Effects of specific conjugated linoleic acid isomers on growth characteristics in obese Zucker rats.

Growing female obese Zucker (fa/fa) rats were treated (via intragastric gavage) for 21 d with either a (i) vehicle [corn oil; 0.9 g/kg body weight (BW)], (ii) CLA mixture [50:50; trans-10, cis-12 and cis-9, trans-11 CLA], (iii) cis-9,trans-11 CLA, or (iv) trans- 10, cis-12 CLA (CLA treatments at 1.5 g CLA/kg BW). Compared with controls, average daily gain (g/d) was reduced 24 and 44% by the CLA mixture and trans-10, cis-12 CLA, respectively. There was no treatment effect on average whole-body (minus heart and liver) composition (dry matter basis): fat (70.2%), protein (21.0%), and ash (4.3%). Compared with animals treated with cis-9,trans-11 CLA, obese Zucker rats treated with trans-10, cis-12 and the CLA mixture had 7.8% more carcass water. Treatment had no effect on heart or liver weights or on heart or liver weights as a percentage of body weight, but compared with the other treatments trans-10, cis-12 CLA increased liver lipid content by 33%. Hepatic lipid ratios of 16:1/16:0 and 18:1/18:0 (a proxy for delta9-desaturase capability) were not affected by treatment (0.1 and 0.6, respectively). Similar to previous reports, CLA increased hepatic lipid content and altered both liver and carcass FA composition (i.e., reduced arachidonic acid content), but the ability of CLA to manipulate body composition in obese Zucker rats remains questionable.