Ghrelin improves renal function in mice with ischemic acute renal failure

Gut Microbiota and Neonatal Acute Kidney Injury

OBJECTIVE

 To characterize the relationship between gut microbiota and neonatal acute kidney injury biomarkers based on the gut-kidney axis.

STUDY DESIGN

 The Pubmed database was primarily searched to include relevant literature on gut microbiota and neonatal acute kidney injury biomarkers, which was subsequently organized and analyzed and a manuscript was written.

RESULTS

 Gut microbiota was associated with neonatal acute kidney injury biomarkers. These biomarkers included TIMP-2, IGFBP-7, VEGF, calbindin, GST, B2MG, ghrelin, and clusterin.

CONCLUSION

 The gut microbiota is strongly associated with neonatal acute kidney injury biomarkers, and controlling the gut microbiota may be a potential target for ameliorating neonatal acute kidney injury.

KEY POINTS

· There is a bidirectional association between gut microbiota and AKI.. · Gut microbiota is closely associated with biomarkers of nAKI.. · Manipulation of gut microbiota may improve nAKI..

Enteroendocrine cells and gut hormones as potential targets in the crossroad of the gut-kidney axis communication

Recent studies suggest that disruptions in intestinal homeostasis, such as changes in gut microbiota composition, infection, and inflammatory-related gut diseases, can be associated with kidney diseases. For instance, genomic investigations highlight how susceptibility genes linked to IgA nephropathy are also correlated with the risk of inflammatory bowel disease. Conversely, investigations demonstrate that the use of short-chain fatty acids, produced through fermentation by intestinal bacteria, protects kidney function in models of acute and chronic kidney diseases. Thus, the dialogue between the gut and kidney seems to be crucial in maintaining their proper function, although the factors governing this crosstalk are still emerging as the field evolves. In recent years, a series of studies have highlighted the significance of enteroendocrine cells (EECs) which are part of the secretory lineage of the gut epithelial cells, as important components in gut-kidney crosstalk. EECs are distributed throughout the epithelial layer and release more than 20 hormones in response to microenvironment stimuli. Interestingly, some of these hormones and/or their pathways such as Glucagon-Like Peptide 1 (GLP-1), GLP-2, gastrin, and somatostatin have been shown to exert renoprotective effects. Therefore, the present review explores the role of EECs and their hormones as regulators of gut-kidney crosstalk and their potential impact on kidney diseases. This comprehensive exploration underscores the substantial contribution of EEC hormones in mediating gut-kidney communication and their promising potential for the treatment of kidney diseases.

Molecular Mechanisms and Health Benefits of Ghrelin: A Narrative Review

Ghrelin, an endogenous brain-gut peptide, is secreted in large quantities, mainly from the stomach, in humans and rodents. It can perform the biological function of activating the growth hormone secretagogue receptor (GHSR). Since its discovery in 1999, ample research has focused on promoting its effects on the human appetite and pleasure-reward eating. Extensive, in-depth studies have shown that ghrelin is widely secreted and distributed in tissues. Its role in neurohumoral regulation, such as metabolic homeostasis, inflammation, cardiovascular regulation, anxiety and depression, and advanced cancer cachexia, has attracted increasing attention. However, the effects and regulatory mechanisms of ghrelin on obesity, gastrointestinal (GI) inflammation, cardiovascular disease, stress regulation, cachexia treatment, and the prognosis of advanced cancer have not been fully summarized. This review summarizes ghrelin's numerous effects in participating in a variety of biochemical pathways and the clinical significance of ghrelin in the regulation of the homeostasis of organisms. In addition, potential mechanisms are also introduced.

Kampo medicine for the holistic approach to older adults with heart failure

Heart failure (HF) is a leading cause of hospitalization, morbidity, and mortality in older adults and represents a significant clinical and economic burden on the health care system. However, there are many challenges in assessing and managing HF in elderly patients, who often have coexisting multimorbidity, frailty, and malnutrition. Therefore, it is often difficult to solve these problems with Western medicine alone, and a holistic approach, including Kampo medicine, can be helpful. In particular, managing volume control and frailty by adding Kampo formulas may help improve health-related quality of life and substantially impact prognosis in HF. This review article summarizes the role of Kampo medicine for older patients with HF and frailty.

Discovery of Novel Proteomic Biomarkers for the Prediction of Kidney Recovery from Dialysis-Dependent AKI Patients

BACKGROUND

AKI requiring dialysis (AKI-D) is associated with prolonged hospitalization, mortality, and progressive CKD among survivors. Previous studies have examined only select urine or serum biomarkers for predicting kidney recovery from AKI.

METHODS

Serum samples collected on day 8 of randomized RRT from 72 patients enrolled in the Veteran's Affairs/National Institutes of Health Acute Renal Failure Trial Network study were analyzed by the SOMAscan proteomic platform to profile 1305 proteins in each sample. Of these patients, 38 recovered kidney function and dialysis was discontinued, whereas another 34 patients remained on dialysis by day 28.

RESULTS

Differential serum levels of 119 proteins, with 53 higher and 66 lower, were detected in samples from patients who discontinued dialysis, compared with patients who remained on dialysis by day 28. Patients were classified into tertiles on the basis of SOMAscan protein measurements for the 25 proteins most differentially expressed. The association of serum levels of each protein with kidney recovery was further evaluated using logistic regression analysis. Higher serum levels of CXCL11, CXCL2/CXCL3, CD86, Wnt-7a, BTK, c-Myc, TIMP-3, CCL5, ghrelin, PDGF-C, survivin, CA2, IL-9, EGF, and neuregulin-1, and lower levels of soluble CXCL16, IL1RL1, stanniocalcin-1, IL-6, and FGF23 when classified in tertiles were significantly associated with better kidney recovery. This significant association persisted for each of these proteins after adjusting for potential confounding risk factors including age, sex, cardiovascular SOFA score, congestive heart failure, diabetes, modality of intensive dialysis treatment, cause of AKI, baseline serum creatinine, day 8 urine volume, and estimated 60-day mortality risk.

CONCLUSIONS

These results suggest concerted changes between survival-related proteins and immune-regulatory chemokines in regulating angiogenesis, endothelial and epithelial remodeling, and kidney cell regeneration, illustrating potential mechanisms of kidney recovery. Thus, this study identifies potential novel predictive biomarkers of kidney recovery in patients with AKI-D.

Anti-Cancer Effect of Panax Ginseng and Its Metabolites: From Traditional Medicine to Modern Drug Discovery

Cancer incidence and mortality rate are growing worldwide. The effectiveness of cancer therapy depends on the degree of cancer development. Anticancer prevention, screening tests, detection of precancerous conditions or cancers at an early stage of development help to prevent the development of cancer, and in the event of cancer development, they provide the best chance for a full recovery. However, in most cases of advanced cancer, there is no method that can fully cure this disease. Recently, natural products have gained more attention in cancer therapy. Panax ginseng (PG), one of the most popular natural products, is reported to have a wide range of pharmacological activities in cancer. Therefore, the anti-cancer effects and mechanisms of PG and its metabolites (compound K, Ginsenoside Rh1, Rh2, Rh3 and F1) in five major cancers (lung cancer, breast cancer, colon cancer, prostate cancer and stomach cancer) are reviewed in this study. It is confirmed that PG and its metabolites regulated apoptosis, epithelial mesenchymal transition (EMT), angiogenesis, cell cycle arrest and multidrug resistance (MDR) in vitro and in vivo cancer models. In particular, ginsenoside Rh2 showed anticancer effects in all five major cancers. This review could improve the understanding of anticancer mechanisms of PG and its metabolites against major five cancers. Further clinical studies are needed for development anti-cancer drugs using PG and its metabolites.

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.

Gastrin, via activation of PPARα, protects the kidney against hypertensive injury

Hypertensive nephropathy (HN) is a common cause of end-stage renal disease with renal fibrosis; chronic kidney disease is associated with elevated serum gastrin. However, the relationship between gastrin and renal fibrosis in HN is still unknown. We, now, report that mice with angiotensin II (Ang II)-induced HN had increased renal cholecystokinin receptor B (CCKBR) expression. Knockout of CCKBR in mice aggravated, while long-term subcutaneous infusion of gastrin ameliorated the renal injury and interstitial fibrosis in HN and unilateral ureteral obstruction (UUO). The protective effects of gastrin on renal fibrosis can be independent of its regulation of blood pressure, because in UUO, gastrin decreased renal fibrosis without affecting blood pressure. Gastrin treatment decreased Ang II-induced renal tubule cell apoptosis, reversed Ang II-mediated inhibition of macrophage efferocytosis, and reduced renal inflammation. A screening of the regulatory factors of efferocytosis showed involvement of peroxisome proliferator-activated receptor α (PPAR-α). Knockdown of PPAR-α by shRNA blocked the anti-fibrotic effect of gastrin in vitro in mouse renal proximal tubule cells and macrophages. Immunofluorescence microscopy, Western blotting, luciferase reporter, and Cut&tag-qPCR analyses showed that CCKBR may be a transcription factor of PPAR-α, because gastrin treatment induced CCKBR translocation from cytosol to nucleus, binding to the PPAR-α promoter region, and increasing PPAR-α gene transcription. In conclusion, gastrin protects against HN by normalizing blood pressure, decreasing renal tubule cell apoptosis, and increasing macrophage efferocytosis. Gastrin-mediated CCKBR nuclear translocation may make it act as a transcription factor of PPAR-α, which is a novel signaling pathway. Gastrin may be a new potential drug for HN therapy.

Brain and kidney GHS-R1a underexpression is associated with changes in renal function and hemodynamics during neurogenic hypertension

Ghrelin is a peptide hormone whose effects are mediated by the growth hormone secretagogue receptor subtype 1a (GHS-R1a), mainly expressed in the brain but also in kidneys. The hypothesis herein raised is that GHS-R1a would be player in the renal contribution to the neurogenic hypertension pathophysiology. To investigate GHS-R1a role on renal function and hemodynamics, we used Wistar (WT) and spontaneously hypertensive rats (SHR). First, we assessed the effect of systemically injected vehicle, ghrelin, GHS-R1a antagonist PF04628935, ghrelin plus PF04628935 or GHS-R1a synthetic agonist MK-677 in WT and SHR rats housed in metabolic cages (24 h). Blood and urine samples were also analyzed. Then, we assessed the GHS-R1a contribution to the control of renal vasomotion and hemodynamics in WT and SHR. Finally, we assessed the GHS-R1a levels in brain areas, aorta, renal artery, renal cortex and medulla of WT and SHR rats using western blot. We found that ghrelin and MK-677 changed osmolarity parameters of SHR, in a GHS-R1a-dependent manner. GHS-R1a antagonism reduced the urinary Na⁺ and K⁺ and creatinine clearance in WT but not in SHR. Ghrelin reduced arterial pressure and increased renal artery conductance in SHR. GHS-R1a protein levels were decreased in the kidney and brain areas of SHR when compared to WT. Therefore, GHS-R1a role in the control of renal function and hemodynamics during neurogenic hypertension seem to be different, and this may be related to brain and kidney GHS-R1a downregulation.

In silico strategy for detailing the binding modes of a novel family of peptides proven as ghrelin receptor agonists

Ghrelin is a peptide hormone involved in multiple functions, including growth hormone release stimulation, food intake regulation, and metabolic and cytoprotective effect. A novel family of peptides with internal cycles was designed as ghrelin analogs and the biological activity of two of them (A228 and A233) was experimentally studied in-depth. In this work, an in silico strategy was developed for describing and assessing the binding modes of A228 and A233 to GHS-R1a (ghrelin receptor) comparing it with ghrelin and GHRP-6 peptides. Several reported structures of different G protein coupled receptors were used as templates, to obtain a good quality model of GHS-R1a. The best model was selected by preliminary molecular docking with ghrelin and GHRP-6. Docking was used to estimate peptide orientations in the binding site of the best model, observing a superposition of its N-terminal and its first aromatic residue. To test the complex stability in time, the C-terminal fragments of each peptide were added and the complexes were inserted a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membrane, performing a molecular dynamic simulation for 100 ns using the CHARMM36 force field. Despite of the structural differences, the studied peptides share a common binding mode; the N-terminal interacts with E124 and the aromatic residue close to it, with the aromatic cluster (F279, F309, and F312). A preliminary pharmacophore model, consisting in a positive charged amine and an aromatic ring at an approximate distance of 0.79 nm, can be proposed. The results here described could represent a step forward in the efficient search of new ghrelin analogs.

Postoperative peritoneal adhesion: an update on physiopathology and novel traditional herbal and modern medical therapeutics

Postoperative peritoneal adhesion (PPA) is a serious clinical condition that affects the high percentage of patients after abdominal surgery. In this review, we have tried to focus on pathophysiology and different underlying signal pathways of adhesion formation based on recent progress in the molecular and cellular mechanisms. Also, the strategies, developed based on traditional herbal and modern medicines, to prevent and treat the PPA via regulation of the molecular mechanisms were investigated. The search engines such as Google Scholar, PubMed, Scopus, and Science Direct have been used to evaluate the current literature related to the pathogenesis of adhesion formation and novel products. Recently, different mechanisms have been defined for adhesion formation, mainly categorized in fibrin formation and adhesion fibroblast function, inflammation, and angiogenesis. Therefore, the suppression of these mechanisms via traditional and modern medicine has been suggested in several studies. While different strategies with encouraging findings have been developed, most of the studies showed contradictory results and were performed on animals. The herbal products have been introduced as safe and effective agent which can be considered in future preclinical and clinical studies. Although a wide range of therapeutics based on traditional and modern medicines have been suggested, there is no agreement in the efficacy of these methods to prevent or treat adhesion formation after surgeries. Further basic and clinical researches are still needed to propose the efficiency of recommended strategies for prevention and treatment of PPA.

The Association Between Kidney Disease and Diabetes Remission in Bariatric Surgery Patients With Type 2 Diabetes

RATIONALE & OBJECTIVE

The association between bariatric surgery, type 2 diabetes, and chronic kidney disease (CKD) is poorly understood. We studied whether remission of type 2 diabetes induced by bariatric surgery influences markers of kidney disease, if CKD is associated with remission of diabetes after bariatric surgery, and if baseline levels of gut hormones and peptides modify these associations.

STUDY DESIGN

Prospective observational study.

STUDY PARTICIPANTS

737 bariatric surgery patients with type 2 diabetes who participated in a multicenter cohort study for up to 5 years.

PREDICTORS

Demographics, blood pressure, medications, type of bariatric surgery, anthropometrics, markers of kidney disease, and circulating levels of gut hormones and peptides.

OUTCOMES

Estimated glomerular filtration rate (eGFR), urinary albumin excretion, prognostic risk for CKD, and remission of diabetes.

ANALYTICAL APPROACH

Linear mixed models for eGFR; generalized linear mixed models with logit link for albuminuria, prognostic risk for CKD, and diabetes remission.

RESULTS

Remission of diabetes at 5 years post-bariatric surgery was not independently associated with eGFR but was associated with lower risk for moderate/severe increase in albuminuria (risk ratio, 0.66; 95% CI, 0.48-0.90) and stabilization in prognostic risk for CKD. These findings were modified by baseline ghrelin level. Lower preoperative eGFR and greater prognostic risk for CKD were independently associated with reduced likelihood of diabetes remission. The association with preoperative GFR was modified by C-peptide level. Higher baseline circulating ghrelin level was independently associated with a lower prognostic risk for CKD.

LIMITATIONS

A minority of participants had baseline CKD; lack of comparison group; no information on duration of diabetes, other clinical end points, or kidney biopsy results.

CONCLUSIONS

Remission of type 2 diabetes 5 years after bariatric surgery was associated with improvements in albuminuria and stabilized prognostic risk for CKD, but not with eGFR. Lower kidney function and greater prognostic risk at the time of bariatric surgery was linked to a lower likelihood of diabetes remission. These results highlight the need to identify the mechanisms through which bariatric surgery may delay the long-term progression of CKD in type 2 diabetes.

Protective effects of ghrelin on kidney tissue in rats with partial ureteral obstruction

Background/aim

The aim was to investigate the protective and therapeutic effects of ghrelin, which has antioxidant and antiinflammatory activity, on preventing kidney damage that occurs by induced partial ureteral obstruction in rats

Materials and methods

Twenty-eight adult male rats were included in the study, and the rats were divided into 4 groups. After the laparotomy operation on the sham group, the ureter was identified in the retroperitoneal area and was duly sutured (n = 7). Ghrelin was administered for seven days intraperitoneally, and after the nephrectomy performed on the 15th day, the rats were sacrificed (n = 7). A partial ureteral obstruction was performed after the laparotomy on the PUO group. The rats were sacrificed after the nephrectomy operation performed on the 15th day (n = 7). A partial ureteral obstruction was formed after the laparotomy followed by seven days of waiting in the PUO + ghrelin group. Ghrelin was given in the dose of 10 ng/kg per day intraperitoneally for the next 7 days, and the rats were sacrificed after the nephrectomy operation performed on the 15th day (n = 7). All groups were evaluated for histological damage and catalase, superoxide dismutase, total glutathione, malondialdehyde, and myeloperoxidase levels were measured in the same tissues

Results

When the 2nd group and the sham group were compared histologically, it was observed that the damage had increased by a statistically significant level in the partial ureteral obstruction group (P = 0.001). When the group which was ghrelin-treated after the partial ureteral obstruction was compared to the group with just partial ureteral obstruction, the histopathological changes were found to decrease significantly in that group (P = 0.001). While the statistical significance of the levels of CAT, GSH, and MPO enzymes was detected among biochemical changes in the 2nd group when compared to the sham group (P < 0.01), the 3rd group showed a statistically significant difference in the levels of SOD and GSH enzymes compared to the 4th group (P < 0.05).

Conclusion

Ghrelin administration to rats after the formation of an experimental partial unilateral ureteral obstruction reduces tissue damage due to ghrelin’s antiinflammatory and antioxidant effects. Ghrelin administration may prevent tissue damage biochemically and histopathologically in obstructive uropathy cases

Effects of rikkunshito on renal fibrosis and inflammation in angiotensin II-infused mice

The underlying pathogenesis of chronic kidney disease involves an activated renin-angiotensin system and systemic inflammation which ultimately develop renal injury. Rikkunshito (RKT) has been reported to exert anti-fibrotic and anti-inflammatory effects through enhancement of ghrelin signaling pathway. In this study, we investigated the effects of RKT on renal fibrosis and inflammation in angiotensin II (Ang II)-induced renal injury model. Ang II-infused mice exhibited hypertension, cardiac hypertrophy, increases in blood urea nitrogen and serum creatinine, moderate albuminuria and renal pathological changes such as mild urinary cast, interstitial macrophage infiltration and modest interstitial fibrosis. RKT had no evident effects on the Ang II-induced renal functional insufficiency and fibrosis, but attenuated renal interstitial macrophage infiltration. In addition, RKT significantly restored the Ang II-induced alteration in the expression of renal fibrosis- and inflammation-related genes such as type 3 collagen, transforming growth factor-β, monocyte chemoattractant protein-1 and interleukin-6. Furthermore, although RKT did not affect the expression of renal ghrelin receptor, an Ang II-induced decrease in renal sirtuin 1 expression, a critical down-stream pathway of the ghrelin receptor, was restored by RKT. These findings suggest that RKT potentially has a renal anti-inflammatory effect in the development of renal injury, and this effect could be mediated by the ghrelin signaling pathway.

Potential Therapeutic Effects of Gut Hormones, Ghrelin and Obestatin in Oral Mucositis

Chemotherapy and/or head and neck radiotherapy are frequently associated with oral mucositis. Oral pain, odynophagia and dysphagia, opioid use, weight loss, dehydration, systemic infection, hospitalization and introduction of a feeding tube should be mentioned as the main determinated effect of oral mucositis. Oral mucositis leads to a decreased quality of life and an increase in treatment costs. Moreover, oral mucositis is a life-threatening disease. In addition to its own direct life-threatening consequences, it can also lead to a reduced survival due to the discontinuation or dose reduction of anti-neoplasm therapy. There are numerous strategies for the prevention or treatment of oral mucositis; however, their effectiveness is limited and does not correspond to expectations. This review is focused on the ghrelin and obestatin as potentially useful candidates for the prevention and treatment of chemo- or/and radiotherapy-induced oral mucositis.

The Role of Ghrelin in Anorexia Nervosa

Ghrelin, a 28-amino acid peptide hormone expressed in X/A-like endocrine cells of the stomach, is the only known peripherally produced and centrally acting peptide that stimulates food intake and therefore attracted a lot of attention with one major focus on the treatment of conditions where an increased energy intake or body weight gain is desired. Anorexia nervosa is an eating disorder characterized by a pronounced reduction of body weight, a disturbed body image and hormonal alterations. Ghrelin signaling has been thoroughly investigated under conditions of anorexia nervosa. The present review will highlight these alterations of ghrelin in anorexia and discuss possible treatment strategies targeting ghrelin signaling. Lastly, gaps in knowledge will be mentioned to foster future research.

Insulin-Like Growth Factor-1 as a Possible Alternative to Bone Morphogenetic Protein-7 to Induce Osteogenic Differentiation of Human Mesenchymal Stem Cells in Vitro

Growth factors and mesenchymal stem cells (MSC) support consolidation of bone defects. Bone Morphogenetic Protein-7 (BMP-7) has been used clinically and experimentally, but the outcomes remain controversial. Increased systemic expression of Insulin-like Growth Factor-1 (IGF-1) significantly correlates with successful regeneration of bone healing disorders, making IGF-1 a promising alternative to BMP-7. There is no experimental data comparing the osteoinductive potential of IGF-1 and BMP-7. Therefore, in this study, the influence of IGF-1 and BMP-7 in different concentrations on the osteogenic differentiation of two human MSC-subtypes, isolated from reaming debris (RMSC) and iliac crest bone marrow (BMSC) has been assessed. A more sensitive reaction of BMSC towards stimulation with IGF-1 in concentrations of 400–800 ng/mL was found, leading to a significantly higher degree of osteogenic differentiation compared to stimulation with BMP-7. RMSC react more sensitively to stimulation with BMP-7 compared to BMSC. Lower concentrations of IGF-1 were necessary to significantly increase osteogenic differentiation of RMSC and BMSC compared to BMP-7. Therefore, IGF-1 should be considered as a valuable option to improve osteogenic differentiation of MSC and merits further experimental consideration. The MSC subtype and method of differentiation factor application also have to be considered, as they affect the outcome of osteogenic differentiation.

Essential Role of Growth Hormone and IGF-1 in Therapeutic Effect of Ghrelin in the Course of Acetic Acid-Induced Colitis

Previous studies have shown that ghrelin exhibits a protective and therapeutic effect in the gut. The aim of the present study was to examine whether administration of ghrelin affects the course of acetic acid-induced colitis and to determine what is the role of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) in this effect. In sham-operated or hypophysectomized male Wistar rats, colitis was induced by enema with 1 mL of 3% solution of acetic acid. Saline or ghrelin (given at the dose of 8 nmol/kg/dose) was administered intraperitoneally twice a day. Seven days after colitis induction, rats were anesthetized and the severity of the colitis was assessed. Treatment with ghrelin reduced the area of colonic mucosa damage in pituitary-intact rat. This effect was associated with increase in serum levels of GH and IGF-1. Moreover, administration of ghrelin improved blood flow in colonic mucosa and mucosal cell proliferation, as well as reduced mucosal concentration of proinflammatory interleukin-1β (IL-1β) and activity of myeloperoxidase. Hypophysectomy reduced serum levels of GH and IGF-1 and increased the area of colonic damage in rats with colitis. These effects were associated with additional reduction in mucosal blood follow and DNA synthesis when compared to pituitary-intact rats. Mucosal concentration of IL-1β and mucosal activity of myeloperoxidase were maximally increased. Moreover, in hypophysectomized rats, administration of ghrelin failed to affect serum levels of GH or IGF-1, as well as the healing rate of colitis, mucosal cell proliferation, and mucosal concentration of IL-1β, or activity of myeloperoxidase. We conclude that administration of ghrelin accelerates the healing of the acetic acid-induced colitis. Therapeutic effect of ghrelin in experimental colitis is mainly mediated by the release of endogenous growth hormone and IGF-1.

Protective roles of bioactive peptides during ischemia-reperfusion injury: From bench to bedside

Ischemia-reperfusion (I/R) is a well-known pathological condition which may lead to disability and mortality. I/R injury remains an unresolved and complicated situation in a number of clinical conditions, such as cardiac arrest with successful reanimation, as well as ischemic events in brain and heart. Peptides have many attractive advantages which make them suitable candidate drugs in treating I/R injury, such as low toxicity and immunogenicity, good solubility property, distinct tissue distribution pattern, and favorable pharmacokinetic profile. An increasing number of studies indicate that peptides could protect against I/R injury in many different organs and tissues. Peptides also face several therapeutic challenges that limit their clinical application. In this review, we present the mechanisms of action of peptides in reducing I/R injury, as well as further discuss modification strategies to improve the functional properties of bioactive peptides.

Therapeutic Potential of Targeting the Ghrelin Pathway

Ghrelin was discovered in 1999 as the endogenous ligand of the growth-hormone secretagogue receptor 1a (GHSR1a). Since then, ghrelin has been found to exert a plethora of physiological effects that go far beyond its initial characterization as a growth hormone (GH) secretagogue. Among the numerous well-established effects of ghrelin are the stimulation of appetite and lipid accumulation, the modulation of immunity and inflammation, the stimulation of gastric motility, the improvement of cardiac performance, the modulation of stress, anxiety, taste sensation and reward-seeking behavior, as well as the regulation of glucose metabolism and thermogenesis. Due to a variety of beneficial effects on systems’ metabolism, pharmacological targeting of the endogenous ghrelin system is widely considered a valuable approach to treat metabolic complications, such as chronic inflammation, gastroparesis or cancer-associated anorexia and cachexia. The aim of this review is to discuss and highlight the broad pharmacological potential of ghrelin pathway modulation for the treatment of anorexia, cachexia, sarcopenia, cardiopathy, neurodegenerative disorders, renal and pulmonary disease, gastrointestinal (GI) disorders, inflammatory disorders and metabolic syndrome.

Exogenous Ghrelin Accelerates the Healing of Acetic Acid-Induced Colitis in Rats

Previous studies have shown that ghrelin reduces colonic inflammation induced by trinitrobenzene sulfonic acid and dextran sodium sulfate. In the present study we determined the effect of treatment with ghrelin on the course of acetic acid-induced colitis in rats. Rectal administration of 3% acetic acid solution led to induction of colitis in all animals. Damage of the colonic wall was accompanied by an increase in mucosal concentration of pro-inflammatory interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), as well mucosal activity of myeloperoxidase. Moreover, induction of colitis led to a reduction in colonic blood flow and DNA synthesis. Administration of ghrelin after induction of colitis led to faster regeneration of the colonic wall and reduction in colonic levels of IL-1β, TNF-α, and myeloperoxidase. In addition, treatment with ghrelin improved mucosal DNA synthesis and blood flow. Our study disclosed that ghrelin exhibits a strong anti-inflammatory and healing effect in acetic acid-induced colitis. Our current observation in association with previous findings that ghrelin exhibits curative effect in trinitrobenzene sulfonic acid- and dextran sodium sulfate-induced colitis suggest that therapeutic effect of ghrelin in the colon is universal and independent of the primary cause of colitis.

Remote ischemic postconditioning protects against renal ischemia/reperfusion injury by activation of T-LAK-cell-originated protein kinase (TOPK)/PTEN/Akt signaling pathway mediated anti-oxidation and anti-inflammation

BACKGROUND

Recent clinical and animal studies suggested that remote limb ischemic postconditioning (RIPostC) can invoke potent cardioprotection or neuroprotection. However, the effect and mechanism of RIPostC against renal ischemia/reperfusion injury (IRI) are poorly understood. T-LAK-cell-originated protein kinase (TOPK) is crucial for the proliferation and migration of tumor cells. However, the function of TOPK and the molecular mechanism underlying renal protection remain unknown. Therefore, this study aimed to evaluate the role of TOPK in renoprotection induced by RIPostC.

MATERIALS AND METHODS

The renal IRI model was induced by left renal pedicle clamping for 45min followed by 24h reperfusion and right nephrectomy. All mice were intraperitoneally injected with vehicle, TOPK inhibitor HI-TOPK-032 or Akt inhibitor LY294002. After 24h reperfusion, renal histology, function, and inflammatory cytokines and oxidative stress were assessed. The proteins were measured by Western blotting.

RESULTS

The results showed that RIPostC significantly protected the kidneys against IRI. The protective effects were accompanied by the attenuation of renal dysfunction, tubular damage, inflammation and oxidative stress. In addition, RIPostC increased the phosphorylation of TOPK, PTEN, Akt, GSK3β and the nuclear translocation of Nrf2 and decreased the nuclear translocation of NF-κB. However, all of the above renoprotective effects of RIPostC were eliminated either by the inhibition of TOPK or Akt with HI-TOPK-032 or LY294002.

CONCLUSIONS

The current data reveal that RIPostC protects against renal IRI via activation of TOPK/PTEN/Akt signaling pathway mediated anti-oxidation and anti-inflammation.

Improvement of cisplatin-related renal dysfunction by synthetic ghrelin: a prospective randomised phase II trial

Background:

Ghrelin, a 28-amino acid peptide predominantly produced by the stomach, exerts powerful renal protective effects by increasing levels of insulin-like growth factor-1 (IGF-1). The aim of this study was to evaluate the effects of ghrelin on the incidence of renal dysfunction in patients receiving cisplatin-based chemotherapy.

Methods:

Forty patients with oesophageal cancer receiving cisplatin-based chemotherapy were assigned to either the ghrelin group (n=20), which received ghrelin (0.5 μg kg⁻¹ h⁻¹) for 5 days, or a placebo group (n=20). The primary endpoint was serum creatinine. Secondary endpoints were serum cystatin C, chemotherapy-related adverse events, changes in serum ghrelin-related hormone levels, correlation between markers of renal injury and hormone concentrations, and effects on the second cycle of chemotherapy.

Results:

Blood acyl ghrelin, total ghrelin, and IGF-1 concentrations on day 4 were significantly higher in the ghrelin group. The renal dysfunction, serum creatinine and cystatin C levels, dose reduction, and delay in the initiation of the second cycle of chemotherapy were lower in the ghrelin group than in the control group. Serum creatinine levels were significantly correlated with serum IGF-1 levels.

Conclusion:

Continuous synthetic ghrelin administration during cisplatin-based chemotherapy attenuated renal dysfunction and harmful effects on subsequent chemotherapy, possibly by increasing IGF-1 levels.

Ghrelin Inhibits Post-Operative Adhesions via Blockage of the TGF-β Signaling Pathway

Post-operative adhesions are a critical problem in pelvic and abdominal surgery despite a multitude of studies dedicated to finding modalities to prevent their occurrence. Ghrelin administration promotes an anti-fibrotic response in a surgical mouse model of adhesion-induction, but the mechanisms mediating this effect have not been established. In the current study, the molecular mechanisms that underlie the anti-adhesion effect of ghrelin were investigated. Post-surgical adhesions were experimentally created in C57BL/6 wild-type mice via a combination of ischemic peritoneal buttons and cecal multiple abrasions. Ghrelin or saline intraperitoneal injections were given twice daily from two days before surgery to selected time points post-surgically to assess the phenotypic and molecular effects of treatment (1 day (n = 20), 4 days (n = 20) and 20 days (n = 40) after surgery). Endpoints included the scoring of adhesions and gene and protein expression analysis of pro-fibrogenic factors conducted on peritoneal ischemic tissue by quantitative PCR and Western blot. Ghrelin administration significantly reduced post-surgical adhesions and down-regulated pro-inflammatory gene and protein expression, including Tgfb3 and Tgfbr2. The up-regulation of inhibitory proteins Smad6 and Smad7 confirmed the ghrelin-induced blockage of TGF-β signaling. Ghrelin is a candidate therapeutic drug for post-operative adhesion prevention, inhibiting inflammatory responses via blockage of the TGF-β signaling pathway at the onset of surgery before the occurrence of the granulation-remodeling phase.

Change in intrarenal Ghrelin expression in immune complex-mediated glomerular disease in dogs

Ghrelin is a peptide hormone that is mainly produced by the stomach. The kidney is a major source of local ghrelin, and maintaining body fluid balance is considered a critical role of renal ghrelin. However, there are no reports on renal ghrelin in small animal medicine. The present study investigated the intrarenal localization of and change in ghrelin expression in dogs with immune complex-mediated glomerulonephritis (ICGN). Ghrelin immunoreactivity (IR) was observed in the distal tubules of normal kidneys. Ghrelin IR was weak in ICGN kidneys, and the quantitative ghrelin IR score was significantly lower in ICGN kidneys than in normal kidneys. In cases of ICGN, plasma creatinine concentrations showed a positive correlation with the ghrelin IR score.

Comparison of Renoprotective Effect of Dabigatran With Low-Molecular-Weight Heparin

OBJECTIVE

The susceptibility of tissue to ischemia-reperfusion (I/R) injury is a major obstacle to tissue regeneration and cellular survival. In this study, we investigated the possible renoprotective effect of dabigatran in an experimental renal I/R model.

METHOD

A total of 25 rats were randomly divided into 5 equal groups. The control group was used to obtain basal values of oxidant and antioxidant biomarkers. The sham group was used to obtain renal prolidase and malondialdehyde (MDA) levels after renal ischemia (for 45 minutes) and reperfusion (for 1 hour). A standard diet was followed. Oral 15 mg/kg dabigatran etexilate was administrated to group I, intraperitoneal 250 U/kg enoxaparin sodium was administrated to group II, and intraperitoneal 250 U/kg bemiparin sodium was administrated to group III for 1 week before the renal I/R was performed. Renal tissue samples were obtained during the first hour of reperfusion to detect renal prolidase and MDA levels in these groups, after which the rats were euthanized.

RESULTS

Renal prolidase levels were significantly higher in the sham group compared with the control group (1834.2 ± 982.3 U/g protein vs 238.8 ± 43.6U/g protein; P = .001). Lower prolidase levels were observed in groups II (838.7 ± 123.8 U/g protein) and III (1012.9 ± 302.3 U/g protein), and the lowest prolidase levels occurred in group I (533.8 ± 96.2 U/g protein; P < .05) when compared with the sham group. The MDA levels were significantly lower (P < .05) in groups I, II, and III (163.9 ± 41.5, 185.4 ± 51.0, and 138.2 ± 22.6 μmol/g protein, respectively) compared with the sham group.

CONCLUSION

Dabigatran etexilate, a univalent direct thrombin inhibitor, may protect the renal tissue more effectively when compared to low-molecular-weight heparins.

Ghrelin attenuates renal fibrosis and inflammation of obstructive nephropathy

PURPOSE

Ghrelin is a gastric peptide that modulates multiple biological functions, of which the stimulation of food intake is the most well-known function. Ghrelin also exerts potential anti-inflammatory and antifibrotic properties in different organs but to our knowledge whether ghrelin inhibits the progression of renal fibrosis is unknown. Thus, we investigated the effect and underlying mechanisms of ghrelin in a rat model of renal fibrosis.

MATERIALS AND METHODS

Male Sprague Dawley® rats were divided into 4 groups, including vehicle or ghrelin treated sham operated groups and vehicle or ghrelin treated unilateral ureteral obstruction groups. Kidneys harvested on postoperative day 7 or 14 were evaluated for renal inflammation, fibrosis and apoptosis, and the expression of profibrotic and proinflammatory factors.

RESULTS

Ghrelin inhibited renal fibrosis by attenuating collagen production, extracellular matrix deposition, and α-smooth muscle actin and fibronectin expression. Ghrelin administration decreased macrophage infiltration and several proinflammatory cytokines, including tumor necrosis factor-α, interleukin-1β and monocyte chemotactic protein-1, as well as phosphorylated nuclear factor-κB p65. Ghrelin also inhibited myofibroblast accumulation by blocking the transforming growth factor-β1/Smad3 signaling pathway. Furthermore, ghrelin attenuated renal tubular cell apoptosis and epithelial-mesenchymal transition processes induced by unilateral ureteral obstruction injury.

CONCLUSIONS

These findings indicate that ghrelin is a potent antifibrotic agent that may have therapeutic potential in patients with obstructive nephropathy.

Obestatin improves ischemia/reperfusion-induced renal injury in rats via its antioxidant and anti-apoptotic effects: role of the nitric oxide

Obestatin was shown to have anti-inflammatory effects in several inflammatory models. To elucidate the potential renoprotective effects of obestatin, renal I/R injury was induced in male Sprague Dawley rats by placing a clamp across left renal artery for 60min following a right nephrectomy. Clamp was released and the rats were injected with either saline or obestatin (10, 30, 100μg/kg). In some experiments, obestatin (10μg/kg) was administered with L-NAME (10mg/kg) or L-Nil (0.36mg/kg). Following a 24-h reperfusion, the rats were decapitated to measure serum creatinine and nitrite/nitrate levels, renal malondialdehyde (MDA), glutathione (GSH) levels and myeloperoxidase (MPO) activity and to assess cortical necrosis and apoptosis scores. Obestatin treatment reduced I/R-induced increase in creatinine levels, renal MPO activity and renal MDA levels, while renal GSH levels were significantly increased by obestatin. Histological analysis revealed that severe I/R injury and high apoptosis score in the kidney samples of saline-treated rats were significantly reduced and the cortical/medullary injury was ameliorated by obestatin. Expression of eNOS, which was increased by I/R injury, was further increased by obestatin, while serum NO levels were significantly decreased. iNOS inhibitor L-Nil reduced oxidative renal damage and improved the functional and histopathological parameters. I/R-induced elevation in eNOS expression, which was further increased by obestatin, was depressed by L-NAME and L-Nil treatments. The present data demonstrate that obestatin ameliorates renal I/R-injury by its possible anti-oxidative, anti-inflammatory and anti-apoptotic properties, which appear to involve the suppression of neutrophil accumulation and modulation of NO metabolism.

Conditional knockout of proximal tubule mitofusin 2 accelerates recovery and improves survival after renal ischemia

Proximal tubule (PT) cells are critical targets of acute ischemic injury. Elimination of the mitochondrial fusion protein mitofusin 2 (Mfn2) sensitizes PT cells to apoptosis in vitro. However, the role of PT Mfn2 in ischemic AKI in vivo is unknown. To test its role, we evaluated the effects of conditional KO of PT Mfn2 (cKO-PT-Mfn2) on animal survival after transient bilateral renal ischemia associated with severe AKI. Forty-eight hours after ischemia, 28% of control mice survived compared with 86% of cKO-PT-Mfn2 animals (P<0.001 versus control). Although no significant differences in histologic injury score, apoptosis, or necrosis were detected between genotypes, cKO-PT-Mfn2 kidneys exhibited a 3.5-fold increase in cell proliferation restricted to the intrarenal region with Mfn2 deletion. To identify the signals responsible for increased proliferation, primary PT cells with Mfn2 deficiency were subjected to stress by ATP depletion in vitro. Compared with normal Mfn2 expression, Mfn2 deficiency significantly increased PT cell proliferation and persistently activated extracellular signal-regulated kinase 1/2 (ERK1/2) during recovery from stress. Furthermore, stress and Mfn2 deficiency decreased the interaction between Mfn2 and Ras detected by immunoprecipitation, and purified Mfn2 dose-dependently decreased Ras activity in a cell-free assay. Ischemia in vivo also reduced the Mfn2-RAS interaction and increased both RAS and p-ERK1/2 activity in the renal cortical homogenates of cKO-PT-Mfn2 mice. Our results suggest that, in contrast to its proapoptotic effects in vitro, selective PT Mfn2 deficiency accelerates recovery of renal function and enhances animal survival after ischemic AKI in vivo, partly by increasing Ras-ERK-mediated cell proliferation.

Fasting protects liver from ischemic injury through Sirt1-mediated downregulation of circulating HMGB1 in mice

BACKGROUND & AIMS

Fasting and calorie restriction are associated with a prolonged life span and an increased resistance to stress. The protective effects of fasting have been exploited for the mitigation of ischemic organ injury, yet the underlying mechanisms remain incompletely understood. Here, we investigated whether fasting protects liver against ischemia reperfusion (IR) through energy-preserving or anti-inflammatory mechanisms.

METHODS

Fasted C57BL6 mice were subjected to partial hepatic IR. Injury was assessed by liver enzymes and histology. Raw264-7 macrophage-like cells were investigated in vitro. Sirt1 and HMGB1 were inhibited using Ex527 and neutralizing antibodies, respectively.

RESULTS

Fasting for one, but not two or three days, protected from hepatic IR injury. None of the investigated energy parameters correlated with the protective effects. Instead, inflammatory responses were dampened in one-day-fasted mice and in starved macrophages. Fasting alone led to a reduction in circulating HMGB1 associated with cytoplasmic HMGB1 translocation, aggregate formation, and autophagy. Inhibition of autophagy re-elevated circulating HMGB1 and abolished protection in fasted mice, as did supplementation with HMGB1. In vitro, Sirt1 inhibition prevented HMGB1 translocation, leading to elevated HMGB1 in the supernatant. In vivo, Sirt1 inhibition abrogated the fasting-induced protection, but had no effect in the presence of neutralizing HMGB1 antibody.

CONCLUSIONS

Fasting for one day protects from hepatic IR injury via Sirt1-dependent downregulation of circulating HMGB1. The reduction in serum HMGB1 appears to be mediated by its engagement in the autophagic response. These findings integrate Sirt1, HMGB1, and autophagy into a common framework that underlies the anti-inflammatory properties of short-term fasting.

Ghrelin protects against renal damages induced by angiotensin-II via an antioxidative stress mechanism in mice

We explored the renal protective effects by a gut peptide, Ghrelin. Daily peritoneal injection with Ghrelin ameliorated renal damages in continuously angiotensin II (AngII)-infused C57BL/6 mice as assessed by urinary excretion of protein and renal tubular markers. AngII-induced increase in reactive oxygen species (ROS) levels and senescent changes were attenuated by Ghrelin. Ghrelin also inhibited AngII-induced upregulations of transforming growth factor-β (TGF-β) and plasminogen activator inhibitor-1 (PAI-1), ameliorating renal fibrotic changes. These effects were accompanied by concomitant increase in mitochondria uncoupling protein, UCP2 as well as in a key regulator of mitochondria biosynthesis, PGC1α. In renal proximal cell line, HK-2 cells, Ghrelin reduced mitochondria membrane potential and mitochondria-derived ROS. The transfection of UCP2 siRNA abolished the decrease in mitochondria-derived ROS by Ghrelin. Ghrelin ameliorated AngII-induced renal tubular cell senescent changes and AngII-induced TGF-β and PAI-1 expressions. Finally, Ghrelin receptor, growth hormone secretagogue receptor (GHSR)-null mice exhibited an increase in tubular damages, renal ROS levels, renal senescent changes and fibrosis complicated with renal dysfunction. GHSR-null mice harbored elongated mitochondria in the proximal tubules. In conclusion, Ghrelin suppressed AngII-induced renal damages through its UCP2 dependent anti-oxidative stress effect and mitochondria maintenance. Ghrelin/GHSR pathway played an important role in the maintenance of ROS levels in the kidney.

Growth hormone, insulin-like growth factor-1, and the kidney: pathophysiological and clinical implications

Besides their growth-promoting properties, GH and IGF-1 regulate a broad spectrum of biological functions in several organs, including the kidney. This review focuses on the renal actions of GH and IGF-1, taking into account major advances in renal physiology and hormone biology made over the last 20 years, allowing us to move our understanding of GH/IGF-1 regulation of renal functions from a cellular to a molecular level. The main purpose of this review was to analyze how GH and IGF-1 regulate renal development, glomerular functions, and tubular handling of sodium, calcium, phosphate, and glucose. Whenever possible, the relative contributions, the nephronic topology, and the underlying molecular mechanisms of GH and IGF-1 actions were addressed. Beyond the physiological aspects of GH/IGF-1 action on the kidney, the review describes the impact of GH excess and deficiency on renal architecture and functions. It reports in particular new insights into the pathophysiological mechanism of body fluid retention and of changes in phospho-calcium metabolism in acromegaly as well as of the reciprocal changes in sodium, calcium, and phosphate homeostasis observed in GH deficiency. The second aim of this review was to analyze how the GH/IGF-1 axis contributes to major renal diseases such as diabetic nephropathy, renal failure, renal carcinoma, and polycystic renal disease. It summarizes the consequences of chronic renal failure and glucocorticoid therapy after renal transplantation on GH secretion and action and questions the interest of GH therapy in these conditions.

Treatment of cachexia: melanocortin and ghrelin interventions

Cachexia is a condition typified by wasting of fat and LBM caused by anorexia and further endocrinological modulation of energy stores. Diseases known to cause cachectic symptoms include cancer, chronic kidney disease, and chronic heart failure; these conditions are associated with increased levels of proinflammatory cytokines and increased resting energy expenditure. Early studies have suggested the central melanocortin system as one of the main mediators of the symptoms of cachexia. Pharmacological and genetic antagonism of these pathways attenuates cachectic symptoms in laboratory models; effects have yet to be studied in humans. In addition, ghrelin, an endogenous orexigenic hormone with receptors on melanocortinergic neurons, has been shown to ameliorate symptoms of cachexia, at least in part, by an increase in appetite via melanocortin modulation, in addition to its anticatabolic and anti-inflammatory effects. These effects of ghrelin have been confirmed in multiple types of cachexia in both laboratory and human studies, suggesting a positive future for cachexia treatments.

Ghrelin and toxicity: recent findings and future challenges

Ghrelin is a novel brain-gut peptide that plays various roles in mammals, including control of food intake and growth hormone release, as well as gastric motility and acid secretion in the gastrointestinal tract. It is mainly secreted by the gastric mucosa, but is also expressed in various other tissues. Different studies confirm the multiple biological roles of and possible protective effects of ghrelin. Multiple in vitro and in vivo studies support the powerful protective action of ghrelin against heart, gastric and liver injury. Moreover, ghrelin has been reported to be beneficial in renal tissue injury and excretory function after ischemia-reperfusion and to exert neuroprotective effects in cerebral ischemic regions. The aim of this review is to summarize and evaluate all the currently available in vivo and in vitro studies regarding the effects of ghrelin on tissue injury induced in different organs and tissues.

Insulin-like growth factor-1 (IGF-1) inhibits the basolateral Cl channels in the thick ascending limb of the rat kidney

The aim of the present study is to test the hypothesis that insulin-like-growth factor-1 (IGF-1) plays a role in the regulation of basolateral Cl channels in the thick ascending limb (TAL). The patch-clamp experiments demonstrated that application of IGF-I or insulin inhibited the basolateral 10-pS Cl channels. However, the concentration of insulin required for the inhibition of the Cl channels by 50% (K(1/2)) was ten times higher than those of IGF-1. The inhibitory effect of IGF-I on the 10-pS Cl channels was blocked by suppressing protein tyrosine kinase or by blocking phosphoinositide 3-kinase (PI3K). In contrast, inhibition of phospholipase C (PLC) failed to abolish the inhibitory effect of IGF-1 on the Cl channels in the TAL. Western blot analysis demonstrated that IGF-1 significantly increased the phosphorylation of phospholipid-dependent kinase (PDK) at serine residue 241 (Ser(241)) and AKT at Ser(473) in the isolated medullary TAL. Moreover, inhibition of PI3K with LY294002 abolished the effect of IGF-1 on the phosphorylation of PDK and AKT. The notion that the effect of IGF-1 on the 10-pS Cl channels was induced by stimulation of PDK-AKT-mTOR pathway was further suggested by the finding that rapamycin completely abolished the effect of IGF-1 on the 10-pS Cl channels in the TAL. We conclude that IGF-1 inhibits the basolateral Cl channels by activating PI3K-AKT-mTOR pathways. The inhibitory effect of IGF-1 on the Cl channels may play a role in ameliorating the ischemia-induced renal injury through IGF-1 administration.

Acute renal venous obstruction is more detrimental to the kidney than arterial occlusion: implication for murine models of acute kidney injury

In this study, we compared the traditional murine model with renal pedicle clamp with models that clamped the renal artery or vein alone as well as to a whole body ischemia-reperfusion injury (WBIRI) model. Male C57BL/6J mice underwent either clamping of the renal artery, vein, or both (whole pedicle) for 30 or 45 min followed by reperfusion, or 10 min of cardiac arrest followed by resuscitation up to 24 h. After 30 min of ischemia, the mice with renal vein clamping showed the mostly increased serum creatinine and the most severe renal tubule injury. After 45 min of ischemia, all mice with renal vasculature clamping had a comparable increase in serum creatinine but the renal tubule injury was most severe in renal artery-clamped mice. Renal arterial blood flow was most decreased in mice with a renal vein clamp compared with a renal artery or pedicle clamp. A 30-or 45-min renal ischemia time led to a significant increase in the protein level of interleukin-6, keratinocyte-derived chemokine (KC), and granular colony-stimulating factor in the ischemic kidney, but the KC was the highest in the renal pedicle-clamped kidney and the lowest in the renal vein-clamped kidney. Of note, 10 min of WBIRI led to kidney dysfunction and structural injury, although less than longer time clamping of isolated renal vasculature. Our data demonstrate important differences in ischemic AKI models. Understanding these differences is important in designing future experimental studies in mice as well as clinical trials in humans.

Administration of obestatin accelerates the healing of chronic gastric ulcers in rats

Background

Previous studies have shown that administration of obestatin exhibits a protective effect in the pancreas, attenuating the development of acute pancreatitis. The aim of the present study was to investigate the influence of obestatin administration on the healing of chronic gastric ulcers.

Material/Methods

Chronic gastric ulcers were induced in rats by 100% acetic acid applied to the serosal surface of the gastric wall. Obestatin was given twice a day intraperitoneally at the dose of 4, 8 or 16 nmol/kg/dose for 6 days. Six days after induction of ulcers, rats were anesthetized and the stomach was exposed for measurement of gastric blood flow and ulcer area. Biopsy samples from the gastric mucosa were taken for determination of mucosal DNA synthesis and for measurement of gastric expression of mRNA for interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α).

Results

Induction of gastric ulcers alone increased mucosal blood flow and tissue expression of mRNA for TNF-α and IL-1β, whereas gastric mucosal DNA synthesis was reduced. In rats with gastric ulcers, administration of obestatin increased gastric mucosal blood flow, accelerated the healing rate of these ulcers and partly reversed the gastric ulcer-induced reduction in gastric mucosal DNA synthesis. These results were associated with a reduction in gastric mucosal expression of pro-inflammatory IL-1β and TNF-α.

Conclusions

Treatment with obestatin increases gastric mucosal blood flow and cell proliferation, leading to acceleration of healing of gastric ulcers. These effects are associated with a reduction in mucosal expression of pro-inflammatory IL-1β and TNF-α.

Preoperative fasting induced protection against renal ischemia/reperfusion injury is independent of ghrelin in mice

One of the factors negatively influencing the outcome after kidney transplantation is ischemia-reperfusion (I/R) injury. Preoperative fasting is able to confer protection against I/R injury. We hypothesized that the protection imposed by preoperative fasting is mediated by increased levels of acylated ghrelin. Male C57BL/6 mice, 10 to 12 weeks old, were fasted for 1, 2, or 3 days, after which, acylated ghrelin levels were determined. Ad libitum fed mice were injected with acylated ghrelin or phosphate-buffered saline before renal I/R injury. Furthermore, mice were fasted for 3 days during which they were injected with a growth hormone secretagogue receptor antagonist, to block the effects of ghrelin, or a vehiculum. Bilateral renal I/R injury was induced by clamping the artery and vein of the left and right kidney simultaneously for 37 minutes. Kidney function was assessed by means of serum urea values determined at 24 and 48 hours after reperfusion. Fasting significantly increased acylated ghrelin serum levels. Ghrelin suppletion in ad libitum fed animals or ghrelin receptor blockade in fasted animals did not affect renal function after I/R injury. Our data suggest that the increased levels of acylated ghrelin induced by fasting do not mediate its protection against renal I/R injury.

Augmenting Effect of DA-9601 on Ghrelin in an Acute Gastric Injury Model

BACKGROUND/AIMS

Acute gastric injury by alcohol or indomethacin has been reported to be prevented by DA-9601, an extract of the herb Artemisia asiatica. Ghrelin, an endogenously produced gastrointestinal peptide hormone, has also been demonstrated to play a role in gastric mucosal defense. The aim of this study was to investigate the effects of DA-9601 on ghrelin in an acute gastric injury model induced by alcohol or indomethacin.

METHODS

A total of 140 Sprague-Dawley rats were divided into two groups, a placebo group and a DA-9601-pretreated group. Thirty minutes later, half of the rats in each group received ethanol injury and the other half received indomethacin injury. Levels of serum ghrelin and gastric mucosal ghrelin mRNA were measured by ELISA and RT-PCR, respectively.

RESULTS

Immediately after ethanol administration, ghrelin increased in both groups pretreated with DA-9601 and placebo. However, the increase occurred more rapidly and was higher in the DA-9601-pretreated rats than in the controls that did not receive DA-9601-pretreatment. Similarly, from 30 minutes to 2 hours after indomethacin administration, the DA-9601-pretreated rats showed a significant increase in serum and gastric mucosal ghrelin concentrations, whereas placebo-pretreated rats showed only a mild increase.

CONCLUSIONS

DA-9601 potentiates the endogenous production and secretion of ghrelin in acute gastric injury models induced by ethanol or indomethacin.

Current and potential roles of ghrelin in clinical practice

Ghrelin is a novel GH-releasing peptide, which has been identified as an endogenous ligand for GH-secretagogue receptor. Ghrelin is mainly secreted by the stomach and plays a critical role in a variety of physiological processes including endocrine, metabolic, cardiovascular, immunological, and other actions. Ghrelin stimulates food intake via hypothalamic neurons and causes a positive energy balance and body weight gain by decreasing fat utilization and promoting adiposity. Given the multiple effects of ghrelin, its potential clinical applications have been evaluated in various conditions. Preliminary trials have shown that it may prove valuable in the management of disease-induced cachexia. Ghrelin may improve the wasting syndrome through GH-dependent or GH-independent effects. Moreover, ghrelin may play a role in the management of disorders of gut motility and obesity. Finally, other potential clinical applications of ghrelin include the treatment of patients with diabetes mellitus, infections, rheumatological diseases or GH deficiency and the diagnosis of this hormonal disorder.

Integrating GHS into the Ghrelin System

Oligopeptide derivatives of metenkephalin were found to stimulate growth-hormone (GH) release directly by pituitary somatotrope cells in vitro in 1977. Members of this class of peptides and nonpeptidyl mimetics are referred to as GH secretagogues (GHSs). A specific guanosine triphosphatate-binding protein-associated heptahelical transmembrane receptor for GHS was cloned in 1996. An endogenous ligand for the GHS receptor, acylghrelin, was identified in 1999. Expression of ghrelin and homonymous receptor occurs in the brain, pituitary gland, stomach, endothelium/vascular smooth muscle, pancreas, placenta, intestine, heart, bone, and other tissues. Principal actions of this peptidergic system include stimulation of GH release via combined hypothalamopituitary mechanisms, orexigenesis (appetitive enhancement), insulinostasis (inhibition of insulin secretion), cardiovascular effects (decreased mean arterial pressure and vasodilation), stimulation of gastric motility and acid secretion, adipogenesis with repression of fat oxidation, and antiapoptosis (antagonism of endothelial, neuronal, and cardiomyocyte death). The array of known and proposed interactions of ghrelin with key metabolic signals makes ghrelin and its receptor prime targets for drug development.

Short-term dietary restriction and fasting precondition against ischemia reperfusion injury in mice

Dietary restriction (DR) extends lifespan and increases resistance to multiple forms of stress, including ischemia reperfusion injury to the brain and heart in rodents. While maximal effects on lifespan require long-term restriction, the kinetics of onset of benefits against acute stress is not known. Here, we show that 2-4 weeks of 30% DR improved survival and kidney function following renal ischemia reperfusion injury in mice. Brief periods of water-only fasting were similarly effective at protecting against ischemic damage. Significant protection occurred within 1 day, persisted for several days beyond the fasting period and extended to another organ, the liver. Protection by both short-term DR and fasting correlated with improved insulin sensitivity, increased expression of markers of antioxidant defense and reduced expression of markers of inflammation and insulin/insulin-like growth factor-1 signaling. Unbiased transcriptional profiling of kidneys from mice subject to short-term DR or fasting revealed a significant enrichment of signature genes of long-term DR. These data demonstrate that brief periods of reduced food intake, including short-term daily restriction and fasting, can increase resistance to ischemia reperfusion injury in rodents and suggest a rapid onset of benefits of DR in mammals.

Ghrelin improves burn-induced multiple organ injury by depressing neutrophil infiltration and the release of pro-inflammatory cytokines

Mechanisms of burn-induced skin and remote organ injury involve oxidant generation and the release of pro-inflammatory cytokines. In this study the possible antioxidant and anti-inflammatory effects of ghrelin were evaluated in a rat model of thermal trauma. Wistar albino rats were exposed to 90 degrees C bath for 10 s to induce thermal trauma. Ghrelin, was administered subcutaneously (10 ng/kg/day) after the burn injury and repeated twice daily. Rats were decapitated at 6 h and 48 h after burn injury and blood was collected for the analysis of pro-inflammatory cytokines (TNF-alpha and IL-1beta), lactate dehydrogenase (LDH) activity and antioxidant capacity (AOC). In skin, lung and stomach tissue samples malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) and Na(+)-K(+)-ATPase activity were measured in addition to the histological analysis. DNA fragmentation ratio in the gastric mucosa was also evaluated. Burn injury caused significant increase in both cytokine levels, and LDH activity, while plasma AOC was found to be depleted after thermal trauma. On the other hand, in tissue samples the raised MDA levels, MPO activity and reduced GSH levels, Na(+)-K(+)-ATPase activity due to burn injury were found at control levels in ghrelin-treated groups, while DNA fragmentation in the gastric tissue was also reduced. According to the findings of the present study, ghrelin possesses a neutrophil-dependent anti-inflammatory effect that prevents burn-induced damage in skin and remote organs and protects against oxidative organ damage.

Peripheral ghrelin treatment stabilizes body weights of senescent male Brown Norway rats at baseline and after surgery

Unintentional weight loss may occur spontaneously in older humans and animals. Further weight losses after surgery or illness in the older patients result in increased morbidity, mortality, and hospital readmission rate. A growing body of work has shown increased appetite and weight gain in response to administration of ghrelin, the “hunger hormone.” We conducted two studies in senescent male Brown Norway rats to assess the ability of peripheral administration of ghrelin to increase body weight and food intake. One study assessed the effect of 2 wk of daily subcutaneous ghrelin administration (1 mg·kg−1·day−1) to senescent rats in a baseline condition; a second study used the same administration protocol in an interventional experiment with aged rats subjected to a surgery with 10–15% blood loss as a model of elective surgery. In both studies, animals receiving ghrelin maintained their body weights, whereas control animals lost weight. Body weight stability was achieved in ghrelin-treated animals despite a lack of increase in daily or cumulative food intake in both experiments. Hormone and proinflammatory cytokine levels were measured before surgery and after 14 days of treatment. Ghrelin treatment appeared to blunt declining ghrelin levels and also to blunt cytokine increases seen in the surgical control group. The ability of peripheral ghrelin treatment to maintain body weights of senescent rats without concomitant increases in food intake may be due to its known ability to decrease sympathetic activity and metabolic rate, perhaps by limiting cytokine-driven inflammation.