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Shankar K, Varshney S, Gupta D, Mani BK, Osborne-Lawrence S, Metzger NP, Richard CP, Zigman JM. Ghrelin does not impact the blunted counterregulatory response to recurrent hypoglycemia in mice. Front Endocrinol (Lausanne) 2023; 14:1181856. [PMID: 37334290 PMCID: PMC10272800 DOI: 10.3389/fendo.2023.1181856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 05/23/2023] [Indexed: 06/20/2023] Open
Abstract
Introduction Recurrent episodes of insulin-induced hypoglycemia in patients with diabetes mellitus can result in hypoglycemia-associated autonomic failure (HAAF), which is characterized by a compromised response to hypoglycemia by counterregulatory hormones (counterregulatory response; CRR) and hypoglycemia unawareness. HAAF is a leading cause of morbidity in diabetes and often hinders optimal regulation of blood glucose levels. Yet, the molecular pathways underlying HAAF remain incompletely described. We previously reported that in mice, ghrelin is permissive for the usual CRR to insulin-induced hypoglycemia. Here, we tested the hypothesis that attenuated release of ghrelin both results from HAAF and contributes to HAAF. Methods C57BL/6N mice, ghrelin-knockout (KO) + control mice, and GhIRKO (ghrelin cell-selective insulin receptor knockout) + control mice were randomized to one of three treatment groups: a "Euglycemia" group was injected with saline and remained euglycemic; a 1X hypoglycemia ("1X Hypo") group underwent a single episode of insulin-induced hypoglycemia; a recurrent hypoglycemia ("Recurrent Hypo") group underwent repeated episodes of insulin-induced hypoglycemia over five successive days. Results Recurrent hypoglycemia exaggerated the reduction in blood glucose (by ~30%) and attenuated the elevations in plasma levels of the CRR hormones glucagon (by 64.5%) and epinephrine (by 52.9%) in C57BL/6N mice compared to a single hypoglycemic episode. Yet, plasma ghrelin was equivalently reduced in "1X Hypo" and "Recurrent Hypo" C57BL/6N mice. Ghrelin-KO mice exhibited neither exaggerated hypoglycemia in response to recurrent hypoglycemia, nor any additional attenuation in CRR hormone levels compared to wild-type littermates. Also, in response to recurrent hypoglycemia, GhIRKO mice exhibited nearly identical blood glucose and plasma CRR hormone levels as littermates with intact insulin receptor expression (floxed-IR mice), despite higher plasma ghrelin in GhIRKO mice. Conclusions These data suggest that the usual reduction of plasma ghrelin due to insulin-induced hypoglycemia is unaltered by recurrent hypoglycemia and that ghrelin does not impact blood glucose or the blunted CRR hormone responses during recurrent hypoglycemia.
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Affiliation(s)
- Kripa Shankar
- Center for Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Salil Varshney
- Center for Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Deepali Gupta
- Center for Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Bharath K. Mani
- Center for Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Sherri Osborne-Lawrence
- Center for Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Nathan P. Metzger
- Center for Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Corine P. Richard
- Center for Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Jeffrey M. Zigman
- Center for Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States
- Division of Endocrinology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, United States
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Bensreti H, Alhamad DW, Gonzalez AM, Pizarro-Mondesir M, Bollag WB, Isales CM, McGee-Lawrence ME. Update on the Role of Glucocorticoid Signaling in Osteoblasts and Bone Marrow Adipocytes During Aging. Curr Osteoporos Rep 2023; 21:32-44. [PMID: 36564571 PMCID: PMC9936962 DOI: 10.1007/s11914-022-00772-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/15/2022] [Indexed: 12/25/2022]
Abstract
PURPOSE OF REVIEW Bone marrow adipose tissue (BMAT) in the skeleton likely plays a variety of physiological and pathophysiological roles that are not yet fully understood. In elucidating the complex relationship between bone and BMAT, glucocorticoids (GCs) are positioned to play a key role, as they have been implicated in the differentiation of bone marrow mesenchymal stem cells (BMSCs) between osteogenic and adipogenic lineages. The purpose of this review is to illuminate aspects of both endogenous and exogenous GC signaling, including the influence of GC receptors, in mechanisms of bone aging including relationships to BMAT. RECENT FINDINGS Harmful effects of GCs on bone mass involve several cellular pathways and events that can include BMSC differentiation bias toward adipogenesis and the influence of mature BMAT on bone remodeling through crosstalk. Interestingly, BMAT involvement remains poorly explored in GC-induced osteoporosis and warrants further investigation. This review provides an update on the current understanding of the role of glucocorticoids in the biology of osteoblasts and bone marrow adipocytes (BMAds).
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Affiliation(s)
- Husam Bensreti
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Dima W Alhamad
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Alejandro Marrero Gonzalez
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Manuel Pizarro-Mondesir
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Wendy B Bollag
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, GA, USA
- Charlie Norwood VA Medical Center, Augusta, GA, USA
| | - Carlos M Isales
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA, USA
- Department of Orthopaedic Surgery, Medical College of Georgia, Augusta University, Augusta, GA, USA
- Department of Medicine, Medical College of Georgia, Augusta University, Augusta, GA, USA
| | - Meghan E McGee-Lawrence
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta University, Augusta, GA, USA.
- Department of Orthopaedic Surgery, Medical College of Georgia, Augusta University, Augusta, GA, USA.
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Rawlinson S, Reichenbach A, Clarke RE, Nuñez-Iglesias J, Dempsey H, Lockie SH, Andrews ZB. In Vivo Photometry Reveals Insulin and 2-Deoxyglucose Maintain Prolonged Inhibition of VMH Vglut2 Neurons in Male Mice. Endocrinology 2022; 163:6631280. [PMID: 35788848 DOI: 10.1210/endocr/bqac095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Indexed: 11/19/2022]
Abstract
The ventromedial hypothalamic (VMH) nucleus is a well-established hub for energy and glucose homeostasis. In particular, VMH neurons are thought to be important for initiating the counterregulatory response to hypoglycemia, and ex vivo electrophysiology and immunohistochemistry data indicate a clear role for VMH neurons in sensing glucose concentration. However, the temporal response of VMH neurons to physiologically relevant changes in glucose availability in vivo has been hampered by a lack of available tools for measuring neuronal activity over time. Since the majority of neurons within the VMH are glutamatergic and can be targeted using the vesicular glutamate transporter Vglut2, we expressed cre-dependent GCaMP7s in Vglut2 cre mice and examined the response profile of VMH to intraperitoneal injections of glucose, insulin, and 2-deoxyglucose (2DG). We show that reduced available glucose via insulin-induced hypoglycemia and 2DG-induced glucoprivation, but not hyperglycemia induced by glucose injection, inhibits VMH Vglut2 neuronal population activity in vivo. Surprisingly, this inhibition was maintained for at least 45 minutes despite prolonged hypoglycemia and initiation of a counterregulatory response. Thus, although VMH stimulation, via pharmacological, electrical, or optogenetic approaches, is sufficient to drive a counterregulatory response, our data suggest VMH Vglut2 neurons are not the main drivers required to do so, since VMH Vglut2 neuronal population activity remains suppressed during hypoglycemia and glucoprivation.
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Affiliation(s)
- Sasha Rawlinson
- Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria, 3800, Australia
| | - Alex Reichenbach
- Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria, 3800, Australia
| | - Rachel E Clarke
- Department of Neurosciences, Medical University of South Carolina, Charleston, South Carolina 29425, USA
| | - Juan Nuñez-Iglesias
- Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, 3800, Australia
| | - Harry Dempsey
- Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria, 3800, Australia
| | - Sarah H Lockie
- Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria, 3800, Australia
| | - Zane B Andrews
- Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria, 3800, Australia
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4
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Affiliation(s)
- Julio E Ayala
- Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, TN, USA
- Vanderbilt Diabetes Research Center, Vanderbilt University, Nashville, TN, USA
- Mouse Diabetes Clinic at Vanderbilt, Vanderbilt University, Nashville, TN, USA
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Louise Lantier
- Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, TN, USA
- Vanderbilt Diabetes Research Center, Vanderbilt University, Nashville, TN, USA
- Mouse Diabetes Clinic at Vanderbilt, Vanderbilt University, Nashville, TN, USA
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Owen P McGuinness
- Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, TN, USA
- Vanderbilt Diabetes Research Center, Vanderbilt University, Nashville, TN, USA
- Mouse Diabetes Clinic at Vanderbilt, Vanderbilt University, Nashville, TN, USA
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, TN, USA
| | - David H Wasserman
- Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, TN, USA.
- Vanderbilt Diabetes Research Center, Vanderbilt University, Nashville, TN, USA.
- Mouse Diabetes Clinic at Vanderbilt, Vanderbilt University, Nashville, TN, USA.
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, TN, USA.
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5
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dos Santos WO, Gusmao DO, Wasinski F, List EO, Kopchick JJ, Donato J. Effects of Growth Hormone Receptor Ablation in Corticotropin-Releasing Hormone Cells. Int J Mol Sci 2021; 22:9908. [PMID: 34576072 PMCID: PMC8465163 DOI: 10.3390/ijms22189908] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 09/09/2021] [Accepted: 09/10/2021] [Indexed: 01/11/2023] Open
Abstract
Corticotropin-releasing hormone (CRH) cells are the dominant neuronal population responsive to the growth hormone (GH) in the paraventricular nucleus of the hypothalamus (PVH). However, the physiological importance of GH receptor (GHR) signaling in CRH neurons is currently unknown. Thus, the main objective of the present study was to investigate the consequences of GHR ablation in CRH-expressing cells of male and female mice. GHR ablation in CRH cells did not cause significant changes in body weight, body composition, food intake, substrate oxidation, locomotor activity, glucose tolerance, insulin sensitivity, counterregulatory response to 2-deoxy-D-glucose and ghrelin-induced food intake. However, reduced energy expenditure was observed in female mice carrying GHR ablation in CRH cells. The absence of GHR in CRH cells did not affect anxiety, circadian glucocorticoid levels or restraint-stress-induced corticosterone secretion and activation of PVH neurons in both male and female mice. In summary, GHR ablation, specifically in CRH-expressing neurons, does not lead to major alterations in metabolism, hypothalamic-pituitary-adrenal axis, acute stress response or anxiety in mice. Considering the previous studies showing that central GHR signaling regulates homeostasis in situations of metabolic stress, future studies are still necessary to identify the potential physiological importance of GH action on CRH neurons.
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Affiliation(s)
- Willian O. dos Santos
- Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo 05508-000, SP, Brazil; (W.O.d.S.); (D.O.G.); (F.W.)
| | - Daniela O. Gusmao
- Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo 05508-000, SP, Brazil; (W.O.d.S.); (D.O.G.); (F.W.)
| | - Frederick Wasinski
- Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo 05508-000, SP, Brazil; (W.O.d.S.); (D.O.G.); (F.W.)
| | - Edward O. List
- Edison Biotechnology Institute and Heritage College of Osteopathic Medicine, Ohio University, Athens, OH 45701, USA; (E.O.L.); (J.J.K.)
| | - John J. Kopchick
- Edison Biotechnology Institute and Heritage College of Osteopathic Medicine, Ohio University, Athens, OH 45701, USA; (E.O.L.); (J.J.K.)
| | - Jose Donato
- Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo 05508-000, SP, Brazil; (W.O.d.S.); (D.O.G.); (F.W.)
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Sankar A, Khodai T, McNeilly AD, McCrimmon RJ, Luckman SM. Experimental Models of Impaired Hypoglycaemia-Associated Counter-Regulation. Trends Endocrinol Metab 2020; 31:691-703. [PMID: 32563715 DOI: 10.1016/j.tem.2020.05.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 05/14/2020] [Accepted: 05/26/2020] [Indexed: 01/24/2023]
Abstract
Impaired awareness of hypoglycaemia (IAH) affects around a quarter of patients with diabetes who receive insulin treatment. This condition is characterised by a progressive reduction in symptomatic and behavioural responses to hypoglycaemia, increasing risk of deeper drops in blood glucose, unconsciousness, and collapse. Thus, patients with IAH experience severe hypoglycaemic episodes more frequently, resulting in significant morbidity and mortality. IAH is thought to develop as a consequence of whole-body adaptations to repeated insulin-induced hypoglycaemia (RH), with widespread deficits in the hypoglycaemia counter-regulatory response (CRR). Despite this important insight, the precise pathophysiology by which RH leads to an attenuated CRR is unknown. Studies into the underlying mechanisms of IAH have employed a variety of protocols in humans and experimental species. The use of animal models has many investigational benefits, including the unprecedented increase in the availability of transgenic strains. However, modelling impaired hypoglycaemia-associated counter-regulation remains challenging and appropriate interpretation of findings across species and protocols even more so. Here, we review the experimental modelling of IAH and impaired hypoglycaemia-associated counter-regulation, with a focus on understanding species-specific variation in glucose homeostasis. This review will aid investigators in interpreting outputs from different studies in IAH and aid progress in the field.
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Affiliation(s)
- Adhithya Sankar
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Tansi Khodai
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Alison D McNeilly
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, UK
| | - Rory J McCrimmon
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, UK
| | - Simon M Luckman
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.
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7
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Malmgren S, Ahrén B. Deciphering the Hypoglycemic Glucagon Response: Development of a Graded Hyperinsulinemic Hypoglycemic Clamp Technique in Female Mice. Endocrinology 2015; 156:3866-71. [PMID: 26132921 DOI: 10.1210/en.2015-1314] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Glucose lowering therapy in type 1 and type 2 diabetes is often associated with hypoglycemic events. To avoid this, glucose lowering therapies need to be developed that support the hypoglycemic defense mechanisms. Such development needs a tool for evaluating counterregulatory mechanisms in vivo. A sustained glucagon release during hypoglycemia is of most importance to hypoglycemic defense mechanisms. We have therefore developed a graded hyperinsulinemic hypoglycemic clamp in mice and used it to evaluate counterregulatory glucagon dynamics. Glucose was clamped at narrow intervals aiming at 2.5, 3.5, 4.5, and 6.0 mmol/L. Glucagon levels were increased during hypoglycemia in a glucose-dependent way with a glucagon counterregulatory threshold between 3.5 and 4.0 mmol/L. Modelling the glucose-glucagon relationship using a hyperbolic curve with the equation: plasma glucagon = -4.20 + 90.79/blood glucose showed high correlation. When comparing this method to the insulin tolerance test as an approach to study glucagon dynamics in vivo, we found that the graded clamp more efficiently evoked a robust, predictable, glucagon response with considerably less variation in blood glucose. In conclusion, we have developed a tool for the study of in vivo glucagon dynamics during hypoglycemia in mice and demonstrated a hyperbolic glucose-counterregulatory glucagon relationship.
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Affiliation(s)
- Siri Malmgren
- Department of Clinical Sciences, Lund, Medicine, Lund University, SE-221 84 Lund, Sweden
| | - Bo Ahrén
- Department of Clinical Sciences, Lund, Medicine, Lund University, SE-221 84 Lund, Sweden
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Maity‐Kumar G, Thal DR, Baumann B, Scharffetter‐Kochanek K, Wirth T. Neuronal redox imbalance results in altered energy homeostasis and early postnatal lethality. FASEB J 2015; 29:2843-58. [DOI: 10.1096/fj.14-265157] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Accepted: 03/09/2015] [Indexed: 12/15/2022]
Affiliation(s)
| | - Dietmar R. Thal
- Laboratory of Neuropathology, Institute for Pathology, University of UlmUlmGermany
| | - Bernd Baumann
- Institute of Physiological Chemistry, University of UlmUlmGermany
| | | | - Thomas Wirth
- Institute of Physiological Chemistry, University of UlmUlmGermany
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9
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Hughey CC, Wasserman DH, Lee-Young RS, Lantier L. Approach to assessing determinants of glucose homeostasis in the conscious mouse. Mamm Genome 2014; 25:522-38. [PMID: 25074441 DOI: 10.1007/s00335-014-9533-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 07/04/2014] [Indexed: 01/11/2023]
Abstract
Obesity and type 2 diabetes lessen the quality of life of those afflicted and place considerable burden on the healthcare system. Furthermore, the detrimental impact of these pathologies is expected to persist or even worsen. Diabetes is characterized by impaired insulin action and glucose homeostasis. This has led to a rapid increase in the number of mouse models of metabolic disease being used in the basic sciences to assist in facilitating a greater understanding of the metabolic dysregulation associated with obesity and diabetes, the identification of therapeutic targets, and the discovery of effective treatments. This review briefly describes the most frequently utilized models of metabolic disease. A presentation of standard methods and technologies on the horizon for assessing metabolic phenotypes in mice, with particular emphasis on glucose handling and energy balance, is provided. The article also addresses issues related to study design, selection and execution of metabolic tests of glucose metabolism, the presentation of data, and interpretation of results.
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Affiliation(s)
- Curtis C Hughey
- Department of Molecular Physiology and Biophysics, School of Medicine, Vanderbilt University, 823 Light Hall, 2215 Garland Ave, Nashville, TN, 37232, USA,
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Sakamoto R, Matsubara E, Nomura M, Wang L, Kawahara Y, Yanase T, Nawata H, Takayanagi R. Roles for corticotropin-releasing factor receptor type 1 in energy homeostasis in mice. Metabolism 2013; 62:1739-48. [PMID: 24054833 DOI: 10.1016/j.metabol.2013.08.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 08/09/2013] [Accepted: 08/13/2013] [Indexed: 12/25/2022]
Abstract
OBJECTIVE Expression of corticotropin-releasing factor type 1 receptor (CRFR1) has been shown on pancreatic β cells, and its activation potentiates glucose-stimulated insulin secretion (GSIS). However, the roles of CRFR1 in energy metabolism beyond insulin release remain elusive. MATERIALS/METHODS We characterized the metabolic phenotypes of mice lacking CRFR1 (CRFR1KO mice) under conditions of energy excess. RESULTS When fed a normal diet, the glucose profile of CRFR1KO mice in response to a glucose tolerance test was similar to that of wild-type (WT) mice, while serum insulin levels were significantly lower in CRFR1KO mice, reflecting high insulin sensitivity in part due to very low glucocorticoid levels. Histology of the pancreas revealed islet hypoplasia in CRFR1KO mice, suggesting a role of CRFR1 in maintaining the β cell mass in a manner similar to incretins. In response to a high-fat diet, CRFR1KO mice showed insulin resistance, but serum insulin levels during glucose challenge remained at a low level, indicating defective GSIS. In addition, CRFR1KO mice showed resistance to diet-induced obesity and hepatic steatosis. Although total food intake was not different between CRFR1KO and WT mice, oxygen consumption was significantly increased in CRFR1KO mice. The increased energy expenditure may explain the lean phenotype of CRFR1KO mice under conditions of energy excess. CONCLUSIONS Our results suggest that CRFR1 plays important roles in whole body energy homeostasis, providing compelling evidence of the close relationship between energy homeostasis and the function of the hypothalamic-pituitary-adrenal axis.
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Affiliation(s)
- Ryuichi Sakamoto
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Science, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812-8582, Japan
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11
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Yi CX, Foppen E, Abplanalp W, Gao Y, Alkemade A, la Fleur SE, Serlie MJ, Fliers E, Buijs RM, Tschöp MH, Kalsbeek A. Glucocorticoid signaling in the arcuate nucleus modulates hepatic insulin sensitivity. Diabetes 2012; 61:339-45. [PMID: 22210324 PMCID: PMC3266416 DOI: 10.2337/db11-1239] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Glucocorticoid receptors are highly expressed in the hypothalamic paraventricular nucleus (PVN) and arcuate nucleus (ARC). As glucocorticoids have pronounced effects on neuropeptide Y (NPY) expression and as NPY neurons projecting from the ARC to the PVN are pivotal for balancing feeding behavior and glucose metabolism, we investigated the effect of glucocorticoid signaling in these areas on endogenous glucose production (EGP) and insulin sensitivity by local retrodialysis of the glucocorticoid receptor agonist dexamethasone into the ARC or the PVN, in combination with isotope dilution and hyperinsulinemic-euglycemic clamp techniques. Retrodialysis of dexamethasone for 90 min into the ARC or the PVN did not have significant effects on basal plasma glucose concentration. During the hyperinsulinemic-euglycemic clamp, retrodialysis of dexamethasone into the ARC largely prevented the suppressive effect of hyperinsulinemia on EGP. Antagonizing the NPY1 receptors by intracerebroventricular infusion of its antagonist largely blocked the hepatic insulin resistance induced by dexamethasone in the ARC. The dexamethasone-ARC-induced inhibition of hepatic insulin sensitivity was also prevented by hepatic sympathetic denervation. These data suggest that glucocorticoid signaling specifically in the ARC neurons modulates hepatic insulin responsiveness via NPY and the sympathetic system, which may add to our understanding of the metabolic impact of clinical conditions associated with hypercortisolism.
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Affiliation(s)
- Chun-Xia Yi
- Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, the Netherlands.
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Ayala JE, Bracy DP, Malabanan C, James FD, Ansari T, Fueger PT, McGuinness OP, Wasserman DH. Hyperinsulinemic-euglycemic clamps in conscious, unrestrained mice. J Vis Exp 2011:3188. [PMID: 22126863 PMCID: PMC3308587 DOI: 10.3791/3188] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Type 2 diabetes is characterized by a defect in insulin action. The hyperinsulinemic-euglycemic clamp, or insulin clamp, is widely considered the "gold standard" method for assessing insulin action in vivo. During an insulin clamp, hyperinsulinemia is achieved by a constant insulin infusion. Euglycemia is maintained via a concomitant glucose infusion at a variable rate. This variable glucose infusion rate (GIR) is determined by measuring blood glucose at brief intervals throughout the experiment and adjusting the GIR accordingly. The GIR is indicative of whole-body insulin action, as mice with enhanced insulin action require a greater GIR. The insulin clamp can incorporate administration of isotopic 2[14C]deoxyglucose to assess tissue-specific glucose uptake and [3-3H]glucose to assess the ability of insulin to suppress the rate of endogenous glucose appearance (endoRa), a marker of hepatic glucose production, and to stimulate the rate of whole-body glucose disappearance (Rd). The miniaturization of the insulin clamp for use in genetic mouse models of metabolic disease has led to significant advances in diabetes research. Methods for performing insulin clamps vary between laboratories. It is important to note that the manner in which an insulin clamp is performed can significantly affect the results obtained. We have published a comprehensive assessment of different approaches to performing insulin clamps in conscious mice1 as well as an evaluation of the metabolic response of four commonly used inbred mouse strains using various clamp techniques2. Here we present a protocol for performing insulin clamps on conscious, unrestrained mice developed by the Vanderbilt Mouse Metabolic Phenotyping Center (MMPC; URL: www.mc.vanderbilt.edu/mmpc). This includes a description of the method for implanting catheters used during the insulin clamp. The protocol employed by the Vanderbilt MMPC utilizes a unique two-catheter system3. One catheter is inserted into the jugular vein for infusions. A second catheter is inserted into the carotid artery, which allows for blood sampling without the need to restrain or handle the mouse. This technique provides a significant advantage to the most common method for obtaining blood samples during insulin clamps which is to sample from the severed tip of the tail. Unlike this latter method, sampling from an arterial catheter is not stressful to the mouse1. We also describe methods for using isotopic tracer infusions to assess tissue-specific insulin action. We also provide guidelines for the appropriate presentation of results obtained from insulin clamps.
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Affiliation(s)
- Julio E Ayala
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute at Lake Nona, USA.
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Poplawski MM, Mastaitis JW, Mobbs CV. Naloxone, but not valsartan, preserves responses to hypoglycemia after antecedent hypoglycemia: role of metabolic reprogramming in counterregulatory failure. Diabetes 2011; 60:39-46. [PMID: 20811039 PMCID: PMC3012195 DOI: 10.2337/db10-0326] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE Hypoglycemia-associated autonomic failure (HAAF) constitutes one of the main clinical obstacles to optimum treatment of type 1 diabetes. Neurons in the ventromedial hypothalamus are thought to mediate counterregulatory responses to hypoglycemia. We have previously hypothesized that hypoglycemia-induced hypothalamic angiotensin might contribute to HAAF, suggesting that the angiotensin blocker valsartan might prevent HAAF. On the other hand, clinical studies have demonstrated that the opioid receptor blocker naloxone ameliorates HAAF. The goal of this study was to generate novel hypothalamic markers of hypoglycemia and use them to assess mechanisms mediating HAAF and its reversal. RESEARCH DESIGN AND METHODS Quantitative PCR was used to validate a novel panel of hypothalamic genes regulated by hypoglycemia. Mice were exposed to one or five episodes of insulin-induced hypoglycemia, with or without concurrent exposure to valsartan or naloxone. Corticosterone, glucagon, epinephrine, and hypothalamic gene expression were assessed after the final episode of hypoglycemia. RESULTS A subset of hypothalamic genes regulated acutely by hypoglycemia failed to respond after repetitive hypoglycemia. Responsiveness of a subset of these genes was preserved by naloxone but not valsartan. Notably, hypothalamic expression of four genes, including pyruvate dehydrogenase kinase 4 and glycerol 3-phosphate dehydrogenase 1, was acutely induced by a single episode of hypoglycemia, but not after antecedent hypoglycemia; naloxone treatment prevented this failure. Similarly, carnitine palmitoyltransferase-1 was inhibited after repetitive hypoglycemia, and this inhibition was prevented by naloxone. Repetitive hypoglycemia also caused a loss of hypoglycemia-induced elevation of glucocorticoid secretion, a failure prevented by naloxone but not valsartan. CONCLUSIONS Based on these observations we speculate that acute hypoglycemia induces reprogramming of hypothalamic metabolism away from glycolysis toward β-oxidation, HAAF is associated with a reversal of this reprogramming, and naloxone preserves some responses to hypoglycemia by preventing this reversal.
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Affiliation(s)
- Michal M. Poplawski
- Fishberg Center for Neurobiology, Mount Sinai School of Medicine, New York, New York
| | - Jason W. Mastaitis
- Department of Internal Medicine, The Anlyan Center, Yale University School of Medicine, New Haven, Connecticut
| | - Charles V. Mobbs
- Fishberg Center for Neurobiology, Mount Sinai School of Medicine, New York, New York
- Corresponding author: Charles V. Mobbs,
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Ayala JE, Samuel VT, Morton GJ, Obici S, Croniger CM, Shulman GI, Wasserman DH, McGuinness OP. Standard operating procedures for describing and performing metabolic tests of glucose homeostasis in mice. Dis Model Mech 2010; 3:525-34. [PMID: 20713647 DOI: 10.1242/dmm.006239] [Citation(s) in RCA: 529] [Impact Index Per Article: 37.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The Mouse Metabolic Phenotyping Center (MMPC) Consortium was established to address the need to characterize the growing number of mouse models of metabolic diseases, particularly diabetes and obesity. A goal of the MMPC Consortium is to propose standard methods for assessing metabolic phenotypes in mice. In this article, we discuss issues pertaining to the design and performance of various tests of glucose metabolism. We also propose guidelines for the description of methods, presentation of data and interpretation of results. The recommendations presented in this article are based on the experience of the MMPC Consortium and other investigators.
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Affiliation(s)
- Julio E Ayala
- Vanderbilt-NIH Mouse Metabolic Phenotyping Center, Nashville, TN 37232, USA.
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15
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Taborsky GJ, Mei Q, Hackney DJ, Figlewicz DP, LeBoeuf R, Mundinger TO. Loss of islet sympathetic nerves and impairment of glucagon secretion in the NOD mouse: relationship to invasive insulitis. Diabetologia 2009; 52:2602-11. [PMID: 19798480 DOI: 10.1007/s00125-009-1494-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Accepted: 07/06/2009] [Indexed: 10/20/2022]
Abstract
AIMS/HYPOTHESIS We hypothesised that non-obese diabetic mice (NOD) mice have an autoimmune-mediated loss of islet sympathetic nerves and an impairment of sympathetically mediated glucagon responses. We aimed: (1) to determine whether diabetic NOD mice have an early impairment of the glucagon response to insulin-induced hypoglycaemia (IIH) and a coincident loss of islet sympathetic nerves; (2) to determine whether invasive insulitis is required for this nerve loss; and (3) to determine whether sympathetically mediated glucagon responses are also impaired. METHODS We measured glucagon responses to both IIH and tyramine in anaesthetised mice. We used immunohistochemistry to quantify islet sympathetic nerves and invasive insulitis. RESULTS The glucagon response to IIH was markedly impaired in NOD mice after only 3 weeks of diabetes (change, -70%). Sympathetic nerve area within the islet was also markedly reduced at this time (change, -66%). This islet nerve loss was proportional to the degree of invasive insulitis. More importantly, blocking the infiltration prevented the nerve loss. Mice with autoimmune diabetes had an impaired glucagon response to sympathetic nerve activation, whereas those with non-autoimmune diabetes did not. CONCLUSIONS/INTERPRETATION The invasive insulitis seen in diabetic NOD mice causes early sympathetic islet neuropathy. Further studies are needed to confirm that early sympathetic islet neuropathy is responsible for the impaired glucagon response to tyramine.
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Affiliation(s)
- G J Taborsky
- Division of Endocrinology/Metabolism (S-151), Veterans Affairs Puget Sound Health Care System, 1660 S. Columbian Way, Seattle, WA 98108, USA.
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16
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McGuinness OP, Ayala JE, Laughlin MR, Wasserman DH. NIH experiment in centralized mouse phenotyping: the Vanderbilt experience and recommendations for evaluating glucose homeostasis in the mouse. Am J Physiol Endocrinol Metab 2009; 297:E849-55. [PMID: 19638507 PMCID: PMC2763792 DOI: 10.1152/ajpendo.90996.2008] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This article addresses two topics. We provide an overview of the National Institutes of Health Mouse Metabolic Phenotyping Center (MMPC) Program. We then discuss some observations we have made during the first eight years of the Vanderbilt MMPC regarding common phenotyping practices. We include specific recommendations to improve phenotyping practices for tests of glucose tolerance and insulin action. We recommend that methods for experiments in vivo be described in manuscripts. We make specific recommendations for data presentation, interpretation, and experimental design for each test. To facilitate and maximize the exchange of scientific information, we suggest that guidelines be developed for methods used to assess glucose tolerance and insulin action in vivo.
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Affiliation(s)
- Owen P McGuinness
- Vanderbilt-NIH Mouse Metabolic Phenotyping Center, Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA.
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17
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Berglund ED, Li CY, Poffenberger G, Ayala JE, Fueger PT, Willis SE, Jewell MM, Powers AC, Wasserman DH. Glucose metabolism in vivo in four commonly used inbred mouse strains. Diabetes 2008; 57:1790-9. [PMID: 18398139 PMCID: PMC2453626 DOI: 10.2337/db07-1615] [Citation(s) in RCA: 204] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
OBJECTIVE To characterize differences in whole-body glucose metabolism between commonly used inbred mouse strains. RESEARCH DESIGN AND METHODS Hyperinsulinemic-euglycemic (approximately 8.5 mmol/l) and -hypoglycemic (approximately 3.0 mmol/l) clamps were done in catheterized, 5-h-fasted mice to assess insulin action and hypoglycemic counter-regulatory responsiveness. Hyperglycemic clamps (approximately 15 mmol/l) were done to assess insulin secretion and compared with results in perifused islets. RESULTS Insulin action and hypoglycemic counter-regulatory and insulin secretory phenotypes varied considerably in four inbred mouse strains. In vivo insulin secretion was greatest in 129X1/Sv mice, but the counter-regulatory response to hypoglycemia was blunted. FVB/N mice in vivo showed no increase in glucose-stimulated insulin secretion, relative hepatic insulin resistance, and the highest counter-regulatory response to hypoglycemia. In DBA/2 mice, insulin action was lowest among the strains, and islets isolated had the greatest glucose-stimulated insulin secretion in vitro. In C57BL/6 mice, in vivo physiological responses to hyperinsulinemia at euglycemia and hypoglycemia were intermediate relative to other strains. Insulin secretion by C57BL/6 mice was similar to that in other strains in contrast to the blunted glucose-stimulated insulin secretion from isolated islets. CONCLUSIONS Strain-dependent differences exist in four inbred mouse strains frequently used for genetic manipulation and study of glucose metabolism. These results are important for selecting inbred mice to study glucose metabolism and for interpreting and designing experiments.
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Affiliation(s)
- Eric D Berglund
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
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Kleiman A, Tuckermann JP. Glucocorticoid receptor action in beneficial and side effects of steroid therapy: lessons from conditional knockout mice. Mol Cell Endocrinol 2007; 275:98-108. [PMID: 17587493 DOI: 10.1016/j.mce.2007.05.009] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 05/12/2007] [Accepted: 05/12/2007] [Indexed: 01/19/2023]
Abstract
Glucocorticoids (GCs) are potent immune suppressive drugs with unfortunately severe side effects. Different molecular modes of actions of the GC receptor (GR) have been identified. Transcriptional transactivation by binding of a dimerized GR protein complex to the promoter of GC regulated genes or interference with activity of pro-inflammatory transcription factors by GR monomers are considered as the two major mechanisms. It has been hypothesized that selective GR agonists (SEGRAs) addressing dimer-independent function would reveal potent steroid therapeutic activity with reduced side effects. Recent studies of a mouse knock-in strain with a dimerization-deficient GR demonstrate that some inflammatory processes can be suppressed by GCs, while others cannot. Also side effects of GCs occur in these mice. Thus, depending on the process that is treated, SEGRA could be therapeutically more or less effective and not all side effects of steroid therapy may be reduced.
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Affiliation(s)
- Anna Kleiman
- Leibniz Institute for Age Research, Fritz Lipmann Institute, Group of Tissue specific Hormone Action, Beutenberg Str. 11, D-07745 Jena, Germany
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19
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Bibliography. Current world literature. Diabetes and the endocrine pancreas II. Curr Opin Endocrinol Diabetes Obes 2007; 14:329-57. [PMID: 17940461 DOI: 10.1097/med.0b013e3282c3a898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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20
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Bibliography. Current world literature. Diabetes and the endocrine pancreas. Curr Opin Endocrinol Diabetes Obes 2007; 14:170-96. [PMID: 17940437 DOI: 10.1097/med.0b013e3280d5f7e9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Jacobson L, Ansari T, McGuinness OP. Counterregulatory deficits occur within 24 h of a single hypoglycemic episode in conscious, unrestrained, chronically cannulated mice. Am J Physiol Endocrinol Metab 2006; 290:E678-84. [PMID: 16533951 PMCID: PMC1414786 DOI: 10.1152/ajpendo.00383.2005] [Citation(s) in RCA: 40] [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: 01/09/2023]
Abstract
Hypoglycemia-induced counterregulatory failure is a dangerous complication of insulin use in diabetes mellitus. Controlled hypoglycemia studies in gene knockout models, which require the use of mice, would aid in identifying causes of defective counterregulation. Because stress can influence counterregulatory hormones and glucose homeostasis, we developed glucose clamps with remote blood sampling in conscious, unrestrained mice. Male C57BL/6 mice implanted with indwelling carotid artery and jugular vein catheters were subjected to 2 h of hyperinsulinemic glucose clamps 24 h apart, with a 6-h fast before each clamp. On day 1, blood glucose was maintained (euglycemia, 178 +/- 4 mg/dl) or decreased to 62 +/- 1 mg/dl (hypoglycemia) by insulin (20 mU x kg(-1) x min(-1)) and variable glucose infusion. Donor blood was continuously infused to replace blood sample volume. Baseline plasma epinephrine (32 +/- 8 pg/ml), corticosterone (16.1 +/- 1.8 microg/dl), and glucagon (35 +/- 3 pg/ml) were unchanged during euglycemia but increased significantly during hypoglycemia, with a glycemic threshold of approximately 80 mg/dl. On day 2, all mice underwent a hypoglycemic clamp (blood glucose, 64 +/- 1 mg/dl). Compared with mice that were euglycemic on day 1, previously hypoglycemic mice had significantly higher glucose requirements and significantly lower plasma glucagon and corticosterone (n = 6/group) on day 2. Epinephrine tended to decrease, although not significantly, in repeatedly hypoglycemic mice. Pre- and post-clamp insulin levels were similar between groups. We conclude that counterregulatory responses to acute and repeated hypoglycemia in unrestrained, chronically cannulated mice reproduce aspects of counterregulation in humans, and that repeated hypoglycemia in mice is a useful model of counterregulatory failure.
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Affiliation(s)
- Lauren Jacobson
- Center for Neuropharmacology and Neuroscience, Albany Medical College, MC-136, Albany, NY 12208, USA.
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