761

trans Fatty Acids. 5. Fatty Acid Composition of Lipids of the Brain

and Other Organs in Suckling Piglets Jan Pettersen and Johannes Opstvedt* Norwegian Herring Oil and Meal Industry Research Institute, N-5033 Fyllingsdalen, Bergen, Norway

The effects of dietary trans fatty acids on the fatty acid composition of the brain in comparison with other organs were studied in 3-wk-old suckling piglets. In Experiment {Expt.} I the piglets were delivered from sows fed partially hydrogenated fish oil (PHFO) (28% trans), partially hydrogenated soybean oil (PHSBO) {36% trans} or lard (0% trans). In Expt. 2 the piglets were delivered from sows fed PHFO, hydrogenated fish oil (HFO) {19% trans} or coconut fat {CF} (0% trans) with two levels of dietary linoleic acid (1 and 2.7%} according to factorial design. In both experiments the mother's milk was the piglets' only food. The level of incorporation of trans fatty acids in the organs was dependent on the levels in the diets and independent of fat source {/.e., PHSBO, PHFO or HFO). Incorporation of trans fatty acids into brain PE {phosphatidylethanolamine) was non-detectable in Expt. 1. In Expt. 2, small amounts {less than 0.5%} of 18:1 trans isomers were found in the brain, the level being slightly more on the lower level of dietary linoleic acid compared to the higher. In the other organs the percentage of 18:1 trans increased in the following order: heart PE, liver mitochondria PE, plasma lipids and subcutaneous adipose tissue. Small amounts of 20:1 trans were found in adipose tissue and plasma lipids. Other very long,chain fatty acids from PHFO or HFO (Le., 20:1 c/s and 22:1 cis + trans} were found in all organ lipids except for brain PE. Dietary trans fatty acids increased the percentage of 22:5n-6 in brain PE. Except for the brain and the heart, dietary trans fatty acids reduced the percentage of saturated fatty acids and increased the percentage of monoenoic acids (including trans}. The overall conclusion was that dietary trans fatty acids had no noticeable effect on the brain PE composition but slight to moderate effects on the fatty acid profile of other organs of suckling piglets. Lipids 27, 761-769 (1992).

Human diets in Western society contain about 0.6-2 percent trans fatty acids (1,2) that mostly come from industrially processed fat with only small amounts being consumed in fats from ruminant animals. The fact that most of the trans fatty acids are of industrial rather than natural origin has been of concern and has led to a number of studies. In vitro studies have shown that trans fatty acids may inhibit the synthesis of longer chain essential n-6 and n-3 fatty acids from their lower homologues (3,4). These findings have led to speculation that trans fatty acids may interfere with the formation of eicosanoids (1,2,5,6) and may affect the biological properties of membranes (7).

Because it has been shown that long-chain polyunsaturated fatty acids (LC-PUFA) are essential for nerve function {8,9), it is particularly important to ascertain whether consumption of trans fatty acids causes incorporation of trans fatty acids or alters the LC-PUFA profile in nerve tissue In humans, brain growth occurs during late prenatal and early postnatal life (10), i.a, the structural lipids of nerve tissues are formed in a relatively early stage. In a series of experiments comprising prenatal life ill) and the growth period to maturation (12), we have studied the effect of trans fatty acids with emphasis on nerve tissues. The observations include histology and functionality of nerve tissues (13) in addition to examining the content of trans fatty acids and fatty acid composition in general in the brain and several other organs {11,12). This final study concerned the effect of dietary trans fatty acids consumed from the mothers' milk during early postnatal life. The transfer of trans fatty acids from the mothers' diet to the milk has been reported {14}. We have used pigs as models because of their physiological resemblance to humans (15,16), particularly with regard to brain growth (10) and accretion of LC-PUFA in nervous tissue (17). Further, we decided to focus on the very longchain (i.a, 20 and 22 carbon atoms) trans fatty acids found in partially hydrogenated fish oil (18); previous studies have mainly used partially hydrogenated vegetable oils that do not contain very long-chain trans fatty acids. The present study consisted of two experiments. The first experiment compared diets with trans fatty acids from partially hydrogenated soybean oil and partially hydrogenated fish oil. The second experiment compared two fish oils differing in trans fatty acid contents when fed with two levels of dietary linoleic acid. Our analytical capacity did not allow us to analyze more than one phospholipid class. Since phosphatidylethanolamine (PE) has a high content of long-chain PUFA (19), which are assumed to be of particular importance for membrane structure and function, PE was chosen as the target lipid class. Lipid samples were obtained from the offspring after three weeks of suckling as the only nutrient supply. The brain was the principal organ of this investigation, but in order to compare the results from this study with those from previous ones, other tissues were analyzed as well.

EXPERIMENTAL PROCEDURES

Generalprocedures. From 1 to 4 (depending on litter size) male and female piglets from each Norwegian Landrace sow were allowed to suckle and had no access to other feeds until they were three weeks old, when they were sacrificed by electrocution. Samples of 3 g each from heart, liver and adipose tissues, and 2.5 g from brain plus *To whom correspondence should be addressed. 1 mL of blood {right ventricle) plasma were immediately Abbreviations: CF, coconutfat; GLC,gas-liquidchromatography; obtained for chemical analysis. Samples from individual HFO, hydrogenatedfish oil; HPLC, high-performanceliquid chromatography; LC, long-chain;PE, phosphatidylethanolamine;PHFO, piglets of each sex were pooled to two composite samples partially hydrogenated fish off; PHSBO, partially hydrogenated per sow {litter), i.e., 8 (2 • 4) composite samples per diet. soybean oil; PUFA, polyunsaturated fatty acids; SFO, sunflower In Expt. 1 the piglets were bred from sows that from three seed oil. weeks of age were fed diets based on cereals, solvent LIPIDS, Vol. 27, no. 10 (1992)

762

J. PETTERSEN AND J. OPSTVEDT extracted soybean meal, and 4 wt percent SFO (sunflower seed oil, 65% linoleic acid). To the respective diets were added 14 wt percent lard (control, diet 1), P H F O (partially hydrogenated capelin oil, m.p. 30-32~ diet 2) or P H S B O (partially hydrogenated soybean oil, m.p. 40~ diet 3). In Expt. 2, the piglets were bred from sows t h a t through gestation were fed diets based on cereal grains and solvent extracted soybean meal to which was added 14 wt percent CF (coconut fat, diet 1.1 and 2.1), P H F O (diet 1.2 and 2.2) or HFO (hydrogenated fish oil, m.p. 50-52~ diet 1.3 and 2.3) either without (diet 1,1, 1.2 and 1.3) or with (diet 2.1, 2,2 and 2.3) the addition of 3 wt percent SFO according to a 3 • 2 factorial design. B o t h experiments used four sows (litters). Details of the sows' diets and management have been presented earlier (13). The design of the experiments and the f a t t y acid composition of the sows' diets are shown in Table 1. C h e m i c a l m e t h o d s . Total lipids were extracted from the different organs by the m e t h o d described by Folch e t al. (20) except in the case of the brain, for which a slight modification of the Folch procedure was used (21). Membrane lipids of liver mitochondria were isolated as described by Hby and Hblmer (22). All lipids were stored at - 2 5 ~C pending further analysis. Phosphatidylethanolamine (PE) of the liver mitochondria, heart and brain was

isolated by high-performance liquid chromatography (HPLC). PE plasmalogen was not separated from PE since both coeluted in HPLC. The f a t t y acid composition reported for P E is therefore the combined composition of P E and P E plasmalogen. The f a t t y acid composition was analyzed by gas-liquid chromatography (GLC) using a capillary (CP Sil 88) column as described earlier (12). The contents of 16:1 t r a n s f a t t y acids were determined only for the dietary fats used in Expt. 2 (Table 1). The 16:1 t r a n s isomers of organ lipids could not be identified due to interference by other components on the chromatograms. Some organ lipids apparently contained 22:1 trans, but due to the low content, the t r a n s a n d cis isomers could not be separated quantitatively. S t a t i s t i c a l m e t h o d s . The basic principle of the statistical methods used was estimation of m a x i m u m likelihood. The program package used was BMDP, program P2V (23). RESULTS B r a i n . The f a t t y acid composition of brain PE is shown

in Table 2. A l t h o u g h the percentages of some of the f a t t y acids in the offspring were significantly influenced by the dietary fats fed to the sows, the differences between diets were small. No t r a n s f a t t y acids were incorporated into

TABLE 1 F a t t y Acid Composition (%) of the Dietary Fats (total) Fed to Sows a

Experiment 1b

Fatty acids 8:0 10:0 12:0 14:0 16:0 18:0 20:0 22:0 24:0 16:1 cis 16:1 trans c 18:1 cis 18:1 trans 20:1 cis 20:1 trans 22:1 cis 22:1 trans 24:1 18:2n-6 18:3n-3 Others Sum PUFAd Sum monoenoic Sum saturated Sum trans P/S e

Experiment 2

Added SFO (4%) Lard PHFO PHSBO 1 2 3

Added SFO (0%) CF PHFO HFO 1.1 1.2 1.3 7.1 6.1 40.9 16.7 10.8 3.2

22.6 14.8 0.3

16.3 5.6 2.2 2.0

11.2 13.2 0.6

1.5

1.1

0.6

0.2

34.6 0.3 0.7

14.1 6.8 3.9 6.0 5.7 5.3

29.1 24.3 0.2

6.8

20.8 1.8 2.6 22.6 37.1 37.7 0.3 0.60

20.1 2.2 8.7 22.3 42.9 26.1 18.1 0.85

18.3 1.9 0.6 20.2 54.2 25.0 24.3 0.81

5:2 2.2 0.8 7.4 7.0 84.8 0.0 0.09

1.0 8.0 15.5 4.2 2.6 2.1 0.1 2.9 4.8 10.3 7.7 5.8 9.5 6.0 6.7 0.5 5.5 1.6 5.4 7.1 54.2 33.5 28.7 0.21

0.2 8.0 20.5 14.3 13.2 10.5 0.6 0.5 1.9 4.2 3.1 2.0 5.9 2.0 4.4 0.6 5.9 1.4 0.8 7.3 24.6 67.3 15.3 0.11

Added SFO (3%) CF PHFO HFO 2.1 2.2 2.3 10.5 5.8 34.7 13.0 9.1 3.0

0.2 8.4

13.2 1.8 0.3 15.0 8.6 76.1 0.0 0.20

2.1 7.2 14.8 4.7 2.4 2.0 0.1 2.7 3.9 9.8 5.8 5.2 7.9 5.2 5.5 0.4 14.5 1.1 4.7 15.6 46.4 33.3 23.1 0.47

aFed from 3 wk of age through pregnancy in Expt. 1, from gestation through pregnancy in Expt. 2. bSFO, sunflower seed oil; PHFO, partially hydrogenated fish oil; PHSBO, partially hydrogenated soybean off; CF, coconut fat. c16:1 trans was not identified in Expt. 1. dpUFA, polyunsaturated fatty acid. eRelative amount of sum PUFA (P) to sum saturated fatty acids (S). LIPIDS, Vol. 27, no. 10 (1992)

0.2 6.7 17.6 12.2 10.6 8.5 0.5 0.6 1.9 6.6 2.9 2.2 5.3 3.2 3.6 0.5 13.7 1.3 1.9 15.0 26.8 56.3 13.7 0.27

763

DIETARY T R A N S FATTY ACIDS TABLE 2 Fatty Acid Composition (%) in Phosphatidylethanolamine of Total Lipids in Brain of 3-Wk-Old Suckling Piglets a

Fatty acids

Experiment 1 Added SFO (4%) Significant Lard PHFO PHSBO Pooled std. experimental 1 2 3 dev. factors b

14:0 16:0 18:0 16:1 18:1 cis 18:1 trans 20:1 cis 20:3n-9 18:2n-6 20:3n-6 20:4n-6 22:3n-6 22:4n-6 22:5n-6 22:5n-3 22:6n-3 Sum PUFAn-6 Sum PUFAn-3 Sum PUFA total Sum monoenoic Sum saturated Sum trans

5.0 20.1 0.8 15.3 n.d. c 0.9 0.8 1.3 0.9 20.6 0.5 11.3 2.6 0.9 18.5 37.2 19.4 57.4 17.0 25.1 0.0

5.4 19.6 0.9 15.8 n.d. 1.2 0.8 1.8 0.8 20.0 0.7 11.4 4.7 1.0 15.8 39.4 16.8 57.0 17.9 25.0 0.0

5.1 19.2 1.0 17.9 n.d. 1.0 0.8 2.1 0.9 19.8 0.6 10.9 3.6 0.9 15.5 37.9 16.4 55.1 19.9 24.3 0.0

0.2 0.3 0.1 0.7 0.1 0.1 0.2 0.1 0.4 0.1 0.2 0.3 0.1 0.6

C C C C C C C C

Experiment 2 Added SFO ( 0 % ) Added SFO (3%) CF PHFO HFO CF PHFO HFO Pooled Significant std. experimental 1.1 1.2 1.3 2.1 2.2 2.3 dev. factors 0.1 6.2 19.8 0.7 17.6 0.05 1.0 0.7 1.4 0.9 17.6 0.7 8.2 1.5 1.2 18.2 30.3 19.4 50.4 19.35 26.1 0.05

0.2 6.7 19.4 0.9 16.8 0.39 1.1 1.0 2.0 1.0 17.7 0.7 7.3 1.5 1.2 18.4 30.2 19.6 50.8 19.19 26.3 0.39

0.1 5.9 21.7 0.8 18.1 0.06 1.1 1.0 1.0 1.0 17.0 1.0 8.2 1.3 1.9 15.8 29.5 17.7 48.2 20.06 27.7 0.06

0.3 9.0 20.9 0.3 17.8 n.d. 1.1 0.4 1.4 0.8 19.1 0.5 9.3 1.9 0.7 13.8 33.0 14.5 47.9 19.2 30.2 0.00

0.2 6.8 19.4 0.6 17.4 0.18 0.8 0.6 1.6 0.9 18.4 0.6 9.7 2.8 0.8 16.2 34.0 17.0 51.6 18.98 26.4 0.18

0.2 7.1 20.1 0.5 15.6 0.05 1.1 0.5 1.4 0.8 18.7 0.7 10.5 2.7 0.9 16.6 34.8 17.7 53.0 17.25 27.4 0.05

0.2 2.3 2.2 0.4 1.9 0.09 0.3 0.1 0.9 0.2 2.1 0.3 1.0 0.4 0.4 2.1

B B A,B,C B,C B B B B A,B,C B,C A,B

aFrom mothers fed these diets from 3 wk of age through pregnancy (Expt. 1) and from gestation through pregnancy (Expt. 2). All abbreviations as in Table 1. bsignificance means (P < 0.05): A, Interactions of experimental fats and SFO-level; B, effect of SFO-level; C, effect of experimental fats. Average of eight replicates. Pooled std. dev., pooled standard deviation, (error mean square) 1/2. Cn.d., Not detectable.

b r a i n P E in E x p t . 1. I n E x p t . 2 low, b u t s i g n i f i c a n t , a m o u n t s of t r a n s 18:1 were d e t e c t e d w h e n t h e sows were fed P H F O . T h e p e r c e n t a g e of 18:1 t r a n s w a s h i g h e r w h e n P H F O w a s fed in c o m b i n a t i o n w i t h t h e lower level of linoleic a c i d c o m p a r e d w i t h t h e h i g h e r level. I n n e i t h e r of t h e e x p e r i m e n t s w a s 20:1 t r a n s f o u n d in t h e o f f s p r i n g . P e r c e n t 20:1 cis w a s slightly, b u t s i g n i f i c a n t l y , i n c r e a s e d in o f f s p r i n g f r o m sows f e d P H F O in E x p t . 1. T h i s effect w a s n o t f o u n d in P H F O o r in H F O in E x p t . 2. N e i t h e r in E x p t . 1 n o r in E x p t . 2 c o u l d 22:1 cis a n d t r a n s b e detected. I n E x p t . 2, f e e d i n g h y d r o g e n a t e d f a t s t o t h e sows inc r e a s e d t h e p e r c e n t a g e of 20:3n-9 in t h e i r o f f s p r i n g . T h i s effect w a s i n d e p e n d e n t of t h e d i e t a r y level of linoleic acid. However, a n i n c r e a s e in p e r c e n t 20:3n-9 w a s a l s o f o u n d a s a c o n s e q u e n c e of low d i e t a r y levels of linoleic acid, indep e n d e n t l y of t h e c o n t e n t of h y d r o g e n a t e d f a t s in t h e diets. I n E x p t . 1 t h e c o n t e n t of linoleic a c i d i n c r e a s e d a n d t h e c o n t e n t of a r a c h i d o n i c a c i d d e c r e a s e d in t h e o f f s p r i n g w h e n h y d r o g e n a t e d f a t s were fed t o t h e sows. T h i s w a s n o t o b s e r v e d in E x p t . 2. I n E x p t . 2 h y d r o g e n a t e d f a t inc r e a s e d t h e c o n t e n t of 22:5n-6. T h i s w a s o b s e r v e d in E x p t . 2 o n l y w h e n h y d r o g e n a t e d f a t w a s fed in c o m b i n a t i o n w i t h t h e h i g h e r level of linoleic acid. I n E x p t . 1, f e e d i n g P H F O a n d P H S B O to t h e sows r e d u c e d t h e c o n t e n t of 22:6n-3 in t h e o f f s p r i n g . I n E x p t . 2, P H F O a n d H F O i n c r e a s e d 22:6n-3 in sows fed t h e h i g h e r level of E F A a n d h a d v a r i a b l e effects on sows on d i e t s w i t h r e s t r i c t e d a m o u n t s of E F A .

Total c o n t e n t of P U F A was a b o u t 10% h i g h e r in E x p t . 1 c o m p a r e d w i t h E x p t . 2. T h e f a t s o u r c e s fed t o t h e sows h a d o n l y m i n o r effects on t h e t o t a l c o n t e n t s of s a t u r a t e d , m o n o e n o i c a n d p o l y u n s a t u r a t e d f a t t y a c i d s in t h e offs p r i n g , b u t t h e h i g h e r d i e t a r y level of linoleic a c i d inc r e a s e d t h e c o n t e n t s of all n-6 f a t t y acids, e x c e p t linoleic acid, a n d d e c r e a s e d t h e c o n t e n t of n-3 f a t t y acids. H e a r t . T h e f a t t y a c i d c o m p o s i t i o n of P E f r o m t h e h e a r t is s h o w n in Table 3. I n b o t h e x p e r i m e n t s , f e e d i n g p a r t i a l l y h y d r o g e n a t e d f a t t o t h e sows l e d t o e l e v a t e d levels of 18:1 t r a n s in t h e offspring. However, lower b u t d e t e c t a b l e levels of 18:1 t r a n s were a l s o f o u n d in o f f s p r i n g f r o m t h e sows fed t h e c o n t r o l d i e t s w i t h o u t p a r t i a l l y h y d r o g e n a t e d fat. T h e c o n t e n t of 18:1 t r a n s in t h e o f f s p r i n g w a s n o t influe n c e d b y t h e levels of linoleic a c i d in t h e d i e t s of t h e sows in E x p t . 2. F e e d i n g h y d r o g e n a t e d f a t s in c o m b i n a t i o n w i t h t h e lower level of linoleic a c i d t o t h e sows in E x p t . 2 i n c r e a s e d t h e c o n t e n t of 20:3n-9 in t h e o f f s p r i n g . T h i s effect of h y d r o g e n a t e d f a t s w a s n o t s e e n w h e n fed t o g e t h e r w i t h t h e h i g h e r level of linoleic acid. F e e d i n g p a r t i a l l y hydrog e n a t e d f a t to t h e sows in b o t h e x p e r i m e n t s i n c r e a s e d t h e c o n t e n t of linoleic a c i d a n d linolenic acid, and, e x c e p t for t h e H F O in E x p t . 2, d e c r e a s e d t h e c o n t e n t of a r a c h i d o n i c a c i d in t h e o f f s p r i n g . I n b o t h e x p e r i m e n t s , P H F O inc r e a s e d t h e c o n t e n t of 20:3n-6. P H F O a n d H F O in E x p t . 2 i n c r e a s e d t h e c o n t e n t of 20:5n-3. T h e c o n t e n t of m o n o e n o i c f a t t y a c i d s in t h e offs p r i n g r e f l e c t e d t h a t of t h e f a t s f e d t o t h e sows in b o t h LIPIDS, VoI. 27, no. 10 (1992)

764 J. PETTERSEN AND J. OPSTVEDT TABLE 3 Fatty Acid Composition (%) in Phosphatidylethanolamine of Total Lipids in Heart of 3-Wk-Old Suckling Piglets a

Experiment 1 Added SFO (4%) Fatty acids

Lard PHFO PHSBO 1 2 3

14:0 16:0 18:0 16:1 18:1 cis 18:1 trans 20:1 cis 22:1 cis + trans 20:3n-9 18:2n-6 20:2n-6 20:3n-6 20:4n-6 22:4n-6 22:5n-6 18:3n-3 20:5n-3 22:5n-3 22:6n-3 Sum PUFAn-6 Sum PUFAn-3 Sum PUFA total Sum monoenoic Sum saturated Sum trans

5.2 21.1 0.3 8.4 0.8 0.1 n.d. c 0.2 15.0 0.4 0.9 38.6 1.6 0.4 0.3 1.3 3.3 2.8 56.9 7.7 64.8 9.6 26.3 0.8

6.1 15.2 0.6 10.3 1.9 0.9 n.d. 0.1 25.9 0.3 1.1 28.3 1.4 0.7 0.5 1.4 2.7 2.4 57.7 7.0 64.8 13.7 21.3 1.9

4.9 12.9 0.3 13.6 3.8 0.5 n.d. 0.1 19.0 0.3 0.8 33.1 1.6 0.6 0.4 1.5 3.7 2.8 55.4 8.4 63.9 18.2 17.8 3.8

Pooled Significant std. experimental dev. factors b 1.0 1.0 0.1 1.1 0.8 0.1 0.1 1.3 0.1 0.1 1.9 0.3 0.5 0.1 0.2 0.3 0.5

C C C C C

C C C C C

Experiment 2 Added SFO ( 0 % ) Added SFO (3%) CF 1.1 0.3 5.0 22.2 1.1 8.8 0.1 0.5 0.5 0.7 7.5 0.2 1.1 32.6 0.9 0.6 0.2 4.9 3.6 3.4 42.9 12.1 55.7 11.0 27.5 0.1

PHFO HFO 1.2 1.3 0.1 6.7 17.8 0.8 12.2 2.7 1.2 0.1 1.2 11.5 0.3 1.5 24.6 0.5 0.2 0.6 6.9 3.1 2.9 38.6 13.5 53.3 17.0 24.6 2.7

n.d. 5.1 20.7 0.5 9.4 0.6 0.3 trace 1.1 9.3 0.2 1.2 33.2 0.9 0.2 0.5 5.8 4.0 3.0 45.0 13.3 59.4 10.8 25.8 0.6

CF 2.1 0.6 8.8 20.3 1.3 10.3 0.5 0.5 0.2 0.4 8.7 0.2 0.7 32.7 1.3 0.4 0.2 0.9 3.1 2.6 44.0 6.8 51.2 12.8 29.7 0.5

PHFO HFO 2.2 2.3 0.1 5.8 19.7 0.7 10.2 2.4 1.0 0.4 0.4 13.4 0.2 1.2 30.1 1.1 0.8 0.2 1.1 2.4 2.5 46.8 6.2 53.4 14.7 25.6 2.4

0.1 4.1 21.2 0.4 7.4 1.0 0.2 0.1 0.5 12.3 0.2 0.9 36.6 1.3 0.3 0.1 2.1 3.3 2.6 51.6 8.1 60.2 9.1 25.4 1.0

Pooled Significant std. experimental dev. factors 0.3 2.8 2.4 0.7 3.1 0.8 0.6 0.5 0.2 1.7 0.2 0.2 4.5 0.3 0.6 0.1 1.4 0.7 0.6

C A C C C A,B,C B,C B,C B,C B,C A,B,C B,C B,C B

aFrom mothers fed these diets from 3 wk of age through pregnancy (Expt. 1) and from gestation through pregnancy (Expt. 2). All abbreviations as in Table 1. bSignificance means {P < 0.05): A, Interactions of experimental fats and SFO-level; B, effect of SFO-level; C, effect of experimental fats. Average of eight replicates. Pooled std. dev., pooled standard deviation, (error mean square) 1/2. Cn.d., Not detectable. e x p e r i m e n t s . However, o n l y low levels of 22:1 c i s p l u s t r a n s were f o u n d a n d 20:1 t r a n s w a s n o t d e t e c t e d . I n E x p t . 1, f e e d i n g p a r t i a l l y h y d r o g e n a t e d f a t t o t h e sows d e c r e a s e d t h e c o n t e n t of s a t u r a t e d f a t t y acids, inc r e a s e d t h e c o n t e n t of m o n o e n o i c a c i d s b u t w a s w i t h o u t effect on t h e P U F A in t h e o f f s p r i n g . S i m i l a r effects were f o u n d for P H F O in E x p t . 2, while H F O i n c r e a s e d t h e cont e n t of P U F A b u t h a d o n l y m i n o r effects on t h e m o n o e n o i c acids. I n c r e a s i n g t h e level of linoleic acid in t h e sows' diets in E x p t . 2 i n c r e a s e d t h e c o n t e n t of t h e n-6 f a t t y a c i d s a n d r e d u c e d t h e c o n t e n t of 20:3n-9 a n d n-3 f a t t y a c i d s in t h e offspring. L i v e r . T h e f a t t y a c i d c o m p o s i t i o n of liver m i t o c h o n d r i a P E f r o m t h e p i g l e t s is s h o w n in Table 4. I n b o t h exp e r i m e n t s , feeding all t y p e s of p a r t i a l l y h y d r o g e n a t e d f a t s t o t h e sows i n c r e a s e d t h e c o n t e n t of 18:1 t r a n s in t h e offs p r i n g . C o n t r a r y t o w h a t w a s f o u n d for b r a i n a n d h e a r t , f e e d i n g of P H F O also l e d t o i n c o r p o r a t i o n of 20:1 t r a n s . T h e level of linoleic a c i d in t h e sows' d i e t s h a d no effect on t h e level of t r a n s f a t t y a c i d s in t h e o f f s p r i n g ( E x p t . 2). T h e f a t t y a c i d profiles of t h e f a t s fed to t h e sows inf l u e n c e d t h e f a t t y a c i d c o m p o s i t i o n of liver P E of t h e offspring. I n E x p t . 1, P H S B O c a u s e d a m a r k e d i n c r e a s e in t h e p e r c e n t a g e of 18:1 c i s a n d a m a r k e d r e d u c t i o n in t h e p e r c e n t a g e of 20:4n-6, 22:5n-3 a n d 22:6n-3. I t is w o r t h LIPIDS, Vol. 27, no. 10 (1992)

n o t i n g t h a t d e s p i t e a r e l a t i v e l y h i g h c o n t e n t of 20:1 c i s a n d 20:1 t r a n s a n d of 22:1 c i s 4- t r a n s in t h e d i e t s of t h e sows fed P H F O a n d H F O , o n l y v e r y low t o n o n - d e t e c t a b l e levels of t h e s e f a t t y a c i d s were f o u n d in t h e o f f s p r i n g . I n t o t a l , f e e d i n g P H F O to t h e sows in b o t h e x p e r i m e n t s inc r e a s e d t h e p e r c e n t a g e of m o n o e n o i c a c i d s a n d r e d u c e d t h e p e r c e n t a g e of s a t u r a t e d acids. I n E x p t . 1, f e e d i n g PHFO increased and PHSBO decreased the percentage of P U F A in t h e offspring. I n c r e a s e d levels of linoleic a c i d in t h e sows' d i e t s in E x p t . 2 r e d u c e d t h e p e r c e n t a g e of 20:3n-9 a n d 20:5n-3 a n d i n c r e a s e d t h e p e r c e n t a g e of 18:2n-6, 20:4n-6 a n d 22:4n-6 in t h e offspring. F u r t h e r , linoleic a c i d a d d i t i o n s increase d t h e p e r c e n t a g e of P U F A n-6 a n d t o t a l P U F A a n d reduce d t h e p e r c e n t a g e of m o n o u n s a t u r a t e d acids. B l o o d T h e f a t t y acid c o m p o s i t i o n of t o t a l p l a s m a l i p i d s of v e n o u s b l o o d is s h o w n in Table 5. I n b o t h e x p e r i m e n t s , t h e p e r c e n t a g e of 18:1 t r a n s in t h e o f f s p r i n g i n c r e a s e d s i g n i f i c a n t l y w h e n t h e l a c t a t i n g sows were fed hydrog e n a t e d fats, b u t were n o t i n f l u e n c e d b y t h e d i e t a r y level of linoleic a c i d in E x p t . 2. F e e d i n g P H F O , a n d t o a l e s s e r d e g r e e H F O , t o t h e sows g a v e a p p r e c i a b l e levels of 20:1 t r a n s in t h e o f f s p r i n g . I n c o n t r a s t t o w h a t w a s f o u n d for 18:1 t r a n s , 20:1 t r a n s w a s h i g h e r in p i g l e t s f r o m sows fed t h e d i e t w i t h t h e lower level of linoleic a c i d c o m p a r e d w i t h t h e h i g h e r level. T h e p e r c e n t a g e s of 20:1 cis, 22:1 c i s +

765

DIETARY T R A N S FATTY ACIDS TABLE 4 Fatty Acid Composition (%) in Phosphatidylethanolamine of Liver Mitochondria of 3-Wk-Old Suckling Piglets a

Experiment 1 Added SFO (4%) Fatty acids

Lard PHFO PHSBO 1 2 3

14:0 16:0 18:0 16:1 18:1 cis 18:1 trans 20:1 cis 20:1 trans 22:1 cis + trans 20:3n-9 18:2n-6 20:2n-6 20:3n-6 20:4n-6 22:4n-6 22:5n-6 18:3n-3 20:5n-3 22:5n-3 22:6n-3 Sum PUFAn-6 Sum PUFAn-3 Sum PUFA total Sum monoenoic Sum saturated Sum trans

7.7 35.9 0.5 9.2 0.1 0.2 n.d. c n.d. 0.1 9.2 0.3 0.5 24.6 1.0 0.2 0.2 0.3 2.6 7.4 35.8 10.5 46.4 10.0 43.6 0.1

7.5 23.8 0.8 9.3 6.0 0.8 0.3 n.d. 0.1 12.9 0.3 0.8 25.3 1.0 0.8 0.1 0.5 2.7 7.0 41.1 10.3 51.5 17.2 31.3 6.3

8.5 27.9 1.0 17.2 7.6 0.5 n.d. n.d. 0.1 9.0 0.3 0.4 16.6 0.6 0.1 trace 0.3 1.1 4.0 27.0 5.4 32.5 26.3 36.4 7.6

Pooled Significant std. experimental dev. factors b 1.2 5.4 0.3 1.0 1.3 0.2 0.0 1.7 0.1 0.1 3.1 0.2 0.1 0.1 0.1 0.4 1.1

C C C C C

C C C C C C

Experiment 2 Added SFO ( 0 % ) Added SFO {3%) CF PHFO HFO CF PHFO HFO Pooled Significant std. experimental dev. factors 1.1 1.2 1.3 2.1 2.2 2.3 0.2 10.1 34.2 1.1 10.0 0.6 0.2 n.d. 0.1 0.4 6.7 0.2 0.5 18.0 0.7 0.2 0.1 0.7 2.4 7.3 26.3 10.5 37.2 12.0 44.5 0.6

0.3 8.4 25.4 1.4 13.6 4.2 1.7 0.3 0.2 0.4 7.3 0.1 0.8 16.4 0.4 0.4 0.1 2.2 2.6 7.8 25.4 12.7 38.5 21.4 34.1 4.5

0.1 8.4 26.9 1.0 9.3 1.1 0.5 trace 0.2 0.4 7.0 0.1 0.7 24.1 0.9 0.8 0.2 1.9 4.0 10.3 33.6 16.4 50.4 12.1 35.4 1.1

0.1 8.3 28.7 0.7 7.0 0.1 0.2 n.d. n.d. 0.1 8.4 0.3 0.7 25.9 1.9 0.8 trace 0.1 3.0 10.0 38.0 13.1 51.2 8.0 37.1 0.1

0.2 6.2 25.6 0.5 9.0 4.0 1.0 0.1 0.7 0.1 9.0 0.2 0.8 26.0 0.8 0.4 0.1 0.3 2.7 7.7 37.2 10.8 48.1 15.3 32.0 4.1

0.2 7.7 27.8 0.9 9.4 1.2 0.3 trace 0.2 0.4 8.7 0.1 0.5 23.9 1.3 0.4 0.2 0.6 3.1 8.0 34.9 11.9 47.2 12.0 35.7 1.2

0.1 1.5 4.4 0.5 2.1 0.9 0.5 0.1 0.8 0.2 1.5 0.2 0.2 5.1 0.7 0.3 0.1 0.6 1.0 2.6

A B,C C B

A,B,C C B,C C B B A,B B,C A C A,B,C C A

aFrom mothers fed these diets from 3 wk of age through pregnancy (Expt. 1) and from gestation through pregnancy (Expt. 2). All abbreviations as in Table 1. bsignificance means (P < 0.05}: A, Interactions of experimental fats and SFO-level; B, effect of SFO-level; C, effect of experimental fats. Average of eight replicates. Pooled std. dev., pooled standard deviation, (error mean square) 1/2. Cn.d., Not detectable.

t r a n s a n d 20:0 in t h e o f f s p r i n g i n c r e a s e d w h e n P H F O or H F O w a s fed t o t h e sows in E x p t . 2. I n E x p t . 1 t h e p e r c e n t a g e of linoleic a c i d increased, a n d in b o t h e x p e r i m e n t s t h e p e r c e n t a g e of a r a c h i d o n i c a c i d d e c r e a s e d in t h e o f f s p r i n g w h e n h y d r o g e n a t e d f a t w a s fed t o t h e sows. F e e d i n g C F l e d to a s i g n i f i c a n t i n c r e a s e in t h e p e r c e n t a g e of 12:0 a n d 14:0 in t h e offspring, e s p e c i a l l y w h e n t h e sows were fed t h e d i e t s w i t h t h e lower level of linoleic acid. T h e overall effect of f e e d i n g h y d r o g e n a t e d f a t t o t h e sows on t h e f a t t y a c i d c o m p o s i t i o n in t h e o f f s p r i n g w a s a r e d u c t i o n in t h e p e r c e n t a g e of s a t u r a t e d acids w h i c h w a s c o m p e n s a t e d for b y an increase in t h e p e r c e n t a g e of monou n s a t u r a t e d acids. F u r t h e r m o r e , t h e p e r c e n t a g e of t o t a l n-6 P U F A w a s i n c r e a s e d a n d t h e p e r c e n t a g e of n-3 P U F A d e c r e a s e d w h e n t h e sows were fed t h e d i e t w i t h t h e h i g h e r level of linoleic a c i d c o m p a r e d w i t h t h e lower level. A d i p o s e t i s s u e s . T h e f a t t y a c i d c o m p o s i t i o n of t h e t o t a l l i p i d s of s u b c u t a n e o u s a d i p o s e t i s s u e of t h e p i g l e t s is s h o w n in Table 6. I n b o t h e x p e r i m e n t s t h e p e r c e n t a g e of 18:1 t r a n s i n c r e a s e d in t h e o f f s p r i n g w h e n h y d r o g e n a t e d f a t s were fed t o t h e sows. F u r t h e r m o r e , t h e p e r c e n t a g e of 20:1 t r a n s i n c r e a s e d a s a c o n s e q u e n c e of P H F O or H F O feeding, t h e p e r c e n t a g e of 20:1 t r a n s b e i n g h i g h e r w h e n

P H F O w a s fed t o g e t h e r w i t h t h e lower level of linoleic a c i d c o m p a r e d w i t h t h e h i g h e r d i e t a r y level. T h e p e r c e n t a g e of 20:0, 20:1 c i s a n d 22:1 c i s + t r a n s inc r e a s e d w h e n P H F O o r H F O w a s fed. F e e d i n g hydrog e n a t e d f a t s t o t h e sows h a d v a r i a b l e a n d i n c o n s i s t e n t effects on t h e p e r c e n t a g e of linoleic a c i d in t h e o f f s p r i n g . Thus, in E x p t . 1, t h e p e r c e n t a g e of linoleic a c i d i n c r e a s e d w h e n P H F O w a s fed, w h i l e t h e o p p o s i t e o c c u r r e d u p o n P H S B O - f e e d i n g . I n E x p t . 2 f e e d i n g P H F O a n d H F O inc r e a s e d t h e p e r c e n t a g e of linoleic a c i d in t h e o f f s p r i n g w h e n fed t o g e t h e r w i t h t h e h i g h e r d i e t a r y level of linoleic acid, while P H F O a n d H F O r e d u c e d t h e p e r c e n t a g e of linoleic a c i d w h e n fed t o g e t h e r w i t h t h e lower level of linoleic acid. T h e p e r c e n t a g e of a r a c h i d o n i c a c i d d e c r e a s e d in t h e offs p r i n g w h e n P H F O or H F O w a s fed t o g e t h e r w i t h t h e lower d i e t a r y level of linoleic a c i d in E x p t . 2 b u t n o t w h e n fed t o g e t h e r w i t h t h e h i g h e r level. F e e d i n g C F i n c r e a s e d t h e p e r c e n t a g e of 12:0 a n d 14:0. A s s h o w n for t h e o t h e r o r g a n lipids, f e e d i n g hydrog e n a t e d f a t s t o t h e sows d e c r e a s e d t h e p e r c e n t a g e of s a t u r a t e d f a t t y a c i d s in t h e o f f s p r i n g a n d t h i s w a s p a r t l y c o m p e n s a t e d b y a n i n c r e a s e in t h e p e r c e n t a g e of m o n o enoic acids, i.e., c i s p l u s t r a n s i s o m e r s . LIPIDS, Vol. 27, no. 10 (1992)

766

J. PETTERSEN AND J. OPSTVEDT TABLE 5 Fatty Acid Composition (%) of Total Plasma Lipids of Venous Blood from 3-Wk-Old Suckling Piglets a

Experiment 1 Added SFO (4%) Fatty acids 12:0 14:0 16:0 18:0 20:0 16:1 18:1cis 18:ltrans 20:lcis 20:ltrans 22:lcis + trans

18:2n-6 20:2n-6 20:3n-6 20:4n-6 22:4n-6 18:3n-3 20:5n-3 22:5n-3 22:6n-3 Sum PUFAn-6 Sum PUFAn-3 Sum PUFA total Sum monoenoic Sum saturated Sum trans

Lard PHFO PHSBO 1 2 3

22.0 12.2 n.d. c 2.1 24.0 n.d. 0.3 n.d. n.d. 27.9 0.2 0.3 6.0 0.1 1.1 0.3 0.8 1.6 34.5 3.8 38.3 26.4 34.2 0.0

18.6 8.4 n.d. 2.6 16.5 4.5 1.4 0.5 0.1 36.5 n.d. 0.4 5.2 0.1 1.4 0.3 0.7 1.1 42.2 3.5 45.7 25.6 27.0 5.0

14.0 8.1 1.3 27.9 8.9 0.7 n.d. n.d. 29.8 0.1 0.2 5.0 0.1 1.2 0.2 0.6 1.0 35.2 3.0 38.2 38.8 22.1 8.9

Experiment 2 Added SFO ( 0 % ) Added SFO (3%) Pooled Significant std. experimental dev. factors b

1.0 0.5 n.d. 0.2 0.9 0.4 0.2 0.1 0.0 1.1 0.1 0.1 0.2 0.1 0.3 0.1 0.2 0.1

C C C C C C C C C C

C

CF 1.1 2.5 4.8 22.6 11.9 trace 4.1 19.5 0.3 0.2 n.d. 0.1 19.3 0.2 0.5 5.3 0.1 1.4 1.2 1.1 2.0 25.4 5.6 31.0 24.2 41.8 0.3

PHFO HFO 1.2 1.3 n.d. 2.0 18.1 8.7 0.2 4.4 20.4 4.1 1.9 1.5 0.7 18.2 0.3 0.5 3.7 n.d. 1.5 1.1 1.0 2.0 22.7 5.6 28.3 33.0 29.0 5.6

n.d. 2.6 21.0 10.4 1.0 4.4 20.0 1.6 1.8 0.2 0.2 18.3 0.2 0.4 5.1 0.1 1.2 1.1 1.3 1.9 24.1 5.5 29.6 28.2 35.0 1.8

CF 2.1 1.7 3.5 21.8 12.6 trace 2.4 13.9 0.1 0.2 n.d. 0.1 27.5 0.2 0.5 7.5 0.3 0.8 0.4 1.1 2.1 36.0 4.4 40.4 16.7 39.6 0.1

PHFO HFO 2.2 2.3 n.d. 1.7 16.7 9.7 0.2 2.6 18.2 3.7 1.5 0.7 0.3 28.5 0.2 0.5 5.5 0.1 0.8 0.4 0.8 1.5 34.8 3.5 38.3 27.0 28.3 4.4

n.d. 2.3 20.5 10.3 0.4 2.9 16.0 1.6 1.4 ~a~ ~ace 28.2 0.2 0.3 6.0 0.1 1.0 0.4 1.0 1.6 38.8 4.0 38.8 21.9 33.5 1.6

Pooled Significant std. experimental dev. factors 0.5 0.7 0.9 1.5 0.3 0.6 2.4 0.4 0.5 0.7 0.2 1.9 0.1 0.1 0.8 0.1 0.4 0.2 0.2 0.3

A,C B,C B,C A,B,C A,C B

B,C C C A,C C B A C C A,C B A,C C

aFrom mothers fed these diets from 3 wk of age through pregnancy (Expt. 1) and from gestation through pregnancy (Expt. 2). All abbreviations as in Table 1. bSignificance means (P < 0.05): A, Interactions of experimental fats and SFO-level; B, effect of SFO-level; C, effect of experimental fats. Average of eight replicates. Pooled std. dev., pooled standard deviation, (error mean square) 1/2, Cn.d., Not detectable. F u r t h e r a d d i t i o n s of linoleic a c i d to t h e sows' d i e t s inc r e a s e d t h e p e r c e n t a g e of n-6 P U F A b u t h a d l i t t l e effect on t h e p e r c e n t a g e of n-3 P U F A in t h e o f f s p r i n g .

DISCUSSION N e r v o u s t i s s u e c o n t a i n s l a r g e q u a n t i t i e s of l o n g - c h a i n p o l y u n s a t u r a t e d , e s s e n t i a l n-6 a n d n-3 f a t t y a c i d s (LCP U F A ) w h i c h p l a y i m p o r t a n t roles in n e r v e s t r u c t u r e a n d f u n c t i o n (24). I t is t h e r e f o r e a n t i c i p a t e d t h a t n u t r i t i o n a l deficiencies a n d i m b a l a n c e s a n d m e t a b o l i c d i s o r d e r s t h a t affect f a t t y acid m e t a b o l i s m m a y have a p a r t i c u l a r l y detrim e n t a l effect on n e r v o u s t i s s u e A c c r e t i o n of n e r v o u s tissue occurs over a r e l a t i v e l y brief p e r i o d of t i m e d u r i n g l a t e g e s t a t i o n a n d e a r l y p o s t n a t a l life (10,25). Since in v i t r o (3,4,26) a n d in v i v o (27-29) s t u d i e s h a v e i n d i c a t e d t h a t t r a n s f a t t y a c i d s m a y i n t e r f e r e w i t h t h e m e t a b o l i s m of ess e n t i a l f a t t y acids, t h e c o n t e n t of t r a n s f a t t y a c i d s in t h e m a t e r n a l d i e t d u r i n g p r e g n a n c y a n d n u r s i n g is of c o n c e r n for t h e d e v e l o p m e n t of n e r v o u s t i s s u e in t h e offspring. O u r p r e v i o u s s t u d i e s s h o w e d no effect of t r a n s f a t t y a c i d s in t h e m a t e r n a l d i e t on n e r v o u s t i s s u e h i s t o l o g y a n d funct i o n in 3-wk-old s u c k l i n g p i g l e t s (13). However, we d i d find t h a t t r a n s f a t t y a c i d s in t h e d i e t s of t h e sows were t r a n s f e r r e d i n t o t h e m i l k b u t h a d o n l y m a r g i n a l effects on t h e overall f a t t y a c i d c o m p o s i t i o n of t h e m i l k (14}. LIPIDS, Vol. 27, no. 10 (1992)

T h e p r e s e n t s t u d y f o c u s e d on t h e effect of t h e c o n t e n t of t r a n s f a t t y acids in t h e m a t e r n a l diet (and c o n s e q u e n t l y in t h e milk) on t h e f a t t y a c i d c o m p o s i t i o n of t h e o f f s p r i n g a f t e r n u r s i n g for t h r e e weeks a f t e r birth. I n addition, comp a r i s o n s were m a d e in E x p t . 1 b e t w e e n a h y d r o g e n a t e d f a t of v e g e t a b l e o r i g i n ( P H S B O ) c o n t a i n i n g t r a n s f a t t y a c i d s w i t h 16 a n d 18 c a r b o n s a n d a h y d r o g e n a t e d f a t of fish origin ( P H F O ) w h i c h in a d d i t i o n t o C16 a n d Cls t r a n s f a t t y a c i d s a l s o c o n t a i n e d t r a n s f a t t y a c i d s w i t h 20 a n d 22 c a r b o n s . S i n c e d i e t a r y levels of linoleic a c i d h a v e b e e n c l a i m e d to i n f l u e n c e t h e effect of t r a n s f a t t y a c i d s (1,30), d i f f e r e n t levels of t r a n s f a t t y a c i d s in h y d r o g e n a t e d f i s h oils were s t u d i e d a t t w o levels of d i e t a r y linoleic a c i d in E x p t . 2. T h e general o u t c o m e of t h e s t u d y is c o n s i s t e n t w i t h t h e r e s u l t s of o u r p r e v i o u s i n v e s t i g a t i o n s a n d w i t h m a t u r e p i g s b e i n g fed d i e t s w i t h t r a n s f a t t y acids for a s i x - m o n t h p e r i o d (12). Thus, t r a n s f a t t y a c i d s p r e s e n t in t h e m i l k were a b s o r b e d b y t h e y o u n g p i g l e t s a n d d e p o s i t e d in v a r i o u s t i s s u e s . T h e s e r e s u l t s a r e also c o n s i s t e n t w i t h p r e v i o u s f i n d i n g s in s u c k l i n g r a t s (31). I n a g r e e m e n t w i t h our earlier r e s u l t s w i t h new b o r n (11) a n d m a t u r e (12) pigs, t h e d e p o s i t i o n of t r a n s f a t t y a c i d s v a r i e d g r e a t l y b e t w e e n d i f f e r e n t o r g a n s , b e i n g h i g h e s t in a d i p o s e t i s s u e a n d l o w e s t in brain. Thus, d e s p i t e t h e f a c t t h a t a p p r e c i a b l e levels of t r a n s f a t t y a c i d s were p r e s e n t in t h e m i l k (14),

767

DIETARY T R A N S FATTY ACIDS TABLE 6 Fatty Acid Composition (%) of Subcutaneous Adipose Tissue of 3-Wk-Old Suckling Piglets a

Experiment 1 Added SFO (4%) Fatty acids 12:0 14:0 16:0 18:0 20:0 16:1 18:1 cis 18:1 trans 20:1 cis 20:1 trans 22:1 cis + trans 20:3n-9 18:2n-6 20:2n-6 20:4n-6 18:3n-3 22:5n-3 22"6n-3 Sum PUFAn-6 Sum PUFAn-3 Sum PUFA total Sum monoenoic Sum saturated Sum trans

Lard PHFO PHSBO 1 2 3

21.4 20.8 6.3 4.2 n.d. c n.d. 3.8 7.5 44.4 26.9 n.d. 5.1 0.7 4.0 n.d. 3.8 0.1 1.0 0.6 1.0 20.0 22.5 0.2 0.2 0.6 0.8 1.7 1.8 0.2 trace 0.1 0.1 20.8 23.5 2.0 1.9 23.4 26.4 49.0 48.3 27.7 25.0 0.0 8.9

14.1 5.3 n.d. 2.7 42.9 11.0 1.2 0.2 n.d. 0.8 18.4 0.1 0.5 1.5 trace 0.1 19.0 1.6 21.4 58.0 19.4 11.2

Pooled Significant std. experimental dev. factors b

0.5 0.5

C C

0.3 1.5 1.0 0.4 0.3 0.1 0.2 0.5 0.1 0.3 0.1

C C C C C C C C C

0.1

Experiment 2 Added SFO ( 0 % ) Added SFO (3%) CF 1.1 3.4 11.0 26.2 5.1 0.1 8.8 31.8 0.1 0.4 n.d. trace 0.1 6.9 0.2 0.9 1.4 0.4 0.3 8.0 2.1 10.2 41.1 45.8 0.1

PHFO HFO 1.2 1.3 0.1 4.8 20.1 3.7 0.4 8.2 30.1 6.3 4.8 2.7 1.1 0.1 5.8 0.4 0.3 1.3 0.2 0.1 6.5 1.6 8.2 53.2 29.1 9.0

0.1 5.2 25.5 5.8 0.9 8.6 34.9 2.4 3.1 0.8 0.1 0.1 6.3 0.1 0.4 1.6 0.1 0.1 6.8 1.8 8.7 49.9 37.5 3.2

CF 2.1 2.9 10.2 24.6 5.1 0.1 6.9 30.3 0.1 0.4 n.d. trace 0.2. 14.5 0.3 0.8 1.2 0.3 0.2 15.6 1.7 17.5 37.7 42.9 0.1

PHFO HFO 2.2 2.3 0.1 3.9 18.1 4.2 0.4 5.8 29.3 6.1 4.7 2.1 1.0 0.2 15.6 0.5 0.5 1.1 0.1 0.1 16.6 1.3 18.1 49.0 26.7 8.2

trace 4.3 23.3 5.5 1.0 5.0 29.0 2.2 2.4 0.9 0.3 0.2 17.8 0.3 0.9 1.3 0.3 0.2 19.0 1.8 21.0 39.8 34.1 3.1

Pooled Significant std. experimental dev. factors 0.5 0.9 1.3 0.7 0.1 0.5 3.1 0.7 0.8 0.3 0.2 0.1 0.8 0.1 0.3 0.2 0.1 0.1

C B,C B,C C A,C A,B,C C C A,C A,C B A,B,C C A,B B,C A,C C

aFrom mothers fed these diets from 3 wk of age through pregnancy (Expt. 1) and from gestation through pregnancy (Expt. 2). All abbreviations as in Table 1. bsignificance means (P < 0.05): A, Interactions of experimental fats and SFO-level; B, effect of SFO-level; C, effect of experimental fats. Average of eight replicates. Pooled std. dev., pooled standard deviation, (error mean square} 112. Cn.d., Not detectable. t r a n s f a t t y a c i d s were n o t d e t e c t e d in t h e b r a i n s of t h e o f f s p r i n g in E x p t . 1, a n d o n l y low levels of 18:1 t r a n s a n d n o 20:1 t r a n s were f o u n d in E x p t . 2. T h e s e r e s u l t s a r e in entire agreement with our previous results from mature a n d n e w b o r n p i g s (11,12}. I n e x p e r i m e n t s w i t h r a t s , C o o k (32) f o u n d t h a t s m a l l a m o u n t s {0.2%} of e l a i d i c a c i d (18:1 t r a n s ) i n j e c t e d i n t o t h e s t o m a c h of y o u n g r a t s were recovered in t h e brain. I t t h e r e f o r e a p p e a r s t h a t a l t h o u g h t r a n s f a t t y a c i d s m a y p a s s t h e b l o o d - b r a i n b a r r i e r in suckl i n g a n i m a l s , t h e a m o u n t a c t u a l l y b e i n g d e p o s i t e d in t h e b r a i n is i n d e e d v e r y l i m i t e d . Table 7 s h o w s t h e d i s c r i m i n a t i o n f a c t o r s {i.e., t h e relat i o n of t h e p e r c e n t a g e of t r a n s i s o m e r s of t h e t o t a l m o n o ene c o n t e n t s of t h e o r g a n l i p i d s t o t h a t of t h e r e s p e c t i v e d i e t a r y lipids) in t h e d i f f e r e n t o r g a n s of t h e 3-wk-old p i g l e t s c o m p a r e d to t h o s e of m a t u r e (12) a n d n e o n a t a l I l l ) pigs. I n o r d e r to r e l a t e t h e f i n d i n g s in t h e 3-wk-old p i g l e t s to m a t e r n a l n u t r i t i o n , t h e c a l c u l a t i o n is b a s e d b o t h on t h e m i l k a n d on t h e sows' d i e t s . T h e r e l a t i v e v a l u e s b e t w e e n t h e d i f f e r e n t o r g a n s were s i m i l a r in 3-wk-old a n d m a t u r e pigs, b u t r e l a t i v e l y m o r e t r a n s f a t t y a c i d s f r o m t h e d i e t {i.e., milk} were i n c o r p o r a t e d i n t o t h e o r g a n s of t h e 3-wko l d p i g s c o m p a r e d t o t h e m a t u r e pigs. I n d e e d , t h e p e r c e n t a g e of t h e t r a n s f a t t y a c i d s in t h e mothers' diet incorporated into the suckling piglets was s i m i l a r t o t h a t f o u n d in t h e m o t h e r s t h e m s e l v e s {12}. I t is p o s s i b l e t h a t t h e r e l a t i v e l y h i g h i n c o r p o r a t i o n of t r a n s

f a t t y a c i d s in t h e 3-wk-old p i g s w a s d u e to a low d e n o v o f a t t y a c i d s y n t h e s i s in t h e s e a n i m a l s c o n s u m i n g m i l k in w h i c h a v e r y h i g h p o r t i o n of t h e t o t a l e n e r g y c a m e f r o m fat. E x c e p t for liver m i t o c h o n d r i a in w h i c h r e l a t i v e l y m o r e t r a n s f a t t y a c i d s were i n c o r p o r a t e d f r o m t h e P H F O t h a n f r o m P H S B O , t h e d i s c r i m i n a t i o n f a c t o r s were s i m i l a r for t h e t w o f a t sources in c o m m o n w i t h t h a t f o u n d for m a t u r e pigs. W i t h t h e e x c e p t i o n of t h e brain, in w h i c h t h e incorp o r a t i o n of 18:1 t r a n s w a s s i g n i f i c a n t l y i n c r e a s e d on t h e lower d i e t a r y levels of linoleic a c i d c o m p a r e d w i t h t h e h i g h e r levels, d i e t a r y levels of linoleic a c i d d i d n o t a f f e c t t h e i n c o r p o r a t i o n of t r a n s f a t t y acids. T h i s r e s u l t is cont r a d i c t o r y t o t h o s e of H i l l e t al. (33) w h o f o u n d a signific a n t effect f r o m d i e t a r y levels of linoleic a c i d on t r a n s f a t t y a c i d i n c o r p o r a t i o n . T h e r e a s o n for t h i s d i s c r e p a n c y is n o t i m m e d i a t e l y e v i d e n t . To w h a t e x t e n t t h e levels of t r a n s f a t t y a c i d s in t h e o r g a n s c o n t i n u e to i n c r e a s e over a life s p a n is a n i n t r i g u i n g q u e s t i o n . T h e n e w b o r n a n d 3-wk-old p i g s were offspri n g of t h e m a t u r e p i g s u s e d in t h i s s t u d y {i.e., E x p t . 1), a n d all p i g s were s u b j e c t e d to t h e s a m e d i e t a r y r e g i m e n . T h e d a t a therefore l e n d t h e m s e l v e s to s h o w i n g age effects on t h e levels of t r a n s f a t t y a c i d s in v a r i o u s organs. F i g u r e 1 shows t h e p e r c e n t a g e of t r a n s f a t t y a c i d s in P E of heart, liver m i t o c h o n d r i a a n d a d i p o s e t i s s u e of n e w b o r n , 3-wkold a n d m a t u r e p i g s w h e n fed P H F O a n d P H S B O in E x p t . 1. T h e figure shows t h a t in t h e s e o r g a n s t h e r e w a s a s h a r p LIPIDS, Vol. 27, no. 10 (1992)

768

J. PETTERSEN AND J. OPSTVEDT TABLE 7 Ratio of Percentage t r a n s Isomers of the Total Monoene Content of Organ Lipids to that of the Respective Dietary Fats in 3-Wk-Old Suckling Piglets, Newborn Piglets (11) and Their Adult Mothers (12) in Experiment I a

18:1 trans PHFO PHSBO Brain Adult Neonatal Postnatal/diet Postnatal/milk Heart Adult Neonatal Postnatal/diet Postnatal/mill( Liver Adult Neonatal Postnatal/diet Postnatal]milk Blood Adult Neonatal Postnatal/diet Postnated/mill~ Adipose Adult Neonatal Postnatal/diet Postnatal]milk

20:1 trans PHFO

0 0 0 0

0 0 0 0

0 0 0 0

0.45 0.17 0.48 0.70

0.32 0.13 0.48 0.69

0.15 0 0 0

0.94 0.37 1.21 1.75

0.76 0.31 0.67 0.97

0.41 0 0.45 0.69

0.63 0.20 0.66 0.96

0.51 0.14 0.53 0.78

0 0 0.43 0.66

0.64 0 0.49 0.71

0.58 0.01 0.45 0.64

0.87 0 0.80 1.23

aFed the diets from 3 wk of age through gestation. For the suckling piglets (i.e., postnatal) discrimination factors based on the respective milk lipids (14) also were calculated. All abbreviations as in Table 1.

Heart

It

Liver

AdiposelJssue

FIG. 1. Average percentage of 18:1 trans (white bars; animals fed PHFO and PHSBO) and 20:1 t r a n s (black bars; animal fed PHFO) in organs of newborn, 3-wk~ld, and mature pigs.

increase in the percentage of t r a n s f a t t y acids during the first three weeks of life and t h a t no consistent changes occurred thereafter. I t thus appears t h a t the content of t r a n s f a t t y acids reaches a steady level early in life and is dependent on the dietary level of t r a n s f a t t y acids. LIPIDS, Vol. 27, no. 10 (1992)

Previous i n v i t r o studies have shown t h a t t r a n s f a t t y acids m a y interfere with the m e t a b o l i s m of the essential n-6 and n-3 f a t t y acids t h r o u g h inhibition of the A5 (4,26) and A6 {3,4,26,30} desaturases. If such effects were of significant magnitude, they could influence f a t t y acid composition of the brain and consequently brain function. In the present s t u d y the effects of t r a n s f a t t y acids on brain f a t t y acid composition were negligible although a slight increase in 18:2n-6 and 22:5m6, and a small and inconsistent decrease in 20:4n-6 and 22:6n-3 were seen. These findings are in agreement with our previous results on newborn i l l ) and m a t u r e (12) pigs and with those of Lawson e t aL (27) on r a t s being fed t r a n s f a t t y acid for two generations. They are also in agreement with the findings of Sanders e t al. (34) who found a reduction in brain 22:6n-3 and an increase in brain 22:5n-6 when fed t r a n s f a t t y acid containing margarine to rats. The effect of t r a n s f a t t y acids on the f a t t y acid composition {i.e., the levels of n-6 and n-3 f a t t y acids} in the other organs was similar in nature b u t of s o m e w h a t greater m a g n i t u d e t h a n t h a t found in the brain, and this is in agreement with our previous results w i t h newborn i l l ) and m a t u r e pigs {12}. This p a p e r concludes a series of experiments with the aim of s t u d y i n g the effects of dietary t r a n s f a t t y acids, with emphasis on nervous t i s s u e Since knowledge of the effect of long-chain t r a n s f a t t y acids is meager, comparisons were m a d e between partially hydrogenated soybean off and partially hydrogenated fish oil Pigs were used as model animals due to their resemblance to humans with regard to lipid m e t a b o l i s m and nerve tissue accretion (10,17). The study comprised the intrauterine period, early p o s t n a t a l life (sucldlng period} and the growth period through the first pregnancy. The pigs were fed diets t h a t resembled h u m a n diets in Western society with regard to content of fat {about 40 cal%) and linoleic acid (2 to 9 cal%) and had a P/S (polyuns a t u r a t e d f a t t y acids/saturated f a t t y acids} ratio from a b o u t 0.1 to 0.8, b u t contained 2 to 4 times more t r a n s f a t t y acids {i.e., 6 to 12 cal% vs. 3 - 4 cal%) (1). The combined results allow us to draw the following conclusions. t r a n s F a t t y acids were absorbed and deposited in the body of juvenile and m a t u r e pigs, b u t the level of depositoin varied between different organs. Since t r a n s f a t t y acids were absent or only present at very low levels in brain PE of pigs of all ages, the transfer of t r a n s f a t t y acids through the blood-brain barrier m u s t have been very limited. Moreover, no effects of t r a n s f a t t y acids on nerve histology and function were found. PE of heart and liver mitochondria, and of lipids in adipose tissues and in p l a s m a contained t r a n s f a t t y acids at levels t h a t reflected the dietary content, the level being somewhat lower in the former than in the two latter tissues. The levels of t r a n s f a t t y acids were generally lower in the tissues compared to t h a t in the corresponding diets. The reason for this finding m a y be t h a t the t r a n s f a t t y acids were catabolized rather than deposited, b u t m a y also be due to the t r a n s f a t t y acids, being diluted in the tissues with d e n o v o synthesized cis monoenoic f a t t y acids. Since t r a n s f a t t y acids were found in the tissues of the newborn pigs, transfer of t r a n s f a t t y acids t h r o u g h the placenta m u s t have occurred, t r a n s F a t t y acids were secreted into the milk with little discrimination and absorbed and deposited in the b o d y of the suckling pig. Newborn pigs

769

DIETARY TRANS FATTY ACIDS f r o m m o t h e r s fed trans f a t t y a c i d s h a d m a r k e d l y lower levels of trans f a t t y a c i d s in t h e i r b o d i e s t h a n t h e i r m o t h e r s . T h e levels of trans f a t t y a c i d s r o s e q u i c k l y duri n g t h e f i r s t w e e k s of s u c k l i n g a n d h a d r e a c h e d t h e levels of t h e m a t u r e a n i m a l s t h r e e w e e k s a f t e r b i r t h . T h e depositions of 18:1 trans were s i m i l a r in P H S B O a n d P H F O . T h e d e p o s i t i o n of 20:1 trans, o n l y p r e s e n t in P H F O , w a s m a r k e d l y lower t h a n t h a t of 18:1 trans in P E , while t h e t w o i s o m e r s were d e p o s i t e d t o a s i m i l a r d e g r e e in a d i p o s e tissues. T h e d i e t a r y c o n t e n t of linoleic a c i d h a d no c o n s i s t e n t effect on t h e d e p o s i t i o n of trans f a t t y acids. D i e t a r y trans f a t t y a c i d s h a d m i n o r b u t c o n s i s t e n t effects o n t h e profile of e s s e n t i a l f a t t y a c i d s (i.e., n-6 f a t t y acids) in t h e o r g a n s , c a u s i n g a m i n o r i n c r e a s e in t h e c o n t e n t of t h e lower h o m o l o g s a n d a m i n o r d e c r e a s e in t h e c o n t e n t of t h e c h a i n - e l o n g a t e d a n d d e s a t u r a t e d h i g h e r homologs. A l l t o g e t h e r , c o n s u m p t i o n of trans f a t t y a c i d s f r o m P H S B O a n d P H F O a t levels of t h r e e t i m e s t h a t c o n s u m e d b y h u m a n s in W e s t e r n s o c i e t y s h o w e d no effects in t h e p i g s that could be considered detrimental. ACKNOWLEDGM ENTS The authors thank J. H. Knudsen, Department of Political Sciences, University of Bergen, for conducting the statistical calculations. This work was supported by the Royal Norwegian Council for Scientific and Industrial Research, and the Research Fund of Norwegian Dietary Fat Producers. REFERENCES 1. Gurr, M.I. (1983) Doc. Int. Dairy Fed., BulL 166, 5-18. 2. Emken, E.A. (1984) Ann. Rev. Nutr. 4, 339-376. 3. Mahfouz, M.M., Smith, T.L., and Kummerow, F.A. (1984) Lipids 19, 214-222. 4. Svensson, L. (1983) Lipids 18, 171-178. 5. Royce, S.M., Holmes, R.P., Takagi, T., and Kummerow, F.A. (1984) Am. J. Clira Nutr. 39, 215-222. 6. Zevenbergen, J.L., and Haddeman, E. (1989) Lipids 24, 555-563. 7. Gurr, M. (1990) Lipid Technology 2, 105-107. 8. Crawford, M.A. (1980) Prog. Food Nutr. Sci. 4, 75-80.

9. 10. 11. 12. 13. 14. 15. 16. 17.

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LIPIDS, VoI. 27, no. 10 (1992)