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Abstract
Beta cell dysfunction and insulin resistance are inherently complex with their interrelation for triggering the pathogenesis of diabetes also somewhat undefined. Both pathogenic states induce hyperglycemia and therefore increase insulin demand. Beta cell dysfunction results from inadequate glucose sensing to stimulate insulin secretion therefore elevated glucose concentrations prevail. Persistently elevated glucose concentrations above the physiological range result in the manifestation of hyperglycemia. With systemic insulin resistance, insulin signaling within glucose recipient tissues is defective therefore hyperglycemia perseveres. Beta cell dysfunction supersedes insulin resistance in inducing diabetes. Both pathological states influence each other and presumably synergistically exacerbate diabetes. Preserving beta cell function and insulin signaling in beta cells and insulin signaling in the glucose recipient tissues will maintain glucose homeostasis.
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Affiliation(s)
- Marlon E. Cerf
- Diabetes Discovery Platform, South African Medical Research CouncilCape Town, South Africa
- *Correspondence: Marlon E. Cerf, Diabetes Discovery Platform, South African Medical Research Council, PO Box 19070, Tygerberg, Cape Town 7505, South Africa. e-mail:
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Stojanovic I, Saksida T, Timotijevic G, Sandler S, Stosic-Grujicic S. Macrophage migration inhibitory factor (MIF) enhances palmitic acid- and glucose-induced murine beta cell dysfunction and destruction in vitro. Growth Factors 2012; 30:385-93. [PMID: 23137174 DOI: 10.3109/08977194.2012.734506] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Although several reports suggest a potentially deleterious role of macrophage migration inhibitory factor (MIF) in type 2 diabetes (T2D) pathology, it is still unclear how this pro-inflammatory cytokine acts on pancreatic beta cells. The aim of the present study was to evaluate MIF effects on murine beta cells in the in vitro settings mimicking T2D-associated conditions. Results indicate that recombinant MIF further increased apoptosis of pancreatic islets or MIN6 cells upon exposure to palmitic acid or glucose. This was accompanied by upregulation of several pro-apoptotic molecules. Furthermore, MIF potentiated nutrient-induced islet cell dysfunction, as revealed by lower glucose oxidation rate, ATP content, and depolarized mitochondrial membrane. The final outcome was potentiation of mitochondrial apoptotic pathway. The observed upregulation of nutrient-induced islet cell dysfunction and apoptosis by MIF implicates that silencing MIF may be beneficial for maintaining integrity of endocrine pancreas in obesity-associated T2D.
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Affiliation(s)
- Ivana Stojanovic
- Department of Immunology, Institute for Biological Research "Sinisa Stankovic", University of Belgrade, Serbia.
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53
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Genes in the ureteric budding pathway: association study on vesico-ureteral reflux patients. PLoS One 2012; 7:e31327. [PMID: 22558067 PMCID: PMC3338743 DOI: 10.1371/journal.pone.0031327] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2011] [Accepted: 01/06/2012] [Indexed: 11/19/2022] Open
Abstract
Vesico-ureteral reflux (VUR) is the retrograde passage of urine from the bladder to the urinary tract and causes 8.5% of end-stage renal disease in children. It is a complex genetic developmental disorder, in which ectopic embryonal ureteric budding is implicated in the pathogenesis. VUR is part of the spectrum of Congenital Anomalies of the Kidney and Urinary Tract (CAKUT). We performed an extensive association study for primary VUR using a two-stage, case-control design, investigating 44 candidate genes in the ureteric budding pathway in 409 Dutch VUR patients. The 44 genes were selected from the literature and a set of 567 single nucleotide polymorphisms (SNPs) capturing their genetic variation was genotyped in 207 cases and 554 controls. The 14 SNPs with p<0.005 were included in a follow-up study in 202 cases and 892 controls. Of the total cohort, ~50% showed a clear-cut primary VUR phenotype and ~25% had both a duplex collecting system and VUR. We also looked for association in these two extreme phenotype groups. None of the SNPs reached a significant p-value. Common genetic variants in four genes (GREM1, EYA1, ROBO2 and UPK3A) show a trend towards association with the development of primary VUR (GREM1, EYA1, ROBO2) or duplex collecting system (EYA1 and UPK3A). SNPs in three genes (TGFB1, GNB3 and VEGFA) have been shown to be associated with VUR in other populations. Only the result of rs1800469 in TGFB1 hinted at association in our study. This is the first extensive study of common variants in the genes of the ureteric budding pathway and the genetic susceptibility to primary VUR.
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54
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Li MX, Gui HS, Kwan JSH, Bao SY, Sham PC. A comprehensive framework for prioritizing variants in exome sequencing studies of Mendelian diseases. Nucleic Acids Res 2012; 40:e53. [PMID: 22241780 PMCID: PMC3326332 DOI: 10.1093/nar/gkr1257] [Citation(s) in RCA: 209] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Exome sequencing strategy is promising for finding novel mutations of human monogenic disorders. However, pinpointing the casual mutation in a small number of samples is still a big challenge. Here, we propose a three-level filtration and prioritization framework to identify the casual mutation(s) in exome sequencing studies. This efficient and comprehensive framework successfully narrowed down whole exome variants to very small numbers of candidate variants in the proof-of-concept examples. The proposed framework, implemented in a user-friendly software package, named KGGSeq (http://statgenpro.psychiatry.hku.hk/kggseq), will play a very useful role in exome sequencing-based discovery of human Mendelian disease genes.
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Affiliation(s)
- Miao-Xin Li
- Department of Psychiatry, University of Hong Kong, Pokfulam, Hong Kong, China.
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55
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Russo C, Salina A, Aloi C, Iafusco D, Lorini R, d'Annunzio G. Mother and daughter carrying the same KCNJ11 mutation but with a different response to switching from insulin to sulfonylurea. Diabetes Res Clin Pract 2011; 94:e50-2. [PMID: 21871684 DOI: 10.1016/j.diabres.2011.07.039] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 07/20/2011] [Accepted: 07/26/2011] [Indexed: 11/16/2022]
Abstract
KCNJ11 gene mutations are related to permanent neonatal diabetes mellitus (PNDM). Glycemic stability minimizes the risk of complications. Sulfonylureas (SU) are the proven best therapeutic option. We report a 18-month follow-up of switching from insulin to SU in a mother and her daughter with PNDM due to KCNJ11 mutation.
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Affiliation(s)
- Chiara Russo
- Pediatric Clinic, University of Genoa, IRCCS G Gaslini Institute, Genoa, Italy
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56
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Lopes MC, Zeggini E, Panoutsopoulou K. Do genome-wide association scans have potential for translation? Clin Chem Lab Med 2011; 50:255-60. [PMID: 22022988 DOI: 10.1515/cclm.2011.748] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 09/17/2011] [Indexed: 11/15/2022]
Abstract
The success of genome-wide association studies (GWAS) in identifying replicating associations has greatly contributed to understanding of the genetic aetiology of complex diseases. This review discusses and provides examples of the potential of GWAS findings to be translated into clinical practice, i.e., diagnosis, prediction, prognosis, novel treatments and response to treatment of common diseases. The biological insights afforded by newly-identified robust associations represent the largest, albeit indirect, translational contribution of GWAS.
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Ketterer C, Müssig K, Heni M, Dudziak K, Randrianarisoa E, Wagner R, Machicao F, Stefan N, Holst JJ, Fritsche A, Häring HU, Staiger H. Genetic variation within the TRPM5 locus associates with prediabetic phenotypes in subjects at increased risk for type 2 diabetes. Metabolism 2011; 60:1325-33. [PMID: 21489577 DOI: 10.1016/j.metabol.2011.02.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 01/28/2011] [Accepted: 02/04/2011] [Indexed: 01/17/2023]
Abstract
The functional knockout of the calcium-sensitive, nonselective cation channel TRPM5 alters glucose-induced insulin secretion and glucose tolerance. We hypothesized that genetic variation in the TRPM5 gene may contribute to prediabetic phenotypes, including pancreatic β-cell dysfunction. We genotyped 1798 white subjects at increased type 2 diabetes mellitus risk for 9 TRPM5 single nucleotide polymorphisms (namely, rs2301696, rs800344, rs800345, rs800347, rs800348, rs2074234, rs2301698, rs886277, and rs2301699) and also performed correlational analyses with metabolic traits. An oral glucose tolerance test (OGTT) was conducted on all subjects, and a subset (n = 525) additionally underwent a hyperinsulinemic-euglycemic clamp. The 9 chosen single nucleotide polymorphisms cover 100% of the common genetic variation (minor allele frequency ≥0.05) within the TRPM5 locus (D' = 1.0; r² ≥ 0.8). Rs800344, rs800345, and rs2301699 were significantly associated with area under the curve (AUC) glucose during the OGTT in the additive and dominant models after adjustment for sex, age, and body mass index (all Ps ≤ .0025). Furthermore, rs800344 was significantly associated with 2-hour glucose in the dominant model (P = .0009). After stratification for sex, rs2301699 was significantly associated with the ratio of AUC insulin 0 to 30 minutes to AUC glucose 0 to 30 minutes in women (P = .0097), but not in men (P = .3), in the dominant model. Female minor allele carriers of rs2301699 showed significantly lower glucagon-like peptide-1 levels at 30 minutes during the OGTT compared with major allele homozygotes (P = .0124), whereas in male subjects, no significant differences were found (P = .3). In our German population, the common TRPM5 variants are likely to be associated with prediabetic phenotypes; and this may in turn contribute to the development of type 2 diabetes mellitus.
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Affiliation(s)
- Caroline Ketterer
- Division of Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry, Department of Internal Medicine, Eberhard Karls University Tübingen, Otfried-Müller-Str. 10, 72076 Tübingen, Germany
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58
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Abstract
BACKGROUND Recent genome-wide association studies enlarged our knowledge about the genetic background of type 2 diabetes. AIMS This review provides an overview of the role of these novel genetic findings for the pathophysiology, prediction and treatment of type 2 diabetes. RESULTS The genetic susceptibility to type 2 diabetes appears to be determined by many common variants in multiple gene loci with low effect sizes. Although at least 36 diabetes-associated genes were identified, only about 10% of the heritability of type 2 diabetes can be explained. Most of the discovered gene variants have been linked to beta-cell dysfunction rather than insulin resistance, which might challenge established thinking of type 2 diabetes as a predominant disorder of insulin action. Genetic data can lead to statistically significant, but not to clinically relevant contributions to risk prediction for type 2 diabetes. Nevertheless, preliminary evidence suggests interactions between genotypes and response to lifestyle changes or drug treatment. CONCLUSIONS Future studies need to target the issue of hidden heritability and to detect the causal gene variants within the identified gene loci. Improved understanding of the genetic contribution to type 2 diabetes may then help addressing the questions whether genotyping is useful to predict individual diabetes risk, identifies individual responsiveness to preventive and therapeutic interventions or at least allows for breaking down type 2 diabetes into smaller, clinically meaningful subtypes.
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Affiliation(s)
- Christian Herder
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research at Heinrich Heine University Düsseldorf, Germany.
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59
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Li S, Zhao JH, Luan J, Langenberg C, Luben RN, Khaw KT, Wareham NJ, Loos RJF. Genetic predisposition to obesity leads to increased risk of type 2 diabetes. Diabetologia 2011; 54:776-82. [PMID: 21267540 PMCID: PMC3052481 DOI: 10.1007/s00125-011-2044-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 12/10/2010] [Indexed: 01/10/2023]
Abstract
AIMS/HYPOTHESIS Obesity is a major risk factor for type 2 diabetes. Recent genome-wide association (GWA) studies have identified multiple loci robustly associated with BMI and risk of obesity. However, information on their associations with type 2 diabetes is limited. Such information could help increase our understanding of the link between obesity and type 2 diabetes. We examined the associations of 12 obesity susceptibility loci, individually and in combination, with risk of type 2 diabetes in the population-based European Prospective Investigation of Cancer (EPIC) Norfolk cohort. METHODS We genotyped 12 SNPs, identified by GWA studies of BMI, in 20,428 individuals (aged 39-79 years at baseline) with an average follow-up of 12.9 years, during which 729 individuals developed type 2 diabetes. A genetic predisposition score was calculated by adding the BMI-increasing alleles across the 12 SNPs. Associations with incidence of type 2 diabetes were examined by logistic regression models. RESULTS Of the 12 SNPs, eight showed a trend with increased risk of type 2 diabetes, consistent with their BMI-increasing effects. Each additional BMI-increasing allele in the genetic predisposition score was associated with a 4% increased odds of developing type 2 diabetes (OR 1.041, 95% CI 1.005-1.078; p = 0.02). Adjustment for BMI completely abolished the association with incident type 2 diabetes (OR 1.003, 95% CI 0.967-1.039; p = 0.89). CONCLUSIONS/INTERPRETATION The genetic predisposition to obesity leads to increased risk of developing type 2 diabetes, which is completely mediated by its obesity-predisposing effect.
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Affiliation(s)
- S. Li
- MRC Epidemiology Unit, Institute of Metabolic Science, Box 285, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0QQ UK
| | - J. H. Zhao
- MRC Epidemiology Unit, Institute of Metabolic Science, Box 285, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0QQ UK
| | - J. Luan
- MRC Epidemiology Unit, Institute of Metabolic Science, Box 285, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0QQ UK
| | - C. Langenberg
- MRC Epidemiology Unit, Institute of Metabolic Science, Box 285, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0QQ UK
| | - R. N. Luben
- Department of Public Health and Primary Care, Institute of Public Health, University of Cambridge, Cambridge, UK
| | - K. T. Khaw
- Department of Public Health and Primary Care, Institute of Public Health, University of Cambridge, Cambridge, UK
| | - N. J. Wareham
- MRC Epidemiology Unit, Institute of Metabolic Science, Box 285, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0QQ UK
| | - R. J. F. Loos
- MRC Epidemiology Unit, Institute of Metabolic Science, Box 285, Addenbrooke’s Hospital, Hills Road, Cambridge, CB2 0QQ UK
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Abstract
BACKGROUND
Multiple genes that are associated with the risk of developing diabetes or the risk of diabetes complications have been identified by candidate gene analysis and genomewide scanning. These molecular markers, together with clinical data and findings from proteomics, metabolomics, pharmacogenetics, and other methods, lead to a consideration of the extent to which personalized approaches can be applied to the treatment of diabetes mellitus.
CONTENT
Known genes that cause monogenic subtypes of diabetes are reviewed, and several examples are discussed in which the genotype of an individual with diabetes can direct considerations of preferred choices for glycemic therapy. The extent of characterization of polygenic determinants of type 1 and type 2 diabetes is summarized, and the potential for using this information in personalized management of glycemia and complications in diabetes is discussed. The application and current limitations of proteomic and metabolomic methods in elucidating diabetes heterogeneity is reviewed.
SUMMARY
There is established heterogeneity in the determinants of diabetes and the risk of diabetes complications. Understanding the basis of this heterogeneity provides an opportunity for personalizing prevention and treatment strategies according to individual patient clinical and molecular characteristics. There is evidence-based support for benefits from a personalized approach to diabetes care in patients with certain monogenic forms of diabetes. It is anticipated that strategies for individualized treatment decisions in the more common forms of diabetes will emerge with expanding knowledge of polygenic factors and other molecular determinants of disease.
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Affiliation(s)
- Noemi Malandrino
- Division of Endocrinology, Department of Medicine, Alpert Medical School of Brown University, Providence, RI; Hallett Center for Diabetes and Endocrinology, Rhode Island Hospital, Providence, RI
| | - Robert J Smith
- Division of Endocrinology, Department of Medicine, Alpert Medical School of Brown University, Providence, RI; Hallett Center for Diabetes and Endocrinology, Rhode Island Hospital, Providence, RI
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Malecki MT. The search for undiagnosed MODY patients: what is the next step? Diabetologia 2010; 53:2465-7. [PMID: 20865241 DOI: 10.1007/s00125-010-1908-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 08/23/2010] [Indexed: 11/28/2022]
Affiliation(s)
- M T Malecki
- Department of Metabolic Diseases, Jagiellonian University Medical College, 15 Kopernika Street, 31-501 Krakow, Poland.
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Genetic polymorphisms in diabetes: influence on therapy with oral antidiabetics. ACTA PHARMACEUTICA 2010; 60:387-406. [PMID: 21169132 DOI: 10.2478/v10007-010-0040-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Due to new genetic insights, etiologic classification of diabetes is under constant scrutiny. Hundreds, or even thousands, of genes are linked with type 2 diabetes. Three common variants (Lys23 of KCNJ11, Pro12 of PPARG, and the T allele at rs7903146 of TCF7L2) have been shown to be predisposed to type 2 diabetes mellitus across many large studies. Individually, each of these polymorphisms is only moderately predisposed to type 2 diabetes. On the other hand, monogenic forms of diabetes such as MODY and neonatal diabetes are characterized by unique clinical features and the possibility of applying a tailored treatment.Genetic polymorphisms in drug-metabolizing enzymes, transporters, receptors, and other drug targets have been linked to interindividual differences in the efficacy and toxicity of a number of medications. Mutations in genes important in drug absorption, distribution, metabolism and excretion (ADME) play a critical role in pharmacogenetics of diabetes.There are currently five major classes of oral pharmacological agents available to treat type 2 diabetes: sulfonylureas, meglitinides, metformin (a biguanide), thiazolidinediones, and α-glucosidase inhibitors. Other classes are also mentioned in literature.In this work, different types of genetic mutations (mutations of the gene for glucokinase, HNF 1α, HNF1β and Kir6.2 and SUR1 subunit of KATP channel, PPAR-γ, OCT1 and OCT2, cytochromes, direct drug-receptor (KCNJ11), as well as the factors that influence the development of the disease (TCF7L2) and variants of genes that lead to hepatosteatosis caused by thiazolidinediones) and their influence on the response to therapy with oral antidiabetics will be reviewed.
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Ketterer C, Müssig K, Machicao F, Stefan N, Fritsche A, Häring HU, Staiger H. Genetic variation within the NR1H2 gene encoding liver X receptor β associates with insulin secretion in subjects at increased risk for type 2 diabetes. J Mol Med (Berl) 2010; 89:75-81. [PMID: 21042792 DOI: 10.1007/s00109-010-0687-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 08/23/2010] [Accepted: 09/08/2010] [Indexed: 01/17/2023]
Abstract
The liver X receptors (LXRs)-α and -β play a crucial role in control of insulin production and secretion in pancreatic β-cells. We hypothesized that common variants in the NR1H2 and NR1H3 genes, encoding LXR-β and -α, respectively, may alter pancreatic β-cell function. One thousand five hundred seventy-four subjects of European ancestry with elevated risk for type 2 diabetes were genotyped for the two NR1H2 single nucleotide polymorphisms (SNPs) rs2248949 and rs1405655 and for the four NR1H3 SNPs rs11039149, rs3758673, rs12221497 and rs2279238, and association studies with metabolic traits were performed. Metabolic characterization comprised an oral glucose tolerance test (OGTT) in all participants and, in addition, a hyperinsulinemic-euglycemic clamp and an intravenous glucose tolerance test (IVGTT) in subsets. One hundred per cent of common genetic variation (minor allele frequency ≥1%) within the NR1H2 and NR1H3 loci (D' = 1.0; r² ≥ 0.8) were covered by the six chosen tagging SNPs. NR1H2 rs2248949 was nominally associated with OGTT-derived first-phase insulin secretion and proinsulin conversion to insulin and significantly associated with the AUC of insulin levels during the IVGTT (p = 0.007) after adjustment for age, gender, BMI and insulin sensitivity in the dominant model, with the minor allele conferring reduced pancreatic β-cell function to the carriers. In subjects of European ancestry at increased risk for type 2 diabetes, common variation within the NR1H2 gene impaired insulin secretion, which may facilitate the development of type 2 diabetes.
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Affiliation(s)
- Caroline Ketterer
- Division of Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry, Department of Internal Medicine, Eberhard Karls University Tübingen, German Center for Diabetes Research (DZD), Otfried-Müller-Str. 10, 72076, Tübingen, Germany
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Støy J, Steiner DF, Park SY, Ye H, Philipson LH, Bell GI. Clinical and molecular genetics of neonatal diabetes due to mutations in the insulin gene. Rev Endocr Metab Disord 2010; 11:205-15. [PMID: 20938745 PMCID: PMC2974937 DOI: 10.1007/s11154-010-9151-3] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
Over the last decade our insight into the causes of neonatal diabetes has greatly expanded. Neonatal diabetes was once considered a variant of type 1 diabetes that presented early in life. Recent advances in our understanding of this disorder have established that neonatal diabetes is not an autoimmune disease, but rather is a monogenic form of diabetes resulting from mutations in a number of different genes encoding proteins that play a key role in the normal function of the pancreatic beta-cell. Moreover, a correct genetic diagnosis can affect treatment and clinical outcome. This is especially true for patients with mutations in the genes KCNJ11 or ABCC8 that encode the two protein subunits (Kir6.2 and SUR1, respectively) of the ATP-sensitive potassium channel. These patients can be treated with oral sulfonylurea drugs with better glycemic control and quality of life. Recently, mutations in the insulin gene (INS) itself have been identified as another cause of neonatal diabetes. In this article, we review the role of INS mutations in the pathophysiology of neonatal diabetes.
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Affiliation(s)
- Julie Støy
- Department of Internal Medicine and Endocrinology, Aarhus University Hospital, Nørrebrogade 44, 8000, Aarhus C, Denmark.
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Njølstad PR, Hertel JK, Søvik O, Raeder H, Johansson S, Molven A. [Progress in diabetes genetics]. TIDSSKRIFT FOR DEN NORSKE LEGEFORENING 2010; 130:1145-9. [PMID: 20531501 DOI: 10.4045/tidsskr.09.1035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
BACKGROUND Diabetes is classified as Type 1 diabetes, Type 2 diabetes, gestational diabetes and other types. Our goal was to provide an overview of new genetic knowledge of monogenic and type 2 diabetes. MATERIAL AND METHOD The article is based on literature identified through a non-systematic search in PubMed and own experience concerning research in diabetes genetics and treatment of patients with monogenic diabetes. RESULTS 18 genes have been found for which one single mutation may cause diabetes. The most common causes for such monogenic diabetes are mutations in the genes KCNJ11, ABCC8 and INS when the condition is diagnosed at the age 0 - 6 months, and in the genes HNF1A, GCK, HNF4A and HNF1B when the diagnosis is made later than six months of age. Genetic testing is appropriate in assessment of monogenic diabetes, because antidiabetic tablets rather that insulin injections can be used to treat patients with mutations in certain genes; i.e. KCNJ11, ABCC8, HNF1A and HNF4A. Genome-wide association studies have recently identified about 20 genetic variants that increase the risk of Type 2 diabetes, but which have a low predictive value for development of disease. How these genetic variants can cause Type 2 diabetes has not been assessed and clinical relevance remains to be shown. INTERPRETATION So far, genetic findings only affect diagnosis and treatment of monogenic diabetes.
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Affiliation(s)
- Pål R Njølstad
- Senter for diabetesgenetikk, Barneklinikken, Haukeland universitetssykehus, 5021 Bergen, Norway.
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68
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Donelan W, Koya V, Li SW, Yang LJ. Distinct regulation of hepatic nuclear factor 1alpha by NKX6.1 in pancreatic beta cells. J Biol Chem 2010; 285:12181-9. [PMID: 20106981 PMCID: PMC2852957 DOI: 10.1074/jbc.m109.064238] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 01/19/2010] [Indexed: 01/12/2023] Open
Abstract
Hepatic nuclear factor 1alpha (HNF1alpha) is a key regulator of development and function in pancreatic beta cells and is specifically involved in regulation of glycolysis and glucose-stimulated insulin secretion. Abnormal expression of HNF1alpha leads to development of MODY3 (maturity-onset diabetes of the young 3). We report that NK6 homeodomain 1 (NKX6.1) binds to a cis-regulatory element in the HNF1alpha promoter and is a major regulator of this gene in beta cells. We identified an NKX6.1 recognition sequence in the distal region of the HNF1alpha promoter and demonstrated specific binding of NKX6.1 in beta cells by electrophoretic mobility shift and chromatin immunoprecipitation assays. Site-directed mutagenesis of the NKX6.1 core-binding sequence eliminated NKX6.1-mediated activation and substantially decreased activity of the HNF1alpha promoter in beta cells. Overexpression or small interfering RNA-mediated knockdown of the Nkx6.1 gene resulted in increased or diminished HNF1alpha gene expression, respectively, in beta cells. We conclude that NKX6.1 is a novel regulator of HNF1alpha in pancreatic beta cells. This novel regulatory mechanism for HNF1alpha in beta cells may provide new molecular targets for the diagnosis of MODY3.
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Affiliation(s)
- William Donelan
- From the Department of Pathology, Immunology, and Laboratory Medicine, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Vijay Koya
- From the Department of Pathology, Immunology, and Laboratory Medicine, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Shi-Wu Li
- From the Department of Pathology, Immunology, and Laboratory Medicine, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Li-Jun Yang
- From the Department of Pathology, Immunology, and Laboratory Medicine, University of Florida College of Medicine, Gainesville, Florida 32610
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Smith RJ, Nathan DM, Arslanian SA, Groop L, Rizza RA, Rotter JI. Individualizing therapies in type 2 diabetes mellitus based on patient characteristics: what we know and what we need to know. J Clin Endocrinol Metab 2010; 95:1566-74. [PMID: 20194712 PMCID: PMC5393381 DOI: 10.1210/jc.2009-1966] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 01/25/2010] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Type 2 diabetes is heterogeneous in its clinical features, pathogenesis, and predisposing or causal genetic factors. This report examines what is known and what needs to be learned about the potential to individualize glycemic therapies in type 2 diabetes, based on phenotypes and genotypes. PARTICIPANTS A 29-member international working group with expertise in diabetes epidemiology, physiology, genetics, clinical trials, and clinical care participated in formal presentations and discussions at a conference on April 16-17, 2009. A writing group subsequently prepared this summary and recommendations. The conference was coendorsed by The Endocrine Society and the American Diabetes Association and was supported by an unrestricted educational grant from Novo Nordisk. EVIDENCE Participants reviewed and discussed published literature, plus their own unpublished data. CONSENSUS PROCESS The summary and recommendations were supported unanimously by the writing group as representing the majority or unanimous opinions of the working group. CONCLUSIONS Recent advances in genetics, such as the identification of Kir6.2 mutations and the responsible genes for several forms of maturity onset diabetes of the young (MODY), have established precedents linking specifically effective therapies to defined diabetes subtypes. The recent increase in identified polygenic factors related to type 2 diabetes and our understanding of the pathogenesis of diabetes provide potential opportunities to individualize therapy. To further this process, we recommend expanded analysis of existing data sources and the development of new basic and clinical research studies, including a greater focus on identifying type 2 diabetes subtypes, their response to different therapies, and quantitation of cost-effectiveness.
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Affiliation(s)
- Robert J Smith
- Division of Endocrinology and the Hallett Center for Diabetes and Endocrinology, Alpert Medical School of Brown University, Providence, Rhode Island 02903, USA.
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70
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Smith SB, Qu HQ, Taleb N, Kishimoto NY, Scheel DW, Lu Y, Patch AM, Grabs R, Wang J, Lynn FC, Miyatsuka T, Mitchell J, Seerke R, Désir J, Vanden Eijnden S, Abramowicz M, Kacet N, Weill J, Renard ME, Gentile M, Hansen I, Dewar K, Hattersley AT, Wang R, Wilson ME, Johnson JD, Polychronakos C, German MS. Rfx6 directs islet formation and insulin production in mice and humans. Nature 2010; 463:775-80. [PMID: 20148032 PMCID: PMC2896718 DOI: 10.1038/nature08748] [Citation(s) in RCA: 235] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Accepted: 12/07/2009] [Indexed: 02/07/2023]
Abstract
Insulin from the beta-cells of the pancreatic islets of Langerhans controls energy homeostasis in vertebrates, and its deficiency causes diabetes mellitus. During embryonic development, the transcription factor neurogenin 3 (Neurog3) initiates the differentiation of the beta-cells and other islet cell types from pancreatic endoderm, but the genetic program that subsequently completes this differentiation remains incompletely understood. Here we show that the transcription factor Rfx6 directs islet cell differentiation downstream of Neurog3. Mice lacking Rfx6 failed to generate any of the normal islet cell types except for pancreatic-polypeptide-producing cells. In human infants with a similar autosomal recessive syndrome of neonatal diabetes, genetic mapping and subsequent sequencing identified mutations in the human RFX6 gene. These studies demonstrate a unique position for Rfx6 in the hierarchy of factors that coordinate pancreatic islet development in both mice and humans. Rfx6 could prove useful in efforts to generate beta-cells for patients with diabetes.
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Affiliation(s)
- Stuart B Smith
- Diabetes Center, University of California San Francisco, San Francisco, California 94143, USA
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71
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Boesgaard TW, Pruhova S, Andersson EA, Cinek O, Obermannova B, Lauenborg J, Damm P, Bergholdt R, Pociot F, Pisinger C, Barbetti F, Lebl J, Pedersen O, Hansen T. Further evidence that mutations in INS can be a rare cause of Maturity-Onset Diabetes of the Young (MODY). BMC MEDICAL GENETICS 2010; 11:42. [PMID: 20226046 PMCID: PMC2848224 DOI: 10.1186/1471-2350-11-42] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Accepted: 03/12/2010] [Indexed: 11/16/2022]
Abstract
Background Insulin gene (INS) mutations have recently been described as a common cause of permanent neonatal diabetes (PNDM) and a rare cause of diabetes diagnosed in childhood or adulthood. Methods INS was sequenced in 116 maturity-onset diabetes of the young (MODYX) patients (n = 48 Danish and n = 68 Czech), 83 patients with gestational diabetes mellitus (GDM), 34 type 1 diabetic patients screened negative for glutamic acid decarboxylase (GAD), and 96 glucose tolerant individuals. The control group was randomly selected from the population-based sampled Inter99 study. Results One novel heterozygous mutation c.17G>A, R6H, was identified in the pre-proinsulin gene (INS) in a Danish MODYX family. The proband was diagnosed at 20 years of age with mild diabetes and treated with diet and oral hypoglycaemic agent. Two other family members who carried the INS R6H were diagnosed with diabetes when 51 years old and with GDM when 27 years old, respectively. A fourth mutation carrier had normal glucose tolerance when 20 years old. Two carriers of INS R6H were also examined twice with an oral glucose tolerance test (OGTT) with 5 years interval. They both had a ~30% reduction in beta-cell function measured as insulinogenic index. In a Czech MODYX family a previously described R46Q mutation was found. The proband was diagnosed at 13 years of age and had been treated with insulin since onset of diabetes. Her mother and grandmother were diagnosed at 14 and 35 years of age, respectively, and were treated with oral hypoglycaemic agents and/or insulin. Conclusion Mutations in INS can be a rare cause of MODY and we conclude that screening for mutations in INS should be recommended in MODYX patients.
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Affiliation(s)
- Trine W Boesgaard
- Steno Diabetes Centre and Hagedorn Research Institute, Gentofte, Denmark.
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72
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Cnop M, Hughes SJ, Igoillo-Esteve M, Hoppa MB, Sayyed F, van de Laar L, Gunter JH, de Koning EJP, Walls GV, Gray DWG, Johnson PRV, Hansen BC, Morris JF, Pipeleers-Marichal M, Cnop I, Clark A. The long lifespan and low turnover of human islet beta cells estimated by mathematical modelling of lipofuscin accumulation. Diabetologia 2010; 53:321-30. [PMID: 19855953 DOI: 10.1007/s00125-009-1562-x] [Citation(s) in RCA: 160] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Accepted: 08/24/2009] [Indexed: 12/17/2022]
Abstract
AIMS/HYPOTHESIS Defects in pancreatic beta cell turnover are implicated in the pathogenesis of type 2 diabetes by genetic markers for diabetes. Decreased beta cell neogenesis could contribute to diabetes. The longevity and turnover of human beta cells is unknown; in rodents <1 year old, a half-life of 30 days is estimated. Intracellular lipofuscin body (LB) accumulation is a hallmark of ageing in neurons. To estimate the lifespan of human beta cells, we measured beta cell LB accumulation in individuals aged 1-81 years. METHODS LB content was determined by electron microscopical morphometry in sections of beta cells from human (non-diabetic, n = 45; type 2 diabetic, n = 10) and non-human primates (n = 10; 5-30 years) and from 15 mice aged 10-99 weeks. Total cellular LB content was estimated by three-dimensional (3D) mathematical modelling. RESULTS LB area proportion was significantly correlated with age in human and non-human primates. The proportion of human LB-positive beta cells was significantly related to age, with no apparent differences in type 2 diabetes or obesity. LB content was low in human insulinomas (n = 5) and alpha cells and in mouse beta cells (LB content in mouse <10% human). Using 3D electron microscopy and 3D mathematical modelling, the LB-positive human beta cells (representing aged cells) increased from >or=90% (<10 years) to >or=97% (>20 years) and remained constant thereafter. CONCLUSIONS/INTERPRETATION Human beta cells, unlike those of young rodents, are long-lived. LB proportions in type 2 diabetes and obesity suggest that little adaptive change occurs in the adult human beta cell population, which is largely established by age 20 years.
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Affiliation(s)
- M Cnop
- Laboratory of Experimental Medicine and Division of Endocrinology, Université Libre de Bruxelles, Brussels, Belgium
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73
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Lango Allen H, Johansson S, Ellard S, Shields B, Hertel JK, Raeder H, Colclough K, Molven A, Frayling TM, Njølstad PR, Hattersley AT, Weedon MN. Polygenic risk variants for type 2 diabetes susceptibility modify age at diagnosis in monogenic HNF1A diabetes. Diabetes 2010; 59:266-71. [PMID: 19794065 PMCID: PMC2797932 DOI: 10.2337/db09-0555] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Mutations in the HNF1A gene are the most common cause of maturity-onset diabetes of the young (MODY). There is a substantial variation in the age at diabetes diagnosis, even within families where diabetes is caused by the same mutation. We investigated the hypothesis that common polygenic variants that predispose to type 2 diabetes might account for the difference in age at diagnosis. RESEARCH DESIGN AND METHODS Fifteen robustly associated type 2 diabetes variants were successfully genotyped in 410 individuals from 203 HNF1A-MODY families, from two study centers in the U.K. and Norway. We assessed their effect on the age at diagnosis both individually and in a combined genetic score by summing the number of type 2 diabetes risk alleles carried by each patient. RESULTS We confirmed the effects of environmental and genetic factors known to modify the age at HNF1A-MODY diagnosis, namely intrauterine hyperglycemia (-5.1 years if present, P = 1.6 x 10(-10)) and HNF1A mutation position (-5.2 years if at least two isoforms affected, P = 1.8 x 10(-2)). Additionally, our data showed strong effects of sex (females diagnosed 3.0 years earlier, P = 6.0 x 10(-4)) and age at study (0.3 years later diagnosis per year increase in age, P = 4.7 x 10(-38)). There were no strong individual single nucleotide polymorphism effects; however, in the combined genetic score model, each additional risk allele was associated with 0.35 years earlier diabetes diagnosis (P = 5.1 x 10(-3)). CONCLUSIONS We show that type 2 diabetes risk variants of modest effect sizes reduce the age at diagnosis in HNF1A-MODY. This is one of the first studies to demonstrate that clinical characteristics of a monogenic disease can be modified by common polygenic variants.
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Affiliation(s)
- Hana Lango Allen
- Genetics of Complex Traits, Peninsula College of Medicine and Dentistry, University of Exeter, Exeter, U.K.
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74
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't Hart LM, Simonis-Bik AM, Nijpels G, van Haeften TW, Schäfer SA, Houwing-Duistermaat JJ, Boomsma DI, Groenewoud MJ, Reiling E, van Hove EC, Diamant M, Kramer MHH, Heine RJ, Maassen JA, Kirchhoff K, Machicao F, Häring HU, Slagboom PE, Willemsen G, Eekhoff EM, de Geus EJ, Dekker JM, Fritsche A. Combined risk allele score of eight type 2 diabetes genes is associated with reduced first-phase glucose-stimulated insulin secretion during hyperglycemic clamps. Diabetes 2010; 59:287-92. [PMID: 19808892 PMCID: PMC2797935 DOI: 10.2337/db09-0736] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE At least 20 type 2 diabetes loci have now been identified, and several of these are associated with altered beta-cell function. In this study, we have investigated the combined effects of eight known beta-cell loci on insulin secretion stimulated by three different secretagogues during hyperglycemic clamps. RESEARCH DESIGN AND METHODS A total of 447 subjects originating from four independent studies in the Netherlands and Germany (256 with normal glucose tolerance [NGT]/191 with impaired glucose tolerance [IGT]) underwent a hyperglycemic clamp. A subset had an extended clamp with additional glucagon-like peptide (GLP)-1 and arginine (n = 224). We next genotyped single nucleotide polymorphisms in TCF7L2, KCNJ11, CDKAL1, IGF2BP2, HHEX/IDE, CDKN2A/B, SLC30A8, and MTNR1B and calculated a risk allele score by risk allele counting. RESULTS The risk allele score was associated with lower first-phase glucose-stimulated insulin secretion (GSIS) (P = 7.1 x 10(-6)). The effect size was equal in subjects with NGT and IGT. We also noted an inverse correlation with the disposition index (P = 1.6 x 10(-3)). When we stratified the study population according to the number of risk alleles into three groups, those with a medium- or high-risk allele score had 9 and 23% lower first-phase GSIS. Second-phase GSIS, insulin sensitivity index and GLP-1, or arginine-stimulated insulin release were not significantly different. CONCLUSIONS A combined risk allele score for eight known beta-cell genes is associated with the rapid first-phase GSIS and the disposition index. The slower second-phase GSIS, GLP-1, and arginine-stimulated insulin secretion are not associated, suggesting that especially processes involved in rapid granule recruitment and exocytosis are affected in the majority of risk loci.
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Affiliation(s)
- Leen M 't Hart
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, the Netherlands.
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75
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Abstract
Metabolic diseases represent a growing threat to world-wide public health. In general, these disorders result from the interaction of heritable factors with environmental influences. Here, I will focus on two important metabolic disorders, namely type 2 diabetes and obesity, and explore the extent to which human molecular genetic research has illuminated our understanding of their underlying pathophysiological mechanisms.
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Affiliation(s)
- Stephen O'Rahilly
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK.
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76
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Abstract
Although the genetic causes of monogenic disorders have been successfully identified in the past, the success in dissecting the genetics of complex polygenic diseases has until now been limited. With the introduction of whole genome wide association studies (WGAS) in 2007, the picture has been dramatically changed. Today we know of about 20 genetic variants increasing the risk of type 2 diabetes (T2D). Most of them seem to influence the capacity of beta-cells to increase insulin secretion to meet the demands imposed by an increase in body weight and insulin resistance. This probably represents only the tip of the iceberg, and over the next few years refined tools will provide a more complete picture of the genetic complexity of T2D. This will not only include the current dissection of common variants increasing the susceptibility of the disease but also rare variants with stronger effects, copy number variations and epigenetic effects like DNA methylation and histone acetylation. For the first time, we can anticipate with some confidence that the genetics of a complex disease like T2D really can be dissected.
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Affiliation(s)
- L Groop
- Department of Clinical Sciences/Diabetes and Endocrinology, and Lund University Diabetes Centre, Lund University, University Hospital Malmoe, Sweden.
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77
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Ehses JA, Ellingsgaard H, Böni-Schnetzler M, Donath MY. Pancreatic islet inflammation in type 2 diabetes: from alpha and beta cell compensation to dysfunction. Arch Physiol Biochem 2009; 115:240-7. [PMID: 19645635 DOI: 10.1080/13813450903025879] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Evidence in support of the concept of local pancreatic islet inflammation as a mechanism of beta cell failure in type 2 diabetes is accumulating. Observations in human islets from type 2 diabetic patients and rodent models of the disease indicate the increased presence of IL-1 driven cytokines and chemokines in pancreatic islets, concomitant with immune cell infiltration. Inflammation is the body's protective response to harmful stimuli and tissue damage. However, under chronic stress (e.g. metabolic stress in obesity and type 2 diabetes) the body's own defensive response may become deleterious to tissue function. Here, we summarize the current evidence that islet inflammation is a feature of type 2 diabetes, and discuss its role with respect to alpha and beta cell compensation and eventual beta cell failure.
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Affiliation(s)
- Jan A Ehses
- Division of Endocrinology, Diabetes and Nutrition, Center for Integrated Human Physiology, University Hospital of Zürich, 8091 Zürich, Switzerland.
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78
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McCarthy MI. Exploring the unknown: assumptions about allelic architecture and strategies for susceptibility variant discovery. Genome Med 2009; 1:66. [PMID: 19591663 PMCID: PMC2717392 DOI: 10.1186/gm66] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Identification of common-variant associations for many common disorders has been highly effective, but the loci detected so far typically explain only a small proportion of the genetic predisposition to disease. Extending explained genetic variance is one of the major near-term goals of human genetic research. Next-generation sequencing technologies offer great promise, but optimal strategies for their deployment remain uncertain, not least because we lack a clear view of the characteristics of the variants being sought. Here, I discuss what can and cannot be inferred about complex trait disease architecture from the information currently available and review the implications for future research strategies.
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Affiliation(s)
- Mark I McCarthy
- Oxford Centre for Diabetes, Endocrinology & Metabolism, University of Oxford, Churchill Hospital, Oxford OX3 7LJ, UK, and the Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX7 7BN, UK.
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79
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Current literature in diabetes. Diabetes Metab Res Rev 2009; 25:i-xii. [PMID: 19405078 DOI: 10.1002/dmrr.973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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80
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Meigs JB. Prediction of type 2 diabetes: the dawn of polygenetic testing for complex disease. Diabetologia 2009; 52:568-70. [PMID: 19214469 DOI: 10.1007/s00125-009-1296-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Accepted: 01/26/2009] [Indexed: 01/23/2023]
Affiliation(s)
- J B Meigs
- Department of Medicine, Massachusetts General Hospital, Boston, MA, USA.
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81
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Abstract
PURPOSE OF REVIEW To highlight recent type 2 diabetes (T2D)-associated genetic discoveries and their potential for clinical application. RECENT FINDINGS The advent of genome-wide association screening has uncovered many loci newly associated with T2D. This review describes the techniques applied to discover novel T2D genes and compares their relative strengths, biases, and findings to date. The results of large-scale genome-wide association studies carried out since 2007 are summarized, and limitations of interpreting this preliminary data are offered. Recent studies exploring the clinical potential of these discoveries are reviewed, focusing on insights into T2D pathogenesis, risk prediction of future diabetes, and utility in guiding pharmacotherapy. The new T2D-associated loci have been implicated in beta-cell development and function, highlighting insulin secretion in the disease process. Preliminary risk prediction studies show that more loci are needed to improve T2D risk indices. Studies have also revealed that genes may play a role in the pharmacologic response to antidiabetic medications. SUMMARY Since 2007, genome-wide association studies have rapidly increased the number of T2D-associated loci. This review summarizes the history of genetic association studies, the results from the new genome-wide association studies, and the clinical application of these findings.
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Affiliation(s)
- Amit R Majithia
- Diabetes Research Center (Diabetes Unit), Massachusetts General Hospital, Boston, Boston, MA 02114, USA
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