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Yuan YC, Wang H, Jiang ZJ, Liu C, Li Q, Zhou SR, Yang JK. Potassium voltage-gated channel subfamily H member 2 (KCNH2) is a promising target for incretin secretagogue therapies. Signal Transduct Target Ther 2024; 9:207. [PMID: 39128897 PMCID: PMC11317495 DOI: 10.1038/s41392-024-01923-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 06/16/2024] [Accepted: 07/14/2024] [Indexed: 08/13/2024] Open
Abstract
Derived from enteroendocrine cells (EECs), glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) are pivotal incretin hormones crucial for blood glucose regulation. Medications of GLP-1 analogs and GLP-1 receptor activators are extensively used in the treatment of type 2 diabetes (T2D) and obesity. However, there are currently no agents to stimulate endogenous incretin secretion. Here, we find the pivotal role of KCNH2 potassium channels in the regulation of incretin secretion. Co-localization of KCNH2 with incretin-secreting EECs in the intestinal epithelium of rodents highlights its significance. Gut epithelial cell-specific KCNH2 knockout in mice improves glucose tolerance and increases oral glucose-triggered GLP-1 and GIP secretion, particularly GIP. Furthermore, KCNH2-deficient primary intestinal epithelial cells exhibit heightened incretin, especially GIP secretion upon nutrient stimulation. Mechanistically, KCNH2 knockdown in EECs leads to reduced K+ currents, prolonged action potential duration, and elevated intracellular calcium levels. Finally, we found that dofetilide, a KCNH2-specific inhibitor, could promote incretin secretion in enteroendocrine STC-1 cells in vitro and in hyperglycemic mice in vivo. These findings elucidate, for the first time, the mechanism and application of KCNH2 in regulating incretin secretion by EECs. Given the therapeutic promise of GLP-1 and GIP in diabetes and obesity management, this study advances our understanding of incretin regulation, paving the way for potential incretin secretagogue therapies in the treatment of diabetes and obesity.
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Affiliation(s)
- Ying-Chao Yuan
- Beijing Key Laboratory of Diabetes Research and Care, Department of Endocrinology and Metabolism, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China
- Laboratory for Clinical Medicine, Capital Medical University, Beijing, 100069, China
| | - Hao Wang
- Beijing Key Laboratory of Diabetes Research and Care, Department of Endocrinology and Metabolism, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.
- Laboratory for Clinical Medicine, Capital Medical University, Beijing, 100069, China.
| | - Ze-Ju Jiang
- Beijing Key Laboratory of Diabetes Research and Care, Department of Endocrinology and Metabolism, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China
- Laboratory for Clinical Medicine, Capital Medical University, Beijing, 100069, China
| | - Chang Liu
- Beijing Key Laboratory of Diabetes Research and Care, Department of Endocrinology and Metabolism, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China
| | - Qi Li
- Beijing Key Laboratory of Diabetes Research and Care, Department of Endocrinology and Metabolism, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China
- Laboratory for Clinical Medicine, Capital Medical University, Beijing, 100069, China
| | - Si-Rui Zhou
- Beijing Key Laboratory of Diabetes Research and Care, Department of Endocrinology and Metabolism, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China
- Laboratory for Clinical Medicine, Capital Medical University, Beijing, 100069, China
| | - Jin-Kui Yang
- Beijing Key Laboratory of Diabetes Research and Care, Department of Endocrinology and Metabolism, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.
- Laboratory for Clinical Medicine, Capital Medical University, Beijing, 100069, China.
- Subcenter of State Key Laboratory of Kidney Disease, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.
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Transfer of Proteins from Cultured Human Adipose to Blood Cells and Induction of Anabolic Phenotype Are Controlled by Serum, Insulin and Sulfonylurea Drugs. Int J Mol Sci 2023; 24:ijms24054825. [PMID: 36902257 PMCID: PMC10003403 DOI: 10.3390/ijms24054825] [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: 11/29/2022] [Revised: 02/10/2023] [Accepted: 02/27/2023] [Indexed: 03/06/2023] Open
Abstract
Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are anchored at the outer leaflet of eukaryotic plasma membranes (PMs) only by carboxy-terminal covalently coupled GPI. GPI-APs are known to be released from the surface of donor cells in response to insulin and antidiabetic sulfonylureas (SUs) by lipolytic cleavage of the GPI or upon metabolic derangement as full-length GPI-APs with the complete GPI attached. Full-length GPI-APs become removed from extracellular compartments by binding to serum proteins, such as GPI-specific phospholipase D (GPLD1), or insertion into the PMs of acceptor cells. Here, the interplay between the lipolytic release and intercellular transfer of GPI-APs and its potential functional impact was studied using transwell co-culture with human adipocytes as insulin-/SU-responsive donor cells and GPI-deficient erythroleukemia as acceptor cells (ELCs). Measurement of the transfer as the expression of full-length GPI-APs at the ELC PMs by their microfluidic chip-based sensing with GPI-binding α-toxin and GPI-APs antibodies and of the ELC anabolic state as glycogen synthesis upon incubation with insulin, SUs and serum yielded the following results: (i) Loss of GPI-APs from the PM upon termination of their transfer and decline of glycogen synthesis in ELCs, as well as prolongation of the PM expression of transferred GPI-APs upon inhibition of their endocytosis and upregulated glycogen synthesis follow similar time courses. (ii) Insulin and SUs inhibit both GPI-AP transfer and glycogen synthesis upregulation in a concentration-dependent fashion, with the efficacies of the SUs increasing with their blood glucose-lowering activity. (iii) Serum from rats eliminates insulin- and SU-inhibition of both GPI-APs' transfer and glycogen synthesis in a volume-dependent fashion, with the potency increasing with their metabolic derangement. (iv) In rat serum, full-length GPI-APs bind to proteins, among them (inhibited) GPLD1, with the efficacy increasing with the metabolic derangement. (v) GPI-APs are displaced from serum proteins by synthetic phosphoinositolglycans and then transferred to ELCs with accompanying stimulation of glycogen synthesis, each with efficacies increasing with their structural similarity to the GPI glycan core. Thus, both insulin and SUs either block or foster transfer when serum proteins are depleted of or loaded with full-length GPI-APs, respectively, i.e., in the normal or metabolically deranged state. The transfer of the anabolic state from somatic to blood cells over long distance and its "indirect" complex control by insulin, SUs and serum proteins support the (patho)physiological relevance of the intercellular transfer of GPI-APs.
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Kalra S, Bahendeka S, Sahay R, Ghosh S, Md F, Orabi A, Ramaiya K, Al Shammari S, Shrestha D, Shaikh K, Abhayaratna S, Shrestha PK, Mahalingam A, Askheta M, A. Rahim AA, Eliana F, Shrestha HK, Chaudhary S, Ngugi N, Mbanya JC, Aye TT, Latt TS, Akanov ZA, Syed AR, Tandon N, Unnikrishnan AG, Madhu SV, Jawa A, Chowdhury S, Bajaj S, Das AK. Consensus Recommendations on Sulfonylurea and Sulfonylurea Combinations in the Management of Type 2 Diabetes Mellitus - International Task Force. Indian J Endocrinol Metab 2018; 22:132-157. [PMID: 29535952 PMCID: PMC5838894 DOI: 10.4103/ijem.ijem_556_17] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
For decades, sulfonylureas (SUs) have been important drugs in the antidiabetic therapeutic armamentarium. They have been used as monotherapy as well as combination therapy. Focus on newer drugs and concerns about the risk of severe hypoglycemia and weight gain with some SUs have led to discussion on their safety and utility. It has to be borne in mind that the adverse events associated with SUs should not be ascribed to the whole class, as many modern SUs, such as glimepiride and gliclazide modified release, are associated with better safety profiles. Furthermore, individualization of treatment, using SUs in combination with other drugs, backed with careful monitoring and patient education, ensures maximum benefits with minimal side effects. The current guidelines, developed by experts from Africa, Asia, and the Middle East, promote the safe and smart use of SUs in combination with other glucose-lowering drugs.
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Affiliation(s)
- Sanjay Kalra
- Department of Endocrinology, Bharti Hospital, Karnal, Haryana, India
| | - Silver Bahendeka
- Department of Internal Medicine, Diabetes & Endocrinology, St. Francis Hospital, Nsambya, Kampala, Uganda
| | - Rakesh Sahay
- Department of Endocrinology, Osmania Medical College, Hyderabad, Telangana, India
| | - Sujoy Ghosh
- Department of Endocrinology, IPGMER and SSKM Hospital, Kolkata, West Bengal, India
| | - Fariduddin Md
- Department of Endocrinology, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh
| | - Abbas Orabi
- Department of Internal Medicine, Faculty of Medicine, Zagazig University, Zagazig, Egypt
| | - Kaushik Ramaiya
- Department of Internal Medicine, Hindu Mandal Hospital, Dar es Salaam, Tanzania
| | | | - Dina Shrestha
- Department of Endocrinology, Norvic International Hospital and Medical College, and Hospital for Advanced Medicine and Surgery, Maharajganj, Kathmandu, Nepal
| | - Khalid Shaikh
- Department of Diabetes, Faculty of Internal Medicine, Royal Oman Police Hospital, Muscat, Oman
| | - Sachitha Abhayaratna
- Department of Pharmacology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
| | - Pradeep K. Shrestha
- Department of Medicine, Tribhuvan University Teaching Hospital, Maharajganj, Kathmandu, Nepal
| | | | | | - Aly Ahmed A. Rahim
- Department of Internal Medicine, Diabetes & Metabolism Unit, Faculty of Medicine, Alexandria University, Alexandria, Egypt
| | - Fatimah Eliana
- Department of Internal Medicine, Faculty of Medicine, YARSI University, Jakarta, Indonesia
| | - Hari K. Shrestha
- Department of Internal Medicine, Kathmandu University Hospital, Dhulikhel, Nepal
| | | | - Nancy Ngugi
- Department of Endocrinology, Kenyatta National Hospital, Nairobi, Kenya
| | - Jean Claude Mbanya
- Department of Internal Medicine and Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaoundé, Yaounde, Cameroon
| | - Than Than Aye
- Department of Endocrinology, University of Medicine 2, Yangon, Myanmar
| | - Tint Swe Latt
- Department of Medicine, University of Medicine 2, Yangon, Myanmar
| | - Zhanay A. Akanov
- Center of Diabetes, Clinic of Internal Diseases, Asfendiyarov Kazakh National Medical University, Almaty, Republic of Kazakhstan
| | - Abbas Raza Syed
- Department of Endocrinology, Shaukat Khanum Hospital and Research Center, Lahore, Pakistan
| | - Nikhil Tandon
- Department of Endocrinology, Metabolism and Diabetes, All India Institute of Medical Sciences, Pune, Maharashtra, India
| | - A. G. Unnikrishnan
- Department of Endocrinology and Diabetes, Chellaram Diabetes Institute, Pune, Maharashtra, India
| | - S. V. Madhu
- Department of Medicine, University of Delhi, New Delhi, India
| | - Ali Jawa
- Department of Endocrinology, Diabetes and Metabolism, Wilshire Cardiovascular and Endocrine Center of Excellence, Lahore, Pakistan
| | - Subhankar Chowdhury
- Department of Endocrinology, IPGMER and SSKM Hospital, Kolkata, West Bengal, India
| | - Sarita Bajaj
- Department of Medicine, MLN Medical College, Allahabad, Uttar Pradesh, India
| | - Ashok Kumar Das
- Department of General Medicine, Pondicherry Institute of Medical Sciences, Puducherry, India
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Kalra S, Aamir AH, Raza A, Das AK, Azad Khan AK, Shrestha D, Qureshi MF, Md Fariduddin, Pathan MF, Jawad F, Bhattarai J, Tandon N, Somasundaram N, Katulanda P, Sahay R, Dhungel S, Bajaj S, Chowdhury S, Ghosh S, Madhu SV, Ahmed T, Bulughapitiya U. Place of sulfonylureas in the management of type 2 diabetes mellitus in South Asia: A consensus statement. Indian J Endocrinol Metab 2015; 19:577-96. [PMID: 26425465 PMCID: PMC4566336 DOI: 10.4103/2230-8210.163171] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Since their introduction in clinical practice in the 1950's, Sulfonylureas (SUs) have remained the main-stay of pharmacotherapy in the management of type 2 diabetes. Despite their well-established benefits, their place in therapy is inappropriately being overshadowed by newer therapies. Many of the clinical issues associated with the use of SUs are agent-specific, and do not pertain to the class as such. Modern SUs (glimepiride, gliclazide MR) are backed by a large body of evidence, experience, and most importantly, outcome data, which supports their role in managing patients with diabetes. Person-centred care, i.e., careful choice of SU, appropriate dosage, timing of administration, and adequate patient counseling, will ensure that deserving patients are not deprived of the advantages of this well-established class of anti-diabetic agents. Considering their efficacy, safety, pleiotropic benefits, and low cost of therapy, SUs should be considered as recommended therapy for the treatment of diabetes in South Asia. This initiative by SAFES aims to encourage rational, safe and smart prescription of SUs, and includes appropriate medication counseling.
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Affiliation(s)
- Sanjay Kalra
- Department of Endocrinology, Bharti Hospital and BRIDE, Karnal, Haryana, India
| | - A H Aamir
- Department of Endocrinology, Post Graduate Medical Institute Hayatabad Medical Complex, Peshawar, Pakistan
| | - Abbas Raza
- Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Pakistan
| | - A K Das
- Department of Endocrinology, Pondicherry Institute of Medical Sciences, Puducherry, India
| | - A K Azad Khan
- Department of Public Health, Bangladesh University of Health Sciences, Dhaka, Bangladesh
| | - Dina Shrestha
- Department of Endocrinology, Norvic International Hospital, Kathmandu, Nepal
| | - Md Faisal Qureshi
- Department of Endocrinology, Al-Khaliq Medicare Hospital, Dhaka, Bangladesh
| | - Md Fariduddin
- Department of Endocrinology, Bangabandhu Sheikh Mujib Medical University, Shahbag, Dhaka, Bangladesh
| | | | - Fatema Jawad
- Department of Diabetology, Medilink Clinics, Karachi, Pakistan
| | - Jyoti Bhattarai
- Department of Medicine, Trivuvan University, Kathmandu, Nepal
| | - Nikhil Tandon
- Department of Endocrinology and Metabolism, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Noel Somasundaram
- South Asian Federation of Endocrine Societies, National Hospital, Dhaka, Bangladesh
| | - Prasad Katulanda
- Department of Clinical Medicines, Diabetes Research Unit, University of Colombo, Colombo, Sri Lanka
| | - Rakesh Sahay
- Department of Endocrinology, Osmania Medical College, Hyderabad, Telangana, India
| | - Sanjib Dhungel
- Department of Medicine, Nepal Medical College Teaching Hospital, Kathmandu, Nepal
| | - Sarita Bajaj
- Department of Medicine, MLN Medical College, Allahabad, Uttar Pradesh, India
| | - Subhankar Chowdhury
- Department of Endocrinology, IPGMER and SSKM Hospital, Kolkata, West Bengal, India
| | - Sujoy Ghosh
- Department of Endocrinology and Metabolism, IPGMER, Kolkata, West Bengal, India
| | - S V Madhu
- Department of Medicine and Head, Centre for Diabetes, Endocrinology and Metabolism, UCMS-GTB Hospital, New Delhi, India
| | - Tofail Ahmed
- Department of Endocrinology, BIRDEM, Dhaka, Bangladesh
| | - Uditha Bulughapitiya
- Department of Endocrinology, Kalubowila South Teaching Hospital, Kalubowila, Sri Lanka
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Kuum M, Veksler V, Kaasik A. Potassium fluxes across the endoplasmic reticulum and their role in endoplasmic reticulum calcium homeostasis. Cell Calcium 2014; 58:79-85. [PMID: 25467968 DOI: 10.1016/j.ceca.2014.11.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 11/07/2014] [Accepted: 11/10/2014] [Indexed: 12/16/2022]
Abstract
There are a number of known and suspected channels and exchangers in the endoplasmic reticulum that may participate in potassium flux across its membrane. They include trimeric intracellular cation channels permeable for potassium, ATP-sensitive potassium channels, calcium-activated potassium channels and the potassium-hydrogen exchanger. Apart from trimeric intracellular cation channels, which are specific to the endoplasmic reticulum, other potassium channels are also expressed in the plasma membrane and/or mitochondria, and their specific role in the endoplasmic reticulum has not yet been fully established. In addition to these potassium-selective channels, the ryanodine receptor and, potentially, the inositol 1,4,5-trisphosphate receptor are permeable to potassium ions. Also, the role of potassium fluxes across the endoplasmic reticulum membrane has remained elusive. It has been proposed that their main role is to balance the charge movement that occurs during calcium release and uptake from or to the endoplasmic reticulum. This review aims to summarize current knowledge on endoplasmic reticulum potassium channels and fluxes and their potential role in endoplasmic reticulum calcium uptake and release.
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Affiliation(s)
- Malle Kuum
- Department of Pharmacology, Centre of Excellence for Translational Medicine, University of Tartu, Ravila 19, Tartu, Estonia
| | - Vladimir Veksler
- INSERM, U-769, Châtenay-Malabry F-92296, France; Univ Paris-Sud, Châtenay-Malabry F-92296, France
| | - Allen Kaasik
- Department of Pharmacology, Centre of Excellence for Translational Medicine, University of Tartu, Ravila 19, Tartu, Estonia.
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Kotagiri H, Gannu R, Palem CR, Yamsani SK, Yamsani VV, Yamsani MR. SIMULTANEOUS DETERMINATION OF GLIMEPIRIDE AND ATORVASTATIN IN HUMAN SERUM BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY: APPLICATION TO PHARMACOKINETIC STUDY. J LIQ CHROMATOGR R T 2011. [DOI: 10.1080/10826076.2011.591023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Affiliation(s)
- Harshini Kotagiri
- a Centre for Biopharmaceutics and Pharmacokinetics, University College of Pharmaceutical Sciences, Kakatiya University , Andhra Pradesh, India
| | - Ramesh Gannu
- a Centre for Biopharmaceutics and Pharmacokinetics, University College of Pharmaceutical Sciences, Kakatiya University , Andhra Pradesh, India
| | - Chinna Reddy Palem
- a Centre for Biopharmaceutics and Pharmacokinetics, University College of Pharmaceutical Sciences, Kakatiya University , Andhra Pradesh, India
| | - Shravan Kumar Yamsani
- a Centre for Biopharmaceutics and Pharmacokinetics, University College of Pharmaceutical Sciences, Kakatiya University , Andhra Pradesh, India
| | - Vamshi Vishnu Yamsani
- a Centre for Biopharmaceutics and Pharmacokinetics, University College of Pharmaceutical Sciences, Kakatiya University , Andhra Pradesh, India
| | - Madhsusudan Rao Yamsani
- a Centre for Biopharmaceutics and Pharmacokinetics, University College of Pharmaceutical Sciences, Kakatiya University , Andhra Pradesh, India
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Briscoe VJ, Griffith ML, Davis SN. The role of glimepiride in the treatment of type 2 diabetes mellitus. Expert Opin Drug Metab Toxicol 2010; 6:225-35. [PMID: 20055691 DOI: 10.1517/17425250903512955] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
IMPORTANCE OF THE FIELD Type 2 diabetes mellitus (T2DM) is increasingly prevalent throughout the world; controlling glycemia is an important part of preventing serious complications of diabetes. Sulfonylureas have been used in the treatment of type 2 diabetes for many years. AREAS COVERED IN THIS REVIEW This article reviews the pharmacological and clinical aspects of glimepiride, a second-generation sulfonylurea. Literature search was conducted in PubMed, and articles selected for relevance to pharmacology or clinical efficacy data from 1994 to 2009, with older references sought as indicated. WHAT THE READER WILL GAIN Pharmacology of glimepiride, data regarding clinical efficacy, key comparisons to other agents and emerging concepts related to glimepiride are discussed. TAKE HOME MESSAGE Therapy with glimepiride improves the relative insulin secretory deficit found in T2DM, has antihyperglycemic efficacy equal to other secretagogues with reduced potential for hypoglycemia and may have additional actions contributing to glycemic control in T2DM.
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Affiliation(s)
- Vanessa J Briscoe
- Vanderbilt University, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, 7465 MRB IV, 2213 Garland Avenue, Nashville, TN 37232-0475, USA.
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Müller G, Schulz A, Hartz D, Dearey EA, Wetekam EM, Okonomopulos R, Crecelius A, Wied S, Frick W. Novel glimepiride derivatives with potential as double-edged swords against type II diabetes. Arch Physiol Biochem 2010; 116:3-20. [PMID: 20166804 DOI: 10.3109/13813450903575720] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Sulphonylurea drugs have been widely used in the safe and efficacous therapy of type II diabetes during the past five decades. They lower blood glucose predominantly via the stimulation of insulin release from pancreatic beta-cells. However, a moderate insulin-independent regulation of fatty acid esterification and release in adipose tissue cells has been reported for certain sulphonylureas, in particular for glimepiride. On basis of the known pleiotropic pathogenesis of type II diabetes with a combination of beta-cell failure and peripheral, including adipocyte, insulin resistance, anti-diabetic drugs exerting both insulin releasing- and fatty acid-metabolizing activities in a more balanced and potent fashion may be of advantage. However, the completely different molecular mechanisms underlying the insulin-releasing and fatty acid-metabolizing activities, as have been delineated so far for glimepiride, may hamper their optimization within a single sulphonylurea molecule. By analyzing conventional sulphonylureas and novel glimepiride derivatives for their activities at the primary targets and downstream steps in both beta-cells and adipocytes in vitro we demonstrate here that the insulin-releasing and fatty acid-metabolizing activities are critically dependent on both overlapping and independent structural determinants. These were unravelled by the parallel losses of these two activities in a subset of glimepiride derivatives and the impairment in the insulin-releasing activity in parallel with elevation in the fatty acid-metabolizing activity in a different subset. Together these findings may provide a basis for the design of novel sulphonylureas with blood glucose-lowering activity relying on less pronounced stimulation of insulin release from pancreatic beta-cells and more pronounced insulin-independent stimulation of esterification as well as inhibition of release of fatty acids by adipocytes than provoked by the sulphonylureas currently used in therapy.
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Affiliation(s)
- Günter Müller
- Therapeutic Department Metabolism and Medicinal Chemistry, Frankfurt am Main, Germany.
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Ye B, Kroboth SL, Pu JL, Sims JJ, Aggarwal NT, McNally EM, Makielski JC, Shi NQ. Molecular identification and functional characterization of a mitochondrial sulfonylurea receptor 2 splice variant generated by intraexonic splicing. Circ Res 2009; 105:1083-93. [PMID: 19797704 DOI: 10.1161/circresaha.109.195040] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Cardioprotective pathways may involve a mitochondrial ATP-sensitive potassium (mitoK(ATP)) channel but its composition is not fully understood. OBJECTIVE We hypothesized that the mitoK(ATP) channel contains a sulfonylurea receptor (SUR)2 regulatory subunit and aimed to identify the molecular structure. METHODS AND RESULTS Western blot analysis in cardiac mitochondria detected a 55-kDa mitochondrial SUR2 (mitoSUR2) short form, 2 additional short forms (28 and 68 kDa), and a 130-kDa long form. RACE (Rapid Amplification of cDNA Ends) identified a 1.5-Kb transcript, which was generated by a nonconventional intraexonic splicing (IES) event within the 4th and 29th exons of the SUR2 mRNA. The translated product matched the predicted size of the 55-kDa short form. In a knockout mouse (SUR2KO), in which the SUR2 gene was disrupted, the 130-kDa mitoSUR2 was absent, but the short forms remained expressed. Diazoxide failed to induce increased fluorescence of flavoprotein oxidation in SUR2KO cells, indicating that the diazoxide-sensitive mitoK(ATP) channel activity was associated with 130-kDa-based channels. However, SUR2KO mice displayed similar infarct sizes to preconditioned wild type, suggesting a protective role for the remaining short form-based channels. Heterologous coexpression of the SUR2 IES variant and Kir6.2 in a K(+) transport mutant Escherichia coli strain permitted improved cell growth under acidic pH conditions. The SUR2 IES variant was localized to mitochondria, and removal of a predicted mitochondrial targeting sequence allowed surface expression and detection of an ATP-sensitive current when coexpressed with Kir6.2. CONCLUSIONS We identify a novel SUR2 IES variant in cardiac mitochondria and provide evidence that the variant-based channel can form an ATP-sensitive conductance and may contribute to cardioprotection.
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Affiliation(s)
- Bin Ye
- Department of Medicine, University of Wisconsin, Madison, WI 53706, USA
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Cardiac sulfonylurea receptor short form-based channels confer a glibenclamide-insensitive KATP activity. J Mol Cell Cardiol 2007; 44:188-200. [PMID: 18001767 DOI: 10.1016/j.yjmcc.2007.09.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Revised: 08/16/2007] [Accepted: 09/07/2007] [Indexed: 11/23/2022]
Abstract
The cardiac sarcolemmal ATP-sensitive potassium channel (K(ATP)) consists of a Kir6.2 pore and an SUR2 regulatory subunit, which is an ATP-binding cassette (ABC) transporter. K(ATP) channels have been proposed to play protective roles during ischemic preconditioning. An SUR2 mutant mouse was previously generated by disrupting the first nucleotide-binding domain (NBD1), where a glibenclamide action site was located. In the mutant ventricular myocytes, a non-conventional glibenclamide-insensitive (10 microM), ATP-sensitive current (I(KATPn)) was detected in 33% of single-channel recordings with an average amplitude of 12.3+/-5.4 pA per patch, an IC(50) to ATP inhibition at 10 microM and a mean burst duration at 20.6+/-1.8 ms. Newly designed SUR2 isoform- or variant-specific antibodies identified novel SUR2 short forms in the sizes of 28 and 68 kDa in addition to a 150-kDa long form in the sarcolemmal membrane of wild-type (WT) heart. We hypothesized that channels constituted by these short forms that lack NBD1 confer I(KATPn). The absence of the long form in the mutant corresponded to loss of the conventional glibenclamide-sensitive K(ATP) currents (I(KATP)) in isolated cardiomyocytes and vascular smooth muscle cells but the SUR2 short forms remained intact. Nested exonic RT-PCR in the mutant indicated that the short forms lacked NBD1 but contained NBD2. The SUR2 short forms co-immunoprecipitated with Kir6.1 or Kir6.2 suggesting that the short forms may function as hemi-transporters reported in other eukaryotic ABC transporter subgroups. Our results indicate that different K(ATP) compositions may co-exist in cardiac sarcolemmal membrane.
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Matsuki M, Matsuda M, Kohara K, Shimoda M, Kanda Y, Tawaramoto K, Shigetoh M, Kawasaki F, Kotani K, Kaku K. Pharmacokinetics and pharmacodynamics of glimepiride in type 2 diabetic patients: compared effects of once- versus twice-daily dosing. Endocr J 2007; 54:571-6. [PMID: 17603225 DOI: 10.1507/endocrj.k06-052] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
To compare the pharmacokinetic and pharmacodynamic effects of glimepiride between once- and twice-daily dosing in type 2 diabetic patients. Eight Japanese type 2 diabetic patients, who had been treated with 2 mg glimepiride alone over 4 weeks (age 40-70, body mass index <or=25 kg/m2, hemoglobin A 1C<8.0%), were randomly assigned to the crossover study with glimepiride 2 mg once-daily and 1 mg twice-daily for 4 weeks for each regime. Serum concentrations of glimepiride, plasma glucose, insulin and C-peptide were measured over 24 h at the fixed time intervals on the last day of each crossover period, and HbA 1C was measured at the same day. Pharmacokinetic profiles in two regimens were different to each others; a single peak of serum glimepiride concentration was observed in once-daily, and double peaks in twice-daily dosing. Drug concentration increased immediately, and peaked at 2 h after administration irrespective of dosage. Cmax value in once-daily dose was higher than those in twice-daily doses. AUC values were not different between two regimens. Pharmacodynamic profiles for plasma glucoses, serum insulin and C-peptide showed no statistically significant differences between two regimens, and parameters were not different each other. Analyses of adverse events and laboratory data demonstrated a favorable safety profile of glimepiride. The present results suggest that glimepiride may be suitable for once-daily dosing with respect to clinical usefulness.
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Affiliation(s)
- Michihiro Matsuki
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama 701-0192, Japan
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12
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Khan MA, Sinha S, Vartak S, Bhartiya A, Kumar S. LC determination of glimepiride and its related impurities. J Pharm Biomed Anal 2005; 39:928-43. [PMID: 16040224 DOI: 10.1016/j.jpba.2005.06.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Revised: 05/31/2005] [Accepted: 06/01/2005] [Indexed: 10/25/2022]
Abstract
Five impurities in glimepiride drug substance were detected and quantified using a simple isocratic reverse phase HPLC method. For the identification and characterization purpose these impurities were isolated from a crude reaction mixture of glimepiride using a normal phase HPLC system. Based on the spectroscopic data like NMR, FTIR, UV and MS these impurities were characterized and used as impurity standards for determining the relative response factor during the validation of the proposed isocratic reverse phase HPLC method. The chromatographic separation was achieved on a Phenomenex Luna C8 (2) 100 A, 5 microm, 250 mm x 4.6 mm using a mobile phase consisting of phosphate buffer (pH 7.0)-acetonitrile-tetrahydrofuran (73:18:09, v/v/v) with UV detection at 228 nm and a flow rate of 1 ml/min. The column temperature was maintained at 35 degrees C through out the analysis. The method has been validated as per international guidelines on method validation and can be used for the routine quality control analysis of glimepiride as active pharmaceutical ingredient (API).
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Affiliation(s)
- Mubeen Ahmad Khan
- Analytical Research Lab, Glenmark Research Centre, Plot A-607, TTC Industrial Area, MIDC, Mahape, 400709 Navi Mumbai, India.
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13
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Yuriev E, Kong DCM, Iskander MN. Investigation of structure-activity relationships in a series of glibenclamide analogues. Eur J Med Chem 2005; 39:835-47. [PMID: 15464617 DOI: 10.1016/j.ejmech.2004.06.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Revised: 06/11/2004] [Accepted: 06/14/2004] [Indexed: 12/25/2022]
Abstract
In this study, the synthesis of 15 new glibenclamide analogues is described. The conformational trends of these analogues were investigated using Monte Carlo conformational analysis. The conformational analysis results resolved the discrepancy between previous molecular modelling simulations of glibenclamide and allowed rationalizing the effect of aqueous environment on the overall conformation. The 3D-QSAR study was carried out with respect to the compounds' ability to antagonize the [(3)H]-glibenclamide binging in rat cerebral cortex. Superimposition of the antagonists was performed using the conformations derived from atom-by-atom fit to the glibenclamide crystal structure and this alignment was used to develop CoMFA models. CoMFA provided a good predictability: number of PLS components = 2, q(2) = 0.876, R(2) = 0.921, SEE = 0.455 and F = 70. Best CoMFA models showed the steric and lipophilic properties as the major interacting forces whilst the electrostatic property contribution was a minor factor.
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Affiliation(s)
- Elizabeth Yuriev
- Department of Medicinal Chemistry, Victorian College of Pharmacy, Monash University, 381 Royal Parade, Parkville 3052, Victoria, Australia
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14
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Davis SN. The role of glimepiride in the effective management of Type 2 diabetes. J Diabetes Complications 2004; 18:367-76. [PMID: 15531188 DOI: 10.1016/j.jdiacomp.2004.07.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2003] [Accepted: 07/07/2004] [Indexed: 10/26/2022]
Abstract
Type 2 diabetes mellitus, a disorder of impaired insulin secretion and insulin resistance, has reached epidemic proportions. The effective management of Type 2 diabetes is of vital concern to clinicians. The identification of high-risk individuals and lifestyle management can help control diabetes; however, most patients require pharmacologic intervention. The goals of pharmacologic therapy are to achieve adequate glycemic control while avoiding hypoglycemia and weight gain and to minimize the risk of future micro- and macrovascular complications. There are a number of available glucose-lowering agents from which to choose. This review focuses on the sulfonylureas, the first oral agents introduced for the management of Type 2 diabetes, which are effective, well-tolerated, and well-established drugs, Second-generation sulfonylureas are now widely used in the management of Type 2 diabetes. The most recent addition, glimepiride, can be used in combination with metformin, the thiazolidinediones, alpha-glucosidase inhibitors, and insulin. The unique properties of glimepiride may provide advantages over other currently available insulin secretagogues.
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Affiliation(s)
- Stephen N Davis
- Division of Diabetes Endocrinology and Metabolism, Vanderbilt University Medical School, 715 Preston Research Building, Nashville, TN 37232-6303, USA.
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15
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Weitgasser R, Lechleitner M, Luger A, Klingler A. Effects of glimepiride on HbA(1c) and body weight in Type 2 diabetes: results of a 1.5-year follow-up study. Diabetes Res Clin Pract 2003; 61:13-9. [PMID: 12849919 DOI: 10.1016/s0168-8227(02)00254-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Sulphonylureas are effective and well tolerated in patients with Type 2 diabetes, but may be associated with weight gain, and lack of compliance due to multiple daily dosing. This open, uncontrolled surveillance study examined the efficacy and safety of glimepiride, a new sulphonylurea, administered once daily in patients with Type 2 diabetes. A total of 1,770 patients were enrolled in the study, and 284 patients were selected for follow-up. Patients received 0.5 to >4 mg glimepiride once daily for 1.5 years. HbA(1c) was reduced from 8.4% at baseline to 7.1% after 4 months and 6.9% after 1 and 1.5 years (median intra-individual change from baseline: -1.4, -1.5, and -1.7%, respectively; P<0.0001). Treatment with glimepiride also resulted in significant and stable weight loss relative to baseline, with the exception of patients with a body mass index of <25 kg/m(2). Mean body weight was reduced from 79.8 kg at baseline to 77.9 kg after 4 months, 77.2 kg after 1 year, and 76.9 kg after 1.5 years (mean intra-individual change from baseline: -1.9 kg, P<0.0001; -2.9 kg, P<0.05; -3.0 kg, P<0.005, respectively). Therefore, once daily glimepiride provides effective glycaemic control, and may have advantages over other sulphonylureas, because it exhibits weight neutralizing/reducing effects in patients with Type 2 diabetes.
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Affiliation(s)
- Raimund Weitgasser
- 1st Department of Medicine, St. Johanns Spital - Salzburg General Hospital, Salzburg, Austria.
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16
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Massi-Benedetti M. Glimepiride in type 2 diabetes mellitus: a review of the worldwide therapeutic experience. Clin Ther 2003; 25:799-816. [PMID: 12852703 DOI: 10.1016/s0149-2918(03)80109-1] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
BACKGROUND Sulfonylureas (SUs) have been used for many years as first-line therapy for patients with type 2 diabetes mellitus whose blood glucose levels have not been effectively controlled by diet and exercise alone. Glimepiride is a once-daily SU that was introduced in 1995. Since then, a considerable body of evidence has been amassed regarding its use in type 2 diabetes. OBJECTIVE This review provides a comprehensive summary of available data on the pharmacology, pharmacokinetics, efficacy, and safety profile of glimepiride in the treatment of type 2 diabetes. It also examines the use of glimepiride to achieve and maintain good glycemic control in patients with type 2 diabetes in current clinical practice. METHODS Relevant articles were identified through a search of MEDLINE for English-language studies published from 1990 to 2002. The search terms used were glimepiride, sulfonylureas, and type 2 diabetes mellitus. The manufacturer of glimepiride provided additional information. RESULTS Glimepiride differs from other SUs in a number of respects. In clinical studies, glimepiride was generally associated with a lower risk of hypoglycemia and less weight gain than other SUs. Results of other studies suggest that glimepiride can be used in older patients and those with renal compromise. There is evidence that glimepiride preserves myocardial preconditioning, a protective mechanism that limits damage in the event of an ischemic event. Glimepiride can be used in combination with other oral antidiabetic agents or insulin to optimize glycemic control. CONCLUSION Based on the evidence to date, glimepiride is an effective and well-tolerated once-daily antidiabetic drug and provides an important treatment option for the management of type 2 diabetes.
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Abstract
Blood glucose levels are sensed and controlled by the release of hormones from the islets of Langerhans in the pancreas. The beta-cell, the insulin-secreting cell in the islet, can detect subtle increases in circulating glucose levels and a cascade of molecular events spanning the initial depolarization of the beta-cell membrane culminates in exocytosis and optimal insulin secretion. Here we review these processes in the context of pharmacological agents that have been shown to directly interact with any stage of insulin secretion. Drugs that modulate insulin secretion do so by opening the K(ATP) channels, by interacting with cell-surface receptors, by altering second-messenger responses, by disrupting the beta-cell cytoskeletal framework, by influencing the molecular reactions at the stages of transcription and translation of insulin, and/or by perturbing exocytosis of the insulin secretory vesicles. Drugs acting primarily at the K(ATP) channels are the sulfonylureas, the benzoic acid derivatives, the imidazolines, and the quinolines, which are channel openers, and finally diazoxide, which closes these channels. Methylxanthines also work at the cell membrane level by antagonizing the purinergic receptors and thus increase insulin secretion. Other drugs have effects at multiple levels, such as the calcineurin inhibitors and somatostatin. Some drugs used extensively in research, e.g., colchicine, which is used to study vesicular transport, have no effect at the pharmacological doses used in clinical practice. We also briefly discuss those drugs that have been shown to disrupt beta-cell function in a clinical setting but for which there is scant information on their mechanism of action.
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Affiliation(s)
- Máire E Doyle
- Diabetes Section, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224, USA
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Horimoto H, Nakai Y, Mieno S, Nomura Y, Nakahara K, Sasaki S. Oral hypoglycemic sulfonylurea glimepiride preserves the myoprotective effects of ischemic preconditioning. J Surg Res 2002; 105:181-8. [PMID: 12121705 DOI: 10.1006/jsre.2002.6379] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND To investigate whether the sulfonylurea glimepiride affects the myoprotective effects of ischemic preconditioning (IPC), isolated rabbit hearts were perfused with Krebs-Henseleit solution. METHODS Eight hearts underwent IPC consisting of two cycles of 5 min global ischemia and reperfusion. Six hearts received a 5-min infusion of 10 microM glimepiride, six hearts received a 5-min infusion of 50 microM glimepiride, and seven hearts received a 5-min infusion of 10 microM glibenclamide before IPC. Seven hearts received a 5-min infusion of the selective mitochondrial K(ATP) channel opener diazoxide (50 microM). Other hearts received a 5-min infusion of 10 microM glimepiride (n = 6), 50 microM glimepiride (n = 6), or 10 microM glibenclamide (n = 7) before diazoxide. Seven hearts served as a control. All groups then were subjected to 1 h of regional ischemia, followed by 1 h of reperfusion. LV pressures, monophasic action potential duration (APD(50)), and infarct size were measured. RESULTS Both IPC and diazoxide significantly prolonged APD(50) and preserved diastolic function at 60 min of reperfusion compared to control. In addition, both groups reduced infarct size compared to control. Glibenclamide, but not glimepiride reversed these effects. CONCLUSION Glimepiride offers less cardiovascular effects than glibenclamide, possibly due to its lower affinity for the mitochondrial K(ATP) channels.
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Affiliation(s)
- Hitoshi Horimoto
- Department of Thoracic and Cardiovascular Surgery, Osaka Medical College, Takatsuki, Osaka, Japan.
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20
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Hu S. Interaction of nateglinide with K(ATP) channel in beta-cells underlies its unique insulinotropic action. Eur J Pharmacol 2002; 442:163-71. [PMID: 12020694 DOI: 10.1016/s0014-2999(02)01499-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Nateglinide is a novel insulinotropic agent for the treatment of type 2 diabetes. It is a D-phenylalanine derivative, chemically distinct from repaglinide and sulphonylureas (glyburide or glimepiride). Although each agent is known to stimulate insulin release via the signaling cascade initiated by closure of ATP-dependent K+ (K(ATP)) channels in pancreatic beta-cells, the pharmacological effect of nateglinide is reportedly fast-acting, short-lasting, sensitive to ambient glucose and more resistant to metabolic inhibition. The aim of the present study was to elucidate the molecular mechanism(s) underlying the distinct properties of the insulinotropic action of nateglinide. By using the patch-clamp methods, we comparatively characterized the potency and kinetics of the effect of these agents on K(ATP) channels in rat beta-cells at normal vs. elevated glucose and under physiological condition vs. experimentally induced metabolic inhibition. Our results demonstrated that the mode of the action of nateglinide on K(ATP) current was unique in (a) glucose dependency; (b) increased potency and efficacy under ATP depletion and uncoupling of mitochondrial oxidative phosphorylation than physiological condition; (c) substantially more rapid onset and offset kinetics. The data provide mechanistic rationale for the unique in vivo and ex vivo activity profile of nateglinide and may contribute to reduced hypoglycemic potential associated with excessive insulin secretion.
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Affiliation(s)
- Shiling Hu
- Metabolic/Cardiovascular Diseases, Research Department, Novartis Institute for Biomedical Research, Summit, NJ 07901, USA.
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21
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Abstract
The role of postprandial hyperglycemia (PPHG) in diabetes mellitus is being increasingly recognized. It is known that PPHG contributes to the increased risk of both micro- and macrovascular complications in patients with diabetes mellitus. This review looks at the clinical significance of PPHG and the currently available therapeutic modalities. The causes of PPHG are influenced by many factors which include a rapid flux of glucose from the gut, impaired insulin release, endogenous glucose production by the liver and peripheral insulin resistance. Knowledge of the pathophysiology of PPHG is essential when adopting treatment options to tackle the problem. Although most oral antihyperglycemic agents and insulins lower both fasting and postprandial blood glucose levels, drugs are now available which specifically act to control PPHG. These drugs may be classified based on the site of their action. alpha-Glucosidase inhibitors like acarbose and miglitol attenuate the rate of absorption of sucrose by acting on the luminal enzymes. Adverse effects of these agents are predominantly gastrointestinal. Newer insulin secretagogues have been developed which attempt to mimic the physiological release of insulin and thus ameliorate PPHG. These include third generation sulfonylureas like glimepiride and nonsulfonylurea secretagogues like repaglinide and nateglinide. Rapid-acting insulin analogs, the amino acid sequences of which have been altered such that they have a faster onset of action, help to specifically target PPHG. Pre-mixed formulations of the analogs have also been developed. Finally, drugs under development which hold promise in the management of patients with PPHG include pramlintide, an amylin analog, and glucagon-like peptide-1 and its analogs.
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Affiliation(s)
- Rajasekaran Sudhir
- MV Diabetes Specialities Centre and Madras Diabetes Research Foundation, Chennai, India
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Bajgar R, Seetharaman S, Kowaltowski AJ, Garlid KD, Paucek P. Identification and properties of a novel intracellular (mitochondrial) ATP-sensitive potassium channel in brain. J Biol Chem 2001; 276:33369-74. [PMID: 11441006 DOI: 10.1074/jbc.m103320200] [Citation(s) in RCA: 215] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Protection of heart against ischemia-reperfusion injury by ischemic preconditioning and K(ATP) channel openers is known to involve the mitochondrial ATP-sensitive K(+) channel (mitoK(ATP)). Brain is also protected by ischemic preconditioning and K(ATP) channel openers, and it has been suggested that mitoK(ATP) may also play a key role in brain protection. However, it is not known whether mitoK(ATP) exists in brain mitochondria, and, if so, whether its properties are similar to or different from those of heart mitoK(ATP). We report partial purification and reconstitution of a new mitoK(ATP) from rat brain mitochondria. We measured K(+) flux in proteoliposomes and found that brain mitoK(ATP) is regulated by the same ligands as those that regulate mitoK(ATP) from heart and liver. We also examined the effects of opening and closing mitoK(ATP) on brain mitochondrial respiration, and we estimated the amount of mitoK(ATP) by means of green fluorescence probe BODIPY-FL-glyburide labeling of the sulfonylurea receptor of mitoK(ATP) from brain and liver. Three independent methods indicate that brain mitochondria contain six to seven times more mitoK(ATP) per milligram of mitochondrial protein than liver or heart.
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Affiliation(s)
- R Bajgar
- Department of Biochemistry and Molecular Biology, OGI School of Science and Engineering, Oregon Health & Science University, Beaverton, Oregon 97006-8921, USA
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Song DK, Ashcroft FM. Glimepiride block of cloned beta-cell, cardiac and smooth muscle K(ATP) channels. Br J Pharmacol 2001; 133:193-9. [PMID: 11325810 PMCID: PMC1572773 DOI: 10.1038/sj.bjp.0704062] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
1. We examined the effect of the sulphonylurea glimepiride on three types of recombinant ATP-sensitive potassium (K(ATP)) channels. 2. K(ATP) channels share a common pore-forming subunit, Kir6.2, which associates with different sulphonylurea receptor isoforms (SUR1 in beta-cells, SUR2A in heart and SUR2B in smooth muscle). 3. Kir6.2 was coexpressed with SUR1, SUR2A or SUR2B in Xenopus oocytes and macroscopic K(ATP) currents were recorded from giant inside-out membrane patches. Glimepiride was added to the intracellular membrane surface. 4. Glimepiride inhibited Kir6.2/SUR currents by interaction with two sites: a low-affinity site on Kir6.2 (IC(50)= approximately 400 microM) and a high-affinity site on SUR (IC(50)=3.0 nM for SUR1, 5.4 nM for SUR2A and 7.3 nM for SUR2B). The potency of glimepiride at the high-affinity site is close to that observed for glibenclamide (4 nM for SUR1, 27 nM for SUR2A), which has a similar structure. 5. Glimepiride inhibition of Kir6.2/SUR2A and Kir6.2/SUR2B currents, but not Kir6.2/SUR1 currents, reversed rapidly. 6. Our results indicate that glimepiride is a high-affinity sulphonylurea that does not select between the beta-cell, cardiac and smooth muscle types of recombinant K(ATP) channel, when measured in inside-out patches. High-affinity inhibition is mediated by interaction of the drug with the sulphonylurea receptor subunit of the channel.
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Affiliation(s)
- Dae-Kyu Song
- Department of Physiology, Keimyung University School of Medicine, 194 Dongsan Dong, Choong Gu, Taegu, 700-712 Korea
| | - Frances M Ashcroft
- University Laboratory of Physiology, Parks Road, Oxford OX1 3PT
- Author for correspondence:
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Müller G. The Molecular Mechanism of the Insulin-mimetic/sensitizing Activity of the Antidiabetic Sulfonylurea Drug Amaryl. Mol Med 2000. [DOI: 10.1007/bf03401827] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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Blicklé JF, Andres E, Neyrolles N, Brogard JM. [Present status in the treatment of type 2 diabetes mellitus. Insulin-secreting agents]. Rev Med Interne 1999; 20 Suppl 3:351s-359s. [PMID: 10480186 DOI: 10.1016/s0248-8663(99)80508-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The functional defect of the pancreatic beta cell represents one of the main therapeutic targets in type 2 diabetes mellitus. Among the currently available oral antidiabetic drugs, only hypoglycaemic sulfonylureas exhibit beta cell stimulating properties. However, their use has some limits, particularly those related to the risk of hypoglycaemia and the frequent secondary therapeutic failure. These drugs have largely contributed to the knowledge of the mechanisms of insulin secretion. Besides some galenic modifications of existing sulfonylureas and the development of new drugs of this family with original properties, like glimepiride, the research is essentially focused on drugs derived from the non sulfonylurea moiety of some sulfonylureas, particularly the meglitinide family, which will probably be available for the clinician in the near future. These drugs act however grossly by the same mechanism than sulfonylureas, even if their binding site on a protein coupled with the ATP sensitive K channel appears different. Among the other possible approaches suggested by the theoretical data concerning the mechanisms of insulin secretion, GLP-1 derivatives probably represent good candidates, if stable analogues are developed.
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Affiliation(s)
- J F Blicklé
- Service de médecine interne B, hôpital civil, hôpitaux universitaires de Strasbourg, France
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Campbell RK. Glimepiride: role of a new sulfonylurea in the treatment of type 2 diabetes mellitus. Ann Pharmacother 1998; 32:1044-52. [PMID: 9793597 DOI: 10.1345/aph.17360] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
OBJECTIVE To review the clinical pharmacology data regarding the sulfonylurea glimepiride, and to summarize the clinical trials of glimepiride efficacy and safety alone and in combination with insulin for the treatment of type 2 diabetes mellitus. DATA SOURCES A MEDLINE database search (English language, January 1985-April 1997) was performed to identify relevant published articles, including reviews and abstracts; the manufacturer (Hoechst Marion Roussel, Kansas City, MO) provided unpublished data. STUDY SELECTION Pharmacology information was taken from representative original research articles. Eight clinical studies were selected for analysis on the basis of large enrollment, appropriate study design, and publication of results. DATA EXTRACTION All clinical trials, published and unpublished, were reviewed. DATA SYNTHESIS Glimepiride is a sulfonylurea that is pharmacologically distinct from other sulfonylureas because of differences in receptor-binding properties and potentially selective effects on ATP-sensitive K+ channels. The pharmacokinetic and pharmacodynamic profile of glimepiride makes it suitable for once-daily dosing. The safety and efficacy of glimepiride have been confirmed in studies involving more than 5000 patients with type 2 diabetes. In one study, once-daily doses of 1-8 mg reduced fasting plasma glucose from baseline by 43-74 mg/dL more than did placebo (p < 0.001), and hemoglobin (Hb) A1C values decreased by 1.2-1.9% more than with placebo (p < 0.001). Two-thirds of patients achieved tight control (i.e., HbA1C < or = 7.2%). Glimepiride was as effective as second-generation sulfonylureas. The most common adverse events were dizziness and headache, but no single adverse event occurred in more than 2% of patients. CONCLUSIONS Glimepiride appears to be a useful option for patients with type 2 diabetes not controlled by diet and exercise and who want to achieve tight glucose control. Glimepiride can be used alone, in combination with other antihyperglycemic agents, or in patients with secondary sulfonylurea failure, as an adjunct to insulin therapy.
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Affiliation(s)
- R K Campbell
- College of Pharmacy, Washington State University, Pullman 99164, USA.
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Schade DS, Jovanovic L, Schneider J. A placebo-controlled, randomized study of glimepiride in patients with type 2 diabetes mellitus for whom diet therapy is unsuccessful. J Clin Pharmacol 1998; 38:636-41. [PMID: 9702849 DOI: 10.1002/j.1552-4604.1998.tb04471.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This multicenter, randomized, placebo-controlled study of glimepiride, a new oral sulfonylurea, was conducted in patients with type 2 diabetes for whom dietary treatment was unsuccessful (fasting plasma glucose [FPG] = 151-300 mg/dL) during a 1-week screening period. Patients were randomized to receive glimepiride (n = 123) or placebo (n = 126) once daily for a 10-week dose-titration period, then maintained on an individually determined optimal dose (1-8 mg of glimepiride or placebo) for 12 weeks. Glimepiride lowered FPG by 46 mg/dL, hemoglobin A1C (HbA1C) by 1.4%, and 2-hour postprandial glucose by 72 mg/dL more than placebo. Glimepiride improved postprandial insulin and C-peptide responses without producing clinically meaningful increases in fasting insulin or C-peptide levels. Good glycemic control (HbA1C < or = 7.2%) was achieved by 69% of the patients taking glimepiride versus 32% of those taking placebo. The overall incidence of adverse events was similar in both groups. No clinically noteworthy abnormal laboratory values or hypoglycemia (blood glucose < 60 mg/dL) occurred. Glimepiride is safe and effective for treatment of patients with type 2 diabetes for whom diet therapy is unsuccessful.
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Affiliation(s)
- D S Schade
- Department of Internal Medicine/Endocrinology, University of New Mexico, Albuquerque 87131, USA
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28
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Abstract
The classical type of KATP channel is an octameric (4:4) complex of two structurally unrelated subunits, Kir6.2 and SUR. The former serves as an ATP-inhibitable pore, while SUR is a regulatory subunit endowing sensitivity to sulphonylurea and K+ channel opener drugs, and the potentiatory action of MgADP. Both subunits are required to form a functional channel.
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Affiliation(s)
- S J Tucker
- University Laboratory of Physiology, Oxford, UK
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29
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Niki I, Coles B, Ashcroft FM, Ashcroft SJ. Effects of protein phosphorylation on the sulphonylurea receptor of the pancreatic beta-cell. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 426:59-69. [PMID: 9544256 DOI: 10.1007/978-1-4899-1819-2_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- I Niki
- Nuffield Department of Clinical Biochemistry, John Radcliffe Hospital Headington, Oxford, United Kingdom
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30
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Abstract
UNLABELLED Glimepiride is a sulphonylurea agent that stimulates insulin release from pancreatic beta-cells and may act via extrapancreatic mechanisms. It is administered once daily to patients with type 2 (non-insulin-dependent) diabetes mellitus in whom glycaemia is not controlled by diet and exercise alone, and may be combined with insulin in patients with secondary sulphonylurea failure. The greatest blood glucose lowering effects of glimepiride occur in the first 4 hours after the dose. Glimepiride has fewer and less severe effects on cardiovascular variables than glibenclamide (glyburide). Pharmacokinetics are mainly unaltered in elderly patients or those with renal or liver disease. Few drug interactions with glimepiride have been documented. In patients with type 2 diabetes, glimepiride has an effective dosage range of 0.5 to 8 mg/day, although there is little difference in efficacy between dosages of 4 and 8 mg/day. Glimepiride was similar in efficacy to glibenclamide and glipizide in 1-year studies. However, glimepiride appears to reduce blood glucose more rapidly than glipizide over the first few weeks of treatment. Glimepiride and gliclazide were compared in patients with good glycaemic control at baseline in a 14-week study that noted no differences between their effects. Glimepiride plus insulin was as effective as insulin plus placebo in helping patients with secondary sulphonylurea failure to reach a fasting blood glucose target level of < or = 7.8 mmol/L, although lower insulin dosages and more rapid effects on glycaemia were seen with glimepiride. Although glimepiride monotherapy was generally well tolerated, hypoglycaemia occurred in 10 to 20% of patients treated for < or = 1 year and > or = 50% of patients receiving concomitant insulin for 6 months. Pooled clinical trial data suggest that glimepiride may have a lower incidence of hypoglycaemia than glibenclamide, particularly in the first month of treatment. Dosage is usually started at 1 mg/day, titrated to glycaemic control at 1- to 2-week intervals to a usual dosage range of 1 to 4 mg/day (maximum 6 mg/day in the UK or 8 mg/day in the US). CONCLUSIONS Glimepiride is a conveniently administered alternative to other sulphonylureas in patients with type 2 diabetes mellitus not well controlled by diet alone. Its possible tolerability advantages and use in combination with other oral antidiabetic drugs require further study. Glimepiride is also reported to reduce exogenous insulin requirements in patients with secondary sulphonylurea failure when administered in combination with insulin.
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Affiliation(s)
- H D Langtry
- Adis International Limited, Auckland, New Zealand.
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31
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Edwards G, Weston AH. Recent advances in potassium channel modulation. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 1997; 49:93-121. [PMID: 9388385 DOI: 10.1007/978-3-0348-8863-9_3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- G Edwards
- School of Biological Sciences, University of Manchester, UK
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Sonnenberg GE, Garg DC, Weidler DJ, Dixon RM, Jaber LA, Bowen AJ, DeChemey GS, Mullican WS, Stonesifer LD. Short-term comparison of once- versus twice-daily administration of glimepiride in patients with non-insulin-dependent diabetes mellitus. Ann Pharmacother 1997; 31:671-6. [PMID: 9184703 DOI: 10.1177/106002809703100601] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
OBJECTIVE To investigate the metabolic effects and frequency of adverse events with 6 mg of glimepiride, a new oral sulfonylurea, given both in once- and twice-daily dosages to patients with non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS This 15-week study involved 161 subjects with NIDDM. Subjects were randomized into two groups. For 4 weeks, group 1 received glimepiride 3 mg twice daily, and group 2 received glimepiride 6 mg once daily. After a 3-week placebo-washout period, twice- and once-daily regimens were crossed over for a second 4-week treatment period. Subjects were hospitalized at the end of each placebo or active-treatment phase. Their glucose concentrations were recorded at 20 time points over a 24-hour period, and their insulin and C-peptide concentrations were recorded at 16 time points over the same period. Parameters that were calculated included fasting, 24-hour, and postprandial concentrations of glucose, insulin, and C-peptide. RESULTS One hundred six patients were randomized to receive treatment; 94 completed the entire study. Existing physiologic mechanisms of glucose control were apparently unimpaired by glimepiride treatment. Insulin concentrations increased more during the postprandial glucose peaks than when subjects were fasting. Both twice- and once-daily regimens proved equally effective in reducing concentrations of fasting, postbreakfast, postlunch, and postdinner plasma glucose. Twenty-four-hour mean glucose concentrations showed a slightly greater decrease from baseline for the twice-daily regimen; the difference between the regimens was statistically significant but not clinically meaningful. The incidence of adverse events with glimepiride approximated that obtained with placebo, with both groups reporting only one adverse event, headache, in more than 5% of the subjects. CONCLUSIONS Glimepiride is equally effective whether administered once or twice daily. Glimepiride seems to stimulate insulin production primarily after meals, when plasma glucose concentrations are highest, but controls blood glucose throughout the day.
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Affiliation(s)
- G E Sonnenberg
- Division of Endocrinology, Metabolism, and Clinical Nutrition, Medical College of Wisconsin, Milwaukee 53226, USA
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Abstract
In subjects with type 2 diabetes, both defects of insulin secretion and insulin resistance contribute to the development of hyperglycaemia. The major goals of treatment are to optimise blood glucose control, and normalise the associated lipid disturbances and elevated blood pressure. Pharmacologic treatment is often necessary. This paper discusses new forms of oral treatment for subjects with type 2 diabetes. These include a new sulphonylurea compound glimepiride (Amaryl), which binds to a different protein of the putative sulphonylurea receptor than glibenclamide, and seems to have a lower risk of hypoglycaemia. A new class of drugs with insulin secretory capacity, of which repaglinide (NovoNorm) is the leading compound, is now in phase III clinical trials. Alpha-glucosidase inhibitors reversibly inhibit alpha-glucosidase enzymes in the small intestine, which delays cleavage of oligo- and disaccharides to monosaccharides. This leads to a delayed and reduced blood glucose rise after a meal. Two compounds are in development or have been marketed, ie, miglitol and acarbose (Glucobay). Another new class of drugs is the thiazolidine-diones, which seem to work by enhancing insulin action. The 'insulin sensitising' effects of the leading compounds, troglitazone and BRL 49653C, do not involve any effect on insulin secretion. These drugs also seem to beneficially influence serum cholesterol and triglyceride levels. Oral antihyperglycaemic agents can be used only during a limited period of time in most patients, after which the diabetic state 'worsens' and insulin therapy has to be started. In this light, two new forms of treatment which require subcutaneous injections are also discussed: the synthetic human amylin analogue AC137 (pramlintide) and glucagon-like peptide-1 (7-36)-amide, a strong glucose-dependent stimulator of insulin secretion. It remains to be seen whether these compounds can be developed further for clinical use in patients with diabetes.
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Affiliation(s)
- B H Wolffenbuttel
- Department of Endocrinology and Metabolism, University Hospital, Masstricht, The Netherlands
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Bijlstra PJ, Lutterman JA, Russel FG, Thien T, Smits P. Interaction of sulphonylurea derivatives with vascular ATP-sensitive potassium channels in humans. Diabetologia 1996; 39:1083-90. [PMID: 8877293 DOI: 10.1007/bf00400658] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cardiovascular adenosine-5'-triphosphate-sensitive potassium (KATP) channels have been reported to play an important role in endogenous cardioprotective mechanisms. Sulphonylurea derivatives can inhibit these cardioprotective mechanisms in animal models. We investigated whether therapeutic concentrations of sulphonylurea derivatives can block vascular KATP channels in humans. The forearm vasodilator responses to administration of the specific KATP channel opener diazoxide into the brachial artery of healthy male volunteers were recorded by venous occlusion plethysmography. This procedure was repeated with concomitant intraarterial infusion of:1) the sulphonylurea derivative glibenclamide (0.33 or 3.3 micrograms. min-1. dl-1, both n = 12), 2) the new sulphonylurea derivative glimepiride (2.5 micrograms.min-1. dl-1, n = 12) or 3) placebo (n = 12). The effects of glibenclamide on the vasodilator responses to sodium nitroprusside were also studied (n = 12). Glibenclamide significantly inhibited the diazoxide-induced increase in forearm blood flow ratio (ANOVA with repeated measures: p < 0.01). During the highest diazoxide dose this ratio (mean +/- SEM) was lowered from 892 +/- 165 to 449 +/- 105%, and from 1044 +/- 248 to 663 +/- 114% by low- and high-dose glibenclamide, respectively. In contrast, neither glimepiride nor placebo attenuate diazoxide-induced vasodilation. Furthermore, glibenclamide did not affect nitroprusside-induced vasodilation. We conclude that therapeutic concentrations of the classical sulphonylurea derivative glibenclamide result in significant blockade of vascular KATP channels in humans. The newly developed glimepiride seems to be devoid of these properties.
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Affiliation(s)
- P J Bijlstra
- Department of Internal Medicine, University Hospital Nijmegen, The Netherlands
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Gregorio F, Ambrosi F, Cristallini S, Filipponi P, Santeusanio F. Effects of glimepiride on insulin and glucagon release from isolated rat pancreas at different glucose concentrations. Acta Diabetol 1996; 33:25-9. [PMID: 8777281 DOI: 10.1007/bf00571936] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
The effects of glimepiride, the newest sulphonylureic compound, on pancreatic insulin and glucagon secretion were studied using the classical, isolated, perfused rat pancrease model. The influence of four different environmental glucose conditions (during a glycaemic stimulus with glucose increasing from 5 to 8.33 mM and at stable 0, 5 and 2.22 mM glucose levels) on the effects of glimepiride was also assessed. At a pharmacological concentration glimepiride strongly stimulated beta-cell activity, producing a characteristic biphasic insulin release with a sharp first-phase secretory peak, followed by a prolonged and sustained second phase. Environmental glucose concentrations markedly influenced the extent, but not the pattern of glimepiride-induced insulin secretion, as hormone release dropped significantly when the glucose level was reduced. Glimepiride failed to influence alpha-cell activity at any of the environmental glycaemic levels.
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Affiliation(s)
- F Gregorio
- Department of Internal Medicine, Endocrine and Metabolic Science, University of Perugia, Italy
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36
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Müller G, Gross E, Wied S, Bandlow W. Glucose-induced sequential processing of a glycosyl-phosphatidylinositol-anchored ectoprotein in Saccharomyces cerevisiae. Mol Cell Biol 1996; 16:442-56. [PMID: 8524327 PMCID: PMC231021 DOI: 10.1128/mcb.16.1.442] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Transfer of spheroplasts from the yeast Saccharomyces cerevisiae to glucose leads to the activation of an endogenous (glycosyl)-phosphatidylinositol-specific phospholipase C ([G]PI-PLC), which cleaves the anchor of at least one glycosyl-phosphatidylinositol (GPI)-anchored protein, the cyclic AMP (cAMP)-binding ectoprotein Gce1p (G. Müller and W. Bandlow, J. Cell Biol. 122:325-336, 1993). Analyses of the turnover of two constituents of the anchor, myo-inositol and ethanolamine, relative to the protein label as well as separation of the two differently processed versions of Gce1p by isoelectric focusing in spheroplasts demonstrate the glucose-induced conversion of amphiphilic Gce1p first into a lipolytically cleaved hydrophilic intermediate, which is then processed into another hydrophilic version lacking both myo-inositol and ethanolamine. When incubated with unlabeled spheroplasts, the lipolytically cleaved intermediate prepared in vitro is converted into the version lacking all anchor constituents, whereby the anchor glycan is apparently removed as a whole. The secondary cleavage ensues independently of the carbon source, attributing the key role in glucose-induced anchor processing to the endogenous (G)PI-PLC. The secondary processing of the lipolytically cleaved intermediate of Gce1p at the plasma membrane is correlated with the emergence of a covalently linked high-molecular-weight form of a cAMP-binding protein at the cell wall. This protein lacks anchor components, and its protein moiety appears to be identical with double-processed Gce1p detectable at the plasma membrane in spheroplasts. The data suggest that glucose-induced double processing of GPI anchors represents part of a mechanism of regulated cell wall expression of proteins in yeast cells.
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Affiliation(s)
- G Müller
- Hoechst Aktiengesellschaft Frankfurt am Main, Frankfurt, Germany
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Fosset M, Allard B, Lazdunski M. Coexistence of two classes of glibenclamide-inhibitable ATP-regulated K+ channels in avian skeletal muscle. Pflugers Arch 1995; 431:117-24. [PMID: 8584408 DOI: 10.1007/bf00374384] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Avian skeletal muscle expresses two types of ATP-sensitive K+ channels which have a unitary conductance of 15pS. These K+ channels can be distinguished pharmacologically by their high or low sensitivity to the antidiabetic sulphonylurea blocker glibenclamide. Both channels are activated by the K+ channel opener cromakalim. Chick skeletal muscle expresses high-affinity binding sites for [3H]glibenclamide (Kd = 0.6nM) which presumably correspond to the ATP-sensitive K+ channels with the greatest sensitivity to glibenclamide. The density of these high-affinity binding sites varies during muscle development. The maximum density (500fmol/mg protein) appears at 16 days in ovo, i.e. at a period when myoblasts have differentiated into myotubes and when innervation of myotubes has started. After this maximum, the level of [3H]glibenclamide-binding sites decreases to a plateau value of 100fmol/mg protein at 2-5 days post-natal. When muscle cells are put in cultures, the high-affinity binding sites disappear rapidly. Neither glibenclamide nor cromakalim have any effect on normal physiological chick muscle contraction. They have no effect on contracture and/or 86Rb+ efflux produced by metabolic poisoning.
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Affiliation(s)
- M Fosset
- Institut de Pharmacologie Moléculaire et Cellulaire, 660 route des Lucioles, Sophia Antipolis, F-06560 Valbonne, France
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Müller G, Hartz D, Pünter J, Okonomopulos R, Kramer W. Differential interaction of glimepiride and glibenclamide with the beta-cell sulfonylurea receptor. I. Binding characteristics. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1191:267-277. [PMID: 8172912 DOI: 10.1016/0005-2736(94)90177-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Glimepiride is a novel sulfonylurea drug for treatment of non-insulin-dependent diabetes mellitus with higher blood sugar lowering efficacy in diabetic patients than glibenclamide raising the question whether this characteristics is in line with different binding of glimepiride and glibenclamide to the beta-cell sulfonylurea receptor. Scatchard plot analysis of [3H]sulfonylurea binding to membranes isolated from rat beta-cell tumors and (RINm5F) insulinoma cells and to RINm5F cells demonstrated that glimepiride has a 2.5-3-fold lower affinity than glibenclamide. This corresponded well to the 8-9-fold higher koff and 2.5-3-fold higher kon rates of glimepiride compared to glibenclamide as revealed by the dissociation and association kinetics of [3H]sulfonylurea binding and the Kd values calculated thereof. In agreement, the concentrations required for half-maximal displacement of [3H]sulfonylurea bound to beta-cell membranes were significantly higher for glimepiride compared to glibenclamide. However, the binding affinity of glimepiride measured by both equilibrium binding and kinetic binding studies upon solubilization of beta-cell tumor membranes and RINm5F cell membranes increased up to the value for glibenclamide. This was primarily based on a drastic decrease of the dissociation rate constant of glimepiride whereas the kinetics of glibenclamide binding remained largely unaffected upon solubilization. These data suggest that the Kd value alone is not sufficient for characterization of a sulfonylurea drug, since the kinetic binding parameters may also determine its acute blood sugar lowering efficacy.
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Affiliation(s)
- G Müller
- Hoechst AG Frankfurt am Main, Pharmaceutical Research Division, SBU Metabolic Diseases H 825, Germany
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