title: The biologically active isomers of conjugated linoleic acid.
abstract: Numerous physiological effects are attributed to conjugated linoleic acid (CLA). The purpose of this presentation is to consider these effects with respect to the cis-9,trans-11 and trans-10,cis-12 CLA isomers. We review previously published data and present new findings that relate to underlying biochemical mechanisms of action. Both isomers are natural products. The cis-9,trans-11 isomer is the principal dietary form of CLA, but the concentrations of this isomer and the trans-10,cis-12 isomer in dairy products or beef vary depending on the diet fed to cows or steers, respectively. The trans-10,cis-12 CLA isomer exerts specific effects on adipocytes, in particular reducing the uptake of lipid by inhibiting the activities of lipoprotein lipase and stearoyl-CoA desaturase. The trans-10,cis-12 CLA isomer also affects lipid metabolism in cultured Hep-G2 human liver cells, whereas both the cis-9,trans-11 and trans-10,cis-12 CLA isomers appear to be active in inhibiting carcinogenesis in animal models. We present new findings indicating that the cis-9,trans-11 CLA isomer enhances growth and probably feed efficiency in young rodents. Accordingly, the effects of CLA on body composition (induced by trans-10,cis-12 CLA) and growth/feed efficiency (induced by cis-9,trans-11 CLA) appear to be due to separate biochemical mechanisms. We also show that a 19-carbon CLA cognate (conjugated nonadecadienoic acid, CNA) inhibits lipoprotein lipase activity as effectively as CLA in cultured 3T3-L1 adipocytes. Presumably, CNA is metabolized differently than the 18-carbon CLA isomers, so this finding indicates direct activity of the administered compound as opposed to acting via a metabolite.
authors: Department of Food Microbiology and Toxicology, Food Research Institute, University of Wisconsin-Madison, 53706, USA. mwpariza@facstaff.wisc.edu
authors: M W
authors: MW
authors: Pariza
authors: Y
authors: Y
authors: Park
authors: M E
authors: ME
authors: Cook
mesh_terms: D017667:Adipocytes / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D002417:Cattle; D003611:Dairy Products; D006801:Humans; D007328:Insulin / Q000378:metabolism; D008041:Linoleic Acids / Q000737:chemistry / Q000378:metabolism* / Q000627:therapeutic use; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism*; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy; D008460:Meat; D051379:Mice; D018482:Muscle, Skeletal / Q000378:metabolism; D020033:Protein Isoforms / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D051381:Rats
chemical_list: D000970:Antineoplastic Agents; D007328:Insulin; D008041:Linoleic Acids; D020033:Protein Isoforms