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Liu F, Gong L, Qin W, Cui C, Chen L, Zhang M. Glucagon-Like Peptide 1 Attenuates Lipotoxicity-Induced Islet Dysfunction in ApoE -/- Mice. Diabetes Metab Syndr Obes 2020; 13:2701-2709. [PMID: 32801816 PMCID: PMC7395686 DOI: 10.2147/dmso.s262479] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 07/08/2020] [Indexed: 11/23/2022] Open
Abstract
AIM Glucagon-like peptide-1 (GLP1) is known to decrease glucagon release and may be beneficial for the reduction of elevated blood glucose. However, its role and mechanism of action in diabetes remain elusive. This study aimed to examine the function of GLP1 and analyze the mechanism of effect that GLP1exerts on inducible nitric oxide synthase (iNOS) in diabetic mice. METHODS A diabetes model was established in ApoE-/- mice fed a high-fat diet and treated with GLP1 and/or lentivirus-expressing PARP1. PARP1, iNOS, and inflammatory factors in islets were detected by Western blot and ELISA. Islet α cells and β cells and CD8+ T lymphocytes were detected by immunostaining. Islet-cell apoptosis was detected by TUNEL. RESULTS GLP1 inhibited the expression of PARP1 and iNOS in islets, alleviated decrease in β cells, and suppressed cell apoptosis induced by the high-fat diet. Moreover, GLP1 recovered the decline in insulin sensitivity and glucose tolerance in ApoE-/- mice fed the high-fat diet, and the effects of GLP1 were related to the inhibition of COX2 and NFκB expression. CONCLUSION GLP1 significantly alleviated the decrease in β-cell numbers, suppressed β-cell apoptosis induced by the high-fat diet, inhibited the expression of iNOS, and alleviated inflammatory islet injury via inhibiting the COX2-NFκB pathway.
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Affiliation(s)
- Fuqiang Liu
- Department of Endocrinology, Qilu Hospital, Shandong University, Jinan250012, People’s Republic of China
- Institute of Endocrine and Metabolic Diseases, Shandong University, Jinan250012, People’s Republic of China
- Key Laboratory of Endocrine and Metabolic Diseases, Shandong Province Medicine and Health, Jinan, People’s Republic of China
- Jinan Clinical Research Center for Endocrine and Metabolic Diseases, Jinan, People’s Republic of China
| | - Lei Gong
- Department of Endocrinology, Qilu Hospital, Shandong University, Jinan250012, People’s Republic of China
- Institute of Endocrine and Metabolic Diseases, Shandong University, Jinan250012, People’s Republic of China
- Key Laboratory of Endocrine and Metabolic Diseases, Shandong Province Medicine and Health, Jinan, People’s Republic of China
- Jinan Clinical Research Center for Endocrine and Metabolic Diseases, Jinan, People’s Republic of China
| | - Weidong Qin
- Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Public Health, Qilu Hospital, Shandong University, JinanShandong250012, People’s Republic of China
| | - Chen Cui
- Department of Endocrinology, Qilu Hospital, Shandong University, Jinan250012, People’s Republic of China
- Institute of Endocrine and Metabolic Diseases, Shandong University, Jinan250012, People’s Republic of China
- Key Laboratory of Endocrine and Metabolic Diseases, Shandong Province Medicine and Health, Jinan, People’s Republic of China
- Jinan Clinical Research Center for Endocrine and Metabolic Diseases, Jinan, People’s Republic of China
| | - Li Chen
- Department of Endocrinology, Qilu Hospital, Shandong University, Jinan250012, People’s Republic of China
- Institute of Endocrine and Metabolic Diseases, Shandong University, Jinan250012, People’s Republic of China
- Key Laboratory of Endocrine and Metabolic Diseases, Shandong Province Medicine and Health, Jinan, People’s Republic of China
- Jinan Clinical Research Center for Endocrine and Metabolic Diseases, Jinan, People’s Republic of China
| | - Mingxiang Zhang
- Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Public Health, Qilu Hospital, Shandong University, JinanShandong250012, People’s Republic of China
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Xu L, Lin X, White RR, Hanigan MD, Hu Z, Hou Q, Wang Y, Wang Z. Plasma and Pancreas Islet Hormone Concentrations in Lactating Rats Are Associated with Dietary Protein Amounts. J Nutr 2018; 148:364-372. [PMID: 29546314 DOI: 10.1093/jn/nxx068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Accepted: 12/12/2017] [Indexed: 01/05/2023] Open
Abstract
Background Circulating amino acid (AA) and nitric oxide (NO) concentrations and hepatic gluconeogenesis are affected by previous protein intake. However, information about their relations and islet hormone responses is limited. Objective This study investigated the associations between islet hormone concentrations with circulating AA and NO concentrations as well as with hepatic gluconeogenesis in lactating rats. Methods At delivery, 18 Wistar rats aged 14 wk were assigned either to low-protein (LP; 9% protein), standard-protein (SP; 21% protein), or high-protein (HP; 35% protein) diets for 15 d in groups of 6 pups/dam. Circulating AA and NO concentrations, circulating and pancreas islet hormone concentrations, and the activities and gene expressions of hepatic phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) were measured at the end of treatment. Results Circulating insulin and glucagon concentrations were greater in the HP than in the LP (25% and 17%, respectively) and SP (37% and 31%) diet groups, whereas compared with the SP group, pancreatic concentrations were lower in the LP (32% and 49%) and HP (34% and 46%) groups (P < 0.01). Hepatic PEPCK and G6Pase activities in the HP group were greater than those in the SP (15% and 15%) and LP (8% and 19%) groups (P < 0.05). In all groups, plasma NO concentrations were correlated negatively to circulating insulin (r = -0.77, P = 0.0003) and positively to pancreas insulin and glucagon concentrations and the insulin-to-glucagon ratio (r = 0.50-0.63; P < 0.05). Some circulating AAs correlated positively to circulating insulin and pancreas insulin and glucagon (r = 0.50-0.82, P < 0.05) but negatively to circulating glucagon (r = -0.53-0.68, P < 0.05). Conclusion Variations in circulating AA and NO concentrations and hepatic gluconeogenic enzyme activities are likely intermediary responses involved in the effects of dietary protein amounts on the synthesis and secretion of islet hormones in lactating rats.
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Affiliation(s)
- Lianbin Xu
- Ruminant Nutrition and Physiology Laboratory, College of Animal Science and Technology, Shandong Agricultural University, Taian, China
| | - Xueyan Lin
- Ruminant Nutrition and Physiology Laboratory, College of Animal Science and Technology, Shandong Agricultural University, Taian, China
| | - Robin R White
- Department of Dairy Science, Virginia Tech, Blacksburg, VA
| | - Mark D Hanigan
- Department of Dairy Science, Virginia Tech, Blacksburg, VA
| | - Zhiyong Hu
- Ruminant Nutrition and Physiology Laboratory, College of Animal Science and Technology, Shandong Agricultural University, Taian, China
| | - Qiuling Hou
- Ruminant Nutrition and Physiology Laboratory, College of Animal Science and Technology, Shandong Agricultural University, Taian, China
| | - Yun Wang
- Ruminant Nutrition and Physiology Laboratory, College of Animal Science and Technology, Shandong Agricultural University, Taian, China
| | - Zhonghua Wang
- Ruminant Nutrition and Physiology Laboratory, College of Animal Science and Technology, Shandong Agricultural University, Taian, China
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Lundquist I, Mohammed Al-Amily I, Meidute Abaraviciene S, Salehi A. Metformin Ameliorates Dysfunctional Traits of Glibenclamide- and Glucose-Induced Insulin Secretion by Suppression of Imposed Overactivity of the Islet Nitric Oxide Synthase-NO System. PLoS One 2016; 11:e0165668. [PMID: 27820841 PMCID: PMC5098820 DOI: 10.1371/journal.pone.0165668] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 10/14/2016] [Indexed: 01/15/2023] Open
Abstract
Metformin lowers diabetic blood glucose primarily by reducing hepatic gluconeogenesis and increasing peripheral glucose uptake. However, possible effects by metformin on beta-cell function are incompletely understood. We speculated that metformin might positively influence insulin secretion through impacting the beta-cell nitric oxide synthase (NOS)-NO system, a negative modulator of glucose-stimulated insulin release. In short-time incubations with isolated murine islets either glibenclamide or high glucose augmented insulin release associated with increased NO production from both neural and inducible NOS. Metformin addition suppressed the augmented NO generation coinciding with amplified insulin release. Islet culturing with glibenclamide or high glucose revealed pronounced fluorescence of inducible NOS in the beta-cells being abolished by metformin co-culturing. These findings were reflected in medium nitrite-nitrate levels. A glucose challenge following islet culturing with glibenclamide or high glucose revealed markedly impaired insulin response. Metformin co-culturing restored this response. Culturing murine islets and human islets from controls and type 2 diabetics with high glucose or high glucose + glibenclamide induced a pronounced decrease of cell viability being remarkably restored by metformin co-culturing. We show here, that imposed overactivity of the beta-cell NOS-NO system by glibenclamide or high glucose leads to insulin secretory dysfunction and reduced cell viability and also, importantly, that these effects are relieved by metformin inhibiting beta-cell NO overproduction from both neural and inducible NOS thus ameliorating a concealed negative influence by NO induced by sulfonylurea treatment and/or high glucose levels. This double-edged effect of glibenclamide on the beta-cellsuggests sulfonylurea monotherapy in type 2 diabetes being avoided.
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Affiliation(s)
- Ingmar Lundquist
- Department of Clinical Science, SUS, Division of Islet Cell Physiology University of Lund, Malmö, Sweden
- Department of Experimental Medical Science, University of Lund, Lund, Sweden
| | - Israa Mohammed Al-Amily
- Department of Clinical Science, SUS, Division of Islet Cell Physiology University of Lund, Malmö, Sweden
| | - Sandra Meidute Abaraviciene
- Department of Clinical Science, SUS, Division of Islet Cell Physiology University of Lund, Malmö, Sweden
- Dept. of Physiology, Biochemistry, Microbiology and Laboratory Medicine Vilnius University, and Dep. of Regenerative Medicine, State Research Institute Center for Innovative Medicine, Vilnius, Lithuania
| | - Albert Salehi
- Department of Clinical Science, SUS, Division of Islet Cell Physiology University of Lund, Malmö, Sweden
- Department of Neuroscience and Physiology, Metabolic Research Unit, University of Gothenburg, Gothenburg, Sweden
- * E-mail:
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Meidute Abaraviciene S, Muhammed SJ, Amisten S, Lundquist I, Salehi A. GPR40 protein levels are crucial to the regulation of stimulated hormone secretion in pancreatic islets. Lessons from spontaneous obesity-prone and non-obese type 2 diabetes in rats. Mol Cell Endocrinol 2013; 381:150-9. [PMID: 23911664 DOI: 10.1016/j.mce.2013.07.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 06/27/2013] [Accepted: 07/22/2013] [Indexed: 12/21/2022]
Abstract
The role of islet GPR40 protein in the pathogenesis of diabetes is unclear. We explored the influence of GPR40 protein levels on hormone secretion in islets from two rat models of spontaneous type 2 diabetes displaying either hyperlipidaemia or hyperglycaemia. GPR40 expression was analysed by confocal microscopy, Western blot and qPCR in islets from preobese Zucker (fa/fa) rats, diabetic Goto-Kakizaki (GK) rats, and controls. Confocal microscopy of control islets showed expression of GPR40 protein in insulin, glucagon and somatostatin cells. GPR40 expression was strongly increased in islets of hyperlipidaemic fa/fa rats and coincided with a concentration-related increase in palmitate-induced release of insulin and glucagon and its inhibition of somatostatin release. Conversely, hyperglycaemic GK islets displayed an extremely faint expression of GPR40 as did high-glucose-cultured control islets. This was reflected in abolished palmitate-induced hormone response in GK islets and high-glucose-cultured control islets. The palmitate antagonist rosiglitazone promoted reappearance of GPR40 in high-glucose-cultured islets and served as partial agonist in glucose-stimulated insulin release. GPR40 protein is abundantly expressed in pancreatic islets and modulates stimulated hormone secretion. Mild hyperlipidaemia in obesity-prone diabetes creates increased GPR40 expression and increased risk for an exaggerated palmitate-induced insulin response and lipotoxicity, a metabolic situation suitable for GPR40 antagonist treatment. Chronic hyperglycaemia creates abrogated GPR40 expression and downregulated insulin release, a metabolic situation suitable for GPR40 agonist treatment to avoid glucotoxicity. GPR40 protein is interactively modulated by both free fatty acids and glucose and is a promising target for pharmacotherapy in different variants of type 2 diabetes.
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Affiliation(s)
- Sandra Meidute Abaraviciene
- Department of Clinical Science, SUS, Division of Islet Cell Physiology, University of Lund, Sweden; Department of Stem Cell Biology, State Research Institute Centre of Innovative Vilnius, Lithuania
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Muhammed SJ, Lundquist I, Salehi A. Pancreatic β-cell dysfunction, expression of iNOS and the effect of phosphodiesterase inhibitors in human pancreatic islets of type 2 diabetes. Diabetes Obes Metab 2012; 14:1010-9. [PMID: 22687049 DOI: 10.1111/j.1463-1326.2012.01632.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 03/16/2012] [Accepted: 06/04/2012] [Indexed: 11/30/2022]
Abstract
AIMS Induction of inducible nitric oxide synthase (iNOS) in pancreatic islets leads to exaggerated nitric oxide (NO) production associated with dysfunctional β-cells. We examined insulin secretion, iNOS expression and its relationship to the cAMP system in islets from human type 2 diabetes. METHODS Insulin, glucagon and cAMP were analysed by RIA; iNOS or phosphodiesterase (PDE) expression by quantitative PCR (qPCR), Western blot and confocal microscopy; cell viability by MTS. RESULTS Diabetic islets displayed impaired insulin and glucagon responses to glucose, disturbed cAMP generation and high inducible nitric oxide synthase (iNOS) mRNA and protein expression. Confocal microscopy showed iNOS protein expression in diabetic islets being confined to insulin, glucagon and somatostatin cells. Culture of diabetic islets at 5.5 mmol/l glucose with dibutyryl-cAMP (Bt(2) -cAMP) for 24 h was accompanied by marked suppression of iNOS mRNA, reduced nitrite production and increased insulin secretion. Diabetic islets displayed marked increase in PDE3A and PDE3B mRNA expression. Short-time incubation of diabetic islets showed, among the PDE inhibitors tested, cilostazol being most favourable to increase insulin secretion. Diabetic islets were most susceptible to long-term (72 h) culture at high glucose (20 mmol/l) reacting with increased apoptosis. Bt(2) -cAMP and the PDE inhibitors cilostazol, milrinone and IBMX efficiently increased cell viability at high glucose during culture. Defective glucose-stimulated insulin release upon induction of iNOS was restored by iNOS inhibitor aminoguanidine. CONCLUSION Our results suggest that in islets from type 2 diabetes, stimulatory effects in certain cAMP-compartments induced by PDE inhibitors might play a central role in the suppression of iNOS, resulting in increased β-cell viability and improved secretory response to glucose.
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Affiliation(s)
- S J Muhammed
- Department of Clinical Science, Division of Endocrine Pharmacology, SUS, Malmö, University of Lund, Malmö, Sweden.
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Eckersten D, Henningsson R. Nitric oxide (NO)--production and regulation of insulin secretion in islets of freely fed and fasted mice. ACTA ACUST UNITED AC 2011; 174:32-7. [PMID: 22120830 DOI: 10.1016/j.regpep.2011.11.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 10/18/2011] [Accepted: 11/10/2011] [Indexed: 10/15/2022]
Abstract
Production of nitric oxide through the action of nitric oxide synthase (NOS) has been detected in the islets of Langerhans. The inducible isoform of NOS (iNOS) is induced by cytokines and might contribute to the development of type-1 diabetes, while the constitutive isoform (cNOS) is thought to be implicated in the physiological regulation of insulin secretion. In the present study we have detected and quantified islet cNOS- and iNOS-derived NO production concomitant with measuring its influence on insulin secretion in the presence of different secretagogues: glucose, L-arginine, L-leucine and α-ketoisocaproic acid (KIC) both during fasting and freely fed conditions. In intact islets from freely fed mice both cNOS- and iNOS-activity was greatly increased by glucose (20 mmol/l). Fasting induced islet iNOS activity at both physiological (7 mmol/l) and high (20 mmol/l) glucose concentrations. NOS blockade increased insulin secretion both during freely fed conditions and after fasting. L-arginine stimulated islet cNOS activity and did not affect islet iNOS activity. l-leucine or KIC, known to enter the TCA cycle without affecting glycolysis, did not affect either islet cNOS- or iNOS activity. Accordingly, insulin secretion stimulated by L-leucine or KIC was unaffected by addition of L-NAME both during feeding and fasting. We conclude that both high glucose concentrations and fasting increase islet total NO production (mostly iNOS derived) which inhibit insulin secretion. The insulin secretagogues L-leucine and KIC, which do not affect glycolysis, do not interfere with the islet NO-NOS system.
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Affiliation(s)
- Dag Eckersten
- Department of Nephrology and Transplantation Skane University Hospital, Sweden
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Jimenez-Feltstrom J, Salehi A, Meidute Abaraviciene S, Henningsson R, Lundquist I. Abnormally decreased NO and augmented CO production in islets of the leptin-deficient ob/ob mouse might contribute to explain hyperinsulinemia and islet survival in leptin-resistant type 2 obese diabetes. ACTA ACUST UNITED AC 2011; 170:43-51. [DOI: 10.1016/j.regpep.2011.04.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 03/24/2011] [Accepted: 04/16/2011] [Indexed: 01/14/2023]
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Meidute-Abaraviciene S, Mosen H, Lundquist I, Salehi A. Imidazoline-induced amplification of glucose- and carbachol-stimulated insulin release includes a marked suppression of islet nitric oxide generation in the mouse. Acta Physiol (Oxf) 2009; 195:375-83. [PMID: 18764864 DOI: 10.1111/j.1748-1716.2008.01896.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM The role of islet nitric oxide (NO) production in insulin-releasing mechanisms is unclear. We examined whether the beneficial effects of the imidazoline derivative RX 871024 (RX) on beta-cell function might be related to perturbations of islet NO production. METHODS Experiments were performed with isolated islets or intact mice challenged with glucose or carbachol with or without RX treatment. Insulin was determined with radioimmunoassay, NO generation with high-performance liquid chromatography and expression of inducible NO synthase (iNOS) with confocal microscopy. RESULTS RX treatment, in doses lacking effects on basal insulin, greatly amplified insulin release stimulated by the NO-generating secretagogues glucose and carbachol both in vitro and in vivo. RX also improved the glucose tolerance curve. Islets incubated at high glucose levels (20 mmol L(-1)) displayed increased NO production derived from both neuronal constitutive NO synthase (ncNOS) and iNOS. RX abrogated this glucose-induced NO production concomitant with amplification of insulin release. Confocal microscopy revealed abundant iNOS expression in beta cells after incubation of islets at high but not low glucose levels. This was abolished after RX treatment. Similarly, islets cultured for 24 h at high glucose levels showed intense iNOS expression in beta cells. This was abrogated with RX and followed by an amplified glucose-induced insulin release. CONCLUSION RX effectively counteracts the negative impact of beta-cell NO generation on insulin release stimulated by glucose and carbachol suggesting imidazoline compounds by virtue of NOS inhibitory properties being of potential therapeutic value for treatment of beta-cell dysfunction in hyperglycaemia and type 2 diabetes.
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Affiliation(s)
- S Meidute-Abaraviciene
- Department of Clinical Science, Division of Endocrine Pharmacology, University of Lund, Malmö, Sweden.
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Qader S. The role of nitric oxide synthase in post-operative hyperglycaemia. Libyan J Med 2008; 3:144-7. [PMID: 21516149 PMCID: PMC3074270 DOI: 10.4176/080416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Post-operative hyperglycaemia is important with regard to outcomes of surgical operations. It affects post-operative morbidity, length of hospital stay, and mortality. Poor peri-operative blood glucose control leads to a higher risk of post-operative complication. Insulin resistance as a cause of post-operative hyperglycaemia has been blamed for some time. Nitric Oxide (NO) is produced by nitric oxide synthase (NOS) isoenzymes. Inducible nitric oxide synthase (iNOS) is not a normal cellular constitute. It is expressed by cytokines and non-cytokines e.g. fasting, trauma, intravenous glucose, and lipid infusion, which are encountered in surgical operations. Review of current published data on postoperative hyperglycaemia was completed. Our studies and others were explored for the possible role of NO in this scenario. Induction and expression of iNOS enzyme in pancreatic islet cells is included in the chaotic postoperative blood glucose control. The high concentrations of iNOS derived NO are toxic to pancreatic β-cells and may inhibit insulin secretion postoperatively. Hence, current peri-operative management is questionable regarding post-operative hyperglycaemia and necessitates development of a new strategy.
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Affiliation(s)
- Ss Qader
- Department of Surgery, Hawler Medical University, Erbil, Iraq and Department of Clinical Science, Lund University, Malmö, Sweden
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Impaired glucose-stimulated insulin secretion in the GK rat is associated with abnormalities in islet nitric oxide production. ACTA ACUST UNITED AC 2008; 151:139-46. [PMID: 18662725 DOI: 10.1016/j.regpep.2008.07.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2008] [Revised: 05/23/2008] [Accepted: 07/02/2008] [Indexed: 11/24/2022]
Abstract
We investigated implications of nitric oxide (NO) derived from islet neuronal constitutive NO synthase (ncNOS) and inducible NOS (iNOS) on insulin secretory mechanisms in the mildly diabetic GK rat. Islets from GK rats and Wistar controls were analysed for ncNOS and iNOS by HPLC, immunoblotting and immunocytochemistry in relation to insulin secretion stimulated by glucose or l-arginine in vitro and in vivo. No obvious difference in ncNOS fluorescence in GK vs control islets was seen but freshly isolated GK islets displayed a marked iNOS expression and activity. After incubation at low glucose GK islets showed an abnormal increase in both iNOS and ncNOS activities. At high glucose the impaired glucose-stimulated insulin release was associated with an increased iNOS expression and activity and NOS inhibition dose-dependently amplified insulin secretion in both GK and control islets. This effect by NOS inhibition was also evident in depolarized islets at low glucose, where forskolin had a further amplifying effect in GK but not in control islets. NOS inhibition increased basal insulin release in perfused GK pancreata and amplified insulin release after glucose stimulation in both GK and control pancreata, almost abrogating the nadir separating first and second phase in controls. A defective insulin response to l-arginine was seen in GK rats in vitro and in vivo, being partially restored by NOS inhibition. The results suggest that increased islet NOS activities might contribute to the defective insulin response to glucose and l-arginine in the GK rat. Excessive iNOS expression and activity might be deleterious for the beta-cells over time.
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Salehi A, Meidute Abaraviciene S, Jimenez-Feltstrom J, Ostenson CG, Efendic S, Lundquist I. Excessive islet NO generation in type 2 diabetic GK rats coincides with abnormal hormone secretion and is counteracted by GLP-1. PLoS One 2008; 3:e2165. [PMID: 18478125 PMCID: PMC2367446 DOI: 10.1371/journal.pone.0002165] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 03/25/2008] [Indexed: 11/22/2022] Open
Abstract
Background A distinctive feature of type 2 diabetes is inability of insulin-secreting β-cells to properly respond to elevated glucose eventually leading to β-cell failure. We have hypothesized that an abnormally increased NO production in the pancreatic islets might be an important factor in the pathogenesis of β-cell dysfunction. Principal Findings We show now that islets of type 2 spontaneous diabetes in GK rats display excessive NO generation associated with abnormal iNOS expression in insulin and glucagon cells, increased ncNOS activity, impaired glucose-stimulated insulin release, glucagon hypersecretion, and impaired glucose-induced glucagon suppression. Pharmacological blockade of islet NO production by the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) greatly improved hormone secretion from GK islets suggesting islet NOS activity being an important target to inactivate for amelioration of islet cell function. The incretin hormone GLP-1, which is used in clinical practice suppressed iNOS and ncNOS expression and activity with almost full restoration of insulin release and partial restoration of glucagon release. GLP-1 suppression of iNOS expression was reversed by PKA inhibition but unaffected by the proteasome inhibitor MG132. Injection of glucose plus GLP-1 in the diabetic rats showed that GLP-1 amplified the insulin response but induced a transient increase and then a poor depression of glucagon. Conclusion The results suggest that abnormally increased NO production within islet cells is a significant player in the pathogenesis of type 2 diabetes being counteracted by GLP-1 through PKA-dependent, nonproteasomal mechanisms.
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Affiliation(s)
- Albert Salehi
- Department of Clinical Science, Universitetssjukhuset Malmö Allmäna Sjukhus, Division of Endocrine Pharmacology, Karolinska Institute, Stockholm, Sweden.
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Palmitate-induced beta-cell dysfunction is associated with excessive NO production and is reversed by thiazolidinedione-mediated inhibition of GPR40 transduction mechanisms. PLoS One 2008; 3:e2182. [PMID: 18478115 PMCID: PMC2366067 DOI: 10.1371/journal.pone.0002182] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Accepted: 03/13/2008] [Indexed: 11/19/2022] Open
Abstract
Background Type 2 diabetes often displays hyperlipidemia. We examined palmitate effects on pancreatic islet function in relation to FFA receptor GPR40, NO generation, insulin release, and the PPARγ agonistic thiazolidinedione, rosiglitazone. Principal Findings Rosiglitazone suppressed acute palmitate-stimulated GPR40-transduced PI hydrolysis in HEK293 cells and insulin release from MIN6c cells and mouse islets. Culturing islets 24 h with palmitate at 5 mmol/l glucose induced β-cell iNOS expression as revealed by confocal microscopy and increased the activities of ncNOS and iNOS associated with suppression of glucose-stimulated insulin response. Rosiglitazone reversed these effects. The expression of iNOS after high-glucose culturing was unaffected by rosiglitazone. Downregulation of GPR40 by antisense treatment abrogated GPR40 expression and suppressed palmitate-induced iNOS activity and insulin release. Conclusion We conclude that, in addition to mediating acute FFA-stimulated insulin release, GPR40 is an important regulator of iNOS expression and dysfunctional insulin release during long-term exposure to FFA. The adverse effects of palmitate were counteracted by rosiglitazone at GPR40, suggesting that thiazolidinediones are beneficial for β-cell function in hyperlipidemic type 2 diabetes.
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Qader S. The Role of Nitric Oxide Synthase in Post-Operative Hyperglycaemia. Libyan J Med 2008. [DOI: 10.3402/ljm.v3i3.4780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Qader SS, Jimenez-Feltström J, Ekelund M, Lundquist I, Salehi A. Expression of islet inducible nitric oxide synthase and inhibition of glucose-stimulated insulin release after long-term lipid infusion in the rat is counteracted by PACAP27. Am J Physiol Endocrinol Metab 2007; 292:E1447-55. [PMID: 17264229 DOI: 10.1152/ajpendo.00172.2006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic exposure of pancreatic islets to elevated plasma lipids (lipotoxicity) can lead to beta-cell dysfunction, with overtime becoming irreversible. We examined, by confocal microscopy and biochemistry, whether the expression of islet inducible nitric oxide synthase (iNOS) and the concomitant inhibition of glucose-stimulated insulin release seen after lipid infusion in rats was modulated by the islet neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP)27. Lipid infusion for 8 days induced a strong expression of islet iNOS, which was mainly confined to beta-cells and was still evident after incubating islets at 8.3 mmol/l glucose. This was accompanied by a high iNOS-derived NO generation, a decreased insulin release, and increased cyclic GMP accumulation. No iNOS expression was found in control islets. Addition of PACAP27 to incubated islets from lipid-infused rats resulted in loss of iNOS protein expression, increased cyclic AMP, decreased cyclic GMP, and suppression of the activities of neuronal constitutive (nc)NOS and iNOS and increased glucose-stimulated insulin response. These effects were reversed by the PKA inhibitor H-89. The suppression of islet iNOS expression induced by PACAP27 was not affected by the proteasome inhibitor MG-132, which by itself induced the loss of iNOS protein, making a direct proteasomal involvement less likely. Our results suggest that PACAP27 through its cyclic AMP- and PKA-stimulating capacity strongly suppresses not only ncNOS but, importantly, also the lipid-induced stimulation of iNOS expression, possibly by a nonproteasomal mechanism. Thus PACAP27 restores the impairment of glucose-stimulated insulin release and additionally might induce cytoprotection against deleterious actions of iNOS-derived NO in beta-cells.
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Ekelund M, Qader SS, Jimenez-Feltstrom J, Salehi A. Selective induction of inducible nitric oxide synthase in pancreatic islet of rat after an intravenous glucose or intralipid challenge. Nutrition 2006; 22:652-60. [PMID: 16635563 DOI: 10.1016/j.nut.2006.01.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Revised: 12/23/2005] [Accepted: 12/23/2005] [Indexed: 11/24/2022]
Abstract
OBJECTIVE Constant exposure of pancreatic islets to high levels of glucose or free fatty acids can lead to irreversible beta-cell dysfunction, a process referred to as glucotoxicity or lipotoxicity, respectively. In this context a role for nitric oxide generated by pancreatic islet has been suggested. The present investigation examined whether the route of glucose administration, i.e., given orally (OG) or infused intravenously (IVG), could have any effect on the expression and activity of inducible nitric oxide synthase (iNOS) in pancreatic islets. METHODS Rats were infused with glucose (50%) or Intralipid intravenously for 24 h or given glucose orally. A freely fed control group (FF) was also included. At 24 h rats were killed and blood samples were drawn for analysis of plasma insulin, glucagon, and glucose. Pancreatic islets were harvested from each animal and investigated for the occurrence of iNOS by the use of confocal microscopy, western blot, and high-performance liquid chromatographic analysis. The effect of intravenously infused glucose was then compared with the effect of an intravenous infusion of Intralipid (IL). RESULTS Plasma insulin levels were markedly decreased after 24 h of infusion of glucose (IVG group) or Intralipid (IL group) compared with the FF or OG group. Plasma glucagon and glucose levels were markedly increased in the IVG group, whereas both parameters were decreased in the IL group. No significant differences in plasma insulin, glucagon, or glucose were found between the OG and FF groups. Immunocytochemical (confocal microscopy), western blot, and biochemical (high-performance liquid chromatographic) analyses showed that a sustained increase in plasma level of glucose or free fatty acids by an intravenous infusion of either nutrient for 24 h resulted in a marked expression and activity of iNOS in pancreatic islets. No sign of iNOS expression could, however, be detected in the islets of FF control or OG rats. CONCLUSION The data suggest that impaired beta-cell function found after 24 h of an intravenous infusion of glucose or Intralipid might be mediated, at least in part, by the induction of iNOS in pancreatic islets. This may subsequently result in an exclusive production of nitric oxide, which is deleterious for beta-cells.
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Affiliation(s)
- Mats Ekelund
- Department of Surgery, Division of Diabetes, Metabolism and Endocrinology, University of Lund, Lund, Sweden
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Salehi A, Flodgren E, Nilsson NE, Jimenez-Feltstrom J, Miyazaki J, Owman C, Olde B. Free fatty acid receptor 1 (FFA(1)R/GPR40) and its involvement in fatty-acid-stimulated insulin secretion. Cell Tissue Res 2005; 322:207-15. [PMID: 16044321 DOI: 10.1007/s00441-005-0017-z] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Accepted: 05/10/2005] [Indexed: 11/30/2022]
Abstract
Free fatty acids (FFA) have generally been proposed to regulate pancreatic insulin release by an intracellular mechanism involving inhibition of CPT-1. The recently de-orphanized G-protein coupled receptor, FFA(1)R/GPR40, has been shown to be essential for fatty-acid-stimulated insulin release in MIN6 mouse insulinoma cells. The CPT-1 inhibitor, 2-bromo palmitate (2BrP), was investigated for its ability to interact with mouse FFA(1)R/GPR40. It was found to inhibit phosphatidyl inositol hydrolysis induced by linoleic acid (LA) (100 muM in all experiments) in HEK293 cells transfected with FFA(1)R/GPR40 and in the MIN6 subclone, MIN6c4. 2BrP also inhibited LA-stimulated insulin release from mouse pancreatic islets. Mouse islets were subjected to antisense intervention by treatment with a FFA(1)R/GPR40-specific morpholino oligonucleotide for 48 h. Antisense treatment of islets suppressed LA-stimulated insulin release by 50% and by almost 100% when islets were pretreated with LA for 30 min before applying the antisense. Antisense treatment had no effect on tolbutamide-stimulated insulin release. Confocal microscopy using an FFA(1)R/GPR40-specific antibody revealed receptor expression largely localized to the plasma membrane of insulin-producing cells. Pretreating the islets with LA for 30 min followed by antisense oligonucleotide treatment for 48 h reduced the FFA(1)R/GPR40 immunoreactivity to background levels. The results demonstrate that FFA(1)R/GPR40 is inhibited by the CPT-1 inhibitor, 2BrP, and confirm that FFA(1)R/GPR40 is indeed necessary, at least in part, for fatty-acid-stimulated insulin release.
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Affiliation(s)
- A Salehi
- Section of Diabetes and Endocrinology, BMC B11, 22184 Lund, Sweden
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Qader SS, Salehi A, Håkanson R, Lundquist I, Ekelund M. Long-term infusion of nutrients (total parenteral nutrition) suppresses circulating ghrelin in food-deprived rats. ACTA ACUST UNITED AC 2005; 131:82-8. [PMID: 16102855 DOI: 10.1016/j.regpep.2005.07.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2004] [Revised: 06/30/2005] [Accepted: 07/05/2005] [Indexed: 01/23/2023]
Abstract
BACKGROUND Ghrelin derives from endocrine cells (A-like cells) in the stomach (mainly the oxyntic mucosa). Its concentration in the circulation increases during fasting and decreases upon re-feeding. This has fostered the notion that the absence of food in the upper gastrointestinal (GI) tract stimulates the secretion of ghrelin. The purpose of the present study was to determine the concentration of ghrelin in serum and oxyntic mucosa after replacing food with intravenous (iv) infusion of nutrients for 8 days using the technique known as total parenteral nutrition (TPN) MATERIALS AND METHODS: Male Sprague-Dawley rats (200-250 g) were given nutrients (lipids, glucose, amino acids, minerals and vitamins) by iv infusion for 8 days during which time they were deprived of food and water; another group was deprived of food for 24-48 h (fasted controls), while fed controls had free access to food and water. Serum ghrelin, gastrin and pancreastatin concentrations were measured together with the ghrelin content of the oxyntic mucosa. Plasma insulin and glucose as well as serum lipid concentrations were also determined. RESULTS Fasted rats had higher serum ghrelin than TPN rats and fed controls. The oxyntic mucosal ghrelin concentration (and content) was lower in TPN rats than in fasted rats or fed controls. The serum gastrin and pancreastatin concentrations were lower in TPN rats and fasted rats than in fed controls. The plasma insulin concentration was 87 pmol/l+/-8 (SEM) in TPN rats compared to 101+/-16 pmol/l in fed controls; it was 26+/-14 pmol/l in fasted rats. The basal plasma glucose level was 11+/-0.6 mmol/l in TPN rats and 12+/-0.8 mmol/l in fed controls; it was 7+/-0.3 mmol/l in fasted rats. In TPN rats, the serum concentrations of free fatty acids, triglycerides and cholesterol were increased by 100%, 50% and 25%, respectively, compared to fed controls. Fasted rats had higher circulating concentrations of free fatty acids (20%) and lower concentrations of triglycerides (-40%) than fed controls; fasted rats did not differ from fed controls with respect to serum cholesterol. CONCLUSION The circulating ghrelin concentration is high in situations of nutritional deficiency (starvation) and low in situations of nutritional plenty (free access to food or TPN). The actual presence or absence of food in the GI tract seems irrelevant. Circulating insulin and glucose concentrations did not differ much between TPN rats and fed controls; serum lipids, however, were elevated in the TPN rats. We suggest that elevated blood lipid levels contribute to the suppression of circulating ghrelin in rats subjected to TPN for 8 days.
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Affiliation(s)
- Saleem S Qader
- Department of Clinical Sciences, Division of Surgery, Lund University Hospital, SE-221 85, Sweden
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Qader SS, Lundquist I, Ekelund M, Håkanson R, Salehi A. Ghrelin activates neuronal constitutive nitric oxide synthase in pancreatic islet cells while inhibiting insulin release and stimulating glucagon release. ACTA ACUST UNITED AC 2005; 128:51-6. [PMID: 15721487 DOI: 10.1016/j.regpep.2004.12.018] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 11/24/2004] [Accepted: 12/11/2004] [Indexed: 12/25/2022]
Abstract
In view of our previous data, showing that ghrelin and nitric oxide (NO) display apparently parallel effects on insulin secretion (inhibitory) and glucagon secretion (stimulatory), we have now investigated the effect of ghrelin on islet hormone secretion in relation to its effect on NO synthase (NOS) isoenzymes in isolated rat pancreatic islets. Dose-response studies revealed that ghrelin at concentrations of 0.01-1 micromol l-1 inhibited insulin secretion stimulated by 8.3 mmol l-1 glucose, while ghrelin at concentrations lower than the physiological range (0.01 pmol l-1 to 1 nmol l-1) were without effect. In contrast, glucagon secretion was stimulated by 1.0 nmol l-1 to 1 micromol l-1 ghrelin. These effects of ghrelin on insulin and glucagon secretion were accompanied by increased NO production through activation of neuronal constitutive NOS (ncNOS). Ghrelin had no appreciable effect on the activity of inducible NOS (iNOS) in the islets. Addition of an NO scavenger (cPTIO) or the NOS inhibitor L-NAME to the incubation medium prevented the effects of ghrelin on hormone secretion from isolated islets. The present results confirm our previous data showing that ghrelin inhibits insulin and stimulates glucagon secretion from pancreatic islets of the mouse and we now show similar effects in rat islets. The effects of ghrelin were accompanied by an increased rate of NO production. Conceivably, ncNOS activation partly accounts for to the inhibitory effect of ghrelin on insulin secretion and the stimulatory effect of ghrelin on glucagon secretion.
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Jimenez-Feltstrom J, Lundquist I, Obermuller S, Salehi A. Insulin feedback actions: complex effects involving isoforms of islet nitric oxide synthase. ACTA ACUST UNITED AC 2005; 122:109-18. [PMID: 15380928 DOI: 10.1016/j.regpep.2004.06.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Revised: 05/19/2004] [Accepted: 06/01/2004] [Indexed: 11/18/2022]
Abstract
The present study examined the effects of exogenous insulin on C-peptide release in relation to islet activities of neural constitutive nitric oxide synthase (ncNOS) and inducible NOS (iNOS). The dose-response curves for glucose-stimulated insulin and C-peptide release from isolated islets were practically identical: 0.05-0.1 nmol/l insulin stimulated, 1-100 nmol/l had no effect, whereas concentrations >/=250 nmol/l ("high insulin"), inhibited C-peptide release. Both the stimulatory and inhibitory effects were abolished by the phosphatidylinositol 3'-kinase inhibitor wortmannin. Addition of a NOS inhibitor partially reversed the inhibitory action of high insulin, but had no effect on the stimulatory action of low insulin (0.1 nmol/l). Moreover, high insulin markedly increased islet ncNOS activity and induced a strong iNOS activity. As shown biochemically and with confocal microscopy, the stimulatory action of high insulin on NOS activities and the associated inhibition of C-peptide release were reversed by raising cyclic AMP through addition of either glucagon-like peptide 1 (GLP-1) or dibutyryl cyclic AMP (Bt(2)cAMP) to the incubated islets. We conclude that the positive feedback mechanisms of action of insulin are independent of islet NOS activities and remain unclear. The negative feedback action of insulin, however, can be explained by its ability to stimulate both islet ncNOS activity and the expression and activity of iNOS. The effects on iNOS are most likely transduced through phosphatidylinositol 3'-kinase and are counteracted by raising islet cyclic AMP levels.
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Affiliation(s)
- Javier Jimenez-Feltstrom
- Institute of Physiological Sciences, Department of Pharmacology, University of Lund, BMC F13 S-221 84 Lund, Sweden.
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Mosén H, Salehi A, Alm P, Henningsson R, Jimenez-Feltström J, Ostenson CG, Efendic S, Lundquist I. Defective glucose-stimulated insulin release in the diabetic Goto-Kakizaki (GK) rat coincides with reduced activity of the islet carbon monoxide signaling pathway. Endocrinology 2005; 146:1553-8. [PMID: 15564331 DOI: 10.1210/en.2004-0851] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Goto-Kakizaki (GK) rat displays a markedly reduced insulin response to glucose, a defect that is thought to be coupled to an impaired glucose signaling in the beta-cell. We have examined whether carbon monoxide (CO), derived from beta-cell heme oxygenase (HO), might be involved in the secretory dysfunction. Immunocytochemical labeling of constitutive HO (HO-2) showed no overt difference in fluorescence pattern in islets from GK vs. Wistar controls. However, isolated islets from GK rats displayed a markedly impaired HO activity measured as CO production (-50%), and immunoblotting revealed an approximately 50% reduction of HO-2 protein expression compared with Wistar controls. Furthermore, there was a prominent expression of inducible HO (HO-1) in GK islets. Incubation of isolated islets showed that the glucose-stimulated CO production and the glucose-stimulated insulin response were considerably reduced in GK islets compared with Wistar islets. Addition of the HO activator hemin or gaseous CO to the incubation media brought about a similar amplification of glucose-stimulated insulin release in GK and Wistar islets, suggesting that distal steps in the HO-CO signaling pathway were not appreciably affected. We conclude that the defective insulin response to glucose in the GK rat can be explained, at least in part, by a marked impairment of the glucose-HO-CO signaling pathway as manifested by a prominent decrease in glucose stimulation of islet CO production and a reduced expression of HO-2. A possible role of HO-1 expression as a compensatory mechanism in the GK islets is presently unclear.
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Affiliation(s)
- Henrik Mosén
- Department of Pharmacology, Institute of Physiological Sciences, University of Lund, BMC F13, S-221 84 Lund, Sweden.
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Jimenez-Feltstrom J, Lundquist I, Salehi A. Glucose stimulates the expression and activities of nitric oxide synthases in incubated rat islets: an effect counteracted by GLP-1 through the cyclic AMP/PKA pathway. Cell Tissue Res 2004; 319:221-30. [PMID: 15558323 DOI: 10.1007/s00441-004-1013-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Accepted: 09/27/2004] [Indexed: 01/11/2023]
Abstract
We have examined the expression and activity of inducible nitric oxide synthase (iNOS) and the activity of neuronal constitutive NOS (ncNOS) in isolated rat pancreatic islets, stimulated by a "hyperglycaemic" concentration of glucose, and whether the NOS activities could be modulated by activation of the cyclic AMP/protein kinase A (cyclic AMP/PKA) system in relation to the insulin secretory process. Here, we show that glucose stimulation (20 mmol/l) induces iNOS and increases ncNOS activity. No iNOS is detectable at basal glucose levels (3.3 mmol/l). The addition of glucagon-like-peptide 1 (GLP-1) or dibutyryl-cAMP to islets incubated with 20 mmol/l glucose results in a marked suppression of iNOS expression and activity, a reduction in ncNOS activity and increased insulin release. The GLP-1-induced suppression of glucose-stimulated iNOS activity and expression and its stimulation of insulin release is, at least in part, PKA dependent, since the PKA inhibitor H-89 reverses the effects of GLP-1. These observations have been confirmed by confocal microscopy showing the glucose-stimulated expression of iNOS, its suppression by GLP-1 and its reversion by H-89 in beta-cells. We have also found that the NO scavenger cPTIO and the NOS inhibitor L-NAME potentiate the insulin response to glucose, again suggesting that NO is a negative modulator of glucose-stimulated insulin release. We conclude that the induction of iNOS and the increase in ncNOS activity caused by glucose in rat islets is suppressed by the cyclic AMP/PKA system. The inhibition of iNOS expression by the GLP-1/cyclic AMP/PKA pathway might possibly be of therapeutic potential in NO-mediated beta-cell dysfunction and destruction.
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Affiliation(s)
- Javier Jimenez-Feltstrom
- Department of Pharmacology, Institute of Physiological Sciences, University of Lund, 221 84 Lund, Sweden
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