Growth hormone replacement normalizes impaired fibrinolysis: new insights into endothelial dysfunction in patients with hypopituitarism and growth hormone deficiency

[Unfavourable cardiovascular consequences of adult growth hormone deficiency]

The growth hormone-insulin-like growth factor-1 (GH-IGF-1) axis plays a crucial role in maintaining the normal function of the cardiovascular system. Results of the last decades demonstrated that GH-IGF-1 takes part in regulating peripheral resistance and contributes to preserving physiological cardiac mass and left ventricular function. Vasculoprotective functions of the GH-IGF-1 axis are believed to counteract atherosclerosis. Unlike in childhood, when GH-deficiency results in growth retardation, GH deficiency does not cause specific symptoms in adults. Adult growth hormone deficiency (AGHD) is characterized by a clustering of cardiometabolic risk factors resulting in a clinical picture similar to the metabolic syndrome. Besides visceral obesity, dyslipidemia and insulin resistance, novel cardiovascular risk factors, such as chronic low-grade inflammation, oxidative stress and prothrombotic state have also been reported in AGHD and may contribute to the increased cardiometabolic risk. Based on a growing body of evidence, long-term GH-replacement improves lipid profile significantly and has a favorable impact on body composition, endothelial function, left ventricular mass as well as the novel, non-traditional cardiometabolic risk factors. Increased mortality associated with the disease is now considered to be multicausal and as such cannot be solely attributed to the GH-deficiency. The etiology of GH-deficiency, treatment of the underlying pathology as well as the inadequate treatment of coexisting hormonal deficiencies might also be responsible for the increased mortality. Nevertheless, in hypopituitarism, adequate replacement therapy including GH-substitution may result in a mortality that is comparable to the general population. Orv Hetil. 2023; 164(41): 1616-1627.

COVID-19 and hypopituitarism

Besides the pulmonary manifestations caused by severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2), an emerging endocrine phenotype, which can heavily impact on the severity of the syndrome, has been recently associated with coronavirus disease 2019 (COVID-19). Patients with pituitary diseases or the pituitary gland itself may also be involved in COVID-19 clinical presentation and/or severity, causing pituitary apoplexy.Moreover, hypopituitarism is frequently burdened by several metabolic complications, including arterial hypertension, hyperglycemia, obesity and vertebral fractures, which have all been associated with poor outcomes and increased mortality in patients infected by SARS-CoV-2.This review will discuss hypopituitarism as a condition that might have a bidirectional relationship with COVID-19 due to the frequent presence of metabolic comorbidities, to the direct or indirect pituitary damage or being per se a potential risk factor for COVID-19. Finally, we will address the current recommendations for the clinical management of vaccines in patients with hypopituitarism and adrenal insufficiency.

Obesity and its impact on COVID-19

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic has proven a challenge to healthcare systems since its first appearance in late 2019. The global spread and devastating effects of coronavirus disease 2019 (COVID-19) on patients have resulted in countless studies on risk factors and disease progression. Overweight and obesity emerged as one of the major risk factors for developing severe COVID-19. Here we review the biology of coronavirus infections in relation to obesity. In particular, we review literature about the impact of adiposity-related systemic inflammation on the COVID-19 disease severity, involving cytokine, chemokine, leptin, and growth hormone signaling, and we discuss the involvement of hyperactivation of the renin-angiotensin-aldosterone system (RAAS). Due to the sheer number of publications on COVID-19, we cannot be completed, and therefore, we apologize for all the publications that we do not cite.

Is Growth Hormone Insufficiency the Missing Link Between Obesity, Male Gender, Age, and COVID-19 Severity?

Evidence has emerged regarding an increased risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with worse prognosis in elderly male patients with obesity, and blunted growth hormone (GH) secretion represents a feature of this population subgroup. Here, a comprehensive review of the possible links between GH-insulinlike growth factor 1 axis impairment and coronavirus disease 2019 (COVID-19) severity is offered. First, unequivocal evidence suggests that immune system dysregulation represents a key element in determining SARS-CoV-2 severity, as well as the association with adult-onset GH deficiency (GHD); notably, if GH is physiologically involved in the development and maintenance of the immune system, its pharmacological replacement in GHD patients seems to positively influence their inflammatory status. In addition, the impaired fibrinolysis associated with GHD may represent a further link between GH-insulin-like growth factor 1 axis impairment and COVID-19 severity, as it has been associated with both conditions. In conclusion, several sources of evidence have supported a relationship between GHD and COVID-19, and they also shed light upon potential beneficial effects of recombinant GH treatment on COVID-19 patients.

Sitagliptin Decreases Visceral Fat and Blood Glucose in Women With Polycystic Ovarian Syndrome

CONTEXT

Women with polycystic ovarian syndrome (PCOS) have decreased growth hormone (GH), which can result in increased visceral adiposity (VAT) and impaired vascular function. GH-releasing hormone, a dipeptidyl peptidase-4 (DPP4) substrate, stimulates GH secretion.

OBJECTIVE

We tested the hypothesis that DPP4 inhibition increases GH and improves glucose levels and vascular function in women with PCOS.

METHODS

Eighteen women with PCOS participated in a double-blind, crossover study. They received sitagliptin either 100 mg or placebo daily for 1 month, with crossover treatments separated by an 8-week washout. During each treatment, women underwent a 75-gram oral glucose tolerance test (OGTT) and assessments of vascular function and body composition. Overnight GH secretion was assessed via venous sampling every 10 minutes for 12 hours and analyzed using an automated deconvolution algorithm.

RESULTS

During OGTT, sitagliptin increased glucagon-like peptide-1 (P < 0.001), early insulin secretion (from mean [± SD] insulinogenic index 1.9 ± 1.2 to 3.2 ± 3.1; P = 0.02), and decreased peak glucose (mean -17.2 mg/dL [95% CI, -27.7 to -6.6]; P < 0.01). At 1 month, sitagliptin decreased VAT (from 1141.9 ± 700.7 to 1055.1 ± 710.1 g; P = 0.02) but did not affect vascular function. Sitagliptin increased GH half-life (from 13.9 ± 3.6 to 17.0 ± 6.8 min, N = 16; P = 0.04) and interpulse interval (from 53.2 ± 20.0 to 77.3 ± 38.2 min, N = 16; P < 0.05) but did not increase mean overnight GH (P = 0.92 vs placebo).

CONCLUSIONS

Sitagliptin decreased the maximal glucose response to OGTT and VAT. Sitagliptin did not increase overnight GH but increased GH half-life and the interpulse interval.

CLINICAL TRIAL REGISTRATION

This study was registered at www.clinicaltrials.gov as NCT02122380 prior to enrollment of the first participant.

Adult growth hormone deficiency: clinical advances and approaches to improve adherence

Introduction: There have been significant clinical advances in the understanding of the diagnosis and benefits of long-term recombinant human growth hormone (rhGH) replacement in adults with GH deficiency (GHD) since its approval in 1996 by the United States Food and Drug Administration.Areas covered: We searched PubMed, Medline, CINAHL, EMBASE and PsychInfo databases between January 2000 and June 2019 for published studies evaluating adults with GHD. We reviewed the data of the oral macimorelin test compared to the GHRH plus arginine and the insulin tolerance tests that led to its approval by the United States FDA and European Medicines Agency for adult diagnostic testing. We summarize the clinical advances of long-term benefits of rhGH therapy and the potential effects of GH receptor polymorphisms on individual treatment responsiveness. We identify that non-adherence and discontinuation rates are high and recommend strategies to support patients to improve adherence. We also provide an overview of several long-acting GH (LAGH) preparations currently under development and their potential role in improving treatment adherence.Expert opinion: This article summarizes recent clinical advances in rhGH replacement therapy, the biological and molecular aspects that may influence rhGH action, and offers practical strategies to enhance adherence in adults with GHD.

Biochemical and in silico evaluation of recombinant E. coli aminopeptidase and in vitro processed human interferon α-2b

Escherichia coli is an extensively used host for the production of recombinant proteins, making its N-terminal methionine aminopeptidase (MAP) an attractive candidate for studies on posttranslational protein processing. The present study describes the recombinant production and properties of MAP from the DH5α strain of E. coli. The soluble and active enzyme was produced in E. coli BL21 (DE3) RIL - codon plus cells under a T7 promoter system and purified by anion-exchange chromatography. It exhibited a molecular weight of 29,200.94 Da by MALDI-TOF analysis. The purified enzyme showed specific activity of 1.64 U/mg with methionylp-nitroanilide and 1.51 U/mg with synthetic tetrapeptide substrate 'MGMM' in a discontinuous HPLC-based assay. In vitro studies showed the processing of up to 36% of Met-INFα-2b in 40 min. In silico studies revealed that the ES-complex formation between the enzyme and interferon has a ΔG -683.07 kJ/mol. Molecular docking results showed that the processed INFα-2b has greater binding affinity with IFNAR2 receptor as indicated by ΔG -784.53 kJ/mol, significantly lower than that of methionine containing INFα-2b (ΔG -717.63 kJ/mol). These findings emphasize the functional superiority or better efficacy of N-terminal methionine processed recombinant interferon.

Treatment of adult growth hormone deficiency with human recombinant growth hormone: an update on current evidence and critical review of advantages and pitfalls

Adult-onset growth-hormone (GH) deficiency (GHD) is a rare disorder, which most commonly results from pituitary or peripituitary tumors and their treatment, and is characterized by alterations in body composition, carbohydrate and lipid metabolism, bone mineral density, cardiovascular risk profile and quality of life, all of which may contribute to an increased morbidity and mortality. Since recombinant human GH (rhGH) became available in 1985, several studies have provided evidence of its beneficial effects, despite the potential risk of developing adverse effects, and much clinical experience has been accumulated. However, in adults, the precise therapeutic role of GH replacement therapy and the individual response to it remains highly variable and is still a matter of debate. In this article, we present a critical review of the available evidence on rhGH replacement therapy in GHD adults, emphasizing the pitfalls clinicians encounter in the diagnosis of GHD and monitoring of rhGH replacement therapy. We will cover all the relevant aspects regarding the potential usefulness of GH treatment, including the hot topic of mortality.

Dipeptidyl Peptidase-4 Inhibition Potentiates Stimulated Growth Hormone Secretion and Vasodilation in Women

BACKGROUND

Diminished growth hormone (GH) is associated with impaired endothelial function and fibrinolysis. GH-releasing hormone is the primary stimulus for GH secretion and a substrate of dipeptidyl peptidase-4. We tested the hypothesis that dipeptidyl peptidase-4 inhibition with sitagliptin increases stimulated GH secretion, vasodilation, and tissue plasminogen activator (tPA) activity.

METHODS AND RESULTS

Healthy adults participated in a 2-part double-blind, randomized, placebo-controlled, crossover study. First, 39 patients (29 women) received sitagliptin or placebo on each of 2 days separated by a washout. One hour after study drug, blood was sampled and then arginine (30 g IV) was given to stimulate GH. Vasodilation was assessed by plethysmography and blood sampled for 150 minutes. Following a washout, 19 of the original 29 women received sitagliptin alone versus sitagliptin plus antagonist to delineate GH receptor (GHR)- (n=5), nitric oxide- (n=7), or glucagon-like peptide-1 receptor- (n=7) dependent effects. Sitagliptin enhanced stimulated GH secretion (P<0.01 versus placebo, for 30 minutes) and free insulin-like growth factor-1 (P<0.001 versus placebo, after adjustment for baseline) in women. Vasodilation and tPA increased in all patients, but sitagliptin enhanced vasodilation (P=0.01 versus placebo) and increased tPA (P<0.001) in women only. GHR blockade decreased free insulin-like growth factor-1 (P=0.04 versus sitagliptin alone) and increased stimulated GH (P<0.01), but decreased vascular resistance (P=0.01) such that nadir vascular resistance correlated inversely with GH (rs=-0.90, P<0.001). GHR blockade suppressed tPA. Neither nitric oxide nor glucagon-like peptide-1 receptor blockade affected vasodilation or tPA.

CONCLUSIONS

Sitagliptin enhances stimulated GH, vasodilation, and fibrinolysis in women. During sitagliptin, increases in free insulin-like growth factor-1 and tPA occur via the GHR, whereas vasodilation correlates with GH but occurs through a GHR-independent mechanism.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01701973.

Growth Hormone (GH) and Cardiovascular System

This review describes the positive effects of growth hormone (GH) on the cardiovascular system. We analyze why the vascular endothelium is a real internal secretion gland, whose inflammation is the first step for developing atherosclerosis, as well as the mechanisms by which GH acts on vessels improving oxidative stress imbalance and endothelial dysfunction. We also report how GH acts on coronary arterial disease and heart failure, and on peripheral arterial disease, inducing a neovascularization process that finally increases flow in ischemic tissues. We include some preliminary data from a trial in which GH or placebo is given to elderly people suffering from critical limb ischemia, showing some of the benefits of the hormone on plasma markers of inflammation, and the safety of GH administration during short periods of time, even in diabetic patients. We also analyze how Klotho is strongly related to GH, inducing, after being released from the damaged vascular endothelium, the pituitary secretion of GH, most likely to repair the injury in the ischemic tissues. We also show how GH can help during wound healing by increasing the blood flow and some neurotrophic and growth factors. In summary, we postulate that short-term GH administration could be useful to treat cardiovascular diseases.

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

The generation of new blood vessels is a complex process mediated by a variety of growth factors, and the growth hormone (GH) has been shown to act as a proangiogenic factor. In fact, human GH deficiency or excess are associated with endothelial dysfunction. Moreover, mouse models have revealed the action of GH in both tissue repair and in the microvascular circulation of normal tissues. In this study, we investigated the in vitro effects of GH on endothelial cells. Using a murine endothelioma cell line (tEnd.1), we demonstrated that GH has a mitogenic effect. The hormone also affected the endothelial cellular morphology and augmented the deposition of the extracellular matrix molecules, laminin, and fibronectin, on tEnd.1 surface. GH could stimulate tEnd.1 cell fugetaxis, in transwell chambers migration assay, and increased the formation of capillary-like structures in Matrigel®-coated plates. Given the important role of angiogenesis during tissue injury, for example, at ischemic lesions, these findings shed light on therapeutic angiogenesis, particularly in pathologies where the cardiovascular system has been compromised.

Impact of adult growth hormone deficiency on metabolic profile and cardiovascular risk [Review]

Adult growth hormone deficiency (GHD) is a well defined clinical condition, which is characterized by abnormal body composition, impaired physical activity and decreased quality of life. In addition, in recent years, growing interest has been shown towards cardiovascular risks in adult patients affected by GHD. In this regard, GHD is widely known to be associated with increased mortality, likely due to the increase of risk factors, such as central obesity, impaired lipid and glucose profiles and other less-known risk factors, such as inflammatory cytokines, endothelial dysfunction and oxidative stress. However, very few papers have recently discussed this topic. In this review, the aim is to clarify this issue by discussing evidence regarding the effects of adult GHD on metabolic and cardiovascular profiles.

Growth hormone, insulin-like growth factor-1 and the aging brain

Growth hormone (GH) and insulin-like growth factor (IGF)-1 regulate the development and function of cells throughout the body. Several clinical diseases that result in a decline in physical and mental functions are marked by mutations that disrupt GH or IGF-1 signaling. During the lifespan there is a robust decrease in both GH and IGF-1. Because GH and IGF-1 are master regulators of cellular function, impaired GH and IGF-1 signaling in aging/disease states leads to significant alterations in tissue structure and function, especially within the brain. This review is intended to highlight the effects of the GH and IGF-1 on neuronal structure, function, and plasticity. Furthermore, we address several potential mechanisms through which the age-related reductions in GH and IGF-1 affect cognition. Together, the studies reviewed here highlight the importance of maintaining GH and IGF-1 signaling in order to sustain proper brain function throughout the lifespan.