Common variations in the FTO gene and obesity in Thais: A family-based study

The composite alliance of FTO locus with obesity-related genetic variants

Obesity has become a genuine global pandemic due to lifestyle and environmental modifications, and is associated with chronic lethal comorbidities. Various environmental factors such as lack of physical activity due to modernization and higher intake of energy-rich diets are primary obesogenic factors in pathogenesis of obesity. Genome-wide association study has identified the crucial role of FTO (fat mass and obesity) in human obesity. A bunch of SNPs in the first intron of FTO has been identified and subsequently correlated to body mass index and body composition. Findings of in silico, in vitro, and in vivo studies have manifested the robust role of FTO in regulation of energy expenditure and food consumption. Numerous studies have highlighted the mechanistic pathways behind the concomitant functions of FTO in adipogenesis and body size. Current investigation has also revealed the link of FTO neighbouring genes i.e., RPGRIP1L, IRX3 and IRX5 and epigenetic factors with obesity phenotypes. The motive behind this review is to cite the consequences of FTO on obesity vulnerability.

Association and interaction of the FTO rs1421085 with overweight/obesity in a sample of Pakistani individuals

PURPOSE

Genetic variants determine the predisposition of an individual to obesity in a given environment. The present study was conducted to seek an association of the FTO variant rs1421085 with overweight/obesity and related traits in 612 Pakistani subjects in a case-control manner (overweight/obese = 306 and non-obese = 306). Moreover, interaction effects of the rs1421085 and overweight/obesity on multiple metabolic traits were also investigated, which were never explored before in Pakistani as well as in any other population.

MATERIALS AND METHODS

Anthropometric traits were measured by standard procedures, while metabolic parameters were determined by biochemical assays. Genotyping of the rs1421085 was carried out by TaqMan allelic discrimination assay. The data were analysed using SPSS software version 19.

RESULTS

The study revealed a significant association of the rs1421085 with overweight/obese phenotype with respect to over-dominant model indicated by h-index. The CT genotype of the rs1421085 was observed to increase the risk of being overweight/obese by 1.583 times (95% CI 1.147-2.185, p = 0.005). The CT genotype was also found to be associated with higher values of all anthropometric variables (except height and waist-to-hip ratio). Moreover, the interaction between the CT genotype of the rs1421085 and overweight/obesity was found to influence several metabolic parameters (raised blood pressure, product of triglyceride and glucose index, triglyceride levels, LDL-C, VLDL-C, coronary risk index, atherogenic index, and triglyceride-to-HDL-C ratio).

CONCLUSION

In conclusion, the rs1421085 was found to be associated with overweight/obesity and related anthropometric traits independent of age and gender in Pakistani population. Moreover, this variant was found to influence various metabolic traits in the presence of overweight/obesity.

LEVEL OF EVIDENCE

Level III, case-control analytic study.

The effect of rs9930506 FTO gene polymorphism on obesity risk: a meta-analysis

Obesity is associated with polymorphisms of the fat mass and obesity associated gene (FTO). This meta-analysis aimed to investigate the association of the rs9930506 FTO gene polymorphism and obesity. To the best of our knowledge, this study is the first meta-analysis to evaluate the relation between FTO rs9930506 polymorphism and obesity. We searched PubMed, Web of Science, and Embase to identify studies investigating the relations between the rs9930506 FTO gene polymorphism and obesity risk. We pooled adjusted odds ratios (OR) as overall and in continent subgroups. A Fixed-effects model was used to analyze the results of these studies in dominant and recessive models. By examining 3337 obesity cases and 3159 healthy controls, we identified 8 eligible case-control studies. Considering the dominant model of inheritance, there was a relationship between the rs9939506 polymorphism and obesity (OR=1.34 [1.03- 1.74]). The association remained significant in the European subgroup (OR=1.68 [1.2-2.36]), but not in the Asian subgroup. Using the recessive model, we also found a significant relationship when the overall association was investigated (OR=2.47; 95% CI 1.56-3.91). In conclusion, this study identified that the carriers of the risk allele of FTO rs9930506 polymorphism are at higher risk for obesity.

Associations of AHR, CYP1A1, EPHX1, and GSTP1 genetic polymorphisms with small-for-gestational-age infants

OBJECTIVE

To investigate the influences of aryl hydrocarbon (AHR), cytochrome P450 (CYP1A1), epoxide hydrolase 1 (EPHX1), and glutathione S-transferase P1 (GSTP1) genetic polymorphisms on small-for-gestational-age (SGA) infants.

METHODS

This nested case-control study (126 cases and 381 controls) was based on a prospective cohort study in Shanxi Province, China. We collected the general information of subjects using questionnaire and identified their single nucleotide polymorphisms by the MassARRAY genotyping platform.

RESULTS

The polymorphisms of CYP1A1 (rs4646421 and rs4646903) and EPHX1 (rs1051740) were significantly associated with SGA. Neonates of women with EPHX1 (rs1051740) and GSTP1 (rs1695) variant alleles were at a significantly increased risk of SGA compared with the reference group (OR  =  5.26; 95% CI, 1.08-25.66), as were neonates of women with CYP1A1 (rs4646903) and EPHX1 (rs1051740) variant alleles (OR  =  7.11; 95% CI, 1.55-32.62). The results of strata analysis by AHR (rs2282883 and rs17137566) showed that the associations between the polymorphisms of CYP1A1 (rs4646421 and rs4646903) EPHX1 (rs1051740), GSTP1 (rs1695) and SGA were of significance in women with variant heterozygous or homozygous genotype.

CONCLUSIONS

CYP1A1 (rs4646421 and rs4646903), EPHX1 (rs1051740), and GSTP1 (rs1695) genetic variances might increase the risk of SGA. AHR (rs2282883 and rs17137566) resulted in estimated effects varying across strata on CYP1A1 (rs4646421 and rs4646903), EPHX1 (rs1051740), and GSTP1 (rs1695).

Assessment of the FTO gene polymorphisms (rs1421085, rs17817449 and rs9939609) in exercise-trained men and women: the effects of a 4-week hypocaloric diet

Background

Variations in the fat mass and obesity-associated gene (FTO) are associated with obesity; however, it is unclear if changes in energy intake affect the adaptive response to caloric restriction in those with risk variants. The three FTO single nucleotide polymorphisms (SNPs), rs1421085, rs17817449 and rs9939609, are in strong linkage disequilibrium. Thus, the purpose of this investigation was to determine the role of these FTO SNPs vis-à-vis the effects of a 4-week hypocaloric diet on body composition in exercise-trained men and women. Two salivary biomarkers that associate with energy expenditure were also assessed (cortisol and salivary alpha-amylase, sAA).

Methods

Forty-seven exercise-trained men (n = 11) and women (n = 36) (mean ± SD: age 32 ± 9 years; height 169 ± 8 cm, body mass index 24.5 ± 2.9 kg/m², hours of aerobic training per week 4.9 ± 3.8, hours of weight training per week 3.9 ± 2.4, years of training experience 13.4 ± 7.0) completed a 4-week hypocaloric diet (i.e., decrease total calories by ~ 20–25% while maintaining a protein intake of ~ 2.0 g/kg/d). Subjects were instructed to maintain the same training regimen and to decrease energy intake via carbohydrate and/or fat restriction during the treatment period. Body composition was assessed via dual-energy X-ray absorptiometry (DXA) (Model: Hologic Horizon W; Hologic Inc., Danbury CT USA). Total body water was determined via a multifrequency bioelectrical impedance (BIA) device (InBody 770). Saliva samples were collected pre and post intervention in order to genotype the participants as well as to determine the concentrations of cortisol and sAA.

Results

Of the 47 subjects, 15 were of normal risk for obesity whereas 32 were carriers of the FTO gene risk alleles. Subjects were grouped based on their genotype for the three FTO SNPs (i.e., rs1421085, rs17817449 and rs9939609) due to their strong linkage disequilibrium. We have classified those with the normal obesity risk as “non-risk allele” versus those that carry the “risk allele” (i.e., both heterozygous and homozygous). Both groups experienced a significant decrease in total energy intake (p < 0.01); non-risk allele: pre kcal 2081 ± 618, post kcal 1703 ± 495; risk allele: pre kcal 1886 ± 515, post kcal 1502 ± 366). Both groups lost a significant amount of body weight (p < 0.01); however, there was no difference between groups for the change (post minus pre) in each group (risk allele change: − 1.0 ± 1.2 kg, non-risk allele change: − 1.2 ± 1.4 kg). Additionally, both groups lost a significant amount of fat mass (p < 0.01) with no differences between groups for the change in fat mass (risk allele change for fat mass: 1.1 ± 0.7 kg, non-risk allele change − 0.9 ± 0.4 kg). There were no significant changes in either group for fat free mass or total body water. The change in salivary alpha-amylase or cortisol was not different between groups.

Conclusions

In the short-term (i.e., 4 weeks), exercise-trained men and women consuming a hypocaloric diet that is relatively high in protein experience similar changes in body composition due exclusively to a decrement in fat mass and independent of FTO allele status. Therefore, weight and fat loss on a hypocaloric diet is, at least in the short-term, unaffected by the FTO gene.

A novel association of rs13334070 in the RPGRIP1L gene with adiposity factors discovered by joint linkage and linkage disequilibrium analysis in Iranian pedigrees: Tehran Cardiometabolic Genetic Study (TCGS)

Understanding the genetic and metabolic bases of obesity is helpful in planning and developing health strategies. Therefore, the first family-based joint linkage and linkage disequilibrium study was conducted in Iranian pedigrees to assess the relationship between obesity and single-nucleotide polymorphisms (SNPs) located in the 16q12.2 region. In the present study, a total of 13,344 individuals were included, of whom 12,502 individuals were within 3,109 pedigrees and 842 were unrelated singletons. To investigate the relationship between obesity and genetic variants, a joint model of linkage and linkage disequilibrium was applied. Moreover, a sequence kernel association test (SKAT) was used to evaluate the association of the SNP set with body size and lipid profile measurements. The joint model showed that rs13334070, in the intron 4 of the RPGRIP1L gene, has a significant association with obesity. According to the 4-gamete rule, which is a procedure for constructing SNP sets by considering recombination occurrence between SNPs, this polymorphism has a high correlation with six nearby SNPs that make an SNP set. SKAT showed that this SNP set has a significant association with body size factors, but almost no association with most of the lipid profile measurements. In conclusion, from the result of this study, it might be reasonable to consider RPGRIP1L as an important gene whose variations could be associated with obesity risk factors.

Genetic variation of FTO: rs1421085 T>C, rs8057044 G>A, rs9939609 T>A, and copy number (CNV) in Mexican Mayan school-aged children with obesity/overweight and with normal weight

OBJECTIVES

Genetic variation of the fat mass and obesity associated gene (FTO) has been identified as a risk factor for obesity and obesity traits. Distribution of FTO single nutleotide polymorphisms (SNPs) rs1421085T>C, rs9939609T>A, rs8057044G>A and copy number variation (CNV) was evaluated in association with childhood obesity or overweight status in children with Mayan ethnicity.

METHODS

We included 318 school-aged children with obesity or overweight status (body mass index [BMI]: >85th percentile) and 303 children with normal weight (BMI: 15th-85th percentile). Genotyping was performed using real-time polymerase chain reaction (RT-PCR) with TaqMan probes. The cross-sectional study was carried out using univariate and multivariate logistic regression models adjusted for gender.

RESULTS

FTO-SNP rs1421085 showed significant differences between children with obesity and children with normal weight for the heterozygous genotype (P = 0.003) and for allele frequencies (P = 0.023). Adjusting by gender, significant differences were found in frequencies of the hetezygous genotype of SNPs rs9939609 (P = 0.023) and rs1421085 (P = 0.003) as well as in allele frequencies (P = 0.042 and P = 0.013, respectively) between girls with obesity and girls without obesity. In contrast, SNP rs8057044 was significantly different only between heterozygous overweight versus normal weight boys (P = 0.035) and for the allele frequency of rs8057044 (P = 0.021). The mean relative CNV was significantly higher in male overweight children than in boys with normal weight (P = 0.000).

CONCLUSIONS

The FTO SNP rs1421085 is a genetic factor associated with obesity in Mayan school-aged children. FTO SNPs rs1421085 and rs9939609 affect genetic susceptibility for obesity only in girls, whereas, SNP rs8057044 and CNV are associated with overweight status only in boys.

Association of fat mass and obesity-associated and retinitis pigmentosa guanosine triphosphatase (GTPase) regulator-interacting protein-1 like polymorphisms with body mass index in Chinese women

Body mass index (BMI) is the most commonly used quantitative measure of adiposity. It is a kind of complex genetic diseases which are caused by multiple susceptibility genes. The first intron of fat mass and obesity-associated (FTO) has been widely discovered to be associated with BMI. Retinitis pigmentosa GTPase regulator-interacting protein-1 like (RPGRIP1L) is located in the upstream region of FTO and has been proved to be linked with obesity through functional tests. We carried out a genetic association analysis to figure out the role of the FTO gene and the RPGRIP1L gene in BMI. A quantitative traits study with 6,102 Chinese female samples, adjusted for age, was performed during our project. Among the twelve SNPs, rs1421085, rs1558902, rs17817449, rs8050136, rs9939609, rs7202296, rs56137030, rs9930506 and rs12149832 in the FTO gene were significantly associated with BMI after Bonferroni correction. Meanwhile, rs9934800 in the RPGRIP1L gene showed significance with BMI before Bonferroni correction, but this association was eliminated after Bonferroni correction. Our results suggested that genetic variants in the FTO gene were strongly associated with BMI in Chinese women, which may serve as targets of pharmaceutical research and development concerning BMI. Meanwhile, we didn't found the significant association between RPGRIP1L and BMI in Chinese women.

A haplotype of three SNPs in FTO had a strong association with body composition and BMI in Iranian male adolescents

Background

Single-nucleotide polymorphisms (SNPs), which are located in the first intron of the FTO gene, are reported to be associated with body weight and the body mass index (BMI). However, their effects on anthropometric measurements in adolescents are poorly understood.

Objective

This study aimed to investigate the association of three adjacent polymorphisms (rs9930506, rs9930501, & rs9932754) in the FTO gene with anthropometric indices in Iranian adolescent males.

Design

The participants comprised a total of 237 adolescent males who were recruited randomly from two high schools in Tehran, Iran. The DNA samples were genotyped for the FTO gene polymorphisms by DNA sequencing. BMI, body fat percentage (BF%), and body muscle percentage (BM%) were determined using a validated bioelectrical impedance analysis scale. The association of the FTO polymorphisms with weight, height, BMI, BF%, and BM% was investigated.

Results

A haplotype of rs9930506, rs9930501, and rs9932754 (GGT) in the first intron of the FTO with complete linkage disequilibrium (LD) was found to be significantly associated with higher weight (OR = 1.32), BMI (OR = 5.36) and BF% (OR = 1.46), and lower BM% (OR = 3.59) (all P<0.001). None of the students with GGC genotypes were underweight, while all of the students with AAT genotypes had high muscle mass.

Conclusions

A haplotype in the first intron of the FTO gene had a strong association with obesity indices in Iranian adolescent males. The FTO gene polymorphisms might have greater effects on anthropometric indices than what was previously imagined. Moreover, we suggested that the FTO gene exerted their effects on anthropometric measurements through haplotypes (and not single SNPs).

FTO rs9939609 Does Not Interact with Physical Exercise but Influences Basal Insulin Metabolism in Brazilian Overweight and Obese Adolescents

PURPOSE

The rs9939609 SNP (T > A) in FTO gene is associated with obesity and type 2 diabetes. The present study aimed at verifying whether this SNP influenced biochemical outcomes of children and adolescents who are overweight/obese submitted to a program of physical exercise and also if there was influence on basal levels of these biochemical variables.

METHODS

The sample was composed by 432 children and adolescents grouped in three ways (obese, overweight, and normal weight); of these, 135 children and adoloescents who are obese and overweight were submitted to a physical exercise program for 12 weeks. All were genotyped by TaqMan SNP genotyping assay.

RESULTS

The children and adolescents who are overweight/obese and carriers of AA genotype had higher levels of insulin (p=0.03) and HOMA (p=0.007) and lower levels of glucose (p=0.003), but the SNP did not modulate the response to physical exercise.

CONCLUSIONS

In our study, the rs9939609 AA genotype was associated with parameters related to insulin metabolism but did not interact with physical exercise.

FTO rs9939609 A allele influences anthropometric outcome in response to dietary intervention, but not in response to physical exercise program

PURPOSE

The fat mass and obesity-associated (FTO) gene is involved in energy homeostasis. The A allele of the rs9939609 (SNP; T>A) is associated with obesity and higher food intake, while its effect in energy expenditure remains unclear. The aim of this study is to examine whether FTO rs9939609 is associated with the anthropometric outcomes of a physical exercise program and a dietary intervention.

METHODS

We studied two independent samples. The first was composed by children and adolescents in which overweight and obese individuals were submitted to a physical exercise program (n = 136) and normal weight participants served as a control group (n = 172). The second sample was composed by obese women submitted to a hypocaloric dietary intervention (n = 126).

RESULTS

Physical exercise and dietary intervention were effective, independently of genotype. We found no association of FTO rs9939609 with obesity in children and adolescents (p = 0.67). The rs9939609 affected the response to dietary intervention in obese women: A allele carriers reduced 2.7 cm less of abdominal circumference (AC) than homozygous TT (p = 0.04), while no effect was observed in response to physical exercise in overweight and obese children and adolescents.

CONCLUSIONS

The A allele is associated with a worse outcome in response to the hypocaloric dietary intervention regarding abdominal circumference reduction; the same allele did not show interaction with any anthropometric outcomes in response to the exercise program applied.

Association between FTO gene polymorphisms and type 2 diabetes mellitus, serum levels of apelin and androgen hormones among Iranian obese women

BACKGROUND AND AIMS

Recent studies show that FTO single nucleotide polymorphisms (SNPs) are associated with obesity and type 2 diabetes mellitus (T2DM). On the other hand, many animal models and clinical studies have demonstrated that apelin, an adipocytokine, is related to the obesity and T2DM. Additionally, obese women are at risk of Hyperandrogenemia. So, the aim of this study was to investigate the relationship between FTO variants (rs763967273, rs759031579, rs141115189, rs9926289, rs76804286 and rs9939609) with T2DM, serum apelin and androgenic hormones in Iranian obese women.

SUBJECTS AND METHODS

197 obese women (123 women with T2DM and 74 women as healthy control) were participated in this study. Anthropometrical and biochemical characteristics were measured. Serum apelin and androgen hormones levels were determined in 66 subjects consisting of 33 cases and 33 controls. PCR were carried out and subsequently, the PCR production was genotyped by Sanger sequencing assay.

RESULTS

Our observations showed that all SNPs are related to T2DM. The rs9926289 FTO variant had a strong association with serum apelin and dehydroepiandrosterone-sulfate levels (P=0.04 and P=0.03, respectively) among SNPs. In addition, apelin and androgenic hormones were correlated with T2DM. Two polymorphisms including rs9939609 and rs9926289 had a strong Linkage disequilibrium (r²=1).

CONCLUSION

FTO variants not only were associated with T2DM, but also some variants had a strong association with apelin and androgenic hormones profile.

Complex Relationship between Obesity and the Fat Mass and Obesity Locus

In the 21st century, obesity has become a serious problem because of increasing obese patients and numerous metabolic complications. The primary reasons for this situation are environmental and genetic factors. In 2007, FTO (fat mass and obesity associated) was the first gene identified through a genome-wide association study (GWAS) associated with obesity in humans. Subsequently, a cluster of single nucleotide polymorphisms (SNPs) in the first intron of the FTO gene was discovered to be associated with BMI and body composition. Various studies have explored the mechanistic basis behind this association. Thus, emerging evidence showed that FTO plays a key role regulating adipose tissue development and functions in body size and composition. Recent prevalent research topic concentrated in the three neighboring genes of FTO: RPGRIP1L, IRX3 and IRX5, as having a functional link between obesity-associated common variants within FTO and the observed human phenotypes. The purpose of this review is to present a comprehensive picture of the impact of FTO on obesity susceptibility and to illuminate these new studies of FTO function in adipose tissue.