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

A 9‑gene expression signature to predict stage development in resectable stomach adenocarcinoma

BACKGROUND

Stomach adenocarcinoma (STAD) is a highly heterogeneous disease and is among the leading causes of cancer-related death worldwide. At present, TNM stage remains the most effective prognostic factor for STAD. Exploring the changes in gene expression levels associated with TNM stage development may help oncologists to better understand the commonalities in the progression of STAD and may provide a new way of identifying early-stage STAD so that optimal treatment approaches can be provided.

METHODS

The RNA profile retrieving strategy was utilized and RNA expression profiling was performed using two large STAD microarray databases (GSE62254, n = 300; GSE15459, n = 192) from the Gene Expression Omnibus (GEO) and the RNA-seq database within the Cancer Genome Atlas (TCGA, n = 375). All sample expression information was obtained from STAD tissues after radical resection. After excluding data with insufficient staging information and lymph node number, samples were grouped into earlier-stage and later-stage. Samples in GSE62254 were randomly divided into a training group (n = 172) and a validation group (n = 86). Differentially expressed genes (DEGs) were selected based on the expression of mRNAs in the training group and the TCGA group (n = 156), and hub genes were further screened by least absolute shrinkage and selection operator (LASSO) logistic regression. Receiver operating characteristic (ROC) curves were used to evaluate the performance of the hub genes in distinguishing STAD stage in the validation group and the GSE15459 dataset. Univariate and multivariate Cox regressions were performed sequentially.

RESULTS

22 DEGs were commonly upregulated (n = 19) or downregulated (n = 3) in the training and TCGA datasets. Nine genes, including MYOCD, GHRL, SCRG1, TYRP1, LYPD6B, THBS4, TNFRSF17, SERPINB2, and NEBL were identified as hub genes by LASSO-logistic regression. The model achieved discrimination in the validation group (AUC = 0.704), training-validation group (AUC = 0.743), and GSE15459 dataset (AUC = 0.658), respectively. Gene Set Enrichment Analysis (GSEA) was used to identify the potential stage-development pathways, including the PI3K-Akt and Calcium signaling pathways. Univariate Cox regression indicated that the nine-gene score was a significant risk factor for overall survival (HR = 1.28, 95% CI 1.08-1.50, P = 0.003). In the multivariate Cox regression, only SCRG1 was an independent prognostic predictor of overall survival after backward stepwise elimination (HR = 1.21, 95% CI 1.11-1.32, P < 0.001).

CONCLUSION

Through a series of bioinformatics and validation processes, a nine-gene signature that can distinguish STAD stage was identified. This gene signature has potential clinical application and may provide a novel approach to understanding the progression of STAD.

"Sibling" battle or harmony: crosstalk between nesfatin-1 and ghrelin

Ghrelin was first identified as an endogenous ligand of the growth hormone secretagogue receptor (GHSR) in 1999, with the function of stimulating the release of growth hormone (GH), while nesfatin-1 was identified in 2006. Both peptides are secreted by the same kind of endocrine cells, X/A-like cells in the stomach. Compared with ghrelin, nesfatin-1 exerts opposite effects on energy metabolism, glucose metabolism, gastrointestinal functions and regulation of blood pressure, but exerts similar effects on anti-inflammation and neuroprotection. Up to now, nesfatin-1 remains as an orphan ligand because its receptor has not been identified. Several studies have shown the effects of nesfatin-1 are dependent on the receptor of ghrelin. We herein compare the effects of nesfatin-1 and ghrelin in several aspects and explore the possibility of their interactions.

Ghrelin protects against lipopolysaccharide-induced acute respiratory distress syndrome through the PI3K/AKT pathway

Pulmonary endothelial barrier dysfunction is a major pathophysiology observed in acute respiratory distress syndrome (ARDS). Ghrelin, a key regulator of metabolism, has been shown to play protective roles in the respiratory system. However, its effects on lipopolysaccharide (LPS)-induced pulmonary endothelial barrier injury are unknown. In this study, the effects of ghrelin on LPS-induced ARDS and endothelial cell injury were evaluated in vivo and in vitro. In vivo, mice treated with LPS (3 mg/kg intranasal application) were used to establish the ARDS model. Annexin V/propidium iodide apoptosis assay, scratch-wound assay, tube formation assay, transwell permeability assay, and Western blotting experiment were performed to reveal in vitro effects and underlying mechanisms of ghrelin on endothelial barrier function. Our results showed that ghrelin had protective effects on LPS-induced ARDS and endothelial barrier disruption by inhibiting apoptosis, promoting cell migration and tube formation, and activating the PI3K/AKT signaling pathway. Furthermore, ghrelin stabilized LPS-induced endothelial barrier function by decreasing endothelial permeability and increasing the expression of the intercellular junction protein vascular endothelial cadherin. LY294002, a specific inhibitor of the PI3K pathway, reversed the protective effects of ghrelin on the endothelial cell barrier. In conclusion, our findings indicated that ghrelin protected against LPS-induced ARDS by impairing the pulmonary endothelial barrier partly through activating the PI3K/AKT pathway. Thus, ghrelin may be a valuable therapeutic strategy for the prevention or treatment of ARDS.

Acylated Ghrelin Attenuates l-Thyroxin-induced Cardiac Damage in Rats by Antioxidant and Anti-inflammatory Effects and Downregulating Components of the Cardiac Renin-angiotensin System

ABSTRACT

This study investigated the protective effect of acylated ghrelin (AG) against l-thyroxin (l-Thy)-induced cardiac damage in rats and examined possible mechanisms. Male rats were divided into five intervention groups of 12 rats/group: control, control + AG, l-Thy, l-Thy + AG, and l-Thy + AG + [D-Lys3]-GHRP-6 (AG antagonist). l-Thy significantly reduced the levels of AG and des-acyl ghrelin and the AG to des-acyl ghrelin ratio. Administration of AG to l-Thy-treated rats reduced cardiac weights and levels of reactive oxygen species and preserved the function and structure of the left ventricle. In addition, AG also reduced the protein levels of cleaved caspase-3 and cytochrome c and prevented mitochondrial permeability transition pore opening. In the left ventricle of both control + AG-treated and l-Thy + AG-treated rats, AG significantly increased left ventricular levels of manganese superoxide dismutase (SOD2), total glutathione (GSH), and Bcl2. It also reduced the levels of malondialdehyde, tumor necrosis factor-α (TNF-α), interleukin-6, and Bax and the nuclear activity of nuclear factor-kappa B. Concomitantly, in both treated groups, AG reduced the mRNA and protein levels of NADPH oxidase 1, angiotensin (Ang) II type 1 receptor, and Ang-converting enzyme 2. All the beneficial effects of AG in l-Thy-treated rats were prevented by the coadministration of [D-Lys3]-GHRP-6, a selective growth hormone secretagogue receptor subtype 1a antagonist. In conclusion, AG protects against hyperthyroidism-induced cardiac hypertrophy and damage, which is mainly due to its antioxidant and anti-inflammatory potentials and requires the activation of GHS-R1a.

Potentiality of ghrelin as antioxidant and protective agent

Background

Oxidative stress is the result of cellular troubles related to aerobic metabolism. Furthermore, this stress is always associated with biological responses evoked by physical, chemical, environmental, and psychological factors. Several studies have developed many approaches of antioxidant defense to diminish the severity of many diseases. Ghrelin was originally identified from the rat stomach, and it is a potent growth hormone-releasing peptide that has pleiotropic functions.

Methods

A systematic review was conducted within PubMed, ScienceDirect, MEDLINE, and Scopus databases using keywords such as ghrelin, antioxidant, oxidative stress, and systemic oxidative stress sensor.

Results

In the last decade, many studies show that ghrelin exhibits protection effects against oxidative stress derived probably from its antioxidant effects. Pieces of evidence demonstrate that systemic oxidative stress increase ghrelin levels in the plasma. The expression of ghrelin and its receptor in ghrelin peripheral tissues and extensively in the central nervous system suggests that this endogenous peptide plays an important role as a systemic oxidative stress sensor

Conclusion

The current evidence confirms that ghrelin and its derived peptides (Desacyl-ghrelin, obestatin) act as a protective antioxidant agent. Therefore, stressor modality, duration, and intensity are the parameters of oxidative stress that must be taken into consideration to determine the role of ghrelin, Desacyl-ghrelin, and obestatin in the regulation of cell death pathways.

Regulatory effects of ghrelin on endoplasmic reticulum stress, oxidative stress, and autophagy: Therapeutic potential

Ghrelin is a regulatory peptide that is the endogenous ligand of the growth hormone secretagogue 1a (GHS-R1a) which belongs to the G protein-coupled receptor family. Ghrelin and GHS-R1a are widely expressed in the central and peripheral tissues and play therapeutic potential roles in the cytoprotection of many internal organs. Endoplasmic reticulum stress (ERS), oxidative stress, and autophagy dysfunction, which are involved in various diseases. In recent years, accumulating evidence has suggested that ghrelin exerts protective effects by regulating ERS, oxidative stress, and autophagy in diverse diseases. This review article summarizes information about the roles of the ghrelin system on ERS, oxidative stress, and autophagy in multiple diseases. It is suggested that ghrelin positively affects the treatment of diseases and may be considered as a therapeutic drug in many illnesses.

Relationships between Ghrelin and Obestatin with MDA, Proinflammatory Cytokines, GSH/GSSG Ratio, Catalase Activity, and Semen Parameters in Infertile Patients with Leukocytospermia and Varicocele

Ghrelin and obestatin are involved in many biological functions including reproduction. Growing evidences suggest that both peptides could exert protective and antioxidant activities. In this study, the relationships between ghrelin/obestatin, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), malondialdehyde (MDA), reduced glutathione (GSH), oxidized glutathione (GSSG), expressed as the GSH/GSSG ratio, catalase (CAT), and semen parameters in infertile patients with varicocele or leukocytospermia and controls were investigated. Fifty-six infertile patients (32 with leukocytospermia and 24 with varicocele) and 14 controls participated in this study. Semen analysis was performed following the WHO guidelines. Apoptotic and necrotic sperm were scored by annexin V/propidium iodide assay. Seminal plasma samples were used for the following determinations: ghrelin, obestatin, IL-6, and TNF-α were measured by an immunological method, GSH/GSSG by an enzymatic method, and CAT by spectrophotometric determination. With respect to controls, both the leukocytospermia and varicocele groups showed altered sperm parameters, significantly increased sperm apoptosis (P = 0.009 and P = 0.011, respectively), IL-6 (P = 0.0001 and P = 0.004, respectively), and TNF-α levels (P = 0.0001 and P = 0.002, respectively); both groups had significantly decreased levels of ghrelin (P = 0.0001), obestatin (P = 0.0001 and P = 0.006, respectively), and GSH/GSSG ratio (P = 0.003 and P = 0.0001, respectively). The MDA concentration was significantly increased in the leukocytospermia group vs. controls (P = 0.0001), in the varicocele group vs. controls (P = 0.011), and in the leukocytospermia group vs. the varicocele group (P = 0.008). CAT activity was augmented in both the leukocytospermia and varicocele groups (P = 0.0001)vs. controls. The results indicate that both ghrelin and obestatin may play a protective role in human semen and this effect is probably due to their antioxidant properties.

Streptozotocin-Induced Diabetes Mellitus in Neonatal Rats: An Insight into its Applications to Induce Diabetic Complications

BACKGROUND

Diabetic complications are the major contributor in the mortality of diabetic patients despite controlling blood glucose level. In the journey of new drug discovery, animal models have to play a major role. A large number of chemical-induced and genetically modified animal models have been investigated to induce diabetic complications but none of them was found to be mimicking the pathophysiology of the human. Therefore, the search and identification of the appropriate animal model become essential.

OBJECTIVE

In the present review, we have made an attempt to understand the pathophysiology of diabetic complication in the neonatal streptozotocin-diabetic rat model and tried to identify the targets for therapeutic agents. The review will help the researchers to explore the animal model to induce diabetic complications, to identify targets and further to find lead molecules for treatment or prevention of diabetic complications.

METHODS

We have compiled the available research work from 1974 by using prominent databases, organized the available information and analyzed the data to improve the understanding of the pathophysiology of streptozotocin-induced diabetic complications in neonates of rats.

RESULTS

The neonatal streptozotocin-diabetic rat model is frequently used and well-established animal model for type 2 diabetes mellitus. We have found that this model has been used to study the pathogenesis of various micro and macrovascular diabetic complications and also investigated for its effects on the liver, thymus gland, and brain. The underlying pathophysiology for complications had a resemblance to the human.

CONCLUSION

The neonatal streptozotocin-diabetic rat model may demonstrate symptomatic diabetic complications due to persistent hyperglycemia at the age of approximately 18-24 weeks. Critical interpretations of available research work showed that the researcher can explore split dose STZ (90- 100mg/kg b.w) model to induce Type 2 DM in neonates of rats at 2nd or 3rd postnatal day.

Effect of Ghrelin on Caspase 3 and Bcl2 Gene Expression in H2O2 Treated Rat's Bone Marrow Stromal Cells

Purpose: The antiapoptotic effect of ghrelin in various cell lines including bone marrow stromal cells (BMSCs) has been proved. However, the real mechanism of this effect is not clear. Caspase3 and Bcl2 are well-known pro- and antiapoptotic regulatory genes in eukaryotes. The aim of the study was to find out the effect of ghrelin on Caspase 3 and Bcl2 change in BMSCs.

Methods: Rat BMSCs were cultivated in DMEM. Passage 3 BMSCs were treated with ghrelin 100 μM for 48 h. Real-time PCR for Caspase 3 and Bcl2 was carried out from B (untreated BMSCs), BH (BMSCs treated with 125 µM H2O2), BGH (BMSCs treated with 100 µM ghrelin then 125 µM H2O2) and BG (BMSCs treated with 100 µM ghrelin) groups. For immunofluorescence, cells were incubated with anti Caspase 3 and Bcl2monoclonal antibodies. Primary antibodies were visualized using the FITC method. All data are presented as means ± SEM. Values of P<0.05 were considered statistically significant.

Results: Ghrelin decreased mRNA expressions of Caspase-3 significantly as compared to the BH group (P<0.05). Also, Bcl-2 gene expression showed an increment in BG group as compare with BH and BGH groups (P<0.05). A high present of Bcl-2 positive cells were observed in the BGH group while Caspase-3 positive cells were significantly decreased in the BGH group compared with the BH group (P<0.05).

Conclusion: Ghrelin probably enhances BMSCs viability through regulation of pro- and antiapoptotic genes Caspase 3 and Bcl2. However the signaling pathway of this effect should be elucidated in the future.

Ghrelin Protects Human Lens Epithelial Cells against Oxidative Stress-Induced Damage

Oxidative stress has been recognized as an important mediator in the pathogenesis of age-related cataracts; using antioxidant supplements is one plausible strategy to protect the antioxidative defense system against oxidative stress. Ghrelin administration is expected to reduce ROS, preventing the onset of different diseases. The role of ghrelin, if any, in protecting against oxidative stress in HLECs has never been examined. In the present study, we investigated the effects of ghrelin against H₂O₂-induced oxidative stress and the associated molecular mechanisms in HLECs and rat lenses. The results showed that pretreatment with ghrelin reduced H₂O₂-induced cellular apoptosis and ROS accumulation, increased the expression levels of SOD and CAT, and decreased the expression level of MDA. The morphological examination showed that the ghrelin-treated lens organ culture maintained transparency. This is the first report to show that ghrelin can protect HLECs from H₂O₂-induced oxidative stress. Our findings suggest that ghrelin may prevent the progression of cataracts, which has treatment value for ophthalmologists.

CB-1R and GLP-1R gene expressions and oxidative stress in the liver of diabetic rats treated with sitagliptin

BACKGROUND

Type 2 diabetes is a major health problem affecting millions of people. Controlled eating and regular physical activity are important for the management of type 2 diabetes. Dipeptidyl peptidase-4 enzyme (DPP-4) inhibitor sitagliptin is a potent agent for the treatment of type-2 diabetes. The aim of this study was to examine the effects of sitagliptin on the liver of rats with streptozotocin (STZ)-induced diabetes, in terms of (i) the expression levels of the cannabinoid 1 receptor (CB-1R) and glucagon-like peptide 1 receptor (GLP-1R), (ii) alterations in the number and localization of these peptides, and (iii) changes in histological and oxidative damage.

METHODS

Thirty-two neonatal (two-day-old) rats, which were divided into four groups, were treated with saline (control), sitagliptin (control; 1.5mg/kg/day for 15 days starting from day 5 of the experimental period), STZ (diabetes; 100mg/kg single dose), STZ+sitagliptin (diabetes+sitagliptin). After 20 days, hepatic tissues were obtained from rats.

RESULTS

The expressions of GLP-1R and CB-1R mRNA increased approximately 1.89- and 2.94-fold, respectively, in the diabetes+sitagliptin group as compared to the diabetic group. Additionally the number of GLP-1R immunopositive cells decreased and CB-1R immunopositive cells increased in comparison to the diabetic group; however, this was not statistically significant. Glutathione levels increased, but malondialdehyde and protein carbonyl levels decreased in the diabetes+sitagliptin group more than the diabetic group.

CONCLUSION

Our findings indicate that sitagliptin treatment regulates GLP-1R and CB-1R gene expressions, which are associated with appetite regulation in diabetic rat, and may decrease oxidative stress and liver tissue damage.