Effect of dietary fat type on plasma lipid profile and leptin concentration in rats fed on high-sucrose diets

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1 ORIGINAL ARTICLE Journl of Pre-Clinicl nd Clinicl Reserch, 2010, Vol 4, No 1, Effect of dietry ft type on plsm lipid profile nd leptin concentrtion in rts fed on high-sucrose diets Agt Krwczyńsk, Ktrzyn Okręglick, Elżiet Olczk, Jonn Gromdzk-Ostrowsk Division of Nutrition Physiology, Deprtment of Dietetics, Fculty of Humn Nutrition nd Consumer Science, Wrsw University of Life Sciences SGGW, Wrsw, Polnd Astrct: The im of the study ws to investigte the effect of different dietry ft type on plsm leptin concentrtion nd lipid profile in mle Wistr rts fed normo-ft, normo-protein, high-sucrose (5, 19 nd 35 % w/w, respectively) diets. The experiment ws conducted on 21 dult mle rts (260 ± 20g) fed diets with different ft sources: lrd (L), grpeseed oil (G) nd flxseed oil (F). Rdioimmunossy ws used to mesure leptin concentrtion nd enzymticcolorimetric methods to estimte lipid profile. Totl cholesterol (TC), high density lipoprotein cholesterol (HDL) nd triglycerides (TG) plsm concentrtions were higher in group L nd G thn F (ANOVA p 0,01; p 0,05 nd p 0,005, respectively), wheres low density lipoprotein cholesterol (LDL) level ws higher in group L thn G nd F (ANOVA p 0,05). Leptin concentrtion ws significntly higher in group L in comprison to F (ANOVA p 0,04). Significnt positive correltions were found etween plsm leptin concentrtion nd finl ody weight, TC, HDL nd TG (r = 0,64, p 0,006; r=0,72, p 0,002; r=0,69, p 0,003; r=0,86, p 0,00004 respectively). It cn e oserved tht flxseed oil rich in n-3 polyunsturted ftty cids (PUFA) profitly influenced not only lipid profile lowering its prmeters ut lso reduced leptin concentrtion which cn suggest pproximte lipidogenic potentil of oth grpeseed oil (rich in PUFA n-6) nd lrd (rich in monounsturted nd sturted ftty cids). The results provided evidence tht dietry ft type cn influence crdiovsculr disese risk prmeters when high-sucrose diet is consumed. Key words: diet, flxseed oil, grpeseed oil, lrd, leptin, lipid profile, rt, sucrose INTRODUCTION When in 1994 Zhn nd colleges discovered leptin, its role ws limited to the regultion of food consumption nd energy expenditure [1]. This 167-mino cid polypeptide produced minly y dipocytes (white dipose tissue) in direct proportion to ody ft stores ws sid to ct on hypothlmic centres nd peripherl orgns, dipose tissue, liver, muscles nd pncres. But further investigtions reveled the presence of leptin receptors (OB-R) lso in tissues not connected with mcronutrients metolism or energy lnce. They were found in reproductive s well s in crdiovsculr systems [2]. Cusing endothelil dysfunction, stimulting inflmmtory rection, pltelet ggregtion nd provoking migrtion nd prolifertion of vsculr smooth muscle cells, leptin is sid to exert proterogenic effects [2, 3]. Pthologicl ctions of leptin in crdiovsculr system ensue from leptin resistnce which is ssocited with oesity. This highly incresed plsm leptin concentrtion is sid to e new fctor of crdiovsculr pthology [4]. The connections etween leptin nd diet re generlly known. Long consumption of high-ft diet seems to e one of the crucil cuses of leptin resistnce [5]. Also, the insulin-stimulting influence on leptin secretion shows link etween crohydrtes consumption nd leptin gene (o gene) expression [6, 7]. Moreover, dietry ftty cid profile s Corresponding uthor: Dr. Agt Krwczyńsk, Division of Nutrition Physiology, Deprtment of Dietetics, Fculty of Humn Nutrition nd Consumer Science, Wrsw University of Life Sciences - SGGW, Nowoursynowsk 159c, Wrsw, Polnd. E-mil: gt_krwczynsk@sggw.pl Received: 14 April 2010; ccepted: 23 June 2010 well s dietry ft nd crohydrtes levels ws found to e fctor which ffects endocrine function of dipose tissue [8]. However, there is discrepncy etween the results of effects exerted y sturted, monounsturted nd polyunsturted ftty cids (SFA, MUFA, PUFA, respectively) on leptin secretion; therefore, more reserch is needed. A second ut etter known nd investigted diet-dependent fctor of crdiovsculr pthology is plsm lipid profile. It is well documented tht high consumption of sucrose rises triglycerides (TG) plsm concentrtion [9]. Moreover, elevted plsm levels of totl nd in prticulr low-density lipoprotein (LDL) cholesterol which, like TG re ssocited with n incresed risk of coronry events, re positively correlted with SFA intke. On the other hnd, consumption of dietry ft rich in PUFA hs hypocholesterolemic effect, with differences etween n-6 nd 3, s s reviewed y Poli et l. [10]. It hs een shown tht long chin n-3 PUFAs (eicospentenoic nd docoshexenoic cids) found in fish oils or (α-linolenic cid) in flxseed oil not only decrese plsm LDL nd increse HDL levels, ut lso modulte the inflmmtion process preferring production of the less inflmmtory series 3 eicosnoides nd 5 series of leukotriens [11,12]. Endothelium relxtion is lso intensified y stimultion of production of nitric oxide y omeg-3 [13]. On the other hnd, n-6 ftty cids re the precursors of proinflmmtion nd pro-greggtion series 2 eicosnoides (such s thromoxne 2 TXA 2 ) which re minly produced from rchidonic cid y enzyme cyclooxygense 2 (COX-2) [14]. In the light of the sid rtio of n-6 to n-3 ftty cids, this hs een suggested y some uthors to e prticulrly importnt [15].

2 58 Ft type effect on plsm lipids nd leptin in rts Agt Krwczyńsk et l As cn e seen ove there is very close connection etween leptin, plsm lipids nd diet composition. Becuse there re mny rticles which focus on either crohydrtes or ft influences on leptin homeostsis, we decided to conduct experiments which would connect these prmeters. We therefore proposed the hypothesis tht ny ltertions in plsm leptin nd lipids concentrtion would e oserved s the effects of mnipultions with dietry ft type in rts fed high-sucrose diet. MATERIALS AND METHODS Animls, diets nd experimentl design. The experiment, pproved y the Third Locl Animl Cre nd Use Committee in Wrsw, ws conducted on 21 mle dult Wistr rts with initil ody weights of 260 ± 20g. The initil ody weights were mesured fter week of cclimtiztion during which nimls were fed stndrd rodents feed (Lofeed H, Andrzej Morwski Feed Production Plnt, Kcyni, Polnd). Rts were kept individully in polypropylene cges in stle environmentl conditions (temperture 22 C; humidity 50%; 12:12 light:drk cycle). They were given free ccess to food nd wter. After one-week dpttion period, the nimls were divided into three experimentl groups receiving highsucrose (35% w/w), normo-ft (5% w/w) nd normo-protein (19% w/w) semi-synthetic diets sed on dt providedy Mert et l. [16] (T. 1), ut with different types of dietry ft source: F flxseed oil (rich in n-3 PUFAs), G grpe seed oil (rich in n-6 PUFAs) nd L lrd (rich in oth MUFAs nd SFAs). Ftty cids content in ech dietry ft ws ssyed y GC nlysis performed t the Anliticl Centre of SGGW (Wrsw, Polnd) (T. 2.). The nimls styed on the experimentl diets for 3 weeks. Tle 1 Component Composition of diet. Amount [g/kg] Sucrose 350 Whet strch Csein 190 Ft 50 Minerl Mixture 50 Potto strch 36.7 Vitmin mixture 10 DL-Methionine 3 Choline chloride 3 Minerl mix composition (AIN-93M-MX Minerl Mix) ccording to Reeves P.G. [17] (in 100g of mix): CCO 3 35,7g, K 2 HPO 4 25g, NCl 7.4g, K 2 SO g, C 6 H 5 K 3 O 7 *H 2 O 2.8g, MgO 2,4g, C 6 H 5 FeO 7 606mg, ZnCO 3 165mg, N 2 SiO 3 *9H 2 O 145mg, MnCO 3 63mg, CuCO 3 30mg, CrK(SO 4 ) 2 *12H 2 O 27.5mg, H 3 BO mg, NF 6.35mg, NiCO mg, Li 2 CO mg, N 2 SeO mg, KIO 3 1mg, (NH 4 ) 6 Mo 7 O 24 *4H 2 O 0.795mg, NH 4 VO mg, powder sucrose up to 100g of mix. Vitmin mix composition (AIN-93-VX Vitmin Mix) ccording to certificte of producer MP Biomedicls (USA) (%): Nicotinic Acid 3,00, D-Clcium Pntothente 1.60, Pyridoxine HCl 0.70, Thimine HCl 0.60, Rioflvin 0.60, Folic Acid 0.20, D-Biotin 0.02, Vitmin B 12 (0.1% triturted in mnnitol) 2.50, Alph Tocopherol Powder (250 U/gm) 30,00, Vitmin A Plmitte (250,000 U/gm) 1,60, Vitmin D 3 (400,000 U/gm) 0.25, Phylloquinone 0.075, Powdered Sucrose 959,655 Food intke ws quntified y monitoring the mount of consumed diet ech dy through the whole experimentl period. Also, the nimls ody weight ws monitored once ech week. After 12 hours of food deprivtion, the rts were nesthetized with Thiopentl (120 mg/kg ody weight) nd completely led Tle 2 Content of ftty cids in dietry ft sources. Ftty AIDS weight % of ftty cids in dietry fts Numer of Type Flxseed Grpeseed Lrd cron toms Oil Oil nd doule ounds C10:0 SFA 0.12 C12:0 SFA 0.11 C14:0 SFA C14:1 (cis-9) MUFA n C15:0 SFA 0.1 C16:0 SFA C16:1 (cis-9) MUFA n C17:0 SFA C17:1 (cis-10) MUFA n C18:0 SFA C18:1 (trns-9) MUFA n C18:1 (cis-9) MUFA n C18:2 (ll-trns-9,12) PUFA n C18:2 (ll-cis-9,12) PUFA n C18:3 (ll-cis-6,9,12) PUFA n C18:3 (ll-cis-9,12,15) PUFA n C20:0 SFA C20:1 (cis-11) MUFA n C20:2 (ll-cis-11,14) PUFA n C20:3 (ll-cis-8,11,14) PUFA n C20:3 (ll-cis-11,14,17) PUFA n C20:4 (ll-cis-5,8,11,14) PUFA n C22:0 SFA C24:0 SFA Totl SFA Totl MUFA Totl PUFA Totl PUFA n Totl PUFA n SFA sturted ftty cids, MUFA monounsturted ftty cids, PUFA polyunsturted ftty cids. y crdic puncture. Blood ws centrifuged nd plsm stored t -20 C until further nlysis. Bodies nd orgns were used in different nlyses. Leptin rdioimmunologicl ssy. Plsm leptin concentrtion ws mesured using Rt Leptin RIA Kit (Ct. # RL-83K, LINCO Reserch, USA). The intr- nd inter-ssy precision ws 2.4% nd 4.8%, respectively. Sensitivity of test ws 0.5ng/ml. The ssy ws conducted ccording to the kit mnul. Leptin concentrtion ws expressed s ng per ml of plsm. Plsm lipid profile colorimetric ssys. Concentrtions of plsm totl cholesterol (TC), triglycerides (TG) nd highdensity lipoprotein cholesterol (HDL) were mesured using enzymtic-colorimetric methods. Kits contining redy to use liquid regents were purchsed from PTH Hydrex (Wrsw, Polnd). The nlyses were conducted ccording to kit mnuls. Concentrtions were expressed s mg per 100ml of plsm. Journl of Pre-Clinicl nd Clinicl Reserch, 2010, Vol 4, No 1

3 Ft type effect on plsm lipids nd leptin in rts Agt Krwczyńsk et l 59 Concentrtion of low-density lipoprotein cholesterol (LDL) ws clculted from Friedewld s formul: LDL = TC HDL TG/5 [18]. Sttisticl nlysis. Sttisticl nlysis ws undertken y STATISTICA v (SttSoft Polsk Sp z o.o., Crcow, Polnd). Simple regression nd one-wy vrince nlysis ANOVA followed y post-hoc NIR Fisher s test were clculted. Differences with vlue of p 0.05 were considered significnt. Before conducting ANOVA tests, two ssumptions were tested: norml distriution nd homogeneity of vrinces. All dt re showed s mens ± SD. RESULTS Finl ody weight nd food intke. There were no significnt differences in finl ody weight nd ody mss gin per dy (ANOVA, NS) (T. 3.). Diet nd totl ft intke were lso not sttisticlly different. However, ftty cids consumption ws highly differentited etween dietry groups (ANOVA for consumption of SFA, MUFA, PUFA, n-6 nd n-3, p 0,00 for ech) (T. 4.) in ccordnce with ftty cids content in dietry ft source. As this stems from the ftty cids composition of used dietry fts, the highest consumption of SFA nd MUFA ws in group L (NIR, L vs. F nd G p 0,00), PUFA n-3 in group F (NIR, F vs. G nd L p 0,00) nd PUFA n-6 in group G (NIR, G vs. F nd L p 0,00). Tle 3 Initil weight, finl weight, ody mss gin, nd food intke (men ± SD). Diet n Initil ody Finl ody Body mss Food intke Group weight, [g] weight, [g] gin [g/d] [g/d/100g ody mss] F ± ± ± ± 0.4 G ± ± ± ± 0.3 L ± 15, ± ± ± 0.3 F diet with flxseed oil; G diet with grpeseed oil; L diet with lrd; ANOVA NS for ech prmeter. Tle 4 Intke of totl ft, SFA, MUFA, PUFA, n-3, n-6 [g/d/100g ody mss]. Diet Totl SFA MUFA PUFA n-3 n-6 Group ft F ± ± 0.064± 0.209± 0.168± 0.040± G ± 0.031± 0.052± 0.225± 0.000± 0.224± 0, c L ± 0.127± 0.146± 0.036± 0.003± 0.033± c F diet with flxseed oil; G diet with grpeseed oil; L diet with lrd; SFA - sturted ftty cids; MUFA monounsturted ftty cids; PUFA polyunsturted ftty cids;,,c - indicte vlues significntly different (p 0.05) within columns. Plsm lipid profile. Dietry ft type significntly ffected TC, HDL, LDL nd TG (ANOVA p 0.01; p 0.05; p 0.02 nd p 0.005, respectively). As shown in Fig. 1, higher TC concentrtions were found in groups G nd L thn in F (NIR, G vs. F p 0.01; L vs. F p 0.005). Similr results for plsm TG (NIR, G vs. F p 0.002; L vs. F p 0.02) nd HDL (NIR, G vs. F p 0.02; L vs. F p 0.05) concentrtions were shown. Concentrtion [mg/dl] Figure 1 Plsm concentrtion of totl cholesterol (TC), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), triglycerides (TG) [mg/dl]; F diet with flxseed oil; G diet with grpeseed oil; L diet with lrd;, indicte vlues significntly different (p 0,05). Plsm leptin concentrtion [ng/ml] ,5 2,0 1,5 1,0 0,5 0,0 Figure 2 Plsm leptin concentrtion [ng/ml]; F diet with flxseed oil; G diet with grpeseed oil; L diet with lrd;, indicte vlues significntly different (p 0,05). LDL concentrtion ws not significntly different in groups F nd G, ut we oserved sttisticlly higher LDL vlue in group L (NIR, L vs. F p 0.01; L vs. G p 0.04). Plsm leptin concentrtion. Plsm leptin concentrtion differed significntly etween the groups fed different dietry ft sources (ANOVA p 0.04) with higher vlue in group L compred to group F (NIR, L vs. F p 0.02). There were no significnt differences etween group G nd the other groups (Fig. 2.). As clculted y regression nlysis, positive correltions etween plsm leptin concentrtion nd finl ody weight, TC, HDL s well s TG (r = 0.64, p 0.006; r=0.72, p 0.002; r=0.69, p 0.003; r=0.86, p , respectively) were found. DISSCUSION TC HDL LDL TG Diet is one of the most importnt fctors which exerts n influence on ody mss, lipid plsm profile nd the circultion of hormones. It is generlly known tht high-sucrose diet F G L Groups F G L Journl of Pre-Clinicl nd Clinicl Reserch, 2010, Vol 4, No 1

4 60 Ft type effect on plsm lipids nd leptin in rts Agt Krwczyńsk et l not only increses ody mss gin nd plsm lipid profile, ut lso influences leptin secretion y insulin chnges. The im of this study ws to confirm the hypothesis tht different compositions of ftty cids in diet cn modulte lterntions developed y high sucrose intke. Body weight nd diet consumption. As we oserved, diets sed on high mount of sucrose (35% w/w) nd the norml level (5% w/w) of ll three types of dietry ft (lrd, grpeseed oil, flxseed oil) were well tolerted. The prticulr ft contined in diet did not influence overll consumption, nd the nimls gined weight with no differences etween groups. Similrly, no effect of the type of dietry ft on ody weight gin ws oserved in the experiment conducted on mle Wistr rts fed diets with 10% (w/w) of plm, rpeseed nd sunflower oil nd lrd [19]. The sme results were lso otined y Hynes et l. [20] who did not oserve ny effect of dietry ft type on these prmeters in mle Sprgue-Dwley rts fed high-ft diets (20% w/w) contining fish oil, sfflower oil or eef tllow s ft source. However, Stchoń et l. [21] oserved tht rts fed diet with 40% (w/w) of rpeseed oil (rich in MUFA) s source of dietry ft, gined less weight thn nimls fed sunflower or plm oil, or even lrd diets contining lrd. It seems tht the dietry ft type cn ffect ody mss gin only in nimls fed rich-ft diets which promote ft deposition nd higher ody weight gin. Plsm lipid profile. It is generlly known tht highsucrose diet modifies triglycerides nd cholesterol plsm concentrtions. In the experiment conducted y Yng et l. [22], high-sucrose diet cused increses in oth stted prmeters, s well s heptic triglycerides content. The sme oservtion, together with HDL increse, ws seen y Ryu et l. [23]. Becuse in our experiment sttisticlly importnt differences were oserved etween nimls fed high-sucrose diets contining lrd or grpeseed oil nd flxseed oil, we hypothesize tht sucrose-rich diet effects the plsm lipid profile, depending on the dietry ftty cids composition. This hypothesis might e confirmed y the results of Cintr et l. [24]. In their experiment, rts fed diet with flxseed hd lower plsm cholesterol concentrtion in comprison to rts fed diet rich in SFA from chicken skin. The sme effect ws found y Tkeuchi et l. [25] who stted tht triglycerides, HDL nd totl cholesterol levels were significntly lower in rts fed diets with flxseed or srdine oil in comprison to rts fed diet with triplmitin, tristerin nd corn oil mixture. The results of Murno et l. [26], conducted on Sprgue-Dwley mle rts, lso indicted tht n intke of lrd enriched y linolenic cid suppresses the ctivity of heptic ftty cids synthse (FAS), nd this suppression my led to the reduction of the plsm triglycerides concentrtion. Reserchers hve pointed out tht PUFAs hve influence on FAS gene expression y suppression of Sterol Regultory Element-Binding (SREBP) 1c [27]. On the other hnd, it hs een oserved tht PUFAs ctivte Peroxisome Prolifertors- Activted Receptor α (PPARα), which leds to the induction of crnitine plmitoyltrnsferse which regulte ftty cids oxidtion [28]. Thus, higher ctivity of β-oxidtion nd the lower concentrtion of plsm triglycerides in nimls with high linolenic cid intke cn e stted. In nother study, Morgdo et l. [29] found tht rts fed high mounts of n-3 PUFA from fish oil hd significntly lower plsm totl nd HDL cholesterol. They stted tht n n-3 PUFA-rich diet significntly chnged the heptic memrnes n-3/n-6 ftty cids rtio, which in turn cused plsm cholesterol reduction. They did not oserve ny modifiction in the expression levels of lecithin cholesterol cylotrnsferse, heptic lipse, po A-I nd po E mrna, which my suggest tht reverse cholesterol trnsport is not chnged y n-3 PUFAs. However, n-3 PUFAs from fish (eicospentenoic nd docoshexenoic cid EPA nd DHA) differ the from flxseed oil PUFAs (α-linolenic cid - ALA) which ws used in our study. It therefore seems importnt to refer to the study y Riediger et l. [30], the purpose of which ws to investigte the crdiovsculr enefits of oth these oils. Reserchers hve stted tht plsm totl cholesterol levels were reduced in oth fish nd flx groups y 27% nd 36%, respectively, compred to controls t the endpoint fter 16 weeks of experiments. The mechnism of such ctions hs een proposed y Du et l. [31] who suggested decrese in HMG-CoA reductse ctivity in high DHA nd ALA groups. In our study, rts fed diet rich in oth n-6 PUFA (grpeseed oil) or SFA nd MUFA (lrd) showed higher concentrtion of cholesterol nd triglycerides thn nimls fed diet rich in α-linolenic cid (flxseed oil). It seems pproprite to stte tht ll mechnisms mentioned ove could e involved in lowering the properties of flxseed oil on plsm lipid profile, s lso seen in our study. But we cnnot omit the suggestion mde y Cintr et l [24], tht flxseeds contin dietry fire nd lignns vitl for the orgnism, which cn lso decrese the serum cholesterol level. However, compring the oil otined from flxseeds in the cold-pressed process with its whole seeds, the content of lignns nd fires is much higher in the seeds [personl communiction]. On the North Americn nd New Zelnd mrkets, cold-pressed flxseed oil is commercilly ville in low nd high-lignn forms [32], depending on whether the oil ws produced from whole seeds or only from husks. In our cse, the oil ws produced from whole seeds nd we cn ssume tht the content of lignns ws rther low. Tking this into considertion, this seems tht minly due to the n-3 ftty cids content nd only slightly to lignns, nd the presence of fires in diet rich in flxseed oil is the most efficient in oth decresing lood cholesterol nd triglycerides, or protecting the liver prenchym. Plsm leptin concentrtion. Mel composition nd nutrients intke might ffect plsm leptin concentrtion. This cn e modified minly y energy-yielding nutrients such s dietry crohydrtes or ft. Peyron-Cso et l. [33] found tht oth 3- nd 6-week feeding with sucrose-rich diets (57.5%) induced prllel increse in oth plsm leptin level nd diposity. It hs een demonstrted tht glucose metolism is the primry determinnt of leptin secretion rther thn insulin concentrtion [34]. Thus, the ility of high-crohydrte diet to induce n increse in the leptin peripherl level my e medited y its insulin response, which promotes glucose uptke in dipose tissue [6]. Moreover, s reviewed y Orr nd Dvy [6], high-crohydrte, low-ft mels produce higher leptin concentrtion when compred to high-ft, low-crohydrte mels. Knowing tht sucrose-enriched diet rised the leptin level, we wnted to check the effects of different dietry ftty cids on the plsm leptin level in rts consuming high-sucrose (35%) ut normo-ft (5%) diet. Generlly, the studies focused on peripherl leptin level nd dietry ft re sed on high-ft diets with modifiction Journl of Pre-Clinicl nd Clinicl Reserch, 2010, Vol 4, No 1

5 Ft type effect on plsm lipids nd leptin in rts Agt Krwczyńsk et l 61 of used ft source. It hs een shown tht high-ft diet incresed o gene expression in dipose tissue of mle Sprgue- Dwley rts [35], cusing the development of leptin resistnce. However, further investigtions demonstrted tht different dietry ft sources cn modulte this hormone concentrtion, depending on their ftty cids composition. A previous study conducted in our deprtment y Stchoń et l. [21] showed tht consumption of high-ft diet (40% w/w) with sunflower oil rich in n-6 ftty cids s source of dietry ft cused the highest increse in plsm leptin concentrtion in Wistr mle rts, in comprison with the consumption of diets with rpeseed oil, plm oil nd lrd. The influence of dietry ft type ws lso oserved y Wng et l. [36], who found in mice tht 7-week consumption of diet rich in mixture of sfflower (n-6) nd eef tllow (SPA nd MUFA) resulted in higher plsm leptin concentrtion, compred to consumption of diets rich in n-3 from fish oil or n-6 from sfflower lone. Also, Ukropec et l. [37] found tht high-ft diet contining 10% n-3 PUFA nd 18% SFA, in comprison with high-ft diet contining 28% SFA, lowered plsm leptin level nd leptin mrna in dipose tissue. Our results lso showed tht mnipultion with ftty cids composition cn modify leptin level, even if the diet is high-sucrose nd normo-ft. We oserved tht incresed n-3 ftty cids intke lowered leptin level in comprison to high SFA, ut not n-6 intke. PPARs nd SREBP-1 hs een tried to explin the connection etween ftty cids nd leptin metolism. Reselnd et l. [38] oserved tht n-3 PUFAs decrese leptin gene expression y mechnisms ssocited with reduced PPARγ nd SREBP-1 gene expression. The sme issue ws studied y De Vos et l. [39]. They lso found tht in rts, oth lignds of PPARγ thizolidinedione BRL nd ftty cids (EPA nd DHA given with diet enriched in fish oil) cused decrese of o mrna expression y 40% nd 33%, respectively. In view of the sence of consensus of PPRE (PPAR response element) in the o gene, the uthors find it importnt to identify the moleculr mechnism of PPARγ which my e connected with positive modultors of o trnscription, such s C/EBPα (CCAAT/enhncer inding protein α) or Sp1 trnscription fctor. But much still remins unknown out the mechnisms involved in ftty cids control of leptin metolism, nd more reserch is needed. In our study we lso found significnt positive correltions etween the plsm leptin concentrtion nd plsm lipid prmeters. Especilly interesting seems to e correltion etween leptin nd TG concentrtions. As stted y Bnks et l. [40], there is strict reltionship etween TG nd leptin trnsport cross the lood-rin rrier (BBB). They showed tht diet with milk (s source of TG) immeditely inhiited leptin trnsport in vivo, in vitro nd in situ models of the BBB. Thus, it cn e stted tht diet rich in sucrose cusing n increse of TG, slows down leptin trnsport through BBB nd increses leptin serum concentrtion. Any fctor which reverses the sucrose effects lowering TG (e. g. flxseed oil used in our experiment), which would t the sme time decrese the leptin level ccelerting its trnsport to the rin. To summrize, the results of our study indicte tht plsm leptin nd lipids concentrtion in rts fed high-sucrose diets were ffected y the dietry ft type, with the lowest vlue in nimls fed flxseed oil s dietry ft source. CONCLUSIONS 1. The dietry ft type supplied is n importnt fctor in plsm leptin nd lipoprotein level regultion when highsucrose diet is consumed. 2. 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