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Huber G, Ogrodnik M, Wenzel J, Stölting I, Huber L, Will O, Peschke E, Matschl U, Hövener JB, Schwaninger M, Jurk D, Raasch W. Telmisartan prevents high-fat diet-induced neurovascular impairments and reduces anxiety-like behavior. J Cereb Blood Flow Metab 2021; 41:2356-2369. [PMID: 33730932 PMCID: PMC8393307 DOI: 10.1177/0271678x211003497] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Angiotensin II receptor blockers (telmisartan) prevent rodents from diet-induced obesity and improve their metabolic status. Hyperglycemia and obesity are associated with reduced cerebral blood flow and neurovascular uncoupling which may lead to behavioral deficits. We wanted to know whether a treatment with telmisartan prevents these changes in obesity.We put young mice on high-fat diet and simultaneously treated them with telmisartan. At the end of treatment, we performed laser speckle imaging and magnetic resonance imaging to assess the effect on neurovascular coupling and cerebral blood flow. Different behavioral tests were used to investigate cognitive function.Mice developed diet-induced obesity and after 16, not 8 weeks of high-fat diet, however, the response to whisker pad stimulation was about 30% lower in obese compared to lean mice. Simultaneous telmisartan treatment increased the response again by 10% compared to obese mice. Moreover, telmisartan treatment normalized high-fat diet-induced reduction of cerebral blood flow and prevented a diet-induced anxiety-like behavior. In addition to that, telmisartan affects cellular senescence and string vessel formation in obesity.We conclude, that telmisartan protects against neurovascular unit impairments in a diet-induced obesity setting and may play a role in preventing obesity related cognitive deficits in Alzheimer's disease.
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Affiliation(s)
- Gianna Huber
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany.,CBBM (Centre for Brain, Behavior and Metabolism), University of Lübeck, Lübeck, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Lübeck, Germany
| | - Mikolaj Ogrodnik
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester MN, USA.,Ludwig Boltzmann Research Group Senescence and Healing of Wounds at LBI Trauma, Vienna, Austria
| | - Jan Wenzel
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany.,CBBM (Centre for Brain, Behavior and Metabolism), University of Lübeck, Lübeck, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Lübeck, Germany
| | - Ines Stölting
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany.,CBBM (Centre for Brain, Behavior and Metabolism), University of Lübeck, Lübeck, Germany
| | - Lukas Huber
- Section Biomedical Imaging, MOIN CC, Department of Radiology and Neuroradiology, UKSH, Kiel University, Kiel, Germany
| | - Olga Will
- Section Biomedical Imaging, MOIN CC, Department of Radiology and Neuroradiology, UKSH, Kiel University, Kiel, Germany
| | - Eva Peschke
- Section Biomedical Imaging, MOIN CC, Department of Radiology and Neuroradiology, UKSH, Kiel University, Kiel, Germany
| | - Urte Matschl
- Department Virus Immunology, Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Jan-Bernd Hövener
- Section Biomedical Imaging, MOIN CC, Department of Radiology and Neuroradiology, UKSH, Kiel University, Kiel, Germany
| | - Markus Schwaninger
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany.,CBBM (Centre for Brain, Behavior and Metabolism), University of Lübeck, Lübeck, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Lübeck, Germany
| | - Diana Jurk
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester MN, USA
| | - Walter Raasch
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany.,CBBM (Centre for Brain, Behavior and Metabolism), University of Lübeck, Lübeck, Germany.,DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Lübeck, Germany
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Coucha M, Abdelsaid M, Ward R, Abdul Y, Ergul A. Impact of Metabolic Diseases on Cerebral Circulation: Structural and Functional Consequences. Compr Physiol 2018; 8:773-799. [PMID: 29687902 DOI: 10.1002/cphy.c170019] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Metabolic diseases including obesity, insulin resistance, and diabetes have profound effects on cerebral circulation. These diseases not only affect the architecture of cerebral blood arteries causing adverse remodeling, pathological neovascularization, and vasoregression but also alter the physiology of blood vessels resulting in compromised myogenic reactivity, neurovascular uncoupling, and endothelial dysfunction. Coupled with the disruption of blood brain barrier (BBB) integrity, changes in blood flow and microbleeds into the brain rapidly occur. This overview is organized into sections describing cerebrovascular architecture, physiology, and BBB in these diseases. In each section, we review these properties starting with larger arteries moving into smaller vessels. Where information is available, we review in the order of obesity, insulin resistance, and diabetes. We also tried to include information on biological variables such as the sex of the animal models noted since most of the information summarized was obtained using male animals. © 2018 American Physiological Society. Compr Physiol 8:773-799, 2018.
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Affiliation(s)
- Maha Coucha
- South University, School of Pharmacy, Savannah, Georgia, USA
| | | | - Rebecca Ward
- Department of Neuroscience & Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Yasir Abdul
- Charlie Norwood VA Medical Center, Augusta, Georgia, USA.,Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
| | - Adviye Ergul
- Charlie Norwood VA Medical Center, Augusta, Georgia, USA.,Department of Physiology, Medical College of Georgia, Augusta University, Augusta, Georgia, USA
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Li C, Jiang Z, Lu W, Arrick D, McCarter K, Sun H. Effect of obesity on early blood–brain barrier disruption following transient focal cerebral ischemia. Obes Sci Pract 2016. [DOI: 10.1002/osp4.30] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- C. Li
- Department of Cellular Biology and AnatomyLouisiana State University Health Sciences Center‐Shreveport Shreveport LA USA
| | - Z. Jiang
- Department of Cellular Biology and AnatomyLouisiana State University Health Sciences Center‐Shreveport Shreveport LA USA
| | - W. Lu
- Department of Cellular Biology and AnatomyLouisiana State University Health Sciences Center‐Shreveport Shreveport LA USA
| | - D. Arrick
- Department of Cellular Biology and AnatomyLouisiana State University Health Sciences Center‐Shreveport Shreveport LA USA
| | - K. McCarter
- Department of Cellular Biology and AnatomyLouisiana State University Health Sciences Center‐Shreveport Shreveport LA USA
| | - H. Sun
- Department of Cellular Biology and AnatomyLouisiana State University Health Sciences Center‐Shreveport Shreveport LA USA
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Abstract
Nitric oxide (NO) generated by endothelial cells to relax vascular smooth muscle is one of the most intensely studied molecules in the past 25 years. Much of what is known about NO regulation of NO is based on blockade of its generation and analysis of changes in vascular regulation. This approach has been useful to demonstrate the importance of NO in large scale forms of regulation but provides less information on the nuances of NO regulation. However, there is a growing body of studies on multiple types of in vivo measurement of NO in normal and pathological conditions. This discussion will focus on in vivo studies and how they are reshaping the understanding of NO's role in vascular resistance regulation and the pathologies of hypertension and diabetes mellitus. The role of microelectrode measurements in the measurement of [NO] will be considered because much of the controversy about what NO does and at what concentration depends upon the measurement methodology. For those studies where the technology has been tested and found to be well founded, the concept evolving is that the stresses imposed on the vasculature in the form of flow-mediated stimulation, chemicals within the tissue, and oxygen tension can cause rapid and large changes in the NO concentration to affect vascular regulation. All these functions are compromised in both animal and human forms of hypertension and diabetes mellitus due to altered regulation of endothelial cells and formation of oxidants that both damage endothelial cells and change the regulation of endothelial nitric oxide synthase.
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Affiliation(s)
- Harold Glenn Bohlen
- Department of Cellular and Integrative Physiology, Indiana University Medical School, Indianapolis, Indiana, Indiana, USA
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Dorrance AM, Matin N, Pires PW. The effects of obesity on the cerebral vasculature. Curr Vasc Pharmacol 2015; 12:462-72. [PMID: 24846235 DOI: 10.2174/1570161112666140423222411] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Revised: 04/08/2013] [Accepted: 05/01/2013] [Indexed: 12/18/2022]
Abstract
The incidence of obesity in the population is increasing at an alarming rate, with this comes an increased risk of insulin resistance (IR). Obesity and IR increase an individual's risk of having a stroke and they have been linked to several forms of dementia. Stroke and dementia are associated with, or exacerbated by, reduced cerebral blood flow, which has recently been described in obese patients. In this review we will discuss the effects of obesity on cerebral artery function and structure. Regarding their function, we will focus on the endothelium and nitric oxide (NO) dependent dilation. NO dependent dilation is impaired in cerebral arteries from obese rats, and the majority of evidence suggests this is a result of increased oxidative stress. We will also describe the limited studies showing that inward cerebral artery remodeling occurs in models of obesity, and that the remodeling is associated with an increase in the damage caused by cerebral ischemia. We will also discuss some of the more paradoxical findings associated with stroke and obesity, including the evidence that obesity is a positive factor for stroke survival. Finally we will discuss the evidence that links these changes in vascular structure and function to cognitive decline and dementia.
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Affiliation(s)
| | | | - Paulo W Pires
- Department of Pharmacology and Toxicology, Michigan State University, 1355 Bogue Street, East Lansing, MI 48824, USA.
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Tajbakhsh N, Sokoya EM. Sirtuin 1 is upregulated in young obese Zucker rat cerebral arteries. Eur J Pharmacol 2013; 721:43-8. [PMID: 24113524 DOI: 10.1016/j.ejphar.2013.09.057] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 09/20/2013] [Accepted: 09/26/2013] [Indexed: 12/11/2022]
Abstract
Many diseases, including metabolic syndrome, are characterised by endothelial dysfunction mediated by reduced nitric oxide bioavailability and oxidative stress. Sirtuin 1 is a protein deacetylase that targets endothelial nitric oxide synthase resulting in enhanced nitric oxide bioavailability. Although it has been highlighted as a potential therapeutic target, we still have no understanding of vascular SIRT1 changes during obesity. Therefore, the aim of the present study was to measure vascular function, SIRT1 protein levels of expression and markers of oxidative stress in obese Zucker rats. Middle cerebral arteries from nondiabetic obese and lean Zucker rats were mounted in a pressure myograph to assess nitric oxide-dependent dilations. Western blotting was used to measure protein levels of SIRT1, p53, acetylated p53, eNOS, phosphorylated eNOS and markers of oxidative stress (nitrotyrosine, Nox4 and SOD2) in cerebral vascular tissue. SIRT1 expression was two-fold greater in both cerebral arteries and aorta from obese compared to lean Zucker rats. Acetylation of p53 at the SIRT1-specific lysine 379 site was markedly decreased. At the same time, there was noted cerebral vascular impairment however markers of oxidative stress were not increased. In fact, Nox4 appeared to be downregulated in obesity. Thus, SIRT1 protein levels within the vasculature are greater in obese compared to lean Zucker rats and are associated with higher SIRT1 activity and lower Nox4 expression. We propose that the increased expression and activity of SIRT1 may be a vascular adaptive mechanism in obesity, aiming to prevent oxidative stress.
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Affiliation(s)
- Negara Tajbakhsh
- Disciplines of Medical Biotechnology, School of Medicine, Flinders University, Bedford Park, SA 5042, Australia
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Ergul A, Kelly-Cobbs A, Abdalla M, Fagan SC. Cerebrovascular complications of diabetes: focus on stroke. Endocr Metab Immune Disord Drug Targets 2012; 12:148-58. [PMID: 22236022 DOI: 10.2174/187153012800493477] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 09/27/2011] [Indexed: 12/18/2022]
Abstract
Cerebrovascular complications make diabetic patients 2-6 times more susceptible to a stroke event and this risk is magnified in younger individuals and in patients with hypertension and complications in other vascular beds. In addition, when patients with diabetes and hyperglycemia experience an acute ischemic stroke they are more likely to die or be severely disabled and less likely to benefit from the one FDA-approved therapy, intravenous tissue plasminogen activator. Experimental stroke models have revealed that chronic hyperglycemia leads to deficits in cerebrovascular structure and function that may explain some of the clinical observations. Increased edema, neovascularization and protease expression as well as altered vascular reactivity and tone may be involved and point to potential therapeutic targets. Further study is needed to fully understand this complex disease state and the breadth of its manifestation in the cerebrovasculature.
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Affiliation(s)
- Adviye Ergul
- Program in Clinical and Experimental Therapeutics, University of Georgia College of Pharmacy, Augusta, GA 30912, USA
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Li W, Sachidanandam K, Ergul A. Comparison of selective versus dual endothelin receptor antagonism on cerebrovascular dysfunction in diabetes. Neurol Res 2012; 33:185-91. [PMID: 21801593 DOI: 10.1179/016164111x12881719352417] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVES Cerebrovascular tone plays a key role in controlling cerebral blood flow. Our studies have demonstrated that the endothelin system is upregulated in type 2 diabetes leading to increased sensitivity to endothelin-1 and decreased relaxation in basilar artery. While chronic endothelin A receptor blockade restored relaxation, selective endothelin B receptor blockade caused paradoxical constriction in diabetes. Whether this effect was due to activation of endothelin A receptors in the presence of endothelin B receptor blockade or due to the loss of vasculoprotective effects of endothelin B receptors remained unknown. The current study hypothesizes that due to the antagonism of the vasculoprotective endothelin receptor B, dual blockade will not be as effective as selective endothelin receptor A antagonism in improving cerebrovascular dysfunction in type 2 diabetes. METHODS These studies were done in non-obese, type 2 diabetic Goto-Kakizaki rats administered either vehicle, selective endothelin receptor A antagonist Atrasentan (5 mg/kg) or dual endothelin antagonist Bosentan (100 mg/kg) for 4 weeks. At termination, basilar arteries were collected and mounted on a wire myograph and cumulative dose-response curves to endothelin-1 (1-500 nM) and acetylcholine (1 nM-5 μm) were studied. RESULTS Basilar artery was highly sensitive to endothelin-1-mediated constriction in diabetic animals. While neither Atrasentan nor Bosentan affected endothelium-dependent vascular relaxation in control animals, both treatments improved the maximum dilatation in diabetes and Atrasentan also improved sensitivity to acetylcholine. CONCLUSION In light of our previous data which showed that endothelin B receptors are vasculoprotective and blockade of this receptor worsens relaxation, current findings suggest that when blocked simultaneously with the endothelin receptor A, the endothelin receptor B antagonism is protective by reducing the hyperreactivity and improving cerebrovascular function in diabetes.
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Affiliation(s)
- Weiguo Li
- Department of Physiology, Medical College of Georgia, Augusta, GA 30912, USA
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Kelly-Cobbs AI, Prakash R, Coucha M, Knight RA, Li W, Ogbi SN, Johnson M, Ergul A. Cerebral myogenic reactivity and blood flow in type 2 diabetic rats: role of peroxynitrite in hypoxia-mediated loss of myogenic tone. J Pharmacol Exp Ther 2012; 342:407-15. [PMID: 22570365 DOI: 10.1124/jpet.111.191296] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Dysregulation of cerebral vascular function and, ultimately, cerebral blood flow (CBF) may contribute to complications such as stroke and cognitive decline in diabetes. We hypothesized that 1) diabetes-mediated neurovascular and myogenic dysfunction impairs CBF and 2) under hypoxic conditions, cerebral vessels from diabetic rats lose myogenic properties because of peroxynitrite (ONOO(-))-mediated nitration of vascular smooth muscle (VSM) actin. Functional hyperemia, the ability of blood vessels to dilate upon neuronal stimulation, and myogenic tone of isolated middle cerebral arteries (MCAs) were assessed as indices of neurovascular and myogenic function, respectively, in 10- to 12-week control and type 2 diabetic Goto-Kakizaki rats. In addition, myogenic behavior of MCAs, nitrotyrosine (NY) levels, and VSM actin content were measured under normoxic and hypoxic [oxygen glucose deprivation (OGD)] conditions with and without the ONOO(-) decomposition catalyst 5,10,15,20-tetrakis(4-sulfonatophenyl) prophyrinato iron (III), chloride (FeTPPs). The percentage of myogenic tone was higher in diabetes, and forced dilation occurred at higher pressures. Functional hyperemia was impaired. Consistent with these findings, baseline CBF was lower in diabetes. OGD reduced the percentage of myogenic tone in both groups, and FeTPPs restored it only in diabetes. OGD increased VSM NY in both groups, and although FeTPPs restored basal levels, it did not correct the reduced filamentous/globular (F/G) actin ratio. Acute alterations in VSM ONOO(-) levels may contribute to hypoxic myogenic dysfunction, but this cannot be solely explained by the decreased F/G actin ratio due to actin nitration, and mechanisms may differ between control and diabetic animals. Our findings also demonstrate that diabetes alters the ability of cerebral vessels to regulate CBF under basal and hypoxic conditions.
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Arrick DM, Sun H, Patel KP, Mayhan WG. Chronic resveratrol treatment restores vascular responsiveness of cerebral arterioles in type 1 diabetic rats. Am J Physiol Heart Circ Physiol 2011; 301:H696-703. [PMID: 21666113 PMCID: PMC3191086 DOI: 10.1152/ajpheart.00312.2011] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 06/01/2011] [Indexed: 11/22/2022]
Abstract
Decreased dilation of cerebral arterioles via an increase in oxidative stress may be a contributing factor in the pathogenesis of diabetes-induced complications leading to cognitive dysfunction and/or stroke. Our goal was to determine whether resveratrol, a polyphenolic compound present in red wine, has a protective effect on cerebral arterioles during type 1 diabetes (T1D). We measured the responses of cerebral arterioles in untreated and resveratrol-treated (10 mg·kg(-1)·day(-1)) nondiabetic and diabetic rats to endothelial (eNOS) and neuronal (nNOS) nitric oxide synthase (NOS)-dependent agonists and to a NOS-independent agonist. In addition, we harvested brain tissue from nondiabetic and diabetic rats to measure levels of superoxide under basal conditions. Furthermore, we used Western blot analysis to determine the protein expression of eNOS, nNOS, SOD-1, and SOD-2 in cerebral arterioles and/or brain tissue from untreated and resveratrol-treated nondiabetic and diabetic rats. We found that T1D impaired eNOS- and nNOS-dependent reactivity of cerebral arterioles but did not alter NOS-independent vasodilation. While resveratrol did not alter responses in nondiabetic rats, resveratrol prevented T1D-induced impairment in eNOS- and nNOS-dependent vasodilation. In addition, superoxide levels were higher in brain tissue from diabetic rats and resveratrol reversed this increase. Furthermore, eNOS and nNOS protein were increased in diabetic rats and resveratrol produced a further increased eNOS and nNOS proteins. SOD-1 and SOD-2 proteins were not altered by T1D, but resveratrol treatment produced a decrease in SOD-2 protein. Our findings suggest that resveratrol restores vascular function and oxidative stress in T1D. We suggest that our findings may implicate an important therapeutic potential for resveratrol in treating T1D-induced cerebrovascular dysfunction.
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Affiliation(s)
- Denise M Arrick
- Department of Cellular Biology and Anatomy, Louisiana State University Health Sciences Center, School of Medicine in Shreveport, Shreveport, Louisiana, USA
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Osmond JM, Mintz JD, Dalton B, Stepp DW. Obesity increases blood pressure, cerebral vascular remodeling, and severity of stroke in the Zucker rat. Hypertension 2008; 53:381-6. [PMID: 19104000 DOI: 10.1161/hypertensionaha.108.124149] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Obesity is a risk factor for stroke, but the mechanisms by which obesity increases stroke risk are unknown. Because microvascular architecture contributes to the outcome of stroke, we hypothesized that middle cerebral arteries (MCAs) from obese Zucker rats (OZRs) undergo inward remodeling and develop increased myogenic tone compared with those in lean Zucker rats (LZRs). We further hypothesized that OZRs have an increased infarct after cerebral ischemia and that changes in vascular structure and function correlate with the development of hypertension in OZRs. Blood pressure was measured by telemetry in LZRs and OZRs from 6 to 17 weeks of age. Vessel structure and function were assessed in isolated MCAs. Stroke damage was assessed after ischemia was induced for 60 minutes followed by 24 hours of reperfusion. Although mean arterial pressure was similar between young rats (6 to 8 weeks old), mean arterial pressure was higher in adult (14 to 17 weeks old) OZRs than in LZRs. MCAs from OZRs had a smaller lumen diameter and increased myogenic vasoconstriction compared with those from LZRs. After ischemia, infarction was 58% larger in OZRs than in LZRs. Before the development of hypertension, MCA myogenic reactivity and lumen diameter, as well as infarct size, were similar between young LZRs and OZRs. Our results indicate that the MCAs of OZRs undergo structural remodeling and that these rats have greater cerebral injury after cerebral ischemia. These cerebrovascular changes correlate with the development of hypertension and suggest that the increased blood pressure may be the major determinant for stroke risk in obese individuals.
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Affiliation(s)
- Jessica M Osmond
- Department of Physiology, Vascular Biology Center, Medical College of Georgia, 1459 Laney Walker Blvd, CB3212A, Augusta, GA 30912, USA
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13
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Song D, Yao R, Pang CC. Altered vasodilator role of nitric oxide synthase in the pancreas, heart and brain of rats with spontaneous type 2 diabetes. Eur J Pharmacol 2008; 591:177-81. [DOI: 10.1016/j.ejphar.2008.06.036] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Revised: 05/23/2008] [Accepted: 06/05/2008] [Indexed: 10/21/2022]
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Sachidanandam K, Elgebaly MM, Harris AK, Hutchinson JR, Mezzetti EM, Portik-Dobos V, Ergul A. Effect of chronic and selective endothelin receptor antagonism on microvascular function in type 2 diabetes. Am J Physiol Heart Circ Physiol 2008; 294:H2743-9. [PMID: 18424628 DOI: 10.1152/ajpheart.91487.2007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Vascular dysfunction, which presents either as an increased response to vasoconstrictors or an impaired relaxation to dilator agents, results in worsened cardiovascular outcomes in diabetes. We have established that the mesenteric circulation in Type 2 diabetes is hyperreactive to the potent vasoconstrictor endothelin-1 (ET-1) and displays increased nitric oxide-dependent vasodilation. The current study examined the individual and/or the relative roles of the ET receptors governing vascular function in the Goto-Kakizaki rat, a mildly hyperglycemic, normotensive, and nonobese model of Type 2 diabetes. Diabetic and control rats received an antagonist to either the ET type A (ETA; atrasentan; 5 mg x kg(-1) x day(-1)) or type B (ET(B); A-192621; 15 or 30 mg x kg(-1) x day(-1)) receptors for 4 wk. Third-order mesenteric arteries were isolated, and vascular function was assessed with a wire myograph. Maximum response to ET-1 was increased in diabetes and attenuated by ETA antagonism. ETB blockade with 15 mg/kg A-192621 augmented vasoconstriction in controls, whereas it had no further effect on ET-1 hyperreactivity in diabetes. The higher dose of A-192621 showed an ETA-like effect and decreased vasoconstriction in diabetes. Maximum relaxation to acetylcholine (ACh) was similar across groups and treatments. ETB antagonism at either dose had no effect on vasorelaxation in control rats, whereas in diabetes the dose-response curve to ACh was shifted to the right, indicating a decreased relaxation at 15 mg/kg A-192621. These results suggest that ETA receptor blockade attenuates vascular dysfunction and that ETB receptor antagonism exhibits differential effects depending on the dose of the antagonists and the disease state.
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Affiliation(s)
- Kamakshi Sachidanandam
- Program in Clinical and Experimental Therapeutics, University of Georgia College of Pharmacy, Medical College of Georgia, Augusta, Georgia, USA
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Harris AK, Elgebaly MM, Li W, Sachidanandam K, Ergul A. Effect of chronic endothelin receptor antagonism on cerebrovascular function in type 2 diabetes. Am J Physiol Regul Integr Comp Physiol 2008; 294:R1213-9. [PMID: 18287215 DOI: 10.1152/ajpregu.00885.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Diabetes increases the risk of stroke and contributes to poor clinical outcomes in this patient population. Myogenic tone of the cerebral vasculature, including basilar arteries, plays a key role in controlling cerebral blood flow. Increased myogenic tone is ameliorated with ET receptor antagonism in Type 1 diabetes. However, the role of endothelin-1 (ET-1) and its receptors in cerebrovascular dysfunction in Type 2 diabetes, a common comorbidity in stroke patients, remains poorly elucidated. Therefore, we hypothesized that 1) cerebrovascular dysfunction occurs in the Goto-Kakizaki (GK) model of Type 2 diabetes, and 2) pharmacological antagonism of ETA receptors ameliorates, while ETB receptor blockade augments vascular dysfunction. GK or control rats were treated with antagonists to either ETA (atrasentan, 5 mg.kg(-1).day(-1)) or ETB (A-192621, 15 or 30 mg.kg(-1).day(-1)) receptors for 4 wk and vascular function of basilar arteries was assessed using a wire myograph. GK rats exhibited increased sensitivity to ET-1. ET(A) receptor antagonism caused a rightward shift, indicating decreased sensitivity in diabetes, while it increased sensitivity to ET-1 in control rats. Endothelium-dependent relaxation was impaired in diabetes. ETA receptor blockade restored relaxation to control values in the GK animals with no significant effect in Wistar rats and ETB blockade with 30 mg.kg(-1).day(-1) A-192621 caused paradoxical constriction in diabetes. These studies demonstrate that cerebrovascular dysfunction occurs and may contribute to altered regulation of myogenic tone and cerebral blood flow in diabetes. While ETA receptors mediate vascular dysfunction, ETB receptors display differential effects. These results underscore the importance of ETA/ETB receptor balance and interactions in cerebrovascular dysfunction in diabetes.
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Affiliation(s)
- Alex K Harris
- Program in Clinical and Experimental Therapeutics, University of Georgia College of Pharmacy, Augusta, Georgia, USA
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16
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Bohlen HG. Microvascular Consequences of Obesity and Diabetes. Microcirculation 2008. [DOI: 10.1016/b978-0-12-374530-9.00021-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Wu G, Collins JK, Perkins-Veazie P, Siddiq M, Dolan KD, Kelly KA, Heaps CL, Meininger CJ. Dietary supplementation with watermelon pomace juice enhances arginine availability and ameliorates the metabolic syndrome in Zucker diabetic fatty rats. J Nutr 2007; 137:2680-5. [PMID: 18029483 DOI: 10.1093/jn/137.12.2680] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Watermelon is rich in L-citrulline, an effective precursor of L-arginine. This study was conducted to determine whether dietary supplementation with watermelon pomace juice could ameliorate the metabolic syndrome in the Zucker diabetic fatty (ZDF) rat, an animal model of noninsulin-dependent diabetes mellitus. Nine-week-old ZDF rats were assigned randomly to receive drinking water containing 0% (control) or 0.2% L-arginine (as 0.24% L-arginine-HCl), 63% watermelon pomace juice, 0.01% lycopene, or 0.05% citrus pectin (n = 6 per treatment). At the end of the 4-wk supplementation period, blood samples, aortic rings, and hearts were obtained for biochemical and physiological analyses. Feed or energy intakes did not differ among the 5 groups of rats. However, dietary supplementation with watermelon pomace juice or L-arginine increased serum concentrations of arginine; reduced fat accretion; lowered serum concentrations of glucose, free fatty acids, homocysteine, and dimethylarginines; enhanced GTP cyclohydrolase-I activity and tetrahydrobiopterin concentrations in the heart; and improved acetylcholine-induced vascular relaxation. Compared with the control, dietary supplementation with lycopene or citrus pectin did not affect any measured parameter. These results provide the first evidence to our knowledge for a beneficial effect of watermelon pomace juice as a functional food for increasing arginine availability, reducing serum concentrations of cardiovascular risk factors, improving glycemic control, and ameliorating vascular dysfunction in obese animals with type-II diabetes.
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Affiliation(s)
- Guoyao Wu
- Faculty of Nutrition and Department of Animal Science, Texas A&M University, College Station, TX 77843, USA.
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Abstract
Admission hyperglycemia complicates approximately one-third of acute ischemic strokes and is associated with a worse clinical outcome. Both human and animal studies have showed that hyperglycemia is particularly detrimental in ischemia/reperfusion. Decreased reperfusion blood flow has been observed after middle cerebral artery occlusion in acutely hyperglycemic animals, suggesting the vasculature as an important site of hyperglycemic reperfusion injury. This paper reviews biochemical and molecular pathways in the vasculature that are rapidly affected by hyperglycemia and concludes that these changes result in a pro-vasoconstrictive, pro-thrombotic and pro-inflammatory phenotype that renders the vasculature vulnerable to reperfusion injury. Understanding these pathways should lead to the development of rational therapies that reduce hyperglycemic reperfusion injury and thus improve outcome in this large subset of acute ischemic stroke patients.
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Affiliation(s)
- Sharyl R Martini
- Department of Neurology, Baylor College of Medicine and the Michael E DeBakey Veterans Affairs Medical Center Stroke Program, Houston, TX 77030, USA
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Didion SP, Lynch CM, Faraci FM. Cerebral vascular dysfunction in TallyHo mice: a new model of Type II diabetes. Am J Physiol Heart Circ Physiol 2006; 292:H1579-83. [PMID: 17122191 DOI: 10.1152/ajpheart.00939.2006] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to characterize vascular responses and to examine mechanisms of vascular dysfunction in TallyHo mice, a new polygenic model of Type II diabetes. Responses of cerebral arterioles and carotid arteries were examined in vivo by using a cranial window and in vitro by using tissue baths, respectively. Dilatation of cerebral arterioles (baseline diameter = 33 +/- 1 micro m) in response to acetylcholine, but not to nitroprusside, was markedly reduced (P < 0.05) in TallyHo mice. Responses of cerebral arterioles to acetylcholine in TallyHo mice were restored to normal with polyethylene glycol-superoxide dismutase (100 U/ml; a superoxide scavenger). Responses to acetylcholine were also greatly impaired (P < 0.05) in the carotid arteries from TallyHo mice. Phenylephrine- and serotonin-, but not to KCl- or U46619-, induced contraction was increased two- to fourfold (P < 0.05) in carotid arteries of TallyHo mice. Responses to phenylephrine and serotonin were reduced to similar levels in the presence of Y-27632 (an inhibitor of Rho kinase; 3 micro mol/l). These findings provide the first evidence that vascular dysfunction is present in TallyHo mice and that oxidative stress and enhanced activity of Rho kinase may contribute to altered vascular function in this genetic model of Type II diabetes.
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Affiliation(s)
- Sean P Didion
- Dept of Internal Medicine, The Univ of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.
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Matsumoto T, Kobayashi T, Wachi H, Seyama Y, Kamata K. Vascular NAD(P)H oxidase mediates endothelial dysfunction in basilar arteries from Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Atherosclerosis 2006; 192:15-24. [PMID: 16831440 DOI: 10.1016/j.atherosclerosis.2006.06.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2005] [Revised: 04/13/2006] [Accepted: 06/02/2006] [Indexed: 11/20/2022]
Abstract
We examined the responses of basilar arteries taken from Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a type 2 diabetes model. Both the nitric oxide (NO)-mediated relaxation and the cyclic 3',5'-guanosine monophosphate (cGMP) production elicited by acetylcholine (ACh) were much weaker in OLETF rats than in age-matched control Long Evans Tokushima Otsuka (LETO) rats. The contraction induced by an NO synthase (NOS) inhibitor [N(G)-nitro-L-arginine (L-NNA)] was weaker in the OLETF group. In that group, application of apocynin, an NAD(P)H oxidase inhibitor, normalized (i) ACh-induced relaxation, (ii) L-NNA-induced contraction, and (iii) ACh-induced cGMP production to the LETO levels. Superoxide anion production was greater in basilar arteries from OLETF rats than in those from LETO rats. The protein expression of gp91(phox), an NAD(P)H oxidase subunit, was upregulated in the OLETF arteries (versus LETO ones). These results suggest that the existence of endothelial dysfunction in basilar arteries in type 2 diabetes is related to increased oxidative stress mediated via NAD(P)H oxidase. Possibly, an impairment of NO-dependent relaxation responses and a basal impairment of NO signaling may be responsible for the increased risk of adverse cerebrovascular events in type 2 diabetes.
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Affiliation(s)
- Takayuki Matsumoto
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo 142-8501, Japan
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21
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Busija DW, Miller AW, Katakam P, Erdos B. Adverse effects of reactive oxygen species on vascular reactivity in insulin resistance. Antioxid Redox Signal 2006; 8:1131-40. [PMID: 16910761 DOI: 10.1089/ars.2006.8.1131] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Insulin resistance (IR) has adverse effects on the reactivity of arteries and arterioles and promotes arterial hypertension and vascular occlusive diseases. Altered reactivity of resistance vessels occurs at both the endothelium and smooth-muscle levels. One major mechanism of vascular dysfunction with IR involves the augmented generation, availability, and/or actions of reactive oxygen species (ROS). Scavengers of ROS are able immediately to restore normal dilator responsiveness in arteries from IR animals. Other factors, such as increased importance of constrictor agents such as endothelin, also restrict normal dilator responses. The basis of ROS-mediated vascular dysfunction in IR may be secondary to underlying inflammatory processes throughout the arterial wall. Although ROS scavengers may be beneficial in the short term, prolonged treatments involving behavioral approaches, such as changes in diet, weight loss, and regular exercise, and pharmacological approaches, involving the use of insulin-sensitizing agents, inhibitors of the renin-angiotensin system, or administration of statins, appear to offer benefits against the detrimental vascular effects of IR. Nonetheless, the most effective approach appears to involve prevention of IR via adoption of a healthy lifestyle by young people.
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Affiliation(s)
- David W Busija
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA.
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Li Z, Rodríguez-Iturbe B, Ni Z, Shahkarami A, Sepassi L, Vaziri ND. Effect of hereditary obesity on renal expressions of NO synthase, caveolin-1, AKt, guanylate cyclase, and calmodulin. Kidney Int 2006; 68:2766-72. [PMID: 16316351 DOI: 10.1111/j.1523-1755.2005.00747.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Obesity has emerged as a major cause of diabetes, cardiovascular disease, and renal insufficiency worldwide. Obese Zucker rats exhibit hyperphagia, obesity, insulin resistance, hyperlipidemia, and glomerulosclerosis and are frequently used as a model to study hereditary form of metabolic syndrome. Nitric oxide plays a major role in preservation of renal function and structure. The present study was designed to test the hypothesis that renal disease in this model may be associated with down-regulation of endothelial (eNOS) and neuromal NO synthases (nNOS) in the kidney. The study further sought to explore expressions of caveolin-1, phospho AKt, and calmodulin, which regulate activities of constituitive NOS isoforms, as well as soluble guanylate cyclase (sGC), which is involved in NO signaling. METHODS Twenty-two-week-old male obese and lean Zucker rats were studied. Body weight, serum lipids, urine albumin excretion, and renal tissue abundance of the above proteins were determined. RESULTS Serum glucose and arterial pressure were unchanged, whereas urinary NO metabolite (NO(chi)) excretion and renal tissue nitrotyrosine abundance were markedly reduced (denoting depressed NO production) in the obese versus lean Zucker rats. This was accompanied by significant glomerulosclerosis, tubulointerstitial damage, renal immune cell infiltration, marked down-regulations of renal tissue eNOS and nNOS, mild reduction of caveolin-1, and unchanged calmodulin, phospho-AKt, and sGC. CONCLUSION Hereditary obesity can result in down-regulations of kidney eNOS and nNOS, marked reduction of NO production, and glomerulosclerosis prior to the onset of frank diabetes and hypertension.
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Affiliation(s)
- Zhen Li
- Renal Service, Hospital Universitario, Universidad del Zulia, Instituto de Investigaciones Biomédicas, Maracaibo, Venezuela
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Mori M, Stokes KY, Vowinkel T, Watanabe N, Elrod JW, Harris NR, Lefer DJ, Hibi T, Granger DN. Colonic blood flow responses in experimental colitis: time course and underlying mechanisms. Am J Physiol Gastrointest Liver Physiol 2005; 289:G1024-9. [PMID: 16081759 DOI: 10.1152/ajpgi.00247.2005] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Human inflammatory bowel diseases (IBD) are associated with significant alterations in intestinal blood flow, the direction and magnitude of which change with disease progression. The objectives of this study were to determine the time course of changes in colonic blood perfusion that occur during the development of dextran-sodium-sulfate (DSS)-induced colonic inflammation and to address the mechanisms that may underlie these changes in blood flow. Intravital microscopy was used to quantify blood flow (from measurements of vessel diameter and red blood cell velocity) in different-sized submucosal arterioles of control and inflamed colons in wild-type (WT) mice. A significant (18-30%) reduction in blood flow was noted in the smallest arterioles (<40 microm diameter) on days 4-6 of DSS colitis. The arteriolar responses to bradykinin in control and DSS-treated WT mice revealed an impaired endothelium-dependent, but not endothelium-independent, vasodilation in the inflamed colon. However, this impaired vasodilatory response to bradykinin after DSS treatment was not evident in mutant mice that overexpress Cu,Zn-superoxide dismutase. Rescue of the bradykinin-induced vasodilation during DSS colitis was also observed in mice that are genetically deficient in the NAD(P)H oxidase subunit gp91(phox). These findings indicate that the decline in blood flow during experimental colitis may result from a diminished capacity of colonic arterioles to respond to endogenous endothelium-dependent vasodilators like bradykinin and that NAD(P)H oxidase-derived superoxide plays a major role in the induction of the inflammation-induced endothelium-dependent arteriolar dysfunction.
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Affiliation(s)
- Mikiji Mori
- Dept. of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA
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24
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Frisbee JC. Reduced nitric oxide bioavailability contributes to skeletal muscle microvessel rarefaction in the metabolic syndrome. Am J Physiol Regul Integr Comp Physiol 2005; 289:R307-R316. [PMID: 15802560 DOI: 10.1152/ajpregu.00114.2005] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study tested the hypothesis that chronically elevated oxidant stress contributes to impaired active hyperemia in skeletal muscle of obese Zucker rats (OZR) vs. lean Zucker rats (LZR) through progressive deteriorations in microvascular structure. Twelve-week-old LZR and OZR were given 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (tempol) in the drinking water for ∼4 wk. Subsequently, perfusion of in situ gastrocnemius muscle was determined during incremental elevations in metabolic demand, while a contralateral skeletal muscle arteriole and the gastrocnemius muscle was removed to determine dilator reactivity, vessel wall mechanics, and microvessel density. Under control conditions, active hyperemia was impaired at all levels of metabolic demand in OZR, and this was correlated with a reduced microvessel density, increased arteriolar stiffness, and impaired dilator reactivity. Chronic tempol ingestion improved perfusion during moderate to high metabolic demand only and was associated with improved arteriolar reactivity and microvessel density; passive vessel mechanics were unaltered. Combined antioxidant therapy and nitric oxide synthase inhibition in OZR prevented much of the restored perfusion and microvessel density. In LZR, treatment with Nω-nitro-l-arginine methyl ester (l-NAME) hydrochloride and hydralazine (to prevent hypertension) impaired active hyperemia, dilator reactivity, and microvessel density, although arteriolar distensibility was not altered. These results suggest that with the development of the metabolic syndrome, chronic reductions in nitric oxide bioavailability, in part via the scavenging actions of oxidative free radicals, contribute to a loss of skeletal muscle microvessels, leading to impaired muscle perfusion with elevated metabolic demand.
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Affiliation(s)
- Jefferson C Frisbee
- Center for Interdisciplinary Research in Cardiovascular Science, Dept. of Physiology and Pharmacology, Robert C. Byrd Health Sciences Center, PO Box 9105, West Virginia University School of Medicine, Morgantown, WV 26505, USA.
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Katakam PVG, Tulbert CD, Snipes JA, Erdös B, Miller AW, Busija DW. Impaired insulin-induced vasodilation in small coronary arteries of Zucker obese rats is mediated by reactive oxygen species. Am J Physiol Heart Circ Physiol 2005; 288:H854-60. [PMID: 15650157 DOI: 10.1152/ajpheart.00715.2004] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin resistance (IR) and associated hyperinsulinemia are major risk factors for coronary artery disease. Mechanisms linking hyperinsulinemia to coronary vascular dysfunction in IR are unclear. We evaluated insulin-induced vasodilation in isolated small coronary arteries (SCA; approximately 225 microm) of Zucker obese (ZO) and control Zucker lean (ZL) rats. Vascular responses to insulin (0.1-100 ng/ml), ACh (10(-9)-10(-5) mol/l), and sodium nitroprusside (10(-8)-10(-4) mol/l) were assessed in SCA by measurement of intraluminal diameter using videomicroscopy. Insulin-induced dilation was decreased in ZO compared with ZL rats, whereas ACh and sodium nitroprusside elicited similar vasodilations. Pretreatment of arteries with SOD (200 U/ml), a scavenger of reactive oxygen species (ROS), restored the vasorelaxation response to insulin in ZO arteries, whereas ZL arteries were unaffected. Pretreatment of SCA with N-nitro-L-arginine methyl ester (100 micromol/l), an inhibitor of endothelial nitric oxide (NO) synthase (eNOS), elicited a vasoconstrictor response to insulin that was greater in ZO than in ZL rats. This vasoconstrictor response was reversed to vasodilation in ZO and ZL rats by cotreatment of the SCA with SOD or apocynin (10 micromol/l), a specific inhibitor of vascular NADPH oxidase. Lucigenin-enhanced chemiluminescence showed increased basal ROS levels as well as insulin (330 ng/ml)-stimulated production of ROS in ZO arteries that was sensitive to inhibition by apocynin. Western blot analysis revealed increased eNOS expression in ZO rats, whereas Mn SOD and Cu,Zn SOD expression were similar to ZL rats. Thus IR in ZO rats leads to decreased insulin-induced vasodilation, probably as a result of increased production of ROS by vascular NADPH oxidase, leading to decreased NO bioavailability, despite a compensatory increase in eNOS expression.
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Affiliation(s)
- Prasad V G Katakam
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston-Salem, North Carolina 27157, USA
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26
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Didion SP, Lynch CM, Baumbach GL, Faraci FM. Impaired endothelium-dependent responses and enhanced influence of Rho-kinase in cerebral arterioles in type II diabetes. Stroke 2005; 36:342-7. [PMID: 15637328 DOI: 10.1161/01.str.0000152952.42730.92] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Although the incidence of type II diabetes is increasing, very little is known regarding vascular responses in the cerebral circulation in this disease. The goals of this study were to examine the role of superoxide in impaired endothelium-dependent responses and to examine the influence of Rho-kinase on vascular tone in the cerebral microcirculation in type II diabetes. METHODS Diameter of cerebral arterioles (29+/-1 microm; mean+/-SE) was measured in vivo using a cranial window in anesthetized db/db and control mice. RESULTS Dilatation of cerebral arterioles in response to acetylcholine (ACh; 1 and 10 micromol/L), but not to nitroprusside, was markedly reduced in db/db mice (eg, 10 micromol/L ACh produced 29+/-1% and 9+/-1% in control and db/db mice, respectively). Superoxide levels were increased (P<0.05) in cerebral arterioles from db/db mice (n=6) compared with controls (n=6). Vasodilatation to ACh in db/db mice was restored to normal by polyethylene glycol-superoxide dismutase (100 U/mL). Y-27632 (1 to 100 micromol/L; a Rho-kinase inhibitor) produced modest vasodilatation in control mice but much greater responses in db/db mice. N(G)-nitro-L-arginine (100 micromol/L; an inhibitor of NO synthase) significantly enhanced Y-27632-induced dilatation in control mice to similar levels as observed in db/db mice. CONCLUSIONS These findings provide the first evidence for superoxide-mediated impairment of endothelium-dependent responses of cerebral vessels in any model of type II diabetes. In addition, the influence of Rho-kinase on resting tone appears to be selectively enhanced in the cerebral microcirculation in this genetic model of type II diabetes.
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Affiliation(s)
- Sean P Didion
- Department of Internal Medicine, University of Iowa Carver College of Medicine Iowa City, IA 52242, USA.
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Cellek S, Anderson PN, Foxwell NA. Nitrergic neurodegeneration in cerebral arteries of streptozotocin-induced diabetic rats: a new insight into diabetic stroke. Diabetes 2005; 54:212-9. [PMID: 15616031 DOI: 10.2337/diabetes.54.1.212] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Although autonomic neuropathy is recognized as an independent risk factor for stroke in diabetes, the mechanism by which autonomic nerves are involved in this pathology is unknown. Parasympathetic (cholinergic) nerves of the autonomic nervous system are known to innervate and to cause relaxation of cerebral arteries by releasing nitric oxide (NO); hence, they are called nitrergic nerves. However, the effect of diabetes on nitrergic nerves is unknown. Here, we show that perivascular nitrergic nerves around the cerebral arteries degenerate in two phases in streptozotocin-induced diabetic rats. In the first phase, perivascular nitrergic nerve fibers remain intact while they lose their neuronal NO synthase content. This phase is reversible with insulin treatment. In the second phase, nitrergic cell bodies in the ganglia are lost via apoptosis in an irreversible manner. Throughout the two phases, irreversible thickening of the smooth muscle layer of cerebral arteries is observed. This is the first demonstration of nitrergic degeneration in diabetic cerebral arteries, which could elucidate the link between diabetic autonomic neuropathy and stroke.
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Affiliation(s)
- Selim Cellek
- Wolfson Institute for Biomedical Research, University College London, Gower St., Cruciform Building, London WC1E 6BT, UK.
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Fulton D, Harris MB, Kemp BE, Venema RC, Marrero MB, Stepp DW. Insulin resistance does not diminish eNOS expression, phosphorylation, or binding to HSP-90. Am J Physiol Heart Circ Physiol 2004; 287:H2384-93. [PMID: 15271670 DOI: 10.1152/ajpheart.00280.2004] [Citation(s) in RCA: 37] [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: 11/22/2022]
Abstract
Previously, using an animal model of syndrome X, the obese Zucker rat (OZR), we documented impaired endothelium-dependent vasodilation. The aim of this study was to determine whether reduced expression or altered posttranslational regulation of endothelial nitric oxide synthase (eNOS) underlies the vascular dysfunction in OZR rats. There was no significant difference in the relative abundance of eNOS in hearts, aortas, or skeletal muscle between lean Zucker rats (LZR) and OZR regardless of age. There was no difference in eNOS mRNA levels, as determined by real-time PCR, between LZR and OZR. The inability of insulin resistance to modulate eNOS expression was also documented in two additional in vivo models, the ob/ob mouse and the fructose-fed rat, and in vitro via adenoviral expression of protein tyrosine phosphatase 1B in endothelial cells. We next investigated whether changes in the acute posttranslational regulation of eNOS occurs with insulin resistance. Phosphorylation of eNOS at S632 (human S633) and T494 was not different between LZR and OZR; however, phosphorylation of S1176 was significantly enhanced in OZR. Phosphorylation of S1176 was not different in the ob/ob mouse or in fructose-fed rats. The association of heat shock protein 90 with eNOS, a key regulatory step controlling nitric oxide and aberrant O2−production, was not different between OZR and LZR. Taken together, these results suggest that changes in eNOS expression or posttranslation regulation do not underlie the vascular dysfunction seen with insulin resistance and that other mechanisms, such as altered localization, reduced availability of cofactors, substrates, and the elevated production of O2−, may be responsible.
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Affiliation(s)
- David Fulton
- Vascular Biology Center, Medical College of Georgia, 1459 Laney Walker Blvd., Augusta, GA 30912, USA.
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Phillips SA, Sylvester FA, Frisbee JC. Oxidant stress and constrictor reactivity impair cerebral artery dilation in obese Zucker rats. Am J Physiol Regul Integr Comp Physiol 2004; 288:R522-30. [PMID: 15514104 DOI: 10.1152/ajpregu.00655.2004] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study tested the hypothesis that evolution of the metabolic syndrome in obese Zucker rats (OZR) leads to impaired dilator reactivity of cerebral resistance arteries vs. responses determined in lean Zucker rats (LZR). Middle cerebral arteries (MCA) from 17-wk-old male LZR and OZR were isolated and cannulated with glass micropipettes. Vascular reactivity was assessed in response to challenge with ACh, sodium nitroprusside (SNP), reductions and elevations in Po2, 5-HT, and increased intralumenal pressure. Vessels were treated with the free radical scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (tempol) to assess the role of superoxide production in altering reactivity, and passive vascular wall mechanics was assessed in each vessel. Vascular superoxide production was assessed in isolated arteries using fluorescence microscopy. Vessel dilation to ACh and hypoxia was impaired in OZR vs. LZR, although responses to SNP were normal. Vessel constriction to 5-HT, elevated Po2, and elevated intralumenal pressure was enhanced in OZR vs. LZR. Fluorescence microscopy demonstrated an increased superoxide production in arteries of OZR vs. LZR, correctable by incubation with tempol. Although treatment of vessels from OZR with tempol improved dilation to ACh and hypoxia, constrictor responses to 5-HT, elevated Po2, and pressure were not altered by tempol treatment. Indexes of vessel wall mechanics were comparable between groups. These results suggest that vasodilator reactivity of MCA of OZR in response to endothelium-dependent dilator stimuli is impaired vs. LZR and that this may represent a reduced bioavailability of signaling molecules due to oxidant scavenging. However, oxidative stress-independent increases in myogenic tone and constrictor reactivity may contribute to blunted dilator responses of cerebral microvessels.
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Affiliation(s)
- Shane A Phillips
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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Mayhan WG, Sun H, Mayhan JF, Patel KP. Influence of exercise on dilatation of the basilar artery during diabetes mellitus. J Appl Physiol (1985) 2004; 96:1730-7. [PMID: 14729730 DOI: 10.1152/japplphysiol.01185.2003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Our goal was to examine whether exercise training alleviates impaired nitric oxide synthase (NOS)-dependent dilatation of the basilar artery in Type 1 diabetic rats. To test this hypothesis, we measured in vivo diameter of the basilar artery in sedentary and exercised nondiabetic and diabetic rats in response to NOS-dependent (acetylcholine) and -independent (nitroglycerin) agonists. To determine the potential role for nitric oxide in vasodilatation in sedentary and exercised nondiabetic and diabetic rats, we examined responses after NG-monomethyl-l-arginine (l-NMMA). We found that acetylcholine produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic rats. Acetylcholine produced only minimal vasodilatation in sedentary diabetic rats. However, exercise alleviated impaired acetylcholine-induced vasodilatation in diabetic rats. Nitroglycerin produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic and diabetic rats. l-NMMA produced similar inhibition of acetylcholine-induced dilatation of the basilar artery in sedentary and exercised nondiabetic and diabetic rats. Finally, we found that endothelial NOS (eNOS) protein in the basilar artery was higher in diabetic compared with nondiabetic rats and that exercise increased eNOS protein in the basilar artery of nondiabetic and diabetic rats. We conclude that 1) exercise can alleviate impaired NOS-dependent dilatation of the basilar artery during diabetes mellitus, 2) the synthesis and release of nitric oxide accounts for dilatation of the basilar artery to acetylcholine in sedentary and exercised nondiabetic and diabetic rats, and 3) exercise may exert its affect on cerebrovascular reactivity during diabetes by altering levels of eNOS protein in the basilar artery.
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Affiliation(s)
- William G Mayhan
- Department of Physiology and Biophysics, University of Nebraska Medical Center, 985850 Nebraska Medical Center, Omaha, Nebraska 68198-5850, USA.
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