Postprandial responses in hunger and satiety are associated with the rs9939609 single nucleotide polymorphism in FTO

The interaction of the FTO gene and age interferes with macronutrient and vitamin intake in women with morbid obesity

Fat mass and obesity-related (FTO) gene single nucleotide polymorphisms (SNPs) interferes with food preferences that impact macronutrient intake. Few studies have investigated the relationship of this polymorphisms with the intake of micronutrients. Moreover, studies have shown multiple micronutrient deficiencies in patients with obesity. This work evaluated the effect of the FTO rs9939609 gene polymorphism on dietary nutritional quality and food intake of macronutrients and vitamins in of women with obesity candidates for metabolic surgery. The study included 106 women (24 to 60 years old) with BMIs of 36.1 to 64.8 kg/m2. A food frequency questionnaire validated for the local population was applied to obtain information about food intake. The Index of Nutritional Quality (INQ) was used to assess the adequacy of macronutrient and vitamin intake. Energy, protein and lipid intakes were higher in carriers of the A allele compared to TT in the younger age groups but were similar in the class of subjects aged ≥45 years. The INQ for protein was higher in carriers of the A allele than in carriers of the TT allele. The INQs for protein, carbohydrate, vitamins B2, B3 and B6 decreased, whereas the INQ for vitamin C increased with advancing age. The INQ for vitamin A was lower in AA than in TT, regardless of age, whereas vitamin E was higher in younger AA than in older AA. The INQ for vitamin B9 was higher in younger women than in older women. In conclusion, the FTO gene contributed to the intake of more energy, protein and lipids and interfered with the intake of vitamins B9, A and E. With the exception of vitamin A, the effect of the genotype was attenuated with ageing.

Associations Between rs9939609 FTO Polymorphism With Nutrient and Food Intake and Adherence to Dietary Patterns in an Urban Argentinian Population

BACKGROUND

The A allele of rs9939609 polymorphism at the FTO gene has been consistently associated with higher body mass index in different populations, but conflicting results have been found regarding its contribution to food intake variability.

OBJECTIVE

This study aimed to investigate the association between this genetic variant and nutrient and food intake in an urban Argentinian population.

DESIGN

A cross-sectional, analytic investigation was performed between October 2018 and February 2020.

PARTICIPANTS/SETTINGS

Adults of both sexes residing in La Plata, Argentina, were recruited through social networks (Instagram and Facebook). Of 179 eligible adults, a total of 173 adults were included in the final analyses.

OUTCOME MEASURES

Nutrient and food group intake data were obtained by an interview-administered food frequency questionnaire. Height and weight were measured, and genotypes were obtained by real-time polymerase chain reaction.

STATISTICAL ANALYSES

The per-allele effect on nutrient and food group intake was assessed by general linear models, adjusting for age, sex, educational level, total energy intake, and body mass index. Dietary patterns were derived by principal component analysis. The association of the A allele with adherence to each dietary pattern was also evaluated by the general linear model.

RESULTS

The frequency of the risk allele was 27%. A-carriers showed a higher total fat (1.88 [0.55, 3.21] % of total energy intake), saturated fatty acids (0.82 [0.25-1.39] % of total energy intake), and monounsaturated fatty acids (0.66 [0.08, 1.24] % of total energy intake), and a lower carbohydrate (-1.99 [-3.48, -0.50] % of total energy intake) intake than TT homozygous. A-carriers also reported a higher "milk and yogurt" (1.08 [0.24, 1.91] % of total energy intake), "animal fats" (1.09 [0.14-2.03] % of total energy intake), and fat-rich ultraprocessed foods (2.10 [0.52, 3.67] % of total energy intake) intake in comparison with TT homozygous. Furthermore, A-carriers showed higher adherence to the Western dietary pattern.

CONCLUSION

The A allele contributed to nutrient and food intake variability in the studied population and was associated with the consumption of saturated fatty acids-enriched foods.

Efficacy of a Comprehensive Weight Reduction Intervention in Male Adolescents With Different FTO Genotypes

BACKGROUND

The FTO gene polymorphisms may influence the effects of lifestyle interventions on obesity. The present study aimed to assess the influence of the rs9930506 FTO gene polymorphism on the success of a comprehensive weight loss intervention in male adolescents with overweight and obesity.

METHODS

This study was carried out on 96 adolescent boys with overweight and obesity who were randomly assigned to the intervention (n = 53) and control (n = 43) groups. The blood samples of the participants were collected, and the FTO gene was genotyped for the rs9930506 polymorphism. A comprehensive lifestyle intervention including changes in diet and physical activity was performed for 8 weeks in the intervention group.

RESULTS

Following the lifestyle intervention, BMI and fat mass decreased significantly in the intervention group compared with the control group (both p < 0.05), while no change was found in weight, height or body muscle percentage between the groups. The participants in the intervention group with the AA/AG genotype and not in carriers of the GG genotype had a significantly higher reduction in BMI (-1.21 vs. 1.87 kg/m2, F = 4.07, p < 0.05) compared with the control group.

CONCLUSION

The intervention in individuals with the AA/AG genotype has been significantly effective in weight loss compared with the control group. The intervention had no association effect on anthropometric indices in adolescents with the GG genotype of the FTO rs9930506 polymorphism.

TRIAL REGISTRATION

Name of the registry: National Nutrition and Food Technology Research Institute; Trial registration number: IRCT2016020925699N2; Date of registration: 24/04/2016; URL of trial registry record: https://www.irct.ir/trial/21447.

Specific Genotypes Associated with Differences in Fasting Insulin Levels and Body Mass Index in Healthy Young Males: Implications for Gene-Nutrient Interactions-an Exploratory Study

Background

Genetic variation may significantly impact an individual's susceptibility to diseases, particularly when combined with specific nutrients. Additionally, genetic variations can lead to interindividual differences in metabolic responses.

Objective

The present study explores the association between gene variants and observed interindividual differences in metabolic responses.

Methods

The study included 30 healthy males (aged 20-34) who underwent a fasting period and subsequently consumed a standardized meal. Blood samples were collected both before and after the meal to assess metabolic changes. BMI served as an indirect measure for assessing physiological responses associated with body composition. Appetite changes were assessed using an online Visual Analog 100-point Scale. Buccal swabs were collected to analyze genetic variants in single nucleotide polymorphisms (SNPs).

Results

The data underwent multiple regression analysis, revealing significant associations with 3 SNPs and their metabolic status: the insulin-receptor substrate 1 (IRS1) gene variant rs2943641, genotypes CT and CC, with elevated fasting insulin levels (R2 = 0.639, P = < 0.0001); the mitochondrial uncoupling protein 1 (UCP1) gene variant rs1800592, genotypes GG and GA, with increased BMI (R2 = 0.261, P = 0.007); and the peroxisome proliferator-activated receptor γ2 (PPARγ2) gene variant rs1801282, genotypes GG and GC, with increased BMI (R2 = 0.200, P = 0.024).

Conclusions

Therefore, our study established significant associations between these 3 SNPs and differences in fasting insulin levels and BMI within our cohort.

Impact of the FTO Gene Variation on Appetite and Fat Oxidation in Young Adults

The FTO rs9939609 gene, which presents three polymorphisms (AA, AT, and TT), has been associated with the development of obesity through an increased fat accumulation; however, the associations of the gene with other physiological mechanisms, such as appetite or fat oxidation, are still unclear. Therefore, this study aims to evaluate the influence of the FTO rs9939609 gene on different obesity-related factors in young adults. The FTO rs9939609 polymorphism was genotyped in 73 participants (28 women, 22.27 ± 3.70 years). Obesity-related factors included dietary assessment, physical activity expenditure, body composition, appetite sensation, resting metabolic rate, maximal fat oxidation during exercise (MFO), and cardiorespiratory fitness. Our results showed that TT allele participants expressed higher values of hunger (p = 0.049) and appetite (p = 0.043) after exercising compared to the AT allele group. Moreover, the TT allele group showed significantly higher values of MFO (p = 0.031) compared to the AT group, regardless of sex and body mass index. Thus, our results suggest that the FTO rs9939609 gene has an influence on appetite, hunger, and fat oxidation during exercise, with TT allele participants showing significantly higher values compared to the AT allele group. These findings may have practical applications for weight loss and exercise programs.

Technologies, strategies, and cautions when deconvoluting genome-wide association signals: FTO in focus

Genome-wide association studies have revealed a plethora of genetic variants that correlate with polygenic conditions. However, causal molecular mechanisms have proven challenging to fully define. Without such information, the associations are not physiologically useful or clinically actionable. By reviewing studies of the FTO locus in the genetic etiology of obesity, we wish to highlight advances in the field fueled by the evolution of technical and analytic strategies in assessing the molecular bases for genetic associations. Particular attention is drawn to extrapolating experimental findings from animal models and cell types to humans, as well as technical aspects used to identify long-range DNA interactions and their biological relevance with regard to the associated trait. A unifying model is proposed by which independent obesogenic pathways regulated by multiple FTO variants and genes are integrated at the primary cilium, a cellular antenna where signaling molecules that control energy balance convene.

Minor alleles in the FTO SNPs contributed to the increased risk of obesity among Korean adults: meta-analysis from nationwide big data-based studies

BACKGROUND/OBJECTIVES

Many studies have revealed an association between fat mass and the obesity-related gene (FTO) and obesity. On the other hand, no meta-analysis was conducted with data from only Koreans. Therefore, this study performed a meta-analysis using Korean data to provide evidence for the association between FTO single nucleotide polymorphisms (SNPs) and the risk of obesity among Korean adults.

SUBJECT/METHODS

Meta-analysis was finally conducted with data extracted from seven datasets of four studies performed on Korean adults after the screening passed. Five kinds of FTO SNPs (rs9939609, rs7193144, rs9940128, rs8050136, and rs9926289) were included, and the relationship between FTO SNPs and body mass index (BMI) was investigated using linear regression with an additive model adjusted for covariants, such as age, sex, and area.

RESULTS

The minor alleles of FTO SNPs were associated with increased BMI (odds ratio [OR], 1.31; 95% confidence interval [CI], 1.21-1.42). In sub-group analysis, FTO rs9939609 T>A was significantly associated with BMI (OR, 1.23; 95% CI, 1.06-1.42). The other FTO SNPs together were significantly associated with BMI (OR, 1.37; 95% CI, 1.25-1.49). The publication bias was not observed based on Egger's test.

CONCLUSIONS

This meta-analysis showed that minor alleles in the FTO SNPs were significantly associated with an increased BMI among Korean adults. This meta-analysis is the first to demonstrate that minor alleles in the FTO SNPs contribute significantly to the increased risk of obesity among Korean adults using data from a Korean population.

Time of day differences in appetite and gut hormone responses to meal and stress challenges in adults with normal-weight and obesity

BACKGROUND

. Lifestyle factors like time of eating and stress exposure may impact physiology to promote excess weight gain. To understand behavioral and physiological mechanisms underlying these potential effects, we compared appetite and gut hormone responses to a series of meal and stress challenges beginning in the morning and the afternoon, in adults with normal-weight and obesity.

METHOD

. Thirty-two adults (16 with normal-weight, 16 with obesity) underwent the same test protocol on different days, each following an 8 h fast. On one day the protocol began in the morning (AM condition); on the other day it began in the late afternoon (PM condition). On each day they first received a standardized liquid meal (9:00am/4:00pm), then a stress test (Socially-Evaluated Cold Pressor Test, 11:10am/6:10pm), then an ad libitum buffet meal (11:40am/6:40pm). Appetite and stress ratings were obtained, and blood was drawn for measures of ghrelin, PYY, GLP-1, insulin, glucose, cortisol and leptin. Acetaminophen was administered as a tracer to assess gastric emptying of the liquid meal.

RESULTS

. Across all three challenges, AUC cortisol was lower in the PM vs. AM condition (all p<.001), and AUC insulin and leptin were higher in the obesity vs. normal-weight group (all p<.001). For the standardized liquid meal only, AUC hunger, desire to eat and ghrelin were greater in the PM vs. AM condition (all p<0.05), and AUC ghrelin was lower in the obesity vs. normal-weight group, even when controlling for baseline values (p<0.05). AUC glucose was higher in the evening for the normal-weight group only (condition x group interaction p<0.05). Post-liquid meal gastric emptying as indexed by AUC acetaminophen was slower in the PM vs. AM (p<.01). For the stress test, AUC cortisol was lower in the PM than the AM condition even when controlling for baseline values (p<.05). AUC leptin was lower in the evening in the obesity group only (condition x group interaction p<0.01). PYY showed an acute decrease post-stressor in the normal-weight but not the obesity group (p<.05). Post-stress ad libitum buffet meal intake was similar in the evening and morning conditions, and higher in the obesity group (p<0.05). Only among the obesity group in the evening condition, higher stressor-associated stress ratings were associated with lesser fullness in relation to the buffet meal (p<0.05).

CONCLUSIONS

. Normal-weight individuals and those with obesity may be at risk of evening overeating as a result of differential appetite and gut hormone responses following meal intake and stress exposure.

The Role of Genetics in a Personalized Approach in Patients with Feeding Problems, Overweight and Obesity

Aim: For the last 20 years a large amount of data was gathered showing a genetic predisposition to overweight and obesity. The aim of this study was to demonstrate a personalized, genetic-based approach in normalizing the patients’ weight and eating habits.

Materials and methods: Eight patients – seven women and one man – aged 28-51 years with BMI ranging from 17,58 to 38,95 kg/m2 were examined. Two of them were underweight, two – with normal weight, two – overweight, and two – obese. Patients were genotyped for: APOA2 (rs5082), ADIPOQ, (rs17300539), FTO (rs9939609), KCTD10 (rs10850219), LIPC (rs1800588), MMAB (rs2241201), PPARG (rs1801282), ANKK1/DRD2 (rs1800497), TAS2R38 (rs1726866), LEPR (rs2025804) and SLC2A2 (rs5400). Based on the genetic results, the type of diet (balanced, Mediterranean, low-fat and low-carbohydrate) was determined; the predisposition to unhealthy eating habits was described and followed by a genetic counseling to clarify the findings as well as a dietitian consultation to formulate a personalized diet.

Results: Our results showed that the patients’ actual diet was equivocally different from the genetically determined one. Аll patients, except for one, had hereditary predispositions to a particular unhealthy eating habit.

Conclusion: The inclusion of genetic testing and personalization of the diet facilitates the long-term maintenance of optimal body weight.

Ramadan Diurnal Intermittent Fasting Is Associated With Attenuated FTO Gene Expression in Subjects With Overweight and Obesity: A Prospective Cohort Study

Aim and Background

A growing body of evidence supports the impact of intermittent fasting (IF) on normalizing body weight and that the interaction between body genes and environmental factors shapes human susceptibility to developing obesity. FTO gene is one of these genes with metabolic effects related to energy metabolism and body fat deposition. This research examined the changes in FTO gene expression upon Ramadan intermittent fasting (RIF) in a group of metabolically healthy subjects with overweight and obesity.

Methods

Sixty-three (63) subjects were recruited, of which 57 (17 males and 40 females, mean age 38.4 ± 11.2 years) subjects with overweight and obesity (BMI = 29.89 ± 5.02 kg/m2were recruited and monitored before and at the end of Ramadan month), and 6 healthy subjects with normal BMI (21.4 ± 2.20 kg/m2) recruited only to standardize the reference for normal levels of FTO gene expression. In the two-time points, anthropometric, biochemical, and dietary assessments were undertaken, and FTO gene expression tests were performed using RNA extracted from the whole blood sample.

Results

In contrast to normal BMI subjects, the relative gene expressions in overweight/obese were significantly decreased at the end of Ramadan (-32.30%, 95% CI-0.052 -0.981) in comparison with the pre-fasting state. Significant reductions were found in body weight, BMI, fat mass, body fat percent, hip circumference, LDL, IL-6, TNF-α (P<0.001), and in waist circumference (P<0.05), whilst HDL and IL-10 significantly increased (P<0.001) at the end of Ramadan in comparison with the pre-fasting levels. Binary logistic regression analysis for genetic expressions showed no significant association between high-energy intake, waist circumference, or obesity and FTO gene expression.

Conclusions

RIF is associated with the downregulation of the FTO gene expression in subjects with obesity, and this may explain, at least in part, its favorable metabolic effects. Hence, RIF presumably may entail a protective impact against body weight gain and its adverse metabolic-related derangements in subjects with obesity.

Nutrigenetic variants and response to diet/lifestyle intervention in obese subjects: a pilot study

AIMS

Nutritional and lifestyle interventions can contribute to prevent and treat obesity and its complications; however, genetic background may influence the success of a therapy. The aim of this pilot study is to evaluate the effects of the interaction between nutrigenetic variants and nutritional intervention, as well as the changes in clinical parameters and the adherence to Mediterranean diet (MedDiet) and to physical activity, of 18 overweight or obese subjects affected by T2D or dysglycemia included in a nutritional program.

METHODS

The subjects' clinical parameters as well as their PREDIMED score and physical activity levels were recorded and compared at baseline, at 6 months and at the end of the intervention. Rs9939609 in FTO, rs17782313 near MC4R, rs326 in LPL, rs16147 in NPY, rs2943641 near IRS-1 were genotyped.

RESULTS

The subjects carrying the A allele in FTO lost less weight (p = 0.022) and had a lower BMI decrease from baseline to 12 months (p-interaction = 0.047) than TT carriers. In addition, there was a significant PREDIMED score modification over time, according to genotypes for FTO rs9939609 (p = 0.025) and NPY rs16147 (p = 0.039), respectively.

CONCLUSIONS

These preliminary findings show a significant interaction between genetic variants and the PREDIMED score, suggesting that individuals carrying the FTO variant may lose less weight than non-carriers through diet/lifestyle intervention.

Association of ADIPOQ-rs2241766 and FTO-rs9939609 genetic variants with body mass index trajectory in women of reproductive age over 6 years of follow-up: the PREDI study

BACKGROUND

Interindividual variations in body mass index (BMI) can be partially explained by genetic differences. We aimed to examine the association of the ADIPOQ-rs2241766, LEP-rs7799039 and FTO-rs9939609 genetic variants with BMI trajectory in women of reproductive age over 6 years of follow-up.

METHODS

This was a prospective study that used data from 435 women of the PREDI Study conducted in Brazil. Socioeconomic, biological and anthropometric data were collected at four time points: 2012 (baseline) in the maternity hospital, and 2013-14, 2016-17 and 2018 (1^st, 2^nd and 3^rd follow-ups) at the participant's home. Genotyping was performed by PCR-RFLP. Linear mixed-effect and Poisson regression models were used to address the association of ADIPOQ, LEP and FTO genotypes with BMI and overweight/obesity status.

RESULTS

Women carrying the risk allele (TA or AA) of the FTO-rs9939609 genetic variant had a 1.16 kg/m² higher BMI over the follow-up period than those carrying the wild-type genotype (TT), even when adjusted for potential confounders (95% CI: 0.23-2.10, p = 0.015). The risk of obesity associated with the FTO-TA or AA genotype decreased over the years, demonstrating an influence of time on its trajectory (IRR = 0.99, 95% CI: 0.98-0.99, p = 0.016). There was no variation in BMI trajectories for the ADIPOQ-rs2241766, LEP-rs7799039 or FTO-rs9939609 genetic variant.

CONCLUSIONS

The results of this study suggest that monitoring women of reproductive age with ADIPOQ-rs2241766 TG/GG or FTO-rs9939609 TA/AA genotypes may be an important strategy to reduce maternal excess body weight and, consequently, the long-term public health burden of obesity.

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.

Associations of nicotidamide-N-methyltransferase, FTO, and IRX3 genetic variants with body mass index and resting energy expenditure in Mexican subjects

The enzyme nicotidamide-N-methyltransferase (NNMT) regulates adipose tissue energy expenditure through increasing nicotinamide adenosine dinucleotide (NAD⁺) content. NNMT methylates nicotinamide to N¹-methylnicotidamide (MNA-1) using S-adenosyl methionine. The rs694539 NNMT polymorphism is associated with non-alcoholic steatohepatitis, and rs1941404 is associated with hyperlipidemia. The rs1421085 FTO is related to poor eating behaviors, and rs3751723 IRX3 is associated with obesity. To investigate the association of rs694539 and rs1941404 NNMT, rs140285 FTO and rs3751723 IRX3 polymorphisms with MNA-1 concentrations, resting energy expenditure (REE) and BMI, we included clinically healthy Mexican subjects 30 to 50 years old, 100 subjects (35 men/65 women) with BMI > 30 kg/m² and 100 subjects (32 men/68 women) with BMI < 25 kg/m². Glucose, lipid profile, insulin, leptin, acylated ghrelin, and MNA-1 (LC–MS) were quantified. Resting energy expenditure (REE) was estimated using indirect calorimetry with a Fitmate instrument. Genotyping was performed using PCR–RFLP, and allelic discrimination was examined using TaqMan probes. MNA-1 concentrations and REE were significantly higher in obese subjects. Subjects with the rs694539AA NNMT genotype (recessive model) had lower weight, BMI, and REE. BMI showed an association with HDL-C, triglycerides, MNA-1, acetylated ghrelin, leptin, insulin concentrations, HOMA-IR, REE, and rs1421085. Subjects with the TC or CC genotypes of rs1421085 FTO showed 6 kg and 2 units of BMI more than did those with the TT wild type. The CG of the rs1421085 and rs3751723 haplotypes was associated with BMI. These findings showed that BMI was strongly associated with REE, rs1421085 FTO and the CG rs1421085 FTO and rs3751723 IRX3 haplotypes. We used the GMDR approach in obesity phenotype to show the interaction of four SNPs and metabolic variables.

Childhood obesity and the associated rise in cardiometabolic complications

Childhood obesity is one of the most serious global public-health challenges of the twenty-first century. Over the past four decades, the number of children and adolescents with obesity has risen more than tenfold. Worldwide, an increasing number of youth are facing greater exposure to obesity throughout their lives, and this increase will contribute to the early development of type 2 diabetes, fatty liver and cardiovascular complications. Herein, we provide a brief overview of trends in the global shifts in, and environmental and genetic determinants of, childhood obesity. We then discuss recent progress in the elucidation of the central role of insulin resistance, the key element linking obesity and cardiovascular-risk-factor clustering, and the potential mechanisms through which ectopic lipid accumulation leads to insulin resistance and its associated cardiometabolic complications in obese adolescents. In the absence of effective prevention and intervention programs, childhood obesity will have severe public-health consequences for decades to come.

Association of FTO and ADRB2 gene variation with energy restriction induced adaptations in resting energy expenditure and physical activity

Background

Energy restriction induces adaptations in resting energy expenditure (REE) and physical activity; inter-individual variability could be ascribed to genetic predisposition.The aim was to examine if changes in REE and physical activity as a result of weight loss were affected by candidate single nucleotide polymorphisms (SNPs).

Methods

148 subjects (39 men, 109 women), mean ± SD age: 41 ± 9 year; body mass index (BMI): 31.9 ± 3.0 kg/m², followed a very low energy diet for 8 weeks. SNPs were selected from six candidate genes: ADRB2, FTO, MC4R, PPARG2, PPARD and PPARGC1A. REE (ventilated hood) and physical activity (tri-axial accelerometer) were assessed before and after the diet. General linear modelling included gender, age and additional relevant covariates for all parameters.

Results

The heterozygotic genotype of FTO was associated with a higher amount of physical activity (1.71 Mcounts/d; CI 1.62-1.81) compared to the homozygotic major genotype (1.50 Mcounts/d; CI 1.40-1.59) (P < 0.001) while the homozygotic risk allele genotype was not different (1.56 Mcounts/d; CI 1.39-1.74) at baseline; moreover, a similar pattern was observed after energy restriction. Carrying the homozygotic minor genotype of ADRB2 was associated with a larger decrease in REE (P < 0.05) and greater adaptive thermogenesis (P < 0.05) after weight loss.

Conclusion

Carrying the minor ADRB2 allele homozygous was associated with a larger diet induced metabolic adaptation in energy expenditure and suggest a central role for reduced lipid mobilization. Carrying the risk allele of FTO homozygous was not associated with lower physical activity at baseline or after weight loss. Heterozygous carriers of one FTO risk allele showed greater physical activity before and after weight loss which might protect them in part from the higher obesity risk associated with FTO.

Ciliary gene RPGRIP1L is required for hypothalamic arcuate neuron development

Intronic polymorphisms in the α-ketoglutarate-dependent dioxygenase gene (FTO) that are highly associated with increased body weight have been implicated in the transcriptional control of a nearby ciliary gene, retinitis pigmentosa GTPase regulator-interacting protein-1 like (RPGRIP1L). Previous studies have shown that congenital Rpgrip1l hypomorphism in murine proopiomelanocortin (Pomc) neurons causes obesity by increasing food intake. Here, we show by congenital and adult-onset Rpgrip1l deletion in Pomc-expressing neurons that the hyperphagia and obesity are likely due to neurodevelopmental effects that are characterized by a reduction in the Pomc/Neuropeptide Y (Npy) neuronal number ratio and marked increases in arcuate hypothalamic-paraventricular hypothalamic (ARH-PVH) axonal projections. Biallelic RPGRIP1L mutations result in fewer cilia-positive human induced pluripotent stem cell-derived (iPSC-derived) neurons and blunted responses to Sonic Hedgehog (SHH). Isogenic human ARH-like embryonic stem cell-derived (ESc-derived) neurons homozygous for the obesity-risk alleles at rs8050136 or rs1421085 have decreased RPGRIP1L expression and have lower numbers of POMC neurons. RPGRIP1L overexpression increases POMC cell number. These findings suggest that apparently functional intronic polymorphisms affect hypothalamic RPGRIP1L expression and impact development of POMC neurons and their derivatives, leading to hyperphagia and increased adiposity.

Learning one's genetic risk changes physiology independent of actual genetic risk

Millions of people now access personal genetic risk estimates for diseases such as Alzheimer's, cancer and obesity¹. While this information can be informative^2-4, research on placebo and nocebo effects^5-8 suggests that learning of one's genetic risk may evoke physiological changes consistent with the expected risk profile. Here we tested whether merely learning of one's genetic risk for disease alters one's actual risk by making people more likely to exhibit the expected changes in gene-related physiology, behaviour and subjective experience. Individuals were genotyped for actual genetic risk and then randomly assigned to receive either a 'high-risk' or 'protected' genetic test result for obesity via cardiorespiratory exercise capacity (experiment 1, N = 116) or physiological satiety (experiment 2, N = 107) before engaging in a task in which genetic risk was salient. Merely receiving genetic risk information changed individuals' cardiorespiratory physiology, perceived exertion and running endurance during exercise, and changed satiety physiology and perceived fullness after food consumption in a self-fulfilling manner. Effects of perceived genetic risk on outcomes were sometimes greater than the effects associated with actual genetic risk. If simply conveying genetic risk information can alter actual risk, clinicians and ethicists should wrestle with appropriate thresholds for when revealing genetic risk is warranted.

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.

Associations between obesity candidate gene polymorphisms (fat mass and obesity-associated (FTO), melanocortin-4 receptor (MC4R), leptin (LEP) and leptin receptor (LEPR)) and dietary intake in pregnant women

Genetic variants associated with dietary intake may be important as factors underlying the development of obesity. We investigated the associations between the obesity candidate genes (fat mass and obesity-associated (FTO), melanocortin-4 receptor (MC4R), leptin (LEP) and leptin receptor) and total energy intake and percentage of energy from macronutrients and ultra-processed foods before and during pregnancy. A sample of 149 pregnant women was followed up in a prospective cohort in Rio de Janeiro, Brazil. A FFQ was administered at 5-13 and 30-36 weeks of gestation. Genotyping was performed using real-time PCR. Associations between polymorphisms and the outcomes were investigated through multiple linear regression and ANCOVA having pre-pregnancy dietary intake as a covariate. The A-allele of FTO-rs9939609 was associated with a -6·5 % (95 % CI -12·3, -0·4) decrease in the percentage of energy from protein and positively associated with the percentage of energy from carbohydrates before pregnancy (β=2·6; 95 % CI 0·5, 4·8) and with a 13·3 % (95 % CI 0·7, 27·5) increase in the total energy intake during pregnancy. The C-allele of MC4R-rs17782313 was associated with a -7·6 % (95 % CI -13·8, -1·0) decrease in the percentage of energy from protein, and positively associated with the percentage of energy from ultra-processed foods (β=5·4; 95 % CI 1·1, 9·8) during pregnancy. ANCOVA results revealed changes in dietary intake from pre-pregnancy to pregnancy for FTO-rs9939609 (percentage of energy from ultra-processed foods, P=0·03), MC4R-rs17782313 (total energy intake, P=0·02) and LEP-rs7799039 (total energy intake, P=0·04; percentage of energy from protein, P=0·04). These findings suggest significant associations between FTO-rs9939609, MC4R-rs17782313 and LEP-rs7799039 genes and the components of dietary intake in pregnant women.

Association of the FTO fat mass and obesity-associated gene rs9939609 polymorphism with rewarding value of food and eating behavior in Chilean children

OBJECTIVES

The aim of this study was to assess the association between the single-nucleotide polymorphism rs9939609 in the FTO gene and homeostatic/non-homeostatic eating behavior patterns in Chilean children.

METHODS

A cross-sectional study was conducted in 258 children (44% female; 8-14 y of age). Anthropometric measurements (weight, height, Z-score of height, body mass index, and waist circumference) were performed. Eating behavior was assessed using the Eating in Absence of Hunger Questionnaire; the Child Eating Behavior Questionnaire; the Three Factor Eating Questionnaire, and the Food Reinforcement Value Questionnaire. Genotype of rs9939609 was determined by a Taqman assay. Association of rs9939609 with eating behavior was assessed using non-parametric tests.

RESULTS

Allelic frequencies of rs9939609 were estimated as 77% for the A allele and 23% for the T allele. We found that normal-weight girl A carriers had higher scores of Satiety Responsiveness and Slowness on the Eating subscale. Normal-weight boy A carriers showed significantly higher scores on the Negative Affect and lower scores of the Desire to Drink subscale. In overweight children, A carriers showed higher scores on the Food Responsiveness, Emotional Overeating, Enjoyment of Food, and Food Choice subscales and lower scores on the Satiety- Responsiveness and Slowness in Eating subscales. In obese children, we found higher scores on the Cognitive Restrained subscale and lower Food Choice.

CONCLUSION

The rs9939609 A allele of the FTO gene is associated with eating behavior traits and may predispose to obesity.

Influence of FTO rs9939609 polymorphism on appetite, ghrelin, leptin, IL6, TNFα levels, and food intake of women with morbid obesity

BACKGROUND

The fat mass and obesity-related (FTO) gene has a strong relationship with obesity, extreme obesity and inflammatory state, and may also be associated with food intake regulation.

OBJECTIVE

The aim of the present study was to evaluate the influence of the rs9939609 single-nucleotide polymorphism of the FTO gene on appetite, ghrelin, leptin, interleukin 6 (IL6), tumor necrosis factor α (TNFα) levels and food intake of morbidly obese women.

MATERIALS AND METHODS

The study comprised 70 women, aged between 20 and 48 years, from Rio de Janeiro, Brazil. The participants were selected according to the body mass index between 40 and 60 kg/m². Anthropometric and biochemical data were measured during fasting. Hormones and inflammatory data were measured before and after the participants ate an isocaloric meal. Dietary records were calculated and analyzed using a nutritional assessment program. Visual analog scales were used for behaviors of the sensations of appetite and food preferences. The FTO rs9939609 variant was genotyped using real-time polymerase chain reaction.

RESULTS

Participants with the AA genotype had lower values of ghrelin and IL6 and higher values of leptin than those with TT and TA in the postprandial period. Comparing the plasma concentrations of ghrelin, insulin, IL6 and TNFα intragenotypes, it was observed that those with TT had decreased leptin and increased IL6 at the postprandial period. Subjects with TA showed increased postprandial IL6, and those with AA had decreased postprandial ghrelin. There was no difference in TNFα intra- and intergenotypes. The postprandial sensations of hunger were lower in AA than those with TT. There were differences between genotypes regarding ingested grams of protein by weight, cholesterol, B3, B5, B6 and B12 vitamins, and selenium potassium and sodium minerals.

CONCLUSION

These findings suggest that genetics may exert an influence on physiologic factors and might alter eating behavior.

FTO affects food cravings and interacts with age to influence age-related decline in food cravings

The fat mass and obesity associated gene (FTO) was the first gene identified by genome-wide association studies to correlate with higher body mass index (BMI) and increased odds of obesity. FTO remains the locus with the largest and most replicated effect on body weight, but the mechanism whereby FTO affects body weight and the development of obesity is not fully understood. Here we tested whether FTO is associated with differences in food cravings and a key aspect of dopamine function that has been hypothesized to influence food reward mechanisms. Moreover, as food cravings and dopamine function are known to decline with age, we explored effects of age on relations between FTO and food cravings and dopamine function. Seven-eight healthy subjects between 22 and 83years old completed the Food Cravings Questionnaire and underwent genotyping for FTO rs9939609, the first FTO single nucleotide polymorphism associated with obesity. Compared to TT homozygotes, individuals carrying the obesity-susceptible A allele had higher total food cravings, which correlated with higher BMI. Additionally, food cravings declined with age, but this age effect differed across variants of FTO rs9939609: while TT homozygotes showed the typical age-related decline in food cravings, there was no such decline among A carriers. All subjects were scanned with [18F]fallypride PET to assess a recent proposal that at the neurochemical level FTO alters dopamine D2-like receptor (DRD2) function to influence food reward related mechanisms. However, we observed no evidence of FTO effects on DRD2 availability.

FTO associations with obesity and telomere length

This review examines the biology of the Fat mass- and obesity-associated gene (FTO), and the implications of genetic association of FTO SNPs with obesity and genetic aging. Notably, we focus on the role of FTO in the regulation of methylation status as possible regulators of weight gain and genetic aging. We present a theoretical review of the FTO gene with a particular emphasis on associations with UCP2, AMPK, RBL2, IRX3, CUX1, mTORC1 and hormones involved in hunger regulation. These associations are important for dietary behavior regulation and cellular nutrient sensing via amino acids. We suggest that these pathways may also influence telomere regulation. Telomere length (TL) attrition may be influenced by obesity-related inflammation and oxidative stress, and FTO gene-involved pathways. There is additional emerging evidence to suggest that telomere length and obesity are bi-directionally associated. However, the role of obesity risk-related genotypes and associations with TL are not well understood. The FTO gene may influence pathways implicated in regulation of TL, which could help to explain some of the non-consistent relationship between weight phenotype and telomere length that is observed in population studies investigating obesity.

rs9939609 FTO genotype associations with FTO methylation level influences body mass and telomere length in an Australian rural population

BACKGROUND

The fat mass- and obesity-associated (FTO) gene influences energy homeostasis in humans. Although the obesity-related variant, rs9939609 has been replicated across a number of cohort studies, there remains significant variance and a low to modest association. Telomere length is another commonly reported obesity risk factor. We hypothesize understanding the associations between FTO rs9939609 with FTO methylation and telomere length will provide a more accurate assessment of obesity risk.

METHODS

Overall, 942 participants free of diabetes or pre-diabetes were included in the retrospective study. Leukocyte genomic DNA was analyzed for rs9939609 genotyping, FTO gene methylation and leukocyte telomere length (LTL) measurement.

RESULTS

In general linear models, rs9939609 AA genotypes were associated with increased fat percentage (3.15%, P=0.001), fat mass (4.16 kg, P=0.001), body mass index (BMI) (1.38, P=0.006) and waist circumference (3.35 cm, P=0.006), but not with FTO methylation or LTL in this overall population. However, when participants were stratified into higher and lower FTO methylation groups, the AA genotype possesses a 2.04-fold increased obesity risk in comparison to TT genotype (95%CI, 1.07-3.89, P=0.031) in participants with a higher FTO methylation level, but this association was absent in the lower FTO methylation sub-group. Moreover, AT and AA genotype carriers were associated with shorter LTL compared to TT carriers (P=0.020 and P=0.111, respectively) in the higher FTO methylation level group. However, this association was absent in the lower methylation group. Furthermore, FTO gene methylation level was significantly associated with LTL in the 942 samples (P=0.017).

CONCLUSIONS

FTO rs9939609 is associated with obesity risk and LTL in this study, where this association is only observed at higher, but not lower, FTO methylation levels of participants. Our data suggest association of multiple factors, including FTO methylation level, may be involved in one of several mechanisms underlying the commonly reported obesity risk of this FTO polymorphism.

Assessing gene-environment interaction effects of FTO, MC4R and lifestyle factors on obesity using an extreme phenotype sampling design: Results from the HUNT study

BACKGROUND

Our aim was to assess the influence of age, gender and lifestyle factors on the effect of the obesity-promoting alleles of FTO and MCR4.

METHODS

The HUNT study comprises health information on the population of Nord-Trøndelag county, Norway. Extreme phenotype participants (gender-wise lower and upper quartiles of waist-hip-ratio and BMI ≥ 35 kg/m2) in the third survey, HUNT3 (2006-08), were genotyped for the single-nucleotide polymorphisms rs9939609 (FTO) and rs17782313 (MC4R); 25686 participants were successfully genotyped. Extreme sampling was chosen to increase power to detect genetic and gene-environment effects on waist-hip-ratio and BMI. Statistical inference was based on linear regression models and a missing-covariate likelihood approach for the extreme phenotype sampling design. Environmental factors were physical activity, diet (artificially sweetened beverages) and smoking. Longitudinal analysis was performed using material from HUNT2 (1995-97).

RESULTS

Cross-sectional and longitudinal genetic effects indicated stronger genetic associations with obesity in young than in old, as well as differences between women and men. We observed larger genetic effects among physically inactive compared to active individuals. This interaction was age-dependent and seen mainly in 20-40 year olds. We observed a greater FTO effect among men with a regular intake of artificially sweetened beverages, compared to non-drinkers. Interaction analysis of smoking was mainly inconclusive.

CONCLUSIONS

In a large all-adult and area-based population survey the effects of obesity-promoting minor-alleles of FTO and MCR4, and interactions with life style factors are age- and gender-related. These findings appear relevant when designing individualized treatment for and prophylaxis against obesity.

Obesity-related genetic polymorphisms and adiposity indices in a young Italian population

Pediatric obesity develops when a complex biological predisposition collides with an obesogenic environment. To further elucidate the role of genetics in obesity onset, we performed a candidate-gene association study in a young and sportive Italian population by testing the association of functional polymorphisms in ACE (rs4646994), FTO (rs9939609), MC4R (rs17782313) and PPARG (rs1801282) genes with body mass index (BMI) and waist-to-height ratio (WHtR). We also tested the combinations of identified risk genotypes and epistatic interactions among them to determine the existence of cumulative effects in predicting the predisposition to gain weight. Our results confirm a significant direct influence of MC4R rs17782313 and PPARG rs1801282 on body composition, that is, minor allele homozygotes showed significantly higher BMI (rs17782313, β = 1.258, P = 0.031; rs1801282, β = 6.689, P = 1.2 × 10^-4 ) and WHtR (rs17782313, β = 0.021, P = 0.005; rs1801282, β = 0.069, P = 0.003) values. Moreover, by leveraging multifactor dimensionality reduction and general linear model (GLM) approaches we identified an epistatic interaction between ACE and MC4R, where heterozygosity at ACE rs4646994 seems to protect from the unfavorable predisposition to gain weight given by C/C genotype at MC4R rs17782313 (GLM, P = 0.004). In conclusion, to clarify the role of genetics in multifactorial diseases remains a difficult goal, even for the most investigated polymorphisms and in controlled populations. Further studies on epistasis and gene-gene interaction will help to elucidate this complex scenario. © 2017 IUBMB Life, 69(2):98-105, 2017.

FTO genotype and weight loss in diet and lifestyle interventions: a systematic review and meta-analysis

BACKGROUND

Studies have suggested that the fat mass and obesity-associated (FTO) genotype is associated with individual variability in weight loss in response to diet/lifestyle interventions, but results are inconsistent.

OBJECTIVE

We aimed to provide a summary of the literature evaluating the relation between the FTO genotype and weight loss in response to diet/lifestyle interventions.

DESIGN

A search of English-language articles in the PubMed and Embase databases (through 30 April 2015) was performed. Eligible studies were diet/lifestyle weight-loss intervention studies conducted in adults that reported changes in body weight or body mass index (BMI) by the FTO variant rs9939609 (or its proxy). Differences in weight loss between FTO genotypes across studies were pooled with the use of fixed-effect models.

RESULTS

A meta-analysis of 10 studies (comprising 6951 participants) that reported the results of additive genetic models showed that individuals with the FTO TA genotype and AA genotype (those with the obesity-predisposing A allele) had 0.18-kg (95% CI: -0.09-, 0.45-kg;P= 0.19; NS) and 0.44-kg (95% CI: 0.09-, 0.79-kg;P= 0.015) greater weight loss, respectively, than those with the TT genotype. A meta-analysis of 14 studies (comprising 7700 participants) that reported the results of dominant genetic models indicated a 0.20-kg (-0.43-, 0.04-kg) greater weight loss in the TA/AA genotype than in the TT genotype (P= 0.10). In addition, differences in weight loss between the AA genotype and TT genotype were significant in studies with a diet intervention only, adjustment for baseline BMI or body weight, and several other subgroups. However, the relatively small number of studies limited these stratified analyses, and there was no statistically significant difference between subgroups.

CONCLUSIONS

This meta-analysis suggests that individuals carrying the homozygous FTO obesity-predisposing allele may lose more weight through diet/lifestyle interventions than noncarriers. Our data provide evidence for genetic variability in response to diet/lifestyle interventions on weight loss, although clinical applications of these findings need further investigations.

Maternal intuitive eating as a moderator of the association between concern about child weight and restrictive child feeding

Mothers who are concerned about their young child's weight are more likely to use restrictive feeding, which has been associated with increased food seeking behaviors, emotional eating, and overeating in young children across multiple prospective and experimental studies. In the present study, we examined whether mothers' intuitive eating behaviors would moderate the association between their concern about their child's weight and their use of restrictive feeding. In a sample of 180 mothers of young children, two maternal intuitive eating behaviors (i.e., eating for physical reasons, trust in hunger and satiety cues) moderated this association after controlling for maternal age, body mass index, years of education, race/ethnicity, awareness of hunger and satiety cues and perceptions of child weight. More specifically, concern about child weight was unrelated to restrictive feeding for mothers with higher levels of eating for physical reasons and trust in hunger and satiety cues. However, concern about child weight was positively related to restrictive feeding among mothers with lower or average levels of eating for physical reasons and trust in hunger and satiety cues. These findings indicate that it may be important address maternal intuitive eating within interventions designed to improve self-regulated eating in children, as mothers who attend these interventions tend to be highly concerned about their child's weight and, if also low in intuitive eating, may be at risk for using restrictive feeding behaviors that interfere with children's self-regulated eating.

Genetic and epigenetic associations to obesity-related appetite phenotypes among African-American children

BACKGROUND

Genetic and epigenetic variations may be an important contributer to altered eating behaviors in childhood which may lead to weight gain and obesity later in life.

OBJECTIVE

This study aimed to evaluate epigenetic as well as genetic associations with appetite in young children.

SUBJECTS AND METHODS

Participants were 32 non-obese and 32 obese African-American children aged 5-6 years. Saliva was collected from each child, and RNA and DNA were extracted for analysis. Individuals were genotyped for eating- and obesity-associated single nucleotide polymorphisms in seven candidate genes (FTO, MAOA, SH2B1, LEPR, DNMT3B, BDNF and CCKAR), and DNA methylation levels were measured in the upstream promoter region of each. Transcript levels of MAOA and FTO were also assessed. The Children's Eating Behavior Questionnaire (CEBQ) was used to assess the aspects of appetite. Child obesity was assessed using measured height and weight, and percent body fat was measured by dual-energy X-ray absorptiometry.

RESULTS

Food responsiveness was higher and satiety responsiveness was lower among obese than non-obese female children (P = 0.001 and P = 0.031), but did not differ among male children. Epigenetic analysis of the BDNF promoter revealed associations with altered satiety responsiveness among female children (P < 0.01).

CONCLUSION

The findings provide new evidence of epigenetic associations with altered appetite among young African-American girls.

Association of the fat mass and obesity-associated gene risk allele, rs9939609A, and reward-related brain structures

OBJECTIVE

Recently, the fat mass and obesity-associated gene (FTO) has been identified as a genetic risk factor for developing obesity. The underlying mechanisms remain speculative. SNPs within FTO have been associated with brain atrophy in frontal and occipital regions, suggesting that FTO might affect body weight through cerebral pathways. Behavioral studies suggested a relationship between FTO and the reward-related behavioral traits. Therefore the relationship between the FTO risk allele rs9939609A and volumes of reward-related brain structures has been investigated.

METHODS

Four hundred and ninety-two Dutch individuals (56% males, age: 70-82 years) participating in the PROSPER study underwent a 3D-T1-weighted MRI to assess the volumes of reward-related brain structures (e.g., amygdala, nucleus accumbens) and of gray matter and white matter. Linear regression analysis was performed to test for the association of subcortical and cortical structures with rs9939609A.

RESULTS

rs9939609A is associated with lower volumes of the nucleus accumbens (p=0.03) and trended toward lower cortical gray matter volumes (p=0.08). This association is independent of gender, age, and BMI, FDR corrected.

CONCLUSIONS

The FTO risk allele is associated with lower nucleus accumbens volumes, suggesting that the higher body weight of risk-allele carriers might be due to changes within reward-related brain structures.

Appetitive traits as behavioural pathways in genetic susceptibility to obesity: a population-based cross-sectional study

The mechanisms through which genes influence body weight are not well understood, but appetite has been implicated as one mediating pathway. Here we use data from two independent population-based Finnish cohorts (4632 adults aged 25–74 years from the DILGOM study and 1231 twin individuals aged 21–26 years from the FinnTwin12 study) to investigate whether two appetitive traits mediate the associations between known obesity-related genetic variants and adiposity. The results from structural equation modelling indicate that the effects of a polygenic risk score (90 obesity-related loci) on measured body mass index and waist circumference are partly mediated through higher levels of uncontrolled eating (β_indirect= 0.030–0.032, P < 0.001 in DILGOM) and emotional eating (β_indirect= 0.020–0.022, P < 0.001 in DILGOM and β_indirect= 0.013–0.015, P = 0.043–0.044 in FinnTwin12). Our findings suggest that genetic predispositions to obesity may partly exert their effects through appetitive traits reflecting lack of control over eating or eating in response to negative emotions. Obesity prevention and treatment studies should examine the impact of targeting these eating behaviours, especially among individuals having a high genetic predisposition to obesity.

Maternal intuitive eating as a moderator of the association between concern about child weight and restrictive child feeding

Mothers who are concerned about their young child's weight are more likely to use restrictive feeding, which has been associated with increased food seeking behaviors, emotional eating, and overeating in young children across multiple prospective and experimental studies. In the present study, we examined whether mothers' intuitive eating behaviors would moderate the association between their concern about their child's weight and their use of restrictive feeding. In a sample of 180 mothers of young children, two maternal intuitive eating behaviors (i.e., eating for physical reasons, trust in hunger and satiety cues) moderated this association after controlling for maternal age, body mass index, years of education, race/ethnicity, awareness of hunger and satiety cues and perceptions of child weight. More specifically, concern about child weight was unrelated to restrictive feeding for mothers with higher levels of eating for physical reasons and trust in hunger and satiety cues. However, concern about child weight was positively related to restrictive feeding among mothers with lower or average levels of eating for physical reasons and trust in hunger and satiety cues. These findings indicate that it may be important address maternal intuitive eating within interventions designed to improve self-regulated eating in children, as mothers who attend these interventions tend to be highly concerned about their child's weight and, if also low in intuitive eating, may be at risk for using restrictive feeding behaviors that interfere with children's self-regulated eating.

Ghrelin

BACKGROUND

The gastrointestinal peptide hormone ghrelin was discovered in 1999 as the endogenous ligand of the growth hormone secretagogue receptor. Increasing evidence supports more complicated and nuanced roles for the hormone, which go beyond the regulation of systemic energy metabolism.

SCOPE OF REVIEW

In this review, we discuss the diverse biological functions of ghrelin, the regulation of its secretion, and address questions that still remain 15 years after its discovery.

MAJOR CONCLUSIONS

In recent years, ghrelin has been found to have a plethora of central and peripheral actions in distinct areas including learning and memory, gut motility and gastric acid secretion, sleep/wake rhythm, reward seeking behavior, taste sensation and glucose metabolism.

The 'Fat Mass and Obesity Related' (FTO) gene: Mechanisms of Impact on Obesity and Energy Balance

A cluster of single nucleotide polymorphisms (SNPs) in the first intron of the fat mass and obesity related (FTO) gene were the first common variants discovered to be associated with body mass index and body fatness. This review summarises what has been later discovered about the biology of FTO drawing together information from both human and animal studies. Subsequent work showed that the 'at risk' alleles of these SNPs are associated with greater food intake and increased hunger/lowered satiety, but are not associated with altered resting energy expenditure or low physical activity in humans. FTO is an FE (II) and 2-oxoglutarate dependent DNA/RNA methylase. Contrasting the impact of the SNPs on energy balance in humans, knocking out or reducing activity of the Fto gene in the mouse resulted in lowered adiposity, elevated energy expenditure with no impact on food intake (but the impact on expenditure is disputed). In contrast, overexpression of the gene in mice led to elevated food intake and adiposity, with no impact on expenditure. In rodents, the Fto gene is widely expressed in the brain including hypothalamic nuclei linked to food intake regulation. Since its activity is 2-oxoglutarate dependent it could potentially act as a sensor of citrate acid cycle flux, but this function has been dismissed, and instead it has been suggested to be much more likely to act as an amino acid sensor, linking circulating AAs to the mammalian target of rapamycin complex 1. This may be fundamental to its role in development but the link to obesity is less clear. It has been recently suggested that although the obesity related SNPs reside in the first intron of FTO, they may not only impact FTO but mediate their obesity effects via nearby genes (notably RPGRIP1L and IRX3).

FTO gene variation, macronutrient intake and coronary heart disease risk: a gene-diet interaction analysis

PURPOSE

The fat mass and obesity-associated gene (FTO) is related to obesity and coronary heart disease (CHD). We studied interaction between macronutrient intake and FTO in association with CHD risk or body mass index (BMI).

METHODS

The pooled population-based case-control studies, SHEEP and INTERGENE, included 1,381 first-time CHD patients and 4,290 population controls genotyped for FTO rs9939609 (T/A). Diet data were collected in self-administered food frequency questionnaires. Macronutrients were dichotomized into low/high energy percentages (E%) by median levels in controls. Association of FTO genotype (TA/AA vs. TT) with CHD risk was analysed by multiple logistic regression, and with BMI by multiple linear regression. Interaction between FTO and macronutrient was assessed by introducing an interaction term FTO × macronutrient. Interaction on CHD as deviation from additive effects was assessed by calculating relative excess risk due to interaction.

RESULTS

No statistically significant interaction was found between FTO genotype and any macronutrient on CHD risk or BMI on either the multiplicative or additive scale. However, FTO genotype (TA/AA vs. TT) was associated with significantly increased CHD risk only in subjects with low E% from fat (OR 1.36, 95% CI 1.11-1.66) or saturated fatty acids (OR 1.36, 95% CI 1.10-1.69), or in subjects with high E% from carbohydrate (OR 1.32, 95% CI 1.07-1.61) or protein (OR 1.41, 95% CI 1.13-1.75). Mean BMI was 0.3-0.6 kg/m(2) higher in control subjects with TA/AA compared to TT, regardless of macronutrient E%.

CONCLUSIONS

We found no evidence of interactions between FTO genotype and macronutrient intake on CHD risk or BMI.

Genetic susceptibility testing and readiness to control weight: Results from a randomized controlled trial

OBJECTIVE

To test the hypothesis that adding obesity gene feedback (FTO) to simple weight control advice at a life stage with raised risk of weight gain (university) increases readiness to control weight.

METHODS

Individually randomized controlled trial comparing the effect of: (i) simple weight control advice plus FTO feedback (FA) and (ii) simple weight control advice only (AO) on readiness to engage with weight control. Differences in stage of change by genotype and differential weight control behaviors were secondary outcomes.

RESULTS

Of 1,016 participants randomized, only 279 completed follow-up, yielding 90% power to detect a small effect for readiness to control weight. As predicted, FA participants were more likely to be in the contemplation stage than AO participants (P = 0.023). Participants receiving higher-risk genetic results were at a higher stage of change than controls (P = 0.003), with a trend toward a higher stage of change than those getting lower-risk results (P = 0.051). Lower-risk results did not decrease weight control intentions compared with controls (P = 0.55). There were no group differences in adherence to recommended weight control behaviors (P = 0.87).

CONCLUSIONS

Adding FTO feedback to weight control advice enhanced readiness to control weight, without evidence for genetic determinism, but had no more effect on behavior than weight control advice alone.

The Association of FTO SNP rs9939609 with Weight Gain at University

AIM

We tested the hypothesis that the obesity-associated FTO SNP rs9939609 would be associated with clinically significant weight gain (≥ 5% of initial body weight) in the first year of university; a time identified as high risk for weight gain.

METHODS

We collected anthropometric data from university students (n = 1,411, mean age: 22.4 ± 2.5 years, 49.1% male) at the beginning and end of the academic year. DNA was analysed for FTO rs9939609. Associations of FTO genotype with BMI at baseline were analysed using ANCOVA, and with risk of 5% weight gain over follow-up with logistic regression; both analyses adjusting for age and sex. The alpha level was reduced to 0.0125 to account for multiple testing.

RESULTS

Using an additive model, FTO status was not associated with higher BMI at baseline (22.2 vs. 21.9 kg/m2, p = 0.059). Dropout was high but unrelated to genotype. Among the 310 (21.9%) completing follow-up, those with AT genotypes had twice the odds of ≥ 5% weight gain compared with TTs (OR = 2.05, 95% CI = 1.05-4.01, p = 0.036), but this was no longer significant after Bonferroni correction. There was a trend for AA carriers for ≥ 5% weight gain compared with TT carriers (p = 0.089), but sample size was small.

CONCLUSION

This study provides nominal evidence for the genetic susceptibility hypothesis, but findings need to be replicated.

Gender-specific genetic associations of polymorphisms in ACE, AKR1C2, FTO and MMP2 with weight gain over a 10-year period

Weight gain, when it leads to overweight or obesity, is nowadays one of the major health problems. ACE, FTO, AKR1C2, TIMP4 and MMP2 genes have been implicated in previous studies on weight regulation. This study investigated the contribution of polymorphisms in these five candidate genes to the risk of weight gain over a 10-year time period. Two groups were selected from participants of the Doetinchem cohort study who were followed over a 10-year period: A stable weight group (±2 kg/10 year; n = 259) and a weight gainers group who increased their body weight by roughly 10 % (>8 kg/10 year; n = 237). Starting BMI was between 20 and 35 kg/m(2) and baseline age between 20 and 45 years. Selected SNPs and insert/deletion in candidate genes were measured in each group. In men, the allelic distribution of FTO rs9939609 (χ (2) p = 0.005), ACE rs4340 (χ (2) p = 0.006) and AKR1C2 rs12249281 (χ (2) p = 0.019) differed between the weight stable and weight gainers group. Interaction between FTO rs9939609 and ACE rs4340 was observed. In women, the allelic distribution of MMP2 rs1132896 differed between the weight stable and weight gainers group (χ (2) p = 0.00001). The A-allele of FTO was associated with a 1.99× higher risk of gaining weight in men (OR 1.99, p = 0.020), while in women, the C-allele of MMP2 was associated with a 2.50× higher risk of weight gain (OR 2.50, p = 0.001) over the 10-year period. We found that FTO in men and MMP2 in women are associated with weight gain over a 10-year follow-up period.

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.

Hypomorphism for RPGRIP1L, a ciliary gene vicinal to the FTO locus, causes increased adiposity in mice

Common polymorphisms in the first intron of FTO are associated with increased body weight in adults. Previous studies have suggested that a CUX1-regulatory element within the implicated FTO region controls expression of FTO and the nearby ciliary gene, RPGRIP1L. Given the role of ciliary genes in energy homeostasis, we hypothesized that mice hypomorphic for Rpgrip1l would display increased adiposity. We find that Rpgrip1l⁺/⁻ mice are hyperphagic and fatter, and display diminished suppression of food intake in response to leptin administration. In the hypothalamus of Rpgrip1l⁺/⁻ mice, and in human fibroblasts with hypomorphic mutations in RPGRIP1L, the number of AcIII-positive cilia is diminished, accompanied by impaired convening of the leptin receptor to the vicinity of the cilium, and diminished pStat3 in response to leptin. These findings suggest that RPGRIP1L may be partly or exclusively responsible for the obesity susceptibility signal at the FTO locus.

Obesity susceptibility loci and uncontrolled eating, emotional eating and cognitive restraint behaviors in men and women

OBJECTIVE

Many confirmed genetic loci for obesity are expressed in regions of the brain that regulate energy intake and reward-seeking behavior. Whether these loci contribute to the development of specific eating behaviors has not been investigated. The relationship between a genetic susceptibility to obesity and cognitive restraint, uncontrolled and emotional eating was examined.

METHODS

Eating behavior and body mass index (BMI) were determined by questionnaires for 1471 men and 2381 women from two US cohorts. Genotypes were extracted from genome-wide scans and a genetic-risk score (GRS) derived from 32 obesity-loci was calculated.

RESULTS

The GRS was positively associated with emotional and uncontrolled eating (P<0.002). In exploratory analysis, BMI-increasing variants of MTCH2, TNNI3K, and ZC3H4 were positively associated with emotional eating and those of TNNI3K and ZC3H4 were positively associated with uncontrolled eating. The BMI-increasing variant of FTO was positively and those of LRP1B and TFAP2B were inversely associated with cognitive restraint. These associations for single SNPs were independent of BMI but were not significant after multiple-testing correction.

CONCLUSIONS

An overall genetic susceptibility to obesity may also extend to eating behaviors. The link between specific loci and obesity may be mediated by eating behavior but larger studies are warranted to confirm these results.

The fat mass and obesity-associated (FTO) gene: Obesity and beyond?

Genome wide association studies undoubtedly linked variants of the fat mass and obesity-associated protein (FTO) to obesity. To date, however, knowledge on the mechanisms coupling variants in the intron of the FTO gene to its expression or enzymatic activity to alter metabolism remains scarce. Until recently, the investigation of the molecular function of FTO had not led to conclusive results concerning the 'where', 'when' and 'how' of FTO activity. Finally, since FTO was identified as a RNA modifying enzyme, demethylating N6-methyladenosine on single stranded RNA, novel understanding of the molecular function is gathered. These and other studies suggest the requirement for a further reaching approach to further investigate FTO function, since the phenotype of aberrant FTO function may encompass more than just obesity. Taking these new insights and translating them into appropriate paradigms for functional research in humans may lead to a deeper understanding of the human physiology and disease. This article is part of a Special Issue entitled: From Genome to Function.

Programming effects of FTO in the development of obesity

It is becoming increasingly recognized that early-life nutritional, metabolic and environmental factors can have a long-term impact on the early onset of obesity, type 2 diabetes and cardiovascular diseases. Numerous experimental and epidemiological observations support the concept that an individual's response to their adult lifestyle and nutritional environment depends not only on their genetic susceptibility but also on their previous early-life experiences. The current research challenge is to determine the primary pathways contributing to 'non- or epi-genetic' causes of excess adult weight gain and adiposity. Evidence from the fields of genetic epidemiology, life course modelling and diet-induced foetal programming all support a role for the FTO gene in this complex biological interaction. It may provide a missing link in the developmental regulation of energy metabolism. Our review therefore considers the role of the FTO gene in the early-life determination of body weight, body composition and energy balance. We will summarize current knowledge on FTO biology combining human genetic epidemiology, molecular models and findings from animal studies. Notably, we will focus on the role of FTO in energy balance in humans, the importance of FTO polymorphisms in childhood growth and the impact of foetal nutrition. Ultimately, we propose a new hypothesis for future research designed to understand the role of FTO in setting gene expression in metabolically active tissues.

The biology of FTO: from nucleic acid demethylase to amino acid sensor

Genome-wide association studies have revealed that single-nucleotide polymorphisms in the first intron of the gene encoding fat mass and obesity-associated protein (FTO) are robustly associated with BMI and obesity. Subsequently, this association with body weight, which is replicable across multiple populations and different age groups, has been unequivocally linked to increased food intake. Although evidence from a number of animal models with perturbed FTO expression indicates a role for FTO in energy homeostasis, to date, no conclusive link has been made between the risk alleles and FTO expression or its physiological role. FTO is a nucleic acid demethylase, and a deficiency in FTO leads to a complex phenotype highlighted by postnatal growth retardation, pointing to some fundamental developmental role. Recent emerging data now points to a role for FTO in the sensing of nutrients and the regulation of translation and growth. In this review, we explore the in vivo and in vitro evidence detailing the complex biology of FTO and discuss how these might link to the regulation of body weight.

Individual genetic variations related to satiety and appetite control increase risk of obesity in preschool-age children in the STRONG kids program

BACKGROUND/AIMS

The burden of the childhood obesity epidemic is well recognized; nevertheless, the genetic markers and gene-environment interactions associated with the development of common obesity are still unknown. In this study, candidate genes associated to satiety and appetite control pathways with obesity-related traits were tested in Caucasian preschoolers from the STRONG Kids project.

METHODS

Eight genetic variants in genes related to obesity (BDNF, LEPR, FTO, PCSK1, POMC, TUB, LEP, and MC4R) were genotyped in 128 children from the STRONG Kids project (mean age 39.7 months). Data were analyzed for individual associations and to test for genetic predisposition scores (GPSs) with body mass index (BMI) and anthropometric traits (Z-scores, e.g. height-for-age Z-score, HAZ). Covariates included age, sex, and breastfeeding (BF) duration.

RESULTS

Obesity and overweight prevalence was 6.3 and 19.5%, respectively, according to age- and sex-specific BMI percentiles. Individual genetic associations of MC4R and LEPR markers with HAZ were strengthened when BF duration was included as a covariate. Our GPSs show that, as the number of risk alleles increased, the risk of higher BMI and HAZ also increased. Overall, the GPSs assembled were able to explain 2-3% of the variability in BMI and HAZ phenotypes.

CONCLUSION

Genetic associations with common obesity-related phenotypes were found in the STRONG Kids project. GPSs assembled for specific candidate genes were associated with BMI and HAZ phenotypes.