The separation of non phosphorus lipids and phospholipids of rat heart using Sep‐pack Silica cartridges is described. No cartridge preparation is necessary before utilization. The separation of lipid extracts is very fast. A complete partition of non phosphorus lipids and phospholipid is obtained.

No abstract

Long-chain polyunsaturated fatty acids (LC-PUFA) of the n-3 series, particularly eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid, have specific activities especially in the functionality of the central nervous system. Due to the occurrence of numerous methylene-interrupted ethylenic double bonds, these fatty acids are very sensitive to air (oxygen) and temperature. Non-volatile degradation products, which include polymers, cyclic fatty acid monomers (CFAM) and geometrical isomers of EPA and DHA, were evaluated in fish oil samples obtained by deodorization under vacuum of semi-refined fish oil at 180, 220 and 250 7C. Polymers are the major degradation products generated at high deodorization temperatures, with 19.5% oligomers being formed in oil deodorized at 250 7C. A significant amount of CFAM was produced during deodorization at temperatures above or equal to 220 7C. In fact, 23.9 and 66.3 mg/g of C20 and C22 CFAM were found in samples deodorized at 220 and 250 7C, respectively. Only minor changes were observed in the EPA and DHA trans isomer content and composition after deodorization at 180 7C. At this temperature, the formation of polar compounds and CFAM was also low. However, the oil deodorized at 220 and 250 7C contained 4.2% and 7.6% geometrical isomers, respectively. Even after a deodorization at 250 7C, the majority of geometrical isomers were mono-and di-trans. These results indicate that deodorization of fish oils should be conducted at a maximal temperature of 180 7C. This temperature seems to be lower than the activation energy required for polymerization (intra and inter) and geometrical isomerization.

Conjugated linoleic acid (CLA) is a collective term that describes different isomers of linoleic acid with conjugated double bonds. Although the main dietary isomer is 9cis,11trans-18:2, which is present in dairy products and ruminant fat, the biological effects of CLA generally have been studied using mixtures in which the 9cis,11trans- and the 10trans,12cis-18:2 were present at similar levels. In the present work, we have studied the impact of each isomer (9cis,11 trans- and 10trans,12cis-18:2) given separately in the diet of rats for 6 wk. The 10trans,12cis-18:2 decreased the triacylglycerol content of the liver (-32%) and increased the 18:0 content at the expense of 18:1 n-9, suggesting an alteration of the delta9 desaturase activity, as was already demonstrated in vitro. This was not observed when the 9cis,11trans-18:2 was given in the diet. Moreover, the 10trans,12cis-18:2 induced an increase in the C22 polyunsaturated fatty acids in the liver lipids. The 10trans,12cis-18:2 was mainly metabolized into conjugated 16:2 and 18:3, which have been identified. The 9cis,11trans isomer was preferentially metabolized into a conjugated 20:3 isomer. Thus, the 9cis,11trans- and the 10trans,12cis-CLA isomers are metabolized differently and have distinct effects on the metabolism of polyunsaturated fatty acids in rat liver while altering liver triglyceride levels differentially.

Male weanling Wistar rats (n = 15), weighing 200-220 g, were allocated for 6 wk to diets containing 1% (by weight) of conjugated linoleic acid (CLA), either as the 9c,11 t-isomer, the 10t,12c-isomer, or as a mixture containing 45% of each of these isomers. The five rats of the control group received 1% of oleic acid instead. Selected enzyme activities were determined in different tissues after cellular subfractionation. None of the CLA-diet induced a hepatic peroxisome-proliferation response, as evidenced by a lack of change in the activity of some characteristic enzymes [i.e., acyl-CoA oxidase, CYP4A1, but also carnitine palmitoyltransferase-I (CPT-I)] or enzyme affected by peroxisome-proliferators (glutathione S-transferase). In addition to the liver, the activity of the rate-limiting beta-oxidation enzyme in mitochondria, CPT-I, did not change either in skeletal muscle or in heart. Conversely, its activity increased more than 30% in the control value in epididymal adipose tissue of the animals fed the CLA-diets containing the 10t,12c-isomer. Conversely, the activity of phosphatidate phosphohydrolase, a rate-limiting enzyme in glycerolipid neosynthesis, remained unchanged in adipose tissue. Kinetic studies conducted on hepatic CPT-I and peroxisomal acyl-CoA oxidase with CoA derivatives predicted a different channeling of CLA isomers through the mitochondrial or the peroxisomal oxidation pathways. In conclusion, the 10t,12c-CLA isomer seems to be more efficiently utilized by the cells than its 9c,11t homolog, though the Wistar rat species appeared to be poorly responsive to CLA diets for the effects measured.