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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recently, common noncoding variants in the TCF7L2 gene were strongly associated with increased risk of type 2 diabetes in samples from Iceland, Denmark, and the U.S. We genotyped 13 single nucleotide polymorphisms (SNPs) across TCF7L2 in 8,310 individuals in family-based and case-control designs from Scandinavia, Poland, and the U.S. We convincingly confirmed the previous association of TCF7L2 SNPs with the risk of type 2 diabetes (rs7903146T odds ratio 1.40 [95% CI 1.30-1.50], P = 6.74 x 10(-20)). In nondiabetic individuals, the risk genotypes were associated with a substantial reduction in the insulinogenic index derived from an oral glucose tolerance test (risk allele homozygotes have half the insulin response to glucose of noncarriers, P = 0.003) but not with increased insulin resistance. These results suggest that TCF7L2 variants may act through insulin secretion to increase the risk of type 2 diabetes.
Diabetes 2006 Oct
PMID:Common single nucleotide polymorphisms in TCF7L2 are reproducibly associated with type 2 diabetes and reduce the insulin response to glucose in nondiabetic individuals. 1700 58

Recently, case-control studies demonstrated that a TCF7L2 (transcription factor 7-like 2 gene) noncoding variant (rs7903146 T at-risk allele) was strongly associated with an increased risk of type 2 diabetes. However, the predictive value of this marker in a nonselected general population remains unknown. In this study, our aim was to assess the contribution of this variant to the prevalence and incidence of hyperglycemia (type 2 diabetes and impaired fasting glucose) and insulin regulation in a 9-year prospective study of 4,976 middle-aged participants in the French DESIR (Data from an Epidemiological Study on the Insulin Resistance Syndrome) cohort. Our data support previous studies associating the T at-risk allele with a higher prevalence of hyperglycemia at baseline (P = 0.049) and a higher incidence of hyperglycemia after 9 years of follow-up (P = 0.014). The population-attributable risk to develop hyperglycemia due to the T at-risk allele was estimated to be 10.4% at the end of the prospective study. The most likely inheritance model was found to be additive (P = 0.002) rather than deviating from linearity (hazard ratio 1.21 [95% CI 1.05-1.39], P = 0.008) [corrected] An increase in the incidence of hyperglycemia was confirmed by survival analyses among C/C, C/T, and T/T carriers during the 9 years of follow-up (P = 0.028 by log-rank test). Interestingly, in control individuals, there was weak evidence of association of the T at-risk allele with reduced fasting insulin levels and insulin secretion index (homeostasis model assessment of beta-cell function) in control individuals. We conclude that the TCF7L2 T at-risk allele variation (rs7903146) predicts hyperglycemia incidence in a general French population, possibly through a deleterious effect on insulin secretion.
Diabetes 2006 Nov
PMID:TCF7L2 variation predicts hyperglycemia incidence in a French general population: the data from an epidemiological study on the Insulin Resistance Syndrome (DESIR) study. 1706 61

TCF7L2 acts as both a repressor and transactivator of genes, as directed by the Wnt signaling pathway. Recently, several highly correlated sequence variants located within a haplotype block of the TCF7L2 gene were observed to associate with type 2 diabetes in three Caucasian cohorts. We previously reported linkage of type 2 diabetes in the San Antonio Family Diabetes Study (SAFADS) cohort consisting of extended pedigrees of Mexican Americans to the region of chromosome 10q harboring TCF7L2. We therefore genotyped 11 single nucleotide polymorphisms (SNPs) from nine haplotype blocks across the gene in 545 SAFADS subjects (178 diabetic) to investigate their role in diabetes pathogenesis. We observed nominal association between four SNPs (rs10885390, rs7903146, rs12255372, and rs3814573) in three haplotype blocks and type 2 diabetes, age at diagnosis, and 2-h glucose levels (P = 0.001-0.055). Furthermore, we identified a common protective haplotype defined by these four SNPs that was significantly associated with type 2 diabetes and age at diagnosis (P = 4.2 x 10(-5), relative risk [RR] 0.69; P = 6.7 x 10(-6), respectively) and a haplotype that confers diabetes risk that contains the rare alleles at SNPs rs10885390 and rs12255372 (P = 0.02, RR 1.64). These data provide evidence that variation in the TCF7L2 genomic region may affect risk for type 2 diabetes in Mexican Americans, but the attributable risk may be lower than in Caucasian populations.
Diabetes 2007 Feb
PMID:Haplotypes of transcription factor 7-like 2 (TCF7L2) gene and its upstream region are associated with type 2 diabetes and age of onset in Mexican Americans. 1725 83

Rapidly accumulating evidence shows that common T-cell transcription factor (TCF)7L2 polymorphisms confer risk of type 2 diabetes through unknown mechanisms. We examined the association between four TCF7L2 single nucleotide polymorphisms (SNPs), including rs7903146, and measures of insulin sensitivity and insulin secretion in 1,697 Europid men and women of the population-based MRC (Medical Research Council)-Ely study. The T-(minor) allele of rs7903146 was strongly and positively associated with fasting proinsulin (P = 4.55 x 10(-9)) and 32,33 split proinsulin (P = 1.72 x 10(-4)) relative to total insulin levels; i.e., differences between T/T and C/C homozygotes amounted to 21.9 and 18.4% respectively. Notably, the insulin-to-glucose ratio (IGR) at 30-min oral glucose tolerance test (OGTT), a frequently used surrogate of first-phase insulin secretion, was not associated with the TCF7L2 SNP (P > 0.7). However, the insulin response (IGR) at 60-min OGTT was significantly lower in T-allele carriers (P = 3.5 x 10(-3)). The T-allele was also associated with higher A1C concentrations (P = 1.2 x 10(-2)) and reduced beta-cell function, assessed by homeostasis model assessment of beta-cell function (P = 2.8 x 10(-2)). Similar results were obtained for the other TCF7L2 SNPs. Of note, both major genes involved in proinsulin processing (PC1, PC2) contain TCF-binding sites in their promoters. Our findings suggest that the TCF7L2 risk allele may predispose to type 2 diabetes by impairing beta-cell proinsulin processing. The risk allele increases proinsulin levels and diminishes the 60-min but not 30-min insulin response during OGTT. The strong association between the TCF7L2 risk allele and fasting proinsulin but not insulin levels is notable, as, in this unselected and largely normoglycemic population, external influences on beta-cell stress are unlikely to be major factors influencing the efficiency of proinsulin processing.
Diabetes 2007 Jul
PMID:TCF7L2 polymorphisms modulate proinsulin levels and beta-cell function in a British Europid population. 1741 97

Identification and characterization of genetic variants that either cause or predispose to diabetes are a major focus of biomedical research. As of early 2007, the molecular basis of most forms of monogenic diabetes resulting from beta-cell dysfunction is known and, in particular, there has been recent success in delineating the genetic aetiology of neonatal diabetes. Finding genes predisposing to more common, multifactorial forms of type 2 diabetes represents a far greater challenge, and only a handful of robust, well-replicated examples have been established. Nevertheless, 2006 heralded identification of the most important type 2 diabetes susceptibility gene known so far, TCF7L2, and in 2007 large-scale genome-wide association studies are destined to provide novel insights into the genetic architecture and biology of type 2 diabetes.
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PMID:Genetics of type 2 diabetes. 1746 12

TCF7L2 variants have been consistently associated with type 2 diabetes (T2D) in populations of different ethnic descent. Among them, the rs7903146 T allele is probably the best proxy to evaluate the effect of this gene on T2D risk in additional ethnic groups. In the present study, we investigated the association between the TCF7L2 rs7903146 polymorphism and T2D in Moroccans (406 normoglycemic individuals and 504 T2D subjects) and in white Austrians (1,075 normoglycemic individuals and 486 T2D subjects). Then, we systematically reviewed the association of this single nucleotide polymorphism (SNP) with T2D risk in a meta-analysis, combining our data with data from previous studies. The allelic odds ratios (ORs) for T2D were 1.56 [1.29-1.89] (p = 2.9 x 10(-6)) and 1.52 [1.29-1.78] (p = 3.0 x 10(-7)) in Moroccans and Austrians, respectively. No heterogeneity was found between these two different populations by Woolf test (chi (2) = 0.04, df = 1, p = 0.84). We found 28 original published association studies dealing with the TCF7L2 rs7903146 polymorphism in T2D. A meta-analysis was then performed on 29,195 control subjects and 17,202 cases. No heterogeneity in genotypic distribution was found (Woolf test: chi (2) = 31.5, df = 26, p = 0.21; Higgins statistic: I2 = 14.1%). A Mantel-Haenszel procedure was then performed to provide a pooled odds ratio (OR) of 1.46 [1.42-1.51] (p = 5.4 x 10(-140)). No publication bias was detected, using the conservative Egger's regression asymmetry test (t = -1.6, df = 25, p = 0.11). Compared to any other gene variants previously confirmed by meta-analysis, TCF7L2 can be distinguished by its tremendous reproducibility of association with T2D and its OR twice as high. In the near future, large-scale genome-wide association studies will fully extend the genome coverage, potentially delivering other common diabetes-susceptibility genes like TCF7L2.
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PMID:TCF7L2 is reproducibly associated with type 2 diabetes in various ethnic groups: a global meta-analysis. 1747 72

The role of genes in normal birth-weight variation is poorly understood, and it has been suggested that the genetic component of fetal growth is small. Type 2 diabetes genes may influence birth weight through maternal genotype, by increasing maternal glycemia in pregnancy, or through fetal genotype, by altering fetal insulin secretion. We aimed to assess the role of the recently described type 2 diabetes gene TCF7L2 in birth weight. We genotyped the polymorphism rs7903146 in 15,709 individuals whose birth weight was available from six studies and in 8,344 mothers from three studies. Each fetal copy of the predisposing allele was associated with an 18-g (95% confidence interval [CI] 7-29 g) increase in birth weight (P=.001) and each maternal copy with a 30-g (95% CI 15-45 g) increase in offspring birth weight (P=2.8x10-5). Stratification by fetal genotype suggested that the association was driven by maternal genotype (31-g [95% CI 9-48 g] increase per allele; corrected P=.003). Analysis of diabetes-related traits in 10,314 nondiabetic individuals suggested the most likely mechanism is that the risk allele reduces maternal insulin secretion (disposition index reduced by ~0.15 standard deviation; P=1x10-4), which results in increased maternal glycemia in pregnancy and hence increased offspring birth weight. We combined information with the other common variant known to alter fetal growth, the -30G-->A polymorphism of glucokinase (rs1799884). The 4% of offspring born to mothers carrying three or four risk alleles were 119 g (95% CI 62-172 g) heavier than were the 32% born to mothers with none (for overall trend, P=2x10-7), comparable to the impact of maternal smoking during pregnancy. In conclusion, we have identified the first type 2 diabetes-susceptibility allele to be reproducibly associated with birth weight. Common gene variants can substantially influence normal birth-weight variation.
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PMID:Type 2 diabetes TCF7L2 risk genotypes alter birth weight: a study of 24,053 individuals. 1750 32

In 1988 the task of identifying Type 2 diabetes genes was described as a nightmare. For the next 17 years this proved to be largely correct. In the meantime the prevalence of Type 2 diabetes rose sharply due to non-genetic factors, compounding the problem of trying to find genes. Despite a huge amount of effort, progress was disappointing and only two genes, PPARG and KCNJ11, were confirmed beyond doubt as Type 2 diabetes risk factors in multiple studies. The reasons for this have been well documented and mainly consist of the use of inappropriate levels of statistical inference given the many hundreds of thousands of potential risk polymorphisms in the genome and their small effect sizes. The good news is that these problems are now surmountable and prospects for finding many more genes are bright. This year saw the identification of a third gene, TCF7L2, that has a greater impact on risk than the first two and provided important lessons for Type 2 diabetes genetic studies. The most important of these lessons was that previously unsuspected genes may be involved. In this review I discuss why this year is the start of a new era in our understanding of Type 2 diabetes genes and how this may lead to improved patient care.
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PMID:A new era in finding Type 2 diabetes genes-the unusual suspects. 1756 64

Common variants of TCF7L2, encoding a beta-cell-expressed transcription factor, are strongly associated with increased risk of type 2 diabetes (T2D). We examined this association using both prospective and case-control designs. A total of 2,676 healthy European white middle-aged men from the prospective NPHSII (158 developed T2D over 15 years surveillance) were genotyped for two intronic SNPs [rs 7903146 (IVS3C>T) and rs12255372 (IVS4G>T)] which showed strong linkage disequilibrium (D' = 0.88, p<0.001; R(2)=0.76, p<0.001). The IVS5T allele frequency was 0.28 (95% CI 0.27-0.29) and 0.33 (0.28-0.39) in healthy and T2D, respectively (p=0.04). Compared to CC men, CT and TT men had an adjusted [for age, body mass index, systolic blood pressure, triglyceride and C-reactive protein levels] hazard ratio for T2D of 1.65 (1.13-2.41) and 1.87 (0.99-3.53), respectively, p<0.01. The population attributable fraction for diabetes risk was 17%. In 1459, European white T2D men and women (60% male), T allele frequency was 0.36 (0.34-0.38), and compared to NPHSII healthy men the OR for T2D for the CT and TT subjects was 1.43 (1.24-1.65) and 2.11 (1.69-2.63), respectively p=<0.0001. A similar effect was observed in 919 T2D Indian Asians [OR=1.50 (1.14-1.99) and 1.64 (1.03-2.63) p=0.003] and 385 Afro-Caribbean subjects [OR=1.25 (0.90-1.75) and 1.32 (0.74-2.33) p=0.17] compared to non-diabetic ethnically matched subjects from South London. Weaker associations were found for the IVS4G>T in all studies. Linkage disequilibrium between the two SNPs was high in Indian Asians (D'=0.94), but much weaker in Afro-Caribbeans (D'=0.17) and haplotype frequencies differed markedly in this group. These results extend previous observations to other ethnic groups, and strongly confirm that TCF7L2 genotype is a major risk factor for development of T2D.
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PMID:Common variants in the TCF7L2 gene and predisposition to type 2 diabetes in UK European Whites, Indian Asians and Afro-Caribbean men and women. 1766 14

Type 2 diabetes (T2D) is a common, polygenic chronic disease with high heritability. The purpose of this whole-genome association study was to discover novel T2D-associated genes. We genotyped 500 familial cases and 497 controls with >300,000 HapMap-derived tagging single-nucleotide-polymorphism (SNP) markers. When a stringent statistical correction for multiple testing was used, the only significant SNP was at TCF7L2, which has already been discovered and confirmed as a T2D-susceptibility gene. For a replication study, we selected 10 SNPs in six chromosomal regions with the strongest association (singly or as part of a haplotype) for retesting in an independent case-control set including 2,573 T2D cases and 2,776 controls. The most significant replicated result was found at the AHI1-LOC441171 gene region.
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PMID:Type 2 diabetes whole-genome association study in four populations: the DiaGen consortium. 1766 82


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