Experimental research Effects of ghrelin on protein expression of antioxidative enzymes and iNOS in the rat liver

Abstract

IntroductionWe investigated the effects of ghrelin on protein expression of the liver antioxidant enzymes superoxide dismutases (SODs), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR), nuclear factor κB (NFκB) and inducible nitric oxide synthase (iNOS). Furthermore, we aimed to investigate whether extracellular regulated protein kinase (ERK1/2) and protein kinase B (Akt) are involved in ghrelin-regulated liver antioxidant enzymes and iNOS protein expression.Material and methodsMale Wistar rats were treated with ghrelin (0.3 nmol/5 µl) injected into the lateral cerebral ventricle every 24 h for 5 days, and 2 h after the last treatment the animals were sacrificed and the liver excised. The Western blot method was used to determine expression of antioxidant enzymes, iNOS, phosphorylation of Akt, ERK1/2 and nuclear factor κB (NFκB) subunits 50 and 65.ResultsThere was significantly higher protein expression of CuZnSOD (p < 0.001), MnSOD (p < 0.001), CAT (p < 0.001), GPx, (p < 0.001), and GR (p < 0.01) in the liver isolated from ghrelin-treated animals compared with control animals. In contrast, ghrelin significantly (p < 0.01) reduced protein expression of iNOS. In addition, phosphorylation of NFκB subunits p65 and p50 was significantly (p < 0.001 for p65; p < 0.05 for p50) reduced by ghrelin when compared with controls. Phosphorylation of ERK1/2 and of Akt was significantly higher in ghrelin-treated than in control animals (p < 0.05 for ERK1/2; p < 0.01 for Akt).ConclusionsThe results show that activation of Akt and ERK1/2 is involved in ghrelin-mediated regulation of protein expression of antioxidant enzymes and iNOS in the rat liver.

Effects of altered hepatic lipid metabolism on regulation of hepatic iNOS

“…Animal studies have shown that altered hepatic lipid metabolism interferes with activation of inflammatory signaling pathways, leading to upregulation of iNOS and alteration of IRS/PI3K/Akt insulin signaling pathway and consequent hepatic IR and injury as shown by us [29] and others [18,[64][65][66]. Clinical trials have shown similar results and indicate that excessive lipid accumulation triggers an immune system response through proinflammatory cytokines, leading to increased iNOS activation and development of inflammation, oxidative damage and IR [41,46,83,89].…”

“…It is biosynthesized by three distinct isoforms of NOS enzyme: nNOS, eNOS and iNOS [10,26]. All three isoforms of NOS enzyme are expressed in the liver [27], but unlike eNOS and nNOS, which are constitutively expressed in physiological condition, iNOS is expressed when stimulated by different factors including inflammation and oxidative stress [11,[28][29]. Once expressed iNOS may generate large amounts of NO over long period of time [30].…”

Treatment with either obestatin or ghrelin attenuates mesenteric ischemia–reperfusion-induced oxidative injury of the ileum and the remote organ lung

“…Ghrelin promotes an antioxidative defense mechanism in the rat liver, not only by reducing the NF-B protein levels but also by increasing the protein expression of antioxidative enzymes (e.g., superoxide dismutase, catalase, and GSH peroxidase) [17]. Accordingly, in the present study, suppression of NF-B activation by ghrelin or obestatin during mesenteric I/R also enhanced the antioxidant content of both the ileal and pulmonary tissues and protected them against injury.…”

The role of ghrelin on apoptosis, cell proliferation and oxidant‐antioxidant system in the liver of neonatal diabetic rats

“…There are limited studies referring to a relationship between ghrelin and oxidative stress enzymes in liver. Dobutovic et al (2014) reported that ghrelin stimulation increased antioxidative enzymes in rat liver. We also evaluated oxidative stress markers and anti-oxidants in STZ-diabetic and ghrelin-treated rat livers.…”

“…It has been reported that ghrelin has antioxidant effects and stimulates the liver antioxidative proteins. It is known that increased oxidative stress plays a major role in the development and progression of diabetes (Dobutovic et al, ). Therefore, the purpose of the present study was to investigate antiapoptotic, cell proliferative and antioxidative effects of ghrelin administration in the liver of diabetic rats.…”