Vegetable oils affect the composition of lipoproteins in sea bream (Sparus aurata)

Transcription

1 British Journl of Nutrition (2006), 96, q The Authors 2006 DOI: /BJN Vegetle oils ffect the composition of lipoproteins in se rem (Sprus urt) Mri José Cllero 1 *, Bente E. Torstensen 2, Lidi Roin 3, Dniel Montero 3 nd Mrisol Izquierdo 3 1 Deprtment of Comprtive Pthology, Trsmontñ, s/n, 3516 Arucs, Ls Plms de Grn Cnri, Cnry Islnds, Spin 2 Ntionl Institute of Nutrition nd Sefood Reserch, PO Box 2029 Nordnes, 5817 Bergen, Norwy 3 Group Aquculture Reserch. Instituto Cnrio de Ciencis Mrins, PO Box 56, 35200, Telde, Ls Plms de Grn Cnri, Cnry Islnds, Spin (Received 1 Decemer 2005 Revised 20 June 2006 Accepted 21 June 2006) The im of the present study ws to determine the influence of the dietry ftty cid profile on the lipoprotein composition in se rem fed different vegetle oils. Six experimentl diets were formulted comining fish oil with three vegetle oils (soyen, rpeseed, linseed) in order to otin % (w/w) fish-oil replcement. VLDL, LDL nd HDL in plsm smples were otined y sequentil centrifugl flottion. The lipid clss, protein content nd ftty cid composition of ech lipoprotein frction were nlysed. HDL ws the predominnt lipoprotein in se rem plsm contining the highest proportion of protein (3 %) nd phosphtidylcholine. LDL presented high content of cholesterol, wheres tricylglycerol comprised lrger proportion of VLDL. The lipid clss of the lipoprotein frctions ws ffected y the dietry vegetle oils. Thus, high dietry inclusion of soyen nd linseed oil (80 %) incresed the cholesterol in HDL nd LDL in comprison to fish oil. Similrly, the tricylglycerol concentrtion of VLDL ws incresed in fish fed 80 % soyen nd linseed oils owing to the low n-3 highly unsturted ftty cid content of these diets. Lipoprotein ftty cid composition esily responded to dietry ftty cid composition. VLDL ws the frction more ffected y dietry ftty cid, followed y LDL nd HDL. The n-3 highly unsturted ftty cid content incresed in the order VLDL less thn LDL nd less thn HDL, regrdless of dietry vegetle oils. Se rem: Lipoproteins: VLDL: LDL: HDL: Vegetle oils: Cholesterol: Tricylglycerols: Phosphtidylcholine: Sterol esters: n-3 highly unsturted ftty cids As in mmmls, the trnsport of ftty cids nd other lipid-solule components to the peripherl tissues in fish is medited minly y lipoproteins. Exogenous lipids sored y the intestine re predominntly integrted into chylomicrons nd VLDL (Sire et l. 1981; Cllero et l. 2003), wheres endogenous lipids re trnsported in VLDL, LDL nd HDL (Sheridn, 1988; Bin & Vernier, 1989; Iijim et l. 1995). Proteins nd lipids integrted into the different lipoproteins interct with enzymes or cellulr receptors, resulting in lipoprotein degrdtion or trnsformtion, with the susequent trnsfer of products from tissues to lipoproteins or vice vers. Initilly, chylomicrons nd VLDL-tricylglycerols (TAG) re hydrolysed y the enzyme lipoprotein lipse, relesing ftty cids tht re up tken y dipose tissue for storge or y other orgns, such s muscle, for oxidtion (Auwerx et l. 1992). The withdrwl of the LDL prticles is minly medited y specific extrheptic LDL receptors (Brown & Goldstein, 1997). One of the principl roles of HDL is to crry cholesterol from the peripherl cells to the liver. A key enzyme in this process is lecithin:cholesterol cyltrnsferse, responsile for trnsferring cholesterol nd ftty cids from phosphtidylcholine to cholesterol esters on the surfce of the HDL. Lecithin:cholesterol cyltrnsferse ctivity hs een oserved in the plsm of teleost fish (Blck et l. 1985). The lipid proportion nd composition of ech lipoprotein re ffected y, mong other fctors, dietry composition (Sheridn et l. 1985). For instnce, the ftty cid composition of lipoproteins is reported to e ffected y dietry ftty cid composition in Atlntic slmon (Slmo slr; Lie et l. 1993; Torstensen et l. 2000, 2001). The incresing glol demnd on fish oil nd the unpredictility of its production imposes limittions on the utiliztion of vegetle oils in commercil qu feeds (Food & Agriculture Orgniztion, 1997). A prtil replcement of fish oil y certin vegetle oils hs, in severl species, een proved to e fesile without ffecting growth (Cllero et l. 2002; Bell et l. 2003; Regost et l. 2003; Izquierdo et l. 2003, 2005; Montero et l. 2005). Little informtion is, however, ville on how these dietry ftty cids influence lipid trnsport in se rem. Recent studies (Cllero et l. 2003, 2006) hve reported tht vegetle lipid sources ffect intestinl TAG nd phospholipid iosynthesis, interfering with the types of lipoprotein produced y the intestine of se rem. In order to complete this informtion, n experiment ws conducted to determine the influence of the dietry ftty Arevitions: HUFA, highly unsturted ftty cids; TAG, tricylglycerol. * Corresponding uthor: Dr Mri José Cllero, fx þ , emil mcllero@dmor.ulpgc.es Downloded from IP ddress: , on 11 Jn 2019 t 01:29:25, suject to the Cmridge Core terms of use, ville t

2 Vegetle oils ffect the composition of lipoproteins in se rem (Sprus urt) 831 cid profile on the lipoprotein composition in se rem fed different vegetle oils. Mteril nd methods Fish The studies were crried out t the Instituto Cnrio de Ciencis Mrins (Cnry Islnds, Spin), nd ll fish were otined from locl fish frm (ADSA, Cnry Islnds, Spin). Three hundred gilthed se rem (Sprus urt) with n verge initil ody weight of g were rndomly distriuted in 100-litre polyethylene circulr tnks (20 fish/ tnk). Tnks were supplied with continuous sewter (36 ) flow nd ertion. The fish were fed under nturl photoperiod conditions of pproximtely 12 h/12 h drk light. The wter temperture nd dissolved O 2 concentrtion during the experimentl period rnged etween 20 0 nd 2 2 8C nd 5 0 nd 8 32 ppm, respectively. Fish were cclimtised to the experimentl tnks nd fed the control diet for 2 weeks efore eginning the experiment. They were fed the experimentl diets until pprent stition three times dy, t 09.00, nd hours, 6 dys week for 101 dys. Ech diet ws ssyed in triplicte tnks. Experimentl diets Six isoenergetic nd isonitrogenous experimentl diets were formulted to contin 22 % crude lipid nd 5 % crude protein. Wheres the control (100FO) diet contined nchovy oil s the only dded lipid source, nchovy oil in ll the other diets ws prtly replced y vegetle oils (Tle 1). Sixty per cent of the nchovy oil ws replced y either soyen, rpeseed or linseed oil in diets 60SO, 60RO nd 60LO, wheres 80 % ws replced y either soyen or linseed oil in diets 80SO nd 80LO. Anchovy oil ws included in ll the diets t level high enough to keep the content of n-3 highly unsturted ftty cid (HUFA), with twenty or more cron toms nd three or more doule onds, over 3 % in order to meet the essentil ftty cid requirements of this species (Montero et l. 1996). An nlysis of the ftty cid composition of the diets (Tle 2) showed the highest sturted ftty cid nd n-3 HUFA content in diet 100FO, the highest linoleic cid (18 : 2n-6) level in diets 60SO nd 80SO, the highest linolenic cid (18 : 3n-3) in diets 60LO nd 80LO, nd the highest oleic cid (18 : 1n-9) concentrtion in diet 60RO. The dietry rtios of n-3 to n-6 differed etween the experimentl diets, minly due to the different 18 : 2n-6 content of the plnt oils used, rnging from 1 in diet 100FO to 0 5 in diet 60SO nd 0 3 in diet 80SO. Diets 60LO nd 80LO hd n n-3:n-6 rtio higher thn 2, minly due to the higher 18 : 3n-3 content. Diets 80SO nd 80LO hd the lowest n-3 HUFA content, prticulrly in terms of rchidonic cid (20 : n-6), EPA (20 : 5n-3) nd DHA (22 : 6n-3). Smpling procedure The fish were smpled t the end of the feeding tril. The fish were fsted for 2 h prior to smpling. Twenty rndomly smpled fish per tnk were nesthetised with chloroutnol (200 mg/l). Blood ws collected from the cudl veins using EDTA-contining Vcutiners (Becton Dickinson, Frnklin Lkes, NJ, USA). Plsm ws seprted from the lood smples y centrifugtion t 3000 rpm for 10 min. The twenty plsm smples from ech tnk were pooled into three smples (nine smples for ech diet tested) nd stored on ice (8C) until lipoprotein frctiontion. Seprtion of lipoproteins VLDL, LDL nd HDL in pooled plsm smples were otined y sequentil centrifugl flottion, s descried y Lie et l. (199), using Pegsus 65 ultrcentrifuge equipped with 70- Ti fixed-ngle rotor (Beckmn Coulter Inc., Fullerton, CA, USA). Centrifugtion ws crried out t rpm nd 8C. The density intervls were otined y dding solid KBr (Wrnick et l. 1979). The run times for lipoprotein seprtion were: d, g/ml over 20 h for VLDL; 1 015, d, g/ml over 20 h for LDL; 1 085, d, 1 21 g/ml over h for HDL. The different lipoprotein frctions otined were weighed on n nlyticl lnce (Mettler AJ100; Mettler Toledo S. A. E., L Hospitlet de Lloregt, Brcelon) nd stored t 2808C until further nlysis. Tle 1. Composition of experimentl diets contining different lipid sources Diet 100FO (g/kg) 60SO (g/kg) 60RO (g/kg) 60LO (g/kg) 80SO (g/kg) 80LO (g/kg) Fish mel (LT) Corn gluten Whet Lysine (99 %) Premix* Anchovy oil Soyen oil Rpeseed oil Linseed oil Composition Crude lipids Crude protein LT, low temperture. * Premix of vitmins nd minerls ccording to Ntionl Reserch Council (1993) recommendtions for fish. Crude vegetle oils. Downloded from IP ddress: , on 11 Jn 2019 t 01:29:25, suject to the Cmridge Core terms of use, ville t

3 832 M. J. Cllero et l. Tle 2. Min ftty cid composition of diets contining fish oil in comintion with different vegetle lipid sources Diet 100FO (g/100 g ftty 60SO (g/100 g ftty 60RO (g/100 g ftty 60LO (g/100 g ftty 80SO (g/100 g ftty 80LO (g/100 g ftty 1 : : : Sum sturted : 1n : : 1n : 1n ND 1 5 ND ND 20 : 1n : 1n : 1n Sum monoenes n : 2n : 3n : n : 3n : n Sum n : n : 3n : n : n : 5n : n : 5n : 6n Sum n Sum n-3 highly unsturted ftty cids n-3:n Lipids (% DW) ND, not detected. Anlyticl procedures Lipids from pooled smples were extrcted with chloroform methnol (2:1, v:v) mixture s descried y Folch et l. (1957). Ftty cid methyl esters were otined y trnsesterifiction with 1 % H 2 SO in CH 3 OH (Christie, 1982) using heneicosenoic cid (10 % of totl lipids) s n internl stndrd. Ftty cid methyl esters were purified y dsorption chromtogrphy on NH 2 sep-pck crtridges (Wters SA, Milford, MA, USA) s decried y Fox (1990), nd seprted nd quntified y GLC following the conditions descried y Izquierdo et l. (1990). The lipid clsses of ech lipoprotein frction were seprted y high-precision TLC into sterol esters, TAG, cholesterol nd phosphtidylcholine, phosphtidylethnolmine, phosphtidylinositol nd phosphtidylserine, nd quntified y flme ionistion detector system (Itroscn MK-5, Itron Lortories Inc., Tokyo, Jpn) ccording to the method descried y Rønnestd et l. (1995). The totl protein content of ech lipoprotein frction ws determined y Lowry ssy (Lowry et l. 1951). Sttistics Results were expressed s mens nd stndrd devitions. Dt were compred y ANOVA, nd Tukey s test for comprison of mens ws pplied (P, 0 05). When vrinces were not normlly distriuted, the Kruskl Wllis non-prmetric test ws pplied to the dt, nd for comprison of medins, the Box nd Whisker-notched test ws pplied (Sokl & Rolf, 1995). Results The mount of ech lipoprotein frction per grm of se rem plsm ws 26 (SD 37 6) mg/g for HDL, 19 2 (SD 3 7) mg/g for VLDL nd only (SD 1 5) mg/g for LDL. Totl protein nd lipid content Tle 3 shows the totl protein nd lipid content of the lipoprotein frctions expressed s milligrms of protein or lipid per grm of lipoprotein frction. No significnt differences were found in the totl protein (verge 5 mg protein/g HDL) or lipid (verge 11 2 mg lipid/g HDL) contents of the HDL frction mong fish fed the experimentl diets. In the LDL frction, the protein content ws similr in ll the experimentl groups (verge 0 mg protein/g LDL), wheres higher content of totl lipids ws present in fish fed the 80SO nd 80LO (1 2 mg lipid/g LDL) diets, fish fed 100FO showing the lowest lipid content (0 mg lipid/g LDL). No significnt differences were found in the totl protein (verge 0 mg protein/g VLDL) for the VLDL frction mong fish Downloded from IP ddress: , on 11 Jn 2019 t 01:29:25, suject to the Cmridge Core terms of use, ville t

4 Vegetle oils ffect the composition of lipoproteins in se rem (Sprus urt) 833 Tle 3. Totl protein nd lipid content of the lipoprotein frctions of se rem fed the experimentl diets (Mens nd stndrd devitions; three smples from ech tnk, nine for ech experimentl diet) Protein content Lipid content mg protein/g HDL mg protein/g LDL mg protein/g VLDL mg lipid/g HDL mg lipid/g LDL mg lipid/g VLDL Diets Men SD Men SD Men SD Men SD Men SD Men SD 100FO SO c RO c LO SO cd LO d Superscript letters in the sme row denote significntly different (P # 0 05). fed the experimentl diets, ut the lowest content of totl lipid for this frction ws gin found in fish fed diet 100FO (0 8 mg lipid/g VLDL). Lipid clss composition The lipid clss composition nd percentge of protein in ech lipoprotein frction re shown in Fig. 1 nd expressed s g lipid/g protein. An increse in the neutrl lipid (sterol esters, TAG, cholesterol) content of the lipoproteins occurred concomitntly with decresed protein content nd density of lipoproteins (VLDL, LDL, HDL) for ll the experimentl diets tested. Phosphtidylcholine ws the mjor phospholipids in ll lipoprotein frctions, wheres only trce levels of the other glycerophospholipids (phosphtidylethnolmine, phosphtidylinositol, phosphtidylserine) were found. In VLDL, TAG comprised lrger proportion thn the other frctions. The proportion of sterol esters ws higher in the lipid of LDL thn in HDL. HDL consisted minly of protein (3 %) nd phosphtidylcholine. The lipid clss composition of the different lipoprotein frctions expressed in mg lipid clss/g plsm ws ffected y the experimentl diets. In HDL (Fig. 2), fish fed diet 100FO hd the lowest TAG content, eing significntly different (P, 0 05) from tht of fish fed diet 80SO. g lipid/g protein % of totl protein* 2 71 % of totl protein* 3 18 % of totl protein* VLDL LDL HDL Fig. 1. Lipid clss composition (g lipid/g protein) of VLDL, LDL nd HDL from se rem fed the experimentl diets for 101 d (mens nd stndrd devitions). *Amount of protein in the lipoprotein frction, clculted s (mount of protein in the lipoprotein frction) / (mount of protein in VLDL þ LDL þ HDL þ rest) 100 %. p, Sterol esters; A, Tricylglycerol; I, Cholesterol; B, Phosphtidylcholine. In ddition, these ltter fish presented the highest cholesterol content (P, 0 05). No differences were found in the sterol esters nd phosphtidylcholine content mong fish fed the different experimentl diets. In LDL (Fig. 3), fish fed the 100FO diet showed the lowest level of TAG, cholesterol nd phosphtidylcholine in comprison to the other experimentl groups. High levels of cholesterol nd phosphtidylcholine were found in fish fed diets 80SO nd 80LO. In VLDL (Fig. ), lipid clsses showed lrge vrition etween the different experimentl groups. Thus, fish fed the 60RO diet presented mrkedly high sterol esters content in comprison to other fish. In ddition, fish fed the 100FO diet showed the lowest level of cholesterol, this eing significntly (P, 0 05) different from those of the other fish, except for those fed 60RO. Finlly, the highest vlues of TAG were found in fish fed diets 80SO nd 80LO, vlues eing significntly different from those of fish fed diets 100FO nd 60RO. Ftty cid composition Tle shows the ftty cid composition of the VLDL frction. The dietry influence of the composition of this frction ws demonstrted y the high level of 18 : 1n-9 (30 %) in the 60RO fish, 18 : 2n-6 (21 % nd 26 %) in the 60SO nd 80SO fish, nd 18 : 3n-3 (12 % nd 18 %) in the 60LO nd 80LO fish. The highest levels of n-3 HUFA were found in fish fed diet 100FO (P,0 05), prticulrly due to the high content of DHA. The LDL frction (Tle 5) ws chrcterised y high levels of sturted ftty cid, prticulrly 16 : 0, in comprison with VLDL. Dietry ftty cid composition ws lso reflected in the contents of oleic, linoleic nd linolenic cids, lthough to lesser extent thn those found in VLDL frction. The DHA content of the LDL frction ws lso elevted in ll experimentl groups, irrespective of dietry content. The HDL ftty cid composition (Tle 6) in prticulr ws chrcterised y mrkedly high n-3 HUFA content in ll experimentl groups, with vlues rnging from 2 6 % (80SO fish) to 38 8 % (100FO fish), minly due to the high level of DHA. In ddition, this frction lso hd higher content of rchidonic cid (20 : n-6) in comprison with the other lipoprotein frctions. The HDL content of 18 : 1n-9; 18 : 2n-6 nd 18 : 3n-3 reflected the dietry composition, lthough there ws considerle reduction in ftty cids of 18 crons in Downloded from IP ddress: , on 11 Jn 2019 t 01:29:25, suject to the Cmridge Core terms of use, ville t

5 83 M. J. Cllero et l. 7 6 mg lipid clss/g HDL c c 0 Sterol esters Tricylglycerol Cholesterol Phosphtidylcholine Fig. 2. HDL lipid clss composition from se rem fed the experimentl diets (mens nd stndrd devitions; three smples from ech tnk, nine for ech experimentl diet). For the diet groups, men vlues with unlike superscript letters were significntly different (P # 0 05). Diets: B, 100FO;, 60SO;, 60RO;, 60LO;, 80SO; A, 80LO mg lipid clss/g LDL c c c c 0 Sterol esters Tricylglycerol Cholesterol Phosphtidylcholine Fig. 3. LDL lipid clss composition from se rem fed the experimentl diets (mens nd stndrd devitions; three smples from ech tnk, nine for ech experimentl diet). For the diet groups, men vlues with unlike superscript letters were significntly different (P # 0 05). Diets: B, 100FO;, 60SO;, 60RO;, 60LO;, 80SO; A, 80LO. 0 7 mg lipid clss / g VLDL Sterol esters Tricylglycerol Cholesterol Phosphtidylcholine Fig.. VLDL lipid clss composition from se rem fed the experimentl diets (mens nd stndrd devitions; three smples from ech tnk, nine for ech experimentl diet). For the diet groups, men vlues with unlike superscript letters were significntly different (P # 0 05). Diets: B, 100FO;, 60SO;, 60RO;, 60LO;, 80SO; A, 80LO. Downloded from IP ddress: , on 11 Jn 2019 t 01:29:25, suject to the Cmridge Core terms of use, ville t

6 Vegetle oils ffect the composition of lipoproteins in se rem (Sprus urt) 835 Tle. Ftty cid composition of VLDL from se rem fed the experimentl diets for 12 weeks (Mens nd stndrd devitions; three smples from ech tnk, nine for ech experimentl diet) Diet 100FO (g/100 g ftty 60SO (g/100 g ftty 60RO (g/100 g ftty 60LO (g/100 g ftty 80SO (g/100 g ftty 80LO (g/100 g ftty Men SD Men SD Men SD Men SD Men SD Men SD 1 : : : Sum sturted : 1n : 1n : 1n : 1n : 1n ND ND Sum monoenes : 2n c c : n Sum n : 3n c d 20 : 5n : 5n : 6n Sum n c d Sum n-3 highly unsturted ftty cids Superscript letters in the sme row denote significntly different (P # 0 05). ND, not detected. Tle 5. Ftty cid composition of LDL from se rem fed the experimentl diets for 12 weeks (Mens nd stndrd devitions; three smples from ech tnk, nine for ech experimentl diet) Diet 100FO 60SO 60RO 60LO 80SO 80LO Men SD Men SD Men SD Men SD Men SD Men SD 1 : : v : Sum sturted : 1n : 1n : 1n : 1n : 1n : 1n ND Sum monoenes : 2n : n ND ND : n-6 ND ND Sum n : 3n c c 20 : n ND ND : 5n : 5n : 6n Sum n Sum n-3 highly unsturted ftty cids Superscript letters in the sme row denote significntly different (P # 0 05). ND, not detected. Downloded from IP ddress: , on 11 Jn 2019 t 01:29:25, suject to the Cmridge Core terms of use, ville t

7 836 M. J. Cllero et l. Tle 6. Ftty cid composition of HDL from se rem fed the experimentl diets for 12 weeks (Mens nd stndrd devitions; three smples from ech tnk, nine for ech experimentl diet) Diet 100FO 60SO 60RO 60LO 80SO 80LO Men SD Men SD Men SD Men SD Men SD Men SD 1 : : : Sum sturted : 1n : 1n c : 1n : 1n : 1n : 1n Sum monoenes : 2n cd c e d 20 : 2n : n c c c 22 : n Sum n c c d c 18 : 3n cd d 20 : n : 5n c c c 22 : 5n : 6n Sum n Sum n-3 highly unsturted ftty cids Superscript letters in the sme row denote significntly different (P # 0 05). ND, not detected. comprison to the VLDL frction. High levels of 16 : 0 ftty cids were lso found in the HDL frction. Discussion HDL ws the myor lipoprotein found in se rem, confirming tht this is the min lipoprotein involved in lipid trnsport s it lso occurs in other species (Nelson & Shore, 197; Chpmn et l. 1980; Bin & Vernier, 1989; Sntulli et l. 1989; Iijim et l. 1990; Lie et l. 1993). Such predominnce of HDL might e the consequence of lower degrdtion of this frction in comprison with other lipoproteins, fster degrdtion of VLDL y lipoprotein lipse or n incresed synthesis in liver nd intestine (Léger, 1988; Iijim et l. 1990). The lipid nd protein composition of ech lipoprotein frction in se rem ws similr to tht of other teleost fish. Thus, the chemicl composition of HDL ws chrcterised y high content of protein nd phospholipids, prticulrly phosphtidylcholine (Chpmn, 1980; Lie et l. 1993). HDL nd LDL were the two min lipoproteins involved in cholesterol trnsport in se rem. Although the highest cholesterol contents were found in the LDL frction, in greement with other species (Frrell & Munt, 1983; Frrell et l. 1986; Lie et l. 1993; Torstensen et l. 2000), the min ulk of plsm cholesterol ws trnsported y HDL, which ws the more undnt lipoprotein in se rem. Despite this, VLDL ws found to e present in minor mounts in the serum of other species (Sntulli et l. 1997). In se rem plsm, the content of VLDL ws found to e higher thn tht of LDL, reflecting the VLDL synthesis oserved y electron microscopy in the enterocytes of this fish (Cllero et l. 2003). The VLDL frction, rich in TAG s in other fish (McKy et l. 1985; Finru et l. 1988; Bin & Vernier, 1989; Torstensen et l. 2001), is implicted minly in the trnsport of TAG to vrious tissues. Interestingly, dietry ftty cids ffected the lipid clss composition of the lipoproteins. Thus, sustitution of 80 % fish oil y either soyen or linseed oil rised the cholesterol content of the HDL nd LDL. Although the fish-oil diets contined higher proportion of sturted ftty cids (27 9 % v % nd 16 3 % in the vegetle-oil diets), which re reported to increse plsm cholesterol level (Hyes et l. 1997), this effect my e reduced in fish in view of their lower digestiility (out 85 % in se rem) in comprison with n-3 HUFA (95 % in se rem). The elevtion in cholesterol cused y the reduction in dietry fish oil could insted e relted to the high n-3 HUFA content of this oil (17 96 % in fish-oil diets v. 6 9 % nd 7 %, in vegetle-oil diets), in view of the high correltions found etween the dietry n-3 HUFA nd the HDL-cholesterol or LDL-cholesterol (Fig. 5(A), (B)). Despite the lck of studies in fish, considerle dt re ville on the effects of n-3 PUFA, with eighteen or more cron toms nd two or more doule onds, on the plsm levels of cholesterol in mmmls. Thus, in humn sujects, the hypocholesterolemic effect of ftty cids follows the pttern n-3 PUFA less thn n-6 PUFA less thn sturted ftty cids (Willims, 1998). As in Downloded from IP ddress: , on 11 Jn 2019 t 01:29:25, suject to the Cmridge Core terms of use, ville t

8 Vegetle oils ffect the composition of lipoproteins in se rem (Sprus urt) (A) (B) Dietry n-3 HUFA y = 17 93x r = 0 820, P < 0 05 Dietry n-3 HUFA y = 59 12x r = 0 870, P < mg cholesterol/g HDL mg cholesterol/g LDL 1 (C) 12 (D) EPA content of HDL y = 11 39x r = 0 833, P < 0 05 EPA content of LDL y = x r = 0 86, P < mg cholesterol/g HDL mg cholesterol/g LDL Fig. 5. Reltionships etween dietry n-3 highly unsturted ftty cids (HUFA) nd cholesterol level in HDL nd LDL frctions ((A), (B)). Reltionships etween EPA content in HDL nd LDL nd the cholesterol level of those frctions ((C), (D)). Ech point represents the dietry group. mmmls, dietry n-3 HUFA could, in the present experiment, enhnce the ctivity of the enzyme lecithin:cholesterol cyltrnsferse locted in the HDL (Thornurg et l. 1995; Prks et l. 2000), which ctlyses the trnsfer of ftty cid from phosphtidylcholine to cholesterol to form sterol esters, s the cholesterolsterol esters rtios in HDL were douled in fish fed 80 % fish-oil sustitution with vegetle oils thn in those fed 100 % fish oil. In ddition, fish fed fish oil hd lower content of phosphtidylcholine, nother sustrte for lecithin:cholesterol cyltrnsferse. In ddition, significnt inverse reltionships were lso found etween EPA nd HDL-cholesterol or LDL-cholesterol (Fig. 5(C), 5(D)). Spdy (1993) descried, in rts, how high levels of EPA nd DHA decresed the LDLcholesterol level y enhncing the ctivity of LDL-receptors in the liver. In turn, Tripodi et l. (1991) reported tht the high ffinity of the LDL frction towrds its liver receptors induced hypocholesterolemi in rt fed those ftty cids. Similrly, in se rem fed the fish-oil diet, with higher content of these ftty cids, there ws reduction in LDL-cholesterol. As LDL receptors re proteins locted in cell memrnes, their function my e ffected y the ftty cid composition of the memrne. Chnges in the lipid composition of the memrne cn induce structurl nd functionl ltertions in specific receptors (Gurr & Hrwood, 1991). The TAG content of ll the lipoprotein frctions ws lso reduced y feeding fish oil. In humn sujects, high dietry content of n-3 PUFA reduces VLDL-TAG levels vi decrese in TAG synthesis in the liver (Hrris et l. 1983; Berge et l. 1999). The ftty cid composition of the VLDL ws more redily ffected y the diet thn tht of HDL, which could e relted to the higher TAG content of the former lipoprotein s, in fish, neutrl lipids re esily influenced y dietry ftty cids (Brodtkor et l. 1997; Olsen & Henderson, 1997). In ddition, the specific ftty cid composition of the lipoprotein would e relted to the functionl differences nd the different metolism nd site of synthesis of the lipoproteins. Finlly, HDL ws chrcterised y high levels of 22 : 6n-3, independent of dietry ftty cids. These results re in ccordnce with those of other studies (Lie et l. 1993; Torstensen et l. 2000) nd suggest tht HDL, the dominnt lipoprotein in se rem, is minly implicted in the trnsport of DHA to the tissues (Brodtkor et l. 1997). In conclusion, dietry fish oil sustitution y up to 60 % of soyen, linseed or rpeseed oil did not mrkedly ffected lipoprotein composition, wheres 80 % sustitution y soyen or linseed oil incresed plsm cholesterol nd TAG concentrtions owing to the low n-3 HUFA content of these diets. Downloded from IP ddress: , on 11 Jn 2019 t 01:29:25, suject to the Cmridge Core terms of use, ville t

9 838 M. J. Cllero et l. Acknowledgements The present study ws supported y the Europen Union under Qulity of Life nd Mngement of Living Resources through project Q5RS RAFOA, which gve prtil (four diets) grnt to the reserch, nd y the Spnish government under the FEDER progrmme, project 1FD , which grnted the rest of the diets. References Auwerx J, Leroy P & Schoonjns K (1992) Lipoprotein lipse: recent contriutions from moleculr iology. Crit Rev Clin L Sci 29, Bin PJ & Vernier JM (1989) Plsm lipoproteins in fish. J Lipid Res 30, Bell JG, McGhee F, Cmpell PJ & Srgent JR (2003) Rpeseed oil s n lterntive to mrine fish oil in diets of post-smolt Atlntic slmon (Slmo slr): chnges in flesh ftty cid composition nd effectiveness of susequent fish oil wsh out. 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