FTO Biology and Obesity: Why Do a Billion of Us Weigh 3 kg More?

Body fat, cardiovascular risk factors and polymorphism in the FTO gene: randomized clinical trial and different physical exercise for adolescents

OBJECTIVE

To investigate the effects of different physical exercise programs and polymorphisms of the FTO (fat mass and obesity-associated gene) on body composition and cardiovascular risk factors in adolescents with overweight and obesity.

METHODS

A randomized, parallel, double-blind clinical trial consisting of the adolescent overweight from the state public network, in a simple representative random sample, who participated in an aerobic exercise or weight training intervention for 10 weeks. Anthropometry, body composition, biochemical markers, sexual maturation, and rs9939609 polymorphism in the FTO gene were assessed. 347 adolescents had their characterization of nutritional status. 72 individuals with overweight and obesity were invited to participate. 39 remained for the start of the program and were randomly allocated to both types of intervention. In the end, 26 subjects participated in the intervention programs, with 12 and 14 in the aerobic and weight training programs, respectively.

RESULTS

Heterozygous and homozygous bearers of risk allele A participating in the aerobic program showed improvements in glycemia (p = 0.002) and total cholesterol (p = 0.023) and a reduction in body fat mass (p = 0.041). The weight training program reduced glycemia in patients with the risk allele A (p = 0.027). Cameron's stage four sexual maturation participants were 2.1 times more likely to improve their body fat (CI = 1.31-3.39).

CONCLUSION

Aerobic exercises produced exclusively a significant decrease in fat mass and total cholesterol in patients with risk allele A. Distinct physical exercise programs may cause diverse changes in risk variables related to the health of adolescents.

Nutrigenetics and nutrigenomics-A personalized approach to nutrition

The prevalence of non-communicable diseases has been on an upward trajectory for some time and this puts an enormous burden on the healthcare expenditure. Lifestyle modifications including dietary interventions hold an immense promise to manage and prevent these diseases. Recent advances in genomic research provide evidence that focussing these efforts on individual variations in abilities to metabolize nutrients (nutrigenetics) and exploring the role of dietary compounds on gene expression (nutrigenomics and nutri-epigenomics) can lead to more meaningful personalized dietary strategies to promote optimal health. This chapter aims to provide examples on these gene-diet interactions at multiple levels to support the need of embedding targeted dietary interventions as a way forward to prevent, avoid and manage diseases.

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 of FTO rs1421085 with obesity, diet, physical activity, and socioeconomic status: A longitudinal birth cohort study

BACKGROUND AND AIMS

Fat mass and obesity-associated protein (FTO) variants are among genetic variants frequently associated with obesity. We analyzed the association between FTO rs1421085 polymorphism and obesity, dietary intake, cardiorespiratory fitness (CRF), physical activity, and socioeconomic status (SES) from the age of 9-25 years.

METHODS AND RESULTS

The sample included both birth cohorts (originally n = 1176) of the Estonian Children Personality Behaviour and Health Study. The association between FTO rs1421085 and obesity, dietary intake, CRF, physical activity, and SES from the age of 15-25 years was assessed using linear mixed-effects regression models. Associations at ages 9 (younger cohort only), 15, 18, and 25 years were assessed by one-way ANOVA. Male C-allele carriers had significantly (p < 0.05) higher body mass index (BMI), sum of 5 skinfolds, body fat percentage, and hip circumference from the age of 15-25 years. Findings were similar at the age of 9 years. In female subjects, waist-to-hip ratio was significantly greater in CC homozygotes. Interestingly, female CC homozygotes had a greater decrease in the rate of change in daily energy intake and lipid intake per year and higher physical activity score at every fixed time point. Moreover, in females, an effect of FTO × SES interaction on measures of obesity was observed.

CONCLUSION

The FTO rs1421085 polymorphism was associated with obesity and abdominal obesity from childhood to young adulthood in males, and with abdominal obesity from adolescence to young adulthood in females. This association is rather related to differences in adipocyte energy metabolism than lifestyle.

Body Adiposity Changes After Lifestyle Interventions in Children/Adolescents and the NYD-SP18 and TMEM18 Variants

Background

This study was carried out to determine the relationship between the common TMEM-18 (rs4854344, G>T) and NYD-SP18 (rs6971091, G>A) gene variants and weight loss after lifestyle interventions (increased physical activity in conjunction with optimal dietary intake) in overweight/obese children/adolescents.

Material/Methods

We genotyped 684 unrelated, white, non-diabetic children (age 12.7±2.1 years, average BMI at baseline 30.66±4.80 kg/m²). Anthropometric and biochemical examinations were performed before and after 4 weeks of an intensive lifestyle intervention.

Results

The mean weight loss achieved was 5.20±2.02 kg (P<0.001). NYDSP-18 AA homozygotes had significantly higher abdominal skinfold value before and after the intervention (both, P=0.001). No significant associations between BMI decrease and the NYD-SP18 and TMEM18 variants were found. Associations between all anthropometrical and biochemical changes and genes remained non-significant after data were adjusted for sex, age, and baseline values.

Conclusions

Decreased body weight in overweight/obese children is not significantly influenced by the NYD-SP18 rs6971091 or TMEM18 rs4854344 polymorphisms.

The FTO Gene Is Associated with Growth and Omega-3/-6 Ratio in Asian Seabass

Polymorphisms in the FTO gene are associated with obesity and body mass index in humans and livestock. Little information of whether FTO plays an important role in aquaculture fish species is available. We cloned and characterized the FTO gene in an economically important food fish species: Asian seabass (Lates calcarifer). The full-length cDNA of the gene is 3679 bp, containing an ORF of 1935 bp encoding 644 amino acids, a 216 bp 5' UTR and a 1538 bp 3' UTR. The gene consisted of nine exons and eight introns and was 117,679 bp in length. Phylogenetic analysis revealed that the gene in Asian seabass was closely related to those of Japanese flounder and Nile tilapia. Analysis of its expressions using qRT-PCR showed that it was expressed ubiquitously, but was higher in the liver, stomach and intestine. Comparative analysis of the genomic sequences of part of intron 1 of the gene among 10 unrelated individuals identified two SNPs. Analysis of associations between SNPs and traits (i.e. growth, oil content, omega-3 and -6 contents) in an F₂ family demonstrated that the two SNPs were significantly associated with growth, oil content, omega-3 content and omega-3/-6 ratio. Altogether, our data suggest that the gene or/and its linked genes play an important role in growth and fatty acid synthesis, and that the SNPs associated with traits may be used as markers for selecting quicker growth and higher omega-3/-6 ratio at the fingerling stage.

Strong gender-specific additive effects of the NYD-SP18 and FTO variants on BMI values

The role of the FTO gene in obesity development is well established in populations around the world. The NYD-SP18 variant has been suggested to have a similar effect on BMI, but the role of this gene in determining BMI has not yet been verified. The objective of our study was to confirm the association between NYD-SP18 rs6971019 SNP and BMI in the Slavic population and to analyze i) the gender-specific effects of NYD-SP18 on BMI and ii) the simultaneous effect of FTO rs17817449 and NYD-SP18 on BMI. We analyzed a sample of a large adult population based on the post-MONICA study (1,191 males and 1,368 females). Individuals were analyzed three times over 9 years. NYD-SP18 rs6971019 SNP is related to BMI in males (2000/1 GG 28.3+/-3.7 kg/m(2) vs. +A 27.5+/-3.7 kg/m(2) P<0.0005; in other examinations P<0.05 and <0.005), but not in females (all P values over 0.48 in all three examinations). Further analysis revealed the significant additive effect (but not the interaction) of FTO and NYD-SP18 SNPs on BMI in males (all P<0.01). These results suggest that association between NYD-SP18 rs6971019 SNP and BMI may be restricted to males. Furthermore, variants within NYD-SP18 and FTO genes revealed a significant additive effect on BMI values in males.

Body Composition Changes in Adult Females after Lifestyle Intervention Are Influenced by the NYD-SP18 Variant

AIM

The study focuses on the analysis of the possible relationship between a common NYD-SP18 (rs6971091, G>A) gene polymorphism and weight loss after lifestyle intervention (combined dietary intake and physical activity) in overweight/obese females.

METHODS

We genotyped 139 unrelated non-diabetic Czech females (49.5 ± 13.3 years, average BMI at baseline 32.2 ± 4.6 kg/m². Biochemical and anthropometrical measurements were performed before and after ten weeks of lifestyle intervention.

CONCLUSION

Overweight/obese female carriers of the NYD-SP18 rs6971091 GG genotype exhibited a more beneficial response to the intensive lifestyle intervention than others.

Rs7206790 and rs11644943 in FTO gene are associated with risk of obesity in Chinese school-age population

To evaluate the associations between candidate FTO single nucleotide polymorphisms (SNPs) and obesity, a case-control study was conducted among Chinese school-age children, which included 500 obese cases and 500 matched controls (age, gender and location). We selected 24 candidate FTO tag-SNPs via bio-informatics analysis and performed genotyping using SNPScan technology. Results indicated that rs7206790 and rs11644943 were significantly associated with obesity among school-age children in both additive and recessive models (P<0.05) after adjusting confounders. Comparing rs7206790 CC and CG genotype of carriers, those carrying the GG genotype had an increased risk of obesity (adjusted odds ratio [OR], 3.76; 95% Confidence interval [CI], 1.24–11.43). Carriers of the AA allele of rs11644943 had a lower risk of obesity (adjusted OR, 0.16; 95% CI, 0.04–0.72) compared with those of the T allele (TT and TA). These two SNPs (rs7206790 and rs11644943) were not Linkage Disequilibrium (LD) with previous reported obesity-associated SNPs. Under the recessive model adjusted for age and gender and location, rs7206790 GG allele carriers had significantly increased BMIs (P = 0.012), weight (P = 0.012), waist circumferences (WC) (P = 0.045) and hip circumferences (HC) (P = 0.033). Conversely, rs11644943 AA allele carriers had significantly decreased BMIs (P = 0.006), WC (P = 0.037) and Waist-to-height ratios (WHtR) (P = 0.012). A dose-response relationship was found between the number of risk alleles in rs7206790, rs11644943 and rs9939609 and the risk of obesity. The Genetic Risk Score (GRS) of the reference group was 3; in comparison, those of 2, 4, and ≥5 had ORs for obesity of 0.24 (95%CI, 0.05–1.13), 1.49 (95%CI, 1.10–2.01), and 5.20 (95%CI, 1.75–15.44), respectively. This study confirmed the role of FTO variation on genetic susceptibility to obesity. We reported two new obesity-related FTO SNPs (rs7206790 and rs11644943) among Chinese school-age children.

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.

Mapping and significance of the mRNA methylome

Internal methylation of eukaryotic mRNAs in the form of N6-methyladenosine (m(6)A) and 5-methylcytidine (m(5)C) has long been known to exist, but progress in understanding its role was hampered by difficulties in identifying individual sites. This was recently overcome by high-throughput sequencing-based methods that mapped thousands of sites for both modifications throughout mammalian transcriptomes, with most sites found in mRNAs. The topology of m(6)A in mouse and human revealed both conserved and variable sites as well as plasticity in response to extracellular cues. Within mRNAs, m(5)C and m(6)A sites were relatively depleted in coding sequences and enriched in untranslated regions, suggesting functional interactions with post-transcriptional gene control. Finer distribution analyses and preexisting literature point toward roles in the regulation of mRNA splicing, translation, or decay, through an interplay with RNA-binding proteins and microRNAs. The methyltransferase (MTase) METTL3 'writes' m(6)A marks on mRNA, whereas the demethylase FTO can 'erase' them. The RNA:m(5)C MTases NSUN2 and TRDMT1 have roles in tRNA methylation but they also act on mRNA. Proper functioning of these enzymes is important in development and there are clear links to human disease. For instance, a common variant of FTO is a risk allele for obesity carried by 1 billion people worldwide and mutations cause a lethal syndrome with growth retardation and brain deficits. NSUN2 is linked to cancer and stem cell biology and mutations cause intellectual disability. In this review, we summarize the advances, open questions, and intriguing possibilities in this emerging field that might be called RNA modomics or epitranscriptomics.