Ir aq i J.Pharm.Sc i., Vol.15 (1 ) ,2006 53 Gender Differences of Serum Leptin Hormone Levels in Iraqi Population Be sma I.Mustafa Received 16-6-2004 Accepted 21-10-2004 ABSTRACT To e va luate and comp are se rum Leptin ho rmo ne leve l be twe en Iraqi male & female and the re la tion betwee n this ho rmo ne & BMI in the se two groups. A to ta l of 44 normal ma le & fema le sub je cts were inc luded in this s tudy { Gro up 1 : 2 2 fe male } , { Gro up 2 : 2 2 male} . Serum Leptin hormone ,BMI &fas ting b lo od gluc os e were mea sure d fo r bo th gro ups . Se rum Leptin le vel in gro up 1 wa s (8 .8 2 + 2.9 μg/L) where as in group 2 it was (4.65 + 3 .2 μ g/L) . The se c ha nge s were statistically significant. Fa sting blood gluco se lev els were technica lly within the no rma l va lue (1 16.43 + 3 .4 mg /dl) fo r group 1 & (11 8.52 + 2.9 mg /dl) for gro up 2 . BMI leve ls we re co mparab le in bo th gro ups d uring the stud y, with slight eleva tio n in group 1 [ 24 + 1.73 kg /m2 for group 1 & 23 + 1 .9 8 kg /m2fo r group 2 ] which within the ac ce ptable limit as far a s sa fe ty conce rn. Le ptin, a n ad ip ocyte -d eriv ed ho rmo ne know n to p la y an impo rtant role in bod y-weight regula tion, the re sult of this s tudy s hows that Lep tin is pres ented d ifferentially in Iraqi men a nd women ; in whic h it is significantly higher in wo men than in men s erum . Thes e obs erva tions are po te ntia lly impo rtant for the understanding o f diffe rence s be twe en me n and wo men in re gula tion o f food intake, we ight gain, and bod y fa t distrib utio n.The relation be tween Leptin & the BMI in ma le and fe male in this s tudy may ope n anothe r ap proac h fo r this ho rmo ne to be inv olved in –fertility & in pub erta l de velop ment. الخالصة  ن مون اللبتي هر ة رن مقا غرض قياس و مع نسبة كتلة ) Leptin(ل ر مذكو مون ال هر مستوى ال وعالقة ق را ي الع إلناث ف كور وا بين الذ ن BMIالجسم . في كال الجنسي سة را ملت الد 4ش موعتين 4 مج ى هم إل خص ٬ تم تقسيم ت : ش ة الثانية تضمنت 22األولى ضم موع را 22أنثى والمج اس . ذك تم قـي وعتين ـج ال الم حالة الصيام لك ي ر الدم ف سك وى ومست ن اللبتين ونسبة كتلة الجسم رمو ي . مستوى ه ون ـف هرمـ اس ال ائج قـي رت نـت أظهـ عة األولى مو 8المج .8 2  2 غرام 9. و كر ة . لتر /ماي عة الثاني جمو ون في الم رم ى اله كان مستو ن حي ي رو غرام  3.2 4.65ف / مايك ن الفر ة لتر ٬ حيث أ رة واضح معنويا بصو ة . ق كان من القيم الطبيعي كر الدم ض مستوى س ن كا 11: و 6.43  3.4 رام مل 100/ملغ عة األولى و مو 118للمج .5 2  2.9 غرام 10/مل ة 0 وعة الثاني جم ود .مل للم ع وج عتين م مو ة بين المج رب سم متقا ة الج كتل ة وكانت نسب الولى ة ا موع ع قليل في المج ل 2م/ كغم  1.73 24(ارتفا 23 1مقاـب .9 ة ) 2م/ كغـم 8 ة الثانـي موعـ مج ويات ) لل مسـت من ال ي ضـ ـه و ة عي . الطبي وزن الحسم وم بتنظيم هنية ليق مشتق من الخاليا الد ن مو هو هر ن اللبتين و ون اللبتين . ا رم مستوى ه ة ان هذه الدراس ج رت نتائ لقد اظه حيث ا عراقيين ٬ حة بين الرجال والنساء ال واض روقا هر ف جال يظ هو في الر ما وياته اعلى في النساء م ست مة . ن م مه حظات ان هذه المال ن في الجسم هو ع الد زي زن وتو وزيادة الو ي تنظيم تقبل الطعام ساء ف رجال والن مستوى . للمساعدة في فهم الفروقات بين ال ن عالقة بي ان ال ة ق هذه الدراس ي من الرجال والنساء ف جسم في كل ة كتلة ال سب ون ن مو خصوبة الهر ة مع درج ن رمو وى هذا اله ست ة عالقة م مهد لدراس د ي ال الجنسين غ في ك طور البلو . وت Dep artmen t of Clin ic al Labo rator y Sc ie nce s ,Colle ge o f Ph arma cy,Un iver sity of Baghdad , Baghdad –I raq . Ir aq i J.Pharm.Sc i., Vol.15 (1 ) ,2006 54 INTRODUCTION Leptin is a rece ntly disc ove re d ho rmo ne1 that is mainly s ynthes ized b y ad ip ose c ells and se creted into the bloo ds tream in a mounts re lativ e to the q ua ntity of bod y fa t. Plas ma le ptin leve ls in humans a re s trongly co rrelated with b ody ma ss inde x (BMI) and to tal fat ma ss (Figure 1) a nd are elev ated in obe se s ub je cts.2 Fig.1. S che matic re pre s e ntatio n of ce ntral and pe riphe ral ac tions o f le ptin on bo dy- we ight re g ulatio n and o n me tabolic and e ndoc rine para me te rs LEPR = le ptin re ce pto r; NPY = ne urope ptide Y; GLP -1 = gluc ago n-like pe ptide -1; MSH = me lanocy te -s timulating ho rmo ne ; LH = lute iniz ing hormone ; FS H = follicle - stimulating ho rmo ne ; ACTH = adre noco rtic otro pic hormone ; TSH = thyroid-s timula ting ho rmone . Adapte d and update d from Sc ott J. Ne w c ha pte r fo r the fa t co ntrolle r. Lep tin is tho ught to ha ve an "a dipos ta t" func tion;that is, it ac ts a s a signal informing the brain ab out the amo unt of fat stored in the bod y, through which the brain can regulate energy intake and e ne rgy exp enditure in orde r to keep bo dy weight constant (F igure 1 ).3,4 The re fo re , whe n lep tin le ve ls are low, ap petite will be s timula te d with limited use of energy, a nd w hen le ptin leve ls are high, ap petite is re duc ed a nd e ne rgy us e is stimulated . In rod ent e xp erime nts, leptin ad minis tration lead s to weight lo ss through re duc tion in food intake and increas ed e nergy exp end iture .5 In humans, howe ve r, le ptin le vels are ve ry high in o bes e peo ple , which sugge sts the exis tenc e of a lep tin – resis ta nce state , a nalogous to insulin-re sistance in type 2 diabe te s,4 the exac t me chanis ms for this re sistance are not c le ar yet. The lep tin rece ptors in brain is ma inly pre se nt in the hypo thalamus a nd choro id plexus,6 where fo od inta ke is regulated through the modula tion o f sev eral ne urotra ns mitter pathwa ys , s uch a s ne urope ptid e -Y, gluc agon- like pep tide -1 , a nd melanocyte -s timula ting hormone pathways . Le ptin may als o modula te pituitary se cretion of thyro id -s timula ting hormone, ad re no cortic otro pic hormone , and gonado trop ins,thus influencing indirectly the sec re tion of triio dothyro nine / thyroxine, cortis ol, and se x ho rmo nes , res pec tiv ely, a ll of which have e ffec ts on e nergy b alance7. MATERIALS and METHODS: Fo rty four a pp arently hea lthy male & fema le (a ge be tw een 2 3 and 3 5 ye ars) we re inc luded in this s tudy and co nse de red a s two group s to determine s erum le ptin co nc entratio n, BMI and fas ting blood gluco se for e ac h individua l . EXCLUSION CRITERIA: Any individua l that ha s hype rglyce mia or BMI > 25 wa s exclude d from this s tudy. METHODS Veno us bloo d s amp le s (6 ml) were ta ken from ea ch subjec t to mes ure serum leptin and fa sting blood gluco se lev els. The sa mple was transferre d into a clean p la in tube, le ft at roo m te mperature for 30 minutes for clotting, centrifuged , a nd then the serum fro m all blood samp le s was sep arated a nd s to re d at –20 C for sub se que nt study .  De ter mination of fasting blood gluc ose : Enzyma tic & c olorime tric me thod ( Gluc ose oxida se GOD/ Pe roxidas e POD ) , the princ iple of this me thod d epe nds on enzymatic determination of gluc os e ac co rd ing to the fo llowing rea ctio n9 : Glucos e + O2 + H2O GOD Gluconic acid + H2O2 2H2O2 +4 aminoantipyrine + p henol P OD q uino neimine + 4 H2 O Ir aq i J.Pharm.Sc i., Vol.15 (1 ) ,2006 55  Dete rmination of serum Leptin (ELISA): Enzyme immunoa ssa y (microtite r strip s) for the qua ntita tive de terminatio n o f Lep tin in human s erum. 10 STATISTICAL ANALYSIS: Mea sure ment of variables do ne by us ing numbers, pe rc enta ge , me ans +/- s tand ard de viatio n. Diffe re nc es b etwee n variables were mea sure d by us ing ANOVA tes t when it ne ede d. RESULT The s tudied v aria bles are lis te d in table 1. Serum lep tin ho rmo ne leve ls a re p re se nted in ta ble 2 (8.82 + 2.9 μg/L) in gro up 1 & (4 .6 5 + 3.2 μg/L) in gro up 2 ,The va riation be tween the tw o gro ups wa s statistic ally s ignific ant (P < 0.05 ) . Gender d ifferenc es be tw een the two groups in se rum Lep tin shown c learly in Figure 2,while fig 3 sho ws the difference in se rum lep tin leve ls betwee n Iraq i women and the referenc e va lues for fe mal s ub je cts. Table (1) The s tudie d va riable s are lis te d Table (2 )Serum le ptin ho rmo ne leve ls are prese nte d in table 2 Fig 2 : Ge nde r diffe re nces in Le ptin le ve l be twee n the two groups Fig 3 : Comparis on be twee n Ira qi (1)and othe r normal fe ma le ( 2) in Le ptin le ve ls CUSSION:DIS This stud y is one of the ne wes t stud ie s that discuss the variatio n in one of the ne wly disco vered hormones (Le ptin) be twe en male & fe male subjects in Iraq .The knowled ge of this re la tion is very impo rtant to und erstand vario us problems a ss ociated with ob esity, pub erty & infertility8. Fro m the re sults (tab le 2 &fig 2 )of this study serum Le ptin le vels are significa ntly highe r in women tha n in men (p< 0.05 ). This study which is do ne in Iraq to ev alua te the value s of le ptin ho rmo ne in norma l ma le & fema le sub je cts to b e c omp ared with the s tudy of Reitman & co workers the re sults s ho ws a highe r va lues in Iraq i fe male (Me an =8.82 ug/L) tha n other female v alue s (me an = 7 .4 Va riable s Group –1- (n=22 )fe ma le Group –2 - (n=2 2)male Age (ye ars) 27 .4 ± 4.18 30 .5 6 ± 3.26 BMI (K g/m2) 2 4 ± 1 .73 23 ± 1.98 F asting b lo od gluco se ( mg /d l) 3.4 +116.43 2.9 +1 18 .52 Group –1- (n=22)fe male Group –2- (n=22)male Le ptin hormone (μg/L) 8.82 ± 2.9 4.65 ± 3.2 Re fe rence Value 3.2 +7.4 2.8+ 3.9 0 1 2 3 4 5 6 7 8 9 10 1 2 L e p ti n L e v e l (u g /L ) 0 1 2 3 4 5 6 7 8 Serum Leptin (Ug /L) 1 2 Groups Ir aq i J.Pharm.Sc i., Vol.15 (1 ) ,2006 56 ug/L) 3; Thes e difference s may be d ue to the fa ct tha t Iraq i wome n hav e highe r fa t mas s than the o ther women. A co mpa ra ble res ults was found in male with different s tudies . At firs t, such diffe re nc es be tween Iraqi male & fe male subjects were thought to re flec t the difference s in b ody comp os itio n be twe en me n and women. Wome n in general have a higher pe rc entage o f fa t mas s for the s ame bod y weight or BMI. Sinc e le ptin reflec ts ma inly the amo unt of bod y fa t, this see med to be a lo gical explana tion for the ob se rv ed gende r difference s11. Ho weve r, the se gender difference s a nd their relations hip to bod y co mpos ition we re e xamined ,and lep tin lev els were found to be s ignific antly higher in wome n with c ompa ra ble BMI or fa t ma ss. A s eco nd exp la na tion was thought in the difference s in fa t distrib utio n be twe en me n and wome n. Women ge nerally hav e more pe riphe ra l fat a cc umulation (es pec ia lly at the le ve l of the hips ), wherea s obe se me n hav e more abd omina l (e spe cially v is ceral) fat. It was shown in s ev eral in v itro s tudies that subcuta ne ous adipo cytes pro duce more leptin than fat c ells de rive d from the ome ntal fat de pot; this is es pec ia lly true in wo men.12,13 In vivo s tudies a ls o showed that lep tin lev els ha d a s tro nge r ass oc ia tion with pe ripheral14 or subcuta ne ous fa t than with intra - ab domina l or visc eral fa t, as meas ured b y co mpute d to mogra phy s ca n.15 Thus, the fac t tha t wome n ha ve more sub cuta ne ous fat, which s ec re te s more leptin, s ee ms an a dd itiona l reas on for the higher lep tin leve ls in wo men. Howe ve r, eve n after co rrec ting for the amount of subcuta ne ous fa t, le ptin le vels a re s till found to be s ignifica ntly highe r in wome n.10 CONCLUSION The res ults of this s tudy are p otentially importa nt fo r the understanding o f difference s be twe en me n and women in regulatio n of foo d intake , weight gain, a nd bo dy fat d is tribution; but sinc e these d ifferenc es in bod y co mpos ition b etween men a nd wome n may not be the o nly re as on to explain the diffe re nce s in le ptin lev els c omp le te ly, othe r fa ctors must play a role, like Ste ro id hormones b ut the exact mec hanism o r inte ra ction is not ye t known. The se findings se em to indicate that this re ce ntly d is co vered hormone ma y play a role obe sity, infe rtility & o ther d is ea se s ta te s. REFERENCES 1. Zhang Y, P ro enc a R, Ma ffei M, et a l, P ositio na l cloning of the mous e ob ese gene a nd its huma n homologue . Nature; . 199 4 3 72,42 5-431 . 2. 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