Effects of Intracerebroventricularly (ICV) Injected Ghrelin on Cardiac Inducible Nitric Oxide Synthase Activity/Expression in Obese Rats

The aim of this study was to examine the effects of ghrelin on regulation of cardiac inducible nitric oxide synthase (iNOS) activity/expression in high fat (HF), obese rats. For this study, male Wistar rats fed with HF diet (30 % fat) for 4 weeks were injected every 24 h for 5 days intracerebroventriculary (ICV) with ghrelin (0.3 nmol/5 mu l) or with an equal volume of phosphate buffered saline (PBS). Control rats were ICV injected with an equal volume of PBS. Glucose, insulin and nitric oxide (NO) concentrations were measured in serum, while arginase activity and citrulline concentrations were measured in heart lysate. Protein iNOS and regulatory subunit of nuclear factor-kappa B (NF kappa B-p65), phosphorylation of enzymes protein kinase B (Akt) at Ser(473), and extracellular signal-regulated kinases 1/2 (ERK1/2) at Tyr(202)/Tyr(204) were determined in heart lysate by Western blot. For gene expression of iNOS qRT-PCR was used. Results show significantly (p < 0.01) higher serum NO production in ghrelin treated HF rats compared with HF rats. Ghrelin significantly reduced citrulline concentration (p < 0.05) and arginase activity (p < 0.01) in HF rats. In ghrelin treated HF rats, gene and protein expression of iNOS and NF kappa B-p65 levels were significantly (p < 0.05) increased compared with HF rats. Increased phosphorylation of Akt (p < 0.01) and decreased (p < 0.05) ERK1/2 phosphorylation were detected in HF ghrelin treated rats compared with HF rats hearts. Results from this study indicate that exogenous ghrelin induces expression and activity of cardiac iNOS via Akt phosphorylation followed by NF kappa B activation in HF rats.