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Bagheripour F, Jeddi S, Kashfi K, Ghasemi A. Metabolic effects of L-citrulline in type 2 diabetes. Acta Physiol (Oxf) 2023; 237:e13937. [PMID: 36645144 DOI: 10.1111/apha.13937] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 01/01/2023] [Accepted: 01/10/2023] [Indexed: 01/17/2023]
Abstract
The prevalence of type 2 diabetes (T2D) is increasing worldwide. Decreased nitric oxide (NO) bioavailability is involved in the pathophysiology of T2D and its complications. L-citrulline (Cit), a precursor of NO production, has been suggested as a novel therapeutic agent for T2D. Available data from human and animal studies indicate that Cit supplementation in T2D increases circulating levels of Cit and L-arginine while decreasing circulating glucose and free fatty acids and improving dyslipidemia. The underlying mechanisms for these beneficial effects of Cit include increased insulin secretion from the pancreatic β cells, increased glucose uptake by the skeletal muscle, as well as increased lipolysis and β-oxidation, and decreased glyceroneogenesis in the adipose tissue. Thus, Cit has antihyperglycemic, antidyslipidemic, and antioxidant effects and has the potential to be used as a new therapeutic agent in the management of T2D. This review summarizes available literature from human and animal studies to explore the effects of Cit on metabolic parameters in T2D. It also discusses the possible mechanisms underlying Cit-induced improved metabolic parameters in T2D.
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Affiliation(s)
- Fatemeh Bagheripour
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Sajad Jeddi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Khosrow Kashfi
- Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, New York, USA
| | - Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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The Effect of Cinnamaldehyde on iNOS Activity and NO-Induced Islet Insulin Secretion in High-Fat-Diet Rats. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2021; 2021:9970678. [PMID: 34335851 PMCID: PMC8292039 DOI: 10.1155/2021/9970678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 06/07/2021] [Accepted: 07/03/2021] [Indexed: 10/28/2022]
Abstract
Introduction Obesity and insulin resistance are associated with alterations in nitric oxide level and insulin secretion. Previous studies demonstrated that cinnamaldehyde (CNMA) improved islet insulin secretion and restored nitric oxide (NO) level, but its underlying mechanisms have not been investigated. This study aimed to investigate the effect of CNMA on inducible nitric oxide synthase (iNOS) activity and NO-induced islet insulin secretion in high-fat-diet (HFD) treated rats. Materials and Methods Forty male Wistar rats (12 weeks old) were randomly divided into four equal groups, namely, control, CNMA, HFD, and HFD + CNMA. Control and CNMA groups were treated with standard laboratory animals' diet, while HFD and HDF + CNMA groups were fed with an HFD diet enriched with 25% W/W tail fat for 16 weeks. CNMA was administrated orally (20 mg/kg body weight, daily) during the study period. Islet insulin secretion and the inducible NOS activity in the presence or absence of L-NAME (NO synthase inhibitor, 5 mmol/L) were evaluated. Results L-NAME-suppressed insulin secretion in control, HFD, and HFD + CNMA groups; however, in the CNMA group, it could not exhibit such effect (P < 0.01). Islets of HFD-treated animals showed significantly higher iNOS activity than controls. CNMA treatment significantly suppressed iNOS activities in CNMA and HFD + CNMA groups compared with control and HFD, respectively. Conclusion These results suggest that the beneficial effect of CNMA on insulin secretion might be due to its inhibitory effect on iNOS activity.
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Kim K, Kwak MK, Bae GD, Park EY, Baek DJ, Kim CY, Jang SE, Jun HS, Oh YS. Allomyrina dichotoma larva extract attenuates free fatty acid-induced lipotoxicity in pancreatic beta cells. Nutr Res Pract 2021; 15:294-308. [PMID: 34093971 PMCID: PMC8155218 DOI: 10.4162/nrp.2021.15.3.294] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 09/28/2020] [Accepted: 12/09/2020] [Indexed: 12/19/2022] Open
Abstract
BACKGROUD/OBJECTIVES Allomyrina dichotoma larva (ADL), one of the many edible insects recognized as future food resources, has a range of pharmacological activities. In a previous study, an ADL extract (ADLE) reduced the hepatic insulin resistance of high-fat diet (HFD)-induced diabetic mice. On the other hand, the associated molecular mechanisms underlying pancreatic beta-cell dysfunction remain unclear. This study examined the effects of ADLE on palmitate-induced lipotoxicity in a beta cell line of a rat origin, INS-1 cells. MATERIALS/METHODS ADLE was administered to high-fat diet treated mice. The expression of apoptosis-related molecules was measured by Western blotting, and reactive oxidative stress generation and nitric oxide production were measured by DCH-DA fluorescence and a Griess assay, respectively. RESULTS The administration of ADLE to HFD-induced diabetic mice reduced the hyperplasia, 4-hydroxynonenal levels, and the number of apoptotic cells while improving the insulin levels compared to the HFD group. Treatment of INS-1 cells with palmitate reduced insulin secretion, which was attenuated by the ADLE treatment. Furthermore, the ADLE treatment prevented palmitate-induced cell death in INS-1 cells and isolated islets by reducing the apoptotic signaling molecules, including cleaved caspase-3 and PARP, and the Bax/Bcl2 ratio. ADLE also reduced the levels of reactive oxygen species generation, lipid accumulation, and nitrite production in palmitate-treated INS-1 cells while increasing the ATP levels. This effect corresponded to the decreased expression of inducible nitric oxide synthase (iNOS) mRNA and protein. CONCLUSIONS ADLE helps prevent lipotoxic beta-cell death in INS-1 cells and HFD-diabetic mice, suggesting that ADLE can be used to prevent or treat beta-cell damage in glucose intolerance during the development of diabetes.
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Affiliation(s)
- Kyong Kim
- Department of Food Nutrition, College of Bio Convergence, Eulji University, Seongnam 13135, Korea
| | - Min-Kyu Kwak
- Department of Food Nutrition, College of Bio Convergence, Eulji University, Seongnam 13135, Korea
| | - Gong-Deuk Bae
- Institute of Lee Gil Ya Cancer and Diabetes, Department of Molecular Medicine, Gachon University, Incheon 21999, Korea
| | - Eun-Young Park
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Dong-Jae Baek
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Chul-Young Kim
- College of Pharmacy, Hanyang University, Ansan 15588, Korea
| | - Se-Eun Jang
- Department of Food Nutrition, College of Bio Convergence, Eulji University, Seongnam 13135, Korea
| | - Hee-Sook Jun
- College of Pharmacy and Gachon Institute of Pharmaceutical Science, Gachon University, Incheon 21936, Korea
| | - Yoon Sin Oh
- Department of Food Nutrition, College of Bio Convergence, Eulji University, Seongnam 13135, Korea
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Gheibi S, Ghasemi A. Insulin secretion: The nitric oxide controversy. EXCLI JOURNAL 2020; 19:1227-1245. [PMID: 33088259 PMCID: PMC7573190 DOI: 10.17179/excli2020-2711] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 08/31/2020] [Indexed: 12/14/2022]
Abstract
Nitric oxide (NO) is a gas that serves as a ubiquitous signaling molecule participating in physiological activities of various organ systems. Nitric oxide is produced in the endocrine pancreas and contributes to synthesis and secretion of insulin. The potential role of NO in insulin secretion is disputable - both stimulatory and inhibitory effects have been reported. Available data indicate that effects of NO critically depend on its concentration. Different isoforms of NO synthase (NOS) control this and have the potential to decrease or increase insulin secretion. In this review, the role of NO in insulin secretion as well as the possible reasons for discrepant findings are discussed. A better understanding of the role of NO system in the regulation of insulin secretion may facilitate the development of new therapeutic strategies in the management of diabetes.
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Affiliation(s)
- Sevda Gheibi
- Department of Clinical Sciences in Malmö, Unit of Molecular Metabolism, Lund University Diabetes Centre, Clinical Research Center, Malmö University Hospital, Lund University, Malmö, Sweden
| | - Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Bahadoran Z, Mirmiran P, Ghasemi A. Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism. Trends Endocrinol Metab 2020; 31:118-130. [PMID: 31690508 DOI: 10.1016/j.tem.2019.10.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Revised: 09/29/2019] [Accepted: 10/03/2019] [Indexed: 01/20/2023]
Abstract
Nitric oxide (NO) contributes to carbohydrate metabolism and decreased NO bioavailability is involved in the development of type 2 diabetes mellitus (T2DM). NO donors may improve insulin signaling and glucose homeostasis in T2DM and insulin resistance (IR), suggesting the potential clinical importance of NO-based interventions. In this review, site-specific roles of the NO synthase (NOS)-NO pathway in carbohydrate metabolism are discussed. In addition, the metabolic effects of physiological low levels of NO produced by constitutive NOS (cNOS) versus pathological high levels of NO produced by inducible NOS (iNOS) in pancreatic β-cells, adipocytes, hepatocytes, and skeletal muscle cells are summarized. A better understanding of the NOS-NO system in the regulation of glucose homeostasis can hopefully facilitate the development of new treatments for T2DM.
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Affiliation(s)
- Zahra Bahadoran
- Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Parvin Mirmiran
- Department of Clinical Nutrition and Human Dietetics, Faculty of Nutrition Sciences and Food Technology, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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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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Koppe L, Nyam E, Vivot K, Manning Fox JE, Dai XQ, Nguyen BN, Trudel D, Attané C, Moullé VS, MacDonald PE, Ghislain J, Poitout V. Urea impairs β cell glycolysis and insulin secretion in chronic kidney disease. J Clin Invest 2016; 126:3598-612. [PMID: 27525435 DOI: 10.1172/jci86181] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 06/24/2016] [Indexed: 12/25/2022] Open
Abstract
Disorders of glucose homeostasis are common in chronic kidney disease (CKD) and are associated with increased mortality, but the mechanisms of impaired insulin secretion in this disease remain unclear. Here, we tested the hypothesis that defective insulin secretion in CKD is caused by a direct effect of urea on pancreatic β cells. In a murine model in which CKD is induced by 5/6 nephrectomy (CKD mice), we observed defects in glucose-stimulated insulin secretion in vivo and in isolated islets. Similarly, insulin secretion was impaired in normal mouse and human islets that were cultured with disease-relevant concentrations of urea and in islets from normal mice treated orally with urea for 3 weeks. In CKD mouse islets as well as urea-exposed normal islets, we observed an increase in oxidative stress and protein O-GlcNAcylation. Protein O-GlcNAcylation was also observed in pancreatic sections from CKD patients. Impairment of insulin secretion in both CKD mouse and urea-exposed islets was associated with reduced glucose utilization and activity of phosphofructokinase 1 (PFK-1), which could be reversed by inhibiting O-GlcNAcylation. Inhibition of O-GlcNAcylation also restored insulin secretion in both mouse models. These results suggest that insulin secretory defects associated with CKD arise from elevated circulating levels of urea that increase islet protein O-GlcNAcylation and impair glycolysis.
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Long-term in vivo polychlorinated biphenyl 126 exposure induces oxidative stress and alters proteomic profile on islets of Langerhans. Sci Rep 2016; 6:27882. [PMID: 27292372 PMCID: PMC4904407 DOI: 10.1038/srep27882] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 05/24/2016] [Indexed: 12/15/2022] Open
Abstract
It has been recently proposed that exposure to polychlorinated biphenyls (PCBs) is a risk factor to type 2 diabetes mellitus (DM2). We investigated this hypothesis using long-term in vivo PCB126 exposure to rats addressing metabolic, cellular and proteomic parameters. Male Wistar rats were exposed to PCB126 (0.1, 1 or 10 μg/kg of body weight/day; for 15 days) or vehicle by intranasal instillation. Systemic alterations were quantified by body weight, insulin and glucose tolerance, and blood biochemical profile. Pancreatic toxicity was measured by inflammatory parameters, cell viability and cycle, free radical generation, and proteomic profile on islets of Langerhans. In vivo PCB126 exposure enhanced the body weight gain, impaired insulin sensitivity, reduced adipose tissue deposit, and elevated serum triglycerides, cholesterol, and insulin levels. Inflammatory parameters in the pancreas and cell morphology, viability and cycle were not altered in islets of Langerhans. Nevertheless, in vivo PCB126 exposure increased free radical generation and modified the expression of proteins related to oxidative stress on islets of Langerhans, which are indicative of early β-cell failure. Data herein obtained show that long-term in vivo PCB126 exposure through intranasal route induced alterations on islets of Langerhans related to early end points of DM2.
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Bhardwaj A, Kaur J, Wuest F, Knaus EE. Do nitric oxide-releasing drugs offer a potentially new paradigm for the management of cardiovascular risks in diabetes? Expert Rev Cardiovasc Ther 2014; 12:533-6. [PMID: 24725228 DOI: 10.1586/14779072.2014.897227] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cardiovascular complications are frequently observed in diabetic patients and are mostly caused by endothelial dysfunction associated with a decline in biosynthesis of nitric oxide (NO). In response to this concern, a remarkable increase in the interest for development of NO-releasing hybrid drugs has been observed. The NO-donating entity was linked to known drugs with the belief that NO is a vasorelaxant and an inhibitor of platelet aggregation or reduces thrombotic events. Many of these NO-releasing hybrid drugs have shown significant improvement in cardiovascular safety. In this editorial the potential roles of NO-releasing drugs for the treatment of cardiovascular complications in diabetes will be discussed.
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Affiliation(s)
- Atul Bhardwaj
- Department of Oncology, University of Alberta, Edmonton, AB, T6G 1Z2, Canada
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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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Galal O, Podlogar J, Verspohl EJ. Impact of ADMA (asymmetric dimethylarginine) on physiology with respect to diabetes mellitus and respiratory system BEAS-2B cells (human bronchial epithelial cells). ACTA ACUST UNITED AC 2012; 65:253-63. [PMID: 23278693 DOI: 10.1111/j.2042-7158.2012.01590.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 08/12/2012] [Indexed: 11/27/2022]
Abstract
OBJECTIVES Asymmetric dimethylarginine (ADMA) is a non-selective nitric oxide (NO) synthase inhibitor associated with cardiovascular and metabolic disorders. This study aimed to investigate ADMA with respect to both diabetes and respiratory disease. METHODS Glucose was determined by hexokinase method, insulin by a radioimmunoassay. Griess test was used for NO assay and cytokinines were assayed by ELISA. Ciliary beat frequency was determined by high speed video using a microscope. KEY FINDINGS ADMA induced an increase in blood glucose and plasma insulin levels in rats; the ratio of these effects indicates the induction of a diabetic situation (insulin resistance). L-arginine increased blood glucose and initially slightly decreased plasma insulin. A pretreatment with ADMA abolished these effects. ADMA shows similar effects in vitro (insulin-secreting cell line, INS-1 cells). L-arginine increased production of NO, which was reversed by ADMA (INS-1 cells). ADMA also reduced NO production positively modulated by various substances, namely metformin, ciglitazone, losartan and nateglinide, but nevertheless inhibited insulin release induced by these compounds. ADMA stimulated the production of cytokines such as interleukin (IL-6) and macrophage inflammatory protein-2 (MIP-2) (rat IL-8 analogue) from INS-1 cells. 5-Aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR), a direct adenosine monophosphate protein kinase (AMPK) activator and anti-inflammatory agent, induced NO production and reduced cytokine release. In contrast to diabetes parameters, ADMA had no effect of on the respiratory system (cytokine secretion from BEAS-2B cells (IL-8, regulated on activation, normal T cell expressed and secreted, and tumour necrosis factor-α), ciliary beat frequency and smooth muscle contraction of rat trachea). CONCLUSIONS ADMA has a pathophysiological impact leading to a diabetic situation but has no impact on the respiratory system.
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Affiliation(s)
- Omneya Galal
- Department of Pharmacology, Inst Medicinal Chem, Muenster, Germany
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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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Zhang HH, Feng L, Livnat I, Hoh JK, Shim JY, Liao WX, Chen DB. Estradiol-17beta stimulates specific receptor and endogenous nitric oxide-dependent dynamic endothelial protein S-nitrosylation: analysis of endothelial nitrosyl-proteome. Endocrinology 2010; 151:3874-87. [PMID: 20519370 PMCID: PMC2940521 DOI: 10.1210/en.2009-1356] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Covalent adduction of a nitrosyl group to cysteines [S-nitrosylation (S-NO)] is emerging as a key route for nitric oxide (NO) to directly modulate protein functions. Here, we studied the effects of estrogens on endothelial protein S-NO and analyzed the nitrosyl-proteomes by biotin/CyDye switch technique combined with two-dimensional fluorescence difference gel electrophoresis and identified nitrosoproteins by matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Estradiol-17beta (E2) rapidly stimulated protein S-NO in human umbilical vein endothelial cells, maximizing within 10- to 30-min post-E2 (10 nm) exposure. E2-BSA also rapidly stimulated protein S-NO. Both E2 and E2-BSA-induced protein S-NO was blocked by ICI 182,780 and N-nitro-l-arginine-methylester. Human umbilical vein endothelial cells expressed estrogen receptor (ER)alpha and ERbeta; both seemed to be required for E2 stimulation of protein S-NO because: 1) neither ERalpha or ERbeta agonist alone, but their combination, stimulated protein S-NO; and 2) either ERalpha or ERbeta antagonist blocked E2-induced protein S-NO. Numerous nitrosoproteins (spots) were observed on two-dimensional fluorescence difference gel. One hundred spots of interest were picked up; 58 were identified and, of which 15 were novel nitrosoproteins, 28 were up-regulated, 11 were decreased, and the rest were unchanged by E2. Pathway analysis suggested that nitrosoproteins are involved in regulating various endothelial functions, including apoptosis, cell structure and metabolism, redox homeostasis, etc. Thus, estrogens stimulate dynamic endothelial protein S-NO via mechanisms linked to specific ERs possibly on the plasma membrane and endogenous NO. These findings signify a critical next step for the understanding of the biological targets of enhanced NO production by estrogens.
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Affiliation(s)
- Hong-Hai Zhang
- Department of Obstetrics and Gynecology, University of California Irvine, Irvine, California 92697, USA
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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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Khairallah RJ, Khairallah M, Gélinas R, Bouchard B, Young ME, Allen BG, Lopaschuk GD, Deschepper CF, Des Rosiers C. Cyclic GMP signaling in cardiomyocytes modulates fatty acid trafficking and prevents triglyceride accumulation. J Mol Cell Cardiol 2008; 45:230-9. [PMID: 18590915 DOI: 10.1016/j.yjmcc.2008.05.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2008] [Revised: 05/05/2008] [Accepted: 05/20/2008] [Indexed: 12/21/2022]
Abstract
While the balance between carbohydrates and fatty acids for energy production appears to be crucial for cardiac homeostasis, much remains to be learned about the molecular mechanisms underlying this relationship. Given the reported benefits of cGMP signaling on the myocardium, we investigated the impact of its chronic activation on cardiac energy metabolism using mice overexpressing a constitutively active cytoplasmic guanylate cyclase (GC(+/0)) in cardiomyocytes. Ex vivo working GC(+/0) heart perfusions with (13)C-labeled substrates revealed an altered pattern of exogenous substrate fuel selection compared to controls, namely a 38+/-9% lower contribution of exogenous fatty acids to acetyl-CoA formation, while that of carbohydrates remains unchanged despite a two-fold increase in glycolysis. The lower contribution of exogenous fatty acids to energy production is not associated with changes in energy demand or supply (contractile function, oxygen consumption, tissue acetyl-CoA or CoA levels, citric acid cycle flux rate) or in the regulation of beta-oxidation (acetyl-CoA carboxylase activity, tissue malonyl-CoA levels). However, GC(+/0) hearts show a two-fold increase in the incorporation of exogenous oleate into triglycerides. Furthermore, the following molecular data are consistent with a concomitant increase in triglyceride hydrolysis: (i) increased abundance of hormone sensitive lipase (HSL) protein (24+/-11%) and mRNA (22+/-4%) as well as (ii) several phosphorylation events related to HSL inhibitory (AMPK) and activation (ERK 1/2) sites, which should contribute to enhance its activity. These changes in exogenous fatty acid trafficking in GC(+/0) hearts appear to be functionally relevant, as demonstrated by their resistance to fasting-induced triglyceride accumulation. While the documented metabolic profile of GC(+/0) mouse hearts is partly reminiscent of hypertrophied hearts, the observed changes in lipid trafficking have not been previously documented, and may be part of the molecular mechanism underlying the benefits of cGMP signaling on the myocardium.
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Affiliation(s)
- Ramzi J Khairallah
- Montreal Heart Institute, University of Montreal, Montreal, Quebec, Canada
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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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Dual effect of nitric oxide on ATP-sensitive K+ channels in rat pancreatic beta cells. Pflugers Arch 2008; 456:573-9. [PMID: 18239934 DOI: 10.1007/s00424-008-0463-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Revised: 01/11/2008] [Accepted: 01/17/2008] [Indexed: 10/22/2022]
Abstract
We have previously shown that NO has stimulatory and inhibitory effects on insulin secretion at low and high concentrations, respectively. The present study investigated effects of NO on K ATP channels of rat beta cells by patch clamp analysis to elucidate the mechanism for the dual effect. NOC7 at 0.5 microM suppressed K ATP channels activated by diazoxide in the cell-attached and perforated whole-cell modes but failed to suppress them in the inside-out mode. The inhibitory effect in the cell-attached mode was abolished by the soluble guanylate cyclase inhibitor ODQ and by the protein kinase G inhibitor KT5823. Moreover, 0.5 microM NOC7 failed to suppress the channel activity in the presence of the mitochondrial uncoupler FCCP. In contrast, 10 microM NOC7 activated K ATP channels in the cell-attached and perforated whole-cell modes, although it had no effect on the channels in the inside-out mode. The K ATP currents evoked by 10 microM NOC7 in the cell-attached mode were not inhibited by ODQ. The dual effect of NOC7 at 0.5 and 10 microM was observed in the same patch. Taken together, these results suggest that low-concentration NO exerts an inhibitory effect on K ATP channels of beta cells, which is induced through the cGMP/protein kinase G pathway, whereas high-concentration NO activates K ATP channels through the mechanism independent of cGMP.
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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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Abstract
In numerous mammals, nitric oxide (NO) influences the activity of the exocrine and endocrine pancreas. In this study, immunocytochemistry was utilized to investigate the expression of neuronal nitric oxide synthase (nNOS) in the pancreas of sheep. In double immunocytochemical staining, the co-localization of nNOS with vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY) or substance P (SP) was studied. The presence of nNOS was confined to the intrapancreatic neurones (9.6 +/- 1.3%) as well as to nerve fibres of the endocrine pancreas and intrapancreatic ganglia. nNOS-immunoreactive (IR) neurones were round and oval in shape and predominantly (83.3 +/- 2.6%) belonged to the middle-size group (25-50 mum). Numerous, fine islets supplying nNOS-IR nerve terminals were devoid of VIP, SP or NPY. Moderately numerous, non-varicose nNOS-IR nerve fibres of intrapancreatic ganglia frequently expressed VIP or NPY, but not SP; 2.2 +/- 0.6% of nNOS-IR intrapancreatic neurones displayed lack of VIP, whereas 7.5 +/- 0.8% were VIP-IR. All nNOS-IR neurones were devoid of SP. The frequencies of nNOS-IR/NPY-IR and nNOS-IR/NPY-negative intrapancreatic neurones were 2.2 +/- 0.4% and 6.1 +/- 1.1%, respectively. Comparison with other mammals indicated that nitrergic innervation of the ovine pancreas is species-determined and may be a reflection of the ruminants' digestion specificity. The possible origin of nNOS-IR nerve fibres and functional significance of NO in the pancreas of sheep were discussed.
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Affiliation(s)
- M B Arciszewski
- Department of Animal Anatomy and Histology, Faculty of Veterinary Medicine, Agricultural University, Akademicka 12, 20-033 Lublin, Poland.
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Vasilijevic A, Buzadzic B, Korac A, Petrovic V, Jankovic A, Korac B. Beneficial effects of L-arginine nitric oxide-producing pathway in rats treated with alloxan. J Physiol 2007; 584:921-33. [PMID: 17717015 PMCID: PMC2276988 DOI: 10.1113/jphysiol.2007.140277] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In an attempt to elucidate molecular mechanisms and factors involved in beta cell regeneration, we evaluated a possible role of the L-arginine-nitric oxide (NO)-producing pathway in alloxan-induced diabetes mellitus. Diabetes was induced in male Mill Hill rats with a single alloxan dose (120 mg kg(-1)). Both non-diabetic and diabetic groups were additionally separated into three subgroups: (i) receiving L-arginine . HCl (2.25%), (ii) receiving L-NAME . HCl (0.01%) for 12 days as drinking liquids, and (iii) control. Treatment of diabetic animals started after diabetes induction (glucose level > or = 12 mmol l(-1)). We found that disturbed glucose homeostasis, i.e. blood insulin and glucose levels in diabetic rats was restored after L-arginine treatment. Immunohistochemical findings revealed that L-arginine had a favourable effect on beta cell neogenesis, i.e. it increased the area of insulin-immunopositive cells. Moreover, confocal microscopy showed colocalization of insulin and pancreas duodenum homeobox-1 (PDX-1) in both endocrine and exocrine pancreas. This increase in insulin-expressing cells was accompanied by increased cell proliferation (observed by proliferating cell nuclear antigen-PCNA immunopositivity) which occurred in a regulated manner since it was associated with increased apoptosis (detected by the TUNEL method). Furthermore, L-arginine enhanced both nuclear factor-kB (NF-kB) and neuronal nitric oxide synthase (nNOS) immunopositivities. The effect of L-arginine on antioxidative defence was observed especially in restoring to control level the diabetes-induced increase in glutathione peroxidase activity. In contrast to L-arginine, diabetic pancreas was not affected by L-NAME supplementation. In conclusion, the results suggest beneficial L-arginine effects on alloxan-induced diabetes resulting from the stimulation of beta cell neogenesis, including complex mechanisms of transcriptional and redox regulation.
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Affiliation(s)
- Ana Vasilijevic
- Department of Physiology, Institute for Biological Research, Sinia Stankovi, University of Belgrade, Bulevar Despota Stefana 142, 11060, Belgrade, Serbia
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Kitiphongspattana K, Khan TA, Ishii-Schrade K, Roe MW, Philipson LH, Gaskins HR. Protective role for nitric oxide during the endoplasmic reticulum stress response in pancreatic beta-cells. Am J Physiol Endocrinol Metab 2007; 292:E1543-54. [PMID: 17264231 DOI: 10.1152/ajpendo.00620.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Higher requirements for disulfide bond formation in professional secretory cells may affect intracellular redox homeostasis, particularly during an endoplasmic reticulum (ER) stress response. To assess this hypothesis, we investigated the effects of the ER stress response on the major redox couple (GSH/GSSG), endogenous ROS production, expression of genes involved in ER oxidative protein folding, general antioxidant defense, and thiol metabolism by use of the well-validated MIN6 beta-cell as a model and mouse islets. The data revealed that glucose concentration-dependent decreases in the GSH/GSSG ratio were further decreased significantly by ER-derived oxidative stress induced by inhibiting ER-associated degradation with the specific proteasome inhibitor lactacystin (10 microM) in mouse islets. Notably, minimal cell death was observed during 12-h treatments. This was likely attributed to the upregulation of genes encoding the rate limiting enzyme for glutathione synthesis (gamma-glutamylcysteine ligase), as well as genes involved in antioxidant defense (glutathione peroxidase, peroxiredoxin-1) and ER protein folding (Grp78/BiP, PDI, Ero1). Gene expression and reporter assays with a NO synthase inhibitor (Nomega-nitro-L-arginine methyl ester, 1-10 mM) indicated that endogenous NO production was essential for the upregulation of several ER stress-responsive genes. Specifically, gel shift analyses demonstrate NO-independent binding of the transcription factor NF-E2-related factor to the antioxidant response element Gclc-ARE4 in MIN6 cells. However, endogenous NO production was necessary for activation of Gclc-ARE4-driven reporter gene expression. Together, these data reveal a distinct protective role for NO during the ER stress response, which helps to dissipate ROS and promote beta-cell survival.
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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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Nunemaker CS, Buerk DG, Zhang M, Satin LS. Glucose-induced release of nitric oxide from mouse pancreatic islets as detected with nitric oxide-selective glass microelectrodes. Am J Physiol Endocrinol Metab 2007; 292:E907-12. [PMID: 17122087 DOI: 10.1152/ajpendo.00518.2006] [Citation(s) in RCA: 7] [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: 11/22/2022]
Abstract
Nitric oxide (NO) is believed to play an important role in pancreatic islet physiology and pathophysiology. Research in this area has been hampered, however, by the use of indirect methods to measure islet NO. To investigate the role of NO in islet function, we positioned NO-sensitive, recessed-tip microelectrodes in close proximity to individual islets and monitored oxidation current to detect subnanomolar NO in the bath. NO release from islets consisted of a series of rapid bursts lasting several seconds and/or slow oscillations with a period of approximately 100-300 s. Average baseline NO near the islets in 2.8 mM glucose was 524+/-59 nM (n=12). Raising glucose from 2.8 to 11.1 mM augmented NO release by 429+/-133 nM (n=12, P<0.05), an effect blocked by the NO synthase inhibitor L-NAME (n=3). We also observed that glucose-stimulated increases in NO release were contemporaneous with changes in NAD(P)H and O2 but occurred well before increases in calcium associated with glucose-stimulated insulin secretion. In summary, we demonstrate that NO release from islets is oscillatory and rapidly augmented by glucose, suggesting that NO release occurs early following an increase in glucose metabolism and may contribute to the stimulated insulin secretion triggered by suprathreshold glucose.
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Affiliation(s)
- Craig S Nunemaker
- University of Virginia Health Sciences, Department of Internal Medicine, Charlottesville, VA 23298, USA
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25
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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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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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Stanley WC, Recchia FA, Lopaschuk GD. Myocardial substrate metabolism in the normal and failing heart. Physiol Rev 2005; 85:1093-129. [PMID: 15987803 DOI: 10.1152/physrev.00006.2004] [Citation(s) in RCA: 1391] [Impact Index Per Article: 73.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The alterations in myocardial energy substrate metabolism that occur in heart failure, and the causes and consequences of these abnormalities, are poorly understood. There is evidence to suggest that impaired substrate metabolism contributes to contractile dysfunction and to the progressive left ventricular remodeling that are characteristic of the heart failure state. The general concept that has recently emerged is that myocardial substrate selection is relatively normal during the early stages of heart failure; however, in the advanced stages there is a downregulation in fatty acid oxidation, increased glycolysis and glucose oxidation, reduced respiratory chain activity, and an impaired reserve for mitochondrial oxidative flux. This review discusses 1) the metabolic changes that occur in chronic heart failure, with emphasis on the mechanisms that regulate the changes in the expression of metabolic genes and the function of metabolic pathways; 2) the consequences of these metabolic changes on cardiac function; 3) the role of changes in myocardial substrate metabolism on ventricular remodeling and disease progression; and 4) the therapeutic potential of acute and long-term manipulation of cardiac substrate metabolism in heart failure.
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Affiliation(s)
- William C Stanley
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, Ohio 44106-4970, USA.
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Jansson L, Carlsson PO, Bodin B, Andersson A, Källskog O. Neuronal nitric oxide synthase and splanchnic blood flow in anaesthetized rats. ACTA ACUST UNITED AC 2005; 183:257-62. [PMID: 15743385 DOI: 10.1111/j.1365-201x.2004.01396.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS To evaluate to what extent the neuronal form of constitutive nitric oxide synthase (nNOS) contributes to the blood perfusion of splanchnic organs, including the islets of Langerhans. METHODS The nNOS inhibitor 7-nitroindazole (300 mg kg(-1) i.p.) was administered to anaesthetized Sprague-Dawley rats, some of which were pre-treated with the ganglionic blocker hexamethonium (20 mg kg(-1) i.v.) The blood perfusion of the splanchnic organs, including the pancreatic islets was then measured with a microsphere technique. RESULTS Nitroindazole decreased total pancreatic, duodenal and renal blood flow, whereas pancreatic islet, colonic and adrenal blood flows were unchanged. A slight increase in mean arterial blood pressure was seen after nitroindazole treatment. Nitroindazole did not affect blood glucose or serum insulin concentrations. In separate experiments, hexamethonium affected none of the studied blood flow values, suggesting that the effects of nNOS-inhibition were not mediated from the nervous system. CONCLUSION Nitric oxide derived from the activity of nNOS contributes to the blood perfusion in the upper portions of the gastrointestinal tract, viz. the parts supplied by the cranial mesenteric artery, and the kidneys, whilst no effects are seen on colonic or adrenal blood flow. Pancreatic islet blood flow was unaffected by nNOS inhibition, thereby suggesting that NO derived from the other isoforms of NOS maintains the high basal islet blood perfusion.
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Affiliation(s)
- L Jansson
- Department of Medical Cell Biology, Biomedical Center, Uppsala University, SE 751 23 Uppsala, 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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Farret A, Vignaud M, Dietz S, Vignon J, Petit P, Gross R. P2Y purinergic potentiation of glucose-induced insulin secretion and pancreatic beta-cell metabolism. Diabetes 2004; 53 Suppl 3:S63-6. [PMID: 15561924 DOI: 10.2337/diabetes.53.suppl_3.s63] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Purine nucleotides and their analogs increase insulin secretion through activation of pancreatic beta-cell P2Y receptors. The present study aimed at determining the role of glucose metabolism in the response to P2Y agonists and whether ATP-activated K+ channels (KATP channels) are involved in this response. The experiments were performed in the rat isolated pancreas, perfused with a Krebs-bicarbonate buffer supplemented with 2 g/l bovine serum albumin under dynamic glucose conditions from 5 mmol/l baseline to 11 mmol/l. ADPbetaS (0.5 micromol/l) was selected as a stable and selective P2Y agonist. This compound, ineffective on the 5 mmol/l glucose background, induced a significant threefold increase in insulin release triggered by the glucose challenge. The effect of ADPbetaS was markedly reduced (P <0.001) in the presence of an inhibitor of glucose metabolism. In addition to glucose, the ADP analog also amplified the beta-cell insulin response to 15 mmol/l methyl pyruvate (P <0.05), but it was ineffective on the insulin response to 2.5 mmol/l methyl succinate. A nonmetabolic stimulus was applied using tolbutamide (185 micromol/l). Insulin secretion induced by the KATP channel blocker was strongly reinforced by ADPbetaS (P <0.001), which prompted us to check a possible interplay of KATP channels in the effect of ADPbetaS. In the presence of diazoxide 250 micromol/l and 21 mmol/l KCl, ADPbetaS still amplified the second phase of glucose-induced insulin secretion (P <0.001). We conclude that P2Y receptor activation is able to promote insulin secretion through a mechanism, involving beta-cell metabolism and a rise in intracellular calcium; this effect does not result from a direct inhibitory effect on KATP channels.
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Affiliation(s)
- A Farret
- Center for Pharmacology and Health Biotechnology, CNRS UMR 5160, Faculté de Médecine, Institut de Biologie, 4 Boulevard Henri IV, CS89508, 34960 Montpellier Cedex 2, France
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31
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Stoppiglia LF, Rezende LF, Ferreira F, Filiputti E, Carneiro EM, Boschero AC. Characterization of the peroxidase system at low H2O2 concentrations in isolated neonatal rat islets. Biochim Biophys Acta Mol Basis Dis 2004; 1690:159-68. [PMID: 15469905 DOI: 10.1016/j.bbadis.2004.06.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2004] [Revised: 06/09/2004] [Accepted: 06/14/2004] [Indexed: 11/18/2022]
Abstract
B cell destruction during the onset of diabetes mellitus is associated with oxidative stress. In this work, we attempted to further trace the fate of H2O2 inside the pancreatic islets and determine whether it is mediated by enzymatic (peroxidase) activity or by chemical reaction with thiols from any protein chain. Our results suggest that the islet cells have a very similar peroxidase activity at the hydrophilic (cytoplasm) and hydrophobic compartments (organelles and nucleus), independent of the catalase content of the samples. This activity is composed of sacrificial thiols and by proteins with Fe3+/Mn3+ ions at non-heme catalytic sites. The capacity of the hydrophobic fraction to scavenge O2- was increased in the presence of high concentrations of NADP* and RS* and was highly dependent on RSH. On the contrary, the hydrophilic fraction exhibited a low RSH-dependent activity where the O2- scavenging is related to metal Cu2+/Fe3+/Mn3+ ions attached to the protein molecules.
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Affiliation(s)
- Luiz F Stoppiglia
- Departamento de Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas, CP 6109, 13083-970, SP, Brazil
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32
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Lajoix AD, Pugnière M, Roquet F, Mani JC, Dietz S, Linck N, Faurie F, Ribes G, Petit P, Gross R. Changes in the dimeric state of neuronal nitric oxide synthase affect the kinetics of secretagogue-induced insulin response. Diabetes 2004; 53:1467-74. [PMID: 15161750 DOI: 10.2337/diabetes.53.6.1467] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We previously showed that pancreatic beta-cells express a neuronal isoform of nitric oxide synthase (nNOS) that controls insulin secretion by exerting two enzymatic activities: nitric oxide (NO) production and cytochrome c reductase activity. We now bring evidence that two inhibitors of nNOS, N-omega-nitro-l-arginine methyl ester (l-NAME) and 7-nitroindazole (7-NI), increase glucose-induced insulin secretion but affect beta-cell function differently. In the presence of l-NAME, insulin response is monophasic, whereas 7-NI preserves the normal biphasic secretory pattern. In addition, the alterations of beta-cell functional response induced by the inhibitors also differ by their sensitivity to a substitutive treatment with sodium nitroprusside, a chemical NO donor. These differences are probably related to the nature of the two inhibitors. Indeed, using low-temperature SDS-PAGE and real-time analysis of nNOS dimerization by surface plasmon resonance, we could show that 7-NI, which competes with arginine and tetrahydrobiopterin (BH(4)), an essential cofactor for nNOS dimer formation, inhibits dimerization of the enzyme, whereas the substrate-based inhibitor l-NAME stabilizes the homodimeric state of nNOS. The latter effect could be reproduced by the two endogenous inhibitors of NOS, N-omega-methyl-l-arginine and asymmetric dimethylarginine, and resulted interestingly in a reduced ability of the protein inhibitor of nNOS (PIN) to dissociate nNOS dimers. We conclude that intracellular factors able to induce abnormalities in the nNOS monomer/dimer equilibrium could lead to pancreatic beta-cell dysfunction.
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Affiliation(s)
- Anne-Dominique Lajoix
- CNRS UMR 5160, Institut de Biologie, 4 Boulevard Henri IV, 34960 Montpellier Cedex 2, France
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Kaneko Y, Ishikawa T, Amano S, Nakayama K. Dual effect of nitric oxide on cytosolic Ca2+ concentration and insulin secretion in rat pancreatic beta-cells. Am J Physiol Cell Physiol 2003; 284:C1215-22. [PMID: 12529241 DOI: 10.1152/ajpcell.00223.2002] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In isolated rat pancreatic beta-cells, the nitric oxide (NO) donor NOC-7 at 1 microM reduced the amplitude of the oscillations of cytosolic Ca(2+) concentration ([Ca(2+)](c)) induced by 11.1 mM glucose, and at 10 microM terminated them. In the presence of N(G)-nitro-l-arginine (l-NNA), however, NOC-7 at 0.5 and 1 microM increased the amplitude of the [Ca(2+)](c) oscillations, although the NO donor at 10 microM still suppressed them. Aqueous NO solution also had a dual effect on the [Ca(2+)](c) oscillations. The soluble guanylate cyclase inhibitor LY-83583 and the cGMP-dependent protein kinase inhibitor KT5823 inhibited the stimulatory effect of NO, and 8-bromo-cGMP increased the amplitude of the [Ca(2+)](c) oscillations. Patch-clamp analyses in the perforated configuration showed that 8-bromo-cGMP inhibited whole cell ATP-sensitive K(+) currents in the isolated rat pancreatic beta-cells, suggesting that the inhibition by cGMP of ATP-sensitive K(+) channels is, at least in part, responsible for the stimulatory effect of NO on the [Ca(2+)](c) oscillations. In the presence of l-NNA, the glucose-induced insulin secretion from isolated islets was facilitated by 0.5 microM NOC-7, whereas it was suppressed by 10 microM NOC-7. These results suggest that NO facilitates glucose-induced [Ca(2+)](c) oscillations of beta-cells and insulin secretion at low concentrations, which effects are mediated by cGMP, whereas NO inhibits them in a cGMP-independent manner at high concentrations.
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Affiliation(s)
- Yukiko Kaneko
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka City, Shizuoka 422-8526, Japan
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Smukler SR, Tang L, Wheeler MB, Salapatek AMF. Exogenous nitric oxide and endogenous glucose-stimulated beta-cell nitric oxide augment insulin release. Diabetes 2002; 51:3450-60. [PMID: 12453899 DOI: 10.2337/diabetes.51.12.3450] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The role nitric oxide (NO) plays in physiological insulin secretion has been controversial. Here we present evidence that exogenous NO stimulates insulin secretion, and that endogenous NO production occurs and is involved in the regulation of insulin release. Radioimmunoassay measurement of insulin release and a dynamic assay of exocytosis using the dye FM1-43 demonstrated that three different NO donors-hydroxylamine (HA), sodium nitroprusside, and 3-morpholinosydnonimine (SIN-1)-each stimulated a marked increase in insulin secretion from INS-1 cells. Pharmacological manipulation of the guanylate cyclase/guanosine 3',5'-cyclic monophosphate pathway indicated that this pathway was involved in mediating the effect of the intracellular NO donor, HA, which was used to simulate endogenous NO production. This effect was further characterized as involving membrane depolarization and intracellular Ca(2+) ([Ca(2+)](i)) elevation. SIN-1 application enhanced glucose-induced [Ca(2+)](i) responses in primary beta-cells and augmented insulin release from islets in a glucose-dependent manner. Real-time monitoring of NO using the NO-sensitive fluorescent dye, diaminofluorescein, was used to provide direct and dynamic imaging of NO generation within living beta-cells. This showed that endogenous NO production could be stimulated by elevation of [Ca(2+)](i) levels and by glucose in both INS-1 and primary rat beta-cells. Scavenging endogenously produced NO-attenuated glucose-stimulated insulin release from INS-1 cells and rat islets. Thus, the results indicated that applied NO is able to exert an insulinotropic effect, and implicated endogenously produced NO in the physiological regulation of insulin release.
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Affiliation(s)
- Simon R Smukler
- Department of Physiology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
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35
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Stoppiglia LF, Nogueira TA, Leite AR, Carneiro EM, Boschero AC. Protective effect of D-glucose, L-leucine and fetal calf serum against oxidative stress in neonatal pancreatic islets. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1588:113-8. [PMID: 12385774 DOI: 10.1016/s0925-4439(02)00154-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
B-cell destruction during the onset of diabetes mellitus is associated with oxidative stress. In this work, we investigated the mechanisms of defense against oxidative stress present in neonatal islets and their modulation by D-glucose, L-leucine and fetal calf serum (FCS). Culturing neonatal rat islets in the presence of low D-glucose concentrations (2.8-5.6 mmol/l) and 1 mmol/l H(2)O(2) increased the D-glucose uptake by islets sixfold compared to control levels. This effect was dose-dependently inhibited by D-glucose or FCS and by high concentrations of L-leucine. These supplements allowed islets to increase cytoplasmic catalase (CAT) activity only in response to H(2)O(2), with no decrease in NO formation. Although L-leucine increased CAT activity and restored D-glucose uptake, it did not prevent damage to the islets. These data indicate that the most important H(2)O(2) scavenger system in the islets is CAT and that this system can be modulated by metabolic substrates.
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Affiliation(s)
- Luiz F Stoppiglia
- Departamento de Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), CP 6109, Campinas 13083-970, SP, Brazil
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36
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Henningsson R, Salehi A, Lundquist I. Role of nitric oxide synthase isoforms in glucose-stimulated insulin release. Am J Physiol Cell Physiol 2002; 283:C296-304. [PMID: 12055099 DOI: 10.1152/ajpcell.00537.2001] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The role of islet constitutive nitric oxide synthase (cNOS) in insulin-releasing mechanisms is controversial. By measuring enzyme activities and protein expression of NOS isoforms [i.e., cNOS and inducible NOS (iNOS)] in islets of Langerhans cells in relation to insulin secretion, we show that glucose dose-dependently stimulates islet activities of both cNOS and iNOS, that cNOS-derived nitric oxide (NO) strongly inhibits glucose-stimulated insulin release, and that short-term hyperglycemia in mice induces islet iNOS activity. Moreover, addition of NO gas or an NO donor inhibited glucose-stimulated insulin release, and different NOS inhibitors effected a potentiation. These effects were evident also in K+-depolarized islets in the presence of the ATP-sensitive K+ channel opener diazoxide. Furthermore, our results emphasize the necessity of measuring islet NOS activity when using NOS inhibitors, because certain concentrations of certain NOS inhibitors might unexpectedly stimulate islet NO production. This is shown by the observation that 0.5 mmol/l of the NOS inhibitor N(G)-monomethyl-L-arginine (L-NMMA) stimulated cNOS activity in parallel with an inhibition of the first phase of glucose-stimulated insulin release in perifused rats islets, whereas 5.0 mmol/l of L-NMMA markedly suppressed cNOS activity concomitant with a great potentiation of the insulin secretory response. The data strongly suggest, but do not definitely prove, that glucose indeed has the ability to stimulate both cNOS and iNOS in the islets and that NO might serve as a negative feedback inhibitor of glucose-stimulated insulin release. The results also suggest that hyperglycemia-evoked islet NOS activity might be one of multiple factors involved in the impairment of glucose-stimulated insulin release in type II diabetes mellitus.
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Affiliation(s)
- Ragnar Henningsson
- Institute of Physiological Sciences, Department of Pharmacology, University of Lund, S-221 84 Lund, Sweden
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37
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Thomas WJ, Thomas DL, Knezetic JA, Adrian TE. The role of oxygen-derived free radicals and nitric oxide in cytokine-induced antiproliferation of pancreatic cancer cells. Pancreas 2002; 24:161-8. [PMID: 11854621 DOI: 10.1097/00006676-200203000-00007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
INTRODUCTION Pancreatic cancer cells are susceptible to antiproliferative effects of cytokines such as tumor necrosis factor-alpha (TNF-alpha). However, little is known about the mechanisms involved. AIM To determine the mechanisms of the antiproliferative effects of TNF-alpha on pancreatic cancer cells. METHODOLOGY AND RESULTS In the current study, four of five pancreatic cancer cell lines tested were responsive to the antiproliferative effects of TNF-alpha. In two cell lines, the effects of TNF-alpha were completely abolished by superoxide dismutase, suggesting that superoxide anion mediates the effects. Further, inhibition of nitric oxide (NO) synthase by L-NAME potentiated the TNF-alpha response, suggesting a protective role for endogenously produced NO in these two cell lines. MiaPaCa-2 cells, which were unresponsive to the antiproliferative effects of TNF-alpha, produced five times more nitrite than the other cell lines. Treatment of MiaPaCa-2 cells with interferon-gamma (IFN-gamma) increased inducible nitric oxide synthase mRNA as shown by reverse transcription-polymerase chain reaction. This induction was potentiated by TNF-alpha and further enhanced by a combination of three cytokines (INF-gamma, TNF-alpha, and interleukin 1-beta (IL-1beta). This combination of cytokines increased nitrite accumulation fourfold and inhibited the proliferation of this resistant cell line. These effects were prevented by L-NAME. CONCLUSIONS These studies suggest that TNF-alpha inhibits proliferation of pancreatic cancer cells by increasing the production of superoxide anion and that endogenously produced NO protects against this effect. In addition, there is a direct correlation between the amount of NO produced and resistance to TNF-alpha in the only resistant cell line. In contrast, treatment with a combination of IFN-gamma, TNF-alpha and IL-1beta upregulates inducible nitric oxide synthase, and the resulting markedly enhanced NO production inhibits pancreatic cancer cell growth. This pathway may provide a valuable target for therapy of this devastating disease.
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Affiliation(s)
- William J Thomas
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska, U.S.A
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38
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Recchia FA, Osorio JC, Chandler MP, Xu X, Panchal AR, Lopaschuk GD, Hintze TH, Stanley WC. Reduced synthesis of NO causes marked alterations in myocardial substrate metabolism in conscious dogs. Am J Physiol Endocrinol Metab 2002; 282:E197-206. [PMID: 11739101 DOI: 10.1152/ajpendo.2002.282.1.e197] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To test whether the acute reduction of nitric oxide (NO) synthesis causes changes in cardiac substrate metabolism and in the activity of key enzymes of fatty acid and glucose oxidation, we blocked NOS by giving N(omega)-nitro-L-arginine methyl ester (L-NAME; 35 mg/kg iv two times) to nine chronically instrumented dogs. [3H]oleate, [14C]glucose, and [13C]lactate were infused to measure the rate of cardiac substrate uptake and oxidation. Glyceraldehyde-3-phosphate dehydrogenase, acetyl-CoA carboxylase, and malonyl-CoA decarboxylase activities were measured in myocardial biopsies. In eight control dogs, ANG II was infused (20-40 ng x kg(-1) x min(-1)) to mimic the hemodynamic effects of L-NAME. After L-NAME, significant changes occurred for fatty acid oxidation (from 9.8 +/- 0.8 to 7.1 +/- 1.2 micromol/min), glucose uptake (from 12.9 +/- 5.5 to 45.0 +/- 14.2 micromol/min), and oxidation (from 4.4 +/- 1.2 to 19.9 +/- 2.3 micromol/min). ANG caused only a significantly lower increase in glucose oxidation. Lactate uptake increased by more than twofold in both groups. The enzyme activities did not differ significantly between the two groups. In conclusion, the acute inhibition of NO synthesis causes marked metabolic alterations that do not involve key rate-controlling enzymes of fatty acid oxidation nor glyceraldehyde-3-phosphate dehydrogenase.
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Affiliation(s)
- Fabio A Recchia
- Department of Physiology, New York Medical College, Valhalla, New York 10595, USA.
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39
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Salehi A, Ekelund M, Henningsson R, Lundquist I. Total parenteral nutrition modulates hormone release by stimulating expression and activity of inducible nitric oxide synthase in rat pancreatic islets. Endocrine 2001; 16:97-104. [PMID: 11887940 DOI: 10.1385/endo:16:2:097] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The expression and activities of constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) in relation to insulin and glucagon secretory mechanisms were investigated in islets isolated from rats subjected to total parenteral nutrition (TPN) for 10 d. TPN is known to result in significantly increased levels of plasma lipids during the infusion time. In comparison with islets from freely fed control rats, islets taken from TPN rats at d 10 displayed a marked decrease in glucose-stimulated insulin release (4.65 +/- 0.45 ng/[islet x h] vs 10.25 +/- 0.65 for controls) (p < 0.001) accompanied by a strong iNOS activity (18.3 +/- 1.1 pmol of NO/[min x mg of protein]) and a modestly reduced cNOS activity (11.3 +/- 3.2 pmol of NO/[min x mg of protein] vs 17.7 +/- 1.7 for controls) (p < 0.01). Similarly, Western blots showed the expression of iNOS protein as well as a significant reduction in cNOS protein in islets from TPN-treated rats. The enhanced NO production, which is known to inhibit glucose-stimulated insulin release, was manifested as a strong increase in the cyclic guanosine 5'-monophosphate content in the islets of TPN-treated rats (1586 +/- 40 amol/islet vs 695 +/- 64 [p < 0.001] for controls). Moreover, the content of cyclic adenosine monophosphate (cAMP) was greatly increased in the TPN islets (80.4 +/- 2.1 fmol/islet vs 42.6 +/- 2.6 [p < 0.001] for controls). The decrease in glucose-stimulated insulin release was associated with an increase in the activity of the secretory pathway regulated by the cAMP system in the islets of TPN-treated rats, since the release of insulin stimulated by the phosphodiesterase inhibitor isobutylmethylxanthine was greatly increased both in vivo after iv injection and after in vitro incubation of isolated islets. By contrast, the release of glucagon was clearly reduced in islets taken from TPN-treated rats (33.5 +/- 1.5 pg/[islet x h] vs 45.5 +/- 2.2 for controls) (p < 0.01) when islets were incubated at low glucose (1.0 mmol/L). The data show that long-term TPN treatment in rats brings about impairment of glucose-stimulated insulin release, that might be explained by iNOS expression and a marked iNOS-derived NO production in the beta-cells. The release of glucagon, on the other hand, is probably decreased by a direct "nutrient effect" of the enhanced plasma lipids. The results also suggest that the islets of TPN-treated rats have developed compensatory insulin secretory mechanisms by increasing the activity of their beta-cell cAMP system.
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Affiliation(s)
- A Salehi
- Institute of Physiological Sciences, Department of Pharmacology, University of Lund, Sweden.
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Takeda T, Tsuura Y, Fujita J, Fujimoto S, Mukai E, Kajikawa M, Hamamoto Y, Kume M, Yamamoto Y, Yamaoka Y, Yamada Y, Seino Y. Heat shock restores insulin secretion after injury by nitric oxide by maintaining glucokinase activity in rat islets. Biochem Biophys Res Commun 2001; 284:20-5. [PMID: 11374865 DOI: 10.1006/bbrc.2001.4933] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heat shock protein (hsp), including hsp70, has been reported to restore the glucose-induced insulin release suppressed by nitric oxide (NO). However, the mechanism underlying this recovery remains unclear. In the present study, we examine the effects, in rat islets, of heat shock on insulin secretion inhibited by a small amount of NO and also on glucose metabolism, the crucial factor in insulin release. Exposure to a higher dose (15 U/ml) of interleukin-1beta (IL-1beta) abolished the insulin release by stimulation of glucose or KCl in both control and heat shocked islets. In rat islets exposed to a lower dose (1.5 U/ml) of IL-1beta, insulin secretion in response to glucose, but not to glyceraldehydes (GA), ketoisocaproate (KIC), or KCl, was selectively impaired, concomitantly with lower ATP concentrations in the presence of 16.7 mM glucose, while such suppression of insulin secretion and ATP content was not observed in heat shock-treated islets. NO production in islets exposed to 1.5 U/ml IL-1beta was significantly, but only partly, decreased by heat shock treatment. The glucose utilization rate measurement using [5-3H]-glucose and [2-3H]-glucose and the glucokinase activity in vitro were reduced in islets treated with 1.5 U/ml IL-1beta. In heat shock-treated islets, glucose utilization and glucokinase activity were not affected by 1.5 U/ml IL-1beta. These data suggest that heat shock restores glucose-induced insulin release inhibited by NO by maintaining glucokinase activity and the glucose utilization rate in islets in addition to reducing endogenous NO production.
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Affiliation(s)
- T Takeda
- Department of Metabolism and Clinical Nutrition, Kyoto University, Kyoto, Japan.
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41
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Lajoix AD, Reggio H, Chardès T, Péraldi-Roux S, Tribillac F, Roye M, Dietz S, Broca C, Manteghetti M, Ribes G, Wollheim CB, Gross R. A neuronal isoform of nitric oxide synthase expressed in pancreatic beta-cells controls insulin secretion. Diabetes 2001; 50:1311-23. [PMID: 11375331 DOI: 10.2337/diabetes.50.6.1311] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Evidence is presented showing that a neuronal isoform of nitric oxide synthase (NOS) is expressed in rat pancreatic islets and INS-1 cells. Sequencing of the coding region indicated a 99.8% homology with rat neuronal NOS (nNOS) with four mutations, three of them resulting in modifications of the amino acid sequence. Double-immunofluorescence studies demonstrated the presence of nNOS in insulin-secreting beta-cells. Electron microscopy studies showed that nNOS was mainly localized in insulin secretory granules and to a lesser extent in the mitochondria and the nucleus. We also studied the mechanism involved in the dysfunction of the beta-cell response to arginine and glucose after nNOS blockade with N(G)-nitro-L-arginine methyl ester. Our data show that miconazole, an inhibitor of nNOS cytochrome c reductase activity, either alone for the experiments with arginine or combined with sodium nitroprusside for glucose, is able to restore normal secretory patterns in response to the two secretagogues. Furthermore, these results were corroborated by the demonstration of a direct enzyme-substrate interaction between nNOS and cytochrome c, which is strongly reinforced in the presence of the NOS inhibitor. Thus, we provide immunochemical and pharmacological evidence that beta-cell nNOS exerts, like brain nNOS, two catalytic activities: a nitric oxide production and an NOS nonoxidating reductase activity, both of which are essential for normal beta-cell function. In conclusion, we suggest that an imbalance between these activities might be implicated in beta-cell dysregulation involved in certain pathological hyperinsulinic states.
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Affiliation(s)
- A D Lajoix
- Unité mixte de recherche 5094 du Centre National de la Recherche Scientifique (CNRS), Université Montpellier I, 34060 Montpellier Cedex 1, France
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Ihara Y, Yamada Y, Toyokuni S, Miyawaki K, Ban N, Adachi T, Kuroe A, Iwakura T, Kubota A, Hiai H, Seino Y. Antioxidant alpha-tocopherol ameliorates glycemic control of GK rats, a model of type 2 diabetes. FEBS Lett 2000; 473:24-6. [PMID: 10802052 DOI: 10.1016/s0014-5793(00)01489-7] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We have shown recently that oxidative stress by chronic hyperglycemia damages the pancreatic beta-cells of GK rats, a model of non-obese type 2 diabetes, which may worsen diabetic condition and suggested the administration of antioxidants as a supportive therapy. To determine if natural antioxidant alpha-tocopherol (vitamin E) has beneficial effects on the glycemic control of type 2 diabetes, GK rats were fed a diet containing 0, 20 or 500 mg/kg diet alpha-tocopherol. Intraperitoneal glucose tolerance test revealed a significant increment of insulin secretion at 30 min and a significant decrement of blood glucose levels at 30 and 120 min after glucose loading in the GK rats fed with high alpha-tocopherol diet. The levels of glycated hemoglobin A1c, an indicator of glycemic control, were also reduced. Vitamin E supplementation clearly ameliorated diabetic control of GK rats, suggesting the importance of not only dietary supplementation of natural antioxidants but also other antioxidative intervention as a supportive therapy of type 2 diabetic patients.
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Affiliation(s)
- Y Ihara
- Department of Metabolism and Clinical Nutrition, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto, Japan.
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