Heritability variations of body linearity and obesity indicators during growth

Gene-gene interactions and associations of six hypertension related single nucleotide polymorphisms with obesity risk in a Chinese children population

Obesity is a major risk for hypertension. However, the associations between hypertension susceptibility loci and the risk of obesity as well as the effects of gene-gene interactions are unclear, especially in the Chinese children population. Six single nucleotide polymorphisms (SNPs) (ATP2B1 rs17249754, CSK rs1378942, MTHFR rs1801133, CYP17A1 rs1004467, STK39 rs3754777, FGF5 rs16998073) were genotyped for 3503 Chinese children, aged 6-18 years. Of them, 758 obese cases and 2745 controls were identified based on the International Obesity Task Force age- and sex-specific BMI references. Among the six SNPs, three were associated with obesity risk (CSK rs1378942: odds ratio (OR) = 1.20, 95% confidence interval (CI) 1.01-1.43, P = 0.042; MTHFR rs1801133: OR = 1.19, 95% CI 1.05-1.34, P = 0.006; FGF5 rs16998073: OR = 1.14, 95% CI 1.00-1.29, P = 0.047). The genetic risk score (GRS), based on these three SNPs (CSK rs1378942, MTHFR rs1801133, FGF5 rs16998073), showed a positive association with risk of obesity (OR = 1.18, 95% CI 1.09-1.28, P = 7.60 × 10^-5). The same association signals were also detected in the subgroups of puberty and inactivity. In addition, interaction analyses among these loci implied a potential gene-gene interaction between MTHFR and FGF5. These findings show a significant association of hypertension susceptibility loci in Chinese children, suggesting a likely influence of genetic and environmental factors on the risk of obesity.

Genotype by energy expenditure interaction and body composition traits: The Portuguese Healthy Family Study

Background and Aims. Energy expenditure has been negatively correlated with fat accumulation. However, this association is highly variable. In the present study we applied a genotype by environment interaction method to examine the presence of Genotype x by Total Daily Energy Expenditure and Genotype x by Daily Energy Expenditure interactions in the expression of different body composition traits. Methods and Results. A total of 958 subjects from 294 families of The Portuguese Healthy Family Study were included in the analysis. TDEE and DEE were assessed using a physical activity recall. Body fat percentages were measured with a bioelectrical impedance scale. GxTDEE and GxDEE examinations were performed using SOLAR 4.0 software. All BC traits were significantly heritable, with heritabilities ranging from 21% to 34%. The GxTDEE and GxDEE interaction models fitted the data better than the polygenic model for all traits. For all traits, a significant GxTDEE and GxDEE interaction was due to variance heterogeneity among distinct levels of TDEE and DEE. For WC, GxTDEE was also significant due to the genetic correlation function. Conclusions. TDEE and DEE are environmental constraints associated with the expression of individuals' BC genotypes, leading to variability in the phenotypic expression of BC traits.

Sex-dependent associations of genetic variants identified by GWAS with indices of adiposity and obesity risk in a Chinese children population

OBJECTIVE

Recent genome-wide association studies have identified a few single nucleotide polymorphisms (SNPs), which are associated with body mass index (BMI)/obesity. This study aimed to examine the identified associations among a population of Chinese children.

RESEARCH DESIGN AND METHODS

Five SNPs (SEC16B rs10913469, SH2B1 rs4788102, PCSK1rs6235, KCTD15 rs29941, BAT2 rs2844479) were genotyped for a group of Chinese children (N = 2849, age range 6-18 years). A total of 1230 obese cases and 1619 controls with normal weight were identified based on the Chinese age- and sex-specific BMI references.

RESULTS

Of five studied variants, only two (SEC16B rs10913469, SH2B1 rs4788102) were nominally associated with indices of adiposity and obesity risk in girls and only SEC16B rs10913469 in children at puberty (p < 0·05), while no statistical associations was found for three other variants (PCSK1rs6235, KCTD15 rs29941, BAT2 rs2844479). After false discovery rate (FDR) adjustment for multiple testing, none were statistically significant. Further analysis indicated that the genetic risk score (GRS) was associated with BMI, waist circumference and risk of obesity (defined by BMI) in girls, even after FDR adjustment for multiple testing. However, there was no statistical association of GRS with indices of adiposity and risk of obesity in children at puberty after multiple comparison correction.

CONCLUSIONS

This study confirmed the synthetic effect of SNPs on the indices of adiposity and risk of obesity in Chinese girls, but failed to replicate the effect of five separate variants. We also did not found cumulative effect of SNPs in children at puberty.