Influence of common variants near INSIG2, in FTO, and near MC4R genes on overweight and the metabolic profile in adolescence: the TRAILS (TRacking Adolescents' Individual Lives Survey) Study

Association and interaction of the MC4R rs17782313 polymorphism with plasma ghrelin, GLP-1, cortisol, food intake and eating behaviors in overweight/obese Iranian adults

BACKGROUND

Recent studies have shown that obesity is largely influenced by heredity and created by the interactions between several genes and environmental and behavioral factors. This study aimed to examine association between variant rs17782313 near melanocortin-4 receptor (MC4R) gene and behavioral and hormonal factors then evaluated interactions between variant MC4R rs17782313 with behavioral and hormonal factors on obesity.

METHODS

This cross-sectional study included 403 subjects, overweight and/or obesity, aged 20-50 years from Iran. The MC4R rs17782313 data were measured by the PCR-RFLP method. Dietary intake, physical activity, stress, anxiety, depression, appetite and emotional eating were assessed by using validated questionnaires. Ghrelin, glucagon-like peptide-1 and cortisol were measured by radioimmunoassay in plasma samples. Participants were also divided into three groups based on rs17782313 genotype and BMI.

RESULTS

After adjustment for age, gender, energy intake and PA, significant associations were observed between food intake, appetite, emotional eating, stress and physical activity with MC4R rs17782313 (p ˂0.05). Also, significant interactions were observed between fat intake (p-interaction = 0.002), protein intake (p-interaction = 0.01), energy intake (p-interaction = 0.01), emotional eating (p-interaction = 0.02), appetite (p-interaction = 0.04), stress (p-interaction = 0.04), ghrelin (p-interaction = 0.03), cortisol (p-interaction = 0.04) and physical activity (p-interaction = 0.04) and MC4R rs17782313 in terms of BMI.

CONCLUSION

Interactions between the CC genotype and high intakes of fat and energy, emotional eating, high appetite, and too much stress with high levels of cortisol and ghrelin probably can have an effect on BMI in overweight/obese subjects.

The MC4R SNPs, their haplotypes and gene-environment interactions on the risk of obesity

Background

Little is known about the correlation between the melanocortin 4 receptor gene (MC4R) single nucleotide polymorphisms (SNPs) and the risk of obesity. This research sought to test the MC4R rs17782313, rs476828 and rs12970134 SNPs, their haplotypes and gene-environment interactions on the risk of obesity in the Maonan ethnic group, an isolated minority in China.

Methods

A case-control study comprised of 1836 participants (obesity group, 858; and control group, 978) was conducted. Genotypes of the three SNPs were determined by the next-generation sequencing (NGS) technology.

Results

The genotypic frequencies of the three SNPs were different between the obesity and control groups (P <  0.05 for all). The minor allelic frequency of the MC4R rs17782313C, rs476828C and rs12970134A was higher in obesity than in control groups (13.8% vs. 8.3%, P <  0.001, 17.1% vs. 10.9%, P <  0.001; and 15.5% vs. 11.5%, P <  0.001; respectively). Additionally, the dominant model of rs17782313 and rs476828 SNPs revealed an increased morbidity function on the risk of obesity (P <  0.05). A correlation between SNP-environment and the risk of obesity was also observed. The rs17782313C-rs476828C-rs12970134A haplotype was associated with high risk of obesity (OR = 1.796, 95% CI = 1.447–2.229), whereas the rs17782313T-rs476828T-rs12970134G and rs17782313T-rs476828T-rs12970134A haplotypes were associated with low risk of obesity (OR = 0.699, 95% CI = 0.586–0.834 and OR = 0.620, 95% CI = 0.416–0.925; respectively). The interactions between haplotype and waist circumference on the risk of obesity were also noted.

Conclusions

We discovered that the MC4R rs17782313, rs476828 and rs12970134 SNPs and their haplotypes were associated with the risk of obesity in the Chinese Maonan population.

Melanocortin-4 receptor (MC4R) rs17782313 polymorphism interacts with Dietary Approach to Stop Hypertension (DASH) and Mediterranean Dietary Score (MDS) to affect hypothalamic hormones and cardio-metabolic risk factors among obese individuals

BACKGROUND AND AIM

The association with obesity of a common variant near the melanocortin-4 receptor (MC4R) gene (rs17782313) has been indicated in various studies. Adherence to dietary quality indices also have shown to have potential favorable effects on obesity-related health outcomes. However, no study has examined the interaction between rs17782313 and the Dietary Approach to Stop Hypertension (DASH) score and the Mediterranean Dietary Score (MDS) on cardio-metabolic risk factors and hypothalamic hormones. Therefore, the purpose of the current study was to examine whether adherence to these dietary quality indices modifies the association of the MC4R rs17782313 polymorphism with cardio-metabolic risk factors and hypothalamic hormones among obese adults.

METHOD

Two hundred eighty-eight healthy obese adults were recruited in this cross-sectional study. Diet quality indices, including DASH score and MDS, were calculated from a validated 147-item food frequency questionnaire (FFQ). MC4R s17782313 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). An ANCOVA multivariate interaction model was used to assess the gene-diet interaction.

RESULTS

Significant interactions were detected between DASH score and MC4R rs17782313 genotypes on systolic blood pressure (SBP), atherogenic index of plasma (AIP), and serum glucose and triglyceride (TG) among the female group (p_Interaction < 0.05). In the male group, there were gene-DASH and gene-MDS interactions in relation to serum glucose concentration and plasma α-melanocyte stimulating hormone (MSH) levels, but these were found only in multi-adjusted interaction models (p_Interaction < 0.05). In addition, there was a significant interaction between MC4R rs17782313 polymorphism and DASH score on plasma agouti-related peptide (AgRP) concentrations in the female group in a multivariate interaction model (p_Interaction < 0.05). An inverse association between DASH score and chance of having the CC genotype in a multivariate-adjusted model among women was also revealed.

CONCLUSION

MC4R rs17782313 interacts with healthy dietary pattern (DASH score and MDS) to influence cardio-metabolic risk factors and hypothalamic hormones in obese individuals. Prospective cohort studies are needed to further assess these findings.

Common genetic variation in obesity, lipid transfer genes and risk of Metabolic Syndrome: Results from IDEFICS/I.Family study and meta-analysis

As the prevalence of metabolic syndrome (MetS) in children and young adults is increasing, a better understanding of genetics that underlie MetS will provide critical insights into the origin of the disease. We examined associations of common genetic variants and repeated MetS score from early childhood to adolescence in a pan-European, prospective IDEFICS/I.Family cohort study with baseline survey and follow-up examinations after two and six years. We tested associations in 3067 children using a linear mixed model and confirmed the results with meta-analysis of identified SNPs. With a stringent Bonferroni adjustment for multiple comparisons we obtained significant associations(p < 1.4 × 10⁻⁴) for 5 SNPs, which were in high LD (r² > 0.85) in the 16q12.2 non-coding intronic chromosomal region of FTO gene with strongest association observed for rs8050136 (effect size(β) = 0.31, p_Wald = 1.52 × 10⁻⁵). We also observed a strong association of rs708272 in CETP with increased HDL (p = 5.63 × 10⁻⁴⁰) and decreased TRG (p = 9.60 × 10⁻⁵) levels. These findings along with meta-analysis advance etiologic understanding of childhood MetS, highlighting that genetic predisposition to MetS is largely driven by genes of obesity and lipid metabolism. Inclusion of the associated genetic variants in polygenic scores for MetS may prove to be fundamental for identifying children and subsequently adults of the high-risk group to allow earlier targeted interventions.

Association of Obesity-Related Genetic Variants (FTO and MC4R) with Breast Cancer Risk: A Population-Based Case-Control Study in Iran

Background:

Heterogeneous breast cancer is the most common cause of cancer-related mortality. Obesity defined by BMI is a known major risk factor for breast cancer.

Objectives:

The purpose of this study was to explore the role of obesity related-polymorphisms rs9939609 Fat Mass and Obesity-associated (FTO) and rs17782313 MC4R in breast cancer development.

Materials and Methods:

Matched peripheral blood serum was obtained from 64 breast cancer patients and 83 normal controls. Height and weight were measured to calculate BMI. All were genotyped for the SNPs rs9939609 and rs17782313 using a Tetra-primer ARMS-PCR method. For statistical analysis, the chi-square test and SPSS software were used.

Results:

In subgroup analyses defined by BMI, FTO rs9939609 genotypes (TT/AA/AT) were significantly associated with the risk of breast cancer only in non-obese subjects (p < 0.005). TT genotypes of MC4R rs17782313 in non-obese and genotypes TT/CC in the overweight group were also statistically associated with breast cancer (p &lt; 0.005). No significant associations between any variants and breast cancer risk were seen in obese subjects.

Conclusion:

Based on the absence of an association between obesity-related SNPs and breast cancer in obese subjects, it is proposed that weight gain in Iranian women will help prevent breast cancer risk. The result help for preparing and designing a safe and versatile recombinant drug in future.

Behavioral, contextual and biological factors associated with obesity during adolescence: A systematic review

INTRODUCTION/OBJECTIVE

Adolescence is a critical period for the development of obesity. Obesity arises from a complex interaction between several factors, which are not yet fully understood. Therefore, the purpose of this review was to identify and assess the peer-reviewed scientific literature on the behavioral, contextual and biological factors associated with obesity in adolescents.

METHODS

PubMed and Scopus were systematically searched to identify prospective cohort studies concerning the relation between behavioral, contextual and biological factors and obesity in adolescents aged 10 to 18 years.

RESULTS

40 studies published between the year 2000 and 2018 were included. A positive consistent association between genetic factors and obesity during adolescence was found. Also, there is evidence to support the association between socioeconomic status and obesity. There was conflicting evidence for the contribution of dietary intake, physical activity, sedentary behavior, sleep, food store environment, school food environment. For the remaining factors no associations were found, or no conclusions could be drawn due to the limited number of studies identified.

CONCLUSIONS

Further prospective studies that assess multiple obesity determinants simultaneously and use state-of-art measures are warranted to aid in the development of effective strategies and interventions to prevent obesity during adolescence.

Physical activity modifies the FTO effect on body mass index change in Japanese adolescents

BACKGROUND

Evidence of the effects of fat mass and obesity-associated (FTO) variation and long-term effects of physical activity (PA) on adiposity in adolescents is largely scarce. This study therefore investigated whether PA modulates the effects of the FTO on body mass index (BMI) changes in Japanese adolescents between the ages of 13 and 18 years.

METHODS

Data on 343 subjects (156 boys; 187 girls) who were enrolled in 2006 and 2007 at schools in Shunan City, Japan, were collected. Genotyping (rs1558902) was conducted, and anthropometry and blood test results were recorded for subjects in the eighth grade. A second survey involving self-reporting of anthropometry was conducted when the subjects were in the 12th grade. PA was estimated using the International Physical Activity Questionnaire. BMI and the standard deviation score for BMI (BMI-SDS) were calculated. BMI changes and BMI-SDS changes were compared between FTO genotypes using a multivariate model.

RESULTS

The effect of the interaction between PA and the FTO genotype on BMI changes was significant in boys but not in girls. In boys, PA had a significant negative influence on BMI-SDS changes in those with the AA genotype and a significant positive influence on BMI and BMI-SDS changes in those with the TT genotype.

CONCLUSION

The influence of PA on BMI change and BMI-SDS change varies on the basis of genotype. PA modified the effect of FTO on BMI change in Japanese boys.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

MC4R variant rs17782313 and manifestation of obese phenotype in Pakistani females

MC4R represents a key player involved in melanocortin-mediated control of energy balance. Recently identified near MC4R variant rs17782313 (T > C) can serve as a contributing factor for obese phenotype but its association with obesity has never been sought in a sample of the Pakistani population. The role of genetic variants as causal factors varies across populations. Association studies in a specific population can help us to distinguish global from local gene–gene and gene–environment interactions. This is the first study that investigated the association of rs17782313 with obesity and various obesity-linked anthropometric, metabolic, physical, and behavioural traits in Pakistani subjects including 306 OW/OB (overweight and obese) and 300 NW (normal weight) individuals. The comparison of various aforementioned obesity-linked continuous and categorical variables between OW/OB and NW subjects revealed that almost all variables were found significantly aberrant (p < 0.05) in OW/OB subjects as compared to their age- and gender-matched NW controls indicating greater risk of developing various cardio-metabolic disorders. The genotyping of rs17782313 showed significant association of this variant with obesity and obesity-linked anthropometric traits in females suggesting the gender-specific effect of this variant in our population. The minor allele C increased the risk of obesity by 1.55 times (95% CI = 1.1–2.18, p = 0.01) whereas homozygous CC genotype increased the risk by 2.43 times (95% CI = 1.19–4.96, p = 0.015) in females. However, no association of rs17782313 was observed with any of the obesity-linked metabolic, physical, and behavioural traits except random eating timings. In conclusion, the current study significantly contributes to the knowledge of the genetic proneness to obesity in Pakistani females. This could also be helpful for forthcoming meta-analysis studies elucidating which variants are truly associated with the susceptibility to develop an obese phenotype.

The current study significantly contributes to the knowledge of the genetic proneness to obesity in Pakistani females and could also be helpful for forthcoming meta-analysis studies.

Two obesity susceptibility loci in LYPLAL1 and ETV5 independently associated with childhood hypertension in Chinese population

AIMS

Genome-wide association studies have identified novel obesity-associated susceptibility loci. Associations of these variants with childhood obesity have been studied in our previous research. The purpose of this study is to investigate if these loci are associated with hypertension being independent of obesity in Chinese children and adolescents.

METHODS

Nineteen candidate SNPs were genotyped using Sequenom MassARRAY platform among Chinese children (N=2954, 514 hypertension and 2440 controls, aged 7-17years). Dietary behaviors were assessed through face to face investigations.

RESULTS

Of the nineteen obese related SNPs, ten SNPs were found to be associated with systolic blood pressure (SBP) or diastolic blood pressure (DBP) in Chinese children. After adjusting for age, sex and WHtR, rs2605100 in LYPLAL1was found to be associated with high blood pressure (HBP) under dominant model (P=0.024) with the OR of 1.274 (95% CI =1.033-1.572, effect genotype=GG). The distribution of genotype of rs7647305 in ETV5 showed significant difference between HBP and non-HBP subjects under dominant model (P=0.011) with the OR of 0.654 (95% CI=0.471-0.909, effect genotype=CC). Using rs2605100 and rs7647305, the genetic risk score (GRS) analysis showed that, after adjusted for age, sex and WHtR, subjects carrying one or two risk alleles had the risks of hypertension with the ORs 1.797 (95% CI, 1.168-2.765), 2.149 (95% CI, 1.375-3.357) comparing with the subjects with non-risk-allele.

CONCLUSIONS

Genetic variations of obesity-associated loci, LYPLAL1 rs2605100 and ETV5 rs7647305 independently associate with the risk of childhood hypertension in China.

Physical Activity and Sedentary Behaviors Modify the Association between Melanocortin 4 Receptor Gene Variant and Obesity in Chinese Children and Adolescents

Effects of MC4R variants in previous Chinese population studies were inconsistent. Gene-environment interactions might influence the effect of MC4R variants on obesity, which was still unclear. We performed the study to clarify the association of variants near MC4R gene with obesity-related phenotypes and gene-environment interactions in Chinese children and adolescents. Two common variants (rs12970134 and rs17782313) near MC4R were genotyped in 2179 children and adolescents aged 7-18 years in Beijing of China. Associations between the variants and obesity-related phenotypes together with gene-environment interactions were analyzed. The A-alleles of rs12970134 were nominally associated with risk of overweight/obesity (Odds Ratios (OR) = 1.21, 95%CI: 1.03-1.44, P = 0.025) and BMI (β = 0.33 kg/m2, 95%CI: 0.02-0.63, P = 0.025), respectively. The rs12970134 was also associated with HDL-C (β = -0.03mmol/L per A-allele, 95%CI: -0.05, -0.01, P = 0.013) independent of BMI. In the further analysis, we found the significant interaction of rs12970134 and physical activity/sedentary behaviors on BMI (Pinteraction = 0.043). The rs12970134 was found to be associated with BMI only in children with physical activity<1h/d and sedentary behaviors ≥2h/d (BMI: β = 1.27 kg/m2, 95%CI: 0.10-2.45, P = 0.034). The association was not detected in their counterparts with physical activity≥1h/d or sedentary behaviors <2h/d. We identified the effect of MC4R rs12970134 on overweight/obesity and BMI, and we also found physical activity and sedentary behaviors modified the association between the rs12970134 and BMI in Chinese children and adolescents.

Behavioral and Environmental Modification of the Genetic Influence on Body Mass Index: A Twin Study

Body mass index (BMI) has a strong genetic basis, with a heritability around 0.75, but is also influenced by numerous behavioral and environmental factors. Aspects of the built environment (e.g., environmental walkability) are hypothesized to influence obesity by directly affecting BMI, by facilitating or inhibiting behaviors such as physical activity that are related to BMI, or by suppressing genetic tendencies toward higher BMI. The present study investigated relative influences of physical activity and walkability on variance in BMI using 5079 same-sex adult twin pairs (70 % monozygotic, 65 % female). High activity and walkability levels independently suppressed genetic variance in BMI. Estimating their effects simultaneously, however, suggested that the walkability effect was mediated by activity. The suppressive effect of activity on variance in BMI was present even with a tendency for low-BMI individuals to select into environments that require higher activity levels. Overall, our results point to community- or macro-level interventions that facilitate individual-level behaviors as a plausible approach to addressing the obesity epidemic among US adults.

The association of MC4R rs17782313 polymorphism with dietary intake in Iranian adults

BACKGROUND

Malfunction in the energy homeostasis system is a major cause of developing obesity. Melanocortin-4 receptor (MC4R) plays a crucial role in this system as a key receptor. Although MC4R gene as an obesity candidate gene is associated with higher BMI, only few attempts have been carried out to understand the mechanism underlying body-weight regulation.

OBJECTIVE

The aim of this study is to investigate the association between variant rs17782313 near MC4R gene and both dietary energy and macronutrient intakes.

METHODS

An Iranian population, 400 adults aged over 22years were selected from the Iranian Multicenter Osteoporosis Study (IMOS). Genotyping for the near MC4R rs17782313 was performed by PCR-RFLP. Weight and height were measured. Dietary intake and physical activity were assessed by using validated questionnaires. Analysis was carried out in two groups with regard to BMI. Multiple linear regression models adjusted for covariates were used to examine the association between rs17782313 and dietary intake.

RESULTS

MC4R rs17782313 was associated with high energy intake (P<0.001), and low carbohydrate and protein intakes (P<0.001 and P<0.01 respectively). In addition, the significant association between variant rs17782313 and fat intake disappeared after adjusting for energy.

CONCLUSIONS

The rs17782313 variant contributes to the variety of dietary energy and energy-dense macronutrient intakes. Moreover, a novel association was suggested between this polymorphism and dietary fat intake.

Cohort Profile Update: the TRacking Adolescents' Individual Lives Survey (TRAILS)

TRAILS consists of a population cohort (N = 2230) and a clinical cohort (N = 543), both of which were followed from about age 11 years onwards. To date, the population cohort has been assessed five times over a period of 11 years, with retention rates ranging between 80% and 96%. The clinical cohort has been assessed four times over a period of 8 years, with retention rates ranging between 77% and 85%. Since the IJE published a cohort profile on the TRAILS in 2008, the participants have matured from adolescents into young adults. The focus shifted from parents and school to entry into the labour market and family formation, including offspring. Furthermore, psychiatric diagnostic interviews were administered, the database was linked to a Psychiatric Case Registry, and the availability of genome-wide SNP variations opened the door to genome-wide association studies regarding a wide range of (endo)phenotypes. With some delay, TRAILS data are available to researchers outside the TRAILS consortium without costs; access can be obtained by submitting a publication proposal (see www.trails.nl).

A polymorphism near MC4R gene (rs17782313) is associated with serum triglyceride levels in the general Japanese population: the J-MICC Study

Previously reported associations of a common polymorphism near melanocortin-4 receptor (MC4R) gene (rs17782313) with BMI/obesity were inconsistent, especially in East Asia, and the associations of the polymorphism with serum lipid levels have not been fully elucidated. This study evaluated the association between rs17782313 and obesity-related traits and serum lipid levels in the general Japanese population. A total of 2,035 subjects (aged 35-69 years, 1,024 males and 1,011 females) enrolled in the Japan Multi-Institutional Collaborative Cohort (J-MICC) Study. We examined the associations between near MC4R polymorphism (rs17782313) and obesity-related traits [height, weight, body mass index (BMI), weight change from 20 years old], serum lipid levels (triglycerides, total and HDL-cholesterol), and intake of nutrients (total energy and macronutrients). Polymorphism of rs17782313 (minor C allele) was positively associated with serum triglyceride levels (P for trend = 0.020) adjusted for age and sex. Analysis using a general linear model revealed that the number of minor C alleles was positively associated with serum triglyceride levels after adjustment for age, sex, and potential confounders (P for trend = 0.004). Statistical significance did not change after further adjustment for total energy intake and BMI. There was no significant association between rs17782313 and obesity-related traits including BMI. Interactions between rs17782313 and sex, BMI, or total energy intake for triglyceride levels were not significant. To our knowledge, this study demonstrated for the first time that rs17782313 was associated with serum triglyceride levels in Asian population. Further studies are needed to confirm this result.

Variation in the MC4R gene is associated with bone phenotypes in elderly Swedish women

Osteoporosis is characterized by reduced bone mineral density (BMD) and increased fracture risk. Fat mass is a determinant of bone strength and both phenotypes have a strong genetic component. In this study, we examined the association between obesity associated polymorphisms (SNPs) with body composition, BMD, Ultrasound (QUS), fracture and biomarkers (Homocysteine (Hcy), folate, Vitamin D and Vitamin B12) for obesity and osteoporosis. Five common variants: rs17782313 and rs1770633 (melanocortin 4 receptor (MC4R); rs7566605 (insulin induced gene 2 (INSIG2); rs9939609 and rs1121980 (fat mass and obesity associated (FTO) were genotyped in 2 cohorts of Swedish women: PEAK-25 (age 25, n = 1061) and OPRA (age 75, n = 1044). Body mass index (BMI), total body fat and lean mass were strongly positively correlated with QUS and BMD in both cohorts (r² = 0.2–0.6). MC4R rs17782313 was associated with QUS in the OPRA cohort and individuals with the minor C-allele had higher values compared to T-allele homozygotes (TT vs. CT vs. CC: BUA: 100 vs. 103 vs. 103; p = 0.002); (SOS: 1521 vs. 1526 vs. 1524; p = 0.008); (Stiffness index: 69 vs. 73 vs. 74; p = 0.0006) after adjustment for confounders. They also had low folate (18 vs. 17 vs. 16; p = 0.03) and vitamin D (93 vs. 91 vs. 90; p = 0.03) and high Hcy levels (13.7 vs 14.4 vs. 14.5; p = 0.06). Fracture incidence was lower among women with the C-allele, (52% vs. 58%; p = 0.067). Variation in MC4R was not associated with BMD or body composition in either OPRA or PEAK-25. SNPs close to FTO and INSIG2 were not associated with any bone phenotypes in either cohort and FTO SNPs were only associated with body composition in PEAK-25 (p≤0.001). Our results suggest that genetic variation close to MC4R is associated with quantitative ultrasound and risk of fracture.

Melanocortin-4 receptor polymorphism rs17782313: association with obesity and eating in the absence of hunger in Chilean children

OBJECTIVE

The aim of this study was to assess the association between melanocortin-4 receptor (MC4R) rs17782313 alleles with obesity and eating behavior scores in Chilean children.

METHODS

A case-control study was conducted with 139 normal-weight and 238 obese children (ages 6-12 y). MC4R rs17782313 genotypes were determined by quantitative-polymerase chain reaction allelic-discrimination assays. Eating behavior scores were evaluated in a subset of participants using the Chilean version of the Child Eating Behavior Questionnaire (CEBQ). Additionally, five normal-weight C-allele carriers of rs17782313 were matched by sex, age, and body mass index (BMI) to five TT homozygous children to carry out the Eating in the Absence of Hunger (EAH) test.

RESULTS

The frequency of the C-allele of MC4R rs17782313 was higher in the obese group than in the control group, without achieving statistical significance (odds ratio, 1.4; 95% confidence interval, 0.8-2.4; P = 0.16). CEBQ scores of "enjoyment of food" were higher (P = 0.04) and "satiety responsiveness" were lower (P = 0.02) in children with CC genotype than in those with TT genotype matched by sex, age, and BMI. In the EAH test, all five non-obese carriers of the C-allele (three CC and two CT) showed increased sweet snack consumption compared with five matched (by sex-age-BMI) non-carriers after a preload meal, without achieving statistical significance (P = 0.06).

CONCLUSION

MC4R polymorphism rs17782313 may contribute to childhood obesity, affecting enjoyment of food, satiety responsiveness, and possibly eating in the absence of hunger.

Interaction between obesity-related genes, FTO and MC4R, associated to an increase of breast cancer risk

Breast cancer (BC) is a complex disease and obesity is a well-known risk factor for its development, especially after menopause. Several studies have shown Single Nucleotide Polymorphisms (SNPs) linked to overweight and obesity, such as: rs1121980 (T/C) and rs9939609 (A/T) in Fat Mass and Obesity Associated gene (FTO) and rs17782313 (T/C) in Melanocortin 4 Receptor gene (MC4R). Thus, we aimed to investigate the association between these obesity-related SNPs and BC risk. One hundred BC patients and 148 healthy women from Santa Catarina, Brazil entered the study. SNPs were genotyped using Taqman assays. For statistical analyses SNPStats and SPSS softwares were used. Association analyses were performed by logistic regression and were adjusted for age and Body mass index (BMI). Multiple SNPs inheritance models (log-additive, dominant, recessive, codominant) were performed to determine odds ratios (ORs), assuming 95 % confidence interval (CI) and P value = 0.05 as the significance limit. When analyzed alone, FTO rs1121980 and rs9939609 did not show significant associations with BC development, however MC4R rs17782313 showed increased risk for BC even after adjustments (P-value = 0.032). Interestingly, the interaction of FTO and MC4R polymorphisms showed a powerful association with BC. We observed a 4.59-fold increased risk for woman who have the allele combination C/T/C (FTO rs1121980/FTO rs9939609/MC4R rs17782313) (P-value = 0.0011, adjusted for age and BMI). We found important and unpublished associations between these obesity-related genes and BC risk. These associations seem to be independent of their effect on BMI, indicating a direct role of the interaction between FTO and MC4R polymorphisms in BC development.

Growth during infancy and childhood, and adiposity at age 16 years: ages 2 to 7 years are pivotal

OBJECTIVE

To assess the period during infancy and childhood in which growth is most associated with adolescent adiposity and the metabolic syndrome (MS) and whether this differs depending on maternal smoking during pregnancy.

STUDY DESIGN

A longitudinal population-based cohort study among 772 girls and 708 boys.

RESULTS

Weight gains between ages 2-4 years and ages 4-7 years were most strongly associated with higher body mass index (BMI), sum of skinfold measurements, body fat percentage, and waist circumference at age 16. A one SD increase in weight between ages 2-4 and 4-7 years was associated with increases in outcome measures of +0.82 to +1.47 SDs (all P < .001), and with a less favorable MS score. In children whose mothers smoked during pregnancy, the association of relative weight gain during ages 2-4 years with adolescent BMI was stronger than in children whose mothers did not smoke. For adolescent BMI, the increase was 0.42 SD higher (P = .01). This was similar for the other adiposity measures.

CONCLUSIONS

Large relative increases in weight from ages 2 to 7 years are associated with adolescent adiposity and MS. This is more pronounced in adolescents whose mothers smoked during pregnancy.

Statistical and biological gene-lifestyle interactions of MC4R and FTO with diet and physical activity on obesity: new effects on alcohol consumption

Background

Fat mass and obesity (FTO) and melanocortin-4 receptor (MC4R) and are relevant genes associated with obesity. This could be through food intake, but results are contradictory. Modulation by diet or other lifestyle factors is also not well understood.

Objective

To investigate whether MC4R and FTO associations with body-weight are modulated by diet and physical activity (PA), and to study their association with alcohol and food intake.

Methods

Adherence to Mediterranean diet (AdMedDiet) and physical activity (PA) were assessed by validated questionnaires in 7,052 high cardiovascular risk subjects. MC4R rs17782313 and FTO rs9939609 were determined. Independent and joint associations (aggregate genetic score) as well as statistical and biological gene-lifestyle interactions were analyzed.

Results

FTO rs9939609 was associated with higher body mass index (BMI), waist circumference (WC) and obesity (P<0.05 for all). A similar, but not significant trend was found for MC4R rs17782313. Their additive effects (aggregate score) were significant and we observed a 7% per-allele increase of being obese (OR = 1.07; 95%CI 1.01–1.13). We found relevant statistical interactions (P<0.05) with PA. So, in active individuals, the associations with higher BMI, WC or obesity were not detected. A biological (non-statistical) interaction between AdMedDiet and rs9939609 and the aggregate score was found. Greater AdMedDiet in individuals carrying 4 or 3-risk alleles counterbalanced their genetic predisposition, exhibiting similar BMI (P = 0.502) than individuals with no risk alleles and lower AdMedDiet. They also had lower BMI (P = 0.021) than their counterparts with low AdMedDiet. We did not find any consistent association with energy or macronutrients, but found a novel association between these polymorphisms and lower alcohol consumption in variant-allele carriers (B+/−SE: −0.57+/−0.16 g/d per-score-allele; P = 0.001).

Conclusion

Statistical and biological interactions with PA and diet modulate the effects of FTO and MC4R polymorphisms on obesity. The novel association with alcohol consumption seems independent of their effects on BMI.

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

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

Associations of variants in FTO and near MC4R with obesity traits in South Asian Indians

Recent genome-wide association studies show that loci in FTO and melanocortin 4 receptor (MC4R) associate with obesity-related traits. Outside Western populations the associations between these variants have not always been consistent and in Indians it has been suggested that FTO relates to diabetes without an obvious intermediary obesity phenotype. We investigated the association between genetic variants in FTO (rs9939609) and near MC4R (rs17782313) with obesity- and type 2 diabetes (T2DM)-related traits in a longitudinal birth cohort of 2,151 healthy individuals from the Vellore birth cohort in South India. The FTO locus displayed significant associations with several conventional obesity-related anthropometric traits. The per allele increase is about 1% for BMI, waist circumference (WC), hip circumference (HC), and waist-hip ratio. Consistent associations were observed for adipose tissue-specific measurements such as skinfold thickness reinforcing the association with obesity-related traits. Obesity associations for the MC4R locus were weak or nonsignificant but a signal for height (P < 0.001) was observed. The effect on obesity-related traits for FTO was seen in adulthood, but not at younger ages. The loci also showed nominal associations with increased blood glucose but these associations were lost on BMI adjustment. The effect of FTO on obesity-related traits was driven by an urban environmental influence. We conclude that rs9939609 variant in the FTO locus is associated with measures of adiposity and metabolic consequences in South Indians with an enhanced effect associated with urban living. The detection of these associations in Indians is challenging because conventional anthropometric obesity measures work poorly in the Indian "thin-fat" phenotype.

The complex interplay of genetic and lifestyle risk factors in type 2 diabetes: an overview

Type 2 diabetes (T2D) is one of the scourges of modern times, with many millions of people affected by the disease. Diabetes occurs most frequently in those who are overweight or obese. However, not all overweight and obese persons develop diabetes, and there are those who develop the disease who are lean and physically active. Certain ethnicities, especially indigenous populations, are at considerably higher risk of obesity and diabetes than those of white European ancestry. The patterns and distributions of diabetes have led some to speculate that the disease is caused by interactions between genetic and obesogenic lifestyle factors. Whilst to many this is a plausible explanation, remarkably little reliable evidence exists to support it. In this review, an overview of published literature relating to genetic and lifestyle risk factors for T2D is provided. The review also describes the concepts and rationale that have motivated the view that gene-lifestyle interactions cause diabetes and overviews the empirical evidence published to date to support this hypothesis.

Association between common polymorphism near the MC4R gene and obesity risk: a systematic review and meta-analysis

BACKGROUND

Genome-wide association studies on Europeans have shown that two polymorphisms (rs17782313, rs12970134) near the melanocortin 4 receptor (MC4R) gene were associated with increased risk of obesity. Subsequently studies among different ethnic populations have shown mixed results with some confirming and others showing inconsistent results, especially among East Asians and Africans. We performed a comprehensive meta-analysis of various studies from different ethnic populations to assess the association of the MC4R polymorphism with obesity risk.

METHODS

We retrieved all published literature that investigated association of MC4R variants with obesity from PubMed and Embase. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using fixed- or random-effects model.

RESULTS

A total of 61 studies (80,957 cases/220,223 controls) for rs17782313 polymorphism (or proxy) were included in the meta-analysis. The results suggested that rs17782313 polymorphism was significantly associated with obesity risk (OR=1.18, 95%CI=1.15-1.21, p<0.001). Similar trends were observed among subgroups of Europeans and East Asians, adults and children, studies with high quality score, and for each five MC4R polymorphisms independently.

CONCLUSIONS

The present meta-analysis confirms the significant association of MC4R polymorphism with risk of obesity. Further studies should be conducted to identify the causal variant and the underlying mechanisms of the identified association.

Association between FTO variant and change in body weight and its interaction with dietary factors: the DiOGenes study

Although FTO is an established obesity-susceptibility locus, it remains unknown whether it influences weight change in adult life and whether diet attenuates this association. Therefore, we investigated the association of FTO-rs9939609 with changes in weight and waist circumference (WC) during 6.8 years follow-up in a large-scale prospective study and examined whether these associations were modified by dietary energy percentage from fat, protein, carbohydrate, or glycemic index (GI). This study comprised data from five countries of European Prospective Investigation into Cancer and Nutrition (EPIC) and was designed as a case-cohort study for weight gain. Analyses included 11,091 individuals, of whom 5,584 were cases (age (SD), 47.6 (7.5) years), defined as those with the greatest unexplained annual weight gain during follow-up and 5,507 were noncases (48.0 (7.3) years), who were compared in our case-noncase (CNC) analyses. Furthermore, 6,566 individuals (47.9 (7.3) years) selected from the total sample (all noncases and 1,059 cases) formed the random subcohort (RSC), used for continuous trait analyses. Interactions were tested by including interaction terms in the models. In the RSC-analyses, FTO-rs9939609 was associated with BMI (β (SE), 0.17 (0.08) kg·m(-2)/allele; P = 0.034) and WC (0.47 (0.21) cm/allele; P = 0.026) at baseline, but not with weight change (5.55 (12.5) g·year(-1)/allele; P = 0.66) during follow up. In the CNC-analysis, FTO-rs9939609 was associated with increased risk of being a weight-gainer (OR: 1.1; P = 0.045). We observed no interaction between FTO-rs9939609 and dietary fat, protein and carbohydrate, and GI on BMI and WC at baseline or on change in weight and WC. FTO-rs9939609 is associated with BMI and WC at baseline, but association with weight gain is weak and only observed for extreme gain. Dietary factors did not influence the associations.

Beyond the fourth wave of genome-wide obesity association studies

Obesity and related complications are major health burdens. Almost 700 million adults are currently obese globally and the prevalence is predicted to rise towards 2030. The sudden change of lifestyle with physical inactivity and excessive calorie intake undoubtedly have a major part of the epidemic development; however, some individuals seem to be more prone to be affected by an unhealthy lifestyle than others. Hence, genetic predisposition also has an essential role in determining disease susceptibility and response to lifestyle factors. Since the introduction of genome-wide association studies (GWAS), the success of identifying obesity susceptibility variants have increased, and a total of 32 variants have been identified associating genome-wide significantly with body mass index (BMI) and 18 with measures of fat distribution during four overall obesity GWAS waves. However, the immediate success of the GWAS approach has eased off, but the proportion of explained variance for BMI by the identified obesity variants remains low. This review suggests and discusses new initiatives to take GWAS of obesity to the next level, including gene–environment interactions as modulating/masking factors, low-frequent or rare variants and ways to address such analyses, and finally reflections about the applicability of epigenetic modifications when elucidating the genetic background of obesity.

Association of FTO gene variants with body composition in UK twins

The association of FTO gene variants with body mass index (BMI) and other obesity characteristics is well established. However, uncertainties remain whether the association is present only in young populations and whether it is attributable to body fat mass specifically. We aimed to clarify these two questions in a large sample (N= 4,523 individuals) of middle-aged and older (range 40–80 years) British female twins. The women were assessed for BMI, waist and hip circumference, total lean (LBM) and fat (FBM) body mass. Since the majority of FTO association signals have been reported in a haploblock bordering 52,355–52,408 kb (on chromosome 16q12.2), we examined five genotyped and 43 imputed SNPs mapped to this block. Canonical correlation and other association analyses showed significant and consistent association between the selected SNP and studied body composition phenotypes, with p-values reaching p= 0.000004. Of particular interest, in addition to the expected significant associations between FTO variants and FBM, we also identified significant associations with LBM. These results suggest that the association between FTO variants and body composition phenotypes is present across a wide range of ages, and that FTO appears primarily to affect the amount of body soft tissue, influencing both fat and lean mass.

Genetic determinants of common obesity and their value in prediction

Genome-wide association studies (GWAS) have revolutionised the discovery of genes for common traits and diseases, including obesity-related traits. In less then four years time, 52 genetic loci were identified to be unequivocally associated with obesity-related traits. This vast success raised hope and expectations that genetic information would become soon an integral part of personalised medicine. However, these loci have only small effects on obesity-susceptibility and explain just a fraction of the total variance. As such, their accuracy to predict obesity is poor and not competitive with the predictive ability of traditional risk factors. Nevertheless, some of these loci are being used in commercially available personal genome tests to estimate individuals' lifetime risk of obesity. While proponents believe that personal genome profiling could have beneficial effects on behaviour, early reports do not support this hypothesis. To conclude, the most valuable contribution of GWAS-identified loci lies in their contribution to elucidating new physiological pathways that underlie obesity-susceptibility.

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

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

Genetic variants in FTO associated with metabolic syndrome: a meta- and gene-based analysis

The objective of this study was to examine the effect of genetic variants in fat mass and obesity associated (FTO) gene on metabolic syndrome (MetS). A systematic literature search was performed and random-effects meta-analysis was used to evaluate genetic variants in FTO with MetS. A gene-based analysis was conducted to investigate the cumulative effects of genetic polymorphisms in FTO. A total of 18 studies from 13 published papers were included in our analysis. Random-effects meta-analysis yielded an estimated odds ratio of 1.19 (95% CI 1.12-1.27; P = 1.38 × 10(-7)) for rs9939609, 1.19 (95% CI 1.05-1.35; P = 0.008) for rs8050136, and 1.89 (95% CI 1.20-2.96; P = 0.006) for rs1421085. The gene-based analysis indicated that FTO is strongly associated with MetS (P < 10(-5)). This association remains after excluding rs9939609, a SNP that was frequently reported to have strong association with obesity and MetS. In this study, we concluded that the FTO gene may play a critical role in leading to MetS. Targeting this gene may provide novel therapeutic strategies for the prevention and treatment of metabolic syndrome.

Developments in obesity genetics in the era of genome-wide association studies

Obesity is an important factor contributing to the global burden of morbidity and mortality. By identifying obesity susceptibility genes, scientists aim to elucidate some of its aetiology. Early studies used candidate gene and genome-wide linkage approaches to search for such genes with limited success. However, the advent of genome-wide association studies (GWAS) has dramatically increased the pace of gene discovery. So far, GWAS have identified at least 50 loci robustly associated with body mass index (BMI), waist-to-hip ratio, body fat percentage and extreme obesity. Some of these have been shown to replicate in non-white populations and in children and adolescents. Furthermore, for some loci interaction studies have shown that the BMI-increasing effect is attenuated in physically active individuals. Despite many successful discoveries, the effect sizes of the established loci are small, and combined they explain only a fraction of the inter-individual variation in BMI. The low predictive value means that their value in mainstream health care is limited. However, as most of these newly established loci were not previously linked to obesity, they may provide new insights into body weight regulation. Continued efforts in gene discovery, using a range of approaches, will be needed to increase our understanding of obesity.

Physical activity attenuates the influence of FTO variants on obesity risk: a meta-analysis of 218,166 adults and 19,268 children

BACKGROUND

The FTO gene harbors the strongest known susceptibility locus for obesity. While many individual studies have suggested that physical activity (PA) may attenuate the effect of FTO on obesity risk, other studies have not been able to confirm this interaction. To confirm or refute unambiguously whether PA attenuates the association of FTO with obesity risk, we meta-analyzed data from 45 studies of adults (n = 218,166) and nine studies of children and adolescents (n = 19,268).

METHODS AND FINDINGS

All studies identified to have data on the FTO rs9939609 variant (or any proxy [r(2)>0.8]) and PA were invited to participate, regardless of ethnicity or age of the participants. PA was standardized by categorizing it into a dichotomous variable (physically inactive versus active) in each study. Overall, 25% of adults and 13% of children were categorized as inactive. Interaction analyses were performed within each study by including the FTO×PA interaction term in an additive model, adjusting for age and sex. Subsequently, random effects meta-analysis was used to pool the interaction terms. In adults, the minor (A-) allele of rs9939609 increased the odds of obesity by 1.23-fold/allele (95% CI 1.20-1.26), but PA attenuated this effect (p(interaction)  = 0.001). More specifically, the minor allele of rs9939609 increased the odds of obesity less in the physically active group (odds ratio  = 1.22/allele, 95% CI 1.19-1.25) than in the inactive group (odds ratio  = 1.30/allele, 95% CI 1.24-1.36). No such interaction was found in children and adolescents.

CONCLUSIONS

The association of the FTO risk allele with the odds of obesity is attenuated by 27% in physically active adults, highlighting the importance of PA in particular in those genetically predisposed to obesity.

Advances in exercise, fitness, and performance genomics in 2010

This review of the exercise genomics literature emphasizes the strongest articles published in 2010 as defined by sample size, quality of phenotype measurements, quality of the exercise program or physical activity exposure, study design, adjustment for multiple testing, quality of genotyping, and other related study characteristics. One study on voluntary running wheel behavior was performed in 448 mice from 41 inbred strains. Several quantitative trait loci for running distance, speed, and duration were identified. Several studies on the alpha-3 actinin (ACTN3) R577X nonsense polymorphism and the angiotensin-converting enzyme (ACE) I/D polymorphism were reported with no clear evidence for a joint effect, but the studies were generally underpowered. Skeletal muscle RNA abundance at baseline for 29 transcripts and 11 single nucleotide polymorphisms (SNPs) were both found to be predictive of the V˙O2max response to exercise training in one report from multiple laboratories. None of the 50 loci associated with adiposity traits are known to influence physical activity behavior. However, physical activity seems to reduce the obesity-promoting effects of at least 12 of these loci. Evidence continues to be strong for a role of gene-exercise interaction effects on the improvement in insulin sensitivity after exposure to regular exercise. SNPs in the cAMP-responsive element binding position 1 (CREB1) gene were associated with training-induced HR response, in the C-reactive protein (CRP) gene with training-induced changes in left ventricular mass, and in the methylenetetrahydrofolate reductase (MTHFR) gene with carotid stiffness in low-fit individuals. We conclude that progress is being made but that high-quality research designs and replication studies with large sample sizes are urgently needed.

Detailed analysis of variants in FTO in association with body composition in a cohort of 70-year-olds suggests a weakened effect among elderly

Background

The rs9939609 single-nucleotide polymorphism (SNP) in the fat mass and obesity (FTO) gene has previously been associated with higher BMI levels in children and young adults. In contrast, this association was not found in elderly men. BMI is a measure of overweight in relation to the individuals' height, but offers no insight into the regional body fat composition or distribution.

Objective

To examine whether the FTO gene is associated with overweight and body composition-related phenotypes rather than BMI, we measured waist circumference, total fat mass, trunk fat mass, leg fat mass, visceral and subcutaneous adipose tissue, and daily energy intake in 985 humans (493 women) at the age of 70 years. In total, 733 SNPs located in the FTO gene were genotyped in order to examine whether rs9939609 alone or the other SNPs, or their combinations, are linked to obesity-related measures in elderly humans.

Design

Cross-sectional analysis of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) cohort.

Results

Neither a single SNP, such as rs9939609, nor a SNP combination was significantly linked to overweight, body composition-related measures, or daily energy intake in elderly humans. Of note, these observations hold both among men and women.

Conclusions

Due to the diversity of measurements included in the study, our findings strengthen the view that the effect of FTO on body composition appears to be less profound in later life compared to younger ages and that this is seemingly independent of gender.

From GWAS to biology: lessons from FTO

Genome-wide association studies have been very powerful, uncovering potentially new biology that would not have been possible using a candidate gene approach. A prime example of this is the gene FTO (fat mass and obesity associated), which first came to light in 2007, when single nucleotide polymorphisms in its first intron were robustly associated with body mass index and obesity. Subsequently, as it became clear that this association with body weight, and increasingly food intake, was replicable across multiple populations and different age groups, attention was turned to studying the biology of FTO, about which absolutely nothing was known. This review focuses on the genetic and biochemical approaches as well as animal models that have been used by us and others since 2007 to try and uncover the complex biology of FTO.

The genetic epidemiology of melanocortin 4 receptor variants

While rare MC4R mutations are the commonest cause of monogenic forms of extreme, early-onset obesity, growing evidence shows that common MC4R variants contribute to obesity in the general population. Candidate gene studies have focussed on the V103I and I251L MC4R variants that both affect MC(4) receptor function in vitro. Individual association studies, which are typically small and underpowered, have found no association between V103I (frequency of 103I-allele: ~4%) or I251L (251L-allele: ~2%) and the risk of obesity in the general population. However, large-scale meta-analyses have confirmed that both variants reduce the risk of obesity by -21% in 103I-allele carriers (P<10(-4)) and by -50% in 251L-allele carriers (P<10(-4)). Recently, genome-wide association studies have identified a common variant (minor allele frequency: ~27%) at ~188kb downstream of MC4R showing robust association (P<5×10(-8)) with BMI and obesity in adults and children. Each additional minor allele increases BMI by 0.20kg/m(2), body weight by 700-1000g, and obesity risk by 14% in adults. Interestingly, this variant also showed association with increased height, consistent with the phenotype seen for rare MC4R mutations. Although MC4R is the nearest gene and phenotypic associations are consistent with those of MC4R mutations, it has not yet been established whether this variant indeed reflects MC(4) receptor function. Taken together, common MC4R variants contribute to variation in BMI and obesity risk in the general population. Of particular interest is the finding from genome-wide association studies that suggests that the region downstream of MC4R contributes to its regulation.

Genetic susceptibility to obesity and related traits in childhood and adolescence: influence of loci identified by genome-wide association studies

OBJECTIVE

Large-scale genome-wide association (GWA) studies have thus far identified 16 loci incontrovertibly associated with obesity-related traits in adults. We examined associations of variants in these loci with anthropometric traits in children and adolescents.

RESEARCH DESIGN AND METHODS

Seventeen variants representing 16 obesity susceptibility loci were genotyped in 1,252 children (mean ± SD age 9.7 ± 0.4 years) and 790 adolescents (15.5 ± 0.5 years) from the European Youth Heart Study (EYHS). We tested for association of individual variants and a genetic predisposition score (GPS-17), calculated by summing the number of effect alleles, with anthropometric traits. For 13 variants, summary statistics for associations with BMI were meta-analyzed with previously reported data (N(total) = 13,071 children and adolescents).

RESULTS

In EYHS, 15 variants showed associations or trends with anthropometric traits that were directionally consistent with earlier reports in adults. The meta-analysis showed directionally consistent associations with BMI for all 13 variants, of which 9 were significant (0.033-0.098 SD/allele; P < 0.05). The near-TMEM18 variant had the strongest effect (0.098 SD/allele P = 8.5 × 10(-11)). Effect sizes for BMI tended to be more pronounced in children and adolescents than reported earlier in adults for variants in or near SEC16B, TMEM18, and KCTD15, (0.028-0.035 SD/allele higher) and less pronounced for rs925946 in BDNF (0.028 SD/allele lower). Each additional effect allele in the GPS-17 was associated with an increase of 0.034 SD in BMI (P = 3.6 × 10(-5)), 0.039 SD, in sum of skinfolds (P = 1.7 × 10(-7)), and 0.022 SD in waist circumference (P = 1.7 × 10(-4)), which is comparable with reported results in adults (0.039 SD/allele for BMI and 0.033 SD/allele for waist circumference).

CONCLUSIONS

Most obesity susceptibility loci identified by GWA studies in adults are already associated with anthropometric traits in children/adolescents. Whereas the association of some variants may differ with age, the cumulative effect size is similar.