title: GABA selectively increases mucin-1 expression in isolated pig jejunum.
abstract: The inhibitory neurotransmitter GABA (γ-aminobutyric acid) is synthesized by glutamic acid decarboxylase, which is expressed in the central nervous system and in various other tissues including the intestine. Moreover, GABA can be ingested in vegetarian diets or produced by bacterial commensals in the gastrointestinal tract. As previous studies in lung have suggested a link between locally increased GABA availability and mucin 5AC production, the present study sought to test whether the presence or lack of GABA (and its precursor glutamine) has an effect on intestinal mucin expression. Porcine jejunum epithelial preparations were incubated with two different amounts of GABA or glutamine on the mucosal side for 4 h, and changes in the relative gene expression of seven different mucins, enzymes involved in mucin shedding, GABA B receptor, enzymes involved in glutamine/GABA metabolism, glutathione peroxidase 2, and interleukin 10 were examined by quantitative PCR (TaqMan(®) assays). Protein expression of mucin-1 (MUC1) was analyzed by Western blot. On the RNA level, only MUC1 was significantly up-regulated by both GABA concentrations compared with the control. Glutamine-treated groups showed the same trend. On the protein level, all treatment groups showed a significantly higher MUC1 expression than the control group. We conclude that GABA selectively increases the expression of MUC1, a cell surface mucin that prevents the adhesion of microorganisms, because of its size and negative charge, and therefore propose that the well-described positive effects of glutamine on enterocytes and intestinal integrity are partly attributable to effects of its metabolite GABA.
authors.affiliation: Institute of Veterinary Physiology, FU Berlin, Oertzenweg 19b, 14163 Berlin, Germany.
authors.forename: Hannah-Sophie
authors.initials: HS
authors.lastname: Braun
authors.affiliation: Institute of Veterinary Physiology, FU Berlin, Oertzenweg 19b, 14163 Berlin, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Sponder
authors.affiliation: Institute of Animal Nutrition, FU Berlin, Koenigin-Luise-Str. 49, 14195 Berlin, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Pieper
authors.affiliation: Institute of Veterinary Physiology, FU Berlin, Oertzenweg 19b, 14163 Berlin, Germany.
authors.forename: Jörg R
authors.initials: JR
authors.lastname: Aschenbach
authors.affiliation: Institute of Veterinary Physiology, FU Berlin, Oertzenweg 19b, 14163 Berlin, Germany.
authors.forename: Carolin
authors.identifier: 0000-0003-4047-625X
authors.initials: C
authors.lastname: Deiner
keywords: GABA; Glutamic acid decarboxylase; Glutamine; Gut health; Mucin