Effect of dietary conjugated linoleic acid (CLA) on metabolism of isotope-labeled oleic, linoleic, and CLA isomers in women.
The purpose of this study was to investigate the effect of dietary CLA on accretion of 9c-18:1, 9c,12c-18:2, 10t,12c-18:2, and 9c,11t-18:2 and conversion of these FA to their desaturated, elongated, and chain-shortened metabolites. The subjects were six healthy adult women who had consumed normal diets supplemented with 6 g/d of sunflower oil or 3.9 g/d of CLA for 63 d. A mixture of 10t,2c-18:2-d4, 9c,11t-18:2-d6, 9c-18:1-d8, and 9c,12c-18:2-d2, as their ethyl esters, was fed to each subject, and nine blood samples were drawn over a 48-h period. The results show that dietary CLA supplementation had no effect on the metabolism of the deuterium-labeled FA. These metabolic results were consistent with the general lack of a CLA diet effect on a variety of physiological responses previously reported for these women. The 2H-CLA isomers were metabolically different. The relative percent differences between the accumulation of 9c,11t-18:2-d6 and 10t,12c-18:2-d4 in plasma lipid classes ranged from 9 to 73%. The largest differences were a fourfold higher incorporation of 10t,12c-18:2-d4 than 9c,11t-18:2-d6 in 1-acyl PC and a two- to threefold higher incorporation of 9c,11t-18:2-d6 than 10t,12c-18:2-d4 in cholesterol esters. Compared to 9c-18:1-d8 and 9c,12c-18:2-d2, the 10t,12c-18:2-d4 and 9c,11t-18:2-d6 isomers were 20-25% less well absorbed. Relative to 9c-18:1, incorporation of the CLA isomers into 2-acyl PC and cholesterol ester was 39-84% lower and incorporation of 10t,12c-18:2 was 50% higher in 1-acyl PC. This pattern of selective incorporation and discrimination is similar to the pattern generally observed for trans and cis 18:1 positional isomers. Elongated and desaturated CLA metabolites were detected. The concentration of 6c,10t,12c-18:3-d4 in plasma TG was equal to 6.8% of the 10t,12c-18:2-d4 present, and TG was the only lipid fraction that contained a CLA metabolite present at concentrations sufficient for reliable quantification. In conclusion, no effect of dietary CLA was observed, absorption of CLA was less than that of 9c-18:1, CLA positional isomers were metabolically different, and conversion of CLA isomers to desaturated and elongated metabolites was low.
Emken
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USDA, ARS, National Center for Agricultural Utilization Research, Food & Industrial Oils, Peoria, Illinois 61604, USA. eaemken@npoint.net
Adlof
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Duval
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Nelson
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Benito
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D000327:Adsorption; D000328:Adult; D019540:Area Under Curve; D003903:Deuterium; D004042:Dietary Fats, Unsaturated / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D007536:Isomerism; D019787:Linoleic Acid / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D008055:Lipids / Q000097:blood* / Q000145:classification; D019301:Oleic Acid / Q000737:chemistry / Q000493:pharmacokinetics*; D013997:Time Factors
D004042:Dietary Fats, Unsaturated; D008055:Lipids; D019301:Oleic Acid; D019787:Linoleic Acid; D003903:Deuterium