Large effects on body mass index and insulin resistance of fat mass and obesity associated gene (FTO) variants in patients with polycystic ovary syndrome (PCOS)

BACKGROUND: The polycystic ovary syndrome (PCOS), a common endocrine disorder in women of child-bearing age, mainly characterised by chronic anovulation and hyperandrogenism, is often associated with insulin resistance (IR) and obesity. Its etiology and the role of IR and obesity in PCOS are not fully understood. We examined the influence of validated genetic variants conferring susceptibility to obesity and/or type 2 diabetes mellitus (T2DM) on metabolic and PCOS-specific traits in patients with PCOS. METHODS: We conducted an association study in 386 patients with PCOS (defined by the Rotterdam-criteria) using single nucleotide polymorphisms (SNPs) in or in proximity to the fat mass and obesity associated gene (FTO), insulin-induced gene-2 (INSIG2), transcription factor 7-like 2 gene (TCF7L2) and melanocortin 4 receptor gene (MC4R). To compare the effect of FTO obesity risk alleles on BMI in patients with PCOS to unselected females of the same age range we genotyped 1,971 females from the population-based KORA-S4 study (Kooperative Gesundheitsforschung im Raum Augsburg, Survey 4). RESULTS: The FTO risk allele was associated with IR traits and measures of increased body weight. In addition, the TCF7L2 SNP was associated with body weight traits. For the SNPs in the vicinity of INSIG2 and MC4R and for the other examined phenotypes there was no evidence for an association. In PCOS the observed per risk allele effect of FTO intron 1 SNP rs9939609 on BMI was +1.56 kg/m2, whereas it was +0.46 kg/m2 in females of the same age range from the general population as shown previously. CONCLUSION: The stronger effect on body weight of the FTO SNP in PCOS might well have implications for the etiology of the disease

Citogenético and molecular study of a population of alcoolistas

O alcoolismo é uma doença multifatorial que consiste numa interação de influências genéticas e ambientais, sendo um dos principais causadores de danos à saúde. Deste modo, é muito importante a realização de estudos que envolvam a investigação de danos provocados ao material genético pelo consumo excessivo de bebidas alcoólicas bem como daqueles que investiguem a susceptibilidade individual às doenças causadas pelo alcoolismo. As aberrações cromossômicas e os polimorfismos para enzimas de metabolização de xenobióticos são importantes instrumentos para estes estudos. Neste trabalho foram investigados o possível efeito clastogênico do álcool e também a possível associação entre a ocorrência dos genótipos nulos GSTM1 e GSTT1 e dos polimorfismos CYP1A1-MspI, CYP2D6-BstN1 e CYP2E1-PstI com o desenvolvimento de cirrose e pancreatite, além da freqüência da mutação TaqA1 do gene DRD2 em alcoolistas. Os indivíduos analisados foram alcoolistas com consumo diário de álcool >60g. Para a análise de AC foram analisados 26 alcoolistas e 22 indivíduos controles. Para o estudo dos polimorfismos genéticos a amostra compreendeu 124 alcoolistas crônicos e 124 controles. Os alcoolistas não-fumantes apresentaram um valor de IM maior do que os controles não-fumantes (p = 0,03). As freqüências de ACs nos alcoolistas não foram diferentes das do grupo controle. Não foram encontradas associações de risco entre os genótipos nulos dos genes GSTM1 e GSTT1, e os genótipos mutantes de CYP2D6 e CYP2E1, e o desenvolvimento de cirrose e pancreatite. O genótipo homozigoto mutante m2/m2 do gene CYP1A1 apresentou um risco significativo para o desenvolvimento de cirrose e pancratite em alcoolistas. Não foram encontradas freqüências significativas na ocorrência do alelo A1 do gene DRD2 em alcoolistas.Alcoholism is a disease consisted of an interaction of genetic and environmental factors, being responsible for serious damage to human health. This way, studies that investigate damage caused by heavy consumption of alcohol as well those that investigate individual susceptibility originated by alcoholism are very important to our society. Chromosomal aberrations (CAs) and polymorphisms to xenobiotic metabolizing enzymes are important tools to these studies. In this work we investigated the possible clastogenic effect of alcohol and the possible association between the occurrence of null genotypes for GSTM1 and GSTT1 enzymes and polymorphisms CYP1A1-MspI, CYP2D6-BstN1 and CYP2E1-PstI with the development of cirrhosis and pancreatitis. Furthermore, we investigate the possible association of TaqA1 polymorphism for DRD2 neurotransmitter in alcoholic. Our sample consisted of alcoholic classified as heavy consumers (>60g alcohol/day). For CA assay we have analysed 26 alcoholic and 22 healthy individuals as control group. For the polymorphism study, 124 alcoholic and 124 healthy individuals were genotyped using PCR and RFLP techniques. Non-smokers alcoholics showed higher mitotic index than nonsmokers controls (p=0,03). Acs frequencies in alcoholics were similar to controls. No risk associations were found between null genotypes for GSTM1 and GSTT1 genes and mutant genotypes for CYP2D6 and CYP2E1 genes and the occurrence of cirrhosis or pancreatic disease. Homozygous mutant for CYP1A1 gene (m2/m2) presented significant risk to development of cirrhosis or pancreatic disease in alcoholic. No significant frequencies were found in the occurrence of A1 allele in alcoholic

Investigation of a genome wide association signal for obesity: synthetic association and haplotype analyses at the melanocortin 4 receptor gene locus.

BACKGROUND: Independent genome-wide association studies (GWAS) showed an obesogenic effect of two single nucleotide polymorphisms (SNP; rs12970134 and rs17782313) more than 150 kb downstream of the melanocortin 4 receptor gene (MC4R). It is unclear if the SNPs directly influence MC4R function or expression, or if the SNPs are on a haplotype that predisposes to obesity or includes functionally relevant genetic variation (synthetic association). As both exist, functionally relevant mutations and polymorphisms in the MC4R coding region and a robust association downstream of the gene, MC4R is an ideal model to explore synthetic association. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed a genomic region (364.9 kb) encompassing the MC4R in GWAS data of 424 obesity trios (extremely obese child/adolescent and both parents). SNP rs12970134 showed the lowest p-value (p = 0.004; relative risk for the obesity effect allele: 1.37); conditional analyses on this SNP revealed that 7 of 78 analyzed SNPs provided independent signals (p≤0.05). These 8 SNPs were used to derive two-marker haplotypes. The three best (according to p-value) haplotype combinations were chosen for confirmation in 363 independent obesity trios. The confirmed obesity effect haplotype includes SNPs 3' and 5' of the MC4R. Including MC4R coding variants in a joint model had almost no impact on the effect size estimators expected under synthetic association. CONCLUSIONS/SIGNIFICANCE: A haplotype reaching from a region 5' of the MC4R to a region at least 150 kb from the 3' end of the gene showed a stronger association to obesity than single SNPs. Synthetic association analyses revealed that MC4R coding variants had almost no impact on the association signal. Carriers of the haplotype should be enriched for relevant mutations outside the MC4R coding region and could thus be used for re-sequencing approaches. Our data also underscore the problems underlying the identification of relevant mutations depicted by GWAS derived SNPs

Global transmission disequilibrium tests (HAP-TDT) of all three best two-marker haplotype combinations (according to p-values) in the genomic region covering the melanocortin 4 receptor gene (<i>MC4R</i>) in 424 obesity trios of the detection sample, the confirmation sample of 363 obesity trios and in the joint sample of 787 obesity trios.

a<p>base pair position on chromosome 18 according to <a href="http://www.ncbi.nlm.nih.gov" target="_blank">http://www.ncbi.nlm.nih.gov</a> (hg18);</p>b<p>permutation-based p-value based on 10⁶ simulations;</p>c<p>haplotypic relative risk (hRR) relative to the most frequent haplotype for the haplotype comprising the two obesity risk alleles of the 1^st and 2^nd SNP with 95% confidence intervals (95% CI).</p

Single-marker transmission disequilibrium tests in the detection sample (424 obesity trios), the confirmation sample (363 obesity trios) and in the joint sample (787 obesity trios).

a<p>base pair position on chromosome 18 according to <a href="http://www.ncbi.nlm.nih.gov" target="_blank">http://www.ncbi.nlm.nih.gov</a> (hg18);</p>b<p>obesity effect allele frequency;</p>c<p>confidence interval;</p>d<p>p-values were calculated using PLINKs′ adaptive permutation procedure with 10⁶ permutations.</p><p>Displayed are the SNPs included in the three best haplotypes (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013967#pone-0013967-t001" target="_blank">Table 1</a>) for the explored genomic region surrounding the melanocortin 4 receptor gene (MC4R, location: chromosome 18: 55,879,013–56,243,921 bps). The obesity-predisposing allele (obesity effect allele) within each sample is highlighted in bold.</p

Description of the investigated two independent German family-based data sets (detection and confirmation sample).

a<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0013967#pone.0013967-Speliotes1" target="_blank">[33]</a>.</p

Conditional logistic regression analysis including effects of the two-marker haplotype SNPs (rs12970134, rs1943229), the two coding polymorphisms (weight lowering effect: Val103Ile, Ile251Leu) and any other functionally relevant obesity <i>MC4R</i> mutations.

a<p>model 1 included rs12970134, rs1943229 whereas model 2 included either the non-synonymous MC4R polymorphisms (Val103Ile and Ile251Leu) (left and right panel) or the functionally relevant obesity MC4R mutations (right panel) as one explanatory variables; in model 3, both rs12970134, rs1943229 and the coding variants were included;</p>b<p>wild-type alleles at the non-synonymous MC4R polymorphisms (Val103Ile and Ile251Leu) were combined into one covariable; c mutation alleles Ser30Phe, [Tyr35Stop; 110A>T], Pro78Leu, Ser94Arg, Thr112Met, Ile121Thr, Ser127Leu, Arg165Trp, Ala175Thr, Gly181Asp, Met200Val, Ala244Glu, L211fsX216, Ile317Thr were combined into one covariable; the 525 obesity trios are a subset of all 787 trios for which information on functionally relevant obesity MC4R mutations were available.</p

<i>MC4R</i> coding variants and their relationship to haplotype frequencies and transmission ratios of the two-marker haplotype comprising the SNPs rs12970134 (3′end) and rs1943229 (5′end) in the <i>MC4R</i> region.

a<p>note that the minor alleles of the two non-synonymous polymorphisms (Val103Ile and Ile251Leu; left panel) are negatively associated with obesity whereas the functionally relevant mutations (right) are all obesity-related;</p>b<p>here, all 787 obesity trios were incorporated in the haplotype estimation;</p>c<p>here, a subset of 525 obesity trios for which information on functionally relevant obesity <i>MC4R</i> mutations was available and incorporated in the haplotype estimation;</p>d<p>decimals in transmitted and non-transmitted haplotypes result from haplotype estimations;</p>e<p>transmission ratios were obtained from FAMHAP (version 18).</p