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Zhou DR, Eid R, Boucher E, Miller KA, Mandato CA, Greenwood MT. Stress is an agonist for the induction of programmed cell death: A review. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:699-712. [DOI: 10.1016/j.bbamcr.2018.12.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/17/2018] [Accepted: 12/01/2018] [Indexed: 02/07/2023]
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Glucagon, a key factor in the pathophysiology of type 2 diabetes. Biochimie 2017; 143:33-36. [PMID: 29024725 DOI: 10.1016/j.biochi.2017.10.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 10/05/2017] [Indexed: 11/20/2022]
Abstract
Excessive circulating glucagon levels have been reported in all forms of diabetes, clinical or experimental. The hyperglucagonemia of diabetes results from an excessive secretion of the hormone secondary from a deficit in insulin secretion and/or a dysfunction of various cells within the islets of Langerhans (somatostatin) leading to the notion of "paracrinopathy". Hyperglucagonemia contributes to the fasting and postprandial hyperglycemia in diabetic patients through an increased hepatic glucose production (mainly gluconeogenesis). The aim of the present review is to summarize the clinical and experimental arguments suggesting that glucagon is essential for the development of glucose dysregulation in diabetes.
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Fetal endocannabinoids orchestrate the organization of pancreatic islet microarchitecture. Proc Natl Acad Sci U S A 2015; 112:E6185-94. [PMID: 26494286 DOI: 10.1073/pnas.1519040112] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Endocannabinoids are implicated in the control of glucose utilization and energy homeostasis by orchestrating pancreatic hormone release. Moreover, in some cell niches, endocannabinoids regulate cell proliferation, fate determination, and migration. Nevertheless, endocannabinoid contributions to the development of the endocrine pancreas remain unknown. Here, we show that α cells produce the endocannabinoid 2-arachidonoylglycerol (2-AG) in mouse fetuses and human pancreatic islets, which primes the recruitment of β cells by CB1 cannabinoid receptor (CB1R) engagement. Using subtractive pharmacology, we extend these findings to anandamide, a promiscuous endocannabinoid/endovanilloid ligand, which impacts both the determination of islet size by cell proliferation and α/β cell sorting by differential activation of transient receptor potential cation channel subfamily V member 1 (TRPV1) and CB1Rs. Accordingly, genetic disruption of TRPV1 channels increases islet size whereas CB1R knockout augments cellular heterogeneity and favors insulin over glucagon release. Dietary enrichment in ω-3 fatty acids during pregnancy and lactation in mice, which permanently reduces endocannabinoid levels in the offspring, phenocopies CB1R(-/-) islet microstructure and improves coordinated hormone secretion. Overall, our data mechanistically link endocannabinoids to cell proliferation and sorting during pancreatic islet formation, as well as to life-long programming of hormonal determinants of glucose homeostasis.
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Le Marchand SJ, Piston DW. Glucose suppression of glucagon secretion: metabolic and calcium responses from alpha-cells in intact mouse pancreatic islets. J Biol Chem 2010; 285:14389-98. [PMID: 20231269 DOI: 10.1074/jbc.m109.069195] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucagon is released from alpha-cells present in intact pancreatic islets at glucose concentrations below 4 mm, whereas higher glucose levels inhibit its secretion. The mechanisms underlying the suppression of alpha-cell secretory activity are poorly understood, but two general types of models have been proposed as follows: direct inhibition by glucose or paracrine inhibition from non-alpha-cells within the islet of Langerhans. To identify alpha-cells for analysis, we utilized transgenic mice expressing fluorescent proteins targeted specifically to these cells. Measurements of glucagon secretion from pure populations of flow-sorted alpha-cells show that contrary to its effect on intact islets, glucose does stimulate glucagon secretion from isolated alpha-cells. This observation argues against a direct inhibition of glucagon secretion by glucose and supports the paracrine inhibition model. Imaging of cellular metabolism by two-photon excitation of NAD(P)H autofluorescence indicates that glucose is metabolized in alpha-cells and that glucokinase is the likely rate-limiting step in this process. Imaging calcium dynamics of alpha-cells in intact islets reveals that inhibiting concentrations of glucose increase the intracellular calcium concentration and the frequency of alpha-cell calcium oscillations. Application of candidate paracrine inhibitors leads to reduced glucagon secretion but did not decrease the alpha-cell calcium activity. Taken together, the data suggest that suppression occurs downstream from alpha-cell calcium signaling, presumably at the level of vesicle trafficking or exocytotic machinery.
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Affiliation(s)
- Sylvain J Le Marchand
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232, USA
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Sandoval DA, Obici S, Seeley RJ. Targeting the CNS to treat type 2 diabetes. Nat Rev Drug Discov 2009; 8:386-98. [PMID: 19404312 DOI: 10.1038/nrd2874] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Research on the role of peripheral organs in the regulation of glucose homeostasis has led to the development of various monotherapies that aim to improve glucose uptake and insulin action in these organs for the treatment of type 2 diabetes. It is now clear that the central nervous system (CNS) also plays an important part in orchestrating appropriate glucose metabolism, with accumulating evidence linking dysregulated CNS circuits to the failure of normal glucoregulatory mechanisms. There is evidence that there is substantial overlap between the CNS circuits that regulate energy balance and those that regulate glucose levels, suggesting that their dysregulation could link obesity and diabetes. These findings present new targets for therapies that may be capable of both inducing weight loss and improving glucose regulation.
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Affiliation(s)
- Darleen A Sandoval
- Department of Psychiatry, Genome Research Institute, University of Cincinnati, 2170 East Galbraith Road, Cincinnati, Ohio 45237, USA
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6
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Abstract
Ketone bodies accumulate in the plasma in conditions of fasting and uncontrolled diabetes. The initiating event is a change in the molar ratio of glucagon:insulin. Insulin deficiency triggers the lipolytic process in adipose tissue with the result that free fatty acids pass into the plasma for uptake by liver and other tissues. Glucagon appears to be the primary hormone involved in the induction of fatty acid oxidation and ketogenesis in the liver. It acts by acutely dropping hepatic malonyl-CoA concentrations as a consequence of inhibitory effects exerted in the glycolytic pathway and on acetyl-CoA carboxylase (EC 6.4.1.2). The fall in malonyl-CoA concentration activates carnitine acyltransferase I (EC 2.3.1.21) such that long-chain fatty acids can be transported through the inner mitochondrial membrane to the enzymes of fatty acid oxidation and ketogenesis. The latter are high-capacity systems assuring that fatty acids entering the mitochondria are rapidly oxidized to ketone bodies. Thus, the rate-controlling step for ketogenesis is carnitine acyltransferase I. Administration of food after a fast, or of insulin to the diabetic subject, reduces plasma free fatty acid concentrations, increases the liver concentration of malonyl-CoA, inhibits carnitine acyltransferase I and reverses the ketogenic process.
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Rocheleau JV, Piston DW. Chapter 4 Combining Microfluidics and Quantitative Fluorescence Microscopy to Examine Pancreatic Islet Molecular Physiology. Methods Cell Biol 2008; 89:71-92. [DOI: 10.1016/s0091-679x(08)00604-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Pinheiro EC, Taddei VA, Migliorini RH, Kettelhut IC. Effect of fasting on carbohydrate metabolism in frugivorous bats (Artibeus lituratus and Artibeus jamaicensis). Comp Biochem Physiol B Biochem Mol Biol 2006; 143:279-84. [PMID: 16455278 DOI: 10.1016/j.cbpb.2005.11.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Revised: 10/21/2005] [Accepted: 11/16/2005] [Indexed: 10/25/2022]
Abstract
The compensatory changes of carbohydrate metabolism induced by fasting were investigated in frugivorous bats, Artibeus lituratus and Artibeus jamaicensis. For this purpose, plasma levels of glucose and lactate, liver and muscle glycogen content, rates of liver gluconeogenesis and the activity of related enzymes were determined in male bats. After a decrease during the first 48 h of fasting, plasma glucose levels remained constant until the end of the experimental period. Plasma lactate levels, extremely high in fed bats, decreased after 48 h of fasting. Similarly, liver glycogen content, markedly high in fed animals, was reduced to low levels after 24 h without food. Muscle glycogen was also reduced in fasted bats. The expected increase in liver gluconeogenesis during fasting was observed after 48 h of fasting. The activities of liver glucose-6-phosphatase and fructose-1,6-bisphosphatase were not affected by food withdrawn. On the other hand, fasting for 24 h induced an increase in the activity of liver cytosolic phosphoenolpyruvate carboxykinase. The data indicate that liver gluconeogenesis has an important role in the glucose homeostasis in frugivorous bats during prolonged periods of food deprivation. During short periods of fasting liver glycogenolysis seems to be the main responsible for the maintenance of glycemia.
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Affiliation(s)
- Eliana C Pinheiro
- Department of Physiological Sciences, Institute of Biological Sciences, University of Brasilia-UnB, Brasília-DF, Brazil.
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Rocheleau JV, Walker GM, Head WS, McGuinness OP, Piston DW. Microfluidic glucose stimulation reveals limited coordination of intracellular Ca2+ activity oscillations in pancreatic islets. Proc Natl Acad Sci U S A 2004; 101:12899-903. [PMID: 15317941 PMCID: PMC516492 DOI: 10.1073/pnas.0405149101] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The pancreatic islet is a functional microorgan involved in maintaining normoglycemia through regulated secretion of insulin and other hormones. Extracellular glucose stimulates insulin secretion from islet beta cells through an increase in redox state, which can be measured by NAD(P)H autofluorescence. Glucose concentrations over approximately 7 mM generate synchronous oscillations in beta cell intracellular Ca2+ concentration ([Ca2+]i), which lead to pulsatile insulin secretion. Prevailing models assume that the pancreatic islet acts as a functional syncytium, and the whole islet [Ca2+]i response has been modeled in terms of islet bursting and pacemaker models. To test these models, we developed a microfluidic device capable of partially stimulating an islet, while allowing observation of the NAD(P)H and [Ca2+]i responses. We show that beta cell [Ca2+]i oscillations occur only within regions stimulated with more than approximately 6.6 mM glucose. Furthermore, we show that tolbutamide, an antagonist of the ATP-sensitive K+ channel, allows these oscillations to travel farther into the nonstimulated regions of the islet. Our approach shows that the extent of Ca2+ propagation across the islet depends on a delicate interaction between the degree of coupling and the extent of ATP-sensitive K+-channel activation and illustrates an experimental paradigm that will have utility for many other biological systems.
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Affiliation(s)
- Jonathan V Rocheleau
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232-0615, USA
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11
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Abstract
No quantitative data are available regarding the rate of occurrence of nerve cells in association with endocrine pancreas (i.e.. neuroinsular complexes type I [NICs]), or the difference in the distribution of NICs in normal and diabetic pancreas. In this report, pancreata from 20-day, 7-week, and 9-month-old lean (Umeå +/?) and obese (Umeå ob/ob) mice, as well as 10-month-old C57BL/6JBom and Umeå ob/ob mice, were analyzed with regard to the association of acetylcholinesterase (AChE)-positive and protein gene product 9.5-like (PGP-LI) immunoreactive perikarya with islets, and not in association with islets. NIC profiles were regularly observed, but were more frequent in the 20-day-old mice than in the 9-month-old +/? and ob/ob mice. The NIC profiles were often located close to a duct or blood vessel, significantly more frequently than islet profiles in general. The data did not reveal any gross abnormality in ob/ob mice as regards the frequency of NICs or the number of AChE-positive and PGP-LI perikarya. However, the 9-month-old ob/ob mice demonstrated smaller clusters of perikarya in their NIC profiles as compared to the other mice, probably reflecting the fact that the perikarya were more widely spread out in the hyperplastic islets of adult ob/ob mice. The results show that NICs are common and represent a substantial proportion of the islets in mouse pancreas, supporting the idea that they play a role in islet physiology.
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12
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Brunicardi FC, Dyen Y, Brostrom L, Kleinman R, Colonna J, Gelabert H, Gingerich R. The circulating hormonal milieu of the endocrine pancreas in healthy individuals, organ donors, and the isolated perfused human pancreas. Pancreas 2000; 21:203-11. [PMID: 10975715 DOI: 10.1097/00006676-200008000-00014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Although basal circulating levels of individual islet cell hormones have been measured, few studies compared the molar ratios of the major hormones secreted by the endocrine pancreas. This study examined the basal levels of four major islet hormones: insulin, C-peptide (C-P), glucagon (G), and pancreatic polypeptide (PP) in normal subjects, in organ donors with brain death, and in the isolated perfused human pancreas. Basal blood samples were taken from normal, fasted control subjects (NCs). Pancreata were obtained from 17 organ donors (ODs) with donor portal vein (DPV) and radial arterial (DRA) blood samples taken before organ procurement. Single-pass perfusion was performed on the procured pancreata, and after rewarming and equilibration, basal samples were collected from the splenic vein (SV) for 30 min. Radioimmunoassays of insulin, C-P, G, and PP were performed on all samples, and basal levels of all hormones were expressed as a common unit, femtomoles per milliliter. The data suggest that in the basal state, these four major islet hormones circulate in a relatively constant molar ratio. The ratio of the hormones is altered in brain death and with in vitro perfusion of the pancreas. The isolated perfused human pancreas secretes a relatively constant molar ratio of these hormones; however, this ratio is markedly different from the circulating ratio seen in either the NC group or the OD group. We conclude that a relatively constant hormonal milieu is secreted from the normal endocrine pancreas, and this hormonal milieu is altered after brain death and with isolation and perfusion of the human pancreas.
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Affiliation(s)
- F C Brunicardi
- Department of Surgery, Baylor College of Medicine, Houston, Texas 77030, USA.
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O'Doherty RM, Jensen PB, Anderson P, Jones JG, Berman HK, Kearney D, Newgard CB. Activation of direct and indirect pathways of glycogen synthesis by hepatic overexpression of protein targeting to glycogen. J Clin Invest 2000; 105:479-88. [PMID: 10683377 PMCID: PMC289167 DOI: 10.1172/jci8673] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Glycogen-targeting subunits of protein phosphatase-1, such as protein targeting to glycogen (PTG), direct the phosphatase to the glycogen particle, where it stimulates glycogenesis. We have investigated the metabolic impact of overexpressing PTG in liver of normal rats. After administration of PTG cDNA in a recombinant adenovirus, animals were fasted or allowed to continue feeding for 24 hours. Liver glycogen was nearly completely depleted in fasted control animals, whereas glycogen levels in fasted or fed PTG-overexpressing animals were 70% higher than in fed controls. Nevertheless, transgenic animals regulated plasma glucose, triglycerides, FFAs, ketones, and insulin normally in the fasted and fed states. Fasted PTG-overexpressing animals receiving an oral bolus of [U-(13)C]glucose exhibited a large increase in hepatic glycogen content and a 70% increase in incorporation of [(13)C]glucose into glycogen. However, incorporation of labeled glucose accounted for only a small portion of the glycogen synthesized in PTG-overexpressing animals, consistent with our earlier finding that PTG promotes glycogen synthesis from gluconeogenic precursors. We conclude that hepatic PTG overexpression activates both direct and indirect pathways of glycogen synthesis. Because of its ability to enhance glucose storage without affecting other metabolic indicators, the glycogen-targeting subunit may prove valuable in controlling blood glucose levels in diabetes.
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Affiliation(s)
- R M O'Doherty
- Gifford Laboratories for Diabetes Research, Marjorie Touchstone Diabetes Center, Department of Biochemistry, Dallas, Texas, USA
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Willing AE, Koopmans HS, Walls EK. Hepatic portal and vena cava insulin infusion increase food intake in diabetic rats. Physiol Behav 1994; 56:993-1001. [PMID: 7824602 DOI: 10.1016/0031-9384(94)90334-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
To test whether the route of insulin delivery has a major effect on the increase in daily food intake associated with chronic insulin treatment, insulin was continuously infused into either the vena cava (VC) or the hepatic portal (HP) vein of 23 diabetic Lewis rats. Increasing insulin doses in both the VC (2 to 6 U/day) and HP (1.5 to 3.5 U/day) groups significantly increased daily food intake (p < .05). Intake was higher in the VC group at 3 U/day but not at 2U/day. When insulin was delivered at a low fixed dose, daily food intake of both the VC and HP groups only increased after urinary glucose losses increased. The rate of weight gain increased significantly in the VC varied group (p < .05). Insulin administration also increased energy expenditure (p < .01). These results suggest that the extent of the increase in daily food intake and body weight that occurs with peripheral exogenous insulin administration is dependent on the route of infusion.
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Affiliation(s)
- A E Willing
- Department of Medical Science, University of Calgary, Alberta, Canada
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15
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Madureira ML. Ultrastructural characterization of a regular schwann-axon-islet complex after the autograft of pancreatic fragments into the spleen of the adult dog. Cell Transplant 1994; 3:153-62. [PMID: 8012731 DOI: 10.1177/096368979400300203] [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: 01/28/2023] Open
Abstract
After autotransplantation of pancreatic fragments into the dog's spleen, the morphogenesis of the reinnervating process has evolved as an highly differentiated model, reproducing the most peculiar and systematic relationships between schwann cells, axons, and islet cells reported in the dog's islet, despite it's modulation by the restrictive conditions derived from the intrasplenic location of the dispersed pancreatic tissue. The reinnervating process is described, emphasizing the peculiar ultrastructural features and topography of the schwann cells and of the axonal network that impose the concept of a true anatomical reinnervation, which make previsible the possibility of a very selective and direct neurochemical and/or electrotonic control of the engrafted islet cells. The schwann-axon-islet complexes are a very peculiar and regular arrangement between islet cells and nervous elements and are reproduced after the autotransplant without the engrafted ganglia, whose potential but aleatory contribution could not be unequivocally characterized. Axonal profiles or schwann cells on the abundant regenerated ductal-acinar structures were not identified.
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Affiliation(s)
- M L Madureira
- Department of Surgery, University of Oporto School of Medicine, Portugal
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Meacham LR, Caplan DB, McKean LP, Buchanan CN, Parks JS, Culler FL. Preservation of somatostatin secretion in cystic fibrosis patients with diabetes. Arch Dis Child 1993; 68:123-5. [PMID: 8094610 PMCID: PMC1029198 DOI: 10.1136/adc.68.1.123] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Immunohistochemical studies of pancreatic tissue from patients with cystic fibrosis associated with diabetes mellitus (CFDM) show increased numbers of somatostatin secreting delta cells. To look for a possible functional correlate to this finding basal and arginine stimulated plasma somatostatin and serum C peptide concentrations in eight insulin treated patients with cystic fibrosis and eight normal male controls were measured. Mean basal somatostatin concentrations were not different in the two groups. Mean peak somatostatin concentrations were significantly higher in the group with CFDM: 11.60 pmol/l v 7.14 pmol/l in controls. Mean peak C peptide concentrations were significantly lower in the group with cystic fibrosis: 0.89 nmol/l v 4.27 nmol/l in controls. This observation provides a physiological correlate to the pathological finding of increased somatostatin content in pancreatic tissue from patients with CFDM. Selective preservation of somatostatin secretion in patients with cystic fibrosis may further complicate pancreatic endocrine insufficiencies through paracrine inhibition of insulin and glucagon secretion.
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Affiliation(s)
- L R Meacham
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia
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Koiter TR, Faas MM, Visscher A, Kievit C, Steffens AB, Schuiling GA. Regulation of peripheral glucagon concentrations in cyclic, pregnant, and lactating rats. Physiol Behav 1992; 51:1173-8. [PMID: 1641417 DOI: 10.1016/0031-9384(92)90304-k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In the rat, peripheral glucagon concentrations were studied throughout pregnancy and lactation. Basal glucose concentrations were decreased during late pregnancy and during lactation, but basal glucagon concentrations were not affected. Infusion of glucose (7.4 mg/min) caused an elevation of the glucose concentrations, which became lower in the course of lactation, and a suppression of the glucagon concentrations which was the same throughout pregnancy and lactation. Ingestion of 336 mg of glucose or 1 g of rat chow throughout pregnancy and lactation induced a transient increase of the glucose concentrations and a biphasic glucagon response: following a short-lasting elevation, the glucagon concentrations became suppressed. The glucagon responses to these tests did not change during pregnancy and lactation. It is concluded that the regulation of the peripheral glucagon concentration is not affected by pregnancy or lactation, and that the response of the glucagon concentration to a metabolic challenge varies with the kind of test (oral or intravenous) used.
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Affiliation(s)
- T R Koiter
- Department of Obstetrics and Gynaecology, University of Groningen, The Netherlands
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18
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Abstract
Serum viscosity's increase in diabetes has been linked to the presence of microvascular sequelae and to changes in serum protein composition. The major change is a decline in albumin and an increase in the levels of acute-phase proteins. In this study, albumin and five acute phase proteins--alpha-1 acid glycoprotein, alpha-1 antitrypsin, haptoglobin, ceruloplasmin, and C-reactive protein--were measured. Levels in adult diabetes (principally type II) were compared with those in both subjects with glucose intolerance and control subjects (healthy subjects and nondiabetic ambulatory patients). Haptoglobin, alpha-1 acid glycoprotein, and C-reactive protein increased markedly in both diabetes and glucose intolerance; ceruloplasmin and alpha-1 antitrypsin increased more marginally. Serum albumin level decreased more strikingly as hyperglycemia advanced. Acute-phase proteins also increased in advanced glucose intolerance as in established diabetes. The acute-phase protein elevation did not differ with degree of control or duration of diabetes. When diabetics were divided into those with and without clinically detectable evidence of microvascular sequelae, elevation of haptoglobin, C-reactive protein and alpha-1 acid glycoprotein, and depression of albumin were found to progress with number of sequelae. The levels of these proteins, particularly haptoglobin, were also highly correlated with serum viscosity expressed as viscosity number. Mild serum albumin depression and a more striking acute-phase protein elevation are greater in diabetes with microangiopathy, develop in glucose intolerance, and contribute substantially to elevated plasma viscosity in diabetes.
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Affiliation(s)
- D E McMillan
- Sansum Medical Research Foundation, University of South Florida College of Medicine, Tampa
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19
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Stagner JI, Samols E, Marks V. The anterograde and retrograde infusion of glucagon antibodies suggests that A cells are vascularly perfused before D cells within the rat islet. Diabetologia 1989; 32:203-6. [PMID: 2568960 DOI: 10.1007/bf00265095] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have suggested that the order of cellular vascular perfusion within the islet is important in the regulation of islet hormone secretion. Anatomically, the A and D cells appear to be randomly dispersed throughout the mantle. Although islet capillary blood flow is known to be from the B-cell core to the A- and D-cell mantle, it has not yet been established whether the cells of the mantle may influence one another vascularly. Rat pancreata were perfused in vitro anterogradely and retrogradely with or without glucagon antibody in order to determine the order of cellular perfusion and interaction between the A and D cells in the islet mantle. Anterograde infusion of glucagon antibody did not affect insulin secretion, but rapidly decreased somatostatin secretion -46 +/- 8%, (p less than 0.005). Retrograde infusion of glucagon antibody decreased insulin secretion (-27 +/- 8%, p less than 0.005) but had no effect upon somatostatin secretion. This study not only confirms a core to mantle islet perfusion but also establishes that the A cell precedes the D cell in the terms of vascular perfusion. Thus within the islet, vascular borne insulin regulates the release of glucagon, which in turn, regulates the release of somatostatin. Somatostatin is vascularly neutral owing to its downstream position in the sequence (B to A to D) of cellular perfusion.
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20
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Hazelwood RL, Cieslak SR. In vitro release of pancreatic hormones following 99% pancreatectomy in the chicken. Gen Comp Endocrinol 1989; 73:308-17. [PMID: 2565276 DOI: 10.1016/0016-6480(89)90104-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In vitro assessment was made of the hormone-release capability of splenic pancreatic tissue 16 days after adult chickens had 99% of the pancreatic mass surgically removed. The objective of this study was to evaluate if the enlargement of the splenic lobe remnant after 99% pancreatectomy was attended by alterations in the responsivity of hormone release and, if so, were such changes reflective of all pancreatic hormones. After a 24-hr fast, splenic lobe tissue was obtained from young adult chickens on Postoperative Day 16, diced into 18-22 mg cubes, and incubated in vitro in media containing varying amounts of glucose with or without added somatostatin (SRIF). At 15-min intervals, the tissue cubes were transferred to fresh media and samples of each medium measured for insulin, glucagon, and APP. Viability of the tissue after 75 min was tested by tissue response to added 5 mM phenylalanine. The results obtained indicated that while total content of all four hormones (including SRIF) increased with tissue enlargement, the concentration of each decreased significantly except for SRIF, which remained at control levels. Further, the sensitivity of the B-cell in releasing insulin when confronted by a glucose challenge was not altered by previous pancreatectomy, while that of glucagon release from the A-cell was depressed. A-cell responsivity to SRIF does not appear to be adversely affected by previous 99% pancreatectomy. APP release was least affected by SRIF addition to the media, although depression by high glucose occurred. It is concluded that differential alterations occur in chicken pancreatic hormone-releasing cells as a result of 99% pancreatectomy. The efficacy in maintaining low, but still adequate, plasma I/G molar ratios (reported earlier) by the splenic remnant tissue either reflects a remarkable functional readjustment to surgical removal of 99% of the pancreatic mass in chickens or, alternatively, suggests the existence of extrapancreatic sources of insulin and glucagon, but not APP.
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Affiliation(s)
- R L Hazelwood
- Department of Biology, University of Houston, Texas 77204-5513
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21
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Newgard CB, Hwang PK, Fletterick RJ. The family of glycogen phosphorylases: structure and function. Crit Rev Biochem Mol Biol 1989; 24:69-99. [PMID: 2667896 DOI: 10.3109/10409238909082552] [Citation(s) in RCA: 295] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Glycogen phosphorylase plays a central role in the mobilization of carbohydrate reserves in a wide variety of organisms and tissues. While rabbit muscle phosphorylase remains the most studied and best characterized of phosphorylases, recombinant DNA techniques have led to the recent appearance of primary sequence data for a wide variety of phosphorylase enzymes. The functional properties of rabbit muscle phosphorylases are reviewed and then compared to properties of phosphorylases from other tissues and organisms. Tissue expression patterns and the chromosomal localization of mammalian phosphorylases are described. Differences in functional properties among phosphorylases are related to new structural information. Evolutionary relationships among phosphorylases as afforded by comparative analysis of proteins and gene sequences are discussed.
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Affiliation(s)
- C B Newgard
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas
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Issad T, Coupé C, Pastor-Anglada M, Ferré P, Girard J. Development of insulin-sensitivity at weaning in the rat. Role of the nutritional transition. Biochem J 1988; 251:685-90. [PMID: 3046600 PMCID: PMC1149059 DOI: 10.1042/bj2510685] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This study was undertaken to determine the factors involved in the development of insulin-sensitivity at weaning. Glucose kinetics were studied in suckling rats and in rats weaned on to a high-carbohydrate (HC) or a high-fat (HF) diet, in the basal state and during euglycaemic-hyperinsulinaemic-clamp studies. These studies were coupled with the 2-deoxyglucose technique, allowing a measure of glucose utilization by individual tissues. In the basal state, the glycaemia was higher in HF-weaned rats (124 +/- 4 mg/dl) than in suckling (109 +/- 1 mg/dl) and HC-weaned rats (101 +/- 3 mg/dl). Glucose turnover rates were similar in the three groups of animals (14 mg/min per kg). Nevertheless, basal metabolic glucose clearance rate was 20% lower in HF-weaned rats than in the other groups. During the euglycaemic-hyperinsulinaemic experiments, hepatic glucose production was suppressed by 90% in HC-weaned rats, whereas it remained at 40% of basal value in suckling and HF-weaned rats, indicating an insulin resistance of liver of these animals. Glucose clearance rate during the clamp was 18.3 +/- 0.9 ml/min per kg in suckling rats, whereas it was 35.3 +/- 1.2 ml/min per kg in HC-weaned rats and 27.8 +/- 1.1 ml/min per kg in HF-weaned rats, indicating an insulin resistance of glucose utilization in suckling, and to a lower extent, in HF-weaned rats. The deoxyglucose technique showed that peripheral insulin resistance was localized in muscles and white adipose tissue of suckling and HF-weaned rats. These results indicate that the switch from milk to a HC diet is an important determinant of the development of insulin-sensitivity at weaning in the rat.
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Affiliation(s)
- T Issad
- Centre de Recherches sur la Nutrition, CNRS, Meudon-Bellevue, France
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Grossman SP. The role of glucose, insulin and glucagon in the regulation of food intake and body weight. Neurosci Biobehav Rev 1986; 10:295-315. [PMID: 3095717 DOI: 10.1016/0149-7634(86)90015-1] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Glucose and related pancreatic hormones play a major role in the metabolism of monogastric mammals yet their influence on hunger and/or satiety is, as yet, poorly understood. Glucose, insulin and glucagon rise during a meal and gradually decline to baseline levels shortly after a meal. A sudden drop in plasma glucose as well as insulin have been reported just prior to the onset of a meal but the functional significance of this is not yet clear. Systemic injections of glucose have no acute satiety effects but intraduodenal and intrahepatic infusions reduce food intake and free-feeding and deprived animals respectively. Treatments which decrease cellular glucose utilization directly (2-DG) or indirectly (insulin) increase food intake while exogenous glucagon (which produces hyperglycemia) decreases it. There is considerable evidence that some or all of these effects may be due to a direct central action of glucose, 2-DG, insulin, and glucagon on brain mechanisms concerned with the regulation of hunger and satiety although influences on peripheral "glucoreceptors" have been demonstrated as well. The functional significance of glucoprivic feeding is, however, questioned. The feeding response to 2-DG and related compounds is capricious, and its temporal course does not parallel the hyperglycemic reaction which presumably reflects cellular glucopenia. Moreover, numerous brain lesions which increase, decrease, or have no effect on ad lib intake and often have no effect on the response to deprivation have been shown to severely impair or abolish feeding responses to systemic injections of 2-DG that produce severe central as well as peripheral glucopenia. Feeding responses to insulin are intact after most of these lesions, suggesting that this hormone may influence food intake in a fundamentally different fashion. The mechanism of insulin action is not understood--the classic feeding response is obtained only with doses that are pharmacological when compared to normal plasma levels and there is increasing evidence that lower doses may have opposite, inhibitory effects on food intake and body weight. Relatively small doses of glucagon decrease food intake (although opposite facilitatory effects have been reported after even smaller doses) but the effect does not appear to be due to hepatic mobilization of glucose as initially assumed. Decreases in food intake after intracranial injections of very small doses suggest a direct central action.
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Stagner JI, Samols E. Retrograde perfusion as a model for testing the relative effects of glucose versus insulin on the A cell. J Clin Invest 1986; 77:1034-7. [PMID: 3512599 PMCID: PMC423513 DOI: 10.1172/jci112356] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
In order to determine whether the A cell may be directly suppressed by glucose in the absence of insulin, canine pancreata were perfused in vitro, both antegrade, through the arterial system and retrograde, through the venous system. Studies of the islet microvasculature have suggested that blood flows from the B cell core to the mantle; thus, the A cell may be tonically inhibited by intra-islet insulin. Retrograde perfusion may then be expected to prevent insulin from reaching the A cell, releasing it from inhibition. Retrograde perfusion with 88 mg/dl glucose markedly increased both insulin and glucagon secretion relative to antegrade levels. In a series of experiments, glucose concentrations were changed from 88 to 200 mg/dl. An antegrade glucose change resulted in increased insulin (134+/-21%; P less than 0.0025) and decreased glucagon (-26+/-9%, P less than 0.025) secretion. A retrograde glucose increase resulted in increased secretion of both insulin (91+/-15%; P less than 0.0005) and glucagon (23+/-9%; P less than 0.0125). To confirm that retrograde perfusion deprived the A cell of endogenous core derived, vascularly delivered insulin, possibly resulting in increased insulin sensitivity, 0.3 mU/ml exogenous porcine insulin was infused. Antegrade, 0.3 mU/ml insulin, had no effect on glucagon secretion (P less than 0.250), while retrograde infusion of 0.3 mU/ml insulin significantly inhibited glucagon secretion (-31 + 8%; P less than 0.0005). The results of our study support the concept that the direction of blood flow and of flow-dependent intra-islet hormone interactions are from the islet B cell core to the mantle. It was further concluded that the normal A cell may not be suppressed by glucose in the absence of insulin.
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Steffens AB, Scheurink AJ, Luiten PG. Interference of the nutritional condition of the rat with peripheral glucose regulation determined by CNS mechanisms. Physiol Behav 1985; 35:405-10. [PMID: 3906710 DOI: 10.1016/0031-9384(85)90316-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Glucose and insulin levels of the cerebrospinal fluid (CSF) were changed by an infusion of either glucose, insulin or a mixture of glucose and insulin in the third ventricle of freely moving undisturbed rats. Before, during and after infusions venous blood samples were withdrawn to determine insulin- and glucose concentrations. In rats on carbohydrate rich food neither plasma insulin nor blood glucose changed during infusion of either glucose, insulin or a mixture of both. However, in rats on carbohydrate free food an immediate decline in blood glucose of about 7 mg/dl occurred 15 min after the start of the infusion. During infusion of a mixture of glucose and insulin, blood glucose rose slightly and reached a value which was in between those attained when glucose and insulin were infused separately. Plasma insulin did not change following central infusions. It is argued that the central nervous system (CNS) is sensitive to changes in CSF levels of glucose and insulin and affects peripheral glucose homeostasis mainly by changing glucose output from the liver. This action of the CNS, however, is dependent on the nutritional condition of the animal.
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Abstract
Recent advances in the understanding of glucagon-insulin relationships at the level of the islets of Langerhans and of hepatic fuel metabolism are reviewed and their impact on our understanding of glucagon physiology and pathophysiology is considered. It now appears that alpha cells can respond directly to hyperglycaemia in the absence of insulin and beta cells, but that antecedent hyperglycaemia masks or attenuates this response. Insulin appears to exert ongoing release inhibition upon glucagon secretion, probably via the intra-islet microvascular system that connects beta cells to alpha cells. Diabetic hyperglucagonemia in insulin deficient states appears to be secondary to lack of the restraining influence of insulin. The alpha cell response to glucopenia, by contrast, may be in large part mediated by release of noradrenaline from nerve endings in contact with alpha cells. Glucagon's action on glucose and ketone production by hepatocytes is mediated by increase in cyclic-AMP-dependent protein kinase. The opposing action of insulin upon glucagon-mediated events probably occurs largely at this level. Consequently, when glucagon secretion or action is blocked, cyclic-AMP-dependent protein kinase activity is low even in the absence of insulin, explaining why marked glucose and ketone production is absent in bihormonal deficiency states.
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Draznin B, Leitner JW, Sussman KE. A unique control mechanism in the regulation of insulin secretion. Secretagogue-induced somatostatin receptor recruitment. J Clin Invest 1985; 75:1510-6. [PMID: 2581996 PMCID: PMC425490 DOI: 10.1172/jci111855] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In this study, we have correlated the translocation of somatostatin (SRIF) receptors from the cell interior to the plasma membrane with the ability of SRIF to inhibit insulin release. Islets were perifused with glucose (30, 100, 165, 200, or 300 mg/dl) in the presence of sodium isethionate. Sodium isethionate inhibits insulin release, but not the recruitment of SRIF receptors. Thus, the recruitment of SRIF receptors to the surface membrane continued without the lysis of secretion vesicles. SRIF binding rose from 3.75 +/- 0.16 to 6.46 +/- 0.28 fmol/10 islets as glucose concentration increased. Sodium isethionate was then removed, islets perifused with low glucose (30 mg/dl), and challenged with 400 microM isobutylmethylxanthine (IBMX) with or without SRIF (5 micrograms/ml). In the islets perifused with high glucose concentration, IBMX lysed a greater number of vesicles and caused enhanced release of insulin. The greater the number of secretion vesicles marginated to the plasma membrane by glucose, the greater the response to IBMX. Colchicine (1 mM) prevented secretion vesicle migration and this potentiation effect of higher concentrations of glucose was eliminated. In experiments with IBMX and SRIF, the degree of inhibition of IBMX-induced insulin release by SRIF was proportional to the magnitude of SRIF binding to these islets. SRIF inhibited insulin release by 20 microU/100 islets initially perifused with low glucose (30 mg/dl) and by 875 microU/100 islets perifused with high glucose (300 mg/dl). The maximal effect of SRIF was observed when its binding reached a level of 5.4 fmol/10 islets. We conclude that inhibition of insulin release by SRIF is proportional to the SRIF receptor concentration, and that translocation of SRIF receptors during exocytosis plays an important role in paracrine regulation of insulin secretion by rendering the islets more sensitive to SRIF.
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Madureira ML, Adolfo A, Dias J, Sebe M, Carvalhais HA, von Hafe P. Reinnervation of the endocrine pancreas after autotransplantation of pancreatic fragments in the spleen of the dog: a morphofunctional study. World J Surg 1985; 9:335-47. [PMID: 3922131 DOI: 10.1007/bf01656330] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Duong TN, Ghazi A, Levan VH. Glucagon and insulin release in totally gastrectomized rats. EXPERIMENTAL PATHOLOGY 1985; 27:227-31. [PMID: 3896839 DOI: 10.1016/s0232-1513(85)80063-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In the fasting state, totally gastrectomized rats had higher glycemia, higher glucagonemia and lower insulinemia than normal rats. However, they are not prediabetic or diabetic, because after a glucose tolerance test the response of glucagon secretion, though accentuated at the beginning, decreased sharply when insulin secretion was stimulated. The evolution of glucagonemia and insulinemia indicated that the positive-negative feedback of the couple alpha-beta cells of islets of Langerhans still regulated glucose homeostasis. Hypoglycemia seen after the glucose test in operated rats disappeared when soluble starch replaced glucose. With soluble starch, hyperglycemia, hyperglucagonemia and hyperinsulinemia were less marked than with glucose at 30 min. Therefore, we conclude that 1) Gastrectomy, in removing the stomach with all its physiological role, has conferred to the operated rat in the fasting state a new level of hormonal glucose counterregulation close to the diabetic or prediabetic situation; but once the animal is fed, its endocrine pancreas responses quite normally, and 2) In the sugar tolerance test, soluble starch induces less release of glucagon and insulin than glucose.
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30
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Borghi VC, Wajchenberg BL, Cesar FP. Plasma glucagon suppressibility after oral glucose in obese subjects with normal and impaired glucose tolerance. Metabolism 1984; 33:1068-74. [PMID: 6390086 DOI: 10.1016/0026-0495(84)90089-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Blood glucose, plasma insulin, and glucagon responses after a 75 g oral glucose-tolerance test were assessed in 9 normal controls, 5 obese nondiabetics (ON), 5 obese nondiabetics with fasting hyperinsulinemia (obese "resistant" nondiabetics--OR), 9 obese with impaired glucose tolerance (O-IGT), and 9 nonobese insulin-dependent diabetics (IDD). Fasting plasma glucagon concentrations were significantly higher in all groups of patients in comparison to the normal controls. Insulin secretion, evaluated in all but the IDD, was similar to normal in the ON and increased in the OR and O-IGT. Normal glucagon suppression was observed in the lean controls and ON but not in OR, O-IGT, and IDD. We suggested that the resistance to glucagon suppression after glucose load in the OR and O-IGT in the presence of increased insulin response could be an indication that the A cell participates in the relative insulin insensitivity of these subjects.
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Mills SE, Lyle RR, Beitz DC, Young JW. In vitro hepatic gluconeogenesis during experimental ketosis produced in steers by 1,3-butanediol and phlorizin. J Dairy Sci 1984; 67:2265-73. [PMID: 6501646 DOI: 10.3168/jds.s0022-0302(84)81574-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Adaptations of in vitro incorporation of gluconeogenic substrates into glucose and adaptations of metabolite concentrations of liver to subcutaneous phlorizin and dietary 1,3-butanediol were examined for liver samples from dairy steers. Later, the same adaptations were examined after 6 days of feed restriction. Feeding 1,3-butanediol significantly decreased conversion of carbon-14 of lactate and propionate to glucose and to carbon dioxide. There were no changes of concentrations of hepatic glycogen or triglyceride, and increases were only minor for beta-hydroxybutyrate concentration. Both phlorizin, with or without 1,3-butanediol, and feed restriction significantly increased rates of carbon incorporation into glucose from aspartate, lactate, and propionate but did not change rates of oxidation to carbon dioxide. Phlorizin had no effect on hepatic glycogen or triglyceride concentrations, but feed restriction decreased liver glycogen and increased triglyceride concentrations. Changes associated with either phlorizin treatment or feed restriction are consistent with a decreased ratio of insulin to glucagon of blood plasma. When combined, phlorizin and 1,3-butanediol seem to have some utility for developing a ketosis model.
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32
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Kennedy L, Baynes JW. Non-enzymatic glycosylation and the chronic complications of diabetes: an overview. Diabetologia 1984; 26:93-8. [PMID: 6370764 DOI: 10.1007/bf00281113] [Citation(s) in RCA: 229] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Abstract
To investigate whether glucose has an effect on the pancreatic A cell independent of intraislet or paracrine B cell mediation, we have tested the ability of changes in plasma glucose (PG) level to influence the acute glucagon response (AGR) to 5 g of intravenous arginine in 8 C-peptide negative insulin dependent diabetics (IDD). Insulin was infused (1 mU/kg/min) for a 90 min basal period during which PG levels were maintained constant by the glucose clamp technique. Basal AGR was then determined. In 4 of the diabetics, the PG level was subsequently lowered to a new steady state and, in 2 diabetics, PG level was raised. In 2 additional IDDs, two manipulations in PG level were carried out (PG ranges 51-390 mg/dl). The same insulin infusion was continued throughout. The acute glucagon response to arginine was determined at each PG level. The ability of unit changes in PG to influence (modulate) the AGR (MdIRG) was calculated as the difference in AGRs divided by the PG difference. MdIRG was consistent between diabetics (means +/- SEM = 2.1 +/- 0.2) and was independent of both direction and magnitude of the PG change. Thus, in vivo, in man, glucose has an effect on the pancreatic A cell which is independent of intraislet B cell influences.
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Nakadate T, Nakaki T, Yamamoto S, Kato R. Protection against alloxan-induced diabetes in mice by stimulation of alpha 2-adrenergic receptors. Life Sci 1983; 32:697-702. [PMID: 6131370 DOI: 10.1016/0024-3205(83)90301-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A single intravenous injection of alloxan in mice induced hyperglycemia in a dose dependent fashion. This diabetogenic action of alloxan was prevented by a single intraperitoneal injection of the alpha 2-adrenergic agonists, i.e. oxymetazoline, clonidine or epinephrine 40 min prior to the injection of alloxan. The alpha 1-adrenergic agonists, i.e. methoxamine and phenylephrine, and a beta-adrenergic agonist, isoproterenol, failed to prevent the diabetogenic action of alloxan. The inhibitory effect of clonidine on alloxan-induced diabetes was antagonized by yohimbine or phentolamine, but not by prazosin. Although alpha 2-adrenergic agonists caused a transient hyperglycemia at the time of alloxan administration (40 min after the administration of alpha 2-adrenergic agonists), the plasma glucose level at the time of alloxan injection did not correlate with the anti-diabetogenic effect of alpha 2-adrenergic agents. These results clearly demonstrate that the alpha 2-adrenergic mechanism which inhibits insulin release from pancreatic B cells prevented the diabetogenic action of alloxan in mice.
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Wood SM, Polak JM, Bloom SR. Neuropeptides in the control of the islets of Langerhans. ADVANCES IN METABOLIC DISORDERS 1983; 10:401-20. [PMID: 6141707 DOI: 10.1016/b978-0-12-027310-2.50021-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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36
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Hoo-Paris R, Hamsany M, Sutter BC, Assan R, Boillot J. Plasma glucose and glucagon concentrations in the hibernating hedgehog. Gen Comp Endocrinol 1982; 46:246-54. [PMID: 7106546 DOI: 10.1016/0016-6480(82)90206-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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37
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