FTO gene polymorphisms are associated with obesity and type 2 diabetes in East Asian populations: an update

Fat mass and obesity-associated (FTO) and leptin receptor (LEPR) gene polymorphisms in Egyptian obese subjects

BACKGROUND

Several studies addressed the contribution of fat mass and obesity-associated (FTO) and leptin receptor (LEPR) polymorphisms for the susceptibility to obesity among different ethnic subjects. The main purpose of this work is to evaluate the association of these polymorph\isms with obesity among Egyptian subjects.

SUBJECTS AND METHODS

This case-control study was carried out on 110 unrelated obese Egyptian subjects who were compared with 122 controls. Their genomic DNA was genotyped using the PCR technique.

RESULTS

The allelic frequencies of FTO rs9939609 (A) and LEPR rs1137101 (223R) were significantly higher in obese subjects compared with non-obese controls (p < .001). Comparing different phenotype frequencies including clinical, anthropometric, and biochemical parameters in obese subjects revealed no significant difference in relation to their genotype frequencies (p> .05).

CONCLUSIONS

This study designates a strong association for FTO and LEPR variants with the risk of obesity among Egyptian subjects.

Is FTO gene variant related to cancer risk independently of adiposity? An updated meta-analysis of 129,467 cases and 290,633 controls

Previous studies have examined the association between the fat mass and obesity-associated (FTO) gene variant and risk of cancer in diverse populations. However, the results have been inconsistent. PubMed and Embase databases were searched for the eligible publications in English language by July, 2016. The associations of FTO variants with cancer risk were estimated by calculating the pooled odds ratios and 95% confidence intervals by meta-analyses. A total of 27 publications (129,467 cancer cases and 290,633 normal controls) were included in our meta-analysis. Overall, FTO rs9939609 variant (or its proxy) was not associated with cancer risk without adjustment for body mass index, as well as additional adjustment for body mss index. However, FTO rs9939609 variant was associated with some types of cancer in the subgroup analysis. In addition, overall, there was no significant association between FTO rs1477196 variant and cancer risk regardless of adjustment for body mass index. However, FTO rs11075995 variant risk allele was associated with breast cancer risk without adjustment for body mass index, but the association disappeared with further adjustment for body mass index. This study overall does not support that the FTO variant is associated with cancer risk independently of the adiposity.

The effects of genetic variation in FTO rs9939609 on obesity and dietary preferences in Chinese Han children and adolescents

The association of the rs9939609 single nucleotide polymorphism in FTO gene with obesity has been extensively investigated in studies of populations of European, African, and Asian ancestry. However, inconsistent results have been reported in Asian populations, and the relationship of FTO variation and dietary behaviors has only rarely been examined in Chinese children and adolescents. The aim of this study was to assess the association of rs9939609 with obesity and dietary preferences in childhood in a Chinese population. Epidemiological data including dietary preferences were collected in interviews using survey questionnaires, and rs9939609 genotype was determined by real-time PCR. The associations of rs9939609 genotypes with obesity and dietary preferences were analyzed by multivariate logistic regression using both additive and dominant models. The results showed that subjects with a TA or AA genotype had an increased risk of obesity compared with the TT participants; the odds ratios (ORs) were 1.47 (95% CI: 1.25–1.71, P = 1.73×10⁻⁶), and 3.32 (95% CI: 2.01–5.47, P = 2.68×10⁻⁶), respectively. After adjusting for age and gender, body mass index, waist circumference, hip circumference, systolic blood pressure, diastolic blood pressure, fasting blood glucose, triglycerides, and low-density lipoprotein cholesterol were higher, and high-density lipoprotein cholesterol was lower in TA and AA participants than in those with the TT genotype. After additionally controlling for body mass index, the association remained significant only for systolic blood pressure (P = 0.005). Compared with TT participants, those with the AA genotype were more likely to prefer a meat-based diet (OR = 2.81, 95% CI: 1.52–5.21). The combined OR for obesity in participants with TA/AA genotypes and preference for a meat-based diet was 4.04 (95% CI: 2.8–5.81) compared with the TT participants who preferred a plant-based diet. These findings indicate the genetic variation of rs9939609 is associated with obesity and dietary preferences in Chinese children and adolescents.

Effect of FTO Gene and Physical Activity Interaction on Trunk Fat Percentage Among the Newfoundland Population

OBJECTIVE

To explore the effect of FTO gene and physical activity interaction on trunk fat percentage.

DESIGN AND METHODS

Subjects are 3,004 individuals from Newfoundland and Labrador whose trunk fat percentage and physical activity were recorded, and who were genotyped for 11 single-nucleotide polymorphisms (SNPs) in the FTO gene. Subjects were stratified by gender. Multiple tests and multiple regressions were used to analyze the effects of physical activity, variants of FTO, age, and their interactions on trunk fat percentage. Dietary information and other environmental factors were not considered.

RESULTS

Higher levels of physical activity tend to reduce trunk fat percentage in all individuals. Furthermore, in males, rs9939609 and rs1421085 were significant (α = 0.05) in explaining central body fat, but no SNPs were significant in females. For highly active males, trunk fat percentage varied significantly between variants of rs9939609 and rs1421085, but there is no significant effect among individuals with low activity. The other SNPs examined were not significant in explaining trunk fat percentage.

CONCLUSIONS

Homozygous male carriers of non-obesity risk alleles at rs9939609 and rs1421085 will have significant reduction in central body fat from physical activity in contrast to homozygous males of the obesity-risk alleles. The additive effect of these SNPs is found in males with high physical activity only.

Cross-sectional and longitudinal replication analyses of genome-wide association loci of type 2 diabetes in Han Chinese

This study aimed to examine genomic loci of type 2 diabetes (T2D) initially identified by genome-wide association studies in populations of European ancestry for their associations with T2D and quantitative glycemic traits, as well as their effects on longitudinal change in fasting plasma glucose (FPG) and T2D development, in the Chinese population. Single nucleotide polymorphisms (SNP) from 25 loci were genotyped in a large case-control sample of 10,001 subjects (5,338 T2D cases and 4,663 controls) and a prospective cohort of 1,881 Chinese. In the case-control sample, 8 SNPs in or near WFS1, CDKAL1, CDKN2A/2B, CDC123, HHEX, TCF7L2, KCNQ1, and MTNR1B were significantly associated with T2D (P<0.05). Thirteen SNPs were associated with quantitative glycemic traits. For example, the most significant SNP, rs10811661 near CDKN2A/2B (P = 1.11×10⁻⁸ for T2D), was also associated with 2-h glucose level of an oral glucose tolerance test (P = 9.11×10⁻³) and insulinogenic index (P = 2.71×10⁻²). In the cohort study, individuals carrying more risk alleles of the replicated SNPs had greater FPG increase and T2D incidence in a 7.5-year follow-up period, with each quartile increase in the number of risk alleles being associated with a 0.06 mmol/l greater increase in FPG (P = 0.03) and 19% higher odds of developing T2D (P = 0.058). Our study identified the associations of several established T2D-loci in Europeans with T2D and quantitative glycemic traits in the Chinese population. The prospective data also suggest their potential role in the risk prediction of T2D in the Chinese population.

Moderation of antipsychotic-induced weight gain by energy balance gene variants in the RUPP autism network risperidone studies

Second-generation antipsychotic exposure, in both children and adults, carries significant risk for excessive weight gain that varies widely across individuals. We queried common variation in key energy balance genes (FTO, MC4R, LEP, CNR1, FAAH) for their association with weight gain during the initial 8 weeks in the two NIMH Research Units on Pediatric Psychopharmacology Autism Network trials (N=225) of risperidone for treatment of irritability in children/adolescents aged 4-17 years with autism spectrum disorders. Variants in the cannabinoid receptor (CNR)-1 promoter (P=1.0 × 10(-6)), CNR1 (P=9.6 × 10(-5)) and the leptin (LEP) promoter (P=1.4 × 10(-4)) conferred robust-independent risks for weight gain. A model combining these three variants was highly significant (P=1.3 × 10(-9)) with a 0.85 effect size between lowest and highest risk groups. All results survived correction for multiple testing and were not dependent on dose, plasma level or ethnicity. We found no evidence for association with a reported functional variant in the endocannabinoid metabolic enzyme, fatty acid amide hydrolase, whereas body mass index-associated single-nucleotide polymorphisms in FTO and MC4R showed only trend associations. These data suggest a substantial genetic contribution of common variants in energy balance regulatory genes to individual antipsychotic-associated weight gain in children and adolescents, which supersedes findings from prior adult studies. The effects are robust enough to be detected after only 8 weeks and are more prominent in this largely treatment naive population. This study highlights compelling directions for further exploration of the pharmacogenetic basis of this concerning multifactorial adverse event.

Recapitulation of four hypertension susceptibility genes (CSK, CYP17A1, MTHFR, and FGF5) in East Asians

OBJECTIVE

A recent genome wide association study identified eight hypertension susceptibility loci in Europeans. Subsequently, several studies have investigated these associations in East Asian populations. The results of these studies, however, have been inconsistent. A meta-analysis was performed to assess the associations of the most published polymorphisms, including CSK rs1378942, CYP17A1 rs11191548, MTHFR rs17367504, and FGF5 rs16998073 polymorphisms with hypertension.

METHODS

Published literature from PubMed and Embase databases was retrieved. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using fixed- or random-effects model.

RESULTS

Seven studies (16,368 cases /19,707 controls) for CSK rs1378942 polymorphism, seven studies (15,688 cases /18,784 controls) for CYP17A1 rs11191548 polymorphism, four studies (7994 cases / 12,844 controls) for MTHFR rs17367504 polymorphism, and three studies (6026 cases / 8393 controls) for FGF5 rs16998073 polymorphism were included in the meta-analysis. The results suggested that both CYP17A1 rs11191548 and FGF5 rs16998073 polymorphisms were significantly associated with hypertension risk in East Asians (CYP17A1 rs11191548 (random effect model): OR=1.16, 95% CI 1.07-1.25, p=3.59×10(-4), I(2)=78.2%, p (heterogeneity)=1.14×10(-4); FGF5 rs16998073 (random effect model): OR=1.30, 95% CI 1.23-1.37, p=6.29×10(-21), I(2)=65.0%, p (heterogeneity)=0.009); whereas no significant association was observed for CSK rs1378942 (fix effect model: OR=1.09, 95% CI 0.98-1.22, p=0.128, I(2)=0.0%, p (heterogeneity)=0.820), or MTHFR rs17367504 (fix effect model: OR=1.06, 95% CI 0.98-1.14, p=0.126, I(2)=0.0%, p (heterogeneity)=0.822).

CONCLUSION

The present meta-analysis indicated significant associations of both CYP17A1 rs11191548 and FGF5 rs16998073 polymorphisms with hypertension susceptibility in East Asians.

Determination of the obesity-associated gene variants within the entire FTO gene by ultra-deep targeted sequencing in obese and lean children

BACKGROUND

The Fat mass and obesity-associated gene (FTO) was the first gene reliably associated with body mass index in genome-wide association studies on a population level. At present, the genetic variations within the FTO gene are still the common variants that have the largest influence on body mass index.

METHODS

In the current study, we amplified the entire FTO gene, in total 412 Kbp, in over 200 long-range PCR fragments from each individual, from 524 severely obese and 527 lean Swedish children, and sequenced the products as two DNA pools using massive parallel sequencing (SOLiD).

RESULTS

The sequencing achieved very high coverage (median 18 000 reads) and we detected and estimated allele frequencies for 705 single nucleotide polymorphisms (SNPs) (19 novel) and 40 indels (24 novel) using a sophisticated statistical approach to remove false-positive SNPs. We identified 19 obesity-associated SNPs within intron one of the FTO gene, and validated our findings with genotyping. Ten of the validated obesity-associated SNPs have a stronger obesity association (P<0.007) than the commonly studied rs9939609 SNP (P<0.012).

CONCLUSIONS

This study provides a comprehensive obesity-associated variation map of FTO, identifies novel lead SNPs and evaluates putative causative variants. We conclude that intron one is the only region within the FTO gene associated with obesity, and finally, we establish next generation sequencing of pooled DNA as a powerful method to investigate genetic association with complex diseases and traits.

Common variant (rs9939609) in the FTO gene is associated with metabolic syndrome

Recent genome-wide association studies have showed that common variant (rs9939609) in fat mass and obesity associated (FTO) gene was significantly associated with type 2 diabetes through an effect on human body mass index/obesity. Further studies have suggested that this variant was also involved in the development of metabolic syndrome (MetS). However, the results have been inconsistent. In this study, we performed a meta-analysis to clarify the association between rs9939609 polymorphism and the risk of MetS. Published literature from PubMed, EMBASE and other databases were searched. All studies assessing the association between rs9939609 polymorphism and the risk of MetS were identified. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using fixed-effects model. Thirteen studies (8,370 cases and 23,156 controls) using NCEP ATPIII criteria for MetS were pooled with a meta-analysis. The overall result showed that there was a statistically significant association between rs9939609 polymorphism and MetS risk (OR = 1.11, 95% CI = 1.06-1.17). Subgroup analysis based on ethnicity showed that effect size was only statistically significant in Europeans (OR = 1.11, 95% CI = 1.05-1.16). Eight studies (1,256 cases and 2,551 controls) using IDF criteria for MetS were pooled with a meta-analysis. The overall analysis suggested that rs9939609 polymorphism was significantly associated with MetS risk (OR = 1.32, 95% CI = 1.13-1.54). Subgroup analysis stratified by ethnicity suggested that effect size was only statistically significant in Asians (OR = 1.33, 95% CI = 1.10-1.61). Our results suggested that FTO rs9939609 polymorphism was significantly associated with the increased risk of MetS in European and Asian populations. Mechanistic investigation is also needed to clarify the effect of FTO gene in the predisposition to MetS.

GST polymorphisms are associated with hepatocellular carcinoma risk in Chinese population

AIM: To investigate the association between GSTM1 and GSTT1 polymorphisms and the risk of hepatocellular carcinoma (HCC) in Chinese population.

METHODS: Literature databases including PubMed, ISI web of science and other databases were searched. Pooled odds ratio (OR) and 95% CI were calculated using random- or fixed- effects model. Subgroup analysis and sensitivity analysis were also performed.

RESULTS: Nineteen studies of GSTM1 (2660 cases and 4017 controls) and 16 studies of GSTT1 (2410 cases and 3669 controls) were included. The GSTM1/GSTT1 null genotypes were associated with increased risk of HCC in Chinese population (for GSTM1, OR = 1.487, 95% CI: 1.159 to 1.908, P = 0.002; for GSTT1, OR = 1.510, 95% CI: 1.236 to 1.845, P = 0.000). No publication bias was detected. In subgroup analysis, glutathione S-transferases polymorphisms were significantly associated with HCC risk among the subjects living in high-incidence areas, but not among the subjects living in low-incidence areas.

CONCLUSION: The present meta-analysis suggests that GSTM1/GSTT1 null genotypes are associated with increased risk of HCC in Chinese population.

Influence of physical inactivity on associations between single nucleotide polymorphisms and genetic predisposition to childhood obesity

Childhood obesity is a complex disease that is influenced by both genetic and environmental factors. The authors' aim was to determine whether sedentary behavior and physical activity modulate the association between single nucleotide polymorphisms (SNPs) and obesity risk in Chinese children. A population-based study was carried out in 2,848 children (6-18 years of age) in Beijing, China, in 2004. It included 1,229 obese cases and 1,619 normal-weight controls. Lifestyle information was collected through the use of a validated questionnaire, and 6 SNPs were genotyped. The association between the 6 SNPs and obesity risk was modulated by sedentary behavior and physical activity. A higher risk of obesity was observed in children who carried the high-risk alleles of the 6 SNPs and engaged in sedentary behavior ≥2 hours/day outside of school or participated in low or moderate physical activity. Most notably, the association between 5 SNPs (Fas apoptotic inhibitory molecule 2 rs7138803, Niemann-Pick disease, type C1 rs1805081, fat mass- and obesity-associated gene rs6499640, melanocortin 4 receptor gene rs17782313, and brain-derived neurotrophic factor rs6265) and obesity risk was only observed in children who had moderate-to-low physical activity levels or engaged in sedentary behavior, regardless of which risk alleles they carried. The results indicated that encouraging less sedentary behavior and higher levels of physical activity could alleviate the influence of risk alleles on genetic predisposition to childhood obesity, thereby serving as a promising prevention strategy.