1
|
Wang J, Alexanian A, Ying R, Kizhakekuttu TJ, Dharmashankar K, Vasquez-Vivar J, Gutterman DD, Widlansky ME. Acute exposure to low glucose rapidly induces endothelial dysfunction and mitochondrial oxidative stress: role for AMP kinase. Arterioscler Thromb Vasc Biol 2011; 32:712-20. [PMID: 22207730 DOI: 10.1161/atvbaha.111.227389] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
OBJECTIVE Hypoglycemia is associated with increased mortality. The reasons for this remain unclear, and the effects of low glucose exposure on vascular endothelial function remain largely unknown. We endeavored to determine the effects of low glucose on endothelial cells and intact human arterioles. METHODS AND RESULTS We exposed human umbilical vein endothelial cells to low glucose conditions in a clinically relevant range (40-70 mg/dL) and found rapid and marked reductions in nitric oxide (NO) bioavailability (P<0.001). This was associated with concomitantly increased mitochondrial superoxide production (P<0.001) and NO-dependent mitochondrial hyperpolarization (P<0.001). Reduced NO bioavailability was rapid and attributable to reduced endothelial nitric oxide synthase activity and destruction of NO. Low glucose rapidly activated AMP kinase, but physiological activation failed to restore NO bioavailability. Pharmacological AMP kinase activation led to phosphorylation of endothelial nitric oxide synthase's Ser633 activation site, reversing the adverse effects of low glucose. This protective effect was prevented by L-NG-Nitroarginine methyl ester. Intact human arterioles exposed to low glucose demonstrated marked endothelial dysfunction, which was prevented by either metformin or TEMPOL. CONCLUSION Our data suggest that moderate low glucose exposure rapidly impairs NO bioavailability and endothelial function in the human endothelium and that pharmacological AMP kinase activation inhibit this effect in an NO-dependent manner.
Collapse
Affiliation(s)
- Jingli Wang
- Department of Medicine, Division of Cardiovascular Medicine, Graduate School of Bioscience, Medical College of Wisconsin, 9200 W Wisconsin Ave, FEC Ste E5100, Milwaukee, WI 53226, USA
| | | | | | | | | | | | | | | |
Collapse
|
2
|
Irat AM, Aktan F, Ozansoy G. Effects of L-carnitine treatment on oxidant/antioxidant state and vascular reactivity of streptozotocin-diabetic rat aorta. J Pharm Pharmacol 2010; 55:1389-95. [PMID: 14607021 DOI: 10.1211/0022357021909] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Abstract
In this study, the effects of L-carnitine treatment on lipids, lipid peroxidation of plasma, reactivity and antioxidant enzyme activity of aorta were evaluated in streptozotocin (STZ)-diabetic rats. Treatment with L-carnitine (0.6 g kg−1 daily, i.p.) was started 8 weeks after the induction of diabetes and continued for 2 weeks. Diabetes was induced by a single injection of streptozotocin (45 mg kg−1, i.p.). Plasma cholesterol, triglyceride and thiobarbituric acid reactive substance (TBARS) levels and blood glucose levels were significantly increased, although free carnitine levels were markedly decreased in diabetic rats. L-Carnitine treatment completely normalized plasma cholesterol, triglyceride, free carnitine and TBARS levels but partially restored blood glucose levels of diabetic rats. STZ-diabetes caused a significant reduction in the endothelium-dependent relaxation response to acetylcholine (ACh). In diabetic aorta, TBARS levels and catalase (CAT) activity were significantly increased but glutathione peroxidase (GSH-Px) activity was unchanged. Treatment of diabetic rats with L-carnitine resulted in partial restoration of the endothelium-dependent relaxation response to ACh and completely normalized the oxidant/antioxidant state. These results suggested that the beneficial effects of L-carnitine treatment partially improve vascular reactivity and antioxidant property beyond its reduction of plasma lipids and it may have an important therapeutic approach in the treatment of diabetic vascular complications.
Collapse
Affiliation(s)
- Ali Murat Irat
- Ankara University, Faculty of Pharmacy, Department of Pharmacology, Ankara, Turkey
| | | | | |
Collapse
|
3
|
Rajasekar P, Palanisamy N, Anuradha C. Increase in Nitric Oxide and Reductions in Blood Pressure, Protein Kinase C β II and Oxidative Stress by L-Carnitine: A Study in the Fructose-Fed Hypertensive Rat. Clin Exp Hypertens 2009; 29:517-30. [DOI: 10.1080/10641960701743998] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
4
|
Bueno R, Alvarez de Sotomayor M, Perez-Guerrero C, Gomez-Amores L, Vazquez CM, Herrera MD. L-carnitine and propionyl-L-carnitine improve endothelial dysfunction in spontaneously hypertensive rats: Different participation of NO and COX-products. Life Sci 2005; 77:2082-97. [PMID: 15958269 DOI: 10.1016/j.lfs.2005.01.035] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2004] [Accepted: 01/17/2005] [Indexed: 10/25/2022]
Abstract
L-carnitine and propionyl-L-carnitine are supplements to therapy in cardiovascular pathologies. Their effect on endothelial dysfunction in hypertension was studied after treatment with either 200 mg/kg of L-carnitine or propionyl-L-carnitine during 8 weeks of spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). Endothelial function was assessed in aortic rings by carbachol-induced relaxation (CCh 10(-8) to 10(-4) M) and factors involved were characterized in the presence of the inhibitors: L-NAME, indomethacin, the TXA2/PGH2 Tp receptor antagonist ICI-192,605 and the thromboxane synthetase inhibitor-Tp receptor antagonist, Ro-68,070. The effect on phenylephrine-induced contractions was also observed. To identify the nature of vasoactive COX-derived products, enzyme-immunoassay of incubation media was assessed. Involvement of reactive oxygen species was evaluated by incubating with superoxide dismutase and catalase. Nitric oxide production was evaluated by serum concentration of NO2+NO3.Treatment with both compounds improved endothelial function of rings from SHR without blood pressure change. Propionyl-L-carnitine increased NO participation in WKY and SHR. L-carnitine reduced endothelium-dependent responses to CCh in WKY due to an increase of TXA2 production. In both SHR and WKY, L-carnitine enhanced concentration of PGI2 and increased participation of NO. Results in the presence of SOD plus catalase show that it might be related to antioxidant properties of L-carnitine and propionyl-L-carnitine. Comparison between the effect of both compounds shows that both may reduce reactive oxygen species and increase NO participation in endothelium-dependent relaxations in SHR. However, only L-carnitine was able to increase the release of the vasodilator PGI2 and even enhanced TXA2 production in normotensive rats.
Collapse
Affiliation(s)
- Rosario Bueno
- Departamento de Farmacologia, Facultad de Farmacia, Universidad de Sevilla, C/Profesor Garcia-Gonzalez no 2. 41012 Seville, Spain
| | | | | | | | | | | |
Collapse
|
5
|
Shankar SS, Mirzamohammadi B, Walsh JP, Steinberg HO. L-carnitine may attenuate free fatty acid-induced endothelial dysfunction. Ann N Y Acad Sci 2005; 1033:189-97. [PMID: 15591016 DOI: 10.1196/annals.1320.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have recently shown that elevated levels of free fatty acid (FFA) seen in insulin-resistant obese subjects are associated with endothelial dysfunction. L-carnitine, which is required for mitochondrial FFA transport/oxidation, has been reported to improve vascular function in subjects with diabetes and heart disease. Here, we tested the hypothesis that L-carnitine attenuates FFA-induced endothelial dysfunction. We studied leg blood flow (LBF) responses and leg vascular resistance (LVR) to graded intrafemoral artery infusions of the endothelium-dependent vasodilator, methacholine chloride (MCh). A group (n = 7) of normal lean subjects was studied under basal conditions (saline), after 2 h of FFA elevation (FFA), and then after 2 h of superimposing L-carnitine on FFA elevation. FFA elevation caused the maximal LBF increment in response to MCh to decrease from 0.388 +/- 0.08 to 0.212 +/- 0.071 L/min (P < 0.05). Similarly, FFA blunted the maximum decrease in LVR in response to MCh from -315 +/- 41 U to -105 +/- 46 U (P < 0.05). The superimposed L-carnitine restored the LBF increment in response to MCh to 0.488 +/- 0.088 L/min (P < 0.05 vs. FFA) and the maximum fall in LVR to -287 +/- 75 U (P < 0.05 vs. FFA), indicating that L-carnitine elevation may attenuate FFA-induced endothelial dysfunction. In conclusion, our data suggest that increasing L-carnitine levels may improve FFA-induced and obesity-associated endothelial dysfunction. This improved endothelial function may delay or prevent the development of excess cardiovascular disease.
Collapse
Affiliation(s)
- Sudha S Shankar
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202-5111, USA
| | | | | | | |
Collapse
|
6
|
Horvath P, Szilvassy J, Nemeth J, Peitl B, Szilasi M, Szilvassy Z. Decreased sensory neuropeptide release in isolated bronchi of rats with cisplatin-induced neuropathy. Eur J Pharmacol 2005; 507:247-52. [PMID: 15659315 DOI: 10.1016/j.ejphar.2004.11.053] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Revised: 11/17/2004] [Accepted: 11/23/2004] [Indexed: 10/26/2022]
Abstract
We studied if attenuated neurogenic bronchoconstriction was associated with a change in sensory neuropeptide release in preparations from rats with cisplatin-induced neuropathy. Electrical field stimulation (100 stimuli, 20 V, 0.1 ms, 20 Hz) induced an increase in the release of somatostatin, calcitonin gene-related peptide (CGRP) and substance P determined by radioimmunoassay from baseline 0.18+/-0.01, 0.17+/-0.01 and 0.86+/-0.02, to 0.59+/-0.02, 1.77+/-0.04 and 5.96 fmol/mg wet tissue weight, respectively, in organ fluid of tracheal tubes from rats. This was significantly attenuated to post-stimulation values of 0.36+/-0.02, 0.45+/-0.02, 4.68+/-0.24 fmol/mg wet tissue weight for somatostatin, CGRP, and substance P, respectively, with a significant decrease in field stimulation-induced contraction of bronchial preparations from animals 11 days after a 5-day treatment period with cisplatin (1.5 mg/kg i.p. once a day). The cisplatin-treated animals developed sensory neuropathy characterized by a 40% decrease in femoral nerve conduction velocity. The results show that a decrease in tracheo-bronchial sensory neuropeptide release associates with feeble bronchomotor responses in rats with cisplatin-induced sensory neuropathy.
Collapse
Affiliation(s)
- Peter Horvath
- Department of Pharmacology and Pharmacotherapy, University of Debrecen, H-4032 Debrecen, Nagyerdei krt 98, Hungary
| | | | | | | | | | | |
Collapse
|
7
|
Szilvássy J, Sziklai I, Horvath P, Szilasi M, Németh J, Kovács P, Szilvássy Z. Feeble bronchomotor responses in diabetic rats in association with decreased sensory neuropeptide release. Am J Physiol Lung Cell Mol Physiol 2002; 282:L1023-30. [PMID: 11943667 DOI: 10.1152/ajplung.00409.2000] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Type I diabetes is associated with a low incidence of asthma. We tested whether a decrease in sensory neuropeptide release is associated with an attenuated bronchoconstrictive response to field stimulation (FS; 100 stimuli, 20 V, 0.1 ms, 20 Hz) in streptozotocin (STZ)-induced diabetes. The organ fluid of the preparations were also tested for substance P, calcitonin gene-related peptide (CGRP), and somatostatin concentrations by RIA. Preparations were from either normal rats or those pretreated with 50 mg/kg STZ iv 8 wk before experiment. A group of STZ-treated animals was supplied with insulin delivery (4 IU/day sc) implants between 4 and 8 wk. A subgroup was formed to study the effect of capsaicin desensitization. The atropine-resistant contraction was attenuated by diabetes without capsaicin-sensitive relaxation response. Exogenous CGRP and substance P potentiated, whereas somatostatin inhibited (1 nM-10 microM) the FS-induced contractions in rings from either group. FS released somatostatin, CGRP, and substance P from 0.17 +/- 0.024, 0.15 +/- 0.022, and 1.65 +/- 0.093 to 0.58 +/- 0.032, 0.74 +/- 0.122, and 5.34 +/- 0.295 in preparations from normal, and from 0.19 +/- 0.016, 0.11 +/- 0.019, and 0.98 +/- 0.116 to 0.22 +/- 0.076, 0.34 +/- 0.099, and 1.84 +/- 0.316 fmol/mg wet wt in preparations from diabetic rats. Insulin supplementation restored neuropeptide release in rings from STZ-treated rats. The results show that the decreased FS-induced contractions occurred with a decrease in sensory neuropeptide release in STZ-diabetic rats.
Collapse
Affiliation(s)
- Judith Szilvássy
- Department of Oto-rhino-laryngology, Medical University of Debrecen, H-4032 Debrecen, Hungary.
| | | | | | | | | | | | | |
Collapse
|
8
|
Obrosova IG, Van Huysen C, Fathallah L, Cao X, Stevens MJ, Greene DA. Evaluation of α 1‐adrenoceptor antagonist on diabetes‐induced changes in peripheral nerve function, metabolism, and antioxidative defense. FASEB J 2000. [DOI: 10.1096/fj.99-0803com] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Irina G. Obrosova
- Division of Endocrinology and MetabolismDepartment of Internal MedicineUniversity of Michigan Medical CenterAnn ArborMichigan48109‐0354USA
| | - Carol Van Huysen
- Division of Endocrinology and MetabolismDepartment of Internal MedicineUniversity of Michigan Medical CenterAnn ArborMichigan48109‐0354USA
| | - Lamia Fathallah
- Division of Endocrinology and MetabolismDepartment of Internal MedicineUniversity of Michigan Medical CenterAnn ArborMichigan48109‐0354USA
| | - Xianghui Cao
- Division of Endocrinology and MetabolismDepartment of Internal MedicineUniversity of Michigan Medical CenterAnn ArborMichigan48109‐0354USA
| | - Martin J. Stevens
- Division of Endocrinology and MetabolismDepartment of Internal MedicineUniversity of Michigan Medical CenterAnn ArborMichigan48109‐0354USA
| | - Douglas A. Greene
- Division of Endocrinology and MetabolismDepartment of Internal MedicineUniversity of Michigan Medical CenterAnn ArborMichigan48109‐0354USA
| |
Collapse
|
9
|
Németh J, Thán M, Sári R, Peitl B, Oroszi G, Farkas B, Szolcsányi J, Szilvássy Z. Impairment of neurogenic inflammatory and anti-inflammatory responses in diabetic rats. Eur J Pharmacol 1999; 386:83-8. [PMID: 10611467 DOI: 10.1016/s0014-2999(99)00724-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effect was studied of a primary (preconditioning) neurogenic inflammatory challenge induced by electrical stimulation of the peripheral stump of the sciatic nerve (20 V, 0.5 ms, 5 Hz, for 5 min) on neurogenic oedema (5 min later) induced by stimulation of the contralateral sciatic nerve. Plasma extravasation due to the second stimulation was decreased by 52.7+/-3.1% (P<0.01) in normal animals and by 29.7+/-2.2 and 18.1+/-1.5% with 50 mg/kg streptozotocin pretreatment i.v. 4 and 8 weeks previously, respectively. Subsequently, bilateral sciatic nerve stimulation increased baseline plasma somatostatin levels from 6.4+/-0.3, 11. 7+/-1.4, and 16.8+/-3.8 to 28.3+/-2.9 (P<0.01), 17.9+/-3.7, and 25. 1+/-1.7 pmol/l in normal, and 4- and 8-week diabetic animals, respectively. We conclude that experimental diabetes impairs the capability of a preconditioning neurogenic inflammatory episode to elicit a systemic anti-inflammatory effect. This is accompanied by a deficiency in elevation of the plasma somatostatin level in response to nerve stimulation, although the baseline plasma somatostatin level increases proportionally to the duration of experimental diabetes.
Collapse
Affiliation(s)
- J Németh
- Neuropharmacology Research Group of the Hungarian Academy of Sciences, H-7601 P.O. Box 99, Pécs, Hungary
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Jack AM, Cameron NE, Cotter MA. Effects of the diacylglycerol complexing agent, cremophor, on nerve-conduction velocity and perfusion in diabetic rats. J Diabetes Complications 1999; 13:2-9. [PMID: 10232703 DOI: 10.1016/s1056-8727(98)00014-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The contribution of diacylglycerol (DAG) and protein kinase C (PKC) to diabetic complications has been the subject of debate. In vascular tissues, diabetes increases DAG content, which activates PKC and causes abnormal tissue perfusion. Reduced nerve blood flow has been implicated in the development of neuropathy. However, nerve DAG/PKC activity is not increased and may even be reduced by diabetes, which has also been implicated in neuropathy. The aim was to test whether 2 weeks of treatment with cremophor, an agent that complexes DAG and prevents PKC activation, could correct nerve-conduction velocity (NCV) deficits in rats with 6 weeks of untreated diabetes, as predicted on a vascular hypothesis, or whether this worsened the deficits, as predicted for a direct effect on nerve fibers. Diabetes caused 17.9 +/- 0.9% (+/- SEM) and 15.5 +/- 1.6% reductions in sciatic motor and saphenous sensory NCV, respectively, that were largely (79.6 +/- 6.3% and 57.8 +/- 11.5%) corrected by 100 mg x kg(-1) x day(-1) cremophor treatment. The effects of cremophor on motor and sensory NCV were completely attenuated by co-treatment with the nitric oxide synthase inhibitor, N(G)-nitro-l-arginine. In contrast, co-treatment with the cyclooxygenase inhibitor, flurbiprofen, had no effect on NCV. Sciatic nutritive and total endoneurial perfusion were 49.7 +/- 3.4% and 51.8 +/- 4.2% reduced by diabetes, respectively, and these deficits were 69.5 +/- 7.4% and 79.0 +/- 11.6% corrected by cremophor treatment. Thus the data suggest that an increased DAG/PKC vascular mechanism, perhaps linked to the nitric oxide system, contributes to the etiology of diabetic nerve dysfunction.
Collapse
Affiliation(s)
- A M Jack
- Department of Biomedical Sciences, University of Aberdeen, Marischal College, Scotland, United Kingdom
| | | | | |
Collapse
|
11
|
Cotter MA, Cameron NE. Correction of neurovascular deficits in diabetic rats by beta2-adrenoceptor agonist and alpha1-adrenoceptor antagonist treatment: interactions with the nitric oxide system. Eur J Pharmacol 1998; 343:217-23. [PMID: 9570470 DOI: 10.1016/s0014-2999(97)01533-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The aims were to test whether 2 weeks treatment with the beta2-adrenoceptor agonist, salbutamol, or the alpha1-adrenoceptor antagonist, doxazosin, could correct nerve blood flow and conduction velocity deficits in 8 week streptozotocin-diabetic rats and to examine neurovascular mechanisms using co-treatment with the nitric oxide synthase inhibitor, NG-nitro-L-arginine. Sciatic motor conduction velocity, 20.3% reduced by diabetes, was corrected by 88.2 and 88.5% for salbutamol and doxazosin, respectively. A 47.6% diabetic deficit in sciatic nutritive endoneurial blood, was substantially reversed by salbutamol (117.0%) and doxazosin (61.0%) treatment. The effects of alpha1-adrenoceptor blockade and beta2-adrenoceptor stimulation on nerve blood flow and conduction velocity were almost completely (76.7-91.7%) attenuated by NG-nitro-L-arginine co-treatment. Thus, the data stress the importance of vasa nervorum alpha1 and beta2 adrenoceptors and the permissive role of nitric oxide in nerve blood flow control mechanisms. They also indicate that beta2-adrenoceptor agonists may be suitable for clinical trials of diabetic neuropathy.
Collapse
Affiliation(s)
- M A Cotter
- Department of Biomedical Sciences, Marischal College, University of Aberdeen, Scotland, UK
| | | |
Collapse
|