Role of angiotensin II and oxidative stress in vascular insulin resistance linked to hypertension.
Insulin activation of the phosphatidylinositol 3-kinase (PI3K) pathway stimulates glucose uptake in peripheral tissues and synthesis of nitric oxide (NO) in the endothelium. Insulin resistance (IR) and hypertension frequently coexist, particularly among individuals with salt-sensitive hypertension. The mechanisms underlying this association are poorly understood. We investigated these mechanisms in a model of salt-sensitive hypertension in which we have previously shown that endothelial dysfunction is mediated by superoxide anion (O(2)(-)) linked to local ANG II. Dahl salt-sensitive rats were fed, for 6 wk, a normal salt diet (NS; 0.5% NaCl), high-salt diet (HS; 4% NaCl), HS plus the ANG II type 1 receptor (AT(1)R) blocker (ARB) candesartan (10 mg.kg(-1).day(-1)), or HS plus the antioxidant tempol (172 mg/l in drinking water). Hypertensive (mean arterial pressure: 145 +/- 4 vs. 102 +/- 5 mmHg in NS, P < 0.05) rats manifested increased aortic AT(1)R mRNA (210%) and protein (101%) expression and O(2)(-) production (104%) and impaired endothelium-dependent relaxation (EDR) to acetylcholine [maximal response (E(max)): 68 +/- 9 vs. 91 +/- 8% in NS, P < 0.05]. ARB or tempol normalized O(2)(-) and EDR despite that they did not normalize mean arterial pressure, which was reduced only 25%. Hypertensive rats manifested metabolic IR (36% reduction in the glucose infusion rate by insulin clamp), impaired NO-mediated insulin-induced EDR (E(max): 12 +/- 5 vs. 32 +/- 4% in NS, P < 0.05), and impaired insulin activation of PI3K/endothelial NO synthase. ARB or tempol improved insulin-mediated EDR, PI3K, Akt/ endothelial NO synthase phosphorylation, and metabolic IR (all P < 0.05). This study provides insight into the mechanisms that underlie the association between metabolic and hypertensive cardiovascular diseases and support the notion that O(2)(-) overproduction linked to tissue ANG II interferes with shared insulin signaling pathways in metabolic and cardiovascular tissues.
Zhou
Ming-Sheng
MS
Nephrology-Hypertension Sect., Veterans Affairs Medical Center, and Vascular Biology Institute, Miller School of Medicine, Univ. of Miami, 1201 NW 16th St., Rm. A-1009, Miami, FL 33125, USA. mzhou2@med.miami.edu
Schulman
Ivonne Hernandez
IH
Raij
Leopoldo
L
D000109:Acetylcholine / Q000494:pharmacology; D000804:Angiotensin II / Q000378:metabolism*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001562:Benzimidazoles / Q000494:pharmacology; D001713:Biphenyl Compounds; D001794:Blood Pressure; D001835:Body Weight; D002097:C-Reactive Protein / Q000378:metabolism; D003497:Cyclic N-Oxides / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D006973:Hypertension / Q000188:drug therapy / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020303:Rats, Inbred Dahl; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D044139:Receptor, Angiotensin, Type 2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D017673:Sodium Chloride, Dietary; D013113:Spin Labels; D013482:Superoxide Dismutase / Q000378:metabolism; D013777:Tetrazoles / Q000494:pharmacology; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology
D000109:Acetylcholine; D000804:Angiotensin II; D047228:Angiotensin II Type 1 Receptor Blockers; D000975:Antioxidants; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D002097:C-Reactive Protein; D003497:Cyclic N-Oxides; D007328:Insulin; D048031:JNK Mitogen-Activated Protein Kinases; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D017673:Sodium Chloride, Dietary; D013113:Spin Labels; D013482:Superoxide Dismutase; D013777:Tetrazoles; D014665:Vasodilator Agents; C496316:Nos3 protein, rat; C081643:candesartan; C001803:tempol