Effects of conjugated linoleic acid supplementation on fatty acid composition in the plasma, liver, and epididymal fat pads of male-Sprague Dawley rats

The purpose of this study was to investigate the effects of conjugated linoleic acid (CLA) on the fatty acid composition of plasma, liver, and epididymal fat pads in rats. Seventy-two male Sprague-Dawley rats were divided into four groups and received beef tallow (BT), fish oil (FO), beef tallow with CLA (BTC), and fish oil with CLA (FOC). All the rats were fed an experimental diet containing 12% (wt/wt) total fat, including CLA at 1%, for 30 weeks. The fatty acid analyses of the plasma, liver, and epididymal fat pads were performed by the one-step methylation method, followed by gas chromatography. Monounsaturated fatty acid (MUFA) levels in the plasma were significantly reduced in the BTC group as compared to the BT group. The levels of C18:1 and C20:4 in the liver were significantly lower in the BTC group than in the BT group (P < .05). CLA was detected in the epididymal fat pads of the rats that did not receive supplemental CLA (the BT and FO groups), indicating de novo synthesis. CLA caused significant decreases in C18:1 fatty acid levels in both the BTC and FOC groups in epididymal fat pads. C22:6 was significantly higher in the liver microsomes of the BTC group, as compared to the BT group. MUFA was stored at higher levels in the epididymal fat pads and was significantly lower in level in the CLA-supplemented (BTC and FOC) groups as compared to the BT and FO groups (P < .05). In conclusion, dietary CLA supplementation in rats altered fatty acid composition in a tissue-specific manner. CLA was stored mainly in the epididymal fat pad. The results also suggested that CLA may inhibit the conversions of C18:0 to C18:1 and C18:2 to C20:4 fatty acid, resulting in significantly lower levels of C18:1 and C20:4 in the livers of the BTC group as compared to the BT group.