Abstract
The main effects on the host of some extracellular bacterial products, short-chain fatty acids (SCFAs), menaquinones and ubiquinones, are described in this paper. While few data are available on menaquinone and ubiquinone effects on mammalian cell properties, a vast literature exists on SCFAs. They are major by-products of anaerobic fermentation of unabsorbed starch and non-starch polysaccharides (i.e., dietary plant fibers) and constitute approximately two-thirds of the colon anion concentration. The term SCFAs refers to a group of C 2 -C 6 mono-carboxylic acids, but of these compounds the major SCFAs involved in mammalian physiology are the straight chain fatty acid acetate c2, propionate c3 and butyrate c4. Data are briefly reviewed regarding the production of SCFAs, their role in the maintenance of human intestinal 'mucosal health', their implication in the pathogenesis of several diseases and their controversial effects on colon cancer and polyps. The role of SCFAs as virulence factors of anaerobic bacteria (effect in the pathogenesis of periodontal diseases and impairment of phagocytic cell functions) is also discussed.