinal hormone through the analysis of weight loss and gastrointestinal hormones changes.

METHODS

The PubMed and Medline databases, and the Cochrane Library, were searched using the following keywords. A total of 10 animal trials (n=144), 15 human trials (n=270) were included for analysis. After GAE, we mainly evaluated the changes in body weight loss (BWL) and body mass index (BMI), as well as metabolic indexes, such as blood glucose, lipids, and gastrointestinal hormones levels.

RESULTS

Animal subjects received either chemical or particle embolization, while human subjects only received particle embolization. In animal trials (growing period), the GAE group gained weight significantly slower than the sham-operated group, ghrelin levels decreased. In human trials, GAE brought more weight loss in the early stages, with a trend towards weight recovery after several months that was still lower than baseline levels. Besides weight loss, abnormal metabolic indicators, such as blood glucose and lipids were modified, and the quality of life (QOL) scores of obese patients improved. In addition, weight loss positively correlates with ghrelin.

CONCLUSION

GAE may help people lose weight and become a new minimally invasive and effective surgery for the treatment of modest obesity. Physiologic changes in gastrointestinal tract of gastrointestinal hormones level may be one reason for weight loss in GAE.

Potential Roles of Enterochromaffin Cells in Early Life Stress-Induced Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, also known as disorders of the gut–brain interaction; however, the pathophysiology of IBS remains unclear. Early life stress (ELS) is one of the most common risk factors for IBS development. However, the molecular mechanisms by which ELS induces IBS remain unclear. Enterochromaffin cells (ECs), as a prime source of peripheral serotonin (5-HT), play a pivotal role in intestinal motility, secretion, proinflammatory and anti-inflammatory effects, and visceral sensation. ECs can sense various stimuli and microbiota metabolites such as short-chain fatty acids (SCFAs) and secondary bile acids. ECs can sense the luminal environment and transmit signals to the brain via exogenous vagal and spinal nerve afferents. Increasing evidence suggests that an ECs-5-HT signaling imbalance plays a crucial role in the pathogenesis of ELS-induced IBS. A recent study using a maternal separation (MS) animal model mimicking ELS showed that MS induced expansion of intestinal stem cells and their differentiation toward secretory lineages, including ECs, leading to ECs hyperplasia, increased 5-HT production, and visceral hyperalgesia. This suggests that ELS-induced IBS may be associated with increased ECs-5-HT signaling. Furthermore, ECs are closely related to corticotropin-releasing hormone, mast cells, neuron growth factor, bile acids, and SCFAs, all of which contribute to the pathogenesis of IBS. Collectively, ECs may play a role in the pathogenesis of ELS-induced IBS. Therefore, this review summarizes the physiological function of ECs and focuses on their potential role in the pathogenesis of IBS based on clinical and pre-clinical evidence.

Pancreatic Neuroendocrine Neoplasias in Multiple Endocrine Neoplasia Type 1 Are Predominantly Located in the Dorsal Anlage: An Endoscopic Ultrasound Study

OBJECTIVES

Pancreatic neuroendocrine neoplasias (pNENs) frequently occur in multiple endocrine neoplasia type 1 (MEN1). Their distribution referring to embryology, that is, the pancreatic anlagen, has not been investigated yet.

METHODS

In the time between 1998 and 2019, we studied the distribution of pNENs in MEN1 concerning the embryologic origin of the pancreas, that is, the dorsal versus ventral anlage using endoscopic ultrasound in 117 MEN1 patients: 56 women, 61 men; aged 40 years (standard deviation, 14 years) at first endoscopic ultrasound.

RESULTS

In 105 patients, a total of 628 pNENs were detected. They were located in the pancreatic tail: 231; pancreatic body: 177; pancreatic head/uncinate process: 220. Of the latter, 22 were located in the ventral anlage, 176 in the dorsal anlage, and 22 remained undefined. In summary, just 3.5% of all detected pNENs were located in the ventral anlage, 93.0% in the dorsal anlage, and 3.5% could not be assigned.

CONCLUSIONS

Our study indicates that the vast majority of pNENs in MEN1 is located in the dorsal anlage, whereas the ventral anlage of the pancreas seems to be to a large extend spared from pNENs. Implications for new surgical strategies might be considered.

Therapeutic efficiency of adipose-derived mesenchymal stem cells in healing of experimentally induced gastric ulcers in rats

Gastric (peptic) ulcer is a major gastrointestinal disorder with high morbidity and mortality. While several drugs have been used to treat gastric ulcers, such as proton pump inhibitor-based triple therapy for Helicobacter pylori eradication, but hey result in adverse side effects. Therefore, development of new alternative therapies is desirable. Many recent studies have shown that mesenchymal stem cells (MSCs) might have an enhancing effect on the ulcerated gastric mucosa. The aim of this study is to evaluate the efficacy of MSCs in the treatment of indomethacin-induced gastric ulcer, and to compare it with the normal ulcer autohealing. This work was performed on 36 adult male albino rats, divided into four groups: Group I (control group), Group II (ulcer group), Group III (autohealing group), and Group IV (stem cells-treated group). The histological changes of gastric mucosa were examined in sections stained with H&E using light microscope for expression of vascular endothelial growth factors (VEGF) and proliferating cell nuclear antigen (PCNA) in immunohistochemical stained sections using image analyzer. The results from MSCs-treated group revealed restoration of the normal architecture of the gastric mucosa with comparison to the autohealing group which showed excessive granulation tissue and heavy cellular infiltration with disorganized architecture of the fundic mucosa. Immunohistochemical examination showed strong expression of both VEGF and PCNA in the MSCs-treated group. So it was concluded that MSCs accelerate gastric ulcer healing when injected intraperitoneally, compared to autohealing process which showed delayed healing.

Expression of Cholecystokinin and its Receptors in the Intestinal Tract of Type 2 Diabetes Patients and Healthy Controls

BACKGROUND

Cholecystokinin (CCK) is a gut hormone originally known for its effects on gallbladder contraction and release of digestive enzymes. CCK, however, also mediates satiety and stimulate insulin secretion. Knowledge of the distribution of CCK-producing enteroendocrine cells (I cells) in humans is sparse. The general notion, based on animal data, is that I cells are present mainly in the proximal small intestine. We examined the occurrence of I cells (immunohistochemically) and the expression of CCK messenger RNA (mRNA) as well as CCK1 and CCK2 receptor mRNA along the intestines in healthy individuals and patients with type 2 diabetes.

METHODS

Mucosal biopsies collected with 30-cm intervals in the small intestine and from seven anatomical locations in the large intestine (using double-balloon enteroscopy) from 12 patients with type 2 diabetes and 12 gender-, age-, and body mass index-matched healthy individuals were analyzed using mRNA sequencing and immunohistochemical staining.

RESULTS

We observed a gradual decrease in CCK mRNA expression and density of CCK-immunoreactive cells from duodenum to ileum. Very few CCK-immunoreactive cells and nearly undetectable CCK mRNA expression were found in the large intestine. No significant differences were seen between the groups. Expression of CCK receptors was observed in the duodenum of both groups.

CONCLUSIONS

Both density of CCK cells and expression of CCK mRNA decreased through the small intestine in both groups with low levels in the large intestine. Patients with type 2 diabetes did not have altered density of CCK cells or expression of CCK mRNA in intestinal mucosa.

Pain in Inflammatory Bowel Disease: Optogenetic Strategies for Study of Neural-Epithelial Signaling

Abdominal pain is common in patients with active inflammation of the colon but can persist even in its absence, suggesting other mechanisms of pain signaling. Recent findings suggest colon epithelial cells are direct regulators of pain-sensing neurons. Optogenetic activation of epithelial cells evoked nerve firing and pain-like behaviors. Inhibition of epithelial cells caused the opposite effect, reducing responses to colon distension and inflammatory hypersensitivity. Thus, epithelial cells alone can regulate the activation of pain circuits. Future goals are to define the anatomical and cellular mechanisms that underlie epithelial-neural pain signaling and how it is altered in response to colon inflammation.

Cholecystokinin and the hormone concept

The birth certificate for endocrinology was Bayliss' and Starling's demonstration in 1902 that regulation of bodily functions is not only neuronal but also due to blood-borne messengers. Starling named these messengers hormones. Since then transport via blood has defined hormones. This definition, however, may be too narrow. Thus, today we know that several peptide hormones are not only produced and released to blood from endocrine cells but also released from neurons, myocytes, immune cells, endothelial cells, spermatogenic cells, fat cells, etc. And they are often secreted in cell-specific molecular forms with more or less different spectra of activity. The present review depicts this development with the story about cholecystokinin which was discovered in 1928 as a hormone and still in 1976 was conceived as a single blood-borne peptide. Today's multifaceted picture of cholecystokinin suggests that time may be ripe for expansion of the hormone concept to all messenger molecules, which activate their target cells - irrespective of their road to the target (endocrine, neurocrine, neuronal, paracrine, autocrine, etc.) and irrespective of their kind of activity as classical hormone, growth factor, neurotransmitter, adipokine, cytokine, myokine, or fertility factor.

Expression of TAS2R14 in the intestinal endocrine cells of non-human primates

BACKGROUND

Recent studies have demonstrated that genes related to bitter taste receptors (TAS2Rs) on various chromosomes are expressed in extra-oral organs of various animals. The bitter taste receptor TAS2R14 is conserved among primate species and shows broad ligand sensitivity. Mice have a number of orthologues to primate TAS2R14 located in tandem on chromosome 16; however, their expression patterns are not unique.

OBJECTIVE

We characterized the expression of TAS2R14 in various cell types in the intestines of the rhesus macaque and evaluated its role in hormone production in the gut.

METHODS

TAS2R14 expression was examined in the intestines of rhesus macaques, a common non-human primate model, by RT-qPCR and immunohistochemical staining.

RESULTS

Mean expression levels of TAS2R14 in the duodenum, ileum, and colon were similar to each other and were lower than those in circumvallate papillae. An immunohistochemical analysis revealed TAS2R14 immunoreactivity in enteroendocrine cells positive for cholecystokinin, serotonin, and the G protein GNAT3.

CONCLUSION

These results suggest that primate TAS2R14 is broadly expressed in the intestine, mainly in enteroendocrine cells, and promotes gut hormone secretion in response to bitter stimuli.

Supplementing Synbiotic in Sows' Diets Modifies Beneficially Blood Parameters and Colonic Microbiota Composition and Metabolic Activity in Suckling Piglets

Nutrients in the maternal diet favor the growth and development of suckling piglets and alter their gut microbiota composition and metabolic activity, thus affecting the hosts. The present study analyzed, in suckling piglets from sows receiving antibiotic or synbiotic supplements from pregnancy to lactation, several biochemical parameters, oxidative/anti-oxidative indices, inflammatory cytokines, and ingestion-related factor levels in plasma, as well as colonic microbiota composition and metabolic activity, and mucosal expression of genes related to the intestinal barrier function. Compared with the control group, maternal synbiotic supplementation decreased (P < 0.05) the plasma levels of glucose, AMM, TC, low-density lipoprotein-cholesterol (LDL-C), MDA, H₂O₂, ghrelin, CCK, PP, IL-1β, IL-2, IL-6, TNF-α, Ala, Cys, Tau, and β-AiBA, the levels of propionate and total short-chain fatty acids (SCFAs) in the colonic luminal content, and colonic abundances of RFN20, Anaerostipes, and Butyricimonas; while increased (P < 0.05) the plasma levels of urea nitrogen (UN), Ile, Leu, α-AAA, α-ABA, and 1-Mehis, as well as colonic abundances of Sphingomonas, Anaerovorax, Sharpea, and Butyricicoccus. Compared with the antibiotic group, maternal synbiotic supplementation decreased (P < 0.05) the plasma levels of glucose, gastrin, and Ala, as well as abundances of Pasteurella and RFN20 and propionate level in the colonic content. Expression of genes coding for E-cadherin, Occludin, ZO-1, ZO-2, IL-10, and interferon-α were down-regulated in the colonic mucosa. The synbiotic supplementation increased (P < 0.05) the plasma levels of UN, Leu, α-ABA, and 1-Mehis, the abundances of Anaerovorax, Sharpea, and Butyricicoccus and expression of genes coding for E-cadherin, Occludin, ZO-1, ZO-2, IL-10, and interferon-α. Spearman correlation analysis showed that there was a positive correlation between colonic Anaerostipes abundance and acetate and SCFAs levels; whereas a negative correlation between Fusobacteria and Fusobacterium abundances and acetate level. These findings suggest that synbiotic supplementation in the maternal diet improved nutrient metabolism and intestinal barrier permeability, reduced oxidative stress, and modified colonic microbiota composition and metabolic activity in suckling piglets.

Molecular Mechanism Contributing to Malnutrition and Sarcopenia in Patients with Liver Cirrhosis

Liver cirrhosis is frequently accompanied by disease-related malnutrition (DRM) and sarcopenia, defined as loss of skeletal muscle mass and function. DRM and sarcopenia often coexist in cirrhotic patients and are associated with increased morbidity and mortality. The clinical manifestation of both comorbidities are triggered by multifactorial mechanisms including reduced nutrient and energy intake caused by dietary restrictions, anorexia, neuroendocrine deregulation, olfactory and gustatory deficits. Maldigestion and malabsorption due to small intestinal bacterial overgrowth, pancreatic insufficiency or cholestasis may also contribute to DRM and sarcopenia. Decreased protein synthesis and increased protein degradation is the cornerstone mechanism to muscle loss, among others mediated by disease- and inflammation-mediated metabolic changes, hyperammonemia, increased myostatin and reduced human growth hormone. The concise pathophysiological mechanisms and interactions of DRM and sarcopenia in liver cirrhosis are not completely understood. Furthermore, most knowledge in this field are based on experimental models, but only few data in humans exist. This review summarizes known and proposed molecular mechanisms contributing to malnutrition and sarcopenia in liver cirrhosis and highlights remaining knowledge gaps. Since, in the prevention and treatment of DRM and sarcopenia in cirrhotic patients, more research is needed to identify potential biomarkers for diagnosis and development of targeted therapeutic strategies.

Serotonin transporter and cholecystokinin in diarrhea-predominant irritable bowel syndrome: Associations with abdominal pain, visceral hypersensitivity and psychological performance

BACKGROUND

Visceral hypersensitivity and psychological performance are the main pathophysiological mechanisms of irritable bowel syndrome (IBS). Previous studies have found that cholecystokinin (CCK) can enhance colon movement and that serotonin transporter (SERT) is a transmembrane transport protein with high affinity for 5-hydroxytryptamine, which can rapidly reuptake 5-hydroxytryptamine and then regulate its action time and intensity. We speculate that SERT and CCK might play a role in the pathogenesis of diarrhea-predominant IBS (IBS-D) by affecting visceral sensitivity and the brain-gut axis.

AIM

To determine SERT and CCK levels in IBS-D patients diagnosed using Rome IV criteria and to analyze their associations with abdominal pain, visceral hypersensitivity and psychological performance.

METHODS

This study collected data from 40 patients with IBS-D at the China-Japan Friendship Hospital from September 2017 to April 2018 and 18 healthy controls. The severity of abdominal pain, visceral sensitivity and psychological performance were evaluated in IBS-D patients and healthy controls, the levels of SERT and CCK in plasma and colonic mucosa were evaluated, and the correlations between them were analyzed.

RESULTS

There were significant differences in the initial sensation threshold (31.00 ± 8.41 mL vs 52.22 ± 8.09 mL, P < 0.001), defecating sensation threshold (51.75 ± 13.57 mL vs 89.44 ± 8.73 mL, P < 0.001) and maximum tolerable threshold (97.25 ± 23.64 mL vs 171.11 ± 20.83 mL, P < 0.001) between the two groups. IBS-D patients had more severe anxiety (7.78 ± 2.62 vs 2.89 ± 1.02, P < 0.001) and depressive (6.38 ± 2.43 vs 2.06 ± 0.73, P < 0.001) symptoms than healthy controls. Significant differences were also found in mucosal CCK (2.29 ± 0.30 vs 1.66 ± 0.17, P < 0.001) and SERT (1.90 ± 0.51 vs 3.03 ± 0.23, P < 0.001) between the two groups. There was a significant positive correlation between pain scores and mucosal CCK (r = 0.96, 0.93, 0.94, P < 0.001). Significant negative correlations between anxiety (r = -0.98; P < 0.001), depression (r = -0.99; P < 0.001), pain evaluation (r = -0.96, -0.93, -0.95, P < 0.001) and mucosal SERT were observed.

CONCLUSION

IBS-D patients had psychosomatic disorders and visceral hypersensitivity. SERT and CCK might be involved in the pathogenesis of IBS-D by regulating the brain-gut axis and affecting visceral sensitivity. This provides a new potential method for identifying a more specific and effective therapeutic target.

Premises for Cholecystokinin and Gastrin Peptides in Diabetes Therapy

Gastrin and cholecystokinin (CCK) are classical gastrointestinal peptide hormones. Their biogenesis, structures, and intestinal secretory patterns are well-known with the striking feature that their receptor-bound 'active sites' are highly homologous and that this structure is conserved for more than 500 million years during evolution. Consequently, gastrin and CCK are agonists for the same receptor (the CCK2 receptor). But in addition, tyrosyl O-sulphated CCK are also bound to the specific CCK1 receptor. The receptors are widely expressed in the body, including pancreatic islet-cell membranes. Moreover, CCK and gastrin peptides are at various developmental stages and diseases expressed in pancreatic islets; also in human islets. Accordingly, bioactive gastrin and CCK peptides stimulate islet-cell growth as well as insulin and glucagon secretion. In view of their insulinotropic effects, gastrin and CCK peptides have come into focus as drug targets, either alone or in combination with other insulinotropic gut hormones or growth factors. So far, modified CCK and gastrin peptides are being examined as potential drugs for therapy of type 1 as well as type 2 diabetes mellitus.

Branched chain amino acids stimulate gut satiety hormone cholecystokinin secretion through activation of the umami taste receptor T1R1/T1R3 using an in vitro porcine jejunum model

Branched chain amino acids (BCAAs) are essential amino acids involved in regulation of feed intake. The function of BCAAs on the central nervous system has been extensively studied, but effects of BCAAs on secretion of gut satiety hormones and their underlying mechanisms are largely unknown. In this study, we evaluated the distribution of gut hormones and amino acid receptors in the porcine GI tract and found cholecystokinin (CCK) and taste dimeric receptor type 1 member 1/3 (T1R1/T1R3) were predominantly expressed in the jejunum and functionally interrelated. We further evaluated the effects of l-leucine, l-isoleucine, l-valine, and BCAAs on CCK and T1R1/T1R3 expression in porcine jejunum tissue. Our data demonstrated that stimulation of porcine jejunum tissue with 10 mM l-leucine, l-isoleucine or BCAAs mix (l-leucine : l-isoleucine : l-valine = 1 : 0.51 : 0.63) for 2 hours significantly increased mRNA expression and protein abundance of T1R1/T1R3 and secretion of CCK (P < 0.05). However, the l-valine treatment only increased the mRNA and protein abundance of T1R1 and T1R3 (P < 0.05), but not CCK secretion (P > 0.10). l-Leucine-, l-isoleucine- or BCAAs mix-induced CCK secretion was significantly decreased after tissues were pretreated with lactisole, a T1R1/T1R3 inhibitor (P < 0.05). Furthermore, the increased mRNA and protein abundance of T1R1/T1R3 were also largely attenuated by blocking T1R1/T1R3 with lactisole (P < 0.05). l-Leucine, l-isoleucine and BCAAs mix appeared to induce the gut satiety hormone CCK secretion through jejunal T1R1/T1R3. These results indicate over-supplementation with BCAAs in the diet might decrease food intake in swine and humans through gastrointestinal feedback.

Quantitation and chemical coding of enteroendocrine cell populations in the human jejunum

Recent studies reveal substantial species and regional differences in enteroendocrine cell (EEC) populations, including differences in patterns of hormone coexpression, which limit extrapolation between animal models and human. In this study, jejunal samples, with no histologically identifiable pathology, from patients undergoing Whipple's procedure were investigated for the presence of gastrointestinal hormones using double- and triple-labelling immunohistochemistry and high-resolution confocal microscopy. Ten hormones (5-HT, CCK, secretin, proglucagon-derived peptides, PYY, GIP, somatostatin, neurotensin, ghrelin and motilin) were localised in EEC of the human jejunum. If only single staining is considered, the most numerous EEC were those containing 5-HT, CCK, ghrelin, GIP, motilin, secretin and proglucagon-derived peptides. All hormones had some degree of colocalisation with other hormones. This included a population of EEC in which GIP, CCK and proglucagon-derived peptides are costored, and four 5-HT cell populations, 5-HT/GIP, 5-HT/ghrelin, 5-HT/PYY, and 5-HT/secretin cell groups, and a high degree of overlap between motilin and ghrelin. The presence of 5-HT in many secretin cells is consistent across species, whereas lack of 5-HT and CCK colocalisation distinguishes human from mouse. It seems likely that the different subclasses of 5-HT cells subserve different roles. At a subcellular level, we examined the vesicular localisation of secretin and 5-HT, and found these to be separately stored. We conclude that hormone-containing cells in the human jejunum do not comply with a one-cell, one-hormone classification and that colocalisations of hormones are likely to define subtypes of EEC that have different roles.

Fructose malabsorption induces cholecystokinin expression in the ileum and cecum by changing microbiota composition and metabolism

Current fructose consumption levels often overwhelm the intestinal capacity to absorb fructose. We investigated the impact of fructose malabsorption on intestinal endocrine function and addressed the role of the microbiota in this process. To answer this question, a mouse model of moderate fructose malabsorption [ketohexokinase mutant (KHK)^-/-] and wild-type (WT) littermate mice were used and received a 20%-fructose (KHK-F and WT-F) or 20%-glucose diet. Cholecystokinin (Cck) mRNA and protein expression in the ileum and cecum, as well as preproglucagon (Gcg) and neurotensin (Nts) mRNA expression in the cecum, increased in KHK-F mice. In KHK-F mice, triple-label immunohistochemistry showed major up-regulation of CCK in enteroendocrine cells (EECs) that were glucagon-like peptide-1 (GLP-1)⁺/Peptide YY (PYY^-) in the ileum and colon and GLP-1^-/PYY^- in the cecum. The cecal microbiota composition was drastically modified in the KHK-F in association with an increase in glucose, propionate, succinate, and lactate concentrations. Antibiotic treatment abolished fructose malabsorption-dependent induction of cecal Cck mRNA expression and, in mouse GLUTag and human NCI-H716 cells, Cck mRNA expression levels increased in response to propionate, both suggesting a microbiota-dependent process. Fructose reaching the lower intestine can modify the composition and metabolism of the microbiota, thereby stimulating the production of CCK from the EECs possibly in response to propionate.-Zhang, X., Grosfeld, A., Williams, E., Vasiliauskas, D., Barretto, S., Smith, L., Mariadassou, M., Philippe, C., Devime, F., Melchior, C., Gourcerol, G., Dourmap, N., Lapaque, N., Larraufie, P., Blottière, H. M., Herberden, C., Gerard, P., Rehfeld, J. F., Ferraris, R. P., Fritton, J. C., Ellero-Simatos, S., Douard, V. Fructose malabsorption induces cholecystokinin expression in the ileum and cecum by changing microbiota composition and metabolism.

Enterochromaffin cells and gastrointestinal diseases

Enterochromaffin cells (ECs), known for their special histochemical characteristics, originate from enteroblasts. For their important role in physiological and pathophysiological conditions, ECs in the gut could synthesize and secrete about 95% of 5-hydroxytryptamine (5-HT) in the body, which is an important humoral factor. As a chemosensor, ECs can regulate nutrition absorption and satiety through the sensory neural pathways. In addition, ECs participate in immune regulation. What's more, ECs and 5-HT are closely related to many kinds of gastrointestinal diseases.

Procholecystokinin expression and processing in cardiac myocytes

The mammalian heart is by now an established endocrine organ whose myocytes in a regulated manner release atrial and ventricular natriuretic peptides (ANP and BNP). But like other hormone-producing cells in classic endocrine organs, the cardiac myocytes also express genes of additional peptide hormones. One such hormone gene is that of the well-known pleiotropic gut-brain peptide system, cholecystokinin (CCK), which is expressed at mRNA and protein levels in both atrial and ventricular cardiac myocytes. The posttranslational processing of proCCK in the myocytes, however, deviates substantially from that of other CCK-producing cells. Hence, the predominant cardiac proCCK product is devoid of the N-terminal 1-24 fragment, and besides O-sulfated at three C-terminal tyrosyl residues (Y₇₆, Y₉₀, and Y₉₂). Moreover, carboxyamidated CCK peptides are present only in very low trace amounts (≤0.1%) in comparison with the truncated and triple-sulfated proCCK fragment. The present review first summarizes present knowledge about the wide-spread expression of the CCK system in mammals, and then discusses the possible function and biomarker role of the specific cardiac proCCK variant. The review concludes that the many unsettled questions about the specific cardiac expression cascade as well as the functional and diagnostic roles of cardiac CCK are worth pursuing.

Vitamin E supplementation and caloric restriction promotes regulation of insulin secretion and glycemic homeostasis by different mechanisms in rats

Vitamin E and caloric restriction have antioxidant effects in mammals. The aim of this study was to evaluate effects of vitamin E supplementation and caloric restriction upon insulin secretion and glucose homeostasis in rats. Male Wistar rats were distributed among the following groups: C, control group fed ad libitum; R, food quantity reduction of 40%; CV, control group supplemented with vitamin E [30 mg·kg^-1·day^-1]; and RV, food-restricted group supplemented with vitamin E. The experiments ran for 21 days. Glucose tolerance and insulin sensitivity was higher in the CV, R, and RV groups. Insulin secretion stimulated with different glucose concentrations was lower in the R and RV groups, compared with C and CV. In the presence of glucose and secretagogues, insulin secretion was higher in the CV group and was lower in the R and RV groups. An increase in insulin receptor occurred in the fat pad and muscle tissue of groups CV, R, and RV. Levels of hepatic insulin receptor and phospho-Akt protein were higher in groups R and RV, compared with C and CV, while muscle phospho-Akt was increased in the CV group. There was a reduction in hepatic RNA levels of the hepatocyte growth factor gene and insulin degrading enzyme in the R group, and increased levels of insulin degrading enzyme in the CV and RV groups. Thus, vitamin E supplementation and caloric restriction modulate insulin secretion by different mechanisms to maintain glucose homeostasis.

Diversity of enteroendocrine cells investigated at cellular and subcellular levels: the need for a new classification scheme

Enteroendocrine cells were historically classified by a letter code, each linked to a single hormone, deduced to be the only hormone produced by the cell. One type, the L cell, was recognised to store and secrete two products, peptide YY (PYY) and glucagon-related peptides. Many other exceptions to the one-cell one-hormone classifications have been reported over the last 40 years or so, and yet the one-hormone dogma has persisted. In the last 6 years, a plethora of data has appeared that makes the concept unviable. Here, we describe the evidence that multiple hormone transcripts and their products reside in single cells and evidence that the hormones are often, but not always, processed into separate storage vesicles. It has become clear that most enteroendocrine cells contain multiple hormones. For example, most secretin cells contain 5-hydroxytryptamine (5-HT), and in mouse many of these also contain cholecystokinin (CCK). Furthermore, CCK cells also commonly store ghrelin, glucose-dependent insulinotropic peptide (GIP), glucagon-like peptide-1 (GLP-1), neurotensin, and PYY. Several hormones, for example, secretin and 5-HT, are in separate storage vesicles at a subcellular level. Hormone patterns can differ considerably between species. Another complication is that relative levels of expression vary substantially. This means that data are significantly influenced by the sensitivities of detection techniques. For example, a hormone that can be detected in storage vesicles by super-resolution microscopy may not be above threshold for detection by conventional fluorescence microscopy. New nomenclature for cell clusters with common attributes will need to be devised and old classifications abandoned.

Tuft cells: Distribution and connections with nerves and endocrine cells in mouse intestine

Tuft cells are gastrointestinal (GI) sensory cells recognized by their characteristic shape and their microvilli "tuft". Aims of the present study were to elucidate their regional distribution and spatial connections with satiety associated endocrine cells and nerve fibers throughout the intestinal tract. C57BL/6 J mice were used in the experiments. The small intestine was divided into five segments, and the large intestine was kept undivided. The segments were coiled into "Swiss rolls". Numbers and topographic distribution of tuft cells and possible contacts with endocrine cells and nerve fibers were estimated in the different segments, using immunocytochemistry. Tuft cells were found throughout the intestines; the highest number was in proximal small intestine. Five percent of tuft cells were found in close proximity to cholecystokinin-immunoreactive (IR) endocrine cells and up to 10% were in contact with peptide YY- and glucagon-like peptide-1-IR endocrine cells. Sixty percent of tuft cells in the small intestine and 40% in the large intestine were found in contact with nerve fibers. Calcitonin gene-related peptide-IR fibers constituted one-third of the fiber-contacts in the small intestine and two-thirds in the large intestine. These observations highlight the possibility of tuft cells as modulators of GI activities in response to luminal signaling.

Gastrointestinal distribution of chicken gastrin-cholecystokinin family transcript expression and response to short-term nutritive state

The related peptide hormones cholecystokinin (CCK) and gastrin are conserved throughout vertebrate clades and implicated in energy homeostasis. CCK is generally accepted as a satiety hormone in poultry, but the role of gastrin remains poorly studied. Functional dissection of these ligands is required to characterise the molecular control of growth & satiety in the domestic chicken, for which there is an increasingly pressing mandate. There are limited descriptions of physiological distributions for the two genes in birds, and these are mostly reliant on immunohistochemistry which can prove problematic due to the shared structure of the targets. Therefore, we have defined the tissue distributions of CCK and gastrin in the chicken, focussing on the gastrointestinal tract, by using transcript-dependent techniques to improve reliability by increasing specificity. Though considerably more highly expressed in the brain, gastrointestinal CCK transcripts were dispersed throughout the small intestine and particularly around the proximal ileum. Gastrin expression was strictly limited to the gastric antrum region of the intestinal tract, albeit very highly expressed. We demonstrate that CCK mRNA expression does not respond as expected for a short-term satiety hormone, and that the short-term response of gastrin expression is paradoxical compared to its role in mammals. These results partially corroborate previous peptide distribution studies and initiate exploration of the nutrient-responsive roles of these hormones in avian energy balance.