TCF7L2 gene polymorphisms confer an increased risk for early impairment of glucose metabolism and increased height in obese children

"GENYAL" Study to Childhood Obesity Prevention: Methodology and Preliminary Results

Objective

This article describes the methodology and summarizes some preliminary results of the GENYAL study aiming to design and validate a predictive model, considering both environmental and genetic factors, that identifies children who would benefit most from actions aimed at reducing the risk of obesity and its complications.

Design

The study is a cluster randomized clinical trial with 5-year follow-up. The initial evaluation was carried out in 2017. The schools were randomly split into intervention (nutritional education) and control schools. Anthropometric measurements, social and health as well as dietary and physical activity data of schoolchildren and their families are annually collected. A total of 26 single nucleotide polymorphisms (SNPs) were assessed. Machine Learning models are being designed to predict obesity phenotypes after the 5-year follow-up.

Settings

Six schools in Madrid.

Participants

A total of 221 schoolchildren (6-8 years old).

Results

Collected results show that the prevalence of excess weight was 19.0, 25.4, and 32.2% (according to World Health Organization, International Obesity Task Force and Orbegozo Foundation criteria, respectively). Associations between the nutritional state of children with mother BMI [β = 0.21 (0.13-0.3), p (adjusted) <0.001], geographical location of the school [OR = 2.74 (1.24-6.22), p (adjusted) = 0.06], dairy servings per day [OR = 0.48 (0.29-0.75), p (adjusted) = 0.05] and 8 SNPs [rs1260326, rs780094, rs10913469, rs328, rs7647305, rs3101336, rs2568958, rs925946; p (not adjusted) <0.05] were found.

Conclusions

These baseline data support the evidence that environmental and genetic factors play a role in the development of childhood obesity. After 5-year follow-up, the GENYAL study pretends to validate the predictive model as a new strategy to fight against obesity.

Clinical Trial Registration

This study has been registered in ClinicalTrials.gov with the identifier NCT03419520, https://clinicaltrials.gov/ct2/show/NCT03419520.

Single and multi-locus association study of TCF7L2 gene variants with susceptibility to type 2 diabetes mellitus in an Iranian population

Prior studies indicated that some of transcription factor 7-like 2 (TCF7L2) gene variants such as rs7903146, rs12255372 and rs11255372 are constantly associated with Type 2 diabetes mellitus (T2DM) in various populations and ethnic groups. The purpose of this study was to assess the association between TCF7L2 variants (rs7903146, rs11196205, and rs11255372) and T2DM by TaqMan assay. Statistical analysis was performed through SNPAlyze and SPSS. Significant associations of rs7903146 (P = 1.9 × 10-7), and rs11255372 (P = 2.98 × 10-10) both under a dominant model were found. Based on allele frequency, there was a significant difference between the two study groups at rs7903146 and rs12255372 variants (P = 6.8 × 10-10, and P = 9.3 × 10-11, respectively). Two haplotypes including Hap-1 (C-G-G) and Hap-2 (T-G-T) indicated a significant difference between the two study groups (P = 1.174 × 10-9and P = 7.432 × 109 respectively). In conclusion, rs7903146 and rs12255372 were significantly associated with T2DM in the specified Northern Iranian population.

The BDNF Val66Met polymorphism is associated with lower BMI, lower postprandial glucose levels and elevated carbohydrate intake in children and adolescents

BACKGROUND

The amino acid-changing exonic variant rs6265 (Val66Met polymorphism) in the brain-derived neurotrophic factor (BDNF) has been linked to obesity in several genotype-phenotype association studies.

OBJECTIVE

To identify metabolic factors by which this effect might be conveyed, we aimed to investigate its correlation with (i) obesity, (ii) metabolic parameters, (iii) serum levels of BDNF and (iv) measures of energy intake in children and adolescents.

METHODS

We genotyped the variant in 2131 subjects (age 6-18 years) and checked for an association with obesity. Secondly, we correlated the genotype with parameters of glucose and lipid metabolism (fasting/postprandial glucose and insulin levels, HbA1c, homeostasis model assessment, Matsuda, high-density lipoprotein, low-density lipoprotein, total cholesterol and triglycerides) in a smaller subset of 845 subjects. We determined BDNF serum levels in 177 individuals by enzyme-linked immunosorbent assay and assessed the association with genotype and metabolic parameters. Finally, we investigated the association between genotype and macronutrient intake from self-reported food diaries (n = 146).

RESULTS

The minor Met allele was associated with lower BMI standard deviation score (p = 0.002). Post-pubertal Met allele carriers showed lower postprandial glucose levels and a lower HbA1c (β = 0.15, p = 0.046 and β = 0.27, p = 0.012, respectively). Neither the genotype nor any of the metabolic parameters correlated with BDNF serum levels. We observed an increased total calorie intake (β = -0.21, p = 0.007) with increased carbohydrate and protein intake (β = -0.22, p = 0.005 and β = -0.14, p = 0.028, respectively) in Met allele carriers.

CONCLUSIONS

We confirmed the association of the minor Met allele with lower BMI in children and provide new data that it is associated with lower postprandial glucose in post-pubertal subjects. Moreover, Met allele carriers reported to consume more carbohydrates and proteins.

The rs7903146 Variant in the TCF7L2 Gene Increases the Risk of Prediabetes/Type 2 Diabetes in Obese Adolescents by Impairing β-Cell Function and Hepatic Insulin Sensitivity

OBJECTIVE

In this study, we aimed to explore the mechanism by which TCF7L2 rs7903146 risk allele confers susceptibility to impaired glucose tolerance (IGT) or type 2 diabetes (T2D) in obese adolescents.

RESEARCH DESIGN AND METHODS

The rs7903146 variant in the TCF7L2 gene was genotyped in a multiethnic cohort of 955 youths. All subjects underwent an oral glucose tolerance test with the use of the Oral Minimal Model to assess insulin secretion, and 33 subjects underwent a hyperinsulinemic-euglycemic clamp. In 307 subjects, a follow-up oral glucose tolerance test was repeated after 3.11 ± 2.36 years.

RESULTS

The TCF7L2 rs7903146 risk allele was associated with higher 2-h glucose levels in Caucasians (P = 0.006) and African Americans (P = 0.009), and a trend was seen also in Hispanics (P = 0.072). Also, the T allele was associated with decreased β-cell responsivity and IGT (P < 0.05). Suppression of endogenous hepatic glucose production was lower in subjects with the risk variant (P = 0.006). Finally, the odds of showing IGT/T2D at follow-up were higher in subjects carrying the minor allele (odds ratio 2.224; 95% CI 1.370-3.612; P = 0.0012).

CONCLUSIONS

The rs7903146 variant in the TCF7L2 gene increases the risk of IGT/T2D in obese adolescents by impairing β-cell function, and hepatic insulin sensitivity predicts the development of IGT/T2D over time.

Rare Variant Analysis of Human and Rodent Obesity Genes in Individuals with Severe Childhood Obesity

Obesity is a genetically heterogeneous disorder. Using targeted and whole-exome sequencing, we studied 32 human and 87 rodent obesity genes in 2,548 severely obese children and 1,117 controls. We identified 52 variants contributing to obesity in 2% of cases including multiple novel variants in GNAS, which were sometimes found with accelerated growth rather than short stature as described previously. Nominally significant associations were found for rare functional variants in BBS1, BBS9, GNAS, MKKS, CLOCK and ANGPTL6. The p.S284X variant in ANGPTL6 drives the association signal (rs201622589, MAF~0.1%, odds ratio = 10.13, p-value = 0.042) and results in complete loss of secretion in cells. Further analysis including additional case-control studies and population controls (N = 260,642) did not support association of this variant with obesity (odds ratio = 2.34, p-value = 2.59 × 10-3), highlighting the challenges of testing rare variant associations and the need for very large sample sizes. Further validation in cohorts with severe obesity and engineering the variants in model organisms will be needed to explore whether human variants in ANGPTL6 and other genes that lead to obesity when deleted in mice, do contribute to obesity. Such studies may yield druggable targets for weight loss therapies.

Hypothalamic Wnt Signalling and its Role in Energy Balance Regulation

Wnt signalling and its downstream effectors are well known for their roles in embryogenesis and tumourigenesis, including the regulation of cell proliferation, survival and differentiation. In the nervous system, Wnt signalling has been described mainly during embryonic development, although accumulating evidence suggests that it also plays a major role in adult brain morphogenesis and function. Studies have predominantly concentrated on memory formation in the hippocampus, although recent data indicate that Wnt signalling is also critical for neuroendocrine control of the developed hypothalamus, a brain centre that is key in energy balance regulation and whose dysfunction is implicated in metabolic disorders such as type 2 diabetes and obesity. Based on scattered findings that report the presence of Wnt molecules in the tanycytes and ependymal cells lining the third ventricle and arcuate nucleus neurones of the hypothalamus, their potential importance in key regions of food intake and body weight regulation has been investigated in recent studies. The present review brings together current knowledge on Wnt signalling in the hypothalamus of adult animals and discusses the evidence suggesting a key role for members of the Wnt signalling family in glucose and energy balance regulation in the hypothalamus in diet-induced and genetically obese (leptin deficient) mice. Aspects of Wnt signalling in seasonal (photoperiod sensitive) rodents are also highlighted, given the recent evidence indicating that the Wnt pathway in the hypothalamus is not only regulated by diet and leptin, but also by photoperiod in seasonal animals, which is connected to natural adaptive changes in food intake and body weight. Thus, Wnt signalling appears to be critical as a modulator for normal functioning of the physiological state in the healthy adult brain, and is also crucial for normal glucose and energy homeostasis where its dysregulation can lead to a range of metabolic disorders.

Dietary Intake, FTO Genetic Variants, and Adiposity: A Combined Analysis of Over 16,000 Children and Adolescents

The FTO gene harbors variation with the strongest effect on adiposity and obesity risk. Previous data support a role for FTO variation in influencing food intake. We conducted a combined analysis of 16,094 boys and girls aged 1-18 years from 14 studies to examine the following: 1) the association between the FTO rs9939609 variant (or a proxy) and total energy and macronutrient intake; and 2) the interaction between the FTO variant and dietary intake, and the effect on BMI. We found that the BMI-increasing allele (minor allele) of the FTO variant was associated with increased total energy intake (effect per allele = 14.3 kcal/day [95% CI 5.9, 22.7 kcal/day], P = 6.5 × 10(-4)), but not with protein, carbohydrate, or fat intake. We also found that protein intake modified the association between the FTO variant and BMI (interactive effect per allele = 0.08 SD [0.03, 0.12 SD], P for interaction = 7.2 × 10(-4)): the association between FTO genotype and BMI was much stronger in individuals with high protein intake (effect per allele = 0.10 SD [0.07, 0.13 SD], P = 8.2 × 10(-10)) than in those with low intake (effect per allele = 0.04 SD [0.01, 0.07 SD], P = 0.02). Our results suggest that the FTO variant that confers a predisposition to higher BMI is associated with higher total energy intake, and that lower dietary protein intake attenuates the association between FTO genotype and adiposity in children and adolescents.

β-catenin links hepatic metabolic zonation with lipid metabolism and diet-induced obesity in mice

β-catenin regulates the establishment of hepatic metabolic zonation. To elucidate the functional significance of liver metabolic zonation in the chronically overfed state in vivo, we fed a high-fat diet (HFD) to hepatocyte-specific β-catenin transgenic (TG) and knockout (KO) mice. Chow-fed TG and KO mice had normal liver histologic findings and body weight. However, HFD-fed TG mice developed prominent perivenous steatosis with periportal sparing. In contrast, HFD-fed KO mice had increased lobular inflammation and hepatocyte apoptosis. HFD-fed TG mice rapidly developed diet-induced obesity and systemic insulin resistance, but KO mice were resistant to diet-induced obesity. However, β-catenin did not directly affect hepatic insulin signaling, suggesting that the metabolic effects of β-catenin occurred via a parallel pathway. Hepatic expression of key glycolytic and lipogenic genes was higher in HFD-fed TG and lower in KO mice compared with wild-type mice. KO mice also exhibited defective hepatic fatty acid oxidation and fasting ketogenesis. Hepatic levels of hypoxia inducible factor-1α, an oxygen-sensitive transcriptional regulator of glycolysis and a known β-catenin binding partner, were higher in HFD-fed TG and lower in KO mice. KO mice had attenuated perivenous hypoxia, suggesting disruption of the normal sinusoidal oxygen gradient, a major determinant of liver carbohydrate and liver metabolism. Canonical Wnt signaling in hepatocytes is essential for the development of diet-induced fatty liver and obesity.

Effects of genetic variants in ADCY5, GIPR, GCKR and VPS13C on early impairment of glucose and insulin metabolism in children

Objective

Recent genome-wide association studies identified novel candidate genes for fasting and 2 h blood glucose and insulin levels in adults. We investigated the role of four of these loci (ADCY5, GIPR, GCKR and VPS13C) in early impairment of glucose and insulin metabolism in children.

Research Design and Methods

We genotyped four variants (rs2877716; rs1260326; rs10423928; rs17271305) in 638 Caucasian children with detailed metabolic testing including an oGTT and assessed associations with measures of glucose and insulin metabolism (including fasting blood glucose, insulin levels and insulin sensitivity/secretion indices) by linear regression analyses adjusted for age, sex, BMI-SDS and pubertal stage.

Results

The major allele (C) of rs2877716 (ADCY5) was nominally associated with decreased fasting plasma insulin (P = 0.008), peak insulin (P = 0.009) and increased QUICKI (P = 0.016) and Matsuda insulin sensitivity index (P = 0.013). rs17271305 (VPS13C) was nominally associated with 2 h blood glucose (P = 0.009), but not with any of the insulin or insulin sensitivity parameters. We found no association of the GIPR and GCKR variants with parameters of glucose and insulin metabolism. None of the variants correlated with anthropometric traits such as height, WHR or BMI-SDS, which excluded potential underlying associations with obesity.

Conclusions

Our data on obese children indicate effects of genetic variation within ADCY5 in early impairment of insulin metabolism and VPS13C in early impairment of blood glucose homeostasis.

Single nucleotide polymorphisms of TCF7L2 are linked to diabetic coronary atherosclerosis

Background

Coronary artery disease (CAD) shares common risk factors with type 2 diabetes (T2DM). Variations in the transcription factor 7-like 2 (TCF7L2) gene, particularly rs7903146, increase T2DM risk. Potential links between genetic variants of the TCF7L2 locus and coronary atherosclerosis are uncertain. We therefore investigated the association between TCF7L2 polymorphisms and angiographically determined CAD in diabetic and non-diabetic patients.

Methodology/Principal Findings

We genotyped TCF7L2 variants rs7903146, rs12255372, and rs11196205 in a cross-sectional study including 1,650 consecutive patients undergoing coronary angiography for the evaluation of established or suspected stable CAD. Significant CAD was diagnosed in the presence of coronary stenoses ≥50%. Variant rs7903146 in the total study cohort was significantly associated with significant CAD (adjusted additive OR = 1.29 [1.09–1.53]; p = 0.003). This association was strong and significant in T2DM patients (n = 393; OR = 1.91 [1.32–2.75]; p = 0.001) but not in non-diabetic subjects (OR = 1.09 [0.90–1.33]; p = 0.370). The interaction risk allele by T2DM was significant (p_interaction = 0.002), indicating a significantly stronger impact of the polymorphism on CAD in T2DM patients than in non-diabetic subjects. TCF7L2 polymorphisms rs12255372 and rs11196205 were also significantly associated with CAD in diabetic patients (adjusted additive OR = 1.90 [1.31–2.74]; p = 0.001 and OR = 1.75 [1.22–2.50]; p = 0.002, respectively). Further, haplotype analysis demonstrated that haplotypes including the rare alleles of all investigated variants were significantly associated with CAD in the whole cohort as well as in diabetic subjects (OR = 1.22 [1.04–1.43]; p = 0.013 and OR = 1.67 [1.19–2.22]; p = 0.003, respectively).

Conclusions/Significance

These results suggest that TCF7L2 variants rs7903146 rs12255372, and rs11196205 are significantly associated with angiographically diagnosed CAD, specifically in patients with T2DM. TCF7L2 therefore appears as a genetic link between diabetes and atherosclerosis.

TCF7L2 and therapeutic response to sulfonylureas in patients with type 2 diabetes

Background

Variants in the TCF7L2 have been shown to be associated with an increased risk for type 2 diabetes (T2D). Since the association with diabetes could be explained by effects on insulin secretion, we investigated whether patients with diabetes risk alleles at rs7903146 might have an altered hypoglycaemic response to sulfonylureas (SUs).

Methods

We recruited 189 patients with T2D being treated with SUs and determined the rs7903146 diabetes risk genotype. We used a logistic regression with secondary SU failure defined as an A1C ≥7.0% after 6 months of SU treatment.

Results

In univariate regression analyses, TCF7L2 genotype was the only predictor of SU treatment failure. The rs7903146 T allele was significantly more frequent in the group of patients who failed to respond to SU (36%) than in the control group (26%) [P = 0.046; odds ratio (OR): 1.57 (1.01-2.45) in an additive mode of inheritance].

Conclusions

Our data suggest that patients with diabetes risk alleles in TCF7L2 have an altered hypoglycaemic response to SUs resulting in earlier secondary failure.

Genetic predisposition to long-term nondiabetic deteriorations in glucose homeostasis: Ten-year follow-up of the GLACIER study

OBJECTIVE

To assess whether recently discovered genetic loci associated with hyperglycemia also predict long-term changes in glycemic traits.

RESEARCH DESIGN AND METHODS

Sixteen fasting glucose-raising loci were genotyped in middle-aged adults from the Gene x Lifestyle interactions And Complex traits Involved in Elevated disease Risk (GLACIER) Study, a population-based prospective cohort study from northern Sweden. Genotypes were tested for association with baseline fasting and 2-h postchallenge glycemia (N = 16,330), and for changes in these glycemic traits during a 10-year follow-up period (N = 4,059).

RESULTS

Cross-sectional directionally consistent replication with fasting glucose concentrations was achieved for 12 of 16 variants; 10 variants were also associated with impaired fasting glucose (IFG) and 7 were independently associated with 2-h postchallenge glucose concentrations. In prospective analyses, the effect alleles at four loci (GCK rs4607517, ADRA2A rs10885122, DGKB-TMEM195 rs2191349, and G6PC2 rs560887) were nominally associated with worsening fasting glucose concentrations during 10-years of follow-up. MTNR1B rs10830963, which was predictive of elevated fasting glucose concentrations in cross-sectional analyses, was associated with a protective effect on postchallenge glucose concentrations during follow-up; however, this was only when baseline fasting and 2-h glucoses were adjusted for. An additive effect of multiple risk alleles on glycemic traits was observed: a weighted genetic risk score (80th vs. 20th centiles) was associated with a 0.16 mmol/l (P = 2.4 × 10⁻⁶) greater elevation in fasting glucose and a 64% (95% CI: 33-201%) higher risk of developing IFG during 10 years of follow-up.

CONCLUSIONS

Our findings imply that genetic profiling might facilitate the early detection of persons who are genetically susceptible to deteriorating glucose control; studies of incident type 2 diabetes and discrete cardiovascular end points will help establish whether the magnitude of these changes is clinically relevant.

Evaluation of A2BP1 as an obesity gene

OBJECTIVE

A genome-wide association study (GWAS) in Pima Indians (n = 413) identified variation in the ataxin-2 binding protein 1 gene (A2BP1) that was associated with percent body fat. On the basis of this association and the obese phenotype of ataxin-2 knockout mice, A2BP1 was genetically and functionally analyzed to assess its potential role in human obesity.

RESEARCH DESIGN AND METHODS

Variants spanning A2BP1 were genotyped in a population-based sample of 3,234 full-heritage Pima Indians, 2,843 of whom were not part of the initial GWAS study and therefore could serve as a sample to assess replication. Published GWAS data across A2BP1 were additionally analyzed in French adult (n = 1,426) and children case/control subjects (n = 1,392) (Meyre et al. Nat Genet 2009;41:157-159). Selected variants were genotyped in two additional samples of Caucasians (Amish, n = 1,149, and German children case/control subjects, n = 998) and one additional Native American (n = 2,531) sample. Small interfering RNA was used to knockdown A2bp1 message levels in mouse embryonic hypothalamus cells.

RESULTS

No single variant in A2BP1 was reproducibly associated with obesity across the different populations. However, different variants within intron 1 of A2BP1 were associated with BMI in full-heritage Pima Indians (rs10500331, P = 1.9 × 10(-7)) and obesity in French Caucasian adult (rs4786847, P = 1.9 × 10(-10)) and children (rs8054147, P = 9.2 × 10(-6)) case/control subjects. Reduction of A2bp1 in mouse embryonic hypothalamus cells decreased expression of Atxn2, Insr, and Mc4r.

CONCLUSIONS

Association analysis suggests that variation in A2BP1 influences obesity, and functional studies suggest that A2BP1 could potentially affect adiposity via the hypothalamic MC4R pathway.

Type 2 diabetes in children and adolescents

The emergence of Type 2 diabetes (T2D) in children and adolescents parallels the rising rates of childhood obesity. As a condition of impaired insulin sensitivity and relative insulin deficiency resulting in hyperglycemia, T2D has a complex underlying physiology that is reflected by the multiple approaches used to optimize medical care and prevent the myriad of diabetes-related complications. T2D diagnosed in children and adolescents represents a distinct and challenging condition to evaluate and treat. Here, we highlight the epidemiology, pathophysiology, risk factors, clinical presentation and diagnosis, treatment and public health impact of T2D in children and adolescents.

Insulin signaling regulating genes: effect on T2DM and cardiovascular risk

Type 2 diabetes mellitus (T2DM) is a complex disorder that has a heterogeneous genetic and environmental background. In this Review, we discuss the role of relatively infrequent polymorphisms of genes that regulate insulin signaling (including the K121Q polymorphism of ENPP1, the G972R polymorphism of IRS1 and the Q84R polymorphism of TRIB3) in T2DM and other conditions related to insulin resistance. The biological relevance of these three polymorphisms has been very thoroughly characterized both in vitro and in vivo and the available data indicate that they all affect insulin signaling and action as well as insulin secretion. They also affect insulin-mediated regulation of endothelial cell function. In addition, several reports indicate that the effects of all three polymorphisms on the risk of T2DM and cardiovascular diseases related to insulin resistance depend on the clinical features of the individual, including their body weight and age at disease onset. Thus, these polymorphisms might be used to demonstrate how difficult it is to ascertain the contribution of relatively infrequent genetic variants with heterogeneous effects on disease susceptibility. Unraveling the role of such variants might be facilitated by improving disease definition and focusing on specific subsets of patients.

IRS1 G972R polymorphism and type 2 diabetes: a paradigm for the difficult ascertainment of the contribution to disease susceptibility of 'low-frequency-low-risk' variants

AIMS/HYPOTHESIS

The aim of the study was to determine the association between IRS1 G972R polymorphism and type 2 diabetes; published data concerning this association have been conflicting. To obtain further insight into this topic, we performed a meta-analysis of all available case-control studies.

METHODS

We performed a meta-analysis of 32 studies (12,076 cases and 11,285 controls).

RESULTS

The relatively infrequent R972 variant was not significantly associated with type 2 diabetes (OR 1.09, 95% CI 0.96-1.23, p = 0.184 under a dominant model). Some evidence of heterogeneity was observed across studies (p = 0.1). In the 14 studies (9,713 individuals) in which the mean age at type 2 diabetes diagnosis was available, this variable explained 52% of the heterogeneity (p = 0.03). When these studies were subdivided into tertiles of mean age at diagnosis, the OR for diabetes was 1.48 (95% CI 1.17-1.87), 1.22 (95% CI 0.97-1.53) and 0.88 (95% CI 0.68-1.13) in the youngest, intermediate and oldest tertile, respectively (p = 0.0022 for trend of ORs).

CONCLUSIONS/INTERPRETATION

Our findings illustrate the difficulties of ascertaining the contribution of 'low-frequency-low-risk' variants to type 2 diabetes susceptibility. In the specific context of the R972 variant, approximately 200,000 study individuals would be needed to have 80% power to identify a 9% increase in diabetes risk at a genome-wide significance level. Under these circumstances, a strategy aimed at improving outcome definition and decreasing its heterogeneity may critically enhance our ability to detect genetic effects, thereby decreasing the required sample size. Our data suggest that focusing on early-onset diabetes, which is characterised by a stronger genetic background, may be part of such a strategy.

Genetic variation of FTO and TCF7L2 in premature adrenarche

Premature adrenarche (PA) has been associated with increased body mass index. Our aim was to determine whether the obesity-associated variant at fat mass and obesity gene (FTO) is more frequent in PA subjects. Furthermore, we hypothesized that altered Wnt signaling due to genetic variants at transcription factor 7-like 2 (TCF7L2) could play a role in the polygenic pathogenesis of PA. We genotyped polymorphisms at FTO rs9939609 and at TCF7L2 rs7903146 and rs12255372 in 73 Finnish white prepubertal children with PA and in 97 age- and sex-matched healthy controls. In addition, we investigated the associations of these genetic variations with weight, height, circulating adrenocortical hormone levels, glucose metabolism, lipid profile, and blood pressure. The differences in the minor allele frequencies (MAFs) of rs9939609, rs7903146, and rs12255372 were not statistically significant between the PA and control groups (difference in MAFs [95% confidence interval]: -0.06 [-0.18, 0.05], 0.04 [-0.05, 0.12], and 0.01 [-0.07, 0.10]; P = .3, .4, and .8, respectively). However, the risk allele at TCF7L2 rs7903146 was more frequent in PA subjects than in controls when we restricted the analysis to the subjects with lower weight-for-height than the median of the PA subjects (weight-for-height <108%, corresponding body mass index SD score <0.79; difference in MAFs [95% confidence interval]: 0.12 [-0.001, 0.23]; P = .038). Risk variant at FTO rs9939609 associated with higher weight-for-height in the healthy children (P = .001). In conclusion, the minor variant at FTO rs9939609 seems to play no major role in the increased weight-for-height of PA subjects; but the risk allele at TCF7L2 rs7903146 may have a role in the pathogenesis of PA in lean subjects.

Single nucleotide transcription factor 7-like 2 (TCF7L2) gene polymorphisms in antiislet autoantibody-negative patients at onset of diabetes

CONTEXT

There is controversy as to whether type 2 diabetes genetic susceptibility contributes to type 1 diabetes, and it is not known what proportion of islet autoantibody-negative new onset subjects have type 2 diabetes risk alleles.

OBJECTIVES

We designed this study to evaluate whether two type 2 diabetes-associated single nucleotide polymorphisms (SNPs) of transcription factor 7-like 2 (TCF7L2) gene are associated with the development of islet autoantibody-negative diabetes vs. islet autoantibody-positive diabetes in young patients and whether these SNPs are associated with specific clinical phenotypes.

DESIGN

Autoantibody against glutamic acid decarboxylase 65, islet cell antibody 512bdc (form of IA-2), insulin, ZnT8 transporter, and cytoplasmic islet cell antibody were assayed in patients with new onset diabetes seen at the Barbara Davis Center using sera obtained within 2 wk of diagnosis. We genotyped two noncoding variants in the TCF7L2 gene, rs12255372 and rs7903146, in diabetic subjects and normal controls.

RESULTS

A total of 140 patients (15.7%) were negative for all islet autoantibodies among 893 subjects less than age 25 at the onset of diabetes. The allele and genotype frequencies of two SNPs showed that these are associated (odds ratio up to 4) with the development of diabetes in the autoantibody-negative diabetic cohort, but not in the autoantibody-positive diabetic cohort.

CONCLUSION

TCF7L2 type 2 diabetes susceptibility alleles are associated with islet autoantibody-negative but not autoantibody-positive new onset diabetes in young patients.

TCF7L2 gene expression in human visceral and subcutaneous adipose tissue is differentially regulated but not associated with type 2 diabetes mellitus

Variants in the TCF7L2 gene have been associated with type 2 diabetes mellitus (T2DM), but the causal variant(s) is still unknown. We studied the TCF7L2 messenger RNA (mRNA) expression in paired samples of visceral and subcutaneous adipose tissue from 49 subjects using quantitative real-time polymerase chain reaction and its relation to obesity and T2DM. All subjects were genotyped for the previously described TCF7L2 diabetes risk variants. Independent of age, sex, obesity, and diabetes status, we found >3-fold higher TCF7L2 mRNA expression in subcutaneous compared with visceral adipose tissue. There was no correlation between visceral and subcutaneous TCF7L2 expression. No differences in adipose tissue TCF7L2 mRNA expression levels were found between diabetic and nondiabetic subjects, or between lean and obese subjects (all Ps > .05). In addition, there was no association between TCF7L2 genetic variants and mRNA expression. Based on our data, TCF7L2 mRNA expression is fat-depot specific but does not seem to provide the mechanistic link explaining genetic association with T2DM.

Impaired glucose regulation and type 2 diabetes in children and adolescents

Diabetes mellitus in paediatric patients used to be almost exclusively type 1, but in recent years, case series as well as hospital-based and population-based studies indicated that the number of children and adolescents with type 2 diabetes (T2DM) has been increasing. This development is alarming since T2DM in youth is usually not an isolated condition, but accompanied by other cardiovascular risk factors such as obesity, dyslipidaemia, hypertension and low-grade inflammation. In adults, numerous studies provided detailed data on prevalence, incidence and risk factors for the development of T2DM, but for children and adolescents clinical and experimental data are still rather limited. This review provides an overview about the epidemiology and pathogenesis of T2DM in youth and about impaired glucose regulation as major risk factor for diabetes development with a special focus on the recent literature on clinical and lifestyle-related risk factors. Differences in incidence and prevalence across different populations indicate that ethnic background and genetic pre-disposition may be important risk determinants. In addition, epigenetic factors and foetal programming appear to confer additional risk before birth. Among the environmental and lifestyle-related risk factors there is evidence that obesity, hypercaloric diet, physical inactivity, socio-economic position (SEP), smoking, low-grade inflammation, psychosocial stress and sleeping patterns contribute to the risk for T2DM. However, the assessment of the relevance of risk factors and of incidence or prevalence estimates in youth is complicated by methodological issues that are also discussed.

The clinical utility of genetic risk variants in type 2 diabetes

BACKGROUND

Type 2 diabetes is one of the first success stories in the application of genome-wide linkage and association studies to find genetic variants contributing to its risk.

OBJECTIVE

Are the genetic markers found so far useful in predicting which individuals are more likely to develop type 2 diabetes? Can they find which patients with prediabetes are more likely to convert to type 2 diabetes and therefore may benefit the most from lifestyle or pharmacologic prevention strategies?

METHODS

The literature pertaining to the discovery and replications of genes contributing to type 2 diabetes was focused on.

RESULTS/CONCLUSION

Substantial risk for type 2 diabetes is represented by the top 8 genes, including TCF7L2, and in certain circumstances may be useful for prevention strategies targeted to those with highest risk.

Genetics and type 2 diabetes in youth

The rapid increase in the population prevalence of type 2 diabetes mellitus (T2DM) in youth can only be explained by changes in lifestyle. However, even when most members of a population have changed their lifestyle, only a minority of children develop diabetes, and genetic factors are important in determining which children are affected. Support for the role of genetic factors comes from epidemiological evidence that diabetes in youth is most common in high diabetes prevalence racial groups, in subjects with a strong family history, and in girls. Defining the genes predisposing to T2DM is extremely difficult as there are multiple genes involved each contributing only a small amount and lifestyle factors play a large role. Defining the molecular genetics of T2DM in youth is even harder because in addition to the low number of subjects, there is also the ethnic heterogeneity of the subjects and the lack of robust diagnostic criteria. Recently, there has been considerable progress in defining the predisposing genes for adults with T2DM using thousands of cases and controls and a collaborative genome-wide approach. Similar numbers will be needed to assess if the genes found in adults also predispose to T2DM of youth and this will require large multi-center studies. Progress to date in the molecular genetics of T2DM in youth is limited to one population, the Oji-Cree Native Canadians, where the private variant - G319S - a variant of HNF1A strongly predisposes to diabetes in children as well as in adults.

Variation in FTO contributes to childhood obesity and severe adult obesity

We identified a set of SNPs in the first intron of the FTO (fat mass and obesity associated) gene on chromosome 16q12.2 that is consistently strongly associated with early-onset and severe obesity in both adults and children of European ancestry with an experiment-wise P value of 1.67 x 10(-26) in 2,900 affected individuals and 5,100 controls. The at-risk haplotype yields a proportion of attributable risk of 22% for common obesity. We conclude that FTO contributes to human obesity and hence may be a target for subsequent functional analyses.