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Kain V, Sawant MA, Dasgupta A, Jaiswal G, Vyas A, Padhye S, Sitasawad SL. A novel SOD mimic with a redox-modulating mn (II) complex, ML1 attenuates high glucose-induced abnormalities in intracellular Ca 2+ transients and prevents cardiac cell death through restoration of mitochondrial function. Biochem Biophys Rep 2016; 5:296-304. [PMID: 28955837 PMCID: PMC5600348 DOI: 10.1016/j.bbrep.2016.01.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 12/25/2015] [Accepted: 01/07/2016] [Indexed: 02/06/2023] Open
Abstract
A key contributor to the pathophysiology of diabetic cardiomyopathy, mitochondrial superoxide can be adequately countered by Mn-superoxide dismutase, which constitutes the first line of defense against mitochondrial oxidative stress. Our group has recently synthesized low molecular weight SOD mimics, demonstrating superior protection against oxidative damages to kidney cells. In the current study, we sought to evaluate the protective effect of the SOD mimic ML1 against high glucose induced cardiomyopathy in diabetes. Mechanistic studies using rat cardiac myoblast H9c2 showed that ML1 markedly inhibited High Glucose (HG) induced cytotoxicity. This was associated with increased Mn-SOD expression along with decreased mitochondrial [Formula: see text], ONOO- and Ca2+ accumulation, unveiling its anti-oxidant potentials. ML1 also attenuated HG-induced loss of mitochondrial membrane potential (ΔΨm) and release of cytochrome c, suggesting that ML1 effectuates its cytoprotective action via the preservation of mitochondrial function. In an ex-vivo model normal adult rat ventricular myocytes (ARVMs) were isolated and cultured in either normal glucose (5.5 mmol/l glucose) or HG (25.5 mmol/l glucose) conditions and the efficiency of ML-1 was analyzed by studying contractile function and calcium indices. Mechanical properties were assessed using a high-speed video-edge detection system, and intracellular Ca2+ transients were recorded in fura-2-loaded myocytes. Pretreatment of myocytes with ML1 (10 nM) ameliorated HG induced abnormalities in relaxation including depressed peak shortening, prolonged time to 90% relenghthening, and slower Ca2+ transient decay. Thus, ML1 exhibits significant cardio protection against oxidative damage, perhaps through its potent antioxidant action via activation of Mn-SOD.
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Affiliation(s)
- Vasundhara Kain
- National Centre for Cell Science, S.P. Pune University Campus, Ganeshkhind Road, Pune 411007, Maharashtra, India
| | - Mithila A Sawant
- National Centre for Cell Science, S.P. Pune University Campus, Ganeshkhind Road, Pune 411007, Maharashtra, India
| | - Aparajita Dasgupta
- National Centre for Cell Science, S.P. Pune University Campus, Ganeshkhind Road, Pune 411007, Maharashtra, India
| | - Gaurav Jaiswal
- National Centre for Cell Science, S.P. Pune University Campus, Ganeshkhind Road, Pune 411007, Maharashtra, India
| | - Alok Vyas
- ISTRA, Department of Chemistry, Abeda Inamdar Senior College, University of Pune, Pune 411001, India
| | - Subhash Padhye
- ISTRA, Department of Chemistry, Abeda Inamdar Senior College, University of Pune, Pune 411001, India
| | - Sandhya L Sitasawad
- National Centre for Cell Science, S.P. Pune University Campus, Ganeshkhind Road, Pune 411007, Maharashtra, India
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Avsar UZ, Avsar U, Aydin A, Yayla M, Ozturkkaragoz B, Un H, Saritemur M, Mercantepe T. L-carnitine alleviates sciatic nerve crush injury in rats: functional and electron microscopy assessments. Neural Regen Res 2014; 9:1020-4. [PMID: 25206754 PMCID: PMC4146308 DOI: 10.4103/1673-5374.133163] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2014] [Indexed: 11/06/2022] Open
Abstract
Several studies have demonstrated that L-carnitine exhibits neuroprotective effects on injured sciatic nerve of rats with diabetes mellitus. It is hypothesized that L-carnitine exhibits neuroprotective effects on injured sciatic nerve of rats. Rat sciatic nerve was crush injured by a forceps and exhibited degenerative changes. After intragastric administration of 50 and 100 mg/kg L-carnitine for 30 days, axon area, myelin sheath area, axon diameter, myelin sheath diameter, and numerical density of the myelinated axons of injured sciatic nerve were similar to normal, and the function of injured sciatic nerve also improved significantly. These findings suggest that L-carnitine exhibits neuroprotective effects on sciatic nerve crush injury in rats.
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Affiliation(s)
- Ummü Zeynep Avsar
- Department of Medical Education, Faculty of Medicine, Ataturk University, Yakutiye, Erzurum, Turkey
| | - Umit Avsar
- Department of Family Medicine, Faculty of Medicine, Ataturk University, Yakutiye, Erzurum, Turkey
| | - Ali Aydin
- Department of Orthopedics and Traumatology, Faculty of Medicine, Ataturk University, Yakutiye, Erzurum, Turkey
| | - Muhammed Yayla
- Department of Pharmacology, Faculty of Medicine, Ataturk University, Yakutiye, Erzurum, Turkey
| | - Berna Ozturkkaragoz
- Department of Pharmacology, Faculty of Pharmacy, Agrı University, Agrı, Turkey
| | - Harun Un
- Department of Biochemistry, Faculty of Pharmacy, Agrı University, Agrı, Turkey
| | - Murat Saritemur
- Department of Emergency Medicine, Faculty of Medicine, Ataturk University, Yakutiye, Erzurum, Turkey
| | - Tolga Mercantepe
- Department of Histology and Embryology, Faculty of Medicine, Ataturk University, Yakutiye, Erzurum, Turkey
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3
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Abstract
As ensheathing and secretory cells, Schwann cells are a ubiquitous and vital component of the endoneurial microenvironment of peripheral nerves. The interdependence of axons and their ensheathing Schwann cells predisposes each to the impact of injury in the other. Further, the dependence of the blood-nerve interface on trophic support from Schwann cells during development, adulthood, and after injury suggests these glial cells promote the structural and functional integrity of nerve trunks. Here, the developmental origin, injury-induced changes, and mature myelinating and nonmyelinating phenotypes of Schwann cells are reviewed prior to a description of nerve fiber pathology and consideration of pathogenic mechanisms in human and experimental diabetic neuropathy. A fundamental role for aldose-reductase-containing Schwann cells in the pathogenesis of diabetic neuropathy, as well as the interrelationship of pathogenic mechanisms, is indicated by the sensitivity of hyperglycemia-induced biochemical alterations, such as polyol pathway flux, formation of reactive oxygen species, generation of advanced glycosylation end products (AGEs) and deficient neurotrophic support, to blocking polyol pathway flux.
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Affiliation(s)
- Andrew P Mizisin
- Department of Pathology, School of Medicine, University of California San Diego, La Jolla, CA, USA.
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4
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Bennett LL, Seefeldt T. The Role of Antioxidants on Oxidative Stress in Diabetes Mellitus. J Pharm Technol 2010. [DOI: 10.1177/875512251002600507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Objective: To evaluate the literature on the role of oxidative stress in diabetes mellitus and search sources of promising antioxidants: pharmaceutical, dietary supplements, or investigational compounds. Data Sources: A preliminary literature search of PubMed (1966-June 2010) was performed, using the MeSH database when possible, with the terms antioxidants, oxidative stress, antioxidants and diabetes, insulin resistance, and antioxidants and diabetic neuropathy. Bibliographies of all articles retrieved were also reviewed. Study Selection and Data Extraction: All studies published in English with data describing the role of antioxidants and oxidative stress in humans or animals were included. Data Synthesis: Oxidative stress plays a significant role in the pathogenesis of diabetes and insulin resistance. α-Lipoic acid (ALA) and N-acetylcysteine (NAC) were shown to be potent antioxidants in several clinical trials, including the SYDNEY trial, SYDNEY 2 trial, and ALADIN III study, in diabetes with albuminuria, and in women with polycystic ovarian syndrome. Conclusions: ALA and NAC supplementations, along with a well-balanced diet rich in fruits and vegetables containing antioxidants, provide a potential approach in the treatment of diabetes associated with oxidative stress.
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Affiliation(s)
- Lunawati L Bennett
- LUNAWATI L BENNETT PhD PharmD, Assistant Professor of Pharmaceutical Science, Lloyd Gregory School of Pharmacy, Palm Beach Atlantic University, West Palm Beach, FL
| | - Teresa Seefeldt
- TERESA SEEFELDT PhD PharmD, Assistant Professor of Pharmaceutical Science, College of Pharmacy, South Dakota State University, Brookings, SD
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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.
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Affiliation(s)
- Ali Murat Irat
- Ankara University, Faculty of Pharmacy, Department of Pharmacology, Ankara, Turkey
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6
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Wilson ADH, Hart A, Wiberg M, Terenghi G. Acetyl-l-carnitine increases nerve regeneration and target organ reinnervation - a morphological study. J Plast Reconstr Aesthet Surg 2009; 63:1186-95. [PMID: 19664977 DOI: 10.1016/j.bjps.2009.05.039] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 05/04/2009] [Accepted: 05/21/2009] [Indexed: 11/19/2022]
Abstract
Peripheral nerve injury frequently results in functional morbidity since standard management fails to adequately address many of the neurobiological hurdles to optimal regeneration. Neuronal survival and regeneration are neurotrophin dependent and require increased aerobic capacity. Acetyl-l-carnitine (ALCAR) facilitates this need and prevents neuronal loss. ALCAR is clinically safe and is shown here to significantly improve nerve regeneration and target organ reinnervation. Two groups of five rats underwent sciatic nerve division followed by immediate repair. One group received parenteral ALCAR (50mg/kg/day) from time of operation until termination at 12 weeks. A 'sham treatment' group received normal saline. A third group was left unoperated and did not receive any treatment. A segment of nerve was harvested between 5mm proximal and 10mm distal to the repair in operated groups, and at the corresponding level in the unoperated group. Mean axonal count in normal, non-axotomised nerve was 14,720 (SD 2378). That of the saline group (17,217 SD 1808) was not significantly different from normal nerve (P=0.0985). Mean number of myelinated axons in the ALCAR group (24,460 SD 3750) was significantly greater than both sham group (P<0.01) and normal nerve (P=0.0012). Mean myelin thickness in the saline treated group (0.408 microm SD 0.067 microm) was less than normal nerve (0.770 microm SD 0.143 microm) (P<0.001). Mean myelin thickness in the ALCAR group (0.627 microm SD 0.052 microm) was greater than the sham (saline) group (P<0.01) and not statistically different from normal nerve (P=0.07). ALCAR increased dermal PGP9.5 staining by 210% compared to sham treatment (P<0.0001) and significantly reduced the mean percentage weight loss in gastrocnemius muscle (ALCAR group 0.203% vs. 0.312% in sham group P=0.015). ALCAR not only increases the number of regenerating nerve fibres but also morphologically improves the quality of regeneration and target organ reinnervation. Adjuvant ALCAR treatment may improve both sensory and motor outcomes and merits further investigation.
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Affiliation(s)
- Andrew D H Wilson
- Blond McIndoe Research Laboratories, Tissue Injury and Repair Group, University of Manchester, Room 3.106 Stopford Building, Oxford Road, Manchester M13 9PT, UK.
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7
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Cunha JM, Jolivalt CG, Ramos KM, Gregory JA, Calcutt NA, Mizisin AP. Elevated lipid peroxidation and DNA oxidation in nerve from diabetic rats: effects of aldose reductase inhibition, insulin, and neurotrophic factors. Metabolism 2008; 57:873-81. [PMID: 18555826 PMCID: PMC2518323 DOI: 10.1016/j.metabol.2008.01.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Accepted: 01/28/2008] [Indexed: 12/11/2022]
Abstract
We investigated the effect of treatment with an aldose reductase inhibitor, insulin, or select neurotrophic factors on the generation of oxidative damage in peripheral nerve. Rats were either treated with streptozotocin to induce insulin-deficient diabetes or fed with a diet containing 40% d-galactose to promote hexose metabolism by aldose reductase. Initial time course studies showed that lipid peroxidation and DNA oxidation were significantly elevated in sciatic nerve after 1 week or 2 weeks of streptozotocin-induced diabetes, respectively, and that both remained elevated after 12 weeks of diabetes. The increase in nerve lipid peroxidation was completely prevented or reversed by treatment with the aldose reductase inhibitor, ICI 222155, or by insulin, but not by the neurotrophic factors, prosaptide TX14(A) or neurotrophin-3. The increase in nerve DNA oxidation was significantly prevented by insulin treatment. In contrast, up to 16 weeks of galactose feeding did not alter nerve lipid peroxidation or protein oxidation, despite evidence of ongoing nerve conduction deficits. These observations demonstrate that nerve oxidative damage develops early after the onset of insulin-deficient diabetes and that it is not induced by increased hexose metabolism by aldose reductase per se, but rather is a downstream consequence of flux through this enzyme. Furthermore, the beneficial effect of prosaptide TX14(A) and neurotrophin-3 on nerve function and structure in diabetic rats is not due to amelioration of increased lipid peroxidation.
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Affiliation(s)
- Joice M. Cunha
- Department of Pathology, University of California San Diego, La Jolla, CA
| | | | - Khara M. Ramos
- Department of Pathology, University of California San Diego, La Jolla, CA
| | - Joshua A. Gregory
- Department of Pathology, University of California San Diego, La Jolla, CA
| | - Nigel A. Calcutt
- Department of Pathology, University of California San Diego, La Jolla, CA
| | - Andrew P. Mizisin
- Department of Pathology, University of California San Diego, La Jolla, CA
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8
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Son SM. Role of vascular reactive oxygen species in development of vascular abnormalities in diabetes. Diabetes Res Clin Pract 2007; 77 Suppl 1:S65-70. [PMID: 17467110 DOI: 10.1016/j.diabres.2007.01.036] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/29/2007] [Indexed: 02/07/2023]
Abstract
Macrovascular and microvascular diseases are currently the principal causes of morbidity and mortality in patients with diabetes. Oxidative stress has been postulated to be a major contributor to the pathogenesis of these events. There is considerable evidence that many biochemical pathways adversely affected by hyperglycemia and other substances that are found at elevated levels in diabetic patients are associated with the generation of reactive oxygen species, ultimately leading to increased oxidative stress in a variety of tissues. In the absence of an appropriate compensation by the endogenous antioxidant defense network, increased oxidative stress leads to the activation of stress-sensitive intracellular signaling pathways and the formation of gene products that cause cellular damage and contribute to the late complications of diabetes. It has recently been suggested that diabetic subjects with vascular complications may have a defective cellular antioxidant response against the oxidative stress generated by hyperglycemia. This raises the concept that antioxidant therapy may be of great interest in these patients. Although our understanding of how hyperglycemia-induced oxidative stress ultimately leads to tissue damage has advanced considerably in recent years, effective therapeutic strategies to prevent or delay the development of this damage remain limited. Thus, further investigations of therapeutic interventions to prevent or delay the progression of diabetic vascular complications are needed.
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Affiliation(s)
- Seok Man Son
- Department of Internal Medicine, Pusan National University School of Medicine, 1Ga-10, Ami-dong, Seo-ku, Busan 602-739, Korea.
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9
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Abstract
PURPOSE OF REVIEW Diabetic neuropathy is a debilitating consequence of type 1 and 2 diabetes. Hyperglycemia disrupts the normal function of neurons and their supporting glia at multiple levels. The complexity of this complication, combined with difficulties of delivering therapy to sensory, sympathetic and parasympathetic neurons, contributes to the intractability of this serious diabetic complication. This review summarizes recent reviews examining the state of research on and treatment of diabetic neuropathy and highlights areas of clinical and basic research that may yield new diagnostic and treatment options. RECENT FINDINGS Recent reviews summarize the effects of hyperglycemia on the peripheral nervous system as well as diagnosis and treatment of patients with diabetic neuropathy. Advances in the analysis of intraepidermal fiber densities could shorten the time course of clinical trials and extend data analyses to include sympathetic as well as sensory information. Unchecked glucose-mediated oxidative stress and advanced glycation endproduct signaling through receptors for advanced glycation endproducts are implicated in diabetic neuropathy and may serve as new therapeutic targets. SUMMARY The best efforts of countless investigators have yet to find effective treatments either to stop the progression of axonal degeneration and cell death or regrow damaged axons. Basic research into the prevention of oxidative stress caused by excess glucose as well as the prevention of advanced glycation endproduct/receptor for advanced glycation endproduct signaling may offer new therapeutic targets. The use of skin biopsies may aid in early detection of both sensory and autonomic neuropathy, and perhaps in the case of patients with type 2 diabetes, diagnose neuropathy prior to the onset of symptoms.
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Affiliation(s)
- Kelli A Sullivan
- Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109, USA
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10
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Abstract
A carnitina, uma amina quaternária (3-hidroxi-4-N-trimetilamino-butirato), é sintetizada no organismo (fígado, rins e cérebro) a partir de dois aminoácidos essenciais: lisina e metionina, exigindo para sua síntese a presença de ferro, ácido ascórbico, niacina e vitamina B6. Tem função fundamental na geração de energia pela célula, pois age nas reações transferidoras de ácidos graxos livres do citosol para mitocôndrias, facilitando sua oxidação e geração de adenosina Trifosfato. A concentração orgânica de carnitina é resultado de processos metabólicos - como ingestão, biossíntese, transporte dentro e fora dos tecidos e excreção - que, quando alterados em função de diversas doenças, levam a um estado carencial de carnitina com prejuízos relacionados ao metabolismo de lipídeos. A suplementação de L-carnitina pode aumentar o fluxo sangüíneo aos músculos devido também ao seu efeito vasodilatador e antioxidante, reduzindo algumas complicações de doenças isquêmicas, como a doença arterial coronariana, e as conseqüências da neuropatia diabética. Por esse motivo, o objetivo do presente trabalho foi descrever possíveis benefícios da suplementação de carnitina nos indivíduos com necessidades especiais e susceptíveis a carências de carnitina, como os portadores de doenças renais, neuropatia diabética, síndrome da imunodefeciência adquirida e doenças cardiovasculares.
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11
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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.
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Affiliation(s)
- Sudha S Shankar
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202-5111, USA
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Stevens MJ, Zhang W, Li F, Sima AAF. C-peptide corrects endoneurial blood flow but not oxidative stress in type 1 BB/Wor rats. Am J Physiol Endocrinol Metab 2004; 287:E497-505. [PMID: 15126237 DOI: 10.1152/ajpendo.00048.2004] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Oxidative stress and neurovascular dysfunction have emerged as contributing factors to the development of experimental diabetic neuropathy (EDN) in streptozotocin-diabetic rodents. Additionally, depletion of C-peptide has been implicated in the pathogenesis of EDN, but the mechanisms of these effects have not been fully characterized. The aims of this study were therefore to explore the effects of diabetes on neurovascular dysfunction and indexes of nerve oxidative stress in type 1 bio-breeding Worcester (BB/Wor) rats and type 2 BB Zucker-derived (ZDR)/Wor rats and to determine the effects of C-peptide replacement in the former. Motor and sensory nerve conduction velocities (NCVs), hindlimb thermal thresholds, endoneurial blood flow, and indicators of oxidative stress were evaluated in nondiabetic control rats, BB/Wor rats, BB/Wor rats with rat II C-peptide replacement (75 nmol C-peptide.kg body wt(-1).day(-1)) for 2 mo, and diabetes duration-matched BBZDR/Wor rats. Endoneurial perfusion was decreased and oxidative stress increased in type 1 BB/Wor rats. C-peptide prevented NCV and neurovascular deficits and attenuated thermal hyperalgesia. Inhibition of nitric oxide (NO) synthase, but not cyclooxygenase, reversed the C-peptide-mediated effects on NCV and nerve blood flow. Indexes of oxidative stress were unaffected by C-peptide. In type 2 BBZDR/Wor rats, neurovascular deficits and increased oxidative stress were unaccompanied by sensory NCV slowing or hyperalgesia. Therefore, nerve oxidative stress is increased and endoneurial perfusion decreased in type 1 BB/Wor and type 2 BBZDR/Wor rats. NO and neurovascular mechanisms, but not oxidative stress, appear to contribute to the effects of C-peptide in type 1 EDN. Sensory nerve deficits are not an inevitable consequence of increased oxidative stress and decreased nerve perfusion in a type 2 diabetic rodent model.
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Affiliation(s)
- Martin J Stevens
- Department of Internal Medicine, University of Michigan, Ann Arbor 48109, USA.
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13
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Abstract
Vascular complications of diabetes represent the leading cause of morbidity and mortality in affected patients. Production of reactive oxygen species is increased in diabetic patients, especially in those with poor glycemic control. Reactive oxygen species affect vascular smooth muscle cell growth and migration, endothelial function, including abnormal endothelium-dependent relaxation and expression of a proinflammatory phenotype, and modification of the extracellular matrix. All of these events contribute to the development of diabetic microvascular and macrovascular complications, suggesting that the sources of reactive oxygen species and the signaling pathways that they modify may represent important therapeutic targets.
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Affiliation(s)
- Seok Man Son
- Emory University School of Medicine, Division of Cardiology, 319 WMB, 1639 Pierce Drive, Atlanta, GA 30322, USA
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14
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Ceriello A. New insights on oxidative stress and diabetic complications may lead to a "causal" antioxidant therapy. Diabetes Care 2003; 26:1589-96. [PMID: 12716823 DOI: 10.2337/diacare.26.5.1589] [Citation(s) in RCA: 495] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Evidence implicates hyperglycemia-derived oxygen free radicals as mediators of diabetic complications. However, intervention studies with classic antioxidants, such as vitamin E, failed to demonstrate any beneficial effect. Recent studies demonstrate that a single hyperglycemia-induced process of overproduction of superoxide by the mitochondrial electron-transport chain seems to be the first and key event in the activation of all other pathways involved in the pathogenesis of diabetic complications. These include increased polyol pathway flux, increased advanced glycosylation end product formation, activation of protein kinase C, and increased hexosamine pathway flux. Superoxide overproduction is accompanied by increased nitric oxide generation, due to an endothelial NOS and inducible NOS uncoupled state, a phenomenon favoring the formation of the strong oxidant peroxynitrite, which in turn damages DNA. DNA damage is an obligatory stimulus for the activation of the nuclear enzyme poly(ADP-ribose) polymerase. Poly(ADP-ribose) polymerase activation in turn depletes the intracellular concentration of its substrate NAD(+), slowing the rate of glycolysis, electron transport, and ATP formation, and produces an ADP-ribosylation of the GAPDH. These processes result in acute endothelial dysfunction in diabetic blood vessels that, convincingly, also contributes to the development of diabetic complications. These new findings may explain why classic antioxidants, such as vitamin E, which work by scavenging already-formed toxic oxidation products, have failed to show beneficial effects on diabetic complications and may suggest new and attractive "causal" antioxidant therapy. New low-molecular mass compounds that act as SOD or catalase mimetics or L-propionyl-carnitine and lipoic acid, which work as intracellular superoxide scavengers, improving mitochondrial function and reducing DNA damage, may be good candidates for such a strategy, and preliminary studies support this hypothesis. This "causal" therapy would also be associated with other promising tools such as LY 333531, PJ34, and FP15, which block the protein kinase beta isoform, poly(ADP-ribose) polymerase, and peroxynitrite, respectively. While waiting for these focused tools, we may have other options: thiazolinediones, statins, ACE inhibitors, and angiotensin 1 inhibitors can reduce intracellular oxidative stress generation, and it has been suggested that many of their beneficial effects, even in diabetic patients, are due to this property.
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Affiliation(s)
- Antonio Ceriello
- Department of Pathology and Medicine, Experimental and Clinical, University of Udine, Italy.
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15
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Kocer I, Kulacoglu D, Altuntas I, Gundogdu C, Gullulu G. Protection of the retina from ischemia-reperfusion injury by L-carnitine in guinea pigs. Eur J Ophthalmol 2003; 13:80-5. [PMID: 12635679 DOI: 10.1177/112067210301300112] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE To investigate the efficacy of L-carnitine in preventing retinal injury followed by ischemia-reperfusion. METHODS The eyes of 34 guinea pigs were used in this experiment. The guinea pigs were divided into two groups: the first group (n=17) was given L-carnitine intraperitoneally (500 mg/kg) and second group (n=17) received the same dose of saline solution. Under general anesthesia, peritomy was performed. Retro-orbital tissues were ligated for 90 minutes and ischemia was induced, followed by 4 hours of reperfusion. One of the enucleated eye was stained with hematoxylin and eosin (H&E) and retinal thicknesses were evaluated. Thiobarbituric acid reactive substances (TBARS) levels were determined in the retina of the other eye. RESULTS Mean TBARS levels in retinal tissue were found lower in L-carnitine group (2.77 +/- 0.55 microM) than in the control group (6.57 +/- 1.19 microM), (p<0.01). On the other hand, mean retinal thickness was found to be increased in the control group (47.47 +/- 5.62 microm) when compared to the L-carnitine group (26.52 +/- 4.65 microm), (p<0.01). In correlation analysis, significantly positive relationships were found between retinal TBARS level and retinal thickness both in the control and L-carnitine groups (r=0.981, p<0.01 and r= 0.967, p<0.01 respectively). CONCLUSIONS L-carnitine is effective in preventing retinal injury followed by ischemia-reperfusion.
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Affiliation(s)
- I Kocer
- Department of Ophthalmology, Faculty of Medicine, Atatürk University, Erzurum, Turkey.
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Barker GA, Green S, Askew CD, Green AA, Walker PJ. Effect of propionyl-L-carnitine on exercise performance in peripheral arterial disease. Med Sci Sports Exerc 2001; 33:1415-22. [PMID: 11528327 DOI: 10.1097/00005768-200109000-00001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Supplementation with propionyl-L-carnitine (PLC) may be of use in improving the exercise capacity of people with peripheral arterial disease. METHODS After a 2-wk exercise familiarization phase, seven subjects displaying intermittent claudication were studied over a 12-wk period consisting of three 4-wk phases, baseline (B), supplementation (S), and placebo (P). PLC was supplemented at 2 g x d(-1), and subjects were blinded to the order of supplementation. Unilateral calf strength and endurance were assessed weekly. Walking performance was assessed at the end of each phase using an incremental protocol, during which respiratory gases were collected. RESULTS Although there was not a significant increase in maximal walking time ( approximately 14%) in the whole group, walking time improved to a greater extent than the individual baseline coefficient of variation in four of the seven subjects. The changes in walking performance were correlated with changes in the respiratory exchange ratio both at steady state (r = 0.59) and maximal exercise (r = 0.79). Muscle strength increased significantly from 695 +/- 198 N to 812 +/- 249 N by the end of S. Changes in calf strength from B to S were modestly related to changes in walking performance (r = 0.56). No improvements in calf endurance were detected throughout the study. CONCLUSIONS These preliminary data suggest that, in addition to walking performance, muscle strength can be increased in PAD patients after 4 wk of supplementation with propionyl-L-carnitine.
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Affiliation(s)
- G A Barker
- School of Human Movement Studies, Queensland University of Technology, Brisbane, Australia
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Abstract
The aims were to ascertain whether L-carnitine could prevent nerve blood flow and conduction deficits in 1-month diabetic rats and to examine potential neurovascular mechanisms using co-treatment with the nitric oxide synthase inhibitor, NG-nitro-L-arginine. A 19.8% diabetic deficit in sciatic motor conduction velocity was 57.4% attenuated by L-carnitine treatment. Similarly, a 47.7% reduction in sciatic nutritive (capillary) endoneurial blood flow was 48.6% blocked by L-carnitine. Joint treatment with NG-nitro-L-arginine completely abolished the effects on nerve conduction and nutritive flow. However, L-carnitine treatment did not alter a 50.8% diabetic deficit in total sciatic endoneurial flow, which was further depressed (61%) by NG-nitro-L-arginine co-treatment. Thus, the effect of L-carnitine on nerve conduction in diabetic rats depends on changes in the endoneurial perfusion pattern by an action that may involve the nitric oxide system of vasa nervorum.
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Affiliation(s)
- N E Cameron
- Department of Biomedical Sciences, University of Aberdeen, Marischal College, UK
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