Metabolism of conjugated linoleic acids and 18 : 1 fatty acids by ruminal bacteria: products and mechanisms.
Cultures of ruminal bacteria known to metabolize unsaturated fatty acids were grown in medium containing 50 microg ml(-1) of geometric and positional isomers of conjugated linoleic acid (CLA) or 18 : 1 fatty acids and 37.4 % deuterium oxide to investigate the mechanisms responsible for fatty acid metabolism. Butyrivibrio fibrisolvens JW11 converted cis-9,trans-11-18 : 2 and trans-9,trans-11-18 : 2 to trans-11-18 : 1 as the main product, labelled at C-9, and metabolized trans-10,cis-12-18 : 2 to trans-10-18 : 1, labelled at C-13, and smaller amounts of trans-12-18 : 1 and cis-12-18 : 1. Butyrivibrio proteoclasticus P-18 did not grow in the presence of cis-9,trans-11-18 : 2 or trans-10,cis-12-18 : 2, but grew in medium containing trans-9,trans-11-18 : 2, forming 18 : 0. Propionibacterium acnes, a ruminal species that isomerizes linoleic acid to trans-10,cis-12-18 : 2, did not metabolize CLA isomers further. B. fibrisolvens metabolized small amounts of trans-10-18 : 1, trans-11-18 : 1 and cis-9-18 : 1, but the products formed were not detected. B. proteoclasticus, on the other hand, carried out substantial conversion of 18 : 1 substrates to 18 : 0. P. acnes hydrated cis-9-18 : 1 and trans-11-18 : 1 to 10-OH-18 : 0, which was further oxidized to yield 10-O-18 : 0. The deuterium enrichment in the intermediates formed during incubations with 9,11 geometric isomers of CLA was about half that of the products from trans-10,cis-12 CLA and 18 : 1 isomers, suggesting that the reduction of 9,11 geometric isomers CLA by ruminal bacteria occurs via different mechanisms compared with the metabolism of other unsaturated fatty acids.
McKain
Nest
N
Rowett Institute of Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK.
Shingfield
Kevin J
KJ
Animal Production Research, MTT Agrifood Research Finland, Jokioinen, FI-31600, Finland.
Wallace
R John
RJ
Rowett Institute of Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK.
D000818:Animals; D045856:Butyrivibrio / Q000378:metabolism*; D004041:Dietary Fats / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D044243:Linoleic Acids, Conjugated / Q000378:metabolism*; D012417:Rumen / Q000378:metabolism / Q000382:microbiology*; D013237:Stereoisomerism
D004041:Dietary Fats; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D044243:Linoleic Acids, Conjugated