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Marketou ME, Maragkoudakis S, Anastasiou I, Nakou H, Plataki M, Vardas PE, Parthenakis FI. Salt-induced effects on microvascular function: A critical factor in hypertension mediated organ damage. J Clin Hypertens (Greenwich) 2019; 21:749-757. [PMID: 31002481 DOI: 10.1111/jch.13535] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 03/07/2019] [Accepted: 03/19/2019] [Indexed: 12/17/2022]
Abstract
Salt has been linked very closely to the occurrence and complications of arterial hypertension. A large percentage of patients with essential hypertension are salt-sensitive; that is, their blood pressure increases with increased salt intake and decreases with its reduction. For this reason, emphasis is placed on reducing salt intake to better regulate blood pressure. In day-to-day clinical practice this is viewed as mandatory for hypertensive patients who are judged to be salt-sensitive. Previous studies have highlighted the negative effect of high-salt diets on macrovascular function, which also affects blood pressure levels by increasing peripheral resistances. More recent studies provide a better overview of the pathophysiology of microvascular disorders and show that they are largely due to the overconsumption of salt. Microvascular lesions, which have a major impact on the functioning of vital organs, are often not well recognized in clinical practice and are not paid sufficient attention. In general, the damage caused by hypertension to the microvascular network is likely to be overlooked, while reversion of the damage is only rarely considered as a therapeutic target by the treating physician. The purpose of this review is to summarize the impact and the harmful consequences of increased salt consumption in the microvascular network, their significance and pathophysiology, and at the same time to place some emphasis on their treatment and reversion, mainly through diet.
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Affiliation(s)
- Maria E Marketou
- Department of Cardiology, Heraklion University Hospital, Heraklion, Greece
| | | | - Ioannis Anastasiou
- Department of Cardiology, Heraklion University Hospital, Heraklion, Greece
| | - Helen Nakou
- Barts Heart Centre, St Bartholomew's Hospital, London, UK
| | - Marina Plataki
- Department of Cardiology, Heraklion University Hospital, Heraklion, Greece
| | - Panos E Vardas
- Department of Cardiology, Heraklion University Hospital, Heraklion, Greece
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Allen LA, Schmidt JR, Thompson CT, Carlson BE, Beard DA, Lombard JH. High salt diet impairs cerebral blood flow regulation via salt-induced angiotensin II suppression. Microcirculation 2019; 26:e12518. [PMID: 30481399 DOI: 10.1111/micc.12518] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 10/03/2018] [Accepted: 11/22/2018] [Indexed: 01/11/2023]
Abstract
OBJECTIVES This study sought to determine whether salt-induced ANG II suppression contributes to impaired CBF autoregulation. METHODS Cerebral autoregulation was evaluated with LDF during graded reductions of blood pressure. Autoregulatory responses in rats fed HS (4% NaCl) diet vs LS (0.4% NaCl) diet were analyzed using linear regression analysis, model-free analysis, and a mechanistic theoretical model of blood flow through cerebral arterioles. RESULTS Autoregulation was intact in LS-fed animals as MAP was reduced via graded hemorrhage to approximately 50 mm Hg. Short-term (3 days) and chronic (4 weeks) HS diet impaired CBF autoregulation, as evidenced by progressive reductions of laser Doppler flux with arterial pressure reduction. Chronic low dose ANG II infusion (5 mg/kg/min, i.v.) restored CBF autoregulation between the pre-hemorrhage MAP and 50 mm Hg in rats fed short-term HS diet. Mechanistic-based model analysis showed a reduced myogenic response and reduced baseline VSM tone with short-term HS diet, which was restored by ANG II infusion. CONCLUSIONS Short-term and chronic HS diet lead to impaired autoregulation in the cerebral circulation, with salt-induced ANG II suppression as a major factor in the initiation of impaired CBF regulation.
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Affiliation(s)
- Linda A Allen
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - James R Schmidt
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Christopher T Thompson
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Brian E Carlson
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Daniel A Beard
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
| | - Julian H Lombard
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin
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Boegehold MA, Drenjancevic I, Lombard JH. Salt, Angiotensin II, Superoxide, and Endothelial Function. Compr Physiol 2015; 6:215-54. [PMID: 26756632 DOI: 10.1002/cphy.c150008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Proper function of the vascular endothelium is essential for cardiovascular health, in large part due to its antiproliferative, antihypertrophic, and anti-inflammatory properties. Crucial to the protective role of the endothelium is the production and liberation of nitric oxide (NO), which not only acts as a potent vasodilator, but also reduces levels of reactive oxygen species, including superoxide anion (O2•-). Superoxide anion is highly injurious to the vasculature because it not only scavenges NO molecules, but has other damaging effects, including direct oxidative disruption of normal signaling mechanisms in the endothelium and vascular smooth muscle cells. The renin-angiotensin system plays a crucial role in the maintenance of normal blood pressure. This function is mediated via the peptide hormone angiotensin II (ANG II), which maintains normal blood volume by regulating Na+ excretion. However, elevation of ANG II above normal levels increases O2•- production, promotes oxidative stress and endothelial dysfunction, and plays a major role in multiple disease conditions. Elevated dietary salt intake also leads to oxidant stress and endothelial dysfunction, but these occur in the face of salt-induced ANG II suppression and reduced levels of circulating ANG II. While the effects of abnormally high levels of ANG II have been extensively studied, far less is known regarding the mechanisms of oxidant stress and endothelial dysfunction occurring in response to chronic exposure to abnormally low levels of ANG II. The current article focuses on the mechanisms and consequences of this less well understood relationship among salt, superoxide, and endothelial function.
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Affiliation(s)
| | - Ines Drenjancevic
- Faculty of Medicine, Josip Juraj Strossmayer University of Osijek, Osijek, Croatia
| | - Julian H Lombard
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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Boegehold MA. The effect of high salt intake on endothelial function: reduced vascular nitric oxide in the absence of hypertension. J Vasc Res 2013; 50:458-67. [PMID: 24192502 DOI: 10.1159/000355270] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 08/21/2013] [Indexed: 11/19/2022] Open
Abstract
Within the last 25 years, it has become increasingly clear that high dietary salt intake represents a risk factor for the development of cardiovascular disease that is independent of its well-known ability to increase arterial pressure in some individuals. Studies in normotensive experimental animals and human subjects have revealed that a key feature of this pressure-independent effect of dietary salt is a profound reduction in vascular nitric oxide (NO) bioavailability that limits endothelium-dependent dilation. This reduction in NO is strongly associated with increased levels of reactive oxygen species (ROS) generated by NAD(P)H oxidase, xanthine oxidase or uncoupled endothelial NO synthase within the vascular wall, leading not only to scavenging of NO but also to disruption of some signaling pathways that mediate its production. The mechanistic link between high salt intake and elevated levels of enzymatically generated ROS in the peripheral vasculature is not clear, but a reduction in circulating angiotensin II may play a key role in this regard. Additional studies are needed to further elucidate the mechanisms, both at the systemic level and within the vascular wall, that trigger these salt-induced deficits in endothelial function, and to further clarify how the attendant loss of NO may disrupt tissue blood flow regulation and ultimately lead to adverse cardiovascular events.
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Affiliation(s)
- Matthew A Boegehold
- Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, W.Va., USA
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Bravo A. I, Michea A. L. Analysis of experimental evidence that shows adverse effects of salt and its relation to hypertension. Medwave 2012. [DOI: 10.5867/medwave.2012.02.5303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Lombard JH, Frisbee JC, Roman RJ, Falck JR. Evaluation of Cytochrome P450-4A ω-Hydroxylase and 20-Hydroxyeicosatetraenoic Acid as an O2 Sensing Mechanism in the Microcirculation. Methods Enzymol 2004; 381:140-65. [PMID: 15063671 DOI: 10.1016/s0076-6879(04)81009-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Julian H Lombard
- Department of Physiology, Medical College of Wisconsin, Milwaukee 53226-1408, USA
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FRISBEE JEFFERSONC, SYLVESTER FRANCISA, LOMBARD JULIANH. Contribution of Extrinsic Factors and Intrinsic Vascular Alterations to Reduced Arteriolar Reactivity with High-Salt Diet and Hypertension. Microcirculation 2000. [DOI: 10.1111/j.1549-8719.2000.tb00128.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Frisbee JC, Lombard JH. Alterations in skeletal muscle microvascular hematocrit with short-term reduced renal mass hypertension. Microvasc Res 2000; 59:390-3. [PMID: 10792971 DOI: 10.1006/mvre.1999.2235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- J C Frisbee
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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Frisbee JC, Lombard JH. Reduced renal mass hypertension, but not high salt diet, alters skeletal muscle arteriolar distensibility and myogenic responses. Microvasc Res 2000; 59:255-64. [PMID: 10684731 DOI: 10.1006/mvre.1999.2230] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of high salt diet and reduced renal mass hypertension (RRM-HT) on skeletal muscle arteriolar distensibility and myogenic responses were investigated in male Sprague-Dawley rats. Rats were enclosed in an air-tight box with the in situ cremaster muscle exteriorized and viewed via television microscopy. Normotensive rats were fed low salt (0.4% NaCl) or high salt (4.0% NaCl) diet and RRM-HT rats were fed high salt diet for 4-6 weeks. With the cremaster muscle superfused with either physiological salt solution (for myogenic responses) or Ca(2+)-free physiological salt solution (for arteriolar distensibility), box pressure (and therefore, intravascular pressure) was increased in 5 mm Hg increments to a maximum of +30 mm Hg. The myogenic responses of arterioles were not altered by high salt diet, but were enhanced with RRM-HT. Arteriolar distensibility was not affected by high salt diet, but was reduced in RRM-HT rats compared to either normotensive rat group. These data suggest that high salt diet does not significantly alter either myogenic responses or the distensibility of rat cremasteric arterioles. However, RRM-HT enhances myogenic responses of these vessels while reducing arteriolar distensibility. The impact of these effects must be taken into account when interpreting data describing alterations in skeletal muscle microvessel reactivity for animals on high salt diet or with RRM hypertension.
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Affiliation(s)
- J C Frisbee
- Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
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