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Bunsawat K, Skow RJ, Kaur J, Wray DW. Neural control of the circulation during exercise in heart failure with reduced and preserved ejection fraction. Am J Physiol Heart Circ Physiol 2023; 325:H998-H1011. [PMID: 37682236 PMCID: PMC10907034 DOI: 10.1152/ajpheart.00214.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 08/23/2023] [Accepted: 09/06/2023] [Indexed: 09/09/2023]
Abstract
Patients with heart failure with reduced (HFrEF) and preserved ejection fraction (HFpEF) exhibit severe exercise intolerance that may be due, in part, to inappropriate cardiovascular and hemodynamic adjustments to exercise. Several neural mechanisms and locally released vasoactive substances work in concert through complex interactions to ensure proper adjustments to meet the metabolic demands of the contracting skeletal muscle. Specifically, accumulating evidence suggests that disease-related alterations in neural mechanisms (e.g., central command, exercise pressor reflex, arterial baroreflex, and cardiopulmonary baroreflex) contribute to heightened sympathetic activation and impaired ability to attenuate sympathetic vasoconstrictor responsiveness that may contribute to reduced skeletal muscle blood flow and severe exercise intolerance in patients with HFrEF. In contrast, little is known regarding these important aspects of physiology in patients with HFpEF, though emerging data reveal heightened sympathetic activation and attenuated skeletal muscle blood flow during exercise in this patient population that may be attributable to dysregulated neural control of the circulation. The overall goal of this review is to provide a brief overview of the current understanding of disease-related alterations in the integrative neural cardiovascular responses to exercise in both HFrEF and HFpEF phenotypes, with a focus on sympathetic nervous system regulation during exercise.
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Affiliation(s)
- Kanokwan Bunsawat
- Division of Geriatrics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
- Geriatric Research, Education, and Clinical Center, George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, Utah, United States
| | - Rachel J Skow
- Department of Kinesiology, The University of Texas at Arlington, Arlington, Texas, United States
- Faculty of Nursing, University of Alberta, Edmonton, Alberta, Canada
| | - Jasdeep Kaur
- Department of Kinesiology and Health Education, The University of Texas at Austin, Austin, Texas, United States
| | - D Walter Wray
- Division of Geriatrics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
- Geriatric Research, Education, and Clinical Center, George E. Wahlen Department of Veterans Affairs Medical Center, Salt Lake City, Utah, United States
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, United States
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2
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Santos ÁRC, Abreu ARR, Noronha SISR, Reis TO, Santos DM, Chianca-Jr DA, da Silva LG, de Menezes RCA, Velloso-Rodrigues C. Thermoregulatory responses, heart rate, and the susceptibility to anxiety in obese animals subjected to stress. Physiol Behav 2023; 266:114181. [PMID: 37019294 DOI: 10.1016/j.physbeh.2023.114181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 03/25/2023] [Accepted: 04/02/2023] [Indexed: 04/05/2023]
Abstract
Obesity and stress are related to cardiovascular diseases. Rats fed a high-fat diet (HFD) show increased cardiovascular reactivity to emotional stress and altered defensive behavioral responses. Indeed, changes in thermoregulatory responses in an aversive environment are observed in these animals. However, studies aimed at clarifying the physiological mechanisms linking obesity, stress hyperreactivity and behavioral changes are needed. The aim of this study was to evaluate the changes in thermoregulatory responses, heart rate, and the susceptibility to anxiety in obese animals subjected to stress. Nine-week high-fat diet protocol was effective in inducing obesity by increasing weight gain, fat mass, adiposity index, white epididymal, retroperitoneal, inguinal and brown adipose tissue. Animals induced to obesity and subjected to stress (HFDS group) by the intruder animal method showed increases in heart rate (HR), core body temperature and tail temperature. HFDS showed an increase in the first exposure to the closed arm (anxiety-like behavior) in elevated T-Maze (ETM). The groups did not differ with respect to panic behavior assessed in the ETM and locomotor activity in the open field test. Our study shows that HFDS animals presented increased reactivity to stress with higher stress hyperthermia and anxious behavior. Thus, our results present relevant information regarding stress responsiveness and behavioral changes in obese animals.
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Affiliation(s)
- Áquila Rodrigues Costa Santos
- Laboratory on Thymus Research, Oswaldo Cruz Institute, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil; Department of Basic Life Sciences, Federal University of Juiz de Fora, Governador Valadares, Brazil
| | - Aline Rezende R Abreu
- Laboratory of Cardiovascular Physiology, Department of Biological Sciences, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Sylvana I S R Noronha
- Laboratory of Cardiovascular Physiology, Department of Biological Sciences, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Thayane Oliveira Reis
- Laboratory of Cardiovascular Physiology, Department of Biological Sciences, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Daisy Motta Santos
- Department of Sports, School of Physical Education, Physiotherapy and Occupational Therapy, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Deoclécio Alves Chianca-Jr
- Laboratory of Cardiovascular Physiology, Department of Biological Sciences, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Luiz Gonzaga da Silva
- Department of Basic Life Sciences, Federal University of Juiz de Fora, Governador Valadares, Brazil
| | - Rodrigo Cunha Alvim de Menezes
- Laboratory of Cardiovascular Physiology, Department of Biological Sciences, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Cibele Velloso-Rodrigues
- Department of Basic Life Sciences, Federal University of Juiz de Fora, Governador Valadares, Brazil.
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do Carmo JM, da Silva AA, Hall JE. Impact of Mineralocorticoid Receptor and Angiotensin II Type 1 Receptor Antagonism on Blood Pressure Regulation in Obese Zucker Rats: Role of Sex Differences. Am J Hypertens 2021; 34:999-1005. [PMID: 33075125 DOI: 10.1093/ajh/hpaa170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 09/29/2020] [Accepted: 10/14/2020] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Previous studies suggest that obesity-induced hypertension in females, but not males, is due to leptin-mediated stimulation of aldosterone secretion and subsequent activation of the mineralocorticoid receptor (MR). Although angiotensin II type 1 receptor (AT1R) antagonism lowers blood pressure (BP) in male obese Zucker rats (OZR), which have defective leptin signaling, the potential role of sex differences in BP responses to renin-angiotensin-aldosterone system blockade, including MR antagonism, in obesity is still unclear. We tested the cardiovascular effects of MR antagonism, alone or in combination with AT1R blockade in male and female OZR (n = 5/sex) and lean Zucker rats (n = 7/sex). METHODS BP and heart rate (HR) were measured by telemetry 24 hour/day. After a 6-day control period, spironolactone (40 mg/kg/day) was given for 10 days followed by a 7-day combined treatment with losartan (20 mg/kg/day), and followed by 6-day post-treatment recovery period. RESULTS Compared with lean rats, OZR were hypertensive (mean arterial pressure: 115 ± 4 vs. 104 ± 2 and 111 ± 1 vs. 100 ± 3 mm Hg for males and females) and had lower HR (355 ± 9 vs. 393 ± 7 and 367 ± 10 vs. 412 ± 13 bpm). MR blockade alone did not alter BP or HR in lean or obese male and female Zucker rats, whereas combined treatment reduced BP in obese and lean rats by 31 ± 3 vs. 21 ± 1 and 8 ± 1 vs. 5 ± 1 mm Hg in males and females, respectively. No changes were observed in HR. CONCLUSIONS These results suggest that there are important sex differences in BP responses to chronic AT1R blockade but no major involvement of MR activation in BP regulation in OZR.
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Affiliation(s)
- Jussara M do Carmo
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Alexandre A da Silva
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - John E Hall
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular-Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi, USA
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DeVallance ER, Branyan KW, Olfert IM, Pistilli EE, Bryner RW, Kelley EE, Frisbee JC, Chantler PD. Chronic stress induced perivascular adipose tissue impairment of aortic function and the therapeutic effect of exercise. Exp Physiol 2021; 106:1343-1358. [PMID: 33913209 DOI: 10.1113/ep089449] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 04/19/2021] [Indexed: 12/15/2022]
Abstract
NEW FINDINGS What is the central question of this study? Thoracic perivascular adipose tissue (tPVAT) is known to, in part, regulate aortic function: what are the effects of unpredictable chronic mild stress (UCMS) on the tPVAT regulation of aortic function and what is the role of exercise training in alleviating the potential negative actions of UCMS on tPVAT? What is the main finding and its importance? UCMS causes tPVAT to disrupt endothelium-dependent dilatation, increases inflammatory cytokine production and diminishes tPVAT-adiponectin. Exercise training proved efficacious in preventing tPVAT-mediated disruption of aortic function. The data support a tPVAT mechanism through which chronic stress negatively impacts vascular health, which adds to our knowledge of how psychological disorders might increase the risk of cardiovascular disease. ABSTRACT Chronic stress is a major risk for cardiovascular disease. Perivascular adipose tissue (PVAT) has been shown to regulate vascular function; however, the impact of chronic stress and the comorbidity of metabolic syndrome (MetS) on thoracic (t)PVAT is unknown. Additionally, aerobic exercise training (AET) is known to combat the pathology of MetS and chronic stress, but the role of tPVAT in these actions is also unknown. Therefore, the purpose of this study was to examine the effects of unpredictable chronic mild stress (UCMS) on the tPVAT regulation of aortic function and the preventative effect of AET. Lean (LZR) and obese (OZR) Zucker rats (16-17 weeks old) were exposed to 8 weeks of UCMS with and without treadmill exercise (AET). In LZR, UCMS impaired aortic endothelium-dependent dilatation (EDD) (assessed ex vivo by wire myography) and aortic stiffness (assessed by elastic modulus) with no change in OZR subject to UCMS. However, both LZR and OZR UCMS tPVAT impaired EDD compared to respective controls. LZR and OZR subject to UCMS had higher oxidative stress production, diminished adiponectin and impaired aortic nitric oxide levels. Divergently, UCMS induced greater inflammatory cytokine production in LZR UCMS tPVAT, but not in OZR UCMS tPVAT. AET prevented the tPVAT impairment of aortic relaxation with UCMS in LZR and OZR. Additionally, AET reduced aortic stiffness in both LZR and OZR. These beneficial effects on tPVAT regulation of the aorta are likely due to AET preservation of adiponectin, reduced oxidative stress and inflammation, and enhanced nitric oxide. UCMS impaired tPVAT-regulated aortic function in LZR, and augmented MetS-induced EDD in OZR. Conversely, AET in combination with UCMS largely preserved aortic function and the tPVAT environment, in both groups.
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Affiliation(s)
- Evan R DeVallance
- Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, WV, USA
| | - Kayla W Branyan
- Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, WV, USA
| | - I Mark Olfert
- Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, WV, USA
| | - Emidio E Pistilli
- Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, WV, USA
| | - Randall W Bryner
- Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, WV, USA
| | - Eric E Kelley
- Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, WV, USA
| | - Jefferson C Frisbee
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Paul D Chantler
- Department of Exercise Physiology, West Virginia University School of Medicine, Morgantown, WV, USA.,Department of Neuroscience, West Virginia University School of Medicine, Morgantown, WV, USA
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Mima A. Sodium-Glucose Cotransporter 2 Inhibitors in Patients with Non-Diabetic Chronic Kidney Disease. Adv Ther 2021; 38:2201-2212. [PMID: 33860925 DOI: 10.1007/s12325-021-01735-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 03/27/2021] [Indexed: 01/08/2023]
Abstract
BACKGROUND Sodium-glucose cotransporter 2 (SGLT2) inhibitors can reduce cardiovascular morbidity and mortality in patients with type 2 diabetes. Furthermore, recent clinical studies have revealed that SGLT2 inhibitors decrease the risk of renal function impairment in patients with type 2 diabetes. However, the effects of SGLT2 inhibitors on non-diabetic chronic kidney disease (CKD) remains unclear. Regarding long-term clinical outcomes, the Dapagliflozin and Prevention of Adverse Outcomes in Heart Failure (DAPA-HF) trial explicitly showed improvements in cardiovascular outcomes in patients presenting with heart failure, even in the absence of diabetes. The reduction in heart failure in patients without diabetes was confirmed following empagliflozin administration in the EMPagliflozin outcomE tRial in patients with chrOnic heart failure with Reduced ejection fraction (EMPEROR-Reduced) trial. A recent systematic review and meta-analysis of DAPA-HF and EMPEROR-Reduced showed improvements in the composite renal endpoint regardless of the presence of diabetes or baseline estimated glomerular filtration rate. The Dapagliflozin and Prevention of Adverse outcomes in Chronic Kidney Disease (DAPA-CKD) trial evaluated patients with CKD with or without type 2 diabetes, irrespective of whether SGLT2 inhibitor dapagliflozin was added for renin-angiotensin system blockade as background renoprotective therapy. In this trial, dapagliflozin reduced the hazard ratio for a composite renal and cardiovascular death endpoint in patients with CKD attributed to various causes, with or without type 2 diabetes.
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Guyenet PG, Stornetta RL, Souza GMPR, Abbott SBG, Brooks VL. Neuronal Networks in Hypertension: Recent Advances. Hypertension 2020; 76:300-311. [PMID: 32594802 DOI: 10.1161/hypertensionaha.120.14521] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Neurogenic hypertension is associated with excessive sympathetic nerve activity to the kidneys and portions of the cardiovascular system. Here we examine the brain regions that cause heightened sympathetic nerve activity in animal models of neurogenic hypertension, and we discuss the triggers responsible for the changes in neuronal activity within these regions. We highlight the limitations of the evidence and, whenever possible, we briefly address the pertinence of the findings to human hypertension. The arterial baroreflex reduces arterial blood pressure variability and contributes to the arterial blood pressure set point. This set point can also be elevated by a newly described cerebral blood flow-dependent and astrocyte-mediated sympathetic reflex. Both reflexes converge on the presympathetic neurons of the rostral medulla oblongata, and both are plausible causes of neurogenic hypertension. Sensory afferent dysfunction (reduced baroreceptor activity, increased renal, or carotid body afferent) contributes to many forms of neurogenic hypertension. Neurogenic hypertension can also result from activation of brain nuclei or sensory afferents by excess circulating hormones (leptin, insulin, Ang II [angiotensin II]) or sodium. Leptin raises blood vessel sympathetic nerve activity by activating the carotid bodies and subsets of arcuate neurons. Ang II works in the lamina terminalis and probably throughout the brain stem and hypothalamus. Sodium is sensed primarily in the lamina terminalis. Regardless of its cause, the excess sympathetic nerve activity is mediated to some extent by activation of presympathetic neurons located in the rostral ventrolateral medulla or the paraventricular nucleus of the hypothalamus. Increased activity of the orexinergic neurons also contributes to hypertension in selected models.
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Affiliation(s)
- Patrice G Guyenet
- From the Department of Pharmacology, University of Virginia, Charlottesville (P.G.G., R.L.S., G.M.P.R.S., S.B.G.A.)
| | - Ruth L Stornetta
- From the Department of Pharmacology, University of Virginia, Charlottesville (P.G.G., R.L.S., G.M.P.R.S., S.B.G.A.)
| | - George M P R Souza
- From the Department of Pharmacology, University of Virginia, Charlottesville (P.G.G., R.L.S., G.M.P.R.S., S.B.G.A.)
| | - Stephen B G Abbott
- From the Department of Pharmacology, University of Virginia, Charlottesville (P.G.G., R.L.S., G.M.P.R.S., S.B.G.A.)
| | - Virginia L Brooks
- Department of Chemical Physiology and Biochemistry, Oregon Health & Sciences University, Portland (V.L.B.)
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Pruett WA, Clemmer JS, Hester RL. Physiological Modeling and Simulation-Validation, Credibility, and Application. Annu Rev Biomed Eng 2020; 22:185-206. [PMID: 32501771 DOI: 10.1146/annurev-bioeng-082219-051740] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this review, we discuss the science of model validation as it applies to physiological modeling. There is widespread disagreement and ambiguity about what constitutes model validity. In areas in which models affect real-world decision-making, including within the clinic, in regulatory science, or in the design and engineering of novel therapeutics, this question is of critical importance. Without an answer, it impairs the usefulness of models and casts a shadow over model credibility in all domains. To address this question, we examine the use of nonmathematical models in physiological research, in medical practice, and in engineering to see how models in other domains are used and accepted. We reflect on historic physiological models and how they have been presented to the scientific community. Finally, we look at various validation frameworks that have been proposed as potential solutions during the past decade.
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Affiliation(s)
- W Andrew Pruett
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA; , ,
| | - John S Clemmer
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA; , ,
| | - Robert L Hester
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA; , , .,John D. Bower School of Population Health, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA
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Lopes NR, Milanez MIO, Martins BS, Veiga AC, Ferreira GR, Gomes GN, Girardi AC, Carvalho PM, Nogueira FN, Campos RR, Bergamaschi CT, Nishi EE. Afferent innervation of the ischemic kidney contributes to renal dysfunction in renovascular hypertensive rats. Pflugers Arch 2020; 472:325-334. [PMID: 31925527 DOI: 10.1007/s00424-019-02346-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 11/27/2019] [Accepted: 12/30/2019] [Indexed: 12/21/2022]
Abstract
The ablation of renal nerves, by destroying both the sympathetic and afferent fibers, has been shown to be effective in lowering blood pressure in resistant hypertensive patients. However, experimental studies have reported that the removal of sympathetic fibers may lead to side effects, such as the impairment of compensatory cardiorenal responses during a hemodynamic challenge. In the present study, we evaluated the effects of the selective removal of renal afferent fibers on arterial hypertension, renal sympathetic nerve activity, and renal changes in a model of renovascular hypertension. After 4 weeks of clipping the left renal artery, afferent renal denervation (ARD) was performed by exposing the left renal nerve to a 33 mM capsaicin solution for 15 min. After 2 weeks of ARD, we found reduced MAP (~ 18%) and sympathoexcitation to both the ischemic and contralateral kidneys in the hypertensive group. Moreover, a reduction in reactive oxygen species was observed in the ischemic (76%) and contralateral (27%) kidneys in the 2K1C group. In addition, ARD normalized renal function markers and proteinuria and podocin in the contralateral kidney. Taken altogether, we show that the selective removal of afferent fibers is an effective method to reduce MAP and improve renal changes without compromising the function of renal sympathetic fibers in the 2K1C model. Renal afferent nerves may be a new target in neurogenic hypertension and renal dysfunction.
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Affiliation(s)
- Nathalia R Lopes
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil
| | - Maycon I O Milanez
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil
| | - Beatriz S Martins
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil
| | - Amanda C Veiga
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil
| | - Giovanna R Ferreira
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil
| | - Guiomar N Gomes
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil
| | - Adriana C Girardi
- Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Polliane M Carvalho
- Department of Biomaterials and Oral Biology, Dentistry Faculty, Universidade de São Paulo, São Paulo, Brazil
| | - Fernando N Nogueira
- Department of Biomaterials and Oral Biology, Dentistry Faculty, Universidade de São Paulo, São Paulo, Brazil
| | - Ruy R Campos
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil
| | - Cássia T Bergamaschi
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil
| | - Erika E Nishi
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, Brazil.
- Cardiovascular and Respiratory Physiology Division, Department of Physiology, Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), Rua Botucatu, 862, São Paulo, SP, 04023-060, Brazil.
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Zhou JJ, Ma HJ, Shao J, Wei Y, Zhang X, Zhang Y, Li DP. Downregulation of Orexin Receptor in Hypothalamic Paraventricular Nucleus Decreases Blood Pressure in Obese Zucker Rats. J Am Heart Assoc 2019; 8:e011434. [PMID: 31213116 PMCID: PMC6662376 DOI: 10.1161/jaha.118.011434] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Background Orexin and its receptors are critical regulating sympathetic vasomotor tone under physiological and pathophysiological conditions. Orexin receptor 1 (OXR1) is upregulated in the paraventricular nucleus (PVN) in the hypothalamus and contributes to increased sympathetic outflow in obese Zucker rats (OZRs). We hypothesized that silencing OXR1 expression in the PVN decreases heightened blood pressure and elevated sympathetic outflow in OZRs. Methods and Results An adeno‐associated virus (AAV) vector containing a short hairpin RNA (shRNA) targeting rat OXR1 was designed to silence OXR1 expression in the PVN. The AAV‐OXR1‐shRNA or scrambled shRNA was injected into the PVN in OZRs. The arterial blood pressure in free‐moving OZRs was continuously monitored by using a telemetry approach. The firing activity of spinally projecting PVN neurons in rat brain slices was recorded 3 to 4 weeks after injection of viral vectors. The free‐moving OZRs treated with AAV‐OXR1‐shRNA had markedly lower OXR1 expression and lower mean arterial blood pressure, heart rate, and ratio of low‐ to high‐frequency components of heart rate variability compared with OZRs treated with scrambled shRNA. Furthermore, AAV‐OXR1‐shRNA treatment markedly reduced renal sympathetic nerve activity and attenuated sympathoexcitatory response induced by microinjection of orexin A into the PVN. In addition, treatment with AAV‐OXR1‐shRNA substantially decreased the basal firing activity of spinally projecting PVN neurons in OZRs and attenuated the excitatory effect of orexin A on the firing activity of these neurons. Conclusions These data suggest that chronic downregulation of OXR1 expression in the PVN reduces sympathetic vasomotor tone in obesity‐related hypertension.
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Affiliation(s)
- Jing-Jing Zhou
- 1 Division of Anesthesiology & Critical Care The University of Texas MD Anderson Cancer Center Houston TX
| | - Hui-Jie Ma
- 1 Division of Anesthesiology & Critical Care The University of Texas MD Anderson Cancer Center Houston TX.,2 Department of Physiology Hebei Medical University Shijiazhuang China
| | - Jianying Shao
- 1 Division of Anesthesiology & Critical Care The University of Texas MD Anderson Cancer Center Houston TX
| | - Yan Wei
- 3 Key Laboratory of Medical Electrophysiology Ministry of Education Institute of Cardiovascular Research Southwest Medical University Luzhou China
| | - Xiangjian Zhang
- 4 Hebei Collaborative Innovation Center for Cardiocerebrovascular Disease 2nd Hospital of Hebei Medical University Shijiazhuang China.,5 Department of Neurology 2nd Hospital of Hebei Medical University Shijiazhuang China
| | - Yi Zhang
- 2 Department of Physiology Hebei Medical University Shijiazhuang China.,4 Hebei Collaborative Innovation Center for Cardiocerebrovascular Disease 2nd Hospital of Hebei Medical University Shijiazhuang China
| | - De-Pei Li
- 1 Division of Anesthesiology & Critical Care The University of Texas MD Anderson Cancer Center Houston TX.,6 Department of Medicine Center for Precision Medicine University of Missouri Columbia MO
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11
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Nishi EE, Lopes NR, Gomes GN, Perry JC, Sato AYS, Naffah-Mazzacoratti MG, Bergamaschi CT, Campos RR. Renal denervation reduces sympathetic overactivation, brain oxidative stress, and renal injury in rats with renovascular hypertension independent of its effects on reducing blood pressure. Hypertens Res 2018; 42:628-640. [PMID: 30573809 DOI: 10.1038/s41440-018-0171-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 10/19/2018] [Accepted: 10/31/2018] [Indexed: 12/27/2022]
Abstract
The underlying mechanisms by which renal denervation (RD) decreases blood pressure (BP) remain incompletely understood. In this study, we investigated the effects of ischemic kidney denervation on different sympathetic outflows, brain and renal expression of angiotensin-II receptors, oxidative stress and renal function markers in the 2-kidney, 1-clip (2K-1C) rat model. Surgical RD was performed in Wistar male rats 4-5 weeks after clip implantation. After 10 days of RD, BP, and the activity of sympathetic nerves projecting to the contralateral kidney (rSNA) and splanchnic region were partially reduced in 2K-1C rats, with no change in systemic renin-angiotensin system (RAS). To distinguish the effects of RD from the reduction in BP, 2K-1C rats were treated with hydralazine by oral gavage (25 mg/kg/day for 1 week). RD, but not hydralazine, normalized oxidative stress in the sympathetic premotor brain regions and improved intrarenal RAS, renal injury, and proteinuria. Furthermore, different mechanisms led to renal injury and oxidative stress in the ischemic and contralateral kidneys of 2K-1C rats. Injury and oxidative stress in the ischemic kidney were driven by the renal nerves. Although RD attenuated rSNA, injury and oxidative stress persisted in the contralateral kidney, probably due to increased BP. Therefore, nerves from the ischemic kidney at least partially contribute to the increase in BP, sympathetic outflows, brain oxidative stress, and renal alterations in rats with renovascular hypertension. Based on these findings, the reduction in oxidative stress in the brain is a central mechanism that contributes to the effects of RD on Goldblatt hypertension.
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Affiliation(s)
- Erika E Nishi
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil.
| | - Nathalia R Lopes
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Guiomar N Gomes
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Juliana C Perry
- Department of Psychobiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Alex Y S Sato
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Maria G Naffah-Mazzacoratti
- Department of Neurology and Neurosurgery, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Cássia T Bergamaschi
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Ruy R Campos
- Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
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Mima A. Renal protection by sodium-glucose cotransporter 2 inhibitors and its underlying mechanisms in diabetic kidney disease. J Diabetes Complications 2018; 32:720-725. [PMID: 29880432 DOI: 10.1016/j.jdiacomp.2018.04.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 04/23/2018] [Accepted: 04/24/2018] [Indexed: 12/12/2022]
Abstract
AIM Diabetic kidney disease (DKD) is the most frequent cause of mortality and morbidity, leading a global health burden. This review will focus on the potential therapeutic interventions using Sodium-glucose cotransporter-2 (SGLT2) inhibitors that could prevent the development and progression of DKD. RESULTS SGLT2 inhibitors have been widely used as anti-diabetic drugs. Recent clinical studies have demonstrated that these drugs, which improve glycemic control and hypertension and decrease body weight, decrease the risk of renal function impairment and heart failure in patients with type 2 diabetes. With regard to long-term clinical outcomes, the Empagliflozin, Cardiovascular Outcomes, and Mortality in Type 2 Diabetes (EMPA-REG OUTCOME), the EMPA-REG Renal OUTCOME, and the CANagliflozin cardioVascular Assessment Study (CANVAS) program which have been integrated from CANVAS and CANVAS-Renal (CANVAS-R) trials reported significant risk reductions in primary combined major adverse cardiovascular events. Furthermore, regarding renal outcomes, the EMPA-REG Renal OUTCOME and CANVAS program clearly showed improvements in renal outcomes, including decreases in albuminuria and progression of nephropathy, doubling of serum creatinine levels, and initiation of renal replacement therapy. CONCLUSIONS Potential mechanisms of SGLT2 inhibitors related to renoprotection can be divided into two categories: hemodynamic actions and metabolic actions.
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Affiliation(s)
- Akira Mima
- Department of Nephrology, Kindai University Faculty of Medicine, Kindai University Nara Hospital, Nara, Japan.
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13
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Miller GD. Appetite Regulation: Hormones, Peptides, and Neurotransmitters and Their Role in Obesity. Am J Lifestyle Med 2017; 13:586-601. [PMID: 31662725 DOI: 10.1177/1559827617716376] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 05/18/2017] [Accepted: 05/31/2017] [Indexed: 12/29/2022] Open
Abstract
Understanding body weight regulation will aid in the development of new strategies to combat obesity. This review examines energy homeostasis and food intake behaviors, specifically with regards to hormones, peptides, and neurotransmitters in the periphery and central nervous system, and their potential role in obesity. Dysfunction in feeding signals by the brain is a factor in obesity. The hypothalamic (arcuate nucleus) and brainstem (nucleus tractus solitaris) areas integrate behavioral, endocrine, and autonomic responses via afferent and efferent pathways from and to the brainstem and peripheral organs. Neurons present in the arcuate nucleus express pro-opiomelanocortin, Neuropeptide Y, and Agouti Related Peptide, with the former involved in lowering food intake, and the latter two acutely increasing feeding behaviors. Action of peripheral hormones from the gut, pancreas, adipose, and liver are also involved in energy homeostasis. Vagal afferent neurons are also important in regulating energy homeostasis. Peripheral signals respond to the level of stored and currently available fuel. By studying their actions, new agents maybe developed that disable orexigenic responses and enhance anorexigenic signals. Although there are relatively few medications currently available for obesity treatment, a number of agents are in development that work through these pathways.
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Affiliation(s)
- Gary D Miller
- Department of Health and Exercise Science, Wake Forest University, Winston-Salem, North Carolina
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14
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Lincevicius GS, Shimoura CG, Nishi EE, Oliveira T, Cespedes JG, Bergamaschi CT, Campos RR. Differential effects of renal denervation on arterial baroreceptor function in Goldblatt hypertension model. Auton Neurosci 2017; 208:43-50. [PMID: 28688830 DOI: 10.1016/j.autneu.2017.06.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 06/09/2017] [Accepted: 06/19/2017] [Indexed: 01/19/2023]
Abstract
Sympathetic vasomotor activity is significantly increased in renovascular hypertension. Renal denervation (DnX) has emerged as a novel therapy for resistant hypertension to drug therapy. However, the underlying mechanisms regarding the reduction in blood pressure (BP) after DnX remain unclear. Thus, the aim of this study was to evaluate the effects of DnX of a clipped kidney on the baseline and baroreceptor reflex control of post-ganglionic sympathetic activity to the contralateral kidney (rSNA) and lumbar (lSNA) nerves in Goldblatt hypertensive rats (2K1C). Renal denervation of an ischaemic kidney (DxX - all visible bundles of nerves were dissected - 10% phenol) was performed 5weeks after clipping (gap width: 0.2mm). Ten days after DnX, BP was significantly reduced (16%) in the 2K1C compared with the undenervated 2K1C (p<0.05). DnX significantly reduced basal rSNA (control group (CT): 110±8, n=14; 2K1C: 150±8, n=12; 2K1C DnX: 89±7, spikes per second (spikes/s); p<0.05, n=8) and lSNA (CT: 137±8, n=8; 2K1C: 202±7, n=11; 2K1C DnX: 131±7, spikes/s; p<0.05, n=8) only in 2K1C rats. DnX significantly improved the arterial baroreceptor sensitivity of rSNA (CT: -2.3±0.2, n=11; 2K1C: -0.7±0.1, n=8; 2K1C DnX: -1.5±0.2, spikes/s/mmHg; p<0.05, n=5) and heart rate for tachycardic response (CT: -3.9±0.5, n=7; 2K1C: -1.9±0.1, n=8; 2K1C DnX: -3.3±0.4, bpm/mmHg; p<0.05, n=8), but not for lSNA in 2K1C rats. The results show that DnX normalized baseline sympathetic vasomotor activity to the lumbar and renal nerves, followed by a differential improvement in the arterial baroreceptor sensitivity. Whether the baroreceptor function sensitivity improvement induced by DnX is a cause or a consequence of BP reduction remains to be determined.
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Affiliation(s)
- Gisele S Lincevicius
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Caroline G Shimoura
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Erika E Nishi
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Tales Oliveira
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Juliana G Cespedes
- Instituto de Ciência e Tecnologia, Universidade Federal de São Paulo, Campus São José dos Campos, Brazil
| | - Cássia T Bergamaschi
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil
| | - Ruy R Campos
- Cardiovascular Division, Department of Physiology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil.
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Rani M, Kumar R, Krishan P. Implicating the potential role of orexin in hypertension. Naunyn Schmiedebergs Arch Pharmacol 2017; 390:667-676. [DOI: 10.1007/s00210-017-1378-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 04/19/2017] [Indexed: 12/12/2022]
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16
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17
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Asirvatham-Jeyaraj N, Fiege JK, Han R, Foss J, Banek CT, Burbach BJ, Razzoli M, Bartolomucci A, Shimizu Y, Panoskaltsis-Mortari A, Osborn JW. Renal Denervation Normalizes Arterial Pressure With No Effect on Glucose Metabolism or Renal Inflammation in Obese Hypertensive Mice. Hypertension 2016; 68:929-36. [PMID: 27550916 PMCID: PMC5016252 DOI: 10.1161/hypertensionaha.116.07993] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Accepted: 07/31/2016] [Indexed: 12/18/2022]
Abstract
Hypertension often occurs in concurrence with obesity and diabetes mellitus, commonly referred to as metabolic syndrome. Renal denervation (RDNx) lowers arterial pressure (AP) and improves glucose metabolism in drug-resistant hypertensive patients with high body mass index. In addition, RDNx has been shown to reduce renal inflammation in the mouse model of angiotensin II hypertension. The present study tested the hypothesis that RDNx reduces AP and renal inflammation and improves glucose metabolism in obesity-induced hypertension. Eight-week-old C57BL/6J mice were fed either a low-fat diet (10 kcal%) or a high-fat diet (45 kcal%) for 10 weeks. Body weight, food intake, fasting blood glucose, and glucose metabolism (glucose tolerance test) were measured. In a parallel study, radiotelemeters were implanted in mice for AP measurement. High fat-fed C57BL/6J mice exhibited an inflammatory and metabolic syndrome phenotype, including increased fat mass, increased AP, and hyperglycemia compared with low-fat diet mice. RDNx, but not Sham surgery, normalized AP in high-fat diet mice (115.8±1.5 mm Hg in sham versus 96.6±6.7 mm Hg in RDNx). RDNx had no significant effect on AP in low-fat diet mice. Also, RDNx had no significant effect on glucose metabolism or renal inflammation as measured by the number of CD8, CD4, and T helper cells or levels of inflammatory cytokines in the kidneys. These results indicate that although renal nerves play a role in obesity-induced hypertension, they do not contribute to impaired glucose metabolism or renal inflammation in this model.
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Affiliation(s)
- Ninitha Asirvatham-Jeyaraj
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - Jessica K Fiege
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - Ruijun Han
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - Jason Foss
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - Christopher T Banek
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - Brandon J Burbach
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - Maria Razzoli
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - Alessandro Bartolomucci
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - Yoji Shimizu
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - Angela Panoskaltsis-Mortari
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis
| | - John W Osborn
- From the Department of Integrative Biology and Physiology (N.A.-J., R.H., J.F., C.T.B., M.R., A.B., J.W.O.), Laboratory Medicine and Pathology (J.K.F., B.J.B., Y.S.), and Pediatrics (A.P.-M.), University of Minnesota, Minneapolis.
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Schindler C. Review: The metabolic syndrome as an endocrine disease: is there an effective pharmacotherapeutic strategy optimally targeting the pathogenesis? Ther Adv Cardiovasc Dis 2016; 1:7-26. [DOI: 10.1177/1753944707082662] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The metabolic syndrome (MetS) represents a combination of cardiovascular risk determinants such as obesity, insulin resistance and lipid abnormalities such as hypertriglyceridemia, increased free fatty acids, low high-density-cholesterol and hypertension. As a multiple component condition it imparts a doubling of relative risk for atherosclerotic cardiovascular disease (ASCVD). It is currently controversial which component of the syndrome carries what weight. There is even a considerable debate whether the risk for ASCVD is greater in patients diagnosed with MetS than that by the individual risk factors. At present, no unifying pathogenetic mechanism can explain the metabolic syndrome and there is no unique treatment for it. This review summarizes and critically reviews the currently available clinical and scientific evidence for the concept that the MetS is causally an endocrine disease and discusses pharmacotherapeutic strategies targeting the pathogenesis rather than single symptoms of the cluster.
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Affiliation(s)
- Christoph Schindler
- Institute of Clinical Pharmacology, Medical Faculty, Technical University of Dresden, Fiedlerstrasse 27, 01307 Dresden, Germany christoph.schindler@ tu-dresden.de
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19
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Zhou JJ, Yuan F, Zhang Y, Li DP. Upregulation of orexin receptor in paraventricular nucleus promotes sympathetic outflow in obese Zucker rats. Neuropharmacology 2015; 99:481-90. [PMID: 26277341 PMCID: PMC4841448 DOI: 10.1016/j.neuropharm.2015.08.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 07/26/2015] [Accepted: 08/06/2015] [Indexed: 11/21/2022]
Abstract
Sympathetic vasomotor tone is elevated in obesity-related hypertension. Orexin importantly regulates energy metabolism and autonomic function. We hypothesized that alteration of orexin receptor in the paraventricular nucleus (PVN) of the hypothalamus leads to elevated sympathetic vasomotor tone in obesity. We used in vivo measurement of sympathetic vasomotor tone and microinjection into brain nucleus, whole-cell patch clamp recording in brain slices, and immunocytochemical staining in obese Zucker rats (OZRs) and lean Zucker rats (LZRs). Microinjection of orexin 1 receptor (OX1R) antagonist SB334867 into the PVN reduced basal arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA) in anesthetized OZRs but not in LZRs. Microinjection of orexin A into the PVN produced greater increases in ABP and RSNA in OZRs than in LZRs. Western blot analysis revealed that OX1R expression levels in the PVN were significantly increased in OZRs compared with LZRs. OX1R immunoreactivity was positive in retrogradely labeled PVN-spinal neurons. The basal firing rate of labeled PVN-spinal neurons was higher in OZRs than in LZRs. SB334867 decreased the basal firing activity of PVN-spinal neurons in OZRs but had no effect in LZRs. Orexin A induced a greater increase in the firing rate of PVN-spinal neurons in OZRs than in LZRs. In addition, orexin A induced larger currents in PVN-spinal neurons in OZRs than in LZRs. These data suggest that upregulation of OX1R in the PVN promotes hyperactivity of PVN presympathetic neurons and elevated sympathetic outflow in obesity.
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Affiliation(s)
- Jing-Jing Zhou
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei 050017, China; Department of Critical Care, The University of Texas, M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Fang Yuan
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei 050017, China
| | - Yi Zhang
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei 050017, China; Hebei Collaborative Innovation Center for Cardio-cerebrovascular Disease, Shijiazhuang, Hebei 050000, China.
| | - De-Pei Li
- Department of Critical Care, The University of Texas, M.D. Anderson Cancer Center, Houston, TX 77030, USA.
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20
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Hepatic denervation and dyslipidemia in obese Zucker (fa/fa) rats. Int J Obes (Lond) 2015; 39:1655-8. [PMID: 26134416 DOI: 10.1038/ijo.2015.122] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 06/01/2015] [Accepted: 06/12/2015] [Indexed: 11/09/2022]
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Vaněčková I, Maletínská L, Behuliak M, Nagelová V, Zicha J, Kuneš J. Obesity-related hypertension: possible pathophysiological mechanisms. J Endocrinol 2014; 223:R63-78. [PMID: 25385879 DOI: 10.1530/joe-14-0368] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Hypertension is one of the major risk factors of cardiovascular diseases, but despite a century of clinical and basic research, the discrete etiology of this disease is still not fully understood. The same is true for obesity, which is recognized as a major global epidemic health problem nowadays. Obesity is associated with an increasing prevalence of the metabolic syndrome, a cluster of risk factors including hypertension, abdominal obesity, dyslipidemia, and hyperglycemia. Epidemiological studies have shown that excess weight gain predicts future development of hypertension, and the relationship between BMI and blood pressure (BP) appears to be almost linear in different populations. There is no doubt that obesity-related hypertension is a multifactorial and polygenic trait, and multiple potential pathogenetic mechanisms probably contribute to the development of higher BP in obese humans. These include hyperinsulinemia, activation of the renin-angiotensin-aldosterone system, sympathetic nervous system stimulation, abnormal levels of certain adipokines such as leptin, or cytokines acting at the vascular endothelial level. Moreover, some genetic and epigenetic mechanisms are also in play. Although the full manifestation of both hypertension and obesity occurs predominantly in adulthood, their roots can be traced back to early ontogeny. The detailed knowledge of alterations occurring in the organism of experimental animals during particular critical periods (developmental windows) could help to solve this phenomenon in humans and might facilitate the age-specific prevention of human obesity-related hypertension. In addition, better understanding of particular pathophysiological mechanisms might be useful in so-called personalized medicine.
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Affiliation(s)
- Ivana Vaněčková
- Institute of PhysiologyAcademy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech RepublicInstitute of Organic Chemistry and BiochemistryAcademy of Sciences of the Czech Republic v.v.i., Prague, Czech Republic
| | - Lenka Maletínská
- Institute of PhysiologyAcademy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech RepublicInstitute of Organic Chemistry and BiochemistryAcademy of Sciences of the Czech Republic v.v.i., Prague, Czech Republic
| | - Michal Behuliak
- Institute of PhysiologyAcademy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech RepublicInstitute of Organic Chemistry and BiochemistryAcademy of Sciences of the Czech Republic v.v.i., Prague, Czech Republic
| | - Veronika Nagelová
- Institute of PhysiologyAcademy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech RepublicInstitute of Organic Chemistry and BiochemistryAcademy of Sciences of the Czech Republic v.v.i., Prague, Czech Republic
| | - Josef Zicha
- Institute of PhysiologyAcademy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech RepublicInstitute of Organic Chemistry and BiochemistryAcademy of Sciences of the Czech Republic v.v.i., Prague, Czech Republic
| | - Jaroslav Kuneš
- Institute of PhysiologyAcademy of Sciences of the Czech Republic v.v.i., Videnska 1083, 14220 Prague 4, Czech RepublicInstitute of Organic Chemistry and BiochemistryAcademy of Sciences of the Czech Republic v.v.i., Prague, Czech Republic
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Dunn TN, Adams SH. Relations between metabolic homeostasis, diet, and peripheral afferent neuron biology. Adv Nutr 2014; 5:386-93. [PMID: 25022988 PMCID: PMC4085187 DOI: 10.3945/an.113.005439] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
It is well established that food intake behavior and energy balance are regulated by crosstalk between peripheral organ systems and the central nervous system (CNS), for instance, through the actions of peripherally derived leptin on hindbrain and hypothalamic loci. Diet- or obesity-associated disturbances in metabolic and hormonal signals to the CNS can perturb metabolic homeostasis bodywide. Although interrelations between metabolic status and diet with CNS biology are well characterized, afferent networks (those sending information to the CNS from the periphery) have received far less attention. It is increasingly appreciated that afferent neurons in adipose tissue, the intestines, liver, and other tissues are important controllers of energy balance and feeding behavior. Disruption in their signaling may have consequences for cardiovascular, pancreatic, adipose, and immune function. This review discusses the diverse ways that afferent neurons participate in metabolic homeostasis and highlights how changes in their function associate with dysmetabolic states, such as obesity and insulin resistance.
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Affiliation(s)
- Tamara N. Dunn
- Graduate Group in Nutritional Biology and Department of Nutrition, University of California, Davis, CA; and
| | - Sean H. Adams
- Graduate Group in Nutritional Biology and Department of Nutrition, University of California, Davis, CA; and,Obesity and Metabolism Research Unit, USDA–Agricultural Research Service Western Human Nutrition Research Center, Davis, CA,To whom correspondence should be addressed. E-mail:
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Guimaraes PS, Oliveira MF, Braga JF, Nadu AP, Schreihofer A, Santos RA, Campagnole-Santos MJ. Increasing Angiotensin-(1–7) Levels in the Brain Attenuates Metabolic Syndrome–Related Risks in Fructose-Fed Rats. Hypertension 2014; 63:1078-85. [DOI: 10.1161/hypertensionaha.113.01847] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We evaluated effects of chronic intracerebroventricular infusion of angiotensin (Ang)-(1–7) on cardiovascular and metabolic parameters in fructose-fed (FF) rats. After 6 weeks of fructose intake (10% in drinking water), Sprague-Dawley rats were subjected to intracerebroventricular infusion of Ang-(1–7) (200 ng/h; FF+A7 group) or 0.9% sterile saline (FF group) for 4 weeks with continued access to fructose. Compared with control rats, FF rats had increased mean arterial pressure and cardiac sympathetic tone with impaired baroreflex sensitivity. FF rats also presented increased circulating triglycerides, leptin, insulin, and glucose with impaired glucose tolerance. Furthermore, relative weights of liver and retroperitoneal adipose tissue were increased in FF rats. Glycogen content was reduced in liver, but increased in muscle. In contrast, fructose-fed rats subjected to chronic intracerebroventricular infusion of Ang-(1–7) presented reduced cardiac sympathetic tone with normalized mean arterial pressure, baroreflex sensitivity, glucose and insulin levels, and improved glucose tolerance. Relative weight of liver, and hepatic and muscle glycogen contents were also normalized in FF+A7 rats. In addition, FF+A7 rats had reduced mRNA expression for neuronal nitric oxide synthase and NR1 subunit of
N
-methyl-
d
-aspartate receptor in hypothalamus and dorsomedial medulla. Ang-(1–7) infusion did not alter fructose-induced hyperleptinemia and increased relative weight of retroperitoneal adipose tissue. There were no differences in body weights, neither in liver mRNA expression of phosphoenolpyruvate carboxykinase or glucose-6-phosphatase among the groups. These data indicate that chronic increase in Ang-(1–7) levels in the brain may have a beneficial role in fructose-fed rats by ameliorating cardiovascular and metabolic disorders.
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Affiliation(s)
- Priscila S. Guimaraes
- From the Department of Physiology and Biophysics, Biological Science Institute, National Institute of Science and Technology-Nanobiofar, Federal University of Minas Gerais, Belo Horizonte, Brazil (P.S.G., M.F.O., J.F.B., A.P.N., R.A.S.S., M.J.C.-S.); and Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX (A.S.)
| | - Mariana F. Oliveira
- From the Department of Physiology and Biophysics, Biological Science Institute, National Institute of Science and Technology-Nanobiofar, Federal University of Minas Gerais, Belo Horizonte, Brazil (P.S.G., M.F.O., J.F.B., A.P.N., R.A.S.S., M.J.C.-S.); and Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX (A.S.)
| | - Janaína F. Braga
- From the Department of Physiology and Biophysics, Biological Science Institute, National Institute of Science and Technology-Nanobiofar, Federal University of Minas Gerais, Belo Horizonte, Brazil (P.S.G., M.F.O., J.F.B., A.P.N., R.A.S.S., M.J.C.-S.); and Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX (A.S.)
| | - Ana Paula Nadu
- From the Department of Physiology and Biophysics, Biological Science Institute, National Institute of Science and Technology-Nanobiofar, Federal University of Minas Gerais, Belo Horizonte, Brazil (P.S.G., M.F.O., J.F.B., A.P.N., R.A.S.S., M.J.C.-S.); and Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX (A.S.)
| | - Ann Schreihofer
- From the Department of Physiology and Biophysics, Biological Science Institute, National Institute of Science and Technology-Nanobiofar, Federal University of Minas Gerais, Belo Horizonte, Brazil (P.S.G., M.F.O., J.F.B., A.P.N., R.A.S.S., M.J.C.-S.); and Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX (A.S.)
| | - Robson A.S. Santos
- From the Department of Physiology and Biophysics, Biological Science Institute, National Institute of Science and Technology-Nanobiofar, Federal University of Minas Gerais, Belo Horizonte, Brazil (P.S.G., M.F.O., J.F.B., A.P.N., R.A.S.S., M.J.C.-S.); and Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX (A.S.)
| | - Maria Jose Campagnole-Santos
- From the Department of Physiology and Biophysics, Biological Science Institute, National Institute of Science and Technology-Nanobiofar, Federal University of Minas Gerais, Belo Horizonte, Brazil (P.S.G., M.F.O., J.F.B., A.P.N., R.A.S.S., M.J.C.-S.); and Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX (A.S.)
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Abstract
PURPOSE This review highlights the physiological mechanisms underlying the neural regulation of the kidney, normally to maintain cardiovascular homeostasis, and in pathophysiological states of hypertension and renal disease. It is relevant because of the demonstration that bilateral renal denervation in different hypertensive groups causes a sustained reduction in blood pressure. RECENT FINDINGS There are patients groups in whom their hypertension is resistant to antihypertensive drugs or with renal diseases in which they are contraindicated. Recently, medical devices have been developed to manipulate the sympathetic nervous system, for example, implantation of carotid sinus nerve stimulating electrodes and ablation of the renal innervation. These approaches have been relatively successful but there remains a lack of understanding of the neural mechanisms impinging on the kidney that regulate long-term control of blood pressure. SUMMARY The observation that bilateral renal nerve ablation can reduce blood pressure represents an important therapeutic milestone. Nonetheless, questions arise as to the underlying mechanisms, the long-term consequences, whether there may be re-innervation over a number of years, or whether some unknown consequence to the denervation may arise. This may point to the development of novel compounds targeted to the innervation of the kidney.
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Guimaraes PS, Huber DA, Campagnole-Santos MJ, Schreihofer AM. Development of attenuated baroreflexes in obese Zucker rats coincides with impaired activation of nucleus tractus solitarius. Am J Physiol Regul Integr Comp Physiol 2014; 306:R681-92. [PMID: 24573182 DOI: 10.1152/ajpregu.00537.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adult obese Zucker rats (OZR; >12 wk) develop elevated sympathetic nerve activity (SNA) and mean arterial pressure (MAP) with impaired baroreflexes compared with adult lean Zucker rats (LZR) and juvenile OZR (6-7 wk). In adult OZR, baroreceptor afferent nerves respond normally to changes in MAP, whereas electrical stimulation of baroreceptor afferent fibers produces smaller reductions in SNA and MAP compared with LZR. We hypothesized that impaired baroreflexes in OZR are linked to reduced activation of brain stem sites that mediate baroreflexes. In conscious adult rats, a hydralazine (HDZ)-induced reduction in MAP evoked tachycardia that was initially blunted in OZR, but equivalent to LZR within 5 min. In agreement, HDZ-induced expression of c-Fos in the rostral ventrolateral medulla (RVLM) was comparable between groups. In contrast, phenylephrine (PE)-induced rise in MAP evoked markedly attenuated bradycardia with dramatically reduced c-Fos expression in the nucleus tractus solitarius (NTS) of adult OZR compared with LZR. However, in juvenile rats, PE-induced hypertension evoked comparable bradycardia in OZR and LZR with similar or augmented c-Fos expression in NTS of the OZR. In urethane-anesthetized rats, microinjections of glutamate into NTS evoked equivalent decreases in SNA, heart rate (HR), and MAP in juvenile OZR and LZR, but attenuated decreases in SNA and MAP in adult OZR. In contrast, microinjections of glutamate into the caudal ventrolateral medulla, a target of barosensitive NTS neurons, evoked comparable decreases in SNA, HR, and MAP in adult OZR and LZR. These data suggest that OZR develop impaired glutamatergic activation of the NTS, which likely contributes to attenuated baroreflexes in adult OZR.
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Abreu AR, de Abreu AR, Santos LT, de Souza AA, da Silva LG, Chianca DA, de Menezes RC. Blunted GABA-mediated inhibition within the dorsomedial hypothalamus potentiates the cardiovascular response to emotional stress in rats fed a high-fat diet. Neuroscience 2014; 262:21-30. [PMID: 24397951 DOI: 10.1016/j.neuroscience.2013.12.053] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 12/23/2013] [Accepted: 12/24/2013] [Indexed: 11/25/2022]
Abstract
Rats fed a high-fat diet (HFD) present an exaggerated endocrine response to stress conditions, which, like obesity, show a high correlation with cardiovascular diseases. Meanwhile the GABAergic neurotransmission within the dorsomedial hypothalamus (DMH) is involved in the regulation of the physiological responses during emotional stress. Here we evaluated the influence of obesity, induced by a HFD, on the cardiovascular responses induced by air jet stress in rats, and the role of the GABAergic tonus within the DMH in these changes. Our results showed that consumption of a HFD (45% w/w fat) for 9 weeks induced obesity and increases in baseline mean arterial pressure (MAP) and heart rate (HR). Moreover, obesity potentiated stress responsiveness, evidenced by the greater changes in MAP and HR induced by stress in obese rats. The injection of muscimol into the DMH reduced the maximal increases in HR and MAP induced by stress in both groups; however, the reduction in the maximal increases in MAP in the HFD group was less pronounced. Moreover, the injection of muscimol into the DMH of obese rats was less effective in reducing the stress-induced tachycardia, since the HR attained the same levels at the end of the stress paradigm as after the vehicle injection. Injection of bicuculline into DMH induced increases in MAP and HR in both groups. Nevertheless, obesity shortened the tachycardic response to bicuculline injection. These data show that obesity potentiates the cardiovascular response to stress in rats due to an inefficient GABAA-mediated inhibition within the DMH.
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Affiliation(s)
- A R Abreu
- Department of Biological Sciences, Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil.
| | - A R de Abreu
- Department of Biological Sciences, Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil.
| | - L T Santos
- Department of Biological Sciences, Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil.
| | - A A de Souza
- Department of Biological Sciences, Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil.
| | - L G da Silva
- Department of Biological Sciences, Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil.
| | - D A Chianca
- Department of Biological Sciences, Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil.
| | - R C de Menezes
- Department of Biological Sciences, Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil.
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Fellmann L, Regnault V, Greney H, Gasparik V, Muscat A, Max JP, Gigou L, Oréa V, Chetrite G, Pizard A, Niederhoffer N, Julien C, Lacolley P, Fève B, Bousquet P. A New Pyrroline Compound Selective for I1-Imidazoline Receptors Improves Metabolic Syndrome in Rats. J Pharmacol Exp Ther 2013; 346:370-80. [DOI: 10.1124/jpet.113.205328] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Xiang L, Clemmer JS, Lu S, Mittwede PN. Impaired blood pressure compensation following hemorrhage in conscious obese Zucker rats. Life Sci 2013; 93:214-219. [PMID: 23782999 DOI: 10.1016/j.lfs.2013.06.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 06/03/2013] [Accepted: 06/06/2013] [Indexed: 11/16/2022]
Abstract
AIMS Hemorrhagic shock leads to a higher risk of mortality and morbidity in obese patients, however the mechanisms for these outcomes are unclear. We hypothesized that following severe hemorrhage, blood pressure control in conscious obese Zucker rats (OZ) is impaired. MAIN METHODS Experiments were performed in conscious lean Zucker rats (LZ) and OZ. Blood pressure, heart rate, cardiac output, total peripheral resistance (TPR), plasma renin activity (PRA), plasma antidiuretic hormone (ADH), and blood gasses were measured before and after severe hemorrhage (35% of the total blood volume). KEY FINDINGS Basal blood pressure, cardiac output, TPR, PRA, and ADH levels were not different between LZ and OZ. Compared to LZ, OZ exhibited impaired baroreflex control of heart rate and showed higher levels of vascular adrenergic tone. One hour after the hemorrhage, LZ and OZ exhibited similar decreases in cardiac output. However, blood pressure, heart rate, TPR, PRA, and ADH levels were lower in OZ than in LZ. SIGNIFICANCE These results indicate that conscious OZ has impaired blood pressure compensation after hemorrhage due to a blunted increase in TPR. This is due at least in part to an impaired regulation of vasoconstrictor hormones. To our knowledge, the current study is the first to demonstrate that hemodynamic responses and associated hormone secretion are impaired in a conscious obese model.
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Affiliation(s)
- Lusha Xiang
- Department of Physiology and Biophysics University of Mississippi Medical Center
| | - John S Clemmer
- Department of Physiology and Biophysics University of Mississippi Medical Center
| | - Silu Lu
- Department of Physiology and Biophysics University of Mississippi Medical Center
| | - Peter N Mittwede
- Department of Physiology and Biophysics University of Mississippi Medical Center
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Lehnen AM, Rodrigues B, Irigoyen MC, De Angelis K, Schaan BD. Cardiovascular changes in animal models of metabolic syndrome. J Diabetes Res 2013; 2013:761314. [PMID: 23691518 PMCID: PMC3647579 DOI: 10.1155/2013/761314] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 02/06/2013] [Accepted: 02/12/2013] [Indexed: 01/01/2023] Open
Abstract
Metabolic syndrome has been defined as a group of risk factors that directly contribute to the development of cardiovascular disease and/or type 2 diabetes. Insulin resistance seems to have a fundamental role in the genesis of this syndrome. Over the past years to the present day, basic and translational research has used small animal models to explore the pathophysiology of metabolic syndrome and to develop novel therapies that might slow the progression of this prevalent condition. In this paper we discuss the animal models used for the study of metabolic syndrome, with particular focus on cardiovascular changes, since they are the main cause of death associated with the condition in humans.
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Affiliation(s)
- Alexandre M. Lehnen
- Laboratório de Experimentação Animal e Laboratório de Cardiologia Celular e Molecular, Instituto de Cardiologia do Rio Grande do Sul/Fundação Universitária de Cardiologia do Rio Grande do Sul, Porto Alegre, Brazil
- Divisão de Endocrinologia, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Bruno Rodrigues
- Laboratório do Movimento Humano, Universidade São Judas Tadeu, São Paulo, Brazil
| | - Maria Cláudia Irigoyen
- Unidade de Hipertensão, Instituto do Coração (InCor), Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Kátia De Angelis
- Laboratório de Fisiologia Translacional, Universidade Nove de Julho, São Paulo, Brazil
| | - Beatriz D'Agord Schaan
- Divisão de Endocrinologia, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- *Beatriz D'Agord Schaan:
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Park J, Middlekauff HR, Campese VM. Abnormal sympathetic reactivity to the cold pressor test in overweight humans. Am J Hypertens 2012; 25:1236-41. [PMID: 22895452 DOI: 10.1038/ajh.2012.115] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Overweight individuals (body mass index (BMI) 25-29.9 kg/m²) are at higher risk for developing cardiovascular disease and hypertension when compared with lean individuals of normal weight (BMI 18.5-24.9 kg/m²). The purpose of this study was to test the hypothesis that exaggerated sympathetic nervous system responses to stressors may be one potential mechanism that predisposes overweight individuals to developing hypertension. METHODS We compared heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA) using microneurography, in normotensive overweight individuals compared with age-matched lean controls, at baseline and during two sympathoexcitatory maneuvers: cold pressor test (CPT), and static handgrip exercise (SHG 30%). RESULTS During CPT, MSNA increased in both groups, but the magnitude of MSNA response was significantly greater (P = 0.03) in overweight (+18.1 ± 2.8 bursts/min) compared with lean controls (+10.8 ± 1.2 bursts/min). MSNA response to SHG at 30% maximum voluntary contraction (MVC) was similar between the two groups. There were no significant differences in systolic (SBP) or diastolic BP (DBP) responses or HR responses between the two groups during either maneuver. CONCLUSIONS Normotensive overweight individuals have an exaggerated MSNA response to the CPT. Augmented sympathetic reactivity to cold stress may contribute to increased risk of hypertension in overweight individuals.
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da Silva Mattos AM, Xavier CH, Karlen-Amarante M, da Cunha NV, Fontes MAP, Martins-Pinge MC. Renal sympathetic nerve activity is increased in monosodium glutamate induced hyperadipose rats. Neurosci Lett 2012; 522:118-22. [DOI: 10.1016/j.neulet.2012.06.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2012] [Revised: 05/30/2012] [Accepted: 06/07/2012] [Indexed: 10/28/2022]
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Ando K, Fujita M. Reactive oxygen species and the central nervous system in salt-sensitive hypertension: possible relationship with obesity-induced hypertension. Clin Exp Pharmacol Physiol 2012; 39:111-6. [PMID: 21388436 DOI: 10.1111/j.1440-1681.2011.05510.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. There are multiple and complex mechanisms of salt-induced hypertension; however, central sympathoexcitation plays an important role. In addition, the production of reactive oxygen species (ROS) is increased in salt-sensitive hypertensive humans and animals. Thus, we hypothesized that brain ROS overproduction may increase blood pressure (BP) by central sympathostimulation. 2. Recently, we demonstrated that ROS levels were elevated in the hypothalamus of salt-sensitive hypertensive animals. Moreover, intracerebroventricular anti-oxidants suppressed BP and renal sympathetic nerve activity more in salt-sensitive than non-salt-sensitive hypertensive rats. Thus, brain ROS overproduction increased BP through central sympathoexcitation in salt-sensitive hypertension. 3. Salt sensitivity of BP is enhanced in obesity and metabolic syndrome. Interestingly, it is also suggested that, in obesity-induced hypertension models, increases in BP are caused by brain ROS-induced central sympathoexcitation. 4. Recent studies suggest that increased ROS production in the brain and central sympathoexcitation may share a common pathway that increases BP in both salt- and obesity-induced hypertension.
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Affiliation(s)
- Katsuyuki Ando
- Department of Nephrology and Endocrinology, University of Tokyo Graduate School of Medicine, Tokyo, Japan.
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Motosugi Y, Ando H, Ushijima K, Maekawa T, Ishikawa E, Kumazaki M, Fujimura A. Tissue-Dependent Alterations of the Clock Gene Expression Rhythms in Leptin-Resistant Zucker Diabetic Fatty Rats. Chronobiol Int 2011; 28:968-72. [DOI: 10.3109/07420528.2011.613325] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Huber DA, Schreihofer AM. Altered regulation of the rostral ventrolateral medulla in hypertensive obese Zucker rats. Am J Physiol Heart Circ Physiol 2011; 301:H230-40. [PMID: 21536848 DOI: 10.1152/ajpheart.00075.2011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Obese Zucker rats (OZR) have elevated sympathetic nerve activity (SNA) and mean arterial pressure (MAP) compared with lean Zucker rats (LZR). We examined whether altered tonic glutamatergic, angiotensinergic, or GABAergic inputs to the rostral ventrolateral medulla (RVLM) contribute to elevated SNA and MAP in OZR. Male rats (14-18 wk) were anesthetized with urethane (1.5 g/kg iv), ventilated, and paralyzed to record splanchnic SNA, heart rate (HR), and MAP. Inhibition of the RVLM by microinjections of muscimol eliminated SNA and evoked greater decreases in MAP in OZR vs. LZR (P < 0.05). Antagonism of angiotensin AT(1) receptors in RVLM with losartan yielded modest decreases in SNA and MAP in OZR but not LZR (P < 0.05). However, antagonism of ionotropic glutamate receptors in RVLM with kynurenate produced comparable decreases in SNA, HR, and MAP in OZR and LZR. Antagonism of GABA(A) receptors in RVLM with gabazine evoked smaller rises in SNA, HR, and MAP in OZR vs. LZR (P < 0.05), whereas responses to microinjections of GABA into RVLM were comparable. Inhibition of the caudal ventrolateral medulla, a major source of GABA to the RVLM, evoked attenuated rises in SNA and HR in OZR (P <0.05). Likewise, inhibition of nucleus tractus solitarius, the major excitatory input to caudal ventrolateral medulla, produced smaller rises in SNA and HR in OZR. These results suggest the elevated SNA and MAP in OZR is derived from the RVLM and that enhanced angiotensinergic activation and reduced GABAergic inhibition of the RVLM may contribute to the elevated SNA and MAP in the OZR.
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Affiliation(s)
- Domitila A Huber
- Dept. of Integrative Physiology, Univ. of North Texas Health Science Center, 3500 Camp Bowie Blvd., Fort Worth, TX 76107, USA
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Davis G. Baroreflex and somato-reflex control of blood pressure, heart rate and renal sympathetic nerve activity in the obese Zucker rat. Exp Physiol 2011; 96:623-34. [PMID: 21527543 DOI: 10.1113/expphysiol.2011.057638] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
It has been reported that the baroreflex control of heart rate (HR) and sympathetic nerve activity (SNA) is attenuated in obese Zucker rats (OZRs) compared with age-matched lean animals (LZRs). What is not known, however, is the extent to which the baroreflex control of mean arterial blood pressure (MAP) is altered in the OZR. In addition, it is not known whether the interactions of other sensory nerve inputs on autonomic control are altered in the OZR compared with the LZR. The aim of this study was to determine the baroreflex control of MAP, HR and renal SNA (RSNA) in the OZR and LZR using an open-loop baroreflex approach. In addition, the effect of brachial nerve stimulation (BNS) on the baroreflex control was determined in these animals. Age-matched, male LZRs and OZRs were anaesthetized, and the carotid baroreceptors were vascularly isolated, bilaterally. The carotid sinus pressure was increased in 20 mmHg increments from 60 to 180 mmHg using an oscillating pressure stimulus. Baroreflex function curves were constructed using a four-parameter logistic equation, and gain was calculated from the first derivative, which gave a measure of baroreceptor sensitivity, before and during BNS. The range over which the baroreflex could change MAP (28 ± 6 versus 87 ± 5 mmHg; mean ± SEM), HR (17 ± 4 versus 62 ± 11 beats min(-1)) and normalized RSNA (NormNA; 22 ± 4 versus 76 ± 11%) was significantly decreased in the OZR compared with the LZR. Likewise, the maximal gain was lower in the OZR, as follows: MAP -0.88 ± 0.22 versus -2.26 ± 0.17; HR -0.42 ± 0.18 versus -1.44 ± 0.22 beats min(-1); and NormNA -0.54 ± 0.14 versus -1.65 ± 0.30% mmHg(-1). There was no difference in the mid-point of the baroreflex curve for each variable between the OZR and LZR. However, the minimal values obtained when the baroreceptors were maximally loaded were higher in the OZR (MAP 68 ± 5 versus 53 ± 4 mmHg; HR 455 ± 7 versus 390 ± 13 beats min(-1); and NormNA -19 ± 4 versus -48 ± 8%). Brachial nerve stimulation in the LZR resulted in an upward and rightward resetting of the baroreflex control of MAP and RSNA, and abolished baroreflex control of HR. The baroreflex control of RSNA in the OZR during BNS was further attenuated and reset upwards and to the right, while the HR response was abolished. With respect to MAP, the baroreflex curve reset upwards and to the right to a point comparable with the LZR during BNS. These data show that there is an attenuated baroreflex control in the OZR and that the ability to reset to higher arterial pressure during somatic afferent nerve stimulation is similar to that in the LZR.
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Affiliation(s)
- Gerard Davis
- University of Otago, Physiology, Lindo-Fergusen Building, New Zealand.
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Laville M. [Renal consequences of obesity]. Nephrol Ther 2011; 7:80-5. [PMID: 21208837 DOI: 10.1016/j.nephro.2010.11.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 11/30/2010] [Accepted: 11/30/2010] [Indexed: 11/25/2022]
Abstract
The steady increase in the prevalence of obesity contributes to the increase in the prevalence of chronic kidney disease, through renal damages associated with type-2 diabetes and hypertension. Obesity is also an independent risk factor for the kidney, since it is associated with an increased risk of albuminuria and glomerulosclerosis, and worsens the course of chronic kidney disease regardless of the primary renal disease. The existence of a metabolic syndrome, constant in type-2 diabetes, and associated with abdominal obesity, is not the only requirement for renal anomalies of which the translation is a functional hyperfiltration, a clinical microalbuminuria and histologically a glomerulomegaly and glomerulosclerosis. The estimated glomerular filtration rate (GFR) in obese patients is strongly influenced by the weight or indexation to body surface area, and it is logical to take into account the value of non-indexed GFR to assess renal risk and treatment effects, especially if they lead to weight loss. Hypertension is promoted by salt sensitivity, potentially reversible, and overactivity of the renin-angiotensin system (RAS) in part due to adipose tissue. The cytokines secreted by adipose tissue (adipokines), induce sympathetic hyperactivity through leptin, and low-grade inflammatory state that contributes to the development of glomerular sclerosis lesions, especially because a resistance to adiponectin. The treatment relies on weight loss, possibly through bariatric surgery, and antagonists of the RAS.
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Affiliation(s)
- Maurice Laville
- Inserm U 886, service de néphrologie, hôpital Édouard-Herriot, université de Lyon, 69437 Lyon cedex 03, France.
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Ye ZY, Li DP. Activation of the melanocortin-4 receptor causes enhanced excitation in presympathetic paraventricular neurons in obese Zucker rats. ACTA ACUST UNITED AC 2010; 166:112-20. [PMID: 20937332 DOI: 10.1016/j.regpep.2010.10.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 08/26/2010] [Accepted: 10/04/2010] [Indexed: 10/19/2022]
Abstract
Sympathetic nerve activity is increased in obesity-related hypertension. However, the central mechanisms involved in the increased sympathetic outflow remain unclear. The hypothalamic melanocortin system is important for regulating energy balance and sympathetic outflow. To understand the mechanisms by which the melanocortin systems regulates sympathetic outflow, we investigated the role of melanocortin 4 receptors (MC4R) in regulating presympathetic paraventricular nucleus (PVN) neurons. We performed whole-cell patch-clamp recordings on retrogradely labeled PVN neurons projecting to the rostral ventrolateral medulla in brain slices from obese zucker rats (OZRs) and lean zucker rats (LZRs). The MC4R agonists melanotan II (MTII) and α-melanocyte-stimulating hormone (α-MSH) increased the firing activity and depolarized the labeled PVN neurons from both LZRs and OZRs in a concentration-dependent manner. MTII produced significant greater increase in the firing activity in OZRs than in LZRs. Blocking MC4R with the specific antagonist SHU9119 had no effect on the basal firing rate but abolished the MTII-induced increase in the firing rate in both OZRs and LZRs. Furthermore, intracellular dialysis of guanosine 5'-O-(2-thodiphosphate), but not bath application of kynurenic acid and bicuculline, eliminated the MTII-induced increase in firing activity. In addition, MTII had no effect on the frequency and amplitude of glutamatergic excitatory postsynaptic currents and GABAergic inhibitory postsynaptic currents in labeled PVN neurons. Collectively, our findings suggest that MC4R contributes to the elevated excitability of PVN presympathetic neurons, which may be involved in obesity-related hypertension.
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Affiliation(s)
- Zeng-You Ye
- Department of Anesthesiology and Perioperative Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA
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Malpas SC. Sympathetic nervous system overactivity and its role in the development of cardiovascular disease. Physiol Rev 2010; 90:513-57. [PMID: 20393193 DOI: 10.1152/physrev.00007.2009] [Citation(s) in RCA: 431] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
This review examines how the sympathetic nervous system plays a major role in the regulation of cardiovascular function over multiple time scales. This is achieved through differential regulation of sympathetic outflow to a variety of organs. This differential control is a product of the topographical organization of the central nervous system and a myriad of afferent inputs. Together this organization produces sympathetic responses tailored to match stimuli. The long-term control of sympathetic nerve activity (SNA) is an area of considerable interest and involves a variety of mediators acting in a quite distinct fashion. These mediators include arterial baroreflexes, angiotensin II, blood volume and osmolarity, and a host of humoral factors. A key feature of many cardiovascular diseases is increased SNA. However, rather than there being a generalized increase in SNA, it is organ specific, in particular to the heart and kidneys. These increases in regional SNA are associated with increased mortality. Understanding the regulation of organ-specific SNA is likely to offer new targets for drug therapy. There is a need for the research community to develop better animal models and technologies that reflect the disease progression seen in humans. A particular focus is required on models in which SNA is chronically elevated.
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Affiliation(s)
- Simon C Malpas
- Department of Physiology and the Auckland Bioengineering Institute, University of Auckland and Telemetry Research Ltd., Auckland, New Zealand.
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Huber DA, Schreihofer AM. Attenuated baroreflex control of sympathetic nerve activity in obese Zucker rats by central mechanisms. J Physiol 2010; 588:1515-25. [PMID: 20211978 DOI: 10.1113/jphysiol.2009.186387] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Adult obese Zucker rats (OZRs) have reduced sympathetic responses to evoked changes in arterial pressure (AP) compared to lean Zucker rats (LZRs). This study examined whether attenuated sympathetic baroreflexes in OZRs may be due to altered sensory or central mechanisms. The OZRs had elevated baseline splanchnic sympathetic nerve activity (SNA) and mean AP (MAP) compared to age-matched LZRs under urethane anaesthesia (P < 0.05). Aortic depressor nerve activity (ADNA) was measured while AP was altered by infusions of phenylephrine or nitroprusside (+/-60 mmHg over 60-90 s) in rats treated with atropine and propranolol to eliminate changes in heart rate. Although baseline ADNA was higher in the hypertensive OZRs, the relationship between MAP and ADNA was comparable in OZRs and LZRs. In contrast, electrical stimulation of the ADN afferent fibres (5 s train, 2 ms pulses, 4 V, 0.5-48 Hz) produced dramatically smaller reductions in SNA and MAP in OZRs compared to LZRs (P < 0.05). After blockade of alpha-adrenergic receptors to prevent sympathetically mediated depressor responses, OZRs still had reduced sympathetic responses to stimulation of the ADN. In addition, stimulation of vagal afferent nerves electrically or with phenylbiguanide (1, 2, 4 and 8 microg, i.v.) produced smaller inhibitions of SNA in OZRs compared with LZRs (P < 0.05). These data suggest that attenuated sympathetic baroreflexes are the result of altered central mechanisms in OZRs, and not deficits in the responsiveness of aortic baroreceptors to AP. Furthermore, central deficits in the regulation of SNA in OZRs extend to other sympathoinhibitory reflexes initiated by vagal afferent nerves.
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Affiliation(s)
- Domitila A Huber
- Department of Physiology, Medical College of Georgia, 1120 15th Street, CA-3147, Augusta, GA 30912-3000, USA
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Guild SJ, Barrett CJ, McBryde FD, Van Vliet BN, Head GA, Burke SL, Malpas SC. Quantifying sympathetic nerve activity: problems, pitfalls and the need for standardization. Exp Physiol 2009; 95:41-50. [DOI: 10.1113/expphysiol.2008.046300] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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El-Wazir YM, Li SG, Smith R, Silcox DL, Brown DR, Randall DC. Parasympathetic response to acute stress is attenuated in young Zucker obese rats. Auton Neurosci 2008; 143:33-9. [PMID: 18722824 DOI: 10.1016/j.autneu.2008.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Revised: 07/11/2008] [Accepted: 07/14/2008] [Indexed: 10/21/2022]
Abstract
We compared arterial blood pressure (BP) and heart rate (HR) control in 9- to 11-week old obese Zucker rats (n=10; weight=452+/-45 g, average+/-SD) to age-matched, lean Zucker animals (n=13; weight=280+/-46 g). BP was measured by indwelling catheter. Baseline pressure was 113.1+/-7.0 mm Hg in the lean vs. 111.7+/-5.6 in the obese rats (NS). Baseline HR was 413+/-43 in the lean vs. 422+/-22 bpm in the obese animals (NS). Rats were classically conditioned by following a 15-second tone (CS+) with a 0.5-second tail shock. There were no between-group differences in the BP response to CS+. Conversely, heart rate (HR) decreased significantly (p<0.05) more during the last 10 s of the tone in the lean group (-46.0+/-21.5 bpm) vs. the obese (-17.8+/-21.7 bpm). This bradycardia was blocked by atropine. Finally, the change in HR divided by the change in arterial BP (DeltaHR/DeltaBP) following an intravenous bolus of phenylephrine (PE; 5 microg/kg) and following sodium nitroprusside (NP; 5 microg/kg) was determined. The DeltaHR/DeltaBP following PE was smaller in the obese (n=6; -1.36+/-0.60) vs. lean (n=5; -2.80+/-0.92); there was no difference in the response following NP. These data indicate that the BP response to a behavioral challenge did not differ in the obese rat vs. the lean animal, but that the obese subjects had an attenuated parasympathetic response to the stress, probably secondary to alterations in baroreflex function.
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Affiliation(s)
- Yasser M El-Wazir
- Department of Physiology, Faculty of Medicine, Suez Canal University, Ismailia, Egypt
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Alzoubi KH, Aleisa AM, Alkadhi KA. Expression of gLTP in sympathetic ganglia of obese Zucker rats in vivo: molecular evidence. J Mol Neurosci 2008; 35:297-306. [PMID: 18563301 DOI: 10.1007/s12031-008-9110-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 05/21/2008] [Indexed: 12/20/2022]
Abstract
Long-term potentiation in sympathetic ganglia (gLTP) is similar to LTP of the hippocampal area CA1 in that its expression involves similar changes in signaling molecules. We have shown previously that the stress-prone, hypertensive obese Zucker rats (OZR) expressed gLTP in sympathetic ganglia and that high blood pressure was reduced by treatment with 5-HT(3) receptor antagonists. In the present study, we present additional electrophysiological evidence for the pre-expression of gLTP in sympathetic ganglia from OZR indicated by failure of repetitive stimulation to express gLTP in isolated superior cervical ganglia (SCG) and inhibition of baseline ganglionic transmission by a 5-HT(3) receptor antagonist. We have also investigated the role of key signaling molecules in the expression of gLTP in the hypertensive OZR. Immunoblot analysis showed a significant increase in the levels of phosphorylated (P-)CaMKII and protein kinase C gamma (PKCgamma) in SCG from OZR. The ratio of P-CaMKII to the total CaMKII was markedly increased in OZR ganglia, suggesting increased phosphorylation of this molecule. Additionally, there was a significant decrease in the levels of calcineurin in ganglia. Furthermore, the neural nitric oxide synthase and hemeoxygenase II, which are essential for the expression of gLTP, were significantly elevated in OZR ganglia. The present findings confirm that ganglia from OZR have expressed gLTP and that synaptic plasticity in sympathetic ganglia may involve a molecular cascade similar to that of LTP of the brain hippocampal area CA1.
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Affiliation(s)
- K H Alzoubi
- Department of Clinical Pharmacy, Faculty of Pharmacy, Jordan University of Science and Technology, Irbid, Jordan
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Naik JS, Xiang L, Hodnett BL, Hester RL. Alpha-adrenoceptor-mediated vasoconstriction is not involved in impaired functional vasodilation in the obese Zucker rat. Clin Exp Pharmacol Physiol 2008; 35:611-6. [PMID: 18177478 PMCID: PMC2788304 DOI: 10.1111/j.1440-1681.2007.04849.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. Obesity/metabolic syndrome is associated with augmented a-adrenoceptor sensitivity and impaired hyperaemic responses to exercise. Thus, it is possible that this elevated a-adrenoceptor constriction contributes to the blunted hyperaemic response. 2. Male lean and obese Zucker rats were instrumented for acute measurements of blood pressure (BP) and iliac blood flow (BF). Changes in BP and BF were determined in anaesthetized animals in response to intravenous administration of increasing doses of the a(1)-adrenoceptor agonist phenylephrine (PE). Once BF and BP returned to normal, a single bolus of the a-adrenoceptor antagonist phentolamine (0.5 mg) was administered. In separate animals, the spinotrapezius muscle was exteriorized for direct in situ observation of the microcirculation in response to phentolamine and muscle contraction. 3. Administration of PE demonstrated that iliac BF is highly autoregulated in the face of increasing perfusion pressure. Iliac conductance following phentolamine was significantly greater in obese rats. Following phentolamine administration, iliac vascular conductance was significantly greater in obese rats compared with lean animals. However, a-adrenoceptor blockade did not significantly alter arteriolar diameter in the spinotrapezius muscle during muscle contraction in either lean or obese animals. 4. These results suggest a greater contribution of the a-adrenoceptors in basal hindlimb vascular tone in obese rats. Furthermore, an augmented a-adrenoceptor-mediated vasoconstriction may not contribute to the impaired functional dilation in anaesthetized obese rats.
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Affiliation(s)
- Jay S Naik
- Department of Biology, New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA
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Kopp UC, Cicha MZ, Yorek MA. Impaired responsiveness of renal sensory nerves in streptozotocin-treated rats and obese Zucker diabetic fatty rats: role of angiotensin. Am J Physiol Regul Integr Comp Physiol 2008; 294:R858-66. [DOI: 10.1152/ajpregu.00830.2007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Increasing afferent renal nerve activity decreases efferent renal nerve activity and increases urinary sodium excretion. Activation of renal pelvic mechanosensory nerves is impaired in streptozotocin (STZ)-treated rats (model of type 1 diabetes). Decreased activation of renal sensory nerves would lead to increased efferent renal nerve activity, sodium retention, and hypertension. We examined whether the reduced activation of renal sensory nerves in STZ rats was due to increased renal angiotensin activity and whether activation of the renal sensory nerves was impaired in obese Zucker diabetic fatty (ZDF) rats (model of type 2 diabetes). In an isolated renal pelvic wall preparation from rats treated with STZ for 2 wk, PGE2failed to increase the release of substance P, from 5 ± 1 to 6 ± 1 pg/min. In pelvises from sham STZ rats, PGE2increased substance P release from 6 ± 1 to 13 ± 2 pg/min. Adding losartan to the incubation bath increased PGE2-mediated release of substance P in STZ rats, from 5 ± 1 to 10 ± 2 pg/min, but had no effect in sham STZ rats. In pelvises from obese ZDF rats (22–46 wk old), PGE2increased substance P release from 12.0 ± 1.2 to 18.3 ± 1.2 pg/min, which was less than that from lean ZDF rats (10.3 ± 1.6 to 22.5 ± 2.4 pg/min). Losartan had no effect on the PGE2-mediated substance P release in obese or lean ZDF rats. We conclude that the mechanisms involved in the decreased responsiveness of the renal sensory nerves in STZ rats involve activation of the renin angiotensin system in STZ but not in obese ZDF rats.
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Carey RM. Pathophysiology of Primary Hypertension. Microcirculation 2008. [DOI: 10.1016/b978-0-12-374530-9.00020-6] [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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Janiak P, Poirier B, Bidouard JP, Cadrouvele C, Pierre F, Gouraud L, Barbosa I, Dedio J, Maffrand JP, Le Fur G, O'Connor S, Herbert JM. Blockade of cannabinoid CB1 receptors improves renal function, metabolic profile, and increased survival of obese Zucker rats. Kidney Int 2007; 72:1345-57. [PMID: 17882151 DOI: 10.1038/sj.ki.5002540] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Obesity is a major risk factor in the development of chronic renal failure. Rimonabant, a cannabinoid CB1 receptor antagonist, improves body weight and metabolic disorders; however, its effect on mortality and chronic renal failure associated with obesity is unknown. Obese Zucker rats received either rimonabant or vehicle for 12 months and were compared to a pair-fed but untreated group of obese rats. Mortality in the obese rats was significantly reduced by rimonabant along with a sustained decrease in body weight, transient reduction in food intake, and an increase in plasma adiponectin. This was associated with significant reduction in plasma total cholesterol, low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio, triglycerides, glucose, norepinephrine, plasminogen activator inhibitor 1, and preservation of pancreatic weight and beta-cell mass index. The cannabinoid antagonist attenuated the increase in proteinuria, urinary N-acetylglucosaminidase excretion, plasma creatinine, and urea nitrogen levels while improving creatinine clearance. Renal hypertrophy along with glomerular and tubulointerstitial lesions were reduced by rimonabant. Although the drug did not modify hemodynamics, it normalized the pressor response to angiotensin II. Our study suggests that in a rat model of chronic renal failure due to obesity, rimonabant preserves renal function and increases survival.
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MESH Headings
- Adiponectin/blood
- Animals
- Body Weight/drug effects
- Body Weight/physiology
- Disease Models, Animal
- Eating/drug effects
- Eating/physiology
- Kidney/drug effects
- Kidney/physiology
- Kidney Failure, Chronic/etiology
- Kidney Failure, Chronic/prevention & control
- Lipids/blood
- Male
- Obesity/complications
- Obesity/drug therapy
- Obesity/metabolism
- Piperidines/pharmacology
- Piperidines/therapeutic use
- Pyrazoles/pharmacology
- Pyrazoles/therapeutic use
- Rats
- Rats, Zucker
- Receptor, Cannabinoid, CB1/antagonists & inhibitors
- Receptor, Cannabinoid, CB1/drug effects
- Receptor, Cannabinoid, CB1/physiology
- Rimonabant
- Survival Analysis
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Affiliation(s)
- P Janiak
- Cardiovascular Therapeutic Department, Sanofi-Aventis Research & Development, Chilly-Mazarin, France.
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Morrison RG, Mills C, Moran AL, Walton CE, Sadek MH, Mangiarua EI, Wehner PS, McCumbee WD. A moderately high fat diet promotes salt-sensitive hypertension in obese zucker rats by impairing nitric oxide production. Clin Exp Hypertens 2007; 29:369-81. [PMID: 17729054 DOI: 10.1080/10641960701578360] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The objective of this research was to examine the contribution of a moderately high fat (MHF) diet to the development of salt-sensitive hypertension in obese Zucker rats. Lean and obese Zucker rats were fed either a MHF diet or a diet of standard rat chow (control diet) for 10 weeks. From week 4 through week 10, the drinking water was supplemented with 1% NaCl. Blood pressure was measured weekly, and urinary excretion of nitric oxide metabolites (NO(x)) was determined at weeks 4 and 10. At week 10, renal nitric oxide synthase (NOS) activity was assessed in kidney homogenates. Blood pressures of obese, but not lean, rats on the MHF fat diet were significantly increased by salt-supplementation, whereas blood pressures of rats on the control diet were not appreciably affected. NO(x) excretion was increased in response to salt-supplementation in rats on the control diet, with the effect being particularly dramatic in obese rats. After salt-supplementation, NO(x) excretion by rats on the MHF diet was lower than rats on the control diet. In obese rats on the MHF diet, this decrease in NO production was accompanied by a reduction in renal NOS activity. These results indicate that obese rats are more inclined than lean rats to develop diet-induced hypertension in response to a moderately high fat, salt-supplemented diet. Furthermore, they suggest that MHF diet-induced defects in NO production may promote the salt-sensitivity of blood pressure in obese Zucker rats, which appear to require more NO to maintain blood pressure during a salt challenge.
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Affiliation(s)
- Ryan G Morrison
- Department of Pharmacology, Physiology and Toxicology, Marshall University, Joan C. Edwards School of Medicine, Huntington, West Virginia 25755, USA
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Stepp DW, Boesen EI, Sullivan JC, Mintz JD, Hair CD, Pollock DM. Obesity augments vasoconstrictor reactivity to angiotensin II in the renal circulation of the Zucker rat. Am J Physiol Heart Circ Physiol 2007; 293:H2537-42. [PMID: 17693541 DOI: 10.1152/ajpheart.01081.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Obesity is an emerging risk factor for renal dysfunction, but the mechanisms are poorly understood. Obese patients show heightened renal vasodilation to blockade of the renin-angiotensin system, suggesting deficits in vascular responses to angiotensin II (ANG II). This study tested the hypothesis that obesity augments renal vasoconstriction to ANG II. Lean (LZR), prediabetic obese (OZR), and nonobese fructose-fed Zucker rats (FF-LZR) were studied to determine the effects of obesity and insulin resistance on reactivity of blood pressure and renal blood flow to vasoconstrictors. OZR showed enlargement of the kidneys, elevated urine output, increased sodium intake, and decreased plasma renin activity (PRA) vs. LZR, and renal vasoconstriction to ANG II was augmented in OZR. Renal reactivity to norepinephrine and mesenteric vascular reactivity to ANG II were similar between LZR and OZR. Insulin-resistant FF-LZR had normal reactivity to ANG II, indicating the insulin resistance was an unlikely explanation for the changes observed in OZR. Four weeks on a low-sodium diet (0.08%) to raise PRA reduced reactivity to ANG II in OZR back to normal levels without effect on LZR. From these data, we conclude that in the prediabetic stages of obesity, a decrease in PRA is observed in Zucker rats that may lead to increased renal vascular reactivity to ANG II. This increased reactivity to ANG II may explain the elevated renal vasodilator effects observed in obese humans and provide insight into early changes in renal function that predispose to nephropathy in later stages of the disease.
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Affiliation(s)
- David W Stepp
- Vascular Biology Center, Medical College of Georgia, 1459 Laney Walker Blvd., Augusta, GA 30912, USA.
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50
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Alkadhi K, Alzoubi K. Role of long-term potentiation of sympathetic ganglia (gLTP) in hypertension. Clin Exp Hypertens 2007; 29:267-86. [PMID: 17653963 DOI: 10.1080/10641960701500356] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Ganglionic long-term potentiation (gLTP) is an activity-dependent sustained increase in the synaptic efficacy of the nicotinic pathway that has been demonstrated in autonomic ganglia. Sustained enhancement in ganglionic transmission as in chronic mental stress may affect the activity of autonomic functions, including blood pressure and heart rate. An increase in sympathetic activity associated with psychosocial stress and stress-prone conditions such as obesity and aging could result in in vivo expression of gLTP leading to hypertension of a neural origin. Recent reports indicated that the prevention of the expression of gLTP in animal models of hypertension prevented or reduced high blood pressure. Although stress-induced hypertension normalizes within a few days of stress relief, prolonged mild-moderate hypertension may contribute to atherosclerotic cardiovascular diseases. The relation between hypertension and enhanced ganglionic transmission as a result of in vivo expression of gLTP is discussed in this review.
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Affiliation(s)
- Karim Alkadhi
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas 77204-5515, USA.
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