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OBJECTIVE The association between FTO rs9939609 and obesity is modified by physical activity (PA) and/or insulin sensitivity (IS). We aimed to assess whether these modifications are independent, to assess whether PA and/or IS modify the association between rs9939609 and cardiometabolic traits, and to elucidate underlying mechanisms. RESEARCH DESIGN AND METHODS Genetic association analyses comprised up to 19,585 individuals. PA was self-reported, and IS was defined based on inverted HOMA insulin resistance index. Functional analyses were performed in muscle biopsies from 140 men and in cultured muscle cells. RESULTS The BMI-increasing effect of the FTO rs9939609 A allele was attenuated by 47% with high PA (β [SE], −0.32 [0.10] kg/m2, P = 0.0013) and by 51% with high IS (−0.31 [0.09] kg/m2, P = 0.00028). Interestingly, these interactions were essentially independent (PA, −0.20 [0.09] kg/m2, P = 0.023; IS, −0.28 [0.09] kg/m2, P = 0.0011). The rs9939609 A allele was also associated with higher all-cause mortality and certain cardiometabolic outcomes (hazard ratio, 1.07–1.20, P > 0.04), and these effects tended to be weakened by greater PA and IS. Moreover, the rs9939609 A allele was associated with higher expression of FTO in skeletal muscle tissue (0.03 [0.01], P = 0.011), and in skeletal muscle cells, we identified a physical interaction between the FTO promoter and an enhancer region encompassing rs9939609. CONCLUSIONS Greater PA and IS independently reduced the effect of rs9939609 on obesity. These effects might be mediated through altered expression of FTO in skeletal muscle. Our results indicated that PA and/or other means of increasing insulin sensitivity could counteract FTO-related genetic predisposition to obesity.

Genome-wide association studies (GWAS) have found few common variants that influence fasting measures of insulin sensitivity. We hypothesized that a GWAS of an integrated assessment of fasting and dynamic measures of insulin sensitivity would detect novel common variants. We performed a GWAS of the modified Stumvoll Insulin Sensitivity Index (ISI) within the Meta-Analyses of Glucose and Insulin-Related Traits Consortium. Discovery for genetic association was performed in 16,753 individuals, and replication was attempted for the 23 most significant novel loci in 13,354 independent individuals. Association with ISI was tested in models adjusted for age, sex, and BMI and in a model analyzing the combined influence of the genotype effect adjusted for BMI and the interaction effect between the genotype and BMI on ISI (model 3). In model 3, three variants reached genome-wide significance: rs13422522 (NYAP2; P = 8.87 × 10−11), rs12454712 (BCL2; P = 2.7 × 10−8), and rs10506418 (FAM19A2; P = 1.9 × 10−8). The association at NYAP2 was eliminated by conditioning on the known IRS1 insulin sensitivity locus; the BCL2 and FAM19A2 associations were independent of known cardiometabolic loci. In conclusion, we identified two novel loci and replicated known variants associated with insulin sensitivity. Further studies are needed to clarify the causal variant and function at the BCL2 and FAM19A2 loci.

Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) associated with waist circumference and waist-to-hip ratio adjusted for body mass index (WCadjBMI, WHRadjBMI), but it remains unclear whether these SNPs relate to change in WCadjBMI or WHRadjBMI with lifestyle intervention. We hypothesized that polygenic scores (PS) comprised of 59 SNPs previously associated with central adiposity would predict less of a reduction in WCadjBMI or WHRadjBMI at eight-to-ten weeks in two lifestyle intervention trials, NUGENOB and DiOGenes, and at one year in 5 lifestyle intervention trials, Look AHEAD, Diabetes Prevention Program, Diabetes Prevention Study, DIETFITS, and PREDIMED-Plus. One standard deviation higher PS related to smaller one-year change in WCadjBMI in the lifestyle intervention arms at year 1, and thus predicted poorer response (beta=0.007, SE=0.003, p=0.03) among White participants overall and in White men (beta=0.01, SE=0.004, p=0.01). At average weight loss, this amounted to 0.20-0.28 cm per standard deviation. No significant findings emerged in White women, African American men, for the 8-10 week outcomes or for WHRadjBMI. Findings were heterogeneous in African American women. These results indicate that polygenic risk relates to change in WCadjBMI with lifestyle intervention but the effects are small and not of sufficient magnitude to be clinically significant.

Objective The association between FTO rs9939609 and obesity is modified by physical activity (PA) and/or insulin sensitivity (IS). We aimed to assess whether these modifications are independent, if PA and/or IS modify the association between rs9939609 and cardiometabolic traits, and to elucidate underlying mechanisms. Research Design and Methods Genetic association analyses comprised up to 19,585 individuals. PA was self-reported and IS was defined based on inverted HOMA-IR. Functional analyses were performed in muscle biopsies from 140 men, and in cultured muscle cells. Results The BMI-increasing effect of the FTO rs9939609 A-allele was attenuated by 47% with high PA (β (standard error (SE)), -0.32 (0.10) kg/m2, p=0.0013), and by 51% with high IS (-0.31 (0.09) kg/m2, p=0.00028). Interestingly, these interactions were essentially independent (PA, -0.20 (0.09) kg/m2, p=0.023; IS, -0.28 (0.09) kg/m2, p=0.0011). The rs9939609 A-allele was also associated with higher all-cause mortality and certain cardiometabolic outcomes (hazard ratio, 1.07-1.20, p>0.04), and these effects tended to be weakened by greater PA and IS. Moreover, the rs9939609 A-allele was associated with higher expression of FTO in skeletal muscle tissue (0.03 (0.01), p=0.011), and in skeletal muscle cells, we identified a physical interaction between the FTO promoter and an enhancer region encompassing rs9939609. Conclusions Greater PA and IS independently reduced the effect of rs9939609 on obesity. These effects might be mediated through altered expression of FTO in skeletal muscle. Our results indicated that PA and/or other means of increasing insulin sensitivity could counteract FTO–related genetic predisposition to obesity.

Background: Ectopic fat deposition resulting from impaired subcutaneous adipose tissue expandability may take center stage in the pathophysiological events linking low birth weight (LBW) with increased risk of developing Type 2 diabetes (T2D) . However, the extent to which adult LBW subjects exhibit increased hepatic fat accumulation is controversial. Methods and Results: Using 1H MR spectroscopy, we found a significantly increased hepatic fat content (P=0.014) in 26 early middle-aged and non-obese LBW males compared with 21 BMI- and age-matched normal birth weight (NBW) controls. Interestingly, 5 LBW (20%) versus no NBW subjects, had previously unrecognized overt nonalcoholic fatty liver disease (NAFLD) with a median hepatic fat content of 9.45%. The LBW w/NAFLD displayed widespread metabolic changes compared with both NBW and LBW w/o NAFLD subjects including hepatic insulin resistance (P=0.02) , increased fasting plasma triglycerides (TGs) (P=0.03) , cholesterol (P=0.05) , leptin, C-peptide and GLP-1 levels, as well as decreased adiponectin levels (P-range: 0.02-0.007) . Among 65 distinct metabolites and 279 lipids identified by untargeted serum metabolomic and lipidomic analyses, the levels of 7 metabolites including ornithine and citrulline, were different (P Conclusion: The data support a role for ectopic fat deposition in the pathophysiological events and trajectories linking LBW with increased risk of developing T2D and associated cardiometabolic traits including dyslipidemia. Disclosure L.Elingaard-larsen: None. T.Hansen: None. C.Brøns: Stock/Shareholder; Novo Nordisk. A.A.Vaag: Stock/Shareholder; AstraZeneca. L.Justesen: None. S.O.Villumsen: None. A.B.Thuesen: None. J.Størling: None. L.M.Sparks: None. M.Kim: None. C.Legido-quigley: None. E.R.Danielsen: None. Funding Novo Nordisk Foundation (NNF15OC0016692) , Aase and Ejnar Danielsens Fond, Augustinus Foundation, Simon Spies Fonden, TrygFonden.

Background: We hypothesized that low birth weight (LBW) subjects with a known increased risk of type 2 diabetes exhibit increased sensitivity towards the deleterious metabolic effects of 4-weeks high carbohydrate overfeeding (HCOF) compared with normal birth weight (NBW) controls. Methods: Untargeted serum metabolomics and lipidomics were measured before and after 4-weeks HCOF (+25% energy) in 26 non-obese men with LBW (2789±174 g) and 21 normal birth weight (NBW) men/controls (3804±172 g) matched for BMI and age. Data were analyzed using a combination of advanced statistical and bioinformatical tools. Results: Among 65 identified metabolites, 8 metabolites were affected differentially by HCOF between the two groups (p Conclusion: The results document severe differential perturbations of lipid metabolism in LBW men exposed to HCOF. Public health initiatives promoting low carbohydrate diets in LBW subjects are warranted. Disclosure S.O.Villumsen: None. A.A.Vaag: Stock/Shareholder; AstraZeneca. L.Justesen: None. L.Elingaard-larsen: None. A.B.Thuesen: None. M.Kim: None. C.Legido-quigley: None. E.R.Danielsen: None. T.Hansen: None. C.Brøns: Stock/Shareholder; Novo Nordisk.

Mutations in hepatocyte nuclear factor 1-alpha (HNF1A) cause HNF1A-diabetes (or maturity-onset diabetes of the young type 3 (MODY3)) . Treatment of HNF1A-diabetes is primarily based on sulphonylureas (SU) and secondarily insulins, glucagon-like peptide 1 receptor agonists (GLP1-RA) and dipeptidyl peptidase-4 inhibitors (DPP4i) . Sodium-glucose cotransporter-2 inhibitors (SGLT2i) are effective glucose-lowering agents, cause body weight loss and protect from chronic kidney disease, heart failure and major adverse cardiovascular events. The utility of SGLT2i in patients with HNF1A-diabetes is unknown. Here, we describe a case series of five patients with HNF1A-diabetes treated with SGLT2i. Patient characteristics (median [range]) : age: 52 [35; 68] years; men/women: n=4/1; diabetes duration: 23 [9; 55] years; age at diabetes onset: 18 [13; 44] years; HbA1c: 6.9 [6.0; 7.4]% (52 [42; 57] mmol/mol) ; body weight: 92.3 [65.5; 95.1] kg; BMI: 25.6 [23.8; 29.4] kg/m2. At baseline, patients were treated with SU (n=5) , insulin (n=3; total daily dose: 15 [6; 25] IE divided into 1-4 injections/day) , DPP-4i (n=3) , GLP1-RA (n=2) , metformin (n=1) . All patients were started on empagliflozin mg QD. Follow-up was 1.5 [0.7; 1.8] years (total 6.2 patient years) . After three to six months of SGLT2i therapy, HbA1c was 6.1 [5.5; 7.5]% (43 [37; 59] mmol/mol) and had decreased in four patients (HbA1c change: -0.5 [-1.3; 0.7]% (-5 [-14; 8] mmol/mol)) , while body weight had decreased in all patients (change: -3.4 [-5.9; -1.5] kg) . During SGLT2i treatment, insulin was fully ceased in two patients and insulin dose was reduced from 15 IE/day to 3 IE/day in one patient. No serious adverse events were reported. Our data suggest that SGLT2i is safe, have glucose-lowering effects and is well-tolerated in HNF1A-diabetes, but randomized controlled trials are needed. Disclosure H.Maagensen: None. S.Haedersdal: None. J.Krogh: None. T.Hansen: None. F.K.Knop: Advisory Panel; Boehringer Ingelheim International GmbH, Eli Lilly and Company, Merck Sharp & Dohme Corp., Novo Nordisk, Sanofi, ShouTi, Zucara Therapeutics, Consultant; AstraZeneca, Eli Lilly and Company, Novo Nordisk, Pharmacosmos A/S, Sanofi, ShouTi, Zealand Pharma A/S, Zucara Therapeutics, Research Support; AstraZeneca, Novo Nordisk, Sanofi, Zealand Pharma A/S, Speaker's Bureau; AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Eli Lilly and Company, Novo Nordisk, Sanofi, Stock/Shareholder; Antag Therapeutics. T.Vilsbøll: Consultant; AstraZeneca, Bristol-Myers Squibb Company, Eli Lilly and Company, Gilead Sciences, Inc., GlaxoSmithKline plc., Merck Sharp & Dohme Corp., Mundipharma, Novo Nordisk, Sun Pharmaceutical Industries Ltd.

Background: Low birth weight (LBW) individuals are at increased risk of developing Type 2 diabetes (T2D) , especially when exposed to an affluent dietary pattern. Impaired subcutaneous adipose tissue expandability and ectopic fat storage may represent key features explaining the link between LBW and risk of T2D. We hypothesized that a 4-week simple carbohydrate overfeeding challenge (+25% energy) (COF) would adversely influence dysmetabolic traits including hepatic fat content in LBW compared to normal birth weight (NBW) men. Methods: Twenty-two non-obese LBW and 21 age- and BMI-matched NBW men with a mean age of 37.6 years were included. Body composition, hepatic fat (MR spectroscopy) , glucose and insulin metabolism, hepatic glucose production (HGP; deuterium glucose) , energy metabolism (indirect calorimetry) and selected plasma biomarkers (multiplex ELISA) were measured before and after 4 weeks COF. Results: Fasting plasma glucose and C-peptide levels, as well as energy expenditure (EE) and fat oxidation (FOX) rates increased significantly more in response to COF among the LBW compared to NBW subjects (all P Conclusion: LBW compared to NBW subjects respond to COF with differential increments in plasma glucose, C-peptide, leptin and FGF21 levels, as well as increased EE and FOX rates. The results underscore the importance of LBW individuals avoiding simple carbohydrate overfeeding. Further studies are needed to understand the role of increased hepatic fat and insulin resistance as key mechanisms linking LBW with increased risk of T2D. Disclosure C.Brøns: Stock/Shareholder; Novo Nordisk. A.B.Thuesen: None. L.Justesen: None. L.Elingaard-larsen: None. J.Størling: None. E.R.Danielsen: None. T.Hansen: None. A.A.Vaag: Stock/Shareholder; AstraZeneca. Funding Novo Nordisk Foundation (NNF15OC0016692) , Aase and Ejnar Danielsens Fond, Augustinus Foundation, Simon Spies Fonden, TrygFonden.

Background: Low birth weight, indictive of a poor fetal environment, is a risk factor for type 2 diabetes (T2D) . Most previous studies were based on cross sectional prevalence data and not designed to study the timing of onset of T2D in relation to birth weight (BW) . Furthermore, earlier studies have not adjusted for common genetic variation influencing BW. We aimed to examine associations of BW with age-specific incidence of T2D using BW polygenetic risk scores (BWPRS) to adjust for genetic confounding. Methods: Adults (30-60 years) enrolled in the Inter99 cohort from 1999-20with information on BW from original birth records, and without diabetes at baseline were eligible. Birth records were linked with individual-level data on T2D incidence from the Danish Diabetes Register and key covariates from the Inter99 study. Incidence rates of T2D as a function of age, sex and BW were modelled using Poisson regression and adjusted for adult BMI, socioeconomic status, maternal history of diabetes and BWPRS. Results: Among 4584 participants there were 438 incident cases of T2D during a mean follow-up of 18 years. BW was inversely associated with T2D with a higher incidence in men. T2D incidence increased with age and the rate of increase was higher in persons with lower BW compared with higher BW in a dose-response manner. Conclusion: A lower birth weight is associated with a greater increase in incidence rate of T2D in a non-genetic manner. Disclosure R.Wibaek: Stock/Shareholder; Novo Nordisk A/S. G.S.Andersen: Stock/Shareholder; Novo Nordisk A/S. A.Linneberg: None. N.Grarup: None. T.Hansen: None. C.Brøns: Stock/Shareholder; Novo Nordisk. D.Vistisen: Research Support; Bayer AG, Boehringer Ingelheim International GmbH, Novo Nordisk A/S, Sanofi, Stock/Shareholder; Novo Nordisk A/S. A.A.Vaag: Stock/Shareholder; AstraZeneca. Funding Danish Diabetes Academy, which is funded by the Novo Nordisk Foundation (NNF17SA0031406)

Sulfonylureas (SUs) provide an efficacious first-line treatment in patients with hepatocyte nuclear factor 1α (HNF1A) diabetes, but SUs have limitations due to risk of hypoglycemia. Treatment based on the incretin hormones glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide 1 (GLP-1) is characterized by their glucose-dependent insulinotropic actions without risk of hypoglycemia. The effect of SUs together with GIP or GLP-1, respectively, on insulin and glucagon secretion in patients with HNF1A diabetes is currently unknown. To investigate this, 10 HNF1A mutation carriers and 10 control subjects without diabetes were recruited for a double-blinded, placebo-controlled, crossover study including 6 experimental days in a randomized order involving 2-h euglycemic-hyperglycemic clamps with coadministration of: 1) SU (glimepiride 1 mg) or placebo, combined with 2) infusions of GIP (1.5 pmol/kg/min), GLP-1 (0.5 pmol/kg/min), or saline (NaCl). In HNF1A mutation carriers, we observed: 1) hypoinsulinemia, 2) insulinotropic effects of both GIP and GLP-1, 3) additive to supra-additive effects on insulin secretion when combining SU+GIP and SU+GLP-1, respectively, and 4) increased fasting and arginine-induced glucagon levels compared with control subjects without diabetes. Our study suggests that a combination of SU and incretin-based treatment may be efficacious in patients with HNF1A diabetes via potentiation of glucose-stimulated insulin secretion.

In the Greenlandic Inuit population a common nonsense TBC1D4 p.Arg684Ter variant in muscle is found with an allele frequency of 17%. Homozygous carriers of this variant have impaired glucose tolerance, and a 10-fold increased risk of type 2 diabetes. Here we investigate whether the TBC1D4 p.Arg684Ter affects regulation of skeletal muscle glucose uptake during exercise and during insulin stimulation in the post exercise period. Inuits carrying zero (n=8) or two (n=8) alleles of TBC1D4 p.Arg684Ter were recruited from population surveys in Greenland. Glucose tolerance was measured during a 6 hour oral glucose tolerance test (OGTT). Skeletal muscle glucose uptake was measured by applying arterial-venous balance technique across the legs during one-legged exercise and during subsequent euglycemic hyperinsulinemic clamp. Glucose uptake was measured in both the rested and the exercised leg. During the OGTT blood glucose was similar at fasting but markedly elevated (by 4.4 mM) in TBC1D4 p.Arg684Ter carriers compared to matched controls at 2 hours, and variants became hypoglycemic at 4 hours (3.3 vs. 4.7 mM) and similar to controls at 6 hours. During exercise, TBC1D4 variant carriers and controls displayed similar glucose uptake in skeletal muscle. During insulin clamp, glucose uptake in the previously rested leg was lower (~50%) in TBC1D4 variant carriers compared to controls. In the prior exercised leg, glucose uptake during the insulin clamp was higher in both groups compared to the rested leg. However, glucose uptake in the previously exercised leg from TBC1D4 variant carriers was comparable to the previously rested leg in controls and thus still markedly lower than controls. In conclusion: TBC1D4 p.Arg684Ter carriers have impaired insulin stimulated but normal exercise stimulated glucose uptake in skeletal muscle. A single bout of exercise improves muscle glucose uptake in carriers to levels seen in non-exercise muscle of controls. Disclosure J. M. Kristensen: None. T. Hansen: None. M. E. Jørgensen: Research Support; Self; Boehringer Ingelheim International GmbH, Sanofi-Aventis, Stock/Shareholder; Self; Novo Nordisk A/S. J. F. P. Wojtaszewski: None. T. L. J. Larsen: None. C. S. Carl: None. A. Thorup: None. J. Hingst: None. J. Onslev: None. J. S. Olesen: None. M. L. Pedersen: None. E. A. Richter: None. Funding Novo Nordisk Foundation (NNF14OC0013057, NNF17OC0028136); Independent Research Fund Denmark (FSS802000288B5855628)

Lifestyle intervention, combining calorie restriction and physical activity to induce weight loss, is the frontline treatment for overweight or obesity and well-known to reduce waist circumference (WC). Genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) associated with WC adjusted for body mass index (WCadjBMI), but it remains unclear whether these SNPs relate to the change in WCadjBMI with lifestyle intervention. Here, we examined whether 59 SNPs previously associated with WCadjBMI in GWAS predicted change in WCadjBMI at one year in 5 lifestyle intervention trials and at 8-10 weeks in two lifestyle intervention trials. Look AHEAD, Diabetes Prevention Program, Diabetes Prevention Study, DIETFITS, and PrediMed Plus contributed one-year data, and NUGENOB and DiOGenes contributed 8-10 week data. Genetic risk scores (GRS) combined associated alleles for each SNP weighted by association with WCadjBMI from Shungin et al, 2015 and meta-analyses with random effects for each trial were used to pool results. Among White participants, higher GRS related to smaller year one change in WCadjBMI in the lifestyle intervention arms, and thus predicted poorer response (p=0.009). With a point estimate of 0.002 (SE=0.001) across trials, for a person with an initial BMI of 34 and a year 1 reduction in BMI of 2.5, each weighted risk allele in the GRS contributed to a 0.06 cm (SE=0.03) higher WC at year 1. With a 25th%ile, median, and 75th%ile GRS of 42.77, 46.75, and 50.48, this translates to 0.46 cm less change in WC between the 25th%ile and 75th%ile. No significant findings emerged in men and women separately, in the African-American subset, for the 8-10 week outcomes, or for the individuals SNPs after correcting for multiple comparisons. These results may help to define the molecular pathways through which lifestyle intervention impacts central adiposity. Disclosure J. Mccaffery: None. T. Hansen: None. T. O. Kilpelainen: None. D. Corella: None. W. H. M. Saris: Advisory Panel; Self; Friesland Campina International, Consultant; Self; Nutrition et sante. T. I. A. Sørensen: None. J. Tuomilehto: None. R. R. Wing: None. T. Agurs-collins: None. K. A. Jablonski: None. Q. Pan: None. A. Astrup: Consultant; Self; Groupe Éthique et Santé, France, Employee; Self; Novo Nordisk Foundation, Other Relationship; Self; Flaxslim ApS, Denmark, Gelesis, Personalized Weight Management Research Consortium ApS (Gluco-Diet. dk). M. R. Christiansen: None. L. M. Corso: None. J. C. Florez: Consultant; Self; Goldfinch Bio, Inc., Other Relationship; Self; Novo Nordisk. P. W. Franks: Advisory Panel; Self; Zoe Global Limited, Consultant; Self; Eli Lilly and Company, Novo Nordisk. C. D. Gardner: None. Funding WESTAT/National Cancer Institute

OBJECTIVE Sulfonylureas are first-line treatment of hepatocyte nuclear factor 1-alpha (HNF1A)-diabetes [maturity onset diabetes of the young type 3], but many patients do not achieve optimal glycemic control without episodes of hypoglycemia. We investigated the combination of the sulfonylurea, glimepiride, and the dipeptidyl peptidase-4 inhibitor, linagliptin, versus glimepiride monotherapy with respect to glycemic variability, glycemic control and risk of hypoglycemia. RESEARCH DESIGN AND METHODS In a randomized, double-blinded, crossover trial, patients with HNF1A-diabetes (n = 19, [mean ± SD]; age: 43 ± 14 years; BMI 24.8 ± 2.8 kg/m2; glycated hemoglobin (HbA1c) 7.4 ± 0.2% [57.1 ± 7.3 mmol/mol]) were randomly assigned to treatment with glimepiride + linagliptin 5 mg (16 weeks), wash-out (4 weeks) and glimepiride + placebo (16 weeks) (or vice versa). Glimepiride was titrated targeting a fasting plasma glucose of 4.5-6.0 mM without hypoglycemia. Treatments were evaluated by continuous glucose monitoring (CGM), HbA1c and meal test. RESULTS Compared to glimepiride + placebo, glimepiride + linagliptin did not significantly improve the primary endpoint mean amplitude of glycemic excursions (MAGE) ([mean difference] -0.7 mM, P = 0.1540) but displayed significant reductions in coefficient of variation (CV) on CGM (-3.6%, P = 0.0401), HbA1c (-0.5%, P = 0.0048) and glimepiride dose (-0.7 mg/day, P = 0.0099). Beta cell glucose sensitivity (assessed as C-peptide:glucose) during meal test improved with glimepiride + linagliptin. Incidences of hypoglycemia were similar with both treatments. CONCLUSION Linagliptin as add-on treatment to glimepiride improved glycemic variability and control without increasing risk of hypoglycemia in patients with HNF1A-diabetes.

Sulfonylureas (SUs) provide an efficacious first-line treatment in patients with hepatocyte nuclear factor 1-alpha (HNF1A)-diabetes, but SUs have limitations due to risk of hypoglycemia. Treatment based on the incretin hormones, glucose-dependent insulinotropic peptide (GIP) and glucagon-like-peptide 1 (GLP-1), are characterized by their glucose-dependent insulinotropic actions without risk of hypoglycemia. The effect of SUs together with GIP or GLP-1, respectively, on insulin and glucagon secretion in patients with HNF1A-diabetes is currently unknown. To investigate this, ten HNF1A mutation carriers and ten non-diabetic controls were recruited for a double-blinded, placebo-controlled, crossover study including six experimental days in a randomized order involving 2h euglycemic-hyperglycemic clamps with co-administration of 1) SU (glimepiride 1 mg) or placebo, combined with 2) infusions of either GIP (1.5 pmol/kg/min), GLP-1 (0.5 pmol/kg/min) or saline (NaCl). In HNF1A mutation carriers we observed: 1) hypoinsulinemia, 2) insulinotropic effects of both GIP and GLP-1, 3) additive to supra-additive effects on insulin secretion when combining SU+GIP and SU+GLP1, respectively, and 4) increased fasting and arginine-induced glucagon levels compared to non-diabetic controls. Our study suggests that a combination of SU and incretin-based treatment may be efficacious in patients with HNF1A-diabetes via potentiation of glucose-stimulated insulin secretion.

Objective: Congenital sucrase-isomaltase deficiency is prevalent in Arctic populations. Recently, a frameshift mutation, c.273-274delAG, in the sucrose-isomaltase encoding gene (SI) was identified. This mutation was predicted to cause complete loss of enzymatic function, and thus is a diagnostic marker for Congenital sucrase-isomaltase deficiency. We aimed to characterize the metabolic health among adult Greenlanders carrying the c.273-274delAG mutation. Material and Methods: We genotyped the c.273-274delAG mutation in two cohorts of Greenlanders comprising 4600 (Cohort I) and 1500 participants (Cohort II), respectively. We assessed the effect of the variant on markers of metabolic health. Results: In cohort I, homozygous carriers of the c.273-274delAG mutation had a markedly healthier metabolic profile than the remaining population, including lower BMI (beta, -2.0 kg/m2, p=3.1x10-5), fat% (-3.3 %, p=0.0004), weight (-4.8 kg, p=0.0005), and levels of triglycerides (-0.27 mmol/l, p=2.3x10-6) and remnant cholesterol (-0.11 mmol/l, p=4.2x10-5). Even though homozygous carriers had a significantly lower consumption of sugar, this did not fully explain the healthier phenotype in these individuals. In cohort II, metabolomics data revealed that particularly HDL metabolism was altered among homozygous carriers of the mutation, and that these individuals had markedly increased levels of circulating acetate (1.78 mmol/l, p=2.1x10-26). Based on these findings, we hypothesize that the observed phenotype is caused by increased fermentation of undigested carbohydrates in the gut, leading to increased amounts of circulating acetate, which increases lipid oxidation and reduces storage of fat. Conclusion: Our results show, that homozygous c.273-274delAG mutation carriers have a markedly healthier metabolic profile, and indicate that SI constitutes a promising new drug target, with potential to prevent obesity and dyslipidemia. Disclosure M.E. Jørgensen: Research Support; Self; Amgen, AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Sanofi-Aventis. Stock/Shareholder; Self; Novo Nordisk A/S. M.K. Andersen: None. L. Skotte: None. E. Jørsboe: None. N. Grarup: None. P. Bjerregaard: None. B. Soborg: None. O. Pedersen: None. B. Feenstra: Employee; Spouse/Partner; Novo Nordisk Inc. N.J.K. Færgeman: None. A. Koch: None. I. Moltke: None. T. Hansen: None. A. Albrechtsen: None.

OBJECTIVE Cardiovascular mortality risk remains high among patients with type 2 diabetes. Oxidative stress indicated by high urinary excretion of the biomarker for RNA oxidation, 8-oxo-7,8-dihydroguanosine (8-oxoGuo), is associated with an increased risk of death in newly diagnosed and treated patients. We assessed whether 8-oxoGuo is associated with specific cardiovascular and all-cause mortality risk. RESEARCH DESIGN AND METHODS Urinary biomarkers for nucleic acid oxidation were measured in a cohort of patients with type 2 diabetes aged ≥60 years (n = 1,863), along with biochemical measurements, questionnaire findings, and Central Person Registry information to estimate the hazard ratios (HRs) for log2-transformed RNA oxidation using Cox regression. RESULTS During the 5-year follow-up, 173 of 1,863 patients had died (9.3%), including 73 patients who died of cardiovascular disease (42.2%). Doubling of RNA oxidation was associated with an HR of all-cause mortality of 2.10 (95% CI 1.63–2.71; P < 0.001) and an HR of cardiovascular death of 1.82 (95% CI 1.20–2.77; P = 0.005) after multiple adjustments. The 5-year absolute risks (ARs) of all-cause mortality (AR 13.9 [95% CI 10.8–17.0] vs. AR 6.10 [95% CI 4.00–8.30]) and cardiovascular mortality (AR 5.49 [95% CI 3.44–7.55] vs. AR 3.16 [95% CI 1.59–4.73]) were approximately two times higher in the highest quartile of RNA oxidation than in the lowest quartile. CONCLUSIONS We conclude that high RNA oxidation is associated with all-cause and cardiovascular mortality risk in patients with type 2 diabetes. Targeting oxidative stress via interventions with long-term follow-up may reveal the predictive potential of the biomarker 8-oxoGuo.

Hyperinsulinemia is an adaptive mechanism that enables the maintenance of normoglycemia in the presence of insulin resistance. We assessed whether glucagon is also involved in the adaptation to insulin resistance. A total of 1,437 individuals underwent an oral glucose tolerance test with measurements of circulating glucose, insulin, and glucagon concentrations at 0, 30 and 120 min. Early glucagon suppression was defined as suppression in the period from 0 to 30 min, and late glucagon suppression as 30 to 120 min after glucose intake. Insulin sensitivity was estimated by the validated insulin sensitivity index. Individuals with screen-detected diabetes had 30% higher fasting glucagon levels and diminished early glucagon suppression, but greater late glucagon suppression when compared with individuals with normal glucose tolerance (P ≤ 0.014). Higher insulin resistance was associated with higher fasting glucagon levels, less early glucagon suppression, and greater late glucagon suppression (P < 0.001). The relationship between insulin sensitivity and fasting glucagon concentrations was nonlinear (P < 0.001). In conclusion, increased fasting glucagon levels and delayed glucagon suppression, together with increased circulating insulin levels, develop in parallel with insulin resistance. Therefore, glucose maintenance during insulin resistance may depend not only on hyperinsulinemia but also on the ability to suppress glucagon early after glucose intake.

Background: The nonsense polymorphism p.Arg684Ter in the TBC1D4 gene is associated with severe skeletal muscle insulin resistance and postprandial hyperglycemia in the Greenlandic population. Homozygous carriers have an increased risk for type 2 diabetes (odds ratio of 10.3) and the variant has an allele frequency of 17% with 4% homozygous carriers in the population. However, we do not know, if p.Arg684Ter carrier status also confers a greater risk of cardiovascular disease (CVD). Thus the aim is to investigate if carriers of the variant are more at risk of CVD than non-carriers. Materials and Methods: The study included adult participants in the Inuit Health in Transition study completed in the years 2005-2010 with sampling from 12 regions in Greenland (n= 3115) and the B99 study conducted from 1999-2001 (n=1401). Outcome was a first time CVD event from the Greenlandic Patien Register or the Causes of Death Register. Incidence rates of CVD were estimated by Poisson regression for wild type, heterozygous and homozygous carriers followed until the end of 2013, adjusted for European admixture proportion, age, sex, smoking, lipids, blood pressure, lipid- and blood pressure lowering drugs, blood glucose and known diabetes. Results: During a median follow-up time of 7 years [IQR: 5.0, 10.0], 273 had an incident CVD event, 13 events among homozygous (HO), and 78 events among heterozygous (HE) carriers. Both in crude and adjusted analyses, there was a higher risk of incident CVD with p.Arg684Ter carrier status, although not statistically significant, with unadjusted incidence rate ratios (IRR) of 2.2 [CI 0.3- 15.5] for HO vs. WT; multivariable adjusted IRR 1.6 [0.12-19.5] for HO vs. WT. The same pattern was seen for HE vs. WT. Conclusions: Overall, there was a trend towards increased risk of incident CVD with the TBC1D4 p.Arg684Ter variant although not statistically significant. Lack of statistical power may partly explain this, and replication in a larger sample or longer follow-up is needed. Disclosure M.E. Jørgensen: Stock/Shareholder; Self; Novo Nordisk A/S. Research Support; Self; AstraZeneca, Amgen Inc.. M. Tvermosegaard: None. P.F. Rønn: Employee; Spouse/Partner; Novo Nordisk A/S. Stock/Shareholder; Spouse/Partner; Novo Nordisk A/S. P. Bjerregaard: None. I.K. Dahl-Petersen: None. C.V. Larsen: None. M.L. Pedersen: None. A. Albrechtsen: None. I. Moltke: None. N. Grarup: None. T. Hansen: None.

The role of glucose-stimulated release of glucagon-like peptide-1 (GLP-1) in the development of obesity and type 2 diabetes is unclear. We assessed GLP-1 response to oral glucose in a large study population of lean and obese men and women with normal and impaired glucose regulation. Circulating concentrations of glucose, insulin and GLP-1 during an oral glucose tolerance test (OGTT) were analyzed in individuals with normal glucose tolerance (NGT, n=774), pre-diabetes (n=523) or screen-detected type 2 diabetes (n=163) who attended the Danish ADDITION-PRO study (n=1,462). Compared with individuals with NGT, women with pre-diabetes or type 2 diabetes had 25% lower GLP-1 response to an OGTT, and both men and women with pre-diabetes or type 2 diabetes had 16-21% lower 120-min GLP-1 concentrations independent of age and obesity. Obese and overweight individuals had 20% reduced GLP-1 response to oral glucose compared with normal weight individuals independent of glucose tolerance status. Higher GLP-1 responses were associated with better insulin sensitivity and beta cell function, higher age and lower degree of obesity. Our findings indicate that a reduction in GLP-1 response to oral glucose occurs prior to the development of type 2 diabetes and obesity, which can have consequences for early prevention strategies for diabetes.

Maturity-onset diabetes of the young (MODY) is a clinically and genetically heterogeneous subgroup of non-autoimmune diabetes, constituting 1-2% of all diabetes. Because little is known about incretin function in patients with MODY, we studied the incretin effect and hormone responses to oral and intravenous glucose loads in patients with glucokinase (GCK)-diabetes (MODY2) and hepatocyte nuclear factor 1 alpha (HNF1A)-diabetes (MODY3), respectively, and in matched healthy control subjects. Both MODY groups exhibited glucose intolerance after oral glucose (most pronounced in patients with HNF1A-diabetes), but only patients with HNF1A-diabetes had impaired incretin effect and inappropriate glucagon responses to OGTT. Both groups of patients with diabetes showed normal suppression of glucagon in response to intravenous glucose. Thus, HNF1A-diabetes, similar to type 2 diabetes, is characterized by an impaired incretin effect and inappropriate glucagon responses, whereas incretin effect and glucagon response to oral glucose remain unaffected in GCK-diabetes, reflecting important pathogenetic differences between the two MODY forms. Maturity-onset diabetes of the young (MODY) is a clinically and genetically heterogeneous subgroup of non-autoimmune diabetes, constituting 1-2% of all diabetes. Because little is known about incretin function in patients with MODY, we studied the incretin effect and hormone responses to oral and intravenous glucose loads in patients with glucokinase (GCK)-diabetes (MODY2) and hepatocyte nuclear factor 1a (HNF1A)-diabetes (MODY3), respectively, and in matched healthy control subjects. Both MODY groups exhibited glucose intolerance after oral glucose (most pronounced in patients with HNF1A-diabetes), but only patients with HNF1A-diabetes had impaired incretin effect and inappropriate glucagon responses to OGTT. Both groups of patients with diabetes showed normal suppression of glucagon in response to intravenous glucose. Thus, HNF1A-diabetes, similar to type 2 diabetes, is characterized by an impaired incretin effect and inappropriate glucagon responses, whereas incretin effect and gluca-gon response to oral glucose remain unaffected in GCK-diabetes, reflecting important pathogenetic differences between the two MODY forms.

Patients with established type 2 diabetes display both beta-cell dysfunction and insulin resistance. To define fundamental processes leading to the diabetic state, we examined the relationship between type 2 diabetes risk variants at 37 established susceptibility loci, and indices of proinsulin processing, insulin secretion, and insulin sensitivity. We included data from up to 58,614 nondiabetic subjects with basal measures and 17,327 with dynamic measures. We used additive genetic models with adjustment for sex, age, and BMI, followed by fixed-effects, inverse-variance meta-analyses. Cluster analyses grouped risk loci into five major categories based on their relationship to these continuous glycemic phenotypes. The first cluster (PPARG, KLF14, IRS1, GCKR) was characterized by primary effects on insulin sensitivity. The second cluster (MTNR1B, GCK) featured risk alleles associated with reduced insulin secretion and fasting hyperglycemia. ARAP1 constituted a third cluster characterized by defects in insulin processing. A fourth cluster (TCF712, SLC30A8, HHEX/IDE, CDKAL1, CDKN2A/2B) was defined by loci influencing insulin processing and secretion without a detectable change in fasting glucose levels. The final group contained 20 risk loci with no clear-cut associations to continuous glycemic traits. By assembling extensive data on continuous glycemic traits, we have exposed the diverse mechanisms whereby type 2 diabetes risk variants impact disease predisposition. Patients with established type 2 diabetes display both b-cell dysfunction and insulin resistance. To define fundamental processes leading to the diabetic state, we examined the relationship between type 2 diabetes risk variants at 37 established susceptibility loci, and indices of proinsulin processing, insulin secretion, and insulin sensitivity. We included data from up to 58,614 nondiabetic subjects with basal measures and 17,327 with dynamic measures. We used additive genetic models with adjustment for sex, age, and BMI, followed by fixed-effects, inverse-variance meta-analyses. Cluster analyses grouped risk loci into five major categories based on their relationship to these continuous glycemic phenotypes. The first cluster (PPARG, KLF14, IRS1, GCKR) was characterized by primary effects on insulin sensitivity. The second cluster (MTNR1B, GCK) featured risk alleles associated with reduced insulin secretion and fasting hyperglycemia. ARAP1 constituted a third cluster characterized by defects in insulin processing. A fourth cluster (TCF7L2, SLC30A8, HHEX/IDE, CDKAL1, CDKN2A/2B) was defined by loci influencing insulin processing and secretion without a detectable change in fasting glucose levels. The final group contained 20 risk loci with no clear-cut associations to continuous glycemic traits. By assembling extensive data on continuous glycemic traits, we have exposed the diverse mechanisms whereby type 2 diabetes risk variants impact disease predisposition.

OBJECTIVE We studied whether patterns of glucose absorption during oral glucose tolerance tests (OGTTs) were abnormal in individuals with impaired glucose regulation and whether they were related to sex and body size (height and fat-free mass). We also examined how well differences in insulin sensitivity and β-cell function measured by gold-standard tests were reflected in the corresponding OGTT-derived estimates. RESEARCH DESIGN AND METHODS With validated methods, various aspects of glucose absorption were estimated from 12-point, 3-h, 75-g OGTTs in 66 individuals with normal glucose tolerance (NGT), isolated impaired fasting glucose (i-IFG), or isolated impaired glucose tolerance (i-IGT). Insulin sensitivity and β-cell function were measured with the euglycemic-hyperinsulinemic clamp and intravenous glucose tolerance tests, respectively. Surrogate markers of both conditions were calculated from OGTTs. RESULTS More rapid glucose absorption (P ≤ 0.036) and reduced late glucose absorption (P ≤ 0.039) were observed in the i-IFG group relative to NGT and i-IGT groups. Women with i-IGT had a lower early glucose absorption than did men with i-IGT (P = 0.041); however, this difference did not persist when differences in body size were taken into account (P > 0.28). Faster glucose absorption was related to higher fasting (P = 0.001) and lower 2-h (P = 0.001) glucose levels and to greater height and fat-free mass (P < 0.001). All OGTT-derived measures of insulin sensitivity, but only one of three measures of β-cell function, reflected the differences for these parameters between those with normal and impaired glucose regulation as measured by gold-standard tests. CONCLUSIONS Glucose absorption patterns during an OGTT are significantly related to plasma glucose levels and body size, which should be taken into account when estimating β-cell function from OGTTs in epidemiological studies.

OBJECTIVE Genome-wide association studies and linkage studies have identified 20 validated genetic variants associated with obesity and/or related phenotypes. The variants are common, and they individually exhibit small-to-modest effect sizes. RESEARCH DESIGN AND METHODS In this study we investigate the combined effect of these variants and their ability to discriminate between normal weight and overweight/obese individuals. We applied receiver operating characteristics (ROC) curves, and estimated the area under the ROC curve (AUC) as a measure of the discriminatory ability. The analyses were performed cross-sectionally in the population-based Inter99 cohort where 1,725 normal weight, 1,519 overweight, and 681 obese individuals were successfully genotyped for all 20 variants. RESULTS When combining all variants, the 10% of the study participants who carried more than 22 risk-alleles showed a significant increase in probability of being both overweight with an odds ratio of 2.00 (1.47–2.72), P = 4.0 × 10−5, and obese with an OR of 2.62 (1.76–3.92), P = 6.4 × 10−7, compared with the 10% of the study participants who carried less than 14 risk-alleles. Discrimination ability for overweight and obesity, using the 20 single nucleotide polymorphisms (SNPs), was determined to AUCs of 0.53 and 0.58, respectively. When combining SNP data with conventional nongenetic risk factors of obesity, the discrimination ability increased to 0.64 for overweight and 0.69 for obesity. The latter is significantly higher (P < 0.001) than for the nongenetic factors alone (AUC = 0.67). CONCLUSIONS The discriminative value of the 20 validated common obesity variants is at present time sparse and too weak for clinical utility, however, they add to increase the discrimination ability of conventional nongenetic risk factors.

OBJECTIVE The aim of this study was to determine whether the type 2 diabetes–associated T-allele of transcription factor 7-like 2 (TCF7L2) rs7903146 associates with impaired insulin secretion to compensate for insulin resistance induced by bed rest. RESEARCH DESIGN AND METHODS A total of 38 healthy young Caucasian men were studied before and after bed rest using the hyperinsulinemic-euglycemic clamp technique combined with indirect calorimetry preceded by an intravenous glucose tolerance test. The TCF7L2 rs7903146 was genotyped using allelic discrimination performed with an ABI 7900 system. The genetic analyses were done assuming a dominant model of inheritance. RESULTS The first-phase insulin response (FPIR) was significantly lower in carriers of the T-allele compared with carriers of the CC genotype before bed rest, with and without correction for insulin resistance. The incremental rise of FPIR in response to insulin resistance induced by bed rest was lower in carriers of the T-allele (P < 0.001). Fasting plasma glucagon levels were significantly lower in carriers of the T-allele before and after bed rest. While carriers of the CC genotype developed increased hepatic insulin resistance, the TCF7L2 rs7903146 did not influence peripheral insulin action or the rate of lipolysis before or after bed rest. CONCLUSIONS Healthy carriers of the T-allele of TCF7L2 rs7903146 exhibit a diminished increase of insulin secretion in response to intravenous glucose to compensate for insulin resistance as induced by bed rest. Reduced paracrine glucagon stimulation may contribute to the impairment of β-cell function in the carriers TCF7L2 rs7903146 T-allele associated with increased risk of type 2 diabetes.

OBJECTIVE Genome-wide association studies have identified several variants within the MTNR1B locus that are associated with fasting plasma glucose (FPG) and type 2 diabetes. We refined the association signal by direct genotyping and examined for associations of the variant displaying the most independent effect on FPG with isolated impaired fasting glycemia (i-IFG), isolated impaired glucose tolerance (i-IGT), type 2 diabetes, and measures of insulin release and peripheral and hepatic insulin sensitivity. RESEARCH DESIGN AND METHODS We examined European-descent participants in the Inter99 study (n = 5,553), in a sample of young healthy Danes (n = 372), in Danish twins (n = 77 elderly and n = 97 young), in additional Danish type 2 diabetic patients (n = 1,626) and control subjects (n = 505), in the Data from the Epidemiological Study on the Insulin Resistance Syndrome (DESIR) study (n = 4,656), in the North Finland Birth Cohort 86 (n = 5,258), and in the Haguenau study (n = 1,461). RESULTS The MTNR1B intronic variant, rs10830963, carried most of the effect on FPG and showed the strongest association with FPG (combined P = 5.3 × 10−31) and type 2 diabetes. The rs10830963 G-allele increased the risk of i-IFG (odds ratio [OR] 1.64, P = 5.5 × 10−11) but not i-IGT. The G-allele was associated with a decreased insulin release after oral and intravenous glucose challenges (P < 0.01) but not after injection of tolbutamide. In elderly twins, the G-allele associated with hepatic insulin resistance (P = 0.017). CONCLUSIONS The G-allele of MTNR1B rs10830963 increases risk of type 2 diabetes through a state of i-IFG and not through i-IGT. The same allele associates with estimates of β-cell dysfunction and hepatic insulin resistance.

OBJECTIVE— We evaluated the impact on diabetes-related intermediary traits of common novel type 2 diabetes–associated variants in the JAZF1 (rs864745), CDC123/CAMK1D (rs12779790), TSPAN8 (rs7961581), THADA (rs7578597), ADAMTS9 (rs4607103), and NOTCH2 (rs10923931) loci, which were recently identified by meta-analysis of genome-wide association data. RESEARCH DESIGN AND METHODS— We genotyped the six variants in 4,516 middle-aged glucose-tolerant individuals of the population-based Inter99 cohort who were all characterized by an oral glucose tolerance test (OGTT). RESULTS— Homozygous carriers of the minor diabetes risk G-allele of the CDC123/CAMK1D rs12779790 showed an 18% decrease in insulinogenic index (95% CI 10–27%; P = 4 × 10−5), an 18% decrease in corrected insulin response (CIR) (8.1–29%; P = 4 × 10−4), and a 13% decrease in the ratio of area under the serum-insulin and plasma-glucose curves during an OGTT (AUC-insulin/AUC-glucose) (5.8–20%; P = 4 × 10−4). Carriers of the diabetes-associated T-allele of JAZF1 rs864745 had an allele-dependent 3% decrease in BIGTT-AIR (0.9–4.3%; P = 0.003). Furthermore, the diabetes-associated C-allele of TSPAN8 rs7961581 associated with decreased levels of CIR (4.5% [0.5–8.4]; P = 0.03), of AUC-insulin/AUC-glucose ratio (3.9% [1.2–6.7]; P = 0.005), and of the insulinogenic index (5.2% [1.9–8.6]; P = 0.002). No association with traits of insulin release or insulin action was observed for the THADA, ADAMTS9, or NOTCH2 variants. CONCLUSIONS— If replicated, our data suggest that type 2 diabetes at-risk alleles in the JAZF1, CDC123/CAMK1D, and TSPAN8 loci associate with various OGTT-based surrogate measures of insulin release, emphasizing the contribution of abnormal pancreatic β-cell function in the pathogenesis of type 2 diabetes.

OBJECTIVE—The gene encoding the α2 Heremans-Schmid glycoprotein (AHSG) is a credible biological and positional candidate gene for type 2 diabetes and the metabolic syndrome, and previous attempts to relate AHSG variation with type 2 diabetes and obesity in Swedish and French Caucasians have been largely successful. We related seven frequent AHSG tag single nucleotide polymorphisms to a range of metabolic traits, including type 2 diabetes, obesity, and dyslipidemia. RESEARCH DESIGN AND METHODS—The polymorphisms were genotyped in 7,683 white Danish subjects using Taqman allelic discrimination or chip-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, providing a statistical power of >99% to replicate previous findings. Data were analyzed in case-control and haplotype settings, and quantitative metabolic traits were examined for association. Moreover, epistatic effects between AHSG variants and insulin receptor substrate-1 (IRS1) and β-2-adrenergic receptor polymorphisms were investigated. RESULTS—The −469T>G (rs2077119) and IVS6+98C>T (rs2518136) polymorphisms were associated with type 2 diabetes (P = 0.007 and P = 0.006, respectively, or Pcorr = 0.04 and Pcorr = 0.03, respectively, following correction for multiple hypothesis testing), and in a combined analysis of the present and a previous study −469T>G remained significant (odds ratio 0.90 [95% CI 0.84–0.97]; P = 0.007). Furthermore, two AHSG haplotypes were associated with dyslipidemia (P = 0.003 and Pcorr = 0.009). Thr248Met (rs4917) tended to associate with lower fasting and post–oral glucose tolerance test serum insulin release (P = 0.02, Pcorr = 0.1 for fasting and P = 0.04, Pcorr = 0.2 for area under the insulin curve) and improved insulin sensitivity estimated by the homeostasis model assessment of insulin resistance (9.0 vs. 8.6 mmol · l−1 · pmol−1 · l−1; P = 0.01, Pcorr = 0.06). Indications of epistatic effects of AHSG variants with the IRS1 Gly971Arg polymorphism were observed for fasting serum triglyceride concentrations. CONCLUSIONS—Based on present and previous findings, common variation in AHSG may contribute to the interindividual variation in metabolic traits.

OBJECTIVE—We evaluated the association of variants in the sterol regulatory element-binding factor 1 gene (SREBF1) with type 2 diabetes. Due to the previous inconclusive quantitative trait associations, we also did studies of intermediate quantitative phenotypes. RESEARCH DESIGN AND METHODS—We genotyped four variants in SREBF1 in the population-based Inter99 cohort (n = 6,070), the Danish ADDITION study (n = 8,662), and in additional type 2 diabetic patients (n = 1,002). The case-control studies involved 2,980 type 2 diabetic patients and 4,522 glucose-tolerant subjects. RESULTS—The minor alleles of rs2297508, rs11868035, and rs1889018 (linkage disequilibrium R2 = 0.6–0.8) associated with a modestly increased risk of type 2 diabetes (rs2297508: OR 1.17 [95% CI 1.05–1.30], P = 0.003), which was confirmed in meta-analyses of all published studies (rs2297508 G-allele: 1.08 [1.03–1.14] per allele, P = 0.001). The diabetes-associated alleles also associated strongly with a higher plasma glucose at 30 and 120 min and serum insulin at 120 min during an oral glucose tolerance test (all P < 0.006) and the minor allele of rs1889018 with a surrogate measure of insulin sensitivity (P = 0.03). Furthermore, the diabetes-associated alleles associated with a modestly increased A1C level in the population-based Inter99 of middle-aged subjects and in the ADDITION study of high-risk individuals (P = 0.006 and P = 0.008, respectively). CONCLUSIONS—We associate sequence variation in SREBF1 with a modestly increased predisposition to type 2 diabetes. In the general population, the diabetes-associated alleles are discreetly associated with hyperglycemia presumably due to decreased insulin sensitivity. Because sterol regulatory element–binding protein-1c is a mediator of insulin action, the findings are consistent with the presence of a yet undefined subtle loss-of-function SREBF1 variant.

OBJECTIVE—The role of intrauterine hyperglycemia and future risk of type 2 diabetes in human offspring is debated. We studied glucose tolerance in adult offspring of women with either gestational diabetes mellitus (GDM) or type 1 diabetes, taking the impact of both intrauterine hyperglycemia and genetic predisposition to type 2 diabetes into account. RESEARCH DESIGN AND METHODS—The glucose tolerance status following a 2-h 75-g oral glucose tolerance test (OGTT) was evaluated in 597 subjects, primarily Caucasians, aged 18–27 years. They were subdivided into four groups according to maternal glucose metabolism during pregnancy and genetic predisposition to type 2 diabetes: 1) offspring of women with diet-treated GDM (O-GDM), 2) offspring of genetically predisposed women with a normal OGTT (O-NoGDM), 3) offspring of women with type 1 diabetes (O-type 1), and 4) offspring of women from the background population (O-BP). RESULTS—The prevalence of type 2 diabetes and pre-diabetes (impaired glucose tolerance or impaired fasting glucose) in the four groups was 21, 12, 11, and 4%, respectively. In multiple logistic regression analysis, the adjusted odds ratios (ORs) for type 2 diabetes/pre-diabetes were 7.76 (95% CI 2.58–23.39) in O-GDM and 4.02 (1.31–12.33) in O-type 1 compared with O-BP. In O-type 1, the risk of type 2 diabetes/pre-diabetes was significantly associated with elevated maternal blood glucose in late pregnancy: OR 1.41 (1.04–1.91) per mmol/l. CONCLUSIONS—A hyperglycemic intrauterine environment appears to be involved in the pathogenesis of type 2 diabetes/pre-diabetes in adult offspring of primarily Caucasian women with either diet-treated GDM or type 1 diabetes during pregnancy.

OBJECTIVE—In recent genome-wide association studies, two single nucleotide polymorphisms (SNPs) near the HHEX locus were shown to be more frequent in type 2 diabetic patients than in control subjects. Based on HHEX's function during embryonic development of the ventral pancreas in mice, we investigated whether these SNPs affect β-cell function in humans. RESEARCH DESIGN AND METHODS—A total of 854 nondiabetic subjects, collected from five European clinical centers, were genotyped for the HHEX SNPs rs1111875 and rs7923837 and thoroughly characterized by an oral glucose tolerance test (OGTT). To assess glucose-stimulated insulin release, a subgroup of 758 subjects underwent an intravenous glucose tolerance test (IVGTT). RESULTS—SNPs rs1111875 and rs7923837 were not associated with anthropometric data (age, weight, height, BMI, body fat, and waist and hip circumference). After adjustment for center, family relationship, sex, age, and BMI, both SNPs were also not associated with glucose and insulin concentrations in the fasting state and during the OGTT or with measures of insulin sensitivity. Furthermore, HHEX SNP rs1111875 was not associated with insulin release during the IVGTT. By contrast, the minor A-allele of HHEX SNP rs7923837 was significantly associated with higher IVGTT-derived first-phase insulin release before and after appropriate adjustment (P = 0.013 and P = 0.014, respectively). CONCLUSIONS—A common genetic variation in the 3′-flanking region of the HHEX locus, i.e., SNP rs7923837, is associated with altered glucose-stimulated insulin release. This SNP's major allele represents a risk allele for β-cell dysfunction and, thus, might confer increased susceptibility of β-cells toward adverse environmental factors.

OBJECTIVE— In the present study, we aimed to validate the type 2 diabetes susceptibility alleles identified in six recent genome-wide association studies in the HHEX/KIF11/IDE (rs1111875), CDKN2A/B (rs10811661), and IGF2BP2 (rs4402960) loci, as well as the intergenic rs9300039 variant. Furthermore, we aimed to characterize quantitative metabolic risk phenotypes of the four variants. RESEARCH DESIGN AND METHODS— The variants were genotyped in the population-based Inter99 cohort (n = 5,970), the ADDITION Study (n = 1,626), a population-based sample of young healthy subjects (n = 377), and in additional type 2 diabetic case (n = 2,111) and glucose-tolerant (n = 521) subjects. The case-control studies involved a total of 4,089 type 2 diabetic patients and 5,043 glucose-tolerant control subjects. RESULTS— We validated association of variants near HHEX/KIF11/IDE, CDKN2A/B, and IGF2BP2 with type 2 diabetes. Interestingly, in middle-aged people, the rs1111875 C-allele of HHEX/KIF11/IDE strongly associated with lower acute insulin response during an oral glucose tolerance test (P = 6 × 10−7). In addition, decreased insulin release following intravenous tolbutamide injection was observed in young healthy subjects (P = 0.02). Also, a reduced insulin release was observed for the CDKN2A/B rs10811661 T-allele after both oral and intravenous glucose challenges (P = 0.001 and P = 0.009, respectively). CONCLUSIONS— We validate that variants in the proximity of the HHEX/KIF11/IDE, CDKN2A/B, and IFG2BP2 loci associate with type 2 diabetes. Importantly, variations within the HHEX/KIF11/IDE and CDKN2A/B loci confer impaired glucose- and tolbutamide-induced insulin release in middle-aged and young healthy subjects, suggesting a role for these variants in the pathogenesis of pancreatic β-cell dysfunction.

Mutations in LMNA encoding lamin A and C proteins cause monogenic syndromes characterized by muscular dystrophy and familial partial lipodystrophy. Eight tag single nucleotide polymorphisms in the LMNA locus were genotyped in 7,495 Danish whites and related to metabolic and anthropometric traits. The minor T-allele of rs4641 was nominally associated with type 2 diabetes (odds ratio 1.14 [95% CI 1.03–1.26], P = 0.01) in a study of 1,324 type 2 diabetic patients and 4,386 glucose-tolerant subjects and with elevated fasting plasma glucose levels in a population-based study of 5,395 middle-aged individuals (P = 0.008). The minor T-allele of rs955383 showed nominal association with obesity in a study of 5,693 treatment-naïve subjects (1.25 [1.07–1.64], P = 0.01), and after dichotomization of waist circumference, the minor alleles of rs955383 and rs11578696 were nominally associated with increased waist circumference (1.14 [1.04–1.23], P = 0.003; 1.12 [1.00–1.25], P = 0.04). The minor G-allele of rs577492 was associated with elevated fasting serum cholesterol and short stature (P = 3.0 · 10−5 and P = 7.0 · 10−4). The findings are not corrected for multiple comparisons and are by nature exploratory. However, if replicated, these findings suggest that less severe variation in a gene locus known to harbor severe mutations causing monogenic syndromes may modestly increase susceptibility to common metabolic and anthropometrical phenotypes of polygenic origin.

OBJECTIVE—Insulin resistance and impaired β-cell function are key elements in the pathogenesis of type 2 diabetes. We aimed to develop valid algorithms for estimation of the insulin sensitivity index (SI) and acute insulin response (AIR) derived from simple and cheap physiological measurements that could be used in large-scale metabolic, genetic, and epidemiological studies. RESEARCH DESIGN AND METHODS—For our purpose, data from an oral glucose tolerance test (OGTT) (18 samples during 240 min) and a tolbutamide-modified intravenous glucose tolerance test (IVGTT) (33 samples during 180 min) from 258 individuals with fasting plasma glucose RESULTS—We demonstrate that it is possible to obtain estimates of SI (BIGTT-SI) and AIR (BIGTT-AIR) that are highly correlated to IVGTT-derived values of SI (R2 = 0.77) and AIR (R2 = 0.54). In the two validation datasets we obtained similar results. CONCLUSIONS—Data from OGTTs can provide accurate measures of insulin sensitivity and β-cell function, which can be used in large scale metabolic, genetic, and epidemiological studies.

The short-chain l-3-hydroxyacyl-CoA dehydrogenase (SCHAD) protein is involved in the penultimate step of mitochondrial fatty acid oxidation. Previously, it has been shown that mutations in the corresponding gene (HADHSC) are associated with hyperinsulinism in infancy. The presumed function of the SCHAD enzyme in glucose-stimulated insulin secretion led us to the hypothesis that common variants in HADHSC on chromosome 4q22-26 might be associated with development of type 2 diabetes. In this study, we have performed a large-scale association study in four different cohorts from the Netherlands and Denmark (n = 7,365). Direct sequencing of HADHSC cDNA and databank analysis identified four tagging single nucleotide polymorphisms (SNPs) including one missense variant (P86L). Neither the SNPs nor haplotypes investigated were associated with the disease, enzyme function, or any relevant quantitative measure (all P > 0.1). The present study provides no evidence that the specific HADHSC variants or haplotypes examined do influence susceptibility to develop type 2 diabetes. We conclude that it is unlikely that variation in HADHSC plays a major role in the pathogenesis of type 2 diabetes in the examined cohorts.

Recently, it has been shown that mutations in the P2 promoter of the hepatocyte nuclear factor (HNF)-4α gene (HNF4A) cause maturity-onset diabetes of the young (MODY), while single nucleotide polymorphisms in this locus are associated with type 2 diabetes. In this study, we examined 1,189 bp of the P2 promoter and the associated exon 1D of HNF4A for variations associated with diabetes in 114 patients with type 2 diabetes, 72 MODYX probands, and 85 women with previous gestational diabetes mellitus. A −192c/g mutation was found in five patients. We screened 1,587 diabetic subjects and 4,812 glucose-tolerant subjects for the −192c/g mutation and identified 5 diabetic and 1 glucose-tolerant mutation carriers (P = 0.004). Examination of the families showed that carriers of the −192c/g mutation had a significantly impaired glucose-stimulated insulin release and lower levels of serum total cholesterol compared with matched control subjects. Furthermore, the mutation disrupted the binding of an unidentified sequence-specific DNA binding complex present in human islet extracts. Also, two novel linked polymorphisms in the P2 promoter at positions −1107g/t and −858c/t were identified. These variants were not significantly associated with type 2 diabetes or any pre-diabetic traits. In conclusion, a rare, novel mutation that disrupts a protein binding site in the pancreatic HNF4A promoter associates with late-onset diabetes.

Recent data show that homozygous Ncb5or−/− knock-out mice present with an early-onset nonautoimmune diabetes phenotype. Furthermore, genome-wide scans have reported linkage to the chromosome 6q14.2 region close to the human NCB5OR. We therefore considered NCB5OR to be a biological and positional candidate gene and examined the coding region of NCB5OR in 120 type 2 diabetic patients and 63 patients with maturity-onset diabetes of the young using denaturing high-performance liquid chromatography. We identified a total of 22 novel nucleotide variants. Three variants [IVS5+7del(CT), Gln187Arg, and His223Arg] were genotyped in a case-control design comprising 1,246 subjects (717 type 2 diabetic patients and 529 subjects with normal glucose tolerance). In addition, four rare variants were investigated for cosegregation with diabetes in multiplex type 2 diabetic families. The IVS5+7del(CT) variant was associated with common late-onset type 2 diabetes; however, we failed to relate this variant to any diabetes-related quantitative traits among the 529 control subjects. Thus, variation in the coding region of NCB5OR is not a major contributor in the pathogenesis of nonautoimmune diabetes.

Recently, various subtypes of familial hyperinsulinemic hypoglycemia with an autosomal-dominant inheritance have been etiologically characterized. In the present study, we have delineated the genetics and metabolic phenotype of a novel form of hypoglycemia in a large pedigree with an apparent autosomal-dominant transmission. After initial investigations of the proband, her mother, and a sister, the study was extended to 19 family members in three generations. Glucose tolerance was assessed by a 5-h oral glucose tolerance test (OGTT) and insulin sensitivity by euglycemic-hyperinsulinemic clamp in six affected family members and six control subjects. To identify the genetic cause of hypoglycemia, linkage analysis and mutation analysis of genomic DNA from all family members were performed. All affected family members were characterized by postprandial hypoglycemia, fasting hyperinsulinemia, and an elevated serum insulin-to-C-peptide ratio. The 5-h OGTT demonstrated hyperinsulinemic hypoglycemia, and the clamp studies showed reduced insulin sensitivity and clearance of serum insulin in affected family members compared with control subjects. Linkage analysis and subsequent mutation screening revealed a missense mutation (Arg1174Gln) in the tyrosine kinase domain of the insulin receptor gene that cosegregated with the disease phenotype (logarithm of odds [LOD] score 3.21). In conclusion, we report a novel syndrome of autosomal-dominant hyperinsulinemic hypoglycemia. The findings demonstrate the coexistence of severe postprandial hypoglycemia, insulin resistance, and impaired insulin clearance and suggest that hypoglycemia should be considered as a phenotype linked to heterozygote mutations in the insulin receptor gene.

Women with gestational diabetes mellitus (GDM) are known to be at increased risk of having overt diabetes, especially type 2 diabetes, later in life. Most long-term studies, however, involved non-European populations and did not distinguish between dietary and insulin treatment. The investigators determined the long-term risk of diabetes in Danish women having diet-treated GDM. An "old" cohort of 241 women presented in 1978-1985 and followed up for 2 to 11 years. A "new" cohort of 512 women presented at the same center in 1987-1996 and were reassessed in 2000-2002. The oral glucose tolerance test, done using 50 or 75 g of glucose, was read as abnormal if at least 2 of 7 blood glucose values exceeded 3 standard deviations above the mean for nonpregnant women. A total of 481 women, nearly two thirds of the total, were followed up a median of 9.8 years after the index pregnancy. Diabetes was present at follow up in 40% of women and impaired glucose tolerance or impaired fasting glucose in 27%. Type 2 diabetes was diagnosed in 171 of 192 patients affected. All 12 women with overt diabetes in the postpartum period had diabetes at follow up. The incidence of diabetes was more than 2-fold higher in the new cohort than in the old one in 1990, but rates were similar at follow up in 2002. On multiple logistic regression analysis, diabetes was independently associated with being in the new cohort, overweight or obesity before pregnancy, an early diagnosis of GDM, a high fasting glucose at the time of oral glucose tolerance testing, and impaired glucose tolerance in the postpartum period. This study demonstrated a doubling in the incidence of diabetes and impaired glucose tolerance or impaired fasting glucose over a 10-year period in women having diet-treated GDM. Prepregnancy obesity further increased the risk, suggesting that timely intervention might prevent or delay the development of overt diabetes.

The SLC2A10 gene encodes the GLUT10 facilitative glucose transporter, which is expressed in high amounts in liver and pancreas. The gene is mapped to chromosome 20q12-q13.1, a region that has been shown to be linked to type 2 diabetes. The gene was examined in 61 Danish type 2 diabetic patients, and a total of six variants (−27C→T, Ala206Thr, Ala272Ala, IVS2 + 10G→A, IVS4 + 18T→G, and IVS4 + 26G→A) were identified and investigated in an association study, which included 503 type 2 diabetic patients and 510 glucose-tolerant control subjects. None of the variants were associated with type 2 diabetes. Interestingly, carriers of the codon 206 Thr allele had 18% lower fasting serum insulin levels (P = 0.002) and 20% lower insulinogenic index (P = 0.03) than homozygous carriers of the Ala allele. These results suggest that variation in the coding region of SLC2A10 does not contribute substantially to the pathogenesis of type 2 diabetes in the examined study population. However, the codon 206 polymorphism may be related to the interindividual variation in fasting and oral glucose-induced serum insulin levels.

Maturity-onset diabetes of the young (MODY) is a heterogeneous single gene disorder characterized by non–insulin-dependent diabetes, an early onset and autosomal dominant inheritance. Mutations in six genes have been shown to cause MODY. Approximately 15–20% of families fitting MODY criteria do not have mutations in any of the known genes. These families provide a rich resource for the identification of new MODY genes. This will potentially enable further dissection of clinical heterogeneity and bring new insights into mechanisms of β-cell dysfunction. To facilitate the identification of novel MODY loci, we combined the results from three genome-wide scans on a total of 23 families fitting MODY criteria. We used both a strict parametric model of inheritance with heterogeneity and a model-free analysis. We did not identify any single novel locus but provided putative evidence for linkage to chromosomes 6 (nonparametric linkage [NPL]score 2.12 at 71 cM) and 10 (NPL score 1.88 at 169–175 cM), and to chromosomes 3 (heterogeneity LOD [HLOD] score 1.27 at 124 cM) and 5 (HLOD score 1.22 at 175 cM) in 14 more strictly defined families. Our results provide evidence for further heterogeneity in MODY.

The Pro12Ala polymorphism in the PPARγ2 gene has been associated with reduced risk of type 2 diabetes and insulin resistance. Recently, an association between dizygotic twinning and PPARγ gene polymorphisms has been proposed. We investigated the phenotypic appearance of the two polymorphisms (Pro12Ala and exon 6 C→T) in PPARγ among elderly twins (207 monozygotic [MZ] and 342 dizygotic [DZ]) and evaluated whether they could explain previously reported differences in plasma glucose and insulin profiles among MZ and DZ twins. We demonstrated a significant impact of the Pro12Ala polymorphism on glucose tolerance, diabetic status, homeostasis model assessment for insulin resistance, and plasma insulin profiles in twins. No impact of the silent exon 6 polymorphism on glucose homeostasis or plasma insulin profiles was found. Independent of the polymorphisms, we observed a significant impact of zygosity status per se on the plasma insulin profile after oral glucose ingestion, with the MZ twins being more hyperinsulinemic, indicating insulin resistance, than the DZ twins. Nonsignificantly higher glucose concentrations were observed among MZ compared with DZ twins. We demonstrated an association between the Ala allele and reduced risk of diabetes and insulin resistance in twins. However, the differences in metabolic profiles among MZ and DZ twins were not explained by differences in frequencies of the genetic variants and may be due to intrauterine environmental factors operating in twins independent of genotype. Accordingly, our study simultaneously supports a role for both the intrauterine environment (thrifty phenotype) and for genetics (thrifty genotype) in the etiology of insulin resistance and perhaps glucose intolerance in twins.

In this study, a second case of hyperinsulinemic hypoglycemia due to activation of glucokinase is reported. The 14-year-old proband had a history of neonatal hypoglycemia, treated with diazoxide. He was admitted with coma and convulsions due to nonketotic hypoglycemia. His BMI was 34 kg/m2, and his fasting blood glucose ranged from 2.1 to 2.7 mmol/l, associated with inappropriately high serum levels of insulin, C-peptide, and proinsulin. An oral glucose tolerance test (OGTT) showed exaggerated responses of these peptides followed by profound hypoglycemia. Treatment with diazoxide and chlorothiazide was effective. His mother never had clinical hypoglycemic symptoms, even though her fasting blood glucose ranged from 2.9 to 3.5 mmol/l. Increases in serum insulin, C-peptide, and proinsulin in response to an OGTT suggested a lower threshold for glucose-stimulated insulin release (GSIR). Screening for mutations in candidate genes revealed a heterozygous glucokinase mutation in exon 10, substituting valine for alanine at codon 456 (A456V) in the proband and his mother. The purified recombinant glutathionyl S-transferase fusion protein of the A456V glucokinase revealed a decreased glucose S0.5 (the concentration of glucose needed to achieve the half-maximal rate of phosphorylation) from 8.04 (wild-type) to 2.53 mmol/l. The mutant’s Hill coefficient was decreased, and its maximal specific activity kcat was increased. Mathematical modeling predicted a markedly lowered GSIR threshold of 1.5 mmol/l. The theoretical and practical implications are manifold and significant.

In humans, the Met326Ile missense variant of the p85α regulatory subunit of the phosphoinositide 3-kinase (PI3K) has been associated with either significant reductions in glucose effectiveness and intravenous glucose tolerance in Caucasians or a significantly higher insulin secretory response in Pima Indians. In the present study, we genotyped 1,190 Caucasian males to evaluate the impact in vivo of the Met326Ile variant of the p85α subunit of PI3K on the acute insulin response, intravenous glucose tolerance, insulin-mediated glucose uptake, and the prevalence of type 2 diabetes after 20 years of follow-up. We also expressed the variant in vitro to evaluate the impact on insulin-stimulated activation of protein kinase B (PKB). The Met326Ile variant of p85α was not associated with type 2 diabetes or with alterations in insulin secretion, insulin sensitivity, or intravenous glucose tolerance in vivo. Expressed in vitro, the Ile326 and the Met326 variant acted equally as a dominant-negative and prevented (60–70% inhibition) insulin-mediated activation of PKB by inhibiting the phosphorylation of PKB at Thr308. We conclude that the Met326Ile variant of the p85α regulatory subunit of PI3K is likely to be as functionally normal in vivo as in vitro.

The human plasma-cell membrane differentiation antigen-1 (PC-1) has been shown to inhibit insulin receptor tyrosine kinase activity. Recently, a K121Q polymorphism in the human PC-1 gene was found in a Sicilian population and was shown to be strongly associated with insulin resistance. The objectives of the present investigation were to examine in the Danish Caucasian population whether the K121Q variant was associated with type 2 diabetes or, in glucose-tolerant subjects, with impaired whole-body insulin sensitivity. We genotyped 404 Danish type 2 diabetic patients and found that the allele frequency of the variant was 0.14 (95% CI 0.12-0.16), whereas the allele frequency was 0.16 (95% CI 0.13-0.19) among 237 matched glucose-tolerant control subjects (P = 0.6). In the control subjects, there were no significant differences among wild-type, heterozygous, or homozygous subjects in regard to 1) serum insulin and plasma glucose levels at fasting, 60 min, or 120 min during an oral glucose tolerance test (OGTT) or 2) the estimates of insulin resistance obtained from the homeostasis model assessment (HOMA). Furthermore, we investigated the impact of the variant in 2 other Danish population samples that comprised 356 young healthy subjects and 226 glucose-tolerant offspring of type 2 diabetic probands, respectively. In all of the study populations, the polymorphism was not associated with an altered insulin sensitivity index as estimated from an intravenous glucose tolerance test in combination with an intravenous injection of tolbutamide. In addition, among the 226 offspring, the variations in serum insulin and serum C-peptide responses measured during an OGTT were not related to the PC-1 genotype. In conclusion, the K121Q polymorphism of the human PC-1 gene is not associated with type 2 diabetes or insulin resistance among Danish Caucasians.

A polymorphism (PP1ARE) in the 3'-untranslated region of the gene encoding the glycogen-associated regulatory subunit of type 1 protein phosphatase PPP1R3 is associated with insulin resistance in Pima Indians. The aim of this study was to investigate whether two common variants in the PPP1R3 gene, Asp905Tyr and PP1ARE, are associated with reduced insulin sensitivity or can predict the development of impaired glucose tolerance (IGT) or type 2 diabetes during a 20-year follow-up period in 696 50-year-old Caucasian men. The allelic frequency of Tyr905 was 0.11 (95% CI 0.09-0.13) and of PP1ARE 0.34 (0.31-0.37) and the two polymorphisms were in linkage disequilibrium (chi2 = 46, P < 0.0001, Fisher's exact test). None of the polymorphisms was associated with the development of IGT or type 2 diabetes, but the PP1ARE polymorphism was weakly correlated to whole-body insulin sensitivity (r = -0.08, P = 0.04). In conclusion, we found no evidence in Swedish men that the PP1ARE or the Asp905Tyr variants over a 20-year period predict the development of IGT or type 2 diabetes, but the PP1ARE polymorphism could have a higher penetrance in other populations.

Phosphatidylinositol 3-kinase (PI3-K) may regulate the basal plasma membrane glucose transporter recycling and the organization of the transporter intracellular pool in addition to being an insulin signal for translocation of glucose transporters to the plasma membrane. The objectives of the present study were to examine for genetic variability in the human regulatory p85α subunit of PI3-K, to look for an association between gene variants and NIDDM in a case-control study, and to relate identified variability to potential changes in whole-body insulin sensitivity and glucose turnover in a phenotype study. Single-strand conformational polymorphism and heteroduplex analysis of the coding region of the regulatory p85α subunit in cDNA isolated from human muscle tissue from 70 insulin-resistant NIDDM patients and 12 control subjects revealed three silent polymorphisms and a missense mutation at nucleotide position 1020 (G→A), changing a Met to He at codon 326. Using allele-specific oligohybridization, we found a similar allelic frequency of the codon 326 Met→Ile variant in 404 NIDDM patients (0.15 [95% CI 0.13–0.17]) and 224 matched glucose tolerant control subjects (0.16 [0.13–0.19]). In a random sample of 380 unrelated healthy young Caucasians aged 18–32 years, in whom we have performed a tolbutamide modified intravenous glucose tolerance test, we identified 263 wildtype subjects, 109 heterozygous subjects, and 8 subjects homozygous for the codon 326 variant (allelic frequency = 0.16 [0.13–0.19]). No difference in glucose disappearance constant ( K G ), insulin sensitivity index ( S I ), and glucose effectiveness ( S G ) was observed between wildtype and heterozygous subjects. However, compared with the combined values for wildtype and heterozygous carriers, K G was reduced by 40% ( P = 0.004) and S G by 23% ( P = 0.03) in homozygous carriers of the p85α variant. Moreover, in homozygous carriers, a 32% reduction was found in SI ( P = 0.08). In conclusion, a codon 326 Met→Ile variant in the gene encoding the PI3-K p85α regulatory subunit is found in 31% of a random sample of young healthy Caucasians. About 2% of the subjects in this population carry the gene variant in its homozygous form, and these carriers are characterized by significant reductions in whole-body glucose effectiveness and intravenous glucose disappearance constant. In itself, the gene variant does not confer an increased risk of diabetes.

In recent genome-wide association studies, two single nucleotide polymorphisms (SNPs) near the HHEX locus were shown to be more frequent in type 2 diabetic patients than in control subjects. Based on HHEX's function during embryonic development of the ventral pancreas in mice, we investigated whether these SNPs affect beta-cell function in humans.A total of 854 nondiabetic subjects, collected from five European clinical centers, were genotyped for the HHEX SNPs rs1111875 and rs7923837 and thoroughly characterized by an oral glucose tolerance test (OGTT). To assess glucose-stimulated insulin release, a subgroup of 758 subjects underwent an intravenous glucose tolerance test (IVGTT).SNPs rs1111875 and rs7923837 were not associated with anthropometric data (age, weight, height, BMI, body fat, and waist and hip circumference). After adjustment for center, family relationship, sex, age, and BMI, both SNPs were also not associated with glucose and insulin concentrations in the fasting state and during the OGTT or with measures of insulin sensitivity. Furthermore, HHEX SNP rs1111875 was not associated with insulin release during the IVGTT. By contrast, the minor A-allele of HHEX SNP rs7923837 was significantly associated with higher IVGTT-derived first-phase insulin release before and after appropriate adjustment (P = 0.013 and P = 0.014, respectively).A common genetic variation in the 3'-flanking region of the HHEX locus, i.e., SNP rs7923837, is associated with altered glucose-stimulated insulin release. This SNP's major allele represents a risk allele for beta-cell dysfunction and, thus, might confer increased susceptibility of beta-cells toward adverse environmental factors.