Transmission of Type 2 diabetes to sons and daughters: the D.E.S.I.R. cohort.

AIMS: To document the family transmission of Type 2 diabetes to men and women. METHOD: The French D.E.S.I.R. cohort followed men and women over 9 years, with 3-yearly testing for incident Type 2 diabetes. First- and/or second-degree family histories of diabetes were available for 2187 men and 2282 women. Age-adjusted hazard ratios were estimated for various family members and groupings of family members, as well as for a genetic diabetes risk score, based on 65 diabetes-associated loci. RESULTS: Over 9 years, 136 men and 63 women had incident Type 2 diabetes. The hazard ratios for diabetes associated with having a first-degree family member with diabetes (parents, siblings, children) differed between men [1.21 (95% CI 0.80, 1.85)] and women [3.02 (95% CI 1.83, 4.99); Pinteraction =0.006]. The genetic risk score was predictive of diabetes in both men and women, with similar hazard ratios 1.10 (95% CI 1.06, 1.15) and 1.08 (95% CI 1.02, 1.14) respectively, for each additional at-risk allele. In women, the risk associated with having a family member with diabetes persisted after adjusting for the genetic score. CONCLUSION: Women with a family history of diabetes (paternal or maternal) were at risk of developing Type 2 diabetes and this risk was independent of a genetic score; in contrast, for men, there was no association. Diabetes screening and prevention may need to more specifically target women with diabetes in their family, but further studies are required as the number of people with diabetes in this study was small.

Interaction between GPR120 p.R270H loss-of-function variant and dietary fat intake on incident type 2 diabetes risk in the D.E.S.I.R. study.

BACKGROUND AND AIMS: GPR120 (encoded by FFAR4) is a lipid sensor that plays an important role in the control of energy balance. GPR120 is activated by long chain fatty acids (FAs) including omega-3 FAs. In humans, the loss of function p.R270H variant of the gene FFAR4 has been associated with a lower protein activity, an increased risk of obesity and higher fasting plasma glucose levels. The aim of this study was to investigate whether p.R270H interacts with dietary fat intake to modulate the risk of type 2 diabetes (T2D, 198 incident; 368 prevalent cases) and overweight (787 incident and 2891 prevalent cases) in the prospective D.E.S.I.R. study (n = 5,212, 9 years follow-up). METHODS AND RESULTS: The association of p.R270H with dietary fat and total calories was assessed by linear mixed models. The interaction between p.R270H and dietary fat on T2D and overweight was assessed by logistic regression analysis. The p.R270H variant had a minor allele frequency of 1.45% and was not significantly associated with total calories intake, fat intake or the total calories derived from fat (%). However, there was a significant interaction between p.R270H and dietary fat modulating the incidence of T2D (Pinteraction = 0.02) where the H-carriers had a higher risk of T2D than RR homozygotes in the low fat intake category only. The interaction between p.R270H and fat intake modulating the incidence and prevalence of overweight was not significant. CONCLUSION: The p.R270H variant of GPR120 modulates the risk of T2D in interaction with dietary fat intake in the D.E.S.I.R.

A nonsense loss-of-function mutation in PCSK1 contributes to dominantly inherited human obesity.

BACKGROUND: A significant proportion of severe familial forms of obesity remain genetically elusive. Taking advantage of our unique cohort of multigenerational obese families, we aimed to assess the contribution of rare mutations in 29 common obesity-associated genes to familial obesity, and to evaluate in these families the putative presence of nine known monogenic forms of obesity. METHODS: Through next-generation sequencing, we sequenced the coding regions of 34 genes involved in polygenic and/or monogenic forms of obesity in 201 participants (75 normal weight individuals, 54 overweight individuals and 72 individuals with obesity class I, II or III) from 13 French families. In vitro functional analyses were performed to investigate the mutation PCSK1-p.Arg80* which was identified in a family. RESULTS: A novel heterozygous nonsense variant in PCSK1 (p.Arg80*), encoding a propeptide truncated to less than two exons (out of 14), was found to co-segregate with obesity in a three-generation family. We demonstrated that this mutation inhibits PCSK1 enzyme activity and that this inhibition most likely does not involve a strong physical interaction. Furthermore, both mutations PCSK1-p.Asn180Ser and POMC-p.Phe144Leu, which had previously been reported to be associated with severe obesity, were also identified in this study, but did not co-segregate with obesity. Finally, we did not identify any rare mutations co-segregating with obesity in common obesity susceptibility genes, except for CADM2 and QPCTL, where we found two novel variants (p.Arg81His and p.Leu98Pro, respectively) in three obese individuals. CONCLUSIONS: We showed for the first time that a nonsense mutation in PCSK1 was likely to cause dominantly inherited human obesity, due to the inhibiting properties of the propeptide fragment encoded by the null allele. Furthermore, the present family sequencing design challenged the contribution of previously reported mutations to monogenic or at least severe obesity.

Placental antiangiogenic prolactin fragments are increased in human and rat maternal diabetes.

INTRODUCTION/OBJECTIVES: The role of the placenta in diabetic mothers on fetal development and programming is unknown. Prolactin (PRL) produced by decidual endometrial cells may have an impact. Although full-length PRL is angiogenic, the processed form by bone morphogenetic protein-1 (BMP-1) and/or cathepsin D (CTSD) is antiangiogenic. The objectives were to investigate the involvement of decidual PRL and its antiangiogenic fragments in placentas from type-1 diabetic women (T1D) and from pregnant diabetic rats with lower offspring weights than controls. METHODS: PRL, BMP-1, and CTSD gene expressions and PRL protein level were assessed in T1D placentas (n=8) at delivery and compared to controls (n=5). Wistar rats received, at day 7 of pregnancy, streptozotocin (STZ) (n=5) or nicotinamide (NCT) plus STZ (n=9) or vehicle (n=9). Placental whole-genome gene expression and PRL western blots were performed at birth. RESULTS: In human placentas, PRL (p<0.05) and BMP-1 (p<0.01) gene expressions were increased with a higher amount of cleaved PRL (p<0.05) in T1D than controls. In rats, diabetes was more pronounced in STZ than in NCT-STZ group with intra-uterine growth restriction. Decidual prolactin-related protein (Dprp) (p<0.01) and Bmp-1 (p<0.001) genes were up-regulated in both diabetic groups, with an increased cleaved PRL amount in the STZ (p<0.05) and NCT-STZ (p<0.05) groups compared to controls. No difference in CTSD gene expression was observed in rats or women. CONCLUSIONS: Alterations in the levels of the PRL family are associated with maternal diabetes in both rats and T1D women suggesting that placental changes in these hormones impact on fetal development.

Transcription factor gene MNX1 is a novel cause of permanent neonatal diabetes in a consanguineous family.

AIM: Permanent neonatal diabetes mellitus (PNDM) is a rare monogenic form of non-autoimmune diabetes. Genetic defects have been identified in∼60% of cases, with mutations in ABCC8, KCNJ11 and INS being the most frequent causes of PNDM. Recognition of genetic subtypes strongly impacts on both patients' care and family counseling. This study aimed to identify the genetic aetiology of PNDM in a diabetic girl born of consanguineous parents. METHODS: DNA samples from both the proband and her non-diabetic parents were analyzed for homozygosity mapping, using Illumina Infinium 660K SNP microarrays, focusing on the runs of homozygosity (ROHs) detected only in the patient. Standard Sanger sequencing of candidate genes (MNX1 and GATA6) present in the ROHs was subsequently performed, as well as expression analyses on human embryonic and adult pancreatic islet samples. RESULTS: A putative causal homozygous mutation in the transcription factor gene MNX1 (c.816C>A/p.Phe272Leu) was identified in the PNDM patient, who was clinically diagnosed as a typical case of PNDM with no developmental pancreatic defects or other clinical features. The probable deleterious mutation was located within the MNX1 homeodomain helix 2 that is highly conserved between species. In human embryonic pancreatic islet samples, it has been shown that MNX1 expression is significantly enriched in pancreatic epithelium compared with mesenchyme, suggesting a role for MNX1 in human pancreatic beta-cell development. CONCLUSION: This study found a new putative cause of PNDM in a consanguineous family. Replication in other cohorts would help to clarify the clinical spectrum of MNX1 mutations in PNDM patients.

Multiple functional polymorphisms in the G6PC2 gene contribute to the association with higher fasting plasma glucose levels.

AIMS/HYPOTHESIS: We previously identified the G6PC2 locus as a strong determinant of fasting plasma glucose (FPG) and showed that a common G6PC2 intronic single nucleotide polymorphism (SNP) (rs560887) and two common G6PC2 promoter SNPs (rs573225 and rs13431652) are highly associated with FPG. However, these promoter SNPs have complex effects on G6PC2 fusion gene expression, and our data suggested that only rs13431652 is a potentially causative SNP. Here we examine the effect of rs560887 on G6PC2 pre-mRNA splicing and the contribution of an additional common G6PC2 promoter SNP, rs2232316, to the association signal. METHODS: Minigene analyses were used to characterise the effect of rs560887 on G6PC2 pre-mRNA splicing. Fusion gene and gel retardation analyses characterised the effect of rs2232316 on G6PC2 promoter activity and transcription factor binding. The genetic association of rs2232316 with FPG variation was assessed using regression adjusted for age, sex and BMI in 4,220 Europeans with normal FPG. RESULTS: The rs560887-G allele was shown to enhance G6PC2 pre-mRNA splicing, whereas the rs2232316-A allele enhanced G6PC2 transcription by promoting Foxa2 binding. Genetic analyses provide evidence for association of the rs2232316-A allele with increased FPG (ß = 0.04 mmol/l; p = 4.3 × 10(-3)) as part of the same signal as rs560887, rs573225 and rs13431652. CONCLUSIONS/INTERPRETATION: As with rs13431652, the in situ functional data with rs560887 and rs2232316 are in accord with the putative function of G6PC2 in pancreatic islets, and suggest that all three are potentially causative SNPs that contribute to the association between G6PC2 and FPG.

Macrophage gene expression in adipose tissue is associated with insulin sensitivity and serum lipid levels independent of obesity.

OBJECTIVE: Obesity is linked to both increased metabolic disturbances and increased adipose tissue macrophage infiltration. However, whether macrophage infiltration directly influences human metabolism is unclear. The aim of this study was to investigate if there are obesity-independent links between adipose tissue macrophages and metabolic disturbances. DESIGN AND METHODS: Expression of macrophage markers in adipose tissue was analyzed by DNA microarrays in the SOS Sib Pair study and in patients with type 2 diabetes and a BMI-matched healthy control group. RESULTS: The expression of macrophage markers in adipose tissue was increased in obesity and associated with several metabolic and anthropometric measurements. After adjustment for BMI, the expression remained associated with insulin sensitivity, serum levels of insulin, C-peptide, high density lipoprotein cholesterol (HDL-cholesterol) and triglycerides. In addition, the expression of most macrophage markers was significantly increased in patients with type 2 diabetes compared to the control group. CONCLUSION: Our study shows that infiltration of macrophages in human adipose tissue, estimated by the expression of macrophage markers, is increased in subjects with obesity and diabetes and associated with insulin sensitivity and serum lipid levels independent of BMI. This indicates that adipose tissue macrophages may contribute to the development of insulin resistance and dyslipidemia.

Contribution of 24 obesity-associated genetic variants to insulin resistance, pancreatic beta-cell function and type 2 diabetes risk in the French population.

CONTEXT: Obesity is the major determinant of type 2 diabetes (T2D), presumably through its effect on insulin resistance. Genome-wide association studies reported many single-nucleotide polymorphisms (SNPs) that increase obesity risk and body mass index (BMI), but their impact on T2D-related traits and risk is unclear. OBJECTIVE: We aimed at analyzing the effect of 24 obesity risk alleles, separately and in combination, on variation of both insulin resistance and ß-cell dysfunction, and on T2D risk. DESIGN: We genotyped 24 obesity-associated SNPs and calculated an obesity genotype score (sum of the obesity risk alleles per individual). We analyzed the contribution of each SNP and this score to the variation of four metabolic indices: homeostasis model assessment of insulin resistance (HOMA-IR), homeostasis model assessment of the pancreatic ß-cell function (HOMA-B), insulin sensitivity index (ISI) and insulinogenic index (II) (in up to 8050 nondiabetic French individuals) and to T2D risk (in 2077 T2D cases and 3085 controls). RESULTS: We found a highly significant effect of the obesity genotype score on increased insulin resistance adjusted for age and gender (ß=0.02; P-value=7.16 × 10(-9) for HOMA-IR). Individually, we identified nominal or significant association between increased insulin resistance and risk alleles in FAIM2, FTO, GNPDA2, MC4R, NPC1, PTER and SH2B1. Most signals, including the obesity genotype score and FTO SNP, were also associated with increased ß-cell function (ß=0.01; P-value=1.05 × 10(-6) and ß=0.04; P-value=3.45 × 10(-4), respectively). In our T2D case-control study, only the obesity genotype score and the well-known FTO locus significantly contributed to T2D risk (OR=1.03; P-value=9.99 × 10(-3) and OR=1.15; P-value=9.46 × 10(-4), respectively). Adjustment for BMI abolished all significant associations. CONCLUSIONS: Genetic predisposition to obesity contributes to increased insulin resistance and to its compensation through increased ß-cell function, and weakly increases the T2D risk. These associations are mediated by BMI.

Reassessment of the putative role of BLK-p.A71T loss-of-function mutation in MODY and type 2 diabetes.

AIMS/HYPOTHESIS: MODY is believed to be caused by at least 13 different genes. Five rare mutations at the BLK locus, including only one non-synonymous p.A71T variant, were reported to segregate with diabetes in three MODY families. The p.A71T mutation was shown to abolish the enhancing effect of BLK on insulin content and secretion from pancreatic beta cell lines. Here, we reassessed the contribution of BLK to MODY and tested the effect of BLK-p.A71T on type 2 diabetes risk and variations in related traits. METHODS: BLK was sequenced in 64 unelucidated MODY samples. The BLK-p.A71T variant was genotyped in a French type 2 diabetes case-control study including 4,901 cases and 4,280 controls, and in the DESIR (Data from an Epidemiological Study on the Insulin Resistance Syndrome) and SUVIMAX (Supplementation en Vitamines et Mineraux Antioxydants) population-based cohorts (n = 6,905). The variant effects were assessed by logistic and linear regression models. RESULTS: No rare non-synonymous BLK mutations were found in the MODY patients. The BLK p.A71T mutation was present in 52 normoglycaemic individuals, making it very unlikely that this loss-of-function mutation causes highly penetrant MODY. We found a nominal association between this variant and increased type 2 diabetes risk, with an enrichment of the mutation in the obese diabetic patients, although no significant association with BMI was identified. CONCLUSIONS/INTERPRETATION: No mutation in BLK was found in our MODY cohort. From our findings, the BLK-p.A71T mutation may weakly influence type 2 diabetes risk in the context of obesity; however, this will require further validation.

TCF7L2 rs7903146 impairs islet function and morphology in non-diabetic individuals.

AIMS/HYPOTHESIS: Transcription factor 7-like 2 (TCF7L2) is a Wnt-signalling-associated transcription factor. Genetic studies have clearly demonstrated that DNA polymorphisms within TCF7L2 confer the strongest known association with increased risk of type 2 diabetes. However, the impact of the TCF7L2 type-2-diabetes-associated rs7903146 T allele on biological function and morphology of human pancreatic islets is unknown. METHODS: Paraffin sections of pancreases from 187 brain-deceased donors (HbA(1c) <6.5% [48 mmol/mol]) were used to genotype the TCF7L2 variant rs7903146 and evaluate its impact on islet morphology and alpha and beta cell subpopulations following immunostaining for glucagon and C-peptide. Following islet isolation, we investigated the correlation between TCF7L2 genotype and in vitro islet functional variables from our in-house pancreatic database. RESULTS: TCF7L2 rs7903146 (T/T) was associated with reduced basal and glucose-stimulated insulin secretion in isolated human islets, and reduced islet density in whole pancreas. Morphological analysis demonstrated islet size was increased in T/T carriers. Furthermore, rs7903146 was associated with an increased glucagon/C-peptide ratio, especially in bigger islets. CONCLUSION/INTERPRETATION: The TCF7L2 variant rs7903146 risk allele is associated with impaired insulin secretion, reduction of total islet number and quantitative as well as qualitative morphological changes in human islets. Understanding how the TCF7L2 genotype modulates its activity and how TCF7L2 impacts the islet morphology may aid the design of new therapeutic approaches for the treatment of type 2 diabetes.

European genetic variants associated with type 2 diabetes in North African Arabs.

AIMS: Recent genome-wide association studies (GWAS) and previous approaches have identified many genetic variants associated with type 2 diabetes (T2D) in populations of European descent, but their contribution in Arab populations from North Africa is unknown. Our study aimed to validate these markers and to assess their combined effects, using large case-control studies of Moroccan and Tunisian individuals. METHODS: Overall, 44 polymorphisms, located at 37 validated European loci, were first analyzed in 1055 normoglycaemic controls and 1193 T2D cases from Morocco. Associations and trends were then assessed in 942 normoglycaemic controls and 1446 T2D cases from Tunisia. Finally, their ability to discriminate cases from controls was evaluated. RESULTS: Carrying a genetic variant in BCL11A, ADAMTS9, IGF2BP2, WFS1, CDKAL1, TP53INP1, CDKN2A/B, TCF7L2, KCNQ1, HNF1A, FTO, MC4R and GCK increased the risk of T2D when assessing the Moroccan and Tunisian samples together. Each additional risk allele increased the susceptibility for developing the disease by 12% (P = 9.0 × 10(-9)). Genotype information for 13 polymorphisms slightly improved the classification of North Africans with and without T2D, as assessed by clinical parameters, with an increase in the area under the receiver operating characteristic curve from 0.64 to 0.67 (P = 0.004). CONCLUSION: In addition to TCF7L2, 12 additional loci were found to be shared between Europeans and North African Arabs. As for Europeans, the reliability of genetic testing based on these markers to determine the risk for T2D is low. More genome-wide studies, including next-generation sequencing, in North African populations are needed to identify the genetic variants responsible for ethnic disparities in T2D susceptibility.

Alcohol consumption and risk of type 2 diabetes in European men and women: influence of beverage type and body size The EPIC-InterAct study.

OBJECTIVE: To investigate the association between alcohol consumption and type 2 diabetes, and determine whether this is modified by sex, body mass index (BMI) and beverage type. DESIGN: Multicentre prospective case-cohort study. SETTING: Eight countries from the European Prospective Investigation into Cancer and Nutrition cohort. SUBJECTS: A representative baseline sample of 16 154 participants and 12 403 incident cases of type 2 diabetes. INTERVENTIONS: Alcohol consumption assessed using validated dietary questionnaires. MAIN OUTCOME MEASURES: Occurrence of type 2 diabetes based on multiple sources (mainly self-reports), verified against medical information. RESULTS: Amongst men, moderate alcohol consumption was nonsignificantly associated with a lower incidence of diabetes with a hazard ratio (HR) of 0.90 (95% CI: 0.78-1.05) for 6.1-12.0 versus 0.1-6.0 g day(-1) , adjusted for dietary and diabetes risk factors. However, the lowest risk was observed at higher intakes of 24.1-96.0 g day(-1) with an HR of 0.86 (95% CI: 0.75-0.98). Amongst women, moderate alcohol consumption was associated with a lower incidence of diabetes with a hazard ratio of 0.82 (95% CI: 0.72-0.92) for 6.1-12.0 g day(-1) (P interaction gender <0.01). The inverse association between alcohol consumption and diabetes was more pronounced amongst overweight (BMI ≥ 25 kg m(-2) ) than normal-weight men and women (P interaction < 0.05). Adjusting for waist and hip circumference did not alter the results for men, but attenuated the association for women (HR=0.90, 95% CI: 0.79-1.03 for 6.1-12.0 g day(-1) ). Wine consumption for men and fortified wine consumption for women were most strongly associated with a reduced risk of diabetes. CONCLUSIONS: The results of this study show that moderate alcohol consumption is associated with a lower risk of type 2 diabetes amongst women only. However, this risk reduction is in part explained by fat distribution. The relation between alcohol consumption and type 2 diabetes was stronger for overweight than normal-weight women and men.

Dietary fat intake and polymorphisms at the PPARG locus modulate BMI and type 2 diabetes risk in the D.E.S.I.R. prospective study.

CONTEXT: Fat-rich diets are involved in many disorders such as obesity and type 2 diabetes (T2D). The Pro12Ala variant of peroxisome proliferator-activated receptor-γ (PPARγ) is known to modulate body mass index (BMI) and T2D risk. OBJECTIVE: Our aim was to study the interaction effect between PPARγ gene (PPARG) polymorphisms Pro12Ala and 1431C>T and fat intake on incident T2D and BMI in a 9-year prospective cohort drawn from the French general population, the D.E.S.I.R. (Data from an Epidemiological Study on the Insulin Resistance Syndrome) study (n=4676). METHODS: Nutritional intake was assessed by a food frequency self-questionnaire completed by each participant. Statistical analyses included logistic regression, analysis of covariance and haplotype analysis, with adjustment for confounding variables. RESULTS: A high fat consumption (the third sex-specific tertile of fat intake, as a percentage of energy intake) was associated with an increased T2D risk among ProPro and CC homozygotes (P(interaction)=0.05, odds ratio (OR) (95% confidence interval (95% CI))=1.73 (1.19-2.52) P=0.004 and OR=1.85 (1.27-2.71) P=0.001, respectively) but not in Ala and T carriers. There was a significant interaction effect between Pro12Ala and 1431C>T on BMI (P(interaction)=0.004); Ala was associated with lower BMI in CC homozygotes and with higher BMI in T carriers while the opposite was found for ProPro. There was also an interaction effect between Pro12Ala and dietary fat intake on BMI (P(interaction)=0.02); AlaAla individuals had a higher BMI than Pro carriers among high fat consumers (27.1 ± 1.0 versus 24.9 ± 0.1 for AlaAla and Pro+, respectively). There was no interaction effect between the 1431C>T single-nucleotide polymorphism and fat intake on BMI. CONCLUSION: Our results indicate strong genetic and nutritional interaction effects on BMI and T2D risk at the PPARG locus in a general population.

Replication of 13 obesity loci among Singaporean Chinese, Malay and Asian-Indian populations.

OBJECTIVE: Recent genome-wide association studies (GWAS) have identified 38 obesity-associated loci among European populations. However, their contribution to obesity in other ethnicities is largely unknown. METHODS: We utilised five GWAS (N=10 482) from Chinese (three cohorts, including one with type 2 diabetes and another one of children), Malay and Indian ethnic groups from Singapore. Data sets were analysed individually and subsequently in combined meta-analysis for Z-score body-mass index (BMI) associations. RESULTS: Variants at the FTO locus showed the strongest associations with BMI Z-score after meta-analysis (P-values 1.16 × 10(-7)-7.95 × 10(-7)). We further detected associations with nine other index obesity variants close to the MC4R, GNPDA2, TMEM18, QPCTL/GIPR, BDNF, ETV5, MAP2K5/SKOR1, SEC16B and TNKS/MSRA loci (meta-analysis P-values ranging from 3.58 × 10(-4)-1.44 × 10(-2)). Three other single-nucleotide polymorphisms (SNPs) from CADM2, PTBP2 and FAIM2 were associated with BMI (P-value ≤ 0.0418) in at least one dataset. The neurotrophin/TRK pathway (P-value=0.029) was highlighted by pathway-based analysis of loci that had statistically significant associations among Singaporean populations. CONCLUSION: Our data confirm the role of FTO in obesity predisposition among Chinese, Malays and Indians, the three major Asian ethnic groups. We additionally detected associations for 12 obesity-associated SNPs among Singaporeans. Thus, it is likely that Europeans and Asians share some of the genetic predisposition to obesity. Furthermore, the neurotrophin/TRK signalling may have a central role for common obesity among Asians.

Differential coexpression analysis of obesity-associated networks in human subcutaneous adipose tissue.

OBJECTIVE: To use a unique obesity-discordant sib-pair study design to combine differential expression analysis, expression quantitative trait loci (eQTLs) mapping and a coexpression regulatory network approach in subcutaneous human adipose tissue to identify genes relevant to the obese state. STUDY DESIGN: Genome-wide transcript expression in subcutaneous human adipose tissue was measured using Affymetrix U133 Plus 2.0 microarrays (Affymetrix, Santa Clara, CA, USA), and genome-wide genotyping data was obtained using an Applied Biosystems (Applied Biosystems; Life Technologies, Carlsbad, CA, USA) SNPlex linkage panel. SUBJECTS: A total of 154 Swedish families ascertained through an obese proband (body mass index (BMI) >30 kg m(-2)) with a discordant sibling (BMI>10 kg m(-2) less than proband). RESULTS: Approximately one-third of the transcripts were differentially expressed between lean and obese siblings. The cellular adhesion molecules (CAMs) KEGG grouping contained the largest number of differentially expressed genes under cis-acting genetic control. By using a novel approach to contrast CAMs coexpression networks between lean and obese siblings, a subset of differentially regulated genes was identified, with the previously GWAS obesity-associated neuronal growth regulator 1 (NEGR1) as a central hub. Independent analysis using mouse data demonstrated that this finding of NEGR1 is conserved across species. CONCLUSION: Our data suggest that in addition to its reported role in the brain, NEGR1 is also expressed in subcutaneous adipose tissue and acts as a central 'hub' in an obesity-related transcript network.

A large multi-centre European study validates high-sensitivity C-reactive protein (hsCRP) as a clinical biomarker for the diagnosis of diabetes subtypes.

AIMS/HYPOTHESIS: An accurate molecular diagnosis of diabetes subtype confers clinical benefits; however, many individuals with monogenic diabetes remain undiagnosed. Biomarkers could help to prioritise patients for genetic investigation. We recently demonstrated that high-sensitivity C-reactive protein (hsCRP) levels are lower in UK patients with hepatocyte nuclear factor 1 alpha (HNF1A)-MODY than in other diabetes subtypes. In this large multi-centre study we aimed to assess the clinical validity of hsCRP as a diagnostic biomarker, examine the genotype-phenotype relationship and compare different hsCRP assays. METHODS: High-sensitivity CRP levels were analysed in individuals with HNF1A-MODY (n = 457), glucokinase (GCK)-MODY (n = 404), hepatocyte nuclear factor 4 alpha (HNF4A)-MODY (n = 54) and type 2 diabetes (n = 582) from seven European centres. Three common assays for hsCRP analysis were evaluated. We excluded 121 participants (8.1%) with hsCRP values >10 mg/l. The discriminative power of hsCRP with respect to diabetes aetiology was assessed by receiver operating characteristic curve-derived C-statistic. RESULTS: In all centres and irrespective of the assay method, meta-analysis confirmed significantly lower hsCRP levels in those with HNF1A-MODY than in those with other aetiologies (z score -21.8, p < 5 × 10(-105)). HNF1A-MODY cases with missense mutations had lower hsCRP levels than those with truncating mutations (0.03 vs 0.08 mg/l, p < 5 × 10(-5)). High-sensitivity CRP values between assays were strongly correlated (r (2) ≥ 0.91, p ≤ 1 × 10(-5)). Across the seven centres, the C-statistic for distinguishing HNF1A-MODY from young adult-onset type 2 diabetes ranged from 0.79 to 0.97, indicating high discriminative accuracy. CONCLUSIONS/INTERPRETATION: In the largest study to date, we have established that hsCRP is a clinically valid biomarker for HNF1A-MODY in European populations. Given the modest costs and wide availability, hsCRP could translate rapidly into clinical practice, considerably improving diagnosis rates in monogenic diabetes.

Design and cohort description of the InterAct Project: an examination of the interaction of genetic and lifestyle factors on the incidence of type 2 diabetes in the EPIC Study.

AIMS/HYPOTHESIS: Studying gene-lifestyle interaction may help to identify lifestyle factors that modify genetic susceptibility and uncover genetic loci exerting important subgroup effects. Adequately powered studies with prospective, unbiased, standardised assessment of key behavioural factors for gene-lifestyle studies are lacking. This case-cohort study aims to investigate how genetic and potentially modifiable lifestyle and behavioural factors, particularly diet and physical activity, interact in their influence on the risk of developing type 2 diabetes. METHODS: Incident cases of type 2 diabetes occurring in European Prospective Investigation into Cancer and Nutrition (EPIC) cohorts between 1991 and 2007 from eight of the ten EPIC countries were ascertained and verified. Prentice-weighted Cox regression and random-effects meta-analyses were used to investigate differences in diabetes incidence by age and sex. RESULTS: A total of 12,403 verified incident cases of type 2 diabetes occurred during 3.99 million person-years of follow-up of 340,234 EPIC participants eligible for InterAct. We defined a centre-stratified subcohort of 16,154 individuals for comparative analyses. Individuals with incident diabetes who were randomly selected into the subcohort (n = 778) were included as cases in the analyses. All prevalent diabetes cases were excluded from the study. InterAct cases were followed-up for an average of 6.9 years; 49.7% were men. Mean baseline age and age at diagnosis were 55.6 and 62.5 years, mean BMI and waist circumference values were 29.4 kg/m(2) and 102.7 cm in men, and 30.1 kg/m(2) and 92.8 cm in women, respectively. Risk of type 2 diabetes increased linearly with age, with an overall HR of 1.56 (95% CI 1.48-1.64) for a 10 year age difference, adjusted for sex. A male excess in the risk of incident diabetes was consistently observed across all countries, with a pooled HR of 1.51 (95% CI 1.39-1.64), adjusted for age. CONCLUSIONS/INTERPRETATION: InterAct is a large, well-powered, prospective study that will inform our understanding of the interplay between genes and lifestyle factors on the risk of type 2 diabetes development.

TCF7L2 is associated with type 2 diabetes in nonobese individuals from Tunisia.

The transcription factor 7-like 2 (TCF7L2) rs7903146 T allele was associated with type 2 diabetes (T2D) in most populations worldwide. In individuals of European descent, the association with T2D was recently found to be modulated by obesity status. However, further studies are necessary to clarify if whether interaction exists among subjects of non-European descent. In the present study, we analyzed the association of rs7903146 with T2D in 90 nonobese (Body Mass Index [BMI] <25kg/m(2)), 171 overweight (25≤BMI<30kg/m(2)) et 98 obese (BMI≥30kg/m(2)) individuals from Tunisia. The T allele was nominally associated with T2D in nonobese subjects (Odds Ratio [OR]=3.24 [1.10-9.53], P=0.021) whereas no effect was detected in overweight (P=0.3) and obese (P=0.22) individuals. Consequently, the same risk allele decreased susceptibility to obesity in T2D subjects (OR=0.47 [0.23-0.94], P=0.029) but not in normoglycemic controls (P=0.44). When analyzed all together, no allelic association was observed with T2D (P=0.20) whereas an artefactual association with decreased obesity (0.59 [0.38-0.90], P=0.013) was detected. As in Europeans, TCF7L2 is therefore not a risk factor for obesity in Tunisians, but its effect on T2D risk is modulated by obesity. In conclusion, the TCF7L2 rs7903146 T allele is nominally associated with T2D susceptibility in nonobese individuals from Tunisia.

Several obesity- and nutrient-related gene polymorphisms but not FTO and UCP variants modulate postabsorptive resting energy expenditure and fat-induced thermogenesis in obese individuals: the NUGENOB study.

BACKGROUND: Part of the heterogeneity of the obesity phenotype may originate from genetic differences between obese individuals that may influence energy expenditure (EE). OBJECTIVE: To examine if common single-nucleotide polymorphisms (SNPs) in genes related to obesity-associated phenotypes are associated with postabsorptive resting energy expenditure (REE) and postprandial REE in obese individuals. DESIGN AND METHODS: Postabsorptive REE and 3-h postprandial REE (liquid test meal containing 95% fat, energy content 50% of estimated REE) were measured in 743 obese individuals from eight clinical centres in seven European countries. The analysis assessed the association of genotypes of 44 SNPs in 28 obesity-related candidate genes with postabsorptive REE and postprandial REE taking into consideration the influence of body composition, habitual physical activity, insulin sensitivity, circulating thermogenic hormones and metabolites. RESULTS: After adjustment for fat-free mass (FFM), age, sex and research centre, SNPs in CART, GAD2, PCSK1, PPARG3, HSD11B1 and LIPC were significantly associated with postabsorptive REE. SNPs in GAD2, HSD11B1 and LIPC remained significantly associated with postabsorptive REE after further adjustment for fat mass (FM). SNPs in CART, PPARG2 and IGF2 were significantly associated with postprandial REE after similar adjustments. These associations with postprandial REE remained significant after further adjustment for FM. FTO, UCP2 and UCP3 variants were not associated with postabsorptive or postprandial REE. CONCLUSIONS: Several gene polymorphisms associated with obesity-related phenotypes but not FTO and UCP variants may be responsible for some of the inter-individual variability in postabsorptive REE and fat-induced thermogenesis unaccounted for by FFM, FM, age and sex. The association between FTO and obesity that has been reported earlier may not be mediated directly through modulation of EE in obese individuals.