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1.
JAMA Netw Open ; 2(9): e1910915, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31539074

RESUMO

Importance: Observational studies have shown associations of birth weight with type 2 diabetes (T2D) and glycemic traits, but it remains unclear whether these associations represent causal associations. Objective: To test the association of birth weight with T2D and glycemic traits using a mendelian randomization analysis. Design, Setting, and Participants: This mendelian randomization study used a genetic risk score for birth weight that was constructed with 7 genome-wide significant single-nucleotide polymorphisms. The associations of this score with birth weight and T2D were tested in a mendelian randomization analysis using study-level data. The association of birth weight with T2D was tested using both study-level data (7 single-nucleotide polymorphisms were used as an instrumental variable) and summary-level data from the consortia (43 single-nucleotide polymorphisms were used as an instrumental variable). Data from 180 056 participants from 49 studies were included. Main Outcomes and Measures: Type 2 diabetes and glycemic traits. Results: This mendelian randomization analysis included 49 studies with 41 155 patients with T2D and 80 008 control participants from study-level data and 34 840 patients with T2D and 114 981 control participants from summary-level data. Study-level data showed that a 1-SD decrease in birth weight due to the genetic risk score was associated with higher risk of T2D among all participants (odds ratio [OR], 2.10; 95% CI, 1.69-2.61; P = 4.03 × 10-5), among European participants (OR, 1.96; 95% CI, 1.42-2.71; P = .04), and among East Asian participants (OR, 1.39; 95% CI, 1.18-1.62; P = .04). Similar results were observed from summary-level analyses. In addition, each 1-SD lower birth weight was associated with 0.189 SD higher fasting glucose concentration (ß = 0.189; SE = 0.060; P = .002), but not with fasting insulin, 2-hour glucose, or hemoglobin A1c concentration. Conclusions and Relevance: In this study, a genetic predisposition to lower birth weight was associated with increased risk of T2D and higher fasting glucose concentration, suggesting genetic effects on retarded fetal growth and increased diabetes risk that either are independent of each other or operate through alterations of integrated biological mechanisms.

2.
Int J Obes (Lond) ; 2019 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-31388097

RESUMO

BACKGROUND: Genome-wide association studies (GWAS) have identified more than 250 loci associated with body mass index (BMI) and obesity. However, post-GWAS functional genomic investigations have been inadequate for understanding how these genetic loci physiologically impact disease development. METHODS: We performed a PCR-free expression assay targeting genes located nearby the GWAS-identified SNPs associated with BMI/obesity in a large panel of human tissues. Furthermore, we analyzed several genetic risk scores (GRS) summing GWAS-identified alleles associated with increased BMI in 4236 individuals. RESULTS: We found that the expression of BMI/obesity susceptibility genes was strongly enriched in the brain, especially in the insula (p = 4.7 × 10-9) and substantia nigra (p = 6.8 × 10-7), which are two brain regions involved in addiction and reward. Inversely, we found that top obesity/BMI-associated loci, including FTO, showed the strongest gene expression enrichment in the two brain regions. CONCLUSIONS: Our data suggest for the first time that the susceptibility genes for common obesity may have an effect on eating addiction and reward behaviors through their high expression in substantia nigra and insula, i.e., a different pattern from monogenic obesity genes that act in the hypothalamus and cause hyperphagia. Further epidemiological studies with relevant food behavior phenotypes are necessary to confirm these findings.

3.
Nat Genet ; 50(11): 1505-1513, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30297969

RESUMO

We expanded GWAS discovery for type 2 diabetes (T2D) by combining data from 898,130 European-descent individuals (9% cases), after imputation to high-density reference panels. With these data, we (i) extend the inventory of T2D-risk variants (243 loci, 135 newly implicated in T2D predisposition, comprising 403 distinct association signals); (ii) enrich discovery of lower-frequency risk alleles (80 index variants with minor allele frequency <5%, 14 with estimated allelic odds ratio >2); (iii) substantially improve fine-mapping of causal variants (at 51 signals, one variant accounted for >80% posterior probability of association (PPA)); (iv) extend fine-mapping through integration of tissue-specific epigenomic information (islet regulatory annotations extend the number of variants with PPA >80% to 73); (v) highlight validated therapeutic targets (18 genes with associations attributable to coding variants); and (vi) demonstrate enhanced potential for clinical translation (genome-wide chip heritability explains 18% of T2D risk; individuals in the extremes of a T2D polygenic risk score differ more than ninefold in prevalence).

4.
Nat Genet ; 50(4): 559-571, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29632382

RESUMO

We aggregated coding variant data for 81,412 type 2 diabetes cases and 370,832 controls of diverse ancestry, identifying 40 coding variant association signals (P < 2.2 × 10-7); of these, 16 map outside known risk-associated loci. We make two important observations. First, only five of these signals are driven by low-frequency variants: even for these, effect sizes are modest (odds ratio ≤1.29). Second, when we used large-scale genome-wide association data to fine-map the associated variants in their regional context, accounting for the global enrichment of complex trait associations in coding sequence, compelling evidence for coding variant causality was obtained for only 16 signals. At 13 others, the associated coding variants clearly represent 'false leads' with potential to generate erroneous mechanistic inference. Coding variant associations offer a direct route to biological insight for complex diseases and identification of validated therapeutic targets; however, appropriate mechanistic inference requires careful specification of their causal contribution to disease predisposition.

5.
PLoS Med ; 14(9): e1002383, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28898252

RESUMO

BACKGROUND: Glycated hemoglobin (HbA1c) is used to diagnose type 2 diabetes (T2D) and assess glycemic control in patients with diabetes. Previous genome-wide association studies (GWAS) have identified 18 HbA1c-associated genetic variants. These variants proved to be classifiable by their likely biological action as erythrocytic (also associated with erythrocyte traits) or glycemic (associated with other glucose-related traits). In this study, we tested the hypotheses that, in a very large scale GWAS, we would identify more genetic variants associated with HbA1c and that HbA1c variants implicated in erythrocytic biology would affect the diagnostic accuracy of HbA1c. We therefore expanded the number of HbA1c-associated loci and tested the effect of genetic risk-scores comprised of erythrocytic or glycemic variants on incident diabetes prediction and on prevalent diabetes screening performance. Throughout this multiancestry study, we kept a focus on interancestry differences in HbA1c genetics performance that might influence race-ancestry differences in health outcomes. METHODS & FINDINGS: Using genome-wide association meta-analyses in up to 159,940 individuals from 82 cohorts of European, African, East Asian, and South Asian ancestry, we identified 60 common genetic variants associated with HbA1c. We classified variants as implicated in glycemic, erythrocytic, or unclassified biology and tested whether additive genetic scores of erythrocytic variants (GS-E) or glycemic variants (GS-G) were associated with higher T2D incidence in multiethnic longitudinal cohorts (N = 33,241). Nineteen glycemic and 22 erythrocytic variants were associated with HbA1c at genome-wide significance. GS-G was associated with higher T2D risk (incidence OR = 1.05, 95% CI 1.04-1.06, per HbA1c-raising allele, p = 3 × 10-29); whereas GS-E was not (OR = 1.00, 95% CI 0.99-1.01, p = 0.60). In Europeans and Asians, erythrocytic variants in aggregate had only modest effects on the diagnostic accuracy of HbA1c. Yet, in African Americans, the X-linked G6PD G202A variant (T-allele frequency 11%) was associated with an absolute decrease in HbA1c of 0.81%-units (95% CI 0.66-0.96) per allele in hemizygous men, and 0.68%-units (95% CI 0.38-0.97) in homozygous women. The G6PD variant may cause approximately 2% (N = 0.65 million, 95% CI 0.55-0.74) of African American adults with T2D to remain undiagnosed when screened with HbA1c. Limitations include the smaller sample sizes for non-European ancestries and the inability to classify approximately one-third of the variants. Further studies in large multiethnic cohorts with HbA1c, glycemic, and erythrocytic traits are required to better determine the biological action of the unclassified variants. CONCLUSIONS: As G6PD deficiency can be clinically silent until illness strikes, we recommend investigation of the possible benefits of screening for the G6PD genotype along with using HbA1c to diagnose T2D in populations of African ancestry or groups where G6PD deficiency is common. Screening with direct glucose measurements, or genetically-informed HbA1c diagnostic thresholds in people with G6PD deficiency, may be required to avoid missed or delayed diagnoses.


Assuntos
Diabetes Mellitus Tipo 2/diagnóstico , Diabetes Mellitus Tipo 2/genética , Variação Genética , Estudo de Associação Genômica Ampla , Hemoglobina A Glicada/genética , Diabetes Mellitus Tipo 2/epidemiologia , Hemoglobina A Glicada/metabolismo , Humanos , Fenótipo , Risco
6.
Mol Metab ; 6(6): 459-470, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28580277

RESUMO

OBJECTIVES: Genome-wide association studies (GWAS) have identified >100 loci independently contributing to type 2 diabetes (T2D) risk. However, translational implications for precision medicine and for the development of novel treatments have been disappointing, due to poor knowledge of how these loci impact T2D pathophysiology. Here, we aimed to measure the expression of genes located nearby T2D associated signals and to assess their effect on insulin secretion from pancreatic beta cells. METHODS: The expression of 104 candidate T2D susceptibility genes was measured in a human multi-tissue panel, through PCR-free expression assay. The effects of the knockdown of beta-cell enriched genes were next investigated on insulin secretion from the human EndoC-ßH1 beta-cell line. Finally, we performed RNA-sequencing (RNA-seq) so as to assess the pathways affected by the knockdown of the new genes impacting insulin secretion from EndoC-ßH1, and we analyzed the expression of the new genes in mouse models with altered pancreatic beta-cell function. RESULTS: We found that the candidate T2D susceptibility genes' expression is significantly enriched in pancreatic beta cells obtained by laser capture microdissection or sorted by flow cytometry and in EndoC-ßH1 cells, but not in insulin sensitive tissues. Furthermore, the knockdown of seven T2D-susceptibility genes (CDKN2A, GCK, HNF4A, KCNK16, SLC30A8, TBC1D4, and TCF19) with already known expression and/or function in beta cells changed insulin secretion, supporting our functional approach. We showed first evidence for a role in insulin secretion of four candidate T2D-susceptibility genes (PRC1, SRR, ZFAND3, and ZFAND6) with no previous knowledge of presence and function in beta cells. RNA-seq in EndoC-ßH1 cells with decreased expression of PRC1, SRR, ZFAND6, or ZFAND3 identified specific gene networks related to T2D pathophysiology. Finally, a positive correlation between the expression of Ins2 and the expression of Prc1, Srr, Zfand6, and Zfand3 was found in mouse pancreatic islets with altered beta-cell function. CONCLUSIONS: This study showed the ability of post-GWAS functional studies to identify new genes and pathways involved in human pancreatic beta-cell function and in T2D pathophysiology.

7.
PLoS Genet ; 10(4): e1004235, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24699409

RESUMO

Variants in the growth factor receptor-bound protein 10 (GRB10) gene were in a GWAS meta-analysis associated with reduced glucose-stimulated insulin secretion and increased risk of type 2 diabetes (T2D) if inherited from the father, but inexplicably reduced fasting glucose when inherited from the mother. GRB10 is a negative regulator of insulin signaling and imprinted in a parent-of-origin fashion in different tissues. GRB10 knock-down in human pancreatic islets showed reduced insulin and glucagon secretion, which together with changes in insulin sensitivity may explain the paradoxical reduction of glucose despite a decrease in insulin secretion. Together, these findings suggest that tissue-specific methylation and possibly imprinting of GRB10 can influence glucose metabolism and contribute to T2D pathogenesis. The data also emphasize the need in genetic studies to consider whether risk alleles are inherited from the mother or the father.


Assuntos
Proteína Adaptadora GRB10/genética , Proteína Adaptadora GRB10/metabolismo , Ilhotas Pancreáticas/metabolismo , Alelos , Diabetes Mellitus Tipo 2 , Jejum/metabolismo , Estudo de Associação Genômica Ampla/métodos , Glucose/genética , Glucose/metabolismo , Humanos , Insulina/genética , Insulina/metabolismo , Resistência à Insulina/genética , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único/genética , Receptor de Insulina/genética , Receptor de Insulina/metabolismo , Transdução de Sinais/genética
8.
Diabetologia ; 57(4): 785-96, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24463962

RESUMO

AIMS/HYPOTHESIS: Gene polymorphisms of TCF7L2 are associated with increased risk of type 2 diabetes and transcription factor 7-like 2 (TCF7L2) plays a role in hepatic glucose metabolism. We therefore addressed the impact of TCF7L2 isoforms on hepatocyte nuclear factor 4α (HNF4α) and the regulation of gluconeogenesis genes. METHODS: Liver TCF7L2 transcripts were analysed by quantitative PCR in 33 non-diabetic and 31 type 2 diabetic obese individuals genotyped for TCF7L2 rs7903146. To analyse transcriptional regulation by TCF7L2, small interfering RNA transfection, luciferase reporter and co-immunoprecipitation assays were performed in human hepatoma HepG2 cells. RESULTS: In livers of diabetic compared with normoglycaemic individuals, five C-terminal TCF7L2 transcripts showed increased expression. The type 2 diabetes risk allele of rs7903146 positively correlated with TCF7L2 expression in livers from normoglycaemic individuals only. In HepG2 cells, transcript and TCF7L2 protein levels were increased upon incubation in high glucose and insulin. Of the exon 13 transcripts, six were increased in a glucose dose-responsive manner. TCF7L2 transcriptionally regulated 29 genes related to glucose metabolism, including glucose-6-phosphatase. In cultured HepG2 cells, TCF7L2 did not regulate HNF4Α and FOXO1 transcription, but did affect HNF4α protein expression. The TCF7L2 isoforms T6 and T8 (without exon 13 and with exon 15/14, respectively) specifically interacted with HNF4α. CONCLUSIONS/INTERPRETATION: The different levels of expression of alternative C-terminal TCF7L2 transcripts in HepG2 cells, in livers of normoglycaemic individuals carrying the rs7901346 type 2 diabetes risk allele and in livers of diabetic individuals suggest that these transcripts play a role in the pathophysiology of type 2 diabetes. We also report for the first time a protein interaction in HepG2 cells between HNF4α and the T6 and T8 isoforms of TCF7L2, which suggests a distinct role for these specific alternative transcripts.


Assuntos
Gluconeogênese/fisiologia , Fator 4 Nuclear de Hepatócito/metabolismo , Fígado/metabolismo , Proteína 2 Semelhante ao Fator 7 de Transcrição/metabolismo , Adulto , Western Blotting , Feminino , Gluconeogênese/genética , Células Hep G2 , Fator 4 Nuclear de Hepatócito/genética , Humanos , Imunoprecipitação , Masculino , Pessoa de Meia-Idade , Ligação Proteica , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteína 2 Semelhante ao Fator 7 de Transcrição/genética
9.
Mol Biol Evol ; 31(4): 975-83, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24448642

RESUMO

Lactase persistence (LP) is a genetically determined trait whereby the enzyme lactase is expressed throughout adult life. Lactase is necessary for the digestion of lactose--the main carbohydrate in milk--and its production is downregulated after the weaning period in most humans and all other mammals studied. Several sources of evidence indicate that LP has evolved independently, in different parts of the world over the last 10,000 years, and has been subject to strong natural selection in dairying populations. In Europeans, LP is strongly associated with, and probably caused by, a single C to T mutation 13,910 bp upstream of the lactase (LCT) gene (-13,910*T). Despite a considerable body of research, the reasons why LP should provide such a strong selective advantage remain poorly understood. In this study, we examine one of the most widely cited hypotheses for selection on LP--that fresh milk consumption supplemented the poor vitamin D and calcium status of northern Europe's early farmers (the calcium assimilation hypothesis). We do this by testing for natural selection on -13,910*T using ancient DNA data from the skeletal remains of eight late Neolithic Iberian individuals, whom we would not expect to have poor vitamin D and calcium status because of relatively high incident UVB light levels. None of the eight samples successfully typed in the study had the derived T-allele. In addition, we reanalyze published data from French Neolithic remains to both test for population continuity and further examine the evolution of LP in the region. Using simulations that accommodate genetic drift, natural selection, uncertainty in calibrated radiocarbon dates, and sampling error, we find that natural selection is still required to explain the observed increase in allele frequency. We conclude that the calcium assimilation hypothesis is insufficient to explain the spread of LP in Europe.


Assuntos
Cálcio/metabolismo , Absorção Intestinal/genética , Lactase/genética , Seleção Genética , DNA Mitocondrial/genética , Evolução Molecular , Feminino , França , Frequência do Gene , Deriva Genética , Humanos , Modelos Genéticos , Polimorfismo de Nucleotídeo Único , Análise de Sequência de DNA , Espanha
10.
Diabetes ; 63(6): 2158-71, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24296717

RESUMO

Patients with established type 2 diabetes display both ß-cell dysfunction and insulin resistance. To define fundamental processes leading to the diabetic state, we examined the relationship between type 2 diabetes risk variants at 37 established susceptibility loci, and indices of proinsulin processing, insulin secretion, and insulin sensitivity. We included data from up to 58,614 nondiabetic subjects with basal measures and 17,327 with dynamic measures. We used additive genetic models with adjustment for sex, age, and BMI, followed by fixed-effects, inverse-variance meta-analyses. Cluster analyses grouped risk loci into five major categories based on their relationship to these continuous glycemic phenotypes. The first cluster (PPARG, KLF14, IRS1, GCKR) was characterized by primary effects on insulin sensitivity. The second cluster (MTNR1B, GCK) featured risk alleles associated with reduced insulin secretion and fasting hyperglycemia. ARAP1 constituted a third cluster characterized by defects in insulin processing. A fourth cluster (TCF7L2, SLC30A8, HHEX/IDE, CDKAL1, CDKN2A/2B) was defined by loci influencing insulin processing and secretion without a detectable change in fasting glucose levels. The final group contained 20 risk loci with no clear-cut associations to continuous glycemic traits. By assembling extensive data on continuous glycemic traits, we have exposed the diverse mechanisms whereby type 2 diabetes risk variants impact disease predisposition.


Assuntos
Diabetes Mellitus Tipo 2/genética , Predisposição Genética para Doença , Resistência à Insulina/genética , Células Secretoras de Insulina/metabolismo , Insulina/metabolismo , Locos de Características Quantitativas/genética , Alelos , Análise por Conglomerados , Feminino , Frequência do Gene , Variação Genética , Estudo de Associação Genômica Ampla , Humanos , Masculino , Polimorfismo de Nucleotídeo Único , Fatores de Risco , Fatores de Transcrição/metabolismo
11.
Nat Genet ; 45(5): 501-12, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23563607

RESUMO

Approaches exploiting trait distribution extremes may be used to identify loci associated with common traits, but it is unknown whether these loci are generalizable to the broader population. In a genome-wide search for loci associated with the upper versus the lower 5th percentiles of body mass index, height and waist-to-hip ratio, as well as clinical classes of obesity, including up to 263,407 individuals of European ancestry, we identified 4 new loci (IGFBP4, H6PD, RSRC1 and PPP2R2A) influencing height detected in the distribution tails and 7 new loci (HNF4G, RPTOR, GNAT2, MRPS33P4, ADCY9, HS6ST3 and ZZZ3) for clinical classes of obesity. Further, we find a large overlap in genetic structure and the distribution of variants between traits based on extremes and the general population and little etiological heterogeneity between obesity subgroups.


Assuntos
Antropometria , Estatura/genética , Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Obesidade/genética , Polimorfismo de Nucleotídeo Único/genética , Locos de Características Quantitativas , Índice de Massa Corporal , Estudos de Casos e Controles , Grupo com Ancestrais do Continente Europeu/genética , Genótipo , Humanos , Metanálise como Assunto , Fenótipo , Relação Cintura-Quadril
12.
Nat Genet ; 44(9): 991-1005, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22885924

RESUMO

Through genome-wide association meta-analyses of up to 133,010 individuals of European ancestry without diabetes, including individuals newly genotyped using the Metabochip, we have increased the number of confirmed loci influencing glycemic traits to 53, of which 33 also increase type 2 diabetes risk (q < 0.05). Loci influencing fasting insulin concentration showed association with lipid levels and fat distribution, suggesting impact on insulin resistance. Gene-based analyses identified further biologically plausible loci, suggesting that additional loci beyond those reaching genome-wide significance are likely to represent real associations. This conclusion is supported by an excess of directionally consistent and nominally significant signals between discovery and follow-up studies. Functional analysis of these newly discovered loci will further improve our understanding of glycemic control.


Assuntos
Glicemia/genética , Estudo de Associação Genômica Ampla/estatística & dados numéricos , Redes e Vias Metabólicas/genética , Locos de Características Quantitativas , Adulto , Animais , Glicemia/metabolismo , Jejum/sangue , Jejum/metabolismo , Feminino , Frequência do Gene , Humanos , Insulina/sangue , Masculino , Camundongos , Concentração Osmolar , Locos de Características Quantitativas/fisiologia
13.
Diabetes ; 61(8): 2176-86, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22698912

RESUMO

Exploring genetic pleiotropy can provide clues to a mechanism underlying the observed epidemiological association between type 2 diabetes and heightened fracture risk. We examined genetic variants associated with bone mineral density (BMD) for association with type 2 diabetes and glycemic traits in large well-phenotyped and -genotyped consortia. We undertook follow-up analysis in ∼19,000 individuals and assessed gene expression. We queried single nucleotide polymorphisms (SNPs) associated with BMD at levels of genome-wide significance, variants in linkage disequilibrium (r(2) > 0.5), and BMD candidate genes. SNP rs6867040, at the ITGA1 locus, was associated with a 0.0166 mmol/L (0.004) increase in fasting glucose per C allele in the combined analysis. Genetic variants in the ITGA1 locus were associated with its expression in the liver but not in adipose tissue. ITGA1 variants appeared among the top loci associated with type 2 diabetes, fasting insulin, ß-cell function by homeostasis model assessment, and 2-h post-oral glucose tolerance test glucose and insulin levels. ITGA1 has demonstrated genetic pleiotropy in prior studies, and its suggested role in liver fibrosis, insulin secretion, and bone healing lends credence to its contribution to both osteoporosis and type 2 diabetes. These findings further underscore the link between skeletal and glucose metabolism and highlight a locus to direct future investigations.


Assuntos
Densidade Óssea/genética , Diabetes Mellitus Tipo 2/genética , Fraturas Ósseas/etiologia , Integrina alfa1/genética , Tecido Adiposo/metabolismo , Adulto , Glicemia/genética , Glicemia/metabolismo , Índice de Massa Corporal , Feminino , Fraturas Ósseas/genética , Estudo de Associação Genômica Ampla , Humanos , Insulina/genética , Desequilíbrio de Ligação , Fígado/metabolismo , Proteínas dos Microfilamentos/genética , Osteoporose/genética , Polimorfismo de Nucleotídeo Único
14.
PLoS One ; 7(6): e37423, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22701567

RESUMO

BACKGROUND: Maturity-onset of the young (MODY) is a clinically heterogeneous form of diabetes characterized by an autosomal-dominant mode of inheritance, an onset before the age of 25 years, and a primary defect in the pancreatic beta-cell function. Approximately 30% of MODY families remain genetically unexplained (MODY-X). Here, we aimed to use whole-exome sequencing (WES) in a four-generation MODY-X family to identify a new susceptibility gene for MODY. METHODOLOGY: WES (Agilent-SureSelect capture/Illumina-GAIIx sequencing) was performed in three affected and one non-affected relatives in the MODY-X family. We then performed a high-throughput multiplex genotyping (Illumina-GoldenGate assay) of the putative causal mutations in the whole family and in 406 controls. A linkage analysis was also carried out. PRINCIPAL FINDINGS: By focusing on variants of interest (i.e. gains of stop codon, frameshift, non-synonymous and splice-site variants not reported in dbSNP130) present in the three affected relatives and not present in the control, we found 69 mutations. However, as WES was not uniform between samples, a total of 324 mutations had to be assessed in the whole family and in controls. Only one mutation (p.Glu227Lys in KCNJ11) co-segregated with diabetes in the family (with a LOD-score of 3.68). No KCNJ11 mutation was found in 25 other MODY-X unrelated subjects. CONCLUSIONS/SIGNIFICANCE: Beyond neonatal diabetes mellitus (NDM), KCNJ11 is also a MODY gene ('MODY13'), confirming the wide spectrum of diabetes related phenotypes due to mutations in NDM genes (i.e. KCNJ11, ABCC8 and INS). Therefore, the molecular diagnosis of MODY should include KCNJ11 as affected carriers can be ideally treated with oral sulfonylureas.


Assuntos
Diabetes Mellitus Tipo 2/genética , Exoma/genética , Predisposição Genética para Doença/genética , Canais de Potássio Corretores do Fluxo de Internalização/genética , Sequência de Bases , Mapeamento Cromossômico , Análise Mutacional de DNA , França , Genótipo , Humanos , Escore Lod , Dados de Sequência Molecular , Linhagem
15.
Nat Genet ; 44(6): 659-69, 2012 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-22581228

RESUMO

Recent genome-wide association studies have described many loci implicated in type 2 diabetes (T2D) pathophysiology and ß-cell dysfunction but have contributed little to the understanding of the genetic basis of insulin resistance. We hypothesized that genes implicated in insulin resistance pathways might be uncovered by accounting for differences in body mass index (BMI) and potential interactions between BMI and genetic variants. We applied a joint meta-analysis approach to test associations with fasting insulin and glucose on a genome-wide scale. We present six previously unknown loci associated with fasting insulin at P < 5 × 10(-8) in combined discovery and follow-up analyses of 52 studies comprising up to 96,496 non-diabetic individuals. Risk variants were associated with higher triglyceride and lower high-density lipoprotein (HDL) cholesterol levels, suggesting a role for these loci in insulin resistance pathways. The discovery of these loci will aid further characterization of the role of insulin resistance in T2D pathophysiology.


Assuntos
Glicemia/metabolismo , Índice de Massa Corporal , Resistência à Insulina/genética , Insulina/metabolismo , Polimorfismo de Nucleotídeo Único , HDL-Colesterol/metabolismo , Diabetes Mellitus Tipo 2/genética , Estudo de Associação Genômica Ampla , Humanos
16.
PLoS One ; 7(5): e35810, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22606236

RESUMO

BACKGROUND: The Nuclear Receptor 2F2 (NR2F2/COUP-TFII) heterozygous knockout mice display low basal insulinemia and enhanced insulin sensitivity. We previously established that insulin represses NR2F2 gene expression in pancreatic ß-cells. The cis-regulatory region of the NR2F2 promoter is unknown and its influence on metabolism in humans is poorly understood. The present study aimed to identify the regulatory regions that control NR2F2 gene transcription and to evaluate the effect of NR2F2 promoter variation on glucose homeostasis in humans. METHODOLOGY/PRINCIPAL FINDINGS: Regulation of the NR2F2 promoter was assessed using gene reporter assays, ChIP and gel shift experiments. The effects of variation at SNP rs3743462 in NR2F2 on quantitative metabolic traits were studied in two European prospective cohorts. We identified a minimal promoter region that down-regulates NR2F2 expression by attenuating HNF4α activation in response to high glucose concentrations. Subjects of the French DESIR population, who carried the rs3743462 T-to-C polymorphism, located in the distal glucose-responsive promoter, displayed lower basal insulin levels and lower HOMA-IR index. The C-allele at rs3743462 was associated with increased NR2F2 binding and decreased NR2F2 gene expression. CONCLUSIONS/SIGNIFICANCE: The rs3743462 polymorphism affects glucose-responsive NR2F2 promoter regulation and thereby may influence whole-body insulin sensitivity, suggesting a role of NR2F2 in the control of glucose homeostasis in humans.


Assuntos
Fator II de Transcrição COUP/genética , Glucose/metabolismo , Resistência à Insulina/genética , Polimorfismo de Nucleotídeo Único , Regiões Promotoras Genéticas , Adulto , Animais , Sequência de Bases , Glicemia/metabolismo , Fator II de Transcrição COUP/deficiência , Fator II de Transcrição COUP/metabolismo , Linhagem Celular , Estudos de Coortes , DNA/genética , Regulação da Expressão Gênica , Fator 4 Nuclear de Hepatócito/metabolismo , Humanos , Insulina/sangue , Resistência à Insulina/fisiologia , Células Secretoras de Insulina/metabolismo , Camundongos , Camundongos Knockout , Dados de Sequência Molecular , Estudos Prospectivos , Homologia de Sequência do Ácido Nucleico
17.
Nat Genet ; 44(5): 526-31, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22484627

RESUMO

Multiple genetic variants have been associated with adult obesity and a few with severe obesity in childhood; however, less progress has been made in establishing genetic influences on common early-onset obesity. We performed a North American, Australian and European collaborative meta-analysis of 14 studies consisting of 5,530 cases (≥95th percentile of body mass index (BMI)) and 8,318 controls (<50th percentile of BMI) of European ancestry. Taking forward the eight newly discovered signals yielding association with P < 5 × 10(-6) in nine independent data sets (2,818 cases and 4,083 controls), we observed two loci that yielded genome-wide significant combined P values near OLFM4 at 13q14 (rs9568856; P = 1.82 × 10(-9); odds ratio (OR) = 1.22) and within HOXB5 at 17q21 (rs9299; P = 3.54 × 10(-9); OR = 1.14). Both loci continued to show association when two extreme childhood obesity cohorts were included (2,214 cases and 2,674 controls). These two loci also yielded directionally consistent associations in a previous meta-analysis of adult BMI(1).


Assuntos
Loci Gênicos , Marcadores Genéticos , Estudo de Associação Genômica Ampla , Obesidade/genética , Polimorfismo de Nucleotídeo Único/genética , Adolescente , Adulto , Índice de Massa Corporal , Estudos de Casos e Controles , Predisposição Genética para Doença , Humanos , Adulto Jovem
18.
PLoS One ; 7(3): e32327, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22403646

RESUMO

Haptoglobin is an acute phase inflammatory marker. Its main function is to bind hemoglobin released from erythrocytes to aid its elimination, and thereby haptoglobin prevents the generation of reactive oxygen species in the blood. Haptoglobin levels have been repeatedly associated with a variety of inflammation-linked infectious and non-infectious diseases, including malaria, tuberculosis, human immunodeficiency virus, hepatitis C, diabetes, carotid atherosclerosis, and acute myocardial infarction. However, a comprehensive genetic assessment of the inter-individual variability of circulating haptoglobin levels has not been conducted so far.We used a genome-wide association study initially conducted in 631 French children followed by a replication in three additional European sample sets and we identified a common single nucleotide polymorphism (SNP), rs2000999 located in the Haptoglobin gene (HP) as a strong genetic predictor of circulating Haptoglobin levels (P(overall) = 8.1 × 10(-59)), explaining 45.4% of its genetic variability (11.8% of Hp global variance). The functional relevance of rs2000999 was further demonstrated by its specific association with HP mRNA levels (ß = 0.23 ± 0.08, P = 0.007). Finally, SNP rs2000999 was associated with decreased total and low-density lipoprotein cholesterol in 8,789 European children (P(total cholesterol) = 0.002 and P(LDL) = 0.0008).Given the central position of haptoglobin in many inflammation-related metabolic pathways, the relevance of rs2000999 genotyping when evaluating haptoglobin concentration should be further investigated in order to improve its diagnostic/therapeutic and/or prevention impact.


Assuntos
Estudo de Associação Genômica Ampla , Haptoglobinas/genética , Haptoglobinas/metabolismo , Polimorfismo de Nucleotídeo Único , Adulto , Doenças Cardiovasculares/sangue , Doenças Cardiovasculares/genética , Criança , Feminino , Genótipo , Humanos , Masculino , Fatores de Risco
19.
Nature ; 483(7389): 350-4, 2012 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-22343897

RESUMO

Free fatty acids provide an important energy source as nutrients, and act as signalling molecules in various cellular processes. Several G-protein-coupled receptors have been identified as free-fatty-acid receptors important in physiology as well as in several diseases. GPR120 (also known as O3FAR1) functions as a receptor for unsaturated long-chain free fatty acids and has a critical role in various physiological homeostasis mechanisms such as adipogenesis, regulation of appetite and food preference. Here we show that GPR120-deficient mice fed a high-fat diet develop obesity, glucose intolerance and fatty liver with decreased adipocyte differentiation and lipogenesis and enhanced hepatic lipogenesis. Insulin resistance in such mice is associated with reduced insulin signalling and enhanced inflammation in adipose tissue. In human, we show that GPR120 expression in adipose tissue is significantly higher in obese individuals than in lean controls. GPR120 exon sequencing in obese subjects reveals a deleterious non-synonymous mutation (p.R270H) that inhibits GPR120 signalling activity. Furthermore, the p.R270H variant increases the risk of obesity in European populations. Overall, this study demonstrates that the lipid sensor GPR120 has a key role in sensing dietary fat and, therefore, in the control of energy balance in both humans and rodents.


Assuntos
Obesidade/metabolismo , Receptores Acoplados a Proteínas-G/metabolismo , Adipócitos/metabolismo , Adipócitos/patologia , Adipogenia , Tecido Adiposo/metabolismo , Tecido Adiposo/patologia , Animais , Sinalização do Cálcio , Diferenciação Celular , Análise Mutacional de DNA , Dieta Hiperlipídica , Metabolismo Energético , Europa (Continente)/etnologia , Grupo com Ancestrais do Continente Europeu/genética , Éxons/genética , Fígado Gorduroso/complicações , Fígado Gorduroso/genética , Regulação da Expressão Gênica , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Glucose/metabolismo , Intolerância à Glucose/complicações , Humanos , Insulina/metabolismo , Resistência à Insulina , Lipogênese , Fígado/metabolismo , Macrófagos/metabolismo , Camundongos , Mutação/genética , Obesidade/complicações , Obesidade/genética , Obesidade/patologia , Receptores Acoplados a Proteínas-G/deficiência , Receptores Acoplados a Proteínas-G/genética , Transdução de Sinais/genética
20.
Diabetes ; 60(6): 1805-12, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21515849

RESUMO

OBJECTIVE: To investigate whether associations of common genetic variants recently identified for fasting glucose or insulin levels in nondiabetic adults are detectable in healthy children and adolescents. RESEARCH DESIGN AND METHODS: A total of 16 single nucleotide polymorphisms (SNPs) associated with fasting glucose were genotyped in six studies of children and adolescents of European origin, including over 6,000 boys and girls aged 9-16 years. We performed meta-analyses to test associations of individual SNPs and a weighted risk score of the 16 loci with fasting glucose. RESULTS: Nine loci were associated with glucose levels in healthy children and adolescents, with four of these associations reported in previous studies and five reported here for the first time (GLIS3, PROX1, SLC2A2, ADCY5, and CRY2). Effect sizes were similar to those in adults, suggesting age-independent effects of these fasting glucose loci. Children and adolescents carrying glucose-raising alleles of G6PC2, MTNR1B, GCK, and GLIS3 also showed reduced ß-cell function, as indicated by homeostasis model assessment of ß-cell function. Analysis using a weighted risk score showed an increase [ß (95% CI)] in fasting glucose level of 0.026 mmol/L (0.021-0.031) for each unit increase in the score. CONCLUSIONS: Novel fasting glucose loci identified in genome-wide association studies of adults are associated with altered fasting glucose levels in healthy children and adolescents with effect sizes comparable to adults. In nondiabetic adults, fasting glucose changes little over time, and our results suggest that age-independent effects of fasting glucose loci contribute to long-term interindividual differences in glucose levels from childhood onwards.


Assuntos
Glicemia/genética , Jejum/sangue , Loci Gênicos/genética , Adenilil Ciclases/genética , Adolescente , Criança , Criptocromos/genética , Feminino , Estudo de Associação Genômica Ampla , Transportador de Glucose Tipo 2/genética , Glucose-6-Fosfatase/genética , Proteínas de Homeodomínio/genética , Humanos , Masculino , Polimorfismo de Nucleotídeo Único/genética , Proteínas Serina-Treonina Quinases/genética , Fatores de Transcrição/genética , Proteínas Supressoras de Tumor/genética
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