Gender Differences of Serum Leptin Hormone Levels in Iraqi Population

To evaluate and compare serum Leptin hormone level between Iraqi male & female and the relation between this hormone & BMI in these two groups. A total of 44 normal male & female subjects were included in this study {Group 1 : 22 female } , { Group 2 : 22 male}. Serum Leptin hormone ,BMI &fasting blood glucose were measured for both groups. Serum Leptin level in group 1 was (8.82 + 2.9 μg/L) where as in group 2 it was (4.65 + 3.2 μg/L) . These changes were statistically significant. Fasting blood glucose levels were technically within the normal value (116.43 + 3.4mg /dl) for group 1 & (118.52 + 2.9 mg /dl) for group 2 . BMI levels were comparable in both groups during the study, with slight elevation in group 1 [ 24 + 1.73 kg /m for group 1 & 23 + 1.98 kg /mfor group 2 ] which within the acceptable limit as far as safety concern. Leptin, an adipocyte-derived hormone known to play an important role in body-weight regulation, the result of this study shows that Leptin is presented differentially in Iraqi men and women ; in which it is significantly higher in women than in men serum . These observations are potentially important for the understanding of differences between men and women in regulation of food intake, weight gain, and body fat distribution.The relation between Leptin & the BMI in male and female in this study may open another approach for this hormone to be involved in –fertility & in pubertal development. ةصلاخلا ن يتبللا نومره ة نراقمو سايق ضرغل ) Leptin ( ةلتك ةبسن عم روكذملا نومرهلا ىوتسم ةقلاعو ق ارعلا يف ثانلإاو روكذلا نيب مسجلا BMI ن يسنجلا لاك يف . ةس اردلا تلمش 44 نيتعومجم ىلإ مهميسقت مت ٬ صخش : تمض ىلولأا 22 تنمضت ةيناثلا ةعومجملاو ىثنأ 22 اركذ . سا يـق مت نيتعو جـملا لاكل مايصلا ةلاح يف مدلا ركس ىوتسمو مسجلا ةلتك ةبسنو نيتبللا نومره ىوتسم . ي فـ نو ـمرهلا سا يـق جئا تـن ترـهظأ ىلولأا ةعومجملا 8.82  2.9 مارغ وركيام / رتل . ة يناثلا ةعومجملا يف نومرهلا ىوتسم ناك ن يح يف 4.65  3.2 مارغ وركيام / رفلا ن أ ثيح ٬ رتل ةحضاو ةروصب ايونعم ناك ق . ة يعيبطلا ميقلا نمض مدلا ركس ىوتسم ن اكو : 116.43  3.4 مارغلم / 100 لم و ىلولأا ةعومجملل 118.52  2.9 مارغلم / 100 ة يناثلا ةعومجملل لم . دوجو عم نيتعومجملا نيب ة براقتم مسجلا ة لتك ة بسن تناكو ىلولاا ةعومجملا يف ليلق عافترا ) 24  1.73 مغك / م 2 ل بـاقم 23  1.98 مـغك / م 2 ( ة يـناثلا ة ـعومجملل ( تايو تـسملا نمـض ي هـو ة يعيبطلا . مسحلا نزو ميظنتب موقيل ةينهدلا ايلاخلا نم قتشم نومره وهو نيتبللا ن ا . نيتبللا نومره ىوتسم نا ةساردلا هذه ج ئاتن ترهظا دقل ا ثيح ٬ نييقارعلا ءاسنلاو لاجرلا نيب ةحضاو اقورف رهظي لاجرلا يف وه امم ءاسنلا يف ىلعا هتايو تسم ن . ةمهم تاظحلاملا هذه نا مسجلا يف نوهدلا عيزوتو نزولا ةدايزو ماعطلا لبقت ميظنت يف ءاس نلاو لاجرلا نيب تاقورفلا مهف يف ةدعاسملل . ىوتسم ن يب ةقلاعلا نا ق ةساردلا هذه يف ءاسنلاو لاجرلا نم لك يف مسجلا ةلتك ة بس نو نومرهلا ةبوصخ ةجرد عم نومرهلا اذه ىوتسم ةقلاع ةساردل دهمي د نيسنجلا لاك يف غولبلا روطتو . Department of Clinical Laboratory Sciences ,College of Pharmacy,University of Baghdad , Baghdad –Iraq . Iraqi J.Pharm.Sci., Vol.15 (1) ,2006 54


INTRODUCTION
Leptin is a recently discovered hormone 1 that is mainly synthesized by adipose cells and secreted into the bloodstream in amounts relative to the quantity of body fat. Plasma leptin levels in humans are strongly correlated with body mass index (BMI) and total fat mass ( Figure 1) and are elevated in obese subjects. 2 Leptin is thought to have an "adipostat" function;that is, it acts as a signal informing the brain about the amount of fat stored in the body, through which the brain can regulate energy intake and energy expenditure in order to keep body weight constant ( Figure 1). 3,4 Therefore , when leptin levels are low, appetite will be stimulated with limited use of energy, and w hen leptin levels are high, appetite is reduced and energy use is stimulated.
In rodent experiments, leptin administration leads to weight loss through reduction in food intake and increased energy expenditure. 5 In humans, however, leptin levels are very high in obese people , which suggests the existence of a leptinresistance state , analogous to insulin-resistance in type 2 diabetes, 4 the exact mechanisms for this resistance are not clear yet. The leptin receptors in brain is mainly present in the hypothalamus and choroid plexus, 6 where food intake is regulated through the modulation of several neurotransmitter pathways, such as neuropeptide -Y, glucagonlike peptide-1, and melanocyte-stimulating hormone pathways. Leptin may also modulate pituitary secretion of thyroid-stimulating hormone, adrenocorticotropic hormone, and gonadotropins,thus influencing indirectly the secretion of triiodothyronine / thyroxine, cortisol, and sex hormones, respectively, all of which have effects on energy balance 7 .

MATERIALS and METHODS:
Forty four apparently healthy male & female (age betw een 23 and 35 years) were included in this study and consedered as two groups to determine serum leptin concentration, BMI and fasting blood glucose for each individual .

EXCLUSION CRITERIA:
Any individual that has hyperglycemia or BMI > 25 was excluded from this study.

METHODS
Venous blood samples (6 ml) were taken from each subject to mesure serum leptin and fasting blood glucose levels. The sample was transferred into a clean plain tube, left at room temperature for 30 minutes for clotting, centrifuged, and then the serum from all blood samples was separated and stored at -20 C for subsequent study .

Determination of serum Leptin (ELISA):
Enzyme immunoassay (microtiter strips) for the quantitative determination of Leptin in human serum. 10

STATISTICAL ANALYSIS:
Measurement of variables done by using numbers, percentage, means +/-standard deviation. Differences between variables were measured by using ANOVA test when it needed.

RESULT
The studied variables are listed in table 1. Serum leptin hormone levels are presented in table 2 (8.82 + 2.9 μg/L) in group 1 & (4.65 + 3.2 μg/L) in group 2,The variation between the tw o groups was statistically significant (P < 0.05) . Gender differences betw een the two groups in serum Leptin shown clearly in    3 ; These differences may be due to the fact that Iraqi women have higher fat mass than the other women. A comparable results was found in male with different studies. At first, such differences between Iraqi male & female subjects were thought to reflect the differences in body composition between men and women. Women in general have a higher percentage of fat mass for the same body weight or BMI. Since leptin reflects mainly the amount of body fat, this seemed to be a logical explanation for the observed gender differences 11 .
However, these gender differences and their relationship to body composition were examined ,and leptin levels were found to be significantly higher in women with comparable BMI or fat mass. A second explanation was thought in the differences in fat distribution between men and women. Women generally have more peripheral fat accumulation (especially at the level of the hips), whereas obese men have more abdominal (especially visceral) fat. It was shown in several in vitro studies that subcutaneous adipocytes produce more leptin than fat cells derived from the omental fat depot; this is especially true in women. 12,13 In vivo studies also showed that leptin levels had a stronger association with peripheral 14 or subcutaneous fat than with intra-abdominal or visceral fat, as measured by computed tomography scan. 15 Thus, the fact that women have more subcutaneous fat, which secretes more leptin, seems an additional reason for the higher leptin levels in women. However, even after correcting for the amount of subcutaneous fat, leptin levels are still found to be significantly higher in women. 10

CONCLUSION
The results of this study are potentially important for the understanding of differences between men and women in regulation of food intake, weight gain, and body fat distribution; but since these differences in body composition between men and women may not be the only reason to explain the differences in leptin levels completely, other factors must play a role, like Steroid hormones but the exact mechanism or interaction is not yet known. These findings seem to indicate that this recently discovered hormone may play a role obesity, infertility & other disease states.