DISTRIBUTIONS OF CONJUGATED LINOLEIC-ACID (CLA) ISOMERS IN TISSUE LIPID CLASSES OF PIGS FED A COMMERCIAL CLA MIXTURE DETERMINED BY GAS-CHROMATOGRAPHY AND SILVER ION HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY
Jkg. Kramer et al., DISTRIBUTIONS OF CONJUGATED LINOLEIC-ACID (CLA) ISOMERS IN TISSUE LIPID CLASSES OF PIGS FED A COMMERCIAL CLA MIXTURE DETERMINED BY GAS-CHROMATOGRAPHY AND SILVER ION HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY, Lipids, 33(6), 1998, pp. 549-558
Pigs were fed a commercial conjugated linoleic acid (CLA) mixture, pre
pared by alkali isomerization of sunflower oil, at 2% of the basal die
t, from 61.5 to 106 kg live weight, and were compared to pigs fed the
same basal diet with 2% added sunflower ail. The total lipids from liv
er, heart, inner back fat, and omental fat of pigs fed the CLA diet we
re analyzed for the incorporation of CLA isomers into all the tissue l
ipid classes. A total of 10 lipid classes were isolated by three-direc
tional thin-layer chromatography and analyzed by gas chromatography (G
C) on long capillary columns and by silver-ion highperformance liquid
chromatography (Ag+-HPLC); cholesterol was determined spectrophotometr
ically. Only trace amounts (<0.1%; by CC) of the 9,11-18:2 cis/trans a
nd trans,trans isomers were observed in pigs fed the control diet. Ten
and twelve CLA isomers in the diet and in pig tissue lipids were sepa
rated by GC and Ag+-HPLC, respectively. The relative concentration of
all the CLA isomers in the different lipid classes ranged from 1 to 6%
of the total fatty acids. The four major cis/trans isomers (18.9% 11
cis,13 trans-18:2; 26.3% 10 trans,12 cis-18:2; 20.4% 9 cis,ll trans-18
:2; and 16.1% 8 trans,10 cis-18:2) constituted 82% of the total CIA.is
omers in the dietary CLA mixture, and smaller amounts of the correspon
ding cis,cis (7.4%) and trans, trans (10.1%) isomers were present. The
distribution of CLA isomers in inner back fat and in omental fat of t
he pigs was similar to that found in the diet. The liver triacylglycer
ols (TAG), free fatty acids (FFA), and cholesteryl esters showed a sim
ilar pattern to that found in the diet. The major liver phospholipids
showed a marked increase of 9 cis, 11 trans-18:2, ranging from 36 to 5
4%, compared to that present in the diet. However, liver diphosphatidy
lglycerol (DPC) showed a high incorporation of the 11 cis,13 trans-18:
2 isomer (43%). All heart lipid classes, except TAG, showed a high con
tent of 11 cis,13 trans-18:2, which was in marked contrast to results
in the liver. The relative proportion of 11 cis,13 trans-18:2 ranged f
rom 30% in the FFA to 77% in DPC. The second major isomer in all heart
lipids was 9 cis,ll trans-18:2. In both liver and heart lipids the re
lative proportions of both 10 trans,12 cis-18:2 and 8 Irans,10 cis18:2
were significantly lower compared to that found in the diet. The FFA
in liver and heart showed the highest content of trans,trans isomers (
31 to 36%) among all the lipid classes. The preferential accumulation
of the 11 cis,13 trans-18:2 into cardiac lipids, and in particular the
major phospholipid in the inner mitochondrial membrane, DPG, in both
heart and liver, appears unique and may be of concern. The levels of 1
1 cis,13 trans-18:2 naturally found in foods have not been established
.