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[The genome and diabetes.]
Ugeskr. Laeg.
PUBLISHED: 11-15-2014
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In terms of their genetic architecture monogenic diabetes and type 2 diabetes represent two extremes. Whereas each subtype of monogenic diabetes is caused by one penetrant, rare mutation in a single gene, the genetic susceptibility to type 2 diabetes can be attributed to many low-penetrant variants across the genome. At present, only 10% of the genetic susceptibility to type 2 diabetes can be explained by the hitherto identified 90 genomic loci. Here we briefly review the genetics of monogenic diabetes and type 2 diabetes and outline future directions of research within this field.
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[Gut microbiota may influence childhood and adolescent onset obesity.]
Ugeskr. Laeg.
PUBLISHED: 10-09-2014
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Childhood and adolescent onset obesity has reached epidemical proportions worldwide. Recent evidence suggests that obesity is associated with phylogenetic changes in the gut microbiota, which could potentially reveal new avenues for obesity prevention and treatment. A vast number of variables are influencing the gut microbial ecology and though many are proposed, the exact physiological processes behind the relationship are yet to be revealed. This review is focusing on recent advances addressing the potential role of the human gut microbiota in childhood and adolescent onset obesity.
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A glycogene mutation map for discovery of diseases of glycosylation.
Glycobiology
PUBLISHED: 09-28-2014
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Glycosylation of proteins and lipids involves over 200 known glycosyltransferases (GTs), and deleterious defects in many of the genes encoding these enzymes cause disorders collectively classified as congenital disorders of glycosylation (CDGs). Most known CDGs are caused by defects in glycogenes that affect glycosylation globally. Many GTs are members of homologous isoenzyme families and deficiencies in individual isoenzymes may not affect glycosylation globally. In line with this, there appears to be an underrepresentation of disease-causing glycogenes among these larger isoenzyme homologous families. However, genome-wide association studies have identified such isoenzyme genes as candidates for different diseases, but validation is not straightforward without biomarkers. Large-scale whole-exome sequencing (WES) provides access to mutations in, for example, GT genes in populations, which can be used to predict and/or analyze functional deleterious mutations. Here, we constructed a draft of a functional mutational map of glycogenes, GlyMAP, from WES of a rather homogenous population of 2000 Danes. We cataloged all missense mutations and used prediction algorithms, manual inspection and in case of carbohydrate-active enzymes family GT27 experimental analysis of mutations to map deleterious mutations. GlyMAP (http://glymap.glycomics.ku.dk) provides a first global view of the genetic stability of the glycogenome and should serve as a tool for discovery of novel CDGs.
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A combined analysis of 48 type 2 diabetes genetic risk variants shows no discriminative value to predict time to first prescription of a glucose lowering drug in Danish patients with screen detected type 2 diabetes.
PLoS ONE
PUBLISHED: 08-26-2014
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To investigate the genetic influence of 48 type 2 diabetes susceptibility variants on disease progression measured as risk of early prescription redemption of glucose lowering drugs in screen-detected patients with type 2 diabetes.
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FTO genetic variants, dietary intake and body mass index: insights from 177 330 individuals.
Qibin Qi, Tuomas O Kilpeläinen, Mary K Downer, Toshiko Tanaka, Caren E Smith, Ivonne Sluijs, Emily Sonestedt, Audrey Y Chu, Frida Renstrom, Xiaochen Lin, Lars H Angquist, Jinyan Huang, Zhonghua Liu, Yanping Li, Muhammad Asif Ali, Min Xu, Tarunveer Singh Ahluwalia, Jolanda M A Boer, Peng Chen, Makoto Daimon, Johan Eriksson, Markus Perola, Yechiel Friedlander, Yu-Tang Gao, Denise H M Heppe, John W Holloway, Denise K Houston, Stavroula Kanoni, Yu-Mi Kim, Maarit A Laaksonen, Tiina Jääskeläinen, Nanette R Lee, Terho Lehtimäki, Rozenn N Lemaitre, Wei Lu, Robert N Luben, Ani Manichaikul, Satu Mannisto, Pedro Marques-Vidal, Keri L Monda, Julius S Ngwa, Louis Pérusse, Frank J A van Rooij, Yong-Bing Xiang, Wanqing Wen, Mary K Wojczynski, Jingwen Zhu, Ingrid B Borecki, Claude Bouchard, Qiuyin Cai, Cyrus Cooper, George V Dedoussis, Panos Deloukas, Luigi Ferrucci, Nita G Forouhi, Torben Hansen, Lene Christiansen, Albert Hofman, Ingegerd Johansson, Torben Jørgensen, Shigeru Karasawa, Kay-Tee Khaw, Mi-Kyung Kim, Kati Kristiansson, Huaixing Li, Xu Lin, Yongmei Liu, Kurt K Lohman, Jirong Long, Vera Mikkilä, Dariush Mozaffarian, Kari North, Oluf Pedersen, Olli Raitakari, Harri Rissanen, Jaakko Tuomilehto, Yvonne T van der Schouw, André G Uitterlinden, M Carola Zillikens, Oscar H Franco, E Shyong Tai, Xiao Ou Shu, David S Siscovick, Ulla Toft, W M Monique Verschuren, Peter Vollenweider, Nicholas J Wareham, Jacqueline C M Witteman, Wei Zheng, Paul M Ridker, Jae H Kang, Liming Liang, Majken K Jensen, Gary C Curhan, Louis R Pasquale, David J Hunter, Karen L Mohlke, Matti Uusitupa, L Adrienne Cupples, Tuomo Rankinen, Marju Orho-Melander, Tao Wang, Daniel I Chasman, Paul W Franks, Thorkild I A Sørensen, Frank B Hu, Ruth J F Loos, Jennifer A Nettleton, Lu Qi.
Hum. Mol. Genet.
PUBLISHED: 08-07-2014
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FTO is the strongest known genetic susceptibility locus for obesity. Experimental studies in animals suggest the potential roles of FTO in regulating food intake. The interactive relation among FTO variants, dietary intake and body mass index (BMI) is complex and results from previous often small-scale studies in humans are highly inconsistent. We performed large-scale analyses based on data from 177 330 adults (154 439 Whites, 5776 African Americans and 17 115 Asians) from 40 studies to examine: (i) the association between the FTO-rs9939609 variant (or a proxy single-nucleotide polymorphism) and total energy and macronutrient intake and (ii) the interaction between the FTO variant and dietary intake on BMI. The minor allele (A-allele) of the FTO-rs9939609 variant was associated with higher BMI in Whites (effect per allele = 0.34 [0.31, 0.37] kg/m(2), P = 1.9 × 10(-105)), and all participants (0.30 [0.30, 0.35] kg/m(2), P = 3.6 × 10(-107)). The BMI-increasing allele of the FTO variant showed a significant association with higher dietary protein intake (effect per allele = 0.08 [0.06, 0.10] %, P = 2.4 × 10(-16)), and relative weak associations with lower total energy intake (-6.4 [-10.1, -2.6] kcal/day, P = 0.001) and lower dietary carbohydrate intake (-0.07 [-0.11, -0.02] %, P = 0.004). The associations with protein (P = 7.5 × 10(-9)) and total energy (P = 0.002) were attenuated but remained significant after adjustment for BMI. We did not find significant interactions between the FTO variant and dietary intake of total energy, protein, carbohydrate or fat on BMI. Our findings suggest a positive association between the BMI-increasing allele of FTO variant and higher dietary protein intake and offer insight into potential link between FTO, dietary protein intake and adiposity.
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Glucose-lowering effects and low risk of hypoglycemia in patients with maturity-onset diabetes of the young when treated with a GLP-1 receptor agonist: a double-blind, randomized, crossover trial.
Diabetes Care
PUBLISHED: 06-16-2014
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The most common form of maturity-onset diabetes of the young (MODY), hepatocyte nuclear factor 1? (HNF1A diabetes: MODY3) is often treated with sulfonylureas that confer a high risk of hypoglycemia. We evaluated treatment with GLP-1 receptor agonists (GLP-1RAs) in patients with HNF1A diabetes.
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Gene-lifestyle interaction and type 2 diabetes: the EPIC interact case-cohort study.
PLoS Med.
PUBLISHED: 05-01-2014
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Understanding of the genetic basis of type 2 diabetes (T2D) has progressed rapidly, but the interactions between common genetic variants and lifestyle risk factors have not been systematically investigated in studies with adequate statistical power. Therefore, we aimed to quantify the combined effects of genetic and lifestyle factors on risk of T2D in order to inform strategies for prevention.
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Genetic susceptibility to type 2 diabetes and obesity: from genome-wide association studies to rare variants and beyond.
Diabetologia
PUBLISHED: 04-22-2014
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During the past 7 years, genome-wide association studies have shed light on the contribution of common genomic variants to the genetic architecture of type 2 diabetes, obesity and related intermediate phenotypes. The discoveries have firmly established more than 175 genomic loci associated with these phenotypes. Despite the tight correlation between type 2 diabetes and obesity, these conditions do not appear to share a common genetic background, since they have few genetic risk loci in common. The recent genetic discoveries do however highlight specific details of the interplay between the pathogenesis of type 2 diabetes, insulin resistance and obesity. The focus is currently shifting towards investigations of data from targeted array-based genotyping and exome and genome sequencing to study the individual and combined effect of low-frequency and rare variants in metabolic disease. Here we review recent progress as regards the concepts, methodologies and derived outcomes of studies of the genetics of type 2 diabetes and obesity, and discuss avenues to be investigated in the future within this research field.
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An integrated catalog of reference genes in the human gut microbiome.
Nat. Biotechnol.
PUBLISHED: 04-01-2014
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Many analyses of the human gut microbiome depend on a catalog of reference genes. Existing catalogs for the human gut microbiome are based on samples from single cohorts or on reference genomes or protein sequences, which limits coverage of global microbiome diversity. Here we combined 249 newly sequenced samples of the Metagenomics of the Human Intestinal Tract (MetaHit) project with 1,018 previously sequenced samples to create a cohort from three continents that is at least threefold larger than cohorts used for previous gene catalogs. From this we established the integrated gene catalog (IGC) comprising 9,879,896 genes. The catalog includes close-to-complete sets of genes for most gut microbes, which are also of considerably higher quality than in previous catalogs. Analyses of a group of samples from Chinese and Danish individuals using the catalog revealed country-specific gut microbial signatures. This expanded catalog should facilitate quantitative characterization of metagenomic, metatranscriptomic and metaproteomic data from the gut microbiome to understand its variation across populations in human health and disease.
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Incretin effect and glucagon responses to oral and intravenous glucose in patients with maturity-onset diabetes of the young--type 2 and type 3.
Diabetes
PUBLISHED: 03-27-2014
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Maturity-onset diabetes of the young (MODY) is a clinically and genetically heterogeneous subgroup of nonautoimmune 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? (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.
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Pleiotropic genes for metabolic syndrome and inflammation.
Mol. Genet. Metab.
PUBLISHED: 02-25-2014
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Metabolic syndrome (MetS) has become a health and financial burden worldwide. The MetS definition captures clustering of risk factors that predict higher risk for diabetes mellitus and cardiovascular disease. Our study hypothesis is that additional to genes influencing individual MetS risk factors, genetic variants exist that influence MetS and inflammatory markers forming a predisposing MetS genetic network. To test this hypothesis a staged approach was undertaken. (a) We analyzed 17 metabolic and inflammatory traits in more than 85,500 participants from 14 large epidemiological studies within the Cross Consortia Pleiotropy Group. Individuals classified with MetS (NCEP definition), versus those without, showed on average significantly different levels for most inflammatory markers studied. (b) Paired average correlations between 8 metabolic traits and 9 inflammatory markers from the same studies as above, estimated with two methods, and factor analyses on large simulated data, helped in identifying 8 combinations of traits for follow-up in meta-analyses, out of 130,305 possible combinations between metabolic traits and inflammatory markers studied. (c) We performed correlated meta-analyses for 8 metabolic traits and 6 inflammatory markers by using existing GWAS published genetic summary results, with about 2.5 million SNPs from twelve predominantly largest GWAS consortia. These analyses yielded 130 unique SNPs/genes with pleiotropic associations (a SNP/gene associating at least one metabolic trait and one inflammatory marker). Of them twenty-five variants (seven loci newly reported) are proposed as MetS candidates. They map to genes MACF1, KIAA0754, GCKR, GRB14, COBLL1, LOC646736-IRS1, SLC39A8, NELFE, SKIV2L, STK19, TFAP2B, BAZ1B, BCL7B, TBL2, MLXIPL, LPL, TRIB1, ATXN2, HECTD4, PTPN11, ZNF664, PDXDC1, FTO, MC4R and TOMM40. Based on large data evidence, we conclude that inflammation is a feature of MetS and several gene variants show pleiotropic genetic associations across phenotypes and might explain a part of MetS correlated genetic architecture. These findings warrant further functional investigation.
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Discovery of biomarkers for glycaemic deterioration before and after the onset of type 2 diabetes: rationale and design of the epidemiological studies within the IMI DIRECT Consortium.
Diabetologia
PUBLISHED: 02-24-2014
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The DIRECT (Diabetes Research on Patient Stratification) Study is part of a European Union Framework 7 Innovative Medicines Initiative project, a joint undertaking between four industry and 21 academic partners throughout Europe. The Consortium aims to discover and validate biomarkers that: (1) predict the rate of glycaemic deterioration before and after type 2 diabetes onset; (2) predict the response to diabetes therapies; and (3) help stratify type 2 diabetes into clearly definable disease subclasses that can be treated more effectively than without stratification. This paper describes two new prospective cohort studies conducted as part of DIRECT.
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High heritability and genetic correlation of intravenous glucose- and tolbutamide-induced insulin secretion among non-diabetic family members of type 2 diabetic patients.
Diabetologia
PUBLISHED: 02-13-2014
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The aim of this study was to estimate the heritability of quantitative measures of glucose regulation obtained from a tolbutamide-modified frequently sampled IVGTT (t-FSIGT) and to correlate the heritability of the glucose-stimulated beta cell response to the tolbutamide-induced beta cell response. In addition, single nucleotide polymorphisms (SNPs) having an exclusive effect on either glucose- or tolbutamide-stimulated insulin release were identified.
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Identification and assembly of genomes and genetic elements in complex metagenomic samples without using reference genomes.
Nat. Biotechnol.
PUBLISHED: 02-12-2014
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Most current approaches for analyzing metagenomic data rely on comparisons to reference genomes, but the microbial diversity of many environments extends far beyond what is covered by reference databases. De novo segregation of complex metagenomic data into specific biological entities, such as particular bacterial strains or viruses, remains a largely unsolved problem. Here we present a method, based on binning co-abundant genes across a series of metagenomic samples, that enables comprehensive discovery of new microbial organisms, viruses and co-inherited genetic entities and aids assembly of microbial genomes without the need for reference sequences. We demonstrate the method on data from 396 human gut microbiome samples and identify 7,381 co-abundance gene groups (CAGs), including 741 metagenomic species (MGS). We use these to assemble 238 high-quality microbial genomes and identify affiliations between MGS and hundreds of viruses or genetic entities. Our method provides the means for comprehensive profiling of the diversity within complex metagenomic samples.
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Lessons from whole-exome sequencing in MODYX families.
Diabetes Res. Clin. Pract.
PUBLISHED: 02-11-2014
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We report the first results from whole-exome sequencing performed in families with Maturity-Onset Diabetes of the Young without a known genetic cause of diabetes (MODYX). This next generation sequencing technique pointed out that routine testing of MODY needs constant awareness and regular re-evaluation of both clinical criteria and primer sequences.
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Loss-of-function mutations in SLC30A8 protect against type 2 diabetes.
Nat. Genet.
PUBLISHED: 02-10-2014
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Loss-of-function mutations protective against human disease provide in vivo validation of therapeutic targets, but none have yet been described for type 2 diabetes (T2D). Through sequencing or genotyping of ~150,000 individuals across 5 ancestry groups, we identified 12 rare protein-truncating variants in SLC30A8, which encodes an islet zinc transporter (ZnT8) and harbors a common variant (p.Trp325Arg) associated with T2D risk and glucose and proinsulin levels. Collectively, carriers of protein-truncating variants had 65% reduced T2D risk (P = 1.7 × 10(-6)), and non-diabetic Icelandic carriers of a frameshift variant (p.Lys34Serfs*50) demonstrated reduced glucose levels (-0.17 s.d., P = 4.6 × 10(-4)). The two most common protein-truncating variants (p.Arg138* and p.Lys34Serfs*50) individually associate with T2D protection and encode unstable ZnT8 proteins. Previous functional study of SLC30A8 suggested that reduced zinc transport increases T2D risk, and phenotypic heterogeneity was observed in mouse Slc30a8 knockouts. In contrast, loss-of-function mutations in humans provide strong evidence that SLC30A8 haploinsufficiency protects against T2D, suggesting ZnT8 inhibition as a therapeutic strategy in T2D prevention.
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Interaction between genetic predisposition to obesity and dietary calcium in relation to subsequent change in body weight and waist circumference.
Am. J. Clin. Nutr.
PUBLISHED: 02-05-2014
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Studies indicate an effect of dietary calcium on change in body weight (BW) and waist circumference (WC), but the results are inconsistent. Furthermore, a relation could depend on genetic predisposition to obesity.
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Evaluation of a target region capture sequencing platform using monogenic diabetes as a study-model.
BMC Genet.
PUBLISHED: 01-29-2014
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Monogenic diabetes is a genetic disease often caused by mutations in genes involved in beta-cell function. Correct sub-categorization of the disease is a prerequisite for appropriate treatment and genetic counseling. Target-region capture sequencing is a combination of genomic region enrichment and next generation sequencing which might be used as an efficient way to diagnose various genetic disorders. We aimed to develop a target-region capture sequencing platform to screen 117 selected candidate genes involved in metabolism for mutations and to evaluate its performance using monogenic diabetes as a study-model.
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Variation and association to diabetes in 2000 full mtDNA sequences mined from an exome study in a Danish population.
Eur. J. Hum. Genet.
PUBLISHED: 01-22-2014
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In this paper, we mine full mtDNA sequences from an exome capture data set of 2000 Danes, showing that it is possible to get high-quality full-genome sequences of the mitochondrion from this resource. The sample includes 1000 individuals with type 2 diabetes and 1000 controls. We characterise the variation found in the mtDNA sequence in Danes and relate the variation to diabetes risk as well as to several blood phenotypes of the controls but find no significant associations. We report 2025 polymorphisms, of which 393 have not been reported previously. These 393 mutations are both very rare and estimated to be caused by very recent mutations but individuals with type 2 diabetes do not possess more of these variants. Population genetics analysis using Bayesian skyline plot shows a recent history of rapid population growth in the Danish population in accordance with the fact that >40% of variable sites are observed as singletons.
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Dietary ascorbic acid and subsequent change in body weight and waist circumference: associations may depend on genetic predisposition to obesity--a prospective study of three independent cohorts.
Nutr J
PUBLISHED: 01-20-2014
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Cross-sectional data suggests that a low level of plasma ascorbic acid positively associates with both Body Mass Index (BMI) and Waist Circumference (WC). This leads to questions about a possible relationship between dietary intake of ascorbic acid and subsequent changes in anthropometry, and whether such associations may depend on genetic predisposition to obesity. Hence, we examined whether dietary ascorbic acid, possibly in interaction with the genetic predisposition to a high BMI, WC or waist-hip ratio adjusted for BMI (WHR), associates with subsequent annual changes in weight (?BW) and waist circumference (?WC).
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MTHFR C677T genotype and cardiovascular risk in a general population without mandatory folic acid fortification.
Eur J Nutr
PUBLISHED: 01-14-2014
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Meta-analyses have suggested an effect of MTHFR C677T genotype (rs1801133), a proxy for blood total homocysteine, on cardiovascular disease (CVD) in populations with low population dietary folate. The aim was to examine the association and effect modification by serum folate and vitamin B12 levels between MTHFR and CVD-related outcomes in a general population with no mandatory folic acid fortification policy.
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A common Greenlandic TBC1D4 variant confers muscle insulin resistance and type 2 diabetes.
Nature
PUBLISHED: 01-09-2014
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The Greenlandic population, a small and historically isolated founder population comprising about 57,000 inhabitants, has experienced a dramatic increase in type 2 diabetes (T2D) prevalence during the past 25 years. Motivated by this, we performed association mapping of T2D-related quantitative traits in up to 2,575 Greenlandic individuals without known diabetes. Using array-based genotyping and exome sequencing, we discovered a nonsense p.Arg684Ter variant (in which arginine is replaced by a termination codon) in the gene TBC1D4 with an allele frequency of 17%. Here we show that homozygous carriers of this variant have markedly higher concentrations of plasma glucose (? = 3.8?mmol?l(-1), P = 2.5?×?10(-35)) and serum insulin (? = 165?pmol?l(-1), P = 1.5?×?10(-20)) 2 hours after an oral glucose load compared with individuals with other genotypes (both non-carriers and heterozygous carriers). Furthermore, homozygous carriers have marginally lower concentrations of fasting plasma glucose (? = -0.18 mmol?l(-1), P = 1.1?×?10(-6)) and fasting serum insulin (? = -8.3?pmol?l(-1), P = 0.0014), and their T2D risk is markedly increased (odds ratio (OR) = 10.3, P = 1.6?×?10(-24)). Heterozygous carriers have a moderately higher plasma glucose concentration 2 hours after an oral glucose load than non-carriers (? = 0.43?mmol?l(-1), P = 5.3?×?10(-5)). Analyses of skeletal muscle biopsies showed lower messenger RNA and protein levels of the long isoform of TBC1D4, and lower muscle protein levels of the glucose transporter GLUT4, with increasing number of p.Arg684Ter alleles. These findings are concomitant with a severely decreased insulin-stimulated glucose uptake in muscle, leading to postprandial hyperglycaemia, impaired glucose tolerance and T2D. The observed effect sizes are several times larger than any previous findings in large-scale genome-wide association studies of these traits and constitute further proof of the value of conducting genetic association studies outside the traditional setting of large homogeneous populations.
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Identification of low-frequency and rare sequence variants associated with elevated or reduced risk of type 2 diabetes.
Nat. Genet.
PUBLISHED: 01-06-2014
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Through whole-genome sequencing of 2,630 Icelanders and imputation into 11,114 Icelandic cases and 267,140 controls followed by testing in Danish and Iranian samples, we discovered 4 previously unreported variants affecting risk of type 2 diabetes (T2D). A low-frequency (1.47%) variant in intron 1 of CCND2, rs76895963[G], reduces risk of T2D by half (odds ratio (OR) = 0.53, P = 5.0 × 10(-21)) and is correlated with increased CCND2 expression. Notably, this variant is also associated with both greater height and higher body mass index (1.17 cm per allele, P = 5.5 × 10(-12) and 0.56 kg/m(2) per allele, P = 6.5 × 10(-7), respectively). In addition, two missense variants in PAM, encoding p.Asp563Gly (frequency of 4.98%) and p.Ser539Trp (frequency of 0.65%), confer moderately higher risk of T2D (OR = 1.23, P = 3.9 × 10(-10) and OR = 1.47, P = 1.7 × 10(-5), respectively), and a rare (0.20%) frameshift variant in PDX1, encoding p.Gly218Alafs*12, associates with high risk of T2D (OR = 2.27, P = 7.3 × 10(-7)).
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Blood Pressure Levels in Male Carriers of Arg82Cys in CD300LG.
PLoS ONE
PUBLISHED: 01-01-2014
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The genetics of hypertension has been scrutinized in large-scale genome-wide association studies (GWAS) with a large number of common genetic variants identified, each exerting subtle effects on disease susceptibility. An amino acid polymorphism, p.Arg82Cys, in CD300LG was recently found to be associated with fasting HDL-cholesterol and triglyceride levels. The polymorphism has not been detected in hypertension GWAS potentially due to its low frequency, but CD300LG has been linked to blood pressure as CD300LG knockout mice have changes in blood pressure. Twenty-four-hour ambulatory blood pressure was obtained in human CD300LG CT-carriers to follow up on these observations.
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KCNQ1 Long QT syndrome patients have hyperinsulinemia and symptomatic hypoglycemia.
Diabetes
PUBLISHED: 12-18-2013
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Patients with loss of function mutations in KCNQ1 have KCNQ1 long QT syndrome (LQTS). KCNQ1 encodes a voltage-gated K(+) channel located in both cardiomyocytes and pancreatic beta cells. Inhibition of KCNQ1 in beta cells increases insulin secretion. Therefore KCNQ1 LQTS patients may exhibit increased insulin secretion.Fourteen patients, from six families, diagnosed with KCNQ1 LQTS were individually matched to two randomly chosen BMI-age-gender-matched control participants and underwent oral glucose tolerance test, hypoglycemia questionnaire and continuous glucose monitoring.KCNQ1 mutation carriers showed increased insulin release (AUC:45.6±6.3vs.26.0±2.8 min*nmol/l insulin), and beta cell glucose sensitivity and had lower levels of plasma glucose and serum potassium upon oral glucose stimulation and increased hypoglycemic symptoms. Prolonged oral glucose tolerance test in four available patients and matched controls revealed hypoglycemia in carriers after 210 min. (range:1.4-3.6vs.4.1-5.3 mmol/l glucose), and 24-hour glucose profiles showed that the patients spent 77±18 min. per 24-hours in hypoglycemic states (<3.9 mmol/l glucose) with 36±10 min. <2.8 mmol/l glucose vs. 0 min (<3.9 mmol/l glucose) for the control participants.The phenotype of patients with KCNQ1 LQTS, caused by mutations in KCNQ1, includes, besides long QT, hyperinsulinemia, clinically relevant symptomatic reactive hypoglycemia and low potassium following an oral glucose challenge, suggesting that KCNQ1 mutations may explain some cases of "essential" reactive hypoglycemia.
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Impact of type 2 diabetes susceptibility variants on quantitative glycemic traits reveals mechanistic heterogeneity.
Diabetes
PUBLISHED: 12-02-2013
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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 non-diabetic subjects with basal measures, and 17,327 with dynamic measures. We employed 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 (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 (including TCF7L2, SLC30A8, HHEX/IDE, CDKAL1, CDKN2A/2B) was defined by loci influencing insulin processing and secretion without detectable change in fasting glucose. The final group contained twenty 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.
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Richness of human gut microbiome correlates with metabolic markers.
Nature
PUBLISHED: 07-26-2013
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We are facing a global metabolic health crisis provoked by an obesity epidemic. Here we report the human gut microbial composition in a population sample of 123 non-obese and 169 obese Danish individuals. We find two groups of individuals that differ by the number of gut microbial genes and thus gut bacterial richness. They contain known and previously unknown bacterial species at different proportions; individuals with a low bacterial richness (23% of the population) are characterized by more marked overall adiposity, insulin resistance and dyslipidaemia and a more pronounced inflammatory phenotype when compared with high bacterial richness individuals. The obese individuals among the lower bacterial richness group also gain more weight over time. Only a few bacterial species are sufficient to distinguish between individuals with high and low bacterial richness, and even between lean and obese participants. Our classifications based on variation in the gut microbiome identify subsets of individuals in the general white adult population who may be at increased risk of progressing to adiposity-associated co-morbidities.
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Mendelian randomization studies do not support a causal role for reduced circulating adiponectin levels in insulin resistance and type 2 diabetes.
Diabetes
PUBLISHED: 07-08-2013
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Adiponectin is strongly inversely associated with insulin resistance and type 2 diabetes, but its causal role remains controversial. We used a Mendelian randomization approach to test the hypothesis that adiponectin causally influences insulin resistance and type 2 diabetes. We used genetic variants at the ADIPOQ gene as instruments to calculate a regression slope between adiponectin levels and metabolic traits (up to 31,000 individuals) and a combination of instrumental variables and summary statistics-based genetic risk scores to test the associations with gold-standard measures of insulin sensitivity (2,969 individuals) and type 2 diabetes (15,960 case subjects and 64,731 control subjects). In conventional regression analyses, a 1-SD decrease in adiponectin levels was correlated with a 0.31-SD (95% CI 0.26-0.35) increase in fasting insulin, a 0.34-SD (0.30-0.38) decrease in insulin sensitivity, and a type 2 diabetes odds ratio (OR) of 1.75 (1.47-2.13). The instrumental variable analysis revealed no evidence of a causal association between genetically lower circulating adiponectin and higher fasting insulin (0.02 SD; 95% CI -0.07 to 0.11; N = 29,771), nominal evidence of a causal relationship with lower insulin sensitivity (-0.20 SD; 95% CI -0.38 to -0.02; N = 1,860), and no evidence of a relationship with type 2 diabetes (OR 0.94; 95% CI 0.75-1.19; N = 2,777 case subjects and 13,011 control subjects). Using the ADIPOQ summary statistics genetic risk scores, we found no evidence of an association between adiponectin-lowering alleles and insulin sensitivity (effect per weighted adiponectin-lowering allele: -0.03 SD; 95% CI -0.07 to 0.01; N = 2,969) or type 2 diabetes (OR per weighted adiponectin-lowering allele: 0.99; 95% CI 0.95-1.04; 15,960 case subjects vs. 64,731 control subjects). These results do not provide any consistent evidence that interventions aimed at increasing adiponectin levels will improve insulin sensitivity or risk of type 2 diabetes.
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Genetic risk score of 46 type 2 diabetes risk variants associates with changes in plasma glucose and estimates of pancreatic ?-cell function over 5 years of follow-up.
Diabetes
PUBLISHED: 07-08-2013
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More than 40 genetic risk variants for type 2 diabetes have been validated. We aimed to test whether a genetic risk score associates with the incidence of type 2 diabetes and with 5-year changes in glycemic traits and whether the effects were modulated by changes in BMI and lifestyle. The Inter99 study population was genotyped for 46 variants, and a genetic risk score was constructed. During a median follow-up of 11 years, 327 of 5,850 individuals developed diabetes. Physical examinations and oral glucose tolerance tests were performed at baseline and after 5 years (n = 3,727). The risk of incident type 2 diabetes was increased with a hazard ratio of 1.06 (95% CI 1.03-1.08) per risk allele. While the population in general had improved glucose regulation during the 5-year follow-up period, each additional allele in the genetic risk score was associated with a relative increase in fasting, 30-min, and 120-min plasma glucose values and a relative decrease in measures of ?-cell function over the 5-year period, whereas indices of insulin sensitivity were unaffected. The effect of the genetic risk score on 5-year changes in fasting plasma glucose was stronger in individuals who increased their BMI. In conclusion, a genetic risk score based on 46 variants associated strongly with incident type 2 diabetes and 5-year changes in plasma glucose and ?-cell function. Individuals who gain weight may be more susceptible to the cumulative impact of type 2 diabetes risk variants on fasting plasma glucose.
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Gene × physical activity interactions in obesity: combined analysis of 111,421 individuals of European ancestry.
PLoS Genet.
PUBLISHED: 07-01-2013
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Numerous obesity loci have been identified using genome-wide association studies. A UK study indicated that physical activity may attenuate the cumulative effect of 12 of these loci, but replication studies are lacking. Therefore, we tested whether the aggregate effect of these loci is diminished in adults of European ancestry reporting high levels of physical activity. Twelve obesity-susceptibility loci were genotyped or imputed in 111,421 participants. A genetic risk score (GRS) was calculated by summing the BMI-associated alleles of each genetic variant. Physical activity was assessed using self-administered questionnaires. Multiplicative interactions between the GRS and physical activity on BMI were tested in linear and logistic regression models in each cohort, with adjustment for age, age(2), sex, study center (for multicenter studies), and the marginal terms for physical activity and the GRS. These results were combined using meta-analysis weighted by cohort sample size. The meta-analysis yielded a statistically significant GRS × physical activity interaction effect estimate (Pinteraction ?=?0.015). However, a statistically significant interaction effect was only apparent in North American cohorts (n?=?39,810, Pinteraction ?=?0.014 vs. n?=?71,611, Pinteraction ?=?0.275 for Europeans). In secondary analyses, both the FTO rs1121980 (Pinteraction ?=?0.003) and the SEC16B rs10913469 (Pinteraction ?=?0.025) variants showed evidence of SNP × physical activity interactions. This meta-analysis of 111,421 individuals provides further support for an interaction between physical activity and a GRS in obesity disposition, although these findings hinge on the inclusion of cohorts from North America, indicating that these results are either population-specific or non-causal.
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Chronic Mild Hyperglycemia in GCK-MODY Patients Does Not Increase Carotid Intima-Media Thickness.
Int J Endocrinol
PUBLISHED: 06-27-2013
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Aim. GCK-MODY is an autosomal dominant form of diabetes caused by heterozygous mutations in the glucokinase gene leading to a lifelong mild hyperglycemia. The risk of macrovascular complications is considered low, but studies are limited. We, therefore, investigated the carotid intima-media thickness (CIMT) as an indicator of macrovascular complications in a group of patients with GCK-MODY. Methods. Twenty-seven GCK mutation carriers and 24 controls recruited among their first-degree relatives were compared, all aging over 35 years. The CIMT was tested using a high-resolution B-mode carotid ultrasonography. Medical history, anthropometry, and biochemical blood workup were obtained. Results. The mean CIMT was 0.707 ± 0.215?mm (mean ± SD) in GCK mutation carriers and 0.690 ± 0.180?mm in control individuals. When adjusted for age, gender, and family status, the estimated mean difference in CIMT between the two groups increased to 0.049?mm (P = 0.19). No difference was detected for other characteristics, with the exception of fasting blood glucose (GCK-MODY 7.6?mmol/L ± 1.2 (136.4?mg/dL); controls 5.3?mmol/L ± 0.3 (95.4?mg/dL); P < 0.0001) and glycated hemoglobin HbA1c (GCK-MODY 6.9% ± 1.0%, 52?mmol/mol ± 10; controls 5.7% ± 0.4%, 39?mmol/mol ± 3; P < 0.0001). The frequency of myocardial infarction and ischemic stroke did not differ between groups. Conclusion. Our data indicate that the persistent hyperglycemia in GCK-MODY is associated with a low risk of developing diabetic macrovascular complications.
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Insulin resistance and impaired pancreatic ?-cell function in adult offspring of women with diabetes in pregnancy.
J. Clin. Endocrinol. Metab.
PUBLISHED: 06-24-2013
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Offspring of women with diabetes during pregnancy have an increased risk of glucose intolerance in adulthood, but the underlying mechanisms are unknown.
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Metagenomic species profiling using universal phylogenetic marker genes.
Nat. Methods
PUBLISHED: 06-18-2013
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To quantify known and unknown microorganisms at species-level resolution using shotgun sequencing data, we developed a method that establishes metagenomic operational taxonomic units (mOTUs) based on single-copy phylogenetic marker genes. Applied to 252 human fecal samples, the method revealed that on average 43% of the species abundance and 58% of the richness cannot be captured by current reference genome-based methods. An implementation of the method is available at http://www.bork.embl.de/software/mOTU/.
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Whole-exome sequencing of 2,000 danish individuals and the role of rare coding variants in type 2 diabetes.
Am. J. Hum. Genet.
PUBLISHED: 06-07-2013
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It has been hypothesized that, in aggregate, rare variants in coding regions of genes explain a substantial fraction of the heritability of common diseases. We sequenced the exomes of 1,000 Danish cases with common forms of type 2 diabetes (including body mass index > 27.5 kg/m(2) and hypertension) and 1,000 healthy controls to an average depth of 56×. Our simulations suggest that our study had the statistical power to detect at least one causal gene (a gene containing causal mutations) if the heritability of these common diseases was explained by rare variants in the coding regions of a limited number of genes. We applied a series of gene-based tests to detect such susceptibility genes. However, no gene showed a significant association with disease risk after we corrected for the number of genes analyzed. Thus, we could reject a model for the genetic architecture of type 2 diabetes where rare nonsynonymous variants clustered in a modest number of genes (fewer than 20) are responsible for the majority of disease risk.
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Genetic architecture of vitamin B12 and folate levels uncovered applying deeply sequenced large datasets.
PLoS Genet.
PUBLISHED: 06-01-2013
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Genome-wide association studies have mainly relied on common HapMap sequence variations. Recently, sequencing approaches have allowed analysis of low frequency and rare variants in conjunction with common variants, thereby improving the search for functional variants and thus the understanding of the underlying biology of human traits and diseases. Here, we used a large Icelandic whole genome sequence dataset combined with Danish exome sequence data to gain insight into the genetic architecture of serum levels of vitamin B(12) (B12) and folate. Up to 22.9 million sequence variants were analyzed in combined samples of 45,576 and 37,341 individuals with serum B(12) and folate measurements, respectively. We found six novel loci associating with serum B(12) (CD320, TCN2, ABCD4, MMAA, MMACHC) or folate levels (FOLR3) and confirmed seven loci for these traits (TCN1, FUT6, FUT2, CUBN, CLYBL, MUT, MTHFR). Conditional analyses established that four loci contain additional independent signals. Interestingly, 13 of the 18 identified variants were coding and 11 of the 13 target genes have known functions related to B(12) and folate pathways. Contrary to epidemiological studies we did not find consistent association of the variants with cardiovascular diseases, cancers or Alzheimers disease although some variants demonstrated pleiotropic effects. Although to some degree impeded by low statistical power for some of these conditions, these data suggest that sequence variants that contribute to the population diversity in serum B(12) or folate levels do not modify the risk of developing these conditions. Yet, the study demonstrates the value of combining whole genome and exome sequencing approaches to ascertain the genetic and molecular architectures underlying quantitative trait associations.
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The CTRB1/2 locus affects diabetes susceptibility and treatment via the incretin pathway.
Diabetes
PUBLISHED: 05-14-2013
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The incretin hormone glucagon-like peptide 1 (GLP-1) promotes glucose homeostasis and enhances ?-cell function. GLP-1 receptor agonists (GLP-1 RAs) and dipeptidyl peptidase-4 (DPP-4) inhibitors, which inhibit the physiological inactivation of endogenous GLP-1, are used for the treatment of type 2 diabetes. Using the Metabochip, we identified three novel genetic loci with large effects (30-40%) on GLP-1-stimulated insulin secretion during hyperglycemic clamps in nondiabetic Caucasian individuals (TMEM114; CHST3 and CTRB1/2; n = 232; all P ? 8.8 × 10(-7)). rs7202877 near CTRB1/2, a known diabetes risk locus, also associated with an absolute 0.51 ± 0.16% (5.6 ± 1.7 mmol/mol) lower A1C response to DPP-4 inhibitor treatment in G-allele carriers, but there was no effect on GLP-1 RA treatment in type 2 diabetic patients (n = 527). Furthermore, in pancreatic tissue, we show that rs7202877 acts as expression quantitative trait locus for CTRB1 and CTRB2, encoding chymotrypsinogen, and increases fecal chymotrypsin activity in healthy carriers. Chymotrypsin is one of the most abundant digestive enzymes in the gut where it cleaves food proteins into smaller peptide fragments. Our data identify chymotrypsin in the regulation of the incretin pathway, development of diabetes, and response to DPP-4 inhibitor treatment.
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Type 2 diabetes risk alleles near BCAR1 and in ANK1 associate with decreased ?-cell function whereas risk alleles near ANKRD55 and GRB14 associate with decreased insulin sensitivity in the Danish Inter99 cohort.
J. Clin. Endocrinol. Metab.
PUBLISHED: 03-01-2013
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Recently, 10 novel type 2 diabetes (T2D) susceptibility single nucleotide polymorphisms (SNPs) in ZMIZ1, ANK1, KLHDC5, TLE1, ANKRD55, CILP2, MC4R, BCAR1, HMG20A, and GRB14 loci were discovered in MetaboChip-genotyped populations of European ancestry.
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Studies of association of AGPAT6 variants with type 2 diabetes and related metabolic phenotypes in 12,068 Danes.
BMC Med. Genet.
PUBLISHED: 02-18-2013
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Type 2 diabetes, obesity and insulin resistance are characterized by hypertriglyceridemia and ectopic accumulation of lipids in liver and skeletal muscle. AGPAT6 encodes a novel glycerol-3 phosphate acyltransferase, GPAT4, which catalyzes the first step in the de novo triglyceride synthesis. AGPAT6-deficient mice show lower weight and resistance to diet- and genetically induced obesity. Here, we examined whether common or low-frequency variants in AGPAT6 associate with type 2 diabetes or related metabolic traits in a Danish population.
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Chronic family stress moderates the association between a TOMM40 variant and triglyceride levels in two independent Caucasian samples.
Biol Psychol
PUBLISHED: 02-07-2013
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TOMM40 SNP rs157580 has been associated with triglyceride levels in genome-wide association studies (GWAS). Chronic caregiving stress moderates the association between triglyceride levels and a nearby SNP rs439401 that is associated with triglyceride levels in GWAS. Here, we report data from two independent Caucasian samples (242 U.S. women and men; 466 Danish men) testing the hypothesis that chronic family stress also moderates the association between rs157580 and triglyceride levels. The interaction of rs157580 and family stress in predicting triglyceride levels was statistically significant in the U.S. sample (p=0.004) and marginally significant (p=0.075) in the Danish sample. The G allele of rs157580 was associated with increased triglyceride levels among family stressed cases in both samples compared with A/A cases, but not among controls. Chronic family stress moderates the association of rs157580 variants with triglyceride levels and should be taken into account for disease risk assessment and potential intervention.
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Does DNA methylation of PPARGC1A influence insulin action in first degree relatives of patients with type 2 diabetes?
PLoS ONE
PUBLISHED: 02-04-2013
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Epigenetics may play a role in the pathophysiology of type 2 diabetes (T2D), and increased DNA methylation of the metabolic master regulator peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A) has been reported in muscle and pancreatic islets from T2D patients and in muscle from individuals at risk of T2D. This study aimed to investigate DNA promoter methylation and gene expression of PPARGC1A in skeletal muscle from first degree relatives (FDR) of T2D patients, and to determine the association with insulin action as well as the influence of family relation. We included 124 Danish FDR of T2D patients from 46 different families. Skeletal muscle biopsies were excised from vastus lateralis and insulin action was assessed by oral glucose tolerance tests. DNA methylation and mRNA expression levels were measured using bisulfite sequencing and quantitative real-time PCR, respectively. The average PPARGC1A methylation at four CpG sites situated 867-624 bp from the transcription start was associated with whole-body insulin sensitivity in a paradoxical positive manner (??=?0.12, P?=?0.03), supported by a borderline significant inverse correlation with fasting insulin levels (??=?-0.88, P?=?0.06). Excluding individuals with prediabetes and overt diabetes did not affect the overall result. DNA promoter methylation was not associated with PPARGC1A gene expression. The familiality estimate of PPARGC1A gene expression was high (h(2) =?79±27% (h(2)±SE), P?=?0.002), suggesting genetic regulation to play a role. No significant effect of familiality on DNA methylation was found. Taken together, increased DNA methylation of the PPARGC1A promoter is unlikely to play a major causal role for the development of insulin resistance in FDR of patients with T2D.
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Genetic variants associated with glycine metabolism and their role in insulin sensitivity and type 2 diabetes.
Diabetes
PUBLISHED: 02-01-2013
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Circulating metabolites associated with insulin sensitivity may represent useful biomarkers, but their causal role in insulin sensitivity and diabetes is less certain. We previously identified novel metabolites correlated with insulin sensitivity measured by the hyperinsulinemic-euglycemic clamp. The top-ranking metabolites were in the glutathione and glycine biosynthesis pathways. We aimed to identify common genetic variants associated with metabolites in these pathways and test their role in insulin sensitivity and type 2 diabetes. With 1,004 nondiabetic individuals from the RISC study, we performed a genome-wide association study (GWAS) of 14 insulin sensitivity-related metabolites and one metabolite ratio. We replicated our results in the Botnia study (n = 342). We assessed the association of these variants with diabetes-related traits in GWAS meta-analyses (GENESIS [including RISC, EUGENE2, and Stanford], MAGIC, and DIAGRAM). We identified four associations with three metabolites-glycine (rs715 at CPS1), serine (rs478093 at PHGDH), and betaine (rs499368 at SLC6A12; rs17823642 at BHMT)-and one association signal with glycine-to-serine ratio (rs1107366 at ALDH1L1). There was no robust evidence for association between these variants and insulin resistance or diabetes. Genetic variants associated with genes in the glycine biosynthesis pathways do not provide consistent evidence for a role of glycine in diabetes-related traits.
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What is the contribution of two genetic variants regulating VEGF levels to type 2 diabetes risk and to microvascular complications?
PLoS ONE
PUBLISHED: 01-03-2013
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Vascular endothelial growth factor (VEGF) is a key chemokine involved in tissue growth and organ repair processes, particularly angiogenesis. Elevated circulating VEGF levels are believed to play a role in type 2 diabetes (T2D) microvascular complications, especially diabetic retinopathy. Recently, a genome-wide association study identified two common single nucleotide polymorphisms (SNPs; rs6921438 and rs10738760) explaining nearly half of the variance in circulating VEGF levels. Considering the putative contribution of VEGF to T2D and its complications, we aimed to assess the effect of these VEGF-related SNPs on the risk of T2D, nephropathy and retinopathy, as well as on variation in related traits.SNPs were genotyped in several case-control studies: French and Danish T2D studies (N(cases)?=?6,920-N(controls)?=?3,875 and N(cases)?=?3,561-N(controls)?=?2,623; respectively), two French studies one for diabetic nephropathy (N(cases)?=?1,242-N(controls)?=?860) and the other for diabetic retinopathy (N(cases)?=?1,336-N(controls)?=?1,231). The effects of each SNP on quantitative traits were analyzed in a French general population-based cohort (N?=?4,760) and two French T2D studies (N?=?3,480). SNP associations were assessed using logistic or linear regressions.In the French population, we found an association between the G-allele of rs6921438, shown to increase circulating VEGF levels, and increased T2D risk (OR?=?1.15; P?=?3.7×10(-5)). Furthermore, the same allele was associated with higher glycated hemoglobin levels (??=?0.02%; P?=?9.2×10(-3)). However, these findings were not confirmed in the Danes. Conversely, the SNP rs10738760 was not associated with T2D in the French or Danish populations. Despite having adequate statistical power, we did not find any significant effects of rs6921438 or rs10738760 on diabetic microvascular complications or the variation in related traits in T2D patients.In spite of their impact on the variance in circulating VEGF, we did not find any association between SNPs rs6921438 and rs10738760, and the risk of T2D, diabetic nephropathy or retinopathy. The link between VEGF and T2D and its complications might be indirect and more complex than expected.
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Validation of a multi-marker model for the prediction of incident type 2 diabetes mellitus: combined results of the Inter99 and Botnia studies.
Diab Vasc Dis Res
PUBLISHED: 11-04-2011
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To assess performance of a biomarker-based score that predicts the five-year risk of diabetes (Diabetes Risk Score, DRS) in an independent cohort that included 15-year follow-up.
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The influence of parental history of diabetes and offspring birthweight on offspring glucose metabolism in adulthood.
Acta Obstet Gynecol Scand
PUBLISHED: 10-18-2011
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Links are well established between both family history of diabetes and reduced birthweight and increased risk of diabetes in adulthood.
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Mechanism-based population modelling for assessment of L-cell function based on total GLP-1 response following an oral glucose tolerance test.
J Pharmacokinet Pharmacodyn
PUBLISHED: 09-08-2011
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GLP-1 is an insulinotropic hormone that synergistically with glucose gives rise to an increased insulin response. Its secretion is increased following a meal and it is thus of interest to describe the secretion of this hormone following an oral glucose tolerance test (OGTT). The aim of this study was to build a mechanism-based population model that describes the time course of total GLP-1 and provides indices for capability of secretion in each subject. The goal was thus to model the secretion of GLP-1, and not its effect on insulin production. Single 75 g doses of glucose were administered orally to a mixed group of subjects ranging from healthy volunteers to patients with type 2 diabetes (T2D). Glucose, insulin, and total GLP-1 concentrations were measured. Prior population data analysis on measurements of glucose and insulin were performed in order to estimate the glucose absorption rate. The individual estimates of absorption rate constants were used in the model for GLP-1 secretion. Estimation of parameters was performed using the FOCE method with interaction implemented in NONMEM VI. The final transit/indirect-response model obtained for GLP-1 production following an OGTT included two stimulation components (fast, slow) for the zero-order production rate. The fast stimulation was estimated to be faster than the glucose absorption rate, supporting the presence of a proximal-distal loop for fast secretion from L: -cells. The fast component (st?) = 8.64·10?? [mg?¹]) was estimated to peak around 25 min after glucose ingestion, whereas the slower component (st? = 26.2·10?? [mg?¹]) was estimated to peak around 100 min. Elimination of total GLP-1 was characterised by a first-order loss. The individual values of the early phase GLP-1 secretion parameter (st?) were correlated (r = 0.52) with the AUC(0-60 min.) for GLP-1. A mechanistic population model was successfully developed to describe total GLP-1 concentrations over time observed after an OGTT. The model provides indices related to different mechanisms of subject abilities to secrete GLP-1. The model provides a good basis to study influence of different demographic factors on these components, presented mainly by indices of the fast- and slow phases of GLP-1 response.
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The effect of PCSK1 variants on waist, waist-hip ratio and glucose metabolism is modified by sex and glucose tolerance status.
PLoS ONE
PUBLISHED: 07-29-2011
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We aimed to evaluate the effects of the G-allele of rs6232 and the C-allele of rs6235 within PCSK1 on measures of body fat and glucose homeostasis in Danish individuals and to assess interactions of genotypes with age, sex and glucose tolerance status. Data were included in meta-analyses of additional Europeans.
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The birth weight lowering C-allele of rs900400 near LEKR1 and CCNL1 associates with elevated insulin release following an oral glucose challenge.
PLoS ONE
PUBLISHED: 07-19-2011
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The first genome-wide association study on birth weight was recently published and the most significant associated birth weight lowering variant was the rs900400 C-allele located near LEKR1 and CCNL1. We aimed to replicate the association with birth weight in the Danish Inter99 study and furthermore to evaluate associations between rs900400 and indices of insulin secretion and insulin sensitivity obtained by oral glucose tolerance tests in adults from the Danish Inter99 study and the Finnish, Metabolic Syndrome in Men (METSIM) sample.
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Genome wide association study identifies KCNMA1 contributing to human obesity.
BMC Med Genomics
PUBLISHED: 06-28-2011
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Recent genome-wide association (GWA) analyses have identified common single nucleotide polymorphisms (SNPs) that are associated with obesity. However, the reported genetic variation in obesity explains only a minor fraction of the total genetic variation expected to be present in the population. Thus many genetic variants controlling obesity remain to be identified. The aim of this study was to use GWA followed by multiple stepwise validations to identify additional genes associated with obesity.
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A germline variant in the TP53 polyadenylation signal confers cancer susceptibility.
Simon N Stacey, Patrick Sulem, Aslaug Jonasdottir, Gisli Masson, Julius Gudmundsson, Daniel F Gudbjartsson, Olafur T Magnusson, Sigurjon A Gudjonsson, Bardur Sigurgeirsson, Kristin Thorisdottir, Rafn Ragnarsson, Kristrun R Benediktsdottir, Bjørn A Nexø, Anne Tjønneland, Kim Overvad, Peter Rudnai, Eugene Gurzau, Kvetoslava Koppova, Kari Hemminki, Cristina Corredera, Victoria Fuentelsaz, Pilar Grasa, Sebastian Navarrete, Fernando Fuertes, Maria D Garcia-Prats, Enrique Sanambrosio, Angeles Panadero, Ana De Juan, Almudena García, Fernando Rivera, Dolores Planelles, Virtudes Soriano, Celia Requena, Katja K Aben, Michelle M van Rossum, Ruben G H M Cremers, Inge M van Oort, Dick-Johan van Spronsen, Jack A Schalken, Wilbert H M Peters, Brian T Helfand, Jenny L Donovan, Freddie C Hamdy, Daniel Badescu, Ovidiu Codreanu, Mariana Jinga, Irma E Csiki, Vali Constantinescu, Paula Badea, Ioan N Mates, Daniela E Dinu, Adrian Constantin, Dana Mates, Sjofn Kristjansdottir, Bjarni A Agnarsson, Eirikur Jonsson, Rosa B Barkardottir, Gudmundur V Einarsson, Fridbjorn Sigurdsson, Pall H Moller, Tryggvi Stefansson, Trausti Valdimarsson, Oskar T Johannsson, Helgi Sigurdsson, Thorvaldur Jonsson, Jon G Jonasson, Laufey Tryggvadóttir, Terri Rice, Helen M Hansen, Yuanyuan Xiao, Daniel H Lachance, Brian Patrick O Neill, Matthew L Kosel, Paul A Decker, Gudmar Thorleifsson, Hrefna Johannsdottir, Hafdis T Helgadottir, Asgeir Sigurdsson, Valgerdur Steinthorsdottir, Annika Lindblom, , Robert S Sandler, Temitope O Keku, Karina Banasik, Torben Jørgensen, Daniel R Witte, Torben Hansen, Oluf Pedersen, Viorel Jinga, David E Neal, William J Catalona, Margaret Wrensch, John Wiencke, Robert B Jenkins, Eduardo Nagore, Ulla Vogel, Lambertus A Kiemeney, Rajiv Kumar, Jose I Mayordomo, Jon H Olafsson, Augustine Kong, Unnur Thorsteinsdottir, Thorunn Rafnar, Kari Stefansson.
Nat. Genet.
PUBLISHED: 05-27-2011
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To identify new risk variants for cutaneous basal cell carcinoma, we performed a genome-wide association study of 16 million SNPs identified through whole-genome sequencing of 457 Icelanders. We imputed genotypes for 41,675 Illumina SNP chip-typed Icelanders and their relatives. In the discovery phase, the strongest signal came from rs78378222[C] (odds ratio (OR) = 2.36, P = 5.2 × 10(-17)), which has a frequency of 0.0192 in the Icelandic population. We then confirmed this association in non-Icelandic samples (OR = 1.75, P = 0.0060; overall OR = 2.16, P = 2.2 × 10(-20)). rs78378222 is in the 3 untranslated region of TP53 and changes the AATAAA polyadenylation signal to AATACA, resulting in impaired 3-end processing of TP53 mRNA. Investigation of other tumor types identified associations of this SNP with prostate cancer (OR = 1.44, P = 2.4 × 10(-6)), glioma (OR = 2.35, P = 1.0 × 10(-5)) and colorectal adenoma (OR = 1.39, P = 1.6 × 10(-4)). However, we observed no effect for breast cancer, a common Li-Fraumeni syndrome tumor (OR = 1.06, P = 0.57, 95% confidence interval 0.88-1.27).
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Physical activity attenuates the influence of FTO variants on obesity risk: a meta-analysis of 218,166 adults and 19,268 children.
Tuomas O Kilpeläinen, Lu Qi, Soren Brage, Stephen J Sharp, Emily Sonestedt, Ellen Demerath, Tariq Ahmad, Samia Mora, Marika Kaakinen, Camilla Helene Sandholt, Christina Holzapfel, Christine S Autenrieth, Elina Hyppönen, Stéphane Cauchi, Meian He, Zoltan Kutalik, Meena Kumari, Alena Stančáková, Karina Meidtner, Beverley Balkau, Jonathan T Tan, Massimo Mangino, Nicholas J Timpson, Yiqing Song, M Carola Zillikens, Kathleen A Jablonski, Melissa E Garcia, Stefan Johansson, Jennifer L Bragg-Gresham, Ying Wu, Jana V van Vliet-Ostaptchouk, N Charlotte Onland-Moret, Esther Zimmermann, Natalia V Rivera, Toshiko Tanaka, Heather M Stringham, Günther Silbernagel, Stavroula Kanoni, Mary F Feitosa, Soren Snitker, Jonatan R Ruiz, Jeffery Metter, Maria Teresa Martinez Larrad, Mustafa Atalay, Maarit Hakanen, Najaf Amin, Christine Cavalcanti-Proença, Anders Grøntved, Göran Hallmans, John-Olov Jansson, Johanna Kuusisto, Mika Kähönen, Pamela L Lutsey, John J Nolan, Luigi Palla, Oluf Pedersen, Louis Pérusse, Frida Renstrom, Robert A Scott, Dmitry Shungin, Ulla Sovio, Tuija H Tammelin, Tapani Rönnemaa, Timo A Lakka, Matti Uusitupa, Manuel Serrano Rios, Luigi Ferrucci, Claude Bouchard, Aline Meirhaeghe, Mao Fu, Mark Walker, Ingrid B Borecki, George V Dedoussis, Andreas Fritsche, Claes Ohlsson, Michael Boehnke, Stefania Bandinelli, Cornelia M van Duijn, Shah Ebrahim, Debbie A Lawlor, Vilmundur Gudnason, Tamara B Harris, Thorkild I A Sørensen, Karen L Mohlke, Albert Hofman, André G Uitterlinden, Jaakko Tuomilehto, Terho Lehtimäki, Olli Raitakari, Bo Isomaa, Pål R Njølstad, Jose C Florez, Simin Liu, Andy Ness, Timothy D Spector, E Shyong Tai, Philippe Froguel, Heiner Boeing, Markku Laakso, Michael Marmot, Sven Bergmann, Chris Power, Kay-Tee Khaw, Daniel Chasman, Paul Ridker, Torben Hansen, Keri L Monda, Thomas Illig, Marjo-Riitta Järvelin, Nicholas J Wareham, Frank B Hu, Leif C Groop, Marju Orho-Melander, Ulf Ekelund, Paul W Franks, Ruth J F Loos.
PLoS Med.
PUBLISHED: 04-21-2011
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The FTO gene harbors the strongest known susceptibility locus for obesity. While many individual studies have suggested that physical activity (PA) may attenuate the effect of FTO on obesity risk, other studies have not been able to confirm this interaction. To confirm or refute unambiguously whether PA attenuates the association of FTO with obesity risk, we meta-analyzed data from 45 studies of adults (n?=?218,166) and nine studies of children and adolescents (n?=?19,268).
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Allelic variants of melanocortin 3 receptor gene (MC3R) and weight loss in obesity: a randomised trial of hypo-energetic high- versus low-fat diets.
PLoS ONE
PUBLISHED: 04-21-2011
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The melanocortin system plays an important role in energy homeostasis. Mice genetically deficient in the melanocortin-3 receptor gene have a normal body weight with increased body fat, mild hypophagia compared to wild-type mice. In humans, Thr6Lys and Val81Ile variants of the melanocortin-3 receptor gene (MC3R) have been associated with childhood obesity, higher BMI Z-score and elevated body fat percentage compared to non-carriers. The aim of this study is to assess the association in adults between allelic variants of MC3R with weight loss induced by energy-restricted diets.
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Enterotypes of the human gut microbiome.
Nature
PUBLISHED: 04-20-2011
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Our knowledge of species and functional composition of the human gut microbiome is rapidly increasing, but it is still based on very few cohorts and little is known about variation across the world. By combining 22 newly sequenced faecal metagenomes of individuals from four countries with previously published data sets, here we identify three robust clusters (referred to as enterotypes hereafter) that are not nation or continent specific. We also confirmed the enterotypes in two published, larger cohorts, indicating that intestinal microbiota variation is generally stratified, not continuous. This indicates further the existence of a limited number of well-balanced host-microbial symbiotic states that might respond differently to diet and drug intake. The enterotypes are mostly driven by species composition, but abundant molecular functions are not necessarily provided by abundant species, highlighting the importance of a functional analysis to understand microbial communities. Although individual host properties such as body mass index, age, or gender cannot explain the observed enterotypes, data-driven marker genes or functional modules can be identified for each of these host properties. For example, twelve genes significantly correlate with age and three functional modules with the body mass index, hinting at a diagnostic potential of microbial markers.
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Intrafamilial Variability of Early-Onset Diabetes due to an INS Mutation.
Case Rep Genet
PUBLISHED: 04-19-2011
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Aim. The objective of this study was to describe the clinical characteristics of two siblings and their father carrying a C95Y mutation in the insulin (INS) gene. Methods/Results. A Danish patient, his sister, and his father were identified to carry the C95Y mutation in the preproinsulin molecule causing permanent neonatal diabetes. All three were diagnosed before 29 weeks of age, were born at term with near-normal birth weight, and were negative for GAD, ICA, IA-2, and IAA autoantibodies. The daily insulin requirement the first six months after diagnosis was <0.5 ?U kg(-1) day(-1) for both children. The father, insulin treated for over 40 years, has bilateral preproliferative retinopathy. Conclusions. These three cases further confirm the essential features of diabetes caused by INS mutations with proteotoxic effect. We conclude that patients with similar features must be investigated for mutations of INS gene.
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Comparison of accuracy of diabetes risk score and components of the metabolic syndrome in assessing risk of incident type 2 diabetes in Inter99 cohort.
PLoS ONE
PUBLISHED: 04-13-2011
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Given the increasing worldwide incidence of diabetes, methods to assess diabetes risk which would identify those at highest risk are needed. We compared two risk-stratification approaches for incident type 2 diabetes mellitus (T2DM); factors of metabolic syndrome (MetS) and a previously developed diabetes risk score, PreDx® Diabetes Risk Score (DRS). DRS assesses 5 yr risk of incident T2DM based on the measurement of 7 biomarkers in fasting blood.
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Genome-wide population-based association study of extremely overweight young adults--the GOYA study.
PLoS ONE
PUBLISHED: 04-06-2011
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Thirty-two common variants associated with body mass index (BMI) have been identified in genome-wide association studies, explaining ?1.45% of BMI variation in general population cohorts. We performed a genome-wide association study in a sample of young adults enriched for extremely overweight individuals. We aimed to identify new loci associated with BMI and to ascertain whether using an extreme sampling design would identify the variants known to be associated with BMI in general populations.
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A possible association between a dysfunctional skin barrier (filaggrin null-mutation status) and diabetes: a cross-sectional study.
BMJ Open
PUBLISHED: 03-15-2011
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Background Filaggrin proteins are located in the skin and prevent epidermal water loss and impede the entry of micro-organisms, allergens and chemicals. Filaggrin null mutations are strongly associated with ichthyosis vulgaris and atopic dermatitis. Objective The authors aimed to investigate the association between filaggrin null mutations, atopic dermatitis and diabetes. Design A random sample of 3335 adults from the general population in Denmark was filaggrin-genotyped for R501X and 2282del4 null-mutations and questioned about atopic dermatitis and diabetes. Furthermore, two independent study populations of patients with type 1 (n=104) or 2 (n=774) diabetes were genotyped. Results In a crude data analysis, a positive association was detected between the filaggrin null genotype and, respectively, subjects from the general population who reported diabetes (p=0.04) and patients with established type 2 diabetes (p=0.073). Adjustment for age and gender resulted in significant associations for patients with type 2 diabetes (p=0.048) and subjects with self-reported diabetes (p=0.032). Conclusions Adult Danes with a filaggrin null genotype had a significantly increased prevalence of self-reported diabetes. This finding was replicated when an independent sample of Danish patients with established type 2 diabetes was compared with control subjects from the general population.
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Estimation of allele frequency and association mapping using next-generation sequencing data.
BMC Bioinformatics
PUBLISHED: 02-24-2011
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Estimation of allele frequency is of fundamental importance in population genetic analyses and in association mapping. In most studies using next-generation sequencing, a cost effective approach is to use medium or low-coverage data (e.g., < 15X). However, SNP calling and allele frequency estimation in such studies is associated with substantial statistical uncertainty because of varying coverage and high error rates.
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Studies of metabolic phenotypic correlates of 15 obesity associated gene variants.
PLoS ONE
PUBLISHED: 02-23-2011
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Genome-wide association studies have identified novel BMI/obesity associated susceptibility loci. The purpose of this study is to determine associations with overweight, obesity, morbid obesity and/or general adiposity in a Danish population. Moreover, we want to investigate if these loci associate with type 2 diabetes and to elucidate potential underlying metabolic mechanisms.
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Studies of a genetic variant in HK1 in relation to quantitative metabolic traits and to the prevalence of type 2 diabetes.
BMC Med. Genet.
PUBLISHED: 02-18-2011
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Single nucleotide polymorphisms (SNPs) within the gene encoding Hexokinase 1 (HK1) are associated with changes in glycated haemoglobin (HbA1c) levels. Our aim was to investigate the effect of HK1 rs7072268 on measures of glucose- and lipid-metabolism in a Danish non-diabetic population and combine the outcome of these analyses in a meta-analysis with previously published results. Furthermore, our aim was to perform a type 2 diabetes case-control analysis and meta-analysis with two previous case-control studies.
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Natural selection affects multiple aspects of genetic variation at putatively neutral sites across the human genome.
PLoS Genet.
PUBLISHED: 02-03-2011
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A major question in evolutionary biology is how natural selection has shaped patterns of genetic variation across the human genome. Previous work has documented a reduction in genetic diversity in regions of the genome with low recombination rates. However, it is unclear whether other summaries of genetic variation, like allele frequencies, are also correlated with recombination rate and whether these correlations can be explained solely by negative selection against deleterious mutations or whether positive selection acting on favorable alleles is also required. Here we attempt to address these questions by analyzing three different genome-wide resequencing datasets from European individuals. We document several significant correlations between different genomic features. In particular, we find that average minor allele frequency and diversity are reduced in regions of low recombination and that human diversity, human-chimp divergence, and average minor allele frequency are reduced near genes. Population genetic simulations show that either positive natural selection acting on favorable mutations or negative natural selection acting against deleterious mutations can explain these correlations. However, models with strong positive selection on nonsynonymous mutations and little negative selection predict a stronger negative correlation between neutral diversity and nonsynonymous divergence than observed in the actual data, supporting the importance of negative, rather than positive, selection throughout the genome. Further, we show that the widespread presence of weakly deleterious alleles, rather than a small number of strongly positively selected mutations, is responsible for the correlation between neutral genetic diversity and recombination rate. This work suggests that natural selection has affected multiple aspects of linked neutral variation throughout the human genome and that positive selection is not required to explain these observations.
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Studies of the association of Arg72Pro of tumor suppressor protein p53 with type 2 diabetes in a combined analysis of 55,521 Europeans.
PLoS ONE
PUBLISHED: 01-20-2011
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A study of 222 candidate genes in type 2 diabetes reported association of variants in RAPGEF1, ENPP1, TP53, NRF1, SLC2A2, SLC2A4 and FOXC2 with type 2 diabetes in 4,805 Finnish individuals. We aimed to replicate these associations in a Danish case-control study and to substantiate any replicated associations in meta-analyses. Furthermore, we evaluated the impact on diabetes-related intermediate traits in a population-based sample of middle-aged Danes.
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Associations between APOE variants and metabolic traits and the impact of psychological stress.
PLoS ONE
PUBLISHED: 01-19-2011
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In a previous study, we observed that associations between APOE rs439401 and metabolic traits were moderated by chronic stress. Thus, in a population of stressed and non-stressed Danish men, we examined whether associations between APOE rs439401 and a panel of metabolic quantitative traits, all metabolic traits which may lead to T2D and CVD were moderated by psychological stress.
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Implications of central obesity-related variants in LYPLAL1, NRXN3, MSRA, and TFAP2B on quantitative metabolic traits in adult Danes.
PLoS ONE
PUBLISHED: 01-10-2011
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Two meta-analyses of genome-wide association studies (GWAS) have suggested that four variants: rs2605100 in lysophospholipase-like 1 (LYPLAL1), rs10146997 in neuroxin 3 (NRXN3), rs545854 in methionine sulfoxide reductase A (MSRA), and rs987237 in transcription factor activating enhancer-binding protein 2 beta (TFAP2B) associate with measures of central obesity. To elucidate potential underlying phenotypes we aimed to investigate whether these variants associated with: 1) quantitative metabolic traits, 2) anthropometric measures (waist circumference (WC), waist-hip ratio, and BMI), or 3) type 2 diabetes, and central and general overweight and obesity.
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Familial mild hyperglycemia associated with a novel ABCC8-V84I mutation within three generations.
Pediatr Diabetes
PUBLISHED: 01-09-2011
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We present a unique case of a 19-year-old man with a positive family history of persistent mild hyperglycemia and a novel V84I mutation in ABCC8. The proband was initially detected to have fasting hyperglycemia (ranging 6.1-6.4 mmol/L) at the age of 12 years. Increased fasting blood glucose was also subsequently detected in five additional family members (in his twin brother, sister, mother, maternal aunt, and grandfather). The grandfather has been known to have mild diabetes since 30 years and has never been treated. After having excluded a causative mutation in five maturity-onset diabetes of the young genes (MODY1-4 and 6), we identified a novel ABCC8 V84I mutation, which segregated with autosomal dominant transmission of mild hyperglycemia within three generations. This mutation that is located in a conserved area of transmembrane domain TMD0 seems to be a rare cause of clinical phenotype resembling glucokinase-deficient diabetes.
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The minor C-allele of rs2014355 in ACADS is associated with reduced insulin release following an oral glucose load.
BMC Med. Genet.
PUBLISHED: 01-06-2011
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A genome-wide association study (GWAS) using metabolite concentrations as proxies for enzymatic activity, suggested that two variants: rs2014355 in the gene encoding short-chain acyl-coenzyme A dehydrogenase (ACADS) and rs11161510 in the gene encoding medium-chain acyl-coenzyme A dehydrogenase (ACADM) impair fatty acid ?-oxidation. Chronic exposure to fatty acids due to an impaired ?-oxidation may down-regulate the glucose-stimulated insulin release and result in an increased risk of type 2 diabetes (T2D). We aimed to investigate whether the two variants associate with altered insulin release following an oral glucose load or with T2D.
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Influences of the common FTO rs9939609 variant on inflammatory markers throughout a broad range of body mass index.
PLoS ONE
PUBLISHED: 01-05-2011
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A recent study reported that the fatness associated A-allele of FTO rs9939609 increased plasma high sensitivity C-reactive protein (hs-CRP) levels independent of fatness. We aimed to investigate if this gene variant had fatness-independent effects on plasma hs-CRP and 10 additional circulating obesity-related adipokines throughout a broad range of body mass index (BMI) among Danish men.
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Bioinformatics-driven identification and examination of candidate genes for non-alcoholic fatty liver disease.
PLoS ONE
PUBLISHED: 01-04-2011
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Candidate genes for non-alcoholic fatty liver disease (NAFLD) identified by a bioinformatics approach were examined for variant associations to quantitative traits of NAFLD-related phenotypes.
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Improved glycemic control induced by both metformin and repaglinide is associated with a reduction in blood levels of 3-deoxyglucosone in nonobese patients with type 2 diabetes.
Eur. J. Endocrinol.
PUBLISHED: 01-04-2011
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Metformin has been reported to reduce ?-dicarbonyls, which are known to contribute to diabetic complications. It is unclear whether this is due to direct quenching of ?-dicarbonyls or to an improvement in glycemic control. We therefore compared the effects of metformin versus repaglinide, an antihyperglycemic agent with an insulin-secreting mechanism, on the levels of the ?-dicarbonyl 3-deoxyglucosone (3DG).
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.