BMI loci and longitudinal BMI from adolescence to young adulthood in an ethnically diverse cohort

MTCH2 in Metabolic Diseases, Neurodegenerative Diseases, Cancers, Embryonic Development and Reproduction

Mitochondrial carrier homolog 2 (MTCH2) is a member of the solute carrier 25 family, located on the outer mitochondrial membrane. MTCH2 was first identified in 2000. The development in MTCH2 research is rapidly increasing. The most well-known role of MTCH2 is linking to the pro-apoptosis BID to facilitate mitochondrial apoptosis. Genetic variants in MTCH2 have been investigated for their association with metabolic and neurodegenerative diseases, however, no intervention or therapeutic suggestions were provided. Recent studies revealed the physiological and pathological function of MTCH2 in metabolic diseases, neurodegenerative diseases, cancers, embryonic development and reproduction via regulating mitochondrial apoptosis, metabolic shift between glycolysis and oxidative phosphorylation, mitochondrial fusion/fission, epithelial-mesenchymal transition, etc. This review endeavors to assess a total of 131 published articles to summarise the structure and physiological/pathological role of MTCH2, which has not previously been conducted. This review concludes that MTCH2 plays a crucial role in metabolic diseases, neurodegenerative diseases, cancers, embryonic development and reproduction, and the predominant molecular mechanism is regulation of mitochondrial function. This review gives a comprehensive state of current knowledgement on MTCH2, which will promote the therapeutic research of MTCH2.

Body Mass Index and Physical Fitness among Chinese Adolescents Aged 15-18: A Cross-Sectional Study of Gender Differences

OBJECTIVE

The aim of this study is to examine the relationship between varying levels of obesity and physical fitness test scores among Chinese adolescents, while also investigating gender differences in physical fitness and overall health. Data on height, weight, 50 m sprints, 1000/800 m runs, standing long jumps, sit and reach exercises, pull-ups/bent-leg sit-ups, and additional variables were collected from the DYH health database. Physical fitness indicators were evaluated based on the revised 2014 National Physical Fitness Standards for Students, and scores were assigned accordingly. An ordinal logistic regression (ologit) model was employed to analyze the relationship between body mass index (BMI) and physical fitness.

RESULTS

(1) Normal-weight boys achieved significantly higher physical fitness test scores than boys in other weight categories. (2) Underweight and normal-weight girls obtained significantly higher physical fitness test scores compared to overweight and obese girls, with underweight girls scoring slightly higher than those with a normal weight.

CONCLUSIONS

(1) There is a significant non-linear relationship between BMI levels and physical fitness test scores. (2) Gender differences were observed in physical fitness and overall health outcome. (3) The findings indicate an inverted U-shaped association between BMI and physical fitness among boys, while girls displayed an inverse relationship. This could be attributed to the cultural association between thinness and beauty among girls in China.

Association between genetic risk score and tri-ponderal mass index growth trajectories among different dietary consumption adolescents in a prospective Taiwanese cohort

BACKGROUND

Single-nucleotide polymorphisms (SNPs) in various genetic loci are associated with childhood obesity; however, their influence on adolescent growth patterns has rarely been explored. This study investigated whether genetic variants could predict tri-ponderal mass index (TMI)-derived growth trajectories and the interaction between genetic and dietary factors.

METHODS

We conducted Taiwan Puberty Longitudinal Study, a prospective cohort that recruited 1,135 children since 2018. Anthropometric measurements were recorded every three months, while dietary nutrition assessment and biological sampling for genotyping were collected during the first visit. TMI growth trajectory groups were identified using growth mixture modeling. A multinomial logistic regression model for different growth trajectories was used to examine the effect of candidate SNPs, and the most related SNPs were used to establish the genetic risk score. We then explored the effect of the genetic risk score in subgroup analysis according to dietary calories and different dietary consumption patterns.

RESULTS

Three TMI-based growth trajectory groups were identified among adolescents. The "increased weight" trajectory group accounted for approximately 9.7% of the participants. FTO/rs7206790 was associated with the increased weight growth trajectory after adjusting for the baseline TMI and other correlated covariates (OR: 2.13, 95% CI: 1.08-4.21). We generated the genetic risk score using 4 SNPs (FTO/rs7206790, ADCY9/rs2531995, TFAP2B/rs4715210, and TMEM18/rs6548238) and selected the threshold of 10 points to define risk categories. There were 11.66% and 3.24% of participants belonged to the increased weight trajectory in high- and low-risk groups, respectively; and the predictive ability of the genetic risk score was notable among low calories intake participants (OR: 1.90, 95% CI: 1.18-3.05 vs. OR: 1.17, 95% CI: 0.78-1.75 in high calories intake group).

CONCLUSION

Our results offer a new perspective on the genetic and dietary basis of changes in adolescent obesity status. Individualized interventions for obesity prevention may be considered among high-risk children.

Do adverse childhood experiences and genetic obesity risk interact in relation to body mass index in young adulthood? Findings from the National Longitudinal Study of Adolescent to Adult Health

BACKGROUND

Few studies have focused on the role of adverse childhood experiences (ACEs) in relation to genetic susceptibility to obesity.

OBJECTIVE

We aimed to examine the interaction between the presence of ACEs (i.e., physical, psychological and sexual abuse) before the age of 18 and BMI polygenic score.

METHODS

Data came from the National Longitudinal Study of Adolescent to Adult Health (Add Health) Wave IV (2007/2008) where saliva samples were collected for DNA genotyping and information on BMI and ACEs were obtained from 5854 European American (EA), 2073 African American (AA) and 1448 Hispanic American (HA) participants aged 24 to 32 years old. Polygenic scores were calculated as the sum of the number of risk alleles of BMI-related SNPs which were weighted by effect size. A race/ethnicity-stratified mixed-effects linear regression model was used to test for differential association between BMI polygenic score and BMI by the presence of ACEs.

RESULTS

We did not find any evidence of significant interaction between ACEs and polygenic score in relation to BMI among EA (p = 0.289), AA (p = 0.618) or HA (p = 0.870). In main effects models, polygenic score was positively associated with BMI in all race/ethnic groups, yet the presence of ACEs was associated with increased BMI only among EA.

CONCLUSION

We did not find any evidence that ACEs exacerbate genetic predisposition to increased BMI in early adulthood.

Diverse effect of MC4R risk alleles on obesity-related traits over a lifetime: Evidence from a well-designed cohort study

This population-based longitudinal study is the first investigation that assesses the association of common MC4R SNPs with the obesity-related parameters over time and determines the effect of risk alleles during the three adulthood life periods (early, middle, and late) in a large Iranian cohort, a population with a unique genetic make-up that has been understudied and relatively unexplored. We obtained the genotype of 5370 unrelated adults who participated in the ongoing Tehran Cardiometabolic Genetic Study (TCGS) cohort project for the common MC4R SNPs. Linear regression and linear mixed model analyses were performed to examine the effect of MC4R polymorphisms on maximum BMI and other obesity-related factors over time. We recognized that several SNPs associated with the maximum BMI and the increased BMI, waist circumference, and waist-hip ratio across Iranian adults over a lifetime. Interestingly, we found that rs9954571-A has a yet unreported protective role against obesity-related factors, including BMI, waist circumference, waist-hip ratio, and triglyceride level. Additionally, a survey of the impact of the MC4R risk score throughout the adulthood life periods indicated that the MC4R risk score is influenced both the elevated BMI and waist circumference only during the early adulthood period. Our findings can expand our knowledge about the MC4R genetic variant's contributions to adulthood obesity and highlight the importance of evaluating the genetic components affecting obesity over a lifetime, which could be considered for obesity clinical screening and treatment.

FTO Obesity Variant-Exercise Interaction on Changes in Body Weight and BMI: The Taiwan Biobank Study

CONTEXT

Gene-exercise interaction on cross-sectional body mass index (BMI) has been extensively studied and is well established. However, gene-exercise interaction on changes in body weight/BMI remains controversial.

OBJECTIVE

To examine the interaction between the FTO obesity variant and regular exercise on changes in body weight/BMI.

PARTICIPANTS

Taiwan Biobank participants aged 30-70 years (N = 20 906) were examined at both baseline and follow-up visit (mean follow-up duration: 3.7 years).

MAIN OUTCOME MEASURES

The interaction between the FTO obesity variant rs1421085 and regular exercise habit (no exercise, ≤20 metabolic equivalent of tasks (METs)/week exercise, >20 METs/week exercise) on changes in body weight/BMI.

RESULTS

Individuals with the risk allele of rs1421085 gained more weight and increased BMI than those without the risk allele if they did not exercise. In contrast, individuals with the risk allele gained less weight and BMI if they exercised regularly, indicating an interaction between rs1421085 and regular exercise habit (P = .030 for Δbody weight and P = .034 for ΔBMI). The effect of exercise on maintaining body weight was larger in those with the risk allele of rs1421085. When we focused on individuals without regular exercise at baseline, individuals with the risk allele again tended to lose more weight than those with a nonrisk allele if they had acquired an exercise habit by the follow-up visit.

CONCLUSION

The beneficial effect of exercise is greater in individuals genetically prone to obesity due to the interaction between the FTO obesity variant rs1421085 and regular exercise on changes in body weight and BMI.

The association between polymorphisms near TMEM18 and the risk of obesity: a meta-analysis

BACKGROUND

Many studies have proposed that the pathogenesis of obesity has a genetic basis, with an important risk factor being the presence of polymorphisms in the region of the TMEM18 gene, which plays a significant role in feeding behaviour; however, subsequent studies among different ethnic populations and age groups have shown inconsistent results. Therefore, this present meta-analysis examines the relationship between TMEM18 polymorphisms with the risk of obesity with regard to age group and ethnic population.

METHODS

A literature database search was conducted for available relevant studies investigating the association between obesity risk and the presence of rs6548238, rs4854344, rs11127485, rs2867125 and rs7561317 polymorphisms in TMEM18. Pooled odds ratio (OR) and 95% confidence intervals (95% CI) were calculated by either a fixed-effects model or random effect model based on a heterogeneity test. The meta-analysis of rs6548238 and its surrogates examined the relationships between 53 395 obesity cases and 123 972 healthy controls from 27 studies and published data from the POPULOUS collection (Poland).

RESULTS

A significant association is observed between rs6548238 (and surrogate) and obesity risk, with OR = 1.25 (95% CI: 1.08-1.45). Regarding population type, a significant association was revealed among groups of Europeans with OR = 1.32 (1.10-1.59) and Mexicans with OR = 1.39 (1.13-1.73). However, a lack of statistical significance was noticed in groups in Asia with OR = 1.11 (95% CI: 0.86-1.42). Regarding age, a significant association was observed among children with OR = 1.28 (95% CI: 1.18-1.39) but not in adults OR = 1.21 (95% CI: 0.92-1.58).

CONCLUSIONS

The polymorphisms near TMEM18 appear to play a role in the development of obesity. Our findings indicate that differences exist between ethnic populations and age groups, supporting those of a previous study showing the various effects of genetic factors on age and ethnic groups.

Associations of MC4R, LEP, and LEPR Polymorphisms with Obesity-Related Parameters in Childhood and Adulthood

MC4R, LEP, and LEPR genes are involved in the hypothalamic leptin-melanocortin regulation pathway, which is important for energy homeostasis. Our study aimed to evaluate the associations between the MC4R rs17782313, LEP rs7799039, and LEPR rs1137101 polymorphisms with obesity-related parameters in childhood and adulthood. The data were obtained from the Kaunas Cardiovascular Risk Cohort study, which started in 1977 with 1082 participants aged 12-13 years. In 2012-2014, the follow-up survey was carried out. Genotype analysis of all respondents (n = 509) aged 48-49 years was performed for the gene polymorphisms using Real-Time Polymerase Chain Reaction. Anthropometric measurements were performed in childhood and adulthood. In childhood, only skinfold thicknesses were associated with gene variants being the lowest in children with MC4R TT genotype and LEP AG genotype. In adulthood, odds of obesity and metabolic syndrome was higher in MC4R CT/CC genotype than TT genotype carriers (OR 1.8; 95% CI 1.2-2.8 and OR 1.6; 95% CI 1.1-2.4, respectively). In men, physical activity attenuated the effect of the MC4R rs17782313 on obesity. The LEP GG genotype was associated with higher BMI, waist circumference, and visceral fat level only in men. No associations of the LEPR rs1137101 polymorphisms with anthropometric measurements and leptin level were found. In conclusion, the associations of the MC4R and LEP gene polymorphisms with obesity-related parameters strengthened with age.

Transcription factor AP-2beta in development, differentiation and tumorigenesis

To date, the AP-2 family of transcription factors comprises five members. Transcription factor AP-2beta (TFAP2B)/AP-2β was first described in 1995. Several studies indicate a critical role of AP-2β in the development of tissues and organs of ectodermal, neuroectodermal and also mesodermal origin. Germline mutation of TFAP2B is known to cause the Char syndrome, an autosomal dominant disorder characterized by facial dysmorphism, patent ductus arteriosus and anatomical abnormalities of the fifth digit. Furthermore, single-nucleotide polymorphisms in TFAP2B were linked to obesity and specific personality traits. In neoplasias, AP-2β was first described in alveolar rhabdomyosarcoma. Immunohistochemical staining of AP-2β is a recommended ancillary test for the histopathological diagnosis of this uncommon childhood malignancy. In neuroblastoma, AP-2β supports noradrenergic differentiation. Recently, the function of AP-2β in breast cancer (BC) has gained interest. AP-2β is associated with the lobular BC subtype. Moreover, AP-2β controls BC cell proliferation and has a prognostic impact in patients with BC. This review provides a comprehensive overview of the current knowledge about AP-2β and its function in organ development, differentiation and tumorigenesis.

Differential Effect of Polymorphisms on Body Mass Index Across the Life Course of Japanese: The Japan Multi-Institutional Collaborative Cohort Study

BACKGROUND

Obesity is a reported risk factor for various health problems. Genome-wide association studies (GWASs) have identified numerous independent loci associated with body mass index (BMI). However, most of these have been focused on Europeans, and little evidence is available on the genetic effects across the life course of other ethnicities.

METHODS

We conducted a cross-sectional study to examine the associations of 282 GWAS-identified single nucleotide polymorphisms with three BMI-related traits, current BMI, BMI at 20 years old (BMI at 20), and change in BMI (BMI change), among 11,586 Japanese individuals enrolled in the Japan Multi-Institutional Collaborative Cohort study. Associations were examined using multivariable linear regression models.

RESULTS

We found a significant association (P < 0.05/282 = 1.77 × 10-4) between BMI and 11 polymorphisms in or near FTO, BDNF, TMEM18, HS6ST3, and BORCS7. The trend was similar between current BMI and BMI change, but differed from that of the BMI at 20. Among the significant variants, those on FTO were associated with all BMI traits, whereas those on TMEM18 and HS6SR3 were only associated with BMI at 20. The association of FTO loci with BMI remained, even after additional adjustment for dietary energy intake.

CONCLUSIONS

Previously reported BMI-associated loci discovered in Europeans were also identified in the Japanese population. Additionally, our results suggest that the effects of each loci on BMI may vary across the life course and that this variation may be caused by the differential effects of individual genes on BMI via different pathways.

The current review of adolescent obesity: the role of genetic factors

Obesity, a complex, multi-factor and heterogeneous condition, is thought to result from the interaction of environmental and genetic factors. Considering the result of adolescence obesity in adulthood, the role of genetic factors comes to the fore. Recently, many genome-wide association studies (GWAS) have been conducted and many loci associated with adiposity have been identified. In adolescents, the strongest association with obesity has been found in single nucleotide polymorphisms (SNP) in the FTO gene. Besides FTO, GWAS showed consistent effects between variants in MC4R, TMEM18, TNNI3K, SEC16B, GNPDA2, POMC and obesity. However, these variants may not have similar effects for all ethnic groups. Although recently genetic factors are considered to contribute to obesity, relatively little is known about the specific loci related to obesity and the mechanisms by which they cause obesity.

Influence of FTO (Fat mass and obesity) gene and parental obesity on Brazilian children and adolescents adiposity

Objectives Evaluate the influence of the genetic variant rs9939609 of the FTO gene on anthropometric characteristics and whether parental obesity is related to children and adolescents being overweight. Methods A total of 2,364 children and adolescents between 6 and 17 years old were genotyped and the lipid profile, plasma glucose level, and anthropometric characteristics were measured to assess adiposity. Results The AA genotype (risk) was associated with higher body mass index (BMI Z-score; p = 0.006), waist circumference (WC; p = 0.001), and triglycerides (p = 0.033). The association of the participants' adiposity characteristics with the parents' BMI and FTO genotypes showed an association of the BMI Z-score when either the mother or father was overweight or obese (p = 0.028 and p = 0.029). In the overweight or obese father/eutrophic mother, we also observe an association of FTO rs9939609 with WC (p = 0.039). The effect of these variables on the risk of obesity was also tested: overweight or obese mother (OR = 1.82, p = 0.041), overweight and obese parents (OR = 3.09, p < 0.0001), and FTO rs9939609 AA genotype (OR = 2.08, p = 0.0004) were associated. With regard to altered WC and high body fat percentage (BF%), either overweight or obese parents (OR = 2.39, p < 0.0001; OR = 1.92, p < 0.002) showed an association. The FTO rs9939609 AA genotype (OR = 1.99, p = 0.0002) was associated with altered WC. Conclusions The results show that parental weight also contributes to obesity and may interact with the FTO genetic make-up.

Longitudinal association of a body mass index (BMI) genetic risk score with growth and BMI changes across the life course: The Cardiovascular Risk in Young Finns Study

BACKGROUND

The role of genetic risk scores associated with adult body mass index (BMI) on BMI levels across the life course is unclear. We examined if a 97 single nucleotide polymorphism weighted genetic risk score (wGRS97) associated with age-related progression in BMI at different life stages and distinct developmental trajectories of BMI across the early life course.

METHODS

2188 Cardiovascular Risk in Young Finns Study participants born pre-1980 who had genotype data and objective measurements of height and weight collected up to 8 times from age 6 to 49 years. Associations were examined using Individual Growth Curve analysis, Latent Class Growth Mixture Modelling, and Poisson modified regression.

RESULTS

The wGRS97 associated with BMI from age 6 years with peak effect sizes observed at age 30 years (females: 1.14 kg/m²; males: 1.09 kg/m² higher BMI per standard deviation increase in wGRS97). The association between wGRS97 and BMI became stronger with age in childhood but slowed in adolescence, especially in females, and weakened at age 35-40 years. A higher wGRS97 associated with an increased BMI velocity in childhood and adulthood, but not with BMI change in adulthood. Compared with belonging to a 'normal stable' life-course trajectory group (normal BMI from childhood to adulthood), a one standard deviation higher wGRS97 associated with a 13-127% increased risk of belonging to a less favourable life-course BMI trajectory group.

CONCLUSIONS

Individuals with genetic susceptibility to higher adult BMI have higher levels and accelerated rates of increase in BMI in childhood/adolescence, and are at increased risk of having a less favourable life-course BMI trajectory.

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.

Implication of genetic variants in overweight and obesity susceptibility among the young Arab population of the United Arab Emirates

OBJECTIVE

Overweight and obesity are major risk factors for Type 2 Diabetes Mellitus (T2DM), cardiovascular disease (CVD) and cancer. Genetic predisposition has been shown to play a key role in obesity, and genome-wide association studies (GWAS) have identified multiple loci linked with obesity in various ethnic groups. The aim of this study was to validate the reported genetic variants associated with obesity and overweight in a young UAE Arab population.

METHODS

Twenty-two associated single nucleotide polymorphisms (SNPs) at 11 loci (FTO, MC4R, TMEM18, KCTD15, MTCH2, SH2B1, TFAP2B, GNPDA2, NEGR1, PCSK1 and BDNF) were studied in 392 controls and 318 overweight/obese young Emiratis (aged 18-35 years).

RESULTS

After adjusting for age and smoking, rs3751812 of the FTO gene was associated with overweight/obesity in male participants (p-value < 0.016), while SNPs rs17782313, rs571312 of the MC4R gene and rs12463617 of the TMEM18 gene were significantly associated with overweight/obesity in female participants (p-value = 0.001, 0.028, 0.044, respectively). Follow-up association tests and logistic regression revealed the contribution of the FTO rs3751812 and MC4R rs571213 SNPs to the risk of overweight/obesity after adjusting for age, sex and smoking (p-value = 0.044, 0.049, respectively). In addition, the FTO rs3751812 was associated with the risk of overweight/obesity after adjusting for the effect of other markers (rs17782313, rs571312, rs2867125, rs6548238 and rs12463617) (p-value = 0.035). A significant gene-gene interaction was seen between FTO, MCR4 and TMEM18 (p-value = 0.013).

CONCLUSIONS

Our data demonstrates that rs3751812 of the FTO gene is the key SNP associated with risk of overweight/obesity among the young UAE Arab population, in alignment with previous findings. Our results also indicate that the identified genes stratify with sex and risk of overweight/obesity. In addition to their direct association with overweight/obesity, rs17782313 and rs571312, as well as rs2867125 and rs6548238, may have a modifying effect on the risk of overweight/obesity caused by the rs3751812. Population-specific, sex-specific genetic profiling is important in understanding the heritability of obesity.

Genomics of Reproductive Traits and Cardiometabolic Disease Risk in African American Women

BACKGROUND

Age at menarche and age at natural menopause occur significantly earlier in African American women than in other ethnic groups. African American women also have twice the prevalence of cardiometabolic disorders related to the timing of these reproductive traits.

OBJECTIVES

The objectives of this integrative review were to (a) summarize the genome-wide association studies of reproductive traits in African American women, (b) identify genes that overlap with reproductive traits and cardiometabolic risk factors in African American women, and (c) propose biological mechanisms explaining the link between reproductive traits and cardiometabolic risk factors.

METHODS

PubMed was searched for genome-wide association studies of genes associated with reproductive traits in African American women. After extracting and summarizing the primary genes, we examined whether any of the associations with reproductive traits had also been identified with cardiometabolic risk factors in African American women.

RESULTS

Seven studies met the inclusion criteria. Associations with both reproductive and cardiometabolic traits were reported in or near the following genes: FTO, SEC16B, TMEM18, APOE, PHACTR1, KCNQ1, LDLR, PIK3R1, and RORA. Biological pathways implicated include body weight regulation, vascular homeostasis, and lipid metabolism.

DISCUSSION

A better understanding of the genetic basis of reproductive traits in African American women may provide insight into the biological mechanisms linking variation in these traits with increased risk for cardiometabolic disorders in this population.

Benefits of normal body mass index on physical fitness: A cross-sectional study among children and adolescents in Xinjiang Uyghur Autonomous Region, China

OBJECTIVE

To assess the association between body mass index (BMI) and physical fitness index (PFI) among children and adolescents in Xinjiang Uyghur Autonomous Region, China.

METHODS

In total, 17,618 children and adolescents aged 7-18 years from the selected region were enrolled in this cross-sectional study (8,800 boys and 8,818 girls). Participants were stratified by age and sex and divided into five groups by BMI percentiles: very low (BMI <5th percentile); low, (5th ≤ BMI < 15th percentile); normal (15th ≤ BMI < 85th percentile); high (85th ≤ BMI < 95th percentile); and very high (BMI ≥95th percentile). PFI was assessed by height, weight, and five health-related fitness indicators (grip strength, standing long jump, sit and reach, 50 m dash, and endurance run).

RESULTS

BMI was significantly associated with PFI during adolescence (13-18 years) in boys and pre-adolescence (7-12 years) in girls. Between the ages of 13 and 18 years, an increase in BMI had a greater impact on PFI in boys than girls. PFI showed a parabolic curvilinear relationship with BMI.

CONCLUSION

Children and adolescents in China's Xinjiang Uyghur Autonomous Region with a normal BMI demonstrated good physical fitness. A BMI below or above the normal range may contribute to poor physical fitness. The relationship between BMI and PFI shows an inverted U-shaped curve.

Genetic determinants of BMI from early childhood to adolescence: the Santiago Longitudinal Study

BACKGROUND

While the genetic contribution to obesity is well established, few studies have examined how genetic variants influence standardized body mass index Z-score (BMIz) in Hispanics/Latinos, especially across childhood and adolescence.

OBJECTIVES

We estimated the effect of established BMIz loci in Chilean children of the Santiago Longitudinal Study (SLS).

METHODS

We examined associations with BMIz at age 10 for 15 loci previously identified in European children. For significant loci, we performed association analyses at ages 5 and 16 years, for which we have smaller sample sizes. We tested associations of unweighted genetic risk scores (GRSs) for previously identified tag variants (GRS_EUR) and from the most significant variants in SLS at each locus (GRS_SLS).

RESULTS

We generalized five variants at age 10 (P < 0.05 and directionally consistent), including rs543874 that reached Bonferroni-corrected significance. The effect on BMIz was greatest at age 10 for all significant loci, except FTO, which exhibited an increase in effect from ages 5 to 16. Both GRSs were associated with BMIz (P < 0.0001), but GRS_SLS explained a much greater proportion of the variation (13.63%).

CONCLUSION

Our results underscore the importance of conducting genetic investigations across life stages and selecting ancestry appropriate tag variants in future studies for disease prediction and clinical evaluation.

Polymorphisms in Genes Involved in the Leptin-Melanocortin Pathway are Associated with Obesity-Related Cardiometabolic Alterations in a Southern Chilean Population

BACKGROUND

Polymorphisms in genes encoding proteins of the leptin-melanocortin pathway have been associated with obesity. The involvement of these polymorphisms with changes in body mass index (BMI) and anthropometric measures could also imply a contribution to the risk of metabolic syndrome (MetS) and metabolic alterations. We evaluated the relationship of leptin-melanocortin system polymorphisms with obesity, MetS, and other metabolic alterations in Southern Chilean individuals.

METHODS

Two-hundred individuals were grouped as normoweight (BMI 18.0-24.9 kg/m²), overweight (BMI 25.0-29.9 kg/m²), and obese (BMI ≥ 30 kg/m²) or according to MetS status. Anthropometric measures (BMI, abdominal circumference, waist-to-hip ratio [WHR]) and biochemical parameters (glycemia and lipid profile) were evaluated. Polymorphisms LEP rs7799039, LEPR rs1137101, MC3R rs3746619 and rs3827103, and MC4R rs17782313 were evaluated by real-time PCR using allelic discrimination assays.

RESULTS

LEPR rs1137101 GG genotype was related to reduced risk of obesity (odds ratio [OR] 0.26, 95% confidence interval [CI] 0.08-0.79; p = 0.018) and MetS (OR 0.36, 95% CI 0.15-0.88; p = 0.024), but it was not significant after Bonferroni correction for multiple tests as compared to the AA genotype (p > 0.01). Moreover, LEPR rs1137101 allele G (AG + GG) was related to lower BMI and WHR (p < 0.01). Further multiple linear regression analysis demonstrated that this genotype was also responsible for reduced BMI in 2.44 kg/m² and WHR in 0.033 units. MC4R rs17782313 allele C (TC + CC) was slightly associated with diminished risk of MetS (OR 0.48, 95% CI 0.23-0.98; p = 0.040) and reduced BMI values in 1.95 kg/m² (p < 0.05). Regarding lipid profile, LEPR rs1137101 allele G carriers had lower triglycerides and very-low-density lipoprotein (VLDL) cholesterol, whereas individuals carrying the MC4R rs17782313 allele C had higher high-density lipoprotein (HDL) cholesterol (p < 0.01). LEP rs7799039 allele A (GA + AA) was slightly associated with reduced total and low-density lipoprotein (LDL) cholesterol (p < 0.05).

CONCLUSIONS

These results suggest that polymorphisms at LEP, LEPR, and MC4R may be useful biomarkers of obesity-related cardiometabolic alterations in our population.

Comprehensive review and annotation of susceptibility SNPs associated with obesity-related traits

We aimed to summarize the results of genetic association studies for obesity and provide a comprehensive annotation of all susceptibility single nucleotide polymorphisms (SNPs). A total of 72 studies were summarized, resulting in 90,361 susceptibility SNPs (738 index SNPs and 89,623 linkage disequilibrium SNPs). Over 90% of the susceptibility SNPs are located in non-coding regions, and it is challenging to understand their functional significance. Therefore, we annotated these SNPs by using various functional databases. We identified 24,623 functional SNPs, including 4 nonsense SNPs, 479 missense SNPs, 399 untranslated region SNPs which might affect microRNA binding, 262 promoter and 5,492 enhancer SNPs which might affect transcription factor binding, 7 splicing sites, 76 SNPs which might affect gene methylation levels, 1,839 SNPs under natural selection and 17,351 SNPs which might modify histone binding. Expression quantitative trait loci analyses for functional SNPs identified 98 target genes, including 69 protein coding genes, 27 long non-coding RNAs and 3 processed transcripts. The percentage of protein coding genes that could be correlated with obesity-related pathways directly or through gene-gene interaction is 75.36 (52/69). Our results may serve as an encyclopaedia of obesity susceptibility SNPs and offer guide for functional experiments.

Genetic contribution to waist-to-hip ratio in Mexican children and adolescents based on 12 loci validated in European adults

BACKGROUND/OBJECTIVES

The prevalence of abdominal obesity in Mexican children has risen dramatically in the past decade. Genome-wide association studies (GWAS) for waist-to-hip ratio (WHR) performed predominantly in European descent adult  populations have identified multiple single-nucleotide polymorphisms (SNPs) with larger effects in women. The contribution of these SNPs to WHR in non-European children is unknown.

SUBJECTS/METHODS

Mexican children and adolescents (N = 1421, 5-17 years) were recruited in Mexico City. Twelve GWAS SNPs were genotyped using TaqMan Open Array and analyzed individually and as a gene score (GS).

RESULTS

Mexican boys and girls displayed 2.81 ± 0.29 and 3.10 ± 0.31 WHR standard deviations higher than children and adolescents from the United States. WHR was positively associated with TG (β = 0.733 ± 0.190, P = 1.1 × 10^-4) and LDL-C (β = 0.491 ± 0.203, P = 1.6 × 10^-2), and negatively associated with HDL-C (β = -0.652 ± 0.195, P = 8.0 × 10^-4), independently of body mass index. The effect allele frequency (EAF) of 8 of 12 (67%) SNPs differed significantly (P < 4.17 × 10^-3) in Mexican children and European adults, with no evidence of effect allele enrichment in both populations (4 depleted and 4 enriched; binomial test, P = 1). Ten out of 12 SNPs (83.3%) had effects that were directionally consistent with those reported in GWAS (P = 0.04). HOXC13 rs1443512 displayed the best fit when modeled recessively, and was significantly associated with WHR under a recessive mode of inheritance (β = 0.140 ± 0.06, P = 2.3 × 10^-2). Significant interactions with sex were also observed for HOXC13 rs1443512 and the GS on WHR (P = 2.2 × 10^-2 and 1.2 × 10^-2, respectively). HOXC13 rs1443512 (β = 0.022 ± 0.012, P = 4.7 × 10^-2) and the GS (β = 0.007 ± 0.003, P = 7.0 × 10^-3) were significantly associated with WHR in girls only.

CONCLUSIONS

This study demonstrates that Mexican children are at high risk for abdominal obesity and detrimental lipid profiles. Our data support a partial transferability of sex-specific European GWAS WHR association signals in children and adolescents from the admixed Mexican population.

The genomic landscape of African populations in health and disease

A deeper appreciation of the complex architecture of African genomes is critical to the global effort to understand human history, biology and differential distribution of disease by geography and ancestry. Here, we report on how the growing engagement of African populations in genome science is providing new insights into the forces that shaped human genomes before and after the Out-of-Africa migrations. As a result of this human evolutionary history, African ancestry populations have the greatest genomic diversity in the world, and this diversity has important ramifications for genomic research. In the case of pharmacogenomics, for instance, variants of consequence are not limited to those identified in other populations, and diversity within African ancestry populations precludes summarizing risk across different African ethnic groups. Exposure of Africans to fatal pathogens, such as Plasmodium falciparum, Lassa Virus and Trypanosoma brucei rhodesiense, has resulted in elevated frequencies of alleles conferring survival advantages for infectious diseases, but that are maladaptive in modern-day environments. Illustrating with cardiometabolic traits, we show that while genomic research in African ancestry populations is still in early stages, there are already many examples of novel and African ancestry-specific disease loci that have been discovered. Furthermore, the shorter haplotypes in African genomes have facilitated fine-mapping of loci discovered in other human ancestry populations. Given the insights already gained from the interrogation of African genomes, it is imperative to continue and increase our efforts to describe genomic risk in and across African ancestry populations.