Association of gene polymorphism of the fat-mass and obesity-associated gene with insulin resistance in Japanese

A Systematic Review of the Gene-Lifestyle Interactions on Metabolic Disease-Related Outcomes in Arab Populations

The increased prevalence of metabolic diseases in the Arab countries is mainly associated with genetic susceptibility, lifestyle behaviours, such as physical inactivity, and an unhealthy diet. The objective of this review was to investigate and summarise the findings of the gene-lifestyle interaction studies on metabolic diseases such as obesity and type 2 diabetes in Arab populations. Relevant articles were retrieved from a literature search on PubMed, Web of Science, and Google Scholar starting at the earliest indexing date through to January 2024. Articles that reported an interaction between gene variants and diet or physical activity were included and excluded if no interaction was investigated or if they were conducted among a non-Arab population. In total, five articles were included in this review. To date, among three out of twenty-two Arab populations, fourteen interactions have been found between the FTO rs9939609, TCF7L2 rs7903146, MC4R rs17782313, and MTHFR rs1801133 polymorphisms and diet or physical activity on obesity and type 2 diabetes outcomes. The majority of the reported gene-diet/ gene-physical activity interactions (twelve) appeared only once in the review. Consequently, replication, comparisons, and generalisation of the findings are limited due to the sample size, study designs, dietary assessment tools, statistical analysis, and genetic heterogeneity of the studied sample.

m6 A mRNA methylation: Biological features, mechanisms, and therapeutic potentials in type 2 diabetes mellitus

As the most common internal post-transcriptional RNA modification in eukaryotic cells, N6-methyladenosine (m6 A) performs a dynamic and reversible role in a variety of biological processes mediated by methyltransferases (writers), demethylases (erasers), and m6 A binding proteins (readers). M6 A methylation enables transcriptome conversion in different signals that regulate various physiological activities and organ development. Over the past few years, emerging studies have identified that mRNA m6 A regulators defect in β-cell leads to abnormal regulation of the target mRNAs, thereby resulting in β-cell dysfunction and loss of β-cell identity and mass, which are strongly associated with type 2 diabetes mellitus (T2DM) pathogenesis. Also, mRNA m6 A modification has been implicated with insulin resistance in muscles, fat, and liver cells/tissues. In this review, we elaborate on the biological features of m6 A methylation; provide a comprehensive overview of the underlying mechanisms that how it controls β-cell function, identity, and mass as well as insulin resistance; highlight its connections to glucose metabolism and lipid metabolism linking to T2DM; and further discuss its role in diabetes complications and its therapeutic potentials for T2DM diagnosis and treatment.

Dietary approach to stop hypertension and healthy eating index 2015, modify the association between FTO polymorphisms and obesity phenotypes

This study aimed to investigate the interaction of the healthy eating index (HEI) and the dietary approach to stop hypertension (DASH) diet scores with FTO polymorphisms in relation to change in obesity traits. A total of 4480 subjects aged ≥ 18 years were selected from participants of the Tehran lipid and glucose study and followed-up 3 years. Selected polymorphisms (rs1421085, rs1121980, rs8050136) were genotyped and genetic risk score (GRS) was computed. HEI and DASH scores were computed based on dietary data. Changes in body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR) and visceral adiposity index (VAI) were measured. Higher adherence to both DASH and HEI scores were increased with higher ages. Individuals with high GRS had a lower change in BMI when they had higher adherence to HEI, compared to subjects with lower HEI score (P trend = 0.01). Change in WC in participants in the fourth quartile of HEI score in minor allele carriers of FTO variants was lower compared to the first quartile; conversely, higher adherence to the DASH score by this genotypic group was related to increase in WC. No significant interaction was seen between FTO polymorphisms and both diet scores regarding changes in any of obesity traits. In conclusion, in individuals with high GRS higher adherence to HEI score was associated with lower change in BMI and WC, while higher adherence to DASH diet was associated with higher change in WC, compared to individuals with lower adherence to both scores.

FTO Common Obesity SNPs Interact with Actionable Environmental Factors: Physical Activity, Sugar-Sweetened Beverages and Wine Consumption

Genetic background is estimated to play >50% in common obesity etiology. FTO single nucleotide polymorphisms (SNPs) are strongly associated with BMI, typically in European cohorts. We investigated the interaction of common FTO SNPs with actionable environmental factors, namely physical activity, sugar-sweetened beverages (SSB) and wine consumption, and verified FTO common SNPs predisposition to obesity in the Israeli population. Adults’ (>18 years old, n = 1720) FTO common SNPs data and lifestyle and nutrition habits questionnaires were analyzed using binary logistic regression models, adjusted for confounding variables (age, sex) assuming dominant, recessive and additive genetic models. Eighteen FTO SNPs were associated with significant increased obesity risk and interacted with physical activity (p < 0.001), wine consumption (p < 0.014) and SSB consumption (p < 0.01). Inactive rs9939609 risk-allele carriers had significantly higher obesity risk compared to their active counterparts (OR = 2.54, 95% CI 1.91−3.39 and OR = 3.77, 95% CI 2.47−5.75; p < 0.001 with 3.1 and 3.5 BMI increment for heterozygotes and homozygotes, respectively). SSB consumption (≥1 serving/day) significantly raised obesity risk and wine consumption (1−3 drinks/weekly) significantly lowered obesity risk for rs9939609 risk-allele carriers (OR = 1.54, 95% CI 1.05−2.27; p = 0.028 and OR = 0.61, 95% CI 0.47−0.79; p < 0.001, respectively). Our findings demonstrate that actionable lifestyle factors modify the common FTO obesity risk in predisposed carriers, and they have personal and public health implications.

The Association of Fat Mass and Obesity-Associated Gene Polymorphism (rs9939609) on the Body Composition of Older People: Systematic Review

BACKGROUND

Population aging is growing faster than any other age group. Associated with aging, the prevalence of overweight and obesity is a potential risk factor for the development and aggravation of numerous pathologies. A genetic factor often associated with obesity is the Fat mass and obesity associated (FTO) (rs9939609) gene polymorphism, which has been extensively investigated in children, young, and adults. However, few studies have been carried out with the older population. This review aimed to verify the influence of the FTO (rs9939609) gene polymorphism on the body composition of the older population.

METHODS

We conducted a systematic review and Meta-analysis of PubMed, Scielo, and LILACS databases. Statistical analysis for meta-analysis was performed using mean values of Body Mass Index (BMI) and standard deviations.

RESULTS

The results did not show significant differences between FTO genotypes and BMI values (-0.32, 95%CI -0.45 to -0.19, I2 = 0%, p = 0.52). However, 59% of the studies identified some influence on body composition, obesity, or comorbidities.

CONCLUSION

Few publications verify FTO polymorphism effects on specific groups of the older, suggesting a reduction in the influence of this gene in the BMI with advancing age. However, we believe that more controlled studies in older populations should be performed.

Association of rs9939609-FTO with metabolic syndrome components among women from Mayan communities of Chiapas, Mexico

Background

Metabolic syndrome (MetS) is a complex cluster of risk factors, considered as a polygenic and multifactorial entity. The objective of this study was to determine the association of rs9939609-FTO polymorphism and MetS components in adult women of Mayan communities of Chiapas.

Methods

In a cross-sectional study, sociodemographic, anthropometric, clinical, and biochemical data were obtained from 291 adult women from three regions of Chiapas, Mexico. The prevalence of MetS and the allele and genotype frequencies of the rs9939609-FTO were estimated. Multivariate logistic regression models were used to assess the association of the single nucleotide polymorphism (SNP) with each of the MetS components.

Results

The MetS prevalence was 60%. We found a statistically significant association between rs9939609-FTO and hyperglycemia in the dominant model (OR 2.6; 95% CI 1.3–5.3; p = 0.007).

Conclusions

Women from Mayan communities of Chiapas presented a high prevalence of MetS and a relevant association of the FTO variant with hyperglycemia. This is the first study carried out in these Mayan indigenous communities from Chiapas.

Dietary diversity modifies the association between FTO polymorphisms and obesity phenotypes

The current study aimed to evaluate the interaction of the dietary diversity score (DDS) and FTO polymorphisms concerning obesity phenotypes. The 4480 subjects of this cohort study were selected. The polymorphisms rs1121980, rs14211085 and rs8050136 were selected and genotyped. The weighted method was used to calculate the genetic risk score (GRS). Obesity marker changes were calculated. Those with minor allele carriers of rs1121980 had lower body mass index changes (Q1: 1.58 ± 0.60 vs. Q4: 0.13 ± 0.59) and visceral adiposity index (VAI) (Q1: -0.00 ± 0.02 vs. Q4: -0.04 ± 0.02) when they had higher DDS (P interaction = 0.05). Carriers of the minor allele of rs8050136 had significant VAI change across DDS quartiles (Q1: -0.01 ± 0.02 vs. Q4: -0.02 ± 0.02, P interaction = 0.05). No significant interaction was found between the GRS and DDS on general obesity. The pattern of dietary diversity may have a mediatory role in improving obesity markers in subjects with a more genetic predisposition to adiposity.

A Comprehensive Genome-Wide and Phenome-Wide Examination of BMI and Obesity in a Northern Nevadan Cohort

The aggregation of Electronic Health Records (EHR) and personalized genetics leads to powerful discoveries relevant to population health. Here we perform genome-wide association studies (GWAS) and accompanying phenome-wide association studies (PheWAS) to validate phenotype-genotype associations of BMI, and to a greater extent, severe Class 2 obesity, using comprehensive diagnostic and clinical data from the EHR database of our cohort. Three GWASs of 500,000 variants on the Illumina platform of 6,645 Healthy Nevada participants identified several published and novel variants that affect BMI and obesity. Each GWAS was followed with two independent PheWASs to examine associations between extensive phenotypes (incidence of diagnoses, condition, or disease), significant SNPs, BMI, and incidence of extreme obesity. The first GWAS examines associations with BMI in a cohort with no type 2 diabetics, focusing exclusively on BMI. The second GWAS examines associations with BMI in a cohort that includes type 2 diabetics. In the second GWAS, type 2 diabetes is a comorbidity, and thus becomes a covariate in the statistical model. The intersection of significant variants of these two studies is surprising. The third GWAS is a case vs. control study, with cases defined as extremely obese (Class 2 or 3 obesity), and controls defined as participants with BMI between 18.5 and 25. This last GWAS identifies strong associations with extreme obesity, including established variants in the FTO and NEGR1 genes, as well as loci not yet linked to obesity. The PheWASs validate published associations between BMI and extreme obesity and incidence of specific diagnoses and conditions, yet also highlight novel links. This study emphasizes the importance of our extensive longitudinal EHR database to validate known associations and identify putative novel links with BMI and obesity.

Diabetes as a risk factor for Alzheimer's disease in the Middle East and its shared pathological mediators

The incidence of Alzheimer's disease (AD) has risen exponentially worldwide over the past decade. A growing body of research indicates that AD is linked to diabetes mellitus (DM) and suggests that impaired insulin signaling acts as a crucial risk factor in determining the progression of this devastating disease. Many studies suggest people with diabetes, especially type 2 diabetes, are at higher risk of eventually developing Alzheimer's dementia or other dementias. Despite nationwide efforts to increase awareness, the prevalence of Diabetes Mellitus (DM) has risen significantly in the Middle East and North African (MENA) region which might be due to rapid urbanization, lifestyle changes, lack of physical activity and rise in obesity. Growing body of evidence indicates that DM and AD are linked because both conditions involve impaired glucose homeostasis and altered brain function. Current theories and hypothesis clearly implicate that defective insulin signaling in the brain contributes to synaptic dysfunction and cognitive deficits in AD. In the periphery, low-grade chronic inflammation leads to insulin resistance followed by tissue deterioration. Thus insulin resistance acts as a bridge between DM and AD. There is pressing need to understand on how DM increases the risk of AD as well as the underlying mechanisms, due to the projected increase in age related disorders. Here we aim to review the incidence of AD and DM in the Middle East and the possible link between insulin signaling and ApoE carrier status on Aβ aggregation, tau hyperphosphorylation, inflammation, oxidative stress and mitochondrial dysfunction in AD. We also critically reviewed mutation studies in Arab population which might influence DM induced AD. In addition, recent clinical trials and animal studies conducted to evaluate the efficiency of anti-diabetic drugs have been reviewed.

The FTO rs9939609 "A" allele is associated with impaired fasting glucose and insulin resistance in Emirati population

BACKGROUND

Fat mass and obesity-associated protein gene variants have shown diverse influence on body weight and metabolism across different populations. Overweight, obesity and metabolic syndrome are multifactorial major health problems in the UAE and worldwide. Insulin resistance represents the link between overweight and development of metabolic syndrome and type 2 diabetes mellitus. We investigated two (FTO) variants in Emirati population, in relation to insulin resistance and different parameters of metabolic syndrome.

METHODS

We recruited 259 Emiratis through the UAE National Diabetes and Lifestyle Project. Ethical approval was obtained. Besides basic data collection, venous blood samples were collected. Fasting blood glucose, Lipid profile, and insulin levels were measured. Genotyping for (FTO) rs9939609 (A>T) and rs9930506 (G>A) were performed using real time-PCR. Insulin resistance were identified using HOMA2-IR calculation; with a cut-off point of 1.4 for female and 1.18 for male subjects.

RESULTS

The study included 259 Emiratis (age range 30-53 years, mean 41.76 years, 54.4% females), 24.5% are diabetic and 30.8% are hypertensive, with body mass index of 28.4 ± 5.9 and 28.7 ± 5.7 kg/m² in female and male subjects, respectively. Homozygous A of rs9939609 showed significantly higher fasting glucose compared to other genotypes (p = 0.04) with a trend of higher insulin level and HOMA-2IR. The A/A diabetic patients (n = 13) showed significantly higher insulin levels compared to other genotypes. G allele of rs9930506 showed a trend of higher fasting glucose and HOMA-2IR, but lower insulin level and HbA1c. No association of genotypes was detected with other components of metabolic syndrome.

CONCLUSION

There is an association of FTO rs9939609 A/A genotype and impaired fasting glucose and insulin resistance. Homozygous A genotype diabetic patients may be more vulnerable to blood glucose fluctuation. Focused genotyping can help the health care providers to identify high risk groups of both normal population and diabetic patients to intervene accordingly.

The rs9939609 polymorphism in the fat mass and obesity associated (FTO) gene is associated with obesity in Tunisian population

CONTEXT

Variations in the fat mass and obesity-associated gene (FTO) has been associated with obesity in many populations, but the results are conflicting.

OBJECTIVE

The aim of this study was to evaluate the effect of the rs9939609 polymorphism in the FTO gene on obesity risk and plasma leptin, adiponectin, insulin and lipid concentrations in Tunisians.

MATERIALS AND METHODS

Four hundred and ninety-four subjects with obesity and 334 non-obese participated in this study. The rs9939609 (T/A) genotype was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

Significant differences in genotype frequencies were observed between cases and controls. In the separate analysis by gender, the association between the AA genotype and obesity was statistically significant in women but not in men. After stratification by obesity class this association remains only with obesity class III.

DISCUSSION

Our study is in agreement with studies on Caucasian, Portuguese and Cebu Filipino populations where a gender-specific association was found between rs9939609 polymorphism and obesity. It is also in agreement with studies on Mexican, Spanish and European populations, where an association was found with obesity class III.

CONCLUSION

The rs9939609 polymorphism of FTO gene is associated with obesity, especially obesity class III in women.

Effect of FTO rs9939609 variant on insulin resistance in obese female adolescents

OBJECTIVES

FTO rs9939609 variant has been shown to be associated with insulin resistance in Caucasian children. However, studies in Asia show inconsistent findings. We investigated the association between FTO rs9939609 polymorphisms and insulin resistance in obese female adolescents in Indonesia, a genetically distinct group within Asia.

RESULTS

A total of 78 obese female adolescents participated in this study. The risk allele (A) frequency of FTO rs9939609 variant in Indonesian obese female adolescence was 44.2%. The frequency of insulin resistance was higher in the subjects with AA (54.6%) or AT (59.6%) than the subject with TT genotype (50%), but did not statistically different (p = 0.81 and p = 0.47, respectively). The insulin resistance rate was also higher in the risk allele (A) than the non-risk allele (T) subjects (0.58 vs. 0.55), but did not statistically different (p = 0.75). There was no association between FTO rs9939609 variant and body mass index, fasting glucose level, fasting insulin level, homeostatic model assessment of insulin resistance, and waist circumference (p > 0.05). In conclusion, FTO rs9939609 variant may not be associated with insulin resistance in Indonesian obese female adolescents. A multicenter study with a larger sample size is needed to clarify these findings.

FTO Gene Polymorphism Is Associated with Type 2 Diabetes through Its Effect on Increasing the Maximum BMI in Japanese Men

Aim

Several studies have demonstrated that polymorphisms within the fat-mass and obesity-associated gene (FTO) are associated with type 2 diabetes (T2D). However, whether the effects of the FTO locus on T2D susceptibility are independent of fat-mass increases remains controversial. To investigate this issue, we examined the association of FTO variants with T2D and various aspects of BMI history during adult life in a Japanese population.

Methods

We genotyped SNPs within FTO (rs1121980 and rs1558902) in 760 Japanese patients with T2D who had reached a lifetime maximum BMI (BMI_max) before or at the time of diagnosis and 693 control individuals with information regarding their BMI_max.

Results

The BMI_max showed the strongest association with T2D risk among the BMIs evaluated in this study. In the sex-combined analysis, FTO SNPs were not associated with any of the BMI variables or with T2D, but in sex-stratified analyses, both SNPs were significantly associated with the BMI_max and rs1558902 was associated with T2D in men. The association of the SNPs with T2D remained significant after adjustments for the current BMI and age, whereas the T2D association of the SNP was no longer significant after adjustments for BMI_max and age.

Conclusions

These results suggest that the effects of FTO polymorphisms on T2D susceptibility in Japanese men are mediated through their effect on increasing the BMI_max before or at the time of diagnosis.

Obesity susceptibility loci in Qataris, a highly consanguineous Arabian population

OBJECTIVES

In Qataris, a population characterized by a small size and a high rate of consanguinity, between two-thirds to three-quarters of adults are overweight or obese. We investigated the relevance of 23 obesity-related loci in the Qatari population.

METHODS

Eight-hundred-four individuals assessed to be third generation Qataris were included in the study and assigned to 3 groups according to their body mass index (BMI): 190 lean (BMI < 25 kg/m(2)); 131 overweight (25 kg/m(2) ≤ BMI < 30 kg/m(2)) and 483 obese (BMI ≥ 30 kg/m(2)). Genomic DNA was isolated from peripheral blood and genotyped by TaqMan.

RESULTS

Two loci significantly associated with obesity in Qataris: the TFAP2B variation (rs987237) (A allele versus G allele: chi-square = 10.3; P = 0.0013) and GNPDA2 variation (rs10938397) (A allele versus G allele: chi-square = 6.15; P = 0.013). The TFAP2B GG genotype negatively associated with obesity (OR = 0.21; P = 0.0031). Conversely, the GNDPA2 GG homozygous genotype associated with higher risk of obesity in subjects of age < 32 years (P = 0.0358).

CONCLUSION

We showed a different genetic profile associated with obesity in the Qatari population compared to Western populations. Studying the genetic background of Qataris is of primary importance as the etiology of a given disease might be population-specific.

An obesity genetic risk score predicts risk of insulin resistance among Chinese children

A great number of body mass index (BMI)/obesity-related loci have been identified by recent genome-wide association studies. The objective of the study is to investigate the associations of 11 obesity-related loci with insulin resistance (IR) in a Chinese children population. Participants included 3,468 Chinese children, aged 6-18 years. The 75 percentile (equal to 2.93) of homeostasis model assessment of IR (HOMA-IR) index was considered as the cut-off of IR. A total of 868 IR cases and 2,600 control children were identified. In age- and sex-adjusted model, only two SNPs in/near GNPDA2 and KCTD15 genes were significantly associated with risk of IR [GNPDA2 rs10938397: allelic odds ratio (OR) = 1.19, 95 % confidence interval (CI) 1.06-1.34, P = 0.003; KCTD15 rs29941: allelic OR = 1.15, 95 % CI = 1.01-1.31, P = 0.034]; genetic risk score was also significantly associated risk of IR (OR = 1.08, 95 % 1.04-1.12, P = 1.18 × 10(-4)). After additional adjustment for BMI, none remained significant. The associations of GNPDA2 rs10938397 and the SNPs in combination with risk of IR remained statistically significant after correction for multiple testing. The present study demonstrated that the associations of GNPDA2 rs10938397 and the SNPs in combination with risk of IR were statistically significant, which were dependent on BMI.

FTO gene variant and risk of hypertension: a meta-analysis of 57,464 hypertensive cases and 41,256 controls

OBJECTIVES

Recent studies have suggested that fat mass and obesity-associated gene (FTO) may predispose individuals to develop hypertension. However, the results have been inconsistent. We performed a meta-analysis to investigate the relationship of FTO gene variant with risk of hypertension and influence of body mass index (BMI) on this risk.

MATERIALS/METHODS

A systematic literature search in PubMed, Embase and ISI web of science databases was performed to identify eligible published literatures. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated.

RESULTS

A total of seven studies comprising 57,464 hypertensive cases and 41,256 controls met the inclusion criteria and were included in the meta-analysis. The FTO gene variant(s) showed significant association with the risk of hypertension (OR=1.16, 95% CI=1.07-1.25, P<0.001) which disappeared on adjustment for BMI (OR=1.04, 95% CI=0.98-1.10, P=0.162). In addition, stratified analysis demonstrated a significant association of the FTO variant with the risk of hypertension in obese subjects (OR=1.10, 95% CI=1.01-1.19, P=0.032) but not in non-obese individuals (OR=1.00, 95% CI=0.97-1.03, P=0.832). Subgroup analysis based on ethnicity showed significant association between FTO variant and hypertension in both European (OR=1.07, 95% CI=1.01-1.14, P=0.028) and Asian populations (OR=1.37, 95% CI=1.23-1.53, P<0.001). However, the association remained significant only in Asians (OR=1.17, 95% CI=1.01-1.35, P=0.035) but not in the Europeans (OR=1.02, 95% CI=0.97-1.07, P=0.390) on adjustment for BMI.

CONCLUSIONS

The present meta-analysis confirms that FTO genotype mediates obesity-related hypertension.

Influence of FTO variants on obesity, inflammation and cardiovascular disease risk biomarkers in Spanish children: a case-control multicentre study

Background

Variants in the FTO gene have been associated with obesity in children, but this association has not been shown with other biomarkers. We assessed the association of 52 FTO polymorphisms, spanning the whole gene, with obesity and estimated the influence of these polymorphisms on anthropometric, clinical and metabolic parameters as well as inflammation and cardiovascular disease (CVD) risk biomarkers among Spanish children.

Methods

A multicentre case–control study was conducted in 534 children (292 obese and 242 with normal-BMI). Anthropometric, clinical, metabolic, inflammation and CVD risk markers were compared using the Student’s t-test for unpaired samples. The genotype relative risk was assessed by comparing the obese and normal-BMI group, calculating the odds ratio. The association of each SNP with phenotypic parameters was analysed using either logistic or linear regression analysis.

Results

All anthropometric, clinical and metabolic factors as well as inflammatory and CVD risk biomarkers were higher in the obese than in the normal-BMI group, except adiponectin and HDL-c that were lower, and glucose, LDL-c, and metalloproteinase-9 that did not show difference. Four polymorphisms (rs9935401, rs9939609, rs9928094 and rs9930333) were positively associated with obesity and in linkage disequilibrium between each other; the haplotype including the risk alleles of these polymorphisms showed a high risk for obesity. The rs8061518 was negatively associated with obesity and the haplotype including this SNP and rs3826169, rs17818902 and rs7190053 showed a decreased risk for obesity. Additionally, the rs8061518 was associated with weight, diastolic blood pressure, insulin, homeostatic model assessment of insulin resistance, leptin, and active plasminogen inhibitor activator-1 after sex and age adjustment; however, after an additional BMI adjustment, this polymorphism remained associated only with leptin.

Conclusions

We validated the previous reported association of genetic variability in intron 1 of the FTO gene with the risk of obesity and found no association with other related traits in this region of the gene. We have observed strong statistical evidence for an association of rs8061518 in intron 3 of the gene with decreased risk of obesity and low concentration of leptin.

Fat-mass and obesity-associated gene variant and changes of body mass index from ages 3 to 13 years

OBJECTIVE

The effect of the fat-mass and obesity-associated (FTO) gene minor allele on the change of adiposity from childhood to adolescence among Asians remains unclear, and is expected to differ among the developmental stages from childhood to adolescence. We assessed the relationship between a FTO variant and changes in body mass index (BMI) between 3 and 13 years of age among Japanese.

METHODS

Subjects were 66 fifth graders (37 boys, 29 girls) enrolled in 2006 from Shunan City, Japan, and genotyped (rs1558902). Anthropometrics were measured at fifth grade and three years later at eighth grade, and data for these individuals recorded at 3 years of age by the health center were included. The effects on BMI and the BMI-standard deviation score (SDS) were analyzed after adjusting for age and sex.

RESULTS

The minor allele of FTO was positively associated with BMI and BMI-SDS among boys at an age of 10 years (β=1.779 and 0.812, respectively). The risk allele was positively associated with changes in BMI among boys between 3 and 10 years of age (β=1.656). However, negative associations with changes in BMI and BMI-SDS were found among boys between 10 and 13 years of age (β=-0.875 and -0.512, respectively).

CONCLUSION

The increment of adiposity at 10 years of age in boys might be influenced by the FTO variant, but this influence was significantly reduced at 13 years.

The effects of fat mass and obesity-associated gene variants on the body mass index among ethnic groups and in children and adults

Genome-wide association analyses have revealed common gene variations related to obesity. Variants of the fat mass and obesity-associated (FTO) gene among more than 40 genes studied were most closely associated with obesity, but the association varies among ethnicities. Moreover, the effect is significant in people of European descent as well as Asians, but less significant among people of African descent. Although the variants were also associated with type 2 diabetes and glucose homeostasis, the associations were attenuated or abolished after adjusting for adiposity. The present review considers our current understanding of the effects of the FTO variants in different ethnic groups and in adults and children.

FTO gene is related to obesity in Chilean Amerindian children and impairs HOMA-IR in prepubertal girls

OBJECTIVE

The objective of this study was to investigate the allelic frequency of the fat mass and obesity-associated (FTO) gene (rs9939609) and its influences on obesity and metabolic risk biomarkers in a cohort of normal weight and obese Chilean children determining its ethnicity.

METHODS

A total of 136 normal weight children and 238 obese children (between 6 and 11 yr old) from an urban setting were recruited for this case-control study. The children were classified as normal weight [body mass index (BMI) ≥ 5th and < 85th percentiles] or obese (BMI >95th percentile), according to the international age- and gender-specific percentiles defined by the Center for Disease Control and Prevention. The analysis of serum markers was carried out using commercial kits. The FTO polymorphism was determined through a high-resolution melting enabled real time polymerase chain reaction. Ethnicity was determined by analyzing mitochondrial DNA by the restriction fragment length polymorphism method.

RESULTS

As much as 85% of the cohort was Amerindian. The minor A allele of rs9939609 was associated with obesity (odds ratio (OR): 1.422 [95% confidence interval (CI) 1.068-1.868] p = 0.015), calculated using an additive model. In sex-stratified analysis we found that the risk variant (A) of rs9939609 was associated with a higher homeostasis model of assessment for insulin (HOMA-IR) in prepubertal obese girls. In male carriers of the A allele, HOMA-IR showed no further deterioration than that already associated with obesity.

CONCLUSIONS

In summary, we confirm the association of the FTO gene single-nucleotide polymorphism rs9939609 with obesity in Chilean Amerindian children. Furthermore we show an association between the risk allele (A) and insulin resistance-related markers in prepubertal obese girls.

The role of obesity-related genetic loci in insulin sensitivity

AIMS

Despite rapid advancements and many new diabetes susceptibility loci found in the past few years, few genetic variants associated with insulin sensitivity have been described, potentially attributable to the lack of larger cohorts examined with gold standard methods for insulin sensitivity assessment. There is a strong link between obesity and insulin sensitivity, and we hypothesized that known obesity susceptibility loci may act via effects on insulin sensitivity.

METHODS

A cohort of 71-year-old men without diabetes (Uppsala Longitudinal Study of Adult Men) underwent a euglycaemic-hyperinsulinaemic clamp and genotyping for genetic variants representing 32 loci recently reported to be associated with BMI (n = 926). The effect of these loci on the insulin sensitivity index (M/I ratio) was examined using linear regression. An in silico replication was performed in publically available data for the three top single-nucleotide polymorphisms from the Meta-Analyses of Glucose and Insulin-related traits Consortium analyses of homeostasis model assessment of insulin resistance (n = 37,037).

RESULTS

Three loci (SH2B1, MTCH2 and NEGR1) were associated with decreased insulin sensitivity at a nominal significance (P ≤ 0.05) after adjustment for BMI, but did not hold for multiple comparison correction. SH2B1 rs7359397 was also associated with homeostasis model assessment of insulin resistance in the Meta-Analyses of Glucose and Insulin-related traits Consortium data set (P = 3.9 × 10(-3)).

CONCLUSIONS

Our study supports earlier reports of SH2B1 to be of importance in insulin sensitivity and, in addition, suggests potential roles of NEGR1 and MTCH2.

FTO, abdominal adiposity, fasting hyperglycemia associated with elevated HbA1c in Japanese middle-aged women

AIM

FTO is the most important polygene for obesity and type 2 diabetes. Our aims were to investigate whether a variant in FTO affects glucose dysregulation through its effect on fat accumulation or distribution, and when and how FTO influences fat accumulation and distribution and glucose dysregulation from birth until midlife.

METHODS

A total of 454 Japanese female university students (mean age: 20 years) and 132 middle-aged women (mean age: 50 years) who were the biological mothers of the students underwent the following: genotyping for rs1558902 in the FTO gene, assessment of fat accumulation and distribution, obesity-related metabolic traits and serum adipokine measurement. A subsample of 364 students reported their weight history since birth.

RESULTS

The A allele in rs1558902 was substantially less common in young and middle-aged Japanese women (18 and 17%, respectively) than in the European population (45%). The strong effect of genotype AA on BMI was evident at age 12, 15, 20 and 50 years whereas there was no effect on birth weight. In young and middle-aged women, the variant was strongly associated with higher body weight and fat mass. The effects on abdominal girth, fasting glucose, homeostasis model assessment insulin resistance and HbA1c were evident in mothers but not in students. In addition, genotype AA was associated with increased white blood cell counts and hsCRP in mothers only. Associations with fasting glucose, insulin resistance, and white blood cell counts remained after correction for BMI, abdominal girth and fat mass. In multiple logistic regression analysis, AA homozygote in FTO was associated with higher odds of overweight (BMI ≥25 kg/m(2)) in young (OR 1.73 (95%CI 1.06-30.0)) and middle-aged women (OR 1.73 (95%CI 1.06-30.0)). It was also associated with higher odds of abdominal fat accumulation (abdominal girth ≥90 cm, OR 1.73 (95%CI 1.06-30.0)) and fasting hyperglycemia (≥100 mg/dL) (OR 1.87(95%CI 1.05-40.4)) in middle-aged mothers.

CONCLUSION

Despite the small sample size, the low average BMI, and the low risk allele frequency, a genetic variation at the FTO locus was related to greater weight gain before age 12 in Japanese women. At age 20, it was related to general adiposity. In midlife, however, it was related to abdominal adiposity in addition to general adiposity, fasting hyperglycemia, higher HbA1c and subtle systemic inflammation. Fasting hyperglycemia associated with higher HbA1c in midlife was independent of its effects on general and abdominal adiposity.

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.

Genetic variants and the metabolic syndrome: a systematic review

Several candidate gene studies on the metabolic syndrome (MetS) have been conducted. However, for most single nucleotide polymorphisms (SNPs) no systematic review on their association with MetS exists. A systematic electronic literature search was conducted until the 2nd of June 2010, using HuGE Navigator. English language articles were selected. Only genes of which at least one SNP-MetS association was studied in an accumulative total population ≥ 4000 subjects were included. Meta-analyses were conducted on SNPs with three or more studies available in a generally healthy population. In total 88 studies on 25 genes were reviewed. Additionally, for nine SNPs in seven genes (GNB3, PPARG, TCF7L2, APOA5, APOC3, APOE, CETP) a meta-analysis was conducted. The minor allele of rs9939609 (FTO), rs7903146 (TCF7L2), C56G (APOA5), T1131C (APOA5), C482T (APOC3), C455T (APOC3) and 174G>C (IL6) were more prevalent in subjects with MetS, whereas the minor allele of Taq-1B (CETP) was less prevalent in subjects with the MetS. After having systematically reviewed the most studied SNP-MetS associations, we found evidence for an association with the MetS for eight SNPs, mostly located in genes involved in lipid metabolism.

Association between the FTO gene and overweight in Japanese children and adolescents

BACKGROUND

The association between the fat mass- and obesity-associated (FTO) gene and a predisposition to obesity is inconsistent in adult Asian populations. We investigated the association of the FTO gene with weight status in Japanese children and adolescents.

DESIGN/SETTING

Nested case-control study and 3-yr longitudinal study - In the Shunan Child Cohort Study, fifth and eighth grade students attending all schools of Shunan completed the questionnaires. Overweight, including obesity, was defined as a percentage of overweight of 20% or in accordance with the International Obesity Task Force. We recruited 133 obese subjects and randomly selected controls from the 2006 cohort. We genotyped three FTO single nucleotide polymorphisms (SNPs): rs3751812, rs9939609, and rs1558902.

RESULTS

The three genotyped SNPs were in tight linkage disequilibrium, with the exception of one case. The minor SNP allele of rs3751812 conferred a predisposition to obesity, and its odds ratio was 2.2 [95% confidence interval (CI), 1.5-3.4] in the additive model and 2.7 (95% CI, 1.6-4.4) in the dominant model (p < 0.001). Although blood parameters and some lifestyle behaviors were significantly different between the cases and controls (p < 0.01), these traits were not significantly different among the genotypes. In addition, we did not find an association between the genotypes and body mass index change during the 3 yr.

CONCLUSION

The FTO gene is associated with the early onset of overweight in the Japanese population as well as in European populations. The results suggest that obesity-related risk factors in fifth and eighth graders appear because of their overweight status.