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Chan KHK, Chacko SA, Song Y, Cho M, Eaton CB, Wu WCH, Liu S. Genetic variations in magnesium-related ion channels may affect diabetes risk among African American and Hispanic American women. J Nutr 2015; 145:418-24. [PMID: 25733456 PMCID: PMC4336527 DOI: 10.3945/jn.114.203489] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Prospective studies consistently link low magnesium intake to higher type 2 diabetes (T2D) risk. OBJECTIVE We examined the association of common genetic variants [single nucleotide polymorphisms (SNPs)] in genes related to magnesium homeostasis with T2D risk and potential interactions with magnesium intake. METHODS Using the Women's Health Initiative-SNP Health Association Resource (WHI-SHARe) study, we identified 17 magnesium-related ion channel genes (583 SNPs) and examined their associations with T2D risk in 7287 African-American (AA; n = 1949 T2D cases) and 3285 Hispanic-American (HA; n = 611 T2D cases) postmenopausal women. We performed both single- and multiple-locus haplotype analyses. RESULTS Among AA women, carriers of each additional copy of SNP rs6584273 in cyclin mediator 1 (CNNM1) had 16% lower T2D risk [OR: 0.84; false discovery rate (FDR)-adjusted P = 0.02]. Among HA women, several variants were significantly associated with T2D risk, including rs10861279 in solute carrier family 41 (anion exchanger), member 2 (SLC41A2) (OR: 0.54; FDR-adjusted P = 0.04), rs7174119 in nonimprinted in Prader-Willi/Angelman syndrome 1 (NIPA1) (OR: 1.27; FDR-adjusted P = 0.04), and 2 SNPs in mitochondrial RNA splicing 2 (MRS2) (rs7738943: OR = 1.55, FDR-adjusted P = 0.01; rs1056285: OR = 1.48, FDR-adjusted P = 0.02). Even with the most conservative Bonferroni adjustment, two 2-SNP-haplotypes in SLC41A2 and MRS2 region were significantly associated with T2D risk (rs12582312-rs10861279: P = 0.0006; rs1056285-rs7738943: P = 0.002). Among women with magnesium intake in the lowest 30% (AA: ≤0.164 g/d; HA: ≤0.185 g/d), 4 SNP signals were strengthened [rs11590362 in claudin 19 (CLDN19), rs823154 in SLC41A1, rs5929706 and rs5930817 in membra; HA: ≥0.313 g/d), rs6584273 in CNNM1 (OR: 0.71; FDR-adjusted P = 0.04) and rs1800467 in potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11) (OR: 2.50; FDR-adjusted P = 0.01) were significantly associated with T2D risk. CONCLUSIONS Our findings suggest important associations between genetic variations in magnesium-related ion channel genes and T2D risk in AA and HA women that vary by amount of magnesium intake.
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Affiliation(s)
| | - Sara A Chacko
- Division of General Medicine and Primary Care, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA
| | - Yiqing Song
- Department of Epidemiology, Indiana University Richard M. Fairbanks School of Public Health, Indianapolis, IN; Departments of
| | - Michele Cho
- Medicine and,Obstetrics and Gynecology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA
| | - Charles B Eaton
- Family Medicine,,Epidemiology, and,Center for Primary Care and Prevention, Memorial Hospital of Rhode Island, Pawtucket, RI
| | - Wen-Chih H Wu
- Medicine, Warren Alpert Medical School, Brown University, Providence, RI;,Vascular Research Laboratory, Providence US Department of Veterans Affairs Medical Center, Providence, RI; and
| | - Simin Liu
- Department of Epidemiology, and Departments of Medicine, Warren Alpert Medical School, Brown University, Providence, RI; Medicine and Obstetrics and Gynecology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA; Division of Endocrinology, Rhode Island Hospital, Providence, RI
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Bonfanti DH, Alcazar LP, Arakaki PA, Martins LT, Agustini BC, de Moraes Rego FG, Frigeri HR. ATP-dependent potassium channels and type 2 diabetes mellitus. Clin Biochem 2015; 48:476-82. [PMID: 25583094 DOI: 10.1016/j.clinbiochem.2014.12.026] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 12/29/2014] [Accepted: 12/30/2014] [Indexed: 12/24/2022]
Abstract
Diabetes mellitus is a public health problem, which affects a millions worldwide. Most diabetes cases are classified as type 2 diabetes mellitus, which is highly associated with obesity. Type 2 diabetes is considered a multifactorial disorder, with both environmental and genetic factors contributing to its development. An important issue linked with diabetes development is the failure of the insulin releasing mechanism involving abnormal activity of the ATP-dependent potassium channel, KATP. This channel is a transmembrane protein encoded by the KCNJ11 and ABCC8 genes. Furthermore, polymorphisms in these genes have been linked to type 2 diabetes because of the role of KATP in insulin release. While several genetic variations have been reported to be associated with this disease, the E23K polymorphism is most commonly associated with this pathology, as well as to obesity. Here, we review the molecular genetics of the potassium channel and discusses its most described polymorphisms and their associations with type 2 diabetes mellitus.
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Affiliation(s)
- Dianne Heloisa Bonfanti
- Health and Biosciences School, Pontifical Catholic University of Parana, Curitiba, Parana, Brazil
| | - Larissa Pontes Alcazar
- Health and Biosciences School, Pontifical Catholic University of Parana, Curitiba, Parana, Brazil
| | - Priscila Akemi Arakaki
- Health and Biosciences School, Pontifical Catholic University of Parana, Curitiba, Parana, Brazil
| | - Laysa Toschi Martins
- Health and Biosciences School, Pontifical Catholic University of Parana, Curitiba, Parana, Brazil
| | - Bruna Carla Agustini
- Health and Biosciences School, Pontifical Catholic University of Parana, Curitiba, Parana, Brazil
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Fatehi M, Raja M, Carter C, Soliman D, Holt A, Light PE. The ATP-sensitive K(+) channel ABCC8 S1369A type 2 diabetes risk variant increases MgATPase activity. Diabetes 2012; 61:241-9. [PMID: 22187380 PMCID: PMC3237651 DOI: 10.2337/db11-0371] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Pancreatic β-cell ATP-sensitive K(+) (K(ATP)) channels are composed of Kir6.2 and SUR1 subunits encoded by the KCNJ11 and ABCC8 genes, respectively. Although rare monogenic activating mutations in these genes cause overt neonatal diabetes, the common variants E23K (KCNJ11) and S1369A (ABCC8) form a tightly heritable haplotype that is associated with an increased susceptibility to type 2 diabetes (T2D) risk. However, the molecular mechanism(s) underlying this risk remain to be elucidated. A homology model of the SUR1 nucleotide-binding domains (NBDs) indicates that residue 1369 is in close proximity to the major MgATPase site. Therefore, we investigated the intrinsic MgATPase activity of K(ATP) channels containing these variants. Electrophysiological and biochemical techniques were used to study the MgATPase activity of recombinant human K(ATP) channels or glutathione S-transferase and NBD2 fusion proteins containing the E23/S1369 (nonrisk) or K23/A1369 (risk) variant haplotypes. K(ATP) channels containing the K23/A1369 haplotype displayed a significantly increased stimulation by guanosine triphosphate compared with the E23/S1369 haplotype (3.2- vs. 1.8-fold). This effect was dependent on the presence of the A1369 variant and was lost in the absence of Mg(2+) ions or in the presence of the MgATPase inhibitor beryllium fluoride. Direct biochemical assays also confirmed an increase in MgATPase activity in NBD2 fusion proteins containing the A1369 variant. Our findings demonstrate that the A1369 variant increases K(ATP) channel MgATPase activity, providing a plausible molecular mechanism by which the K23/A1369 haplotype increases susceptibility to T2D in humans homozygous for these variants.
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MESH Headings
- ATP-Binding Cassette Transporters/chemistry
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- ATP-Binding Cassette Transporters/physiology
- Adenosine Triphosphatases/metabolism
- Adenosine Triphosphate/metabolism
- Alanine/genetics
- Amino Acid Substitution/physiology
- Cells, Cultured
- Diabetes Mellitus, Type 2/genetics
- Enzyme Activation
- Genetic Predisposition to Disease
- Humans
- KATP Channels/chemistry
- KATP Channels/genetics
- KATP Channels/physiology
- Models, Molecular
- Polymorphism, Single Nucleotide/physiology
- Potassium Channels, Inwardly Rectifying/chemistry
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Potassium Channels, Inwardly Rectifying/physiology
- Protein Structure, Tertiary/genetics
- Receptors, Drug/chemistry
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Receptors, Drug/physiology
- Risk Factors
- Serine/genetics
- Sulfonylurea Receptors
- Transfection
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Lang V, Youssef N, Light PE. The molecular genetics of sulfonylurea receptors in the pathogenesis and treatment of insulin secretory disorders and type 2 diabetes. Curr Diab Rep 2011; 11:543-51. [PMID: 21968738 DOI: 10.1007/s11892-011-0233-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Sulfonylurea receptors (SURs) form an integral part of the ATP-sensitive potassium (K(ATP)) channel complex that is present in most excitable cell types. K(ATP) channels couple cellular metabolism to electrical activity and provide a wide range of cellular functions including stimulus secretion coupling in pancreatic β cells. K(ATP) channels are composed of SURs and inward rectifier potassium channel (Kir6.x) subunits encoded by the ABCC8/9 and KCNJ8/11 genes, respectively. Recent advances in the genetics, molecular biology, and pharmacology of SURs have led to an increased understanding of these channels in the etiology and treatment of rare genetic insulin secretory disorders. Furthermore, common genetic variants in these genes are associated with an increased risk for type 2 diabetes. In this review we summarize the molecular biology, pharmacology, and physiology of SURs and K(ATP) channels, highlighting recent advances in their genetics and understanding of rare insulin secretory disorders and susceptibility to type 2 diabetes.
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Affiliation(s)
- Veronica Lang
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
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Villareal DT, Robertson H, Bell GI, Patterson BW, Tran H, Wice B, Polonsky KS. TCF7L2 variant rs7903146 affects the risk of type 2 diabetes by modulating incretin action. Diabetes 2010; 59:479-85. [PMID: 19934000 PMCID: PMC2809956 DOI: 10.2337/db09-1169] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Common variants in the gene TCF7L2 confer the largest effect on the risk of type 2 diabetes. The present study was undertaken to increase our understanding of the mechanisms by which this gene affects type 2 diabetes risk. RESEARCH DESIGN AND METHODS Eight subjects with risk-conferring TCF7L2 genotypes (TT or TC at rs7903146) and 10 matched subjects with wild-type genotype (CC) underwent 5-h oral glucose tolerance test (OGTT), isoglycemic intravenous glucose infusion, and graded glucose infusion (GGI). Mathematical modeling was used to quantify insulin-secretory profiles during OGTT and glucose infusion protocols. The incretin effect was assessed from ratios of the insulin secretory rates (ISR) during oral and isoglycemic glucose infusions. Dose-response curves relating insulin secretion to glucose concentrations were derived from the GGI. RESULTS beta-cell responsivity to oral glucose was 50% lower (47 +/- 4 vs. 95 +/- 15 x 10(9) min(-1); P = 0.01) in the group of subjects with risk-conferring TCF7L2 genotypes compared with control subjects. The incretin effect was also reduced by 30% (32 +/- 4 vs. 46 +/- 4%; P = 0.02) in the at-risk group. The lower incretin effect occurred despite similar glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) responses to oral glucose. The ISR response to intravenous glucose over a physiologic glucose concentration range (5-9 mmol/l) was similar between groups. CONCLUSIONS The TCF7L2 variant rs7903146 appears to affect risk of type 2 diabetes, at least in part, by modifying the effect of incretins on insulin secretion. This is not due to reduced secretion of GLP-1 and GIP but rather due to the effect of TCF7L2 on the sensitivity of the beta-cell to incretins. Treatments that increase incretin sensitivity may decrease the risk of type 2 diabetes.
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Affiliation(s)
- Dennis T. Villareal
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Heather Robertson
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Graeme I. Bell
- Departments of Medicine and Human Genetics, The University of Chicago, Chicago, Illinois
| | - Bruce W. Patterson
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Hung Tran
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Burton Wice
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Kenneth S. Polonsky
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
- Corresponding author: Kenneth S. Polonsky,
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Villareal DT, Koster JC, Robertson H, Akrouh A, Miyake K, Bell GI, Patterson BW, Nichols CG, Polonsky KS. Kir6.2 variant E23K increases ATP-sensitive K+ channel activity and is associated with impaired insulin release and enhanced insulin sensitivity in adults with normal glucose tolerance. Diabetes 2009; 58:1869-78. [PMID: 19491206 PMCID: PMC2712777 DOI: 10.2337/db09-0025] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
OBJECTIVE The E23K variant in the Kir6.2 subunit of the ATP-sensitive K(+) channel (K(ATP) channel) is associated with increased risk of type 2 diabetes. The present study was undertaken to increase our understanding of the mechanisms responsible. To avoid confounding effects of hyperglycemia, insulin secretion and action were studied in subjects with the variant who had normal glucose tolerance. RESEARCH DESIGN AND METHODS Nine subjects with the E23K genotype K/K and nine matched subjects with the E/E genotype underwent 5-h oral glucose tolerance tests (OGTTs), graded glucose infusion, and hyperinsulinemic-euglycemic clamp with stable-isotope-labeled tracer infusions to assess insulin secretion, action, and clearance. A total of 461 volunteers consecutively genotyped for the E23K variant also underwent OGTTs. Functional studies of the wild-type and E23K variant potassium channels were conducted. RESULTS Insulin secretory responses to oral and intravenous glucose were reduced by approximately 40% in glucose-tolerant subjects homozygous for E23K. Normal glucose tolerance with reduced insulin secretion suggests a change in insulin sensitivity. The hyperinsulinemic-euglycemic clamp revealed that hepatic insulin sensitivity is approximately 40% greater in subjects with the E23K variant, and these subjects demonstrate increased insulin sensitivity after oral glucose. The reconstituted E23K channels confirm reduced sensitivity to inhibitory ATP and increase in open probability, a direct molecular explanation for reduced insulin secretion. CONCLUSIONS The E23K variant leads to overactivity of the K(ATP) channel, resulting in reduced insulin secretion. Initially, insulin sensitivity is enhanced, thereby maintaining normal glucose tolerance. Presumably, over time, as insulin secretion falls further or insulin resistance develops, glucose levels rise resulting in type 2 diabetes.
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Affiliation(s)
- Dennis T. Villareal
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Joseph C. Koster
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - Heather Robertson
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Alejandro Akrouh
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - Kazuaki Miyake
- Department of Medicine, University of Chicago, Chicago, Illinois
| | - Graeme I. Bell
- Department of Medicine, University of Chicago, Chicago, Illinois
| | - Bruce W. Patterson
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - Kenneth S. Polonsky
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
- Corresponding author: Kenneth S. Polonsky,
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