Genome Wide Association (GWA) Study for Early Onset Extreme Obesity Supports the Role of Fat Mass and Obesity Associated Gene (FTO) Variants

Background. Obesity is a major health problem. Although heritability is substantial, genetic mechanisms predisposing to obesity are not very well understood. We have performed a genome wide association study (GWA) for early onset (extreme) obesity. Methodology/Principal Findings. a) GWA (Genome-Wide Human SNP Array 5.0 comprising 440,794 single nucleotide polymorphisms) for early onset extreme obesity based on 487 extremely obese young German individuals and 442 healthy lean German controls; b) confirmatory analyses on 644 independent families with at least one obese offspring and both parents. We aimed to identify and subsequently confirm the 15 SNPs (minor allele frequency $10%) with the lowest p-values of the GWA by four genetic models: additive, recessive, dominant and allelic. Six single nucleotide polymorphisms (SNPs) in FTO (fat mass and obesity associated gene) within one linkage disequilibrium (LD) block including the GWA SNP rendering the lowest p-value (rs1121980; log-additive model: nominal p = 1.13610 27, corrected p = 0.0494; odds ratio (OR)CT 1.67, 95 % confidence interval (CI) 1.22–2.27; OR TT 2.76, 95 % CI 1.88–4.03) belonged to the 15 SNPs showing the strongest evidence for association with obesity. For confirmation we genotyped 11 of these in the 644 independent families (of the six FTO SNPs we chose only two representing the LD bock). For both FTO SNPs the initial association was confirmed (both Bonferroni corrected p,0.01). However, none of the nine non-FTO SNPs revealed significant transmission disequilibrium

Association between Variants of the Leptin Receptor Gene (LEPR) and Overweight: A Systematic Review and an Analysis of the CoLaus Study

BACKGROUND: Three non-synonymous single nucleotide polymorphisms (Q223R, K109R and K656N) of the leptin receptor gene (LEPR) have been tested for association with obesity-related outcomes in multiple studies, showing inconclusive results. We performed a systematic review and meta-analysis on the association of the three LEPR variants with BMI. In addition, we analysed 15 SNPs within the LEPR gene in the CoLaus study, assessing the interaction of the variants with sex. METHODOLOGY/PRINCIPAL FINDINGS: We searched electronic databases, including population-based studies that investigated the association between LEPR variants Q223R, K109R and K656N and obesity- related phenotypes in healthy, unrelated subjects. We furthermore performed meta-analyses of the genotype and allele frequencies in case-control studies. Results were stratified by SNP and by potential effect modifiers. CoLaus data were analysed by logistic and linear regressions and tested for interaction with sex. The meta-analysis of published data did not show an overall association between any of the tested LEPR variants and overweight. However, the choice of a BMI cut-off value to distinguish cases from controls was crucial to explain heterogeneity in Q223R. Differences in allele frequencies across ethnic groups are compatible with natural selection of derived alleles in Q223R and K109R and of the ancient allele in K656N in Asians. In CoLaus, the rs10128072, rs3790438 and rs3790437 variants showed interaction with sex for their association with overweight, waist circumference and fat mass in linear regressions. CONCLUSIONS: Our systematic review and analysis of primary data from the CoLaus study did not show an overall association between LEPR SNPs and overweight. Most studies were underpowered to detect small effect sizes. A potential effect modification by sex, population stratification, as well as the role of natural selection should be addressed in future genetic association studies

Novel codon 15 RHO gene mutation associated with retinitis pigmentosa

 Manuel AP Vilela,1 Roberta K Menna Barreto,2 Pedro K Menna Barreto,1 Juliana MF Sallum,3 Vanessa S Mattevi1 1Department of Ophthalmology, Federal Health Sciences University of Porto Alegre, Porto Alegre, Brazil; 2Medical School, Federal University of Rio Grande do Sul, Rio Grande do Sul, Brazil; 3Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil Objective: To describe, in a multimodal way, a new RHO gene mutation with lysine-for-asparagine substitution in autosomal dominant retinitis pigmentosa.Methods: Case report. Retrospective data analysis.Results: The mutation is located within codon 15 of exon 1 of the RHO gene. A single base-pair transversion lead to a specific lysine-for-asparagine substitution (Asn15Lys). Hypoacusis, myopia, dyschromatopsis and diffuse retinitis pigmentosa were detected. Detailed multimodal images for the posterior segment are presented.Conclusion: We present a new mutation with a specific substitution that may cause eye disease and which has not been described previously. There is no description of this variant in the genetic databases. Keywords: tapetoretinal degeneration, rod-cone dystrophy, pigmentary retinopathy, opsins, retinal pigment

Polymorphisms in the NPY and AGRP genes and body fatness in Dutch adults.

OBJECTIVE: To investigate the association between DNA polymorphisms in the NPY and AGRP genes and body fatness. DESIGN AND METHODS: The association between the AGRP Ala67Thr or the NPY Leu7Pro polymorphisms and indicators of body fatness (baseline leptin levels, body mass index (BMI) values and prevalence of overweight) are investigated in 582 participants of two large cohorts in The Netherlands (total 18 500 adult men and women), aged 20-40 years whose weight remained relatively constant or whose weight increased substantially (range 5.5-47 kg) during a mean follow-up of 7 years. RESULTS: No consistent associations were found for the indicators of body fatness for men and women. Among women, BMI values, leptin levels and prevalence of overweight were not statistically different for carriers of the mutant alleles compared to that of the non-carriers. Among men, carriers of the Thr67-allele of the AGRP gene had similar leptin levels, but higher BMI values compared to those with the genotyping Ala67/Ala67: mean adjusted BMI 25.6 kg/m2 (95% CI 24.3-27.0) vs 23.9 kg/m2 (23.6-24.3). Also, the risk of being overweight at baseline tended to be higher for male carriers of the Thr67-allele of the AGRP gene (OR 2.52; 95% CI 0.86-7.4). Furthermore, male carriers of the Pro7-allele of the NPY gene had on average higher leptin levels and BMI values vs non-carriers of this allele: 4.7 microg/l (95% CI 3.7-6.0) and 25.7 kg/m2 (95% CI 24.4-27.0) vs 3.1 microg/l (95% CI 2.9-3.4) and 23.9 kg/m2 (95% CI 23.5-24.3), respectively. These male carriers had also a higher risk on being overweight at baseline (OR 3.3 (95% CI 1.2-8.9)) compared to non-carriers of the Pro7-allele. CONCLUSION: The consistent findings among men suggest that the NPY Leu7Pro polymorphism (or another linked marker) might be involved in the development of obesity at younger ages. The findings for the AGRP Ala67Thr were less consistent and need further investigation. Among women, these polymorphisms do not play an important role