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1.  Common genetic variation in the melatonin receptor 1B gene (MTNR1B) is associated with decreased early-phase insulin response 
Diabetologia  2009;52(8):1537-1542.
Aims/hypothesis
We investigated whether variation in MTNR1B, which was recently identified as a common genetic determinant of fasting glucose levels in healthy, diabetes-free individuals, is associated with measures of beta cell function and whole-body insulin sensitivity.
Methods
We studied 1,276 healthy individuals of European ancestry at 19 centres of the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study. Whole-body insulin sensitivity was assessed by euglycaemic–hyperinsulinaemic clamp and indices of beta cell function were derived from a 75 g oral glucose tolerance test (including 30 min insulin response and glucose sensitivity). We studied rs10830963 in MTNR1B using additive genetic models, adjusting for age, sex and recruitment centre.
Results
The minor (G) allele of rs10830963 in MTNR1B (frequency 0.30 in HapMap Centre d’Etude du Polymorphisme [Utah residents with northern and western European ancestry] [CEU]; 0.29 in RISC participants) was associated with higher levels of fasting plasma glucose (standardised beta [95% CI] 0.17 [0.085, 0.25] per G allele, p = 5.8 × 10−5), consistent with recent observations. In addition, the G-allele was significantly associated with lower early insulin response (−0.19 [−0.28, −0.10], p = 1.7 × 10−5), as well as with decreased beta cell glucose sensitivity (−0.11 [−0.20, −0.027], p = 0.010). No associations were observed with clamp-assessed insulin sensitivity (p = 0.15) or different measures of body size (p > 0.7 for all).
Conclusions/interpretation
Genetic variation in MTNR1B is associated with defective early insulin response and decreased beta cell glucose sensitivity, which may contribute to the higher glucose levels of non-diabetic individuals carrying the minor G allele of rs10830963 in MTNR1B.
Electronic supplementary material
The online version of this article (doi:10.1007/s00125-009-1392-x) contains a list of the members of the RISC Consortium, which is available to authorised users.
doi:10.1007/s00125-009-1392-x
PMCID: PMC2709880  PMID: 19455304
Genome-wide association; Glucose sensitivity; Insulin resistance; Insulin sensitivity; Melatonin receptor 1B; MTNR1B
2.  Genetic predisposition influences plasma lipids of participants on habitual diet, but not the response to reductions in dietary intake of saturated fatty acids 
Atherosclerosis  2011;215(2):421-427.
Objective
SNPs identified from genome-wide association studies associate with lipid risk markers of cardiovascular disease. This study investigated whether these SNPs altered the plasma lipid response to diet in the ‘RISCK’ study cohort.
Methods
Participants (n = 490) from a dietary intervention to lower saturated fat by replacement with carbohydrate or monounsaturated fat, were genotyped for 39 lipid-associated SNPs. The association of each individual SNP, and of the SNPs combined (using genetic predisposition scores), with plasma lipid concentrations was assessed at baseline, and on change in response to 24 weeks on diets.
Results
The associations between SNPs and lipid concentrations were directionally consistent with previous findings. The genetic predisposition scores were associated with higher baseline concentrations of plasma total (P = 0.02) and LDL (P = 0.002) cholesterol, triglycerides (P = 0.001) and apolipoprotein B (P = 0.004), and with lower baseline concentrations of HDL cholesterol (P < 0.001) and apolipoprotein A-I (P < 0.001). None of the SNPs showed significant association with the reduction of plasma lipids in response to the dietary interventions and there was no evidence of diet-gene interactions.
Conclusion
Results from this exploratory study have shown that increased genetic predisposition was associated with an unfavourable plasma lipid profile at baseline, but did not influence the improvement in lipid profiles by the low-saturated-fat diets.
doi:10.1016/j.atherosclerosis.2010.12.039
PMCID: PMC3407860  PMID: 21292264
Dietary saturated fat; Plasma lipids; SNP; Genetic predisposition score; Lipoprotein; Gene–diet-interaction
3.  Genetic predisposition to obesity leads to increased risk of type 2 diabetes 
Diabetologia  2011;54(4):776-782.
Aims/hypothesis
Obesity is a major risk factor for type 2 diabetes. Recent genome-wide association (GWA) studies have identified multiple loci robustly associated with BMI and risk of obesity. However, information on their associations with type 2 diabetes is limited. Such information could help increase our understanding of the link between obesity and type 2 diabetes. We examined the associations of 12 obesity susceptibility loci, individually and in combination, with risk of type 2 diabetes in the population-based European Prospective Investigation of Cancer (EPIC) Norfolk cohort.
Methods
We genotyped 12 SNPs, identified by GWA studies of BMI, in 20,428 individuals (aged 39–79 years at baseline) with an average follow-up of 12.9 years, during which 729 individuals developed type 2 diabetes. A genetic predisposition score was calculated by adding the BMI-increasing alleles across the 12 SNPs. Associations with incidence of type 2 diabetes were examined by logistic regression models.
Results
Of the 12 SNPs, eight showed a trend with increased risk of type 2 diabetes, consistent with their BMI-increasing effects. Each additional BMI-increasing allele in the genetic predisposition score was associated with a 4% increased odds of developing type 2 diabetes (OR 1.041, 95% CI 1.005–1.078; p = 0.02). Adjustment for BMI completely abolished the association with incident type 2 diabetes (OR 1.003, 95% CI 0.967–1.039; p = 0.89).
Conclusions/interpretation
The genetic predisposition to obesity leads to increased risk of developing type 2 diabetes, which is completely mediated by its obesity-predisposing effect.
Electronic supplementary material
The online version of this article (doi:10.1007/s00125-011-2044-5) contains supplementary material, which is available to authorized users.
doi:10.1007/s00125-011-2044-5
PMCID: PMC3052481  PMID: 21267540
Genetic predisposition; Genome-wide association studies; Obesity; Type 2 diabetes
4.  Polymorphisms in the gene encoding sterol regulatory element-binding factor-1c are associated with type 2 diabetes 
Diabetologia  2006;49(11):2642-2648.
Aims/hypothesis
The sterol regulatory element-binding factor (SREBF)-1c is a transcription factor involved in the regulation of lipid and glucose metabolism. We have previously found evidence that a common SREBF1c single-nucleotide polymorphism (SNP), located between exons 18c and 19c, is associated with an increased risk of type 2 diabetes. The present study aimed to replicate our previously reported association in a larger case–control study and to examine an additional five SREBF1c SNPs for their association with diabetes risk and plasma glucose concentrations.
Methods
We genotyped six SREBF1c SNPs in two case–control studies (n=1,938) and in a large cohort study (n=1,721) and tested for association with type 2 diabetes and with plasma glucose concentrations (fasting and 120-min post-glucose load), respectively.
Results
In the case–control studies, carriers of the minor allele of the previously reported SNP (rs11868035) had a significantly increased diabetes risk (odds ratio [OR]=1.20 [95% CI 1.04–1.38], p=0.015). Also, three other SNPs (rs2236513, rs6502618 and rs1889018), located in the 5′ region, were significantly associated with diabetes risk (OR ≥1.21, p≤0.006). Furthermore, two SNPs (rs2236513 and rs1889018) in the 5′ region were weakly (p<0.09) associated with plasma glucose concentrations in the cohort study. Rare homozygotes had increased (p≤0.05) 120-min post-load glucose concentrations compared with carriers of the wild-type allele. Haplotype analyses showed significant (p=0.04) association with diabetes risk and confirmed the single SNP analyses.
Conclusions/interpretation
In summary, we replicated our previous finding and found evidence for SNPs in the 5′ region of the SREBF1c gene to be associated with the risk of type 2 diabetes and plasma glucose concentration.
doi:10.1007/s00125-006-0430-1
PMCID: PMC2668914  PMID: 17019602
Case–control study; Cohort study; Plasma glucose concentration; Polymorphism; Population-based; Sterol regulatory element-binding factor; Type 2 diabetes
5.  Anthropometry, carbohydrate and lipid metabolism in the East Flanders Prospective Twin Survey: heritabilities 
Diabetologia  2007;50(10):2107-2116.
Aims/hypothesis
We determined the genetic contribution of 18 anthropometric and metabolic risk factors of type 2 diabetes using a young healthy twin population.
Methods
Traits were measured in 240 monozygotic (MZ) and 138 dizygotic (DZ) twin pairs aged 18 to 34 years. Twins were recruited from the Belgian population-based East Flanders Prospective Twin Survey, which is characterised by its accurate zygosity determination and extensive collection of perinatal and placental data, including information on chorionicity. Heritability was estimated using structural equation modelling implemented in the Mx software package.
Results
Intra-pair correlations of the anthropometric and metabolic characteristics did not differ between MZ monochorionic and MZ dichorionic pairs; consequently heritabilities were estimated using the classical twin approach. For body mass, BMI and fat mass, quantitative sex differences were observed; genetic variance explained 84, 85 and 81% of the total variation in men and 74, 75 and 70% in women, respectively. Heritability estimates of the waist-to-hip ratio, sum of four skinfold thicknesses and lean body mass were 70, 74 and 81%, respectively. The heritability estimates of fasting glucose, fasting insulin, homeostasis model assessment of insulin resistance and beta cell function, as well as insulin-like growth factor binding protein-1 levels were 67, 49, 48, 62 and 47%, in that order. Finally, for total cholesterol, LDL-cholesterol, HDL-cholesterol, total cholesterol:HDL-cholesterol ratio, triacylglycerol, NEFA and leptin levels, genetic factors explained 75, 78, 76, 79, 58, 37 and 53% of the total variation, respectively.
Conclusions/interpretation
Genetic factors explain the greater part of the variation in traits related to obesity, glucose intolerance/insulin resistance and dyslipidaemia.
Electronic supplementary material
The online version of this article (doi:10.1007/s00125-007-0784-z) contains supplementary material, which is available to authorised users.
doi:10.1007/s00125-007-0784-z
PMCID: PMC2039867  PMID: 17694296
Anthropometry; Carbohydrate metabolism; Chorionicity; East Flanders Prospective Twin Survey; Heritability; Lipid metabolism; Metabolic risk factors; Structural equation modelling; Twin study; Type 2 diabetes

Results 1-5 (5)