1
|
Weir GC, Bonner-Weir S. Conflicting Views About Interactions Between Pancreatic α-Cells and β-Cells. Diabetes 2023; 72:1741-1747. [PMID: 37983524 PMCID: PMC10658062 DOI: 10.2337/db23-0292] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Accepted: 08/16/2023] [Indexed: 11/22/2023]
Abstract
In type 1 diabetes, the reduced glucagon response to insulin-induced hypoglycemia has been used to argue that β-cell secretion of insulin is required for the full glucagon counterregulatory response. For years, the concept has been that insulin from the β-cell core flows downstream to suppress glucagon secretion from the α-cells in the islet mantle. This core-mantle relationship has been supported by perfused pancreas studies that show marked increases in glucagon secretion when insulin was neutralized with antisera. Additional support comes from a growing number of studies focused on vascular anatomy and blood flow. However, in recent years this core-mantle view has generated less interest than the argument that optimal insulin secretion is due to paracrine release of glucagon from α-cells stimulating adjacent β-cells. This mechanism has been evaluated by knockout of β-cell receptors and impairment of α-cell function by inhibition of Gi designer receptors exclusively activated by designer drugs. Other studies that support this mechanism have been obtained by pharmacological blocking of glucagon-like peptide 1 receptor in humans. While glucagon has potent effects on β-cells, there are concerns with the suggested paracrine mechanism, since some of the supporting data are from isolated islets. The study of islets in static incubation or perifusion systems can be informative, but the normal paracrine relationships are disrupted by the isolation process. While this complicates interpretation of data, arguments supporting paracrine interactions between α-cells and β-cells have growing appeal. We discuss these conflicting views of the relationship between pancreatic α-cells and β-cells and seek to understand how communication depends on blood flow and/or paracrine mechanisms.
Collapse
Affiliation(s)
- Gordon C. Weir
- Joslin Diabetes Center, Harvard Medical School, Boston, MA
| | | |
Collapse
|
2
|
Li C, Liu C, Nissim I, Chen J, Chen P, Doliba N, Zhang T, Nissim I, Daikhin Y, Stokes D, Yudkoff M, Bennett MJ, Stanley CA, Matschinsky FM, Naji A. Regulation of glucagon secretion in normal and diabetic human islets by γ-hydroxybutyrate and glycine. J Biol Chem 2012; 288:3938-51. [PMID: 23266825 DOI: 10.1074/jbc.m112.385682] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Paracrine signaling between pancreatic islet β-cells and α-cells has been proposed to play a role in regulating glucagon responses to elevated glucose and hypoglycemia. To examine this possibility in human islets, we used a metabolomic approach to trace the responses of amino acids and other potential neurotransmitters to stimulation with [U-(13)C]glucose in both normal individuals and type 2 diabetics. Islets from type 2 diabetics uniformly showed decreased glucose stimulation of insulin secretion and respiratory rate but demonstrated two different patterns of glucagon responses to glucose: one group responded normally to suppression of glucagon by glucose, but the second group was non-responsive. The non-responsive group showed evidence of suppressed islet GABA levels and of GABA shunt activity. In further studies with normal human islets, we found that γ-hydroxybutyrate (GHB), a potent inhibitory neurotransmitter, is generated in β-cells by an extension of the GABA shunt during glucose stimulation and interacts with α-cell GHB receptors, thus mediating the suppressive effect of glucose on glucagon release. We also identified glycine, acting via α-cell glycine receptors, as the predominant amino acid stimulator of glucagon release. The results suggest that glycine and GHB provide a counterbalancing receptor-based mechanism for controlling α-cell secretory responses to metabolic fuels.
Collapse
Affiliation(s)
- Changhong Li
- Division of Endocrinology, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
3
|
Doliba NM, Fenner D, Zelent B, Bass J, Sarabu R, Matschinsky FM. Repair of diverse diabetic defects of β-cells in man and mouse by pharmacological glucokinase activation. Diabetes Obes Metab 2012; 14 Suppl 3:109-19. [PMID: 22928571 PMCID: PMC4433321 DOI: 10.1111/j.1463-1326.2012.01652.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glucokinase activators (GKAs) are being developed and clinically tested for potential antidiabetic therapy. The potential benefits and limitations of this approach continue to be intensively debated. To contribute to the understanding of experimental pharmacology and therapeutics of GKAs, we have tested the efficacy of one of these agents (Piragliatin) in isolated islets from humans with type 2 diabetes mellitus (T2DM), from mice with glucokinase (GK) mutations induced by ethyl-nitroso-urea (ENU) as models of Maturity Onset Diabetes of the Young linked to GK and Permanent Neonatal Diabetes Mellitus linked to GK (PNDM-GK) and finally of islets rendered glucose insensitive by treatment with the sulphonyl urea compound glyburide in organ culture. We found that the GKA repaired the defect in all three instances as manifest in increased glucose-induced insulin release and elevated intracellular calcium responses. The results show the remarkable fact that acute pharmacological activation of GK reverses secretion defects of β-cells caused by molecular mechanism that differ vastly in nature, including the little understood multifactorial lesion of β-cells in T2DM of man, the complex GK mutations in mice resembling GK disease and acute sulphonylurea failure of mouse β-cells in tissue culture. The implications of these results are to be discussed on the theoretical basis underpinning the strategy of developing these drugs and in light of recent results of clinical trials with GKAs that failed for little understood reasons.
Collapse
|
4
|
Higashimura Y, Shimoju R, Maruyama H, Kurosawa M. Electro-acupuncture improves responsiveness to insulin via excitation of somatic afferent fibers in diabetic rats. Auton Neurosci 2009; 150:100-3. [PMID: 19556171 DOI: 10.1016/j.autneu.2009.06.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Revised: 06/01/2009] [Accepted: 06/05/2009] [Indexed: 11/19/2022]
Abstract
The effects of electro-acupuncture (EA) on plasma concentration of glucose and on responsiveness to insulin were examined in an animal model of diabetes, the streptozotocin-treated rat. Two weeks after treatment with streptozotocin, rats were anesthetized with urethane-chloralose and subjected to the EA for 10 min delivered to the tibialis anterior muscle of one side. The stimulation produced no significant changes in plasma glucose concentration. In contrast, EA increased the response of plasma glucose to insulin (0.2 U kg(-1)). The effect of EA on the responsiveness to insulin was abolished by section of both sciatic and femoral nerves ipsilateral to the side of the EA. These results show that EA in diabetic rats has no effect on plasma glucose concentration while it augments the responsiveness to insulin, and we show that this occurs via a mechanism that involves the somatic afferent nerves.
Collapse
Affiliation(s)
- Yukie Higashimura
- Center for Medical Science, International University of Health and Welfare, Otawara, Tochigi, Japan
| | | | | | | |
Collapse
|
5
|
Abstract
Glucokinase, a unique isoform of the hexokinase enzymes, which are known to phosphorylate D-glucose and other hexoses, was identified during the past three to four decades as a new, promising drug target for type 2 diabetes. Glucokinase serves as a glucose sensor of the insulin-producing pancreatic islet beta-cells, controls the conversion of glucose to glycogen in the liver and regulates hepatic glucose production. Guided by this fundamental knowledge, several glucokinase activators are now being developed, and have so far been shown to lower blood glucose in several animal models of type 2 diabetes and in initial trials in humans with the disease. Here, the scientific basis and current status of this new approach to diabetes therapy are discussed.
Collapse
|
6
|
Steiner DF. Insulin-induced liver hyperplasia: evidence for a negative liver-size-correcting process. CIBA FOUNDATION SYMPOSIUM 2008:229-36. [PMID: 248002 DOI: 10.1002/9780470720363.ch12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The fate of the increased liver DNA induced by insulin treatment of rats with chronic steptozotocin-induced diabetes was studied. The DNA content of the organ was restored to normal by an active process having a half-time of 32 days. The half-time of disappearance of thymidine-labelled DNA in the same livers was 81 days. The results indicate the existence of a mechnanism which acts to restore normal liver cellularity when an over-production of cells has occurred.
Collapse
|
7
|
Araujo EP, Amaral MEC, Souza CT, Bordin S, Ferreira F, Saad MJA, Boschero AC, Magalhães EC, Velloso LA. Blockade of IRS1 in isolated rat pancreatic islets improves glucose-induced insulin secretion. FEBS Lett 2002; 531:437-42. [PMID: 12435589 DOI: 10.1016/s0014-5793(02)03580-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Several neural, hormonal and biochemical inputs actively participate in the balance of insulin secretion induced by blood glucose fluctuations. The exact role of insulin as an autocrine and paracrine participant in the control of its own secretion remains to be determined, mostly due to insufficient knowledge about the molecular phenomena that govern insulin signaling in pancreatic islets. In the present experiments we demonstrate that higher insulin receptor and insulin receptor substrates-1 and -2 (IRS1 and IRS2) concentrations are predominantly encountered in cells of the periphery of rat pancreatic islets, as compared to centrally located cells, and that partial blockade of IRS1 protein expression by antisense oligonucleotide treatment leads to improved insulin secretion induced by glucose overload, which is accompanied by lower steady-state glucagon secretion and blunted glucose-induced glucagon fall. These data reinforce the inhibitory role of insulin upon its own secretion in isolated, undisrupted pancreatic islets.
Collapse
Affiliation(s)
- Eliana P Araujo
- Department of Physiology and Biophysics, University of Campinas, Campinas, Brazil
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Kieffer TJ, Hussain MA, Habener JF. Glucagon and Glucagon‐like Peptide Production and Degradation. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
9
|
Detimary P, Dejonghe S, Ling Z, Pipeleers D, Schuit F, Henquin JC. The changes in adenine nucleotides measured in glucose-stimulated rodent islets occur in beta cells but not in alpha cells and are also observed in human islets. J Biol Chem 1998; 273:33905-8. [PMID: 9852040 DOI: 10.1074/jbc.273.51.33905] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucose metabolism by pancreatic beta and alpha cells is essential for stimulation of insulin secretion and inhibition of glucagon secretion. Studies using rodent islets have suggested that the ATP/ADP ratio serves as second messenger in beta cells. This study compared the effects of glucose on glucose oxidation ([U-14C]glucose) and adenine nucleotides (luminometric method) in purified rat alpha and beta cells. The rate of glucose oxidation at 1 mM glucose was higher in beta than alpha cells (4.5-fold, i.e. approximately 2-fold after normalization for cell size). It was more strongly stimulated by 10 mM glucose in beta cells (9-fold) than in alpha cells (5-fold). At 1 mM glucose, ATP levels were similar in both cell types, which corresponds to an approximately 2-fold higher concentration in alpha cells ( approximately 6.5 mM) than in beta cells ( approximately 3 mM). In beta cells, glucose dose-dependently increased ATP and decreased ADP levels, causing a rise in the ATP/ADP ratio from 2.4 to 11.6 at 1 and 10 mM, respectively. In alpha cells, glucose did not affect ATP and ADP levels, and the ATP/ADP ratio remained stable around 7.5. In human islets, the ATP/ADP ratio progressively increased between 1 and 10 mM glucose. In duct cells, which often contaminate human islet preparations, an increase in the ATP/ADP ratio sometimes occurred between 1 and 3 mM glucose. In conclusion, the present observations establish that the regulation of glucagon secretion by glucose does not involve changes in alpha cell adenine nucleotides and further support the role of the ATP/ADP ratio in the control of insulin secretion.
Collapse
Affiliation(s)
- P Detimary
- Unit of Endocrinology and Metabolism, Université Catholique de Louvain, B 1200 Brussels, Belgium
| | | | | | | | | | | |
Collapse
|
10
|
Expression and function of GLUT-1 and GLUT-2 glucose transporter isoforms in cells of cultured rat pancreatic islets. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41918-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
|
11
|
Ghosh A, Ronner P, Cheong E, Khalid P, Matschinsky F. The role of ATP and free ADP in metabolic coupling during fuel-stimulated insulin release from islet beta-cells in the isolated perfused rat pancreas. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54437-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
12
|
Colella RM, May JM, Bonner-Weir S, Leahy JL, Weir GC. Glucose utilization in islets of hyperglycemic rat models with impaired glucose-induced insulin secretion. Metabolism 1987; 36:335-7. [PMID: 3550372 DOI: 10.1016/0026-0495(87)90203-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Under most experimental conditions islet glucose metabolism is well-correlated with short-term glucose-induced insulin secretion. Two hyperglycemic rat models (neonatal streptozotocin and glucose infusion) have been previously found to have markedly impaired insulin responses to glucose, and the glucose utilization of islets isolated from these models was therefore studied to see if reduced glucose metabolism might be related to the secretory abnormalities. It was found that glucose utilization in the islets of the two models was similar or higher than in comparable control islets. These data suggest that the secretory defect of these models, which is presumably induced by chronic hyperglycemia, is at a step in the secretion process distal to glucose metabolism.
Collapse
|
13
|
Ostenson CG, Nylén A, Grill V, Gutniak M, Efendić S. Sulfonylurea-induced inhibition of glucagon secretion from the perfused rat pancreas: evidence for a direct, non-paracrine effect. Diabetologia 1986; 29:861-7. [PMID: 3106122 DOI: 10.1007/bf00870141] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The effects of sulfonylurea on glucagon secretion were characterized in the perfused rat pancreas using glibenclamide (1 microgram/ml) or tolazamide (10 micrograms/ml) in the presence of 3.3 mmol/l glucose. Glucagon release, which was unaffected by glibenclamide at 2.75 mmol/l calcium, was suppressed at 1.19 and 0.64 mmol/l but transiently stimulated at 0.25 mmol/l extracellular calcium. The insulinogenic effect of glibenclamide at 0.64 and 0.25 mmol/l calcium was enhanced by 35% and 89%, respectively, compared to the response at 2.75 mmol/l calcium. The stimulatory effect of the compound on somatostatin secretion, however, was lost at the lower calcium levels. The effects of tolazamide at 2.75 and 0.64 mmol/l calcium mimicked those of glibenclamide, thus indicating that our results with the latter compound may be representative for all sulfonylureas. In pancreata from insulin-deficient alloxan-diabetic rats, glibenclamide completely lost its inhibitory effect on glucagon release at 0.64 mmol/l calcium. Inhibition was not restored by adding insulin (25 U/l) to the perfusate. However, when diabetic rats had been treated with insulin for 6-7 days, glibenclamide suppressed glucagon release at low calcium levels in the absence of stimulated insulin and somatostatin release. It is concluded that, at low calcium concentrations, sulfonylureas suppress glucagon secretion by a direct action on the A cell and not through paracrine interactions by insulin and somatostatin. Prolonged insulin deficiency impairs the sulfonylurea action on glucagon secretion.
Collapse
|
14
|
Metabolic concomitants in pure, pancreatic beta cells during glucose-stimulated insulin secretion. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)66980-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
|
15
|
Meglasson MD, Matschinsky FM. Pancreatic islet glucose metabolism and regulation of insulin secretion. DIABETES/METABOLISM REVIEWS 1986; 2:163-214. [PMID: 2943567 DOI: 10.1002/dmr.5610020301] [Citation(s) in RCA: 371] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
16
|
|
17
|
Rebolledo OR, Gagliardino JJ. Glucagon and insulin secretion during acid-base alterations. ACTA DIABETOLOGICA LATINA 1983; 20:211-20. [PMID: 6356736 DOI: 10.1007/bf02581265] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Previously, we reported that change from the normal pH of 7.4 surrounding the islet cells to 7.8 results in a decreased B-cell response to 16.6 mM glucose, 10 mM arginine or 400 micrograms/ml tolbutamide. In the present report we studied the effect of modifications in the extracellular pH on glucose- and arginine-induced glucagon and insulin secretion by the perfused rat pancreas. It was found that at pH 7.8, arginine-induced glucagon secretion was significantly greater than at pH 7.4. On the other hand, the switch from pH 7.4 to 7.8 in a pancreas already stimulated by either low glucose or arginine, produced fast and transient glucagon release. Sequential extracellular pH changes from 7.4 to 7.8 and back to 7.4 in the presence of 8.3 mM glucose and a 5 mM arginine stimulus demonstrated that A- and B-cells rapidly modify their secretion in response to extracellular alkalosis in opposite directions. While glucagon output was enhanced (mean secretory rates at pH 7.4, 0.692 +/- 0.042 ng/min and 0.948 +/- 0.57 at pH 7.8), insulin secretion was clearly reduced (72.6 +/- 6.2 ng/min and 35.7 +/- 2.8 ng/min at pH 7.4 and 7.8, respectively). The above observations, together with our previously reported data, indicate that extracellular pH plays an important role in the regulation of glucagon and insulin release. Particularly, extracellular alkalosis enhances A-cell response to 2.3 mM glucose and 5 mM arginine while partially inhibiting B-cell secretion in the perfused rat pancreas.
Collapse
|
18
|
Grill V, Efendić S. Loss of a priming effect of glucose on A and D cell secretion in perfused pancreases from alloxan-diabetic rats: role of insulin and alloxan. Diabetologia 1983; 24:47-51. [PMID: 6131006 DOI: 10.1007/bf00275947] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Under normal conditions, glucose acutely influences pancreatic islet B, A and D cell secretion. In addition, prior exposure to glucose modulates the secretory responsiveness of these cells (priming effect). We have tested whether alloxan diabetes influences priming effects of glucose on A and D cell secretion. Rat pancreases were perfused 72 h after alloxan treatment. A 20 min infusion of 27.7 mmol/l of glucose failed to induce priming effects, i.e. it did not inhibit the glucagon nor amplify the somatostatin response to a subsequent (15 min later) infusion of 8 mmol/l of arginine. Insulin treatment in vivo for 48 h restored a priming effect of glucose on glucagon secretion in the perfused pancreas, i.e. exposure to 27.7 mmol/l of glucose now inhibited subsequent arginine-induced glucagon secretion by 48% relative to a stimulation period with arginine preceding the glucose pulse (from 5.0 +/- 0.7 to 2.6 +/- 0.5 ng/min, p less than 0.01). Conversely, insulin treatment in vivo did not restore a priming effect of glucose on somatostatin secretion. Other effects noted were failure of 27.7 mmol/l glucose to stimulate, during its presence, the release of somatostatin from pancreases of the diabetic rats whether untreated or insulin-treated. Furthermore, insulin treatment abolished the arginine-induced somatostatin secretion observed in pancreases from untreated rats. It is concluded that short-term alloxan diabetes leads to loss of a priming effect of glucose on glucagon secretion and that this abnormality is secondary to direct or indirect effects of insulinopenia. Concomittant abnormalities of glucose regulation of somatostatin secretion may, in part, be secondary to a cytotoxic effect of alloxan on the D cell.
Collapse
|
19
|
Honey RN, Schwarz JA, Mathe CJ, Weir GC. Insulin, glucagon, and somatostatin secretion from isolated perfused rat and chicken pancreas-duodenum. THE AMERICAN JOURNAL OF PHYSIOLOGY 1980; 238:E150-6. [PMID: 6444782 DOI: 10.1152/ajpendo.1980.238.2.e150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Insulin, glucagon, and somatostatin secretion were evaluated in the following isolated perfused models: rat pancreas-duodenum (both normal and streptozotocin-diabetic animals) and the chicken pancreas with and without duodenum. Insulin secretion in response to glucose or arginine was greater from the normal rat than either the diabetic rat or the chicken. Glucagon release from both species was suppressed by glucose and stimulated by arginine except that poor inhibition by glucose was found in the diabetic rat. Somatostatin could be measured in the effluent from both normal and diabetic rats, but the responses to glucose and arginine were variable and modest. Clear increases of secretion in the rat were only observed in response to a combination of glucose, arginine, theophylline, and isoproterenol. In contrast, the chicken somatostatin secretion was markedly stimulated by glucose and by arginine. In conclusion, the perfused chicken pancreas-duodenum has been shown to secrete large amounts of somatostatin in comparison to the rat and should prove to be a useful system for the study of D-cell regulation.
Collapse
|
20
|
Ostenson CG. Regulation of glucagon release: effects of insulin on the pancreatic A2-cell of the guinea pig. Diabetologia 1979; 17:325-30. [PMID: 387506 DOI: 10.1007/bf01235889] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
|
21
|
Leclercq-Meyer V, Marchand J, Leclercq R, Malaisse WJ. Interactions of alpha-ketoisocaproate, glucose and arginine in the secretion of glucagon and insulin from the perfused rat pancreas. Diabetologia 1979; 17:121-6. [PMID: 385405 DOI: 10.1007/bf01222213] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The effects of alpha-ketoisocaproate (KIC, 10 mmol/l) on glucagon and insulin release were studied in the in vitro perfused rat pancreas. The experiments were performed at low glucose concentration (3.3 mmol/l) in the absence or presence of arginine (10 mmol/l). In all the experiments KIC induced a marked and not rapidly reversible inhibition of glucagon release. This inhibition was more pronounced in the absence (76 percent) than presence of arginine (61 percent). These inhibitory patterns closely duplicated those which were seen in parallel experiments which included a rise in the concentration of glucose (from 3.3 to 11.1 mmol/l). KIC was also a potent stimulator of insulin release. The results are compatible with the view that the intracellular metabolism of KIC and glucose plays an essential role in the regulation of glucagon release by exogenous substrates.
Collapse
|
22
|
A comparison of the effects of glucose and acetylcholine on insulin release and intermediary metabolism in rat pancreatic islets. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(18)50675-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
|
23
|
Abstract
The current controversy concerning the role of glucagon in the pathogenesis of diabetes is reviewed. The traditional "unihormonal abnormality concept," namely, that all of the metabolic derangements of diabetes are the direct consequence of deficient insulin secretion or activity, and the newer so-called bihormonal abnormality hypothesis, proposing that the fullblown diabetic syndrome requires, in addition to the insulin abnormality, a relative glucagon excess, are scrutinized. The relationship of insulin deficiency to the A-cell malfunction of diabetes, the conflicting evidence concerning the essential role of glucagon in mediating the marked overproduction of glucose and ketones in severe insulin deficiency and the contribution of glucagon to the endogenous hyperglycemia of diabetics without insulin deficiency are examined. Finally, the possibility that therapeutic suppression of diabetic hyperglucagonemia may make possible better control of hyperglycemia than is presently attainable by conventional therapeutic methods is considered. It is concluded that (1) although insulin lowers glucagon levels, restoration to normal of the A-cell dysfunction of diabetes requires that plasma insulin levels vary appropriately with glycemic change; (2) that glucagon mediates the severe endogenous hyperglycemia and hyperketonemia observed in the absence of insulin; (3) that in diabetics in whom insulin is present but relatively fixed an increase in glucagon causes hyperglycemia and glycosuria; and (4) that glucagon suppression could be a potentially useful adjunct to conventional antihyperglycemic treatment of diabetics.
Collapse
|