Obesity Research & Clinical Practice (2013) 7, e75—e80
Serum leptin concentrations in Mongolian women Qimuge Suyila, Hongwei Cui, Ling Yang, Lingyan Zhao, Ruifang Zhang, Xiulan Su ∗ Clinical Research Center of Afﬁliated Hospital, Inner Mongolia Medical College, Hohhot, Inner Mongolia, China Received 5 January 2011 ; received in revised form 31 August 2011; accepted 9 September 2011
KEYWORDS Obesity; Leptin; Body mass index; Percent body fat; Mongolian
Summary Objective: The aim of our study is to elucidate the association between leptin and obesity in Mongolian women. Method: Total 181 women participated in the study including 118 Mongolians and 63 Han. Body mass index (BMI) was calculated by weight (kg) divided by square height (m2 ). Percent body fat (%fat) was detected by bioelectrical impedance analysis (BIA). Fasting serum leptin was determined by ELISA. Result: The average BMI and %fat of Mongolian and Han women was 25.14 ± 4.48 kg/m2 , 24.30 ± 3.62 kg/m2 and 36.10 ± 6.23%, 33.84 ± 5.98%, respectively. Fasting serum leptin level in obese women (BMI ≥ 25) was remarkably higher than in normal weight women (18.5 < BMI < 25) in Mongolian and Han ethnic groups (all P < 0.001). Fasting serum leptin level in Mongolian women had borderline signiﬁcance compared with it in Han women (P = 0.049). Multiple linear regression models revealed that ethnicity, %fat and BMI were associated with serum leptin concentrations independent of age. Conclusion: In Mongolian and Han women, fasting serum leptin level was positively associated with BMI and %fat (all P < 0.001). © 2011 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.
Introduction Obesity is a common problem worldwide, and its prevalence is still rising. The impact of obesity on ill health is thoroughly studied, even though the ∗ Corresponding author at: Clinical Medical Research Center of Afﬁliated Hospital, No. 1 Tongdao North Street, Hohhot, 010050, China. Tel.: +86 471 6636128; fax: +86 471 6636128. E-mail address: [email protected]
mechanisms are incompletely understood . A study shows that the effect of obesity on chronic disease risk differs by ethnicity . Asians experience a higher risk for hypertension, diabetes, and cardiovascular disease at lower levels of body mass index (BMI) compared to Caucasians . The adipocyte-derived hormone leptin is important for adipose tissue and several metabolic pathways [4,5], and may have effects on cardiovascular disease [6,7].
1871-403X/$ — see front matter © 2011 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.
e76 Concentration of leptin has been studied in various ethnic groups and diseases. Asian women have lower serum leptin level than Caucasian women, but may have a higher risk of chronic disease . There is higher concentration of serum leptin in South Asians and Aboriginal population compared with Europeans and Chinese [9,10]. Leptin is correlated with South Asian, insulin resistance, smoking and high density lipoprotein cholesterol [9,10]. Asian Indians have higher leptin level than Creoles and Europids. Male Creoles and Asian Indians are independent association with high leptin concentration . It is reported that in 2002 there are 17.3% of Chinese were overweight or obesity . Although the prevalence of obesity in China is lower than in Western countries, it increases rapidly. Thus, obesity has been drawn more attention by medical staff and researchers in China. Chinese have lower level of leptin compared to Caucasians , South Asian and Aboriginal people . Leptin is informative biomarker for obesity and abnormal metabolic proﬁle even in normal weight Chinese children , and may be the predictive factor of the insulin resistance in general Chinese population . However, there is no report about leptin level and obesity in Mongolians. Mongolians are traditional nomadic peoples, and have quite different dietary and living habits from other ethnic groups. Additionally, there are more obese Mongolian women than men, and it is reported that obesity is correlated with diseases in women [15—17]. Therefore, our present study investigates the BMI, percent body fat (%fat), fasting serum leptin level in Mongolian women who live in Inner Mongolia, and the association between fasting serum leptin level and BMI, %fat and age, as well as the differences from Han women.
Materials and methods
Q. Suyila et al. and 78 obese women. The following data were recorded for each subject: name, age, gender, ethnicity, height, weight. BMI was calculated by weight (kg) divided by square height (m2 ), and %fat was detected by bioelectrical impedance analysis (BIA) using TANITA TBF-215 (TANITA Corporation, Tokyo, Japan), which was described elsewhere . Blood samples were drawn after an overnight fast; serum was separated and stored at −80 ◦ C. Concentration of serum leptin was assessed by double-antibody enzyme-linked immunosorbent-assay (ELISA) (R&D Systems, Minneapolis, MN, USA) according to the manufacturer’s speciﬁcations. Our experiment was approved by Inner Mongolia Medical College Afﬁliated Hospital Ethics Committee.
Power calculation and statistical analysis We hypothesized the signiﬁcant differences in concentration of serum leptin between normal weight and overweight or obesity women in two ethnic groups. Within ethnic groups, the required number of subjects to obtain signiﬁcant (P < 0.05) correlation coefﬁcient of at least 0.6, with a power of 80%, was 20 subjects. All the experimental data were expressed as mean ± standard deviation. Differences in characteristics of subjects and comparison of leptin, %fat and age between normal weight and overweight or obesity Mongolian and Han women were determined by t test. The association between BMI, %fat and fasting serum leptin level after adjusting age was determined using the Pearson correlation analysis. To determine the independent effects of variables on the serum leptin concentration, multiple linear regression analyses were performed. All statistics were performed using SPSS 13.0 for Windows. Data were considered signiﬁcant if P < 0.05.
Subjects Total 181 Mongolian and Han women were selected to perform physical examination. There were 118 Mongolian women with an age range between 30 and 66 years and age matched 63 Han women with an age range between 31 and 67 years. Mongolian and Han women were from families which had been living in the Damao County, Baotou, Inner Mongolian for at least 3 generations. All the subjects gave informed consent. According to the WHO criteria, 18.5 < BMI < 25 was considered as normal weight, BMI ≥ 25 was considered as over weight or obesity . There were 103 normal weight women
Characteristics of Mongolian and Han women in Inner Mongolia Total 181 women were selected in the study including 118 Mongolian women (age range between 31 and 66 years, average age of 44.94 ± 7.48 years) and 63 Han women (age range between 31 and 57 years, average age of 45.67 ± 7.51 years). Information of fasting serum leptin, BMI, %fat and age between Mongolian and Han women was shown in Table 1. The BMI ranged from 18.23 to 39.04 kg/m2 . The average BMI of Mongolian and Han women was 25.14 ± 4.48 kg/m2
Serum leptin concentrations in Mongolian women Table 1
Characteristics of subjects (mean ± Standard deviation).
Number Age span (year) Age (year) Leptin (ng/ml) BMI (kg/m2 ) %Fat (%)
118 31—66 44.94 ± 7.48 3.58 ± 1.85 25.14 ± 4.48 36.10 ± 6.23
63 31—57 45.67 ± 7.51 3.02 ± 1.75 24.30 ± 3.62 33.84 ± 5.98
0.535 0.049 0.200 0.020
and 24.30 ± 3.62 kg/m2 , respectively. Mean fasting serum leptin level and %fat of Mongolian and Han women was 3.58 ± 1.85 ng/ml, 3.02 ± 1.75 ng/ml and 36.10 ± 6.23%, 33.84 ± 5.98%, respectively. There were no signiﬁcant effects of ethnicity on age and BMI (P = 0.535 and 0.200). Serum leptin and %fat were all affected by ethnicity. Mongolian women had higher mean fasting serum leptin level and %fat than Han women (P = 0.049 and 0.020). Mean fasting serum leptin level of normal weight, obese Mongolian and Han women was 2.35 ± 1.39 ng/ml, 5.09 ± 1.07 ng/ml, 2.18 ± 1.41 ng/ml and 4.30 ± 1.42 ng/ml, respectively. Obese women had about 2 times higher mean fasting serum leptin level than normal weight women in two ethnic groups (all P < 0.001 Table 2). The %fat of normal weight, obese Mongolian and Han women were 31.67 ± 3.87%, 41.54 ± 3.78%, 30.53 ± 3.89% and 38.88 ± 5.02%, respectively. The %fat in obese women was much higher than in normal weight women in two ethnic groups (all P < 0.001). Obese Mongolian women had higher fasting serum leptin level and %fat than obese Han women (P = 0.014 and 0.007, respectively Table 2). There were no signiﬁcant effects of BMI on age in two ethnic groups (P = 0.710 and 0.487, respectively Table 2).
Association between BMI, %fat and age and fasting serum leptin level in Mongolian and Han women In Mongolian and Han women, BMI (P < 0.001) and %fat (P < 0.001) were strongly and positively correlated to the serum leptin concentration after adjusting age (Table 3). Results from multiple linear regression models revealed that ethnicity (P = 0.032), %fat (P < 0.001) and BMI (P < 0.001) were associated with serum leptin concentrations independent of age (Table 4). As shown in Fig. 1 the concentration of fasting serum leptin elevated with the increasing of BMI and %fat in Mongolian or Han women. The BMI and %fat was positive association
with leptin level (P < 0.001 in Mongolian women, P < 0.001 in Han women).
Discussion Obesity is a disease caused by imbalance of food intake and energy expense, multiple factors such as genetic susceptibility, environment and dietary structure have been implicated in the pathogenesis . Leptin is one of the most important adipose derived hormones . Leptin inhibits expression and secretion of neuropeptide Y by binding receptors in the hypothalamus to regulate energy intake and expenditure, including appetite and metabolism [22,23]. To our knowledge, it is the ﬁrst study to investigate the serum leptin concentrations in Mongolian women. We examined the inﬂuence of ethnicity, BMI and %fat on serum leptin concentrations in Mongolian and Han women, and found that the difference of serum leptin concentrations between two ethnic groups may be explained by differences in BMI and %fat. Our result is consistent with studies carried out in Whites, African Americans, Hawaiians and Japanese , Caucasian and Mapuche groups from Chile  and Chinese women , indicating that leptin, BMI and %fat could be inﬂuenced by ethnicity. Our study found that the leptin concentration of Mongolian and Han women was 3.58 ± 1.85 ng/ml, 3.02 ± 1.75 ng/ml, which was much lower than mean leptin level in South Asians (4.7, 7.3, 11.82 ng/ml), Asians (11.7 ng/ml), Creoles (4.0 ng/ml), Caucasians (6.75, 19.5 ng/ml), Aboriginal people (11.13 ng/ml), Europeans (4.2, 4.3, 5.1, 9.21 ng/ml), Chinese (8.25 ng/ml), Native Hawaiian (20.0 ng/ml) [8—11]. There was much difference of leptin concentration among different ethnic groups or even in the same ethnic group. This may due to difference of genetic background, environment, dietary and physical activity in ethnic groups enrolled in different studies. Additionally, the concentration of fasting serum leptin in 1.89% (1/53) of obese Mongolian women and 4% (2/25) of
Q. Suyila et al.
Table 2 Comparison of leptin, %fat and age between normal weight and overweight or obesity Mongolian and Han women.
Leptin (ng/ml) %Fat Age (year)
Normal weight (18.5 < BMI < 25)
Overweight or obesity (BMI ≥ 25)
Mongolian (n = 65)
Han (n = 38)
Mongolian (n = 53)
Han (n = 25)
2.35 ± 1.39 31.67 ± 3.87c,i 44.71 ± 7.58e,l
2.18 ± 1.41 30.53 ± 3.89 45.13 ± 7.50
5.09 ± 1.07 41.54 ± 3.78 45.23 ± 7.40
4.30 ± 1.42b,h 38.88 ± 5.02d,k 46.48 ± 7.61f,m
Compared with overweight or obesity Mongolian women: a P < 0.001; b P = 0.014; c P < 0.001; d P = 0.007; e P = 0.710; f P = 0.493. Compared with normal weight Han women: g P = 0.521; h P < 0.001; i P = 0.168; k P < 0.001; l P = 0.783; m P = 0.487.
Correlation analyses of the variables on leptin concentration after adjusting age. Pearson correlation coefﬁcient Mongolian (118) 2
BMI (kg/m ) %Fat
obese Han women was lower than the average concentration of fasting serum leptin in normal weight Mongolian and Han women, respectively. The difference of leptin resistance between Mongolian and Han women may provide new hints for leptin treatment.