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Rodriguez R, Minas JN, Vazquez-Medina JP, Nakano D, Parkes DG, Nishiyama A, Ortiz RM. Chronic AT1 blockade improves glucose homeostasis in obese OLETF rats. J Endocrinol 2018; 237:271-284. [PMID: 29643115 PMCID: PMC5945211 DOI: 10.1530/joe-17-0678] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 04/11/2018] [Indexed: 12/17/2022]
Abstract
Obesity is associated with the inappropriate activation of the renin-angiotensin system (RAS), which increases arterial pressure, impairs insulin secretion and decreases peripheral tissue insulin sensitivity. RAS blockade reverses these detriments; however, it is not clear whether the disease state of the organism and treatment duration determine the beneficial effects of RAS inhibition on insulin secretion and insulin sensitivity. Therefore, the objective of this study was to compare the benefits of acute vs chronic angiotensin receptor type 1 (AT1) blockade started after the onset of obesity, hyperglycemia and hypertension on pancreatic function and peripheral insulin resistance. We assessed adipocyte morphology, glucose intolerance, pancreatic redox balance and insulin secretion after 2 and 11 weeks of AT1 blockade in the following groups of rats: (1) untreated Long-Evans Tokushima Otsuka (lean control; n = 10), (2) untreated Otsuka Long-Evans Tokushima Fatty (OLETF; n = 12) and (3) OLETF + ARB (ARB; 10 mg olmesartan/kg/day by oral gavage; n = 12). Regardless of treatment duration, AT1 blockade decreased systolic blood pressure and fasting plasma triglycerides, whereas chronic AT1 blockade decreased fasting plasma glucose, glucose intolerance and the relative abundance of large adipocytes by 22, 36 and 70%, respectively. AT1 blockade, however, did not improve pancreatic oxidative stress or reverse impaired insulin secretion. Collectively, these data show that AT1 blockade after the onset of obesity, hyperglycemia and hypertension improves peripheral tissue insulin sensitivity, but cannot completely reverse the metabolic derangement characterized by impaired insulin secretion once it has been compromised.
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Affiliation(s)
- Ruben Rodriguez
- Department of Molecular & Cellular BiologyUniversity of California, Merced, California, USA
| | - Jacqueline N Minas
- Department of Molecular & Cellular BiologyUniversity of California, Merced, California, USA
| | | | - Daisuke Nakano
- Department of PharmacologyKagawa University Medical School, Kagawa, Japan
| | | | - Akira Nishiyama
- Department of PharmacologyKagawa University Medical School, Kagawa, Japan
| | - Rudy M Ortiz
- Department of Molecular & Cellular BiologyUniversity of California, Merced, California, USA
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Minas JN, Thorwald MA, Conte D, Vázquez-Medina JP, Nishiyama A, Ortiz RM. Angiotensin and mineralocorticoid receptor antagonism attenuates cardiac oxidative stress in angiotensin II-infused rats. Clin Exp Pharmacol Physiol 2016; 42:1178-88. [PMID: 26234762 DOI: 10.1111/1440-1681.12473] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 06/30/2015] [Accepted: 06/30/2015] [Indexed: 11/30/2022]
Abstract
Angiotensin II (Ang II) and aldosterone contribute to hypertension, oxidative stress and cardiovascular damage, but the contributions of aldosterone during Ang II-dependent hypertension are not well defined because of the difficulty to assess each independently. To test the hypothesis that during Ang II infusion, oxidative and nitrosative damage is mediated through both the mineralocorticoid receptor (MR) and angiotensin type 1 receptor (AT1), five groups of Sprague-Dawley rats were studied: (i) control; (ii) Ang II infused (80 ng/min × 28 days); (iii) Ang II + AT1 receptor blocker (ARB; 10 mg losartan/kg per day × 21 days); (iv) Ang II + mineralocorticoid receptor (MR) antagonist (Epl; 100 mg eplerenone/day × 21 days); and (v) Ang II + ARB + Epl (Combo; × 21 days). Both ARB and combination treatments completely alleviated the Ang II-induced hypertension, whereas eplerenone treatment only prolonged the onset of the hypertension. Eplerenone treatment exacerbated the Ang II-mediated increase in plasma and heart aldosterone 2.3- and 1.8-fold, respectively, while ARB treatment reduced both. Chronic MR blockade was sufficient to ameliorate the AT1-mediated increase in oxidative damage. All treatments normalized protein oxidation (nitrotyrosine) levels; however, only ARB and Combo treatments completely reduced lipid peroxidation (4-hydroxynonenal) to control levels. Collectively, these data suggest that receptor signalling, and not the elevated arterial blood pressure, is the principal culprit in the oxidative stress-associated cardiovascular damage in Ang II-dependent hypertension.
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Affiliation(s)
- Jacqueline N Minas
- Molecular Cell Biology, School of Natural Sciences, University of California, Merced, CA, USA
| | - Max A Thorwald
- Molecular Cell Biology, School of Natural Sciences, University of California, Merced, CA, USA
| | - Debra Conte
- Molecular Cell Biology, School of Natural Sciences, University of California, Merced, CA, USA
| | | | - Akira Nishiyama
- Department of Pharmacology, Kagawa Medical University, Kagawa, Japan
| | - Rudy M Ortiz
- Molecular Cell Biology, School of Natural Sciences, University of California, Merced, CA, USA
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Abstract
The development of the immunoblot to detect and characterize a protein with an antisera, even in a crude mixture, was a breakthrough with wide-ranging and unpredictable applications across physiology and medicine. Initially, this technique was viewed as a tool for qualitative, not quantitative, analyses of proteins because of the high number of variables between sample preparation and detection with antibodies. Nonetheless, as the immunoblot method was streamlined and improved, investigators pushed it to quantitate protein abundance in unpurified samples as a function of treatment, genotype, or pathology. This short review, geared at investigators, reviewers, and critical readers, presents a set of issues that are of critical importance for quantitative analysis of protein abundance: 1) Consider whether tissue samples are of equivalent integrity and assess how handling between collection and assay influences the apparent relative abundance. 2) Establish the specificity of the antiserum for the protein of interest by providing clear images, molecular weight markers, positive and negative controls, and vendor details. 3) Provide convincing evidence for linearity of the detection system by assessing signal density as a function of sample loaded. 4) Recognize that loading control proteins are rarely in the same linear range of detection as the protein of interest; consider protein staining of the gel or blot. In summary, with careful attention to sample integrity, antibody specificity, linearity of the detection system, and acceptable loading controls, investigators can implement quantitative immunoblots to convincingly assess protein abundance in their samples.
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Affiliation(s)
- Alicia A McDonough
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California; and
| | - Luciana C Veiras
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California; and
| | - Jacqueline N Minas
- School of Natural Sciences, University of California, Merced, California
| | - Donna Lee Ralph
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California; and
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Minas JN, Rodriguez R, Awayda MS, Ortiz RM. High fat diet contributes to improper kidney AT1 activation and impaired sodium regulation through ENaC cleavage in a model of insulin resistance. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.lb864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Ruben Rodriguez
- School of Natural SciencesUniversity of California, MercedMercedCA
| | - Mouhamed S. Awayda
- Department of Physiology and BiophysicsState University of New York at BuffaloBuffaloNY
| | - Rudy M. Ortiz
- School of Natural SciencesUniversity of California, MercedMercedCA
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Araiza DN, Minas JN, Rodriguez R, Nakano D, Nishiyama A, Ortiz RM. Adipose Angiotensinogen is Upregulated during Insulin Resistance in OLETF Rats. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.1183.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Rodriguez R, Viscarra JA, Minas JN, Lee A, Nakano D, Nishiyama A, Ortiz RM. Decreased Pancreatic Insulin Secretion is associated with increased AT1 Activation during Glucose Supplementation in a Model of Metabolic Syndrome. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.713.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Ruben Rodriguez
- School of Natural SciencesUniversity of California MercedMercedCA
| | - Jose A. Viscarra
- School of Natural SciencesUniversity of California MercedMercedCA
| | | | - Andrew Lee
- School of Natural SciencesUniversity of California MercedMercedCA
| | - Daisuke Nakano
- Department of PharmacologyKagawa University Medical SchoolKagawaJapan
| | - Akira Nishiyama
- Department of PharmacologyKagawa University Medical SchoolKagawaJapan
| | - Rudy M. Ortiz
- School of Natural SciencesUniversity of California MercedMercedCA
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Rodriguez R, Viscarra JA, Minas JN, Nakano D, Nishiyama A, Ortiz RM. Angiotensin receptor blockade increases pancreatic insulin secretion and decreases glucose intolerance during glucose supplementation in a model of metabolic syndrome. Endocrinology 2012; 153:1684-95. [PMID: 22355070 PMCID: PMC3320242 DOI: 10.1210/en.2011-1885] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Renin-angiotensin system blockade improves glucose intolerance and insulin resistance, which contribute to the development of metabolic syndrome. However, the contribution of impaired insulin secretion to the pathogenesis of metabolic syndrome is not well defined. To assess the contributions of angiotensin receptor type 1 (AT₁) activation and high glucose intake on pancreatic function and their effects on insulin signaling in skeletal muscle and adipose tissue, an oral glucose tolerance test (oGTT) was performed in five groups (n = 10/group) of rats: 1) lean strain-control 2) obese Otsuka Long-Evans Tokushima Fatty (OLETF), 3) OLETF + angiotensin receptor blocker (ARB; 10 mg/kg · d olmesartan for 6 wk; OLETF ARB), 4) OLETF + 5% glucose water (HG) for 6 wk (OLETF HG), and 5) OLETF + HG + ARB (OLETF HG/ARB). The glucose response to the oGTT increased 58% in OLETF compared with lean-strain control, whereas glucose supplementation increased it an additional 26%. Blockade of angiotensin receptor reduced the oGTT response 19% in the ARB-treated groups and increased pancreatic insulin secretion 64 and 113% in OLETF ARB and OLETF HG/ARB, respectively. ARB treatment in OLETF ARB and OLETF HG/ARB did not have an effect on insulin signaling proteins in skeletal muscle; however, it reduced pancreatic AT₁ protein expression 20 and 27%, increased pancreatic glucagon-like peptide-1 (GLP-1) receptor protein expression 41 and 88%, respectively, and increased fasting plasma GLP-1 approximately 2.5-fold in OLETF ARB. The results suggest that improvement of glucose intolerance is independent of an improvement in muscle insulin signaling, but rather by improved glucose-stimulated insulin secretion associated with decreased pancreatic AT₁ activation and increased GLP-1 signaling.
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MESH Headings
- Adipose Tissue/drug effects
- Adipose Tissue/metabolism
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Animals
- Blood Pressure/drug effects
- Dietary Supplements
- Disease Models, Animal
- Glucagon-Like Peptide-1 Receptor
- Glucose/administration & dosage
- Glucose/pharmacology
- Glucose Intolerance/metabolism
- Glucose Intolerance/prevention & control
- Insulin/metabolism
- Leptin/blood
- Male
- Metabolic Syndrome/metabolism
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Pancreas/metabolism
- Rats
- Rats, Inbred OLETF
- Rats, Inbred Strains
- Receptor, Angiotensin, Type 1/drug effects
- Receptor, Angiotensin, Type 1/metabolism
- Receptors, Glucagon/metabolism
- Triglycerides/blood
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Affiliation(s)
- Ruben Rodriguez
- School of Natural Sciences, University of California, Merced, 5200 North Lake Road, Merced, California 95343, USA
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Sood J, Balayan S, Minas JN, Rodriguez R, Aguil J, Nakano D, Nishiyama A, Awayda MS, Ortiz R. Enriched Cholesterol Diet Increases Expression of Renal Epithelial Na+ Channel Gamma Subunit in Rats. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.867.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jessica Sood
- Department of Natural SciencesUniversity of California MercedCA
| | - Shaina Balayan
- Department of Natural SciencesUniversity of California MercedCA
| | | | - Ruben Rodriguez
- Department of Natural SciencesUniversity of California MercedCA
| | - Jennifer Aguil
- Department of Natural SciencesUniversity of California MercedCA
| | - Daisuke Nakano
- Department of PharmacologyKagawa Medical UniversityKagawaJapan
| | - Akira Nishiyama
- Department of PharmacologyKagawa Medical UniversityKagawaJapan
| | - Mouhamed S. Awayda
- Department of Physiology and BiophysicsState University of New YorkBuffaloNY
| | - Rudy Ortiz
- Department of Natural SciencesUniversity of California MercedCA
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