Opposite metabolic response to fenofibrate treatment in pregnant and virgin rats

Transcription

1 Opposite metoli response to fenofirte tretment in pregnnt n virgin rts An Sori, Crlos Boos, n Emilio Herrer 1 Fult e Cienis Experimentles y e l Slu, Universi Sn Plo-CEU, Ctr. Boill el Monte km 5,300, E Boill el Monte (Mri), Spin Astrt The level of mternl irulting triglyeries uring lte pregnny hs een orrelte to neworns weight in humns. To investigte the response to fenofirte, hypotriglyeriemi gent, in pregnnt rts, 0, 100, or 200 mg of fenofirte/kg oy weight s orl oses were given twie y from y 16 of gesttion n stuie t y 20. Virgin rts were stuie in prllel. Liver weight ws higher in pregnnt thn in virgin rts, n either ose of fenofirte inrese this vrile in oth groups. The highest ose of fenofirte erese fetl weight. Although plsm triglyeries erese uring the first 2 ys of fenofirte tretment in pregnnt rts, the effet isppere on y 3, n plsm triglyeries were even enhne t y 4. In virgin rts, fenofirte erese plsm triglyeries throughout the experiment. Plsm holesterol levels in pregnnt rts erese uring the first 3 ys of tretment, n the effet isppere on y 4, wheres in virgin rts, vlues remine erese. Chnges in plsm triglyeries prllele those of VLDL triglyeries. In pregnnt rts, VLDL holesterol levels inrese while LDL holesterol erese with the tretment, wheres in virgin rts, holesterol levels erese in ll lipoprotein frtions. Only in virgin rts i liver triglyerie onentrtion inrese with fenofirte tretment. Lumr ipose tissue LPL ws lower in pregnnt thn in virgin rts, n fenofirte tretment erese this vrile in oth groups. Mternl fenofirte tretment inrese fetl plsm n liver triglyerie n holesterol onentrtions. It is propose tht the opposite effets of fenofirte tretment in virgin n pregnnt rts re onsequene of oth the enhne liver pility for VLDL triglyerie proution n reoun response to the rug in the ltter. Sori, A., C. Boos, n E. Herrer. Opposite metoli response to fenofirte tretment in pregnnt n virgin rts. J. Lipi Res : Supplementry key wors pregnny firtes triglyerie VLDL triglyerie holesterol lipoprotein lipse rt Elevte plsm triglyerie levels n low HDL holesterol levels hve een shown to e inepenent risk ftors for ererovsulr n oronry hert isese (1 3), n firtes hve een effetively use to reue these ftors (4). The moleulr ses for the tion of firtes on lipi metolism hve een reently eluite (5), n involve the tivtion of trnsriptionl ftors known s peroxisome prolifertor-tivte reeptors (PPAR), espeilly the PPAR- form tht is expresse in liver. Throughout this mehnism, firtes hve een reporte to erese polipoprotein (po)c-iii (6), to inrese yl-oenzyme A synthetse n ftty i trnsport protein (7), to inrese poa-i n poa-ii (8, 9), n to inue the expression n tivity of LPL in the liver (10). This ltter effet ours espite tht uner norml onitions, the ult liver oes not express LPL, n it hs een propose tht y reverting this sitution, firtes might enhne the liver lerne of triglyerie-rih lipoproteins (10), this effet ontriuting to their hypotriglyeriemi tion. Although these effets re lerly estlishe, still there re spets of firtes effets on lipi metolism tht remin to e unerstoo, inluing their effets on liver lipi onentrtion, triglyeries, n holesterol, whih hve een foun to e either unhnge (11), erese (12, 13), or even enhne (14), lthough liver weight ws onsistently enhne n, therefore, totl lipi ontent my result ugmente. Some firtes lso hve een shown to hve opposite effets on plsm n liver lipis epening on the egree of hypertriglyeriemi in the rts (14). In ition, firtes hve een shown to hve ifferent regultory effets in roents thn in humns. Thus, wheres in roents firtes my erese HDL holesterol (14) s result of oth erese expression of the genes for HDL polipoproteins, poa-i n poa-ii (15 18), s well s of the enzymes involve in their metolism suh s hepti lipse n LCAT (19, 20), in humns they hve positive effet on HDL holesterol s well s on poa-i n poa-ii onentrtions (21, 22). This ifferent response seems to resie in ifferenes etween the two speies in the poa-i gene promoter (23). This ifferent omposition llows the inution of the poa-i gene expression y firtes to e meite vi the intertion 1 To whom orresponene shoul e resse. e-mil: eherrer@eu.es 74 Journl of Lipi Reserh Volume 43, 2002

2 of PPAR with its peroxisome prolifertor response element (PPRE) in humns, wheres in roents, this PPRE nnot e use y PPAR (24). In ition, wheres rts re responsive to hepti peroxisome prolifertion upon firte ministrtion, humns seem to e nonresponsive speies (25), n ifferenes in the mount of hepti PPAR n/or the omposition of PPRE in puttive trget genes hve een propose to explin interspeies ifferenes in the firte response (25). During lte pregnny, hypertriglyeriemi rther thn hyperholesterolemi is onsistently evelope (26) s onsequene of enhne ipose tissue lipolyti tivity (27 30), enhne liver proution of VLDL (31, 32), n erese extrhepti LPL tivity (33, 34). Although tretment with hypoholesterolemi rugs in pregnnt rts hs een shown to impir fetl growth (35, 36), no stuies hve een rrie out to etermine the effets of phrmologil reutions of irulting triglyeries, espite the propose role of mternl hypertriglyeriemi on fetl growth in humns (32, 37). The present work ws therefore unertken to etermine how tretment with fenofirte, s hypotriglyeriemi gent, ffets mternl lipii metolism, n to etermine its onsequenes to fetl growth uring lte pregnny in the rt. For omprison, norml virgin rts were stuie in prllel, n results show tht in ition to impiring fetl growth, fenofirte responsiveness gretly iffers etween pregnnt n virgin nimls. MATERIAL AND METHODS Animls, rug ministrtion, n olletion of smples Femle Sprgue Dwley rts from our niml qurter weighing g, ys ol, were fe liitum stnr rt how (B&K Universl, Brelon, Spin) n house uner ontrolle light n temperture onitions (12 h light-rk yle; 22 1 C). The experimentl protool ws pprove y the Animl Reserh Committee of the University Sn Plo- CEU in Mri, Spin. One-hlf of the nimls were mte (y 0 of pregnny ws etermine when spermtozois were foun in vginl smers), wheres the other hlf ws kept virgin. From y 16 of gesttion, rts were given, y orl gvge, two ily oses of 100 or 200 mg/kg oy weight of fenofirte (from Sigm, St. Louis, MO), one t 8:00 m n the other t 6:00 pm, suspene in 2% Tween-80. Controls reeive only the meium y orl gvge. The oses of fenofirte were hosen uner the se of previous stuies in the rt (6, 13, 17, 38). Just efore the ily morning tretments, loo ws ollete from the til into reeptles ontining N 2 -EDTA, wheres on the morning of y 20 of pregnny, 14 h fter the lst ose, rts were epitte n loo ws ollete into tues ontining N 2 -EDTA. Liver n lumr ft ps were immeitely issete, n liquots of oth tissues were ple into liqui nitrogen n kept t 80 C until nlysis. The oneptus ws lso issete n, fter eing weighe, fetuses were ounte n weighe. Fetuses were epitte n loo from ll pups of the sme mother ws ollete n poole into reeptles ontining N 2 -EDTA. Fetus livers were lso issete n ple in liqui nitrogen, n those from the sme mother were poole. Virgin rts reeive the sme tretment n were lwys stuie in prllel. Determintions Plsm liquots were proesse fresh for lipoprotein isoltion y ultrentrifuge sequentil frtiontion following the metho previously esrie (39), wheres other liquots were kept t 30 C until proessing for the nlysis of triglyeries, holesterol, n FFA y enzymti ommeril kits (Menrini, Menrini, n Wko, respetively). Frozen liver liquots were use for lipi extrtion (40), n liquots of lipi extrts were quntifie fter imge nlysis n seprtion y one-imensionl TLC (41) using the G5-700 BIOIMAGE TLC snner of Bio-R (Herules, CA). Spots were quntifie s integrte optil ensities ginst n internl stnr of holesteryl formte n lirtion urves of triglyerie stnrs. LPL tivity ws mesure in etone powers from frozen ipose tissue liquots y the metho previously esrie (42). Expression of results n sttistil evlution Results were expresse s mens SEM. When neessry, t were log trnsforme to hieve equl vrine mong mens. Tretment effets were nlyze y one-wy ANOVA using omputer softwre system (Systt Version 5.03; Wilkinson, Evnston, IL). When tretment effets were signifintly ifferent (P 0.05), mens were teste y Tukey s test. Differenes etween two groups were nlyze y Stuent s t-test. RESULTS As shown in Tle 1, treting rts twie ily with either 100 mg or 200 mg fenofirte/kg oy weight/y for 4 ys i not moify net oy weight in pregnnt (free of oneptus) or virgin rts. Liver weight ws higher in pregnnt thn in virgin rts, n either ose of fenofirte inrese this vrile in oth groups. Fenofirte tretment i not moify fetl numer, ut lthough the mg/kg oy weight/y ose i not moify fetl oy weight, this vrile ws signifintly erese with the mg ose (Tle 1). The hypolipiemi effet of fenofirte iffere etween pregnnt n virgin rts. As shown in Fig. 1, in ontrol virgin rts, plsm triglyeries remine unhnge throughout the experiment, wheres either ose of fenofirte signifintly erese plsm triglyerie levels fter y 1 of tretment, n the effet remine stle up to the en of the experiment (y 4 of tretment). However, in ontrol pregnnt rts, plsm triglyeries inrese, lthough not signifintly, t y 4 of the experiment, orresponing to y 20 of gesttion. In ition, in pregnnt rts, lthough plsm triglyeries were lower fter y 1 n 2 of tretment with either ose of fenofirte, the effet isppere fter y 3, n ws even reverte in ose-epenent mnner fter y 4. In ft, vlues in pregnnt rts trete with the highest ose were signifintly higher thn in the sme rts prior to the onset of tretment (y 0) s well s in ontrol rts on the sme y of gesttion. In ifferent set of rts reeiving the sme tretment, loo ws ollete 2 h fter the evening rug ministrtion, n it ws foun tht plsm triglyerie levels were onsistently lower in fenofirtetrete pregnnt rts thn in ontrols (t not shown), Sori, Boos, n Herrer Response to fenofirte in pregnnt rts 75

3 TABLE 1. Effets of fenofirte on oy n liver weight in virgin n pregnnt rts, n on fetl numer n weight Dose Initil oy weight (g) Virgin Pregnnt Finl net oy weight (g) Virgin Pregnnt Liver weight (g) Virgin Pregnnt , , Fetus Numer/litter Averge oy weight (g) Results re men SEM, n 10/group. Dose given in mg/kg oy weight/y. Two orl oses of fenofirte were given per y. P from virgin rts. P from ose 0. Fig. 1. Plsm triglyerie levels in virgin n pregnnt rts t ifferent ys of tretment with fenofirte. Vlues re mens SEM, n 10. Within-group sttistil omprisons for rts reeiving the sme tretment t ifferent ys re shown y lowerse letters, wheres omprisons etween groups reeiving ifferent tretments for virgin n pregnnt rts re shown y upperse letters. Different letters inite signifint ifferenes etween the groups (P 0.05). initing tht the enhne vlues foun in the morning extrtions uring the lst ys of tretment orrespone to reoun effet. As shown in Fig. 2, the hnge in plsm holesterol levels prllele tht of triglyeries in virgin rts euse either ose of fenofirte signifintly erese this vrile fter y 1 of tretment, n vlues remine stle until y 4. Plsm holesterol levels in ontrol pregnnt rts remine stle throughout the experiment, wheres they erese in trete rts fter y 1, 2, n 3 of tretment, to return to sl vlues (y 0) on y 4 of tretment, the effet eing similr with either ose (Fig. 2). At the time of srifie, orresponing to 14 h fter the lst ose, plsm lipoprotein frtiontion ws seure. Lipoprotein istriution in virgin rts showe tht the erese in plsm triglyeries minly orrespone to those of VLDL, lthough the effet in rts reeiving the mg ose i not reh sttistil signifine (Fig. 3). In pregnnt rts, the inrese in plsm triglyeries seen 14 h fter the lst tretment lso orrespone to VLDL triglyeries, n lthough the ifferene in the rts reeiving the mg ose i not reh sttistil signifine, signifint inrese in HDL triglyeries ws lso foun in rts trete with the mg ose (Fig. 3). As shown in Fig. 4, in virgin rts, the erese in plsm holesterol levels foun 14 h fter the lst ministrtion of fenofirte (y 4) orrespons to signifint reution in the holesterol ssoite to ll lipoprotein frtions, VLDL, LDL, n HDL, the effet eing similr with either ose. However, in pregnnt rts, fenofirte tretment enhne plsm VLDL holesterol onentrtion n erese LDL holesterol levels without moifying HDL holesterol, the effets eing similr for either ose (Fig. 4). To unerstn the hnges tking ple in plsm VLDL, liver lipis were mesure. In virgin rts (Tle 2), fenofirte tretment gretly inrese liver triglyerie onentrtion (mg/g) n ontent (mg/orgn), wheres 76 Journl of Lipi Reserh Volume 43, 2002

4 Fig. 2. Plsm holesterol levels in virgin n pregnnt rts t ifferent ys of tretment with fenofirte. Vlues re mens SEM, n 10. Within-group sttistil omprisons for rts reeiving the sme tretment t ifferent ys re shown y lowerse letters, wheres omprisons etween groups reeiving ifferent tretments for virgin n pregnnt rts re shown y upperse letters. Different letters inite signifint ifferenes etween the groups (P 0.05). Fig. 3. Plsm triglyeries in VLDL, LDL, n HDL in virgin n 20-y pregnnt rts fter 4 ys of tretment with fenofirte. Vlues re mens SEM, n 8. Sttistil omprison etween rts reeiving ifferent oses, for the sme vrile, is shown y lowerse letters. Different letters inite signifint ifferenes etween the groups (P 0.05). liver holesterol ontent (mg/orgn) inrese only uner the mg ose. However in pregnnt rts, fenofirte tretment i not moify either liver triglyerie or holesterol onentrtions, the vlues eing signifintly lower thn in virgin rts, exept for holesterol vlues expresse per totl orgn ontent (Tle 2). To etermine whether hnges in liver triglyeries oul e relte to the mount of inoming FFA, plsm FFA onentrtions were lso mesure (Tle 3). This vrile ws lwys higher in pregnnt thn in virgin rts, n lthough fenofirte tretment further inrese plsm FFA in ose-epenent mnner in pregnnt rts, no effet ws foun in virgin rts. As it woul e expete, lumr ipose tissue LPL tivity ppere lower in pregnnt thn in virgin rts not reeiving the rug (Tle 4). Fenofirte tretment signifintly erese LPL tivity in oth groups of rts, n the effet in virgin rts ws ose epenent. Beuse lumr ipose tissue in rts reeiving the fenofirte tretment weighe less thn in ontrol rts, totl tissue LPL tivity in fenofirte-trete rts erese even more thn when expresse per unit of fresh tissue (t not shown). Mternl tretment with fenofirte ffete fetl lipi metolism, s shown y inrements in fetl plsm n liver triglyerie n holesterol onentrtions, the effet eing espeilly mrke n signifint with the highest ose use (Tle 5). DISCUSSION The present stuy shows tht from the first y, n long 4 ys of tretment with high oses of fenofirte, plsm triglyerie n holesterol levels erese in virgin rts, the effet orresponing to speifi reutions in plsm VLDL triglyeries n plsm holesterol ssoite with ll lipoprotein frtions. However, in pregnnt rts, fter n initil reution, plsm triglyeries inrese over vlues seen in untrete ontrols t the fourth y of tretment, n this effet orrespone to n inrese in the triglyerie ontent oth in VLDL n HDL, the effet eing espeilly mrke in the former. Sori, Boos, n Herrer Response to fenofirte in pregnnt rts 77

5 Fig. 4. Plsm holesterol in VLDL, LDL, n HDL in virgin n 20-y pregnnt rts fter 4 ys of tretment with fenofirte. Vlues re mens SEM, n 8. Sttistil omprison etween rts reeiving ifferent oses, for the sme vrile, is shown y lowerse letters. Different letters inite signifint ifferenes etween the groups (P 0.05). Cholesterol levels lso eline shortly fter fenofirte tretment in pregnnt rts to return lter on to sl vlues, the effet orresponing to n inrese in VLDL holesterol tht ws ompenste y reution in LDL TABLE 2. holesterol. These hnges re followe y mjor ifferenes in the liver lipi ontent: n intense umultion of triglyeries in the liver of virgin rts reeiving the fenofirte tretment, no hnges in the onentrtion of holesterol in these sme rts, n unhnge liver triglyerie n holesterol onentrtion in pregnnt nimls. In virgin rts, the erese in plsm VLDL triglyeries use y fenofirte seems to e the result of their erese liver proution, s suggeste y the onomitnt umultion of liver triglyeries. This fining oul e the result of the erese liver VLDL triglyerie proution (43) n/or n enhne liver LPL tivity (10) reporte in rts reeiving firte tretment. In ft, it hs een shown previously tht onitions where there is n inrese in liver LPL tivity suh s in the fste lte pregnnt rt or uner Intrlipi ministrtion to fste virgin rts, ontriute to liver triglyerie umultion (44, 45), swithing the liver from triglyerie exporter orgn into n eptor. An enhne extrhepti VLDL tolism seonry to erese hepti poc-iii expression hs een propose to ontriute to the firtemeite triglyerie lowering (6). Beuse previous stuies hve emonstrte tht LPL tivity is inhiite y high mounts of poc-iii (46), it ws propose tht reutions in plsm poc-iii levels woul filitte LPL-meite VLDL tolism (6). However, firtes hve shown lk of regultion of ipose tissue LPL in rts n in humns (10, 11, 47), n we foun, even here, tht high oses of fenofirte use signifint reutions oth in plsm VLDL triglyeries n ipose tissue LPL tivity. Inrements in ipose tissue LPL, however, hve een reporte in firte-trete rts (48), even y ourselves (12), ut epening on the type of rug use n the ose, firtes hve een lso reporte to use opposite effets on ifferent vriles (14). In ny se, euse reutions of ipose tissue LPL were foun here uner onitions where fenofirte h use signifint reutions in plsm VLDL triglyeries in normolipiemi virgin rts, no possiility exists to lim n enhne removl of triglyeries unless LPL in Effets of fenofirte tretment on liver triglyeries n holesterol onentrtions in virgin n pregnnt rts Dose Gesttion Liver Triglyeries Liver Cholesterol mg/g mg/orgn mg/g mg/orgn g f g g g f e g g g Results re men SEM, n 10/group. Dose given in mg/kg oy weight/y. Two orl oses of fenofirte were given per y. P 0.05 from ose 0. P from ose 0. e P 0.05 from virgin rts. f P 0.01 from virgin rts. g P from virgin rts. 78 Journl of Lipi Reserh Volume 43, 2002

6 TABLE 3. Effets of fenofirte on plsm free ftty is in virgin n pregnnt rts Dose Free Ftty Ais mm Virgin Pregnnt , , Results re men SEM, n 10/group. Dose given in mg/kg oy weight/y. Two orl oses of fenofirte were given per y. P from virgin rts. P from ose 0. TABLE 4. Effets of fenofirte on lumr ipose tissue LPL tivity in virgin n pregnnt rts Dose LPL pktl/g of fresh tissue Virgin 1, Pregnnt Results re men SEM, n 5/group. Dose given in mg/kg oy weight/y. Two orl oses of fenofirte were given per y. P 0.05 from ose 0. P 0.05 from virgin rts. other extrhepti tissues suh s skeletl musle ws enhne. If this ws the se, inrements in plsm HDL holesterol woul hve een preite uner the se of stuies in humns (49, 50) n in rts (51); however, to the ontrry, reution ws lerly foun here in greement with similr results foun y others fter ezfirte tretment (14), whih lso uses liver triglyerie umultion. The mehnism for suh effet is not yet known, ut fenofirte hs een shown to erese VLDL polipoprotein synthesis (43), n it hs een shown y us n others tht firi i erivtives in the nonpregnnt rt erese liver VLDL triglyeries proution (11, 12). This is the first time tht the effet of fenofirte hs een stuie in lte pregnnt rts where hypertriglyeriemi onition is normlly present. This onition is use y enhne liver VLDL triglyeries proution (31), prtilly supporte y n enhne rrivl of FFA n glyerol to the liver s result of enhne ipose tissue lipolyti tivity (30, 52), n erese irulting lerne of these lipoproteins ue to erese ipose tissue LPL (33, 53). The inrese in VLDL triglyeries seen here fter 4 ys of tretment with fenofirte in pregnnt rts inste of the erese seen in virgin rts my result from the enhne VLDL triglyeries proution pility of the mother (54, 55). Suh inrese VLDL triglyeries proution in the liver of the fenofirtetrete pregnnt rts llows these nimls to voi the liver triglyerie umultion seen in virgin rts, n must e supporte y n enhne rrivl of FFA to the liver. This possiility is supporte y the ft tht signifint liner orreltions re foun when iniviul vlues of plsm FFA (Tle 3) re plotte ginst plsm triglyeries in pregnnt rts reeiving mg fenofirte/ kg oy weight/y (FFA TG 0.01, n 13, R , P 0.01) or mg fenofirte/kg oy weight/y (FFA TG , n 14, R , P 0.01), wheres this reltionship ws not signifint in the se of pregnnt ontrols or in virgin rts eing trete or not (t not shown). Inrements in plsm VLDL triglyeries in fenofirte-trete pregnnt rts re followe y prllel hnges in VLDL holesterol, whih together with erese LDL holesterol levels, fit with the erese ipose tissue LPL tivity seen in these nimls, suggesting tht the onversion of VLDL to LDL is impire in these nimls. If the tion of firtes on lipi metolism is primrily meite y its role s ligns for PPAR (56), the enhne rrivl of FFA (whih re lso ligns for PPAR ) (56) to the liver in the lte pregnnt rt (52) oul erese the vilility of the former to their orresponing PPAR site. This woul sustntilly reue the pility of firtes to tivte PPAR n, onsequently, its metoli effets. Furthermore, isplement of firtes for ining to ftty i-ining protein y FFA, whih woul e influene y their intrellulr onentrtion, nnot e rule out (57). On the other hn, reent eviene suggests tht ltertion of gene trnsription y FFA n firtes is often isonnete (58). Thus, the enhne rrivl of FFA to liver in pregnnt rts, long with firte, might e ffeting n itionl ttery of genes in whih trnsription woul e ltere, in omprison to the sitution in virgin rts. Inrements in plsm triglyeries seen in pregnnt rts fter 4 ys of tretment with fenofirte were preee y mintine hypotriglyeriemi uring the first 2 ys of tretment, n ourre 14 h fter the lst fenofirte ministrtion when the rug still use trnsitory hypotriglyeriemi effet. Thus, suh hypertriglyeriemi ppers to e the result of reoun effet tht tkes ple uring lte pregnny when the mother is known to e in toli onition (26) n when ipose tissue lipolyti tivity is enhne (30, 59, 60). Suh TABLE 5. Effets of mternl tretment with fenofirte on fetl plsm n liver lipis Dose Plsm triglyeries (mg/l) Plsm holesterol (mg/l) Liver triglyeries (mg/g) Liver holesterol (mg/g) Results re men SEM, n 10/group for plsm lipis; n 6/ group for liver lipis. Dose given in mg/kg oy weight/y. Two orl oses of fenofirte were given per y. P 0.05 from ose 0. P from ose 0. Sori, Boos, n Herrer Response to fenofirte in pregnnt rts 79

7 reoun effet hs not een previously reporte for fenofirte, ut there re reports of reoun effets of other hypolipiemi ntilypoliti rugs suh s Aipimox fter semihroni tretments in humns hving stimulte ipose tissue lipolysis suh s non-insulin-epenent ietes mellitus ptients (61). Although we o not know whether the hypotriglyeriemi followe y hypertriglyeriemi use y fenofirte tretment in the lte pregnnt rt woul ffet fetl growth, iret effet of the rug to the fetus n/or response of the fetus to mternl ltertions in lipoprotein metolism nnot e isre. In ft, lthough neither VLDL triglyeries nor holesterol iretly seem to ross the plentl rrier in the rt (62 64), the presene of lipse tivities in the plent llows onitions of mternl-exggerte hypertriglyeriemi to inrese fetl triglyeries (53). In ition, mternl holestyrmine feeing, nonsorle ile i ining resin, is known to inue 3-hyroxy-3- methylglutryl oenzyme A reutse n ftty i synthetse tivities n the onsequent holesterol n ftty i synthesis in the fetus (65, 66). Therefore, the inrements of plsm n liver holesterol n triglyerie onentrtions seen here in fetus of ms trete with fenofirte oul e onsequene of the rug-inue perturtion of mternl lipoprotein metolism. Although similr explntion oul e given to justify the negtive effet of the highest ose of fenofirte on fetl oy weight, iret effet of the rug rossing the plent on fetl evelopment nnot e isre, s hs een lrey shown for lofirte (67). Thus, present results show opposite effets of fenofirte tretment in virgin n pregnnt rts, the min responsile ftor for the ifferene eing oth the known enhne liver pility for VLDL triglyerie proution n reoun response to the rug in the ltter. This work ws supporte y grnts from the Fono e Investigión Snitri, Instituto e Slu Crlos III (98/0158 n 99/0205), Universi Sn Plo-CEU (10/99-00) of Spin, n the Europen Community (FATLINK, FAIR-CT ). An Sori ws reipient of postotorl fellowship from the Universi Nionl el Litorl, Snt Fe, Argentin. The exellent tehnil ssistne of Milgros Mornte n the eitoril help of Dr. Betriz Rmos re gretly ppreite. Mnusript reeive 10 April 2001, in revise form 20 July 2001, n in rerevise form 10 Otoer REFERENCES 1. Hvel, R MCollum Awr Leture, 1993: Triglyerie-rih lipoproteins n theroslerosis new perspetives. Am. J. Clin. Nutr. 59: Linenstrom, E., G. Boysen, n J. Nyoe Influene of totl holesterol, high ensity lipoprotein holesterol, n triglyeries on risk of ererovsulr isese: the Copenhgen City Hert stuy. Br. Me. J. 309: Zilversmit, D. B Atherogeni nture of triglyeries, postprnil lipiemi, n triglyerie-rih remnnt lipoproteins. Clin. Chem. 41: Wtts, G. F., n S. B. 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