Metabolic basis of host-flora interactions in the gut - Role of CLA

Background and Aims: The bacterial metabolites that signal host-nom interactions in the gut are poorly understood, partly because of technologic difficulty culturing much of the flora. One candidate metabolite that may exert a conditioning effect oil mucosal homeostasis is the cis -9, trans -11 conjugated linoleic acid (CLA) isomer, which has immunomodulatory and anti-proliferative properties similar to other ligands for PPARs (peroxisome proliferator-activator receptor). The aims of this study were: (a) to examine the profile of different strains of the genus Bifidobacterium from human neonatal fecal microflora for production of CLA isomer in vitro arid (h) to determine the impact of CIA and similar ligand on cytokine production by intestinal lymphocytes. Methods A total of 46 isolates from feces of six neonates were confirmed to be Bifidobacterium species based on a combination of the fructose-6-phosphate phosphoketolase assay (F-6-PPK), RAPD PCR, pulsed field gel electrophoresis (PFGE) and partial 16S rDNA sequencing. All genetically-distinct strains were screened for CLA production following 72 h incubation with 0.5 mg ml(-1) free linoleic acid using gas-liquid chromatography (GLC). The influence of CLA on cytokine production by CD2/CD2-stimulated mucosal lymphocytes after 48 hour culture was assessed by ELISA. Results Bifidobacterin with capacity to produce CLA were found to develop in neonates shortly after birth, but there was considerable genomic diversity among the colonizing Bifidobacterium population, Bifidobacterium breve and Bifidobacterium bifidum sp. were the most efficient producers of CLA, converting 29% and 18% of linoleic acid to CLA/mu g dry, cells, respectively. Both CLA and the PPAR agonist 15dPGJ2 and to a lesser degree ciglitazone exhibited a significant dose-dependent (