ABSTRACT
The chemosensory components shared by both lingual and intestinal epithelium play a critical role in food consumption and the regulation of intestinal functions. In addition to nutrient signals, other luminal contents, including micro-organisms, are important in signalling across the gastrointestinal mucosa and initiating changes in digestive functions. A potential role of gut microbiota in influencing food intake, energy homeostasis and weight gain has been suggested. However, whether gut microbiota modulates the expression of nutrient-responsive receptors and transporters, leading to altered food consumption, is unknown. Thus, we examined the preference for nutritive (sucrose) and non-nutritive (saccharin) sweet solutions in germ-free (GF, C57BL/6J) mice compared with conventional (CV, C57BL/6J) control mice using a two-bottle preference test. Then, we quantified mRNA and protein expression of the sweet signalling protein type 1 taste receptor 3 (T1R3) and α-gustducin and Na glucose luminal transporter-1 (SGLT-1) of the intestinal epithelium of both CV and GF mice. Additionally, we measured gene expression of T1R2, T1R3 and α-gustducin in the lingual epithelium. We found that, while the preference for sucrose was similar between the groups, GF mice consumed more of the high concentration (8 %) of sucrose solution than CV mice. There was no difference in either the intake of or the preference for saccharin. GF mice expressed significantly more T1R3 and SGLT-1 mRNA and protein in the intestinal epithelium compared with CV mice; however, lingual taste receptor mRNA expression was similar between the groups. We conclude that the absence of intestinal microbiota alters the expression of sweet taste receptors and GLUT in the proximal small intestine, which is associated with increased consumption of nutritive sweet solutions.
Subject(s)
Dietary Sucrose/administration & dosage , Food Preferences , Intestinal Mucosa/metabolism , Intestinal Mucosa/microbiology , Receptors, G-Protein-Coupled/metabolism , Sodium-Glucose Transporter 1/metabolism , Up-Regulation , Animals , Appetite Regulation , Down-Regulation , Duodenum , Germ-Free Life , Heterotrimeric GTP-Binding Proteins/genetics , Heterotrimeric GTP-Binding Proteins/metabolism , Jejunum , Male , Mice , Mice, Inbred C57BL , Mouth Mucosa/metabolism , Mouth Mucosa/microbiology , Protein Isoforms/genetics , Protein Isoforms/metabolism , RNA, Messenger/metabolism , Receptors, G-Protein-Coupled/genetics , Saccharin/administration & dosage , Sodium-Glucose Transporter 1/genetics , TongueABSTRACT
AIMS: To compare in vitro the inhibitory activity of four bacteriocin-producing Escherichia coli to a well-characterized panel of Salmonella strains, recently isolated from clinical cases in Switzerland. METHODS AND RESULTS: A panel of 68 nontyphoidal Salmonella strains was characterized by pulsed-field gel electrophoresis analysis and susceptibility to antibiotics. The majority of tested strains were genetically different, with 40% resistant to at least one antibiotic. E. coli Mcc24 showed highest in vitro activity against Salmonella (100%, microcin 24), followed by E. coli L1000 (94%, microcin B17), E. coli 53 (49%, colicin H) and E. coli 52 (21%, colicin G) as revealed using a cross-streak activity assay. CONCLUSIONS: Escherichia coli Mcc24, a genetically modified organism producing microcin 24, and E. coli L1000, a natural strain isolated from human faeces carrying the mcb-operon for microcin B17-production, were the most effective strains in inhibiting in vitro both antibiotic resistant and sensitive Salmonella isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: Due to an increasing prevalence of antibiotic resistant Salmonella strains, alternative strategies to fight these foodborne pathogens are needed. E. coli L1000 appears to be a promising candidate in view of developing biotechnological alternatives to antibiotics against Salmonella infections.
