Inhibitory effect of linoleic acid on chain elongation and desaturation of 18∶2 c,t isomers in lactating and neonatal rats

Abstract

The previous studies showed that dietary 18:2 c,t isomers could be chain-elongated and desaturated to produce unusual 20:4 isomers. The present study was undertaken to determine the minimal amount of 18:2n-6 required to suppress the chain elongation and desaturation of 18:2 c,t isomers in the lactating and neonatal rats when animals were fed 15% partially hydrogenated canola oil diet containing 1.72% energy as 18:2 c,t isomers and varying amounts of free 18:2n-6. These diets induced marginal essential fatty acid (EFA) deficiency states (0.56% energy 18:2n-6) to EFA adequacy (2.56% energy 18:2n-6). After feeding for 50 d, the female animals were mated with males by overnight pairing. After conception, the lactating rats were killed, together with one pup from each dam, at term and day 26 of lactation. Two unusual 20:4 isomers in both maternal and neonatal liver phospholipids were identified as 20:4delta5c,8c,11c,14t and 20:4delta5c,8c,11c,15t, which were derived from 18:2delta9c,12t and 18:2delta9c,13t, respectively. The results showed that 18:2n-6 at about 2.0% of total energy in maternal diet was required to block the production of 20:4delta5c,8c,11c,14t and 20:4delta5c,8c,11c,15t in the maternal liver, whereas 18:2n-6 at about 2.5% of total energy in maternal diet was required to suppress production of these unusual 20:4 isomers in the neonatal liver.

Preferential incorporation oftrans,trans-conjugated linoleic acid isomers into the liver of suckling rats

“…The animals were fed one of two diets containing either no CLA (control) or a 2 % CLA mixture (Bioriginal Food & Science Corp., Saskatoon, SK, Canada). The control diet was prepared as previously described (Kwan et al 1998) by mixing the powdered ingredients in the following proportions (g): casein, 235; rapeseed oil, 100; maize starch, 338; sucrose, 243; mineral mix, 35; vitamin mix, 10; cellulose, 32; choline bitartrate, 4 DL-methionine, 3. The CLA-supplemented diet was prepared by adding 2 % CLA mixture to the control diet (14•6 g/kg diet).…”

Preferential incorporation of <I>trans</I>, <I>trans</I>-conjugated linoleic acid isomers into the liver of suckling rats

“…The control diet was prepared as previously described (Kwan et al 1998) by mixing the powdered ingredients in the following proportions (g): casein, 235; rapeseed oil, 100; maize starch, 338; sucrose, 243; mineral mix, 35; vitamin mix, 10; cellulose, 32; choline bitartrate, 4 DL-methionine, 3. The CLA-supplemented diet was prepared by adding 2 % CLA mixture to the control diet (14·6 g/kg diet).…”

Accumulation and apparent oxidation ofcis,trans-18 : 2 isomers relative to linoleic acid in rats

“…10cis,13cis,16cis-22 : 4 and D4cis,7cis,10cis,13cis,16cis-22 : 5, whereas the LCP for D9cis,13trans-18 : 2 and D9cis,12trans-18 : 2 would include D5cis,8cis,11cis, 15trans-20 : 4 and D5cis,8cis,11cis,14trans-20 : 4, respectively (Kwan et al 1998;Ratnayake et al 1994). No other LCP for cis,trans-18 : 2 isomers and trans-18 : 1 isomers was found in the carcass lipids.…”

“…Two cis,trans-18 : 2 isomers, D9cis,13trans-18 : 2 and D9cis,12trans-18 : 2, can be chain-elongated and desaturated to form D5cis,8cis,11cis,15trans-20 : 4 and D5cis,8cis, 11cis,14trans-20 : 4 respectively (Kwan et al 1998;Ratnayake et al 1994). Among groups B -E the wholebody partitioning of D9cis,13trans-18 : 2 was 68-72 % to apparent oxidation, 25-31 % to accumulation, and 0 : 9-2 : 7 % to the LCP.…”