Skeletal muscle insulin resistance in salt-sensitive hypertension: role of angiotensin II activation of NFκB.
BACKGROUND
We have previously shown that in hypertensive Dahl salt-sensitive (DS) rats, impaired endothelium-dependent relaxation to acetylcholine and to insulin is mechanistically linked to up-regulation of angiotensin (Ang) II actions and the production of reactive oxygen species (ROS) and to activation of the proinflammatory transcription factor (NF)κB. Here we investigated whether Ang II activation of NFκB contributed to insulin resistance in the skeletal muscle of this animal model.


METHODS
DS rats were fed either a normal (NS, 0.5% NaCl) or high (HS, 4% NaCl) salt diet for 6 weeks. In addition, 3 separate groups of HS rats were given angiotensin receptor 1 blocker candesartan (ARB, 10 mg/kg/day in drinking water), antioxidant tempol (1 mmol/L in drinking water) or NFκB inhibitor PDTC (150 mg/kg in drinking water).


RESULTS
DS rats manifested an increase in soleus muscle Ang II content, ROS production and phosopho-IκBα/IκBα ratio, ARB or tempol reduced ROS and phospho-IκBα/IκBα ratio. Hypertensive DS rats also manifested a reduction in glucose infusion rate, impaired insulin-induced Akt phosphorylation and Glut-4 translocation in the soleus muscle, which were prevented with treatment of either ARB, tempol, or PDTC. Data from the rat diabetes signaling pathway PCR array showed that 8 genes among 84 target genes were altered in the muscle of hypertensive rats with the increase in gene expression of ACE1 and 5 proinflammatory genes, and decrease of 2 glucose metabolic genes. Incubation of the muscle with NFκB SN50 (a specific peptide inhibitor of NFκB) ex vivo reversed changes in hypertension-induced gene expression.


CONCLUSIONS
The current findings strongly suggest that the activation of NFκB inflammatory pathway by Ang II play a critical role in skeletal muscle insulin resistance in salt-sensitive hypertension.
Department of Physiology, Liaoning Medical University, Jinzhou, China. zhoums1963@163.com.|Hypertension/Nephrology Section, Miami VA Medical Center, Miami, FL, USA. zhoums1963@163.com.
Ming-Sheng
MS
Zhou
Department of Endocrinology, Liaoning Medical University, Jinzhou, China. liuchang1971@163.com.
Chang
C
Liu
Hypertension/Nephrology Section, Miami VA Medical Center, Miami, FL, USA. Tianrx@yahoo.com.
Runxia
R
Tian
Department of Pharmacology, Kagawa University School of Medicine, Kagawa, Japan. Akira@kms.ac.jp.
Akira
A
Nishiyama
Hypertension/Nephrology Section, Miami VA Medical Center, Miami, FL, USA. LRaij@med.miami.edu.|Hypertension/Nephrology section, Vascular Biology Institute, University of Miami Miller School of Medicine, Miami, FL, USA. LRaij@med.miami.edu.
Leopoldo
L
Raij
D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D006973:Hypertension / Q000139:chemically induced / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D051381:Rats; D020303:Rats, Inbred Dahl; D017207:Rats, Sprague-Dawley; D017673:Sodium Chloride, Dietary / Q000633:toxicity*
D016328:NF-kappa B; D017673:Sodium Chloride, Dietary; D000804:Angiotensin II