Cardioprotective effects of ghrelin in heart failure: from gut to heart

New and future heart failure drugs

In the past decade, our understanding of heart failure pathophysiology has advanced significantly, resulting in the development of new medications such as angiotensin-neprilysin inhibitors, sodium-glucose cotransporter-2 inhibitors and oral soluble guanylate cyclase stimulators. Backed by positive findings from large randomized controlled trials, recommendations for their use were recently included in the 2022 AHA/ACC/HFSA guidelines and 2023 ESC guidelines for management of heart failure. Promising drugs for future heart failure treatment include agents that modulate the neurohormonal system, vasodilators, anti-inflammatory drugs, mitotropes, which improve deranged energy metabolism of the failing heart, and myotropes, which increase cardiac contractility by affecting cardiac sarcomere function. Here, we discuss these new and future heart failure drugs. We explain their mechanisms of action, critically evaluate their performance in clinical trials and summarize the clinical scenarios in which the latest guidelines recommend their use. This Review aims to offer clinicians and researchers a comprehensive overview of novel therapeutic classes in heart failure treatment.

What endocrinologists can do to prevent cardiovascular complications in adults with Prader-Willi syndrome: Lessons from a case series

CONTEXT

Prader-Willi syndrome (PWS) is a complex rare genetic syndrome. Mortality in patients with PWS is 3% per year. In nearly half of the patients, the cause of death is of cardiopulmonary origin. Prevention, diagnosis and treatment of cardiovascular (CV) disease in PWS adults is complicated by the behavioral phenotype, reduced ability to express physical complaints, high pain threshold and obesity.

OBJECTIVE

To describe the challenges in prevention, diagnosis and treatment of CV disease in PWS adults, in order to increase awareness and improve medical care.

METHODS

Retrospective study of medical records of adults visiting the Dutch PWS reference center.

RESULTS

We describe the challenges encountered during diagnosis and treatment of four PWS adults with heart failure. All had pre-existent peripheral edema. CV risk factors in these patients were obesity (n=4), type 2 diabetes mellitus (n=2), hypertension (n=2), hypogonadism (n=3) and sleep apnea (n=2). Remarkably, all patients were younger than 40 years during their first cardiac decompensation. All patients presented with progressive shortness of breath and/or orthopnea and progressive pitting edema. In 117 controls with PWS without CV problems, 31% had leg edema.

CONCLUSION

Diagnosing CV problems in PWS adults is challenging. Peripheral edema is common in PWS adults without CV morbidity, which makes edema in general a poor marker for heart failure. However, when edema is of the pitting kind and progressive, this is a strong predictor of cardiac decompensation. We provide practical recommendations for diagnosing and treating CV problems in this vulnerable patient population.

Highlighting the Role of Obesity and Insulin Resistance in Type 1 Diabetes and Its Associated Cardiometabolic Complications

PURPOSE OF REVIEW

This narrative review appraises research data on the potentially harmful effect of obesity and insulin resistance (IR) co-existence with type 1 diabetes mellitus (T1DM)-related cardiovascular (CVD) complications and evaluates possible therapeutic options.

RECENT FINDINGS

Obesity and IR have increasingly been emerging in patients with T1DM. Genetic, epigenetic factors, and subcutaneous insulin administration are implicated in the pathogenesis of this coexistence. Accumulating evidence implies that the concomitant presence of obesity and IR is an independent predictor of worse CVD outcomes. The prevalence of obesity and IR has increased in patients with T1DM. This increase can be partly attributed to general population trends but, additionally, to iatrogenic weight gain caused by insulin treatment. This association might be the missing link explaining the excess CVD burden observed in patients with T1DM despite optimal glycemic control. Data on newer agents for type 2 diabetes mellitus (T2DM) treatment are unraveling novel ways to challenge this aggravating coexistence.

The Additional Prognostic Value of Ghrelin for Mortality and Readmission in Elderly Patients with Acute Heart Failure

Purpose

To evaluate the prognostic value of ghrelin, a growth hormone-releasing peptide, for mortality and readmission in elderly patients with acute heart failure (AHF).

Patients and Methods

We measured plasma ghrelin and pro B-type natriuretic peptide (NT-proBNP) levels upon emergency admission in 241 prospectively recruited elderly AHF patients (61.0% men). The outcomes were all-cause mortality and/or readmission due to heart failure (HF). Multivariate Cox proportional hazards regression analyses were used to evaluate the prognostic value of ghrelin. Discrimination, calibration, and reclassification indices were compared between models, with or without ghrelin.

Results

During 1.2 years of follow-up, we observed 90 events (57 deaths and 33 readmissions due to HF). Plasma ghrelin levels were significantly elevated in elderly AHF patients, when compared to healthy control subjects (P < 0.001). Patients with events had significantly higher baseline ghrelin levels, when compared to those without (P < 0.001). Ghrelin levels were positively correlated with NT-proBNP levels and HF severity, whereas they were negatively correlated with nutritional status (all P < 0.05). Log transformed ghrelin levels were independently associated with AHF events (hazard ratio = 2.64, 95% confidence interval = 1.11–6.25, P = 0.028). The incorporation of ghrelin into the reference model, or reference with the NT-proBNP model, both improved C-statistics (from 0.742–0.780 and 0.836–0.857; P = 0.074 and 0.044, respectively), resulting in an improvement in net reclassification index (14.42% and 10.45%, P = 0.020 and 0.025, respectively), and integrated discrimination index (5.64% and 3.60%, both P < 0.001). Patients who displayed the above NT-proBNP and ghrelin median levels had a markedly higher risk of AHF adverse events (P < 0.001).

Conclusion

Plasma ghrelin is an independent predictor of adverse events in elderly AHF patients. Ghrelin may provide additional value to clinical parameters or NT-proBNP for prognostic risk stratification in AHF.

Obesity or BMI Paradox? Beneath the Tip of the Iceberg

The obesity paradox refers to extant evidence showing that obesity in older subjects or in patients with several chronic diseases may be protective and associated with decreased mortality. A number of mechanisms have been postulated to support the existence of obesity paradox; however, marked heterogeneity was found across studies and this has cast doubt on the actual presence of this phenomenon. The aim of the present narrative review is to summarize evidence underlying the concept of obesity paradox, focusing on limitations and bias related to this phenomenon, with emphasis on the use of body mass index (BMI). A major cause of the discrepancy between studies may be related to the use of BMI in the definition of obesity, that should consider, instead, excess body fat as the main characteristic of this disease and as the unique determinant of its complications. In addition, the adjustment for potential confounders (e.g., stage and grade of diseases, smoking habit, inability to capture the presence of signs of undernutrition in the normal-weight comparative group, consideration of body composition) may significantly scale down the protective role of obesity in terms of mortality. However, it is still necessary to acknowledge few biases (e.g., reverse causation, attrition bias, selection bias of healthy obese subjects or resilient survivors) that would still apply to obesity even when defined according with body composition. Further research should be prompted in order to promote correct phenotyping of patients in order to capture properly the trajectories of mortality in a number of diseases.

Effect of ghrelin on VEGF-B and connexin-43 in a rat model of doxorubicin-induced cardiomyopathy

Background Since their discovery in the early 1960s, doxorubicin (DOX) remains the most effective anticancer drug. However, this drug has confirmed to be a double-edged sword because it causes a cardiomyopathy that leads to congestive heart failure. Ghrelin, a multi-functional peptide, plays an important role in cardiovascular protection. Therefore, we investigated the effects of ghrelin on vascular endothelial growth factor-beta (VEGF-B) and connexin-43 (Cx43) expression in DOX-induced cardiomyopathy. Methods Forty adult male rats were divided randomly into four groups: normal, normal + ghrelin, DOX-induced cardiomyopathy, and DOX-induced cardiomyopathy + ghrelin. Biochemical and histopathological analysis, electrocardiograph (ECG), heart rate, systolic blood pressure (SBP), and immunohistochemical staining of VEGF-B and Cx43 were assessed for all rats in heart tissue specimens. The duration of the study was 2 weeks. Results DOX-induced cardiomyopathy in rats showed significant ECG changes such as prolongation of PR, QT, QTC intervals and ST segment, a decrease in amplitude and an increase in the duration of QRS complex, bradycardia, and a decrease in SBP. Also, rats in the DOX group showed myocardial histopathological damage in the form of severe fibrosis with decreased expression of Cx43 and a non-significant difference in expression of VEGF-B when compared to normal rats. Treatment with ghrelin resulted in a significant improvement in all the studied parameters and was associated with an increase in VEGF-B and Cx43 expression. Conclusions Ghrelin has a beneficial effect against DOX-induced cardiomyopathy which may be mediated through VEGF-B and Cx43 expression in the myocardium. Ghrelin is a promising cardioprotective drug in DOX-induced cardiomyopathy patients, but further studies are needed to evaluate its use.

Effects of ghrelin supplementation on the acute phase of Chagas disease in rats

Background

Trypanosoma cruzi is the causative agent of Chagas disease, which is endemic to subtropical and tropical Americas. The disease treatment remains partially ineffective, involving therapies directed to the parasite as well as palliative strategies for the clinical manifestations. Therefore, novel candidates for disease control are necessary. Additionally, strategies based on parasite inhibition via specific targets and application of compounds which improve the immune response against the disease is welcomed. Ghrelin is a peptide hormone pointed as a substance with important cardioprotective, vasodilatory, anti-apoptotic, anti-oxidative and immune modulatory functions. The aims of this study were to evaluate the immunomodulatory effects of ghrelin in male Wistar rats infected with the Y strain of T. cruzi.

Methods

In order to delineate an immune response against T. cruzi mediated by ghrelin, we evaluated the following parameters: quantification of blood and cardiac parasites; analysis of cell markers (CD3⁺, CD8⁺, NK, NKT, CD45RA⁺, macrophage and RT1B⁺); nitric oxide (NO) production; lymphoproliferation assays; splenocyte apoptosis; and INF-γ, IL-12 and IL-6 quantification in sera.

Results

The animals infected with T. cruzi and supplemented with ghrelin demonstrated an upregulated pattern in macrophage and NO production, whereas an anti-inflammatory response was observed in T cells and cytokines. The low response against T. cruzi mediated by T cells probably contributed to a higher colonization of the cardiac tissue, when compared to infected groups. On the other side, the peptide decreased the inflammatory infiltration in cardiac tissue infected with T. cruzi.

Conclusions

Ghrelin demonstrated a dual function in animals infected with T. cruzi. Further studies, especially related to the decrease of cardiac tissue inflammation, are needed in order to determine the advantages of ghrelin supplementation in Chagas disease, mostly for populations from endemic areas.

The role of appetite-regulating hormones: Ghrelin and leptin in the nutritional status of children with neurogenic bladder due to myelomeningocele

AIM

We wanted to investigate serum levels of ghrelin and leptin - appetite-regulating hormones - and their correlation with the nutritional status of children with neurogenic bladder (NB) due to myelomeningocele (MMC) in comparison to healthy individuals.

METHODS

This prospective analysis was conducted on 67 children with NB after MMC and 20 healthy children. Children's medical charts were analysed to determine age, gender, anthropometric measurements, body mass index (BMI), activity assessment using Hoffer's scale and renal function parameters. Serum total ghrelin and leptin levels were measured using the enzyme-linked immunosorbent assay.

RESULTS

There were no differences in the age, gender, weight and BMI between the studied groups. Median serum levels of ghrelin and leptin were higher compared with the reference group. A significant negative correlation between serum leptin concentration and Hoffer's scale was found in children with NB.

CONCLUSIONS

Elevated levels of leptin and ghrelin could be considered factors influencing nutritional status in children with NB due to MMC. Children with NB after MMC may have disturbed endocrine regulation of energy homeostasis. Physical activity may be the factor that affects serum leptin concentration.

[Ghrelin Physiology and Pathophysiology: Focus on the Cardiovascular System]

Ghrelin is a multifunctional peptide hormone, mainly synthesized by P / D1 cells of the stomach fundus mucosa. Its basic effect, which is realized via GHS-R1 α receptor in the arcuate and the ventromedial nucleuses of hypothalamus, is stimulation of the synthesis of pituitary hormones. Ghrelin is involved in control of appetite and energy balance, regulation of carbohydrate and lipid metabolism, cell proliferation and apoptosis, as well as modulation of functioning of gastrointestinal, cardiovascular, pulmonary and immune systems. It was found that cardiomyocytes are able to synthesize ghrelin. High concentrations of GHS-R1α in the heart and major blood vessels evidence for its possible participation in functioning of cardiovascular system. Ghrelin inhibits apoptosis of cardiomyocytes and endothelial cells, and improves the functioning of the left ventricle (LV) after injury of ischemia-reperfusion mechanism. In rats with heart failure (HF) ghrelin improves LV function and attenuates development of cardiac cachexia. In addition, ghrelin exerts vasodilatory effects in humans, improves cardiac function and reduces peripheral vascular resistance in patients with chronic HF. The review contains of the predictive value of ghrelin in the development and prevention of cardiovascular disease.

Ghrelin and acyl ghrelin levels are associated with inflammatory and nutritional markers and with cardiac and vascular dysfunction parameters in hemodialysis patients

PURPOSE

Exogenous ghrelin is associated with cardiovascular protection in experimental and human studies. Nevertheless ESRD patients have increased ghrelin levels and severe cardiovascular comorbidities. This study aims to elucidate the metabolic factors influencing endogenous ghrelin/acyl ghrelin levels and to analyze the relation between endogenous ghrelin/acyl ghrelin levels and cardiac and vascular function markers in hemodialysis patients.

METHODS

The cross-sectional study was conducted in hemodialysis patients (n = 88); 50 of them were men, mean age 61.1 ± 13.5 years, 17% had diabetes. We assessed nutritional and inflammatory status and analyzed the determinants of ghrelin/acyl ghrelin and their relation with cardiac and vascular function.

RESULTS

Ghrelin is correlated with IL-1β (r = 0.88, p < 0.0001), triglycerides, total cholesterol (TC), and Kt/V. IL-1β is the strongest predictor of ghrelin levels (p < 0.0001). Acyl ghrelin is correlated with TC (r = 0.36, p = 0.001), LDL-cholesterol, serum bicarbonate, body mass index. TC is the strongest predictor for acyl ghrelin levels (p = 0.038). Patients with high ghrelin levels had significantly decreased nitroglycerin-mediated dilation (p = 0.05) and higher IL-1β levels (p < 0.001); increased NT-proBNP is associated with lower levels of acyl ghrelin (r = - 0.33, p = 0.02) in male patients.

CONCLUSION

The inflammatory marker IL-1β is in our study the strongest predictor of ghrelin levels while the nutritional marker-total cholesterol is the strongest predictor for acyl ghrelin levels in HD patients. High endogenous ghrelin level is associated with high IL-1β and with vascular smooth muscle cell dysfunction. Low acyl ghrelin level is associated with high NT-proBNP (a cardiac dysfunction marker) in male HD patients. There is a direct correlation between endogenous ghrelin level and inflammatory markers, which is not related with cardiovascular protection.

Ghrelin for the management of cachexia associated with cancer

BACKGROUND

Cancer sufferers are amongst the most malnourished of all the patient groups. Studies have shown that ghrelin, a gut hormone can be a potential therapeutic agent for cachexia (wasting syndrome) associated with cancer. A variety of mechanisms of action of ghrelin in people with cancer cachexia have been proposed. However, safety and efficacy of ghrelin for cancer-associated cachexia have not been systematically reviewed. The aim of this review was to assess whether ghrelin is associated with better food intake, body composition and survival than other options for adults with cancer cachexia.

OBJECTIVES

To assess the efficacy and safety of ghrelin in improving food intake, body composition and survival in people with cachexia associated with cancer.

SEARCH METHODS

We searched CENTRAL, MEDLINE and Embase without language restrictions up to July 2017. We also searched for ongoing studies in trials registers, performed handsearching, checked bibliographic references of relevant articles and contacted authors and experts in the field to seek potentially relevant research. We applied no restrictions on language, date, or publication status.

SELECTION CRITERIA

We included randomised controlled (parallel-group or cross-over) trials comparing ghrelin (any formulation or route of administration) with placebo or an active comparator in adults (aged 18 years and over) who met any of the international criteria for cancer cachexia.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility. Two review authors then extracted data and assessed the risk of bias for individual studies using standard Cochrane methodology. For dichotomous variables, we planned to calculate risk ratio with 95% confidence intervals (CI) and for continuous data, we planned to calculate mean differences (MD) with 95% CI. We assessed the evidence using GRADE and created 'Summary of findings' tables.

MAIN RESULTS

We screened 926 individual references and identified three studies that satisfied the inclusion criteria. Fifty-nine participants (37 men and 22 women) aged between 54 and 78 years were randomised initially, 47 participants completed the treatment. One study had a parallel design and two had a cross-over design. The studies included people with a variety of cancers and also differed in the dosage, route of administration, frequency and duration of treatment.One trial, which compared ghrelin with placebo, found that ghrelin improved food intake (very low-quality evidence) and had no adverse events (very low-quality evidence). Due to unavailability of data we were unable to report on comparisons for ghrelin versus no treatment or alternative experimental treatment modalities, or ghrelin in combination with other treatments or ghrelin analogues/ghrelin mimetics/ghrelin potentiators. Two studies compared a higher dose of ghrelin with a lower dose of ghrelin, however due to differences in study designs and great diversity in the treatment provided we did not pool the results. In both trials, food intake did not differ between participants on higher-dose and lower-dose ghrelin. None of the included studies assessed data on body weight. One study reported higher adverse events with a higher dose as compared to a lower dose of ghrelin.All studies were at high risk of attrition bias and bias for size of the study. Risk of bias in other domains was unclear or low.We rated the overall quality of the evidence for primary outcomes (food intake, body weight, adverse events) as very low. We downgraded the quality of the evidence due to lack of data, high or unclear risk of bias of the studies and small study size.

AUTHORS' CONCLUSIONS

There is insufficient evidence to be able to support or refute the use of ghrelin in people with cancer cachexia. Adequately powered randomised controlled trials focusing on evaluation of safety and efficacy of ghrelin in people with cancer cachexia is warranted.

Ghrelin inhibits atherosclerotic plaque angiogenesis and promotes plaque stability in a rabbit atherosclerotic model

Intraplaque angiogenesis associates with the instability of atherosclerotic plaques. In the present study, we investigated the effects of ghrelin on intraplaque angiogenesis and plaque instability in a rabbit model of atherosclerosis. The rabbits were randomly divided into three groups, namely, the control group, atherosclerotic model group, and ghrelin-treated group, with treatments lasting for 4 weeks. We found that the thickness ratio of the intima to media in rabbits of the ghrelin-treated group was significantly lower than that in rabbits of the atherosclerotic model group. The number of neovessels and the levels of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (VEGFR2) decreased dramatically in rabbits of the ghrelin-treated group compared to those of the atherosclerotic model group. Ghrelin significantly decreased the plaque content of macrophages, matrix metalloproteinase (MMP)-2, and MMP-9, in a rabbit model of atherosclerosis. In addition, the level of the pro-inflammatory factor monocyte chemoattractant protein (MCP)-1 was significantly lower in rabbits of the ghrelin-treated group than in rabbits of the atherosclerotic model group. In summary, ghrelin can inhibit intraplaque angiogenesis and promote plaque stability by down-regulating VEGF and VEGFR2 expression, inhibiting the plaque content of macrophages, and reducing MCP-1 expression at an advanced stage of atherosclerosis in rabbits.

Synthetic Growth Hormone-Releasing Peptides (GHRPs): A Historical Appraisal of the Evidences Supporting Their Cytoprotective Effects

BACKGROUND

Growth hormone-releasing peptides (GHRPs) constitute a group of small synthetic peptides that stimulate the growth hormone secretion and the downstream axis activity. Mounting evidences since the early 1980s delineated unexpected pharmacological cardioprotective and cytoprotective properties for the GHRPs. However, despite intense basic pharmacological research, alternatives to prevent cell and tissue demise before lethal insults have remained as an empty niche in the clinical armamentarium. Here, we have rigorously reviewed the investigational development of GHRPs and their clinical niching perspectives.

METHODOLOGY

PubMed/MEDLINE databases, including original research and review articles, were explored. The search design was date escalated from 1980 and included articles in English only.

RESULTS AND CONCLUSIONS

GHRPs bind to two different receptors (GHS-R1a and CD36), which redundantly or independently exert relevant biological effects. GHRPs' binding to CD36 activates prosurvival pathways such as PI-3K/AKT1, thus reducing cellular death. Furthermore, GHRPs decrease reactive oxygen species (ROS) spillover, enhance the antioxidant defenses, and reduce inflammation. These cytoprotective abilities have been revealed in cardiac, neuronal, gastrointestinal, and hepatic cells, representing a comprehensive spectrum of protection of parenchymal organs. Antifibrotic effects have been attributed to some of the GHRPs by counteracting fibrogenic cytokines. In addition, GHRP family members have shown a potent myotropic effect by promoting anabolia and inhibiting catabolia. Finally, GHRPs exhibit a broad safety profile in preclinical and clinical settings. Despite these fragmented lines incite to envision multiple pharmacological uses for GHRPs, especially as a myocardial reperfusion damage-attenuating candidate, this family of "drugable" peptides awaits for a definitive clinical niche.

Body habitus in heart failure: understanding the mechanisms and clinical significance of the obesity paradox

The prevalence of obesity among adults and children worldwide has reached epic proportions and has become a major independent risk factor for the development of heart failure (HF), in addition to a contributor of hypertension and cardiovascular disease. The implications of obesity in the development of HF involve adverse effects on cardiac structure and function. Despite all of this, in the setting of chronic HF, excess body mass is associated with improved clinical outcomes, demonstrating the presence of an obesity paradox. In this review, we will discuss the gender differences, global application, potential mechanisms and role of interventions based on fitness and purposeful weight loss as potential therapeutic strategies.

Upregulation of miR-21 by Ghrelin Ameliorates Ischemia/Reperfusion-Induced Acute Kidney Injury by Inhibiting Inflammation and Cell Apoptosis

Renal ischemia-reperfusion (I/R) injury can be caused by cardiac surgery, renal vascular obstruction, and kidney transplantation, mainly leading to acute kidney injury (AKI), which is complicated by lack of effective preventative and therapeutic strategies. Ghrelin has recently been reported to possess anti-inflammatory properties in several types of cells; however, little attention has been given to the role of ghrelin in I/R-induced AKI. The aim of this study is to explore the role of ghrelin in I/R-induced AKI. In this study, an I/R-induced rat AKI model and a hypoxia-induced NRK-52E cell I/R model were successfully constructed. Ghrelin expression was increased significantly in these rat and cell models. After enhancing ghrelin level by injecting exogenous ghrelin into rats or transfecting a ghrelin-pcDNA3.1 vector into renal tubular epithelial cells, we observed that I/R-induced AKI can be ameliorated by ghrelin, as shown by alterations in histology, as well as changes in serum creatinine (SCr) level, cell apoptosis, and the levels of inflammatory factors. Based on the importance of microRNA-21 (miR-21) in renal disease and the modulation effect of ghrelin on miR-21 in gastric epithelial cells, we tested whether miR-21 participates in the protective effect of ghrelin on I/R-induced AKI. Ghrelin could upregulate the PI3K/AKT signaling pathway by increasing the miR-21 level, which led to the protective effect of ghrelin on I/R-induced AKI by inhibiting the inflammatory response and renal tubular epithelial cell apoptosis. Our research identifies that ghrelin can ameliorate I/R-induced AKI by upregulating miR-21, which advances the understanding of mechanisms by which ghrelin ameliorates I/R-induced AKI.

Ghrelin ameliorates impaired angiogenesis of ischemic myocardium through GHSR1a-mediated AMPK/eNOS signal pathway in diabetic rats

OBJECTIVES

Ghrelin, an endogenous ligand of the growth hormone secretagogue receptor (GHSR), has been found to stimulate angiogenesis in vivo and in vitro. However, the effect and the corresponding mechanisms of ghrelin on impaired myocardial angiogenesis in diabetic and myocardial infarction (MI) rat model are still unknown.

METHODS

In the present study, adult SD rats were randomly divided into 4 groups: control, DM, DM+ghrelin, DM+ghrelin+[D-Lys3]-GHRP-6 groups. DM was induced by streptozotocin (STZ) 60 mg/kg body weight. 12 weeks post STZ injection all groups were subjected to MI, which was induced by ligation left anterior descending artery (LAD). Ghrelin and [D-Lys3]-GHRP-6 were administered via intraperitoneal injection at the doses 200 μg/kg and 50mg/kg for 4 weeks, respectively. Left ventricular function, microvascular density (MVD), myocardial infarct size, the expression of hypoxia-inducible factor (HIF1α), vascular endothelial growth factor (VEGF), fetal liver kinase-1 (Flk-1) and fms-like tyrosine kinase-1 (Flt-1), AMPK and endothelial nitric oxide synthase (eNOS) phosphorylation were examined.

RESULTS

Compared with the DM group, left ventricular ejection fraction (LVEF), fractional shortening (FS), and MVD were increased, whereas myocardial infarct size decreased remarkably in DM+ghrelin group. For the mechanism study, we found that ghrelin promoted the HIF1α, VEGF, Flk-1 and Flt-1 expression, AMPK and eNOS phosphorylation in diabetic rats. However, the above biochemical events in ghrelin treated diabetic rats were completely inhibited by GHSR-1a blocker [D-Lys3]-GHRP-6.

CONCLUSIONS

These results suggest that administration of ghrelin ameliorates impaired angiogenesis in diabetic MI rats. And these beneficial effects derive from regulating GHSR1a-mediated AMPK/eNOS signal pathway by upregulating of HIF1α, VEGF and its receptors Flk-1, Flt-1 expressions.

Octanoylated ghrelin attenuates angiogenesis induced by oxLDL in human coronary artery endothelial cells via the GHSR1a-mediated NF-κB pathway

OBJECTIVE

Low concentrations of oxidized low-density lipoprotein (oxLDL) promote the in vitro angiogenesis of endothelial cells and play an important role in plaque angiogenesis, which may cause plaque vulnerability and enhance the risk of intravascular thrombosis. The aim of this research was to investigate the effects of octanoylated ghrelin on oxLDL-induced angiogenesis and the underlying molecular mechanisms involved in this process.

MATERIALS/METHODS

Human coronary artery endothelial cells (HCAECs) were incubated with 5 μg/ml oxLDL and treated with various concentrations of octanoylated ghrelin (10(-9)-10(-6)M) with or without inhibitors for 24h. Cell proliferation, migration, and in vitro angiogenesis were analyzed by bromodeoxyuridine (BrdU) staining and BrdU enzyme-linked immunosorbent assay (ELISA), transwell assay, and tube formation on Matrigel, respectively. NF-κB (nuclear factor κB) expression was determined by Western-blot analysis.

RESULTS

Treatment with oxLDL at 5 μg/ml enhanced the proliferation, migration and tube formation of HCAECs. In contrast, pretreatment with octanoylated ghrelin significantly attenuated in vitro angiogenesis in oxLDL-induced HCAECs. In addition, Western blot analysis indicated that NF-κB expression was increased after oxLDL treatment, and that this effect was significantly reversed by pretreatment with octanoylated ghrelin. However, the NF-κB inhibitor PDTC or the GHSR1a inhibitor [D-Lys3]-GHRP-6 abolished the effects of octanoylated ghrelin on the inhibition of angiogenesis and NF-κB p65 expression induced by oxLDL.

CONCLUSIONS

These findings suggest that octanoylated ghrelin attenuates angiogenesis induced by oxLDL in HCAECs via the inhibition of GHSR1a-mediated NF-κB pathway. Furthermore, octanoylated ghrelin may promote the stability of vulnerable plaques by inhibiting plaque angiogenesis.

60 YEARS OF NEUROENDOCRINOLOGY: The hypothalamo-GH axis: the past 60 years

At the time of the publication of Geoffrey Harris's monograph on 'Neural control of the pituitary gland' 60 years ago, the pituitary was recognised to produce a growth factor, and extracts administered to children with hypopituitarism could accelerate growth. Since then our understanding of the neuroendocrinology of the GH axis has included identification of the key central components of the GH axis: GH-releasing hormone and somatostatin (SST) in the 1970s and 1980s and ghrelin in the 1990s. Characterisation of the physiological control of the axis was significantly advanced by frequent blood sampling studies in the 1980s and 1990s; the pulsatile pattern of GH secretion and the factors that influenced the frequency and amplitude of the pulses have been defined. Over the same time, spontaneously occurring and targeted mutations in the GH axis in rodents combined with the recognition of genetic causes of familial hypopituitarism demonstrated the key factors controlling pituitary development. As the understanding of the control of GH secretion advanced, developments of treatments for GH axis disorders have evolved. Administration of pituitary-derived human GH was followed by the introduction of recombinant human GH in the 1980s, and, more recently, by long-acting GH preparations. For GH excess disorders, dopamine agonists were used first followed by SST analogues, and in 2005 the GH receptor blocker pegvisomant was introduced. This review will cover the evolution of these discoveries and build a picture of our current understanding of the hypothalamo-GH axis.

Effect of ghrelin on mortality and cardiovascular outcomes in experimental rat and mice models of heart failure: a systematic review and meta-analysis

BACKGROUND

Heart failure (HF) continues to be a challenging condition in terms of prevention and management of the disease. Studies have demonstrated various cardio-protective effects of Ghrelin. The aim of the study is to determine the effect of Ghrelin on mortality and cardiac function in experimental rats/mice models of HF.

METHODS

Data sources: PUBMED, Scopus. We searched the Digital Dissertations and conference proceedings on Web of Science. Search methods: We systematically searched for all controlled trials (upto November 2014) which assessed the effects of Ghrelin (irrespective of dose, form, frequency, duration and route of administration) on mortality and cardiac function in rats/ mice models of HF. Ghrelin administration irrespective of dose, form, frequency, duration and route of administration. Data collection and analysis: Two authors independently assessed each abstract for eligibility and extracted data on characteristics of the experimental model used, intervention and outcome measures. We assessed the methodological quality by SYRCLE's risk of bias tool for all studies and the quality of evidence by GRADEpro. We performed meta-analysis using RevMan 5.3.

RESULTS

A total of 325 animals (rats and mice) were analyzed across seven studies. The meta-analysis revealed that the mortality in Ghrelin group was 31.1% and in control group was 40% (RR 0.83, 95% CI 0.46 to 1.47) i.e Ghrelin group had 68 fewer deaths per 1000 (from 216 fewer to 188 more) as compared to the control group. The meta-analysis reveals that the heart rate in rats/mice on Ghrelin was higher (MD 13.11, 95% CI 1.14 to 25.08, P=0.66) while the mean arterial blood pressure (MD -1.38, 95% CI -5.16 to 2.41, P=0.48) and left ventricular end diastolic pressure (MD -2.45, 95% CI -4.46 to -0.43, P=0.02) were lower as compared to the those on placebo. There were insignificant changes in cardiac output (SMD 0.28, 95% CI -0.24 to 0.80, P=0.29) and left ventricular end systolic pressure (MD 1.48, 95% CI -3.86 to 6.82, P=0.59).

CONCLUSIONS

The existing data provides evidence to suggest that Ghrelin may lower the risk of mortality and improve cardiovascular outcomes. However; the quality of evidence as assessed by GRADEpro is low to very low. Clinical judgments to administer Ghrelin to patients with HF must be made on better designed animal studies.

Ghrelin O Acyl Transferase (GOAT) as a Novel Metabolic Regulatory Enzyme

BACKGROUND

Obesity and Type 2 Diabetes Mellitus (T2DM) presents a growing threat to the global health. Evidences highlight an important role of ghrelin as a key regulator of glucose metabolism. The physiological functions of ghrelin are mediated by enzyme ghrelin-O-acyltransferase (GOAT) which is capable of generating the active form of this metabolic hormone. However, its exact mechanism of action and influence on energy balance and glucose metabolism is yet to be explored.

OBJECTIVES

To review the physiological role of GOAT in the regulation of energy balance and glucose metabolism and explore the potential therapeutic avenues of modulators of GOAT to counter the progression of obesity and T2DM.

METHODS

Publications were sought through electronic searches. The bibliographies of all papers, book, chapters and editorials were scanned and hand searches were also conducted for journals, and conference proceedings.

CONCLUSION

GOAT peptide modulates the insulin secretion as well as insulin sensitivity. Modulators of GOAT signaling like inhibitors of GOAT increases insulin secretion, enhance peripheral insulin sensitivity and thus counters obesity and T2DM. Modulators of GOAT can be a probable therapy for modifying food intake and for countering obesity and T2DM.