The effects of conjugated linoleic acid (CLA) on body composition were investigated. ICR mice were fed a control diet containing 5.5% corn oil or a CLA-supplemented diet (5.0% corn oil plus 0.5% CLA). Mice fed CLA-supplemented diet exhibited 57% and 60% lower body fat and 5% and 14% increased lean body mass relative to controls (P < 0.05). Total carnitine palmitoyltransferase activity was increased by dietary CLA supplementation in both fat pad and skeletal muscle; the differences were significant for fat pad of fed mice and skeletal muscle of fasted mice. In cultured 3T3-L1 adipocytes CLA treatment (1 x 10(-4)M) significantly reduced heparin-releasable lipoprotein lipase activity (-66%) and the intracellular concentrations of triacylglyceride (-8%) and glycerol (-15%), but significantly increased free glycerol in the culture medium (+22%) compared to control (P < 0.05). The effects of CLA on body composition appear to be due in part to reduced fat deposition and increased lipolysis in adipocytes, possibly coupled with enhanced fatty acid oxidation in both muscle cells and adipocytes.

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We investigated the effects of conjugated linoleic acid (CLA) preparations, which were enriched for the cis-9,trans-11 CLA isomer or the trans-10,cis-12 CLA isomer, on body composition in mice. Body composition changes (reduced body fat, enhanced body water, enhanced body protein, and enhanced body ash) were associated with feeding the trans-10,cis-12 CLA isomer. In cultured 3T3-L1 adipocytes, the trans-10,cis-12 isomer reduced lipoprotein lipase activity, intracellular triacylglycerol and glycerol, and enhanced glycerol release into the medium. By contrast, the cis-9,trans-11 and trans-9,trans-11 CLA isomers did not affect these biochemical activities. We conclude that CLA-associated body composition change results from feeding the trans-10,cis-12 isomer.

Trans-10,cis-12 conjugated linoleic acid (CLA) has previously been shown to be the CLA isomer responsible for CLA-induced reductions in body fat in animal models, and we have shown that this isomer, but not the cis-9,trans-11 CLA isomer, specifically decreased triglyceride (TG) accumulation in primary human adiopcytes in vitro. Here we investigated the mechanism behind the isomerspecific, CLA-mediated reduction in TG accumulation in differentiating human preadipocytes. Trans-10,cis-12 CLA decreased insulin-stimulated glucose uptake and oxidation, and reduced insulin-dependent glucose transporter 4 gene expression. Furthermore, trans-10,cis-12 CLA reduced oleic acid uptake and oxidation when compared with all other treatments. In parallel to CLA's effects on metabolism, trans-10,cis-12 CLA decreased, whereas cis-9,trans-11 CLA increased, the expression of peroxisome proliferator-activated receptor γ (PPARγ) and several of its downstream target genes when compared with vehicle controls. Transient transfections demonstrated that both CLA isomers antagonized ligand-dependent activation of PPARγ. Collectively, trans-10,cis-12, but not cis-9, trans-11, CLA decreased glucose and lipid uptake and oxidation and preadipocyte differentiation by altering preadipocyte gene transcription in a manner that appeared to be due, in part, to decreased PPARγ expression. Supplementary key wordsconjugated linoleic acid; fatty acids; lipid metabolism; glucose metabolism; triglycerides; peroxisome proliferator-activated receptor gamma Abbreviations ACBP, acyl-CoA binding protein; ACC, acetyl-CoA carboxylase; aP2/FABP, adipocyte fatty acid binding protein; BCA, bicinchoninic acid; BMI, body mass index; BSA, bovine serum albumin; CD-36, fatty acid translocase; C/EBPα, CAAT/enhancer binding protein α; CLA, conjugated linoleic acid; GC, gas chromatography; GLUT4, insulin-dependent glucose transporter 4; GPDH, glycerol-3-phosphate dehydrogenase; HSL, hormone-sensitive lipase; IBMX, isobutylmethylxanthine; LA, linoleic acid; LPL, lipoprotein lipase; MUFA, monounsaturated fatty acid; ORO, oil red O; PPAR, 1 To whom correspondence should be addressed. e-mail:mkmcinto@uncg.edu. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript peroxisome proliferator-activated receptor; PPRE, peroxisome proliferator response element; SCD-1, stearoyl-CoA desaturase-1; SFA, saturated fatty acid; SV, stromal vascular; TG, triglyceride Conjugated linoleic acid (CLA) refers to a group of geometric and positional dienoic isomers of linoleic acid (LA) [18:2(n-6)]. The two predominant isomers of CLA found in food and commercial preparations are cis-9,trans-11 CLA and trans-10,cis-12 CLA. CLA is found in ruminant meats, pasteurized cheeses, and dairy products, and therefore is a natural part of the diet. CLA has been extensively studied due to its potentially beneficial effects on carcinogenesis (1-3), diabetes (4,5), atherosclerosis (6,7), immune function (8-10), and body composition (11)(12)(13)(14)(15)(16).Collectivel...

Two experiments were conducted. In Experiment 1, 8-wk-old mice were fed control diet or diet supplemented with 0.5% conjugated linoleic acid (CLA) to study the effect of CLA on body composition (CLA: 40.8-41.1% c-9,t-11 isomer, 43.5-44.9% t-10,c-12 isomer). The data for CLA-fed mice vs. controls described parallel but significantly distinct responses for both absolute and relative changes in body fat mass (reduced in CLA-fed mice) and for relative changes in whole body protein and whole body water (both of which were increased in CLA-fed mice). In the CLA-fed mice, the effect on whole body protein appeared to precede the reduction in body fat mass. In Experiment 2, weanling mice were fed control diet or diet supplemented with 0.5% CLA for 4 wk (test group), at which time all mice were fed control diet devoid of added CLA. The test group exhibited significantly reduced body fat and significantly enhanced whole body water relative to controls at the time of diet change. Time trends for changes in relative body composition were described by parallel lines where the test group exhibited significantly less body fat but significantly more whole body protein, whole body water, and whole body ash than controls. Tissue CLA levels declined following the withdrawal of CLA from the diet. In skeletal muscle of mice fed CLA-supplemented diet, the t-10,c-12 isomer was cleared significantly faster than the c-9,t-11 CLA isomer.