Dietary conjugated linolenic acid in relation to CLA differently modifies body fat mass and serum and liver lipid levels in rats.

The present study compared the effect of dietary conjugated linolenic acid (CLNA) on body fat and serum and liver lipid levels with that of CLA in rats. FFA rich in linoleic acid, a-linolenic acid, CLA, or CLNA were used as experimental fats. Male Sprague-Dawley rats (4 wk old) were fed purified diets containing 1% of one of these experimental fats. After 4 wk of feeding, adipose tissue weights, serum and liver lipid concentrations, serum tumor necrosis factor (TNF)-alpha and leptin levels, and hepatic beta-oxidation activities were measured. Compared with linoleic acid, CLA and, more potently, CLNA were found to reduce perirenal adipose tissue weight. The same trend was observed in the weight of epididymal adipose tissue. CLNA, but not CLA, was found to significantly increase serum and liver TG concentrations. Serum FFA concentration was also increased in the CLNA group more than in the other groups. The activity of beta-oxidation in liver mitochondria and peroxisomes was significantly higher in the CLNA group than in the other groups. Thus, the amount of liver TG exceeded the ability of hepatic beta-oxidation. Significant positive correlation was found between the adipose tissue weights and serum leptin levels in all animals (vs. perirenal: r = 0.557, P < 0.001; vs. epididymal: r = 0.405, P < 0.05). A less significant correlation was found between adipose tissue weights and serum TNF-alpha level (vs. perirenal: r = 0.069, P > 0.1; vs. epididymal: r = 0.382, P < 0.05). Although the mechanism for the specific effect of CLNA is not clear at present, these findings indicate that in rats CLNA modulated the body fat and TG metabolism differently from CLA.