Significant utilization of dietary arachidonic acid is for brain adrenic acid in baboon neonates

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1 Significnt utiliztion of dietry rchidonic cid is for rin drenic cid in oon neontes Vsuki Wijendrn,* Peter Lwrence,* Gun-Yeu Diu,* G. Boehm, P. W. Nthnielsz, nd J. T. Brenn 1, * Division of Nutritionl Sciences,* nd Lortory for Pregnncy nd Neworn Reserch, Cornell University Svge Hll Ithc, NY 14853; nd NUMICO Reserch Group, Bhnstrße 14-30, Friedrichsdorf, Germny Astrct Dietry rchidonic cid (20:4n-6) utiliztion invivo for cron recycling into de-novo lipogenesis nd conversion to n-6 long chin polyunsturtes ws investigted in oon neontes using [U- 13 C]20:4n-6. Neontes consuming formul typicl of humn milk received single orl dose of [ 13 C]rchidonic cid in sn-2 position of either triglyceride or phosphtidylcholine t dys of postntl life. Neonte rin, retin, liver, nd plsm were otined 10 dys lter (28 29 dys of life). Low isotopic enrichment ( %Totl lel) ws detected in dihomo- -linolenic cid (20:3n-6) in ll tissues, ut lel incorportion into sturtes or monounsturtes ws not detected. In neonte rin nd retin, 16% nd 11% of totl lel ws recovered in 22:4n-6, respectively. The reltive contriution of dietry ftty cids to postntl rin 22:4n-6 ccretion cn e estimted for dietry 20:4n-6 nd preformed 22:4n-6 s 17% nd 8%, respectively, corresponding to efficiencies of 0.48% nd 0.54% of dietry levels, respectively. These results demonstrte in term oon neontes tht in vivo 1) 20:4n-6 ws retroconverted to 20:3n-6, 2) 20:4n-6 did not contriute significntly to de novo lipogenesis of sturtes nd monounsturtes, nd 3) the preformed 20:4n-6 contriution to rin 22:4n-6 ccumultion ws quntittively significnt metolic fte for dietry 20:4n-6. Wijendrn, V., P. Lwrence, G-Y. Diu, G. Boehm, P. W. Nthnielsz, nd J. T. Brenn. Significnt utiliztion of dietry rchidonic cid is for rin drenic cid in oon neontes. J. Lipid Res : Supplementry key words infnt primte stle isotope trcer cron recycling polyunsturted ftty cids dihomo-gmm linolenic cid Archidonic cid (20:4n-6) nd docoshexenoic cid (22:6n-3) re well known to e essentil constituents of the centrl nervous system (CNS) (1, 2). 20:4n-6 lso serves s precursor for series two eicosnoids, which ply importnt roles in the regultion of severl physiologicl processes. 20:4n-6 nd 22:6n-3 rpidly ccumulte in the CNS during humn rin growth spurt, which strts t the eginning of the third trimester of pregnncy nd imposes high demnds until out 2 yers of ge in humns (3). Prominent dietry sources of these long chin PUFAs (LCP, C 20) for the neworn re preformed 20:4n-6 nd 22:6n-3 nd their precursor ftty cids linoleic cid (18:2n-6) nd linolenic cid (18:3n-3), ll of which re present in humn milk. There re t lest two other mjor ftes for the dietry essentil ftty cids 18:2n-6 nd 18:3n-3. They cn e oxidized exhustively s energy sustrtes (4 6); t lest 80% of 18:3n-3 intke ws oxidized to CO 2 in young nimls (5). They lso re suject to prtil oxidtion to cette tht is susequently used for de novo synthesis of sturted (SFA) nd monounsturted ftty cids (MUFA), referred to s cron recycling (7 10). Recent studies hve clerly estlished tht cron recycling into de novo lipogenesis is quntittively mjor pthwy for 18:2n-6 nd 18:3n-3 utiliztion in pregnnt, fetl, nd neworn nimls (9, 10). Similr metolic ftes re in principle ville to 20:4n-6. Quntittive informtion on dietry 20:4n-6 prtitioning etween totl oxidtion, oxidtive chin shortening, nd cron recycling, or chin elongtion/desturtion to 22-cron n-6 LCP re currently lcking. An erly study y Sinclir et l. (11) using rdioleled 20:4n-6 in rts showed tht the mjor frction (91%) of the lel ws in tissue lipid 20:4n-6 pool nd smll mount of 20:4n-6 lel ws incorported into SFA nd MUFA in developing rin lipids t 1 2 dys post-dose. In vitro studies using isolted rt heptocytes nd peroxisomes (12 14) showed tht 20:4n-6 ws oxidized to shorter chin products nd to cette, which could e recycled. Further, significnt retroconversion of 20:4n-6 to dihomo- -linolenic cid (20:3n-6) nd 18:2n-6 ws demonstrted in vitro in skin firolst cells in culture (15, 16) nd isolted rt hepto- Arevitions: CNS, centrl nervous system; FAME, ftty cid methyl ester; LCP, long chin PUFA; MUFA, monounsturted ftty cids; PC-20:4*, phosphtidylcholine with 20:4* in the sn-2 position nd plmitte in the sn-1 position; SFA, sturted ftty cids; TG-20:4*, triglyceride with 20:4* in the sn-2 position nd plmitte in the sn-1, 3 positions; 20:4*, [ 13 C]rchidonic cid. 1 To whom correspondence should e ddressed. e-mil: jt4@cornell.edu Copyright 2002 y Lipid Reserch, Inc. 762 Journl of Lipid Reserch Volume 43, 2002 This pper is ville online t

2 cytes (17). Quntittive informtion on 22:6n-3 retroconversion (18) nd cron recycling into de novo lipogenesis (9) in vivo hs een etter chrcterized. A potentilly importnt spect of 20:4n-6 metolism in vivo is its function s the immedite precursor for drenic cid (22:4n-6). 22:4n-6 is the third most undnt PUFA (C 18) in the rin nd is prticulrly enriched in myelin lipids (1, 19, 20). Rpid ccumultion of 22:4n-6 in rin, comprle to 20:4n-6 ccretion levels, occurs during the erly post-ntl period of rin growth spurt in humn infnts (1). Humn milk contins smll mount ( 3 mg/dl) of 22:4n-6 (21). While the specific functions of 22:4n-6 re not yet cler, it is suggested to ply n importnt role in myelintion in neurl tissues (20, 22), its normlity is implicted in the pthogenesis of Alzheimer s disese (23), nd in vitro evidence indictes tht it serves s sustrte for dihomoeicosnoid formtion (24, 25). Conversion of 20:4n-6 to 22:4n-6 proceeds vi single chin elongtion step, wheres the other s (18:2n-6, 18:3n-6, nd 20:3n-6) must undergo desturtion nd elongtion with 20:4n-6 s n intermedite product, hence 20:4n-6 my e n efficient dietry source for 22:4n-6 compred with other precursors in vivo. The conversion of 20:4n-6 to 22:4n-6 my represent quntittively n importnt pthwy of 20:4n-6 utiliztion in infnts to meet the rpid increse of 22:4n-6 in neurl tissues during the erly post-ntl period. To our knowledge, 20:4n-6 contriution to 22:4n-6 in developing CNS hs not een reported in ny species. The ojective of this study ws to investigte the quntittive significnce of 20:4n-6 utiliztion in vivo for cron recycling into products of de novo lipogenesis, retroconversion to precursors, nd conversion to n-6 LCP compred with 20:4n-6 ccumultion in oon neonte tissues. Previously, we reported tissue ccretion of preformed 20:4n-6 originting s dietry triglyceride or phospholipids in these oon neontes (26). In the present report we show metolic prtitioning of 20:4n-6 utiliztion mong ville ftes using single orl dose of stle isotope trcer [U- 13 C]20:4n-6 nd high precision gs chromtogrphy comustion isotope rtio mss spectrometry (GCC-IRMS). METHODS Animls nd diet Pregnnt oons were red t the Southwest Foundtion for Biomedicl Reserch (Sn Antonio, Texs). After confirmtion of pregnncy they were trnsported to Cornell University (Ithc, NY). The Cornell Institutionl Animl Cre nd Use Committee pproved the cre of nimls nd study protocol. Detils on the cre of pregnnt oons hve een descried previously (27). Neontes were delivered y Cesren-section under hlothne nesthesi t estimted conceptul ges of 176 to 178 dg. Neonte detils re summrized in Tle 1. They were housed initilly in enclosed incutors nd trnsferred fter 5 dys of ge to individul stinless steel cges in controlledccess nursery where the temperture (28 C) nd humidity (50%) were controlled. TABLE 1. Chrcteristics of neonte oons Gesttionl ge t CS (d) Birth Weight (g) Body weight t scrifice (g) Weight gin (g) Gender 5M, 2 F Age t dosing (d) Age t scrifice (d) Time etween dosing nd scrifice (d) 10 Dose mount (mg) Orgn Weights (g) Brin Liver Dt expressed s men SD (n 7). CS Cesren section. 20:4n-6 concentrtion (mg) nlyzed in the dose orlly dministered to the neontes. Neonte oons consumed formul contining 20:4n-6 nd 22:6n-3, provided y Numico Reserch Group (Friedrichsdorf, Germny). Formul LCP were derived from microlgl nd fungl sources, nd the ftty cid composition of the formul hs een reported in detil elsewhere (26). Formul ftty cid composition ws similr to humn milk nd contined 0.4 g/dl of 18:2n-6 (14.0% wt), 15.8 mg/dl of 20:4n-6 (0.55% wt), 7 mg/dl of 22:4n-6 (0.25% wt), 46mg/dl of 18:3n-3 (1.6% wt), nd 8.6mg/dl of 22:6n-3 (0.30% wt). Doses nd smpling Leled dose contining [U- 13 C]20:4n-6 (20:4*) in triglyceride (TG) or phosphtidylcholine (PC) ws chemiclly synthesized nd provided y Roche (Switzerlnd). The TG trcer (TG- 20:4*) contined 20:4* in the sn-2 position with unleled 16:0 in the remining positions. PC trcer (PC-20:4*) contined 20:4* in sn-2 position with 16:0 in the sn-1 position. The TG or the PC dose did not contin ny other ftty cids in detectle levels. Either TG-20:4* or PC-20:4* ws weighed nd sonicted into 2.5 ml wrm reconstituted formul with unleled PC (soy lecithin, Sigm Chemicl, St Louis, MO) nd olive oil crriers. A 50 l smple of the dose ws sved for ftty cid nlysis. Neontes were rndomized to receive either single olus dose of TG- 20:4* (n 3) or PC-20:4* (n 4). Doses long with three rinses were dministered orlly to the neontes t dys of ge. Neontes were fed their norml formul s usul immeditely fter orl dministrtion of the leled dose. Neontes were euthnized 10 dys post dose (28 29 dys of ge) y exsnguintion under hlothne nesthesi. Neonte rin, retin, liver, nd plsm were collected. Blood ws collected with heprin s nticogulnt, nd plsm ws seprted immeditely y centrifugtion t 4 C nd frozen in liquid N 2. The rin nd liver tissues were quickly removed, weighed, liquoted, nd immeditely frozen in liquid N 2. Retin ws collected in sline nd immeditely frozen in liquid N 2. All smples were stored t 80 C until nlysis. Lipid extrction nd nlysis Totl lipids were extrcted from smples of rin occipitl loe including the visul cortex, right liver loe, whole retin, nd plsm y the Bligh nd Dyer method (28). Butylted hydroxytoluene ws used s n ntioxidnt. Ftty cid methyl esters (FAME) were prepred using 14% BF 3 in methnol (29). FAME were nlyzed using Hewlett Pckrd 5890 series II gs chromtogrph-flme ioniztion detector (GC-FID) with BPX 70 column (60 m 0.32 mm I.D m film) nd H 2 s crrier gs. Quntittive profiles were clculted using the internl stndrd (17:0) nd n equl weight FAME mixture to derive re- Wijendrn et l. Archidonic cid utiliztion in oon neontes 763

3 sponse fctors for ech FA. GC-FID conditions nd clirtion detils hve een reported previously (29). Trcer enrichment nlysis ws performed using high precision GC-comustion isotope rtio mss spectrometry (GCC- IRMS) descried in detil previously (30). Briefly, high precision dt re presented s the reltive devition of the smple isotope rtio from the stndrd Pee Dee Belemnite (PDB) with 13 C/ 12 C isotope rtio R PDB , s: δ 13 R C X R PDB R PDB X = = R PDB R PDB where 13 C PDB is referred to in permil ( ) units nd X refers to the smple. R X derived from the ove eqution ws directly converted to tom percent (AP) 13 C, which is mesure of the percent of 13 C in ech ftty cid pek. Atom percent excess (APE), descriing the trcer/trcee rtio in ech ftty cid (30), ws determined y sutrcting seline isotope levels. Bseline isotope rtios were otined from two undosed control nimls. The solute mss (g or mol) of 20:4* trcer in ny smpled pool ws clculted y multiplying APE y the concentrtion of 20:4n-6 determined y GC-FID. Percent of totl leled ftty cids (percent totl) ws clculted for ech leled ftty cid which reflects the distriution of 20:4* lel into ftty cids in prticulr pool, fter correcting for the rtio of cron in the nlyte ftty cid to tht in 20:4*. We previously reported differences in solute tissue ccretion of 20:4n-6 in these nimls from TG or PL doses (26). Distriution of lel into tissue ftty cids expressed s percent totl lel (%Totl) is clculted s the percent rtio of the lel found in one ftty divided y the sum of ll lel found in ll ftty cids per unit (g, ml) pool. Initil sttisticl nlysis y student s t-test (P 0.05) showed no differences in the distriution of lel into tissue ftty cids (s percentge of totl) etween TG- nd PC-dosed nimls. Therefore, results from TG-20:4n-6* nd PC-20:4n-6* dosed neontes re presented here s pooled dt (n 7). RESULTS Tle 2 presents the results of rin 13 C lel enrichment of ftty cids in 13 C nd APE units. Trcer incorportion TABLE 2. Brin 13 C lel enrichment of ftty cids in neontes fter n orl dose of [U- 13 C]-20:4n-6 TABLE 3. Retinl 13 C lel enrichment of ftty cids in neontes fter n orl dose of [U- 13 C]-20:4n-6 Bseline Neontes (n 7) APE 16: ND 18: ND 18: ND 18: ND 20: : : : :6n Dt presented s men SD. APE, tom percent excess. ND, not detectle. into 16:0, 18:0, 18:1, or 22:6n-3 ws not different etween seline control nd dosed neontes. In contrst, n-6 LCP were ll enriched. The dose ftty cid, 20:4n-6, showed the highest leling, s expected, while its elongtion product 22:4n-6 showed out one third of the APE. Leling ws lso found in 20:3n-6 nd 22:5n-6. Leling in retin ws similr, s shown in Tle 3. Leling ws undetectle in the mjor SFA nd MUFA; however, APE ws greter in n-6 PUFA. Unlike rin, 22:6n-3 showed slight leling. Tles 4 nd 5 show leling dt for liver nd plsm, respectively. No excess 13 C ws detected in SFA nd MUFA, nd lel ws detected in with the sme generl trend. As in rin, no leling ws found in 22:6n-3. 18:2n-6 ws not leled in ny of these tissues. Lel distriution into 20:3n-6 ws %, %, %, nd %Totl lel in the neonte rin, retin, liver, nd plsm respectively, 10 dys post-dose. TABLE 4. Liver 13 C lel enrichment of ftty cids in neontes fter n orl dose of [U- 13 C]-20:4n-6 Bseline Neontes (n 7) APE Bseline Neontes (n 7) APE 16: ND 18: ND 18: ND 18: ND 20: : : : :6n ND Dt presented s men SD. APE, tom percent excess. ND, not detectle. 16: ND 18: ND 18: ND 18: ND 20: : : : :6n ND Dt presented s men SD. APE, tom percent excess. ND, not detectle. 764 Journl of Lipid Reserch Volume 43, 2002

4 TABLE 5. Plsm 13 C lel enrichment of ftty cids in neontes fter n orl dose of [U- 13 C]-20:4n-6 Bseline Figure 1 shows the distriution of lel in mjor n-6 LCP in neonte rin, retin, liver, nd plsm s %Totl detected in ech respective tissue 10 dys post-dose. The distriution in the rin nd retin re similr to one nother ut differ from liver. In rin, out 79% of the lel ppered in 20:4n-6, with 16% present in 22:4n-6; similrly, in retin 79% of lel ppered in 20:4, with 11% recovered s 22:4n-6. In contrst, liver 20:4n-6 ws 92%Totl, nd only 5% in 22:4n-6. Plsm 13 C collected t 10 dys post-dose ws even richer in 20:4n-6 t 97%Totl nd only 2%Totl in 22:4n-6. Lel ppernce in 22:5n-6 rnged from 2 4%Totl lel in the neonte tissues. DISCUSSION Neontes (n 7) APE 16: ND 18: ND 18: ND 18: ND 20: : : :6n ND Dt presented s men SD. APE, tom percent excess. ND, not detectle. Fig. 1. Distriution of [U- 13 C]20:4n-6 lel into n-6 long chin PUFA (LCP) in rin, retin, liver, nd plsm, expressed s %Totl, in 4 weeks old term oon neontes t 10 dys post-dose. In neonte rin nd retin 16% nd 11% of totl lel ws recovered in 22:4n-6, respectively. The present study investigted preformed 20:4n-6 utiliztion nd its metolism in vivo in oon neontes using single orl dose of U- 13 C-leled 20:4n-6. The oon neonte, with rin growth pttern comprle to humns (31), is highly relevnt model for 20:4n-6 utiliztion during humn rin growth spurt. Detection of lel incorportion into 20:3n-6 in ll tissues investigted indictes tht chin shortening nd retro-conversion of 20:4n-6 occurred in vivo. Retroconversion of 20:4n-6 to 20:3n-6 hs een demonstrted in-vitro in rt heptocytes (17) nd humn skin firolst cells (15, 16). However, in oon neontes in vivo, 20:4n-6 contriution to the 20:3n-6 pool ws reltively smll, s evidenced y 1% of totl lel recovered in 20:3n-6. Retroconversion of 20:4n-6 to 18:2n-6, which ws reported in rts (32), ws elow detectle limits in these primte neontes. Evidence from previous studies suggest tht peroxisome-dependent -oxidtion nd chin shortening of 20:4n-6 is one process involved in retroconversion to 20:3n-6 (15, 16). Gordon et l. (15) hve shown tht humn skin firolsts cells in culture converted 20:4n-6 to 16:3n- 6 through peroxisome-dependent oxidtive process. Further, Spector et l. (16) provided evidence tht peroxisoml oxidtion of 20:4n-6 ws min pthwy in retroconversion of 20:4n-6 to 20:3n-6 in humn skin firolsts. In oon neontes, similr process involving 2 cycles of peroxisoml -oxidtion of 20:4n-6 would yield 16:3n-6, which could hve een chin elongted to 20:3n-6. Lel incorportion into 22:6n-3 in retin indictes tht [ 13 C]cette from [U- 13 C]20:4n-6 ws recycled for elongtion of unleled precursors to form leled C20 products. Agin, utiliztion of 20:4n-6 cron for formtion of n-3 LCP ws minor, s evidenced y 2% of totl leled recovered s 22:6n-3. Our dt shows tht preformed 20:4n-6 did not contriute significntly to SFA or MUFA synthesized de novo in the primte neonte. The dilution of lel into lrge endogenous SFA/MUFA pools must to e considered with respect to cron recycling of 20:4n-6. Under the conditions of these mesurements, APE could hve een detected corresponding to lel enrichment s low s 0.8% totl lel in rin or liver 16:0 nd 18:1. Hence, s 20:4n-6 lel distriution into SFA or MFA were 0.8% totl lel in ll tissues investigted, we conclude tht 20:4n-6 contriution to neonte tissue SFA or MFA is minor in term oon infnts. In contrst, sustntil cron recycling of 18:2n-6, 18:3n-3, nd 22:6n-3 into SFA nd MUFA hs een demonstrted in neworn nimls (7 10). In fetl nd neonte rhesus monkeys dosed with [U- 13 C]22:6n-3, out 16% of totl lel in the rin ws detected in SFA nd MUFA, indicting sustntil utiliztion of 22:6n-3 cron for SFA nd MUFA synthesis (9). Thus, 20:4n-6 ppers to e unique in tht it is the only functionlly mjor PUFA studied to dte tht is not utilized to sustntil extent for de novo synthesis of SFA or MUFA in primte infnts. The physiologic significnce of this oservtion is yet to e investigted. A mjor frction of 20:4n-6 consumed (79 93% of totl lel) ccumulted s 20:4n-6 in tissue lipids, consistent with its primry function s predominnt structurl con- Wijendrn et l. Archidonic cid utiliztion in oon neontes 765

5 stituent in memrne lipids. However, sustntil conversion of 20:4n-6 to 22:4n-6 occurred in-vivo in the primte neonte s evidenced y 5 16% totl lel recovered in 22:4n-6 in neonte tissues 10 dys fter dosing. Lel enrichment in 22:5n-6 ws 4%totl lel in ll neonte tissues studied, indicting tht AA utiliztion for 22:5n-6 ws reltively low compred with its conversion to 22:4n-6. Bsed on the trcer dt, we cn quntittively estimte the contriution of dietry preformed 20:4n-6 to rin 22:4n-6 ccumultion. Our clcultions sed on trcer enrichment mesurements indicte tht overll 0.48% of preformed 20:4n-6 consumed in formul ppered s rin 22:4n-6 t 10 dys post-dose (percentge dose of AA* recovered s rin 22:4n-6*). The neontes consumed n verge of 44 mg 20:4n-6/dy. Thus, 0.2 mg ( /100) of formul 20:4n-6/dy ws utilized for conversion to rin 22:4n-6. The oon rin weight t term gesttion of 182 dys is out 80 g (33). Brin 22:4n-6 concentrtion in the fetl oon ws out mg/g wet weight (27), which ws not correlted to gesttionl ge. The men totl 22:4n-6 content of neonte rin t 4 weeks of ge in these neontes ws 90 mg. Comining these fctors, net ccretion of 22:4n-6 during the 4 week postntl period is out 36 mg. Aout 6 mg (0.2 28) of formul 20:4n-6 ppered s rin 22:4n-6 over the 4 weeks period in these neontes. Thus, out 17% (6/36) of rin 22:4n-6 ccrued postntlly ws derived from dietry preformed 20:4n-6 in term oon neontes t 4 weeks of ge. Neonte diets lso contined 18:2n-6, which is mjor contriutor to rin 20:4n-6 (27) nd proly 22:4n-6. The reltive efficcy or solute contriutions of dietry 20:4n-6 compred with 18:2n-6 s source for rin 22:4n- 6 in primtes is not known. Using dt from recent study conducted in our lortory of oon neontes consuming restmilk of similr composition to the formul of the present study, 18:2n-6 conversion to rin 22:4n-6 cn e estimted s 0.087% of 18:2n-6 consumed (unpulished dt). The reltive conversion efficiency of dietry 20:4n-6 versus 18:2n-6 to rin 22:4n-6, on molr sis, cn then e estimted s out 5.5-fold (0.48/0.087). Estimtes of solute contriutions to rin 22:4n-6 must tke into ccount the considerly greter concentrtion of 18:2n-6 compred with 20:4n-6 in formul nd restmilk. The verge 18:2n-6 intke per dy in our neontes ws out 1.1 g/dy; thus 27 mg or out 75% (27/ 36) of rin 22:4n-6 tht ccrued postntlly ws derived from dietry 18:2n-6. Dietry 18:2n-6 nd 20:4n-6 ccount for 75% 17% 92% of rin 22:4n-6 ccumultion. The likely source for the remining estimted 8% or 3 mg ( ) of rin 22:4n-6 is from the 7 mg/dl of preformed 22:4n-6 found in formul. Neontes consumed n verge of 19.5 mg 22:4n-6/dy. Thus, over the course of the study (4 weeks), neontes consumed 553 mg 22:4n-6; n efficiency of 3/553 or 0.54% of dietry preformed 22:4n-6 would ccount for the remining rin 22:4n-6. It should e noted tht these estimtes pply strictly to diets similr to the formul used in this study. This clcultion lso ssumes tht rin 22:4n-6 turnover is negligile compred with input, n ssumption tht is supported y dt for other mjor LCP 22:6n-3 (34) nd 20:4n-6 (27) in rpidly growing oon rin. Nevertheless, the dt indictes tht 20:4n-6 conversion to rin 22:4n-6 is quntittively sustntil pthwy for 20:4n-6 utiliztion in primte neontes. In conclusion, in this study of oon neontes consuming formul with ftty cid nd prticulrly LCP concentrtions similr to primte rest milk, we hve found: 1) 20:4n-6 ws retroconverted to 20:3n-6 in vivo in primte neontes t very low level compred with 20:4n-6 ccumultion in tissue lipids; 2) 20:4n-6 did not contriute significntly to de novo synthesis of SFA nd MUFA; 3) contriution to rin 22:4n-6 ccumultion ws quntittively significnt metolic fte for dietry 20:4n-6; nd 4) the reltive contriutions of dietry 18:2n-6, 20:4n-6, nd preformed 22:4n-6 to rin 22:4n-6 cn e pproximtely estimted to e 75%, 17%, nd 8% respectively, though efficiency of ccretion ws pproximtely equl for dietry 20:4n-6 nd 22:4n-6 ( %). This work ws supported y NIH grnt EY10208 nd Numico Reserch, Germny. Mnuscript received 16 Novemer 2001 nd in revised form 13 Ferury REFERENCES 1. Mrtinez, M Tissue levels of polyunsturted ftty cids during erly humn development. J. Peditr. 120: S129 S Uuy, R., P. Men nd C. Rojs Essentil ftty cids in erly life: Structurl nd functionl role. Proc. Nutr. Soc. 59: Doing, J., nd J. Snds Quntittive growth nd development of humn rin. Arch. Dis. Child. 48: Leyton, J., J. Drury, nd M. A. Crwford Differentil oxidtion of sturted nd unsturted ftty cids in vivo in the rt. Br. J. Nutr. 57: Cunnne, S. C., nd M. J. Anderson The mjority of dietry linolete in growing rts is et-oxidized or stored in viscerl ft. J. Nutr. 127: Szitnyi, P., B. Koletzko, A. Mydlilov, nd H. Demmelmir Metolism of 13c-leled linoleic cid in neworn infnts during the first week of life. Peditr. Res. 45: Menrd, C. R., K. J. Goodmn, T. N. Corso, J. T. Brenn, nd S. C. Cunnne Recycling of cron into lipids synthesized de novo is quntittively importnt pthwy of lph-[u-13c]linolente utiliztion in the developing rt rin. J. Neurochem. 71: Cunnne, S. C., K. Belz, M. J. Anderson, nd M. A. Ryn Sustntil cron recycling from linolete into products of de novo lipogenesis occurs in rt liver even under conditions of extreme dietry linolete deficiency. J. Lipid Res. 39: Sheff Greiner, R. C., Q. Zhng, K. J. Goodmn, D. A. Giussni, W. Nthnielsz, nd J. T. Brenn Linolete, lph-linolente, nd docoshexenote recycling into sturted nd monounsturted ftty cids is mjor pthwy in pregnnt or lctting dults nd fetl or infnt rhesus monkeys. J. Lipid Res. 37: Cunnne, S. C., C. R. Menrd, S. S. Likhodii, J. T. Brenn nd M. A. Crwford Cron recycling into de novo lipogenesis is mjor pthwy in neontl metolism of linolete nd lph-linolente. Prostglndins Leukot. Essent. Ftty Acids. 60: Sinclir, A. J Incorportion of rdioctive polyunsturted ftty cids into liver nd rin of developing rt. Lipids. 10: Hiltunen, J. K., T. Krki, I. E. Hssinen, nd H. Osmundsen Journl of Lipid Reserch Volume 43, 2002

6 Bet-oxidtion of polyunsturted ftty cids y rt liver peroxisomes. A role for 2,4-dienoyl-coenzyme reductse in peroxisoml et- oxidtion. J. Biol. Chem. 261: Hovik, R., nd H. Osmundsen Peroxisoml et-oxidtion of long-chin ftty cids possessing different extents of unsturtion. Biochem. J. 247: Reuset, F. A., J. H. Veerkmp, J. M. Trijels, nd L. A. Monnens Totl nd peroxisoml oxidtion of vrious sturted nd unsturted ftty cids in rt liver, hert nd m. Qudriceps. Lipids. 24: Gordon, J. A., S. K. Heller, T. L. Kduce, nd A. A. Spector Formtion nd relese of peroxisome-dependent rchidonic cid metolite y humn skin firolsts. J. Biol. Chem. 269: Spector, A. A., D. E. Willrd, T. L. Kduce, nd R. L. Widstrom Role of peroxisoml oxidtion in the conversion of rchidonic cid to eicostrienoic cid in humn skin firolsts. Prostglndins Leukot. Essent. Ftty Acids. 60: Fujiym-Fujiwr, Y., R. Umed, nd O. Igrshi Metolism of rchidonic, eicospentenoic, nd docoshexenoic cids in hepg2 cells nd rt heptocytes. J. Nutr. Sci. Vitminol. (Tokyo). 38: Brossrd, N., M. Croset, C. Pchiudi, J. Riou, J. L. Tyot, nd M. Lgrde Retroconversion nd metolism of [13c]22:6n-3 in humns nd rts fter intke of single dose of [13c]22:6n-3-tricylglycerols. Am. J. Clin. Nutr. 64: Wilson, R., nd J. R. Srgent Lipid nd ftty cid composition of rin tissue from drenoleukodystrophy ptients. J. Neurochem. 61: O Brien, J. S., nd E. L. Smpson Ftty cid nd ftty ldehyde composition of the mjor rin lipids in norml humn gry mtter, white mtter, nd myelin. J. Lipid Res. 6: Jensen, R. G The lipids in humn milk. Prog. Lipid Res. 35: Mrtinez, M., nd I. Mougn Ftty cid composition of humn rin phospholipids during norml development. J. Neurochem. 71: Corrign, F. M., D. F. Horroin, E. R. Skinner, J. A. Besson, nd M. B. Cooper Anorml content of n-6 nd n-3 long-chin unsturted ftty cids in the phosphoglycerides nd cholesterol esters of prhippocmpl cortex from lzheimer s disese ptients nd its reltionship to cetyl co content. Int. J. Biochem. Cell Biol. 30: VnRollins, M., L. Horrocks, nd H. Sprecher Metolism of 7,10,13,16-docostetrenoic cid to dihomo-thromoxne, 14- hydroxy-7,10,12-nondectrienoic cid nd hydroxy ftty cids y humn pltelets. Biochim. Biophys. Act. 833: Cmpell, W. B., J. R. Flck, J. R. Okit, A. R. Johnson, nd K. S. Cllhn Synthesis of dihomoprostglndins from drenic cid (7,10,13,16-docostetrenoic cid) y humn endothelil cells. Biochim. Biophys. Act. 837: Wijendrn, V., M-C. Hung, G-Y. Diu, G. Boehm, W. Nthnielsz, nd J. T. Brenn Efficcy of dietry rchidonic cid provided s triglyceride or phospholipid s sustrtes for rin rchidonic cid ccretion in oon neontes. Peditr. Res. In press. 27. Su, H. M., T. N. Corso, W. Nthnielsz, nd J. T. Brenn Linoleic cid kinetics nd conversion to rchidonic cid in the pregnnt nd fetl oon. J. Lipid Res. 40: Bligh, E., nd W. Dyer A rpid method of totl lipid extrction nd purifiction. Cn. J. Biochem. Physiol. 37: Greiner, R. C., J. Winter, W. Nthnielsz, nd J. T. Brenn Brin docoshexenote ccretion in fetl oons: Bioequivlence of dietry lph-linolenic nd docoshexenoic cids. Peditr. Res. 42: Brenn, J. T., T. N. Corso, H. J. Tois, nd R. J. Cimi Highprecision continuous-flow isotope rtio mss spectrometry. Mss Spectrom. Rev. 16: Doing, J., nd J. Snds Comprtive spects of the rin growth spurt. Erly Hum. Dev. 3: Hnsen, H. S., B. Jensen nd P. von Wettstein-Knowles Apprent in vivo retroconversion of dietry rchidonic to linoleic cid in essentil ftty cid-deficient rts. Biochim. Biophys. Act. 878(2): Hendrickx, A Emryology of the oon. University of Chicgo, Chicgo, IL. 34. Su, H. M., L. Bernrdo, M. Mirmirn, X. H. M, T. N. Corso, W. Nthnielsz, nd J. T. Brenn Bioequivlence of dietry lph-linolenic nd docoshexenoic cids s sources of docoshexenote ccretion in rin nd ssocited orgns of neontl oons. Peditr. Res. 45: Wijendrn et l. Archidonic cid utiliztion in oon neontes 767