The biologically active isomers of conjugated linoleic acid

Prog Lipid Res. 2001 Jul;40(4):283-98. doi: 10.1016/s0163-7827(01)00008-x.

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.

Publication types

  • Review

MeSH terms

  • Adipocytes / metabolism
  • Animals
  • Antineoplastic Agents / therapeutic use
  • Cattle
  • Dairy Products
  • Humans
  • Insulin / metabolism
  • Linoleic Acids / chemistry
  • Linoleic Acids / metabolism*
  • Linoleic Acids / therapeutic use
  • Lipid Metabolism
  • Liver / metabolism*
  • Mammary Neoplasms, Experimental / drug therapy
  • Meat
  • Mice
  • Muscle, Skeletal / metabolism
  • Protein Isoforms / biosynthesis
  • Protein Isoforms / chemistry
  • Protein Isoforms / metabolism
  • Rats

Substances

  • Antineoplastic Agents
  • Insulin
  • Linoleic Acids
  • Protein Isoforms