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Food Lipids: Chemistry, Nutrition, and Biotechnology

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pose tissue <strong>and</strong> increased the clearance rate of serum nonesterified fatty acids. In<br />

addition, CLA treatment induced a nonsignificant increase in liver size <strong>and</strong> liver<br />

TBAR (thiobarbituric acid reactive substances) levels were significant higher in rats<br />

given the 2% CLA diet indicating a morphological change in liver caused by increased<br />

peroxidation.<br />

The effect of CLA on body composition was also investigated in a r<strong>and</strong>omized,<br />

double-blind, placebo-controlled study including 60 overweight or obese volunteers<br />

with body mass index (BMI) ranging from 27.5–39.0 kg/m 2 (96). The subjects were<br />

divided into two groups receiving 3.4 g CLA or placebo (4.5 g olive oil) daily for<br />

12 weeks. No difference in adverse events or other safety parameters was found<br />

between the treatment groups. Small changes in the laboratory safety data were not<br />

regarded as clinically significant. In the CLA group, mean weight was reduced by<br />

1.1 kg (paired t-test, p = 0.005), while mean BMI was reduced by 0.4 kg/m 2 (p =<br />

0.007). However the overall treatment of CLA on body weight <strong>and</strong> BMI was not<br />

significant. The results indicate that CLA in the given dose did not adversely impact<br />

a healthy population based on the safety parameters investigated. In another study,<br />

Blankson et al. (97) reported that feeding overweight or obese human subjects (BMI<br />

25–35 kg/m 2 ) up to 6.8 g of CLA per day for 12 weeks reduced the total body mass.<br />

The CLA effect on body fat mass reduction peaked at 3.4 g/day <strong>and</strong> higher dietary<br />

intake did not show a further benefit.<br />

Repartitioning of fat to lean was reported in growing pigs fed CLA. Dugan et<br />

al. (91) demonstrated that in pigs (male <strong>and</strong> female) given a cereal-based basal diet<br />

containing either 2% CLA compared to sunflower oil led to reduced subcutaneous<br />

fat deposition <strong>and</strong> increased lean body mass. Pigs provided with CLA also had<br />

reduced feed intake (5.2%) <strong>and</strong> increased feed efficiency (5.9%) compared with pigs<br />

fed sunflower oil. In another study, finisher pigs were offered six treatments having<br />

from 0 to 10 g CLA/kg of diet for 8 weeks (92). Dietary CLA treatments resulted<br />

in increased feed efficiency <strong>and</strong> lean tissue deposition, <strong>and</strong> decreased fat deposition<br />

(decreased by 31% at the highest CLA level) in growing pigs.<br />

The fat partitioning effect of CLA was further examined in the adipocyte 3T3-<br />

L1 cell culture. Park et al. (93) found that when added during fat accretion in the<br />

3T3-L1 adipocyte culture, CLA (1 � 10 4 M complexed with albumin) reduced lipoprotein<br />

lipase activity <strong>and</strong> enhanced lipolysis leading to less fat deposition. In addition,<br />

skeletal muscle from mice fed CLA exhibited elevated carnitine palmitoyltransferase<br />

activity, which indicates elevated � oxidation of fatty acids. In a recent<br />

study using the same cell culture system (71), a specific CLA isomer, t10,c12-18:2,<br />

was found to reduce lipoprotein lipase activity, lower intracellular triacylglycerol <strong>and</strong><br />

glycerol levels, <strong>and</strong> enhance the release of glycerol into the medium. CLA, especially<br />

the t10,c12 isomer, showed its antiobesity effect at 50–200 �M by inhibiting proliferation,<br />

suppressing triglyceride accumulation, <strong>and</strong> inducing apoptosis in 3T3-L1<br />

preadipocyte cultures compared with albumin vehicle or linoleic treatments (98).<br />

Lin et al. (99) found that the t10,c12 CLA isomer inhibited the activity of<br />

heparin-releasable lipoprotein lipase (HR-LPL) more strongly compared with the<br />

c9,t11 isomer, while both CLA isomers exhibited an inhibitory effect on HR-LPL<br />

compared with the LA treatment in 3T3-L1 adipocyte cultures. Yamasaki et al. (100)<br />

showed in a rat feeding study that 2% dietary CLA lowered serum leptin level after<br />

1 week compared to the 8% safflower oil supplement control group. Leptin level in<br />

perirenal white adipose tissue was also low in animals fed CLA after 12 weeks of<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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