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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.

AimsHypoglycaemia presents a barrier to optimum diabetes management but data are limited on the frequency of hypoglycaemia incidents outside of clinical trials. The present study investigated the rates of self-reported non-severe hypoglycaemic events, hypoglycaemia awareness and physician discussion of events in people with Type 1 diabetes mellitus or insulin-treated Type 2 diabetes mellitus.MethodsPeople in seven European countries aged >15 years with Type 1 diabetes or insulin–treated Type 2 diabetes (basal-only, basal-bolus and other insulin regimens) were recruited via consumer panels, nurses, telephone recruitment and family referrals. Respondents completed four online questionnaires. The first questionnaire collected background information on demographics and hypoglycaemia-related behaviour, whilst all four questionnaires collected data on non-severe hypoglycaemic events in the preceding 7 days.ResultsAnalysis was based on 11 440 respondent-weeks from 3827 respondents. All participants completed the first questionnaire and 57% completed all four. The mean number of events/respondent–week was 1.8 (Type 1 diabetes) and 0.4–0.7 (Type 2 diabetes, with different insulin treatments) corresponding to annual event rates of 94 and 21–36, respectively. A total of 63% of respondents with Type 1 diabetes and 49–64% of respondents with Type 2 diabetes, treated with different insulin regimens, who experienced hypoglycaemic events, reported impaired hypoglycaemia awareness or unawareness. A high proportion of respondents rarely or never informed their general practitioner/specialist about hypoglycaemia: 65% (Type 1 diabetes) and 50–59% (Type 2 diabetes). Overall, 16% of respondents with Type 1 diabetes and 26% of respondents with Type 2 diabetes reported not being asked about hypoglycaemia during routine appointments.ConclusionNon-severe hypoglycaemic events are common amongst people with Type 1 diabetes and insulin–treated Type 2 diabetes in real-world settings. Many rarely or never inform their general practitioner/specialist about their hypoglycaemia and the real burden of hypoglycaemia may be underestimated.

BackgroundAlthough diabetic kidney disease demonstrates both familial clustering and single nucleotide polymorphism heritability, the specific genetic factors influencing risk remain largely unknown.MethodsTo identify genetic variants predisposing to diabetic kidney disease, we performed genome-wide association study (GWAS) analyses. Through collaboration with the Diabetes Nephropathy Collaborative Research Initiative, we assembled a large collection of type 1 diabetes cohorts with harmonized diabetic kidney disease phenotypes. We used a spectrum of ten diabetic kidney disease definitions based on albuminuria and renal function.ResultsOur GWAS meta-analysis included association results for up to 19,406 individuals of European descent with type 1 diabetes. We identified 16 genome-wide significant risk loci. The variant with the strongest association (rs55703767) is a common missense mutation in the collagen type IV alpha 3 chain (COL4A3) gene, which encodes a major structural component of the glomerular basement membrane (GBM). Mutations in COL4A3 are implicated in heritable nephropathies, including the progressive inherited nephropathy Alport syndrome. The rs55703767 minor allele (Asp326Tyr) is protective against several definitions of diabetic kidney disease, including albuminuria and ESKD, and demonstrated a significant association with GBM width; protective allele carriers had thinner GBM before any signs of kidney disease, and its effect was dependent on glycemia. Three other loci are in or near genes with known or suggestive involvement in this condition (BMP7) or renal biology (COLEC11 and DDR1).ConclusionsThe 16 diabetic kidney disease–associated loci may provide novel insights into the pathogenesis of this condition and help identify potential biologic targets for prevention and treatment.

Obesity is frequently associated with type 2 diabetes. We previously observed an association of a functional G/A polymorphism in the uncoupling protein 2 (UCP2) promoter with obesity. The wild-type G allele was associated with reduced adipose tissue mRNA expression in vivo, reduced transcriptional activity in vitro, and increased risk of obesity. On the other hand, studies in animal and cell culture models identified pancreatic beta-cell UCP2 expression as a main determinant of the insulin secretory response to glucose. We therefore ascertained associations of the -866G/A polymorphism with beta-cell function and diabetes risk in obesity. We show here that the pancreatic transcription factor PAX6 preferentially binds to and more effectively trans activates the variant than the wild-type UCP2 promoter allele in the beta-cell line INS1-E. By studying 39 obese nondiabetic humans, we observed genotype differences in beta-cell function; wild-type subjects displayed a greater disposition index (the product of insulin sensitivity and acute insulin response to glucose) than subjects with the variant allele (P < 0.03). By comparing obese subjects with and without type 2 diabetes, we observed genotype-associated differences in diabetes prevalence that translated into a twofold age-adjusted risk reduction in wild-type subjects. Thus, the more common UCP2 promoter G allele, while being conducive for obesity, affords relative protection against type 2 diabetes.