1
|
Role of activating transcription factor 3 in fructose-induced metabolic syndrome in mice. Hypertens Res 2018; 41:589-597. [DOI: 10.1038/s41440-018-0058-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Revised: 12/13/2017] [Accepted: 01/07/2018] [Indexed: 12/31/2022]
|
2
|
Chou CL, Lin H, Chen JS, Fang TC. Renin inhibition improves metabolic syndrome, and reduces angiotensin II levels and oxidative stress in visceral fat tissues in fructose-fed rats. PLoS One 2017; 12:e0180712. [PMID: 28700686 PMCID: PMC5507254 DOI: 10.1371/journal.pone.0180712] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Accepted: 06/20/2017] [Indexed: 12/29/2022] Open
Abstract
Renin–angiotensin system in visceral fat plays a crucial role in the pathogenesis of metabolic syndrome in fructose-fed rats. However, the effects of renin inhibition on visceral adiposity in metabolic syndrome are not fully investigated. We investigated the effects of renin inhibition on visceral adiposity in fructose-fed rats. Male Wistar–Kyoto rats were divided into 4 groups for 8-week experiments: Group Con (standard chow diet), Group Fru (high-fructose diet; 60% fructose), Group FruA (high-fructose diet and concurrent aliskiren treatment; 100 mg/kg body weight [BW] per day), and Group FruB (high-fructose diet and subsequent, i.e. 4 weeks after initiating high-fructose feeding, aliskiren treatment; 100 mg/kg BW per day). The high-fructose diet induced metabolic syndrome, increased visceral fat weights and adipocyte sizes, and augmented angiotensin II (Ang II), NADPH oxidase (NOX) isoforms expressions, oxidative stress, and dysregulated production of adipocytokines from visceral adipose tissues. Concurrent and subsequent aliskiren administration ameliorated metabolic syndrome, dysregulated adipocytokines, and visceral adiposity in high fructose-fed hypertensive rats, and was associated with reducing Ang II levels, NOX isoforms expressions and oxidative stress in visceral fat tissues. Therefore, this study demonstrates renin inhibition could improve metabolic syndrome, and reduce Ang II levels and oxidative stress in visceral fat tissue in fructose-fed rats, and suggests that visceral adipose Ang II plays a crucial role in the pathogenesis of metabolic syndrome in fructose-fed rats.
Collapse
Affiliation(s)
- Chu-Lin Chou
- Division of Nephrology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
- Division of Nephrology, Department of Internal Medicine, Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan
- Division of Nephrology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Heng Lin
- Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Jin-Shuen Chen
- Division of Nephrology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Te-Chao Fang
- Division of Nephrology, Department of Internal Medicine, Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan
- Division of Nephrology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
- Division of Nephrology, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
- * E-mail:
| |
Collapse
|
3
|
Chou CL, Pang CY, Lee TJF, Fang TC. Beneficial effects of calcitriol on hypertension, glucose intolerance, impairment of endothelium-dependent vascular relaxation, and visceral adiposity in fructose-fed hypertensive rats. PLoS One 2015; 10:e0119843. [PMID: 25774877 PMCID: PMC4361671 DOI: 10.1371/journal.pone.0119843] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Accepted: 02/03/2015] [Indexed: 01/23/2023] Open
Abstract
Besides regulating calcium homeostasis, the effects of vitamin D on vascular tone and metabolic disturbances remain scarce in the literature despite an increase intake with high-fructose corn syrup worldwide. We investigated the effects of calcitriol, an active form of vitamin D, on vascular relaxation, glucose tolerance, and visceral fat pads in fructose-fed rats. Male Wistar-Kyoto rats were divided into 4 groups (n = 6 per group). Group Con: standard chow diet for 8 weeks; Group Fru: high-fructose diet (60% fructose) for 8 weeks; Group Fru-HVD: high-fructose diet as Group Fru, high-dose calcitriol treatment (20 ng / 100 g body weight per day) 4 weeks after the beginning of fructose feeding; and Group Fru-LVD: high-fructose diet as Group Fru, low-dose calcitriol treatment (10 ng / 100 g body weight per day) 4 weeks after the beginning of fructose feeding. Systolic blood pressure was measured twice a week by the tail-cuff method. Blood was examined for serum ionized calcium, phosphate, creatinine, glucose, triglycerides, and total cholesterol. Intra-peritoneal glucose intolerance test, aortic vascular reactivity, the weight of visceral fat pads, adipose size, and adipose angiotensin II levels were analyzed at the end of the study. The results showed that the fructose-fed rats significantly developed hypertension, impaired glucose tolerance, heavier weight and larger adipose size of visceral fat pads, and raised adipose angiotensin II expressions compared with the control rats. High- and low-dose calcitriol reduced modestly systolic blood pressure, increased endothelium-dependent aortic relaxation, ameliorated glucose intolerance, reduced the weight and adipose size of visceral fat pads, and lowered adipose angiotensin II expressions in the fructose-fed rats. However, high-dose calcitriol treatment mildly increased serum ionized calcium levels (1.44 ± 0.05 mmol/L). These results suggest a protective role of calcitriol treatment on endothelial function, glucose tolerance, and visceral adiposity in fructose-fed rats.
Collapse
Affiliation(s)
- Chu-Lin Chou
- Institute of Medical Sciences, Tzu Chi University, Hualien, Taiwan
| | - Cheng-Yoong Pang
- Institute of Medical Sciences, Tzu Chi University, Hualien, Taiwan
| | - Tony J. F. Lee
- Institutes of Life Sciences, Pharmacology & Toxicology, and Medical Sciences, Tzu Chi University, Hualien, Taiwan
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois, United States of America
| | - Te-Chao Fang
- Division of Nephrology, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
- Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
- * E-mail:
| |
Collapse
|
4
|
Direct renin inhibitor prevents and ameliorates insulin resistance, aortic endothelial dysfunction and vascular remodeling in fructose-fed hypertensive rats. Hypertens Res 2012; 36:123-8. [PMID: 22895064 DOI: 10.1038/hr.2012.124] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor blockers can improve insulin resistance and vascular dysfunction in insulin-resistant rats; however, there are few reports on the effects of direct renin inhibitors on these conditions. We investigated the effects of a direct renin inhibitor, aliskiren, on insulin resistance, aortic endothelial dysfunction and vascular remodeling in fructose-fed hypertensive rats. Male Wistar-Kyoto rats were divided into four groups (n=6 per group) and studied for 8 weeks: Group Con: standard chow diet; group Fru: high-fructose diet (60% fructose); Group FruA: high-fructose diet with concurrent aliskiren treatment (100 mg kg(-1) per day); and Group FruB: high-fructose diet with subsequent aliskiren treatment 4 weeks later. Blood was collected for biochemical assays, and isolated rings of the thoracic aorta were obtained for analysis of vascular reactivity, vascular structure and lipid peroxide. Rats fed with high-fructose diets developed significant systolic hypertension, decreased plasma nitrite (NO(2); nitric oxide metabolite) levels and increased plasma glucose, insulin, triglyceride, total cholesterol and aortic lipid peroxide levels, and aortic wall thickness compared with control rats. Aliskiren treatment, either concurrent or subsequent, elevated plasma NO(2) levels and reduced systolic hypertension, insulin resistance, dyslipidemia, aortic lipid peroxide levels and aortic wall hypertrophy in FHR. The peak endothelium-dependent aortic relaxations were significantly higher in rats that received aliskiren treatment than in those that did not. In conclusion, our findings suggest that aliskiren prevents and ameliorates insulin resistance, aortic endothelial dysfunction and oxidative vascular remodeling in fructose-fed hypertensive rats.
Collapse
|
5
|
Chou CL, Lai YH, Lin TY, Lee TJ, Fang TC. Aliskiren prevents and ameliorates metabolic syndrome in fructose-fed rats. Arch Med Sci 2011; 7:882-8. [PMID: 22291836 PMCID: PMC3258813 DOI: 10.5114/aoms.2011.25566] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 12/02/2010] [Accepted: 12/07/2010] [Indexed: 01/01/2023] Open
Abstract
INTRODUCTION The renin-angiotensin system plays a major role in the pathogenesis of metabolic syndrome. The objective of this study was to examine the effects of aliskiren, a direct renin inhibitor, on the metabolic syndrome of fructose-fed rats. MATERIAL AND METHODS Male Sprague-Dawley rats were divided into 4 groups (n = 6 for each group). Group Con: rats were fed a standard chow diet for 8 weeks, group Fru: rats were fed a high fructose diet (60% fructose) for 8 weeks, group FruA: rats were fed a high fructose diet and were co-infused with aliskiren (100 mg/kg/day), and group FruB: rats were treated as group Fru, but aliskiren was administered 4 weeks later. Systolic blood pressure (SBP), homeostasis model assessment-insulin resistance (HOMA-IR), and blood profiles were measured. RESULTS By the end of week 4 and 8 of a high fructose diet, SBP had increased significantly from 111 ±5 to 142 ±4 and 139 ±5 mmHg (p < 0.05), respectively. A high fructose diet significantly increased HOMA-IR from baseline (6.15 ±1.59) to 21.25 ±2.08 and 21.28 ±3.1 (p < 0.05) at week 4 and 8, respectively, and significantly induced metabolic syndrome. Concurrent aliskiren treatment prevented the development of hypertension and metabolic syndrome in fructose-fed rats. When fructose-induced hypertension was established, subsequent aliskiren treatment for 4 weeks reversed the elevated SBP and ameliorated metabolic syndrome. There were no significant differences in food, water intake, urine flow or body weight gain among groups. CONCLUSIONS Aliskiren not only prevents but also ameliorates metabolic syndrome in fructose-fed rats.
Collapse
Affiliation(s)
- Chu-Lin Chou
- Institute of Medical Sciences, Medical College, Tzu-Chi University, Hualien, Taiwan
- Department of Medicine, Hualien Armed Forces General Hospital, Hualien, Taiwan
| | - Yu-Hsien Lai
- Division of Nephrology, Buddhist Tzu Chi General Hospital, Hualien, Taiwan
| | - Teng-Yi Lin
- Department of Laboratory Medicine, Buddhist Tzu Chi General Hospital, Hualien, Taiwan
| | - Tony J.F. Lee
- Institutes of Life Sciences, Pharmacology and Toxicology, and Medical Sciences, Tzu-Chi University, Hualien, Taiwan
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, USA
| | - Te-Chao Fang
- Institute of Medical Sciences, Medical College, Tzu-Chi University, Hualien, Taiwan
- Division of Nephrology, Buddhist Tzu Chi General Hospital, Hualien, Taiwan
- Department of Medicine, Medical College, Tzu Chi University, Hualien, Taiwan
- Corresponding author: Te-Chao Fang MD, PhD, Division of Nephrology Buddhist Tzu Chi General Hospital, 707, Section 3, Chung Yang Rd, Hualien 97004, Taiwan, Phone: +886-3-856-1825, ext. 2253, Fax: +886-3-856-4673. E-mail:
| |
Collapse
|
6
|
Johansson ME, Andersson IJ, Alexanderson C, Skøtt O, Holmäng A, Bergström G. Hyperinsulinemic rats are normotensive but sensitized to angiotensin II. Am J Physiol Regul Integr Comp Physiol 2008; 294:R1240-7. [DOI: 10.1152/ajpregu.00493.2007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of insulin on blood pressure (BP) is debated, and an involvement of an activated renin-angiotensin aldosterone system (RAAS) has been suggested. We studied the effect of chronic insulin infusion on telemetry BP and assessed sympathetic activity and dependence of the RAAS. Female Sprague-Dawley rats received insulin (2 units/day, INS group, n = 12) or insulin combined with losartan (30 mg·kg−1·day−1, INS+LOS group, n = 10), the angiotensin II receptor antagonist, for 6 wk. Losartan-treated (LOS group, n = 10) and untreated rats served as controls ( n = 11). We used telemetry to measure BP and heart rate (HR), and acute ganglion blockade and air-jet stress to investigate possible control of BP by the sympathetic nervous system. In addition, we used myograph technique to study vascular function ex vivo. The INS and INS+LOS groups developed euglycemic hyperinsulinemia. Insulin did not affect BP but increased HR (27 beats/min on average). Ganglion blockade reduced mean arterial pressure (MAP) similarly in all groups. Air-jet stress did not increase sympathetic reactivity but rather revealed possible blunting of the stress response in hyperinsulinemia. Chronic losartan markedly reduced 24-h-MAP in the INS+LOS group (−38 ± 1 mmHg P < 0.001) compared with the LOS group (−18 ± 1 mmHg, P ≤ 0.05). While insulin did not affect vascular function per se, losartan improved endothelial function in the aorta of insulin-treated rats. Our results raise doubt regarding the role of hyperinsulinemia in hypertension. Moreover, we found no evidence that insulin affects sympathetic nervous system activity. However, chronic losartan treatment revealed an important interaction between insulin and RAAS in BP control.
Collapse
|
7
|
Muntzel MS, Crespo R, Joseph T, Onwumere O. Dietary salt loading exacerbates the increase in sympathetic nerve activity caused by intravenous insulin infusion in rats. Metabolism 2007; 56:373-9. [PMID: 17292726 DOI: 10.1016/j.metabol.2006.10.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2006] [Accepted: 10/09/2006] [Indexed: 11/22/2022]
Abstract
Obesity and type 2 diabetes mellitus frequently produce chronic elevations in blood insulin levels. Importantly, hyperinsulinemia stimulates increases in sympathetic nerve activity that may predispose to hypertension, atherosclerosis, and end-organ damage. Because depletion of dietary salt (NaCl) increases angiotensin II levels, which has been shown to enhance sympathetic responses to excitatory stimuli such as thermal stimulation and bicuculline in the hypothalamus, we predicted that insulin-induced elevations in lumbar sympathetic activity would be augmented by low NaCl and suppressed by high dietary NaCl. Adult male Sprague-Dawley rats were randomized into groups receiving low (0.0 mEq/d, n = 10), normal (2.0 mEq/d, n = 10), and high (5.7 mEq/d, n = 10) NaCl for a period of 8 days. After this, the animals were anesthetized for measurement of heart rate, mean arterial pressure, and lumbar sympathetic nerve activity during 110 minutes of intravenous insulin infusion (15 mU/kg per minute) with euglycemic clamp. Insulin administration caused modest blood pressure decreases accompanied by heart rate increases that were similar across the 3 dietary groups. Unexpectedly, sympathetic increases to insulin were lowest in the low-NaCl group (100%-135% +/- 24%), moderate in the normal-NaCl group (100%-170% +/- 23%), and greatest in the high-NaCl group (100%-252% +/- 39%). Dietary NaCl level did not affect baseline blood glucose or insulin sensitivity as assessed by euglycemic clamp. These findings indicate that dietary salt loading exacerbates the lumbar sympathoexcitatory response to intravenous insulin infusion in rats.
Collapse
Affiliation(s)
- Martin S Muntzel
- Department of Biological Sciences, Lehman College, Bronx, NY 10468-1589, USA.
| | | | | | | |
Collapse
|
8
|
Perlstein TS, Gerhard-Herman M, Hollenberg NK, Williams GH, Thomas A. Insulin Induces Renal Vasodilation, Increases Plasma Renin Activity, and Sensitizes the Renal Vasculature to Angiotensin Receptor Blockade in Healthy Subjects. J Am Soc Nephrol 2007; 18:944-51. [PMID: 17287426 DOI: 10.1681/asn.2006091026] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Insulin stimulates the renin-angiotensin system and induces renal vasodilation. The relationship between these opposing influences of insulin on renal vascular tone has not been explored. A hyperinsulinemic euglycemic clamp and sham insulin clamp each of 270 min duration were performed in 15 healthy individuals during high sodium balance. An angiotensin receptor blocker was administered at time 180 min. Renal plasma flow and plasma renin activity were measured serially. The response to insulin or sham insulin infusion was defined as the change from time 0 to 180 min; the response to angiotensin receptor blockade (ARB) was defined as the change from time 180 to 270 min. Insulin infusion increased plasma renin activity (P < 0.01) and renal plasma flow (P < 0.01); the latter effect plateaued by time 150 min. ARB caused a greater vasodilator response during insulin infusion compared with during sham insulin infusion (P = 0.02). Increasing renin response to insulin predicted blunting of the renal vasodilator response to insulin infusion (R(2) = 0.36, P = 0.02) and sensitizing of the renal vasodilator response to ARB during insulin infusion (R(2) = 0.59, P < 0.01). Insulin-induced activation of the renin-angiotensin system modulates insulin-induced renal vasodilation in healthy individuals. Further studies are warranted to address this balance in states of insulin resistance and the possible implications for the association of insulin resistance with risk for chronic kidney disease.
Collapse
Affiliation(s)
- Todd S Perlstein
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | | | | | | | | |
Collapse
|
9
|
Villafaña S, Huang F, Hong E. Role of the sympathetic and renin angiotensin systems in the glucose-induced increase of blood pressure in rats. Eur J Pharmacol 2005; 506:143-50. [PMID: 15588734 DOI: 10.1016/j.ejphar.2004.10.055] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2004] [Accepted: 10/18/2004] [Indexed: 10/26/2022]
Abstract
The pressor effect induced by acute hyperglycemia is not well understood, therefore, it was of interest to study the effect of intravenous glucose infusion on the mean arterial pressure of anesthetized Wistar rats. Animals received glucose (100 mg/kg/min, i.v.), mannitol or saline during 30 min, but only glucose increased the mean arterial pressure (about 40 mm Hg), plasma glucose, insulin and nitric oxide (NO). Pretreatment with reserpine or indorenate (a central antihypertensive) inhibited completely the pressor effect of glucose. Reserpine also decreased the plasma NO levels. Pretreatment with ramipril or with streptozotocin decreased the late phase of the glucose-induced pressor response and the NO levels, the latter treatment also abolishes insulin plasma concentrations. The present results suggest that the pressor effect induced by glucose has an early phase due to an increase of efferent sympathetic discharges and a delayed phase produced by the activation of the renin angiotensin system.
Collapse
Affiliation(s)
- Santiago Villafaña
- Departamento de Farmacobiología, CINVESTAV-I.P.N., Calzada de los tenorios 235, Col. Granjas Coapa, Deleg. Tlalpan, México, D.F., C.P. 14330, Mexico
| | | | | |
Collapse
|
10
|
Muntzel MS, Joseph T, Onwumere O. Effect of insulin-induced hypokalemia on lumbar sympathetic nerve activity in anesthetized rats. J Hypertens 2004; 22:1755-60. [PMID: 15311104 DOI: 10.1097/00004872-200409000-00020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Acute euglycemic hyperinsulinemia produces sympathoexcitation and a profound fall in plasma potassium levels. Because hypokalemia may activate the renin-angiotensin system to produce the observed increases in sympathetic nerve activity (SNA), the present study was designed to determine whether acute euglycemic-hyperinsulinemia in rats causes decreases in plasma potassium accompanied by increases in plasma renin activity (PRA) as well as elevations in SNA, and whether these alterations would be prevented by maintaining normokalemia with an exogenous potassium infusion. METHODS We infused vehicle (control; n = 10) or insulin (10 mU/min) in anesthetized untreated rats (insulin; n = 11), or in rats receiving simultaneous KCl infusion (Insulin + K+; n = 10), while measuring mean arterial pressure (MAP), heart rate (HR), SNA, plasma potassium, and PRA during euglycemic clamp. RESULTS As expected, insulin rats had a large fall in plasma potassium (4.6 +/- 0.1 to 3.9 +/- 0.1 mEq/l), contrasting with no change in the control (4.8 +/- 0.2 to 4.8 +/- 0.2 mEq/l) and insulin + K+ (4.4 +/- 0.1 to 4.6 +/- 0.2 mEq/l) groups. However, PRA levels at study completion were not different in the three experimental groups. In addition, insulin rats had large increases in lumbar SNA (194 +/- 11% from 100% baseline) compared with modest elevations in control rats (122 +/- 10%), and prevention of hypokalemia failed to affect sympathetic increases (213 +/- 20%) in insulin + K+ rats. MAP and HR did not change in any of the experimental groups. CONCLUSIONS These findings indicate that insulin per se, rather than insulin-induced hypokalemia or hormonal and compensatory adjustments secondary to hypokalemia, is the main mechanism that triggers increases in lumbar SNA.
Collapse
Affiliation(s)
- Martin S Muntzel
- Department of Biological Sciences, Lehman College, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589, USA.
| | | | | |
Collapse
|
11
|
Ghatta S, Ramarao P. Increased contractile responses to 5-Hydroxytryptamine and Angiotensin II in high fat diet fed rat thoracic aorta. Lipids Health Dis 2004; 3:19. [PMID: 15287987 PMCID: PMC509282 DOI: 10.1186/1476-511x-3-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Accepted: 08/02/2004] [Indexed: 11/23/2022] Open
Abstract
Background Feeding normal rats with high dietary levels of saturated fat leads to pathological conditions, which are quite similar to syndrome X in humans. These conditions such as hypertriglyceridemia, hypercholesterolemia, obesity, and hyperglycemia might induce hypertension through various mechanisms. Metabolic syndrome and the resulting NIDDM represent a major clinical challenge because implementation of treatment strategies is difficult. Vascular abnormalities probably contribute to the etiology of many diabetic complications including nephropathy, neuropathy, retinopathy, and cardiomyopathy. It has been shown that in Streptozotocin induced diabetic animals there is an increase in maximal responses to 5-Hydroxytryptamine and Angiotensin II. The purpose of this study was to evaluate High fat diet fed rats for the development of hypertriglyceridemia, hypercholesterolemia, hyperinsulinemia and hyperglycemia and to assess their vascular responses to 5-Hydroxytryptamine and Angiotensin II. Methods Male Sprague Dawley rats were used for this study and were divided into two equal groups. One of the groups was fed with normal pellet diet and they served as the control group, whereas the other group was on a high fat diet for 4 weeks. Body weight, plasma triglycerides, plasma cholesterol, and plasma glucose were measured every week. Intraperitoneal glucose tolerance test was performed after 4 weeks of feeding. At the end of fourth week of high fat diet feeding, thoracic aortae were removed, and cut into helical strips for vascular reactivity studies. Dose-response curves of 5-Hydroxytryptamine and Angiotensin II were obtained. Results There was no significant difference in pD2, with 5-Hydroxytryptamine and Angiotensin II in both groups but Emax was increased. Conclusions These results suggest that hypertension in high fat diet rats is associated with increased in vitro vascular reactivity to 5-HT and Ang II.
Collapse
Affiliation(s)
- Srinivas Ghatta
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota 58105, USA
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research, Sector 67, Phase-X, S.A.S. Nagar 160 062, Punjab, India
| | - Poduri Ramarao
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research, Sector 67, Phase-X, S.A.S. Nagar 160 062, Punjab, India
| |
Collapse
|
12
|
Roysommuti S, Mozaffari MS, Wyss JM. Insulin-exacerbated hypertension in captopril-treated spontaneously hypertensive rats: role of sympathoexcitation. Can J Physiol Pharmacol 2003; 81:1036-41. [PMID: 14719038 DOI: 10.1139/y03-095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin excess exacerbates hypertension in spontaneously hypertensive rats (SHR). This study examined the relative contribution of the reninangiotensin system and the sympathetic nervous system in this phenomenon. In SHR, daily subcutaneous injections of insulin were initiated either before short-term angiotensin-converting enzyme inhibition with captopril or after lifetime captopril treatment. Insulin treatment resulted in significant increases in mean arterial pressure and heart rate and captopril treatment lowered arterial pressure, but captopril did not lower arterial pressure more in the insulin-treated compared with control rats. To test the contribution of the sympathetic nervous system to this form of hypertension, each rat was intravenously infused with either a ganglionic blocker (i.e., hexamethonium) or a centrally acting α2-adrenergic receptor agonist (i.e., clonidine). Administration of either agent largely eliminated the differences in mean arterial pressure and heart rate between the insulin-treated and saline-treated SHR, irrespective of captopril treatment. These data indicate that in SHR, the ability of insulin to increase blood pressure is closely related to sympathoexcitation, which is unresponsive to blockade of angiotensin-converting enzyme.Key words: blood pressure, insulin, captorpil, hexamethonium, clonidine, rat.
Collapse
Affiliation(s)
- Sanya Roysommuti
- Department of Cell Biology, University of Alabama at Birmingham, 35294-0006, USA
| | | | | |
Collapse
|
13
|
Muntzel MS, Malena H, Drüeke T. Inhibition of nitric oxide synthesis attenuates insulin-mediated sympathetic activation in rats. J Hypertens 2001; 19:1625-31. [PMID: 11564983 DOI: 10.1097/00004872-200109000-00015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
BACKGROUND AND OBJECTIVES Infusion of insulin produces sympathoexcitation, nitric oxide (NO) generation and NO-mediated vasodilation. Because central nervous system NO may inhibit sympathetic outflow, the present study was designed to determine whether NO synthase blockade would enhance insulin-mediated sympathetic activation. We additionally aimed to determine whether augmented sympathoexcitation and reduced NO-mediated vasodilation, during combined NO synthase blockade and hyperinsulinemia, would result in a blood pressure increase. DESIGN AND METHODS We infused vehicle (Control; n = 7) or insulin (10 mU/min) in anaesthetized rats receiving either no pretreatment (Insulin; n = 7) or after pretreatment with the NO blocker, NG-monomethyl-L-arginine (L-NMMA-insulin; 0.25 mg/kg per min; n = 7), while measuring mean arterial pressure (MAP), heart rate and lumbar sympathetic nerve activity (SNA) during euglycemic clamp. An additional control group received L-NMMA (L-NMMA; n = 7). RESULTS Insulin rats had large SNA increases (190 +/- 22% from 100% baseline), contrasting with small increases in the Control (136 +/- 10%) and L-NMMA (135 +/- 20%) groups. Unexpectedly, NO blockade abolished insulin-induced SNA increases in the L-NMMA-insulin group (96 +/- 12%). In agreement with the SNA findings, Insulin rats had heart rate increases while no heart rate changes were observed in the L-NMMA-insulin, Control, or L-NMMA groups. In addition, there was an unexpected was a lack of MAP increase in L-NMMA-insulin rats. MAP also did not change in the Control, L-NMMA or Insulin groups. CONCLUSIONS These findings suggest that NO is necessary for insulin to exert its sympathoexcitatory effects, and that insulin-induced NO release may play a role in activating increases in lumbar SNA.
Collapse
Affiliation(s)
- M S Muntzel
- Department of Biological Sciences, Lehman College, Bronx, New York 10468, USA.
| | | | | |
Collapse
|
14
|
Ter Maaten JC, Bakker SJ, Serné EH, Moshage HJ, Donker AJ, Gans RO. Insulin-mediated increases in renal plasma flow are impaired in insulin-resistant normal subjects. Eur J Clin Invest 2000; 30:1090-8. [PMID: 11122324 DOI: 10.1046/j.1365-2362.2000.00749.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
BACKGROUND Impaired vasodilatation in skeletal muscle is a possible mechanism linking insulin resistance to blood pressure regulation. Increased renal vascular resistance has been demonstrated in the offspring of essential hypertensives. We assessed whether insulin-mediated renal vasodilatation is impaired in insulin-resistant normal subjects. DESIGN In two groups of 10 insulin-resistant and 10 insulin-sensitive normal subjects, we compared the effects of sequential physiological and supraphysiological insulin dosages (50 and 150 mU kg(-1) h(-1)) on renal plasma flow (RPF) and leg blood flow using the euglycaemic clamp technique, 131I-labelled Hippuran clearances and venous occlusion plethysmography. Time-control experiments were performed in the same subjects. RESULTS Whole-body glucose uptake amounted to 4.9 +/- 2.1 and 11.0 +/- 2.4 mg kg(-1) min(-1) in the insulin-resistant and to 12.7 +/- 2.3 and 17.4 +/- 2.6 mg kg(-1) min(-1) in the insulin-sensitive subjects during physiological and supraphysiological hyperinsulinaemia, respectively. RPF increased more in insulin-sensitive compared to insulin-resistant subjects during physiological hyperinsulinaemia (13.7 vs. 6.8%, P < 0.05). RPF increased to comparable levels during supraphysiological hyperinsulinaemia. Insulin-mediated changes in leg blood flow did not differ between groups. In the combined group, we found a positive correlation between insulin-mediated glucose uptake and changes in RPF during physiological hyperinsulinaemia (r = 0.57, P = 0.009), whereas insulin-mediated glucose uptake correlated with changes in leg blood flow during supraphysiological hyperinsulinaemia (r = 0.54. P = 0.017). CONCLUSIONS Our results suggest that the sensitivities of the skeletal muscle and renal vascular bed differ for insulin's vasodilatory action. Insulin-mediated increases in RPF are impaired in insulin-resistant but otherwise normal subjects during physiological hyperinsulinaemia.
Collapse
Affiliation(s)
- J C Ter Maaten
- University Hospital Groningen, Groningen, The Netherlands.
| | | | | | | | | | | |
Collapse
|
15
|
Katovich MJ, Pachori A. Effects of inhibition of the renin-angiotensin system on the cardiovascular actions of insulin. Diabetes Obes Metab 2000; 2:3-14. [PMID: 11220351 DOI: 10.1046/j.1463-1326.2000.00044.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- M J Katovich
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville 32610, USA.
| | | |
Collapse
|
16
|
Muntzel MS. Insulin-mediated sympathoexcitation in obesity and type 2 diabetes. Nephrol Dial Transplant 1999; 14:2282-5. [PMID: 10528643 DOI: 10.1093/ndt/14.10.2282] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|