Growth hormone modulates in vitro endothelial cell migration and formation of capillary-like structures

Intrathymic somatotropic circuitry: consequences upon thymus involution

Growth hormone (GH) is a classic pituitary-derived hormone crucial to body growth and metabolism. In the pituitary gland, GH production is stimulated by GH-releasing hormone and inhibited by somatostatin. GH secretion can also be induced by other peptides, such as ghrelin, which interacts with receptors present in somatotropic cells. It is well established that GH acts directly on target cells or indirectly by stimulating the production of insulin-like growth factors (IGFs), particularly IGF-1. Notably, such somatotropic circuitry is also involved in the development and function of immune cells and organs, including the thymus. Interestingly, GH, IGF-1, ghrelin, and somatostatin are expressed in the thymus in the lymphoid and microenvironmental compartments, where they stimulate the secretion of soluble factors and extracellular matrix molecules involved in the general process of intrathymic T-cell development. Clinical trials in which GH was used to treat immunocompromised patients successfully recovered thymic function. Additionally, there is evidence that the reduction in the function of the somatotropic axis is associated with age-related thymus atrophy. Treatment with GH, IGF-1 or ghrelin can restore thymopoiesis of old animals, thus in keeping with a clinical study showing that treatment with GH, associated with metformin and dehydroepiandrosterone, could induce thymus regeneration in healthy aged individuals. In conclusion, the molecules of the somatotrophic axis can be envisioned as potential therapeutic targets for thymus regeneration in age-related or pathological thymus involution.

Covert actions of growth hormone: fibrosis, cardiovascular diseases and cancer

Since its discovery nearly a century ago, over 100,000 studies of growth hormone (GH) have investigated its structure, how it interacts with the GH receptor and its multiple actions. These include effects on growth, substrate metabolism, body composition, bone mineral density, the cardiovascular system and brain function, among many others. Recombinant human GH is approved for use to promote growth in children with GH deficiency (GHD), along with several additional clinical indications. Studies of humans and animals with altered levels of GH, from complete or partial GHD to GH excess, have revealed several covert or hidden actions of GH, such as effects on fibrosis, cardiovascular function and cancer. In this Review, we do not concentrate on the classic and controversial indications for GH therapy, nor do we cover all covert actions of GH. Instead, we stress the importance of the relationship between GH and fibrosis, and how fibrosis (or lack thereof) might be an emerging factor in both cardiovascular and cancer pathologies. We highlight clinical data from patients with acromegaly or GHD, alongside data from cellular and animal studies, to reveal novel phenotypes and molecular pathways responsible for these actions of GH in fibrosis, cardiovascular function and cancer.

Role of the GH-IGF1 system in progression of cancer

Emerging evidence links the growth hormone (GH)-insulin-like growth factor-1 (IGF1) endocrine axis to cancer development. While this putative correlation is of major translational relevance, most clinical and epidemiological reports to date found no causal linkage between GH therapy and enhanced cancer risk. Thus, it is generally agreed that GH therapy constitutes a safe pharmacological intervention. The present review focuses on a number of issues in the area of GH-IGF1 action in cancer development. Emphasis is given to the idea that GH and IGF1 do not conform to the definition of oncogenic factors. Specifically, these hormones, even at high pharmacological doses, are unable to induce malignant transformation. However, the GH-IGF1 axis is capable of 'pushing' already transformed cells through the various phases of the cell cycle. Viral and cellular oncogenes require an intact IGF1 signaling pathway in order to elicit transformation; in other words, oncogenic agents adopt the IGF1 pathway. This universal mechanism of action of oncogenes has broad implications in oncology. Our review provides an in-depth analysis of the interplay between the GH-IGF1 axis and cancer genes, including tumor suppressors p53 and BRCA1. Finally, the safety of GH therapy in both children and adults needs further long-term follow-up studies.

Interactions between thymic endothelial cells and thymocytes are influenced by growth hormone

Growth hormone (GH), in addition to its classic actions on growth and metabolism in the body, exerts pleiotropic effects on the immune system, particularly on the thymus. The aim of this study was to evaluate the influence of GH on the interactions between mature thymocytes and the thymic endothelium involved in the migratory process. To this end, fresh thymocytes (C57BL/6 mice) and the thymic endothelial cell line (tEnd.1) were used. In the cell adhesion assay, the GH-treated thymocytes adhered more to tEnd.1 cells. Additionally, there was an improvement in the deposition of fibronectin by tEnd.1 cells when co-cultured with GH-pre-treated thymocytes. Furthermore, GH induced thymocyte F-actin polymerization. In the transendothelial migration assay, a large number of GH-treated thymocytes, mainly the CD4^-CD8⁺ subset, migrated towards the endothelium under the stimulus of insulin-like growth factor 1. In conclusion, we demonstrated the positive actions of GH in thymocyte/thymic endothelium interactions, including transendothelial migration.

Why Should Growth Hormone (GH) Be Considered a Promising Therapeutic Agent for Arteriogenesis? Insights from the GHAS Trial

Despite the important role that the growth hormone (GH)/IGF-I axis plays in vascular homeostasis, these kind of growth factors barely appear in articles addressing the neovascularization process. Currently, the vascular endothelium is considered as an authentic gland of internal secretion due to the wide variety of released factors and functions with local effects, including the paracrine/autocrine production of GH or IGF-I, for which the endothelium has specific receptors. In this comprehensive review, the evidence involving these proangiogenic hormones in arteriogenesis dealing with the arterial occlusion and making of them a potential therapy is described. All the elements that trigger the local and systemic production of GH/IGF-I, as well as their possible roles both in physiological and pathological conditions are analyzed. All of the evidence is combined with important data from the GHAS trial, in which GH or a placebo were administrated to patients suffering from critical limb ischemia with no option for revascularization. We postulate that GH, alone or in combination, should be considered as a promising therapeutic agent for helping in the approach of ischemic disease.

The Change in Distance Between Bilateral Internal Carotid Arteries in Acromegaly and Its Risk Factors

Background: Studies investigating the change in distance between the bilateral internal carotid arteries (ICAs) in acromegalic patients have provided ambiguous results. The influencing factors of these changes have not been well-identified. Objective: To further investigate the change in distance between bilateral ICAs in acromegaly patients and identify the influencing factors of the change. Method: Patients diagnosed as acromegaly from Jan 2016 to Sep 2019 in the Department of Neurosurgery of the First Affiliated Hospital of Fujian Medical University, were included in this study. Computed tomography angiography (CTA) or magnetic resonance angiography (MRA) data were obtained for all patients for three-dimensional reconstruction of the ICAs. Distance between bilateral ICAs was measured and recorded for assessment. Result: 172 patients including 86 cases with acromegaly in the study group and 86 cases with non-functional pituitary adenoma in the control group were enrolled in this study. The difference of adenoma sizes between two groups was not statistically significant. Patients in acromegaly group had significantly larger maximum distances between bilateral siphon carotid ectasias (25.5 ± 4.1 vs. 23.4 ± 3.5 mm, P = 0.001) and between bilateral lacerum segments (26.2 ± 3.2 vs. 24.1 ± 4.3 mm, P < 0.001) compared with those of patients with non-functional pituitary adenomas. Multivariate analysis showed that the increased bilateral ICAs distance was associated with disease duration (odds ratio = 1.01, 95% confidence interval = 1.01-1.02, P = 0.005) and refractory pituitary adenoma (odds ratio = 9.8, 95% confidence interval = 1.1-88.7, P = 0.043) but not with level of growth hormone (GH), insulin-like growth factor-1 (IGF-1) and adenoma size in acromegaly. Conclusion: Our study showed significant change in distance between the bilateral ICAs in acromegalic patients, comparing to patients with non-functional pituitary adenomas. The increased intercarotid artery distance is associated with disease duration but not with preoperative level of GH and IGF-1. Refractory pituitary adenoma and longer disease duration are the both risk factors of the increased ICAs distance in patient with acromegly.

Non‑toxic sulfur enhances growth hormone signaling through the JAK2/STAT5b/IGF‑1 pathway in C2C12 cells

Insulin‑like growth factor‑1 (IGF‑1) regulates cell growth, glucose uptake and protein metabolism, and is required for growth hormone (GH) signaling‑mediated insulin production and secretion. IGF1 expression is associated with STAT5, which binds to a region (TTCNNNGAA) of the gene. Although sulfur is used in various fields, the toxicity of this element is a significant disadvantage as it causes indigestion, vomiting, diarrhea, pain and migraine. Therefore, it is difficult to conduct in vitro experiments to directly determine the effects of dietary sulfur. Additionally, it is difficult to dissolve non‑toxic sulfur (NTS). The present study aimed to identify the role of NTS in GH signaling as a Jak2/STAT5b/IGF‑1 pathway regulator. MTT assay was used to identify an optimum NTS concentration for C2C12 mouse muscle cells. Western blotting, RT‑PCR, chromatin immunoprecipitation, overexpression and small interfering RNA analyses were performed. NTS was dissolved in 1 mg/ml DMSO and could be used in vitro. Therefore, the present study determined whether NTS induced mouse muscle cell growth via GH signaling. NTS notably increased STAT5b binding to the Igf1 promoter. NTS also promoted GH signaling by upregulating GH receptor expression, similar to GH treatment. NTS enhanced GH signaling by regulating Jak2/STAT5b/IGF‑1 signaling pathway factor expression in C2C12 mouse muscle cells. Thus, NTS may be used as a GH‑enhancing growth stimulator.

The Endothelium in Acromegaly

Growth hormone (GH) and insulin like growth factor-1 (IGF-1) excess induce well-known deleterious effects on the cardiovascular system, especially after long-term exposition. Acromegaly, a condition of chronic GH and IGF-1 hypersecretion, is frequently associated to cardiovascular complications, although recent studies have shown a reduction in the prevalence of these comorbidities in well-controlled patients and a mortality risk similar to normal aging population. Many factors could contribute to the increased cardiovascular risk of acromegaly patients. Among these factors, the endothelium plays a key role in the pathogenesis of atherosclerotic plaques and could be considered an early marker of atherosclerosis and cardiovascular dysfunction. In this review we examined the relationship between GH/IGF-1 excess and the endothelium, from basic studies to clinical evidence. Many studies involving various arterial districts (microvascular arteries of retina, kidney and brain, and major vessels as carotid and aorta) showed that GH/IGF-1 excess promotes endothelial dysfunction via several different mechanisms. Increased endothelial proliferation, dysfunction of endothelial progenitor cells, increased oxidative stress, and compromised oxidative defenses are the main factors that are associated with endothelial dysfunction. In the general population, these alterations are associated with the development of atherosclerosis with an increased incidence of coronary artery disease and cerebrovascular complications. However, in acromegaly this is still a debated issue, despite the presence of many pro-atherogenic factors and comorbidities, such as hypertension, diabetes, sleep apnoea, and metabolic syndrome. Preclinical markers of atherosclerosis as arterial intima media thickness, pulse wave velocity and flow mediated dilation seem to be impaired in acromegaly and partly mediated by the endothelium dysfunction. In conclusion, the pathophysiology of endothelial dysfunction in the condition of GH and IGF-1 excess remains a crucial area of investigation to fully dissect the association of acromegaly with cardiovascular disease complications.

Effects of preadipocytes derived from mice fed with high fat diet on the angiogenic potential of endothelial cells

BACKGROUND AND AIMS

Obesity promotes a persistent inflammatory process in the adipose tissue, activating the endothelium and leading to vascular dysfunction. Preadipocytes can interact with endothelial cells in a paracrine way stimulating angiogenesis. However, the potential of preadipocytes from adipose tissue of high fat diet (HFD) fed animal to stimulate angiogenesis has not been evaluated yet. The aim of this study was to investigate the effects of such diet on the angiogenic potential of preadipocytes in a mice model.

METHODS AND RESULTS

We have evaluated body weight gain, fasting glucose levels and insulin resistance, mRNA expression in preadipocytes and endothelial cells after co-culture with preadipocytes, in vivo vascular function and in vitro endothelial cell migration and tubulogenesis. High fat diet promoted an increase in body weight, glycemic index and insulin resistance in mice. Preadipocytes mRNA expression of factors involved in angiogenesis was higher in these animals. In endothelial tEnd cells mRNA expression of factors involved in vessel growth were higher after co-culture with preadipocytes derived from mice fed with HFD. Although no significant differences were observed in in vivo vasodilatation response between control and HFD groups, endothelial tEnd cells showed an increase in migration and tubulogenesis when cultivated with conditioned media from preadipocytes derived from mice fed with HFD.

CONCLUSION

Hypoxic and growth factors produced by preadipocytes derived from mice fed with HFD have higher capacity than preadipocytes derived from mice fed with standard diet to stimulate the angiogenic potential of endothelial cells, contributing to vascular disorders in obesity.

Somatolactogens and diabetic retinopathy

IMPORTANCE

Diabetic retinopathy (DR) is one of the most common of all diabetic complications. The number of people with DR in the United States is expected to increase to 16 million by 2050. DR is the leading cause of blindness among working-age adults in many different countries, including the United States. In later DR stages, neovascularization is associated with extensive retinal capillary non-perfusion and vitreo-proliferation leading to retinal detachment. This neovascularization is orchestrated by an imbalance of growth factors in the retina from which somatolactogens (pituitary growth hormone, GH-N; placental growth hormone, GH-V; prolactin, PRL; and placental lactogen, PL, also referred as chorionic somatomammotropin, CSH), may play an important role.

OBSERVATIONS

Somatolactogens are a group of hormones that share many structural and functional features. They are important for physiological changes in pregnancy, for adequate development of the fetus, and in the case of GH-N, for promoting growth after birth. GH-N is synthesized by the anterior pituitary, GH-V and PL are secreted by the placenta, whereas, PRL is synthesized by the anterior pituitary and uterine decidua. However, in recent years the expression of GH-N and PRL and their receptors have been detected in other tissues including the retina, acting as neuroprotective and pro-angiogenic agents. The relationship of GH-N and diabetic retinopathy (DR) was established many years ago when it was observed that its deficiency was related to regression of DR while an increase in serum levels of GH-N, GH-V, and PL promoted DR. While more studies are needed to define the potential implications of GH-V and PL in DR pathogenesis, it has been demonstrated that GH-N and PRL participate in DR by enhancing neovascularization. Some PRL isoforms, however, have shown an anti-angiogenic activity rather than pro-angiogenesis and appears to be PRL's main role in the regulation of retinal vasculature.

CONCLUSIONS

Somatolactogens are a group of hormones with a significant role in neuroprotection and angiogenesis regulation in the eye. Understanding the mechanisms of angiogenesis regulation by somatolactogens will potentially lead to the development of new drugs for DR.

[Thrombotic microangiopathy/haemolytic uraemic syndrome. Histopathology update]

Thrombotic microangiopathy (TMA) encompasses different entities known as haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). The histopathological characteristics have remained constant since the initial description and consist in glomerular-type affectation with the presence of double contours, mesangiolysis and microthrombi. It is generally accepted that the vascular damage is related to the prognosis. Ultrastructure, together with conventional histology, shows notable changes in both capillaries and endothelial cells. A comprehensive histopathological study of the renal biopsy, using electronmicroscopy, is useful in the confirmation of a clinical suspicion and demonstrates the pathogenetic mechanisms in the microcirculatory damage. The close resemblance between the ultrastructural appearance and that seen with the light microscope of TMA and transplant glomerulopathy (TG) is precisely what suggests that both entities are subject to the same etiopathogenetic mechanism in which the endothelial cell is targeted. Recent advances in the pathology of atypical HUS, its relation with complement system and the discovery of specific therapeutic targets, has rekindled an interest in the study of TMA and the importance of renal biopsy.

Human Placental Growth Hormone Variant in Pathological Pregnancies

Growth hormone (GH), an endocrine hormone, primarily secreted from the anterior pituitary, stimulates growth, cell reproduction, and regeneration and is a major regulator of postnatal growth. Humans have two GH genes that encode two versions of GH proteins: a pituitary version (GH-N/GH1) and a placental GH-variant (GH-V/GH2), which are expressed in the syncytiotrophoblast and extravillous trophoblast cells of the placenta. During pregnancy, GH-V replaces GH-N in the maternal circulation at mid-late gestation as the major circulating form of GH. This remarkable change in spatial and temporal GH secretion patterns is proposed to play a role in mediating maternal adaptations to pregnancy. GH-V is associated with fetal growth, and its circulating concentrations have been investigated across a range of pregnancy complications. However, progress in this area has been hindered by a lack of readily accessible and reliable assays for measurement of GH-V. This review will discuss the potential roles of GH-V in normal and pathological pregnancies and will touch on the assays used to quantify this hormone.

Chronic limb-threatening ischemia could benefit from growth hormone therapy for wound healing and limb salvage

Revascularization for chronic limb-threatening ischemia (CLTI) is necessary to alleviate symptoms and wound healing. When it fails or is not possible, there are few alternatives to avoid limb amputation in these patients. Although experimental studies with stem cells and growth factors have shown promise, clinical trials have demonstrated inconsistent results because CLTI patients generally need arteriogenesis rather than angiogenesis. Moreover, in addition to the perfusion of the limb, there is the need to improve the neuropathic response for wound healing, especially in diabetic patients. Growth hormone (GH) is a pleiotropic hormone capable of boosting the aforementioned processes and adds special benefits for the redox balance. This hormone has the potential to mitigate symptoms in ischemic patients with no other options and improves the cardiovascular complications associated with the disease. Here, we discuss the pros and cons of using GH in such patients, focus on its effects on peripheral arteries, and analyze the possible benefits of treating CLTI with this hormone.