The role of the genetic variants IRX3 rs3751723 and FTO rs9939609 in the obesity phenotypes of children and adolescents

Polymorphisms of Fat Mass and Obesity-Associated Gene in the Pathogenesis of Child and Adolescent Metabolic Syndrome

Childhood metabolic syndrome (MetS) is prevalent around the world and is associated with a high likelihood of suffering from severe diseases such as cardiovascular disease later in adulthood. MetS is associated with genetic susceptibility that involves gene polymorphisms. The fat mass and obesity-associated gene (FTO) encodes an RNA N6-methyladenosine demethylase that regulates RNA stability and molecular functions. Human FTO contains genetic variants that significantly contribute to the early onset of MetS in children and adolescents. Emerging evidence has also uncovered that FTO polymorphisms in intron 1, such as rs9939609 and rs9930506 polymorphisms, are significantly associated with the development of MetS in children and adolescents. Mechanistic studies reported that FTO polymorphisms lead to aberrant expressions of FTO and the adjacent genes that promote adipogenesis and appetite and reduce steatolysis, satiety, and energy expenditure in the carriers. The present review highlights the recent observations on the key FTO polymorphisms that are associated with child and adolescent MetS with an exploration of the molecular mechanisms underlying the development of increased waist circumference, hypertension, and hyperlipidemia in child and adolescent MetS.

Association of common genetic variants with body mass index in Russian population

BACKGROUND

Overweight is the scourge of modern society and a major risk factor for many diseases. For this reason, understanding the genetic component predisposing to high body mass index (BMI) seems to be an important task along with preventive measures aimed at improving eating behavior and increasing physical activity.

METHODS

We analyzed genetic data of a European cohort (n = 21,080, 47.25% women, East Slavs ancestry >80%) for 5 frequently found genes in the context of association with obesity: IPX3 (rs3751723), MC4R (rs17782313), TMEM18 (rs6548238), PPARG (rs1801282) and FTO (rs9939609).

RESULTS

Our study revealed significant associations of FTO (rs9939609) (β = 0.37 (kg/m²)/allele, p = <2 × 10^-16), MC4R (rs17782313) (β = 0.28 (kg/m²)/allele, p = 5.79 × 10^-9), TMEM18 (rs6548238) (β = 0.29 (kg/m²)/allele, p = 2.43 × 10^-8) with BMI and risk of obesity.

CONCLUSIONS

The results confirm the contribution of FTO, M4CR, and TMEM18 genes to the mechanism of body weight regulation and control.

What is the role of cardiorespiratory fitness and sedentary behavior in relationship between the genetic predisposition to obesity and cardiometabolic risk score?

Background

Genetic factors along with inadequate lifestyle habits are associated with the development of cardiometabolic alterations. Thus, the present study aimed to examine the role of sedentary behavior on the relationship between rs9939609 polymorphism (fat mass and obesity-associated gene-FTO) and cardiometabolic risk score according to cardiorespiratory fitness (CRF) levels in children and adolescents.

Methods

A cross-sectional study with 1215 children and adolescents (692 girls), aged between 6 and 17 years. Screen time as a marker of sedentary behavior was evaluated through a self-reported questionnaire and CRF was estimated using the 6-min walking and running test. The genotyping of the FTO rs9939609 polymorphism was performed using a real-time polymerase chain reaction. Clustered cardiometabolic risk score (cMetS) was calculated by summing z-scores of total cholesterol/high-density lipoprotein cholesterol ratio, triglycerides, glucose, systolic blood pressure, and waist circumference, and dividing it by five. Moderation analyses were tested using multiple linear regression models.

Results

The coefficient of the interaction term of FTO (rs9939609) and screen time indicated that screen time was a significant moderator on the relationship between FTO rs9939609 polymorphism and cMetS (p = 0.047) in children and adolescents classified with low CRF (β = 0.001; 95% CI = 0.001; 0.002). It was observed a significant association between genotype risk (AA) of FTO polymorphism and cMetS, in participants that spent more than 378 min a day in front of screen-based devices (β = 0.203; 95% CI = 0.000; 0.405). No interaction term was found for those with high CRF.

Conclusions

High sedentary behavior seems to influence the relationship between genetic predisposition to obesity and cardiometabolic risk factors in children and adolescents with low CRF.

Whole Genome Interpretation for a Family of Five

Although best practices have emerged on how to analyse and interpret personal genomes, the utility of whole genome screening remains underdeveloped. A large amount of information can be gathered from various types of analyses via whole genome sequencing including pathogenicity screening, genetic risk scoring, fitness, nutrition, and pharmacogenomic analysis. We recognize different levels of confidence when assessing the validity of genetic markers and apply rigorous standards for evaluation of phenotype associations. We illustrate the application of this approach on a family of five. By applying analyses of whole genomes from different methodological perspectives, we are able to build a more comprehensive picture to assist decision making in preventative healthcare and well-being management. Our interpretation and reporting outputs provide input for a clinician to develop a healthcare plan for the individual, based on genetic and other healthcare data.

Prevalence of overweight and obesity in Brazilian children and adolescents: a systematic review

abstract It is important to know about overweight and obesity situation of Brazilian children and adolescents. The present study aims to update scientific production, through a systematic review, on the prevalence and factors associated with overweight and obesity in Brazilian children and adolescents. Nine databases were verified, and 1,316 references were examined from 2018 to 2019. The electronic search was conducted by three independent researchers. All review steps followed a strategy based on PRISMA. 40 studies were included in this systematic review. Most studies use the World Health Organization classification criteria. The prevalence of overweight in Brazilian children and adolescents varies from 8.8% to 22.2% (boys: 6.2% to 21%; girls: 6.9% to 27.6%). The prevalence of obesity varied from 3.8% to 24% (boys: 2.4% to 28.9%; girls: 1.6% to 19.4%). It was observed that the socioeconomic factors (sex, skin color, economic level, region, mother's educational level, living in a rented house and without access to the internet), hereditary/genetic (family history of dyslipidemia and overweight and rs9939609 genotype) and behavioral (physical activity, screen time, eating habits, perceived body weight, health vulnerability, presence of a result close to home, alcoholic beverages, cigarette consumption) were associated with the outcome. It is concluded that the prevalence of overweight and obesity among Brazilian children and adolescents are worrisome and most of the factors associated with the outcomes are subject to change from the adoption of a healthy lifestyle.

Physical fitness attenuates the genetic predisposition to obesity in children and adolescents

Obesity is an important risk factor associated with non-communicable cardiometabolic diseases. Previous studies have indicated that children and adolescents with a predisposed genetic risk for obesity could benefit from an active lifestyle, but there are no studies investigating whether physical fitness moderates the association of genetics and obesity. The aim of this study was to verify the moderating role of physical fitness in the relationship between genetic risk score (GRS) and body mass index (BMI) in children and adolescents. This cross-sectional study was carried out with 1471 children and adolescents, aged between 6 and 17 years from Santa Cruz do Sul, Brazil. Weight and height were assessed to determine BMI. Physical fitness components (cardiorespiratory fitness [CRF], lower limb strength [LLS], upper limb strength, and abdominal strength) were evaluated. The GRS was based on previously associated obesity single-nucleotide polymorphism rs9939609 (FTO), rs6548238 (TMEM18), and rs16835198 (FNDC5). Moderation analyses were tested using linear regression models, and the interactions were represented by physical fitness components X GRS (categorical variable). All analyses were adjusted for skin color/ethnicity, sex, and sexual maturation. Significant interactions for CRF (P = 0.041), LLS (P = 0.041), and abdominal strength (P = 0.046) X 5 and 6 risk alleles with BMI were found only in adolescents. In addition, there was evidence that fitness components attenuated the high genetic predisposition to high BMI. Physical fitness components are moderators in the relationship between GRS and BMI in adolescents. These findings highlight the need for interventions targeting to improve this aspect, which is an important health indicator in all ages.

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.