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)kappa B. Here we investigated whether Ang II activation of NF kappa B 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 NF kappa B inhibitor PDTC (150 mg/kg in drinking water). Results: DS rats manifested an increase in soleus muscle Ang II content, ROS production and phosopho-I kappa Ba/I kappa Ba ratio, ARB or tempol reduced ROS and phospho-I kappa Ba/I kappa Ba 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 NF kappa B SN50 (a specific peptide inhibitor of NF kappa B) ex vivo reversed changes in hypertension-induced gene expression. Conclusion: The current findings strongly suggest that the activation of NF kappa B inflammatory pathway by Ang II play a critical role in skeletal muscle insulin resistance in salt-sensitive hypertension.