FTO基因与我国汉族儿童肥胖的关系及其对膳食和身体活动的影响
摘要
研究背景
遗传和环境因素在肥胖的发生和发展中共同发挥着重要的作用,遗传因素增加了机体对肥胖的易感性。但是,即使存在遗传因素影响,肥胖的发生发展也是环境因素及生活方式等多种因素相互作用的结果。研究遗传和环境因素与儿童肥胖关系对于肥胖的预防和控制具有重要意义。近年来,全基因组关联研究(genome-wide association studies, GWAS)发现了一系列肥胖相关基因,其中,FTO (fat mass and obesity associated gene)基因在最大程度上解释了BMI和肥胖的变异。
在欧美人群中,FTO基因与BMI和肥胖的关系已经明确。但在亚洲人群中,FTO基因与肥胖关系的研究未得出一致的结论,尚需要更多的重复性研究来验证FTO基因在中国人群中的作用,了解FTO基因与环境因素对儿童肥胖的相对影响,对于进一步了解肥胖基因的作用机制将有所帮助。同时,进一步研究遗传与环境因素之间的关系对于肥胖的预防和控制具有重要意义。
研究目的
本研究利用“2002年中国居民营养与健康状况调查”和北京市汉族儿童的资料,以中国汉族7-17岁儿童为研究对象,探讨FTO基因SNP rs9939609多态性与中国汉族儿童肥胖及其相关代谢指标的关系,并进一步研究FTO基因与膳食和身体活动的相互作用,以探讨FTO在调控机体能量平衡中的作用,为深入研究遗传因素在肥胖发生中的作用及肥胖的预防控制提供理论依据。
研究对象与方法
随机从-80℃保存的“2002年中国居民营养与健康状况调查”2000名7～17岁汉族儿童及其母亲的血样中选取1253名汉族7-17岁儿童及其母亲的静脉血,抽提全基因组DNA,采用Taqman-MGB探针技术进行FTO SNP rs9939609分型。
为进一步分析FTO基因SNP rs9939609多态性与中国汉族儿童肥胖、体成分及其相关代谢指标的关系,在本研究中,我们进一步从2005年中国疾病预防控制中心营养与食品安全所在北京市开展的“以学校为基础的身体活动干预研究”项目的1000份-80℃冻存血样中随机选择674名8-11岁汉族儿童,利用该人群的基线数据进行FTO基因SNP rs9939609多态性与中国汉族儿童肥胖、体成分及其相关代谢指标的关系。
应用Logistic回归分析进行AA/AT携带者和TT携带者之间的超重率和肥胖率比较；多元线性模型分析FTO rs9939609与肥胖及其相关代谢指标之间的关系。
研究结果
1.FTO基因与我国汉族儿童肥胖及相关代谢指标的关系
在“2002年中国居民营养与健康状况调查”和“以学校为基础的身体活动干预研究”项目中,我国汉族儿童rs9939609 A等位基因表达频率分别为12.7%和12.2%,仅分别有1.4%和1.2%的儿童同时携带两个A等位基因,AA、AT、TT基因型分布均符合Hardy-Weinberg平衡。
分析“2002年中国居民营养与健康状况调查”的数据,未发现FTO基因与我国汉族儿童BMI和肥胖存在相关性。而以北京市汉族儿童为研究对象的“以学校为基础的身体活动干预研究”项目的数据则证实了FTO SNP rs9939609与BMI和肥胖之间的关系。该研究结果为,携带AA/AT基因型的汉族儿童肥胖的发生率显著高于TT基因型携带者(36.4%vs.22.6%,P=0.004),AA/AT基因型携带者发生肥胖的OR值为1.8(95％CI 1.2-2.7).FTO导致我国汉族儿童肥胖的人群归因危险度百分比(PAR%)为12.4%。其原因可能是,“2002年中国居民营养与健康状况调查”的检验效率显著低于“以学校为基础的身体活动干预研究”项目中的北京市汉族儿童(12% vs.44%)。
在北京市汉族儿童中,与TT基因型携带者相比,携带AA/AT基因型的汉族儿童的体重、BMI、腰臀比、髂前上棘位皮褶厚度、肩胛下皮褶厚度、体脂、瘦体重均显著升高。SNP rs9939609与北京市汉族儿童甘油三脂、脂联素、空腹血糖存在相关性,该相关性在进一步调整BMI的影响后消失。而总胆固醇、低密度脂蛋白胆固醇、高密度脂蛋白胆固醇、胰岛素、瘦素、Ghrelin、收缩压、舒张压、胰岛素抵抗指数和胰岛素敏感指数等指标均未发现相关性。
2.FTO基因与我国汉族儿童膳食能量摄入和身体活动的关系
在北京市汉族儿童中,与TT基因型携带者相比,携带AA/AT基因型的汉族儿童的膳食总能量摄入边缘性升高(P=0.095),其脂肪摄入量和脂肪供能比(Rfat)均显著升高(P=0.02),进一步调整BMI的影响后,差异仍存在显著性。两种基因型携带者之间的身体活动时间、睡眠和静坐时间以及身体活动能量消耗差异均无显著性(P>0.05),进一步调整BMI的影响后,差异仍无显著性。
调整年龄、性别、家庭经济收入水平及青春发育期的影响,在高膳食能量摄入水平下,不论是否携带FTO危险型基因,其BMI、超重、肥胖发生率差异均没有显著性(P>0.05)；在低膳食能量摄入水平下,FTO危险型基因携带者BMI及其肥胖发生的危险性均显著高于未携带者(P=0.02,0.01, respevtively),但两种基因型携带者超重/肥胖的发生率差异无显著性。不论是否携带FTO危险型基因,高膳食能量摄入和低膳食能量摄入儿童的BMI、超重、肥胖发生率差异均没有显著性(P>0.05),进一步调整身体活动水平后,各组间统计学差异未发生变化。
调整年龄、性别、家庭经济收入水平及青春发育期的影响,在高身体活动水平下,FTO危险型基因携带者的BMI以及超重/肥胖率与未携带者间差异均没有显著性(P>0.05),但其发生肥胖的危险性显著高于未携带者(P=0.04)；在低身体活动水平下,FTO危险型基因携带者BMI以及发生肥胖的危险性均显著高于未携带者(P<0.05),但两种基因型携带者超重/肥胖的发生率差异无显著性。不论是否携带FTO危险型基因,高身体活动水平和低身体活动水平儿童的BMI、超重、肥胖发生率差异亦均没有显著性(P>0.05)。
3.FTO基因对我国汉族儿童膳食多样化评分、食物选择和营养素摄入充足状况的影响
本研究发现,与TT基因型携带者相比,AA/AT基因型儿童的膳食多样化总评分DDS有升高的趋势。携带AA/AT基因型儿童的不同食物种类组内多样化评分中,谷类及制品、畜肉类及制品和糖蜜饯类均边缘性升高,其他种类食物的组内多样化评分两组间差异没有显著性。
与TT基因型携带者相比,携带AA/AT基因型儿童的薯类、淀粉及制品的每日摄入量边缘性升高,糖蜜饯类的每日摄入量显著升高；携带AA/AT基因型儿童的水果类及制品的供能比边缘性降低,而糖蜜饯类的供能比边缘性升高；携带AA/AT基因型的汉族儿童每日选择能量密度>100kcal/100g、>200kcal/100g、>300kcal/100g的食物频次均显著高于TT基因型携带者,进一步调整BMI的影响后,差异仍有显著性。
与TT基因型携带者相比,携带AA/AT基因型的儿童能量的营养素充足比边缘性升高,同时AA/AT基因型儿童维生素B6的NAR显著升高,而其他各营养素的充足比及平均充足比两组间差异没有显著性。
4.FTO基因与我国汉族成年女性肥胖的相关性
我国汉族成年女性FTO SNP rs9939609 A等位基因表达频率为13.6%,仅有1.8%同时携带两个A等位基因；AA、AT、TT基因型的表达频率分别1.8%、23.7%和74.5%,符合Hardy-Weinberg平衡(X2检验,P=0.80)。
本研究在汉族成年女性中证实了FTO SNP rs9939609与肥胖之间的关系,但并未发现其与BMI之间存在显著关系。携带AA/AT基因型的汉族成年女性的肥胖率显著高于携带TT基因型的汉族成年女性(14.5% vs.9.4%,P=0.01,OR=1.6,95%CI 1.1-2.4)。
5.我国汉族儿童及其母亲FTO SNP rs9939609变异的现况及母子BMI的相关性
母亲和孩子均携带FTO SNP rs9939609AA基因型的比例仅为0.2%,均携带TT基因型的比例为65.5%,均携带AT基因型的比例为12.0%。母子均至少携带一个A危险型等位基因的比例为15.0%；母亲携带A危险型等位基因而孩子不携带的比例为10.5%；母亲不携带A危险型等位基因而孩子携带的比例为9.0%。
调整儿童年龄、性别、母亲年龄、受教育水平、职业、地区和家庭经济状况的影响后,母亲BMI与孩子BMI呈显著正相关(P<0.0001),相关系数为0.26(SE=0.02)。进一步调整儿童及母亲FTO SNP rs9939609的影响后,仍呈显著正相关(P<0.0001),相关系数为0.25(SE=0.02)。
调整儿童年龄、性别、母亲年龄、受教育水平、职业、地区和家庭经济状况的影响,将母亲是否携带FTO危险型基因作为分组因素,母亲携带FTO危险型基因组母子BMI相关系数高于母亲不携带FTO危险型基因组,各组母亲BMI和孩子BMI均呈显著正相关。同时对两组间儿童BMI、超重率和肥胖率比较发现,母亲携带FTO危险型基因组儿童BMI有高于母亲不携带FTO危险型基因组儿童的趋势(18.7±0.2 vs.18.5±0.1),但两组儿童的BMI无显著性差异(P=0.15)；两组儿童的超重率(12.2% vs.9.6%)、肥胖率(2.8% vs.2.6%)均无显著性差异(P=0.27 and 0.96, respectively)。
进一步比较母亲及孩子在四种不同FTO SNP rs9939609基因型组合下,母亲BMI和孩子BMI均呈显著正相关,母子均不携带FTO危险型基因时其相关系数最小,但四组间的差异没有显著性。同时对四组间儿童BMI、超重率和肥胖率比较发现,母子均携带FTO危险型基因组儿童BMI有高于母子均不携带FTO危险型基因组儿童的趋势(18.8±3.1 vs.18.5±3.0),但差异无统计学意义(P=0.16),其余各组间两两比较亦未发现统计学差异(P>0.40)。四组儿童的超重、肥胖发生率均无显著性差异(P>0.20)。
结论
1.我国汉族儿童FTO SNP rs9939609 A等位基因表达频率为12%,显著低于欧美人群。
2.携带FTO SNP rs9939609 A等位基因的汉族儿童发生肥胖的危险性增加。
3.FTO基因可能通过影响我国汉族儿童膳食能量摄入影响能量平衡,但对身体活动水平的影响不显著。
4. FTO SNP rs9939609可能通过调节饮食,包括食物摄入量和不同种类食物的选择,进而影响机体膳食能量摄入。
5.FTO基因在母子BMI相关性中发挥了一定的作用,但作用并不显著。
Background
Genetic and environmental factors play an important role in the emergence and development of obesity. Genetic factors increase the susceptibility to obesity. However, even in the presence of genetic factors, obesity is the interactive result of various environmental factors and lifestyle. Research on the ralationship between genetic and environmental factors and obesity is significant in the prevention and control of childhood obesity. Recent genome-wide association (GWA) studies identified a group of loci associated with obesity. Among those genes, FTO explained the largest variation of BMI and obesity.
The association of FTO genetic variants with BMI and obesity was unequivocally replicated in European and Hispanic populations. However, these associations were controversial with regard to Asian populations. Its still need replicated studies on the associations of FTO rs9939609 with obesity and obesity-related metabolic traits in Chinese population, as well as its interaction with environmental factors, to explore the possible pathway of FTO gene's association with obesity. At the same time, further research on the relationship of genetic and environmental factors is of great significance in the prevention and control of obesity.
Objectives
The subjects included children aged 7-17 years old and their parents, a subsample of the 2002 China National Nutrition and Health Survey, to explore the associations of FTO rs9939609 with obesity and obesity-related metabolic traits in Chinese children. At the same time, further studies on the interaction of FTO with diet and physical activities can help to explain the role of FTO in governing energy balance and provide scientific basis for further research on the role of genetic factors in the emergence and development of obesity and prevention and control of obesity.
Subjects and methods
1253 Han children and their mothers'blood of 2002 China National Nutrition and Health Survey saved in-80℃were randomly selected. Genomic DNA was successfully extracted. Taqman-MGB probe method was used to detect the FTO SNP rs9939609 polymorphism.
In this study, we further randomly selected 674 Han students aged 8-11 years from the School-based Physical Activity Intervention Research Project launched by National Institute for Nutrition and Food Safety, Chinese Center for Disease Control and Prevention in 2005. The baseline data was used for further study on the associations of FTO SNP rs9939609 with obesity, body composition and obesity-related metabolic traits in Chinese Han children.
Logistic regression analysis was performed to compare the likelihood of overweight and obesity between the carriers of TT genotype and the carrier of AA/AT genotype. Association of FTO rs9939609 with obesity-related measures and obesity-related metabolic traits were performed with General Linear Model, using the children's age, sex, family income and puberty stage and mother's age, vocation, education level and area as covariates. The variates of non-normal distributions were natural logarithm transformed before analysis. PAR and PAR% were calculated according to the incidence of obesity.
Results
1. The associations of FTO gene with obesity and obesity-related metabolic traits in Chinese Han children
In 2002 China National Nutrition and Health Survey and School-based Physical Activity Intervention Research Project, the rs9939609 A allele frequency of the Han children of China and Beijing were 12.7% and 12.2% respectively. The frequency of homozygote of the A allele were 1.4% and 1.2%, respectively. And the genotype distributions of FTO SNP rs9939609 were consistent with Hardy-Weinberg equilibrium.
No significant associations of rs9939609 with BMI and obesity were found in the 2002 China National Nutrition and Health Survey. This population was powered at 12% to detect odds ratios (OR) of 1.15 for obesity, significantly lower than the study on the Han children in Beijing.
The associations of FTO rs9939609 with BMI and obesity in Beijing Han children were confirmed. The prevalence of obesity among the carriers of AA/AT genotypes was significantly higher than that among those with TT genotype (36.4% vs.22.6%, P=0.004). Compared to the carrier of TT genotype, the likelihood of obesity was 1.8 (95% confidence interval (95% CI) 1.2-2.7) for the carrier of AA/AT genotype. The percentage of population attributable risk was 12.4%.
Compared with the TT genotype, the weight, BMI, waist-to-hip ratio (WHR), subscapular skinfold thickness, suprailiac skinfold thickness, body fat and lean body mass of carriers with the AA/AT genotype were significantly higher than those with TT genotype. The height, birth weight and percent of body fat were not significantly different between the children with TT and AA/AT genotype.
The associations of FTO rs9939609 with triglyceride, adiponectin and glucose were confirmed. While, after further adjustment for BMI, the evidence of associations was reduced. There was weak evidence of associations between rs9939609 and other obesity-related metabolic traits including TC, LDL, HDL, leptin, ghrelin, bloodpressure, insulin, and insulin resistance.
2. The associations of FTO gene with dietary energy intake and physical activity level
Compared with the TT genotype, we found marginally increasing level of dietary energy intake in the AA/AT genotype subjects (P=0.095). The consumption of fat, energy from fat and the percentage from fat were found obviously higher. After further adjustment for BMI, the associations were still significant. While, there was weak evidence of associations between rs9939609 and physical activity including physical activity time, sleeping time, sedentary time and energy expenditure of physical activity. After further adjustment for BMI, there were still no significant associations.
3. Effects of FTO SNP rs9939609 on DDS, the selection of food and NAR
Compared with the TT genotype, there was increasing tendency for DDS in the AA/AT genotype subjects. The intra-group diversity scores of cereals and cereal products, meat and meat products, sugars and preserves marginally increased in the AA/AT carriers. There were no significant differences in other intra-group diversity scores.
Compared with the TT genotype, the daily intake of tubers, starches and products marginally increased and the daily intake of sugars and preserves obviously increased in the AA/AT carriers. The percentage of energy intake from fruit and fruit products marginally decreased in the AA/AT carriers. While, the percentage of sugars and preserves marginally increased. The selection frequences of food of high energy density (>100kcal/100g or>200kcal/100g or 300kcal/100g) were found obviously higher. After further adjustment for BMI, the differencess were still significant.
Compared with the TT genotype, the NAR of energy marginally increased and the NAR of vitamin B6 obviously increased in the AA/AT carriers. And there were no significant differences in the NAR of other nutrients and MAR.
4. The association of FTO SNP gene with obesity in Chinese adult women
The rs9939609 A allele frequency of the Han adult women was 13.6%. The frequency of homozygote of the A allele was 1.8%. And the genotype distributions of FTO SNP rs9939609 were consistent with Hardy-Weinberg equilibrium (P=0.80).
The association of FTO rs9939609 with obesity in Chinese adult women was confirmed. No significant association of rs9939609 with BMI was found. The prevalence of obesity among the carriers of AA/AT genotypes was significantly higher than that among those with TT genotype (14.5% vs.9.4%,P=0.O1). Compared to the carrier of TT genotype, the likelihood of obesity was 1.63 (95% confidence interval (95% CI) 1.13-2.44) for the carrier of AA/AT genotype. The percentage of population attributable risk was 12.1%.
There was weak evidence of associations between rs9939609 and obesity-related metabolic traits including glucose, TG, TC, LDL, HDL and bloodpressure.
No significant differences of dietary energy intake, consumptions of protein, fat, carbohydrate and fiber, energy from protein, energy from fat, energy from carbohydrate and the percentages from protein, fat and carbohydrate between carriers with TT genotype and AA/AT genotype were found. And, there was weak evidence of associations between rs9939609 and physical activity including daily physical exercise time, sleeping time, sedentary time and housework time.
5. The allele frequencies of rs9939609 of FTO gene in Chinese Han children and their mothers and the relation of BMI between Chinese Han children and their mothers
The frequencies of homozygote of the A allele and T allele both in Chinese Han children and their mothers were 0.2% and 65.5%, respectively. The frequency of the AT genotype both in Chinese Han children and their mothers was 12.0%. The rate of both children and their mothers carring at least one dangerous allele was 15.0%. The rate of mothers with at least one dangerous allele and children without A allele was 10.5%. While, the rate of children with at least one dangerous allele and mothers without A allele was 9.0%.
After ajustment of the children's age, sex, family income and puberty stage and mother's age, vocation, education level and area, the BMI of mothers was positively related with the children's BMI (P<0.0001) and the correlation coefficient is o.26 (SE=0.02). After further ajustment of the genotype of FTO SNP rs9939609, the BMI of mothers was still positively related with the children's BMI (P<0.0001) and the correlation coefficient is o.25 (SE=0.02).
After ajustment of the children's age, sex, family income and puberty stage and mother's age, the correlation coefficient of BMI between Chinese Han children and their mothers was higher in the group of mothers with A allele than the group of mother without A allele. Compared with the group of mother without A allele, there was increasing tendency for the BMI of children in the group of mothers with A allele, but there was no stastically different (P=0.15). And there were no stastical differences in overweight and obesity rate between the two groups (P=0.27 and 0.96, respectively).
Further analysis of the relation of BMI between children and their mothers under four different combinations of FTO SNP rs9939609 genotype showed that, the BMI of mothers was positively related with the children's BMI under the four different combinations and the correlation coefficient between children and their mothers both without A allele was smallest. Compared with the group of children and their mothers both with A allele, there was increasing tendency for the BMI of children in the group of children and their mothers both without A allele, but there was no stastically different (P=0.16). And there were no stastical differences in overweight and obesity rate between the two groups, but no statistically significant differenc between anyother two groups (P>0.40). There were no stastical differences in overweight and obesity rate among the four groups (P>0.20).
Conclusions
1. The rs9939609 A allele frequency was substantially lower in Chinese Han children as compared with the European populations (12 vs.45%).
2. The associations of FTO rs9939609 with BMI and obesity are confirmed in Beijing Han children.
3. Influence on the energy intake of dietary is one of the ways of FTO gene affects energy balance. However, the effect of FTO SNP rs9939609 on physical activity is not found.
4. FTO gene may adjust energy intake through its effect on diet, including food intake and selection of different kinds of food.
5. FTO SNP rs9939609 plays a role in the relation of BMI between Chinese Han children and their mothers, but the effect was not significant.
遗传和环境因素在肥胖的发生和发展中共同发挥着重要的作用,遗传因素增加了机体对肥胖的易感性。但是,即使存在遗传因素影响,肥胖的发生发展也是环境因素及生活方式等多种因素相互作用的结果。研究遗传和环境因素与儿童肥胖关系对于肥胖的预防和控制具有重要意义。近年来,全基因组关联研究(genome-wide association studies, GWAS)发现了一系列肥胖相关基因,其中,FTO (fat mass and obesity associated gene)基因在最大程度上解释了BMI和肥胖的变异。
在欧美人群中,FTO基因与BMI和肥胖的关系已经明确。但在亚洲人群中,FTO基因与肥胖关系的研究未得出一致的结论,尚需要更多的重复性研究来验证FTO基因在中国人群中的作用,了解FTO基因与环境因素对儿童肥胖的相对影响,对于进一步了解肥胖基因的作用机制将有所帮助。同时,进一步研究遗传与环境因素之间的关系对于肥胖的预防和控制具有重要意义。
研究目的
本研究利用“2002年中国居民营养与健康状况调查”和北京市汉族儿童的资料,以中国汉族7-17岁儿童为研究对象,探讨FTO基因SNP rs9939609多态性与中国汉族儿童肥胖及其相关代谢指标的关系,并进一步研究FTO基因与膳食和身体活动的相互作用,以探讨FTO在调控机体能量平衡中的作用,为深入研究遗传因素在肥胖发生中的作用及肥胖的预防控制提供理论依据。
研究对象与方法
随机从-80℃保存的“2002年中国居民营养与健康状况调查”2000名7～17岁汉族儿童及其母亲的血样中选取1253名汉族7-17岁儿童及其母亲的静脉血,抽提全基因组DNA,采用Taqman-MGB探针技术进行FTO SNP rs9939609分型。
为进一步分析FTO基因SNP rs9939609多态性与中国汉族儿童肥胖、体成分及其相关代谢指标的关系,在本研究中,我们进一步从2005年中国疾病预防控制中心营养与食品安全所在北京市开展的“以学校为基础的身体活动干预研究”项目的1000份-80℃冻存血样中随机选择674名8-11岁汉族儿童,利用该人群的基线数据进行FTO基因SNP rs9939609多态性与中国汉族儿童肥胖、体成分及其相关代谢指标的关系。
应用Logistic回归分析进行AA/AT携带者和TT携带者之间的超重率和肥胖率比较；多元线性模型分析FTO rs9939609与肥胖及其相关代谢指标之间的关系。
研究结果
1.FTO基因与我国汉族儿童肥胖及相关代谢指标的关系
在“2002年中国居民营养与健康状况调查”和“以学校为基础的身体活动干预研究”项目中,我国汉族儿童rs9939609 A等位基因表达频率分别为12.7%和12.2%,仅分别有1.4%和1.2%的儿童同时携带两个A等位基因,AA、AT、TT基因型分布均符合Hardy-Weinberg平衡。
分析“2002年中国居民营养与健康状况调查”的数据,未发现FTO基因与我国汉族儿童BMI和肥胖存在相关性。而以北京市汉族儿童为研究对象的“以学校为基础的身体活动干预研究”项目的数据则证实了FTO SNP rs9939609与BMI和肥胖之间的关系。该研究结果为,携带AA/AT基因型的汉族儿童肥胖的发生率显著高于TT基因型携带者(36.4%vs.22.6%,P=0.004),AA/AT基因型携带者发生肥胖的OR值为1.8(95％CI 1.2-2.7).FTO导致我国汉族儿童肥胖的人群归因危险度百分比(PAR%)为12.4%。其原因可能是,“2002年中国居民营养与健康状况调查”的检验效率显著低于“以学校为基础的身体活动干预研究”项目中的北京市汉族儿童(12% vs.44%)。
在北京市汉族儿童中,与TT基因型携带者相比,携带AA/AT基因型的汉族儿童的体重、BMI、腰臀比、髂前上棘位皮褶厚度、肩胛下皮褶厚度、体脂、瘦体重均显著升高。SNP rs9939609与北京市汉族儿童甘油三脂、脂联素、空腹血糖存在相关性,该相关性在进一步调整BMI的影响后消失。而总胆固醇、低密度脂蛋白胆固醇、高密度脂蛋白胆固醇、胰岛素、瘦素、Ghrelin、收缩压、舒张压、胰岛素抵抗指数和胰岛素敏感指数等指标均未发现相关性。
2.FTO基因与我国汉族儿童膳食能量摄入和身体活动的关系
在北京市汉族儿童中,与TT基因型携带者相比,携带AA/AT基因型的汉族儿童的膳食总能量摄入边缘性升高(P=0.095),其脂肪摄入量和脂肪供能比(Rfat)均显著升高(P=0.02),进一步调整BMI的影响后,差异仍存在显著性。两种基因型携带者之间的身体活动时间、睡眠和静坐时间以及身体活动能量消耗差异均无显著性(P>0.05),进一步调整BMI的影响后,差异仍无显著性。
调整年龄、性别、家庭经济收入水平及青春发育期的影响,在高膳食能量摄入水平下,不论是否携带FTO危险型基因,其BMI、超重、肥胖发生率差异均没有显著性(P>0.05)；在低膳食能量摄入水平下,FTO危险型基因携带者BMI及其肥胖发生的危险性均显著高于未携带者(P=0.02,0.01, respevtively),但两种基因型携带者超重/肥胖的发生率差异无显著性。不论是否携带FTO危险型基因,高膳食能量摄入和低膳食能量摄入儿童的BMI、超重、肥胖发生率差异均没有显著性(P>0.05),进一步调整身体活动水平后,各组间统计学差异未发生变化。
调整年龄、性别、家庭经济收入水平及青春发育期的影响,在高身体活动水平下,FTO危险型基因携带者的BMI以及超重/肥胖率与未携带者间差异均没有显著性(P>0.05),但其发生肥胖的危险性显著高于未携带者(P=0.04)；在低身体活动水平下,FTO危险型基因携带者BMI以及发生肥胖的危险性均显著高于未携带者(P<0.05),但两种基因型携带者超重/肥胖的发生率差异无显著性。不论是否携带FTO危险型基因,高身体活动水平和低身体活动水平儿童的BMI、超重、肥胖发生率差异亦均没有显著性(P>0.05)。
3.FTO基因对我国汉族儿童膳食多样化评分、食物选择和营养素摄入充足状况的影响
本研究发现,与TT基因型携带者相比,AA/AT基因型儿童的膳食多样化总评分DDS有升高的趋势。携带AA/AT基因型儿童的不同食物种类组内多样化评分中,谷类及制品、畜肉类及制品和糖蜜饯类均边缘性升高,其他种类食物的组内多样化评分两组间差异没有显著性。
与TT基因型携带者相比,携带AA/AT基因型儿童的薯类、淀粉及制品的每日摄入量边缘性升高,糖蜜饯类的每日摄入量显著升高；携带AA/AT基因型儿童的水果类及制品的供能比边缘性降低,而糖蜜饯类的供能比边缘性升高；携带AA/AT基因型的汉族儿童每日选择能量密度>100kcal/100g、>200kcal/100g、>300kcal/100g的食物频次均显著高于TT基因型携带者,进一步调整BMI的影响后,差异仍有显著性。
与TT基因型携带者相比,携带AA/AT基因型的儿童能量的营养素充足比边缘性升高,同时AA/AT基因型儿童维生素B6的NAR显著升高,而其他各营养素的充足比及平均充足比两组间差异没有显著性。
4.FTO基因与我国汉族成年女性肥胖的相关性
我国汉族成年女性FTO SNP rs9939609 A等位基因表达频率为13.6%,仅有1.8%同时携带两个A等位基因；AA、AT、TT基因型的表达频率分别1.8%、23.7%和74.5%,符合Hardy-Weinberg平衡(X2检验,P=0.80)。
本研究在汉族成年女性中证实了FTO SNP rs9939609与肥胖之间的关系,但并未发现其与BMI之间存在显著关系。携带AA/AT基因型的汉族成年女性的肥胖率显著高于携带TT基因型的汉族成年女性(14.5% vs.9.4%,P=0.01,OR=1.6,95%CI 1.1-2.4)。
5.我国汉族儿童及其母亲FTO SNP rs9939609变异的现况及母子BMI的相关性
母亲和孩子均携带FTO SNP rs9939609AA基因型的比例仅为0.2%,均携带TT基因型的比例为65.5%,均携带AT基因型的比例为12.0%。母子均至少携带一个A危险型等位基因的比例为15.0%；母亲携带A危险型等位基因而孩子不携带的比例为10.5%；母亲不携带A危险型等位基因而孩子携带的比例为9.0%。
调整儿童年龄、性别、母亲年龄、受教育水平、职业、地区和家庭经济状况的影响后,母亲BMI与孩子BMI呈显著正相关(P<0.0001),相关系数为0.26(SE=0.02)。进一步调整儿童及母亲FTO SNP rs9939609的影响后,仍呈显著正相关(P<0.0001),相关系数为0.25(SE=0.02)。
调整儿童年龄、性别、母亲年龄、受教育水平、职业、地区和家庭经济状况的影响,将母亲是否携带FTO危险型基因作为分组因素,母亲携带FTO危险型基因组母子BMI相关系数高于母亲不携带FTO危险型基因组,各组母亲BMI和孩子BMI均呈显著正相关。同时对两组间儿童BMI、超重率和肥胖率比较发现,母亲携带FTO危险型基因组儿童BMI有高于母亲不携带FTO危险型基因组儿童的趋势(18.7±0.2 vs.18.5±0.1),但两组儿童的BMI无显著性差异(P=0.15)；两组儿童的超重率(12.2% vs.9.6%)、肥胖率(2.8% vs.2.6%)均无显著性差异(P=0.27 and 0.96, respectively)。
进一步比较母亲及孩子在四种不同FTO SNP rs9939609基因型组合下,母亲BMI和孩子BMI均呈显著正相关,母子均不携带FTO危险型基因时其相关系数最小,但四组间的差异没有显著性。同时对四组间儿童BMI、超重率和肥胖率比较发现,母子均携带FTO危险型基因组儿童BMI有高于母子均不携带FTO危险型基因组儿童的趋势(18.8±3.1 vs.18.5±3.0),但差异无统计学意义(P=0.16),其余各组间两两比较亦未发现统计学差异(P>0.40)。四组儿童的超重、肥胖发生率均无显著性差异(P>0.20)。
结论
1.我国汉族儿童FTO SNP rs9939609 A等位基因表达频率为12%,显著低于欧美人群。
2.携带FTO SNP rs9939609 A等位基因的汉族儿童发生肥胖的危险性增加。
3.FTO基因可能通过影响我国汉族儿童膳食能量摄入影响能量平衡,但对身体活动水平的影响不显著。
4. FTO SNP rs9939609可能通过调节饮食,包括食物摄入量和不同种类食物的选择,进而影响机体膳食能量摄入。
5.FTO基因在母子BMI相关性中发挥了一定的作用,但作用并不显著。
Background
Genetic and environmental factors play an important role in the emergence and development of obesity. Genetic factors increase the susceptibility to obesity. However, even in the presence of genetic factors, obesity is the interactive result of various environmental factors and lifestyle. Research on the ralationship between genetic and environmental factors and obesity is significant in the prevention and control of childhood obesity. Recent genome-wide association (GWA) studies identified a group of loci associated with obesity. Among those genes, FTO explained the largest variation of BMI and obesity.
The association of FTO genetic variants with BMI and obesity was unequivocally replicated in European and Hispanic populations. However, these associations were controversial with regard to Asian populations. Its still need replicated studies on the associations of FTO rs9939609 with obesity and obesity-related metabolic traits in Chinese population, as well as its interaction with environmental factors, to explore the possible pathway of FTO gene's association with obesity. At the same time, further research on the relationship of genetic and environmental factors is of great significance in the prevention and control of obesity.
Objectives
The subjects included children aged 7-17 years old and their parents, a subsample of the 2002 China National Nutrition and Health Survey, to explore the associations of FTO rs9939609 with obesity and obesity-related metabolic traits in Chinese children. At the same time, further studies on the interaction of FTO with diet and physical activities can help to explain the role of FTO in governing energy balance and provide scientific basis for further research on the role of genetic factors in the emergence and development of obesity and prevention and control of obesity.
Subjects and methods
1253 Han children and their mothers'blood of 2002 China National Nutrition and Health Survey saved in-80℃were randomly selected. Genomic DNA was successfully extracted. Taqman-MGB probe method was used to detect the FTO SNP rs9939609 polymorphism.
In this study, we further randomly selected 674 Han students aged 8-11 years from the School-based Physical Activity Intervention Research Project launched by National Institute for Nutrition and Food Safety, Chinese Center for Disease Control and Prevention in 2005. The baseline data was used for further study on the associations of FTO SNP rs9939609 with obesity, body composition and obesity-related metabolic traits in Chinese Han children.
Logistic regression analysis was performed to compare the likelihood of overweight and obesity between the carriers of TT genotype and the carrier of AA/AT genotype. Association of FTO rs9939609 with obesity-related measures and obesity-related metabolic traits were performed with General Linear Model, using the children's age, sex, family income and puberty stage and mother's age, vocation, education level and area as covariates. The variates of non-normal distributions were natural logarithm transformed before analysis. PAR and PAR% were calculated according to the incidence of obesity.
Results
1. The associations of FTO gene with obesity and obesity-related metabolic traits in Chinese Han children
In 2002 China National Nutrition and Health Survey and School-based Physical Activity Intervention Research Project, the rs9939609 A allele frequency of the Han children of China and Beijing were 12.7% and 12.2% respectively. The frequency of homozygote of the A allele were 1.4% and 1.2%, respectively. And the genotype distributions of FTO SNP rs9939609 were consistent with Hardy-Weinberg equilibrium.
No significant associations of rs9939609 with BMI and obesity were found in the 2002 China National Nutrition and Health Survey. This population was powered at 12% to detect odds ratios (OR) of 1.15 for obesity, significantly lower than the study on the Han children in Beijing.
The associations of FTO rs9939609 with BMI and obesity in Beijing Han children were confirmed. The prevalence of obesity among the carriers of AA/AT genotypes was significantly higher than that among those with TT genotype (36.4% vs.22.6%, P=0.004). Compared to the carrier of TT genotype, the likelihood of obesity was 1.8 (95% confidence interval (95% CI) 1.2-2.7) for the carrier of AA/AT genotype. The percentage of population attributable risk was 12.4%.
Compared with the TT genotype, the weight, BMI, waist-to-hip ratio (WHR), subscapular skinfold thickness, suprailiac skinfold thickness, body fat and lean body mass of carriers with the AA/AT genotype were significantly higher than those with TT genotype. The height, birth weight and percent of body fat were not significantly different between the children with TT and AA/AT genotype.
The associations of FTO rs9939609 with triglyceride, adiponectin and glucose were confirmed. While, after further adjustment for BMI, the evidence of associations was reduced. There was weak evidence of associations between rs9939609 and other obesity-related metabolic traits including TC, LDL, HDL, leptin, ghrelin, bloodpressure, insulin, and insulin resistance.
2. The associations of FTO gene with dietary energy intake and physical activity level
Compared with the TT genotype, we found marginally increasing level of dietary energy intake in the AA/AT genotype subjects (P=0.095). The consumption of fat, energy from fat and the percentage from fat were found obviously higher. After further adjustment for BMI, the associations were still significant. While, there was weak evidence of associations between rs9939609 and physical activity including physical activity time, sleeping time, sedentary time and energy expenditure of physical activity. After further adjustment for BMI, there were still no significant associations.
3. Effects of FTO SNP rs9939609 on DDS, the selection of food and NAR
Compared with the TT genotype, there was increasing tendency for DDS in the AA/AT genotype subjects. The intra-group diversity scores of cereals and cereal products, meat and meat products, sugars and preserves marginally increased in the AA/AT carriers. There were no significant differences in other intra-group diversity scores.
Compared with the TT genotype, the daily intake of tubers, starches and products marginally increased and the daily intake of sugars and preserves obviously increased in the AA/AT carriers. The percentage of energy intake from fruit and fruit products marginally decreased in the AA/AT carriers. While, the percentage of sugars and preserves marginally increased. The selection frequences of food of high energy density (>100kcal/100g or>200kcal/100g or 300kcal/100g) were found obviously higher. After further adjustment for BMI, the differencess were still significant.
Compared with the TT genotype, the NAR of energy marginally increased and the NAR of vitamin B6 obviously increased in the AA/AT carriers. And there were no significant differences in the NAR of other nutrients and MAR.
4. The association of FTO SNP gene with obesity in Chinese adult women
The rs9939609 A allele frequency of the Han adult women was 13.6%. The frequency of homozygote of the A allele was 1.8%. And the genotype distributions of FTO SNP rs9939609 were consistent with Hardy-Weinberg equilibrium (P=0.80).
The association of FTO rs9939609 with obesity in Chinese adult women was confirmed. No significant association of rs9939609 with BMI was found. The prevalence of obesity among the carriers of AA/AT genotypes was significantly higher than that among those with TT genotype (14.5% vs.9.4%,P=0.O1). Compared to the carrier of TT genotype, the likelihood of obesity was 1.63 (95% confidence interval (95% CI) 1.13-2.44) for the carrier of AA/AT genotype. The percentage of population attributable risk was 12.1%.
There was weak evidence of associations between rs9939609 and obesity-related metabolic traits including glucose, TG, TC, LDL, HDL and bloodpressure.
No significant differences of dietary energy intake, consumptions of protein, fat, carbohydrate and fiber, energy from protein, energy from fat, energy from carbohydrate and the percentages from protein, fat and carbohydrate between carriers with TT genotype and AA/AT genotype were found. And, there was weak evidence of associations between rs9939609 and physical activity including daily physical exercise time, sleeping time, sedentary time and housework time.
5. The allele frequencies of rs9939609 of FTO gene in Chinese Han children and their mothers and the relation of BMI between Chinese Han children and their mothers
The frequencies of homozygote of the A allele and T allele both in Chinese Han children and their mothers were 0.2% and 65.5%, respectively. The frequency of the AT genotype both in Chinese Han children and their mothers was 12.0%. The rate of both children and their mothers carring at least one dangerous allele was 15.0%. The rate of mothers with at least one dangerous allele and children without A allele was 10.5%. While, the rate of children with at least one dangerous allele and mothers without A allele was 9.0%.
After ajustment of the children's age, sex, family income and puberty stage and mother's age, vocation, education level and area, the BMI of mothers was positively related with the children's BMI (P<0.0001) and the correlation coefficient is o.26 (SE=0.02). After further ajustment of the genotype of FTO SNP rs9939609, the BMI of mothers was still positively related with the children's BMI (P<0.0001) and the correlation coefficient is o.25 (SE=0.02).
After ajustment of the children's age, sex, family income and puberty stage and mother's age, the correlation coefficient of BMI between Chinese Han children and their mothers was higher in the group of mothers with A allele than the group of mother without A allele. Compared with the group of mother without A allele, there was increasing tendency for the BMI of children in the group of mothers with A allele, but there was no stastically different (P=0.15). And there were no stastical differences in overweight and obesity rate between the two groups (P=0.27 and 0.96, respectively).
Further analysis of the relation of BMI between children and their mothers under four different combinations of FTO SNP rs9939609 genotype showed that, the BMI of mothers was positively related with the children's BMI under the four different combinations and the correlation coefficient between children and their mothers both without A allele was smallest. Compared with the group of children and their mothers both with A allele, there was increasing tendency for the BMI of children in the group of children and their mothers both without A allele, but there was no stastically different (P=0.16). And there were no stastical differences in overweight and obesity rate between the two groups, but no statistically significant differenc between anyother two groups (P>0.40). There were no stastical differences in overweight and obesity rate among the four groups (P>0.20).
Conclusions
1. The rs9939609 A allele frequency was substantially lower in Chinese Han children as compared with the European populations (12 vs.45%).
2. The associations of FTO rs9939609 with BMI and obesity are confirmed in Beijing Han children.
3. Influence on the energy intake of dietary is one of the ways of FTO gene affects energy balance. However, the effect of FTO SNP rs9939609 on physical activity is not found.
4. FTO gene may adjust energy intake through its effect on diet, including food intake and selection of different kinds of food.
5. FTO SNP rs9939609 plays a role in the relation of BMI between Chinese Han children and their mothers, but the effect was not significant.
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20. Willer CJ, Speliotes EK, Loos RJ, et al. Six new loci associated with body mass index highlight a neuronal influence on body weight regulation. Nat Genet,2009,41(1):25-34.
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31.中国肥胖问题工作组.中国学龄儿童青少年超重、肥胖筛查体重指数数值分类标准.中华流行病学杂志,2004,2(25)：97-102.
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36. Li H, Wu Y, Loos RJ, Hu FB, et al. Variants in the fat mass-and obesity-associated (FTO) gene are not associated with obesity in a Chinese Han population. Diabetes,2008,57:264-268.
37. Chang YC, Liu PH, Lee WJ, et al. Common variation in the fat mass and obesity-associated (FTO) gene confers risk of obesity and modulates BMI in the chinese population. Diabetes, 2008,57(8):2245-2252.
38. Lopez-Bermejo A, Petry CJ, Diaz M, et al. The association between the FTO gene and fat mass in humans develops by the postnatal age of two weeks. J Clin Endocrinol Metab,2008, 93(4):1501-1505.
39. Andreasen CH, Stender-Petersen KL, Mogensen MS, et al. Low physical activity accentuates the effect of the FTO rs9939609 polymorphism on body fat accumulation. Diabetes,2008, 57(1):95-101.
40. Scuteri A, Sanna S, Chen W-M, et al. Genome-wide association scan shows genetic variants in the FTO gene are associated with obesity-related traits. PLoS Genet,2007,3:e115.
41. Ohashi J, Naka I, Kimura R, et al. FTO polymorphisms in oceanic populations. J Hum Genet, 2007,52:1031-1035.
42. Tan JT, Dorajoo R, Seielstad M, et al. FTO variants are associated with obesity in the chinese and malay populations in Singapore. Diabetes,2008,57(10):2851-2857.
43. Omori S, Tanaka Y, Takahashi A, et al. Association of CDKAL1, IGF2BP2, CDKN2A/B, HHEX, SLC30A8, and KCNJ11 with susceptibility to type 2 diabetes in a Japanese population. Diabetes,2008,57:791-795.
44. Hotta K, Nakata Y, Matsuo T, et al. Variations in the FTO gene are associated with severe obesity in the Japanese. J Hum Genet,2008,53(6):546-553.
45. Cha SW, Choil SM, Kim KS, et al. Replication of genetic effects of FTO polymorphisms on BMI in a Korean population. Obesity,2008,16(9):2187-2189.
46. Horikoshi M, Hara K, lto C, et al. Variations in the HHEX gene are associated with increased risk of type 2 diabetes in the Japanese population. Diabetologia,2007,50(12):2461-2466.
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