Demonstration of direct effects of growth hormone on neonatal cardiomyocytes

An Overview of Cardiovascular Risk in Pituitary Disorders

Cardiovascular comorbidities owing to hormonal excess or deficiency are the main cause of mortality in patients with pituitary disorders. In patients with Cushing's Disease, there is an increased prevalence of cardiovascular diseases and/or risk factors including visceral obesity, insulin resistance, atherosclerosis, arterial hypertension, dyslipidaemia, hypercoagulability as well as structural and functional changes in the heart, like cardiac hypertrophy and left ventricle (LV) dysfunction. Notably, these demonstrate limited reversibility even after remission. Furthermore, patients with acromegaly may manifest insulin resistance but also structural and functional heart changes, also known as "acromegalic cardiomyopathy". Patients with prolactinomas demonstrate an aggravation of metabolic parameters, obesity, dysregulation of glucose and lipid metabolism as well as endothelial dysfunction. Hypopituitarism and conventional hormonal replacement therapy may also contribute to an unhealthy metabolic status, which promotes atherosclerosis and may lead to premature mortality. This review discusses the literature on cardiovascular risk in patients with pituitary disorders to increase physician awareness regarding this aspect of management in patients with pituitary disorders.

Augmented Cardiac Growth Hormone Signaling Contributes to Cardiomyopathy Following Genetic Disruption of the Cardiomyocyte Circadian Clock

Circadian clocks regulate numerous biological processes, at whole body, organ, and cellular levels. This includes both hormone secretion and target tissue sensitivity. Although growth hormone (GH) secretion is time-of-day-dependent (increased pulse amplitude during the sleep period), little is known regarding whether circadian clocks modulate GH sensitivity in target tissues. GH acts in part through induction of insulin-like growth factor 1 (IGF1), and excess GH/IGF1 signaling has been linked to pathologies such as insulin resistance, acromegaly, and cardiomyopathy. Interestingly, genetic disruption of the cardiomyocyte circadian clock leads to cardiac adverse remodeling, contractile dysfunction, and reduced lifespan. These observations led to the hypothesis that the cardiomyopathy observed following cardiomyocyte circadian clock disruption may be secondary to chronic activation of cardiac GH/IGF1 signaling. Here, we report that cardiomyocyte-specific BMAL1 knockout (CBK) mice exhibit increased cardiac GH sensitivity, as evidenced by augmented GH-induced STAT5 phosphorylation (relative to littermate controls) in the heart (but not in the liver). Moreover, Igf1 mRNA levels are approximately 2-fold higher in CBK hearts (but not in livers), associated with markers of GH/IGF1 signaling activation (e.g., p-ERK, p-mTOR, and p-4EBP1) and adverse remodeling (e.g., cardiomyocyte hypertrophy and interstitial fibrosis). Genetic deletion of one allele of the GH receptor (GHR) normalized cardiac Igf1 levels in CBK hearts, associated with a partial normalization of adverse remodeling. This included attenuated progression of cardiomyopathy in CBK mice. Collectively, these observations suggest that excessive cardiac GH/IGF1 signaling contributes toward cardiomyopathy following genetic disruption of the cardiomyocyte circadian clock.

Diabetes Mellitus Predicts Weight Gain After Surgery in Patients With Acromegaly

OBJECTIVE

Metabolic complications are common in patients with acromegaly. However, this occasionally does not improve post-surgery and may be related to postoperative weight gain. We aimed to investigate the postoperative weight change and factors associated with postoperative weight gain in patients with acromegaly.

DESIGN AND METHODS

Overall, 113 consecutive patients with body weight records pre- and 3-6 months post-surgery between October 2009 and March 2021 were enrolled. Patients were divided into three groups: weight loss (weight decrease ≥3%), stable, and weight gain (weight increase ≥3%). Hormone status, metabolic comorbidities, and anthropometric parameters were compared between the groups.

RESULTS

Among 113 patients, 29 (25.7%) and 26 (23.0%) patients lost and gained weight, respectively, post-surgery. There were no significant differences in baseline characteristics, including age at diagnosis, sex, body mass index, and growth hormone levels among the three groups. The prevalence of diabetes mellitus at diagnosis was significantly higher in the weight gain group than in the other groups. Patients with diabetes (n=22) had a 5.2-fold higher risk of postoperative weight gain than those with normal glucose tolerance (n=37) (P=0.006). In the diabetes mellitus group, the percentage lean mass decreased (-4.5 [-6.6-2.0]%, P=0.002), and the percentage fat mass significantly increased post-surgery (18.0 [4.6-36.6]%, P=0.003), whereas the normal glucose tolerance group did not show body composition changes post-surgery.

CONCLUSION

In patients with acromegaly, 23% experienced ≥3% weight gain post-surgery. Diabetes mellitus at diagnosis is a significant predictor of weight and fat gain post-surgery.

Relevance of mitochondrial dysfunction in heart disease associated with insulin resistance conditions

Insulin resistance plays a key role in the development and progression of obesity, diabetes, and their complications. Moreover, insulin resistance is considered the principal link between metabolic diseases and cardiovascular diseases. Heart disease associated with insulin resistance is one of the most important consequences of both obesity and diabetes, and it is characterized by impaired cardiac energetics, diastolic dysfunction, and finally heart failure. Mitochondrion plays a key role in cell energy homeostasis and is the main source of reactive oxygen species. Obesity and diabetes are associated with alterations in mitochondrial function and dynamics. Mitochondrial dysfunction is characterized by changes in mitochondrial respiratory chain with reduced ATP production and elevated reactive oxygen species production. These mitochondrial alterations together with inflammation contribute to the development and progression of heart disease under insulin resistance conditions. Finally, numerous miRNAs participate in the regulation of energy substrate metabolism, reactive oxygen species production, and apoptotic pathways within the mitochondria. This notion supports the relevance of interactions between miRNAs and mitochondrial dysfunction in the pathophysiology of metabolic heart disease.

New aspects of endocrine control of atrial fibrillation and possibilities for clinical translation

Hormones are potent endo-, para-, and autocrine endogenous regulators of the function of multiple organs, including the heart. Endocrine dysfunction promotes a number of cardiovascular diseases, including atrial fibrillation (AF). While the heart is a target for endocrine regulation, it is also an active endocrine organ itself, secreting a number of important bioactive hormones that convey significant endocrine effects, but also through para-/autocrine actions, actively participate in cardiac self-regulation. The hormones regulating heart-function work in concert to support myocardial performance. AF is a serious clinical problem associated with increased morbidity and mortality, mainly due to stroke and heart failure. Current therapies for AF remain inadequate. AF is characterized by altered atrial function and structure, including electrical and profibrotic remodelling in the atria and ventricles, which facilitates AF progression and hampers its treatment. Although features of this remodelling are well-established and its mechanisms are partly understood, important pathways pertinent to AF arrhythmogenesis are still unidentified. The discovery of these missing pathways has the potential to lead to therapeutic breakthroughs. Endocrine dysfunction is well-recognized to lead to AF. In this review, we discuss endocrine and cardiocrine signalling systems that directly, or as a consequence of an underlying cardiac pathology, contribute to AF pathogenesis. More specifically, we consider the roles of products from the hypothalamic-pituitary axis, the adrenal glands, adipose tissue, the renin–angiotensin system, atrial cardiomyocytes, and the thyroid gland in controlling atrial electrical and structural properties. The influence of endocrine/paracrine dysfunction on AF risk and mechanisms is evaluated and discussed. We focus on the most recent findings and reflect on the potential of translating them into clinical application.

Myocardium Metabolism in Physiological and Pathophysiological States: Implications of Epicardial Adipose Tissue and Potential Therapeutic Targets

The main energy substrate of adult cardiomyocytes for their contractility are the fatty acids. Its metabolism generates high ATP levels at the expense of high oxygen consumption in the mitochondria. Under low oxygen supply, they can get energy from other substrates, mainly glucose, lactate, ketone bodies, etc., but the mitochondrial dysfunction, in pathological conditions, reduces the oxidative metabolism. In consequence, fatty acids are stored into epicardial fat and its accumulation provokes inflammation, insulin resistance, and oxidative stress, which enhance the myocardium dysfunction. Some therapies focused on improvement the fatty acids entry into mitochondria have failed to demonstrate benefits on cardiovascular disorders. Oppositely, those therapies with effects on epicardial fat volume and inflammation might improve the oxidative metabolism of myocardium and might reduce the cardiovascular disease progression. This review aims at explain (a) the energy substrate adaptation of myocardium in physiological conditions, (b) the reduction of oxidative metabolism in pathological conditions and consequences on epicardial fat accumulation and insulin resistance, and (c) the reduction of cardiovascular outcomes after regulation by some therapies.

Metabolic Fingerprint of Acromegaly and its Potential Usefulness in Clinical Practice

Insulin-like growth factor-1 (IGF-1) and growth hormone (GH) levels are the main targets for monitoring acromegaly activity, but they are not in close relationship with the clinical course of the disease and the associated comorbidities. The present study was aimed at identifying metabolites that could be used as biomarkers for a better disease phenotyping. For this purpose, metabolic fingerprint using an untargeted metabolomic approach was examined in serum from 30 patients with acromegaly and 30 age-matched controls. Patients with acromegaly presented fewer branched-chain amino acids (BCAAs) compared to the control group (valine: 4.75 ± 0.87 vs. 5.20 ± 1.06 arbitrary units (AUs), p < 0.05; isoleucine: 2.54 ± 0.41 vs. 2.80 ± 0.51 AUs; p < 0.05). BCAAs were also lower in patients with active disease compared to patients with normal levels of IGF-1 with or without medical treatment. GH, but not IGF-1, serum levels were inversely correlated with both valine and isoleucine. These findings indicate that low levels of BCAAs represent the main metabolic fingerprint of acromegaly and that GH, rather than IGF-1, might be the primary mediator. In addition, our results suggest that the assessment of BCAAs could help to identify active disease and to monitor the response to therapeutic strategies.

Incidence rate and risk factors of early repolarization in patients with growth hormone-secreting pituitary adenoma: a cohort study

Purpose

To investigate the incidence and risk factors for early repolarization (ER) in patients with growth hormone (GH)-secreting pituitary adenomas.

Methods

From August 2014 to August 2016, patients with GH-secreting pituitary adenomas and non-functioning pituitary adenomas admitted to the First Affiliated Hospital, Sun Yat-sen University, were prospectively enrolled. Logistic regression analysis was used to investigate risk factors for ER development.

Results

A total of 118 patients with GH-secreting pituitary adenomas (41 with concomitant ER) and 103 patients with non-functioning pituitary adenomas were included. Compared with the non-functioning adenoma group GH and IGF-1 levels, left ventricular mass index (LVMI), and incidence of ER were significantly higher in the GH-secreting pituitary adenoma group (all P<0.05). LVMI was an independent risk factor for ER. Bivariate correlation analysis showed that course of disease, GH, IGF-1, and diabetes were correlated with LVMI. Course of disease and IGF-1 were directly correlated with LVMI. Two-year follow-up of patients who underwent transsphenoidal resection showed that incidence of ER was significantly decreased in patients with normal GH and IGF-1 levels.

Conclusion

Compared with non-functioning pituitary adenoma patients, patients with GH-secreting pituitary adenomas have a significantly higher incidence of ER. Elevation of serum GH and IGF-1 had positive correlations with cardiac muscle cell hypertrophy and increased LVMI.

Abrogation of GH action in Kupffer cells results in increased hepatic CD36 expression and exaggerated nonalcoholic fatty liver disease

OBJECTIVE

To investigate the effects of GH signaling on Kupffer cells and the resulting changes in lipid homeostasis and their underlying mechanism(s) in the livers of diet-induced obese (DIO) mice.

DESIGN

Male macrophage specific-growth hormone receptor knockout mice (MacGHR KO) and their litter mate controls were fed a high fat diet containing 60% calories from fat for 26 weeks. Lipid content and lipid profiles in the liver and circulation were analyzed. Expression levels of CD36 in the liver were quantified by RT-PCR and Western Blot.

RESULTS

Increased hepatic lipid content and abundance of long-chain unsaturated fatty acids were observed in the liver of MacGHR KO mice. These findings were associated with increased steady state levels of CD36 mRNA and protein in MacGHR KO mice when compared with their litter mate controls.

CONCLUSION

GH action in Kupffer cells is required for maintaining hepatic lipid homeostasis, in part via regulation of hepatic CD36 expression.

Cardiovascular Disease in Acromegaly

In patients with acromegaly, chronic excess of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) leads to the development of acromegalic cardiomyopathy. Its main features are biventricular hypertrophy, diastolic dysfunction, and in later stages, systolic dysfunction and congestive heart failure. Surgical and/or pharmacological treatment of acromegaly and control of cardiovascular risk factors help reverse some of these pathophysiologic changes and decrease the high risk of cardiovascular complications.

The Heart of the Matter: Cardiac Manifestations of Endocrine Disease

Endocrine disorders manifest as a disturbance in the milieu of multiple organ systems. The cardiovascular system may be directly affected or alter its function to maintain the state of homeostasis. In this article, we aim to review the pathophysiology, diagnosis, clinical features and management of cardiac manifestations of various endocrine disorders.

Effects of long-term combined treatment with somatostatin analogues and pegvisomant on cardiac structure and performance in acromegaly

To date, no data are available on the effects of long-term combined treatment with somatostatin analogues (SA) and pegvisomant (PEG) on cardiovascular complications in acromegaly. The current study aimed at investigating the effects of long-term SA + PEG on cardiac structure and performance. Thirty-six patients (14 M, 22 F, aged 52.3 ± 10.2 years) entered this study. Weight, BMI, systolic (SBP) and diastolic (DBP) blood pressure, IGF-I, fasting glucose (FG), fasting insulin (FI), HOMA-IR, HbA_1c, and lipids were evaluated at baseline (T0), after long-term (median 36 months) SA (T1), after 12 (T12) and 60 (T60) months of SA + PEG, and at last follow-up (LFU, median 78 months). At each time point, all patients underwent echocardiography. At T1, induced a slight but not significant decrease in IGF-I (p = 0.077), whereas FI (p = 0.004), HOMA-IR (p = 0.013), ejection fraction (EF, p = 0.013), early (E) to late (A) ventricular filling velocities (E/A, p = 0.001), and isovolumetric relaxation time (IVRT, p = 0.000) significantly improved. At T12, IGF-I (p = 0.000) significantly reduced compared to T0, and FI (p = 0.001), HOMA-IR (p = 0.000), LVMI (p = 0.000), and E/A (p = 0.006) further improved compared to T1. At T60, FI (p = 0.027), HOMA-IR (p = 0.049), and E/A (p = 0.005) significantly improved as compared to T1. At LFU IGF-I normalized in 83.3 %, FI (p = 0.000), HOMA-IR (p = 0.000), LVMi (p = 0.000), and E/A (p = 0.005) further improved as compared to T1. PEG dose significantly correlated with LVMi at T12 (r = 0.575, p = 0.000) and T60 (r = 0.403, p = 0.037). Long-term PEG addition to SA improves cardiac structure and performance, particularly diastolic dysfunction, in acromegalic patients resistant to SA.

Complications of acromegaly: cardiovascular, respiratory and metabolic comorbidities

Acromegaly is associated with an enhanced mortality, with cardiovascular and respiratory complications representing not only the most frequent comorbidities but also two of the main causes of deaths, whereas a minor role is played by metabolic complications, and particularly diabetes mellitus. The most prevalent cardiovascular complications of acromegaly include a cardiomyopathy, characterized by cardiac hypertrophy and diastolic and systolic dysfunction together with arterial hypertension, cardiac rhythm disorders and valve diseases, as well as vascular endothelial dysfunction. Biochemical control of acromegaly significantly improves cardiovascular disease, albeit completely recovering to normal mainly in young patients with short disease duration. Respiratory complications, represented mainly by sleep-breathing disorders, particularly sleep apnea, and respiratory insufficiency, frequently occur at the early stage of the disease and, although their severity decreases with disease control, this improvement does not often change the indication for a specific therapy directed to improve respiratory function. Metabolic complications, including glucose and lipid disorders, are variably reported in acromegaly. Treatments of acromegaly may influence glucose metabolism, and the presence of diabetes mellitus in acromegaly may affect the choice of treatments, so that glucose homeostasis is worth being monitored during the entire course of the disease. Early diagnosis and prompt treatment of acromegaly, aimed at obtaining a strict control of hormone excess, are the best strategy to limit the development or reverse the complications and prevent the premature mortality.

Altered lipid metabolism in the aging kidney identified by three layered omic analysis

Aging-associated diseases and their comorbidities affect the life of a constantly growing proportion of the population in developed countries. At the center of these comorbidities are changes of kidney structure and function as age-related chronic kidney disease predisposes to the development of cardiovascular diseases such as stroke, myocardial infarction or heart failure. To detect molecular mechanisms involved in kidney aging, we analyzed gene expression profiles of kidneys from adult and aged wild-type mice by transcriptomic, proteomic and targeted lipidomic methodologies. Interestingly, transcriptome and proteome analyses revealed differential expression of genes primarily involved in lipid metabolism and immune response. Additional lipidomic analyses uncovered significant age-related differences in the total amount of phosphatidylethanolamines, phosphatidylcholines and sphingomyelins as well as in subspecies of phosphatidylserines and ceramides with age. By integration of these datasets we identified Aldh1a1, a key enzyme in vitamin A metabolism specifically expressed in the medullary ascending limb, as one of the most prominent upregulated proteins in old kidneys. Moreover, ceramidase Asah1 was highly expressed in aged kidneys, consistent with a decrease in ceramide C16. In summary, our data suggest that changes in lipid metabolism are involved in the process of kidney aging and in the development of chronic kidney disease.

Neonatal hyper- and hypothyroidism alter the myoglobin gene expression program in adulthood

Myoglobin acts as an oxygen store and a reactive oxygen species acceptor in muscles. We examined myoglobin mRNA in rat cardiac ventricle and skeletal muscles during the first 42 days of life and the impact of transient neonatal hypo- and hyperthyroidism on the myoglobin gene expression pattern. Cardiac ventricle and skeletal muscles of Wistar rats at 7-42 days of life were quickly removed, and myoglobin mRNA was determined by Northern blot analysis. Rats were treated with propylthiouracil (5-10 mg/100 g) and triiodothyronine (0.5-50 µg/100 g) for 5, 15, or 30 days after birth to induce hypo- and hyperthyroidism and euthanized either just after treatment or at 90 days. During postnatal (P) days 7-28, the ventricle myoglobin mRNA remained unchanged, but it gradually increased in skeletal muscle (12-fold). Triiodothyronine treatment, from days P0-P5, increased the skeletal muscle myoglobin mRNA 1.5- to 4.5-fold; a 2.5-fold increase was observed in ventricle muscle, but only when triiodothyronine treatment was extended to day P15. Conversely, hypothyroidism at P5 markedly decreased (60%) ventricular myoglobin mRNA. Moreover, transient hyperthyroidism in the neonatal period increased ventricle myoglobin mRNA (2-fold), and decreased heart rate (5%), fast muscle myoglobin mRNA (30%) and body weight (20%) in adulthood. Transient hypothyroidism in the neonatal period also permanently decreased fast muscle myoglobin mRNA (30%) and body weight (14%). These results indicated that changes in triiodothyronine supply in the neonatal period alter the myoglobin expression program in ventricle and skeletal muscle, leading to specific physiological repercussions and alterations in other parameters in adulthood.

GH and the cardiovascular system: an update on a topic at heart

In this review, the importance of growth hormone (GH) for the maintenance of normal cardiac function in adult life is discussed. Physiological effects of GH and underlying mechanisms for interactions between GH and insulin-like growth factor I (IGF-I) and the cardiovascular system are covered as well as the cardiac dysfunction caused both by GH excess (acromegaly) and by GH deficiency in adult hypopituitary patients. In both acromegaly and adult GH deficiency, there is also increased cardiovascular morbidity and mortality possibly linked to aberrations in GH status. Finally, the status of the GH/IGF-I system in relation to heart failure and the potential of GH as a therapeutic tool in the treatment of heart failure are reviewed in this article.

Combined vaccination with HER-2 peptide followed by therapy with VEGF peptide mimics exerts effective anti-tumor and anti-angiogenic effects in vitro and in vivo

Overexpression of HER-2 and VEGF plays a key role in the development and metastasis of several human cancers. Many FDA-approved therapies targeting both HER-2 (Trastuzumab, Herceptin) and VEGF (Bevacizumab, Avastin) are expensive, have unacceptable toxicities and are often associated with the development of resistance. Here, we evaluate the dual antitumor effects of combining designed particular HER-2 peptide vaccine with VEGF peptide mimics. In vitro, HER-2 phosphorylation and antibody-dependent cellular toxicity were used to validate whether combining HER-2- and VEGF-targeting therapies would be effective. Moreover, a two-pronged approach was tested in vivo: (1) active immunotherapy with conformational HER-2 B-cell epitope vaccines and (2) anti-angiogenic therapy with a peptide structured to mimic VEGF. A transplantable BALB/c mouse model challenged with TUBO cells was used to test the effects of the HER-2 peptide vaccine combined with VEGF peptide mimics. Tumor sections after treatment were stained for blood vessel density and actively dividing cells. Our results show that immunization with an HER-2 peptide epitope elicits high affinity HER-2 native antibodies that are effective in inhibiting tumor growth in vivo, an effect that is enhanced by VEGF peptide mimics. We demonstrate that the combination of HER-2 and VEGF peptides induces potent anti-tumor and anti-angiogenic responses.

JAK-STAT signaling and myocardial glucose metabolism

JAK-STAT signaling occurs in virtually every tissue of the body, and so does glucose metabolism. In this review, we summarize the regulation of glucose metabolism in the myocardium and ponder whether JAK-STAT signaling participates in this regulation. Despite a paucity of data directly pertaining to cardiac myocytes, we conclude that JAK-STAT signaling may contribute to the development of insulin resistance in the myocardium in response to various hormones and cytokines.

Transcriptional profiling reveals progeroid Ercc1(-/Δ) mice as a model system for glomerular aging

Background

Aging-related kidney diseases are a major health concern. Currently, models to study renal aging are lacking. Due to a reduced life-span progeroid models hold the promise to facilitate aging studies and allow examination of tissue-specific changes. Defects in genome maintenance in the Ercc1^-/Δ progeroid mouse model result in premature aging and typical age-related pathologies. Here, we compared the glomerular transcriptome of young and aged Ercc1-deficient mice to young and aged WT mice in order to establish a novel model for research of aging-related kidney disease.

Results

In a principal component analysis, age and genotype emerged as first and second principal components. Hierarchical clustering of all 521 genes differentially regulated between young and old WT and young and old Ercc1^-/Δ mice showed cluster formation between young WT and Ercc1^-/Δ as well as old WT and Ercc1^-/Δ samples. An unexpectedly high number of 77 genes were differentially regulated in both WT and Ercc1^-/Δ mice (p < 0.0001). GO term enrichment analysis revealed these genes to be involved in immune and inflammatory response, cell death, and chemotaxis. In a network analysis, these genes were part of insulin signaling, chemokine and cytokine signaling and extracellular matrix pathways.

Conclusion

Beyond insulin signaling, we find chemokine and cytokine signaling as well as modifiers of extracellular matrix composition to be subject to major changes in the aging glomerulus. At the level of the transcriptome, the pattern of gene activities is similar in the progeroid Ercc1^-/Δ mouse model constituting a valuable tool for future studies of aging-associated glomerular pathologies.

Acromegalic cardiomyopathy in an extensively admixed population: is there a role for GH/IGF-I axis?

BACKGROUND

A specific acromegaly-related cardiomyopathy has been described in the literature, largely in Caucasians, which is independent of other risk factors, mainly hypertension.

OBJECTIVE

This study assessed the cardiac changes in acromegalics of significant ethnic diversity and also the relevance of the aetiopathogenic factors involved, such as disease activity and hypertension.

DESIGN

It is a cross-sectional study with a comparative control group.

PATIENTS AND METHODS

In this study, 37 acromegalic patients (20 Intermediate-skinned (IS), 14 Dark-skinned (DS) and three Light-skinned (LS) individuals) and 74 controls matched by age, gender and hypertension were evaluated. Cardiac morphology and function were addressed using echocardiography parameters.

RESULTS

The mean age of patients was 46.9 ± 12.8 years, with 67.6% being women and 43.2% hypertensive. The prevalence of left ventricular hypertrophy (LVH) between acromegalics was 56.8% vs 10.8% in the controls (P < 0.001). About 86% of patients with LVH had active disease (P = 0.023). Logistic regression revealed that disease activity presented a stronger association (OR = 5.925; CI = 1.085-32.351; P = 0.040) with LVH than hypertension (OR = 3.237; CI = 0.702-14.924; P = 0.132). When DS acromegalics were compared with IS ones, no statistically significant differences were observed.

CONCLUSION

Chronically hyperactive somatotropic axis remains as an independent and determining factor in the development of left ventricular hypertrophy, as it is more associated with this condition than hypertension in a largely admixed population with a high degree of African ancestry.

Growth hormone and the cardiovascular system

Growth hormone (GH) exerts its effects through insulin-like growth factor-1, and although ubiquitous in human tissues, it has a significant role in cardiovascular function. In recent years, there has been a great deal of interest in GH as an etiologic factor in many cardiovascular disease states. Acromegaly, a state of endogenous GH excess, results in myocardial hypertrophy and decreased cardiac performance with increased cardiovascular mortality. Additional insight into the role of excess GH on the cardiovascular system has been gained from data collected in athletes doping with GH. Likewise, GH deficiency is associated with increased mortality, possibly from the associated increase in atherosclerosis, lipid abnormalities, and endothelial dysfunction. However, further research is required to clarify the benefit of GH treatment in both deficient states and in heart failure patients.

Myocardial AKT: the omnipresent nexus

One of the greatest examples of integrated signal transduction is revealed by examination of effects mediated by AKT kinase in myocardial biology. Positioned at the intersection of multiple afferent and efferent signals, AKT exemplifies a molecular sensing node that coordinates dynamic responses of the cell in literally every aspect of biological responses. The balanced and nuanced nature of homeostatic signaling is particularly essential within the myocardial context, where regulation of survival, energy production, contractility, and response to pathological stress all flow through the nexus of AKT activation or repression. Equally important, the loss of regulated AKT activity is primarily the cause or consequence of pathological conditions leading to remodeling of the heart and eventual decompensation. This review presents an overview compendium of the complex world of myocardial AKT biology gleaned from more than a decade of research. Summarization of the widespread influence that AKT exerts upon myocardial responses leaves no doubt that the participation of AKT in molecular signaling will need to be reckoned with as a seemingly omnipresent regulator of myocardial molecular biological responses.

Urocortin-induced cardiomyocytes hypertrophy is associated with regulation of the GSK-3β pathway

Urocortin-1 (UCN), a member of the corticotropin-releasing factor, is a cardioprotective peptide, and is also involved in cardiac hypertrophy. The involvement of GSK-3β, a pivotal kinase in cardiac hypertrophy, in response to UCN is not yet documented. Cardiomyocytes from adult rats were stimulated for 48 h with UCN. Cell size, protein, and DNA contents were determined. Phosphorylated and total forms GSK-3β and the total amount of β-catenin were quantified by Western immunoblots. The effects of astressin, a UCN competitive receptor antagonist, were also evaluated. UCN increased cell size and the protein-to-DNA ratio, in accordance with a hypertrophic response. This effect was associated with increased phosphorylation of GSK-3β and marked accumulation of β-catenin, a downstream element to GSK-3β. All these effects were prevented by astressin and LY294002, an inhibitor of the phosphatidyl-inositol-3-kinase. UCN-induced cardiomyocytes hypertrophy is associated with regulation of GSK-3β, a pivotal kinase involved in cardiac hypertrophy, in a PI3K-dependent manner. Furthermore, the pharmacological blockade of UCN receptors was able to prevent UCN-induced hypertrophy, which leads to inhibition of the Akt/GSK-3β pathway.

Uncoupling antisense-mediated silencing and DNA methylation in the imprinted Gnas cluster

There is increasing evidence that non-coding macroRNAs are major elements for silencing imprinted genes, but their mechanism of action is poorly understood. Within the imprinted Gnas cluster on mouse chromosome 2, Nespas is a paternally expressed macroRNA that arises from an imprinting control region and runs antisense to Nesp, a paternally repressed protein coding transcript. Here we report a knock-in mouse allele that behaves as a Nespas hypomorph. The hypomorph mediates down-regulation of Nesp in cis through chromatin modification at the Nesp promoter but in the absence of somatic DNA methylation. Notably there is reduced demethylation of H3K4me3, sufficient for down-regulation of Nesp, but insufficient for DNA methylation; in addition, there is depletion of the H3K36me3 mark permissive for DNA methylation. We propose an order of events for the regulation of a somatic imprint on the wild-type allele whereby Nespas modulates demethylation of H3K4me3 resulting in repression of Nesp followed by DNA methylation. This study demonstrates that a non-coding antisense transcript or its transcription is associated with silencing an overlapping protein-coding gene by a mechanism independent of DNA methylation. These results have broad implications for understanding the hierarchy of events in epigenetic silencing by macroRNAs.

Genomic imprinting is a process resulting in expression of genes according to parental origin. Some imprinted genes are expressed when paternally derived and others when maternally derived. Thus imprinted genes are monoallelically expressed and one copy has to be silenced. There is evidence that some long non-coding RNAs, acting in cis, have a role in silencing. We investigated the role of Nespas, a gene for a non-coding RNA that is only expressed from the paternally derived chromosome in the Gnas cluster and runs antisense to its sense counterpart, Nesp. Expression of Nespas is associated with silencing of Nesp and a repressive methylation mark on the Nesp DNA. We generated a Nespas mutant with reduced levels of activity and showed that it down-regulated its sense counterpart Nesp, in the absence of a DNA methylation mark, but in the presence of an altered chromatin mark. We conclude that Nespas can repress Nesp by a mechanism independent of DNA methylation, by modulating a chromatin mark.

Update: Systemic Diseases and the Cardiovascular System (II). The endocrine system and the heart: a review

Normal endocrine function is essential for cardiovascular health. Disorders of the endocrine system, consisting of hormone hyperfunction and hypofunction, have multiple effects on the cardiovascular system. In this review, we discuss the epidemiology, diagnosis, and management of disorders of the pituitary, thyroid, parathyroid, and adrenal glands, with respect to the impact of endocrine dysfunction on the cardiovascular system. We also review the cardiovascular benefits of restoring normal endocrine function.

Update: Systemic Diseases and the Cardiovascular System (II). The endocrine system and the heart: a review

Normal endocrine function is essential for cardiovascular health. Disorders of the endocrine system, consisting of hormone hyperfunction and hypofunction, have multiple effects on the cardiovascular system. In this review, we discuss the epidemiology, diagnosis, and management of disorders of the pituitary, thyroid, parathyroid, and adrenal glands, with respect to the impact of endocrine dysfunction on the cardiovascular system. We also review the cardiovascular benefits of restoring normal endocrine function.

The glomerular podocyte as a target of growth hormone action: implications for the pathogenesis of diabetic nephropathy

Involvement of the growth hormone (GH) / insulin-like growth factor 1 (IGF-I) axis in the pathogenesis of diabetic nephropathy (DN) is strongly suggested by studies investigating the impact of GH excess and deficiency on renal structure and function. GH excess in both the human (acromegaly) and in transgenic animal models is characterized by significant structural and functional changes in the kidney. In the human a direct relationship has been noted between the activity of the GH/IGF-1 axis and renal hypertrophy, microalbuminuria, and glomerulosclerosis. Conversely, states of GH deficiency or deficiency or inhibition of GH receptor (GHR) activity confer a protective effect against DN. The glomerular podocyte plays a central and critical role in the structural and functional integrity of the glomerular filtration barrier and maintenance of normal renal function. Recent studies have revealed that the glomerular podocyte is a target of GH action and that GH's actions on the podocyte could be detrimental to the structure and function of the podocyte. These results provide a novel mechanism for GH's role in the pathogenesis of DN and offer the possibility of targeting the GH/IGF-1 axis for the prevention and treatment of DN.

Growth hormone (GH)-dependent expression of a natural antisense transcript induces zinc finger E-box-binding homeobox 2 (ZEB2) in the glomerular podocyte: a novel action of gh with implications for the pathogenesis of diabetic nephropathy

Growth hormone (GH) excess results in structural and functional changes in the kidney and is implicated as a causative factor in the development of diabetic nephropathy (DN). Glomerular podocytes are the major barrier to the filtration of serum proteins, and altered podocyte function and/or reduced podocyte number is a key event in the pathogenesis of DN. We have previously shown that podocytes are a target for GH action. To elucidate the molecular basis for the effects of GH on the podocyte, we conducted microarray and RT-quantitative PCR analyses of immortalized human podocytes and identified zinc finger E-box-binding homeobox 2 (ZEB2) to be up-regulated in a GH dose- and time-dependent manner. We established that the GH-dependent increase in ZEB2 levels is associated with increased transcription of a ZEB2 natural antisense transcript required for efficient translation of the ZEB2 transcript. GH down-regulated expression of E- and P-cadherins, targets of ZEB2, and inhibited E-cadherin promoter activity. Mutation of ZEB2 binding sites on the E-cadherin promoter abolished this effect of GH on the E-cadherin promoter. Whereas GH increased podocyte permeability to albumin in a paracellular albumin influx assay, shRNA-mediated knockdown of ZEB2 expression abrogated this effect. We conclude that GH increases expression of ZEB2 in part by increasing expression of a ZEB2 natural antisense transcript. GH-dependent increase in ZEB2 expression results in loss of P- and E-cadherins in podocytes and increased podocyte permeability to albumin. Decreased expression of P- and E-cadherins is implicated in podocyte dysfunction and epithelial-mesenchymal transition observed in DN. We speculate that the actions of GH on ZEB2 and P- and E-cadherin expression play a role in the pathogenesis of microalbuminuria of DN.

The cardiovascular phenotype of a mouse model of acromegaly

BACKGROUND

Although, it is accepted that there is an excess of cardiovascular mortality in acromegaly, it is uncertain whether this is due to the direct effects of growth hormone-induced-cardiomyopathy or is a consequence of atherosclerosis secondary to the metabolic syndrome often observed in this condition. Direct comparison of a mouse model of acromegaly to a mouse model of Laron's syndrome allowed us to carry out detailed phenotyping and better understand the role GH plays in the circulatory system.

METHODS AND RESULTS

Transgenic mice that overexpress the growth hormone gene (GH) developed gigantism, including insulin resistance and higher blood pressures commensurate with increased body mass. In these giant mice, the hearts were hypertrophied but haemodynamic studies suggested contractile function was normal. Segments of small arteries mounted in a pressure myograph showed vascular wall hypertrophy but a preserved lumen diameter. Vascular contractile function was normal. Mice in which the GH receptor gene was disrupted or 'knocked out' were dwarf and had low blood pressure, small hearts and blood vessels but a normally functioning circulation. Correlations of body mass with cardiovascular parameters suggested that blood pressure and structural characteristics develop in line with body size.

CONCLUSION

In this transgenic mouse model of acromegaly, there is cardiac and vascular hypertrophy commensurate with GH excess but normal function. Our findings support the contention that the excess mortality in this condition may be due to the development of hypertrophic cardiomyopathy rather than increased rates of atherosclerotic coronary artery disease.

JAK redux: a second look at the regulation and role of JAKs in the heart

A number of type 1 receptor cytokine family members protect the heart from acute and chronic oxidative stress. This protection involves activation of two intracellular signaling cascades: the reperfusion injury salvage kinase (RISK) pathway, which entails activation of phosphatidylinositol 3-kinase (PI3-kinase) and ERK1/2, and JAK-STAT signaling, which involves activation of transcription factor signal transducer and activator of transcription 3 (STAT3). Obligatory for activation of both RISK and STAT3 by nearly all of these cytokines are the kinases JAK1 and JAK2. Yet surprisingly little is known about how JAK1 and JAK2 are regulated in the heart or how they couple to PI3-kinase activation. Although the JAKs are linked to antioxidative stress programs in the heart, we recently reported that these kinases are inhibited by oxidative stress in cardiac myocytes. In contrast, others have reported that cardiac JAK2 is activated by acute oxidative stress by an undefined process. Here we summarize recent insights into the regulation of JAK1 and JAK2. Besides oxidative stress, inhibitory regulation involves phosphorylation, nitration, and intramolecular restraints. Stimulatory regulation involves phosphorylation and adaptor proteins. The net effect of stress on JAK activity in the heart likely represents the sum of both inhibitory and stimulatory processes, along with their dynamic interaction. Thus the regulation of JAKs in the heart, once touted as the paragon of simplicity, is proving rather complicated indeed, requiring a second look. It is our contention that a better understanding of the regulation of this kinase family that is implicated in cardiac protection could translate into effective therapeutic strategies for preventing myocardial damage or repairing the injured heart.

Identification, treatment and management of cardiovascular risks in patients with acromegaly

Acromegaly, a syndrome related to growth hormone/IGF-1 excess, is frequently complicated by cardiovascular abnormalities (acromegalic cardiomyopathy). Extremely frequent are left ventricular hypertrophy and alterations of diastolic filling, which may progress to systolic dysfunction and eventually heart failure. Cardiac abnormalities may normalize after successful medical or surgical treatment of acromegaly, particularly in young patients with short-lasting disease, but this is less likely to occur in elderly patients. Both hypertension and cardiac valve disease are frequently encountered in acromegaly, but neither seems to be favorably influenced by disease control. The prevalence of coronary heart disease (CHD) is controversial but is probably not increased in acromegaly. Arrhythmias are relatively common in untreated acromegalic patients, although their clinical relevance is unknown. A cardiac evaluation of acromegalic patients should include echocardiography, basal electrocardiogram and blood pressure measurement, and evaluation of common risk factors for CHD. Appropriate and prompt treatment allowing a rapid control of growth hormone/IGF-1 hypersecretion is warranted because many features of acromegalic cardiomyopathy may be reverted, particularly in younger patients. In view of the lack of association with acromegaly, common risk factors for CHD, hypertension, arrhythmias or valve disease should be managed independently, irrespective of control of disease activity.

The long-term cardiovascular outcome of different GH-lowering treatments in acromegaly

The aim of this longitudinal study was to evaluate the echocardiographic outcome of acromegalic heart disease in patients undergoing different therapeutic approaches, in order to investigate whether SSA could provide therapeutic advantages as compared with neurosurgery. In total of 36, consecutive patients undergoing SSA treatment after neurosurgery were enrolled in this study (Gr.Surg.-SSA). After 12 months of treatment, 21 patients had a controlled disease, while the remaining 15 patients displayed uncontrolled disease. Twelve acromegalic patients who did not undergo SSA treatment due to controlled disease after neurosurgery were enrolled as control group (Gr.Surg). The echocardiographic-Doppler study was performed before neurosurgery and after 12-months of follow-up. After follow-up, a significant reduction in serum GH and IGF-I values, Left Ventricular Mass index (LVMi) and LVH rate with an improvement in diastolic function was observed in both groups of patients. We found a significant reduction of LVMi either in patients with controlled disease or in those with poorly controlled disease undergoing SSA treatment. Diastolic function and of LVH percentage improved in all groups, but significantly so only in controlled patients, no significant difference in any echocardiographic parameters and in the prevalence of the LVH rate were observed between the three groups of patients at the end of follow-up. Therefore, our data appear to show that for echographic parameters medical treatment additive beneficial effects is compared to neurosurgery alone. SSA also appears to contribute to the improvement of acromegalic cardiomyopathy also in patients who did not achieve biochemical control of the disease.

Identification of the glomerular podocyte as a target for growth hormone action

GH excess in both the human and transgenic animal models is characterized by significant changes in blood pressure and renal function. The GH/GH receptor (GHR) axis is also implicated in the development of diabetic nephropathy. However, it is not clear whether GH's actions on renal function are due to indirect actions mediated via changes in blood pressure and vascular tone or due to direct action of GH on the kidney. We hypothesized that functional GHRs are expressed on the glomerular podocyte enabling direct actions of GH on glomerular function. Real-time PCR, immunohistochemistry, and Western blot analysis of murine podocyte cells (MPC-5) and kidney glomeruli demonstrated expression of GHR mRNA and protein. Exposure of both murine and human podocytes to GH (50-500 ng/ml) resulted in an increase in abundance of phosphorylated signal transducer and activator of transcription-5, Janus kinase-2, and ERK1/2 proteins. Exposure of podocytes to GH also caused changes in the intracellular distribution of the Janus kinase-2 adapter protein Src homology 2-Bbeta, stimulation of focal adhesion kinase, increase in reactive oxygen species, and GH-dependent changes in the actin cytoskeleton. We conclude that glomerular podocytes express functional GHRs and that GH increases levels of reactive oxygen species and induces reorganization of the actin cytoskeleton in these cells. These results provide a novel mechanistic link between GH's actions and glomerular dysfunction in disorders such as acromegaly and diabetic glomerulosclerosis.

Recombinant bovine growth hormone-induced reduction of atrial natriuretic peptide is associated with improved left ventricular contractility and reverse remodeling in cardiomyopathic UM-X7.1 hamsters with congestive heart failure

OBJECTIVE

To assess the effect of short-term treatment with GH on left ventricular contractility and remodeling, after the development of heart failure in cardiomyopathic hamsters (CMH).

DESIGN

Two groups of 200-day-old UM-X7.1 CMH received daily subcutaneous injections of recombinant bovine (rb) GH (1mg/kg/day) or 0.9% NaCl for 40 days. Golden Syrian hamsters (GSH) were used as controls. At 240-day-old, the hamsters were randomly subjected to (i) assessment of left ventricular systolic function in a Langendorff perfused mode followed by the determination of the passive diastolic pressure-volume relationship and morphometric measurements; (ii) assessment of left ventricular mRNA expression of genes belonging to the fetal gene program including atrial (ANP) and brain (BNP) natriuretic peptides and cardiac myosin heavy chain isoforms and of the circulating levels of the natriuretic peptides.

RESULTS

Hearts from CMH were hypertrophied and dilated (p<0.05) compared to hearts from GSH, along with a approximately 10-fold increase in the circulating ANP and BNP levels. Left ventricular BNP and ANP mRNAs were elevated by 2- and 3-fold, respectively, compared to GSH. rbGH reduced both ANP mRNA and ANP circulating levels by 34% (p<0.01) but did not significantly modulate BNP levels. This effect was associated with a preserved systolic function and reverse remodeling as assessed by a leftward shift of the passive diastolic pressure-volume relationship indicating reduced ventricular dilatation.

CONCLUSIONS

The data show that a short-term administration of GH in the terminal phase of the disease confers cardioprotection by attenuating systolic dysfunction and by inducing beneficial reverse remodeling.

Conditional cardiovascular response to growth hormone therapy in adult patients with Prader-Willi syndrome

CONTEXT

In Prader-Willi syndrome (PWS), an altered GH secretion has been related to reduced cardiac mass and systolic function when compared with controls.

OBJECTIVES

The objective of the study was to evaluate the cardiovascular response to GH therapy in adult PWS patients.

STUDY PARTICIPANTS

Thirteen obese PWS adults (seven males and six females, aged 26.9+/-1.2 yr, body mass index 46.3+/-1.6 kg/m2) participated in the study.

METHODS

Determination of IGF-I, metabolic parameters, echocardiography, and cardioscintigraphy with dobutamine stimulation was made during 12 months GH therapy, with results analyzed by repeated-measures ANOVA.

RESULTS

GH therapy increased IGF-I (P<0.0001); decreased C-reactive protein levels (P<0.05); and improved lean mass (P<0.001), fat mass (P<0.05), and visceral fat (P<0.001). Echocardiography showed that 6- and 12-month GH therapy increased left ventricle mass in 76 and in 61% of patients, respectively (P<0.05), did not change diastolic function, and slightly decreased the left ventricle ejection fraction (LVEF) (P=0.054). Cardioscintigraphy documented stable values of LVEF throughout the study, whereas right ventricle ejection fraction decreased significantly (P<0.05) being normally responsive to dobutamine infusion. A positive association between IGF-I z-scores and LVEF occurred at the 6- and 12-month follow-up (P<0.05).

CONCLUSIONS

In PWS, GH therapy increased cardiac mass devoid of diastolic consequences. The observation of a slight deterioration of right heart function as well as the association between IGF-I and left ventricular function during GH therapy suggest the need for appropriate cardiac and hormonal monitoring in the therapeutic strategy for Prader-Willi syndrome.

Treatment with growth hormone receptor antagonist in acromegaly: effect on cardiac structure and performance

AIM

The aim of the current study was to evaluate the effect of short-term (6 months) and long-term (18 months) treatment with pegvisomant on cardiac structure and performance in patients with acromegaly.

PATIENTS

Seventeen patients (nine women, eight men, 27-61 yr) with active acromegaly entered and 12 completed the long-term study. After a baseline evaluation, including measurement of hemodynamic, biochemical, and hormonal parameters, and a standard Doppler echocardiography, treatment with pegvisomant was started at the initial dose of 10 mg/d, increasing by 5 mg/d every 6 wk on the basis of IGF-I levels until normalization or the achievement of a maximal dose of 40 mg/d.

RESULTS

After short-term treatment, IGF-I levels were normalized in 10 of the 17 (59%) patients. Left ventricular mass index (LVMi) was significantly decreased without changes in diastolic and systolic performance. After long-term treatment, IGF-I levels were normalized in 10 of the 12 (83%) patients. Blood glucose and serum insulin levels were decreased compared with baseline. LVMi was further decreased compared with short-term treatment, so that the prevalence of left ventricle hypertrophy decreased from 50% at baseline to 17% after 18 months of treatment. Moreover, ejection fraction as well as early to late (atrial) peak velocity ratio (E/A) were significantly increased, whereas isovolumic relaxation time was significantly decreased compared with baseline, demonstrating an improvement of both diastolic and systolic function. A significant correlation was found between the change in IGF-I levels and that of left ventricular ejection fraction. In general, the prevalence of cardiac insufficiency was present in 13 of the 17 (76%) patients at baseline and in one (8%) patient after 18 months of treatment.

CONCLUSIONS

Long-term treatment with the GH receptor antagonist improves acromegalic cardiomyopathy by decreasing cardiac hypertrophy and enhancing diastolic and systolic function, and consequently partially or completely reverting the cardiac insufficiency.

Growth hormone promotes skeletal muscle cell fusion independent of insulin-like growth factor 1 up-regulation

Growth hormone (GH) participates in the postnatal regulation of skeletal muscle growth, although the mechanism of action is unclear. Here we show that the mass of skeletal muscles lacking GH receptors is reduced because of a decrease in myofiber size with normal myofiber number. GH signaling controls the size of the differentiated myotubes in a cell-autonomous manner while having no effect on size, proliferation, and differentiation of the myoblast precursor cells. The GH hypertrophic action leads to an increased myonuclear number, indicating that GH facilitates fusion of myoblasts with nascent myotubes. NFATc2, a transcription factor regulating this phase of fusion, is required for GH action because GH is unable to induce hypertrophy of NFATc2-/- myotubes. Finally, we provide three lines of evidence suggesting that GH facilitates cell fusion independent of insulin-like growth factor 1 (IGF-1) up-regulation. First, GH does not regulate IGF-1 expression in myotubes; second, GH action is not mediated by a secreted factor in conditioned medium; third, GH and IGF-1 hypertrophic effects are additive and rely on different signaling pathways. Taken together, these data unravel a specific function of GH in the control of cell fusion, an essential process for muscle growth.

The transcription factors Slug and Snail act as repressors of Claudin-1 expression in epithelial cells

Claudin-1 is an integral membrane protein component of tight junctions. The Snail family of transcription factors are repressors that play a central role in the epithelial-mesenchymal transition, a process that occurs during cancer progression. Snail and Slug members are direct repressors of E-cadherin and act by binding to the specific E-boxes of its proximal promoter. In the present study, we demonstrate that overexpression of Slug or Snail causes a decrease in transepithelial electrical resistance. Overexpression of Slug and Snail in MDCK (Madin-Darby canine kidney) cells down-regulated Claudin-1 at protein and mRNA levels. In addition, Snail and Slug are able to effectively repress human Claudin-1-driven reporter gene constructs containing the wild-type promoter sequence, but not those with mutations in two proximal E-box elements. We also demonstrate by band-shift assay that Snail and Slug bind to the E-box motifs present in the human Claudin-1 promoter. Moreover, an inverse correlation in the levels of Claudin-1 and Slug transcripts were observed in breast cancer cell lines. E-box elements in the Claudin-1 promoter were found to play a critical negative regulatory role in breast cancer cell lines that expressed low levels of Claudin-1 transcript. Significantly, in invasive human breast tumours, high levels of Snail and Slug correlated with low levels of Claudin-1 expression. Taken together, these results support the hypothesis that Claudin-1 is a direct downstream target gene of Snail family factors in epithelial cells.

Effect of nutrient restriction on the somatotropes and substance P-immunoreactive cells in the pituitary of the female ovine fetus

The maternal environment affects fetal development and may influence the physiology of the adult. Fetal growth hormone (GH) is increased by maternal undernutrition but the mechanisms responsible are unknown. This study determined the effect of maternal undernutrition on the development of fetal pituitary somatotropes in the female. Ewes were grouped randomly into control (fed 100% of requirements) or nutrient restricted (fed 50%) from Days 28 to 78 of gestation. At Day 78, the ewes were killed and fetuses collected (Day 78 NR (nutrient restricted): n=6; Day 78C (control): n=6). Remaining ewes were realimented to 100% of nutritional requirements and were killed at Day 135 (Day 135 NR (nutrient restricted): n=6; Day 135 C (control): n=6). Somatotropes were visualized immunocytochemically and the size, mean density, total percentage and proportion colocalized with substance P were determined for each group. Nutrient restriction increased (p<0.01) the density of pituitary cells in Day 78 fetuses but this difference was no longer apparent by Day 135 after realimentation. The density and proportion of somatotropes were not different between treatment groups at Day 78 but were significantly (p<0.05) lower in the nutrient restricted Day 135 fetuses as compared to the Day 135 control animals. Somatotropes from restricted fetuses were significantly (p<0.001) larger at Day 78. Nutrient restriction increased the density (p<0.001) and percentage (p<0.05) of substance P-immunoreactive cells Day 135 fetuses. Similarly, the proportion of somatotropes that expressed substance P was significantly (p<0.05) increased by nutrient restriction in the Day 135 fetuses. Although nearly two thirds of substance P-immunoreactive cells co-expressed GH, there was no significant effect of treatment on this co-expression. Additional studies are required to determine if other components of the neuroendocrine GH axis are affected by this nutritional insult, if the alterations that we have observed, particularly in the tachykinin system, persist into adulthood and, importantly, what are the long-term consequences of an altered GH axis.

The total length of myocytes and capillaries, and total number of myocyte nuclei in the rat heart are time-dependently increased by growth hormone

Growth hormone (GH) can increase size and dimensions of rat hearts. The aim was to study how GH administration influences the growth of cardiac myocytes and capillaries in relation to time. Three-month-old female rats were divided into 10 groups (n=3), and injected with either GH (5mg/kg/day) or vehicle for 5, 10, 20, 40, or 80 days. From the left ventricle (LV) histological sections were made and stereological methods applied. Linear regression showed that GH time-dependently increased: LV volume (r=0.96, P<0.001), total volume of myocytes (r=0.96, P<0.001) and capillaries (r=0.64, P<0.05), total length of myocytes (r=0.90, P<0.001) and capillaries (r=0.78, P<0.001), and total number of myocyte nuclei (r=0.85, P<0.001). In conclusion, during 80 days of GH treatment the total volume and length of myocytes and capillaries, and total number of myocyte nuclei increased in a linear way. The results indicate that GH is a potent mediator of myocardial growth.

The influence of growth hormone therapy on ultrasound myocardial tissue characterization in patients with childhood onset GH deficiency

BACKGROUND

In growth hormone deficiency (GHD), a reduction in left ventricular mass (LV-mass) and impairment of systolic function has been shown. In this study, we investigated the effects of 12 months of GH replacement therapy on cardiac structure and functional indices measured by echocardiographic techniques in adult patients with childhood onset GH deficiency.

METHODS

Sixteen patients (age 42.3+/-13.1 years, 10 males) were investigated before and after 12 months of GH treatment at a dose of 0.02 IU/kg/day (7 microg/kg/day). Echocardiography was performed including the ultrasound myocardial tissue characterization technique. We measured two parameters of the ultrasonic tissue characterization with integrated backscatter: the magnitude of the cardiac-cycle-dependent variation in integrated backscatter signals (CV-IBS) and the mean value of integrated backscatter signals calibrated by the pericardium (cal-IBS).

RESULTS

Left ventricular diameter and wall thickness did not change after GH treatment, although systolic increase in interventricular septum thickness (IVS%) and systolic increase in posterior wall thickness (PWT%) increased significantly (IVS% 52.2+/-31.9% vs. 67.3+/-30.4% and PWT% 48.7+/-20.2% vs. 58.0+/-17.7%, p<0.01 and p<0.01, respectively). Ejection fraction increased from 56.2+/-7.2% to 63.2+/-6.1% (p<0.01). LV-mass index did not change after GH treatment (78.4+/-22.1 vs. 81.9+/-21.1 g/m(2)). CV-IBS increased significantly after GH treatment (p<0.05), in both the interventricular septum and the left ventricular posterior wall (4.7+/-1.5 vs. 5.8+/-1.9 dB for the interventricular septum, 4.9+/-1.8 vs. 6.5+/-2.4 dB for the left ventricular posterior wall, p<0.05 and p<0.05, respectively). Cal-IBS also increased significantly after GH treatment (-23.5+/-4.1 vs.-21.8+/-4.2 dB for the interventricular septum, -23.0+/-4.4 vs. -21.8+/-4.3 dB for the left ventricular posterior wall, p<0.01 and p<0.05, respectively).

CONCLUSION

Twelve months GH treatment in adults with childhood onset GHD resulted in improvement of cardiac contractile performance. Observed changes in cal-IBS and CV-IBS suggest that GH treatment in this patient group can lead to a further somatic maturation of the heart, probably not accomplished previously.

Growth Hormone Receptor Is a Target for Presenilin-dependent γ-Secretase Cleavage

Growth hormone receptor (GHR) is a cytokine receptor superfamily member that binds growth hormone (GH) via its extracellular domain and signals via interaction of its cytoplasmic domain with JAK2 and other signaling molecules. GHR is a target for inducible metalloprotease-mediated cleavage in its perimembranous extracellular domain, a process that liberates the extracellular domain as the soluble GH-binding protein and leaves behind a cell-associated GHR remnant protein containing the transmembrane and cytoplasmic domains. GHR metalloproteolysis can be catalyzed by tumor necrosis factor-alpha-converting enzyme (ADAM-17) and is associated with down-modulation of GH signaling. We now study the fate of the GHR remnant protein. By anti-GHR cytoplasmic domain immunoblotting, we observed that the remnant induced in response to phorbol ester or platelet-derived growth factor has a reliable pattern of appearance and disappearance in both mouse preadipocytes endogenously expressing GHR and transfected fibroblasts expressing rabbit GHR. Lactacystin, a specific proteasome inhibitor, did not appreciably change the time course of remnant appearance or clearance but allowed detection of the GHR stub, a receptor fragment slightly smaller than the remnant but containing the C terminus of the remnant (receptor cytoplasmic domain). In contrast, MG132, another (less specific) proteasome inhibitor, strongly inhibited remnant clearance and prevented stub appearance. Inhibitors of gamma-secretase, an aspartyl protease, also prevented the appearance of the stub, even in the presence of lactacystin, and concomitantly inhibited remnant clearance in the same fashion as MG132. In addition, mouse embryonic fibroblasts derived from presenilin 1 and 2 (PS1/2) knockouts recapitulated the gamma-secretase inhibitor studies, as compared with their littermate controls (PS1/2 wild type). Confocal microscopy indicated that the GHR cytoplasmic domain became localized to the nucleus in a fashion dependent on PS1/2 activity. These data indicate that the GHR is subject to sequential proteolysis by metalloprotease and gamma-secretase activities and may suggest GH-independent roles for the GHR.

Cardiac resistance to growth hormone in uremia

BACKGROUND

Cardiovascular disease is a major cause of death in end-stage renal disease (ESRD). Since growth hormone is required for maintaining normal cardiac structure and function and as growth hormone has a salutary effect on cardiac remodeling in disease, we postulated that if cardiac resistance to growth hormone develops in chronic renal failure (CRF) this may predispose to the cardiomyopathy of uremia. We set out to test whether in CRF there is resistance to the cardiac action of growth hormone and whether this defect might be caused by altered growth hormone signaling.

METHODS

Growth hormone-deficient (dw/dw) rats and growth hormone-intact Sprague-Dawley rats underwent a subtotal nephrectomy or sham operation and pair feeding.

RESULTS

In dw/dw rats treated with growth hormone for 8 days there was a significant increase in insulin-like growth factor-1 (IGF-1) mRNA levels in controls but this response was attenuated in CRF. Next, growth hormone-stimulated Janus kinase-signal transducers and activators of transcription (JAK2-STAT5) signaling was studied 15 minutes after intravenous growth hormone in dw/dw and Sprague-Dawley rats. Growth hormone receptor, JAK2, STAT5a, and STAT5b protein levels were unaltered in CRF. Growth hormone-induced JAK2, growth hormone receptor (GHR), and STAT5 tyrosine phosphorylation was significantly depressed in CRF as was nuclear translocation of phosphorylated STAT5. When rats were treated with pharmacologic dose growth hormone, STAT5 phosphorylation increased similarly in CRF and control rats.

CONCLUSION

Uremic rats develop cardiac resistance to growth hormone caused at least, in part, by a postreceptor defect in growth hormone-induced signaling that is characterized by impaired phosphorylation and nuclear translocation of STAT5. These findings raise the question whether growth hormone resistance contributes to the cardiac changes of uremia.

Leptin does not induce hypertrophy, cell cycle alterations, or production of MCP-1 in cultured rat and mouse cardiomyocytes

BACKGROUND

Leptin has been proposed as an important mediator in cardiovascular pathophysiology. Patients with congestive heart failure (CHF) present high plasma leptin levels. CHF is generally preceded by myocardial remodeling involving hypertrophy, necrosis, and apoptosis.

AIM

To investigate whether leptin causes hypertrophy or cell cycle alterations, or induces MCP-1 synthesis in cardiomyocytes.

METHODS

Primary cultures of neonatal rat cardiomyocytes (PC) and murine cell line HL-1 were used. RT-PCR was used to identify Ob-Rb gene expression. Metabolic activity and proliferation of cardiomyocytes was studied using MTT and BrdU uptake, while apoptosis was assayed with Hoechst dye vital staining and flow cytometry. Measurement of the cell surface area was used to determine hypertrophy. MCP-1 levels were measured by ELISA.

RESULTS

RT-PCR showed Ob-Rb mRNA expression in HL-1 cells. Exposure to leptin induced no changes in metabolic activity, proliferation, and apoptotic rates, and did not alter cell cycle in cardiomyocytes. Leptin did not increase cell size of cardiomyocytes, and MCP-1 synthesis was not detected in PC and HL-1 cells treated with leptin.

CONCLUSION

This work shows that leptin does not induce changes in viability, proliferation, size or apoptosis of rat neonatal and HL-1 cardiomyocytes, and it does not induce MCP-1 secretion in these cells.

Modulation of gene expression in neonatal rat cardiomyocytes by surface modification of polylactide-co-glycolide substrates

Myocardial tissue engineering presents a potential treatment option for heart disease. Cardiomyocytes isolated at various stages of development retain the ability to form contractile networks in vitro, which suggests that it should be possible to reconstitute viable myocardium given the appropriate architecture, stimuli, and cardiomyogenic cell source. This study investigates the effects of modifying substrate surface energy (by plasma etching) and protein coating (by fibronectin adsorption) on neonatal rat ventricular myocyte (NRVM) function. Primary NRVMs were cultured for 96 h on modified and control films of a common degradable polymer, polylactide-co-glycolide. Cultures were analyzed for cell spreading, protein content, and mRNA expression of atrial natriuretic factor and beta-myosin heavy chain. The results demonstrate that NRVMs cultured on etched films significantly increased in spreading, myofibril development, protein content, and gene expression of atrial natriuretic factor and beta-myosin heavy chain compared with unetched films, and that this surface energy effect is overwhelmed by the addition of fibronectin. Conclusions from this study are that surface energy and protein adsorption influence the gene expression of adherent NRVMs, and may be important for modulating the function of engineered myocardium.

Organ-specific stress induces mouse pancreatic keratin overexpression in association with NF-kappaB activation

Keratin polypeptides 8 and 18 (K8/K18) are the major intermediate filament proteins of pancreatic acinar cells and hepatocytes. Pancreatic keratin function is unknown, whereas hepatocyte keratins protect from mechanical and non-mechanical forms of stress. We characterized steady-state pancreatic keratin expression in Balb/c mice after caerulein and choline-deficient ethionine-supplemented diet (CDD), or on exposure to the generalized stresses of heat and water immersion. Keratins were studied at the protein, RNA and organizational levels. Isolated acini were used to study the role of nuclear factor (NF)-kappaB using selective inhibitors. Keratins were found to be abundant proteins making up 0.2%, 0.3% and 0.5% of the total cellular protein of pancreas, liver and small intestine, respectively. Caerulein and CDD caused a threefold transcription-mediated overall increase in K8/K18/K19/K20 proteins. Keratin overexpression begins on tissue recovery, peaks 2 days after caerulein injection, or 1 day after CDD discontinuation, and returns to basal levels after 10 days. K19/K20-containing cytoplasmic filaments are nearly absent pre-injury but form post-injury then return to their original membrane-proximal distribution after 10 days. By contrast, generalized stresses of heat or water-immersion stress do not alter keratin expression levels. Caerulein-induced keratin overexpression is associated with NF-kappaB activation when tested using ex vivo acinar cell cultures. In conclusion, keratins are abundant proteins that can behave as stress proteins in response to tissue-specific but not generalized forms of injury. Pancreatic keratin overexpression is associated with NF-kappaB activation and may serve unique functions in acinar or ductal cell response to injury.

Beta-catenin is required for endothelial-mesenchymal transformation during heart cushion development in the mouse

During heart development endocardial cells within the atrio-ventricular (AV) region undergo TGFβ-dependent epithelial-mesenchymal transformation (EMT) and invade the underlying cardiac jelly. This process gives rise to the endocardial cushions from which AV valves and part of the septum originate. In this paper we show that in mouse embryos and in AV explants TGFβ induction of endocardial EMT is strongly inhibited in mice deficient for endothelial β-catenin, leading to a lack of heart cushion formation. Using a Wnt-signaling reporter mouse strain, we demonstrated in vivo and ex vivo that EMT in heart cushion is accompanied by activation of β-catenin/TCF/Lef transcriptional activity. In cultured endothelial cells, TGFβ2 induces α-smooth muscle actin (αSMA) expression. This process was strongly reduced in β-catenin null cells, although TGFβ2 induced smad phosphorylation was unchanged. These data demonstrate an involvement of β-catenin/TCF/Lef transcriptional activity in heart cushion formation, and suggest an interaction between TGFβ and Wnt-signaling pathways in the induction of endothelial-mesenchymal transformation.

Keratin-8 null mice have different gallbladder and liver susceptibility to lithogenic diet-induced injury

Keratin transgenic mouse models and the association of human keratin mutations with liver disease highlight the importance of keratins in protecting the liver from environmental insults, but little is known regarding keratins and their function in the gallbladder. We characterized keratin expression pattern and filament organization in normal and keratin polypeptide-8 (K8)-null, K18-null and K19-null gallbladders, and examined susceptibility to liver and gallbladder injury induced by a high-fat lithogenic diet (LD) in K8-null mice. The major keratins of normal mouse gallbladder are K8>K19>K18 which become markedly depleted in K8-null mice with minor K18/K19 remnants and limited K7 over-expression. Compensatory K18/K20 protein and RNA overexpression occur in K19-null but not in K18-null gallbladders, probably because of the higher levels of K19 than K18 in normal gallbladder. LD challenge causes more severe liver injury in K8-null than wild-type mice without altering keratin protein levels. In contrast, wild-type and K8-null gallbladders are equally susceptible to LD-induced injury and stone formation, but wild-type gallbladders do overexpress keratins upon LD challenge. LD-induced injury triggers keratin hyperphosphorylation in wild-type livers and gallbladders. Hence, mouse gallbladder K8/K18/K19 expression is induced in response to cholelithiasis injury. A high-fat LD increases the susceptibility of K8-null mice to liver but not gallbladder injury, which suggests that keratin mutations may increase the risk of liver damage in patients with steatohepatitis. Differences between K8-null mouse gallbladder and hepatocyte susceptibility to injury may be related to their minimal versus absent keratin expression, respectively.