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Lv X, Gao J, Yang J, Zou Y, Chen J, Sun Y, Song J, Liu Y, Wang L, Xia L, Yu S, Wei Z, Chen L, Hou X. Clinical and functional characterization of a novel KCNJ11 (c.101G > A, p.R34H) mutation associated with maturity-onset diabetes mellitus of the young type 13. Endocrine 2024:10.1007/s12020-024-03873-6. [PMID: 38761346 DOI: 10.1007/s12020-024-03873-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 05/09/2024] [Indexed: 05/20/2024]
Abstract
PURPOSE This study aimed to describe the clinical features, diagnostic and therapeutic course of a patient with MODY13 caused by KCNJ11 (c.101G > A, p.R34H) and how it contributes to the pathogenesis of MODY13, and to explore new therapeutic targets. METHODS Whole-exome sequencing was used to screen prediagnosed individuals and family members with clinically suspected KCNJ11 mutations. Real-time fluorescence quantitative PCR, western blotting, thallium flux of potassium channels, glucose-stimulated insulin secretion (GSIS), and immunofluorescence assays were used to analyze the regulation of insulin secretion by the KCNJ11 mutant in MIN6 cells. Daily blood glucose levels were continuously monitored for 14 days in the proband using the ambulatory blood glucose meter (SIBIONICS). RESULTS Mutation screening of the entire exon of the gene identified a heterozygous KCNJ11 (c.101G > A, p.R34H) mutation in the proband and his mother. Cell-based GSIS assays after transfection of MIN6 using wild-type and mutant plasmids revealed that this mutation impaired insulin secretory function. Furthermore, we found that this impaired secretory function is associated with reduced functional activity of the mutant KCNJ11 protein and reduced expression of the insulin secretion-associated exocytosis proteins STXBP1 and SNAP25. CONCLUSION For the first time, we revealed the pathogenic mechanism of KCNJ11 (c.101G > A, p.R34H) associated with MODY13. This mutant can cause alterations in KATP channel activity, reduce sensitivity to glucose stimulation, and impair pancreatic β-cell secretory function by downregulating insulin secretion-associated exocytosis proteins. Therefore, oral sulfonylurea drugs can lower blood glucose levels through pro-insulinotropic effects and are more favorable for patients with this mutation.
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Affiliation(s)
- Xiaoyu Lv
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Jing Gao
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Jingwen Yang
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Ying Zou
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Jun Chen
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Yujing Sun
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Jia Song
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Yiran Liu
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Liming Wang
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Longqing Xia
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Shijia Yu
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Zichun Wei
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
| | - Li Chen
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China
- Institute of Endocrine and Metabolic Diseases of Shandong University, Jinan, 250012, Shandong, China
- Key Laboratory of Endocrine and Metabolic Diseases, Shandong Province Medicine & Health, Jinan, 250012, Shandong, China
- Jinan Clinical Research Center for Endocrine and Metabolic Disease, Jinan, 250012, Shandong, China
| | - Xinguo Hou
- Department of Endocrinology, Qilu Hospital of Shandong University, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, China.
- Institute of Endocrine and Metabolic Diseases of Shandong University, Jinan, 250012, Shandong, China.
- Key Laboratory of Endocrine and Metabolic Diseases, Shandong Province Medicine & Health, Jinan, 250012, Shandong, China.
- Jinan Clinical Research Center for Endocrine and Metabolic Disease, Jinan, 250012, Shandong, China.
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Khoshavi Najafabadi F, Sadraei H, Mehranfard N, Ghasemi M. Motor Dysfunction of Gastric Antral Smooth Muscle in Diabetic Rats: Contribution of ATP-Dependent Potassium Channels. Adv Biomed Res 2023; 12:199. [PMID: 37694236 PMCID: PMC10492619 DOI: 10.4103/abr.abr_44_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 05/14/2023] [Accepted: 05/20/2023] [Indexed: 09/12/2023] Open
Abstract
Background The goal of the current research was to further elucidate the role of adenosine triphosphate (ATP)-sensitive potassium (KATP) channels in the motility and contractility force of gastric smooth muscle of diabetic rats. Materials and Methods Male Wistar rats (190-230 g) were grouped into control and streptozotocin (STZ)-induced diabetes (55 mg/kg) rats. Thirty days later, gastric muscle contractility was measured using a myograph and a force transducer of antral segments immersed in a tissue bath. Gastric emptying response was measured through feeding of standard pellet. Furthermore, the expression of KATP channel subunits in antral smooth muscle was determined by western blot technique. Results The amplitude of KCl-evoked twitch contractions of diabetic antral strips was about 25% more than control (P < 0.05). Application of minoxidil, a KATP channel opener, dose dependently decreased the force of twitch contractions in both normal and diabetic antral strips. Application of 10 μM glibenclamide, a KATP channel blocker, did not antagonize the minoxidil-induced relaxation of antral strips. Diabetic gastric emptying was faster than normal, although not significant. Despite the relaxant effect of minoxidil on gastric emptying rate in normal rats (P < 0.05), this effect was not observed in diabetic rats. Also, glibenclamide increased gastric emptying and antagonized minoxidil-induced relaxation in normal rats (P < 0.05). Furthermore, the expression of KATP Kir6.1 and SUR2B subunits was substantially reduced in antral smooth muscle in diabetic condition (P < 0.01). Conclusion These results propose that KATP channels may contribute to the development of gastric motility disorders in diabetes.
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Affiliation(s)
- Fatameh Khoshavi Najafabadi
- Department of Pharmacology and Toxicology, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Hassan Sadraei
- Department of Pharmacology and Toxicology, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Nasrin Mehranfard
- Neurophysiology Research Center, Cellular and Molecular Medicine Research Institute, Urmia University of Medical Sciences, Urmia, Iran
| | - Maedeh Ghasemi
- Department of Physiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
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Mao X, Chen H, Lin AZ, Kim S, Burczynski ME, Na E, Halasz G, Sleeman MW, Murphy AJ, Okamoto H, Cheng X. Glutaminase 2 knockdown reduces hyperammonemia and associated lethality of urea cycle disorder mouse model. J Inherit Metab Dis 2022; 45:470-480. [PMID: 34988999 PMCID: PMC9302672 DOI: 10.1002/jimd.12474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 12/29/2021] [Accepted: 01/04/2022] [Indexed: 11/12/2022]
Abstract
Amino acids, the building blocks of proteins in the cells and tissues, are of fundamental importance for cell survival, maintenance, and proliferation. The liver plays a critical role in amino acid metabolism and detoxication of byproducts such as ammonia. Urea cycle disorders with hyperammonemia remain difficult to treat and eventually necessitate liver transplantation. In this study, ornithine transcarbamylase deficient (Otcspf-ash ) mouse model was used to test whether knockdown of a key glutamine metabolism enzyme glutaminase 2 (GLS2, gene name: Gls2) or glutamate dehydrogenase 1 (GLUD1, gene name: Glud1) could rescue the hyperammonemia and associated lethality induced by a high protein diet. We found that reduced hepatic expression of Gls2 but not Glud1 by AAV8-mediated delivery of a short hairpin RNA in Otcspf-ash mice diminished hyperammonemia and reduced lethality. Knockdown of Gls2 but not Glud1 in Otcspf-ash mice exhibited reduced body weight loss and increased plasma glutamine concentration. These data suggest that Gls2 hepatic knockdown could potentially help alleviate risk for hyperammonemia and other clinical manifestations of patients suffering from defects in the urea cycle.
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Affiliation(s)
- Xia Mao
- Regeneron PharmaceuticalsTarrytownNew YorkUSA
| | - Helen Chen
- Regeneron PharmaceuticalsTarrytownNew YorkUSA
| | | | - Sun Kim
- Regeneron PharmaceuticalsTarrytownNew YorkUSA
| | | | - Erqian Na
- Regeneron PharmaceuticalsTarrytownNew YorkUSA
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Maqoud F, Scala R, Hoxha M, Zappacosta B, Tricarico D. ATP-sensitive potassium channel subunits in the neuroinflammation: novel drug targets in neurodegenerative disorders. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2021; 21:130-149. [PMID: 33463481 DOI: 10.2174/1871527320666210119095626] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 08/07/2020] [Accepted: 08/28/2020] [Indexed: 11/22/2022]
Abstract
Arachidonic acids and its metabolites modulate plenty of ligand-gated, voltage-dependent ion channels, and metabolically regulated potassium channels including ATP-sensitive potassium channels (KATP). KATP channels are hetero-multimeric complexes of sulfonylureas receptors (SUR1, SUR2A or SUR2B) and the pore-forming subunits (Kir6.1 and Kir6.2) likewise expressed in the pre-post synapsis of neurons and inflammatory cells, thereby affecting their proliferation and activity. KATP channels are involved in amyloid-β (Aβ)-induced pathology, therefore emerging as therapeutic targets against Alzheimer's and related diseases. The modulation of these channels can represent an innovative strategy for the treatment of neurodegenerative disorders; nevertheless, the currently available drugs are not selective for brain KATP channels and show contrasting effects. This phenomenon can be a consequence of the multiple physiological roles of the different varieties of KATP channels. Openings of cardiac and muscular KATP channel subunits, is protective against caspase-dependent atrophy in these tissues and some neurodegenerative disorders, whereas in some neuroinflammatory diseases benefits can be obtained through the inhibition of neuronal KATP channel subunits. For example, glibenclamide exerts an anti-inflammatory effect in respiratory, digestive, urological, and central nervous system (CNS) diseases, as well as in ischemia-reperfusion injury associated with abnormal SUR1-Trpm4/TNF-α or SUR1-Trpm4/ Nos2/ROS signaling. Despite this strategy is promising, glibenclamide may have limited clinical efficacy due to its unselective blocking action of SUR2A/B subunits also expressed in cardiovascular apparatus with pro-arrhythmic effects and SUR1 expressed in pancreatic beta cells with hypoglycemic risk. Alternatively, neuronal selective dual modulators showing agonist/antagonist actions on KATP channels can be an option.
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Affiliation(s)
- Fatima Maqoud
- Department of Pharmacy-Pharmaceutical Science, University of Bari Aldo Moro, via Orabona 4, 70125-I. Italy
| | - Rosa Scala
- Department of Pharmacy-Pharmaceutical Science, University of Bari Aldo Moro, via Orabona 4, 70125-I. Italy
| | - Malvina Hoxha
- Department of Chemical-Toxicological and Pharmacological Evaluation of Drugs, Faculty of Pharmacy, "Catholic University Our Lady of Good Counsel", Tirana. Albania
| | - Bruno Zappacosta
- Department of Chemical-Toxicological and Pharmacological Evaluation of Drugs, Faculty of Pharmacy, "Catholic University Our Lady of Good Counsel", Tirana. Albania
| | - Domenico Tricarico
- Department of Pharmacy-Pharmaceutical Science, University of Bari Aldo Moro, via Orabona 4, 70125-I. Italy
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Pipatpolkai T, Usher S, Stansfeld PJ, Ashcroft FM. New insights into K ATP channel gene mutations and neonatal diabetes mellitus. Nat Rev Endocrinol 2020; 16:378-393. [PMID: 32376986 DOI: 10.1038/s41574-020-0351-y] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/17/2020] [Indexed: 12/12/2022]
Abstract
The ATP-sensitive potassium channel (KATP channel) couples blood levels of glucose to insulin secretion from pancreatic β-cells. KATP channel closure triggers a cascade of events that results in insulin release. Metabolically generated changes in the intracellular concentrations of adenosine nucleotides are integral to this regulation, with ATP and ADP closing the channel and MgATP and MgADP increasing channel activity. Activating mutations in the genes encoding either of the two types of KATP channel subunit (Kir6.2 and SUR1) result in neonatal diabetes mellitus, whereas loss-of-function mutations cause hyperinsulinaemic hypoglycaemia of infancy. Sulfonylurea and glinide drugs, which bind to SUR1, close the channel through a pathway independent of ATP and are now the primary therapy for neonatal diabetes mellitus caused by mutations in the genes encoding KATP channel subunits. Insight into the molecular details of drug and nucleotide regulation of channel activity has been illuminated by cryo-electron microscopy structures that reveal the atomic-level organization of the KATP channel complex. Here we review how these structures aid our understanding of how the various mutations in the genes encoding Kir6.2 (KCNJ11) and SUR1 (ABCC8) lead to a reduction in ATP inhibition and thereby neonatal diabetes mellitus. We also provide an update on known mutations and sulfonylurea therapy in neonatal diabetes mellitus.
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Affiliation(s)
- Tanadet Pipatpolkai
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Samuel Usher
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Phillip J Stansfeld
- Department of Biochemistry, University of Oxford, Oxford, UK
- School of Life Sciences, University of Warwick, Coventry, UK
- Department of Chemistry, University of Warwick, Coventry, UK
| | - Frances M Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
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Saponara S, Fusi F, Spiga O, Trezza A, Hopkins B, Brimble MA, Rennison D, Bova S. The Selective Rat Toxicant Norbormide Blocks K ATP Channels in Smooth Muscle Cells But Not in Insulin-Secreting Cells. Front Pharmacol 2019; 10:598. [PMID: 31191321 PMCID: PMC6540933 DOI: 10.3389/fphar.2019.00598] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 05/09/2019] [Indexed: 12/02/2022] Open
Abstract
Norbormide is a toxicant selective for rats to which it induces a widespread vasoconstriction. In a recent paper, we hypothesized a role of ATP-sensitive potassium (KATP) channels in norbormide-induced vasoconstriction. The current study was undertaken to verify this hypothesis by comparing the effects of norbormide with those of glibenclamide, a known KATP channel blocker. The whole-cell patch-clamp method was used to record KATP currents in myocytes freshly isolated from the rat and mouse caudal artery and from the rat gastric fundus, as well as in insulin-secreting pancreatic beta cells (INS-1 cells). Smooth muscle contractile function was assessed on either rat caudal artery rings or gastric fundus strips. Molecular modeling and docking simulation to KATP channel proteins were investigated in silico. Both norbormide (a racemic mixture of endo and exo isomers) and glibenclamide inhibited KATP currents in rat and mouse caudal artery myocytes, as well as in gastric fundus smooth muscle cells. In rat INS-1 cells, only glibenclamide blocked KATP channels, whereas norbormide was ineffective. The inhibitory effect of norbormide in rat caudal artery myocytes was not stereo-specific as both the endo isomers (active as vasoconstrictor) and the exo isomers (inactive as vasoconstrictor) had similar inhibitory activity. In rat caudal artery rings, norbormide-induced contraction was partially reverted by the KATP channel opener pinacidil. Computational approaches indicated the SUR subunit of KATP channels as the binding site for norbormide. KATP channel inhibition may play a role in norbormide-induced vasoconstriction, but does not explain the species selectivity, tissue selectivity, and stereoselectivity of its constricting activity. The lack of effect in INS-1 cells suggests a potential selectivity of norbormide for smooth muscle KATP channels.
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Affiliation(s)
- Simona Saponara
- Department of Life Sciences, University of Siena, Siena, Italy
| | - Fabio Fusi
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Ottavia Spiga
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Alfonso Trezza
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Brian Hopkins
- Landcare Research, Lincoln, New Zealand.,School of Chemical Sciences, University of Auckland, Auckland, New Zealand
| | - Margaret A Brimble
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand
| | - David Rennison
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand
| | - Sergio Bova
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy
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Trezza A, Cicaloni V, Porciatti P, Langella A, Fusi F, Saponara S, Spiga O. From in silico to in vitro: a trip to reveal flavonoid binding on the Rattus norvegicus Kir6.1 ATP-sensitive inward rectifier potassium channel. PeerJ 2018; 6:e4680. [PMID: 29736333 PMCID: PMC5936070 DOI: 10.7717/peerj.4680] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 04/09/2018] [Indexed: 12/18/2022] Open
Abstract
Background ATP-sensitive inward rectifier potassium channels (Kir), are a potassium channel family involved in many physiological processes. KATP dysfunctions are observed in several diseases such as hypoglycaemia, hyperinsulinemia, Prinzmetal angina–like symptoms, cardiovascular diseases. Methods A broader view of the KATP mechanism is needed in order to operate on their regulation, and in this work we clarify the structure of the Rattus norvegicus ATP-sensitive inward rectifier potassium channel 8 (Kir6.1), which has been obtained through a homology modelling procedure. Due to the medical use of flavonoids, a considerable increase in studies on their influence on human health has recently been observed, therefore our aim is to study, through computational methods, the three-dimensional (3D) conformation together with mechanism of action of Kir6.1 with three flavonoids. Results Computational analysis by performing molecular dynamics (MD) and docking simulation on rat 3D modelled structure have been completed, in its closed and open conformation state and in complex with Quercetin, 5-Hydroxyflavone and Rutin flavonoids. Our study showed that only Quercetin and 5-Hydroxyflavone were responsible for a significant down-regulation of the Kir6.1 activity, stabilising it in a closed conformation. This hypothesis was supported by in vitro experiments demonstrating that Quercetin and 5-Hydroxyflavone were capable to inhibit KATP currents of rat tail main artery myocytes recorded by the patch-clamp technique. Conclusion Combined methodological approaches, such as molecular modelling, docking and MD simulations of Kir6.1 channel, used to elucidate flavonoids intrinsic mechanism of action, are introduced, revealing a new potential druggable protein site.
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Affiliation(s)
- Alfonso Trezza
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Vittoria Cicaloni
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy.,Toscana Life Sciences Foundation, Siena, Italy
| | - Piera Porciatti
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Andrea Langella
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Fabio Fusi
- Department of Life Sciences, University of Siena, Siena, Italy
| | - Simona Saponara
- Department of Life Sciences, University of Siena, Siena, Italy
| | - Ottavia Spiga
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
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Hashimoto Y, Dateki S, Hirose M, Satomura K, Sawada H, Mizuno H, Sugihara S, Maruyama K, Urakami T, Sugawara H, Shirai K, Yorifuji T. Molecular and clinical features of K ATP -channel neonatal diabetes mellitus in Japan. Pediatr Diabetes 2017; 18:532-539. [PMID: 27681997 DOI: 10.1111/pedi.12447] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 08/13/2016] [Accepted: 08/17/2016] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND There are few reports pertaining to Asian patients with neonatal diabetes mellitus (NDM) caused by activating mutations in the ATP-sensitive potassium channel genes (KATP-NDM). OBJECTIVES To elucidate the characteristics of Japanese patients with KATP-NDM. METHODS By the amplification and direct sequencing of all exons and exon-intron boundaries of the KCNJ11 and ABCC8 genes, 25 patients with KATP-NDM were identified from a total of 70 patients with NDM. Clinical data were collected from the medical charts. RESULTS Sixteen patients had mutations in KCNJ11 and nine in ABCC8. Eight novel mutations were identified; two in KCNJ11 (V64M, R201G) and six in ABCC8 (R216C, G832C, F1176L, A1263V, I196N, T229N). Interestingly, V64M caused DEND (developmental delay, epilepsy, neonatal diabetes) syndrome in our patient, while mutation of the same residue (V64G) had been reported to cause congenital hyperinsulinism. Mutations in ABCC8 were associated with TNDM (4/9) or isolated PNDM (5/9), whereas those in KCNJ11 were associated with more severe phenotypes, including DEND (3/16), iDEND (intermediate DEND, 4/16), or isolated PNDM (6/16). Switching from insulin to glibenclamide monotherapy was successful in 87.5% of the patients. Neurological improvement was observed in two patients, one with DEND (T293N) and one with iDEND (R50P) syndrome. Three others with iDEND mutations (R201C, G53D, and V59M) remained neurologically normal at 5, 1, and 4 years of age, respectively, with early introduction of sulfonylurea. CONCLUSION Overall, clinical presentation of KATP-NDM in Japanese patients was similar to those of other populations. Early introduction of sulfonylurea appeared beneficial in ameliorating neurological symptoms.
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Affiliation(s)
- Yukiko Hashimoto
- Department of Pediatric Endocrinology and Metabolism, Children's Medical Center, Osaka City General Hospital, Osaka, Japan.,Clinical Research Center, Osaka City General Hospital, Osaka, Japan
| | - Sumito Dateki
- Department of Pediatrics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Masakazu Hirose
- Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Kenichi Satomura
- Department of Pediatric Nephrology and Metabolism, Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Japan
| | - Hirotake Sawada
- Department of Reproductive and Developmental Medicine, University of Miyazaki, Miyazaki, Japan
| | - Haruo Mizuno
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Shigetaka Sugihara
- Department of Pediatrics, Tokyo Women's Medical University Medical Center East, Tokyo, Japan
| | - Koichi Maruyama
- Department of Pediatric Neurology, Aichi Prefectural Colony Central Hospital, Aichi, Japan
| | - Tatsuhiko Urakami
- Department of Pediatrics, Nihon University School of Medicine, Tokyo, Japan
| | - Hidenori Sugawara
- Department of Pediatrics, Yokohama City University Medical Center, Kanagawa, Japan
| | - Kenji Shirai
- Department of Pediatrics, Seirei-Mikatahara General Hospital, Shizuoka, Japan
| | - Tohru Yorifuji
- Department of Pediatric Endocrinology and Metabolism, Children's Medical Center, Osaka City General Hospital, Osaka, Japan.,Clinical Research Center, Osaka City General Hospital, Osaka, Japan
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Borschel WF, Wang S, Lee S, Nichols CG. Control of Kir channel gating by cytoplasmic domain interface interactions. J Gen Physiol 2017; 149:561-576. [PMID: 28389584 PMCID: PMC5412532 DOI: 10.1085/jgp.201611719] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 12/29/2016] [Accepted: 03/01/2017] [Indexed: 12/19/2022] Open
Abstract
The pore-forming unit of ATP-sensitive K channels is composed of four Kir6.2 subunits. Borschel et al. show that salt bridges between the cytoplasmic domain of adjacent Kir6.2 subunits determine the degree to which channels inactivate after removal of ATP. Inward rectifier potassium (Kir) channels are expressed in almost all mammalian tissues and play critical roles in the control of excitability. Pancreatic ATP-sensitive K (KATP) channels are key regulators of insulin secretion and comprise Kir6.2 subunits coupled to sulfonylurea receptors. Because these channels are reversibly inhibited by cytoplasmic ATP, they link cellular metabolism with membrane excitability. Loss-of-function mutations in the pore-forming Kir6.2 subunit cause congenital hyperinsulinism as a result of diminished channel activity. Here, we show that several disease mutations, which disrupt intersubunit salt bridges at the interface of the cytoplasmic domains (CD-I) of adjacent subunits, induce loss of channel activity via a novel channel behavior: after ATP removal, channels open but then rapidly inactivate. Re-exposure to inhibitory ATP causes recovery from this inactivation. Inactivation can be abolished by application of phosphatidylinositol-4,5-bisphosphate (PIP2) to the cytoplasmic face of the membrane, an effect that can be explained by a simple kinetic model in which PIP2 binding competes with the inactivation process. Kir2.1 channels contain homologous salt bridges, and we find that mutations that disrupt CD-I interactions in Kir2.1 also reduce channel activity and PIP2 sensitivity. Kir2.1 channels also contain an additional CD-I salt bridge that is not present in Kir6.2 channels. Introduction of this salt bridge into Kir6.2 partially rescues inactivating mutants from the phenotype. These results indicate that the stability of the intersubunit CD-I is a major determinant of the inactivation process in Kir6.2 and may control gating in other Kir channels.
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Affiliation(s)
- William F Borschel
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110
| | - Shizhen Wang
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110
| | - Sunjoo Lee
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110 .,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110
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10
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Salomon-Estebanez M, Flanagan SE, Ellard S, Rigby L, Bowden L, Mohamed Z, Nicholson J, Skae M, Hall C, Craigie R, Padidela R, Murphy N, Randell T, Cosgrove KE, Dunne MJ, Banerjee I. Conservatively treated Congenital Hyperinsulinism (CHI) due to K-ATP channel gene mutations: reducing severity over time. Orphanet J Rare Dis 2016; 11:163. [PMID: 27908292 PMCID: PMC5133749 DOI: 10.1186/s13023-016-0547-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2016] [Accepted: 11/22/2016] [Indexed: 02/24/2023] Open
Abstract
BACKGROUND Patients with Congenital Hyperinsulinism (CHI) due to mutations in K-ATP channel genes (K-ATP CHI) are increasingly treated by conservative medical therapy without pancreatic surgery. However, the natural history of medically treated K-ATP CHI has not been described; it is unclear if the severity of recessively and dominantly inherited K-ATP CHI reduces over time. We aimed to review variation in severity and outcomes in patients with K-ATP CHI treated by medical therapy. METHODS Twenty-one consecutively presenting patients with K-ATP CHI with dominantly and recessively inherited mutations in ABCC8/KCNJ11 were selected in a specialised CHI treatment centre to review treatment outcomes. Medical treatment included diazoxide and somatostatin receptor agonists (SSRA), octreotide and somatuline autogel. CHI severity was assessed by glucose infusion rate (GIR), medication dosage and tendency to resolution. CHI outcome was assessed by glycaemic profile, fasting tolerance and neurodevelopment. RESULTS CHI presenting at median (range) age 1 (1, 240) days resolved in 15 (71%) patients at age 3.1(0.2, 13.0) years. Resolution was achieved both in patients responsive to diazoxide (n = 8, 57%) and patients responsive to SSRA (n = 7, 100%) with earlier resolution in the former [1.6 (0.2, 13.0) v 5.9 (1.6, 9.0) years, p = 0.08]. In 6 patients remaining on treatment, diazoxide dose was reduced in follow up [10.0 (8.5, 15.0) to 5.4 (0.5, 10.8) mg/kg/day, p = 0.003]. GIR at presentation did not correlate with resolved or persistent CHI [14.9 (10.0, 18.5) v 16.5 (13.0, 20.0) mg/kg/min, p = 0.6]. The type of gene mutation did not predict persistence; resolution could be achieved in recessively-inherited CHI with homozygous (n = 3), compound heterozygous (n = 2) and paternal mutations causing focal CHI (n = 2). Mild developmental delay was present in 8 (38%) patients; adaptive functioning assessed by Vineland Adaptive Behavior Scales questionnaire showed a trend towards higher standard deviation scores (SDS) in resolved than persistent CHI [-0.1 (-1.2, 1.6) v -1.2 (-1.7, 0.03), p = 0.1]. CONCLUSIONS In K-ATP CHI patients managed by medical treatment only, severity is reduced over time in the majority, including those with compound heterozygous and homozygous mutations in ABCC8/KCNJ11. Severity and treatment requirement should be assessed periodically in all children with K-ATP CHI on medical therapy.
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Affiliation(s)
- Maria Salomon-Estebanez
- Department of Paediatric Endocrinology, Royal Manchester Children's Hospital, Central Manchester University Hospitals, Oxford Road, Manchester, M13 9WL, UK. .,Faculty of Biology, Medicine and Health, University of Manchester, Oxford Rd, Manchester, M13 9PL, UK.
| | - Sarah E Flanagan
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD Building, RD&E Hospital Wonford, Barrack Road, Exeter, EX2 5DW, UK
| | - Sian Ellard
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD Building, RD&E Hospital Wonford, Barrack Road, Exeter, EX2 5DW, UK
| | - Lindsey Rigby
- Department of Paediatric Endocrinology, Royal Manchester Children's Hospital, Central Manchester University Hospitals, Oxford Road, Manchester, M13 9WL, UK
| | - Louise Bowden
- Department of Paediatric Endocrinology, Royal Manchester Children's Hospital, Central Manchester University Hospitals, Oxford Road, Manchester, M13 9WL, UK
| | - Zainab Mohamed
- Department of Paediatric Endocrinology and Diabetes, Nottingham Children's Hospital, Nottingham University Hospitals, Derby Road, Nottingham, NG7 2UH, UK
| | - Jacqueline Nicholson
- Paediatric Psychosocial Department, Royal Manchester Children's Hospital, Central Manchester University Hospitals, Oxford Road, Manchester, M13 9WL, UK
| | - Mars Skae
- Department of Paediatric Endocrinology, Royal Manchester Children's Hospital, Central Manchester University Hospitals, Oxford Road, Manchester, M13 9WL, UK
| | - Caroline Hall
- Therapy and Dietetic Department, Royal Manchester Children's Hospital, Central Manchester University Hospitals, Oxford Road, Manchester, M13 9WL, UK
| | - Ross Craigie
- Department of Paediatric Surgery, Royal Manchester Children's Hospital, Central Manchester University Hospitals, Oxford Road, Manchester, M13 9WL, UK
| | - Raja Padidela
- Department of Paediatric Endocrinology, Royal Manchester Children's Hospital, Central Manchester University Hospitals, Oxford Road, Manchester, M13 9WL, UK
| | - Nuala Murphy
- Department of Diabetes and Endocrinology, Children's University Hospital, Temple Street, Dublin, Ireland
| | - Tabitha Randell
- Department of Paediatric Endocrinology and Diabetes, Nottingham Children's Hospital, Nottingham University Hospitals, Derby Road, Nottingham, NG7 2UH, UK
| | - Karen E Cosgrove
- Faculty of Biology, Medicine and Health, University of Manchester, Oxford Rd, Manchester, M13 9PL, UK
| | - Mark J Dunne
- Faculty of Biology, Medicine and Health, University of Manchester, Oxford Rd, Manchester, M13 9PL, UK
| | - Indraneel Banerjee
- Department of Paediatric Endocrinology, Royal Manchester Children's Hospital, Central Manchester University Hospitals, Oxford Road, Manchester, M13 9WL, UK.,Faculty of Biology, Medicine and Health, University of Manchester, Oxford Rd, Manchester, M13 9PL, UK
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11
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Notary AM, Westacott MJ, Hraha TH, Pozzoli M, Benninger RKP. Decreases in Gap Junction Coupling Recovers Ca2+ and Insulin Secretion in Neonatal Diabetes Mellitus, Dependent on Beta Cell Heterogeneity and Noise. PLoS Comput Biol 2016; 12:e1005116. [PMID: 27681078 PMCID: PMC5040430 DOI: 10.1371/journal.pcbi.1005116] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 08/23/2016] [Indexed: 11/29/2022] Open
Abstract
Diabetes is caused by dysfunction to β-cells in the islets of Langerhans, disrupting insulin secretion and glucose homeostasis. Gap junction-mediated electrical coupling between β-cells in the islet plays a major role in coordinating a pulsatile secretory response at elevated glucose and suppressing insulin secretion at basal glucose. Previously, we demonstrated that a critical number of inexcitable cells can rapidly suppress the overall islet response, as a result of gap junction coupling. This was demonstrated in a murine model of Neonatal Diabetes Mellitus (NDM) involving expression of ATP-insensitive KATP channels, and by a multi-cellular computational model of islet electrical activity. Here we examined the mechanisms by which gap junction coupling contributes to islet dysfunction in NDM. We first verified the computational model against [Ca2+] and insulin secretion measurements in islets expressing ATP-insensitive KATP channels under different levels of gap junction coupling. We then applied this model to predict how different KATP channel mutations found in NDM suppress [Ca2+], and the role of gap junction coupling in this suppression. We further extended the model to account for stochastic noise and insulin secretion dynamics. We found experimentally and in the islet model that reductions in gap junction coupling allow progressively greater glucose-stimulated [Ca2+] and insulin secretion following expression of ATP-insensitive KATP channels. The model demonstrated good correspondence between suppression of [Ca2+] and clinical presentation of different NDM mutations. Significant recoveries in [Ca2+] and insulin secretion were predicted for many mutations upon reductions in gap junction coupling, where stochastic noise played a significant role in the recoveries. These findings provide new understanding how the islet functions as a multicellular system and for the role of gap junction channels in exacerbating the effects of decreased cellular excitability. They further suggest novel therapeutic options for NDM and other monogenic forms of diabetes. Diabetes is a disease reaching a global epidemic, which results from dysfunction to the islets of Langerhans in the pancreas and their ability to secrete the hormone insulin to regulate glucose homeostasis. Islets are multicellular structures that show extensive coupling between heterogeneous cellular units; and central to the causes of diabetes is a dysfunction to these cellular units and their interactions. Understanding the inter-relationship between structure and function is challenging in biological systems, but is crucial to the cause of disease and discovering therapeutic targets. With the goal of further characterizing the islet of Langerhans and its excitable behavior, we examined the role of important channels in the islet where dysfunction is linked to or causes diabetes. Advances in our ability to computationally model perturbations in physiological systems has allowed for the testing of hypothesis quickly, in systems that are not experimentally accessible. Using an experimentally validated model and modeling human mutations, we discover that monogenic forms of diabetes may be remedied by a reduction in electrical coupling between cells; either alone or in conjunction with pharmacological intervention. Knowledge of biological systems in general is also helped by these findings, in that small changes to cellular elements may lead to major disruptions in the overall system. This may then be overcome by allowing the system components to function independently in the presence of dysfunction to individual cells.
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Affiliation(s)
- Aleena M. Notary
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Matthew J. Westacott
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Thomas H. Hraha
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Marina Pozzoli
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
| | - Richard K. P. Benninger
- Department of Bioengineering, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
- Barbara Davis Center for Diabetes, University of Colorado, Anschutz Medical campus, Aurora, Colorado, United States of America
- * E-mail:
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12
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Velasco M, Díaz-García CM, Larqué C, Hiriart M. Modulation of Ionic Channels and Insulin Secretion by Drugs and Hormones in Pancreatic Beta Cells. Mol Pharmacol 2016; 90:341-57. [PMID: 27436126 DOI: 10.1124/mol.116.103861] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/18/2016] [Indexed: 12/11/2022] Open
Abstract
Pancreatic beta cells, unique cells that secrete insulin in response to an increase in glucose levels, play a significant role in glucose homeostasis. Glucose-stimulated insulin secretion (GSIS) in pancreatic beta cells has been extensively explored. In this mechanism, glucose enters the cells and subsequently the metabolic cycle. During this process, the ATP/ADP ratio increases, leading to ATP-sensitive potassium (KATP) channel closure, which initiates depolarization that is also dependent on the activity of TRP nonselective ion channels. Depolarization leads to the opening of voltage-gated Na(+) channels (Nav) and subsequently voltage-dependent Ca(2+) channels (Cav). The increase in intracellular Ca(2+) triggers the exocytosis of insulin-containing vesicles. Thus, electrical activity of pancreatic beta cells plays a central role in GSIS. Moreover, many growth factors, incretins, neurotransmitters, and hormones can modulate GSIS, and the channels that participate in GSIS are highly regulated. In this review, we focus on the principal ionic channels (KATP, Nav, and Cav channels) involved in GSIS and how classic and new proteins, hormones, and drugs regulate it. Moreover, we also discuss advances on how metabolic disorders such as metabolic syndrome and diabetes mellitus change channel activity leading to changes in insulin secretion.
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Affiliation(s)
- Myrian Velasco
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Carlos Manlio Díaz-García
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Carlos Larqué
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Marcia Hiriart
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
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13
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Babiker T, Vedovato N, Patel K, Thomas N, Finn R, Männikkö R, Chakera AJ, Flanagan SE, Shepherd MH, Ellard S, Ashcroft FM, Hattersley AT. Successful transfer to sulfonylureas in KCNJ11 neonatal diabetes is determined by the mutation and duration of diabetes. Diabetologia 2016; 59:1162-6. [PMID: 27033559 PMCID: PMC4869695 DOI: 10.1007/s00125-016-3921-8] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 02/17/2016] [Indexed: 10/29/2022]
Abstract
AIMS/HYPOTHESIS The finding that patients with diabetes due to potassium channel mutations can transfer from insulin to sulfonylureas has revolutionised the management of patients with permanent neonatal diabetes. The extent to which the in vitro characteristics of the mutation can predict a successful transfer is not known. Our aim was to identify factors associated with successful transfer from insulin to sulfonylureas in patients with permanent neonatal diabetes due to mutations in KCNJ11 (which encodes the inwardly rectifying potassium channel Kir6.2). METHODS We retrospectively analysed clinical data on 127 patients with neonatal diabetes due to KCNJ11 mutations who attempted to transfer to sulfonylureas. We considered transfer successful when patients completely discontinued insulin whilst on sulfonylureas. All unsuccessful transfers received ≥0.8 mg kg(-1) day(-1) glibenclamide (or the equivalent) for >4 weeks. The in vitro response of mutant Kir6.2/SUR1 channels to tolbutamide was assessed in Xenopus oocytes. For some specific mutations, not all individuals carrying the mutation were able to transfer successfully; we therefore investigated which clinical features could predict a successful transfer. RESULTS In all, 112 out of 127 (88%) patients successfully transferred to sulfonylureas from insulin with an improvement in HbA1c from 8.2% (66 mmol/mol) on insulin, to 5.9% (41 mmol/mol) on sulphonylureas (p = 0.001). The in vitro response of the mutation to tolbutamide determined the likelihood of transfer: the extent of tolbutamide block was <63% for the p.C166Y, p.I296L, p.L164P or p.T293N mutations, and no patients with these mutations successfully transferred. However, most individuals with mutations for which tolbutamide block was >73% did transfer successfully. The few patients with these mutations who could not transfer had a longer duration of diabetes than those who transferred successfully (18.2 vs 3.4 years, p = 0.032). There was no difference in pre-transfer HbA1c (p = 0.87), weight-for-age z scores (SD score; p = 0.12) or sex (p = 0.17). CONCLUSIONS/INTERPRETATION Transfer from insulin is successful for most KCNJ11 patients and is best predicted by the in vitro response of the specific mutation and the duration of diabetes. Knowledge of the specific mutation and of diabetes duration can help predict whether successful transfer to sulfonylureas is likely. This result supports the early genetic testing and early treatment of patients with neonatal diabetes aged under 6 months.
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Affiliation(s)
- Tarig Babiker
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Natascia Vedovato
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Kashyap Patel
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Nicholas Thomas
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Roisin Finn
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Roope Männikkö
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
- UCL Institute of Neurology, MRC Centre for Neuromuscular Diseases, London, UK
| | - Ali J Chakera
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
- Department of Diabetes and Endocrinology, Royal Sussex County Hospital, Brighton and Sussex University Hospitals, Brighton, UK
| | - Sarah E Flanagan
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Maggie H Shepherd
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Sian Ellard
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK
| | - Frances M Ashcroft
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK.
| | - Andrew T Hattersley
- Department of Diabetes and Endocrinology, Royal Devon and Exeter NHS Foundation Trust, Exeter, UK.
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, Exeter, EX2 5DW, UK.
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14
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Maejima Y, Hasegawa S, Horita S, Kumamoto K, Galvanovskis J, Takenoshita S, Shimomura K. Water intake disorder in a DEND syndrome afflicted patient with R50P mutation. Endocr J 2015; 62:387-92. [PMID: 25739471 DOI: 10.1507/endocrj.ej14-0392] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
In this study, we present a case of developmental delay, epilepsy and neonatal diabetes (DEND) syndrome in a young male patient with the R50P mutation located in the Kir6.2 subunit of the ATP-sensitive K(+) (KATP) channel. Whereas most patients with DEND syndrome are resistant to sulfonylurea therapy, our patient was responsive to sulfonylurea, lacked the most common neurological symptoms, such as epilepsy, but refused to drink water. His serum electrolytes and plasma osmolarity were normal but the serum vasopressin level was increased. To investigate the underlying mechanism of his water intake disorder, a 5 μL aliquot of 340 μM KATP channel opener diazoxide or 100 μM KATP channel inhibitor glibenclamide was injected into the third ventricle of the rat brain, and water intake was monitored. Although the injection of glibenclamide had no effect, injection of diazoxide significantly increased water intake by about 1.5 fold without affecting food intake. This result indicates that the KATP channel activity in the brain may have an influence on water intake. Here, we present the first case of a DEND syndrome-afflicted patient with water intake disorder and increased serum vasopressin level, possibly related to altered KATP channel activity.
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Affiliation(s)
- Yuko Maejima
- Department of Electrophysiology and Oncology, Fukushima Medical University School of Medicine, Fukushima, Japan
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15
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Mohnike K, Wieland I, Barthlen W, Vogelgesang S, Empting S, Mohnike W, Meissner T, Zenker M. Clinical and genetic evaluation of patients with KATP channel mutations from the German registry for congenital hyperinsulinism. Horm Res Paediatr 2014; 81:156-68. [PMID: 24401662 DOI: 10.1159/000356905] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 10/03/2013] [Indexed: 11/19/2022] Open
Abstract
Congenital hyperinsulinism (CHI) causes hypoglycemia due to irregular insulin secretion. In infants, a rapid diagnosis and appropriate management to avoid severe hypoglycemia is mandatory. CHI is a heterogeneous condition at the clinical and genetic level, and disease-causing genes have been identified in about half of the patients. The majority of mutations have been identified in the ABCC8 and KCNJ11 genes encoding subunits of the KATP channel responsible for two distinct histological forms. The diffuse form is caused by autosomal recessive or dominant inherited mutations, whereas the focal form is caused by a paternally transmitted recessive mutation and a second somatic event. We report on an unselected cohort of 136 unrelated patients from the German CHI registry. Mutations in either the ABCC8 or KCNJ11 gene were identified in 61 of these patients (45%). In total, 64 different mutations including 38 novel ones were detected in this cohort. We observed biparental (recessive) inheritance in 34% of mutation-positive patients, dominant inheritance in 11% and paternal transmission of a mutation associated with a focal CHI type in 38%. In addition, we observed inheritance patterns that do not exactly follow the classical recessive or dominant mode, further adding to the genetic complexity of this disease.
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Affiliation(s)
- Klaus Mohnike
- Department of Pediatrics, Otto von Guericke University Magdeburg, Magdeburg, Germany
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16
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Su C, Gong C, Sanger P, Li W, Wu D, Gu Y, Cao B. Long-term follow-up and mutation analysis of 27 chinese cases of congenital hyperinsulinism. Horm Res Paediatr 2014; 81:169-76. [PMID: 24434300 DOI: 10.1159/000356911] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 09/24/2013] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVES Long-term clinical follow-up and mutation analysis were performed in 27 Chinese congenital hyperinsulinism patients. METHOD 27 hypoglycemia patients were diagnosed with CHI within 2 years of age. The long-term clinical outcome was analyzed and mutation analysis of 5 hyperinsulinism candidate genes was performed. RESULTS The median onset age of hypoglycemia in the patients was 60 days; 11 patients showed hypoglycemic symptoms in the neonatal stage, and hypoglycemia in most of the patients was first expressed as a seizure. Blood was collected during the hypoglycemic episode and insulin levels were significantly elevated. ABCC8, KCNJ11, GCK, HNF4a and GLUD1 genes were screened for mutation analysis. 14 mutations in ABCC8 or KCNJ11 genes in 12 cases were identified (44%). 57% (8/14) of the mutations have not been reported before. 83% (10/12) of the patients have a monoallelic mutation. 58% of these 12 patients were predicted to be focal. 73% of the patients without KATP channel mutations were sensitive to diazoxide. 26 patients were followed over a period of 1-13 years. 50% of all 27 patients showed brain impairment. CONCLUSIONS Chinese CHI patients are similar to other ethnic groups in terms of prevalence of KATP-HI, onset age, severity of hypoglycemia and treatment. Mutations in ABCC8 and KCNJ11 are common causes of CHI in Chinese patients. Mutation analysis showed more novel and monoallele mutations in KATP genes.
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Affiliation(s)
- Chang Su
- Department of Endocrinology, Genetics and Metabolism, Beijing Children's Hospital, Capital Medical University, Beijing, China
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17
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Arya VB, Guemes M, Nessa A, Alam S, Shah P, Gilbert C, Senniappan S, Flanagan SE, Ellard S, Hussain K. Clinical and histological heterogeneity of congenital hyperinsulinism due to paternally inherited heterozygous ABCC8/KCNJ11 mutations. Eur J Endocrinol 2014; 171:685-95. [PMID: 25201519 DOI: 10.1530/eje-14-0353] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
CONTEXT Congenital hyperinsulinism (CHI) has two main histological types: diffuse and focal. Heterozygous paternally inherited ABCC8/KCNJ11 mutations (depending upon whether recessive or dominant acting and occurrence of somatic maternal allele loss) can give rise to either phenotype. However, the relative proportion of these two phenotypes in a large cohort of CHI patients due to paternally inherited heterozygous ABCC8/KCNJ11 mutations has not been reported. OBJECTIVE The purpose of this study is to highlight the variable clinical phenotype and to characterise the distribution of diffuse and focal disease in a large cohort of CHI patients due to paternally inherited heterozygous ABCC8/KCNJ11 mutations. DESIGN A retrospective chart review of the CHI patients due to heterozygous paternally inherited ABCC8/KCNJ11 mutations from 2000 to 2013 was conducted. RESULTS Paternally inherited heterozygous ABCC8/KCNJ11 mutations were identified in 53 CHI patients. Of these, 18 (34%) either responded to diazoxide or resolved spontaneously. Fluorine-18 l-3, 4-dihydroxyphenylalanine positron emission tomography computerised tomography 18F DOPA-PET CT) scanning in 3/18 children showed diffuse disease. The remaining 35 (66%) diazoxide-unresponsive children either had pancreatic venous sampling (n=8) or 18F DOPA-PET CT (n=27). Diffuse, indeterminate and focal disease was identified in 13, 1 and 21 patients respectively. Two patients with suspected diffuse disease were identified to have focal disease on histology. CONCLUSIONS Paternally inherited heterozygous ABCC8/KCNJ11 mutations can manifest as a wide spectrum of CHI with variable 18F DOPA-PET CT/histological findings and clinical outcomes. Focal disease was histologically confirmed in 24/53 (45%) of CHI patients with paternally inherited heterozygous ABCC8/KCNJ11 mutations.
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Affiliation(s)
- Ved Bhushan Arya
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
| | - Maria Guemes
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
| | - Azizun Nessa
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
| | - Syeda Alam
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
| | - Pratik Shah
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
| | - Clare Gilbert
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
| | - Senthil Senniappan
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
| | - Sarah E Flanagan
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
| | - Sian Ellard
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
| | - Khalid Hussain
- Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK Developmental Endocrinology Research GroupClinical and Molecular Genetics Unit, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UKLondon Centre for Paediatric EndocrinologyGreat Ormond Street Hospital for Children, London WC1N 3JH, UKInstitute of Biomedical and Clinical ScienceUniversity of Exeter Medical School, Exeter EX2 5DW, UK
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Zubcevic L, Bavro VN, Muniz JRC, Schmidt MR, Wang S, De Zorzi R, Venien-Bryan C, Sansom MSP, Nichols CG, Tucker SJ. Control of KirBac3.1 potassium channel gating at the interface between cytoplasmic domains. J Biol Chem 2014; 289:143-51. [PMID: 24257749 PMCID: PMC3879539 DOI: 10.1074/jbc.m113.501833] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 11/04/2013] [Indexed: 01/22/2023] Open
Abstract
KirBac channels are prokaryotic homologs of mammalian inwardly rectifying potassium (Kir) channels, and recent structures of KirBac3.1 have provided important insights into the structural basis of gating in Kir channels. In this study, we demonstrate that KirBac3.1 channel activity is strongly pH-dependent, and we used x-ray crystallography to determine the structural changes that arise from an activatory mutation (S205L) located in the cytoplasmic domain (CTD). This mutation stabilizes a novel energetically favorable open conformation in which changes at the intersubunit interface in the CTD also alter the electrostatic potential of the inner cytoplasmic cavity. These results provide a structural explanation for the activatory effect of this mutation and provide a greater insight into the role of the CTD in Kir channel gating.
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Affiliation(s)
- Lejla Zubcevic
- From the Biological Physics Group, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Vassiliy N. Bavro
- From the Biological Physics Group, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
- the School of Immunity and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Joao R. C. Muniz
- the Sao Carlos Institute of Physics, University of Sao Paulo, Sao Paulo SP 13560-970, Brazil
| | - Matthias R. Schmidt
- the Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Shizhen Wang
- the Department of Cell Biology and Physiology and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | | | - Catherine Venien-Bryan
- Harvard Medical School, Boston, Massachusetts 02115
- the Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC), CNRS-UMR 7590, Université Pierre et Marie Curie, 75005 Paris, France, and
| | - Mark S. P. Sansom
- the Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
- the OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Colin G. Nichols
- the Department of Cell Biology and Physiology and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Stephen J. Tucker
- From the Biological Physics Group, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
- the OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford OX1 3PT, United Kingdom
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Kapoor RR, Flanagan SE, Arya VB, Shield JP, Ellard S, Hussain K. Clinical and molecular characterisation of 300 patients with congenital hyperinsulinism. Eur J Endocrinol 2013; 168:557-64. [PMID: 23345197 PMCID: PMC3599069 DOI: 10.1530/eje-12-0673] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Congenital hyperinsulinism (CHI) is a clinically heterogeneous condition. Mutations in eight genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, HNF4A and HNF1A) are known to cause CHI. AIM To characterise the clinical and molecular aspects of a large cohort of patients with CHI. METHODOLOGY Three hundred patients were recruited and clinical information was collected before genotyping. ABCC8 and KCNJ11 genes were analysed in all patients. Mutations in GLUD1, HADH, GCK and HNF4A genes were sought in patients with diazoxide-responsive CHI with hyperammonaemia (GLUD1), raised 3-hydroxybutyrylcarnitine and/or consanguinity (HADH), positive family history (GCK) or when CHI was diagnosed within the first week of life (HNF4A). RESULTS Mutations were identified in 136/300 patients (45.3%). Mutations in ABCC8/KCNJ11 were the commonest genetic cause identified (n=109, 36.3%). Among diazoxide-unresponsive patients (n=105), mutations in ABCC8/KCNJ11 were identified in 92 (87.6%) patients, of whom 63 patients had recessively inherited mutations while four patients had dominantly inherited mutations. A paternal mutation in the ABCC8/KCNJ11 genes was identified in 23 diazoxide-unresponsive patients, of whom six had diffuse disease. Among the diazoxide-responsive patients (n=183), mutations were identified in 41 patients (22.4%). These include mutations in ABCC8/KCNJ11 (n=15), HNF4A (n=7), GLUD1 (n=16) and HADH (n=3). CONCLUSIONS A genetic diagnosis was made for 45.3% of patients in this large series. Mutations in the ABCC8 gene were the commonest identifiable cause. The vast majority of patients with diazoxide-responsive CHI (77.6%) had no identifiable mutations, suggesting other genetic and/or environmental mechanisms.
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Affiliation(s)
| | - Sarah E Flanagan
- Institute of Biomedical and Clinical Science, University of Exeter Medical SchoolExeter, EX2 5DWUK
| | | | - Julian P Shield
- Department of Child Health, Bristol Royal Hospital for ChildrenBristol, BS2 8BJUK
| | - Sian Ellard
- Institute of Biomedical and Clinical Science, University of Exeter Medical SchoolExeter, EX2 5DWUK
| | - Khalid Hussain
- (Correspondence should be addressed to K Hussain who is now at Molecular Genetics Unit, Developmental Endocrinology Research Group, Institute of Child Health, University College London, 30 Guilford Street, London WC1N 1EH, UK; )
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20
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Zylbergold P, Sleno R, Hébert TE. A novel, radiolabel-free pulse chase strategy to study Kir3 channel ontogeny. J Recept Signal Transduct Res 2013; 33:144-52. [DOI: 10.3109/10799893.2013.764898] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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21
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Flanagan SE, Kapoor RR, Banerjee I, Hall C, Smith VV, Hussain K, Ellard S. Dominantly acting ABCC8 mutations in patients with medically unresponsive hyperinsulinaemic hypoglycaemia. Clin Genet 2011; 79:582-7. [PMID: 20573158 PMCID: PMC3375476 DOI: 10.1111/j.1399-0004.2010.01476.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Accepted: 05/17/2010] [Indexed: 11/30/2022]
Abstract
Recessive inactivating mutations in the ABCC8 and KCNJ11 genes encoding the adenosine triphosphate-sensitive potassium (K(ATP)) channel subunit sulphonylurea receptor 1 (SUR1) and inwardly rectifying potassium channel subunit (Kir6.2) are the most common cause of hyperinsulinaemic hypoglycaemia (HH). Most of these patients do not respond to treatment with the (K(ATP)) channel agonist diazoxide. Dominant inactivating ABCC8 and KCNJ11 mutations are less frequent, but are usually associated with a milder form of hypoglycaemia that is responsive to diazoxide therapy. We studied five patients from four families with HH who were unresponsive to diazoxide and required a near total pancreatectomy. Mutations in KCNJ11 and ABCC8 were sought by sequencing and dosage analysis. Three novel heterozygous ABCC8 mis-sense mutations (G1485E, D1506E and M1514K) were identified in four probands. All the mutations affect residues located within the Nucleotide Binding Domain 2 of the SUR1 subunit. Testing of family members showed that the mutations had arisen de novo with dominant inheritance in one pedigree. This study extends the clinical phenotype associated with dominant (K(ATP)) channel mutations to include severe congenital HH requiring near total pancreatectomy in addition to a milder form of diazoxide responsive hypoglycaemia. The identification of dominant vs recessive mutations does not predict clinical course but it is important for estimating the risk of HH in future siblings and offspring.
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Affiliation(s)
- S E Flanagan
- Institute of Biomedical and Clinical Science, Peninsula Medical School, University of Exeter, Exeter, UK
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22
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Abstract
The use of mouse models in medical research has greatly contributed to our understanding of the development of type 2 diabetes mellitus and the mechanisms of disease progression in the context of insulin resistance and β-cell dysfunction. Maintenance of glucose homeostasis involves a complex interplay of many genes and their actions in response to exogenous stimuli. In recent years, the availability of large population-based cohorts and the capacity to genotype enormous numbers of common genetic variants have driven various large-scale genome-wide association studies, which has greatly accelerated the identification of novel genes likely to be involved in the development of type 2 diabetes. The increasing demand for verifying novel genes is met by the timely development of new mouse resources established as various collaborative projects involving major transgenic and phenotyping centres and laboratories worldwide. The surge of new data will ultimately enable translational research into potential improvement and refinement of current type 2 diabetes therapy options, and hopefully restore quality of life for patients.
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Lang V, Light PE. The molecular mechanisms and pharmacotherapy of ATP-sensitive potassium channel gene mutations underlying neonatal diabetes. Pharmgenomics Pers Med 2010; 3:145-61. [PMID: 23226049 PMCID: PMC3513215 DOI: 10.2147/pgpm.s6969] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Indexed: 12/14/2022] Open
Abstract
Neonatal diabetes mellitus (NDM) is a monogenic disorder caused by mutations in genes involved in regulation of insulin secretion from pancreatic β-cells. Mutations in the KCNJ11 and ABCC8 genes, encoding the adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channel Kir6.2 and SUR1 subunits, respectively, are found in ∼50% of NDM patients. In the pancreatic β-cell, K(ATP) channel activity couples glucose metabolism to insulin secretion via cellular excitability and mutations in either KCNJ11 or ABCC8 genes alter K(ATP) channel activity, leading to faulty insulin secretion. Inactivation mutations decrease K(ATP) channel activity and stimulate excessive insulin secretion, leading to hyperinsulinism of infancy. In direct contrast, activation mutations increase K(ATP) channel activity, resulting in impaired insulin secretion, NDM, and in severe cases, developmental delay and epilepsy. Many NDM patients with KCNJ11 and ABCC8 mutations can be successfully treated with sulfonylureas (SUs) that inhibit the K(ATP) channel, thus replacing the need for daily insulin injections. There is also strong evidence indicating that SU therapy ameliorates some of the neurological defects observed in patients with more severe forms of NDM. This review focuses on the molecular and cellular mechanisms of mutations in the K(ATP) channel that underlie NDM. SU pharmacogenomics is also discussed with respect to evaluating whether patients with certain K(ATP) channel activation mutations can be successfully switched to SU therapy.
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Affiliation(s)
- Veronica Lang
- Department of Pharmacology and Alberta Diabetes Institute, Faculty of Medicine and Dentistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Peter E Light
- Department of Pharmacology and Alberta Diabetes Institute, Faculty of Medicine and Dentistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Alberta, Canada
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Persistent hyperinsulinemic hypoglycemia of infancy due to homozygous KCNJ11 (T294M) mutation. Indian J Pediatr 2010; 77:803-4. [PMID: 20589481 DOI: 10.1007/s12098-010-0100-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2010] [Accepted: 03/09/2010] [Indexed: 10/19/2022]
Abstract
Hyperinsulinemic hypoglycemia is the most common cause of persistent hypoglycemia in infancy. While most of the cases are sporadic more than 100 mutations have been reported in the familial type. The authors report a case of familial hyperinsulinemic hypoglycemia with homozygous T294M mutation of the KCNJ11 gene, which responded to diazoxide therapy.
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McTaggart JS, Clark RH, Ashcroft FM. The role of the KATP channel in glucose homeostasis in health and disease: more than meets the islet. J Physiol 2010; 588:3201-9. [PMID: 20519313 DOI: 10.1113/jphysiol.2010.191767] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
ATP-sensitive potassium (K(ATP)) channels are critical for the maintenance of glucose homeostasis. They are essential for glucose-stimulated insulin secretion from pancreatic beta-cells, contribute to the mechanisms by which hypoglycaemia stimulates glucagon release from pancreatic alpha-cells, and are involved in glucose uptake into skeletal muscle, glucose production and release from the liver, and feeding behaviour. Not surprisingly, loss- or gain-of-function mutations in K(ATP) channel genes have profound effects, giving rise to congenital hyperinsulinaemia and neonatal diabetes respectively. This symposium review focuses on our current understanding of the role of the K(ATP) channel in glucose homeostasis in health and disease.
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Affiliation(s)
- James S McTaggart
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, and OXION Centre for Ion Channel Studies, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
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Männikkö R, Jefferies C, Flanagan SE, Hattersley A, Ellard S, Ashcroft FM. Interaction between mutations in the slide helix of Kir6.2 associated with neonatal diabetes and neurological symptoms. Hum Mol Genet 2009; 19:963-72. [PMID: 20022885 DOI: 10.1093/hmg/ddp554] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
ATP-sensitive potassium (K(ATP)) channels regulate insulin secretion from pancreatic beta-cells. Gain-of-function mutations in the genes encoding the Kir6.2 and SUR1 subunits of this channel cause neonatal diabetes. We report two novel mutations on the same haplotype (cis), F60Y and V64L, in the slide helix of Kir6.2 in a patient with neonatal diabetes, developmental delay and epilepsy. Functional analysis revealed the F60Y mutation increases the intrinsic channel open probability (Po(0)), thereby indirectly producing a marked decrease in channel inhibition by ATP and an increase in whole-cell K(ATP) currents. When expressed alone, the V64L mutation caused a small reduction in apparent ATP inhibition, by enhancing the ability of MgATP to stimulate channel activity. The V64L mutation also ameliorated the deleterious effects on the F60Y mutation when it was expressed on the same (but not a different) subunit. These data indicate that F60Y is the pathogenic mutation and reveal that interactions between slide helix residues can influence K(ATP) channel gating.
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Affiliation(s)
- Roope Männikkö
- Henry Wellcome Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
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