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Prior LJ, Davern PJ, Burke SL, Lim K, Armitage JA, Head GA. Exposure to a High-Fat Diet During Development Alters Leptin and Ghrelin Sensitivity and Elevates Renal Sympathetic Nerve Activity and Arterial Pressure in Rabbits. Hypertension 2014; 63:338-45. [DOI: 10.1161/hypertensionaha.113.02498] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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77
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Tikellis C, Brown R, Head GA, Cooper ME, Thomas MC. Angiotensin-converting enzyme 2 mediates hyperfiltration associated with diabetes. Am J Physiol Renal Physiol 2014; 306:F773-80. [PMID: 24477684 DOI: 10.1152/ajprenal.00264.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The degradation of ANG II by angiotensin-converting enzyme 2 (ACE2), leading to the formation of ANG(1-7), is an important step in the regulation of the renin-angiotensin-aldosterone system (RAAS), and one that is significantly altered in the diabetic kidney. This study examined the role of ACE2 in the hyperfiltration associated with diabetes. Streptozotocin diabetes was induced in male C57BL6 mice and ACE2 knockout (KO) mice. C57BL6 mice were further randomized to receive the selective ACE2 inhibitor MLN-4760. After 2 wk of study, animals were subjected to micropuncture experiments. The renal reserve was further assessed in C57BL6 mice and ACE2 KO mice after exposure to a high-protein diet. The induction of diabetes in wild-type mice was associated with increased renal ACE2 activity, hyperfiltration, and renal hypertrophy. On micropuncture, diabetes was associated with increased tubular free flow and stop-flow pressure, enhanced tubuloglomerular feedback reactivity, and an increased maximal response indicative of increased glomerular hydrostatic capillary pressure. Each of these increases were prevented in diabetic ACE2 KO mice and diabetic mice treated with a selective ACE2 inhibitor for 2 wk. However, unlike chronically treated animals, ACE2 inhibition with MLN-4760 had no acute effect on stop-flow pressure or tubuloglomerular feedback reactivity. ACE2 KO mice also failed to increase their creatinine clearance in response to a high-protein diet. The results of our study suggest that ACE2 plays a key role in the recruitment of the renal reserve and hyperfiltration associated with diabetes.
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Jackson KL, Nguyen-Huu TP, Davern PJ, Head GA. Energy metabolism in BPH/2J genetically hypertensive mice. Hypertens Res 2013; 37:413-21. [DOI: 10.1038/hr.2013.156] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Revised: 10/21/2013] [Accepted: 10/29/2013] [Indexed: 11/09/2022]
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79
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Jancovski N, Bassi JK, Carter DA, Choong YT, Connelly A, Nguyen TP, Chen D, Lukoshkova EV, Menuet C, Head GA, Allen AM. Stimulation of angiotensin type 1A receptors on catecholaminergic cells contributes to angiotensin-dependent hypertension. Hypertension 2013; 62:866-71. [PMID: 24001896 DOI: 10.1161/hypertensionaha.113.01474] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hypertension contributes to multiple forms of cardiovascular disease and thus morbidity and mortality. The mechanisms inducing hypertension remain unclear although the involvement of homeostatic systems, such as the renin-angiotensin and sympathetic nervous systems, is established. A pivotal role of the angiotensin type 1 receptor in the proximal tubule of the kidney for the development of experimental hypertension is established. Yet, other systems are involved. This study tests whether the expression of angiotensin type 1A receptors in catecholaminergic cells contributes to hypertension development. Using a Cre-lox approach, we deleted the angiotensin type 1A receptor from all catecholaminergic cells. This deletion did not alter basal metabolism or blood pressure but delayed the onset of angiotensin-dependent hypertension and reduced the maximal response. Cardiac hypertrophy was also reduced. The knockout mice showed attenuated activation of the sympathetic nervous system during angiotensin II infusion as measured by spectral analysis of the blood pressure. Increased reactive oxygen species production was observed in forebrain regions, including the subfornical organ, of the knockout mouse but was markedly reduced in the rostral ventrolateral medulla. These studies demonstrate that stimulation of the angiotensin type 1A receptor on catecholaminergic cells is required for the full development of angiotensin-dependent hypertension and support an important role for the sympathetic nervous system in this model.
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Hodgson JM, Head GA. Reply to ML Zwinkels et al. Am J Clin Nutr 2013; 98:857-8. [PMID: 24137696 DOI: 10.3945/ajcn.113.066712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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81
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Jackson KL, Marques FZ, Watson AMD, Palma-Rigo K, Nguyen-Huu TP, Morris BJ, Charchar FJ, Davern PJ, Head GA. A novel interaction between sympathetic overactivity and aberrant regulation of renin by miR-181a in BPH/2J genetically hypertensive mice. Hypertension 2013; 62:775-81. [PMID: 23897069 DOI: 10.1161/hypertensionaha.113.01701] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Genetically hypertensive mice (BPH/2J) are hypertensive because of an exaggerated contribution of the sympathetic nervous system to blood pressure. We hypothesize that an additional contribution to elevated blood pressure is via sympathetically mediated activation of the intrarenal renin-angiotensin system. Our aim was to determine the contribution of the renin-angiotensin system and sympathetic nervous system to hypertension in BPH/2J mice. BPH/2J and normotensive BPN/3J mice were preimplanted with radiotelemetry devices to measure blood pressure. Depressor responses to ganglion blocker pentolinium (5 mg/kg i.p.) in mice pretreated with the angiotensin-converting enzyme inhibitor enalaprilat (1.5 mg/kg i.p.) revealed a 2-fold greater sympathetic contribution to blood pressure in BPH/2J mice during the active and inactive period. However, the depressor response to enalaprilat was 4-fold greater in BPH/2J compared with BPN/3J mice, but only during the active period (P=0.01). This was associated with 1.6-fold higher renal renin messenger RNA (mRNA; P=0.02) and 0.8-fold lower abundance of micro-RNA-181a (P=0.03), identified previously as regulating human renin mRNA. Renin mRNA levels correlated positively with depressor responses to pentolinium (r=0.99; P=0.001), and BPH/2J mice had greater renal sympathetic innervation density as identified by tyrosine hydroxylase staining of cortical tubules. Although there is a major sympathetic contribution to hypertension in BPH/2J mice, the renin-angiotensin system also contributes, doing so to a greater extent during the active period and less during the inactive period. This is the opposite of the normal renin-angiotensin system circadian pattern. We suggest that renal hyperinnervation and enhanced sympathetically induced renin synthesis mediated by lower micro-RNA-181a contributes to hypertension in BPH/2J mice.
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Burke SL, Prior LJ, Lukoshkova EV, Lim K, Barzel B, Davern PJ, Armitage JA, Head GA. Reduced preprandial dipping accounts for rapid elevation of blood pressure and renal sympathetic nerve activity in rabbits fed a high-fat diet. Chronobiol Int 2013; 30:726-38. [PMID: 23688116 DOI: 10.3109/07420528.2013.784771] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Consumption of a high-fat diet (HFD) by rabbits results in increased blood pressure (BP), heart rate (HR), and renal sympathetic nerve activity (RSNA) within 1 wk. Here, we determined how early this activation occurred and whether it was related to changes in cardiovascular and neural 24-h rhythms. Rabbits were meal-fed a HFD for 3 wks, then a normal-fat diet (NFD) for 1 wk. BP, HR, and RSNA were measured daily in the home cage via implanted telemeters. Baseline BP, HR, and RSNA over 24 h were 71 ± 1 mm Hg, 205 ± 4 beats/min and 7 ± 1 normalized units (nu). The 24-h pattern was entrained to the feeding cycle and values increased from preprandial minimum to postprandial maximum by 4 ± 1 mm Hg, 51 ± 6 beats/min, and 1.6 ± .6 nu each day. Feeding of a HFD markedly diminished the preprandial dip after 2 d (79-125% of control; p < 0.05) and this reduction lasted for 3 wks of HFD. Twenty-four-hour BP, HR, and RSNA concurrently increased by 2%, 18%, and 22%, respectively. Loss of preprandial dipping accounted for all of the BP increase and 50% of the RSNA increase over 3 wks and the 24-h rhythm became entrained to the light-dark cycle. Resumption of a NFD did not alter the BP preprandial dip. Thus, elevated BP induced by a HFD and mediated by increased sympathetic nerve activity results from a reduction in preprandial dipping, from the first day. Increased calories, glucose, insulin, and leptin may account for early changes, whereas long-term loss of dipping may be related to increased sensitivity of sympathetic pathways.
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Hodgson JM, Croft KD, Woodman RJ, Puddey IB, Fuchs D, Draijer R, Lukoshkova E, Head GA. Black tea lowers the rate of blood pressure variation: a randomized controlled trial. Am J Clin Nutr 2013; 97:943-50. [PMID: 23553154 DOI: 10.3945/ajcn.112.051375] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Measures of blood pressure variation have been associated with cardiovascular disease and related outcomes. The regular consumption of black tea can lower blood pressure, but its effects on blood pressure variation have yet to be investigated. OBJECTIVE We aimed to assess the effects of black tea consumption on the rate of ambulatory blood pressure variation. DESIGN Men and women (n = 111) with systolic blood pressure between 115 and 150 mm Hg at screening were recruited in a randomized, controlled, double-blind, 6-mo parallel-designed trial designed primarily to assess effects on blood pressure. Participants consumed 3 cups/d of either powdered black tea solids (tea) or a flavonoid-free caffeine-matched beverage (control). The 24-h ambulatory blood pressure level and rate of measurement-to-measurement blood pressure variation were assessed at baseline, day 1, and 3 and 6 mo. RESULTS Across the 3 time points, tea, compared with the control, resulted in lower rates of systolic (P = 0.0045) and diastolic (P = 0.016) blood pressure variation by ~10% during nighttime (2200-0600). These effects, which were immediate at day 1 and sustained over 6 mo, were independent of the level of blood pressure and heart rate. The rate of blood pressure variation was not significantly altered during daytime (0800-2000). CONCLUSIONS These findings indicate that a component of black tea solids, other than caffeine, can influence the rate of blood pressure variation during nighttime. Thus, small dietary changes have the potential to significantly influence the rate of blood pressure variation. This trial was registered at the Australian New Zealand Clinical Trials Registry as ACTR12607000543482.
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84
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Jackson KL, Nguyen‐Huu T, Palma‐Rigo K, Davern PJ, Head GA. Importance of the medial amygdala to the neurogenic hypertension in Schlager mice. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.699.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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85
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Anilovitch JL, Davern PJ, Burke SL, Evans RG, Head GA. Habituation to repeated stress is reversed by systemic angiotensin II: a mechanism involving nitric oxide in the paraventricular nucleus of the hypothalamus. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.926.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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86
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Lim K, Burke SL, Barzel B, Armitage JA, Head GA. Early changes to circadian rhythm account for elevated blood pressure and sympathetic activity during a high fat diet in rabbits. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.926.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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87
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Rajapakse NW, Karim F, Head GA, Kaye DM. L‐arginine Transporters: A New Treatment Target in Obesity Induced Hypertension? FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.905.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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88
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Barzel B, Burke SL, Armitage JA, Head GA. Alpha melanocortin stimulating hormone actions at the ventromedial hypothalamus increase renal sympathetic nerve activity in fat fed rabbits. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.955.21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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89
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Jackson KL, Marques FZ, Watson AM, Nguyen‐Huu T, Morris BJ, Charchar FJ, Davern PJ, Head GA. Diurnal difference in sympathetic stimulation and microRNA regulation of renin in Schlager hypertensive mice. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.695.13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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90
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Head GA, Abegaz B, Jackson KL, Bassi JK, Connelly A, Choong Y, Allen AM, Davern PJ. Angiotensin type 1A receptors transfected into the nucleus tractus solitarii of AT1a−/− mice increase blood pressure and cardiovascular responses to aversive stress. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.926.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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91
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Head GA, Burke SL, Lukoshkova EV. Augmented response of renal sympathetic nerve single units to chemoreceptor stimuli in rabbits with angiotensin induced hypertension. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.1117.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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92
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Head GA, Burke SL, Barzel B, Eikelis N, Lim K, Armitage JA. Factors influencing blood pressure and sympathetic nerve activity during a high fat diet in rabbits. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.955.20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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93
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Eppel GA, Armitage JA, Eikelis N, Head GA, Evans RG. Progression of cardiovascular and endocrine dysfunction in a rabbit model of obesity. Hypertens Res 2013; 36:588-95. [PMID: 23407240 DOI: 10.1038/hr.2013.2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 11/29/2012] [Accepted: 12/04/2012] [Indexed: 11/09/2022]
Abstract
In rabbits, mean arterial pressure (MAP) increases in response to fat feeding, but does not increase further with progressive weight gain. We documented the progression of adiposity and the alterations in endocrine/cardiovascular function in response to fat feeding in rabbits, to determine whether stabilization of MAP after 3 weeks could be explained by stabilization of neurohormonal factors. Rabbits were fed a control diet or high-fat diet for 9 weeks (n=23). Fat feeding progressively increased body mass and adiposity. Heart rate (HR) was elevated by week 3 (15±3%) but changed little thereafter. The effects of fat feeding on MAP were dependent on baseline MAP and peaked at 3 weeks. From baseline, MAP 80 mm Hg, MAP had increased by 8.1±1.3, 4.7±1.7 and 5.6±1.2 mm Hg, respectively, 3, 6 and 9 weeks after commencing the high-fat diet, but by only 2.6±1.5, 3.0±1.7 and 3.9±1.4 mm Hg, respectively, in control rabbits. Fat feeding did not increase MAP from a baseline >80 mm Hg. Plasma concentrations of leptin and insulin increased during the first 3-6 weeks of fat feeding and then stabilized (increasing by 111±17% and 731±302% by week 9, respectively), coinciding with the pattern of changes in MAP and HR. Plasma total cholesterol, triglycerides, renin activity, aldosterone and atrial natriuretic peptide were not significantly altered by fat feeding. Given that the changes in plasma leptin and insulin mirrored the changes in MAP and HR, leptin and insulin may be important factors in the development of hypertension and tachycardia in the rabbit model of obesity.
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94
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Luo Y, Wang YL, Wu YB, Xu Y, Head GA, Barry M, Liang YL. Association between the rate of the morning surge in blood pressure and cardiovascular events and stroke. Chin Med J (Engl) 2013; 126:510-514. [PMID: 23422116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023] Open
Abstract
BACKGROUND The exaggerated surge in morning blood pressure (BP) that many patients experience upon awakening may be closely related to target organ damage and may be a predictor of cardiovascular complications. However, no previous studies have evaluated the rate of this surge independently of the evening period. It remains unclear whether the rate of increase experienced during the surge is a significant or independent determinant of cardiovascular events. METHODS We randomly selected 340 ambulatory BP monitoring (ABPM) patients. All subjects without type 2 diabetes mellitus were divided into two groups: hypertensive group (n = 170) and normotensive group (n = 170). We analyzed ambulatory blood pressure recordings using a double logistic curve-fitting procedure to determine whether the magnitude of the surge in BP and heart rate (HR) in the morning is related to the level of BP in hypertensive individuals. We evaluated the association between the rate of the morning surge in systolic BP (SBP) and the incidence of myocardial infarction and stroke in normotensive and hypertensive subjects. RESULTS Comparisons between hypertensive and normotensive subjects showed that the rates of the morning surges in SBP, mean BP (MBP), and diastolic BP (DBP) were greater in the hypertensive group (P < 0.05) than in the normotensive group. The rate of morning surge in BP was found to be correlated with the daytime SBP (r = 0.236, P < 0.01), the difference between the day and night plateau (r = 0.249, P < 0.01), and the night SBP (r = -0.160, P < 0.05), respectively. After controlling for age, sex, and mean systolic pressure within 24 hours (24 h SBP), the rate of morning surge in SBP was closely correlated with daytime SBP (r = 0.463, P < 0.001), night SBP (r = -0.173, P < 0.05), and the difference between the day and night plateau (r = 0.267, P < 0.001). Logistic regression analysis revealed that the rate of morning surge in SBP was an independent determinant of myocardial infarction (OR = 1.266, 95% CI = 1.153 - 1.389, P < 0.001) and stroke (OR = 1.367, 95% CI = 1.174 - 1.591, P < 0.001). CONCLUSIONS The rate of the morning surge in BP is greater in hypertensive subjects than in normotensive subjects. Daytime SBP may be the best predictor of the rate of morning surge in SBP. The rate of the morning surge in BP is associated with cardiovascular and stroke events.
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Lim K, Burke SL, Head GA. Obesity-related hypertension and the role of insulin and leptin in high-fat-fed rabbits. Hypertension 2013; 61:628-34. [PMID: 23339171 DOI: 10.1161/hypertensionaha.111.00705] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Feeding a high-fat diet (HFD) to rabbits results in increased blood pressure and renal sympathetic nerve activity (RSNA) and marked increases in plasma leptin and insulin. We determined the contribution of insulin and leptin signaling in the central nervous system to the increased blood pressure and RSNA during a HFD using specific antagonists. New Zealand White rabbits were implanted with an intracerebroventricular (ICV) catheter and RSNA electrode and placed on a normal or 13.5% HFD for 1 or 3 weeks. Blood pressure, heart rate, and RSNA were recorded before and for 90 minutes after ICV administration of a leptin antagonist (100 µg), insulin antagonist (0.5 U), or vehicle (50 µL) on separate days. Rabbits had higher blood pressure (+8%, +17%) and RSNA (+55%, +71%), at 1 and 3 weeks, respectively, of HFD compared with controls (n=7-11). ICV leptin antagonist reduced blood pressure by 9% and RSNA by 17% (P<0.001) after 3 weeks of HFD but had no effect at week 1. ICV administration of the insulin antagonist reduced blood pressure by ≈5% at both times (P<0.05) but there was no effect on RSNA. Leptin and insulin antagonist doses were confirmed to effectively block the pressor responses to ICV leptin and insulin, respectively. The elevation of blood pressure and RSNA induced by a HFD is predominantly mediated by central actions of leptin. Central actions of insulin contribute a smaller proportion of the hypertension but independently of RSNA.
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96
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Head GA, McGrath BP, Nelson MR, Stowasser M. Importance of ambulatory blood pressure in hypertension management. Med J Aust 2013; 198:26. [DOI: 10.5694/mja12.11516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2012] [Accepted: 10/28/2012] [Indexed: 11/17/2022]
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97
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Myers MG, Nelson MR, Head GA. Automated office blood pressure measurement for routine clinical practice. Med J Aust 2012; 197:372-3. [DOI: 10.5694/mja11.11545] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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98
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Henry SL, Barzel B, Wood-Bradley RJ, Burke SL, Head GA, Armitage JA. Developmental origins of obesity-related hypertension. Clin Exp Pharmacol Physiol 2012; 39:799-806. [DOI: 10.1111/j.1440-1681.2011.05579.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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99
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Kiriazis H, Jennings NL, Davern P, Lambert G, Su Y, Pang T, Du X, La Greca L, Head GA, Hannan AJ, Du XJ. Neurocardiac dysregulation and neurogenic arrhythmias in a transgenic mouse model of Huntington's disease. J Physiol 2012; 590:5845-60. [PMID: 22890713 DOI: 10.1113/jphysiol.2012.238113] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Huntington's disease (HD) is a heritable neurodegenerative disorder, with heart disease implicated as one major cause of death. While the responsible mechanism remains unknown, autonomic nervous system (ANS) dysfunction may play a role. We studied the cardiac phenotype in R6/1 transgenic mice at early (3 months old) and advanced (7 months old) stages of HD. While exhibiting a modest reduction in cardiomyocyte diameter, R6/1 mice had preserved baseline cardiac function. Conscious ECG telemetry revealed the absence of 24-h variation of heart rate (HR), and higher HR levels than wild-type littermates in young but not older R6/1 mice. Older R6/1 mice had increased plasma level of noradrenaline (NA), which was associated with reduced cardiac NA content. R6/1 mice also had unstable R-R intervals that were reversed following atropine treatment, suggesting parasympathetic nervous activation, and developed brady- and tachyarrhythmias, including paroxysmal atrial fibrillation and sudden death. c-Fos immunohistochemistry revealed greater numbers of active neurons in ANS-regulatory regions of R6/1 brains. Collectively, R6/1 mice exhibit profound ANS-cardiac dysfunction involving both sympathetic and parasympathetic limbs, that may be related to altered central autonomic pathways and lead to cardiac arrhythmias and sudden death.
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Head GA, McGrath BP, Nelson MR, Stowasser M. Importance of ambulatory blood pressure in hypertension management. Med J Aust 2012; 197:143-4. [PMID: 22860780 DOI: 10.5694/mja11.11637] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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