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Abstract
Hypoglycaemia (blood glucose concentration below the normal range) has been recognised as a complication of insulin treatment from the very first days of the discovery of insulin, and remains a major concern for people with diabetes, their families and healthcare professionals today. Acute hypoglycaemia stimulates a stress response that acts to restore circulating glucose, but plasma glucose concentrations can still fall too low to sustain normal brain function and cardiac rhythm. There are long-term consequences of recurrent hypoglycaemia, which are still not fully understood. This paper reviews our current understanding of the acute and cumulative consequences of hypoglycaemia in insulin-treated diabetes.
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Affiliation(s)
- Stephanie A Amiel
- Department of Diabetes, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King's College London, London, UK.
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2
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Riopel M, Seo JB, Bandyopadhyay GK, Li P, Wollam J, Chung H, Jung SR, Murphy A, Wilson M, de Jong R, Patel S, Balakrishna D, Bilakovics J, Fanjul A, Plonowski A, Koh DS, Larson CJ, Olefsky JM, Lee YS. Chronic fractalkine administration improves glucose tolerance and pancreatic endocrine function. J Clin Invest 2018; 128:1458-1470. [PMID: 29504946 DOI: 10.1172/jci94330] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 01/18/2018] [Indexed: 01/09/2023] Open
Abstract
We have previously reported that the fractalkine (FKN)/CX3CR1 system represents a novel regulatory mechanism for insulin secretion and β cell function. Here, we demonstrate that chronic administration of a long-acting form of FKN, FKN-Fc, can exert durable effects to improve glucose tolerance with increased glucose-stimulated insulin secretion and decreased β cell apoptosis in obese rodent models. Unexpectedly, chronic FKN-Fc administration also led to decreased α cell glucagon secretion. In islet cells, FKN inhibited ATP-sensitive potassium channel conductance by an ERK-dependent mechanism, which triggered β cell action potential (AP) firing and decreased α cell AP amplitude. This results in increased glucose-stimulated insulin secretion and decreased glucagon secretion. Beyond its islet effects, FKN-Fc also exerted peripheral effects to enhance hepatic insulin sensitivity due to inhibition of glucagon action. In hepatocytes, FKN treatment reduced glucagon-stimulated cAMP production and CREB phosphorylation in a pertussis toxin-sensitive manner. Together, these results raise the possibility of use of FKN-based therapy to improve type 2 diabetes by increasing both insulin secretion and insulin sensitivity.
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Affiliation(s)
- Matthew Riopel
- Department of Medicine, Division of Endocrinology and Metabolism, UCSD, La Jolla, California, USA
| | - Jong Bae Seo
- Department of Medicine, Division of Endocrinology and Metabolism, UCSD, La Jolla, California, USA.,Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Gautam K Bandyopadhyay
- Department of Medicine, Division of Endocrinology and Metabolism, UCSD, La Jolla, California, USA
| | - Pingping Li
- Department of Medicine, Division of Endocrinology and Metabolism, UCSD, La Jolla, California, USA.,State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
| | - Joshua Wollam
- Department of Medicine, Division of Endocrinology and Metabolism, UCSD, La Jolla, California, USA
| | - Heekyung Chung
- Department of Medicine, Division of Endocrinology and Metabolism, UCSD, La Jolla, California, USA
| | - Seung-Ryoung Jung
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Anne Murphy
- Department of Pharmacology, UCSD, La Jolla, California, USA
| | - Maria Wilson
- Cardiovascular and Metabolic Diseases Drug Discovery Unit, Takeda Pharmaceuticals, San Diego, California, USA
| | - Ron de Jong
- Cardiovascular and Metabolic Diseases Drug Discovery Unit, Takeda Pharmaceuticals, San Diego, California, USA
| | - Sanjay Patel
- Cardiovascular and Metabolic Diseases Drug Discovery Unit, Takeda Pharmaceuticals, San Diego, California, USA
| | - Deepika Balakrishna
- Cardiovascular and Metabolic Diseases Drug Discovery Unit, Takeda Pharmaceuticals, San Diego, California, USA
| | - James Bilakovics
- Cardiovascular and Metabolic Diseases Drug Discovery Unit, Takeda Pharmaceuticals, San Diego, California, USA
| | - Andrea Fanjul
- Cardiovascular and Metabolic Diseases Drug Discovery Unit, Takeda Pharmaceuticals, San Diego, California, USA
| | - Artur Plonowski
- Cardiovascular and Metabolic Diseases Drug Discovery Unit, Takeda Pharmaceuticals, San Diego, California, USA
| | - Duk-Su Koh
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Christopher J Larson
- Cardiovascular and Metabolic Diseases Drug Discovery Unit, Takeda Pharmaceuticals, San Diego, California, USA.,Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California, USA
| | - Jerrold M Olefsky
- Department of Medicine, Division of Endocrinology and Metabolism, UCSD, La Jolla, California, USA
| | - Yun Sok Lee
- Department of Medicine, Division of Endocrinology and Metabolism, UCSD, La Jolla, California, USA.,Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
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Ahrén B, Foley JE, Dejager S, Akacha M, Shao Q, Heimann G, Dworak M, Schweizer A. Higher Risk of Hypoglycemia with Glimepiride Versus Vildagliptin in Patients with Type 2 Diabetes is not Driven by High Doses of Glimepiride: Divergent Patient Susceptibilities? Diabetes Ther 2014; 5:459-69. [PMID: 25230877 PMCID: PMC4269641 DOI: 10.1007/s13300-014-0082-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Indexed: 11/30/2022] Open
Abstract
INTRODUCTION In a previously published study, vildagliptin showed a reduced risk of hypoglycemia versus glimepiride as add-on therapy to metformin at similar efficacy. Glimepiride was titrated from a starting dose of 2 mg/day to a maximum dose of 6 mg/day. It is usually assumed that the increased hypoglycemia with glimepiride was driven by the 6 mg/day dose; it was therefore of interest to assess whether the risk of hypoglycemia is also different between vildagliptin and a low (2 mg/day) dose of glimepiride. METHODS Data (n = 3,059) were from the aforementioned randomized, double-blind study. Comparisons between vildagliptin (50 mg twice daily) and glimepiride (subgroups of patients on 2 mg/day, 6 mg/day, and 'other', and overall glimepiride group) were done by modeling hypoglycemia risk as a function of time and last-measured glycated hemoglobin (HbA1c) using discrete event time modeling, with treatment, age, gender as additional covariates. RESULTS The hypoglycemia risk was significantly lower in patients receiving vildagliptin versus patients remaining on glimepiride 2 mg/day throughout the study, with similar results unadjusted or adjusted for last HbA1c [adjusted hazard ratio (HR) = 0.06 (95% CI 0.03, 0.11)]. The risk of hypoglycemia was very low with vildagliptin over the full HbA1c range, while the risk with glimepiride 2 mg/day increased with lower HbA1c. The increase for lower levels of HbA1c was more pronounced in the glimepiride 2 mg/day than 6 mg/day subgroup, with the 6 mg/day subgroup showing the lowest hypoglycemia risk among the glimepiride groups [adjusted HR vildagliptin vs. 6 mg/day glimepiride = 0.21 (95% CI 0.11, 0.40)]. CONCLUSION The data show a substantially lower risk of confirmed hypoglycemia with vildagliptin compared to low-dose (2 mg/day) glimepiride. The analysis indicates that the previously reported results are not driven by high doses of glimepiride and points to interesting differences among patients regarding the susceptibility to hypoglycemia with sulfonylureas.
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Schweizer A, Halimi S, Dejager S. Experience with DPP-4 inhibitors in the management of patients with type 2 diabetes fasting during Ramadan. Vasc Health Risk Manag 2013; 10:15-24. [PMID: 24391442 PMCID: PMC3878957 DOI: 10.2147/vhrm.s54585] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
A large proportion of Muslim patients with type 2 diabetes mellitus (T2DM) elect to fast during the holy month of Ramadan. For these patients hypo- and hyperglycemia constitute two major complications associated with the profound changes in food pattern during the Ramadan fast, and efficacious treatment options with a low risk of hypoglycemia are therefore needed to manage their T2DM as effectively and safely as possible. Dipeptidyl peptidase-4 (DPP-4) inhibitors modulate insulin and glucagon secretion in a glucose-dependent manner, and consequently a low propensity of hypoglycemia has consistently been reported across different patient populations with these agents. Promising data with DPP-4 inhibitors have now also started to emerge in patients with T2DM fasting during Ramadan. The objective of this review is to provide a comprehensive overview of the currently available evidence and potential role of DPP-4 inhibitors in the management of patients with T2DM fasting during Ramadan whose diabetes is treated with oral antidiabetic drugs, and to discuss the mechanistic basis for their beneficial effects in this setting.
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Affiliation(s)
| | - Serge Halimi
- Department of Diabetology, Endocrinology and Nutrition, University Hospital of Grenoble, France
- Joseph Fourier University, Grenoble, France
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Sherr J, Xing D, Ruedy KJ, Beck RW, Kollman C, Buckingham B, White NH, Fox L, Tsalikian E, Weinzimer S, Arbelaez AM, Tamborlane WV. Lack of association between residual insulin production and glucagon response to hypoglycemia in youth with short duration of type 1 diabetes. Diabetes Care 2013; 36:1470-6. [PMID: 23288858 PMCID: PMC3661789 DOI: 10.2337/dc12-1697] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 11/30/2012] [Indexed: 02/03/2023]
Abstract
OBJECTIVE To examine the loss of glucagon response to hypoglycemia and its relationship with residual β-cell function early in the course of type 1 diabetes (T1D) in youth. RESEARCH DESIGN AND METHODS Twenty-one youth with T1D duration <1 year (ages 8-18 years, T1D duration 6-52 weeks) underwent mixed-meal tolerance tests (MMTTs) to assess residual β-cell function and hypoglycemic clamps to assess glucagon responses to hypoglycemia. Glucagon responses to hypoglycemia in T1D subjects were compared with those in 12 nondiabetic young adults (ages 19-25 years). RESULTS Peak MMTT-stimulated C-peptide levels (range 0.12-1.43) were ≥ 0.2 nmol/L in all but one T1D subject. As expected, the median of glucagon responses to hypoglycemia in the T1D subjects (18 pg/mL [interquartile range 7-32]) was significantly reduced compared with the responses in nondiabetic control subjects (38 pg/mL [19-66], P = 0.02). However, there was no correlation between the incremental increase in plasma glucagon during the hypoglycemic clamp and the incremental increase and peak plasma C-peptide level during the MMTT. Similarly, the seven T1D subjects who failed to achieve an increase in glucagon ≥ 12 pg/mL (i.e., 3 SD above baseline values) had C-peptide response ≥ 0.2 nmol/L (0.54-1.12), and the one T1D subject with peak stimulated <0.2 nmol/L had a 14 pg/mL increase in plasma glucagon in response to hypoglycemia. CONCLUSIONS Impaired plasma glucagon responses to hypoglycemia are evident in youth with T1D during the first year of the disease. Moreover, defective and absent glucagon responses to hypoglycemia were observed in patients who retained clinically important residual endogenous β-cell function.
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Affiliation(s)
- Jennifer Sherr
- Pediatric Endocrinology, Yale University, New Haven, Connecticut
| | | | | | - Roy W. Beck
- Jaeb Center for Health Research, Tampa, Florida
| | | | - Bruce Buckingham
- Pediatric Endocrinology, Stanford University, Stanford, California
| | - Neil H. White
- Department of Pediatrics, Washington University, St. Louis, Missouri
| | - Larry Fox
- Pediatric Endocrinology, Nemours Children’s Clinic, Jacksonville, Florida
| | - Eva Tsalikian
- Pediatric Endocrinology, University of Iowa, Iowa City, Iowa
| | - Stuart Weinzimer
- Pediatric Endocrinology, Yale University, New Haven, Connecticut
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Ahrén B. Avoiding hypoglycemia: a key to success for glucose-lowering therapy in type 2 diabetes. Vasc Health Risk Manag 2013; 9:155-63. [PMID: 23637538 PMCID: PMC3639216 DOI: 10.2147/vhrm.s33934] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Type 2 diabetes carries a risk for hypoglycemia, particularly in patients on an intensive glucose control plan as a glucose-lowering strategy, where hypoglycemia may be a limitation for the therapy and also a factor underlying clinical inertia. Glucose-lowering medications that increase circulating insulin in a glucose-independent manner, such as insulin and sulfonylurea therapy, are the most common cause of hypoglycemia. However, other factors such as a delayed or missed meal, physical exercise, or drug or alcohol consumption may also contribute. Specific risk factors for development of hypoglycemia are old age, long duration of diabetes, some concomitant medication, renal dysfunction, hypoglycemia unawareness, and cognitive dysfunction. Hypoglycemia is associated with acute short-term symptoms related to either counterregulation, such as tachycardia and sweating, or to neuroglycopenia, such as irritability, confusion, and in severe cases stupor, coma, and even death. However, there are also long-term consequences of hypoglycemia such as reduced working capacity, weight gain, loss of self-confidence with reduced quality of life, and increased risk for cardiovascular diseases. For both the patients, the health care system, and the society at large, hypoglycemia carries a high cost. Strategies to mitigate the risk of hypoglycemia include awareness of the condition; education of patients, relatives, and health care providers; and selecting appropriate glucose-lowering medication that also judges the risk for hypoglycemia to prevent this complication. This article summarizes the current knowledge of hypoglycemia and its consequences with a special emphasis on its consequences for the choice of glucose-lowering therapy.
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Affiliation(s)
- Bo Ahrén
- Department of Clinical Sciences, Lund, Faculty of Medicine, Lund University, Lund, Sweden.
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Abstract
The counterregulatory response to hypoglycemia is a complex and well-coordinated process. As blood glucose concentration declines, peripheral and central glucose sensors relay this information to central integrative centers to coordinate neuroendocrine, autonomic, and behavioral responses and avert the progression of hypoglycemia. Diabetes, both type 1 and type 2, can perturb these counterregulatory responses. Moreover, defective counterregulation in the setting of diabetes can progress to hypoglycemia unawareness. While the mechanisms that underlie the development of hypoglycemia unawareness are not completely known, possible causes include altered sensing of hypoglycemia by the brain and/or impaired coordination of responses to hypoglycemia. Further study is needed to better understand the intricacies of the counterregulatory response and the mechanisms contributing to the development of hypoglycemia unawareness.
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Affiliation(s)
- Nolawit Tesfaye
- Department of Medicine, Division of Endocrinology and Diabetes, University of Minnesota, 420 Delaware St. SE, Minneapolis, MN 55455, USA
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Affiliation(s)
- Stephanie A. Amiel
- From the Department of Medicine, King's College London School of Medicine, London, England
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Abstract
The primary cause of hypoglycaemia in Type 2 diabetes is diabetes medication-in particular, those which raise insulin levels independently of blood glucose, such as sulphonylureas (SUs) and exogenous insulin. The risk of hypoglycaemia is increased in older patients, those with longer diabetes duration, lesser insulin reserve and perhaps in the drive for strict glycaemic control. Differing definitions, data collection methods, drug type/regimen and patient populations make comparing rates of hypoglycaemia difficult. It is clear that patients taking insulin have the highest rates of self-reported severe hypoglycaemia (25% in patients who have been taking insulin for > 5 years). SUs are associated with significantly lower rates of severe hypoglycaemia. However, large numbers of patients take SUs in the UK, and it is estimated that each year > 5000 patients will experience a severe event caused by their SU therapy which will require emergency intervention. Hypoglycaemia has substantial clinical impact, in terms of mortality, morbidity and quality of life. The cost implications of severe episodes-both direct hospital costs and indirect costs-are considerable: it is estimated that each hospital admission for severe hypoglycaemia costs around pound1000. Hypoglycaemia and fear of hypoglycaemia limit the ability of current diabetes medications to achieve and maintain optimal levels of glycaemic control. Newer therapies, which focus on the incretin axis, may carry a lower risk of hypoglycaemia. Their use, and more prudent use of older therapies with low risk of hypoglycaemia, may help patients achieve improved glucose control for longer, and reduce the risk of diabetic complications.
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Affiliation(s)
- S A Amiel
- King's College London School of Medicine, London, UK
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MacDonald PE, De Marinis YZ, Ramracheya R, Salehi A, Ma X, Johnson PRV, Cox R, Eliasson L, Rorsman P. A K ATP channel-dependent pathway within alpha cells regulates glucagon release from both rodent and human islets of Langerhans. PLoS Biol 2007; 5:e143. [PMID: 17503968 PMCID: PMC1868042 DOI: 10.1371/journal.pbio.0050143] [Citation(s) in RCA: 179] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Accepted: 03/20/2007] [Indexed: 12/18/2022] Open
Abstract
Glucagon, secreted from pancreatic islet α cells, stimulates gluconeogenesis and liver glycogen breakdown. The mechanism regulating glucagon release is debated, and variously attributed to neuronal control, paracrine control by neighbouring β cells, or to an intrinsic glucose sensing by the α cells themselves. We examined hormone secretion and Ca2+ responses of α and β cells within intact rodent and human islets. Glucose-dependent suppression of glucagon release persisted when paracrine GABA or Zn2+ signalling was blocked, but was reversed by low concentrations (1–20 μM) of the ATP-sensitive K+ (KATP) channel opener diazoxide, which had no effect on insulin release or β cell responses. This effect was prevented by the KATP channel blocker tolbutamide (100 μM). Higher diazoxide concentrations (≥30 μM) decreased glucagon and insulin secretion, and α- and β-cell Ca2+ responses, in parallel. In the absence of glucose, tolbutamide at low concentrations (<1 μM) stimulated glucagon secretion, whereas high concentrations (>10 μM) were inhibitory. In the presence of a maximally inhibitory concentration of tolbutamide (0.5 mM), glucose had no additional suppressive effect. Downstream of the KATP channel, inhibition of voltage-gated Na+ (TTX) and N-type Ca2+ channels (ω-conotoxin), but not L-type Ca2+ channels (nifedipine), prevented glucagon secretion. Both the N-type Ca2+ channels and α-cell exocytosis were inactivated at depolarised membrane potentials. Rodent and human glucagon secretion is regulated by an α-cell KATP channel-dependent mechanism. We propose that elevated glucose reduces electrical activity and exocytosis via depolarisation-induced inactivation of ion channels involved in action potential firing and secretion. Glucagon is a critical regulator of glucose homeostasis. Its major action is to mobilize glucose from the liver. Glucagon secretion from α cells of the pancreatic islets of Langerhans is suppressed by elevated blood sugar, a response that is often perturbed in diabetes. Much work has focused on the regulation of α-cell glucagon secretion by neuronal factors and by paracrine factors from neighbouring cells, including the important islet hormone insulin. In contrast, we provide evidence in support of a direct effect of glucose on α cells within intact rodent and human islets. Notably, our work implicates an α-cell glucose-sensing pathway similar to that found in insulin-secreting β cells, involving closure of ATP-dependent K+ channels in the presence of glucose. Furthermore, we find that membrane depolarisation results in inhibition of Na+ and Ca2+ channel activity and α-cell exocytosis. Thus, we propose that elevated blood glucose reduces α-cell electrical activity and glucagon secretion by inactivating the ion channels involved in action potential firing and secretion. Elevated glucose levels reduce electrical activity and the release of glucagon via inactivation of ion channels in pancreatic islet cells.
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Affiliation(s)
- Patrick E MacDonald
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, United Kingdom.
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Israelian Z, Gosmanov NR, Szoke E, Schorr M, Bokhari S, Cryer PE, Gerich JE, Meyer C. Increasing the decrement in insulin secretion improves glucagon responses to hypoglycemia in advanced type 2 diabetes. Diabetes Care 2005; 28:2691-6. [PMID: 16249541 DOI: 10.2337/diacare.28.11.2691] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE In advanced beta-cell failure, counterregulatory glucagon responses may be impaired due to a reduced decrement in insulin secretion during the development of hypoglycemia. The present studies were therefore undertaken to test the hypothesis that these may be improved by increasing this decrement in insulin secretion. RESEARCH DESIGN AND METHODS Twelve subjects with type 2 diabetes who have been insulin requiring were studied as a model of advanced beta-cell failure. Glucagon responses were examined during a 90-min hypoglycemic clamp (approximately 2.8 mmol/l) on two separate occasions. On one occasion, tolbutamide was infused for 2 h before the clamp so that the decrement in insulin secretion during the induction of hypoglycemia would be increased. On the other occasion, normal saline was infused as a control. RESULTS Before the hypoglycemic clamp, infusion of tolbutamide increased insulin secretion approximately 1.9-fold (P < 0.001). However, during hypoglycemia, insulin secretion decreased to similar rates on both occasions (P = 0.31) so that its decrement was approximately twofold greater following the tolbutamide infusion (1.63 +/- 0.20 vs. 0.81 +/- 0.17 pmol x kg(-1) x min(-1), P < 0.001). This was associated with more than twofold-greater glucagon responses (42 +/- 11 vs. 19 +/- 8 ng/l, P < 0.002) during the hypoglycemic clamp but unaltered glucagon responses to intravenous arginine immediately thereafter (449 +/- 50 vs. 453 +/- 50 ng/l, P = 0.78). CONCLUSIONS Increasing the decrement in insulin secretion during the development of hypoglycemia improves counterregulatory glucagon responses in advanced beta-cell failure. These findings further support the concept that the impaired counterregulatory glucagon responses in advanced beta-cell failure may at least partially be due to a reduced decrement in insulin secretion.
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Affiliation(s)
- Zarmen Israelian
- Department of Endocrinology, Carl T. Hayden VA Medical Center, Phoenix, AZ 85012, USA
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12
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Hussain K, Bryan J, Christesen HT, Brusgaard K, Aguilar-Bryan L. Serum glucagon counterregulatory hormonal response to hypoglycemia is blunted in congenital hyperinsulinism. Diabetes 2005; 54:2946-51. [PMID: 16186397 DOI: 10.2337/diabetes.54.10.2946] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The mechanisms involved in the release of glucagon in response to hypoglycemia are unclear. Proposed mechanisms include the activation of the autonomic nervous system via glucose-sensing neurons in the central nervous system, via the regulation of glucagon secretion by intra-islet insulin and zinc concentrations, or via direct ionic control, all mechanisms that involve high-affinity sulfonylurea receptor/inwardly rectifying potassium channel-type ATP-sensitive K(+) channels. Patients with congenital hyperinsulinism provide a unique physiological model to understand glucagon regulation. In this study, we compare serum glucagon responses to hyperinsulinemic hypoglycemia versus nonhyperinsulinemic hypoglycemia. In the patient group (n = 20), the mean serum glucagon value during hyperinsulinemic hypoglycemia was 17.6 +/- 5.7 ng/l compared with 59.4 +/- 7.8 ng/l in the control group (n = 15) with nonhyperinsulinemic hypoglycemia (P < 0.01). There was no difference between the serum glucagon responses in children with diffuse, focal, and diazoxide-responsive forms of hyperinsulinism. The mean serum epinephrine and norepinephrine concentrations in the hyperinsulinemic group were 2,779 +/- 431 pmol/l and 2.9 +/- 0.7 nmol/l and appropriately rose despite the blunted glucagon response. In conclusion, the loss of ATP-sensitive K(+) channels and or elevated intraislet insulin cannot explain the blunted glucagon release in all patients with congenital hyperinsulinism. Other possible mechanisms such as the suppressive effect of prolonged hyperinsulinemia on alpha-cell secretion should be considered.
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Affiliation(s)
- Khalid Hussain
- The London Centre for Pediatric Endocrinology and Metabolism, Great Ormond Street Hospital for Children National Health Service Trust, University College London, UK.
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Evans ML, McCrimmon RJ, Flanagan DE, Keshavarz T, Fan X, McNay EC, Jacob RJ, Sherwin RS. Hypothalamic ATP-sensitive K + channels play a key role in sensing hypoglycemia and triggering counterregulatory epinephrine and glucagon responses. Diabetes 2004; 53:2542-51. [PMID: 15448082 DOI: 10.2337/diabetes.53.10.2542] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
It has been postulated that specialized glucose-sensing neurons in the ventromedial hypothalamus (VMH) are able to detect falling blood glucose and trigger the release of counterregulatory hormones during hypoglycemia. The molecular mechanisms used by glucose-sensing neurons are uncertain but may involve cell surface ATP-sensitive K(+) channels (K(ATP) channels) analogous to those of the pancreatic beta-cell. We examined whether the delivery of sulfonylureas directly into the brain to close K(ATP) channels would modulate counterregulatory hormone responses to either brain glucopenia (using intracerebroventricular 5-thioglucose) or systemic hypoglycemia in awake chronically catheterized rats. The closure of brain K(ATP) channels by global intracerebroventricular perfusion of sulfonylurea (120 ng/min glibenclamide or 2.7 microg/min tolbutamide) suppressed counterregulatory (epinephrine and glucagon) responses to brain glucopenia and/or systemic hypoglycemia (2.8 mmol/l glucose clamp). Local VMH microinjection of a small dose of glibenclamide (0.1% of the intracerebroventricular dose) also suppressed hormonal responses to systemic hypoglycemia. We conclude that hypothalamic K(ATP) channel activity plays an important role in modulating the hormonal counterregulatory responses triggered by decreases in blood glucose. Our data suggest that closing of K(ATP) channels in the VMH (much like the beta-cell) impairs defense mechanisms against glucose deprivation and therefore could contribute to defects in glucose counterregulation.
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Affiliation(s)
- Mark L Evans
- Diabetes Endocrine Research Center, Fitkin 1, Yale School of Medicine, 333 Cedar St., New Haven, CT 06520, USA
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Hope KM, Tran POT, Zhou H, Oseid E, Leroy E, Robertson RP. Regulation of alpha-cell function by the beta-cell in isolated human and rat islets deprived of glucose: the "switch-off" hypothesis. Diabetes 2004; 53:1488-95. [PMID: 15161753 DOI: 10.2337/diabetes.53.6.1488] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The "switch-off" hypothesis to explain beta-cell regulation of alpha-cell function during hypoglycemia has not been assessed previously in isolated islets, largely because they characteristically do not respond to glucose deprivation by secreting glucagon. We examined this hypothesis using normal human and Wistar rat islets, as well as islets from streptozotocin (STZ)-administered beta-cell-deficient Wistar rats. As expected, islets perifused with glucose and 3-isobutryl-1-methylxanthine did not respond to glucose deprivation by increasing glucagon secretion. However, if normal rat islets were first perifused with 16.7 mmol/l glucose to increase endogenous insulin secretion, followed by discontinuation of the glucose perifusate, a glucagon response to glucose deprivation was observed (peak change within 10 min after switch off = 61 +/- 15 pg/ml [mean +/- SE], n = 6, P < 0.01). A glucagon response from normal human islets using the same experimental design was also observed. A glucagon response (peak change within 7 min after switch off = 31 +/- 1 pg/ml, n = 3, P < 0.01) was observed from beta-cell-depleted, STZ-induced diabetic rats whose islets still secreted small amounts of insulin. However, when these islets were first perifused with both exogenous insulin and 16.7 mmol/l glucose, followed by switching off both the insulin and glucose perifusate, a significantly larger (P < 0.05) glucagon response was observed (peak change within 7 min after switch off = 71 +/- 11 pg/ml, n = 4, P < 0.01). This response was not observed if the insulin perifusion was not switched off when the islets were deprived of glucose or when insulin was switched off without glucose deprivation. These data uniquely demonstrate that both normal, isolated islets and islets from STZ-administered rats can respond to glucose deprivation by releasing glucagon if they are first provided with increased endogenous or exogenous insulin. These results fully support the beta-cell switch-off hypothesis as a key mechanism for the alpha-cell response to hypoglycemia.
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Affiliation(s)
- Kristine M Hope
- Pacific Northwest Research Institute, 720 Broadway, Seattle, WA 98122, USA
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Zhou H, Tran POT, Yang S, Zhang T, LeRoy E, Oseid E, Robertson RP. Regulation of alpha-cell function by the beta-cell during hypoglycemia in Wistar rats: the "switch-off" hypothesis. Diabetes 2004; 53:1482-7. [PMID: 15161752 DOI: 10.2337/diabetes.53.6.1482] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The glucagon response is the first line of defense against hypoglycemia and is lost in insulin-dependent diabetes. The beta-cell "switch-off" hypothesis proposes that a sudden cessation of insulin secretion from beta-cells into the portal circulation of the islet during hypoglycemia is a necessary signal for the glucagon response from downstream alpha-cells. Although indirect evidence exists to support this hypothesis, it has not been directly tested in vivo by provision and then discontinuation of regional reinsulinization of alpha-cells at the time of a hypoglycemic challenge. We studied streptozotocin (STZ)-induced diabetic Wistar rats that had no glucagon response to a hypoglycemic challenge. We reestablished insulin regulation of the alpha-cell by regionally infusing insulin (0.025 microU/min) directly into the superior pancreaticoduodenal artery (SPDa) of STZ-administered rats at an infusion rate that did not alter systemic venous glucose levels. SPDa insulin infusion was switched off simultaneously when blood glucose fell to <60 mg/dl after a jugular venous insulin injection. This maneuver restored the glucagon response to hypoglycemia (peak change within 5-10 min = 326 +/- 98 pg/ml, P < 0.05; and peak change within 15-20 min = 564 +/- 148 pg/ml, P < 0.01). No response was observed when the SPDa insulin infusion was not turned off (peak change within 5-10 min = 44 +/- 85 pg/ml, P = NS; and peak change within 15-20 min = 67 +/- 97 pg/ml, P = NS) or when saline instead of insulin was infused and then switched off (peak change within 5-10 min = -44 +/- 108 pg/ml, P = NS; and peak change within 15-20 min = -13 +/- 43 pg/ml, P = NS). No responses were observed during euglycemia (peak change within 5-10 min = 48 +/- 35 pg/ml, P = NS; and peak change within 15-20 min = 259 +/- 129 pg/ml, P = NS) or hyperglycemia (peak change within 5-10 min = 49 +/- 62 pg/ml, P = NS; and peak change within 15-20 min = 138 +/- 87 pg/ml, P = NS). Thus, the glucagon response to hypoglycemia that was absent in rats made diabetic by STZ was restored by regional infusion and then discontinuation of insulin. These data provide direct in vivo support for the beta-cell "switch-off" hypothesis and indicate that the alpha-cell is not intrinsically abnormal in insulin-dependent diabetes because of STZ-induced destruction of beta-cells.
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Affiliation(s)
- Huarong Zhou
- Pacific Northwest Research Institute, 720 Broadway, Seattle, WA 98122, USA
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Banarer S, McGregor VP, Cryer PE. Intraislet hyperinsulinemia prevents the glucagon response to hypoglycemia despite an intact autonomic response. Diabetes 2002; 51:958-65. [PMID: 11916913 DOI: 10.2337/diabetes.51.4.958] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Because absence of the glucagon response to falling plasma glucose concentrations plays a key role in the pathogenesis of iatrogenic hypoglycemia in patients with insulin-deficient diabetes and the mechanism of this defect is unknown, and given evidence in experimental animals that a decrease in intraislet insulin is a signal to increased glucagon secretion, we examined the role of endogenous insulin in the physiological glucagon response to hypoglycemia. We tested the hypothesis that intraislet hyperinsulinemia prevents the glucagon response to hypoglycemia despite an intact autonomic-adrenomedullary, sympathetic neural, and parasympathetic neural-response and a low alpha-cell glucose concentration. Twelve healthy young adults were studied on three separate occasions. Insulin was infused in hourly steps in relatively low doses (1.5, 3.0, 4.5, and 6.0 pmol.kg(-1).min(-1)) from 60 through 300 min on all three occasions. Plasma glucose levels were clamped at euglycemia ( approximately 5.0 mmol/l, approximately 90 mg/dl) on one occasion and at hourly steps of approximately 4.7, 4.2, 3.6, and 3.0 mmol/l ( approximately 85, 75, 65, and 55 mg/dl) from 60 through 300 min on the other two occasions. On one of the latter occasions, the beta-cell secretagogue tolbutamide was infused in a dose of 1.0 g/h from 60 through 300 min. Hypoglycemia with tolbutamide infusion, compared with similar hypoglycemia alone, was associated with higher (P < 0.0001) C-peptide levels (final values of 1.0 +/- 0.2 vs. 0.1 +/- 0.0 nmol/l), higher (P < 0.0001) rates of insulin secretion (final values of 198 +/- 60 vs. 15 +/- 4 pmol/min), and higher (P < 0.0001) insulin levels (final values of 325 +/- 30 vs. 245 +/- 20 pmol/l) as expected. The glucagon response to hypoglycemia was prevented during tolbutamide infusion (P < 0.0001). Glucagon levels were 17 +/- 1 pmol/l at baseline on both occasions, 14 +/- 1 vs. 15 +/- 1 pmol/l, respectively, during the initial hyperinsulinemic euglycemia, and 15 +/- 1 vs. 22 +/- 2 pmol/l, respectively, during hypoglycemia with and without tolbutamide infusion. Autonomic-adrenomedullary (plasma epinephrine), sympathetic neural (plasma norepinephrine), and parasympathetic neural (plasma pancreatic polypeptide)-responses to hypoglycemia were not reduced during tolbutamide infusion. We conclude that intraislet hyperinsulinemia prevents the glucagon response to hypoglycemia despite an intact autonomic response and a low alpha-cell glucose concentration.
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Affiliation(s)
- Salomon Banarer
- Division of Endocrinology, Diabetes and Metabolism and the General Clinical Research Center and the Diabetes Research and Training Center, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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ter Braak EWMT, Appelman AMMF, van der Tweel I, Erkelens DW, van Haeften TW. The sulfonylurea glyburide induces impairment of glucagon and growth hormone responses during mild insulin-induced hypoglycemia. Diabetes Care 2002; 25:107-12. [PMID: 11772910 DOI: 10.2337/diacare.25.1.107] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE The sulfonylurea (SU) glyburide may cause severe and prolonged episodes of hypoglycemia. We aimed at investigating the impact of glyburide on glucose counterregulatory hormones during stepwise hypoglycemic clamp studies. RESEARCH DESIGN AND METHODS We performed stepwise hypoglycemic clamp studies in 16 healthy volunteers (7 women and 9 men aged 44 +/- 10 years). We investigated counterregulatory hormonal and symptom responses at arterialized venous plasma glucose levels (PG) of 3.8, 3.2, and 2.6 mmol/l, comparing 10 mg glyburide orally and placebo in a double-blind, randomized crossover fashion. RESULTS The increase in plasma glucagon with time from PG = 3.8 onward was smaller for glyburide than for placebo (P = 0.014). Plasma glucagon area under the curve (AUC)(60-180) was lower after glyburide than after placebo (1,774 +/- 715 vs. 2,161 +/- 856 pmol. l(-1). min, P = 0.014). From PG = 3.8 onward, plasma growth hormone (GH) levels with placebo were nearly two times (1.9 [95% CI 1.2-2.9]) as high as with glyburide (P = 0.011). AUC(60-180) for GH was lower after glyburide than after placebo (geometric mean [range] 665 [356-1,275] and 1,058 [392-1,818] mU. l(-1). min, respectively; P = 0.04). No significant differences were observed for plasma cortisol, epinephrine and norepinephrine, or incremental symptom scores. CONCLUSIONS The SU glyburide induces multiple defects in glucose counterregulatory hormonal responses, notably decreases in both glucagon and GH release.
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Affiliation(s)
- Edith W M T ter Braak
- Department of Internal Medicine University Medical Center, Utrecht, the Netherlands.
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